FI128836B - Method for producing reactive lignin - Google Patents

Abstract

According to an aspect of the present invention, there is provided a method of producing reactive lignin from an alkaline lignin containing stream, such as black liquor, e.g. kraft lignin, by using thermal treatment with temperatures between 200 and 250 °C, and a retention time of 1h or less, for activation and precipitation of the lignin.

Description

METHOD FOR PRODUCING REACTIVE LIGNIN FIELD

[0001] The present invention relates to a method for activating and separating lignin from an alkaline lignin containing stream, such as black liquor. More precisely, this invention relates to a lignin product obtained and the use of the product.

BACKGROUND

[0002] Black liquor is the by-product from alkaline pulping processes, such as kraft and soda pulping, where most of the lignin, but also some hemicelluloses and extractives are removed from the lignocellulosic feedstocks to free the cellulosic fibers for paper making. Black liquor contains more than half of the energy content of the wood fed into the digester, and pulp mills typically use black liquor as an energy source by burning it in the recovery boiler.

[0003] Lignin is the main organic component in black liquor (25-30 %). It is aromatic biopolymer, and in addition to use as energy source, it could also find higher value uses as a sustainable bio based raw material in chemical industry. Therefore, lignin separation technologies have been recently developed, and some of them have been implemented into commercial scale. All presently available lignin separation technologies, such as LignoBoost, LignoForce and SLRP, are based on lignin precipitation by acidification using carbon dioxide. Precipitated lignin is then purified, e.g. by using two- > step acidic washing process as described in EP 1794363. In this washing step the final pH N is around 2.5. According to some alternatives, the black liguor is oxidized at 75*C before = acidification to improve the filtration properties. It is also possible to precipitate the lignin - continuously in a column reactor, e.g. at slightly higher temperature (such as 115°C at a E pressure of 6.2 bar) Typically, dense liguid-lignin droplets are then formed, which 2 coalesce into a bulk liguid-lignin phase that can be separated by gravity. The liguid lignin 3 is then typically reacted continuously with sulfuric acid to achieve a pH of 2-3 as in other > processes. Currently, the precipitated lignins are mainly used as fuel.

[0004] Other approaches for upgrading black liguor have also been investigated.

WO 2012/091906 describes a process to reduce one or more insoluble solids from heat-

treated black liquor comprising the steps of providing a black liquor stream and treating the black liquor at an increased temperature 250-300° C. In the process, lignin is depolymerized to lower molecular weight lignin compounds, such as phenolic oligomers and monomers. These compounds are dissolved, thus reducing the solids composition in the black liquor. Afterwards, the produced liquid including the degraded compounds can be separated and processed for use in downstream aromatic and other chemical processes. However, in the publication thermal treatment is used to degrade lignin in black liquor to lower molecular compounds. In the present invention the polymeric structure of precipitated lignin remains, and lower treatment temperature is used.

[0005] Similarly, EP 2591166 (Stora Enso) is directed to a thermal treatment of black liquor at temperatures of 150 to 200 °C during a short retention time that preferably is 1-5 minutes, and to a subsequent precipitation in order to produce a lignin with a low hemicellulose content, lower molar mass and thus reduced viscosity, to be used in biorefinery-related applications. No activation of the lignin is described.

[0006] Likewise, FI 20155505 A, US 2976273 A, US 2802815 A, US 2013066116 Al and Mahmood, N. et al. (in Bioresource Technology, 2013-04-06, Vol. 139, 13-20) describe processes for recovering lignin, the processes including thermal treatments. However, in these processes, the conditions, such as the temperature and the pH, have not been sufficiently optimized to provide an activated precipitated lignin product with a controlled structure.

[0007] EP 3036247 (Valmet) describes a process for precipitating lignin using an acid treatment step, and subsequently subjecting the separated lignin fraction to carbonization, while EP 3030598 and WO 2016/020383 (Suncoal Industries) describe a N process for extracting carbonized lignin from black liguor using a pH adjustment and a = hydrothermal carbonization. = [0008] High temperatures together with long retention times cause carbonization by * decreasing the amount of hydrogen and oxygen, while polymerization and condensation & increase the molecular weight of the product. The carbonization methods are, thus, = particularly aimed for producing carbon-rich products, using high temperatures combined N with long retention times.

SUMMARY OF THE INVENTION

[0009] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0010] According to a first aspect, it is provided herein a thermal treatment method for separating and activating lignin from lignin containing streams.

[0011] According to a second aspect, it is provided herein an activation and precipitation method for producing reactive lignin, which has specific structure and properties that can be altered by varying the process conditions.

[0012] According to a further aspect, the structure of separated lignin and the degree of activation is also dependent on the composition of the raw material stream, favouring especially alkaline lignin containing streams, such as black liquor from kraft or soda processes.

[0013] According to even further aspect, process yield can be increased and structure of the final lignin modified in alkaline raw materials by optional adding of acid either before, during and/or after the thermal treatment.

[0014] The present invention thus aims at activating and separating lignin from dissolved lignin containing streams. In contrast to technologies described in prior art, this invention uses heat treatment to chemically activate the lignin, while the prior art focuses on either depolymerizing lignin at higher temperatures or carbonating/carbonizing and hence condensating the lignin with longer reaction times. The carbonization is, on the contrary, avoided and condensation minimised in the present invention, by selecting a

O N suitable combination of reaction conditions (particularly temperature, pH and retention

N a time) with main focus on lignin separation and activation. - [0015] The used raw materials are lignin containing streams. Examples of suitable E streams are alkaline streams, where lignin is dissolved or colloidal (for example from 0 alkaline pulping processes). Alternatively, non-alkaline or isolated lignins from other O . . . O sources (as for example by-products from biofuel production or breweries) can be S dispersed in an alkaline agueous media.

[0016] The present invention provides means for enabling the utilization of lignin in higher value products than fuel, such as in PF and other phenolic resins, antioxidants,

surface active dispersants, surfactants or chelates, UV-stabilizers, reinforcing fillers and pigments in various applications such as in tyre and other rubber products and composites. Alternatively, the activated and separated lignin can be used as a raw material in activated carbon manufacture.

[0017] Considerable advantages are obtained by means of the invention. High temperature with optional pH adjustment before, during and/or after thermal treatment is utilized for lignin activation and precipitation instead of the traditional acidic precipitation that produces non-activated lignin. The new process leads to simultaneous lignin demethylation and/or demethoxylation, providing unique method for producing highly reactive lignin, for example for PF and epoxy resin applications, or highly functional lignin for composite, dispersant, antioxidant, chelation or hot-melt adhesive applications. Unlike the publications describing methods to carbonize lignin using high temperatures and long retention times, the present application uses a shorter thermal treatment, which activates lignin by demethylating/demethoxylating and creates more phenolic functionalities.

[0018] The amount of the reactive sites of lignin increases significantly compared to the present commercial lignins precipitated with acid, making the lignin material more suitable for several applications.

[0019] The structure of the produced lignin can be optimized in the process by varying process conditions so that the lignin material can be utilized in thermoset resins, or in rubber, plastic and glue applications, or as replacement of fossil-based carbon black, as additive providing reinforcement, UV-stability, antioxidative properties, colouring and thermal stability for applications such as rubber, composites, inks and paints. Alternatively, it can be used as a raw material in activated carbon manufacture.

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N A [0020] Next, the present technology will be described more closely with reference to 7 certain embodiments.

= a & EMBODIMENTS © > [0021] The present invention is illustrated in the attached drawings, where FIGURE 1 illustrates the general concept of the present technology,

FIGURE 2 illustrates an embodiment of the invention, FIGURE 3 is a graphical presentation of the viscosity development in PF (phenol formaldehyde) resin synthesis, and FIGURE 4 is a graphical presentation of resin curing at high phenol substitution levels.

[0022] Thus the present invention relates to a method of producing highly reactive lignin from dissolved lignin containing streams, such as black liguor. The general concept of the present technology is shown in FIGURE 1, where the dissolved lignin containing stream (1) in a dry matter content between 10 and 50% is subjected to an optional pH adjustment step (AO) before or during a heat treatment step (HT), followed by an optional acidification step (A1), filtration step (F1), and acidic washing step (W1). In case that the lignin containing stream is black liguor from kraft pulp mill, a fraction of the black liguor stream is extracted from evaporation plant to the lignin extraction (1). The filtrates from the filtration step (6) and washing step (7) are returned to the evaporation plant.

[0023] The method of the invention thus comprises carrying out a thermal treatment on an alkaline lignin-containing feedstock by applying temperatures of more than 200 °C, preferably within the range of from more than 200 to less than 250 °C and a retention time of 1h or less, preferably between 0.05 and 1 h, more preferably from 0.1 to < 1 hours, and subsequently separating the precipitated lignin material from the filtrate as such or after reduction of pH.

[0024] Such thermal treatment increases the reactivity, i.e. the amount of reactive > sites, of lignin, without causing any significant condensation or carbonization.

O N [0025] The first optional pH adjustment step (AO) is intended to lower the pH to a 7 value between 11 and 13. In case of the lignin containing stream being black liguor, this = optional slight pH adjustment does not cause significant precipitation of the lignin but S improves yield during heat treatment. For alkaline streams, pH adjustment (2) is done by S introducing any acidic steam, such as CO», acidic exhaust gases, sulfuric acid, citric acid e etc.

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[0026] The heat treatment step (HT) is done in a temperature between 200 and 250°C for a time of 1 hour or less, in order to facilitate activation of the lignin and also precipitation of a fraction of the lignin. In contrast to the methods described in prior art, the goal of the heat treatment is to activate the lignin, not to carbonize or condensate the lignin. Significant activation is only achieved by using temperatures > 200 °C, while carbonization typically requires both high temperatures and long residence times.

[0027] Preferably, the method operates at a temperature between 210 and 240 °C, particularly at a temperature of between 220 and 240 °C, during a retention time of less than 1h, preferably between 0.25 and <1 h.

[0028] The process is preferably operated at a pressure between 15-40 bars, which typically is a self-generated pressure of the present process.

[0029] Typically, the method is operated at an alkaline pH, such as between 9 and

14. Yield can be increased and structure of the final lignin can be modified in alkaline raw materials by optional addition of acid for adjusting the pH to desired level before, during and/or after the thermal treatment.

[0030] In order to increase the yield of precipitated lignin, the second optional acidification step (A1) can be carried out. In said step, pH of the liquor is lowered below pH 11, preferably almost to a pH range of 9-10 in order to precipitate more lignin. Acidification agent (3) can be any acid, particularly any commonly used and readily available acid, e.g. carbon dioxide, carbonic acid, acidic exhaust gas, sulfuric acid, hydrochloric acid, nitric acid, citric acid or acetic acid, preferably carbon dioxide, acidic exhaust gas or sulphuric acid. The filtration step can be performed using any solid-liquid separation equipment such as filter press, belt press, centrifuge etc. > [0031] Acidic washing step (W1) is carried out to purify the precipitated lignin. N Preferably acidic washing water (4) is used, most suitably at pH 2-3. In FIGURE 1, stream = 5 represents the washed lignin.

[0032] Using this embodiment, lignin with highly reduced methoxyl content can be S produced from alkaline lignin containing feedstock, obtained for example from alkaline S pulping process, such as kraft black liguor, by using the method of the present invention as 3 herein described, in which lignin is precipitated and activated simultaneously. However, N the method can be utilized also for recovery of any other alkaline lignin containing stream.

[0033] Lignin precipitation accompanied by activation through demethylation and/or demethoxylation provides better means for utilisation of otherwise less reactive lignin. Further, the present invention provides means for adjusting the lignin structure, e.g. by providing a more narrow range for the molar mass, reactivity or degree of condensation of the lignin product, compared to the prior processes.

[0034] Another embodiment is illustrated in FIGURE 2. Dissolved lignin containing stream (1) in a dry matter content between 10 and 50% is subjected to an optional pH adjustment step (AO), followed by a heat treatment step (HT) and filtration step (FO). A solid lignin separated in filtration step (FO) is subjected to washing step (WO). Stream (4) contains the washed lignin that was precipitated during the heat treatment step (HT). Filtrate from the first filtration step (FO) is subjected to acidification step (Al), filtration step (F1), and acidic washing step (W1). Stream (7) contains lignin precipitated in the acidification step (Al). In case that the lignin containing stream is black liquor from kraft pulp mill, a fraction of the black liquor stream is extracted from evaporation plant to the lignin extraction (1). The filtrate (8) from the filtration steps and filtrate (9) from washing step can be returned to the evaporation plant.

[0035] The properties of the lignin precipitated in the second step Al-F1 are different from the properties of the lignin precipitated during heat treatment step HT.

[0036] Thus, the purpose of said late-stage pH adjustment is, according to one alternative, to increase the yield of lignin, and according to another alternative, to provide means for adjusting the lignin structure (e.g. molar mass, reactivity or degree of condensation of the lignin product, compared to the prior processes). N [0037] Important features of the embodiments of the invention are that carbonization a and condensation is avoided by maintaining a short retention time in the thermal treatment. - [0038] The process is suitable for alkaline lignin containing streams where lignin is E either dissolved or colloidal, or alternatively any type of lignin can be dispersed or 2 dissolved in alkaline agueous solution. Such streams can originate as such from kraft, and 3 soda cooking processes. Alternatively, lignin can be hydrolysis lignin from 2"! generation > bioethanol residues or from breweries if dissolved or dispersed for example for lignin extraction.

[0039] Particularly, the selected stream originates from the kraft process, whereby kraft lignin is used.

[0040] Thus, according to a preferred embodiment, the method of the present invention includes the following steps: - placing black liquor having dry content of 10-50 wt-%, into a reactor, - optionally, adjusting pH of the black liquor by using a pH lowering agent, to obtain a pH between 11-13 before or during the following heat treatment step, - thermally treating the optionally pH-adjusted black liquor in temperatures between >200 °C and 250 °C under pressures between 15-40 bars for less than 1 hour, providing fractions of a) activated and precipitated lignin and b) remaining liquid, - separating the lignin fraction a) from the remaining liquid fraction b) - optionally, adjusting the pH of the liquid fraction b) before or after separation of fraction a), and thus precipitating and recovering a further fraction of lignin, - washing the separated lignin fractions at pH 2-3 one or more times to purify the lignin, and - drying one or more fractions of precipitated lignin product, either separately or after combination of two or more separately precipitated fractions.

[0041] In addition to the production method, a lignin material obtainable by the herein described process belongs to the scope of the present invention.

[0042] Such lignin material may be used for example in phenol formaldehyde and epoxy resin applications, in composites, rubber, dispersants, antioxidants and hot-melt adhesives. S [0043] It is to be understood that the embodiments of the invention disclosed are not N limited to the particular structures, process steps, or materials disclosed herein, but are - extended to eguivalents thereof as would be recognized by those ordinarily skilled in the z relevant arts. It should also be understood that terminology employed herein is used for a © the purpose of describing particular embodiments only and is not intended to be limiting.

O 3 [0044] 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. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0045] 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 unigue member. Thus, no individual member of such list should be construed as a de facto eguivalent 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 eguivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0046] 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.

ES [0047] While the forgoing examples are illustrative of the principles of the present N invention in one or more particular applications, it will be apparent to those of ordinary 2 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 z principles and concepts of the invention. Accordingly, it is not intended that the invention XQ be limited, except as by the claims set forth below.

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O = [0048] The verbs “to comprise” and “to include” are used in this document as open N limitations that neither exclude nor reguire 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", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0049] At least some embodiments of the present invention find industrial application in generating highly reactive or functional lignin, which makes the lignin material more suitable for several industrial applications, such as in manufacturing PF and epoxy resins, composites, dispersants, antioxidants, hot melt adhesives, rubber and plastic products, and metal chelation e.g. in waste water treatment. Alternatively, the lignin can be used as a raw material in activated carbon manufacture, or for other carbonized products.

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EXAMPLES EXAMPLE 1 — GENERAL METHOD Raw material - Black liquor from softwood and hardwood kraft pulping process - Dry content of the raw material: 10-50 wt-%, Trials done at between 20 wt- % and 40 wt-% Method - Temperature of 200 to 250°C - Residence time 1 h or lower - Self-generated pressure 15-40 bar - pH alkaline, i.e. above 9 - Product purification after the activation and precipitation: the lignin material is purified by acidic washing In this example, black liquor from softwood and hardwood kraft pulping processes having dry content of 20-40 wt-% was placed into a reactor and pH was adjusted between 9-13 using CO; as a pH lowering agent.

Then the black liquor was thermally treated in the temperature of from 200 or above 200 to 220 °C under pressures between 15-40 bars for 1 hour or less.

Then the activated and precipitated lignin was separated from the remaining liquid in a centrifuge.

The separated lignin was purified using acidic washing and dried.

Table 1 shows the amounts of different phenolic hydroxyl group species (mmol/g) in o softwood (SW) and hardwood (HW) lignin samples after the thermal treatment determined O by ”P NMR.

Significantly lower amount of methoxylated guaiacyl units and higher N content of non-methoxylated catechol and p-hydroxyphenyl type units was detected I compared to a to typical industrial softwood and hardwood kraft lignins recovered by E traditional acidic precipitation when thermal treatment was performed at 220*C, showing © the activating effect of the method.

Total content of phenolic hydroxyl and carboxylic acid S groups was also higher, whereas the content of aliphatic hydroxyl groups was lower.

The = performance was similar for black liquors (BL) originating from different pulp mills - regardless of the wood species (SW-BL1, SW-BL2, HW-BL), and also when process was scaled-up from laboratory to pilot. However, at temperatures lower than 200°C the activating effect was not detected. Table 1. mmol/g Aliphatic Carboxylic Condensed Guaiacyl Catechols p-OH- Phenolic Total %0CH39 OH acid (+ syringyl) phenyl OH OH Softwood SW-BLI- 220C 0.9 0.7 2.4 1.2 1.2 0.7 SW-BL2- 220C-Batchl 0.8 0.8 2.5 1.1 1.6 1.2 SW-BL2- 220C-Batch2 0.8 0.8 22 1.0 1.4 0.8 SW-BL2- 220C-Batch3 0.7 0.8 2.7 0.9 1.9 1.3 SW-BL2- 220C-Pilot 0.7 0.8 2.5 1 1.8 1.3 SW-BL2- 200C 0.6 0.4 0.9 0.3 0.4 0.2 1.9 2.8 Reference lignins: commercial 1.7 0.4 2.0 2.3 000 02 — 44 6.5 12.9 lignin Indulin AT” 2.0 0.2 1.6 23 0.3 43 7.6 14.6 Hardwood HW-BL-220C 0.7 0.8 3.8 0.6 1.5 0.8 Reference lignin: HW KL» 1.5 0.6 24 0.5 0.3 0.2 3.4 5.5 17.4 Kraft Lignin” — 09 0.2 2.8 3.8 *Beis S H (2010) Fast pyrolysis of lignin. BioResources 5(3) 1408-1424 9) Hardwood kraft lignin precipitated from black liquor at pH 2.5 with hydrochloric acid 9 All values are measured according to Pregl. Table 2 shows the average molar mass values of softwood and hardwood lignins S determined by SEC in 0.1M NaOH relative to the polystyrene sulphonate standards.

O N Results show that the polymeric nature of lignin is retained. Softwood black liguor samples

N N SW-BL2-Batch2 and SW-BL2-Batch3 show that the molar mass of lignin can be varied by T selection of process conditions in addition to the activating effect. = a x Table 2.

O 3 ee © Mn MW PD S - Oo ooo ooo oo N Softwood SW-BLI 1800 3100 SW-BL2-Batchl 2100 3700

SW-BL2-Batch2 1900 3500 SW-BL2-Batch3 2400 4200 1.7 SW-BL2-Pilot 2100 3600 HW-BL 2000 2900 Reference lignins: Commercial lignin 2290 4450 1.9 Indulin AT ” 1580 3410 22 Hardwood HW KL’ 1260 2310 1.8 ” J. Ropponen, L. Räsänen, S. Rovio, T. Ohra-aho, T. Liitiä, H. Mikkonen, D. van de Pas, T.

Tamminen, Solvent extraction as a means of preparing homogenous lignin fraction. Holzforschung 65 (2011), 543-549.

9 Hardwood kraft lignin precipitated from black liquor at pH 2.5 with hydrochloric acid EXAMPLE 2 — VISCOSITY DEVELOPMENT IN PHENOL FORMALDEHYDE

RESIN SYNTHESIS PF resin synthesis were performed using 100% phenol (PF Ref), and substituting 50% phenol with commercial softwood kraft lignin or thermally separated and activated lignins.

Formaldehyde/phenol ratio of 2 and NaOH/phenol ratio of 0.55 was used according to Danielson et al (1998). For the lignin part, formaldehyde dosage was calculated 1:1 according to the reactive functionalities detected by *'P NMR. After complete dissolution N of lignin into alkali, the formaldehyde was added slowly at 55-60 °C. After that the N reaction temperature was increased to 80°C for the actual condensation phase. The reaction n was terminated when the target viscosity of 350-450 cP was reached. E FIGURE 3 illustrates the viscosity development in PF (phenol formaldehyde) resin co synthesis. As shown in the Figure, the viscosity increase of thermally separated and 3 activated lignin during resin synthesis were faster or slower compared to the commercial 2 reference kraft lignin separated by acid precipitation depending on used separation protocol. This shows that the resin synthesis rate can be adjusted by lignin separation conditions making it easier to control durig resin synthesis, without affecting the resin reactivity. Both the thermally separated and activated lignins have higher curing rate at constant viscosity, as shown in Example 3. Thus, by variable lignin separation conditions, the viscosity increase during resin synthesis can be reduced without loosing the reactivity, making the resin synthesis easier to control. EXAMPLE 3: RESIN CURING AT HIGH PHENOL SUBSTITUTION LEVELS

ACCORDING TO THE GEL TIMES PF resin syntheses were performed by substituting 50%, 70% and 90% of phenol with lignin. Commercial softwood kraft lignin was compared with the thermally separated and activated softwood lignins . Formaldehyde/phenol ratio of 2 and NaOH/phenol ratio of

0.55 was used according to Danielson et al (1998). For the lignin part, formaldehyde dosage was calculated 1:1 according to the reactive functionalities detected by *'P NMR. After complete dissolution of lignin into alkali, the formaldehyde was slowly added at 55- 60 °C. After that the reaction temperature was increased to 80°C for the actual condensation phase. The reaction was terminated when the target viscosity of 350-450 cP was reached. The curing rate of resins was evaluated according to gel times. An in-house method was used, where a glass test tube with 5 g of the resin was immersed in water bath at 100°C and the resin was stirred with a glass rod until the tube was lifted with the rod. FIGURE 4 illustrates resin curing at high phenol substitution levels of 50-90% according to the gel times. As shown in the Figure, all thermally separated and activated lignins had o shorter gel times at 50% replacement level regardless of the separation conditions used, or O origin of black liguor, indicating in all cases faster curing rate compared to the acid N precipitated reference lignins. Better reactivity of thermally separated and activated lignins - was even more emphasised at higher phenol substitution level of 70% and 90%. The curing z rate of reference lignins was significantly reduced at 70% and 90% substitution level N unlike with the thermally activated lignin. :

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CITATION LIST Patent Literature: EP 1794363 EP 2591166 EP 3030598 EP 3036247WO 2012/091906 WO02016/020383 Non Patent Literature: Beis, SH, Mukkamala, S., Hill, N., Joseph, J., Baker, C., Jensen, B., Stemmler, EA, Wheeler, M.C., Frederick, B. G., van Heiningen, A., Berg, A.G., DeSisto W.J., 2010, Fast pyrolysis of lignin. BioResources 5(3) 1408-1424 Danielson & Simonson, 1998, Kraft lignin in phenol formaldehyde resin. Part 1. Partial replacement of phenol by kraft lignin in phenol formaldehyde adhesives for plywood J. Adhesion Sci. Technol., Vol. 12(9), 923-939. Ropponen, J., Räsänen, L., Rovio, S., Ohra-aho, T., Liitiä, T., Mikkonen, H., van de Pas, D., Tamminen, T., 2011, Solvent extraction as a means of preparing homogenous lignin fraction. Holzforschung 65, 543-549 Tomani P., 2010, The LignoBoost process, Cellulose Chem. Technol., 44 (1-3), pp. 53-58.

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Claims (12)

CLAIMS:

1. A method for activating and recovering lignin from alkaline lignin containing feedstock by a thermal treatment, characterized in that the method comprises — providing a feedstock having a pH above 9, — carrying out a pH adjustment to a level of 11-13, — carrying out a thermal treatment of the feedstock having said pH 11-13, by applying temperature within the range from >200 to 250 °C and a retention time of 1h or less, in order to cause a simultaneous activation and precipitation of lignin, avoiding carbonization and minimizing condensation, providing an activated lignin fraction, — precipitating further portion of lignin with further pH adjustment, and — separating the lignin material from the filtrate before or after optional pH adjustment by acid.

2. The method of claim 1, characterized in that the alkaline lignin containing feedstock is from alkaline pulping process.

3. The method of claim 1 or 2, characterized in that the alkaline lignin containing feedstock is kraft black liquor.

4. The method of any preceding claims, characterized in that a pH adjustment is carried out before, during or after the thermal treatment, to a level of 9 or more, preferably a level of 11-13. © N

5. The method of any preceding claims, characterized in that the dry content of the 3 alkaline lignin containing feedstock during the activation and precipitation step is between S 10 and 50 wt-%, preferably between 20 and 40 wt-%.

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6. The method of any preceding claims, characterized by applying a temperature of 3 between 200-250 °C, and most suitably 210-240 °C during the thermal step. N

7. The method of any preceding claims, characterized by operating at a pressure between 15 and 40 bars, typically a self-generated pressure.

8. The method of any preceding claims, characterized by operating the thermal step using a retention time of 0.05—1 hours, preferably 0.1-1 hours, and particularly less than 1 hour.

9. The method of any preceding claims, characterized in that the thermal treatment step is followed by a step of treating at least a main fraction of the filtrate, or of the thermally treated feedstock, before recovery of the filtrate, by pH adjustment to a pH level of 9-10, to precipitate a further portion of lignin.

10. The method of claim 9, characterized by adjusting the pH by using an acid addition, preferably addition of carbon dioxide (CO,), , carbonic acid, acidic exhaust gas, sulfuric acid, hydrochloric acid, nitric acid, citric acid or acetic acid, more preferably carbon dioxide, acidic exhaust gas or sulphuric acid and most suitable carbon dioxide

11. A lignin material having been produced using the method of any preceding claims.

12. Use of the lignin material according to claim 11 in thermoset resins, tyres and rubber products, plastic products, carbonized products, and in dispersant, surfactant, chelant and antioxidant applications as well as in hot melt adhesives.

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