An eleven-layer ultra-high barrier polyethylene low-carbon environmental protection film material and its preparation method

Abstract

The present invention relates to the technical field of research and development of single PE eleven-layer composite structure film materials, and discloses an eleven-layer ultra-high barrier polyethylene low-carbon environmental protection film material and a preparation method thereof, including: synthesizing a DOPO-based silane coupling agent, modifying the DOPO-based silane coupling agent on the surface of sodium-based vermiculite to obtain flame-retardant modified vermiculite, and uniformly dispersing the flame-retardant modified vermiculite in an ethylene-vinyl alcohol copolymer matrix to prepare a flame-retardant barrier material; introducing the flame-retardant barrier material into a PE coextrusion film, and adopting an eleven-layer coextrusion blow molding process to prepare a single PE material eleven-layer composite structure film with a thickness of 50-200 μm. The present invention provides a preparation method of a single PE material eleven-layer composite structure film, and an eleven-layer film single product is prepared, which has excellent barrier properties and belongs to ultra-high barrier materials, and can be used as the best alternative for the dairy product packaging field.

Description

Technical Field

[0001] The present invention relates to the technical field of research and development of single PE eleven-layer composite structure film materials, and specifically to an eleven-layer ultra-high barrier polyethylene low-carbon environmental protection film material and a preparation method thereof. Background Art

[0002] With the increasing global attention to environmental protection, the food packaging industry is facing an urgent need to reduce plastic pollution. As an environmentally friendly material, plastic packaging materials with a single material do not need to be sorted during recycling and can be recycled repeatedly, gradually becoming the development trend of the packaging industry.

[0003] Search found that: The extension of the shelf life of boxed ambient milk is mainly attributed to the barrier performance of the packaging box. The high-barrier film materials independently developed by domestic enterprises for food and drug packaging are expected to replace the existing milk packaging boxes. Among them, a dairy packaging composite material with a multi-layer composite structure of a single all-plastic material (such as polyethylene) composed of a high-barrier film is expected to be used as the best alternative for the dairy packaging field. For example, the patent with the publication number CN116604907A prepared a single-material high-barrier recyclable composite film by adding a small amount of EVOH barrier material to polyethylene material and using a multi-layer co-extrusion method.

[0004] Search found that: Vermiculite is a natural layered silicate with a high porosity and a large specific surface area. By adding organically modified vermiculite to the polymer matrix material, the movement path of gas in the material can be changed, thereby significantly improving the barrier performance of the material. In addition, traditional plastic materials used for commodity packaging have poor flame retardant performance and are easy to burn, posing a safety hazard. Therefore, it is imperative to carry out flame retardant modification on traditional plastics. Summary of the Invention

[0005] The present invention provides an eleven-layer film single product with a multi-layer composite structure of a single all-plastic material (such as polyethylene, PE) composed of a high-barrier film, which can be used to prepare a green low-carbon environmental protection film material for the dairy packaging field through a heat-sealing test machine and a multi-functional automatic film sealing machine; on the one hand, the present invention realizes the technical improvement goal of reducing the cost of dairy packaging by canceling the aluminum foil structure, on the other hand, realizes the technical improvement goal of reducing aluminum consumption and carbon emissions by canceling the aluminum foil structure, and thirdly, utilizes the multi-layer composite structure of a single all-plastic material to promote the rapid recycling and reuse of plastics, realizing the technical improvement goal of reducing packaging waste.

[0006] A preparation method of a single PE material eleven-layer composite structure film comprises the following steps:

[0007] Step 1: Synthesize the DOPO-based silane coupling agent, modify the DOPO-based silane coupling agent on the surface of sodium vermiculite to obtain flame-retardant modified vermiculite, and uniformly disperse the flame-retardant modified vermiculite in an ethylene-vinyl alcohol copolymer matrix to prepare a flame-retardant barrier material;

[0008] The DOPO-based silane coupling agent is one of flame-retardant coupling agent I, flame-retardant coupling agent II, and flame-retardant coupling agent III;

[0009] The chemical structural formula of the flame-retardant coupling agent I is:

[0010]

[0011] The chemical structural formula of the flame-retardant coupling agent II is:

[0012]

[0013] The chemical structural formula of the flame-retardant coupling agent III is:

[0014]

[0015] Step 2: Adopt an eleven-layer coextrusion blow molding process to prepare an eleven-layer composite structure film made of a single PE material with a thickness of 50 - 200 μm; the eleven-layer composite structure film made of a single PE material contains the flame-retardant barrier material.

[0016] Preferably, the formula and dosage of the eleven-layer composite structure film made of a single PE material are as follows:

[0017] The first layer: the formula is 50 - 70 wt% LDPE + 30 - 50 wt% LLDPE, and the dosage is 5 - 15 wt%;

[0018] The second layer: the formula is 20 - 50 wt% HDPE + 50 - 80 wt% m-LLDPE, and the dosage is 3 - 10 wt%;

[0019] The third layer: the formula is 40 - 80 wt% LDPE + 10 - 30 wt% LLDPE + 10 - 30 wt% m-LLDPE, and the dosage is 5 - 15 wt%;

[0020] The fourth layer: the formula is 100 wt% PE-g-MAH, and the dosage is 1 - 5 wt%;

[0021] The fifth layer: the formula is 90 - 95 wt% LDPE + 5 - 10 wt% EVOH, and the dosage is 5 - 15 wt%;

[0022] The sixth layer: the formula is 905 - 95 wt% LDPE + 5 - 10 wt% flame-retardant barrier material, and the dosage is 10 - 40 wt%;

[0023] The seventh layer: The formulation is 90 - 95 wt% LDPE + 5 - 10 wt% EVOH, and the dosage is 5 - 15 wt%;

[0024] The eighth layer: The formulation is 100 wt% PE-g-MAH, and the dosage is 1 - 5 wt%;

[0025] The ninth layer: The formulation is 40 - 80 wt% LDPE + 10 - 30 wt% LLDPE + 10 - 30 wt% m-LLDPE, and the dosage is 5 - 15 wt%;

[0026] The tenth layer: The formulation is 20 - 50 wt% HDPE + 50 - 80 wt% m-LLDPE, and the dosage is 3 - 10 wt%;

[0027] The eleventh layer: The formulation is 25 - 45 wt% LDPE + 25 - 45 wt% LLDPE + 10 - 50% HDPE, and the dosage is 5 - 15 wt%.

[0028] Preferably, the preparation method of the flame retardant coupling agent I is: The P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes an addition reaction with the alkenyl functional group of methacryloxypropyltriethoxysilane to generate the flame retardant coupling agent I.

[0029] Preferably, the preparation method of the flame retardant coupling agent II is:

[0030] Step S4-1: The P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes an addition reaction with the alkenyl functional group of allyldiphenylphosphine to generate the DOPO-based tertiary phosphine monomer;

[0031] Step S4-2: Using the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the DOPO-based tertiary phosphine monomer undergoes a quaternary phosphination reaction with the bromine functional group of 3-bromopropyltrimethoxysilane to generate the flame retardant coupling agent II.

[0032] Preferably, the preparation method of the flame retardant coupling agent III is:

[0033] Step S5-1: The P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes an addition reaction with the alkenyl functional group of triallylphosphine to generate the tris(DOPO-based) tertiary phosphine monomer;

[0034] Step S5-2: Using the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the tris(DOPO-based) tertiary phosphine monomer undergoes a quaternary phosphination reaction with the bromine functional group of 3-bromopropyltrimethoxysilane to generate the flame retardant coupling agent III.

[0035] The water vapor transmission rate of a single PE material eleven-layer composite structure film prepared according to the above method is 1.0 to 2.0 [g / (m 2 ·24 h)], and the oxygen transmission rate is 1.0 to 1.5 [cm 3 / (m 2 ·24 h·0.1 MPa)].

[0036] Beneficial effects

[0037] First, the present invention designed and synthesized three new types of flame-retardant coupling agents. Then, the sodium-based vermiculite was modified with the flame-retardant coupling agents to prepare flame-retardant modified vermiculite. And the flame-retardant modified vermiculite was uniformly dispersed in the ethylene-vinyl alcohol copolymer matrix to prepare a flame-retardant barrier material (specifically: EVOH / flame-retardant modified vermiculite composite material). Finally, the flame-retardant barrier material was introduced into the PE coextrusion film, and an eleven-layer coextrusion blow molding process was used to prepare an eleven-layer film product, which has excellent barrier properties and belongs to an ultra-high barrier material, and can be used as the best alternative for the dairy packaging field. Description of the drawings

[0038] Figure 1 is the synthesis route of flame-retardant coupling agent I;

[0039] Figure 2 is the synthesis route of flame-retardant coupling agent II;

[0040] Figure 3 is the synthesis route of flame-retardant coupling agent III;

[0041] Figure 4 is the performance test result of the eleven-layer coextrusion film. Detailed implementation manners

[0042] Experimental example 1:

[0043] Prepare flame-retardant coupling agent I. As Figure 1 shown, its preparation method is: an addition reaction occurs between the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and the alkenyl functional group of methacryloxypropyltriethoxysilane to generate flame-retardant coupling agent I. The specific experimental steps are as follows: Add 2.2 g of DOPO and 30 mL of tetrahydrofuran to a four-necked flask, stir at room temperature until completely dissolved, then add 30 mL of methacryloxypropyltriethoxysilane solution (prepared from 2.9 g of methacryloxypropyltriethoxysilane and 30 mL of tetrahydrofuran) to the four-necked flask, heat to 75 °C and stir under reflux for 5 h, cool to room temperature, rotate and evaporate the solvent at 40 °C in a water bath, and dry under vacuum to obtain flame-retardant coupling agent I;

[0044] The 1H NMR characterization of the flame retardant coupling agent Ⅰ is as follows: 1 1H NMR (DMSO-d 6 , 400 MHz) δ: 0.63 - 0.67 (t, 2H), 1.15 - 1.24 (m, 12H), 1.78 - 1.85 (m, 2H), 2.78 - 2.85 (m, 3H), 3.72 - 3.80 (m, 6H), 4.09 - 4.13 (t, 2H), 7.26 - 8.05 (m, 8H, Ar-H).

[0045] Experimental Example 2:

[0046] Prepare the flame retardant coupling agent Ⅱ, as Figure 2 shown, and its preparation process is as follows:

[0047] (1) Prepare the DOPO-based tertiary phosphine monomer. The preparation method is: through the addition reaction of the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with the vinyl functional group of allyldiphenylphosphine to generate the DOPO-based tertiary phosphine monomer. The specific experimental steps are the same as those of the preparation experiment of the flame retardant coupling agent Ⅰ, and the only difference is that: 2.3 g of allyldiphenylphosphine is used to replace 2.9 g of methacryloyloxypropyltriethoxysilane;

[0048] (2) Prepare the flame retardant coupling agent Ⅱ. The preparation method is: using the nucleophilic substitution reaction mechanism, through the quaternary phosphination reaction of the tertiary phosphine group of the DOPO-based tertiary phosphine monomer with the bromine functional group of 3-bromopropyltrimethoxysilane to generate the flame retardant coupling agent Ⅱ. The specific experimental steps are: add 2.2 g of the DOPO-based tertiary phosphine monomer and 50 mL of N,N-dimethylformamide into a four-necked flask. Under the protection of nitrogen and mechanical stirring, heat up to 40 °C. After the temperature is stable, dropwise add 1.0 mL of 3-bromopropyltrimethoxysilane into the four-necked flask, continue to heat up to 100 °C and stir for 12 h. After cooling, perform rotary evaporation, wash with ethyl acetate, and dry under vacuum to obtain the flame retardant coupling agent Ⅱ;

[0049] The 1H NMR characterization of the flame retardant coupling agent Ⅱ is as follows: 1 1H NMR (DMSO-d 6 , 400 MHz) δ: 0.50 - 0.54 (t, 2H), 1.27 - 1.33 (m, 4H), 1.85 - 1.95 (m, 2H), 2.55 - 2.64 (m, 2H), 3.58 (s, 9H), 7.14 - 8.13 (m, 18H, Ar-H).

[0050] Experimental Example 3:

[0051] Prepare the flame retardant coupling agent Ⅲ, as Figure 3 shown, and its preparation process is as follows:

[0052] (1) Prepare tris(DOPO-based)tertiary phosphine monomer. The preparation method is as follows: Through the addition reaction of the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with the alkenyl functional group of triallylphosphine, tris(DOPO-based)tertiary phosphine monomer is generated. The specific experimental steps are the same as those for the preparation of flame retardant coupling agent I, and the only difference lies in that: 0.5 g of triallylphosphine is used to replace 2.9 g of methacryloxypropyltriethoxysilane;

[0053] (2) Prepare flame retardant coupling agent III. The preparation method is as follows: Utilize the nucleophilic substitution reaction mechanism. Through the quaternary phosphination reaction of the tertiary phosphine group of tris(DOPO-based)tertiary phosphine monomer with the bromine functional group of 3-bromopropyltrimethoxysilane, flame retardant coupling agent III is generated. The specific experiment is the same as that for the preparation of flame retardant coupling agent II, and the only difference lies in that: 3.9 g of tris(DOPO-based)tertiary phosphine monomer is used to replace DOPO-based tertiary phosphine monomer;

[0054] The 1H NMR characterization of flame retardant coupling agent III is as follows: 1 H NMR(DMSO-d 6 , 400 MHz)δ: 0.50 - 0.55(t, 2H), 1.26 - 1.34(m, 6H), 1.76 - 2.03(m, 6H), 2.47 - 2.75(m, 4H), 3.58(s, 9H), 3.95 - 4.03(m, 2H), 7.09 - 8.15(m, 24H, Ar-H).

[0055] Example 1:

[0056] (1) Prepare flame retardant modified vermiculite I. The preparation method is as follows: Use flame retardant coupling agent I to modify sodium-based vermiculite (with hydroxyl functional groups in the zircon structure) to obtain flame retardant modified vermiculite I. The specific experimental steps are as follows: Add 2.0 g of flame retardant coupling agent I and 20 mL of ethanol into a four-necked flask, stir and react for 1 h under the condition of a 40 °C water bath. Then add 0.5 g of sodium-based vermiculite into the four-necked flask, raise the temperature to 60 °C and stir and react for 3 h. Cool to room temperature, let it stand for 10 h, filter by suction, wash with deionized water, centrifuge, and dry under vacuum to obtain flame retardant modified vermiculite I;

[0057] Prepare EVOH / flame retardant modified vermiculite I composite material. The preparation method is as follows: Disperse flame retardant modified vermiculite I in an ethylene-vinyl alcohol copolymer matrix to prepare EVOH / flame retardant modified vermiculite I composite material. The specific experimental steps are as follows: Add 30 g of ethylene-vinyl alcohol copolymer resin and 5 g of flame retardant modified vermiculite I into a twin-screw extruder, and through the twin-screw extruder, blend, melt, extrude, and pelletize to prepare EVOH / flame retardant modified vermiculite I composite material;

[0058] (2) Preparation of flame-retardant modified vermiculite II. The preparation method is as follows: Modify sodium-based vermiculite with flame-retardant coupling agent II to obtain flame-retardant modified vermiculite II. The specific experimental steps are the same as those for the preparation of flame-retardant modified vermiculite I, and the only difference is that 3.4 g of flame-retardant coupling agent II is used to replace 2.0 g of flame-retardant coupling agent I;

[0059] Preparation of EVOH / flame-retardant modified vermiculite II composite material. The preparation method is as follows: Disperse flame-retardant modified vermiculite II in an ethylene-vinyl alcohol copolymer matrix to prepare an EVOH / flame-retardant modified vermiculite II composite material. The specific experimental steps are the same as those for the preparation of EVOH / flame-retardant modified vermiculite I composite material, and the only difference is that flame-retardant modified vermiculite II is used to replace flame-retardant modified vermiculite I;

[0060] (3) Preparation of flame-retardant modified vermiculite III. The preparation method is as follows: Modify sodium-based vermiculite with flame-retardant coupling agent III to obtain flame-retardant modified vermiculite III. The specific experimental steps are the same as those for the preparation of flame-retardant modified vermiculite I, and the only difference is that 5.0 g of flame-retardant coupling agent III is used to replace 2.0 g of flame-retardant coupling agent I;

[0061] Preparation of EVOH / flame-retardant modified vermiculite III composite material. The preparation method is as follows: Disperse flame-retardant modified vermiculite III in an ethylene-vinyl alcohol copolymer matrix to prepare an EVOH / flame-retardant modified vermiculite III composite material. The specific experimental steps are the same as those for the preparation of EVOH / flame-retardant modified vermiculite I composite material, and the only difference is that flame-retardant modified vermiculite III is used to replace flame-retardant modified vermiculite I;

[0062] The preparation method of sodium-based vermiculite is as follows: Add vermiculite powder into 1 mol / L sodium chloride aqueous solution (control the content of vermiculite to be 20 wt%), stir and react at room temperature for 12 h, centrifuge (detect that there is no Cl in the supernatant with 0.1 mol / L silver nitrate solution - ), dry, and grind with a ball mill to prepare sodium-based vermiculite;

[0063] Among them, ethylene-vinyl alcohol copolymer resin (EVOH) is purchased from Guangzhou Best New Materials Technology Co., Ltd., and its grade is ET3803RB; vermiculite powder is purchased from Mineral Products Processing Factory in Lingshou County, Hebei Province, and its impurity content is <0.5%;

[0064] Among them, the process parameters of the twin-screw extruder are set as follows: the temperatures of zones 1-3 are 150 °C, 170 °C, and 195 °C respectively, and the rotation speed is 40 r / min.

[0065] Example 2:

[0066] (1) Preparation of modified eleven-layer coextruded film I: Use W&H ( Anhui Zijin New Materials Technology Co., Ltd. self-made an 11-layer blown film production line and prepared a modified 11-layer coextruded film Ⅰ with a thickness of 80 μm. The specific steps are as follows:

[0067] Step 1: Plasticize and extrude the mixed raw materials in an extruder according to the formula of each layer in Table 1; count the weight of the raw materials passing through per unit time, adjust the speed of the extruder and the pressure at the die head outlet by the speed of the metering pump to keep the raw material flowing out of the die head stable, and further plasticize the raw materials;

[0068] Step 2: Add the prepared mixture into the hoppers of the corresponding layers of the 11-layer coextrusion blown film machine according to the mass ratio of the 11-layer distribution in Table 1, heat up according to the process parameters in Table 1, wait until the temperature rises to the required temperature, the mixture enters the screw and melts, and start the 11-layer blown film production line of the W&H equipment for extrusion and inflation;

[0069] Step 3: Through the bubble stabilizer frame to the upper traction guide roller, after corona treatment of the outer layer, then conduct the second traction, after passing through the guide roller, enter the third traction, and conduct folding and winding to obtain the modified 11-layer coextruded film Ⅰ.

[0070] Table 1 Experimental formula and process parameters of the modified 11-layer coextruded film Ⅰ

[0071]

[0072]

[0073] (2) Preparation of the modified 11-layer coextruded film Ⅱ: Only use the EVOH / flame retardant modified vermiculite Ⅱ composite material to replace the EVOH / flame retardant modified vermiculite Ⅰ composite material in the modified 11-layer coextruded film Ⅰ to prepare the modified 11-layer coextruded film Ⅱ.

[0074] (3) Preparation of the modified 11-layer coextruded film Ⅲ: Only use the EVOH / flame retardant modified vermiculite Ⅲ composite material to replace the EVOH / flame retardant modified vermiculite Ⅰ composite material in the modified 11-layer coextruded film Ⅰ to prepare the modified 11-layer coextruded film Ⅲ.

[0075] (4) Preparation of the 11-layer coextruded film: Use EVOH to replace the EVOH / flame retardant modified vermiculite Ⅰ composite material in the modified 11-layer coextruded film Ⅰ, and prepare the 11-layer coextruded film according to the same experimental steps and reaction conditions, which is used as a comparative example.

[0076] The specifications and manufacturers of the raw materials used in the specific implementation manner are shown in Table 2;

[0077] Table 2 Experimental raw materials

[0078]

[0079] Performance test:

[0080] (1) Barrier performance: Use a Y110 oxygen transmission rate tester and a TC-03 water vapor transmission rate tester to test the barrier performance of the samples according to GB / T 1038-2000 and GB / T 1037-2021 respectively;

[0081] (2) Flame retardant performance: Vertically fix a 2 cm × 4 cm rectangular sample and burn it, recording the ignition time of the sample;

[0082] (3) Mechanical properties: Fix a 30 mm × 5 mm sample on an Instron 5565 universal tensile testing machine and conduct a tensile test at a tensile rate of 5 mm / min, recording the tensile strength in the longitudinal and transverse directions respectively;

[0083] The above experimental results are shown in Table 3 and Figure 4 .

[0084] Table 3 Performance experimental results of the eleven-layer coextruded film

[0085]

[0086] The following conclusions can be drawn from the results of the performance test:

[0087] (1) All three flame-retardant barrier materials (i.e., EVOH / flame-retardant modified vermiculite I composite material, EVOH / flame-retardant modified vermiculite II composite material, EVOH / flame-retardant modified vermiculite III composite material) can significantly improve the barrier performance of the single-PE-material eleven-layer composite structure film product, and the improvement effects of the three flame-retardant barrier materials are not very different;

[0088] (2) All three flame-retardant barrier materials can significantly enhance the flame retardant ability of the single-PE-material eleven-layer composite structure film product, and the EVOH / flame-retardant modified vermiculite III composite material has the best improvement effect.

Claims

1. A method for preparing a single PE material eleven-layer composite structure film, characterized in that: The following steps are involved: Step 1: synthesizing a DOPO-based silane coupling agent, modifying the DOPO-based silane coupling agent onto the surface of sodium-based vermiculite to obtain a flame-retardant modified vermiculite, and uniformly dispersing the flame-retardant modified vermiculite in an ethylene-vinyl alcohol copolymer matrix to prepare a flame-retardant barrier material; The DOPO-based silane coupling agent is a flame retardant coupling agent II or a flame retardant coupling agent III; The chemical structural formula of the flame retardant coupling agent II is: ； The chemical structural formula of the flame retardant coupling agent III is: ； Step 2: Using an eleven-layer co-extrusion blow molding film-forming process, a single PE material eleven-layer composite structure film with a thickness of 50-200 μm is prepared; the single PE material eleven-layer composite structure film contains the flame-retardant barrier material in step one.

2. The method for preparing a single PE material eleven-layer composite structure film according to claim 1, characterized in that: The formula and dosage of the single PE material eleven-layer composite structure film are as follows: First layer: formula is 50~70wt% LDPE + 30~50wt% LLDPE, dosage is 5~15wt%; The second layer: the formula is 20~50wt%HDPE+50~80wt%m-LLDPE, the dosage is 3~10wt%; The third layer: the formula is 40~80wt% LDPE + 10~30wt% LLDPE + 10~30wt% m-LLDPE, the dosage is 5~15wt%; The fourth layer: the formula is 100wt% PE-g-MAH, the dosage is 1~5wt%; The fifth layer: the formula is 90~95wt% LDPE+5~10wt% EVOH, the dosage is 5~15wt%; The sixth layer: the formula is 90~95wt% LDPE + 5~10wt% of the flame-retardant barrier material, and the amount is 10~40wt%; The seventh layer: the formula is 90~95wt% LDPE+5~10wt% EVOH, the dosage is 5~15wt%; The eighth layer: the formula is 100wt% PE-g-MAH, the dosage is 1~5wt%; Ninth layer: The formula is 40~80wt% LDPE + 10~30wt% LLDPE + 10~30wt% m-LLDPE, and the dosage is 5~15wt%; The tenth layer: the formula is 20~50wt%HDPE+50~80wt%m-LLDPE, the dosage is 3~10wt%; Eleventh layer: The formula is 25~45wt% LDPE + 25~45wt% LLDPE + 10~50% HDPE, and the dosage is 5~15wt%.

3. The method for preparing a single PE material eleven-layer composite structure film according to claim 1, characterized in that: The preparation method of the flame retardant coupling agent II is: Step S3-1: generating a DOPO-based tertiary phosphine monomer by reacting the PH bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with the alkenyl functional group of allyl diphenylphosphine; Step S3-2: utilizing the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the DOPO-based tertiary phosphine monomer undergoes a quaternary phosphine reaction with the bromine functional group of 3-bromopropyltrimethoxysilane to generate a flame retardant coupling agent II.

4. The method for preparing a single PE material eleven-layer composite structure film according to claim 1, characterized in that: The preparation method of the flame retardant coupling agent III is: Step S4-1: generating a tri(DOPO-based) tertiary phosphine monomer by reacting the PH bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with the alkenyl functional group of triallylphosphine; Step S4-2: utilizing the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the tri(DOPO-based) tertiary phosphine monomer undergoes a quaternary phosphine reaction with the bromine functional group of 3-bromopropyltrimethoxysilane to generate a flame retardant coupling agent III.

5. A single PE material eleven-layer composite structure film prepared by the method according to any one of claims 1 to 4, characterized in that: The water vapor permeability of the single PE material eleven-layer composite structure film is 1.0-2.0 [g / (m 2 •24h)], oxygen permeability is 1.0~1.5[cm 3 / (m 2 •24h•0.1MPa)].

6. Application of the single PE material eleven-layer composite structure film according to claim 5 in the field of dairy product packaging.

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