Grease composition using lignocellulosic biomass and method for preparing same

Abstract

The present invention relates to a method for preparing a grease composition using lignocellulosic biomass as a raw material, and a grease composition prepared therefrom.

Description

Grease composition using lignocellulosic biomass and method for manufacturing the same

[0001] The present invention relates to a grease composition using lignocellulosic biomass and a method for manufacturing the same, and more specifically, to a grease composition having improved lubricating properties that can replace existing perfluorinated compound-based grease additives using lignocellulosic biomass as a raw material and a method for manufacturing the same.

[0002] Perfluorinated compounds (PFAS, Per- and polyfluoroalkyl Substances) are substances in which hydrogen in the basic framework of a hydrocarbon is substituted with fluorine, and are classified into polymer and non-polymer categories. Representative PFAS include PFOA (Perfluorooctanoic acid), PFOS (Perfluorooctanesulfonic acid), PFOSA (Perfluorooctane Sulfonamide), PFHxI (Perfluorohexyl Iodide), and FTOH (Fluorotelomer alcohols).

[0003] The above polymer-based PFAS has the characteristic of not easily getting wet with water, grease, oil, etc., and preventing contamination by dirt, etc., so it is used in various everyday consumer goods including clothing, carpets and rugs, cosmetics, firefighting foam, food contact materials and articles, and cooking utensils.

[0004] In particular, PTFE (polytetrafluoroethylene) is widely used in various industrial fields, such as electrical wires, automobiles, semiconductors, and aircraft parts, due to its excellent properties including heat resistance, chemical resistance, weather resistance, non-stick properties, friction resistance, and wear resistance. Furthermore, because it exhibits a low coefficient of friction and excellent lubrication effects even under high stress, it is widely utilized as an additive to reduce the coefficient of friction in sliding parts of mechanical components or bearing parts; a typical example is its application as a lubricating additive in grease products.

[0005] However, fluorine, which is very dangerous to the human body, is used in the manufacturing process of PFAS, and since these are very expensive materials, they lower the economic feasibility of grease production, making the development of alternative materials urgent. In addition, the aforementioned PFAS does not decompose easily and can cause environmental problems, so there are issues regarding regulations on the use of PFAS.

[0006] Regarding such PFAS substitute materials, Korean Published Patent Application No. 10-2024-0090367 (published on June 21, 2024) discloses a PFAS-free grease composition comprising two or more fluorine-free materials and a base oil, selected from: a fluorine-free polymer containing aromatic, heteroaromatic and / or heterocyclic groups; a silicone resin; an inorganic layered silicate; nanoparticle-type silica functionalized by organic groups; a phosphorus compound; and a melamine derivative.

[0007] Nevertheless, in addition to the fluorine-free materials presented in the aforementioned prior art, efforts to replace PFAS while possessing improved properties must continue. In particular, given the stricter carbon emission regulations and the recycling of eco-friendly resources, there is a continuous demand for the development of eco-friendly biomaterials using biomass, which is a low-cost and sustainable resource.

[0008] The objective of the present invention is to provide a method for preparing a grease composition comprising a method for preparing cross-linked lignocellulose and / or cross-linked lignin solid powder derived from lignocellulosic biomass, which can replace conventional PFAS as a grease additive.

[0009] In addition, another objective of the present invention is to provide an eco-friendly grease composition produced from the above manufacturing method, and said grease composition can exhibit an excellent lubricating effect sufficient to replace a grease composition using a conventional polymer-based perfluorinated compound additive.

[0010] To solve the above problem, the present invention provides a method for preparing a grease composition comprising cross-linked lignocellulose, comprising: (a) a step of obtaining cross-linked lignocellulose by adding an acid to lignocellulosic biomass to hydrolyze at least a portion of hemicellulose and / or cellulose within the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between lignin and cellulose components; (b) a step of obtaining solid particles comprising cross-linked lignocellulose by adding a base to the cross-linked lignocellulose obtained from step (a) to neutralize the remaining acid, and then removing a water-soluble substance from the neutralized product; and (c) a step of grinding the solid particles obtained from step (b). and (d) a step of mixing the pulverized solid particles obtained from step (c) with a lubricating base oil for grease; wherein the number average molecular weight of the cross-linked lignocellulose in the solid particles obtained from step (c) is 5 x 10 4 Up to 5 x 10 24 A method for preparing a grease composition characterized by g / mol is provided.

[0011] In addition, the present invention provides a method for preparing a grease composition containing cross-linked lignin, comprising: (a) adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass to obtain cross-linked lignin; (b) adding a base to the cross-linked lignin obtained from step (a) to neutralize residual acidic components, and then removing water-soluble substances or substances soluble in organic solvents from the neutralized product to obtain solid particles containing cross-linked lignin; and (c) grinding the solid particles obtained from step (b). and (d) a step of mixing the pulverized solid particles obtained from step (c) with a lubricating base oil for grease; wherein the number average molecular weight of the cross-linked lignin in the solid particles obtained from step (c) is 5 x 10 4 Up to 5 x 10 24 A method for preparing a grease composition characterized by g / mol is provided.

[0012] In one embodiment, step (a) may be carried out by adding a solvent containing an acid to lignocellulosic biomass or low molecular weight lignin and heating and / or pressurizing it at a temperature of 50 to 300 °C, or (a2) adding a cellulose degrading enzyme and a hemicellulose degrading enzyme; and a cellulose crosslinking enzyme and a hemicellulose crosslinking enzyme; to hydrolyze and crosslink at least a portion of the cellulose and hemicellulose, or (a3) ​​adding a solvent containing an acid and steam explosion at a temperature of 50 to 300 °C, or (a4) through a process mixed with the processes according to (a1) to (a3).

[0013] As an example, the particle size distribution of the crushed solid particles obtained from step (c) above may be 0.05 to 100 μm.

[0014] As an example, the acid in step (a) above may be selected from an organic acid having 1 to 20 carbon atoms; an inorganic acid selected from sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid or a mixture thereof; a mixture of the organic acid and the inorganic acid; or a mixture of the organic acid and the mixture of inorganic acids.

[0015] As an example, the acid may be an aqueous solution selected from hydrochloric acid, sulfuric acid, and nitric acid, or a mixture thereof, and the concentration of the acid may be in the range of 0.5 to 70 wt% based on the total content of biomass and the aqueous solution containing the acid.

[0016] As an example of the present invention, as the base used in step (b), one base selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), and sodium bicarbonate (NaHCO3) or a mixture of two or more of the bases may be used, or an aqueous solution of the one base or an aqueous solution of a mixture of two or more of the bases may be used.

[0017] As a preferred example of the present invention, as the base used in step (b), calcium hydroxide (Ca(OH)2) may be used, or a mixture with one or more bases selected from calcium hydroxide (Ca(OH)2); and sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), and sodium bicarbonate (NaHCO3).

[0018] In addition, the present invention can provide a grease composition prepared from the above-described manufacturing method.

[0019] In addition, the present invention relates to a grease composition comprising one or more of a lubricating base oil; a cross-linked lignocellulose powder having a carbohydrate content of 1 to 60 wt%; and a cross-linked lignin powder having a carbohydrate content of 0.01 to 1 wt%, wherein the number average molecular weight of each of the cross-linked lignocellulose powder and the cross-linked lignin powder is 5 x 10⁻⁶ 4 Up to 5 x 10 24 A grease composition characterized by being in the range of g / mol can be provided.

[0020] As one embodiment of the grease composition according to the present invention, the grease composition may include calcium sulfate (CaSO4).

[0021] As one embodiment of the grease composition according to the present invention, the grease composition may additionally include a thickener.

[0022] As one embodiment, the grease composition may comprise 55 to 90 wt% of a lubricating base oil based on the content of the total grease composition; 0.01 to 40 wt% of one or more components of cross-linked lignocellulose powder with a carbohydrate content of 1 to 60 wt% and cross-linked lignin powder with a carbohydrate content of 0.01 to 1 wt%; and 0.01 to 40 wt% of a thickener.

[0023] In one embodiment, the cross-linked lignocellulose powder in the grease composition may be produced by a manufacturing method comprising: (a) adding an acid to lignocellulosic biomass to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between lignin and cellulose components, thereby obtaining cross-linked lignocellulose; (b) adding a base to the cross-linked lignocellulose obtained from step (a) to neutralize the remaining acid, and then removing a water-soluble substance from the neutralized product to obtain solid particles containing cross-linked lignocellulose; and (c) grinding the solid particles obtained from step (b).

[0024] As an example, the cross-linked lignin powder in the grease composition may be produced by a manufacturing method comprising: (a) adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass to obtain cross-linked lignin; (b) adding a base to the cross-linked lignin obtained from step (a) to neutralize residual acidic components, and then removing water-soluble substances or substances soluble in organic solvents from the neutralized product to obtain solid particles containing cross-linked lignin; and (c) grinding the solid particles obtained from step (b).

[0025] The method for manufacturing a grease composition according to the present invention utilizes low-cost and harmless lignocellulosic biomass, thereby being environmentally friendly and economical from the raw material stage. Furthermore, it has the advantage of being able to manufacture a grease composition with high yield through low production costs and a simple process resulting from the acid treatment of lignocellulosic biomass, which is a low-cost bio-raw material.

[0026] In addition, the grease additive produced by the above manufacturing method according to the present invention comprises cross-linked lignocellulose powder and / or cross-linked lignin powder with a carbohydrate content of 0.01 to 1 wt%, thereby having improved lubricating properties, which can replace the expensive PTFE additives previously used, thereby significantly lowering the manufacturing cost of grease, and by using eco-friendly materials, the carbon dioxide emissions generated during grease manufacturing compared to existing petroleum-based PFTE materials can be significantly reduced and the environmental burden can be reduced.

[0027] FIG. 1(a) is an SEM image of a solid particle containing cross-linked lignocellulose in the present invention, and FIG. 1(b) is an SEM image of a solid particle containing cross-linked lignin in the present invention.

[0028] FIG. 2(a) is a photograph showing that solid particles containing cross-linked lignocellulose neutralized with calcium hydroxide obtained according to the present invention do not dissolve in various solvents, and FIG. 2(b) is a photograph showing that solid particles containing cross-linked lignocellulose neutralized with sodium hydroxide do not dissolve in various solvents.

[0029] FIGS. 3 to 6 are figures showing the particle size distribution of solid particles containing cross-linked lignin and solid particles containing cross-linked lignocellulose obtained according to the present invention.

[0030] Figure 7 is a graph showing the results of the wear resistance evaluation of the grease composition according to the embodiments and comparative examples of the present invention.

[0031] FIG. 8 is a graph showing the load-bearing evaluation results of grease compositions according to embodiments and comparative examples of the present invention.

[0032] FIG. 9 is a graph showing the friction coefficients of grease compositions according to embodiments and comparative examples of the present invention.

[0033] The present invention will be described in more detail below with reference to the examples and drawings. However, the following examples are provided as examples to aid in understanding the invention and the scope of the invention is not limited thereto. The present invention may be subject to various modifications and may be implemented in various different forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the invention.

[0034] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0035] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0036] The present invention provides a method for preparing a grease composition comprising cross-linked lignocellulose and a method for preparing a grease composition comprising cross-linked lignin.

[0037] Here, the 'cross-linked lignocellulose' refers to a mixed component of a high-molecular-weight carbohydrate component and a high-molecular-weight lignin component, wherein the above-mentioned 'cross-linked lignocellulose' comprises a cross-linked high-molecular-weight carbohydrate component derived from the cellulose component or the hemicellulose component within the lignocellulose biomass in a range of 1 to 60 wt% by partially hydrolyzing and cross-linking the lignocellulose biomass through acid treatment, etc., and the remaining component is a high-molecular-weight lignin component derived from the lignin component within the lignocellulose biomass by cross-linking the lignocellulose biomass or low-molecular-weight lignin through acid treatment, etc. The composition comprises a component in a range of 1 wt% or less, preferably in a range of 0.01 to 1 wt%, and the remaining component is a high molecular weight lignin derived from the lignin component in the lignocellulosic biomass or low molecular weight lignin, wherein the cross-linked lignin means that the majority of the content (99 wt% or more) consists of a cross-linked high molecular weight lignin component, and below, the expressions 'cross-linked lignocellulosic' and 'cross-linked lignin' in the grease composition according to the present invention may be interpreted according to the above definitions.

[0038] Meanwhile, the low molecular weight lignin used in the present invention is a component obtained by removing cellulose and hemicellulose from lignocellulosic biomass to leave only lignin. For example, biorefinery lignin, kraft lignin, lignosulfonate lignin, soda lignin, organosolv lignin, ionic liquid lignin, or a mixture thereof may be used, and preferably, their number average molecular weight is 5 x 10⁻⁶ 4 g / mol or less, more preferably 1 X 10⁻⁶ 4 Below, more preferably 5 X 10 3 Lignin with a g / mol or less can be used.

[0039] A method for preparing a grease composition containing the cross-linked lignocellulose according to the present invention comprises: (a) a step of obtaining cross-linked lignocellulose by adding an acid to lignocellulosic biomass to hydrolyze at least a portion of hemicellulose and / or cellulose within the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between lignin and cellulose components; (b) a step of obtaining solid particles containing the cross-linked lignocellulose by adding a base to the cross-linked lignocellulose obtained from step (a) to neutralize the remaining acid, and then removing water-soluble substances from the neutralized product; and (c) a step of grinding the solid particles obtained from step (b). and (d) a step of mixing the pulverized solid particles obtained from step (c) with a lubricating base oil for grease; wherein the number average molecular weight of the cross-linked lignocellulose in the solid particles obtained from step (c) is 5 x 10 4 Up to 5 x 10 24 It is characterized by being g / mol.

[0040] Herein, as a first step in a method for preparing a grease composition containing the cross-linked lignocellulose, the step (a) is to obtain cross-linked lignocellulose by adding an acid to the raw material, the lignocellulose biomass, to hydrolyze at least some of the hemicellulose and / or cellulose within the lignocellulose biomass, while simultaneously inducing cross-linking between the lignin components or between the lignin and cellulose components, respectively; wherein the addition of the acid may preferably involve adding a solution containing the acid, and the solution used may be an aqueous solution containing the acid.

[0041] In addition, as another aspect of the present invention, a method for preparing a grease composition containing cross-linked lignin comprises: (a) adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, while simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass to obtain cross-linked lignin; (b) adding a base to the cross-linked lignin obtained from step (a) to neutralize residual acidic components, and then removing water-soluble substances or substances soluble in organic solvents from the neutralized product to obtain solid particles containing cross-linked lignin; and (c) grinding the solid particles obtained from step (b). and (d) a step of mixing the pulverized solid particles obtained from step (c) with a lubricating base oil for grease; wherein the number average molecular weight of the cross-linked lignin in the solid particles obtained from step (c) is 5 x 10 4 Up to 5 x 10 24 It is characterized by being g / mol.

[0042] Herein, as a first step in a method for preparing a grease composition containing the cross-linked lignin, the step (a) is a step of obtaining cross-linked lignin by adding an acid to the raw material, which is lignocellulosic biomass or low molecular weight lignin, to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass and simultaneously induce cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass; wherein the addition of the acid may preferably be a solution containing the acid, and the solution used may be an aqueous solution containing the acid.

[0043] Here, the low molecular weight lignin component may be biorefinery lignin, kraft lignin, lignosulfonate lignin, soda lignin, organosolv lignin, ionic liquid lignin, or a mixture thereof, as previously described, and preferably, their number average molecular weight is 5 x 10⁻⁶ 4 g / mol or less, more preferably 1 X 10⁻⁶ 4 Below, more preferably 5 X 10 3 Lignin with a g / mol or less can be used.

[0044] Meanwhile, the difference between the method for preparing a grease composition containing the 'cross-linked lignin' in the present invention and the method for preparing a grease composition containing the 'cross-linked lignocellulose' in the present invention is, as previously explained, that cross-linked lignocellulose contains a cross-linked high molecular weight carbohydrate component (a carbohydrate component cross-linked by acid treatment of hemicellulose and cellulose components) in a range of 1 to 60 wt%, and the remaining component refers to a mixed component of high molecular weight carbohydrate components and high molecular weight lignin components, wherein the remaining component is a cross-linked high molecular weight lignin component derived from the lignin component in the lignocellulosic biomass through the aforementioned acid treatment, etc. In the case of cross-linked lignin, almost all of the cellulose components and hemicellulose components in the lignocellulosic biomass are removed through acid treatment, etc. of the lignocellulosic biomass or low molecular weight lignin, thereby being derived from the cellulose component in the lignocellulosic biomass or from the hemicellulose component It means that it contains a derived, cross-linked high molecular weight carbohydrate component in a range of 1 wt% or less, preferably in a range of 0.01 to 1 wt%, and the remaining component consists of a cross-linked high molecular weight lignin component.

[0045] Accordingly, the cross-linked lignin can be obtained by increasing the acid treatment time, increasing the acid content, increasing the acid concentration to lower the pH of the aqueous solution, or a combination thereof, until the carbohydrate-based cross-linking component derived from hemicellulose and cellulose, respectively, is included in a range of 1 wt% or less, preferably in the range of 0.01 to 1 wt%, or by controlling the process conditions so that the carbohydrate component is lowered and only the lignin is cross-linked.

[0046] Conversely, the cross-linked lignocellulose can be obtained by controlling process conditions such that the carbohydrate component and lignin are each cross-linked within an appropriate range by controlling any one of the acid treatment time, acid content, and acid concentration, or by controlling a combination thereof, so that the cross-linked component derived from hemicellulose and cellulose, respectively, can be included in a range of 1 to 60 wt% relative to the total component of the cross-linked lignocellulose.

[0047] Accordingly, in the method for preparing a grease composition containing the cross-linked lignin in the present invention, the processes of steps b) to d) may each be identical compared to the method for preparing a grease composition containing the cross-linked lignocellulose.

[0048] Meanwhile, the lignocellulosic biomass in step (a) according to the present invention is a material comprising lignin; and at least one of cellulose and hemicellulose; preferably, it may include all of lignin, cellulose, and hemicellulose, and such lignocellulosic biomass may be a woody biomass derived from herbaceous plants, conifers or deciduous trees (conventional wood), or various biomass such as rice straw, corn stalks, palm fruit shells, sugarcane, etc.

[0049] In addition, the lignocellulosic biomass used as a raw material in step (a) above may be used after undergoing a drying process and grinding. In order to ensure uniformity in subsequent processes, it is preferable to grind the size to be 10 µm or more and 50 mm or less, preferably 20 µm or more and 20 mm or less, and more preferably in the range of 10 to 0.001 mm.

[0050] Here, in order to obtain the cross-linked lignocellulose in the present invention, the rigid crystallization structure of lignin and cellulose in the raw material lignocellulosic biomass is destroyed by the addition of acid according to step (a), and at least some hemicellulose and at least some cellulose are hydrolyzed, preferably most of the hemicellulose is hydrolyzed so that the hemicellulose-derived component in the raw material lignocellulosic biomass remains at 5 wt% or less, preferably 3 wt% or less, and the cellulose component remains at 1 to 90 wt%, preferably 1 to 80 wt%, more preferably 1 to 70 wt%, and more preferably 2 to 60 wt% of the content of the cellulose-derived component in the raw material lignocellulosic biomass, and these are cross-linked intermolecularly with each other, thereby converting into a cross-linked high molecular weight lignocellulose form.

[0051] In addition, due to the addition of the above acid, the lignin in the lignocellulosic biomass is hardly hydrolyzed, and only intermolecular or cross-linking with the cellulose component occurs, resulting in conversion into high molecular weight lignin or a mixed component of high molecular weight lignin and cellulose.

[0052] That is, the present invention, as a major component of a grease composition, cross-linked lignocellulose obtained by acid treatment has a mixed component with a high molecular weight that exceeds the molecular weight of the existing lignin and cellulose components due to the cross-linking, and since it mainly contains hydrocarbon components containing carbon-carbon double bonds, it can have improved high durability and friction characteristics, and thus contribute to improving the lubrication characteristics in the grease composition.

[0053] In addition, to obtain the cross-linked lignin in the present invention, the rigid crystallization structure of lignin and cellulose in the raw material lignocellulosic biomass is destroyed by the addition of acid according to step (a), and at least some hemicellulose and at least some cellulose are hydrolyzed, preferably most of the hemicellulose and cellulose are hydrolyzed so that the sum of the hemicellulose-derived components and cellulose-derived components in the raw material lignocellulosic biomass remains at 5 wt% or less, preferably 3 wt% or less, more preferably 1 wt% or less, and even more preferably 0.5 wt% or less, based on the total sum of hemicellulose and cellulose in the added lignocellulosic biomass. Furthermore, by the addition of acid, the lignin in the lignocellulosic biomass is hardly hydrolyzed, and only intermolecular cross-linking occurs, converting it into a high molecular weight lignin component.

[0054] That is, the present invention, as a major component of a grease composition, cross-linked lignin obtained by acid treatment has high molecular weight lignin components that exceed the lignin components or low molecular weight lignin contained in conventional untreated lignocellulose due to the cross-linking, and since these mainly contain hydrocarbon components containing carbon-carbon double bonds, they can have improved high durability and friction characteristics, thereby contributing to the improvement of lubrication characteristics in the grease composition.

[0055] As an example of a process for obtaining cross-linked lignocellulose or cross-linked lignin according to the present invention, the acid in step (a) may be selected from an organic acid having 1 to 20 carbon atoms; an inorganic acid selected from sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid or a mixture thereof; a mixture of the organic acid and the inorganic acid; or a mixture of the organic acid and the mixture of inorganic acids.

[0056] In this case, the organic acid is a carbon compound containing a carboxylic acid, and depending on the number of carboxylic acids, monocarboxylic acid, biscarboxylic acid, triscarboxylic acid, tetracarboxylic acid, etc. may be used, and depending on the number of carbon atoms, an organic acid having 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms may be used, and more preferably, acetic acid, formic acid, propionic acid, etc. may be used.

[0057] In addition, as a preferred example of the acid component used as the inorganic acid, any one selected from hydrochloric acid, sulfuric acid, and nitric acid, or a mixture thereof may be used, and the preferred acid concentration may be in the range of 0.01 to 70 wt%, more preferably in the range of 0.5 to 70 wt%, more preferably in the range of 0.6 to 65 wt%, and more preferably in the range of 0.7 to 60 wt% based on the total content of biomass; and an aqueous solution containing acid; and as a more preferred example, sulfuric acid may be used in the range of 0.5 to 70 wt%, more preferably in the range of 0.6 to 65 wt%, and more preferably in the range of 0.7 to 60 wt% based on the total content of crushed biomass and an aqueous solution containing acid.

[0058] As an example of a process for obtaining cross-linked lignocellulose or cross-linked lignin according to the present invention, the acid in step (a) is an aqueous solution selected from hydrochloric acid, sulfuric acid, and nitric acid, or a mixture thereof, and the concentration of the acid may be in the range of 0.5 to 70 wt%, preferably 2 to 70 wt%, based on the total content of biomass; and the aqueous solution containing the acid.

[0059] As an example of a process for obtaining cross-linked lignocellulose or cross-linked lignin according to the present invention, step (a) may be carried out by adding a solvent containing an acid to the lignocellulose biomass and heating and / or pressurizing it at a temperature of 50 to 300 °C, preferably 80 to 250 °C, or (a2) adding a cellulose degrading enzyme and a hemicellulose degrading enzyme; and a cellulose cross-linking enzyme and a hemicellulose cross-linking enzyme; to hydrolyze and cross-link at least a portion of the cellulose and hemicellulose, or (a3) ​​adding a solvent containing an acid and steam-explosing it at a temperature of 50 to 300 °C, preferably 80 to 250 °C, or (a4) through a process in which the processes according to (a1) to (a3) ​​are mixed.

[0060] Here, among the processes of step (a) above, the process of heating and / or pressurizing (a1) may include a process of reacting a mixture comprising lignocellulosic biomass and a solvent containing acid at 100 to 250°C, more preferably 120 to 200°C for 2 minutes to 2 days, preferably 4 hours to 1 day, at atmospheric pressure or 10 atmospheres or less, and then filtering the solids by reducing the pressure.

[0061] In addition, the process of adding the above (a2) cellulose and hemicellulose degrading enzyme and crosslinking enzyme may be used without limitation as long as it is an enzyme that degrades cellulose and hemicellulose, and an enzyme that induces intermolecular crosslinking of at least one of lignin, cellulose, and hemicellulose to form one or more of crosslinked lignocellulose and crosslinked lignin.

[0062] In addition, the steam explosion process (a3) ​​may include a process of reacting a mixture comprising lignocellulosic biomass and a solvent containing acid using steam, preferably at 100 to 250°C, more preferably at 120 to 200°C for 1 hour to 1 day, preferably 10 minutes to 8 hours, and then reacting by instantaneously reducing the pressure.

[0063] At this time, the concentration of the acid introduced in step (a) above can be introduced in a range of concentrations depending on conditions such as the type of acid, reaction temperature, and pressure.

[0064] Meanwhile, instead of degrading and crosslinking lignocellulose by enzymatic reaction in step (a2) above, a known chemical degrading agent and a chemical crosslinking agent may be used, or the degrading enzyme and crosslinking enzyme and the known chemical degrading agent and chemical crosslinking agent may be used together.

[0065] Meanwhile, step (b) in the present invention is a step of neutralizing residual acid by adding a base to the cross-linked lignocellulose or cross-linked lignin obtained from step (a), and then removing water-soluble substances from the neutralized product to obtain solid particles containing cross-linked lignocellulose or cross-linked lignin; wherein the residual acid component is removed by neutralizing it using a base because if the acid component remains in a subsequent process using the grease composition according to the present invention, it may have an adverse effect on grease manufacturing and physical properties.

[0066] More specifically, the process of adding the base to neutralize residual acidic components can neutralize residual acid using a basic aqueous solution, and can also wash with an aqueous solution to remove water-soluble substances from the neutralized product.

[0067] As one embodiment, the base used to neutralize the residual acid component in step (b) may be one base selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), and sodium bicarbonate (NaHCO3), or a mixture of two or more of the bases, or an aqueous solution of one base or an aqueous solution of a mixture of two or more of the bases, but is not limited thereto, and any base capable of neutralizing the acid component may be used without limitation.

[0068] In addition, as a preferred example of the present invention, as the base used in step (b), calcium hydroxide (Ca(OH)2) may be used, or a mixture with calcium hydroxide (Ca(OH)2) and one or more bases selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), and sodium bicarbonate (NaHCO3) may be used.

[0069] At this time, between step (a), which is a process for obtaining the cross-linked lignocellulose or cross-linked lignin in the present invention, and step (b), which is a neutralization reaction and a step for removing water-soluble substances, a step of washing the residual acid component in the mixed component containing the cross-linked lignocellulose and acid component obtained through step (a); or the mixed component containing the cross-linked lignin and acid component; by adding water before neutralizing the residual acid component may be additionally included, and the acid contained in the aqueous solution obtained after washing may be recovered and reused.

[0070] The present invention may include a washing process in which water or an organic solvent is added after the neutralization of step (b) to wash and additionally remove the water-soluble substance. In this case, the water-soluble substance refers to a component that can be dissolved in water or an organic solvent, selected from one or a mixture thereof, of a low molecular weight soluble substance containing residual sugar components derived from biomass, a substance derived from the acid addition process, or a substance derived from the base addition process.

[0071] In addition, in the method for preparing a grease composition containing the cross-linked lignin, when cross-linked lignin is obtained by acid treatment using the low molecular weight lignin as a raw material, the residual acidic component can be neutralized by adding a base in step (b), and then water-soluble substances or substances soluble in organic solvents can be removed from the neutralized product. That is, in the process of obtaining a cross-linked lignin component using the low molecular weight lignin as a raw material, water can be used to remove water-soluble substances, but in addition, solid particles containing cross-linked lignin can be obtained by using an organic solvent to remove substances soluble in the organic solvent. The organic solvent used at this time may include, but is not limited to, ketones having 1 to 4 carbon atoms, alcohols having 1 to 6 carbon atoms, alcohol ethers having 1 to 8 carbon atoms, cyclic ethers having 1 to 8 carbon atoms, alkylarenes having 6 to 16 carbon atoms, alkenes having 5 to 16 carbon atoms.

[0072] Meanwhile, in the method for preparing a grease composition containing cross-linked lignocellulose or cross-linked lignin according to the present invention, step (c) is a step of grinding the solid particles obtained from each of the above steps (b). This is performed to produce the particles in powder form so that they have better dispersibility when used as a grease composition, improved compatibility with other additives, and are easy to handle. The grinding method may apply any known grinding method including ball milling, spex milling, and nano milling without limitation, and the particle size distribution obtained after grinding may be in the range of 0.05 to 100 μm, preferably 0.1 to 50 μm, and more preferably 0.3 to 20 μm.

[0073] In one embodiment, when the pulverized solid particles obtained through step (c) include cross-linked lignocellulose, the cross-linked lignocellulose may include 1 to 60 wt% of a carbohydrate component derived from hemicellulose and cellulose, 60 to 99 wt% of a high molecular weight lignin component derived from lignin, preferably 3 to 35 wt% of the carbohydrate component and 65 to 97 wt% of the high molecular weight lignin component, more preferably 5 to 30 wt% of the carbohydrate component and 70 to 95 wt% of the high molecular weight lignin component.

[0074] As previously described, the carbohydrate component in the present invention refers to a polysaccharide component derived from hemicellulose and cellulose, obtained by acid treatment of cellulose and hemicellulose contained in lignocellulosic biomass.

[0075] In addition, as an example, when the crushed solid particles obtained through step (c) include cross-linked lignin, the cross-linked lignin may include 0.01 to 1 wt% of a carbohydrate component derived from hemicellulose and cellulose, 99 to 99.99 wt% of a high molecular weight lignin component derived from lignin, preferably 0.02 to 0.9 wt% of the carbohydrate component, 99.1 to 99.98 wt% of the high molecular weight lignin component, and more preferably 0.05 to 0.8 wt% of the carbohydrate component, and 99.2 to 99.95 wt% of the high molecular weight lignin component.

[0076] The number average molecular weight of the cross-linked lignocellulose or cross-linked lignin in the solid particles obtained through step (c) in the method for preparing a grease composition comprising cross-linked lignocellulose or cross-linked lignin according to the present invention is 5 x 10 4 ~ 5 X 10 24 g / mol, preferably 5 x 10 5 ~ 5 X 10 24g / mol, more preferably 5 x 10 6 ~ 5 X 10 24 g / mol, more preferably 5 x 10 7 ~ 5 X 10 24 g / mol, more preferably 5 x 10 8 ~ 5 X 10 24 It can be in the g / mol range.

[0077] In this case, the measurement of the number average molecular weight above refers to a value estimated through dry particle size analysis in accordance with the ISO 13320 procedure.

[0078] The reason the above-mentioned cross-linked lignocellulose or cross-linked lignin has an ultra-high molecular weight is due to cross-linking between lignin molecules resulting from the addition of acid in step (a) above, cross-linking between cellulose and hemicellulose component molecules, and cross-linking between each of these components, thereby enabling the above-mentioned ultra-high molecular weight cross-linked lignocellulose or cross-linked lignin to have physical properties suitable for a grease composition.

[0079] In one embodiment, one or more of the cross-linked lignocellulose and cross-linked lignin in the pulverized solid particles obtained through step (c) may each have a solubility of less than 10 wt% in water, tetrahydrofuran, and toluene, preferably less than 5 wt%, and more preferably less than 3 wt%.

[0080] Additionally, step (d) in the present invention is a step of mixing the crushed solid particles obtained from step (c) with a lubricating base oil for grease; wherein the lubricating base oil may be a mineral oil, synthetic oil, vegetable oil, or a mixture thereof without limitation, and as an example, one or more of the following may be used: a mineral oil including paraffinic base oil and naphthenic base oil; a synthetic oil including polyalphaolefin (PAO), ester base oil, polyalkylene glycol (PAG), and silicone oil; or a vegetable oil including canola oil, soybean oil, castor oil, and sunflower oil. The mixing of the lubricating base oil and the solid particles may be performed by directly mixing the solid particles as a single component into the lubricating base oil, or by mixing the components after pre-mixing them with an added additive.

[0081] The present invention can also provide a grease composition manufactured by the method for manufacturing the grease composition described above. The grease composition manufactured according to the present invention utilizes low-cost and harmless lignocellulosic biomass, as described above, thereby being environmentally friendly and economical from the raw material stage. Furthermore, it has the advantage of being able to manufacture the grease composition with high yield through low production costs and a simple process, thus replacing the expensive PTFE additives previously used.

[0082] In addition, as a more specific example of a grease composition according to the present invention, the grease composition comprises one or more of: a lubricating base oil; a cross-linked lignocellulose powder having a carbohydrate content of 1 to 60 wt%; and a cross-linked lignin powder having a carbohydrate content of 0.01 to 1 wt%. The number average molecular weight of each of the cross-linked lignocellulose powder and the cross-linked lignin powder is 5 x 10⁻⁶ 4 Up to 5 x 10 24 A grease composition is provided that is characterized by being in the range of g / mol.

[0083] Here, the carbohydrate refers to a component derived from hemicellulose and cellulose by the acid treatment, as previously explained.

[0084] In addition, as a more preferred embodiment of the grease composition according to the present invention, the carbohydrate content of the cross-linked lignocellulose powder may be in the range of 3 to 60 wt%, more preferably in the range of 5 to 40 wt%, and the carbohydrate content of the cross-linked lignin powder may be in the range of 0.02 to 0.9 wt%, more preferably in the range of 0.05 to 0.8 wt%.

[0085] The lubricating base oil in the grease composition according to the present invention may be a mineral oil, synthetic oil, vegetable oil, or a mixture thereof without limitation. For example, one or more of the following may be used: a mineral oil including a paraffinic base oil or a naphthenic base oil; a synthetic oil including a polyalphaolefin (PAO), an ester base oil, a polyalkylene glycol (PAG), or a silicone oil; or a vegetable oil including canola oil, soybean oil, castor oil, or sunflower oil.

[0086] In one embodiment, the grease composition may further include a thickener, and the thickener may be a component that combines with the base oil to maintain a semi-solid viscosity and optimize lubrication properties, and may be a soap-based thickener, a non-soap-based thickener, or a mixture thereof without limitation. For example, one or more of the following may be used: a single metal soap-based thickener including lithium simple soap, calcium simple soap, sodium simple soap, and aluminum simple soap; a complex soap-based thickener including lithium complex soap, calcium complex soap, and aluminum complex soap; an inorganic thickener including bentonite and silica; and an organic thickener including polyurea and PTFE.

[0087] As an embodiment of the grease composition according to the present invention, the grease composition may include calcium sulfate (CaSO4), and more specifically, one or more of the cross-linked lignocellulose powder and cross-linked lignin powder in the grease composition may include calcium sulfate (CaSO4), and exemplarily, the cross-linked lignocellulose powder may include calcium sulfate (CaSO4), or the cross-linked lignin powder may include calcium sulfate (CaSO4), or both the cross-linked lignocellulose powder and the cross-linked lignin powder may include calcium sulfate (CaSO4).

[0088] In this case, the content of the calcium sulfate may be in the range of 3 to 30 wt%, preferably 5 to 25 wt%, more preferably 7 to 18 wt%, and even more preferably 8 to 15 wt% relative to the total weight of each of the cross-linked lignocellulose powder or cross-linked lignin powder.

[0089] In addition, as a specific example of the grease composition in the present invention, the present invention provides a grease composition comprising, based on the content of the total grease composition, 55 to 90 wt% of a lubricating base oil; 0.01 to 40 wt% of one or more components selected from cross-linked lignocellulose powder with a carbohydrate content of 1 to 60 wt% and cross-linked lignin powder with a carbohydrate content of 0.01 to 1 wt%; and 0.01 to 40 wt% of a thickener.

[0090] Here, a more preferred content for the components of the grease composition may be in the range of 55 to 85 wt% of a lubricating base oil; 7 to 40 wt% of one or more components of cross-linked lignocellulose powder and cross-linked lignin powder; and 0.01 to 35 wt% of a thickener, and more preferably may comprise 50 to 85 wt% of a lubricating base oil; 12 to 40 wt% of one or more components of cross-linked lignocellulose powder and cross-linked lignin powder; and 0.01 to 35 wt% of a thickener.

[0091] In addition, the cross-linked lignocellulose powder and cross-linked lignin powder in the grease composition may be in the form of solid particles, and the particle size distribution of each solid particle may be in the range of 0.05 to 100 μm, preferably 0.1 to 50 μm, and more preferably 0.3 to 20 μm.

[0092] Additionally, the cross-linked lignocellulose powder in the grease composition of the present invention may be produced by a manufacturing method comprising: (a) a step of obtaining cross-linked lignocellulose by adding an acid to lignocellulose biomass to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulose biomass, while simultaneously inducing cross-linking between lignin components or between lignin and cellulose components; (b) a step of obtaining solid particles containing cross-linked lignocellulose by adding a base to the cross-linked lignocellulose obtained from step (a) to neutralize the remaining acid, and then removing water-soluble substances from the neutralized product; and (c) a step of grinding the solid particles obtained from step (b).

[0093] In addition, the cross-linked lignin powder in the grease composition of the present invention may be produced by a manufacturing method comprising: (a) a step of obtaining cross-linked lignin by adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass while simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass; (b) a step of obtaining solid particles containing cross-linked lignin by adding a base to the cross-linked lignin obtained from step (a) to neutralize residual acidic components, and then removing water-soluble substances from the neutralized product; and (c) a step of grinding the solid particles obtained from step (b).

[0094] Steps a) to (c) in the method for preparing the cross-linked lignocellulose powder and cross-linked lignin powder in the grease composition according to the present invention are identical to those previously described, so a redundant description is omitted.

[0095] The present invention will be explained in more detail below through preferred embodiments.

[0096] <Preparation of Ultra-High Molecular Weight Cross-linked Lignocellulose and Cross-linked Lignin via Biomass Acid Treatment>

[0097] <Preparation Example 1>

[0098] The biomass raw material used for the production of ultra-high molecular weight cross-linked lignocellulose and ultra-high molecular weight cross-linked lignin was sawdust mixed with pine and acacia trees, and wood powder was prepared by grinding before use to obtain a particle size of 100 µm to less than 10 mm. Before use, the wood powder was dried to a moisture content of 10 wt%.

[0099] Subsequently, the pine wood powder and water were each introduced into a Teflon-coated stainless steel reactor in a mass ratio of 1:10, and 10 wt% sulfuric acid was added to each of the total mass of the introduced wood powder and water. Then, the reaction system was hydrolyzed under closed conditions at 130°C for 180 minutes with stirring to obtain cross-linked lignocellulose, and hydrolyzed at 160°C for 360 minutes with stirring to obtain cross-linked lignin.

[0100] The obtained cross-linked lignocellulose and cross-linked lignin were neutralized using calcium hydroxide Ca(OH)2 and sodium hydroxide (NaOH), respectively, to a pH of 6 to 8, and then washed twice with water to finally obtain solid cross-linked lignocellulose and cross-linked lignin particles. When neutralized with calcium hydroxide, residual sulfuric acid reacts to form the sparingly soluble salt CaSO4, so most of the CaSO4 remains in the cross-linked lignocellulose and cross-linked lignin even after washing.

[0101] Subsequently, each obtained solid particle was dried in a 140°C dryer for 6 hours, and then subjected to continuous grinding using an air classified mill while introducing hot air of 120°C or higher to obtain cross-linked lignocellulose and cross-linked lignin in the form of ground fine powder.

[0102] Among these, chemical component analysis was performed on cross-linked lignocellulose and cross-linked lignin, which were neutralized with sodium hydroxide to minimize residual salts. It was confirmed that cross-linked lignocellulose consisted of 85 wt% lignin, 14 wt% carbohydrate components, and 1 wt% other components (ash, etc.), while cross-linked lignin consisted of 99.7 wt% lignin and approximately 0.3 wt% carbohydrate components.

[0103] Meanwhile, it was confirmed that cross-linked lignocellulose neutralized with calcium hydroxide consists of 76 wt% lignin, 12.5 wt% carbohydrates, and 10.9 wt% calcium sulfate (CaSO4), and that cross-linked lignin neutralized with calcium hydroxide consists of 89.7 wt% lignin, 0.25 wt% carbohydrates, and 10.02 wt% calcium sulfate (CaSO4).

[0104] <Experiment on the Molecular Weight Measurement of Cross-linked Lignocellulose and Cross-linked Lignin>

[0105] Meanwhile, cross-linked lignocellulose and cross-linked lignin solid particles, which were pulverized by neutralizing with calcium hydroxide, were photographed using an electron microscope and are shown in FIGS. 1a and 1b. To determine the molecular weight, the solubility of the cross-linked lignocellulose and cross-linked lignin in different solvents was analyzed, and the results are shown in Table 1, FIGS. 2a, and FIGS. 2b. Here, FIGS. 2(a) is a photograph showing that solid particles containing cross-linked lignocellulose neutralized with calcium hydroxide obtained according to the present invention do not dissolve in various solvents, and FIGS. 2(b) is a photograph showing that solid particles containing cross-linked lignocellulose neutralized with sodium hydroxide do not dissolve in various solvents.

[0106] Weight before solvent test (g) Weight after test (g) Solubility (%) Lignocellulose lignin Lignocellulose lignin Lignocellulose lignin Neutralizing agent Ca(OH)2NaOH Ca(OH)2NaOH Ca(OH)2NaOH Ca(OH)2NaOH Ca(OH)2NaOH DI 0.1029 0.1023 0.1021 0.1020 0.1009 0.1002 0.1006 0. 10051.942.0531.471.47THF0.10350.10320.10310.10300.10100.10090.10200.10212.422.2291.070.87Tol0.10280.10260.10290.10250.10180.10170.10170.10150.970.8771.170.98<Explanation of Solvent Abbreviations>1) DI: DI water2) THF: Tetrahydrofuran3) Tol: Toluene

[0107] Referring to Table 1, Figures 2a and 2b above, the cross-linked lignocellulose and cross-linked lignin obtained in Preparation Example 1 were hardly soluble in both hydrophilic and hydrophobic solvents, so the number average molecular weight (Mn) was estimated through dry particle size analysis in accordance with the ISO 13320 procedure. The measurement results are shown in Table 2 below, and based on the number average molecular weight (Mn), the cross-linked lignocellulose and cross-linked lignin were 4.28 × 10⁻⁶, respectively, when Ca(OH)₂ was used. 12 g / mol and 4.18×10 12 It was estimated to be g / mol.

[0108] In addition, when the above Ca(OH)2 was used, the estimated molecular weight (g / mol) distribution according to the particle size distribution of cross-linked lignocellulose divided into 70 sections was calculated as 2.45×10⁻⁶ 10 g / mol ~ 5.96×10 18 It was calculated in g / mol.

[0109] The number average molecular weight (Mn) in Table 2 can be calculated by substituting the particle size analysis results (Table 3) for each section and the density values ​​of the sample into the equation below.

[0110]

[0111] 1: Sphere per molecule (1 / molecule)

[0112] d: Diameter of the polymer (㎛)

[0113] π: 3.1416

[0114] ρ: Density of polymer (g / cm³) 3 )

[0115] 10,000: Correction constant (㎛ / cm)

[0116] N: Avogadro's number (6.02×10⁻⁶ 23 )

[0117] j: Number of particle size analysis intervals

[0118] Wi: Content of each polymer

[0119] Mi: Molecular weight of each polymer

[0120] Here, when estimating the number average molecular weight (Mn) through particle size analysis, it is assumed that all dispersed particles exist in a spherical shape and that all particles do not swell in the dispersion medium.

[0121] Average molecular weight (Mn) (g / mol) Lignocellulose Lignin Neutralizer Ca(OH)2NaOH Ca(OH)2NaOH 14,295,894,010,487 4,285,753,203,421 4,152,283,389,323 4,215,326,332,874 24,257,639,207,810 4,264,632,725,213 4,177,388,293,672 4,106,320,875,326 Average 4,276,716,609,148 4,275,192,964,317 4,176,387,983,744 4,160,823,604,100

[0122] For example, to explain the process regarding the first repeated molecular weight measurement of cross-linked lignocellulose neutralized with Ca(OH)2 in Table 2 above, first, the density value of the sample (ρ = 1.4726 g / cm³) 3After measuring the particle size, particle size analysis was performed as shown in Table 3 below, and the molecular weight (Mi) for each section was derived by substituting the particle density (ρ) and diameter value (d) for each section. Subsequently, the derived molecular weight (Mi) for each section and the particle content (Wi) for each section were substituted into Equation 2 to calculate the final number-average molecular weight (Mn) for all sample particles. This process was repeated twice, and the average values ​​are shown in Table 2. The number-average molecular weight of each sample was calculated by applying the same method.

[0123] Meanwhile, the particle diameter (d), content (Wi), and molecular weight (Mi) for each particle size range (j) of the sample are shown in Table 3 below.

[0124]

[0125]

[0126]

[0127]

[0128] In addition, the results of particle size analysis of the powder obtained after the grinding process of cross-linked lignocellulose and cross-linked lignin according to the present invention, performed according to the ISO 13320 procedure, are shown in FIGS. 3 to 6.

[0129] Referring to Figure 3 above, the average particle size of the cross-linked lignocellulose was found to be approximately 22.1 μm, with a particle size distribution ranging from 9.8 μm (Dv 10) to 38.3 μm (Dv 90). In Figure 4, the average particle size of the cross-linked lignin was found to be approximately 18.9 μm, with a particle size distribution ranging from 8.8 μm (Dv 10) to 51.4 μm (Dv 90).

[0130] In addition, to observe changes in lubrication characteristics according to the particle size, the crushed particles were pulverized using a standard sieve with a sieve size of 20 μm to obtain finer ultra-high molecular weight cross-linked lignocellulose particles with an average particle size of 2.4 μm and a particle size distribution of 0.58 μm (Dv 10) to 4.58 μm (Dv 90) (Fig. 5) and finer ultra-high molecular weight cross-linked lignin with an average particle size of 5.2 μm and a particle size distribution of 2.8 μm (Dv 10) to 8.7 μm (Dv 90) (Fig. 6).

[0131] In addition, to compare the lubricating effect of cross-linked lignocellulose and cross-linked lignin containing CaSO4, a sparingly soluble salt remaining after neutralization, with that of CaSO4, cross-linked lignocellulose and cross-linked lignin recovered after neutralization with sodium hydroxide were also ground and pulverized in the same manner as above. It was observed that the average particle size was about 20.1 μm and the particle size distribution ranged from 9.5 μm (Dv 10) to 36.3 μm (Dv 90), and the average particle size of the cross-linked lignin was about 17.9 μm and the particle size distribution ranged from 8.1 μm (Dv 10) to 50.9 μm (Dv 90).

[0132] In addition, to observe changes in lubrication characteristics according to the particle size, the crushed particles were pulverized using a standard sieve with a sieve size of 20 μm to obtain finer ultra-high molecular weight cross-linked lignocellulose particles with an average particle size of 3.1 μm and a particle size distribution of 0.48 μm (Dv 10) to 4.44 μm (Dv 90), and finer ultra-high molecular weight cross-linked lignin with an average particle size of 4.8 μm and a particle size distribution of 2.7 μm (Dv 10) to 9.1 μm (Dv 90).

[0133] An additive for grease with lubricating properties was prepared using pulverized solid particles containing insoluble, cross-linked lignocellulose and cross-linked lignin having the above-mentioned ultra-high molecular weight.

[0134] <Examples and Comparative Examples - Preparation of Grease Compositions>

[0135] First, using the lignocellulose and lignin neutralized with calcium hydroxide of Preparation Example 1 above, the grease composition of the example according to the composition of Table 4 below and the grease composition of the comparative example according to the composition of Table 5 were prepared.

[0136] Examples 1 to 4 represent grease compositions containing 5 wt%, 10 wt%, and 20 wt% of ultra-high molecular weight cross-linked lignocellulose prepared in Preparation Example 1, respectively, and Examples 5 and 6 represent grease compositions containing 5 wt% of ultra-high molecular weight cross-linked lignin, Comparative Example 1 uses a basic grease composition without any additive containing ultra-high molecular weight lignin or lignocellulose, and Comparative Examples 2 and 3 each prepare grease resin compositions containing 5 wt% of PTFE and low molecular weight commercial lignin (West Fraser, Amaline HPH, Mw 5,000 - 8,000 Da) in the basic grease composition.

[0137] In addition, grease compositions of Examples 7 to 10 according to the composition of Table 4 below were prepared using lignocellulose and lignin neutralized with sodium hydroxide instead of calcium hydroxide in Preparation Example 1 above.

[0138] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Lubricating base oil (PAO) (%) 76767264767672727272 Lithium simple soap thickener (%) 19191816191918181818 CaSO4 neutralized lignocellulose content (wt%) Average particle size 22.1㎛5 Average particle size 2.4㎛5 1020 CaSO4 neutralized lignin content (wt%) Average particle size 18.9㎛5 Average particle size 5.2㎛5 NaOH neutralized lignocellulose content Average particle size 20.1㎛10 Average particle size 3.1㎛10 NaOH neutralized lignin content Average particle size 17.9㎛10 Average particle size 4.8㎛10

[0139] Comparative Example 1 Comparative Example 2 Comparative Example 3 Lubricating base oil (PAO) (wt%) 80 76 76 Lithium simple soap Thickener (wt%) 20 19 19 PTFE content (wt%) 0 50 Mw 5 X 10 3 ~ 8 X 10 3 Dalignin * Content (wt%) 005

[0140] <Experimental Example 1: Evaluation of Physical Properties of Grease> Grease was prepared using the grease compositions prepared according to the above examples and comparative examples, and its basic physical properties and performance were measured through the method described below. The results are shown in Table 6 and Figures 7 to 9 below.

[0141] 1) Unworked penetration test

[0142] A viscosity test was conducted to measure the hardness of the grease. The non-miscible viscosity test was performed according to the ASTM D217 method. After filling the test container with grease according to the prescribed method, a specified cone was dropped free-falling onto the grease surface for 5 seconds at a test temperature of 25 ± 0.5 ℃ without mixing, and the depth to which the cone penetrated the grease was measured. A smaller measured depth value indicates better sealing performance and splash prevention, but lower penetration, which may result in inadequate supply to the lubrication point.

[0143] 2) Dripping point test

[0144] A dropping point test was conducted to compare the heat resistance of the grease. The dropping point test was performed according to the method of ASTM D566-02. Grease was filled into a dropping point test cup according to the prescribed method and placed in a prescribed test tube. Subsequently, the test tube was placed in a dropping point tester capable of heating with a water bath, and the water bath liquid was heated slowly while stirring. As the temperature rose, the temperature was measured at the moment when the base oil of the grease separated from the dropping point test cup and a single drop fell. The higher the measured dropping point, the better the heat resistance.

[0145] 3) Sand dune extreme pressure test (extreme pressure properties test)

[0146] A four-ball extreme pressure test was conducted to measure load-carrying performance. The test method was performed in accordance with ASTM D 2596. The extreme pressure test evaluates the ability of grease to withstand high loads; three balls are fixed to the bottom of the testing machine, and test grease is applied to cover the three balls. After application, one ball is fixed to the rotating shaft at the top and rotated over the three balls while the load is gradually increased. The lowest load at which fusion occurs between the single rotating ball and the three fixed balls is measured; this load is referred to as the fusion load or extreme pressure, and this value is recorded as the load-carrying performance in kgf units. The extreme pressure test conditions were a rotation speed of 1770 ± 60 revolutions / min and a test temperature of 27 ± 8 ℃. A higher result indicates superior load-carrying performance.

[0147] 4) Wear preventive characteristics test

[0148] A ball wear test was conducted to measure wear resistance performance. The test method was performed in accordance with ASTM D 2266. The wear test evaluates the ability of grease to reduce wear on a component; three balls are fixed to the bottom of the testing machine, and test grease is applied to cover all three balls. After application, one ball is fixed to the rotating shaft at the top and rotated over the three balls under specific conditions. After the test is completed, the wear marks on the three balls at the bottom of the machine are measured, and the average value is recorded as the wear resistance performance in mm. The wear resistance test conditions are a rotation speed of 1200 ± 50 revolutions / min, a test temperature of 75 ± 1.7 ℃, a load of 40 kgf, and an experiment time of 60 ± 1 minute. A lower result indicates superior wear resistance performance.

[0149] 5) SRV test (Linear oscillation test)

[0150] To measure the coefficient of friction, an SRV test was conducted using a high-frequency linear vibration tester. The test method was carried out according to ASTM D 5707. The test conditions were a frequency of 50 Hz, a stroke of 1.0 mm, a load of 200 N, a temperature of 80 ℃, and a test time of 60 minutes. After the test, the coefficient of friction was measured and the average value was calculated.

[0151] Unit Test Method Comparison Example 1 Comparison Example 2 Comparison Example 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Immiscibility Material 0.1 mm ASTM D 217 280 285 280 282 289 285 282 285 286 265 270 265 270 Dropping Point ℃ ASTM D 56 6 204 207 186 203 206 202 19 2205 204 185 178 190 188 Dungeon Abrasion (Abrasion Resistance) mm ASTM D 226 6 1.23 0.66 0.98 0.63 0.67 0.63 0.51 0.63 0.62 0.72 0.66 0.69 0.72 Dungeon Extreme Pressure (Load Capacity) kgf ASTM D2596120245137160265315650155260240255225230SRV Friction Coefficient ASTM D57070.1740.1490.1710.1490.1350.1240.1230.1500.1340.1490.1360.1350.129

[0152] It can be confirmed that the grease composition of Example 1, containing ultra-high molecular weight cross-linked lignocellulose and ultra-high molecular weight cross-linked lignin prepared in Preparation Example 1, exhibits lubrication characteristics equivalent to those of Comparative Example 2, which contains commercial PTFE additives, and appears to be capable of replacing the existing additive, PTFE. Furthermore, when comparing Examples 1 and 2 containing ultra-high molecular weight cross-linked lignocellulose, and Examples 5 and 6 containing ultra-high molecular weight cross-linked lignin, respectively, it can be seen that load-carrying characteristics improve as the particle size decreases, and when comparing Examples 2 and 6 with Comparative Example 2, it can be seen that they have superior load-carrying characteristics compared to grease containing PTFE.

[0153] In addition, the grease compositions of Example 1, containing ultra-high molecular weight cross-linked lignocellulose, and Example 5, containing ultra-high molecular weight cross-linked lignin, were found to have higher lubricating properties compared to Comparative Example 3, containing low molecular weight lignin, and Examples 2 and 5, containing ultra-high molecular weight cross-linked lignocellulose and ultra-high molecular weight cross-linked lignin with smaller particle sizes, respectively, were found to have significantly improved lubricating properties.

[0154] In addition, when examining the physical properties of the grease compositions of Examples 2 to 4 regarding the effect of the content of ultra-high molecular weight cross-linked lignocellulose with smaller particle size, it was confirmed that the lubricating properties improved as the content of these increased.

[0155] In addition, in the case of lignocellulose and lignin (Examples 7 to 10) prepared by neutralization with sodium hydroxide and washing with water and not containing CaSO4, lubrication characteristics at a level capable of replacing PTFE were confirmed when compared to Comparative Example 2 containing CaSO4, but when compared to Example 3 containing CaSO4, the results of the evaluation of ballast wear, ballast extreme pressure, and SVR were observed to be lower overall, confirming that CaSO4 can further improve lubrication characteristics.

[0156] From the foregoing description, those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. In this regard, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention should be interpreted as including all modifications or variations derived from the meaning and scope of the claims set forth below and their equivalents, rather than from the detailed description above.

Claims

1. A method for preparing a grease composition comprising cross-linked lignocellulose, wherein (a) a step of obtaining cross-linked lignocellulose by adding an acid to lignocellulosic biomass to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, and simultaneously inducing cross-linking between lignin components or between lignin and cellulose components; (b) a step of adding a base to the cross-linked lignocellulose obtained from step (a) above to neutralize the remaining acid, and then removing water-soluble substances from the neutralized product to obtain solid particles containing cross-linked lignocellulose; (c) a step of grinding the solid particles obtained from step (b) above; and (d) a step of mixing the crushed solid particles obtained from step (c) above with a lubricating base oil for grease; comprising, The number average molecular weight of the cross-linked lignocellulose in the solid particles obtained from step (c) above is 5 x 10 4 Up to 5 x 10 24 A method for preparing a grease composition characterized by g / mol.

2. A method for preparing a grease composition containing cross-linked lignin, wherein (a) a step of obtaining cross-linked lignin by adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, and simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass; (b) a step of adding a base to the cross-linked lignin obtained from step (a) above to neutralize residual acidic components, and then removing water-soluble substances or substances soluble in organic solvents from the neutralized product to obtain solid particles containing cross-linked lignin; (c) a step of grinding the solid particles obtained from step (b) above; and (d) a step of mixing the crushed solid particles obtained from step (c) above with a lubricating base oil for grease; comprising, The number average molecular weight of the cross-linked lignin in the solid particles obtained from step (c) above is 5 x 10 4 Up to 5 x 10 24 A method for preparing a grease composition characterized by g / mol.

3. In Paragraph 1 or 2, A method for preparing a grease composition, characterized in that step (a) above is performed by adding a solvent containing an acid to lignocellulosic biomass or low molecular weight lignin and heating and / or pressurizing it at a temperature of 50 to 300 ℃, or (a2) adding a cellulose degrading enzyme and a hemicellulose degrading enzyme; and a cellulose crosslinking enzyme and a hemicellulose crosslinking enzyme; to hydrolyze and crosslink at least a portion of the cellulose and hemicellulose, or (a3) ​​adding a solvent containing an acid and steam explosion at a temperature of 50 to 300 ℃, or (a4) through a process mixed with the processes according to (a1) to (a3).

4. In Paragraph 1 or 2, A method for preparing a grease composition, characterized in that the particle size distribution of the crushed solid particles obtained from step (c) above is 0.05 to 100 μm.

5. In Paragraph 1 or 2, A method for preparing a grease composition, characterized in that the acid in step (a) above is selected from an organic acid having 1 to 20 carbon atoms; an inorganic acid selected from sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, or a mixture thereof; a mixture of the organic acid and the inorganic acid; or a mixture of the organic acid and the mixture of inorganic acids.

6. In Paragraph 5, The above acid is an aqueous solution selected from hydrochloric acid, sulfuric acid, and nitric acid, or a mixture thereof. A method for preparing a grease composition characterized by using the concentration of the acid in a range of 0.5 to 70 wt% based on the total content of biomass and an aqueous solution containing the acid.

7. In Paragraph 1 or 2, A method for preparing a grease composition, characterized in that, as the base used in step (b) above, one base selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), and sodium bicarbonate (NaHCO3), or a mixture of two or more of the above bases, or an aqueous solution of the one base or an aqueous solution of a mixture of two or more of the above bases.

8. In Paragraph 7, A method for preparing a grease composition characterized by using, as the base used in step (b) above, calcium hydroxide (Ca(OH)2) or, calcium hydroxide (Ca(OH)2); and a mixture with one or more bases selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium hydroxide (LiOH), calcium carbonate (CaCO3), potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium bicarbonate (KHCO3), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO) and sodium bicarbonate (NaHCO3).

9. A grease composition manufactured from the manufacturing method of any one of claims 1 to 8.

10. Lubricating base oil; and, A grease composition comprising one or more of: cross-linked lignocellulose powder having a carbohydrate content of 1 to 60 wt%; and cross-linked lignin powder having a carbohydrate content of 0.01 to 1 wt%, wherein The number average molecular weight of each of the above-mentioned cross-linked lignocellulose powder; and cross-linked lignin powder; is 5 x 10 4 Up to 5 x 10 24 Grease composition characterized by being in the range of g / mol 11. In Paragraph 10, The grease composition is characterized by additionally including a thickener.

12. In Paragraph 10, The grease composition comprises, based on the content of the total grease composition, 55 to 90 wt% of a lubricating base oil; 0.01 to 40 wt% of one or more components selected from cross-linked lignocellulose powder with a carbohydrate content of 1 to 60 wt% and cross-linked lignin powder with a carbohydrate content of 0.01 to 1 wt%; and 0.01 to 40 wt% of a thickener.

13. In Paragraph 10, The cross-linked lignocellulose powder in the above grease composition is (a) a step of obtaining cross-linked lignocellulose by adding an acid to lignocellulosic biomass to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, and simultaneously inducing cross-linking between lignin components or between lignin and cellulose components; (b) a step of adding a base to the cross-linked lignocellulose obtained from step (a) above to neutralize the residual acid, and then removing a water-soluble substance from the neutralized product to obtain solid particles containing cross-linked lignocellulose; and (c) a step of grinding solid particles obtained from step (b) above; a grease composition characterized by being manufactured by a manufacturing method comprising: (c) a step of grinding solid particles obtained from step (b) above.

14. In Paragraph 10, The cross-linked lignin powder in the above grease composition is (a) a step of obtaining cross-linked lignin by adding an acid to lignocellulosic biomass or low molecular weight lignin to hydrolyze at least some of the hemicellulose and / or cellulose in the lignocellulosic biomass, and simultaneously inducing cross-linking between lignin components or between low molecular weight lignin components in the lignocellulosic biomass; (b) a step of adding a base to the cross-linked lignin obtained from step (a) above to neutralize residual acidic components, and then removing water-soluble substances or substances soluble in organic solvents from the neutralized product to obtain solid particles containing cross-linked lignin; and (c) a step of grinding solid particles obtained from step (b) above; a grease composition characterized by being manufactured by a manufacturing method comprising: (c) a step of grinding solid particles obtained from step (b) above.

15. In Paragraph 10, The grease composition is characterized by including calcium sulfate (CaSO4).

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