A cellulose-inorganic material composite and its preparation method

Abstract

The present invention belongs to the technical field of cellulose composite materials, and provides a cellulose-inorganic material composite, a preparation method thereof, and an application thereof. In the present invention, the mass percentage content of the inorganic material is controlled to be 8.3-28.4%, which maximally avoids the agglomeration caused by excessive doping amount of the inorganic material and ensures the dispersibility of the inorganic material. At the same time, lignin is introduced into the composite material in the present invention. Lignin has the following advantages: First, lignin can improve the dispersion stability of the inorganic material; Second, lignin can act as an interfacial cross-linking agent to mediate the assembly of the inorganic material and the cellulose molecular chain, improve the dispersibility of the inorganic material, enhance the activity of the cellulose molecular chain, and improve the mechanical properties of the cellulose composite material; Third, lignin can be inserted between the molecular chains of cellulose, which can reduce the formation of a rich hydrogen bond network between the cellulose molecular chains, improve the activity of the molecular chains, and improve the toughness of the final cellulose composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of cellulose composite materials, and particularly relates to a cellulose-inorganic material composite and a preparation method thereof. Background Art

[0002] Cellulose is the most abundant natural polymer material on the earth, an inexhaustible and renewable biomass resource, and has the advantages of wide sources (in natural plant biomass such as trees, bamboos, straws, etc.), low price, renewable, degradable, and derivatizable. Cellulose film is also called cellophane industrially and is widely used in the fields of food packaging, water treatment, and biomedicine.

[0003] However, cellulose film materials have deficiencies such as brittleness, limited strength, and single function, which limit their application scope. Combining cellulose with inorganic materials to prepare composite materials can not only retain the biological material properties of cellulose itself, but also endow it with functions such as antibacterial property, electrical conductivity, heat insulation property, battery shielding, and photothermal conversion performance, greatly expanding the application of cellulose in the fields of optoelectronics, thermal management, water treatment, and biomedicine.

[0004] There are many methods for compounding cellulose and inorganic materials, such as chemical vapor deposition method, biomimetic mineralization method, blending method, etc. These methods have their own characteristics. The chemical vapor deposition method can deposit a coating quickly, and the coating thickness is controllable, but the chemical vapor deposition method has high requirements for equipment and reaction conditions, and only forms a coating on the surface, and the cost is also high. The biomimetic mineralization method can form a relatively uniform inorganic material on the surface of cellulose porous materials, but the efficiency of biomimetic mineralization is extremely low. Comparatively speaking, the blending method is the most economical and efficient method, and the amount of inorganic materials can reach a relatively high proportion.

[0005] However, there is a key problem in the process of blending inorganic materials and cellulose, that is, the poor dispersibility of inorganic materials, resulting in a low content of inorganic materials in the cellulose composite material, and the aggregation of inorganic materials has a great impact on the performance of the composite material. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a cellulose-inorganic material composite and a preparation method thereof. The cellulose-inorganic material composite provided by the present invention has a high content of inorganic materials, and the obtained cellulose-inorganic material composite has high toughness and strength.

[0007] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a cellulose-inorganic material composite, comprising the following components in mass percentage:

[0009] Cellulose: 66.7 - 90.1%, lignin: 0.66 - 8.3%, inorganic material: 8.3 - 28.4%.

[0010] Preferably, the inorganic material includes one or more of MXene, graphene, carbon nanotubes, molybdenum disulfide, calcium hydrogen phosphate, and boron nitride.

[0011] Preferably, the cellulose-inorganic material composite is in the form of a film.

[0012] The present invention also provides a method for preparing the cellulose-inorganic material composite according to the above technical solution, comprising the following steps:

[0013] Mix an inorganic base, urea, and water to obtain a cellulose solvent;

[0014] Mix cellulose and the cellulose solvent to obtain a cellulose solution;

[0015] Mix lignin, the inorganic material, and the cellulose solvent to obtain a lignin-inorganic material dispersion;

[0016] Mix the cellulose solution and the lignin-inorganic material dispersion, and successively perform film formation and drying to obtain the cellulose-inorganic material composite.

[0017] Preferably, the mass ratio of the inorganic base, urea, and water is 12 - 20:4 - 7:76 - 81.

[0018] Preferably, the mass concentration of the cellulose solution is 5 - 6%.

[0019] Preferably, the mass concentration of lignin in the lignin-inorganic material dispersion is 5 - 9.09%, and the mass concentration of the inorganic material is 9.09 - 50%.

[0020] Preferably, in the system obtained by mixing the cellulose solution and the lignin-inorganic material dispersion, the mass concentration of cellulose is 4.67 - 5.94%, the mass concentration of lignin is 0.048 - 0.48%, and the mass concentration of the inorganic material is 0.47 - 1.95%.

[0021] Preferably, the film formation method includes a casting method or a continuous wet film formation method.

[0022] The present invention provides a cellulose-inorganic material composite, comprising components in the following mass percentages: 66.7-90.1% of cellulose, 0.66-8.3% of lignin, and 8.3-28.4% of inorganic material. In the cellulose-inorganic material composite of the present invention, the mass percentage of the inorganic material is controlled to be 8.3-28.4%, which maximally avoids the agglomeration caused by excessive dosage of the inorganic material and ensures the dispersibility of the inorganic material. Meanwhile, lignin is added to the cellulose-inorganic material composite of the present invention. Lignin has the following advantages: First, lignin can improve the dispersion stability of the inorganic material; Second, lignin can act as an interfacial crosslinking agent to mediate the assembly of the inorganic material and the cellulose molecular chain, improve the dispersibility of the inorganic material, enhance the activity of the cellulose molecular chain, and improve the mechanical properties of the cellulose composite; Third, lignin can insert between the molecular chains of cellulose, reduce the formation of a rich hydrogen bond network between the cellulose molecular chains, improve the activity of the molecular chains, and improve the toughness of the final cellulose composite.

[0023] The present invention also provides a preparation method of the cellulose-inorganic material composite described in the above technical solution. The preparation method provided by the present invention is simple in operation and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 SEM photographs of the cross-section of the freeze-dried cellulose / boron nitride composite hydrogel film obtained in (6) of Example 1 (a) and Example 2 (b);

[0025] Figure 2 Tensile mechanical property diagrams of the hydrogel films obtained in (6) of Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention provides a cellulose-inorganic material composite, comprising components in the following mass percentages:

[0027] 66.7-90.1% of cellulose, 0.66-8.3% of lignin, and 8.3-28.4% of inorganic material.

[0028] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0029] The cellulose-inorganic material composite provided by the present invention comprises 66.7-90.1% of cellulose by mass percentage, preferably 70-85%, and more preferably 75-80%.

[0030] The cellulose-inorganic material composite provided by the present invention comprises 0.66-8.3% of lignin by mass percentage, preferably 1-7%, and more preferably 4-6%.

[0031] The cellulose-inorganic material composite provided by the present invention comprises an inorganic material in a mass percentage of 8.3 to 28.4%, preferably 10 to 25%, and more preferably 15 to 20%. In the present invention, the inorganic material preferably comprises one or more of MXene, graphene, carbon nanotubes, molybdenum disulfide, calcium hydrogen phosphate, and boron nitride.

[0032] In the present invention, the cellulose-inorganic material composite is preferably in the form of a film.

[0033] The present invention also provides a method for preparing the cellulose-inorganic material composite described in the above technical solution, comprising the following steps:

[0034] Mix an inorganic base, urea, and water to obtain a cellulose solvent;

[0035] Mix cellulose and the cellulose solvent to obtain a cellulose solution;

[0036] Mix lignin, an inorganic material, and the cellulose solvent to obtain a lignin-inorganic material dispersion;

[0037] Mix the cellulose solution and the lignin-inorganic material dispersion, and successively perform film formation and drying to obtain the cellulose-inorganic material composite.

[0038] In the present invention, an inorganic base, urea, and water are mixed to obtain a cellulose solvent.

[0039] In the present invention, the inorganic base preferably comprises sodium hydroxide and / or potassium hydroxide. In the present invention, the mass ratio of the inorganic base, urea, and water is preferably 12 to 20: 4 to 7: 76 to 81, and more preferably 12: 7: 81 or 20: 4: 76. In the present invention, the temperature of the mixing is preferably 0 to -20°C. In the present invention, the storage temperature of the cellulose solvent is preferably 0 to -20°C.

[0040] After obtaining the cellulose solvent, in the present invention, cellulose and the cellulose solvent are mixed to obtain a cellulose solution.

[0041] In the present invention, the mixing method is preferably stirring. The present invention does not specifically limit the rotation speed and time of the stirring, as long as the cellulose can be dissolved in the cellulose solvent. After the cellulose and the cellulose solvent are mixed, the present invention preferably further includes filtration. In the present invention, the mass concentration of the cellulose solution is preferably 5 to 6%.

[0042] After obtaining the cellulose solvent, lignin, an inorganic material, and the cellulose solvent are mixed to obtain a lignin-inorganic material dispersion.

[0043] In the present invention, the particle size of the lignin is preferably 1 to 100 μm. In the present invention, the inorganic material is preferably a two-dimensional inorganic material, more preferably a flaky two-dimensional inorganic material; the size of the flaky two-dimensional inorganic material is preferably 10 nm to 100 μm, more preferably 10 nm to 1000 nm; the thickness is preferably 0 to 10 nm, more preferably 1 to 10 nm, and even more preferably 4 to 5 nm. In the present invention, the mixing of the lignin, the inorganic material and the cellulose solvent preferably includes: mixing the lignin and the cellulose solvent to obtain a lignin dispersion; mixing the lignin dispersion and the inorganic material. In the present invention, the mass concentration of lignin in the lignin-inorganic material dispersion is preferably 5 to 9.09%, and the mass concentration of the inorganic material is preferably 9.09 to 50%.

[0044] After obtaining the cellulose solution and the lignin-inorganic material dispersion, the present invention mixes the cellulose solution and the lignin-inorganic material dispersion, and successively performs film formation and drying to obtain the cellulose-inorganic material composite.

[0045] In the present invention, the temperature for mixing the cellulose solution and the lignin-inorganic material dispersion is preferably 0 to -20°C. In the present invention, the mixing of the cellulose solution and the lignin-inorganic material dispersion preferably includes: adding the cellulose solution to the lignin-inorganic material dispersion. In the present invention, the mixing is preferably carried out under stirring conditions, and the present invention does not specifically limit the rotation speed of the stirring, as long as the substances can be fully mixed.

[0046] After mixing the cellulose solution and the lignin-inorganic material dispersion, the present invention preferably further includes a defoaming treatment, and the defoaming treatment method is preferably filtration defoaming, centrifugal defoaming or centrifugation. In the present invention, the filtration defoaming preferably includes filtration and defoaming in sequence; the pore size of the filter element for filtration is preferably 5 to 20 μm; the defoaming is preferably vacuum defoaming or static defoaming; the time for vacuum defoaming is preferably 4 to 6 h, and the time for static defoaming is preferably 12 to 24 h. In the present invention, the centrifugal defoaming preferably includes centrifugation and defoaming in sequence; the rotation speed of the centrifugation is preferably 100 rpm, and the time is preferably 30 min; the defoaming is preferably vacuum defoaming or static defoaming; the time for vacuum defoaming is preferably 4 to 6 h, and the time for static defoaming is preferably 12 to 24 h. In the present invention, the rotation speed of the centrifugation is preferably 1000 rpm, and the time is preferably 30 min.

[0047] In the present invention, in the system obtained by mixing the cellulose solution and the lignin-inorganic material dispersion, the mass concentration of cellulose is preferably 4.67-5.94%, the mass concentration of lignin is preferably 0.048-0.48%, and the mass concentration of the inorganic material is preferably 0.47-1.95%.

[0048] In the present invention, the film-forming method preferably includes a casting method or a continuous wet film-forming method. In the present invention, the casting method preferably includes: regenerating a film from the system obtained by mixing the cellulose solution and the lignin-inorganic material dispersion in a coagulation bath by the casting method. In the present invention, the continuous wet film-forming method preferably includes: extruding the system obtained by mixing the cellulose solution and the lignin-inorganic material dispersion through a slit extrusion device and continuously forming a wet film in a coagulation bath. In the present invention, the coagulation bath in the casting method and the coagulation bath in the continuous wet film-forming method are independently preferably an organic solvent, an acid or a salt; the organic solvent is preferably an ethanol aqueous solution with a volume concentration of 60%; the acid is preferably sulfuric acid with a mass concentration of 10%, and the salt is preferably sodium citrate with a mass concentration of 10%.

[0049] In the present invention, the casting method can obtain an isotropic hydrogel film; the isotropic hydrogel film means that the cellulose molecular chains form a uniform network and the inorganic materials are randomly distributed inside the film. In the present invention, the continuous wet film-forming method can obtain an anisotropic hydrogel film; the anisotropic hydrogel film means that the cellulose molecular chains are oriented along the extrusion direction, and the inorganic materials, such as two-dimensional sheet materials, are arranged along the extrusion plane.

[0050] After film formation, the present invention preferably further includes washing, and the washing reagent is preferably water. The present invention does not specifically limit the amount of the washing reagent and the number of washing times, as long as the alkali and salt can be washed clean.

[0051] The present invention does not specifically limit the drying parameters, as long as the excess solvent can be removed cleanly.

[0052] The following examples are used to illustrate in detail the cellulose-inorganic material composite and its preparation method provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0053] Example 1

[0054] (1) Mix sodium hydroxide, urea and water according to a mass ratio of 12:7:81 and pre-cool at -12°C to obtain a cellulose solvent.

[0055] (2) Add 5.31 g of cellulose to 100 g of the cellulose solvent in (1), stir to dissolve and filter to obtain a cellulose solution of about 5 wt%.

[0056] (3) 0.531 g of lignin (particle size ~50 μm) was added to 4.779 g of the (1) cellulose solvent and dissolved thoroughly; then 2.124 g of boron nitride nanosheets (size 100 - 300 nm, thickness ~5 nm) was added to obtain a lignin - boron nitride dispersion.

[0057] (4) The cellulose solution in (2) was added to the (3) lignin - boron nitride dispersion and stirred evenly, where the stirring temperature was 0 °C.

[0058] (5) The composite solution obtained in (4) was centrifuged at 1000 rpm for 30 min.

[0059] (6) The defoamed solution in (5) was regenerated into a film by the casting method in a 60% ethanol (volume concentration) coagulation bath, and finally washed clean to obtain an isotropic cellulose / boron nitride composite hydrogel film. The mass content of cellulose was about 4.5%, the mass content of lignin was 0.45%, and the mass content of boron nitride was 1.8%.

[0060] (7) The hydrogel film in (6) was dried to form an isotropic cellulose composite film with a mass ratio of cellulose : lignin : boron nitride = 10 : 1 : 4.

[0061] The tensile mechanical properties of the cellulose / boron nitride composite hydrogel film obtained in step (6) were tested by the plastic film tensile property test method, and the results were as follows: the tensile strength of the obtained cellulose / boron nitride composite hydrogel film was 1.32 MPa.

[0062] The cellulose / boron nitride composite hydrogel film obtained in (6) was freeze - dried, and then the cross - section of the obtained freeze - dried cellulose / boron nitride composite hydrogel film was observed by scanning electron microscope SEM. The results were as Figure 1 shown in (a) of Figure 1 From (a) of

[0063] Example 2

[0064] (1) Sodium hydroxide, urea, and water were mixed at a mass ratio of 12 : 7 : 81 and pre - cooled at - 12 °C to obtain a cellulose solvent.

[0065] (2) 5.31 g of cellulose was added to 100 g of the (1) cellulose solvent, stirred and dissolved, and then filtered to obtain a ~5 wt% cellulose solution.

[0066] (3) Add 0.531 g of lignin (particle size ~50 μm) to 4.779 g of the (1) cellulose solvent and dissolve it thoroughly; then add 2.124 g of boron nitride nanosheet material (size 100 - 300 nm, thickness ~5 nm) to obtain a lignin-boron nitride dispersion.

[0067] (4) Add the cellulose solution in (2) to the (3) lignin-boron nitride dispersion and stir well. The stirring temperature is 0 °C.

[0068] (5) Filter the composite solution obtained in (4) through a 5-μm filter element to remove the aggregated inorganic materials, and then perform vacuum degassing for 6 h or static degassing for 24 h.

[0069] (6) Extrude the degassed solution in (5) through a 200-μm slit and continuously form a film in a 10% sulfuric acid coagulation bath. Finally, wash it clean with water to obtain an anisotropic cellulose / boron nitride composite hydrogel film. The mass content of cellulose is about 4.5%, the mass content of lignin is 0.45%, and the mass content of boron nitride is 1.8%.

[0070] (7) Dry the hydrogel film in (6) to form an anisotropic cellulose composite film with a mass ratio of cellulose:lignin:boron nitride = 10:1:4.

[0071] Use the plastic film tensile property test method to test the tensile mechanical properties of the cellulose / boron nitride composite hydrogel film obtained in step (6). The result is that the tensile strength of the obtained cellulose / boron nitride composite hydrogel film is 2.33 MPa.

[0072] Freeze-dry the cellulose / boron nitride composite hydrogel film obtained in (6), and then observe the cross-section of the obtained freeze-dried cellulose / boron nitride composite hydrogel film by scanning electron microscope SEM. The result is as Figure 1 shown in (b) of Figure 1 From (b) of

[0073] Example 3

[0074] (1) Mix potassium hydroxide, urea, and water in a mass ratio of 20:4:76 and pre-cool at -12 °C to obtain a cellulose solvent.

[0075] (2) Add 5.31 g of cellulose to 100 g of the (1) cellulose solvent, stir to dissolve and filter to obtain a ~5 wt% cellulose solution.

[0076] (3) Add 0.531 g of lignin (particle size ~50 μm) to 4.779 g of the (1) fiber solvent and dissolve it thoroughly; then add 1.062 g of MXene nanosheets (size 300 - 3000 nm, thickness ~4 nm) to obtain a lignin-MXene dispersion.

[0077] (4) Add the cellulose solution in (2) to the (3) lignin-MXene dispersion and stir well. The stirring temperature is 20 °C.

[0078] (5) Filter the composite solution obtained in (4) through a 20-μm filter element to remove the aggregated inorganic materials, then perform vacuum degassing for 4 h and static degassing for 12 h.

[0079] (6) Extrude the degassed solution in (5) through a 200-μm slit and regenerate the film in a 10% aqueous sodium citrate solution (mass concentration) coagulation bath, and finally wash it clean to obtain an isotropic cellulose / MXene composite hydrogel film. The mass content of cellulose is about 4.5%, the mass content of lignin is 0.45%, and the mass content of MXene is 0.9%.

[0080] (7) Dry the hydrogel film in (6) to form an isotropic cellulose composite film with a mass ratio of cellulose:lignin:MXene = 10:1:2.

[0081] The tensile mechanical properties of the cellulose / MXene composite hydrogel film obtained in step (6) were tested using the plastic film tensile property test method. The results were as follows: the tensile strength of the obtained cellulose / MXene composite hydrogel film was 2.23 MPa.

[0082] Example 4

[0083] (1) Mix potassium hydroxide, urea, and water in a mass ratio of 20:4:76 and pre-cool at -12 °C to obtain a cellulose solvent.

[0084] (2) Add 6.39 g of cellulose to 100 g of the (1) cellulose solvent, stir to dissolve and filter to obtain a ~6 wt% cellulose solution.

[0085] (3) Add 0.383 g of lignin (particle size ~50 μm) to 3.447 g of the (1) cellulose solvent and dissolve it thoroughly; then add 1.917 g of calcium hydrogen phosphate microplates (size 10 - 100 μm, thickness ~5 nm) to obtain a lignin-calcium hydrogen phosphate dispersion.

[0086] (4) Add the cellulose solution in (2) to the (3) lignin-calcium hydrogen phosphate dispersion and stir well. The stirring temperature is 0 °C.

[0087] (5) Centrifuge the composite solution obtained in (4) at 100 rpm for 30 min; perform vacuum degassing for 4 h and static degassing for 12 h.

[0088] (6) Cast the degassed solution in (5) into a film by the casting method in a 10% sodium citrate aqueous solution (mass concentration) coagulation bath, and finally wash it with water to obtain an isotropic cellulose / calcium hydrogen phosphate composite hydrogel film. The mass content of cellulose is about 5.8%, the mass content of lignin is 0.29%, and the mass content of calcium hydrogen phosphate is 1.74%.

[0089] (7) Dry the hydrogel film in (6) to form an isotropic cellulose composite film, with the mass ratio of cellulose: lignin: calcium hydrogen phosphate = 20:1:6.

[0090] Use the plastic film tensile property test method to test the tensile mechanical properties of the cellulose / calcium hydrogen phosphate composite hydrogel film obtained in step (6). The results are as follows: the tensile strength of the obtained cellulose / calcium hydrogen phosphate composite hydrogel film is 1.80 MPa.

[0091] Comparative Example 1

[0092] (1) Mix potassium hydroxide, urea, and water in a mass ratio of 20:4:76, and pre-cool at -12 °C to obtain a cellulose solvent.

[0093] (2) Add 6.39 g of cellulose to 100 g of the cellulose solvent in (1), stir to dissolve and filter to obtain a cellulose solution of about 6 wt%.

[0094] (3) Add 1.917 g of calcium hydrogen phosphate microplates (size 10 - 100 μm, thickness ~ 5 nm) to 3.447 g of the cellulose solvent in (1) to obtain a calcium hydrogen phosphate dispersion.

[0095] (4) Add the cellulose solution in (2) to the calcium hydrogen phosphate dispersion in (3), and stir well. The stirring temperature is 0 °C.

[0096] (5) In the composite solution obtained in (4), calcium hydrogen phosphate is prone to aggregation and sedimentation. Obvious precipitation occurs after centrifuging at 100 rpm for 30 min, or the filtration efficiency of 100 μm is very poor, and the aggregates clog the filter element.

[0097] (6) Cast the degassed solution in (5) into a film by the casting method in a 10% sodium citrate coagulation bath, and finally wash it with water to obtain an isotropic cellulose / calcium hydrogen phosphate composite hydrogel film. The mass content of cellulose is about 5.8%, the mass content of lignin is 0.29%, and the mass content of calcium hydrogen phosphate is 1.74%.

[0098] (7) Dry the hydrogel film in (6) to form an isotropic cellulose composite film, with a mass ratio of cellulose: lignin: calcium hydrogen phosphate = 20:1:6.

[0099] Use the plastic film tensile property test method to conduct a tensile mechanical property test on the cellulose / calcium hydrogen phosphate composite hydrogel film obtained in step (6). The results are as follows: the tensile strength of the obtained cellulose / calcium hydrogen phosphate composite hydrogel film is 0.98 MPa.

[0100] Comparative Example 2

[0101] (1) Mix sodium hydroxide, urea, and water according to a mass ratio of 12:7:81, and pre-cool at -12°C to obtain a cellulose solvent.

[0102] (2) Add 5.31 g of cellulose to 100 g of the cellulose solvent in (1), stir to dissolve and filter to obtain a cellulose solution of about 5 wt%.

[0103] (3) Add 0.531 g of lignin (particle size of ~50 μm) to 4.779 g of the cellulose solvent in (1), and dissolve it fully; then add 3.786 g of boron nitride nanosheets (size of 100 - 300 nm, thickness of ~5 nm) to obtain a lignin-boron nitride dispersion.

[0104] (4) Add the cellulose solution in (2) to the lignin-boron nitride dispersion in (3), and stir evenly. Among them, the stirring temperature is 0°C.

[0105] (5) Centrifuge the composite solution obtained in (4) at 1000 rpm for 30 min, and obvious boron nitride precipitation appears, indicating that the content of boron nitride should not be too high.

[0106] Figure 2 It is the tensile mechanical property diagram of the hydrogel films obtained in (6) of Examples 1 - 4 and Comparative Example 1. From Figure 2 It can be seen that: the mechanical properties of the hydrogel film obtained in Comparative Example 1 without adding lignin are poor, indicating that the addition of lignin can improve the dispersion of inorganic materials and ultimately improve the performance of cellulose composites.

[0107] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A cellulose-inorganic material composite, characterized in that, it comprises components with the following mass percentages: cellulose 66.7 - 90.1%, lignin 0.66 - 8.3%, inorganic material 8.3 - 28.4%; the inorganic material is calcium hydrogen phosphate; the preparation method of the cellulose-inorganic material composite comprises the following steps: Mix an inorganic base, urea and water to obtain a cellulose solvent; Mix cellulose and the cellulose solvent to obtain a cellulose solution; Mix lignin, the inorganic material and the cellulose solvent to obtain a lignin-inorganic material dispersion; Mix the cellulose solution and the lignin-inorganic material dispersion, and successively carry out film formation and drying to obtain the cellulose-inorganic material composite; the mass ratio of the inorganic base, urea and water is 12 - 20:4 - 7:76 - 81; the inorganic base includes sodium hydroxide and / or potassium hydroxide.

2. The cellulose-inorganic material composite according to claim 1, characterized in that, the cellulose-inorganic material composite is in the form of a thin film.

3. The preparation method of the cellulose-inorganic material composite according to any one of claims 1 - 2, characterized in that, it comprises the following steps: Mix an inorganic base, urea and water to obtain a cellulose solvent; Mix cellulose and the cellulose solvent to obtain a cellulose solution; Mix lignin, the inorganic material and the cellulose solvent to obtain a lignin-inorganic material dispersion; Mix the cellulose solution and the lignin-inorganic material dispersion, and successively carry out film formation and drying to obtain the cellulose-inorganic material composite; the mass ratio of the inorganic base, urea and water is 12 - 20:4 - 7:76 - 81; the inorganic base includes sodium hydroxide and / or potassium hydroxide.

4. The preparation method according to claim 3, characterized in that, the mass concentration of the cellulose solution is 5 - 6%.

5. The preparation method according to claim 3, characterized in that, the mass concentration of lignin in the lignin-inorganic material dispersion is 5 - 9.09%, and the mass concentration of the inorganic material is 9.09 - 50%.

6. The preparation method according to claim 3, characterized in that, in the system obtained by mixing the cellulose solution and the lignin-inorganic material dispersion, the mass concentration of cellulose is 4.67 - 5.94%, the mass concentration of lignin is 0.048 - 0.48%, and the mass concentration of the inorganic material is 0.47 - 1.95%.

7. The preparation method according to claim 3, characterized in that, the film formation method includes the casting method or the continuous wet film formation method.

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