Epoxy resin-based hardening composition

Abstract

Composition able to be hardened comprising an epoxy resin, one or more unsaturated compounds and a hardening compound. This composition allows to achieve the invisible or low halo effect on the surface of the stone material on which it is applied.

Description

“EPOXY RESIN-BASED HARDENING COMPOSITION”FIELD OF THE INVENTIONThe embodiments described here concern an epoxy resin-based hardening composition, known in the industry as “invisible” or also low halo, which can be used to treat stone material for example, in particular rough surfaces of stone material, such as natural stone for example, for the purpose of impregnating, reinforcing, and / or filling holes, cracks or fissures.The composition is able to be applied on white and / or light-colored stone materials, not very porous and also very porous. Stone materials are understood in their entirety, materials from old quarries, new quarries, future quarries.The hardening composition described here is free of trimethylolpropane triacrylate (TMPTA, CAS n°. 15625-89-5 I EC N°. 239-701-3), or it has a maximum TMPTA content of 1% w / w.BACKGROUND OF THE INVENTIONResin-based compositions for treating rough surfaces of stone material are known, in particular for stone material used for decorating or furnishing outdoor or indoor spaces. These resins are generally used with the aim of impregnating, gluing, reinforcing and / or filling holes, cracks or fissures. Known compositions can also be used for gluing and repairing broken pieces of stone material.Given the intended use of the stone material, it has to have perfectly flat surfaces, generally free of defects, especially when the stone material is of a refined type such as marble, dolomite or white or light-colored quartzites.The slabs of stone material that originate from quarries, despite the treatments and cuttings carried out in the quarry, very often have defects in their surfaces, in particular cracks or fissures, or sometimes even breaks. These damaged marble slabs cannot be used for decoration or furnishing, and a step providing treatment with a composition as indicated above is required. The same type of problem is also found with stone material other than marble.Known epoxy resin compositions for these applications are generally of the two- component type, with a liquid resin to which a hardening compound is added able to react with the resin in order to induce its polymerization and thereby make it solid. The resin and the hardening compound are both in liquid form, so that theycan be applied homogeneously on the stone material and so as to fill the holes, cracks or fissures to be rectified so as to obtain a perfectly smooth surface. In particular applications, these formulations can also be in the form of pastes.The hardening is allowed by the polymeric nature of the compounds based on which the resins are prepared. Depending on the nature of the polymer compounds used, different hardening mechanisms are involved and, therefore, different triggers of the hardening reaction. For example, the hardening reaction can be triggered by exposure to UV rays (photocatalysis) or by exposure to heat (thermal catalysis).A particular property of two-component thermosetting epoxy resins is to have a great wet power on the stone mediums. This is considered a great advantage if treating dark and black materials. Unfortunately, in the case of light color or white materials this property is seen as a major defect. In fact, white or light color stone changes in color, becoming too grey, thus compromising its natural color. This phenomenon is also called “wet effect” and is particularly evident even to the naked eye, comparing a surface of the same material treated with traditional resin, of the type as above, with an untreated one.Indeed, epoxy resins called “invisible”, that is, low halo, have been on the market for more than fifteen years. The composition of these known epoxy resins allows to limit or almost eliminate the wet effect on natural stones. An acrylic monomer, TMPTA as defined above, is generally always used as an unsaturated compound of the formulation in the composition of these known low halo “invisible” resins. The aesthetic purpose of the TMPTA is to limit the wet effect that the epoxy resin would give if it did not contain this component. The w / w percentages of use of the TMPTA in these known compositions generally range from 1% to 50% w / w.It has been experimentally verified for more than fifteen years that epoxy resins containing this acrylic monomer provide aesthetic benefits on all white and light color, porous and non-porous natural stones, where there is a need to not alter the natural color of the treated material.However, due to a new European reclassification, as of 23 November 2023 TMPTA will be labelled “category 2 carcinogen”. This wording makes any compositions for epoxy resins that contain TMPTA unusable, for health reasons,in the scope of application discussed here, leading to the technical problem of replacing these products on the market with products that are equally technically functional but do not contain TMPTA.Document EP 3.835.378 Al describes a two-component, hardening and de- bondable adhesive composition comprising: (i) a first part comprising: (a) epoxy resin; b) 10% to 30% wt. % of monomer (met)acrylate which may be trimethylolpropane triacrylate (cf. paragraphs

[0088] to

[0090] and

[0140] ); c) an electrolyte; d) a solubilizer; and e) a filler; and (ii) a second part comprising: (a) a hardening agent consisting of at least one compound possessing at least two epoxy reactive groups per molecule; b) an accelerator; and c) a filler.The paper Surh Inok et al. doi:10.1016 / J.FCT.2014.01.048 discloses a study showing that TMPTA is a skin irritant at the site of application in rats and mice, both male and female. Increases in the incidence of tumors were observed in male rats and female mice away from the site of application. These findings raise concerns regarding chronic human exposure.Document WO 2022 / 224288 Al describes a composition suitable for hardening comprising an epoxy resin, an unsaturated compound such as trimethylolpropane triacrylate TMPTA (cf. example 1) and a hardening compound. The composition is suitable for hardening by UV photocatalysis and by thermal catalysis.There is therefore the need to perfect a composition for epoxy resin of the “invisible”, low halo type that can overcome this technical drawback.In particular, one purpose of the present invention is to provide an epoxy resinbased hardening composition free of TMPTA, or with a percentage of TMPTA lower than 1% w / w, which however, once applied on a surface to be treated, has the same “invisible” effect, also called low halo, on the treated stone materials.Another purpose of the present invention is to provide an epoxy resin-based hardening composition that is durably very resistant from a chemical point of view, as well as from a mechanical point of view, in particular to the elements.Another purpose is to perfect a method for producing the hardening composition as above.The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.SUMMARY OF THE INVENTIONThe present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.In accordance with the above purposes, the Applicant has developed a composition for epoxy resin which overcomes the limits of the state of the art and eliminates the defects present therein.In accordance with some embodiments, a hardening composition is provided comprising an epoxy resin, at least one unsaturated compound and a nucleophilic hardening compound able to react with the epoxy resin and with the at least one unsaturated compound.In accordance with possible embodiments, the hardening composition described here can be free of TMPTA, or it can have a TMPTA content lower than 1% w / w.The aforementioned at least one unsaturated compound of the hardening composition described here, or the combination of two or more unsaturated compounds described here, effectively replace the TMPTA, while still achieving the result of limiting the wet effect that the epoxy resin would give if this component were not present in it. One or more unsaturated compounds can be used to replace the TMPTA.For example, in the hardening composition described here, one, two, three or even more than three unsaturated compounds can be provided that effectively replace the TMPTA, if it is absent or in the event its content is lower than 1% w / w.According to some embodiments, the aforementioned at least one unsaturated compound can have more than one acrylic, methacrylic or vinyl function, that is, more than one double bond between two carbon atoms.According to some embodiments, the aforementioned at least one unsaturated compound can be an acrylic compound with between 1 and 8 double bonds, in particular between 2 and 5 double bonds, more in particular an acrylic compound with for example three double bond functions between two carbon atoms, or it can be a polymer having 1 or more unsaturated bonds available to the Michael addition reaction. In possible embodiments, the unsaturated compounds selected to replace the TMPTA can for example be one or more unsaturated compounds selected from acrylic, methacrylic, vinyl compounds and resins, or oligomers containingunsaturated bonds that are added. Some examples of these compounds can be selected from a group consisting of: ethoxylated trimethylolpropane triacrylate (EO3-TMPTA, CAS n° 28961-43-5, where EO3 indicates the degree of ethoxylation, in particular in this case 3 ethoxy groups), propylidynetrimethanol, ethoxylate, esters with acrylic acid, 1 ,6-hexanediol diacrylate (HDD A), hexane- 1 ,6-diyl bisacrylate, di(trimethylolpropane)tetraacrylate (DiTMPTA), 2-({2,2- bis[(prop-2-enoyloxy)methyl]butoxy}methyl)-2-[(prop-2-enoyloxy)methyl]butyl prop-2-enoate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dipentaerythritol hexaacrylate (DPHA), 2-[[3-[(l- Oxoallyl)oxy]-2,2-bis[[(l-oxoallyl)oxy]methyl]propoxy]methyl]-2-[[(l- oxoallyl)oxy] methyl] -1,3 -propanediyl diacrylate, diacrylate ester of bisphenol A epoxy resin, glyceryl propoxy triacrylate (GPTA), propoxylated glyceryl triacrylate (PO3-GTA), pentaerythritol triacrylate, pentaerythritol tetraacrylate, 2- propenoic acid, reaction products with pentaerythritol (PETIA and PETTA, sometimes PET A or PETRA), pentaerythritol ethoxylated triacrylate, pentaerythritol ethoxylated tetraacrylate, pentaerythritol propoxylate, or esters with unsaturated bonds usable with the Michael addition mechanism, such as diethyl maleate (DEM), dibutyl maleate (DBM), dioctyl maleate (DOM), dimethyl fumarate (DMF).As stated, these unsaturated compounds can be used individually or even in mixtures of between 2 and 20 of them. Furthermore, it is also possible to use prepolymers or adduct compounds from these unsaturated compounds listed above and a percentage % w / w of diamine.The hardening compound is a nucleophilic compound, preferably an amino compound, more preferably a diamine, for example 1,3- bis(aminomethyl)cyclohexane (1,3 BAC), 3-aminomethyl 3,5,5- trimethylcyclohexylamine (IPDA), 4,4'-diaminodicyclohexylmethane (PACM), diethylenetriamine (DETA), 2-piperazin-l-ylethylamine (AEP), 3,6-diazaoctane- 1,8-diamine (TETA), meta- xylenediamine (MXDA), trimethylhexamethylenediamine (TMD), 1 ,2-diaminocyclohexane (DCH-99), 2- methylpentane- 1 ,5-diamine (Dytek®-A), N'-(6-aminohexyl)hexane- 1 ,6-diamine (BHMT), hexane- 1 ,6-diamine (HMD- Dytek®-HMD), all polyetheramines with molecular weight 100 to 1000. Included are the BADGE-DIAMINE adducts of theabove-listed diamines with bisphenol A and bisphenol F epoxy resins in all possible molar ratios comprised between 1 and 50.By epoxy resin (sometimes also called epoxy polymer in the present disclosure) we generally mean, in the embodiments described here, standard liquid bisphenol A and bisphenol F epoxy resins, with Epoxy Equivalent Weight (EEW) of 180- 190 and viscosity between 3000-15000 mPas at 25°C. It is also possible to use bisphenol A and bisphenol F epoxy resins with EEW higher or lower than 180- 190, to use epoxy resins with lower viscosity or even higher viscosity, even becoming solid or semi-solid resins with average molecular weights Mw that are lower than 700 g / mol, between 700 and 1000 g / mol, and higher than 1000 g / mol. We also conveniently mean all epoxy derivatives called reactive plasticizers and / or reactive diluents with 1, 2, 3, 4, 5, 6, 7, 8 epoxy functions. Non-reactive diluents can also be used in the formulation, such as benzyl alcohol and other similar non- reactive products with the function of plasticizers / accelerants. It is also possible to use resins called epoxy-phenolics and epoxy-novolacs with one or more functions. All resins, polymers, oligomers, monomers and / or substances that contain reactive epoxy rings (oxirane ring) are also included.Due to the presence of both the epoxy resin and also the unsaturated compound, the hardening composition described here, which is generally in liquid form, can be hardened through an amine nature epoxy hardener, a polyamide, mannich based, mercaptan based epoxy hardener, thiol compounds containing the S-H group, and both through UV photocatalysis and also thermal catalysis.In fact, in addition to hardening through poly-addition, a Michael addition also occurs between the unsaturated compound, in particular of the acrylic, methacrylic or vinyl type as defined above, and the nucleophilic hardening compound, which act as a Michael acceptor and Michael donor, respectively. The Michael addition occurs as soon as they are placed in the presence of each other, spontaneously and quickly.By providing a diamine as a nucleophilic compound, a particularly fast and effective Michael addition is achieved, also called a “click” reaction. The unsaturated compound is more preferentially an acrylic or methacrylic compound, which are better Michael acceptors than a vinyl compound. Even more preferentially, the unsaturated compound is an acrylic compound.The combination of the two hardening mechanisms, namely the Michael addition and the poly-addition, has been well known for at least twenty years. This allows to obtain an epoxy resin-based hardening composition with mechanical properties, in particular final hardness, comparable to the classic epoxy resin without Michael addition.The epoxy resin-based hardening composition according to the embodiments described here has a hardness that makes it particularly suitable to treat stone material, in particular for stones that are intended to remain outdoors.Furthermore, the presence of the Michael addition allows to achieve the “invisible” effect that is not achieved with traditional epoxy resins. The high reaction speed between the unsaturated compound as described above and the diamine allows to achieve an application effect known as “pre-gel effect”, which avoids the greasy and wet effect on the slab thanks to an increase in molecular weight which occurs almost instantly upon the addition of the hardening compound to the epoxy resin.In accordance with some embodiments, the total quantity of hardening compound is the sum of a first quantity intended to react with the unsaturated compound in the aza-Michael addition, and a second quantity intended to react with the epoxy resin in the poly-addition.Preferably, the first quantity of hardening compound is such that the proportion in quantity of matter (unsaturated compound): (hardening compound) is comprised between 1 :0.5 and 1 :2.5. More preferably, the proportion in quantity of matter (unsaturated compound): (hardening compound) is comprised between 1 : 1 and 1 :2.Advantageously, the second quantity of compound is such that the proportion in quantity of matter (epoxy polymer): (hardening compound) is comprised between 4:1 and 1 :1. More advantageously, the proportion in quantity of matter (epoxy polymer): (hardening compound) is comprised between 2.5:1 and 1.5:1.The composition described here is able to be hardened by means of thermal catalysis between +5°C and +150°C or catalysis which occurs in a mixed manner of thermal catalysis and UV photocatalysis.The hardening composition described here can be in the form of a two- component resin, with the unsaturated compound, or several compounds, dissolved and diluted in the epoxy resin and the hardening compound supplied separately, tobe mixed with the resin when the hardening is to be carried out.The hardening composition described here can be made commercially available in a kit comprising the epoxy resin and the unsaturated compound mixed together, while the hardening compound is supplied separately. By the expression “supplied separately” we mean that the hardening compound is supplied in a form not mixed with the resin and the unsaturated compound, but ready to be mixed with them in order to initiate the hardening of the composition. For example, the hardening compound can be supplied in a separate package, or in the same package as the other compounds, provided it is properly isolated from them.It has been found that the best results are achieved with a compound in which the hardening composition described here is present between 1% and 50% by weight.According to one aspect, there is also provided a method for hardening a hardening composition, comprising: making available an epoxy resin in which an unsaturated compound as described above is included and mixing the resin with the hardening compound. By the term “included” we mean that the unsaturated compound, or compounds, are dissolved, or diluted, in the epoxy resin. Subsequently, the method provides to subject the resulting mixture to a heat treatment. The heat treatment can be aimed at thermal catalysis. The thermal catalysis can be an active heating phase, in which the temperature of the mixture is raised above room temperature, or the thermal catalysis can occur at room temperature, that is, at the temperature at which the aforementioned mixture is prepared, without necessarily providing heat by heating.The present disclosure also concerns the use of the composition according to the embodiments described here to treat stone material.The present disclosure further concerns the use of the composition according to the embodiments described here to produce a tool for working stone material.The epoxy resin-based hardening composition described here can be used or applied in current industrial plants and possibly also using, or in combination with, the hardening composition described in the Italian industrial invention patent n°. 102021000010049 in the name of the Applicant, obviously without using TMPTA or limiting TMPTA to below 1% w / w, which is essentially replaced with one or more of the unsaturated compounds described here.The absence of TMPTA, or its presence below 1% w / w, in the hardening composition according to the present disclosure allows to offer this hardening composition on the market with a better CLP labelling classification than what it would have if TMPTA was used, and which will be provided after 23 November 2023. In particular, it will no longer require the presence of the phrase H351 (“Suspected of causing cancer”) nor any pictograms (GHS 08 LABEL) symbolizing “health hazard”.DESCRIPTION OF SOME EMBODIMENTSWe will now refer in detail to the possible embodiments of the invention, by way of a non-limiting example. The phraseology and terminology used here is also for the purposes of providing non-limiting examples.Unless otherwise defined, all the technical and scientific terms used here and hereafter have the same meaning as commonly understood by a person with ordinary experience in the field of the art to which the present invention belongs. Even if methods and materials similar or equivalent to those described here can be used in practice and in the trials of the present disclosure, the methods and materials are described hereafter as an example. In the event of conflict, the present application shall prevail, including its definitions. The materials, methods and examples have a purely illustrative purpose and shall not be understood restrictively.All measurements are carried out at 25°C (room temperature) and at atmospheric pressure, unless otherwise indicated. All temperatures are expressed in degrees Celsius, unless otherwise indicated.All percentages and ratios indicated shall be understood to refer to the weight of the total composition (w / w), unless otherwise indicated.All percentage ranges indicated here are given with the provision that the sum with respect the overall composition is 100%, unless otherwise indicated.All the ranges reported here shall be understood to include the extremes, including those that report an interval “between” two values, unless otherwise indicated.The present description also includes the ranges that derive from uniting or overlapping two or more ranges described, unless otherwise indicated.The present description also includes the ranges that can derive from thecombination of two or more values taken at different points, unless otherwise indicated.In the context of the present application, quantity of matter is understood as the quantity of substance, also called chemical quantity, and expressed in moles. As is well known to the people of skill in the art, the quantity of matter is obtained with the mass / (molecular mass) ratio of a same chemical compound.The epoxy resin-based hardening composition according to the embodiments described here comprises an epoxy resin in which one or more unsaturated compounds are diluted, in particular unsaturated monomeric compounds selected from vinyl compounds, acrylic compounds and methacrylic compounds.The hardening composition described here is free of TMPTA, or has a TMPTA content lower than 1% w / w.According to the embodiments described here, a single unsaturated compound, or two, three or even more than three unsaturated compounds can be provided.Preferred vinyl compounds have an electron donor group connected to one of the two carbons. Acrylic and methacrylic compounds are preferred, since they have a carboxyl COOH or ester COOR group that has good electron donor properties. These vinyl, acrylic and methacrylic compounds can for example be selected from a group that consists of: ethoxylated trimethylolpropane triacrylate (EO3-TMPTA, CAS n° 28961-43-5), propylidinitrimethanol, ethoxylate, esters with acrylic acid, 1,6-hexanediol diacrylate (HDD A), hexane- 1,6-diyl bisacrylate, di(trimethylolpropane)tetraacrylate (DiTMPTA), 2-( {2,2-bis[(prop-2- enoy loxy )methy 1] butoxy } methy l)-2- [(prop-2-enoy loxy)methy 1] butyl prop-2- enoate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dipentaerythritol hexaacrylate (DPHA), 2-[[3-[(l-Oxoallyl)oxy]-2,2- bis [ [( 1 -oxoally l)oxy] methy 1] propoxy] methyl] -2- [ [( 1 -oxoally l)oxy] methyl] -1,3- propanediyl diacrylate, diacrylate ester of bisphenol A epoxy resin, glyceryl propoxy triacrylate (GPTA), propoxylated glyceryl triacrylate (PO3-GTA), pentaerythritol triacrylate, pentaerythritol tetraacrylate, 2-propenoic acid, reaction products with pentaerythritol (PETIA and PETTA, sometimes PETA or PETRA), pentaerythritol ethoxylated triacrylate, pentaerythritol ethoxylated tetraacrylate, pentaerythritol propoxylate, or esters with unsaturated bonds usable with the Michael addition mechanism, such as diethyl maleate (DEM), dibutyl maleate(DBM), dioctyl maleate (DOM), dimethyl fumarate (DMF).The hardening composition described here also comprises a hardening compound able to react with the epoxy resin and with the one or more unsaturated compounds. In particular, the hardening compound is a nucleophilic compound and has one or more active hydrogens to react with the epoxy resin through a polyaddition, subject to heating. Please note that the heating preferably does not provide very high temperatures, for example temperatures below 100°C, of the order of 50°C or even 35°C, may suffice.A particularly suitable class of compounds for the hardening compound is that of diamines, since they have both nucleophilic properties and also different hydrogen atoms able to participate in the poly-addition reaction with the epoxy resin. For this purpose, it is preferable that both amine functions are primary amines. In addition, the amines react very well as part of the aza-Michael addition, allowing the reaction to run very quickly and very effectively. With this reaction, the total or almost total consumption of the unsaturated compound can occur in just a few minutes, for example five minutes or less.The aza-Michael addition is further promoted if the unsaturated compound has multiple functions with double bond between two carbon atoms, since they represent the precise point with which the hardening compound interacts. Increasing the number of functions also promotes better resin hardness after subsequent treatments. In fact, it has been verified that the hardest resins are obtained with tri-functional unsaturated compounds, that is, equipped with three C=C functions.The reaction results in the formation of an adduct between the unsaturated compound and the hardening compound. In the event the hardener is a diamine, it should be noted that the two amine functions each still have at least one hydrogen atom available for the subsequent poly-addition with the epoxy resin.The quantity of matter, in terms of moles, of the hardening compound is advantageously such that it reacts with both the unsaturated compound and also the epoxy resin. Once the aza-Michael addition reaction is finished, part of the quantity of hardening compound is still available to react with the epoxy resin. To guarantee a sufficient quantity of hardening compound after the aza-Michael addition reaction, an excess of hardening compound should be provided, at leastwith respect to the quantity of epoxy resin.The percentage, in quantity of matter of unsaturated compound, or mixtures thereof, is advantageously comprised between 1% and 50%, preferably between 1% and 40%. In this way, there is a good compromise between the hardness of the adduct between unsaturated compound and hardening compound, and the hardness due to the poly-addition with thermal catalysis of the epoxy polymer with the hardening compound.Taking a diamine as an example of hardening compound, knowing that it potentially binds with four epoxy polymer molecules, a proportion in quantity of matter epoxy polymer: diamine of 2:1 (mol / mol) can be provided. An additional quantity of diamine should be added to this quantity, intended to react with the unsaturated compound. The quantity of diamine is to be determined based on the proportion unsaturated compound:diamine to be obtained.An example of how to use the hardening composition described here is to supply it in two separate components, with the epoxy resin and the unsaturated compound on the one hand, the unsaturated compound being dissolved and diluted in the epoxy resin, and the hardening compound on the other hand. This prevents the unsaturated compound and the hardening compound from reacting with each other earlier than necessary.When using the composition, in order to harden it, the hardening compound is mixed into the epoxy resin. This immediately results in the initiation of the azaMichael addition reaction between the unsaturated compound and the hardening compound, which also results in heat development. The Michael addition leads to the formation of an adduct.At this point, the mixture contains epoxy polymer molecules, adduct molecules and hardening compound molecules, the latter having been introduced in excess with respect to the quantity of unsaturated compound. Given the efficiency and yield of the aza-Michael addition, the unsaturated compound has been consumed entirely or almost entirely.Subsequently, heat is applied to the mixture, in order to initiate the polyaddition between the hardening compound and the epoxy polymer, but also between the adduct, which entails active hydrogen atoms available for this reaction, and the epoxy polymer. This concludes the hardening of the epoxy resin-basedcomposition described here.The epoxy resin-based composition described here is in itself, because of its hardening capacity, well suited for use in the treatment of stone material. To do this, it can be provided to spread the epoxy resin-based composition described here after the hardening compound has been mixed. Please note that, as a result of the Michael addition, the composition remains liquid, or in any case spreadable, and has not hardened.EXAMPLE 1In this example, a traditional standard formula for a hardening composition of a known type was modified by replacing the 5% TMPTA with an unsaturated compound which, in this example, is ethoxylated trimethylolpropane triacrylate (EO3-TMPTA, CAS n°. 28961-43-5) (with a molar mass equal to 428 g / mol), acrylate compound with three acrylic functions. In this way, the hardening composition according to this example of the present invention is free of TMPTA (that is, 0% w / w of TMPTA in the formulation). As the hardening compound, for example, the diamine l,3-bis(aminomethyl)cyclohexane) (1,3BAC) (molar mass 142.24 g / mol) was used. The epoxy resin is a standard epoxy resin with EEW of 190, based on an epoxy polymer with a molecular mass of 380.00 g / mol.The example composition according to the present invention was prepared with a resin with 71.3% epoxy polymer, 7% EO3-TMPTA, 18.9% 1 ,6-hexanediol diacrylate (HDD A) and with the remaining 2.8% additives and stabilizers to reach 100%. More precisely, the total mass of diamine was determined by considering a first quantity equal to 1 mole of 1.3BAC per 2 moles of epoxy polymer, and a second quantity equal to a variable quantity of 1.3BAC per mole of EO3-TMPTA. The total quantity of diamine added to the resin is the sum of the first and second quantities as above.Below are the two formulations, traditional with TMPTA and, according to the example of the present invention, without TMPTA:The formulation with 5% w / w TMPTA has to be labelled with the indication of “health hazard” according to European CLP labelling, while the formulation without TMPTA does not require such commercial labelling.To produce the hardening composition according to example 1, the resins were first prepared by mixing the epoxy polymer and the acrylate and additives at 50°C under continuous stirring, by means of a magnetic stirrer, for 120 minutes. The resin thus obtained was left to rest overnight at room temperature.The predetermined quantity of 1.3BAC was added to each of the samples, as per the laboratory test results table that follows.In detail, some laboratory tests were performed to evaluate the differences between the two formulations under comparison. These were: Brookfield viscosity in mPas; gel time in mass at 25°C in a water bath expressed in minutes; gel time in mass outdoors expressed in minutes; APHA color scale; hardness measurement on SHORE D scale.For the hardness, resin disks 5mm high and 85mm were prepared with each of the samples, each weighing 40g, by pouring the mixture of resin + 1,3BAC into special metal plates. An aging test was also performed in a Qsun climatic cell (Xenon test chamber model Xe-3-HCS), according to regulation ASTM-D904, 300-hour outdoor cycle and some application tests on the resin applied / spread in a thin layer. The outdoor cycle parameters are in the following table. A Q-sun - outdoor cycle was used; this method is used to test adhesives, glues, resins andmastics placed outside and refers to regulation ASTM D 904.Below is a table with the results of the laboratory tests performed:The formulation of the composition indicated above, without TMPTA, proved acceptable and was therefore applied on Greek marble tiles called Volakas. This material is a white dolomite that changes color abruptly if it is treated with a traditional epoxy resin. It is necessary to use an invisible epoxy resin-based composition. The test is visual and was performed by comparing the composition with 5% TMPTA and the composition free of TMPTA according to the example. 100 gr / m2of resin+hardener composition were applied in both cases. These were polymerized in an oven for 4 hours at 40°C. After 24 hours, the excess resin was removed, and the tiles were polished with a marble polisher. The tiles were then left to rest for 60 min., and the following visual parameters were evaluated:EXAMPLE 2A composition in accordance with a second example of the present invention was compared with another known traditional composition, with 20% TMPTA in the formula. This known composition is generally applied on Brazilian white quartzites and on white granites such as Alaska white. This formulation was catalyzed with a 1.3 BAC-based hardener containing 16.5% benzyl alcohol. The composition of example 2 is a reformulation of the known composition with 20% TMPTA as above. Below is a comparison of the two compositions suggested, a first traditional one and a second one in which TMPTA was replaced with 1,6- hexanediol diacrylate (HDD A) and pentaerythritol tetraacrylate (PETTA) in accordance with example 2:TOTAL | 100.00The known formulation with 20% TMPTA has to be labelled with the indication of “health hazard” according to European CLP labelling, while the formulation without TMPTA does not require such commercial labelling.All laboratory tests already listed in example 1 were performed. The table with the results follows:Although it was possible to observe slight differences between the results of the two compositions, these were considered acceptable since the final technical effect that matters is not to alter the natural color of the treated surface and the parameters measured in the laboratory are within the expected ranges. The SHORE D hardness parameter has to be no lower than 70 to allow the resin to be polished and smoothed. The application tests were performed in the manner of example 1, in this case using a white quartzite as the stone material that was subjected to application of the two compositions.It is clear that modifications and / or additions of parts may be made to the epoxy resin-based hardening composition as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims. EXAMPLE 3A composition in accordance with a second example of the present invention was compared with another known traditional composition, with 11% TMPTA in the formula. This known composition is generally applied on Carrara marble or Greek marble from Volakas or Pirgos. This formulation was catalyzed with a hardener based on 1.3 BAC+BADGE adduct containing 12.9% benzyl alcohol.The composition of example 3 is a reformulation of the known composition with 11% TMPTA as above. Below is a comparison of the two compositions suggested, a first traditional one and a second one in which TMPTA was replaced with pentaerythritol triacrylate, pentaerythritol triacrylate PETIA and dioctyl maleate DOM in accordance with example 3:The known formulation with 11% TMPTA has to be labelled with the indication of “health hazard” according to European CLP labelling, while the formulation without TMPTA does not require such commercial labelling. All laboratory tests already listed in example 1 were performed. The table with the results follows:Although it is possible to observe slight differences between the results of the two compositions, these were considered acceptable since the final technical effect that matters is not to alter the natural color of the treated surface and the parameters measured in the laboratory are within the expected ranges. The SHORE D hardness parameter has to be no lower than 70 to allow the resin to be polished and smoothed. The application tests were performed in the manner of example 1, in this case using a white Carrara marble as the stone material that was subjected to application of the two compositions.It is clear that modifications and / or additions of parts may be made to the epoxy resin-based hardening composition as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

Claims

CLAIMS1. Liquid hardening composition, characterized in that it comprises an epoxy resin, at least one unsaturated compound selected from vinyl, acrylic and methacrylic compounds, and a nucleophilic hardening compound selected from diamines and able to react both with the epoxy resin and also with said at least one unsaturated compound, wherein said hardening composition is free of trimethylolpropane triacrylate (TMPTA) or has a TMPTA content lower than 1% w / w.

2. Composition as in claim 1 , characterized in that said at least one unsaturated compound is an acrylic compound with between 1 and 8 double bonds, in particular between 2 and 5 double bonds, more in particular an acrylic compound with three double bond functions between two carbon atoms, or it is a polymer having 1 or more unsaturated bonds available to the Michael addition reaction.

3. Composition as in claim 1 or 2, characterized in that said vinyl, acrylic and methacrylic compounds are selected from a group consisting of: ethoxylated trimethylolpropane triacrylate (EO3-TMPTA, CAS n° 28961-43-5), propylidinitrimethanol, ethoxylate, esters with acrylic acid, 1 ,6-hexanediol diacrylate (HDD A), hexane- 1,6-diyl bisacrylate, di(trimethylolpropane)tetraacrylate (DiTMPTA), 2-( {2,2-bis[(prop-2- enoyloxy)methyl]butoxy}methyl)-2-[(prop-2-enoyloxy)methyl]butyl prop-2- enoate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dipentaerythritol hexaacrylate (DPHA), 2-[[3-[(l-Oxoallyl)oxy]-2,2- bis [ [( 1 -oxoally l)oxy] methyl] propoxy ] methyl] -2- [ [( 1 -oxoally l)oxy] methyl] -1,3- propanediyl diacrylate, diacrylate ester of bisphenol A epoxy resin, glyceryl propoxy triacrylate (GPTA), propoxylated glyceryl triacrylate (PO3-GTA), pentaerythritol triacrylate, pentaerythritol tetraacrylate, 2-propenoic acid, reaction products with pentaerythritol (PETIA and PETTA, sometimes PETA or PETRA), pentaerythritol ethoxylated triacrylate, pentaerythritol ethoxylated tetraacrylate, pentaerythritol propoxylate, or esters with unsaturated bonds usable with the Michael addition mechanism, such as diethyl maleate (DEM), dibutyl maleate (DBM), dioctyl maleate (DOM), dimethyl fumarate (DMF).

4. Composition as in any claim hereinbefore, characterized in that it provides a first quantity of hardening compound able to react with said at least oneunsaturated compound and a second quantity of hardening compound able to react with the epoxy resin, in that the first quantity of hardening compound is such that the proportion in quantity of matter (unsaturated compound): (hardening compound) is comprised between 1 :0.5 and 1 :2.5 (mokmol), and in that the second quantity of hardening compound is such that the proportion in quantity of matter (epoxy polymer) ’.(hardening compound) is comprised between 4: 1 and 1 :1.

5. Composition as in any claim hereinbefore, characterized in that it is able to be hardened by means of thermal catalysis between +5°C and +150°C or catalysis which occurs in a mixed manner of thermal catalysis and UV photocatalysis.

6. Method for hardening a resin, comprising:- making available an epoxy resin in which an unsaturated compound selected from vinyl compounds, acrylic compounds and methacrylic compounds is diluted;- making available a nucleophilic hardening compound selected from diamines and able to react both with the epoxy resin and also with the unsaturated compound;- mixing the hardening compound into the epoxy resin;- subsequent exposure to the heat of an oven or to room temperature; wherein said vinyl, acrylic and methacrylic compounds are selected from a group consisting of: ethoxylated trimethylolpropane triacrylate (EO3-TMPTA, CAS n° 28961-43-5), propylidinitrimethanol, ethoxylate, esters with acrylic acid, 1,6- hexanediol diacrylate (HDD A), hexane- 1,6-diyl bisacrylate, di(trimethylolpropane)tetraacrylate (DiTMPTA), 2-( {2,2-bis[(prop-2- enoy loxy)methy 1] butoxy } methy l)-2- [(prop-2-enoy loxy)methy 1] butyl prop-2- enoate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dipentaerythritol hexaacrylate (DPHA), 2-[[3-[(l-Oxoallyl)oxy]-2,2- bis[[(l-oxoallyl)oxy]methyl]propoxy]methyl]-2-[[(l-oxoallyl)oxy]methyl]-l,3- propanediyl diacrylate, diacrylate ester of bisphenol A epoxy resin, glyceryl propoxy triacrylate (GPTA), propoxylated glyceryl triacrylate (PO3-GTA), pentaerythritol triacrylate, pentaerythritol tetraacrylate, 2-propenoic acid, reaction products with pentaerythritol (PETIA and PETTA, sometimes PETA or PETRA), pentaerythritol ethoxylated tri aery late, pentaerythritol ethoxylated tetraacrylate, pentaerythritol propoxylate, or esters with unsaturated bonds usable with the Michael addition mechanism, such as diethyl maleate (DEM), dibutyl maleate (DBM), dioctyl maleate (DOM), dimethyl fumarate (DMF).

7. Method as in claim 6, characterized in that the mixing of the hardening compound into the epoxy resin causes an aza-Michael addition reaction between the hardening compound and the unsaturated compound, and in that the heating step determines a thermal catalysis of a polyaddition reaction between the hardening compound and the epoxy resin.

8. Use of the composition as in any claim from 1 to 5 to treat stone material.

9. Use of the composition as in any claim from 1 to 5 to produce a tool for working stone material.

10. Kit comprising a hardening composition as in any claim from 1 to 5, wherein the epoxy resin and the unsaturated compound are mixed together, and the hardening compound is provided separately.

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