MXPA00007353A - Association based on microfibrils and mineral particles, preparation and uses - Google Patents

Abstract

The invention concerns an association in dry form, comprising:microfibrils whereof the mean diameter is less than 0.8 mm;and at least one mineral particle. It also concerns a method for preparing said association, which consists in preparing a suspension comprising the microfibrils and the mineral particles, which are then dried. Finally, the invention concerns the use of such an association in compositions comprising (co)polymers including elastomers, thermoplastic polymers, their alloys and mixtures.

Description

ASSOCIATION BASED ON MICROFIBRILLES AND MINERAL PARTICLES, PREPARATION AND USES DESCRIPTION OF THE INVENTION The present invention aims at an association, which is presented under the dry form, and which comprises on the one hand microfibrils and on the other hand mineral particles. The present invention also relates to a method of preparation as well as to the use of such an association in compositions comprising polymers. By polymers, it is intended to designate both polymers or copolymers such as elastomers, thermoplastic polymers, their alloys or their mixtures. This proves to be particularly interesting in the case of compositions comprising mainly crosslinked elastomers by any means known to the person skilled in the art (peroxides, sulfur, etc.). The use of fibers in elastomer-based compositions is known but is still poorly developed. Indeed, if the introduction of short fibers, such as Santoweb fibers, in such compositions makes it possible to improve the stiffness of the additive material by these short fibers, this nevertheless affects the resistance to rupture and fatigue. In this way, a commitment of satisfactory properties can not be achieved. Recently, it has been thought to prepare compositions based on elastomers that include fibers of smaller size, such as Kevlar pulp comprising partially fibrillated fibers. In this case, the rigidity properties are improved in relation to those obtained with the short fibers, mainly as regards the final properties of the material. However, it seems that the resistance to fatigue is altered. In addition, there is a problem of redispersion of these fibrils within the composition of elastomers, which makes their incorporation into the composition mandatory while the latter is in the form of a latex. It seems therefore that it is possible to improve the commitment of the properties by changing the morphology of the fibers used; but in this case, we have to face a problem of redispersion of these fibers within the polymer matrix.

The main purpose of the present invention is to solve this problem of redispersion. This consists of a particular association, comprising microfibrils, which is easily dispersible in polymer compositions, such as elastomers or thermoplastic polymers, whatever the form in which these compositions are found (latex or not). Furthermore, and this constitutes a considerable advantage of the present invention, the compositions as well as these additives, which also form part of the invention, present very surprising mechanical properties. Thus, for a vulcanized elastomer (crosslinked with sulfur), on the one hand a significant increase in the secant modulus (stress to strain ratio) and stress, more particularly between approximately 50 to 300% deformation, is observed. And, contrary to what would be expected by right, in this case, the final properties of the material added in this way, such as resistance to breakage for example, are not altered. On the other hand, the viscoelastic behavior of the material obtained is very surprising. The person skilled in the art would expect to observe an increase in energy dissipation after the addition by the microfibrils. This is not the case when these are incorporated into the elastomer by means of the association according to the invention. Thus, the present invention aims at an association that occurs under the dry form, and which comprises: microfibrils whose average diameter is less than 0.8 μm, and at least one mineral particle. Yet another object of the present invention is constituted by a method for obtaining this association, which consists of preparing a suspension comprising the microfibrils and at least one mineral particle, which is then dried. The present invention also aims to use the combination according to the invention in polymers, in particular in elastomers and thermoplastic polymers, their alloys or their mixtures. Finally, the invention relates to articles based on polymers comprising the association according to the invention.

It has been found totally unexpectedly that an association based on microfibrils such as those defined above, combined with mineral particles, could be incorporated easily and homogeneously in formulations based on elastomers or polymers. In fact, the association according to the invention is very easy to put into operation, given the fact that it is in a dry or anhydrous form, that is to say solid, and more particularly under the individualized solid form (powder, particles sensibly spherical, granulated). In addition, the association can be incorporated into a polymer composition, for which said polymer is either in the form of bulk polymer, or in the form of a solution or a suspension. It has been found in the same way, and this unexpectedly, that the presence of microfibrils associated with the mineral particles would lead to a significant lowering of the value of the tangent maximum of the loss angle tan d, under a deformation of less than 50%, at room temperature, ie approximately 20 ° C.

It is recalled that the maximum of the tangent of the angle of loss corresponds to the maximum of the obtained curve determining the relation of the modules E " (viscous modulus) and E '(elastic modulus) as a function of the deformation under sinusoidal solicitation of the sample. The tangent d gives an indication of the ability of the material to dissipate the energy. The higher its value rises, the greater the dissipation of energy within the material. In known systems comprising, for example, latexes and microfibers, a low stiffness has been noted from the deformations of 1 to 5%. This phenomenon has been attributed to the rupture of the network of percolated microfibers, that is, to a damage that should be accompanied by an energy dissipation. In the case of the present invention, the person skilled in the art would therefore expect to observe an increase in energy dissipation resulting from this same phenomenon. But such has not been the case. It has been observed, in addition, an interesting supplementary phenomenon linked to the maximum value of tan d, to the passage of the mechanical glass transition temperature (or main relaxation temperature a). This value of tan d is obtained from the curve that measures the evolution of the real E 'and imaginary E "modules as a function of temperature, at constant frequency, in a domain of weak sinusoidal deformation (less than 0.1%). The person skilled in the art would normally expect, as is usually the case when a charge is introduced into a polymer, to observe a lowering of the maximum value of tan d.However, it has been noted that, on the contrary: this value would be at least conserved, if not increased, but other advantages and characteristics of the present invention will appear more clearly when reading the following description, examples and figure: It should be noted that Figure 1 represents the evolution of the secant modulus in function of the deformation, of a vulcanized elastomeric composition comprising the association according to the invention, and of a vulcanized elastomer-based composition that does not comprise more than Minerals Figure 2 represents the evolution of the relation E "/ E 'as a function of the deformation that allows access to tan d.

Figure 3 represents the evolution of the real modulus E 'as a function of deformation. As already indicated above, the association according to the invention comprises microfibrils having an average diameter of less than 0.8 μm. Advantageously, the microfibrils have an average diameter of less than 0.5 μm. The average diameter is more particularly less than 0.1 μm, preferably less than 0.05 μm. The average diameter of the microfibrils is preferably between 0.5 and 20 nm, and still more preferably between 5 and 20 nm. An important feature of the microfibrils of the invention is their shape factor which is defined by the ratio between the average length of the microfibril and D its average diameter (L / D). Thus, in the context of the present invention, microfibrils have a relationship L / D greater than or equal to 15, more particularly greater than or equal to 20, preferably greater than or equal to 100. The choice of microfibrils, mainly in terms of diameter and shape factor, must be such that the average length of said microfibrils are always lower than 30 μm.

The average diameter can be measured, for example, by transmission electron microscopy (TEM). According to the dimensions of the fiber, the average length can be determined, for example, by scanning electron microscopy (SEM) or by transmission electron microscopy (MET). According to a preferred embodiment of the invention, the association comprises microfibrils having an average diameter of less than 0.8 μm and an L / D ratio greater than or equal to 15, more particularly greater than or equal to 20, preferably greater than or equal to Of course, the average length of the microfibrils is less than 30 μm. Another yet more preferred embodiment of the invention consists in putting into operation microfibrils having an average diameter comprised between 0.5 and 20 nanometers. More particularly, the average diameter is between 5 and 20 nm. The shape factor is greater than or equal to 15, more particularly greater than or equal to 20, preferably greater than or equal to 100. Obviously, the average length of the microfibrils is less than 30 μm.

The sources of the microfibrils that have the characteristics indicated above, are very varied. According to a first possibility, these are chosen among the ceramic microfibrils.

For example, microfibrils of silicon carbide, of silicon nitride, of boron nitride can be cited. Also suitable are asbestos, titanate, alumina or aluminum dihydroxycarbonate, and / or magnesium fibers. A second possibility is to put into operation carbon microfibrils, possibly hollow. According to a third possibility, the microfibrils put into operation are organic microfibrils. By way of example, mention may be made of microfibrils of polyvinyl alcohol, polyamide, or cellulose. In the case where microfibrils are cellulose microfibrils, these can be of plant origin, such as cellulose from the plant parenchyma; of bacterial origin; or even of animal origin, such as cellulose such as tunicin, obtained from marine animals.

According to a particularly interesting variant of the invention, the association comprises essentially amorphous cellulose microfibrils. By essentially amorphous, microfibrils having a crystallinity rate less than or equal to 50% are designated. Preferably, this rate is less than 50%. The crystallinity rate is still more preferably greater than or equal to 15% and less than 50%. The cellulose microfibrils put into operation in the present invention are more particularly from cells consisting of at least 80% by weight of primary walls. Preferably, the amount of primary walls is at least 85% by weight. They have such characteristics mainly with the cells of the parenchyma. Sugar beet pulp, citrus fruits such as lemons, oranges, grapefruits, and most fruits and vegetables are examples of parenchyma. On the other hand, the cellulose microfibrils are, according to a particularly advantageous variant, surface-loaded with carboxylic acids and acidic polysaccharides, alone or as a mixture. By carboxylic acids, simple carboxylic acids are understood, as well as their salts. These acids are preferably chosen from uronic acids. More particularly, said uronic acids are more particularly galacturonic acid, or glucuronic acid. As acid polysaccharides, there may be mentioned pectins, which are more particularly polygalacturonic acids. These acid polysaccharides can be present in mixture by the hemicelluloses. Such cellulose microfibrils have been described in the European patent application EP-726, 356. It should be noted that it would not fall outside the scope of the present invention to put into operation the cellulose microfibrils that do not possess such surface charges, such as those obtained according to the procedure described in European patent EP-102,829. On the other hand, it would be quite considerable to put into operation the cellulose microfibrils of this type, mixed with carboxylic acids and / or acidic polysaccharides such as those described above. According to another possibility, the cellulose microfibrils can be mixed at least one acid chosen from dithiodipropionic, tetrathiodipropionic or ercaptopropionic acids. According to a particularly advantageous embodiment of the present invention, the cellulose microfibrils are obtained by putting into operation the treatment to be described later. More particularly, this treatment is carried out on the pulp of vegetables with primary walls, such as, for example, the beet pulp after it has undergone a stage of prior extraction of the sucrose, according to methods known in the art. This procedure consists in putting into operation the following stages: a) first acid or basic extraction, at the exit of which a first solid waste is recovered, b) possibly the second extraction carried out under alkaline conditions of the first solid waste, at out of which, a second solid residue is recovered, c) washing of the first or second solid residue, d) optionally bleaching the washed residue, e) diluting the third solid residue obtained at the output of stage (d) , in order to obtain a rate or proportion of dry materials comprised between 2 and 10% by weight, f) homogenization of the diluted suspension. It should be noted that this procedure has been described in detail in the European patent application EP-726,356 filed on 07/02/96, to which reference may be made if necessary. He Example 20 of this text mainly gives a way of preparing the suspension of essentially amorphous cellulose microfibrils, particularly advantages. The cellulose microfibrils that enter the association according to the invention can be used in the form of a suspension directly from the microfibril preparation process.

These can also, advantageously, be used in a dry form. In this case, these will be redispersed before the contact with the mineral particles. Note that in the case of cellulose microfibrils, a dry form designates cellulose microfibrils that have a proportion of dry materials of at least 40% by weight. More particularly, the proportion of dry materials is at least 60%, preferably, it is at least 70% by weight. The cellulose microfibrils which enter into the association according to the invention can optionally be added with at least one additive chosen, for example, from carboxylated cellulose, natural polysaccharides, polyols, etc. In the case where the cellulose microfibrils are used in a dry form, they are preferably associated with at least one additive chosen from carboxylated cellulose, natural polysaccharides, polyols. The carboxylated cellulose used as an additive is, more particularly, carboxymethylated cellulose. Cellulose is a polymer made up of glucose monomer units. The carboxylated group is introduced in a manner known per se, by reacting the chloroacetic acid with the cellulose. The degree of substitution corresponds to the number of carboxymethylated groups per glucose unit. The maximum theoretical degree is 3. The degree of substitution of the carboxymethylated cellulose can be either less than or equal to 0.95 (low degree of substitution), or higher than 0.95 (high degree of substitution). It is quite important to put into operation cellulose microfibrils that simultaneously comprise the two categories of carboxymethyl cellulose. The additive can be a natural polysaccharide. The latter may be of bacterial, animal or vegetable origin. Polysaccharides are polymers that comprise osidic units. Preferably, the polysaccharides which are in an anionic or non-ionic form are put into operation. Among the suitable anionic polysaccharides, xanthan gum, succinoglycans, carrageenans, alginates may be mentioned without intending to limit them; with xanthan gum being preferred. As non-ionic polysaccharides, for example, galactomannans such as guar gum, locust bean gum can be mentioned. They also agree with starch and its non-ionic derivatives, as well as the non-ionic derivatives of cellulose. Among the suitable polyols, mention may be made more particularly of polyvinyl alcohols, polyalkylene glycols (polyethylene glycol, propylene glycol, mixtures and copolymers). The microfibrils, if they are added, can also comprise at least one co-option selected from: the osidic monomers or oligomers, - the compounds of the formula (R1R2N) COA, formula in which R1 or R2, identical or different, have the hydrogen or an alkyl radical of 1 to 10 carbon atoms, preferably of 1 to 5 carbon atoms, A represents hydrogen, an alkyl radical of 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, or even the group R'XR'2N with R'1, R'2, identical or different, representing hydrogen or an alkyl radical of 1 to 10 carbon atoms, preferably of 1 to 5 carbon atoms, - cationic or amphoteric surfactants, these coadditives can be used alone or as a mixture. Among the osidic monomers or oligomers, sorbitol, sucrose, and fructose may be mentioned more particularly and without intention of limiting them. Concerning compounds of the type (R2R2N) COA, it is preferred to use the compounds comprising two amide functional groups. Preferably, urea is used. Among cationic surfactants, mention may be made of cationic quaternary ammonium derivatives, such as, for example, cationic imidazoline derivatives, alkyltrimethylammonium halides, dialkyldimethylammonium halides, alkyldimethibenzylammonium halides, alkyldimethylethylammonium halides, and Quat Esters. Among the amphoteric surfactants, there may be mentioned, without intending to limit them, the amphoteric derivatives of alkylpoly acids, alkylbetaines, alkyldi ethylbetaines, alkylamidopropibetaines, alkylamidopropyl dimethylbetaines, alkyltrimethyl sulphobetaines, imidazoline derivatives such as alkylamphoacetates, alkylamphodiacetates, alkylamphopropionates, alkylamphodipropionates. , alkyl sultaines or alkylamidopropyl hydroxysultaines, the condensation products of fatty acids and protein hydrolysates, these compounds being able to be used alone or as a mixture. The proportions of additive and co-additive, if the latter is present, can vary within wide limits. However, in the case of the essentially amorphous cellulose microfibrils, it is preferred that the total proportions of additive and optionally co-additive are not higher than 50% by weight with respect to the weight of the cellulose microfibrils, of the additives and optionally of the coaditivos. Preferably, the proportions are less than or equal to 30% by weight relative to the weight of the cellulose microfibrils, the additive and optionally the coadditive. But the characteristics of such cellulose microfibrils that occur under the dry form, as well as their preparation, are described in the applications WO 98/02486 and WO 98/02487, to which reference may be made for more details. It is equally important to put into operation cellulose microfibrils that form the target of a surface treatment.

Thus, by way of example, the procedure described in WO 97/12917 can be cited. There, cellulose microfibrils characterized by the fact that at least 25% by number of the hydroxyl functional groups present on the surface thereof are esterified by at least one organic compound comprising at least one functional group which can react with the hydroxyl groups of cellulose. The process of preparing such microfibrils with modified surface consists of: a) dispersing the microfibrils of cellulose in a liquid and non-destructive medium of the cellulose microfibrils, b) adding in the dispersion an esterifying agent of the hydroxyl functional groups of the cellulose , and optionally a catalyst and / or an activator of the esterification reaction, c) stopping the esterification reaction after obtaining the desired degree of esterification, d) extracting the partially esterified microfibrils from the dispersion. The esterification agent is more particularly an organic compound selected from the group comprising the anhydrides or the halide of acetic, propionic, butyric, acrylic, methacrylic acid and the corresponding acids. It could likewise be considerable to operate such a process, with at least one acid chosen from dithiodipropionic, tetrathiodipropionic or mercaptopropionic acids. The catalyst for the esterification reaction is chosen from the group comprising the basic catalysts and the acid catalysts, and more particularly the mineral, organic and tertiary amines. It is also possible to operate the microfibrils, and especially the cellulose microfibrils, treated superficially such that they have a polypyrrole coating. The process comprises the following steps: a) it is placed in contact in distilled water, a colloidal suspension of microfibrils, pyrrole, and ferric chloride, b) it is allowed to react at a temperature comprised between 5 ° C and room temperature, c ) the obtained solids are washed and dispersed in water by means of ultrasound of the resulting solids. This procedure has been mainly described in the European application EP-783,015. Very obviously, it would not be outside the scope of the present invention to put microfibrils of different types into operation. The microfibrils thus defined are thus associated to at least one mineral particle. The microfibrils may be associated with one or a mixture of mineral particles. The granulometry of the mineral particles varies in a wide domain. However, mineral particles are put into operation which, when the association is used in the polymer matrix, make it possible to obtain dispersed particles with an average diameter ranging from a few nanometers to several micrometers. For example, the average diameter may be between 3 nm and 10 μm, and preferably between 3 nm and 5 μm. According to a first variant, the mineral particles are chosen from the oxides, hydroxides, hydroxycarbonates, or their combinations, of the elements of columns IIA, IIB, IIIB, IVA, IVB, VB of the periodic classification of the elements (published in the supplement to the Bulletin of the Chemical Society of France No. 1, January 1966), preferably titanium, aluminum, silicon, zinc, calcium, magnesium, or their mixtures. As possible combinations, we can cite, without intending to limit them, mainly mica, silicoalu inatos such as clays, such as kaolin, for example. It should be noted that these can be put into operation from a dry form that is redispersed before or at the time of use, to prepare the association according to the invention. It is also possible to use the suspensions directly from the process for preparing said mineral particles, generally by putting into operation a precipitation stage. By operating in this way it is possible to avoid the stage of redispersion of the particles. In this wayit is quite important to contact the microfibrils with a suspension of oxide, hydroxide and / or hydroxycarbonate particles, after the precipitation stage, or after the filtration and suspension step (mechanical or chemical placement) . It is also possible to use oxides, hydroxides and / or hydroxycarbonates which have undergone a high temperature treatment (calcination). In this case, the microfibrils are introduced after this calcination step, in order to avoid any degradation of the latter. According to a second variant, the mineral particles are chosen from carbonates, acid carbonates, alkali metal or alkaline earth metal phosphates or their mixtures. Preferably, alkaline earth metal compounds, and more particularly calcium and magnesium compounds, are put into operation. A third variant is constituted by the mineral particles chosen from the cerium or lanthanum compounds. Thus, sulfides, oxides or mixtures thereof can be mentioned in particular. A fourth variant consists of particles of silicon carbide. Most obviously, it would not be outside the scope of the present invention to use various types of mineral particles in the association according to the invention. Finally, a fifth variant of the invention consists in putting into operation, as mineral particles, the carbon black particles, even if the "mineral" rating of these particles represents rather an abuse of the language. Note that it would not go beyond the scope of the invention, putting into operation particles comprising carbon in its molecule, coated with at least one compound corresponding to four variants indicated above, ie by at least one compound chosen from oxides, hydroxides or hydroxycarbonates of elements of columns IIA, IIB, IIIB, IVA, IVB, VB of the periodic classification of elements; carbonates, acid carbonates, alkali metal or alkaline earth metal phosphates; or even silicon carbide. According to a particular embodiment of the present invention, mineral particles having a specific BET surface area greater than 30 m2 / g, more particularly between 50 and 400 m2 / g, are put into operation. It should be noted that the BET specific surface area is determined according to the Brunauer-Emmet-Teller method, described in "The Journal of the American Society", Vol. 60, page 309, February 1938 and corresponding to Standard NF T 45007 (November 1987). Preferably, the particles put into operation of the invention have a specific surface comprised between 80 and 250 m 2 / g. A particularly advantageous embodiment consists in putting into operation the mineral particles chosen from the oxides, hydroxides or hydroxycarbonates having a specific surface area. in the domain indicated above. According to a still more advantageous embodiment of the invention, the mineral particles are chosen from precipitated silicas, more particularly having a specific surface comprised between 110 and 230 m2 / g, and for example between 140 and 220 m2 / g. . On the other hand, the mineral particles that form the objective of a previous surface treatment, total or partial, can be put into operation. By way of example, mention may be made of the surface treatments carried out on titanium dioxide by silica or a silicoaluminate, or even the treatment carried out on silica by polyethylene glycol. One can even mention the partial treatment of the surface of the calcium carbonate particles with a carboxylic acid. The amount of microfibrils in the combination is advantageously between 0.1 and 100 g, more particularly between 1 and 10 g, relative to 100 g of mineral particles. Preferably, such a proportion is between 2 and 5 g for 100 g of mineral particles. In the case where the microfibrils comprise additives or coadditives, the ranges indicated above prove to be valid, since they are the total proportion of microfibrils and of additives or coadditives. A process for preparing the composition according to the invention is now to be described. This consists of preparing a suspension comprising the microfibrils and mineral particles indicated above, which are then dried. Thus, in a first stage, a suspension is prepared comprising the microfibrils, optionally in the presence of additives or coadditives, and the mineral particles.

Classically, a suspension is prepared in water. However, it is possible to replace all or part of the water with a dispersing liquid, inert to the mineral particles and the microfibrils, preferably not to solubilize them. In addition, this dispersant is chosen so as to be compatible with the drying conditions of the suspension. More particularly alcohols such as ethanol, and methanol can be used. Usually, the proportion of dry materials of the suspension obtained in this way, comprising the microfibrils and the mineral particles, is between 10 and 40% by weight. Although this is not mandatory, it may be preferable to put into operation a homogenization step or any treatment that allows a deagglomeration of the particles and the microfibrils, such as wet grinding, ultrasound, for example. In addition, it may be advantageous to introduce a stabilizer into the suspension. In this way, hydrocolloids can be mentioned. Once the suspension is obtained, the latter is dried.

Any classic means can be used in the measure where the temperature reached by the association during drying, does not involve degradation of the elements that constitute it. By way of illustration, the drying is carried out under conditions such that the temperature reached by the combination of microfibrils / mineral particles is between room temperature and a temperature below 170 ° C, more particularly below 150 ° C, and preference less than 120 ° C. Drying is generally done under air, but it is possible to do it under an inert atmosphere (nitrogen, rare gases). In this way, the suspension can be dried in any type of known apparatus, such as furnaces on movable roller conveyors, induction or not, radiant or not, rotary kilns, fluidized beds or even lyophilizers. According to a particular embodiment of the invention, the drying can be carried out by atomization, that is by spraying the suspension in a hot atmosphere (spray drying). The atomization can be performed by means of any sprayer known per se, for example by means of a liquid pressure nozzle, or other device. It is also possible to use so-called turbine atomizers. Regarding the various spray techniques that may be put into operation in this procedure, reference may be made principally to MASTERS 'base work entitled "SPRAY-DRYING" (second edition, 1976, George Godwin Editions - London). It will be noted that it is also possible to carry out the drying operation by atomization by means of an "instant" reactor, for example of the type described mainly in the French patent applications Nos. 2,257,326, 2,419,754 and 2,431,321. In this case, the treatment gases (hot gases) are provided with a helical movement and flows in a well-vortex. The mixture to be dried is injected following a trajectory confused with the axis of symmetry of the helical trajectories of said gases, which allows to perfectly transfer the amount of movement of the gases to the mixture to be treated. The gases thus ensure a double function: on the one hand the pulverization, that is to say the transformation into fine particles, of the initial mixture, and on the other hand the drying of the obtained particles. On the other hand, the extremely small residence time (generally less than about 1/10 of a second) of the particles in the reactor has the advantage, among others, of limiting the possible risks of subsequent overheating to a very prolonged contact with the gases hot With respect to the instantaneous reactor mentioned above, reference may be made to Figure 1 of the French patent application 2,431,321. Upon leaving this stage, the association according to the invention is obtained, appearing under the dry (solid) form. It should be noted that the association may have a residual proportion of water or dispersing liquid. This residual proportion is such that the appearance of the individualized particles of the association is conserved. This depends strongly on the nature of each of the constituent elements of the association. By way of example, this residual proportion is generally less than or equal to 20%, preferably less than or equal to 10%.

In this step, the association obtained by drying can be in the form of substantially spherical particles. This variant is particularly advantageous when the mineral particles are chosen from the oxides. Reference may be made to the conditions described in patent applications EP-520,862, EP-670,813, EP-670, 814. The resulting product can, if necessary and in order to limit the powder conversion phenomenon, be placed in contact with a mixture comprising a mineral oil and optionally a polymer. The mineral oil can be, for example, a naphthenic oil. The polymer is preferably a polymer or copolymer of ethylene, of propylene, and optionally of a diene (such as hexadiene or even ethylidene norbornene), in which the proportion of ethylene is from 60 to 90% by weight, the proportion of propylene is from 10 to 35% by weight and that of the diene, if present, it is 2 to 10% by weight. It may refer mainly to the international application PCT / GB96 / 03222. The dried product can, if necessary, undergo a grinding or de-agglomeration step.

If desired, it is possible to put into operation a stage of shaping the dry product, to make it more practical to use. In this way, it is possible to carry out, among others, a granulation, a compaction, an extrusion. These operations are perfectly classical for the expert in the field. These generally consist, in the case of granulation or extrusion, in adding the required amount of a binder which is chosen from the compounds compatible with the compositions in which the association is subsequently used, to granulate or extrude the whole in classic appliances, then drying the resulting product, if necessary. As for the compaction, it is usually carried out by subjecting it to a strong pressure of association, possibly in the presence of an appropriate binder according to the subsequent use of the latter. As a binder, mention may be made principally of polyethylene glycol, or stearic acid. The association according to the invention, optionally after shaping, is usually presented in a dry form, where the size of the objects comprising it is between 0.5 μm and 5 mm; more particularly between 5 μm and 5 mm. The association according to the invention can be used in numerous domains. Advantageously, the combination according to the invention is used in compositions based on polymers or copolymers, mainly in the manner of reinforcing fillers. In the following, reference will not be made, for reasons of simplification of the text, more than to the polymers, knowing that by this term, polymers, copolymers, their alloys or their mixtures are covered at the same time. Among the suitable polymers, mention may be made of elastomers, polymers or copolymers, which have a glass transition temperature comprised between -150 ° C and + 20 ° C. As suitable compounds, the elastomers or synthetic (co) polymers or natural products may be mentioned, however without intending to limit them. For example, mention may be made of natural rubber, polymers or copolymers derived from aliphatic or aromatic monomers, comprising at least one unsaturation, such as, in particular, ethylene, propylene, butadiene, isoprene, styrene; Butyl polyacrylate, or its associations. The silicone elastomers can likewise suit the embodiment of the present invention, as well as the halogenated polymers, such as PVC and halogenated elastomers. According to the present invention, a mixture is formed comprising the association of microfibrils and mineral particles, the polymer and, as the case may be, the additives adapted for the application. In this way, the polymer compositions may comprise vulcanization ingredients in the particular case of elastomers, coupling agents, plasticizers, stabilizers, lubricants, pigments, etc. The volumetric ratio represented by the association according to the invention in the composition of the polymer can vary over a wide range, even in certain applications, representing a higher amount than the polymer. However, more particularly, the volume of the association according to the invention represents from 0.1 to 50% with respect to the volume of the polymer, which optionally comprises the aforementioned additives. Preferably, this volume represents from 0.1 to 25% of the volume of the polymer, which optionally comprises the aforementioned additives. It should be noted, and this constitutes a further advantage of the present invention, that the association according to the invention can be put into operation either with a bulk polymer, with a polymer latex or with a polymer solution. It is necessary that by latex, the suspensions of polymer in water or any other suitable dispersing liquid be understood. In fact, contrary to the known fiber-based or microfibrillar agents, the association according to the invention is perfectly adapted for the polymer composition and disperses perfectly, whatever the shape of the composition. The putting into operation and putting into shape of the polymer comprising the association according to the invention are conventional in the art. These do not demand specific material or procedures. Thus, in the case where the elastomer is not in the form of latex, a homogeneous mixture of the association according to the invention, the elastomer, and the additives is prepared, inter alia, of any type of known mixer following the start-up procedures well known to the person skilled in the art. This mixture is formed by molding or extrusion mainly, and is carried out, if necessary, a thermal treatment at a temperature lower than the degradation temperature of the association according to the invention. This is more particularly the case of the vulcanization of the elastomers. Usually, the temperature of the operation is lower than 170 ° C. In the case where the polymer is in the form of latex or solution, the mixture of latex or solution is made, with the association according to the invention, then the liquid phase is eliminated, in a conventional manner. The resulting product can then be set in a conventional manner. In the case where the polymer is a thermoplastic polymer, the homogeneous mixture of the association, the polymer and the additives can be obtained by any means known to the person skilled in the art, which allows the incorporation of mineral charges in a thermoplastic polymer, in particular by means of a double screw extruder.

The mixture is immediately put into shape by calendering or injection, mainly. The articles based on polymers and comprising the association according to the invention, obtained in this way, can be used as technical plastics or technical elastomers, in applications as varied as in the domain of automobiles. In this way, they can be used as floor coverings, engine mounts, vehicle chain parts, shoe soles, cable car wheels, electrically operated device seals, sheaths, cables, transmission belts, etc. In this way, the present invention makes it possible to obtain articles in which the polymer is an elastomer or an alloy or mixture of elastomers, and preferably vulcanized, which can be used in any part of the tire. In this particular case, it should be noted that the proportion in the association according to the invention is such that the proportion of microfibrils in the involved part of the tire is between 0.1 and 20 g for 100 g of elastomers, of polymers or of copolymers.

Finally, the articles according to the invention can find applications as a battery separator. Concrete but not limiting examples of the invention will now be presented.

EXAMPLE 1 This example illustrates the preparation of an association according to the invention, comprising precipitated silica and cellulose microfibrils. Example 12 of the European patent EP-520,862 is carried out until a precipitated silica broth is obtained which is filtered and washed by means of a filter press in order to recover a silica cake whose fire loss is 79% (21% of the proportion of silica). This cake is then fluidized by mechanical and chemical action via the addition of an amount of sodium aluminate corresponding to an Al / SiO2 weight ratio of 3000 ppm. The suspension obtained in this way thus has a pH of 6.3, and a precipitated silica content of about 21% by mass.

To 2641 g of the previous suspension, 2419 g of water and 1300 g of pulp of cellulose microfibrils are added. This pulp is obtained according to the procedure described in the European patent application EP-726,356, according to Example 20 before concentration, with the exception that the proportion of dry materials of the suspension is 2.3%. The suspension of silica and microfibrils is homogenized with a RAYNERI apparatus, to obtain a suspension with a precipitated silica content of 9%. The mass ratio of microfibrils / silica is of the order of 5.4%. This suspension is atomized on the APV turbine atomizer. The product obtained has: * a BET surface area of 165 m2 / g * a total porous volume of 3.2 ml / g * an average pore diameter of 24 nm.

NB: The porous volume is measured by porosimetry with mercury, the pore diameters being calculated by the Washburn ratio with a contact angle of 140 ° and a surface tension of 484 dynes / c. Porosity measurements are carried out on products dried at 150 ° C under a pressure of 1 Pa. The porous volume Vp is relative to pores whose radius is less than 1 μm; the average diameter of the pores corresponds to the maximum of the derivative of the curve V = f (log d) for the part relative to the mesopores (porosity path for pores with a diameter smaller than 0.1 μm).

EXAMPLE 2 The purpose of this example is to obtain precipitated silica particles alone (reference). At 4797 g of the suspension described in Example 1, 6205 g of water are added in order to form a suspension having a 9% proportion of precipitated silica. This suspension is atomized on an APV turbine atomizer under the same conditions as for the preceding example. The product obtained has: * a BET surface of 165 m2 / g * a total pore volume of 3.5 ml / g * an average pore diameter of 25 nm.

It is noted that the products of Examples 1 and 2 have similar texture and surface.

EXAMPLE 3 The objective of this example is to evaluate the properties of the elastomers, which comprises the products from Examples 1 (Composition A - composition including the association according to the invention) and 2 (Composition B - Composition based on precipitated silica alone) . Two following elastomer compositions are prepared: The amounts are expressed in weight per hundred parts of elastomer. (*) Copolymer of styrene-butadiene synthesized in solution (SBR Buna VSL 5525-1 / Bayer) containing 27. 3% oil (**) Si69 is bis (triethoxysilylpropyl) tetrasulfide (Degussa) (***) Antioxidant: N- (1,3-dimethyl-butyl) -N'-phenyl-p-phenylenediamine. (****) Sulfenamide: N-cyclohexyl-2-benzothiazole-sulfenamide.

Each composition is made by a thermo-mechanical work in an internal mixer of 1 liter, in two stages, for an average speed of the blades of 80 revolutions per minute, until reaching a temperature of 160 ° C at the end of each of these two stages, and followed by a finishing stage on the external mixer. The vulcanization of the compositions is adapted to the vulcanization kinetics of each mixture. The physical properties of the mixtures are recorded in the following table.

The measurements are made according to the following methods: • Viscosity MLl + 14 on crude mixture of Mooney: according to the norm NF T43005 • Contraction It uses a mixer of Apparatus s: cylinders MAL ATC 01 (calendered the speed of front cylinder - rear cylinder is of 18 revolutions per minute) Temperature: 20 ° C Separation of the guides: 10 cm Separation of the cylinders: 2 cm (bead approximately 1 cm) Mode of operation: Allow to mix 30 seconds 220 g of mixtures. Cut 10 times to 2/3 (5 to the left - 5 to the right). After 2 minutes, remove the cylinders until the full shot of the staff. Flatten the mixture over the entire width. Let the rubber band rest on a tacked board for 24 hours and measure the length of the band. The retraction or contraction is then given by (D-L) / D * 100, formula in which D represents the circumference of the cylinder and L the length of the band after 24 hours of rest. Traction: The modules are measured on the vulcanized according to the NF T46002 standard. It should be noted that the 100% modulus, in rubber materials, refers to the contraction measured at 100% of the tensile strain; the 300% module refers to the tension measured at 300% strain in tension.

According to the preceding recapitulant table, it is found that the composition containing the combination of silica and microfibrils according to the invention leads to a significantly higher mechanical stress around 100% deformation with respect to the reference composition. This indicates that the microfibrils have been evenly distributed in the elastomer. In addition, as shown in Figure 1, which shows the evolution of the secant modulus (defined as the ratio of the stress to a deformation on the deformation) as a function of the deformation, the modules are improved to more than 300% deformation. It is remarkable and quite unexpected for the person skilled in the art to note that the gain in the modulus of the composition of the elastomer comprising the association according to the invention occurs without prejudice to the rheology of the raw mixture, nor to the resistance to rupture and elongation of the vulcanized mixture. On the other hand, obtained in this way presents a better resistance to shrinkage than the control composition, which only comprises silica, which is an advantage in terms of shape-setting by extrusion or calendering, in particular.

EXAMPLE 4 The purpose of this example is to show the influence of the association according to the invention on the evolution of the viscoelastic properties and in particular of the tan of the angle of loss (tan d) as a function of deformation and temperature. Measurement method: The real (E ') and imaginary (E ") modules as well as the tan of the loss angle (tan d), defined as the ratio of E "over E ', have been measured at different rates of deformation, on a mechanical spectrometry apparatus (Viscoanalyzer VA2000 of Metravib RDS).

The test conditions are as follows: • The test pieces are parallelepipedic (length 6 mm, height 6 mm, thickness 2.5 mm approximately). • At 23 ° C, the specimen is subjected to a test that resembles a tensile test, consisting of subjecting the specimen to bearings of increasing deformation force. After each bearing, a sinusoidal deformation of a frequency of 5 Hz and an amplitude of 10 micrometers is applied to the specimen, which makes it possible to measure the modules E 'and E "of the tan d.

After the vulcanization, according to the above embodiment, the compositions A and B described in Example 3 have been tested. It can be seen, as shown in Figure 2, that the maximum value of tan d of the Composition A, which contains the cellulose microfibrils introduced into the elastomer by means of the association according to the invention, is 0.30 while that of composition B is 0.32. This result is totally unexpected. In fact, in the known systems comprising latex and microfibrils, a lowering of rigidity has been noted from the deformations of 1 to 5%. This phenomenon is attributed by the person skilled in the art to the rupture of a network of percolated fibers, then to deterioration. This deterioration is usually accompanied by a dissipation of energy, after an increase of tan d. Note also in figure 3, the smallest value of the elastic modulus E 'of the composition A, at very small deformation and the increase of the latter to very strong deformation in relation to the values obtained with the composition B. It has also been observed an interesting supplementary phenomenon linked to the maximum value of tan d, to the passage of the mechanical glass transition temperature (or main relaxation temperature a). This value of tan d is obtained from the curve that measures the evolution of the real (E '), imaginary (E ") modules as a function of the temperature at constant frequency, in a domain of small deformations (less than 0.1% It is verified that the maximum value of tan d to the step of the mechanical glass transition (observation to Hz at a main relaxation temperature a) of composition A is 0.77 while that of composition B is 0.76. The person skilled in the art would normally have expected to observe a decrease in the maximum value of the tangent to the passage of the mechanical glass transition.

Now, it has been noted that this value would be at least conserved, if not increased. This result is surprising, because in the composition A, the proportion of the polymer that overcomes the mechanical glass transition is smaller due to the addition of fibers, than in the composition B. It should therefore be observed a decrease in the maximum value of the so d to the step of the vitrea mechanical transition. The particular behavior of the composition A in Examples 2 and 3 indicates, in a manner evident to the person skilled in the art, that an association according to the invention, of a reinforcing mineral charge (for example a precipitated dispersible silica) and Cellulose microfibrils (for example from cellulose parenchymas from plant products) can be used in a manner to improve the commitment of the properties of virtually all parts of a tire.

EXAMPLE 5 The purpose of this example is to evaluate the properties of the elastomers comprising the products from Examples 1 (composition C) and 2 (composition D) in a formula based on natural rubber and polybutadiene. Two following elastomer compositions are prepared: The amounts are expressed in weight per hundred parts of elastomer. (*) Natural rubber. (**) Polybutadiene: Cariflex BR 1220 L (Shell Chimie). (***) YES69 and Sulfenamide: see Example 3. (****) Oil: Shell Ferumil Oil.

Each composition is made by a thermo-mechanical work in an internal mixer of 1 liter, in one stage, for an average speed of the blades of 80 revolutions per minute, until reaching a temperature of 160 ° C at the end of the stage, and followed by an acceleration and finishing step in the external mixer. The vulcanization of the compositions is adapted to the vulcanization kinetics of each mixture. The physical properties of the mixtures are reported in the following table.

The measurements are made according to the following methods: • traction As in Example 3, according to the norm NF T46002 • tearing pants: According to the norm NF T46035 • Abrasion According to the norm NF T46012 • G'0: Real module, measured by a dynamic single shear test, which is performed at increasing strain, at 5 Hz and at 23 ° C. G'0 is measured at 0.01% deformation. Tan d m, ax The maximum of the tangent of the loss angle, measured by a dynamic single shear test performed with increasing strain at 5 Hz and at 23 ° C. so d max may correspond to the maximum value reached by tan d at the moment of the deformation sweep.

After the recapitulant table, it is found that the composition containing the combination of silica and microfibrils according to the invention (composition C) leads to considerably higher mechanical constraints at 10, 100 and 300% deformation with respect to the composition (D) of reference and to a resistance to abrasion and tearing significantly higher than the reference composition. It is remarkable and quite unexpected for the person skilled in the art to note that the modulus gain of the elastomer composition comprising the association according to the invention occurs without damaging the rheology of the crude mixture or the breaking strength and the elongation of the vulcanized mixture. On the contrary, it is found that the composition containing the association has a viscosity smaller than the reference composition (D). On the other hand, the mixture obtained in this way has a dynamic behavior which differs from that of the reference composition, which comprises only silica, by a rigidity with weaker deformation and a maximum dissipation, which is smaller. which is an advantage in tire applications, particularly for the flanks.

EXAMPLE 6 The purpose of this example is to evaluate the properties of the elastomers comprising the products from Examples 1 (composition E) and 2 (composition F) compared to an elastomer comprising reinforcing carbon black (composition G). Three compositions of the following elastomers are prepared: The amounts are expressed in weight per hundred parts of elastomer. (*) see Example 5. (**) N 234: carbon black (Cabot). (**) Wax: Microwax 2000 (***) Antioxidant: N- (1,3-dimethyl-butyl) -N'-phenyl-p-phenylenediamine.

Each composition is made by a thermo-mechanical work in an internal mixer of 1 liter, in one stage, for an average pallet speed of 80 revolutions per minute, until reaching a temperature of 160 ° C at the end of the stage, and followed of an acceleration and finishing stage on the external mixer. The vulcanization of the compositions is adapted to the vulcanization kinetics of each mixture. The physical properties of the mixtures are recorded in the following table.

The measurements are made according to the same methods as in Example 5.

According to the recapitulant table, it is found that the composition containing the combination of silica and microfibrils according to the invention (composition E) leads to a hardness and mechanical constraints significantly higher than 10, 100 of deformation in relation to the compositions ( F and G), and this without damaging the rheology of the raw mixture or the breaking strength, the elongation at break or the tear strength of the vulcanized mixture. On the other hand, the mixture containing the combination of silica and microfibrils (E) has a dynamic behavior comparable to that of the reference composition based on silica (F), but which differs from that composition based on black of carbon (G) by a stiffness with weaker deformation and a maximum of weaker dissipation, which is an advantage in pneumatic applications, particularly for heavy weights.

Claims (36)

1. Association that is presented in the dry or anhydrous form, comprising: microfibrils whose average diameter is less than 0.8 μm and which have a length / diameter ratio L / D greater than or equal to 15, and at least one mineral particle.

2. Association according to the preceding claim, characterized in that the microfibrils have an average diameter of less than 0.5 μ.

3. Association according to any of claims 1 or 2, characterized in that the microfibrils have an average diameter comprised between 0.5 and 10 nm.

4. Association according to any of the preceding claims, characterized in that the L / D ratio is greater than or equal to 20, preferably greater than or equal to 100.

5. Association according to any of the preceding claims, characterized in that the microfibrils have an average diameter and a shape factor such that their average length is always less than 30 μm.

6. Association according to any of claims 1 to 5, characterized in that the microfibrils are ceramic microfibrils.

7. Association according to any of claims 1 to 5, characterized in that the micro-fibers are microfibrils of asbestos, titanate, alumina or dihydroxycarbonate of aluminum and / or magnesium.

8. Association according to any of claims 1 to 5, characterized in that the microfibrils are carbon microfibrils, possibly hollow.

9. Association according to any of claims 1 to 5, characterized in that the microfibrils are organic microfibrils, such as the microfibrils of polyvinyl alcohols, of polyamides, or of cellulose.

10. Association according to claim 9, characterized in that the microfibrils are cellulose microfibrils.

11. Association according to the preceding claim, characterized in that the cellulose microfibrils are of vegetable, bacterial or even animal origin.

12. Association according to any of the preceding claims, characterized in that the microfibrils have a crystallinity rate less than or equal to 50%.

13. Association according to the preceding claim, characterized in that the microfibrils are from cells consisting of at least 80% of primary walls.

14. Association according to any of the preceding claims, characterized in that the microfibrils are surface-loaded with carboxylic acids and acidic polysaccharides, alone or as a mixture.

15. Association according to any of the preceding claims, characterized in that the microfibrils are associated with at least one additive chosen from carboxylated cellulose, natural polysaccharides, or polyols.

16. Association according to the preceding claim, characterized in that the cellulose microfibrils are associated to at least one coaditr selected from: the osidic monomers or oligomers; the compounds of formula (RaR2N) COA, formula in which R1 or R2 identical or different, represent hydrogen or an alkyl radical of 1 to 10 carbon atoms, A represents hydrogen, an alkyl radical of 1 to 10 carbon atoms, or even the group R'1R, N with R'1, R'2, identical or different, representing hydrogen or an alkyl radical of 1 to 10 carbon atoms; the cationic or amphoteric surfactants; these additives can be used alone or as a mixture.

17. Association according to any of claims 1 to 16, characterized in that the cellulose microfibrils are surface treated so that they carry a polypyrrole coating.

18. Association according to any of the preceding claims, characterized in that the mineral particles are chosen from the oxides, hydroxides, hydroxy carbonates, or combinations thereof, of the elements of columns IIA, IIB, IIIB, IVA, IVB, VB of the Periodic clasification of the elements.

19. Association according to the preceding claim, characterized in that the mineral particles are oxides, hydroxides, hydroxycarbonates or combinations thereof, of titanium, of aluminum, of silicon, of zinc, of calcium, of magnesium, or their mixtures.

20. Association according to any of claims 1 to 17, characterized in that the mineral particles are chosen from carbonates, acid carbonates, alkali metal or alkaline earth metal phosphates or their mixtures.

21. Association according to any of claims 1 to 17, characterized in that the mineral particles are chosen from the cerium or lanthanum compounds.

22. Association according to any of claims 1 to 17, characterized in that the mineral particles are silicon carbide.

23. Association according to any of claims 1 to 17, characterized in that the mineral particles are carbon black particles.

24. Association according to any of claims 1 to 17, characterized in that the mineral particles comprise carbon in their molecule and are coated by at least one compound selected from the oxides, hydroxides or - acid carbonates of the elements of the columns IIA, IIB, IIIB, IVA, IVB, VB of the periodic classification of the elements, the carbonates, acidic carbonates, the alkaline or alkaline earth metal phosphates, or even the silicon carbide.

25. Association according to any of the preceding claims, characterized in that the mineral particles have a specific surface greater than 30 m2 / g, preferably between 50 and 400 m2 / g.

26. Association according to any of the preceding claims, characterized in that the amount of microfibrils is comprised between 0.1 and 100 g, more particularly between 1 and 10 g, relative to 100 g of mineral particles.

27. Association according to any of the preceding claims, which is presented under the dry form, comprising microfibrils whose average diameter is less than 0.8 μm and at least one mineral particle, which can be obtained by preparing a suspension comprising the microfibrils and the particles minerals, which dry up.

28. The process for preparing an association according to any of claims 1 to 26, characterized in that a suspension comprising microfibrils and mineral particles is prepared, which are then dried.

29. The use of the association according to any of claims 1 to 27, in the polymers.

30. The use of the association according to the preceding claim, characterized in that the polymer is chosen from elastomers, polymers or copolymers having a vitreous transition temperature that is comprised between -150 ° C and + 20 ° C, its alloys or its mixtures

31. Polymer-based article, which comprises the association according to any of claims 1 to 27.

32. Article according to claim 31, characterized in that it is based on elastomers, polymers or copolymers having a vitreous transition temperature that is comprised between -150 ° C and + 20 ° C, their alloys or their mixtures.

33. Polymer-based article according to any of claims 31 or 32, characterized in that it is an elastomer and can be used as a floor covering, motor support, vehicle track chain parts, shoe sole, cable car roller, board of household appliances, pods, cables, transmission belts.

34. Tire based on elastomers, polymers or copolymers, where at least one of the parts comprises the association according to any of claims 1 to 27.

35. A tire according to claim 34, characterized in that the proportion in the association is such that the proportion of microfibrils in the part in question of the tire is between 0.1 and 20 g for 100 g of elastomers, of polymers or of copolymers.

36. Polymer-based battery separator, characterized in that it comprises the association according to any of claims 1 to 27.