Lignin-based aqueous sizing composition for binding natural organic fibers or mineral fibers

Abstract

The present invention relates to an aqueous sizing composition for binding natural organic fibers or mineral fibers, characterized in that it comprises: - at least one lignin, - at least one organic polycarboxylic acid, - at least one salt of a hydroxycarboxylic 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 wherein 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 wherein 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. The present invention also relates to the method for manufacturing an insulation product comprising natural organic fibers or mineral fibers which uses the aforementioned aqueous sizing composition, and to an insulation product obtainable by such a method.

Description

[0001] Description

[0002] Title: Waterborne lignin-based sizing composition for bonding mineral or natural organic fibers

[0003] The present invention relates to an aqueous 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 aqueous 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.

[0004] 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 cross-linking said aqueous lignin-based sizing composition. Furthermore, the invention relates to the insulation products obtained by such a method.

[0005] 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):

[0006] - 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

[0007] - 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.

[0008] In general, esterification reactions between an alcohol and a carboxylic acid are favored by increasing the temperature or by using a catalyst.

[0009] 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.

[0010] 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. These bonds 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 the application and heating of said sizing composition onto bonded mineral or natural organic fibers. The resulting polymeric network allows for the establishment of bonds at the fiber junctions during the manufacture of insulating products.

[0011] Thus, sizing 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).

[0012] Applications WO 2010 / 029266 A1 and WO 2018 / 134544 A1 described 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. However, these phosphorus-based catalysts are expensive, toxic to humans, and can harm aquatic life.

[0013] Furthermore, the two aforementioned types of catalysts (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). This 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 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.

[0014] 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

[0015] Polyol-OH + HOP(O)H2^ Polyol-OP(O)H2+ H2O Polyol-P(O)(OH)H + H2O

[0016] The side reaction with a catalyst (cat.) such as an alkali salt of a carboxylic acid (denoted R'-COOX) can be described as follows: HOOC-R-COOH + R'-COOX → HOOC-R-COO X + + R'-COOH (acidic form of the catalyst)

[0017] Polyol-OH + R'-COOH Polyol-OC(=O)-R' + H2O

[0018] Indeed, since the aforementioned catalysts are monofunctional species (meaning 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-OC(=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.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 an aqueous sizing composition.

[0019] Thus, the aim of the invention is to provide an aqueous sizing composition, which is capable of thermal crosslinking, to form an organic binder with an optimal crosslinking density, allowing both natural organic fibers and mineral fibers to be bonded together, in order to obtain insulating products with improved mechanical properties.

[0020] In the course of this research, the inventors discovered that using a specific catalyst, such as a salt of a hydroxylated carboxylic acid of formula (I) or (II) below, in an aqueous sizing composition comprising at least one lignin and at least one polycarboxylic acid, prevented side reactions; in other words, this type of catalyst prevented the interruption of polymerization between at least one lignin and at least one polycarboxylic acid. According to the invention, the salt of a hydroxylated carboxylic acid has the general formula (I): HO-(C)R 1 R 2 -(CH2)n-COOX, or of general formula (II): (HO-(C)R 1 R 2 -(CH2)n-COO)2Y, in which

[0021] R 1 is a hydrogen atom, or a methyl group CHs or an alkyl group of formula (A): -(CH2) P -CH3 in which p is an integer between 0 and 6, and

[0022] R 2is 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

[0023] X is an element chosen from among sodium, potassium, and lithium, and

[0024] Y is an element chosen from among calcium, magnesium, beryllium and zinc.

[0025] 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 possessing both an alcohol functional group (a hydroxyl group -OH) and a carboxylic acid functional group (a carboxyl group -COOH). The inventors discovered that, according to the present invention, the hydroxylated carboxylic acid, by virtue of these two types of functional groups, can react with lignin, not only with hydroxyl groups of lignin according to reaction (1) but also with carboxyl groups of lignin according to reaction (2) as follows:

[0026] HOOC-R-COOH + HO-R'-COOX (cat.) HOOC-R-COO + + HO-R'-COOH

[0027] (1) Lignin-OH + HO-R'-COOH Lignin-OC(=O)-R'-OH + H2O

[0028] Lignin-OC(=O)-R'-OH + HOOC-R-COOH or HOOC-R-COO +or Lignin-COOH and

[0029] (2) Lignin-COOH + HO-R'-COOH Lignin-C(=O)-O-R'-COOH + H2O

[0030] Lignin-C(=O)-O-R'-COOH + HO-R'-COOX or HO-R'-COOH or Lignin-OH — —

[0031] 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:

[0032] - either hydroxyl groups (Lignin-OC(=O)-R'-OH) (1 ),

[0033] - either carboxyl groups (Lignin-C(=O)-O-R'-COOH) (2), which can in turn react further:

[0034] - either with at least one polycarboxylic acid (in salt form or not) (1 ),

[0035] - either with at least one hydroxylated carboxylic acid (in salt form or not) (2),

[0036] - either with a lignin (1) and (2); the polymerization reactions between the lignin and at least one polycarboxylic acid can thus continue.

[0037] Furthermore, the inventors observed that insulating products made from the specific aqueous sizing composition described above exhibited superior 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 attributed to the optimal crosslinking density of the organic binder obtained from the aqueous sizing composition comprising the aforementioned specific reagents, and especially thanks to the catalyst of a hydroxylated carboxylic acid salt of formula (I) or (II).

[0038] Thus, the present application relates more specifically to an aqueous sizing composition for bonding mineral or natural organic fibers, characterized in that it comprises the specific combination:

[0039] - at least one lignin,

[0040] - at least one polycarboxylic organic acid,

[0041] - at least one salt of a hydroxylated carboxylic acid: of general formula (I): HO-(C)R 1 R 2 -(CH2)n-COOX, or of general formula (II): (HO-(C)R 1 R 2 -(CH2)n-COO)2Y, in which

[0042] R 1 is a hydrogen atom, or a methyl group CHs or an alkyl group of formula (A): -(CH2) P -CH3 in which p is an integer between 0 and 6, and

[0043] R 2 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

[0044] X is an element chosen from among sodium, potassium, and lithium, and

[0045] Y is an element chosen from among calcium, magnesium, beryllium and zinc.

[0046] 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 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.

[0047] The amount of salt of a hydroxylated carboxylic acid of formula (I) or (II) introduced into the aqueous sizing composition may 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%. 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 polymeric macromolecules (the tannin family in the broad sense), and which is one of the main components of wood along with cellulose and hemicellulose. Native lignin is a macromolecule having a molar mass much greater than 10,000 g / mol. 1and is not soluble in water. Native lignin is found primarily in vascular plants and 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, and 18 to 33% in woody stems (18 to 25% of the hardwood in angiosperm trees, 27 to 33% of the softwood in gymnosperm trees). It is less abundant in annual plants than in perennial plants, and very abundant in trees. Native lignin is mainly located between cells, but a significant amount is also found within the cells themselves.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.

[0048] Lignin, according to the invention, is a macromolecule whose possible structure is shown in Figure 1 [Fig. 1]. Lignin, according to the invention, is extracted by cleaving the [3-O-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 between 1000 g. mol' 1 and 9,000 g. mol' 1 .

[0049] The lignin according to the invention can be selected from alkali lignins, also known as kraft lignins, lignosulfonates, organosolv lignins, sodium lignins, lignins obtained from the biorefining of lignocellulosic raw materials, or a mixture thereof. The four groups of lignins available on the market are alkali or kraft lignins, lignosulfonates, 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 known as kraft lignin. Furthermore, lignin can be oxidized lignin.

[0050] 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 most abundant reactive functional group in 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.

[0051] In the aqueous 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.

[0052] According to the invention, at least one lignin reacts with at least one polyfunctional crosslinking agent that is a polycarboxylic organic acid. The polycarboxylic organic acid can be a "non-polymeric" or "polymeric" acid.

[0053] According to a first embodiment, the polycarboxylic organic acid is a "non-polymeric" polycarboxylic organic acid. In this 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 / mol. 1 and 350 g. mol' 1 linked together by repetitive covalent bonds.

[0054] Preferably, polycarboxylic acids chosen from the group consisting of dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids will be used.

[0055] 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 atom of boron or chlorine, tetrahydrophthalic acid and its derivatives, in particular containing at least one atom of chlorine 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, aconitic acid, hemimellitic acid, trimellitic acid and trimesic acid.Tetracarboxylic acids include, for example, 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.

[0056] Even more preferably, the non-polymeric polycarboxylic organic acid is chosen from maleic acid, succinic acid, glutaric acid, itaconic acid and citric acid.

[0057] 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.

[0058] Examples of polymeric polycarboxylic organic acids include 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, and α,p-methyleneglutaric acid; monoesters of unsaturated dicarboxylic acids, such as C1-C10 alkyl maleates and fumarates; 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, or (meth)acrylamide. by alkyl groups in C1-C10, the alkyl (meth)acrylates, notably 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.

[0059] According to another embodiment, the aqueous sizing composition comprises at least one non-polymeric polycarboxylic organic acid, optionally mixed with at least one polymeric polycarboxylic organic acid.

[0060] In the aqueous 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.

[0061] The sizing composition according to the invention is an aqueous composition that may contain from 70 to 99% by weight of water, preferably from 70 to 95% by weight, more preferably from 80 to 95%, and even more preferably from 85 to 90% by weight. In other words, the aqueous sizing composition may have a dry matter content of between 1 and 30% by weight, preferably between 5 and 30% by weight, more preferably between 5 and 20%, and even more preferably between 10 and 15% by weight. 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 aqueous sizing composition.

[0062] Preferably, the sizing composition has a pH between 1 and 6, preferably between 2 and 5, at 10% by weight in aqueous solution.

[0063] 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.

[0064] The preparation of the gluing composition is preferably carried out by simply mixing the aforementioned constituents.

[0065] This application also relates to a method for manufacturing an insulation product comprising mineral fibers or natural organic fibers bonded by an organic binder, using an aqueous sizing composition according to the invention.

[0066] This process includes the following steps:

[0067] (a) the application of an aqueous sizing composition as described above to said mineral fibers or said natural organic fibers,

[0068] (b) the formation of an assembly of said mineral fibres or said natural organic fibres bonded together, and

[0069] (c) heating the assembly of said mineral fibers or said natural organic fibers until said sizing composition hardens to form the organic binder. In this application, the term "sizing composition" means considerably less concentrated aqueous solutions or dispersions having a dry matter content of 30% or less by weight, preferably between 1 and 30% by weight, in particular between 5 and 30% by weight, more particularly between 5 and 20%, and even more particularly between 10 and 15% by weight. They have sufficiently low viscosities to permit their application to the natural organic fibers or to the mineral fibers by spraying through 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 assembly of said fibers.

[0070] In a preferred embodiment of the process of the invention, step (a) of applying the aqueous 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.

[0071] The aqueous sizing composition is applied to the mineral 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 or natural organic fibers, in order to give the insulating product the desired mechanical properties.

[0072] The mineral fibers, according to the invention, are preferably mineral wools and even more preferably glass wool, rock wool, or slag wool, 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% combined, Al2O3: between 10 and 27%.

[0073] 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.

[0074] Mineral fibers can be glass fibers or rock fibers, particularly basalt (or wollastonite). More specifically, the mineral fibers according to the invention are aluminosilicate glass fibers, particularly aluminosilicate glass fibers comprising aluminum oxide, Al₂O₃, in a mass fraction of between 10% and 27%. In another embodiment, the mineral fibers can be glass fibers containing a composition conforming to the following formulation, expressed as a percentage by weight:

[0075] SiÛ2: between 50 and 75%, preferably between 60 and 70%,

[0076] Na2O: between 10 and 25%, preferably between 10 and 20%,

[0077] CaO: between 5 and 15%, preferably between 5 and 10%,

[0078] MgO: between 1 and 10%, preferably between 2 and 5%,

[0079] CaO and MgO together preferably represent between 5 and 20%,

[0080] B2O3: between 0 and 10%, preferably between 2 and 8%,

[0081] AI2O3: between 0 and 8%, preferably between 1 and 6%,

[0082] K2O: between 0 and 5%, preferably between 0.5 and 2%,

[0083] Na2O and K2O together preferably represent between 12 and 20%,

[0084] Iron oxide: between 0 and 3%, preferably less than 2%, preferably even less than 1%, other oxide(s): between 0 and 5% by weight cumulatively, preferably less than 3% cumulatively, the remainder being made up of unavoidable impurities.

[0085] The diameter of the mineral fibers is advantageously between 0.1 and 25 µm.

[0086] The diameter of the natural organic fibers is advantageously between 5 and 100 µm, preferably between 10 and 50 µm. The natural organic fibers according to the invention are advantageously 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 fibers of plant origin based on lignocellulosic material, that is, 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, cereal straw, or rice straw.

[0087] 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.

[0088] 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.

[0089] The lignocellulosic fibers are preferably softwood fibers, particularly pine, obtained by mechanical defibration. Their diameter is advantageously between 10 and 70 µm, preferably between 30 and 50 µm.

[0090] The application of the aqueous sizing composition a) preferably precedes step (b) of forming an assembly of mineral fibers or natural organic fibers, during which the sizing fibers are gathered together, before being heated consecutively or extemporaneously to harden the sizing composition thus forming the organic binder which binds the fibers.

[0091] Thus, step b) of forming an assembly of mineral 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 box. The wire mesh box is preferably filled with a volume of loose fibers exceeding its capacity and is then closed with a wire mesh lid. The fibers are thus compressed to a greater or lesser degree depending on the excess volume of the filling.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%.

[0092] 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.

[0093] Furthermore, the fibers can be assembled:

[0094] - in flexible fiber mattresses that can be rolled up, compressed or folded,

[0095] - in sheets or panels of fibers, denser and more rigid than roll-up mattresses,

[0096] - in molded fiber-based products, for example duct or pipe linings,

[0097] - in woven or non-woven textiles, such as non-woven mats of glass or organic fibers.

[0098] 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 process 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 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 encased in a sheath of dried sizing.

[0099] 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 fluid-circulating or heating element mold.During this heating stage of 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.

[0100] 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.

[0101] 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 an aqueous 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 an aqueous sizing composition without a catalyst or using an aqueous sizing composition employing an alkali salt of a strong acid or an alkali salt of a carboxylic acid as a catalyst.The insulating product can have a thickness of between 10 and 400 mm, preferably between 35 and 240 mm, measured according to standard EN 823:2013 and a density of between 5 and 200 kg / m³. 3 , preferably between 8 and 180 kg / m 3 The resulting insulating product can be used to make panels for exterior and interior building insulation. This insulating product can be, in particular, a mineral fiber veil, such as glass or rock wool. Consequently, the resulting insulating product can be a thermal and / or acoustic insulator. Examples

[0102] In all examples, the lignin used is a kraft lignin marketed under the name Lignova™.

[0103] Example No. 1: Manufacturing of wood fiber test specimens

[0104] Aqueous sizing compositions are prepared as follows:

[0105] - Composition 1, outside the scope of this 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 (dicarboxylic acid) dissolved in water; the weight percentage being relative to the total weight of the mixture consisting of the lignin and succinic acid. The sizing composition 1 therefore contains no catalyst.

[0106] - Composition 1 bis, outside the scope of this invention (i.e., comparative sample (comp.)), is prepared by mixing 50% by weight of lignin dissolved in water with 50% by weight of citric acid (tricarboxylic acid) dissolved in water; the weight percentage being relative to the total weight of the mixture consisting of the lignin and citric acid. The sizing composition 1 bis therefore contains no catalyst.

[0107] - 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 catalyst) is added in powder form relative to the total weight of the lignin and succinic acid,

[0108] - 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,

[0109] - 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 of general formula (I)) is added in aqueous solution form relative to the total weight of the lignin and succinic acid,

[0110] - 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 of general formula (I)) is added in powder form, relative to the total weight consisting of lignin and succinic acid,

[0111] - composition 6, according to the invention: in an aqueous solution / dispersion of lignin and citric acid in a weight ratio of 50 / 50, 9% by weight of sodium lactate (catalyst of general formula (I)) is added in the form of aqueous solution relative to the total weight constituted by the lignin and citric acid.

[0112] All aqueous sizing compositions 1, 1 bis, 2, 3, 4 and 6 contain 88% by weight of water and 12% by weight of dry matter and have a pH between 3 and 3.5.

[0113] 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.

[0114] The impregnated wood fibers are then deposited uniformly in a steel mold with an open cavity measuring 60 mm x 10 mm x 12 mm. Steel bars measuring 60 mm x 10 mm x 10 mm are placed on top of the wood fibers, and the assembly is heated for 10 minutes in a thermostatically controlled press at 150°C and under a pressure of 10 bar. The mold is then allowed to cool to room temperature before removing the resulting lignocellulosic fiber specimen (60 mm x 10 mm x 2 mm).

[0115] The wood fibre test specimens thus obtained have a density of approximately 180 kg / m³ 3 .

[0116] 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).

[0117] The operating parameters of the measuring device are as follows: Temperature: 25 °C Poisson's ratio: 0.45

[0118] Duration of the oscillatory mechanical stress: 120 seconds

[0119] Oscillation frequency: 1.0 Hz, Deformation: 0.1%

[0120] Sampling rate: 10 points / second.

[0121] 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 measurements.

[0122] Results

[0123] [Table 1]

[0124] It is observed that the gluing composition 4, according to the invention, specifically comprising: lignin, succinic acid (dicarboxylic 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:

[0125] - insulating products obtained using a catalyst-free adhesive composition (composition 1, 41 MPa), or

[0126] - insulating products obtained using a gluing composition employing HPS as a catalyst, which is an alkali salt of a strong acid (composition 2.84 MPa),

[0127] - insulating products obtained using a gluing composition using sodium propionate as a catalyst, which is an alkali salt of carboxylic acid (composition 3.95 MPa).

[0128] It is also noted that the gluing composition 6, according to the invention, specifically comprising: lignin, citric acid (tricarboxylic acid) and sodium lactate which is a salt of a particular hydroxylated carboxylic acid, makes it possible to obtain wood fiber-based insulating products with better mechanical properties (90 MPa) compared to insulating products obtained using a gluing composition without a catalyst (composition 1 bis, 46 MPa).

[0129] Example No. 2: Manufacturing of wood fiber test specimens

[0130] Other wood fiber test specimens are manufactured according to the same protocol as that described in example No. 1 but using different wood fibers and a higher lignin particle size and by impregnation with sizing compositions prepared as follows:

[0131] - Composition w, outside the scope of this 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 (non-polymeric dicarboxylic acid) dissolved in water; the weight percentage being relative to the total weight of the mixture consisting of the lignin and succinic acid. The sizing composition w therefore contains no catalyst.

[0132] - the composition x, 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 of general formula (I)) is added in aqueous solution form relative to the total weight of the lignin and succinic acid,

[0133] - the composition y, 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 calcium lactate (catalyst of general formula (II)) is added in aqueous solution form relative to the total weight of the lignin and succinic acid, and

[0134] - the composition z: in an aqueous solution / dispersion of lignin and polyacrylic acid (polymeric acid) in a weight ratio of 50 / 50, 9% by weight of sodium lactate (catalyst of general formula (I)) is added in aqueous solution form relative to the total weight of lignin and polyacrylic acid.

[0135] The flexural strength modulus (three-point bending) measured by dynamic thermomechanical analysis (DMTA) is identical to that described in Example 1, and the results are shown in Table 1 bis below. This table shows the strength modulus of the wood fiber specimens obtained after curing of each of the sizing compositions. Each strength modulus value is the average calculated from two to four individual measurements.

[0136] [Table 1 bis]

[0137] It is observed that the aqueous sizing compositions x and y, according to the invention, specifically comprising: lignin, succinic acid and sodium lactate which is a salt of a particular hydroxylated carboxylic acid of general formula (I) (monovalent salt) or calcium lactate which is a salt of a particular hydroxylated carboxylic acid of general formula (II) (divalent salt), makes it possible to obtain wood fiber-based insulating products exhibiting better mechanical properties (73 MPa and 85 MPa respectively) compared to insulating products obtained using a sizing composition without a catalyst (composition w, 47 MPa).

[0138] Furthermore, when succinic acid, a non-polymeric polycarboxylic organic acid, is replaced by polyacrylic acid, a polymeric polycarboxylic organic acid (composition x / composition z), the resulting wood fiber-based insulation products also exhibit very good mechanical properties (composition z, 123 MPa). Example No. 3: Manufacture of fiberglass paper

[0139] Compositions 1, 1 bis to 6, as previously described in Example No. 1, are then used to form insulating products based on glass fibers.

[0140] Two other aqueous sizing compositions, according to the invention, are prepared as follows:

[0141] - Composition 7: In an aqueous solution / dispersion of lignin and citric acid in a 50 / 50 weight ratio, 9% by weight of calcium lactate (catalyst of general formula (II)) is added as an aqueous solution relative to the total weight of the lignin and citric acid, and

[0142] - Composition 8: In an aqueous solution / dispersion of lignin and polyacrylic acid (polymeric acid) in a weight ratio of 50 / 50, 9% by weight of sodium lactate (catalyst of general formula (I)) is added in aqueous solution form relative to the total weight of lignin and polyacrylic acid.

[0143] In the following tests, all aqueous sizing compositions 1, 1 bis to 8 contain 91% by weight of water and 9% by weight of dry matter and have a pH between 3 and 3.5.

[0144] To achieve this, two overlapping 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.

[0145] 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.

[0146] Table 2 below shows the preservation modulus of the fiberglass papers obtained after curing each of the sizing compositions. Each preservation modulus value is the average calculated from two to four individual measurements. Results

[0147] [Table 2]

[0148] It is observed that the aqueous sizing compositions 4 and 5, according to the invention, specifically comprising: lignin, succinic acid (dicarboxylic acid) and sodium lactate or sodium glycolate, which are particular hydroxylated carboxylic acid salts of general formula (I) according to the invention, make it possible to obtain glass fiber-based insulating products exhibiting better mechanical properties (124 and 145 MPa respectively) in comparison:

[0149] - insulating products obtained using a catalyst-free adhesive composition (composition 1, 35 MPa), or

[0150] - insulating products obtained using a sizing composition employing HPS as a catalyst, which is an alkali salt of a strong acid (composition 2.108 MPa), or

[0151] - insulating products obtained using a gluing composition using sodium propionate as a catalyst, which is an alkali salt of carboxylic acid (composition 3.107 MPa).

[0152] It is also noted that aqueous sizing compositions 6 and 7, according to the invention, specifically comprising: lignin, citric acid (tricarboxylic acid) and sodium lactate which is a salt of a particular hydroxylated carboxylic acid of general formula (I) (monovalent salt) or calcium lactate which is a salt of a particular hydroxylated carboxylic acid of general formula (II) (divalent salt), makes it possible to obtain insulating products based on glass fibers exhibiting better mechanical properties (511 MPa and 391 MPa respectively) compared to insulating products obtained using a sizing composition without catalyst (composition 1 bis, 360 MPa).

[0153] Also, it is observed that when non-polymeric polycarboxylic organic acid such as succinic acid or citric acid in a gluing composition (compositions 4 or 6) is replaced by a polymeric polycarboxylic organic acid such as polyacrylic acid, the resulting glass fiber-based insulating products also exhibit very good mechanical properties (composition 8, 280 MPa).

Claims

Demands 1. Aqueous 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)R 1 R 2 -(CH2)n-COOX, or of general formula (II): (HO-(C)R 1 R 2 -(CH2)n-COO)2Y, in which R 1 is a hydrogen atom, or a methyl group CHs or an alkyl group of formula (A): -(CH2) P -CH3 in which p is an integer between 0 and 6, and R 2 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 among sodium, potassium, and lithium, and Y is an element chosen from among calcium, magnesium, beryllium and zinc.

2. Aqueous sizing 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 bio-refining process of lignocellulosic raw materials or a mixture thereof.

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

4. Aqueous sizing 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 acid, and tetracarboxylic acids, in particular 1,2,3,4-butanetetracarboxylic acid and pyromellitic acid.

5. Aqueous gluing 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. Aqueous sizing 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. Water-based sizing composition according to any one of the preceding claims, characterized in that it contains from 70 to 99% by weight of water.

8. Aqueous 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. Aqueous sizing 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. Aqueous sizing 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 process for manufacturing an insulation product comprising mineral fibers or natural organic fibers bonded by an organic binder, said process comprising the following steps: (a) the application of an aqueous sizing composition according to any one of claims 1 to 10 on 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.

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 steam press.

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

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