BINDER CONTAINING CLAY

The invention relates to the field of binders, in particular binders for construction products such as concretes and mortars. Traditionally, concretes and mortars include binders and aggregates. The binders can be organic, in particular based on resins, but are most often mineral, hydraulic or non-hydraulic binders. Hydraulic mineral binders (that is to say binders which set irreversibly on contact with water and which can harden under water) are most often cements such as Portland cements (optionally added to minus one other product chosen from blast furnace slags or crushed granules or pozzolanic compounds such as fly ash), aluminous cements, tallowaluminous cements.

Today there is a need for binders that are both low carbon footprint and non-irritant. The production of Portland cements, but also aluminous and sulpho-aluminous cements, requires very high temperature firing treatments which cause significant emissions of carbon dioxide. Portland cement is also irritating to the skin and eyes.

In order to meet this need, the present invention relates to a binder comprising:

at least one raw clay comprising at least one clay mineral, the total weight content of clay mineral ranging from 1 to 60% relative to the weight of binder, at least one calcareous or dolomitic filler,

at least one water-retaining agent,

at least one additive chosen from flocculants, water repellents, latexes, hydraulic binders, tackifiers and cationic surfactants,

provided that, when the binder comprises a hydraulic binder, the total weight content of hydraulic binder is less than the total weight content of clay mineral.

In the present text, the contents indicated for the constituents of the binder, respectively of the mortar, are weight contents expressed relative to the total weight of the binder composition, respectively of the mortar composition.

Surprisingly, it turned out that the use of raw clay as the majority binder, with little or no hydraulic binder, made it possible to achieve good performance. In the case, for example, of tile adhesives, good tensile adhesion values ​​are obtained. Although devoid of hydraulic properties, raw clays have been shown to be able to bind mortar or concrete aggregates very effectively.

The term “clay” is understood to mean a pulverulent material predominantly comprising at least one clay mineral. Clay can consist of one clay mineral or several clay minerals. Alternatively, the clay may contain, in addition to one or more clay minerals, other minerals, such as for example quartz, feldspar, mica, etc. This is in particular the case when the clay is obtained by grinding an argillaceous rock. Clay can also come from excavated soil, especially during construction activities.

Clay minerals are hydrated aluminosilicates of the phyllosilicate family. At least one clay mineral is preferably chosen from kaolinite, smectites (in particular montmorillonite, saponite or beidellite), illite, sepiolite, attapulgite (also called palygorskite), hectorite and laponite. The clay preferably does not include a fibrous clay mineral.

Clay minerals exhibit a two-dimensional sheet structure made up of two types of layers (tetrahedral and octahedral) connected by their tops. In tetrahedral layers, silicon atoms are surrounded by four oxygen atoms, while in octahedral layers, atoms of a metal such as aluminum are surrounded by six oxygen atoms. By virtue of their structure with a very large specific surface area, clays have a capacity to admit numerous exchanges of cations or anions by insertion into the interfoliar network or by adsorption at the surface of the layers. In the case of kaolinite, the ion exchange capacity remains low and the interfoliar space is occupied by molecules of water and maintained by hydrogen bonds between the hydroxyl groups of the octahedral sheets and the oxygen of the tetrahedral sheets. In the case of smectites, the ion exchange capacity is higher because the aluminum cation in the octahedral layer of the sheet is partially substituted by a divalent cation of the magnesium type. In this case, the overall negative charge is counterbalanced by sodium and / or calcium ions in the interfoliar space. Since the layers are held together by relatively weak forces, water and other polar molecules can enter the interfoliar space, most often causing dimensional variation of the entire material. ion exchange is higher because the aluminum cation in the octahedral layer of the sheet is partially substituted by a divalent cation of the magnesium type. In this case, the overall negative charge is counterbalanced by sodium and / or calcium ions in the interfoliar space. Since the layers are held together by relatively weak forces, water and other polar molecules can enter the interfoliar space, most often causing dimensional variation of the entire material. ion exchange is higher because the aluminum cation in the octahedral layer of the sheet is partially substituted by a divalent cation of the magnesium type. In this case, the overall negative charge is counterbalanced by sodium and / or calcium ions in the interfoliar space. Since the layers are held together by relatively weak forces, water and other polar molecules can enter the interfoliar space, most often causing dimensional variation of the entire material.

At least one green clay is preferably chosen from kaolins and bentonites, in particular sodium, calcium or magnesium bentonites. Bentonites mainly contain montmorillonite.

The binder can contain several clays or several clay minerals. In all cases, it is the total weight content of clay mineral that must be considered, that is to say the sum of the respective weight contents of each of the clay minerals included in the binder composition.

The total weight content of clay mineral in the binder is preferably at least 2%, in particular at least 3% or at least 4%, or even at least 5%. Contents of at least 10%, in particular of at least 12% and even of at least 14% are preferred. It is preferably at most 50%, in particular at most 40%, or even at most 30% or at most 25%. It has for example been observed that good traction adhesion values, useful when the binder is used in the composition of a tile adhesive, were obtained even for low clay mineral contents, of the order for example of 10 to 30%, which demonstrates a surprisingly high capacity of raw clays to bind aggregates.

By “filler” is meant a pulverulent material having a volume particle size distribution such that the value of d90 is less than 250 μm. Preferably, the value of d50 is less than 20 µm, especially 10 µm. The particle size distribution can be determined by laser particle size distribution.

Limestone is mainly composed of calcium carbonate (calcite) and dolomite of calcium and magnesium carbonate (dolomite). Preferably, the limestone filler, respectively dolomitic, comprises at least 80% by weight, in particular at least 90% by weight, of calcite, respectively of dolomite.

Without wishing to be bound by any scientific theory, it would seem that the limestone and dolomitic fillers have a stabilizing effect on the clay, by providing alkaline-earth ions which will compensate the charges of the clay. The fillers therefore play an active role in the binder according to the invention.

The content by weight of limestone and / or dolomitic fillers in the binder is preferably between 10 and 90%, in particular between 20 and 80%, or even between 30 and 75%, limits included.

The water retaining agent is preferably a cellulose ether or a starch ether. It improves the consistency, in particular the workability, of the final concrete or mortar before application. The water-retaining agent also makes it possible to prevent the clay from drying out too quickly. Cellulose ether is also a thickening agent and improves the adhesion properties of the final mortar. The total weight content of water-retaining agent in the binder is preferably between 0.01 and 10%, in particular between 0.05 and 5%, or even between 0.1 and 3%, limits included.

The binder further comprises at least one additive selected from flocculants, water repellents, latexes, hydraulic binders, tackifiers and cationic surfactants. It may comprise a mixture of several of these additives, for example a mixture of one or more flocculants and one or more water-repellent agents, a mixture of one or more flocculants and one or more latexes, a mixture one or more water-repellent agents and one or more latexes, or a mixture of these six additives.

The total weight content of these additives in the binder is preferably between 0.05 and 40%, in particular between 1 and 30%, or even between 2 and 20% or between 3 and 10%, limits included.

The flocculating agent, by promoting the aggregation of the clay particles, improves the cohesion of the clay binder, and therefore the mechanical properties of the final concrete or mortar.

The flocculating agent is preferably a polycationic polymer, in particular a polyquaternary ammonium. This agent is particularly effective when at least one raw clay is a bentonite, probably because the latter is relatively charged. Without wishing to be bound by any scientific theory, it would seem that the polycationic polymer is capable, by being adsorbed on the sheets, of bridging several particles between them.

The quaternary polyammonium preferably has a molecular mass of between 10,000 and 1,000,000. It can be obtained by a polycondensation reaction between epichlorohydrin and a primary or secondary amine, for example dimethylamine. The quaternary ammonium function (cationic site) is then located on the main chain of the polymer. Alternatively, the quaternary ammonium function can be located on side chains. The quaternary polyammonium can in this case be obtained by reacting an allyl chloride and dimethylamine.

The weight content of polycationic polymer in the binder is preferably between 0.05 and 30%, in particular between 0.2 and 15%, or even between 0.5 and 5%.

The flocculating agent can also be a source of polyvalent cations. The polyvalent cation is preferably an alkaline earth cation, preferably calcium, or even magnesium. Other polyvalent cations include aluminum, zinc and iron. The source of polyvalent cations is preferably a hydroxide (for example 1 calcium hydroxide) or a salt, in particular an inorganic salt, such as a sulfate, a nitrate or a chloride.

The total weight content of source of polyvalent cations in the binder, in particular of salt or of calcium hydroxide, is preferably between 0.05 and 30%, in particular between 1 and 20%, or even between 2 and 10%, limits included .

Sources of polyvalent cations are particularly effective when at least one raw clay contains kaolinite.

The water-repellent agent makes it possible to improve the resistance to water, and in particular the tensile adhesion of the mortar after immersion in water, which is particularly advantageous for applications as tile adhesive. It is preferably chosen from waxes, silicones (for example polydimethylsiloxane), silanes, and stearates and oleates of zinc, calcium, magnesium or sodium. The wax is preferably in the form of a micronized powder, with an d50 of 2 to 50 µm. The wax is, for example, a paraffin wax. The total content by weight of water-repellent agent in the binder is preferably between 0.05 and 30%, in particular between 1 and 25%, or even between 2 and 20 or between 3 and 15%, limits included.

By “latex” is meant an aqueous polymeric dispersion or a powder capable of forming such a dispersion (redispersible powder). The latex is preferably based on a copolymer of ethylene and vinyl acetate, on a copolymer of ethylene and vinyl versatate or on a copolymer of styrene and butadiene. The latex has a film-forming effect which improves the flexibility in the hardened state of the mortar or the final concrete as well as its adhesion properties. The latex content by weight in the binder is preferably between 0.05 and 30%, in particular between 0.5 and 20%, or even between 1 and 10%, or between 2 and 5%, limits included.

By hydraulic binder within the meaning of the invention is meant a binder chosen from:

- Portland cements,

- granulated blast furnace slag crushed with activator,

- class C fly ash,

aluminous cements,

- sulpho-aluminous cements,

- belitic cements,

hydraulic lime,

- phosphate cements (for example phospho-magnesian cements).

By "Portland cement" is meant not only CEM I cements but also composite Portland cements (CEM II, including Portlands slag, silica fume, pozzolan, fly ash, calcined shale, limestone), blast furnace cements (CEM III), pozzolanic cements (CEM IV) and compound cements (CEM V), within the meaning of standard EN 197-1.

Ground granulated blast furnace slags are only considered as hydraulic binders in the presence of activators, for example alkaline activators such as sodium silicate or sodium carbonate. A preferred activator mixture contains alkali silicate, alkali tripolyphosphate and an alkaline earth source, for example lime.

The total weight content of hydraulic binder in the binder corresponds to the sum of the respective weight contents of each of these compounds or mixtures of compounds (including, where appropriate, the blast furnace slag activator).

The total weight content of hydraulic binder may be zero.

In order to improve the performance after immersion in water of the final mortar or concrete, the binder advantageously comprises at least one of the aforementioned hydraulic binders, or a mixture of several of the aforementioned hydraulic binders. For example, the presence of aluminous cement is particularly beneficial.

The total weight content of hydraulic binder in the binder is preferably at most 25% or at most 20%, in particular at most 15% or at most 10%, or even at most 4% or not more than 2%. It can advantageously be at least 1%, in particular at least 2%, or even at least 4%.

The ratio between the total weight content of hydraulic binder and the total weight content of clay mineral is preferably at most 0.9, in particular at most 0.8 and even at most 0.7 or at most. plus 0.6. It can advantageously be at least 0.1, in particular at least 0.2.

Preferably, the binder is either free from Portland cement or contains it but in a weight content of at most 2%, in particular at most 1%, in order to reduce the irritant properties. This content can advantageously be zero. A content of at least 0.2%, in particular at least 0.4%, for example between 0.6 and 2% is however beneficial from the point of view of the properties of the final mortar or concrete after immersion in the water, without having a negative impact on the irritant nature of the mortar or concrete.

The tackifiers are preferably chosen from amylose, amylopectin and their derivatives. The addition of starch, for example wheat, makes it possible to provide these two agents. It may be starch modified in order to change its gelatinization temperature and its impact on viscosity. The starch may have undergone a pre-gelatinization step. The tackifiers make it possible to improve the mechanical performances and the water resistance of the binders.

Cationic surfactants make it possible to stabilize the binder in a humid environment, in particular by intercalation between the layers of charged clays or by adsorption on the surface of the sheets, making the clay exchange surfaces hydrophobic.

The cationic surfactants are preferably salts (in particular iodides or bromides) of quaternary ammonium or of phosphonium. Mention may in particular be made of the salts of tetraethylphosphonium, tetrabutylphosphonium, tetrahexylphosphonium, tetraoctylphosphonium, cetyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, butyldiammonium dichloride, ammonium chloride, ammonium chloride, hexadimethyltrimethyltrimethyltrimethyltrimethyltrimethyltrimethyl, butyldiammonium, chloroethylethyl-methyl-methyl-hexadecldimethyltrimethyl, tetramethylammonium acetate, benzyltriethylammonium chloride, tetraethylammonium bromide, tetra-n-butylammonium chloride.

The binder can be in the form of a mixture of dry powders, ready to mix, optionally with the addition of aggregates during or before mixing. In this case, the latex is present in the mixture in the form of a redispersible powder.

A subject of the invention is also a construction product, in particular a concrete or a mortar comprising a binder according to the invention, and optionally aggregates. The construction product can also be a prefabricated product.

The mortar is preferably a facade plaster mortar, an adhesive mortar, a screed, a base layer mortar for an exterior insulation system or a jointing mortar. The mortar according to the invention is preferably an adhesive mortar, more precisely a tile adhesive. The mortar is preferably in the form of a mixture of dry powders, ready to mix with a mixing liquid, in particular water. The mixing rate is preferably between 5 and 40%, in particular between 10 and 30%, limits included.

Preferably, the concrete or the mortar does not include any other binder than the binder according to the invention. Advantageously, the concrete or the mortar consists of the binder according to the invention and aggregates.

The aggregates are preferably sands, in particular of siliceous or calcareous nature. The total weight content of aggregates in the mortar or concrete (excluding limestone or dolomite fillers, which form part of the binder) is preferably between 5 and 85%, in particular between 10 and 70%, limits included.

Limestone sands are preferred because they make it possible to obtain, in the context of an application as an adhesive mortar, a much better adhesion by traction after immersion in water. Without wishing to be bound by any scientific theory, it would seem that the calcium ions brought by the limestone sands could influence the compactness of the clay and that the absorption of water by the limestone particles could strengthen the clay network due to the hydrogen bonds caused by absorbed water.

The mortar is preferably a dry mortar.

The mortar, in particular dry mortar, preferably comprises from 2 to 10%, in particular from 3 to 8%, of clay mineral, from 10 to 30%, in particular from 12 to 25% of limestone or dolomitic filler and from 50 to 85% , in particular from 55 to 80% sand, in particular limestone. The content of water-retaining agent is preferably between 0.1 and 1%. The mortar preferably comprises a latex in a weight content of between 1 and 5%. The mortar preferably comprises a water-repellent agent in a content of between 2 and 8%.

The binder or the concrete or mortar may include other additives, for example fibers (mineral or organic, for example glass fibers, cellulose, natural fibers, such as flax or hemp fibers), aggregates light (e.g. perlite, vermiculite, expanded calcined clay, expanded glass), water reducing agents (including plasticizers or superplasticizers, such as lignosulfonates, polycarboxylates, polymelamine sulfonates, polynaphthalene sulfonates), pigments, biocides, surfactants, super-absorbents (eg based on sodium polyacrylates).

The fiber content by weight in the concrete or mortar is preferably at most 10%, in particular 5%.

The binder according to the invention, by virtue of the good performance which it confers on mortars in terms of traction adhesion, is particularly well suited to the production of tile adhesives.

The invention therefore also relates to a process for producing a tiling on a support, comprising a step in which is applied, on the tiles or slabs of said tiling and / or on said support, at least one layer of a paste obtained by. mixing with a mixing liquid of an adhesive mortar according to the invention or an adhesive mortar comprising a binder according to the invention. The invention also relates to the use of an adhesive mortar according to the invention or an adhesive mortar comprising a binder according to the invention as tiling adhesive, for bonding tiles or slabs of a tiling to a support. .

The support is typically a wall or a partition, or a floor, for example a screed.

The tiles or slabs of the tiling can be made of various materials, such as ceramic, stoneware, cement, stone, marble, etc. The glue can for example be applied by means of a glue comb, a float, a trowel or a notched spatula.

The binder is also well suited for making a base layer of an exterior insulation system. Such a system comprises from the wall to be insulated - typically a masonry wall, an insulating panel (for example made of mineral wool or polystyrene) glued or mechanically fixed to said wall, a base layer incorporating a reinforcement typically made of glass fibers, then at least one coating finish.

The examples which follow illustrate the invention in a nonlimiting manner. The compositions and their properties are reproduced in Tables 1 to 7 below. Examples of which the reference begins with the letter C are comparative examples.

The tables indicate compositions of dry mortars obtained by mixing binders according to the invention with aggregates (in this case siliceous or limestone sands). The contents are therefore expressed in percentages by weight relative to the total weight of the mortar composition. The dry mortar composition is then mixed with water, the mixing rate corresponding to the amount of water added relative to the weight of the dry mortar composition.

The exemplified mortars are particularly suitable as tile adhesives. Tensile adhesion is measured according to standard EN 12004-2, after 7 days unless otherwise indicated. The tile used is a type Bla tile within the meaning of standard EN 14411, consequently exhibiting a water absorption of at most 0.5%.

Wax 1 is a Ceretan MX 2919 micronized wax sold by the company Münzig. Wax 2 is a wax sold under the reference HydroWax 170 by the company Sasol Wax.

Latex 1, based on a copolymer of ethylene and vinyl acetate, is sold under the reference Vinnapas 5010 N by the company Wacker. The latex 2, based on a copolymer of styrene and of acrylate, is sold under the reference Acronal S735P by the company BASF. These two latexes are in the form of redispersible powder.

The product called “Polycation” is a flocculating agent of the quaternary polyammonium type sold under the reference Floset EVA 45P by the company SNF.

Portland cement is a CEM I 52.5 R cement from Heidelberg. The aluminous cement is marketed by the company Kerneos under the reference Ternal White.

“Na bentonite” is sodium bentonite and “Mg bentonite” is magnesium bentonite.

Limestone filler 1 has a dlO of 1.8 ym, a d50 of 8.8 ym and a d90 of 34 ym. The limestone filler 2 has an dlO of 1.6 ym, a d50 of 5.2 ym and a d90 of 21 ym.

Siliceous sands are distinguished by their granulometry. Sand 1 has a dlO of 260 ym, a d50 of 520 ym and a d90 of 820 ym. Sand 2 has a dlO of 180 ym, a d50 of 280 ym and a d90 of 450 ym. Sand 3 has a dlO of 85 ym, a d50 of 154 ym and a d90 of 273 ym. Sand 1 is therefore the coarsest and sand 3 the finest.

Limestone sand has a dlO of 11 ym, a d50 of

78 ym and a d90 of 275 ym.

Table 1

Table 2

Table 3

Table 4

Comparative Examples C1 to C4 do not make it possible to achieve the required performance in terms of traction adhesion for tile adhesives (minimum of 0.5 N / mm 2 ), unlike the examples according to the invention.

In the absence of clay (example C1) or cellulose ether (example C2), the mortar has no adhesive property. The adhesion is almost non-existent in the case of Example C3, which contains a very large amount of raw clay and no lime filler. The absence of additive does not allow example C4 to achieve good performance.

Mechanical resistance tests after immersion in water were also carried out. To do this, parallelepipedal test pieces of 2 * 2 * 10 cm 3 were produced by hardening the mortar compositions for 14 days in molds, then by immersing the test pieces in water for 3, 7 and 14 days. Indentation resistance is measured using a penetrometer and is the force to be exerted to drive a conical indenter through the specimen. The compositions tested are reported in Table 5 below. The composition of Example 12 corresponds to that of Comparative Example C5 with the addition, relative to the latter, of 5% wax and 5% aluminous cement.

Table 5

In the case of example C5 (comparative), the resistance to indentation is zero. For example 12, on the other hand, the resistance to indentation is 0.3 N / mm 2 after 3, 7 and 14 days of immersion. The resistance to indentation after 3 days of immersion is 0.6 N / mm 2 in the case of Example 13. The addition of hydraulic binder therefore makes it possible to considerably improve the mechanical properties after immersion in the. water.

Table 6

The examples in Table 6 show the beneficial effect of calcareous sands over siliceous sands on tensile adhesion after immersion in water.

The addition of latex, as well as the use of finer silica sand, improves traction adhesion.

Table 7 compares different clays with each other.

Table 7

CLAIMS

1. Binder comprising:

at least one raw clay comprising at least one clay mineral, the total weight content of clay mineral ranging from 1 to 60% relative to the weight of binder, at least one calcareous or dolomitic filler,

at least one water-retaining agent,

at least one additive chosen from flocculants, water repellents, latexes, hydraulic binders, tackifiers and cationic surfactants,

provided that, when the binder comprises a hydraulic binder, the total weight content of hydraulic binder is less than the total weight content of clay mineral.

2. Binder according to claim 1, wherein the total weight content of hydraulic binder is at most 25%.

3. Binder according to one of the preceding claims, which is free from Portland cement or which contains Portland cement in a weight content of at most 2%.

4. Binder according to one of the preceding claims, in which at least one clay mineral is chosen from kaolinite, smectites, illite, sepiolite, attapulgite, hectorite and laponite.

5. Binder according to the preceding claim, in which at least one raw clay is chosen from kaolins and bentonites.

6. Binder according to one of the preceding claims, wherein the total weight content of clay mineral is between 5 and 50%, in particular between 10 and 30%.

7. Binder according to one of the preceding claims, such that the flocculating agent is a polycationic polymer, in particular a polyquaternary ammonium.

8. Binder according to one of claims 1 to 6, such that the flocculating agent is a source of polyvalent cations, in particular a source of calcium or magnesium.

9. Binder according to one of the preceding claims, such that the water-repellent agent is chosen from waxes, silicones, silanes, and stearates and oleates of zinc, calcium, magnesium or sodium.

10. Binder according to one of the preceding claims, such that the water-retaining agent is a cellulose ether or a starch ether.

11. Binder according to one of the preceding claims, such that the cationic surfactants are quaternary ammonium or phosphonium salts.

12. Binder according to one of the preceding claims, which is in the form of a mixture of dry powders.

13. Construction product, in particular concrete or mortar, such as mortar for facade plaster, adhesive mortar, screed, mortar for the base layer of a thermal insulation system from the outside, jointing mortar, comprising a binder according to one of the preceding claims, and optionally aggregates.

14. Construction product according to the preceding claim, such that the aggregates comprise calcareous sands.

15. Construct product according to one of claims 13 or 14, which is a dry mortar comprising from 2 to 10% of clay mineral from 10 to 30% of limestone or dolomitic filler and from 50 to 85% of sand, especially limestone.