AQUEOUS ADHESIVE COMPOSITION CONTAINING A HEAT-SETTING RESIN AND AMMONIUM SALTS

Abstract

The invention relates to an aqueous adhesive composition, comprising a thermosetting resin based on: - at least one aromatic compound A1 comprising at least one aromatic ring bearing at least two functions, one of these functions being an aldehyde or a hydroxymethyl function, the other being an aldehyde or a hydroxymethyl function; - at least one aromatic polyphenol A2 comprising at least one aromatic ring bearing at least two hydroxyl functions in meta positions relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted; and in that the aqueous adhesive composition comprises an ammonium salt at a mass percentage of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.05.

Description

Title of the invention: AQUEOUS ADHESIVE COMPOSITION COMPRISING A THERMOCURRING RESIN AND AMMONIUM SALTS

[0001] The field of the present invention relates to aqueous adhesive compositions intended for adhering elements, the use and the method of manufacturing such a composition, the method of assembling elements using these compositions as well as the assemblies manufactured using these compositions.

[0002] Phenoplasts or "phenol-formaldehyde resins" (PF) are derived from formaldehyde and phenol. Since phenol is a molecule with several reactive sites, a three-dimensional network is ultimately formed. Phenoplasts are used in particular as adhesives, for example in the manufacture of chipboard or composite materials reinforced with glass fibers, textile fibers, etc.

[0003] In the field of wood, a phenol-aldehyde type composition is described in US2360376. This composition comprises a phenol-aldehyde resin based on formaldehyde and phenol. The molar ratio of formaldehyde to phenol is in a range of values ​​from 2 to 3.5. This composition is used in a process for gluing plywood articles comprising several wooden plies. During this process, one or more plies are coated with a layer of the composition, the plies are joined together via the layer of composition and the plies thus joined are pressure-cured. The glued assembly thus obtained has high cohesion thanks to the excellent adhesive properties of the composition.

[0004] However, the use of formaldehyde (or formalin), which is moreover in excess compared to phenol, leads to the release of formaldehyde not only during pressure cooking but also during storage and use of the bonded assembly. However, due to recent changes in regulations, in particular European regulations on this type of compound, it is desirable to limit as much as possible, or even eliminate the use of formaldehyde or formaldehyde precursors.

[0005] In its application WO2017 / 168109, the Applicant proposed aqueous adhesive compositions for bonding wood, comprising a thermosetting resin based on phloroglucinol and 5-(hydroxymethyl)-furfural, having high adhesive properties and free of formaldehyde.

[0006] However, the hot reactivity of phenolic resins is an important characteristic for the productivity of manufacturing based on these resins both for the reduction of cooking time and for the stability of the composition. A hot reactivity A greater heat reactivity will lead to a reduction in the cooking time under the heating press. It is all the more interesting to be able to obtain this greater heat reactivity without affecting the storage stability of the composition.

[0007] The aim of the invention is to provide an aqueous adhesive composition, comprising a thermosetting resin, having high adhesive properties, free of formaldehyde, and offering a higher hot reactivity than the adhesive composition of document WO2017 / 168109 without penalizing the lifetime of the adhesive composition and thus providing greater flexibility of use.

[0008] However, during its research, the Applicant discovered an aqueous adhesive composition not using free formaldehyde, very reactive when hot, which makes it possible to meet the above objective.

[0009] Thus, an object of the invention relates to an aqueous adhesive composition comprising a thermosetting resin based on: - at least one aromatic compound Al comprising at least one aromatic nucleus carrying at least two functions, one of these functions being an aldehyde function or a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function; - at least one aromatic polyphenol A2 comprising at least one aromatic nucleus carrying at least two hydroxyl functions in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted; and in that the aqueous adhesive composition comprises an ammonium salt at a mass content of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.05.

[0010] The Applicant thus hypothesizes that the addition of the ammonium salt as an activator at a given rate will make it possible to increase the hot reactivity without, however, altering the lifetime of the aqueous adhesive composition or the processing qualities of the composition. This will result in a reduction in the gelling time of the resin at a given temperature, here at a temperature above 70°C for example. Thus, this reduction in the gelling time leads to a reduction in the curing time of the resins under a heating press and a reduction in the energy consumption associated with curing.

[0011] Preferably, the ammonium salt has a mass content of dry extract in the adhesive composition of less than or equal to 0.03, preferably less than or equal to 0.02.

[0012] Preferably, the ammonium salt is at a mass content of dry extract of the adhesive composition greater than or equal to 0.003 and preferably greater than or equal to 0.005.

[0013] Over this range of ammonium salt concentrations, the hot reactivity is optimal and the lifetime of the composition allows greater flexibility of use.

[0014] Another subject of the invention relates to the use of the aqueous adhesive composition according to the invention, for bonding at least two cellulosic elements, advantageously at least two wooden elements.

[0015] The invention also relates to a method of gluing two cellulosic elements, advantageously two wooden elements, in which: - a layer of the aqueous adhesive composition as defined above is applied to at least one of the elements, and, - the elements are joined together using a layer of aqueous adhesive composition.

[0016] The invention also relates to a bonded assembly of two elements comprising a layer of the aqueous adhesive composition as defined above joining at least one of the elements to the other.

[0017] The invention and its advantages will be easily understood in light of the following description.

[0018] I - FORMULATION OF THE AQUEOUS ADHESIVE COMPOSITION

[0019] In the present description, unless expressly indicated otherwise, all percentages (%) indicated are % by mass.

[0020] By "position meta relative to each other", it is meant that the functions in question, for example the hydroxyl functions in the aromatic polyphenol, are carried by carbons of the aromatic nucleus separated from each other by a single other carbon of the aromatic nucleus.

[0021] By "position para to each other" it is meant that the functions referred to are opposite each other, i.e. in positions 1 and 4 of the 6-membered aromatic ring. Similarly, "the position para" to a function is a position opposite the function on the 6-membered aromatic ring carrying the function.

[0022] By "in the ortho position of a function" is meant the position occupied by the carbon of the aromatic ring immediately adjacent to the carbon of the aromatic ring bearing the function. Similarly, "the ortho position" with respect to a function is the position adjacent to the function on the aromatic ring bearing the function.

[0023] By "member" of a ring is meant a constituent atom of the skeleton of the ring. Thus, for example, a benzene ring comprises six members, each member being constituted by a carbon atom. In another example, a furan ring comprises five members, four members each being constituted by a carbon atom and the remaining member being constituted by an oxygen atom.

[0024] “CHO” represents the aldehyde function.

[0025] “CH2OH” represents the hydroxymethyl function.

[0026] “Compound Al” designates, within the framework of the invention, the aromatic compound defined in paragraph 1.1.

[0027] “Compound A2” designates, within the framework of the invention, the compound based on aromatic polyphenol defined in paragraph 1.2.

[0028] The ammonium salt is defined in paragraph 1.3.

[0029] By “aromatic polyphenol” is meant an aromatic compound comprising at least one benzene nucleus carrying more than one hydroxyl function.

[0030] In the context of the invention, the carbon products mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass.

[0031] Within the framework of the invention, it may also be envisaged that the carbon products mentioned in the description comprise isotopes of certain chemical elements.

[0032] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (i.e., limits a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e., including the strict limits a and b).

[0033] By the expression "composition based on", it is of course necessary to understand a composition comprising the mixture and / or the reaction product of the different basic constituents used for this composition, some of which may be intended to react or capable of reacting with each other or with their close chemical environment, at least in part, during the different phases of manufacture of the composition, the textile material, the composites or finished articles comprising such composites, in particular during a cooking step.

[0034] The aqueous adhesive composition according to the invention therefore comprises at least one (i.e. one or more) thermosetting resin according to the invention, this thermosetting resin is based on at least one (i.e. one or more) aromatic compound, at least one (i.e. one or more) aromatic polyphenol, and the aqueous adhesive composition comprises an ammonium salt, constituents which will be described in detail below.

[0035] According to the invention, the basic constituents of the aqueous adhesive composition therefore comprise at least one compound Al, at least one compound A2 and at least one ammonium salt. In one embodiment, the basic constituents may comprise other additional constituents different from the compound Al, the compound A2 and the ammonium salt. In another embodiment, the basic constituents consist of at least one compound Al, at least one compound A2 and at least one ammonium salt.

[0036] Preferably, in the embodiment where the base constituents comprise other additional constituents, these other additional constituents are free of formaldehyde and / or free of methylene donor selected from the group consisting of hexa-methylenetetramine (HMT), hexamethoxymethylmelamine (H3M), hexaethoxymethylmelamine, lauryloxymethylpyridinium chloride, ethoxymethylpyridinium chloride, hexamethoxymethylmelamine polymers of formaldehyde trioxane, rhexakis(methoxymethyl)melamine, N,N',N"-trimethyl / -N,N',N"-trimethylolmelamine, hexamethylolmelamine, N-methylolmelamine, N,N'-dimethylolmelamine, N,N',N"-tris(methoxymethyl)melamine, N,N',N"-tributyl-N,N',N"-trimethylolmelamine. More preferably, these other additional constituents are free of formaldehyde and free of the methylene donors described in this paragraph.

[0037] More preferably, in the embodiment where the basic constituents comprise other additional constituents, these other additional constituents are free of formaldehyde and / or free of methylene donor chosen from the group consisting of hexamethylenetetramine, hexaethoxymethylmelamine, hexamethoxymethylmelamine, lauryloxymethylpyridinium chloride, ethoxymethylpyridinium chloride, trioxane hexamethoxymethylmelamine and N-substituted oxymethylmelamines corresponding to the general formula: / wœ \ F; / Fs

[0038] in which Q represents an alkyl group containing from 1 to 8 carbon atoms; F1, F2, F3, F4 and F5 are selected, independently of one another, from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 8 carbon atoms, the group -CH2OQ and their condensation products. More advantageously, these other additional constituents are free of formaldehyde and free of the methylene donors described in this paragraph.

[0039] Even more preferably, in the embodiment where the constituents of base include other additional constituents, these other additional constituents are free of formaldehyde and / or free of methylene donor. More advantageously, these other additional constituents are free of formaldehyde and free of methylene donors.

[0040] By formaldehyde-free or methylene donor-free, it is meant that the total mass content of formaldehyde or of the methylene donor(s) belonging to the groups described above by total weight of the compound(s) Al in the basic constituents is less than or equal to 10%, preferably 5%, more preferably 2% and even more preferably 1%.

[0041] By formaldehyde-free and methylene donor-free, it is meant that the total mass content of formaldehyde and of the methylene donor(s) belonging to the groups described above by total weight of the compound(s) Al in the basic constituents is less than or equal to 10%, preferably 5%, more preferably 2% and even more preferably 1%. 1.1 - Aromatic compound Al

[0042] The first essential constituent of the thermosetting resin according to the first embodiment of the invention is an aromatic compound comprising at least one aromatic nucleus carrying at least two functions, one of these functions being an aldehyde function or a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function. Thus, in accordance with the invention, it is said aromatic nucleus which carries the hydroxymethyl functions or the hydroxymethyl and aldehyde functions. The compound according to the invention therefore corresponds to the general formula (I): B-Ar-C (I) where Ar represents an aromatic nucleus and B, C represent respectively CHO or ch2oh.

[0043] The aromatic ring is advantageously a 5 or 6-membered ring, comprising, as a member, carbon atoms and optionally one or more heteroatoms, in particular nitrogen, oxygen, sulfur atoms, optionally oxidized in the form of N-oxide or S-oxide. In one variant, the aromatic ring comprises 0, 1 or 2 heteroatom(s). The remainder of the aromatic ring may be substituted or not.

[0044] The aromatic nucleus may carry 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0045] The aromatic nucleus may carry 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0046] In addition, the aromatic nucleus may also carry 0, 1 or 2 other function(s), in particular hydroxyl.

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] In the embodiment in which the aromatic ring is a 6-membered ring, the B and hydroxymethyl functions are advantageously in the meta or para position relative to each other. In the embodiment in which the aromatic ring is a 5-membered ring, the ring may comprise one or more heteroatoms, in particular nitrogen, oxygen, sulfur atoms, optionally oxidized in the form of N-oxide or S-oxide. Advantageously, the aromatic ring comprises 1 or 2 heteroatom(s), preferably 1 heteroatom. In this embodiment in which the aromatic ring is a 5-membered ring, at least one of the following three conditions is met: - the aromatic nucleus comprises 0 or a single aldehyde function; - the aromatic nucleus comprises one or two hydroxymethyl functions; - the aromatic nucleus includes one or two aldehyde functions. Advantageously, apart from the aldehyde and hydroxymethyl functions, the remainder of the aromatic nucleus is not substituted. Advantageously, in a first case, the aromatic nucleus comprises: - a single aldehyde function; - a single hydroxymethyl function; - apart from the aldehyde and hydroxymethyl functions, the rest of the aromatic nucleus is not substituted. Advantageously, in a second case, the aromatic nucleus comprises: - two hydroxymethyl functions; - apart from the hydroxymethyl functions, the rest of the aromatic nucleus is not substituted. Advantageously, in a third case, the aromatic nucleus comprises: - two aldehyde functions; - apart from the aldehyde functions, the rest of the aromatic nucleus is not substituted. Advantageously, the aromatic compound Al corresponds to the general formula (II): X K. bX / / C (2) in which B and C represent respectively CHO or CH2OH, X represents O, NRi, NO, S, SO, SO2, SR2R3, Ri, R2, R3 each represent, independently of one another, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group. In a first variant, the compound Al has the general formula (II'):

[0056] in which X, B are as defined previously.

[0057] In a particularly advantageous embodiment, B represents CHO. In another embodiment, B represents CH2OH.

[0058] According to a preferred embodiment, X represents O.

[0059] In this embodiment, the compound Al is of formula (IIa): O ho—4*— y B being as defined previously

[0060] and more particularly of formula (II'al) or (II'a2):

[0061] 5-(Hydroxymethyl)furfural (Il'al) is a particularly suitable aldehyde, given that this organic compound can easily be derived from renewable resources. Indeed, it is derived in particular from the dehydration of certain sugars such as fructose, glucose, sucrose, cellulose and rinulin.

[0062] In a second variant, the compound Al is of general formula (II”): 8 B being as defined previously

[0063] and more particularly of formula (II”al) or (II”a2): OHC-A" TL-CHO ho--H:iC-y ,pCHO

[0064]

[0065] In another embodiment, X represents NRi or NO, advantageously NRp Ri is as defined previously. In one variant, the compound Al has the formula (IIb): Ri

[0066] B being as defined previously and more particularly of formula (II'bl) or (II'b2): (O1) (Ifb2)

[0067]

[0068]

[0069]

[0070]

[0071] in which Ri represents a hydrogen, an alkyl, aryl, arylalkyl, al-kylaryl or cycloalkyl group. Advantageously Ri represents a hydrogen or a C1-C6 alkyl group. In another embodiment, X represents S, SO, SO2 or SR2R3. In this embodiment, the compound Al is of formula (Ile): B being as defined previously with X representing S, SR2R3, SO, SO2R2, R3 each representing, independently of one another, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group, B being as defined above; and more particularly of formula (II'cl) or (II'c2): 0M) (irc2)

[0072]

[0073] in which X represents S, SR2R3, SO, SO2R2, R3 each represent, independently of one another, a hydrogen, an alkyl, aryl, arylalkyl, al-kylaryl or cycloalkyl group. The compound Al can thus be: O LO \ . / -..-110 O HO ——CIC Rs HO— CHS ^CH2OH (lied) -----y c. 0 bn / (H«)

[0074]

[0075] Advantageously, R2 and R3 each represent, independently of the other, a C1-C6 alkyl radical. The compound Al is advantageously of formula (II'cl) or (II'c2).

[0076] In another variant, the aromatic ring is a 6-membered ring, which may comprise 0, one or more heteroatoms, in particular nitrogen, optionally oxidized in the form of N-oxide. In one variant, the aromatic ring comprises 0, 1, or 2 heteroatom(s).

[0077] The B and hydroxymethyl functions are advantageously in the meta or para position relative to each other.

[0078] The aromatic nucleus may carry 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0079] The aromatic nucleus may carry 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0080] Advantageously, the compound Al is of general formula (III): ( ho—h,cJ-4- ( ™ ) in which D represents hydrogen, alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl, or a hydroxyalkyl group. According to the invention, p+n>1 and m<5.

[0081] Advantageously m is 0 or 1.

[0082] Advantageously D represents a hydrogen or hydroxymethyl group.

[0083] In a variant, n is 1 and p is 1.

[0084] In another variant, n is 3 and p is 0.

[0085] In another variant, n is 2 and p is 1.

[0086] In another variant, n is 1 and p is 2.

[0087] In another variant, n is 0 and p is 2.

[0088] In another variant, n is 0 and p is 3.

[0089] Preferably, the aromatic nucleus of the aromatic compound Al is a benzene nucleus. More preferably, this aldehyde is chosen from the group consisting of 2-hydroxymethyl-benzene-1-carboxaldehyde, 3-hydroxymethyl-benzene-1-carboxaldehyde, 4-hydroxymethyl-benzene-1-carboxaldehyde, 1,2-hydroxymethyl-benzene, 1,3-hydroxymethyl-benzene, 1,4-hydroxymethyl-benzene, 2-Methoxybenzaldehyde, 3-Methoxybenzaldehyde, 4-Methoxybenzaldehyde, 2,6-Dimethoxybenzaldehyde, 2,4,6-Trimethoxybenzaldehyde, and mixtures of these compounds.

[0090] Even more preferably the aromatic compound Al used is l-hydroxymethyl-benzene-4-carboxaldehyde of formula (Ilia) or 1,4-hydroxymethyl-benzene of formula (IIIb) or terephthalic acid of formula (III'b): CHO CHyOH ch2oh ch2oh (IIM (tt)

[0091] Preferably, when the thermosetting resin is based on polyphenol and one or more compounds of formula (I), the composition is free of formaldehyde.

[0092] When the thermosetting resin is based on polyphenol, one or more compounds of formula (I) and aldehydes, each aldehyde is preferably different from formaldehyde. The composition is then also free of formaldehyde.

[0093] In other words and preferably, when an aldehyde is present, the or each aldehyde of the thermosetting resin is different from formaldehyde.

[0094] By formaldehyde-free, it is meant that the mass content of formaldehyde in total weight of the aldehyde(s) is less than or equal to 10%, preferably 5% and more preferably 2%, these percentages corresponding to traces likely to be present in the aldehyde(s) used industrially.

[0095] 1.2 - Aromatic polyphenol and / or aromatic monophenol - compounds A2

[0096] According to the first embodiment of the invention, the second essential constituent of the thermosetting resin is an aromatic polyphenol A2 comprising one or more aromatic nuclei. The aromatic polyphenol comprises at least one aromatic nucleus carrying at least two hydroxyl functions in the meta position, one relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted.

[0097] In accordance with the invention, compound A2 may be, in one embodiment, a simple molecule of aromatic polyphenol comprising one or more aromatic nuclei, at least one of these aromatic nuclei, or even each aromatic nucleus, carrying at least two hydroxyl functions in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted.

[0098] According to the invention, compound A2 may be, in another embodiment, a pre-condensed resin based on: • at least one aromatic polyphenol, comprising at least one aromatic nucleus carrying at least two hydroxyl functions in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted; and • at least one compound capable of reacting with said aromatic polyphenol comprising at least one aldehyde function and / or at least one compound capable of reacting with said aromatic polyphenol comprising at least two hydroxymethyl functions carried by an aromatic nucleus.

[0099] Such a pre-condensed resin based on aromatic polyphenol conforms to the definition of compound A2 and comprises, unlike the simple molecule described above, a repeating unit. In this case, the repeating unit comprises at least one aromatic nucleus carrying at least two hydroxyl functions in the meta position relative to each other.

[0100] In the following particular embodiments, the aromatic nucleus(s) of the aromatic polyphenol and / or aromatic monophenol are described. For the sake of clarity, the “aromatic polyphenol” and / or “aromatic monophenol” are described in their single molecule form. This aromatic polyphenol and / or aromatic monophenol may then be condensed and will partly define the repeating unit. The characteristics of the pre-condensed resin are described in more detail below. Aromatic polyphenol A2

[0101] In a preferred embodiment, the aromatic nucleus of the aromatic polyphenol carries three hydroxyl functions in meta position relative to each other.

[0102] Preferably, the two ortho positions of each hydroxyl function are unsubstituted. This means that the two carbon atoms located on either side (in the ortho position) of the hydroxylated carbon atom (i.e., carrying the hydroxyl function) carry a single hydrogen atom.

[0103] Even more preferably, the remainder of the aromatic nucleus is unsubstituted. This means that the other carbon atoms in the rest of the aromatic nucleus (those other than the carbon atoms carrying the hydroxyl functions) carry a single hydrogen atom.

[0104] In one embodiment, the aromatic polyphenol comprises several aromatic nuclei, at least two of which each carry at least two hydroxyl functions in the meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions of at least one aromatic nucleus being unsubstituted.

[0105] In a preferred embodiment, at least one of the aromatic nuclei of the aromatic polyphenol carries three hydroxyl functions in meta position relative to each other.

[0106] Preferably, the two ortho positions of each hydroxyl function of at least one aromatic nucleus are unsubstituted.

[0107] Even more preferably, the two ortho positions of each hydroxyl function of each aromatic nucleus are unsubstituted.

[0108] Even more preferably, the remainder of each of the aromatic nuclei is unsubstituted. This means that the other carbon atoms of the remainder of each aromatic nucleus (those other than the carbon atoms carrying the hydroxyl functions or carrying the group linking the aromatic nuclei together) carry a single hydrogen atom.

[0109] Advantageously, the aromatic nucleus carrying at least two hydroxyl functions in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted, is a benzene nucleus.

[0110] Advantageously, each aromatic nucleus of the aromatic polyphenol is a benzene nucleus.

[0111] As an example of an aromatic polyphenol comprising a single aromatic nucleus, we can cite in particular resorcinol and phloroglucinol, as a reminder of the developed formulas (IV) and (V) respectively: OH

[0112] As examples, in the case where the aromatic polyphenol comprises several aromatic nuclei, at least two of these aromatic nuclei, identical or different, are chosen from those of general formulas:

[0113] in which the symbols Zb Z2, identical or different if there are several of them on the same aromatic nucleus, represent an atom (for example carbon, sulfur or oxygen) or a linking group by definition at least divalent, which links at least these two aromatic nuclei to the rest of the aromatic polyphenol.

[0114] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl sulfide of the following structural formula (VII):

[0115] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl benzophenone of the following structural formula (VIII):

[0116] It is noted that each compound VII and VIII is an aromatic polyphenol comprising two aromatic nuclei (of formulas VI-c) each of which carries at least two (in this case two) hydroxyl functions in the meta position relative to each other.

[0117] It is noted that in the case of an aromatic polyphenol comprising at least one aromatic nucleus in accordance with the formula VI-b, the two ortho positions of each hydroxyl function of at least one aromatic nucleus are unsubstituted. In the case of an aromatic polyphenol comprising several aromatic nuclei in accordance with the formula VI-b, the two ortho positions of each hydroxyl function of each nucleus aromatic are unsubstituted.

[0118] According to one embodiment of the invention, the aromatic polyphenol is chosen from the group consisting of resorcinol, phloroglucinol, 2,2',4,4'-tetrahydroxydiphenyl sulfide, 2,2',4,4'-tetrahydroxybenzophenone, and mixtures of these compounds. In a particularly advantageous embodiment, the aromatic polyphenol is phloroglucinol.

[0119] In one embodiment, compound A2 comprises a pre-condensed resin based on the aromatic polyphenol as described in any of these embodiments.

[0120] This pre-condensed resin is advantageously based on: - at least one aromatic polyphenol as defined above, and preferably chosen from the group consisting of resorcinol (IV), phloroglucinol (V), 2,2',4,4'-tetrahydroxydiphenyl sulfide (VII), 2,2',4,4'-tetrahydroxybenzophenone (VIII), and mixtures thereof; and - at least one compound capable of reacting with said aromatic polyphenol comprising at least one aldehyde function and / or at least one compound capable of reacting with said aromatic polyphenol comprising at least two hydroxymethyl functions carried by an aromatic nucleus.

[0121] The compound capable of reacting with said aromatic polyphenol may be an aromatic compound as defined previously in paragraph 1.1, a compound of formula Ar-(CHO)2, where Ar is as defined previously for the aromatic compound of paragraph 1.1, or any other aldehyde. Advantageously, said compound is chosen from the group consisting of an aromatic compound comprising an aromatic nucleus carrying at least two functions, one of these functions being a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function, formaldehyde, furfuraldehyde, 2,5-furanedicarboxaldehyde, 1,4-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,2-benzenedicarboxaldehyde and mixtures of these compounds.Very advantageously, when the compound is an aromatic compound comprising an aromatic nucleus carrying at least two functions, one of these functions being a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function, this compound is chosen from the group consisting of 5-(hydroxymethyl)-furfural, 2,5-di(hydroxymethyl)furan and mixtures of these compounds.

[0122] Thus, in the pre-condensed resin based on aromatic polyphenol, the repeating unit meets the characteristics of the aromatic polyphenol defined previously with at least one of the carbon atoms of the aromatic nucleus, which was unsubstituted, linked to another unit.

[0123] Whatever the compound other than the aromatic polyphenol at the base of the resin pre-condensed, this pre-condensed resin is free of free formaldehyde. Indeed, even in the case where the pre-condensed resin is based on an aromatic polyphenol as described above and formaldehyde, the formaldehyde having already reacted with the aromatic polyphenol, the pre-condensed resin is free of free formaldehyde likely to be able to react with an Al compound in accordance with the invention in a subsequent step.

[0124] Compound A2 may also comprise a mixture of a free molecule of aromatic polyphenol and a pre-condensed resin based on aromatic polyphenol, as described above. In particular, compound A2 may also comprise a mixture of phloroglucinol and a pre-condensed resin based on phloroglucinol. 1.3 - Compound 1.3 - ammonium salt

[0125] The third essential constituent of the aqueous adhesive composition is an ammonium salt.

[0126] Advantageously, the ammonium salt is chosen from ammonium chloride, ammonium fluoride, ammonium bromide, ammonium iodide, phosphorus-based ammonium derivatives, sulfur-based ammonium derivatives, organic acid-based ammonium derivatives, carbonate ammonium derivatives, nitrogen-based ammonium derivatives and mixtures of these compounds and preferably the ammonium salt is ammonium chloride.

[0127] Advantageously, the phosphorus-based derivatives are such as ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0128] Advantageously, the phosphorus-based derivatives are such as ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0129] Advantageously, the sulfur-based derivatives are such as ammonium sulfate, ammonium hydrogen sulfate.

[0130] Advantageously, the organic acid-based derivatives are such as ammonium citrate, ammonium acetate.

[0131] Advantageously, the carbonate derivatives are such as ammonium carbonate, ammonium hydrogen carbonate.

[0132] Advantageously, the nitrogen-based derivatives are such as ammonium nitrate.

[0133] According to the invention, the activator is preferably to be chosen from ammonium salts such as ammonium chloride. Other organic acids, for example citric acid or inorganic acids, aluminum sulfate, also react with the resin but are not necessarily soluble or cause heterogeneities in the resin so that the hot reactivity of the composition is not affected. is not improved and the implementation of the composition is more difficult.

[0134] As indicated above, preferably, the mass content of ammonium chloride ranges from 0.1% to 5% relative to a mass content of dry extract of the adhesive composition. Over this range, the hot reactivity is optimal and the processing qualities of the composition are preserved without affecting the flexibility of use of the aqueous adhesive composition.

[0135] A rate higher than 5% would greatly improve the hot reactivity but the very short-term lifespan of the composition as well as its processing qualities would be greatly degraded for its use in a gluing process.

[0136] A rate lower than 0.1% would not be sufficient to shift the properties of the composition.

[0137] 1.4 Additives - Manufacture of the aqueous adhesive composition

[0138] The aqueous adhesive composition of the invention may of course comprise all or part of the usual additives for aqueous adhesive compositions such as those used in conventional phenolic glues; for example, bases such as ammonia, sodium, potassium or ammonium hydroxide, colorants, fillers such as carbon black, silica, chalk, olive pomace or any other natural fillers, antioxidants or other stabilizers, thickeners, for example carboxymethylcellulose, or gelling agents, for example gelatin, making it possible to increase the viscosity of the composition.

[0139] Typically, during the preparation of the resin, the constituents of the thermosetting resin itself are mixed in no predefined order but advantageously by first mixing the water with the soda, then the aromatic polyphenol A2, then the aromatic compound Al. The resin can be left to rest in its current state, which may correspond to a storage time, for example. Those skilled in the art will be able to adjust this time to use the resin at the desired viscosity for use in an aqueous adhesive composition. For example, the resin can be left to rest for 24 hours before adding the ammonium salt, or the ammonium salt can be added 15 minutes before using the aqueous adhesive composition.

[0140] The production of the thermosetting resin can be carried out at a pH between 7 and 14, more preferably between 9 and 12.

[0141] Thus, the aqueous adhesive composition is obtained by mixing: - the aromatic compound Al, and - aromatic polyphenol A2; in a basic solvent preferably having a pH between 7 and 14, more preferably between 9 and 12 to obtain a thermosetting resin; and after mixing the resin, the ammonium salt is added at a mass rate of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.05 to obtain the aqueous adhesive composition.

[0142] The concentration of the composition can be adjusted according to its specific use (opening time, viscosity).

[0143] Advantageously, in the final aqueous adhesive composition thus prepared, the dry extract content of thermosetting resin according to the invention ranges from 5 to 80%, more preferably from 10 to 60% by weight of the dry extract of adhesive composition.

[0144] In the case where the final application of the adhesive composition requires a higher viscosity, a person skilled in the art will know how to adjust the final viscosity characteristics of the adhesive composition by adding thereto a thickener or any type of known fillers (for example olive stone powder and / or chalk).

[0145] The composition may be used immediately or stored at room temperature (23°C) for a maturation time which may typically vary from one to several hours or even several days. Before its final use, a person skilled in the art will determine the possible storage time based on the concentration of the composition.

[0146] Preferably, the water content of the aqueous adhesive composition ranges from 20 to 95% by weight, preferably from 40 to 90% by weight.

[0147] By total dry extract rate of the adhesive composition is meant the ratio between the mass of residue obtained after drying of the adhesive composition to the mass of the adhesive composition before drying.

[0148] By dry extract rate of the thermosetting resin, we mean the ratio between the mass of the thermosetting resin obtained after drying of the adhesive composition and the mass of the adhesive composition before drying.

[0149] These two dry extract rates are measured in accordance with standard NF EN 827 (March 2006).

[0150] By water content of the aqueous adhesive composition is meant the weight of water relative to the total weight of the adhesive composition. II - GLUED ASSEMBLY OF THE INVENTION II. 1 - Definitions; examples

[0151] As indicated previously, the present invention also relates to the use of the aqueous adhesive composition previously described, for bonding at least two cellulosic elements, advantageously at least two wooden elements.

[0152] Thus, a bonded assembly of two elements according to the invention comprises a layer of the aqueous adhesive composition as described previously joining the two elements to each other.

[0153] In one embodiment, these two elements are made of wood.

[0154] Wood means the plant tissue derived from woody plants. Examples of plant tissue are the trunk, branches and roots. For example, the woody plants from which plant tissue is derived are oak, chestnut, ash, walnut, beech, poplar, fir, pine, olive, alder or birch.

[0155] The glue can also be used for bonding elements made from materials other than wood, for example plastics, for example thermosetting or thermoplastic materials, textiles, mineral materials or mixtures of these materials, including with wood.

[0156] By element is meant any particle or monolithic piece. Examples of wooden elements are plies intended to form a plywood assembly, laths intended to form a slatted assembly, particles such as shavings, sawdust, flour or flakes, to form an agglomerated assembly, whether the particles are oriented or not, fibers intended to form a fiber assembly such as a high or medium density panel, pieces of solid wood, also called lumber, intended to form assemblies such as furniture, frames.

[0157] Advantageously, the wooden elements may be wood veneers, wood slats, wood fibers, wood particles or a mixture of these compounds. n.2 - Manufacturing of the glued assembly

[0158] The glued assembly of the invention can be prepared according to a method of gluing at least two cellulosic elements, advantageously two wooden elements, in which: - a layer of the aqueous adhesive composition according to the invention is applied to at least one of the elements, and, - the elements are joined together using a layer of aqueous adhesive composition.

[0159] Advantageously, cooking is carried out by steam cooking, cooking by contact with the plates of a cooking press or cooking by high frequency.

[0160] The step of applying the adhesive composition to one or more elements can be carried out using any appropriate method, in particular by any known coating technique such as, for example, spraying, impregnation, injection under pressure or even by a combination of one or more of these techniques.

[0161] For example, for wood veneers, it is preferable to use a rate of aqueous adhesive composition ranging from 50 to 400 gr.m2 and preferably from 70 to 300 gr.m2. Those skilled in the art will be able to adapt the weight of aqueous adhesive composition to their wooden elements and their own process.

[0162] After the step of applying the adhesive composition, a step of curing: the bonded assembly is heated to a temperature ranging from 30°C to 250°C, preferably from 50°C to 200°C, very preferably from 80°C to 160°C depending on the intended applications. This heat treatment aims to eliminate any solvent or water and to crosslink the thermosetting resin. Depending on the areas of application, the heat treatment may be carried out in two stages: a first heat treatment aimed at eliminating any solvent or water, a second heat treatment aimed at completing the crosslinking of the thermosetting resin.

[0163] In a first embodiment, the elements joined by the adhesive composition are subjected to a steam cooking step, advantageously at a temperature greater than or equal to 100°C.

[0164] In a second embodiment, the elements joined by the adhesive composition are subjected to a cooking step by contact with the plates of a cooking press, advantageously at a temperature greater than or equal to 80°C.

[0165] In a third embodiment, the elements joined by the adhesive composition are subjected to a high frequency cooking step, advantageously ranging from 300 GHz to 300 MHz.

[0166] Preferably, the bonded assembly is maintained under pressure, for example under a pressure of up to 18 kg.cm2. More preferably, the pressure maintenance step is carried out simultaneously with the heating step.

[0167] The duration of the heating and / or pressurization step varies from a few minutes to a few hours depending on the case, in particular depending on the temperature-pressure pair used.

[0168] In one embodiment, the two elements to be assembled are made of wood.

[0169] Those skilled in the art will know how to adjust, where appropriate, the temperature and duration of the above heat treatment, depending on the particular conditions of implementation of the invention, in particular the exact nature of the element. In particular, those skilled in the art will benefit from carrying out temperature and treatment duration scans as well as aqueous adhesive composition grammage scans, so as to search, by successive approaches, for the operating conditions leading to the best adhesion and viscosity results for each particular embodiment of the invention.

[0170] III - EXAMPLES OF CARRYING OUT THE INVENTION AND COMPARATIVE TESTS

[0171] These tests demonstrate that the bonding performance of two wooden elements with an aqueous adhesive composition according to the invention is equivalent or even improved and the reactivity, i.e. the gel time at 95°C, of ​​the aqueous adhesive composition according to the invention is less significant compared to a conventional adhesive composition without formaldehyde.

[0172] For this, seven aqueous adhesive compositions were prepared, two in accordance with the embodiment of the invention (hereinafter denoted C1 and C-2), one composition of the state of the art according to WO2017 / 168109 denoted T0 and four not in accordance with the invention (control compositions hereinafter denoted T1 to T4). Their formulations (expressed as a percentage by weight) are presented in Table 1 below. The quantities listed in this table are those of the constituents in the dry state, brought to a total of 100 parts by weight of aqueous adhesive composition (i.e. the constituents and the water).

[0173] Adhesive composition C-0 is a state-of-the-art composition based on 5-(hydroxymethyl)-furfural and phloroglucinol.

[0174] The adhesive compositions C1 and C-2 according to the invention are compositions based on 5-(hydroxymethyl)-furfural and phloroglucinol and ammonium chloride.

[0175] Control adhesive compositions T1 and T-2 are compositions based on 5-(hydroxymethyl)-furfural and phloroglucinol and aluminum sulfate.

[0176] Control adhesive compositions T-3 and T-4 are compositions based on 5-(hydroxymethyl)-furfural and phloroglucinol and citric acid.

[0177] Protocol for producing the aqueous adhesive composition

[0178] In a 250mL flask equipped with a mechanical stirring system, the aromatic compound Al (for example phloroglucinol) and the sodium hydroxide are introduced. Stirring is carried out for 1 to 10 minutes to homogenize (for example at 250 rpm). Then the compound A2 (5 HMF for example) is added, stirring is carried out for 1 to 20 minutes, and for a temperature ranging from 20°C to 90°C. Depending on the reaction temperature chosen, a cooling step can be applied to the preparation to bring the reaction medium to room temperature, for example. The resin obtained can be stored for a few minutes or even several hours or several days. Those skilled in the art will be able to adapt the storage time before use depending on the intended application or depending on the quantities of reagents used. At room temperature, after mixing the resin, the ammonium salt (for example ammonium chloride) is added, followed by the technical fillers described above.Depending on the ingredients added, wait between 5 and 15 minutes under mechanical stirring at room temperature. After this time, the aqueous adhesive composition is ready to be used.

[0179] [Tableauxl] Adhesive compositions C-0 Cl C-2 Tl T-2 T-3 T-4 5-(hydroxymethyl)-furfural (1) 27.9 29.7 27.5 29.5 27.5 29.5 27.5 Phloroglucinol (2) 7.6 5.9 7.5 5.9 7.5 5.9 7.5 Ammonium chloride (3) 0 0.30 0.36 0 0 0 0 Aluminum sulfate (4) 0 0 0 0.36 0.35 0 0 Citric acid (5) 0 0 0 0 0 0.35 0.35 Sodium hydroxide (6) 1.7 1.2 1.6 1.15 1.65 1.15 1.65 Total weight of dry extract of adhesive composition 64.4 64.0 63.9 63.8 63.9 63.8 63.9 Water weight 35.6 36.0 36.1 36.2 36.1 36.2 36.1 Olive stone powder (7) 9.1 9.0 9.0 9.0 9.0 9.0 9.0 Chalk (8) 18.1 17.9 17.9 17.9 17.9 17.9 17.9 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 1. HMF (from Aldrich; purity > 99%); 2. Phloroglucinol (from Aldrich; 99% purity); 3. Ammonium chloride (from Aldrich; 99% purity); 4. Aluminum sulfate (from Aldrich; 99% purity); 5. Citric acid (from Aldrich; 99% purity); 6. Sodium hydroxide (from Aldrich; diluted to 99%); 7. Olive kernel powder from the company La Provençale; 8. Chalk from the Imerys company.

[0180] Freezing time

[0181] After preparing the various aqueous adhesive compositions, the gel time is measured. The gel time of the resin at 95°C is determined using Gelnorm-Geltimer PST1 equipment. This measurement is described in standard NF EN ISO 9396 - February 2001. This measurement makes it possible to determine the time it takes for the resin to gel, i.e. to begin solidifying at a given temperature. The measurements are made using approximately 12g of resin. These 12g of resin are placed in a specific test tube, available from Gel Instrumente AG, equipped with a rim adapted to the equipment. A foam ring is used to crimp the test tube and is wedged against the rim of the test tube. The measurement takes place at a temperature of 95°C. This temperature is maintained throughout the measurement duration. A special aluminum rod is immersed in the resin and connected to the measuring device. A laser sensor located above the rim of the test tube detects any vertical movement of the test tube. The device can oscillate the rod vertically in the resin. The rod is always immersed in the resin during oscillation. The oscillation frequency of the rod is low, approximately one complete oscillation every 10 seconds. At the start of the measurement, when the oscillation begins, the device simultaneously starts a timer. When the resin is still fluid, the rod can freely move in and out of the resin, the test tube is stationary and the timer is still running. On the other hand, when the resin hardens sufficiently, the oscillating rod is blocked in the resin and the oscillating movement then lifts the rod and the test tube simultaneously.The laser sensor detects the presence of the test tube out of position or at standard height, which stops the timer and stops the measurement. The value read on the machine timer then corresponds to the gel time. Three measurements are taken per sample and the average value of the three measurements constitutes the gel time of the sample.

[0182] The results are reported in Table 2 below in which the gel time of the control composition C-0 is set at 100 and the different compositions will be compared. The lower the value, the more the composition will be reactive when hot.

[0183] We will also look at the homogeneous or non-homogeneous appearance of the aqueous adhesive composition. A non-homogeneous composition may penalize the implementation and stability of the composition.

[0184] Protocol for producing the test piece

[0185] A plywood panel of approximately 15mm thickness made up of 7 layers is manufactured from layers of wood, okoumé for example, with a unit thickness of 2.6mm. Each layer of wood measures 50cm x 50cm. The first 6 layers of wood are coated with 190 g / m2 of resin-based glue of the invention. These layers of wood coated with glue are then stacked on top of each other, glued side against unglued side. A person skilled in the art will know how to alternate the orientation of each layer of wood along the axis of the wood grain in order to constitute the wood composite structure [0° / 90°] which is a plywood (0° parallel to the axis of the wood grain, 90° perpendicular to the wood grain). The last layer of wood completes the stacking. The stack thus formed can be cooked under different cooking and pressure conditions that the person skilled in the art will be able to adapt according to his needs, for example for 12 minutes at 120°C at 10 bars (IMPa) of pressure.The final panel obtained, coming off the press, measures approximately 50cm x 50cm x 15mm.

[0186] 24 hours after this cooking step, the test specimens are cut, in the 7-layer plywood panel previously obtained, according to the recommendations of the standard EN NF 314-1 2005 in order to determine the shear strength of the panel bonding. The bonding performance is established by stressing the central wood layer of the plywood panel. The skilled person will be able to adapt the cuts of the standardized test pieces described according to EN314-1 to do this. 5 standardized test pieces cut according to EN 314-1 are then placed in a boiling water bath and oven at 60°C according to test 5.1.3, i.e. immersion for 4 hours in boiling water, then drying in a ventilated drying oven at 60°C + / - 3°C for 16 to 20 hours, then immersion for 4 hours in boiling water, followed by cooling in water at 20°C + / - 3°C for at least 1 hour. At the end of the last cooling step of the test pieces undergoing test 5.1.3, the test piece is placed as is, i.e. without drying, in the jaws of a tensile machine, then pulled at a given speed and temperature (e.g. 10 mm / minute and 20°C).

[0187] The adhesion levels are characterized by measuring the shear force noted Fmax to separate the two elements from each other via a break in the bonding layer. The force Fmax is related to the sheared section, i.e. 25 x 25 mm2, to obtain the shear stress noted Fv. The arithmetic mean of the 5 Fv values ​​measured on the 5 specimens tested is taken. The EN 314-2 standard stipulates that the average shear stress Fv must be greater than 1 Mpa for the bonding to be compliant. The adhesion levels are characterized by measuring the so-called tear-off force (noted Fmax) to separate the two elements from each other via a break in the bonding layer. A value higher than that of the control specimen used with composition C-0, arbitrarily set at 100 reported in Table 2 below, indicates an improved result, i.e. a tear force higher than that of the control specimen.A value greater than 90 corresponds to a shear stress greater than IMPa.

[0188] [Tables2] Adhesive compositions C-0 Cl C-2 Tl T-2 T-3 T-4 Adhesion Adhesive performance 100 133 112 Not available Not available Not available Not available Gelling time at 95C Gelling time 100 24 42 100 100 100 100 State of composition Homogeneity + + + - - - -

[0189] The aqueous adhesive compositions according to the invention C1 and C-2 have a greater peeling force than the control composition C-0. The test could not be carried out for the non-compliant compositions T1 to T-4 because the compositions were heterogeneous.

[0190] It is also noted that the gel time of these compositions C1 and C-2 according to the invention is greatly improved compared to the control composition C-0 and compared to the non-compliant compositions T1 to T-4.

[0191] Comparative tests with non-compliant compositions T1 to T-4 clearly show that the presence of ammonium salts in the composition allows it to have high adhesive properties, while providing it with stronger reactivity compared to the adhesive composition of document WO2017 / 168109 without reducing the flexibility of use while maintaining a homogeneous appearance to the aqueous adhesive composition.

[0192] The invention is not limited to the embodiments previously described.

Claims

Claims

1. Aqueous adhesive composition, characterized in that it comprises a thermosetting resin based on: - at least one aromatic compound A1 comprising at least one aromatic nucleus carrying at least two functions, one of these functions being an aldehyde function or a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function; - at least one aromatic polyphenol A2 comprising at least one aromatic nucleus carrying at least two hydroxyl functions in the meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted; and in that the aqueous adhesive composition comprises an ammonium salt at a mass content of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.

05.

2. Composition according to the preceding claim, in which the ammonium salt is at a mass content of dry extract of the adhesive composition less than or equal to 0.03, preferably less than or equal to 0.

02.

3. Composition according to any one of the preceding claims, in which the ammonium salt is at a mass content of dry extract of the adhesive composition greater than or equal to 0.003 and preferably greater than or equal to 0.

005.

4. A composition according to any preceding claim, wherein the ammonium salt is selected from ammonium chloride, ammonium fluoride, ammonium bromide, ammonium iodide, phosphorus-based ammonium derivatives, sulfur-based ammonium derivatives, organic acid-based ammonium derivatives, carbonate ammonium derivatives, nitrogen-based ammonium derivatives and mixtures of these compounds and preferably the ammonium salt is ammonium chloride.

5. A composition according to any one of the preceding claims, wherein the aromatic compound Al corresponds to the general formula (II): (a b-aV ^g where B and C represent CHO or CH2OH respectively, X represents 0, NRb NO, S, SO, SO2, SR2R3, Ri represents hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group, R2, R3 each represent, independently of one another, hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group.

6. Composition according to any one of the preceding claims, in which the aromatic compound Al corresponds to the general formula (II'al) or (II'a2): ...¾ ^0---.--° V ' / 'V\ X'”' V' 1 l /

7. Composition according to any one of the preceding claims, in which the aromatic nucleus of the aromatic polyphenol A2 carries three hydroxyl functions in the meta position relative to each other.

8. A composition according to any one of the preceding claims, wherein the aromatic polyphenol A2 is selected from the group consisting of resorcinol, phloroglucinol, 2,2',4,4'-tetrahydroxydiphenyl sulfide, 2,2',4,4'-tetrahydroxybenzophenone, and mixtures of these compounds, advantageously phloroglucinol.

9. Composition according to any one of the preceding claims, in which the aqueous adhesive composition is obtained by mixing: - the aromatic compound A1, and - the aromatic polyphenol A2; in a basic solvent preferably having a pH of between 7 and 14, more preferably between 9 and 12 to obtain a thermosetting resin; and after mixing the resin, the ammonium salt is added at a mass content of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.05 to obtain the aqueous adhesive composition.

10. Use of an adhesive composition according to any one of claims 1 to 9 for bonding at least two cellulosic elements, advantageously at least two wooden elements.

11. Method for bonding at least two cellulosic elements, advantageously two wooden elements, in which: - a layer of the aqueous adhesive composition according to any one of claims 1 to 9 is applied to at least one of the elements, and, - the elements are joined to each other by means of the layer of the aqueous adhesive composition.

12. Method according to the preceding claim in which a cooking step is carried out after the step of applying the aqueous adhesive composition in which the cooking is carried out by cooking with water vapor, cooking by contact with the plates of a cooking press or cooking by high frequency.

13. Glued assembly of two elements, advantageously made of wood, comprising a layer of the aqueous adhesive composition according to any one of claims 1 to 9 joining at least one of the elements to the other.