Field of the Invention

This invention is directed to resins made from aldehydes and organic aldehyde-reactive compounds.

Background of the Invention

Resins made from aldehydes and organic aldehyde-reactive compounds have been described, particularly, the so-called phenolic resins from aldehydes and phenolic compounds such as phenol itself, and other activated aromatic compounds, see, e. g., C. Ellis, The Chemistry of Synthetic Resins, New York 1935, pages 277 to 488.

Organic aldehyde-reactive compounds comprise "activated aromatic compounds" which are defined herein as organic compounds that have at least one, preferably two or more, aromatic C-H group(s) in their molecules, where the carbon atom C of the said aromatic C-H group is a part of an aromatic carbocyclic or heterocyclic ring, which ring bears a hydroxyl group or an alkoxy group at another carbon atom C' in the same carbocyclic or heterocyclic ring in ortho position (immediately adjacent to the said carbon atom C of the said aromatic C-H group) or in para position (with an even number of carbon atoms between the said carbon atom C of the said aromatic C-H group, and the carbon atom C' that bears the said hydroxyl or alkoxy group), and which organic compound forms an addition product by reacting with an aldehyde. This addition product is characterised by a hydroxyalkyl group attached to the said carbon atom C of the said aromatic C-H group of the said organic ompound. Such activated aromatic compounds, hereinafter also referred to as "reactive aromatic compounds", have increased reactivity in electrophilic substitution reactions, compared to benzene. Representative compounds are phenol, alkylphenols such as cresols and xylenols, and longer-chain alklyphenolic compounds such as butylphenol, nonylphenol, and cardanol, dihydroxy phenols such as resorcinol, cardol, and dinuclear phenols such as bisphenol A, Mixtures of two or more reactive aromatic compounds can also be used. Other organic aldehyde-reactive compounds are organic amines, imines, imides and amides having at least one, preferably two or more, groups selected from the group consisting of amino groups, imino groups, imide groups, and amide groups. These compounds, also referred to as "aminoplast formers", form addition products with aldehydes which are characterised by hydroxyalkyl groups attached to the aminic, iminic, imidic, or amidic nitrogen atom which is the nitrogen atom in an amino, imino, imide, or amide group. The nitrogen atom in the amide, imino, or in the imide group may be a ring atom of a heterocyclic ring, or bound to a ring atom in a carbocyclic or heterocyclic ring, and the nitrogen atom of the amino group is bound to a ring atom in a carbocyclic or heterocyclic ring. Examples of these are the classes of aromatic amines, amides of carboxylic acids, cyanamides, guanamines, guanidines, ureas, sulphonamides, sulphurylamides, thioureas, triazines, and urethanes, individual compounds include melamine, benzoguanamine, acetoguanamine, caprinoguanamine, urea, cyclic ureas such as ethylene urea (imidazolidin-2- one), propylene urea (4-methyl-2-imidazolidinone), and glycoluril (tetrahydroimidazo[4,5- d]i midazole-2, 5(1 H,3H)-dione), as well as mixtures of two or more of the said organic amines, imines, imides, and amides.

Mixtures of one or more reactive aromatic compounds with one or more of the nitrogen- containing aldehyde-reactive compounds selected from the group consisting of organic amines, imines, imides and amides can also be used.

Aledehydes that are used in the invention include aliphatic, cycloaliphatic, and aromatic aldehydes, Apart from formaldehyde, the use of other aldehydes such as acetaldehyde, butyraldehyde, and acrolein has also been mentioned (ibid.). The use of higher aldehydes is also mentioned in Ullmann's Encyclopedia of Chemical Industry, 5 ^th ed. 1991, vol. A19, Phenolic Resins, chapter 3.2, pages 374 and 375 - Aldehydes, particularly, butyraldehyde, benzaldehyde, salicylaldehyde, acrolein, crotonaldehyde, acetaldehyde and glyoxal. Other resins, the so-called amino resins, are made by reacting aldehydes with organic compounds having amino, imino, imide, or amide groups. These compounds are frequently referred to as aminoplast formers. Well-known examples of these resins are urea-formaldehyde resins and melamine-formaldehyde resins. The need to reduce formaldehyde emissions and to at least partially replace phenol by renewable raw materials, as well as the search for low energy processes for the synthesis of the components, and the production of the resin therefrom have led to efforts for the development of new chemistry and technology in the resins business. It is therefore an object of the invention to provide components that are able to replace partially or completely the phenol and aldehyde components in phenolic resins, and the aminoplast formers and aldehyde components in amino resins while maintaining the desired properties of the resins so formed.

Many efforts have been made to at least partially replace phenols by lignin materials that stem from the cellulose and paper industry, in phenolic resins. Lignin is a naturally occurring organic compound that fulfils the definition of an activated aromatic compound as defined hereinabove. See, e. g., P. Solt et al., "Lignin Phenol Formaldehyde Resoles Using Base-Catalysed Depolymerised Kraft Lignin", Polymers 2018, 10, 1162, S. Kalami et al., "Replacing 100 % of Phenol in Phenolic Adhesive Formulations with Lignin", J. Appl. Polym. Sci. 2017, 45124, and WO 2021/005270 Al.

Lignins are generally classified into the groups of softwood, hardwood, and grass lignins. These native lignins are typically separated from the wood or other lignocelluloses in the form of "milled wood lignin" (MWL), "dioxane lignin", or "enzymatically liberated lignin". Industrially based technical lignins are by-products of chemical pulping: Kraft lignin (or sulphate lignin), alkali lignin (or soda lignin), and lignosulphonates are derived from the Kraft, the soda-anthraquinone, and sulphite pulping processes of lignocellulose. These pulping processes are directed to isolate the fibrous material (cellulose) from the lignocellulose. A further lignin source is the so-called acid hydrolysis lignin which is still mostly converted to pellets for firing. Other lignin grades have been made accessible by newer processes, viz., the organosolv process which provides a sulphur-free high purity lignin grade, and the hydrolysis process which is acid-catalysed and leads to formation of the so-called Hibbert ketones and of free phenolic moieties. Other emerging processes are the steam-explosion process and the ammonia-fibre expansion process. Any of these lignin materials may be used in the present invention, with the exception of lignosulphonates. Lignin materials provided by different sources and separated from the cellulose and hemicellulose accompanying materials in lignocellulose by the different processes as detailed supra differ from each other, not only in the composition with regard to the shares of 4- hydroxyphenyl-, guaiacyl- (3-methoxy-4-hydroxyphenyl-), and syringyl- (3,5-dimethyoxy-4- hydroxyphenyl-) units of the C9-building blocks in lignin, which is different for gymnosperms (predominantly guaiacyl units), angiosperms (both guaiacyl and syringyl units), and grass (predominantly 4-hydroxylphenyl units) but also in the decomposition that follows different routes depending on the kind of pulping process. Therefore, the lignins obtained by the processes supra have also variations in the molar mass, as reported in "Molar mass determination of lignins by size-exclusion chromatography", S. Baumberger et al., Holzforschung 2007 (61), pages 459 to 468.

It is also possible to generate fractions of high molar mass lignin, and low molar mass lignin by fractionated precipitation, see WO 2013/144 453 Al. These lignin fractions may be collected, e. g., in a first mixture comprising substantially lignin oligomers and polymers of a low degree of polymerisation (hereinafter each individually, and all collectively referred to as low molar mass lignins, "LML") having from 1 to 10 monomer units, and in a second mixture comprising substantially lignin polymers (hereinafter collectively referred to as high molar mass lignins, "HML") having from 11 to 70 monomer units. Any larger number of mixtures, each comprising different groups of oligomers and polymers, may also be collected from the isolated fractions provided by controlled precipitation, or other separation processes. The molar masses of lignin can be determined according to the method described in Linping Wang et al., Holzforschung 2019; 73(4): 363 to 369, by size-exclusion chromatography of acetylated samples of the lignin fractions. These mixtures can be condensed individually with aldehydes, and mixed thereafter, or they can be condensed in sequence, and the addition time of phenol and aldehyde can be varied. In WO 2013/144453 Al, variations of the condensation process lead to different levels of the possibility of substitution of phenol by lignin. Similar results have been obtained in our investigations when using such lignin fractions prepared according to WO 2013/144453 Al, together with monomeric 5-hydroxymethylfurfural (IUPAC name: (5-hydroxymethyl)furan-2-carbalde- hyde, in the description of the present invention referred to as "HI") as aldehyde component, alone, or in mixture with other aldehydes. In the course of the investigations which have led to the present invention, two or more than two lignin fractions which are reacted with HI have been found to lead to good results. Therefore, it is also an embodiment of the invention to use at least two, preferably more than two, and particularly, three or more, lignin fractions having different values of the average degree of polymerisation together with HI as aldehyde component, alone, or in mixture with other aldehydes for the preparation of the resin according to the invention. An example is the use of a mixture of four different fractions of lignin in the reaction with HI. The first of these fractions FI comprises lignin oligomers having a degree of oligomerisation of from 1 to n, the second of these fractions F2 comprises lignin oligomers or polymers having a degree of oligomerisation or polymerisation of from n+1 to m, the third of these fractions F3 comprises lignin oligomers having a degree of oligomerisation or polymerisation of from m+1 to o, and the fourth of these fractions F4 comprises lignin oligomers or polymers having a degree of oligomerisation or polymerisation of o+l or more. The degree of oligomerisation is the number of lignin monomer units in a oligomer or polymer molecule. Given an average molar mass of approximately 180 g/mol of a phenylpropane monomer unit having one methoxy group, useful values for n, m, and o, in the case of four groups, is n = 7, m = 14, o = 21, where n is at least 7, m is at least 14, and o is at least 21, and if n is increased by 1, the value of m is increased by 2 and the value of o is increased by 3. Other useful values are therefore n = 8, m= 16, and o = 24, and increasing values of n, m, and o to 9, 18, and 27; 10, 20, and 30; 11, 22, and 33; and 12, 24, and 36; and so forth by increasing the values for n, m, and o by one, two, and three, respectively, until 20, 40, and 60.

Lower molar mass lignins which have higher reactivity can be obtained by controlled degradation, or decomposition. Several ways of achieving controlled degradation, or decomposition have been described in the literature, including enzymatic decomposition, oxy dative cleavage, pyrolysis, and treatment with radical forming systems.

It is also possible to purify lignin from any of the sources mentioned, by a plethora of methods including ultrasonic extraction, solvent extraction, dialysis, and hot water treatment. It is particularly important to remove inorganic impurities such as sulphur which stems from the process chemicals. The reactivity of lignin can be increased by various processes, including demethylation, methylolation/hydroxymethylation, phenolation/phenolysis, reduction, oxydation, hydro lysis, and alkalation. See, e.g. Hu, FiHong, et al., Bioresources 6(3), pages 3515 to 3525, and WO 2013/144 454 Al. These techniques have been used to improve purity and reactivity of the lignin samples used in this invention.

Other naturally occurring organic materials that comprise activated aromatic compounds for use in this invention are tannins. They are usually classified as gallotannin (GT) [1], ellagitannin (ET) [2], complex tannin (XT) [3], and condensed tannin (CT) [4], see Formulae [1] to [4] infra (from "Tannins: Classification and Definition", K. Khanbabaee and T. van Ree, Nat. Prod. Rep., 2001, 18, pages 641 to 649):

Other aldehydes have been used to replace formaldehyde, both in phenolic resins, and in amino resins. See, e. g., P. Solt et al., "Technological Performance of Formaldehyde-free Adhesive Alternatives for Particleboard Industry", Int. J. Adhesion and Adhesives 94 (2019), pp. 99 to 131.

Alternatives for both formaldehyde and phenol have been considered in P. R. Sarika et al., "Bio-Based Alternatives to Phenol and Formaldehyde for the Production of Resins", Polymers 2020, volume 12, pages 2237 et seq. Such alternatives are mainly lignin, tannin and cardanol which are used in place of, or together with, phenols, and furfural, 5- hydroxymethylfurfural, glyoxal, which are used in place of, or together with, formaldehyde.

A resin where both the aldehyde and the activated aromatic compound or the aminoplast former are derived from renewable sources would be desirable, in view of the reasons mentioned supra that lead to the object of the present invention. At least a substantial amount of the aldehyde component used in the synthesis of the desired resin should be different from formaldehyde, and at least a substantial amount of the activated aromatic compound or aminoplast former used in the synthesis of the desired resin should be different from the aldehyde-reactive organic compound, i. e. phenols and/or aminoplast formers, commonly used in the synthesis of phenolic resins and amino resins. A substantial amount, in the context of the present invention, is at least 10 % of the mass of the aldehyde component, or of the aldehyde-reactive organic compound, or at least 5 % of the mass of both the aldehyde component, and at least 5 % of the mass of the aldehyde-reactive organic compound.

5-(Hydroxymethyl)-furfural is an aldehyde which can be prepared from cellulose and cellulose-containing material by hydrolysis to glucose, isomerisation to fructose, and subsequent dehydration in attractive yields. See, e. g., "Highly efficient preparation of 5- hydroxymethylfurfural Yu, Song-Bai et al., Chinese Chemical Letters 28 (2017), p. 1479 et seq.

In the discussion of documents of the state of the art, the names of chemical compounds, and the abbreviations therefor are those used in the cited documents.

In the patent application EP 3366468 Al, a process for the preparation of thermally curable resins is described comprising a step where "a polycondensable phenolic compound and/or an aminoplast former is reacted with 5-hydroxymethylfurfural ("HMF") under conditions leading to formation of polycondensates wherein the HMF comprises at least one HMF oligomer" (claim 1). In a preferred embodiment of this patent application, the mass fraction of HMF oligomers in the HMF component used is from 0.05 % to 100 % (see paragraph [0018] No results from the determination of the mass fractions of such oligomers are disclosed in this patent application; there is only a statement that the methods for such determination like high pressure liquid chromatography or nuclear magnetic resonance are known to a person skilled in the art (paragraph [0034]). In paragraph [0025], it is stated that the pH (apparently of the reaction mixture) may vary in a broad range, for example from 6 to 10, and preferably from 7 to 8.5. A person skilled in the art would choose alkaline conditions for hydroxymethylation (hydroxycycloalkylation in the case of using 5-hydroxymethylfurfural as the aldehyde component), as taught in the chapter "4.1.1 Hydroxymethylation" of the "Amino Resins" article in "Ullmann's Encyclopedia of Industrial Chemistry", 5 ^th edition 1985, Vol. A2, page 119, and acid conditions during the condensation step when alkylene (methylene in the case of formaldehyde) links between two aminoplast moieties are formed, as taught in the chapter 4.1.2 (loc. cit, page 120). It is noted that in the only example of this patent application EP 3 366 468 Al, the reaction between urea and an aqueous solution of 5-hydroxy methylfurfural which was treated according to the teaching of paragraph [0036], particularly in the second and third sentences, of this patent application, to promote the formation of oligomers, i. e., concentrated and matured by heating in a rotary evaporator at 45 °C and a pressure of 3 kPa (30 mbar) is conducted at a pH of 2 during the whole reaction time (see paragraph [0061], line 25), contrary to the general teaching in paragraph [0025]; only the temperature is varied: for the first two and one half hours, it is 90 °C, and then "20 °C for several hours", see paragraph [0061], line 26.

In the patent application EP 3 366 714 Al which claims the priority of EP 3 366 468 Al (supra), a process is described for the preparation of thermally curable phenolic resins which comprises "the step of reaction of a polycondensable phenolic compound with 5- hydroxymethylfurfural (HMF) under conditions leading to formation of polycondensates wherein the HMF comprises at least one HMF oligomer, and wherein the reaction is conducted at a pH of more than 7 for more than sixty minutes" (claim 1). These conditions are defined in the description as being known per se (paragraph [0019]), using known solvents which can be any liquid medium where poly condensates are formed. Preferred is a reaction in an aqueous solvent, especially in water. The alkaline pH can be adjusted by suitable bases at the start of the reaction step, such as alkali hydroxides, alkaline earth hydroxides, sodium carbonate, ammonia, and tertiary amines, sodium hydroxide being particularly suitable. Reaction times of more than sixty minutes at basic values of pH with HMF comprising at least one HMF oligomer are said to lead to phenolic resins having high bonding strength. The reaction is preferably conducted until the desired viscosity has been reached, or the reaction has ceased. Desired viscosities are said to be between 100 mPa-s and 1200 mPa-s, preferably more than 200 mPa-s, particularly preferred, more than 800 mPa-s, and especially preferred, more than 850 mPa-s. There is no mention of concentration of solute, nor of the solvent used in the measurement, for measuring such viscosity, nor of a temperature, nor of a shear rate. Preferred ranges for pH, reaction temperature, number of reaction steps, molar ratio of HMF to phenolic compound, mass fraction of oligomers in the HMF component, and degree of oligomerisation (average number of monomer units in the oligomer molecules) are stated in paragraphs [0023] to [0030] In paragraphs [0035] to [0052], details regarding the assumed structure of the oligomers are disclosed, but no analytical evidence such as NMR data or mass spectroscopy data are disclosed that support the assumed structure with carbon-carbon bonds in the preferred oligomers which are said to differ from the ether, acetal and hemiacetal structures common in aldehyde oligomers. It is further stated (paragraph [0029]) that in a preferred embodiment, the mass fraction of oligomers in the HMF component is from 0.05 % to 10 %, preferably from 0.1 % to 8 %, and particularly preferred, from 2 % to 4 %. In the last sentence of this paragraph, it is stated that a mass fraction of up to (almost) 100 % is also comprised in that invention. According to the preferred embodiment described in paragraph [0030], the oligomer has from two to twenty monomer units, more preferred, from two to ten monomer units, and especially preferred, from two to four monomer units. As stated in paragraphs [0037] and [0038], the preferred oligomers have carbon-carbon bonds in their structure (and not only the ether, hemiacetal or acetal bonds resulting from the reaction of aldehyde and hydroxyl groups) which are said to be formed both in acid and alkaline conditions. When the proposed structures are considered, it is obvious that there are not more functional groups formed due to oligomerisation: from two molecules each having one aldehyde group and one primary hydroxyl group, adding up to a total of four reactive groups, the C-C bonded dimer structures formed (see have one remaining aldehyde group, two remaining primary hydroxyl groups, and one tertiary hydroxyl group which adds up to a total of four reactive groups. A tertiary hydroxyl group reacts slower than a primary hydroxyl group due to sterical hindrance Thus, by formation of a dimer having a C-C bond, one reactive aldehyde group is transformed to a much less reactive tertiary hydroxyl group.

In the patent application US 2016/0 355 631 Al, there is disclosed a "method for the preparation of a crosslinkable resin, the method comprising the step of: (i) converting a hexose to 5-hydroxymethyl furfural (HMF) in the presence of a phenolic compound and a catalyst that promotes formation of covalent bonds between a carbon atom of the aromatic ring of the phenolic compound and the carbon of the formyl group of the HMF to form the resin". See claim 1. The phenolic compounds used are defined in paragraph [0016] as "a compound containing a hydroxy-substituted phenyl ring in which at least one of the ortho- and para-carbons of the ring, relative to the carbon atom bearing the hydroxyl group, is unsubstituted, i. e., bears a hydrogen". Mentioned are phenol itself, and "bio-phenol", e. g., phenolated depolymerised lignin (second last sentence of paragraph [0016]).

A resin from phenol and HMF was made under conversion of glucose to HMF in the ionic liquid tetraethylammonium chloride (TEAC), the experimental results are summarised in tables 1 and 2, showing that in the reaction system used (120 ° C; 3 h; varying ratio of phenol to glucose from between 1 mol : 0.6 mol to 1 mol : 1.5 mol; with a catalyst system of varied quantities of CrC12, CrC13, and TEAC; with and without water; see table 1), glucose conversions were in the range of from 90 % to 100 %, and phenol conversion was between 35 % and 84 %; a very low concentration of free HMF (mostly less than a mass fraction of 1.5 % in the reaction mixture) was detected. See paragraph [0079] and table 1.

"The BPHMF resin (bio-phenol - HMF resin, see paragraph [0016], last sentence) was synthesized with the phenolated de-polymerized hydrolysis lignin (PDHF), following the same synthesis method of PHMF. The gross yield of synthesized BPHMF resins was 85 % under the conditions as described in the experimental section: 14.10 g phenolated DHF (containing 50 wt% phenol and 50 wt % DHF), 13.5 g (0.075 mol) glucose, and 3 g water and a total of 0.3 g catalysts were reacted at 120 °C for 8 hours". See paragraph [0090] The depolymerised hydrolysis lignin (DHF) has a mass average molar mass Mw of from 1400 g/mol to 1500 g/mol (see Table 3 in paragraph [0091] The resin is heat-curable using cross- linking agents such as tetraethylammonium chloride or lignin.

As the generated 5-hydroxymethyl furfural is subjected to heat for extended periods of time in both series of experiments, it can be expected, following the discussion in the patent application EP 3366468 Al, that the formation of oligomers is promoted as described in part (a) of the only example thereof, by treatment of an aqueous solution of 5-hydroxymethyl furfural at 45 °C for a time sufficient to concentrate the solution from a mass fraction of solute of 16 % to a final mass fraction of 50 %, i. e., removing 68 g of water from 100 g of the original solution with a mass fraction of solute of 16 %, and of course, also during the following reaction of this concentrated solution of 5-hydroxymethyl furfural with urea at 90 °C for 2.5 hours.

In paragraph [0050], it is stated that "A cured composition of the invention can also be described as including a cross-linked polymer, wherein the polymer comprises monomeric units of HMF and phenol or bio-phenol, and molecules of the polymer are cross-linked to each other by reaction with a polyhydroxyl compound. The polyhydroxyl compound can be lignin." This does not disclose that a resin is formed from a polyhydroxyl compound, or lignin, and 5-hydroxymethylfurfural. The nature of a polymer is governed by the monomers used for its preparation. Therefore, the polymer (or resin) formed is obtained by reacting the monomers 5-hydroxymethylfurfural and phenol or "biophenol". Lignin is clearly not a part of the polymer. The molecules of this polymer may, however, be crosslinked by reaction of the polymer molecules with polyhydroxyl compound, which may also be lignin, as is literally written in the said paragraph [0050]

In the journal article "Lignin-derivatives based polymers, blends and composites: A review" by A. Naseem et ak, Int. J. Biological Macromolecules 93 (2016), pp. 296 to 313, reference is made to "Lignophenol Based Polymers" in section 5.4, where the lignophenols are prepared by the phase separation method from a mixture of cellulose, hemicellulose and lignin, wherein cellulose and hemicellulose are hydrolysed to sugars, and lignin is converted to a light-coloured polymer generally referred to as "Lignophenol". As is known to a person skilled in the art, the phase separation method has a first step where lignocellulosic material is solvated by phenol derivatives, ether linkages are cleaved, and the carbohydrates are hydrolysed by addition of acid. The second step includes cleavage of C- b -aryl ether linkages by switching functions of lignophenol under mild alkaline conditions. The third step is demethylation of the aromatic methoxy groups in the presence of boron tribromide from lignophenol depolymerised products. The isolated lignophenols have high phenolic content, and light colour.

The term "Hydrolysis Lignin" as used in this section refers to residues obtained from the biomass enzymatic hydrolysis process, and is therefore different from lignin. See page 307, third an second lines from the bottom of the page. In the patent application US 2019/0 112 512 Al, an aqueous adhesive composition is disclosed which comprises, per claim 1, a thermosetting resin based on: (Al) at least one aromatic compound comprising at least one aromatic ring bearing at least two functions, one of these functions being a hydroxymethyl function and the other being an aldehyde function or a hydroxymethyl function; and (A2) at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted.

Further descriptions of the nature of A2 can be found in paragraph [0095] where it is stated that second essential constituent of the thermosetting resin is an aromatic polyphenol A2 comprising one or more aromatic ring(s). The aromatic polyphenol comprises at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted. In paragraphs [0096] to [0100], the second essential constituent is a mixture of the aromatic polyphenol A2 as described above and aromatic monophenol A2' comprising at least one six-membered aromatic ring bearing a single hydroxyl function. On this aromatic monophenol, the two positions ortho to the hydroxyl function are unsubstituted, or else at least one position ortho to and the position para to the hydroxyl function are unsubstituted. Thus, in this embodiment, the thermosetting resin according to the invention is also based on: A2') at least one aromatic monophenol comprising at least one six-membered aromatic ring bearing a single hydroxyl function, the two positions ortho to the hydroxyl function being unsubstituted, or at least one position ortho to and the position para to the hydroxyl function being unsubstituted.

Per paragraph [0101], the compound A2) may be, in one embodiment, a simple aromatic polyphenol molecule comprising one or more aromatic rings, at least one of these aromatic rings, or even each aromatic ring, bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted. In paragraphs [0102] and [0103], the compound A2') is characterised as, in one embodiment, a simple aromatic monophenol molecule comprising one or more six- membered aromatic rings, at least one of these six-membered aromatic rings, or even each six-membered aromatic ring, bearing a single hydroxyl function, the two positions ortho to the hydroxyl function are unsubstituted, or else at least one position ortho to and the position para to the hydroxyl function are unsubstituted. Such simple molecules do not comprise a repeat unit.

Per paragraphs [0104] to [0106], the compound A2) may be, in another embodiment, a pre condensed resin based: on at least one aromatic polyphenol comprising at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another, the two positions ortho to at least one of the hydroxyl functions being unsubstituted; and on 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 borne by an aromatic ring. Such a pre-condensed resin based on aromatic polyphenol is in accordance with the invention and comprises, unlike the simple molecule described above, a repeat unit. In this instance, the repeat unit comprises at least one aromatic ring bearing at least two hydroxyl functions in the meta position relative to one another.

Per paragraph [0107] to [0112], the compound A2') may be, in another embodiment, a precondensed resin based on: at least one aromatic monophenol comprising at least one six- membered aromatic ring bearing a single hydroxyl function: the two positions ortho to the hydroxyl function are unsubstituted, or at least one position ortho to and the position para to the hydroxyl function are unsubstituted; at least one compound capable of reacting with said aromatic monophenol comprising at least one aldehyde function and/or at least one compound capable of reacting with said aromatic monophenol comprising at least two hydroxymethyl functions borne by an aromatic ring. Such a pre-condensed resin based on aromatic monophenol is in accordance with the invention and comprises, unlike the simple molecule described above, a repeat unit. In this instance, the repeat unit comprises at least one six-membered aromatic ring bearing a single hydroxyl function. In another embodiment, the compound A2) and/or A2') is a mixture of an aromatic polyphenol that forms a simple molecule and of a pre-condensed resin based on aromatic polyphenol. In paragraphs [0113] to [0148], examples of the aromatic rings and further details of the compounds A2 are stated. In paragraphs [0149] to [0156], further details and examples are given, also for precondensed resins. Lignin does not fall under anyone of the above definitions for compounds Al, A2, and AT. In the patent application WO 2021/186 127 Al, a water-based adhesive composition is disclosed which comprises a heat-curable resin based: on at least one aromatic compound Al comprising at least one aromatic ring which bears at least two functions, one of these being a hydroxymethyl group, and the other being an aldehyde group or a hydroxymethyl group; on at least one aromatic polyphenol A2 comprising at least one aromatic ring which has at least two hydroxyl groups in meta position which regard to each other, wherein the two ortho positions of at least one of the carbon atoms carrying a hydroxyl group are unsubstituted; on at least one phenol which may optionally be substituted by a single alkyl group, or a single alkenyl group; and/or at least one aromatic hydrocarbon A3 comprising at least two aromatic rings which carry a single hydroxyl group, wherein at least one of the ortho positions with regard to the hydroxyl group on each of the rings is unsubstituted.

In a mixture of monomers, dimers, and higher oligomers of 5-hydroxymethyl furfural, comparable to the so-called "paraformaldehyde" which is a white crystalline solid mixture of oligomers formed from formaldehyde, hemiacetal structures are found which are formed in an acetalisation reaction, where one primary hydroxyl group of the first monomer molecule HI and one aldehyde group of the second monomer molecule which is referred to as HI' are transformed to a hemiacetal structure as shown in the example below (Formula [5});

HO - CH ₂ - X ¹ - CH(OH) - O - CH ₂ - X ^1' - CHO (dimer H2 made from two monomer molecules HI and HI', Formula [5]) which conserves one primary hydroxyl group, and one aldehyde group (both put in bold print), X ¹ and X ^1' each standing for the furan-2,5-diyl group (Formula [6])

O

/ \

- C ⁵ C ² -

HC ⁴ — C ³ H (Formula [6]).

Higher oligomers having a degree of polymerisation of n and a hemiacetal structure may be formed in the same way, which obey the formula [7]:

HO - CH ₂ - [ X ¹ - CH(OH) - O - CH ₂ -] _n-i - X ^1' - CHO (Formula [7]). Under acid catalysis, the secondary hydroxyl group of one or more of the entities in square brackets of the n-oligomer of formula [7] supra may be reacted with a hydroxymethyl group of another monomeric (HI, m=l) or oligomeric (Ho with degree of polymerisation m) mono- or oligo-(5-hydroxymethyl)-furfural molecule under formation of a branched acetal (assumed to be formed on a terminal part of an oligomer in this example of Formula [8]) (Formula [8]), where all of X ¹ , X ^1' , X ^1" , and X ^1"’ each stand for the furan-2,5-diyl group (Formula [6]).

While hemiacetals are formed easily in an addition reaction, even without acid catalyst, formation of acetals requires addition of an acid catalyst, and removal of water.

The hydroxyl functionality of a hemiacetal oligomer of Formula [7] comprising n monomer units is equal to n, where only one primary hydroxyl group and n-1 (less reactive) secondary hydroxyl groups are present; the aldehyde functionality of a hemiacetal oligomer of Formula [7] is always 1. The number of reactive aldehyde groups is thus drastically reduced in a hemiacetal oligomer; the number of aldehyde groups N(-CHO, mixture) in a mixture comprising both monomers HI and oligomers Ho of 5-hydroxymethylfurfural in a sample Smi of a mixture having a certain mass ra(Smix) is always smaller than the number of aldehyde groups N(-CHO, HI) in a sample SHI having the same mass ( ra(Sm) = ra(Smix) ) where only the monomer HI of 5-hydroxymethylfurfural is present by a factor of n which is the average number of monomers in the molecules constituting the said mixture: for TO(SHI) = ra(Smix), N(-CHO, pure monomer HI) = n ^c N(-CHO, mixture).

In the acetal-hemiacetal oligomer of formula [8] comprising n+m monomer units, the hydroxyl functionality is 1 + (n-2) + (m-1) = m+n-2, only one of these being a primary hydroxyl group, and the aldehyde functionality is 2.

An ether according to formula [9] might be formed under consumption of the two hydroxymethyl groups from two molecules of HI (monomeric 5-hydroxymethylfurfural-2), usually under acid catalysis, O = C - X ¹ - C 2 - O - C 2 - X ^1' - c=o (Formula [9])

H H where X ¹ and X ^1' have the meaning of a furan-2,5-diyl group, see formula [6] supra. This condensation consumes two hydroxyl groups from the hydroxymethyl functional group under formation of an ether bond, and conserves the aldehyde groups.

A further route to oligomer formation is the so-called aldol addition, in the case of 5- hydroxymethylfurfural, it is a vinylogous aldol addition where a vinylogous enolate reacts at the terminal position of the double bond system (the gamma carbon atom, or the carbon atom with number 4 in the furan ring of the 5-hydroxymethylfurfural monomer, instead of the alpha carbon atom immediately adjacent to the carbonyl group, as would a simple enolate). This leads to the formation of an aldol compound having one remaining aldehyde group, two primary hydroxyl groups in the 5-position of both furan rings, and one tertiary hydroxyl group in the connecting methylene group. The remaining aldehyde group is capable of a further addition reaction with a further 5-hydroxymethylfurfural molecule to from a trimer, and so on.

During the experiments which have led to the present invention, it has been found that for a combined addition and condensation reaction of an aldehyde component M comprising a mixture H of 5-hydroxymethylfurfural monomer HI, and optionally, oligomers Ho thereof, with organic aldehyde-reactive compounds, particularly lignin, no prior step of oligomerisation of the monomer HI is needed; on the contrary, a higher specific amount of substance _j S(-CHO) of the reactive aldehyde groups, measured as the ratio _j S(-CHO) = n(- CHO)/ m( M) of the amount of substance n(-CHO) of aldehyde groups -C(H)0 and the mass m{ M) of the aldehyde component M is present in a sample comprising only hydroxymethylfurfural monomers HI, compared to a sample comprising a mixture of monomer and oligomers as used in EP 3366468 A1 and EP 3366 714 Al. The higher amount of aldehyde groups contributes to increasing the speed of reaction with organic aldehyde- reactive compounds, particularly lignin. Therefore, it is preferred to use an aldeyhde component M comprising monomeric 5-hydroxymethylfurfural HI, or a solution thereof in water, or a mixture H of monomeric 5-hydroxymethylfurfural HI with oligomers Ho derived from 5-hydroxymethylfurfural where the mass fraction ro(Ho) of 5-hydroxymethyl- furfural oligomers Ho in the aldehyde component M is low, i.e., not more than 1 % of the sum of the mass ra(Hl) of monomeric 5-hydroxymethylfurfural HI and of the mass ra(Ho) of oligomers of 5-hydroxymethylfurfural in the aldehyde component M, preferably not more than 0.5 %, more preferably, not more than 0.1 %, and particularly preferably, zero or below the detection limit of about 0.05 %. This measurement of the mass fraction TC(H 1 ) of 5- hydroxymethylfurfural monomers HI and the mass fractions ro(Ho,i) of 5-hydroxymethyl- furfural oligomers Ho,i having a degree of oligomerisation i of more than 1, i.e. at least 2 has been made using a Waters gel permeation chromatograph using four "Ultra-Hydrogel® DP" columns with a pore size of approximately 120 A (12 nm) in series, at 25 °C and a flow rate of 0.8 ml/min, with 0.005 M H ₂ SO ₄ (concentration of sulphuric acid: 0.005 mol/L) in water as solvent and eluent, and with a UV detector. A sample of a mixture H comprising monomeric 5-hydroxymethyl furfural HI is said to comprise no 5-hydroxymethyl furfural oligomers Ho in a mass fraction ro(Ho) thereof that is higher that the detection limit means that there is no additional peak in the elugramme before the monomer peak which is higher than the height value of three times the usual baseline noise, which corresponds to a mass fraction of the lowest oligomer (dimer) of 0.05 % in the mixture H of monomeric 5-hydroxymethyl furfural HI and oligomeric 5-hydroxymethyl furfural Ho. The mass fraction ro(Ho) is the sum åi Tc(Ho,i) for all (integer) values of i of more than 1 for all mass fractions ro(Ho,i) as defined supra. As is common in the definition of the composition of a mixture comprising a monomeric compound, and oligomers thereof, the mass fractions are defined as w(Hl) = ra (HI) / [ ra(Hl) + å. w(Ho,i)], w(Ho,i=2) = ra(Ho,i=2) / [ ra(Hl) + åi ir>(Ho,i)], etc.

Summary of the Invention

The invention relates to resins made from an aldehyde component M which comprises a mixture H comprising monomeric 5-hydroxymethyl furfural HI and an aldehyde-reactive organic component A which preferably comprises lignin. The mixture H may comprise, in addition to monomeric 5-hydroxymethyl furfural HI, a solvent, preferably, water, and optionally, a small quantity of oligomeric 5-hydroxymethyl furfural Ho, where the quantity of oligomers Ho corresponds to a mass fraction ro(Ho) = ra(Ho) / [ra(Hl) + ra(Ho)] of 0.5 % or less, preferably of 0.1 % or less, and particularly preferred, of 0.05 % or less. An aldehyde mixture H comprising monomeric 5-hydroxymethyl furfural HI and an mass fraction of less than 0.05 % of oligomers Ho of 5-hydroxymethyl furfural is used exclusively in the examples that are a part of the specification.

The aldehyde-reactive organic component A is selected from at least one of the activated aromatic compounds as described hereinbefore, or from at least one of the aminoplast formers as described hereinbefore, or from mixtures of at least one of the said activated aromatic compounds and at least one of the said aminoplast formers.,

Resins from H with phenol ("P") alone, with alkylphenols alone, with other phenol derivatives including resorcinol, with lignin ("L") alone, with a tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m-cresol (MC), o-cresol (OC), and p-cresol (PC), 2,6-xylenol (XL), mixtures of these, as well as p-tert-butylphenol (BP), 4-isooctylphenol (OP), 4-nonylphenol (NP), and 4-hydroxybiphenyl (HP) have been used as alkylphenols, and one compound each of the tannin classes, viz., gallotannin (GT), ellagitannin (ET), complex tannin (XT), and condensed tannin (CT), see formulae 1 to 4 supra, and also mixtures of these, and also with any different lignin grades including Kraft lignin, soda lignin, lignosulphonates, Organosolv lignins, hydrolysis lignins, ionic liquid lignins, dioxane lignin, steam explosion lignin, and enzymatically liberated lignin as mentioned supra.

It was found in the experiments whereupon the present invention is based that alkylphenols, or mixtures of these with each other, or with phenol, form more homogeneous resins together with lignin, in an alkali-catalysed addition-condensation reaction, apparently due to the reduced functionality of alkylphenols which resembles the reduced functionality of lignin due to methoxy substitution on the aromatic nuclei. Similar sets of resins have been made by using formaldehyde (hereinafter referred to as "F") alone, as aldehyde component, and mixtures of 5-hydroxymethylfurfural with formaldehyde, where mixtures were made with amount of substance-fractions of 20 %, 40 %, 60 %, and 80 % of formaldehyde, with amount of substance-fractions of 80 %, 60 %, 40 %, and 20 % of H, with phenol alone, with alkylphenols alone, with lignin alone, with tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m-cresol, o-cresol, and p-cresol, 2,6-xylenol, mixtures of these, as well as p-tert-butylphenol, 4-isooctylphenol, 4-nonylphenol, and 4- hydroxybiphenyl have been used as alkylphenols. Lignosulphonates are always excepted in the production of these resins according to the invention.

Instead of using formaldehyde in the preparation of resins, corresponding resins have also been prepared using homologues of formaldehyde, viz., acetaldehyde (AA), propionaldehyde (PA), isobutyraldehyde (BA), with phenol alone, with alkylphenols alone, with lignin alone, with tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m- cresol, o-cresol, and p-cresol, 2,6-xylenol, mixtures of these, as well as p-tert-butylphenol, 4- isooctylphenol, 4-nonylphenol, and 4-hydroxybiphenyl have been used as alkylphenols. Due to their side reactions with bases (aldol reaction), only acid-catalysed condensation can be made with the said higher aldehydes which leads to hard and brittle resins. These resins can be cured like novolaks. Lignosulphonates are always excepted in the production of these resins according to the invention. It is also possible to use dialdehydes alone, or together with H to produce addition- condensation resins with activated aromatic compounds. As dialdehydes have two aldehyde groups in one molecule, it suffices to use about one half of the amount of substance of the dialdehyde, theroretically, but according to experience, the second aldehyde group is less reactive, most probably due to sterical hindrance. Therefore, it is recommended to use more than half of the amount of substance of a dialdehyde to replace a given amount of substance of a monofunctional aldehyde. The factor f which should be applied to the amount of substance of dialdehydes therefore usually ranges from 0.6 to 0.9, depending on the dialdehyde used, and must be determined experimentally.

Sets of resins have been made by using an aqueous solution of glyoxal (hereinafter referred to as "GO") alone, as aldehyde component, and mixtures of H with GO, where mixtures were made with amount of substance-fractions of 20 %, 40 %, 60 %, and 80 % of GO, with amount of substance-fractions of 80 %, 60 %, 40 %, and 20 % of H, with phenol alone, with alkylphenols alone, with lignin alone, with tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m-cresol, o-cresol, and p-cresol, 2,6-xylenol, mixtures of these, as well as p-tert- butylphenol, 4-isooctylphenol, 4-nonylphenol, and 4-hydroxybiphenyl have been used as alkylphenols. Lignosulphonates are always excepted in the production of these resins according to the invention.

A further set of resins has been made where 2,5-furandialdehyde (hereinafter referred to as "FD") was used as aldehyde component, alone, and in mixture with H, where mixtures were made with amount of substance-fractions of 20 %, 40 %, 60 %, and 80 % of 2,5- furandialdehyde, with amount of substance-fractions of 80 %, 60 %, 40 %, and 20 % of H, with phenol alone, with alkylphenols alone, with lignin alone, with tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m-cresol, o-cresol, and p-cresol, 2,6-xylenol, mixtures of these, as well as p-tert-butylphenol, 4-isooctylphenol, 4-nonylphenol, and 4-hydroxy- biphenyl have been used as alkylphenols. Lignosulphonates are always excepted in the production of these resins according to the invention.

2,5-furandialdehyde (FD) can be prepared from 5-hydroxymethylfurfural by catalytic oxydation or directly from fructose in a one-step dehydration/oxydation (see Dai, J., Green Energy and Environment, https://doi.Org/10.1016/j.gee.2020.06.013), and is therefore also a very promising intermediate for resins.

Further sets of resins have been made by using aliphatic dialdehydes (alkanedials, hereinafter referred to as "AD") having from three to eight carbon atoms, viz., from malondialdehyde, succindialdehyde, glutardialdehyde, pimelindialdehyde and octane- dialdehyde, mixtures of these, and also mixtures of H with any of these dialdehydes, or with two or more of these dialdehydes, where mixtures were made with amount of substance- fractions of 20 %, 40 %, 60 %, and 80 % of dialdehyde or dialdehyde mixture, with amount of substance-fractions of 80 %, 60 %, 40 %, and 20 % of H, with phenol alone, with alkylphenols alone, with lignin alone, with tannin alone, with mixtures of phenol and alkylphenols, with mixtures of phenol and lignin, with mixtures of phenol and tannin, with mixtures of alkylphenols and lignin, with mixture of alkylphenols and tannin, with mixtures of lignin and tannin, as well as with mixtures of phenol, alkylphenols, and lignin, with mixtures of phenol, alkylphenols, and tannin, with mixtures of alkylphenols, lignin, and tannin, and with mixtures of phenol, alkylphenols, lignin, and tannin have been prepared, where m- cresol, o-cresol, and p-cresol, 2,6-xylenol, mixtures of these, as well as p-tert-butylphenol, 4- isooctylphenol, 4-nonylphenol, and 4-hydroxybiphenyl have been used as alkylphenols. It has been found that resins made with mixtures of H and these dialdehydes exhibit accelerated curing, compared to resins made with H alone. Lignosulphonates are always excepted in the production of these resins according to the invention. Further sets of resins have been prepared from H with aminoplast formers, viz., amines or amides or mixtures of both, where the amines are selected from the group consisting of aminotriazines having at least two amino groups per molecule which are either primary or secondary amino groups, preferably, melamine, acetoguanamine, butyroguanamine, caprinoguanamine, benzoguanamine, N,N',N"-trimethylmelamine, and the amides are selected from the group consisting of urea, N,N'-dimethylurea, thiourea, ethyleneurea (2- imidazolidinone), propyleneurea (4-methyl-2-imidazolidinone), and glycoluril, and also from amides of aliphatic dicarboxylic acids preferably having from three to fifteen carbon atoms, such as malonic acid diamide, succinic acid diamide, glutaric acid diamide, adipic acid diamide, and also amides of tricarboxylic acids such as citric acid diamide, and further, sulphonamides, such as toluenesulphonic acid amide, cyanamide, and dicyandiamide.

A further set of resins has been made where 2,5-furandialdehyde (FD) was used as aldehyde component, alone, and in mixture with H, where mixtures were made with amount of substance-fractions of 20 %, 40 %, 60 %, and 80 % of FD, with amount of substance-fractions of 80 %, 60 %, 40 %, and 20 % of H, with aminoplast formers, viz., amines or amides or mixtures of both, where the amines are selected from the group consisting of aminotriazines having at least two amino groups per molecule which are either primary or secondary amino groups, preferably, melamine, acetoguanamine, butyroguanamine, caprinoguanamine, benzoguanamine, N,N ^, ,N"-trimethylmelamine, and the amides are selected from the group consisting of urea, N,N'-dimethylurea, thiourea, ethyleneurea (2-imidazolidinone), propyleneurea (4-methyl-2-imidazolidinone), and glycoluril, and also from amides of aliphatic dicarboxylic acids preferably having from three to fifteen carbon atoms, such as malonic acid diamide, succinic acid diamide, glutaric acid diamide, adipic acid diamide, and also amides of tricarboxylic acids such as citric acid diamide, and further, sulphonamides, such as toluenesulphonic acid amide, cyanamide, and dicyandiamide.

The most important of these aminoplast formers used in resins mainly together with formaldehyde are melamine and urea, each alone or in combination, while the others mentioned are mostly used as modifiers, or in special applications such as textile finishing. Formaldehyde-free resins based on cyclic ureas and glyoxal have been developed as crosslinkers for coatings. Mixtures of amino resins and phenolic resins have been used as adhesives in wood products. Similar mixtures have also been made from amino resins based on H, or mixtures thereof with other aldehydes, and resins from activated aromatic compounds as defined hereinbefore, with H or mixtures of H with other aldehydes, particularly FD, GO, AD, and also with formaldehyde, the latter preferably being used in minor quantities to reduce formaldehyde emission during preparation and use of resins made therewith.

The following table illustrates comprehensively the combinations of resin formers considered in this invention.

The following embodiments are comprised in this invention:

1. A resin made from an aldehyde component which comprises 5-hydroxymethyl furfural, and an aldehyde-reactive compound which comprises a reactive aromatic compound, or organic amines, imines, imides and amides having at least one, preferably two or more, groups selected from the group consisting of amino groups, imino groups, imide groups, and amide groups, also referred to as "aminoplast formers", wherein the nitrogen atom in the amide, imino, or in the imide group may be a ring atom of a heterocyclic ring, or bound to a ring atom in a carbocyclic or heterocyclic ring, and the nitrogen atom of the amino group is bound to a ring atom in a carbocyclic or heterocyclic ring, or.a mixture of at least one aminoplast former and at least one reactive aromatic compound, wherein a reactive aromatic compound is an organic compound that has at least one aromatic C-H group, where the carbon atom C of the said aromatic C-H group is a part of an aromatic carbocyclic or heterocyclic ring, which said ring bears a hydroxyl or alkoxy group at another carbon atom in ortho (directly bound to the said carbon atom C of the said aromatic C-H group) or para (with an even number of carbon atoms between the said carbon atom C of the said aromatic C-H group, and the carbon atom that bears the said hydroxyl or alkoxy group) position, and which reactive aromatic compound comprises lignin, with the exception of lignosulphonates, or a mixture thereof with a further reactive aromatic compound, characterised in that the aldehyde component is a mixture comprising monomeric 5- hydroxymethyl furfural (also referred to as "HI"), and optionally, also oligomers "Ho" of 5- hydroxymethyl furfural wherein the mass fraction io(Ho) = ra(Ho) / [ra(Hl) + ra(Ho)] of 5- hydroxymethyl furfural oligomers Ho in the aldehyde component is not more than 1 %, based on the sum of the mass ra(Hl) of the 5-hydroxymethyl furfural monomer HI and the mass ra(Ho) of the 5-hydroxymethyl furfural oligomers Ho present in the said mixture.

2. The resin of embodiment 1 wherein the mass fraction ®(Ho) of 5-hydroxymethyl furfural oligomers Ho in the aldehyde component is not more than 0.05 %, based on the sum of the mass m( HI) of the 5-hydroxymethyl furfural monomer HI and the mass ra(Ho) of the 5-hydroxymethyl furfural oligomers Ho present in the said mixture.

3. The resin of embodiment 1 wherein the mass fraction of oligomers Ho in the aldehyde component is not more than 0.01 %, based on the sum of masses of the monomer HI and the masses of the oligomers Ho present in the said mixture.

4. The resin of any one of embodiments 1, 2, and 3 wherein the reactive aromatic compound comprises a mixture of at least two, preferably at least three lignin components, wherein the first lignin component comprises oligomeric lignin molecules consisting of from 1 to n lignin monomers, the second component comprises oligomeric or polymeric lignin molecules consisting of from n+1 to m lignin monomers, the third component, if present, comprises oligomeric or polymeric lignin molecules consisting of from m+1 to o lignin monomers, and the fourth component, if present, comprises oligomeric or polymeric lignin molecules consisting of from at least o+l lignin monomers, where n is at least 7, m is at least 14, and o is at least 21, and if n is increased by 1, the value of m is increased by 2, and the value of o is increased by 3.

5. The resin of embodiment 1 or of embodiment 4 wherein the lignin is any one of hardwood lignin, softwood lignin, and grass lignin.

6. The resin of embodiment 5 wherein the lignin is isolated by any process selected from the group consisting of: the Kraft lignin (or sulphate lignin) process, the alkali lignin (or soda lignin) process, the soda-anthraquinone process, the sulphite pulping process, the acid hydrolysis process, the organosolv process, the hydrolysis process, the steam-explosion process, and the ammonia-fibre expansion process, with the exception of lignosulphonates.

7. The resin of embodiment 6 wherein the lignin is purified by at least one method selected from the group consisting of ultrasonic extraction, solvent extraction, dialysis, hot water treatment. 8. The resin of embodiment 6 wherein the reactivity of lignin is increased by at least one of the processes selected from the group consisting of demethylation, methylolation /hydroxymethylation, phenolation/phenolysis, reduction, oxydation, hydrolysis, and alkalation.

9. The resin of any one of embodiments 5 to 8 wherein the reactive aromatic compound comprises a mixture of lignin components, and phenol components selected from the group consisting of phenol, alkylphenols, resorcinol, novolaks, and saligenin.

10. A method of use of the resin of any one of embodiments 1 to 9 as binder.

11. A method of use of the resin of any one of embodiments 1 to 9 as binder in an adhesive.

12. A method of use of the resin of any one of embodiments 1 to 9 as binder in an adhesive for inorganic and organic materials including wood, engineered wood, paper, cardboard, stone, concrete, plaster, thermoplastic and duroplastic polymers, metals, textiles, fibres including also carbon fibres, nonwovens, felts, leather, ceramics, and glass.

Examples

The aqueous solutions of monomeric 5-HMF as used in these examples have been prepared from freshly distilled HMF (as described in US patent 2,994,645 A issued to R. E. Jones et al).

Example 1: Resin from Phenol and 5-Hydroxymethylfurfural

A resin kettle equipped with thermometer, stirrer, and a charging funnel for solids was heated to approximately 35 °C, and charged under stirring, in sequence, with 17.87 g of phenol, 0.68 g of aqueous sodium hydroxide solution (mass fraction of solids: 45 %), and 114.16 g of an aqueous solution of monomeric 5-hydroxymethylfurfural (mass fraction of solute 42 %). By distillation under low pressure (between 4 kPa and 5 kPa, corresponding to 40 mbar and 50 mbar) at 35 °C, approximately 50 mL of water were removed from the reaction mixture. The kettle was further stirred and heated to 100 °C to support the reaction which was stopped after a sample drawn showed a dynamic viscosity of between 350 mPa-s and 400 mPa-s, measured in a cone-and-plate viscometer at 20 °C.

70 g of resin were collected, having the following data: dynamic viscosity (conditions as supra): 381 mPa-s

B-time at 130 °C (DIN 16916-2; with HMTA ¹ ): 50 min 55 s

B-time at 150 °C (as supra) 14 min 37 s mass fraction of non-volatile solids (ISO 3251) 67.15 % mass fraction of water 3.8 % water dilutability (ISO 8989 ² ) 0.7 mL/g pH at 23 °C (undiluted) 5.03

1: "HMTA" = hexamethylene tetramine, added in a mass ratio ra(HMTA)/ra(Resin) = 10 %

2: Measurement made as described in this standard; however, the value indicated here is the specific volume b = H(water) / ra(resin), where H(water) is the volume of water added until the cloudiness of the mixture persists from at least 30 s, and ra(resin) is the mass of the resin sample, with the multiple "mL/g" (millilitre per gramme) of the SI unit for a specific volume (in the standard, the water dilutability is inconsistently defined in section 3 as "the amount of water as mass fraction in percent which is needed to effect a persisting cloudiness of the liquid phenolic resin". The water dilutability is defined in section 8 of the standard as "WM = (V/m) x 100 where V is the volume in mL of water added, and m is the mass of the sample in g". A ratio of a volume and mass is definitely not a mass fraction, nor can it be expressed in a unit "%"; see section 5.3.7, 4 ^th paragraph, of the SI brochure 8 [2006] or section 5.4.7, 3 ^rd paragraph, of the SI brochure 9 [2019]).

Example 2: Resin from Lignin and 5-Hydroxymethylfurfural

A resin kettle equipped with thermometer, stirrer, and a charging funnel for solids was heated to approximately 35 °C, and charged under stirring, in sequence, with 27.74 g of lignin powder (purified kraft softwood lignin, dark brown powder having a mass fraction of solids of 65 %, a mass fraction of ash after incineration at 700 °C of less than 2 %, and a mass average molar mass of 5 kg/mol, as determined according to G. Sinovyev et ak, ChemSusChem 2018, 11, pages 3259 et seq.), 12.92 g of an aqueous solution of sodium hydroxide (mass fraction of solids 45 %), 18.75 g of deionised water, and 114.16 g of an aqueous solution of monomeric 5-hydroxymethylfurfural (mass fraction of solute 42 %, prepared as described supra). When charging was completed, a sample was taken, and the pH of the reaction mixture at 38 °C was 12.4. The kettle was further stirred and heated to 100 °C to support dissolution and initiate the reaction.

The mixture was then heated under continued stirring to 100 °C, and samples were taken after one-hour intervals each to determine the dynamic viscosity r _j in a cone-and plate viscometer (conditions as supra). The following results were obtained:

The reaction was discontinued after nine hours when a value between 350 mPa-s and 400 mPa-s for a sample taken was reached.

145 g of a yellow-brown resin were removed from the kettle, cooled down to ambient temperature (23 °C) and then stored in a refrigerator at 4 °C. The dynamic viscosity of a sample was 401 mPa-s (conditions as stated supra), and the B-time was measured at 150 °C (111 s) and at 130 °C (148 s). The mass fraction of residual water was determined to be 53.6 %, and the mass fraction of non-volatile material was determined by heating for one hour at 135 °C as 54.3 % (DIN EN ISO 3251). Water dilutability according to DIN EN ISO 8989 was determined as being more than 20 mL/g; pH of an undiluted sample of the resin was 8.9.

Example 3: Resin from a Lignin Slurry and 5-Hydroxymethylfurfural

A resin kettle equipped with thermometer, stirrer, and a charging funnel for solids was charged, in sequence, with 59.57 g of an aqueous alkaline slurry of lignin having a mass fraction of solids of 30 % which was prepared from Kraft lignin with a mass average molar mass M _m of about 5 kg/mol, and a mass fraction of ash after incineration at 700 °C of less than 0.5 %, by dispersing 27.96 g of the said Kraft lignin in a mixture of 18.97 g of water and 13.07 g of an aqueous solution of sodium hydroxide having a mass fraction of solids of 50 %, and 114.16 g of an aqueous solution of monomeric 5-hydroxymethylfurfural (mass fraction of solute: 42 %). During charging, the kettle was stirred and heated to 55 °C to support mixing. Measurement of the pH of the mixture after cooling the sample taken to 38 °C yielded a result of 10.7.

The mixture was then heated under continued stirring to 100 °C for nine hours, and samples were taken after one-hour intervals each to determine the dynamic viscosity h in a cone-and plate viscometer at 20 °C and a shear rate of 400 s ¹ . The following results were obtained:

155 g of a yellow-brown resin were removed from the kettle, cooled down to ambient temperature (23 °C) and then stored in a refrigerator at 4 °C. The dynamic viscosity of a sample was 559 mPa-s (conditions as stated supra), and the B-time was measured at 150 °C (105 s) and at 130 °C (163 s). The mass fraction of residual water was determined to be 56.16 %, and the mass fraction of non-volatile material was determined by heating for one hour at 135 °C as 44.8 %. Water dilutability was determined according to DIN EN ISO 8989 as more than 20 ml/g; pH of an undiluted sample of the resin was 8.91.

Example 4: Preparation of Plywood One set each of three layers of beech veneers were coated on one side with the resins of examples 1, 2, and 3, the areic mass of the resin having been chosen in each case as 200 g/m ² . In the case of the resin of example 1, hexamethylenetetramine was added (as in the determination of B time, see example 1). A decor layer was combined on top of each of the three sets, and these piles were then pressed for ten minutes at 140 °C with a pressure of 20 bar (2 MPa). Stable plywood plates were produced in all cases.