FIELD OF THE INVENTION

The present disclosure relates to a bio-based composite material and to a method for producing a biobased composite material . Further, the present disclosure relates to a bio-based composite and to a method for producing the bio-based composite .

BACKGROUND OF THE INVENTION

A bio-composite is a composite formed by a matrix ( resin) and a reinforcement of natural fibers . Environmental aspects and cost of synthetic fibers has promoted the research toward using natural fibers as reinforcement in polymeric composites . The matrix phase may be formed by polymers derived from renewable and nonrenewable resources . In addition to holding the fibers together, the matrix provides the fibers protection against environmental degradation and mechanical damage . Further development of bio-composites is requested for many industrial applications .

SUMMARY

A bio-based composite material is disclosed . The bio-based composite comprises sawdust and a resin matrix based on lignin and tannin, wherein the bio-based composite material comprises sawdust in a total amount of 25 - 90 weight-% based on the total weight of the bio-based composite material .

Further is disclosed a method for producing a bio-based composite material . The method comprises :

- providing a resin matrix, wherein the resin matrix is formed by polymeri zing lignin and tannin with a crosslinking agent, and has a viscosity value of 50 - 1000 mPa • s ; - providing sawdust having a dry matter content of 50 - 100 % ;

- spraying the resin matrix on the sawdust with simultaneous mixing to combine the resin matrix with the sawdust , to form the bio-based composite material , wherein the composite material comprises sawdust in a total amount of 25 - 90 weight-% based on the total weight of the composite material .

Further is disclosed a bio-based composite made by compounding the bio-based composite material as disclosed in the current specification .

Further is disclosed a method for producing a bio-based composite . The method comprises :

- compounding the bio-based composite material as disclosed in the current specification by subj ecting the bio-based composite material to moulding while keeping the temperature of the bio-based composite material at 80 - 200 °C .

DETAILED DESCRIPTION

A bio-based composite material is disclosed . The bio-based composite material comprises sawdust and a resin matrix, based on lignin and tannin, wherein the bio-based composite material comprises sawdust in a total amount of 25 - 90 weight-% based on the total weight of the bio-based composite material .

The bio-based composite material may comprise in addition to sawdust and the resin matrix, water and/or inorganic salt .

In one embodiment, the bio-based composite material consists of sawdust and the resin matrix . In one embodiment , the bio-based composite material consists of sawdust , the resin matrix, and water . In one embodiment , the bio-based composite material consists of sawdust , the resin matrix, and inorganic salt . In one embodiment , the bio-based composite material consists of sawdust, the resin matrix, inorganic salt, and optionally water. In one embodiment, the bio-based composite material consists of sawdust, the resin matrix, inorganic salt, and water.

In one embodiment, the bio-based composite material is formed of the resin matrix that has been sprayed on sawdust with simultaneous mixing to combine the resin matrix with the sawdust.

In one embodiment, the resin matrix is formed by polymerizing lignin and tannin with a crosslinking agent .

In one embodiment, no compound selected from the class of phenols is used for forming the resin matrix. In this specification, unless otherwise stated, the term "compound selected from the class of phenols" should be understood as meaning a fossil-based compound of phenols. I.e. phenols are compounds consisting of a single aromatic ring where to one or more hydroxyls (— OH) are bonded. Such a compound selected from the class of phenols may be e.g. phenol, cresol, or resorcinol.

The inventors surprisingly found out that a fully bio-based resin matrix can be used together with sawdust to produce a bio-based composite material. When using a resin matrix prepared with using both lignin and tannin, which are biopolymers, one is able to provide a resin matrix that may be efficiently mixed with sawdust to provide a bio-based composite material from which a "liquid wood" like composite may be formed. The biobased composite material has the added utility of curing in the presence of heat without having to use any additional hardener or curing agent.

The sawdust may have an average particle size of 0.001 - 1 mm, or 0.01 - 0.8 mm, or 0.05 - 0.6 mm, or 0.1 - 0.4 mm, or 0.15 - 0.2 mm. The average particle size of the sawdust may be determined by a vibrating sieving method in which different mesh sizes are used (5 sieves, between 1.4 mm - 100 pm mesh size) . After vibrating, particles of different size may stay on the sieve, through which they are too large to pass.

The bio-based composite material may comprise sawdust in a total amount of 30 - 88, or 40 - 86 weight- % , or 50 - 84 weight-%, or 60 - 82 weight-%, or 65 - 80 weight-%, or 70 - 78 weight-%, based on the total weight of the bio-based composite material. The bio-based composite material may comprise resin matrix in a total amount of 10 - 75 weight-%, or 12 - 70 weight-%, or 14 - 60 weight-%, or 16 - 50 weight-%, or 18 - 40 weight- % , or 20 - 35 weight-%, or 22 - 30 weight-%, based on the total weight of the bio-based composite material.

Further is disclosed a method for producing a bio-based composite material. The method comprises:

- providing a resin matrix, wherein the resin matrix is formed by polymerizing lignin and tannin with a crosslinking agent to form a resin matrix with a viscosity value of 50 - 1000 mPa-s;

- providing sawdust having a dry matter content of 50 - 100 %;

- spraying the resin matrix on the sawdust with simultaneous mixing to combine the resin matrix with the sawdust, to form the bio-based composite material, wherein the composite material comprises sawdust in a total amount of 25 - 90 weight-% based on the total weight of the composite material.

The crosslinking agent may be an aldehyde, such as formaldehyde or paraformaldehyde. In one embodiment, the aldehyde is prepared from bio-methanol. The aldehyde may thus be of biobased origin. The aldehyde may alternatively be of fossil origin. I.e. produced from a fossil material. In one embodiment, the aldehyde is prepared from methanol.

The method comprises providing sawdust with a dry matter content of 50 - 100 % . In one embodiment, the dry matter content of the provided sawdust is 55 - 95 % , or 60 - 92 %, 70 - 90 %, or 80 - 85 %. The dry matter content may be determined after removing the liquid from a sample followed by drying 1 g of the sample at a temperature of 105 °C for 3 hours. The effectiveness of the drying may be assured by weighing the sample, drying for a further two hours at the specified temperature, and reweighing the sample. If the measured weights are the same, the drying has been complete, and the total weight may be recorded.

The "total weight" should in this specification be understood, unless otherwise stated, as the weight of both the dry matter and the liquid part, e.g. water.

The molar ratio of crosslinking agent to lignin and tannin may be 0.9 - 1.7, or 1.0 - 1.6, or 1.1 - 1.7, or 1.2 - 1.6. In the current specification, the molar ratio (MR) is calculated as follows:

MR = n (Fa) / (n (T) +n (L) ) wherein n = the amount of substance in moles

Fa = crosslinking agent

T = tannin

L = lignin

The amount of substance in moles are calculated as follows : n = M/m wherein

M = the molar mass of substance in g/mol m = the mass of substance in grams

The following values are used for the above calculations in this specification: M(tannin) = 320 g/mol (estimate based on literature and assumed chemical structure)

M(lignin) = 180 g/mol (estimate based on literature and assumed chemical structure)

The weight ratio of tannin to lignin may be 0.05 - 1.0, or 0.1 - 0.43, or 0.15 - 0.33.

In the context of this specification, the term "lignin" may refer to lignin originating from any suitable lignin source. In one embodiment, the lignin is essentially pure lignin. By the expression "essentially pure lignin" should be understood as at least 70 % pure lignin, or at least 90 % pure lignin, or at least 95 % pure lignin, or at least 98 % pure lignin. The essentially pure lignin may comprise at most 30 % , or at most 10 % , or at most 5 % , or at most 2 % , of other components and/or impurities. Extractives and carbohydrates such as hemicelluloses can be mentioned as examples of such other components.

Further, in the context of this specification, the term "tannin" may refer to tannin originating from any suitable tannin source. In one embodiment, the tannin is essentially pure tannin. By the expression "essentially pure tannin" should be understood as at least 70 % pure tannin, or at least 90 % pure tannin, or at least 95 % pure tannin, or at least 98 % pure tannin. The essentially pure tannin may comprise at most 30 % , or at most 10 % , or at most 5 % , or at most 2 % , of other components and/or impurities.

The lignin may contain less than 30 weight-%, or less than 10 weight-%, or less than 5 weight-%, or less than 3 weight-%, or less than 2.5 weight-%, or less than 2 weight-% of carbohydrates. The tannin may contain less than 20 weight-%, or less than 15 weight-%, or less than 10 weight-% of carbohydrates. The amount of carbohydrates present in lignin or tannin can be measured by high performance anion exchange chromatography with pulsed amperometric detector (HPAE- PAD) in accordance with standard SCAN-CM 71.

The ash percentage of lignin may be less than 7.5 weight-%, or less than 5 weight-%, or less than 3 weight-%, or less than 1.5 weight-%. The ash percentage of tannin may be less than 10 weight-%, or less than 5 weight-%, or less than 3 weight-%. The ash content can be determined in the following manner: Dry solid content of the sample is determined first in an oven at 105°C for 3h. Ceramic crucibles are pre-heated to 700 °C for 1 hour and weight after cooling. A sample (1.5 g - 2.5 g) is weighted into a ceramic crucible. The crucible with a lip is put into a cold oven. Temperature of the oven is raised: 20-200 °C, 30 min => 200-600 °C, 60 min => 600-700 °C, 60 min. Burning is continued without the lid at 700 °C for 60 min. The crucible is let to cool in desiccator and few drops of hydrogen peroxide (H2O2, 30 %) is added to the sample followed by burning in the oven at 700 °C for 30 minutes. If there are still dark spots in the ash, the hydrogen peroxide treatment and burning is repeated. The crucible is cooled down and weighted. All weigh-in is done with a precision of 0.1 mg and after cooling in a desiccator.

Calculation of the results

Ash content % = (100 a x 100) / (b x c) wherein a = weight of the ash, g b = weight of the sample, g c = dry solids of the sample, %

Ash content of a sample refers to the mass that remains of the sample after burning and annealing, and it is presented as percentage of the sample's dry content. In one embodiment , the lignin is technical lignin . In the context of thi s speci fication, the term "technical lignin" may refer to lignin that i s derived from lignin in any biomass by any technical process . In one embodiment , technical lignin is lignin received from an industrial process .

The lignin used for preparing the resin matrix may be selected from a group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitated lignin, biomass originating lignin, lignin from alkaline pulping process , lignin from soda process , lignin from organosolv pulping, lignin from alkali process , lignin from enzymatic hydrolysis process , and any combination thereof . In one embodiment , the lignin is wood based lignin . The lignin can originate from softwood, hardwood, annual plants or from any combination thereof .

By " kraft lignin" is to be understood in this specification, unless otherwise stated, lignin that originates from kraft black liquor . Black l iquor is an alkaline aqueous solution of lignin residues , hemicellulose , and inorganic chemicals used in a kraft pulping process . The black liquor from the pulping process comprises components originating from different softwood and hardwood species in various proportions . Lignin can be separated from the black liquor by di fferent , techniques including e . g. precipitation and filtration . Lignin usual ly begins precipitating at pH values below 11 - 12 . Different pH values can be used in order to precipitate lignin fractions with different properties . These lignin fractions differ from each other by molecular weight distribution, e . g. Mw and Mn, polydispersity, hemicellulose and extractive contents . The molar mass of lignin precipitated at a higher pH value is higher than the molar mass of lignin precipitated at a lower pH value . Further, the molecular weight distribution of lignin fraction precipitated at a lower pH value is wider than of lignin fraction precipitated at a higher pH value . The precipitated lignin can be purified from inorganic impurities , hemicellulose and wood extractives using acidic washing steps . Further purification can be achieved by filtration .

The term "flash precipitated lignin" should be understood in this specification as lignin that has been precipitated from black liquor in a continuous process by decreasing the pH of a black liquor flow, under the influence of an over pressure of 200 - 1000 kPa, down to the precipitation level of lignin using a carbon dioxide based acidifying agent , preferably carbon dioxide, and by suddenly releasing the pressure for precipitating lignin . The method for producing flash precipitated lignin is disclosed in patent application FI 20106073 . The residence time in the above method is under 300 s . The flash precipitated lignin particles , having a particle diameter of les s than 2 pm, form agglomerates , which can be separated from black liquor using e . g. filtration . The advantage of the flash precipitated lignin is its higher reactivity compared to normal kraft lignin . The flash precipitated lignin can be purif ied and/or activated if needed for the further processing .

The lignin may be derived from an alkali process . The alkali process can begin with liquidi zing biomass with strong alkali followed by a neutrali zation proces s . After the al kal i treatment , the l ignin can be precipitated in a similar manner as presented above .

The lignin may be derived from steam explosion . Steam explosion is a pulping and extraction technique that can be applied to wood and other fibrous organic material .

By "biorefinery lignin" is to be understood in this specification, unless otherwise stated, lignin that can be recovered from a refining facility or process where biomass is converted into fuel, chemicals and other materials.

By "supercritical separation lignin" is to be understood in this specification, unless otherwise stated, lignin that can be recovered from biomass using supercritical fluid separation or extraction technique. Supercritical conditions correspond to the temperature and pressure above the critical point for a given substance. In supercritical conditions, distinct liquid and gas phases do not exist. Supercritical water or liquid extraction is a method of decomposing and converting biomass into cellulosic sugar by employing water or liquid under supercritical conditions. The water or liquid, acting as a solvent, extracts sugars from cellulose plant matter and lignin remains as a solid particle.

The lignin may be derived from a hydrolysis process. The lignin derived from the hydrolysis process can be recovered from paper-pulp or wood-chemical processes.

The lignin may originate from an organosolv process. Organosolv is a pulping technique that uses an organic solvent to solubilize lignin and hemicellulose.

In one embodiment, the lignin consists of softwood Kraft lignin. In one embodiment, the lignin is softwood Kraft lignin. In one embodiment, the lignin is a combination of softwood lignin and hardwood lignin. In one embodiment, at most 30 weight-%, or at most 25 weight-%, or at most 10 weight-%, or at most 5 weight % of the lignin originates from hardwood.

The weight average molecular weight of the softwood Kraft lignin may be 2500 - 9000 Da, or 3000 - 8000 Da, or 3500 - 7000 Da. The lignin, e.g. the Kraft lignin, may have a polydispersity index of 2.9 - 6.0, or 3.0 - 5.0, or 3.2 - 4.5.

The weight average molecular weight may be determined by using gel permeation chromatography (GPC) equipped with UV detector (280nm) in the following manner: A sample is dissolved into 0.1 M NaOH. The sample solution is filtered with 0.45 micron PTFE filter. The measurement is performed in 0.1 M NaOH eluent (0.5 ml/min, T = 30 °C) using PSS MCX precolumn, 1000 A and 100 000 A columns, with sulfonated styrene-divinylben- zene copolymer matrix. The molecular weight distribution of the sample is calculated in relation to Na-polysty- rene sulfonate standards (6 pieces) Mw 891 - 65400. Values Mw (weight average molecular weight) and Mn (number average molecular weight) , polydispersity index (PDI, Mw/Mn) are reported based on two parallel measurements .

The amount of alkali insoluble matter of the softwood Kraft lignin may be below 10 % , or below 5 % , or below 0.5 % . The amount of alkali insoluble matter may be determined in the following manner: Dry solid content of the sample is determined first in an oven at 105°C for 3h. 100 g of sample is dissolved into 277 g NaOH-water solution (pH 12 - 13) at mixed at 50 - 60 °C for 30 min. Solution is filtrated with a Buchner funnel through a glass filter. The residue on the filter is washed with 0. IM NaOH and finally with water. The filter with the residue is dried in an oven and then weighted. The amount of alkali insoluble matter is then calculated as follows:

Alkali insoluble matter, % = [weight of the filter with residue (dryed) (g) - weight of the filter] / [weight of the sample (g) * dry solid content of the samples (%) ]

The amount of condensed and syringul groups of softwood Kraft lignin may be below 3.0 mmol/g, or below 2.5 mmol/g, or below 2.0 mmol/g when determined with 31P NMR. The amount of aliphatic OH groups of softwood Kraft lignin may be below 3,0 mmol/g, or below 2.5 mmol/g when determined with 31P NMR. The amount of Guaiacyl OH of softwood Kraft lignin may be at least 1.5 mmol/g when determined with 31P NMR.

The measurements conducted with 31P NMR spectroscopy after phosphitylation can be used for quantitative determination of functional groups (aliphatic and phenolic hydroxyl groups, and carboxylic acid groups) . Sample preparation and measurement are performed according to method by Granata and Argyropoulos (Granata, A., Argyropoulos, D., J. Agric. Food Chem. 1995, 43:1538-1544) . Accurately weighted sample (~25 mg) is dissolved in N, N-dimethylf ormamide, and mixed with pyridine and internal standard solution (ISTD) endo-N-Hy- droxy-5-norbornene-2 , 3-dicarboximide (e-HNDI) . Phosphitylation reagent (200 pl) 2-chloro-4, 4, 5, 5-tetrame- thyl-1, 3, 2-dioxaphopholane is added slowly, and finally a 300 pl CDCI3 is added. NMR measurements are performed immediately after addition of the reagent. Spectra are measured with spectrometer, equipped with a broadband detection optimized probehead.

In one embodiment, the tannin used originates from any wood species. Tannin may originate from e.g. bark or heartwood. Quebracho tree, beech tree, oak tree, chestnut, pine, spruce, and acacia tree species are presented as examples of possible sources of tannin.

In one embodiment, the tannin used originates from softwood bark. The tannin may be separated from softwood bark of debarking units in sawmills or pulp mills. The separation process can be combined with an ethanol extraction process, a hot water extraction process, a hot steam extraction process or a water-ethanol extraction process of softwood bark.

In one embodiment, the tannin is condensed tannin. Condensed tannin has a high dry content and is therefore suitable to be used in the method as disclosed in the current specification. The dry matter content of condensed tannin may vary between 40 - 100 % and is suitably between 60 - 90 % or between 70 - 80 % . Tannin with such dry matter content can easily be dispersed, whereby a good reactivity with the other reactant components is achieved. The tannin may also be hydrolysable tannin .

The tannin may have a weight average molecular weight (Mw) of 1500 - 5000 Da, or 2000 - 4500 Da, or 2500 - 4000 Da. The tannin may have a polydispersity index of 2.8 -• 1.0, or 2.6 - 1.3, or 2.4 -• 1.5.

In one embodiment, hexamine is used in preparing the resin matrix. In one embodiment, the resin matrix comprises hexamine. The use of hexamine when preparing the resin matrix has the added utility of providing a stronger structure as the hexamine may be considered to act as a curing agent.

In one embodiment, the resin matrix has a viscosity value of 50 - 1000 mPa -s, or 50 - 250 mPa -s, or 250 - 600 mPa-s. The viscosity can be measured at a temperature of 25 °C by using a rotary viscometer (Digital Brookfield viscometer LVDV-II+ Pro; cone spindle) . The inventors surprisingly found out that when the resin matrix has the above viscosity value, e.g. 50 - 250 mPa -s, one is able to mix it evenly with the sawdust by spraying .

Providing the sawdust may comprise mixing sawdust with water. Providing the sawdust may comprise mixing sawdust with water in an amount of 5 - 20 weight- % , or 6 - 10 weight-%, based on the total weight of the provided sawdust.

Providing the sawdust may comprise mixing sawdust with an inorganic salt solution, in an amount of 5 - 20 weight-%, or 6 - 10 weight-%, based on the total weight of the provided sawdust. Chlorides, phosphates, and nitrates may be mentioned as examples of salt types that may be used. Sodium sulfate (Na2SO4) may be mentioned as one specific example only. Mixing the sawdust with a solution of inorganic salt may reduce electricity of the sawdust whereby the bio-based composite material is easier to handle, and the following compounding can be carried out efficiently. The concentration of the inorganic salt solution may be 1 - 10 weight-%, or 2 - 8 weight-%, or 3 - 6 weight-%.

In one embodiment, the water or the inorganic salt solution is mixed with the sawdust prior to spraying the resin matrix on the sawdust. In one embodiment, the water is mixed with the sawdust prior to spraying the resin matrix on the sawdust. In one embodiment, the inorganic salt solution is mixed with the sawdust prior to spraying the resin matrix on the sawdust.

The inventors surprisingly found out that the viscosity of the resin matrix together with the fact that the resin matrix is sprayed on the sawdust, instead of e.g. being simply blended together, enabled the production of a bio-based composite material that in addition to being formed of bio-based materials may be cured into a bio-based composite by subjecting the same to heating without having to use additional curing agent.

Spraying of the resin matrix on the sawdust is carried out while simultaneous mixing. I.e. mixing of the combination of the sawdust and the resin matrix is carried out at the same time as the resin matrix is sprayed. In one embodiment, the mixing comprises high shear mixing. The mixing, such as high shear mixing, can be carried out at a rotation speed of 360 - 1000 rpm, or 450 - 900 rpm, or 650 - 800 rpm. The high shear mixing may be carried out with e.g. a (conical) mixing vessel with central paddle rotor equipped with impact blades at the top. An example of a high shear mixer is the one under the name Cyclomix™.

The spraying of the resin matrix may be carried out through e.g. a nozzle in order to decompose the resin matrix into droplets that are evenly sprayed or distributed on or over the sawdust. The spraying may be conducted at a pressure of 0.1 - 5 MPa, or 0.5 - 4 MPa, or 1 - 3 MPa, or 1.5 - 2.5 MPa.

In one embodiment, the formed bio-based composite material is a powder-like material. The bio-based composite material being a powder-like material may be taken to resemble kinetic sand or magic sand. Thus, the bio-based composite material is not in liquid form nor like a dough but a powder-like or sand-like material.

The bio-based composite material has the added utility of having a good stock stability, i.e. it keeps its powder-like physical form when being restored in room temperature conditions.

Thus, further is disclosed a bio-based composite made by compounding the bio-based composite material as disclosed in the current specification.

Compounding is taken in this specification, unless otherwise stated, to describe the process of forming the bio-based composite material into a biobased composite of a desired shape.

In one embodiment, the visual appearance of the bio-based composite is liquid wood-like. Liquid wood is a bioplastic composed of natural components: lignin, cellulose fibers and some additives. As a thermoplastic, it can be molded and is therefore also called "liquid wood". I.e. liquid wood has a similar composition, appearance, and properties to those of wood, but it can be melted upon heating and molded like a thermoplastic.

The bio-based composite as disclosed in the current specification has the added utility of being a wood-like material when it comes to its visual appearance but having the mechanical properties similar to traditional thermoset materials or thermoplastics.

The maximum bending stress of the bio-based composite may be 12 - 20 MPa, or 13 - 19 MPa, or 14 - 18 MPa. The maximum bending stress may be determined according to standard ISO 178:2010 (span length 48 mm, testing speed 5 mm/min) .

The flexural modulus of the bio-based composite may be 1400 - 2400 MPa, or 1500 - 2300 MPa, or 1600 - 2200 MPa. The flexural modulus may be determined according to standard ISO 178:2010 (span length 48 mm, testing speed 5 mm/min) .

These mechanical properties of the bio-based composite show that the formed bio-based composite is mouldable, i.e. it may be compressed into a desired form.

Disclosed is also a method for producing a biobased composite. The method comprises:

- compounding the bio-based composite material as disclosed in the current specification by subjecting the bio-based composite material to moulding while keeping the temperature of the bio-based composite material at 80 - 200 °C.

In one embodiment, the bio-based composite material is compounded by subjecting the bio-based composite material to moulding while keeping the temperature of the bio-based composite material at 90 - 180 °C, or 100 - 170 °C, or 110 - 160 °C, or 120 - 150 °C, or 130 - 140 °C.

In one embodiment, the moulding is carried out by compression moulding, injection moulding, or extrusion.

In one embodiment, the moulding is carried out under a pressure of 1.2 - 140 MPa, 2 - 120 MPa, or 5 - 100 MPa, or 10 - 90 MPa, or 20 - 80 MPa, or 40 - 70 MPa, or 50 - 60 MPa.

In one embodiment, the moulding is carried out by compression moulding, under a pressure of 1.2 - 140 MPa, 2 - 120 MPa, or 5 - 100 MPa, or 10 - 90 MPa, or 20 - 80 MPa, or 40 - 70 MPa, or 50 - 60 MPa.

In one embodiment, the moulding is carried out by injection moulding under a pressure of 1.2 - 140 MPa, 2 - 120 MPa, or 5 - 100 MPa, or 10 - 90 MPa, or 20 - 80 MPa, or 40 - 70 MPa, or 50 - 60 MPa .

In one embodiment , the moulding is carried out by extrusion under a pressure of 1 . 2 - 140 MPa ( 12 - 1400 bar) , 2 - 120 MPa, or 5 - 100 MPa, or 10 - 90 MPa, or 20 - 80 MPa, or 40 - 70 MPa, or 50 - 60 MPa .

In one embodiment , the moulding is carried out for 0 . 5 - 60 minutes , or 1 - 45 minutes , or 5 - 30 minutes .

In one embodiment , no additional curing agent is used for compounding the bio-based composite material .

The bio-based composite material as disclosed in the current specification has the added utility of being formed of a high amount of sawdust . The bio-based composite material has the added utility of having the visual appearance of a wood-like material , while the mechanical properties for many applications are fulfilled .

The method as disclosed in the current specification has the added utility of providing a bio-based composite material that may be used to replace fossil based thermoset materials or thermoplastics . The biobased composite material and thus the bio-based composite may be produced of 100 % of biological components .

EXAMPLES

Reference will now be made in detail to the embodiments of the present disclosure .

The description below discloses some embodiments in such a detail that a person skilled in the art i s able to utili ze the method based on the disclosure . Not all steps of the embodiments are discussed in detail , as many of the steps will be obvious for the person skilled in the art based on this disclosure .

Example 1 - Producing a bio-based composite material Firstly a resin matrix was provided. The fol- lowing components and their amounts were used: water 100 % 27 kg

NaOH I 50 % 9 kg kraft lignin 68 % 31 kg

NaOH II 50 % 3 kg formaldehyde 40 % 15 kg

NaOH 111 50 % 2.7 kg tannin 40 % (in alkaline solution) 13 kg NaOH IV 50 % 1.4 kg

The percentages of the components (based on total weight and calculated based on the dry matter content) used in this example were the following:

NaOH about 8.0 % kraft lignin about 21 % tannin about 5.2 % formaldehyde about 6.0 %

The molar ratio of formaldehyde to lignin and tannin was 1.5.

Firstly, water and the NaOH I were mixed at room temperature and heating of the same was started. When the temperature reached 70 °C, lignin was added to the mixture and the mixing and the heating of the same were continued for 30 minutes while keeping the temperature at about 90 °C. Then the temperature of the mixture was allowed to cool to 60 °C, and formaldehyde was added.

Mixing and heating of the formed mixture was continued for 45 minutes at a temperature of about 72 °C. Then NaOH II was added, mixing and heating continued at a temperature of about 70 - 75 °C for 45 minutes. Then NaOH III was added and mixing and heating was continued for 1 hours 15 minutes at a temperature of about 87 - 89 °C. Then NaOH IV was added followed by adding the tannin and the mixing and heating of the same was continued at about 90 oC until the viscosity of the formed mixture reached about 170 - 180 mPa-s (as measured at 25 °C) . Then the mixture was cooled to 30 °C.

The formed resi matrix had the following meas- ured properties:

Solids, % 34.7 (3 hours at 105 °C) pH 13.2

Viscosity, mPa-s 250 (R Brookfield RV, 25 °C,

50 rpm)

Alkalinity, % 5.1

Free formaldehyde, % 0.12

Then sawdust was provided. 1.5 kg of sawdust (particle size of 125 pm) was mixed with 190 g of sodium sulfate (Na2SO4) solution (6 %) . The moisture content of the provided sawdust was 17 % .

1.35 kg of the sawdust above was moved into a cup of a high shear mixer. 0.15 kg of resin matrix was then sprayed to the cup by using a 1.2 mm spray nozzle with a pressure of 5 bar, while simultaneously mixing the sawdust in high shear mixer at 750 rpm. Mixing was continued until a homogenous mixture was achieved.

Example 2 - Producing a bio-based composite material

In this example a bio-based composite material was produced.

Firstly a resin matrix was provided. The following components and their amounts were used: water 100 % 27 kg

NaOH I 50 % 9 kg kraft lignin 68 % 31 kg

NaOH IT 50 % 3 kg formaldehyde 40 % 15 kg NaOH 111 50 % 2.7 kg tannin 40 % (in alkaline solution) 13 kg NaOH IV 50 % 1.4 kg

The percentages of the components (based on total weight and calculated based on the dry matter content) used in this example were the following:

NaOH about 8.0 % kraft lignin about 21 % tannin about 5.2 % formaldehyde about 6.0 %

The molar ratio of formaldehyde to lignin and tannin was 1.5.

Firstly, water and the NaOH I were mixed at room temperature and heating of the same was started. When the temperature reached 70 °C, lignin was added to the mixture and the mixing and the heating of the same were continued for 30 minutes while keeping the temperature at about 90 °C. Then the temperature of the mixture was allowed to cool to 60 °C, and formaldehyde was added.

Mixing and heating of the formed mixture was continued for 45 minutes at a temperature of about 72 °C. Then NaOH II was added, mixing and heating continued at a temperature of about 70 - 75 °C for 45 minutes. Then NaOH III was added and mixing and heating was continued for 1 hours 15 minutes at a temperature of about 87 - 89 °C. Then NaOH IV was added followed by adding the tannin and the mixing and heating of the same was continued at about 90 oC until the viscosity of the formed mixture reached about 170 - 180 mPa-s (as measured at 25 °C) . Then the mixture was cooled to 30 °C. Then 0.4 kg hexamine (100 %) was combined in the mixture.

The formed resin matrix had the following measured properties: Solids, % 34.8 (3 hours at 105 °C) pH 13.4

Viscosity, mPa -s 196 (R Brookfield RV, 25 °C, 50 rpm)

Alkalinity, % 5.7 Free formaldehyde, % 0.15

Then sawdust was provided. 1.5 kg of sawdust (particle size of 125 pm) was mixed with 190 g of sodium sulfate (Na2SO4) solution (6 %) . The moisture content of the provided sawdust was 17 % .

Five samples were prepared with different ratios of sawdust and resin matrix. Sawdust was placed into a cup of a high shear mixer. An amount of resin matrix was then sprayed to the cup by using a 1.2 mm spray nozzle with a pressure of 5 bar, while simultaneously mixing the sawdust in nigh shear mixer at 750 rpm. Mixing was continued until a homogenous mixture was achieved. In table 1 is shown the samples prepared:

Table 1. Prepared samples of bio-based composite mate- rials

Example 3 - Producing bio-based composite

In this example bio-based composites were produced by using samples 1, 4, and 5 prepared in example 2. Each of the samples were compounded by subjecting the same to compress ion moulding carried out in a temperature chamber at 120 °C and under a pressure of 3 . 9 MPa for 20 minutes . During this period of time the temperature of the samples reached 120 °C .

The preparade composites were tested as to their maximum bending stress and flexural modulus . The results are presented in table 2 .

Table 2 . The maximum bending stress and the flexural modulus of the prepared bio-based composites

From the above results one may see that the mechanical properties of the prepared bio-based composites fulfill the criteria requested in many applications where the prepared bio-based composites may be used .

It is obvious to a person skil led in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims .

The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A bio-based composite material , a bio-based composite , and a method, as disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items. The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts.