WO2016084036A1

WO2016084036A1 - Use of a component in low-surfactant detergents and process for making said component

Info

Publication number: WO2016084036A1
Application number: PCT/IB2015/059160
Authority: WO
Inventors: Maria Fernanda Garcia; Maria De Los Angeles Garcia
Original assignee: Solbat Srl
Current assignee: Solbat Srl
Priority date: 2014-11-27
Filing date: 2015-11-27
Publication date: 2016-06-02
Anticipated expiration: 2017-05-27
Also published as: EP3234090A1

Abstract

A component for detergents having the form of a gel comprises water in a weight percentage between the 70% and 95%; nanoparticles, preferably of amorphous silica or of aluminium hydroxide, of size between 5 and 250, in particular between 20 and 100 nanometres; selective anions selected from the group consisting of: HCO₃-, CIO^-, CH₃COO^-, OCO₂O⁼, C₆H₅O₇ ^3-, CH₃COOO-, adsorbed on the nanoparticles. By adding a certain an amount of gel to the conventional detergents, detergents are obtained that have lower critical micellar concentration (CMC) values, therefore a higher detergent power. By another point of view, the gel drastically reduces the presence of surfactants in the common detergents, while maintaining the detergent power, with the advantage of reducing the environmental impact and the production cost. A process to obtain this component provides mixing a water solution of a nanoparticles-forming compound, in particular silicate of Li, preferably Na or K, or a soluble aluminium salt with a pH higher than a minimum predetermined value, with a gelling agent configured to cause the pH to decrease, and amorphous silica or of aluminium hydroxide to precipitate, respectively said gelling agent selected from the group consisting of: chlorine; carbon dioxide; sodium hydroxide; a compound as a organic acid or inorganic, or a salt, soluble in water adapted to provide, starting from a concentration between 1N and 5N, a solution having pH lower than or equal to 9; and gelling the gelification mixture obtained forming a gel of nanoparticles that have a size set between 5 and 250 nanometres. The process provides also adsorbing said selective anions on the nanoparticles. The adsorption of the anions can be effected in situ during the mixing/gelling, in particular with a gelling agent as CO₂ and CI₂ adapted to releasing the selective anions, or it can be effected on an already formed gel.

Description

TITLE

USE OF A COMPONENT IN LOW-SURFACTANT DETERGENTS AND

PROCESS FOR MAKING SAID COMPONENT

DESCRIPTION

Field of the invention

[0001] The following invention relates to a component for formulations of strong detergency detergents, and/or for very low-surfactant detergents, with respect to prior art detergents, to be used, for instance, for home cleaning, dish-washing, or for the laundry, as well as for personal hygiene.

[0002] Moreover, the invention relates to a process for manufacturing said component.

Description of the prior art

[0003] As well known, surfactants are used to obtain water solutions that have a detergent power, which is not the case for water alone, in particular, to treat grease dirt particles. Chemically, they are organic compounds in which the molecules have a hydrophobic zone, usually comprising a hydrocarbon chain comprising 10 to 20 carbon atoms, and a water soluble hydrophilic zone of various chemical nature. Surfactants can decrease the surface tension between two liquids, in this case a washing solution and a grease or oily material, which usually has a positive charge and forms the dirt stuck on a surface to be cleaned. Surfactants can also decrease the interface tension between the washing solution and the surface itself, which has a negative charge.

[0004] In a solution, surfactants create micelles, which are aggregates of molecules. These have a central structure in which the hydrophobic zone is at the centre and can capture the dirt particles, while peripheral hydrophilic zones can solubilize the complexes formed by micelles and dirt particles, and maintain them in a solution state. More in detail, the surfactant molecules surround the grease particles and give them an electric charge that has the same sign of the surface to be cleaned. This way, the adhesion forces between the surface and the grease decrease until the grease particle is detached, synergistically with the agitation of the washing solution and with the solubilization of the micelles.

[ 0005 ] As well-known, surfactants have caused environmental problems, in particular, in water ecosystems, due the widespread of industrial and household detergents since the 50ies. The surfactant are poorly biodegradable and, if they are discharged into water bodies:

can form steady foams that limits the aeration and the lighting;

since they contain nitrogen and phosphorus, they can cause eutrophication, i.e. an unwanted proliferation of life forms such as algae; - they can dissolve cell membranes and remove dangerous deposits, and disperse them consequently.

[ 0006] Moreover, if they are discharged to soil, the surfactant can pollute the water table. Not lastly, the sequestering or chelating substances contained therein, which are often also toxic substances, cause further dissolution of harmful metal precipitates and disperse them into the environment.

[ 0007 ] US 2006/009370 describes a process for removing soil from a cotton or a cotton/wool blend material and to protect it, wherein a step is provided of contacting the material with a composition in which nanoparticles are provided of size set between 5 to 500 nm, comprising, in particular, silicates, as well as an hydrophilizing agent selected among C2-C4 alcohols, alkyl ethers of various glycols, polyglycols that are liquid at room temperature, esters of carboxylic acids, or a mixture thereof.

Summary of the invention

[ 0008 ] It is therefore a feature of the present invention to provide a component for detergents, such as household, dishwashing, laundry products, as well as detergents for personal hygiene, which contain a very low surfactant amount, with respect to conventional detergents, while having a same detergent power.

[ 0009] It is also a feature of the present invention to provide a component for detergents that have a higher detergent power, with respect to conventional detergents, and that have a lower, or at most the same surfactant content. [0010] It is also a feature of the invention to provide a process for making said component for detergents.

[0011] It is also a feature of the invention to provide detergent formulations that contain less surfactants than the prior art detergents, without substantially reducing the detergent power.

[0012] These and other objects are achieved by a component for detergents, said component having the form of a gel, whose main feature is that it comprises:

water, in a weight percentage set between 70% and 95% of the total weight of the component;

nanoparticles having a size set between 5 and 250 nanometres, in particular between 20 and 100 nanometres;

selective anions selected from the group consisting of: bicarbonate anions (HCO3 ); hypochlorite anions (CIO ); acetate anions (CH3COO-); oxalate anions (O(CO)2O⁼); citrate anions (C6H5O7^3"); peroxyacetate anions (CH3COOO-); a combination thereof,

wherein the selective anions are adsorbed on said nanoparticles.

[0013] In particular, such nanoparticles have a surface microporosity, so as to enhance the adsorption of said selective anions.

[0014] It has been actually observed that, if a certain amount of such a gel is added to a formulation of a conventional detergent, i.e. to a solution of a given surfactant, detergents are obtained that have a critical micellar concentration (CMC) lower than in the case of the initial detergents, regardless of the surfactant concentration in the washing solution, as shown by the examples given hereinafter and by the curves of Figs. 4-6, which are described more in detail hereinafter. This increases the detergent power.

[0015] The critical micellar concentration of a surfactant is the concentration of a solution thereof beyond which, above a certain critical micellar temperature, a certain number of surfactant molecules aggregate to form micelles. In these conditions, the above described effect of "emulsifying" the grease particles occurs, which makes easier to remove them. With reference to Fig. 1 , beyond CMC 10, a further surfactant addition to a washing solution causes the production of new micelles, or the growth of the existing ones, but it does not remarkably increase the free surfactant concentration, from which the detergent power depends. Therefore, detergent power 13 does not increase, and surface tension 11 and interface tension 12 does not change as well. Therefore, the lower the CMC, the more is enhanced the production of micelles, and the stronger is the detergent power. From a chemical-physical viewpoint, low CMC values improve the kinetic and thermodynamic stability of the micelles, and prevent them from reverting to the state of free molecules.

[0016] More in detail, as diagrammatically shown in Fig. 2, the above mentioned selective anions A^", are adsorbed on the microporous surface of nanoparticles 20 and there they form, in particular, a negatively charged layer. As shown in Fig. 3, gel particles 20, negatively charged by anions A^" (Fig. 2) electrostatically attract positive grease particles 31 , and remove them from substrate 22. Grease 31 is strongly fixed to gel microporous structure 20, which creates a gel-grease system 30, whereas the positive ions layer 32 formed about nanoparticle 30, along with the agitation of washing solution 33, causes nanoparticle-dirt system 30 to detach from the surface 34 to be cleaned, and to disperse it into washing solution 32.

[0017] From another point of view, gel-grease system 30 becomes a sort of neutral micelle that drastically limits the electrostatic attractive forces between micelles 35 of the surfactant of the detergent, spacing them apart, and then substantially preventing them from forming larger surfactant aggregates. In these conditions, the surfactant is exploited more effectively. This way, all the nanoparticles that are not associated become substantially active.

[0018] This reduces the amount of surfactants that are used in the detergent formulations, however, without affecting the detergent power of the final product. This way, a part of the surfactant is replaced by chemically and biologically inert and non-toxic products.

[0019] Therefore, the introduction of the above mentioned gel in the detergent formulations has the advantage of reducing their environmental impact, since it drastically reduces the surfactants, while maintaining the detergent power. [0020 ] Moreover, with the gel-containing formulation, detergents are obtained that are less expensive, while having a same detergent power.

[ 0021 ] Furthermore, the detergents obtained by adding the gel are particularly well-suited for body hygiene, since it has been shown that low CMC values have a less irritating effect on the skin.

[0022 ] The anions adsorbed on the nanoparticles are indicated as selective anions because they differ from one another for their specific effects in connection with a particular type of dirt. More in detail,

bicarbonate ions distinguish themselves for a whitening, degreasing and odour-absorbing effect;

hypochlorite ions distinguish themselves for a whitening and bactericidal effect;

oxalate ions distinguish themselves for a whitening and rust-preventing effect;

citrate ions distinguish themselves for a scale-preventing effect;

acetate ions have scale-preventing and degreasing effects,

peroxyacetate ions have whitening and bactericidal effects.

[ 0023] Advantageously, the component comprises an amount of a thickening agent, which can be an organic agent such as xanthan gum or guar gum, or an inorganic agent, such as bentonite, of a type compatible with a detergent use. This is to enhance the rheological balance and therefore the stability of the gel.

[ 0024 ] According to an aspect of the invention, the use is provided of such a component in a surfactant-containing detergent. In particular the surfactants have a weight percentage lower than 5% of the detergent, more in particular, the surfactants comprise an anionic surfactant that has a weight percentage set between 1 % and 4%.

[ 0025] Advantageously, the gel nanoparticles comprise a compound selected from the group consisting of: amorphous silica; aluminium hydroxide; activated alumina.

As is described hereinafter, amorphous silica has the advantage of being obtained starting from low cost raw materials, such as the sodium silicate, which reduces the gel manufacturing costs. Moreover, the gel obtained starting from sodium silicate has the advantage of being substantially transparent, as it is desirable in some types of detergents. On the contrary, alumina or aluminium hydroxide-containing gels are normally white.

[ 0026 ] According to another aspect of the invention, a process for making a component for detergents, said component having the form of a gel, comprises the steps of:

forming a gel comprising water and nanoparticles that have a size set between 5 and 250 nanometres;

adsorbing selective anions on the nanoparticles, wherein the selective anions are selected from the group consisting of: bicarbonate anions (HCO3 ); hypochlorite anions (CIO-); acetate anions (CH3COO^"); oxalate anions (O(CO)2O⁼); citrate anions (C6H5O7^3"); peroxyacetate anions (CH3COOO-); a combination of such selective anions,

wherein the water has a weight percentage set between 70% and 95% of the total weight of the component. As already indicated more in detail, each selective anions adsorbed on the nanoparticles distinguish itself for a specific action in connection with a particular type of dirt.

[ 0027 ] Advantageously, the step of forming the gel comprises the steps of:

prearranging a water solution of a nanoparticles-forming compound selected between a silicate and a water-soluble aluminium salt, said water solution having a predetermined initial pH value;

mixing the solution of the nanoparticles-forming compound with a gelling agent configured to cause the pH value to change until it reaches a final pH value adapted to cause amorphous silica SiO2.H2O or aluminium hydroxide AI(OH)3 to precipitate, respectively, from the water solution, i.e. adapted to form a gelification mixture, and to cause a step of gelling the gelification mixture, forming nanoparticles of amorphous silica S1O2.H2O or of aluminium hydroxide AI(OH)3, respectively. In other words, the nanoparticles are formed in situ by a controlled gelling process starting from the solution of the nanoparticles-forming compound.

[ 0028 ] In particular, the water solution of a nanoparticles-forming compound is a solution of a silicate, in particular of an alkali metal selected from the group consisting of: Lithium (Li), Sodium (Na) and Potassium (K), or a combination thereof, and the step of mixing occurs with a pH decrease down to a final pH value lower than 9, preferably close to 9, in order to cause a gel comprising amorphous silica nanoparticles to form by a precipitation step. In particular, the silicate of an alkali metal has the general formula xSi02:M20, wherein M is selected from the group consisting of: Li, Na and K, or a combination thereof, and x is a molar ratio between moles of silica S1O2 and moles of M2O.

[0029] As an alternative, the water solution of a nanoparticles-forming compound is a solution of an aluminium salt, for example Aluminium chloride (AlC ) or Aluminium sulfate (Al2(SO4)₃), or Aluminium nitrate (AI(N03)3) or a combination thereof. In this case, the gelling agent can be a hydroxide selected from the group consisting of: sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2) and the step of mixing the solution of the nanoparticles-forming compound with the gelling agent occurs with a pH increase up to a final pH value higher than 5, preferably higher than 8, in order to cause a gel comprising aluminium hydroxide nanoparticles to form by a precipitation step. This way, aluminium, which is an amphoteric element, is prevented from being changed from insoluble hydroxide into soluble aluminate. The gelling, i.e. the precipitation of aluminium hydroxide, is actually carried out at a pH set between 5 and 11 , preferably at pH of about 8.

[0030] More in detail, if the nanoparticles-forming compound in water is a soluble aluminium salt comprising a given anion, the gelling agent is selected among the hydroxides of cations that form a soluble salt with this anion.

[0031] For instance, if aluminium chloride or aluminium sulfate or aluminium nitrate is the nanoparticles-forming compound, the gelling agent can be sodium hydroxide, and the gel formation reactions are respectively:

AlCb + 3 NaOH AI(OH)₃ + 3 NaCI;

- AI₂(SO₄)3 + 6 NaOH - 2AI(OH)₃ + 3Na₂SO4.

AI(NO₃)₃ + 3NaOH - AI(OH)₃ + 3NaNO₃.

[0032] The gelling agent can be Chlorine. Chlorine, besides gelling the silicate solution, causes the formation of specific hypochlorite anion CIO-, which has a whitening and bactericidal effect, as shown hereinafter. More in detail, the reaction takes place:

CI2 + H2O -> H⁺ CIO- + H⁺CI ^"

at room temperature, by which ions H⁺ are formed that cause the solution to gel and hypochlorite ions to be adsorbed on the microporous nanoparticle surface.

[ 0033 ] The gelling agent can be carbon dioxide. In fact, in this case, if the water solution of the precursor is brought into contact with CO2, the latter reacts with the water to form carbonic acid H2CO3, an instable acid, according to the reaction

CO2 (g) + H2O (I)— ->H₂CO₃ < > HCO3- + H⁺

where free H⁺ ions are formed, which lowers the pH of the sodium silicate solution until a gelling occurs, which occurs starting from when a pH value close to 9 is reached. In this reaction, bicarbonate ions HCO3^' are also formed, which have a degreasing and whitening effect.

[ 0034 ] The gelling agent can be a water-soluble compound adapted to provide, starting from a concentration set between 1 N and 5N, a solution having a pH value lower than or equal to 9.

[ 0035 ] The gelling agent can be a buffer solution, comprising in particular sodium acetate and acetic acid (pad ChbCOONa/Ch COOH), or sodium oxalate and oxalic acid (pad NaOOC-COONa /HOOC-COOH), or sodium citrate and citric acid (CeHsOyNas/CeHsO?). Effects and advantages specific of these compounds, acids and respective salts, and of the buffer solutions, will be described hereinafter.

[ 0036 ] Accordingly, the gel formation reactions, i.e. the reactions of forming amorphous silica SiO2.H2O from silicate, in this case, from sodium silicate Na2SiO3, are the following:

- 2CH3COOH + ChbCOONa +Na₂SiO₃ S1O2.H2O + 3 CHsCOONa

- 2 CeHsOy + NasCeHsO? + 3 Na2SiO₃ -> 3 S1O2.H2O + 3 NasCeHsO?

- HOOC-COOH + NaOOC-COONa + Na2SiO₃ - S1O2.H2O + 2NaOOC-COONa

[ 0037 ] For instance, the sodium silicate solution has a pH set between 1 1 and 13.5. [ 0038 ] Preferably, the nanoparticles-forming compound in water is sodium silicate Na2Si03, as described. Sodium silicate is preferable due to its low cost and also because it leads to a transparent gel.

[ 0039] Preferably, the sodium silicate solution has a concentration set between 5% and 10% by weight. In particular, the step of prearranging a water solution of sodium silicate as the nanoparticles-forming compound comprises a step of diluting an initial solution of Na2Si03 that has, for instance, a density set between 38°Be and 40°Be.

[ 0040 ] For example, preferably in the case of use of a silicate as the nanoparticles-forming compound, the gelling agent is selected from the group consisting of: hydrochloric acid (HCI); nitric acid (HNO3); phosphoric acid (H3PO4); sulfuric acid (H2SO4); perchloric acid (HCIO4); boric acid (H3BO3); acetic acid (CH3COOH); sodium acetate (Ch COONa); oxalic acid (HOOC- COOH); sodium oxalate (NaOOC-COONa); propionic acid (CH3CH2COOH); citric acid (C6H8O7); sodium citrate (Na3C6Hs07); peroxyacetic acid (CH3COOOH); sodium bicarbonate (NaHC03); ammonium sulfate ((NH₄)2S04); ammonium chloride (NH4CI); a combination thereof. Correspondingly, the gel formation reactions, i.e. the reactions for producing amorphous silica S1O2.H2O from silicate, in this case, from sodium silicate Na2Si03, are the following:

Na₂Si0₃ + 2HCI S1O2.H2O + 2 NaCI;

Na2Si0₃ + 2HNO3 - S1O2.H2O + 2 NaNOs;

3 Na₂Si0₃ + 2 H3PO4 -» 3 S1O2.H2O + 2 Na₃P04;

Na2Si03 + H2S0₄ -» S1O2.H2O + Na2S04;

- Na₂Si0₃ + 2 HCIO4 -» S1O2.H2O + 2 NaCI0₄;

3 Na₂Si0₃ + 2 H3BO3 -» 3 S1O2.H2O + 2 NasBOs;

- Na₂Si0₃ + 2 CH3COOH -» S1O2.H2O + 2 CHsCOONa;

Na₂Si0₃ + HOOC-COOH -» S1O2.H2O + Na₂C₂04;

- Na₂Si0₃ +2 CH3CH2COOH - Si0₂.H20 + 2CHsCH2COONa;

- 3 Na₂Si03 + 2 CeHsO? 3 S1O2.H2O + 2 NasCeHsOz;

Na₂Si0₃ + 2 CH3COOOH ^ S1O2.H2O + 2 ChhCOOONa;

- Na₂Si0₃ + 3 NaHCOs -> S1O2.H2O + 2 Na₂C0₃ +NaHC0₃;

- Na₂Si0₃ + (NH4)2S0₄ -> S1O2.H2O + Na₂S0₄ + 2NH₃†; NaaSiOs + 2NH₄CI - Si0₂.H₂0 +2 NaCI +2NH₃.

[ 0041 ] Gelling agents comprising citric acid and/or sodium citrate, i.e. solutions of one of these two compounds, or the corresponding buffer solution, besides causing a gelification of the silicate solution, also cause specific citrate ions to be produced, with a scale-preventing effect.

[ 0042 ] Gelling agents comprising acetic acid and/or sodium acetate, i.e. solutions of one of these two compounds or the corresponding buffer solution, besides causing a gelification of the silicate solution, also cause specific acetate ions to be produced, with a scale-preventing and degreasing effect

[ 0043] Gelling agents comprising oxalic acid and/or sodium oxalate, i.e. solutions of one of these two compounds or the corresponding buffer solution, besides causing a gelification of the silicate solution, also cause specific oxalate ions to be produced, with a whitening power and rust preventing effect.

[ 0044 ] A gelling agent comprising sodium bicarbonate, besides causing a gelification of the silicate solution, also causes specific bicarbonate ions to be produced, with a degreasing and whitening effect.

[0045] A gelling agent comprising peroxyacetic acid, besides causing a gelification of the silicate solution, also causes specific peroxyacetate ions to be produced, with a whitening and bactericidal effect.

[ 0046] Preferably, this compound, in particular an inorganic acid, has a concentration set between 1 N and 5N. Such dilution is useful to avoid that lumps are formed, due to the electrostatic interaction between the ions produced from the acids in the water solution.

[ 0047 ] As well known, the pH of a solution of a silicate depends, in an obvious way for a skilled person, on the concentration and on the molar ratio, i.e. on the ratio between S1O2 moles and Na₂0 moles of the effective ionic formula of the silicate, Na₂0 xSi0₂, in this case sodium silicate, which is normally indicated by the simplified formula Na₂Si03, for the sake of simplicity.

[ 0048 ] Preferably, the step of adsorption of selective anions is carried out by bringing the gelification mixture into contact with an adsorption reagent selected from the group consisting of:

carbon dioxide (C0₂), in the form of a gas, in order to cause HCO3" ions to be adsorbed on the nanoparticles; chlorine (CI2), in the form of a gas, in order to cause CIO- ions to be adsorbed on the nanoparticles;

sodium bicarbonate (NaHCOs), in order to cause bicarbonate ions to be adsorbed on the nanoparticles;

- oxalic acid (HOOC-COOH), in order to cause 0(CO)20⁼ ions to be adsorbed on the nanoparticles;

citric acid (ΟθΗβΟζ), which has a scale-preventing effect, in order to cause

C6H5O7^3" ions to be adsorbed on the nanoparticles;

acetic acid solution (CH3COOH), in order to cause CH3COO- ions to be adsorbed on the nanoparticles,

so as to obtain components comprising specific selective anions, which imparts specific properties to the detergents in connection with particular types of dirt, as previously indicated.

[ 0049 ] In an exemplary embodiment, the step of adsorbing selective anions on the nanoparticles is carried out in situ during the step of mixing and of gelling the gelification mixture.

[ 0050] In particular, the gelling agent can be selected among the compounds capable of forming selective anions, in other words the gelling agent itself is adapted to provide these selective anions. In particular, in this case, the gelling agent can be selected from the group consisting of:

chlorine gas;

carbon dioxide gas;

a salt or an organic acid, which in water is adapted to provide a solution having a pH value lower than or equal to 9, starting from a concentration between 1 N and 5N,

or a combination thereof. In the case of CI2 and of CO2, the gel formation reactions take place:

Na₂Si0₃ + CI2 (g) S1O2. H2O + NaCIO + NaCI

Na₂Si0₃ + 2C0₂ (g) -» S1O2. H2O + 2NaHC0₃,

respectively.

[ 0051 ] In particular, the gelling agent comprises chlorine gas and, during the step of mixing and gelling, the gelification mixture is maintained at a reaction temperature lower than a predetermined temperature, in particular the reaction temperature is close to or lower than 20°C. In order to form the gel in the presence of chlorine gas, the reaction temperature must be maintained at about 20°C, in order to avoid the formation of different compounds.

[0052] As an alternative, the step of adsorbing selective anions on the nanoparticles is carried out on the gel once the step of mixing and gelling the gelification mixture has occurred

[ 0053] According to a further aspect, it falls within the scope of the invention a detergent comprising a component as described above, and/or obtained according to the above described method.

[ 0054] In an exemplary embodiment, the step of forming a gel comprises a step of dispersing in water nanoparticles having a specific surface area, i.e. a ratio between the overall surface of the nanoparticle and the weight of the particle set between 250 and 450 m²/g. In other words, the gel is produced from already formed nanoparticles. In particular, these nanoparticles comprise activated alumina.

[ 0055] Advantageously, the process comprises a step of adding a thickening agent, which can be of an organic type, such as xanthan gum, guar gum, or of an inorganic type, for example a bentonite compatible with detergents formulations. As anticipated, the thickening agent is used to assist the Theological balance.

[ 0056 ] The amount of thickening agent can generally be set between 0.1 % and 0.3% by weight in the final detergent.

[0057 ] The step of mixing the solution of the nanoparticles-forming compound with a gelling agent can be carried out in a conventional container equipped with an agitator and, possibly, with a recycle duct. Preferably, the agitator comprises blades configured in such a way to limit foam formation.

[ 0058 ] In an operating mode, some water is added to the solution of the nanoparticles-forming compound, and then the gelling agent it is added gradually, always under stirring. A recycle stream is permanent caused to flow between a discharge port and an inlet port of the container. The recycle can be useful for enhancing the mixing.

[ 0059] The end of the step of mixing and gelling can be identified by reading the pH value of the mixture, in particular it can be identified when the pH value drops below a predetermined value, which is lower than or equal to 9.

[0060] In order to form the gel, different ratios between the silicate solution and the initial osmotized water can be selected. For instance, if the nanoparticles-forming compound in water is sodium silicate, in a sodium silicate solution of density 38-40°Be, i.e. 1.4 g/cm³, and a concentration of about 35% by weight, volume ratios (H20:Na2Si03) can be used from 4:1 to 8: 1 , as shown in table 1. Preferably, a ratio of 6:1 is used.

- Table 1 -

Water/silicate volume ratio during the gel formation step

[0061] It falls within the scope of the invention also a detergent having a formulation as indicated below:

a gel as described above, in a weight percentage between 50% and 85%; surfactants, in a weight percentage lower than the 5%;

- further water in addition to the water contained in the gel.

[0062] The presence of surfactants, even at a low concentration, is necessary for lowering the surface tension of the water, so that the gel can express its detergent power.

[0063] In particular, these surfactants may comprise:

- an anionic surfactant, in a weight percentage set between 1 % and 3%; a non-ionic surfactant, in a weight percentage lower than 1 %.

[0064 ] It falls within the scope of the invention also a dishwashing detergent having a formulation as indicated below:

a gel as described above, in a weight percentage set between 50% and 85%; surfactants, in a weight percentage set between 1 % and 4%; further water in addition to the water contained in the gel.

[0065] In particular, the surfactants may comprise:

an anionic surfactant, in a weight percentage set between 1% and 3%; a non-ionic surfactant, in a weight percentage lower than 1 %.

[ 0066 ] Other minor components can be contained in the dishwashing detergent, such as perfume, for instance in an amount of 0÷0.5% by weight.

[ 0067 ] Comparing this formulation with the commercially available dishwashing detergents formulations, i.e.:

Anionic and/or non-ionic and/or amphoteric surfactants: 10÷35%

Ethanol: 0÷3%

Perfume: 0÷0.5%

Inorganic salts: 0÷5%

Water balance to 100%,

a drastic decrease is observed of the content of surfactants, which means an important decrease of the environmental impact and of the production cost, above all, since about 90% of the gel is water.

[ 0068 ] It falls within the scope of the invention also laundry detergents having a formula comprising:

a gel as described above, in a weight percentage set between 50% and

85%

surfactants, in a weight percentage set between 1% and 4%;

further water in addition to the water contained in the gel.

[ 0069 ] In particular, the surfactants may comprise:

[ 0070 ] Other minor components can be contained in the dishwashing detergent, such as perfume and preservatives, for example in an amount of 0.2÷0.5% by weight.

[ 0071 ] Comparing this formula with the commercially available laundry detergents formulations, i.e.:

anionic and non-ionic surfactants: 10-35%

amphoteric surfactants: 0-5% Ethanol / isopropyl alcohol: 0-10%

Sodium citrate: 0-5%

anti-redeposers: 0.2-5%

other components such as perfume, enzymes, optical brighteners, antifoam agents, silicones, stabilizers, preservatives: 0.2-0.5%

water balance to 100%,

a significant decrease is observed also in this case of the content of surfactants, which remarkably reduces the environmental impact and the production cost.

Brief description of the drawings

[0072] The invention will be now shown with the following description of its exemplary embodiments, exemplifying but not limitative, with reference to the attached drawings in which:

Fig. 1 is diagram that diagrammatically shows the trend of the properties of a surfactant versus its concentration;

Fig. 2 diagrammatically shows the structure of a nanoparticle after adsorption of selective anions;

Fig. 3 diagrammatically shows the mechanism of action of a surfactant in comparison with the mechanism of action of the nanoparticles;

Figs. 4, 5 and 6 are comparative CMC curves for three different types of detergents, for hand and machine laundry, for wool and delicate fabrics, and for dishwashing, in the presence of and without the component according to the invention.

Examples

Gel

[0073] Several gels have been produced that can be used as components for detergents, starting from:

a sodium silicate (Na2Si03) solution as the nanoparticles-forming compound, hydrochloric acid (HCI) as the gelling agent, and solid sodium bicarbonate (NaHC03) to provide selective anions, in this case bicarbonate ions (example 1 );

a solution of potassium silicate (K2S1 3) as the nanoparticles-forming compound, pure carbon dioxide (CO2) as the gelling agent, and to provide selective anions, also in this case bicarbonate ions (example 2).

[0074 ] Exemplary pel n. 1

60 litres of osmotized water were arranged into a container equipped with an agitator, to which were added 10 litres of Na2Si03 of the density of 38°Be, thus obtaining a Na2Si03 water solution.

Then 35 litres HCI were added slowly as an 1 N water solution, which caused the reaction:

Na₂Si0₃ + 2HCI -> S1O2.H2O + 2 NaCI

to occur until completely gelling the obtained mixture.

Subsequently, 4 Kg of solid sodium bicarbonate (NaHC03) were added to the mixture in the form of a gel, which were dissolved into the mixture forming bicarbonate ions (HCO3^"). The agitation was continued until complete dissolution, causing the HCO3^" ions to be adsorbed and obtaining a gel with these selective ions adsorbed on its own surface.

[ 0075] Exemplary gel n. 2

100 litres of osmotized water were arranged into a container equipped with an agitator, to which were added 12.5 litres of K2S1O3 at a concentration of 50% by weight and of a density of 35°Be, thus obtaining a K2Si0₃ water solution. Subsequently, 35 litres of HCI were added slowly as an 1 N water solution, causing the reaction:

Na₂Si0₃ + 2HCI - S1O2.H2O + 2 NaCI to occur until completely gelling the obtained mixture, at pH < 9.

[ 0076 ] Exemplary pel n. 3

50 litres of osmotized water were arranged in a jacketed container equipped with an agitator and with a bubbling means, to which were added 14 kg of Na2Si03 of the density of 38-40°Be, thus obtaining a 7.65% by weight Na2Si0₃ water solution.

Subsequently, 2.9 Kg of chlorine gas were bubbled slowly, ensuring a good contact between the liquid phase and the gas. The reaction was maintained at a temperature of 20°C in order to ensure the production of the hypochlorite ion, according to the reaction:

Na₂Si0₃ + CI2 -» S1O2.H2O + NaCIO + NaCI, which was adsorbed on the gel surface, imparting it whitening and bactericidal properties. The pH value at the end of the gelling step was 8.9.

[0077 ] Exemplary pel n. 4

40 litres of osmotized water were arranged into a container equipped with an agitator and a bubbling means, to which were added 12.5 kg of Na2Si03 of the density of 38-40°Be, thus obtaining a 8.3% by weight Na2Si03 water solution. Subsequently, 3.3 Kg of CO2 gas were bubbled slowly, ensuring a good contact between the liquid phase and the gas. In these conditions, the reaction occurred:

Na2Si0₃ + 2C0₂ (g) -> S1O2.H2O + 2NaC03.

The pH value at the end of the gelling step was 9.

[ 0078] Exemplary pel n. 5

60 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 8.2 kg of K2S1O3 at a concentration of 50% by weight and with a density of 35°Be, thus obtaining a 6% by weight K2S1O3 water solution.

Subsequently, 18 litres of a 3N acetic acid (CH3COOH) solution were added slowly until gelling. In these conditions, the gel was formed at the same time as specific acetate anions (CH3COO ) were adsorbed on the gel, which have a degreasing and scale-preventing effect, according to the reaction:

K2S1O3 + 2CH3COOH S1O2.H2O + 2 CH3COOK.

[0079 ] Exemplary pel n. 6

60 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 14 kg of Na2Si03 with a density of 38- 40°Be, thus obtaining a 6.6% by weight Na2Si03 water solution.

Subsequently, 16 litres of a 5N oxalic acid solution were added slowly until gelling. In these conditions, the gel was formed at the same time as specific oxalate anions ( OC-COO^") were adsorbed on the gel, which have a whitening and rust preventing effect, according to the following reaction:

Na₂Si0₃ + HOOC-COOH S1O2.H2O + NaOOC-COONa. [0080] Exemplary ael n. 7

35 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 10 kg of Na2Si03 with density of 38-40°Be, thus obtaining a 7.8% by weight Na2Si03 water solution.

Subsequently, 9.6 litres of a 4N citric acid solution were added slowly until gelling. In these conditions, the gel was formed at the same time as specific citrate anions were adsorbed on the gel, which have a scale-preventing effect, according to the reaction:

3 Na₂Si0₃ + 2 CeHsO? 3 S1O2. H2O + 2 NasCeHsOr.

[ 0081] Exemplary gel n. 8

50 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 15 kg of Na2Si03 with a density of 38- 40°Be, thus obtaining an 8.1 % by weight Na₂Si03 water solution.

Subsequently, 17 litres of a 5N peroxyacetic acid solution were added slowly until gelling. In these conditions, the gel was formed at the same time as specific peroxyacetate anions were adsorbed on the gel, which have a whitening and bactericidal effect, according to the reaction:

Na₂Si0₃ + 2 CHsCOOOH Si0₂.H₂0 + 2 ChhCOOONa.

[0082] Exemplary gel n. 9

80 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 20 kg of Na2Si03 with a density of 38-40°Be, thus obtaining a 7% by weight Na2Si03 water solution.

Subsequently, 29 litres of a 4N solution ammonium sulfate were added slowly until gelling at pH 9, causing the reaction:

Na₂Si0₃ + (NH₄)₂S04 -» Si0₂.H₂0 + Na₂S0₄ + 2NH₃†.

5 Kg of solid sodium citrate (NasCeHsO?) were then added to the mixture in the form of a gel, which were dissolved into the mixture forming citrate ions (C6H5O7³ ). The agitation was continued until complete dissolution, causing an adsorption of the citrate ions, which have a scale-preventing effect, obtaining a gel with these selective ions adsorbed on its own surface.

[0083] Exemplary gel n. 10

65 litres of osmotized water were arranged into a container equipped with an agitation means, to which were added 12 kg of Na2Si0₃ with a density of 38-40°Be, thus obtaining a 5.5% by weight Na₂Si03 water solution. Subsequently, 27.5 litres of a solution of 2.5N acetic acid and of 2N sodium acetate were added slowly until gelling. In these conditions, the gel was formed at the same time as the specific acetate anions (CH3COO-) were adsorbed on the gel, which have a degreasing and scale-preventing effect, according to the reaction:

2CH3COOH + CHsCOONa +Na₂Si0₃ -» S1O2.H2O + 3 CHsCOONa.

[0084 ] Exemplary gel n. 11

50 litres of a water solution of aluminium chloride of concentration 150 g/litre were prepared in a container equipped with an agitation means. Subsequently, always under stirring, 38.5 litres of 15% caustic soda were added until gelling, at a final pH of 8.1. In these conditions, a microporous gel was formed, according to the reaction:

AlC +3 NaOH ->AI(OH)₃ + 3NaCI.

3.5 Kg of sodium bicarbonate were then progressively added into the same container. The agitation was continued until complete dissolution, causing an adsorption of the bicarbonate ions, and obtaining a gel with these selective ions adsorbed on its own surface.

[ 0085] Exemplary gel n. 12

30 litres of a water solution of aluminium nitrate of concentration 200 g/litre were prepared in a container equipped with an agitation means. Subsequently, always under stirring, 20.8 Kg of a 15% lime slurry were added until gelling, at a final pH of 7.8. In these conditions a microporous gel was formed, according to the following reaction:

2AI(N0₃)3 +3Ca(OH)₂ ->2AI(OH)₃ + 3Ca(N0₃)₂ 5 Kg of sodium citrate were then progressively added into the same container.

The agitation was continued until complete dissolution, causing an adsorption of the citrate ions, obtaining a gel with these selective ions adsorbed on its own surface.

[0086] Exemplary gel n. 13

35 litres of a water solution of aluminium sulfate of concentration 170 g/litre were prepared in a container equipped with an agitation means. Subsequently, always under stirring, 34 litres of a 15% KOH solution were added until gelling, at a final pH of 8. In these conditions, a gel microporous was formed, according to the following reaction: Al2(S0₄)3 + 6 KOH - 2AI(OH)₃ + 3 K2SO4.

4 Kg of solid sodium acetate were then progressively added into the same container. The agitation was continued until complete dissolution, causing an adsorption of the acetate ions, which have a degreasing and scale-preventing effect, obtaining a gel with these selective ions adsorbed on its own surface.

Detergent Formulations

[ 0087 ] Three known detergents were prearranged as reference products: a detergent for hand and machine laundry;

a detergent for wool and delicate fabrics;

- a dishwashing detergent.

[ 0088 ] As described more in detail hereinafter, three detergents containing the component according to the invention, indicated hereinafter as test detergents, were prepared for hand and machine laundry, for wool and delicate fabrics and for dishwashing.

[ 0089] In order to evaluate and characterize in laboratory the different formulations of detergents, a Kruss-K100MK3 processor tensiometer was used, which can automatically determine the following parameters:

surface tension (surfactant - air);

surface tension (surfactant - oil);

- critical micellar concentration (CMC).

[ 0090 ] The CMC curves of the three known detergents were determined as well as the curves of the three test detergents, in the form of tension (mN/m) vs. detergent concentration plots. These curves are shown:

in Fig. 4, for detergents for hand and machine laundry;

- In Fig. 5, for detergents for wool and delicate fabrics;

In Fig. 6, for dishwashing detergents,

respectively as

curves 41 , 51 and 61 for the three reference detergents;

curves 42, 52 and 62 for the three test detergents.

[ 0091 ] From Figs. 4 and 5 it is observed how the test detergents for laundry and for wool and delicate fabrics always show a surface tension higher than the corresponding reference detergents, regardless of the concentration value. The contrary occurs in the case of dishwashing detergents, as shown in Fig. 6.

[ 0092 ] Starting from the curves of Figs. 4, 5 and 6, the critical micellar concentrations or charges were calculated, which are given in Table 2. As it can be observed, the CMC values of each test detergent are remarkably lower than the CMC values of the corresponding reference detergents.

- Table 2 - CMC values of the test detergents

and of the reference detergents, in mg/litre

a) Detergent for dishwashing

[ 0093] Different inventive formulations for dishwashing were investigated in laboratory and compared with the commercially available detergents. A reference commercial dishwashing detergent has been identified having the following formulation:

Anionic surfactants: 5÷15%;

Non-ionic surfactants: < 5%;

Minor components: preservatives, perfume.

[ 0094 ] An exemplary dishwashing detergent was prepared according to the invention, containing an amount of gel of the type of exemplary gel n.1 , which had bicarbonate ions adsorbed on the gel surface, and had the following formula:

gel with bicarbonate ions: 75%;

anionic surfactants: 1.35%;

non-ionic surfactants: 0.5%;

minor components: preservatives.

[ 0095] The performances of this gel-containing detergent were compared with of the reference detergent, at various detergent concentrations in the washing solution. More in detail, comparative tests were performed for removing a predetermined load of grease on microscopy slides. The amount of grease present on the slides was normalized at 0.4 g for each glass slide, measuring the weight by a Mod. CP124S Sartorius analytic scale.

[ 0096] The slides were immersed into a rinsing water, i.e. into a solution of the detergent in 500 ml of water from the aqueduct maintained at 40°C, and were slowly rotated (180 RPM) during 60 minutes.

[ 0097 ] Washing solutions were used at decreasing concentrations of the reference detergent and of the nano-detergent, starting from the concentration recommended by the producer, assumed as 100% concentration, and then decreasing it progressively to 80%, 60%, 40% and 20%.

[0098 ] The slides were then rinsed out with distilled water and dried with hot air.

[0099] For each sample of slides, the brightness of the clean glass slides, of the dirty slides and of the washed slides was measured. The brightness measurements were carried out by a model ETB-0833 (BRAND) 20° 60° 85° glossmeter. On the basis of these measurements, the cleaning ratio was calculated as an efficiency parameter of the detergent. The results are given in Table 3.

[0100] As Table 3 shows, the performances of both detergents are practically identical for any detergent concentration value in the washing solution, with the advantage, however, that the exemplary detergent of the invention contains about 0 times less surfactants.

- Table 3 -

Comparative tests with dishwashing detergents g. of detergent / Cleaning ratio

Cone.

500 ml water Test detergent Reference detergent

100% 3.70 98.56% 98.58%

80% 3.00 98.58% 98.09%

60% 2.22 98.73% 98.82%

40% 1.50 98.43% 98.29%

20% 0.75 95.93% 95.85%

MEDIA 98.00% 97.90% b) Detergent for laundry

[0101] Several inventive formulations for laundry were investigated in laboratory and compared with the commercial detergents to understand their behaviour. A reference commercial laundry detergent has been identified having the following formulation:

anionic surfactants: 5÷15%

non-ionic surfactants: < 5%

soap, methylchloroisothiazoline, methylisotioazolinone, perfume.

[0102] An exemplary laundry detergent was prepared according to the invention, containing an amount of gel of the type of exemplary gel n.6, which had the following formulation:

gel with oxalate ions: 75%

anionic surfactants: 1 %

minor components : preservatives, perfume.

[0103] The performances of this gel-containing detergent were compared with the reference detergent. More in detail, comparative washing tests were performed on standard spots. The washing tests were made using aqueduct water as the solvent, at a ratio as indicated by the producer, and maintaining the solution at a temperature of 40°C for a cycle of washing that lasted 60 minutes.

[0104] For the evaluation, the spot photometric values were read by a model PCE-RGB (PCE Group) spectral colorimeter. Good results were obtained, since the same detergents capacities as the reference detergents could be attained with much less surfactant. The results are given in Table 4, where the photometric values refer to the resulting chromatic vector (x,y,z). The higher this value, the closer is the reading to the white colour, and therefore the more effective is the washing.

[0105] As table 4 shows, the performances of the exemplary laundry detergent are comparable with those of the reference detergent, when they are not better, however, with the advantage that the exemplary detergent of the invention contains about 10 times less surfactants. - Table 4 -

[0106] Similar results are obtained using formulations of detergents comprising commercially available products and components obtained by aluminium salt as nanoparticles-forming compound, wherein the nanoparticles are based on aluminium hydroxide.

[0107] The foregoing description of specific examples of the component for detergents according to the invention, and of methods to obtain this component, will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.

Claims

Use of a component having the form of a gel, said component comprising:

water, in a weight percentage set between 70% and 95% of the total weight of said component;

nanoparticles having a size set between 5 and 250 nanometres; selective anions selected from the group consisting of:

bicarbonate anions (HCO3^");

hypochlorite anions (CIO );

acetate anions (CH3COO^");

oxalate anions (O(CO)2O⁼);

citrate anions (C6H5O7^3");

peroxyacetate anions (CH3COOO );

a combination thereof,

wherein said selective anions are adsorbed on said nanoparticles, in a detergent containing a surfactant.

The use of said component, according to claim 1 , wherein said detergent comprises said surfactant at a weight percentage lower than 5%.

The use of said component, according to claim 1 , wherein said surfactant comprises a weight percentage of an anionic surfactant set between 1% and 4%.

Use of said component, according to claim 1 , wherein said nanoparticles comprise a compound selected from the group consisting of:

amorphous silica;

aluminium hydroxide;

activated alumina.

A process for making a component for detergents, said component having the form of a gel, said process comprising the steps of:

adsorbing selective anions on said nanoparticles, wherein said selective anions are selected from the group consisting of:

bicarbonate anions (HCO3 ); hypochlorite anions (CIO^");

acetate anions (CH3COO^");

oxalate anions (O(CO)2O⁼);

citrate anions (C6H5O7^3");

peroxyacetate anions (CH3COOO^")

a combination of such selective anions,

wherein said water has a weight percentage set between 70% and 95% of the total weight of said component.

6. A process according to claim 5, wherein said step of forming a gel comprises the steps of:

adding a gelling agent to said water solution and mixing said water solution of said nanoparticles-forming compound with a gelling agent configured to cause the pH value to change until it reaches a final pH value adapted to cause amorphous silica or aluminium hydroxide to precipitate from said water solution, respectively, so as to form a gelification mixture, and to cause a step of gelling said gelification mixture forming a gel comprising nanoparticles of amorphous silica or of aluminium hydroxide, respectively.

7. A process according to claim 6, wherein said water solution of a nanoparticles-forming compound is a solution of a silicate of an alkali metal selected from the group consisting of: Lithium; Sodium; Potassium; a combination thereof, and said step of mixing occurs with a pH decrease down to a final pH value lower than 9, preferably close to 9, in order to cause a gel comprising amorphous silica nanoparticles to form by a precipitation step.

8. A process according to claim 6, wherein said water solution of a nanoparticles-forming compound is a solution of an aluminium salt, said gelling agent is a hydroxide selected from the group consisting of: sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH OH), calcium hydroxide (Ca(OH)2), and said step of mixing said solution of said nanoparticles-forming compound with said gelling agent occurs with a pH increase up to a final pH value higher than 5, preferably higher than 8, in order to cause a gel comprising aluminium hydroxide nanoparticles to form by a step of precipitation.

9. A process according to claim 6, wherein said gelling agent is Chlorine.

10. A process according to claim 6, wherein said gelling agent is Carbon dioxide.

11. A process according to claim 6, wherein said gelling agent is a water soluble compound adapted to provide, starting from a concentration set between 1 N and 5N, a solution having a pH value lower than or equal to

9.

12. A process according to claim 6, wherein said gelling agent is a buffer solution selected from the group consisting of:

a buffer solution comprising sodium acetate and acetic acid;

- a buffer solution comprising sodium oxalate and oxalic acid;

a buffer solution comprising sodium citrate and citric acid.

13. A process according to claim 7, wherein said sodium silicate solution has a pH set between 11 and 13.5.

14. A process according to claim 7, wherein said sodium silicate solution has a concentration set between 5% and 10% by weight.

15. A process according to claim 8, wherein said aluminium salt is selected from the group consisting of: Aluminium chloride (AlC ), Aluminium sulfate (Al2(S0₄)3), Aluminium nitrate (AI(N03)3) or a combination thereof.

16. A process according to claim 11 , wherein said water soluble compound adapted to provide, starting from a concentration set between 1 N and 5N, a solution having pH lower than or equal to 9 is selected from the group consisting of:

hydrochloric acid (HCI);

nitric acid (HNO3);

- phosphoric acid (H3PO4);

sulfuric acid (H2SO4);

perchloric acid (HCI0₄);

boric acid (H3BO3); acid acetic (CH3COOH);

sodium acetate (CHbCOONa)

oxalic acid (HOOC-COOH);

sodium oxalate (NaOOC-COONa)

- propionic acid (CH3CH2COOH);

citric acid (C6H8O7);

sodium citrate (Na3C6Hs07);

peroxyacetic acid (CH3COOOH);

sodium bicarbonate (NaHCOs);

- ammonium sulfate ((NH4)2S04);

ammonium chloride (NH4CI);

a combination thereof.

17. A process according to claim 16, wherein said gelling agent has a concentration set between N and 5N.

18. A process according to claim 5, wherein said step of adsorbing selective anions on said nanoparticles is selected from the group consisting of: an adsorption step carried out during said step of mixing and of gelling said gelification mixture;

an adsorption step carried out on said gel after said step of mixing and of gelling said gelification mixture has occurred.

19. A process according to claim 6, wherein said gelling agent is adapted to form said selective anions, and is selected from the group consisting of: chlorine gas;

carbon dioxide gas;

- an organic acid, or a salt, in water adapted to provide, starting from a concentration set between 1 N and 5N, a solution having a pH value lower than or equal to 9.

20. A process according to claim 5, wherein said step of forming said gel comprises a step of dispersing nanoparticles having a specific surface area set between 250 and 450 m²/g into water.

21. A process according to claim 20, wherein said nanoparticles comprise activated alumina.