A transparent antistatic polyethylene composite film and its preparation method

Abstract

The present invention discloses a transparent antistatic polyethylene composite film and a preparation method thereof, belonging to the technical field of functional plastic films. The transparent antistatic polyethylene composite film comprises a first antistatic layer, a skeleton layer and a second antistatic layer which are connected in sequence. In the present invention, a PE-grafted polyethylene glycol resin is used as the main raw material of the antistatic layer, and there is no need to additionally add an antistatic agent, which overcomes the problems of migration, precipitation of traditional antistatic agents and incompatibility with resin substrates. In addition, the polyethylene glycol branches in the PE-grafted polyethylene glycol resin added in the present invention can not only improve transparency, but also have hydrophilicity. The polarity difference between the polyethylene glycol branches and the hydrophobic PE resin of the skeleton layer is relatively large. In an environment with specific temperature and humidity, the polyethylene glycol branches 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. While ensuring the mechanical properties, the antistatic performance of the transparent antistatic polyethylene composite film is further increased.

Description

Technical Field

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

[0002] Polyethylene (PE) is a common polymer material and is widely used in many fields. In the packaging field, PE is a very important packaging film material. Since PE itself is a high-insulation material, PE packaging films tend to generate static electricity during production, processing, and application, and the resulting inconveniences and even production accidents are not uncommon. When used as a packaging material for high-precision electronic components, the accumulated charge can 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 films 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 copolymer, sodium polystyrene sulfonate, etc. For example, Chinese Patent Application No. CN202411902276.9 discloses an antistatic plastic film and a preparation method thereof. The antistatic plastic film consists of a PET base film and an antistatic coating cured from an antistatic coating. The antistatic coating includes, by weight: 100 parts of silicone resin, 12-18 parts of antistatic agent, 0.8-1.1 parts of dispersant, 0.4-0.6 parts of bridging agent, 0.15-0.2 parts of leveling agent, and 55-60 parts of solvent; the antistatic agent uses lamellar graphene as the static charge release matrix, introduces amino modification to the lamellar surface by silane coupling agent KH-550, then substitutes the amino group grafted on the lamella by methyl chloroacetate, and finally conducts a quaternization reaction between iodomethane and the substituted amine compound to introduce quaternary ammonium cations to the graphene lamellar surface, which forms a continuous current-collecting layer in the coating, and then timely conducts the generated static charge, thereby endowing the film material with excellent antistatic properties. However, there is a problem that the peeling of the antistatic coating affects the antistatic performance. Another example is the patent of Chinese Patent Application No. CN202210558259.2, which discloses a composition of an antistatic degradable plastic film. The plastic film in this patent uses base materials such as PBAT, polylactic acid, and starch, and is compounded with a carbon nanotube synergistic graphene modifier electrostatic aid to prepare the plastic film material. However, the carbon nanotube synergistic graphene modifier electrostatic aid has migration properties, which also affects 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 promoters, it is often difficult for antistatic agents to be evenly dispersed 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:

[0006] A transparent antistatic polyethylene composite film, which comprises 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;

[0007] Among them, both the first antistatic layer and the second antistatic layer comprise 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, 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 200 g / mol - 4000 g / mol;

[0008] The skeleton layer comprises 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.

[0009] 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.

[0010] Further, the preparation method of the PE-grafted polyethylene glycol resin is as follows:

[0011] Mix PE resin, maleic anhydride monomer, and initiator evenly in proportion to obtain a mixture;

[0012] Put the mixture into the first twin-screw extruder for the first reaction. 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 of the TME type with strong shear action, and the number is not less than 80%, to obtain PE-grafted maleic anhydride resin;

[0013] Transfer the hot PE-grafted maleic anhydride resin to the second twin-screw extruder, and at the same time inject molten amino polyethylene glycol monomethyl ether at the side feeding port for the second reaction. The temperature of the reaction zone 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.

[0014] 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.

[0015] Further, the first auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent, and filler.

[0016] Further, the transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

[0017] Further, the second auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent, and filler.

[0018] 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:

[0019] Mix the preparation raw materials of the first antistatic layer evenly to obtain the premix of the first antistatic layer;

[0020] Mix the preparation raw materials of the second antistatic layer evenly to obtain the premix of the second antistatic layer;

[0021] Mix the preparation raw materials of the skeleton layer evenly to obtain the premix of the skeleton layer;

[0022] According to the layer design of the transparent antistatic polyethylene composite film, put them into the corresponding channels of the multi-layer melt co-extrusion casting equipment respectively, and co-extrusion casting molding to obtain the composite film in one step, and cool and wind up for standby;

[0023] 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 10 h to 72 h to obtain the transparent antistatic polyethylene composite film.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 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 additionally add antistatic agents, overcoming the problems of migration, precipitation of traditional antistatic agents, and incompatibility with resin substrates. 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.

[0026] 2. The polyethylene glycol branches in the PE-grafted polyethylene glycol resin added in the present invention have hydrophilicity, and have a large polarity difference from the hydrophobic PE resin in the skeleton layer. In an environment with 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 antistatic performance, making the transparent antistatic polyethylene composite film of the present invention have more excellent antistatic performance.

[0027] 3. The transparent antistatic polyethylene composite film prepared by 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 green, efficient, and low cost, and having higher economic value. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the transparent antistatic polyethylene composite film prepared in Example 1 of the present invention;

[0029] Figure 2 It is a schematic principle diagram of Example 1 of the present invention.

[0030] Description of the Reference Numerals:

[0031] 1. First antistatic layer; 2. Skeleton layer; 3. Second antistatic layer; 4. Polyethylene glycol chain segment. Detailed Embodiments

[0032] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below 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.

[0033] 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 in the specification of the present invention herein 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.

[0034] 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;

[0035] 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 the first auxiliary material;

[0036] The skeleton layer includes the following parts by weight of preparation raw materials: 100 parts of PE resin, 0.1 - 0.5 parts of transparent nucleating agent, and 0 - 2 parts of the second auxiliary material.

[0037] In the above solution, the thickness of the first antistatic layer and the second antistatic layer is limited. While ensuring their excellent antistatic performance, they also have excellent mechanical properties and do not increase production costs.

[0038] In one embodiment, the PE grafted polyethylene glycol resin is a functional polymer with a PE molecular chain backbone and polyethylene glycol as side chains.

[0039] 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 - 30 g / 10 min, preferably 5 g / 10 min - 20 g / 10 min; within this range, the PE grafted polyethylene glycol resin has better processing performance.

[0040] In one embodiment, 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; the molecular weight range of the polyethylene glycol side chain is 200 g / mol - 4000 g / mol. Within this range, the PE grafted polyethylene glycol resin has better antistatic effect. If it is lower than this range value, the chain length of the polyethylene glycol side chain is relatively small and is easily wrapped by the PE main chain, or the quantity 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.

[0041] In one embodiment, the preparation method of the PE grafted polyethylene glycol resin is as follows:

[0042] Mix PE resin, maleic anhydride monomer, and initiator evenly in proportion to obtain a mixture;

[0043] Put the mixture into the first twin-screw extruder for the first reaction. 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, and the number is not less than 80% to obtain PE-grafted maleic anhydride resin;

[0044] Transfer the hot PE-grafted maleic anhydride resin to the second twin-screw extruder, and at the same time inject molten amino polyethylene glycol monomethyl ether at the side feeding port for the second reaction. The temperature of the reaction zone 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.

[0045] 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.

[0046] In one embodiment, the initiator is a peroxide initiator.

[0047] In one embodiment, the initiator is at least one of dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, tert-butyl lauroperoxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, bis(tert-butylperoxyisopropyl)benzene, tert-butyl cumyl peroxide, tert-butyl peroxybenzoate, and tert-butyl peroxyacetate.

[0048] In one embodiment, the maleic anhydride monomer is of industrial grade or above purity.

[0049] 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 hot. This is beneficial to improving the mixing uniformity.

[0050] When the present invention prepares PE-grafted polyethylene glycol resin, 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 can inhibit 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.

[0051] In one embodiment, the first auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent, and filler.

[0052] 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.

[0053] In one embodiment, the transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

[0054] 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.

[0055] 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.

[0056] 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:

[0057] Mix the raw materials for preparing the first antistatic layer evenly to obtain a premix of the first antistatic layer;

[0058] Mix the raw materials for preparing the second antistatic layer evenly to obtain a premix of the second antistatic layer;

[0059] Mix the raw materials for preparing the skeleton layer evenly to obtain a premix of the skeleton layer;

[0060] According to the layer design of the transparent antistatic polyethylene composite film, respectively put 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, cool and wind it up for standby;

[0061] 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 10 h to 72 h to obtain the transparent antistatic polyethylene composite film.

[0062] In one embodiment, the melting temperature of the coextrusion casting is 180°C to 250°C.

[0063] In one embodiment, the cooling temperature is 0 to 10°C.

[0064] The transparent antistatic polyethylene composite film prepared by the above solution has excellent antistatic performance while ensuring its mechanical properties, and is green and efficient, with low preparation cost and strong operability for large-scale production.

[0065] Next, the implementation scheme of the present invention will be described in detail with specific embodiments.

[0066] Example 1:

[0067] 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;

[0068] 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.

[0069] Table 1: Preparation raw materials of the first antistatic layer and the second antistatic layer

[0070]

[0071] Table 2: Preparation raw materials of the skeleton layer

[0072]

[0073] A method for preparing a transparent antistatic polyethylene composite film in Example 1 includes the following steps:

[0074] 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;

[0075] 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 coextrusion cast to form a composite film in one step, and cool and wind it up for standby. Control parameters such as the feeding speed and winding rate of the materials 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;

[0076] 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 hours to obtain a transparent antistatic polyethylene composite film.

[0077] 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.

[0078] Example 2:

[0079] 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;

[0080] 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.

[0081] Table 3: Preparation Raw Materials of the First Antistatic Layer and the Second Antistatic Layer

[0082]

[0083] Table 4: Preparation Raw Materials of the Skeleton Layer

[0084]

[0085] A preparation method of a transparent antistatic polyethylene composite film in Example 2 includes the following steps:

[0086] 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;

[0087] 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 materials to regulate the total thickness and the thickness ratio of each layer of the composite film; set the casting melting temperature to 190 °C and the cooling temperature to 8 °C;

[0088] S3: Place the composite film obtained in step S2 in an environment with a temperature of 75 °C and a relative humidity of 85% and let it stand for 48 h to obtain the transparent antistatic polyethylene composite film.

[0089] 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.

[0090] Example 3:

[0091] 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;

[0092] 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.

[0093] Table 5: Preparation Raw Materials of the First Antistatic Layer

[0094]

[0095] Table 6: Preparation raw materials of the second antistatic layer

[0096]

[0097] Table 7: Preparation raw materials of the skeleton layer

[0098]

[0099] A preparation method of a transparent antistatic polyethylene composite film in Example 3 includes the following steps:

[0100] S1: According to the weight ratio, 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;

[0101] 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 coextrusion cast to form a composite film in one step, then cool and wind it for standby. Control parameters such as the feeding speed of the material and the winding rate to regulate the total thickness of the composite film and the thickness ratio of each layer; the casting melting temperature is set at 250 °C, and the cooling temperature is set at 0 °C;

[0102] S3: Place the composite film obtained in step S2 in an environment with a temperature of 100 °C and a relative humidity of 90% and let it stand for 10 h to obtain a transparent antistatic polyethylene composite film.

[0103] 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.

[0104] Example 4:

[0105] 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;

[0106] 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.

[0107] Table 8: Preparation raw materials of the first antistatic layer

[0108]

[0109] Table 9: Preparation raw materials of the second antistatic layer

[0110]

[0111] Table 10: Preparation raw materials of the skeleton layer

[0112]

[0113] A preparation method of a transparent antistatic polyethylene composite film in Example 4 includes the following steps:

[0114] S1: According to the weight ratio, 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;

[0115] 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 coextrusion cast to form a composite film in one step, then cool and wind it up for standby. Control parameters such as the feeding speed of the material and the winding rate to regulate the total thickness of the composite film and the thickness ratio of each layer; the casting melting temperature is set at 235 °C and the cooling temperature is set at 2 °C;

[0116] S3: Place the composite film obtained in step S2 in an environment with a temperature of 85 °C and a relative humidity of 85% and let it stand for 72 h to obtain a transparent antistatic polyethylene composite film.

[0117] 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.

[0118] Comparative Example 1:

[0119] 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.

[0120] Comparative Example 2:

[0121] 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.

[0122] Comparative Example 3:

[0123] Compared with Example 1, the difference in Comparative Example 3 is that the composite film in Comparative Example 3 was not subjected to the process of standing still in a damp and hot environment of "standing still at a temperature of 83°C and a relative humidity of 77% for 24 hours", and the rest is the same as in Example 1.

[0124] Comparative Example 4:

[0125] Compared with Example 1, the difference in Comparative Example 4 is that in Comparative Example 4, the PE-grafted polyethylene glycol resin was replaced with a blend of PE and polyethylene glycol, and the rest is the same as in Example 1.

[0126] Comparative Example 5:

[0127] Compared with Example 1, the difference in Comparative Example 5 is that Comparative Example 5 does not contain a skeleton layer, and the rest is the same as in Example 1.

[0128] Comparative Example 6:

[0129] Compared with Example 1, the difference in Comparative Example 6 is that the thickness of the first antistatic layer in Comparative Example 6 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 rest is the same as in Example 1.

[0130] The samples of the transparent antistatic polyethylene composite films prepared in Examples 1 to 4 and the comparative samples of Comparative Examples 1 to 6 were subjected to performance tests, and the results are shown in Table 11.

[0131] (1) Appearance evaluation: Used to judge the appearance quality of the product. The test method is as follows: Evaluated by visual method, and it is required that the film surface is flat and smooth, without visible pores, crystal points and foreign matters to the naked eye.

[0132] (2) Surface resistance test: The test standard is GB / T 31838.3. For the same sample, randomly select no less than 5 regions for testing, and record the maximum value as the test result.

[0133] (3) Transparency test: The test standard is GB / T 2410. For the same sample, randomly select no less than 5 regions for testing. For the light transmittance, record the minimum value as the test result; for the haze, record the maximum value as the test result.

[0134] (4) Tensile strength test: The test standard is GB / T1040.3. For the same sample, randomly select no less than 5 regions for testing. The tensile rate is fixed at 300 mm / min. Record the average value as the test result.

[0135] Table 11: Test results

[0136]

[0137] As can be seen from the test results in Table 11, the surface of the transparent antistatic polyethylene composite film prepared by the present invention is flat and smooth, without pores or foreign matters, and has excellent antistatic performance.

[0138] Comparing Comparative Example 1 with Example 1, in Comparative Example 1, polyethylene glycol with a higher molecular weight was selected, and the monomer viscosity was relatively large and there was a molecular shielding effect, resulting in a low actual reaction grafting efficiency, so that there was a relatively large amount of residual polyethylene glycol monomer 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.

[0139] 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, and its compatibility with the PE resin in the skeleton layer became poor, resulting in microphase separation, and the appearance of the coextruded composite film was uneven.

[0140] Comparing Comparative Example 3 with Example 1, the transparency of Comparative Example 3 is relatively close to that of Example 1, but because the process of heat and humidity curing is lacking, the hydrophilic material on the surface layer cannot be fully extended and the adsorbed water molecules are relatively few, so the surface resistance is higher than that of Example 1 and the antistatic performance is slightly worse.

[0141] Comparing Comparative Example 4 with Example 1, in Comparative Example 4, polyethylene glycol and PE were simply blended, and their compatibility was poor and they could not be mixed evenly, resulting in serious phase separation. The appearance of the obtained composite film was unqualified, and its antistatic effect and transparency were also poor.

[0142] Comparing Comparative Example 5 with Example 1, the composite film in Comparative Example 5 is composed of PE-grafted polyethylene glycol resin and does not contain a skeleton layer, so phase separation will not occur during the curing process, and the hydrophilic polyethylene glycol chain segments will not spontaneously aggregate on the surface, so the surface resistance is slightly higher and the antistatic effect is worse than that of Example 1.

[0143] Comparing Comparative Example 6 with Example 1, the thickness of the antistatic layer in Comparative Example 6 is relatively large, and the migration degree of the polyethylene glycol chain segments is less than that of Example 1, and the antistatic effect is worse than that of Example 1.

[0144] 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, and the results are shown in Table 12.

[0145] Table 12: Tensile strength test results

[0146]

[0147] As can be seen from the test results in Table 12: In Comparative Example 5, there is no skeleton layer, and the tensile strength of the composite film as a whole decreases significantly, and its mechanical properties are greatly affected. Although Comparative Example 6 contains a skeleton layer, the thickness of the skeleton layer is small, and its tensile strength is also inferior to 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, so as to have better application performance.

[0148] In summary, Examples 1-4 adopt a three-layer coextrusion composite method to obtain a transparent antistatic polyethylene composite film. Among them, the PE-grafted polyethylene glycol resin is used as the main material for the first antistatic layer and the second antistatic layer. Within the optimized range of polyethylene glycol content, it has good hydrophilicity, and at the same time has good bonding force with the PE resin of the skeleton layer, and does 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 heat and moisture curing, so as 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.

[0149] In addition, Figure 1 FIG. is a schematic 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 FIG. is a schematic principle diagram of Example 1 of the present invention. As can be seen from Figure 2 : When the composite film is extruded from the melt coextrusion casting equipment, its structure is as shown in Figure 2 FIG. (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 placed in an environment with a temperature of 83 °C and a relative humidity of 77% and left standing for 24 h) for curing. At this curing temperature, the composite film softens, and the molecular chains are allowed to be freely adjusted. 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 2as shown in (b). Meanwhile, under higher humidity conditions, the polyethylene glycol segments 4 of the first antistatic layer and the second antistatic layer can fully absorb water vapor in the environment to form a water film in the first antistatic layer and the second antistatic layer (as shown in Figure 2 as shown in (c)), constructing an effective conductive channel to avoid excessive charge accumulation, thereby having an excellent antistatic effect. Examples 2 to 4 are similar to Example 1 and will not be described in detail here.

[0150] 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 embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0151] The above-described embodiments only represent several implementation manners of the present invention. The description 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 should 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% - 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; Wherein, both the first antistatic layer and the second antistatic layer comprise the following raw materials in parts by weight: 100 parts of PE-grafted polyethylene glycol resin and 0 - 2 parts of a 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 200 g / mol - 4000 g / mol; The skeleton layer comprises the following raw materials in parts by weight: 100 parts of PE resin, 0.1 - 0.5 parts of a transparent nucleating agent and 0 - 2 parts of a second auxiliary material; The transparent antistatic polyethylene composite film undergoes a process of standing in a humid and hot environment, and the process conditions of standing in the humid and hot environment are: standing for 10 h - 72 h in an environment with a temperature of 70°C - 100°C and a relative humidity of 50% - 90%; The preparation method of the PE-grafted polyethylene glycol resin is as follows: Mix PE resin, maleic anhydride monomer and initiator evenly to obtain a mixture; Put the mixture into a first twin-screw extruder for the first reaction, and 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 while it is hot to a second twin-screw extruder, and at the same time inject molten amino polyethylene glycol monomethyl ether at the side feeding port for the second reaction, and the reaction zone temperature of the second twin-screw extruder is controlled at 150°C - 200°C, the screw speed is controlled at 200 rpm - 400 rpm to obtain PE-grafted polyethylene glycol resin.

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

3. The transparent antistatic polyethylene composite film according to claim 2, 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.

4. The transparent antistatic polyethylene composite film according to claim 1, wherein The first auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent and filler.

5. The transparent antistatic polyethylene composite film according to claim 1, wherein The transparent nucleating agent is dibenzylidene sorbitol and its derivatives.

6. The transparent antistatic polyethylene composite film according to claim 1, wherein The second auxiliary material includes at least one of antioxidant, ultraviolet absorber, nucleating agent, slip agent and filler.

7. A preparation method of a transparent antistatic polyethylene composite film, characterized in that, The preparation method is used to prepare the transparent antistatic polyethylene composite film as described in any one of claims 1 - 6, 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, put them into the corresponding channels of the multi-layer melt co-extrusion casting equipment respectively, and co-extrusion cast to form 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 10 h to 72 h to obtain the transparent antistatic polyethylene composite film.

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