WO2005097918A1

WO2005097918A1 - Coating or moulding composition for composites or mastic containing cellulose microfibril-based additives

Info

Publication number: WO2005097918A1
Application number: PCT/FR2005/000514
Authority: WO
Inventors: Alain Hill; Isabelle Silberzan
Original assignee: Cray Valley S.A.
Priority date: 2004-03-08
Filing date: 2005-03-03
Publication date: 2005-10-20
Also published as: FR2867193B1; FR2867193A1

Abstract

The invention relates to coating or moulding composition for composites or a mastic containing by weight: (A) 100 part of at least one type reactive or non-reactive organic binder, (B) from 0.001 to 20 parts of at least one type of additive comprising cellulose microfibrils which are surface-modified by at least one type of compound (B1) and whose aspect ratio (l/d) is greater than 20 and the average section (d) ranges from 1 to 50 mm, wherein said compound (B1) contains at least one hydrophobe part and said microfibrils are physically surface-modified by physically absorbing at least one type of said compound (B1), C) optionally, at least one type of organic solvent and D) optionally, up to 300 parts of at least one type of compound selected form fillers, fibres, pigments, colorants and other conventional additives. A related method for preparing the inventive composition and the related use of an intermediate composition for preparing said composition are also disclosed.

Description

COATING OR MOLDING COMPOSITION FOR COMPOSITES OR MASTIC CONTAINING ADDITIVES BASED ON CELLULOSE MICROFIBRILLES. The present invention relates to coating or molding compositions for composites or mastic containing specific additives based on cellulose microfibrils, a specific process for the preparation of these compositions, specific uses and an intermediate composition for the preparation of such compositions. These specific additives are rheology agents here called generally thixotropic in the description, having a shear-thinning effect, and more particularly thixotropic significantly improved compared to the usual thixotropic agents of the state of the art. The use of thixotropic agents, in coating compositions based on organic solvents also called non-aqueous coating compositions, of the paints, varnishes, gel coats, inks, adhesives in solvent medium, sealing agents, molding compositions for composites, mastics, is well known and widely used in the industries concerned. Among the rheology additives most commonly used in the preparation of such compositions, there are mineral agents such as bentonites or other clays, in particular hydrophobic modified clays or silicas including hydrophobic modified silicas or organic agents based on diamides of fatty acid or of castor oil or alkyd derivatives modified by a polyester or a polyamide or of the diurea-diurethane type. However, the use of such rheology additives is limited by dispersion and / or sedimentation problems in the application formulas. The use of such compositions, and in particular of such a formulated coating, thus becomes relatively difficult: low speed of recovery after shearing, low resistance to sagging, in particular for thick layers. More particularly, for fatty acid diamides, particularly for powders, there is as an important limitation a step of in situ thermal activation of the additive, which lengthens the manufacturing time of said composition, and makes performance final dependent on the thermal history of the activated formula. Cellulose microfibrils are known from the prior art for their ability to act as a thickening agent, in particular in an aqueous medium; this is due to their very large form factor which corresponds to the ratio of the length of the microfibril over its section, and to the good dispersibility of the microfibrils in an aqueous medium. Obtaining such cellulose microfibrils is carried out by mechanical treatment of cellulose fibers of various origins, so as to significantly increase their specific surface area and reduce their size in terms of section and in length, up to the optimal size of the microfibrils. Such treatment is described in US 4,341,807. More particularly, according to EP 726 356, the microfibrils of cellulose of parenchyma have a shear-thinning and thixotropic effect in an aqueous medium. However, when it is sought to disperse these cellulose microfibrils in organic solvents, in particular apolar or weakly polar, a very rapid flocculation takes place, explained by the pronounced hydrophilic nature of the cellulose. This characteristic promotes interactions between microfibrils by hydrogen bonds and disadvantages interactions with the solvent, and therefore the stability of the dispersion. Surface treatments of the cellulose have been proposed, to make it hydrophobic, and therefore compatible with a solvent medium. So,

WO 02/18486 describes the use of cellulose fibers, obtained by bacterial fermentation, mixed with surfactants and / or other coagents, as a rheology-modifying agent. However, the cellulose fibers used have a higher cross-section than the above-mentioned microfibrils, and therefore a lower specific surface. EP 1,114,065 describes chemically modified cellulose microfibrils via ether bridges grafted onto the hydroxyls present on the surface of the cellulose microfibrils. On the other hand, EP 1 192 215 describes cellulose microfibrils modified by adsorption of a surfactant type compound, but does not describe the utility or the use in the compositions defined according to the present invention. The technical problem of the invention, compared with the prior art, is essentially based on the search for a compromise in performance not satisfied by the state of the prior art, for coating or molding compositions for composites or putty, in terms of: higher resistance to sagging, in particular to be able to deposit thick layers, stability in storage, - absence of delamination between two layers of coating, need for a thixotropic additive which is simple to use without conditions limiting. The resolution of this problem is based on the use of specific additives based on modified cellulose microfibrils, as thixotropic agent requiring no prior thermal activation and easy to use in the final formula. Thus, the present invention demonstrates that it is possible to overcome the drawbacks of the additives traditionally used in coating compositions, of the paint or varnish or gel coat or ink or adhesive type in solvent medium or sealing agent, or of composition of molding for composites or mastic, by the use of additives based on specifically modified cellulose microfibrils, under specific conditions and depending on the application of the final formula. The present invention proposes, as a solution to the problem defined above, a coating or molding composition for composites or mastic comprising, in addition to an organic binder A, as thixotropic agent at least one specific additive B based on modified cellulose microfibrils. at the surface with at least one compound B1, said cellulose microfibrils having a form factor 1 / d (1 being the length) greater than 20 and an average section d ranging from 1 to 50 nm, said compound B 1 having: i) at least one hydrophilic part and at least one hydrophobic part, in the case of a modification by physical means, ii) at least one hydrophobic part and a group reactive with respect to the surface functions of the cellulose microfibrils, in the case a chemical modification. The solution according to the present invention allows deposits of coating or molding layers for very thick composites or mastic at one time, without sagging or without creep, as well as improving the mechanical performance of the composition according to the invention, especially hardness. The preparation of these compositions is very easy because the thixotropic agent mixes easily with the composition, it can be added at any time and it does not require physical or chemical activation either prior or in situ, and its performance is independent the thermal history of the activated formula and the storage conditions before use. Among the additional advantages of the present invention with respect to the state of the prior art, the following may be mentioned: application with a strong shear-thinning character over a wide range of shear speed. This wide range of speed and shear allows various applications, ranging from application with a brush to application with an airless spray gun, making it possible to obtain very thick layers (several millimeters in a single pass), without generating sagging. The composition modified by the additive based on cellulose microfibrils has also a thixotropic effect which is not affected by a rise in temperature during storage. Other advantages of the invention: very good adhesion, without delamination between two layers of coating, with increased resistance to delamination, - the moment of introduction of the microfibrils into the coating or molding composition for composites or mastic is left at the choice of the formulator, significantly reduced time of exposure of the operator to volatile organic compounds (VOC) generated by the formulations, - reduced cost of application, and reduced time of immobilization of the application equipment, resulting in a significantly increased productivity. More particularly, among the advantages of the sealant compositions according to the invention, there may be mentioned: their application at constant flow rate, the thickness of the sealant then being uniform, the sealant compositions thus thixotropic being extrudable, and maintaining the form given at the start, with exceptional dimensional stability and requiring no thermal activation. The rate of additive based on cellulose microfibrils according to the invention can be adapted as a function of: the desired thixotropic effect, of the application and of the final implementation. The first object of the invention is a coating or molding composition for composites or putty comprising at least one organic binder A and at least one specific additive B based on cellulose microfibrils surface modified with at least one compound B 1 having: i) at least one hydrophilic part and at least one hydrophobic part, in the case of a physical modification, ii) at least one hydrophobic part and a group reactive with respect to the surface functions of cellulose microfibrils , in the case of a chemical modification. The second object of the invention is a simple process for the preparation of such compositions from modified cellulose microfibrils from plant or bacterial sources, with the additional advantage of adapting the additive more specifically to each of the targeted applications, and with easy implementation. Another object of the invention is the use of the composition according to the invention for different types of applications, such as paints, varnishes, gel coats, inks, adhesives in a solvent medium, sealants, molding compositions for composites and sealant compositions. The term “molding composition” means, wherever it is mentioned in the present invention, a composition for molded parts, SMC or laminate type, boat hull type or composite panels, or casting parts. The invention also covers an intermediate composition, pre-concentrated in additive, which can be used for the preparation of the final application composition according to the invention, this intermediate composition comprising the thixotropic additive at a more concentrated rate than the coating composition or molding for composites or final mastic as defined according to the invention. The first object of the invention is therefore a coating or molding composition for composites or mastic which comprises in parts by weight:

A) 100 parts of at least one organic binder, which can be reactive or non-reactive,

B) 0.001 to 20, preferably 0.01 to 10, and more preferably 0.05 to 5 parts, of at least one additive comprising cellulose microfibrils surface modified with at least one compound B1, said cellulose microfibrils having a form factor 1 / d (1 being the length and d being the mean section) greater than 20 and a mean section d ranging from 1 to 50 nm, said compound B1 having: i) at least one hydrophilic part and at least one hydrophobic part, in the case of a modification by physical route, which is preferred, ii) at least one hydrophobic part and a group reactive with respect to the surface functions of the cellulose microfibrils, and more particularly with respect to surface hydroxyl functions of the cellulose microfibrils, in the case of a chemical modification, C) optionally, at least one organic diluent, which can be reactive or non-reactive with respect to the organic binder A,

D) optionally, up to 300 parts, preferably when it is present from 1 to 300 parts, and more preferably from 1 to 200 parts, of at least one component chosen from fillers such as calcium carbonate, talc or silica, mineral fibers such as carbon or organic fibers such as polyamide, and more particularly glass beads or fibers, pigments, dyes and other usual additives such as spreading agents, wetting agents, dispersants, antioxidants, oxidants, anti stabilizers -UV, biocides. In the case where dispersants are present, these are selected so as to avoid any antagonistic effect on the effect of compound B 1. Modification by the physical route and more particularly by physical adsorption on the surface is the preferred route for questions practical simplicity and cost of the process. The microfibrils before modification can be obtained by various methods already described in the literature. Among these methods, reference may be made, for example, to the methods described in EP 726 356 and EP 1 114 065, the teachings of which are incorporated below. The microfibrils can thus be obtained from the pulp of plants, such as for example the beet pulp, by a process comprising the following stages: a) first acid or basic extraction, at the end of which a first solid residue is recovered , b) optionally, second extraction carried out under alkaline conditions of the first solid residue, after which a second solid residue is recovered, c) washing of the first and of the second solid residue, d) optionally, bleaching of the washed residue, e ) dilution in water of the third solid residue obtained in step d) so as to obtain a dry matter content of between 0.5 and 10% and preferably 0.5 to 5% by weight, f) homogenization of the diluted suspension obtained in step e). In the case where the microfibrils are prepared from paper pulp, said process begins directly at step e). In step a), the term “pulp” is understood to mean moist, dehydrated pulp, preserved by silage or partially defected. The extraction step a) can be carried out in an acidic or basic medium. For acid extraction, the pulp is suspended in a solution of water for a few minutes so as to homogenize the acidified suspension at a pH between 1 and 3, preferably between 1.5 and 2.5, with a solution concentrated of an acid such as hydrochloric acid or sulfuric acid. This step can be advantageous for removing the calcium oxalate crystals which may be present in the pulp and which, because of their significant abrasive nature, can cause difficulties in the homogenization step. - for a basic extraction, the pulp is added to an alkaline solution of a base, for example soda or potash, of concentration less than 9% by weight, preferably less than 6% by weight, and again more preferably between 1 and 2% by weight. A small amount of a water-soluble antioxidant may be added, such as sodium sulfite Na ₂ SO ₃ , in order to limit the oxidation reactions of the cellulose. Step a) is generally carried out at a temperature between about 60 and 100 ° C, and preferably between 70 and 95 ° C. The duration of step a) is between 1 hour and 4 hours. During step a), a partial hydrolysis takes place with release and solubilization of most of the pectins and hemi-celluloses, while preserving the molecular mass of the cellulose. The solid residue is recovered from the suspension from step a) using known methods. Thus, it is possible to separate the solid residue by centrifugation, by vacuum or pressure filtration, with filter cloths, or for example filter presses, or by evaporation. The first residue obtained is optionally subjected to a second extraction step, carried out under alkaline conditions. A second extraction step is carried out, step b), when the first has been carried out under acidic conditions. If the first extraction was carried out under alkaline conditions, the second step is only optional. According to this process, this second extraction is carried out with a base, preferably chosen from soda and potash, the concentration of which is less than 9% by weight, preferably between 1% and 6% by weight. The duration of the alkaline extraction step is between 1 hour and 4 hours, preferably close to 2 hours. At the end of this second extraction, if it takes place, a second solid residue is recovered. In step c), the residue from step a) or b) is washed thoroughly with water in order to recover the residue of cellulosic material. The cellulosic material of step c) is then optionally bleached, in step d), according to conventional methods. For example, a treatment can be carried out with sodium chlorite, sodium hypochlorite, hydrogen peroxide at a rate of 5-20% by weight relative to the amount of dry matter treated. Different concentrations of bleaching agent can be used, at temperatures between 18 and 80 ° C, and preferably between 50 and 70 ° C. The duration of this step d) is between 1 hour and 4 hours, and preferably between 1 hour and 2 hours. A cellulosic material is then obtained containing between 85 and 95% by weight of cellulose. At the end of this bleaching step, it may be preferable to wash the cellulose abundantly with water. The resulting suspension, optionally bleached, is then rediluted in water at a rate of 0.5 to 10% and preferably of

0.5 to 5% dry matter (step e)), before undergoing a homogenization step

(step fi), comprising at least one cycle. The homogenization step corresponds to a mixing, grinding or any high mechanical shearing operation, followed by one or more passages of the suspension through a small diameter orifice, subjecting the suspension to a pressure drop of at least 20 MPa and a high speed shearing action, followed by a deceleration impact at high speed. The mixing or grinding is, for example, carried out by one or more passages in the mixer or grinder for a period ranging from a few minutes to 1 hour, in a Waring Blendor type device equipped with a four-blade propeller or grinder or any other type of mill, such as a colloid mill.

The actual homogenization will advantageously be carried out in a Manton Gaulin type homogenizer in which the suspension is subjected to a shearing action at high speed and pressure, in a narrow passage and against a shock ring. One can also cite as homogenizer the Micro Fluidizer which mainly consists of a compressed air motor which will create very high pressures, an interaction chamber in which the homogenization operation will take place (elongational shear, shock and cavitation) and a low pressure chamber which allows the depressurization of the dispersion. The suspension is introduced into the homogenizer preferably after preheating at a temperature between 40 and 120 ° C, preferably between 85 and

95 ° C. The homogenization operation is carried out at less than 120 ° C, and preferably less than 100 ° C and more preferably less than 80 ° C, at pressures between 20 and 100 MPa, preferably greater than 50 MPa, by a number of successive passages which can vary from 1 to 20, preferably from 5 to 15, until a stable suspension is obtained. The homogenization operation can advantageously be followed by a high mechanical shear operation, for example in a device such as the Ultra

Sylverson Turrax. The cellulose microfibrils are extracted mechanically until practically none of the initial fibers are visible by light microscopy. The efficiency of this step can also be followed by the reduction in the size of the particles as measured by laser granulometry. The cellulose microfibrils which can be used according to the present invention have a form factor 1 / d greater than 20, preferably greater than 50, and even more preferably greater than 100, with an average section d ranging from 1 to 50 nm, preferably ranging from 2 to 20 nm, even more preferably from 5 to 15 nm. The cellulose microfibrils according to the invention come from vegetable sources of cellulose such as wood, cotton, flax, ramie, certain algae, jute, sugar beet pulp, citrus fruits such as lemons, oranges, grapefruits, waste from the food industry, or from bacterial sources of cellulose or animal origin such as tunicate. More particularly, the cellulose microfibrils are wood cellulose microfibrils, preferably obtained from paper pulp, and more preferably from paper pulp obtained according to a pulping process of the kraft or bisulfite type or of microfibrils from beet pulp. The modified cellulose microfibrils which can be used according to the invention preferably have a pronounced aptitude for redispersion in polar or apolar organic medium. Concerning compound Bl, it is preferably soluble in organic binder A and / or organic diluent C. The term "soluble" means a homogeneous and transparent solution resulting from the mixture of compound Bl with organic binder A and / or the diluent organic C. Preferably, it is only relatively soluble, in order to avoid its desorption in a solvent medium. As regards the treatment of cellulose microfibrils, the latter are modified at the surface either chemically or physically, the latter being preferred, as already mentioned above. The chemically modified cellulose microfibrils can be modified by various methods already described in the literature. Among these methods, reference may be made to the method described in EP 1 114 065. The chemical modification of the surface of the cellulose microfibrils can be obtained by various possible reactions of the surface functions of the cellulose microfibrils, and more particularly of the hydroxyl functions, with a compound B1 as defined above in ii), such as for example by: - silylation reactions, etherification reactions, condensations with isocyanates, alkoxylation reactions with alkylene oxides, condensations or subtitutions with glycidyl derivatives. The preferred organic chemical modification compounds reactive with hydroxyl functions are chosen from silylating agents, isocyanates, halogenated alkylating agents, alkylene oxides, and / or glycidyl derivatives. This modification by chemical reaction leads to a surface of the predominant hydrophobic character cellulose microfibrils. The cellulose microfibrils can also be modified by physical means, either by surface adsorption, or by spraying, or by coating, or by encapsulation of the microfibrill. The preferred modified microfibrils according to the invention can be obtained by physical adsorption of at least one compound B1 as defined above, and even more preferably of at least one compound B1 as defined above in i). The expression “predominant hydrophobic character” means that the compound B1 has a solubility in water much lower than that in an organic binder A and / or an organic diluent C, but remains at least water-dispersible. The type B1 compounds as defined in i), having at least one hydrophilic part and at least one hydrophobic part can be compounds of low molecular weight Mw or compounds of higher molecular weight (Mn), such as macromolecular compounds having a molecular weight up to

50,000, and even more preferably up to 20,000, for example block (block) copolymers such as those of ethylene oxide-propylene oxide, or graft copolymers, such as copolymers comprising (meth) acrylic acid or of maleic anhydride with macromonomers of hydrophobic nature (example (meth) acrylate comprising C ₂ -C ₂ alkyl) and / or hydrophilic (example (meth) acrylate of polyethylene or polypropylene glycol or of a mixture of oxyethylene units and oxypropylene) or star or dendrimers or block copolymers or random copolymers such as styrene-acrylic acid or styrene maleic anhydride (SMA) which can be partially esterified or amidified by fatty alcohols or amines having a C 12 to C ₂ alkyl chain or imidified in the form of an SMA imide and derivatives such as the quaternary salts of SMA imide, in particular SMA 40001 (from Sartomer). According to a more particular embodiment of the invention, said compound B1 according to i) comprises at least one surfactant, preferably chosen from the group consisting of at least one anionic surfactant or at least one cationic surfactant or at least one amphoteric surfactant, or at least one nonionic surfactant, the latter being able to be in binary combination with each of the three other surfactants, and said compound B1 comprising even more preferably at least one nonionic surfactant associated with at least one anionic surfactant. In the case where said compound B1 as defined in i) comprises a surfactant, this can more particularly comprise: a hydrophilic part, preferably carrying oxyethylene units, soluble in water and capable of adsorbing on the surface of cellulose microfibrils as defined according to the invention, a hydrophobic part, having a pronounced chemical affinity with the organic binder A and / or the organic diluent C as defined according to the invention, and containing for example a carbon chain in Ce or longer, aromatic or aliphatic or cycloaliphatic or mixed, and capable of interacting with the organic binder A and / or the organic diluent C, as defined according to the invention. The expression “hydrophobic part capable of interacting with organic binder A and / or organic diluent C” means that said part is chemically compatible with organic diluent C, within the meaning of the solubility parameters. Thus, the chemical compatibility between two compounds can be under certain conditions estimated from the difference of δ solubility parameters, that difference should not, according to this estimate exceed 3 units for δ expressed in calories ^{^1/2} / cm ^{^3/2} . Among the nonionic surfactants suitable for the invention, mention may be made of castor oil derivatives ethoxylated with 7 to 60 EO, and preferably from 30 to 40 EO (EO means an ethylene oxide unit), and more particularly derivatives of hydrogenated castor oil ethoxylated with 7 to 60 EO, and preferably from 30 to 40 EO, derivatives of coconut oil ethoxylated, soya lecithin, fatty alcohols

Ce à C ₂₂ , preferably in Ce à C ₂ 2 more preferably in C10 to C22 polyethoxylated (8 to 30 and preferably 15 to 30 EO for C. ₀ to C22) such as Tergitol® 15S20 (C. ₃ , 20 EO ) from Dow, more particularly said Tergitol® in combination with Rhodafac® RS

610 from Rhodia Chimie, more particularly to a weight ratio

Rhodafac ^® / Tergitol ^® ranging from 99/1 to 25/75 and most preferably 75/25 to 40/60 and even more preferred of ± 10% around 1/1, polyethoxylated alkylphenols, ethoxylated aryl phenols such as di - or ethoxylated tri-styrylphenol (8 to 30 and preferably 8 to 25 EO), tridecyl polyglycol alcohol ethers such as tridecylalcohol _, „; to 60 EO (Genapol® X-060 from Clariant), block polyethers of the bi- and tri-block type (Pluronic ^® from BASF, in particular Pluronic ^® F127 or Poloxomer ^® 407 or Lutrol® F127 from BASF of particular formula - (OE ) ιoι- (OP) ₅ ^ (OE) ιoι), sorbitol derivatives comprising 1 to 3 polyoxyethylene chains, 1 to 3 fatty chains C12 to C30, and in particular Cis, such as polyoxyethylene sorbitan trioleate such as Tween ^® 85 which is polyoxyethylene (20 EO) sorbitan trioleate, esters of ethoxylated fatty acids in C ₃ to C ₃ β with 8 to 25 EO, fatty acid derivatives, esters of mono- and di-glycerides of acids fatty in Ce to C ₃ β, and fatty amines in Ce to C22, such as dodecylamine, or mixtures. Among the anionic surfactants suitable for the invention, mention may be made of the following families: alkyl sulfates, alkyl ether sulfates, alkoxylated fatty alcohol sulfates, alkanolamide sulfates, glyceride sulfates, alkyl phosphates, alkyl ether phosphates, alkoxylated fatty alcohol phosphates, alkylbenzene sulfonates such as do-decylbenzenesulfonate, ligno sulfonates, dialkyl sulfosuccinates, alkyldiphenyloxydedisulfonate such as Dowfax® D2A1 from Dow, sarc , acylamino acids, mono-glyceride esters of tartaric acid, mono-glyceride esters of citric acid. Mention may also be made, as anionic and preferred surfactants for the invention, of the sulphate esters (mono or partial di-esters of sulfuric acid with corresponding fatty alcohol) such as Disponil® FES 7715 in ethoxylated C12 (30 EO) or Disponil® FES 993 in ethoxylated C12 (9 EO) of Cognis or phosphates (partial mono or di-esters of phosphoric acid with corresponding fatty alcohol) of fatty alcohols, preferably in Ce to C22. with 2 to 30 oxyalkylene units, preferably with 3 to 6 oxyalkylene (Rhodafac ^® of Rhodia Chimie particular Rhodafac® RS610 in Cι _3, 6 EO phosphate at 25% in water or Servoxyl ^® VPDZ 20/100, phosphate C13, 20 EO, or Servoxyl VPNZ ^® 20/30, phosphate of nonylphenol ethoxylated with 20 EO, or Servoxyl® VDPZ 100, phosphate C_ _3, all 3 of Elementis Specialties), such as phosphate esters oleic fatty alcohol ethoxylated with 2 EO (Empiphos® O3D from Albright & Wilson), ethoxylated oleic alcohol phosphate esters (Crodafos® N from Croda Oleochemicals), keto / stearic alcohol phosphate esters with 2 to 10 OE (Crodafos ^® CS from Croda Oleochemicals), phosphate esters of tridecyl alcohol ethoxylated with 4 to 6 OE (Emphos ^® PS from CK Witco), phosphate esters of fatty alcohol ethoxylates (Crafol® AP from Henkel Iberica), esters sulfates ethoxylated arylphenols, such as di- or tri-styrylphenol ethox ylé (Soprophor® DSS / 7 and Soprophor® 4D384 from Rhodia Chimie), acid esters, organic phosphates, simple or mixed (Beycostat® from Ceca SA, such as for example Beycostat ^® A B09 also known by the common name of BNA), polyalkoxylated alkylphenol phosphate esters in which the alkyl substituent is C1 to C12 with 5 to 25 OE units, said oxyalkylene unit C ₂ -C ₄ arylphenols phosphate esters with 5 to 25 EO, such as phosphate ester of di- or tristyrylphenol ethoxylate (Soprophor ^® 3D33 from Rhodia Chimie), the partially neutralized polycarboxylic acid salts, such than sodium and potassium salts. Even more preferred anionic surfactants for the invention are for example: i) a polyalkoxylated alkylphenol phosphate ester in which the alkyl substituent is C ₂ to Ce and the oxyalkylene in C2, or ii) a simple organic phosphate acid ester or as a mixture particular: Beycostat® A B09, also known under the common name of BNA, mixture of ester and diester of phosphoric acid with an alkylaryl chain, the alkyl substituent of which is C9, with 9 oxyethylene units. iii) Rhodafac ^® RS 610 iv) Disponil® FES 993 The monoester and the diester of phosphoric acid present in the BNA are: nonylphenol ethoxylated nine times monoester of phosphoric acid and the corresponding diester. Their formulas are given below: - monoester: C ₉ Hι ₉ -C ₆ H ₄ -O- (CH ₂ -CH2-O) ₉ P (O) (OH) 2 - diester: (C ₉ Hι ₉ -C ₆ H ₄ -O- (CH ₂ -CH2-O) 9) ₂ P (O) (OH). Even more preferred, the surfactants can be combinations of at least one so-called anionic surfactant such as phosphates more particularly such as Rhodafac® RS 610 or ethoxylated sulfates such as Disponil® FES 993 with at least one so-called nonionic surfactant lesdit as ethoxylated fatty alcohols, preferably C10-C22 with 15 to 30 EO, such as Tergitol ^® 15S20 _(C-3, 20 EO) from Dow. Preferably, such a combination will be with a weight ratio of phosphate or sulphate as mentioned above relative to said ethoxylated fatty alcohol ranging from 99/1 to 25/75, preferably from 75/25 to 40/60 and more preferred ± 10% around 1/1. Among the cationic surfactants suitable for the invention, mention may be made of alkyl quaternary ammonium salts derived from C 6 -C 20 fatty amines and containing 1 to 2 alkyl substituents, such as that didecylmethyl ammonium bromide, amide salts, ester and ether amine salts, oxy and ethoxy amine salts, alkanolamide salts, imide salts or Servamine® KWlOO ntis Specialties which is an alkyl bis hydroxy ethyl, methyl quaternary ammonium sulfate bearing 15 EO. Among the amphoteric surfactants suitable for the invention, mention may be made of compounds having a quaternary ammonium group and an anionic phosphoric group, such as the family of phosphoUpides, derivatives of aliphatic secondary or tertiary amines, in which the aliphatic radical is a chain linear or branched in Ce to C22, and containing at least one water-soluble anionic group such as carboxylates, sulfonates, sulfates, phosphates or phosphonates. Mention may also be made of betaine C1 to C20 alkyl, sulfobetaines, amidoalkyl C1 to Ce betaines C1 to C20 alkyl. C1 to C6 amidoalkyl sulfobetaines C2 to C2 alkyls. Other surfactants of marked hydrophobic nature can also be used, such as, for example, silicone surfactants and fluorinated surfactants. As an example of a physical adsorption treatment method, mention may be made of the method described in FR 2 794 762. This method comprises the following steps: a ') mixing of an aqueous dispersion of cellulose microfibrils with at least one compound Bl such as defined in i), with adjustment of the pH if necessary (for example for phosphates pH = 8) which can be done in the solution of the surfactant B 1 or in the dispersion with the microfibrils, b ') elimination of the water from the dispersion aqueous to obtain a dry mixture of cellulose microfibrils and of compound Bl as defined in i) above. The water is removed by thermal drying at a temperature below 100 ° C and preferably below 80 ° C, or by infrared or by atomization or by solvent exchange. During step a '), the compound is preferably mixed with simple stirring.

Bl as defined in i) to an aqueous dispersion of cellulose microfibrils (0.5 to

20%, preferably 1 to 15%) having the characteristics defined according to the invention. The proportions of compound B1 and of cellulose microfibrils before modification, may depend on the origin of the cellulose microfibrils, and more particularly on their specific surface. A limit ratio by weight of compound B1 on cellulose microfibrils before modification, can be defined as corresponding to the flocculation threshold of the modified microfibrils during re-solventing. This limiting ratio depends on the source of microfibrils and is less than 1 and even less than 0.5, and more particularly for the compound B1 which can be physically adsorbed according to i). The weight ratio of compound B 1, and more particularly of compound B 1 as defined in i), on cellulose microfibrils as such, can be chosen in the range going from 0.5 / 1 to 10/1, preferably from 1/1 to 10/1, and more preferably from 1.5 to 5 and more particularly from 2/1 to 5/1. Said microfibrils are obtained by drying an aqueous dispersion of cellulose microfibrils as defined according to the invention, containing from 1 to 40%, preferably 4 to 40% and more particularly from 10 to 40% by weight of microfibrils (modified ) with respect to said dispersion with said compound B1 present in a ratio as defined above. Additive B can be obtained either as a fine powder by grinding, or as an elastic pre-gel in an organic binder A and / or an organic diluent C as defined according to the invention, or in the form of solid granules sorted granuloma. Said organic binder A according to the composition of the invention can firstly be reactive and selected from: crosslinkable two-component epoxyamines (2K), more particularly epoxy / polyamides, unsaturated polyesters, vinylesters, modified alkyds , for example modified alkyds of acrylic or urethane or styrene type, or unmodified alkyds, crosslinkable two-component polyurethanes more particularly crosslinkable two-component polyurethanes from acrylic polyols or polyesters or polyether polyols or melamine two-component system with polyol acrylic or polyester polyol, acrylic oligomers, acrylic crosslinkable binders thermally or by irradiation under UV and / or EB radiation, silane polyethers modified with alkoxysilanes, silane polyurethanes modified with alkoxysilanes. Said organic diluent C according to the composition of the invention can be reactive or non-reactive depending on the organic binder A, with a content by weight per 100 parts of organic binder A which can vary according to the following cases: for a reactive diluent C, up to '' to 300 parts by weight, for a non-reactive diluent C, up to 100 parts by weight. The first function of this organic diluent C is to be a solvent for the organic binder A. More particularly, the organic binder A can be a non-reactive binder such as a linear polymer soluble in a type C organic diluent. As an example of such polymers, there may be mentioned polyurethanes, polyacrylates, elastomers type SBR, polychloroprene or butyl rubber. The organic diluent C can be an organic solvent or a plasticizer and it is chosen according to the type of organic binder A used: for an organic binder A selected from unsaturated polyesters, vinyl esters or acrylic acrylic oligomers, organic diluent C can be chosen from (meth) acrylic and / or allyl and / or vinylaromatic monomers, preferably styrene and derivatives, including vinyl toluenes, for a non-reactive organic binder A selected from soluble linear polymers such as polyurethanes, acrylic thermoplastic resins (polyacrylates), elastomers type SBR, polychloroprene or butyl rubber, organic diluent C is also non-reactive and can be chosen from aromatic solvents, ketones, alkanes, petroleum ethers, alcohols , alkyl acetates, white spirit or their mixtures, preferably xylenes, toluene, acetone, l acetate or isopropyl acetate, methyl ethyl ketone, hexane, dimethyl sulfoxide, dichloromethane, trichlorethylene, methylene chloride, for a two-component reactive organic binder A which can be selected from: reactive epoxy-amino systems which can comprise at least one epoxy resin comprising at least 2 epoxy groups and at least one amino compound (including polyamide) comprising at least 2 amino groups, 2K epoxy-polyamide systems, polyurethane systems which can comprise at least a polyisocyanate and at least one polyol, polyol-melamine systems, polyester systems from the 2K epoxy / acid or carboxylic anhydride system, or polyol / acid or carboxylic anhydride which may comprise at least one epoxy or polyol and at least one acid or corresponding carboxylic anhydride, polyol-melamine systems, in this case the organic diluent C can be chosen from: hydro aromatic carbides, primary, secondary or tertiary alcohols, in particular those comprising an aliphatic chain and / or an aromatic chain, ketones, glycol ethers, alkyl acetates, white spirit or their mixtures, preferably xylenes, n- or iso-butanol, ethyl acetate, butyl acetate, 1-methoxy-2-propanol acetate, methyl isobutyl ketone, methyl ethyl ketone, butyl glycol, N-methylpyrrolidone, for a binder organic A selected from alkyds, which can be modified (acrylic, urethane or styrene type) or unmodified, the diluent organic C can be chosen from aromatic solvents, gasolines, ketones, alkanes, alkyl acetates, white spirit or their mixtures, preferably xylenes, white spirit, butyl acetate, heptane , methyl isobutyl ketone, methyl ethyl ketone. More particularly, for thermoplastic acrylic resins (polyacrylates), the solvent C can be selected from: aromatic hydrocarbons, primary, secondary or tertiary alcohols, with an aliphatic / aromatic or mixed chain, ketones, glycol ethers, alkyl acetates, white spirit or their mixtures. Most preferred: xylene, toluene, n- or iso-butanol, ethyl and butyl acetate or 2-methoxy-propanol acetate or methyl isobutyl ketone, for an organic binder A selected from binders which are crosslinkable thermally or by irradiation under UV radiation and / or EB and selected from (meth) acrylic oligomers or multifunctional acrylated or allylic acrylic oligomers, the organic diluent C can be chosen from (meth) acrylic and / or allyl and / or vinylaromatic monomers, for an organic binder A selected from silane polyethers or silane polyurethanes, the organic diluent C can be a plasticizer chosen from phthalates, benzoates, glycols or their mixtures, preferably diisobutylphthalate, diisoundecyl or diisodecyl phthalate or polyether glycol. A first type of composition according to the invention is a coating composition, and more particularly a sealing coating. Such a coating composition according to the invention may comprise at least one organic binder A selected from unsaturated polyesters or vinyl esters or acrylic acrylic oligomers, and at least one organic diluent C selected from (me th) acrylic monomers and / or allylics and / or vinylaromatics, preferably styrenes and derivatives, including vinyl toluenes. A more particular case of the above coating composition may be a pigmented or non-pigmented gel coat. Another particular case of coating composition according to the invention can be an adhesive in an organic solvent medium comprising at least one organic binder A which can be a linear polymer soluble in at least one non-reactive organic diluent C. Such organic binders A can be soluble linear polymers, such as polyurethanes, polyacrylates, SBR type elastomers, polychloroprene or butyl rubber. The non-reactive organic diluents C can be aromatic solvents, ketones, alkanes, ethers of petroleum, alcohols, alkyl acetates, white spirit or their mixtures, preferably xylenes, toluene, acetone, ethyl acetate or isopropyl acetate, methyl ethyl ketone, hexane , dimethylsulfoxide, dichloromethane, trichlorethylene. Another type of coating composition possible according to the invention can be a composition based on reactive organic binder A comprising: at least one organic binder A selected from the following crosslinkable two-component reactive systems: epoxy-amine systems comprising at least an epoxy resin, comprising at least 2 epoxy groups, and at least one amino compound including polyamide, comprising at least 2 amino groups, the polyurethane systems comprising at least one polyisocyanate and at least one polyol, the polyol-melamine systems, and the polyester systems based on at least one epoxy or on a polyol reactive with at least one corresponding carboxylic acid or anhydride, polyol-melamine systems, at least one organic diluent C which is not reactive with respect to organic binder A , selected from the following solvents: aromatic hydrocarbons, primary, secondary or tertiary alcohols, in particular those comprising t an aliphatic chain and / or an aromatic chain, ketones, glycol ethers, alkyl acetates, white spirit or their mixtures, preferably xylenes, butanol, ethyl acetate, acetate butyl acetate, 1-methoxy-2-propanol acetate, methyl isobutyl ketone, methyl ethyl ketone, butyl glycol, N-methylpyrrolidone. In the case of a crosslinkable two-component system (2K) leading to a polyurethane or of a polyester system based on epoxy-acid or polyol-acid or polyol-melamine, the polyol may preferably be a hydroxylated acrylic resin obtained, for example, by copolymerization of a non-functional alkyl acrylate type acrylic monomer with a hydroxylated acrylic monomer such as a hydroxy alkyl (me th) acrylate. Another coating composition according to the invention may comprise at least one organic binder A selected from modified alkyds (acrylic, urethane or styrene type), or unmodified, and at least one organic diluent C selected from aromatic solvents, gasolines, ketones, alkanes, alkyl acetates, or mixtures thereof, preferably xylenes, butyl acetate, white spirit, heptane, N-methylpyrrolidone, methylisobutylketone, methylethylketone, or mixtures thereof. Another possible coating composition according to the invention may comprise at least one organic binder A which can be crosslinked thermally or by irradiation under UV and / or EB radiation, and selected from (me th) acrylic oligomers or acrylic or allylic multifunctional acrylic oligomers, having a functionality at least equal to 2, and at least one organic diluent C selected from acrylic (and meth) and / or allylic and / or vinylaromatic monomers. Another more specific coating composition according to the invention is a mastic composition, which can comprise: at least one organic binder A selected from unsaturated polyesters, vinylesters, silane polyethers, polyurethanes and more particularly silane polyurethanes, silicones, at least one organic diluent C selected from (meth) acrylic and / or allyl and / or vinylaromatic monomers, such as styrene and derivatives, including vinyl toluenes, aromatic hydrocarbons, white spirit or their mixtures, if the organic binder A selected is an unsaturated polyester or a vinylester, and if the organic binder A is a silane polyether or a silane polyurethane, the organic diluent C is a plasticizer chosen from phthalates, benzoates, glycols or their mixtures, preferably diisobutylphthalate, diisoundecyl or diisodecyl phthalate or polyether glycol. Another type of composition according to the invention can be a molding composition for composites, the term molding having the meaning defined above, which can comprise, in addition to the additive B as defined according to the invention, at least one binder organic A selected from unsaturated polyesters, vinylesters, cross-linkable epoxy-amine systems, cross-linkable polyurethane systems. The molding compositions according to the invention can comprise SMC-type compositions or laminating compositions, in particular for shipbuilding or composite panels, with application of the composition, either by spraying with a gun or with a brush or with a roller. . The thixotropic effect of such compositions according to the invention makes it possible to obtain a satisfactory compromise between the impregnation of the fibers (sufficiently low viscosity during ι application for impregnating) and preventing sagging (rise in viscosity fast enough to avoid creep / sagging). The second object of the invention is a specific process for the preparation of said compositions. This specific process comprises at least one step of mixing at least one additive B with at least one organic binder A and / or at least one organic diluent C. According to a more particular mode of this process, the mixing takes place under shear, with the additive B introduced in the form of powder or in the form of a pre-concentrated intermediate composition containing it. More particularly, the intermediate composition can be in the form of powder or of an elastic pre-gel or of solid granules of controlled particle size ranging from 0.5 to 20 mm. This shaping facilitates the implementation of the coating or molding compositions for composites or putty according to the invention by simple dispersion under shear, without any need for thermal activation. A variant of this process consists in adding at least one additive B before and / or after the addition of the defined component D, in the case of the presence of a component

D as defined above. The third subject of the invention relates to the use of the composition defined according to the invention in compositions of paints, varnishes, gel coats, inks, adhesives in solvent medium, sealants, or molding for composites, or sealants. The coating compositions according to the invention can be used as protective and / or decorative and / or surface treatment coatings

(cleaning and pickling) of various substrates. The last object of the invention relates to an intermediate composition which can be used for the preparation of a composition as defined according to the invention or obtained according to the process defined according to the invention, comprising at least one additive B at a concentration by weight ranging from 2 to 50%, preferably 5 to 50%, more particularly 5 to 25% and even more particularly 10 to 25% relative to the total weight of said composition, and comprising at least one organic binder A and / or minus an organic diluent C according to the definition of the invention above. According to a variant of this intermediate composition, it can comprise at least one organic diluent C, without any organic binder A. This intermediate composition is particularly suitable for coating or molding or mastic compositions, comprising up to 300 parts by weight of '' a thinner uι _g -uu ₄ ue C reactive for 100 parts of an organic binder A, or up to 100 parts by weight of a non-reactive organic diluent C per 100 parts by weight of an organic binder A. In this type of intermediate composition (organic diluent C only), the organic diluent C is selected from (meth) acrylic and / or allylic and / or vinylaromatic monomers, such as styrene and derivatives, aliphatic solvents, cycloaliphatic solvents such as cyclohexane, aromatic solvents such as toluene or xylenes, white spirit, ketones, primary, secondary or tertiary alcohols, in particular polyalcohols, alcohols comprising an aliphatic chain and / or an aromatic chain such as butanol or isopropanol , C1 to C alkyl esters such as ethyl acetate, glycol esters, plasticizers such as phthalates or benzoates or glycols, or mixtures thereof. According to another possibility, this intermediate composition comprises at least one organic binder A and at least one organic diluent C. Another possible case is that where at least one liquid organic binder is used in place of the organic diluent C, by absence of any organic diluent C. Such liquid binders can be chosen from liquid (meth) acrylic oligomers, vinyl esters, epoxy resins, and other liquid resins which can serve as organic binder A according to the invention. The intermediate composition according to the invention is preferably in the form of a powder or an elastic pre-gel or solid granules of controlled particle size ranging from 0.5 to 20 mm which are easily dispersible in the final application formula.

The examples below illustrate the invention without limiting its scope:

Preparation of beet cellulose microfibrils MCBMl, MCBM3, MCBM4 and MCBM7: Microfibrils extracted from beet are obtained starting from beet pulp: pulping is carried out in a basic medium (0.8 parts of soda per 1 part of pulp) or acid (sulfuric acid at 85 ° C) intended to separate the fibers and extract the pectins. The efficiency of this step is followed by the reduction of the infrared absorption in the area 1720 to 1770 cm ¹ . The time required is several hours. One or more rinses follow until a water with little ionic charge and a pH of between 5.5 and 7 is obtained. After this step, the cellulose microfibrils are released by a strong disintegration of the cell walls in an aqueous medium. One usable means is a Manton Gaulin homogenizer. For a initial concentration of 0.8% fiber, a minimum pressure of 400 bars is used for at least 50 minutes. The aqueous suspension is then treated by adding to the cellulose microfibrils, pH = 8, the surfactant BEYCOSTAT ^® B09 A ECSC SA (BNA), which is a mixture of ester and diester of phosphoric acid chain alkylaryl , whose alkyl substituent is Cg with 9 oxyethylene units, in mass proportion of 4 parts per 1 part by weight of cellulose microfibrils. The suspension is then dried by evaporation of the water in a ventilated oven or by any other effective means such as drying under air flow or freeze-drying.

Preparation of MCBM9 eucalyptus cellulose microfibrils: We start from an industrial paper pulp of long eucalyptus fibers obtained chemically with bisulfite, using ammonium bisulfite. The release of the cellulose microfibrils is obtained by a strong disintegration of the cell walls in an aqueous medium. One usable means is a Manton Gaulin homogenizer. For an initial fiber concentration of 0.8%, a minimum pressure of 40 MPa (400 bar) is used for at least 50 minutes. The aqueous suspension is then treated by adding to the cellulose microfibrils, pH = 8, the surfactant BEYCOSTAT ^® B09 A ECSC SA (BNA), which is a mixture of ester and diester of phosphoric acid chain alkylaryl , whose alkyl substituent is Cg, with 9 oxyethylene units, in mass proportion of 4 parts per 1 part by weight of cellulose microfibrils. The suspension is then dried by evaporation of the water in a ventilated oven or by any other effective means such as drying under air flow or freeze-drying. The microfibrils thus obtained have an average section d of between 10 and 20 nm.

Preparation of pine cellulose microfibrils (resinous) MCBMl 0 to MCBM21: We start from a chemical pulp of long bleached maritime pine fibers (resinous) having undergone bisulfite cooking. This paste is the Biofluff ^® HD reference from the company Tembec Tartas. The release of the cellulose microfibrils is obtained by a strong disintegration of the cell walls in an aqueous medium. One usable means is a Manton Gaulin homogenizer. For an initial concentration of 1% to 1.5% in fibers, a minimum pressure of 40 MPa (400 bars) is used for at least 50 minutes or 10 passages of the suspension in the homogenizer. The aqueous suspension obtained is then treated by adding to the microfibrils of cellulose with stirring the surfactant B1 in the form of a 10% solution, in mass proportion of 4 parts of surfactant for 1 part by weight of cellulose microfibrils. The pH of the solutions of phosphated surfactants is adjusted beforehand to pH = 8 using an ammonia solution, so that the surfactants are completely ionized. The suspension is then dried by lyophilization (samples MCBM10 and MCBM1 1) or by evaporation of water in a ventilated oven at 60 ° C (MCBM12 to MCBM21). After preparation, the modified microfibrils MCBMl 2 to MCBM21 are stored for at least 24 hours in an air-conditioned room at 22 ° C and 50 ± 10% humidity. Note that the preparation of cellulose microfibrils from wood is much faster than those from beet.

Measurement of microfibril parameters: length l, mean section d, form factor l / d. The size of the cellulose microfibrils is measured by atomic force microscopy (AFM). The modified microfibrils are diluted in 1% xylene, then deposited on a blade of cleaved mica. The solvent is left to evaporate naturally.

AFM images were obtained in tapping mode, the frequency of stress is close to the resonance frequency of the tip. The observed area is a square of

10 µm * 10 µm. The scanning speed is 1 Hz and the number of scans is

512. The results are collated in the following table 1:

Table 1

Example 1 (invention): Application in a two-component epoxy-polyarnine paint. The remarkably effective character of cellulose microfibrils as a thixotropic agent is demonstrated by evaluating them in two-component epoxy-polyamine paints. The cellulose microfibrils are used either in the form of a previously ground powder or in the form of a pre-gel obtained by mixing 13% of cellulose microfibrils surface modified with at least one compound B 1 and 87% of xylene. The additive is dispersed in xylene using an Ultra Turrax homogenizer for at least 5 minutes, at room temperature and at a speed of 24,000 rpm. A grinding base is prepared without thixotropic additive. The paint formula is shown in the following table 2:

Table 2: Raw materials References Suppliers Mass proportion used Commercial GRINDING BASE Epoxy resin Araldite GZ 7071X75 VANTICO 17.4 Epoxy resin Araldite GY 783BD VANTICO 13.0 Antifoam Byk A 530 BYK CHEMIE 0.5 Dispersant Disperbik 1 10 BYK CHEMIE 0,5 White pigment Ti02 RCL 535 or Tîona 595 MILLENIUM 1, 9 Yellow pigment Bayferrox 3920 or 915 BAYER 4, 1 Anti-corrosion pigment ZP 10 HENBACH 7.6 Talc filler Finntalc M05 OMYA 9,5 Filler Silica HPF6 SIBEL CO 19,2 n-butanol Rectapur PROLABO 5,4 Thixotropic additive Modified X cellulose microfibrils HARDENER Crayamid 140 CRAY VALLEY reactive polyamide 8.9 terminated with amino functions Xylene Carlo erba PROLABO 12.0 Total 100 + x Dry extract by weight 77.7% Dry extract by volume 64.7% CPV 29, 1% Density 1, 36 x =% of cellulose microfibrils modified compared to the paint formula alone. Any% of modified cellulose microfibrils cited in an application formulation will have this meaning. The paints are additivated with cellulose microfibrils at different rates, or with fatty acid diamides. The additive is dispersed in the grinding base in a Disperlux type disperser. Once the additive has been added, the speed is maintained at 3000 rpm for 20 min (temperature: 55 ° C). The fatty acid diamide is activated according to the supplier's technical sheet. After 24 hours of waiting, the hardener is added (Crayamid 140 from Cray Valley + xylene) to the dispersion, under a shear of 200 revolutions / minute, for 5 minutes and at room temperature. The viscosity of the formulation is adjusted to 0.4 Pa.s with a xylene / butanol mixture of ratio 1/1, at a shear rate of 2500 s ¹ .

Resumption of viscosity of a two-component epoxy-polyamine paint: Resumption of viscosity is evaluated with an SR 5000 rheometer. A shear stress of 700 Pa is applied to the coating formulation at 23 ° C. for 60 seconds. The viscosity of the formulation is then measured under a constant stress of 1 Pa for 120 seconds, at 23 ° C. (this stress simulates the flow of the paint film). The resumption of viscosity is linked to the resistance to sagging of the paint. The viscosity recovery of the beet cellulose microfibrils is compared.

MCBMl with that of fatty acid diamides. Figure 1 shows that MCBMl beet cellulose microfibrils are also effective at a dosage of 0, 1% that the fatty acid diamide Crayvallac Ultra ^® Company Cray Valley SA dosed at 0.8%. This dosage is usual in this type of formulation. The cellulose microfibrils make it possible to obtain a very effective resistance to sagging at much lower active material levels than the fatty acid diamides, without thermal activation.

Resistance to sagging of a two-component epoxy-polyamine paint: Resistance to sagging is measured by a test plate on Lénéta plate, This test consists in depositing increasing thicknesses of paint on this plate using a multi-thickness applicator. The card is immediately put in vertical position, the thinnest strip at the bottom. The plate is examined after drying. When two strips meet, the maximum thickness of the wet film before pouring is given as the resistance to running (according to ASTM D4400). FIGS. 2 and 3 show that an increase in the dosage of beet cellulose microfibrils MCBM1 leads to a considerable improvement in the resistance to sagging of the two-component epoxy-polyamine paints. For Figure 3, the thicknesses deposited without sagging greater than 1075 microns could not be measured, due to the lack of a suitable applicator. 1075 microns therefore means this value or better.

Inter-layer adhesion: To evaluate the inter-layer adhesion, a layer of epoxy-polyamine paint having a thickness between 70 and 80 μm is applied to a bichromate aluminum substrate (Q-Panel QAL46H24 of thickness 0 , 8 mm), previously degreased with ethyl acetate. This application is carried out with a Sheen applicator and the thickness of the dry paint layer is determined by an eddy current device. The aluminum plate is then placed vertically or horizontally in an enclosure under an atmosphere saturated with xylene / butanol solvents (50/50) for 30 minutes (in the first test) and 96 hours (in the second and third tests). A second layer is then applied, the thickness of which after drying is between 70 and 80 μm. Then, at 9 days, a pull-out test is carried out and it is determined where the delamination has taken place, by measuring the thickness of the remaining paint. If the thickness is between 70 and 80 μm, this means that delamination takes place between the 2 layers of paint. If the remaining thickness is significantly less than 70 μm, this means that the delamination is close to the substrate. Inter-layer adhesion is then considered very good. The tearing test is carried out by sticking a 20 mm diameter cylindrical stud to the surface of the coating. The glue used is 3M reference glue 9323 B / A. The glue is left to dry for 24 hours at 23 ° C. The adhesive thickness is 100 μm and the bonding surface 227 mm ² . The stud is pulled out with a dynamometer and the remaining thickness is determined. The results are shown in Table 3 below:

Table 3

Even under very severe conditions, beet cellulose microfibrils do not cause delamination of the second layer of paint. Stability of the resistance to running, storage at 50 ° C.: Two grinding bases are manufactured using 0.4% and 0.8% of MCBM10 respectively as thixotropic agent. This base is split into three equal portions. A portion is stored at 23 ° C. A second portion is stored at 50 ° C for 7 days, and a third portion is stored for 30 days at 50 ° C. The second and third portions of the base are cooled to room temperature. To these 3 bases, the hardener is then added as described in Table 2. The results obtained are shown in Table 4 below:

Table 4:

The resistance to sagging of paints produced with bases stored at 50 ° C is not affected.

Comparison of the different types of microfibrils: Figure 4 compares the flow curves of three epoxy-polyamine paints with added microfibrils of cellulose from MCBMl beet (0.4%) or MCBM9 eucalyptus (0.8%) or pine (softwood) MCBMIO (0.8%). Beet microfibrils are more effective than those from tree cellulose (same effect for a concentration 2 times lower). It is also interesting to note that microfibrils from pine (coniferous) are considerably easier to obtain than those from beet.

Influence of the compound Bl / cellulose microfibrils ratio: Cellulose microfibrils made from beet and modified according to the same process as the MCBMl sample are made, using BNA as compound Bl at different rates.

Table 5:

The modified cellulose microfibrils are then added to the previous epoxy-polyamine paint formula. The level of modified microfibrils B is 0.4% by weight. The results of the sag resistance test are shown in Table 5 above.

Influence of the nature of compound Bl: Cellulose microfibrils are produced from pine (resinous) and modified according to the same process as the MCBMl sample, using different compounds Bl. The compound Bl / cellulose microfibrils ratio is 4/1 by weight. The modified cellulose microfibrils are then added to the previous epoxy-polyamine paint formula. In the case of MCBMIO and 11 microfibrils, gels with 13% B in xylene are used to introduce the additive into the paint. In the case of MCBM12 to MCBM21, 6.5% gels are used. The level of additive B in the final paint is 0.4% by weight. The results of the sag resistance test are shown in Table 6 below. Two sizing measurements were carried out for each paint, the presence of 2 values corresponds to 2 tests having given separate values, the presence of a single value means that the 2 tests gave the same result.

Table 6

Example 2 (invention): Application in a two-component acrylic paint (2K). The procedure described in Example 1 is followed except that component 1 contains a Cray Valley Synocure 878N60 reference acrylic resin and that component 2 is an isocyanate. The paint formula is shown in the following table 7:

Table 7:

Raw materials References Suppliers Mass proportion used Commercial COMPONENT 1 Acrylic resin Synocure 878N60 CRAY VALLEY 46, 1 Pigment Tiθ2 RCL 535 MILLENIUM CHEMICAL 27, 1 Dispersant Disperbyk 161 BYK CHEMIE 0.5 Butyl acetate PROLABO 10.5

1-Methoxy-2- acetate Dowanol PMA ALDRICH 3,5 propanol Ethyl acetate PROLABO 1, 2 Thixotropic additive Modified cellulose X microfibrils COMPONENT 2 Isocyanate Tolonate HDB75MX RHODIA 11, 2 Total 100 + x

The paints are additivated with microfibrils of beet cellulose MCBM 1 introduced into component 1 at different rates. The flow curves of the acrylic paints are shown in FIG. 5. A significant increase in the shear thinning of the acrylic paints is observed when the rate of beet cellulose microfibrils MCBM1 increases.

Example 3 (invention): Application in a polyester resin. The cellulose microfibrils are evaluated in a Cray Valley S21120A commercial orthophthalic unsaturated polyester resin. The microfibrils are added either in the form of previously ground powder, or in the form of a pre-gel obtained by mixing 13% of dry cellulose microfibrils and 87% of styrene. The gels in styrene are obtained in the same way as the gels in xylene according to Example 1. The resins additivated with cellulose microfibrils are compared with the reference resin Cray Valley S21 120A alone and with the reference resin Cray Valley S21120A with 1% by weight of silica as thixotropic agent. The microfibrils gel is added to the resin by manual dispersion with a spatula. FIG. 6 shows the change in viscosity with the shear gradient: the contribution of shear thinning with 1% of modified cellulose microfibrils is comparable to that observed with 1% silica, but without thickening of the resin with a high shear gradient.

Example 4 (invention): Application in a putty. The formula for the sealant is given in the following table 8:

Table 8:

Raw materials used References Suppliers Mass proportion Commercial Silylated polyether resin MS Polymer - S203H KANEKA 15.7 Silylated polyether resin MS Polymer - S203H KANEKA 10.3 Diisoundecyl phthalate plasticizer Jayflex DIUP EXXONMOBIL 18.3 CHEMICAL Pigment TiÛ2 RL 90 TIONA 2.6 Carbonate Calcium Carbital Cl lOS IMERYS 51, 2 Thixotropic additive Modified X microfibrils Cellulose Dynasylan VTMO DEGUSSA 1, 0 (Vinyltrimethoxysilane) Total 100 + x The MCBM7 cellulose microfibrils are dispersed in the cold plasticizer by manual mixing then switching to the Ultraturrax at 24,000 rpm for 5 minutes. The polymers are then mixed with the cellulose microfibrils prepared in the plasticizer until homogenization. Then the dehydrating agent, the fillers and the pigment are added. The stirring speed is brought to 4000 rpm for 2 hours. The temperature rises to 85 ° C under the effect of the grinding of the pigments. The resumption of viscosity is measured using an SR5000 rheometer, with imposed stress. The geometry used is plane-plane with a diameter of 25 mm and with temperature regulation by a Peltier plane at 23 ° C. A shear stress of 1500 Pa is applied to the coating formulation for 15 seconds. The viscosity of the formulation is then measured under a constant stress of 100 Pa for 60 seconds, at 23 ° C. (the stress simulates the running of the sealant sealant). The recovery in viscosity as a function of time of the different sealants is shown in FIG. 7. According to FIG. 7, the preparation of sealants having an acceptable sag resistance (spreading) is therefore possible using cellulose microfibrils as thixotropic agent. The preparation of the putty is then very simplified because the use of cellulose microfibrils does not require thermal activation.

Against example 1 (comparative): A microcrystalline cellulose having a form factor 1 / d <20 is produced, by treating the cellulose microfibrils obtained from wood at a pH = 2 obtained by adjustment with 1M sulfuric acid and left to react with stirring for 1 hour at 80 ° C. The dispersion is then rinsed until neutral pH, then the microcrystalline cellulose is treated with compound B1 as already described. The additive thus produced is tested in an epoxy-amine paint according to the method described in Example 1 and compared to the microfibrils.

Table 9:

We see that a minimum 1 / d ratio is required to obtain a noticeable thixotropic effect.

Figures: Figure 1 shows the comparative efficiency of MCBM1 beet cellulose microfibrils and Crayvallac Ultra ^® fatty acid diamide from Cray Valley in a two-component epoxy-polyamine paint, as described in Example 1. The graph represents the recovery of viscosity after a constraint of 700 Pa, read under a constraint of 1 Pa for 120 seconds.

FIG. 2 shows the viscosity of two-component epoxy-polyamine paints as described in Example 1, as a function of the concentration of beet cellulose microfibrils MCBMl, after a stress-induced precision of 700 Pa, read under a stress of 1 Pa for 120 seconds.

FIG. 3 shows the resistance to sagging of a two-component epoxy-polyamine paint expressed in μm, as a function of the concentration of beet cellulose microfibrils MCBM 1, as described in Example 1.

FIG. 4 presents the comparative efficiency of the microfibrils of beet cellulose MCBM1, of eucalyptus MCBM9 and of pine (resinous) MCBMIO in an epoxy-polyamine paint, as described in example 1. The graph represents the viscosity as a function applied shear rate.

FIG. 5 shows the efficiency of the beet cellulose microfibrils MCBM1 in a two-component acrylic paint, as described in example 2. The graph represents the viscosity as a function of the shear rate applied, for different concentrations of cellulose microfibrils beet MCBM 1.

FIG. 6 shows the comparative efficiency of a polyester resin added with cellulose microfibrils and with silica, as described in Example 3. The graph represents the viscosity as a function of the shear rate applied.

FIG. 7 shows the efficiency of the MCBM7 pine (resinous) cellulose microfibrils in a mastic based on silane polyether resin, as described in Example 4. The graph represents the viscosity as a function of time after destructuring.

Claims

1) Composition for coating or molding for composites or mastic, characterized in that it comprises by weight: A) 100 parts of at least one reactive or non-reactive organic binder,

B) 0.001 to 20 parts of at least one additive comprising cellulose microfibrils surface modified with at least one compound B1, said cellulose microfibrils having a form factor 1 / d greater than 20 and an average section d ranging from 1 at 50 nm, said compound B1 having at least one hydrophilic part and at least one hydrophobic part, said microfibrils being modified on the surface by physical means, by the physical adsorption of at least one compound B 1 as defined,

C) optionally, at least one organic diluent,

D) optionally, up to 300 parts of at least one component chosen from fillers, fibers, pigments, dyes and other usual additives.

2) Composition according to claim 1 characterized in that said compound B1 is relatively soluble in organic binder A and / or organic diluent C.

3) Composition according to claims 1 or 2 characterized in that the cellulose microfibrils of the additive B are selected from those of wood, cotton, linen, ramie, certain algae, jute, sugar beet pulp, citrus fruits, industrial waste food or of bacterial or animal origin.

4) Composition according to one of claims 1 to 3 characterized in that said compound B 1 has a predominant hydrophobic character.

5) Composition according to one of claims 1 to 4 characterized in that said compound B 1 comprises at least one surfactant.

6) Composition according to claim 5 characterized in that said surfactant comprises at least one anionic surfactant or at least one cationic surfactant or at least one amphoteric surfactant or at least one nonionic surfactant, the latter being able to be present in binary combination with each of the three other surfactants. 7) Composition according to claim 6 characterized in that said surfactant comprises at least one nonionic surfactant and at least one anionic surfactant.

8) Composition according to one of claims 1 to 7 characterized in that the rate by weight of compound B1 is such that the ratio of compound B1 to cellulose microfibrils is from 0.5 / 1 to 10/1.

9) Composition according to one of claims 5 to 8 characterized in that said surfactant comprises at least one nonionic surfactant selected from: castor oil derivatives ethoxylated with 7 to 60 EO, oil derivatives ethoxylated hydrogenated castor with 7 to 60 EO, ethoxylated coconut oil derivatives, soy lecithin, C22 to C 22 fatty alcohols polyethoxylated with 8 to 30 EO, polyethoxylated alkylphenols, ethoxylated arylphenols, ethers of tridecyl polyglycol alcohol, polyethers block type bi- and tri-block, sorbitol derivatives comprising 1 to 3 polyoxyethylene chains, 1 to 3 fatty chains in C12 to C ₃ o, ethoxylated fatty acid esters in Cs to C ₃ β with 8 to 30 EO, esters of mono- and di-glycerides of fatty acids in Ce to C ₃ 6, fatty amines in Cs to C22, or mixtures.

10) Composition according to one of claims 5 to 9 characterized in that said surfactant comprises at least one anionic surfactant selected from: sulphate or phosphate esters of fatty alcohols in C ₂ to C ₂ 2, with 2 to 30 oxyalkylene units, polyalkoxylated alkylphenol phosphate esters in which the alkyl substituent is in Ci to Cι ₂ with 5 to 25 EO units, said oxyalkylene unit being in C2 to C, the arylphenol phosphate esters with 5 to 25 EO, the organic acid esters of simple or mixed admixtures , partially neutralized polycarboxylic acid salts.

11) Composition according to claim 10 characterized in that said anionic surfactant is: i) a polyalkoxylated alkylphenol phosphate ester whose alkyl substituent is in C2 to Cs, and oxyalkylene in C ₂ . or ii) a simple organic phosphate acid ester or in a particular mixture: Beycostat ^® A B09, iii) Rhodafac ^® RS610, iv) Disponil ^® FES 933 12) Composition according to one of claims 1 to 1 1 characterized in that said organic binder A is reactive and selected from crosslinkable two-component epoxyamines, unsaturated polyesters, vinyl esters, modified or unmodified alkyds, crosslinkable two-component polyurethanes, acrylated acrylic oligomers, binders which can be crosslinked thermally or by irradiation under UV and / or EB radiation, silane polyethers, silane polyurethanes.

13) Composition according to one of claims 1 to 12 characterized in that said composition is a coating composition.

14) coating composition according to claim 13 characterized in that it comprises at least one organic binder A selected from unsaturated polyesters or vinylesters or acrylic acrylic oligomers, and at least one organic diluent C selected from monomers (me th ) acrylic, allylic, vinyl aromatic.

15) Coating composition according to claim 14 characterized in that said coating is a pigmented or non-pigmented gel coat.

16) Coating composition according to claim 13 characterized in that said coating is a sealing coating.

17) Coating composition according to claim 13 characterized in that it comprises at least one organic binder A selected from the following cross-linkable two-component reactive systems: epoxy-amine or epoxy-polyamide systems comprising at least one epoxy resin comprising at at least 2 epoxy groups and at least one amino or polyamide compound comprising at least 2 amino groups, polyurethane systems comprising at least one polyisocyanate and at least one polyol, polyol-melamine systems and polyester systems based on at least one epoxy or a polyol reactive with at least one corresponding carboxylic acid or anhydride.

18) Coating composition according to claim 17 characterized in that said organic binder A is a cross-linkable polyurethane two-component system or a polyester system from an epoxy-acid or carboxylic anhydride system, or polyol-acid or carboxylic anhydride system , or polyol-melamine system in which polyol is a hydroxylated acrylic resin, or a polyester or polyether polyol.

19) Coating composition according to claim 13 characterized in that the organic binder A is selected from modified or unmodified alkyds.

20) Coating composition according to claim 13, characterized in that it comprises at least one organic binder A which can be crosslinked thermally or by irradiation under UV and / or EB radiation and selected from (meth) acrylic oligomers or acrylic or allyl multifunctional acrylic oligomers .

21) Composition according to one of claims 1 to 12 characterized in that said composition is a mastic composition.

22) mastic composition according to claim 21 characterized in that it comprises at least one organic binder A selected from unsaturated polyesters, vinylesters, silane polyethers, polyurethanes or silicones, silane polyurethanes.

23) Composition according to one of claims 1 to 12 characterized in that said composition is a molding composition for composites.

24) Molding composition for composites according to claim 23 characterized in that it comprises at least one organic binder A selected from: unsaturated polyesters, vinylesters, cross-linkable epoxy-amine or epoxy-polyamide systems, systems cross-linkable two-components leading to polyurethanes.

25) Method for preparing a composition as defined according to one of claims 1 to 24 characterized in that it comprises at least one step of mixing at least one additive such as said additive B with at least one binder such as said organic binder A and / or at least one organic diluent such as said organic diluent C. 26) Preparation process according to claim 25 characterized in that said mixing takes place under shear and that said additive B is introduced in the form of powder or in the form of a pre-concentrated intermediate composition containing it.

27) Use of the composition as defined according to one of claims 1 to 24 or obtained according to the process defined according to one of claims 25 or 26 in compositions of paints, varnishes, gel coats, inks, adhesives in solvent medium, sealants, or molding for composites, or sealants.

28) Intermediate composition usable for the preparation of a composition as defined according to one of claims 1 to 24 or obtained according to the process defined according to one of claims 25 or 26 characterized in that it comprises at least one additive B as described according to one of claims 1 to 11 at a concentration by weight ranging from 5 to 50% relative to the total weight of said composition, comprising at least one organic binder A as defined according to the preceding claims and / or at least one organic diluent C as defined according to one of the preceding claims.

29) Intermediate composition according to claim 28 characterized in that it can be used for the preparation of a composition as defined according to one of claims 1 to 24, and in that it comprises at least one organic diluent C such as defined according to one of the preceding claims, without any organic binder A.

30) Intermediate composition according to claim 29 characterized in that said organic diluent C is selected from (meth) acrylic and / or allyl and / or vinylaromatic monomers, white spirit, alcohols, ketones, alkyl esters in Ci to C, glycol ethers, plasticizers, aromatic, aliphatic, cycloaliphatic solvents or mixtures thereof.

31) Intermediate composition according to claim 28 characterized in that instead of said organic diluent C it comprises only at least one organic binder A liquid, in the absence of any organic diluent C. 32) Intermediate composition according to claim 28 characterized in that it is in the form of powder or elastic pre-gel or solid granules with controlled particle size ranging from 0.5 to 20 mm.