CN118804945A - Method for preparing porous material - Google Patents

Abstract

The present invention relates to a method for preparing a porous material, which comprises at least the following steps: providing a mixture (M1) comprising a water-soluble bio-based polyphenol polymer selected from lignin biopolymers and tannin biopolymers as a compound (C1) and water; contacting the mixture (M1) with an aqueous solution of at least one multivalent metal ion to prepare a gel (A); exposing the obtained gel (A) to a water-miscible solvent (L) to obtain a gel (B); and drying the gel (B). The present invention also relates to the porous material obtainable in this way and the following uses of the porous material: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home and commercial appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

Description

Method for preparing porous material

The present invention relates to a method for preparing a porous material, comprising at least the following steps: providing a mixture (M1) comprising a water-soluble bio-based polyphenol polymer as a compound (C1) and water, the water-soluble bio-based polyphenol polymer being selected from lignin biopolymers and tannin biopolymers; contacting the mixture (M1) with an aqueous solution of at least one multivalent metal ion to prepare a gel (A); exposing the obtained gel (A) to a water-miscible solvent (L) to obtain a gel (B); and drying the gel (B). The present invention also relates to the porous material obtainable in this way and the following uses of the porous material: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for household and commercial appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

Porous materials based on bio-based polymers, such as polymer foams, having pores in the size range of a few microns or well below a few microns and a high porosity of at least 70% are particularly suitable for various applications.

Such porous materials with a small average pore size may be in the form of organic aerogels or xerogels prepared, for example, by a sol-gel process and subsequent drying. In the sol-gel process, a sol based on an organogel precursor is first prepared, which is then gelled to form a gel by a crosslinking step. In order to obtain a porous material (e.g., an aerogel) from the gel, the liquid must be removed. For the sake of simplicity, this step is referred to hereinafter as drying.

The present invention relates to a method for preparing a porous material containing bio-based phenolic polymers, as well as the porous material itself and its use. In particular, the present invention relates to a method for preparing a porous material containing lignin. Lignin is a heterogeneous biopolymer. Depending on its source (e.g. wood and/or plant source) and the extraction method, its properties (e.g. molar mass or degree of condensation) and chemical composition may vary. Generally, lignin is a disordered biopolymer with three main structural units, namely coumarin, coniferyl alcohol and sinapyl alcohol. Other suitable bio-based phenolic polymers are, for example, tannins. Tannins can be natural products found in bark and other biological sources, which are high molecular weight polyphenolic compounds containing hydroxyl groups and other functional groups. There are several types of tannins, which usually differ in the basic unit or monomer unit.

In principle, porous materials based on bio-based phenolic polymers are known in the prior art, for example based on lignin and/or tannin or mixtures of lignin with other polymers. Methods for the preparation of lignin-based aerogels are also known in the prior art.

Several methods are disclosed in the scientific literature. For example, an article in Journal of Supercritical Fluids 2015, 105, 1-8 discloses a method for preparing mixed alginate-lignin aerogels by gelation using pressurized carbon dioxide. Exposing alginates and lignin alkaline aqueous solutions containing calcium carbonate to CO ₂ will form hydrogels.

US020190329208A1 discloses a method for preparing high-purity lignin-based carbon aerogel.

Highly porous organic aerogels based on tannin and lignin are disclosed in "New Tannin-Lignin Aerogels", Grishechko, L. et al., Industrial Crops and Products 2013, 41 347-355. The hydrogels are prepared at a constant solid weight fraction and a constant pH value, but with different tannin/lignin and (tannin+lignin)/formaldehyde weight ratios.

Generally speaking, organic molecules such as isocyanates or aldehydes are used as crosslinking agents. For many applications, these compounds are disadvantageous because they are often harmful and trace amounts may remain in the resulting material.

It is therefore an object of the present invention to avoid the above-mentioned disadvantages. It is an object of the present invention to provide a method for preparing a porous material based on polyphenol polymers, which method avoids harmful materials. It is another object of the present invention to provide a porous material which is suitable as thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for household appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

The porous material should preferably have a high surface area. Furthermore, it is an object of the present invention to provide a method for preparing a homogeneous gel and thereby a homogeneous porous material from bio-based polyphenolic polymers, such as lignin or tannin or mixtures thereof.

According to the present invention, this object is solved by a method for preparing a porous material, said method comprising at least the following steps:

a) providing a mixture (M1) comprising as compound (C1) a water-soluble bio-based polyphenol polymer selected from the group consisting of lignin biopolymers and tannin biopolymers and water,

b) contacting the mixture (M1) with an aqueous solution of at least one multivalent metal ion to produce a gel (A)

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L) to obtain a gel (B),

d) drying the gel (B) obtained in step c).

According to another embodiment, the present invention also relates to a method for preparing a porous material, the method comprising at least the following steps:

a) providing a mixture (M1) comprising as compound (C1) a water-soluble bio-based polyphenol polymer selected from the group consisting of lignin biopolymers and tannin biopolymers and water,

b) contacting the mixture (M1) with an aqueous solution of at least one multivalent metal ion to produce a gel (A)

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L) to obtain a gel (B),

d) drying the gel (B) obtained in step c).

The mixture (M1) further comprises at least one water-soluble polysaccharide having carboxylic acid groups as compound (C2).

According to the invention, water-soluble bio-based polyphenol polymers are used to form the gel. Suitable phenolic polymers are known in principle from the prior art. In the context of the present invention, lignin and tannins are preferably used as bio-based polymers due to the good availability of the starting materials. The use of lignin, tannins and/or their derivatives and/or mixtures thereof is particularly attractive due to their stability, availability, renewability and low toxicity.

In addition, according to another aspect of the present invention, bio-based polymers, inorganic precursors and polysaccharides with carboxylic acid groups are used to form gel. In principle, suitable bio-based polymers, inorganic precursors and polysaccharides with carboxylic acid groups are known in the prior art. Suitable polysaccharides with carboxylic acid groups are, for example, alginate, pectin, modified cellulose, xanthan gum, hyaluronic acid or modified starch. The use of these bio-based polymers and polysaccharides and derivatives thereof is particularly attractive due to their stability, availability, reproducibility and low toxicity. In the context of the present invention, suitable inorganic precursors must be soluble or at least partially dissolved in the mixture (M1), and must solidify in the gelling step.

For the purposes of the present invention, gels are crosslinked systems based on polymers which exist as liquids in contact with a liquid (known as solvogel or lyogel) or in contact with water (aquagel or hydrogel). Here, the polymer phase forms a continuous three-dimensional network.

In the context of the present invention, water-soluble means sufficient solubility in water to form a solution that can be used to prepare a gel.

According to the present invention, the gel is formed from the water-soluble bio-based polyphenol polymer and at least one polyvalent metal ion. In particular, the gel is formed from the components of the mixture (M1) and at least one polyvalent metal ion. The components (C1) and (C2) used in the process according to the present invention must be suitable for forming a gel with polyvalent metal ions, in particular must have suitable functional groups. In particular, the polyphenol polymer used in the process according to the present invention must be suitable for forming a gel with polyvalent metal ions, in particular must have suitable functional groups.

Surprisingly it has been found that the claimed process allows the preparation of aerogels, i.e. aerogels based on water-soluble bio-based polyphenol polymers, having a low solid content and a large surface area, preferably also a large pore volume and a small pore size. The properties of the aerogel can be tailored by adjusting the composition of the mixture (M1), the reaction conditions during the hydrogel (gel (A)) formation phase or during the solvent exchange and in the drying step. According to the invention, the properties of the hydrogel and/or aerogel can be influenced by varying the proportions of the components, as well as by controlling the parameters of step a) and/or step b), such as adjusting the pH value in step a) and by introducing a wide variety of organic and inorganic materials into the gel matrix.

According to the present invention, the water-soluble bio-based polyphenol polymer is preferably selected from lignin biopolymers and tannin biopolymers, in particular selected from alkali lignin, kraft lignin, hydrolyzed lignin, soda lignin, aquasolv solid lignin, enzymatic lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, biorefined lignin, tannic acid or tannin and tannin derivatives.

The mixture (M1) may comprise further components selected from water-soluble bio-based polyphenol polymers and silicon dioxide.

According to another embodiment, the present invention also relates to a method as described above, wherein the water-soluble bio-based polyphenol polymer is selected from lignin biopolymers and tannin biopolymers, in particular selected from alkali lignin, kraft lignin, hydrolyzed lignin, soda lignin, water-soluble solid lignin, enzymatic lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, biorefined lignin, tannic acid or tannin and tannin derivatives.

Compound (C2) can be selected from alginate, pectin, modified cellulose, xanthan gum, hyaluronic acid or modified starch. Therefore, according to another embodiment, the present invention also relates to the method as described above, wherein compound (C2) can be selected from alginate, pectin, modified cellulose, xanthan gum, hyaluronic acid or modified starch, in particular selected from modified cellulose and alginate or selected from alginate.

According to the invention, compound (C1) can be selected, for example, from lignin and tannin. In addition, cellulose, bacterial cellulose, modified cellulose, starch, sugar, chitosan, polyhydroxyalkanoates, whey protein isolate, potato protein isolate, starch protein isolate, gelatin, collagen, casein or derivatives thereof, as well as silicates, titanates, vanadates, zirconates, aluminates, borates, ferrites, chromates, molybdates, tungstates, manganates, cobaltates and metal sulfides, metal oxides and metal carbides can also be used in mixture (M1). According to another embodiment, compound (C1) can be, for example, a mixture of compounds selected from the group consisting of lignin and tannins, cellulose, bacterial cellulose, modified cellulose, starch, sugars, chitosan, polyhydroxyalkanoates, whey protein isolate, potato protein isolate, starch protein isolate, gelatin, collagen, casein or derivatives thereof, as well as silicates, titanates, vanadates, zirconates, aluminates, borates, ferrites, chromates, molybdates, tungstates, manganates, cobaltates and metal sulfides, metal oxides or metal carbides, and compound (C2) can be an alginate or a modified cellulose.

According to the invention, the amount of compounds (C1) and (C2) used in the process may vary, for example depending on the material properties to be achieved. In particular, the amount of bio-based polyphenol polymer used in the process may vary, for example depending on the material properties to be achieved.

Suitable amounts of compound (C1) are, for example, 0.1 to 50% by weight, based on the weight of the mixture (M1), preferably 1.0 to 40% by weight, based on the weight of the mixture (M1), in particular 5.0 to 30% by weight, based on the weight of the mixture (M1).

According to a further embodiment, the present invention therefore also relates to a process as described above, wherein the mixture (M1) comprises from 0.1% to 50% by weight of compound (C1), based on the weight of the mixture (M1).

If the mixture (M1) contains compound (C2), the ratio of compound (C1) to compound (C2) may also vary, depending on the compounds used. Typically, the mixture (M1) contains compound (C1) and compound (C2) in a ratio of 55:45 to 98:2, preferably 60:40 to 95:5.

According to another embodiment, the present invention therefore also relates to a process as described above, wherein the mixture (M1) comprises compound (C1) and compound (C2) in a ratio of 55:45 to 98:2.

Furthermore, a wide variety of organic and inorganic materials can be embedded (ie, physically or co-gelled) in a matrix of a phenolic polymer, such as a lignin matrix, to achieve specific properties. Furthermore, preferably there are no organic by-products associated with the process.

In the context of the present invention, the pH of the mixture (M1) may also vary depending on the compounds used. It has been found that advantageous results are obtained when the pH of the mixture (M1) is from 8 to 14, in particular from 10 to 14, more preferably from 11 to 14.

According to another embodiment, the present invention also relates to a process as described above, wherein the pH value of the mixture (M1) is from 8 to 14.

In the method according to the invention, a mixture (M1) is provided according to step a). The mixture can be prepared by dissolving the desired amount of compound (C1) and optionally (C2) in, for example, distilled water. In the context of the present invention, the pH value of the mixture can also be adjusted to increase solubility.

According to step b), the mixture (M1) is contacted with an aqueous solution of polyvalent metal ions to prepare a gel (A).

The aqueous solution of polyvalent metal ions can be prepared, for example, using a salt of the polyvalent metal ions.

According to the present invention, such multivalent metal ions are suitable: they form poorly soluble compounds with the bio-based polyphenol polymer (especially lignin) used, that is, they act as cross-linking metal ions. In particular, such multivalent metal ions are suitable: they form poorly soluble compounds with the polysaccharide compound (C2) having a carboxylic acid group, and can form poorly soluble compounds with the compound (C1) used. Such multivalent metal ions include, for example, alkaline earth metal ions and transition metal ions, which form poorly soluble compounds with bio-based polyphenol polymers. Alkaline earth metal ions are preferred, such as magnesium or calcium. Calcium is particularly preferred. Trivalent metal ions such as aluminum or iron (III) are also particularly suitable. According to the present invention, calcium salts are particularly preferred because they are physiologically and particularly cosmetically acceptable and have strong crosslinking and/or gelling effects compared to lignin. According to the present invention, mixtures of two or more multivalent ions can also be used, for example mixtures comprising divalent and trivalent ions, such as mixtures comprising calcium and aluminum or mixtures comprising calcium and iron (III). In addition, for example, beryllium, barium, strontium, zinc, cobalt, nickel, copper, manganese, iron, chromium, vanadium, titanium, zirconium, cadmium, molybdenum, tungsten, ruthenium, rhodium, iridium, palladium, platinum, and aluminum can also be used.

The polyvalent metal ions are preferably added in the form of their salts. In principle, the corresponding anions can be selected arbitrarily, as long as they are soluble in water either by themselves or by changing the pH. Preferably, chloride, acetate, nitrate, preferably calcium chloride or trivalent metal salts, such as iron (III) chloride, aluminum chloride or iron (III) nitrate or mixtures thereof, can be used.

The amount of salt of polyvalent metal ions is chosen so that the concentration of the salt in the resulting solution is preferably about 1 to 20% by weight, preferably 1 to 10% by weight, more preferably 1 to 5% by weight and in particular 2 to 3% by weight.

According to a further embodiment, the present invention also relates to a method as described above, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion selected from alkaline earth metal ions.

According to the invention, it is also possible to use mixtures of polyvalent metal ions.

The mixture (M1) provided in step (a) may also comprise other salts, in particular non-gel-forming salts, and customary auxiliaries known to the person skilled in the art as further ingredients.

Furthermore, the mixture (M1) may comprise cosmetically or medicinally active substances.

According to another embodiment, the present invention also relates to a process as described above, wherein in step a) compound (C) is added to a mixture (M1) suitable for forming a gel. Compound (C) may be dissolved or partially dissolved in mixture (M1). In the context of the present invention, compound (C) may also be insoluble in mixture (I).

According to another embodiment, the present invention also relates to a process as described above, wherein a compound (C) is added to the mixture (M1), and the compound (C) is selected from the group consisting of pigments, sunscreens, flame retardants, metals, metal particles, metal nanoparticles, metal fibers, metal meshes, metal oxides, metal oxide particles, metal oxide nanoparticles, metal oxide fibers, metal salts, catalytic metals, catalytic materials, metal carbide or metal sulfide particles or nanoparticles, silicon-based materials, silicon particles, silicon nanoparticles, semiconductor-based materials, semiconductor particles, semiconductor nanoparticles, semiconductor fibers, semiconductor meshes, carbon materials, carbon black, graphite nanoparticles, graphite fibers, graphite flakes, graphite meshes, graphene nanoparticles, graphene fibers, graphene flakes, graphene meshes, metal organic frameworks, sulfur, inorganic and/or organic fillers, nucleating agents, stabilizers, thermal control agents, surfactants, fibers and foam reinforcing materials.

According to another embodiment, the present invention also relates to a process as described above, wherein a water-insoluble solid (S) is added to the mixture (M1).

The solid (S) may be, for example, a porous material or a foam, a carrier or a fibrous material. According to the invention, the mixture (M1) may also be present in the pores of the solid (S).

According to step b) of the present invention, the mixture (M1) is contacted with an aqueous solution of polyvalent metal ions to prepare the gel (A). Suitable mixing steps are known in principle to the person skilled in the art. For example, the mixture (M1) can be added dropwise to the aqueous solution of polyvalent metal ions. The mixture (M1) can also be placed in the pores of the carrier material or mixed with fibers and then contacted with the aqueous solution of polyvalent metal ions to prepare the gel (A). In addition, the mixture (M1) can be contacted with the polyvalent metal ions in an emulsion or during a spraying process.

Gelation itself is known to the person skilled in the art and is described, for example, in WO 2009/027310, page 21, line 19 to page 23, line 13.

Preferably, the temperature and pressure in step b) are adjusted to a state where a gel is formed. A suitable temperature may be 10 to 40° C., preferably 15 to 35° C. According to another embodiment, the present invention also relates to the method as described above, wherein step b) is carried out at a temperature of 10 to 40° C.

By choosing appropriate conditions for step b), the rate of formation of the insoluble gel can be controlled very accurately and easily.

The gel (A) obtained in step b) is a gel comprising water, ie a hydrogel. According to the invention, in step c) of the process of the invention, the gel (A) obtained in step b) is exposed to a water-miscible solvent (L) to obtain a gel (B).

However, it is also possible to use a hydrogel (A) obtained as an intermediate in a process as disclosed above. Hydrogels are known to have many applications. The hydrogel (A) is particularly homogeneous and particles can be prepared according to the invention which can be subjected to further processing steps.

According to the invention, a water-miscible solvent (L) is used in step c). In the context of the present invention, water-miscible means that the solvent is at least partially miscible with water to allow exchange of the solvent in the gel.

The solvent exchange is performed by soaking the gel directly in the new solvent (one step) or by soaking it successively (multiple steps) in different water-to-new solvent mixtures with increasing new solvent content after a certain time (exchange frequency) in the previous soaking step (Robitzer et al., Langmuir 2008, 24, 12547-12552). The solvents selected for the water exchange must meet the following requirements: do not dissolve the gel structure, are completely soluble in their previous solvent (water) and are preferably acceptable for drug preparation. In addition, if the method includes a supercritical drying step, the solvent (L) is preferably at least partially miscible with the supercritical medium.

The solvent (L) can in principle be any suitable compound or mixture of compounds which meets the above-mentioned requirement that the solvent (L) is liquid under the temperature and pressure conditions of step c).

Possible solvents (L) are, for example, alcohols, ketones, aldehydes, alkyl alkanoates, organic carbonates, amides such as formamide and N-methylpyrrolidone, sulfoxides such as dimethyl sulfoxide, aliphatic and alicyclic halogenated or non-halogenated hydrocarbons, halogenated or non-halogenated aromatic compounds and fluorinated ethers. Mixtures of two or more of the abovementioned compounds are likewise possible.

In many cases, particularly suitable solvents (L) are obtained by using two or more completely miscible compounds selected from the abovementioned solvents.

Suitable solvents are, in particular, alcohols and ketones, for example C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

According to another embodiment, the present invention also relates to a process as described above, wherein the solvent (L) used in step c) is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

Particularly suitable are alcohols, such as methanol, ethanol and isopropanol, and ketones, such as acetone and methyl ethyl ketone.

The solvent exchange according to step b) can be carried out in one step, in two steps, in three steps or in multiple steps with different solvent concentrations. According to a preferred embodiment, the gel (A) is immersed in an ethanol/water mixture with a concentration of, for example, 30, 60, 90 and 100% by weight, each time for a duration of 5 min to 12 h, depending on the particle size and porosity. For example, step b) can be carried out in two or three steps using an ethanol/water mixture, wherein the ethanol concentration in the first step is greater than 60% and the ethanol concentration in the last step is greater than 90%, for example the ethanol concentration in the last step is greater than 95% or greater than 98%.

In step c), a gel (B) is obtained. According to step d) of the process of the present invention, the gel (B) obtained in step c) is dried.

The drying in step (d) is carried out in a known manner. Preferably, the drying is carried out under supercritical conditions, preferably after replacing the solvent with CO ₂ or another solvent suitable for the purpose of supercritical drying. Such drying itself is known to the person skilled in the art. Supercritical conditions refer to the temperature and pressure at which CO ₂ or any solvent used to remove the gelling solvent is present in a supercritical state. In this way, the shrinkage of the gel during the removal of the solvent can be reduced.

In the context of the present invention, it is also possible to dry a gel which is obtained by converting the liquid contained in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid contained in the gel.

According to one embodiment, the drying of the obtained gel is preferably carried out by converting the solvent (L) into the gaseous state at a temperature and pressure below the critical temperature and critical pressure of the solvent (L). Therefore, the drying is preferably carried out by removing the solvent (L) present in the reaction without previously replacing it with another solvent.

Such methods are likewise known to the person skilled in the art and are described in WO 2009/027310, page 26, line 22 to page 28, line 36.

According to another embodiment, the invention also relates to a process as described above, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid contained in the gel.

According to another embodiment, the present invention also relates to a process as described above, wherein the drying according to step d) is carried out under supercritical conditions.

The method may also include one or more further modification steps, such as a shaping step of the fibers and/or binder and/or thermoplastic material; a compression step; a lamination step; a post-drying step; a hydrophobizing step or a carbonizing step. For example, one or more of these steps may be combined, such as a post-drying step and a hydrophobizing step.

According to another embodiment, the present invention also relates to a method as described above, wherein the method comprises subjecting the xerogel to one or more further modification steps.

According to another embodiment, the present invention also relates to a method as described above, wherein the modification step is selected from a shaping step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

The present invention also relates to a porous material obtained or obtainable by the above method. The porous material of the present invention is preferably an aerogel, a cryogel or a xerogel.

For the purposes of the present invention, a xerogel is a porous material prepared by a sol-gel process in which the liquid phase is removed from the gel by drying at a temperature below the critical temperature of the liquid phase and below the critical pressure ("subcritical conditions"). A cryogel is a porous material prepared by freezing the solvent in the gel and removing the solid solvent by a sublimation process under ambient conditions. An aerogel is a porous material prepared by a sol-gel process in which the liquid phase is removed from the gel under supercritical conditions.

The method disclosed above results in a porous material with improved properties. The aerogel prepared according to the method of the present invention preferably has a low density and preferably has a large specific surface area, for example 120 to 800 m ² /g or 200 to 800 m ² /g. In addition, for pore diameters <150 nm, a pore volume of 2.1 to 9.5 cm ² /g can be preferably obtained. In addition, for pore diameters <100 nm, a pore volume of 2.1 to 9.5 cm ² /g can be preferably obtained.

Furthermore, the present invention therefore relates to a porous material obtained or obtainable by the method for preparing a porous material disclosed above. In particular, the present invention relates to a porous material obtained or obtainable by the method for preparing a porous material disclosed above, wherein the drying according to step d) is carried out under supercritical conditions.

The porous material according to the invention preferably has a density of 0.005 to 1 g/cm ³ , preferably 0.01 to 0.5 g/cm ³ (determined in accordance with DIN 53420).

The average pore size is determined by scanning electron microscopy and subsequent image analysis using a statistically significant number of pores. Corresponding methods are known to the person skilled in the art. In order to characterize the porous structure of the aerogel, a Nova3000 surface area analyzer from Quantachrome Instruments was used. The analyzer utilizes the adsorption and desorption of nitrogen at a constant temperature of 77K.

The volume average pore size of the porous material is preferably not greater than 1 micrometer. The volume average pore size of the porous material is particularly preferably not more than 750 nm, very particularly preferably not more than 500 nm and in particular not more than 250 nm. The volume average pore size of the porous material can be, for example, 1 to 1000 nm, preferably 2 to 500 nm, in particular 3 to 250 nm, more preferably 5 to 100 nm or particularly preferably 10 to 50 nm.

The porosity of the porous material obtainable according to the invention is preferably at least 70% by volume, in particular 70 to 99% by volume, particularly preferably at least 80% by volume, very particularly preferably at least 85% by volume, in particular 85 to 95% by volume. The porosity expressed in % by volume means that a certain proportion of the total volume of the porous material contains pores. Although very high porosities are generally desired from the perspective of minimum thermal conductivity, the mechanical properties and processability of the porous material limit the upper limit of the porosity.

According to another embodiment, the present invention also relates to a porous material as disclosed above, wherein the specific surface area of the porous material is from 120 to 800 m ² /g, determined using the BET theory according to DIN 66134:1998-0.

According to another embodiment, the present invention also relates to a porous material as disclosed above, wherein the porous material has a specific surface area of 120 to 800 m ² /g, determined using BET theory according to DIN 66134:1998-0 and a pore volume with pore diameters <150 nm of 2.1 to 9.5 cm ³ /g.

Surprisingly, it has been found that according to the invention, even if the starting materials used may contain relatively high amounts of volatile organic compounds, materials with very low contents of volatile organic compounds can be obtained. For example, lignin often contains volatile organic compounds, such as guaiacol, due to its preparation process.

According to another embodiment, the present invention therefore also relates to a porous material as disclosed above, wherein the volatile organic compound (VOC) content in the porous material is less than 50% of the volatile organic compound (VOC) content in the bio-based polyphenol polymer used in the method.

The porous material obtainable according to the invention preferably has a high porosity and a low density. In addition, the porous material preferably has a small average pore size. The combination of the above-mentioned properties allows the material to be used as a thermal insulation material in the field of thermal insulation, in particular as an application as a building material in a ventilated state or in refrigerators, clothing or batteries.

The present invention also relates to the use of a porous material as disclosed above or a porous material obtained according to a method as disclosed above or obtainable by a method for preparing a porous material as disclosed above as a thermal insulation material or for a vacuum insulation panel. The thermal insulation material is, for example, a thermal insulation material for the interior or exterior of a building. The porous material according to the present invention can be advantageously used in thermal insulation systems, such as composite materials.

Furthermore, the present invention relates to the following uses of the porous material according to the invention: for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for cosmetic applications; for biomedical applications; for pharmaceutical applications; for agricultural applications and for the manufacture of medical products. Such cosmetic applications include, for example, products for facial care (such as skin scrubbing or cleaning) or protective products (such as UV protection products or products comprising antioxidants).

According to another aspect, the present invention relates to the following uses of the porous material as disclosed above or obtained by the method as disclosed above or obtainable by the method as disclosed above: as a thermal insulation material, for cosmetic applications, for biomedical applications or for pharmaceutical applications. According to another preferred aspect, the present invention relates to the following uses of the porous material as disclosed above or obtained by the method as disclosed above or obtainable by the method as disclosed above: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for household and commercial appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for battery applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

Preferred embodiments can be found in the claims and the description. Combinations of preferred embodiments do not go beyond the scope of the invention. Preferred embodiments of the components used are described below.

The present invention includes the following embodiments, wherein they include specific combinations of the embodiments defined herein as indicated by the respective inter-reference relationships.

1. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising a water-soluble bio-based polyphenol polymer and water,

b) contacting the mixture (M1) with an aqueous solution of at least one polyvalent metal ion to produce a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c).

2. A method according to embodiment 1, wherein the water-soluble bio-based polyphenol polymer is selected from lignin biopolymers and tannin biopolymers, in particular selected from alkali lignin, kraft lignin, hydrolyzed lignin, soda lignin, water-soluble solid lignin, enzymatic lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, biorefined lignin, tannic acid or tannin and tannin derivatives.

3. The method according to embodiment 1 or 2, wherein the mixture (M1) comprises 0.1% to 50% by weight of bio-based polyphenol polymer, based on the mixture (M1).

Weight scale.

4. The method according to any one of embodiments 1 to 3, wherein the pH value of the mixture (M1) is 8 to 14.

5. The method according to any one of embodiments 1 to 4, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion selected from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion selected from aluminum ions and iron (III) ions.

6. The method according to any one of embodiments 1 to 5, wherein the method comprises a further modification step of the xerogel.

7. The method according to embodiment 6, wherein the modification step is selected from a molding step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

8. The process according to any one of embodiments 1 to 7, wherein the solvent (L) used in step c) is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

9. The process according to any one of embodiments 1 to 8, wherein a water-insoluble solid (S) is added to the mixture (M1).

10. A method according to any one of embodiments 1 to 9, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, heat control agents, fibers and foam reinforcements.

11. The method according to any one of embodiments 1 to 10, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid contained in the gel.

12. The method according to any one of embodiments 1 to 10, wherein according to step d)

The drying is carried out under supercritical conditions.

13. A porous material obtained or obtainable by the method according to any one of embodiments 1 to 12.

14. The porous material according to embodiment 13, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

15. The porous material according to embodiment 13 or 14, wherein the content of volatile organic compounds (VOC) in the porous material is less than that of the raw material used in the method.

50% of the volatile organic compound (VOC) content in the bio-based polyphenol polymer.

16. The following uses of the porous material according to any one of embodiments 13 to 15 or the porous material obtained by the method according to any one of embodiments 1 to 12 or obtainable by the method according to any one of embodiments 1 to 12: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

17. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising a water-soluble bio-based (poly)phenolic polymer and water, said polymer being selected from lignin biopolymers,

b) contacting the mixture (M1) with an aqueous solution of at least one polyvalent metal ion to produce a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c).

18. A method according to embodiment 17, wherein the water-soluble bio-based polyphenol polymer is selected from alkali lignin, sulfate lignin, hydrolyzed lignin, soda lignin, water-soluble solid lignin, enzymatic lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, and biorefined lignin.

19. The method according to embodiment 17 or 18, wherein the mixture (M1) comprises from 0.1% to 50% by weight of bio-based polyphenol polymers, based on the mixture (M1).

Weight scale.

20. The method according to any one of embodiments 17 to 19, wherein the mixture (M1)

The pH value is 8 to 14.

21. The method according to any one of embodiments 17 to 20, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion selected from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion selected from aluminum ions and iron (III) ions.

22. The method according to any one of embodiments 17 to 21, wherein the method comprises a further modification step of the xerogel.

23. A method according to embodiment 22, wherein the modification step is selected from a molding step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

24. The method according to any one of embodiments 17 to 23, wherein in step c)

The solvent (L) used is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

25. The process according to any one of embodiments 17 to 24, wherein a water-insoluble solid (S) is added to the mixture (M1).

26. A method according to any one of embodiments 17 to 25, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, thermal control agents, fibers and foam reinforcing materials.

27. The method according to any one of embodiments 17 to 26, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and pressure below the critical temperature and critical pressure of the liquid contained in the gel.

28. The method according to any one of embodiments 17 to 26, wherein according to step d)

The drying is carried out under supercritical conditions.

29. A porous material obtained or obtainable by the method according to any one of embodiments 17 to 28.

30. The porous material according to embodiment 29, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

31. The porous material according to embodiment 29 or 30, wherein the content of volatile organic compounds (VOC) in the porous material is less than 50% of the content of volatile organic compounds (VOC) in the bio-based polyphenol polymer used in the method.

32. The following uses of the porous material according to any one of embodiments 29 to 31 or the porous material obtained by the method according to any one of embodiments 17 to 28 or obtainable by the method according to any one of embodiments 17 to 28: as a thermal insulation material, as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications;

for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

33. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising a water-soluble bio-based (poly)phenolic polymer and water, said polymer being selected from lignin biopolymers,

b) contacting the mixture (M1) with an aqueous solution of at least one polyvalent metal ion to produce the gel (A), wherein the polyvalent metal ion is a divalent metal ion,

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c).

34. A method according to embodiment 33, wherein the water-soluble bio-based polyphenol polymer is selected from alkali lignin, sulfate lignin, hydrolyzed lignin, soda lignin, water-soluble solid lignin, enzymatic lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, and biorefined lignin.

35. The method according to embodiment 33 or 34, wherein the mixture (M1) comprises 0.1% to 50% by weight of bio-based polyphenol polymer, based on the mixture (M1).

Weight scale.

36. The method according to any one of embodiments 33 to 35, wherein the mixture (M1)

The pH value is 8 to 14.

37. The method according to any one of embodiments 33 to 36, wherein the polyvalent metal ion is a divalent metal ion selected from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion selected from aluminum ions and iron (III) ions.

38. The method according to any one of embodiments 33 to 37, wherein the method comprises a further modification step of the xerogel.

39. A method according to embodiment 38, wherein the modification step is selected from a molding step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

40. The method according to any one of embodiments 33 to 39, wherein in step c)

The solvent (L) used is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

41. The method according to any one of embodiments 33 to 40, wherein a water-insoluble solid (S) is added to the mixture (M1).

42. A method according to any one of embodiments 33 to 41, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, thermal control agents, fibers and foam reinforcing materials.

43. The method according to any one of embodiments 33 to 42, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and pressure below the critical temperature and critical pressure of the liquid contained in the gel.

44. The method according to any one of embodiments 33 to 42, wherein according to step d)

The drying is carried out under supercritical conditions.

45. A porous material obtained or obtainable by the method according to any one of embodiments 33 to 44.

46. The porous material according to embodiment 45, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

47. The porous material according to embodiment 45 or 46, wherein the content of volatile organic compounds (VOC) in the porous material is less than 50% of the content of volatile organic compounds (VOC) in the bio-based polyphenol polymer used in the method.

48. The following uses of the porous material according to any one of embodiments 45 to 47 or the porous material obtained by the method according to any one of embodiments 33 to 44 or obtainable by the method according to any one of embodiments 33 to 44: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications;

for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

49. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising as compound (C1) a water-soluble bio-based polyphenolic polymer selected from the group consisting of lignin biopolymers and tannin biopolymers and water,

b) contacting the mixture (M1) with an aqueous solution of at least one divalent metal ion to produce a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c).

50. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising as compound (C1) a water-soluble bio-based polyphenolic polymer selected from the group consisting of lignin biopolymers and tannin biopolymers and water,

b) contacting the mixture (M1) with an aqueous solution of at least one divalent metal ion to produce a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c),

The mixture (M1) further comprises at least one water-soluble polysaccharide having carboxylic acid groups as compound (C2).

51. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising at least one compound (C1) selected from water-soluble bio-based polyphenol polymers and inorganic precursors and at least one water-soluble polysaccharide having carboxylic acid groups as component (C2) and water,

b) contacting the mixture (M1) with an aqueous solution of polyvalent metal ions to prepare a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain a gel (B),

d) drying the gel (B) obtained in step c).

52. The method according to embodiment 51, wherein compound (C1) is selected from water-soluble bio-based polyphenol polymers and silicon dioxide.

53. The method according to embodiment 51 or 52, wherein the mixture (M1) comprises 0.1% to 50% by weight of compound (C1), based on the weight of the mixture (M1).

54. The method according to any one of embodiments 51 to 53, wherein the mixture (M1)

The compound (C1) and the compound (C2) are contained in a ratio of 55:45 to 98:2.

55. The method according to any one of embodiments 51 to 54, wherein the mixture (M1)

The pH value is 8 to 14.

56. The method according to any one of embodiments 51 to 55, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion selected from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion selected from aluminum ions and iron (III) ions.

57. The method according to any one of embodiments 51 to 56, wherein the method comprises one or more further modification steps of the xerogel, in particular, wherein the modification step is selected from a forming step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

58. The method according to any one of embodiments 51 to 57, wherein in step c)

The solvent (L) used is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

59. The method according to any one of embodiments 51 to 58, wherein a water-insoluble solid (S) is contacted with the mixture (M1).

60. A method according to any one of embodiments 51 to 59, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, thermal control agents, fibers and foam reinforcements.

61. The method according to any one of embodiments 51 to 60, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid contained in the gel.

62. The method according to any one of embodiments 51 to 60, wherein according to step d)

The drying is carried out under supercritical conditions.

63. A porous material obtained or obtainable by the method according to any one of embodiments 51 to 62.

64. The porous material according to embodiment 63, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

65. The porous material according to embodiment 63 or 64, wherein the content of volatile organic compounds (VOC) in the porous material is less than 50% of the content of volatile organic compounds (VOC) in the starting material used in the method.

66. The following uses of the porous material according to any one of embodiments 63 to 65 or the porous material obtained by the method according to any one of embodiments 51 to 62 or obtainable by the method according to any one of embodiments 51 to 62: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

67. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising at least one compound (C1) selected from water-soluble bio-based polyphenol polymers and silicon dioxide and at least one water-soluble polysaccharide having carboxylic acid groups as component (C2) and water,

b) contacting the mixture (M1) with an aqueous solution of polyvalent metal ions to prepare a gel (A)

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain gel (B),

d) drying the gel (B) obtained in step c).

68. The method according to embodiment 67, wherein compound (C1) is selected from lignin biopolymers and silica.

69. The method according to embodiment 67 or 68, wherein the mixture (M1) comprises from 0.1% to 50% by weight of compound (C1), based on the mixture (M1).

Weight scale.

70. The method according to any one of embodiments 67 to 69, wherein the mixture (M1)

The compound (C1) and the compound (C2) are contained in a ratio of 55:45 to 98:2.

71. The method according to any one of embodiments 67 to 70, wherein the mixture (M1)

The pH value is 8 to 14.

72. The method according to any one of embodiments 67 to 71, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion chosen from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion chosen from aluminum ions and iron (III) ions.

73. The method according to any one of embodiments 67 to 722, wherein the method comprises one or more further modification steps of the xerogel, in particular, wherein the modification step is selected from a forming step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

74. The method according to any one of embodiments 67 to 73, wherein in step c)

The solvent (L) used is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

75. The method according to any one of embodiments 67 to 74, wherein a water-insoluble solid (S) is contacted with the mixture (M1).

76. A method according to any one of embodiments 67 to 75, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, thermal control agents, fibers and foam reinforcements.

77. The method according to any one of embodiments 27 to 76, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and pressure below the critical temperature and critical pressure of the liquid contained in the gel.

78. The method according to any one of embodiments 27 to 76, wherein according to step d)

The drying is carried out under supercritical conditions.

79. A porous material obtained or obtainable by the method according to any one of embodiments 27 to 78.

80. The porous material according to embodiment 79, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

81. The porous material according to embodiment 79 or 80, wherein the content of volatile organic compounds (VOC) in the porous material is less than 50% of the content of volatile organic compounds (VOC) in the starting material used in the method.

82. The following uses of the porous material according to any one of embodiments 79 to 81 or the porous material obtained by the method of any one of embodiments 67 to 78 or obtainable by the method of any one of embodiments 67 to 78: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications;

for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

83. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising at least one compound (C1) selected from water-soluble lignin biopolymers and silicon dioxide and at least one water-soluble polysaccharide having carboxylic acid groups as component (C2) and water,

b) contacting the mixture (M1) with an aqueous solution of polyvalent metal ions to prepare a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L)

To obtain gel (B),

d) drying the gel (B) obtained in step c),

Wherein compound (C2) is selected from alginate, pectin, modified cellulose, xanthan gum, hyaluronic acid or modified starch.

84. A method according to embodiment 83, wherein compound (C2) is selected from alginate.

85. The method according to embodiment 83 or 84, wherein the mixture (M1) comprises 0.1% to 50% by weight of compound (C1), based on the weight of the mixture (M1).

86. The method according to any one of embodiments 83 to 85, wherein the mixture (M1)

The compound (C1) and the compound (C2) are contained in a ratio of 55:45 to 98:2.

87. The method according to any one of embodiments 83 to 86, wherein the mixture (M1)

The pH value is 8 to 14.

88. The method according to any one of embodiments 83 to 87, wherein the polyvalent metal ion is a divalent metal ion, in particular a divalent metal ion chosen from alkaline earth metal ions, or wherein the polyvalent metal ion is a trivalent metal ion chosen from aluminum ions and iron (III) ions.

89. The method according to any one of embodiments 83 to 88, wherein the method comprises one or more further modification steps of the xerogel, in particular, wherein the modification step is selected from a forming step, a compression step, a lamination step, a post-drying step, a hydrophobization step and a carbonization step.

90. The method according to any one of embodiments 83 to 89, wherein in step c)

The solvent (L) used is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

91. The method according to any one of embodiments 83 to 90, wherein a water-insoluble solid (S) is contacted with the mixture (M1).

92. A method according to any one of embodiments 83 to 91, wherein a compound (C) is added to the mixture (M1), wherein the compound (C) is selected from pigments, sunscreens, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, thermal control agents, fibers and foam reinforcing materials.

93. The method according to any one of embodiments 83 to 92, wherein the drying according to step d) is carried out by converting the liquid contained in the gel into the gaseous state at a temperature and pressure below the critical temperature and critical pressure of the liquid contained in the gel.

94. The method according to any one of embodiments 83 to 92, wherein according to step d)

The drying is carried out under supercritical conditions.

95. A porous material obtained or obtainable by the method according to any one of embodiments 83 to 94.

96. The porous material according to embodiment 95, wherein the specific surface area of the porous material is 120 to 800 m ² /g or 200 to 800 m 2 /g, and the specific surface area of the porous material is 120 to 800 m 2 /g or 200 to 800 m ² /g according to DIN 66134:1998-0.

The pore volume determined using the BET theory and having a pore diameter of <150 nm is between 2.1 and 9.5 cm ³ /g.

97. A porous material according to embodiment 95 or 96, wherein the content of volatile organic compounds (VOC) in the porous material is less than 50% of the content of volatile organic compounds (VOC) in the starting material used in the method.

98. The following uses of the porous material according to any one of embodiments 95 to 97 or the porous material obtained by the method of any one of embodiments 83 to 94 or obtainable by the method of any one of embodiments 83 to 94: as a thermal insulation material; as a carrier material for loading and releasing active substances; for battery applications; for electrode materials in batteries, fuel cells or electrolysis; for catalysis; for capacitors; for consumer electronics; for building and construction applications; for home appliance applications; for temperature-controlled logistics applications; for vacuum insulation applications; for clothing applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.

99. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising at least one compound (C1) selected from the group consisting of lignin biopolymers and silicon dioxide and at least one water-soluble polysaccharide having carboxylic acid groups as component (C2) and water,

b) contacting the mixture (M1) with an aqueous solution of divalent metal ions or trivalent metal ions to prepare a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L) to obtain a gel (B),

d) drying the gel (B) obtained in step c),

Wherein compound (C2) is selected from alginate, pectin, modified cellulose, xanthan gum, hyaluronic acid or modified starch.

100. A method for preparing a porous material, comprising at least the following steps:

a) providing a mixture (M1) comprising water, at least one compound (C1) selected from the group consisting of lignin biopolymers and silicon dioxide and at least one component (C2) selected from the group consisting of alginates,

b) contacting the mixture (M1) with an aqueous solution of divalent or trivalent metal ions to prepare a gel (A),

c) exposing the gel (A) obtained in step b) to a water-miscible solvent (L) to obtain a gel (B),

d) drying the gel (B) obtained in step c).

The present invention will be described below by way of examples.

Example

1. Materials used

Materials: kraft lignin (UPM), sodium hydroxide (NaOH, Sigma Aldrich), calcium chloride (CaCl ₂ , Sigma Aldrich), pure ethanol (Carl Roth), sodium alginate (Hydagen, BASF), hexamethyldisilazane (HMDZ, Sigma Aldrich), Ludox SM30 (Sigma Aldrich), whey protein (Agropure Ingredients), xanthan gum (Sigma Aldrich), microcrystalline cellulose (MCC, Sigma Aldrich), sodium caseinate (Sigma Aldrich), tannic acid (Sigma Aldrich), potato starch (Sigma Aldrich), gelatin (Sigma Aldrich).

2. Preparation Example

2.1 Preparation of hydrophilic lignin aerogels by kraft lignin-calcium gel method

Solution 1: Kraft lignin powder (~6000 g/mol, UPM) was dispersed in deionized water (20 wt%) at room temperature, and 5 wt% NaOH was added until the pH reached 11.5. After one day, the pH was measured and a further 5 wt% NaOH was added.

% NaOH until the pH reaches 11.5.

Solution 2: Prepare _CaCl2 aqueous solution (20 g/L) at room temperature.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Small hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were filtered through a 125 μm mesh.

The hydrogel particles were immersed in ethanol (93%) for 5 min. The final solvent exchange step was to immerse the hydrogel particles from the previous step in pure ethanol for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 hour to obtain lignin aerogel particles. The aerogel particles did not have the smell of the original kraft lignin raw material.

Surface area: ^297m2 /g

Pore volume: 2.4 cm ³ /g

BJH pore diameter: 12nm

Aerogel density: 200-300g/L

Contact angle: 0°

2.2 Preparation of hydrophilic lignin aerogels by the kraft lignin-zinc gel method

Solution 1: Kraft lignin powder (~6000 g/mol, UPM) was dispersed in deionized water (10 wt%) at room temperature, and 5 wt% NaOH was added until pH reached 11. After one day, the pH was measured and a further 5 wt%

NaOH until pH reaches 11.

Solution 2: Prepare _ZnCl2 aqueous solution (10 g/L) at room temperature.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Small hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain lignin aerogel particles.

The bulk density of the lignin aerogel particles 5 is 80 to 120 g/l.

The surface area and pore volume of the lignin aerogel particles were determined to be 308 m ² /g.

2.3 Preparation of hydrophilic lignin aerogels by the kraft lignin-strontium gel method

Solution 1: Kraft lignin powder (~6000 g/mol, UPM) was dispersed in deionized water (20 wt%) at room temperature, and 5 wt% NaOH was added until the pH reached 11. After one day, the pH was measured and a further 5 wt%

NaOH until the pH reaches 10.5.

Solution 2: Prepare _SrCl2 aqueous solution (10 g/L) (pH 7.8) at room temperature.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Small hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain lignin aerogel particles.

The bulk density of the aerogel particles is 160-200 g/l.

The surface area of the aerogel particles was determined to be 273 ^m2 /g.

2.4 Preparation of hydrophilic lignin aerogels from biorefined lignin

Solution 1: Biorefined lignin powder was dispersed in deionized water (20 wt.

%), and 5 wt % NaOH was added until the pH reached 10.4. One day later, the pH was measured, and further 5 wt % NaOH was added until the pH reached 10.5.

Solution 2: Prepare _CaCl2 aqueous solution (10 g/L) at room temperature.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain lignin aerogel particles.

The surface area of the aerogel particles was measured to be 151 ^m2 /g.

3. Preparation Example - Mixed Materials

3.1 Hydrophilic kraft lignin/alginate hybrid aerogel

Solution 1: Kraft lignin powder was dispersed in deionized water (14 wt%) at room temperature.

5 wt% NaOH was added until the pH reached 10. Sodium alginate was added and dissolved to obtain a kraft lignin and alginate weight ratio of 92:8. Solution 2: A _CaCl2 aqueous solution (10 g/L) was prepared at room temperature and adjusted to pH 10 with 1 M NaOH.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain kraft lignin/alginate mixed aerogel particles.

The bulk density of the aerogel particles is -120 g/l.

The surface area and pore volume of the aerogel particles were determined to be 255 ^m2 /g and 1.88 ^cm3 /g.

3.2 Hydrophilic kraft lignin/alginate hybrid aerogels—different ratios

Solution 1: Kraft lignin powder was dispersed in deionized water (10 wt%) at room temperature.

5 wt % NaOH was added until the pH reached 11. One day later, the pH was measured, and further 5 wt % NaOH was added until the pH reached 11.

Solution 2: Sodium alginate was dissolved in water at room temperature at a concentration of 2 wt%.

Solution 3: Prepare _CaCl2 aqueous solution (20 g/L) at room temperature.

Solutions 1 and 2 were mixed in different weight ratios, and the total concentration of kraft lignin and alginate was adjusted by adding water to obtain solutions 4a-e:

Solution 4a: Kraft lignin/alginate 1:2 (2.7 wt%, pH 10.2)

Solution 4b: Kraft lignin/alginate 1:1 (2.7 wt%, pH 10.6)

Solution 4c: Kraft lignin/alginate 2:1 (2.7 wt%, pH 10.7)

Solution 4d: Kraft lignin/alginate 4:1 (2.7 wt%, pH 10.7)

Solution 4e: Kraft lignin/alginate 9:1 (2.7 wt%, pH 10.7)

50 ml of solution 4a-e was dropped into solution 3 (10×volume) using a pipette. Hydrogel particles 5a-e based on 4a-e were formed and settled to the bottom of solution 3.

The hydrogel particles 5a-e were immersed in ethanol (93%, 10×vol) for 5 min. The final solvent exchange step was to immerse the gel particles 5a-e from the previous step in pure ethanol (10×vol) for 5 min to obtain alcohol gel particles 6a-e (final solvent concentration 94-98%).

Alcogel particles 6a-e were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 hour to obtain kraft lignin/alginate mixed aerogel particles 7a-e. Aerogel particles 7a-e had no kraft lignin odor. Aerogel particles 7a-e were directly used for hydrophobization.

3.3 Hydrophobic kraft lignin/alginate hybrid aerogels—different ratios

50 ml of hydrophilic lignin aerogel particles 7a-e from Example 3.2 above were placed in a filter bag in a 2 L reactor. In addition, 50 ml of HMDZ was placed in a small open container in the reactor. The reactor was closed and heated to 115° C. After 20 hours, the reactor was cooled to room temperature and the hydrophobic aerogel particles 8a-e were removed from the reactor.

The density of the aerogel particles 8a-e is 45 g/l.

The surface area of the aerogel particles 8a-e was measured (depicted). The hydrophobicity was tested by placing the aerogel particles 8a-e on water in a container and observing the color change (from light brown to dark brown when absorbing water) and shrinkage.

8a: Surface area 429 ^m2 /g. When the aerogel particles were placed on water (absorbed water), the color immediately changed from light brown to dark brown and they shrank by -50% in -10 s.

8b: Surface area 394 ^m2 /g. When the aerogel particles were placed on water (absorbed water), the color immediately changed from light brown to dark brown and they shrank by -50% in -30 s.

8c: Surface area 372 ^m2 /g. Aerogel particles shrank by -50% in -10 min when placed on water, and the color of the particles changed from light brown to dark brown (water absorption) in 1 h.

8d: Surface area 330 ^m2 /g. Aerogel particles shrank by -50% in -2 hours when placed on water, and the color of the particles changed from light brown to dark brown (water absorption) in -4 hours.

8e: Surface area 318 ^m2 /g. Aerogel particles shrank by -50% in -4 h when placed on water, and the color of the particles changed from light brown to dark brown (water absorption) in -8 h.

3.4 Hydrophilic lignin sulfonate/xanthan gum hybrid aerogel

Solution 1: Disperse lignin sulfonate powder in deionized water (40 wt%) at room temperature

and added 5 wt% NaOH until the pH reached 13.

Solution 2: Xanthan gum was dispersed in an equal volume of ethanol and then dissolved in water at room temperature at a concentration of 0.7 wt%.

Solution 3: Prepare _CaCl2 aqueous solution (10 g/L) at room temperature.

Solution 4 was obtained by mixing solutions 1 and 2 at a weight ratio of lignin sulfonate to xanthan gum of 95:5.

Solution 4 was added dropwise into solution 3 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 3.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain lignin sulfonate/xanthan gum mixed aerogel particles.

The density of the aerogel particles is ~200 g/l.

The surface area of the aerogel particles was measured to be 290 ^m2 /g.

3.5 Hydrophilic kraft lignin/xanthan gum hybrid aerogel

Solution 1: Kraft lignin powder was dispersed in deionized water (20 wt%) at room temperature.

5 wt% NaOH was added until the pH reached 13.5.

Solution 2: Xanthan gum was dispersed in an equal volume of ethanol and then dissolved in water at room temperature at a concentration of 0.7 wt%.

Solution 3: Prepare _CaCl2 aqueous solution (10 g/L) at room temperature.

Solutions 1 and 2 were mixed at a weight ratio of kraft lignin to xanthan gum of 97:3 to obtain solution 4.

Solution 4 was added dropwise into solution 3 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 3.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain kraft lignin/xanthan gum mixed aerogel particles.

The density of the aerogel particles is -200 g/l.

The surface area of the aerogel particles was determined to be 416 ^m2 /g.

3.6 Hybrid aerogels containing more than two components

Solution 1: Kraft lignin powder was dispersed in deionized water (14 wt%) at room temperature.

5 wt% NaOH was added until the pH reached 10. Ludox SM30 (colloidal silica) was added and sodium alginate was added in different proportions and dissolved.

The concentration was adjusted with water to obtain various solutions 1 as shown in Table 1.

Solution 2: Prepare _CaCl2 aqueous solution (10 g/L) at room temperature and adjust the pH to 10 with 1 M NaOH.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60°C and 120 bar for 1 h to obtain colloidal silica/kraft lignin/alginate mixed aerogel particles as shown in Table 1.

Table 1

3.7 Hybrid aerogels containing various biopolymers

Solution 1: Tannic acid was blended with 2 wt% sodium alginate solution to obtain various solutions having concentrations and weight ratios as shown in Table 2. 40 wt% sodium alginate was added to the different solutions.

NaOH until the pH values shown in Table 2 are obtained.

Solution 2: Prepare _CaCl2 aqueous solution (10 g/L) at room temperature and adjust the pH to 10 with 1 M NaOH.

Solution 1 was added dropwise into solution 2 (10× volume) using a pipette. Hydrogel particles formed and settled to the bottom of solution 2.

The hydrogel particles were immersed in ethanol (93%, 10× volume) for 5 min. The final solvent exchange step was to immerse the gel particles from the previous step in pure ethanol (10× volume) for 5 min to obtain alcohol gel particles (final solvent concentration was 94-98%).

The alcohol gel particles were dried with supercritical carbon dioxide at 60° C. and 120 bar for 1 h to obtain hydrophilic hybrid aerogel particles having a bulk density and surface area as shown in Table 2.

For hydrophobization, 50 ml of hydrophilic aerogel particles were placed in a filter bag in a 2 L reactor. In addition, 50 ml of HMDZ were placed in a small open container in the reactor. The reactor was closed and heated to 115° C. After 20 hours, the reactor was cooled to room temperature and hydrophobic aerogel particles having a surface area as shown in Table 2 were taken out of the reactor.

Table 2

4. Method of use

4.1 Pore volume was measured according to DIN 66134:1998-02 using a Nova4000e pore size analyzer from Quantachrome Instruments. About 15-20 mg of sample was separated from the original sample and placed in a measuring glass cell. The sample was degassed at 50 mm Hg vacuum and 60 ° C for 15 h to remove any adsorbed components on the sample. Before performing surface area and pore size analysis, the sample was weighed again.

4.2 Surface area measurement: The specific surface area was determined by the Brunauer-Emmet-Teller (BET) method using low temperature nitrogen adsorption analysis (at the boiling point of nitrogen, 77 K) within the IUPAC recommended P/P0 range (0.05-0.30). The 1/((w.(P0/P-1)) vs P/P0 plot produced a linear plot with a correlation coefficient (r) exceeding 0.999.

References:

US020190329208A1

Grishechko,L. et al., Industrial Crops and Products 2013,41 347-355WO2009/027310

Robitzer et al., Langmuir 2008, 24, 12547-12552 WO 2009/027310

Claims (15)

1. A method of preparing a porous material, the method comprising at least the steps of:

a) Providing a mixture (M1), the mixture (M1) comprising as compound (C1) a water-soluble biopolyphenol polymer selected from lignin biopolymers and tannin biopolymers, and water,

B) Contacting the mixture (M1) with an aqueous solution of at least one multivalent metal ion to prepare a gel (A),

C) Exposing the gel (A) obtained in step B) to a water-miscible solvent (L) to obtain a gel (B),

D) Drying the gel (B) obtained in step c).

2. The method according to claim 1, wherein the mixture (M1) further comprises at least one water-soluble polysaccharide having carboxylic acid groups as compound (C2).

3. The method of claim 1 or 2, wherein the water-soluble biopolyphenol polymer is selected from alkali lignin, kraft lignin, hydrolyzed lignin, soda lignin, water-soluble solid lignin, enzymatically hydrolyzed lignin, lignin sulfonate, lignin carboxylate, lignin derivatives, biorefinery lignin, tannic acid or tannins and tannin derivatives.

4. A process according to any one of claims 1 to 3, wherein mixture (M1) comprises from 0.1% to 50% by weight of biopolyphenol polymer, based on the weight of mixture (M1).

5. The process according to any one of claims 1 to 4, wherein mixture (M1) comprises compound (C1) and compound (C2) in a ratio of 55:45 to 98:2.

6. The process according to any one of claims 1 to 5, wherein the pH of the mixture (M1) is from 8 to 14.

7. The method according to any one of claims 1 to 6, wherein the multivalent metal ion is a divalent metal ion or a trivalent metal ion, preferably a divalent metal ion or a trivalent metal ion selected from alkaline earth metal ions, aluminum ions and iron (III) ions.

8. The method according to any one of claims 1 to 6, wherein the method comprises a further modification step of the xerogel.

9. The method of claim 8, wherein the modifying step is selected from the group consisting of a shaping step, a compression step, a lamination step, a post-drying step, a hydrophobizing step, and a carbonization step.

10. The process according to any one of claims 1 to 9, wherein the solvent (L) used in step C) is selected from C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

11. The method according to any one of claims 1 to 10, wherein

Water-insoluble solid (S)

And/or

A compound (C) selected from pigments, opacifiers, flame retardants, catalytic materials, metals, metal oxides, metal sulfides, metal carbides, metal salts, silicon-based materials, carbon-based materials, metal organic frameworks, semiconductors, sulfur, fillers, surfactants, heat control agents, fibers and foam reinforcements,

Added to the mixture (M1).

12. A porous material obtainable by the method according to any one of claims 1 to 11 or obtainable by the method according to any one of claims 1 to 11.

13. The porous material of claim 12, wherein the porous material has a specific surface area of 120 to 800m ²/g, measured according to DIN 66134:1998-0 using BET theory and a pore volume of 2.1 to 9.5cm ³/g with a pore size <150 nm.

14. A porous material as claimed in claim 12 or 13, wherein the content of Volatile Organic Compounds (VOCs) in the porous material is less than 50% of the content of Volatile Organic Compounds (VOCs) in the biopolyphenol polymer used in the method.

15. Use of a porous material according to any one of claims 12 to 14 or a porous material obtainable by a method according to any one of claims 1 to 11 or obtainable by a method according to any one of claims 1 to 11: as a heat insulating material; as a carrier material for loading and releasing active substances; for battery applications; electrode materials for use in batteries, fuel cells or electrolysis; for catalysis; for a capacitor; for consumer electronics; for construction and construction applications; for home and business appliance applications; for temperature controlled logistics applications; for vacuum insulation applications; for apparel applications; for food applications; for cosmetic applications; for biomedical applications; for agricultural applications; for consumer applications; for packaging applications or for pharmaceutical applications.