Preparation method of oxygen and water vapor barrier packaging bag

Abstract

The invention belongs to the technical field of packaging bags, and discloses a method for preparing a packaging bag that blocks oxygen and water vapor. The preparation method comprises the following steps: the packaging bag that blocks oxygen and water vapor comprises a first barrier layer, a bag substrate layer, and a second barrier layer that are sequentially stacked; the bag substrate layer is composed of polylactic acid; the first barrier layer is obtained by mixing and drying water-based hydroxy acrylic resin, epoxy resin, a first modified filler, and an auxiliary agent; the second barrier layer is obtained by mixing and drying water-based hydroxy acrylic resin, epoxy resin, a second modified filler, and an auxiliary agent; the first modified filler is obtained by mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, a silane coupling agent, water, and glycerol; the second modified filler is obtained by mixing nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, a silane coupling agent, and water, and carbon nanotubes are also added when adding nano sodium silicate during the preparation process of the first modified filler. The packaging bag has a good effect of blocking oxygen and water vapor.

Description

[0001] This application is a divisional application of an application with an application date of May 24, 2024, application number 202410649713.4, and invention name “A method for preparing a packaging bag that blocks oxygen and water vapor”. Technical Field

[0002] The invention belongs to the technical field of packaging bags, and in particular relates to a method for preparing a packaging bag capable of blocking oxygen and water vapor. Background Art

[0003] Polymer materials are widely used in the packaging field, such as various packaging bags. However, these polymer materials have poor degradation performance and are not very environmentally friendly. Polylactic acid is an environmentally friendly material, so it is gradually being promoted for making packaging bags. However, when polylactic acid is directly used as a packaging bag, its corresponding oxygen and water vapor barrier properties are poor, which is not conducive to the preservation of some foods or medicines.

[0004] In addition, the existing polylactic acid has poor tensile strength, which also limits the use of polylactic acid packaging bags.

[0005] Therefore, there is an urgent need to provide a new polylactic acid packaging bag, which not only has good oxygen barrier properties, but also has good water vapor barrier properties. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for preparing an oxygen- and water vapor-barrier packaging bag. The oxygen- and water vapor-barrier packaging bag prepared by the preparation method of the present invention has good barrier properties to both oxygen and water vapor, and the substrate of the oxygen- and water vapor-barrier packaging bag is polylactic acid, which makes the oxygen- and water vapor-barrier packaging bag of the present invention have good degradation effect and is an environmentally friendly packaging bag.

[0007] The oxygen and water vapor barrier packaging bag of the present invention comprises a first barrier layer, a bag substrate layer, and a second barrier layer which are sequentially stacked. The first barrier layer uses water-based hydroxy acrylic resin and epoxy resin as the main film-forming material. The filler is modified so that the modified filler (first modified filler and second modified filler) can be evenly dispersed in the water-based hydroxy acrylic resin and epoxy resin. After drying and curing, a uniform network cross-linking structure is formed. The first modified filler is obtained by modifying nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent, water, and glycerol. Polyethylene oxide performs surface modification on nano sodium silicate and nano silicon dioxide. When the silane coupling agent is hydrolyzed in water, the nano sodium silicate and nano silicon dioxide can be evenly dispersed, further improving the compatibility with the water-based hydroxy acrylic resin and epoxy resin, so that the structure of the first barrier layer is stable and the first modified filler can be evenly dispersed. The second modified filler is obtained by modifying nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent, and water. By modifying nano molybdenum disulfide and nano silicon dioxide with polyethylene glycol, silane coupling agent and water, the second modified filler and the resin material are evenly dispersed, and a uniform network structure can be formed when dried and cured. By using the first barrier layer and the second barrier layer in combination, the bag substrate layer composed of polylactic acid has a good effect of blocking oxygen and water vapor. By using the first barrier layer and the second barrier layer in combination, the oxygen and water vapor barrier packaging bag also has good mechanical strength, which is conducive to the promotion and application of oxygen and water vapor barrier packaging bags.

[0008] When preparing the second modified filler, chitosan acid solution is also added, which not only improves the antibacterial effect of the second barrier layer, but also makes full use of the polyhydroxy characteristics of chitosan to promote the dispersion of nano-molybdenum disulfide and nano-silicon dioxide, so that the compatibility of the second modified filler with water-based hydroxy acrylic resin and epoxy resin is significantly improved. When the second barrier layer is dried and cured, the hydroxyl substance component can also enhance the network structure strength of the second barrier layer.

[0009] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0010] The preparation method of the oxygen and water vapor barrier packaging bag comprises the following steps:

[0011] The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag base material layer, and a second barrier layer which are stacked in sequence;

[0012] The bag base material layer is composed of polylactic acid;

[0013] The preparation process of the first barrier layer includes: mixing water-based hydroxy acrylic resin, epoxy resin, first modified filler and additives to obtain a first barrier slurry, and then coating it on one side of the bag substrate layer, and drying to obtain the first barrier layer;

[0014] The preparation process of the second barrier layer includes: mixing water-based hydroxy acrylic resin, epoxy resin, second modified filler and additives to obtain a second barrier slurry, and then coating it on the other side of the bag substrate layer, and drying to obtain the second barrier layer;

[0015] The preparation process of the first modified filler comprises: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent, water, and glycerol in a weight ratio of 1: (1-2): (0.5-2): (1.5-3): (5-20): (3-10) to obtain the first modified filler;

[0016] The preparation process of the second modified filler includes: stirring and mixing nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water in a weight ratio of 1: (0.5-2.5): (2-3.5): (5-15): (10-20) to obtain the second modified filler.

[0017] Preferably, chitosan acid solution is further added in the preparation process of the second modified filler, and the preparation process of the second modified filler comprises: mixing chitosan, organic acid and water in a weight ratio of 1: (0.5-2): (10-50) to obtain chitosan acid solution, and then adding nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water, stirring and mixing to obtain the second modified filler;

[0018] The weight ratio of the chitosan acid solution, nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water is (0.5-1.1):1:(1-2.5):(2-3.5):(5-15):(10-20).

[0019] Preferably, the organic acid includes at least one of citric acid and acetic acid.

[0020] Preferably, the preparation process of the first barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 30-50 parts of epoxy resin, 20-40 parts of first modified filler, and 3-8 parts of additives by weight to obtain a first barrier slurry, which is then coated on one side of the bag substrate layer and dried to obtain the first barrier layer.

[0021] Preferably, the preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 30-50 parts of epoxy resin, 15-45 parts of second modified filler, and 3-8 parts of additives to obtain a second barrier slurry, which is then coated on the other side of the bag substrate layer and dried to obtain the second barrier layer.

[0022] Preferably, the thickness of the bag base material layer is 10-30 μm, and more preferably, the thickness of the bag base material layer is 20-25 μm.

[0023] Preferably, the auxiliary agent includes isocyanate and at least one of diethylenetriamine, triethylenetetramine and diethylaminopropylamine.

[0024] Preferably, the weight ratio of isocyanate and at least one of diethylenetriamine, triethylenetetramine and diethylaminopropylamine in the auxiliary agent is (1.5-4):1.

[0025] Preferably, the auxiliary agent also includes polydimethylsiloxane and sodium dodecyl sulfate.

[0026] Preferably, the isocyanate is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate and lysine diisocyanate.

[0027] Preferably, when packaging food or medicine, the second barrier layer is in contact with the food or medicine, that is, the second barrier layer serves as an inner bag structure.

[0028] Preferably, when applying the first barrier slurry, the corresponding coating amount is 10-18 g / m 2 , further preferably, the corresponding coating amount is 16-18g / m 2 .

[0029] Preferably, after the first barrier slurry is applied, the drying temperature is 20-60° C. and the drying time is 24-72 hours. Sufficient drying time allows the film-forming material to fully solidify.

[0030] Preferably, when applying the second barrier slurry, the corresponding coating amount is 10-18 g / m 2 , further preferably, the corresponding coating amount is 16-18g / m 2 .

[0031] Preferably, after coating the second barrier slurry, the drying temperature is 20-60° C. and the drying time is 24-72 hours.

[0032] Preferably, when adding nano-sodium silicate, carbon nanotubes are also added in the preparation process of the first modified filler. The preparation method of the first modified filler of the present invention makes the carbon nanotubes have good dispersibility, thereby significantly improving the tensile properties of the packaging bag that blocks oxygen and water vapor.

[0033] Preferably, the mass ratio of the nano-sodium silicate to the carbon nanotubes is 1:(0.01-0.2), and more preferably 1:(0.05-0.1).

[0034] Preferably, the method for preparing the oxygen and water vapor barrier packaging bag comprises the following steps:

[0035] The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag base material layer, and a second barrier layer which are stacked in sequence;

[0036] The bag base material layer is composed of polylactic acid;

[0037] The preparation process of the first barrier layer comprises: mixing 50 parts of water-based hydroxy acrylic resin, 35-45 parts of epoxy resin, 25-40 parts of first modified filler, and 4-8 parts of auxiliary agent by weight to obtain a first barrier slurry, and then coating it on one side of the bag substrate layer, and drying to obtain the first barrier layer;

[0038] The preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 35-50 parts of epoxy resin, 20-45 parts of second modified filler, and 4-8 parts of auxiliary agent to obtain a second barrier slurry, and then coating it on the other side of the bag substrate layer, and drying to obtain the second barrier layer;

[0039] The preparation process of the first modified filler comprises: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent, water, and glycerol in a weight ratio of 1: (1.2-2): (0.8-2): (1.5-2.5): (8-15): (3-8) to obtain the first modified filler;

[0040] The preparation process of the second modified filler includes: mixing chitosan, organic acid and water in a weight ratio of 1: (0.5-2): (20-50) to obtain chitosan acid solution, then adding nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water, and stirring and mixing the chitosan acid solution, nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water in a weight ratio of (0.5-1.1): 1: (1-2.5): (2-3.5): (5-15): (10-20) to obtain the second modified filler.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] (1) The oxygen and water vapor barrier packaging bag of the present invention comprises a first barrier layer, a bag substrate layer, and a second barrier layer which are sequentially stacked. The first barrier layer uses water-based hydroxy acrylic resin and epoxy resin as the main film-forming material. The filler is modified so that the modified filler (first modified filler and second modified filler) can be uniformly dispersed in the water-based hydroxy acrylic resin and epoxy resin. After drying and curing, a uniform network cross-linking structure is formed. The first modified filler is obtained by modifying nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent, water, and glycerol. Polyethylene oxide performs surface modification on nano sodium silicate and nano silicon dioxide. When the silane coupling agent is hydrolyzed in water, the nano sodium silicate and nano silicon dioxide can be uniformly dispersed, further improving the compatibility with the water-based hydroxy acrylic resin and epoxy resin, so that the structure of the first barrier layer is stable and the first modified filler can be uniformly dispersed. The second modified filler is obtained by modifying nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent, and water. By modifying nano molybdenum disulfide and nano silicon dioxide with polyethylene glycol, silane coupling agent and water, the second modified filler and the resin material are evenly dispersed, and a uniform network structure can be formed when dried and cured. By using the first barrier layer and the second barrier layer in combination, the bag substrate layer composed of polylactic acid has a good effect of blocking oxygen and water vapor. By using the first barrier layer and the second barrier layer in combination, the oxygen and water vapor barrier packaging bag also has good mechanical strength, which is conducive to the promotion and application of oxygen and water vapor barrier packaging bags.

[0043] (2) When preparing the second modified filler, chitosan acid solution is also added, which not only improves the antibacterial effect of the second barrier layer, but also makes full use of the polyhydroxy characteristics of chitosan to promote the dispersion of nano-molybdenum disulfide and nano-silicon dioxide, so that the compatibility of the second modified filler with water-based hydroxy acrylic resin and epoxy resin is significantly improved. When the second barrier layer is dried and cured, the hydroxyl substance component can also enhance the network structure strength of the second barrier layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of the oxygen and water vapor barrier packaging bag prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0045] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0046] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0047] Example 1

[0048] The preparation method of the oxygen and water vapor barrier packaging bag comprises the following steps:

[0049] The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag body substrate layer, and a second barrier layer which are stacked in sequence; Figure 1 This is a schematic structural diagram of an oxygen and water vapor barrier packaging bag prepared in Example 1 of the present invention, wherein 100 represents a first barrier layer, 200 represents a bag body substrate layer, and 300 represents a second barrier layer.

[0050] The bag base material layer is composed of polylactic acid, and the thickness of the bag base material layer is 20 μm;

[0051] The preparation process of the first barrier layer is as follows: by weight, 50 parts of water-based hydroxy acrylic resin, 35 parts of epoxy resin (bisphenol A type epoxy resin), 30 parts of the first modified filler, and 6 parts of additives (2 parts of diethylenetriamine, 3 parts of hexamethylene diisocyanate, 0.5 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate) are mixed, and the stirring speed during mixing is 500 rpm, and the mixing time is 30 minutes to obtain the first barrier slurry, which is then coated (the coating amount is 17g / m 2 ) on one side of the bag substrate layer, drying at a temperature of 40° C. for 36 hours to obtain a first barrier layer;

[0052] The preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 40 parts of epoxy resin (bisphenol F type epoxy resin), 30 parts of the second modified filler, and 6.2 parts of additives (2.2 parts of diethylenetriamine, 3 parts of hexamethylene diisocyanate, 0.5 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate), stirring at a speed of 500 rpm for 30 minutes to obtain a second barrier slurry, and then coating (coating amount is 18g / m 2 ) on the other side of the bag substrate layer, drying at a temperature of 40° C. for 36 hours to obtain a second barrier layer;

[0053] The preparation process of the first modified filler includes: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent KH550, water, and glycerol in a weight ratio of 1:1.3:0.9:1.8:10:5, at a stirring speed of 400 rpm, and a mixing time of 20 minutes to obtain the first modified filler;

[0054] The preparation process of the second modified filler includes: stirring and mixing nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent KH560, and water in a weight ratio of 1:1.5:3.0:12:15, at a stirring speed of 400 rpm, and a mixing time of 25 minutes to obtain the second modified filler.

[0055] Example 2

[0056] The preparation method of the oxygen and water vapor barrier packaging bag comprises the following steps:

[0057] The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag body substrate layer, and a second barrier layer which are stacked in sequence;

[0058] The bag base material layer is composed of polylactic acid, and the thickness of the bag base material layer is 25 μm;

[0059] The preparation process of the first barrier layer is as follows: by weight, 50 parts of water-based hydroxy acrylic resin, 40 parts of epoxy resin (bisphenol A type epoxy resin), 35 parts of the first modified filler, and 7 parts of additives (2 parts of diethylaminopropylamine, 3.5 parts of hexamethylene diisocyanate, 1.0 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate) are mixed, and the stirring speed during mixing is 400 rpm, and the mixing time is 35 minutes to obtain the first barrier slurry, which is then coated (the coating amount is 16g / m 2 ) on one side of the bag substrate layer, drying at a temperature of 45° C. for 30 hours to obtain a first barrier layer;

[0060] The preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 38 parts of epoxy resin (bisphenol A epoxy resin), 35 parts of the second modified filler, and 6.2 parts of additives (2.2 parts of triethylenetetramine, 3 parts of hexamethylene diisocyanate, 0.5 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate), stirring at a speed of 550 rpm for 25 minutes to obtain a second barrier slurry, and then coating (coating amount of 17 g / m 2 ) on the other side of the bag substrate layer, drying at a temperature of 40° C. for 36 hours to obtain a second barrier layer;

[0061] The preparation process of the first modified filler includes: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent KH550, water, and glycerol in a weight ratio of 1:1.8:1.0:1.9:14:6 at a stirring speed of 450 rpm for 20 minutes to obtain the first modified filler;

[0062] The preparation process of the second modified filler includes: stirring and mixing nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent KH550, and water in a weight ratio of 1:1.8:2.5:10:18, at a stirring speed of 450 rpm, and for a mixing time of 25 minutes to obtain the second modified filler.

[0063] Example 3

[0064] The preparation method of the oxygen and water vapor barrier packaging bag comprises the following steps:

[0065] The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag body substrate layer, and a second barrier layer which are stacked in sequence;

[0066] The bag base material layer is composed of polylactic acid, and the thickness of the bag base material layer is 20 μm;

[0067] The preparation process of the first barrier layer is as follows: by weight, 50 parts of water-based hydroxy acrylic resin, 35 parts of epoxy resin (bisphenol A type epoxy resin), 30 parts of the first modified filler, and 6 parts of additives (2 parts of diethylenetriamine, 3 parts of hexamethylene diisocyanate, 0.5 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate) are mixed, and the stirring speed during mixing is 500 rpm, and the mixing time is 30 minutes to obtain the first barrier slurry, which is then coated (the coating amount is 17g / m 2 ) on one side of the bag substrate layer, drying at a temperature of 40° C. for 36 hours to obtain a first barrier layer;

[0068] The preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 40 parts of epoxy resin (bisphenol F type epoxy resin), 30 parts of the second modified filler, and 6.2 parts of additives (2.2 parts of diethylenetriamine, 3 parts of hexamethylene diisocyanate, 0.5 parts of polydimethylsiloxane, and 0.5 parts of sodium dodecyl sulfonate), stirring at a speed of 500 rpm for 30 minutes to obtain a second barrier slurry, and then coating (coating amount is 18g / m 2 ) on the other side of the bag substrate layer, drying at a temperature of 40° C. for 36 hours to obtain a second barrier layer;

[0069] The preparation process of the first modified filler includes: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent KH550, water, and glycerol in a weight ratio of 1:1.3:0.9:1.8:10:5, at a stirring speed of 400 rpm, and a mixing time of 20 minutes to obtain the first modified filler;

[0070] The preparation process of the second modified filler includes: mixing chitosan, acetic acid and water in a weight ratio of 1:1:40 to obtain chitosan acid solution, then adding nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water, and stirring and mixing chitosan acid solution, nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water in a weight ratio of 0.8:1:1.5:3.0:12:15, the stirring speed is 400 rpm, and the mixing time is 25 minutes to obtain the second modified filler.

[0071] Example 4

[0072] Compared with Example 1, the only difference of Example 4 is that, in addition to adding nano-sodium silicate, 0.08 parts of carbon nanotubes are also added in Example 4, and the other components and processes are the same as those in Example 1.

[0073] Comparative Example 1

[0074] Compared with Example 1, the only difference of Comparative Example 1 is that, in the preparation process of the first barrier layer and the second barrier layer, an equal amount of water-based hydroxy acrylic resin is used instead of epoxy resin, and the other components and processes are the same as those of Example 1.

[0075] Comparative Example 2

[0076] Compared with Example 1, the only difference of Comparative Example 2 is that, in the preparation process of the first modified filler, an equal amount of polyethylene glycol is used instead of polyethylene oxide, and the other components and processes are the same as those of Example 1.

[0077] Comparative Example 3

[0078] Compared with Example 1, the difference of Comparative Example 3 is that, in the preparation process of the second modified filler in Comparative Example 3, an equal amount of nano-silicon dioxide is used instead of nano-molybdenum disulfide, and the other components and processes are the same as those in Example 1.

[0079] Product effect testing

[0080] 1. Oxygen and water vapor barrier performance test

[0081] The oxygen and water vapor barrier packaging bags prepared in Examples 1 and 3, as well as the packaging bags prepared in Comparative Examples 1-3, were placed at a relative humidity of 85% and a temperature of 25° C. for 24 hours and 72 hours, and the oxygen permeability and water vapor permeability of the packaging bags were tested. The results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] It can be seen from Table 1 that the oxygen and water vapor barrier packaging bags prepared in Examples 1 and 3 of the present invention have significantly better barrier effects on oxygen and water vapor than Comparative Examples 1 to 3. It can be seen from the results of Examples 1 and 3 that in the preparation process of the second modified filler, the use of chitosan acid solution can further significantly improve the barrier effect on oxygen and water vapor.

[0086] It can be seen from the results of Example 1 and Comparative Example 1 that water-based hydroxylated acrylic resin cannot replace epoxy resin. The reason may be that the film layer formed by drying and curing a single water-based hydroxylated acrylic resin has poor density, unstable structure, and poor barrier properties to oxygen and water vapor.

[0087] It can be seen from the results of Example 1 and Comparative Example 2 that polyethylene oxide cannot be replaced by polyethylene glycol. The reason may be that for different nano-inorganic fillers, specific hydrophilic polymers need to be used for surface modification to make the components of the modified filler have good dispersibility, so that they can be evenly dispersed in the resin film-forming material, thereby improving the barrier effect of the oxygen and water vapor barrier packaging bag on oxygen and water vapor.

[0088] It can be seen from the results of Example 1 and Comparative Example 3 that in the preparation process of the second modified filler, an equal amount of nano-silicon dioxide cannot be used to replace nano-molybdenum disulfide. The reason is that nano-molybdenum disulfide has a two-dimensional structure. The two-dimensional nano-molybdenum disulfide is used in the preparation process of the second modified filler, and the barrier effect of the oxygen and water vapor barrier packaging bag on oxygen and water vapor is also significantly improved.

[0089] 2. Mechanical properties test

[0090] The oxygen and water vapor barrier packaging bags prepared in Example 1, Example 2, and Example 4 were tested for tensile strength according to the method of GB / T1040.1-2006. The results are shown in Table 2.

[0091] Table 2

[0092] Example 1 Example 2 Example 4 Tensile strength(MPa) 46.8 47.0 59.0

[0093] It can be seen from Table 2 that in the preparation process of the first modified filler, carbon nanotubes are added, and the carbon nanotubes can be evenly dispersed without aggregation, thereby significantly improving the tensile strength of the packaging bag that blocks oxygen and water vapor.

Claims

1. A method for preparing a packaging bag that blocks oxygen and water vapor, characterized in that: The following steps are involved: The oxygen and water vapor barrier packaging bag comprises a first barrier layer, a bag base material layer, and a second barrier layer which are stacked in sequence; The bag base material layer is composed of polylactic acid; The preparation process of the first barrier layer includes: mixing water-based hydroxy acrylic resin, epoxy resin, first modified filler and additives to obtain a first barrier slurry, and then coating it on one side of the bag substrate layer, and drying to obtain the first barrier layer; The preparation process of the second barrier layer includes: mixing water-based hydroxy acrylic resin, epoxy resin, second modified filler and additives to obtain a second barrier slurry, and then coating it on the other side of the bag substrate layer, and drying to obtain the second barrier layer; The preparation process of the first modified filler comprises: mixing nano sodium silicate, nano silicon dioxide, polyethylene oxide, silane coupling agent, water, and glycerol in a weight ratio of 1: (1-2): (0.5-2): (1.5-3): (5-20): (3-10) to obtain the first modified filler; The preparation process of the second modified filler comprises: mixing nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, a silane coupling agent, and water in a weight ratio of 1: (0.5-2): (2-3.5): (5-15): (10-20) to obtain the second modified filler; In the preparation process of the first modified filler, carbon nanotubes are also added when nano sodium silicate is added.

2. The preparation method according to claim 1, characterized in that: The preparation process of the second modified filler further includes adding chitosan acid solution, and the preparation process of the second modified filler includes: mixing chitosan, organic acid, and water in a weight ratio of 1: (0.5-2): (10-50) to obtain chitosan acid solution, and then adding nano-molybdenum disulfide, nano-silicon dioxide, polyethylene glycol, silane coupling agent, and water, stirring and mixing to obtain the second modified filler; The weight ratio of the chitosan acid solution, nano molybdenum disulfide, nano silicon dioxide, polyethylene glycol, silane coupling agent and water is (0.5-1.1):1:(1-2.5):(2-3.5):(5-15):(10-20).

3. The preparation method according to claim 2, characterized in that: The organic acid includes at least one of citric acid and acetic acid.

4. The preparation method according to claim 1, characterized in that: The preparation process of the first barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 30-50 parts of epoxy resin, 20-40 parts of first modified filler, and 3-8 parts of additives by weight to obtain a first barrier slurry, which is then coated on one side of the bag substrate layer and dried to obtain the first barrier layer.

5. The preparation method according to claim 1, characterized in that: The preparation process of the second barrier layer includes: mixing 50 parts of water-based hydroxy acrylic resin, 30-50 parts of epoxy resin, 15-45 parts of second modified filler, and 3-8 parts of additives to obtain a second barrier slurry, which is then coated on the other side of the bag substrate layer and dried to obtain the second barrier layer.

6. The preparation method according to claim 1, characterized in that: The thickness of the bag base material layer is 10-30 μm.

7. The preparation method according to claim 1, characterized in that: The auxiliary agent includes isocyanate and at least one of diethylenetriamine, triethylenetetramine and diethylaminopropylamine.

8. The preparation method according to claim 7, characterized in that: The auxiliary agent also includes polydimethylsiloxane and sodium dodecyl sulfate.

9. The preparation method according to claim 1, characterized in that: When applying the first barrier slurry, the corresponding coating amount is 10-18g / m 2 After the first barrier slurry is applied, the drying temperature is 20-60°C and the drying time is 24-72 hours.

10. The preparation method according to claim 1, characterized in that: When applying the second barrier slurry, the corresponding coating amount is 10-18g / m 2 After coating the second barrier slurry, the drying temperature is 20-60°C and the drying time is 24-72 hours.

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