AQUEOUS ADHESIVE COMPOSITION COMPRISING A THERMOCURRING RESIN AND A UREA DERIVATIVE

Abstract

The subject of the invention is an aqueous adhesive composition, comprising 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; anda compound (III): in which each group R1, R2, R3 represents independently of one another, an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, cycloalkyl or hydrogen group, X represents S, O or N-R4 with R4 representing an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl group or the compound (III) is melamine or uracil;with compound (I) being at a mass content of dry extract of the aqueous adhesive composition ranging from 0.003 to 0.160.;

Description

Title of the invention: AQUEOUS ADHESIVE COMPOSITION COMPRISING A THERMOSETTING RESIN AND A UREA DERIVATIVE

[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 cold stability, i.e. at room temperature, of phenolic resins is an important characteristic to enable the transport and storage of the resins before their use in adhesive composition. A more important cold stability bearing will allow the resin to travel longer or even to be stored for longer. It is all the more interesting to be able to obtain this greater cold stability without affecting the hot reactivity of the composition and its bonding qualities.

[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 greater cold stability than the adhesive composition of document WO2017 / 168109 without penalizing the bonding quality 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, more stable when cold, 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 a compound (III): X in which each group RI, R2, R3 independently of one another represents an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, cycloalkyl or hydrogen group, X represents S, O or N-R4 with R4 representing an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl group or compound (III) is melamine or uracil; with compound (III) being at a mass content of dry extract of the aqueous adhesive composition ranging from 0.003 to 0.160.

[0010] By dry extract rate of compound (III), we mean the ratio between the mass of compound (III) and the mass of dry extract of the adhesive composition.

[0011] The Applicant thus hypothesizes that the addition of a compound (III) as sta bilizer at a given rate will increase cold stability without altering the reactivity of the aqueous adhesive composition or the bonding qualities of the composition. This will result in an increase in the lifetime of the resin at a given temperature, here at a temperature above 23°C for example. Thus, this increase in the lifetime of the resin makes it easier to transport these resins and allows for greater production flexibility.

[0012] Advantageously, the compound (III) has a mass content of dry extract of the adhesive composition less than or equal to 0.150, preferably less than or equal to 0.100.

[0013] Advantageously, the compound (III) has a mass content of dry extract in the adhesive composition greater than or equal to 0.004.

[0014] Over this concentration range of compound (III), the cold stability of the resin is optimal and the lifetime of the composition allows greater flexibility of use.

[0015] Another object 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.

[0016] The invention also relates to a method of bonding 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 to each other using a layer of aqueous adhesive composition.

[0017] 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.

[0018] The invention and its advantages will be easily understood in light of the following description.

[0019] I - FORMULATION OF THE AQUEOUS ADHESIVE COMPOSITION

[0020] In the present description, unless expressly indicated otherwise, all percentages (%) indicated are % by mass.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] “CHO” represents the aldehyde function.

[0026] “CH2OH” represents the hydroxymethyl function.

[0027] “Compound Al” designates, within the framework of the invention, the aromatic compound defined in paragraph 1.1.

[0028] “Compound A2” designates, within the framework of the invention, the compound based on aromatic polyphenol defined in paragraph 1.2.

[0029] Compound (III) is defined in paragraph 1.3.

[0030] By “aromatic polyphenol” is meant an aromatic compound comprising at least one benzene nucleus carrying more than one hydroxyl function.

[0031] 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.

[0032] 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.

[0033] 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 up to b (i.e. including the strict limits a and b).

[0034] 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 par- particular during a cooking stage.

[0035] 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 a compound (III), constituents which will be described in detail below.

[0036] 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 compound (III). In one embodiment, the basic constituents may comprise other additional constituents different from the compound Al, the compound A2 and the compound (III). In another embodiment, the basic constituents consist of at least one compound Al, at least one compound A2 and at least one compound (III).

[0037] 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 advantageously, these other additional constituents are free of formaldehyde and free of the methylene donors described in this paragraph.

[0038] 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:

[0039] 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.

[0040] Even 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. More advantageously, these other additional constituents are free of formaldehyde and free of methylene donors.

[0041] 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%.

[0042] 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

[0043] 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 hy- droxymethyl and aldehyde. 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.

[0044] The aromatic nucleus is advantageously a 5- or 6-membered nucleus, 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 nucleus comprises 0, 1 or 2 heteroatom(s). The remainder of the aromatic nucleus may be substituted or not.

[0045] The aromatic nucleus may carry 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0046] The aromatic nucleus can carry 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0047] In addition, the aromatic nucleus may also carry 0, 1 or 2 other function(s), in particular hydroxyl.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Advantageously, in addition to the aldehyde and hydroxymethyl functions, the remainder of the aromatic nucleus is not substituted.

[0052] Advantageously, in a first case, the aromatic nucleus comprises: - a single aldehyde function; - a single hydroxymethyl function; - besides the aldehyde and hydroxymethyl functions, the rest of the aromatic nucleus is not substituted.

[0053] Advantageously, in a second case, the aromatic nucleus comprises: - two hydroxymethyl functions; - in addition to the hydroxymethyl functions, the remainder of the aromatic nucleus is not substituted.

[0054] 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.

[0055] Advantageously, the aromatic compound Al corresponds to the general formula (II): X (II) in which B and C respectively represent 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.

[0056] In a first variant, the compound Al is of general formula (II'):

[0057] in which X, B are as defined previously.

[0058] In a particularly advantageous embodiment, B represents CHO. In another embodiment, B represents CH2OH.

[0059] According to a preferred embodiment, X represents O.

[0060] In this embodiment, the compound Al is of formula (IIa): B being as defined previously

[0061] and more particularly of formula (II'al) or (II'a2): (will go) (Hfa2)

[0062] 5-(Hydroxymethyl)furfural (Il'al) is a particularly suitable aldehyde, being

[0063]

[0064]

[0065]

[0066] given that this organic compound can easily be derived from renewable resources. Indeed, it is produced in particular from the dehydration of certain sugars such as fructose, glucose, sucrose, cellulose and rinulin. In a second variant, the compound Al is of general formula (II”): (IF) B being as defined previously and more particularly of formula (II”al) or (II”a2): ,0 N HO--- / / v___y (IFbl) 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

[0067] B being as defined previously and more particularly of formula (II'bl) or (II'b2): (O1) (I!'b2) 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.

[0068] In another embodiment, X represents S, SO, SO2 or SR2R3.

[0069] In this embodiment, the compound Al is of formula (Ile):

[0070] B being as defined previously

[0071] with X representing S, SR2R3, SO, SO2R2, R3 each represent, independently of one another, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cy-cloalkyl group, B being as defined above;

[0072] and more particularly of formula (II'cl) or (II'c2): (irc1) 0rc2)

[0073] in which X represents S, SR2R3, SO, SO2R2, R3 each represent, independently of one another, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group.

[0074] The compound Al can thus be: CWcD | ^ch2oh

[0075] Advantageously R2, R3 each represent, one independently of the other, a C1-C6 alkyl radical.

[0076] The compound Al is advantageously of formula (II'cl) or (II'c2).

[0077] 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).

[0078] The B and hydroxymethyl functions are advantageously in the meta or para position relative to each other.

[0079] The aromatic nucleus can carry 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0080] The aromatic nucleus can carry 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0081] Advantageously, the compound Al is of general formula (B2): (ho——Hch'o) ' ■'pji: § n 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.

[0082] Advantageously m is 0 or 1.

[0083] Advantageously D represents a hydrogen or hydroxymethyl group.

[0084] In one variant, n is 1 and p is 1.

[0085] In another variant, n is 3 and p is 0.

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

[0087] In another variant, n is 1 and p is 2.

[0088] In another variant, n is 0 and p is 2.

[0089] In another variant, n is 0 and p is 3.

[0090] 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.

[0091] Even more preferably, the aromatic compound Al used is 1-hydroxymethyl-benzene-4-carboxaldehyde of formula (B2a) or 1,4-hydroxymethyl-benzene of formula (B2b) or terephthalic acid of formula (B2b'): CHO CHSOH

[0092] (B2a) CH^OH CHgOH

[0093] (B2b) CHO

[0094] (B2b')

[0095] Preferably, when the thermosetting resin is based on polyphenol and one or more compounds of formula (I), the composition is free of formaldehyde.

[0096] 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.

[0097] In other words and preferably, when an aldehyde is present, the or each aldehyde of the thermosetting resin is different from formaldehyde.

[0098] 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.

[0099] 1.2 - Aromatic polyphenol and / or aromatic monophenol - compounds A2

[0100] 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 meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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

[0105] In a preferred embodiment, the aromatic nucleus 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 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.

[0107] Even more preferably, the remainder of the aromatic nucleus is unsubstituted. This means that the other carbon atoms of the remainder of the aromatic nucleus (those other than the carbon atoms carrying the hydroxyl functions) carry a single hydrogen atom.

[0108] In one embodiment, the aromatic polyphenol comprises several aromatic nuclei, at least two of which each carry at least two hydroxyl functions in 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.

[0109] 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.

[0110] Preferably, the two ortho positions of each hydroxyl function of at least one aromatic nucleus are unsubstituted.

[0111] Even more preferably, the two ortho positions of each hydroxyl function of each aromatic nucleus are unsubstituted.

[0112] 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.

[0113] 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.

[0114] Advantageously, each aromatic nucleus of the aromatic polyphenol is a benzene nucleus.

[0115] 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 respectively (IV) and (V): - (V)

[0116] 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: (W (VLc) (Vl-d)

[0117] 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.

[0118] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl sulfide of the following structural formula (VII): OH OH (V!)

[0119] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl benzophenone of the following structural formula (VIII): (W)

[0120] 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.

[0121] It is noted that in the case of an aromatic polyphenol comprising at least one aromatic nucleus conforming to 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 conforming to formula VI-b, the two ortho positions of each hydroxyl function of each aromatic nucleus are unsubstituted.

[0122] 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.

[0123] In one embodiment, compound A2 comprises a pre-condensed resin based on the aromatic polyphenol as described in any of these embodiments.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] Regardless of the compound other than the aromatic polyphenol at the base of the pre-condensed resin, this pre-condensed resin is free of free formaldehyde. in fact, 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 capable of reacting with a compound Al in accordance with the invention in a subsequent step.

[0128] 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 - compound (III)

[0129] The third essential constituent of the aqueous adhesive composition is compound (III): X RI HN n; in which each group RI, R2, R3 independently represents an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, cycloalkyl or hydrogen group, X represents S, O or N-R4 with R4 representing an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl group or compound (III) is melamine or uracil.

[0130] Preferably, RI and / or R2 and / or R3 represents hydrogen. Preferably X represents O.

[0131] Advantageously, the compound (III) is urea of ​​formula: P HN NH2

[0132] In another embodiment, compound (III) is melamine of formula:

[0133] In another embodiment, compound (III) is uracil of formula: O

[0134] As indicated above, preferably, the mass content of urea ranges from 0.3% to 20% relative to a mass content of dry extract of the adhesive composition. Over this range, the cold stability is optimal and the lifetime of the aqueous adhesive composition allows greater flexibility of use.

[0135] A rate greater than 20% would greatly improve cold stability but adhesive performance would be significantly degraded.

[0136] A rate lower than 0.3% would not be sufficient to shift the properties of the composition. 1.4 Additional compound

[0137] Advantageously, the aqueous adhesive composition further comprises an ammonium salt at a mass content of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.050.

[0138] By dry extract rate of the ammonium salt, we mean the ratio between the mass of ammonium salt and the mass of dry extract of the adhesive composition.

[0139] Preferably, 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.

[0140] Advantageously, the phosphorus-based derivatives are such as ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0141] Advantageously, the phosphorus-based derivatives are such as ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0142] Advantageously, the sulfur-based derivatives are such as ammonium sulfate, ammonium hydrogen sulfate.

[0143] Advantageously, the organic acid-based derivatives are such as ammonium citrate, ammonium acetate.

[0144] Advantageously, the carbonate derivatives are such as ammonium carbonate, ammonium hydrogen carbonate.

[0145] Advantageously, the nitrogen-based derivatives are such as ammonium nitrate.

[0146] Advantageously, the ammonium salt is at a mass content of dry extract of the adhesive composition less than or equal to 0.030, preferably less than or equal to 0.020.

[0147] Advantageously, 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.

[0148] Preferably, the mass content of ammonium chloride preferably ranges from 0.30% to 3.00% relative to a mass content of dry extract of the adhesive composition. Over this range, the hot reactivity is further improved and the processing qualities of the composition are preserved without affecting the flexibility of use of the aqueous adhesive composition.

[0149] 1.5 Additives - Manufacture of the aqueous adhesive composition

[0150] 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.

[0151] 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. Compound (III) is then added in one or more batches. The resin can be left to stand as is, 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 stand for 24 hours before adding the additional compound, or the addition of the additional compound can be done 15 minutes before using the aqueous adhesive composition.

[0152] The production of the thermosetting resin can be carried out at a pH between 7 and 14, more preferably between 9 and 12.

[0153] Thus, the aqueous adhesive composition is obtained by mixing: - of 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, compound (III) is added at a mass rate of dry extract of the aqueous adhesive composition ranging from 0.003 to 0.160 to obtain the aqueous adhesive composition.

[0154] The concentration of the composition can be adjusted according to its specific use (open time, viscosity).

[0155] 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.

[0156] 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).

[0157] 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.

[0158] Preferably, the water content of the aqueous adhesive composition ranges from 20 to 95% by weight, preferably from 40 to 90% by weight.

[0159] By total dry extract rate of the adhesive composition, we mean the ratio between the mass of residue obtained after drying of the adhesive composition and the mass of the adhesive composition before drying.

[0160] 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.

[0161] These two dry extract rates are measured in accordance with standard NF EN 827 (March 2006).

[0162] 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

[0163] 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.

[0164] 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.

[0165] In one embodiment, these two elements are made of wood.

[0166] Wood means plant tissue from woody plants. Examples of tissue Plant tissue consists of the trunk, branches, and roots. For example, woody plants from which plant tissue is derived include oak, chestnut, ash, walnut, beech, poplar, fir, pine, olive, alder, and birch.

[0167] 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.

[0168] By element is meant any monolithic particle or 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.

[0169] 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

[0170] 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 to each other using a layer of aqueous adhesive composition.

[0171] Advantageously, cooking is carried out by steam cooking, cooking by contact with the plates of a cooking press or high frequency cooking.

[0172] 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.

[0173] 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 know how to adapt the weight of aqueous adhesive composition to their wooden elements and to their own process.

[0174] After the step of applying the adhesive composition, a baking step is carried out: 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] The duration of the heating and / or pressurizing step varies from a few minutes to a few hours depending on the case, in particular depending on the temperature-pressure pair used.

[0180] In one embodiment, the two elements to be assembled are made of wood.

[0181] 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.

[0182] III - EXAMPLES OF CARRYING OUT THE INVENTION AND COMPARATIVE TESTS

[0183] 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, the cold stability is improved and the hot reactivity, i.e. the gel time at 95°C, of ​​the aqueous adhesive composition according to the invention is greater compared to a conventional adhesive composition without formaldehyde.

[0184] For this, three aqueous adhesive compositions were prepared, two in accordance with the embodiment of the invention (hereinafter noted C1 and C-2), one composition of the state of the art according to WO2017 / 168109 noted T0. Their for The compositions (expressed as a percentage by weight) are shown 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 water).

[0185] Adhesive composition C-0 is a state-of-the-art composition based on 5-(hydroxymethyl)-furfural and phloroglucinol.

[0186] The adhesive compositions C1 and C-2 according to the invention are compositions based on 5-(hydroxymethyl)-furfural and phloroglucinol and urea for C1 and based on 5-(hydroxymethyl)-furfural and phloroglucinol and ammonium chloride for C-2.

[0187] Protocol for producing the aqueous adhesive composition

[0188] In a 250mL flask equipped with a mechanical stirring system, the aromatic compound A2 (for example phloroglucinol) and the sodium hydroxide are introduced. Stirring is carried out for 1 to 10 minutes to homogenize (for example at 250 revolutions per minute). Then the compound Al (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. The compound Al may be prepared beforehand in aqueous solution. The compound (III), for example urea, may then be added in one or more stages. Depending on the chosen reaction temperature, a cooling stage may be applied to the preparation to bring the reaction medium to room temperature, for example. The resin obtained may 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 additional compound (for example ammonium chloride) is added, followed by the technical fillers described above. Depending on the components added, the mixture is left for 5 to 15 minutes under mechanical stirring at room temperature. After this time, the aqueous adhesive composition is ready for use.

[0189] [Tables 1] Adhesive compositions C-0 Cl C-2 C-3 5-(hydroxymethyl)-furfural (1) 27.6 26.7 26.3 25.2 Phloroglucinol (2) 7.6 7.4 7.3 7.0 Urea (3) 0 1.4 1.4 2.9 Ammonium chloride (4) 0 0 0.4 0.4 Sodium hydroxide (5) 1.6 1.7 1.6 1.6 Total weight of dry extract of adhesive composition 64.1 64.4 63.9 63.9 Urea dry extract rate 0 0.022 0.022 0.045 Ammonium chloride dry extract rate 0 0 0.006 0.006 Water weight 35.9 35.6 36.1 36.1 Olive kernel powder (6) 9.1 9.1 9.0 9.0 Chalk (7) 18.2 18.1 17.8 17.9 Total 100.0 100.0 100.0 100.0 1. HMF (from Aldrich; purity > 99%); 2. Phloroglucinol (from Aldrich; 99% purity); 3. Urea (from Aldrich; 99% purity); 4. Ammonium chloride (from Aldrich; 99% purity); 5. Sodium hydroxide (from Aldrich; diluted to 99%); 6. Olive kernel powder from the company La Provençale; 7. Chalk from the Imerys company.

[0190] Freezing time

[0191] 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, fitted with a rim adapted to the equipment. A foam ring crimps 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.

[0192] 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.

[0193] Protocol for producing the test piece

[0194] 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 composite wood 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.

[0195] 24 hours after this cooking step, the test specimens are cut, in the 7-layer plywood panel previously obtained, according to the recommendations of 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 person skilled in the art 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).

[0196] The adhesion levels are characterized by measuring the shear force denoted 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 denoted 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 (denoted 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 greater than that of the control specimen.A value greater than 90 corresponds to a shear stress greater than IMPa.

[0197] [Tables2] Adhesive compositions C-0 Cl C-2 C-3 Adhesion Adhesive performance 107 103 140 102 Gelling time at 95C Gelling time 100 100 28 31

[0198] To validate the bonding performance, a value greater than 90 is expected compared to the conditions of standard EN314-1. The aqueous adhesive compositions according to the invention C1, C-2 and C-3 have a peel force greater than 90 and substantially equivalent or greater than the control composition C-0.

[0199] It is found that the gel time is considerably reduced by the compositions C-2 and C-3 which improves the hot reactivity of the aqueous adhesive composition and here we can clearly see the effect of the additional ammonium chloride compound.

[0200] Exemplification of the improvement of cold stability on aqueous adhesive composition:

[0201] Protocol for manufacturing aqueous adhesive compositions for monitoring the cold stability of aqueous adhesive compositions:

[0202] 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 revolutions per minute). 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. The compound (III), for example urea, can then be added in one or more stages. Depending on the chosen reaction temperature, a cooling stage can be applied to the preparation to bring the reaction medium to room temperature, for example.

[0203] For this purpose, four aqueous adhesive compositions were prepared, three in accordance with the embodiment of the invention (hereinafter denoted R1 to R-3), one composition of the state of the art according to WO2017 / 168109 denoted R-0. Their formulations (expressed as a percentage by weight) are presented in Table 3 below.

[0204] [Tables3] Adhesive compositions R-0 Rl R-2 R-3 5-(hydroxymethyl)-furfural (1) 37.9 36.7 35.1 32.2 Phloroglucinol (2) 10.5 10.2 9.8 8.9 Urea (3) 0 1.9 4.0 8.0 Sodium hydroxide (4) 2.2 2.3 2.2 1.9 Total weight of dry extract of adhesive composition 50.6 51.1 51.1 51.1 Urea dry extract rate 0 0.04 0.08 0.16 Water weight 49.4 48.9 48.9 48.9 Total 100.0 100.0 100.0 100.0 1. HMF (from Aldrich; purity > 99%); 2. Phloroglucinol (from Aldrich; 99% purity); 3. Urea (from Aldrich; 99% purity); 4. Sodium hydroxide (from Aldrich; diluted to 99%).

[0205] The stability of the adhesive compositions is demonstrated by monitoring the viscosity of the compositions depending on time.

[0206] Viscosity measurement

[0207] After preparing the various aqueous adhesive compositions, the viscosity is measured at different time intervals. The viscosity is measured using a Brookfield viscometer using the LV 02 or No. 62 spindle using the following protocol: the sample is transferred to the thermostatically controlled chamber up to approximately 150 mL, avoiding the formation of air bubbles, the sample is allowed to regulate at the measurement temperature of 20°C for 1 to 20 minutes depending on the starting temperature of the composition. The rotation speed of the spindle is selected, for example 60 rpm or 60 revolutions per minute, and the spindle is started to rotate. The rotating spindle is waited for to stabilize (1 minute) before taking the first reading and the displayed result is read.

[0208] The results are reported in Table 4 below:

[0209] [Tables4] Time in days R-0 Rl R-2 R-3 1 100 100 100 100 2 143 103 103 105 7 520 172 144 123 14 - 319 262 191 23 - 890 520 290 The above results are calculated on a base of 100 to allow for easier comparison.

[0210] It can be seen that the Control composition R-0 reaches the highest viscosity value of the compositions presented in 7 days. It takes 23 days for the composition R-2 to reach a viscosity of 520. The control composition is the least stable when cold because its viscosity increased more quickly than those of the other compositions.

[0211] At 23 days, composition R-3 has the lowest viscosity of all the compositions. It is the most stable composition. This illustrates the contribution of compound (III) to the cold stability of the composition.

[0212] Thus, the aqueous adhesive compositions according to the invention offer greater cold stability than the adhesive composition of document WO2017 / 168109 without penalizing the bonding quality of the adhesive composition and thus providing greater flexibility of use.

[0213] 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 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 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 a compound (III): RI HKN / ' R2 R3 in which each group RI, R2, R3 represents, independently of one another, an alkyl, alkenyl, aryl, arylalkyl, alkylaryl, cy-cloalkyl or hydrogen group, X represents S, O or N-R4 with R4 representing an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl group or the compound (III) is melamine or uracil; with the compound (III) being at a mass content of dry extract of the aqueous adhesive composition ranging from 0.003 to 0.160.;

2. Composition according to the preceding claim, in which the compound (III) is at a mass content of dry extract of the adhesive composition less than or equal to 0.150, preferably less than or equal to 0.

100.

3. Composition according to any one of the preceding claims, in which the compound (III) is at a mass content of dry extract of the adhesive composition greater than or equal to 0.

004.

4. A composition according to any preceding claim, wherein compound (III) is urea.

5. A composition according to any preceding claim, wherein the aromatic compound Al has the general formula (II):

6. ".X.. (II) where B and C represent CHO or CH2OH respectively, X represents O, 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. 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): 0ta2)

7.

8.

9. 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. Composition according to any one of the preceding claims, in which 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. Composition according to any one of the preceding claims, in which the aqueous adhesive composition is obtained by mixing: in a first phase a thermosetting resin by mixing: - the aromatic compound Al, and - the 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 and compound (III) are added at a mass rate of dry extract of the aqueous adhesive composition ranging from 0.003 to 0.160 to obtain the aqueous adhesive composition.

10. Composition according to any one of the preceding claims, further comprising an ammonium salt at a mass content of dry extract of the aqueous adhesive composition ranging from 0.001 to 0.

050.

11. Composition according to the preceding claim in which 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.

12. Use of an adhesive composition according to any one of claims 1 to 11 for bonding at least two cellulosic elements, advantageously at least two wooden elements.

13. 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 11 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.

14. 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.

15. 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 11 joining at least one of the elements to the other.