Method for preparing crosslinked lignin with high specific surface area, crosslinked lignin and industrial rubber article or tire comprising the same

Abstract

The present invention relates to a method for preparing cross-linked lignin in the form of particles using hydrothermal treatment with a liquid made from black liquor, comprising lignin and a cross-linking agent or a precursor thereof, and having an electrical conductivity of more than 15 mS / cm, preferably more than 25 mS / cm to 400 mS / cm. The present invention also relates to cross-linked lignin produced using the above-mentioned method. The present invention also relates to cross-linked lignin particles having a glass transition temperature Tg of at least 160°C or no glass transition temperature and a STSA surface area of at least 10 m 2 / g. The present invention also relates to rubber articles, in particular industrial rubber articles or tires, comprising cross-linked lignin particles as filler.

Description

Background Technology

[0001] Lignin from hardwoods, softwoods, and annual plants exhibits high solubility in many polar and alkaline media after extraction / recovery in forms such as sulfate lignin, sulfonate lignin, or hydrolyzed lignin. Lignin, in particular, largely exhibits a glass transition at temperatures ranging from 80°C to 150°C. The microstructure of lignin particles is altered by softening at low temperatures. Therefore, lignin-containing materials are generally unstable, but their properties change at high temperatures. Furthermore, the solubility of lignin in polar solvents (e.g., dioxane and acetone containing, for example, 10% water) or in alkaline media is typically >95% (Sameni et al., BioResources, 2017, 12, 1548-1565; Podschun et al., European Polymer Journal, 2015, 67, 1-11). Due to these and other properties, lignin has limited use in materials applications (DE102013002574A1).

[0002] In the following text, lignin is understood to be the sum of krasen lignin and acid-soluble lignin. Dry matter may also contain other organic and inorganic components.

[0003] To overcome these drawbacks, a method for preparing stable lignin via hydrothermal carbonization or hydrothermal treatment has been proposed, characterized by a softening temperature (glass transition temperature) exceeding 200°C (WO2015018944A1). By adjusting the pH value, stable lignin with a defined particle size distribution can be obtained (WO2015018944A1).

[0004] The improved method uses lignin as a raw material for preparing particulate carbon materials, which can be used, for example, as functional fillers in elastomers (WO2017085278A1). A fundamental quality parameter of the functional filler is the external surface area of ​​the particulate carbon material, which is determined by measuring the STSA (Specific Surface Area). This method utilizes hydrothermal carbonization of a lignin-containing liquid, typically carried out at temperatures between 150°C and 250°C. Due to the high reactivity of lignin at these temperatures, fine-tuning is required for the pH, ionic strength, and lignin content of the lignin-containing liquid, as well as the temperature and duration of hydrothermal carbonization, to obtain a high specific surface area. This is achieved by adjusting the pH to an alkaline range, typically to a value above 7.

[0005] For this type of particulate carbon material, this offers the possibility of application in materials different from the corresponding starting lignin. Due to its low solubility of less than 40% and greater than 5m... 2 / g and less than 200m 2With a specific surface area of ​​ / g, they can therefore be used as reinforcing fillers, for example, in elastomers, and to completely or partially replace carbon black.

[0006] The disadvantages of these methods are low yields, typically between 40% and 60%. Another drawback is that achieving higher specific surface areas requires significant effort to adapt the properties of the lignin-containing liquid (pH, ionic strength, lignin content) to the hydrothermal carbonization process parameters (temperature and residence time). To obtain a specific surface area greater than 5m... 2 For a surface area of ​​ / g, the electrical conductivity of the lignin-containing liquid must be less than 25 mS / cm. Due to the sensitivity required by the above adjustments, a 40m² surface area was achieved in the laboratory. 2 A surface area ratio of more than / g is more feasible on an industrial scale. It can be inferred that such an adjustment aimed at increasing specific surface area will lead to a decrease in yield.

[0007] A known method for preparing fuel from a dry black liquor and water suspension by increasing the yield of solid matter and the conversion of lignin through hydrothermal carbonization at temperatures between 220°C and 280°C is the addition of formaldehyde [Bioresource Technologie 2012, 110715-718, Kang et al.]. Kang et al. proposed adding 37 g of formaldehyde per 100 g of dry lignin at a solid matter concentration of 20% (a 2.8% formaldehyde solution in 100 ml of 25 g of dry matter obtained by drying black liquor with a lignin content of 30% relative to the dry matter). This can increase the conversion rate of lignin contained in the black liquor to solid matter from 60% to 80% to 90% to 100%, with the highest value reached at temperatures between 220°C and 250°C. This prior art attributes the increase in yield to the polymerization between formaldehyde, the solid matter in the black liquor, and the carbonization products formed from the solid matter (page 716, last paragraph).

[0008] The disadvantages of this existing technology are:

[0009] -A high specific dose of 37 grams of formaldehyde per 100 grams of lignin.

[0010] - The dry matter used and the products made from it have a high ash content.

[0011] - Polymerization between formaldehyde, solids in black liquor, and carbonization products formed from these solids, and

[0012] - Relevant restrictions on using the product for fuel applications (see Kang et al.). Summary of the Invention

[0013] The purpose of this invention is to describe a method for producing cross-linked lignin suitable for material applications while achieving high yield.

[0014] The purpose of this invention is to illustrate a method as follows:

[0015] - Reduces the solubility of lignin in alkaline and / or polar media.

[0016] -Increase or eliminate the glass transition temperature of lignin.

[0017] -Preparation of cross-linked or stable lignin with favorable particulate properties, and

[0018] - It has a high yield.

[0019] This objective specifically provides a method for preparing lignin particles having a high specific surface area, for example, a BET surface area > 20 m². 2 / g, preferably >30m 2 / g or the corresponding STSA surface area, where the method can simplify the treatment of black liquor as a starting material.

[0020] Surprisingly, this objective can be achieved by a method for preparing cross-linked lignin in particulate form, wherein the method includes the following steps:

[0021] a) Provide black liquor with a dry matter content of 5% to 50% by weight.

[0022] b) Preparing a liquid containing lignin and at least one crosslinking agent and / or a precursor of at least one crosslinking agent from the black liquor, the liquid having the following properties:

[0023] -Dry matter content is 5% to 25% by weight.

[0024] - The ash content relative to dry matter is 10% to 45% by weight.

[0025] - 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.

[0026] - Electrical conductivity greater than 15 mS / cm to 400 mS / cm

[0027] The preparation of the liquid includes:

[0028] i) Mixing black liquor with acid and / or acidic gases to lower the pH; and

[0029] ii) Mixing black liquor or a product derived therefrom with at least one crosslinking agent and / or a precursor of the crosslinking agent; and

[0030] iii) Optional addition of liquid to reduce dry matter content,

[0031] c) The liquid containing lignin and at least one crosslinking agent and / or at least one crosslinking agent precursor prepared in step b) is subjected to hydrothermal treatment at a temperature of 150°C to 270°C to form crosslinked lignin particles in the liquid; and

[0032] d) Separate the liquid from the cross-linked lignin particles formed in step c); and

[0033] e) Clean the separated cross-linked lignin particles with a cleaning medium.

[0034] Preferably, the liquid separated in step d) and optionally the used cleaning medium obtained in step e) are supplied to a reprocessing device to recover liquid and / or energy from the components.

[0035] Another object of the present invention is to provide lignin, particularly lignin particles, which are preferably cross-linked, especially more stabilized, and are particularly suitable as an improved, cross-linked, stabilized filler for use in rubber products, particularly industrial rubber products or tires.

[0036] Introducing lignin particles according to the invention as fillers into rubber products based on natural and synthetic rubber, such as industrial rubber products or tires, aims to improve the properties of the rubber products, particularly special properties such as the following:

[0037] -Specific elongation under tension

[0038] -Low loss factor during dynamic deformation

[0039] - High dynamic stiffness

[0040] - Low compression set to improve sealing performance

[0041] - Good electrical insulation properties due to particle morphology

[0042] -Low component weight

[0043] High stiffness and low deformation

[0044] Minimization of polycyclic aromatic compounds

[0045] In this application, unless otherwise stated, all percentages given refer to weight. Typically, liquids may also be, for example, solutions or suspensions. Detailed Implementation

[0046] Black liquid

[0047] According to step a) of the method of the invention, black liquor is provided. Specifically, black liquor (Schwarzlauge) is a lignin-containing liquid, a waste product from alkaline fractionation processes of woody biomass (e.g., sulfate process, pulp production, or sodium hydroxide process). The pH of the black liquor is in the alkaline range, typically between pH 12 and 14. In addition to lignin, black liquor may also contain other organic or inorganic components. For black liquor, typically, the proportion of lignin in the organic dry matter exceeds 50%, particularly exceeding 60% or even 70%, which is significantly higher than the proportion of lignin in woody biomass (15% to 35%). Hereinafter, lignin content is understood as the sum of Klason lignin and acid-soluble lignin.

[0048] Black liquor, generated as alkaline pulping waste in pulp production, is further concentrated in an evaporation unit. In the method of this invention, the black liquor can be taken from or supplied by the evaporation unit.

[0049] The dry matter content of the black liquor used in this method is specifically 5% to 50% by weight, preferably 5% to 40% by weight, and more preferably 10% to 40% by weight, relative to the total weight of the black liquor.

[0050] As step b), the method of the present invention includes preparing a liquid from black liquor containing lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent. The properties of the liquid obtained in step b) will be described below.

[0051] The preparation of liquid from black liquor according to step b) includes at least the following steps:

[0052] i) Mix the black liquor with acid and / or acidic gas to lower the pH value;

[0053] ii) Mixing the black liquor or a product derived therefrom with at least one crosslinking agent and / or a precursor of the crosslinking agent; and

[0054] iii) Optionally, liquid is added to reduce the dry matter content.

[0055] Products derived from black liquor can be those obtained by reprocessing the black liquor, for example, solid lignin feedstock obtained according to variant b2) described below. Suitable liquids for reducing dry matter content are all common inorganic solvents such as water, or organic solvents such as alcohols, preferably water. Suitable embodiments of acids and / or acidic gases are the same as those described below for specific variants b1) and b2). Suitable embodiments of crosslinking agents and / or precursors of crosslinking agents are also described below.

[0056] According to step b), the formation of liquid from black liquor can preferably be carried out via step b1) or via an alternative step b2).

[0057] In an alternative embodiment b1), a liquid containing lignin and at least one crosslinking agent and / or a crosslinking agent precursor is obtained from the black liquor by mixing the black liquor with i) an acid and / or an acidic gas to lower the pH value, and ii) mixing with at least one crosslinking agent and / or a precursor of at least one crosslinking agent.

[0058] The acid used for mixing in step b1) can be an inorganic acid (e.g., sulfuric acid) or an organic acid (e.g., acetic acid or formic acid), wherein the acid can be added as an industrial-grade acid with a water content of less than 10% by weight, preferably less than 5% by weight, or as an aqueous acid. The acidic gas used for mixing in step b1) can be selected from, for example, CO2, H2S, or a mixture of CO2 and H2S. For convenience, the acidic gas is simply introduced into the black liquor.

[0059] To obtain a liquid containing lignin and a crosslinking agent and / or its precursors, the order in which the components are added to each other is not restricted. These components can be mixed simultaneously, sequentially, and / or partially with each other. The liquid can also be moved to achieve proper mixing, for example, by stirring or recycling the liquid.

[0060] In this variant of the method, the dry matter content of the black liquor provided in step a) is preferably higher than 10% and preferably lower than 30%, more preferably lower than 25%. If the black liquor provided in step a) has a dry matter content higher than the above-mentioned preferred range, liquid can be further added in step b1) to adjust the dry matter content of the liquid.

[0061] In alternative embodiment b2), the liquid comprising lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent is prepared from black liquor in the following manner:

[0062] - Mix black liquor with acid or acidic gas to lower the pH value, while forming solid lignin raw materials in the black liquor;

[0063] - Separation of solid lignin raw materials from black liquor;

[0064] - The separated solid lignin raw material is mixed with i) a liquid and ii) at least one crosslinking agent and / or a precursor of the crosslinking agent.

[0065] Optionally, additional acid and / or acidic gases are mixed in to further lower the pH value.

[0066] Regarding the acid used in step b2), i.e., the acid used for mixing with the black liquor and / or optionally for further reducing the pH, it can be, for example, an inorganic acid (e.g., sulfuric acid) or an organic acid (e.g., acetic acid or formic acid), wherein the acid can be added as an industrial-grade acid with a water content of less than 10% by weight, preferably less than 5% by weight, or as an aqueous acid. Regarding the acidic gas used in step b2), i.e., the acidic gas used for mixing with the black liquor and / or optionally for further reducing the pH, it can be selected from, for example, CO2, H2S, or a mixture of CO2 and H2S. For convenience, the acidic gas is simply introduced into the black liquor or into the liquid to reduce the pH.

[0067] The pH of the black liquor is lowered, preferably to a pH of 9.5 to 10.5, by adding acid or introducing acidic gases. As a result, solid lignin feedstock forms or precipitates in the black liquor. The precipitated solid lignin feedstock is preferably separated from the black liquor or its liquid components by filtration. The dry matter of the separated solid lignin feedstock may also contain organic and / or inorganic components other than lignin. The amount of lignin in the dry matter is, for example, at least 60%, preferably at least 70%. However, the amount of lignin in the dry matter is, for example, at most 90%.

[0068] The separated solid lignin feedstock is mixed with i) a liquid and ii) at least one crosslinking agent and / or a precursor of the crosslinking agent, wherein an acid and / or acidic gas is optionally added to further reduce the pH. In this way, a liquid comprising lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent is formed from black liquor.

[0069] To obtain a liquid containing lignin and a crosslinking agent and / or its precursors, the order in which the components are added to each other is not restricted. These components can be mixed simultaneously, sequentially, and / or partially with each other. The liquid can also be moved to achieve proper mixing, for example, by stirring or recycling the liquid.

[0070] The liquid added to the separated solid lignin feedstock can be an inorganic solvent (e.g., water) and / or an organic solvent (e.g., alcohol, such as ethanol), wherein the liquid is preferably water.

[0071] In an optional and preferred embodiment of variant b2), in addition to the added liquid, such as water, an acid and / or acidic gas are mixed to further lower the pH value. If this optional step is performed, the liquid, such as water, and the acid (such as sulfuric acid or acetic acid) and / or acidic gas can be mixed with the solid lignin feedstock separately. However, it is also possible to first mix the liquid (e.g., water) with the acid (e.g., sulfuric acid or acetic acid) or acidic gas, and then mix the mixture with the solid lignin feedstock, or to add a portion of the liquid (e.g., water) itself to the solid lignin feedstock and mix another portion of the liquid (e.g., water) with the acid (e.g., sulfuric acid or acetic acid) or acidic gas, as an aqueous acid alone.

[0072] In a particularly preferred embodiment, for example as a first step in a lignin-boosting process, solid lignin feedstock is recovered from black liquor. In this process, lignin is precipitated by CO2 acidification (introducing CO2 into the black liquor). Hereinafter, precipitation will specifically refer to a major conversion rate of lignin dissolved in the black liquor exceeding 35%, preferably exceeding 40%, and particularly preferably exceeding 45%. The precipitated lignin can be filtered out, and the lignin-containing solids can be recovered in this manner.

[0073] By introducing CO2 into the black liquor, the pH value of the black liquor reaches 9.5 to 10.5, which is sufficient to precipitate lignin.

[0074] Therefore, the filtrate from CO2 lignin dehydration is alkaline and, alternatively, can be simply returned to the pulp mill's liquid recovery. Ash (approximately 15% to 25%) is contained in the CO2 lignin after step c) as dissolved ash, which can be largely separated from the cross-linked lignin particles along with the liquid and then returned to the pulp mill's liquid recovery as an alkaline filtrate. Here, dissolved ash should be specifically understood as inorganic salts dissolved in the liquid.

[0075] In contrast, the filtrate obtained from H2SO4 acidification, another step in the lignin strengthening process, is acidic and must be neutralized upon return to the pulp mill. Furthermore, any introduced sulfur must be separated at the pulp mill. Additionally, recovering cross-linked lignin particles from the lignin obtained from the lignin strengthening process requires the addition of NaOH to raise the pH from 2 to pH > 7.

[0076] Therefore, the use of lignin-containing solids precipitated from black liquor in the presence of CO2 as starting material for the method of the present invention is effective compared to other lignin solids (e.g., lignin from lignin strengthening processes). Surprisingly, it has been shown that if a crosslinking agent is added in step b) and the inventive properties of the liquid containing lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent are adjusted, such a raw material is suitable for the preparation of crosslinked lignin particles.

[0077] Further details are given below regarding the liquid obtained from black liquor in step b) and containing lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent. Unless otherwise explicitly stated, these details apply in the same manner to the liquids formed via step b1) and via alternative step b2).

[0078] As described above, the acid used for mixing in step b) (more generally, step i) or b1) or b2)) can be, for example, an inorganic acid (e.g., sulfuric acid) or an organic acid (e.g., acetic acid or formic acid). The acidic gas used for mixing in step b) (b1) or b2)) can be selected from, for example, CO2, H2S, or a mixture of CO2 and H2S.

[0079] The lignin in the liquid obtained in step b) includes lignin that can be identified as classen lignin and acid-soluble lignin. According to Tappi T 222om-02 (https: / / www.tappi.org / content / SARG / T222.pdf), classen lignin describes the analytical measurement variable after treatment in 72% H2SO4 and is the product to be quantified in this analytical method.

[0080] Lignin possesses functional groups, which enable cross-linking. Lignin can contain, for example, phenolic aromatic compounds, aromatic and aliphatic hydroxyl groups and / or carboxyl groups as cross-linkable units suitable for reaction with cross-linking agents.

[0081] Preferably, in the liquid prepared in step b), at least a portion of the lignin has dissolved in the liquid, and / or during the heating of the liquid prepared in step b) to a temperature suitable for hydrothermal treatment, at least a portion of the lignin dissolves in the liquid. The proportion of dissolved lignin is typically increased by heating the liquid. In any case, hydrothermal treatment of the liquid requires such heating.

[0082] In addition to dissolved lignin, undissolved lignin may also exist in a dispersed form in the liquid obtained in step b). Therefore, for this method, it is not necessary for all lignin to be present in dissolved form in the liquid. However, it is advantageous that, prior to hydrothermal treatment of the liquid in step c), more than 50%, particularly preferably more than 60%, further preferably more than 70%, particularly preferably more than 80%, especially more than 90%, and even more particularly preferably more than 95% of the lignin is dissolved in the liquid.

[0083] Furthermore, in process step b) (more generally, step ii) or b1) or b2), at least one crosslinking agent and / or a precursor of the crosslinking agent are mixed such that the liquid obtained in step b) contains at least one crosslinking agent and / or its precursor. The precursor of the crosslinking agent is understood herein to be a compound that is not itself a crosslinking agent, but is formed in situ by, for example, a thermal decomposition reaction prior to or during the hydrothermal treatment in step c). When available, the following details of the crosslinking agent also apply to crosslinking agents formed in situ from the precursor.

[0084] The crosslinking agent has at least one functional group capable of reacting with the crosslinkable group of lignin. Preferably, the crosslinking agent has at least one functional group selected from aldehydes, carboxylic anhydrides, epoxides, hydroxyl groups, and isocyanate groups, or combinations thereof.

[0085] If the crosslinking agent has a functional group that can react with two crosslinkable groups of lignin during the reaction, such as an aldehyde, anhydride, or epoxy group, one such functional group is sufficient. Otherwise, the crosslinking agent has at least two functional groups, such as hydroxyl or isocyanate groups that can react with the crosslinkable groups of lignin.

[0086] In a particularly preferred embodiment, the at least one crosslinking agent is selected from at least one aldehyde, epoxide, acid anhydride, polyisocyanate, or polyol, wherein the at least one crosslinking agent is preferably selected from aldehydes, particularly formaldehyde, furfural, or sulphuraldehyde. Polyisocyanate is a compound having at least two isocyanate groups, wherein diisocyanate or triisocyanate is preferred. Polyol is a compound having at least two hydroxyl groups, wherein diol or triol is preferred.

[0087] When using a bifunctional crosslinking agent, each mole of the bifunctional crosslinking agent produces two moles of crosslinkable units. Therefore, when using a trifunctional crosslinking agent, each mole of the trifunctional crosslinking agent produces three moles of crosslinkable units, and so on. It should be noted that although crosslinking agents have various functionalities, typically only a portion of the usable groups react, because reactivity decreases as the groups react, partly due to steric hindrance and partly due to charge transfer.

[0088] In the following statements, the crosslinkable unit of a crosslinking agent refers to a unit that can react with the crosslinkable unit of lignin. Therefore, a functional group, such as an aldehyde, anhydride, or epoxy group, that can react with two crosslinkable groups of lignin during the reaction is considered as two crosslinkable units.

[0089] Preferably, a crosslinking agent is added to the liquid obtained in step b), such that the crosslinkable units in the crosslinking agent used are at most 4 moles, preferably at most 3 moles, further preferably at most 2.5 moles, particularly preferably at most 2 moles, and even more preferably at most 1.75 moles, especially at most 1.5 moles, relative to each mole of crosslinkable units in the lignin used.

[0090] Preferably, a crosslinking agent is added to the liquid obtained in step b), such that the crosslinking units present in the crosslinking agent are at least 0.2 moles, preferably at least 0.5 moles, more preferably at least 0.75 moles, more preferably at least 1 mole, particularly preferably at least 1.1 moles, and especially at least 1.15 moles, relative to each mole of crosslinkable units in the lignin used. Preferably, the addition of the crosslinking agent to the liquid obtained in step b) results in the crosslinkable units of the crosslinking agent being from 0.2 moles to 4 moles, more preferably from 0.5 moles to 3 moles, and particularly preferably from 1 mole to 2 moles, relative to each mole of crosslinkable units in the lignin used.

[0091] Crosslinking agents can react on the ortho- and / or para-positions of phenolic rings in lignin (guaiacol and p-hydroxyphenyl). Suitable crosslinking agents for reactions at the ortho- and para-positions of vacant phenolic rings are, for example, aldehydes such as formaldehyde, furfural, 5-hydroxymethylfurfural (5-HMF), hydroxybenzaldehyde, vanillin, syringaldehyde, piperaldehyde, glyoxal, glutaraldehyde, or sulphuraldehyde. Preferred crosslinking agents for phenolic ring reactions are formaldehyde, furfural, and sulphuraldehyde (acetaldehyde / propionaldehyde), such as glyceraldehyde and hydroxyacetaldehyde.

[0092] Furthermore, the crosslinking agent can react with aromatic and aliphatic OH groups (guaiacol, p-hydroxyphenyl, eugenyl) in lignin. For this purpose, bifunctional and polyfunctional compounds having epoxy groups (e.g., glycidyl ether), isocyanate groups (e.g., diisocyanates or oligomeric diisocyanates), or acid anhydrides are preferred. Preferred crosslinking agents for reacting with aromatic and aliphatic OH groups are polyisocyanates (especially diisocyanates or triisocyanates) and acid anhydrides.

[0093] Furthermore, crosslinking agents can also react with carboxyl groups. For this purpose, diols and triols can be used, for example. A preferred crosslinking agent for reaction with carboxyl groups is a diol.

[0094] Furthermore, the crosslinking agent can react with each of the phenolic ring, aromatic and aliphatic OH groups, and carboxyl groups. For this purpose, for example, bifunctional and polyfunctional compounds having at least two of the aforementioned crosslinking functional groups can be used.

[0095] When a crosslinking agent that reacts with the phenolic ring is used, the crosslinkable units in the lignin used are understood to be guaiacol and p-hydroxyphenyl. The concentration of crosslinkable units (mmol / g) is determined, for example, by 31P NMR spectroscopy (Podschun et al., European Polymer Journal, 2015, 67, 1-11), where the guaiacol group contains one crosslinkable unit and the p-hydroxyphenyl group contains two crosslinkable units.

[0096] When using crosslinking agents that react with aromatic and aliphatic OH groups, the crosslinkable units in the lignin used are understood to refer to all aromatic and aliphatic OH groups. The concentration (mmol / g) of crosslinkable units is determined, for example, by 31N PMR spectroscopy, with one OH group corresponding to one crosslinkable unit.

[0097] When a crosslinking agent that reacts with carboxyl groups is used, the crosslinkable unit in the lignin used is understood to refer to all carboxyl groups. The concentration of crosslinkable units (mmol / g) is determined, for example, by 31P NMR spectroscopy, with one carboxyl group corresponding to one crosslinkable unit.

[0098] Preferably, the amount of crosslinking agent in the liquid obtained in step b) is at most 35g / 100g lignin, more preferably at most 30g / 100g lignin, and particularly preferably at most 25g / 100g lignin.

[0099] Preferably, the amount of crosslinking agent (preferably formaldehyde) in the liquid obtained in step b) is at most 25 g / 100 g lignin, more 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. Therefore, the amount of crosslinking agent (preferably formaldehyde) added can be from 1 g / 100 g lignin to 20 g / 100 g lignin, preferably from 5 g / 100 g lignin to 15 g / 100 g lignin, and particularly preferably from 6 g / 100 g lignin to 12 g / 100 g lignin. Alternatively, a precursor of the crosslinking agent (e.g., formaldehyde or other aldehydes) can be added wholly or partially to the liquid, thereby forming the actual crosslinking agent in situ.

[0100] By adjusting the amount of crosslinking agent as described above, the specific surface area of ​​the obtained crosslinked lignin particles can be significantly increased.

[0101] Advantageously, a precursor to the crosslinking agent can be used as a substitute for or in addition to the crosslinking agent, which generates the crosslinking agent in situ before and / or during hydrothermal treatment. The advantage of generating the crosslinking agent in situ is that the amount of crosslinking agent added can be reduced or completely eliminated.

[0102] Advantageous examples of suitable precursors for crosslinking agents are carbohydrates, preferably cellulose, hemicellulose, or glucose, or lignin, each of which can be dispersed or dissolved in a liquid. When carbohydrates, preferably cellulose, hemicellulose, or glucose, are used as precursors, aldehydes, preferably glyceraldehyde or hydroxyacetaldehyde, can be generated in situ from them in the method of the invention, and then they act as crosslinking agents. When lignin is used as a precursor, aldehydes, particularly aldehydes, preferably methandiol or hydroxyacetaldehyde, can be generated in situ from it in the method of the invention, and then it is used as a crosslinking agent.

[0103] Relative to the weight of the liquid obtained in step b), excluding the crosslinking agent and / or the precursor of the crosslinking agent, the proportion of lignin in the total mass of the lignin-containing liquid obtained in step b) is advantageously 3% to 25%, preferably less than 20%, and particularly preferably less than 18%. In a preferred embodiment, the amount of lignin in the liquid obtained in step b) is from 3% to 25% by weight, preferably from 7% to 18% by weight, relative to the weight of the liquid obtained in step b) excluding the crosslinking agent and / or the precursor of the crosslinking agent.

[0104] The dry matter content and ash content of the liquid obtained in step b)

[0105] The liquid obtained in step b) has a dry matter content of 5% to 25% by weight. The liquid obtained in step b) has an ash content of 10% to 45% by weight relative to the dry matter.

[0106] Dry matter content can be determined by thermogravimetric analysis at a temperature adjusted to 105°C. A suitable instrument is, for example, a Sartorius MA35 moisture analyzer. The moisture content, or water content, that is usually measured must then be recalculated to give the dry matter content, for example, dry matter content = 100 - water content (wt%).

[0107] Ash content was determined according to DIN 51719, and the ashing temperature was set to 915℃.

[0108] The pH value of the liquid obtained in step b)

[0109] The liquid containing lignin and at least one crosslinking agent and / or a precursor of the crosslinking agent obtained in step b)(or b1)(or b2)() has 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, preferably 8 to 9.5, and particularly preferably 8 to 9. Experiments have shown that a pH value of about 8.5 to 9 is most suitable for obtaining a high specific surface area, while the obtainable BET and STSA surface areas are significantly reduced when the pH value is below 6.5 or below 7.5 or significantly above 9.

[0110] The pH value is lowered by adding acid and / or acidic gas to the black liquor in step b1), or by adding acid and / or acidic gas to the black liquor in step b2) and optionally mixing additional acid and / or additional acidic gas with the separated solid lignin feedstock.

[0111] The pH value of the liquid obtained in step b) can be determined directly after the liquid is prepared according to step b), specifically the pH value before the hydrothermal treatment according to step c). The pH value is measured at room temperature (23°C).

[0112] In a preferred embodiment, an acid or acidic gas is mixed into the solid lignin raw material separated in step b2) to further reduce the pH value. If another acid is added, the amount of acid (e.g., sulfuric acid, acetic acid, or formic acid) mixed to form the liquid in step b) is preferably 2 to 15 g, more preferably 5 to 12 g, relative to 100 g of lignin in the liquid.

[0113] The electrical conductivity of the liquid obtained in step b)

[0114] The liquid containing lignin and at least one crosslinking agent and / or a precursor of one crosslinking agent prepared in step b) according to b1) or b2) exhibits an electrical conductivity in the range of greater than 15 mS / cm to 400 mS / cm. Despite the high electrical conductivity of the liquid, the method of the present invention can prepare lignin particles with a high specific surface area.

[0115] In a preferred embodiment, the liquid obtained in step b) exhibits a conductivity greater 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) can preferably be greater than 25 mS / cm to 200 mS / cm, preferably in the range of greater than 25 mS / cm to 80 mS / cm, or 25 mS / cm to 60 mS / cm, or 25 to 40 mS / cm. However, it can also be in the range of, for example, 30 mS / cm to 80 mS / cm or 40 mS / cm to 60 mS / cm.

[0116] Here, conductivity is used as a measure of the ion content of the liquid. It refers to the conductivity of the liquid at 23°C and can be measured using a common conductivity meter (e.g., a pH meter designed for this purpose). Conductivity (conductivity values ​​measured at 20°C to 25°C) is measured using the measuring probe of a PCE-PH D1 instrument (a pH meter from PCE Instruments). The conductivity of the liquid obtained in step b) can be measured directly after the liquid preparation in step b), particularly before hydrothermal treatment.

[0117] hydrothermal treatment

[0118] The method of the present invention further includes, as step c), hydrothermal treatment of the liquid containing lignin and / or at least one crosslinking agent and / or a precursor of the crosslinking agent obtained in step b) at a temperature of 150°C to 270°C, to form crosslinked lignin particles in the liquid.

[0119] The hydrothermal treatment temperature is advantageously below 270°C, preferably below 260°C, more preferably below 250°C, and in some cases below 240°C.

[0120] In an advantageous embodiment, the hydrothermal treatment temperature is above 150°C, preferably at least 160°C, more preferably at least 170°C, preferably above 180°C, and even more preferably above 190°C, particularly above 200°C, and in some cases above 210°C.

[0121] In a preferred embodiment, the hydrothermal treatment is carried out in a temperature range of 180°C to 250°C, preferably 210°C to 250°C.

[0122] Advantageously, the duration of 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, more preferably less than 300 minutes, especially less than 180 minutes, and in some cases less than 150 minutes.

[0123] The hydrothermal treatment is carried out under positive pressure. The hydrothermal treatment is preferably carried out in a pressure vessel, particularly in a reactor or autoclave. The pressure during the hydrothermal treatment is preferably at least 1 bar higher than the saturated vapor pressure of the lignin-containing liquid, more preferably at least 2 bar, and most preferably up to 10 bar.

[0124] During hydrothermal treatment, the liquid can also be moved to achieve proper mixing, for example by stirring or recirculating the liquid.

[0125] During hydrothermal treatment, lignin crosslinking occurs via a crosslinking agent, forming crosslinked lignin particles in a liquid. Partial reaction between lignin and the crosslinking agent may also occur during liquid heating prior to hydrothermal treatment. The crosslinked lignin particles obtained through hydrothermal treatment are stable lignin particles, which will be described in detail below.

[0126] Separation of cross-linked lignin particles

[0127] The method of the present invention further includes step d), wherein the cross-linked lignin particles formed in step c) are separated from the liquid.

[0128] To separate the formed cross-linked lignin particles from the liquid, all common solid-liquid separation methods can be used. Preferably, the liquid is separated from the particles by filtration or centrifugation. When using filtration or centrifugation, it is preferable to achieve a dry matter content greater than 15%, preferably greater than 20%, more preferably greater than 25%, particularly preferably greater than 30%, and preferably less than 60%, preferably less than 55%, more preferably less than 50%, particularly preferably less than 45%, and further preferably less than 40%. Another possible way to separate lignin particles is, for example, by evaporating the liquid under elevated temperature and / or reduced pressure.

[0129] Cleaning of cross-linked lignin particles

[0130] The method of the present invention further includes step e), wherein the cross-linked lignin particles separated in step d) are washed with a cleaning medium or cleaning solution. The separated cross-linked lignin particles can be washed once or several times with the cleaning medium. In a preferred embodiment, the used cleaning medium is returned to the evaporation equipment used for black liquor.

[0131] In a particularly advantageous embodiment, the pH of the cleaning medium used is higher than 4, preferably higher than 6, and lower than 10, preferably lower than 9. Suitable cleaning media include, for example, water, such as tap water or preferably desalinated water, optionally containing additives, such as acids or bases.

[0132] Washing removes inorganic compounds from the particles, significantly reducing the ash content of cross-linked lignin particles. This helps improve the particle properties.

[0133] The washed lignin particles are typically dried, with at least a portion of the remaining liquid preferably removed by evaporation, for example, heating and / or reduced pressure. It is preferable to obtain dried or dry-crosslinked lignin particles as the final product. Preferably, the dry matter content is greater than 90%, more preferably greater than 92%, and particularly greater than 95%. In this invention, dried particles are understood to be particles with a dry matter content greater than 90%, more preferably greater than 92%, and particularly greater than 95%.

[0134] Preferably, the liquid separated in step d) and optionally the used cleaning medium obtained in step e) are supplied to a reprocessing device to recover liquid and / or energy from the components.

[0135] Optionally, the liquid separated in step d) and / or the used cleaning medium from step e) may be returned to recover the liquid. Body and / or energy

[0136] The liquid separated in step d) and optionally the used cleaning medium obtained in step e) are optionally and preferably returned to a reprocessing unit, particularly a black liquor evaporation unit, to recover the liquid and / or energy. These components originate from the black liquor used. The black liquor evaporation unit is part of the reprocessing unit. Typically, in addition to the evaporation unit, such a reprocessing unit also includes a liquid recovery boiler and a causticizing unit.

[0137] In a preferred embodiment, the black liquor provided in step a) is taken from an evaporation device for black liquor, and the liquid separated in step d) and optionally the used cleaning medium obtained in step e) are returned to the evaporation device at a location downstream of the black liquor extraction point, so that no recycling occurs.

[0138] Heating and optional intermediate treatment of the liquid obtained in step b).

[0139] In order to achieve the temperature of hydrothermal treatment and / or optional intermediate treatment, the heating rate of the liquid containing lignin and at least one crosslinking agent and / or its precursor obtained in step b) is preferably less than 15 Kelvin / min, more preferably less than 10 Kelvin / min, and particularly preferably less than 5 Kelvin / min.

[0140] Prior to hydrothermal treatment, it may be appropriate to keep the liquid obtained in step b) at a lower temperature for a period of time; this will be referred to as intermediate treatment below.

[0141] In this optional intermediate treatment, prior to the hydrothermal treatment in step c), the liquid prepared in step b) is kept at a temperature of 50°C to below 150°C, more preferably 60°C to 130°C, particularly preferably 70°C to below 100°C for 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.

[0142] As mentioned above, during the heating of the liquid obtained in step b) and the optional intermediate treatment, at least a portion or more of the lignin can dissolve in the liquid.

[0143] Without being bound by any theory, it is speculated that during heating and optional intermediate treatments, a partial reaction between the dissolved lignin and the crosslinking agent may also occur, in which modified dissolved lignin is obtained, where the lignin reacts with the crosslinking agent, but crosslinking by the crosslinking agent does not occur or only occurs partially. In other words, the molecules of the crosslinking agent may bind to the lignin at one site, but with the formation of a second crosslink between the molecule and the lignin, the binding is only partial (or not at all).

[0144] The dissolved modified lignin should be understood in particular as follows:

[0145] Aromatic compounds in lignin are further bonded primarily via ether bonds.

[0146] The para-substituted phenolic ring constitutes more than 95% of the total aromatic ring, preferably more than 97%, particularly preferably 99%, and the content of free phenol is less than 200 ppm, preferably less than 100 ppm, further preferably less than 75 ppm, particularly preferably less than 50 ppm.

[0147] The content of krasen lignin is at least 70%, preferably at least 75%, particularly preferably at least 80%, and especially at least 85%.

[0148] The content of free phenols was determined according to DIN ISO 8974. The content of classen lignin was determined as acid-insoluble lignin according to TAPPI T 222. The quantification and qualitative determination of phenolic groups were performed by 31P-NMR according to M. Zawadzki and A. Ragauskas (Holzforschung 2001, 55, 3).

[0149] Higher reaction selectivity and targeted acquisition of dissolved modified lignin can be ensured by reacting the crosslinking agent with lignin dissolved in liquid during heating and / or in optional intermediate treatments, which is then converted into crosslinked lignin particles in hydrothermal treatment. By implementing heating at the stated heating rate and / or optional intermediate treatment of the liquid obtained in step b), polymerization of the crosslinking agent with lignin and carbonization products that may form from lignin is reduced or completely inhibited. The particle properties of the crosslinked or stable lignin particles can be targeted by converting the modified dissolved lignin into stable crosslinked lignin particles in hydrothermal treatment. Therefore, favorable particle properties can be tuned.

[0150] The temperature of the optional intermediate processing is advantageously above 50°C, preferably above 60°C, particularly preferably above 70°C, and below 180°C, preferably below 150°C, further preferably below 130°C, and particularly preferably below 100°C.

[0151] Advantageously, the average dwell time in the optional 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.

[0152] An advantageous combination of optional intermediate processing time and temperature window is a minimum temperature of 50°C and a maximum temperature below 150°C, with 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. Another advantageous combination of optional intermediate processing time and temperature window is a minimum temperature of 50°C and a maximum temperature below 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.

[0153] In a preferred embodiment of the optional intermediate treatment, the temperature is maintained at 50°C to below 150°C for at least 20 minutes, preferably at least 60 minutes.

[0154] In another preferred embodiment of the optional intermediate treatment, the temperature is maintained at 70°C to below 130°C for at least 10 minutes, preferably at least 50 minutes.

[0155] Optional intermediate treatments can be performed at atmospheric pressure or positive pressure, preferably at positive pressure.

[0156] Cross-linked lignin particles I

[0157] Cross-linked lignin in particulate form is prepared by the method of the present invention. Therefore, the lignin obtained by the method of the present invention exists in the form of cross-linked lignin particles, wherein the final product obtained by the method is preferably a powder, particularly a dry powder. Thus, they are solid particles that can be dispersed in a liquid or exist as a dry powder.

[0158] Preferably, the yield of cross-linked lignin particles is greater than 60%, more preferably greater than 70%, particularly preferably greater than 80%, and especially greater than 85%, relative to the lignin used.

[0159] The cross-linked lignin particles thus obtained are particularly stable lignin particles. Stabilization through cross-linking and hydrothermal treatment leads to improved properties, such as increased specific surface area, decreased solubility in alkaline liquids, and / or an increased glass transition temperature or no measurable glass transition temperature at all. The obtained cross-linked or stable lignin particles preferably exhibit a glass transition temperature greater than 160°C, preferably greater than 180°C, particularly preferably greater than 200°C, and especially greater than 250°C. Preferably, the glass transition temperature is not detectable at all in the obtained cross-linked lignin particles, i.e., there is no glass transition temperature.

[0160] After solid-liquid separation, washing and drying, the glass transition temperature of the dried cross-linked lignin particles was measured according to DIN 53765.

[0161] The stable lignin particles obtained by the method of the present invention have other advantageous particle properties, which makes them usable in material applications.

[0162] Preferably, the cross-linked lignin particles obtained by this method have a d50 value (volume average) of less than 500 μm, more preferably less than 300 μm, further preferably less than 200 μm, particularly less than 100 μm, and especially preferably less than 50 μm. Preferably, the d50 value (volume average) of the particle size distribution is greater than 0.5 μm, more preferably greater than 1 μm, and especially preferably greater than 2 μm.

[0163] The particle size distribution of crosslinked or stabilized lignin was measured by laser diffraction in a distilled water suspension according to ISO 13320. Before and / or during the measurement of particle size distribution, the sample was dispersed ultrasonically until a stable particle size distribution was achieved across multiple measurements. This stability was achieved if individual measurements (e.g., d50) of a series of measurements differed from each other by no more than 5%.

[0164] The obtained cross-linked lignin particles are particularly preferred to have an STSA or STSA surface area of ​​at least 10 m². 2 / g, more preferably at least 20m 2 / g, more preferably at least 30m 2 / g, or even more preferably at least 40m 2 / g, preferably at least 50m 2 / g. Preferably, STSA is less than 200m. 2 / g, preferably less than 180m 2 / g. STSA (Statistical Thickness Surface Area) is a characterization of the external surface area of ​​the obtained lignin particles.

[0165] In this variant of cross-linked lignin particles, the STSA surface area showed a minimum of 10 m². 2 / g to 180m 2 / g, preferably at least 20m 2 / g to 180m 2 / g, further optimized 30m 2 / g to 180m 2 / g, Specially Selected 40m 2 / g to 180m 2 The value of / g.

[0166] Advantageously, the BET surface area of ​​the crosslinked or stabilized lignin differs from the STSA surface area by a maximum of 20%, preferably a maximum of 15%, and more preferably a maximum of 10%. The BET surface area is the total surface area determined by Brunauer, Emmett and Teller from the external and internal surface areas via nitrogen adsorption.

[0167] The surface areas of BET and STSA were determined according to ASTM D 6556-14. However, in contrast, in this invention, sample preparation / degassing for measuring STSA and BET was performed at 150°C.

[0168] The ash content of the cross-linked lignin particles prepared according to the method of the present invention is preferably less than 5% by mass, more preferably less than 3% by mass, and more than 1% by mass.

[0169] Preferably, the obtained cross-linked lignin particles have only low porosity. Advantageously, the pore volume of cross-linked or stabilized lignin is <0.1 cm³. 3 / g, further optimized to <0.01cm 3 / g, with a preferred value of <0.005cm 3 / g. Therefore, this cross-linked or stabilized lignin differs from finely granulated porous materials such as ground bio-activated carbon powder, except that its BET surface area is typically greater than 500m².2 In addition to / g, it can also have up to 10m 2 / g STSA surface area.

[0170] The obtained cross-linked lignin particles differ from lignin resins prepared by reaction with formaldehyde and transformed from solution to a gel state into a solid resin, particularly in terms of preferred advantageous particle properties, such as a d50 value of particle size distribution less than 500 μm or an STSA greater than 10 μm. 2 / g, preferably greater than 20m 2 / g.

[0171] Preferably, the obtained cross-linked lignin particles are conditionally soluble only in alkaline liquids. Preferably, the solubility of undissolved stable lignin is less than 30%, more preferably less than 25%, and particularly preferably less than 20%.

[0172] The alkali solubility of cross-linked or stable lignin particles was determined as follows:

[0173] 1. Separate the lignin particles from the liquid by centrifugation or filtration, and then wash with distilled water.

[0174] 2. Dry the product from step 1 at 105°C for 24 hours.

[0175] 3. To determine the solubility of a solid sample, it must be in the form of a dry, fine powder (DS > 98%). If this is not the case, grind or thoroughly slurry the dry sample before determining the solubility.

[0176] 4. Solubility determination in triplicate. For this purpose, 4g of dry packing material was weighed into each 100ml conical flask containing 80g of 0.1M NaOH.

[0177] 5. Shake the alkaline suspension at a rate of 200 shakes per minute for 2 hours at room temperature (23°C). If the liquid comes into contact with the lid during this process, the shaking rate must be reduced to prevent this from happening.

[0178] 6. The suspension is then transferred as completely as possible to a Buchner funnel fitted with filter paper (55 mm in diameter, with pore sizes of 5 μm to 8 μm, pre-adjusted to the nearest 0.1 mg on an analytical balance) and filtered under vacuum. The filter paper is slightly moistened under vacuum before filtration. After complete filtration, the pH of the filtrate is measured and recorded. The conical flask is then rinsed with 40 ml of distilled water to transfer any remaining residue to the Buchner funnel, while simultaneously removing any soluble substances (e.g., NaOH used) from the filter cake. Filtration continues until the filter cake is dry again.

[0179] 7. After cleaning the filter cake, dry the Buse funnel in a drying oven at 105°C for at least 24 hours until the weight remains constant.

[0180] 8. The alkali solubility of solid substances rich in lignin is calculated as follows:

[0181] The alkali solubility of lignin-rich solids [%] = 100% - X%, where X% = mass of the undissolved portion after centrifugation or filtration and drying [g] × 100 / mass of the dried product obtained in step 2 above [g].

[0182] The present invention also relates to cross-linked lignin particles obtainable by the method of the present invention, wherein the cross-linked lignin particles preferably exhibit a cross-linking density of at least 10 μm. 2 / g, further preferably at least 20m 2 / g, more preferably at least 30m 2 / g, or even more preferably at least 40m 2 / g, preferably at least 50m 2 / g STSA surface area.

[0183] The lignin particles obtained by the method of the present invention preferably exhibit the following properties:

[0184] -STSA is at least 10m 2 / g, preferably at least 20m 2 / g, more preferably at least 30m 2 / g, or even more preferably at least 40m 2 / g, preferably at least 50m 2 / g. Preferably, STSA is less than 200m. 2 / g, preferably small

[0185] At 180m 2 / g;

[0186] - Relative to a methoxyl signal of 54 ppm to 58 ppm, in the solid state at 0 ppm to 50 ppm, preferably at 10 ppm to 40 ppm, and particularly preferably at 25 ppm to 35 ppm 13 The intensity of the C-NMR signal is 1% to 80%, preferably 5% to 60%, particularly preferably 5% to 50%; and is between 125 ppm and 135 ppm, preferably between 127 ppm and 133 ppm. 13 The C-NMR signal was increased compared to the lignin used;

[0187] - Corresponding to the regeneration raw material 14 The carbon content is 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;

[0188] - The carbon content of the ash-free dry matter is 60% to 80% by weight, preferably 65% ​​to 75% by weight;

[0189] - The glass transition temperature is higher than 160°C, more preferably higher than 180°C, particularly preferably higher than 200°C, and especially higher than 250°C.

[0190] Preferably, the cross-linked lignin particles do not have a measurable glass transition temperature.

[0191] - Cross-linked or stabilized lignin has a pore volume of less than 0.1 cm³. 3 / g, further preferably less than 0.01cm 3 / g,

[0192] Preferably less than 0.005cm 3 / g.

[0193] Cross-linked lignin particles II

[0194] The present invention also relates to cross-linked lignin particles exhibiting a glass transition temperature (Tg) of at least 160°C or no glass transition temperature at all. Furthermore, the STSA surface area of ​​the cross-linked lignin particles is at least 10 m². 2 / g. As described above, cross-linked lignin particles are lignin particles cross-linked with a cross-linking agent, wherein possible cross-linking agents are those mentioned above, especially formaldehyde.

[0195] Particularly preferred is that the STSA or STSA surface area of ​​the cross-linked lignin particles is at least 20 m². 2 / g, more preferably at least 30m 2 / g, or even more preferably at least 40m 2 / g, preferably at least 50m 2 / g. Preferably, STSA is less than 200m. 2 / g, preferably less than 180m 2 / g. The STSA surface area of ​​cross-linked lignin particles can, for example, be at least 10 m². 2 / g to 180m 2 / g, preferably at least 20m 2 / g to 180m 2 / g, further optimized 30m 2 / g to 180m 2 / g, with 40m being the preferred choice 2 / g to 180m 2 / g.

[0196] Cross-linked lignin particles preferably exhibit a glass transition temperature greater than 180°C, more preferably greater than 200°C, and particularly greater than 250°C. Preferably, the glass transition temperature cannot be measured at all for cross-linked lignin particles.

[0197] The cross-linked lignin particles are characterized in particular by their reduced solubility in alkaline liquids. In a preferred embodiment, the alkaline solubility of the cross-linked lignin particles in 0.1M NaOH at 23°C is less than 30%, preferably less than 25%, and particularly preferably less than 20%. The alkaline solubility is determined according to the method described above.

[0198] In a preferred embodiment, cross-linked lignin particles 14 The carbon content ranges from 0.20 Bq / g carbon to 0.45 Bq / g carbon.

[0199] In order to determine 14 To determine the carbon content, the material to be studied was sent to the Poznań Radiocarbon Laboratory of the Poznań University Foundation, located in Ul. 46, 61-612 Poznań. Laboratory Director Tomaszgoslar described the methods used on the institute's internet. The relevant information regarding lignin is summarized below:

[0200] Using AMS technology 14 The procedure for C-dynasty dating includes the following steps:

[0201] a) Chemical pretreatment as described by Brock et al., 2010, Radiocarbon, 52, 102-112.

[0202] b) CO2 preparation and graphitization

[0203] c) Measurements were taken using a Compact Carbon AMS spectrometer, according to Goslar T., Czernik J., Goslar E., 2004, Nuclear Instruments and Methods B, 223-224, 5-11. 14 C

[0204] d) 14The calculation and calibration of age C (according to Stuiver, Polach 1977, Radiocarbon, 19, 355; calibrated according to Bronk Ramsey C., 2001, Radiocarbon, 43, 355-363; Bronk Ramsey C., 2009, Radiocarbon, 51, 337-360; Bronk Ramsey C. and Lee S., 2013, Radiocarbon, 55, 720-730 and Reimer PJ et al., 2013, Radiocarbon, 55(4), 1869-1887).

[0205] For archaeological purposes, the analysis yielded the age of the carbon samples. However, the measurement results can also be expressed as specific activity.

[0206] Furthermore, the cross-linked particles of the present invention can also exhibit all the other properties described above under “Cross-linked Lignin Particles I”, such as with respect to particle size distribution, ash content and / or pore volume, and therefore are referred to herein.

[0207] According to one embodiment, the cross-linked lignin particles of the present invention can be functionalized, particularly silanized. This should be understood as modification of the surface of the cross-linked lignin particles with a coupling agent. The coupling agent has functional groups through which chemical bonding with the surface of the cross-linked lignin particles can be achieved. Through this functionalization, particularly silanization, it is particularly possible to achieve improved bonding, for example, chemical bonding with polymers, particularly rubber elastomers, used as matrix materials.

[0208] 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)-oligosulfides or bis(trialkoxysilylalkyl)-polysulfides, mercaptosilanes, aminosilanes, or silanes having unsaturated hydrocarbon groups, such as vinylsilanes.

[0209] The functionalization or silanization of crosslinked lignin particles is preferably carried out ex situ, that is, before mixing with polymers, especially rubber.

[0210] In a preferred embodiment, as described above, the cross-linked lignin particles are lignin particles that can be obtained by the method of the present invention.

[0211] Rubber products containing cross-linked lignin particles, especially industrial rubber products or tires

[0212] The present invention also relates to rubber articles, particularly industrial rubber articles or tires, which comprise cross-linked lignin particles as described above as fillers and at least one polymer, particularly a rubber elastomer, as a matrix or matrix material. Those skilled in the art will know that rubber articles can contain various additives, such as fillers.

[0213] The polymer contained in rubber products as a matrix or matrix material is, in particular, a rubber elastomer. A rubber elastomer can be formed from one or more types of rubber. For example, a rubber elastomer can be formed from natural rubber (1,4-polyisoprene) from the rubber tree *Hevea brasiliensis* or dandelion (*Taraxacum*), synthetic natural rubber and / or synthetic rubber, or mixtures thereof, and then converted into a rubber matrix by vulcanization.

[0214] The crosslinked lignin of the present invention can thus be used in rubber products, particularly industrial rubber products or tires, for example, in an amount of 10% to 150% by weight, preferably 20% to 120% by weight, more preferably 40% to 100% by weight, and particularly preferably 50% to 80% by weight, relative to the weight of rubber used in the rubber product.

[0215] Rubber products, especially industrial rubber products or tires, are products based on rubber or rubber elastomers, i.e., vulcanized rubber, which serves as the matrix material for the product. Rubber products, especially industrial rubber products or tires, are sometimes also referred to as rubber products (Gummiwaren, Kautschukartikel, or Kautschukwaren in German). One of the professional English terms for industrial rubber products is "mechanical rubber products" (abbreviated as MRG). Examples of rubber products, especially industrial rubber products or tires, include vehicle tires, sealing profiles, belts, sheets, conveyor belts, hoses, spring elements, rubber-metal composite parts, roller liners, molded products, rubber seals, and cables.

[0216] In a preferred embodiment, the rubber article, particularly industrial rubber article or tire, may contain additional fillers, particularly carbon black and / or silica and / or other inorganic or surface-treated inorganic fillers, such as chalk and silica.

[0217] The cross-linked lignin particles contained in rubber articles, particularly industrial rubber articles or tires, of the present invention are especially the cross-linked lignin particles of the present invention as described below, "Cross-linked Lignin Particles II". Particularly preferably, the cross-linked lignin particles can be obtained by the method of the present invention as described above.

[0218] The present invention will be described below by way of exemplary embodiments; however, these exemplary embodiments should not be construed as limiting the invention in any way.

[0219] Exemplary Implementation

[0220] In the examples below, BET is given instead of STSA. However, for the undissolved stable lignin prepared in this paper, the difference between BET and STSA is no more than 10%. The lignin content of the feedstock is given here by subtracting the anhydrous ash content from the feedstock mass.

[0221] Example 1 (Comparison)

[0222] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water, the solid matter 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 at the time and temperature given in Table 1. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 1 were obtained. The yield was calculated relative 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 stable lignin in Table 1 was determined after vacuum baking at 150°C.

[0223] Table 1: Variations of the experiment in Example 1 at different additive concentrations

[0224]

[0225] Example 2

[0226] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 19.1% and a pH of 9. The formaldehyde amount 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 at the time and temperature given in Table 2. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 2 were obtained. The yield was calculated relative 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 stable lignin in Table 2 was determined after vacuum baking at 150°C.

[0227] Table 2: Variations of the experiment in Example 2 at different additive concentrations

[0228]

[0229] Example 3

[0230] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter 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 at the time and temperature given in Table 3. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 3 was obtained. The yield was calculated relative 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 stable lignin in Table 3 was determined after vacuum baking at 150°C.

[0231] Table 3: Variations of the experiment in Example 3 at different additive concentrations

[0232]

[0233] Example 4 (Comparison)

[0234] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water, the solid matter 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 at the time and temperature given in Table 4. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 4 was obtained. The yield was calculated relative 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 stable lignin in Table 4 was determined after vacuum baking at 150°C.

[0235] Table 4: Variations of the experiment in Example 4 at different additive concentrations

[0236]

[0237] Example 5

[0238] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 15.3% and a pH of 9.2. The formaldehyde amount 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 at the time and temperature given in Table 5. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 5 was obtained. The yield was calculated relative 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 stable lignin in Table 5 was determined after vacuum baking at 150°C.

[0239] Table 5: Variations of the experiment in Example 5 at different additive concentrations

[0240]

[0241] Example 6

[0242] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 15.5% and a pH of 8.5. The formaldehyde amount 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 at the time and temperature given in Table 6. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 6 was obtained. The yield was calculated relative 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 stable lignin in Table 6 was determined after vacuum baking at 150°C.

[0243] Table 6: Variations of the experiment in Example 6 at different additive concentrations

[0244]

[0245] Example 7 (Comparison)

[0246] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water, the solid matter 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 at the time and temperature given in Table 7. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 7 was obtained. The yield was calculated relative 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 stable lignin in Table 7 was determined after vacuum baking at 150°C.

[0247] Table 7: Variations of the experiment in Example 7 at different additive concentrations

[0248]

[0249] Example 8

[0250] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 9.4% and a pH of 8.8. The formaldehyde amount 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 at the time and temperature given in Table 8. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 8 was obtained. The yield was calculated relative 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 stable lignin in Table 8 was determined after vacuum baking at 150°C.

[0251] Table 8: Variations of the experiment in Example 8 at different additive concentrations

[0252]

[0253] Example 9

[0254] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 10.3% and a pH of 8.6. The formaldehyde amount 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 at the time and temperature given in Table 9. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 9 was obtained. The yield was calculated relative 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 stable lignin in Table 9 was determined after vacuum baking at 150°C.

[0255] Table 9: Variations of the experiment in Example 9 at different additive concentrations

[0256]

[0257] Example 10

[0258] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and acetic acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 10.4% and a pH of 8.6. The formaldehyde amount 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 at the time and temperature given in Table 10. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 10 were obtained. The yield was calculated relative 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 stable lignin in Table 10 was determined after vacuum baking at 150°C.

[0259] Table 10: Variations of the experiment in Example 10 at different additive concentrations

[0260]

[0261] Example 11

[0262] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 27.2%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 11.5% and a pH of 8.7. The formaldehyde amount 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 at the time and temperature given in Table 11. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 11 were obtained. The yield was calculated relative 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 stable lignin in Table 11 was determined after vacuum baking at 150°C.

[0263] Table 11: Variations of the experiment in Example 11 at different additive concentrations

[0264]

[0265] Example 12

[0266] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 10.6% and a pH of 8.6. The formaldehyde amount 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 at the time and temperature given in Table 12. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 12 were obtained. The yield was calculated relative 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 stable lignin in Table 12 was determined after vacuum baking at 150°C.

[0267] Table 12: Variations of the experiment in Example 12 at different additive concentrations

[0268]

[0269] Example 13

[0270] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 10.1% and a pH of 8.4. The formaldehyde amount 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 at the time and temperature given in Table 13. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 13 were obtained. The yield was calculated relative 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 stable lignin in Table 13 was determined after vacuum baking at 150°C.

[0271] Table 13: Variations of the experiment in Example 13 at different additive concentrations

[0272]

[0273] Example 14

[0274] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 19.3%. By adding water and acetic acid, the solid matter 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 at the time and temperature given in Table 14. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 14 were obtained. The yield was calculated relative 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 stable lignin in Table 14 was determined after vacuum baking at 150°C.

[0275] Table 14: Variations of the experiment in Example 14 at different additive concentrations

[0276]

[0277] Example 15

[0278] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid matter 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 as a 23.5% formaldehyde solution. The liquid containing dissolved lignin and the formaldehyde solution were homogenized and subjected to hydrothermal treatment at the time and temperature given in Table 15. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yield recorded in Table 15 was obtained. The yield was calculated relative 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 stable lignin in Table 15 was determined after vacuum baking at 150°C.

[0279] Table 15: Variations of the experiment in Example 15

[0280]

[0281] Example 16

[0282] The raw material was lignin obtained from black liquor of sulfate pulping via CO2 precipitation. The anhydrous ash content of the raw material was determined to be 21.2%. By adding water and sulfuric acid, the solid matter was converted into a liquid containing dissolved lignin, with a dry matter content of 10.5% and a pH of 7.1. The formaldehyde amount specified in Table 16 was added to 11600 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 at the time and temperature given in Table 16. Undissolved stable lignin was recovered by filtration. After washing with twice the amount of demineralized water relative to the recovered filtrate and drying in an air-circulating drying oven, the yields recorded in Table 16 were obtained. The yield was calculated relative 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 stable lignin in Table 16 was determined after vacuum baking at 150°C.

[0283] According to the above measurement method, the alkali solubility of the obtained undissolved stable lignin in 0.1M NaOH was measured to be 9.1%.

[0284] Table 16: Variations of the experiment in Example 16

[0285]

Claims

1. A method for preparing cross-linked lignin in particulate form, wherein, The method includes the following steps: a) Provide a black liquor with a dry matter content of 5% to 50% by weight, wherein the pH of the black liquor is 12 to 14. b) Preparing a liquid containing lignin and at least one crosslinking agent and / or a precursor of at least one crosslinking agent from the black liquor, the liquid having the following properties: - Dry matter content is 5% to 25% by weight. - Ash content relative to dry matter is 10% to 45% by weight. - pH value greater than 6.5 and less than 10, - Electrical conductivity greater than 15 mS / cm to 400 mS / cm, The preparation of the liquid includes: i) Mixing the black liquor with acid and / or acidic gas to lower the pH value; and ii) Mixing the black liquor or a product derived therefrom with at least one crosslinking agent and / or a precursor of the crosslinking agent; and iii) Optionally, liquid may be added to reduce the dry matter content. c) The liquid containing lignin and at least one crosslinking agent and / or a precursor prepared in step b) is subjected to hydrothermal treatment at a temperature of 150°C to 270°C to form crosslinked lignin particles in the liquid; and d) Separate the liquid from the cross-linked lignin particles formed in step c); and e) Clean the separated cross-linked lignin particles with a cleaning medium.

2. The method according to claim 1, wherein, The pH value of the liquid prepared in step b) is greater than 7 and less than 10.

3. The method according to claim 1, characterized in that, The liquid prepared in step b) has a pH value higher than 7.5 and lower than 10.

4. The method according to any one of claims 1 to 3, characterized in that, The liquid prepared in step b) comprising lignin and at least one crosslinking agent and / or a precursor of at least one crosslinking agent has an electrical conductivity greater than 25 mS / cm, and / or has an electrical conductivity of up to 200 mS / cm.

5. The method according to any one of claims 1 to 3, wherein, In the liquid prepared in step b), at least a portion of the lignin has been dissolved in the liquid, and / or during the heating of the liquid prepared in step b) to a temperature for hydrothermal treatment, at least a portion of the lignin dissolves in the liquid.

6. The method according to any one of claims 1 to 3, characterized in that, The at least one crosslinking agent is selected from aldehydes, epoxides, acid anhydrides, polyisocyanates, or polyols, and / or the precursor of the at least one crosslinking agent is selected from compounds that form the crosslinking agent in situ.

7. The method according to any one of claims 1 to 3, characterized in that, The amount of the crosslinking agent in the liquid prepared in step b) is at most 4 moles of crosslinkable units relative to each mole of crosslinkable lignin used; and / or the amount of the crosslinking agent in the liquid prepared in step b) is at least 0.2 moles of crosslinkable units of crosslinking agent relative to each mole of crosslinkable lignin used, wherein, in the case of additional or alternative use of a precursor of the crosslinking agent, the amount of the precursor is selected such that the amount is obtained after the crosslinking agent is formed in situ.

8. The method according to claim 7, wherein, The amount of crosslinking agent in the liquid prepared in step b) is a maximum of 1.15 moles of crosslinkable units of crosslinking agent, relative to the amount of crosslinkable lignin units used per mole.

9. The method according to any one of claims 1 to 3, characterized in that, The liquid containing lignin and at least one crosslinking agent and / or a precursor of at least one crosslinking agent prepared in step b) is prepared from the black liquor in the following manner: b1) Mixing the black liquor with i) an acid and / or an acidic gas to lower the pH value, and ii) mixing with at least one crosslinking agent and / or a precursor of the crosslinking agent, or b2) Mixing the black liquor with an acid and / or an acidic gas to lower the pH value and forming a solid lignin raw material in the black liquor; separating the solid lignin raw material from the black liquor; mixing the separated solid lignin raw material with i) the liquid and ii) at least one crosslinking agent and / or a precursor of the crosslinking agent; wherein, optionally, an acid and / or an acidic gas are mixed to further lower the pH value.

10. The method according to claim 9, characterized in that, The pH of the liquid prepared in step b) is between 8 and 9.5, and / or In step b2), 2g to 15g of acid is added for every 100g of lignin to further lower the pH value.

11. The method according to any one of claims 1 to 3, characterized in that, The acid used for mixing in step i) is selected from sulfuric acid, acetic acid, or formic acid, and / or The acidic gas used for mixing in step i) is selected from CO2, H2S, or a mixture of CO2 and H2S.

12. The method according to any one of claims 1 to 3, characterized in that, The hydrothermal treatment is performed at a temperature of 180°C to 250°C, and / or the hydrothermal treatment is performed at a temperature below 270°C.

13. The method according to any one of claims 1 to 3, characterized in that, The duration of the hydrothermal treatment is at least 10 minutes and / or less than 600 minutes.

14. The method according to any one of claims 1 to 3, characterized in that, The amount of lignin in the liquid prepared in step b) is from 4% to 20% by weight relative to the total weight of the liquid which does not contain the at least one crosslinking agent and / or the precursor of the crosslinking agent.

15. The method according to any one of claims 1 to 3, characterized in that, In the liquid prepared in step b), the amount of crosslinking agent is at most 35 g / 100 g lignin.

16. The method according to any one of claims 1 to 3, wherein, In the liquid prepared in step b), the amount of crosslinking agent is from 1 g / 100 g lignin to 20 g / 100 g lignin.

17. The method according to any one of claims 1 to 3, characterized in that, Prior to the hydrothermal treatment in step c), the liquid prepared in step b) is maintained at a temperature of 50°C to below 150°C for at least 5 minutes and less than 300 minutes, and / or To reach the temperature of the hydrothermal treatment and / or optional intermediate treatment, the liquid prepared in step b) is heated at a heating rate of less than 15 Kelvin / min.

18. The method according to any one of claims 1 to 3, characterized in that, The cleaning medium used in step e) for cleaning cross-linked lignin particles has a pH value greater than 4 and less than 10, and / or The cleaning medium used in step e) for cleaning cross-linked lignin particles includes water or water.

19. The method according to any one of claims 1 to 3, characterized in that, The STSA surface area of ​​the cross-linked lignin particles prepared in the method is at least 10 m². 2 / g.

20. The method according to claim 19, wherein, The STSA surface area of ​​the cross-linked lignin particles prepared in the method is not higher than 180 m². 2 / g.

21. The method according to any one of claims 1 to 3, characterized in that, The cross-linked lignin particles prepared in the method have an ash content of less than 5% by mass and greater than 1% by mass.

22. The method according to any one of claims 1 to 3, characterized in that, The black liquor provided in step a) is taken from an evaporation device for black liquor, and the liquid separated in step d) and optionally the used cleaning medium obtained in step e) are returned to the evaporation device at a location downstream of the extraction point of the black liquor.

23. A cross-linked lignin particle, which can be obtained by any one of claims 1 to 22.

24. The cross-linked lignin particles according to claim 23, wherein, The STSA surface area of ​​the cross-linked lignin particles is at least 10 m². 2 / g.

25. The cross-linked lignin particles according to claim 23, wherein, The STSA surface area of ​​the cross-linked lignin particles is at least 20 m². 2 / g.

26. The cross-linked lignin particles according to claim 23, wherein, The STSA surface area of ​​the cross-linked lignin particles is at least 30 m². 2 / g.

27. The cross-linked lignin particles according to claim 23, wherein, The STSA surface area of ​​the cross-linked lignin particles is at least 40 m². 2 / g.

28. A cross-linked lignin particle, which can be obtained by any one of claims 1 to 22, characterized in that, Its glass transition temperature (Tg) is at least 160 °C or there is no glass transition temperature at all, and the STSA surface area is at least 10 m². 2 / g.

29. The cross-linked lignin particles according to claim 28, characterized in that, Its alkali solubility in 0.1M NaOH at 23℃ is less than 30%.

30. The cross-linked lignin particles according to claim 28, characterized in that, That 14 The carbon content ranges from 0.20 Bq / g carbon to 0.45 Bq / g carbon.

31. The cross-linked lignin particles according to claim 28, characterized in that, It is silanized.

32. The cross-linked lignin particles according to claim 28, characterized in that, Its glass transition temperature is higher than 180℃, or it has no glass transition temperature at all.

33. A rubber article comprising cross-linked lignin particles as a filler according to any one of claims 23 to 32 and at least one polymer as a matrix material.

34. The rubber article according to claim 33, wherein, The rubber product is an industrial rubber product or a tire.

35. The rubber article according to claim 33, wherein, The polymer is a rubber elastomer.

36. The rubber article according to claim 35, wherein, The rubber elastomer is made of natural rubber, synthetic natural rubber, and / or synthetic rubber.

37. The rubber article according to claim 36, wherein, The natural rubber comes from the rubber tree or the dandelion genus.

38. The rubber article of claim 33, wherein it comprises additional filler.

39. The rubber article according to claim 38, wherein, The additional filler is carbon black and / or silica or a surface-treated inorganic filler.

Images