Composite film and method for producing the same

Abstract

The application relates to the field of high polymer composite materials, and particularly discloses a composite film and a preparation method thereof; the composite film is composed of a PET layer, conductive adhesive liquid and an outer layer; the PET layer comprises the following raw materials: polyethylene terephthalate, conductive particles, conductive fibers, a dispersing agent and an additive; the conductive fibers are prepared by loading conductive fiber filaments on sugarcane wax particles; the outer layer comprises the following raw materials: polyurethane, tackifying particles, glyceryl monostearate, hydroxyethyl cellulose and an antioxidant; the preparation method comprises the following steps: preparing the PET layer; preparing the outer layer; uniformly spraying the conductive adhesive liquid on one side surface of the PET layer, then covering the outer layer, and performing post-processing to obtain a finished product; the composite film has high mechanical strength and good antistatic effect.

Description

Technical Field

[0001] This application relates to the field of polymer composite materials, and more specifically, to a composite film and a method for preparing the same. Background Technology

[0002] Composite films are polymer materials composed of two or more layers of different materials. The substrates used are mainly plastic films, such as polyethylene (PE), polypropylene (PP), polystyrene, polyvinyl chloride (PVC), and polyester (PET).

[0003] For some metal or plastic products, PET protective film is often chosen to protect their surfaces. PET protective film utilizes its high tensile strength, impact resistance, and good ductility to protect the products from scratches and wear. However, PET film is prone to static electricity during friction with the substrate, unwinding, and high-speed operation. If dust or other particulate matter is present in the surrounding environment, it can not only affect the adhesion of the PET film but also its protective function.

[0004] Therefore, how to prepare a new composite film that has both high mechanical strength and good antistatic effect is a problem that needs to be solved. Summary of the Invention

[0005] In order to prepare a new composite film that has high mechanical strength and good antistatic effect, this application provides a composite film and its preparation method.

[0006] In a first aspect, this application provides a composite thin film, which adopts the following technical solution:

[0007] A composite film comprising a PET layer, a conductive adhesive liquid, and an outer layer;

[0008] The PET layer contains the following raw materials in parts by weight: 80-120 parts polyethylene terephthalate, 10-20 parts conductive microparticles, 5-15 parts conductive fibers, 1-3 parts dispersant, and 1-4 parts additives; the conductive fibers are made by loading conductive fiber filaments onto sugarcane wax particles; the outer layer contains the following raw materials in parts by weight: 70-100 parts polyurethane, 10-20 parts tackifying particles, 1-4 parts glyceryl monostearate, 1-3 parts hydroxyethyl cellulose, and 1-2 parts antioxidant.

[0009] By adopting the above technical solution, polyethylene terephthalate, conductive microparticles, and conductive fibers are combined. The lubricating effect of sugarcane wax makes it difficult for static electricity to be generated near the sugarcane wax. Near the conductive fibers around the sugarcane wax, the conductive effect of the conductive fibers and conductive microparticles allows the static charge generated on the side of the PET layer that is in contact with the product to be conducted to the side of the PET layer away from the product. The outer surface of the composite film has good antistatic effect because of the hygroscopic and hydrophilic properties of polyurethane, hydroxyethyl cellulose, and glyceryl monostearate.

[0010] This composite film combines polyethylene terephthalate (PET), conductive microparticles, conductive fibers, polyurethane, tackifying particles, glyceryl monostearate, and hydroxyethyl cellulose. The additives and dispersants in the PET layer promote the uniform dispersion of conductive microparticles and fibers within the PET layer. The mechanical strength of the conductive microparticles and fibers enhances the mechanical strength of the PET layer. The polyurethane, aided by the tackifying particles, increases structural viscosity, and the lubricating and dispersing properties of glyceryl monostearate facilitate the uniform dispersion of hydroxyethyl fibers in the outer layer. Since hydroxyethyl cellulose has a melting point higher than the polyurethane's processing temperature, it acts as a filler in the outer layer preparation process, enhancing its mechanical strength. The conductive adhesive, with its good viscosity, facilitates bonding between the PET layer and the outer layer, further improving the composite film's mechanical strength. During use, the composite film gradually develops conductivity. This results in a finished composite film with high mechanical strength and good antistatic properties, while minimizing the adhesion of dust or other particulate matter from the external environment to the film surface, thus protecting its quality.

[0011] Preferably, the conductive particles are composed of zinc oxide micro powder and mica powder in a mass ratio of 1:1-2.8.

[0012] By adopting the above technical solution, zinc oxide micro powder and mica powder are combined. By utilizing the conductivity of both and their own high mechanical strength, the mechanical strength and antistatic effect of the finished composite film can be improved. Moreover, the composite film is not easy to turn black and has a certain degree of transparency or translucency.

[0013] Mica powder utilizes its layered structure and surface hydroxyl groups to improve the adhesion compatibility between mica powder and polyethylene terephthalate (PET), thereby enhancing the adhesion stability of mica powder in the PET layer. This results in a composite film with high mechanical strength and uniform antistatic effect.

[0014] Preferably, the zinc oxide micro powder is prepared by dispersing four needle-shaped zinc oxide whiskers in a polyethylene glycol solution, and then drying and breaking them up sequentially after the dispersion is uniform.

[0015] By adopting the above technical solution, the combination of tetra-needle zinc oxide whiskers and polyethylene glycol solution, and the loading of polyethylene glycol on the tetra-needle zinc oxide whiskers, utilizes the hydroxyl groups in polyethylene glycol to improve the adhesion and compatibility between zinc oxide micropowder and polyethylene terephthalate, thereby improving the adhesion stability of zinc oxide micropowder in the PET layer. At the same time, the large specific surface area of ​​the tetra-needle zinc oxide whiskers further increases the contact area between zinc oxide micropowder and other raw materials in the PET layer, thus giving the PET layer higher mechanical strength.

[0016] Preferably, the conductive fiber is prepared by dispersing silver fiber into a food-grade ethylenediamine solution, and after uniform dispersion, by drying and breaking it up sequentially.

[0017] By adopting the above technical solution, silver fiber filaments and ethylenediamine solution are combined to allow ethylenediamine to adhere to the surface of the silver fiber filaments. The amino groups in ethylenediamine, combined with the hydroxyl groups on the surface of zinc oxide micro powder and mica powder, as well as the carboxyl groups in polyethylene terephthalate, improve the adhesion and compatibility of conductive fiber filaments, conductive microparticles, and polyethylene terephthalate, thereby increasing the cross-linking density of the composite film and giving the composite film higher mechanical strength.

[0018] Uniformly dispersed conductive fibers and conductive microparticles utilize the filamentous divergent structure of silver fibers, combined with the particle filling effect of conductive microparticles. The charge generated around the sugarcane wax particles due to friction is easily conducted to the surface of the conductive fibers. Adjacent conductive fibers or conductive microparticles near the conductive fibers transfer charge, allowing static electricity to gradually transfer to the outer surface. This minimizes the generation of charge between the PET layer and the product surface, preventing the composite film from being difficult to peel off. Furthermore, the conductivity of the outer surface, combined with the surface lubrication, minimizes the adhesion of dust and other particles in the air to the surface of the composite film, giving the finished composite film high mechanical strength and good antistatic properties.

[0019] Preferably, the dispersant is polypropylene wax.

[0020] By adopting the above technical solution, the mechanical strength and wear resistance of PET film are improved by utilizing the good dispersion and external lubrication effect of polypropylene wax. In addition, polypropylene wax has a high melting point and achieves a lubrication effect after the conductive particles and wire fibers are bonded together. Combined with the internal lubrication effect of sugarcane wax, the surface of the PET layer has a good lubrication effect, minimizing the generation of frictional static electricity.

[0021] Preferably, the additive is water-white rosin resin.

[0022] By adopting the above technical solution, the softening point of water-white rosin resin is around 100℃. After softening, combined with the lubricating effect of polypropylene wax, it can not only improve the dispersion uniformity of conductive particles and conductive fibers, but also improve the bonding stability between conductive particles and conductive fibers and polyethylene terephthalate after hot melting, thereby improving the mechanical strength of the finished composite film.

[0023] Preferably, the conductive adhesive is composed of liquid silicone rubber, nano silver powder and curing agent in a mass ratio of 10:1-3:0.5-1.2.

[0024] By adopting the above technical solution, liquid silicone rubber, nano silver powder, and curing agent are combined. After the liquid silicone rubber is cured, the PET layer and the outer layer are bonded together. Meanwhile, the nano silver powder, together with the conductive particles and conductive fibers in the PET layer and the moisture-absorbing water film in the outer layer, enhances the conductivity and improves the antistatic effect of the composite film.

[0025] The combination of liquid silicone rubber and polyurethane utilizes the elasticity of the liquid silicone rubber combined with the elasticity and toughness of the polyurethane to improve the impact resistance of the finished composite film. When coating parts with sharp points, it is important to avoid puncturing the composite film and affecting its service life.

[0026] Preferably, the thickening particles are TPEE particles.

[0027] By adopting the above technical solution, TPEE particles and polyurethane are combined. The good toughness of TPEE and the elasticity of polyurethane are used to further improve the impact resistance of the outer layer and minimize the risk of scratches on the coated parts during transportation or friction. In addition, both TPEE particles and polyurethane have a certain degree of hygroscopicity. Combined with the hydrophilicity of the hydroxyethyl cellulose and glyceryl monostearate ends, it is easy to form a water film on the side of the outer layer away from PET, thereby improving the antistatic effect of the composite film. The PET film has a certain degree of water resistance, which can protect the surface of the coated parts from the influence of moisture.

[0028] Secondly, this application provides a method for preparing a composite thin film, which adopts the following technical solution:

[0029] A method for preparing a composite thin film includes the following steps:

[0030] S1. Weigh the conductive microparticles and conductive fibers, mix and stir evenly, then add them to polyethylene terephthalate and stir evenly. Finally, add the dispersant and additives, mix and stir evenly, and then melt-extrude to obtain the PET layer.

[0031] S2. Weigh out polyurethane, tackifying particles, glyceryl monostearate, hydroxyethyl cellulose, and antioxidant, mix and stir evenly, and then melt extrude to form the outer layer.

[0032] S3. Spray conductive adhesive evenly on one side of the PET layer, with 20-40g of conductive adhesive sprayed per square meter of PET film surface. Then cover with the outer layer and perform post-treatment to obtain the finished product.

[0033] By adopting the above technical solution, conductive microparticles and conductive fibers are first mixed, which facilitates the contact between the conductive fibers and conductive microparticles in the PET layer to achieve conductivity. Electrostatic transfer gradually transfers from the side of the PET layer in contact with the quality inspection to the adhesive layer formed by the conductive adhesive liquid. The conductive effect of the conductive adhesive liquid is used to transfer the charge to the outer layer. The conductive effect of the outer water film formed by polyurethane is used to give the composite film a good antistatic effect. In addition, the composite film has high mechanical strength.

[0034] Preferably, the conductive fiber is prepared by the following method:

[0035] Weigh sugarcane wax granules and conductive fiber filaments at a mass ratio of 1:1-4, mix and stir evenly, then heat to 76-80℃ and hold for 5-20 seconds. After drying and dispersion, the finished product is obtained.

[0036] By adopting the above technical solution, conductive fiber filaments are uniformly attached to the surface of sugarcane wax particles. By limiting the temperature to 76-80℃, the surface of the sugarcane wax particles is partially melted, thereby achieving bonding of the conductive fiber filaments.

[0037] In summary, this application has the following beneficial effects:

[0038] 1. The composite film, made from polyethylene terephthalate, conductive microparticles, conductive fibers, polyurethane, tackifying particles, glyceryl monostearate, and hydroxyethyl cellulose, possesses both high mechanical strength and good antistatic properties. When attached to the surface of metal or plastic products, the film's high mechanical strength helps to prevent scratches during transportation and storage, providing excellent protection. Furthermore, even when attached to surfaces with sharp edges, it is not easily punctured, effectively covering the product. Simultaneously, the film's good antistatic properties prevent dust or other particulate matter from adhering to its surface and affecting its quality.

[0039] 2. The combination of zinc oxide micro powder and mica powder utilizes the hydroxyl groups in polyethylene glycol to improve the adhesion and compatibility between zinc oxide micro powder and polyethylene terephthalate, thereby enhancing the adhesion stability of zinc oxide micro powder in the PET layer. At the same time, the large specific surface area of ​​the four-needle-shaped zinc oxide whiskers further increases the contact area between zinc oxide micro powder and other raw materials in the PET layer, thus giving the PET layer higher mechanical strength.

[0040] 3. Liquid silicone rubber and polyurethane are combined. The elasticity of liquid silicone rubber is combined with the elasticity and toughness of polyurethane to improve the impact resistance of the finished composite film. When coating parts with sharp points, the composite film is punctured as much as possible, which would affect the service life of the composite film. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Example of zinc oxide micro powder preparation

[0043] Preparation Example 1: Zinc oxide micro powder was prepared by the following method:

[0044] Weigh out 1500 of polyethylene glycol and dissolve it in anhydrous ethanol by stirring to obtain a 10% polyethylene glycol solution; the mass fraction of anhydrous ethanol is 99%.

[0045] Weigh 1 kg of tetraneedle-shaped zinc oxide whiskers and disperse them in 2 kg of polyethylene glycol solution. Disperse the solution at 20 kHz for 5 min, then dry and break it up to obtain zinc oxide micro powder. The zinc oxide micro powder is then passed through a 300-mesh sieve.

[0046] Example of preparation of conductive fiber filament

[0047] Preparation Example 2: Conductive fiber filaments were prepared using the following method:

[0048] Weigh out food-grade ethylenediamine and dissolve it in water by stirring to obtain a 5% food-grade ethylenediamine solution;

[0049] 1 kg of silver fiber filaments were weighed and dispersed in 2 kg of food-grade ethylenediamine solution. The silver fiber filaments were 10 μm in length and 40 nm in diameter. The dispersion was carried out at 20 kHz for 5 min. Then, the dispersion was dried and broken up until the silver fiber filaments did not stick together, thus obtaining conductive fiber filaments.

[0050] Example of conductive fiber preparation

[0051] Preparation Example 3: Conductive fibers were prepared using the following method:

[0052] Weigh 1 kg of sugarcane wax microparticles and mix them with 1 kg of conductive fiber filaments until uniform. The sugarcane wax microparticles have a particle size of 38 μm. The conductive fiber filaments are those prepared in Preparation Example 2. The mixture is heated to 78°C and held for 10 seconds. Then, 2 kg of conductive fiber filaments are added. After mixing and rolling until uniform, the mixture is cooled and dispersed to obtain conductive fibers. The conductive fibers are then passed through a 250-mesh sieve.

[0053] Preparation Example 4: Conductive fibers were prepared using the following method:

[0054] Weigh 1 kg of sugarcane wax microparticles and mix them with 0.5 kg of conductive fiber filaments until they are evenly stirred. The sugarcane wax microparticles have a particle size of 40 μm. The conductive fiber filaments are those prepared in Preparation Example 2. The mixture is heated to 76°C and held for 20 seconds. Then, 0.5 kg of conductive fiber filaments are added. After mixing and rolling evenly, the mixture is cooled and dispersed to obtain conductive fibers. The conductive fibers are then passed through a 150-mesh sieve.

[0055] Preparation Example 5: Conductive fibers were prepared using the following method:

[0056] Weigh 1 kg of sugarcane wax microparticles and mix them with 2 kg of conductive fiber filaments until uniform. The sugarcane wax microparticles have a particle size of 40 μm. The conductive fiber filaments are those prepared in Preparation Example 2. The mixture is heated to 80°C and held for 5 seconds. Then, 2 kg of conductive fiber filaments are added. After mixing and rolling until uniform, the mixture is cooled and dispersed to obtain conductive fibers. The conductive fibers are then passed through a 150-mesh sieve.

[0057] Preparation example of conductive adhesive liquid

[0058] Preparation Example 6: The conductive adhesive was prepared by the following method:

[0059] Weigh 10 kg of liquid silicone rubber, 2 kg of nano silver powder, and 1 kg of curing agent, mix and stir evenly. The liquid silicone rubber is 107 liquid silicone rubber; the nano silver powder has a particle size of 100 nm; and the curing agent consists of 0.2 kg of organotin catalyst and 0.8 kg of tetraethyl orthosilicate to prepare a conductive adhesive liquid.

[0060] Preparation Example 7: The difference between this preparation example and Preparation Example 6 is that:

[0061] Weigh 10 kg of liquid silicone rubber, 1 kg of nano silver powder, and 0.5 kg of curing agent, mix and stir evenly to obtain a conductive adhesive liquid; the curing agent consists of 0.1 kg of organotin catalyst and 0.4 kg of tetraethyl orthosilicate.

[0062] Preparation Example 8: The difference between this preparation example and Preparation Example 6 is that:

[0063] Weigh 10 kg of liquid silicone rubber, 3 kg of nano silver powder, and 1.2 kg of curing agent, mix and stir evenly to obtain a conductive adhesive liquid; the curing agent consists of 0.4 kg of organotin catalyst and 0.8 g of tetraethyl orthosilicate.

[0064] Example

[0065] The TPEE used in the following raw materials was purchased from Yucheng (Hongji) Plastics Dongguan Co., Ltd., with a melting point of 180℃; the other raw materials and equipment were all commercially available.

[0066] Example 1: A composite film:

[0067] It consists of a PET layer, a conductive adhesive, and an outer layer;

[0068] The PET layer contains 100 kg of polyethylene terephthalate, 15 kg of conductive microparticles, 10 kg of conductive fibers, 2 kg of dispersant, and 2 kg of additives. The conductive microparticles are composed of alumina powder and mica powder in a mass ratio of 1:2. The alumina powder is selected from the alumina powder prepared in Preparation Example 1, and the mica powder is sieved through a 300-mesh sieve. The conductive fibers are selected from the conductive fibers prepared in Preparation Example 3. The dispersant is polypropylene wax, and the additives are water-white rosin resin.

[0069] The conductive adhesive used was the conductive adhesive prepared in Preparation Example 6;

[0070] The outer layer contains 85 kg of polyurethane, 15 kg of tackifying particles, 2 kg of glyceryl monostearate, 2 kg of hydroxyethyl cellulose, and 0.8 kg of antioxidant. The tackifying particles are TPEE particles with a particle size of 20 μm, and the hydroxyethyl cellulose particles have a particle size of 10 μm. The antioxidant is antioxidant 1024.

[0071] The preparation method is as follows:

[0072] S1. Weigh the conductive microparticles and conductive fibers, mix and stir evenly, then add them to polyethylene terephthalate and stir evenly. Finally, add the dispersant and additives, mix and stir evenly, and melt extrude at 255℃ to obtain a PET layer with a thickness of 0.15mm.

[0073] S2. Weigh out polyurethane, tackifying particles, glyceryl monostearate, hydroxyethyl cellulose, and antioxidant, mix and stir evenly, and melt extrude at 185°C to obtain the outer layer with a thickness of 0.05 mm.

[0074] S3. Spray conductive adhesive liquid evenly on one side of the PET layer, with 30g of conductive adhesive liquid sprayed per square meter of PET film surface. Then cover with the outer layer and after curing treatment, the conductive adhesive liquid is cured into a conductive adhesive layer to obtain the finished product.

[0075] Example 2: The difference between this example and Example 1 is that:

[0076] The PET layer contains 80 kg of polyethylene terephthalate, 10 kg of conductive microparticles, 5 kg of conductive fibers, 1 kg of dispersant, and 1 kg of additives; the conductive microparticles are composed of alumina micro powder and mica powder in a mass ratio of 1:1; the conductive fibers are the conductive fibers prepared in Preparation Example 4.

[0077] The conductive adhesive used was the conductive adhesive prepared in Preparation Example 7;

[0078] The outer layer contains 70 kg of polyurethane, 10 kg of tackifying particles, 1 kg of glyceryl monostearate, 1 kg of hydroxyethyl cellulose, and 0.5 kg of antioxidant.

[0079] During the preparation process:

[0080] S3. Spray conductive adhesive liquid evenly on one side of the PET layer, with 20g of conductive adhesive liquid sprayed per square meter of PET film surface. Then cover with the outer layer and after curing treatment, the conductive adhesive liquid is cured into a conductive adhesive layer to obtain the finished product.

[0081] Example 3: The difference between this example and Example 1 is that:

[0082] The PET layer contains 120 kg of polyethylene terephthalate, 20 kg of conductive microparticles, 15 kg of conductive fibers, 3 kg of dispersant, and 4 kg of additives. The conductive microparticles are composed of alumina micro powder and mica powder in a mass ratio of 1:2.8. The conductive fibers are the conductive fibers prepared in Preparation Example 5.

[0083] The conductive adhesive used was the conductive adhesive prepared in Preparation Example 8;

[0084] The outer layer contains 100 kg of polyurethane, 20 kg of tackifying particles, 4 kg of glyceryl monostearate, 3 kg of hydroxyethyl cellulose, and 1 kg of antioxidant.

[0085] During the preparation process:

[0086] S3. Spray conductive adhesive liquid evenly on one side of the PET layer, with 40g of conductive adhesive liquid sprayed per square meter of PET film surface. Then cover with the outer layer and after curing treatment, the conductive adhesive liquid is cured into a conductive adhesive layer to obtain the finished product.

[0087] Example 4: The difference between this example and Example 1 is that:

[0088] The conductive microparticles are made by replacing the zinc oxide powder with an equal mass of commercially available tetra-needle zinc oxide whiskers, meaning the tetra-needle zinc oxide whiskers have not been treated with polyethylene glycol solution.

[0089] Example 5: The difference between this example and Example 1 is that:

[0090] The conductive fiber is silver fiber, meaning that the silver fiber has not been treated with food-grade ethylenediamine solution.

[0091] Example 6: The difference between this example and Example 1 is that:

[0092] The dispersant is polyethylene wax.

[0093] Example 7: The difference between this example and Example 1 is that:

[0094] No nano-silver powder was added to the conductive adhesive.

[0095] Example 8: The difference between this example and Example 1 is that:

[0096] The tackifying particles are water-white rosin resin.

[0097] Example 9: The difference between this example and Example 1 is that:

[0098] In the process of preparing conductive fibers, 1 kg of sugarcane wax microparticles are weighed and mixed with 3 kg of conductive fiber filaments until uniform, and the conductive fibers are obtained. The conductive fibers are then passed through a 150-mesh sieve.

[0099] Example 10: The difference between this example and Example 1 is that:

[0100] In the preparation of conductive fibers, 1 kg of sugarcane wax microparticles are weighed and mixed with 3 kg of conductive fiber filaments. The mixture is heated to 78°C and held for 10 seconds. After mixing and rolling evenly, the mixture is cooled and dispersed to obtain conductive fibers. The conductive fibers are then passed through a 150-mesh sieve.

[0101] Comparative Example

[0102] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0103] No conductive particles or conductive fibers were added to the PET layer.

[0104] Comparative Example 2: This comparative example differs from Example 1 in that:

[0105] The conductive fibers in the PET layer are carbon fiber filaments, which pass through a 150-mesh sieve.

[0106] Comparative Example 3: The difference between this comparative example and Example 1 is that:

[0107] No hydroxyethyl cellulose was added to the outer layer.

[0108] Comparative Example 4: This comparative example differs from Example 1 in that:

[0109] No glyceryl monostearate was added to the outer layer.

[0110] Performance testing

[0111] 1. Antistatic performance testing

[0112] Finished composite films were prepared using the methods of Examples 1-7, 9-10 and Comparative Examples 1-4, respectively, and the resistivity of the finished composite films was measured using a resistivity meter.

[0113] 2. Tensile strength test

[0114] Finished composite films were prepared using the methods of Examples 1-10 and Comparative Examples 1-4, respectively. Tensile strength was tested according to GB / T1040.1-2006, and the data were recorded.

[0115] 3. Surface inspection

[0116] Finished composite films were prepared using the methods of Examples 1-13 and 8, respectively. The composite film was then applied to the surface of a component with a pointed tip. The two coated components were subjected to sliding friction at their tips for 20 cycles. The composite film was then observed for scratches and marks. The scoring criteria were as follows: 10 points for no scratches and marks; 9-5 points for no scratches but with scratches, where the deeper, longer, and more numerous the scratches, the lower the score; and 4-1 points for scratches and marks, where the deeper, longer, and more numerous the scratches, the lower the score.

[0117] 4. Water vapor transmission rate test

[0118] Finished composite films were prepared using the methods described in Examples 1-3, and the water vapor transmission rate was tested in accordance with GB / T21529-2008.

[0119] 5. Transparency Detection

[0120] The finished composite films were prepared using the methods of Examples 1-3 and Comparative Example 2, respectively, with good transparency scoring 10 points → poor transparency scoring 1 point for completely opaque.

[0121] Table 1 Performance Test Table

[0122]

[0123] As can be seen from Examples 1-3 and Table 1, the composite film prepared in this application has good antistatic effect, high mechanical strength, good scratch resistance, and good transparency.

[0124] Combining Examples 1 and 4-10 with Table 1, it can be seen that the tetra-needle zinc oxide whiskers in Example 4 were not treated with polyethylene glycol solution. Compared with Example 1, the tensile strength of the composite film prepared in Example 4 was lower than that in Example 1. This indicates that the hydroxyl groups of polyethylene glycol on the surface of the tetra-needle zinc oxide whiskers can improve the adhesion compatibility of the tetra-needle zinc oxide whiskers with other raw materials, thereby improving the mechanical strength of the composite film.

[0125] In Example 5, the silver fiber filaments were not treated with food-grade ethylenediamine solution. Compared with Example 1, the tensile strength of the composite film prepared in Example 5 was lower than that in Example 1. This indicates that the amino groups in the ethylenediamine on the surface of the silver fiber filaments can improve the bonding compatibility between the conductive fiber and other raw materials, thereby improving the mechanical strength of the composite film.

[0126] In Example 6, the dispersant was polyethylene wax. Compared to Example 1, the resistivity of the composite film prepared in Example 6 was slightly higher than that in Example 1. This indicates that the polypropylene wax mainly provides external lubrication, making it less likely for the surface of the composite film to generate static electricity through friction, while the polyethylene wax mainly provides internal friction, thus affecting the antistatic effect of the finished composite film.

[0127] In Example 7, no nano-silver powder was added to the conductive adhesive. Compared with Example 1, the resistivity of the composite film prepared in Example 7 was greater than that in Example 1, and the tensile strength was less than that in Example 1. This indicates that the addition of nano-silver powder can not only improve the conductivity, but also improve the mechanical strength, so that the finished composite film has both good antistatic effect and high mechanical strength.

[0128] In Example 8, the tackifying particles were water-white rosin resin. Compared with Example 1, the surface fraction of the composite film prepared in Example 8 was lower than that in Example 1. This indicates that although water-white rosin resin also has a certain tackifying effect, it affects the toughness of the outer layer. Water-white rosin resin is brittle, so TPEE as a tackifying particle cannot improve the toughness of the outer layer but can improve the scratch resistance.

[0129] In Example 9, no heating treatment was performed during the preparation of the conductive fiber. Compared with Example 1, the resistivity of the composite film prepared in Example 9 was greater than that in Example 1, and the tensile strength was slightly lower than that in Example 1. This indicates that heating treatment during the preparation of the conductive fiber facilitates the stable bonding between the sugarcane wax and the conductive fiber filaments. Although it is not easy to generate tribostatic electricity at the sugarcane wax position, the tribostatic electricity generated in the surrounding area can be conducted through the conductive fiber filaments to gradually eliminate the electrostatic bonding between the PET layer and the part.

[0130] In Example 10, during the preparation of conductive fibers, sugarcane wax microparticles and conductive fiber filaments were mixed at one time. Compared with Example 1, the resistivity of the composite film prepared in Example 10 was slightly higher than that in Example 1. This indicates that one-time mixing makes it difficult to form a layered entanglement and coating of sugarcane wax, which can easily affect the conduction of static electricity around the sugarcane wax, thus affecting the antistatic effect of the composite film.

[0131] Based on Example 1 and Comparative Examples 1-4, and in conjunction with Table 1, it can be seen that no conductive microparticles or conductive fibers were added to the PET layer of Comparative Example 1. Compared to Example 1, the resistivity of the composite film prepared in Comparative Example 1 is greater than that in Example 1, and the tensile strength is less than that in Example 1. This indicates that conductive microparticles and conductive fibers can not only improve the antistatic effect of the composite film, but also improve the mechanical strength of the composite film.

[0132] In Comparative Example 2, the conductive fiber in the PET layer is carbon fiber filament, which passes through a 150-mesh sieve. Compared with Example 1, the transparency of the composite film prepared in Comparative Example 2 is lower than that in Example 1. This indicates that although carbon fiber has a filling effect, which can ensure the mechanical strength of the composite film, and carbon fiber has a conductive effect, the appearance of carbon fiber is black, which can easily affect the transparency of the finished composite film.

[0133] In Comparative Example 3, no hydroxyethyl cellulose was added to the outer layer. Compared with Example 1, the resistivity of the composite film prepared in Comparative Example 3 was greater than that in Example 1. This indicates that although hydroxyethyl cellulose is attached to the outer layer, it has a certain degree of hygroscopicity, which facilitates the formation of a water film on the outer surface to improve the antistatic effect of the composite film.

[0134] In Comparative Example 4, no glyceryl monostearate was added to the outer layer. Compared with Example 1, the resistivity of the composite film prepared in Comparative Example 4 was greater than that in Example 1. This indicates that the addition of glyceryl monostearate not only has a dispersing and lubricating effect, but also promotes the formation of a conductive water film, thereby improving the antistatic effect of the composite film.

[0135] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite film, characterized in that, It consists of a PET layer, a conductive adhesive, and an outer layer; The PET layer contains the following raw materials in parts by weight: 80-120 parts polyethylene terephthalate, 10-20 parts conductive microparticles, 5-15 parts conductive fibers, 1-3 parts dispersant, and 1-4 parts additives; the conductive fibers are made by loading sugarcane wax particles onto the surface of conductive fiber filaments. The conductive adhesive is composed of liquid silicone rubber, nano silver powder and curing agent in a mass ratio of 10:1-3:0.5-1.2; The outer layer contains the following raw materials in parts by weight: 70-100 parts polyurethane, 10-20 parts tackifying particles, 1-4 parts glyceryl monostearate, 1-3 parts hydroxyethyl cellulose, and 0.5-1 parts antioxidant. The conductive particles are composed of zinc oxide micro powder and mica powder in a mass ratio of 1:1-2.8; the zinc oxide micro powder is prepared by dispersing four needle-shaped zinc oxide whiskers in a polyethylene glycol solution, and then drying and breaking them up after uniform dispersion. The conductive fiber filament is made by dispersing silver fiber filaments in a food-grade ethylenediamine solution, and after uniform dispersion, it is dried and dispersed in sequence.

2. The composite film according to claim 1, characterized in that, The dispersant is polypropylene wax.

3. The composite film according to claim 1, characterized in that, The additive is water-white rosin resin.

4. A composite film according to claim 1, characterized in that, The thickening particles are TPEE particles.

5. A method for preparing a composite thin film according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Weigh the conductive microparticles and conductive fibers, mix and stir evenly, then add them to polyethylene terephthalate and stir evenly. Finally, add the dispersant and additives, mix and stir evenly, and then melt-extrude to obtain the PET layer. S2. Weigh polyurethane, tackifying particles, glyceryl monostearate, hydroxyethyl cellulose, and antioxidant, mix and stir evenly, and then melt extrude to form the outer layer. S3. Spray conductive adhesive evenly on one side of the PET layer, with 20-40g of conductive adhesive sprayed per square meter of PET film surface. Then cover with the outer layer and perform post-treatment to obtain the finished product.

6. The method for preparing a composite thin film according to claim 5, characterized in that, The conductive fiber is prepared by the following method: Weigh sugarcane wax granules and conductive fiber filaments at a mass ratio of 1:1-4, mix and stir evenly, then heat to 76-80℃ and hold for 5-20 seconds. After drying and dispersion, the finished product is obtained.

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