WO2003068702A2

WO2003068702A2 - Composite materials obtained from a cement material and organic fibres with improved mechanical properties

Info

Publication number: WO2003068702A2
Application number: PCT/FR2003/000477
Authority: WO
Inventors: Delphine Blanc-Magnard; Bertrand Bordes; Gilles Orange; Franck Bouquerel
Original assignee: Rhodianyl
Priority date: 2002-02-14
Filing date: 2003-02-14
Publication date: 2003-08-21
Also published as: AU2003226481A1; FR2835826A1; PE20030829A1; AU2003226481A8; WO2003068702A3

Abstract

The invention relates to reinforced composite materials, the base structure of which is a matrix obtained from at least one cement material or chemical binder and polyamide fibres, treated with one or several additives to improve the mechanical properties of said composite materials.

Description

COMPOSITE MATERIALS OBTAINED FROM HYDRAULIC BINDER AND ORGANIC FIBERS HAVING MECHANICAL BEHAVIOR

IMPROVED

The present invention relates to composite materials whose basic structure is a matrix obtained from at least one hydraulic or chemical binder and comprising polyamide fibers treated with additives. The mechanical behavior of these materials is improved by the presence of said treated fibers reinforcing said matrix.

These composite materials can find application in many areas including the construction, as plasters, cements, mortars, concretes, coatings etc.

[0003] One of the best known composite materials obtained from fiber-reinforced hydraulic binder is fibrocement, which is most commonly used for example as a material for the production of roofing articles, pipe, tanks etc. The most common fiber for this purpose is where was asbestos.

For reasons of public health and environmental protection, it is no longer desirable or even authorized by the laws in force in an ever increasing number of countries, to use asbestos.

There is therefore a significant and urgent need to find substitutes for asbestos fibers, giving composite materials, including fiber cement, sufficient mechanical characteristics.

Many studies have been carried out to provide fiber materials in which asbestos is substituted by natural fibers, artificial or synthetic, organic or inorganic. These studies have already allowed the implementation of different types of replacement fibers.

Thus, among the replacement fibers studied to date, there may be mentioned, inter alia, glass, carbon, steel, polyamide (PA), polyester fibers. (PET), polyvinyl alcohol (PVA), polypropylene (PP), and poly (acrylonitrile) (PAN).

None of these substitute products can reproduce exactly all the characteristics provided by asbestos composite material. In fact, the asbestos fiber contributes to imparting to the composite a particularly high flexural breaking stress. In addition, the behavior of the composite is of fragile rigid type. Whatever the synthetic fiber envisaged, it is not possible to obtain the same levels of bending stress at break.

[0009] It is important to remember that fibrociments traditionally comprise a mixture of cement, water, possibly a rheology agent, a processability agent (flocculant, defoamer, etc.), inorganic fillers (such as only calcium carbonate) and one or more fibrous materials (see for example US Pat. No. 5,891,516).

The most common technique for manufacturing fibrocement materials is the Hatschek process (see patent application AT 5970) which consists of preparing an aqueous slurry of cement, silica, or carbonate, fibers and optionally thickeners. , plasticizers, clays, pigments, etc., to deposit a thin layer of this slurry on a porous treadmill and to pass this slurry on and through a series of rollers to laminate and shape this slurry.

During this operation, the water contained in the slurry is drained through openings in the conveyor belt, either naturally or by applying a vacuum (vacuum) applied under the said carpet. After passing through a series of pressure rollers, the fibrocement sheet can be dried and cut into individual sheets, or collected in a series of superimposed layers on a collector cylinder to form fiber cement tubes. Fibro-cultures can be manufactured in the most diverse forms, flat, corrugated or tubular.

As indicated above, the fiber most used in the preparation of fiber cement was asbestos, the latter having a high modulus, high tensile strength and good adhesion to cement. In the final product, the combination of high tensile strength, high modulus of elasticity, and low elongation at break contributed to a high flexural strength of articles. Fibro-friendly fibers.

Another important characteristic of composite products obtained from asbestos fibers is a fragile rigid type of behavior that is to say a rupture of the composite shortly after the maximum stress, and this for a relatively low elongation at break (a few percent)

However, it should be noted that this brittle rigid behavior is not particularly desired in the case of fiber cement composite materials which, in the form of flat, corrugated or tubular plates are intended for roofing applications, piping, tanks. Indeed, it is necessary to considerably oversize the stress at break and no means can detect the next rupture of the composite material.

Natural, artificial or synthetic fibers making it possible to obtain materials, for example fibrociments, having a maximum bending stress level equivalent to or close to that obtained using asbestos fibers, can not be used. found today.

However, and given the toxicity of asbestos fibers, substitute products have been proposed, and among the most well known today include in particular the polyvinyl alcohol fibers (PVA). ), used alone or in combination. These fibers make it possible to produce composite materials whose mechanical characteristics are satisfactory, without however reaching those conferred by asbestos.

More specifically, these fibers make it possible to obtain a level of stress at break quite interesting and simultaneously to obtain a ductile type behavior, preferred for the reasons mentioned above. It is of course to be noted that, in the case of the fiber cement manufacturing process, the PVA fibers mix very well in the aqueous medium. This is due, among other things, to the hydrophilicity of these fibers and their density (d = 1.3 in the case of PVA). However, their relatively high cost is reflected in the selling price of fiber products, making it a substandard substitute at present.

Other alternatives exist, especially with polypropylene fibers (PP) which offer a priori two major advantages. On the one hand, they are significantly less expensive than PVA fibers and secondly, they offer excellent resistance to alkalis. However, the PP fibers, if they are used as such, have the disadvantage of not adhering sufficiently to the cement matrix and lead to composite materials whose flexural strength is insufficient. Therefore, many works (see for example EP-A-0310100, EP-A-0525737 and WO 99/19268) have been carried out in order to improve the properties of these fibers in the fiber cement.

These fiber cement improvement works, such as those cited in patent applications WO 99/19268 and EP-A-1044939, in particular make it possible to surface treat the PP fibers by conferring on them a better affinity for the matrix.

It should also be noted that these improvement works are often very complex, because it is also to give the PP a hydrophilic character that it does not have intrinsically. Thus, preliminary steps of attacking the surface of the fibers are sometimes necessary, as indicated in the patent application EP-A-1044939.

Despite all the treatments, they do not however improve satisfactorily all of the characteristics required for the fiber cement application. Thus, for example, the density of the PP fibers remains below 1, which means that it is difficult to include them homogeneously in a very dilute aqueous medium.

It is also known that the polyamide fibers can be used as reinforcement of cements to reduce the formation of cracks during setting (so-called secondary reinforcement). However, these fibers do not make it possible to obtain composite materials whose level of flexural stress is sufficient compared to composites comprising asbestos or PVA fibers (so-called primary reinforcement).

It therefore appears today that there are no asbestos fiber substitute products for fibrociments that are completely satisfactory, that is to say fibers having good dispersibility, d a relatively low cost and which make it possible to obtain composite materials, and in particular fibrociments, having high mechanical characteristics (mechanical stress at breakage) in flexion). In addition, it is interesting that the products have non-toxicity and ductile flexural behavior, desired in application.

Thus, a first object of the present invention is to provide composite materials with hydraulic or chemical binder, such as fiber-reinforced cement substituting for asbestos, and not having the disadvantages mentioned above.

Another object of the present invention is to provide composite materials with a hydraulic or chemical binder comprising fibers other than asbestos fibers and imparting to the finished products improved mechanical properties.

The invention also relates to composite materials with hydraulic or chemical binder, comprising fibers other than asbestos fibers and having good mechanical properties of flexural strength.

[0027] Hydraulically or chemically bonded composite materials, comprising fibers other than asbestos fibers, having high flexural strengths and / or increased flexural ductile behavior, form yet another object of the present invention. .

Finally, the purpose of the present invention is to provide composite materials for replacing asbestos fibers with low cost. Other objectives, in addition to those set out above, will become apparent in the description of the invention which follows.

Thus, the present invention relates to reinforced composite materials whose basic structure is a matrix obtained from at least one hydraulic or chemical binder and at least one of polyamide fibers treated with one or more additives to improve the properties. mechanical so-called composite materials.

By hydraulic binder in the sense of the present invention is more particularly meant a hydraulic setting binder such as those known to those skilled in the art, that is to say an inorganic cement and / or a binder or adhesive inorganic which hardens by hydration, that is to say by taking, natural or not, an aqueous suspension and / or dispersion (slurry or "slurry") of various inorganic and / or organic materials. Thus, by way of non-limiting example, the materials comprising at least one hydraulic binder matrix belong to the class of mortars, plasters or concretes, and the hydraulic binder can be a Portland cement, additive or not, a high alumina cement, a slag cement, a calcium sulphate (plaster), autoclaved calcium silicates and combinations of particular binders and other chemical binders.

By chemical binder in the sense of the present invention is more particularly meant a binder which gives rise to a reaction as a result of a chemical reaction, for example acid-base, and not by hydration. An example of a chemical binder can be found in phosphate (MAP) and magnesia mixtures.

The consolidated product (hardened) obtained has mechanical characteristics that can be improved by the addition of natural, artificial or synthetic fibers, organic or inorganic treated with one or more additives. A particularly interesting example in the context of the present invention relates to fiber cement.

More particularly, the invention relates to reinforced composite materials whose basic structure is a matrix obtained from at least one hydraulic or chemical binder and polyamide fibers treated with one or more additives chosen from:

• latexes;

Alkylphosphates and their derivatives such as aminoalkylphosphates and aminoalkyldiphosphates;

Phosphonic acid, polyvinylphosphonic acid, phosphosuccinic acid, polyvinylphosphonic-acrylic copolymers, and their salts;

• polar olefins;

Functional alkoxysilanes; Block copolymers prepared by controlled radical polymerization;

Random copolymers chosen for example from linear polymers with low (meth) acrylic acid, in particular sulphonated or phosphated acids, comb polymers with poly (meth) acrylic acid backbone and cement-compatible grafts as PEG-based grafts, comb polymers with PEG backbone and (meth) acrylic acid-based grafts; • Carboxylic acids and dicarboxides, and in particular lauric acid, adipic acid, glutaric acid and succinic acid, alone or in mixtures, and their salts and derivatives, including dioctylsulfosuccinic;

• products derived from catechol; Polyphenols and in particular sulphonated polyphenols;

Amino acids such as aspartic acid, glutamine, methionine, etc. and their salts;

Polyamide oligomers comprising up to 7 repeating units;

Polyamide oligomers grafted with a function, for example chosen from phosphates, phosphonates, sulphonates, alkoxysilanes, dicarboxylates, amino-carboxylates, anhydrides, epoxys and diols;

• aliphatic acrylate and polyester acrylate urethane resins; and

Water-soluble polyamide resins, in particular resins obtained by introduction of polyamine comonomers and reaction with epichlorohydrin,

these additives can be used alone or in combination of two or more of them.

When the additive is a latex, it may be chosen from: - an aqueous dispersion of acrylic esters; a nanolatex, for example a carboxylated nanolatex, a phosphated nanolatex, or a sulfonated nanolatex; and an alkali-soluble or alkali-swelling latex, in particular comprising more than 30% by weight of methacrylic acid relative to the mass of dry matter.

By alkali-soluble latex is meant a soluble latex totally or partially in at least one basic compound. Alkali-swelling latex means a latex whose particles constituting swell in the presence of at least one basic compound, the latex / base then taking the appearance of a gel.

When the additive is selected from alkylphosphates and alkylphosphonates and their alkali metal salts, they are for example selected from potassium laurylphosphate, potassium decylphosphate and tridecylphosphate potassium.

According to a particular embodiment of the invention, the additive is different from an alkylphosphate and its derivatives such as aminoalkylphosphates and aminoalkyldiphosphates.

When the additive is chosen from polar olefins, these may be chosen from: polymers containing olefinic monomers and polar groups; homopolymers and copolymers of olefinic monomers modified after synthesis with polar groups chosen from maleic anhydride, acrylic acid and methacrylic acid; homopolymers and copolymers of olefinic monomers modified by oxidation; and copolymers of olefinic monomers and polar monomers, optionally neutralized with ions.

When the additive is chosen from functional alkoxysilanes, these are generally of formula (I):

in which :

A represents a hydrolyzable radical, for example chosen from linear or branched alkoxy, alkoxyalkyl and alkoxycarbonyl radicals having from 1 to

6 carbon atoms, advantageously a methoxy or ethoxy radical, it being understood that when 3-n is strictly greater than 1, the radicals A may be identical or different;

Y represents an organic radical substituted with a functional group, in particular a group capable of reacting / interacting with amines, carboxylic acids or amides, for example an unsaturated bond, an acid function, an amino function, an ester function or a functional group. anhydride, epoxy function or isocyanate function;

Z represents an inert organic radical, for example a linear or branched alkyl group comprising from 1 to 6 carbon atoms, it being understood that when n is strictly greater than 1, the radicals Z may be identical or different; and n represents 0, 1 or 2, preferably 0. As alkoxysilanes comprising an unsaturated functional group, there may be mentioned vinyltrialkoxysilanes of general formula CR ¹ R ² = CR ³ - (CH ₂ ) _m -Si (OR ⁴ ) ₃ and their hydrocondensates, where m is an integer, in which general between 0 and 6 inclusive, wherein R ¹ , R ² , R ³ and R ⁴ , identical or different, are selected from hydrogen, alkyl and alkoxyalkyl radicals, alkyl and aikoxy radicals; in the term alkoxyalkyl being linear or branched and having from 1 to 6 carbon atoms, and wherein the vinyltrialkoxysilane is in particular chosen from vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxyethoxysilane, (acryloxyalkyl) trialkoxysilanes, and (methacryloxyalkyl) trialkoxysilanes, in particular 3- (methacryloxy) propyltrimethoxysilane.

Among the alkoxysilanes having a reactive function with the polyamide, there may be mentioned advantageously glycidyloxypropyltrimethoxysilane, isocyanatopropyltriethoxysilane, and aminopropyltriethoxysilane, as well as their hydrocondensates.

When the additive is selected from block copolymers prepared by controlled radical polymerization, these are for example those described in patent applications WO9858974, FR2794463, FR2799471, FR2802208, and FR2812293. These polymers are synthesized from at least one ethylenically unsaturated monomer, at least one source of free radicals and at least one compound in which a homolytic cleavage bond (for example C-O or C-halogen) is possible. The monomers used are more specifically chosen from styrene and its derivatives, butadiene, chloroprene, (meth) acrylic esters, vinyl esters and vinyl nitriles.

Finally, among the acids and dicarboxylic acids, the additives may be chosen for example from lauric acid and its salts and derivatives, and α, ω-dicarboxylic acids, such as, for example, adipic acid, glutaric acid, succinic acid and their salts and derivatives. These acids, and in particular the α, ω-di-carboxylic acids, may advantageously be used alone or as mixtures of two or more of them and, for example, the mixture of adipic, glutaric and succinic acids, obtained as a by-product in the synthesis of adipic acid.

Thus, the composite materials according to the invention comprise polyamide fibers treated with one or more of the previously described additives. The use of Such processed polyamide fibers impart to composite materials which include them mechanical properties, and in particular a bending strength stress, sufficiently high that the material can replace an asbestos composite material.

Indeed, the additives used to treat the polyamide fibers are such that they have an affinity for both the fiber and the cement matrix. In this way, they ensure a better cohesion between the fibers and the matrix with hydraulic or chemical bonding, thus conferring composite materials the mechanical properties of bending strength and ductility sought.

The fibers used for the invention are synthetic fibers available on a large scale, for an acceptable cost in the field of the invention. Another characteristic required for the fibers of the invention and present in the composite materials, such as fiber cement, is besides a great durability and a good resistance to alkalis which are generally present in the cement matrix. Polyamide fibers exhibit the required chemical stability in cementitious media (alkali resistance).

Another advantage related to the use of polyamide fibers is that this polymer has a density slightly higher than that of water (d = 1, 15). In addition, this polymer has a strong hydrophilic character (due to a polar nature of the surface) as for PVA and unlike PP. These two points are particularly important when it is known that the fibrociments are prepared from very dilute aqueous baths, as will be seen in detail below.

The hydrophilic nature of the fibers and the density slightly greater than 1 thus allow better dispersion in the cement slurry (aqueous medium). The fibers thus have the advantage of remaining dispersed after addition of fillers and various additives. A good dispersibility of the fibers is indeed an important factor to avoid the formation of agglomerates and a uniform distribution of the fibers in the final product.

Thus, the polyamides used will advantageously those used usually in the field of textile articles or son, fibers, etc.. with technical applications. By way of example and without limitation, the polyamides that can be used in the present invention include PA 6.6, PA 6, PA copolymer 6.6-PA 6, semi-aromatic polyamides, such as polyamide 6T, Amodel® (marketed by Amoco), HTN® (marketed by DuPont), and other polyamides 11, 12, 4 The polyamides may be of linear or branched structure, for example the star polyamide marketed by Rhodia under the trademark Technylstar®.

The fibers according to the invention are manufactured according to conventional methods known to those skilled in the art and for example by extrusion of the melt (polyamide) through a die and optionally stretching son, ribbons, cables or tablecloths, then cut these fiber products.

Furthermore, any step, conventional in the field of the manufacture of textile fibers, intended for example to dimensionally stabilize the fibers (heat setting) or to give them volume through a compression box (crimping), can be applied. Any other fiber manufacturing process is also suitable.

The fibers used in the present invention may have sections of all shapes, whether round, serrated or fluted, or in the form of beans, but also multilobal, especially trilobed or pentalobées, X-shaped, ribbon, hollow, square, triangular, elliptical and others.

The shape of the fiber section is however not an essential feature of the invention. All forms of fiber section resulting from the method of manufacturing said fibers are acceptable. Likewise, the fibers used in the present invention may be of diameter and / or of constant section or have variations.

Finally, by polyamide fibers according to the invention, it should be understood also multi-component fibers (for example of the "core-skin" type) of which at least one component is a polyamide as defined above.

In general, the fibers used in the composite materials of the present invention are characterized by their title which will generally be greater than 0.2 decitex and less than or equal to 9 decitex (that is to say 9 g). / 10000 meters), advantageously less than 3.3 decitex. Preferably, the title of the incoming fibers in the composition of the composite materials of the invention will be between 0.3 and 3.3 decitex, and more preferably between 0.4 and 2.0 decitex.

In addition, low-titre fibers provide other advantages including a higher density of fibers per cubic centimeter of composite material. This may possibly make it possible to substantially reduce the fiber content, while maintaining equivalent use or mechanical properties (such as flexural strength), and thus to obtain a more economical economic contribution from the reinforcement.

Another important characteristic is the length of the fibers which are incorporated in the fiber fibers of the invention. In general, this length is adapted to the title of the fiber used. Long fiber lengths will thus be avoided so that the latter do not substantially wrap themselves on themselves. Short fibers, on the other hand, will not allow to establish a satisfactory reinforcement between the constitutive particles of the cement matrix, and the finished product will not have the desired mechanical behavior.

Thus, in the context of the present invention, the fibers are cut to a length that can be uniform or non-uniform (including mixed) and generally between 2 mm and 30 mm, preferably between 3 mm and 20 mm. mm, for example about 6 mm.

The composite materials according to the invention may further comprise other organic or inorganic fibers, natural, artificial or synthetic, other than the polyamide fibers described above. These other fibers may or may not be treated with one or more of the additives mentioned above for the treatment of polyamide fibers. The additives can then be identical or different.

By way of example, organic fibers which can be used in combination with the treated polyamide fibers include untreated polyvinyl alcohol, polyester, polypropylene, poly (acrylonitrile), polyamide fibers, aramid, carbon and polyolefins. For example, natural or artificial fibers from cellulose can be added. Among the inorganic fibers which can be used in combination with the polyamide fibers, mention may be made of rock wool, slag wool, glass fibers, wollastonite fibers, ceramic fibers and others.

The amount of fibers present in the composite materials of the invention may vary in large proportions, depending on the use to which said composite materials are intended. Thus, the total amount of the fibers is generally between 0.1% and 25% by weight relative to all the dry constituents of the hydraulic or chemical binder matrix.

In the particular case of fiber fibers, the proportions by weight of fibers relative to the totality of the dry constituents are generally between 0.1% and 10%, preferably between 0.5% and 5% by weight, advantageously between about 1% and about 3% by weight. In fiber proportions of less than 0.1% by weight, the reinforcing effect is considered insufficient. When the fibers are present in a proportion of more than 10% by weight, the implementation in the aqueous bath becomes more difficult, requiring the use of a particular method.

Thus, in the case of composite materials for which a level of 10% to 25% by weight of fibers is required, the implementation technique preferably used is the SIMCON technique ("Slurry Infiltrated Concrete Matte").

The composite materials are generally prepared from an aqueous slurry comprising at least one hydraulic or chemical binder, for example cement, silica, or carbonate, polyamide fibers treated with one or more of the additives defined above, other natural, artificial or synthetic, organic or inorganic fibers, whether or not treated with one or more of the abovementioned additives and, where appropriate, fillers.

These fillers are of the most diverse nature and allow, depending on the case, a quick or slow setting, a better behavior in dripping suspensions on the drip machines. The charges can also be simply inert charges. Among the most commonly used fillers are products such as ashes, pozzolans, blast furnace slags, carbonates, clays, ground rock, ground quartz, amorphous silica and the like. The raw polyamide fiber is treated, before being mixed with the slurry containing the hydraulic binder, with one or more of the previously described additives, according to various known methods. Among these, mention may be made, by way of examples and in a nonlimiting manner, the technique of treating the raw fiber with a roller, by spray or vaporization, by dipping, the technique of padding, as well as any method used in the textile industry processing synthetic fibers.

This treatment can be carried out at different stages of the manufacture of the fiber. These include, among other things, all the steps in which sizing is conventionally added. It is thus possible to apply the additive at the bottom of the spinning machine before winding. It is also possible, in the case of so-called "fiber" processes, to apply the additive before, during or after the steps of drawing, crimping or drying, etc.

As already indicated, these additives can be used alone or in combination of two or more of them for the treatment of raw polyamide fibers. As a rule, an amount of additives of between 0.1% and 10% by weight relative to the total weight of the raw fibers to be treated is sufficient to obtain a composite material having the desired characteristics.

In some cases, it may further be advantageous to subject the polyamide fiber a first pre-treatment (pretreatment) according to methods known to those skilled in the art, to promote the adhesion of the additive to said fiber. In addition, it may also be envisaged to subject the fiber, before or after treatment with additives and / or pretreatment, other chemical or physical treatments such as for example irradiation, dyeing and the like.

The invention also relates to the polyamide fiber treated with one or more of the additives mentioned above. These treated polyamide fibers advantageously find use as reinforcement in materials obtained from a matrix comprising at least one hydraulic or chemical binder, for example fibrociments.

The composite materials comprising the polyamide fibers treated with one or more additives, as described in the present invention, have quite interesting and improved mechanical characteristics. Among these characteristics, the flexural strength, characterized by the maximum stress that can withstand the material, and the ductility, described by the relative variation of the endurable stress by the material during its opening in flexion after breaking of the cement matrix, have proved quite satisfactory. The composite materials according to the invention thus offer an alternative that is quite advantageous for asbestos and fibrocement fiber products comprising other organic fibers used up to now.

Composite materials according to the invention comprising treated polyamide fibers as defined above can therefore be used for the preparation of construction articles in all their forms, flat, corrugated, molded, etc. Thus, the composite materials of the invention find, for example, a use for the manufacture of plates, pavements, roofing or façade cladding, piping, tanks, tanks, especially rainwater tanks, containers, and all other accessory elements of shapes. the most diverse. Such articles comprising at least one composite material according to the present invention are also part of the present invention.

It is essential that the rupture of the material is not of the fragile rigid type (sudden drop in the endurable stress by the material once it is damaged, in other words, macroscopic rupture of the material once the cement matrix is damaged. ) but has a ductile appearance (maintaining the stress endurable by the material even when it is damaged, in other words, preserving the continuity of the material even once the cement matrix is damaged). This aspect is particularly important for roof tiles. This aspect is also important for the transport of parts or their machining by drilling, nailing, cutting, etc.

The present invention is described in more detail in the following specific embodiments. These examples are purely illustrative and are not intended to limit the invention in any way whatsoever.

EXAMPLE 1 (Latex treatment Rhoximai® Dec27 and Sopronyl® 50)

Various composite materials, of fiber cement type, have been prepared as indicated below: Preparation of treated polyamide fibers

The polyamide fibers used are obtained from continuous yarns, sold by Rhodia under the trade name F111, of title 21 dtex and 8 dtex. The characteristics of these wires are given in Table 1 below:

Table 1

The son pass through a thermostatic bath at 50 ° C containing the treatment, then between two squeezing rolls on which is applied a pressure of 3 bar, then in a controlled oven at 130 ° C. The yarns are then cut to an average length of 6 mm. For the fibers A and D (of respective titers 21 dtex and 8 dtex), the treatment bath is a latex, anionic aqueous dispersion of copolymers based on acrylic esters, sold by Rhodia under the trade name Rhoximat® Dec27. The commercial product was diluted with water by a factor of 2.

For the B-fibers (of title 21 dtex), the treatment bath is an aqueous solution of high-density acrylic copolymers sold by Rhodia under the trade name Sopronyl® 50. The commercial product was diluted with water, water and water. The C and E fibers (of respective titers 21 dtex and 8 dtex) are raw polyamide fibers which have not been subjected to an additive treatment and are used for comparison purposes.

The details of the fibers are given in Table 2:

Table 2

Preparation of fiber cement

The composition of the fiber cement used in the examples is as follows:

cement, marketed by Lafarge under the reference HTS 52.5 200 g

silica fume, marketed by Elkem under the reference 940 U 35 g - cellulose extracted from Pinus Radiata 10 g

- polyamide reinforcing fibers A, B, C, D or E as defined 5 g

- water 750 g.

The cellulose is first pulped for one hour with intense stirring, then the other ingredients are added. The whole, after mixing for 15 minutes, is poured into a mold, pulled under a slight primary vacuum. The cake is then subjected to a pressure of 10 tons (10 MPa) in order to shape the samples. For each formulation, 6 specimens of fiber cement are made: dimensions 120 x 30 x 5 mm. These specimens are left for 24 hours at room temperature in a humidity-saturated chamber, then are matured for 24 hours at 60 ° C. in an enclosure still saturated with moisture, and finally left for at least 24 hours in a room conditioned at 20 ° C. and with a relative humidity (RH) of 65% before testing.

The mechanical tests are performed in 3-point bending (between axis: 100 mm) at a test speed of 0.1 mm / min. This test is a standard 3-point bending test. The force-displacement curve is recorded, and the equivalent stress corresponding to the maximum load (σ max) is calculated. The equivalent stress corresponding to an arrow of the 2 mm test specimen is also calculated.

In all cases, there is no evidence of cracking on the edges of the test pieces, even during the long-term aging of the products.

Table 3 shows the relative increase in the maximum stress obtained during the test of a fiber reinforced fibro-cement with treated fibers, compared to the maximum stress obtained during the test of a reinforced fiber cement with untreated fibers. This relative increase is noted Δσ _max . Moreover, the ductile behavior is characterized by a parameter δ which is the percentage of stress still tolerable by the sample for an arrow of 2mm, compared to the maximum stress tolerable by the sample. Table 3

The curves representing the stress supported as a function of the deflection of the specimen are shown in FIG. 1 (fiber-reinforced fibers from fibers A, B and C) and in FIG. 2 (fiber-reinforced fibers from fibers D and E) .

The maximum stress tolerable by the fiber cement is increased in the presence of fiber treatment. In addition, the ductility of the material is greatly increased by the treatment of the fibers, which represents a significant improvement in the properties of use.

The comparison of the results obtained in FIGS. 1 and 2 shows the advantage of using low-titre fibers so as to obtain a maximum gain both on the maximum stress tolerable by the material and on its ductility.

EXAMPLE 2 (Polar olefin type treatment)

Various composite materials, of fiber cement type, have been prepared as indicated below:

Preparation of treated polyamide fibers

Two fibers are used in this example.

On the one hand the unitary title fibers 8 dtex as described in Example 1 (fiber E)

On the other hand polyamide fibers of lower title, of the order of 0.53 dtex. These latter fibers are obtained from continuous yarns, manufactured according to a method of POY type ("Partially Oriented Yarn", partially oriented yarn) and over-stretched in recovery.

They are in the form of a multifilament type 72f136, ie consisting of 136 single strands whose overall title is 72dtex. The title on the strand is therefore

0,53dtex.

The characteristics of two types of threads (unit titles δdtex and 0.53 dtex) are given in Table 4 below: Table 4

The son pass through a thermostatic bath at 50 ° C containing the treatment, then between two squeezing rollers on which is applied a pressure of 2 bar, then in a controlled oven at 130 ° C. The yarns are then cut to an average length of 6 mm.

For the G and I fibers (of respective titers 8 dtex and 0.53dtex), the treatment bath is a polar olefin in emulsion / dispersion sold by Paramelt under the reference Aquaseal 1227®. The commercial product was diluted with water by a factor of 4

F and H fibers (of respective titers 8 dtex and 0.53 dtex) are raw polyamide fibers that have not been subjected to an additive treatment and are used for comparison. The details of the fibers are given in Table 5:

Table 5

Preparation of fiber cement

The composition of the fiber cement used in Example 2 is exactly that of the example

1. The 4 polyamide reinforcing fibers F, G, H or I as defined are added at the height of 5g for 200g of cement and 750g of water.

The protocol adopted adopts the one presented in example 1

The mechanical tests in 3-point bending are also performed according to the protocol described in Example 1. The force-displacement curve is recorded, and the equivalent stress corresponding to the maximum load (σ max) is calculated. The equivalent stress corresponding to an arrow of the 2 mm test specimen is also calculated. In all cases, there is no evidence of cracking on the edges of the test pieces, even during the long-term aging of the products. Table 6 shows the increase in the maximum stress obtained during the test of a fibrocement reinforced with treated fibers, compared to the maximum stress obtained during the test of a reinforced fiber cement with untreated fibers. We find the magnitudes of relative increase Δσ max and ductility δ as defined in Example 1.

Table 6

The curves representing the stress supported as a function of the deflection of the specimen are shown in FIG. 3 (fibrocement reinforced with fibers F and G).

The maximum stress tolerable by the fiber cement is increased in the presence of fiber treatment. Comparison of the results obtained with fibers F or G on the one hand (8dtex) and H or I on the other hand (0.50 dtex) shows once again the interest of using low-grade fibers so as to obtain a maximum gain on both the maximum stress tolerable by the material and its ductility.

EXAMPLE 3 (Bloc / Statistical Processing)

Preparation of treated polyamide fibers

This is an 8dtex fiber as described in Example 2.

The son pass through a thermostatic bath at 50 ° C containing the treatment, then between two squeezing rollers on which is applied a pressure of 2 bar, then in a controlled oven at 130 ° C. The yarns are then cut to an average length of 6 mm. For K-fibers of the title 8 dtex, the treatment bath is a polymer obtained by radical polymerization from Butyl Acrylate, acrylic acid and a acrylic monomer having a ureido function, diluted in water to a concentration of 0.1% by weight.

The title D fiber 8 dtex is a raw polyamide fiber that has not been subjected to an additive treatment and is used for comparison.

The details of the fibers are given in Table 7:

Table 7

Preparation of fiber cement

The composition of the fiber cement used in Example 3 is exactly that of the example

1. The 2 polyamide reinforcing fibers used being the J and K fibers.

The whole of the adopted protocol resumes in detail the one presented in example 1. The 6 specimens of fiber cement made for each type of fiber (J and K) are aged according to the protocol described in example 1.

The mechanical tests in 3-point bending are also performed according to the protocol described in Example 1.

Table 8 presents the gains in mechanical properties by taking up the evaluation criteria of Example 1 (relative increase of the maximum stress noted Δσ max, ductility behavior characterized by a parameter δ).

Table 8

The curves representing the constraint supported as a function of the deflection of the specimen are shown in FIG. 4 (fiber-reinforced fibers from fibers J and K).

The maximum stress tolerable by the fiber cement is increased in the presence of fiber treatment.

EXAMPLE 4 (block treatment)

Preparation of treated polyamide fibers

This is a δdtex fiber as described in Example 2.

The title M fiber 8 dtex passes into a thermostate bath at 55 ° C containing the treatment (concentration of 1.5% by weight), then between two squeezing rollers on which a pressure of 2 bars is applied, then in a oven regulated at 133 ° C. The yarns are then cut to an average length of 6 mm.

For the M 8 dtex fibers, the treatment bath is a diblock copolymer based on polyacrylic acid (PAA) and polyvinyl alcohol (PVOH)

The title L fiber 8 dtex is a raw polyamide fiber which has not been subjected to an additive treatment and is used for comparison.

The details of the fibers are given in Table 9:

Table 9

Preparation of fiber cement

The composition of the fiber cement used in this example 4 is exactly that of Example 1. The 2 polyamide reinforcing fibers used being the fibers L and M

The whole of the adopted protocol resumes in detail the one presented in example 1. The 6 specimens of fiber cement made for each type of fiber (L and M) are aged according to the protocol described in example 1.

Table 10 presents the gains in mechanical properties by taking again the evaluation criteria of example 1 (relative increase of the maximum stress noted Δσ max)

Table 10

EXAMPLE 5 (Polar olefin type treatment)

Preparation of the treated polyamide fibers Two fibers are used in this example 5. These are the 8dtex and 0.50 dtex fibers as described in Example 2. The son pass through a thermostatic bath at 57 ° C containing the treatment, then between two squeezing rollers on which is applied a pressure of 2 bar, then in a controlled oven at 95 ° C. The yarns are then cut to an average length of 6 mm. For the O and Q fibers (of respective titers 8 dtex and 0.50dtex), the treatment bath is obtained from a commercial product of the Michelman company referenced MX 325E reduced by dilution to 5% of dry extract and then to 0.1% sodium adipate and 5% ethanol are added.

The N and P fibers (of respective titers 8 dtex and 0.50 dtex) are raw polyamide fibers which have not been subjected to an additive treatment and are used for comparison purposes.

The details of the fibers are given in Table 11:

Table 11

Preparation of fiber cement

The composition of the fiber cement used in this example is exactly that of Example 1. The 4 polyamide reinforcing fibers used being the fibers N, O, P, Q

The whole of the adopted protocol resumes in detail the one presented in example 1. The 6 specimens of fiber cement made for each type of fiber (N, O, P, Q) are aged according to the protocol described in example 1.

Table 12 shows the gains in mechanical properties by using the evaluation criteria of Example 1 (relative increase in the maximum stress noted Δσ max, ductility behavior characterized by a parameter δ). Table 12

The curves representing the stress supported as a function of the deflection of the specimen are shown in FIG. 5 (fibrocement reinforced with N, O, P, Q fibers).

EXAMPLE 6 (Oligomer Treatments PA)

Preparation of treated polyamide fibers

Only one type of fiber is used in this example 6. It is the 0.50 dtex fibers as described in Example 2.

The son pass through a thermostatic bath at 48 ° ^C. containing the treatment, then between two squeezing rollers on which is applied a pressure of 3 bar, then in a controlled oven at 130 ° C. The yarns are then cut to an average length of 6 mm. For the fiber S (0.50dtex title), the treatment bath is obtained from an oligomer of PA 66 (obtained from 3148 g of a stoichiometric salt of hexamethylenediamine adipate and 630 g of adipic acid), the main characteristics of which are detailed in the table below:

Table 13

By dilution, the oligomer is brought to a concentration of 2.5% by weight and then supplemented with 2.5% ethanol

The fiber R (0.50 dtex title) is a raw polyamide fiber that has not been subjected to an additive treatment and is used for comparison.

The details of the fibers are given in Table 14:

Table 14

Preparation of fiber cement

The composition of the fiber cement used in this example 6 is exactly that of Example 1. The 2 polyamide reinforcing fibers used being the R and S fibers. The entire protocol adopted repeats in detail that presented in Example 1. The 6 specimens of fiber cement produced for each type of fiber (R and S) are aged according to the protocol described in Example 1.

Table 15 shows the gains in mechanical properties by using the evaluation criteria of Example 1 (relative increase of the maximum stress noted Δσ max)

Table 15

The maximum stress tolerable by the fiber cement is increased in the presence of fiber treatment. EXAMPLE 7 (Adipic Acid Treatments)

Preparation of treated polyamide fibers

Only one type of fiber is used in this example 6. This is the 8 dtex fibers as described in Example 1.

The son pass through a thermostatic bath at 50 ° C containing the treatment, then between two squeezing rollers on which is applied a pressure of 3 bar, then in a furnace regulated at 85C. The yarns are then cut to an average length of 6 mm.

For U fiber (of δdtex title), the treatment bath is an aqueous solution (concentrated to 5% by weight) of adipic acid.

T-fiber (of title 8 dtex) is a raw polyamide fiber which has not been subjected to an additive treatment and is used for comparison.

The details of the fibers are given in Table 16

Table 16

Preparation of fiber cement

The composition of the fiber cement used in this example 6 is exactly that of Example 1. The 2 polyamide reinforcing fibers used being the T and U fibers. The whole of the protocol adopted repeats in detail the one presented in Example 1. The 6 fiber cement samples made for each type of fiber (T, U) are aged according to the protocol described in Example 1.

The mechanical tests in 3-point bending are also performed according to the protocol described in Example 1. In all cases, there is no evidence of cracking on the edges of the test pieces, even during the long-term aging of the products.

Table 17 shows the gains in mechanical properties by using the evaluation criteria of Example 1 (relative increase of the maximum stress noted Δσ max, ductility behavior characterized by a parameter δ).

Table 17

The curves representing the stress supported as a function of the deflection of the specimen are shown in FIG. 6 (fiber-reinforced fibers from the T and U fibers).

Claims

1. Reinforced composite material whose basic structure is a matrix obtained from at least one hydraulic or chemical binder and polyamide fibers treated with one or more additives chosen from:

• latexes;

• polar olefins;

Random copolymers chosen for example from linear polymers with low (meth) acrylic acid, in particular sulphonated or phosphated acids, comb polymers with poly (meth) acrylic acid backbone and cement-compatible grafts as PEG-based grafts, comb polymers with PEG backbone and (meth) acrylic acid-based grafts;

• Carboxylic acids and dicarboxides, and in particular lauric acid, adipic acid, glutaric acid and succinic acid, alone or in mixtures, and their salts and derivatives, including dioctylsulfosuccinic;

Amino acids such as aspartic acid, glutamine, methionine, etc. and their salts;

Polyamide oligomers comprising up to 7 repeating units;

• aliphatic acrylate and polyester acrylate urethane resins; and

Water-soluble polyamide resins, in particular resins obtained by introduction of polyamine comonomers and reaction with epichlorohydrin, these additives can be used alone or in combination of two or more of them.

2. Composite material according to claim 1, characterized in that the additive is different from an alkyl phosphate and its derivatives such as aminoalkylphosphates and aminoalkyldiphosphates;

3. Composite material according to claim 1 or 2, characterized in that the additive is a latex chosen from: an aqueous dispersion of acrylic esters; a nanolatex, for example a carboxylated nanolatex, a phosphated nanolatex, or a sulfonated nanolatex; and an alkali-soluble or alkali-swelling latex, in particular comprising more than 30% by mass of methacrylic acid relative to the mass of dry matter.

4. Composite material according to claim 1, characterized in that the additive is chosen from alkylphosphates and alkylphosphonates and their alkali metal salts, these are for example chosen from potassium laurylphosphate, potassium decylphosphate and tridecylphosphate. of potassium.

5. Composite material according to claim 1 or 2, characterized in that the additive is chosen from: polymers comprising olefinic monomers and polar groups; homopolymers and copolymers of olefinic monomers modified after synthesis with polar groups chosen from maleic anhydride, acrylic acid and methacrylic acid; homopolymers and copolymers of olefinic monomers modified by oxidation; and copolymers of olefinic monomers and polar monomers, optionally neutralized with ions.

6. Composite material according to claim 1 or 2, characterized in that the additive is an alkoxysilane of formula (I):

in which :

A represents a hydrolyzable radical, for example chosen from linear or branched alkoxy, alkyloxyalkyl and alkoxycarbonyl radicals containing from 1 to 6 carbon atoms, advantageously a methoxy or ethoxy radical, it being understood that when 3-n is strictly greater than 1, the radicals A may be identical or different;

Z represents an inert organic radical, for example a linear or branched alkyl group comprising from 1 to 6 carbon atoms, it being understood that when n is strictly greater than 1, the radicals Z may be identical or different; and n represents 0, 1 or 2, preferably 0.

7. Composite material according to claim 1, 2 or 6, characterized in that the additive is chosen from vinyltrialkoxysilanes of general formula CR ¹ R ² = CR ³ - (CH ₂ ) _m -Si- (OR ⁴ ) ₃ and their hydrocondensates, where m is an integer, generally between 0 and 6 inclusive, where R ¹ , R ² , R ³ and R ⁴ , which are identical or different, are chosen from hydrogen, alkyl radicals, and an alkyloxyalkyl radical, the alkyl and alkoxy radicals in the term alkoxyalkyl being linear or branched and containing from 1 to 6 carbon atoms, and wherein the vinyltrialkoxysilane is in particular chosen from vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxyethoxysilane and (acryloxyalkyl) trialkoxysilanes, and (methacryloxyalkyl) trialkoxysilanes, in particular 3- (methacryloxy) propyl-trimethoxysilane.

8. composite material according to claim 1, 2 or 6, characterized in that the additive is an alkoxysilane selected from glycidyloxypropyltrimethoxysilane, isocyanatopropyltriethoxysilane, and aminopropyltriethoxysilane, and their hydrocondensates.

9. Composite material according to claim 1 or 2, characterized in that the additive is a block copolymer synthesized by controlled radical polymerization of at least one ethylenically unsaturated monomer selected from styrene and its derivatives, butadiene, chloroprene, (meth) acrylic esters, vinyl esters and vinyl nitriles.

10. Composite material according to claim 1 or 2, characterized in that the additive is a carboxylic acid selected from lauric acid and its salts and derivatives, and α, ω-dicarboxylic acids, such as, for example, adipic acid. , glutaric acid, succinic acid and their salts and derivatives, used alone or as mixtures of two or more of them.

11. Composite material according to any one of the preceding claims, characterized in that the polyamide fibers are chosen from polyamide 6.6 (PA 6.6), polyamide 6 (PA 6) and PA 6.6-PA 6 copolymers, of PA 6.6-PA 6 copolymer, of semi-aromatic polyamides, such as polyamide 6T, and fibers of other polyamides 11, 12, 4-6.

12. Composite material according to any one of the preceding claims, characterized in that the fibers have a titer of between 0.2 and 9 decitex, advantageously between 0.3 and 3.3 decitex, preferably between 0.4 and 2. , 0 decitex.

13. Composite material according to any one of the preceding claims, characterized in that the fibers have a uniform or non-uniform length (including mixed) and between 2 mm and 30 mm, preferably between 3 mm and 20 mm, for example 6 mm.

14. Composite material according to any one of the preceding claims, characterized in that it further comprises other organic or inorganic fibers, natural, artificial or synthetic.

15. Composite material according to any one of the preceding claims, characterized in that the total amount of the fibers is between 0.1% to 25% by weight relative to the totality of the dried constituents of the matrix with hydraulic or chemical binder. .

16. Composite material according to claim 15, characterized in that the proportions by weight of fibers relative to the totality of the dry constituents are between 0.1% and 10%, preferably between 0.5% and 5% by weight. weight, advantageously between

1% and about 3% by weight.

17. Composite material according to any one of the preceding claims, characterized in that the amount of additives is between 0.1% and 10% by weight relative to the total weight of the raw fibers to be treated.

18. Composite material according to any one of the preceding claims, characterized in that the binder is a hydraulic binder selected from Portland cement, additive or not, high alumina cement, slag cement, calcium sulphate (plaster), calcium silicates formed by autoclaving and combinations of particular binders and other chemical binders.

19. Polyamide fiber for reinforcement of material comprising at least one hydraulic or chemical binder, treated with one or more additives chosen from:

• latexes;

• polar olefins;

Amino acids such as aspartic acid, glutamine, methionine, etc. and their salts;

Polyamide oligomers comprising up to 7 repeating units;

Polyamide oligomers grafted with a function, for example chosen from phosphates, phosphonates, sulphonates, alkoxysilanes, dicarboxylates, amino-carboxylates, anhydrides, epoxys and diols; • aliphatic acrylate and polyester acrylate urethane resins; and

these additives can be used alone or in combination of two or more of them.

20. Polyamide fiber according to claim 19, characterized in that the additive is different from an alkylphosphate and its derivatives such as aminoalkylphosphates and aminoalkyldiphosphates;

21. Use of the treated polyamide fibers according to claim 19 or 20 as reinforcement in materials obtained from a matrix comprising at least one hydraulic or chemical binder, for example cement.

22. Use of composite material according to one of claims 1 to 18 for the manufacture of plates, pavements, roofing or facade coating, piping, tanks, tanks, including rainwater tanks, containers.

23. Article obtained using at least one composite material according to one of claims 1 to 18.