A method for manufacturing waterproof nano-coating layer composite paper based on nanocellulose

Abstract

The present invention discloses a method for manufacturing a waterproof nano-coating composite paper based on nanocellulose, and relates to the technical field of coated paper. The present invention adopts nano-scale heat-insulating fillers and cationic starch as the main raw materials of the oil-proof layer coating, which can firmly adhere to the surface of the paper, seal the fiber surface layer and the gaps between the fibers, improve the oil resistance, and then grow nano-scale zinc hydroxide in situ, which synergizes with the heat-insulating filler and the urea inside the heat-insulating filler to exert a flame retardant effect; the present invention adopts long-chain silane, nanocellulose, and hydroxypropyl starch as the main raw materials of the waterproof layer coating, which can achieve the waterproof effect while filling the gaps between the nanoparticle protrusions and wrapping the nanoparticles, so that the surface of the paper is dense and smooth, the barrier performance is improved, and the organic-inorganic efficient flame retardant effect can be achieved with the oil-proof layer.

Description

Technical Field

[0001] The invention relates to the technical field of coated paper, in particular to a method for manufacturing a waterproof nano-coating layer composite paper based on nano-cellulose. Background Art

[0002] Paper is a three-dimensional mesh structure material composed of fibers. There are a lot of holes on the surface of untreated paper, and it is not waterproof or oil-proof. Therefore, in order to achieve the purpose of waterproof and oil-proof, most paper products in recent years are covered with plastic film when used. The materials of plastic film, such as low-density polyethylene (LDPE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), ethylene vinyl acetate copolymer (EVA), etc., cannot be self-degraded after being discarded. Even if incineration is used, a large amount of waste gas will be generated during the combustion process, which has become a major source of environmental pollution. Moreover, the raw materials of these plastic films come from petroleum, which is a non-renewable resource. The large-scale use of plastic films will aggravate the energy crisis.

[0003] Since paper itself is combustible, the actual highest flame retardant grade of existing packaging paper can only reach B2 combustible or B3 flammable. When there is an open flame, the existing flame retardant paper will still burn quickly and cannot actually play a fire retardant effect, posing a great safety hazard.

[0004] In order to solve the shortcomings of traditional paper, such as being flammable and difficult to block water and oil, the present invention creatively proposes to use nanocellulose and nanofillers as nano coating layers, with high surface smoothness and low PPS coarseness. At the same time, the surface coating layer plays the role of water resistance, oil resistance, reinforcement, flame retardancy, and oxygen resistance, improving the functionality of the product, truly realizing the use of paper instead of plastic, paper instead of wood, paper instead of cloth, and paper instead of metal, adapting to the new trend of social development, and can be widely used in production and life fields such as green packaging, medical protection, household goods, and gun display shelves. Summary of the invention

[0005] The object of the present invention is to provide a method for manufacturing a waterproof nano-coating layer composite paper based on nano-cellulose to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a waterproof nano-coating layer composite paper based on nanocellulose, wherein the waterproof nano-coating layer composite paper comprises a waterproof layer, an oil-proof layer, paper, an oil-proof layer, and a waterproof layer from top to bottom.

[0007] Furthermore, the waterproof layer is composed of long-chain silane, nanocellulose, hydroxypropyl starch and volatile solvent.

[0008] Furthermore, the long-chain silane is one or more of dodecyltrimethoxysilane, 1,2-bis(triethoxysilyl)decane, octadecyltrimethoxysilane, and docosyltriethoxysilane.

[0009] Furthermore, the oil-proof layer is composed of urea-modified heat-insulating filler, volatile solvent and cationic starch.

[0010] Furthermore, the urea modified thermal insulation filler is prepared by grinding and calcining silicon dioxide, graphene, bentonite and sawdust to obtain a porous thermal insulation filler, which is then wet-ground with a urea solution.

[0011] A method for preparing a waterproof nano-coating layer composite paper based on nanocellulose, comprising the following preparation steps:

[0012] (1) Mixing the mixed powder, sawdust, carbon powder with a particle size of 10 to 20 μm, and deionized water in a mass ratio of 75 to 90:7:7:10 to 25 and then granulating to obtain nearly spherical particles with a particle size of 1.1 to 1.7 mm, drying at 105 to 200° C. for 4 to 6 hours, and then feeding into a high-temperature electric furnace, heating to 250 to 400° C. at a rate of 2 to 10° C. / min, keeping the temperature for 10 to 30 minutes, then heating to 400 to 600° C. at the same rate, keeping the temperature for 10 to 30 minutes, and then heating to 900 to 1100° C. at a rate of 10 to 20° C. / min, keeping the temperature for 1 to 4 hours, to obtain a porous thermal insulation filler;

[0013] (2) mixing a porous thermal insulation filler and a urea solution in a mass ratio of 1:3 to 8 and grinding the mixture to an average particle size of 100 to 300 nm, filtering out the solid, and drying the solid at room temperature for 24 hours to obtain a urea-modified thermal insulation filler;

[0014] (3) After urea-modified heat-insulating filler and cationic starch are mixed uniformly in a mass ratio of 5-9:8-15, 12-17 parts of deionized water are added, and the mixture is stirred at 50° C. and 60 rpm for 2 h. After cooling to room temperature, polyvinyl alcohol (0.2-0.3 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred uniformly to obtain an oil-proof coating. The oil-proof coating is applied to the surface of paper using a coating machine, and the paper is dried at 50-60° C. for 10-30 min. The paper is suspended and fixed in a container, and a 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz. The atomized liquid is transported to the surface of the paper by argon gas at 50-300 mL / h. After being treated at 85° C. for 40-70 min, the paper is taken out and dried at 100° C. to constant weight to obtain paper containing an oil-proof layer;

[0015] (4) Nanocellulose and anhydrous ethanol are prepared into a nanocellulose dispersion with a concentration of 10 wt%, and long-chain silane is added in an amount of 0.05 to 0.3 times the mass of the nanocellulose. After stirring at 100 rpm for 2 to 3 hours, starch gelatinization liquid is added, and the mass ratio of nanocellulose to hydroxypropyl starch is 1:10 to 25. The mixture is stirred at 400 to 600 rpm for 2 to 4 hours to obtain a waterproof coating. The waterproof coating is applied on the surface of paper containing an oil-proof layer using a coating machine, and the mixture is dried at 60 to 80° C. to a constant weight to obtain a nanocellulose-based waterproof nano-coating composite paper.

[0016] Furthermore, the preparation method of the mixed powder in step (1) is: silicon dioxide, graphene and bentonite are uniformly mixed in a mass ratio of 30-35:10-20:55-65, and then ground to a particle size of 100-200 nm.

[0017] Furthermore, the urea solution in step (2) is a 1 mol / L urea aqueous solution.

[0018] Furthermore, the coating speed of the coating machine in steps (3) and (4) is 3 to 8 cm / s, and the coating amount is 1 to 6 g / m 2 .

[0019] Furthermore, the starch gelatinized liquid in step (4) is prepared by stirring hydroxypropyl starch and 50° C. deionized water in a mass ratio of 13-24:17-25 at 60 rpm for 2 hours.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] The coated composite paper prepared by the present invention is a paper having an oil-proof layer and a waterproof layer coated on both sides of the paper in sequence. By constructing a double-layer structure, the penetration paths of oxygen, water and oil are increased to achieve a barrier effect. At the same time, the organic coating of the waterproof layer can fill the gaps between the nano-particle protrusions of the oil-proof layer, thereby forming a smooth surface, further improving the density of the coating and improving the barrier performance.

[0022] First, the present invention uses silicon dioxide, graphene and bentonite as raw materials, grinds them to nanometer level, forms porous particles with heat insulation effect under the action of sawdust, carbon powder and bentonite pore expansion, and then wet grinds with urea solution to make the heat insulation filler achieve nanometer particle size, and make the urea solution fully infiltrate the surface and interior of the heat insulation particles, and then uses urea-modified heat insulation filler and cationic starch as oil-proof coating, which is coated on the surface of paper. The heat insulation filler in the coating forms hydrogen bonds with paper fibers by relying on the urea on the surface, and the cationic groups in the starch combine with the negatively charged paper fibers, so that the coating layer is firmly attached to the surface of the paper, the bonding force between the paper fibers is increased, and the physical strength of the paper is greatly improved, which is 3 times the strength of ordinary paper. In addition, the oil-proof coating prepared by the present invention also uses volatile solvents. , reducing the penetration of the oil-proof layer coating into the interior of the paper, and then forming a dense film layer on the surface of the paper, sealing the fiber surface and the gaps between the fibers, thereby improving the oil-proof performance, and then performing a semi-curing treatment to make the oil-proof layer semi-soft, and then performing an atomization treatment. The atomization makes the zinc sulfate aqueous solution become extremely fine droplets, and the oil-proof layer is not completely cured, so that it can penetrate the interior of the oil-proof layer and come into contact with the urea-modified thermal insulation filler. Zinc sulfate gradually reacts with part of the urea, causing the alkalinity of the surrounding environment to increase slowly and evenly, delaying the growth of the crystal nucleus into large particles, which is conducive to the formation of nano-scale zinc hydroxide on the surface of the thermal insulation filler. The growth of zinc oxide improves the flame retardant effect of the paper coating, and the remaining urea in the filler decomposes to produce a large amount of gas when encountering a fire, causing the oil-proof layer to expand, further blocking the spread of flames.

[0023] Secondly, the waterproof layer is composed of long-chain silane, nanocellulose, hydroxypropyl starch and volatile solvents. The long-chain silane condenses itself on one side and reacts with the hydroxyl group of cellulose on the other side, causing the waterproof layer to form a dense three-dimensional network structure, reducing the voids in the coating layer on the surface of the paper and improving the barrier properties. The introduction of long-chain silane can greatly improve the water-blocking effect of the waterproof layer, and can also achieve an organic-inorganic high-efficiency flame retardant effect with the oil-proof layer. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the waterproof nano-coating layer composite paper prepared in the following examples are as follows:

[0026] Flame retardant: If the paper sample is burned by open flame, and it does not burn for 1 minute after ignition, and the burning of the paper sample stops within 5 seconds after the open flame is removed after 3 minutes, it is difficult to burn: If the paper sample is burned by open flame, and it does not burn or smolders for 30 seconds after ignition, and the open flame is removed after 1 minute, there is open flame on the paper sample, but the burning stops within 30 seconds, it is flammable: If the paper sample is burned by open flame, and it does not burn for 30 seconds after ignition, and the open flame is removed after 1 minute, there is open flame on the paper sample and the burning does not stop, it is flammable.

[0027] Waterproof: Refer to GB / T 1540-2002 "Determination of water absorption of paper and paperboard - Cobber method"

[0028] Oil resistance: refer to TAPPI T 559cm-02 "Grease resistance test for paper andpaperboard"

[0029] Oxygen barrier: MOCON OX-tran 2 / 21 gas permeameter was used, the temperature was 23°C, and the humidity was 23% RH.

[0030] Example 1

[0031] (1) Silicon dioxide, graphene and bentonite were mixed in a mass ratio of 30:10:55 and then ground to a particle size of 100 nm to obtain a mixed powder. The mixed powder, sawdust, carbon powder with a particle size of 10 μm and deionized water were mixed in a mass ratio of 75:7:7:10 and then granulated to obtain nearly spherical particles with a particle size of 1.1 mm. After drying at 105°C for 6 hours, the particles were placed in a high-temperature electric furnace and heated to 250°C at a rate of 2°C / min, kept warm for 30 minutes, then heated to 400°C at the same rate, kept warm for 30 minutes, and then heated to 900°C at a rate of 10°C / min, kept warm for 4 hours, to obtain a porous thermal insulation filler with a thermal conductivity of 0.22 W / m·K at 800°C.

[0032] (2) The porous thermal insulation filler and 1 mol / L urea aqueous solution were mixed and ground in a mass ratio of 1:3 until the average particle size was 100 nm, the solid was filtered out, and dried at room temperature for 24 h to obtain a urea-modified thermal insulation filler;

[0033] (3) After urea-modified thermal insulation filler and cationic starch are mixed in a mass ratio of 5:8, 12 parts of deionized water are added, and the mixture is stirred at 50°C and 60 rpm for 2 hours. After cooling to room temperature, polyvinyl alcohol (0.2 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred to obtain an oil-proof coating. The oil-proof coating is applied on the surface of paper using a coating machine. After drying at 50°C for 30 minutes, the paper is suspended and fixed in a container. A 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz, and the atomized liquid is transported to the surface of the paper by argon gas at 220 mL / h. After being treated at 85°C for 40 minutes, the paper is taken out and dried at 100°C to constant weight to obtain paper containing an oil-proof layer. The coating speed of the coating machine is 3 cm / s, and the coating amount is 1 g / m 2 ;

[0034] (4) Nanocellulose and anhydrous ethanol are prepared into a nanocellulose dispersion with a concentration of 10 wt %, and long-chain silane is added in an amount 0.1 times the mass of the nanocellulose, wherein the mass ratio of dodecyltrimethoxysilane to 1,2-bis(triethoxysilyl)decane in the long-chain silane is 1:0.4, and the mixture is stirred at 100 rpm for 2 h. Then, starch gelatinization liquid is added, wherein the mass ratio of nanocellulose to hydroxypropyl starch is 1:10, and the mixture is stirred at 400 rpm for 2 h to obtain a waterproof coating. The waterproof coating is applied on the surface of paper containing an oil-proof layer using a coating machine, and dried at 60° C. to constant weight to obtain a nanocellulose-based waterproof nano-coated composite paper; the starch gelatinization liquid is prepared by stirring hydroxypropyl starch and 50° C. deionized water at a mass ratio of 13:17 at 60 rpm for 2 h; the coating speed of the coating machine is 3 cm / s, and the coating amount is 2 g / m 2 .

[0035] Example 2

[0036] (1) Silicon dioxide, graphene and bentonite were mixed in a mass ratio of 32:15:60 and then ground to a particle size of 150 nm to obtain a mixed powder. The mixed powder, sawdust, carbon powder with a particle size of 15 μm and deionized water were mixed in a mass ratio of 83:7:7:20 and then granulated to obtain nearly spherical particles with a particle size of 1.4 mm. After drying at 155°C for 5 hours, the particles were placed in a high-temperature electric furnace and heated to 275°C at a rate of 6°C / min, kept warm for 20 minutes, then heated to 500°C at the same rate, kept warm for 20 minutes, and then heated to 1000°C at a rate of 15°C / min, kept warm for 3 hours, to obtain a porous thermal insulation filler with a thermal conductivity of 0.20 W / m·K at 800°C;

[0037] (2) The porous thermal insulation filler and 1 mol / L urea aqueous solution were mixed and ground at a mass ratio of 1:5.5 to an average particle size of 200 nm, the solid was filtered out, and dried at room temperature for 24 h to obtain a urea-modified thermal insulation filler;

[0038] (3) After urea-modified heat-insulating filler and cationic starch are mixed in a mass ratio of 7:11, 15 parts of deionized water are added, and the mixture is stirred at 50°C and 60 rpm for 2 hours. After cooling to room temperature, polyvinyl alcohol (0.25 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred to obtain an oil-proof coating. The oil-proof coating is applied on the surface of paper using a coating machine, and after drying at 55°C for 20 minutes, the paper is suspended and fixed in a container, and a 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz. The atomized liquid is transported to the surface of the paper by argon gas at 300 mL / h. After being treated at 85°C for 60 minutes, the paper is taken out and dried at 100°C to constant weight to obtain paper containing an oil-proof layer. The coating speed of the coating machine is 5 cm / s, and the coating amount is 2 g / m 2 ;

[0039] (4) Nanocellulose and anhydrous ethanol are prepared into a nanocellulose dispersion with a concentration of 10 wt%, octadecyl trimethoxysilane is added in an amount of 0.22 times the mass of nanocellulose, and the mixture is stirred at 100 rpm for 2.5 h. Then, starch gelatinization liquid is added, the mass ratio of nanocellulose to hydroxypropyl starch is 1:18, and the mixture is stirred at 500 rpm for 3 h to obtain a waterproof coating. The waterproof coating is applied on the surface of paper containing an oil-proof layer using a coating machine, and the mixture is dried at 70°C to a constant weight to obtain a nanocellulose-based waterproof nano-coated composite paper; the starch gelatinization liquid is hydroxypropyl starch and 50°C deionized water in a mass ratio of 19:21 and stirred at 60 rpm for 2 h; the coating speed of the coating machine is 5 cm / s, and the coating amount is 4 g / m 2 .

[0040] Example 3

[0041] (1) Silicon dioxide, graphene and bentonite were mixed in a mass ratio of 35:20:65 and then ground to a particle size of 200 nm to obtain a mixed powder. The mixed powder, sawdust, carbon powder with a particle size of 20 μm and deionized water were mixed in a mass ratio of 90:7:7:25 and then granulated to obtain nearly spherical particles with a particle size of 1.7 mm. After drying at 200°C for 4 hours, the particles were placed in a high-temperature electric furnace and heated to 400°C at a rate of 10°C / min, kept warm for 10 minutes, then heated to 600°C at the same rate, kept warm for 10 minutes, and then heated to 1100°C at 20°C / min, kept warm for 1 hour, to obtain a porous thermal insulation filler with a thermal conductivity of 0.20 W / m·K at 800°C.

[0042] (2) The porous thermal insulation filler and 1 mol / L urea aqueous solution were mixed and ground in a mass ratio of 1:3 to an average particle size of 300 nm, the solid was filtered out, and dried at room temperature for 24 h to obtain a urea-modified thermal insulation filler;

[0043] (3) After urea-modified heat-insulating filler and cationic starch are mixed in a mass ratio of 9:15, 17 parts of deionized water are added, and the mixture is stirred at 50°C and 60 rpm for 2 hours. After cooling to room temperature, polyvinyl alcohol (0.3 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred to obtain an oil-proof coating. The oil-proof coating is applied on the surface of paper using a coating machine, and after drying at 60°C for 30 minutes, the paper is suspended and fixed in a container, and a 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz. The atomized liquid is transported to the surface of the paper by argon gas at 300 mL / h. After being treated at 85°C for 70 minutes, the paper is taken out and dried at 100°C to constant weight to obtain paper containing an oil-proof layer. The coating speed of the coating machine is 8 cm / s, and the coating amount is 3 g / m 2 ;

[0044] (4) Nanocellulose and anhydrous ethanol are prepared into a nanocellulose dispersion with a concentration of 10 wt %, and long-chain silane is added in an amount 0.3 times the mass of the nanocellulose, wherein the mass ratio of 1,2-bis(triethoxysilyl)decane to octadecyltrimethoxysilane in the long-chain silane is 1:2, and the mixture is stirred at 100 rpm for 3 h. Then, starch gelatinization liquid is added, wherein the mass ratio of nanocellulose to hydroxypropyl starch is 1:25, and the mixture is stirred at 600 rpm for 4 h to obtain a waterproof coating. The waterproof coating is applied on the surface of paper containing an oil-proof layer using a coating machine, and the mixture is dried at 80° C. to a constant weight to obtain a nanocellulose-based waterproof nano-coated composite paper; the starch gelatinization liquid is prepared by stirring hydroxypropyl starch and 50° C. deionized water at a mass ratio of 24:25 at 60 rpm for 2 h; the coating speed of the coating machine is 8 cm / s, and the coating amount is 6 g / m 2 .

[0045] Comparative Example 1

[0046] The only difference between Comparative Example 1 and Example 2 is that the porous thermal insulation filler is not wet-ground with 1 mol / L urea aqueous solution, and the remaining steps are the same as Example 2.

[0047] Comparative Example 2

[0048] The difference between Comparative Example 2 and Example 2 is that the paper is completely dried after being coated with the oil-proof coating and then subjected to atomization treatment, and the remaining steps are the same as those of Example 2.

[0049] Comparative Example 3

[0050] The difference between Comparative Example 3 and Example 2 is that the paper is completely dried after being coated with the oil-proof coating and no atomization treatment is performed. The remaining steps are the same as in Example 2.

[0051] Comparative Example 4

[0052] The difference between Comparative Example 4 and Example 2 is that octadecyltrimethoxysilane is not added, and the remaining steps are the same as Example 2.

[0053] Comparative Example 5

[0054] (1) Silicon dioxide, graphene and bentonite were mixed in a mass ratio of 32:15:60 and then ground to a particle size of 150 nm to obtain a mixed powder. The mixed powder, sawdust, carbon powder with a particle size of 15 μm and deionized water were mixed in a mass ratio of 83:7:7:20 and then granulated to obtain nearly spherical particles with a particle size of 1.4 mm. After drying at 155°C for 5 hours, the particles were placed in a high-temperature electric furnace and heated to 275°C at a rate of 6°C / min, kept warm for 20 minutes, then heated to 500°C at the same rate, kept warm for 20 minutes, and then heated to 1000°C at a rate of 15°C / min, kept warm for 3 hours, to obtain a porous thermal insulation filler with a thermal conductivity of 0.20 W / m·K at 800°C;

[0055] (2) The porous thermal insulation filler and 1 mol / L urea aqueous solution were mixed and ground at a mass ratio of 1:5.5 to an average particle size of 200 nm, the solid was filtered out, and dried at room temperature for 24 h to obtain a urea-modified thermal insulation filler;

[0056] (3) After urea-modified thermal insulation filler, cationic starch and nanofibers are mixed in a mass ratio of 7:11:10, 24 parts of deionized water are added, and the mixture is stirred at 50°C and 60 rpm for 2 hours. After cooling to room temperature, polyvinyl alcohol (0.25 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred to obtain a coating. The coating is applied to the surface of paper using a coating machine, and after drying at 55°C for 20 minutes, the paper is suspended and fixed in a container, and a 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz. The atomized liquid is transported to the surface of the paper by argon gas at 300 mL / h. After being treated at 85°C for 60 minutes, the paper is taken out and dried at 100°C to constant weight to obtain a waterproof nano-coated composite paper. The coating speed of the coating machine is 5 cm / s, and the coating amount is 2 g / m 2 .

[0057] Effect example

[0058] Table 1 below shows the performance analysis results of the composite paper with the waterproof nano-coating layer of Examples 1 to 3 of the present invention and Comparative Examples 1 to 5.

[0059] Table 1

[0060]

[0061]

[0062] From the comparison of the experimental data of the embodiment and the comparative example, it can be found that the present invention adopts nano-scale thermal insulation filler and cationic starch as the main raw materials of the oil-proof layer coating, which can be firmly attached to the surface of paper, seal the fiber surface and the gaps between fibers, improve the oil resistance, and then grow zinc hydroxide in situ, which synergizes with the thermal insulation filler and the urea inside the thermal insulation filler to exert a flame retardant effect; the present invention adopts long-chain silane, nanocellulose, and hydroxypropyl starch as the main raw materials of the waterproof layer coating, which can achieve a waterproof effect while filling the gaps between the nanoparticle protrusions and wrapping the nanoparticles, so that the surface of the paper is dense and smooth, the barrier performance is improved, and the organic-inorganic high-efficiency flame retardant effect can be achieved with the oil-proof layer.

[0063] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a waterproof nano-coating composite paper based on nanocellulose, wherein the waterproof nano-coating composite paper comprises a waterproof layer, an oil-proof layer, paper, an oil-proof layer, and a waterproof layer from top to bottom, characterized in that: The method comprises the following preparation steps: (1) Mixing the mixed powder, sawdust, carbon powder with a particle size of 10-20 μm and deionized water in a mass ratio of 75-90:7:7:10-25 and then granulating to obtain nearly spherical particles with a particle size of 1.1-1.7 mm, drying at 105-200° C. for 4-6 hours, and then putting them into a high-temperature electric furnace, heating them to 250-400° C. at a rate of 2-10° C. / min, keeping them warm for 10-30 minutes, then heating them to 400-600° C. at the same rate, keeping them warm for 10-30 minutes, and then heating them to 900-1100° C. at a rate of 10-20° C. / min, keeping them warm for 1-4 hours, to obtain a porous thermal insulation filler; The preparation method of the mixed powder is as follows: mixing silicon dioxide, graphene and bentonite in a mass ratio of 30-35:10-20:55-65 and then grinding them to a particle size of 100-200 nm; (2) The porous thermal insulation filler and the urea solution are mixed and ground in a mass ratio of 1:3-8 until the average particle size is 100-300 nm, the solid is filtered out, and dried at room temperature for 24 hours to obtain a urea-modified thermal insulation filler; (3) After urea-modified thermal insulation filler and cationic starch are mixed in a mass ratio of 5-9:8-15, 12-17 parts of deionized water are added, and the mixture is stirred at 50°C and 60 rpm for 2 hours. After cooling to room temperature, polyvinyl alcohol (0.2-0.3 times the mass of cationic starch) and anhydrous ethanol (0.8 times the mass of cationic starch) are added, and the mixture is stirred to obtain an oil-proof coating. The oil-proof coating is applied on the surface of paper using a coating machine, and the paper is dried at 50-60°C for 10-30 minutes. The paper is suspended and fixed in a container, and a 1 mol / L zinc sulfate aqueous solution is ultrasonically atomized at 30 kHz. The atomized liquid is transported to the surface of the paper by argon gas at a rate of 50-300 mL / h. After being treated at 85°C for 40-70 minutes, the paper is taken out and dried at 100°C to constant weight to obtain paper containing an oil-proof layer. (4) Prepare a nanocellulose dispersion with a concentration of 10 wt% by weight by mixing nanocellulose and anhydrous ethanol, add long-chain silane in an amount of 0.05 to 0.3 times the mass of the nanocellulose, stir at 100 rpm for 2 to 3 h, add starch gelatinization solution, the mass ratio of nanocellulose to hydroxypropyl starch is 1:10 to 25, stir at 400 to 600 rpm for 2 to 4 h to obtain a waterproof coating, apply the waterproof coating on the surface of paper containing an oil-proof layer using a coating machine, dry at 60 to 80 °C to constant weight, and obtain a nanocellulose-based waterproof nano-coating composite paper.

2. The method for preparing a waterproof nano-coating layer composite paper based on nanocellulose according to claim 1, characterized in that: The urea solution in step (2) is a 1 mol / L urea aqueous solution.

3. The method for preparing a waterproof nano-coating layer composite paper based on nanocellulose according to claim 1, characterized in that: The coating speed of the coating machine in steps (3) and (4) is 3-8 cm / s, and the coating amount is 1-6 g / m 2 .

4. The method for preparing a waterproof nano-coating layer composite paper based on nanocellulose according to claim 1, characterized in that: The starch gelatinized liquid in step (4) is prepared by stirring hydroxypropyl starch and 50° C. deionized water in a mass ratio of 13-24:17-25 at 60 rpm for 2 hours.

5. The method for preparing a waterproof nano-coating layer composite paper based on nanocellulose according to claim 1, characterized in that: The long-chain silane in step (4) is one or more of dodecyltrimethoxysilane, 1,2-bis(triethoxysilyl)decane, octadecyltrimethoxysilane, and docosyltriethoxysilane.

Images