Process for manufacturing insulation products based on mineral fibers or natural organic fibers

Abstract

The present invention relates to a method for manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder, comprising the following steps: (a) applying a sizing composition to said mineral fibers or said natural organic fibers, (b) forming an assembly of said mineral fibers or said natural organic fibers, (c) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens, characterized in that said sizing composition comprises: - at least one lignin, optionally oxidized, and - at least one non-polymeric polycarboxylic organic acid. The present invention also relates to the insulating products that can be obtained by such a method.

Description

Title of the invention: Process for manufacturing insulation products based on mineral fibers or natural organic fibers

[0001] The present invention relates to a method for manufacturing insulation products comprising mineral fibers or natural organic fibers bound by an organic binder obtained by hardening or crosslinking a sizing composition containing a lignin, optionally oxidized, and a non-polymeric polycarboxylic organic acid. The invention also relates to the insulating products obtained by such a method.

[0002] The manufacture of insulating products based on mineral fibers, in particular based on mineral wool, generally comprises a step of manufacturing the glass or rock fibers by a centrifugation process. On their path between the centrifugation device and the fiber collection belt, an aqueous sizing composition, also called an aqueous binder composition, is sprayed onto the still-hot fibers, which then undergo a polymerization reaction at temperatures generally above 100°C.

[0003] For several years, the use of various thermosetting resins, as binders, contained in sizing compositions, has made it possible to bind mineral fibers and improve the mechanical performance of the insulation products obtained. The thermosetting resins most commonly used for the manufacture of mineral wool-based insulation products are phenolic resins of the resol type. In addition to their good ability to crosslink under the aforementioned thermal conditions, these resins are soluble in water, have a good affinity for mineral fibers thanks in particular to the presence of silane, and are relatively inexpensive.

[0004] The most common resols are obtained by condensation of phenol and formaldehyde, in the presence of a basic catalyst. Ultimately, these resols contain a certain proportion of unreacted monomers, in particular formaldehyde, the presence of which is not desired because of its proven harmful effects.

[0005] For this reason, resol-based resins are generally treated with urea, which reacts with the 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, since 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.

[0006] It has nevertheless been observed that, under the temperature conditions to which the mineral wool sheet is subjected to obtain crosslinking of the resin, 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 atmosphere of the factory and must then be subject to capture procedures to reduce their impact on the environment. Solutions for replacing formaldehyde-based resins in sizing compositions have therefore been developed.

[0007] The Applicant has proposed in its applications WO2010 / 029266 and WO2013 / 014399 sizing compositions based on hydrogenated sugars, also called sugar alcohols, for binding mineral fibers. These reagents have very good thermal stability and give the final product good mechanical performance.

[0008] Formaldehyde-free binders containing both hydrogenated sugars and reducing or non-reducing sugars have been disclosed in applications WO2013 / 021112 and WO2015 / 159012 respectively in the name of the Applicant for binding mineral fibers. However, these sugar-based resins have proven to be poorly reactive and unstable for binding natural organic fibers.

[0009] To bind natural organic fibers, and in particular for the purpose of obtaining insulating products with a density of less than 250 kg / m3, it is known to use binders obtained after curing or crosslinking sizing compositions comprising polyisocyanates. Among the polyisocyanates most commonly used 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

[0010] [Formula 1] -year

[0011] In order to ensure good wetting of natural organic fibers by hydrophobic pMDI, it is generally necessary to subject the fibers 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 WO2008 / 144770).

[0012] More recently, emusifiable pMDIs (EMDIs) have been proposed, which are either mixtures of pMDI with non-ionic surfactants free of labile hydrogens capable of reacting with 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.

[0013] The use of pMDI in the form of aqueous emulsions allows for a regular distribution of the binder on the natural organic fibers without prior drying, which constitutes a significant energy saving.

[0014] However, the use of polyisocyanate-based binders, even in the form of aqueous pMDI emulsions, poses a significant problem of harmfulness at the site of panel manufacturing, due to the presence of polyisocyanates. In addition, polyisocyanates are highly reactive and remain expensive raw materials.

[0015] The Applicant has therefore sought a method for manufacturing both mineral fiber-based insulating products and natural organic fiber-based insulating products which uses the same type of organic binder, in other words the same sizing composition which makes it possible to bind both mineral fibers and natural organic fibers after hardening; such a sizing composition preferably being bio-sourced, having to be of low toxicity, inexpensive, having good crosslinking ability and being able to be distributed uniformly over any of the aforementioned fibers and making it possible to obtain insulating products with good mechanical properties. The desired sizing composition must also have the advantage of not polymerizing / crosslinking or very little before passing through the appropriate heating device, and / or of polymerizing / crosslinking quickly at the time of passing through the appropriate heating device.

[0016] In the course of this research, the inventors discovered that a sizing composition comprising the specific combination: - at least one lignin, possibly oxidized, and - of at least one non-polymeric polycarboxylic organic acid, presented the desired advantages or properties.

[0017] Thus, the present application more specifically relates to a method for manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder, comprising the following steps: (a) applying a sizing composition to said mineral fibers or said natural organic fibers, (b) the formation of an assembly of said mineral fibers or said natural organic fibers, (c) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens, characterized in that said sizing composition comprises: - at least one lignin, optionally oxidized, and - at least one non-polymeric polycarboxylic organic acid.

[0018] The lignin according to the invention is a biomolecule that is 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. 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 lignin content is 3 to 5% in the leaves, 17 to 24% in the herbaceous stems, 18 to 33% in the woody stems (18 to 25% of the hard wood of angiosperm trees, 27 to 33% of the soft wood of gymnosperm trees). It is less present in annual plants than in perennial plants, it is very present in trees.Lignin is mainly located between cells, but a significant amount is found within them. Although lignin is a complex hydrophobic three-dimensional network, the basic unit is essentially a monolignol unit. After cellulose (constituting 35 to 50% of terrestrial plant biomass) and hemicellulose (30 to 45%), lignin (15 to 25%) forms the third most abundant family of compounds in plants and in terrestrial ecosystems dominated by dead or living plant biomass.

[0019] The lignin 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.

[0020] [Fig. 1] [Fig. 1] shows a possible structure of lignin. We can thus notice that the reactive functional group present in large quantities 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 (a secondary alcohol function being less reactive than a primary alcohol function). It is known that the hydroxyl groups of lignin can react with crosslinking agents such as isocyanates or epoxides, amines or aldehydes leading to a crosslinked structure of 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).

[0021] Thus, the inventors discovered that non-polymeric polycarboxylic acids, which are themselves of low toxicity, could crosslink lignin. Furthermore, they discovered that these non-polymeric polycarboxylic acids, as lignin crosslinking agents, made it possible to bind both mineral fibers and natural organic fibers after hardening or crosslinking of these constituents; also making it possible to obtain insulating products having equally good mechanical performance, or even better mechanical performance, compared to the use of other known crosslinking agents such as formaldehyde or isocyanates.

[0022] In the present application, the term “non-polymeric” organic polycarboxylic acid means an organic polycarboxylic acid which is not a macromolecule consisting of the assembly of monomers having a molar mass of between 90 g.mol1 and 350 g.mol *, linked together by covalent bonds in a repetitive manner. Thus, in the present application the sizing composition is preferably free of polymeric organic polycarboxylic 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 and its derivatives, in particular containing at least one boron or chlorine atom, tetrahydrophthalic acid and its derivatives, 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 chosen from maleic acid, succinic acid, glutaric acid, itaconic acid, and citric acid. Even more preferably, the non-polymeric polycarboxylic organic acid is a tricarboxylic acid, in particular citric acid.

[0023] In other words, it was surprisingly found by the inventors that the Lignin, which is a bio-sourced, inexpensive, non-toxic and low-corrosive material, could, in combination with a non-polymeric, low-toxicity organic polycarboxylic acid, bind mineral fibers or natural organic fibers, after hardening or crosslinking of these constituents; and make it possible to manufacture insulating products with equally good mechanical properties, or even better mechanical performance, than the known and aforementioned binders.

[0024] In one embodiment of the invention, the lignin is diluted in water and the pH is adjusted to between 6.5 and 10.5, preferably between 8 and 9, before the addition of the non-polymeric polycarboxylic organic acid. This pH range allows for a more homogeneous deposition of the sizing composition on the fibers, which consequently has the advantage of improving the mechanical properties of the resulting insulating products.

[0025] Preferably, the sizing composition comprises from 25% to 85% by weight of at least one lignin, and more preferably from 40% to 80% by weight, and even more advantageously from 50% to 75% by weight, relative to the total dry weight of the composition.

[0026] Preferably, the sizing composition comprises from 5% to 75% by weight of at least one non-polymeric polycarboxylic organic acid, and more preferably from 20% to 60% by weight, and even more advantageously from 25% to 50% by weight, relative to the total dry weight of the composition.

[0027] In another preferred embodiment of the process of the invention, the lignin contained in the sizing composition in combination with the non-polymeric polycarboxylic organic acid is an oxidized lignin. In this embodiment, the amount of oxidized lignin is between 50% and 85% by weight, preferably between 55% and 80% by weight, and more preferably between 60% and 75% by weight, relative to the total dry weight of the sizing composition and the oxidized lignin comprises a percentage of carboxylic acid function of between 2% and 20%, preferably between 5% and 15% and a percentage of primary alcohol function of between 2% and 20%, preferably between 5% and 15%.The said percentages of carboxylic acid function and primary alcohol present on the oxidized lignin are measured by infrared spectroscopy; by calculating the ratio of the intensity of the peaks of the C-O bond of the carboxylic acid function (C-OOH) and respectively that of the primary alcohol function (C-OH) of the oxidized lignin compared to the sum of the intensity of the peaks of the C-O bond of all the functions present on the oxidized lignin, all the peaks being located between 1000 cm1 and 1300 cm1. All the functions present on the oxidized lignin having a C-O bond are the following: the primary and secondary alcohol functions (C-OH); the aromatic hydroxyl functions (Ar-OH), the acid functions (C-OOH); aromatic ether (Ar-OC), aliphatic and cycloaliphatic ether (C-OC), and methyl ether (C-OCH3) functions.

[0028] The use of an oxidized lignin (compared to a non-oxidized lignin) has the advantage of reducing the amount of non-polymeric polycarboxylic organic acid to be added to the sizing composition to bind the mineral fibers or the organic fibers. Thus, in this particular embodiment, the amount of non-polymeric polycarboxylic organic acid is between 15% and 50% by weight, preferably between 20% and 45% by weight, and more preferably between 25% and 40% by weight, relative to the total dry weight of the sizing composition.

[0029] Indeed, in the sizing composition comprising the combination of at least one oxidized lignin and at least one non-polymeric polycarboxylic organic acid, the carboxylic acid groups present on the oxidized lignin obtained by splitting the macromolecule then oxidation of the secondary aliphatic hydroxyl groups of the starting lignin will react with some of the aliphatic hydroxyl groups of the oxidized lignin (in particular the primary alcohol functions) during the heating step of the assembly of the fibers initiating self-crosslinking of the oxidized lignin and the other remaining aliphatic hydroxyl groups of the oxidized lignin will then react with the carboxylic acid groups of the non-polymeric polycarboxylic organic acid added as a crosslinking agent to complete the crosslinking of said oxidized lignin.

[0030] Furthermore, the sizing composition according to the invention may be formaldehyde-free. In the present application, the term "formaldehyde-free" means a quantity of formaldehyde of less than 2000 ppm in a sizing composition according to the invention.

[0031] The sizing composition is an aqueous composition which may have a dry matter content of between 0.5% and 50% by weight, preferably between 3% and 30% by weight, and more preferably between 4% and 20% by weight.

[0032] The aqueous sizing composition is, for its part, applied to the mineral fibers or the natural organic fibers, in an amount of between 2% and 20% by weight, preferably between 5% and 15% by weight, said amount being expressed in dry matter relative to the weight of the mineral fibers or the natural organic fibers, in order to give the insulating product the desired mechanical properties.

[0033] In a preferred embodiment of the process of the invention, step (a) 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.

[0034] 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, these may contain a composition corresponding to the formulation following, 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, A12O3: between 10 and 27%, K2O: between 0 and 2%, preferably between 0 and 1%, 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.

[0035] 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, Al2O3, 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%, MgO: between 1 and 10%, preferably between 2 and 5%, CaO and MgO together preferably representing between 5 and 20%, B2O3: between 0 and 10%, preferably between 2 and 8%, A12O3: 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 rest being made up of unavoidable impurities.

[0036] The diameter of the mineral fibers is advantageously between 0.1 and 25 μm.

[0037] The diameter of natural organic fibers is advantageously between 5 and 100 pm, preferably between 10 and 50 pm 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 can have undergone mechanical and / or chemical treatments. These fibers come from plant sources and are advantageously chosen from cotton and lignocellulosic fibers. Lignocellulosic fibers are understood to mean 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, for example hemp, flax, sisal, cotton, jute, coconut, raffia, abaca, or even cereal straw or rice straw.

[0038] The term "lignocellulosic fibers" as used in the present application does not include lignocellulosic materials that have been subjected to thermomechanical or chemical treatments for the purpose of manufacturing paper pulp.

[0039] The lignocellosic 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.

[0040] The lignocellulosic fibers are preferably softwood fibers, in particular pine, obtained by mechanical defibration. 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 10 mm.

[0041] The application of the sizing composition a) preferably precedes step (b) of forming an assembly of mineral fibers or natural organic fibers, during which the sized fibers are gathered together, before being heated consecutively or extemporaneously to harden the sizing composition, thus forming the organic binder which binds the fibers.

[0042] Thus, step b) 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%.

[0043] When the process of the present invention is a continuous process, step b) of The formation of a fiber assembly can be done, for example, by compression using a roller located at the entrance to the cooking oven on a conveyor.

[0044] In addition, the fibers can be assembled: - in flexible fiber mattresses that can be rolled up, compressed or folded, - in fiber plates or panels, denser and more rigid than roll-up mattresses, - in molded fiber-based products, for example conduit or pipe linings, - in woven or non-woven textiles, such as non-woven mats of glass or organic fibers.

[0045] 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 a) and step b), 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 a). This drying step can be carried out by heating, for example in a thermostatically controlled ventilated oven or using a steam heating press. 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 heating temperature close to the boiling point of water is generally sufficient. Drying of the fibers impregnated with aqueous sizing composition is thus preferably carried out by heating to a temperature between 75°C and 150°C, for a duration 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.

[0046] Step (c) of heating the assembly of mineral fibers or natural organic fibers according to the process of the invention is preferably carried out at a temperature of between 100°C and 250°C for a period of between 1 minute and 20 minutes, preferably in a thermo-regulated enclosure or a steam press. In the context of a thermo-regulated 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. During this step of heating the assembly of said mineral fibers or said natural organic fibers, the constituents of the sizing composition (according to the invention) harden / or crosslink / polymerize to form an insoluble organic binder.

[0047] In another particular embodiment of the method according to the invention, the fibers are mineral fibers and after step (c) of heating the assembly of said mineral fibers until the sizing composition hardens, the assembly of mineral fibers has a loss on ignition (LOI) of between 1% and 20%, preferably between 1% and 15% by weight.

[0048] The invention also relates to an insulating product obtainable by the method 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 (as described above) comprising a lignin, optionally oxidized, and a non-polymeric polycarboxylic organic acid. The insulating product obtained has good mechanical properties. The insulating product may have a thickness of between 10 and 300 mm, preferably between 35 and 240 mm, measured according to standard EN 823:2013 and a density of between 30 and 200 kg / m3, preferably between 35 and 180 kg / m3. The insulating product obtained may be used to produce panels for the external insulation of buildings. The insulating product obtained may in particular be a veil of mineral fibers, in particular glass or rock. Examples

[0049] Example 1:

[0050] Aqueous sizing compositions are prepared comprising the constituents listed in Table 1, each expressed as a percentage by weight, relative to the total dry weight of each of the compositions.

[0051] Composition 1, outside the invention (i.e. comparative sample), is prepared by mixing kraft lignin A with water. Compositions 2 to 4, according to the invention, are prepared by mixing a first solution containing lignin A dissolved in water with a second solution containing a particular non-polymeric organic carboxylic acid which is dissolved in water. Compositions 5 and 5a, outside the invention (i.e. comparative sample), are prepared 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.

[0052] All sizing compositions 1 to 5 and 5a contain 90% by weight of water and 10% by weight of dry matter. All compositions are used to form insulating products based on glass fibers.

[0053] Thus, two superimposed pieces (60 mm x 10 mm x 0.250 mm) of non-woven glass fiber papers are impregnated respectively with each of the aqueous sizing compositions, then the glass fiber papers are subsequently hardened. pregnated at a temperature of 150°C for 4 min (for samples 1 to 5) or 210°C for 10 min (for sample 5bis).

[0054] The storage modulus of the samples is measured in three-point bending during cooking by dynamic thermomechanical analysis (DMTA) using a “TA Instruments RSA-G2 Analyzer” device.

[0055] The operating parameters of the measuring device are as follows: Temperature: 25°C Poisson's ratio: 0.45 Duration of oscillatory mechanical stress: 120 seconds Oscillation frequency: 1.0 Hz, Deformation: 0.1% Sampling rate: 10 points / second.

[0056] Table 1 below shows the storage modulus of the glass fiber papers obtained after curing each of the sizing compositions. Each storage modulus value is the average calculated over two to four individual measurement values. Results

[0057] [Tables 1] Sample Glass fiber sizing composition Storage modulus 1 (comp.) 100% lignin A 0.92 GPa 2 (inv.) 50% lignin A + 50% succinic acid 1.18 GPa 3 (inv.) 50% lignin A + 50% glutaric acid 2.69 GPa 4 (inv.) 50% lignin A + 50% citric acid 2.74 GPa 5 (comp.) 150°C, 4 min 100% hydrogenated sugar resin 0.26 GPa 5 bis (comp.) 210°C, 10 min 100% hydrogenated sugar resin 1.18 GPa

[0058] It can be seen that the glass fiber papers prepared in accordance with the invention, i.e. using sizing compositions 2 to 4 comprising the combination of lignin A and a non-polymeric organic polycarboxylic acid, have a storage modulus (between 1.18 GPa and 2.74 GPa) higher than that of the glass fiber papers prepared using sizing composition 1 (0.92 GPa) which comprises a lignin alone (i.e. without crosslinking agent). In addition, It is observed that a higher storage modulus is obtained for the insulating products prepared using the sizing composition comprising lignin A and citric acid (composition 4). It is also observed that the glass fiber papers prepared in accordance with the invention (compositions 2 to 4) exhibit: - a higher conservation modulus than that of glass fiber papers obtained using a well-known thermosetting resin such as hydrogenated sugar-based resin (composition 5, comparative example), or - a conservation modulus of the same order of magnitude as that of glass fibre papers obtained using hydrogenated sugar-based resin, when the temperature and duration of the hardening stage are increased (see example 5a).

[0059] Aqueous sizing compositions are prepared comprising the constituents listed in Table 2, each expressed as a percentage by weight, relative to the total dry weight of each of the compositions.

[0060] Composition 6 (comparative example) is prepared by emulsifying emulsifiable poly(methylene diphenyl isocyanate) (pMDI) with water. Compositions 7 and 8, according to the invention, are prepared by mixing a first solution containing lignin A dissolved in water with a second solution containing succinic acid dissolved in water. Composition 9 (comparative example) is prepared by mixing a first solution containing lignin A dissolved in water with a second solution containing ethylene glycol diglycidyl ether (an epoxide) dissolved in water.

[0061] Sizing composition 6 contains 40% by weight of water and 60% by weight of dry matter. Sizing compositions 7 to 9 contain 90% by weight of water and 10% by weight of dry matter.

[0062] For each test, wood fibers are impregnated with an aqueous sizing composition. The quantity of aqueous sizing compositions 6, 8 and 9 deposited on the wood fibers is equal to 7% by weight expressed as dry matter relative to the weight of the wood fibers. The quantity of aqueous sizing composition 7 deposited on the wood fibers is equal to 10% by weight expressed as dry matter relative to the weight of the wood fibers.

[0063] The impregnated wood fibers are then deposited uniformly in a steel mold having an open cavity of 60 mm x 10 mm x 12 mm. Steel bars of 60 mm x 10 mm x 10 mm are placed on the wood fibers and the assembly is heated for 4 min in a thermostatically controlled press at 150°C and under a pressure of 10 bars. The mold is then allowed to cool to room temperature before removing the test piece of lignocellulosic fibers formed (60 mm x 10 mm x 2 mm).

[0064] The wood fiber specimens thus obtained have a density of approximately 180 kg / m3.

[0065] 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). The operating parameters of the measuring device are the same as those mentioned above.

[0066] Table 2 below shows the storage modulus of the wood fiber specimens obtained after curing each of the sizing compositions. Each storage modulus value is the average calculated over two to four individual measurement values. Results

[0067] [Tables2] Sample Wood fiber sizing composition Composition quantity Storage modulus 6 (comp.) 100% poly(methylene diphenyl isocyanate) 7% 105 MPa 7 (inv.) 50% lignin A + 50% succinic acid 10% 107.6 MPa 8 (inv.) 50% lignin A + 50% succinic acid 7% 50.6 MPa 9 (comp.) 50% lignin A + 50% ethylene glycol diglycidyl ether 7% 30.4 MPa

[0068] It is found that the wood fiber specimens prepared in accordance with the invention, i.e. using the sizing composition 8 comprising the combination of lignin and succinic acid (as a lignin crosslinking agent), have a higher storage modulus (50.6 GPa) than that of the wood fiber specimens prepared using the sizing composition 9 (comparative example) whose lignin crosslinking agent is not a non-polymeric organic carboxylic acid but an epoxide. A storage modulus of the same order of magnitude is obtained for the wood fiber specimens prepared using the known sizing composition 6 and the sizing composition 7 according to the invention with a higher quantity of sizing composition on said fibers.

[0069] In conclusion, Tables 1 and 2 show that a lignin in combination with a non-polymeric organic carboxylic acid makes it possible to bind both mineral fibers and natural organic fibers and also makes it possible to obtain insulating products with equally good mechanical properties, or even better mechanical properties than those obtained using known sizing compositions.

[0070] Example 2:

[0071] Lignin B is taken and the quantity of carboxylic acid functions and primary alcohol functions present on said lignin is determined by infrared spectroscopy by measuring the intensity of the peak of the C-OOH bond of the carboxylic acid function at approximately 1190 cm 1 and that of the C-OH bond of the primary alcohol function at approximately 1040 cm1, relative to the sum of the intensity of the peaks of the CO bond, located between 1000 cm 1 and 1300 cm1, of all the functions present on said lignin B. All the functions present on lignin B having a C-O bond are the following: the primary and secondary alcohol functions (C-OH); the aromatic hydroxyl functions (Ar-OH), the acid functions (C-OOH); the aromatic ether functions (Ar-OC), aliphatic and cycloaliphatic ether (C-OC), and methyl ether (C-OCH3).

[0072] Then, the same measurements are carried out on lignin B which is previously oxidized under the following conditions: in aqueous solution at pH >13 with H2O2 + FeCl3 as oxidizing agent for 120 min at 95°C. In this case, all the functions present on the oxidized lignin B having a C-O bond are the following: the primary and secondary alcohol functions (C-OH); the aromatic hydroxyl functions (Ar-OH), the acid functions (C-OOH); the aromatic ether functions (Ar-OC), aliphatic and cycloaliphatic ether (C-OC) and methyl ether (C-OCH3).

[0073] Two sizing compositions 10 and 11 are then prepared respectively by mixing lignin B and oxidized lignin B dissolved in water with succinic acid dissolved in water. These sizing compositions are deposited on wood fibers in order to manufacture wood fiber panel specimens according to the method described in Example 1. The flexural storage modulus of said wood fiber specimens obtained is measured by dynamic thermomechanical analysis (DMTA) as explained in Example 1.

[0074] Table 3 shows the results obtained for each of the sizing compositions.

[0075] [Tables3] Lignin B composition Sizing composition Storage modulus in (MPa) Primary C-OH function Acid C-OOH function Lignin Succinic acid Lignin B Composition 10 14% < 1% 50% 50% 50.6 Lignin B Composition 10 14% < 1% 62.5% 37.5% 25.0 Oxidized lignin B Composition 11 10% 11% 62.5% 37.5% 49.5 Oxidized lignin B Composition 11 10% 11% 50% 50% 23.8

[0076] It can be seen that the use of oxidized lignin B which contains more carboxylic acid functions than “non-oxidized” lignin B (11% for oxidized lignin compared to <1% for “non-oxidized” lignin) makes it possible to reduce the quantity of succinic acid to be added (37.5% when oxidized lignin is used compared to 50% when “non-oxidized” lignin is used) to obtain a sizing composition whose final insulating product has an equivalent storage modulus.

Claims

Claims

1. A method of manufacturing an insulation product comprising mineral fibers or natural organic fibers bound by an organic binder, comprising the following steps: (a) applying a sizing composition to said mineral fibers or said natural organic fibers, (b) forming an assembly of said mineral fibers or said natural organic fibers, (c) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens to form the organic binder, characterized in that said sizing composition comprises: - at least one lignin, optionally oxidized, and - at least one non-polymeric polycarboxylic organic acid.

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

3. A method according to claim 1 or 2, wherein the amount of lignin is between 25% and 85% by weight, preferably between 40% and 80% by weight, relative to the total dry weight of the sizing composition.

4. A method according to claim 3, wherein the amount of non-polymeric polycarboxylic organic acid is between 15% and 75% by weight, preferably between 20% and 60% by weight, relative to the total dry weight of the sizing composition.

5. Process according to claim 1 or 2, in which the lignin is an oxidized lignin and its quantity is between 50% and 85% by weight, preferably between 55% and 80% by weight, relative to the total dry weight of the sizing composition, and in which the oxidized lignin comprises a percentage of carboxylic acid function between 2% and 20%, preferably between 5% and 15%, and a percentage of primary alcohol function between 2% and 20%, preferably between 5% and 15%.

6. A method according to claim 5, wherein the amount of non-polymeric organic polycarboxylic acid is between 15% and 50% by weight, preferably between 20% and 45% by weight, relative to the total dry weight of the sizing composition.

7. A method according to any one of the preceding claims, wherein the non-polymeric organic polycarboxylic acid is selected 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 and its derivatives, in particular containing at least one boron or chlorine atom, tetrahydrophthalic acid and its derivatives, in particular containing at least one chlorine atom, isophthalic acid, terephthalic acid, mesaconic acid and citraconic, tricarboxylic acids, including citric acid, tricar-ballylic acid, 1,2,4-butanetricarboxylic acid, aconitic acid,hemimellitic acid, trimellitic acid and trimesic acid, and tetracarboxylic acids, including 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.,

8. A method according to any preceding claim, wherein the mineral fibers are glass fibers or rock fibers or slag fibers, or mixtures thereof.

9. A method according to any one of the preceding claims, wherein the natural organic fibers are chosen from wood, hemp, linen, sisal, cotton, jute, coconut, raffia, abaca, or cereal straw or rice straw.

10. A method according to any one of the preceding claims, such that the application of said sizing composition of step a) to the mineral fibers or natural organic fibers is carried out by spraying, roller coating or impregnation.

11. Method according to any one of the preceding claims, characterized in that the assembly of mineral fibers or natural organic fibers during step b) is a fiber mat, a fiber plate or panel, a molded fiber-based product, or a woven or non-woven textile.

12. A method according to any one of the preceding claims, characterized in that step (c) comprises heating said assembly of fibers to a temperature between 100°C and 250°C. for a period of between 1 and 20 minutes, preferably in a temperature-controlled enclosure or steam press.

13. Insulating product obtained by a process according to any one of the preceding claims comprising mineral fibers or natural organic fibers and an organic binder obtained by hardening a sizing composition comprising at least one lignin, optionally oxidized, and a non-polymeric polycarboxylic organic acid.

14. Insulating product according to claim 13 characterized in that it is a veil of mineral fibers.