Method for preparing a thermosetting binder composition based on water-soluble or water-dispersible lignin ester, for binding fibres

Abstract

The present invention relates to a method for preparing a thermosetting binder composition, comprising the following steps: - mixing at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one organic non-polymeric polycarboxylic acid; and - heating said mixture at a temperature of between 90°C and 170°C, preferably between 110°C and 150°C, for a duration of between 5 seconds and 5 minutes, preferably between 15 seconds and 1 minute, so as to form at least one water-soluble or water-dispersible lignin ester. The present invention also relates to a thermosetting binder composition that can be obtained by such a method, said binder composition containing at least one water-soluble or water-dispersible lignin ester, at least one residual lignin, at least one free residual organic non-polymeric polycarboxylic acid, and at least one free residual organic monocarboxylic or sulfonic acid. The present invention also relates to a method for manufacturing an insulation product comprising mineral fibres or natural organic fibres using a thermosetting binder composition as obtained previously, but diluted in water, and to an insulation product that can be obtained by the above-mentioned manufacturing method.

Description

[0001] Description

[0002] Title: Process for preparing a water-soluble or water-dispersible lignin ester-based thermosetting binder composition for binding fibers

[0003] The present invention relates to a process for preparing a thermosetting binder composition based on water-soluble or dispersible lignin ester obtained by reaction between a lignin, in the presence of an organic monocarboxylic or sulfonic acid, with a non-polymeric organic polycarboxylic acid, as well as the thermosetting binder composition obtained by such a process.

[0004] The invention also relates to the use of such a thermosetting binder composition in a method for manufacturing an insulation product. Said thermosetting binder composition, after dilution in water, forms an aqueous sizing composition, making it possible to bind together both natural organic fibers and mineral fibers (after hardening of this sizing composition on the fibers), for the manufacture of insulating products. These insulating products obtained by said method are usually used for the production of low-density wood fiber panels (density less than 250 kg / m 3 ) and mineral fiber panels with a density of less than 120 kg / m 3 .

[0005] It has been known for several years to use aqueous sugar-based compositions as thermosetting binders for binding mineral fibers, particularly mineral wools.

[0006] In particular, it has been proposed to form thermoset polyesters by reacting together reducing sugars and / or non-reducing sugars and / or hydrogenated sugars, bearing 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). However, these sugar-based binders require a very high temperature, generally between 180°C and 210°C, to form over a time generally less than 30 min; this is why they have proven to be poorly suited for binding natural organic fibers, because said organic fibers are then degraded (or even burned) at such temperatures.

[0007] The sizing compositions described in the aforementioned documents are dilute aqueous solutions, of low viscosity and monomer reagents of low molar masses, less than 500 g. mol -1. They are generally sprayed onto the mineral fibers, while they are still hot, immediately after their formation. Immediately after application of the sizing composition to the fibers, the 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 mineral fibers still contains water.

[0008] It is only when the mat of glued mineral fibres 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 all the reactants begins.

[0009] Heating the bonded fiber mat at high temperatures for a few minutes then results in the curing (or crosslinking) of the reactive system and the formation of a water-insoluble organic binder, and consequently the desired insulation product. This final step therefore requires high temperatures, thus requiring a large amount of energy, to produce the desired insulation products.

[0010] For binding both mineral fibers and natural organic fibers, including medium and high density natural organic fibers (densities greater than 250 kg / m 3 ), sizing compositions based on phenolic resins of the resol type are commonly used. In addition to their good crosslinking ability, these resins are soluble in water and are relatively inexpensive.

[0011] The most common resols are obtained by condensation of phenol and formaldehyde, in the presence of a basic catalyst. However, in the end, these resols contain a certain proportion of unreacted monomers, in particular formaldehyde, the presence of which is not desired due to its proven harmful effects. For this reason, resol-based resins are generally treated with urea, which reacts with free formaldehyde, trapping it in the form of non-volatile urea-formaldehyde condensates. The presence of urea in the resin also provides a definite economic advantage due to its low cost, as it can be introduced in relatively large quantities without affecting the working qualities of the resin, in particular without harming the mechanical performance of the final product, which significantly lowers the total cost of the resin.It has nevertheless been observed that, under high temperature conditions to which the fibers are subjected to obtain crosslinking or hardening of the sizing composition based on said resols, the urea-formaldehyde condensates are not stable. They decompose, giving back formaldehyde and urea, in turn degraded at least partially into ammonia, which are released into the factory atmosphere and must then be subject to capture procedures to reduce their impact on the environment.

[0012] Also, to bind natural organic fibers, and in particular with the aim of obtaining insulating products with a density of less than 250 kg / m 3, it is known to use binders obtained after curing or crosslinking sizing compositions comprising polyisocyanates. Among the most commonly used polyisocyanates in the wood fiber industry, mention may be made of poly(methylene diphenyl isocyanate) (pMDI, CAS number 9016-87-9) which is a technical grade mixture containing from 30 to 80% of MDI (methylene diphenyl isocyanate) and higher molecular weight homologues of formula: [Formula 1]

[0013] In order to ensure good wetting of natural organic fibres by hydrophobic pMDI, it is generally necessary to subject the fibres to prior drying so as to lower their water content to a value less than or equal to 6% by weight, in particular between 2 - 6% by weight (see W02008 / 144770).

[0014] More recently, emulsifiable pMDIs (EMDIs) have been proposed, which are either mixtures of pMDI with non-ionic surfactants free of labile hydrogens likely to react with the isocyanate functions (see for example EP0516361), or mixtures of pMDI and a small percentage of pMDI functionalized with hydrophilic chains, for example polyethoxylated chains, making it possible to stabilize the emulsion. The use of pMDI in the form of aqueous emulsions allows a regular distribution of the binder on the natural organic fibers without prior drying, which constitutes a significant energy saving.

[0015] However, the use of polyisocyanate-based binders, even in the form of aqueous pMDI emulsions, poses a significant problem of harmfulness at the manufacturing site of insulation products, due to the presence of polyisocyanates. In addition, polyisocyanates remain expensive raw materials and are highly reactive. Thus, polyisocyanate-based sizing compositions can harden before the insulation product is shaped and heated, which generates tedious cleaning of the equipment and, above all, production shutdown.

[0016] To overcome the above-mentioned drawbacks, the present invention is based on the discovery that it was possible:

[0017] - by a particular process to obtain a thermosetting binder composition, which is not very harmful, inexpensive, stable but sufficiently reactive, so that it can be used (after dilution in water) to bind both mineral fibers and natural organic fibers, and thus manufacture insulating products with good mechanical properties,

[0018] - to lower the temperature and especially to accelerate the duration of the heating step of the assembly of the fibers leading to the hardening of the sizing composition (obtained by dilution in water of the binder composition) on the different types of fibers to form the organic binder; all this by subjecting a system of starting reagents, based on lignin(s) and polyacid(s), beforehand, to a polycondensation (or esterification) reaction in a preferably anhydrous and / or solvent-free medium, in other words well before said reagents are applied to the fibers, in a prepolymerization (or pre-polycondensation) step.

[0019] The present application thus relates to a process for preparing a thermosetting binder composition comprising the following steps:

[0020] - the mixture of at least one lignin, at least one organic monocarboxylic or sulfonic acid and at least one non-polymeric organic polycarboxylic acid, and

[0021] - heating said mixture to a temperature between 90°C and 170°C, preferably between 110°C and 150°C, for a period of between 5 seconds and 5 minutes, preferably between 15 seconds and 1 minute, so as to form at least one lignin ester soluble or dispersible in water.

[0022] In the present application, the terms thermosetting "binder composition" and "sizing composition" are not synonyms. The term thermosetting "binder composition" refers to concentrated aqueous solutions or dispersions, i.e. with a high solids or dry matter 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 or dispersions having a dry matter content of less than 20% by weight. They are generally obtained by diluting the thermosetting binder compositions with water.They have sufficiently low viscosities to allow their application to natural organic fibers or to mineral fibers by spraying using nozzles or by impregnation. Also, in the present application, the term "organic binder" means an insoluble binder obtained by hardening (or crosslinking) of the aqueous sizing composition previously applied to the fibers, during the heating step of the assembly of said fibers.

[0023] It was surprisingly found by the inventors that the process according to the invention made it possible to obtain a pre-polymerized binder composition comprising at least one stable lignin ester that is soluble or dispersible in water at room temperature. Said binder composition comprising at least one lignin ester can in fact form aqueous solutions or dispersions that are pumpable and infinitely dilutable, which can then be used as aqueous sizing compositions for binding both mineral fibers and natural organic fibers. These aqueous solutions or dispersions can have viscosities that are perfectly compatible with a conventional sizing system for different types of fibers by spraying using nozzles for example (such as a spray ring) or by impregnation.In the present application, the term "water-soluble" means a lignin ester which is dissolved up to 30% by weight in water and the term "water-dispersible" means a lignin ester whose particles are dispersed up to 30% in water, without precipitation. In the present application, the term "pre-polymerized" or "prepolymerization" means an esterification reaction between a portion of the aliphatic hydroxyl groups of the lignin and a portion of the carboxyl groups of the non-polymeric polycarboxylic acid(s) and between a portion of the hydroxyl groups of the lignin and a portion of the carboxyl groups of the lignin itself leading to the formation of the lignin ester.

[0024] The mixture, in the process for preparing a thermosetting binder composition according to the invention, comprises at least one lignin. The lignin according to the invention is a lignin extracted from so-called "native" lignin which is a biomolecule forming part of a family of polyphenolic polymer macromolecules (family of tannins lato sensu), which is one of the main components of wood with cellulose and hemicellulose. Native lignin is a macromolecule having a molar mass much greater than 10,000 g. mol' 1and which is not soluble in water. Native lignin is present mainly in vascular plants and in some algae. Its main functions are to provide rigidity, impermeability to water and high resistance to decomposition. All vascular plants, woody and herbaceous, produce lignin. Quantitatively, the native lignin content is 3 to 5% in leaves, 17 to 24% in herbaceous stems, 18 to 33% in woody stems (18 to 25% of the hardwood of angiosperm trees, 27 to 33% of the softwood of gymnosperm trees). It is less present in annual plants than in perennial plants, it is very present in trees. Native lignin is mainly located between cells, but a significant amount is found inside them.After cellulose (constituting 35 to 50% of terrestrial plant biomass) and hemicellulose (30 to 45%), lignin (15 to 25%) forms the third family of compounds in order of abundance in plants and in terrestrial ecosystems where dead or living plant biomass dominates.

[0025] The lignin, according to the invention, is a macromolecule, a possible structure of which is shown in Figure 1 [Fig. 1]. The lignin, according to the invention, is extracted by cleavage of the 0-0-4 ether bonds of native lignin and therefore has a lower molar mass than the native lignin from which it is derived, i.e. an average molar mass of less than 10,000 g. mol' 1 , preferably a molar mass of between 1000 g. mol' 1 and 9,000 g. mol' 1. The lignin, according to the invention, can be chosen from alkaline lignins also called kraft lignins, lignosulfonates, organosolv lignins, sodium lignins, lignins from biorefining processes of lignocellulosic raw materials, or a mixture thereof. The four groups of lignins available on the market are alkaline or kraft lignins, lignosulfonates, organosolv lignins (extracted lignins and sodium lignins). The fifth group is the so-called biorefinery lignin which is a little different because it is not described by its extraction process, but rather by the origin of the process, e.g. by biorefining and it can therefore be similar or different from any of the other groups mentioned. The lignin according to the invention is preferably alkaline lignin, also called kraft lignin.

[0026] Figure 1 shows a possible lignin structure, according to the invention, comprising both hydroxyl groups -OH and carboxyl groups -COOH. It can be noted that the reactive functional group present in the greatest quantity in a typical lignin is the hydroxyl group, which is either an aromatic hydroxyl group or an aliphatic hydroxyl group, i.e. a primary alcohol function or a secondary alcohol function. It is known that the hydroxyl and carboxyl groups of lignin can react with crosslinking agents such as isocyanates or epoxides, amines or aldehydes leading to a crosslinked structure of the lignin, following different crosslinking mechanisms. However, these crosslinking agents are of less interest due to their toxicity (isocyanates, amines, formaldehyde) and / or their cost (epoxides, amines, aldehydes other than formaldehyde).

[0027] Furthermore, it is known to use lignin in binders, however these do not generally offer mechanical properties equivalent to insulating products obtained from usual binders due to their heterogeneous structure and low chemical reactivity.

[0028] In the present application, the inventors have discovered that non-polymeric polycarboxylic acids, which are themselves of low toxicity, could react with lignin and more precisely with the aliphatic hydroxyl functions of lignin (by esterification) to form a thermosetting binder composition based on lignin ester, in order to bind mineral fibers and natural organic fibers and then obtain insulating products having good mechanical properties. Thus, according to the method for preparing a thermosetting binder composition according to the invention, at least one lignin is mixed with at least one “non-polymeric” organic polycarboxylic acid.

[0029] In the present application, the term “non-polymeric” polycarboxylic organic acid means a polycarboxylic organic acid which is not a macromolecule consisting of the assembly of monomers having a molar mass of between 90 g. mol -1and 350 g mol -1, linked together by covalent bonds in a repetitive manner. Thus, in the present application the thermosetting binder composition is preferably free of polymeric polycarboxylic organic acid. The non-polymeric organic polycarboxylic acid according to the invention may be chosen from dicarboxylic acids, in particular oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, malic acid, tartaric acid, tartronic acid, aspartic acid, glutamic acid, fumaric acid, itaconic acid, maleic acid, traumatic acid, camphoric acid, phthalic acid, in particular containing at least one boron or chlorine atom, tetrahydrophthalic acid, in particular containing at least one chlorine atom, isophthalic acid, terephthalic acid, mesaconic acid and citraconic acid, tricarboxylic acids,in particular citric acid, tricarballylic acid, 1,2,4-butanetricarboxylic acid, aconitic acid, hemimellitic acid, trimellitic acid and trimesic acid, and tetracarboxylic acids, in particular 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid. Even more preferably, the non-polymeric polycarboxylic organic acid is selected from maleic acid, succinic acid, glutaric acid, itaconic acid and citric acid.,

[0030] The Applicant has carried out tests to determine the respective proportions of lignin and non-polymeric polycarboxylic organic acid necessary to form the thermosetting binder composition based on lignin ester, in order to obtain, after dilution of said binder composition, an organic binder giving the final insulating product the best mechanical properties. These tests have shown that in the process for preparing the thermosetting binder composition according to the invention, the lignin(s) may represent at least 50% of the total weight of the non-polymeric polycarboxylic organic acid(s)^) and of the lignin(s). Even more preferably, the lignin(s) represent(s) from 50% to 80% of the total weight of the non-polymeric polycarboxylic organic acid(s) and of the lignin(s).Therefore, the non-polymeric polycarboxylic organic acid(s) advantageously represent(s) from 20% to 50% by weight of the total weight of the non-polymeric polycarboxylic organic acid(s) and lignin(s).

[0031] The mixture according to the process of the invention also comprises at least one organic monocarboxylic acid or at least one organic sulfonic acid. Preferably, the organic monocarboxylic or sulfonic acid(s) represent(s) at most 50% of the weight of the mixture consisting of the lignin(s), the non-polymeric organic polycarboxylic acid(s) and the organic monocarboxylic or sulfonic acid(s). More preferably, the organic monocarboxylic or sulfonic acid(s) represent(s) from 5% to 50% of the weight of the mixture consisting of the lignin(s), the non-polymeric organic polycarboxylic acid(s) and the organic monocarboxylic or sulfonic acid(s).

[0032] The role of the organic monocarboxylic or sulfonic acid in the reaction mixture according to the invention is to adjust the pH of the lignin so that it is between 6.5 and 10.5, preferably between 8 and 9, between 10 and 20% in aqueous solution.

[0033] The organic monocarboxylic acid may be selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, pentanoic acid, a or lignin(s), isovalerianic organic acid(s), hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, trans-vaccenic acid, linoleic acid, linolelaidic acid, a-linolenic acid, y-linolenic acid, dihomo-y-linolenic acid, arachidonic acid, eicosapentaenoic acid, clupanodonic acid, docosahexaenoic acid,crepenynic acid, tuberculostearic acid, phytanic acid, lactobacillic acid, malvalic acid, chaulmoogric acid, gorlic acid, 11-cyclohexylundecanoic acid, 13-phenyltridecanoic acid, furanic fatty acids, pentacycloanammoxic acid and benzoic acid. The particularly preferred organic monocarboxylic acid is acetic acid.,

[0034] The organic sulfonic acid preferably has the general formula: RS(=O)2-OH in which R represents an alkyl or aryl group and S(=O)2-OH is sulfonyl hydroxide. And, advantageously, the organic sulfonic acid is selected from the group consisting of methylsulfonic acid, ethylsulfonic acid, propylsulfonic acid, butylsulfonic acid, methanedisulfonic acid, ethanedisulfonic acid, propanedisulfonic acid, butanedisulfonic acid, benzenesulfonic acid and paratoluenesulfonic acid. In particular, the sulfonic acid is paratoluenesulfonic acid.

[0035] In a preferred embodiment, at least one lignin is first mixed with at least one organic monocarboxylic or sulfonic acid in the presence of a water content which may be less than 5% by weight, preferably less than 1% by weight, so that the pH of the lignin in solution is between 6.5 and 10.5, preferably between 8 and 9. Adjusting the pH of the lignin makes it possible to maximize its reactivity with the non-polymeric polycarboxylic organic acid without excessively affecting its solubility in water. Then, at least one non-polymeric polycarboxylic organic acid can then be added to said premix, preferably in the absence of solvent.

[0036] Thus, the reaction mixture of the polycondensation between at least one lignin, in the presence of at least one monocarboxylic or sulfonic acid, with at least one non-polymeric organic polycarboxylic acid, may contain less than 5% water by weight, preferably less than 1% water by weight and more advantageously the mixture is anhydrous. In certain cases, water makes it possible to homogenize the reactants in the reaction mixture. This water, necessary for homogenization, evaporates under the effect of the step of heating the reaction mixture.

[0037] Furthermore, advantageously, the mixture of at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one non-polymeric organic polycarboxylic acid contains less than 5% by weight of aqueous and / or organic solvents, preferably less than 1% by weight of aqueous and / or organic solvents. Even more preferably, said mixture is free of solvents.

[0038] The mixture may be free of polyols, and more particularly of hydrogenated sugars.

[0039] The mixture may further comprise a catalyst which has the function, in particular, of reducing the temperature of the pre-polymerization (crosslinking) between the lignin and the non-polymeric polycarboxylic organic acid. The catalyst may be a phosphorus-containing compound, for example an alkali metal hypophosphite salt, an alkali metal phosphite, an alkali metal polyphosphate, an alkali metal hydrogen phosphate, a phosphoric acid or an alkylphosphonic acid. Preferably, the catalyst is sodium hypophosphite, sodium phosphite and mixtures of these compounds.

[0040] The amount of catalyst introduced into the mixture may represent up to 5% of the weight of the lignin and the non-polymeric polycarboxylic organic acid, preferably up to 3%, and advantageously is at least equal to 2%.

[0041] In another preferred embodiment, the mixture is free of catalyst because the step of heating the mixture of at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one non-polymeric organic polycarboxylic acid makes it possible to avoid the use of such a catalyst, which is often toxic and can promote depolymerization and therefore aging of the final insulating product.

[0042] According to the process of the invention, the reaction mixture is heated to a temperature between 90°C and 170°C, preferably between 110°C and 150°C, for a period of between 5 seconds and 5 minutes, preferably between 15 seconds and 1 minute, so as to form at least one lignin ester soluble or dispersible in water.

[0043] Heating of the mixture can be carried out using a temperature-controlled enclosure or in a reactor equipped with a mechanical stirrer.

[0044] The degree of progress of the polymerization reaction between at least one lignin and at least one non-polymeric polycarboxylic organic acid during heating of the reaction mixture can be monitored by measuring the reaction enthalpy by differential scanning calorimetry (DSC). This involves determining the degree of progress of the reaction by the difference between the initial state (maximum enthalpy) and the final state (enthalpy = 0). The measuring device used by the applicant is the Discovery DSC model from TA Instruments.

[0045] Indeed, when the desired degree of polymerization is reached, the heating is stopped and the thermosetting binder composition based on water-soluble or dispersible lignin ester is obtained according to the process as described.

[0046] The present application also relates to a thermosetting binder composition capable of being obtained by the process as described above, said binder composition contains at least one lignin ester soluble or dispersible in water, at least one residual lignin, at least one free residual non-polymeric polycarboxylic organic acid, and at least one free residual monocarboxylic or sulfonic organic acid.

[0047] The thermosetting binder composition advantageously contains at least one lignin ester with a molar mass of between 1000 g. mol -1 and 20,000 g.mol'1, preferably between 1000 g.mol' 1 and 10000 gmol' 1; the lignin ester being obtained by pre-polymerization, i.e. by esterification reaction between aliphatic hydroxyl groups of the lignin and the carboxyl groups of the non-polymeric polycarboxylic acid(s) and between hydroxyl groups of the lignin and carboxyl groups of the lignin itself.

[0048] Thus, the content of free residual non-polymeric polycarboxylic organic acid may represent at most 45% by weight, relative to the total dry weight of the thermosetting binder composition and the content of free residual monocarboxylic organic acid or the content of free residual sulfonic organic acid represents at most 45% by weight, relative to the total dry weight of the thermosetting binder composition. The term "free residual" means the content of non-polymeric polycarboxylic organic acid which has not reacted with the lignin during the pre-polymerization, or the content of monocarboxylic or sulfonic organic acid which has not exchanged H ions. + with lignin. The thermosetting binder composition obtained by the process contains, as mentioned above; at least one residual lignin, which means a quantity of lignin which has not reacted.

[0049] The thermosetting binder composition has in particular a pH of between 2 and 6, preferably between 2.5 and 5, at 10% in aqueous solution. The water content of the thermosetting binder composition may be less than 3% by weight, preferably less than 0.5% by weight. The inventors have found that the thermosetting binder composition obtainable by the process, due to its acidic pH and its low water concentration, has good storage stability at room temperature and can thus be transported, as explained above.

[0050] Furthermore, the inventors have noted that the use of the lignin ester contained in a thermosetting binder composition as prepared according to the process of the invention:

[0051] - instead of “sugar and polyacid-based” reagents in a sizing composition applied directly to mineral fibers, makes it possible to lower the temperature of the heating step of the assembly of said fibers and also to accelerate the duration of the heating step of the assembly of the fibers,

[0052] - instead of polyisocyanates applied directly to natural organic fibres, avoids hardening of the sizing composition on the said fibres before they pass through the appropriate heating device,

[0053] - instead of the reagents: "at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one non-polymeric organic polycarboxylic acid", in a sizing composition applied directly to any type of fiber (in other words without a pre-polymerization step), makes it possible to shorten, for a given oven temperature, the time required for satisfactory hardening of the binder on the fibers, the heating step of the assembly of said fibers, which allows energy savings for heating the oven or the heating press and the acceleration of the production line of insulation products, while obtaining insulation products with good mechanical properties.

[0054] The third subject of the present application is a method for manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder, using a thermosetting binder composition according to the invention.

[0055] This process includes the following steps:

[0056] (a) preparing a sizing composition by diluting a thermosetting binder composition as described above with water to a dry matter content of between 1% and 20% by weight, preferably between 2 and 10% by weight,

[0057] (b) applying the sizing composition to said mineral fibers or said natural organic fibers,

[0058] (c) forming an assembly of said mineral fibers or said glued natural organic fibers, and

[0059] (d) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens to form the organic binder.

[0060] To obtain good quality insulation 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 or the sizing composition must impregnate the fiber but not too much (with a contact angle slightly less than 90°). The sprayability of the sizing composition is directly linked to the possibility of diluting the concentrated thermosetting binder composition with a large quantity of water. The diluted sizing composition must be a solution or dispersion, stable over time, which does not give rise to demixing phenomena.

[0061] 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 equal to or greater than 1000% at 20°C.

[0062] Thus, the aqueous sizing composition obtained after dilution of the lignin ester-based thermosetting binder composition during step (a) of the aforementioned process may have a dry matter content of between 1% and 20% by weight, preferably between 2% and 10% by weight.

[0063] 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 fibers or natural organic fibers. With regard to mineral fibers, these additives are chosen, for example, from anti-dust additives, silicones and coupling agents. The aqueous sizing composition may be applied to the mineral fibers or natural organic fibers, in an amount of between 1% and 20% by weight, preferably between 2% and 15% by weight, said amount being expressed as dry matter relative to the weight of the mineral fibers or natural organic fibers, in order to give the insulating product the desired mechanical properties.

[0064] In a preferred embodiment of the method of the invention, step (b) of applying the sizing composition to the mineral fibers or natural organic fibers can be carried out by spraying, in particular by means of spray nozzles, or by roller coating or by impregnation.

[0065] The mineral fibers according to the invention are preferably mineral wools and even more preferably glass, rock or slag wools, or mixtures thereof. In particular, when the mineral fibers are mineral wools, they may contain a composition corresponding to the following formulation, in percentage by weight: SiO2: between 30 and 50%, preferably between 35 and 45%, Na2O: between 0 and 10%, preferably between 0.4 and 7%, CaO: between 10 and 35%, preferably between 12 and 25%, MgO: between 1 and 15%, preferably between 5 and 13%, CaO+MgO: between 11 and 40% cumulatively, AI2O3: between 10 and 27%,

[0066] K2O: between 0 and 2%, preferably between 0 and 1%,

[0067] Iron oxide: between 0.5 and 15%, preferably between 3 and 12%, other oxide(s): between 0 and 5% cumulative, preferably less than 3%, the remainder being made up of unavoidable impurities.

[0068] The mineral fibers may be glass fibers, or rock fibers, in particular basalt (or wollastonite). And more particularly, the mineral fibers according to the invention are aluminosilicate glass fibers, in particular aluminosilicate glass fibers comprising aluminum oxide, AI2O3, in a mass fraction of between 14% and 28%. In another embodiment, the mineral fibers may be glass fibers containing a composition corresponding to the following formulation, in percentage by weight: SiO2: between 50 and 75%, preferably between 60 and 70%, Na2O: between 10 and 25%, preferably between 10 and 20%, CaO: between 5 and 15%, preferably between 5 and 10%,

[0069] MgO: between 1 and 10%, preferably between 2 and 5%,

[0070] CaO and MgO together preferably representing between 5 and 20%,

[0071] B2O3: between 0 and 10%, preferably between 2 and 8%,

[0072] AI2O3: between 0 and 8%, preferably between 1 and 6%, K2O: between 0 and 5%, preferably between 0.5 and 2%, Na2O and K2O together preferably representing between 12 and 20%, Iron oxide: between 0 and 3%, preferably less than 2%, more preferably less than 1%, other oxide(s): between 0 and 5% cumulative weight, preferably less than 3% cumulative, the remainder being made up of unavoidable impurities.

[0073] The diameter of the mineral fibers is advantageously between 0.1 and 25 pm.

[0074] The diameter of the natural organic fibers is advantageously between 5 and 100 μm, preferably between 10 and 50 μm and the length of these fibers is in particular between 0.1 and 900 mm, and more particularly between 10 and 120 mm. The natural organic fibers, according to the invention, are advantageously fibers which are not thermoplastic, and which are naturally present in biomass and may have undergone mechanical and / or chemical treatments. These fibers come from plant sources and are advantageously chosen from cotton and lignocellulosic fibers. The term "lignocellulosic fibers" means fibers of plant origin based on lignocellulosic material, i.e. comprising cellulose, hemicellulose and lignin.Lignocellulosic fibers include wood fibers and fibers from other plants, such as hemp, flax, sisal, cotton, jute, coconut, raffia, abaca, cereal straw, and rice straw.

[0075] The term "lignocellulosic fibers" as used in this application does not include lignocellulosic materials that have been subjected to thermomechanical or chemical treatments for the purpose of manufacturing paper pulp.

[0076] The lignocellulosic fibers used in the present invention have therefore simply undergone a mechanical comminution treatment intended to reduce and / or control the size of the fibers. The lignocellulosic fibers are preferably softwood fibers, in particular pine, obtained by mechanical defibering. Their diameter is advantageously between 10 and 70 μm, preferably between 30 and 50 μm and they have a length ranging from 0.1 to 100 mm, preferably from 0.5 to 50 mm, in particular from 1 to 20 mm.

[0077] The application of the sizing composition (b) preferably precedes the step (c) of forming an assembly of the mineral fibers or the natural organic fibers, during which the sized fibers are gathered, before being heated consecutively or extemporaneously to harden the sizing composition, thus forming the organic binder which binds the fibers.

[0078] Thus, step (c) of forming an assembly of mineral fibers or natural organic fibers, which can also be called the step of shaping all the fibers, can be carried out by molding and / or compression. The mold used for molding the products must be made of a material capable of withstanding the temperature of the heating step. It must also have a structure allowing the hot air from the baking oven to easily penetrate into the molded product. The mold can, for example, be formed of a box-shaped metal mesh. The box made of metal mesh is preferably filled with a volume of loose fibers greater than its capacity and is then closed by a metal mesh cover. The fibers are thus more or less compressed depending on the excess filling volume.This excess volume of filling of the box by the fibers is for example between 10% and 150%, preferably between 15 and 100% and in particular between 20 and 80%.

[0079] When the process of the present invention is a continuous process, step (c) of forming an assembly of fibers can be carried out for example by compression by means of a roller located at the entrance to the cooking oven on a conveyor.

[0080] In addition, the fibers can be assembled:

[0081] - in flexible fiber mattresses that can be rolled up, compressed or folded,

[0082] - in sheets or fiber panels, denser and more rigid than roll-up mattresses,

[0083] - in molded fiber-based products, for example linings for conduits or pipes, - in woven or non-woven textiles, such as non-woven mats of glass or organic fibers.

[0084] In a particular embodiment of the method according to the invention, the fibers are natural organic fibers impregnated with aqueous sizing composition and said method further comprises, between step (b) and step (c), a step of drying the fibers which aims to evaporate sufficient water to make the sized or unsized fibers substantially non-sticky. In another embodiment, the drying step can be carried out before step (b). This drying step can be carried out by heating, for example in a thermostatically controlled ventilated oven or by conveying the fibers using dry hot air. It is important to ensure that the drying does not bring the natural organic fibers to too high a temperature which results in the softening of the dried sizing composition, or even in the beginning of crosslinking of the components of the sizing composition.A drying temperature close to the boiling point of water is generally sufficient. The drying of the fibers impregnated with aqueous sizing composition is thus preferably carried out by heating to a temperature between 70°C and 160°C, for a period of between 1 second and 10 seconds. The natural organic fibers obtained at the end of the drying step are surrounded by a sheath of dried sizing composition.

[0085] Step (d) of heating the assembly of mineral fibers or natural organic fibers according to the method of the invention is preferably carried out at a temperature between 90°C and 170°C for a duration between 1 minute and 10 minutes, preferably in a temperature-controlled enclosure or a steam press. In the context of a temperature-controlled enclosure, this may be a forced-air oven into which hot gases of controlled temperature are introduced into one or more compartments, or a heating mold with fluid circulation or heating resistance.

[0086] Therefore, the inventors have shown that preheating at least one lignin with at least one non-polymeric polycarboxylic organic acid in the presence of at least one monocarboxylic or sulfonic organic acid, preferably in an anhydrous and / or solvent-free medium, at a temperature between 90°C and 170°C, for a duration between 5 seconds and 5 minutes, makes it possible to shorten the curing time of the binder during step (d) of the process for manufacturing an insulating product, which represents an energy saving. In addition, it has been observed that the insulating products obtained from the two processes described above have good mechanical properties.

[0087] Thus, finally, the invention relates to an insulation product obtainable by the method of manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder as described above. Said insulating product obtained consequently comprises mineral fibers or natural organic fibers, bound using a binder obtained by hardening or crosslinking a sizing composition obtained by diluting a thermosetting binder composition based on lignin ester soluble or dispersible in water; itself obtained from at least one lignin, at least one monocarboxylic or sulfonic acid, and at least one non-polymeric polycarboxylic organic acid.

[0088] The resulting insulating product has good mechanical properties.

[0089] The insulating product obtained from natural organic fibres can have a thickness between 10 and 300 mm, preferably between 35 and 240 mm, measured according to standard EN 823:2013 and a density between 30 and 250 kg / m 3 , preferably between 100 and 250 kg / m 3 The insulating product obtained can be used to make panels for the external insulation of buildings.

[0090] The insulating products obtained from mineral fibres are preferably mineral fibre panels, in particular wool or rock, which may have a thickness of between 10 and 300 mm, preferably between 30 and 210 mm, measured according to standard EN 823:2013 and a density of between 10 and 120 kg / m 3 , preferably between 15 and 90 kg / m 3 .

[0091] Examples

[0092] Example 1:

[0093] Preparation of a thermosetting binder composition No. 1 according to the invention

[0094] 35% acetic acid by weight is added to 45% kraft lignin A by weight. Then, after homogenizing this premix, 20% succinic acid by weight relative to the total weight of lignin and succinic acid is added. The mixture contains 3% water by weight. The mixture is stirred and placed in a thermostatically controlled oven at 150°C for 30 seconds to provide thermosetting binder composition No. 1 containing prepolymerized lignin ester A. Said binder composition is highly concentrated since the mixture is anhydrous and comprises 20% free residual acetic acid by weight and less than 10% free residual succinic acid by weight, relative to the total dry weight of the thermosetting binder composition.

[0095] In the case where a 10% by weight aqueous solution of the obtained binder composition is prepared to measure the pH, it is equal to 3.6.

[0096] Preparation of aqueous sizing composition No. 1 according to the invention

[0097] The pre-cooked mixture containing the pre-polymerized lignin ester A is ground and diluted with water until a dilute solution with a dry matter content of 10% by weight is obtained.

[0098] Preparation of an aqueous sizing composition No. 2 comparative

[0099] For comparison, a non-prepolymerized aqueous sizing composition No. 2, i.e. one that has not undergone pre-cooking, is prepared by simply mixing: acetic acid / kraft lignin A / succinic acid in a ratio of 35 / 45 / 20 and water is added until a dilute solution is obtained having the same dry matter content of 10% by weight as sizing composition No. 2.

[0100] Preparation of an aqueous sizing composition No. 3, according to the prior art

[0101] A sizing composition No. 3 is prepared by emulsifying emulsifiable poly(methylenediphenyl isocyanate) (pMDI) with water. The dry matter content of the composition is 60% by weight.

[0102] Preparation of an aqueous sizing composition No. 4 according to the prior art

[0103] An aqueous sizing composition No. 3 is prepared by simply mixing a phenolic resin (formaldehyde + phenol) / urea in a ratio of 80 / 20 and water is added until a dilute solution is obtained with a dry matter content of 60% by weight.

[0104] Each sizing composition described above 1, 2, 3 and 4 is then used to impregnate wood fibers. The quantity of the aqueous sizing compositions 1, 2, 3 and 4 deposited on the wood fibers is equal to 7% by weight expressed as dry matter relative to the weight of the wood fibers.

[0105] The impregnated wood fibers are then evenly placed in a stainless steel mold with several open cavities of 60 mm x 10 mm x 10 mm. Stainless steel bars of 60 mm x 10 mm x 8 mm are placed on the wood fibers and for each of the samples the whole is heated for a determined time in a thermostatically controlled press at a given temperature and under a pressure of 10 bars.

[0106] The mold is then allowed to cool to room temperature before removing the specimen of lignocellulosic fibers formed (60 mm x 10 mm x 2 mm).

[0107] The wood fiber samples thus obtained have a density of approximately 180 kg / m 3 .

[0108] The flexural storage modulus (three-point bending) is then determined for each specimen by dynamic thermomechanical analysis (DMTA) using a “TA Instruments RSA-G2 Analyzer” device. The samples are first dried for several hours in a dynamic vacuum desiccator (20 mbar).

[0109] The operating parameters of the measuring device are as follows: Temperature: 25°C Poisson's ratio: 0.45

[0110] Duration of oscillatory mechanical stress: 120 seconds

[0111] Oscillation frequency: 1.0 Hz,

[0112] Deformation: 0.1%

[0113] Sampling rate: 10 points / second.

[0114] Table 1 below shows:

[0115] - the temperature and duration required, during the stage of heating the wood fibres until each of the gluing compositions hardens, to form the organic binder and consequently the insulating product, and

[0116] - the storage modulus of the wood fibre specimens obtained after curing each of the gluing compositions. Each storage modulus value is the average calculated on two to four individual measurement values.

[0117] Results [Table 1]

[0118] It is found that the use of sizing composition No. 1 comprising the pre-polymerized lignin ester A obtained according to the process of the invention (i.e. after dilution of binder composition No. 1 obtained by pre-heating lignin A with succinic acid in the presence of acetic acid in an essentially anhydrous medium, in other words in a medium containing less than 5% water by weight) makes it possible, for a given oven temperature equal to 150°C, to accelerate the time required for the hardening of the sizing composition on the wood fibers to form the organic binder (because duration: 4 minutes), in other words to obtain an insulating product with an equivalent storage modulus (approximately 100 MPa); compared to the use of a binder composition comprising line A which has not undergone pre-polymerization such as sizing composition No. 2 (duration: 10 minutes).

[0119] Also, although the storage modulus obtained for the wood fiber specimens prepared in accordance with the invention is slightly lower (of the order of 100 MPa) compared to wood fibers prepared using known, but harmful, overly reactive sizing compositions, such as poly(methylene diphenyl isocyanate) or phenol-formaldehyde urea resins (whose storage modulus is approximately 155 MPa); the mechanical properties of the wood fibers obtained according to the invention are good. A storage modulus of approximately 100 MPa for insulating products having a density of 180 kg / m 3 is satisfactory. Example 2:

[0120] Two other sizing compositions are prepared, according to the prior art, Nos. 5 and 5 bis, by successively introducing into a container 48 parts by weight of maltitol (as hydrogenated sugar), 52 parts by weight of citric acid, and 5 parts by weight of sodium hypophosphite (catalyst) under vigorous stirring until the constituents are completely dissolved.

[0121] Then, each sizing composition described above No. 1, 2, 5 and 5bis is then used to impregnate glass fibers. All sizing compositions 1, 2, 5 and 5bis contain 90% by weight of water and 10% by weight of dry matter. All compositions are used to form glass fiber insulation products.

[0122] Thus, two pieces (60 mm x 10 mm x 0.250 mm) of superimposed non-woven glass fiber papers are impregnated with each of the aqueous sizing compositions respectively, then the impregnated glass fiber papers are cured at a temperature of 150°C for 4 min (for samples 1, 2, 3, 5) or 210°C for 10 min (for sample 5bis).

[0123] The flexural storage modulus (three-point bending) is then determined for each sample by dynamic thermomechanical analysis (DMTA) using a TA Instruments RSA-G2 Analyzer. The samples are first dried for several hours in a dynamic vacuum desiccator (20 mbar). The operating parameters of the measuring device are the same as those mentioned above.

[0124] Table 2 below shows:

[0125] - the temperature and duration required, during the stage of heating the glass fibres until each of the sizing compositions hardens, to form the organic binder and consequently the insulating product, and

[0126] - the storage modulus of the glass fiber papers obtained after curing each of the sizing compositions. Each storage modulus value is the average calculated on two to four individual measurement values. Results

[0127] (Table 2]

[0128] It is found that the use of sizing composition No. 1 comprising the pre-polymerized lignin ester A obtained according to the process of the invention (i.e. after dilution of binder composition No. 1 obtained by pre-heating lignin A with succinic acid in the presence of acetic acid in an essentially anhydrous medium, in other words in a medium containing less than 5% water by weight) makes it possible, for a given oven temperature equal to 150°C, to accelerate the time required for the hardening of the sizing composition on the glass fibers to form the organic binder (because duration: 4 minutes), in other words to obtain an insulating product with an equivalent storage modulus (1.65 GPa); compared to the use of a binder composition comprising line A which has not undergone prepolymerization such as sizing composition No. 2 (duration: 10 minutes).

[0129] It is also observed that the use of sizing composition No. 1 comprising pre-polymerized lignin ester A makes it possible to obtain glass fiber papers with good mechanical properties (storage modulus equal to 1.65 GPa), and much better than those obtained for glass fiber papers prepared using known sizing compositions 5 and 5 bis based on hydrogenated sugar (storage modulus equal to 0.26 and 1.18 GPa).

[0130] Furthermore, the use of sizing composition No. 1 comprising pre-polymerized lignin ester A makes it possible to lower the temperature of the heating step of the assembly of the glass fibers and to accelerate the duration of the heating step of the assembly of the glass fibers to form the organic binder, compared to the use of a binder composition based on hydrogenated sugar (compositions 5 and 5bis).

Claims

Claims 1. A process for preparing a thermosetting binder composition, comprising the following steps: - the mixture of at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one non-polymeric organic polycarboxylic acid, and - heating said mixture to a temperature between 90°C and 170°C, preferably between 110°C and 150°C, for a period of between 5 seconds and 5 minutes, preferably between 15 seconds and 1 minute, so as to form at least one lignin ester soluble or dispersible in water.

2. Method according to claim 1, in which the mixture of at least one lignin, at least one organic monocarboxylic or sulfonic acid, and at least one non-polymeric organic polycarboxylic acid, contains less than 5% water by weight, preferably less than 1% water by weight and more preferably the mixture is anhydrous.

3. Method according to claim 1 or 2, in which the lignin is chosen from alkaline lignins, also called Kraft lignins, lignosulfonates, organosolv lignins, sodium lignins, lignins originating from a bio-refining process of lignocellulosic raw materials or a mixture thereof.

4. Method according to any one of the preceding claims, in which the non-polymeric organic polycarboxylic acid is chosen from dicarboxylic acids, in particular oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, malic acid, tartaric acid, tartronic acid, aspartic acid, glutamic acid, fumaric acid, itaconic acid, maleic acid, traumatic acid, camphoric acid, phthalic acid, in particular containing at least one atom of boron or chlorine, tetrahydrophthalic acid, in particular containing at least one atom of chlorine, isophthalic acid, terephthalic acid, mesaconic acid and citraconic acid, acids tricarboxylic acids, including citric acid, tricarballylic acid, 1,2,4-butanetricarboxylic acid, aconitic acid, hemimellitic acid,trimellitic acid and trimesic acid, and tetracarboxylic acids, in particular, 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.

5. Process according to any one of the preceding claims, in which the lignin(s) represent(s) at least 50% of the total weight of the non-polymeric polycarboxylic organic acid(s) and of the lignin(s), preferably from 50% to 80% of the total weight of the non-polymeric polycarboxylic organic acid(s) and of the lignin(s).

6. A method according to any one of the preceding claims, wherein the organic monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, pentanoic acid, isovalerianic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, trans-vaccenic acid, linoleic acid, linolelaidic acid, a-linolenic acid, y-linolenic acid, dihomo-y-linolenic acid, arachidonic acid, eicosapentaenoic acid,clupanodonic acid, docosahexaenoic acid, crepenynic acid, tuberculostearic acid, phytanic acid, lactobacillic acid, malvalic acid, chaulmoogric acid, gorlic acid, 11-cyclohexylundecanoic acid, 13-phenyltridecanoic acid, furanic fatty acids, pentacycloanammoxic acid and benzoic acid., 7. Thermosetting binder composition obtainable by the process according to any one of claims 1 to 6, said binder composition containing at least one water-soluble or water-dispersible lignin ester, at least one residual lignin, at least one free residual non-polymeric polycarboxylic organic acid, and at least one free residual monocarboxylic or sulfonic organic acid.

8. Thermosetting binder composition according to claim 7, characterized in that it has a pH of between 2 and 6, preferably between 2.5 and 5, at 10% by weight in aqueous solution.

9. Thermosetting binder composition according to claim 7 or 8, characterized in that it has a water content of less than 3% by weight, preferably less than 0.5% by weight.

10. A thermosetting binder composition according to any one of claims 7 to 9, wherein the free residual non-polymeric polycarboxylic organic acid content represents at most 45% by weight, relative to the total dry weight of the thermosetting binder composition and the free residual monocarboxylic organic acid content or the free residual sulfonic organic acid content represents at most 45% by weight, relative to the total dry weight of the thermosetting binder composition.

11. A method of manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder, said method comprising the following steps: (a) preparing a sizing composition by diluting a thermosetting binder composition according to any one of claims 7 to 10 with water to a dry matter content of between 1% and 20% by weight, preferably between 2 and 10% by weight, (b) applying the sizing composition to said mineral fibers or said natural organic fibers, (c) forming an assembly of said mineral fibers or said glued natural organic fibers, and (d) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens to form the organic binder.

12. The method of claim 11, wherein the mineral fibers are glass fibers or rock fibers or slag fibers, or mixtures thereof.

13. Method according to claim 11, in which the natural organic fibers are chosen from wood, hemp, linen, sisal, cotton, jute, coconut, raffia, abaca fibers, or even cereal straw or rice straw.

14. Method according to any one of claims 11 to 13, characterized in that step (d) comprises heating said assembly of fibers to a temperature between 90°C and 170°C for a period of between 1 and 10 minutes, preferably in a thermo-regulated enclosure or a steam press.

15. Insulation product obtainable by a process according to any one of claims 10 to 14.

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