A preparation method of PVC / LDH electromagnetic shielding film

Abstract

The invention belongs to the technical field of electromagnetic shielding material preparation, and specifically relates to a method for preparing a PVC / LDH electromagnetic shielding film. The invention prepares an LDH / polymer solution by a coprecipitation method, thereby improving the binding property between the polymer and the LDH and avoiding the problem of LDH peeling off in the polymer matrix. Then, a certain water-soluble solvent is added to the LDH / polymer mixed solution to cause part of the polymer to precipitate and deposit on the surface of the LDH layer. The LDH / polymer settles in the solution, and due to the mutual entanglement between the polymer chains, the LDH / polymer has ductility and film-forming characteristics. Then, a surface coating method is used to coat the surface of a non-woven fabric to form an LDH film, and finally a layer of PVC film is coated on the surface of the LDH film to improve the mechanical properties of the film and solve the problem of poor mechanical properties when the content of inorganic nanoparticles is high. By controlling the thickness of the LDH film, PVC / LDH films with different electromagnetic shielding properties are prepared. The preparation process is simple, environmentally friendly, has few by-products, and can reduce industrialization costs.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding material preparation, and particularly relates to a method for preparing a PVC / LDH electromagnetic shielding film. Background Art

[0002] With the advent of the high-frequency, high-speed 5G era, the number of connected devices and antennas has increased exponentially. While electronic technology has brought immense convenience to people's lives, it has also exposed them to constant electromagnetic radiation pollution. Electromagnetic waves generated by various electronic devices can cause electromagnetic interference to surrounding components, disrupting signals and threatening the proper operation of electronic devices, seriously affecting the lifespan and safety of electronic components. To address this issue, numerous measures have been implemented to prevent and control electromagnetic pollution, with the development of electromagnetic shielding materials being one of the most cost-effective means.

[0003] In recent years, lightweight, high-strength electromagnetic shielding has become increasingly common. However, current preparation technologies are complex and expensive, hindering their widespread adoption and application. Furthermore, the preparation of electromagnetic shielding materials with high shielding effectiveness, long service life, and excellent mechanical properties remains challenging, and further research is needed into their preparation methods, mechanisms, and conditions.

[0004] Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are a class of synthetic, two-dimensional nanostructured anionic clays composed of positively charged hydroxide layers bounded by negatively charged anions in the interlayer spaces. LDHs not only possess a stable layered structure but also a high aspect ratio, high specific surface area, and abundant interlayer interfaces. Furthermore, LDHs exhibit certain electronic conductivity properties. These properties make LDHs well-suited for use as fillers in polymer-based electromagnetic shielding composites. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a PVC / LDH electromagnetic shielding film.

[0006] This is achieved specifically through the following technical solutions:

[0007] 1. A method for preparing a PVC / LDH electromagnetic shielding film, comprising the following steps:

[0008] S1: Add solvent to the LDH / polymer solution and mechanically stir for 0.5-2h. After the LDH / polymer is completely settled, pour out the supernatant and degas to obtain the LDH / polymer casting solution;

[0009] The solvent is a water-soluble solvent, specifically one of methanol, ethanol, propanol, and DMAc; the volume ratio of LDH / polymer solution to solvent is 1-0.2:1;

[0010] S2: At room temperature, the LDH / polymer casting solution was scraped onto the nonwoven surface at a speed of 0.1-5.0 m / s;

[0011] S3: solidifying the LDH membrane obtained in S2 in air at room temperature to obtain an LDH membrane with a thickness of 50-150 μm.

[0012] S4: Coat a layer of pure PVC film with a thickness of 50-150 μm on the surface of the LDH film using the pure PVC casting liquid, and place the film in an oven for solvent evaporation and curing to obtain a PVC / LDH film.

[0013] Furthermore, the preparation method of the LDH / polymer casting solution is:

[0014] S1: dissolving a divalent metal ion salt and a trivalent metal ion salt in water to obtain a mixed metal salt solution;

[0015] S2: Using an alkaline solution to adjust the pH value of the mixed metal salt solution so that the pH value of the system does not exceed 10;

[0016] S3: After pH adjustment, add the polymer and stir for 1-6 hours to obtain the LDH / polymer solution;

[0017] S4: Add the solvent dropwise to the LDH / polymer solution, stir mechanically for 0.5-2 hours, pour off the supernatant, and degas thoroughly to obtain the LDH / polymer casting solution.

[0018] Furthermore, the polymer is a styrene / maleic anhydride copolymer having a low molecular weight of 550-5500 and a maleic anhydride content of 25-50%.

[0019] Furthermore, the divalent metal ion in the divalent metal ion salt is a divalent metal ion that can generate hydroxide, specifically Mg 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ 、Cu 2+ 、Mn 2+ , Ca 2+ One or more of the following; the trivalent metal ion in the trivalent metal ion salt is a trivalent metal ion that can generate hydroxide, specifically Al 3+ 、Fe 3+ 、Co 3+ Cr 3+ 、Ga 3+ One or more of the following; the anion in the mixed metal ion salt solution is NO 3-The molar ratio of divalent metal ions to trivalent metal ions is (2-5):1; the mass ratio of trivalent metal ion salt to the polymer is 1:(1-7).

[0020] Furthermore, the reaction temperature in step S2 is 25-80° C., and the alkaline solution is sodium hydroxide solution or potassium hydroxide solution.

[0021] Furthermore, the nonwoven fabric is polyethylene terephthalate or polyamide nonwoven fabric, and has a thickness of 50-150 μm.

[0022] Furthermore, the pure PVC casting solution is obtained by uniformly mixing and stirring 15-25% PVC and a solvent, and the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0023] In summary, the beneficial effects of the present invention are as follows: a polymer that can obtain a polymer salt under alkaline conditions is used as a membrane-forming polymer material, and has the property of being soluble in water but insoluble in solvents; after the pH control is completed by co-precipitation method to prepare LDH, LDH is in the nucleation and growth stage, and then the polymer is introduced. At this time, part of the polymer can be connected with LDH by hydrogen bonds to surround the LDH layer plates, thereby improving the binding between the polymer and LDH and avoiding the problem of LDH peeling off in the polymer matrix; part of the polymer exists in an aqueous solution, and then a certain water-soluble solvent is added to obtain an aqueous phase / solvent phase solution, and the property of the polymer salt being soluble in water but insoluble in solvents is used to precipitate the polymer from the aqueous solution, and the precipitated polymer is deposited on the surface of the LDH layer plates, and the polymer chains deposited on the surface of the LDH layer plates are entangled with the polymer chains in the aqueous phase that are bound to the LDH layer plates, The LDH layer is wrapped, and under the action of gravity, the LDH settles in the solution. The more polymer precipitates, the more polymer wraps the LDH layer, avoiding the stacking between the LDH layers and making the LDH uniformly dispersed in the polymer. In addition, the mutual entanglement between the polymer chains makes the LDH / polymer ductile and has the characteristics of film formation; mechanical stirring is carried out for 0.5-2 hours, and after the LDH / polymer is completely settled, the supernatant is poured out and fully degassed to obtain a flowable LDH / polymer casting liquid; then, the LDH film is coated on the surface of the non-woven fabric by a surface coating method, and finally a layer of PVC film is coated on the surface of the LDH film to improve the mechanical properties of the membrane and solve the problem of poor mechanical properties when the content of inorganic nanoparticles is high; by controlling the thickness of the LDH film, PVC / LDH films with different electromagnetic shielding properties are prepared. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments. Any improvement or replacement based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0025] Example 1

[0026] 1. Dissolve 9.6 g of magnesium nitrate and 4.7 g of aluminum nitrate in 30 ml of deionized water to obtain a mixed metal salt solution;

[0027] 2. Adjust the pH value of the mixed metal salt solution with 4 mol / L NaOH solution at room temperature so that the pH value of the system does not exceed 10;

[0028] 3. After pH adjustment, 32.9 g of styrene maleic anhydride copolymer was dispersed in the mixed solution and stirred at room temperature for 6 h to obtain a MgAlLDH / polymer solution;

[0029] 4. Add 100 ml of ethanol dropwise to the MgAlLDH / polymer solution and stir mechanically for 0.5 h. Pour off the supernatant and degas thoroughly to obtain the MgAlLDH / polymer casting solution.

[0030] 5. Under room temperature, the MgAlLDH / polymer casting solution was scraped onto the surface of a woven fabric with a thickness of 50 μm at a speed of 0.1 m / s to obtain an LDH film;

[0031] 7. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 70 μm;

[0032] 8. Coat the casting solution with a PVC content of 15% on the surface of the LDH membrane and dry it in an oven at 60 degrees to obtain a PVC / LDH membrane with a thickness of 120 μm.

[0033] Example 2

[0034] 1. Dissolve 10.1 g of cobalt nitrate and 5.0 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0035] 2. Adjust the pH value of the mixed metal salt solution with 4 mol / L NaOH solution at 60°C so that the pH value of the system does not exceed 10;

[0036] 3. After pH adjustment, 15 g of styrene maleic anhydride copolymer was dispersed into the above mixed solution and stirred at 60°C for 3 h to obtain a CoFeLDH / polymer solution;

[0037] 4. Add 150 ml of methanol to the CoFeLDH / polymer solution and stir mechanically for 2 hours. Pour off the supernatant and degas thoroughly to obtain the CoFeLDH / polymer casting solution.

[0038] 5. Under room temperature, the CoFeLDH / polymer casting solution was scraped onto the surface of a 50 μm nonwoven fabric at a speed of 5 m / s to obtain an LDH film;

[0039] 6. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 90 μm;

[0040] 7. Coat the casting solution with a PVC content of 20% on the surface of the LDH membrane and dry it in an oven at 60 degrees to obtain a PVC / LDH membrane with a thickness of 150 μm.

[0041] Example 3

[0042] 1. Dissolve 7.23 g of nickel nitrate and 5 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0043] 2. Adjust the pH value of the mixed metal salt solution with 4 mol / L NaOH solution at 70°C so that the pH value of the system does not exceed 10;

[0044] 3. After pH adjustment, 5 g of styrene / maleic anhydride copolymer was dispersed into the above mixed solution and stirred at 70°C for 3 h to obtain a NiFeLDH / polymer solution;

[0045] 4. Add 100 ml of acetone dropwise to the NiFeLDH / polymer solution and stir mechanically for 1 hour. Pour off the supernatant and degas thoroughly to obtain the NiFeLDH / polymer casting solution.

[0046] 5. Under room temperature, the NiFeLDH / polymer casting solution was scraped onto the surface of the nonwoven fabric at a speed of 2 m / s to obtain an LDH film;

[0047] 6. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 80 μm;

[0048] 7. Coat the casting solution with a PVC content of 25% on the surface of the LDH membrane and dry it in an oven at 60 degrees to obtain a PVC / LDH membrane with a thickness of 130 μm.

[0049] Example 4

[0050] 1. Dissolve 7.23 g of nickel nitrate and 5 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0051] 2. Adjust the pH value of the mixed metal salt solution with 4 mol / L NaOH solution at 70°C so that the pH value of the system does not exceed 10;

[0052] 3. After pH adjustment, 5 g of styrene / maleic anhydride copolymer was dispersed into the above mixed solution and stirred at 70°C for 3 h to obtain a NiFeLDH / polymer solution;

[0053] 4. Add 100 ml of acetone dropwise to the NiFeLDH / polymer solution and stir mechanically for 1 hour. Pour off the supernatant and degas thoroughly to obtain the NiFeLDH / polymer casting solution.

[0054] 5. Under room temperature, the NiFeLDH / polymer casting solution was scraped onto the surface of the nonwoven fabric at a speed of 2 m / s to obtain an LDH film;

[0055] 7. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 80 μm;

[0056] 8. Coat the casting solution with a PVC content of 15% on the surface of the LDH membrane and dry it in an oven at 60 degrees to obtain a PVC / LDH membrane with a thickness of 160 μm.

[0057] Example 5

[0058] 1. Dissolve 15.1 g of copper nitrate and 5 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0059] 2. Adjust the pH value of the mixed metal salt solution with 4 mol / L NaOH solution at room temperature so that the pH value of the system does not exceed 10;

[0060] 3. After pH adjustment, 25 g of styrene / maleic anhydride copolymer was dispersed into the above mixed solution and stirred at 70°C for 2 h to obtain a NiFeLDH / polymer solution;

[0061] 4. Add 80 ml of ethanol dropwise to the CuFeLDH / polymer solution and stir mechanically for 0.5 h. Pour off the supernatant and degas thoroughly to obtain the CuFeLDH / polymer casting solution.

[0062] 5. Under room temperature, the CuFeLDH / polymer casting solution was scraped onto the surface of the nonwoven fabric at a speed of 0.1 m / s to obtain an LDH film;

[0063] 7. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 100 μm;

[0064] 8. Coat the casting solution with a PVC content of 15% on the surface of the LDH membrane and dry it in an oven at 60 degrees to obtain a PVC / LDH membrane with a thickness of 150 μm.

[0065] Comparative Example 1:

[0066] 1. Dissolve 15.1 g of copper nitrate and 5 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0067] 2. Adjust the pH value of the mixed solution with 4 mol / L NaOH solution at room temperature so that the pH value of the system does not exceed 10;

[0068] 3. Disperse 25 g of styrene / maleic anhydride copolymer into the above mixed solution and stir at 70°C for 2 h to obtain a CuFeLDH / polymer solution;

[0069] 4. Add 80 ml of ethanol dropwise to the CuFeLDH / polymer solution and stir mechanically for 0.5 h. Pour off the supernatant and degas thoroughly to obtain the CuFeLDH / polymer casting solution.

[0070] 5. Under room temperature, the CuFeLDH / polymer casting solution was scraped onto the surface of the nonwoven fabric at a speed of 0.1 m / s to obtain an LDH film.

[0071] 6. The obtained LDH film body is solidified in air at room temperature to obtain an LDH film with a thickness of 100 μm;

[0072] Comparative Example 2:

[0073] 1. Dissolve 15.1 g of copper nitrate and 5 g of ferric nitrate in 50 ml of deionized water to obtain a mixed metal salt solution;

[0074] 2. Adjust the pH value of the mixed solution with 4 mol / L NaOH solution at room temperature so that the pH value of the system does not exceed 10;

[0075] 3. Disperse 25 g of styrene / maleic anhydride copolymer into the above mixed solution and stir at 70°C for 2 h to obtain a CuFeLDH / polymer solution;

[0076] 4. Centrifuge the above solution, wash the precipitate obtained by centrifugation with water for 5-10 times, and dry it in an oven to obtain CuFeLDH / polymer nanomaterials;

[0077] 5. Add the above-mentioned CuFeLDH nanoparticles to a casting solution with a PVC content of 15%, stir and deaerate, scrape the casting solution on the surface of the non-woven fabric at a speed of 0.1 m / s, and dry it in an oven at 60 degrees to obtain a PVC / LDH film with a thickness of 250 μm.

[0078] 1. PVC / LDH film performance test

[0079] 1.1 Experimental Materials

[0080] The electromagnetic shielding films were prepared using the methods of Examples 1-5 and Comparative Examples 1-2.

[0081] 1.2 Experimental methods

[0082] The electromagnetic shielding performance of the membrane was tested using a vector network analyzer (Agilent E5071C) using the coaxial method.

[0083] Mechanical properties test:

[0084] The mechanical properties of the membrane were tested using a universal testing machine in accordance with GB / T 1040.3-2006. The tensile rate was 10 mm / min. The membrane was cut into strips with smooth edges and no notches as required. The strip width was 15 mm and the length was 200 mm.

[0085] The electromagnetic shielding performance and mechanical properties of the electromagnetic shielding film were tested, and the results are shown in Table 1.

[0086] 1.3 Experimental Results

[0087] Table 1

[0088]

[0089] The experimental results show that the film prepared by this method has better mechanical properties than that of Comparative Example 1. Compared with Comparative Example 2, when the LDH content is high, this experimental method can prepare a PVC / LDH film with effective electromagnetic shielding performance.

[0090] 2. Screening Experiment

[0091] 2.1 Experimental Materials

[0092] Sample 1: An LDH electromagnetic shielding film was prepared using the method of Example 5, except that the LDH film thickness was 150 μm.

[0093]

[0094] The experimental results show that increasing the thickness of LDH slightly reduces the mechanical properties, but the electromagnetic shielding performance can be effectively improved.

Claims

1. A method for preparing a PVC / LDH electromagnetic shielding film, characterized in that: The following steps are involved: S1: dissolving a divalent metal ion salt and a trivalent metal ion salt in water to obtain a mixed metal salt solution; adjusting the pH value of the mixed metal salt solution with an alkaline solution at 25-80°C so that the pH value of the system does not exceed 10; after completing the pH adjustment, adding a polymer and stirring for 1-6 hours to obtain an LDH / polymer solution; adding a solvent dropwise to the LDH / polymer solution, mechanically stirring for 0.5-2 hours, discarding the supernatant, and fully degassing to obtain an LDH / polymer casting solution; The polymer is a low molecular weight polymer with a molecular weight of 550-5500 and a styrene / maleic anhydride copolymer with a maleic anhydride content of 25-50%; The solvent is a water-soluble solvent, specifically one of methanol, ethanol, propanol, and DMAc; the volume ratio of LDH / polymer solution to solvent is 1-0.2:1; S2: At room temperature, the LDH / polymer casting solution was scraped onto the nonwoven surface at a speed of 0.1-5.0 m / s; S3: solidifying the LDH film obtained in S2 in air at room temperature to obtain an LDH film with a thickness of 50-150 μm; S4: Coat a layer of pure PVC film with a thickness of 50-150 μm on the surface of the LDH film using the pure PVC casting liquid, and place the film in an oven for solvent evaporation and curing to obtain a PVC / LDH film.

2. The method for preparing a PVC / LDH electromagnetic shielding film according to claim 1, wherein: The divalent metal ion in the divalent metal ion salt is a divalent metal ion that can generate hydroxide, specifically Mg 2+ 、Co 2+ 、Ni 2+ 、Zn 2 + 、Cu 2+ 、Mn 2+ , Ca 2+ One or more of the following; the trivalent metal ion in the trivalent metal ion salt is a trivalent metal ion that can generate hydroxide, specifically Al 3+ 、Fe 3+ 、Co 3+ Cr 3+ 、Ga 3+ One or more of the following; the anion in the mixed metal salt solution is NO 3- The molar ratio of divalent metal ions to trivalent metal ions is (2-5):1; the mass ratio of trivalent metal ion salt to the polymer is 1:(1-7).

3. The method for preparing a PVC / LDH electromagnetic shielding film according to claim 1, wherein: The alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

4. The method for preparing a PVC / LDH electromagnetic shielding film according to claim 1, wherein: The nonwoven fabric is polyethylene terephthalate or polyamide nonwoven fabric, and has a thickness of 50-150 μm.

5. The method for preparing a PVC / LDH electromagnetic shielding film according to claim 1, wherein: The pure PVC casting solution is obtained by uniformly mixing 15-25% PVC and a solvent, and the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

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