FIELD OF THE INVENTION

The present invention is in the field of a method of forming a thermoset resin from fully biobased raw material typi- cally by a condensation reaction, a urea and alginate or ALE comprising thermoset resin obtainable from said method, and use of a resin obtainable from said method in a product or other application.

BACKGROUND OF THE INVENTION

Recently it has been found that biobased polymeric sub ^¬ stances, such as extracellular polymeric substances, in particular linear polysaccharides, obtainable from granular sludge can be produced in large quantities. These substances relate to biobased carboxylic acid which may be present in an ionic form (e.g. cationic or anionic). Examples of such production methods can be found in WO2015/057067 Al, and

WO2015/050449 Al, whereas examples of extraction methods for obtaining said biobased polymers can be found in Dutch Patent application NL2016441 and in WO2015/190927 Al . Specific exam- pies of obtaining these substances, such as aerobic granular sludge and anammox granular sludge, and the processes used for obtaining them are known from Water Research, 2007,

doi : 10.1016/ . waters .2007.03.0 4 (anammox granular sludge) and Water Science and Technology, 2007, 55(8-9), 75-81 (aerobic granular sludge). Further, Li et al . in "Characterization of alginate-like exopolysaccharides isolated from aerobic granular sludge in pilot plant", Water Research, Elsevier, Amsterdam, NL, Vol. 44, No. 11 (June 1 2010), pp. 3355-3364) recites specific alginates in relatively raw form. These documents, and their contents, are incorporated by reference.

Advantageously, granules of granular sludge can be readily removed from a reactor by e.g. physical separation, settling, centrifugation, cyclonic separation, decantation, filtration, or sieving to provide extracellular polymeric substances in a small volume. Compared to separating material from a liquid phase of the reactor this means that neither huge volumes of organic nor other solvents (for extraction), nor large amounts of energy (to evaporate the liquid) are required for isolation of the extracellular polymeric substances.

Extracellular polymeric substances obtainable from granular sludge (preferably obtained from granular sludge) do not re ^¬ quire further purification or treatment to be used for some applications, hence can be applied directly. When the extracellular polymeric substances are obtained from granular sludge the extracellular polymeric substances are preferably isolated from bacteria (cells) and/or other non-extracellular polymeric substances.

With the term "microbial process" here a microbiological conversion is meant.

Some applications of ionic biopolymeric substances per se or in extracted form have been considered. For instance appli ^¬ cation of the polymers in paper as a sizing agent, and application on a concrete or metal surface have been found beneficial. Further uses and applications, however, are still limited in extent. From another perspective use and application of biobased substances instead of e.g. chemically based substances is nowadays considered an advantage, especially in view of sustainability . Hence there is a need for further fully biobased applications, methods and products.

Some background prior art documents are FR 1 310 992 A, US 2004/253532 Al and FR 2 992 968 Al, recite alginate esters or alginate derivatives or the like, and are otherwise not very relevant .

The present invention relates to a method of forming a thermoset biocompatible resin such as from a biopolymer from a granular sludge, a thermoset resin obtainable by said process, and a use of said thermoset resin, which overcomes one or more of the above drawbacks, without jeopardizing functionality and advantages .

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a method according to claim 1. There a simple and effective method is presented for forming a thermoset resin from e.g. a biobased carboxylic acid having at least two carboxyl groups, such as dense aggregates formed by microbial organisms, and specifically alginates, and a biobased material comprising at least two amine groups, such as 2-5 amine groups, e.g. 3-4 amine groups, such as urea. In the resin the urea is preferably from biobased origin; in a less preferred example the urea is from chemical or fossil origin. The present resin is considered to be biocompatible, that is a quality of not having toxic or injurious effects on biological systems and/or to exist in harmony with biological tissue without causing delete- rious changes. Such is considered rather unexpected as normally it is considered that amines such as urea do not form cross-links. If the carboxylic acid has two carboxyl groups and the biobased material has two amine groups a linear type polymer may be formed. It is noted that for biobased material a number of carboxyl groups and amine groups per molecule, respectively, may not and typically is not an integer, and may be any number, e.g. 2.1. For formation of a resin at least one of the biobased carboxylic acid and biobased material comprising at least two amine groups has more than 2 (e.g. 2.1, 3, 4 etc.) functional groups, respectively carboxyl and amine group. In the process it is preferred to use the biobased carboxylic acid comprising material in its acid form, or at least in a form wherein the carboxylic acid is capable of releasing at least one proton under reaction conditions. The biobased amine material and the biobased carboxylic acid comprising material are found to typically form a homogeneous system under mixing; in this mixture typically some of the amines form a bond with one of the hydrogens being released by a carboxyl group, forming an -NH ⁺ and -COO ^" group, respectively (which may be regarded as an acid-base reaction) ; it has been found that if about 40-60% of the amine groups are positively charged by the above addition of an hydrogen, such as 50%, reaction conditions are further improved; in some case it may be preferred to change the pH of the homogenous mixture by acidifica- tion/alkalization; this homogeneous system may already be formed at room temperature (about 295 K) for some examples, whereas for other examples slightly elevated temperatures are required, such as from 300-350 . The homogeneous system is typically fluidic in nature, typically having a viscosity higher than that of water, such as 10-50% higher and sometimes even a factor higher (@ 298 K (25 °C) ) . It has been found that the formation of the homogeneous system is supported by the presence of water; only a small amount of water is needed in this respect of this support. The biobased amine material and the biobased carboxylic acid comprising material react by in ^¬ creasing the temperature; the increase may be relatively small, e.g. to above 340 K, or somewhat more, preferably above 350 K, such as above 360 K. It is preferred to maintain the temperature below 460 K. Under these conditions a condensation reaction occurs (separation of water, such as Ri (COOH) _q + HR2N- R ₃ -NR ₄ H Ri(COOH) _q -i(CO)-R ₂ N-R ₃ -NR- (CO) Ri (COOH) _q -i + 2 H ₂ 0) forming amongst others amide bonds, as is evidenced by FTIR; the reaction is continued until the reaction results in the thermoset oligomeric or polymeric amide. Typically the biobased amine material is found to form some cross-links. Typically also cross-linking is found between the thermoset polymers. As such a fully biobased thermoset resin can be formed.

As biobased carboxylic acid comprising material a biopolymer may be used, such as an acidic or ionic biopolymer, such as an anionic biopolymer, and specifically alginate (alg) or bacterial alginate (ALE) c.q. the acid form thereof, from an aqueous solution.

It is noted that some of the steps may be performed in a different sequence, and/or at a later or earlier stage.

Thereby the present invention provides a solution to one or more of the above mentioned problems.

Advantages of the present invention are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a method according to claim 1.

In an example of the present method the carboxylic acid comprising material has at least three carboxyl groups, pref- erably at least 4 carboxyl groups, such as 6-10 carboxyl groups. The carboxylic acid comprising material may be represented as Ri(C00H) _q , wherein q>2 and qe<Q>. It has been found that by varying the number of carboxyl groups the properties of the thermoset resin can be adapted; a higher number of car- boxylic groups result in a somewhat better cross-linked resin.

In an example of the present method the carboxylic acid comprising material is an oligomeric or polymeric material with a weight averaged molecular weight of 300-300,000 Da, hence may still be a relatively small molecule. As the carbox- ylic acid comprising material is of biological origin the characteristics thereof may vary somewhat from "batch to batch" and over time; however the characteristics given throughout the description and claims are found to be relatively consistent.

In an example of the present method the carboxylic acid comprising material is provided under acid conditions or as an acid, i.e. at a pH < 7 or at a pH<pK _a (typically pK _a of a pri- mary acid) . It has been found that the carboxylic acid comprising material dissolves better in the amine material, typically dissolves 90% or better (w/w % based on the total amount of carboxylic acid present) , thereby forming a for the eye homogeneous mixture.

In an example of the present method the biobased carboxylic acid comprising material is selected from one or more of alginate, and extracellular polymeric substances, such as substances comprising a major portion consisting exopolysaccha- rides, and a minor portion consisting lipids and/or other com- ponents more hydrophobic than the exopolysaccharides, such as ALE, and algal alginate. These substances are considered fully biobased, may be obtained from waste water and hence contribute to a cyclic economy, can be produced in sufficient quantities, have good characteristics in view of further applica- tion, and provide good thermoset resins.

In an example of the present method the extracellular polymeric substances is bacterial aerobic granular sludge or anammox granular sludge, and is selected form exopolysaccha- ride, preferably comprising mannuronic acid and guluronic acid residues, block-copolymers comprising uronic acid residues, alginate, lipids, and combinations thereof, or wherein the bi- opolymer is an algae biopolymer.

In an example, the exopolysaccharides are block-copolymers comprising uronic acid (e.g. mannuronic acid and gulu- ronic acid) residues. Especially bacterial aerobic granular sludge or anammox granular sludge has been found to produce high amounts of biopolymers, in good quality. By nature the biopolymers produced as such vary in their characteristics, e.g. composition, molecular weight, etc. wherein preferably the extracellular polymeric substances comprise at least 50 % w/w exopolysaccharides, preferably at least 60 % w/w exopolysaccharides, most preferably at least 75 % w/w exopolysaccharides, such as at least 90 % w/w exopolysaccharides, hence a relatively large fraction of exopolysaccharides, more preferably wherein an exopolysaccharide content is less than 100 % and the isolated extracellular polymeric substances further may comprise lipids; the lipids may support further processing of the exopolysaccharides and may contribute beneficially to the characteristics of the thermoset resin. In an example of the present method the extracellular polymeric substances com ^¬ prise a minor portion, such as less than 30 % w/w, typically less than 10 %w/w, such as less than 0.1 %w/w (e.g. after repetitive purification steps), consisting of lipids and/or other components more hydrophobic than the exopolysaccharides.

In an example of the present process the extracellular polymeric substances comprise at least 50 % w/w exopolysaccha ^¬ rides, preferably at least 60 % w/w exopolysaccharides, most preferably at least 75 % w/w exopolysaccharides, such as at least 90 % w/w exopolysaccharides, more preferably wherein an exopolysaccharide content is less than 100 % and the isolated extracellular polymeric substances further may comprise 0.1-10 w/w% lipids, such as 0.2-5 w/w% . The exopolysaccharide content is preferably not 100 %, as a remainder has been found to con- tribute to the present advantageous effects.

In an example of the present method the granular sludge is one or more of aerobic granular sludge and anammox granular sludge. It is preferred that the extracellular polymeric sub ^¬ stances have been obtained from aerobic or anammox granular sludge by a method comprising: (i) extraction of the granular sludge thereby forming extracellular polymeric substances containing extractant; such as by alkaline extraction, by extraction with acetone, by acid extraction, by extraction using bleach and/or peroxides, etc.; (ii) precipitation of extracel- lular polymeric substances from the extractant; such as by ad ^¬ dition of an acid, acetone, etc.; and (iii) collecting the extracellular polymeric substances-containing precipitate. As such a good starting material for the present method is obtained . In an example of the present method the granular sludge has been substantially produced by bacteria belonging to the order Pseudomonadaceae, such as pseudomonas and/or AcetOjacter bacteria (aerobic granular sludge) ; or, by bacteria belonging to the order Planctomycetales (anammox granular sludge) , such as Brocadia anammoxidans, Kuenenia stuttgartiensis or Brocadia fulgida; or, combinations thereof.

In an example of the present method the extracellular polymeric substances are block-copolymers comprising uronic acid residues. In an example of the present method the extracellular polymeric substances are in aqueous solution at a concentration in the range of 0.1-30 % w/w, preferably 1-10 % w/w, most preferably 4-10 % w/w, such as 5-8 % w/w, i.e. at a concentration which is not too high or too low, which can be processed relatively easily, e.g. by pumping, which comprises enough material, etc.

The present biopolymers may be characterized by various (further) parameters. They may be different in various aspects from e.g. known comparable chemically or otherwise obtainable polymers, such is in viscosity behaviour, molecular weight, hydrophobicity, lipid content, microstructure (as can be observed under an electron microscope), etc. For instance, the lipid content of the present biopolymers is much higher than those of prior art comparable biopolymers, namely 2-5 wt. %, such as 3-4 wt . % . Analysis of an exemplary biopolymer using a PerkinElmer 983 double beam dispersive IR spectrometer shows approximately 3.2 wt . % peaks that are attributed to lipids. Typically the present biopolymers are also less pure, i.e. a mixture of polymers is obtained.

The present biopolymer may relate to an alginate, such as ALE. This is different from the alginates e.g. obtainable by pilot plant alginates in various aspects. For instance it may have a decreasing dynamic viscosity with increasing shear rate (@ 298 K (25 °C) ) , wherein a relative decrease is from 5- 50% reduction in dynamic viscosity per 10-fold increase in shear rate. It may have a dynamic viscosity of > 0.2-1 Pa*s (@298 K {25 °C) , @ shear rate of 1/sec) . It may have a weight averaged weight of > 10,000 Dalton, preferably > 50,000 Da, such as > 100,000 Da. It may have a hydrophilic part and hydrophobic part. It may have a tensile strength (according to ISO 37; DIN 53504) of 1-150 MPa . It may have a flexural strength (according to ISO 178) of 5-250 Pa . And it may re- late to combinations of the above.

In an example of the present biopolymer it may have > 30% with a molecular weight of > 300,000 Da, > 10% with a molecu ^¬ lar weight of > 100,000 Da, > 15% with a molecular weight of > 5,000 Da, and < 10% with a molecular weight of < 5,000 Da.

In an example of the present method the biobased material comprising at least two amine groups may be represented as

HR2N-R3-NR4H, is selected from one or more of primary ( R2 and/or R ₄ =H) and secondary amines ( R2 and/or R4 ≠H) , such as alkyl diamine, dialkyl diamine, alkanol diamine, alkyl alkanol diamine, aldehyde diamine, dialdehyde diamine, imine diamine, di- imine diamine, aldehyde imine diamine, urea, N, ' -dialkylurea, N-monoalkylurea, wherein each alkyl/alkanol/aldehyde (R3} is independently selected from C1-C12 alkyls/alkanols/aldehydes, preferably Ci- Ce alkyls/alkanols/aldehydes, more preferably Ci, C2 , C3 , C4, and C5 alkyls/alkanols/aldehydes, such as methyl, ethyl, propyl, iso-propyl, butyl, pentyl, and hexyl (and likewise alkanols and aldehydes), with the proviso that the at least two amine groups are preferably not at a same carbon of the alkyl/alkanol . So a wide range of amines of biological origin can be used to react with the present carboxylic acid comprising material to form a biobased resin.

In an example of the present method at least one of the amine group is attached to the same carbon as the aldehyde or imine, preferably two or more amine groups are attached to the same carbon as the aldehyde or imine; in other words the double bonded oxygen or likewise the double bonded nitrogen is attached to a same carbon as an amine group. It has been found that especially these biobased materials comprising at least two amine groups react particularly well with the present car- boxylic acids.

In an example of the present method the temperature is above a melt temperature of amine, wherein 0-2 wt . % amine solvent, such as water, is present to lower the melt temperature of the amine/solvent , preferably 0.01-1 wt.%, such as 0.1-0.2 wt.%, wherein weight percentages are based on a total weight of the reaction mixture. The present reaction, at least in an example thereof, may be considered as to relate to a melt type

polymerization. It may be preferred to carry out the step of forming a homogeneous mixture under a melt temperature of the amine. In an example the T _me it of the above urea/water is about 343 K (70 °C) whereas T _rae i _t of pure urea is about 407 K (134 °C) ; in addition it has been found that even a small amount of water lowers the TVit of the present amine, which may be bene ^¬ ficial to the present method, e.g. in terms of energy consump ^¬ tion .

In an example of the present method the reaction period is 1-60 minutes, preferably 2-30 minutes, such as 10-30 minutes. The reaction period depends e.g. on the biobased ma ^¬ terials used, the amount of water being present, and on the reaction temperature used. The reaction temperature is preferably 360-425 , such as 375-400 K.

In an example of the present method an amount of water is controlled, at least part of the water being formed by the condensation reaction. The amount of water can be controlled by addition of at least one of a filler, and water absorbent material, such as (dried) celluloses, hemi-celluloses, sawdust, fiber, such as wood fiber, and lignin comprising fiber. The filler may contribute to the characteristics of the present thermoset resin. The filler may be any of fillers typically used in polymers. Fillers may be used to change properties of the present resin. It may minimize resin drainage from vertical surfaces, increase bonding properties, reduce the cost of the resin mix, improve abrasion resistance or improve sanding properties, reduce or increase mixed weight and lower shrinkage rates, effect working and cure properties of the resin. In addition a water absorbent material may be provided, e.g. to remove water generated by the condensation reaction. Such is found beneficial to the reaction in terms of yield, completion, etc. The filler and water absorbing material may be one and the same. Examples are talc, microspheres, such as glass microspheres, clay, graphite, silica, cotton, etc. Fill ^¬ ers may typically be provided in an amount of 0.05-5 wt.%, relative to a total weight of the resin. In an example of the present method the oligo- or polymeric amide has a weight averaged molecular weight of 1,000-300,000 Da, preferably 1,500-100,000, more preferably 2,500-50,000, such as 3,500-25,000. The average weight may be determined by size exclusion chromatography, such as on a Shimadzu LCMS 8050, or by static light scattering, such as by a Malvern Om- nisec .

In an example of the present method alginate-amide is formed, in particular bacterial alginate is reacted with urea or an other diamine.

In second aspect the present invention relates to a ther- moset resin comprising urea and alginate or ALE. To the knowledge of the inventors this is the first time biological compounds are successfully transferred into an amide, in par ^¬ ticular an urea/alginate or urea/ALE resin.

In an example the present resin is obtainable by the present method.

In a third aspect the present invention relates to a use of 0.1-25 wt.% (based on a total weight) of a thermoset resin obtained by a method according to any of claims 1-15, in a prod ^¬ uct, such as in plywood, in a laminate, in fiberboard, such as in MDF, and in HDF, in a textile, in paper, in a casing, in a construction material, in a kitchen utensil, in a foam, as an electrical insulator, in fiber reinforced material, such as fiber reinforced plastic, in graphite or graphene reinforced material, such as graphite or graphene reinforced plastic, in a printed circuit board, as an additive in concrete, in a coating, in a MDF or HDF reinforced laminate plate, cross plate board, fiber reinforced composites, as a replacement of a chemically obtained thermoset resin, and in an adhesive. It is preferred to use 0.2-10 wt.% resin, more preferably 1-5 wt.%, such as 2-3 wt.%.

The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory o nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many var iants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims. FIGURES

Fig. 1 is a photo of an H-alginate (left) and ureic alginate resin (right) .

Fig. 2 shows a FTIR spectrum of ureic alginate and H-alginate.

DETAILED DESCRIPTION OF THE FIGURES.

Fig. 1 is a photo of an H-alginate (left) and transparent ureic alginate resin (right) , as is shown by the underlying letters which are clearly visible.

Fig. 2 shows a FTIR spectrum of ureic alginate and

H-alginate with a visible amide peak (indicated with an arrow at 1630-1690 cm ^-1 ) for ureic alginate resin sample. For the resin further peaks are visible at about 1050 cm ^{" 1} , at about 3230 cm ^-1 , and at about 3350 cm ^-1 . For the H- alginate (smaller) peaks are visible at about 1050 cm ^-1 , and at about 1720 cm ^-1 .

EXAMPLES/EXPERIMENTS

The invention although described in detailed explanatory context may be best understood in conjunction with the accom- panying examples and figures.

Details of the present methods for obtaining and characterizing e.g. ALE and alginate can be found in the documents cited in the introductory part, which documents are also in this respect incorporated by reference.

ALE molecular weight analysis

Size exclusion chromatography was performed with a Superdex 75 10/300 GL column (AKTA Purifier System, GE Healthcare) .

Elution was carried out at room temperature using Phosphate Buffer Saline (PBS) containing 10 mM (ΗΡ0 ₄ ^2" , Η ₂ Ρ0 ₄ -) with a pH of 7.4, and further having 2.7 mM KC1 and 137 mM NaCl, at a constant 0.4 mL/min flow rate. The detection was monitored by following the absorbance of the eluted molecules at a wavelength of 210 nia.

The Superdex 75 10/300 GL column is capable of separating molecules of 1,000 to 70,000 Daltons (Da). Measurement of the elution volume of dextran standards (i.e. 1000 Da, 5000 Da, 12000 Da, 25000 Da and 50000 Da) led to the calibration equation :

Log (MW) = 6.212 - 0.1861 Ve; Wherein M : Molecular Weight of the molecule in Dalton (Da) , and Ve: elution volume in mL (assayed at the top of the peak) . Chromatogram profiles were recorded with UNICORN 5.1 software (GE Healthcare) . Peak retention times and peak areas were di- rectly calculated and delivered by the program.

Results

Table 1 : Molecular weight of different fractions in alginate- like exopolysaccharid.es and their percentage.

Elution volume Molecular weight Percentage of the of the peak fraction

(ml) (kDa) (% peak area)

7.83 >70 29.74

13.48 14.4 18.82

15.57 5.79 45.15

17.58 2.15 4.42

20.13 0.656 1.87

Resin formation Experiments

Inventors have performed experiments and have found that urea and alginic acid form a homogenous system at elevated temperature or even RT which may depend on a method of mixing. Sometimes some water may be required. This may indicate that an alginate C00H proton is exchanging to the urea, apparently allowing the polymer to dissolve. The obtained more or less fluid mass can be 'baked off at elevated temperature and seems to form an isotropic transparent hard 'plastic' , thermo- set resin. FTIR results show that amide bonds are being formed, some bisurea crosslinking seems to occur, so a cross- linked polymer network results. Considering that urea and alginate are both GRAS (e-numbers E401 and E927b) and that an obvious choice of selecting a source of both raw materials could be from wastewater treatment, it appears that the present method provides a totally green, biobased, cyclic economy novel resin system. The resin is considered suitable for household products, packaging, fiber reinforced composites, etc.