A puncture-resistant film and its preparation process

Abstract

This application relates to the technical field of polymer materials, and specifically discloses a puncture-resistant film and its preparation process. A puncture-resistant film is composed of an outer layer, an intermediate layer, and an inner layer, and the outer layer, the intermediate layer, and the inner layer are all bonded by a solvent-free adhesive; the outer layer is a PET film layer; the intermediate layer is a nylon film layer; the inner layer is mainly prepared from the following raw materials in parts by weight: 36-48 parts of LDPE resin, 20-38 parts of LLDPE resin, 5-10 parts of MLLDPE resin, 1-5 parts of HDPE resin, 5-8 parts of nano-organic montmorillonite, 0.5-1 part of nano-silica sol, 5-8 parts of compatibilizer, 0.3-0.5 part of antiblocking agent, 0.3-0.5 part of slip agent, 0.1-0.3 part of antistatic agent, and 0.1-0.2 part of processing aid. This application can improve the puncture resistance of the film.

Description

Technical Field

[0001] This application relates to the technical field of polymer materials, and particularly relates to a puncture-resistant film and its preparation process. Background Art

[0002] The heavy packaging film is a packaging film that can carry 10 kg - 50 kg of solid particles or powdered materials, and is mainly used for packaging plastic raw materials, chemical fertilizers, feeds, rice, soybeans, grains, etc. During the use and circulation of the packaging bag, it is often subject to puncture by sharp parts of the contents, particulate components, or foreign objects outside the packaging. If the puncture resistance of the packaging bag is poor, it is likely to break under the puncture of external force.

[0003] In order to improve the puncture resistance of the packaging bag, in the related art, low-density polyethylene, linear low-density polyethylene, and metallocene polyethylene are blended in a certain proportion, and after extrusion, they are compounded with other functional layers to obtain a puncture-resistant composite film for use in the packaging bag to improve its puncture resistance.

[0004] Regarding the puncture-resistant film in the above-mentioned related art, the applicant found that the following defects exist in this solution: Since metallocene polyethylene is difficult to process, it is easy to cause wear to the equipment, and the blending effect of metallocene polyethylene with other resins is not good, and the improvement of puncture resistance is not obvious enough. Summary of the Invention

[0005] In order to solve the above technical problems, this application provides a puncture-resistant film and its preparation process.

[0006] In the first aspect, the puncture-resistant film provided by this application is achieved through the following technical solutions:

[0007] A puncture-resistant film is composed of an outer layer, a middle layer, and an inner layer, and the outer layer, middle layer, and inner layer are all bonded by a solvent-free adhesive; the outer layer is a PET film layer; the middle layer is a nylon film layer; the inner layer is mainly prepared from the following raw materials in parts by weight:

[0008] 36 - 48 parts of LDPE resin

[0009] 20 - 38 parts of LLDPE resin

[0010] 5 - 10 parts of MLLDPE resin

[0011] 1 - 5 parts of HDPE resin

[0012] 5 - 8 parts of nano-organophilic montmorillonite

[0013] 0.5 - 1 part of nano-silica sol

[0014] 5 - 8 parts of compatibilizer

[0015] 0.3 - 0.5 parts of antiblocking agent

[0016] 0.3 - 0.5 parts of slip agent

[0017] 0.1 - 0.3 parts of antistatic agent

[0018] 0.1 - 0.2 parts of processing aid.

[0019] By adopting the above technical solution, in the raw materials of the anti - puncture film prepared in this application, LDPE resin and LLDPE resin are used as the base materials, MLLDPE is used as the main modification material to improve the anti - puncture performance of the film layer. A small amount of HDPE can improve the processing performance of MLLDPE and the base materials, and a compatibilizer is added to make the mixed modification effect good; the nano - organic montmorillonite is formed by exfoliating dispersion, purification and modification, ultrafine classification, and special organic compound of montmorillonite clay, and has good dispersion performance, which can improve the impact resistance, fatigue resistance, dimensional stability, gas barrier property and toughening and strengthening of the material, thus enhancing the comprehensive physical properties of the polymer, and at the same time improving the processing performance of the material. The nano - silica sol is used as a modification component to enhance the adhesion of the film layer. Finally, a three - layer film is compounded, and the toughness and impact resistance of the obtained anti - puncture film are enhanced, and it has excellent anti - puncture performance.

[0020] Preferably, the melt mass flow rate MFR of the MLLDPE resin at 2.16 kg is 0.5 - 0.8 g / 10 min, and the density is 0.914 - 0.921 g / cm 3 .

[0021] By adopting the above technical solution, the physical property parameters of the MLLDPE resin are limited. The MLLDPE resin within this range has a better mixing effect with HDPE and the base materials, and has a good improvement effect on the comprehensive performance of the film layer.

[0022] Preferably, the melt mass flow rate MFR of the HDPE resin at 2.16 kg is 0.35 - 0.70 g / 10 min, and the density is 0.954 - 0.961 g / cm 3 .

[0023] By adopting the above technical solution, the physical property parameters of the HDPE resin are limited. The HDPE within this range has a better improvement effect on the defect of difficult processing of MLLDPE, and can greatly improve the anti - puncture performance of the film layer.

[0024] Preferably, the mass ratio of the MLLDPE resin to the HDPE resin is (1 - 1.2):(0.2 - 0.4).

[0025] By adopting the above technical solution, within the above mass ratio range, HDPE has a better improvement effect on the processing performance of MLLDPE, and the synergistic effect of the two on enhancing the puncture resistance of the substrate is good.

[0026] Preferably, the apparent density of the nano-organophilic montmorillonite is 0.25 - 0.35 g / cm 3 , and the average crystal wafer thickness is 15 - 25 nm.

[0027] By adopting the above technical solution, defining the physical property parameters of the used nano-organophilic montmorillonite can keep its adsorption capacity and dispersion performance within a good range, with a better mixing effect, thus enhancing the comprehensive physical properties of the polymer.

[0028] Preferably, the nano-silica sol is one of acrylate-modified nano-silica sol, methyl-modified nano-silica sol, and epoxy-group-modified nano-silica sol.

[0029] By adopting the above technical solution, the modified nano-silica sol has good dispersibility and compatibility, excellent transparency, and can improve the adhesion of the inner layer, achieving the effects of wear resistance, strengthening, and toughening.

[0030] Preferably, the compatibilizer is composed of LLDPE grafted maleic anhydride and HDPE grafted maleic anhydride mixed in a volume ratio of (0.3 - 0.6) : (0.4 - 0.7).

[0031] By adopting the above technical solution, LLDPE grafted maleic anhydride grafts maleic anhydride molecules onto the molecular chain of linear low-density polyethylene, and HDPE grafted maleic anhydride grafts maleic anhydride groups onto the molecular chain of high-density polyethylene, both making the polyethylene end have the re-reactivity and strong polarity of maleic anhydride polar molecules. When the two compatibilizers are mixed in an appropriate ratio, the compatibility between the substrate and the modified material can be improved.

[0032] In the second aspect, a preparation process for a puncture-resistant film provided by the present application is achieved through the following technical solutions:

[0033] A preparation process for a puncture-resistant film includes the following steps:

[0034] S1. Preparation of the inner layer

[0035] a: Weigh accurately the LDPE resin, LLDPE resin, MLLDPE resin, HDPE resin, and the compatibilizer, and melt-blend them in a high-speed mixer for 30 - 45 min to obtain a blend A;

[0036] b: Melt and blend the accurately metered nano-silica sol, nano-organophilic montmorillonite and blend A in a high-speed mixer for 10 - 15 min to obtain blend B;

[0037] c: Add the accurately metered opening agent, slip agent, antistatic agent and processing aid to blend B and mix for 15 - 20 min to obtain blend C, and then extrude and cast blend C into a film;

[0038] S2: Composite the outer layer, middle layer and inner layer with a solvent-free adhesive, and then cure the composite film to obtain the finished anti-puncture film.

[0039] By adopting the above technical scheme, the substrate is improved by gradually adding modified substances. The processing difficulty of MLLDPE as a modified material is effectively improved by HDPE. Then, nano-silica sol and nano-organophilic montmorillonite are added to enhance the adhesion of the film layer. Finally, other additives are added, so that a film with excellent anti-puncture performance can be prepared.

[0040] Preferably, in S1, the specific operation of extruding and casting blend C into a film is as follows: extrude blend C, with the screw speed of 400 - 500 r / min, melt it into a fluid at 180 - 210 °C, the first temperature zone is 180 - 185 °C, the second temperature zone is 190 - 195 °C, the third temperature zone is 195 - 200 °C, the fourth temperature zone is 200 - 210 °C, and the die head temperature is 200 - 205 °C; cast, with the temperature of the cooling roll being 20 - 40 °C, to obtain the inner layer.

[0041] By adopting the above technical scheme, through the above operations, under the conditions of limiting the screw speed and the temperature at each stage, the processing effect of the blend is good, and the anti-puncture performance of the prepared inner layer film is excellent.

[0042] In summary, the present application has the following advantages:

[0043] 1. The present application uses MLLDPE and HDPE to modify LDPE and LLDPE. HDPE effectively reduces the processing difficulty of MLLDPE, and at the same time forms a good cooperation relationship with MLLDPE. Under the action of the compatibilizer, the anti-puncture performance of the film layer is well improved. At the same time, nano-organophilic montmorillonite and nano-silica sol are added to further improve the processing performance of the material. Finally, through the composite of the inner layer with the PET film layer and the nylon film layer, an anti-puncture film with excellent performance is prepared.

[0044] 2. The preparation method of the present application is relatively simple, with low operation difficulty, and is convenient for industrial production and manufacturing. Detailed Embodiments

[0045] The present application will be further described in detail below in combination with comparative examples and embodiments.

[0046] Example

[0047] Example 1

[0048] A puncture-resistant film disclosed in the present application is composed of an outer layer, a sandwich layer and an inner layer, and the outer layer, the sandwich layer and the inner layer are all bonded by a solvent-free adhesive. The solvent-free adhesive uses a two-component solvent-free polyurethane adhesive, which is compounded from Agent A FA-817A (10 parts) and Agent B FA-217B (9 parts).

[0049] The outer layer of the puncture-resistant film is a PET film layer, and the sandwich layer is a nylon film layer, both of which use commercially available film materials.

[0050] The inner layer is mainly prepared from the following raw materials:

[0051] 36 parts of LDPE resin, 20 parts of LLDPE resin, 5 parts of MLLDPE resin, 1 part of HDPE resin, 5 parts of nano-organophilic montmorillonite, 0.8 part of nano-silica sol, 2.5 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer, 2.5 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer, 0.4 part of 8000-mesh spherical SiO2, 0.4 part of PATHWEL slip agent - erucamide, 0.2 part of K-YD-C-3 type antistatic agent, 0.2 part of PPA processing aid HD-2810.

[0052] Among them, the melt mass flow rate MFR of the MLLDPE resin is 0.8 g / 10 min at 2.16 kg, and the density is 0.914 g / cm 3 . The melt mass flow rate MFR of the HDPE resin is 0.35 g / 10 min at 2.16 kg, and the density is 0.954 g / cm 3 .

[0053] The nano-organophilic montmorillonite is obtained by using dioctadecyl dimethyl ammonium chloride as the main modifier, with the model DK4, the apparent density of 0.25 - 0.35 g / cm 3 , and the average wafer thickness of 15 - 25 nm. The nano-silica sol uses acrylate-modified nano-silica sol, the size of nano-silica is about 20 nm, and the concentration is 50 wt%.

[0054] A preparation process of a puncture-resistant film includes the following steps:

[0055] S1. Preparation of the inner layer

[0056] a: Weigh accurately the LDPE resin, LLDPE resin, MLLDPE resin, HDPE resin and compatibilizer, and melt-blend them in a high-speed mixer for 35 min to obtain a blend A;

[0057] b: Mix the accurately measured nano-silica sol, nano-organic montmorillonite and blend A in a high-speed mixer for 10 min to obtain blend B;

[0058] c: Add the accurately measured opening agent, slip agent, antistatic agent and processing aid to blend B and mix for 15 min to obtain blend C.

[0059] Extrude blend C with a screw speed of 450 r / min and melt it into a fluid at 180 - 210 °C. The first temperature zone is 185 °C, the second temperature zone is 195 °C, the third temperature zone is 200 °C, the fourth temperature zone is 205 °C, and the die head temperature is 200 °C; Cast it and the temperature of the cooling roll is 30 °C to prepare the inner layer.

[0060] S2. Composite the outer layer, the interlayer and the inner layer with a solvent-free adhesive, and then age the composite film at 25 °C for 24 h to obtain the finished puncture-resistant film. The grammage of the outer layer is 32 g / m 3 , the interlayer is 30 g / m 3 , the inner layer is 43 g / m 3 , and the sizing amount is 15 g / m 3 .

[0061] Example 2

[0062] The difference between Example 2 and Example 1 is that the inner layer is mainly prepared from the following raw materials:

[0063] 48 parts of LDPE resin, 38 parts of LLDPE resin, 10 parts of MLLDPE resin, 5 parts of HDPE resin, 8 parts of nano-organic montmorillonite, 4 parts of LLDPE grafted maleic anhydride (grade W1L) compatibilizer, 4 parts of HDPE grafted maleic anhydride (grade W1H) compatibilizer, 0.8 part of nano-silica sol, 0.4 part of 8000-mesh spherical SiO2, 0.4 part of PATHWEL slip agent - erucamide, 0.2 part of K-YD-C-3 type antistatic agent, 0.2 part of PPA processing aid HD-2810.

[0064] Example 3

[0065] The difference between Example 3 and Example 1 is that the inner layer is mainly prepared from the following raw materials:

[0066] 45 parts of LDPE resin, 30 parts of LLDPE resin, 8 parts of MLLDPE resin, 3 parts of HDPE resin, 6 parts of nano - organic montmorillonite, 3 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer, 3 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer, 0.8 parts of nano - silica sol, 0.4 parts of 8000 - mesh spherical SiO2, 0.4 parts of PATHWEL slip agent - erucamide, 0.2 parts of K - YD - C - 3 type antistatic agent, 0.2 parts of PPA processing aid HD - 2810.

[0067] Example 4

[0068] The difference between Example 4 and Example 3 lies in that in the preparation raw materials of the inner layer, there are 29 parts of LLDPE resin, 9 parts of MLLDPE resin, and 3 parts of HDPE resin.

[0069] Example 5

[0070] The difference between Example 5 and Example 3 lies in that in the preparation raw materials of the inner layer, there are 29 parts of LLDPE resin, 10 parts of MLLDPE resin, and 2 parts of HDPE resin.

[0071] Example 6

[0072] The difference between Example 6 and Example 3 lies in that in the preparation raw materials of the inner layer, there are 31 parts of LLDPE resin, 8 parts of MLLDPE resin, and 2 parts of HDPE resin.

[0073] Example 7

[0074] The difference between Example 7 and Example 6 lies in that in the preparation raw materials of the inner layer, the compatibilizer uses 2.57 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer and 3.43 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer.

[0075] Example 8

[0076] The difference between Example 8 and Example 6 lies in that in the preparation raw materials of the inner layer, the compatibilizer uses 2.77 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer and 3.23 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer.

[0077] Example 9

[0078] The difference between Example 9 and Example 6 lies in that in the preparation raw materials of the inner layer, the compatibilizer uses 2.4 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer and 3.6 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer.

[0079] Example 10

[0080] The difference between Example 10 and Example 9 lies in that in the raw materials for preparing the inner layer, the nano-silica sol is an epoxy-modified nano-silica sol, the size of the nano-silica is about 20 nm, and the concentration is 50 wt%.

[0081] Comparative Example

[0082] The difference between Comparative Example 1 and Example 1 lies in that the inner layer is mainly prepared from the following raw materials:

[0083] 30 parts of LDPE resin, 15 parts of LLDPE resin, 3 parts of MLLDPE resin, 2 parts of nano-organic montmorillonite, 3 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer, 0.8 parts of nano-silica sol, 0.4 parts of 8000-mesh spherical SiO2, 0.4 parts of PATHWEL slip agent - erucamide, 0.2 parts of K-YD-C-3 type antistatic agent, 0.2 parts of PPA processing aid HD-2810.

[0084] The difference between Comparative Example 2 and Example 1 lies in that the inner layer is mainly prepared from the following raw materials:

[0085] 55 parts of LDPE resin, 40 parts of LLDPE resin, 15 parts of MLLDPE resin, 8 parts of HDPE resin, 10 parts of nano-organic montmorillonite, 5 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer, 5 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer, 0.8 parts of nano-silica sol, 0.4 parts of 8000-mesh spherical SiO2, 0.4 parts of PATHWEL slip agent - erucamide, 0.2 parts of K-YD-C-3 type antistatic agent, 0.2 parts of PPA processing aid HD-2810.

[0086] The difference between Comparative Example 3 and Example 3 lies in that in the raw materials for preparing the inner layer, the MLLDPE resin is 9.2 parts and the HDPE resin is 1.8 parts.

[0087] The difference between Comparative Example 4 and Example 3 lies in that in the raw materials for preparing the inner layer, the MLLDPE resin is 6.8 parts and the HDPE resin is 4.2 parts.

[0088] The difference between Comparative Example 5 and Example 1 lies in that in the raw materials for preparing the inner layer, the compatibilizer is replaced with a PE compatibilizer GT-GPE-200.

[0089] The difference between Comparative Example 6 and Example 9 lies in that in the raw materials for preparing the inner layer, the compatibilizer is 1.2 parts of LLDPE graft maleic anhydride (grade W1L) compatibilizer and 4.8 parts of HDPE graft maleic anhydride (grade W1H) compatibilizer.

[0090] The difference between Comparative Example 7 and Example 9 lies in that in the raw materials for preparing the inner layer, 1.5 parts of compatibilizer of LLDPE grafted maleic anhydride (grade W1L) and 4.5 parts of compatibilizer of HDPE grafted maleic anhydride (grade W1H) are used.

[0091] Performance detection test

[0092] Detection method

[0093] Experiment 1. Puncture resistance performance test: The puncture-resistant films prepared in Examples 1-10 and Comparative Examples 1-7 were taken, and the puncture strength of the composite film was measured according to the method specified in GB / T 10004-2008. The equipment used was a puncture force tester.

[0094] Experiment 2. Impact performance test: It was measured by the free-falling dart method of the test method for impact resistance of plastic films and sheets in GB / T 9639.1-2008. The equipment used was a film dart impact testing machine.

[0095] Experiment 3. Tensile performance test: The tensile strength was tested according to GB / T 1040.3—2006. The equipment used was a film tensile strength tester.

[0096] Detection results

[0097] The performance test results of Examples 1-10 and Comparative Examples 1-7 are shown in Tables 1-3.

[0098] Table 1 Performance test data of Examples 1-3 and Comparative Examples 1-2

[0099]

[0100] Combined with Examples 1-3, Comparative Examples 1 and 2 and Table 1, it can be seen that when the amounts of the base materials LDPE and LLDPE, the main modification materials MLLDPE, HDPE, the compatibilizer and the nano-organophilic montmorillonite in the formula are more, the puncture strength of the prepared composite film gradually increases, the impact resistance is better, and at the same time the tensile strength is also enhanced. However, when the amount of the main material exceeds the range defined in this application, too little amount will lead to relatively poor puncture resistance and impact resistance, and the tensile strength will also decrease. When the amount is too much, all performances will also decrease. Considering the comprehensive effect, the amounts of the base materials LDPE and LLDPE, the main modification materials MLLDPE, HDPE, the compatibilizer and the nano-organophilic montmorillonite in Example 3 are the most suitable.

[0101] Table 2 Performance test data of Examples 4-6 and Comparative Examples 3-4

[0102]

[0103]

[0104] Combined with Examples 4-6 and Comparative Examples 3 and 4 and in conjunction with Table 2, it can be seen that on the premise of roughly defining the amounts of the base materials LDPE, LLDPE and other components in the formulation, the mass ratio relationship between MLLDPE and HDPE has a great impact on the enhancement of puncture strength and impact resistance. When the mass ratio of MLLDPE to HDPE is within the range of (1-1.2):(0.2-0.4), the test results of puncture strength, dart impact and tensile strength are all good. After exceeding the range, the improvement effect of HDPE on the processability of MLLDPE becomes poor, and at the same time, the modification effect on the base material is not good, and the cost will also consume a large amount. Considering the comprehensive effect, when the mass ratio between MLLDPE and HDPE in Example 6 is 1:0.25, the obtained composite film has the best puncture strength, good impact resistance and high tensile strength.

[0105] Table 3 Performance test data of Examples 7-10 and Comparative Examples 5-7

[0106]

[0107] Combined with Examples 7-9 and Comparative Example 5 and in conjunction with Table 2, it can be seen that when the amounts of each component in the formulation and the mass ratio between MLLDPE and HDPE are limited, using the same amount of compatibilizer, the improvement effect of the PE general compatibilizer on the blending effect of each component in the formulation is not as good as that of the compound compatibilizer used in this application, and the puncture strength and impact resistance are relatively poor. Considering Examples 6, Examples 7-9 and Comparative Examples 6-7, the ratio relationship between the two compatibilizers in the compatibilizer used in this application also has an impact on the blending effect of each component in the formulation. In Example 9, when the volume ratio of maleic anhydride grafted LLDPE to maleic anhydride grafted HDPE is within the range of (0.3-0.6):(0.4-0.7), the synergistic effect can be better exerted, and the obtained film material has a good mixing effect, thus having better anti-puncture, impact resistance and tensile properties. When the ratio of the two exceeds the limited range, the puncture strength and impact resistance are greatly affected, and the comprehensive performance becomes poor. Considering the comprehensive results, when the volume ratio of maleic anhydride grafted LLDPE to maleic anhydride grafted HDPE is 0.4 / 0.6, the improvement effect of anti-puncture, impact resistance and tensile properties is the best.

[0108] Combined with Example 9 and Example 10, on the premise of limiting the amount of the main material, the mass ratio of the modified components and the composition of the compatibilizer, using epoxy group nano-silica sol has a further enhanced effect on the impact resistance of the film layer. The epoxy group modified nano-silica sol has better dispersibility and good mixing effect with the resin, further enhancing the toughness of the film layer and improving the anti-puncture and tensile properties.

[0109] In summary, the puncture strength and impact resistance of the anti-puncture film of the present application have been significantly improved, and the stretchability of the product has also been significantly enhanced. The problem of difficult processing during the modification of metallocene polyethylene has also been solved. The addition of a compound compatibilizer and nanomaterials further improves the anti-puncture effect of the composite film and enhances its application performance.

[0110] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A puncture-resistant film, characterized in that: It consists of an outer layer, an interlayer and an inner layer, and the outer layer, the interlayer and the inner layer are bonded by a solvent-free adhesive; the outer layer is a PET film layer; the interlayer is a nylon film layer; the inner layer is mainly made of the following raw materials in parts by weight: 36-48 parts of LDPE resin; 20-38 parts of LLDPE resin; 5-10 parts of MLLDPE resin; 1-5 parts of HDPE resin; 5-8 parts of nano-organic montmorillonite; 0.5-1 part of nano-silica sol; 5-8 parts of compatibilizer; 0.3-0.5 parts of opening agent; 0.3-0.5 parts of lubricant; Antistatic agent 0.1-0.3 parts; Processing aid 0.1-0.2 parts; The compatibilizer is prepared by mixing LLDPE grafted maleic anhydride and HDPE grafted maleic anhydride in a volume ratio of (0.3-0.6): (0.4-0.7).

2. The puncture-resistant film according to claim 1, characterized in that: The melt mass flow rate MFR of the MLLDPE resin is 0.5-0.8 g / 10 min at 2.16 kg, and the density is 0.914-0.921 g / cm 3 .

3. The puncture-resistant film according to claim 2, characterized in that: The HDPE resin has a melt mass flow rate (MFR) of 0.35-0.70 g / 10 min at 2.16 kg and a density of 0.954-0.961 g / cm 3 .

4. The puncture-resistant film according to claim 3, characterized in that: The mass ratio of the MLLDPE resin to the HDPE resin is (1-1.2): (0.2-0.4).

5. The puncture-resistant film according to claim 1, characterized in that: The apparent density of the nano-organic montmorillonite is 0.25-0.35 g / cm3, and the average wafer thickness is 15-25 nm.

6. The puncture-resistant film according to claim 1, characterized in that: The nano-silica sol is one of acrylate-modified nano-silica sol, methyl-modified nano-silica sol and epoxy-modified nano-silica sol.

7. A process for preparing a puncture-resistant film according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Inner layer preparation a: Melt-blend accurately measured LDPE resin, LLDPE resin, MLLDPE resin, HDPE resin and compatibilizer in a high-speed mixer for 30-45 minutes to obtain blend A; b: Melt and blend accurately measured nano-silica sol, nano-organic montmorillonite and blend A in a high-speed mixer for 10-15 minutes to obtain blend B; c: Add accurately measured anti-blocking agent, slip agent, antistatic agent, and processing aid to blend B and mix for 15-20 minutes to obtain blend C, which is then extruded and cast into a film; S2. Compounding the outer layer, the interlayer, and the inner layer with a solvent-free adhesive, and then subjecting the composite film to a curing treatment to obtain a puncture-resistant film product.

8. The process for preparing a puncture-resistant film according to claim 7, characterized in that: In the S1, the specific operation of extrusion and casting film formation in step c is to extrude the blend C with a screw speed of 400-500 r / min, melt it into a fluid at 180-210°C, the first temperature zone is 180-185°C, the second temperature zone is 190-195°C, the third temperature zone is 195-200°C, the fourth temperature zone is 200-210°C, and the die head temperature is 200-205°C; casting, the cooling roller temperature is 20-40°C, to obtain the inner layer.

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