A HAP nano-modified composite fiber filter membrane, a preparation method and application thereof

Abstract

The application discloses a kind of based on HAP nano-modified composite fiber filter membrane and its preparation method and application, it is related to the field of insulating oil filtration processing.Preparation method is in hydroxyapatite nanoparticle join alkali solution, 3-glycidyloxypropyl trimethoxysilane reaction preparation surface-modified hydroxyapatite nanoparticle, subsequently with PTFE powder, dispersant is mixed and dispersed to obtain spinning solution, composite fiber filter membrane is prepared using electrostatic spinning machine.The composite fiber filter membrane prepared in the application is doped with surface-modified hydroxyapatite nanoparticle, can efficiently adsorb aging acidic substances in vegetable insulating oil, meanwhile, the filter membrane is intercepted and captured to other micro-impurities, effectively reduces the impurity content in vegetable insulating oil to realize purification, so as to reduce the dielectric loss factor and viscosity of vegetable insulating oil, improve aging life and insulation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of insulating oil filtration treatment, and particularly relates to a HAP nano-modified composite fiber filter membrane and a preparation method and application thereof. BACKGROUND

[0002] Plant insulating oil is an insulating oil extracted from natural oil crops such as soybeans, rapeseed, coconut and the like, and has the characteristics of high ignition point, renewability, biodegradability and non-toxicity. It is considered as a green and environmentally friendly liquid insulating medium, has excellent electrical and physical and chemical properties, and has been successfully applied to distribution transformers.

[0003] However, during the operation of the transformer, it is difficult to avoid contact with air. The plant insulating oil has strong hydrophilicity and can absorb more water, which can accelerate the aging of the insulating oil, thereby causing the plant insulating oil to hydrolyze to generate a large amount of acidic substances. These water and acidic substances can affect the aging life of the insulating oil, greatly accelerate the rise of the viscosity of the plant insulating oil, and promote the decline of the heat conduction performance, thereby greatly deteriorating the insulating performance of the plant insulating oil. SUMMARY

[0004] The present application provides a HAP nano-modified composite fiber filter membrane and a preparation method and application thereof. The impurities existing in the plant insulating oil due to hydrolysis and aging can be accurately filtered, the aged acidic substances can be intercepted and adsorbed, the dielectric loss factor of the plant insulating oil can be reduced, and the aging life can be improved.

[0005] In order to solve the above technical problems, one of the purposes of the present application provides a preparation method of a HAP nano-modified composite fiber filter membrane, comprising the following steps:

[0006] (1) adding an alkali solution and 3-glycidyloxypropyltrimethoxysilane into hydroxyapatite nanoparticles, uniformly heating and stirring and dispersing, and then cooling to room temperature and filtering, and then washing, drying, crushing and sieving to obtain surface-modified hydroxyapatite nanoparticles;

[0007] (2) adding PTFE powder into a container containing a dispersant, stirring uniformly, adding the surface-modified hydroxyapatite nanoparticles, stirring until clear and transparent, and then placing for static defoaming to obtain a spinning solution;

[0008] (3) adding the spinning solution into an electrospinning machine to spin and prepare a composite fiber filter membrane.

[0009] By adopting the above scheme, the composite fiber filter membrane prepared in this application has an extremely high specific surface area and its surface effect is more significant. The added surface-modified hydroxyapatite nanoparticles can efficiently adsorb the aging acidic substances produced by hydrolysis in the plant insulating oil, purify the acid produced by hydrolysis in the aging plant insulating oil, and adsorb and capture other micro impurities, thereby reducing the impurity content in the plant insulating oil, thus more effectively reducing the dielectric loss factor and viscosity of the plant insulating oil and improving its aging life.

[0010] As a preferred embodiment, in step (1), the mass ratio of the hydroxyapatite nanoparticles, alkaline solution, and 3-glycidyloxypropyltrimethoxysilane is (4-5):10:1.

[0011] As a preferred embodiment, the mass ratio of PTFE powder to dispersant is 1:(12-14); the mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder is 1:(10-14).

[0012] As a preferred embodiment, the dispersant is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and polydimethylsiloxane.

[0013] As a preferred embodiment, in step (1), the surface-modified hydroxyapatite nanoparticles have a mesh size of 100-500 mesh.

[0014] As a preferred embodiment, in step (1), the heating temperature is 80-100℃, the stirring and dispersion time is 2-6h, and the product is washed with water and ethanol in sequence.

[0015] As a preferred embodiment, in step (2), the PTFE powder and surface-modified hydroxyapatite nanoparticles are pre-dried at 50-70°C for 15-20 hours.

[0016] As a preferred embodiment, in step (2), the stirring temperature is 30-40℃, the stirring rate is 350-400r / min, and the settling and degassing time is 6-8h.

[0017] As a preferred embodiment, in step (3), the temperature inside the electrospinning machine is controlled at 35-40℃ and the humidity is controlled at 35%-37%. The spinning solution is slowly drawn into a 10mL syringe, and air bubbles in the syringe are fully removed. A stainless steel needle is used and connected to a positive high-voltage DC power source. The flat take-up device is connected to a negative high-voltage DC power source. The tin foil is attached to the flat take-up device using conductive adhesive. The distance between the flat take-up device and the syringe is controlled at 18cm, and the pushing speed of the syringe is 0.75-0.85mL / h.

[0018] As a preferred embodiment, the concentration of the alkaline solution is 4-6 mol / L.

[0019] To address the aforementioned technical problems, a second objective of this invention is to provide a HAP-modified composite fiber filter membrane.

[0020] To address the aforementioned technical problems, a third objective of this invention is to provide an application of HAP-based nano-modified composite fiber filter membranes in the purification of plant insulating oil.

[0021] As a preferred embodiment, the method includes the following steps: cutting the composite fiber filter membrane and installing it on the sand core, and vacuum filtering the vegetable insulating oil, with the vacuum degree set to 0.02-0.05 MPa.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The composite fiber filter membrane prepared in this application has extremely high hydrophobicity. The doped surface-modified hydroxyapatite nanoparticles can efficiently adsorb aging acidic substances in vegetable insulating oil, while also efficiently intercepting and capturing other micro-impurities, effectively reducing the impurity content in vegetable insulating oil and achieving purification. This further reduces the dielectric loss factor and viscosity of vegetable insulating oil, and improves its aging life and insulation performance. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the raw materials used in this application are all commercially available, and the same raw materials are used in parallel experiments.

[0025] The polytetrafluoroethylene is sourced from Daikin Industries, Ltd. of Japan, model number DAIKIN PTFE L-5F;

[0026] Polyvinylidene fluoride (PVDF) is sourced from Shanghai Sanaifu New Material Technology Co., Ltd., model FR904, molecular weight 200,000.

[0027] Example 1

[0028] A HAP-modified composite fiber filter membrane is prepared by the following steps:

[0029] (1) Add a 5 mol / L NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) to hydroxyapatite nanoparticles (HAP), wherein the mass ratio of hydroxyapatite nanoparticles, NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) is 5:10:1. The mixture is ultrasonically stirred at room temperature for 1 h to obtain a stable dispersion. Then, it is heated to 90 °C and stirred for 1 h to mix it thoroughly. After cooling to room temperature, it is filtered and the obtained solid is washed with deionized water and anhydrous ethanol until it is neutral. After drying, pulverizing and sieving, 200 mesh surface-modified hydroxyapatite nanoparticles are obtained.

[0030] (2) The polytetrafluoroethylene (PTFE) powder and the surface-modified hydroxyapatite nanoparticles were placed in a vacuum drying oven and dried for 15 hours at a temperature of 50°C.

[0031] (3) N,N-dimethylacetamide (DMAc) dispersant was placed in a glass bottle and placed on a magnetic stirrer at a temperature of 30°C and a stirring speed of 380 r / min. PTFE powder was slowly poured into the stirring dispersant. The mass ratio of PTFE powder to N,N-dimethylacetamide dispersant was 1:13. The glass bottle was sealed during the stirring process to reduce solvent evaporation. Surface-modified hydroxyapatite nanoparticles were poured into the dispersion solvent during the stirring process. The mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder was 1:11. After stirring until the mixed solution was clear and transparent, it was placed in a vacuum drying oven and allowed to stand for 6 hours to remove bubbles, thus obtaining the spinning solution.

[0032] (4) The temperature inside the WL-2C high-voltage electrospinning machine is controlled at 35℃ and the humidity is controlled at 35%. The spinning solution is slowly drawn into a 10mL syringe, and the air bubbles in the syringe are fully removed. A stainless steel needle is used and connected to a positive high-voltage DC source. The flat take-up device is connected to a negative high-voltage DC source. The tin foil is attached to the flat take-up device with conductive glue. The distance between the flat take-up device and the syringe is controlled at 18cm. The pushing speed of the syringe is 0.75mL / h. The composite fiber filter membrane is prepared.

[0033] Example 2

[0034] A HAP-modified composite fiber filter membrane is prepared by the following steps:

[0035] (1) Add a 5 mol / L NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) to hydroxyapatite nanoparticles (HAP), wherein the mass ratio of hydroxyapatite nanoparticles, NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) is 5:10:1. The mixture is ultrasonically stirred at room temperature for 2 h to obtain a stable dispersion. Then, it is heated to 90 °C and stirred for 2 h to mix it thoroughly. After cooling to room temperature, it is filtered and the obtained solid is washed with deionized water and anhydrous ethanol until it is neutral. After drying, pulverizing and sieving, 200 mesh surface-modified hydroxyapatite nanoparticles are obtained.

[0036] (2) PTFE powder and surface-modified hydroxyapatite nanoparticles were placed in a vacuum drying oven and dried for 17 hours at a temperature of 60°C.

[0037] (3) N,N-dimethylacetamide (DMAc) dispersant was placed in a glass bottle and placed on a magnetic stirrer at a temperature of 35°C and a stirring speed of 390 r / min. PTFE powder was slowly poured into the stirring dispersant. The mass ratio of PTFE powder to N,N-dimethylacetamide dispersant was 1:12. The glass bottle was sealed during the stirring process to reduce solvent evaporation. Surface-modified hydroxyapatite nanoparticles were poured into the dispersion solvent during the stirring process. The mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder was 1:10. After stirring until the mixed solution was clear and transparent, it was placed in a vacuum drying oven and allowed to stand for 7 hours to remove bubbles, thus obtaining the spinning solution.

[0038] (4) The temperature inside the WL-2C high-voltage electrospinning machine is controlled at 38℃ and the humidity is controlled at 36%. The spinning solution is slowly drawn into a 10mL syringe, and the air bubbles in the syringe are fully removed. A stainless steel needle is used and connected to a positive high-voltage DC power source. The flat take-up device is connected to a negative high-voltage DC power source. The tin foil is attached to the flat take-up device with conductive glue. The distance between the flat take-up device and the syringe is controlled at 18cm. The pushing speed of the syringe is 0.8mL / h. The composite fiber filter membrane is prepared.

[0039] Example 3

[0040] A HAP-modified composite fiber filter membrane is prepared by the following steps:

[0041] (1) Add a 5 mol / L NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) to hydroxyapatite nanoparticles (HAP), wherein the mass ratio of hydroxyapatite nanoparticles, NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) is 5:10:1. The mixture is ultrasonically stirred at room temperature for 3 h to obtain a stable dispersion. Then, it is heated to 90 °C and stirred for 3 h to mix it thoroughly. After cooling to room temperature, it is filtered and the obtained solid is washed with deionized water and anhydrous ethanol until it is neutral. After drying, pulverizing and sieving, 200 mesh surface-modified hydroxyapatite nanoparticles are obtained.

[0042] (2) PTFE powder and surface-modified hydroxyapatite nanoparticles were placed in a vacuum drying oven and dried for 20 hours at a temperature of 70°C.

[0043] (3) N,N-dimethylacetamide (DMAc) dispersant was placed in a glass bottle and placed on a magnetic stirrer at a temperature of 40°C and a stirring speed of 400 r / min. PTFE powder was slowly poured into the stirring dispersant. The mass ratio of PTFE powder to N,N-dimethylacetamide dispersant was 1:14. The glass bottle was sealed during the stirring process to reduce solvent evaporation. Surface-modified hydroxyapatite nanoparticles were poured into the dispersion solvent during the stirring process. The mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder was 1:12. After stirring until the mixed solution was clear and transparent, it was placed in a vacuum drying oven and allowed to stand for 8 hours to remove bubbles, thus obtaining the spinning solution.

[0044] (4) The temperature inside the WL-2C high-voltage electrospinning machine is controlled at 40℃ and the humidity is controlled at 37%. The spinning solution is slowly drawn into a 10mL syringe, and the air bubbles in the syringe are fully removed. A stainless steel needle is used and connected to a positive high-voltage DC power source. The flat take-up device is connected to a negative high-voltage DC power source. The tin foil is attached to the flat take-up device with conductive glue. The distance between the flat take-up device and the syringe is controlled at 18cm. The pushing speed of the syringe is 0.85mL / h. The composite fiber filter membrane is prepared.

[0045] Example 4

[0046] A HAP-modified composite fiber filter membrane is prepared in the same way as that in Example 1. The difference is that in step (1), the mass ratio of hydroxyapatite nanoparticles, NaOH aqueous solution and 3-glycidyloxypropyltrimethoxysilane (GPS) is 4:10:1.

[0047] Example 5

[0048] A HAP-modified composite fiber filter membrane is prepared in the same way as that in Example 1. The preparation method, reagents, equipment and process parameters are the same as those in Example 1. The difference is that in step (1), the mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder is 1:14.

[0049] Comparative Example 1

[0050] A HAP-modified composite fiber filter membrane is prepared in the same way as that in Example 1. The preparation method, reagents, equipment and process parameters are the same as those in Example 1. The difference is that in step (3), the amount of surface-modified hydroxyapatite nanoparticles added is 0.

[0051] Comparative Example 2

[0052] A HAP-modified composite fiber filter membrane is prepared in the same way as that in Example 1. The preparation method, reagents, equipment and process parameters are the same as those in Example 1. The difference is that in step (1), the 5 mol / L NaOH solution is replaced by an equal amount of 5 mol / L HCl solution.

[0053] Comparative Example 3

[0054] A HAP-modified composite fiber filter membrane is prepared in the same way as that in Example 1. The preparation method, reagents, equipment and process parameters are the same as those in Example 1. The difference is that in step (1), hydroxyapatite nanoparticles are replaced by silica nanoparticles in equal amounts.

[0055] Comparative Example 4

[0056] A HAP-based nano-modified composite fiber filter membrane is prepared in the same way as that in Example 1, with the same steps, reagents, equipment and process parameters. The difference is that in steps (2) and (3), PTFE powder is replaced by polyvinylidene fluoride in equal amounts.

[0057] Comparative Example 5

[0058] A HAP-modified composite fiber filter membrane is prepared in the same way as Example 1, with the same steps, reagents, equipment and process parameters. The difference is that in step (3), the mass ratio of surface-modified hydroxyapatite nanoparticles to PTFE powder is 1:15.

[0059] Application Example 1-5 and Comparative Application Example 1-5

[0060] An application of HAP-based nano-modified composite fiber filter membrane in purifying insulating oil from aging plant-based transformers includes the following steps:

[0061] The composite fiber filter membrane prepared in the examples or comparative examples was cut into membrane samples with a diameter of 4 cm and installed on the sand core. FR3 soybean vegetable insulating oil was vacuum filtered, with a single filtration of 400 mL. The vacuum degree of the circulating vacuum water pump connected to the filtration device was set to 0.03 MPa. The viscosity, acid value and dielectric loss factor of the vegetable oil samples before and after filtration were measured.

[0062] Application Example 6

[0063] An application of HAP-based nano-modified composite fiber filter membrane in purifying insulating oil from aging plant-based transformers includes the following steps:

[0064] The composite fiber filter membrane prepared in Example 1 was cut into membrane samples with a diameter of 4 cm and installed on the sand core. Karamay No. 25 mineral insulating oil was vacuum filtered, with a single filtration of 400 mL. The vacuum degree of the circulating vacuum water pump connected to the filtration device was set to 0.03 MPa. The viscosity, acid value and dielectric loss factor of the vegetable oil samples before and after filtration were measured.

[0065] Performance testing

[0066] 1. Viscosity: The viscosity of the insulating oil in the application examples and comparative application examples was measured by a DN-79 rotational viscometer at a temperature of 40℃. The test results are shown in Table 1 below.

[0067] 2. Acid value: The acid value content of the insulating oil in the application examples and comparative application examples was tested according to GB / T 28552-2012 standard, and the test results are shown in Table 1 below.

[0068] 3. Dielectric loss factor: The dielectric loss factor of the insulating oil in the application example and the comparative application example was tested according to GB / T5654-2007 standard, and the test results are shown in Table 1 below.

[0069] 4. Water droplet contact angle: Refer to GB / T 30693-2014 standard and use the SDC-100 contact angle measuring instrument to measure the contact angle of the composite fiber filter membrane used in the corresponding use case and comparative application example. Place a water droplet on the surface of the composite fiber filter membrane and measure the contact angle formed by the water droplet on the surface of the composite fiber filter membrane.

[0070] Table 1 - Performance test results of aged insulating oil before and after filtration in application examples and comparative application examples

[0071]

[0072] As shown in Table 1, comparing the solutions of Application Example 1 and Comparative Application Examples 1 and 3, it can be seen that Comparative Example 1 did not add surface-modified hydroxyapatite nanoparticles, while Comparative Example 3 added modified silica nanoparticles. The viscosity and acid value of the filtered vegetable insulating oil did not change significantly. The prepared composite fiber filter membrane had low hydrophobicity and insufficient adsorption capacity for aged acidic substances in the insulating oil, resulting in poor interception effect and a high dielectric loss factor of the vegetable insulating oil. The composite fiber filter membrane prepared in Example 1 of this application is doped with surface-modified hydroxyapatite nanoparticles, which has ultra-high hydrophobicity and filtration accuracy. It can adsorb a large amount of acidic substances in the insulating oil, adsorb and intercept impurities such as acidic aging products in the vegetable insulating oil, purify the acid produced by hydrolysis in the aged vegetable insulating oil, and adsorb and capture other micro impurities, thereby more effectively reducing the acid value, dielectric loss factor, and viscosity of the vegetable insulating oil.

[0073] As shown in Table 1, comparing the solutions of Application Example 1 and Comparative Application Example 6, it can be seen that the composite fiber filter membrane prepared in Example 1 of this application, when used to filter aged vegetable insulating oil and mineral insulating oil respectively, shows that the acid value of the vegetable insulating oil decreases significantly and the viscosity decreases significantly, resulting in a reduction in the dielectric loss factor of the vegetable insulating oil. In contrast, the acid value and viscosity of the mineral insulating oil decrease less, and although the dielectric loss factor decreases, the decrease is not as large as in Application Example 1. This indicates that the composite fiber filter membrane of this application is less effective at purifying aged mineral insulating oil than vegetable insulating oil, and has a superior capture efficiency for water and acidic substances generated by hydrolysis in vegetable insulating oil.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for preparing a HAP-modified nanofiber filter membrane, characterized in that, Includes the following steps: (1) Add an alkaline solution and 3-glycidyloxypropyltrimethoxysilane to hydroxyapatite nanoparticles, heat and stir to disperse evenly, cool to room temperature and filter, wash, dry, pulverize and sieve to obtain surface-modified hydroxyapatite nanoparticles. (2) Add PTFE powder to a container containing dispersant, stir evenly, add surface-modified hydroxyapatite nanoparticles, the mass ratio of the surface-modified hydroxyapatite nanoparticles to PTFE powder is 1:(10-14), stir until clear and transparent, and then let stand to degas to obtain spinning solution. (3) Add the spinning solution to the electrospinning machine and spin to prepare a composite fiber filter membrane.

2. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, In step (1), the mass ratio of the hydroxyapatite nanoparticles, alkaline solution, and 3-glycidyloxypropyltrimethoxysilane is (4-5):10:

1.

3. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, The mass ratio of the PTFE powder to the dispersant is 1:(12-14).

4. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, The dispersant is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and polydimethylsiloxane.

5. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, In step (1), the surface-modified hydroxyapatite nanoparticles have a mesh size of 100-500 mesh.

6. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, Satisfying at least one of the following a)-d): a) In step (1), the heating temperature is 80-100 ℃, the stirring and dispersion time is 2-6 h, and the product is washed with water and ethanol in sequence; b) In step (2), the PTFE powder and the surface-modified hydroxyapatite nanoparticles are pre-dried at 50-70 °C for 15-20 h; c) In step (2), the stirring temperature is 30-40 ℃, the stirring rate is 350-400 r / min, and the standing degassing time is 6-8 h; d) In step (3), the temperature inside the electrospinning machine is controlled at 35-40 ℃ and the humidity is controlled at 35%-37%. The spinning solution is slowly drawn into a 10 mL syringe, and air bubbles in the syringe are fully removed. A stainless steel needle is used and connected to a positive high-voltage DC power source. The flat take-up device is connected to a negative high-voltage DC power source. The tin foil is attached to the flat take-up device with conductive glue. The distance between the flat take-up device and the syringe is controlled at 18 cm. The pushing speed of the syringe is 0.75-0.85 mL / h.

7. The method for preparing a HAP-modified composite fiber filter membrane as described in claim 1, characterized in that, The concentration of the alkaline solution is 4-6 mol / L.

8. A HAP-based nano-modified composite fiber filter membrane prepared by the preparation method of HAP-based nano-modified composite fiber filter membrane as described in any one of claims 1-7.

9. The application of the HAP-based nano-modified composite fiber filter membrane as described in claim 8 in the purification of plant insulating oil.

10. The application of a HAP-based nano-modified composite fiber filter membrane as described in claim 9 in the purification of plant insulating oil, characterized in that, The process includes the following steps: cutting the composite fiber filter membrane and installing it on the sand core, then vacuum filtering the vegetable insulating oil with a vacuum degree of 0.02-0.05 MPa.

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