Transparent antistatic polyethylene composite film and preparation method thereof

Abstract

The invention discloses a transparent antistatic polyethylene composite film and a preparation method thereof, and belongs to the technical field of functional plastic films, and the transparent antistatic polyethylene composite film comprises a first antistatic layer, a skeleton layer and a second antistatic layer which are connected in sequence. The PE grafted polyethylene glycol resin is used as a main raw material of the antistatic layer, an antistatic agent does not need to be additionally added, and the problems of migration, precipitation and incompatibility with a resin base material of a traditional antistatic agent are solved; besides, polyethylene glycol branched chains in the added PE grafted polyethylene glycol resin can improve transparency and have hydrophilicity, the polarity difference between the polyethylene glycol branched chains and hydrophobic PE resin of the framework layer is large, and in the environment with specific temperature and humidity, the polyethylene glycol branched chains are gradually adjusted and tend to be distributed on the outer surface and adsorbed and combined with water vapor in the environment; therefore, the surface resistance is reduced, and the antistatic property of the transparent antistatic polyethylene composite film is further improved while the mechanical property is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of functional plastic films, in particular to a transparent antistatic polyethylene composite film and a preparation method thereof. Background Art

[0002] Polyethylene (PE) is a common polymer material that is widely used in many fields. In the packaging field, PE is a very important packaging film material. Since PE itself is a highly insulating material, PE packaging film is prone to static electricity during production, processing and application, and the inconvenience and even production accidents caused by this are also common. When used as packaging materials for high-precision electronic components, the accumulated charge may even damage the contents and cause economic losses. Based on this, it is very necessary to develop antistatic PE film materials.

[0003] In the prior art, the preparation of antistatic PE film is mostly achieved by adding antistatic agents. Common antistatic agents include inorganic conductive fillers, such as carbon black, graphite, silver ions, etc.; or organic polymer antistatic agents, such as polyethylene oxide, quaternary ammonium salt-based methacrylate copolymers, sodium polyphenylene oxide sulfonate, etc. For example, Chinese patent application number CN202411902276.9 discloses an antistatic plastic film and a preparation method thereof, wherein the antistatic plastic film is composed of a PET base film and an antistatic coating formed by curing an antistatic coating, wherein the antistatic coating comprises, by weight, 100 parts of a silicone resin, 12-18 parts of an antistatic agent, 0.8-1.1 parts of a dispersant, 0.4-0.6 parts of a bridging agent, 0.15-0.2 parts of a leveling agent, and 55-60 parts of a solvent; the antistatic agent is composed of lamellar graphene as a static charge release matrix, and the surface of the lamellar layer is modified by introducing amino groups using a silane coupling agent KH-550, and then methyl chloroacetate replaces the amino groups grafted on the lamellar layer, and finally iodomethane reacts with the substituted amine compound to carry out a quaternization reaction, and quaternary ammonium cations are introduced into the surface of the graphene lamellar layer, which forms a continuous current collecting layer in the coating, thereby promptly conducting away the generated static charge, thereby giving the film material excellent antistatic properties. However, there is a problem that the antistatic coating peels off and affects the antistatic performance. For example, the Chinese patent application number CN202210558259.2 discloses a composition of an antistatic degradable plastic film. The plastic film in the patent is made of PBAT, polylactic acid, starch and other base materials, and is prepared with a carbon nanotube synergistic graphene modifier electrostatic aid. However, the carbon nanotube synergistic graphene modifier electrostatic aid has migration, which will also affect its antistatic performance.

[0004] Therefore, the addition of antistatic agents in the prior art can effectively reduce the charge accumulation of PE films, but it also brings other disadvantages. For example, the introduction of conductive fillers will affect the transparency of PE films and is not suitable for gift packaging occasions with high appearance requirements. Most inorganic / organic antistatic agents have poor compatibility with PE. Even with the help of compatibilizing agents, it is often difficult for antistatic agents to disperse evenly in the PE matrix, thus affecting the appearance and performance of the finished PE film. Therefore, it is necessary to develop a new type of transparent and antistatic PE film by other means. Summary of the Invention

[0005] Based on this, in order to solve one of the above problems, the present invention provides a transparent antistatic polyethylene composite film and a preparation method thereof. The specific technical solutions are as follows: A transparent antistatic polyethylene composite film, which includes a first antistatic layer, a skeleton layer, and a second antistatic layer connected in sequence. The thickness of the first antistatic layer accounts for 3% - 20% of the total thickness of the transparent antistatic polyethylene composite film; the thickness of the second antistatic layer accounts for 3% - 20% of the total thickness of the transparent antistatic polyethylene composite film; Among them, both the first antistatic layer and the second antistatic layer include the following parts by weight of preparation raw materials: 100 parts of PE-grafted polyethylene glycol resin and 0 - 2 parts of a first auxiliary material. In the PE-grafted polyethylene glycol resin, the polyethylene glycol side chain accounts for 10% - 35% of the mass of the PE-grafted polyethylene glycol resin, and the molecular weight range of the polyethylene glycol side chain is 200 g / mol - 4000 g / mol; The skeleton layer includes the following parts by weight of preparation raw materials: 100 parts of PE resin, 0.1 - 0.5 parts of a transparent nucleating agent, and 0 - 2 parts of a second auxiliary material.

[0006] Further, the melt index of the PE-grafted polyethylene glycol resin at 190°C and 2.16 kg is 1 g / 10 min - 30 g / 10 min.

[0007] Further, the preparation method of the PE-grafted polyethylene glycol resin is as follows: Mix PE resin, maleic anhydride monomer, and initiator evenly in proportion to obtain a mixture; Put the mixture into a first twin-screw extruder for the first reaction. The reaction zone temperature of the first twin-screw extruder is controlled at 220°C - 300°C, the screw speed is controlled at 500 rpm - 800 rpm, and the thread elements in the reaction zone are mainly TME-type thread elements with strong shear action, and the number is not less than 80% to obtain PE-grafted maleic anhydride resin; Transfer the PE grafted maleic anhydride resin to the second twin-screw extruder while it is still hot, and at the same time inject molten amino polyethylene glycol monomethyl ether at the side feeding port for the second reaction. The reaction zone temperature of the second twin-screw extruder is controlled at 150°C to 200°C, and the screw speed is controlled at 200 rpm to 400 rpm to obtain PE grafted polyethylene glycol resin.

[0008] Further, the PE resin is at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, metallocene polyethylene, and bimodal polyethylene.

[0009] Further, the first auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent, and filler.

[0010] Further, the transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

[0011] Further, the second auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent, and filler.

[0012] In addition, the present invention also provides a method for preparing a transparent antistatic polyethylene composite film, and the preparation method includes the following steps: Mix the raw materials for preparing the first antistatic layer evenly to obtain a premix of the first antistatic layer; Mix the raw materials for preparing the second antistatic layer evenly to obtain a premix of the second antistatic layer; Mix the raw materials for preparing the skeleton layer evenly to obtain a premix of the skeleton layer; According to the layer design of the transparent antistatic polyethylene composite film, respectively put them into the corresponding channels of a multi-layer melt co-extrusion casting device, co-extrusion cast and form, and obtain the composite film in one step, then cool and wind it up for standby; Place the composite film in an environment with a temperature of 70°C to 100°C and a relative humidity of 50% to 90% and let it stand for 10h to 72h to obtain the transparent antistatic polyethylene composite film.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses PE grafted polyethylene glycol resin as the main raw material for the first antistatic layer and the second antistatic layer, without the need to add additional antistatic agents, overcoming the problems of migration, precipitation, and incompatibility with the resin substrate of traditional antistatic agents. In addition, the introduction of polyethylene glycol branches destroys the regularity of PE molecules and reduces its crystallinity. Compared with ordinary PE resin, its transparency is further improved.

[0014] 2. The polyethylene glycol branches in the PE-grafted polyethylene glycol resin added in the present invention are hydrophilic, and have a large polarity difference from the hydrophobic PE resin in the skeleton layer. Under the environment of specific temperature and humidity, the polyethylene glycol branches will gradually adjust and tend to be distributed on the outer surface, adsorb and combine with water vapor in the environment, thereby reducing the surface resistance and also being beneficial to the improvement of the antistatic performance, making the transparent antistatic polyethylene composite film of the present invention have more excellent antistatic performance.

[0015] 3. The transparent antistatic polyethylene composite film prepared in the present invention includes a first antistatic layer, a skeleton layer, and a second antistatic layer connected in sequence. While ensuring its application performance, it can also reduce the preparation cost of the product, making the present invention have the advantages of being green, efficient, and low-cost, and having higher economic value. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the transparent antistatic polyethylene composite film prepared in Example 1 of the present invention; Figure 2 is a schematic principle diagram of Example 1 of the present invention.

[0017] Description of the Reference Numerals: 1. First antistatic layer; 2. Skeleton layer; 3. Second antistatic layer; 4. Polyethylene glycol chain segment. Detailed Embodiments

[0018] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further details the present invention in conjunction with its embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0020] A transparent antistatic polyethylene composite film in an embodiment of the present invention, the transparent antistatic polyethylene composite film includes a first antistatic layer, a skeleton layer, and a second antistatic layer connected in sequence, and the thickness of the first antistatic layer accounts for 3% - 20% of the total thickness of the transparent antistatic polyethylene composite film; the thickness of the second antistatic layer accounts for 3% - 20% of the total thickness of the transparent antistatic polyethylene composite film; Among them, both the first antistatic layer and the second antistatic layer include the following raw materials for preparation in parts by weight: 100 parts of PE-grafted polyethylene glycol resin and 0 to 2 parts of the first auxiliary material; The skeleton layer includes the following raw materials for preparation in parts by weight: 100 parts of PE resin, 0.1 to 0.5 parts of a transparent nucleating agent, and 0 to 2 parts of a second auxiliary material.

[0021] In the above solution, the thicknesses of the first antistatic layer and the second antistatic layer are limited. While ensuring their excellent antistatic performance, they also have excellent mechanical properties and do not increase production costs.

[0022] In one embodiment, the PE-grafted polyethylene glycol resin is a functional polymer with a PE molecular chain backbone and polyethylene glycol side chains.

[0023] In one embodiment, the melt index of the PE-grafted polyethylene glycol resin at 190 °C and 2.16 kg is 1 g / 10 min to 30 g / 10 min, preferably 5 g / 10 min to 20 g / 10 min; within this range, the PE-grafted polyethylene glycol resin has better processing performance.

[0024] In one embodiment, in the PE-grafted polyethylene glycol resin, the polyethylene glycol side chains account for 10% to 35% of the mass of the PE-grafted polyethylene glycol resin; the molecular weight range of the polyethylene glycol side chains is 200 g / mol to 4000 g / mol. Within this range, the PE-grafted polyethylene glycol resin has a better antistatic effect. If it is lower than this range value, the chain length of the polyethylene glycol side chains is relatively small and is easily wrapped by the PE main chain, or the number is too small to play its role; if it is higher than this range value, the molecular chain of polyethylene glycol is too long or its addition ratio is too large, which will lead to insufficient and incomplete reactions, and the excessive residual polyethylene glycol will affect the appearance and performance of the film.

[0025] In one embodiment, the preparation method of the PE-grafted polyethylene glycol resin is as follows: Mix PE resin, maleic anhydride monomer, and initiator evenly in proportion to obtain a mixture; Put the mixture into a first twin-screw extruder for the first reaction, and control the temperature of the reaction zone of the first twin-screw extruder at 220 °C to 300 °C, the screw speed at 500 rpm to 800 rpm, and the thread elements in the reaction zone are mainly TME-type thread elements with strong shear action, and the number is not less than 80% to obtain PE-grafted maleic anhydride resin; The hot PE grafted maleic anhydride resin is transferred to a second twin-screw extruder, and molten amino polyethylene glycol monomethyl ether is injected into the side feeding port at the same time for a second reaction. The reaction zone temperature of the second twin-screw extruder is controlled at 150°C to 200°C, and the screw speed is controlled at 200 rpm to 400 rpm to obtain PE grafted polyethylene glycol resin.

[0026] In one embodiment, the PE resin is at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, metallocene polyethylene, and bimodal polyethylene.

[0027] In one embodiment, the initiator is a peroxide initiator.

[0028] In one embodiment, the initiator is at least one of dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, tert-butyl lauroyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, bis(tert-butylperoxyisopropyl)benzene, tert-butyl cumyl peroxide, tert-butyl benzoate, and tert-butyl peroxyacetate.

[0029] In one embodiment, the maleic anhydride monomer has an industrial grade or higher purity.

[0030] In one embodiment, the maleic anhydride monomer is heated to 80 - 100°C to melt it before mixing and then mixed with the PE resin and the initiator while it is still hot, which is beneficial to improving the mixing uniformity.

[0031] When preparing the PE grafted polyethylene glycol resin in the present invention, by controlling the conditions of the first twin-screw extruder, the high-temperature and high-shear reaction conditions are beneficial to improving the reaction efficiency, reducing monomer residues, and suppressing the cross-linking side reaction of PE to avoid a sharp drop in the melt index of the reaction product. Reacting the PE grafted maleic anhydride resin while it is hot can inhibit the hydrolysis of maleic anhydride groups, thereby improving the reaction efficiency with amino polyethylene glycol monomethyl ether.

[0032] In one embodiment, the first auxiliary material includes at least one of an antioxidant, an ultraviolet absorber, a nucleating agent, a slip agent, and a filler.

[0033] In one embodiment, the melt index of the PE resin is 1 g / 10 min to 30 g / 10 min, preferably 5 g / 10 min to 20 g / 10 min.

[0034] In one embodiment, the transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

[0035] In one embodiment, the transparent nucleating agent is at least one of methyl dibenzylidene sorbitol, bis(p-methylbenzylidene), bis-(p-ethylbenzylidene isopropyl)sorbitol, tricresyl phosphate, and sodium 2,2-methylenebis(4,6-di-tert-butylphenoxy) phosphate.

[0036] In one embodiment, the second auxiliary material includes at least one of an antioxidant, an ultraviolet absorber, a nucleating agent, a slip agent, and a filler.

[0037] In addition, the present invention also provides a method for preparing a transparent antistatic polyethylene composite film, and the preparation method includes the following steps: Mix the preparation raw materials of the first antistatic layer evenly to obtain a premix of the first antistatic layer; Mix the preparation raw materials of the second antistatic layer evenly to obtain a premix of the second antistatic layer; Mix the preparation raw materials of the skeleton layer evenly to obtain a premix of the skeleton layer; According to the layer design of the transparent antistatic polyethylene composite film, respectively input them into the corresponding channels of a multi-layer melt coextrusion casting device, coextrusion cast and form, and obtain the composite film in one step, then cool and wind it up for standby; Place the composite film in an environment with a temperature of 70°C to 100°C and a relative humidity of 50% to 90% and let it stand for 10h to 72h to obtain the transparent antistatic polyethylene composite film.

[0038] In one embodiment, the melting temperature of the coextrusion casting and forming is 180°C to 250°C.

[0039] In one embodiment, the cooling temperature is 0 to 10°C.

[0040] The transparent antistatic polyethylene composite film prepared by the above scheme has excellent antistatic performance while ensuring its mechanical properties, and is green, efficient, has low preparation cost, and strong operability for large-scale production.

[0041] Next, the implementation scheme of the present invention will be described in detail with specific embodiments.

[0042] Example 1: A transparent antistatic polyethylene composite film, the transparent antistatic polyethylene composite film has a three-layer structure, and the three-layer structure includes a first antistatic layer, a skeleton layer, and a second antistatic layer connected in sequence; The preparation raw materials of the first antistatic layer and the second antistatic layer are the same, as shown in Table 1; the preparation raw materials of the skeleton layer are shown in Table 2.

[0043] Table 1: Preparation raw materials of the first antistatic layer and the second antistatic layer

[0044] Table 2: Preparation raw materials of the skeleton layer

[0045] A preparation method of a transparent antistatic polyethylene composite film in Example 1 includes the following steps: S1: According to the weight ratio, mix the preparation raw materials of the first antistatic layer and the second antistatic layer evenly to obtain the premixes of the first antistatic layer and the second antistatic layer; mix the preparation raw materials of the skeleton layer evenly to obtain the premix of the skeleton layer; S2: According to the design of the first antistatic layer, the skeleton layer and the second antistatic layer, put the premixes obtained in step S1 into the corresponding channels of a three-layer melt coextrusion casting device respectively, and perform coextrusion casting molding to obtain the composite film in one step, then cool and wind it up for standby. Control parameters such as the feeding speed and winding rate of the material to regulate the total thickness and the thickness ratio of each layer of the composite film; the casting melting temperature is set at 220 °C, and the cooling temperature is set at 4 °C; S3: Place the composite film obtained in step S2 in an environment with a temperature of 83 °C and a relative humidity of 77% and let it stand for 24 h to obtain the transparent antistatic polyethylene composite film.

[0046] After testing, the thickness of the transparent antistatic polyethylene composite film in Example 1 is 0.05 mm. The thickness of the first antistatic layer accounts for 6% of the total thickness of the transparent antistatic polyethylene composite film, and the thickness of the second antistatic layer accounts for 6% of the total thickness of the transparent antistatic polyethylene composite film.

[0047] Example 2: A transparent antistatic polyethylene composite film, the transparent antistatic polyethylene composite film has a three-layer structure, and the three-layer structure includes a first antistatic layer, a skeleton layer and a second antistatic layer connected in sequence; The preparation raw materials of the first antistatic layer and the second antistatic layer are the same, as shown in Table 3; the preparation raw materials of the skeleton layer are shown in Table 4.

[0048] Table 3: Preparation raw materials of the first antistatic layer and the second antistatic layer

[0049] Table 4: Preparation raw materials of the skeleton layer

[0050] A preparation method of a transparent antistatic polyethylene composite film in Example 2 includes the following steps: S1: According to the weight ratio, mix the preparation raw materials of the first antistatic layer and the second antistatic layer evenly to obtain the premixes of the first antistatic layer and the second antistatic layer; mix the preparation raw materials of the skeleton layer evenly to obtain the premix of the skeleton layer; S2: According to the design of the first antistatic layer, the skeleton layer and the second antistatic layer, the premixes obtained in step S1 are respectively fed into the corresponding channels of a three-layer melt coextrusion casting device, and coextrusion casting is carried out to obtain a composite film in one step, which is cooled and wound for standby. The total thickness of the composite film and the thickness ratio of each layer are regulated by controlling parameters such as the feeding speed of the material and the winding rate; the casting melting temperature is set at 190 °C, and the cooling temperature is set at 8 °C; S3: The composite film obtained in step S2 is placed in an environment with a temperature of 75 °C and a relative humidity of 85% and left standing for 48 h to obtain a transparent antistatic polyethylene composite film.

[0051] After testing, the thickness of the transparent antistatic polyethylene composite film in Example 2 is 0.05 mm. The thickness of the first antistatic layer accounts for 5% of the total thickness of the transparent antistatic polyethylene composite film, and the thickness of the second antistatic layer accounts for 15% of the total thickness of the transparent antistatic polyethylene composite film.

[0052] Example 3: A transparent antistatic polyethylene composite film, the transparent antistatic polyethylene composite film has a three-layer structure, and the three-layer structure includes a first antistatic layer, a skeleton layer and a second antistatic layer connected in sequence; The preparation raw materials of the first antistatic layer are shown in Table 5, the preparation raw materials of the second antistatic layer are shown in Table 6, and the preparation raw materials of the skeleton layer are shown in Table 7.

[0053] Table 5: Preparation raw materials of the first antistatic layer

[0054] Table 6: Preparation raw materials of the second antistatic layer

[0055] Table 7: Preparation raw materials of the skeleton layer

[0056] The preparation method of a transparent antistatic polyethylene composite film in Example 3 includes the following steps: S1: By weight ratio, the preparation raw materials of the first antistatic layer are mixed evenly to obtain a premix of the first antistatic layer; the preparation raw materials of the second antistatic layer are mixed evenly to obtain a premix of the second antistatic layer; the preparation raw materials of the skeleton layer are mixed evenly to obtain a premix of the skeleton layer; S2: According to the design of the first antistatic layer, the skeleton layer and the second antistatic layer, the premix obtained in step S1 is respectively put into the corresponding channels of a three-layer melt coextrusion casting device, and coextrusion casting is carried out to obtain a composite film in one step, which is cooled and wound for standby. The total thickness of the composite film and the thickness ratio of each layer are regulated by controlling parameters such as the feeding speed of the material and the winding rate; the casting melting temperature is set at 250 °C, and the cooling temperature is set at 0 °C; S3: After the composite film obtained in step S2 is left standing in an environment with a temperature of 100 °C and a relative humidity of 90% for 10 h, a transparent antistatic polyethylene composite film is obtained.

[0057] After testing, the thickness of the transparent antistatic polyethylene composite film in Example 3 is 0.05 mm. The thickness of the first antistatic layer accounts for 18% of the total thickness of the transparent antistatic polyethylene composite film, and the thickness of the second antistatic layer accounts for 3% of the total thickness of the transparent antistatic polyethylene composite film.

[0058] Example 4: A transparent antistatic polyethylene composite film, the transparent antistatic polyethylene composite film has a three-layer structure, and the three-layer structure includes a first antistatic layer, a skeleton layer and a second antistatic layer connected in sequence; The preparation raw materials of the first antistatic layer are shown in Table 8, the preparation raw materials of the second antistatic layer are shown in Table 9, and the preparation raw materials of the skeleton layer are shown in Table 10.

[0059] Table 8: Preparation raw materials of the first antistatic layer

[0060] Table 9: Preparation raw materials of the second antistatic layer

[0061] Table 10: Preparation raw materials of the skeleton layer

[0062] The preparation method of a transparent antistatic polyethylene composite film in Example 4 includes the following steps: S1: By weight ratio, the preparation raw materials of the first antistatic layer are mixed evenly to obtain a premix of the first antistatic layer; the preparation raw materials of the second antistatic layer are mixed evenly to obtain a premix of the second antistatic layer; the preparation raw materials of the skeleton layer are mixed evenly to obtain a premix of the skeleton layer; S2: According to the design of the first antistatic layer, the skeleton layer and the second antistatic layer, the premix obtained in step S1 is respectively put into the corresponding channels of a three-layer melt coextrusion casting device, and coextrusion casting molding is carried out to obtain a composite film in one step, which is cooled and wound for standby. The total thickness of the composite film and the thickness ratio of each layer are regulated by controlling parameters such as the feeding speed of the material and the winding rate; the casting melting temperature is set at 235 °C, and the cooling temperature is set at 2 °C; S3: The composite film obtained in step S2 is placed in an environment with a temperature of 85 °C and a relative humidity of 85% and left standing for 72 h to obtain a transparent antistatic polyethylene composite film.

[0063] After testing, the thickness of the transparent antistatic polyethylene composite film in Example 4 is 0.05 mm. The thickness of the first antistatic layer accounts for 20% of the total thickness of the transparent antistatic polyethylene composite film, and the thickness of the second antistatic layer accounts for 10% of the total thickness of the transparent antistatic polyethylene composite film.

[0064] Comparative Example 1: Compared with Example 1, the difference in Comparative Example 1 is that the molecular weight of the polyethylene glycol side chain of the PE-grafted polyethylene glycol resin in Comparative Example 1 is 10,000 g / mol, and the others are the same as in Example 1.

[0065] Comparative Example 2: Compared with Example 1, the difference in Comparative Example 2 is that the mass ratio of the polyethylene glycol side chain of the PE-grafted polyethylene glycol resin in Comparative Example 2 is 56%, and the others are the same as in Example 1.

[0066] Comparative Example 3: Compared with Example 1, the difference in Comparative Example 3 is that the composite film in Comparative Example 3 is not subjected to the process of standing in a damp and hot environment of "placed in an environment with a temperature of 83 °C and a relative humidity of 77% and left standing for 24 h", and the others are the same as in Example 1.

[0067] Comparative Example 4: Compared with Example 1, the difference in Comparative Example 4 is that in Comparative Example 4, the PE-grafted polyethylene glycol resin is replaced with a blend of PE and polyethylene glycol, and the others are the same as in Example 1.

[0068] Comparative Example 5: Compared with Example 1, the difference in Comparative Example 5 is that Comparative Example 5 does not contain a skeleton layer, and the others are the same as in Example 1.

[0069] Comparative Example 6: Compared with Example 1, the difference in Comparative Example 6 is that in Comparative Example 6, the thickness of the first antistatic layer accounts for 30% of the total thickness of the transparent antistatic polyethylene composite film, and the thickness of the second antistatic layer accounts for 30% of the total thickness of the transparent antistatic polyethylene composite film, and the others are the same as in Example 1.

[0070] The performance tests were carried out on the transparent antistatic polyethylene composite film samples prepared in Examples 1 to 4 and the comparative samples in Comparative Examples 1 to 6, and the results are shown in Table 11.

[0071] (1) Appearance evaluation: It is used to judge the appearance quality of the product. The test method is as follows: It is evaluated by visual method. It is required that the film surface is flat and smooth, without visible pores, crystal points and foreign matters to the naked eye.

[0072] (2) Surface resistance test: The test standard is GB / T 31838.3. For the same sample, no less than 5 regions are randomly selected for the test, and the maximum value is recorded as the test result.

[0073] (3) Transparency test: The test standard is GB / T 2410. For the same sample, no less than 5 regions are randomly selected for the test. For the light transmittance, the minimum value is recorded as the test result; for the haze, the maximum value is recorded as the test result.

[0074] (4) Tensile strength test: The test standard is GB / T1040.3. For the same sample, no less than 5 regions are randomly selected for the test. The tensile rate is fixed at 300 mm / min. The average value is recorded as the test result.

[0075] Table 11: Test results

[0076] It can be seen from the test results in Table 11 that the surface of the transparent antistatic polyethylene composite film prepared by the present invention is flat and smooth, without pores and foreign matters, and has excellent antistatic performance.

[0077] Comparing Comparative Example 1 with Example 1, in Comparative Example 1, polyethylene glycol with a higher molecular weight was selected, the monomer viscosity was relatively large and there was a molecular shielding effect, resulting in a low actual reaction grafting efficiency, so that there were relatively many residual polyethylene glycol monomers in the antistatic layer. Macroscopically, the surface of the composite film was uneven and had crystal points, and its surface resistance and transparency were also affected.

[0078] Comparing Comparative Example 2 with Example 1, in Comparative Example 2, the proportion of grafted polyethylene glycol branches was relatively large, and the hydrophilicity of the PE-grafted polyethylene glycol resin was too strong, resulting in poor compatibility with the PE resin in the skeleton layer and microphase separation, leading to uneven appearance of the coextruded composite film.

[0079] Comparing Comparative Example 3 with Example 1, the transparency of Comparative Example 3 is relatively close to that of Example 1. However, because the wet heat curing process is missing, the hydrophilic material on the surface layer cannot be fully extended and the adsorbed water molecules are relatively few. Therefore, the surface resistance is higher than that of Example 1 and the antistatic performance is slightly worse.

[0080] Comparing Comparative Example 4 with Example 1, in Comparative Example 4, polyethylene glycol and PE were simply blended. Since their compatibility was poor and they could not be mixed evenly, serious phase separation occurred, resulting in an unqualified appearance of the composite film obtained. The antistatic effect and transparency were also poor.

[0081] Comparing Comparative Example 5 with Example 1, the composite film in Comparative Example 5 was composed of PE-grafted polyethylene glycol resin and did not contain a skeleton layer, so phase separation would not occur during the curing process, and the hydrophilic polyethylene glycol chain segments would not spontaneously aggregate on the surface. Therefore, the surface resistance was slightly higher and the antistatic effect was worse than that of Example 1.

[0082] Comparing Comparative Example 6 with Example 1, the thickness of the antistatic layer in Comparative Example 6 was larger, and the migration degree of the polyethylene glycol chain segments was not as good as that of Example 1, so the antistatic effect was worse than that of Example 1.

[0083] In addition, tensile strength tests were also carried out on the transparent antistatic polyethylene composite film sample prepared in Example 1 and the comparative samples prepared in Comparative Example 5 and Comparative Example 6. The results are shown in Table 12.

[0084] Table 12: Tensile strength test results

[0085] It can be seen from the test results in Table 12 that in Comparative Example 5, without a skeleton layer, the overall tensile strength of the composite film decreased significantly, and its mechanical properties were greatly affected. Although Comparative Example 6 contained a skeleton layer, the thickness of the skeleton layer was small, and its tensile strength was also not as good as that of Example 1. This shows that the ratio of the first antistatic layer, the second antistatic layer, and the skeleton layer has an important impact on the mechanical strength of the composite film. The present invention optimizes the composition and the thickness ratio of each layer to ensure its mechanical properties and antistatic properties, making it have better application performance.

[0086] In summary, Examples 1-4 obtained a transparent antistatic polyethylene composite film by a three-layer coextrusion composite method. Among them, PE-grafted polyethylene glycol resin was used as the main material for the first antistatic layer and the second antistatic layer. Within the optimized polyethylene glycol content range, it had good hydrophilicity, and at the same time had good bonding force with the PE resin of the skeleton layer, and did not affect the transparency of the film. The composite film of the present invention adopts a three-layer structure (the first antistatic layer, the skeleton layer, and the second antistatic layer) design, and can adjust the migration of polyethylene glycol chain segments by inducing microphase separation through wet-heat curing to further reduce the surface resistance and enhance its antistatic effect. In addition, the introduction of the three-layer structure can ensure that the product has a high tensile strength, thereby ensuring its mechanical properties. The present invention can prepare a low-cost transparent antistatic polyethylene film in one step, which has the characteristics of environmental protection, high efficiency, and mass production.

[0087] In addition, Figure 1Schematic structural diagram of the transparent antistatic polyethylene composite film prepared in Example 1 of the present invention. The transparent antistatic polyethylene composite film has a three-layer structure, and the three-layer structure includes a first antistatic layer, a skeleton layer, and a second antistatic layer connected in sequence. Figure 2 Schematic diagram of the principle of Example 1 of the present invention. It can be seen from Figure 2 that when the composite film is extruded from the melt co-extrusion casting equipment, its structure is as shown in Figure 2 (a). The main materials of the first antistatic layer and the second antistatic layer are PE-grafted polyethylene glycol resin, and the main material of the skeleton layer is PE resin. Since the composite film is rapidly cooled when it is cast, the polyethylene glycol branches on the PE-grafted polyethylene glycol resin of the first antistatic layer and the second antistatic layer are in a free distribution state. Subsequently, the composite film is placed in a specific temperature and humidity environment (in Example 1, the composite film is left standing for 24 h in an environment with a temperature of 83 °C and a relative humidity of 77%) for curing. At this curing temperature, the composite film softens and the molecular chains are allowed to adjust freely. Since polyethylene glycol is a hydrophilic polymer and PE resin is a hydrophobic molecule, microphase separation occurs between the two, and the polyethylene glycol chain segments 4 tend to adjust towards the outer side of the film, thereby increasing the polyethylene glycol abundance on the surface of the composite film (as shown in Figure 2 (b)). At the same time, under higher humidity conditions, the polyethylene glycol chain segments 4 of the first antistatic layer and the second antistatic layer can fully absorb the water vapor in the environment to form a water film on the first antistatic layer and the second antistatic layer (as shown in Figure 2 (c)), constructing an effective conductive channel and avoiding excessive charge accumulation, thereby having excellent antistatic performance. Examples 2 to 4 are similar to Example 1 and will not be elaborated here.

[0088] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0089] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A transparent antistatic polyethylene composite film, characterized in that: The transparent antistatic polyethylene composite film comprises a first antistatic layer, a skeleton layer and a second antistatic layer which are connected in sequence, and the thickness of the first antistatic layer accounts for 3% to 20% of the total thickness of the transparent antistatic polyethylene composite film; the thickness of the second antistatic layer accounts for 3% to 20% of the total thickness of the transparent antistatic polyethylene composite film; Wherein, the first antistatic layer and the second antistatic layer both comprise the following raw materials in parts by weight: 100 parts of PE grafted polyethylene glycol resin and 0-2 parts of the first auxiliary material, and in the PE grafted polyethylene glycol resin, the polyethylene glycol side chain accounts for 10%-35% of the mass of the PE grafted polyethylene glycol resin, and the molecular weight range of the polyethylene glycol side chain is 200g / mol-4000g / mol; The skeleton layer comprises the following raw materials in parts by weight: 100 parts of PE resin, 0.1-0.5 parts of transparent nucleating agent and 0-2 parts of second auxiliary material.

2. The transparent antistatic polyethylene composite film according to claim 1, characterized in that: The PE grafted polyethylene glycol resin has a melt index of 1 g / 10 min to 30 g / 10 min at 190° C. and 2.16 kg.

3. The transparent antistatic polyethylene composite film according to claim 1, characterized in that: The preparation method of the PE grafted polyethylene glycol resin is as follows: The PE resin, maleic anhydride monomer and initiator are uniformly mixed in proportion to obtain a mixture; The mixture is put into a first twin-screw extruder for a first reaction, wherein the temperature of the reaction zone of the first twin-screw extruder is controlled at 220° C. to 300° C., the screw speed is controlled at 500 rpm to 800 rpm, and the screw elements in the reaction zone are mainly TME-type screw elements with strong shearing action, with the number being not less than 80%, to obtain a PE-grafted maleic anhydride resin; The PE grafted maleic anhydride resin is transferred to the second twin-screw extruder while hot, and molten amino polyethylene glycol monomethyl ether is injected into the side feed port for a second reaction. The reaction zone temperature of the second twin-screw extruder is controlled at 150° C. to 200° C., and the screw speed is controlled at 200 rpm to 400 rpm to obtain a PE grafted polyethylene glycol resin.

4. The transparent antistatic polyethylene composite film according to claim 3, characterized in that: The PE resin is at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, metallocene polyethylene and bimodal polyethylene.

5. The transparent antistatic polyethylene composite film according to claim 1, characterized in that: The first auxiliary material includes at least one of an antioxidant, an ultraviolet absorber, a nucleating agent, a lubricant and a filler.

6. The transparent antistatic polyethylene composite film according to claim 1, characterized in that: The transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

7. The transparent antistatic polyethylene composite film according to claim 1, characterized in that: The second auxiliary material includes at least one of an antioxidant, an ultraviolet absorber, a nucleating agent, a lubricant, and a filler.

8. A method for preparing a transparent antistatic polyethylene composite film, characterized in that: The preparation method is used to prepare the transparent antistatic polyethylene composite film according to any one of claims 1 to 7, and the preparation method comprises the following steps: Mixing the raw materials for preparing the first antistatic layer uniformly to obtain a premix of the first antistatic layer; Mixing the raw materials for preparing the second antistatic layer uniformly to obtain a premix for the second antistatic layer; The raw materials for preparing the skeleton layer are mixed evenly to obtain a premix of the skeleton layer; According to the design of the number of layers of the transparent antistatic polyethylene composite film, they are respectively put into the corresponding flow channels of the multi-layer melt co-extrusion casting equipment, co-extruded and cast, and the composite film is obtained in one step, cooled and rolled for use; The composite film is placed in an environment with a temperature of 70° C. to 100° C. and a relative humidity of 50% to 90% and allowed to stand for 10 h to 72 h to obtain a transparent antistatic polyethylene composite film.

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