Bioadhesive and a method for its production

Abstract

According to the present invention, there is provided a method for the production of an adhesive, said method comprising the following steps: a) providing lignin rich carbohydrate complexes (LCC) by pressurized hot water extraction of softwood biomass, preferably biomass of Norway spruce or Scots pine, or of hardwood biomass, preferably biomass of Birch or Beech, providing bark lignin rich carbohydrate complexes (BLCC) by pressurized hot water extraction of softwood bark, preferably bark of Norway spruce or Scots pine, or providing liquefied biomass by acid-catalyzed liquefaction of biomass including wood saw dust, agricultural residues, plant stalks, recycle carton boards, recycle paper, recycle wood, wood panels, and wood bark side streams, in polyhydric alcohols and phenols; b) reacting the LCCs, BLCCs, or liquefied biomass obtained in step a) with a crosslinking or catalytic agent selected from the group consisting of: carboxylic agents including citric acid, dicarboxylic acids including adipic acid, organic acid anhydrides, tannin, tannic acid, plant derived fatty acids including suberin, and hexamethylenediamine, in order to produce said adhesive. The present invention is also directed to an adhesive produced by the method of the invention and to the use thereof as a bonding agent in wood products or as a coating agent in wood products or mineral wool.

Description

BIOADHESIVE AND A METHOD FOR ITS PRODUCTIONFIELD

[0001] The present disclosure relates to biobased sustainable adhesives suitable for engineered wood products and wood-based panels.BACKGROUND

[0002] The wood veneer based product such as plywood, laminated veneer lumber (LVL); wood particles, strands and fibers panels (WBPs) such as Fiberboards (MDF, Softboard, Hardboard), Particleboard (also known as chipboard), and Oriented strand board (OSB) industries uses almost exclusively (about 95% or ~20 million tons annually) synthetic, petroleum-derived thermosetting adhesives, which are mainly based on the reaction of formaldehyde with urea, melamine, phenol, or co-condensates and isocyanate resins (pMDI). Formaldehyde emission from WBPs during production stages and service life became a matter of concern as the International Agency for Research on Cancer (IARC) classified formaldehyde to be carcinogenic in 2004. In 2016, European Classification, labelling and packaging (CLP) regulation, classified formaldehyde as a Carcinogen Category IB compound. Due to these strong regulations, WBPs industry faces immense pressure to reduce the formaldehyde emission from panels.

[0003] Another concern of these adhesives is the dependency on fossil-based products. The low cost and good adjustable properties of formaldehyde-based adhesives have made it difficult for new bio-based alternatives to enter the market. However, the biobased gluing provides a sustainable solution to emission concerns and fossil dependency, and more potential for cascading, recycling, and reuse of wood-based products. There have been many ongoing attempts to find suitable solutions and replacements for formaldehyde- based resins in WBPs at industrial scale production and application. Very few of them reached industrial scale for product specific applications, however, major success was achieved, e.g., in replacing the synthetic phenol by lignin derived phenol in phenol formaldehyde resin production for plywood manufacturing. Replacement of interior grade urea formaldehyde (UF) resin by protein / starch derived resin is being considered in industrial scale such as IKEA industries. However, the exterior resins mainly phenol formaldehyde (PF) resins replacement is difficult to find because biobased resins do not fulfill the tough boiling test standards [EN 314-2 / Class 2 & 3 (exterior)]. New bio-basedadhesives must not only bond wood at a reasonable price, but also deliver a specified degree of moisture resistance, fast cure rates, and many other factors needed for the diverse array of wood products and their production process.SUMMARY

[0004] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0005] The present invention provides a fully biomass-derived adhesive without the use of fossil derived chemical / polymer, toxic formaldehyde, isocyanate and toxic organic crosslinkers. The prepared bioadhesive conforms with the EN 314-2 / Class 2 and 3 (exterior) requirements, i.e., veneer panels (plywood, LVL) glued with the present bioadhesive are weather- and boil-resistant. Furthermore, the prepared bioadhesive is also suitable for all other exterior / interior grade wood-based panels i.e. fiberboards, particleboard, oriented strand board and natural fibers based panels. This invention provides novel knowledge and increases the resource efficiency through an efficient use of primary and secondary bio-based materials from industrial biomass side-streams, such as liquefied biomass (LBM) and different types of lignin-carbohydrate complexes (LCCs) extracted from various biomass via hot-water and steam extraction processes.

[0006] According to a first aspect of the present invention, there is provided a method to produce an adhesive, said method comprising the following steps: a) providing lignin rich carbohydrate complexes (LCC) by pressurized hot water extraction of softwood biomass, preferably biomass of Norway spruce or Scots pine, or of hardwood biomass, preferably biomass of Birch or Beech, providing bark lignin rich carbohydrate complexes (BLCC) by pressurized hot water extraction of softwood bark, preferably bark of Norway spruce or Scots pine, or providing liquefied biomass by acid-catalyzed liquefaction of biomass including wood saw dust, agricultural residues, plant stalks, recycle carton boards, recycle paper, recycle wood, wood panels, and wood bark side streams, in polyhydric alcohols and phenols; b) reacting the LCCs, BLCCs, or liquefied biomass obtained in step a) with a crosslinking or catalytic agent selected from the group consisting of: carboxylic agents including citric acid, dicarboxylic acids including adipic acid, organic acid anhydrides, starch, tannin,tannic acid, plant derived fatty acids including suberin, cutin, and hexamethylenediamine, in order to produce said adhesive.

[0007] According to a second aspect of the present invention, there is provided an adhesive produced by the method of the present disclosure.

[0008] According to a third aspect of the present invention, there is provided a use of the adhesive produced by the method of the present disclosure as a bonding agent in wood products or as a coating agent in wood products or mineral wool.

[0009] According to a fourth aspect of the present invention, there is provided a use of the adhesive produced by the method of the present disclosure in impregnation of wood products with said adhesive in order to improve the flame retardant properties, the resistance to rot, fungus, mold and insects of the wooden material, and / or to lower the total gaseous emissions of the wooden material.

[0010] According to a fifth aspect of the present invention, there is provided a foam comprising the adhesive produced by the method of the present disclosure.

[0011] According to a sixth aspect of the present invention, there is provided a pressurized hot water extraction method for extracting hemicellulose and lignin rich carbohydrate complexes (LCC) from bark material including bark of Norway spruce or Scots pine, the method comprising the steps of: a) providing bark from side-streams generated by wood processing industry including saw milling, plywood, pulp and paper industries; b) mixing the bark material obtained in step a) into a water solution and subjecting the mix to a temperature in the range of 80-100 °C in order to separate and remove polyphenols including tannins from the bark material; c) increasing the temperature of the bark material in a water solution to a temperature in the range of 150-200 °C in order to separate hemicellulose and lignin rich carbohydrate complexes from the bark material; and d) isolating at least lignin rich carbohydrate complexes from the water solution obtained in step c).BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIGURE 1 shows an overview of the resources and chemistry utilized in the present invention.

[0013] FIGURE 2 shows the crosslinking reaction mechanism for softwood LCC and citric acid, i.e. reaction between phenylglycoside (a model compound for softwood LCC) and citric acid.

[0014] FIGURE 3 shows the bond shear strength (according to BS-EN-314) of plywood in dry form, after treatment in cold water and after boiling water treatment, see Example 11 below.

[0015] FIGURE 4 shows the bond shear strength (according to BS-EN-314) of laminated veneer lumber (LVL) in dry form, after treatment in cold water and after boiling water treatment, see Example 11 below.

[0016] FIGURE 5 shows the bond shear strength (according to BS-EN-314) of plywood in dry form, after treatment in cold water and after boiling water treatment, see Example 12 below.

[0017] FIGURE 6 shows CIEL*a*b* color coordinates before and during the artificial aging of coated and control wood specimens, i.e. the stability of bio glue coated wood specimens against the UV-degradation. The lightness of coated sample was like original color of wood after 1000 h of UV -degradation. Similarly, the redness of coated sample was like original of control sample, see Example 13 below.

[0018] FIGURE 7 shows a DSC thermogram of a crosslinked LCC-CA-BLCC composition, i.e. its curing behavior and kinetics, see Example 2 below.

[0019] FIGURE 8 shows the stages of a pressurized hot water extraction for extracting bark lignin rich carbohydrate complexes (BLCCs) from Norway spruce bark.

[0020] FIGURE 9 shows the rate of heat release due to exposure to fire of different plywood samples.

[0021] FIGURE 10 shows the total smoke production from plywood samples during to exposure to fire.EMBODIMENTS

[0022] In the present context, the term “lignin-carbohydrate complexes” (LCCs) is relating compositions formed from lignin and carbohydrate moieties linked by several chemical bonds (for a review, see Zhao, Y. et al., 2020). LCCs are considered to be sustainable biopolymers suitable for green materials engineering. Main chemical constitutes of LCCs are hemicelluloses (30-80 wt% of total dry weight), lignin (15-60 wt% of total dry weight), and extractives (2-10 wt% of total dry weight), see Tables 1 and 7).

[0023] In the present context, the abbreviation “BLCCs” relates to lignin- carbohydrate complexes prepared from bark, including but not limited to bark of Norway spruce or Scots pine.

[0024] In the present context, the term “crosslinking” relates to covalent bonds established in a chemical reaction between LCCs and BLCCs. Lor example, in a chemical reaction citric acid (CA) forms esters with the -OH groups of lignin rich-carbohydrates (LCCs) as shown in Eigure 2.

[0025] In Eigure 2, PG (phenylglycoside), a model compound of softwood hemicelluloses, reacts with citric acid anhydride upon heating and release the water in open condensation reaction and forms the LCC-CA polyester as main polymer. The final dry weight content of LCC-CA polyester can set with a suitable reaction time at 105 °C, also the final viscosity of bio-resin can be controlled. In a possible second step, BLCCs are mixed and reacted with LCC-CA polyester at 90 °C. BLCCs bring more lignin to system along with carbohydrates to react with residual CA to produce a robust complex LCC-CA- BLCC polyester.

[0026] Examples of chemical compositions of LCCs, BLCCs and crosslinked structures thereof in the present disclosure are given in Table 1 below (for more details see Table 7):'Accelerated solvent extracted,2Acid methanolysis -GC,3Klason lignin + acid soluble lignin with UV, 4CA= citric acid

[0027] In the present context, the term “pressurized hot water extraction” (PH WE) relates to an extraction technique that uses liquid water as extractant (extraction solvent) at temperatures near or above the atmospheric boiling point of water (100 °C / 273 K, 0.1 MPa), but below the critical point of water (374 °C / 647 K, 22.1 MPa). In an example of the PHWE process, Spruce sawdust is extracted with a pressurized hot water flow-through system as disclosed in Kilpelainen et al., 2014, obtain lignin rich carbohydrates. In detail, a sample of fresh sawdust is added into a reactor. After addition, sawdust is first pre-steamed for 26 min with 212 °C steam. Sawdust is then extracted at 170 °C with 20 L / min of continuous water flow for 60 min extraction time. The pressure during the extraction is 13.5 bar. The extract is collected into an intermediate bulk container (IBC) and the pH of the extract is usually around 3.6.

[0028] In another example of PHWE process, Norway spruce bark is subjected to a two-stage PHWE process (Figure 8). At the first stage, lower temperatures (80-110 °C) are used to remove polyphenols such as tannins from the bark material. In the second stage, the temperature is increased to the level of 150-200 °C, when hemicelluloses, BLCC and partially lignin can be extracted from the bark material. The pressure during the extraction is preferably between 1-25 bar. In a specific example, the first stage extracted 9.1% (w / w of dry matter) of original bark and the second stage extracted 31.1% (w / w of dry matter), so totally 40.2% (w / w of dry matter) of bark was extracted during the process. Bark samples can be extracted in batch or flow-through mode. Ultrafiltration-spray drying can be used to obtain the final product BLCCs.

[0029] In the present context, the term “acid-catalyzed liquefaction” relates to biomass converted into liquified biomass using the moderate acid-catalyzed liquefaction in polyhydric alcohols and phenols. In an example process, the solvent mixture contains PEG400 or crude ethylene glycol (EG) and wood biomass material in mass ratio of 4:1, and 4 wt% of H2SO4 as a catalyst. Reaction temperature range is from 120 °C to 190 °C,and reaction time 20 min to 90 min, preferably mixing with 300 rpm in a closed reactor with the aid of 5 bar pressure.

[0030] Cellulose, hemicelluloses, and lignin, the main components in the plant cell wall, have unique chemical structures, properties, and functionality. In plants, cellulose molecules form the supporting network that is embedded within a matrix composed of hemicelluloses and lamellar lignin “sheets”. These are partly bound to each other via chemical bonds. Hemicelluloses selectively connect with cellulose molecules through hydrogen bonding and cover the microfibrillar bundles of cellulose. Hemicelluloses also interact with lignin macromolecules, thus maintaining a consistency between the main components of the wood cell wall. When the plant biomass is processed with certain biorefinery techniques for further fractionations, the lignocellulosic extracts form a hybrid structure by covalently linked lignin and carbohydrates, so called lignin-carbohydrate complexes (LCCs). These LCC structures are recalcitrant and prevent efficient fractionations of biomass, because of stable bonds within lignin and carbohydrate moieties. According to literature, LCCs have formed mostly three types of covalent linkages with carbohydrates or hemicelluloses such as phenylglycoside, benzylether, and y-ester.

[0031] Efforts has been made to use LCCs in several application but still limited to use as emulsifiers for food, cosmetics etc. In the present disclosure, we efficiently converted the LCCs into fully sustainable bio-polymeric adhesive system.

[0032] Accordingly, the present invention is directed to a method to produce an adhesive, said method comprising the following steps: a) providing lignin rich carbohydrate complexes (LCC) by pressurized hot water extraction of softwood biomass, preferably biomass of Norway spruce or Scots pine, or of hardwood biomass, preferably biomass of Birch or Beech, providing bark lignin rich carbohydrate complexes (BLCC) by pressurized hot water extraction of softwood bark, preferably bark of Norway spruce or Scots pine, or providing liquefied biomass by acid-catalyzed liquefaction of biomass including wood saw dust, agricultural residues, plant stalks, recycle carton boards, recycle paper, recycle wood, wood panels, and wood bark side streams, in polyhydric alcohols and phenols; b) reacting the LCCs, BLCCs, or liquefied biomass obtained in step a) with a crosslinking or catalytic agent selected from the group consisting of: carboxylic agents including citricacid, dicarboxylic acids including adipic acid, organic acid anhydrides, tannin, tannic acid, plant derived fatty acids including suberin, and hexamethylenediamine, in order to produce said adhesive.

[0033] In a preferred embodiment, said crosslinking agent is citric acid.

[0034] In another preferred embodiment, said method comprises a further step of contacting the adhesive obtained in step b) from said LCCs or said liquefied biomass with bark lignin rich carbohydrate complexes (BLCC) provided by two stage pressurized hot water extraction of softwood bark biomass, preferably bark biomass of Norway Spruce or Scots pine, wherein the BLCCs obtained from softwood bark biomass are preferably added to said adhesive so that the mixture contains 1% to 30% (w / w) of said BLCCs obtained from softwood bark biomass.

[0035] Said two stage pressurized hot water extraction of softwood bark biomass preferably comprises the steps of: i) providing bark from side-streams generated by wood processing industry including saw milling, plywood, pulp and paper industries; ii) mixing the bark material obtained in step i) into a water solution and subjecting the mix to a temperature in the range of 80-100 °C in order to separate and remove polyphenols including tannins from the bark material; iii) increasing the temperature of the bark material in a water solution to a temperature in the range of 150-200 °C in order to separate hemicellulose and lignin rich carbohydrate complexes from the bark material; and iv) isolating lignin rich carbohydrate complexes from the water solution obtained in step iii). The pressure during the extraction steps is preferably between 1 bar to 25 bar.

[0036] In another preferred embodiment, said method comprises a further step of mixing the adhesive obtained from LCCs of softwood biomass and the adhesive obtained from LCCs of hardwood biomass, preferably in ratios 50:50, 50:40, 50:30, 50:20, and 50:10 with optional further addition of BLCCs from softwood bark biomass.

[0037] In another preferred embodiment, said method comprises a further step of mixing the adhesive obtained from LCCs of softwood biomass and the adhesive obtainedfrom LCCs of hardwood biomass, preferably in ratios 50:50, 50:40, 50:30, 50:20, and 50:10 with further addition of sucrose, xylitol, fructose, calcium carbonates or starch.

[0038] In another preferred embodiment, said method comprises a further step of mixing the adhesive obtained from LCCs of softwood biomass and / or the adhesive obtained from LCCs of hardwood biomass with a nanoproduct selected from the group consisting of cellulose nanofibers (CNF), bacterial cellulose nanofibers, and crystalline nanocelluloses.

[0039] In another preferred embodiment, said method comprises a further step of mixing the adhesive obtained from acid-catalyzed liquefaction of biomass with Kraft lignin so that the amount of Kraft lignin is 1% to 10% (w / w) of the resulting adhesive.

[0040] In another preferred embodiment, said method comprises a further step of mixing the adhesive obtained from step b) with an adhesive containing urea formaldehyde (UF), phenol formaldehyde (PF) and / or melamine urea formaldehyde (MUF) so that the prepared adhesive comprises 5% to 90% of the adhesive obtained from step b).

[0041] In an embodiment, the present invention is also directed to an adhesive produced by the method of the present disclosure.

[0042] In a preferred embodiment, said adhesive comprises crosslinked LCCs or BLCCs (see Figure 2).

[0043] In another preferred embodiment, said adhesive comprises a crosslinked blend of LCCs and BLCCs.

[0044] In an embodiment, the present invention is also directed to a use of the adhesive of the present disclosure as a bonding agent in wood veneer products (plywood and LVL) for exterior grade applications.

[0045] In a preferred embodiment, said adhesive is used as a bonding agent in the production of wood-based panels (MDF, Particle board, HDF, softwood, cellulose foam, wood foams etc.) and for mineral wool insulators.

[0046] In another preferred embodiment, said adhesive is used as a coating agent for wood products to provide improved UV protection.

[0047] In an embodiment, the present invention is also directed to a use of the adhesive of the present disclosure in impregnation of wood products with said adhesive in order to improve the flame-retardant properties, the resistance to rot, fungus, mold and insects of the wooden material, and / or to lower the total gaseous emissions of the wooden material.

[0048] In an embodiment, the present invention is also directed to a foam comprising the adhesive of the present disclosure.

[0049] In a preferred embodiment, said foam is a fire retardant foam.

[0050] In an embodiment, the present invention is also directed to a pressurized hot water extraction method for extracting hemicellulose and lignin rich carbohydrate complexes (LCC) from bark material including bark of Norway spruce or Scots pine, the method comprising the steps of: a) providing bark from side-streams generated by wood processing industry including saw milling, plywood, pulp and paper industries; b) mixing the bark material obtained in step a) into a water solution and subjecting the mix to a temperature in the range of 80-100 °C (preferably about 90 °C) in order to separate and remove polyphenols including tannins from the bark material; c) increasing the temperature of the bark material in a water solution to a temperature in the range of 150-200 °C (preferably about 170 °C) in order to separate hemicellulose and lignin rich carbohydrate complexes from the bark material; and d) isolating at least lignin rich carbohydrate complexes from the water solution obtained in step c).

[0051] As used herein, the term “about” refers to a value which is ± 5% of the stated value.

[0052] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0053] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0054] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0055] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0056] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0057] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.EXPERIMENTAL SECTIONEXAMPLE 1 : Crosslinking reaction of LCCs from softwood (prepared by a PHWE reaction) with citric acid in water as solvent to prepare Bio-glue formulation 1.Ratio of Water (g) / Citric acid (g) / LCCs (g): the water is kept as fixed (100%), the percentage of citric acid varies between 20% to 70% and LCCs percentage varies from 5% to 50%.Reaction conditions: Selected ratio of Water / Citric acid / LCCs reacted together in a reflux condensation glass reactor at fixed temperature of 105 °C, reaction time: 1 h to 5 h to set the desired viscosity and solid content of bio-glue.Curing temperature range: 100 °C to 200 °CApplications: this bioglue is suitable for interior grade engineered wood products, paper packaging, cardboard, and mineral wools.EXAMPLE 2: Preparation of Bio-glue formulation 2.The bioglue formulation 1 of Example 1 was reacted with BLCCs (prepared by a PHWE reaction). The BLCCs were mixed with Bioglue of Example 1 in different weight percentages between 1% to 30% and the reaction was continuously mixed at 90 °C up to 30 min until all the BLCCs were mixed well in bioglue system.Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Mineral wools. Biobased coating and lamination on engineered wood products. Fire retardant coating, wood preservation. Fire retardant foams etc.Curing temperature range: 140 °C to 200 °C, see Figure 7EXAMPLE 3: Preparation of Bio-glue-formulation 3.Reaction of LCCs from hardwood (by PHWE) with citric acid in water as solvent.Ratio of Water (g) / Citric acid (g) / LCCs (g): the water is kept as fixed (100%), the percentage of citric acid varies between 20% to 70% and LCCs percentages varies from 5% to 30%.Reaction conditions: Selected ratio of Water / Citric acid / LCCs reacted together in a reflux condensation glass reactor at fixed temperature of 105 °C, reaction time is 1 h to 5 h to set the desired viscosity and solid content of bio-glue.Applications: this bioglue is suitable for interior grade engineered wood products, paper packaging and cardboard. Mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 4: Preparation of Bio-glue formulation 4.The Bioglue formulation 3 was reacted with BLCCs (prepared by a PHWE reaction). The BLCCs were mixed with Bioglue formulation 3 in different weight percentage between 1% to 30% and were continuously mixing at 90 °C up to 30 min until all the BLCCs were mixed well in the bioglue system.Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products. Fire retardant coating, wood preservation. Fire retardant foams etc. Mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 5: Preparation of Bio-glue formulation 5.Bioglue formulations 1 and 3 were mixed together in different percentages such as 50:50, 50:40, 50:30, 50:20, and 50:10 with further additions of the different weight percentages of BLCCs and mixed well at 90 °C up to 30 min.Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products. Fire retardant coating, wood preservation. Fire retardant foams etc. Mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 6: Preparation of Bioglue formulation 6.Bioglue formulations 1 and 3 were mixed together in different percentages such as 50:50, 50:40, 50:30, 50:20, and 50:10 with further addition of the different weight percentages of sucrose, xylitol and fructose (1% to 10%) and mixed well at 90 °C up to 30 min. Further, sucrose, xylitol, and fructose were mixed with Bioglue formulations 1 and 3 individually in different weight percentages and a similar mixing process followed.Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products. Fire retardant coating, wood preservation. Fire retardant foams etc. Mineral woolsCuring temperature range: 100 °C to 200 °CEXAMPEE 7: Preparation of Bioglue formulation 7.A liquefied biomass was reacted with citric acid or other carboxylic acid. Citric acid was mixed with liquefied biomass with different weight percentages i.e. 10% to 50% and mixed well at 90 °C until all the citric acid was dissolved into the liquefied biomass. After that different weight percentages i.e. 10% to 60% of Bioglue formulations 1 and 3 were mixed with the bioglue prepared from liquefied biomass.Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products and wood preservation etc. Mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 8: Preparation of Bioglue formulation 8.Cellulose nanofibers (CNF), bacterial Cellulose nanofibers, crystalline nanocelluloses were mixed with any of the Bioglues formulationx 1-7 in different weight percentages (5% to 50%).Applications: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products. Fire retardant coating, wood preservation. Fire retardant foams etc. Mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 9: Preparation of Bioglue formulation 9.Kraft lignin (1% to 10%) were mixed with the Bioglue formulation 7 with the aid of high shearing mixture.Application: Bonding agent for all types of engineered wood products, both interior and exterior grade. Biobased coating and lamination on engineered wood products. Mineral woolsEXAMPLE 10: Preparation of Bioglue formulation 10.Partial replacement (5% to 90%) of existing fossil derived adhesives such as Urea Formaldehyde (UF), Phenol formaldehyde (PF) and Melamine Urea Formaldehyde (MUF) by adding any of the Bioglue formulations 1-7 to the fossil derived adhesive.Applications: All interior and exterior grade engineered wood products and mineral woolsCuring temperature range: 100 °C to 200 °C.EXAMPLE 11 : Plywood and laminated veneer lumber bonding quality testing bonded with Bioglue formulation 2.PlywoodAbout 150 g / m2of Bioglue formulation 2 was applied on the veneers to prepare three-layer plywood. After bioglue application, veneers were layered with the fiber directions crosswise to each other and hot-pressed at 180 °C and 1 MPa of pressure, and a pressing time of 1 min / mm was adopted. After hot-pressing, plywood was conditioned at room temperature for three days. The test specimens were trimmed to standard dimensions to determine the shear strength and bending properties of the bond. Figure 3 shows the bond shear strength of plywood in dry, wet and boiling treatment the values of were 1.97 N / mm2, 1.92 N / mm2and 1.54 N / mm2respectively. Further, the plywood showed the bending strength (MOR) of 115 ± 10 MPa and modulus of elasticity (MOE) of 13.4 ± 0.35 GPa.Laminated Veneer Lumber (LVL)About 150 g / m2of Bioglue formulation 2 was applied on the 3 mm thick veneers to prepare the three-layer laminated veneer lumber. After bioglue application, veneers were layered with the fiber directions parallel to each other and hot-pressed at 180 °C and 1 MPa of pressure, and a pressing time of 1 min / mm was adopted. After hot-pressing laminated veneer lumber was conditioned at room temperature for three days. Figure 4, shows the bond shear strength of LVL in dry, wet and boiling treatment the values of were 5.62 N / mm2, 2.62 N / mm2and 2.92 N / mm2respectively.EXAMPLE 12: Plywood bonding quality testing bonded with Bioglue formulation 7.About 150 g / m2 of Bioglue formulation 7 was applied on the veneers to prepare the three layers of plywood. After bioglue application, veneers were layered with the fiber directions crosswise to each other and hot-pressed at 180 °C and 1 MPa of pressure, and 1 min / mm pressing time was adopted. After hot-pressing, plywood was conditioned at room temperature for three days. The test specimens were trimmed to standard dimensions to determine the shear strength and bending properties of the bond. Figure 5 shows the bond shear strength of plywood in dry, wet and boiling treatment the values of were 2.54 N / mm2, 1.92 N / mm2and 1.32 N / mm2respectively. Further, the plywood showed the bending strength (MOR) of 126 ± 10 MPa and modulus of elasticity (MOE) of 10 ± 0.35 GPa, see Figure 5.EXAMPLE 13: UV protection of wood with Bioglue formulation 2 coating in artificial weathering of wood specimens.Pine wood specimens (100 mm* 100mm) were coated (1 layer only) manually by brush with Bioglue formulation 2 and after coating the specimens were cured at 105 °C for 12 hours. The coated specimens and controls were aged in artificial xenon light irradiation according to ISO 16474-2:2013. A xenon light exposure of 60 W / m2using a daylight filter in the 300 nm to 400 nm range, at 65 °C (black panel) and 50% relative humidity in a commercial chamber (ATLAS Xenotest 440) was used. The test was interrupted every 168 hours (=1 week) for color measurements. The surface color of wood specimens for different periods was measured by a spectrophotometer (Konica Minolta CM-2600d). Spectral data between 360 and 740 nm visible wavelength range were converted toCIEL*a*b* color coordinates using 2° standard observer and D65 light source. The results are shown in Figure 6.EXAMPLE 14: LCCs extraction from softwood (Spruce saw dust).Spruce sawdust was extracted with a pressurized hot water flow-through system (Kilpelainen et al., 2014) to obtain lignin rich carbohydrates. After collection, sawdust was stored at -20 °C before extraction. A sample of 99.0 kg of fresh sawdust (45.9 kg of dry mass) was added into a 300 L reactor. After addition, sawdust was first pre-steamed for 26 min with 1.9 kg of 172 °C steam. Sawdust was then extracted at 170 °C with 20 L / min continuous flow for whole 60 min extraction time. The pressure during the extraction was 13.5 bar. The extract (1017 kg) was collected into an intermediate bulk container (IBC) and the pH of the extract was 3.6. Extract’s total dissolved solids (TDS) was 1.15% (w / w), indicating 25.5% (w / w) of sawdust was extracted.EXAMPLE 15: Wood impregnation and durability against wood decaying fungi.Biobased adhesives comprising LCCs (formulation 2) or liquefied wood (LBM) (formulation 7) were vacuum-pressure impregnated into the pine sapwood and cured at 160 °C for 2 h and 105 °C for 24 h. The total weight percentage gain (WPG) was ~50%. The in-vitro experiment described below follows to some extent the procedure described in standard EN 113. Specimens belonged to three groups: LCCs bioadhesive (formulation 2), LBM bioadhesive (formulation 7) & pure sapwood. There were 50 specimens / treatment, total number of 150 specimens + 12 extra specimens from pure sapwood. Decay test was performed in petri dishes having malt agar as culture medium, in each petri dish 1 random piece from each treatment will be exposed to fungal attack = 3 specimens / petri dish. Coniophora puteana (strain BAM Ebw. 15) fungi was used as main wood decaying fungi.Table 2: Weight loss of pine sapwood and bio-adhesive impregnated pine sap wood against the wood-decaying fungi Coniophora puteana as per standard EN 113.ML%=100 x ((Dry mass before decay)-(Dry mass after decay)) / (Dry mass before decay)MC%=100 x ((Wet mass after decay)-(Dry mass after decay)) / (Dry mass after decay)The average weight percentage gained by pine sapwood was -50% after pressure impregnation and curing of bio-adhesive. After 16 weeks of exposure to wood-decaying fungi, the mass loss of untreated pine sapwood was over 31% of dry biomass as shown in Table 2. The impregnated pine sapwood showed around 11.6% mass loss and 16.9% mass loss respectively for LCCs and LBM bio-adhesive. As mentioned earlier, weight percentage gain due treatment was -50%, so majority of weight loss from treated pine sapwood was due to leaching of bio-adhesives. Dry mass biomass (cellulose, hemicellulose, or lignin) degradation was not observed during this decaying test.EXAMPLE 16: Testing process according to ISO-5660 standard: (Reaction-to-fire tests — Heat release, smoke production and mass loss rate)Materials: Three-layer-Birch wood plywood bonded with LCCs (formulation 2) and LBM bio-adhesives (formulation 7) and coated with LCCs bio-adhesive.Sample size: 100mm * 4.5 mm * 100 mmHeat flux: 50 kW / m2Test duration: 600 secondsSample orientation during testing: HorizontalResults are shown in Table 3 and Eigures 9 and 10.Table 3: Reaction-to-fire and different parameters of plywood samples bonded and coated with bio-adhesivesEXAMPLE 17: Total volatile organic compound (TVOC) and formaldehyde emission Spruce laminated veneer lumber (LVL) was prepared via hot pressing bonded with LCCs (formulation 2) and LBM (formulation 7) bio-adhesives and samples were immediately wrapped into plastic and aluminum foils for volatile emission evaluations. The chamber technique used is based on standards ISO 16000-9:2006 and SFS-EN 16516:2017 and the air samples taken from the chamber have been analysed using accredited analysis methods. The emission testing has been carried out after ageing period of 28±2 days. Table 5 and Table 6 disclose the experimental details.Table 4 - Experimental conditions in chemical measurementsTable 5: Methods used in emission sampling and analyses.Table 6: The model room concentration is calculated using the European model room of 30 m3in which the area of the tested product is 31.4 m2. If the concentration is below the limit of quantification, the test result is documented as the limit of quantification with the symbol smaller than (<).b- sample bonded with LCCs bio-adhesive (formulation 7) SER_ specific emission rate LCI values (Lowest Concentration of Interest)Both LCCs (formulation 2) and LBM (formulation 7) bio-adhesives fulfilled the toughest VOCs emission classification as well as carcinogenic compounds emission as disclosed in Table 6. The TVOC according to EN16516 is < 1000 pg / m3and our bioadhesives LCCs and LBM having 220 and 320 pg / m3, respectively. Formaldehyde emission values (El classification (EN 13986)-124 pg / m3) bio-adhesives having 16 pg / m3 (LCCs) and 26 (LBM) pg / m3. The values of Care. 1A and Care. IB are below desired < 1 [pg / m3].CITATIONS1. Kilpelainen, P.O., Hautala, S.S., Byman, O.O. , Tanner, L.J., Korpinen, R.I., Lillandt, M.K., Pranovich, A.V., Kitunen, V.H., Willfor, S.M. and Ilvesniemi, H.S., 2014. Pressurized hot water flow-through extraction system scale up from the laboratory to the pilot scale. Green Chemistry, 76(6), pp.3186-3194.2. Zhao, Y. et al., 2020, Lignin-carbohydrate complexes (LCCs) and its role in biorefinery, Journal of Cleaner Production 253:120076.Table 7: Detailed discerptions of LCCs chemical compositionsAbbreviations: Man, mannose; Glc, glucose; Gal, galactose; Xyl, Xylose; Ara, arabinose; Rha, rhamnose; GlcA, glucuronic acid; GalA, galacturonic acid

Claims

CLAIMS1. A method for the production of an adhesive, said method comprising the following steps: a) providing lignin rich carbohydrate complexes (LCC) by pressurized hot water extraction of softwood biomass, preferably biomass of Norway spruce or Scots pine, or of hardwood biomass, preferably biomass of Birch or Beech, providing bark lignin rich carbohydrate complexes (BLCC) by pressurized hot water extraction of softwood bark, preferably bark of Norway spruce or Scots pine, or providing liquefied biomass by acid-catalyzed liquefaction of biomass including wood saw dust, agricultural residues, plant stalks, recycle carton boards, recycle paper, recycle wood, wood panels, and wood bark side streams, in polyhydric alcohols and phenols; b) reacting the LCCs, BLCCs, or liquefied biomass obtained in step a) with a crosslinking or catalytic agent selected from the group consisting of: carboxylic agents including citric acid, dicarboxylic acids including adipic acid, organic acid anhydrides, tannin, tannic acid, plant derived fatty acids including suberin, and hexamethylenediamine, in order to produce said adhesive.

2. The method according to claim 1, wherein said crosslinking agent is citric acid.

3. The method according to claim 1 or 2, comprising a further step of contacting the adhesive obtained in step b) from said LCCs or said liquefied biomass with bark lignin rich carbohydrate complexes (BLCC) provided by pressurized hot water extraction of softwood bark biomass, preferably bark biomass of Norway spruce or Scots pine, wherein the BLCCs obtained from softwood bark biomass are preferably added to said adhesive so that the mixture contains 1 to 30% (w / w) of said BLCCs obtained from softwood bark biomass.

4. The method according to any of claims 1-3, wherein said bark lignin rich carbohydrate complexes (BLCC) are provided by a two stage pressurized hot water extraction of softwood bark, preferably bark of Norway spruce or Scots pine, the extraction comprising the steps of: i) providing bark from side-streams generated by wood processing industry including saw milling, plywood, pulp and paper industries;ii) mixing the bark material obtained in step i) into a water solution and subjecting the mix to a temperature in the range of 80-100 °C in order to separate and remove polyphenols including tannins from the bark material. iii) increasing the temperature of the bark material in a water solution to a temperature in the range of 150-200 °C in order to separate hemicellulose and lignin rich carbohydrate complexes from the bark material; and iv) isolating lignin rich carbohydrate complexes from the water solution obtained in step iii).

5. The method according to any of claims 1-4, comprising a further step of mixing the adhesive obtained from LCCs of softwood biomass and the adhesive obtained from LCCs of hardwood biomass, preferably in ratios 50:50, 50:40, 50:30, 50:20, and 50:10 with optional further addition of BLCCs from softwood bark biomass.

6. The method according to any of claims 1-4, comprising a further step of mixing the adhesive obtained from LCCs of softwood biomass and the adhesive obtained from LCCs of hardwood biomass, preferably in ratios 50:50, 50:40, 50:30, 50:20, and 50:10 with further addition of sucrose, xylitol, fructose, or starch.

7. The method according to any of claims 1-4, comprising a further step of mixing the adhesive obtained from LCCs of softwood biomass and / or the adhesive obtained from LCCs of hardwood biomass with a nanoproduct selected from the group consisting of cellulose nanofibers (CNF), bacterial cellulose nanofibers, and crystalline nanocelluloses.

8. The method according to claim 1 or 2, comprising a further step of mixing the adhesive obtained from acid-catalyzed liquefaction of biomass with Kraft lignin so that the amount of Kraft lignin is 1% to 10% (w / w) of the resulting adhesive.

9. The method according to any of claims 1-8, comprising a further step of mixing the adhesive obtained from step b) with an adhesive containing urea formaldehyde (UF), phenol formaldehyde (PF) and / or melamine urea formaldehyde (MUF) so that the prepared adhesive comprises 5% to 90% of the adhesive obtained from step b).

10. An adhesive produced by the method according to any of claims 1-9.

11. The adhesive according to claim 10, comprising cross-linked LCCs or BLCCs.

12. The adhesive according to claim 10 or 11, comprising a cross-linked blend of LCCs and BLCCs.

13. Use of the adhesive according to any of claims 10-12 as a bonding agent in wood products or as a coating agent in wood products or mineral wool.

14. The use according claim 13, wherein said adhesive is used as a bonding agent in the production of plywood or MDF / HDF boards.

15. The use according claim 13, wherein said adhesive is used as a coating agent for wood products to provide improved UV protection.

16. Use of the adhesive according to claim 10 in impregnation of wood products with said adhesive in order to improve the flame retardant properties, the resistance to rot, fungus, mold and insects of the wooden material, and / or to lower the total gaseous emissions of the wooden material.

17. A foam comprising the adhesive according to any of claims 10-12.

18. The foam according to claim 17, wherein said foam is a fire retardant foam.

19. A pressurized hot water extraction method for extracting hemicellulose and lignin rich carbohydrate complexes (LCC) from bark material including bark of Norway spruce or Scots pine, the method comprising the steps of: a) providing bark from side-streams generated by wood processing industry including saw milling, plywood, pulp and paper industries; b) mixing the bark material obtained in step a) into a water solution and subjecting the mix to a temperature in the range of 80-100 °C in order to separate and remove polyphenols including tannins from the bark material; c) increasing the temperature of the bark material in a water solution to a temperature in the range of 150-200 °C in order to separate hemicellulose and lignin rich carbohydrate complexes from the bark material; and d) isolating at least lignin rich carbohydrate complexes from the water solution obtained in step c).

20. The method according to claim 19, wherein the temperature in step b) is about 90 °C and the temperature in step c) is about 170 °C.

Images