Stone surface cleaning hydrogel formulation

Abstract

The present patent application concerns a hydrogel formulation for cleaning stone surfaces comprising: a first chelating agent consisting of citric acid, a second chelating agent selected from the group consisting of Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.7 to 1:1.6.

Description

FIELD OF THE INVENTION

[0001] The present invention fits in the technical field of chemical cleaning of stone surfaces, especially of civil / industrial buildings and / or cultural heritage property.STATE OF THE ART

[0002] Stone surfaces (natural or artificial) of civil and industrial buildings are subject to deposition and accumulation of atmospheric particulate matter, carbonaceous residues, products of neoformation or of degradation of metal objects with consequent chromatic alteration. The removal of these deposits or patinas is necessary for both aesthetic and, above all, conservative reasons.

[0003] In addition to the civil field, this need is also evident in other contexts, such as that of cultural heritage property.

[0004] Chemical cleaning is the most frequently used technology for the removal of deposit or neoformation material from stone surfaces, as it is the most sustainable (in terms of material cost and execution time), as well as not requiring particularly specialised personnel.Problems of the background art

[0005] In particular, chemical cleaning consists in the use of solvents or aqueous formulations for the solubilization and removal of unwanted material from the stone surfaces.

[0006] However, it is often necessary to use organic solvents or products characterized by various toxicities to obtain good results. For example, among the most commonly used solvents are organic compounds of various kinds, such as acetone, ethyl or butyl acetate, nitro thinner, ligroin, white spirit, alcohols. The organic solvents tend to be toxic, unsustainable and / or non-biodegradable, and are used in abundant quantities.

[0007] In other cases, the preparation of water-based formulations is instead envisaged. Aqueous formulations known in the art are obtained by solubilizing basic or acidic substances - such as sodium or ammonium carbonate / bicarbonate, EDTA, phosphoric acid, ammonia, sodium hydroxide, hydrochloric acid, ammonium citrate or citric acid - with or without surfactants.

[0008] In the civil sector, the application of organic solvents or aqueous solutions is generally done by spraying, using suitable dispensers, followed by abundant rinsing, often through the use of pressure washers.

[0009] In other cases, where for technical, ecological and / or physical reasons spray application is not feasible, especially in the cleaning of historical-architectural surfaces, the cleaning agent (organic solvent or aqueous solution) is generally supported (by application of "compress"), at the time of use, on "supporting" agents (also called simply "supporting elements"), such as, for example, cellulose pulp, agar-agar, sepiolite, chemical gels (for example, polymers of acrylic acid), and applied by compress.

[0010] This technique of preparing the compress in situ requires expert personnel - especially in determining the appropriate quantities of the various components and in their correct mixing - who must then use it in the following 24-48 hours. Furthermore, as for the spray application, once the compress has been removed, the surface is then abundantly rinsed to remove unwanted residues of the supporting agent and cleaning agent.

[0011] Passaretti et al in "Biologically Derived Gels for the Cleaning of Historical and Artistic Metal Heritage" (Appl. Sci. 2021, 11, 3405. https: / / doi.org / 10.3390 / app11083405) explain that it is possible, for metal surfaces, to use hydrogels or organogels, which are still being implemented.

[0012] Again, the authors Guilminot et al in "The Use of Hydrogels in the Treatment of Metal Cultural Heritage Objects." (Gels. 2023 Mar 2;9(3):191. doi: 10.3390 / gels9030191. PMID: 36975640; PMCID: PMC10048560) explain that, especially for application on metal surfaces, it is possible to use hydrogels based on polysaccharides, such as agar, gellan and xanthan gum. According to the authors, for cleaning copper alloys, the best results are obtained by combining an agar gel with a chelating agent (EDTA (ethylenediaminetetraacetic acid) or TAC (tri-ammonium citrate)). The hot application allows to obtain a "peelable" gel, particularly suitable for historical objects. The authors explain, again, that the electrochemical treatments with hydrogels have been successful for cleaning silver and for the dechlorination of ferrous alloys or copper. The use of hydrogels for cleaning painted aluminium alloys is possible, but must be combined with mechanical cleaning. However, for cleaning archaeological lead, the use of hydrogels was not very effective. The authors conclude that agar seems to be the most promising hydrogel for this type of application.

[0013] Similarly, J. M. van den Burg e K. Seymour in "Dirt and dirt removal (dry and aqueous cleaning)" (2022, Klaas Jan van der Berg and Lia Gorter Editors, Cultural Heritage Agency of the Netherlands, Amersfoort, page 61) explain that xanthan gum can be used to thicken some aqueous detergent solutions. It forms a water-based, non-toxic, biodegradable and stable polymer emulsion gel at any pH. Xanthan gum is a polysaccharide polymer consisting of tangled helical chains that, at higher concentrations, which aggregate to form small cages that retain water molecules. Oxidizing agents, such as bleach, and most cationic materials, such as ammonia, cannot be used because they cause the gel to collapse. The authors explain that one of the main disadvantages of xanthan gum (and of other aqueous emulsifiers) is that, after application, a further cleaning step is necessary. Finally, xanthan gum requires an aqueous solution to be eliminated.

[0014] Therefore, it is clear from these three scientific articles that the use of hydrogels for cleaning surfaces, especially falling within the context of cultural heritage property, is known to the state of the art.

[0015] In other scientific studies, instead, such as those conducted by Infurna G, Cavallaro G, Lazzara G, Milioto S, Dintcheva NT. In "Understanding the Effects of Crosslinking and Reinforcement Agents on the Performance and Durability of Biopolymer Films for Cultural Heritage Protection. Molecules" (2021 Jun 7;26(11):3468. doi: 10.3390 / molecules26113468. PMID: 34200367; PMCID: PMC8201363), the formation of biofilms (or biopolymer films) based on chitosan and pectin, also containing crosslinking agents and natural reinforcers, such as citric acid (CA) and halloysite nanotubes (HNT), is highlighted.

[0016] However, these biofilms are not used for cleaning surfaces; rather, they are suitable as cover films for the protection of cultural heritage.

[0017] Similarly, the authors Li T, Hu Y and Zhang B. in "Biomineralization Induced by Colletotrichum acutatum: A Potential Strategy for Cultural Relic Bioprotection" (Front Microbiol. 2018 Aug 14;9:1884. doi: 10.3389 / fmicb.2018.01884. PMID: 30158913; PMCID: PMC6104437) identify an eco-sustainable method for the preservation of stone artefacts. The authors explain that the fungus Colletotrichum acutatum is capable of initiating biomineralisation (the phenomenon of calcium carbonate formation); in particular, they noted that citric acid is a metabolite produced by C. acutatum. The same authors then evaluated whether the proliferation of C. acutatum could affect the deterioration of the stone finds, finding out that, under low carbon conditions, calcium carbonate was protected from dissolution, thus indicating that the risk of deterioration of the limestone substrates could be controlled if the fungi were used to consolidate or restore monuments or stone surfaces. These results suggest that C. acutatum-induced biomineralisation may be a useful treatment for deteriorated stone objects.

[0018] Therefore, in the latter case, the authors focus on the preservation capabilities of the stone surfaces, and not on actual chemical cleaning techniques.

[0019] Furthermore, the authors Cuvillier, L. et al in "Testing of the siderophore deferoxamine amended in hydrogels for the cleaning of iron corrosion" (Eur. Phys. J. Plus 138, 569 (2023). https: / / doi.org / 10.1140 / epjp / s13360-023-04159-y) disclose the use of siderophores, such as deferoxamine, loaded on polysaccharide hydrogels, for the removal of unwanted corrosion products from iron works of art with a view to the biodegradability of the obtained formulation. Siderophores are secondary metabolites capable of binding iron and are produced by microorganisms when they inhabit areas where the concentration of iron is low (to ensure the iron intake necessary for survival). By virtue of their high affinity for iron, siderophores could be used for a targeted cleaning of objects composed of this metal. Three different types of polysaccharides were tested for hydrogel formation, including agar, gellan gum and xanthan gum, with the first two polysaccharides achieving better results.

[0020] The disclosure "Sitting pretty: collaborative treatment of an early Yayoi Kusama soft-sculpture chair" Baas F. and Hartman L.E.; Proceedings of the Objects Specialty Group Sessions; May 28-June 2, 2017; 45th Annual Meeting Chicago, Illinois. https: / / faic.wpenginepowered.com / osg-postprints / wp-content / uploads / sites / 8 / 2019 / 12 / osg024-017.pdf provides for the use of two different types of gel, including xanthan gum, Pemulen TR2 (an acrylic-derived polymer) and agarose. Xanthan gum and Pemulen TR2 provide a liquid gelled solution with a consistency similar to honey or hair gel, while agarose produces a stiff, gummy gel. The authors focused on the tests with liquid gels. The citric acid solution was gelled with xanthan gum and Pemulen TR2. The authors explain that since xanthan gum remains structurally more stable as a gel over a wider range of pH and conductivity parameters, it was chosen over the use of Pemulen TR2.

[0021] As is clear from the state of the art, the mixtures of citric acid, xanthan gum and mixtures of citric acid and other chelating agents, although known, are prepared shortly before use (preparation in situ) according to variable and customised recipes, characterised by a stability limited to 24-48 hours and an uncertified or certainly not negligible aggressiveness, without providing for a controlled and progressive release of the cleaning solution, thus inhibiting the benefits of the cleaning efficacy.

[0022] Therefore, the Applicant considers that several problems still need to be resolved, including: the need to identify formulations on a water-basis that provide for the use of effective cleaning agents on various lithotypes and on various types of dirt / deposits / patinas, which are non-toxic for the operators and eco-sustainable, i.e. without any impact on the environment; the need to identify supporting agents able to guarantee an effective cleaning and a controlled (slow) release of the cleaning agent, so as to have a superficial wettability and, consequently, an easy control of the cleaning, in this way reducing, as much as possible, the chemical aggression of the matrix or of the innermost part of the material of the surface to be treated, in addition to avoiding the penetration of dirt and / or other unwanted material into the depth of the material of the surface to be treated; the need, again, to identify a standardized or ready-to-use formulation, which is easy to apply on surfaces of any geometry, placed both horizontally and vertically, as well as easy to produce industrially; the need to easily remove the formulation / compress, by applying a gentle rinsing of the surface, avoiding wasting abundant amounts of water; finally, it is also required to obtain a product that is stable over time, which retains its properties and cleaning performance for a relatively long period of time, for example for more than one week and up to about one year, under standard preservation conditions. The known formulations, in addition to not being ready for use, are in fact characterised by a preservation of at least 24 hours up to a maximum of 48 hours. SUMMARY OF THE INVENTION

[0023] A first object of the invention is a cleansing hydrogel formulation of stone surfaces comprising a first chelating agent consisting of citric acid, a second chelating agent selected from the group consisting of: Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.7 to 1:1.6.

[0024] A second object of the invention is a method for applying the aforementioned formulation to a stone surface, comprising the steps of a) applying the hydrogel formulation to the stone surface, b) leaving on for a time comprised between 15 minutes and 120 minutes, c) removing the hydrogel formulation with water, wherein the aforementioned steps a)-c) are repeated for a number of times n comprised between 1 and 3.

[0025] A third further object of the invention is the use of the aforementioned formulation for the cleaning, preferably chemical cleaning, of stone surfaces.Advantages of the invention

[0026] Note that the "first chelating agent / second chelating agent / supporting agent" interaction is of particular importance because, in addition to the complexing role of the first two, it is also possible to ensure that a precise three-dimensional conformation of the hydrogel is achieved through the formation of van der Waals forces. This guarantees a controlled release of the formulation, good cleaning performance and a lower or negligible aggressiveness of the stone surface.

[0027] In particular, the technical advantages of the invention are summarized below: identification of a water-based formulation with cleaning efficacy, which includes effective cleaning agents, non-toxic neither for the environment, nor for the operators, and also eco-sustainable; identification of supporting agents able to guarantee an effective cleaning and a controlled / slow release of the cleaning agent, a mainly superficial wettability and, consequently, a lower or negligible chemical aggressiveness of the surface of the material to be treated, with easier cleaning control, even compared to the cleaning solutions or to the cleaning compresses known so far; the creation of a compress without release of residues on the stone surface to be treated; identification of a ready-to-use formulation, in the sense that it does not require the need to mix the necessary ingredients on site, and is easy to apply on horizontal, vertical and moulded surfaces; the ability to easily remove the formulation / compress, by applying a gentle surface rinsing, avoiding water waste; the ability to achieve a formulation that is stable over time, in the sense that it retains cleaning efficacy properties and performance for more than one week and at least one year, under standard preservation conditions. Also in terms of storage, no particular critical issues (flammability) or precautions to be followed (corrosion of storage vessels) have emerged; the ability to obtain the formulation also at an industrial level, without the need to follow particular technical measures.

[0028] Finally, it should be noted that the application times of the formulation of the invention are typically longer than those for the formulations prepared at the time of use (generally below 15 minutes). This allows greater control of the cleaning power, reducing surface aggressiveness in the event that the application time cannot be met.DESCRIPTION OF THE DRAWINGS

[0029] Figure 1: Image of a Carrara marble slab before cleaning referred to in Example 2. Figure 2: Image of the overall situation after various cleaning tests referred to in Example 2. Figure 3: Image of test # H5v1 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 4: Image of test # H9 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 5: Image of test # H10 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 6: Image of test # H12 (Tridac) after one hour, two and three hours of application, referred to in Example 2. Figure 7: Image of test # H5v4 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 8: Image of test # L6c (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 9: Image of test # L6Neutral (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 10: Image of test # L9v3 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 11: Image of test # L9v4 (Tridac) after one hour, two and three hours of application, referred to in Example 2. Figures 12-14: Image of test # H5v1 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 15-17: Image of test # H9 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 18-20: Image of test # H10 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 21-23: Image of test # H12 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 24-26: Image of test # H5v4 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 27-29: Image of test # L6c (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 30-32: Image of test # L6Neutral (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figure 33-35: Image of test # L9v3 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 36-38: Image of test # L9v4 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figure 39: Clockwise: top left rectangle with whole straight line contour (formulation of the invention: Citric acid 3%; Na 4 -GLDA 3%; Xanthan 5%; DPM 3%; 2Prop 3%; Tridac 1%; Water 82%); top right rectangle with dotted contour (composition: Citric acid 2%; Xanthan 3%; Water 95%); right central rectangle with dashed contour (composition: Citric acid 2%; Xanthan 3%; 2Prop 3%; Water 92%); bottom right rectangle with dot-dash contour (composition: Citric acid 3%; Na 4 -GLDA 3%; Xanthan 3%; DPM 3%; 2Prop 3%; Tridac 1%; Water 84%); bottom left rectangle with whole non-straight line contour (composition: Citric acid 2%; Xanthan 3%; 2Prop 3%; Tridac 1%; Water 91%). Figures 40-43: Light microscope images, Line H, in the order: NT (Untreated), 40 mesh (0.420 mm), 80 mesh (0.177 mm), 200 mesh (0.074 mm). Treatment: 1h+1h. Figures 44-45: Light microscope images, Line H, in the order NT (Untreated), 40 mesh (0.420 mm). Treatment: 24 h. Figures 46-49: Light microscope images, Line L, in the order: NT (Untreated), 40 mesh (0.420 mm), 80 mesh, (0.177 mm) 200 mesh (0.074 mm). Treatment: 1h+1h. Figures 50-51: Respectively: image of the pre-treatment situation and image of the situation after 3 types of treatments (at 2h, at 1h and at 1h+1h) for three Test# of line H (respectively at 40, 80 and 200 mesh). DETAILED DESCRIPTION OF THE INVENTION

[0030] In the following, the invention and its preferred embodiments are described in more detail.

[0031] It should be noted that, although the structure has been organized into paragraphs and sub-paragraphs, the information contained in each section or paragraph or subsection or sub-paragraph is not isolated and can possibly be combined with those contained in other sections / paragraphs or, more generally, with other information contained in the text of the patent application.Cleansing hydrogel formulation of stone surfaces

[0032] A hydrogel (or hydrogel) is defined as a colloid in which the polymer chains of the molecules of the supporting agent consisting of xanthan gum are dispersed in water, wherein the water is in a quantity ≥ 80% by weight, preferably ≥ 80% and ≤ 95% by weight, on the total weight of the formulation. In order to be applied as such, i.e. as a compress and without prior dilution, the components of the formulation of the invention have been suitably balanced. In this sense, the formulation is in the form of a gel to be applied to a stone surface as a compress.

[0033] The viscosity of the formulation is preferably comprised between 11 and 35 Pa·s, preferably between 11 and 33 Pa·s, preferably between 12 and 30 Pa·s, preferably between 13 and 25 Pa·s.

[0034] Viscosity was measured using a controlled shear rotational rheometer (Bohlin C-VOR 120 model, Bohlin Instruments Ltd) equipped with "vane in cup" coaxial cylinders, the latter composed of a smooth outer cylinder with a diameter of 15.4 mm and an inner cylinder with 4 fins (vane) with a diameter of 14 mm (gap 0.7 mm). All viscosity measurements were performed at 20°C and with a constant shear rate of 10 s -1< . Three acquisitions were recorded for each formulation, each lasting 5 minutes. The average viscosity value was expressed in Pa·s with standard deviations comprised between ± 0.5 and 5 Pa*s.

[0035] It should be noted that viscosity values below or above the ranges indicated above are not suitable for obtaining a hydrogel formulation in the form of a compress and ready for use as that of the invention.

[0036] Preferably, the consistency of the hydrogel formulation is similar to that of a viscous cream, not suitable for spray application. The application has in fact been designed to be performed by brush or spatula, as required by the use on delicate and irregular surfaces typical of the stone heritage.

[0037] By cleansing formulation of stone surfaces is meant that the formulation of the invention is suitable for removing deposit or neoformation material from the stone surfaces.

[0038] The stone surfaces can be of natural, artificial or ancient plaster type. Examples of stone surfaces are chosen from the group consisting of: marble, sandstone, travertine, granite, limestone, terracotta, cement conglomerates.

[0039] Still, the present formulation may preferably be useful for treating stone surfaces chosen from: carbonate stones; for example Carrara marble; limestone, for example Lecce stone; silicatic stones, for example serene stone; artificial stones, for example bricks; surfaces of buildings, of the type stones or bricks, which, once put in place, are not plastered ("exposed face").

[0040] Preferably, the deposit or undesired material to be removed, preferably placed at the surface level, can be: atmospheric particulate matter, carbonaceous residues, neoformation products or percolations from degradation of metal objects (iron and copper, both superficial and slightly internal to the matrix), black crusts, and combinations thereof.

[0041] In the context of the invention, by cleaning agent or solution (or mixture) is meant a chemical compound or a solution / mixture of chemical compounds capable of favouring the cleaning of stone surfaces, by removing deposition or unwanted material, which acts mainly on the surface.

[0042] Preferably, the hydrogel formulation is an ecological and / or eco-compatible product, in the sense that it contains ecological and / or eco-compatible ingredients in a quantity comprised between 80% and 100% by weight, preferably between 90% and 100% by weight, on the total weight of the formulation. This is beneficial in terms of environmental sustainability.

[0043] Ecological and / or eco-compatible product or formulation means a chemical compound or a mixture of chemical compounds designed and made in such a way as to minimize environmental impact, ensure a low risk to human health and ensure easy disposal (Legislative Decree 152 / 2006). Ecological and / or eco-compatible product / formulation means a formulation characterized by having: components of natural origin or that are biodegradable, and high reduction of pollutant emissions during the life cycle, and absence or minimum amount of toxic, persistent and bioaccumulative substances. First chelating agent

[0044] Citric acid is the first chelating agent. It is a cleaning agent.

[0045] The citric acid is preferably in a quantity comprised between 0.9% and 4% by weight, preferably between 1% and 4% by weight, preferably between 1.2% and 4% by weight, preferably comprised between 1.2% and 3% by weight, preferably comprised between 1.35% and 3% by weight, preferably equal to 1.2%, or to 1.35% and 3% by weight, on the total weight of the formulation.Second chelating agent

[0046] The second chelating agent is selected from the group consisting of: Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above. The second chelating agent is a cleaning agent.

[0047] Preferably, the second chelating agent is Tetrasodium glutamate diacetate or Trisodium dicarboxymethyl alaninate or combination of the above.

[0048] Preferably, the second chelating agent is in a quantity comprised between 2% and 6.7% by weight, preferably between 3% and 5.5% by weight, preferably between 3% and 5.2% by weight, preferably equal to 3% or 4.65% or 5.1% by weight, on the total weight of the formulation.

[0049] Preferably, when the second chelating agent is Tetrasodium glutamate diacetate, the relative quantity is comprised between 2% and 3.5% by weight, preferably between 3% and 3.5% by weight, preferably equal to 3% or 3.5% by weight, on the total weight of the formulation.

[0050] Preferably, when the second chelating agent is Trisodium dicarboxymethyl alaninate, the relative quantity is comprised between 1% and 4.7% by weight, preferably between 1.5% and 4.65% by weight, preferably equal to 1.6% or 4.65% by weight, on the total weight of the formulation.

[0051] Preferably, when the second chelating agent is the combination of Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, the relative quantity is comprised between 2% and 6.7% by weight, preferably between 3% and 5.5% by weight, preferably equal to 5.1% by weight, of the total weight of the formulation.

[0052] The Applicant intends to point out that the quantity of the second chelating agent influences the pH of the formulation, as well as the effect of surface aggression. An increase in the second chelating agent, e.g. beyond the maximum limit expressed at the above ranges, has a negative impact on these two parameters (see Examples 1-5).

[0053] Preferably, the weight ratio between the at least one surfactant and the sum of the first chelating agent and the second chelating agent is comprised between 1:4 and 1:8, preferably between 1:5 and 1:7, preferably between 1:6 and 1:6.3.

[0054] It should be noted that this weight ratio guarantees cleaning efficacy, and affects the gradual and controlled release of the cleaning agents at the level of the stone surface.

[0055] The Applicant points out that the overall concentration of the chelating agents for the purposes of the invention is clearly higher than that of the at least one surfactant.

[0056] For the purposes of the invention, the chelating agents are important for the cleaning capacity, as they sequester the inorganic components to be removed. In the context of the invention, we speak of "chemical cleaning". The surfactant is intended to improve the wettability of the surface if organic and / or oily residues are present and stabilizes the gel matrix.

[0057] The chemical cleaning of the invention is different from the type of cleaning obtainable through other cleaning compositions, for example in liquid form, whereby the cleaning action is mainly entrusted to surfactants (or mixture of surfactants), which remove dirt of an oily organic nature by hydration or emulsification of the fat and in the presence of water. In order to achieve effective detergency, in the state of the art, surfactants are added in a higher concentration than the rest of the components, including chelating agents; in the state of the art, an inverted "surfactant: chelating agent(s)" weight ratio is therefore used with respect to that of the present invention.Supporting agent

[0058] Supporting agent means a material suitable for generating a hydrogel in the presence of water, capable of forming the compress to be applied on a stone surface; it promotes the progressive release of the cleaning solution. In this sense, the supporting agent acts as a densifier.

[0059] By densifier is meant a chemical compound capable of modifying the consistency or viscosity over time of the formulation.

[0060] The supporting agent consists of xanthan gum.

[0061] Preferably, the xanthan gum is in a quantity comprised between 4.7% to 8% by weight, preferably between 5% to 8% by weight, preferably between 5% to 6% by weight, preferably equal to 5% or 6% by weight, on the total weight of the formulation.

[0062] Preferably, the particle size of the xanthan gum is comprised between 0.595 mm (30 mesh) and 0.297 mm (50 mesh), preferably it is 0.420 mm (40 mesh).

[0063] The Applicant has noted that the use of this particle size range for xanthan gum shows different and improved performance compared to the other two commercially available versions, 80 and 200 mesh, especially in terms of rheological, physical, controlled release properties, therefore control of the surface wettability, properties that affect the cleaning power and stability of the formulation. As can be seen from Example 5, the tests carried out with xanthan gum at 0.177 mm (80 mesh) and 0.0074 mm (200 mesh) showed, after 20 days after performance, the formation of crystalline concretions in the gelatinous matrix consisting of secondary recrystallizations of the chelating agents, formed during the phase of complete hydration of the gelling agent, which however altered the compound reducing its stability and performance.

[0064] The weight ratio between the sum of the first chelating agent and the second chelating agent to the xanthan gum is the ratio defined by formula (I) below

[0065] The sum of the first chelating agent and the second chelating agent is the sum of the quantity of the first chelating agent and the quantity of the second chelating agent.

[0066] It should be noted that this weight ratio guarantees the cleaning effectiveness, the gradual and controlled release of the cleaning agents at the level of the stone surface, that is, without penetrating the matrix of the stone material.

[0067] The weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.6 to 1:1.6, preferably from 1:0.7 to 1:1.4.

[0068] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised from 1:0.7 to 1:1.4, preferably from 1:0.7 to 1:1.35, preferably from 1:0.79 to 1:1.35, preferably from 1:0.79 to 1:1.34, preferably from 1:0.79 to 1:1.34 or comprised from 1:0.79 to 1:1.

[0069] According to a preferred form, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is 1:0.79, or is 1:0.83 or is 1:1.Co-densifier

[0070] Co-densifier means a chemical compound that aids the action of a main densifier, which is, in this case, xanthan gum. For the purposes of the invention, the co-densifier aids in the controlled release of the solution together with the main densifier / supporting agent.

[0071] Preferably, the at least one co-densifier is selected from the group consisting of: Dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, propylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol, and combinations thereof.

[0072] Preferably, the at least one co-densifier is Dipropylene glycol monomethyl ether ("DPM").

[0073] Preferably, the at least one co-densifier is in a quantity comprised between 2% and 4% by weight, preferably equal to 3% by weight, on the total weight of the formulation.

[0074] For the purposes of the invention, sodium carbonate is not considered as a co-densifier.Surfactant

[0075] Surfactant means a chemical substance capable of lowering the surface tension of a liquid, facilitating the wettability of the surfaces.

[0076] Preferably, the surfactant employed for the purposes of the invention is a surfactant that is not soluble in water at room temperature.

[0077] Preferably, the at least one surfactant is selected from the group consisting of: a polyethylene glycol (or polyglycol) ether of a fatty alcohol, an alkyl polyethylene glycol of a fatty alcohol, an ethoxylated propoxylated fatty alcohol, a polypropylene glycol / polyethylene glycol ether of a hydrogenated fatty alcohol, a polyoxyalkylated fatty alcohol ether, and combinations of the foregoing.

[0078] Preferably, the at least one surfactant is selected from the group consisting of: a polyethylene glycol (or polyglycol) ether of an ethoxylated fatty alcohol; a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol; an alkyl polyethylene glycol of a fatty alcohol; an ethoxylated propoxylated fatty alcohol; a polypropylene glycol / polyethylene glycol ether of a hydrogenated fatty alcohol; a polyoxyalkylated fatty alcohol ether; and combinations of the foregoing.

[0079] Preferably, the at least one surfactant is selected from the group consisting of: polyethylene glycol (or polyglycol) ether of a fatty alcohol; a polyethylene glycol ether of an ethoxylated fatty alcohol; a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol; and combinations of the foregoing.

[0080] Preferably, the at least one surfactant is selected from the group consisting of: polyethylene glycol (or polyglycol) ether of a fatty alcohol; polyethylene glycol ether of C9-11 iso, ethoxylated alcohols; polyglycol ether of undecanol, branched and linear, ethoxylated, propoxylated, fatty alcohol; and combinations of the foregoing.

[0081] Preferably, the "polyethylene glycol ether of C9-11 iso alcohols" is composed of a polyethylene glycol ether of iso alcohols, i.e. non-linear chains of the alcohols, in particular the chains of the alcohols are characterized by a number of carbon atoms comprised between 9 and 11; preferably, the chains of the alcohols with 10 carbon atoms (C10) are prevalent with respect to the others, preferably the C10 chains of the alcohols are ≥ 50%, preferably ≥ 60%, preferably ≥ 80%, with respect to the total of the chains.

[0082] Preferably, when the at least one surfactant is derived from an ethoxylated and / or propoxylated fatty alcohol, the moles by ethoxylation and / or by propoxylation (or degree of ethoxylation or propoxylation) are greater than or greater than or equal to (≥) 2.5 moles.

[0083] Preferably, the at least one surfactant is polyethylene glycol ether of a fatty alcohol, preferably it is the commercial product Tridac Iso-3.

[0084] Preferably, the at least one surfactant is a polyethylene glycol ether of an ethoxylated fatty alcohol, preferably it is the polyethylene glycol ether of the C9-11 iso, ethoxylated alcohols (> 2.5 mol EO), preferably it is the commercial product Biodac 410 and / or the commercial product ISOGIFRAN 10_4 M.

[0085] Preferably, the at least one surfactant is a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol, preferably it is the polyglycol ether of the undecanol, branched and linear, ethoxylated and propoxylated fatty alcohol (≥ 2.5 mol EO / PO), preferably it is the commercial product Biodac 2-32.

[0086] Preferably, the at least one surfactant is in a quantity comprised between 0.5% and 2% by weight, preferably equal to 1% by weight, on the total weight of the formulation.

[0087] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.2 and 1:2.

[0088] By sum of the at least one co-densifier and the surfactant is meant the sum between the quantity of the at least one co-densifier and the quantity of the at least one surfactant.

[0089] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.2 and 1:1.5, preferably between 1:1.25 and 1:1.5.

[0090] According to a preferred form, the weight ratio between the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, or equal to 1:1.25.

[0091] According to a further preferred form, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:1.5, or equal to 1:1.5.

[0092] It should be noted that this weight ratio is useful for aiding the cleaning efficacy, the controlled release of the cleaning agents at the level of the stone surface, i.e. without penetrating the matrix of the stone material, and the stability of the formulation. This ratio allows optimal adhesion of the hydrogel compress to the surfaces of interest, without compromising its subsequent easy removal, while ensuring precise control over the diffusion of the solvent, limiting it to the hydrogel / surface contact zone.Antibacterial and / or anti-mould

[0093] The antibacterial and / or anti-mould agent is a chemical substance capable of counteracting bacterial growth and / or mould within the formulation.

[0094] Preferably, the at least one antibacterial and / or anti-mould is selected from the group consisting of: isopropanol, ethanol, phenylethyl alcohol, benzyl alcohol, pentylene glycol, isobutyl alcohol, and combinations of the above, preferably it is isopropanol.

[0095] Preferably, the at least one antibacterial and / or anti-mould is in a quantity comprised between 2% and 4% by weight, preferably of 2.999% by weight, on the total weight of the formulation.

[0096] The Applicant has noted that the analyses carried out on the role of isopropanol in the formulation have made it possible to recognise that, in addition to its active effect deriving from its nature as an alcoholic solvent, it plays a significant preventive role in the formation of moulds and biological alterations during the storage phase. This characteristic makes the formulation not only suitable for production, but also for effective preservation over time, satisfying the stability over time of the formulation (see Example 5.5).Water

[0097] The water is preferably in a quantity ≥ 80% by weight, preferably between 80% and 90% by weight, preferably between 80% and 85% by weight, preferably equal to about 81%, or 81.701% by weight, or 82% by weight, on the total weight of the formulation.

[0098] It should be noted that the first chelating agent consisting of citric acid, the second chelating agent, the at least one co-densifier, the at least one surfactant, the at least one antibacterial agent and / or anti-mould and water constitute the cleaning solution or mixture which is charged and dispersed in the xanthan gum supporting agent to obtain the compress hydrogel formulation.

[0099] Preferably, the formulation of the invention is characterized by a pH that ranges between 4 and 7.6, preferably comprised between 4.1 to 6.8, or, alternatively, preferably comprised between 6.6 to 7.2, in a preferred manner equal to 4.5 or 6.6 or 7.2. The range comprised between 5 and 5.5 is preferably excluded from the above pH ranges.

[0100] The Applicant considers that the pH of the formulation, which derives from the final qualitative-quantitative balancing of the components of the formulation described in the previous sections, influences the cleaning efficacy, but also the surface aggressiveness (refer to Examples 1-3).First embodiment: cleansing hydrogel formulation for stone surfaces of civil buildings or civil property

[0101] Civil buildings or civil property are defined as property of civil and public interest, such as those intended for homes, shops, etc.

[0102] According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of Tetrasodium glutamate diacetate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0103] The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0104] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1.34, preferably equal to 1:0.83.

[0105] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, preferably of 1:1.25.

[0106] Preferably, the formulation of the invention is characterized by a pH that ranges between 4.1 and 4.5, preferably it is equal to 4.2 or 4.3 or 4.5.

[0107] According to a further preferred alternative in accordance with this first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of: Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0108] The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0109] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.79 and 1:1.34, preferably between 1:0.79 and 1:1.3, preferably equal to 1:0.79.

[0110] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, preferably of 1:1.25.

[0111] Preferably, the formulation of the invention is characterized by a pH that ranges between 6.8 and 7.5, preferably between 6.8 and 7.2, preferably equal to 7.1 or 7.2.Second embodiment: cleansing hydrogel formulation for stone surfaces of cultural heritage property

[0112] Cultural heritage property is defined as the property of artistic, historical and archaeological interest.

[0113] According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of cultural heritage property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0114] The technical specifications of the components indicated above are the same as those indicated in the previous sections.

[0115] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably equal to 1:1.

[0116] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:1.5, preferably equal to 1:1.5.

[0117] Preferably, the formulation of the invention is characterized by a pH that ranges between 6.4 and 7, preferably between 6.4 to 6.8, preferably equal to 6.6 or 6.8.Use of the cleansing hydrogel formulation of stone surfaces

[0118] A further object of the invention is the use of the formulation according to the invention for the cleaning, preferably chemical cleaning, of stone surfaces.

[0119] The formulation is as described in the preceding sections, preferably also in accordance with the first and second embodiments.

[0120] Preferably, the use of the formulation is for the cleaning of stone surfaces of civil buildings, preferably in accordance with the first embodiment described above, wherein the second chelating agent is Tetrasodium glutamate diacetate, or, alternatively, the second chelating agent is the combination of Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.79 and 1:1.35, preferably between 1:0.8 and 1:1.35, preferably between 1:0.8 and 1:1.3, preferably equal to 1:0.79 or 1:0.83, wherein the pH of the formulation is comprised between 4.1 and 4.5, preferably equal to 4.2 or 4.5, or, alternatively, the pH is preferably comprised between 6.8 and 7.5, preferably between 6.8 and 7.2, preferably equal to 7.1 or 7.2.

[0121] Alternatively, the use of the formulation is for the cleaning of stone surfaces of cultural heritage property, preferably in accordance with the second embodiment described above, wherein the second chelating agent is Trisodium dicarboxymethyl alaninate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably between 1:0.83 and 1:1, preferably equal to 1:1, wherein the pH of the formulation is comprised between 6.4 and 7, preferably between 6.4 and 6.6, preferably it is 6.6 or 6.8. Method for applying to a stone surface the cleansing hydrogel formulation

[0122] A third object of the invention is the method for applying to a stone surface the formulation according to the invention, comprising the steps of a) applying the hydrogel formulation to the stone surface, b) leaving on for a time comprised between 15 and 120 minutes, preferably between 30 and 90 minutes, preferably between 45 and 90 minutes, preferably equal to 60 minutes, c) removing the hydrogel formulation with water, preferably using a pad soaked in water, preferably the water is demineralised, wherein the aforementioned steps a)-c) (i.e. respectively the steps of: applying the hydrogel formulation on the stone surface; leaving it on; removing the hydrogel formulation with water) are repeated for a number of times n comprised between 1 and 3, preferably between 1 and 2, preferably n is 1 or 2.

[0123] Preferably for use for the cleaning of stone surfaces of buildings or civil property, the formulation may be applied to the surface, then it is left on for a time comprised between 45 and 90 minutes, preferably between 45 and 60 minutes, after which it is rinsed with water, the formulation is applied again for a time comprised between 45 and 90 minutes, preferably between 45 and 60 minutes, and rinsed again.

[0124] Preferably for use for the cleaning of stone surfaces of cultural heritage property, the formulation can be applied to the surface, then it is left on for a time comprised between 45 minutes and 60 minutes, after which it is rinsed with water. In this case, it is possible or not a second application of the formulation in the same period of time just mentioned followed by rinsing.

[0125] Preferably, the formulation is applied to the stone surface by hand or by any suitable means known to a person skilled in the art, such as a spatula or a brush.

[0126] It should be noted that, even if the action times of the formulation are longer than those of the known formulations, the overall time required for cleaning may be shorter as it can be optimised during the application step.

[0127] Preferably, under standard conditions (at room temperature), the hydrogel formulation has a shelf life > 7 days, preferably > 7 days and ≤ 1 year and a half, preferably > 7 days and ≤ 1 year.

[0128] Preferably, the hydrogel formulation is not applied by spray techniques.

[0129] Preferably, the hydrogel formulation does not contain organic solvents of a toxic and / or unsustainable nature.

[0130] Preferably, the hydrogel formulation does not contain traditional and / or toxic and / or unsustainable chelators, such as for example EDTA, NTA or organophosphonates.EXAMPLES

[0131] Examples are given below for illustrative and non-limiting purposes.Glossary

[0132] NT = Untreated; Na 4 -GLDA = Tetrasodium glutamate diacetate; Na 3 -MGDA = Trisodium dicarboxymethyl alaninate; 2 Prop = isopropanol; DPM = Dipropylene glycol monomethyl ether; Tridac (or Tridac Iso-3) = polyethylene glycol ether of a fatty alcohol; Biodac 2-32 = fatty alcohol polyglycol ether - undecanol, branched and linear, ethoxylated, propoxylated (≥2.5 mol EO / PO); Biodac 410 = Fatty alcohol polyethylene glycol ether - Alcohols, C9-11 iso (C10 ≥ 50% on the total of the C9-C11 chains), ethoxylated (>2.5 mol EO). The commercial product "ISOGIFRAN 10_4 M" is equivalent to Biodac 410. Example 1: pH of the formulation based on its qualitative-quantitative chemical composition

[0133] Table 1Test # Citric AcidNa 4 -GLDANa 3 -MGDA2 Prop + DPM + SurfactantXanthan GumH 2 OpHH5v1 (Tridac) 3%3%-7%5%82%4.5H5v4 (Tridac) 2.8%3.2%-7%5%82%5.5H9 (Tridac) 4%2%-7%5%82%3.4H10 (Tridac) 1%5%-7%5%82%7.6H12 (Tridac) 3%3%-7%8%79%4.1L6C (Tridac) 0.94%4.72%1.89%6.60%4.72%81.13%8.9L6Neutral (Tridac) 1.2%3.5%1.6%7%5%81.7%7.2L9v3 (Tridac) 1.35%-4.65%7%5%82%6.6L9v4 (Tridac) 1.35%-4.65%7%6%81%6.6H5v1 (Biodac 410) 3%3%-7%5%82%4.2L6Neutral (Biodac 410) 1.2%3.5%1.6%7%5%81.7%7.1L9v4 (Biodac 410) 1.35%-4.65%7%6%81%6.6H5v1 (Biodac 2-32) 3%3%-7%5%82%4.3L6Neutral (Biodac 2-32) 1.2%3.5%1.6%7%5%81.7%7.2L9v4 (Biodac 2-32) 1.35%-4.65%7%6%81%6.8

[0134] For Test# formulations reported in Table 1: 2 Prop is 2.999% by weight on the total weight of the formulation; DPM is 3% by weight on the total weight of the formulation; Surfactant, which may be Tridac or Biodac 410 or Biodac 2-32, is 1% by weight on the total weight of the formulation.

[0135] Note that the Test# formulations reported in Table 1, in particular those containing Tridac as surfactant, are also employed in the following examples (Examples 2, 3 and 4).Example 2: Evaluation of the cleaning efficacy of the formulation of the invention

[0136] Figures 1-11 report the photos relating to a sample of Carrara marble characterized by surface encrustations of iron oxide, before and after the various applications of the different Test# formulations of Table 1, in particular those containing Tridac as a surfactant.

[0137] The results of the cleaning efficacy are reported in Table 2 below.

[0138] By distinguishing the cleaning effect from that of surface aggression, it is noted that for all tests# a good / excellent degree of cleaning is obtained.Example 3: Evaluation of the aggression of carbonate surfaces by the formulation of the invention

[0139] The morphological results were acquired by optical microscope, relating to the aggression of surfaces by the Test# formulations reported in Example 1, in particular those containing Tridac as a surfactant.

[0140] Images were acquired on non-degraded specimens of Carrara marble before treatment, after 1h of application and after 1h+1h of application. The rinsing took place using a cotton pad soaked with demineralised water.

[0141] The outcomes of an overall evaluation are reported in Table 3 below. Table 3Test#Figure of referenceOutcomeH5v1 (Tridac)Figures 12-14AggressiveH9 (Tridac)Figures 15-17Very aggressiveH10 (Tridac)Figures 18-20Very aggressiveH12 (Tridac)Figures 21-23AggressiveH5v4 (Tridac)Figures 24-26Very aggressiveL6C (Tridac)Figures 27-29AggressiveL6Neutral (Tridac)Figures 30-32AggressiveL9v3 (Tridac)Figures 33-35Slightly aggressiveL9v4 (Tridac)Figures 36-38Very little aggressive

[0142] According to the Applicant, the tests# with an "Aggressive" outcome can in any case be preferably used for application in the civil field, for buildings or civil property, as they are characterised by a good degree of cleanliness. This is because, although the tests# (for example, the H5v1 and H12 tests#) are overall "Aggressive", this evaluation is carried out considering both the outcome after 1h of application, and that after 1h+1h of application.Example 4: Evaluation of the release capacity of the cleaning solution of various compositions.

[0143] With reference to Figure 39, it should be noted that the formulation of the invention (top left rectangle with whole straight line contour; Citric Acid 3%; Na 4 -GLDA 3%; Xanthan Gum 5%; DPM 3%; 2Prop 3%; Tridac 1%; Water 82%) does not show contour halos, indicating a controlled release capacity of the cleaning solution from the hydrogel compress.

[0144] As evidenced by the arrows, however, for the other compositions, different from the formulation of the invention (each lacking at least one component considered essential for the realization of the formulation of the invention), there are halos surrounding the hydrogel compress, a sign of an immediate (therefore not controlled) release capacity of the cleaning solution.

[0145] Below is Table 4 summarizing the conclusions referred to in Examples 1-3. Example 5: Evaluation of the performance of xanthan gum at various particle sizes.

[0146] Following the information relative to the market prices for Xanthan gum, we report the main strengths and weaknesses of the 3 types available on the market, namely Xanthan gum with a particle size of 0.420 mm (40 mesh), 0.177 mm (80 mesh) or 0.074 mm (200 mesh).

[0147] The formulations prepared with the 3 different particle sizes are reported, both for Line H and Line L.

[0148] Test # formulations of Table 5 are those of Example 1 containing Tridac as a surfactant. Table 5Test #Citric AcidGLDAMGDA2 PropDPMXanthan GumMesh H 2 OH5v1 (Tridac)3%3%-3%3%5%40 82%L5v1 (Tridac)1%5%2%3%3%5%40 80%H5v3 (Tridac)3%3%-3%3%5%80 82%L5v3 (Tridac)1%5%2%3%3%5%80 80%H4 (Tridac)3%3%-3%3%5%200 82%L4 (Tridac)1%5%2%3%3%5%200 80% 5.1 Surface aggression

[0149] The aggressiveness of the compositions referred to in Test# (Example 1, in particular formulations containing Tridac as a surfactant) was tested on healthy Carrara marble specimens, i.e. without alterations, deposits or surface encrustations.

[0150] The effects obtained were investigated by observing the stone surfaces with SEM and under an OPTICAL MICROSCOPE in grazing light.

[0151] The results can be summarized as reported below: SEM: the 40 mesh formulations are less aggressive on the surface of the support, if compared with those at 80 and 200, although this analysis did not give the expected results, the images were disturbed due to the difficulty of image processing and acquisition; OPTICAL MICROSCOPE: refer to Figures 40-49, which show the images acquired for visual comparison. Here too, as with the SEM, greater aggressiveness was observed in the products with 80 and 200 mesh Xanthan gum compared to that made with 40 mesh powder. It is worth noting the presence of surface deposits, still to be analysed and characterised, on the surfaces treated with products made with 80 and 200 mesh Xanthan gum. 5.2 Surface performance - cleaning effect

[0152] The surface performance of the three types of Xanthan gum (cleaning effect) was evaluated by applying the formulations of line H on a marble slab with surface incrustation of iron oxide.

[0153] Figures 50 and 51 show the visual result before and after treatment (application time: 2h, 1h and 1h+1h).

[0154] No substantial differences were found attributable to the 3 types of Xanthan gum used.5.3 Adhesion to the support in vertical treatments

[0155] The formulations were tested and applied both on specimens placed horizontally and on case studies placed vertically. Not all formulations showed the same result if placed vertically; for example, in the formulations of line L, made with 80 mesh Xanthan gum, dripping phenomena caused by insufficient adhesive power with the substrate occurred.5.4 Viscosity of the hydrogel

[0156] Substantial differences in the viscosity of the final formulations were found, attributable to the different grain size of the Xanthan gum used. With the same formulation, by increasing the grain size, an increase in viscosity was observed; especially in the line L, the formulations made with 200 mesh powder were extremely viscous and compact, making the application complex and difficult.5.5 Storage, durability

[0157] Table 6Test#Mesh Date of realisationVariationsTest H5v1 (Tridac)40 10 / 07 / 2023NoneL5v1 Test (Tridac)40 10 / 07 / 2023NoneTest H5v3 (Tridac)80 24 / 07 / 2023After 80 days: formation of similar crystals in the gelatinous matrix.L5v3 Test (Tridac)80 24 / 07 / 2023After 80 days: slight increase in viscosity.Test H4 (Tridac)200 31 / 05 / 2023After 163 days: formation of simil-crystals in the gelatinous matrix.Test L4 (Tridac)200 31 / 05 / 2023After 80 days: marked increase in viscosity. 5.6 Conclusions

[0158] Based on the results in our possession to date, the analyses and observations made, Xanthan gum with 40 mesh particle size appears to be the best choice.

[0159] For both the line H and the line L, better performance was found to be linked to: lower surface aggressiveness on the support (more controllable cleaning); a better adhesive power which translates into easier applicability on vertical surfaces; the different state of aggregation (lower viscosity, therefore fewer problems for production during realisation step); improved chemical stability over time, resulting in improved storage durability. Example 6: cleansing hydrogel formulation, suitable for application in the civil field, for buildings or civil property.

[0160] ComponentPercentage by weight on the total weight of the formulation (% w / w)Tetrasodium glutamate diacetate (Na 4 -GLDA)3%Citric Acid3%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32))1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum5%H 2 O82.001%Total100%

[0161] Note that Example 6 where the surfactant is Tridac corresponds to test # H5v1 (Tridac) of Examples 1-5.

[0162] Example 6 where the surfactant is Biodac 410 corresponds to test # H5v1 (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # H5v1 (Biodac 2-32) of Example 1.

[0163] The pH of the formulation with Tridac is 4.5.

[0164] The pH of the formulation with Biodac 410 is 4.2.

[0165] The pH of the formulation with Biodac 2-32 is 4.3.Example 7: cleansing hydrogel formulation, suitable for application in the civil field, for buildings or civil property.

[0166] ComponentPercentage by weight on the total weight of the formulation (% w / w)Tetrasodium glutamate diacetate (Na 4 -GLDA)3.5%Trisodium dicarboxymethyl alaninate (Na 3 -MGDA)1.6%Citric Acid1.2%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32)1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum5%H 2 O81.701%Total100%

[0167] Note that Example 7 in which the surfactant is Tridac corresponds to test # L6Neutral (Tridac) of Examples 1-3.

[0168] Example 7 where the surfactant is Biodac 410 corresponds to test # L6Neutral (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # L6Neutral (Biodac 2-32) of Example 1.

[0169] The pH of the formulation with Tridac is 7.2.

[0170] The pH of the formulation with Biodac 410 is 7.1.

[0171] The pH of the formulation with Biodac 2-32 is 7.2.Example 8: cleansing hydrogel formulation, suitable for application for cultural heritage property.

[0172] ComponentPercentage by weight on the total weight of the formulation (% w / w)Trisodium dicarboxymethyl alaninate (Na 3 -MGDA)4.65%Citric Acid1.35%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32)1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum6%H 2 O81.001%Total100%

[0173] Note that Example 8 where the surfactant is Tridac corresponds to test # L9v4 (Tridac) of Examples 1-3.

[0174] Example 8 where the surfactant is Biodac 410 corresponds to test # L9v4 (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # L9v4 (Biodac 2-32) of Example 1.

[0175] The pH of the formulation with Tridac is 6.6.

[0176] The pH of the formulation with Biodac 410 is 6.6.

[0177] The pH of the formulation with Biodac 2-32 is 6.8.Example 9: viscosity of the formulations H5v1, L9Neutral and L9v4 of Examples 6-8

[0178] The viscosity of the formulations H5v1, L9Neutral and L9v4 of Examples 6-8 was measured using a rotational rheometer with controlled shear stress (Bohlin C-VOR 120 model, Bohlin Instruments Ltd) equipped with "vane in cup" coaxial cylinders, the latter composed of a smooth outer cylinder with a diameter of 15.4 mm and an inner cylinder with 4 vanes with a diameter of 14 mm (gap 0.7 mm).

[0179] All viscosity measurements were performed at 20°C and with a constant shear rate of 10 s -1< .

[0180] Three acquisitions were recorded for each formulation, each lasting 5 minutes. The average viscosity value was expressed in Pa·s. Table 7Formulation Test # (Example 1 and Examples 6-8)VISCOSITY [Pa*s] (10 s -1< , 20°C)H5v1 (Tridac)23.47H5v1 (Biodac 2-32)13.34H5v1 (Biodac 410)23.45L9v4 (Tridac)22.47L9v4 (Biodac 2-32)14.44L9v4 (Biodac 410)17.17L6Neutral (Tridac)13.96L6Neutral (Biodac 2-32)24.99L6Neutral (Biodac 410)15.84

[0181] The name in brackets for the first column from the left of Table 7 indicates the surfactant used in the formulation, the concentration of which is 1% on the total weight of the formulation.Example 10: process for preparing the formulation of the invention.

[0182] By way of illustration of the hydrogel preparation process, the preparation process of formulation L9v4 (Biodac 410) is reported.

[0183] A mixture of isopropanol (2,999 g), dipropylene glycol monomethyl ether (DPM) (3,000 g), surfactant (Biodac 410, Tellerini) (1,000 g) and water (81,000 g) is added to the chelators citric acid (1.35 g) and Na 3 -MGDA (MGDA 40, Tellerini) (11,625 g). Finally, xanthan gum (6,000 g) is added.

Examples

first embodiment

cleansing hydrogel formulation for stone surfaces of civil buildings or civil property

[0101]Civil buildings or civil property are defined as property of civil and public interest, such as those intended for homes, shops, etc.

[0102]According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises

a first chelating agent consisting of citric acid, a second chelating agent consisting of Tetrasodium glutamate diacetate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0103]The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0104]Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1.34, preferably equal to 1:0.83.

[0105]Preferably, the weight ratio of the sum of ...

second embodiment

cleansing hydrogel formulation for stone surfaces of cultural heritage property

[0112]Cultural heritage property is defined as the property of artistic, historical and archaeological interest.

[0113]According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of cultural heritage property comprises

a first chelating agent consisting of citric acid, a second chelating agent consisting of Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0114]The technical specifications of the components indicated above are the same as those indicated in the previous sections.

[0115]Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably equal to 1:1.

[0116]Preferably, the weight ratio of the sum of the at least one co-den...

example 1

pH of the formulation based on its qualitative-quantitative chemical composition

[0133]

Table 1

Test # Citric AcidNa 4 -GLDANa 3 -MGDA2 Prop + DPM + SurfactantXanthan GumH 2 OpH

H5v1 (Tridac) 3%3%-7%5%82%4.5

H5v4 (Tridac) 2.8%3.2%-7%5%82%5.5

H9 (Tridac) 4%2%-7%5%82%3.4

H10 (Tridac) 1%5%-7%5%82%7.6

H12 (Tridac) 3%3%-7%8%79%4.1

L6C (Tridac) 0.94%4.72%1.89%6.60%4.72%81.13%8.9

L6Neutral (Tridac) 1.2%3.5%1.6%7%5%81.7%7.2

L9v3 (Tridac) 1.35%-4.65%7%5%82%6.6

L9v4 (Tridac) 1.35%-4.65%7%6%81%6.6

H5v1 (Biodac 410) 3%3%-7%5%82%4.2

L6Neutral (Biodac 410) 1.2%3.5%1.6%7%5%81.7%7.1

L9v4 (Biodac 410) 1.35%-4.65%7%6%81%6.6

H5v1 (Biodac 2-32) 3%3%-7%5%82%4.3

L6Neutral (Biodac 2-32) 1.2%3.5%1.6%7%5%81.7%7.2

L9v4 (Biodac 2-32) 1.35%-4.65%7%6%81%6.8

[0134]For Test# formulations reported in Table 1:

2 Prop is 2.999% by weight on the total weight of the formulation; DPM is 3% by weight on the total weight of the formulation; Surfactant, which may be Tridac or Biodac 410 or Biodac 2-32, is 1% by weight...

FIELD OF THE INVENTION

[0001] The present invention fits in the technical field of chemical cleaning of stone surfaces, especially of civil / industrial buildings and / or cultural heritage property.STATE OF THE ART

[0002] Stone surfaces (natural or artificial) of civil and industrial buildings are subject to deposition and accumulation of atmospheric particulate matter, carbonaceous residues, products of neoformation or of degradation of metal objects with consequent chromatic alteration. The removal of these deposits or patinas is necessary for both aesthetic and, above all, conservative reasons.

[0003] In addition to the civil field, this need is also evident in other contexts, such as that of cultural heritage property.

[0004] Chemical cleaning is the most frequently used technology for the removal of deposit or neoformation material from stone surfaces, as it is the most sustainable (in terms of material cost and execution time), as well as not requiring particularly specialised personnel.Problems of the background art

[0005] In particular, chemical cleaning consists in the use of solvents or aqueous formulations for the solubilization and removal of unwanted material from the stone surfaces.

[0006] However, it is often necessary to use organic solvents or products characterized by various toxicities to obtain good results. For example, among the most commonly used solvents are organic compounds of various kinds, such as acetone, ethyl or butyl acetate, nitro thinner, ligroin, white spirit, alcohols. The organic solvents tend to be toxic, unsustainable and / or non-biodegradable, and are used in abundant quantities.

[0007] In other cases, the preparation of water-based formulations is instead envisaged. Aqueous formulations known in the art are obtained by solubilizing basic or acidic substances - such as sodium or ammonium carbonate / bicarbonate, EDTA, phosphoric acid, ammonia, sodium hydroxide, hydrochloric acid, ammonium citrate or citric acid - with or without surfactants.

[0008] In the civil sector, the application of organic solvents or aqueous solutions is generally done by spraying, using suitable dispensers, followed by abundant rinsing, often through the use of pressure washers.

[0009] In other cases, where for technical, ecological and / or physical reasons spray application is not feasible, especially in the cleaning of historical-architectural surfaces, the cleaning agent (organic solvent or aqueous solution) is generally supported (by application of "compress"), at the time of use, on "supporting" agents (also called simply "supporting elements"), such as, for example, cellulose pulp, agar-agar, sepiolite, chemical gels (for example, polymers of acrylic acid), and applied by compress.

[0010] This technique of preparing the compress in situ requires expert personnel - especially in determining the appropriate quantities of the various components and in their correct mixing - who must then use it in the following 24-48 hours. Furthermore, as for the spray application, once the compress has been removed, the surface is then abundantly rinsed to remove unwanted residues of the supporting agent and cleaning agent.

[0011] Passaretti et al in "Biologically Derived Gels for the Cleaning of Historical and Artistic Metal Heritage" (Appl. Sci. 2021, 11, 3405. https: / / doi.org / 10.3390 / app11083405) explain that it is possible, for metal surfaces, to use hydrogels or organogels, which are still being implemented.

[0012] Again, the authors Guilminot et al in "The Use of Hydrogels in the Treatment of Metal Cultural Heritage Objects." (Gels. 2023 Mar 2;9(3):191. doi: 10.3390 / gels9030191. PMID: 36975640; PMCID: PMC10048560) explain that, especially for application on metal surfaces, it is possible to use hydrogels based on polysaccharides, such as agar, gellan and xanthan gum. According to the authors, for cleaning copper alloys, the best results are obtained by combining an agar gel with a chelating agent (EDTA (ethylenediaminetetraacetic acid) or TAC (tri-ammonium citrate)). The hot application allows to obtain a "peelable" gel, particularly suitable for historical objects. The authors explain, again, that the electrochemical treatments with hydrogels have been successful for cleaning silver and for the dechlorination of ferrous alloys or copper. The use of hydrogels for cleaning painted aluminium alloys is possible, but must be combined with mechanical cleaning. However, for cleaning archaeological lead, the use of hydrogels was not very effective. The authors conclude that agar seems to be the most promising hydrogel for this type of application.

[0013] Similarly, J. M. van den Burg e K. Seymour in "Dirt and dirt removal (dry and aqueous cleaning)" (2022, Klaas Jan van der Berg and Lia Gorter Editors, Cultural Heritage Agency of the Netherlands, Amersfoort, page 61) explain that xanthan gum can be used to thicken some aqueous detergent solutions. It forms a water-based, non-toxic, biodegradable and stable polymer emulsion gel at any pH. Xanthan gum is a polysaccharide polymer consisting of tangled helical chains that, at higher concentrations, which aggregate to form small cages that retain water molecules. Oxidizing agents, such as bleach, and most cationic materials, such as ammonia, cannot be used because they cause the gel to collapse. The authors explain that one of the main disadvantages of xanthan gum (and of other aqueous emulsifiers) is that, after application, a further cleaning step is necessary. Finally, xanthan gum requires an aqueous solution to be eliminated.

[0014] Therefore, it is clear from these three scientific articles that the use of hydrogels for cleaning surfaces, especially falling within the context of cultural heritage property, is known to the state of the art.

[0015] In other scientific studies, instead, such as those conducted by Infurna G, Cavallaro G, Lazzara G, Milioto S, Dintcheva NT. In "Understanding the Effects of Crosslinking and Reinforcement Agents on the Performance and Durability of Biopolymer Films for Cultural Heritage Protection. Molecules" (2021 Jun 7;26(11):3468. doi: 10.3390 / molecules26113468. PMID: 34200367; PMCID: PMC8201363), the formation of biofilms (or biopolymer films) based on chitosan and pectin, also containing crosslinking agents and natural reinforcers, such as citric acid (CA) and halloysite nanotubes (HNT), is highlighted.

[0016] However, these biofilms are not used for cleaning surfaces; rather, they are suitable as cover films for the protection of cultural heritage.

[0017] Similarly, the authors Li T, Hu Y and Zhang B. in "Biomineralization Induced by Colletotrichum acutatum: A Potential Strategy for Cultural Relic Bioprotection" (Front Microbiol. 2018 Aug 14;9:1884. doi: 10.3389 / fmicb.2018.01884. PMID: 30158913; PMCID: PMC6104437) identify an eco-sustainable method for the preservation of stone artefacts. The authors explain that the fungus Colletotrichum acutatum is capable of initiating biomineralisation (the phenomenon of calcium carbonate formation); in particular, they noted that citric acid is a metabolite produced by C. acutatum. The same authors then evaluated whether the proliferation of C. acutatum could affect the deterioration of the stone finds, finding out that, under low carbon conditions, calcium carbonate was protected from dissolution, thus indicating that the risk of deterioration of the limestone substrates could be controlled if the fungi were used to consolidate or restore monuments or stone surfaces. These results suggest that C. acutatum-induced biomineralisation may be a useful treatment for deteriorated stone objects.

[0018] Therefore, in the latter case, the authors focus on the preservation capabilities of the stone surfaces, and not on actual chemical cleaning techniques.

[0019] Furthermore, the authors Cuvillier, L. et al in "Testing of the siderophore deferoxamine amended in hydrogels for the cleaning of iron corrosion" (Eur. Phys. J. Plus 138, 569 (2023). https: / / doi.org / 10.1140 / epjp / s13360-023-04159-y) disclose the use of siderophores, such as deferoxamine, loaded on polysaccharide hydrogels, for the removal of unwanted corrosion products from iron works of art with a view to the biodegradability of the obtained formulation. Siderophores are secondary metabolites capable of binding iron and are produced by microorganisms when they inhabit areas where the concentration of iron is low (to ensure the iron intake necessary for survival). By virtue of their high affinity for iron, siderophores could be used for a targeted cleaning of objects composed of this metal. Three different types of polysaccharides were tested for hydrogel formation, including agar, gellan gum and xanthan gum, with the first two polysaccharides achieving better results.

[0020] The disclosure "Sitting pretty: collaborative treatment of an early Yayoi Kusama soft-sculpture chair" Baas F. and Hartman L.E.; Proceedings of the Objects Specialty Group Sessions; May 28-June 2, 2017; 45th Annual Meeting Chicago, Illinois. https: / / faic.wpenginepowered.com / osg-postprints / wp-content / uploads / sites / 8 / 2019 / 12 / osg024-017.pdf provides for the use of two different types of gel, including xanthan gum, Pemulen TR2 (an acrylic-derived polymer) and agarose. Xanthan gum and Pemulen TR2 provide a liquid gelled solution with a consistency similar to honey or hair gel, while agarose produces a stiff, gummy gel. The authors focused on the tests with liquid gels. The citric acid solution was gelled with xanthan gum and Pemulen TR2. The authors explain that since xanthan gum remains structurally more stable as a gel over a wider range of pH and conductivity parameters, it was chosen over the use of Pemulen TR2.

[0021] As is clear from the state of the art, the mixtures of citric acid, xanthan gum and mixtures of citric acid and other chelating agents, although known, are prepared shortly before use (preparation in situ) according to variable and customised recipes, characterised by a stability limited to 24-48 hours and an uncertified or certainly not negligible aggressiveness, without providing for a controlled and progressive release of the cleaning solution, thus inhibiting the benefits of the cleaning efficacy.

[0022] Therefore, the Applicant considers that several problems still need to be resolved, including: the need to identify formulations on a water-basis that provide for the use of effective cleaning agents on various lithotypes and on various types of dirt / deposits / patinas, which are non-toxic for the operators and eco-sustainable, i.e. without any impact on the environment; the need to identify supporting agents able to guarantee an effective cleaning and a controlled (slow) release of the cleaning agent, so as to have a superficial wettability and, consequently, an easy control of the cleaning, in this way reducing, as much as possible, the chemical aggression of the matrix or of the innermost part of the material of the surface to be treated, in addition to avoiding the penetration of dirt and / or other unwanted material into the depth of the material of the surface to be treated; the need, again, to identify a standardized or ready-to-use formulation, which is easy to apply on surfaces of any geometry, placed both horizontally and vertically, as well as easy to produce industrially; the need to easily remove the formulation / compress, by applying a gentle rinsing of the surface, avoiding wasting abundant amounts of water; finally, it is also required to obtain a product that is stable over time, which retains its properties and cleaning performance for a relatively long period of time, for example for more than one week and up to about one year, under standard preservation conditions. The known formulations, in addition to not being ready for use, are in fact characterised by a preservation of at least 24 hours up to a maximum of 48 hours. SUMMARY OF THE INVENTION

[0023] A first object of the invention is a cleansing hydrogel formulation of stone surfaces comprising a first chelating agent consisting of citric acid, a second chelating agent selected from the group consisting of: Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.7 to 1:1.6.

[0024] A second object of the invention is a method for applying the aforementioned formulation to a stone surface, comprising the steps of a) applying the hydrogel formulation to the stone surface, b) leaving on for a time comprised between 15 minutes and 120 minutes, c) removing the hydrogel formulation with water, wherein the aforementioned steps a)-c) are repeated for a number of times n comprised between 1 and 3.

[0025] A third further object of the invention is the use of the aforementioned formulation for the cleaning, preferably chemical cleaning, of stone surfaces.Advantages of the invention

[0026] Note that the "first chelating agent / second chelating agent / supporting agent" interaction is of particular importance because, in addition to the complexing role of the first two, it is also possible to ensure that a precise three-dimensional conformation of the hydrogel is achieved through the formation of van der Waals forces. This guarantees a controlled release of the formulation, good cleaning performance and a lower or negligible aggressiveness of the stone surface.

[0027] In particular, the technical advantages of the invention are summarized below: identification of a water-based formulation with cleaning efficacy, which includes effective cleaning agents, non-toxic neither for the environment, nor for the operators, and also eco-sustainable; identification of supporting agents able to guarantee an effective cleaning and a controlled / slow release of the cleaning agent, a mainly superficial wettability and, consequently, a lower or negligible chemical aggressiveness of the surface of the material to be treated, with easier cleaning control, even compared to the cleaning solutions or to the cleaning compresses known so far; the creation of a compress without release of residues on the stone surface to be treated; identification of a ready-to-use formulation, in the sense that it does not require the need to mix the necessary ingredients on site, and is easy to apply on horizontal, vertical and moulded surfaces; the ability to easily remove the formulation / compress, by applying a gentle surface rinsing, avoiding water waste; the ability to achieve a formulation that is stable over time, in the sense that it retains cleaning efficacy properties and performance for more than one week and at least one year, under standard preservation conditions. Also in terms of storage, no particular critical issues (flammability) or precautions to be followed (corrosion of storage vessels) have emerged; the ability to obtain the formulation also at an industrial level, without the need to follow particular technical measures.

[0028] Finally, it should be noted that the application times of the formulation of the invention are typically longer than those for the formulations prepared at the time of use (generally below 15 minutes). This allows greater control of the cleaning power, reducing surface aggressiveness in the event that the application time cannot be met.DESCRIPTION OF THE DRAWINGS

[0029] Figure 1: Image of a Carrara marble slab before cleaning referred to in Example 2. Figure 2: Image of the overall situation after various cleaning tests referred to in Example 2. Figure 3: Image of test # H5v1 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 4: Image of test # H9 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 5: Image of test # H10 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 6: Image of test # H12 (Tridac) after one hour, two and three hours of application, referred to in Example 2. Figure 7: Image of test # H5v4 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 8: Image of test # L6c (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 9: Image of test # L6Neutral (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 10: Image of test # L9v3 (Tridac) after one hour and two hours of application, referred to in Example 2. Figure 11: Image of test # L9v4 (Tridac) after one hour, two and three hours of application, referred to in Example 2. Figures 12-14: Image of test # H5v1 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 15-17: Image of test # H9 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 18-20: Image of test # H10 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 21-23: Image of test # H12 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 24-26: Image of test # H5v4 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 27-29: Image of test # L6c (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 30-32: Image of test # L6Neutral (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figure 33-35: Image of test # L9v3 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figures 36-38: Image of test # L9v4 (Tridac) respectively before application, after one hour of application and after two hours of application referred to in Example 3. Figure 39: Clockwise: top left rectangle with whole straight line contour (formulation of the invention: Citric acid 3%; Na 4 -GLDA 3%; Xanthan 5%; DPM 3%; 2Prop 3%; Tridac 1%; Water 82%); top right rectangle with dotted contour (composition: Citric acid 2%; Xanthan 3%; Water 95%); right central rectangle with dashed contour (composition: Citric acid 2%; Xanthan 3%; 2Prop 3%; Water 92%); bottom right rectangle with dot-dash contour (composition: Citric acid 3%; Na 4 -GLDA 3%; Xanthan 3%; DPM 3%; 2Prop 3%; Tridac 1%; Water 84%); bottom left rectangle with whole non-straight line contour (composition: Citric acid 2%; Xanthan 3%; 2Prop 3%; Tridac 1%; Water 91%). Figures 40-43: Light microscope images, Line H, in the order: NT (Untreated), 40 mesh (0.420 mm), 80 mesh (0.177 mm), 200 mesh (0.074 mm). Treatment: 1h+1h. Figures 44-45: Light microscope images, Line H, in the order NT (Untreated), 40 mesh (0.420 mm). Treatment: 24 h. Figures 46-49: Light microscope images, Line L, in the order: NT (Untreated), 40 mesh (0.420 mm), 80 mesh, (0.177 mm) 200 mesh (0.074 mm). Treatment: 1h+1h. Figures 50-51: Respectively: image of the pre-treatment situation and image of the situation after 3 types of treatments (at 2h, at 1h and at 1h+1h) for three Test# of line H (respectively at 40, 80 and 200 mesh). DETAILED DESCRIPTION OF THE INVENTION

[0030] In the following, the invention and its preferred embodiments are described in more detail.

[0031] It should be noted that, although the structure has been organized into paragraphs and sub-paragraphs, the information contained in each section or paragraph or subsection or sub-paragraph is not isolated and can possibly be combined with those contained in other sections / paragraphs or, more generally, with other information contained in the text of the patent application.Cleansing hydrogel formulation of stone surfaces

[0032] A hydrogel (or hydrogel) is defined as a colloid in which the polymer chains of the molecules of the supporting agent consisting of xanthan gum are dispersed in water, wherein the water is in a quantity ≥ 80% by weight, preferably ≥ 80% and ≤ 95% by weight, on the total weight of the formulation. In order to be applied as such, i.e. as a compress and without prior dilution, the components of the formulation of the invention have been suitably balanced. In this sense, the formulation is in the form of a gel to be applied to a stone surface as a compress.

[0033] The viscosity of the formulation is preferably comprised between 11 and 35 Pa·s, preferably between 11 and 33 Pa·s, preferably between 12 and 30 Pa·s, preferably between 13 and 25 Pa·s.

[0034] Viscosity was measured using a controlled shear rotational rheometer (Bohlin C-VOR 120 model, Bohlin Instruments Ltd) equipped with "vane in cup" coaxial cylinders, the latter composed of a smooth outer cylinder with a diameter of 15.4 mm and an inner cylinder with 4 fins (vane) with a diameter of 14 mm (gap 0.7 mm). All viscosity measurements were performed at 20°C and with a constant shear rate of 10 s -1< . Three acquisitions were recorded for each formulation, each lasting 5 minutes. The average viscosity value was expressed in Pa·s with standard deviations comprised between ± 0.5 and 5 Pa*s.

[0035] It should be noted that viscosity values below or above the ranges indicated above are not suitable for obtaining a hydrogel formulation in the form of a compress and ready for use as that of the invention.

[0036] Preferably, the consistency of the hydrogel formulation is similar to that of a viscous cream, not suitable for spray application. The application has in fact been designed to be performed by brush or spatula, as required by the use on delicate and irregular surfaces typical of the stone heritage.

[0037] By cleansing formulation of stone surfaces is meant that the formulation of the invention is suitable for removing deposit or neoformation material from the stone surfaces.

[0038] The stone surfaces can be of natural, artificial or ancient plaster type. Examples of stone surfaces are chosen from the group consisting of: marble, sandstone, travertine, granite, limestone, terracotta, cement conglomerates.

[0039] Still, the present formulation may preferably be useful for treating stone surfaces chosen from: carbonate stones; for example Carrara marble; limestone, for example Lecce stone; silicatic stones, for example serene stone; artificial stones, for example bricks; surfaces of buildings, of the type stones or bricks, which, once put in place, are not plastered ("exposed face").

[0040] Preferably, the deposit or undesired material to be removed, preferably placed at the surface level, can be: atmospheric particulate matter, carbonaceous residues, neoformation products or percolations from degradation of metal objects (iron and copper, both superficial and slightly internal to the matrix), black crusts, and combinations thereof.

[0041] In the context of the invention, by cleaning agent or solution (or mixture) is meant a chemical compound or a solution / mixture of chemical compounds capable of favouring the cleaning of stone surfaces, by removing deposition or unwanted material, which acts mainly on the surface.

[0042] Preferably, the hydrogel formulation is an ecological and / or eco-compatible product, in the sense that it contains ecological and / or eco-compatible ingredients in a quantity comprised between 80% and 100% by weight, preferably between 90% and 100% by weight, on the total weight of the formulation. This is beneficial in terms of environmental sustainability.

[0043] Ecological and / or eco-compatible product or formulation means a chemical compound or a mixture of chemical compounds designed and made in such a way as to minimize environmental impact, ensure a low risk to human health and ensure easy disposal (Legislative Decree 152 / 2006). Ecological and / or eco-compatible product / formulation means a formulation characterized by having: components of natural origin or that are biodegradable, and high reduction of pollutant emissions during the life cycle, and absence or minimum amount of toxic, persistent and bioaccumulative substances. First chelating agent

[0044] Citric acid is the first chelating agent. It is a cleaning agent.

[0045] The citric acid is preferably in a quantity comprised between 0.9% and 4% by weight, preferably between 1% and 4% by weight, preferably between 1.2% and 4% by weight, preferably comprised between 1.2% and 3% by weight, preferably comprised between 1.35% and 3% by weight, preferably equal to 1.2%, or to 1.35% and 3% by weight, on the total weight of the formulation.Second chelating agent

[0046] The second chelating agent is selected from the group consisting of: Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above. The second chelating agent is a cleaning agent.

[0047] Preferably, the second chelating agent is Tetrasodium glutamate diacetate or Trisodium dicarboxymethyl alaninate or combination of the above.

[0048] Preferably, the second chelating agent is in a quantity comprised between 2% and 6.7% by weight, preferably between 3% and 5.5% by weight, preferably between 3% and 5.2% by weight, preferably equal to 3% or 4.65% or 5.1% by weight, on the total weight of the formulation.

[0049] Preferably, when the second chelating agent is Tetrasodium glutamate diacetate, the relative quantity is comprised between 2% and 3.5% by weight, preferably between 3% and 3.5% by weight, preferably equal to 3% or 3.5% by weight, on the total weight of the formulation.

[0050] Preferably, when the second chelating agent is Trisodium dicarboxymethyl alaninate, the relative quantity is comprised between 1% and 4.7% by weight, preferably between 1.5% and 4.65% by weight, preferably equal to 1.6% or 4.65% by weight, on the total weight of the formulation.

[0051] Preferably, when the second chelating agent is the combination of Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, the relative quantity is comprised between 2% and 6.7% by weight, preferably between 3% and 5.5% by weight, preferably equal to 5.1% by weight, of the total weight of the formulation.

[0052] The Applicant intends to point out that the quantity of the second chelating agent influences the pH of the formulation, as well as the effect of surface aggression. An increase in the second chelating agent, e.g. beyond the maximum limit expressed at the above ranges, has a negative impact on these two parameters (see Examples 1-5).

[0053] Preferably, the weight ratio between the at least one surfactant and the sum of the first chelating agent and the second chelating agent is comprised between 1:4 and 1:8, preferably between 1:5 and 1:7, preferably between 1:6 and 1:6.3.

[0054] It should be noted that this weight ratio guarantees cleaning efficacy, and affects the gradual and controlled release of the cleaning agents at the level of the stone surface.

[0055] The Applicant points out that the overall concentration of the chelating agents for the purposes of the invention is clearly higher than that of the at least one surfactant.

[0056] For the purposes of the invention, the chelating agents are important for the cleaning capacity, as they sequester the inorganic components to be removed. In the context of the invention, we speak of "chemical cleaning". The surfactant is intended to improve the wettability of the surface if organic and / or oily residues are present and stabilizes the gel matrix.

[0057] The chemical cleaning of the invention is different from the type of cleaning obtainable through other cleaning compositions, for example in liquid form, whereby the cleaning action is mainly entrusted to surfactants (or mixture of surfactants), which remove dirt of an oily organic nature by hydration or emulsification of the fat and in the presence of water. In order to achieve effective detergency, in the state of the art, surfactants are added in a higher concentration than the rest of the components, including chelating agents; in the state of the art, an inverted "surfactant: chelating agent(s)" weight ratio is therefore used with respect to that of the present invention.Supporting agent

[0058] Supporting agent means a material suitable for generating a hydrogel in the presence of water, capable of forming the compress to be applied on a stone surface; it promotes the progressive release of the cleaning solution. In this sense, the supporting agent acts as a densifier.

[0059] By densifier is meant a chemical compound capable of modifying the consistency or viscosity over time of the formulation.

[0060] The supporting agent consists of xanthan gum.

[0061] Preferably, the xanthan gum is in a quantity comprised between 4.7% to 8% by weight, preferably between 5% to 8% by weight, preferably between 5% to 6% by weight, preferably equal to 5% or 6% by weight, on the total weight of the formulation.

[0062] Preferably, the particle size of the xanthan gum is comprised between 0.595 mm (30 mesh) and 0.297 mm (50 mesh), preferably it is 0.420 mm (40 mesh).

[0063] The Applicant has noted that the use of this particle size range for xanthan gum shows different and improved performance compared to the other two commercially available versions, 80 and 200 mesh, especially in terms of rheological, physical, controlled release properties, therefore control of the surface wettability, properties that affect the cleaning power and stability of the formulation. As can be seen from Example 5, the tests carried out with xanthan gum at 0.177 mm (80 mesh) and 0.0074 mm (200 mesh) showed, after 20 days after performance, the formation of crystalline concretions in the gelatinous matrix consisting of secondary recrystallizations of the chelating agents, formed during the phase of complete hydration of the gelling agent, which however altered the compound reducing its stability and performance.

[0064] The weight ratio between the sum of the first chelating agent and the second chelating agent to the xanthan gum is the ratio defined by formula (I) below

[0065] The sum of the first chelating agent and the second chelating agent is the sum of the quantity of the first chelating agent and the quantity of the second chelating agent.

[0066] It should be noted that this weight ratio guarantees the cleaning effectiveness, the gradual and controlled release of the cleaning agents at the level of the stone surface, that is, without penetrating the matrix of the stone material.

[0067] The weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.6 to 1:1.6, preferably from 1:0.7 to 1:1.4.

[0068] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised from 1:0.7 to 1:1.4, preferably from 1:0.7 to 1:1.35, preferably from 1:0.79 to 1:1.35, preferably from 1:0.79 to 1:1.34, preferably from 1:0.79 to 1:1.34 or comprised from 1:0.79 to 1:1.

[0069] According to a preferred form, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is 1:0.79, or is 1:0.83 or is 1:1.Co-densifier

[0070] Co-densifier means a chemical compound that aids the action of a main densifier, which is, in this case, xanthan gum. For the purposes of the invention, the co-densifier aids in the controlled release of the solution together with the main densifier / supporting agent.

[0071] Preferably, the at least one co-densifier is selected from the group consisting of: Dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, propylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol, and combinations thereof.

[0072] Preferably, the at least one co-densifier is Dipropylene glycol monomethyl ether ("DPM").

[0073] Preferably, the at least one co-densifier is in a quantity comprised between 2% and 4% by weight, preferably equal to 3% by weight, on the total weight of the formulation.

[0074] For the purposes of the invention, sodium carbonate is not considered as a co-densifier.Surfactant

[0075] Surfactant means a chemical substance capable of lowering the surface tension of a liquid, facilitating the wettability of the surfaces.

[0076] Preferably, the surfactant employed for the purposes of the invention is a surfactant that is not soluble in water at room temperature.

[0077] Preferably, the at least one surfactant is selected from the group consisting of: a polyethylene glycol (or polyglycol) ether of a fatty alcohol, an alkyl polyethylene glycol of a fatty alcohol, an ethoxylated propoxylated fatty alcohol, a polypropylene glycol / polyethylene glycol ether of a hydrogenated fatty alcohol, a polyoxyalkylated fatty alcohol ether, and combinations of the foregoing.

[0078] Preferably, the at least one surfactant is selected from the group consisting of: a polyethylene glycol (or polyglycol) ether of an ethoxylated fatty alcohol; a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol; an alkyl polyethylene glycol of a fatty alcohol; an ethoxylated propoxylated fatty alcohol; a polypropylene glycol / polyethylene glycol ether of a hydrogenated fatty alcohol; a polyoxyalkylated fatty alcohol ether; and combinations of the foregoing.

[0079] Preferably, the at least one surfactant is selected from the group consisting of: polyethylene glycol (or polyglycol) ether of a fatty alcohol; a polyethylene glycol ether of an ethoxylated fatty alcohol; a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol; and combinations of the foregoing.

[0080] Preferably, the at least one surfactant is selected from the group consisting of: polyethylene glycol (or polyglycol) ether of a fatty alcohol; polyethylene glycol ether of C9-11 iso, ethoxylated alcohols; polyglycol ether of undecanol, branched and linear, ethoxylated, propoxylated, fatty alcohol; and combinations of the foregoing.

[0081] Preferably, the "polyethylene glycol ether of C9-11 iso alcohols" is composed of a polyethylene glycol ether of iso alcohols, i.e. non-linear chains of the alcohols, in particular the chains of the alcohols are characterized by a number of carbon atoms comprised between 9 and 11; preferably, the chains of the alcohols with 10 carbon atoms (C10) are prevalent with respect to the others, preferably the C10 chains of the alcohols are ≥ 50%, preferably ≥ 60%, preferably ≥ 80%, with respect to the total of the chains.

[0082] Preferably, when the at least one surfactant is derived from an ethoxylated and / or propoxylated fatty alcohol, the moles by ethoxylation and / or by propoxylation (or degree of ethoxylation or propoxylation) are greater than or greater than or equal to (≥) 2.5 moles.

[0083] Preferably, the at least one surfactant is polyethylene glycol ether of a fatty alcohol, preferably it is the commercial product Tridac Iso-3.

[0084] Preferably, the at least one surfactant is a polyethylene glycol ether of an ethoxylated fatty alcohol, preferably it is the polyethylene glycol ether of the C9-11 iso, ethoxylated alcohols (> 2.5 mol EO), preferably it is the commercial product Biodac 410 and / or the commercial product ISOGIFRAN 10_4 M.

[0085] Preferably, the at least one surfactant is a polyethylene glycol ether of an ethoxylated and propoxylated fatty alcohol, preferably it is the polyglycol ether of the undecanol, branched and linear, ethoxylated and propoxylated fatty alcohol (≥ 2.5 mol EO / PO), preferably it is the commercial product Biodac 2-32.

[0086] Preferably, the at least one surfactant is in a quantity comprised between 0.5% and 2% by weight, preferably equal to 1% by weight, on the total weight of the formulation.

[0087] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.2 and 1:2.

[0088] By sum of the at least one co-densifier and the surfactant is meant the sum between the quantity of the at least one co-densifier and the quantity of the at least one surfactant.

[0089] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.2 and 1:1.5, preferably between 1:1.25 and 1:1.5.

[0090] According to a preferred form, the weight ratio between the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, or equal to 1:1.25.

[0091] According to a further preferred form, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:1.5, or equal to 1:1.5.

[0092] It should be noted that this weight ratio is useful for aiding the cleaning efficacy, the controlled release of the cleaning agents at the level of the stone surface, i.e. without penetrating the matrix of the stone material, and the stability of the formulation. This ratio allows optimal adhesion of the hydrogel compress to the surfaces of interest, without compromising its subsequent easy removal, while ensuring precise control over the diffusion of the solvent, limiting it to the hydrogel / surface contact zone.Antibacterial and / or anti-mould

[0093] The antibacterial and / or anti-mould agent is a chemical substance capable of counteracting bacterial growth and / or mould within the formulation.

[0094] Preferably, the at least one antibacterial and / or anti-mould is selected from the group consisting of: isopropanol, ethanol, phenylethyl alcohol, benzyl alcohol, pentylene glycol, isobutyl alcohol, and combinations of the above, preferably it is isopropanol.

[0095] Preferably, the at least one antibacterial and / or anti-mould is in a quantity comprised between 2% and 4% by weight, preferably of 2.999% by weight, on the total weight of the formulation.

[0096] The Applicant has noted that the analyses carried out on the role of isopropanol in the formulation have made it possible to recognise that, in addition to its active effect deriving from its nature as an alcoholic solvent, it plays a significant preventive role in the formation of moulds and biological alterations during the storage phase. This characteristic makes the formulation not only suitable for production, but also for effective preservation over time, satisfying the stability over time of the formulation (see Example 5.5).Water

[0097] The water is preferably in a quantity ≥ 80% by weight, preferably between 80% and 90% by weight, preferably between 80% and 85% by weight, preferably equal to about 81%, or 81.701% by weight, or 82% by weight, on the total weight of the formulation.

[0098] It should be noted that the first chelating agent consisting of citric acid, the second chelating agent, the at least one co-densifier, the at least one surfactant, the at least one antibacterial agent and / or anti-mould and water constitute the cleaning solution or mixture which is charged and dispersed in the xanthan gum supporting agent to obtain the compress hydrogel formulation.

[0099] Preferably, the formulation of the invention is characterized by a pH that ranges between 4 and 7.6, preferably comprised between 4.1 to 6.8, or, alternatively, preferably comprised between 6.6 to 7.2, in a preferred manner equal to 4.5 or 6.6 or 7.2. The range comprised between 5 and 5.5 is preferably excluded from the above pH ranges.

[0100] The Applicant considers that the pH of the formulation, which derives from the final qualitative-quantitative balancing of the components of the formulation described in the previous sections, influences the cleaning efficacy, but also the surface aggressiveness (refer to Examples 1-3).First embodiment: cleansing hydrogel formulation for stone surfaces of civil buildings or civil property

[0101] Civil buildings or civil property are defined as property of civil and public interest, such as those intended for homes, shops, etc.

[0102] According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of Tetrasodium glutamate diacetate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0103] The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0104] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1.34, preferably equal to 1:0.83.

[0105] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, preferably of 1:1.25.

[0106] Preferably, the formulation of the invention is characterized by a pH that ranges between 4.1 and 4.5, preferably it is equal to 4.2 or 4.3 or 4.5.

[0107] According to a further preferred alternative in accordance with this first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of: Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0108] The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0109] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.79 and 1:1.34, preferably between 1:0.79 and 1:1.3, preferably equal to 1:0.79.

[0110] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:2, preferably of 1:1.25.

[0111] Preferably, the formulation of the invention is characterized by a pH that ranges between 6.8 and 7.5, preferably between 6.8 and 7.2, preferably equal to 7.1 or 7.2.Second embodiment: cleansing hydrogel formulation for stone surfaces of cultural heritage property

[0112] Cultural heritage property is defined as the property of artistic, historical and archaeological interest.

[0113] According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of cultural heritage property comprises a first chelating agent consisting of citric acid, a second chelating agent consisting of Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0114] The technical specifications of the components indicated above are the same as those indicated in the previous sections.

[0115] Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably equal to 1:1.

[0116] Preferably, the weight ratio of the sum of the at least one co-densifier and the surfactant to the xanthan gum is comprised between 1:1.25 and 1:1.5, preferably equal to 1:1.5.

[0117] Preferably, the formulation of the invention is characterized by a pH that ranges between 6.4 and 7, preferably between 6.4 to 6.8, preferably equal to 6.6 or 6.8.Use of the cleansing hydrogel formulation of stone surfaces

[0118] A further object of the invention is the use of the formulation according to the invention for the cleaning, preferably chemical cleaning, of stone surfaces.

[0119] The formulation is as described in the preceding sections, preferably also in accordance with the first and second embodiments.

[0120] Preferably, the use of the formulation is for the cleaning of stone surfaces of civil buildings, preferably in accordance with the first embodiment described above, wherein the second chelating agent is Tetrasodium glutamate diacetate, or, alternatively, the second chelating agent is the combination of Tetrasodium glutamate diacetate and Trisodium dicarboxymethyl alaninate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.79 and 1:1.35, preferably between 1:0.8 and 1:1.35, preferably between 1:0.8 and 1:1.3, preferably equal to 1:0.79 or 1:0.83, wherein the pH of the formulation is comprised between 4.1 and 4.5, preferably equal to 4.2 or 4.5, or, alternatively, the pH is preferably comprised between 6.8 and 7.5, preferably between 6.8 and 7.2, preferably equal to 7.1 or 7.2.

[0121] Alternatively, the use of the formulation is for the cleaning of stone surfaces of cultural heritage property, preferably in accordance with the second embodiment described above, wherein the second chelating agent is Trisodium dicarboxymethyl alaninate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably between 1:0.83 and 1:1, preferably equal to 1:1, wherein the pH of the formulation is comprised between 6.4 and 7, preferably between 6.4 and 6.6, preferably it is 6.6 or 6.8. Method for applying to a stone surface the cleansing hydrogel formulation

[0122] A third object of the invention is the method for applying to a stone surface the formulation according to the invention, comprising the steps of a) applying the hydrogel formulation to the stone surface, b) leaving on for a time comprised between 15 and 120 minutes, preferably between 30 and 90 minutes, preferably between 45 and 90 minutes, preferably equal to 60 minutes, c) removing the hydrogel formulation with water, preferably using a pad soaked in water, preferably the water is demineralised, wherein the aforementioned steps a)-c) (i.e. respectively the steps of: applying the hydrogel formulation on the stone surface; leaving it on; removing the hydrogel formulation with water) are repeated for a number of times n comprised between 1 and 3, preferably between 1 and 2, preferably n is 1 or 2.

[0123] Preferably for use for the cleaning of stone surfaces of buildings or civil property, the formulation may be applied to the surface, then it is left on for a time comprised between 45 and 90 minutes, preferably between 45 and 60 minutes, after which it is rinsed with water, the formulation is applied again for a time comprised between 45 and 90 minutes, preferably between 45 and 60 minutes, and rinsed again.

[0124] Preferably for use for the cleaning of stone surfaces of cultural heritage property, the formulation can be applied to the surface, then it is left on for a time comprised between 45 minutes and 60 minutes, after which it is rinsed with water. In this case, it is possible or not a second application of the formulation in the same period of time just mentioned followed by rinsing.

[0125] Preferably, the formulation is applied to the stone surface by hand or by any suitable means known to a person skilled in the art, such as a spatula or a brush.

[0126] It should be noted that, even if the action times of the formulation are longer than those of the known formulations, the overall time required for cleaning may be shorter as it can be optimised during the application step.

[0127] Preferably, under standard conditions (at room temperature), the hydrogel formulation has a shelf life > 7 days, preferably > 7 days and ≤ 1 year and a half, preferably > 7 days and ≤ 1 year.

[0128] Preferably, the hydrogel formulation is not applied by spray techniques.

[0129] Preferably, the hydrogel formulation does not contain organic solvents of a toxic and / or unsustainable nature.

[0130] Preferably, the hydrogel formulation does not contain traditional and / or toxic and / or unsustainable chelators, such as for example EDTA, NTA or organophosphonates.EXAMPLES

[0131] Examples are given below for illustrative and non-limiting purposes.Glossary

[0132] NT = Untreated; Na 4 -GLDA = Tetrasodium glutamate diacetate; Na 3 -MGDA = Trisodium dicarboxymethyl alaninate; 2 Prop = isopropanol; DPM = Dipropylene glycol monomethyl ether; Tridac (or Tridac Iso-3) = polyethylene glycol ether of a fatty alcohol; Biodac 2-32 = fatty alcohol polyglycol ether - undecanol, branched and linear, ethoxylated, propoxylated (≥2.5 mol EO / PO); Biodac 410 = Fatty alcohol polyethylene glycol ether - Alcohols, C9-11 iso (C10 ≥ 50% on the total of the C9-C11 chains), ethoxylated (>2.5 mol EO). The commercial product "ISOGIFRAN 10_4 M" is equivalent to Biodac 410. Example 1: pH of the formulation based on its qualitative-quantitative chemical composition

[0133] Table 1Test # Citric AcidNa 4 -GLDANa 3 -MGDA2 Prop + DPM + SurfactantXanthan GumH 2 OpHH5v1 (Tridac) 3%3%-7%5%82%4.5H5v4 (Tridac) 2.8%3.2%-7%5%82%5.5H9 (Tridac) 4%2%-7%5%82%3.4H10 (Tridac) 1%5%-7%5%82%7.6H12 (Tridac) 3%3%-7%8%79%4.1L6C (Tridac) 0.94%4.72%1.89%6.60%4.72%81.13%8.9L6Neutral (Tridac) 1.2%3.5%1.6%7%5%81.7%7.2L9v3 (Tridac) 1.35%-4.65%7%5%82%6.6L9v4 (Tridac) 1.35%-4.65%7%6%81%6.6H5v1 (Biodac 410) 3%3%-7%5%82%4.2L6Neutral (Biodac 410) 1.2%3.5%1.6%7%5%81.7%7.1L9v4 (Biodac 410) 1.35%-4.65%7%6%81%6.6H5v1 (Biodac 2-32) 3%3%-7%5%82%4.3L6Neutral (Biodac 2-32) 1.2%3.5%1.6%7%5%81.7%7.2L9v4 (Biodac 2-32) 1.35%-4.65%7%6%81%6.8

[0134] For Test# formulations reported in Table 1: 2 Prop is 2.999% by weight on the total weight of the formulation; DPM is 3% by weight on the total weight of the formulation; Surfactant, which may be Tridac or Biodac 410 or Biodac 2-32, is 1% by weight on the total weight of the formulation.

[0135] Note that the Test# formulations reported in Table 1, in particular those containing Tridac as surfactant, are also employed in the following examples (Examples 2, 3 and 4).Example 2: Evaluation of the cleaning efficacy of the formulation of the invention

[0136] Figures 1-11 report the photos relating to a sample of Carrara marble characterized by surface encrustations of iron oxide, before and after the various applications of the different Test# formulations of Table 1, in particular those containing Tridac as a surfactant.

[0137] The results of the cleaning efficacy are reported in Table 2 below.

[0138] By distinguishing the cleaning effect from that of surface aggression, it is noted that for all tests# a good / excellent degree of cleaning is obtained.Example 3: Evaluation of the aggression of carbonate surfaces by the formulation of the invention

[0139] The morphological results were acquired by optical microscope, relating to the aggression of surfaces by the Test# formulations reported in Example 1, in particular those containing Tridac as a surfactant.

[0140] Images were acquired on non-degraded specimens of Carrara marble before treatment, after 1h of application and after 1h+1h of application. The rinsing took place using a cotton pad soaked with demineralised water.

[0141] The outcomes of an overall evaluation are reported in Table 3 below. Table 3Test#Figure of referenceOutcomeH5v1 (Tridac)Figures 12-14AggressiveH9 (Tridac)Figures 15-17Very aggressiveH10 (Tridac)Figures 18-20Very aggressiveH12 (Tridac)Figures 21-23AggressiveH5v4 (Tridac)Figures 24-26Very aggressiveL6C (Tridac)Figures 27-29AggressiveL6Neutral (Tridac)Figures 30-32AggressiveL9v3 (Tridac)Figures 33-35Slightly aggressiveL9v4 (Tridac)Figures 36-38Very little aggressive

[0142] According to the Applicant, the tests# with an "Aggressive" outcome can in any case be preferably used for application in the civil field, for buildings or civil property, as they are characterised by a good degree of cleanliness. This is because, although the tests# (for example, the H5v1 and H12 tests#) are overall "Aggressive", this evaluation is carried out considering both the outcome after 1h of application, and that after 1h+1h of application.Example 4: Evaluation of the release capacity of the cleaning solution of various compositions.

[0143] With reference to Figure 39, it should be noted that the formulation of the invention (top left rectangle with whole straight line contour; Citric Acid 3%; Na 4 -GLDA 3%; Xanthan Gum 5%; DPM 3%; 2Prop 3%; Tridac 1%; Water 82%) does not show contour halos, indicating a controlled release capacity of the cleaning solution from the hydrogel compress.

[0144] As evidenced by the arrows, however, for the other compositions, different from the formulation of the invention (each lacking at least one component considered essential for the realization of the formulation of the invention), there are halos surrounding the hydrogel compress, a sign of an immediate (therefore not controlled) release capacity of the cleaning solution.

[0145] Below is Table 4 summarizing the conclusions referred to in Examples 1-3. Example 5: Evaluation of the performance of xanthan gum at various particle sizes.

[0146] Following the information relative to the market prices for Xanthan gum, we report the main strengths and weaknesses of the 3 types available on the market, namely Xanthan gum with a particle size of 0.420 mm (40 mesh), 0.177 mm (80 mesh) or 0.074 mm (200 mesh).

[0147] The formulations prepared with the 3 different particle sizes are reported, both for Line H and Line L.

[0148] Test # formulations of Table 5 are those of Example 1 containing Tridac as a surfactant. Table 5Test #Citric AcidGLDAMGDA2 PropDPMXanthan GumMesh H 2 OH5v1 (Tridac)3%3%-3%3%5%40 82%L5v1 (Tridac)1%5%2%3%3%5%40 80%H5v3 (Tridac)3%3%-3%3%5%80 82%L5v3 (Tridac)1%5%2%3%3%5%80 80%H4 (Tridac)3%3%-3%3%5%200 82%L4 (Tridac)1%5%2%3%3%5%200 80% 5.1 Surface aggression

[0149] The aggressiveness of the compositions referred to in Test# (Example 1, in particular formulations containing Tridac as a surfactant) was tested on healthy Carrara marble specimens, i.e. without alterations, deposits or surface encrustations.

[0150] The effects obtained were investigated by observing the stone surfaces with SEM and under an OPTICAL MICROSCOPE in grazing light.

[0151] The results can be summarized as reported below: SEM: the 40 mesh formulations are less aggressive on the surface of the support, if compared with those at 80 and 200, although this analysis did not give the expected results, the images were disturbed due to the difficulty of image processing and acquisition; OPTICAL MICROSCOPE: refer to Figures 40-49, which show the images acquired for visual comparison. Here too, as with the SEM, greater aggressiveness was observed in the products with 80 and 200 mesh Xanthan gum compared to that made with 40 mesh powder. It is worth noting the presence of surface deposits, still to be analysed and characterised, on the surfaces treated with products made with 80 and 200 mesh Xanthan gum. 5.2 Surface performance - cleaning effect

[0152] The surface performance of the three types of Xanthan gum (cleaning effect) was evaluated by applying the formulations of line H on a marble slab with surface incrustation of iron oxide.

[0153] Figures 50 and 51 show the visual result before and after treatment (application time: 2h, 1h and 1h+1h).

[0154] No substantial differences were found attributable to the 3 types of Xanthan gum used.5.3 Adhesion to the support in vertical treatments

[0155] The formulations were tested and applied both on specimens placed horizontally and on case studies placed vertically. Not all formulations showed the same result if placed vertically; for example, in the formulations of line L, made with 80 mesh Xanthan gum, dripping phenomena caused by insufficient adhesive power with the substrate occurred.5.4 Viscosity of the hydrogel

[0156] Substantial differences in the viscosity of the final formulations were found, attributable to the different grain size of the Xanthan gum used. With the same formulation, by increasing the grain size, an increase in viscosity was observed; especially in the line L, the formulations made with 200 mesh powder were extremely viscous and compact, making the application complex and difficult.5.5 Storage, durability

[0157] Table 6Test#Mesh Date of realisationVariationsTest H5v1 (Tridac)40 10 / 07 / 2023NoneL5v1 Test (Tridac)40 10 / 07 / 2023NoneTest H5v3 (Tridac)80 24 / 07 / 2023After 80 days: formation of similar crystals in the gelatinous matrix.L5v3 Test (Tridac)80 24 / 07 / 2023After 80 days: slight increase in viscosity.Test H4 (Tridac)200 31 / 05 / 2023After 163 days: formation of simil-crystals in the gelatinous matrix.Test L4 (Tridac)200 31 / 05 / 2023After 80 days: marked increase in viscosity. 5.6 Conclusions

[0158] Based on the results in our possession to date, the analyses and observations made, Xanthan gum with 40 mesh particle size appears to be the best choice.

[0159] For both the line H and the line L, better performance was found to be linked to: lower surface aggressiveness on the support (more controllable cleaning); a better adhesive power which translates into easier applicability on vertical surfaces; the different state of aggregation (lower viscosity, therefore fewer problems for production during realisation step); improved chemical stability over time, resulting in improved storage durability. Example 6: cleansing hydrogel formulation, suitable for application in the civil field, for buildings or civil property.

[0160] ComponentPercentage by weight on the total weight of the formulation (% w / w)Tetrasodium glutamate diacetate (Na 4 -GLDA)3%Citric Acid3%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32))1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum5%H 2 O82.001%Total100%

[0161] Note that Example 6 where the surfactant is Tridac corresponds to test # H5v1 (Tridac) of Examples 1-5.

[0162] Example 6 where the surfactant is Biodac 410 corresponds to test # H5v1 (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # H5v1 (Biodac 2-32) of Example 1.

[0163] The pH of the formulation with Tridac is 4.5.

[0164] The pH of the formulation with Biodac 410 is 4.2.

[0165] The pH of the formulation with Biodac 2-32 is 4.3.Example 7: cleansing hydrogel formulation, suitable for application in the civil field, for buildings or civil property.

[0166] ComponentPercentage by weight on the total weight of the formulation (% w / w)Tetrasodium glutamate diacetate (Na 4 -GLDA)3.5%Trisodium dicarboxymethyl alaninate (Na 3 -MGDA)1.6%Citric Acid1.2%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32)1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum5%H 2 O81.701%Total100%

[0167] Note that Example 7 in which the surfactant is Tridac corresponds to test # L6Neutral (Tridac) of Examples 1-3.

[0168] Example 7 where the surfactant is Biodac 410 corresponds to test # L6Neutral (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # L6Neutral (Biodac 2-32) of Example 1.

[0169] The pH of the formulation with Tridac is 7.2.

[0170] The pH of the formulation with Biodac 410 is 7.1.

[0171] The pH of the formulation with Biodac 2-32 is 7.2.Example 8: cleansing hydrogel formulation, suitable for application for cultural heritage property.

[0172] ComponentPercentage by weight on the total weight of the formulation (% w / w)Trisodium dicarboxymethyl alaninate (Na 3 -MGDA)4.65%Citric Acid1.35%Isopropanol2.999%Surfactant (Tridac Iso-3 or Biodac 410 or Biodac 2-32)1%Dipropylene glycol monomethyl ether (DPM)3%Xanthan gum6%H 2 O81.001%Total100%

[0173] Note that Example 8 where the surfactant is Tridac corresponds to test # L9v4 (Tridac) of Examples 1-3.

[0174] Example 8 where the surfactant is Biodac 410 corresponds to test # L9v4 (Biodac 410) of Example 1 and that with Biodac 2-32 corresponds to test # L9v4 (Biodac 2-32) of Example 1.

[0175] The pH of the formulation with Tridac is 6.6.

[0176] The pH of the formulation with Biodac 410 is 6.6.

[0177] The pH of the formulation with Biodac 2-32 is 6.8.Example 9: viscosity of the formulations H5v1, L9Neutral and L9v4 of Examples 6-8

[0178] The viscosity of the formulations H5v1, L9Neutral and L9v4 of Examples 6-8 was measured using a rotational rheometer with controlled shear stress (Bohlin C-VOR 120 model, Bohlin Instruments Ltd) equipped with "vane in cup" coaxial cylinders, the latter composed of a smooth outer cylinder with a diameter of 15.4 mm and an inner cylinder with 4 vanes with a diameter of 14 mm (gap 0.7 mm).

[0179] All viscosity measurements were performed at 20°C and with a constant shear rate of 10 s -1< .

[0180] Three acquisitions were recorded for each formulation, each lasting 5 minutes. The average viscosity value was expressed in Pa·s. Table 7Formulation Test # (Example 1 and Examples 6-8)VISCOSITY [Pa*s] (10 s -1< , 20°C)H5v1 (Tridac)23.47H5v1 (Biodac 2-32)13.34H5v1 (Biodac 410)23.45L9v4 (Tridac)22.47L9v4 (Biodac 2-32)14.44L9v4 (Biodac 410)17.17L6Neutral (Tridac)13.96L6Neutral (Biodac 2-32)24.99L6Neutral (Biodac 410)15.84

[0181] The name in brackets for the first column from the left of Table 7 indicates the surfactant used in the formulation, the concentration of which is 1% on the total weight of the formulation.Example 10: process for preparing the formulation of the invention.

[0182] By way of illustration of the hydrogel preparation process, the preparation process of formulation L9v4 (Biodac 410) is reported.

[0183] A mixture of isopropanol (2,999 g), dipropylene glycol monomethyl ether (DPM) (3,000 g), surfactant (Biodac 410, Tellerini) (1,000 g) and water (81,000 g) is added to the chelators citric acid (1.35 g) and Na 3 -MGDA (MGDA 40, Tellerini) (11,625 g). Finally, xanthan gum (6,000 g) is added.

Examples

first embodiment

cleansing hydrogel formulation for stone surfaces of civil buildings or civil property

[0101]Civil buildings or civil property are defined as property of civil and public interest, such as those intended for homes, shops, etc.

[0102]According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of civil property comprises

a first chelating agent consisting of citric acid, a second chelating agent consisting of Tetrasodium glutamate diacetate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0103]The technical specifications of the components indicated above are the same as those reported in the previous sections.

[0104]Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1.34, preferably equal to 1:0.83.

[0105]Preferably, the weight ratio of the sum of ...

second embodiment

cleansing hydrogel formulation for stone surfaces of cultural heritage property

[0112]Cultural heritage property is defined as the property of artistic, historical and archaeological interest.

[0113]According to a first embodiment, the cleansing hydrogel formulation of stone surfaces of cultural heritage property comprises

a first chelating agent consisting of citric acid, a second chelating agent consisting of Trisodium dicarboxymethyl alaninate, a supporting agent consisting of xanthan gum, at least one co-densifier, at least one surfactant, at least one antibacterial and / or anti-mould, water.

[0114]The technical specifications of the components indicated above are the same as those indicated in the previous sections.

[0115]Preferably, the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is preferably comprised between 1:0.8 and 1:1, preferably equal to 1:1.

[0116]Preferably, the weight ratio of the sum of the at least one co-den...

example 1

pH of the formulation based on its qualitative-quantitative chemical composition

[0133]

Table 1

Test # Citric AcidNa 4 -GLDANa 3 -MGDA2 Prop + DPM + SurfactantXanthan GumH 2 OpH

H5v1 (Tridac) 3%3%-7%5%82%4.5

H5v4 (Tridac) 2.8%3.2%-7%5%82%5.5

H9 (Tridac) 4%2%-7%5%82%3.4

H10 (Tridac) 1%5%-7%5%82%7.6

H12 (Tridac) 3%3%-7%8%79%4.1

L6C (Tridac) 0.94%4.72%1.89%6.60%4.72%81.13%8.9

L6Neutral (Tridac) 1.2%3.5%1.6%7%5%81.7%7.2

L9v3 (Tridac) 1.35%-4.65%7%5%82%6.6

L9v4 (Tridac) 1.35%-4.65%7%6%81%6.6

H5v1 (Biodac 410) 3%3%-7%5%82%4.2

L6Neutral (Biodac 410) 1.2%3.5%1.6%7%5%81.7%7.1

L9v4 (Biodac 410) 1.35%-4.65%7%6%81%6.6

H5v1 (Biodac 2-32) 3%3%-7%5%82%4.3

L6Neutral (Biodac 2-32) 1.2%3.5%1.6%7%5%81.7%7.2

L9v4 (Biodac 2-32) 1.35%-4.65%7%6%81%6.8

[0134]For Test# formulations reported in Table 1:

2 Prop is 2.999% by weight on the total weight of the formulation; DPM is 3% by weight on the total weight of the formulation; Surfactant, which may be Tridac or Biodac 410 or Biodac 2-32, is 1% by weight...

Claims

1. Cleansing hydrogel formulation of stone surfaces comprising - a first chelating agent consisting of citric acid, - a second chelating agent selected from the group consisting of: Tetrasodium glutamate diacetate, Trisodium dicarboxymethyl alaninate and combinations of the above, - a supporting agent consisting of xanthan gum, - at least one co-densifier, - at least one surfactant, - at least one antibacterial and / or anti-mould, - water, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum is comprised from 1:0.7 to 1:1.6.

2. Formulation according to claim 1, wherein the weight ratio of the sum of the at least one co-densifier and the at least one surfactant to the xanthan gum is comprised from +1:1.2 to 1:2.

3. Formulation according to claim 1 or 2, wherein the particle size of the xanthan gum is comprised between 0.595 mm and 0.297 mm.

4. Formulation according to any of claims from 1 to 3, wherein the at least one coformulant is chosen from the group consisting of: Dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, propylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol, and combinations thereof.

5. Formulation according to any of claims from 1 to 4, wherein the at least one surfactant is selected from the group consisting of: a polyethylene glycol ether of a fatty alcohol, an alkyl polyethylene glycol of a fatty alcohol, an ethoxylated propoxylated fatty alcohol, a polypropylene glycol / polyethylene glycol ether of a hydrogenated fatty alcohol, a polyoxyalkylated fatty alcohol ether, and combinations of the foregoing.

6. Formulation according to any of claims from 1 to 5, wherein the at least one antibacterial and / or antimould is selected from the group consisting of: isopropanol, ethanol, phenylethyl alcohol, benzyl alcohol, pentylene glycol, isobutyl alcohol, and combinations of the foregoing.

7. Formulation according to any of claims from 1 to 6, wherein the pH ranges between 4 and 7.6.

8. Method for applying to a stone surface the formulation according to any of claims from 1 to 7, comprising the steps of a) applying the hydrogel formulation to the stone surface, b) leaving on for a time comprised between 15 minutes and 120 minutes, c) removing the hydrogel formulation with water, wherein the aforementioned steps a)-c) are repeated for a number of times n comprised between 1 and 3.

9. Use of the formulation according to any of claims from 1 to 7, for cleaning stone surfaces.

10. Use of the formulation according to claim 9, for the cleaning of stone surfaces of buildings or civil property, wherein the second chelating agent is Tetrasodium glutamate diacetate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum ranges from 1:0.7 to 1:1.35, wherein the pH of the formulation is comprised between 4.1 and 4.5 or between 6.8 and 7.5, or for the cleaning of stone surfaces of cultural heritage property, wherein the second chelating agent is Trisodium dicarboxymethyl alaninate, wherein the weight ratio of the sum of the first chelating agent and the second chelating agent to the xanthan gum ranges from 1:0.8 to 1:1, wherein the pH of the formulation is comprised between 6.4 and 7.

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