Preparation method of waterproof tin package

Abstract

The invention discloses a preparation method of a waterproof tin package, and relates to the technical field of packaging bags. Firstly, gallic acid and carnauba wax ester are subjected to chemical reaction and mixed to obtain a mixed wax raw material, the content of fatty alcohol in the mixed wax raw material is reduced, the brittleness is reduced, the toughness is improved, and the packaging bag is not prone to cracking in the using process; the nano silicon dioxide is combined with hydroxyl of gallic acid and is uniformly dispersed to form a rough surface, so that the mechanical property and hydrophobic property of the paper-based packaging material are improved. Secondly, preparing aerogel by compounding tin dioxide and a graphene sheet layer, and preparing an inner layer of the packaging bag; ammonia water and ethyl alcohol are mixed and sprayed for modification, so that the hydrophobicity is improved; graphene and gallic acid are synergistically antibacterial, so that the whole packaging bag is easier to store and not prone to mildewing; the inner layer and the outer layer are not prone to wrinkling and breaking, and can be repeatedly used. The prepared packaging bag has the effects of being waterproof, not prone to damage and long in service life.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging bags, and specifically to a preparation method of a waterproof tin packaging. Background Art

[0002] A packaging bag refers to a bag used for packaging various articles, which facilitates the transportation and storage of goods during the production and circulation processes, and is widely used in daily life and industrial production. Existing packaging bags are generally made of paper or plastic film, formed by pressing two pieces of paper or plastic film together, and used to store items through an internal cavity. Plastic packaging bags have good storage and portability, and can quickly and efficiently store and transport products, and are increasingly widely used in our daily production and life. Plastic film is a common household item for people. Currently, the plastic film on the market is mainly polyethylene plastic film. However, some products may have problems such as wrinkles, poor transparency, uneven thickness, and many film bubbles and fish eyes. Some plastic films are used for food packaging, but they contain toxic plasticizers, which affect the quality of food and endanger human health.

[0003] Currently, the commercially available packaging bags have single performance and do not distinguish different packaging bags according to the special properties of products. In order to continuously improve the safety of packaging, the present invention designs a waterproof tin packaging bag. The present invention utilizes the fact that graphene aerogel has both the mechanical stability and hydrophobicity of graphene, as well as the ultra-light and high porosity characteristics of aerogel, to develop a packaging bag made of another brand-new raw material, while taking into account the advantages of being lightweight, waterproof, and having a long service life. Summary of the Invention

[0004] The purpose of the present invention is to provide a waterproof tin packaging and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A waterproof tin packaging, wherein the packaging is a packaging bag prepared by using a composite aerogel as the inner layer and impregnating the outer layer with a mixed wax.

[0006] Further, the composite aerogel is an aerogel formed by the hydrolysis and oxidation of a tin salt to form tin dioxide and graphene sheets, and modified by spraying with ammonia water / ethanol.

[0007] Further, the mixed wax is a mixed wax liquid prepared by mixing and esterifying gallic acid and carnauba wax, and then adding an inorganic filler, nano-silica, for modification as the outer layer.

[0008] Further, a preparation method of a waterproof tin packaging includes the following preparation steps: (1) In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 0.5 - 50 parts of carnauba wax, 0.05 - 0.09 part of an acidic catalyst, and 4 - 6 parts of the reaction solvent tetrahydrofuran. Carry out magnetic stirring at a stirring speed of 50 - 150 rpm, and slowly heat it to 110 - 130 °C on an oil bath to circulate the catalyst. React for 12 - 18 h until the reaction is complete. Recover the catalyst in the reaction solution under reduced pressure. Filter the remaining solid under reduced pressure, wash it repeatedly with a 10% concentration aqueous NaHCO3 solution, and then wash it 3 times with deionized water until neutral. Recrystallize the crude product twice with a mixed solvent of toluene and water to obtain an intermediate product; take 1 - 3 parts of the intermediate product, add it to 5 parts of absolute ethanol, and heat it in a water bath at 80 - 100 °C for 30 min to obtain a mixed solution; take 0.1 - 0.2 part of hydrophobic fumed silica, add it to the mixed solution, and then carry out magnetic stirring for 15 - 45 min at a stirring speed of 200 - 400 rpm to prepare a mixed wax solution; (2) Mix 5 - 10 parts of graphene oxide with 100 - 200 parts of deionized water, heat up to 80 - 100 °C and stir for 1 - 2 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 15 - 45 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3%, and then centrifuge and wash 5 times with deionized water. Add the washed colloidal product to 80 - 100 parts of deionized water, and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; Mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol according to a volume ratio of 1∶40, ultrasonically disperse it for 20 min at a power of 200 W, then add 3 - 5 parts of stannous chloride dihydrate to the obtained sol, and reflux and stir the resulting reactants at 100 - 140 °C for 1 h, with a stirring speed of 60 rpm. Then, centrifuge to separate and remove the unreacted tin salt, and wash the obtained precipitate 3 - 5 times with deionized water to prepare a composite; Mix 0.4 - 0.8 parts of the composite with 10 parts of deionized water, ultrasonically treat it at 200 W for 15 min, then add 0.1 - 0.3 parts of sodium dodecylbenzenesulfonate aqueous solution to the graphene oxide dispersion, and stir at a rotation speed of 10000 rmp for 15 - 45 min to obtain a foam; Place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool to 25 °C to obtain a mixed hydrogel. Soak and wash the mixed hydrogel with 1 vol% ethanol aqueous solution for 24 h, with a solid - liquid ratio of 1:5, to obtain the washed mixed hydrogel; Take out the washed mixed hydrogel, place it at - 45 °C for freeze - treatment for 2 h, then take it out and heat it up to 25 °C to melt, and dry it at normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.05 - 0.15 cm; Under the protection of nitrogen gas, place the obtained aerogel in a tube furnace at 600 - 800 °C and heat it for 1 - 2 h, take it out and cool it to room temperature; Spray - modify the aerogel for 30 - 60 min by using the self - made modified solution through high - pressure gas - assisted micro - atomization, with a spray particle size of 30 - 50 μm and a spray flow rate of 60 - 100 ml / min to prepare a modified composite aerogel as the inner layer; (3) Immerse the prepared inner layer in the mixed wax liquid, with an impregnation amount of 1 - 5 g / m 2 , after impregnating for 3 - 5 min, dry it at 35 °C for 30 - 60 min, and then place it in an environment with a relative humidity of 50% and a temperature of 25 °C for 24 h to obtain a multi - layer packaging bag material containing tin; Carry out color printing and bag - making on the multi - layer packaging bag material containing tin to obtain a waterproof tin packaging bag.

[0009] Further, in the step (1), the acidic catalyst is one of p - toluenesulfonic acid, copper sulfate, and cerium sulfate.

[0010] Further, in the step (1), the heating rate of the oil bath heating is 10 °C / min.

[0011] Further, in the step (1), the volume ratio of toluene to water in the mixed solvent is 4:1.

[0012] Further, in the step (2), the centrifugal washing speed is 5000 rpm.

[0013] Further, in the step (2), the concentration of the sodium dodecylbenzenesulfonate aqueous solution is 50 mg / ml.

[0014] Further, in the step (2), the self-made modified solution is obtained by mixing 20 vol% ammonia water solution and 90 vol% ethanol water solution at a volume ratio of 4 - 8:1.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention uses composite aerogel as the inner layer and impregnates the outer layer with mixed wax to prepare a waterproof tin packaging bag, so as to achieve the effects of waterproofing, not being easily damaged, and having a long service life.

[0016] First, gallic acid is mixed with carnauba wax. During the heating process, the carboxylic acid groups contained in gallic acid react with carnauba wax to obtain a mixed wax raw material; the esterification reaction not only reduces the fatty alcohol content in the mixed wax, but also further reduces its brittleness and improves its toughness on the excellent mechanical properties of carnauba wax, making the packaging bag not easily crack during use. Moreover, the esterified gallic acid esters have high antioxidant properties, making the packaging bag protected by the mixed wax coating less likely to age during use, thus improving the overall service life of the packaging bag; as an inorganic filler, nano-silica is added to the mixed wax and adsorbed and combined with organic gallic acid through hydroxyl groups, improving the dispersibility of silica particles, enabling them to act more uniformly on the packaging paper mixed wax coating. It has a relatively large surface area and excellent mechanical strength, improving the surface roughness of the packaging paper composite wax coating as fine particles, and being able to reduce the surface energy, achieving the effect of simultaneously improving the mechanical properties and hydrophobic properties of the paper-based packaging material.

[0017] Second, a tin salt is hydrolyzed and oxidized to form a composite of tin dioxide and graphene sheets to prepare the inner layer of the packaging bag; through the growth environment composed of water and organic solvents, the morphology of tin dioxide is controlled, so that in the lamellar composite aerogel material prepared by the present invention, tin dioxide nanoparticles are evenly distributed and spherical, improving its roughness to achieve a hydrophobic effect; the prepared aerogel is then modified by spraying a mixture of ammonia water and ethanol to improve its hydrophobicity; in addition, both graphene in the inner layer and gallic acid in the outer layer have antibacterial effects, so the overall packaging bag is more easily stored and not prone to mildew; the double-layer structure packaging bag relies on the high elasticity of the inner layer aerogel and is combined with the modified mixed wax coating, improving the wrinkles and fractures during the use of the packaging bag, enabling it to be reused repeatedly. Detailed implementation mode

[0018] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] In order to more clearly illustrate the method provided by the present invention, the following examples are used for detailed description. The test methods for various indicators of a waterproof tin packaging produced in the following examples are as follows: Mechanical properties: The samples prepared in the examples and comparative examples were tested for their radial strength and weft strength according to the standard of GB / T8946-2013; and were determined according to the standard of GB / T1040-2006 to determine the maximum tensile stress.

[0020] Waterproof performance: The samples prepared in the examples and comparative examples were subjected to a contact angle test.

[0021] Example 1 (1) In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 0.5 part of carnauba wax, 0.05 part of the acidic catalyst p-toluenesulfonic acid, and 4 parts of the reaction solvent tetrahydrofuran, and carry out magnetic stirring. The stirring speed is 50 rpm. Slowly heat it to 110°C on an oil bath, and the heating rate is 10°C / min to circulate the catalyst. React for 12 h to complete the reaction. Recover the catalyst in the reaction solution under reduced pressure. Filter the remaining solid under reduced pressure, wash it repeatedly with a 10% concentration of aqueous NaHCO3 solution, and then wash it 3 times with deionized water until neutral. The crude product is recrystallized twice with a mixed solvent of toluene and water, and the volume ratio of toluene to water is 4:1 to obtain an intermediate product; take 1 part of the intermediate product and add it to 5 parts of absolute ethanol, heat it in a water bath at 80°C for 30 min to obtain a mixed solution; take 0.1 part of hydrophobic fumed silica and add it to the mixed solution, and then carry out magnetic stirring for 15 min. The stirring speed is 200 rpm to prepare a mixed wax liquid; (2) Mix 5 parts of graphene oxide with 100 parts of deionized water, heat up to 80 °C and stir for 1 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 15 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3% at a rotation speed of 5000 rpm. Next, centrifuge and wash with deionized water 5 times. Add the washed colloidal product to 80 parts of deionized water and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol at a volume ratio of 1:40, ultrasonically disperse it at a power of 200 W for 20 min, then add 3 parts of stannous chloride dihydrate to the obtained sol, reflux and stir the resulting reactants at 100 °C for 1 h with a stirring speed of 60 rpm. Then, centrifuge to remove the unreacted tin salt at a rotation speed of 5000 rpm, wash the obtained precipitate 3 times with deionized water to prepare a composite; mix 0.4 part of the composite with 10 parts of deionized water, ultrasonically treat it at 200 W for 15 min, then add 0.1 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, stir at a rotation speed of 10000 rmp for 15 min to obtain a foam; place the foam at 80 °C for a reduction reaction for 6 h, then naturally cool it to 25 °C to obtain a mixed hydrogel. Immerse the mixed hydrogel in an ethanol aqueous solution of 1 vol% for 24 h with a solid-liquid ratio of 1:5 to obtain the washed mixed hydrogel; take out the washed mixed hydrogel, freeze it at -45 °C for 2 h, then take it out and heat it to 25 °C to melt it, and dry it at normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.05 cm; under the protection of nitrogen gas, place the obtained aerogel in a tube furnace at 600 °C and heat it for 1 h, take it out and cool it to room temperature; mix 20 vol% of ammonia water solution and 90 vol% of ethanol aqueous solution at a volume ratio of 4:1 to obtain a self-made modified solution; spray-modify the aerogel with the self-made modified solution by high-pressure gas-assisted microatomization with a spray particle size of 30 μm and a spray flow rate of 60 ml / min for 30 min to prepare a modified composite aerogel as the inner layer; (3) Immerse the prepared inner layer in the mixed wax liquid with an impregnation amount of 1 g / m 2 , after impregnating for 3 min, dry it at 35 °C for 30 min, and then place it in an environment with a relative humidity of 50% and a temperature of 25 °C for 24 h to obtain a multi-layer packaging bag material containing tin; perform color printing and bag making on the multi-layer packaging bag material containing tin to obtain a waterproof tin packaging bag.

[0022] Example 2 (1) In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 25 parts of carnauba wax, 0.07 part of acidic catalyst copper sulfate, and 5 parts of reaction solvent tetrahydrofuran. Conduct magnetic stirring at a stirring speed of 100 rpm. Slowly heat it to 120 °C on an oil bath with a heating rate of 10 °C / min to circulate the catalyst. React for 15 h until the reaction is complete. Recover the catalyst in the reaction solution under reduced pressure. Filter the remaining solid under reduced pressure. Wash it repeatedly with a 10% concentration of aqueous NaHCO3 solution, and then wash it 3 times with deionized water until neutral. Recrystallize the crude product twice with a mixed solvent of toluene and water with a volume ratio of toluene to water of 4:1 to obtain an intermediate product. Take 2 parts of the intermediate product and add it to 5 parts of absolute ethanol. Heat it in a water bath at 90 °C for 30 min to obtain a mixed solution. Take 0.15 part of hydrophobic fumed silica and add it to the mixed solution, and then conduct magnetic stirring for 30 min at a stirring speed of 300 rpm to prepare a mixed wax solution; (2) Mix 7.5 parts of graphene oxide with 150 parts of deionized water, heat up to 90 °C and stir for 1.5 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 30 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3% at a rotation speed of 5000 rpm. Then, centrifuge and wash 5 times with deionized water. Add the washed colloidal product to 90 parts of deionized water, and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol according to a volume ratio of 1:40, ultrasonically disperse it for 20 min at a power of 200 W, then add 4 parts of stannous chloride dihydrate to the obtained sol, and reflux and stir the obtained reactants at 120 °C for 1 h with a stirring speed of 60 rpm. Then, centrifuge to remove the unreacted tin salt at a rotation speed of 5000 rpm, wash the obtained precipitate 4 times with deionized water to prepare the composite; mix 0.6 part of the composite with 10 parts of deionized water, ultrasonically treat it for 15 min at 200 W, then add 0.2 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, and stir at a rotation speed of 10000 rmp for 30 min to obtain a foam; place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool it to 25 °C to obtain a mixed hydrogel. Immerse the mixed hydrogel in an ethanol aqueous solution with a concentration of 1 vol% for 24 h with a solid-liquid ratio of 1:5 to obtain the washed mixed hydrogel; take out the washed mixed hydrogel, freeze it at -45 °C for 2 h, then take it out and heat it up to 25 °C to melt it, and dry it at normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.1 cm; under the protection of nitrogen gas, place the obtained aerogel in a tubular furnace at 700 °C and heat it for 1.5 h, take it out and cool it to room temperature; mix 20 vol% of ammonia water solution and 90 vol% of ethanol aqueous solution according to a volume ratio of 6:1 to obtain a self-made modified solution; spray-modify the aerogel for 45 min by high-pressure gas-assisted microatomization with a spray particle size of 40 μm and a spray flow rate of 80 ml / min to prepare a modified composite aerogel as the inner layer; (3) Immerse the prepared inner layer in the mixed wax liquid with an impregnation amount of 3 g / m 2 , after impregnating for 4 min, dry it at 35 °C for 45 min, and then place it in an environment with a relative humidity of 50% and a temperature of 25 °C for 24 h to obtain a multi-layer packaging bag material containing tin; perform color printing and bag making on the multi-layer packaging bag material containing tin to obtain a waterproof tin packaging bag.

[0023] Example 3 (1) In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 50 parts of carnauba wax, 0.09 part of acidic catalyst cerium sulfate, and 6 parts of reaction solvent tetrahydrofuran, and perform magnetic stirring at a stirring speed of 150 rpm. Slowly heat it to 130 °C on an oil bath with a heating rate of 10 °C / min to circulate the catalyst. React for 18 h until the reaction is complete. Recover the catalyst in the reaction solution under reduced pressure. Filter the remaining solid under reduced pressure, wash it repeatedly with an aqueous solution of 10% concentration of NaHCO3, and then wash it with deionized water 3 times until neutral. Recrystallize the crude product twice with a mixed solvent of toluene and water with a volume ratio of toluene to water of 4:1 to obtain an intermediate product; Take 3 parts of the intermediate product and add it to 5 parts of absolute ethanol, and heat it in a water bath at 100 °C for 30 min to obtain a mixed solution; Take 0.2 part of hydrophobic fumed silica and add it to the mixed solution, and then perform magnetic stirring for 45 min at a stirring speed of 400 rpm to prepare a mixed wax solution; (2) Mix 10 parts of graphene oxide with 200 parts of deionized water, heat up to 100 °C and stir for 2 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 45 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3% at a rotation speed of 5000 rpm. Then, centrifuge and wash it 5 times with deionized water. Add the washed colloidal product to 100 parts of deionized water and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; Mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol according to a volume ratio of 1:40, ultrasonically disperse it at a power of 200 W for 20 min, then add 5 parts of stannous chloride dihydrate to the obtained sol, and reflux and stir the obtained reactants at 140 °C for 1 h with a stirring speed of 60 rpm. Then, centrifuge to remove the unreacted tin salt at a rotation speed of 5000 rpm, wash the obtained precipitate 5 times with deionized water to prepare a composite; Mix 0.8 part of the composite with 10 parts of deionized water, ultrasonically treat it at 200 W for 15 min, then add 0.3 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, and stir at a rotation speed of 10000 rmp for 45 min to obtain a foam; Place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool it to 25 °C to obtain a mixed hydrogel. Immerse the mixed hydrogel in an ethanol aqueous solution of 1 vol% for soaking and washing for 24 h with a solid-liquid ratio of 1:5 to obtain the washed mixed hydrogel; Take out the washed mixed hydrogel, place it at -45 °C for freezing treatment for 2 h, then take it out and heat it up to 25 °C to melt it, and dry it at normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.15 cm; Under the protection of nitrogen gas, place the obtained aerogel in a tube furnace at 800 °C and heat it for 2 h, take it out and cool it to room temperature; Mix 20 vol% of ammonia water solution and 90 vol% of ethanol aqueous solution according to a volume ratio of 8:1 to obtain a self-made modified solution; Atomize the self-made modified solution by high-pressure gas-assisted microatomization with a spray particle size of 50 μm and a spray flow rate of 100 ml / min, and spray-modify the aerogel for 60 min to prepare a modified composite aerogel as the inner layer; (3) Immerse the prepared inner layer in the mixed wax liquid with an impregnation amount of 5 g / m 2 , after impregnating for 5 min, dry it at 35 °C for 60 min, and then place it in an environment with a relative humidity of 50% and a temperature of 25 °C for 24 h to obtain a multi-layer packaging bag material containing tin; Carry out color printing and bag making on the multi-layer packaging bag material containing tin to obtain a waterproof tin packaging bag.

[0024] Comparative Example 1 The difference between Comparative Example 1 and Example 2 lies in that gallic acid is not added, specifically in Step (1). Step (1) is modified as follows: In a three-necked flask equipped with a thermometer and a solvent circulation device, add 25 parts of carnauba wax to 5 parts of absolute ethanol, heat in a water bath at 90 °C for 30 min to obtain a mixed solution; take 0.15 part of hydrophobic fumed silica, add it to the mixed solution, and then stir magnetically for 30 min at a stirring speed of 300 rpm to prepare a mixed wax solution; the remaining steps are the same as those in Example 2.

[0025] Comparative Example 2 The difference between Comparative Example 2 and Example 2 lies in that nano-silica is not added, specifically in Step (1). Step (1) is modified as follows: In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 25 parts of carnauba wax, 0.07 part of acidic catalyst copper sulfate, and 5 parts of reaction solvent tetrahydrofuran, stir magnetically at a stirring speed of 100 rpm, and slowly heat to 120 °C on an oil bath at a heating rate of 10 °C / min to circulate the catalyst, react for 15 h until the reaction is complete, recover the catalyst in the reaction solution under reduced pressure, filter the remaining solid under reduced pressure, wash it repeatedly with a 10% concentration of NaHCO3 aqueous solution, and then wash it 3 times with deionized water until neutral. The crude product is recrystallized twice with a mixed solvent of toluene and water with a toluene-to-water volume ratio of 4:1 to obtain a mixed wax solution; the remaining steps are the same as those in Example 2.

[0026] Comparative Example 3 The difference between Comparative Example 3 and Example 2 lies in not adding tin salt intercalation, specifically the difference in step (2). Step (2) is modified as follows: Mix 7.5 parts of graphene oxide with 150 parts of deionized water, heat to 90 °C and stir for 1.5 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 30 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3%, at a rotation speed of 5000 rpm, and then centrifuge and wash 5 times with deionized water. Add the washed colloidal product to 90 parts of deionized water, and ultrasonically disperse it for 20 min at a power of 200 W to obtain a graphene oxide dispersion; add 0.2 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, stir at a rotation speed of 10000 rmp for 30 min to obtain a foam; place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool to 25 °C to obtain a hydrogel. Soak and wash the hydrogel with 1 vol% aqueous ethanol solution for 24 h, with a solid-liquid ratio of 1:5, to obtain the washed hydrogel; take out the washed hydrogel, freeze it at -45 °C for 2 h, then take it out and heat it to 25 °C to melt it, and dry it at normal temperature and pressure for 5 h to obtain an aerogel with a thickness of 0.1 cm; under the protection of nitrogen gas, place the obtained aerogel in a tube furnace at 700 °C and heat for 1.5 h, take it out and cool to room temperature; mix 20 vol% ammonia water solution and 90 vol% ethanol water solution in a volume ratio of 6:1 to obtain a self-made modified solution; spray-modify the aerogel with the self-made modified solution by high-pressure gas-assisted microatomization, with a spray particle size of 40 μm and a spray flow rate of 80 ml / min for 45 min to prepare a modified composite aerogel as the inner layer; the remaining steps are the same as in Example 2.

[0027] Comparative Example 4 The difference between Comparative Example 4 and Example 2 lies in not using the mixture of ammonia water and ethanol for modification. Specifically, it is the difference in step (2). Modify step (2) as follows: Mix 7.5 parts of graphene oxide with 150 parts of deionized water, heat up to 90 °C and stir for 1.5 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 30 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3% at a rotation speed of 5000 rpm, and then centrifuge and wash 5 times with deionized water. Add the washed colloidal product to 90 parts of deionized water, and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; Mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol according to a volume ratio of 1:40, ultrasonically disperse it at a power of 200 W for 20 min, then add 4 parts of stannous chloride dihydrate to the obtained sol, reflux and stir the obtained reactants at 120 °C for 1 h, with a stirring speed of 60 rpm, then centrifuge to remove the unreacted tin salt at a rotation speed of 5000 rpm, wash the obtained precipitate 4 times with deionized water to prepare the composite; Mix 0.6 part of the composite with 10 parts of deionized water, ultrasonically disperse it at 200 W for 15 min, then add 0.2 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, and stir at a rotation speed of 10000 rmp for 30 min to obtain a foam; Place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool it to 25 °C to obtain a mixed hydrogel. Soak and wash the mixed hydrogel with 1 vol% ethanol aqueous solution for 24 h, with a solid-liquid ratio of 1:5, to obtain the washed mixed hydrogel; Take out the washed mixed hydrogel, place it at -45 °C for freezing treatment for 2 h, then take it out and heat it up to 25 °C to melt it, and dry it under normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.1 cm; Under the protection of nitrogen gas, place the obtained aerogel in a tubular furnace at 700 °C and heat it for 1.5 h, take it out and cool it to room temperature to prepare a composite aerogel as the inner layer; The remaining steps are the same as those in Example 2.

[0028] Effect Example The following Table 1 shows the performance analysis results of a waterproof tin package using Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0029] Table 1 From the comparison of the experimental data on the mechanical properties of the examples and the comparative examples, it can be found that in the present invention, gallic acid is mixed with carnauba wax. During the heating process, the carboxylic acid groups contained in gallic acid undergo an esterification reaction with the carnauba wax to obtain a mixed wax raw material. The esterification reaction not only reduces the fatty alcohol content in the mixed wax, but also further reduces its brittleness and increases its toughness on the excellent mechanical properties of the carnauba wax, making the packaging bag not easily cracked during use. Moreover, the esterified gallic acid ester compounds have high antioxidant properties, making the packaging bag protected by the mixed wax coating less likely to age during use, thus improving the overall service life of the packaging bag. As an inorganic filler, nano-silica is added to the mixed wax and adsorbed and combined with organic gallic acid through hydroxyl groups, improving the dispersibility of the silica particles and enabling them to act more uniformly on the mixed wax coating of the packaging paper. It has excellent mechanical strength and improves its durability. From the comparison of the experimental data on the hydrophobic properties of the examples and the comparative examples, it can be found that the present invention uses fine silica particles to increase the surface roughness of the composite wax coating of the packaging paper and can reduce the surface energy, achieving the effect of simultaneously improving the mechanical properties and hydrophobic properties of the paper-based packaging material. Secondly, a tin salt is hydrolyzed and oxidized to form a composite of tin dioxide and graphene sheets to prepare an aerogel for the inner layer of the packaging bag. Through the growth environment of the composite of water and organic solvents, the morphology of tin dioxide is controlled, so that in the prepared sheet composite aerogel material, the tin dioxide nanoparticles are uniformly distributed and spherical, increasing its roughness to achieve a hydrophobic effect. The prepared aerogel is then modified by spraying a mixture of ammonia water and ethanol to improve its hydrophobicity. In addition, both the graphene in the inner layer and the gallic acid in the outer layer have antibacterial effects, so the whole packaging bag is more easily stored and not prone to mildew. The double-layer structure of the packaging bag relies on the high elasticity of the inner-layer aerogel and is compounded with the modified mixed wax coating, improving the wrinkles and fractures during the use of the packaging bag and enabling it to be reused repeatedly.

[0030] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A preparation method of a waterproof tin packaging, characterized in that, It includes the following preparation steps: (1) In a three-necked flask equipped with a thermometer and a solvent circulation device, add 1 part of gallic acid, 25 parts of carnauba wax, 0.07 part of acidic catalyst copper sulfate, and 5 parts of reaction solvent tetrahydrofuran. Conduct magnetic stirring at a stirring speed of 100 rpm. Slowly heat it to 120 °C on an oil bath with a heating rate of 10 °C / min to circulate the catalyst. React for 15 h until the reaction is complete. Recover the catalyst in the reaction solution under reduced pressure. Filter the remaining solid under reduced pressure. Wash it repeatedly with an aqueous solution of NaHCO3 with a concentration of 10%, and then wash it 3 times with deionized water until it is neutral. Recrystallize the crude product twice with a mixed solvent of toluene and water, with the volume ratio of toluene to water being 4:1 to obtain an intermediate product. Take 2 parts of the intermediate product and add it to 5 parts of absolute ethanol. Heat it in a water bath at 90 °C for 30 min to obtain a mixed solution. Take 0.15 part of hydrophobic fumed silica and add it to the mixed solution, and then conduct magnetic stirring for 30 min at a stirring speed of 300 rpm to prepare a mixed wax liquid; (2) Mix 7.5 parts of graphene oxide with 150 parts of deionized water, heat up to 90 °C and stir for 1.5 h; then add 10 parts of 30% hydrogen peroxide by mass fraction, stir for 30 min and then filter. Then, centrifuge and wash the obtained filter cake 5 times with hydrochloric acid with a mass fraction of 3% at a rotation speed of 5000 rpm. Next, centrifuge and wash with deionized water 5 times. Add the washed colloidal product to 90 parts of deionized water, and ultrasonically disperse it for 20 min at a power of 200 W to obtain graphene oxide sheet hydrogel; mix 10 parts of graphene oxide sheet hydrogel with ethylene glycol according to a volume ratio of 1:40, ultrasonically disperse it for 20 min at a power of 200 W, then add 4 parts of stannous chloride dihydrate to the obtained sol, reflux and stir the resulting reactants at 120 °C for 1 h, with a stirring speed of 60 rpm. Then, centrifuge to separate the unreacted tin salt at a rotation speed of 5000 rpm, wash the obtained precipitate 4 times with deionized water to prepare a composite; mix 0.6 part of the composite with 10 parts of deionized water, ultrasonically treat it at 200 W for 15 min, then add 0.2 part of an aqueous solution of sodium dodecylbenzenesulfonate with a concentration of 50 mg / ml to the graphene oxide dispersion, and stir at a rotation speed of 10000 rmp for 30 min to obtain a foam; place the foam at 80 °C for a reduction reaction for 6 h, and then naturally cool it to 25 °C to obtain a mixed hydrogel. Soak and wash the mixed hydrogel with 1 vol% ethanol aqueous solution for 24 h, with a solid-liquid ratio of 1:5, to obtain the washed mixed hydrogel; take out the washed mixed hydrogel, place it at -45 °C for freezing treatment for 2 h, then take it out and heat it up to 25 °C to melt it, and dry it at normal temperature and pressure for 5 h to prepare an aerogel with a thickness of 0.1 cm; under the protection of nitrogen gas, place the obtained aerogel in a tubular furnace at 700 °C and heat it for 1.5 h, take it out and cool it to room temperature; mix 20 vol% ammonia water solution and 90 vol% ethanol aqueous solution according to a volume ratio of 6:1 to obtain a self-made modified solution; spray-modify the aerogel for 45 min by high-pressure gas-assisted microatomization, with a spray particle size of 40 μm and a spray flow rate of 80 ml / min, to prepare a modified composite aerogel as the inner layer; (3) Immerse the prepared inner layer into the mixed wax solution, with the impregnation amounts being 3 g / m 2 , respectively. After impregnating for 4 min, dry it at 35 °C for 45 min, and then place it in an environment with a relative humidity of 50% and a temperature of 25 °C for 24 h to obtain a multi-layer packaging bag material containing tin; perform color printing and bag making on the multi-layer packaging bag material containing tin to obtain a waterproof tin packaging bag.

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