A water-resistant and moisture-proof packaging film and its preparation process

Abstract

The present invention relates to the technical field of packaging films, specifically to a water-resistant and moisture-proof packaging film and a preparation process thereof. The scheme uses polyvinyl alcohol as the main material, adds polyethylene glycol, glycerol, dialdehyde starch, starch containing epoxy groups, crosslinking agent and citric acid and other substances, casts into a film, and dries to form a polyvinyl alcohol packaging film. In order to improve the comprehensive performance of the polyvinyl alcohol film, the scheme introduces substances such as polyethylene glycol and crosslinking agent. On the one hand, polyethylene glycol and polyvinyl alcohol have good compatibility. On the other hand, polyethylene glycol can enhance the mechanical properties of the product and improve the tensile strength. At the same time, in order to further improve the water resistance of the product, the scheme also introduces dialdehyde starch, and uses aldehyde groups and hydroxyl groups in the system to crosslink to form a network structure to increase the crosslinking density. The prepared polyvinyl alcohol packaging film not only has excellent moisture-proof and water-resistant properties, but also has high practicality and can be widely used in food packaging, pharmaceutical packaging and other fields.

Description

Technical Field

[0001] The invention relates to the technical field of packaging films, in particular to a water-resistant and moisture-proof packaging film and a preparation process thereof. Background Art

[0002] Polyvinyl alcohol (PVA) is a semi-crystalline polymer formed by the alcoholysis of polyvinyl acetate. PVA has excellent film-forming ability and is usually prepared into films by a casting method. It has the properties of being environmentally friendly, non-toxic, pollution-free, and completely biodegradable. PVA has excellent film-forming properties, chemical stability, and biocompatibility, and has become one of the widely used functional membrane materials.

[0003] However, due to the presence of a large number of hydroxyl groups on the PVA molecular chain, the PVA film is very easy to swell or even dissolve in water, and the mechanical properties of the PVA film are slightly insufficient. These defects limit the application of the PVA film. Therefore, based on this situation, the present application discloses a water-resistant and moisture-proof packaging film and its preparation process to solve this technical problem. Summary of the invention

[0004] The object of the present invention is to provide a water-resistant and moisture-proof packaging film and a preparation process thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A preparation process of a water-resistant and moisture-proof packaging film comprises the following steps:

[0007] Step (1): mixing polyethylene glycol and deionized water, adding polyethylene glycol glycidyl ether, and stirring evenly to obtain a polyethylene glycol solution;

[0008] Step (2): mixing polyvinyl alcohol and deionized water, stirring until fully swollen, and continuing to stir in an oil bath at 90 to 95° C. for 30 to 40 minutes to obtain a polyvinyl alcohol aqueous solution;

[0009] Add glycerol to the polyvinyl alcohol aqueous solution, stir for 1 to 2 hours, then add the polyethylene glycol solution prepared in step (1), dialdehyde starch and starch containing epoxy groups, continue stirring for 1 to 2 hours, add a cross-linking agent and citric acid, continue stirring for 1 to 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0010] In a more optimized solution, in step (2), the amounts of the components used are: by mass: 100-105 parts of polyvinyl alcohol, 25-28 parts of glycerol, 20-25 parts of polyethylene glycol, 3-5 parts of dialdehyde starch, 4-6 parts of starch containing epoxy groups, 25-28 parts of cross-linking agent, and 25-35 parts of citric acid.

[0011] In a more optimized solution, in step (2), the mass concentration of the polyethylene glycol solution is 1-1.5%; the amount of the polyethylene glycol glycidyl ether is 10-15wt% of the total mass of the polyethylene glycol; and the mass concentration of the polyvinyl alcohol aqueous solution is 4-5%.

[0012] In a more optimized solution, the cross-linking agent is any one or more of vanillin or cinnamaldehyde.

[0013] In a more optimized solution, in step (2), the preparation steps of starch containing epoxy groups are:

[0014] S1: octadecyl primary amine and m-phenylenediamine are mixed, dimethyl sulfoxide is dissolved, acetic acid is added, and stirred evenly to obtain an amine solution;

[0015] S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 80-85°C until dissolved, cool to 45-50°C, add amine solution, react for 6-8h under nitrogen environment, then heat to 60-65°C, add epichlorohydrin, keep warm and react for 2-3h, cool to room temperature after the reaction, precipitate the product, filter and wash, and vacuum dry at 50-55°C to obtain starch containing epoxy groups.

[0016] In a more optimized solution, the molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:(0.5-0.6); the molar ratio of the octadecyl primary amine to meta-phenylenediamine is 1:2; the amount of acetic acid used is 4-5wt% of the mass of the dialdehyde starch; and the molar ratio of meta-phenylenediamine to epichlorohydrin is 1:(1-1.1).

[0017] In a more optimized scheme, in step (1), the preparation steps of polyethylene glycol glycidyl ether are: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 40-45°C, epichlorohydrin is added, the temperature is further increased to 50-55°C, sodium hydroxide is added, the reaction is kept warm for 1.5-2.5h, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether.

[0018] In a more optimized solution, the molar ratio of the polyethylene glycol, epichlorohydrin, sodium hydroxide and tetra-n-butylammonium chloride is 1:(1-1.2):(2-2.1):(0.03-0.04).

[0019] A more optimized solution is a packaging film prepared according to any one of the above-mentioned processes for preparing a water-resistant and moisture-proof packaging film.

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

[0021] The present invention discloses a water-resistant and moisture-proof packaging film and a preparation process thereof. The present invention uses polyvinyl alcohol as a main ingredient, and adds polyethylene glycol, glycerol, dialdehyde starch, starch containing epoxy groups, a cross-linking agent, citric acid and other substances, and casts the film, and dries the film to form a polyvinyl alcohol packaging film. The polyvinyl alcohol packaging film not only has excellent moisture-proof and water-resistant properties, but also because of the introduction of polyethylene glycol and other substances, the mechanical strength of the packaging film is also improved, the oxygen barrier performance is also very excellent, the practicality is high, and it can be widely used in food packaging, pharmaceutical packaging and other fields.

[0022] Polyvinyl alcohol is biodegradable and has good biocompatibility, so it is mostly used in the field of food packaging. However, since it contains multiple hydroxyl groups on its molecular chain, it can form hydrogen bonds with water molecules, resulting in poor water resistance and strength that cannot meet actual needs. Therefore, in order to improve the comprehensive performance of polyvinyl alcohol film, the solution introduces substances such as polyethylene glycol and cross-linking agents. On the one hand, polyethylene glycol and polyvinyl alcohol have good compatibility. On the other hand, polyethylene glycol can enhance the mechanical properties of the product and improve the tensile strength. At the same time, in order to further improve the water resistance of the product, the solution also introduces dialdehyde starch, which uses aldehyde groups and hydroxyl groups in the system to cross-link to form a network structure and increase the cross-linking density.

[0023] On this basis, the scheme uses part of the starch containing epoxy groups to replace the dialdehyde starch. The scheme first uses the aldehyde group and amino group reaction of the dialdehyde starch to graft octadecyl primary amine and metaphenylenediamine onto the dialdehyde starch. The grafting of octadecyl primary amine introduces a long-chain alkyl group, which can improve the hydrophobicity of the dialdehyde starch. Adding it to the polyvinyl alcohol system can also improve the water resistance of the packaging film. Another scheme uses metaphenylenediamine as a bridge and performs epoxidation modification through the reaction of amino and epoxy groups to obtain starch containing epoxy groups. In this process, the scheme limits the molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution to 1: (0.5-0.6) to limit the grafting amount of the amino group. On the one hand, it is to avoid that the excessive grafting amount affects the compatibility of the component with the system. On the other hand, the aldehyde group is still retained in the starch containing the epoxy group, and the aldehyde group can be used to cross-link with the hydroxyl group in the system, thereby improving the cross-linking degree of the system and further improving the comprehensive performance of the packaging film.

[0024] The scheme also introduces polyethylene glycol glycidyl ether. During the preparation process of the scheme, it is specified that "the molar ratio of the polyethylene glycol, epichlorohydrin, sodium hydroxide and tetra-n-butylammonium chloride is 1: (1-1.2): (2-2.1): (0.03-0.04)". At this time, the product prepared is a single-end epoxy graft. The introduction of this substance can also improve the water resistance of the product. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the following examples, the crosslinking agent is cinnamaldehyde; the molecular weight of polyethylene glycol is 600; the polyvinyl alcohol is PVA2488; the water content of dialdehyde starch is 9%, the aldehyde content is 23.1%, and it is purchased from Tai'an Jinshan Modified Starch Co., Ltd.

[0027] Embodiment 1: A process for preparing a water-resistant and moisture-proof packaging film, comprising the following steps:

[0028] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0029] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 40°C, epichlorohydrin is added, the temperature is further raised to 50°C, sodium hydroxide is added, the temperature is kept to react for 2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0030] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 40 minutes in a 90° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0031] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 1 hour, then add the polyethylene glycol solution prepared in step (1), 5 parts of dialdehyde starch and 4 parts of starch containing epoxy groups, continue stirring for 2 hours, add 25 parts of cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0032] The preparation steps of starch containing epoxy groups are as follows:

[0033] S1: octadecyl primary amine and m-phenylenediamine are mixed, dimethyl sulfoxide is dissolved, acetic acid is added, and stirred evenly to obtain an amine solution;

[0034] S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 80°C until dissolved, cool to 45°C, add amine solution, react for 8 hours under nitrogen environment, then heat to 60°C, add epichlorohydrin, keep warm and react for 3 hours, cool to room temperature after the reaction, precipitate the product, filter and wash, and vacuum dry at 55°C to obtain starch containing epoxy groups.

[0035] The molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:0.6; the molar ratio of the octadecyl primary amine to metaphenylenediamine is 1:2; the amount of acetic acid used is 4.5wt% of the mass of the dialdehyde starch; the molar ratio of metaphenylenediamine to epichlorohydrin is 1:1.1.

[0036] Embodiment 2: A process for preparing a water-resistant and moisture-proof packaging film, comprising the following steps:

[0037] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0038] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 45°C, epichlorohydrin is added, the temperature is further raised to 55°C, sodium hydroxide is added, the temperature is kept to react for 2 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0039] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 35 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0040] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 1.5 hours, then add the polyethylene glycol solution prepared in step (1), 4 parts of dialdehyde starch and 5 parts of starch containing epoxy groups, continue stirring for 1.5 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 1.5 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0041] The preparation steps of starch containing epoxy groups are as follows:

[0042] S1: octadecyl primary amine and m-phenylenediamine are mixed, dimethyl sulfoxide is dissolved, acetic acid is added, and stirred evenly to obtain an amine solution;

[0043] S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 85°C until dissolved, cool to 50°C, add amine solution, react for 7 hours under nitrogen environment, then heat to 65°C, add epichlorohydrin, keep warm and react for 2.5 hours. After the reaction is completed, cool to room temperature, precipitate the product, filter and wash, and vacuum dry at 55°C to obtain starch containing epoxy groups.

[0044] The molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:0.6; the molar ratio of the octadecyl primary amine to metaphenylenediamine is 1:2; the amount of acetic acid used is 4.5wt% of the mass of the dialdehyde starch; the molar ratio of metaphenylenediamine to epichlorohydrin is 1:1.1.

[0045] Embodiment 3: A process for preparing a water-resistant and moisture-proof packaging film, comprising the following steps:

[0046] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0047] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 45°C, epichlorohydrin is added, the temperature is further raised to 55°C, sodium hydroxide is added, the temperature is kept to react for 2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0048] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 30 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0049] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 2 hours, then add the polyethylene glycol solution prepared in step (1), 3 parts of dialdehyde starch and 6 parts of starch containing epoxy groups, continue stirring for 2 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0050] The preparation steps of starch containing epoxy groups are as follows:

[0051] S1: octadecyl primary amine and m-phenylenediamine are mixed, dimethyl sulfoxide is dissolved, acetic acid is added, and stirred evenly to obtain an amine solution;

[0052] S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 85°C until dissolved, cool to 45°C, add amine solution, react for 8 hours under nitrogen environment, then heat to 65°C, add epichlorohydrin, keep warm and react for 2 hours, cool to room temperature after the reaction, precipitate the product, filter and wash, and vacuum dry at 55°C to obtain starch containing epoxy groups.

[0053] The molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:0.6; the molar ratio of the octadecyl primary amine to metaphenylenediamine is 1:2; the amount of acetic acid used is 4.5wt% of the mass of the dialdehyde starch; the molar ratio of metaphenylenediamine to epichlorohydrin is 1:1.1.

[0054] Comparative Example 1: Compared with Example 3, starch containing epoxy groups was not added in Comparative Example 1, and the other steps remained unchanged.

[0055] A preparation process of a water-resistant and moisture-proof packaging film comprises the following steps:

[0056] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0057] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 45°C, epichlorohydrin is added, the temperature is further raised to 55°C, sodium hydroxide is added, the temperature is kept to react for 2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0058] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 30 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0059] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 2 hours, then add the polyethylene glycol solution prepared in step (1) and 9 parts of dialdehyde starch, continue stirring for 2 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0060] Comparative Example 2: Compared with Example 3, the preparation process of starch containing epoxy groups in Comparative Example 2 was adjusted, and the other steps remained unchanged.

[0061] A preparation process of a water-resistant and moisture-proof packaging film comprises the following steps:

[0062] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0063] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 45°C, epichlorohydrin is added, the temperature is further raised to 55°C, sodium hydroxide is added, the temperature is kept to react for 2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0064] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 30 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0065] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 2 hours, then add the polyethylene glycol solution prepared in step (1), 3 parts of dialdehyde starch and 6 parts of starch containing epoxy groups, continue stirring for 2 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0066] The preparation steps of starch containing epoxy groups are as follows:

[0067] S1: Mix and dissolve m-phenylenediamine and dimethyl sulfoxide, then add acetic acid and stir evenly to obtain an amine solution;

[0068] S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 85°C until dissolved, cool to 45°C, add amine solution, react for 8 hours under nitrogen environment, then heat to 65°C, add epichlorohydrin, keep warm and react for 2 hours, cool to room temperature after the reaction, precipitate the product, filter and wash, and vacuum dry at 55°C to obtain starch containing epoxy groups.

[0069] The molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:0.6; the amount of the acetic acid used is 4.5wt% of the mass of the dialdehyde starch; and the molar ratio of the meta-phenylenediamine to epichlorohydrin is 1:1.1.

[0070] Comparative Example 3: Compared with Example 3, dialdehyde starch and related substances were not added in Comparative Example 3, and the other steps remained unchanged.

[0071] A preparation process of a water-resistant and moisture-proof packaging film comprises the following steps:

[0072] Step (1): 25 parts of polyethylene glycol and deionized water are mixed, polyethylene glycol glycidyl ether is added, and the mixture is stirred evenly to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%; the amount of the polyethylene glycol glycidyl ether is 10wt% of the total mass of the polyethylene glycol.

[0073] The preparation steps of polyethylene glycol glycidyl ether are as follows: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 45°C, epichlorohydrin is added, the temperature is further raised to 55°C, sodium hydroxide is added, the temperature is kept to react for 2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether. The molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide, and tetra-n-butylammonium chloride is 1:1.2:2.1:0.03.

[0074] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 30 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0075] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 2 hours, then add the polyethylene glycol solution prepared in step (1), continue stirring for 2 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0076] Comparative Example 4: Compared with Example 3, in Comparative Example 4, dialdehyde starch and related substances were not added, and polyethylene glycol glycidyl ether was not added, and the other steps remained unchanged.

[0077] A preparation process of a water-resistant and moisture-proof packaging film comprises the following steps:

[0078] Step (1): 26 parts of polyethylene glycol and deionized water are mixed and stirred to obtain a polyethylene glycol solution; the mass concentration of the polyethylene glycol solution is 1%.

[0079] Step (2): 100 parts of polyvinyl alcohol and deionized water are mixed, stirred until fully swollen, and stirred for 30 minutes in a 95° C. oil bath to obtain a polyvinyl alcohol aqueous solution; the mass concentration of the polyvinyl alcohol aqueous solution is 4%.

[0080] Add 25 parts of glycerol to the polyvinyl alcohol aqueous solution, stir for 2 hours, then add the polyethylene glycol solution prepared in step (1), continue stirring for 2 hours, add 25 parts of a cross-linking agent and 28 parts of citric acid, continue stirring for 2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film.

[0081] Detection experiment:

[0082] The packaging films prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were cut into dumbbell-shaped samples according to the method disclosed in ASTM882-95, and their tensile strength was tested at a tensile speed of 50 mm / min. According to the method disclosed in GB / T1034-2008, the films were dried and weighed, and then placed in an environment of 25°C and a relative humidity of 50%, and then taken out and weighed after being placed for 24 hours, and the water absorption was tested and calculated.

[0083] A film with a diameter of 12 cm was taken to test the oxygen permeability coefficient of the film. The instrument was evacuated before the experiment. The test conditions were: 23° C. and 50% relative humidity.

[0084] project Tensile strength MPa Water absorption % <![CDATA[Oxygen permeability coefficient cm 3 ×cm / (cm 2 ×s×Pa)]]> Example 1 26.8 7.6％ <![CDATA[3.78×10 -6 ]]> Example 2 27.1 7.1％ <![CDATA[3.73×10 -6 ]]> Example 3 27.5 6.5％ <![CDATA[3.69×10 -6 ]]> Comparative Example 1 26.4 11.8％ <![CDATA[4.27×10 -6 ]]> Comparative Example 2 26.9 9.2％ <![CDATA[3.96×10 -6 ]]> Comparative Example 3 24.3 13.4％ <![CDATA[4.92×10 -6 ]]> Comparative Example 4 23.7 14.3％ <![CDATA[5.08×10 -6 ]]>

[0085] Conclusion: This scheme discloses a water-resistant and moisture-proof packaging film and its preparation process. The scheme uses polyvinyl alcohol as the main ingredient, and adds polyethylene glycol, glycerol, dialdehyde starch, starch containing epoxy groups, cross-linking agent and citric acid and other substances, and casts the film and dries to form a polyvinyl alcohol packaging film. The polyvinyl alcohol packaging film not only has excellent moisture-proof and water-resistant properties, but also due to the introduction of polyethylene glycol and other substances, the mechanical strength of the packaging film is also improved, the oxygen barrier performance is also very excellent, and the practicability is high. It can be widely used in food packaging, pharmaceutical packaging and other fields.

[0086] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for preparing a water-resistant and moisture-proof packaging film, characterized in that: The following steps are involved: Step (1): mixing polyethylene glycol and deionized water, adding polyethylene glycol glycidyl ether, and stirring evenly to obtain a polyethylene glycol solution; Step (2): Mix polyvinyl alcohol and deionized water, stir until fully swollen, and continue stirring for 30 to 40 minutes in an oil bath at 90 to 95° C. to obtain a polyvinyl alcohol aqueous solution; Add glycerol to the polyvinyl alcohol aqueous solution, stir for 1-2 hours, then add the polyethylene glycol solution prepared in step (1), dialdehyde starch and epoxy-containing starch, continue stirring for 1-2 hours, add a cross-linking agent and citric acid, continue stirring for 1-2 hours to obtain a casting solution, cast into a film, and dry to obtain a packaging film; In step (2), the preparation steps of starch containing epoxy groups are: S1: octadecyl primary amine and m-phenylenediamine are mixed, dimethyl sulfoxide is dissolved, acetic acid is added, and stirred evenly to obtain an amine solution; S2: Mix dialdehyde starch and dimethyl sulfoxide, stir at 80-85°C until dissolved, cool to 45-50°C, add amine solution, react for 6-8 hours under nitrogen environment, then heat to 60-65°C, add epichlorohydrin, keep warm and react for 2-3 hours, cool to room temperature after the reaction, precipitate the product, filter and wash, and vacuum dry at 50-55°C to obtain starch containing epoxy groups.

2. The process for preparing a water-resistant and moisture-proof packaging film according to claim 1, characterized in that: In step (2), the amount of each component is: by mass, 100-105 parts of polyvinyl alcohol, 25-28 parts of glycerol, 20-25 parts of polyethylene glycol, 3-5 parts of dialdehyde starch, 4-6 parts of starch containing epoxy groups, 25-28 parts of cross-linking agent, and 25-35 parts of citric acid.

3. The process for preparing a water-resistant and moisture-proof packaging film according to claim 1, characterized in that: In step (2), the mass concentration of the polyethylene glycol solution is 1-1.5%; the amount of the polyethylene glycol glycidyl ether is 10-15wt% of the total mass of the polyethylene glycol; and the mass concentration of the polyvinyl alcohol aqueous solution is 4-5%.

4. The process for preparing a water-resistant and moisture-proof packaging film according to claim 1, characterized in that: The cross-linking agent is any one or more of vanillin or cinnamaldehyde.

5. The process for preparing a water-resistant and moisture-proof packaging film according to claim 4, characterized in that: The molar ratio of the aldehyde group of the dialdehyde starch to the amino group in the amine solution is 1:(0.5-0.6); the molar ratio of the octadecyl primary amine to meta-phenylenediamine is 1:2; the amount of acetic acid used is 4-5wt% of the mass of the dialdehyde starch; and the molar ratio of meta-phenylenediamine to epichlorohydrin is 1:(1-1.1).

6. The process for preparing a water-resistant and moisture-proof packaging film according to claim 1, characterized in that: In step (1), the preparation steps of polyethylene glycol glycidyl ether are: polyethylene glycol and tetra-n-butylammonium chloride are mixed, heated to 40-45°C, epichlorohydrin is added, the temperature is further increased to 50-55°C, sodium hydroxide is added, the reaction is kept warm for 1.5-2.5 hours, cooled to room temperature, and the product is collected to obtain polyethylene glycol glycidyl ether.

7. The process for preparing a water-resistant and moisture-proof packaging film according to claim 6, characterized in that: The molar ratio of the polyethylene glycol, epichlorohydrin, sodium hydroxide and tetra-n-butylammonium chloride is 1:(1-1.2):(2-2.1):(0.03-0.04).

8. A packaging film prepared according to the process for preparing a water-resistant and moisture-proof packaging film according to any one of claims 1 to 7.