Nanocrystalline electromagnetic shielding material for wireless charging and preparation method thereof

Abstract

This invention discloses a nanocrystalline electromagnetic shielding material for wireless charging and its preparation method. The material comprises the following raw materials in parts by weight: 80-100 parts modified nanocrystals, 8-10 parts modified silicone resin, 1-1.5 parts modified additives, and 1-1.5 parts TPO photoinitiator. When the raw materials are blended and irradiated with ultraviolet light, the modified nanocrystals, modified silicone resin, and modified additives will form free radical polymerization, thereby forming a cross-linked network. The modified silicone resin and the modified nanocrystals formed by in-situ growth of Mn-Zn ferrite nanocrystals on cellulose nanocrystals construct an organic-inorganic hybrid system, which effectively solves the problem of material brittleness. The modified silicone resin side chain contains cyano groups, and the modified additive contains benzene rings. These groups can convert magnetic energy into thermal energy. The cage-like silsesquioxane structure can generate multiple scattering and reflection of incident electromagnetic waves, prolonging their propagation path and increasing losses, thereby improving the electromagnetic shielding effect of the material.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding material preparation technology, specifically to a nanocrystalline electromagnetic shielding material for wireless charging and its preparation method. Background Technology

[0002] With the widespread adoption of smartphones, wearable devices, and electric vehicles, wireless charging technology is rapidly becoming one of the core methods for replenishing energy for modern electronic devices due to its convenience and safety. This technology is primarily based on the principles of magnetic induction or magnetic resonance, achieving wireless power transmission through an alternating magnetic field between the transmitting and receiving coils. However, this process inevitably generates strong near-field electromagnetic leakage. This leaking magnetic field not only interferes with the normal operation of sensitive circuits within the device itself (such as radio frequency antennas and biosensors), leading to decreased charging efficiency and device overheating, but may also cause electromagnetic interference to other surrounding electronic devices, and even raise safety concerns about excessive specific absorption rates in the human body. Therefore, efficient and reliable electromagnetic shielding has become an indispensable key component of wireless charging modules, directly determining charging efficiency, device safety, and user experience. Summary of the Invention

[0003] The purpose of this invention is to provide a nanocrystalline electromagnetic shielding material for wireless charging and its preparation method, which solves the problem of poor electromagnetic shielding effect of current nanocrystalline materials for wireless charging.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a nanocrystalline electromagnetic shielding material for wireless charging specifically includes the following steps:

[0006] Step A1: Mix phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water, purge with nitrogen for protection, and react at a speed of 150-200 r / min and a temperature of 85-90℃ for 3-5 h. Then cool down to 20-25℃ and continue the reaction for 10-15 h to obtain sodium octaphenylcyclotetrasiloxane tetrasilanolate.

[0007] Step A2: Mix octaphenylcyclotetrasiloxane tetrasiloxane sodium, triethylamine and tetrahydrofuran, and purge with nitrogen. Stir and add methyl vinyl dichlorosilane at 120-150 r / min and 0℃. After reacting for 3-5 h, raise the temperature to 20-25℃ and react for 20-25 h to obtain the modified additive.

[0008] Step A3: Mix cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water. Stir at 150-200 r / min and 20-25℃, and add sodium hydroxide solution until the pH value is 9.5-10. Stir for 30-40 min, raise the temperature to 160-165℃, and perform hydrothermal reaction for 8-10 h. Filter to remove the filtrate, and wash the substrate with deionized water until neutral to obtain pretreated nanocrystals.

[0009] Step A4: Disperse the pretreated nanocrystals in ethanol, stir and add methacryloxypropyltrimethoxysilane and deionized water at a speed of 200-300 r / min and a temperature of 70-75℃ for 4-6 h to obtain modified nanocrystals.

[0010] Step A5: Weigh the following raw materials in parts by weight: 80-100 parts of modified nanocrystals, 8-10 parts of modified silicone resin, 1-1.5 parts of modified additives and 1-1.5 parts of TPO photoinitiator. Mix the raw materials evenly and add them to the mold. Under the condition of 365nm ultraviolet light irradiation, irradiate with ultraviolet light for 25-30s to obtain nanocrystal electromagnetic shielding material for wireless charging.

[0011] Furthermore, the ratio of phenyltrimethoxysilane, isopropanol, sodium hydroxide, and deionized water used in step A1 is 120 mmol: 120 mL: 80 mmol: 3 mL.

[0012] Furthermore, the ratio of sodium tetrasiloxane tetrasiloxane, triethylamine, and methylvinyl dichlorosilane used in step A2 is 15 mmol: 4.5 mL: 30 mmol.

[0013] Furthermore, the ratio of cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water in step A3 is 2g:13.3mmol:3.3mmol:3.3mmol:80mL.

[0014] Furthermore, the amount of methacryloyloxypropyltrimethoxysilane used in step A4 is 2% of the mass of the pretreated nanocrystals.

[0015] Furthermore, the modified silicone resin is prepared by the following steps:

[0016] Step B1: Allyl alcohol glycidyl ether, dimethylchlorosilane, caster catalyst and N,N-dimethylformamide are reacted under nitrogen protection at a speed of 200-300 r / min and a temperature of 80-85℃ for 6-8 hours to obtain an intermediate. Lithium dimethylhydrosilyl alcohol is dissolved in N,N-dimethylformamide, and under nitrogen protection, it is stirred and tetramethylcyclotetrasiloxane is added at a speed of 120-150 r / min and a temperature of 0℃. The mixture is heated to 25-30℃ and reacted for 8-10 hours. Then the intermediate is added and the reaction is continued for 1-1.5 hours to obtain the modifier.

[0017] Step B2: Mix octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, and purge with nitrogen. React at 150-200 r / min and 90-95℃ for 10-12 h, then raise the temperature to 105-110℃ and continue the reaction for 2-3 h to obtain aminopolysiloxane. Mix aminopolysiloxane, modifier, tetraethylammonium bromide and N,N-dimethylformamide, and purge with nitrogen. React at 200-300 r / min and 90-100℃ for 6-8 h to obtain pretreated polysiloxane.

[0018] Step B3: Mix pretreated polysiloxane, acrylonitrile, caster catalyst, and N,N-dimethylformamide, and purge with nitrogen. React at 200-300 r / min and 80-85℃ for 8-10 h to obtain modified polysiloxane. Dissolve the modified polysiloxane in N,N-dimethylformamide, purge with nitrogen, and stir at 150-200 r / min and 0℃. Add triethylamine and acryloyl chloride and react for 1-1.5 h. Then raise the temperature to 20-25℃ and continue the reaction for 3-5 h to obtain modified silicone resin.

[0019] Furthermore, the molar ratio of allyl alcohol glycidyl ether and dimethylchlorosilane in step B1 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, tetramethylcyclotetrasiloxane and intermediate is 1:3:1.

[0020] Furthermore, in step B2, the ratio of octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide, and deionized water is 2.2 mol:0.2 mol:2 mol:3 mol:50 mL, the molar ratio of the amino group on the aminopolysiloxane to the modifier is 1:2, and the amount of tetraethylammonium bromide is 1% of the mass of the modifier.

[0021] Furthermore, in step B3, the molar ratio of Si-H bonds on the pretreated polysiloxane to acrylonitrile is 1:1, the amount of caster catalyst is 0.01% of the mass of acrylonitrile, and the molar ratio of modified polysiloxane, triethylamine and acryloyl chloride is 1:1.2:1.

[0022] The beneficial effects of the present invention are as follows: The present invention discloses a nanocrystalline electromagnetic shielding material for wireless charging, comprising the following raw materials: modified nanocrystalline material, modified silicone resin, modified additives and TPO photoinitiator. The modified nanocrystalline material is prepared by using cellulose nanocrystalline material, ferric nitrate nonahydrate, manganese chloride tetrahydrate and zinc nitrate hexahydrate as raw materials. Mn-Zn ferrite nanocrystalline material is grown in situ on the cellulose nanocrystalline material through hydrothermal reaction to obtain pretreated nanocrystalline material. The pretreated nanocrystalline material is then treated with methacryloyloxypropyltrimethoxysilane to graft double bonds onto the surface to obtain the modified nanocrystalline material.

[0023] The modified additive is prepared by hydrolysis and condensation of phenyltrimethoxysilane to obtain sodium octaphenylcyclotetrasiloxane tetrasilanolate. The sodium octaphenylcyclotetrasiloxane tetrasilanolate is then reacted with methylvinyldichlorosilane, causing the Si-Cl bond on the methylvinyldichlorosilane to react with the sodium silanolate on the sodium octaphenylcyclotetrasiloxane tetrasilanolate, thus obtaining the modified additive.

[0024] Modified silicone resin is prepared by reacting allyl glycidyl ether and dimethylchlorosilane, causing the double bond on allyl glycidyl ether to react with the Si-H bond on dimethylchlorosilane to obtain an intermediate. Using lithium dimethylhydrosilanolate as an initiator and tetramethylcyclotetrasiloxane as a polymerization monomer, a polysiloxane with lithium silanolate at one end and Si-H bond at the other end is formed. The intermediate is then added, causing the Si-Cl bond on the intermediate to react with the lithium silanolate to obtain a modifier. Octamethylcyclotetrasiloxane is ring-opened and reacted with 3-aminopropyldiethoxy... Methylsilane is hydrolyzed and condensed, and then tetramethyldisiloxane is used to cap the end of the polysiloxane to obtain an aminopolysiloxane. The aminopolysiloxane is then reacted with a modifier, causing the amino groups on the aminopolysiloxane to react with the epoxy groups on the modifier to form hydroxyl groups, thus obtaining a pretreated polysiloxane. The pretreated polysiloxane is then reacted with acrylonitrile to obtain Si-H bonds on the pretreated polysiloxane and double bonds on the acrylonitrile. The modified polysiloxane is then reacted with acryloyl chloride, causing the hydroxyl groups on the modified polysiloxane to react with the acryloyl chloride on the acryloyl chloride, thus obtaining a modified silicone resin.

[0025] When raw materials are blended and irradiated with ultraviolet light, modified nanocrystals, modified silicone resin, and modifying additives undergo free radical polymerization, forming a cross-linked network. The composite of modified silicone resin and modified nanocrystals formed by in-situ growth of Mn-Zn ferrite nanocrystals on cellulose nanocrystals constructs an organic-inorganic hybrid system. The silicone resin itself has excellent flexibility and low density, and when combined with fibrous nanocrystals, it effectively solves the brittleness problem of the material. The modified silicone resin side chain contains cyano groups, and the modifying additive contains benzene rings. These groups will undergo dipole reorientation polarization or electron cloud distortion under a high-frequency electric field, effectively converting magnetic energy into thermal energy. The cage-like silsesquioxane structure can generate multiple scattering and reflection of incident electromagnetic waves, prolonging their propagation path and increasing losses, thereby improving the electromagnetic shielding effect of the material. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0027] Example 1: A method for preparing a nanocrystalline electromagnetic shielding material for wireless charging, specifically including the following steps:

[0028] Step A1: Mix phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water, purge with nitrogen, and react for 3 hours at a speed of 150 r / min and a temperature of 85°C. Then cool down to 20°C and continue the reaction for 10 hours to obtain sodium octaphenylcyclotetrasiloxane tetrasiloxane.

[0029] Step A2: Mix octaphenylcyclotetrasiloxane tetrasiloxane sodium, triethylamine and tetrahydrofuran, purge with nitrogen, stir and add methyl vinyl dichlorosilane at 120 r / min and 0 °C, react for 3 h, then raise the temperature to 20 °C and react for 20 h to obtain the modified additive.

[0030] Step A3: Mix cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water. Stir at 150 r / min and 20°C, and add sodium hydroxide solution until the pH value is 9.5. Stir for 30 min, raise the temperature to 160°C, and perform hydrothermal reaction for 8 h. Filter to remove the filtrate, and wash the substrate with deionized water until neutral to obtain pretreated nanocrystals.

[0031] Step A4: Disperse the pretreated nanocrystals in ethanol, stir and add methacryloxypropyltrimethoxysilane and deionized water at a speed of 200 r / min and a temperature of 70℃ for 4 h to obtain modified nanocrystals.

[0032] Step A5: Weigh the following raw materials by weight: 80 parts modified nanocrystals, 8 parts modified silicone resin, 1 part modified additive and 1 part TPO photoinitiator. Mix the raw materials evenly and add them to the mold. Under the condition of 365nm ultraviolet light irradiation, irradiate with ultraviolet light for 25s to obtain nanocrystal electromagnetic shielding material for wireless charging.

[0033] The ratio of phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water used in step A1 is 120 mmol: 120 mL: 80 mmol: 3 mL.

[0034] The ratio of sodium tetrasiloxane tetrasiloxane, triethylamine, and methylvinyl dichlorosilane used in step A2 is 15 mmol: 4.5 mL: 30 mmol.

[0035] The ratio of cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water in step A3 is 2g:13.3mmol:3.3mmol:3.3mmol:80mL.

[0036] The amount of methacryloyloxypropyltrimethoxysilane used in step A4 is 2% of the mass of the pretreated nanocrystals.

[0037] The modified silicone resin is prepared by the following steps:

[0038] Step B1: Allyl alcohol glycidyl ether, dimethylchlorosilane, caster catalyst and N,N-dimethylformamide were reacted under nitrogen protection at 200 r / min and 80 °C for 6 h to obtain an intermediate. Lithium dimethylhydrosilyl alcohol was dissolved in N,N-dimethylformamide under nitrogen protection at 120 r / min and 0 °C. Tetramethylcyclotetrasiloxane was added and the mixture was heated to 25 °C and reacted for 8 h. The intermediate was then added and the reaction was continued for 1 h to obtain the modifier.

[0039] Step B2: Octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water are mixed and purged with nitrogen. The mixture is reacted at 150 r / min and 90 °C for 10 h, then heated to 105 °C and reacted for another 2 h to obtain aminopolysiloxane. Aminopolysiloxane, modifier, tetraethylammonium bromide and N,N-dimethylformamide are mixed and purged with nitrogen. The mixture is reacted at 200 r / min and 90 °C for 6 h to obtain pretreated polysiloxane.

[0040] Step B3: Pretreated polysiloxane, acrylonitrile, caster catalyst and N,N-dimethylformamide are mixed, and nitrogen gas is introduced for protection. The mixture is reacted for 8 hours at a speed of 200 r / min and a temperature of 80 °C to obtain modified polysiloxane. The modified polysiloxane is dissolved in N,N-dimethylformamide, and nitrogen gas is introduced for protection. The mixture is stirred and triethylamine and acryloyl chloride are added at a speed of 150 r / min and a temperature of 0 °C. The mixture is reacted for 1 hour, and then the temperature is raised to 20 °C and the reaction is continued for 3 hours to obtain modified silicone resin.

[0041] The molar ratio of allyl alcohol glycidyl ether and dimethylchlorosilane in step B1 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, tetramethylcyclotetrasiloxane and intermediate is 1:3:1.

[0042] In step B2, the ratio of octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide, and deionized water is 2.2 mol:0.2 mol:2 mol:3 mol:50 mL, the molar ratio of the amino group on the aminopolysiloxane to the modifier is 1:2, and the amount of tetraethylammonium bromide is 1% of the mass of the modifier.

[0043] In step B3, the molar ratio of Si-H bonds on the pretreated polysiloxane to acrylonitrile is 1:1, the amount of caster catalyst is 0.01% of the mass of acrylonitrile, and the molar ratio of modified polysiloxane, triethylamine and acryloyl chloride is 1:1.2:1.

[0044] Example 2: A method for preparing a nanocrystalline electromagnetic shielding material for wireless charging, specifically including the following steps:

[0045] Step A1: Mix phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water, purge with nitrogen, and react for 4 hours at a speed of 150 r / min and a temperature of 90℃. Then cool down to 20℃ and continue the reaction for 13 hours to obtain sodium octaphenylcyclotetrasiloxane tetrasiloxane.

[0046] Step A2: Mix octaphenylcyclotetrasiloxane tetrasiloxane sodium, triethylamine and tetrahydrofuran, purge with nitrogen, stir and add methyl vinyl dichlorosilane at 150 r / min and 0 °C, react for 4 h, then raise the temperature to 23 °C and react for 25 h to obtain the modified additive.

[0047] Step A3: Mix cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water. Stir at 150 r / min and 25°C, and add sodium hydroxide solution until the pH value is 9.5. Stir for 35 min, raise the temperature to 165°C, and perform hydrothermal reaction for 9 h. Filter to remove the filtrate, and wash the substrate with deionized water until neutral to obtain pretreated nanocrystals.

[0048] Step A4: Disperse the pretreated nanocrystals in ethanol, stir and add methacryloxypropyltrimethoxysilane and deionized water at a speed of 200 r / min and a temperature of 75℃ for 5 h to obtain modified nanocrystals.

[0049] Step A5: Weigh the following raw materials by weight: 90 parts modified nanocrystals, 9 parts modified silicone resin, 1.3 parts modified additives and 1.3 parts TPO photoinitiator. Mix the raw materials evenly and add them to the mold. Under the condition of 365nm ultraviolet light irradiation, irradiate with ultraviolet light for 25s to obtain nanocrystal electromagnetic shielding material for wireless charging.

[0050] The ratio of phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water used in step A1 is 120 mmol: 120 mL: 80 mmol: 3 mL.

[0051] The ratio of sodium tetrasiloxane tetrasiloxane, triethylamine, and methylvinyl dichlorosilane used in step A2 is 15 mmol: 4.5 mL: 30 mmol.

[0052] The ratio of cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water in step A3 is 2g:13.3mmol:3.3mmol:3.3mmol:80mL.

[0053] The amount of methacryloyloxypropyltrimethoxysilane used in step A4 is 2% of the mass of the pretreated nanocrystals.

[0054] The modified silicone resin is prepared by the following steps:

[0055] Step B1: Allyl alcohol glycidyl ether, dimethylchlorosilane, caster catalyst and N,N-dimethylformamide were reacted under nitrogen protection at 300 r / min and 80 °C for 7 h to obtain an intermediate. Lithium dimethylhydrosilyl alcohol was dissolved in N,N-dimethylformamide under nitrogen protection at 150 r / min and 0 °C, and tetramethylcyclotetrasiloxane was added. The mixture was heated to 25 °C and reacted for 9 h. The intermediate was then added and the reaction was continued for 1.5 h to obtain the modifier.

[0056] Step B2: Octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water are mixed and purged with nitrogen. The mixture is reacted at 150 r / min and 95 °C for 11 h. The temperature is then raised to 108 °C and the reaction is continued for 3 h to obtain aminopolysiloxane. Aminopolysiloxane, modifier, tetraethylammonium bromide and N,N-dimethylformamide are mixed and purged with nitrogen. The mixture is reacted at 200 r / min and 95 °C for 7 h to obtain pretreated polysiloxane.

[0057] Step B3: Pretreated polysiloxane, acrylonitrile, caster catalyst and N,N-dimethylformamide are mixed, and nitrogen gas is introduced for protection. The mixture is reacted at 200 r / min and 85 °C for 9 h to obtain modified polysiloxane. The modified polysiloxane is dissolved in N,N-dimethylformamide, and nitrogen gas is introduced for protection. The mixture is stirred at 150 r / min and 0 °C, and triethylamine and acryloyl chloride are added. The mixture is reacted for 1.3 h, and then the temperature is raised to 20 °C and the reaction is continued for 4 h to obtain modified silicone resin.

[0058] The molar ratio of allyl alcohol glycidyl ether and dimethylchlorosilane in step B1 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, tetramethylcyclotetrasiloxane and intermediate is 1:3:1.

[0059] In step B2, the ratio of octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide, and deionized water is 2.2 mol:0.2 mol:2 mol:3 mol:50 mL, the molar ratio of the amino group on the aminopolysiloxane to the modifier is 1:2, and the amount of tetraethylammonium bromide is 1% of the mass of the modifier.

[0060] In step B3, the molar ratio of Si-H bonds on the pretreated polysiloxane to acrylonitrile is 1:1, the amount of caster catalyst is 0.01% of the mass of acrylonitrile, and the molar ratio of modified polysiloxane, triethylamine and acryloyl chloride is 1:1.2:1.

[0061] Example 3: A method for preparing a nanocrystalline electromagnetic shielding material for wireless charging, specifically including the following steps:

[0062] Step A1: Mix phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water, purge with nitrogen, and react for 5 hours at a speed of 200 r / min and a temperature of 90℃. Then cool down to 25℃ and continue the reaction for 15 hours to obtain sodium octaphenylcyclotetrasiloxane tetrasiloxane.

[0063] Step A2: Mix octaphenylcyclotetrasiloxane tetrasiloxane sodium tetrasiloxane, triethylamine and tetrahydrofuran, purge with nitrogen, stir and add methyl vinyl dichlorosilane at 150 r / min and 0 °C, react for 5 h, then raise the temperature to 25 °C and react for 25 h to obtain the modified additive.

[0064] Step A3: Mix cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water. Stir at 200 r / min and 25°C, and add sodium hydroxide solution until the pH value is 10. Stir for 40 min, raise the temperature to 165°C, and perform hydrothermal reaction for 10 h. Filter to remove the filtrate, and wash the substrate with deionized water until neutral to obtain pretreated nanocrystals.

[0065] Step A4: Disperse the pretreated nanocrystals in ethanol, stir and add methacryloxypropyltrimethoxysilane and deionized water at a speed of 300 r / min and a temperature of 75℃ for 6 h to obtain modified nanocrystals.

[0066] Step A5: Weigh the following raw materials in parts by weight: 100 parts modified nanocrystals, 10 parts modified silicone resin, 1.5 parts modified additives and 1.5 parts TPO photoinitiator. Mix the raw materials evenly and add them to the mold. Under the condition of 365nm ultraviolet light irradiation, irradiate with ultraviolet light for 30s to obtain nanocrystal electromagnetic shielding material for wireless charging.

[0067] The ratio of phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water used in step A1 is 120 mmol: 120 mL: 80 mmol: 3 mL.

[0068] The ratio of sodium tetrasiloxane tetrasiloxane, triethylamine, and methylvinyl dichlorosilane used in step A2 is 15 mmol: 4.5 mL: 30 mmol.

[0069] The ratio of cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water in step A3 is 2g:13.3mmol:3.3mmol:3.3mmol:80mL.

[0070] The amount of methacryloyloxypropyltrimethoxysilane used in step A4 is 2% of the mass of the pretreated nanocrystals.

[0071] The modified silicone resin is prepared by the following steps:

[0072] Step B1: Allyl alcohol glycidyl ether, dimethylchlorosilane, caster catalyst and N,N-dimethylformamide were reacted under nitrogen protection at 300 r / min and 85 °C for 8 h to obtain an intermediate. Lithium dimethylhydrosilyl alcohol was dissolved in N,N-dimethylformamide under nitrogen protection at 150 r / min and 0 °C, and tetramethylcyclotetrasiloxane was added. The mixture was heated to 30 °C and reacted for 10 h. The intermediate was then added and the reaction was continued for 1.5 h to obtain the modifier.

[0073] Step B2: Octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water are mixed and purged with nitrogen. The mixture is reacted at 200 r / min and 95 °C for 12 h, then heated to 110 °C and reacted for another 3 h to obtain aminopolysiloxane. Aminopolysiloxane, modifier, tetraethylammonium bromide and N,N-dimethylformamide are mixed and purged with nitrogen. The mixture is reacted at 300 r / min and 100 °C for 8 h to obtain pretreated polysiloxane.

[0074] Step B3: Pretreated polysiloxane, acrylonitrile, caster catalyst and N,N-dimethylformamide are mixed, and nitrogen gas is introduced for protection. The mixture is reacted for 10 h at a rotation speed of 300 r / min and a temperature of 85 °C to obtain modified polysiloxane. The modified polysiloxane is dissolved in N,N-dimethylformamide, and nitrogen gas is introduced for protection. The mixture is stirred and triethylamine and acryloyl chloride are added at a rotation speed of 200 r / min and a temperature of 0 °C. The mixture is reacted for 1.5 h, and then the temperature is raised to 25 °C and the reaction is continued for 5 h to obtain modified silicone resin.

[0075] The molar ratio of allyl alcohol glycidyl ether and dimethylchlorosilane in step B1 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, tetramethylcyclotetrasiloxane and intermediate is 1:3:1.

[0076] In step B2, the ratio of octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide, and deionized water is 2.2 mol:0.2 mol:2 mol:3 mol:50 mL, the molar ratio of the amino group on the aminopolysiloxane to the modifier is 1:2, and the amount of tetraethylammonium bromide is 1% of the mass of the modifier.

[0077] In step B3, the molar ratio of Si-H bonds on the pretreated polysiloxane to acrylonitrile is 1:1, the amount of caster catalyst is 0.01% of the mass of acrylonitrile, and the molar ratio of modified polysiloxane, triethylamine and acryloyl chloride is 1:1.2:1.

[0078] Comparative Example 1: This comparative example did not include cellulose nanocrystals as in Example 1, but the remaining steps were the same.

[0079] Comparative Example 2: This comparative example did not include any modifying additives compared to Example 1, but the remaining steps were the same.

[0080] Comparative Example 3: This comparative example uses epoxide instead of the modifier as described in Example 1, but the other steps are the same.

[0081] The materials obtained from Examples 1-3 and Comparative Examples 1-3 were prepared into 600mm×600mm×15mm samples according to the standard GB / T 30142-2013, and the shielding efficiency from 100kHz to 6.78MHz was tested. The test results are shown in Table 1 below.

[0082] Table 1

[0083] As shown in Table 1, this application has a very good electromagnetic shielding effect.

[0084] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a nanocrystalline electromagnetic shielding material for wireless charging, characterized in that: Specifically, the steps include the following: Step A1: Mix phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water, purge with nitrogen gas for protection, and react to obtain sodium octaphenylcyclotetrasiloxane tetrasiloxane. Step A2: Mix octaphenylcyclotetrasiloxane tetrasiloxane sodium tetrasilanolate, triethylamine and tetrahydrofuran, purge with nitrogen, stir and add methyl vinyl dichlorosilane to carry out the reaction, and obtain the modified additive. Step A3: Mix cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water, stir, and add sodium hydroxide solution until the pH is alkaline. After hydrothermal reaction, filter to remove the filtrate, and wash the substrate with deionized water until neutral to obtain pretreated nanocrystals. Step A4: Disperse the pretreated nanocrystals in ethanol, stir and add methacryloxypropyltrimethoxysilane and deionized water to react and obtain modified nanocrystals; Step A5: Weigh the following raw materials in parts by weight: 80-100 parts of modified nanocrystals, 8-10 parts of modified silicone resin, 1-1.5 parts of modified additives and 1-1.5 parts of TPO photoinitiator. Mix the raw materials evenly and add them into a mold. Treat with ultraviolet light to obtain nanocrystal electromagnetic shielding material for wireless charging.

2. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 1, characterized in that: The ratio of phenyltrimethoxysilane, isopropanol, sodium hydroxide and deionized water used in step A1 is 120 mmol: 120 mL: 80 mmol: 3 mL.

3. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 1, characterized in that: The ratio of sodium tetrasiloxane tetrasiloxane, triethylamine, and methylvinyl dichlorosilane used in step A2 is 15 mmol: 4.5 mL: 30 mmol.

4. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 1, characterized in that: The ratio of cellulose nanocrystals, ferric nitrate nonahydrate, manganese chloride tetrahydrate, zinc nitrate hexahydrate, and deionized water in step A3 is 2g:13.3mmol:3.3mmol:3.3mmol:80mL.

5. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 1, characterized in that: The amount of methacryloyloxypropyltrimethoxysilane used in step A4 is 2% of the mass of the pretreated nanocrystals.

6. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 1, characterized in that: The modified silicone resin is prepared by the following steps: Step B1: Allyl alcohol glycidyl ether, dimethylchlorosilane, caster catalyst and N,N-dimethylformamide are reacted under nitrogen protection to obtain an intermediate. Lithium dimethylhydrosilyl alcohol is dissolved in N,N-dimethylformamide, under nitrogen protection, stirred and tetramethylcyclotetrasiloxane is added, and after reaction, the intermediate is added and the reaction is continued to obtain the modifier. Step B2: Mix octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, and react under nitrogen protection to obtain aminopolysiloxane. Mix aminopolysiloxane, modifier, tetraethylammonium bromide and N,N-dimethylformamide, and react under nitrogen protection to obtain pretreated polysiloxane. Step B3: Mix pretreated polysiloxane, acrylonitrile, caster catalyst and N,N-dimethylformamide, purge with nitrogen, and react to obtain modified polysiloxane. Dissolve the modified polysiloxane in N,N-dimethylformamide, purge with nitrogen, stir and add triethylamine and acryloyl chloride, and react to obtain modified silicone resin.

7. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 6, characterized in that: The molar ratio of allyl alcohol glycidyl ether and dimethylchlorosilane in step B1 is 1:1, and the molar ratio of lithium dimethylhydrosilyl alcohol, tetramethylcyclotetrasiloxane and the intermediate is 1:3:

1.

8. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 6, characterized in that: The ratio of octamethylcyclotetrasiloxane, 3-aminopropyldiethoxymethylsilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B2 is 2.2 mol:0.2 mol:2 mol:3 mol:50 mL, and the molar ratio of the amino group on the aminopolysiloxane to the modifier is 1:

2.

9. The method for preparing nanocrystalline electromagnetic shielding material for wireless charging according to claim 6, characterized in that: In step B3, the molar ratio of Si-H bonds on the pretreated polysiloxane to acrylonitrile is 1:1, and the molar ratio of modified polysiloxane, triethylamine, and acryloyl chloride is 1:1.2:

1.

10. A nanocrystalline electromagnetic shielding material for wireless charging, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.

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