FIELD OF THE INVENTION

The present invention is in the field of a water-based adhesive, in particular an adhesive for adhering cellulose or cellulose fibres comprising materials and the like, such as paper, cardboard, a method for applying the water-based adhesive, typically by applying heat during a certain time, and a product obtained by said method.

BACKGROUND OF THE INVENTION

Adhesives are typically in the form of one-component (1C) and two-component (2C) adhesives/sealants. It is noted that the difference between these two is rather fundamental. A 1C system can react on its own given an auxiliary trigger or reactant. This trigger or reactant is usually oxygen or water from the air. Without (enough) of this trigger no reaction occurs and the product will not cure from its plastic state into an elastic one. This may happen for example when two plates, impenetrable for oxygen or moisture are glued full sur-face to another. There may be cure at the edges but there it stops. In a 2C system all necessary reactants are contained, not additional trigger or reactant is needed. Therefore both parts will also have to be packed separately and typically mixed intensely before application. Both parts must be stable between production and use. When not properly mixed this will typically lead to inconsistencies in the cured material. Once mixed the curing reaction may start immediately, and therefore the material will have to be applied as soon as possible to prevent a too far cured product which will lead to difficulties in application and adhesion. A well-known system is an epoxy-adhesive where the epoxy is in one part and a curative amine is in the other part. Many other systems are known but all are based on this basic principle: once mixed, all necessary ingredients are there, nothing needs to get in or out. If a 2C product is used as an adhesive between the plates of the example all material, not just the edges but also the middle, will fully cure. Therefore for large surfaces (and other places where one cannot rely on the external trigger) 2C systems are preferred. From above it may be clear that the demands and challenges presented in a 1C product are quite different from a 2C product. Intermixing of components of a 1C and 2C product will typically not be considered by the skilled person; the two products may in fact be considered mutually incompatible.

General properties of adhesives are open time (working time to make a bond, where the surface still retains sufficient tack, which can range from seconds for fast-setting adhesives to infinity for pressure-sensitive adhesives), set time (time to form a bond of acceptable strength), dry time, (initial) tack ((initial)degree of surface stickiness of the adhesive), applicability and adhesion to a diverse range of substrate surfaces, contactibility, flexibility of an adhesive film, temperature stability, storage stability, viscosity, and surface energy (influences wetting of different kind of surfaces).

Adhesives often consist of one base material with various additives. For a two-compo- nent adhesive a first and second component, each component optionally comprising more than one constituent, are mixed before applying, such as by a spray-gun, a sealant-gun typically equipped with a means of mixing both components, and a static mixer. The first and second component can typically not be stored in a mixed form.

Some of the possible base materials, each having advantages and disadvantages, are reactive poly-urethanes, silicones, poly-sulphides, silane-terminated polymers, and various other copolymers.

Many of the prior art adhesives need to be bonded directly, typically within a few seconds, as the open time is relatively short. Thereafter one needs to wait until the adhesive has reacted and has obtained sufficient strength. That characteristic makes such an adhesive not suited for larger surfaces, or not very well accessible surfaces. Others may have a long open time and do not need to be bonded immediately; these consequently will suffer from an increased curing time thus also increasing the complete construction time of a to be bonded product.

It is often also important to have a high initial strength. For many prior art adhesive initial strength is not sufficient. One has to wait until the bond is sufficiently strong. Adhesives are preferably also temperature stable. A fibre-reinforced composite (FRC) is a building material that consists of three components, namely fibres (for strength and stiffness) as a discontinuous or dispersed phase, a matrix (binder) as a continuous phase, and the fine interphase region, also known as the interface. For fibres use can be made of natural fibres, synthetics fibres, or a combination thereof. Examples thereof are flax, hemp, rice husk, rice hull, rice shell, cellulosic (waste streams), and plastic as ingredients. Fibres may need to be refined, blended, and compounded, such as in case of natural fibres from cellulosic waste streams. A high-strength fibre composite material in a polymer matrix can be formed thereby. The designated waste or base raw materials used in this instance are those of waste thermoplastics and various categories of cellulosic waste including straw, rice husk and saw dust.

It is known that microorganisms are capable of producing biochemical compounds, such as lactic acid. Thereto typically a microbial culture is used. Therein microbial organisms reproduce in predetermined culture medium under controlled laboratory conditions. It is often essential to isolate a pure culture of microorganisms. A pure (or axenic) culture is a population of cells or multicellular organisms growing in the absence of other species or types. Remarkably also non-pure cultures are capable of producing chemical substances. Bacteria are capable of producing a wide variety of chemical substances, such as lactic acid, but also methane, and are therefore used in food industry, in waste treatment, and so on.

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

Recently it has been found that biobased polymeric substances, such as extracellular polymeric substances (EPS), in particular polysaccharide comprising materials, obtainable from granular sludge can be produced in large quantities. These substances relate to biobased carboxylic acid-like chemicals, 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 WO20 15/050449 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 examples of obtaining these substances, such as aerobic granular sludge and anam- mox granular sludge, and the processes used for obtaining them are known from Water Research, 2007, doi:10.1016/j.waters.2007.03.044 (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 alginate-like EPS in relatively raw form. Though initially the term “alginate-like”, or “alginate-like EPS” (ALE) was used, the biobased polymeric substances are found to be more complex in terms of chemical building blocks present therein. Therefore the term EPS is preferred. Details of the biopolymers can also be found in these documents, as well as in Dutch Patent applications NL2011609, NL2011542, NL2011852, NL2017470, and NL2012089. Also reference can be made to the Nereda® process. These documents, and there contents, such as characteristics (e.g. molecular weights, dynamic viscosity, shear rate, tensile strength, and flexural strength) of the biobased polymers, are incorporated by reference.

Incidentally, US 2020/087553 Al recites a system and method for treatment of biomass originating from wastewater treatment biosolids to obtain valuable adhesives and composite materials, wherein the method comprises the steps of a. obtaining a biomass; b. denaturing protein in said biomass, thereby generating an adhesive mixture byproduct of said biomass; and c. wherein the denaturing step is a heated, alkaline-based process. Some embodiments do not require purification of a biomass product or residue to produce an adhesive. Some embodiments comprise a treatment of post extraction biomass residue configured to produce an adhesive. Use of post extraction biomass residue adds value to alternative energy produced by extracting oil from biomass.

In general it has been found difficult to further process products of biological origin, or make use thereof, such as (these) microbial products, in particular biopolymers such as EPS, either in pure form as obtained from a reactor, or purified or extracted as indicated above.

The present invention relates to a water-based adhesive, and further aspects thereof, which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a water-based adhesive from wet microorganism biomass comprising concentrated wet biomass produced by and/or obtained from microorganisms, in particular bacteria, and comprising said microorganisms as microbial cells or parts thereof, in particular untreated biomass, that is, the biomass as such, in its original or likewise natural state, hence not treated such as by denaturing or the like, such as a suspension of concentrated wet biomass, and a remainder substantially being water, in particular >50 wt.% water, and < 99 wt.%, in particular < 95 wt.%, wherein a percentage weight is based on a total weight of the adhesive. The present biomass is produced by and/or obtained from microorganisms; such biomass is therefore in terms of characteristics very different from e.g. plant biomass, or likewise animal biomass. It may be used directly, that is without further treatment. The present adhesive is inherently fully biodegradable and relatively cheap. It is clearly non-toxic, requires no solvents other than water, such as no organic solvents, it can be wastebased, so it may be considered fully circular. It is noted that typically such an adhesive, and in particular the biomass, is at least partly, and typically mostly of a hydrophilic nature. The biomass is typically obtained from a reactor or the like. Therein microorganisms are typically grown in the order of 100 ml solution/gram biomass, so about 1 wt.% biomass. Higher wight percentages of up to some 10 wt.% are sometimes feasible.

It came as a surprise that the wet biomass could be used as such as an adhesive. As mentioned, the present adhesive is considered to be fully circular and “green”. The biomass can be used as such, possibly in concentrated form, but needs no further chemical or physical treatment to be used, nor need it to be extracted. So in can be used in un-treated form. In addition, the biomass itself forms the major fraction of the adhesive, at least in terms of active compounds. No further components need to be added. The present biomass can therefore not be considered as an additional component (to other main components, the other main components providing the adhesive properties) or the like in the adhesive. This is considered rather exceptional.

In a second aspect the present invention relates to a method of applying a water-based adhesive according to the invention, comprising providing a first material and a second material, applying the adhesive to at least one surface, such as the surface of the first material or the sur-face of the second material, adhering the first material and second material, and drying the adhesive, such as by heating the adhesive. By heating the adhesive the adhesive is dried, at least mainly dried. In a further aspect the present invention relates to a product obtainable from the method of the present invention, such as adhered paper, adhered cardboard, adhered textile, a chemical filter, and a fibre-reinforcement composite.

The present water-based adhesive may be used for various purposes, such as for paper sizing, for binding, or for laminating.

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 water-based adhesive.

In an exemplary embodiment of the present water-based adhesive the adhesive has a reduced in water content, such as by centrifugation or filter-pressing, such as < 90 wt.%., in particular < 85 wt.%, more in particular < 80 wt.%, and/or > 40 wt.%, such as > 50 wt.%, that is, the water-based adhesive is concentrated in terms of mass/volume. It is noted that the water content can be reduced, at least to some extent, though this is not directly required for the adhesive properties itself. Reduction of water content is somewhat limited from a practical, and hence financial, point of view; the water content may be considered to be rather high, even after the reduction thereof.

In an exemplary embodiment of the present water-based adhesive the concentrated wet biomass is finely divided in the adhesive, such as, if required, by thorough mixing and/or milling, in particular by using a high rotation speed mixer of > 1000 rpm, such as > 10,000 rpm, such as in particles of size < 1mm, in particular < 500 pm. In particular when the biomass is present as granules or the like a more finely divided adhesive could be preferred. Mixing and/or milling are suitable means of finely dividing.

In an exemplary embodiment of the present water-based adhesive the bacteria are selected from bacteria belonging to Proteobacteria, such as Gammaproteobacteria, such as of the order Pseudomonadaceae, such as Pseudomonas, Alphaproteobacteria, such as of the order of Rhodospirillales, such as Acetobacter bacteria (aerobic granular sludge) or, from bacteria belonging to Planctomycetes, such as Planctomycetia, such as the order Planctomycetales (anammox granular sludge), such as Brocadia anammoxidans, Kuenenia stuttgartiensis or Brocadia fulgida,' or from Betaproteobacteria, such as Can- didatis Accumulibacter phosphalis. or, from eukaryotic organisms, typically monocellular organisms, such as algae, such as brown algae. It is rather surprising that these microorganisms, typically monocellular organisms, produce a biomass, or comprise a biomass, that can be used as such for the purpose of adhering materials.

In an exemplary embodiment of the present water-based adhesive the wet biomass comprises > 10 ³ different microorganism species, in particular > 10 ⁴ different microorganism species, more in particular > 10 ⁶ different microorganism species. Albeit the present biomass and/or microorganisms are typically obtained from a reactor or the like, the reactor intended for a certain purpose, e.g., the production of a biological compound, such as lactic acid, or methane, or the cleaning of waste water, the present biomass and/or microorganisms comprise a multitude of different microorganism species. So, albeit reactor conditions are preferred for certain microorganisms, still a multitude of species is and can be present, and said multitude of species is typically found in the present adhesive, as such, or as parts thereof.

In an exemplary embodiment of the present water-based adhesive the wet biomass comprises 0.001-30 wt.% glycoproteins, which are typically oligosaccharide chains, also referred to as glycans, which are covalently attached to amino acid side-chains, in particular 0.1-10 wt.%, more in particular 1-5 wt.%, based on dry biomass. The terms glycan and polysaccharide refer to compounds consisting of a large number of monosaccharides linked glycosidically. The term glycan may also be used to refer to the carbohydrate portion of a glycoconjugate, such as a glycoprotein, glycolipid, or a proteoglycan, even if the carbohydrate is only an oligosaccharide. Glycans usually consist solely of O-glycosidic linkages of monosaccharides. For example, cellulose is a glycan (or, to be more specific, a glucan) composed of P-l,4-linked D-glucose, and chitin is a glycan composed of P-l,4-linked N-acetyl-D-glucosamine. Glycans can be homo- or heteropolymers of monosaccharide residues, and can be linear or branched.

In an exemplary embodiment of the present water-based adhesive the wet biomass comprises 0.00-15 wt.% bio-polyester, in particular 0.1-10 wt.% bio-polyester, more in particular 0.3-3 wt.% bio-polyester, such as 0.4-1 wt.% bio-polyester, based on dry biomass. Said bio-polyester may be present in the reactor or the like, in relative small amounts, in particular when the reactor is intended to produce such bio-polyesters, or parts thereof, such as in the case of lactic acid production.

In an exemplary embodiment of the present water-based adhesive the bio-polyester is selected from polyhydroxy alkanoates (PHA), preferably wherein the PHA is formed from C2-C7 carboxylic acids, such as Poly(3-hydroxybutyrate-co-3 -hydroxyvalerate) (PHBV), polylactic acid (PLA), and poly hydroxy butyrate (PHB), hybrid polymers thereof, and block- or co-polymers thereof, and combinations thereof.

In an exemplary embodiment of the present water-based adhesive the bio-polyester is an intracellular produced bio-polyester.

In an exemplary embodiment of the present water-based adhesive the adhesive is obtained directly from bacterial sludge (such as in a Nereda reactor, or from activated sludge).

In an exemplary embodiment of the present water-based adhesive the biomass is obtained from granular sludge by sieving, such as using a sieve of < 4 mm.

In an exemplary embodiment the present water-based adhesive comprises 0.1-25 wt.% biomass, in particular 1-20 wt.% biomass, more in particular 5-15 wt.% biomass, and 0-23 wt.% bio-polyester, in particular 0.01-12.5 wt.% bio-polyester, more in particular 5-10 wt.% bio-polyester, and 0.0001-15 wt.% glycoproteins, in particular 0.01-10 wt.% glycoproteins, more in particular 0.1-8 wt.% glycoproteins, and 0-15 wt.% lipids, in particular 0.01-10 wt.%, such as 0.02-2 wt.%, and 0-20 wt.% exopolysaccharides, in particular 0.5-10 wt.%, such as 1-5 wt.%, and 0-15 wt.% proteins, in particular 0.1-10 wt.%, such as 1-5 wt.%, a remainder being water.

In an exemplary embodiment of the present water-based adhesive the water-based adhesive comprises a high biomass of 40-60 wt.% bacterial cells thereof, based on a dry mass.

In an exemplary embodiment of the present water-based adhesive the water-based adhesive is a directly applicable adhesive with a low biomass of 5-25 wt.% bacterial cells, based on a dry mass.

In an exemplary embodiment of the present water-based adhesive the concentrated wet bio-mass is produced in a reactor and directly provided therefrom.

In an exemplary embodiment of the present water-based adhesive the adhesive has a tackiness/peel strength of > 30 J/m ² , [ISO 11339:2010], in particular > 100 J/m ² . Such a peel strength is rather high, and sufficient for many applications.

In an exemplary embodiment of the present water-based adhesive the adhesive comprises 10' ⁵ -10 wt.% microbial DNA, in particular 10' ³ -5 wt.%, more in particular 10 ^-1 -3 wt.%, that is, traces of the microbial DNA are typically present in the present adhesive.

In an exemplary embodiment of the present water-based adhesive the adhesive comprises >5 wt.% microbial cells or parts thereof, in particular > 10 wt.% microbial cells.

In an exemplary embodiment of the present water-based adhesive the bio-polyes- ter, when present, in the adhesive has a melting point or melting range of 80-220 °C, in particular 90-130 °C).

In an exemplary embodiment of the present water-based adhesive the bio-polyes- ter of the adhesive has a glass transition temperature of < 50 °C, preferably < 40 °C, such as < 20 °C, in particular < 0 °C, (measured using differential scanning calorimetry with Mettler Toledo TGA2 according to ISO 11357-1 :2016).

In an exemplary embodiment of the present water-based adhesive the biomass comprises biopolymer which is anionic or cationic.

In an exemplary embodiment of the present water-based adhesive the biopolymer is a non-linear biopolymer.

In an exemplary embodiment of the present water-based adhesive the biopolymer has an average molecular weight of >5kDa (size exclusion chromatography), preferably > 10 kDa, more preferably >20 kDa, such as > 100 kDa.

In an exemplary embodiment of the present water-based adhesive the biopolymer has an average molecular weight of <1500 kDa (size exclusion chromatography, preferably < 1000 kDa, more preferably <500 kDa.

In an exemplary embodiment of the present water-based adhesive the biopolymer has a chemical multifunctionality.

The above are some characteristics of exemplary biopolymers that can be present in the present biomass.

In an exemplary embodiment of the present method heat is applied during 0.01-5 minutes, in particular during 0.1-2 minutes, such as 0.5-1 minute.

In an exemplary embodiment of the present method the temperature of the adhesive is increased to 25-300 °C, in particular to 50-200 °C, such as by using an iron.

In an exemplary embodiment of the present method the first material and a second material are each individually selected from natural or processed cellulose or cellulose fibres comprising materials, such as paper, and cardboard, and from hemicellulose comprising materials, and from lignin com-prising materials.

In an exemplary embodiment of the present product is adhered paper, adhered cardboard, adhered textile, a chemical filter, and a fibre-reinforcement composite.

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

EXAMPLE S/EXPERIMENTS

The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples.

Sludge was directly obtained from an aerobic bioreactor fed with leachate from organic waste. The sludge was then concentrated, using a centrifuge at 3000 g during 2 minutes, to a dry solids content of 15% (w/w). The sludge as such was applied on a first piece of cardboard and a second piece of cardboard was placed on top. This “cardboard sandwich” was subsequently heated using an iron at 150-175 °C until the lion-share of the water was evaporated, which was after about 60 seconds. After this, the two pieces of cardboard were found to stick together. The bonding between the two pieces was so strong, that it was not possible to separate the pieces without breaking them. The force applied was estimated to be > 100 N/m (100 N m/m ² or 100 J/m ² ). Suitable test procedures are ISO 11339: Adhesives - T-peel test for flexible-to-flexible bonded assemblies [N/cm]; ISO 16260: Paper and board — Determination of internal bond strength [J/m ² ]; ASTM 3165-07: Standard Test Method for Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies [N/m ² ].