WO2003070658A1

WO2003070658A1 - Extrudable binder composition

Info

Publication number: WO2003070658A1
Application number: PCT/FR2003/000500
Authority: WO
Inventors: Silvia Banfi; Michel Cloitre; Fabienne Morin
Original assignee: Atofina
Priority date: 2002-02-18
Filing date: 2003-02-17
Publication date: 2003-08-28
Also published as: FR2836141A1; FR2836141B1

Abstract

The invention relates to an extrudable or pressable binder composition, comprising: i) at least one binder (C), ii) an agent for controlling the rheology, polymer (P), which is in the form of an emulsion of copolymerised (meth)acrylic acid, branched or straight-chain C1-C22 alkyl (meth)acrylate, optionally with a third monomer of general formula: C(Re)(Rg) = C(Rf)-A1 and, as a further option, with at least one chain-length regulator, (iii) water (E) with a weight ratio of water (E) to binder (C) less than or equal to 0.25, preferably less than or equal to 0.21. The copolymer has the following composition of monomers a), b) and c) and regulating agent in the following weight proportions per 100 weight parts of a) + b) + c):a) 25 - 60 %, preferably 30 to 50 %, b) 40-75 %, preferably 50 to 70 %, c) 0-15 %, preferably 0.5 to 15 % and d) 0 to 5 %, preferably 0 to 0.5 %.

Description

EXTRUDABLE HYDRAULIC BINDER COMPOSITION.

The invention relates to a hydraulic binder composition which may be a cementitious (or concrete) paste, preferably extrudable or which can be implemented by pressing, comprising a rheology control agent based on an emulsion of acrylic copolymer. The invention also relates to a hardened composition, a preparation process and objects obtained from this composition, such as tubes, pipes, barriers or concrete profiles.

It is known that the mechanical performance of cement matrices is a function of the porosity of the hardened material; in particular, they are degraded in the presence of macroscopic defects or of high porosity. One way of reducing the porosity is to produce a hydraulic binder composition, which can be a cementitious paste, with a low water content and to implement it under pressure according to an extrusion or pressing process (compression molding). The extrusion process differs from "dry cast" or "cast molding" type processes in which a cementitious matrix is simply compacted during processing.

The cement extrusion process consists in causing a formulated cementitious paste to flow, under pressure, through a die of variable shape and size. ^' In general, the extrusion of cement calls for the use of rheology control agents, the main function of which is to form a paste capable of flowing through the extruder die, at water ratios. / relatively weak cement. These rheology control agents act as a binder of cement particles to reduce the effects of dilatancy inherent in the granular nature of the dough and the exudation of water during the extrusion or pressing of the dough. cementitious. These agents can also help to reinforce the mechanical properties of the material. EP 055 035 already knows the use of a vinyl acetate hydrolysis polymer or copolymer in combination with certain types of cement, which leads to ^λΛ macro-defect free "materials having very high mechanical performance. (flexural strength: 70-200 MPa) However, the specificity of polyvinyl alcohol-cement interactions largely limits its use to cements rich in aluminous complexes and to specific formulations containing no additional aggregates or fillers. On the other hand, the pronounced hydrophilic nature of this additive increases the sensitivity to water of the products thus prepared and consequently deteriorates their resistance to humidity like other performances which are thus affected (in particular the mechanical performances).

Cellulose ethers or esters such as hydroxypropyl methylcellulose (HPMC), as well as polyoxyethylene (POE), are two other classes of rheology control agents whose use is cited in US Pat. No. 5,891,374 Under normal conditions of use, the flexural strength obtained varies between 17 and 27 MPa in the presence of fibers. In the absence of reinforcing fibers, the flexural strength is much lower. According to this description (US 5,891,374), the fibers are aligned in the cement matrix, with good contact between the fibers and the matrix. However, because of the hydrophilic nature of the rheology control agents used, the mechanical properties of the materials obtained are altered by the sensitivity to water. This results in swelling and a decrease in mechanical performance, with possible crumbling of the finished material. In order to minimize the deterioration in the mechanical performance of materials hardened by absorption of water, it is necessary to limit the quantity of these agents used in the formulations. A second limitation is introduced by their high cost. A third disadvantage of additives of the cellulose derivative type is the risk high gelation potential of the polymer under the heating conditions encountered in extrusion, taking into account the significant shear rates. The existence of a limit rate reduces the flexibility of adjustment of the parameters of the formulation, with an automatic reduction of the feasibility window, defined by the range of possible variation of these parameters.

WO-A-9533606 describes the production by extrusion of cementitious hydraulic compositions with rheology control agents, including polyacrylic acids and derivatives.

WO 01/16048 describes extrudable cement compositions comprising both a rheology control agent and a dispersant. The presence of the dispersing agent has the effect, d ^? after this document, reduce the rate of rheology control agent, especially for high cost rheology agents. Among the rheology control agents mentioned in combination with this dispersant, alkali-soluble acrylic copolymers are mentioned. The major drawbacks of such a system are also linked to the pronounced hydrophilic nature of both such an acrylic copolymer and such a dispersant. More particularly, the salified (neutralized) forms mentioned of acrylic copolymers can have negative interactions with the cement and delay the kinetics of the cement setting.

None of the documents cited above describes or suggests the solution of the present invention which makes it possible to obtain a hydraulic binder composition and more particularly an extrudable cement paste or a pressable cement paste with a low water content, (in general <0.25 expressed in weight ratio water / hydraulic binder) using a particular rheology control agent, which: i) allows a wide range of compositions, in particular in terms of water / cement and polymer / cement ii) at low cost iii) does not require the joint use of a dispersant iv) can be used with a wide range of cements and a wide variety of aggregates and fillers or additives v) can be preferably present under insoluble form in emulsion (non neutralized acid functions).

The present invention results in cured compositions which exhibit high flexural and compressive strength, water resistance, as well as the possibility of being used in combination with aggregates and a variety of fillers.

The solution of the present invention thus overcomes the drawbacks of the solutions known by the prior art and makes it possible to obtain hydraulic binder compositions, preferably of extrudable or pressable cementitious paste, having improved mechanical performance. More particularly, the improvement is especially noticeable in terms of resistance to bending of the hardened material but also in terms of elimination of the negative effects of the dilatance and of the exudation of water in the paste or composition of hydraulic binder with better elasticity and cohesion before shaping and hardening. The possibility with these compositions of the invention of having low water-to-hydraulic binder ratios makes it possible to obtain extrudable or pressable cementitious matrices of very low porosity, of great compactness with increased resistance to bending by compression.

On the other hand, the compositions proposed by the present invention are suitable and adapted for easy implementation with an extrusion and pressing process with forms of complex and variable objects. The compactness of the hardened objects thus obtained contributes to additional advantages as regards the state of surface and formatting precision (absence of defects).

The term ^λ dilatance "signifies the existence, when a dough is sheared, of stresses exerted by a dough in the direction normal to the stress. The presence of dilatance is often associated with the blocking phenomenon which leads to the impossibility of setting processing pasta by extrusion or pressing.

The term "cohesion" means for a so-called cohesive paste that it only fractures beyond a finite threshold deformation. For deformations below the threshold deformation, the dough retains its integrity while deforming elastically. Cohesion is assessed by placing the dough between the two trays striated with a shear rheometer. The stress and the deformation of rupture characterize the cohesion of the dough. It is sometimes useful and convenient to benchmark cohesion using pastes containing higher water levels than the defined limit rates. The threshold deformation of the pastes formulated according to the invention reaches at least 100%. The cohesion of cement pastes without rheology control agent is zero.

With regard to the term "elasticity", a paste is said to be elastic when it supports _. constraints without irreversibly deforming. The elastic modulus of the doughs is measured within the limit of low stresses. <

The term "exudation" or sweating "or" filtration "designates the phenomenon of loss of water under an applied stress.

The first object of the present invention therefore relates to a hydraulic binder composition and preferably a cementitious paste which is extrudable or pressable comprising: (i) at least one hydraulic binder C; (ii) a rheology control agent, polymer P, which is in the form of an emulsion in water of at least one copolymer of: a monomer containing carboxylic functions, chosen from those of general formula a):

Ri R ₂ \ /

/ c - - - c \ a

R ₃ COOH

where Ri, R ₂ and R ₃ are equal or different and they are

H or CH ₃ at least one monomer of general formula b):

Ra R

\ /

R _c COO - A ₀

where R _a , R _h , c are equal or different and they are H or CH ₃ and A ₀ is a linear or branched C1-C22 alkyl, with optional: at least one third monomer of general formula c):

Re Rf

\ /

/ c = c \ σ

Rg Ai

with R _e , R _f , R _g identical or different from: H or

CH ₃ ;

Ai is -COO- (R _t O) _m -R _z or -CO-N (R _p ) - (R _t O) _m -R _z

R _z is a linear or branched C ₁ -C ₃₅ alkyl, which optionally contains hydroxyl groups;

R _p is H or a C1-C5 alkyl group;

R _t is a C1-C alkylene group m is a real number between 1 and 50 and as an additional option: at least one chain length regulating agent d) (iii) of water E so that the weight ratio (W / C) ^M total of water E "to" total of hydraulic binder C "is less than or equal to 0.25 and preferably less than or equal to 0.21 with the copolymer having a composition of monomers a), b), c) and of regulating agent d), as defined above, in the following weight proportions per 100 parts by weight of a) + b) + c): a) 25-60% and preferably 30 to 50%, and more particularly 35 to 45%; b) 40-75% and preferably 50 to 70%; c ) 0-15%, preferably from 0.5 to 15%, and more particularly from 0.5 to 10%, and even more particularly from 1 to 10%; d) 0 to • 5% and preferably from 0 to 0.5%.

This composition preferably has a weight ratio "total dry polymer P" to total ^λλ hydraulic binder C "(W / C) ranging from 0.0025 to 0.1 and preferably from 0.01 to 0.05. P is expressed by weight of dry matter (polymer P).

As preferred monomer of type a), mention may be made of (meth) acrylic acid and more particularly methacrylic acid and as monomer b) of C1 to C ₃ alkyl (meth) acrylates and more particularly of (meth) ethyl acrylate and even more particularly ethyl acrylate.

The presence of the monomer c) may be desired for particular compositions requiring specific performance in terms of elasticity and cohesion or a particular speed of obtaining and processing the pastes before shaping and hardening. The monomer c) is compatible with the monomers a) and b). The most preferred monomers of type c) are those of general formula c) having: m: 5-35 Rt: C2-C4 alkylene

R _z : linear or branched C ₁₈ -C ₃₅ alkyl.

As more particularly preferred examples of monomer type c), mention may be made of methoxypolyethylene glycol (meth) acrylate (MPEGMA) and more particularly MPEGMA with a number of ethoxy units ranging from 10 to 30 or behenyl ether polyethylene glycol methacrylate (BEPEGMA). ). The polymer P, rheology control agent, is present in the form of an aqueous emulsion of at least one copolymer, as described above which is preferably insoluble in water, in non-neutralized form. This emulsion is prepared by emulsion polymerization of the composition of the monomers a) and b) and optionally c) in the possible presence of a chain length regulating agent, said composition being previously emulsified using a common surfactant for emulsion polymerization and in the presence of a water-soluble radical initiator. The conditions for an emulsion polymerization of such a composition are considered to be in the field of art accessible to those skilled in the art. The dry extract (or overall solids content) in this type of emulsion is generally between 20 and 60% and preferably 30 to 50% by weight of the total ^λλ water + polymer ". The emulsion at least a copolymer can also be produced by mixing at least two emulsions of copolymers as described The molecular weight of the copolymer P is variable as a function of the polymerization conditions and of the presence or absence of a chain length regulating agent d) In general, in the absence of a regulatory agent d) the masses are high, ranging from a few hundred thousand to a few million, the presence of the regulatory agent decreases these molecular masses with masses ranging from a few thousand to a few hundred The presence of the chain regulating agent is desirable and preferred in the case of the presence of a monomer type c) for V obtaining specific performances in terms of elasticity / cohesion compromise and a particular speed of implementation of the dough before shaping and final hardening. The type d) chain length regulating agent is a transfer agent which can be selected from: 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptoethanol, thioglycolic acid, mercaptosilanes, HS-Ro-Si (0-R _r ) (where Rr is H or C1-C3 alkyl and Ro is an alkylene chain), phosphites, H ₃ PO ₄ , H ₃ PO ₃ and their salts.

The acid number of the final copolymer depends on the level of (meth) acrylic acid initially used in the composition of the monomers a) and b) and optionally c). More preferably, as indicated above, the proportion of (meth) acrylic acid a) can vary from 30 to 50%, more particularly from 35 to 45%, and the proportion of the monomer b) from 50 to 70%, and if the monomer c) is present, its proportion can vary from 0.5 to 15%, and more particularly from 0.5 to 10% and even more particularly from 1 to 10%, provided that the sum a) + b) + c) is equal to 100%.

The acid functions of the polymer (copolymer) P can be totally or partially neutralized, but preferably the neutralization rate must remain low for the copolymer to remain insoluble in water. The partial salt • formed in such a case will be a metal cation salt, such as lithium, sodium, potassium, magnesium, calcium, strontium, zinc, cadmium. Alkali or alkaline earth cations are preferred. More particularly, the polymer P is preferred in the absence of any neutralization, insofar as such neutralization can affect (delay) the kinetics of cement setting, by possible interaction with the structure of the hydraulic binder C. In fact, the use of '' a non-neutralized or weakly neutralized polymer (insoluble in an aqueous medium) is even more particularly preferred, for certain particular applications, because it makes it possible to avoid the addition of cations

- alkaline and alkaline earth likely to give rise to efflorescence effects on the surface of the cement after hardening.

This polymeric adjuvant P, incorporated into the composition according to the invention, offers the particular advantages linked to the fact that it makes it possible to formulate:

- pastes which can be extruded or which can be processed by pressing with a low water / cement ratio

(<0.25) from Portland cement; extrudable pastes or pastes which can be processed by pressing from Portland cement leading to materials having a high mechanical resistance, with in particular a flexural strength greater than 30 MPa, 28 days after hardening in an atmosphere saturated with water

(measured according to the 3 point method, well known to those skilled in the art), in the absence of any swelling in the water; pastes which can be extruded or which can be processed by pressing from Portland cement and in combination with various aggregates and fillers; - pastes which can be extruded or which can be used by pressing in which the molecular composition of the rheology additive can be modulated in a controlled manner, in order to meet various conditions of extrusion and pressing and for various applications.

It should be noted that, depending on the intended application, the polymeric adjuvant P can be combined with other rheology agents. On the other hand, this polymer P allows good compatibility with other usual additives for cement paste such as superplasticizers and setting accelerators. The hydraulic binder of the composition according to the invention is any hydraulic binder conventionally used, such as pozzolan, gypsum, cement, in particular a Portland cement, optionally a mixture of such binders. A list of suitable hydraulic binders is found on pages 23 to 25 of application WO-A-9533606 with the incorporation of this reference for the need for detailed specification of these binders. The composition of the invention is particularly suitable for Portland cement but also for a wide range of other binders. The water E of the composition according to the present invention comes at least in part from the water of the emulsion of polymer P and the rest of the direct addition of water with the other components to adjust the W / C ratio in the feasibility limit window for a given P / C ratio (see Figure 1). The water content of the composition is low and in all cases remains less than or equal to 25% by weight relative to the total of binder C. Preferably, this content is less than or equal to 21% and more preferably it is located in a range from 10% to 21%. Compositions having very good cohesion, with a very low water content and less than or equal to 16% can still be easily produced according to the present invention. In addition to components C, P and E, other additives may be present, such as aggregates and various fillers, such as fibers, limestone or ground marble or fumes of silica. A list of suitable aggregates and fillers is found on pages 36 to 40 of application WO-A-9533606, which reference is incorporated here for this need for specification.

The quantity used is that conventionally used. Note in particular an increased compatibility of the composition according to the invention with the aggregates (for example crushed limestone).

Other additives, such as setting accelerators are possible, as described on page 43 of the WO-A-9533606, which reference is incorporated here for the purpose of specification. Among the other additives there are defoamers.

A second object of the present invention relates to a process for manufacturing the composition which can be extruded or which can be implemented by pressing. The preparation is obtained by kneading the components according to various known techniques, described in particular on pages 54 and 55 of application WO-A-9533606 citing techniques which can be used in this invention.

A third object of the present invention relates to a process for shaping these components, either by: an extrusion step or a pressing step; or an extrusion step followed by a pressing step

The extrusion of the extrudable composition (paste) prepared by kneading is carried out using a piston or a screw feeding a die in a conventional manner. Corresponding methods and devices are described in particular on pages 46 and 47, as well as 56 to 59 of the application WO-A-

9533606 to which it is returned as necessary. This process is a continuous process and comprises steps of cutting and shaping or adjusting the final shape of the final object obtained, before hardening. The kneading and / or the extrusion can comprise degassing of the composition, in order to avoid defects liable to affect the mechanical performance. Pressing consists in feeding the kneaded dough into a press where the object is molded, for final shaping.

The shaping step by pressing a preform in a mold, can follow the extrusion step. The preform is produced by cutting the material passed through the die. The present invention also relates to a cured composition obtained from the composition of the invention or from a specific curing process which is also one of the objects of the invention. The composition according to the invention is conventionally cured and results in a cured composition, which exhibits significantly improved flexural and water resistance (absence of swelling).

It can be obtained by standard techniques but more particularly by a more specific method of hardening under an atmosphere saturated with water, for example by autoclaving. Curing methods and devices are described in particular on page 60 of application WO-A-9533606 to which it is referred as much as necessary.

A final object of the invention relates to hardened finished articles obtained from the compositions of the invention or by one of the methods of preparation and / or hardening of the invention. As final hardened objects thus obtained, there may be mentioned, among others: tubes, pipes, barriers, various profiles.

The following examples illustrate the invention without limiting it.

Experimental conditions

Synthesis of three polymer emulsions: Pi P ₂ and P ₃ > Polymer Pi

A first emulsion, with 40% solids content, of a Pi copolymer consisting of: methacrylic acid (45% by weight) and ethyl acrylate (55% by weight) is prepared by direct emulsion synthesis. direct emulsion synthesis. In a first tank, a pre-emulsion (A) is prepared containing 270 g of methacrylic acid, 330 g of ethyl acrylate and 600 g of water and a surfactant. In a second tank, 120 g of an aqueous solution are prepared

(B) sodium or ammonium persulfate. The reactor is loaded with 180 g of water and heated to a temperature of 75 ° C. The reactor is continuously supplied with (A) and (B) for 2 hours. Once the reactor feed is complete, the reactor temperature is maintained at 75 ° C for 1 hour. The emulsion produced contains less than 350 ppm of residual monomers.

Polymer P ₂

An emulsion is prepared, with 40% solids content, of a second copolymer P ₂ consisting of: methacrylic acid

(31% by weight), ethyl acrylate (57% by weight) and methoxypolyethylene glycol methacrylate (MPEGMA: 12% by weight). The synthesis is carried out in direct emulsion, operating as in the synthesis of the first polymer Pi, with the only difference being the addition of the monomer MPEGMA.

Polymer P ₃

A third emulsion is prepared, with a dry extract of 30%, of a copolymer P consisting of: methacrylic acid (36.7% by weight), ethyl acrylate (55% by weight) methoxy (polyethylene glycol) behenyl ether methacrylate (MPEGBEMA, 8% by weight) and 3-mercaptopropionic acid (0.3%) by synthesis in direct emulsion. In the laboratory, 1.5 kg of emulsion is prepared. In a first tank, a pre-emulsion (A) is prepared containing 165.15 g of methacylic acid, 247.5 g of ethyl acrylate, 36 g of MPEGBEMA, 1.35 g of 3-mercaptopropionic acid, 600 g of water and a surfactant. In a second tank (B), 120 g of an aqueous solution of sodium or ammonium or potassium persulfate are prepared. The reactor is loaded with 270 g of water and heated to 75-80 ° C. The reactor is continuously supplied with (A) and (B) for 2 hours. Once the feed is complete, the reactor temperature is maintained at 75-80 ° C for 1 hour. The emulsions thus prepared (Pi and P ₂ ) are used as such for the preparation of the cementitious pastes described below. Preparation of cementitious pastes and evaluation

The pasta is prepared by mixing the constituents using a Haake mixer fitted with Came type blades rotating at a rotation speed of 40 rpm. The useful volume of the mixing chamber is 85 cm ³ . All pasta is prepared from 85 g of cement. The formation of a paste is linked to the existence of a high pressure in the chamber which leads to efficient shearing of the granular medium. Optimal conditions are obtained by adjusting the filling rate. We have found that the optimal cement level is obtained when the paste is prepared on the basis of 85 g of cement. Half the quantity of cement is introduced into the open chamber, followed by water and the polymer additive, followed by the rest of the cement. The room is closed. The mixture is kneaded. The value of the torque makes it possible to define the state of the dough: (i) high torque signal (> 10 Nm) and presenting a considerable noise: dry non-cohesive dough; (ii) moderate and not very noisy torque signal: cohesive paste; (iii) weak torque signal (1 Nm): soft non-cohesive paste; (iv) reduction of the torque signal and reflux of the paste when the chamber is opened: dilating paste.

Curing of cement

It is necessary to avoid evaporation of the water during the hardening of the cementitious pastes. For this, the pasta is enclosed in an impermeable polymer film forming a closed enclosure.

Composition example 1 (invention)

A cement paste is prepared according to the conditions described above by adding Italbianco 52.5R (85 g) to white cement and water and the non-neutralized polymer acrylic emulsion Pi so that the water / cement weight ratio (W / C) is equal to 0.21 and the dry polymer / cement ratio (P / C) is equal to 0.015.

An extrudable paste is obtained, without any implementation problem (absence of dilatance and absence of water exudation, with good cohesion and elasticity according to the definitions given above). Thereafter, the term "extrudable" will mean: no problem of implementation with cohesive and elastic hold of the cementitious paste.

Composition example 2

A type P _x polymer is prepared but with a weight proportion of methacrylic acid equal to 0.20.

A cement paste is prepared by adding to white cement Italbianco 52.5R (85 g) water and the acrylic emulsion of this polymer so that P / C = 0.05 and E / C =

0.21. After kneading, a non-cohesive paste is obtained which exhibits the phenomenon of water exudation.

Example 3 of composition (invention) A cement paste is prepared by adding Italbianco 52.5R (85 g) of white cement and Pi emulsion to white cement so as to have the following weight ratios: E / C = 0 , 16 and P / C = 0.05. After kneading, an extrudable paste is obtained.

Composition example 4 (invention)

A cement paste is prepared by adding water and the Pi emulsion to Portland gray cement (85 g) so that E / C = 0.16 and P / C = 0.02. After kneading, an extrudable paste is obtained.

Example 5 of composition (invention)

A cement paste is prepared by adding to white cement Italbianco 52.5R (85 g) water and the polymer emulsion P ₂ , described above, so that the water / cement weight ratio (W / C ) is equal to 0.21 and the dry polymer / cement weight ratio (P / C) is equal at 0.05. After kneading, a cohesive, very elastic paste is obtained which does not exhibit the phenomenon of exudation from water.

Example 6 of composition (invention)

A cement paste is prepared by adding Italbianco 52.5R (85 g) of white cement and water and the emulsion P ₃ , described above, so that E / C = 0.17 and P / C = 0.015 . After mixing, a cohesive, elastic paste is obtained which does not exhibit the phenomenon of exudation of water.

Example 7 of composition (invention)

Cement pastes are prepared using Italbianco 52.5R cement and the polymer Pi as in the previous example but varying the water / cement weight ratio (W / C) and the dry polymer / cement weight ratio (P / C) . FIG. 1 shows the fields of feasibility defined by the limit curves E / C and P / C leading to obtaining cohesive pastes, non-dilating and not exhibiting the phenomenon of exudation of water in the case where the polymer Pi is previously neutralized and the case where it is not neutralized. The properties of the dough

(elasticity in particular) vary in the feasibility diagram so that it is possible to adapt the composition to the constraints of the implementation (mechanical strength for example). >

Example 8 of composition (invention) A cement paste is prepared by adding to a mixture (85 g) Italbianco 52.5R white cement / crushed limestone, water and the emulsion of P _x . The white cement / limestone ratio is varied in the following proportions: 100/0, 75/25, 50/25, 25/75. The P / C ratio is kept equal to 0.03. The W / C ratios are respectively 0.20; 0.20; 0.16; 0.15. In all cases, an extrudable paste is obtained. Example 9 of composition (invention)

A paste prepared from Italbianco 52.5R white cement and Pi emulsion, with characteristics E / C = 0.21 and P / C = 0.05, is extruded using a piston in a die. section 10 x 5 mm. The material is cured as described above. The mechanical resistance to bending after 28 days is 40 ^' MPa. The material after immersion in water retains its dimensions, without any swelling.

Example 10 of composition (invention)

A cement paste is prepared by adding Italbianco 52.5R (85 g) of white cement and water and the acrylic polymer emulsion P ₂ , described above, so that the water / cement weight ratio (E / C) is equal to

0.21 and the dry polymer / cement weight ratio (P / C) is equal to 0.05.

The dough is kneaded as before and extruded using a piston through a 10 x 5 mm die. The material is cured as described above. The mechanical resistance to bending after 28 days is

35 MPa.

Composition example 11

A cement paste is prepared by adding to Italbianco 52.5R white cement (85 g) water and the acrylic polymer emulsion P ₂ , described above, so that the water / cement weight ratio (E / C) is equal to 0.21 and that the dry polymer / cement weight ratio (P / C) is equal to 0.05. A second paste is prepared with an identical composition but the polymer P ₂ is previously neutralized by the required quantity of soda before being introduced into the paste. The pastes are pressed and placed in an impermeable film as described above and their mechanical properties are evaluated as a function of the setting time. The graph in Figure 2 compares the hardness of the two pastes on a scale of 0 (soft) to 5 (hard). At a given quantity of polymer, the introduction of the polymer in its non-neutralized form makes it possible to obtain setting and hardening in a shorter time.

figures

Figure 1 shows the feasibility diagram (E / C = f (P / C) of pasta prepared as described in the example

7 with the polymer Pi added in non neutralized form insoluble in water (open symbols) and added in neutralized form by soda (solid symbols).

FIG. 2 shows the evolution over time of the mechanical properties of cementitious pastes, kneaded and hardened as described in Example 11, with the polymer P ₂ added in non-neutralized form, insoluble in water (open symbols) and neutralized by soda (solid symbols).

Claims

1 - Composition of extrudable or pressable hydraulic binder comprising:

(i) at least one hydraulic binder C;

(ii) a polymer rheology agent P which is in the form of an emulsion of at least one copolymer of: (a) (meth) acrylic acid, and (b) at least one alkyl (meth) acrylate, linear or branched in C1-C22 with optional:

(c) at least one third monomer of general formula: C (R _e ) (R _g ) = C (R _f ) -Aι with:

R _e , R _f , R _g being identical or different and chosen from: H or CH ₃ ;

Ai being -COO- (R _t O) _m -R _z or -CO-N (R _p ) - (R _t O) _m -R _z with R _z being a linear or branched C ₁ -C ₃₅ alkyl group, which optionally contains hydroxyl groups; R _p is H or a C1-C5 alkyl group; m is a real number between 1 and 50; R _t is a C1-Cδ alkylene group and as an additional option: d) at least one agent> regulator of chain length (iii) of water E so that the weight ratio (W / C) "total of water E "on" total hydraulic binder C "is less than or equal to 0.25, and with said copolymer having a composition of monomers a), b), c) and of regulating agent d), as defined above, in the following weight proportions per 100 parts by weight of a) + b) + c): a) 25-60% b) 40-75% c) 0-15% d) 0 to 5%.

2 - Composition according to claim 1, characterized in that it consists of a cementitious paste.

3 - Composition according to claim 1 or 2, characterized in that the weight ratio P / C expressed by weight of dry polymer P on weight of hydraulic binder C varies from 0.0025 to 0.1 and preferably from 0.01 to 0.05. 4 - Composition according to one of claims 1 to 3, characterized in that the monomer a) is present in an amount of 30 to 50%, more particularly from 35 to 45% per 100 parts by weight of a) + b) + c).

5 - Composition according to one of claims 1 to 4, characterized in that the type monomer b) of said copolymer P is selected from (C ₁ -C 3) alkyl (meth) acrylates.

6 - Composition according to one of claims 1 to 5, characterized in that the monomer b) is present in an amount of 50 to 70% per 100 parts by weight of a) + b) + c).

7 - Composition according to one of claims 1 to 6, characterized in that the monomer a) is methacrylic acid and the monomer b) is ethyl (meth) acrylate, where appropriate in the absence of monomer c) .

8 - Composition according to one of claims 1 to 7, characterized in that the third monomer c) is present at a rate of 0.5 to 15%, more particularly from 0.5 to 10% per 100 parts by weight of monomers a) + b) + c).

9 - Composition according to one of claims 1 to 8, characterized in that said third monomer c) is selected from the monomers of general formula c) with: m ranging from 5 to 35, Rt being C ₂ -C ₄ alkylene and Rz being linear or branched Cι ₈ -C ₃ alkyl

10 - Composition according to one of claims 1 to 9, characterized in that said third monomer c) is methoxypolyethylene glycol methacrylate preferably with a number of ethoxy units ranging from 10 to 35 or behenyl ether polyethylene glycol methacrylate (BEPGMA).

11 - Composition according to one of claims 1 to 10, characterized in that said hydraulic binder is a cement and preferably a Portland cement.

12 - Composition according to one of claims 1 to 11, characterized in that it further comprises aggregates and / or fillers. 13 - Composition according to one of claims 1 to 12, characterized in that said copolymer P is introduced therein in insoluble form, not neutralized in emulsion.

14 - Composition ^' according to one of claims 1 to 13, characterized in that the regulator of the chain length type d) is selected from: 2- mercaptopropionic acid, 3-mercaptopropionic acid, mercaptoethanol, thioglycolic acid, mercaptosilanes , HS- Ro-Si (0-R _E ) (where R _r is H or C ₁ -C ₃ alkyl and R ₀ is an alkylene chain), phosphites, H3PO ₄ , H ₃ PO ₃ and their salts.

15 - Process for preparing a composition according to one of claims 1 to 14, characterized in that it comprises a step of mixing the components by kneading. 16 - Cured composition based on a composition according to one of claims 1 to 14.

17 - The cured composition according to claim 16 having at 28 days a mechanical resistance in bending greater than 30 MPa. 18 - Process for preparing the cured composition according to claim 16 or 17, characterized in that it comprises a step of extrusion and / or pressing of the composition defined according to one of claims 1 to

14 and a hardening step. 19 - Process according to claim 18, characterized in that said hardening is carried out in an atmosphere saturated with water. 20 - Method according to one of claims 18 or 19, characterized in that the extrusion and / or pressing is preceded by a mixing step.

21 - Method according to one of claims 18 to 20, characterized in that the extrusion step is ^' followed by a final shaping step by pressing in a mold.

22 - Method according to one of claims 18 to 21, characterized in that the mixing and / or extrusion step comprises. degassing of the composition defined according to one of claims 1 to 14.

23 - Hardened objects obtained from the composition defined according to one of claims 1 to 14 or by the process defined according to one of claims 18 to 21 characterized in that they are selected from tubes, pipes, barriers and concrete profiles.