Degradable waterproof and oil-proof packaging material as well as preparation method and application thereof

Abstract

The invention discloses a degradable waterproof and oil-proof packaging material as well as a preparation method and application thereof. The method comprises the following steps: (1) coating the surface of a paper substrate with an aqueous solution of an oil-proof layer material; or soaking the paper substrate in an aqueous solution of an oil-proof layer material to obtain the paper substrate with an oil-proof layer on the surface layer; and (2) coating the surface of the oil-proof layer of the material obtained in the step (1) with a waterproof layer material dispersion liquid to obtain the packaging material. According to the invention, the oil-proof layer and the waterproof layer with the nanoscale thickness are coated on the paper base body, so that an excellent water-proof and oil-proof effect is realized, the degradability is maintained, the problems that a paper-based packaging material is not waterproof, not oil-proof and not degradable are solved, and the paper-based packaging material has important practical value.

Description

Technical Field

[0001] The invention relates to a degradable waterproof and oil-proof packaging material and a preparation method and application thereof, belonging to the technical field of functional materials and green chemicals. Background Art

[0002] Due to the environmental pollution caused by plastics, paper-based packaging materials have become the main direction of development internationally. However, paper composed of natural cellulose is not waterproof and oil-proof. For this reason, paper-based packaging materials usually need to be coated with polyolefin coatings to enhance their hydrophobicity. Polyolefin coatings are not biodegradable in the environment, resulting in a significant decrease in the degradability of the entire paper-based packaging material. To solve this problem, polylactic acid coatings are applied to paper-based packaging materials. However, polylactic acid can only be degraded under composting conditions, and degrades very slowly in the natural environment, which also affects the degradability of the entire paper-based packaging material. In addition, polyolefin coatings and polylactic acid coatings are not oil-proof because they are lipophilic, and oil can gradually penetrate through the entire packaging material. Therefore, the development of new environmentally friendly waterproof and oil-proof paper-based packaging materials has important practical value. Summary of the invention

[0003] In order to improve the above technical problems, the present invention provides a method for preparing a degradable waterproof and oil-proof packaging material, the method comprising:

[0004] (1) coating an aqueous solution of an oil-proof layer material on the surface of a paper substrate; or immersing the paper substrate in an aqueous solution of an oil-proof layer material to obtain a paper substrate having an oil-proof layer on the surface;

[0005] (2) coating the surface of the oil-proof layer of the material obtained in step (1) with a dispersion of a waterproof layer material to obtain the packaging material.

[0006] According to an embodiment of the present invention, in step (1), the paper substrate comprises natural biomass fibers, and the content of the natural biomass fibers is higher than 60 wt %;

[0007] Preferably, the natural biomass fiber is at least one of base paper, cotton fiber, wood fiber, bamboo fiber, grass fiber, hemp fiber or paper fiber.

[0008] According to an embodiment of the present invention, in step (1), the aqueous solution of the oil-proof layer material is prepared by dissolving the oil-proof layer material in water.

[0009] According to an embodiment of the present invention, in step (1), the oil-proof layer material is selected from at least one of sodium carboxymethyl cellulose, sodium carboxymethyl starch, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxyethyl starch, cellulose nanocrystals (CNC), cellulose nanofibers (CNF), hydrophilic cellulose micro-nanoparticles, starch nanocrystals (SNC), cationic starch, polyvinyl alcohol (PVA), pregelatinized starch or chitosan.

[0010] According to an embodiment of the present invention, in step (1), the concentration of the oil-proof layer material in the aqueous solution of the oil-proof layer material is 0.3-5.0 wt %, preferably 0.5-3.0 wt %.

[0011] According to an embodiment of the present invention, step (1) further comprises a post-treatment step: heating and drying the product prepared in step (1) to remove most of the water.

[0012] According to an embodiment of the present invention, in step (2), the waterproof layer material dispersion refers to dissolving the waterproof layer material in a solvent, and the solvent is selected from at least one of water, n-hexane or ethanol.

[0013] According to an embodiment of the present invention, in step (2), the waterproof layer material is selected from at least one of lignin, silica sol, silica nanoparticles, hydrophobic biowax, hydrophobic cellulose micro-nanoparticles, butyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, [3-(butylamino)propyl]trimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, octadecyltrichlorosilane, hexadecyltrichlorosilane, dodecyltrichlorosilane, trimethylchlorosilane, butyltrichlorosilane, hexyltrichlorosilane or decyltrichlorosilane.

[0014] According to an embodiment of the present invention, in step (2), the concentration of the waterproof layer material in the waterproof layer material dispersion is 0.3-8.0 wt %, preferably 0.5-5.0 wt %.

[0015] According to an embodiment of the present invention, step (2) further comprises a post-treatment step: heating and drying the product prepared in step (2).

[0016] According to the technical solution of the present invention, there is no particular limitation on the coating method, such as spraying.

[0017] According to an embodiment of the present invention, the hydrophobic biological wax is at least one of spermaceti, beeswax, wool wax, ant wax, palm wax, wood wax or flax wax.

[0018] According to an embodiment of the present invention, the hydrophilic cellulose micro-nano particles are cellulose micro-nano particles having at least one of hydroxyl, aldehyde, carboxyl or amino groups on the surface.

[0019] According to an embodiment of the present invention, the diameter of the hydrophilic cellulose micro-nano particles is 10 nm-100 μm.

[0020] According to an embodiment of the present invention, the preparation of the hydrophilic cellulose micro-nano particles adopts one of the following two methods:

[0021] The first method comprises the following steps:

[0022] (S1) dissolving cellulose in a solvent and then coagulating it with a precipitant to obtain an aqueous dispersion of cellulose micro-nanoparticles having hydroxyl groups on the surface;

[0023] (S2) mixing the aqueous dispersion of cellulose micro-nanoparticles having hydroxyl groups on the surface in step (S1) with sodium periodate to obtain hydrophilic cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface;

[0024] (S3) mixing the aqueous dispersion of cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface in step (S2) with an amine substance to obtain hydrophilic cellulose micro-nanoparticles having amino groups on the surface;

[0025] The second method comprises the following steps:

[0026] (M1) dissolving cellulose in a solvent, adding sodium periodate, and then coagulating with a precipitant to obtain an aqueous dispersion of cellulose micro-nano particles having aldehyde groups or carboxyl groups on the surface;

[0027] (M2) Mixing the aqueous dispersion of cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface in step (M1) with an amine substance to obtain hydrophilic cellulose micro-nanoparticles having amino groups on the surface.

[0028] According to an embodiment of the present invention, in step (S1) or (M1), the mass ratio of cellulose to solvent is 1:8-100.

[0029] According to an embodiment of the present invention, in step (S1) or (M1), the solvent is selected from at least one of an ionic liquid, phosphoric acid, an aqueous sodium hydroxide solution, and a mixed aqueous solution of sodium hydroxide and urea;

[0030] Wherein, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium chloride ionic liquid, 1-ethyl-3-methylimidazolium bromide ionic liquid, 1-allyl-3-methylimidazolium chloride ionic liquid (AmimCl), 1-allyl-3-methylimidazolium bromide ionic liquid, 1-butyl-3-methylimidazolium chloride ionic liquid (BmimCl), 1-butyl-3-methylimidazolium bromide ionic liquid, 1-ethyl-3-methylimidazolium acetate ionic liquid (EmimAc), 1-butyl-3-methylimidazolium acetate ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid, 3-methylimidazolium formate ionic liquid, N-methylpicolinate ionic liquid, 1-ethyl-3-methylimidazolium formate ionic liquid or 1-butyl-3-methylimidazolium formate ionic liquid.

[0031] According to an embodiment of the present invention, in step (S1) or (M1), the precipitant is selected from at least one of water, ethanol or an ionic liquid aqueous solution. The content of the precipitant is not particularly limited, so long as it can precipitate cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface. The concentration of the ionic liquid aqueous solution is 10-80wt%.

[0032] According to an embodiment of the present invention, in step (S3) or (M2), the amine substance is selected from at least one of ethylenediamine, phenylenediamine, amphenol, benzoguanamine, triethylenetetramine, tetraethylenepentamine, triethylenetetramine, pentaethylenehexamine, diethylenetriamine, dipropylenetriamine, N-(3-aminopropyl)-N-methyl-1,3-propylenediamine, 2-methyl-1,2-propylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 2-hydroxy-1.3-diaminopropane, 2,2-dimethyl-1,3-propylenediamine or polyethyleneimine.

[0033] According to an embodiment of the present invention, step (S1) further comprises a post-treatment step of centrifuging and washing the prepared product.

[0034] According to an embodiment of the present invention, step (S2) further comprises a post-treatment step of centrifuging and washing the prepared product.

[0035] According to an embodiment of the present invention, step (S3) further comprises a post-treatment step of centrifuging and washing the prepared product.

[0036] According to an embodiment of the present invention, step (M1) further comprises a post-treatment step of centrifuging and washing the prepared product.

[0037] According to an embodiment of the present invention, step (M2) further comprises a post-treatment step of centrifuging and washing the prepared product.

[0038] According to an embodiment of the present invention, the hydrophobic cellulose micro-nano particles are cellulose micro-nano particles having at least one group selected from the group consisting of polylactic acid, fatty acid ester, cinnamate, and phenylpropionate on the surface.

[0039] According to an embodiment of the present invention, the diameter of the hydrophobic cellulose micro-nano particles is 10 nm-100 μm.

[0040] According to an embodiment of the present invention, the preparation method of the hydrophobic cellulose micro-nano particles adopts one of the following two methods:

[0041] The first method comprises the following steps: mixing cellulose, a functional reagent and a catalyst in a solvent, and solidifying the prepared product in a precipitant to obtain the hydrophobic cellulose micro-nano particles;

[0042] The second method comprises the following steps: dissolving a cellulose derivative in an organic solvent and coagulating it in a precipitant to obtain hydrophobic cellulose micro-nano particles.

[0043] According to an embodiment of the present invention, the mass ratio of cellulose to solvent is 1:8-100.

[0044] According to an embodiment of the present invention, the solvent is selected from at least one of ionic liquids, phosphoric acid, sodium hydroxide aqueous solution, and a mixed aqueous solution of sodium hydroxide and urea.

[0045] According to an embodiment of the present invention, the precipitant is selected from at least one of water and ethanol. The content of the precipitant is not particularly limited, as long as it can precipitate the hydrophobic cellulose micro-nano particles.

[0046] According to an embodiment of the present invention, in the first method, the functional reagent is selected from at least one of lactide, cinnamoyl chloride, acetic anhydride, propionic anhydride, valeryl chloride, hexanoyl chloride, oleic acid, stearic acid or phenylpropionyl chloride; wherein the mass ratio of the cellulose to the reaction reagent is 1:0.5-8.

[0047] According to an embodiment of the present invention, in the first method, the catalyst is selected from at least one of 4-dimethylaminopyridine, triethylamine, dicyclohexylcarbodiimide or N,N'-carbonyldiimidazole;

[0048] According to an embodiment of the present invention, in the second method, the cellulose derivative is at least one of cellulose grafted polylactic acid, cellulose fatty acid ester, cellulose unsaturated fatty acid ester, cellulose cinnamate or cellulose phenylpropionate.

[0049] According to an embodiment of the present invention, in the second method, the organic solvent is selected from at least one of DMF, DMAc or DMSO.

[0050] According to an embodiment of the present invention, the first method further comprises a post-treatment step of centrifuging and washing the prepared product.

[0051] According to an embodiment of the present invention, the second method further comprises a post-treatment step of centrifuging and washing the prepared product.

[0052] The present invention also provides a degradable waterproof and oil-proof packaging material, which comprises a paper substrate, an oil-proof layer and a waterproof layer in sequence.

[0053] According to the present invention, the degradable waterproof and oil-proof packaging material is prepared by the above-mentioned method for preparing the degradable waterproof and oil-proof packaging material.

[0054] According to an embodiment of the present invention, the packaging material has three layers, namely, a paper base, an oil-proof layer and a waterproof layer in sequence.

[0055] According to an embodiment of the present invention, the thickness of the oil-proof layer is less than 500 nm.

[0056] According to an embodiment of the present invention, the thickness of the waterproof layer is less than 800 nm.

[0057] According to an embodiment of the present invention, the packaging material has five layers, which are: a waterproof layer, an oil-proof layer, a paper base plate, an oil-proof layer and a waterproof layer.

[0058] The present invention also provides the use of the packaging material in paper lunch boxes, paper cups and waterproof paper bags.

[0059] Beneficial effects of the present invention:

[0060] The present invention achieves excellent waterproof and oil-proof effects by coating an oil-proof layer and a waterproof layer with nanometer thickness on a paper substrate; at the same time, all raw materials are environmentally friendly materials and can be naturally degraded in the environment, solving the problem that paper-based packaging materials are not waterproof, oil-proof, and non-degradable. Compared with traditional polyolefins and the currently popularized polylactic acid, the coating material in the present invention has a more excellent oil-proof effect and degradation performance, achieving a "use and throw away" effect without causing harm to the environment. In addition, the use of two layers of nanometer-thick coatings can achieve waterproof and oil-proof effects, which not only solves scientific challenges, but also reduces the dosage, saves costs, and has important practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 These are photos of the waterproof and oilproof packaging material in Example 1 and a photo of the paper substrate.

[0062] Figure 2 These are the field emission microscopy (SEM) images of the packaging material in Example 2 and the field emission microscopy images after being modified with a coating.

[0063] Figure 3 These are photos and self-cleaning pictures of the modified packaging materials of milk, cola and coffee in Example 3.

[0064] Figure 4 This is a picture of the degradation process of the modified packaging material in Example 4.

[0065] Figure 5 These are pictures showing the packaging material in Example 5's resistance to cold water, hot water, oil, and a mixture of oil and water before and after modification.

[0066] Figure 6 These are photos of the water contact angle, oil contact angle and underwater oil contact angle of the waterproof and oil-proof packaging material in Example 1. DETAILED DESCRIPTION

[0067] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0068] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0069] The following Figure 1-6 In the present invention, uncoated packaging material (ie, uncoated) refers to a material without a modified waterproof layer and an oil-proof layer, that is, a paper substrate.

[0070] Example 1

[0071] The preparation method of the waterproof and oil-proof packaging material is as follows:

[0072] (1) Preparation of oil-proof layer: Weigh 1 g of sodium carboxymethyl cellulose and dissolve it in 99 g of water to prepare a sodium carboxymethyl cellulose aqueous solution with a mass fraction of 1%. Spray the solution onto the base paper, and after the water evaporates, an oil-proof coating is prepared.

[0073] (2) Preparation of waterproof layer: 40 μL of water was added to 2 mL of octadecyltrichlorosilane, followed by mechanical stirring and ultrasonication for 30 min, and finally diluted with n-hexane to prepare a 5% volume fraction octadecyltrichlorosilane / n-hexane dispersion. The dispersion was sprayed on the oil-proof layer to prepare a waterproof layer.

[0074] The modified paper-based materials are effectively water- and oil-proof, while the unmodified paper-based materials have no water- and oil-proof effect.

[0075] Figure 1The photos are of the waterproof and oil-proof packaging material and the paper substrate in Example 1. In the first row, a drop of water is added to the surface of the pure paper substrate and left for different time periods, and the penetration and diffusion of water can be seen.

[0076] Row 2: Add a drop of water to the surface of the waterproof and oil-proof paper packaging material and leave it for different periods of time. It can be seen that the water does not penetrate or spread.

[0077] Row 3: Add a drop of oil to the surface of pure paper substrate and leave it for different periods of time. You can see the penetration and diffusion of the oil.

[0078] Row 4: Add 1 drop of oil to the surface of waterproof and oil-proof paper and leave it for different periods of time. You can see that the oil does not penetrate or spread.

[0079] Figure 6 These are photos of the water contact angle, oil contact angle and underwater oil contact angle of the waterproof and oil-proof packaging material in Example 1.

[0080] Example 2

[0081] (1) Preparation of oil-proof layer: A cellulose nanofiber (water dispersion) with a mass concentration of 0.5% is sprayed onto the base paper, and an oil-proof coating is prepared after the water evaporates.

[0082] (2) Preparation of waterproof layer: 20 μL of water was added to 2 mL of hexadecyltrimethoxysilane, followed by mechanical stirring and ultrasonication for 30 min, and finally diluted with n-hexane to prepare a 5% volume fraction hexadecyltrimethoxysilane / n-hexane dispersion. The dispersion was sprayed on the oil-proof layer to prepare a waterproof layer.

[0083] Figure 2 These are field emission microscopy (SEM) images of the packaging material in Example 2 and field emission microscopy images of the packaging material without modification or with modification and coating.

[0084] Example 3

[0085] (1) Preparation of oil-proof layer: Weigh 1 g of polyvinyl alcohol (PVA) and dissolve it in 99 g of water to prepare a 1% PVA aqueous solution. Spray the aqueous solution onto the base paper, and after the water evaporates, an oil-proof coating is prepared.

[0086] (2) Preparation of waterproof layer: A water dispersion containing 2% by mass of silicon dioxide nanoparticles (diameter 20 nm) and 0.5% dodecyltrimethoxysilane was sprayed on the oil-proof layer to form a micro-nano structure, thereby preparing a waterproof layer.

[0087] The modified paper-based material is not only effectively waterproof and oil-proof, but also resistant to wetting by milk, cola, coffee, etc., and has a self-cleaning function.

[0088] Figure 3The following are photos and self-cleaning pictures of the modified packaging material surfaces of milk, cola and coffee in Example 3. Figure 3 As can be seen from the figure, milk, cola and coffee maintain high contact angles on the surface of the packaging material, indicating that the material has poor affinity for milk, cola and coffee. Since the packaging material has excellent waterproof properties, pollutants on the surface of the material can be quickly washed away with water.

[0089] Example 4

[0090] (1) Preparation of oil-proof layer: Weigh 1 g of hydroxypropyl methylcellulose (HPMC) and dissolve it in 99 g of water to prepare a 1% HPMC aqueous solution. The HPMC aqueous solution is dripped onto the base paper, and an oil-proof coating is prepared after the water evaporates.

[0091] (2) Preparation of waterproof layer: 20 μL of water was added to 2 mL of octadecyltrimethoxysilane, followed by mechanical stirring and ultrasonication for 30 min, and finally diluted with n-hexane to prepare a 5% volume fraction octadecyltrimethoxysilane / n-hexane dispersion. The dispersion was sprayed on the oil-proof layer to prepare a waterproof layer.

[0092] Figure 4 This is a picture of the degradation process of the modified packaging material in Example 4. Figure 4 It can be seen that the material can be completely degraded in 30 days in a buried environment.

[0093] Example 5

[0094] (1) Preparation of oil-proof layer: A 1% by mass aqueous dispersion of hydrophilic cellulose micro-nano particles (diameter 50 nm, chemical composition: cellulose) is sprayed onto base paper, and an oil-proof coating is prepared after the water evaporates.

[0095] The preparation process of the hydrophilic cellulose micro-nano particles is as follows:

[0096] 4 g of cellulose was mixed with 96 g of ionic liquid AmimCl and stirred at 80°C for 2 h to obtain a cellulose / AmimCl solution. The solution was dripped dropwise into a 60% AmimCl aqueous solution and stirred vigorously using a high-speed shear emulsifier; centrifuged and washed with water, and repeated three times to obtain a hydrophilic cellulose micro-nano particle aqueous solution.

[0097] (2) Preparation of waterproof layer: A 1% by mass aqueous dispersion of hydrophobic cellulose nanoparticles (diameter 90 nm, chemical composition: cellulose oleate) is sprayed onto the oil-proof coating and dried to prepare a waterproof layer.

[0098] The preparation method of the hydrophobic cellulose micro-nano particles is as follows: 4 g of cellulose is mixed with 96 g of ionic liquid AmimCl, and stirred at 80°C for 2 hours to obtain a cellulose / AmimCl solution. 6 g of cinnamoyl chloride is added to the solution, and stirred at 80°C for 1 hour. The reaction solution is dripped into an 80% ethanol aqueous solution, and vigorously stirred using a high-speed shear emulsifier; centrifuged, washed with water, and repeated three times to obtain a hydrophobic cellulose micro-nano particle aqueous solution.

[0099] Figure 5 The following are pictures of the packaging material in Example 5 before and after modification to withstand cold water, hot water, oil, and oil-water mixture. The upper left and lower left pictures are of coated packaging materials; the upper right and lower right pictures are of uncoated materials, i.e., paper substrates. Figure 5 It can be seen from the figure that the packaging material of the present invention did not leak when containing hot water, cold water, oil or oil-water mixture; however, leakage occurred when using the paper base.

[0100] The above is an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a degradable waterproof and oil-proof packaging material, characterized in that: The method comprises: (1) coating an aqueous solution of an oil-proof layer material on the surface of a paper substrate; or immersing the paper substrate in an aqueous solution of an oil-proof layer material to obtain a paper substrate having an oil-proof layer on the surface; (2) coating the surface of the oil-proof layer of the material obtained in step (1) with a dispersion of a waterproof layer material to obtain the packaging material.

2. The method according to claim 1, characterized in that: In step (1), the paper substrate comprises natural biomass fibers, and the content of the natural biomass fibers is higher than 60 wt %; The natural biomass fiber is at least one of base paper, cotton fiber, wood fiber, bamboo fiber, grass fiber, hemp fiber or paper fiber.

3. The method according to claim 1, characterized in that In step (1), the aqueous solution of the oil-proof layer material is prepared by dissolving the waterproof layer material in water; In step (1), the oil-proof layer material is selected from at least one of sodium carboxymethyl cellulose, sodium carboxymethyl starch, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxyethyl starch, cellulose nanocrystals, cellulose nanofibers, hydrophilic cellulose micro-nano particles, starch nanocrystals, cationic starch, polyvinyl alcohol, pregelatinized starch or chitosan; In step (1), in the aqueous solution of the oil-proof layer material, the concentration of the oil-proof layer material is 0.3-5.0 wt %.

4. The method according to claim 1, characterized in that In step (2), the waterproof layer material dispersion liquid refers to dissolving the waterproof layer material in a solvent, and the solvent is selected from at least one of water, n-hexane or ethanol; In step (2), the waterproof layer material is selected from at least one of lignin, silica sol, silica nanoparticles, hydrophobic biowax, hydrophobic cellulose micro-nanoparticles, butyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, [3-(butylamino)propyl]trimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, octadecyltrichlorosilane, hexadecyltrichlorosilane, dodecyltrichlorosilane, trimethylchlorosilane, butyltrichlorosilane, hexyltrichlorosilane or decyltrichlorosilane; In step (2), the concentration of the waterproof layer material in the waterproof layer material dispersion is 0.3-8.0 wt %.

5. The method according to claim 4, characterized in that The hydrophobic biological wax is at least one of spermaceti, beeswax, wool wax, ant wax, palm wax, wood wax or flax wax.

6. The method according to claim 3, characterized in that The hydrophilic cellulose micro-nano particles are cellulose micro-nano particles having at least one of hydroxyl, aldehyde, carboxyl or amino groups on the surface; Alternatively, the preparation method of the hydrophilic cellulose micro-nano particles adopts one of the following two methods: The first method: (S1) dissolving cellulose in a solvent and then coagulating it with a precipitant to obtain an aqueous dispersion of cellulose micro-nanoparticles having hydroxyl groups on the surface; (S2) mixing the aqueous dispersion of cellulose micro-nanoparticles having hydroxyl groups on the surface in step (S1) with sodium periodate to obtain hydrophilic cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface; (S3) mixing the aqueous dispersion of cellulose micro-nano particles having aldehyde groups or carboxyl groups on the surface in step (S2) with an amine substance to obtain hydrophilic cellulose micro-nano particles having amino groups on the surface; or, The second method: (M1) dissolving cellulose in a solvent, adding sodium periodate, and then coagulating with a precipitant to obtain an aqueous dispersion of cellulose micro-nano particles having aldehyde groups or carboxyl groups on the surface; (M2) Mixing the aqueous dispersion of cellulose micro-nanoparticles having aldehyde groups or carboxyl groups on the surface in step (M1) with an amine substance to obtain hydrophilic cellulose micro-nanoparticles having amino groups on the surface.

7. The method according to claim 4, characterized in that The hydrophobic cellulose micro-nano particles are cellulose micro-nano particles having at least one group selected from the group consisting of polylactic acid, fatty acid ester, unsaturated fatty acid ester, cinnamate or phenylpropionate on the surface; The preparation method of the hydrophobic cellulose micro-nano particles adopts one of the following two methods: The first method is: mixing cellulose with a reaction reagent and a catalyst in a solvent, and solidifying the prepared product in a precipitant to obtain the hydrophobic cellulose micro-nano particles; or, The second method is to dissolve the cellulose derivative in an organic solvent and solidify it in a precipitant to obtain hydrophobic cellulose micro-nano particles.

8. The packaging material prepared by the method according to any one of claims 1 to 7, wherein the packaging material comprises a paper substrate, an oil-proof layer and a waterproof layer in sequence.

9. The packaging material according to claim 8, characterized in that The thickness of the oil-proof layer is less than 500 nm; Alternatively, the thickness of the waterproof layer is less than 800 nm; Alternatively, the packaging material has five layers, which are: a waterproof layer, an oil-proof layer, a paper base plate, an oil-proof layer and a waterproof layer.

10. Use of the packaging material according to claim 8 or 9 in paper lunch boxes, paper cups or waterproof paper bags.

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