Eleven-layer high-barrier polyethylene co-extruded film for sanitary towel packaging and preparation process

Abstract

The invention relates to the technical field of sanitary napkin packaging materials, and discloses an eleven-layer high-barrier polyethylene co-extruded film for sanitary napkin packaging and a preparation process, the preparation process comprises the following steps: carrying out intercalation modification treatment on graphene oxide through a Gemini surfactant containing an alkenyl functional group to prepare alkenyl functional interface stable graphene oxide; the preparation method comprises the following steps: connecting alkenyl functionalized interface-stable graphene oxide and low-density polyethylene through covalent bonds by using a free radical melt grafting method to realize grafting modification of polyethylene, and extruding and granulating by using a twin-screw extruder to prepare graphene oxide grafted polyethylene PE-g-GO master batch; the eleven-layer high-barrier polyethylene co-extruded film is prepared by taking polyethylene resin as a raw material of an eleven-layer co-extruded film and graphene oxide grafted polyethylene PE-g-GO master batch as a modification reagent of the eleven-layer co-extruded film and adopting an eleven-layer co-extrusion blow molding film forming process, and can be used as a sanitary towel packaging material.

Description

Technical Field

[0001] The invention relates to the technical field of sanitary napkin packaging materials, in particular to an eleven-layer high-barrier polyethylene co-extruded film for sanitary napkin packaging and a preparation process thereof. Background Art

[0002] Sanitary napkin packaging film refers to a film used to protect sanitary napkins from external pollution when they are individually packaged. Its main function is to block dust, bacteria, moisture, oxygen and other impurities to keep sanitary napkins dry, clean and hygienic. The commonly used materials for sanitary napkin packaging films are polyethylene, polypropylene, polyethylene terephthalate, etc. Polyethylene is the most widely used in the field of sanitary napkin packaging due to its many advantages such as low density, easy processing, chemical corrosion resistance, good mechanical properties and low price.

[0003] Polyethylene is a non-polar polymer with weak barrier properties and limited application range. Therefore, polyethylene usually needs to be modified in practical applications. The main methods of polyethylene modification are physical modification and chemical modification. Physical modification includes filling modification and blending modification, which essentially does not change the chain structure; while chemical modification is to graft monomers with special functions onto the molecular chain of polyethylene through chemical reactions, including grafting modification, copolymerization modification and cross-linking modification.

[0004] The grafting modification of polyethylene can be divided into solution grafting, melt grafting and solid phase grafting. The polarity of grafted polyethylene is enhanced and its application range is expanded. Solution grafting and solid phase grafting are not environmentally friendly and have high requirements for equipment. In industrial production considering cost, environmental protection and continuous and efficient production, polyethylene is usually grafted using the melt method using twin-screw reactive extrusion technology.

[0005] Graphene is a new type of impermeable carbon material with a two-dimensional structure of one atomic layer thickness, which has the characteristics of strong chemical stability, high conductivity, and large specific surface area. Impermeable graphene dispersed in a polymer matrix can extend the path of water vapor and small gas molecules through the composite film and improve the barrier properties of the composite film. However, due to the poor dispersibility of graphene oxide (GO) in organic media, it is difficult to form a monolayer dispersion, which limits the application of graphene oxide in organic systems such as polymers and polymer gel electrolytes.

[0006] The study found that the unoxidized sp 2 The delocalized π bonds formed by the hybridized carbon atoms and the electrostatic interaction between the carboxyl groups at the edges of graphene oxide and the cations of cationic surfactants (e.g., didodecyldimethylammonium bromide) allow the cationic surfactant molecules to be inserted between the graphene oxide sheets, thereby improving the dispersibility of graphene oxide in organic media. Summary of the invention

[0007] The invention provides a preparation process of an eleven-layer high barrier polyethylene co-extrusion film based on a unique interlayer formula design, melt grafting modification technology and intercalation modification technology. The film product prepared thereby can be used as a sanitary napkin packaging material.

[0008] A preparation process of an eleven-layer high-barrier polyethylene co-extruded film for sanitary napkin packaging, comprising the following steps: Step 1: synthesizing a Gemini surfactant containing an alkenyl functional group, wherein the Gemini surfactant containing an alkenyl functional group is a Gemini surfactant SAA1 containing an alkenyl functional group or a Gemini surfactant SAA2 containing an alkenyl functional group; Step 2: Using a Gemini surfactant containing an alkenyl functional group to perform intercalation modification on graphene oxide, adsorbing the Gemini surfactant containing an alkenyl functional group on the surface of graphene oxide through electrostatic action, and preparing alkenyl functionalized interface-stabilized graphene oxide; Step 3: Using a free radical melt grafting method, during the melt processing of low-density polyethylene (LDPE) resin, the alkenyl functional groups on the surface of the alkenyl-functionalized interface-stabilized graphene oxide produce a free radical initiation reaction under the action of a peroxide initiator, so that the alkenyl-functionalized interface-stabilized graphene oxide and the low-density polyethylene are connected by covalent bonds to achieve grafting modification, and the graphene oxide-grafted polyethylene PE-g-GO masterbatch is prepared by extrusion granulation through a twin-screw extruder; Step 4: Using polyethylene resin as the raw material of the eleven-layer co-extruded film, graphene oxide grafted polyethylene PE-g-GO masterbatch as the modification agent of the eleven-layer co-extruded film, and adopting the eleven-layer co-extrusion blow molding film forming process, an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging is prepared.

[0009] Preferably, the product structure of the eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging is the following layers arranged in sequence: LDPE layer, the raw material of this layer is low-density polyethylene LDPE resin, and the amount of this layer is 10-20 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin, and the amount of this layer is 3-10 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin, and the amount of this layer is 5-15 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch, and the amount of this layer is 10-20 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch, and the amount of this layer is 10-20 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin, and the amount of this layer is 5-15 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin, and the amount of this layer is 3-10 parts by weight; The m-LLDPE layer is made of metallocene polyethylene m-LLDPE resin, and the usage of the layer is 5-15 parts by weight.

[0010] Preferably, the preparation method of the Gemini surfactant SAA1 containing an alkenyl functional group is: a nucleophilic substitution reaction is carried out between 1 molar equivalent of the hydroxyl functional group of 2-vinylpropane-1,3-diol and 2.01-2.09 molar equivalents of the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to generate the Gemini surfactant SAA1 containing an alkenyl functional group.

[0011] Preferably, the preparation method of the Gemini surfactant SAA2 containing an alkenyl functional group is: 1 molar equivalent of pentaerythritol is first reacted with 0.91-0.99 molar equivalents of 4-bromo-1-butene to undergo a nucleophilic substitution reaction under the catalytic action of a phase transfer catalyst, and then reacted with 3.01-3.09 molar equivalents of the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to undergo a nucleophilic substitution reaction to generate the Gemini surfactant SAA2 containing an alkenyl functional group.

[0012] Preferably, the phase transfer catalyst is one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, benzyltriethylammonium chloride and trioctylmethylammonium chloride.

[0013] Preferably, the mass ratio of the Gemini surfactant containing alkenyl functional groups to the graphene oxide in the alkenyl functionalized interface-stabilized graphene oxide is (0.1-0.8):1; Preferably, the graphene oxide has a thickness of 3-5 nm and a sheet diameter of 8-10 μm.

[0014] Preferably, the mass ratio of low-density polyethylene LDPE resin, olefin-functionalized interface-stabilized graphene oxide and peroxide initiator in the graphene oxide grafted polyethylene PE-g-GO masterbatch is 1:(0.05-0.3):(0.005-0.03); Preferably, the peroxide initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, dibenzoyl peroxide, and tert-butyl perbenzoate.

[0015] The thickness of the eleven-layer high-barrier polyethylene co-extruded film for sanitary napkin packaging prepared according to the above process is 40-80 μm.

[0016] Beneficial effects: The present invention designs and synthesizes a Gemini surfactant containing an alkenyl functional group, and uses the Gemini surfactant containing an alkenyl functional group to perform intercalation modification on graphene oxide with excellent barrier properties, adsorbs it on the surface of graphene oxide based on electrostatic action, and prepares alkenyl functionalized interface-stabilized graphene oxide; By using the free radical melt grafting method, the olefin functionalized interface-stabilized graphene oxide and low-density polyethylene are connected by covalent bonds to achieve the grafting modification of polyethylene, and then extruded and granulated by a twin-screw extruder to prepare graphene oxide grafted polyethylene PE-g-GO masterbatch; An eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging was prepared by using polyethylene resin as the raw material of the eleven-layer co-extruded film and graphene oxide grafted polyethylene PE-g-GO masterbatch as the modifying agent of the eleven-layer co-extruded film by adopting the eleven-layer co-extrusion blow molding film forming process. The experimental results show that the water vapor permeability of the eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging prepared by the present invention is less than 1.5 g / (m 2 •24h), oxygen permeability <1.0cm 3 / (m 2 •24h•0.1MPa), compared with conventional polyethylene co-extruded film, it has achieved beneficial technical results in significantly improving barrier properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the chemical structural formula of Gemini surfactant SAA1 containing alkenyl functional groups; Figure 2 is the chemical structural formula of Gemini surfactant SAA2 containing alkenyl functional groups; Figure 3 These are the performance test results of eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging. DETAILED DESCRIPTION

[0018] Gemini surfactants are new surfactants that connect two or more traditional surfactant molecules together at or near the hydrophilic base through a linker. Due to their special structure, they have many excellent properties, such as extremely low critical micelle concentration, excellent interfacial adsorption capacity, etc., which are beneficial to their modification of the graphene oxide surface. Based on this, the present invention first designs and develops two new Gemini surfactants based on the molecular design mechanism. Embodiment 1:

[0019] Preparation of Gemini surfactant SAA1 containing alkenyl functional groups: The hydroxyl functional group of 1 molar equivalent of 2-vinylpropane-1,3-diol and the bromine functional group of 2.03 molar equivalents of 1-bromo-6-(trimethylammonium)hexyl bromide undergo nucleophilic substitution reaction to generate Gemini surfactant SAA1 containing alkenyl functional groups, whose chemical structure is as follows: Figure 1 As shown; The specific experimental steps for preparing the Gemini surfactant SAA1 containing alkenyl functional groups are as follows: 0.5 g of 2-vinylpropane-1,3-diol, 5 mL of 20 wt% sodium hydroxide aqueous solution and 20 mL of N,N-dimethylformamide are added to a three-necked flask, stirred at room temperature until all dissolved, then 30 mL of N,N-dimethylformamide solution containing 3.0 g of 1-bromo-6-(trimethylammonium)hexyl bromide is added to the three-necked flask, the temperature is raised to 80°C and stirred for reaction for 10 hours, the solvent is removed by rotary evaporation, and vacuum drying is performed to obtain the Gemini surfactant SAA1 containing alkenyl functional groups; The H NMR spectrum of Gemini surfactant SAA1 containing alkenyl functional groups is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 1.41-1.51 (m, 8H), 1.58-1.65 (m, 4H), 1.73-1.80 (m, 4H), 2.44-2.52 (m, 1H), 3.31-3.35 (t, 4 H), 3.43 (s, 18H), 3.49-3.51 (d, 4H), 3.55-3.59 (t, 4H), 5.21-5.25 (d, 2H), 5.82-5.90 (m, 1H). Embodiment 2:

[0020] Preparation of Gemini surfactant SAA2 containing alkenyl functional groups: 1 molar equivalent of pentaerythritol is first reacted with 0.98 molar equivalent of 4-bromo-1-butene under the catalysis of a phase transfer catalyst to undergo nucleophilic substitution reaction, and then reacted with 3.05 molar equivalents of the bromine functional group of 1-bromo-6-(trimethylammonium)hexyl bromide to undergo nucleophilic substitution reaction to generate Gemini surfactant SAA2 containing alkenyl functional groups, whose chemical structure is as follows: Figure 2As shown; Wherein, the phase transfer catalyst is one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, benzyltriethylammonium chloride, and trioctylmethylammonium chloride; in this embodiment, tetrabutylammonium bromide is selected; The specific experimental steps for preparing the Gemini surfactant SAA2 containing alkenyl functional groups are as follows: 1.4 g of pentaerythritol, 5 mL of 20 wt% sodium hydroxide aqueous solution and 20 mL of N, N-dimethylformamide are added to a three-necked flask, stirred at room temperature until all dissolved, then 10 mL of N, N-dimethylformamide solution containing 1.3 g of 4-bromo-1-butene and 5 mL of N, N-dimethylformamide solution containing 0.8 g of tetrabutylammonium bromide are added to the three-necked flask in sequence, the temperature is raised to 70°C and stirred for reaction for 8 hours, after cooling to room temperature, 50 mL of N, N-dimethylformamide solution containing 9.1 g of 1-bromo-6-(trimethylammonium)hexyl bromide is added to the three-necked flask, the temperature is raised to 80°C and stirred for reaction for 12 hours, the solvent is removed by rotary evaporation, and vacuum drying is performed to obtain the Gemini surfactant SAA2 containing alkenyl functional groups; The H NMR spectrum of Gemini surfactant SAA2 containing alkenyl functional groups is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 1.40-1.50 (m, 12H), 1.53-1.60 (m, 6H), 1.66-1.73 (m, 6H), 2.29-2.34 (m, 2H), 3.40-3.43 (t, 6H), 3. 47(s, 27H), 3.51(s, 8H), 3.55-3.58(t, 6H), 3.62-3.66(t, 2H), 5.10-5.13(d, 2H), 5.70-5.80(m, 1H). Embodiment three:

[0021] Preparation of alkenyl functionalized interface-stabilized graphene oxide I: using Gemini surfactant SAA1 containing alkenyl functional groups to perform intercalation modification on graphene oxide, adsorbing Gemini surfactant SAA1 containing alkenyl functional groups on the surface of graphene oxide through electrostatic action, and preparing alkenyl functionalized interface-stabilized graphene oxide I; The specific experimental steps for preparing alkenyl functionalized interface-stabilized graphene oxide I are as follows: 5 g of nano graphene oxide powder (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with a thickness of 3-5 nm and a flake diameter of 8-10 μm), 50 mL of deionized water and 200 mL of N,N-dimethylformamide were added to a three-necked flask, ultrasonicated for 30 min, heated to 50 °C and stirred for 2 h, then 30 mL of Gemini surfactant SAA1 solution containing alkenyl functional groups (prepared with 3.0 g of Gemini surfactant SAA1 containing alkenyl functional groups, 10 mL of deionized water and 20 mL of N,N-dimethylformamide) was added dropwise to the three-necked flask, heated to 70 °C and stirred for 4 h, filtered while hot, washed with deionized water until no precipitate was detected in the silver nitrate solution, and dried in vacuo to obtain alkenyl functionalized interface-stabilized graphene oxide I. Embodiment 4:

[0022] Preparation of alkenyl functionalized interface-stabilized graphene oxide II: Graphene oxide is intercalated and modified using Gemini surfactant SAA2 containing alkenyl functional groups, and the Gemini surfactant SAA2 containing alkenyl functional groups is adsorbed on the surface of graphene oxide through electrostatic action to prepare alkenyl functionalized interface-stabilized graphene oxide II; The specific experimental steps for preparing alkenyl-functionalized interface-stabilized graphene oxide II refer to the preparation experiment of alkenyl-functionalized interface-stabilized graphene oxide I, and the only difference is that the Gemini surfactant SAA1 containing alkenyl functional groups is replaced by the Gemini surfactant SAA2 containing alkenyl functional groups. Embodiment five:

[0023] Preparation of graphene oxide grafted polyethylene PE-g-GO masterbatch I: using a free radical melt grafting method, during the melt processing of low-density polyethylene LDPE resin, the alkenyl functional groups on the surface of alkenyl functionalized interface-stabilized graphene oxide I produce a free radical initiation reaction under the action of a peroxide initiator, so that the alkenyl functionalized interface-stabilized graphene oxide I and low-density polyethylene are connected by covalent bonds to achieve grafting modification, and then extrusion granulation is performed by a twin-screw extruder to prepare graphene oxide grafted polyethylene PE-g-GO masterbatch I; The peroxide initiator is one of dicumyl peroxide (DCP), tert-butyl hydroperoxide (TBHP), dibenzoyl peroxide (BPO), and tert-butyl perbenzoate (TBPB); dicumyl peroxide (DCP) is selected in this embodiment; The specific experimental steps for preparing graphene oxide grafted polyethylene PE-g-GO masterbatch Ⅰ are as follows: first, low-density polyethylene LDPE resin (purchased from Jiangsu Rantai Plastics Co., Ltd., brand LD 150DW) was placed in a vacuum drying oven at 80°C for 12 hours, and then 10g of the dried low-density polyethylene LDPE resin, 1g of olefin-functionalized interface-stabilized graphene oxide Ⅰ and 0.1g of diisopropylbenzene peroxide initiator were added to a high-speed mixer and mixed evenly, and then melted, extruded and granulated by a twin-screw extruder to obtain graphene oxide grafted polyethylene PE-g-GO masterbatch Ⅰ; Among them, the process parameters of the twin-screw extruder are set as: preheating temperature 180°C, temperatures of zones 1-6 are 180°C, 185°C, 185°C, 190°C, 200°C, and 195°C respectively, rotation speed is 60r / min, and melting processing time is 5min. Embodiment six:

[0024] Preparation of graphene oxide grafted polyethylene PE-g-GO masterbatch II: using a free radical melt grafting method, during the melt processing of low-density polyethylene LDPE resin, the alkenyl functional groups on the surface of alkenyl functionalized interface-stabilized graphene oxide II produce a free radical initiation reaction under the action of a peroxide initiator, so that the alkenyl functionalized interface-stabilized graphene oxide II and low-density polyethylene are connected by covalent bonds to achieve grafting modification, and then extruded and granulated by a twin-screw extruder to prepare graphene oxide grafted polyethylene PE-g-GO masterbatch II; The peroxide initiator is one of dicumyl peroxide (DCP), tert-butyl hydroperoxide (TBHP), dibenzoyl peroxide (BPO), and tert-butyl perbenzoate (TBPB); dicumyl peroxide (DCP) is selected in this embodiment; The specific experimental steps for preparing graphene oxide grafted polyethylene PE-g-GO masterbatch II refer to the preparation experiment of graphene oxide grafted polyethylene PE-g-GO masterbatch I, the only difference is that alkenyl functionalized interface-stabilized graphene oxide II is used to replace alkenyl functionalized interface-stabilized graphene oxide I. Embodiment seven:

[0025] An eleven-layer high-barrier polyethylene co-extruded film I for sanitary napkin packaging, the product structure of which is the following layers arranged in sequence: LDPE layer, the raw material of this layer is low-density polyethylene LDPE resin, and the amount of this layer is 15 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin (purchased from Dongguan Longhuang Plastic Raw Materials Co., Ltd., brand FB5600), the amount of this layer is 5 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin (purchased from Yuyao Hongyang Plastic Chemical Co., Ltd., brand 2045G), the amount of this layer is 10 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin (purchased from Dongguan Taotao Plastic Raw Materials Co., Ltd., brand 4288), the amount of this layer is 5 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch I, and the amount of this layer is 15 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 5 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch I, and the amount of this layer is 15 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 5 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin, and the amount of this layer is 10 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin, and the amount of this layer is 5 parts by weight; The m-LLDPE layer, the raw material of which is metallocene polyethylene m-LLDPE resin (purchased from Dongguan Jinshixiang Plastic Raw Materials Co., Ltd., brand SP4020), the usage of which is 10 parts by weight. Embodiment eight:

[0026] A preparation process of an eleven-layer high barrier polyethylene co-extruded film I for sanitary napkin packaging is as follows: According to the formula of eleven-layer high-barrier polyethylene co-extruded film I for sanitary napkin packaging, ingredients are prepared, and the raw materials of each layer are respectively put into the hoppers of eleven screw extruders of the eleven-layer co-extruded film blow molding unit, and the molten resin is merged at the die head through a splitter, extruded through a die head, blown and pulled (the blow-up ratio is controlled at 2.7), cooled and rolled, and the eleven-layer high-barrier polyethylene co-extruded film I for sanitary napkin packaging with a thickness of 50 μm is prepared; Among them, the process parameters of the screw extruder corresponding to the LDPE layer, HDPE layer, LLDPE layer and m-LLDPE layer are all set as follows: the temperatures of zones 1-3 are 120°C, 150°C and 170°C respectively, the flow channel temperature is 165°C, and the rotation speed is 30r / min; The process parameters of the screw extruder corresponding to the PE-g-MAH layer were set as follows: the temperatures of zones 1-3 were 115 °C, 145 °C, and 160 °C, respectively, the flow channel temperature was 150 °C, and the rotation speed was 15 r / min; The process parameters of the screw extruder corresponding to the PE-g-GO layer were set as follows: the temperatures of zones 1-3 were 150 °C, 170 °C, and 200 °C, respectively, the flow channel temperature was 195 °C, and the rotation speed was 60 r / min. Embodiment nine:

[0027] An eleven-layer high-barrier polyethylene co-extruded film II for sanitary napkin packaging, the product structure of which is different from the eleven-layer high-barrier polyethylene co-extruded film I for sanitary napkin packaging in Example 7 only in that: graphene oxide grafted polyethylene PE-g-GO masterbatch II is used to replace graphene oxide grafted polyethylene PE-g-GO masterbatch I; The preparation process of the eleven-layer high barrier polyethylene co-extruded film II for sanitary napkin packaging is the same as the preparation process of the eleven-layer high barrier polyethylene co-extruded film I for sanitary napkin packaging in Example 8. Comparative Example:

[0028] Preparation of conventional polyethylene co-extruded film: Compared with the eleven-layer high barrier polyethylene co-extruded film Ⅰ for sanitary napkin packaging, the only difference is that low-density polyethylene LDPE resin is used to replace graphene oxide grafted polyethylene PE-g-GO masterbatch Ⅰ. Performance Test:

[0029] (1) Barrier performance test: The oxygen permeability test and water vapor permeability test of the samples were carried out in accordance with GB / T 1038.1-2022 "Test method for gas permeability of plastic films and sheets - Part 1: Differential pressure method" and GB / T 1037-2021 "Determination of water vapor permeability of plastic films and sheets - Cup weight gain and weight loss method". The specific test steps are as follows: Place a 30 cm circular sample in a glass desiccator at an ambient temperature of 25°C and anhydrous calcium chloride as a desiccant for 72 hours, and then use a Y110 oxygen permeability tester and a TC-03 water vapor permeability tester to test the barrier properties of the samples; (2) Mechanical properties test: According to GB / T 1040.1-2018 "Determination of tensile properties of plastics", a 150 mm × 20 mm sample (sampled along the film blowing direction) was fixed on an Instron 5565 universal tensile testing machine at room temperature and a tensile test was performed at a tensile rate of 5 mm / min. The above experimental results are shown in Table 1 and Figure 3 .

[0030] Table 1 Performance test results of eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging

[0031] By comprehensively analyzing the above experimental results, the following conclusions can be drawn: Conclusion 1: The water vapor permeability of the eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging prepared by the present invention is less than 1.5 g / (m 2 •24h), oxygen permeability <1.0cm 3 / (m 2 •24h•0.1MPa), compared with conventional polyethylene co-extruded film, it has achieved a significant improvement in barrier properties; Conclusion 2: The mechanical properties of the eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging prepared by the present invention are also significantly improved; The experimental results show that the performance improvement effect of the eleven-layer high-barrier polyethylene co-extrusion film II for sanitary napkin packaging prepared by melt-grafting graphene oxide modified with Gemini surfactant SAA2 containing alkenyl functional groups with polyethylene is the most significant. The mechanism for the above experimental results may be that the Gemini surfactant SAA2 containing alkenyl functional groups contains more alkyl carbon chains and has better hydrophobicity and steric hindrance effects, so its modification effect on graphene oxide will also be more significant.

Claims

1. A process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging, characterized in that: The following steps are involved: Step 1: synthesizing a Gemini surfactant containing an alkenyl functional group, wherein the Gemini surfactant containing an alkenyl functional group is a Gemini surfactant SAA1 containing an alkenyl functional group or a Gemini surfactant SAA2 containing an alkenyl functional group; Step 2: Using a Gemini surfactant containing an alkenyl functional group to perform intercalation modification on graphene oxide, adsorbing the Gemini surfactant containing an alkenyl functional group on the surface of graphene oxide through electrostatic action, and preparing alkenyl functionalized interface-stabilized graphene oxide; Step 3: Based on the method of free radical melt grafting modification of polyethylene, low-density polyethylene is grafted with olefin-functionalized interface-stabilized graphene oxide, and extruded and granulated by a twin-screw extruder to prepare graphene oxide grafted polyethylene PE-g-GO masterbatch; Step 4: Using polyethylene resin as the raw material of the eleven-layer co-extruded film, graphene oxide grafted polyethylene PE-g-GO masterbatch as the modification agent of the eleven-layer co-extruded film, and adopting the eleven-layer co-extrusion blow molding film forming process, an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging is prepared.

2. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 1, characterized in that: The product structure of the eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging is the following layers arranged in sequence: LDPE layer, the raw material of this layer is low-density polyethylene LDPE resin, and the amount of this layer is 10-20 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin, and the amount of this layer is 3-10 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin, and the amount of this layer is 5-15 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch, and the amount of this layer is 10-20 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; PE-g-GO layer, the raw material of this layer is graphene oxide grafted polyethylene PE-g-GO masterbatch, and the amount of this layer is 10-20 parts by weight; PE-g-MAH layer, the raw material of this layer is maleic anhydride grafted polyethylene PE-g-MAH resin, and the amount of this layer is 2-7 parts by weight; LLDPE layer, the raw material of this layer is linear low-density polyethylene LLDPE resin, and the amount of this layer is 5-15 parts by weight; HDPE layer, the raw material of this layer is high-density polyethylene HDPE resin, and the amount of this layer is 3-10 parts by weight; The m-LLDPE layer is made of metallocene polyethylene m-LLDPE resin, and the usage of the layer is 5-15 parts by weight.

3. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 1, characterized in that: The chemical structural formula of the Gemini surfactant SAA1 containing an alkenyl functional group is: 。 4. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 2, characterized in that: The preparation method of the Gemini surfactant SAA1 containing an alkenyl functional group is: a hydroxyl functional group of 1 molar equivalent of 2-vinylpropane-1,3-diol is reacted with a bromine functional group of 2.01-2.09 molar equivalents of 1-bromo-6-(trimethylammonium)hexyl bromide to produce a nucleophilic substitution reaction of the Gemini surfactant SAA1 containing an alkenyl functional group.

5. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 1, characterized in that: The chemical structural formula of the Gemini surfactant SAA2 containing an alkenyl functional group is: 。 6. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 5, characterized in that: The preparation method of the Gemini surfactant SAA2 containing an alkenyl functional group is as follows: 1 molar equivalent of pentaerythritol is first subjected to a nucleophilic substitution reaction with 0.91-0.99 molar equivalents of 4-bromo-1-butene under the catalytic action of a phase transfer catalyst, and then subjected to a nucleophilic substitution reaction with the bromine functional group of 3.01-3.09 molar equivalents of 1-bromo-6-(trimethylammonium)hexyl bromide to generate the Gemini surfactant SAA2 containing an alkenyl functional group.

7. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 6, characterized in that: The phase transfer catalyst is one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, benzyltriethylammonium chloride and trioctylmethylammonium chloride.

8. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 1, characterized in that: The mass ratio of the Gemini surfactant containing alkenyl functional groups to the graphene oxide in the alkenyl functionalized interface-stabilized graphene oxide is (0.1-0.8):1; The graphene oxide has a thickness of 3-5 nm and a sheet diameter of 8-10 μm.

9. The process for preparing an eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging according to claim 1, characterized in that: The mass ratio of low-density polyethylene LDPE resin to olefin-functionalized interface-stabilized graphene oxide in the graphene oxide grafted polyethylene PE-g-GO masterbatch is 1:(0.05-0.3).

10. An eleven-layer high barrier polyethylene co-extruded film for sanitary napkin packaging prepared by the process according to any one of claims 1 to 9, characterized in that: The thickness of the eleven-layer high-barrier polyethylene co-extruded film for raw towel packaging is 40-80 μm.

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