Filtering device as well as preparation method and application thereof

Abstract

The invention provides a filtering device as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, injecting an injection material into a mold to form a filter element blank; the injection material comprises a mixture of metal powder and an adhesive; the adhesive comprises modified polyolefin, paraffin and stearate; s2, the filter element blank is sequentially subjected to first degreasing treatment and second degreasing treatment, and a filter mold blank is obtained; and S3, the filtering mold blank is subjected to aftertreatment, and the filtering device is obtained. In the preparation process, the injection material has relatively good fluidity and stability, so that the problem of non-uniform thickness of a filter element blank in the injection process is solved, and the metal filter element with high precision and high performance is manufactured; the adhesive is effectively removed, and the filter element blank is prevented from deforming or cracking to influence the product quality of a final filter device; the porosity of the filter element can be accurately regulated and controlled, the pore size distribution is uniform, the filtering precision reaches the nanoscale, and small particle impurities can be effectively intercepted.

Description

Technical Field

[0001] The invention relates to a filtering device and a preparation method and application thereof. Background Art

[0002] Modern industrial production, such as semiconductor manufacturing, biopharmaceuticals, and aerospace, places extremely high demands on the filtration precision of liquids and gases. Currently, metal filter elements are manufactured using a variety of methods, including powder metallurgy, braiding, and winding. However, these traditional methods (powder metallurgy) have limitations when manufacturing complex metal filter elements, such as low production efficiency, poor product precision, and uneven porosity.

[0003] Metal Injection Molding (MIM) is a new near-net-shape forming technology that has the advantages of being able to manufacture parts with complex shapes, high production efficiency, and good product consistency. It has gradually been applied to the manufacture of metal filter elements. The existing metal filter element preparation process mainly includes the following steps: (1) preparing blank powder according to different product requirements; (2) loading the blank powder into the corresponding molding mold to form the desired shape. The process includes weighing the powder, loading the powder, pressing, holding the pressure, and demolding; (3) through high-temperature heating, atomic diffusion between the powder particles occurs, and the sintering temperature, time, and sintering atmosphere in the furnace chamber are adjusted to combine the contact surface of the powder particles in the blank to achieve the physical and mechanical properties required by the product; (4) by post-processing the sintered product, the stability of the product is improved; (5) welding the gasket to one end of the sintered filter element, and then welding the other end of the filter element to seal.

[0004] However, the existing metal injection process still has some problems when manufacturing metal filter elements, such as poor fluidity of the injection material and easy deformation of the blank during the degreasing process, which makes it difficult to stably produce high-precision metal filter elements that meet the needs of high-end fields.

[0005] Therefore, it is necessary to develop a new method for manufacturing metal filter elements using a metal injection process to solve the above problems. Summary of the Invention

[0006] In order to overcome the defects of the existing metal injection process such as poor fluidity of the injection material and easy deformation of the blank during the degreasing process, which cause the filter device to deform or crack during the preparation process, thereby reducing the yield rate of the product. The present invention provides a filter device and its preparation method and application. In the preparation process of the present invention, the injection material has good fluidity and stability, so as to overcome the problem of uneven thickness of the filter element blank during the injection process, and produce a high-precision, high-performance metal filter element. The change rate of the product blank gram weight can be effectively controlled within 2%, and its gram weight is stable; in addition, with the multi-stage degreasing process, the adhesive is effectively removed to avoid deformation or cracking of the filter element blank, which affects the product quality of the final filter device. The yield rate of the product obtained by this preparation method can reach more than 95%. The filter device prepared by the present invention can achieve precise control of the filter element porosity within the range of 15%-45%, uniform pore size distribution, and nanometer-level filtration accuracy, which can effectively intercept tiny particle impurities.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The present invention provides a method for preparing a filter device, which comprises the following steps:

[0009] S1. Injecting an injection material into a mold to form a filter element blank; the injection material comprises a mixture of metal powder and a binder; the mass ratio of the metal powder to the binder is (6-9):1; the binder comprises modified polyolefin, paraffin wax, and stearate;

[0010] S2. Performing a first degreasing treatment and a second degreasing treatment on the filter element blank in sequence to obtain a filter mold blank; the first degreasing treatment is performed in an organic solvent system; the second degreasing treatment is performed at a vacuum degree of less than 10 Pa, a temperature of 400-500° C., and a holding time of 2-3 hours;

[0011] S3, post-processing the filtering die to obtain a filtering device.

[0012] In the present invention, by optimizing the degreasing process and combining the first degreasing and the second degreasing, problems such as deformation and cracking of the filter element blank during the degreasing process can be solved, thereby ensuring the integrity of the filter element blank; specifically, in the above-mentioned degreasing process, since the adhesive has a certain lubricating effect, the metal powder undergoes plastic deformation under the action of the surface tension, and the powder particles move slowly under the action of the surface tension, which is similar to the creep of metal at high temperature, making the internal structure more isotropic, effectively improving the phenomenon of uneven pore distribution.

[0013] In some embodiments, in step S1, the metal powder includes stainless steel powder, nickel-based alloy powder, titanium alloy powder, or Hastelloy powder.

[0014] In a specific embodiment, the metal powder is stainless steel powder, such as 316L stainless steel powder, to ensure the corrosion resistance and mechanical strength of the prepared filter element.

[0015] In a preferred embodiment, the purity of the stainless steel powder is above 99%; and the average particle size of the stainless steel powder is 20-55 μm.

[0016] In one embodiment, the purity of the stainless steel powder is greater than 99.95%; and the average particle size of the stainless steel powder is 35 μm.

[0017] In some embodiments, in step S1, in the adhesive, the content of the modified polyolefin is 50%-60%, the content of the paraffin is 30%-40%, and the content of the stearate is 5%-10%, where % is the mass percentage of each component in the adhesive.

[0018] In some embodiments, in step S1, the modified polyolefin includes modified polyethylene or modified polypropylene.

[0019] In a specific embodiment, the modified polyethylene includes ethylene-vinyl acetate copolymer; the ethylene-vinyl acetate copolymer is obtained by copolymerizing ethylene and vinyl acetate.

[0020] In a specific embodiment, the modified polypropylene may include conventional modified polypropylene in the art, which may be polypropylene modified by EPDM rubber.

[0021] In some embodiments, in step S1, the melting point of the paraffin wax is 48-60°C.

[0022] In some embodiments, in step S1, the stearate includes zinc stearate.

[0023] In some embodiments, in step S1, the mass ratio of the metal powder to the binder is (7-8):1.

[0024] In some embodiments, in step S1, the injection material is injected into the mold by an injection molding machine.

[0025] In some embodiments, in step S1, the injection material is processed by a granulator.

[0026] In some embodiments, in step S1, the particle size of the injection material is 2-3 mm.

[0027] In some embodiments, in step S1, the preparation method of the injection material comprises the following steps: mixing the metal powder and the binder at 160-180° C. for 3-5 hours through a twin-screw extruder.

[0028] In the present invention, precision machining and heat treatment can be used to achieve a dimensional accuracy of the filter element blank of ±0.005 mm.

[0029] In some embodiments, in step S1, the conditions for injecting the injection material into the mold meet one or more of the following conditions:

[0030] i. The injection temperature during the injection process is 200-220°C;

[0031] ii. The injection pressure during the injection process is 100-150 MPa;

[0032] iii. The injection speed during the injection process is 40-60 mm / s;

[0033] iv. The mold adopts a hot runner system;

[0034] v. The temperature of the mold is controlled at 50-60°C;

[0035] vi. After the injection process is completed, the pressure is maintained at 80-120 MPa;

[0036] vii. After the injection process is completed, the pressure is maintained for 8-12 seconds.

[0037] Among them, by adopting the above conditions, molding defects can be effectively reduced and the dimensional accuracy and surface quality of the filter element blank can be guaranteed.

[0038] In one embodiment, the injection material is injected into the mold under the following conditions: the injection material is heated to 200°C; the injection temperature is set to 210°C; the injection pressure is 120 MPa; after the injection process is completed, a holding pressure of 100 MPa is applied for 10 seconds; the injection speed is 50 mm / s; the mold uses a hot runner system, and the mold temperature is controlled at 55°C. Furthermore, a multi-stage injection and holding pressure method can be used to ensure injection molding quality.

[0039] In some embodiments, in step S2, the first degreasing process includes: immersing the filter element blank in an organic solvent; under this condition, 70%-80% of the binder can be removed.

[0040] In a specific embodiment, the organic solvent includes chloroform and ethanol.

[0041] In one embodiment, the volume ratio of chloroform to ethanol in the organic solvent is 7:3.

[0042] In a specific embodiment, the soaking temperature is 60-70°C.

[0043] In a specific embodiment, the soaking time is 3-5h.

[0044] In some embodiments, in step S2, after the first debinding treatment and before the second debinding treatment, the filter core blank is buckled on the gasket to form a filter mold blank.

[0045] In a specific embodiment, one side of the gasket is provided with a boss portion, and the difference between the outer diameter of the boss portion and the inner diameter of the open end of the filter core blank is less than or equal to 0.5mm.

[0046] In an embodiment, the boss portion is cylindrical.

[0047] In a specific embodiment, the buckling method includes placing the open end of the filter core blank on the gasket and setting it around the periphery of the boss portion.

[0048] In an embodiment, the buckling process includes the following steps: placing the gasket on the ceramic jig of the graphite disc with the boss portion facing up, and then buckling the open end of the filter core blank onto the gasket with the boss portion inside the filter core blank.

[0049] In an embodiment, the inner wall surface of the filter core blank is in a stepped structure for matching the boss portion of the gasket; the inner diameter of one side of the open end of the filter core blank is 5.8mm, the inner diameter of the side away from the open end of the filter core blank is 5.5mm, and the outer diameter of the boss portion is 5.5mm.

[0050] In the present application, the gasket with a boss portion is used instead of the existing flat gasket, and the boss portion of the gasket is combined with the filter core blank. After high-temperature integrated sintering, the boss portion and the filter core blank are tightly combined together to form a special mortise and tenon structure, which eliminates the difficult-to-control welding process and improves the tensile strength of the filter device.

[0051] In step S2 of the present application, the second debinding treatment can be carried out under negative pressure in an inert atmosphere.

[0052] In some embodiments, in step S2, the second debinding treatment is carried out in a vacuum sintering and debinding integrated furnace.

[0053] In some embodiments, in step S2, the second debinding treatment is carried out in an inert atmosphere.

[0054] In a specific embodiment, the inert atmosphere includes a nitrogen atmosphere.

[0055] In some embodiments, in step S2, the heating rate of the second degreasing treatment is 1-4°C / min.

[0056] In a specific embodiment, the heating rate of the second degreasing treatment is 1-2°C / min.

[0057] In one embodiment, the process conditions of the second degreasing treatment are as follows: under a nitrogen protective atmosphere, slowly heating to 400-500°C at a heating rate of 1-2°C / min and keeping warm for 2-3 hours; under this condition, the adhesive can be removed and deformation or cracking of the filter element blank can be avoided.

[0058] In some embodiments, in step S3, the post-processing includes sintering, cleaning and polishing, and packaging for storage.

[0059] In the present invention, preferably, the welding step is omitted by sintering the filter mold into an integrated whole; compared with the existing welding process, it can not only improve efficiency and reduce costs, but also meet the requirements of high cleanliness and high flatness while meeting the filtration accuracy.

[0060] In a specific embodiment, the sintering temperature is 1300-1400°C.

[0061] In a specific embodiment, the holding time of the sintering treatment is 1.5-2.5 hours.

[0062] In a specific embodiment, the vacuum degree of the sintering process is 10 -3 -10 -4 Pa.

[0063] In a preferred embodiment, the sintering process is performed in a vacuum sintering and debinding integrated furnace.

[0064] In a preferred embodiment, before the sintering treatment, the filter mold base is subjected to a third degreasing treatment; the process of the third degreasing treatment includes the following steps: heating at a heating rate of 10°C / min for 20 minutes, then stopping heating for 5 minutes, repeating 3 times, raising the temperature to 800°C, and holding the temperature for 60 minutes.

[0065] The sintering treatment may be performed by pulse heating, that is, heating for a period of time and then stopping heating briefly to uniformly distribute the temperature in the furnace, promote atomic diffusion and metallurgical bonding between metal powder particles, and improve the density and strength of the filter element.

[0066] Among them, by controlling the vacuum degree of the system at 10 -3 -10 -4 Pa, prevents metal oxidation and ensures stable performance of the filter element.

[0067] In a preferred embodiment, the sintering process also includes vacuum firing, and the conditions for the vacuum firing include: controlling the vacuum firing temperature at 1050°C and maintaining it for 60 minutes; the vacuum firing stage can effectively remove other impurities or other oxides in the powder particles, so that the powder particles enter the high-temperature firing stage while maintaining good purity and precision. In addition, under the protection of inert gas, the displacement changes of the powder particles under high temperature tend to be synchronized, and the pore size and distribution also tend to be uniform, thereby producing qualified products.

[0068] In a preferred embodiment, the heating rate of the sintering process is 5°C / min, the temperature of the sintering process is 1350°C, the holding time of the sintering process is 2h, and the vacuum degree of the sintering process is 10 -3 Pa.

[0069] In a preferred embodiment, after the sintering treatment, a cooling treatment is performed; the conditions of the cooling treatment include: lowering the temperature in the system to 800° C. and maintaining the temperature for 30 minutes.

[0070] In a preferred embodiment, after the sintering treatment, forced cooling is performed; the conditions for the forced cooling include: introducing argon gas into the system to increase the pressure and cooling the system to below 60°C.

[0071] In a specific embodiment, the cleaning and polishing comprises a chemical polishing method.

[0072] In a specific embodiment, the polishing solution for cleaning and polishing includes phosphoric acid, sulfuric acid, nitric acid and a corrosion inhibitor.

[0073] In a specific embodiment, the cleaning and polishing temperature is 60-70°C.

[0074] In a specific embodiment, the cleaning and polishing time is 20-30 minutes.

[0075] The filter device is cleaned and polished to remove surface oxide layers and minor flaws, improving surface smoothness. High-precision testing equipment is then used to comprehensively test the porosity, pore size distribution, filtration accuracy, mechanical strength, and other properties of the filter element in the filter device to ensure that product quality meets high standards.

[0076] Among them, the packaging and warehousing generally include putting into sealed bags and vacuuming, affixing product labels, submitting to the warehousing process, and handing over the finished products to the warehouse.

[0077] The present invention also provides a filtering device, which is prepared by the above-mentioned preparation method of the filtering device.

[0078] The present invention also provides a use of the above-mentioned filtering device in filtering nano-sized particles.

[0079] In the present invention, the filtering device has ultra-high precision and can be used to filter particles of 3nm or 1nm.

[0080] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0081] The reagents and raw materials used in the present invention are commercially available.

[0082] This application includes at least one of the following beneficial technical effects:

[0083] 1. In the preparation process of the present invention, the injection material has good fluidity and stability, so as to overcome the problem of uneven thickness of the filter element blank during the injection process and produce a high-precision, high-performance metal filter element; the change rate of the product blank weight can be effectively controlled within 2%, and its weight is stable; in addition, with the multi-stage degreasing process, the adhesive is effectively removed to avoid deformation or cracking of the filter element blank, which affects the product quality of the final filter device.

[0084] 2. The yield of the product obtained by this preparation method can reach more than 95%.

[0085] 3. The filter device produced by the present invention can achieve precise control of the filter element porosity within the range of 15%-45%, with uniform pore size distribution and nanometer-level filtration accuracy, and can effectively intercept tiny particle impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a schematic diagram of the exploded structure of the gasket and filter element blank of Example 1 of the present application;

[0087] Figure 2 This is the handle force test curve of the filter device with 1 / 2 specifications in Effect Example 1;

[0088] Figure 3 This is the pull force test curve of the 1 / 4 specification filter device in Effect Example 1;

[0089] Figure 4 This is the flow and pressure difference effect diagram of the existing filter;

[0090] Figure 5 This is a flow rate and pressure difference effect diagram of the filtering device of Example 1 of the present application;

[0091] Description of reference numerals:

[0092] Gasket 1; boss portion 101; filter element body 2; open end 201. DETAILED DESCRIPTION

[0093] The application will be further illustrated by the following examples without limiting the application to the examples described. The experimental methods in the following examples, unless otherwise specified, are carried out according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0094] Example 1

[0095] The present example discloses a filter device and a preparation method thereof.

[0096] Preparation before the preparation method of the filter device:

[0097] 1. Structure design of the gasket: the SUS316L stainless steel plate material is processed into the size and shape designed in advance. The outer diameter of the gasket is 19.8 mm, the inner diameter is 5.5 mm, and the gasket upper part retains a hollow cylindrical boss part with a height of 2 mm ± 0.02 mm, an outer diameter of 5.5 mm ± 0.01 mm, and a wall thickness of 0.6 mm ± 0.01 mm. The boss part can be sintered with the filter core by riveting. Since the boss part of the gasket hardly shrinks at high temperature, while the filter core wall will shrink by 8%-12%, the different shrinkage rates of the two will cause a bonding reaction at a certain temperature, firmly bonding them together to achieve the required bonding strength and meet the product application requirements.

[0098] 2. Structure design of the filter core: the filter core structure is designed as one end closed and the other end open. The outer diameter of the filter core is 7.05 mm ± 0.02 mm, the inner diameter is 5.5 mm ± 0.01 mm, and the open end retains a bite step structure (groove) that can match the boss part of the gasket with an inner diameter of 5.85 mm ± 0.01 mm and a depth of 2 mm.

[0099] The preparation method of the filter device includes the following steps:

[0100] 1) Raw material preparation: 316L stainless steel powder with an average particle size of 35 μm and a purity of 99.95% is selected. The binder is a multi-component composite system composed of 55% modified polyethylene (EVA, which is obtained by copolymerization of ethylene and vinyl acetate), 35% low-melting-point paraffin, and 10% zinc stearate. The metal powder and the binder are mixed by a double-screw extruder at 160-180°C for 3-5 hours, and the mass ratio of the metal powder to the binder is 88:12, so that the metal powder is uniformly dispersed in the binder to form injection material with good flowability and stability. The mixed injection material is processed into injection material particles with a particle size of 2-3 mm by a granulator for standby use.

[0101] 2) Injection Molding: Place the injection material pellets prepared in step 1) into the barrel of the injection molding machine, heat the pellets to 200°C, and inject them into the mold. Set the injection temperature to 210°C, injection pressure to 120 MPa, holding pressure to 100 MPa, holding time to 10 seconds, and injection speed to 50 mm / s. The mold utilizes a hot runner system, and the mold temperature is controlled at 55°C. A multi-stage injection and holding pressure method is used to ensure injection molding quality. After injection molding, the filter element blanks undergo a preliminary visual inspection, and products with obvious defects are removed to obtain the filter element blanks.

[0102] 3) First degreasing treatment: (solvent degreasing and decoration)

[0103] 3.1) Solvent degreasing: The filter element blank after injection molding in step 2) is immersed in a 65° C. chloroform solution (composed of chloroform and ethanol in a volume ratio of 7:3) for 5 hours. At this time, the residual binder content in the filter element blank is about 12%.

[0104] 3.2) Ornaments: Figure 1 This is a schematic diagram of the exploded structure of the gasket and filter element blank of this embodiment. Specifically, the stainless steel gasket 1 prepared before implementation is placed on the ceramic jig of the graphite disk with the boss portion 101 facing upward. Then, the open end 201 of the filter element blank 2, which has been solvent-degreased in step 3.1), is buckled downward onto the gasket 1 and positioned around the boss portion 101. The boss portion 101 of the stainless steel gasket 1 is riveted together with the open end 201 of the filter element blank 2, thus obtaining a single, unsintered gasket filter blank. The ceramic jig is also a specialized ceramic jig designed based on the shape and structure of the injection molded blank.

[0105] 4) Second degreasing treatment: After the above-mentioned ornament steps, the filter element body and the gasket have been combined into a filter mold as a whole. Then the filter mold is placed on a special carrier and moved into a vacuum sintering and degreasing integrated furnace. The vacuum sintering and degreasing integrated furnace is evacuated to below 10Pa, and nitrogen is introduced. Under the protection of nitrogen atmosphere, the temperature is increased to 450℃ at a rate of 2℃ / min and kept warm for 150min. At this stage, catalytic degreasing can be completed to obtain a degreased part.

[0106] 5) High temperature sintering:

[0107] The specific steps include:

[0108] 5.1) Vacuum degreasing (third degreasing): After degreasing in step 4), continue to introduce nitrogen into the vacuum sintering and degreasing integrated furnace, heating at a heating rate of 10°C / min for 20 minutes, then stopping heating for 5 minutes. Repeat this three times, then raise the temperature to 800°C and hold for 60 minutes to complete the vacuum degreasing.

[0109] 5.2) Vacuum firing: After the above steps are completed, the furnace is evacuated and the temperature inside the furnace is maintained at 1050°C for 60 minutes to complete the vacuum firing.

[0110] 5.3) Partial pressure sintering: After vacuum sintering, argon gas was introduced and the temperature was raised to 1350°C at a heating rate of 5°C / min. The vacuum degree was controlled at 10 -3 Pa, keep warm for 2 hours, then reduce the furnace temperature to 800℃ and keep warm for 30 minutes.

[0111] 5.4) Forced cooling: After completing step 5.3), stop heating and continue to introduce argon to increase the pressure. Cool the furnace to below 60°C, open the furnace door and take out the product. The sintering process is now complete to obtain a sintered part.

[0112] 6) Cleaning and polishing: Polish and clean the sintered parts obtained in the above steps

[0113] 6.1. Use chemical polishing process and a specific polishing liquid (phosphoric acid, sulfuric acid, and nitric acid mixed in a volume ratio of 6:3:1). Place the sintered gasket filter in the chemical polishing liquid and treat it at 60-70℃ for 25 minutes to remove the surface oxide layer and minor defects and improve the surface finish of the product.

[0114] 6.2) Ultrasonic cleaning: After polishing, take out the polished product and place it in an ultrasonic cleaning tank. Add pure water to the cleaning tank and clean it for 20 minutes. Drain the water and then pour in clean water to clean it. Repeat this cleaning process 3 times.

[0115] 6.3) Drying: Place the cleaned product in an oven, heat to 80°C for 1.5 hours, and dry to obtain the final product.

[0116] 7) Packaging and storage: Take out the products after drying in the above steps, put each product in a plastic bag and vacuum seal it, and hand it over to the warehouse manager to complete storage.

[0117] The filter device prepared by the above preparation method has the following effects:

[0118] 1. Excellent filtration accuracy: By precisely controlling the metal powder particle size, injection material formula and sintering process, the filter element porosity can be precisely controlled within the range of 15%-45%, the pore size distribution is uniform, and the filtration accuracy reaches the nanometer level of 0.001 micron, which can effectively intercept tiny particle impurities and meet the strict requirements of high-end industry for high-precision filtration.

[0119] 2. Excellent product quality: The change rate of the product body weight can be effectively controlled within 2%, and its weight is stable; the product yield obtained by this preparation method can reach more than 95%.

[0120] 3. Excellent mechanical properties: The optimized sintering process and post-processing procedures give the filter element excellent mechanical properties. It can withstand a tensile strength of more than 20MPa. When subjected to high working pressure and fluid impact, it is not easy to deform or damage, ensuring the long-term stable operation of the filter element.

[0121] 4. Complex structure manufacturing capability: The metal injection process combined with innovative mold design can produce metal filter elements with complex internal structures and shapes, such as those with microporous arrays, three-dimensional flow channels, etc., which makes it possible to meet diverse filtration needs and expand the application range of metal filter elements.

[0122] 5. Efficient and low-cost production: While ensuring product quality, the present method improves production efficiency and reduces costs by optimizing process parameters and adopting a batch production approach. Compared with traditional manufacturing methods, material utilization is increased by 40%-50%, effectively more than doubling production efficiency, resulting in significant economic benefits and market competitiveness.

[0123] 6. The sintering temperature of traditional powder metallurgy is relatively low, usually below 1050-1280°C. By optimizing the molding and sintering process, the sintering temperature can be increased to above 1300°C, thereby enhancing the strength of the filter element.

[0124] Effect Example 1

[0125] This effect example examines the integrated sintering pull force effect of the filter device, potential defects such as empty welding, flow pressure difference effect, and filtering effect.

[0126] 1. Integrated sintered handle force effect:

[0127] The center of the gasket is designed with a cylindrical boss of specific dimensions, which can be riveted to the inner wall of the filter element blank after sintering. Because the gasket and filter element shrink differently during heating, the high-temperature sintering ensures a tight bond between them, achieving the required pull force required for product use.

[0128] The pull-out force and pull-out strength of filter devices with 1 / 2-inch and 1 / 4-inch gaskets were tested using industry norms and standard test methods. The measured results are shown in Table 1, which shows the pull-out force test of filter devices of different specifications.

[0129] Table 1

[0130]

[0131] Figure 2 and Figure 3 The pull force test curves of the filter device with 1 / 2 inch and 1 / 4 inch specifications are respectively; read the maximum pull-out force (N) that can be sustained from the curve and divide it by the force-bearing area (mm2 ) can obtain the tensile strength (MPa), and the filtering device of the present application can withstand a tensile strength of more than 20MPa.

[0132] 2. Test for potential defects such as empty welding:

[0133] Conventional testing methods in the art were used to test the filter obtained by welding using a traditional process and the integrated sintered filter device of Example 1.

[0134] Specifically, the weld is irradiated with X-rays or gamma rays, and internal defects (such as incomplete penetration, slag inclusions, and pores) are observed through film or digital imaging.

[0135] Traditional filters utilize welding, a process that can result in hollow welds. A hollow weld in argon arc welding occurs when an effective molten pool or weld seam is not formed. Hollow welds can occur for a variety of reasons and are unavoidable. However, the integrated sintered structure at the junction of the gasket and filter element reduces the welding process and eliminates defects such as hollow welds, cold welds, and discoloration.

[0136] 3. Flow pressure difference effect:

[0137] The nitrogen source gas was passed through the existing filter and the filter device of Example 1 at different flow rates and pressures to test the flow rate and pressure difference effects of the different filter devices.

[0138] Figure 4 This is a flow rate and pressure difference effect diagram of an existing product (MOTT, USA, model GSG-V4-3-S filter); Figure 5 This is a flow rate and pressure difference effect diagram of the filtering device of Example 1;

[0139] Depend on Figure 4-5 It can be clearly seen that under a pressure of 90psi, the pressure loss change rates of flow rates of 10slm and 20slm are compared respectively: the pressure loss of the GSG-V4-3-S filter changes from 12kPa to 50kPa, with a change rate of 416.667%; while the pressure loss of the filter device of Example 1 changes from 9kPa to 18kPa, with a change rate of 200%, which is significantly better than similar products on the market, and the pressure loss change rate is only half of that of similar products on the market.

[0140] And, by Figure 4-5 It can be seen that under the conditions of 90 psi pressure and 20 slm nitrogen source flow rate, the pressure loss of the GSG-V4-3-S filter is about 7.5 psid, while the pressure loss of the filter device of Example 1 is close to 3 psid, which is only 40% of similar products, meaning that the flow rate can be more than doubled (under the same flow rate, the smaller the pressure difference value, the better the product quality).

[0141] 4. Filtering effect:

[0142] The filtration effect of the filtration device of Example 1 was tested using a PSMPS test system; wherein the PSMPS test system is a 1 nm particle generation and measurement system of GRIMM Aerosol Technology Co., Ltd. of Germany.

[0143] The object of the filtration efficiency test is an aerosol source gas, wherein the particle size is in the range of 1-55 nm. The aerosol source gas is passed through the filter device of Example 1 at a flow rate of about 1 slm.

[0144] According to the particle distribution of aerosol, the gas filtration accuracy of the filter reaches >0.001μm (i.e. >1nm), and the filtration efficiency can reach 99.99999%, which fully meets the product design goals.

[0145] Since the product is a porous metal product, it is required to achieve a certain filtration accuracy and filtration efficiency. According to the results of this experimental verification, the expected effect has been fully achieved.

Claims

1. A method for preparing a filtration device, characterized in that: It includes the following steps: S1. Injecting an injection material into a mold to form a filter element blank; the injection material comprises a mixture of metal powder and a binder; the mass ratio of the metal powder to the binder is (6-9):1; the binder comprises modified polyolefin, paraffin wax, and stearate; S2. Performing a first degreasing treatment and a second degreasing treatment on the filter element blank in sequence to obtain a filter mold blank; the first degreasing treatment is performed in an organic solvent system; the second degreasing treatment is performed at a vacuum degree of less than 10 Pa, a temperature of 400-500° C., and a holding time of 2-3 hours; S3, post-processing the filtering die to obtain a filtering device.

2. The method for preparing the filter device according to claim 1, wherein: In step S1, the injection material meets one or more of the following conditions: ① The metal powder includes stainless steel powder, nickel-based alloy powder, titanium alloy powder or Hastelloy powder; ② In the adhesive, the content of the modified polyolefin is 50%-60%, the content of the paraffin is 30%-40%, and the content of the stearate is 5%-10%, where % is the mass percentage of each component in the adhesive; ③ The modified polyolefin includes modified polyethylene or modified polypropylene; ④ The melting point of the paraffin wax is 48-60°C; ⑤ The stearate includes zinc stearate; ⑥ The mass ratio of the metal powder to the adhesive is (7-8):

1.

3. The method for preparing the filter device according to claim 2, wherein: In step S1, the injection material meets one or more of the following conditions: ① The metal powder is stainless steel powder, the purity of the stainless steel powder is above 99%; the average particle size of the stainless steel powder is 20-55 μm; ② The modified polyethylene includes ethylene-vinyl acetate copolymer; ③ The modified polypropylene includes polypropylene modified by EPDM rubber.

4. The method for preparing the filter device according to claim 1, wherein: In step S1, the injection material meets one or more of the following conditions: ① The injection material is injected into the mold through an injection molding machine; ② The injection material is processed by a granulator; ③ The particle size of the injection material is 2-3 mm; ④ The preparation method of the injection material comprises the following steps: mixing the metal powder and the binder at 160-180° C. for 3-5 hours through a twin-screw extruder; ⑤ The conditions for injecting the injection material into the mold meet one or more of the following conditions: i. The injection temperature during the injection process is 200-220°C; ii. The injection pressure during the injection process is 100-150 MPa; iii. The injection speed during the injection process is 40-60 mm / s; iv. The mold adopts a hot runner system; v. The temperature of the mold is controlled at 50-60°C; vi. After the injection process is completed, the pressure is maintained at 80-120 MPa; vii. After the injection process is completed, the pressure is maintained for 8-12 seconds.

5. The method for preparing the filter device according to claim 1, wherein: Step S2 satisfies one or more of the following conditions: ① The first degreasing process includes: soaking the filter element blank in an organic solvent; ② After the first degreasing treatment and before the second degreasing treatment, the filter element blank is buckled onto the gasket to form a filter mold blank; ③ The second degreasing treatment is carried out in a vacuum sintering and degreasing integrated furnace; ④ The second degreasing treatment is carried out under an inert atmosphere; ⑤ The heating rate of the second degreasing treatment is 1-4°C / min.

6. The method for preparing the filter device according to claim 5, wherein: Step S2 satisfies one or more of the following conditions: ① The organic solvent includes chloroform and ethanol; ② The soaking temperature is 60-70°C; ③ The soaking time is 3-5h; ④ A boss portion is provided on one side of the gasket, and the difference between the outer diameter of the boss portion and the inner diameter of the open end of the filter element body is less than or equal to 0.5 mm; ⑤ The buckling method includes: placing the open end of the filter element body on the gasket and arranging it on the periphery of the boss portion; ⑥ The inert atmosphere includes a nitrogen atmosphere; ⑦ The heating rate of the second degreasing treatment is 1-2°C / min.

7. The method for preparing the filter device according to claim 1, wherein: In step S3, the post-processing includes sintering, cleaning and polishing, and packaging and warehousing, and meets one or more of the following conditions: ① The sintering temperature is 1300-1400°C; ② The holding time of the sintering treatment is 1.5-2.5h; ③ The vacuum degree of the sintering process is 10 -3 -10 -4 Pa; ④ The cleaning and polishing includes chemical polishing; 5. The polishing liquid for cleaning and polishing includes phosphoric acid, sulfuric acid, nitric acid and corrosion inhibitor; ⑥ The temperature of the cleaning and polishing is 60-70°C; ⑦ The cleaning and polishing time is 20-30 minutes.

8. The method for preparing the filter device according to claim 7, wherein: In step S3, the sintering process satisfies one or more of the following conditions: ① The sintering process is carried out in a vacuum sintering and degreasing integrated furnace; ② Before the sintering process, the filter mold base is subjected to a third degreasing process; the third degreasing process comprises the following steps: heating at a heating rate of 10°C / min for 20 minutes, then stopping heating for 5 minutes, repeating this process three times, then raising the temperature to 800°C and holding the temperature for 60 minutes; ③ The sintering treatment further includes vacuum firing, and the conditions of the vacuum firing include: controlling the vacuum firing temperature at 1050° C. and maintaining it for 60 minutes; ④ The heating rate of the sintering process is 5℃ / min, the temperature of the sintering process is 1350℃, the holding time of the sintering process is 2h, and the vacuum degree of the sintering process is 10 -3 Pa; ⑤ After the sintering treatment, a cooling treatment is performed; the cooling treatment conditions include: lowering the temperature in the system to 800° C. and holding the temperature for 30 minutes; ⑥ After the sintering treatment, forced cooling is performed; the conditions for the forced cooling include: introducing argon gas into the system to increase the pressure and cooling the system to below 60°C.

9. A filtering device, characterized in that: The filter is prepared by the preparation method of the filter device according to any one of claims 1 to 8.

10. Use of the filtering device according to claim 9 in filtering nano-sized particles.

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