A method for manufacturing a sintered filter plate of a nitrided plastic

Abstract

The application relates to a manufacturing method of a sintered filter plate of nitrided plastic, and belongs to the technical field of high polymer materials. In the application, liquid ammonia is used for primary nitriding, nitrogen atoms are penetrated into a surface layer of ultra-high molecular weight polyethylene material through surface ion nitriding treatment, the nitrogen atoms are combined with carbon atoms in the material to form nitrides, and thus a hard nitride layer is formed on the material surface; after sintering and liquid nitrogen treatment, high-purity nitrogen gas is used for secondary nitriding, the nitriding layer can be more compact and uniform, pulse power is used for plasma nitriding treatment of the material, nitrogen ions are further penetrated into the material, the nitrogen ions are combined with the nitride layer formed in the primary nitriding, a deeper nitride layer is formed, and the performance and service life of the material are further improved; in the application, burr fine particle materials screened out in the nitriding process can be reused in production materials of the ultra-high molecular wear-resistant plate, and the application is green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and relates to a manufacturing method of a nitrided plastic sintered filter plate. BACKGROUND

[0002] Currently, plastic sintered filter plates and filter cartridges, as main filter elements for air pollution control, are playing a role of main force in the field of dust removal in the steel, smelting and automobile industries. In recent years, with the continuous promotion of new productivity and high-quality development, the development of high-purity extraction and separation technology of lithium battery and hydrogen energy storage materials in the new energy industry and laser smoke fine filtration and inert gas pushing in the additive industry all need high-quality and high-precision personalized filter materials, which puts forward new requirements for technical personnel in the plastic sintered filter material industry, and it is also a problem to be solved in the field of environmental protection materials to develop a nitrided plastic sintered filter plate with good wear resistance, high temperature resistance and corrosion resistance to meet the development needs of high-performance plastic sintered filter materials of new productivity.

[0003] Therefore, the scientific and technological personnel in the plastic sintered filter material industry are committed to developing a nitrided plastic sintered filter plate to solve the technical problems in high-purity extraction and laser smoke fine filtration operations, so that the nitrided plastic sintered filter plate can meet the needs of the industry in the development of new productivity and high-quality development.

[0004] The application provides a manufacturing method of a nitrided plastic sintered filter plate, which can play the roles of waterproofing, oil-proofing and corrosion-proofing on the surface of the plastic sintered filter material, so that the plastic sintered filter material can stably work in various acid-base and electric arc smoke gas environments, and the service life of the nitrided plastic sintered filter plate can be prolonged. SUMMARY

[0005] The application aims to provide a manufacturing method of a nitrided plastic sintered filter plate, which has the characteristic of long service life of the manufactured nitrided plastic sintered filter plate.

[0006] The application can be realized by the following technical scheme.

[0007] A manufacturing method of a nitrided plastic sintered filter plate, and the specific process of the manufacturing method of the nitrided plastic sintered filter plate is as follows,

[0008] S1: Put the ultra-high molecular weight polyethylene into a sealed reaction kettle, drive the stirring paddle to rotate forward, rotate while introducing liquid ammonia into the reaction kettle, introduce the direct current power source at the same time, and increase the voltage to 5MPa, perform surface ion nitriding treatment on the ultra-high molecular weight polyethylene as the cathode, continuously stir the reaction kettle by the stirring paddle, and control the temperature at 30 DEG C at the same time, to obtain material A, wherein the mass ratio of the added ultra-high molecular weight polyethylene and liquid ammonia is 50:1;

[0009] S2: The ammonia gas generated in the reaction is absorbed by the VOC purification system, and material A is sieved. Material A with a particle size of 100~150 mesh is selected for sintering and molding to obtain material B.

[0010] S3: Place material B in liquid nitrogen for freezing treatment at a temperature of -196℃ for 2-3 hours. After freezing, rapidly heat it to room temperature under a nitrogen atmosphere to obtain material C.

[0011] S4: Transfer material C to a sealed reactor and introduce ultra-high purity nitrogen gas at a flow rate of 5 L / min. After heating from room temperature to 180°C, use a pulse power supply to perform plasma nitriding treatment on material C. The pulse frequency is 2000 Hz, the voltage is 1000 V, the current is 100 A, and the pressure is increased to 1.5 MPa. The reaction time is 6 h. After the reaction is completed, allow it to cool naturally to room temperature and let it stand for 6 h to obtain the nitrided plastic sintered filter plate.

[0012] Furthermore, the ultra-high molecular weight polyethylene in S1 has a molecular weight of 5 million.

[0013] Furthermore, the particle size of the ultra-high molecular weight polyethylene in S1 is 100-150 mesh.

[0014] Furthermore, the DC power supply in S1 has a voltage of 600V.

[0015] Furthermore, the stirring rate in S1 is 200 r / min.

[0016] Furthermore, the sintering temperature in S2 is 225°C, and the sintering time is 3 hours.

[0017] Furthermore, the heating rate in S3 is 10℃ / min.

[0018] Furthermore, the concentration of ultra-high purity nitrogen in S4 is 99.9999%.

[0019] Furthermore, the heating rate in S4 is 3°C / min.

[0020] Furthermore, in step S4, the mixture is naturally cooled to room temperature in an ultra-high purity nitrogen atmosphere.

[0021] The common plastic-burned plate only focuses on the molecular weight of the ultra-high molecular polyethylene material (such as 3.5 million units, 4.5 million units and 6 million units) when selecting materials, ignores the particle size selection of the ultra-high molecular polyethylene, and also does not consider the roundness of the particle material (in fact, the particle surfaces of these materials are irregular), directly selects the purchased raw materials according to the mark, so that the particle size materials of different sizes are cross-collected together, the size of the gap between the particles is different, the effect of the smooth channel is affected, the efficiency of the opening rate is restricted, and the resistance loss is greatly increased during use.

[0022] In the application, the ultra-high molecular polyethylene is first nitrided by liquid ammonia, the surface ion nitriding treatment is used to improve the surface performance of the ultra-high molecular polyethylene, and the wear resistance is improved. The liquid ammonia nitriding can form a hard layer rich in nitrogen on the surface of the material, significantly improve the surface hardness of the material, and make it more wear-resistant. The liquid ammonia is introduced into the reaction kettle, and a direct current power supply with a voltage of 600V is introduced. The direct current power supply with this intensity can provide sufficient electric field strength to promote the migration of nitrogen ions to the surface of the polyethylene. At the same time, the pressure in the reaction kettle is increased to 5MPa, and the temperature is controlled at 30℃. Under this pressure and temperature, the liquid ammonia is in a gas-liquid coexistence state, which is more conducive to the formation of nitrogen ions. The plastic-burned plate is used as the cathode and placed in the reaction kettle. Under the action of the electric field, the nitrogen ions in the liquid ammonia will be attracted and move towards the cathode. When the nitrogen ions contact the surface of the ultra-high molecular polyethylene, a chemical reaction will occur. These reactions include the combination of nitrogen elements and carbon atoms on the surface of the polyethylene to form a nitride layer. This nitride layer has excellent hardness and wear resistance, which can significantly improve the surface performance of the material. During the entire reaction process, the temperature in the reaction kettle needs to be controlled at 30℃. This temperature range helps to promote the chemical reaction, while avoiding high temperature that leads to material decomposition or burning.

[0023] After the first nitriding is completed, the ultra-high molecular polyethylene is heated to a heat distortion temperature of 225℃ which is higher than the melting point (130-136℃), and the sintering is performed at the temperature of 225℃. The sintering can reduce the gap between the particles in the ultra-high molecular polyethylene material, change the disordered gap into an ordered gap, and thus improve the density of the material. This helps to improve the mechanical properties and wear resistance of the material; the sintering can form a nitride layer with high hardness on the surface of the ultra-high molecular polyethylene material, thereby improving the hardness and wear resistance of the material; the sintering can improve the surface finish and precision of the ultra-high molecular polyethylene material, and reduce the friction coefficient.

[0024] Liquid nitrogen treatment can rapidly reduce the temperature of material B to -196°C, which can cause changes in the molecular chain and crystal structure inside the material. During the freezing process, the movement of molecular chains slows down or even stops, which helps to form a more stable structure. After completing the freezing process, the material is quickly warmed to room temperature in a nitrogen atmosphere, and the molecular chains regain their activity. However, due to the previous freezing treatment, they will rearrange in a more orderly and stable manner, optimizing the material's microstructure. In addition, liquid nitrogen treatment can effectively eliminate residual stress generated during processing through rapid freezing and warming. Stress relief helps to improve the toughness and impact resistance of the material, providing a more stable and uniform basis for subsequent nitriding.

[0025] After liquid nitrogen treatment, the microstructure of material C is optimized, both on the surface and inside, which makes the subsequent nitrogen nitriding process easier. During the nitrogen nitriding process, nitrogen atoms need to penetrate into the material and combine with the atoms in the material to form a nitride layer. Liquid nitrogen treatment optimizes the microstructure of the material, providing more channels and opportunities for nitrogen atom penetration, and also improves the material's adsorption capacity for nitrogen, further promoting the progress of the nitriding process.

[0026] After completing the liquid nitrogen treatment, material C is transferred to a sealed reaction furnace to ensure the closedness of the reaction environment. Ultra-high purity nitrogen gas (concentration of 99.9999%) is introduced at a flow rate of 5L / min to provide sufficient nitrogen source and exclude other gases in the reaction furnace, ensuring the purity of the reaction environment.

[0027] The temperature is raised from room temperature to 180°C at a rate of 3°C / min. This step is to make material C reach the required temperature for nitriding reaction. During the heating process, ultra-high purity nitrogen gas is continuously introduced to ensure the stability of the reaction environment. When the temperature in the reaction furnace reaches 180°C, pulse power is used to perform plasma nitriding treatment on material C.

[0028] The pulse frequency is 2000Hz, the voltage is 1000V, and the current is 100A. These parameters work together on the surface of material C to produce high-energy plasma. Under the action of high-energy plasma, ultra-high purity nitrogen gas is decomposed into primary nitrogen atoms or ions, which further react with carbon and hydrogen elements on the surface of material C to form nitride layers. This reaction process is carried out at a pressure of 1.5MPa to ensure sufficient contact and reaction between nitrogen and the surface of material C. The reaction time is 6h to ensure the formation and stability of the nitride layer. After the reaction is completed, it is naturally cooled to room temperature in an ultra-high purity nitrogen atmosphere. This step is to avoid the nitride layer from cracking or falling off during the cooling process.

[0029] The application uses high-purity nitrogen gas with a concentration of 99.9999% to perform secondary nitriding on sintered and formed materials, which can further deepen the depth of the nitriding layer and improve the nitriding effect; the two nitriding processes can ensure the uniformity of the surface nitriding layer of the ultra-high molecular weight polyethylene material and avoid local insufficient or excessive nitriding; through the two nitriding processes, the hardness, wear resistance and corrosion resistance of the ultra-high molecular weight polyethylene material can be further improved.

[0030] Through ammonia gas fusion reaction on polyethylene raw material particles, active nitrogen atoms are formed by decomposition of ammonia gas, thereby forming nitriding modification of the polyethylene material, solving the problem of surface pitting of the material particles, increasing the bonding degree between the particles, maintaining the regularity of the micropore morphology and structure, reducing the resistance loss of the filter plate, and then through the active reaction of ultra-high purity nitrogen gas on the formed substrate, the surface hardness and wear resistance of the plastic sintering filter plate are innovatively increased, so that it can resist various surface damage and wear, and the surface adsorption capacity is also enhanced, so that the plastic sintering filter material surface can play a role in waterproof, oil-proof, corrosion-proof and the like, so that it can stably work in various acid-base, electric arc flue gas environments, and at the same time, the service life of the nitriding plastic sintering filter plate can be prolonged. In addition, the burr fine particle material screened out during the nitriding process can be reused as production material for the ultra-high molecular wear-resistant plate, so as to improve the temperature resistance and wear resistance of the wear-resistant plate, and make it green and environmentally friendly. On the other hand, due to the specification of the pore size, the standard of the micropore channel is unified, the constant low air resistance operation is met, the energy consumption is reduced, the dust removal efficiency is improved, and the energy saving requirement is met.

[0031] The beneficial effects of the application are as follows:

[0032] The application first uses liquid ammonia for primary nitriding, improves the surface performance of the ultra-high molecular weight polyethylene through surface ion nitriding treatment, the nitrogen atoms penetrate into the surface layer of the ultra-high molecular weight polyethylene material, combine with the carbon atoms in the material to form nitrides, thereby forming a hard nitride layer on the surface of the material; after sintering and forming and liquid nitrogen treatment, secondary nitriding is performed using high-purity nitrogen gas, which can make the nitriding layer more dense and uniform, and plasma nitriding treatment of the material using a pulse power source can make nitrogen ions further penetrate into the material and combine with the nitride layer formed by the primary nitriding to form a deeper nitride layer, thereby further improving the performance and service life of the material; in the application, the burr fine particle material screened out during the nitriding process can be reused as production material for the ultra-high molecular wear-resistant plate, which is green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to facilitate understanding of those skilled in the art, the application will be further described below with reference to the accompanying drawings.

[0034] Figure 1 Comparison diagram of nitriding plastic sintering filter plate material particle structure. DETAILED DESCRIPTION

[0035] In order to further clarify the technical means and effects adopted by the present application to achieve the predetermined inventive purpose, the specific embodiments, structures, features and effects thereof according to the present application are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0036] Example 1

[0037] S1: Put the ultrahigh molecular weight polyethylene with a molecular weight of 5 million into a sealed reaction kettle, the particle size of the ultrahigh molecular weight polyethylene is 100-150 mesh, drive the stirring paddle to rotate forward, the stirring rate is 200 r / min, while rotating, introduce liquid ammonia into the reaction kettle, while introducing the liquid ammonia, introduce a direct current power supply with a voltage of 600 V, and increase the voltage to 5 MPa, carry out surface ion nitriding treatment on the ultrahigh molecular weight polyethylene as the cathode, the stirring paddle continues to stir in the reaction kettle, while stirring, control the temperature at 30℃, obtain material A, wherein the mass ratio of the ultrahigh molecular weight polyethylene and the liquid ammonia added is 50:1;

[0038] S2: The ammonia gas generated in the reaction is absorbed by the VOC purification system, the material A is sieved, the material A with a particle size of 100-150 mesh is selected and sintered to form, the sintering temperature is 225℃, the sintering time is 3h, obtain material B;

[0039] S3: Put the material B into liquid nitrogen for freezing treatment, the temperature is-196℃, the freezing time is 2-3h, after freezing, rapidly warm up to room temperature under nitrogen atmosphere, the warming rate is 10℃ / min, obtain material C;

[0040] S4: Transfer the material C to a sealed reaction furnace, introduce ultrahigh-purity nitrogen gas with a flow rate of 5 L / min, the concentration of the ultrahigh-purity nitrogen gas is 99.9999%, after warming up from room temperature to 180℃, the warming rate is 3℃ / min, use a pulse power source to carry out plasma nitriding treatment on the material C, the pulse frequency is 2000Hz, the voltage is 1000V, the current is 100A, at the same time, increase the voltage to 1.5MPa, the reaction time is 6h, after the reaction is completed, naturally cool to room temperature in the ultrahigh-purity nitrogen gas atmosphere, stand for 6h, obtain the nitrided plastic sintered filter plate.

[0041] Comparative Example 1

[0042] S1: Put the ultra-high molecular weight polyethylene with a molecular weight of 5 million into a sealed reaction kettle, the particle size of the ultra-high molecular weight polyethylene is 100-150 mesh, drive the stirring paddle to rotate forward, the stirring rate is 200 r / min, while rotating, introduce liquid ammonia into the reaction kettle, while introducing the liquid ammonia, introduce a direct current power supply with a voltage of 600V, and increase the voltage to 5 MPa, carry out surface ion nitriding treatment on the ultra-high molecular weight polyethylene as the cathode, the stirring paddle continues to stir in the reaction kettle, while stirring, control the temperature at 30℃, obtain material A, wherein the mass ratio of the ultra-high molecular weight polyethylene and the liquid ammonia added is 50:1;

[0043] S2: The ammonia gas generated in the reaction is absorbed by the VOC purification system, the material A is sieved, the material A with a particle size of 100-150 mesh is selected and sintered to form a sintered filter plate.

[0044] Comparative Example 2

[0045] S1: The ultra-high molecular weight polyethylene with a molecular weight of 5 million and a particle size of 100-150 mesh is sintered to form a sintered filter plate, the sintering temperature is 225℃, and the sintering time is 3h, to obtain material B;

[0046] S2: Put the material B into liquid nitrogen for freezing treatment, the temperature is-196℃, the freezing time is 2-3h, after freezing, rapidly warm up to room temperature in a nitrogen atmosphere, the warming rate is 10℃ / min, to obtain material C;

[0047] S3: Transfer the material C to a sealed reaction furnace, introduce ultra-high purity nitrogen gas with a flow rate of 5 L / min, the concentration of the ultra-high purity nitrogen gas is 99.9999%, after warming up from room temperature to 180℃, the warming rate is 3℃ / min, use a pulse power source to carry out plasma nitriding treatment on the material C, the pulse frequency is 2000Hz, the voltage is 1000V, the current is 100A, at the same time, increase the voltage to 1.5MPa, the reaction time is 6h, after the reaction is completed, naturally cool to room temperature in an ultra-high purity nitrogen gas atmosphere, stand for 6h, to obtain the sintered filter plate of the nitrided plastic.

[0048] Comparative Example 3

[0049] The specific process of the method for manufacturing the sintered filter plate of the nitrided plastic is as follows,

[0050] S1: Put the ultrahigh molecular weight polyethylene with a molecular weight of 5 million into a sealed reaction kettle, the particle size of the ultrahigh molecular weight polyethylene is 100-150 mesh, drive the stirring paddle to rotate forward, the stirring rate is 200 r / min, while rotating, introduce liquid ammonia into the reaction kettle, while introducing the liquid ammonia, introduce a direct current power supply with a voltage of 600 V, and increase the voltage to 5 MPa, carry out surface ion nitriding treatment on the ultrahigh molecular weight polyethylene as the cathode, the stirring paddle continues to stir in the reaction kettle, while stirring, control the temperature at 30℃, obtain material A, wherein the mass ratio of the ultrahigh molecular weight polyethylene and the liquid ammonia added is 50:1;

[0051] S2: The ammonia gas generated in the reaction is absorbed by the VOC purification system, and the material A is sieved, and the material A with a particle size of 100-150 mesh is selected for sintering and forming, the sintering temperature is 225℃, and the sintering time is 3h, to obtain material B;

[0052] S3: Transfer the material B to a sealed reaction furnace, introduce super-high-purity nitrogen gas at a flow rate of 5 L / min, the concentration of the super-high-purity nitrogen gas is 99.9999%, after heating from room temperature to 180℃, the heating rate is 3℃ / min, use a pulse power supply to carry out plasma nitriding treatment on the material C, the pulse frequency is 2000Hz, the voltage is 1000V, the current is 100A, at the same time, increase the voltage to 1.5MPa, the reaction time is 6h, after the reaction is completed, naturally cool to room temperature in the super-high-purity nitrogen gas atmosphere, stand for 6h, to obtain the nitrided plastic sintered filter plate.

[0053] The wind resistance performance of the examples and comparative examples is detected according to the group standard T / XCLC0001-2018 “Plastic-burned filter plate for dust collector”, the sample size is 1500*564*80mm, a certain flow of wind is introduced from one side of the nitrided plastic sintered filter plate to the other side, the pressure on both sides is measured respectively, the pressure difference is calculated, the greater the pressure difference, the greater the resistance of the filter plate, the detection results are arranged in the following table,

[0054] From the experimental data, it can be seen that the example has the best ventilation performance, which shows that the plastic-burned filter plate after secondary nitriding can maintain the regularity of the micropore form and structure, thereby reducing the resistance loss of the filter plate.

[0055] The wear resistance of the examples and comparative examples 1-3 is detected, the sample size is 120*100*80mm, a JMIV type abrasion tester is used, a rotating friction rubber wheel method is used, after 100 grinding revolutions, the average value of mass loss (loss weight method) is used to measure the wear resistance of the application. The load is 10 N, the speed is 80 r / min, the test temperature is 25℃, the relative humidity is 50%, the mass is measured to 0.01 mg, the average value of 3 measurements is taken as the result, the detection results are arranged in the following table,

[0056] 100 mass loss amount / mg Example 1 35.88 Comparative Example 1 41.52 Comparative Example 2 43.65 Comparative Example 3 38.86

[0057] From the experimental data, it can be seen that the embodiment has the best wear resistance, which shows that the plastic burning filter plate treated by liquid nitrogen and then nitrided has better wear resistance and longer service life.

[0058] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application, without departing from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A method for manufacturing a nitrided plastic sintered filter plate, characterized in that, The specific process for manufacturing the nitrided plastic sintered filter plate is as follows. S1: Place ultra-high molecular weight polyethylene into a sealed reactor, drive the stirring paddle to rotate in the forward direction, and simultaneously introduce liquid ammonia into the reactor. At the same time as introducing liquid ammonia, introduce a DC power supply with the parameters of 600V voltage and boosted to 5MPa. Use ultra-high molecular weight polyethylene as the cathode to perform surface ion nitriding treatment. The stirring paddle continuously stirs in the reactor, and the temperature is controlled at 30℃ while stirring to obtain material A, wherein the mass ratio of ultra-high molecular weight polyethylene to liquid ammonia is 50:

1. S2: The ammonia gas generated in the reaction is absorbed by the VOC purification system, and material A is sieved. Material A with a particle size of 100~150 mesh is selected for sintering and molding to obtain material B. S3: Place material B in liquid nitrogen for freezing treatment at a temperature of -196℃ for 2-3 hours. After freezing, rapidly heat it to room temperature under a nitrogen atmosphere to obtain material C. S4: Transfer material C to a sealed reactor and introduce ultra-high purity nitrogen gas at a flow rate of 5 L / min. After heating from room temperature to 180°C, use a pulse power supply to perform plasma nitriding treatment on material C. The pulse frequency is 2000Hz, the voltage is 1000V, the current is 100A, and the pressure is increased to 1.5MPa. The reaction time is 6~8h. After the reaction is completed, allow it to cool naturally to room temperature and let it stand for 6h to obtain the nitrided plastic sintered filter plate.

2. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The ultra-high molecular weight polyethylene in S1 has a molecular weight of 5 million.

3. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The particle size of the ultra-high molecular weight polyethylene in S1 is 100-150 mesh.

4. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The stirring rate in S1 is 200 r / min.

5. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The sintering temperature in S2 is 225℃, and the sintering time is 3h.

6. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The heating rate in S3 is 10℃ / min.

7. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The concentration of ultra-high purity nitrogen in S4 is 99.9999%.

8. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, The heating rate in S4 is 3℃ / min.

9. The method for manufacturing a nitrided plastic sintered filter plate according to claim 1, characterized in that, In step S4, the mixture is naturally cooled to room temperature in an atmosphere of ultra-high purity nitrogen.

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