Aqueous adhesive composition comprising a thermosetting resin having a reduced quantity of polyphenol

Abstract

The invention relates to an aqueous adhesive composition, characterised in that it comprises 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 function or a hydroxymethyl function, the other being an aldehyde function or a hydroxymethyl function; - at least one compound (C) of formula R3-NH-(C=X)-N(R1R2): in which, independently of one another, each group R1, R2, R3 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 or cycloalkyl group, or the compound (C) is melamine or uracil; and in that the aqueous adhesive composition comprises an aromatic polyphenol A2 comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two ortho positions of at least one of the hydroxyl functions being unsubstituted, and the ratio of aromatic polyphenol A2 to compound A1 and compound (C) ranging from 0.1 to 20%.

Description

AQUEOUS ADHESIVE COMPOSITION COMPRISING A THERMO-SETTING RESIN WITH A REDUCED QUANTITY OF POLYPHENOL

[0001] The field of the present invention relates to aqueous adhesive compositions intended for bonding fibrous materials, compounds of aggregated particles, composites based on these fibrous materials, as well as the use of these composites as furniture panels.

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

[0003] We know of the state of the art and in particular of application EP4359455 of thermosetting resins composed of an aminoplast precursor reagent, 5-(hydroxymethyl)-furfural or its oligomers or isomers, glyoxaldehyde and para-toluenesulfonic acid.

[0004] We also know of the state of the art and in particular of application EP3366468 of particle boards glued with a resin based on an aminoplast precursor reacting with 5-(hydroxymethyl)-furfural and its oligomers.

[0005] The drawback of these compositions is that they require the use of a formaldehyde precursor and ammonia as a catalyst, namely hexamethylenetetramine. However, due to recent regulatory changes, particularly European regulations on this type of compound, the aim is to limit, or even eliminate, the use of formaldehyde or formaldehyde precursors as much as possible.

[0006] In its application W02017 / 168109, the Applicant proposed aqueous adhesive compositions for wood bonding, comprising a thermosetting resin based on phloroglucinol and 5-(hydroxymethyl)-furfural, exhibiting high adhesive properties and free from formaldehyde.

[0007] However, the ability of a glued object to maintain cohesion in a humid environment is an important characteristic to guarantee the performance of the adhesive composition, thus allowing the use of these aqueous adhesive compositions to be extended to more extreme conditions in terms of humidity.

[0008] The invention aims to provide an aqueous adhesive composition, comprising a thermosetting resin, exhibiting high adhesive properties, free from formaldehyde, melamine, formaldehyde precursor such as hexamethylenetetramine as a curing catalyst, and offering significant adhesion performance in humid environments, thus providing greater flexibility of use.

[0009] However, during her research, the Applicant discovered an aqueous adhesive composition that does not use free formaldehyde, is more stable at cold temperatures, and meets the above objective.

[0010] Thus, one object of the invention relates to an aqueous adhesive composition comprising a thermosetting resin based on: - of at least one aromatic compound A1 comprising at least one aromatic ring bearing 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; - of at least one compound (C): in which each group R1, 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, or cycloalkyl group, or the compound (C) is melamine or uracil; and in that the aqueous adhesive composition comprises an 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 with the mass ratio of aromatic polyphenol A2 to compound A1 and compound (C) ranging from 0.1 to 20.0%.

[0011] The Applicant proposes an adhesive system free of all additives leading to the emission of toxic compounds such as hexamethylenetetramine, formaldehyde, melamine or glyoxal, presenting by the addition of an aromatic polyphenol A2 new properties for this type of thermosetting resins allowing handling without the need for aspiration to protect the user.

[0012] The Applicant thus hypothesizes that adding an aromatic polyphenol A2 at a given concentration will produce bonded objects resistant to wet immersion, which is entirely new compared to existing knowledge of aldehyde-based resins (excluding formaldehyde) and nitrogenous aminoplast precursors. The aqueous adhesive composition also does not require a formaldehyde precursor such as hexamethylenetetramine as a curing catalyst.

[0013] In addition to the effects mentioned above, the composition ensures a relatively long service life compared to state-of-the-art compositions, thanks in particular to viscosity stability over a range of 300 to 1000 cP.

[0014] Preferably, the mass ratio of aromatic polyphenol A2 to compound A1 and compound (C) ranges from 1.0 to 30.0% and preferably from 1.5 to 10.0%.

[0015] Advantageously, aromatic polyphenol A2 is present in a dry extract level of the adhesive composition ranging from 1.5 to 10%.

[0016] Adding a quantity of aromatic polyphenol A2, necessary for implementing the invention, offers the advantage of allowing the user to handle the resin without the need for suction. Furthermore, the quantity used is relatively small, thus not increasing the cost of the aqueous adhesive composition. This addition also improves the internal cohesion performance in bonding a material composed solely of aromatic compound A1 and compound C.

[0017] Preferably, aromatic compound A1 has a dry extract content in the adhesive composition ranging from 28 to 50%.

[0018] This range allows for the production of dry resin extracts that can be adjusted to the gluing and humidity conditions in order to form a bonded material.

[0019] Advantageously, compound (C) has a dry extract content of the adhesive composition ranging from 6 to 24%.

[0020] The moderate cost of compound (C) compared to compound A2 gives it an advantage in terms of resin production cost. This compound (C) also provides fluidity and stability to the resulting resin.

[0021] Advantageously, the dry extract content of the adhesive composition is less than or equal to 80%.

[0022] Preferably, the dry extract content of the adhesive composition is between 50 and 70%. This water content range allows the resin to be used in applications where excessive water vapor pressure in the bonded material is not acceptable.

[0023] I- FORMULATION OF THE AQUEOUS ADHESIVE COMPOSITION

[0024] In this description, unless expressly stated otherwise, all percentages (%) shown are % by mass.

[0025] By "para position relative to each other," we mean that the functional groups in question are opposite each other, that is, in positions 1 and 4 of the 6-membered aromatic ring. Similarly, the "para position" relative to a functional group is a position opposite that functional group on the 6-membered aromatic ring bearing the functional group.

[0026] By "ortho position of a functional group," we mean the position occupied by the carbon atom of the aromatic ring immediately adjacent to the carbon atom of the aromatic ring bearing the functional group. Similarly, the "ortho position" with respect to a functional group is the position adjacent to the functional group on the aromatic ring bearing the functional group.

[0027] By "meta position of a functional group," we mean the position occupied by the carbon atom of the aromatic ring separated from the carbon atom of the aromatic ring bearing the functional group by a single other carbon atom of the aromatic ring. Similarly, the "meta position" with respect to a functional group is the position adjacent to the "ortho functional group" on the aromatic ring bearing the functional group.

[0028] By "meta position relative to each other", we mean that the functions in question, for example the hydroxyl functions in the aromatic polyphenol, are carried by carbons of the aromatic ring separated from each other by a single other carbon of the aromatic ring.

[0029] By "member" of a nucleus, we mean an atom that makes up the nucleus's skeleton. For example, a benzene ring has six members, each member consisting of a carbon atom. In another example, a furanine ring has five members, four of which are carbon atoms and the remaining member is an oxygen atom.

[0030] “CHO” represents the aldehyde function.

[0031] “CH2OH” represents the hydroxymethyl function.

[0032] "Compound A1" refers, within the context of the invention, to the aromatic compound defined in paragraph 1.1.

[0033] "Compound C" refers, within the context of the invention, to the compound of formula C defined in paragraph I.2.

[0034] "Compound A2" refers, within the context of the invention, to the aromatic polyphenol-based compound defined in paragraph I.3.

[0035] Within the scope of the invention, the carbon products mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass.

[0036] Within the framework of the invention, it may also be envisaged that the carbon products mentioned in the description include isotopes of certain chemical elements.

[0037] 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 (that is, bounds 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 (that is, including the strict bounds a and b).

[0038] The expression "composition based on" should of course be understood as a composition comprising the mixture and / or reaction product of the various basic constituents used for this composition, some of which may be intended to react or likely to react with each other or with their immediate chemical environment, at least in part, during the various manufacturing phases of the composition, textile material, composites or finished articles comprising such composites, in particular during a cooking stage.

[0039] The aqueous adhesive composition according to a first embodiment of the invention therefore comprises at least one (i.e. one or more) thermosetting resin according to the invention, this thermosetting resin is itself based on at least one (i.e. one or more) aromatic compound, based on at least one (i.e. one or more) compound of formula (C) and at least one (i.e. one or more) aromatic polyphenol, constituents which will be described in detail below. 1.1 - Aromatic compound A1

[0040] The first essential constituent of the thermosetting resin is an aromatic compound A1 comprising at least one aromatic ring bearing 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.

[0041] Thus, according to the invention, it is said aromatic ring that bears 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 ring and B, C represent CHO or CH2OH respectively.

[0042] The aromatic ring is advantageously a 5- or 6-membered ring, comprising, as members, carbon atoms and optionally one or more heteroatoms, in particular nitrogen, oxygen, or sulfur atoms, possibly oxidized as N-oxide or S-oxide. In a variant, the aromatic ring comprises 0, 1, or 2 heteroatoms. The remainder of the aromatic ring may or may not be substituted.

[0043] The aromatic ring can bear 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0044] The aromatic ring can bear 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0045] In addition, the aromatic ring can also carry 0, 1 or 2 other function(s), in particular hydroxyl.

[0046] In the embodiment in which the aromatic ring is a 6-membered ring, the B and hydroxymethyl functions are advantageously in meta or para positions relative to each other.

[0047] 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, and sulfur atoms, optionally oxidized as N-oxide or S-oxide. Advantageously, the aromatic ring comprises one or two heteroatoms, preferably one heteroatom.

[0048] 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 only one aldehyde function; - the aromatic nucleus includes one or two hydroxymethyl functions; - the aromatic nucleus comprises one or two aldehyde functions.

[0049] Advantageously, apart from the aldehyde and hydroxymethyl functions, the rest of the aromatic ring is not substituted.

[0050] Advantageously, in the first case, the aromatic core comprises: - a single aldehyde function; - a single hydroxymethyl function; - apart from the aldehyde and hydroxymethyl functions, the rest of the aromatic ring is not substituted.

[0051] Advantageously, in a second case, the aromatic core comprises: - two hydroxymethyl functions; - apart from the hydroxymethyl functions, the rest of the aromatic ring is not substituted.

[0052] Advantageously, in a third case, the aromatic core comprises: - two aldehyde functions; - apart from the aldehyde functions, the rest of the aromatic ring is not substituted.

[0053] Advantageously, the aromatic compound A1 corresponds to the general formula (II): in which B and C represent CHO or CH2OH respectively, X represents O, NR1, NO, S, SO, SO2, SR2R3, Ri, R2, R3 each represent, independently of each other, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group.

[0054] In a first variant, compound A1 has the general formula (II'): in which X, B are as defined previously.

[0055] In a particularly advantageous embodiment, B represents CHO. In another embodiment, B represents CH2OH.

[0056] According to a preferred embodiment, X represents O.

[0057] In this embodiment, compound A1 has the formula (Ha): B being such as defined previously and more specifically of formula (H'a1) or (H'a2): (IFalQ (H'a2)

[0058] Preferably, 5-(hydroxymethyl)furfural (H'a1) is a particularly suitable aldehyde, given that this organic compound can easily be obtained from renewable resources. Indeed, it is produced notably from the dehydration of certain sugars such as fructose, glucose, sucrose, cellulose, and inulin.

[0059] In a second variant, compound A1 has the general formula (II”): B being such as defined previously and more specifically of the formula (H”a1) or (H”a2):

[0060] In another embodiment, X represents NR1 or NO, advantageously NR1. R1 is as defined previously.

[0061] In one variant, compound A1 has the formula (llb): B being such as defined previously and more specifically of formula (H'b1) or (H'b2): in which Ri represents a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl, or cycloalkyl group. Advantageously, Ri represents a hydrogen or an alkyl group in Ci-Ce.

[0062] In another embodiment, X represents S, SO, SO2 or SR2R3.

[0063] In this embodiment, compound A1 has the formula (Ile): B being such as defined previously with X representing S, SR2R3, SO, SO2, R2, R3 each represent, independently of each other, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group, B being as defined previously; and more particularly of formula (H'c1) or (H'c2): in which X represents S, SR2R3, SO, SO2, R2, R3 each represent, independently of each other, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group.

[0064] Compound A1 can therefore be:

[0065] Advantageously R2, R3 each represent, independently of each other, a C1-C6 alkyl radical.

[0066] Compound A1 is advantageously of formula (H'c1) or (I I'c2).

[0067] In another variant, the aromatic ring is a 6-membered ring, which may include 0, one, or more heteroatoms, particularly nitrogen, possibly oxidized as an N-oxide. In a further variant, the aromatic ring comprises 0, 1, or 2 heteroatoms.

[0068] The B and hydroxymethyl functions are advantageously in meta or para positions relative to each other.

[0069] The aromatic ring can bear 0, 1 or 2 aldehyde functions, advantageously 0 or 1 aldehyde function.

[0070] The aromatic ring can bear 1, 2 or 3 hydroxymethyl functions, advantageously 1 or 2 hydroxymethyl functions.

[0071] Advantageously, compound A1 has the general formula (III): in which D represents a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl, or a hydroxyalkyl group. According to the invention, p+n>1 and m<5.

[0072] Advantageously m is equal to 0 or 1.

[0073] Advantageously D represents a hydrogen or hydroxymethyl group.

[0074] In one variant, n equals 1 and p equals 1.

[0075] In another variant, n equals 3 and p equals 0.

[0076] In another variant, n equals 2 and p equals 1.

[0077] In another variant, n equals 1 and p equals 2.

[0078] In another variant, n equals 0 and p equals 2.

[0079] In another variant, n equals 0 and p equals 3.

[0080] Preferably, the aromatic ring of aromatic compound A1 is a benzene ring. More preferably, this aldehyde is chosen from the group consisting of 2-hydroxymethylbenzene-1-carboxaldehyde, 3-hydroxymethylbenzene-1-carboxaldehyde, 4-hydroxymethylbenzene-1-carboxaldehyde, 1,2-hydroxymethylbenzene, 1,3-hydroxymethylbenzene, 1,4-hydroxymethylbenzene, 2-Methoxybenzaldehyde, 3-Methoxybenzaldehyde, 4-Methoxybenzaldehyde, 2,6-Dimethoxybenzaldehyde, 2,4,6-Trimethoxybenzaldehyde, and mixtures of these compounds.

[0081] Even more preferentially the aromatic compound A1 used is 1-hydroxymethyl-benzene-4-carboxaldehyde of formula (Ilia) or 1,4-hydroxymethyl-benzene of formula (lllb) or terephthalic acid of formula (llll'b):

[0082] Preferably, when the thermosetting resin is based on polyphenol and one or more compounds of formula (I), the composition is free of formaldehyde.

[0083] When the thermosetting resin is based on polyphenol, one or more compounds of formula (I) and aldehydes, each aldehyde is preferentially different from formaldehyde. The composition is then also formaldehyde-free.

[0084] In other words, and preferably, when an aldehyde is present, the aldehyde or each aldehyde in the thermosetting resin is different from formaldehyde.

[0085] By formaldehyde-free, we mean that the mass percentage 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. I.2 Compound (C)

[0086] The second essential component of thermosetting resin is a compound with formula (C): in which each group R1, R2, R3 independently represents an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl or hydrogen group, X represents S, O or N-R4 with R4 representing an alkyl, aryl, arylalkyl, alkylaryl, cycloalkyl group.

[0087] Preferably, R1 and / or R2 and / or R3 represent hydrogen. Preferably, X represents O.

[0088] Advantageously, compound (C) is urea with the formula: I.3 - Aromatic phenol compound A2

[0089] The third essential constituent of the thermosetting resin is an aromatic phenol compound A2 bearing at least one aromatic ring bearing at least two hydroxyl functions, the latter being in meta position relative to each other, the two ortho positions of at least one of the hydroxyl functions being unsubstituted.

[0090] In a preferred embodiment, at least one of the aromatic rings of the aromatic polyphenol bears three hydroxyl functions in meta positions relative to each other.

[0091] Preferably, the two ortho positions of each hydroxyl function of at least one aromatic ring are unsubstituted.

[0092] Even more preferentially, the two ortho positions of each hydroxyl function of each aromatic ring are unsubstituted.

[0093] Even more preferably, the remainder of each aromatic ring is unsubstituted. This means that the other carbon atoms of the remainder of each aromatic ring (those other than the carbon atoms bearing the hydroxyl functions or bearing the group linking the aromatic rings together) bear a single hydrogen atom.

[0094] Advantageously, the aromatic ring bearing at least two hydroxyl functions in meta positions relative to each other, with the two ortho positions of at least one of the hydroxyl functions being unsubstituted, is a benzene ring.

[0095] Advantageously, each aromatic ring of the aromatic polyphenol is a benzene ring.

[0096] As an example of an aromatic polyphenol containing a single aromatic ring, we can cite in particular resorcinol and phloroglucinol, for a reminder of their respective structural formulas (IV) and (V):

[0097] For example, in cases where the aromatic polyphenol has several aromatic rings, at least two of these aromatic rings, identical or different, are chosen from those with general formulas: in which the symbols Z1, Z2, identical or different if there are several on the same aromatic nucleus, represent an atom (for example carbon, sulfur or oxygen) or a bonding group by definition at least divalent, which links at least these two aromatic nuclei to the rest of the aromatic polyphenol.

[0098] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl sulfide with the following structural formula (VII):

[0099] Another example of an aromatic polyphenol is 2,2',4,4'-tetrahydroxydiphenyl benzophenone with the following structural formula (VIII):

[0100] It is noted that each compound VII and VIII is an aromatic polyphenol comprising two aromatic rings (of formula Vl-c) each of which carries at least two (in this case two) hydroxyl functions in meta position relative to each other.

[0101] Note that in the case of an aromatic polyphenol with at least one aromatic ring conforming to the formula Vl-b, the two ortho positions of each hydroxyl group of at least one aromatic ring are unsubstituted. In the case of an aromatic polyphenol with several aromatic rings conforming to the formula Vl-b, the two ortho positions of each hydroxyl group of each aromatic ring are unsubstituted.

[0102] According to one embodiment of the invention, the aromatic polyphenol 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.

[0103] In a particularly advantageous embodiment, the aromatic polyphenol is phloroglucinol. I.4 Additives - Manufacturing of the aqueous adhesive composition

[0104] The aqueous adhesive composition according to the embodiment of the invention may, of course, include all or some of the usual additives for aqueous adhesive compositions such as those used in conventional phenolic adhesives; examples include 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, to increase the viscosity of the composition. Also included are additives that modify the setting or gelling time and the open time of the resin.As is well known to those skilled in the art, setting or gel time is the time during which the resin can be applied to its substrate, and open time is the time during which, after application, the resin can be left exposed to air without compromising the quality of the subsequent adhesive bond with the additional substrate. Setting or gel time and open time are dependent on factors such as temperature, pressure, and resin concentration.

[0105] Typically, when preparing the resin, the constituents of the thermosetting resin itself are mixed without a predefined order but advantageously by first mixing the water with the soda then the aromatic compound A1 with the compound (C) then the polyphenolic compound A2.

[0106] Advantageously, in one embodiment, the aqueous adhesive composition is obtained by: In the first phase, we mix: - aromatic compound A1, and - the compound (C); in a basic solvent preferably having a pH between 7 and 14, more preferably between 9 and 12, to obtain a first pre-condensate; then in a second step the previous pre-condensate is stirred in an acidic solvent preferably having a pH between 0.5 and 5, more preferably between 1.5 and 3, to obtain a thermosetting resin, In a third step, the thermosetting resin is basified with a basic solvent at a pH ranging from 6 to 12, more preferably from 8 to 11; and In a fourth step, polyphenol A2 is added to the resin and to a dry extract rate of the adhesive composition ranging from 1.5 to 10.0% to obtain the aqueous adhesive composition.

[0107] The concentration of the composition can be adjusted according to its specific use (opening time, viscosity).

[0108] The characteristics of the adhesive composition described above can be adjusted by adding a number of additives well-known in the literature. These additives include wetting agents, dispersants, thickeners, etc. It is understood that a person skilled in the art will be able to adjust the quantities of these additives according to their own constraints and industrial requirements.

[0109] The composition can be used immediately or stored at room temperature (23°C) or below 23°C to increase the time of use of the composition; a person skilled in the art will determine the possible storage time based on the concentration of the composition.

[0110] Preferably, the composition further comprises a catalyst selected from a mineral acid, an organic acid or an ammoniacal derivative at a dry extract rate of the aqueous adhesive composition ranging from 0.5 to 4%, and preferably an ammonium salt.

[0111] Preferably, the catalyst is chosen from among carboxylic acids, preferably citric acid, methanesulfonic acid, para-toluenesulfonic acid; hydrochloric acid, sulfuric acid, nitric acid and ammonium salts. II. Composite manufacturing and bonding process for fibrous materials

[0112] A second object of the invention relates to a composite comprising materials with a density greater than or equal to 500 kg / m³ 3 bound by the adhesive composition as described previously.

[0113] For example, a composite can be manufactured by bonding fibrous materials with a density greater than or equal to 500 kg / m³. 3, in which: - A layer of the aqueous adhesive composition, as defined above, is applied by spraying onto the fibrous materials, and - the pulverized fibrous materials are heated in a compression system to obtain the desired density and thickness of the material.

[0114] For example, cooking can be done by heating press or by microwave.

[0115] In one embodiment, advantageously, the materials are fibrous materials chosen from natural organic or mineral fibers and synthetic fibers.

[0116] Advantageously, the fibers are chosen from wood fibers, glass fibers, carbon fibers, polyester fibers, polyamide, aramid, rayon or even cellulosic fibers from defibration of hardwood or resinous wood.

[0117] In another embodiment, the materials can be agglomerated particles, wood strips or wood veneers.

[0118] Preferably, the composite should have a quantity of resin ranging from 6% to 15% and preferably from 9% to 13% of the total mass.

[0119] Advantageously, the composite is used for the manufacture of an element with a density greater than or equal to 500 kg / m³ 3 and especially as furniture panels. III - EXAMPLES OF INVENTION IMPLEMENTATION AND COMPARATIVE TESTS

[0120] These tests demonstrate that the performance of furniture panels based on a resin according to the invention as described above is better in maintaining cohesion in humid environments and during aging.

[0121] To this end, four aqueous adhesive compositions were prepared: two according to the embodiment of the invention (hereafter referred to as C1 and C2), and two control compositions, referred to as T1 and T2. Their formulations (expressed as percentages by weight) are presented in Table 1 below. The quantities listed in this table are those of the constituents in their dry state, converted to a total of 100 parts by weight of aqueous adhesive composition (i.e., the constituents without water).

[0122] The adhesive compositions C1 and C2 according to the invention are compositions based on 5-(hydroxymethyl)-furfural, urea and phloroglucinol.

[0123] The T1 and T2 control adhesive compositions are compositions based on 5-(hydroxymethyl)-furfural and urea.

[0124] Protocol for preparing the aqueous adhesive composition

[0125] In a 250 mL round-bottom flask equipped with a mechanical stirring system, water and aromatic compound A1 are introduced. The mixture is stirred for 5 to 10 minutes to homogenize it (e.g., at 250 rpm) at 30 °C. Then, compound C and one-tenth of the total 30% sodium hydroxide solution are added, and the mixture is stirred for 10 to 60 minutes at 70 °C (e.g., at 250 rpm). An acid catalyst, for example, 40% sulfuric acid, is added. The solution is stirred at a pH of 1 to 4, preferably 2, at 80 °C for 20 to 60 minutes. The remaining 30% sodium hydroxide solution is added, and the mixture is stirred while cooling to 70 °C. Aromatic compound A2 is added and the mixture is stirred for 25 to 120 minutes at 70°C, then cooled to the storage temperature. This results in a mixture of the aqueous adhesive composition according to the embodiment of the invention. After this time, the aqueous adhesive composition according to the embodiment of the invention is ready for use.

[0126] [Table 1] 1) HMF (from the Aldrich company; purity > 99%); 2) Phloroglucinol (from the Aldrich company; 99% purity); 3) Urea (from the Aldrich company; 99% purity) 4) Sulfuric acid (from the Aldrich company; concentration 50% in water); 5) Sodium hydroxide (from the Aldrich company; diluted to 30%).

[0127] Viscosity measurement

[0128] After preparing the various aqueous adhesive compositions, the viscosity is measured at different time intervals. Viscosity is measured using a Brookfield viscometer with the LV 02 or No. 62 spindle, following this protocol: the sample is transferred to the temperature-controlled chamber up to approximately 150 mL, avoiding the formation of air bubbles. The sample is allowed to stabilize at the measurement temperature of 20 °C for 1 to 20 minutes, depending on the initial temperature of the composition. The spindle rotation speed is selected, for example, 60 rpm (60 revolutions per minute), and the spindle is set to rotate. The spindle is allowed to stabilize (1 minute) before taking the first reading, and the displayed result is then read.

[0129] The results are shown in Table 2 below:

[0130] [Table 2]

[0131] The results above indicate the viscosity of the composition in mPa.s or in Cp.

[0132] The resin is characterized by its service life, as it maintains a viscosity range suitable for standard industrial applications in the manufacture of insulated process panels, MDF, particleboard, or OSB. The optimum operating range is 250 to 1000 cP for conventional application methods such as micro-droplet spraying.

[0133] It can be observed that the Control composition T2 can be kept for up to 14 days and beyond that a phase shift of the solution is observed, whereas the resins according to the invention (C1 and C2) with the addition of phloroglucinol allow maintenance in the greater viscosity range from 7 days up to 31 days.

[0134] Test tube preparation protocol

[0135] Wood fibers are sprayed with a mixture of 1% paraffin wax (based on the dry extract of the previously described adhesive composition) and 14% paraffin wax (based on the dry extract of the wood mass), to which a catalyst of 0.5% to 3% NH4Cl is added. The coated fiber is pre-formed in a 25 cm square frame, and the fiber cake is then fed into a press at a temperature between 170 and 220 °C. The pressing time is then adjusted to achieve optimal internal cohesion.

[0136] Internal cohesion test

[0137] Internal cohesion is determined in accordance with EN 319. An average of 5 samples gives the internal cohesion value for a panel produced.

[0138] Internal cohesion is the resistance force required to pull a sample of panel perpendicularly.

[0139] Internal cohesion is determined by examining a 5 cm x 5 cm section of the panel, with a thickness equal to that of the panel being characterized. This section is then bonded between two metal plates to create a slit. The tensile force is adjusted to measure the maximum force required to break the panel between 30 and 90 s. The maximum force is measured in MPa.

[0140] Performance is indicated on a scale of 100, with 100 being the reference value of the standard. Values ​​above 100 are validated for the application of the MDF panel.

[0141] cold water inflation test

[0142] The swelling determination is carried out in accordance with the EN 317 standard. An average of 5 samples gives the swelling value for a panel produced.

[0143] The swelling determination is performed on a 5 cm x 5 cm cross-section of the panel, with a thickness equal to that of the panel being characterized. For this test, the thickness of each sample is initially measured. The cut panel sample is then immersed in a water bath at 20°C for 24 hours. After this time, the excess water is removed, and the sample thickness is measured again. The swelling value is then expressed as a percentage of thickness. The performance is indicated on a scale of 100, with 100 being the reference value of the standard. Values ​​below 100 are considered valid for the panel's application to the wet MDF class.

[0144] The results of these two tests are reported in Table 3 below.

[0145] [Table 3]

[0146] Tests show that the adhesive compositions C1 and C2 according to the invention make it possible to obtain glued objects resistant to both wet immersion and having internal cohesion within standards, unlike the control compositions T1 and T2.

[0147] Thus, resins based on aromatic compound A1, compound (C) with the addition of compound A2 allow for performance in maintaining internal cohesion in a humid environment of a glued object while maintaining a viscosity range from 7 days to 30 days, thus guaranteeing greater flexibility of use.

[0148] The invention is not limited to the embodiments described above.

[0149] It will also be possible to combine the characteristics of the different embodiments and variants described or envisaged above, provided that they are compatible with each other.

Claims

DEMANDS 1. Aqueous adhesive composition, characterized in that it comprises a thermosetting resin based on: - of at least one aromatic compound A1 comprising at least one aromatic ring bearing 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; - of at least one compound (C): in which each group R1, 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, or cycloalkyl group, or the compound (C) is melamine or uracil; and in that the aqueous adhesive composition comprises an 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 with the mass ratio of aromatic polyphenol A2 to compound A1 and compound (C) ranging from 0.1 to 20.0%.

2. Composition according to the preceding claim, wherein the aromatic polyphenol A2 is at a dry extract level of the adhesive composition ranging from 1.5 to 10.0%.

3. Composition according to any one of the preceding claims, wherein the aromatic compound A1 is at a dry extract rate of the adhesive composition ranging from 28 to 50%.

4. Composition according to any one of the preceding claims, wherein the compound (C) is at a dry extract content of the adhesive composition ranging from 6 to 24%.

5. Composition according to any one of the preceding claims, wherein the dry extract content of the adhesive composition is less than or equal to 80%.

6. Composition according to any one of the preceding claims, wherein the aromatic compound A1 corresponds to the general formula (II): where B and C represent CHO or CH2OH respectively, X represents O, NR1, NO, S, SO, SO2, SR2R3, Ri represents a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group, R2, R3 each represent, independently of each other, a hydrogen, an alkyl, aryl, arylalkyl, alkylaryl or cycloalkyl group.

7. Composition according to any one of the preceding claims, wherein the aromatic compound A1 corresponds to the general formula (H'a1) or (H'a2): (H'aU) (H a2) 8. Composition according to any one of the preceding claims, wherein compound (C) is urea.

9. Composition according to any one of the preceding claims, wherein the aromatic core of aromatic polyphenol A2 bears three hydroxyl functions in meta positions relative to each other.

10. 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.

11. Composition according to any one of the preceding claims, wherein the mass ratio of aromatic polyphenol A2 to compound A1 and compound (C) ranges from 1.5 to 10.0%.

12. Composite comprising materials with a density greater than or equal to 500 kg / m³ 3bound by the adhesive composition according to any one of the preceding claims.

13. Composite according to the preceding claim, wherein the materials are fibrous materials which are selected from natural organic or mineral fibers and synthetic fibers.

14. A composite according to any one of claims 12 to 13, wherein the amount of resin is from 6% to 15% and preferably from 9% to 13% of the total mass.

15. Use of the composite according to any one of claims 12 to 14 for the manufacture of an element with a density greater than or equal to 500 kg / m³. 3 and especially as furniture panels.

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