Lignin-based sizing composition for bonding mineral or natural organic fibers

Abstract

The present invention relates to a sizing composition for bonding mineral fibers or natural organic fibers, characterized in that it comprises: - at least one lignin, - at least one polycarboxylic organic acid, - at least one salt of a hydroxylated carboxylic acid: of general formula (I): HO−(C)R1R2−(CH2)n−COOX, or of general formula (II): (HO−(C)R1R2−(CH2)n−COO)2Y, in which R1 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): –(CH2)p−CH3, where p is an integer between 0 and 6, and R2 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): –(CH2)p−CH3, where p is an integer between 0 and 6. and 6, and n is an integer between 0 and 2, and X is an element chosen from sodium, potassium and lithium, and Y is an element chosen from calcium, magnesium, beryllium and zinc.The present invention also relates to the method of manufacturing an insulation product comprising mineral fibers or natural organic fibers which uses the aforementioned gluing composition, as well as an insulation product that can be obtained by such a method.

Description

Title of the invention: Lignin-based sizing composition for bonding mineral or natural organic fibers

[0001] The present invention relates to a sizing composition comprising at least one lignin, at least one polycarboxylic organic acid, and at least one salt of a hydroxylated carboxylic acid as a specific catalyst. This sizing composition, capable of thermal crosslinking to form an organic binder, allows for the bonding of both natural organic fibers and mineral fibers during the application of insulation products.

[0002] Thus, the invention also relates to a method for manufacturing insulation products comprising mineral fibers or natural organic fibers bonded by an organic binder obtained by hardening or crosslinking said aqueous lignin-based sizing composition. Furthermore, the invention relates to the insulation products obtained by such a method.

[0003] It is known from patent application WO 2023 / 111465 A1 in the name of the Applicant to use a sizing composition containing at least one lignin and at least one non-polymeric polycarboxylic organic acid to manufacture insulation products based on mineral fibers or natural organic fibers. In this application, it is described that during the step of heating the sizing composition onto the fibers to form the organic binder (in other words, during the crosslinking or hardening step of said sizing composition): - Esterification reactions occur between some of the alcohol functions, and in particular the aliphatic hydroxyl groups of lignin (denoted Lignin-OH), and some of the carboxyl groups of the non-polymeric polycarboxylic organic acid(s) (denoted HOOC-R-COOH), leading to the formation of water and a lignin ester as follows: Lignin-OC(=O)-COOH, but also - Esterification reactions between some of the hydroxyl groups of the aliphatics of lignin (noted Lignin-OH) and some of the carboxyl groups of the lignin itself (noted Lignin-COOH) can also take place, leading to the formation of water and an "other" lignin ester as follows: Lignin-OC(=O)-Lignin.

[0004] In general, esterification reactions between an alcohol and a carboxylic acid are favoured by increasing the temperature or by using a catalyst.

[0005] In particular, when it comes to an esterification reaction between a polyol and at least one polycarboxylic acid, it is known to use as a catalyst, a strong acid or an alkali salt of a strong acid (such as an alkali metal hypophosphite salt) or an alkali salt of a carboxylic acid in order to dehydrate the carboxylic functions of the polycarboxylic acid thus forming a cyclic anhydride which accelerates the polymerization reaction between the carboxylic acid now an anhydride and the polyol; the catalyst is also regenerated.

[0006] Thus, in a sizing composition comprising at least one polyol, at least one polycarboxylic acid, and at least one such catalyst, the carboxyl groups of one or more polycarboxylic acids are capable of reacting with the hydroxyl groups of at least one polyol to form ester bonds that lead to the formation of a polymeric network in the final organic binder after hardening and / or crosslinking of the sizing composition. This occurs during the manufacture of insulating products, after application and heating of said sizing composition onto assembled mineral or natural organic fibers. The polymeric network formed allows for the establishment of bonds at the fiber junction points during the manufacture of insulating products.

[0007] Thus, gluing compositions have been proposed comprising a polyol, a polycarboxylic polymer and a catalyst, which catalyst is a catalyst containing phosphorus (US 5 318 990, US 5 661 213, US 6331 350, US 2003 / 0008978), a fluoroborate (US 5 977 232) or a cyanamide, a dicyanamide or a cyanoguanidine (US 5 932 689).

[0008] In applications WO 2010 / 029266 Al and WO 2018 / 134544 Al, sizing compositions comprising a hydrogenated sugar (as a polyol), polycarboxylic organic acids (capable of reacting with the hydroxyl groups of the hydrogenated sugar), in the presence of a catalyst, such as an alkali salt of a strong acid, preferably sodium hypophosphite or a strong acid, preferably hypophosphorous acid.

[0009] However, these phosphorus-based catalysts are expensive, toxic to humans and can harm aquatic fauna.

[0010] Furthermore, the two types of catalysts mentioned above (alkali salts of strong acids and alkaline salts of carboxylic acids) can also, through a side reaction, react themselves with the polyol (instead of the polycarboxylic acid), in their acidic form (i.e., after exchanging hydrogen atom(s) with the polycarboxylic acid), which leads to a halt in the elongation of the polymer chain between the hydroxyl groups of the polyol and the carboxyl groups of the polycarboxylic acid. The catalyst is then no longer regenerated. This side reaction induces a change in the stoichiometry between the polyol and the polycarboxylic acid during This involves the crosslinking and / or polymerization of an adhesive composition previously applied to fibers and then heated. In other words, the crosslinking density is reduced, resulting in a decrease in the mechanical performance of the resulting insulating products.

[0011] The side reaction with a catalyst (cat.) such as an alkali salt of a strong acid like sodium hypophosphite can be described as follows: HOOC-R-COOH + NaOP(O)H2 -> HOOC-R-COO Na+ + HOP(O)H2 Polyol-OH + HOP(O)H2^ Polyol-OP(O)H 2+ H2O -> Polyol-P(O)(OH)H + H2O

[0012] The side reaction with a catalyst (cat.) such as an alkali salt of carboxylic acid (denoted R'-COOX) can moreover be described as follows: HOOC-R-COOH + R'-COOX -> HOOC-R-COOX++ R'-COOH (acid form of the catalyst) Polyol-OH + R'-COOH -> Polyol-OC(=O)-R'+ H2O

[0013] Indeed, since the aforementioned catalysts are monofunctional species (i.e., they can only react once), if they react according to the side reaction described above, they are not regenerated and the elongation of the polymer chain between the hydroxyl groups of the polyol and the carboxyl groups of the polycarboxylic acid is halted (formation of Polyol-OP(O)H2 or Polyol-O-C(=O)-R', which are compounds without hydroxyl or carboxyl groups). In this case, the formation of the polymer network in the final binder after hardening and / or crosslinking of the adhesive composition is therefore not optimal; the crosslinking density is even reduced, thus lowering the mechanical properties of the resulting insulating products.

[0014] The inventors therefore sought bio-based, biodegradable, non-toxic, inexpensive catalysts capable of not carrying out parasitic reactions, i.e. capable of promoting esterification and polymerization reactions between at least one polycarboxylic organic acid and at least one particular polyol such as a lignin; such reagents being contained in a sizing composition.

[0015] Thus, the object of the invention is to provide a gluing composition, which is capable of thermally crosslinking, to form an organic binder having an optimal crosslinking density, allowing to bind together both natural organic fibers and mineral fibers, in order to obtain insulating products having improved mechanical properties.

[0016] In the course of this research, the inventors discovered that the use of a specific catalyst, such as a salt of a hydroxylated carboxylic acid of formula (I) or (II) below, in a sizing composition comprising at least one lignin and at least one polycarboxylic acid, made it possible to avoid side reactions, In other words, this type of catalyst prevented the polymerization between at least one lignin and at least one polycarboxylic organic acid from being stopped. According to the invention, the salt of a hydroxylated carboxylic acid is: of general formula (I): HO-(C)R1R2-(CH2)n-COOX, or of general formula (II): (HO-(C)R1R2-(CH2)n-COO)2Y, in which R1 is a hydrogen atom, or a methyl group CH3 or an alkyl group of formula (A): -(CH2)p-CH3 in which p is an integer between 0 and 6, and R2 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): -(CH2)p-CH3 in which p is an integer between 0 and 6, and n is an integer between 0 and 2, and X is an element chosen from sodium, potassium, and lithium, and Y is an element chosen from calcium, magnesium, beryllium, and zinc.

[0017] More specifically, a salt of a hydroxylated carboxylic acid (which can be generally denoted for better understanding as "HO-R'-COOX") can, after the exchange of a hydrogen atom "H" with a polycarboxylic acid, lead to a hydroxylated acid having both an alcohol functional group (a hydroxyl group -OH) and a carboxylic acid functional group (a carboxyl group -COOH). The inventors have discovered that, according to the present invention, the hydroxylated carboxylic acid, by virtue of these two types of functional groups, can react with lignin, but not only with hydroxyl groups of lignin according to reaction (1) but also with carboxyl groups of lignin according to reaction (2) as follows: HOOC-R-COOH + HO-R'-COOX (cat.) -> HOOC-R-COO (2) Lignin-COOH + HO-R'-COOH -> Lignin-C(=O)-O-R'-CO OH + H2O Lignin-C(=O)-O-R'-COOH + HO-R'-COOX or HO-R'-COOH or Lignin-OH—>—>

[0018] Thus, the inventors observed that in each of the reactions (1) and (2), the functionality of the grafted lignin, corresponding to a "new" ester lignin formed, remained unchanged since each of the grafted lignins obtained could contain: - either hydroxyl groups (Lignin-OC(=O)-R'-OH) (1), - either carboxyl groups (Lignin-C(=O)-O-R'-CO OH) (2), which can in turn react further: - either with at least one polycarboxylic acid (in salt form or not) (1), - or with at least one hydroxylated carboxylic acid (in salt form or not) (2), - or with a lignin (1) and (2); polymerization reactions between lignin and at least one polycarboxylic acid can thus continue.

[0019] Furthermore, the inventors observed that insulating products made from the particular sizing composition described above exhibited better mechanical properties compared to insulating products obtained using a sizing composition without a catalyst or using a sizing composition employing an alkali salt of a strong acid or an alkali salt of a carboxylic acid as a catalyst. Indeed, without wishing to be bound by any particular theory, this improvement in mechanical properties could be due to the optimal crosslinking density of the organic binder obtained from the sizing composition comprising the aforementioned particular reagents, and especially thanks to the catalyst of a salt of a hydroxylated carboxylic acid of formula (I) or (II).

[0020] Thus, the present application relates more specifically to a sizing composition for bonding mineral fibers or natural organic fibers characterized in that it comprises the specific combination of: - at least one lignin, - at least one polycarboxylic organic acid, - at least one salt of a hydroxylated carboxylic acid: of general formula (I): HO-(C)R1R2-(CH2)n-COOX, or of general formula (II): (HO-(C)R1R2-(CH2)n-COO)2Y, in which R1 is a hydrogen atom, or a methyl group CH3 or an alkyl group of formula (A): -(CH2)p-CH3 in which p is an integer between 0 and 6, and R2 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): -(CH2)p-CH3 in which p is an integer between 0 and 6, and n is an integer between 0 and 2, and X is an element chosen from sodium, potassium, and lithium, and Y is an element chosen from calcium, magnesium, beryllium, and zinc.

[0021] According to the invention, the hydroxylated carboxylic acid of the salt of formula (I) (monovalent salt) or of formula (II) (divalent salt), as defined above, can be chosen from the group consisting of: glycolic acid, lactic acid, mandelic acid, 3-hydroxybutyric acid, 3-hydroxypentanoic acid, 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid, [3-hydroxy [3-methylbutyric acid and 4-hydroxybutanoic acid.

[0022] The amount of salt of a hydroxylated carboxylic acid of formula (I) or (II) introduced into the sizing composition can represent from 3 to 15% of the weight of the mixture consisting of the lignin and the polycarboxylic organic acid, preferably from 5 to 10%.

[0023] The lignin according to the invention is a lignin extracted from so-called "native" lignin, which is a biomolecule belonging to a family of polyphenolic polymer macromolecules (the tannin family in the broad sense), and is one of the main components of wood, along with cellulose and hemicellulose. Native lignin is a macromolecule with a molar mass much greater than 10,000 g / mol and is not soluble in water. Native lignin is found primarily in vascular plants and in some algae. Its main functions are to provide rigidity, water impermeability, and high resistance to decomposition. All vascular plants, both 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, but is very abundant in trees. Native lignin is mainly located between cells, but a significant amount is also found within them. 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.

[0024] Lignin, according to the invention, is a macromolecule, one possible structure of which is shown in [Fig. 1]. Lignin, according to the invention, is extracted by cleaving the [3-0-4] ether bonds of native lignin and therefore has a lower molar mass than that of the native lignin from which it is derived, i.e., an average molar mass of less than 10,000 g.mol1, preferably a molar mass between 1,000 g.mol1 and 9,000 g.mol1.

[0025] The lignin, according to the invention, can be selected from alkali lignins, also called kraft lignins, lignosulfonates, organosolv lignins, sodium lignins, lignins from a biorefining process of lignocellulosic raw materials, or a mixture thereof. The four groups of lignins available on the market are alkali or kraft lignins, lignosulfonates, the Organosolv lignins (extracted lignins and sodium lignins). The fifth group is so-called biorefinery lignin, which is somewhat different because it is not described by its extraction process, but rather by the origin of the process, e.g., biorefining, and it can therefore be similar to or different from any of the other groups mentioned. The lignin, according to the invention, is preferably alkali lignin, also called kraft lignin. Furthermore, the lignin can be oxidized 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 or secondary alcohol function.

[0027] In the sizing composition, lignin can represent from 40 to 80% of the weight of the mixture consisting of lignin and polycarboxylic organic acid, preferably from 50 to 70% by weight.

[0028] According to the invention, at least one lignin reacts with at least one polyfunctional crosslinking agent which is a polycarboxylic organic acid. The polycarboxylic organic acid may be a "non-polymeric" or "polymeric" acid.

[0029] According to a first embodiment, the polycarboxylic organic acid is a "non-polymeric" polycarboxylic organic acid. In the present application, a "non-polymeric" polycarboxylic organic acid is understood to be a polycarboxylic organic acid that is not a macromolecule consisting of an assembly of monomers having a molar mass between 90 g.mol1 and 350 g.mol1, linked together by repetitive covalent bonds.

[0030] Preferably, polycarboxylic acids chosen from the group consisting of dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids will be used.

[0031] Dicarboxylic acids are, for example, chosen from the group formed by 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 such as chlorendic acid, isophthalic acid, terephthalic acid, mesaconic acid and citraconic acid. Tricarboxylic acids are, for example, chosen from the group formed by citric acid, tricarballylic acid, 1,2,4-butanetricarboxylic acid, and... aconitic acid, hemimellitic acid, trimellitic acid, and trimesic acid. Tetracarboxylic acids include, for example, 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.

[0032] Even more preferably, the non-polymeric polycarboxylic organic acid is chosen from maleic acid, succinic acid, glutaric acid, itaconic acid and citric acid.

[0033] According to a second embodiment, the polycarboxylic organic acid is a "polymeric" polycarboxylic organic acid. The polymeric organic acids according to the invention can be homopolymers of unsaturated carboxylic acid and copolymers of at least one unsaturated carboxylic acid and at least one vinyl monomer.

[0034] By way of example of a polymeric polycarboxylic organic acid, one may cite homopolymers of unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, maleic acid, cinnamic acid, 2-methylmaleic acid, fumaric acid, itaconic acid, 2-methylitaconic acid, α,3-methyleneglutaric acid and monoesters of unsaturated dicarboxylic acids, such as alkyl maleates and fumarates in the C1-C10 group, and copolymers of at least one of the aforementioned unsaturated carboxylic acids and at least one vinyl monomer such as styrene substituted or not with alkyl, hydroxyl or sulfonyl groups, or with a halogen atom, (meth)acrylonitrile, the (meth)acrylamide or not by alkyl groups in C1-C1, the alkyl (meth)acrylates, in particular methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate and isobutyl (meth)acrylate, glycidyl (meth)acrylate,Butadiene and a vinyl ester, in particular vinyl acetate.

[0035] According to another embodiment, the sizing composition comprises at least one non-polymeric polycarboxylic organic acid, optionally mixed with at least one polymeric polycarboxylic organic acid.

[0036] In the sizing composition, the polycarboxylic organic acid can represent from 20 to 60% of the weight of the mixture consisting of lignin and the polycarboxylic organic acid, preferably from 30 to 50% by weight.

[0037] The sizing composition according to the invention is an aqueous composition that may contain from 70 to 95% by weight of water, preferably between 80 and 95%, and even more preferably between 80 and 80% by weight of water. Lignin, the polycarboxylic organic acid, and the salt of a hydroxylated carboxylic acid of formula (I) or (II) may together represent at least 90%, preferably at least 95%, of the solid matter of the sizing composition.

[0038] Preferably, the sizing composition has a pH between 1 and 6, preferably between 2 and 5, at 10% by weight in aqueous solution.

[0039] Furthermore, the aqueous gluing composition according to the invention can be formaldehyde-free. For the purposes of this application, "formaldehyde-free" means an amount of formaldehyde less than 2000 ppm in an aqueous gluing composition according to the invention.

[0040] The preparation of the gluing composition is preferably carried out by simply mixing the aforementioned constituents.

[0041] The present application also relates to a method of manufacturing an insulation product comprising mineral fibers or natural organic fibers bonded by an organic binder, using a sizing composition according to the invention.

[0042] This process comprises the following steps: (a) the application of a sizing composition as described above to said mineral fibers or said natural organic fibers, (b) the formation of an assembly of said mineral fibres or said natural organic fibres bonded together, and (c) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens to form the organic binder.

[0043] In this application, the term "sizing composition" refers to considerably less concentrated aqueous solutions or dispersions having a dry matter content of 30% by weight or less, preferably between 5% and 30% by weight, in particular between 5% and 20% by weight, and even more particularly between 1% and 20% by weight. They have sufficiently low viscosities to allow their application to natural organic or mineral fibers by spraying with nozzles or by impregnation. Also, in this application, "organic binder" means an insoluble binder obtained by hardening (or crosslinking) the aqueous sizing composition previously applied to the fibers during the heating step of the fiber assembly.

[0044] 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.

[0045] The aqueous sizing composition is applied to the mineral fibers or natural organic fibers in a quantity of between 2 and 20% by weight, preferably between 5 and 15% by weight, said quantity being expressed in 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.

[0046] The mineral fibers, according to the invention, are preferably mineral wools and even more preferably glass wool, rock wool or slag wool, or mixtures of these. In particular, when the mineral fibers are mineral wools, these may contain a composition corresponding to the following formulation, as a 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% combined, Al2O3: 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% cumulatively, preferably less than 3%, the remainder being unavoidable impurities.

[0047] Mineral fibers can be glass fibers, or rock fibers, particularly basalt (or wollastonite). 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 10% and 27%.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 to 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%, Al2O3: 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%, preferably even 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.

[0048] The diameter of the mineral fibers is advantageously between 0.1 and 25 pm.

[0049] The diameter of natural organic fibers is advantageously between 5 and 100 pm, preferably between 10 and 50 pm. Natural organic fibers, according to The invention advantageously refers to non-thermoplastic fibers that occur naturally in biomass and may have undergone mechanical and / or chemical treatments. These fibers originate from plant sources and are advantageously selected from cotton and lignocellulosic fibers. "Lignocellulosic fibers" are defined as plant-based fibers composed of lignocellulosic material, that is, 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, or rice straw.

[0050] The term "lignocellulosic fibres" 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.

[0051] 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.

[0052] 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.

[0053] 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 sizing fibers are brought together, before being heated consecutively or extemporaneously to harden the sizing composition thus forming the organic binder which binds the fibers.

[0054] Thus, step b) of forming an assembly of mineral fibers or natural organic fibers, which can also be called the fiber assembly shaping step, 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 that allows the hot air from the curing oven to easily penetrate the molded product. The mold can, for example, be made of a wire mesh in the shape of a box. The wire mesh box is preferably filled with a volume of loose fibers greater than its capacity and is then closed with a wire mesh lid. The fibers are thus more or less compressed depending on the excess volume of the filling.This excess volume of fiber filling in the cavity is, for example, between 10% and 150%, preferably between 15% and 100%, and in particular between 20% and 80%.

[0055] When the process of the present invention is a continuous process, step b) of forming a fiber assembly can be done for example by compression using a roller located at the entrance of the baking oven on a conveyor.

[0056] Furthermore, the fibers can be assembled: - in flexible fiber mattresses that can be rolled up, compressed or folded, - in fiber sheets or panels, denser and more rigid than rollable mattresses, - in molded fiber-based products, for example duct or pipe linings, - in woven or non-woven textiles, such as non-woven mats of glass or organic fibers.

[0057] In a particular embodiment of the process according to the invention, the fibers are natural organic fibers impregnated with an aqueous sizing composition, and the process further comprises, between steps a) and b), a fiber drying step intended to evaporate sufficient water to render the sizing or unsizing fibers substantially non-sticky. In another embodiment, the drying step may be carried out before step a). This drying step may be performed by heating, for example in a thermostatically controlled ventilated oven or using a steam press. It is important to ensure that the drying does not raise the temperature of the natural organic fibers too high, which would result in the softening of the dried sizing composition or even the beginning of cross-linking of the components of the sizing composition.A heating temperature close to the boiling point of water is generally sufficient. Drying of fibers impregnated with aqueous sizing composition is therefore preferably carried out by heating at a temperature between 70°C and 150°C for a duration of between 1 and 10 seconds. The natural organic fibers obtained after the drying step are surrounded by a sheath of dried sizing composition.

[0058] Step (c) of heating the fiber assembly according to the process of the invention is preferably carried out, when dealing with natural organic fibers, at a temperature between 90°C and 170°C, preferably between 100°C and 160°C, for a duration of between 1 and 30 minutes, and when dealing with mineral fibers, at a temperature between 170°C and 250°C, preferably between 180°C and 210°C, for a duration of between 1 and 10 minutes, advantageously in a temperature-controlled chamber or a steam press. In the case of a temperature-controlled chamber, this may be a forced-air oven in which hot gases of controlled temperature are introduced into one or more compartments, or a heating mold with fluid circulation or a heating element. During this step of heating the assembly of said mineral fibers or of said natural organic fibers, the constituents of the gluing composition (according to the invention) harden / or crosslink / polymerize to form an insoluble organic binder.

[0059] In another particular embodiment of the process according to the invention, the fibers are mineral fibers and after step (c) of heating the assembly of said mineral fibers until hardening of the sizing composition, the assembly of mineral fibers exhibits a loss on ignition (LOI) of between 1% and 20%, preferably between 1% and 15% by weight.

[0060] The invention also relates to an insulating product obtainable by the process described above. This insulating product comprises mineral fibers or natural organic fibers bonded with a binder obtained by hardening or crosslinking a sizing composition (as described above) comprising lignin, a polycarboxylic organic acid, and a salt of a hydroxylated carboxylic acid of formula (I) or formula (II). The resulting insulating product exhibits improved mechanical properties compared to an insulating product obtained using a sizing composition without a catalyst or using a sizing composition employing as a catalyst an alkali salt of a strong acid or an alkali salt of a carboxylic acid.The insulating product can have a thickness between 10 and 400 mm, preferably between 35 and 240 mm, measured according to standard EN 823:2013, and a density between 5 and 200 kg / m³, preferably between 8 and 180 kg / m³. The resulting insulating product can be used to make panels for the exterior and interior insulation of buildings. The insulating product may, in particular, be a mineral fiber veil, notably glass or rock wool. The resulting insulating product can therefore be a thermal and / or acoustic insulating product.

[0061] Examples In all examples, the lignin used is a kraft lignin marketed under the name Lignova™.

[0062] Example No. 1: Manufacture of wood fiber test specimens. Aqueous sizing compositions are prepared as follows: - Composition 1, outside the scope of the invention (i.e., comparative sample (comp.)), is prepared by mixing 50% by weight of lignin dissolved in water with 50% by weight of succinic acid dissolved in water; the weight percentage being relative to the total weight of the mixture consisting of the lignin and succinic acid. Sizing composition 1 therefore contains no catalyst, - Composition 2, outside the scope of the invention (i.e., comparative sample): in an aqueous solution / dispersion of lignin and succinic acid in a weight ratio of 50 / 50 9% by weight of sodium hypophosphite (noted as "HPS" as a catalyst) is added in powder form relative to the total weight of lignin and succinic acid, - composition 3, outside the scope of the invention (i.e., comparative sample): in an aqueous solution / dispersion of lignin and succinic acid in a weight ratio of 50 / 50, 9% by weight of sodium propionate (catalyst) is added in powder form relative to the total weight of the lignin and succinic acid, - composition 4, according to the invention: in an aqueous solution / dispersion of lignin and succinic acid in a weight ratio of 50 / 50, 9% by weight of sodium lactate (catalyst) is added in aqueous solution form relative to the total weight of the lignin and succinic acid, - composition 5, according to the invention: in an aqueous solution / dispersion of lignin and succinic acid in a weight ratio of 50 / 50, 9% by weight of sodium glycolate (catalyst) in powder form is added, relative to the total weight of the lignin and succinic acid.

[0063] All sizing compositions 1 to 5 contain 88% by weight of water and 12% by weight of dry matter and have a pH of approximately 3.5.

[0064] For each test, wood fibers are impregnated with an aqueous sizing composition. The quantity of aqueous compositions deposited on the wood fibers is equal to 10% by weight expressed as dry matter relative to the weight of the wood fibers.

[0065] 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 10 minutes in a press thermostatically controlled at 150°C and under a pressure of 10 bar. The mold is then allowed to cool to room temperature before removing the specimen of formed lignocellulosic fibers (60 mm x 10 mm x 2 mm).

[0066] The wood fibre test specimens thus obtained have a density of approximately 180 kg / m3.

[0067] The flexural strength modulus (three-point bending) is then determined for each specimen by dynamic thermomechanical analysis (DMTA) using a TA Instruments RSA-G2 Analyzer. The samples are first dried for several hours in a dynamic vacuum dryer (20 mbar).

[0068] The operating parameters of the measuring device are as follows: Temperature: 25 °C Poisson's ratio: 0.45 Duration of the oscillatory mechanical stress: 120 seconds Oscillation frequency: 1.0 Hz, Deformation: 0.1% Sampling rate: 10 points / second.

[0069] Table 1 below shows the storage modulus of the wood fiber specimens obtained after hardening of each of the sizing compositions. Each storage modulus value is the average calculated from two to four individual measurement values. Results

[0070] Sample Catalyst Preservation Module 1 (comp-) without catalyst 41 MPa 2 (cpmp,) HPS 84 MPa 3 (cpmpj sodium propionate 95 MPa 4 (inv.) sodium lactate 152 MPa

[0071] It is observed that the gluing composition 4, according to the invention, specifically comprising: lignin, succinic acid and sodium lactate, which is a salt of a particular hydroxylated carboxylic acid, makes it possible to obtain wood fiber-based insulating products exhibiting better mechanical properties (152 MPa) in comparison: - insulating products obtained using a catalyst-free adhesive composition (composition 1.41 MPa), or - insulating products obtained using a gluing composition using HPS as a catalyst, which is an alkali salt of a strong acid (composition 2.84 MPa), - insulating products obtained using a gluing composition using sodium propionate as a catalyst, which is an alkali salt of a carboxylic acid (composition 3.95 MPa).

[0072] Example No. 2: Manufacture of glass fiber papers

[0073] Compositions 1 to 5, as previously described, are then used to form glass fiber-based insulating products. In the following tests, all sizing compositions 1 to 5 contain 91% by weight of water and 9% by weight of dry matter and have a pH of approximately 3.5.

[0074] To this end, two superimposed pieces (60 mm x 10 mm x 0.250 mm) of non-woven glass fiber paper are impregnated with each of the aqueous sizing compositions, and then the impregnated glass fiber papers are cured at a temperature of 210°C for 4 minutes. The quantity of aqueous compositions deposited on the glass fibers is equal to 10% by weight, expressed as dry matter relative to the weight of the glass fibers.

[0075] The sample preservation module is measured in three-point bending during cooking by dynamic thermomechanical analysis (DMTA) using a TA Instruments RSA-G2 Analyzer. The operating parameters of the measuring device are the same as those mentioned above.

[0076] Table 2 below shows the preservation modulus of the glass fiber papers obtained after hardening of each of the sizing compositions. Each preservation modulus value is the average calculated from two to four individual measurement values. Results Sample Catalyst Preservation Module 1 (comp.) without catalyst 35 MPa 2 (comp.) HPS 108 MPa 3 (cpmp.) sodium propionate 107 MPa 4 (inv.) sodium lactate 124 MPa 5 (inv.) sodium glycolate 145 MPa

[0078] It is observed that the gluing compositions 4 and 5, according to the invention, specifically comprising: lignin, succinic acid and sodium lactate or sodium glycolate, which are salts of particular hydroxylated carboxylic acids, make it possible to obtain insulating products based on glass fibers exhibiting better mechanical properties (124 and 145 MPa respectively) in comparison: - insulating products obtained using a catalyst-free adhesive composition (composition 1.35 MPa), or - insulating products obtained using a gluing composition using HPS as a catalyst, which is an alkali salt of a strong acid (composition 2, 108 MPa), or - insulating products obtained using a gluing composition using sodium propionate as a catalyst, which is an alkali salt of a carboxylic acid (composition 3, 107 MPa).

Claims

Demands

1. A sizing composition for bonding mineral or natural organic fibers, characterized in that it comprises: - at least one lignin, - at least one polycarboxylic organic acid, - at least one salt of a hydroxylated carboxylic acid: of general formula (I): HO-(C)R1R2-(CH2)n-COOX, or of general formula (II): (HO-(C)R1R2-(CH2)n-COO)2Y, wherein R1 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): -(CH2)p-CH3, in which p is an integer from 0 to 6, and R2 is a hydrogen atom, or a methyl group CH3, or an alkyl group of formula (A): -(CH2)p-CH3, in which p is an integer from 0 to 6, and n is an integer from 0 to 6. 2, and X is an element chosen from sodium, potassium and lithium, and Y is an element chosen from calcium, magnesium, beryllium and zinc.

2. A gluing composition according to claim 1, characterized in that the lignin is selected from alkaline lignins, also called Kraft lignins, lignosulfonates, organosolv lignins, sodium lignins, lignins from a biorefining process of lignocellulosic raw materials or a mixture thereof.

3. Adhesive composition according to claim 1 or 2, characterized in that the polycarboxylic organic acid is a non-polymeric polycarboxylic acid.

4. A gluing composition according to any one of the preceding claims, characterized in that the polycarboxylic organic 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, 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, and tetracarboxylic acids, including 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.

5. Adhesive composition according to any one of claims 1 to 2, characterized in that the polycarboxylic organic acid is a polymeric polycarboxylic acid, in particular selected from homopolymers of unsaturated carboxylic acid and copolymers of at least one unsaturated carboxylic acid and at least one vinyl monomer.

6. A gluing composition according to any one of the preceding claims, characterized in that the hydroxylated carboxylic acid of the salt of formula (I) or (II) is selected from the group consisting of: glycolic acid, lactic acid, mandelic acid, 3-hydroxybutyric acid, 3-hydroxypentanoic acid, 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid, [3-hydroxy [3-methylbutyric acid and 4-hydroxybutanoic acid.

7. A gluing composition according to any one of the preceding claims, characterized in that it contains from 70 to 95% by weight of water.

8. A gluing composition according to any one of the preceding claims, characterized in that it has a pH between 1 and 6, preferably between 2 and 5, at 10% by weight in aqueous solution.

9. A gluing composition according to any one of the preceding claims, characterized in that the lignin represents from 40 to 80% of the weight of the mixture consisting of the lignin and the polycarboxylic organic acid, preferably from 50 to 70%.

10. A gluing composition according to any one of the preceding claims, characterized in that the salt of a hydroxylated carboxylic acid of formula (I) or (II) represents from 3 to 15% of the weight of the mixture consisting of lignin and the polycarboxylic organic acid, preferably from 5 to 10%.

11. A method for manufacturing an insulation product comprising mineral fibers or natural organic fibers bonded by an organic binder, said method comprising the following steps: (a) applying a sizing composition according to any one of claims 1 to 10 to said mineral fibers or natural organic fibers, (b) forming an assembly of said bonded mineral fibers or natural organic fibers, and (c) heating the assembly of said mineral fibers or natural organic fibers until said sizing composition hardens to form the organic binder.

12. A method according to claim 11, wherein the mineral fibers are glass fibers or rock fibers or slag fibers, or mixtures thereof.

13. A method according to claim 11, wherein the natural organic fibers are selected from wood fibers, hemp, flax, sisal, cotton, jute, coconut, raffia, abaca, or even cereal straw or rice straw.

14. A method according to any one of claims 11 to 13, characterized in that step (c) comprises heating said natural organic fiber assembly to a temperature between 90°C and 170°C for a period of between 1 minute and 30 minutes or heating said mineral fiber assembly to a temperature between 170°C and 250°C for a period of between 1 and 10 minutes, preferably in a temperature-controlled chamber or a steam press.

15. Insulation product obtainable by a process according to any one of claims 11 to 14.