Preparation method of para-aramid electromagnetic shielding paper
Through the activation of paraaramid fibers, grafted diisocyanate and PAMAM cross-linking reactions, paraaramid electromagnetic shielding paper with uniform dispersion of silver elemental mass was prepared, which solved the problem of silver elemental mass agglomeration and improved the electromagnetic shielding effect and mechanical properties.
Patent Information
- Application Number
- CN202510644600.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-07-29
AI Technical Summary
The existing electromagnetic shielded aramid paper has agglomerated elemental aramid and has poor mechanical properties, resulting in poor electromagnetic shielding effect and degraded mechanical properties.
After activation of para-aramid fibers, they were grafted with diisocyanate, and silver ions were adsorbed through PAMAM and crosslinked with them to form a stable para-aramid-diisocyanate-PAMAM three-dimensional network structure, which was then reduced to silver element and heat-pressed.
It improves the flexibility and corrosion resistance of electromagnetic shielding paper, uniform dispersing of silver element, good electromagnetic shielding effect, and improved mechanical properties.
Smart Images
Figure CN120382676A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electromagnetic shielding materials, and in particular to a method for preparing para-aramid electromagnetic shielding paper. Background Art
[0002] When electronic devices are powered on and running, they continuously emit electromagnetic waves into the environment. Therefore, the problems caused by electromagnetic interference have become a key issue that needs to be addressed urgently. Electromagnetic wave pollution not only interferes with and seriously affects electronic equipment, but also harms human health and the environment. Therefore, electromagnetic interference shielding materials have emerged and are widely used to extend the service life of equipment, improve electromagnetic compatibility and biosystem safety, and reduce the impact and harm of electromagnetic radiation on the human body or human body. Ideal electromagnetic shielding materials must possess a series of excellent properties, including excellent mechanical strength, electrical conductivity, flexibility, and heat resistance. Although traditional metal electromagnetic shielding materials have good electrical conductivity, their application is limited by their high density, poor corrosion resistance, and poor flexibility.
[0003] Aramid fiber, a specialty fiber, boasts exceptional properties such as lightness, flame retardancy, heat resistance, insulation, high strength, and a high elastic modulus. It has been used as an electromagnetic shielding material. Typically, para-aramid is first activated to release hydroxyl and amino activation points. Long-chain polymers are then grafted onto the activation points to form a network-like microstructure. Finally, the fiber is pressed with silver to produce a soft, lightweight, high-strength electromagnetic shielding aramid paper. However, during the preparation of this electromagnetic shielding aramid paper, the silver and polymer are physically combined, making it prone to silver agglomeration. This results in poor electromagnetic shielding effectiveness and reduced mechanical properties. Summary of the Invention
[0004] To address the problem of silver agglomeration and poor mechanical properties in existing electromagnetic shielding aramid paper, the present invention provides a method for preparing para-aramid electromagnetic shielding paper, comprising the following steps: 1) Para-aramid activation Adding para-aramid fiber and KOH powder to a mixed solvent of water and an organic solvent, heating and stirring, and adjusting the pH of the mixed solution for later use; 2) Grafted diisocyanate Heat the diisocyanate, add an organotin catalyst to the mixed solution from step 1), stir evenly, and then add the mixed solution dropwise to the diisocyanate while continuing to stir so that the diisocyanate is grafted onto the activated para-aramid fiber. Filter the product, wash with water, and set aside. 3) PAMAM adsorption of silver ions At room temperature, add PAMAM dendrimers to the silver ion solution, stir thoroughly, let it stand, filter, and wash with water for later use; 4) Cross-linking reaction The material washed in steps 2) and 3) is added to the same mixed solvent as in step 1), an organotin catalyst and a cross-linking agent are added, and then heated. The dendrimer adsorbing silver ions and the para-aramid grafted with diisocyanate are reacted under slow stirring. After the reaction is completed, the material is filtered and the filtrate is washed with water. 5) Reduction reaction Add the product of step 4) to the silver ammonia solution, add the glucose solution dropwise under an ultrasonic constant temperature water bath, and filter and wash the reactants after the reaction is completed; 6) Molding The product of step 5) is mixed with the thermoplastic film BP400, and then heated and pressed to obtain the para-aramid electromagnetic shielding paper.
[0005] Furthermore, in step 1), the mass ratio of para-aramid and KOH is 1:(2-5); in step 2), the diisocyanate is one of MDI, HDI, TDI or HMDI; in step 3), the number average molecular weight of the PAMAM dendrimer is 500-1000; in step 4), the crosslinking agent is one of diglycidyl ether, ethylene glycol diglycidyl ether or diethylene glycol diglycidyl ether.
[0006] Specifically, in step 1), the heating temperature is 30-50°C; in step 2), the heating temperature is 45-70°C; in step 4), the heating temperature is 40-60°C; in step 5), the constant temperature water bath temperature is 30-45°C; in step 6), the heating and pressing temperature is 100-150°C.
[0007] Compared with traditional metal electromagnetic shielding materials, the para-aramid electromagnetic shielding paper of the present invention has greatly increased flexibility and corrosion resistance, and at the same time has good electromagnetic shielding performance, so as to better meet the requirements of different application scenarios for electromagnetic shielding effects. The para-aramid electromagnetic shielding paper of the present invention first adopts activated para-aramid and diisocyanate for grafting, and then uses PAMAM that is saturated with adsorbed silver ions and unreacted isocyanate for cross-linking reaction to form a para-aramid-diisocyanate-PAMAM three-dimensional network structure with diisocyanate as a connecting bridge, and reduces the silver ions adsorbed in PAMAM to silver element, and finally hot presses it. Compared with the existing aramid shielding paper, the silver element in the para-aramid electromagnetic shielding paper of the present invention is evenly dispersed, and the electromagnetic shielding effect is good. The para-aramid, diisocyanate and PAMAM form a stable body polymer through chemical bonds, which makes the aramid paper have good flexibility. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 Graph showing the electromagnetic shielding of the para-aramid paper obtained in Examples 1 to 3 (S1, S2, S3) and Comparative Example 1 (D1).
[0009] Figure 2Bar chart of tensile stress of the para-aramid paper obtained in Examples 1 to 3 (S1, S2, S3) and Comparative Example 1 (D1). Detailed implementation manners
[0010] 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 will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
[0011] Example 1 A preparation method of para-aramid electromagnetic shielding paper includes the following steps: 1. Add 2.5 parts by weight of para-aramid fiber and 7.5 parts by weight of KOH powder into a mixed solvent of 20 parts by weight of water and 480 parts by weight of DMSO, heat to 40 °C, stir at 200 rpm, and adjust the pH of the mixed solution to 8 with dilute hydrochloric acid, and then set aside; 2. Heat MDI to 60 °C, add an organotin catalyst to the mixed solution in step 1, stir evenly, and then dropwise add the mixed solution into MDI drop by drop, continuously stir to graft MDI onto the activated para-aramid fiber, filter the product, wash with water and then set aside; 3. At room temperature, add PAMAM dendrimer with a number-average molecular weight of 1000 into silver nitrate solution, stir well, stand still, filter, wash with water and then set aside; 4. Add the materials washed with water in step 2 and step 3 into the same mixed solvent as in step 1, add an organotin catalyst and 0.3 part by weight of diglycidyl ether, heat to 50 °C, and slowly stir to make the PAMAM dendrimer adsorbed with silver ions react with the para-aramid grafted with MDI. After the reaction is completed, filter, and wash the filtrate with water; 5. Add the product of step 4 into silver ammonia solution, dropwise add glucose solution under ultrasonic 40 °C constant temperature water bath, filter and wash the reactant after the reaction is completed; 6. Mix the product of step 5 with 0.2 part by weight of thermoplastic film BP400, heat to 110 °C, press at 45 MPa to obtain the product.
[0012] Example 2 A preparation method of para-aramid electromagnetic shielding paper includes the following steps: 1. Add 2 parts by weight of para-aramid fiber and 10 parts by weight of KOH powder into a mixed solvent of 40 parts by weight of water and 460 parts by weight of DMAc, heat to 50 °C, stir at 100 rpm, and adjust the pH of the mixed solution to 8 with dilute hydrochloric acid, and then set aside; 2. Heat TDI to 45 °C, add an organotin catalyst to the mixed solution in Step 1, stir evenly, then dropwise add the mixed solution to TDI, continuously stir to graft TDI onto the activated para-aramid fiber, filter the product, wash it with water, and set it aside for later use. 3. At room temperature, add PAMAM dendrimer with a number average molecular weight of 800 to a silver nitrate solution, stir well, let it stand, filter, wash with water, and set it aside for later use. 4. Add the materials washed with water in Step 2 and Step 3 to the same mixed solvent as in Step 1, add an organotin catalyst and 0.1 part by weight of ethylene glycol diglycidyl ether, heat to 60 °C, and slowly stir to react the PAMAM dendrimer adsorbed with silver ions and the para-aramid fiber grafted with TDI. After the reaction is completed, filter, and wash the filtrate with water. 5. Add the product of Step 4 to a silver ammonia solution, dropwise add a glucose solution under ultrasonic wave in a 30 °C constant temperature water bath, filter the reactant after the reaction is completed, and wash it with water. 6. Mix the product of Step 5 with 0.1 part by weight of thermoplastic film BP400, heat to 150 °C, and press at 40 MPa to obtain the product.
[0013] Example 3 A preparation method of para-aramid electromagnetic shielding paper includes the following steps: 1. Add 3 parts by weight of para-aramid fiber and 6 parts by weight of KOH powder to a mixed solvent of 100 parts by weight of water and 400 parts by weight of DMF, heat to 30 °C, stir at 150 rpm, adjust the pH of the mixed solution to 8 with dilute hydrochloric acid, and set it aside for later use. 2. Heat HDI to 75 °C, add an organotin catalyst to the mixed solution in Step 1, stir evenly, then dropwise add the mixed solution to HDI, continuously stir to graft HDI onto the activated para-aramid fiber, filter the product, wash it with water, and set it aside for later use. 3. At room temperature, add PAMAM dendrimer with a number average molecular weight of 500 to a silver nitrate solution, stir well, let it stand, filter, wash with water, and set it aside for later use. 4. Add the materials washed with water in Step 2 and Step 3 to the same mixed solvent as in Step 1, add an organotin catalyst and 0.6 part by weight of diethylene glycol diglycidyl ether, heat to 40 °C, and slowly stir to react the PAMAM dendrimer adsorbed with silver ions and the para-aramid fiber grafted with HDI. After the reaction is completed, filter, and wash the filtrate with water. 5. Add the product of Step 4 to a silver ammonia solution, dropwise add a glucose solution under ultrasonic wave in a 45 °C constant temperature water bath, filter the reactant after the reaction is completed, and wash it with water. 6. Mix the product of Step 5 with 0.3 part by weight of thermoplastic film BP400, heat to 100 °C, and press at 50 MPa to obtain the product.
[0014] Comparative Example 1 A method for preparing para-aramid paper with electromagnetic shielding ability, comprising the following steps: 1. Add 2.5 parts by weight of para-aramid fiber and 7.5 parts by weight of KOH powder into a mixed solvent of 20 parts by weight of water and 480 parts by weight of DMSO, heat to 40 °C, stir at 200 rpm, and adjust the pH of the mixed solution to 8 with dilute hydrochloric acid for standby; 2. At room temperature, add PAMAM dendrimer with a number average molecular weight of 1000 into silver nitrate solution, stir well, stand for filtration, and wash with water for standby; 3. Mix the materials washed in Step 1 and Step 2 with 0.3 part by weight of diglycidyl ether and heat to 50 °C. Under slow stirring, cross-linking reaction occurs among the PAMAM dendrimer adsorbed with silver ions, activated para-aramid, and diglycidyl ether. After the reaction ends, filter, and wash the filtrate with water; 4. Add the product of Step 3 into silver ammonia solution, and dropwise add glucose solution under ultrasonic 40 °C constant temperature water bath. After the reaction ends, filter and wash the reactant with water; 5. Mix the product of Step 4 with 0.2 part by weight of thermoplastic film BP400 and heat to 110 °C, press at 45 MPa to obtain.
[0015] Figure 1 It is the electromagnetic shielding curve graph of the para-aramid paper obtained in Examples 1 to 3 (S1, S2, S3) and Comparative Example 1 (D1). From Figure 1 the curve, it can be seen that the para-aramid electromagnetic shielding paper obtained in Examples 1 to 3 has high electromagnetic shielding ability.
[0016] Figure 2 It is the tensile stress histogram of the para-aramid paper obtained in Examples 1 to 3 (S1, S2, S3) and Comparative Example 1 (D1). From Figure 1 the curve, it can be seen that the para-aramid electromagnetic shielding paper obtained in Examples 1 to 3 has strong tensile strength.
[0017] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather should conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A preparation method of para-aramid electromagnetic shielding paper, characterized in that, The following steps are involved: 1) Para-aramid activation Adding para-aramid fiber and KOH powder to a mixed solvent of water and an organic solvent, heating and stirring, and adjusting the pH of the mixed solution for later use; 2) Grafted diisocyanate Heat the diisocyanate, add an organotin catalyst to the mixed solution of step 1), stir evenly, then add the mixed solution dropwise to the diisocyanate, stir and react, filter the product after the reaction is complete, and wash with water for later use; 3) PAMAM adsorption of silver ions At room temperature, add PAMAM dendrimers to the silver ion solution, stir thoroughly, let it stand, filter, and wash with water for later use; 4) Cross-linking reaction The washed substances from step 2) and step 3) are added to the same mixed solvent as step 1), and an organotin catalyst and a cross-linking agent are added, followed by heating and slow stirring. After the reaction is completed, the filtered substance is filtered and washed with water; 5) Reduction reaction The washed product of step 4) is added to the silver ammonia solution, and the glucose solution is added dropwise under an ultrasonic constant temperature water bath. After the reaction is completed, the reactant is filtered and washed with water; 6) Molding The product of step 5) is mixed with the thermoplastic film BP400, and then heated and pressed to obtain the para-aramid electromagnetic shielding paper.
2. The preparation method according to claim 1, wherein, In step 1), the mass ratio of the para-aramid fiber to KOH is 1:(2-5).
3. The preparation method according to claim 1, wherein In step 2), the diisocyanate is one of MDI, HDI, TDI or HMDI.
4. The preparation method according to claim 1, characterized in that, In step 3), the number average molecular weight of the PAMAM dendrimer is 500-1000.
5. The preparation method according to claim 1, characterized in that, In step 4), the cross-linking agent is one of diglycidyl ether, ethylene glycol diglycidyl ether or diethylene glycol diglycidyl ether.
6. The preparation method according to claim 1, characterized in that, In step 1), the heating temperature is 30-50°C; in step 2), the heating temperature is 45-70°C; in step 4), the heating temperature is 40-60°C; in step 5), the constant temperature water bath temperature is 30-45°C; in step 6), the heating and pressing temperature is 100-150°C.