Oligoester-based binding agent composition, its preparation and its use for binding organic or mineral fibers

Description

[0001] The present application relates to a thermosetting aqueous binder based on water-soluble oligomeric esters obtained by reaction between a carbohydrate and a polycarboxylic acid.

[0002] It also relates to the use of such a binder for binding together organic or mineral fibres, in particular mineral wool fibres, in particular glass or rock wool.

[0003] It has been known for several years to use aqueous compositions based on bio-sourced reagents, particularly based on sugars, as thermosetting binders for mineral wools or non-woven products based on mineral fibers.

[0004] In particular, it has been proposed to form thermoset polyesters by reacting reducing sugars and / or non-reducing sugars and / or hydrogenated sugars, carrying hydroxyl groups, with polycarboxylic acids in the presence of a catalyst, generally sodium hypophosphite (WO 2009 / 080938, WO 2010 / 029266, WO 2013 / 014399, WO 2013 / 021112).

[0005] International application WO2012 / 138723 discloses binder compositions based on oligomeric and / or polymeric carbohydrates (dextrose equivalent 2 - 20) and a crosslinking agent chosen from polycarboxylic acids. These compositions further contain an oligoester with a weight-average mass of between 1500 and 5000, obtained by reaction of polycarboxylic acid and glycerol.

[0006] Application FR2924719 discloses a sizing composition for insulating products based on mineral wool, in particular rock or glass, characterized in that it comprises at least one monosaccharide and / or at least one polysaccharide, and at least one organic polycarboxylic acid having a molar mass less than or equal to 1000.

[0007] The sizing compositions described in the aforementioned documents are dilute, low-viscosity aqueous solutions of the monomer reagents. They are generally sprayed onto the mineral fibers, while still hot, immediately after their formation. Immediately after application of the sizing composition to the fibers, evaporation of the aqueous phase begins. When the fibers are collected and assembled in the form of a mat on the collecting belt, they are sticky and the film of sizing composition that envelops the glass fibers still contains water.

[0008] It is only when the bonded mineral wool mattress enters the oven, typically thermostatically controlled at temperatures above 180°C or even above 200°C, that the evaporation of the water is completed and the esterification reaction between the reactants begins.

[0009] Heating the bonded fiber mat at high temperatures for a few tens or hundreds of seconds results in crosslinking of the reactive system by esterification and the formation of a water-insoluble binder, but also results in the thermal decomposition of part of the reagents and the evaporation of the decomposition products formed. The gaseous components formed in the oven are partially evacuated via the chimney ( stack ) . The exhaust gases, or fumes, are treated in a washing system and the wash water is then recirculated in a closed system.

[0010] When the sizing composition contains carboxylic acids, such as citric acid, the flue gas contains many acidic compounds that must be neutralized by adding bases to prevent corrosion damage to the system. However, the addition of bases is problematic. In glass wool insulation manufacturing plants, the wash water is reinjected into the system and is used in particular for preparing binder and sizing compositions. The presence of bases or salts in large quantities in sizing compositions is likely to increase the pH and disrupt the esterification (crosslinking) reaction.

[0011] The Applicant thus detected, among other things, the presence of citric acid, citraconic acid, itaconic acid, propionic acid, acetic acid, and traces of formic acid in the exhaust gas wash water from a binder system based on sugar alcohols and citric acid.

[0012] The present invention is based on the discovery that it was possible to significantly limit the emissions of acidic volatile components at the chimney of a glass wool curing oven by subjecting the starting reactive system, based on polyols and polyacids, beforehand to an oligomerization reaction by polycondensation (esterification) in an essentially anhydrous medium. The oligomeric esters thus prepared can be used in the same way as the reagents of binders based on sugars and / or sugar alcohols and acids. They are water-soluble and stable in water at room temperature, form infinitely pumpable and dilutable aqueous solutions and have, at the concentrations commonly used for sizing compositions (2 - 6% by weight), viscosities perfectly compatible with a conventional spray sizing system using nozzles (spray crown).

[0013] Furthermore, the use of oligomers, instead of polyol and polyacid reagents, has the advantage of significantly reducing the temperature at which the reactive system begins to crosslink and / or of shortening, for a given oven temperature, the time required for satisfactory hardening of the binder, which allows the acceleration of the glass wool production line and / or energy savings for heating the tank.

[0014] Finally, the reduction of citric acid loss through decomposition and emission in fumes at the level of the stack results in an increase in the efficiency of the industrial line (in English Binder Line Efficiency, BLE), which is equal to the quantity of hardened binder in the final product related to the sum of dry matter of binder and additives sprayed on the fibers.

[0015] The present application relates to a thermosetting binder composition containing water and a water-soluble oligomeric ester of at least one carbohydrate chosen from reducing sugars, non-reducing sugars and hydrogenated sugars, the hydrogenated sugars being chosen from the group consisting of erythritol, arabitol, xylitol, sorbitol, mannitol, iditol, maltitol, isomaltitol, lactitol, cellobitol, palatinitol, maltotritol and hydrogenation products of starch hydrolysates or lignocellulosic materials, and at least one polycarboxylic acid, the binder composition having a solids content of between 40% and 80% by weight and the water-soluble oligomeric ester representing at least 80% by weight, preferably at least 90% by weight, of the solids of the thermosetting binder composition.

[0016] In the present application the term "carbohydrate" has a broader meaning than usual, since it encompasses not only carbohydrates in the strict sense, that is to say reducing sugars or carbohydrates of formula C n (H2O) p , where p = n (monosaccharides) or p = n-1 (oligo- and polysaccharides) having at least one aldehyde or ketone group (reducing group), but also the hydrogenation products of these carbohydrates where the aldehyde or ketone group has been reduced to alcohol. These hydrogenation products are also called alditols, sugar alcohols or hydrogenated sugars. The term carbohydrate also includes non-reducing sugars consisting of several carbohydrate units whose carbons carrying the hemiacetalic hydroxyl are involved in the osidic bonds linking the units together.

[0017] In the present application, the terms "binder composition" and "sizing composition" are not synonyms. The term "binder composition" refers to concentrated aqueous solutions, i.e. with a high solids content (several tens of percent). These compositions can be stored and transported. They are fluid enough to be pumped, but too viscous to be sprayed as such onto the fibers. The term "sizing composition" refers to considerably less concentrated aqueous solutions having a solids content of less than 10% by weight. They are generally obtained by diluting the binder compositions with water. They have sufficiently low viscosities to allow their application to the glass wool fibers by spraying using nozzles.

[0018] The present application also relates to a process for preparing a binder composition comprising a step of synthesizing the oligomers by esterification of the reactants in an essentially anhydrous medium, then a step of diluting the reaction product formed with water.

[0019] More specifically, the process for preparing the binder compositions of the present invention comprises heating a mixture of at least one carbohydrate selected from reducing sugars, non-reducing sugars and hydrogenated sugars, at least one polycarboxylic acid and at least one esterification catalyst, at a temperature of between 105°C and 170°C, preferably between 120 and 150°C, for a period of between 5 minutes and 10 hours, preferably between 20 minutes and 2 hours, so as to form an oligomeric ester, and adding a quantity of water sufficient to obtain a pumpable aqueous solution of the oligomeric ester.

[0020] As explained above, the reaction mixture of this bulk polycondensation is preferably essentially anhydrous, i.e. it preferably contains less than 2% water, preferably less than 1% water. In some cases, it may be necessary to add a small amount of water, generally less than 5% by weight, in order to homogenize the reactants in the reaction mixture. This water necessary for homogenization evaporates under the effect of heating.

[0021] A preferred embodiment of the oligoester synthesis process involves heating the carbohydrate, in the absence of solvent, until complete melting, then adding citric acid and the catalyst. Reaction times depend on the change in viscosity of the medium during synthesis.

[0022] The progress of the oligomerization reaction can be monitored by viscometry as follows: An aliquot of the reaction medium is taken and diluted with distilled water to obtain a solution with a solids content (dry extract) equal to 70%. This solution is introduced into an Anton Paar MCR302 rheometer with a 50 mm cone-plate upper geometry and a 50 mm plane lower geometry which allows high sensitivity to low viscosities. The viscosity of the oligomers is measured at room temperature for shear rates increasing from 5 s -1< to 1000 s -1< , then decreasing again from 1000 s -1< to 5 s -1< . It is found that the viscosity does not depend on the shear rate. The oligomer solutions are therefore Newtonian liquids. Viscosity values ​​are recorded at 20 °C at a shear rate of 100 s -1< .

[0023] The objective of the study of the kinetics of the oligomerization reaction is to find the best compromise between, on the one hand, an acceptable viscosity, that is to say a viscosity low enough so that the binder compositions, which are quite concentrated, remain pumpable, and, on the other hand, the lowest possible crosslinking start temperature.

[0024] The crosslinking start temperature is determined by dynamic thermomechanical analysis (DMTA). Dynamic Mechanical Thermal Analysis) which allows the viscoelastic behavior of a polymeric material to be characterized. Two strips of glass microfiber paper are cut and superimposed. Thirty milligrams of binder composition with a solids content of 30% are deposited homogeneously on the strips which are then fixed horizontally between two jaws of an RSAIII device (Texas Instrument). An oscillating element equipped with a device for measuring the stress as a function of the applied deformation is placed on the upper face of the sample. The device allows the modulus of elasticity E' to be determined. The sample is heated to a temperature varying from 20 to 250°C at a speed of 4°C / min. From the measurements, the curve of variation of the modulus of elasticity E' (in MPa) as a function of the temperature (in °C) is established, the general shape of which is given in the Figure 1 .

[0025] The DMTA curves are modeled as three straight line segments: 1) tangent to the curve before the start of the reaction, 2) slope of the line during the increase in modulus during the reaction, 3) tangent to the curve after the end of the increase in modulus.

[0026] The curing start temperature (TR) is the temperature at the intersection of the first two lines.

[0027] When the desired degree of oligomerization is reached, the heating is stopped and water is added to the reaction mixture so as to obtain the binder compositions of the present invention.

[0028] The Brookfield viscosity of the binder compositions, determined at room temperature (20°C) at a dry matter content of 70% by weight, is advantageously between 0.25 and 4.0 Pa.s, preferably between 0.3 and 1.5 Pa.s, and in particular between 0.35 and 1.0 Pa.s.

[0029] The crosslinking start temperature of the binder compositions of the present invention, determined in the manner described above, is advantageously between 105°C and 125°C,

[0030] In principle, any carbohydrate selected from reducing sugars, non-reducing sugars and hydrogenated sugars can be used for the preparation of the thermosetting binder compositions of the present invention.

[0031] The term "hydrogenated sugar" means all the products resulting from the reduction of a saccharide (carbohydrate) chosen from monosaccharides, disaccharides, oligosaccharides and polysaccharides and mixtures of these products. Hydrogenated sugars are also called sugar alcohols, alditols or polyols. They can be obtained by catalytic hydrogenation of saccharides. The hydrogenation can be carried out by known methods operating under conditions of high hydrogen pressure and temperature, in the presence of a catalyst chosen from the elements of groups IB, IIB, IVB, VI, VII and VIII of the periodic table of elements, preferably from the group comprising nickel, platinum, palladium, cobalt, molybdenum and mixtures thereof. The preferred catalyst is Raney nickel.

[0032] The hydrogenated sugar(s) are selected from the group consisting of erythritol, arabitol, xylitol, sorbitol, mannitol, iditol, maltitol, isomaltitol, lactitol, cellobitol, palatinitol, maltotritol, and hydrogenation products of starch hydrolysates or hydrolysates of lignocellulosic materials, in particular hemicellulose, in particular xylans and xyloglucans. The hydrogenated sugars used in the present invention therefore do not include glycerol or polyglycerol.

[0033] Starch hydrolysates are products obtained by enzymatic and / or acid hydrolysis of starch. The degree of hydrolysis is generally characterized by the dextrose equivalent (DE), defined by the following relationship: DE = 100 × nombre de liaisons glycosidiques rompues nombre de liaisons glycosidiques dans l ′ amidon initial

[0034] Preferred starch hydrolysates have, before the hydrogenation step, a DE of between 5 and 99, and advantageously between 10 and 80.

[0035] Particular preference will be given to using a hydrogenated sugar chosen from the group formed by maltitol, xylitol, sorbitol and the hydrogenation products of starch hydrolysates or lignocellulosic materials.

[0036] Among the hydrogenated sugars described above, sorbitol is the most readily available on the market and the least expensive. However, during its tests aimed at developing binders based on polycarboxylic acids and hydrogenated sugars, the Applicant found that this hydrogenated sugar, when used as such, did not easily allow the production of insulating products with satisfactory mechanical properties (tensile strength, thickness recovery, flexural strength). To give the insulating products obtained a certain mechanical strength, it was necessary to considerably increase the polycarboxylic acids / sorbitol ratio of the sizing compositions. However, such an increase has a threefold disadvantage: it increases the corrosive nature of the sizing compositions, promotes the release of acid degradation products at the stack and reduces the efficiency of the industrial line ( Binder Line Efficiency ) , especially when the acid used is citric acid which undergoes thermal degradation at temperatures below 200°C.

[0037] The present invention makes it possible to avoid the disadvantages described above linked to the use of sorbitol as a hydrogenated sugar. Indeed, the preoligomerization of sorbitol in an anhydrous medium in the presence of polycarboxylic acids gives oligoesters which have properties equivalent to those based on xylitol or maltitol for example.

[0038] In view of the above, obtaining mineral wool insulation products with satisfactory mechanical properties naturally assumes that no, or only very little, free sorbitol is added to the binder composition after the end of the esterification step. In other words, the advantage provided by the present invention, namely obtaining good mechanical properties despite the use of sorbitol, would be cancelled out if free sorbitol were added in excessive quantities at the time of preparation of the sizing composition by diluting the binder composition of the present invention.

[0039] The binder composition and the sizing composition of the present invention therefore contain less than 10% by weight, preferably less than 5% by weight, even more preferably less than 2% by weight of free sorbitol, added after the esterification step or not having reacted during the esterification. These percentages of free sorbitol are based on the total solids content of the binder composition or the sizing composition of the present invention.

[0040] The reducing sugars are preferably chosen from monosaccharides such as glucose, galactose, mannose and fructose, disaccharides such as lactose, maltose, isomaltose and cellobiose, and the starch or lignocellulosic material hydrolysates described above. Glucose and fructose, in particular glucose, will preferably be used.

[0041] Non-reducing sugars are preferably disaccharides such as trehalose, isotrehaloses, sucrose and isosucroses. Sucrose is particularly preferred.

[0042] The polycarboxylic acid(s) used in the present invention are monomeric polycarboxylic acids. In other words, in the present invention this term does not include polymers obtained by polymerization of monomeric carboxylic acids, such as homopolymers or copolymers of acrylic acid or methacrylic acid.

[0043] Polycarboxylic acids selected from the group consisting of dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids will preferably be used. The particularly preferred polycarboxylic acid is citric acid.

[0044] The Applicant has carried out numerous tests to determine the respective proportions of carbohydrate and polycarboxylic acid which result in binders which, in the crosslinked state, give the final glass wool product the best mechanical properties, in particular after accelerated ageing in humid conditions.

[0045] These tests have shown that the carbohydrate / citric acid weight ratio is advantageously between 25 / 75 and 55 / 45, preferably between 30 / 70 and 50 / 50.

[0046] Bulk oligomerization can be carried out in the presence of a known esterification catalyst selected, for example, from strong acids such as sulfuric acid, hydrochloric acid, para-toluenesulfonic acid, trifluoromethanesulfonic acid and trifluoroacetic acid, and Lewis acids commonly used for the catalysis of esterification reactions.

[0047] The bulk oligomerization reaction, when using citric acid, can also be catalyzed by sodium hypophosphite, which is not strictly an esterification catalyst, but is thought to promote the formation of citric acid anhydrides. These are more reactive than the triacid and are capable of reacting with polyols.

[0048] One or the other of these two types of catalysts will therefore be present in the thermosetting binder composition.

[0049] When an esterification catalyst such as a strong acid is used to catalyze the oligomerization reaction, it is desirable to add to the binder composition, before or after dilution with water to obtain the sizing composition, an effective amount of sodium hypophosphite or hypophosphorous acid, for example an amount of between 0.5 and 10% by weight, preferably between 1.0 and 5% by weight, based on the weight of the solids of the binder composition. Sodium hypophosphite and the corresponding acid are, to date, the compounds which most effectively catalyze the curing of oligomers into a thermoset binder, insoluble in water.

[0050] The viscosity and the crosslinking start temperatures of the compositions are not the only criteria to be taken into consideration to evaluate the quality of the binder compositions of the present invention. Another important parameter is the residual content of free polycarboxylic acid, that is to say, not having reacted with a carbohydrate present in the reaction mixture. This residual content of free polycarboxylic acid is preferably as low as possible. Indeed, as explained in the introduction, the polycarboxylic acid, and in particular citric acid, undergoes thermal degradation at the entrance to the oven and in the oven which results in undesirable acid gas emissions.

[0051] The residual polyacid content is lower the higher the polyol / polyacid ratio and the higher the oligomerization reaction progresses.

[0052] The binder compositions of the present invention advantageously contain less than 20% by weight, preferably less than 15% by weight, more preferably less than 10% by weight, and in particular less than 5% by weight, based on the total solids content, of free residual polycarboxylic acid.

[0053] The binder compositions of the present invention must be storable and transportable, i.e., they must be stable upon storage at room temperature and not undergo substantial hydrolysis of the oligoesters to polyols and polyacids, despite the presence of relatively large amounts of water, which may range from 20 to 50% by weight.

[0054] The Applicant has shown that good storage stability of the compositions was obtained when they had a neutral or acidic pH, preferably between 1 and 7, more preferably between 3 and 6.

[0055] Finally, the present application has as its third subject a method for manufacturing a product based on mineral or organic fibers bound by an insoluble organic binder, using a binder composition according to the invention. This method comprises the following successive steps: (a) preparing a sizing composition by diluting a thermosetting binder composition as described above with water to a solids content of between 2 and 10% by weight, (b) applying the sizing composition to mineral or organic fibers, (c) forming an assembly of sized mineral or organic fibers, and (d) heating the resulting assembly of sized mineral or organic fibers until the sizing composition hardens.

[0056] To obtain good quality products, it is necessary that the sizing composition has good sprayability and can be deposited in the form of a thin film on the surface of the fibers in order to bind them effectively. The sprayability of the sizing composition is directly linked to the possibility of diluting the concentrated binder composition with a large quantity of water. The diluted sizing composition must be a solution, stable over time, which does not give rise to demixing phenomena.

[0057] Dilutability is characterized by "dilutability," which is defined as the volume of deionized water that can be added to a unit volume of binder composition at a given temperature before permanent cloudiness occurs. A binder composition is generally considered suitable for use as a sizing agent when its dilutability is 1000% or greater at 20°C.

[0058] The binder compositions of the present invention have a dilutability greater than 2000%.

[0059] It is of course entirely possible to implement the process for manufacturing a product based on mineral or organic fibers of the present invention, by preparing the diluted aqueous sizing composition directly from the oligomerization product obtained by the mass esterification of the polyacid and the carbohydrate, without preparing an intermediate, concentrated solution (binder composition). This variant of the process could be useful when the synthesis of the oligomeric ester is carried out on the same site as the manufacture of the final product based on mineral or organic fibers. It is considered to be perfectly equivalent to that comprising the preparation of an intermediate concentrated solution intended for storage and / or transport.

[0060] The step of preparing the sizing composition advantageously comprises the addition of one or more known additives commonly used in the technical field of mineral wools. These additives are chosen, for example, from anti-dust additives, silicones and coupling agents.

[0061] In a particularly preferred embodiment of the process of the invention, it will be avoided to add to the binder composition significant quantities of monomers capable of reacting with the oligoesters, such as reducing sugars, non-reducing sugars, hydrogenated sugars, or other polyols, or even amines, in particular alkanolamines.

[0062] The sizing composition, when applied to mineral or organic fibers, therefore preferably comprises at least 80% by weight, more preferably at least 85% by weight, or even at least 90% by weight, relative to its total solids content, of water-soluble oligomeric ester.

[0063] In an advantageous embodiment of the method of the invention, the fibers are mineral fibers and the assembly of fibers is mineral wool. Examples Synthesis of an oligomer of xylitol and citric acid

[0064] In a thermostatically controlled reactor at 150°C, 70 parts by weight of xylitol are heated until completely melted, then 30 parts by weight of citric acid and 1 part of sodium hypophosphite are added all at once, while stirring. Stirring and the temperature at 150°C are maintained throughout the reaction.

[0065] After 5, 10, 30, 60, 90 and 120 minutes, an aliquot of reaction mixture is taken and diluted with water to a solids content of 70% by weight.

[0066] This concentrated oligomer solution is used for viscosity determination (Anton Paar MCR302 rheometer, 20 °C, shear rate of 100 s -1< ) ​​and for determination of the crosslinking onset temperature by dynamic thermomechanical analysis (DTMA).

[0067] There Figure 2 shows the evolution of viscosity and crosslinking start temperature as a function of reaction time.

[0068] It is observed that the viscosity of a concentrated oligomer solution (70% by weight of solids) increases steadily throughout the reaction. After 2 hours it is greater than 1.6 Pa.s

[0069] The crosslinking onset temperature decreases sharply during the first hour from over 130°C to about 115°C, then appears to plateau at about 110°C.

[0070] The reaction mixture obtained after 60 minutes of oligomerization at 150°C was used to compare its crosslinking kinetics with that of a xylitol / citric acid / HPS mixture (70 / 30 / 1).

[0071] For this purpose, the reaction mixture is diluted in water until a dilute solution with a solids content of 20% by weight is obtained. For comparison, an aqueous solution of non-preoligomerized xylitol / citric acid / HPS (70 / 30 / 1) with the same solids content is prepared.

[0072] Two sets of glass cloths are impregnated with these two aqueous sizing compositions, respectively, and the cloths are then passed over a suction device to remove the excess solution. The impregnated glass cloths are then cured in a thermostatically controlled oven at 220°C. After 18 seconds, 25 seconds, 35 seconds, 50 seconds and 70 seconds of curing, a sample is subjected to a determination of the tensile strength. For this purpose, the cloths are cut into strips (250 mm x 50 mm) and their ends are inserted into the jaws of a tensile testing machine.

[0073] There Figure 3shows the evolution of the tensile strength as a function of the cooking time at 220°C of the glass fiber fabrics impregnated with a sizing composition according to the invention containing oligomers of xylitol and citric acid and HPS, in comparison, of glass fabrics impregnated with a sizing composition containing xylitol, citric acid and HPS.

[0074] It is found that the crosslinking speed of the sizing composition according to the invention is significantly higher than that of the non-preoligomerized comparative composition. After 35 seconds, the breaking strength of the sample according to the invention has a tensile breaking strength of approximately 80 N, while that of the comparative sample is only 20 N. The two curves converge after 70 seconds of curing, i.e. the final mechanical properties are the same for both fabrics bound by a fully cured binder.

[0075] These results show that thanks to the preoligomerization of hydrogenated sugar and polyacid it is possible to shorten the curing time of the binder, i.e. to speed up the line or to shorten the dimensions of the curing oven, which in both cases represents an energy saving.

[0076] The same two sizing compositions are used for glass wool production on a pilot line.

[0077] Glass wool is manufactured by the internal centrifugation technique in which the molten glass composition is transformed into fibres by means of a tool called a centrifugation plate, comprising a basket forming a chamber for receiving the molten composition and a peripheral strip pierced with a multitude of orifices: the plate is rotated around its vertically arranged axis of symmetry, the composition is ejected through the orifices under the effect of centrifugal force and the material escaping from the orifices is drawn into fibres with the assistance of a current of drawing gas.

[0078] Conventionally, a sizing spray crown is placed below the fiberizing plate so as to evenly distribute the sizing composition over the newly formed glass wool.

[0079] The mineral wool thus bonded is collected on a belt conveyor equipped with internal suction boxes which retain the mineral wool in the form of a felt or a sheet on the surface of the conveyor. The conveyor then circulates in an oven maintained at 200°C where the constituents of the bonding polymerize to form a binder. The resulting insulation product has a nominal density equal to 10.5 kg / m 3< , a nominal thickness of approximately 80 mm and a loss on ignition of around 5%.

[0080] Table 1 below shows the quantities of different acidic chemical species detected in the gaseous emissions captured at the stack level (in English stack ) overlooking the entrance to the cooking tank. Table 1 Acid concentration in stack gas emissions (mg / Nm 3< ) Reduction (%) Comparative sizing composition Preoligomerized sizing composition Citric acid 360 105 70 Citaconic acid 405 250 38 Itaconic acid 55 25 55 Propionic acid 45 25 44 Acetic acid 12 9 25

[0081] It is observed that the prior oligomerization of the reactants dramatically reduces the emissions of acidic species.

Claims

1. A thermosetting binder composition containing water and a water-soluble oligomeric ester - of at least one saccharide selected from reducing sugars, non-reducing sugars and hydrogenated sugars, the hydrogenated sugars being selected from the group consisting of erythritol, arabitol, xylitol, sorbitol, mannitol, iditol, maltitol, isomaltitol, lactitol, cellobitol, palatinitol, maltotritol and hydrogenation products of hydrolyzates of starch or of lignocellulose materials, and - of at least one polycarboxylic acid, the binder composition having a dry matter content of between 40% and 80% by weight, the water-soluble oligomeric ester representing at least 80% by weight, preferably at least 90% by weight, of the dry matter content of the thermosetting binder composition, and the thermosetting binder composition containing less than 10% by weight, preferably less than 5% by weight, with respect to its dry matter content, of free sorbitol.

2. The binder composition as claimed in claim 1, characterized in that the reducing sugars are chosen from monosaccharides and disaccharides.

3. The binder composition as claimed in claim 1, characterized in that the hydrogenated sugars are chosen from the group consisting of xylitol, maltitol, sorbitol and hydrogenation products of hydrolyzates of starch or of lignocellulose materials.

4. The binder composition as claimed in any one of the preceding claims, characterized in that the polycarboxylic acid(s) are chosen from dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids.

5. The binder composition as claimed in any one of the preceding claims, characterized in that the polycarboxylic acid is citric acid.

6. The binder composition as claimed in claim 5, characterized in that the saccharide / citric acid weight ratio is between 25 / 75 and 55 / 45, preferably between 30 / 70 and 50 / 50.

7. The binder composition as claimed in any one of the preceding claims, characterized in that its Brookfield viscosity, determined at 20°C at a solids content of 70% by weight, is between 0.25 and 4.0 Pa.s, preferably between 0.3 and 1.5 Pa.s, in particular between 0.35 and 1.0 Pa.s.

8. The binder composition as claimed in any one of the preceding claims, characterized in that it exhibits a pH of between 1 and 7.

9. The binder composition as claimed in any one of the preceding claims, characterized in that it contains less than 10% by weight, preferably less than 5% by weight, with respect to the content of solid matter, of residual free polycarboxylic acid.

10. The binder composition as claimed in any one of the preceding claims, characterized in that it additionally comprises an esterification catalyst selected from strong acids and Lewis acids.

11. The binder composition as claimed in claim 5, characterized in that it additionally contains sodium hypophosphite.

12. A process for the manufacture of a product based on mineral or organic fibers which are bonded by an organic binder, said process comprising the preparation of a sizing composition by diluting a thermosetting binder composition as claimed in any one of claims 1 - 11 with water down to a content of solid matter of between 2% and 10% by weight, the application of the sizing composition to mineral or organic fibers, the formation of a collection of sized mineral or organic fibers, and the heating of the collection of sized mineral or organic fibers until the sizing composition has cured.

13. The process as claimed in claim 12, characterized in that step (a) of preparation of the sizing composition comprises the addition of one or more additives, preferably chosen from dust-preventing additives, silicones and coupling agents.

14. The process as claimed in claim 12 or 13, characterized in that the fibers are mineral fibers and that the collection of fibers is mineral wool.

15. The process as claimed in one of claims 12 to 14, characterized in that the sizing composition, when it is applied to the mineral or organic fibers, comprises at least 80% by weight, with respect to its total dry matter content, of water-soluble oligomeric ester.

16. The process as claimed in any one of claims 12 to 15, characterized in that the sizing composition, when it is applied to the mineral or organic fibers, comprises less than 10% by weight, preferably less than 5% by weight, with respect to its total dry matter content, of free sorbitol.