WO2025250015A1

WO2025250015A1 - A resin formulation on basis of a lignin based resin

Info

Publication number: WO2025250015A1
Application number: PCT/NL2025/050257
Authority: WO
Inventors: Luca Ferrari; Bernardo Joseph BRUIJNAERS; Kim Mechtilda Ferdinand HELWEGEN
Original assignee: Trespa International BV
Current assignee: Trespa International BV
Priority date: 2024-05-31
Filing date: 2025-05-30
Publication date: 2025-12-04
Anticipated expiration: 2026-11-30

Abstract

The present invention relates to a resin formulation on basis of a resin comprising lignin, phenol and formaldehyde. The present invention also relates to a method for the preparation of such a resin formulation on basis of a resin comprising lignin, phenol and formaldehyde. In addition, the present invention relates to a method for manufacturing a paper impregnated with a resin formulation, too. The furthermore, the present invention relates to a method for manufacturing a laminate and to the use of a laminate.

Description

Title: A resin formulation on basis of a lignin based resin.

Description:

The present invention relates to a resin formulation comprising a resin comprising lignin, phenol and formaldehyde and a non-lignin based resin. The present invention also relates to a method for the preparation of such resin formulation. In addition, the present invention relates to a method for manufacturing a paper impregnated with such resin formulation, too. Furthermore, the present invention relates to a method for manufacturing a laminate and to the use of such laminate.

Laminates are products that are comprised of multiple layers of semi-finished material (either impregnated papers or prepregs), that are then compressed and fused together. In general, laminate products typically contain about 55-80 wt. % wood derived material (e.g. fibres or paper) and about 20-45 wt. % thermosetting resin. The fusing of the compressed stack of layered semi-finished material, is brought about by the condensation (or polymerisation reaction) of the thermosetting resin; which is normally driven by the application of heat, and by such means taken to a desired degree of final curing. This can be achieved using discontinuous or continuous processing methods. A common discontinuous method is the use of a multi-daylight press wherein stacks of layered semi-finished material are placed within the daylights of the press and then subjected to a program of pressurised compression and applied heat, which result in a laminate product. An example of a continuous method is the use of a continuous press; wherein the semi-finished material is continually fed into the press from multiple feeds, the semi-finished material layers are then compressed and heated to form a laminate product. The product norm or standard EN438 has a general definition for laminates termed as HPL (high pressure laminate) or CPL (continuous pressure laminate or continuous pressed laminate), however in this document the definition of laminates as described is somewhat wider.

Decorative high-pressure laminates manufactured by the present applicant are known for both indoor and outdoor applications. Such laminates consist of layers of wood-based fibres (paper and/or wood) impregnated with thermosetting resins and surface layer(s) on one or both sides, having decorative colours or designs. A transparent topcoat can be added to the surface layer(s) and cured to enhance weather and light protecting properties. These components are bonded together with simultaneous application of heat and high specific pressure to obtain a homogeneous non-porous material with increased density and integral decorative surface. These laminates have been disclosed in, inter alia, US Patent No. 4,801 ,495 , US Patent No. 4,789,604, and US publication number 2013/0078437. In the manufacture of HPL panels, the package, comprising the core layers and surface layer or layers, and the paper layers possibly located between them as well, is thermopressed to make a decorative panel; the thermosetting resins are cured in this process. The temperature is in the range from 120 °C to 300 °C, the pressure is in the range from 10 to 100 bar, and the reaction time is from at least 0,2, or at least 1 to 75 minutes.

The environmental aspects and sustainability of phenolic resins are under discussion. Lignin is a natural polymer, which can be extracted from for example wood. As lignin is a natural biopolymer, its use as a component in resins instead of synthetic materials is a way to produce a more environmentally friendly resin composition. Lignin is an aromatic polymer and a major constituent in wood and has been extensively investigated as a suitable substitute for phenol during production of phenolformaldehyde resins. These are used during manufacturing of structural wood products such as plywood, oriented strand board and fibreboard.

Lignin based resins are well known in the art. Lignin-based resins are a type of resin derived from lignin, a complex organic polymer found in the cell walls of plants, particularly in wood. The process of manufacturing lignin-based resins typically involves modifying and processing lignin to improve its properties. A lignin based resin is to be understood as a resin having lignin in the resin formulation, e.g. lignin- formaldehyde resin (LF resin), lignin-phenol-formaldehyde resin (LPF), epoxy based lignin resins and polyurethane based lignin resins.

For example, European patent EP 3609948 in the name of the present applicant discloses a method for manufacturing a high pressure laminate comprising a step of preparing a stack of resin impregnated papers and a step of pressing the stack in a press using an elevated temperature and an elevated pressure, wherein in the step of preparing these resin impregnated papers a lignin-phenol formaldehyde resin is used that is prepared with lignin methylolation and phenol methylolation steps.

Activated lignin compositions are also described in International application WO 2016/157141 , International application WO 2013/144454, International application W02015079107, International application WO2016207493, and International application WO2017006215.

A binder mixture based on modified lignin is known from German Offenlegungsschrift DE 43 31 656. That document discloses a binder mixture containing 45% to 85% by weight of methylol-modified lignin, 5% to 25% by weight of resole and 10% to 30% by weight of a di- or polyisocyanate, wherein the methylol group-modified lignin and the resol are in aqueous solution, further containing 1 % to 15% by weight of ester, e.g. triacetin, as accelerator.

Adhesives based on lignin are known from US Patent No. 5,866,642, US Patent No. 4,113,675, International application WO2014/124541 , International application WO201 2/106808, and International application WO94/24192.

EP 4 001 376 relates to a method for making a multi-part resin system, comprising a step of forming a lignin-formaldehyde resin, forming a phenolformaldehyde resin and mixing the lignin-formaldehyde resin and the phenolformaldehyde resin to form the multi-part resin system, wherein the phenolformaldehyde resin is a resol type phenol-formaldehyde.

US3185654 relates to a method of producing a resin which comprises dissolving alkali lignin in the free acid form in a solution of an alkaline catalyzed A stage resole in a volatile solvent, which solvent consists essentially of a solvent selected from the group consisting of methanol, ethanol, propanols, water and mixtures of said solvents with each other, to form a mutual solution at a pH between about 3 and about 7, the ratio by weight of said lignin to said resole being from about 1 : 10 to about 5:1 , separating the volatile solvent from the solids in said mutual solution and curing the residue.

In an article written by G. Masoumeh et al "Paper-based laminates produced with kraft lignin-rich phenol-formaldehyde resoles meet requirements for outdoor usage", HOLZ ALS ROH- UND WERKSTOFF, SPRINGER-VERLAG. BERLIN, DE, volume 76, nr. 2, 7 November 2017 (2017-11-07), pages 481-487, lignin-phenol- formaldehyde (LPF) resoles were investigated for manufacturing paper-based high- pressure laminates, wherein as lignin source, pine kraft lignin and spruce sodium lignosulfonate were compared, substituting 40 wt.% of phenol by lignin in each case.

JP 2013 064103 relates to a curable lignin resin composition comprising lignin, a nitrogen-containing bridged cyclic compound, and a furan resin. For the production of laminates it is necessary for the resin binder composition to be able to impregnate kraft papers or wood fibres and to have sufficient flow during panel pressing. However, the application of adhesives is a completely different technical field and therefore adhesives are not of interest in the present technical field of impregnation and pressing. Resins synthesized for adhesives for wood products (e.g. plywood) are needed to be rather viscous (high molar weights) to be more applicable on the wood and to avoid penetration of wood surface. In contrast resins to be used for impregnation purposes are manufactured from small molecules, i.e. low molecular weight molecules, typically dissolved in water or water solvent mixtures, to be able to penetrate into the pores of the paper more efficiently.

The present inventors found that using lignin based resins in a process for manufacturing laminates may lead to certain problems. One of such problems is related to a poor saturation of lignin based resins in kraft papers and/or wood fibres. A poor saturation of lignin based resins in the kraft papers and/or wood fibres may lead to a poor product performance, such as warping issues and inferior dimensional stability of the final laminates. This is related to the fact that lignin based resins have higher molecular weights compared to standard phenolic resins used for impregnation. Therefore, lignin based resins are used as an adhesive in e.g. plywood.

Another problem is related to a slower reactivity of the lignin based resins compared to the traditional phenolic resins. This slower reactivity of the based resins will lead to longer processing times and may also result in a lower cross-linking density of the polymer network in the final laminates. A lower cross-linking density of the final polymer could also lead to poor laminates properties, e.g. dimensional stability, and impact resistance.

An object of the present invention is to prepare a resin formulation on basis of a lignin based resin with good impregnation properties.

Another object of the present invention is to prepare a resin formulation on basis of a lignin based resin with a reactivity comparable to the traditional phenolic resins.

Another object of the present invention is to provide a method for manufacturing laminates in which so called layers of semi-finished material will be composed into a stacked package and used in a pressing operation using an elevated temperature and an elevated pressure to form laminates that meet the reference norms for laminates. The present invention thus relates to a resin formulation comprising a resin comprising lignin, phenol and formaldehyde and a non-lignin based resin, wherein the non-lignin based resin is chosen from the group of biobased resins and fossil based resins, or a combination thereof, wherein the amount of resin comprising lignin, phenol and formaldehyde is in a range of at least 10 wt.%, preferably at least 30 wt.% and at most 90 wt.%, preferably at most 70 wt.% and the amount of non-lignin based resin is in a range of at least 10 wt.%, preferably at least 30 wt.% and at most 90 wt.%, preferably at most 70 wt.%, wherein the weight percentage is based on the total amount of resins in the resin formulation

The present inventors found that by using such a resin formulation one or more objects are achieved. The present inventors found that by mixing the resin comprising lignin, phenol and formaldehyde with other resin types as mentioned above a full saturation of the kraft paper is achieved. In addition, when using the present resin formulation a higher reactivity in the manufacturing process of laminates is also achieved enabling to produce material according to the reference norms. From the above description it is clear that the present resin formulation may comprise one or more components other than resins.

The present resin formulation comprises a resin comprising lignin (A), phenol (B) and formaldehyde (C) and a non-lignin based resin (D), i.e. the combination of components A, B, C and D. None of the cited art discussed above discloses a resin formulation wherein the combination of components A, B, C and D is present. In some of the cited art component D is missing, in other cited art the combination of components B and C is missing.

In an example the non-lignin based resin, i.e. the biobased resins and/or the fossil based resins, is chosen from the group of phenol formaldehyde resins, phenol formaldehyde urea resins, phenol formaldehyde melamine resins, phenol formaldehyde melamine urea resins, furan based resins, melamine formaldehyde resins, melamine urea formaldehyde resins and urea formaldehyde resins, or a combination thereof.

Bio-based resins are a category of polymers derived from renewable raw materials rather than traditional fossil based raw materials. These resins are produced using renewable raw materials derived from several types of feedstocks, such as plants, algae, or agricultural waste. The term "bio-based" refers to the origin of the raw materials used in the production process, which are typically rich in renewable carbon and other elements that can be transformed into polymeric materials through various chemical and biological processes. Fossil-based resins are a type of polymer derived from fossil fuels such as petroleum, natural gas, or coal. These raw materials used in those resins are produced through the refining and chemical processing of hydrocarbons, which are the primary components of fossil fuels. The process typically involves cracking and polymerization reactions to create fossil based raw materials that are then reacted together to form the resin.

The present inventors found that mixing the resin comprising lignin, phenol and formaldehyde with phenol-formaldehyde based resins, i.e. a non-lignin based resin, resulted in an improvement of the saturation properties of the resin comprising lignin, phenol and formaldehyde. The present inventors furthermore found that mixing the resin comprising lignin, phenol and formaldehyde with furan based resins, i.e. an example of a non-lignin based resin, resulted in even more improved saturation properties of the lignin based resin.

In an example the lignin used in the resin comprising lignin, phenol and formaldehyde originates from the group of hardwood, softwood and annual plants, or a combination thereof.

In an example the lignin used in the resin comprising lignin, phenol and formaldehyde is chosen from the group of kraft lignin, organosolv lignin, lignosulphonate lignin and lignin extracted from pyrolysis oil, or a combination thereof. The present inventors found that a resin comprising lignin, phenol and formaldehyde produced with lignin from different feedstocks may result in a different impregnation behaviour into a kraft paper. By mixing the resin comprising lignin, phenol and formaldehyde with another type of resin, namely a biobased resin and/or a fossil based resin as discussed above, an acceptable kraft paper saturation will be obtained.

In an example the viscosity of the resin formulation is between 20 mPa-s and 500 mPa-s, preferably between 30 mPa s and 200 mPa s, measured according to method as described in the experimental section of this document. The present inventors found that by using a resin formulation having a viscosity outside the range as mentioned here will lead to processability issues. For example, in a situation wherein the viscosity of the resin formulation is too high, a complete impregnation into the core of the paper will be difficult, whereas a resin formulation having a too low viscosity will be difficult to handle during the impregnation step.

In an example the solid content of the resin formulation is between 20 % m/m and 80% m/m, preferably between 30 % m/m and 60% m/m, based on the total weight of the resin formulation. A solid content of below 20% m/m has a negative effect on the operations, since the amount of solvent that needs to be evaporated for each gram of resin applied to the paper and/or wood fibers is very high, which takes a lot of energy and is thus from an economical point of view not attractive. A solid content of above 80% m/m may lead to an increase of the viscosity of the resin formulation and thus to difficulties with regard to a step of impregnation. In addition, the present inventors have found that for resin formulation having a solid content outside the ranges mentioned here it is difficult to control the amount of resin formulation applied during the impregnation process. Phenol formaldehyde resins and lignin phenol formaldehyde resins are typically dissolved in water or water solvent mixtures, leading to a solid content of 20-80%m/m.

In an example the pH of the resin formulation is between 5.0 and 12.0, preferably between 8.5 - 10.0. For lignin based resins, the pH of the resin formulation needs to be at a pH > 5 for the lignin to properly dissolve. A pH above 12 will lead to a resin formulation in which the resin cures too fast during the impregnation process (B stage), leading to a lack of flow during the pressing process (C-stage) and thus to laminates with poor physical properties, for example delamination and dimensional stability.

In an example the resin formulation comprises a solvent, or a mixture of solvents, in an amount of at least 2 wt.%, preferably at least 5 wt.% and at most 20 wt.%, preferably at most 10 wt.%, based on the total weight of the resin formulation. The presence of one or more solvents in the resin formulation assists in controlling the stability of the resin formulation while also controlling the viscosity to aid in the saturation process of the kraft paper. A high solvent content will be costly since the solvent has to be evaporated in the production process of the laminates.

In an example the solvent is chosen from the group of glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (PEG) and polypropylene glycol (PPG), and alcohols, such as methanol, ethanol, propanol, iso-propanol, butanol, iso-butanol, pentanol and iso-pentanol, higher alcohols and their isomers, or a combination thereof. The present inventors have found that alcohols, especially methanol and isopropanol, are suitable solvents for the present resin formulation on basis of a lignin based resin, where methanol performs slightly better than isopropanol in stabilizing the resin formulation. Furthermore, glycols, such as diethylene glycol, provided an even better result with regard to stabilizing the present resin formulation.

In an example the resin formulation further comprises one or more additives, such as plasticizers, UV stabilizers, flame retardants, stabilizers, curing agents, catalysts, flow promoters, accelerators, hardeners, antifoaming agents, wetting agents, release agents and levelling agents. Such additives are needed to help with processability and (semi-finished) product performance during and after production of the laminates.

In an example the total amount of additives in the resin formulation is in a range of at least 0.4 wt.%, preferably at least 2 wt.% and at most 20 wt.%, preferably at most 10 wt.%, based on the total weight of the resin formulation. Individual amounts of an additive may be in a range of at least 0.2 wt.% and 2 wt.%, based on the total weight of the resin formulation. A total amount of additive that is above 20 wt.% will lead to poor panel properties, for example dimension stability and resistance to wet conditions. This negative effect is attributed to the too high amount of fillers in the final laminate.

The present invention also relates to a method for the preparation of a resin formulation on basis of a resin comprising lignin, phenol and formaldehyde as discussed above, wherein the method comprises the following steps: a) providing a resin comprising lignin, phenol and formaldehyde, b) providing a non-lignin based resin, i.e. a resin chosen from the group of biobased resins and fossil based resins, or a combination thereof, c) mixing a) and b) for obtaining a homogeneous resin formulation.

A homogeneous, well mixed resin formulation is vital for a safe processing of the resin formulation. In addition, the resin formulation needs to be homogeneous in order to fully saturate the paper. The use of one or more solvents contributes to stabilizing the resin formulation and to achieve a full saturation of the kraft paper during impregnation of the paper with the present resin formulation. In an example the method for the preparation of a resin formulation on basis of a resin comprising lignin, phenol and formaldehyde as discussed above further comprises a step d), namely the addition of a solvent to the resin formulation of step c), for obtaining a diluted resin formulation.

In an example step c) is carried out at a temperature below 70°C, preferably in a range of 20°C to 30°C. The present inventors found that it is difficult to carry out step c) at low temperatures, for example <10°C, due to the increased viscosity of the resins. In addition, the present inventors also found that at high temperatures, for example >70°C, there is a risk that the resins will already slowly start to react resulting in a possible change of the properties of the resin formulation and thereby making further processability less predictable and more difficult.

In an example the amount of solvent in step d) is in a range of at least 2 wt.%, preferably at least 5 wt.% and at most 20 wt.%, preferably at most 10 wt. %, based on the total weight of the diluted resin formulation.

In an example the viscosity of the diluted resin formulation after step d) is in a range of at least 5 mPa s, preferably at least 30 mPa s, and at most 250 mPa s, preferably at most 100 mPa s.

The present invention also relates to a method for manufacturing a paper impregnated with a resin formulation, comprising the following steps, i) providing a resin formulation as discussed above or a resin formulation obtained as discussed above, ii) providing a paper having a basis weight of at least 80 g m^-2, preferably at least 140 g m^-2 and at most 260 g m^-2, preferably at most 215 g m^-2, and iii) contacting i) and ii) for obtaining a paper impregnated with a resin formulation.

According to the present invention a plurality of impregnation methods can be used, such as dip-and-squeeze, roller coatings, dip-and-squeeze with sky roll and prewetting, wherein the line parameters are adjusted to suit the resin formulation that is used. During step iii) the amount of resin formulation applied to the paper and the volatile content (amount of moisture still present on the paper after drying) of the impregnated papers are preferably measured and controlled.

In an example the moisture content of the paper according to step ii) is in a range of 2.5 wt.% to 10 wt.%, based on the total weight of the impregnation paper. The present invention also relates to a method for manufacturing a laminate, comprising a step of preparing a stack of papers impregnated with a resin formulation, positioning the stack in a press, and manufacturing the laminate by pressing the stack under conditions of elevated pressure and temperature, wherein papers impregnated with a resin formulation obtained as discussed above are used.

In an example of such a method at least one side of the stack of papers impregnated with a resin formulation is provided with a decorative layer, wherein said decorative layer is applied before manufacturing said laminate by pressing the stack provided with the decorative layer under conditions of elevated pressure and temperature, or said decorative layer is applied after manufacturing said laminate by pressing the stack under conditions of elevated pressure and temperature.

The present invention is specifically applicable to the industrial impregnation of papers which can be pressed to form laminates. Also it is applicable to the impregnation of wood fibres that can be pressed to form "prepreg" boards that can likewise be combined with other elements and pressed to form laminates.

The present invention thus relates to a method for manufacturing a prepreg, comprising the following steps, i) providing a resin formulation as discussed above or a resin formulation obtained according to a method as discussed above, iv) providing a plurality of wood fibers, v) contacting i) and iv) for obtaining a prepreg.

The present invention furthermore relates to a method for manufacturing a laminate, comprising a step of positioning one or more prepregs in a press and manufacturing the laminate by pressing the one or more prepregs under conditions of elevated pressure and temperature, wherein prepregs as discussed above are used.

In an example of such a method at least one side of one or more prepregs is provided with a decorative layer, wherein said decorative layer is applied before pressing one or more prepregs under conditions of elevated pressure and temperature, or said decorative layer is applied after pressing one or more prepregs under conditions of elevated pressure and temperature.

In another example of such a method a construction of a prepreg provided with kraft papers on each side, i.e. a sandwich construction, is positioned in a press and the laminate is manufactured by pressing such construction under conditions of elevated pressure and temperature. A construction of both prepreg and kraft paper can be seen as a duo-core build-up. In another example only one side of the prepreg is provided with kraft paper. A decorative layer can be applied before pressing such construction under conditions of elevated pressure and temperature, or a decorative layer can be applied after pressing such construction under conditions of elevated pressure and temperature.

The present invention is also suitable for the production of CPL ("Continuous Pressure Laminates" or alternatively "Continuous Pressed Laminates"). CPL lines can be operated with a pressure in the range of 20 - 50 bar and temperatures between at least 120°C, preferably at least 150°C and at most 300 °C, preferably at most 170°C. But CPL lines are also capable of achieving pressures in the range of 70 - 100 bar. The conveyor speed may be in a range of 5 to 20 m/min. Hence from a "pressure" point of view there is no difference to the multi daylight presses which are also typically referred as HPL (High Pressure Laminate) presses. The present invention also covers the Double Belt Press (DBP) for the production of CPL. For pressing at elevated temperature and pressure a daylight press (HPL) or a continuous press (CPL) are used.

In the manufacture of HPL panels, the package, comprising the core layers and surface layer or layers, and the paper layers possibly located between them as well, is thermopressed to make a decorative panel; the thermosetting resins are cured in this process. The temperature is in the range from 120 °C to 300 °C, the pressure is in the range from 10 to 100 bar, and the reaction time is from at least 0,2 to 75 minutes. According to an example: a line speed of 20 m/min and a press length of 4,5m results in a retention time of about 13,5 seconds (0,22 minutes).

In a typical CPL line the impregnated papers are continually fed into the press from multiple feeds together with a decorative paper. During the CPL process they are then compressed and heated to form a laminate product. Laminate properties are similar to standard HPL, and a typical thickness range is between 0.4 mm to 1.2 mm. During the step of bonding together the individual components, i.e. the impregnated papers, and the decorative paper, with simultaneous application of heat, for example > 120° C, and high specific pressure (> 70 bars) a homogeneous non-porous laminate with increased density and integral decorative surface is obtained. In addition, the present invention relates to a method for manufacturing a continuously pressed laminate comprising the following steps:

A) providing a plurality of papers impregnated with a resin formulation,

B) pressing of the plurality of papers impregnated with a resin formulation in a CPL process, wherein paper impregnated with a resin formulation obtained according to a method as discussed above are used.

In an example of such a method for manufacturing a continuously pressed laminate a decorative layer is provided on at least one side of the plurality of papers impregnated with a resin formulation, wherein said decorative layer is applied before the step of pressing of the plurality of papers impregnated with a resin formulation in a CPL process, or said decorative layer is applied after the step of pressing of the plurality of papers impregnated with a resin formulation in a CPL process.

The present invention also relates to a laminate obtained according to a method as discussed above having a thickness of at least 0.2 mm, preferably at least 0.5 mm and at most 50 mm, preferably at most 25 mm.

The present laminate can be used in indoor, outdoor, and exterior applications, such as cladding of buildings, for example interior walls, exterior walls, ceilings, and facades. The indoor application relates to the manufacturing of furniture, worktops and tabletops, storage compartments such as lockers and various other products. Examples of furniture are tabletops, laboratory tables, kitchen work tops, nightstands, countertops, benches, chairs, or stools, as well as tables, such as coffee tables, dining tables, cocktail tables, conference tables, side tables, picnic tables, or outdoor tables.

The present invention will now be explained by way of experimental results. It is to be noted that for the entire application the inventors always speak about resins (solid polymers) and the inventors never state that these resins are solutions of polymers in solvents (like water).

Figure 1 shows a 170 g m^-2 kraft paper impregnated with a lignin based resin in which large non-impregnated regions are visible.

Figure 2 shows a 208 g m^-2 kraft paper impregnated with a resin formulation D in which small spots of non-impregnated paper are visible.

Figure 3 shows a 155 g m^-2 kraft paper impregnated with a resin formulation of lignin based resin and furanic based resin showing a full homogeneous penetration of the resin through the entire paper. Figure 4 shows an analysis of the curing behavior of a lignin based resin and a resin formulation made of a lignin based resin and a furanic based resin using DSC.

For all experiments involving the mixing of different resins a 1000 ml glass reactor configured for reflux under atmospheric conditions was used. It also had an electric motor and anchor stirrer that was set to a stirring rate of 250 rpm. Furthermore the reactor was double walled, so that heating could be provided by a recirculating thermostatically controlled oil bath. The reactor also had cooling coils through which cold water could pass. This arrangement allowed good control of the experiment’s temperature. The mixing of the resins following the recipes reported here was performed at 25°C. The mixing time was 10 minutes.

Method for Viscosity Measurements

In the examples, various samples had their viscosity measured; a Brookfield CAP 2000+ cone-plate viscometer was used to measure these. Once the temperature of the samples had been adjusted to 20°C, their viscosities were measured using spindle 1 and 250 rpm settings.

Method for pH determination

Samples were adjusted to 20°C and their pH was measured by inserting a calibrated pH electrode/meter.

Method for water tolerance determination

The water tolerance is indicating how much water can be mixed with a fixed amount of resin. At 20°C sufficient water is added to a certain amount of resin to create a turbidity. The required amount of water is a measure of the water tolerance of the resin. The water tolerance of the resin (in m/m%) is calculated according to:

WT= (m1/m0) X 100%

WT: water tolerance (m/m%), ml : mass of the required amount of water up to the moment of turbidity (g), mO: mass of the analysed resin (g).

Lignin based resin with standard phenol-formaldehyde based resin.

Several mixtures were made with different ratios of a lignin based resin and a standard phenol formaldehyde based (PF) resin as shown in Table 1 below. The term “a lignin based resin” as used here refers to a resin comprising lignin, phenol and formaldehyde. Mixtures were made by first mixing the pure resins together and stirring. When the mixtures are homogeneous no solvents are added. When the mixture is not homogeneous, diethylene glycol (DEG) is added until the mixture is homogeneous. When DEG is required to make the mixture homogeneous, new mixtures are made with a fixed amount of solvent (methanol) and the above described procedure is repeated. These experiments were performed in order to test how multiple solvents influenced the stability of the resin formulations. The properties of the resin formulation are displayed in Table 2 and Table 3 below. Table 1. Composition of different mixtures of a lignin based resin and a standard phenol-formaldehyde resin.

Table 2. Properties of the different resin formulation.

Table 3. Properties of the different resin formulation after 24 hours of storage at room temperature. As can be seen by the composition of the resin formulation, these resin formulations are all homogeneous without the without the addition of DEG or methanol. By comparing the properties of the resin formulation directly after production and after 24 hours of storage, it is seen that the resin formulation are also very stable over time.

Lignin based resin with fire retardant phenol-formaldehyde based resin.

Several mixtures were made with different ratios of a lignin based resin and a fire retardant phenol-formaldehyde based (FR PF) resin as shown in Table 4 below. Mixtures were made by first mixing the pure resins together and stirring. When the mixtures are homogeneous no solvents are added. When the mixture is not homogeneous, diethylene glycol (DEG) is added until the mixture is homogeneous. When DEG is required to make the mixture homogeneous, new mixtures are made with a fixed amount of methanol and the above described procedure is repeated. These experiments were performed in order to test how multiple solvents influenced the stability of the resins formulations. The properties of the resin formulation are displayed in Table 5 and Table 6 below.

Table 4. Composition of different mixtures of a lignin based resin and a fire retardant (FR) phenol-formaldehyde (PF) resin.

Table 5. Properties of the different resin formulation.

Table 6. Properties of the different resin formulation after 24 hours of storage at room temperature. As it can be seen by the composition of the resin formulations, not all resin formulations are homogeneous without the addition of DEG or methanol. However, the addition of solvents makes the mixtures homogeneous. The amount of solvents that needs to be added to obtain a homogeneous mixture can be taken as a measure of how compatible the resins themselves are (the more solvent is required to obtain a homogeneous mixture the less compatible the resins are). Looking at the properties of the resin formulation, the present inventors assume that there is a mismatch in the pH of the two resins which might be the cause of the lower compatibility compared to the mixtures of the lignin based resin and the standard phenol-formaldehyde based resin. By comparing the properties of the resin formulations directly after production and after 24 hours of storage, it is seen that the viscosity of the resin formulation increases over time indicating that these resin formulation are also less stable over time compared to the mixtures of the lignin based resin and the standard phenolformaldehyde based resin.

Lignin based resin with furanic based resin. Several mixtures were made with different ratios of a lignin based resin and a furanic based resin as shown in Table 7 below. Mixtures were made by first mixing the pure resins together and stirring. When the mixtures are homogeneous no solvents are added. When the mixture is not homogeneous, diethylene glycol (DEG) is added until the mixture is homogeneous. When DEG is required to make the mixture homogeneous, new mixtures are made with a fixed amount of methanol and the above described procedure is repeated. These experiments were performed in order to test how multiple solvents influenced the stability of the resins formulations. The properties of the resin formulation are displayed in Table 8 below.

Table 7. Composition of different mixtures of a lignin based resin and a furanic based resin.

Table 8. Properties of the different resin formulation. Table 9. Properties of the different resin formulation after 24 hours of storage at room temperature.

As can be seen by the composition of the resin formulations, not all resin formulation are homogeneous without the addition of DEG or methanol. However, the addition of solvents makes the mixtures homogeneous. The amount of solvents that needs to be added to obtain a homogeneous mixture can be taken as a measure of how compatible the resins themselves are (the more solvent is required to obtain a homogeneous mixture the less compatible the resin is). Looking at the properties of the resin formulations, the present inventors assume that there is a mismatch in the pH of the two resins which might be the cause of the lower compatibility compared to the mixtures of the lignin based resin and the standard phenol-formaldehyde based resin. By comparing the properties of the resin formulations directly after production and after 24 hours of storage, it is seen that the viscosity of the resin formulations increases only slightly over time indicating that these resin formulations are more stable over time compared to the mixtures of the lignin based resin and the fire retardant phenol-formaldehyde based resin. Impregnation of kraft paper with resins

Lignin based resin

In this example a 170 g m^-2 kraft paper was impregnated with a lignin based resin. The resin formulation was pre-heated before impregnation to a temperature of 30°C. The impregnation line speed was 90 m min^-1 and the oven setting profile displayed in Table 10 was used.

Table 10. Oven temperature profile for paper impregnation.

The resin content of the impregnated paper was 34% ± 1% while the volatile content of the impregnated papers was 7% ± 1 %. As displayed in Figure 1 the resin penetration is not good, leaving large areas of non-impregnated paper. As it can be seen, the resin is not present in the core of the kraft paper but only on the surface.

Lignin based resin with standard phenol-formaldehyde based resin

The paper impregnation behavior of the different resin formulation was analyzed on lab scale and varied from good to medium as displayed in Table 2. From these lab scale tests a formulation (D) was selected for industrial scale impregnation trials.

In this example a 208 g m^-2 kraft paper was impregnated with the resin formulation (D) as reported in Table 11 below. The resin formulation was pre-heated before impregnation to a temperature of 34°C. The kraft paper roll was pre-heated before impregnation to a temperature of 70°C. Tablel 1 . Resin formulation for paper impregnation

The impregnation line speed was 98 m min^-1 and the oven setting profile displayed in Table 12 was used.

Table12. Oven temperature profile for paper impregnation.

The resin content of the impregnated paper was 33% ± 1% while the volatile content of the impregnated papers was 6% ± 1%. As shown in Figure 2 the resin penetration into the paper has improved from the pure Lignin based resin.

Lignin based resin with furanic based resin

The paper impregnation behavior of the different resin formulation was analyzed on lab scale and varied from good to bad as displayed in Table 8. From these lab scale tests a formulation was selected for industrial scale impregnation trials.

In this example a 155 g m^-2 kraft paper was impregnated with the resin formulation as reported in Table 13 below. The resin formulation was not pre-heated before impregnation and the kraft paper roll was also not pre-heated before impregnation. Table13. Resin formulation for paper impregnation

The impregnation line speed was 62 m-mirr¹ and the oven setting profile displayed in Table 14 was used.

Table 14. Oven temperature profile for paper impregnation.

The resin content of the impregnated paper was 31 % ± 1% while the volatile content of the impregnated papers was 5,5% ± 1 %. As shown in Figure 3 there is full and homogeneous resin penetration into the complete paper.

Multidaylight pressing process

Lignin based resin

As the impregnation of the lignin based resin reported in the previous experiment for the pure lignin based resin was not successful (poor kraft paper saturation), this material was not utilized for press trials. It is known that a lack of resin in the paper will negatively influence the physical properties of the laminates leading to delamination during pressing and poor physical properties, e.g. dimensional stability, due to the lack of the resin in the kraft paper core.

Lignin based resin with standard phenol-formaldehyde based resin

The stack of impregnated papers was assembled on both sides with an acrylic EB coated decor paper in order to achieve a laminate thickness of 6 mm. Laminates pressing was executed at 150°C and with a pressure of 70 bar.

Physical testing was performed on the pressed laminates. Results are reported in the Table 15 below.

Table 15: Performance results of laminates

Lignin based resin with furanic based resin

Physical testing was performed on the pressed laminates. Results are reported in the Table 16 below. Table 16: Performance results of laminates

Continuous pressing process

Lignin based resin with furanic based resin A build-up consisting of 3 core layers, one decor layer and one layer of parchment paper was pressed on a continuous pressing line (CPL). The target thickness of the laminates was 0,7mm. The temperature profile of the press is displayed in Table 17 below. The pressure was 80 bar and line speed was varied from 5 m min^-1 to 8 m-min^-1.

Table 17. Temperature profile of CPL press

Physical testing of the laminate properties was performed on the produced material. The results are displayed in Table 18. below. Table 18. Test results of laminates produced on CPL line with Lignin based resin and furanic based resin mixture.

Reactivity of resin mixtures The curing behavior of both the lignin based resin and the mixture of the lignin based resin + the furanic based resin was analyzed using DSC measurements. Figure 4 shows an analysis of curing behavior of different resins using DSC. The present inventors found that the temperature at which the maximum curing speed is reached is lowered significantly by mixing the Lignin based resin with the furanic based resin and including the optimal hardener system. The exothermic peak is also steeper at the curing onset, indicating a faster initial curing of the resin mixture compared to the pure Lignin based resin. This allows this resin to be used for the production of thin laminates on a Continuous pressing line (CPL), which is not possible with a pure Lignin based resin.

Claims

1. A resin formulation comprising a resin comprising lignin, phenol and formaldehyde and a non-lignin based resin, wherein the non-lignin based resin is chosen from the group of biobased resins and fossil based resins, or a combination thereof, wherein the amount of resin comprising lignin, phenol and formaldehyde is in a range of at least 10 wt.%, preferably at least 30 wt.% and at most 90 wt.%, preferably at most 70 wt.% and the amount of non-lignin based resin is in a range of at least 10 wt.%, preferably at least 30 wt.% and at most 90 wt.%, preferably at most 70 wt.%, wherein the weight percentage is based on the total amount of resins in the resin formulation.

2. A formulation according to claim 1 , wherein the biobased resins and/or the fossil based resins are chosen from the group of phenol formaldehyde resins, phenol formaldehyde urea resins, phenol formaldehyde melamine resins, phenol formaldehyde melamine urea resins, furan based resins, melamine formaldehyde resins, melamine urea formaldehyde resins and urea formaldehyde resins, or a combination thereof.

3. A formulation according to any one or more of the preceding claims, wherein the lignin in the resin comprising lignin, phenol and formaldehyde originates from the group of hardwood, softwood and annual plants, or a combination thereof.

4. A formulation according to any one or more of the preceding claims, wherein the lignin in the resin comprising lignin, phenol and formaldehyde is chosen from the group of kraft lignin, organosolv lignin, lignosulphonate lignin and lignin extracted from pyrolysis oil, or a combination thereof.

5. A formulation according to any one or more of the preceding claims, wherein the viscosity of the resin formulation is between 20 mPa-s and 500 mPa s, preferably between 30 mPa s and 200 mPa s, measured according to method as described in the experimental section of this document.

6. A resin formulation according to any one or more of the preceding claims, wherein the solid content of the resin formulation is between 20 % m/m and 80% m/m, preferably between 30 % m/m and 60% m/m, based on the total weight of the resin formulation.

7. A resin formulation according to any one or more of the preceding claims, wherein the pH of the resin formulation is between 5.0 and 12.0, preferably between 8.5 - 10.0.

8. A resin formulation according to any one or more of the preceding claims, further comprising a solvent, or a mixture of solvents, in an amount of at least 2 wt.%, preferably at least 5 wt.% and at most 20 wt.%, preferably at most 10 wt.%, based on the total weight of the resin formulation.

9. A resin formulation according to claim 8, wherein the solvent is chosen from the group of glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (PEG) and polypropylene glycol (PPG), and alcohols, such as methanol, ethanol, propanol, iso-propanol, butanol, iso-butanol, pentanol and isopentanol, higher alcohols and their isomers, or a combination thereof.

10. A resin formulation according to any one or more of the preceding claims, further comprising one or more additives, such as plasticizers, UV stabilizers, flame retardants, stabilizers, curing agents, catalysts, flow promoters, accelerators, hardeners, antifoaming agents, wetting agents, release agents and levelling agents.

11. A resin formulation according to claim 10, wherein the total amount of additives is in a range of at least 0.4 wt.%, preferably at least 2 wt.% and at most 20 wt.%, preferably at most 10 wt.%, based on the total weight of the resin formulation.

12. A method for the preparation of a resin formulation on basis of a resin comprising lignin, phenol and formaldehyde according to any one or more of the preceding claims, said method comprising the following steps: a) providing a resin comprising lignin, phenol and formaldehyde, b) providing a resin chosen from the group of biobased resins and fossil based resins, or a combination thereof, c) mixing a) and b) for obtaining said resin formulation.

13. A method according to claim 12, further comprising step d), i.e. adding a solvent to the resin formulation of step c), for obtaining a diluted resin formulation.

14. A method according to claim 13, wherein step c) is carried out at a temperature below 70°C, preferably in a range of 20°C to 30°C.

15. A method according to any one of claims 13-14, wherein the amount of solvent in step d) is in a range of at least 2 wt.%, preferably at least 5 wt.% and at most 20 wt.%, preferably at most 10 wt. %, based on the total weight of the diluted resin formulation.

16. A method according to any one of claims 13-15, wherein the viscosity of the diluted resin formulation after step d) is in a range of at least 5 mPa s, preferably at least 30 mPa s, and at most 250 mPa s, preferably at most 100 mPa s, measured according to method as described in the experimental section of this document.

17. A method for manufacturing a paper impregnated with a resin formulation, comprising the following steps, i) providing a resin formulation according to any one or more of claims 1-11 or a resin formulation obtained according to a method according to any one or more of claims 12-16, ii) providing a paper having a basis weight of at least 80 g m^-2, preferably at least140 g m^-2 and at most 260 g m^-2, preferably at most 215 g m^-2, and iii) contacting i) and ii) for obtaining a paper impregnated with a resin formulation.

18. A method according to claim 17, wherein the moisture content of the paper according to step b) is in a range of 2.5 to 10 wt.%, based on the total weight of the impregnation paper.

19. A method for manufacturing a laminate, comprising a step of preparing a stack of papers impregnated with a resin formulation, positioning the stack in a press and manufacturing the laminate by pressing the stack under conditions of elevated pressure and temperature, wherein as paper impregnated with a resin formulation, papers impregnated with a resin formulation obtained according to a method according to any one or more of claims 17-18 are used.

20. A method according to claim 19, wherein at least one side of the stack of papers impregnated with a resin formulation is provided with a decorative layer, wherein said decorative layer is applied before manufacturing said laminate by pressing the stack provided with the decorative layer under conditions of elevated pressure and temperature, or said decorative layer is applied after manufacturing said laminate by pressing the stack under conditions of elevated pressure and temperature.

21. A method for manufacturing a prepreg, comprising the following steps, i) providing a resin formulation according to any one or more of claims 1-11 or a resin formulation obtained according to a method according to any one or more of claims 12-16, iv) providing a plurality of wood fibers, v) contacting i) and iv) for obtaining a prepreg.

22. A method for manufacturing a laminate, comprising a step of positioning one or more prepregs in a press and manufacturing the laminate by pressing the one or more prepregs under conditions of elevated pressure and temperature, wherein one or more prepregs obtained according to a method of claim 21 are used.

23. A method according to claim 22, wherein at least one side of one or more prepregs is provided with a decorative layer, wherein said decorative layer is applied before pressing the one or more prepregs under conditions of elevated pressure and temperature, or said decorative layer is applied after pressing the one or more prepregs under conditions of elevated pressure and temperature.

24. A method for manufacturing a continuously pressed laminate comprising the following steps:

A) providing a plurality of papers impregnated with a resin formulation,

B) pressing of the plurality of papers impregnated with a resin formulation in a CPL process, wherein as paper impregnated with a resin formulation, a paper impregnated with a resin formulation obtained according to a method according to any one or more of claims 17-18 are used.

25. A method according to claim 24, wherein a decorative layer is provided on at least one side of the plurality of papers impregnated with a resin formulation, wherein said decorative layer is applied before the step of pressing of the plurality of papers impregnated with a resin formulation in a CPL process, or said decorative layer is applied after the step of pressing of the plurality of papers impregnated with a resin formulation in a CPL process.

26. A laminate obtained according to a method according to any one or more of claims 19-20 and 22-25 having a thickness of at least 0.2 mm, preferably at least 0.5 mm and at most 50 mm, preferably at most 25 mm.

27. The use of a laminate according to claim 26 in indoor, outdoor and exterior applications.