Method for producing crosslinked lignin having a high specific surface area, crosslinked lignin, and industrial rubber article or tire containing crosslinked lignin

Abstract

The present invention relates to a method for producing crosslinked lignin in particulate form using hydrothermal treatment of a liquid containing lignin and a crosslinking agent or a precursor thereof, the liquid starting from black liquor, and having an electrical activity of more than 15 mS / cm, preferably in the range of more than 25 mS / cm to 400 mS / cm, and to the crosslinked lignin produced using the method. The present invention further relates to a method for producing crosslinked lignin in particulate form using a liquid containing lignin and a crosslinking agent or a precursor thereof, the liquid having an electrical activity of more than 15 mS / cm, preferably in the range of more than 25 mS / cm to 400 mS / cm, the glass transition temperature Tg of which is at least 160°C, or no glass transition temperature, and a crosslinking temperature of at least 10 mS / cm. 2 The present invention relates to crosslinked lignin particles having an STSA surface area of ​​1000 nm / g, as well as rubber articles, particularly industrial rubber articles or tires, containing the crosslinked lignin particles as a filler.

Description

[Technical Field]

[0001] Lignins derived from hardwoods, softwoods, and annual plants, for example, after extraction / recovery in the form of kraft lignin, lignosulfonates, or hydrolyzed lignin, exhibit high solubility in many polar and alkaline media. Lignins, in particular, exhibit a glass transition, mostly at temperatures between 80°C and 150°C. The microscopic structure of lignin particles changes by softening even at low temperatures. Therefore, lignin-containing materials are usually not stable, but their properties change at high temperatures. Furthermore, the solubility of lignin in polar solvents, such as dioxane and acetone containing 10% water, or in alkaline media, is usually >95% (Sameni et al., BioResources, 2017, 12, pp. 1548-1565; Podschun et al., European Polymer Journal, 2015, 67, pp. 1-11). Due to these and other properties, lignin can only be used to a limited extent in material applications (DE 102013002574 (A1)). [Background technology]

[0002] Hereinafter, lignin is to be understood as the sum of Klason lignin and acid-soluble lignin. Furthermore, the dry mass may contain other organic and inorganic constituents.

[0003] To overcome these drawbacks, it has been proposed to produce stabilized lignin by hydrothermal carbonization or hydrothermal treatment, which is characterized by a softening temperature (glass transition temperature) above 200°C (WO2015018944(A1)). By adjusting the pH value, it is possible to obtain stabilized lignin with a well-defined particle size distribution (WO2015018944(A1)).

[0004] Improved methods have been developed to use lignin as a raw material for producing carbon materials that can be used, for example, as functional fillers in elastomers (WO2017085278(A1)). An essential quality parameter for functional fillers is the external surface area of ​​particulate carbon materials, determined by STSA measurements. Such methods typically involve hydrothermal carbonization of lignin-containing liquids at temperatures between 150°C and 250°C. Because lignin is highly reactive at these temperatures, achieving a high specific surface area requires fine-tuning of the pH, ionic strength, and lignin content of the lignin-containing liquid, as well as the temperature and duration of the hydrothermal carbonization. This is achieved by adjusting the pH to within the alkaline range, typically above 7.

[0005] In the case of such particulate carbon materials, the above opens up the possibility of using materials different from the individual raw lignin materials. Therefore, particulate carbon materials have a low solubility of less than 40% and a specific surface area of ​​5 m 2 / g higher than 200m 2 / g and can therefore be used, for example, as a reinforcing filler in elastomers, completely or partially replacing carbon black.

[0006] The drawback of these methods is the low yield, which is generally between 40% and 60%. A further drawback of these methods is the considerable effort required to adapt the properties of the lignin-containing liquid (pH value, ionic strength, lignin content) to the process parameters of the hydrothermal carbonization (temperature and residence time) in order to achieve a higher specific surface area. 2 To achieve surface areas in the range above 1 / g, the lignin-containing liquid must have a conductivity of less than 25 mS / cm. 2 Surface areas exceeding 10 ...

[0007] To produce fuel from a suspension of dried black liquor and water by hydrothermal carbonization at temperatures between 220 and 280 °C, a known method for increasing the solids yield and lignin conversion is the addition of formaldehyde [Bioressource Technologie 2012, 110, pp. 715-718, Kang et al.]. Kang et al. propose adding 37 g of formaldehyde per 100 g of dry lignin at a 20% solids concentration (100 ml of a 2.8% formaldehyde solution per 25 g of dry matter obtained by drying black liquor with a 30% lignin content relative to dry matter). This allows the conversion of lignin contained in the black liquor to solids to values ​​between 60%-80% and 90%-100%, with the highest value being achieved at temperatures between 220 and 250 °C. This prior art contributes to an improved yield for polymerization between formaldehyde, the solids in the black liquor, and the carbonized product formed from the solids (last paragraph, page 716). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] DE102013002574(A1) [Patent Document 2] WO2015018944(A1) [Patent Document 3] WO2017085278(A1) [Non-patent literature]

[0009] [Non-Patent Document 1] Sameni et al., BioResources, 2017, 12, pp. 1548-1565 [Non-patent document 2] Podschun et al., European Polymer Journal, 2015, 67, pp. 1-11. [Non-patent document 3] https: / / www.tappi.org / content / SARG / T222.pdf Summary of the Invention [Problem to be solved by the invention]

[0010] Disadvantages of this prior art: - high specific dosing of 37 g of formaldehyde per 100 g of lignin, - high ash content of the dry matter used and the products produced therefrom; - Polymerization between formaldehyde, solids in the black liquor and the carbonized products formed from these solids; and - There are limitations regarding the use of the product for fuel applications (see Kang et al.).

[0011] The objective of the present invention is to describe a method that achieves high yields while at the same time resulting in crosslinked lignin suitable for materials applications.

[0012] The object of the present invention is to - a method for reducing the solubility of lignin in alkaline and / or polar media, - a method for increasing or eliminating the glass transition temperature of lignin; - a method that results in a stabilized crosslinked lignin with advantageous particle properties; and - A method with high yield The purpose is to stipulate the following.

[0013] The objective is in particular to provide high specific surface areas, e.g., >20 m 2 / g, preferably >30m 2 The objective of the present invention was to provide a method for producing lignin particles with a BET surface area of ​​1000 nm / g, or a corresponding STSA surface area, which method allows for simplified processing of black liquor as a starting material. [Means for solving the problem]

[0014] Surprisingly, the object is a method for producing crosslinked lignin in dissolved particulate form, said method comprising the following steps: a) providing a black liquor having a dry matter content of 5 to 50% by mass; b) containing lignin and at least one crosslinking agent and / or one precursor of a crosslinking agent, and having the following characteristics: - dry matter content of 5-25% by mass, - ash content, based on dry mass, of 10 to 45% by mass; a pH value greater than 6.5 and less than 10, preferably greater than 7 and less than 10, more preferably greater than 7.5 and less than 10; - Conductivity over 15mS / cm to 400mS / cm from the black liquor, producing a liquid having i) mixing black liquor with an acid and / or acid gas to reduce the pH value; ii) mixing the black liquor or a product derived therefrom with at least one cross-linking agent and / or a precursor of the cross-linking agent; iii) optionally adding liquid to reduce the dry matter content; and c) hydrothermally treating the liquid produced in step b), which contains lignin and at least one crosslinking agent and / or one precursor of the crosslinking agent, at a temperature in the range of 150°C to 270°C to form crosslinked lignin particles in the liquid; d) separating the liquid from the crosslinked lignin particles formed in step c); e) washing the separated cross-linked lignin particles with a washing medium; This can be solved by a method comprising:

[0015] Preferably, the liquid separated in step d) and optionally the spent washing medium obtained in step e) are fed to a treatment plant for recovering liquor and / or energy from the components.

[0016] Another object of the present invention was to provide better crosslinked and in particular better stabilized lignin, in particular lignin particles, which are particularly suitable as improved, crosslinked and stabilized filler for rubber articles, in particular industrial rubber articles or tires.

[0017] The incorporation of the lignin particles according to the invention as a filler into rubber articles based on natural and synthetic rubber, such as industrial rubber articles or tires, is intended to improve the properties of the rubber articles, in particular the following specific properties: - Specific extensibility under tension - Low loss factor during dynamic deformation - High dynamic stiffness - Low compression set for improved sealing performance - Good electrical insulation behavior due to particle morphology - Low component mass - High rigidity and small deformation - Minimization of polycyclic aromatic compounds.

[0018] In this application, all percentages stated refer to mass unless otherwise specified. Generally, the liquid can be, for example, a solution or a suspension. DETAILED DESCRIPTION OF THE INVENTION

[0019] Black liquor According to step a) of the method of the present invention, black liquor is provided. In particular, black liquor is a lignin-containing liquid that is generated as wastewater in alkaline fractionation processes of woody biomass, such as the Kraft process, pulp production, or sodium hydroxide processes. The pH value of black liquor is in the alkaline range, usually between 12 and 14. In addition to lignin, black liquor may contain organic or inorganic components. Typically, the lignin proportion in the organic dry mass of black liquor is greater than 50%, in particular greater than 60% or even greater than 70%, thus significantly exceeding the 15% to 35% lignin proportion in woody biomass. Hereinafter, the lignin content is understood to be the sum of Klason lignin and acid-soluble lignin.

[0020] In addition, black liquor, which is generated as waste liquor from alkaline pulping in pulp production, is further concentrated in the evaporator. In the process according to the invention, the black liquor can be taken from or provided by an evaporation plant.

[0021] The black liquor used in the process has in particular a dry matter content of 5 to 50% by weight, preferably 5 to 40% by weight, more preferably 10 to 40% by weight, relative to the total weight of the black liquor.

[0022] The method according to the invention comprises, as step b), producing from the black liquor a liquid containing lignin and at least one crosslinking agent and / or one precursor of the crosslinking agent. The properties of the liquid obtained in step b) are described below.

[0023] The production of liquid from black liquor according to step b) comprises at least the following steps: i) mixing black liquor with an acid and / or acid gas to reduce the pH value; ii) mixing the black liquor or a product derived therefrom with at least one cross-linking agent and / or a precursor of the cross-linking agent; iii) optionally adding liquid to reduce the dry matter content; Includes.

[0024] The black liquor-derived product may be a product obtained by reprocessing the black liquor, for example a solid lignin raw material obtained according to variant b2) described below. Suitable liquids for reducing the dry matter content are all common inorganic solvents, such as water, or organic solvents, such as alcohols, with water being preferred. Suitable embodiments of the acid and / or acid gas are the same as those described below for the specific variants b1) and b2). Suitable embodiments of the crosslinker and / or precursor of the crosslinker are also described below.

[0025] The formation of liquid from black liquor according to step b) can preferably be carried out via step b1) or alternatively step b2).

[0026] In alternative embodiment b1), a liquid containing lignin and at least one crosslinking agent and / or one precursor of a crosslinking agent is obtained from black liquor by mixing the black liquor with i) an acid and / or an acid gas to reduce the pH value, and ii) at least one crosslinking agent and / or one precursor of a crosslinking agent.

[0027] The acid for mixing in step b1) may be, for example, an inorganic acid such as sulfuric acid, or an organic acid such as acetic acid or formic acid, and the acid may be added as a technical grade acid having a moisture content of less than 10% by weight, preferably less than 5% by weight, or as an aqueous acid. The acid gas for mixing in step b1) may be selected from, for example, CO2, H2S, or a mixture of CO2 and H2S. Advantageously, the acid gas is simply introduced into the black liquor.

[0028] The order in which the components are added to one another to obtain a liquid containing lignin and a crosslinking agent and / or its precursor is not limited. The components can be mixed together simultaneously, sequentially, and / or partially. For proper mixing, the liquid may be moved, for example, by stirring or circulating the liquid.

[0029] In this variant of the method, the dry matter content of the black liquor provided in step a) is preferably more than 10% and preferably less than 30%, more preferably less than 25%. If in step a) a black liquor is provided with a dry matter content that exceeds the preferred range, in step b1) further liquid can be added to the black liquor to adjust the dry matter content of the liquid.

[0030] In alternative embodiment b2), the liquid containing lignin and at least one crosslinking agent and / or one precursor of a crosslinking agent is subjected to the following steps: - mixing acid or acid gas with the black liquor to reduce the pH value and form solid lignin raw material in the black liquor; - separating the solid lignin feedstock from the black liquor; - mixing the separated solid lignin feedstock with i) a liquid and ii) at least one cross-linking agent and / or a precursor of a cross-linking agent, optionally with additional acid and / or acid gas to further reduce the pH value. It is produced from black liquor by

[0031] The admixing acid used in step b2) for mixing with the black liquor and / or optionally further reducing the pH can be, for example, an inorganic acid such as sulfuric acid, or an organic acid such as acetic acid or formic acid, and the acid can be added as a technical grade acid having a moisture content of less than 10% by weight, preferably less than 5% by weight, or as an aqueous acid. The admixing acid gas used in step b2) for mixing with the black liquor and / or optionally further reducing the pH can be selected from, for example, CO2, HS, or a mixture of CO2 and HS. Advantageously, the acid gas is simply introduced into the black liquor or liquid to reduce the pH.

[0032] The pH of the black liquor is lowered, preferably to a pH in the range of 9.5 to 10.5, by adding an acid to the black liquor or by introducing an acid gas. This causes a solid lignin raw material to form or precipitate in the black liquor. The precipitated solid lignin raw material is separated from the black liquor or its liquid components, preferably by filtration. The dry matter of the separated solid lignin raw material may contain further organic and / or inorganic components in addition to lignin. The amount of lignin in the dry matter is, for example, at least 60%, preferably at least 70%, although the amount of lignin in the dry matter may be, for example, up to 90%.

[0033] The separated solid lignin feedstock is mixed with i) a liquid and ii) at least one crosslinker and / or a precursor of the crosslinker, optionally with an acid and / or an acid gas to further lower the pH, thereby forming a liquid containing lignin and at least one crosslinker and / or a precursor of one of the crosslinkers from the black liquor.

[0034] The order in which the components are added to one another to obtain a liquid containing lignin and a crosslinking agent and / or its precursor is not limited. The components can be mixed together simultaneously, sequentially, and / or partially. For proper mixing, the liquid may be moved, for example, by stirring or circulating the liquid.

[0035] The liquid added to the separated solid lignin feedstock may be an inorganic solvent, such as water, and / or an organic solvent, such as an alcohol, for example ethanol, with the liquid preferably being water.

[0036] In an optional preferred embodiment of variant b2), an acid and / or acid gas is added to and mixed with the added liquid, for example, water, to further lower the pH value. When this optional step is performed, the liquid, such as water, the acid, such as sulfuric acid or acetic acid, and / or the acid gas may be mixed separately with the solid lignin feedstock. However, it is also possible to first mix the liquid, such as water, the acid, such as sulfuric acid or acetic acid, or the acid gas, and then mix the mixture with the solid lignin feedstock, or to add a portion of the liquid, such as water, to the solid lignin feedstock and mix another portion of the liquid, such as water, and then mix the acid, such as sulfuric acid or acetic acid, or the acid gas separately as an aqueous acid.

[0037] In a particularly preferred embodiment, solid lignin raw material is recovered from black liquor, for example as a first partial step in the LignoBoost process. In this process, lignin is precipitated by acidification with CO (introduction of CO into black liquor). In the following, precipitation is intended to mean a significant conversion of more than 35%, preferably more than 40%, particularly preferably more than 45% of the lignin dissolved in the black liquor. The precipitated lignin can be filtered off, and the lignin-containing solids can be recovered in this way.

[0038] By introducing CO2 into the black liquor, the pH value in the black liquor reaches 9.5 to 10.5, which is sufficient for lignin precipitation.

[0039] The filtrate of the CO2 lignin dehydration is therefore alkaline and can be optionally returned to the liquid recovery of the pulp mill. The ash (approximately 15-25%) contained in the CO2 lignin, which arises after step c) in the form of dissolved ash, can be separated from the crosslinked lignin particles together with the liquid for the most part and then returned to the liquid recovery of the pulp mill as alkaline filtrate. Dissolved ash is understood here in particular as inorganic salts dissolved in the liquid.

[0040] In contrast, the filtrate obtained from acidification with H2SO4 as a further substep of the LignoBoost process is acidic and must be neutralized after being returned to the pulp mill. Furthermore, any introduced sulfur must be separated within the pulp mill. Also, the recovery of cross-linked lignin particles from lignin obtained from the LignoBoost process requires the addition of NaOH to raise the pH from 2 to >7.

[0041] Therefore, the use of lignin-containing solids precipitated from black liquor in the presence of CO as starting material for the present process is advantageous compared to other lignin solids, such as lignin obtained from the LignoBoost process. Surprisingly, it has been found that such raw materials are suitable for the production of crosslinked lignin particles when a crosslinker is added in step b), and the unique properties of the liquor containing lignin and at least one crosslinker and / or one precursor of the crosslinker are tailored.

[0042] In the following, further details are given for the liquid containing lignin and at least one crosslinking agent and / or one precursor of a crosslinking agent obtained from black liquor in step b), but the details equally apply to the formation of the liquid both via step b1) and alternative step b2), unless explicitly stated otherwise.

[0043] As indicated above, the acid for mixing in step b) (more generally in step i) or b1) or b2)) may be, for example, an inorganic acid such as sulfuric acid, or an organic acid such as acetic acid or formic acid. The acid gas for mixing in step b)(b1) or b2)) may be, for example, selected from CO, HS, or a mixture of CO and HS.

[0044] The lignin in the liquid obtained in step b) contains lignin that can be determined as Klason lignin and acid-soluble lignin. Klason lignin is described as an analytical measurement variable after treatment in 72% H2SO4 according to Tappi T 222 om-02 (https: / / www.tappi.org / content / SARG / T222.pdf) and is the product quantified in this analytical method.

[0045] Lignin provides functional groups that allow for cross-linking, for example, phenolic aromatic, aromatic and aliphatic hydroxy and / or carboxy groups as cross-linkable units suitable for reaction with a cross-linking agent.

[0046] Preferably, at least a portion of the lignin is already dissolved in the liquid produced in step b) and / or dissolves during heating of the liquid produced in step b) to the temperature for the hydrothermal treatment. The proportion of dissolved lignin is usually increased by heating the liquid. Such heating is required in either case to hydrothermally treat the liquid.

[0047] In addition to the dissolved lignin, undissolved lignin may also be present in dispersed form in the liquid obtained in step b). Thus, the method does not require that the entire lignin be present in dissolved form in the liquid. Advantageously, however, more than 50%, particularly preferably more than 60%, even more preferably more than 70%, particularly preferably more than 80%, in particular more than 90%, and even more particularly preferably more than 95% of the lignin is dissolved in the liquid before the liquid is subjected to the hydrothermal treatment in step c).

[0048] Furthermore, in step b) (more generally step ii) or b1) or b2)), at least one crosslinker and / or one precursor of a crosslinker is admixed so that the liquid obtained in step b) contains at least one crosslinker and / or one precursor thereof. A precursor of a crosslinker is understood here to be a compound which is not itself a crosslinker but which forms the crosslinker in situ before or during the hydrothermal treatment in step c), for example by a pyrolysis reaction. The following details regarding the crosslinker also apply, where applicable, to crosslinkers formed in situ from a precursor.

[0049] The cross-linking agent has at least one functional group capable of reacting with the cross-linkable groups of the lignin, and preferably has at least one functional group selected from aldehyde, carboxylic acid anhydride, epoxide, hydroxyl, and isocyanate groups, or combinations thereof.

[0050] If the crosslinker has a functional group, such as an aldehyde, anhydride, or epoxide group, that can react with two crosslinkable groups of lignin during the reaction, one such functional group is sufficient. Alternatively, the crosslinker has at least two functional groups, such as hydroxyl or isocyanate groups, that can react with the crosslinkable groups of lignin.

[0051] In a particularly preferred embodiment, the at least one crosslinking agent is selected from at least one of aldehydes, epoxides, acid anhydrides, polyisocyanates, and polyols, and in this case, the at least one crosslinking agent is preferably selected from aldehydes, particularly preferably formaldehyde, furfural, and sugar aldehydes. The polyisocyanate is a compound having at least two isocyanate groups, and preferably a diisocyanate or triisocyanate. The polyol is a compound having at least two hydroxyl groups, and preferably a diol or triol.

[0052] If a difunctional crosslinker is used, two moles of crosslinkable units are available per mole of difunctional crosslinker. Thus, if a trifunctional crosslinker is used, three moles of crosslinkable units are available per mole of trifunctional crosslinker, etc. It should be noted that even though the crosslinker is multifunctional, in many cases only a portion of the available groups react, as reactivity decreases as groups become unreactive, partly due to steric hindrance and partly due to charge transfer.

[0053] In the following description, the crosslinkable unit of the crosslinker refers to a unit that can react with a crosslinkable unit of lignin. Thus, a functional group that can react with two crosslinkable groups of lignin during the reaction, such as an aldehyde, anhydride or epoxide group, counts as two crosslinkable units.

[0054] Preferably, the dosage of crosslinking agent in the liquid obtained in step b) is carried out so that per mole of crosslinkable units of lignin used, at most 4 mol, preferably at most 3 mol, even more preferably at most 2.5 mol, particularly preferably at most 2 mol, more preferably at most 1.75 mol, in particular at most 1.5 mol of crosslinking agent crosslinkable units are used.

[0055] Preferably, the dosage of crosslinking agent in the liquid obtained in step b) is such that there are at least 0.2 mol, preferably at least 0.5 mol, more preferably at least 0.75 mol, even more preferably at least 1 mol, particularly preferably at least 1.1 mol, and especially at least 1.15 mol of crosslinking agent per mole of crosslinkable unit of the lignin used. Preferably, the dosage of crosslinking agent in the liquid obtained in step b) is such that there are at least 0.2 mol, preferably at least 0.5 mol, more preferably at least 0.75 mol, even more preferably at least 1 mol, particularly preferably at least 1.1 mol, and especially at least 1.15 mol of crosslinking agent per mole of crosslinkable unit of the lignin used. Preferably, the dosage of crosslinking agent in the liquid obtained in step b) is in the range of 0.2 mol to 4 mol, more preferably 0.5 mol to 3 mol, and especially preferably 1 to 2 mol of crosslinking agent per mole of crosslinkable unit of the lignin used.

[0056] The crosslinking agent can react with the free ortho- and / or para-positions of the phenolic rings (phenolic guaiacyl groups and p-hydroxyphenyl groups) of lignin. Suitable crosslinking agents for the reaction with the free ortho- and para-positions of the phenolic rings are, for example, aldehydes such as formaldehyde, furfural, 5-hydroxymethylfurfural (5-HMF), hydroxybenzaldehyde, vanillin, syringaldehyde, piperonal, glyoxal, glutaraldehyde, or sugar aldehydes. Preferred crosslinking agents for the reaction with the phenolic rings are formaldehyde, furfural, and sugar aldehydes (ethanals / propanals), such as glyceraldehyde and glycolaldehyde.

[0057] Furthermore, crosslinkers can react with aromatic and aliphatic OH groups in lignin (phenolic guaiacyl groups, p-hydroxyphenyl groups, syringyl groups). For this purpose, bifunctional compounds, such as glycidyl ethers, isocyanate groups, such as diisocyanates or diisocyanate oligomers, or acid anhydrides, and also polyfunctional compounds, can be preferably used. Preferred crosslinkers for reaction with aromatic and aliphatic OH groups are polyisocyanates, especially diisocyanates or triisocyanates, and acid anhydrides.

[0058] Furthermore, the crosslinking agent can also react with carboxyl groups. For this purpose, for example, diols and triols may be applied. Preferred crosslinking agents for reaction with carboxyl groups are diols.

[0059] Furthermore, the crosslinking agent can react with each of the phenolic rings, aromatic and aliphatic OH groups and carboxyl groups. For this purpose, for example, bifunctional compounds, and also polyfunctional compounds, having at least two of the above-mentioned crosslinkable functional groups may be used.

[0060] When using crosslinkers that react with phenolic rings, the crosslinkable units in the lignin used are understood to mean phenolic guaiacyl groups and p-hydroxyphenyl groups. The concentration of crosslinkable units (mmol / g) is determined, for example, by P NMR spectroscopy (Podschun et al., European Polymer Journal, 2015, 67, pp. 1-11), where the guaiacyl group contains one crosslinkable unit and the p-hydroxyphenyl group contains two crosslinkable units.

[0061] When using crosslinking agents that react with aromatic and aliphatic OH groups, the crosslinkable units in the lignin used are understood to mean all of the aromatic and aliphatic OH groups. The concentration of crosslinkable units (mmol / g) is determined, for example, by P NMR spectroscopy, where one OH group corresponds to one crosslinkable unit.

[0062] When using crosslinking agents that react with carboxyl groups, the crosslinkable units in the lignin used are understood to mean all of the carboxyl groups. The concentration of crosslinkable units (mmol / g) is determined, for example, by 31P NMR spectroscopy, where one carboxyl group corresponds to one crosslinkable unit.

[0063] Preferably, the amount of crosslinker in the liquid obtained in step b) is at most 35 g / 100 g lignin, preferably at most 30 g / 100 g lignin, particularly preferably at most 25 g / 100 g lignin.

[0064] Preferably, the amount of crosslinking agent, preferably formaldehyde, in the liquid obtained in step b) is at most 25 g / 100 g lignin, preferably at most 20 g / 100 g lignin, particularly preferably at most 15 g / 100 g lignin, and especially at most 12 g / 100 g lignin. The amount of crosslinking agent, preferably formaldehyde, added may therefore be in the range of 1 to 20 g / 100 g lignin, preferably 5 to 15 g / 100 g lignin, particularly preferably 6 to 12 g / 100 g lignin. It is also possible instead to add all or part of a precursor of the crosslinking agent, such as formaldehyde or another aldehyde, to the liquid, from which the actual crosslinking agent is formed in situ.

[0065] By adjusting the amount of cross-linking agent, the specific surface area of ​​the resulting cross-linked lignin particles can be significantly increased.

[0066] Advantageously, as an alternative to or in addition to the crosslinking agent, a precursor to the crosslinking agent can be used that generates the crosslinker in situ before and / or during the hydrothermal treatment. The advantage of generating the crosslinker in situ is that the amount of added crosslinker can be reduced or eliminated altogether.

[0067] Advantageous examples of suitable precursors of cross-linking agents are carbohydrates, preferably cellulose, hemicellulose, or glucose, or lignin, each of which may be dispersed or dissolved in a liquid. When carbohydrates, preferably cellulose, hemicellulose, or glucose, are used as precursors, aldehydes, preferably glyceraldehyde or glycolaldehyde, may be generated in situ from these carbohydrates in the process of the present invention, which then act as cross-linking agents. When lignin is used as precursor, in particular aldehydes, preferably methanediol or glycolaldehyde, may be generated in situ from lignin in the process of the present invention, which then act as cross-linking agents.

[0068] The proportion of lignin in the total mass of the lignin-containing liquid obtained in step b) is advantageously between 3% and 25%, preferably less than 20%, particularly preferably less than 18%, relative to the mass of the liquid obtained in step b) without crosslinking agent and / or precursors of the crosslinking agent. In a preferred embodiment, the amount of lignin in the liquid obtained in step b) is in the range of 3 to 25%, preferably 7 to 18%, by mass, relative to the mass of the liquid obtained in step b) without crosslinking agent and / or precursors of the crosslinking agent.

[0069] Dry matter content and ash content of the liquid obtained in step b) The liquid obtained in step b) has a dry matter content in the range of 5 to 25% by mass, and an ash content in the liquid obtained in step b) in the range of 10 to 45% by mass, based on the dry mass.

[0070] The dry matter content can be determined by thermogravimetric determination at a temperature of 105° C. A suitable instrument is, for example, the Sartorius MA35 humidity analyzer. The humidity or moisture content measured must usually be converted to the dry matter content, e.g., dry matter content = 100 - moisture content (respectively in % by mass).

[0071] The ash content is determined in accordance with DIN 51719 and the ashing temperature is set at 915°C.

[0072] pH value of the liquid obtained in step b) The liquid obtained in step b) (or b1) or b2)) containing lignin and at least one crosslinker and / or one precursor of a crosslinker has a pH value in the range of above 6.5 and below 10, preferably above 7 and below 10, more preferably above 7.5 and below 10, preferably between 8 and 9.5, and particularly preferably between 8 and 9. Experiments have shown that to obtain a high specific surface area, a pH value of about 8.5 to 9 is most suitable, while pH values ​​below 6.5 or below 7.5 or significantly above 9 significantly reduce the achievable BET and STSA surface areas.

[0073] The adjustment of these pH values ​​is carried out in step b1) by adding an acid and / or an acid gas to the black liquor to lower the pH, or in step b2) by adding an acid and / or an acid gas to the black liquor and optionally mixing further acid and / or further acid gas with the separated solid lignin raw material.

[0074] The pH of the liquid obtained in step b) can be determined directly after the production of the liquid in step b) and in particular refers to the pH before the hydrothermal treatment in step c). The pH is determined at room temperature (23°C).

[0075] In a preferred embodiment, an acid or acid gas is mixed with the solid lignin feedstock separated in step b2) to further lower the pH. If a separate acid is added, the amount of acid, e.g., sulfuric acid, acetic acid, or formic acid, mixed to form the liquid produced in step b) is preferably in the range of 2 to 15 g, preferably 5 to 12 g, per 100 g of lignin in the liquid.

[0076] Conductivity of the liquid obtained in step b) The liquid containing lignin and at least one crosslinker and / or one precursor of a crosslinker produced in step b) according to b1) or b2) exhibits a conductivity in the range of more than 15 mS / cm to 400 mS / cm. Despite the high electrical conductivity of the liquid, the method according to the invention allows for the production of lignin particles with a high specific surface area.

[0077] In a preferred embodiment, the liquid obtained in step b) has a conductivity of more than 25 mS / cm and / or at most 100 mS / cm, preferably at most 80 mS / cm, more preferably at most 60 mS / cm, and particularly preferably at most 40 mS / cm. The conductivity of the liquid obtained in step b) may be preferably greater than 25 mS / cm to 200 mS / cm, preferably greater than 25 mS / cm to 80 mS / cm, or greater than 25 mS / cm to less than 60 mS / cm, or in the range of 25 to 40 mS / cm. However, it may also be, for example, in the range of 30 mS / cm to 80 mS / cm, or 40 to 60 mS / cm.

[0078] Here, conductivity is used as an indicator of the amount of ions contained in the liquid. This refers to the conductivity of the liquid at 23°C and can be determined with a common conductivity meter, such as a pH meter designed for this purpose. The conductivity was determined with the measuring probe of a PCE-PH D1 device (a pH meter manufactured by PCE Instruments) (the conductivity value was determined at 20°C to 25°C). The conductivity of the liquid obtained in step b) can be determined directly after the production of the liquid in step b), in particular before the hydrothermal treatment.

[0079] Hydrothermal treatment The method according to the invention further comprises, as step c), hydrothermal treatment of the liquid obtained in step b) containing lignin and / or at least one crosslinking agent and / or one precursor of a crosslinking agent at a temperature in the range of 150°C to 270°C to form crosslinked lignin particles in the liquid.

[0080] The temperature of the hydrothermal treatment is advantageously below 270°C, preferably below 260°C, more preferably below 250°C, and in some cases below 240°C.

[0081] In an advantageous embodiment, the temperature of the hydrothermal treatment is above 150°C, preferably at least 160°C, even more preferably at least 170°C, preferably above 180°C, more preferably above 190°C, in particular above 200°C, in some cases above 210°C.

[0082] In a preferred embodiment, the hydrothermal treatment is carried out at a temperature in the range of 180°C to 250°C, preferably 210°C to 250°C.

[0083] Advantageously, the duration of the hydrothermal treatment is at least 10 minutes, more preferably at least 30 minutes, particularly preferably at least 45 minutes, even more preferably at least 90 minutes, and / or less than 600 minutes, preferably less than 480 minutes, particularly preferably less than 450 minutes, even more preferably less than 300 minutes, in particular less than 180 minutes, in some cases less than 150 minutes.

[0084] The hydrothermal treatment is carried out under positive pressure. The hydrothermal treatment is preferably carried out in a pressure-resistant vessel, in particular a reactor or an autoclave. The pressure during the hydrothermal treatment is preferably at least 1 bar, more preferably at least 2 bar, and preferably at most 10 bar above the saturated vapor pressure of the lignin-containing liquid.

[0085] During the hydrothermal treatment, the liquid may be kept in motion by stirring or circulating the liquid for proper mixing.

[0086] During the hydrothermal treatment, the cross-linking agent cross-links the lignin, forming cross-linked lignin particles in the solution. Partial reaction of the lignin with the cross-linking agent may also occur when the solution is heated prior to the hydrothermal treatment. The cross-linked lignin particles obtained by the hydrothermal treatment are stabilized lignin particles, as described in detail below.

[0087] Separation of cross-linked lignin particles The method according to the invention further comprises a step d) of separating the crosslinked lignin particles formed in step c) from the liquid.

[0088] For the separation of the formed crosslinked lignin particles from the liquid, all common solid-liquid separation methods may be used. Preferably, the liquid is separated from the particles by filtration or centrifugation. When using filtration or centrifugation, a dry matter content of more than 15%, preferably more than 20%, more preferably more than 25%, particularly preferably more than 30% and preferably less than 60%, preferably less than 55%, more preferably less than 50%, particularly preferably less than 45%, even more preferably less than 40% is preferably achieved. Another possibility for separating the lignin particles is, for example, evaporation of the liquid at elevated temperature and / or reduced pressure.

[0089] Washing of cross-linked lignin particles The method according to the invention further comprises a step e) in which the crosslinked lignin particles separated in step d) are washed with a washing medium or liquor. The separated crosslinked lignin particles may be washed with the washing medium once or several times. In a preferred embodiment, the used washing medium is returned to the evaporation plant for the black liquor.

[0090] In a particularly advantageous embodiment, the pH value of the washing medium used is greater than 4, preferably greater than 6, and less than 10, preferably less than 9. Suitable as washing medium is water, for example tap water, or preferably demineralized water, optionally also containing additives, for example acids or bases.

[0091] Washing removes inorganic compounds from the particles and significantly reduces the ash content of the cross-linked lignin particles, thereby improving the particle properties.

[0092] The washed lignin particles are usually dried, in which case at least a portion of the remaining liquid is removed, preferably by solvent evaporation, for example by heating and / or reducing the pressure. As a final product, dried or dried crosslinked lignin particles are preferably obtained. Preferably, the dry matter content is greater than 90%, more preferably greater than 92%, in particular greater than 95%. In the present invention, dry particles are understood to be particles having a dry matter content of greater than 90%, more preferably greater than 92%, in particular greater than 95%.

[0093] Preferably, the liquid separated in step d) and optionally the spent washing medium obtained in step e) are fed to a treatment plant for recovering liquor and / or energy from the components.

[0094] Optionally returning the liquid separated in step d) and / or the used washing medium from step e) for liquid and / or energy recovery. The liquid separated in step d) and optionally the spent washing medium obtained in step e) are optionally and preferably returned to a reprocessing plant, in particular an evaporation plant for black liquor, for the recovery of liquor and / or energy. The components originate from the used black liquor. The evaporation plant for black liquor is part of the reprocessing plant. Generally, such a reprocessing plant includes, in addition to the evaporation plant, a liquor recovery boiler and a causticizing plant.

[0095] In a preferred embodiment, the black liquor provided in step a) is removed from a black liquor evaporation plant, and the liquid separated in step d) and optionally the spent washing medium obtained in step e) are returned to the evaporation plant at a location downstream of the black liquor extraction point, so as to avoid circulation.

[0096] Heating of the liquid obtained in step b) and any intermediate treatment The heating rate to bring the liquid obtained in step b), containing lignin and at least one crosslinking agent and / or one precursor thereof, to the temperature for the hydrothermal treatment and / or any intermediate treatments described below, is preferably less than 15 Kelvin / min, more preferably less than 10 Kelvin / min, particularly preferably less than 5 Kelvin / min.

[0097] It may be appropriate to keep the liquid obtained in step b) at low temperature for a certain period of time before the hydrothermal treatment (hereinafter referred to as intermediate treatment).

[0098] In this optional intermediate treatment, the liquid obtained in step b) is kept at a temperature of 50°C to less than 150°C, more preferably 60°C to 130°C, particularly preferably 70°C to less than 100°C, for a period of at least 5 minutes, preferably at least 10 minutes, more preferably at least 15 minutes, and less than 300 minutes, more preferably less than 60 minutes, prior to the hydrothermal treatment carried out in step c).

[0099] As already mentioned, during the heating and any intermediate treatment of the liquid obtained in step b), at least part of the lignin, or more of the lignin, may dissolve in the liquid.

[0100] Without wishing to be bound by any theory, it is hypothesized that during heating and any intermediate treatments, a partial reaction of the dissolved lignin with the cross-linking agent also occurs to provide a dissolved modified lignin, where the lignin reacts with the cross-linking agent but is not or only partially cross-linked via the cross-linking agent, i.e., the cross-linking agent molecule is attached to the lignin at one location, but the second attachment of the cross-linking agent molecule to the lignin, if any, is only partial, upon formation of the cross-link.

[0101] By dissolved modified lignin is understood in particular the following: - The aromatic compounds in lignin are further linked mainly via ether bonds. the proportion of para-substituted phenol rings in the total proportion of aromatic rings is greater than 95%, preferably greater than 97%, particularly preferably greater than 99%, and the content of free phenol is less than 200 ppm, preferably less than 100 ppm, more preferably less than 75 ppm, particularly preferably less than 50 ppm. The Klason lignin content is at least 70%, preferably at least 75%, particularly preferably at least 80%, in particular at least 85%.

[0102] The free phenol content is determined according to DIN ISO 8974. The content of Klason lignin is determined as acid-insoluble lignin according to TAPPI T 222. The quantity and quality of phenolic groups is determined by 31P-NMR according to M. Zawadzki, A. Ragauskas (Holzforschung 2001, 55, 3).

[0103] By reacting the lignin dissolved in the liquid with a crosslinking agent during heating and / or in any intermediate treatment, the selectivity of the reaction can be increased and a dissolved modified lignin can be obtained in a targeted manner, which can then be converted into crosslinked lignin particles by hydrothermal treatment. By heating the liquid obtained in step b) at the aforementioned heating rate and / or by any intermediate treatment, the polymerization of the crosslinking agent and lignin, and possibly the formation of carbonized products from the lignin, can be reduced or completely prevented. By converting the dissolved modified lignin into stabilized crosslinked lignin particles in the hydrothermal treatment, it is possible to target and influence the particle properties of the crosslinked or stabilized lignin particles. In this way, it is possible to adjust advantageous particle properties.

[0104] The temperature of any intermediate treatment is advantageously above 50°C, preferably above 60°C, particularly preferably above 70°C, and below 180°C, preferably below 150°C, more preferably below 130°C, particularly preferably below 100°C.

[0105] Advantageously, the average residence time in any intermediate treatment is at least 5 minutes, more preferably at least 10 minutes, even more preferably at least 15 minutes, particularly preferably at least 30 minutes, especially at least 45 minutes, but less than 300 minutes.

[0106] An advantageous combination of time and temperature range for any intermediate treatment is a residence time of at least 15 minutes, preferably at least 20 minutes, more preferably at least 30 minutes, and particularly preferably at least 45 minutes, with a minimum temperature of 50° C. and a maximum temperature of less than 150° C. An alternative advantageous combination of time and temperature range for any intermediate treatment is a minimum temperature of 50° C. and a maximum temperature of less than 130° C., with a residence time of at least 10 minutes, preferably at least 15 minutes, more preferably at least 20 minutes, particularly preferably at least 30 minutes, and especially at least 45 minutes.

[0107] In a preferred embodiment of the optional intermediate treatment, a temperature of 50° C. to less than 150° C. is maintained for a residence time of at least 20 minutes, preferably at least 60 minutes.

[0108] In another preferred embodiment of the optional intermediate treatment, a temperature of 70° C. to less than 130° C. is maintained for a residence time of at least 10 minutes, preferably at least 50 minutes.

[0109] Any intermediate treatment may be carried out at atmospheric pressure or at positive pressure, preferably at positive pressure.

[0110] Cross-linked lignin particles I The method according to the invention produces particulate crosslinked lignin. The lignin obtained by the method according to the invention is therefore in the form of crosslinked lignin particles, and the end product obtained in the process is preferably a powder, in particular a dry powder. They are therefore solid particles that may be present dispersed in a liquid or as a dried powder or dry powder.

[0111] Preferably, the yield of crosslinked lignin particles relative to the lignin used is greater than 60%, preferably greater than 70%, particularly preferably greater than 80%, in particular greater than 85%.

[0112] The crosslinked lignin particles thus obtained are in particular stabilized lignin particles. Stabilization by crosslinking and hydrothermal treatment leads to improved properties, such as an increase in the specific surface area, a decrease in solubility in alkaline solutions, and / or an increase in the glass transition temperature or the complete absence of a measurable glass transition temperature. The resulting crosslinked or stabilized lignin particles preferably exhibit a glass transition temperature of more than 160°C, preferably more than 180°C, particularly preferably more than 200°C, and in particular more than 250°C. Preferably, no glass transition temperature can be measured in the resulting crosslinked lignin particles, i.e., no glass transition temperature exists.

[0113] The glass transition temperature is measured in accordance with DIN 53765 after the dried crosslinked lignin particles are subjected to solid-liquid separation, washed and dried.

[0114] The stabilized lignin particles obtained by the method according to the invention have other advantageous particle properties that enable their use in material applications.

[0115] Preferably, the crosslinked lignin particles obtained by the process have a particle size distribution d50 value (volume average) of less than 500 μm, preferably less than 300 μm, more preferably less than 200 μm, especially less than 100 μm, and particularly preferably less than 50 μm. Preferably, the particle size distribution d50 value (volume average) is greater than 0.5 μm, preferably greater than 1 μm, and particularly preferably greater than 2 μm.

[0116] The particle size distribution of crosslinked stabilized lignin is measured in a suspension containing distilled water by laser diffraction according to ISO 13320. Before and / or after measuring the particle size distribution, the sample to be measured is dispersed ultrasonically until a particle size distribution that remains stable over several measurements is reached. This stability is reached when the individual measurements of a series, e.g., d50, do not differ from each other by more than 5%.

[0117] The resulting cross-linked lignin particles have a length of at least 10 m 2 / g, more preferably at least 20m 2 / g, more preferably at least 30m 2 / g, and even more preferably at least 40m 2 / g, most preferably at least 50m 2 It is particularly preferred that the STSA has a surface area of ​​200 m / g. 2 / g, more preferably less than 180m 2 / g. STSA (Statistical Thickness Surface Area) is a characterization of the external surface area of ​​the resulting lignin particles.

[0118] In a variation of the present crosslinked lignin particles, the STSA surface area is at least 10 m 2 / g~180m 2 / g, preferably at least 20m 2 / g~180m 2 / g, more preferably 30m 2 / g~180m 2 / g, particularly preferably 40m 2 / g~180m 2 / g values ​​are shown.

[0119] Advantageously, the BET surface area of ​​the crosslinked or stabilized lignin differs from the STSA surface area by at most 20%, preferably at most 15%, more preferably at most 10%. The BET surface area is determined by nitrogen adsorption according to Brunauer, Emmett and Teller from the external and internal surface areas as the total surface area.

[0120] The determination of BET surface area and STSA surface area is carried out in accordance with the ASTM D6556-14 standard, however, in contrast to this, the sample preparation / outgassing for measuring STSA and BET is carried out at 150°C in the present invention.

[0121] The crosslinked lignin particles produced by the method according to the invention preferably have an ash content of less than 5% by weight, preferably less than 3% by weight and more than 1% by weight.

[0122] Preferably, the resulting crosslinked lignin particles have only low porosity. Advantageously, the pore volume of the crosslinked or stabilized lignin is < 0.1 cm 3 / g, more preferably < 0.01 cm 3 / g, particularly preferably < 0.005 cm 3 / g. Thus, this crosslinked or stabilized lignin is different from finely pulverized porous materials such as milled bio-based activated carbon powder, which can have a BET surface area of more than 500 m 2 / g and at most a STSA surface area of 10 m 2 / g.

[0123] The resulting crosslinked lignin particles are produced by reaction with formaldehyde and are based on resins in which lignin converted from a gel state to a duromer in solution, for example, has a d50 value of less than 500 μm in particle size distribution or a STSA of more than 10 m 2 / g, preferably more than 20 m 2 / g, with favorable particle properties.

[0124] Preferably, the resulting crosslinked lignin particles are only soluble in an alkaline solution depending on the conditions. Preferably, the solubility of the undissolved stabilized lignin is less than 30%, preferably less than 25%, particularly preferably less than 20%.

[0125] The alkali solubility of the crosslinked or stabilized lignin particles is determined as follows: 1. Separate the lignin particles from the liquid by centrifugation or filtration and then wash with distilled water. 2. Dry the product of 1 at 105 °C for 24 hours. 3. In order to determine the solubility of the solid sample, this sample must be in the form of dry fine powder (DS > 98%). Otherwise, grind the dry sample or thoroughly triturate it in a mortar before determining the solubility. 4. Solubility is determined in triplicate. For this purpose, 4 g of each dry filler is weighed into 80 g of 0.1 M NaOH in 100 ml Erlenmeyer flasks, respectively. 5. Shake the alkaline suspension at a shaker speed of 200 per minute for 2 hours at room temperature (23°C). If the liquid comes into contact with the lid during this process, the shaker speed should be reduced to prevent this from happening. 6. Next, transfer the suspension as completely as possible to a Büchner funnel with filter paper of φ = 55 mm and pore size 5-8 μm, previously balanced to the nearest 0.1 mg on an analytical balance, and filter under vacuum. Before filtration, slightly moisten the filter paper under vacuum. After complete filtration, measure and record the pH value of the filtrate. Next, rinse the Erlenmeyer flask with 40 ml of distilled water and transfer all remaining material to the Büchner funnel, while simultaneously washing the filter cake from soluble substances such as NaOH used. Filtration continues again until the filter cake is dry. 7. After washing the filter cake, dry the Buchner funnel in a drying oven at 105°C for at least 24 hours to a constant weight. 8. The alkali solubility of the lignin-rich solid is calculated as follows: Alkali solubility of lignin-rich solids [%] = 100% - X% (where X% = mass [g] of undissolved fraction after centrifugation or filtration and drying × 100 / mass [g] of dried material obtained in item 2 above)

[0126] The present invention further relates to crosslinked lignin particles obtainable by the method according to the invention, the crosslinked lignin particles preferably having a length of at least 10 m 2 / g, more preferably at least 20m 2 / g, more preferably at least 30m 2 / g, and even more preferably at least 40m 2 / g, most preferably at least 50m 2 / g STSA surface area.

[0127] The lignin particles obtained according to the process of the present invention preferably exhibit the following properties: - At least 10m 2 / g, preferably at least 20m 2 / g, more preferably at least 30m 2 / g, and even more preferably at least 40m 2 / g, most preferably at least 50m 2 / g STSA. Preferably, the STSA is 200m 2 / g, preferably less than 180m 2 / g or less - a solid-state signal at 0 to 50 ppm, preferably 10 to 40 ppm, particularly preferably 25 to 35 ppm, having an intensity of 1 to 80%, preferably 5 to 60%, particularly preferably 5 to 50% of the signal of the methoxy group at 54 to 58 ppm; 13 C-NMR signal, and improved compared to the lignin used, at 125 to 135 ppm, preferably 127 to 133 ppm; 13 C-NMR signals, - renewable raw materials, preferably greater than 0.20 Bq / g carbon, particularly preferably greater than 0.23 Bq / g carbon, but preferably less than 0.45 Bq / g carbon, respectively 14 C content; a carbon content, based on ash-free dry matter, of between 60% and 80% by weight, preferably between 65% and 75% by weight; a glass transition temperature of more than 160°C, more preferably more than 180°C, particularly preferably more than 200°C, in particular more than 250°C. Preferably, for crosslinked lignin particles, no glass transition temperature can be measured at all. - 0.1cm 3 / g, more preferably less than 0.01 cm 3 / g, particularly preferably less than 0.005 cm 3 / g of pore volume of the crosslinked or stabilized lignin.

[0128] Cross-linked lignin particles II The present invention further relates to crosslinked lignin particles that exhibit a glass transition temperature Tg of at least 160° C. or no glass transition temperature at all. Furthermore, the crosslinked lignin particles have a glass transition temperature of at least 10 m 2 / g As already mentioned above, crosslinked lignin particles are lignin particles which have been crosslinked with a crosslinking agent, possible crosslinking agents being those mentioned above, in particular formaldehyde.

[0129] Cross-linked lignin particles are at least 20 m 2 / g, more preferably at least 30m 2 / g, and even more preferably at least 40m 2 / g, most preferably at least 50m 2 It is particularly preferred that the STSA has a surface area of ​​200 m / g. 2 / g, more preferably less than 180m 2 The crosslinked lignin particles are, for example, at least 10 m 2 / g~180m 2 / g, preferably at least 20m 2 / g~180m 2 / g, more preferably 30m 2 / g~180m 2 / g, particularly preferably 40m 2 / g~180m 2 / g STSA surface area.

[0130] The crosslinked lignin particles preferably exhibit a glass transition temperature of above 180° C., more preferably above 200° C., especially above 250° C. Preferably, in the case of crosslinked lignin particles, no glass transition temperature can be measured at all.

[0131] The crosslinked lignin particles are characterized in particular by a reduced solubility in alkaline solutions. In a preferred embodiment, the crosslinked lignin particles have an alkaline solubility in 0.1 M NaOH at 23° C. of less than 30%, preferably less than 25%, particularly preferably less than 20%. The alkaline solubility is determined according to the method described above.

[0132] In a preferred embodiment, the crosslinked lignin particles have a concentration in the range of 0.20 to 0.45 Bq / g of carbon. 14 Has a C content.

[0133] 14 For the purpose of determining the C content, the materials under investigation were provided to the Poznan Radiocarbon Laboratory, Foundation of the A. Mickiewicz University, ul. Rubiez 46, 61-612 Poznan. The method used is explained by the laboratory head, Tomasz Goslar, in the laboratory's internet presence. The details regarding lignin are summarized below.

[0134] AMS method including the following steps 14 C dating procedure: a) Chemical pretreatment according to Brock et al., 2010, Radiocarbon, 52, 102-112 b) CO2 generation and graphitization c) with the "Compact Carbon AMS" spectrometer according to Goslar T., Czernik J., Goslar E., 2004, Nuclear Instruments and Methods B, pp. 223-224, 5-11 14 Measurement of C d) 14 Calculation and calibration of C ages (calculated according to Stuiver and Polach 1977, Radiocarbon 19, p. 355; Bronk Ramsey C., 2001, Radiocarbon, Vol. 43, pp. 355-363; Bronk Ramsey C., 2009, Radiocarbon, Vol. 51, pp. 337-360; Bronk Ramsey C. and Lee S., 2013, Radiocarbon, Vol. 55, pp. 720-730, and Reimer PJ et al., 2013, Radiocarbon, Vol. 55(4), pp. 1869-1887)

[0135] For archaeological purposes, this analysis allows the dating of carbon samples, although results can also be given as specific activity.

[0136] Furthermore, the crosslinked particles according to the present invention also exhibit and reference is made to all other properties described above for "Crosslinked Lignin Particles I", such as those relating to particle size distribution, ash content and / or pore volume.

[0137] According to one embodiment, the crosslinked lignin particles according to the invention may be functionalized, in particular silanized. This functionalization is understood as the surface modification of the crosslinked lignin particles with a coupling agent. The coupling agent has functional groups through which chemical bonding to the surface of the crosslinked lignin particles occurs. Such functionalization, in particular silanization, makes it possible in particular to improve bonding, for example with polymers, in particular rubber elastomers, that function as matrix materials.

[0138] Such coupling agents or surface modifiers are known to those skilled in the art of fillers. Suitable examples of coupling agents are in particular organosilanes, such as bis(trialkoxysilylalkyl)-oligo- or -polysulfides, mercaptosilanes, aminosilanes or silanes with unsaturated hydrocarbon groups, such as vinylsilanes.

[0139] The functionalization or silanization of the crosslinked lignin particles is preferably carried out ex situ, i.e., before mixing with a polymer, especially a rubber.

[0140] In a preferred embodiment, the crosslinked lignin particles are lignin particles obtainable by the method according to the invention described above.

[0141] Rubber articles, particularly industrial rubber articles or tires, containing crosslinked lignin particles The present invention further relates to a rubber article, in particular an industrial rubber article or tire, containing the above-described crosslinked lignin particles as filler and at least one polymer, in particular a rubber elastomer, as a matrix or matrix material. Those skilled in the art will recognize that rubber articles can contain many additives, such as fillers.

[0142] The polymer contained in the rubber article as a matrix or matrix material is in particular a rubber elastomer, which may be formed from one or more rubbers, such as natural rubber (1,4-polyisoprene) derived from the rubber tree "Hevea brasiliensis" or the dandelion (Taraxacum genus), synthetic natural and / or synthetic rubbers, or mixtures thereof, which can be converted into a rubber matrix by vulcanization.

[0143] Therefore, the crosslinked lignin according to the present invention may be used in rubber articles, particularly industrial rubber articles or tires, in an amount of, for example, 10% by mass to 150% by mass, preferably 20% by mass to 120% by mass, more preferably 40% by mass to 100% by mass, and particularly preferably 50% by mass to 80% by mass, based on the mass of rubber used in the rubber article.

[0144] Rubber articles, especially industrial rubber articles or tires, are articles based on rubber or rubber elastomers, i.e., vulcanized rubber, which serves as the matrix material for the article. Rubber articles, especially industrial rubber articles or tires, are sometimes also called rubber products (Gummiwaren, Kautschukartikel, or Kautschukwaren in German). One of the technical terms for industrial rubber articles in English is "Mechanical Rubber Goods" (abbreviated as MRG). Examples of rubber articles, especially industrial rubber articles or tires, are automobile tires, sealing profiles, belts, bands, conveyor belts, hoses, spring elements, rubber-metal composite parts, roller linings, molded articles, rubber seals, and rubber cables.

[0145] In a preferred embodiment, the rubber article, in particular an industrial rubber article or a tire, may contain additional fillers, in particular carbon black and / or silicic acid and / or other inorganic fillers or surface-treated inorganic fillers (such as, for example, chalk and silica).

[0146] The crosslinked lignin particles contained in the rubber article according to the invention, in particular in an industrial rubber article or a tire, are in particular crosslinked lignin particles according to the invention as described under "Crosslinked lignin particles II". Particularly preferably, the crosslinked lignin particles are obtainable by the process according to the invention described above.

[0147] The present invention will now be described with reference to exemplary embodiments, which should not be construed as limiting the invention in any way.

[0148] Exemplary Embodiments In the examples below, BET is shown instead of STSA. However, for the insoluble stabilized lignin produced herein, BET and STSA do not differ from each other by more than 10%. The lignin content of a feedstock shown here is the feedstock mass minus the dry ash content. [Example]

[0149] (comparison) The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 18.6% and a pH of 10. The amount of formaldehyde specified in Table 1 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 1. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 1 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. After in-vacuo bakeout at 150°C, the specific surface area (BET) of the undissolved stabilized lignin in Table 1 was determined.

[0150] [Table 1] [Example]

[0151] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 19.1% and a pH of 9. The amount of formaldehyde specified in Table 2 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 2. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 2 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. After in-vacuo bakeout at 150°C, the specific surface area (BET) of the undissolved stabilized lignin in Table 2 was determined.

[0152] [Table 2] [Example]

[0153] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 19.2% and a pH of 8.8. The amount of formaldehyde specified in Table 3 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 3. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 3 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. After in-vacuo bakeout at 150°C, the specific surface area (BET) of the undissolved stabilized lignin in Table 3 was determined.

[0154] [Table 3] [Example]

[0155] (comparison) The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 14.8% and a pH of 10. The amount of formaldehyde specified in Table 4 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 4. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 4 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. After in-vacuo bakeout at 150°C, the specific surface area (BET) of the undissolved stabilized lignin in Table 4 was determined.

[0156] [Table 4] [Example]

[0157] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 15.3% and a pH of 9.2. The amount of formaldehyde specified in Table 5 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 5. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 5 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 5 was determined after in-vacuo bakeout at 150°C.

[0158] [Table 5] [Example]

[0159] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 15.5% and a pH of 8.5. The amount of formaldehyde specified in Table 6 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 6. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 6 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. After in-vacuo bakeout at 160°C, the specific surface area (BET) of the undissolved stabilized lignin in Table 6 was determined.

[0160] [Table 6] [Example]

[0161] (comparison) The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 9.8% and a pH of 10. The amount of formaldehyde specified in Table 7 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 7. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 7 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 7 was determined after in-vacuo bakeout at 150°C.

[0162] [Table 7] [Example]

[0163] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 9.4% and a pH of 8.8. The amount of formaldehyde specified in Table 8 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 8. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 8 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 8 was determined after in-vacuo bakeout at 150°C.

[0164] [Table 8] [Example]

[0165] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.3% and a pH of 8.6. The amount of formaldehyde specified in Table 9 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 9. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 9 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 9 was determined after in-vacuo bakeout at 150°C.

[0166] [Table 9] [Example]

[0167] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and acetic acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.4% and a pH of 8.6. The amount of formaldehyde specified in Table 10 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 10. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 10 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 10 was determined after in-vacuo bakeout at 150°C.

[0168] [Table 10] [Example]

[0169] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 27.2%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 11.5% and a pH of 8.7. The amount of formaldehyde specified in Table 11 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 11. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 11 were obtained. The yields were calculated with respect to the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 11 was determined after in-vacuo bakeout at 150°C.

[0170] [Table 11] [Example]

[0171] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.6% and a pH of 8.6. The amount of formaldehyde specified in Table 12 was added to 30 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 12. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 12 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 12 was determined after in-vacuo bakeout at 150°C.

[0172] [Table 12] [Example]

[0173] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.1% and a pH of 8.4. The amount of formaldehyde specified in Table 13 was added to 700 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 13. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 13 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 13 was determined after in-vacuo bakeout at 150°C.

[0174] [Table 13] [Example]

[0175] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 19.3%. By adding water and acetic acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.1% and a pH of 7.9. The amount of formaldehyde specified in Table 14 was added to 700 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 14. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 14 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 14 was determined after in-vacuo bakeout at 150°C.

[0176] [Table 14] [Example]

[0177] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.6% and a pH of 8.6. The amount of formaldehyde specified in Table 15 was added to 700 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 15. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 15 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 15 was determined after in-vacuo bakeout at 150°C.

[0178] [Table 15] [Example]

[0179] The raw material was lignin obtained from black liquor from kraft pulping by CO2 precipitation. The dry ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid was converted into a liquid containing dissolved lignin, with a dry matter content of 10.5% and a pH of 7.1. The amount of formaldehyde specified in Table 16 was added to 11,600 g of this liquid containing dissolved lignin in the form of a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment for the time and temperature shown in Table 16. The undissolved stabilized lignin was recovered by filtration. After washing the recovered filtrate with two volumes of demineralized water and drying in an air-circulating drying cabinet, the yields shown in Table 16 were obtained. The yields were calculated based on the amount of lignin raw material used as dry matter. The amount of formaldehyde used was not included in the yield calculation. The specific surface area (BET) of the undissolved stabilized lignin in Table 16 was determined after in-vacuo bakeout at 150°C.

[0180] According to the above-mentioned measurement method, the alkaline solubility of the obtained non-dissolved stabilized lignin in 0.1 M NaOH was determined to be 9.1%.

[0181] [Table 16]

Claims

1. 1. A method for producing crosslinked lignin in particulate form, the method comprising the steps of: a) providing a black liquor having a dry matter content of 5 to 50% by mass; b) containing lignin and at least one crosslinking agent selected from aldehydes and / or one precursor of a crosslinking agent, and having the following characteristics: - dry matter content of 5-25% by mass, - ash content, based on dry mass, of 10 to 45% by mass; - a pH value greater than 6.5 and less than 10, - Conductivity from over 15mS / cm to 400mS / cm producing a liquid from the black liquor having i) mixing the black liquor with an acid and / or an acid gas to reduce the pH value; ii) mixing said black liquor or a product derived therefrom with at least one cross-linking agent and / or a precursor of a cross-linking agent; iii) optionally adding liquid to reduce the dry matter content; and c) hydrothermally treating the liquid produced in step b), which contains lignin and at least one crosslinking agent selected from aldehydes and / or one precursor of the crosslinking agent, at a temperature in the range of 150°C to 270°C to form crosslinked lignin particles in the liquid; d) separating the liquid from the crosslinked lignin particles formed in step c); e) washing the separated cross-linked lignin particles with a washing medium; A method comprising:

2. 2. The method according to claim 1, characterized in that the liquid produced in step b) has a pH value of greater than 7.5 and less than 10.

3. 3. The method according to claim 1 or 2, characterized in that the liquid produced in step b) containing lignin and at least one crosslinking agent selected from aldehydes and / or one precursor of a crosslinking agent has a conductivity of more than 25 mS / cm and / or a conductivity of at most 200 mS / cm.

4. 4. The method of claim 1, wherein at least a portion of the lignin is already dissolved in the liquid produced in step b) and / or at least a portion of the lignin dissolves in the liquid during heating of the liquid produced in step b) to a temperature for the hydrothermal treatment.

5. 5. The method according to claim 1, wherein the at least one cross-linking agent is selected from formaldehyde, furfural or sugar aldehydes, and / or the at least one precursor of the cross-linking agent is selected from compounds which form such cross-linking agents in situ.

6. 6. A method according to any one of claims 1 to 5, characterized in that the amount of crosslinking agent in the liquid produced in step b) is at most 4 mol of crosslinkable units of crosslinking agent per mol of crosslinkable units of the lignin used and / or the amount of crosslinking agent in the liquid produced in step b) is at least 0.2 mol of crosslinkable units of crosslinking agent per mol of crosslinkable units of the lignin used that can be crosslinked with the crosslinking agent, in the case of the additional or alternative use of a precursor of the crosslinking agent, the amount of precursor being selected so as to obtain such an amount after in situ formation of the crosslinking agent.

7. The liquid produced in step b) containing lignin and at least one crosslinking agent and / or one precursor of a crosslinking agent, b1) mixing the black liquor with i) an acid and / or an acid gas to reduce the pH value, and ii) at least one cross-linking agent and / or a precursor of a cross-linking agent, or b2) mixing the black liquor with an acid and / or an acid gas to reduce the pH value and form a solid lignin feedstock in the black liquor; separating the solid lignin feedstock from the black liquor; mixing the separated solid lignin feedstock with i) a liquid and ii) at least one cross-linking agent and / or a precursor of a cross-linking agent, optionally with an acid and / or an acid gas to further reduce the pH value. The method according to any one of claims 1 to 6, characterized in that it is produced from black liquor by 8. The method according to claim 1, wherein the pH value of the liquid produced in step b) is in the range of 8 to 9.

5.

9. the pH value of the liquid produced in step b) is in the range of 8 to 9.5; In step b2), an acid is added in an amount of 2 to 15 g per 100 g of lignin to further reduce the pH value.

8. The method according to claim 7.

10. the acid for mixing in step i) is selected from sulfuric acid, acetic acid, or formic acid; and / or The acid gas for mixing in step i) is CO 2 , H 2 S or CO 2 and H 2 Selected from a mixture of S The method according to any one of claims 1 to 9, characterized in that

11. 11. The method according to any one of claims 1 to 10, characterized in that the hydrothermal treatment is carried out at a temperature ranging from 180°C to 250°C, the hydrothermal treatment being carried out below 270°C.

12. 12. The method according to any one of claims 1 to 11, characterized in that the duration of the hydrothermal treatment is at least 10 minutes and / or less than 600 minutes.

13. 13. The method according to any one of claims 1 to 12, characterized in that the amount of lignin in the liquid produced in step b) is in the range of 4 to 20% by weight, relative to the total weight of the liquid not including the at least one crosslinker and / or precursor of a crosslinker.

14. 14. The method according to any one of claims 1 to 13, characterized in that the amount of crosslinker in the liquid produced in step b) is at most 35 g per 100 g of lignin.

15. 15. The method according to any one of claims 1 to 14, characterized in that, prior to the hydrothermal treatment carried out in step c), the liquid produced in step b) is kept at a temperature in the range from 50°C to less than 150°C for at least 5 minutes and less than 300 minutes, and / or the liquid produced in step b) is heated at a heating rate of less than 15 Kelvin per minute to reach the temperature for the hydrothermal treatment and / or any intermediate treatment carried out.

16. the washing medium used in step e) for washing the crosslinked lignin particles has a pH value greater than 4 and less than 10, and / or The washing medium used in step e) to wash the crosslinked lignin particles comprises or is water. The method according to any one of claims 1 to 15, characterized in that

17. The crosslinked lignin particles produced in the method have a diameter of at least 10 m 2 17. The method according to claim 1, characterized in that the surface of the silica gel has an STSA surface area of ​​1.0 to 1.0 g / g.

18. 18. The method according to any one of claims 1 to 17, characterized in that the crosslinked lignin particles produced in the method have an ash content of less than 5% by weight and more than 1% by weight.

19. 19. The method according to any one of claims 1 to 18, characterized in that the black liquor provided in step a) is removed from an evaporation plant for black liquor and the liquid separated in step d) and optionally the used washing agent obtained in step e) are returned to the evaporation plant at a point located downstream of the extraction point of the black liquor.

20. Crosslinked lignin particles obtainable by the method according to any one of claims 1 to 19.

21. It has a glass transition temperature Tg of at least 160°C or no glass transition temperature and has a viscosity of at least 10 m 2 / g STSA surface area.

22. 22. The crosslinked lignin particles of claim 21, characterized in that they have an alkaline solubility in 0.1 M NaOH at 23°C of less than 30%.

23. in the range of 0.20 to 0.45 Bq per gram of carbon 14 23. Crosslinked lignin particles according to claim 21 or 22, characterized in that they have a C content.

24. Crosslinked lignin particles according to any one of claims 21 to 23, characterized in that they are functionalized.

25. Crosslinked lignin particles according to any one of claims 21 to 24, characterized in that they have a glass transition temperature above 180°C or no glass transition temperature at all.

26. Crosslinked lignin particles according to any one of claims 21 to 25, characterized in that they are obtainable by a method according to any one of claims 1 to 19.

27. A rubber article comprising crosslinked lignin particles as a filler and at least one polymer as a matrix material.

28. 28. The rubber article of claim 27, including additional fillers.

29. 29. A rubber article according to claim 27 or 28, characterized in that the crosslinked lignin particles are crosslinked lignin particles according to any one of claims 20 to 26.

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