A low-static thin film and its preparation method

Abstract

This invention provides a low-static film and its preparation method, relating to the field of functional membrane material preparation technology. The low-static film includes a core layer composed of polypropylene; a first antistatic layer located on one side of the core layer; and a second antistatic layer located on the other side of the core layer; both the first and second antistatic layers are composed of antistatic polypropylene. This film not only has strong antistatic ability but also maintains strong antistatic ability even at low air humidity.

Description

Technical Field

[0001] This invention relates to the field of functional membrane material preparation technology, specifically to a low-static thin film and its preparation method. Background Technology

[0002] Over the past few decades, biaxially oriented polypropylene (BOP) film has seen significant improvements in production speed, product variety, production capacity, and product quality. Currently, the thickness of BOP glossy films can be below 10 μm. Such films do not exhibit a significant decrease in tensile strength or gloss, and further reduce material waste, achieving energy conservation and emission reduction. However, polypropylene films have poor antistatic properties. As the film thickness decreases, the film's weight also decreases, making it easier for static electricity to cause the film to adhere to object surfaces, causing considerable inconvenience to downstream customers. Therefore, providing a low-static-rate film has become a crucial technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a low-static film and its preparation method, solving the technical problem of poor antistatic ability of polypropylene films.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On the one hand, a low-static film is provided, including

[0008] Core layer, wherein the core layer component comprises polypropylene;

[0009] A first antistatic layer is located on one side of the core layer;

[0010] The second antistatic layer is located on the other side of the core layer;

[0011] Both the first and second antistatic layers are composed of antistatic polypropylene.

[0012] As a preferred embodiment, the method for preparing the antistatic polypropylene includes the following steps:

[0013] S1. Preparation of antistatic agent

[0014] Acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride were sequentially added to a flask, and a solvent of equal mass to the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. After stirring for 35-50 minutes, a first initiator of 0.5%-1.0% of the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. The reaction was carried out at 75℃-95℃ for 3.5-5.5 hours. After the reaction was completed, the solvent was removed, and the mixture was cooled and solidified to remove low molecular weight substances. Then, it was vacuum dried for 12-20 hours to obtain an antistatic agent.

[0015] S2, Preparation of modified antistatic agent

[0016] Undecenol was dissolved in a first solvent to prepare a grafting reaction solution. Benzoyl peroxide was dissolved in a second solvent and then added to the grafting reaction solution. The antistatic agent was dissolved in dimethylformamide and then added to the grafting reaction solution. The reaction was carried out at 70-80°C for 6-8 hours. After the reaction was completed, the mixture was washed with butanone, acetone and deionized water in sequence, and then dried to obtain the modified antistatic agent.

[0017] S3. Preparation of antistatic polypropylene

[0018] The modified antistatic agent is mixed with homopolymer polypropylene, heated to 125℃-165℃, and mixed for 40min-55min. Then, a crosslinking agent is added, the temperature is lowered to 120-130℃, and the mixture is further mixed for 15min-25min. The mixture is then extruded, cooled, and pelletized to obtain antistatic polypropylene masterbatch.

[0019] In a preferred embodiment, the antistatic agent is cationic.

[0020] In a preferred embodiment, the concentration of the grafting reaction solution is (15-25) wt%.

[0021] In a preferred embodiment, the first initiator is selected from at least one of benzoyl peroxide and lauroyl peroxide.

[0022] In a preferred embodiment, the crosslinking agent is selected from at least one of dicumyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxide.

[0023] In a preferred embodiment, the thickness of the low-static film is less than 10 μm.

[0024] In a preferred embodiment, the first solvent is selected from chloroform and methanol; the second solvent is selected from ethanol, diethyl ether, acetone, benzene, and carbon disulfide.

[0025] On the other hand, the present invention provides a method for preparing a low-static-film, comprising the following steps:

[0026] S1. The antistatic polypropylene masterbatch and homopolymer polypropylene are melted and co-extruded to obtain a casting with homopolymer polypropylene as the core layer and antistatic layers on both sides.

[0027] S2. The cast sheet is preheated to 145-160°C, stretched longitudinally at a stretch ratio of 6-10 times, then heated again to 165-185°C, stretched laterally at a stretch ratio of 7-10 times, and then cooled to 35-45°C. After cooling and shaping, the resulting film is wound up to obtain a low-static film.

[0028] In a preferred embodiment, the thickness of the cast sheet is 2mm-4mm.

[0029] (III) Beneficial Effects

[0030] This invention provides a low-static-film and its preparation method. Compared with the prior art, it has the following advantages:

[0031] The low-static film comprises a core layer, a first antistatic layer, and a second antistatic layer. Both the first and second antistatic layers are composed of antistatic polypropylene. Undecenol is selected to graft and modify the antistatic agent. The modified antistatic agent molecules are grafted with hydroxyl groups, thereby allowing the modified antistatic agent in the polypropylene to form chains within the polypropylene through hydrogen bonds, creating an electron transport structure with interconnected conductive clusters. This reduces the resistivity of the first and second antistatic layers, thereby improving the antistatic capability of the film. This electron transport structure is unaffected by air humidity, so the film still has strong antistatic capability even at low humidity. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0034] Example 1

[0035] This embodiment provides a method for preparing a low-static-weight thin film, comprising the following steps:

[0036] S11, Preparation of antistatic agent

[0037] Acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride were added sequentially to a flask in a molar ratio of 1:1.2:1.3:1.1:1.2. Acetonitrile of equal mass to the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. After stirring for 35 min, 0.5% of benzoyl peroxide of the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. The mixture was reacted at 75 °C for 3.5 h. After the reaction was completed, the solvent was removed, and the mixture was cooled and solidified to remove low molecular weight substances. The mixture was then vacuum dried for 12 h to obtain a cationic antistatic agent.

[0038] S12, Preparation of modified antistatic agent

[0039] Undecenol was dissolved in chloroform to prepare a 15wt% grafting reaction solution. Benzoyl peroxide was dissolved in ethanol and then added to the grafting reaction solution. The antistatic agent was dissolved in dimethylformamide and then added to the grafting reaction solution. The reaction was carried out at 70°C for 6 hours. After the reaction was completed, the mixture was washed with butanone, acetone and deionized water in sequence and dried to obtain the modified antistatic agent.

[0040] S13, Preparation of antistatic polypropylene

[0041] The modified antistatic agent was mixed with homopolymer polypropylene, heated to 125°C, and mixed for 40 min. Then, dicumyl peroxide was added, the temperature was lowered to 120°C, and the mixture was mixed for another 15 min. The mixture was then extruded, cooled, and pelletized to obtain antistatic polypropylene masterbatch.

[0042] S14. The antistatic polypropylene masterbatch and homopolymer polypropylene are melted and co-extruded to obtain a 2mm thick casting sheet with homopolymer polypropylene as the core layer and antistatic layers on both sides.

[0043] S2. Preheat the cast sheet to 145°C, stretch it longitudinally at a stretch ratio of 6, then heat it again to 165°C, stretch it laterally at a stretch ratio of 7, then cool it down to 35°C, cool and set it, and then wind up the resulting film to obtain a low-static film.

[0044] Example 2

[0045] This embodiment provides a method for preparing a low-static-weight thin film, comprising the following steps:

[0046] S11, Preparation of antistatic agent

[0047] Acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride were added to a flask in a molar ratio of 1:1.3:1.4:1.2:1.3. Acetonitrile of equal mass to the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. After stirring for 40 min, lauroyl peroxide was added at 0.8% of the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride. The mixture was reacted at 85 °C for 5.0 h. After the reaction was completed, the solvent was removed, and the mixture was cooled and solidified to remove low molecular weight substances. The mixture was then vacuum dried for 18 h to obtain a cationic antistatic agent.

[0048] S12, Preparation of modified antistatic agent

[0049] Undecenol was dissolved in methanol to prepare a grafting reaction solution. Lauroyl peroxide was dissolved in diethyl ether and then added to the grafting reaction solution. The antistatic agent was dissolved in dimethylformamide and then added to the grafting reaction solution. The reaction was carried out at 70°C for 6 hours. After the reaction was completed, the mixture was washed with butanone, acetone and deionized water in sequence and dried to obtain the modified antistatic agent.

[0050] S13, Preparation of antistatic polypropylene

[0051] The modified antistatic agent was mixed with homopolymer polypropylene, heated to 150°C, and mixed for 50 min. Then, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane was added, the temperature was lowered to 125°C, and the mixture was continued to be mixed for 20 min. The mixture was then extruded, cooled, and pelletized to obtain antistatic polypropylene masterbatch.

[0052] S14. The antistatic polypropylene masterbatch and homopolymer polypropylene are melted and co-extruded to obtain a casting with homopolymer polypropylene as the core layer and antistatic layers on both sides.

[0053] S2. Preheat the cast sheet to 150°C, stretch it longitudinally at a stretch ratio of 8, then heat it again to 180°C, stretch it laterally at a stretch ratio of 8, then cool it down to 40°C. After cooling and setting, wind up the resulting film to obtain a low-static film.

[0054] Example 3

[0055] This embodiment provides a method for preparing a low-static-weight thin film, comprising the following steps:

[0056] S11, Preparation of antistatic agent

[0057] Acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride were added sequentially to a flask in a molar ratio of 1:1.2:1.3:1.1:1.2. Acetonitrile equal in mass to the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. After stirring for 50 min, lauroyl peroxide was added at 1.0% of the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride. The mixture was reacted at 95 °C for 5.5 h. After the reaction was completed, the solvent was removed, and the mixture was cooled and solidified to remove low molecular weight substances. The mixture was then vacuum dried for 20 h to obtain a cationic antistatic agent.

[0058] S12, Preparation of modified antistatic agent

[0059] Undecenol was dissolved in methanol to prepare a grafting reaction solution. Lauroyl peroxide was dissolved in acetone and then added to the grafting reaction solution. The antistatic agent was dissolved in dimethylformamide and then added to the grafting reaction solution. The reaction was carried out at 70°C for 6 hours. After the reaction was completed, the mixture was washed with butanone, acetone and deionized water in sequence and dried to obtain the modified antistatic agent.

[0060] S13, Preparation of antistatic polypropylene

[0061] The modified antistatic agent was mixed with homopolymer polypropylene, heated to 165℃, and mixed for 55 min. Then, 2,5-dimethyl-2,5-di-tert-butylperoxide was added, the temperature was lowered to 130℃, and the mixture was continued to be mixed for 25 min. The mixture was then extruded, cooled, and pelletized to obtain antistatic polypropylene masterbatch.

[0062] S14. The antistatic polypropylene masterbatch and homopolymer polypropylene are melted and co-extruded to obtain a casting with homopolymer polypropylene as the core layer and antistatic layers on both sides.

[0063] S2. Preheat the cast sheet to 160°C, stretch it longitudinally at a stretch ratio of 10, then heat it again to 185°C, stretch it laterally at a stretch ratio of 10, then cool it down to 45°C, cool and set it, and then wind up the resulting film to obtain a low-static film.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that step S12 is not included; otherwise, it is the same as Example 1.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that step S12 is not included; otherwise, it is the same as Example 2.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 3 is that step S12 is not included; otherwise, it is the same as Example 3.

[0070] Performance testing

[0071] The surface resistivity of the low electrostatic films prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The surface resistivity was tested at air humidity of 20%RH and 80%RH, respectively. The results are shown in Table 1.

[0072] Surface resistivity: The ratio of the potential gradient in the direction of current flow parallel to the surface of a material to the current per unit width of the surface. Its unit is Ω, and the calculation formula is:

[0073] ρ s =R s 2π / ln d2 / d1

[0074] In the formula,

[0075] R s Surface resistance, in Ω;

[0076] d1 and d2 are the diameter of the measuring electrode and the inner diameter of the protective electrode, respectively, in mm.

[0077] Table 1. Surface resistivity test results of low electrostatic thin films in Examples 1-3 and Comparative Examples 1-3

[0078]

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Any aspects of the present invention not described in detail are well-known to those skilled in the art.

Claims

1. A low-static-weight film, characterized in that, include Core layer, wherein the core layer component comprises polypropylene; A first antistatic layer is located on one side of the core layer; The second antistatic layer is located on the other side of the core layer; Both the first antistatic layer and the second antistatic layer are composed of antistatic polypropylene; The method for preparing the antistatic polypropylene includes the following steps: S1. Preparation of antistatic agent Acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride were sequentially added to a container, and a solvent of equal mass to the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. After stirring for 35-50 minutes, a first initiator of 0.5%-1.0% of the total mass of acrylonitrile, N-ethylacrylamide, glycidyl methacrylate, fatty alcohol polyoxyethylene ether, and acryloyloxyethyltrimethylammonium chloride was added. The reaction was carried out at 75℃-95℃ for 3.5-5.5 hours. After the reaction was completed, the solvent was removed, and after cooling and solidification, low molecular weight substances were removed. Then, the mixture was vacuum dried for 12-20 hours to obtain an antistatic agent. S2, Preparation of modified antistatic agent Undecenol was dissolved in a first solvent to prepare a grafting reaction solution. Benzoyl peroxide was dissolved in a second solvent and then added to the grafting reaction solution. The antistatic agent was dissolved in dimethylformamide and then added to the grafting reaction solution. The reaction was carried out at 70-80°C for 6-8 hours. After the reaction was completed, the mixture was washed with butanone, acetone and deionized water in sequence, and then dried to obtain the modified antistatic agent. S3. Preparation of antistatic polypropylene The modified antistatic agent is mixed with homopolymer polypropylene, heated to 125℃-165℃, and mixed for 40min-55min. Then, a crosslinking agent is added, the temperature is lowered to 120-130℃, and the mixture is further mixed for 15min-25min. The mixture is then extruded, cooled, and pelletized to obtain antistatic polypropylene masterbatch.

2. The low-static film as described in claim 1, characterized in that, The antistatic agent is cationic.

3. The low-static film as described in claim 1, characterized in that, The concentration of the grafting reaction solution is (15-25) wt%.

4. The low-static film as described in claim 1, characterized in that, The first initiator is selected from at least one of benzoyl peroxide and lauroyl peroxide.

5. The low-static film as described in claim 1, characterized in that, The crosslinking agent is selected from at least one of dicumyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxide.

6. The low-static film as described in claim 1, characterized in that, The thickness of the low-static film is less than 10 μm.

7. The low-static film as described in claim 1, characterized in that, The first solvent is selected from chloroform and methanol; the second solvent is selected from ethanol, diethyl ether, acetone, benzene, and carbon disulfide.

8. A method for preparing a low-static thin film as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. The antistatic polypropylene masterbatch and homopolymer polypropylene are melted and co-extruded to obtain a casting with homopolymer polypropylene as the core layer and antistatic layers on both sides. S2. The cast sheet is preheated to 145-160°C, stretched longitudinally at a stretching ratio of 6-10 times, then heated again to 165-185°C, stretched laterally at a stretching ratio of 7-10 times, and then cooled to 35-45°C. After cooling and shaping, a low-static film is obtained.

9. The preparation method according to claim 8, characterized in that, The thickness of the cast sheet is 2mm-4mm.

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