CN211706161U

CN211706161U - Porous film

Info

Publication number: CN211706161U
Application number: CN201922144549.9U
Authority: CN
Inventors: 高麟; 罗长军; 李波; 任德忠
Original assignee: Intermet Technology Chengdu Co Ltd
Current assignee: Intermet Technology Chengdu Co Ltd
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2020-10-20
Anticipated expiration: 2029-12-04

Abstract

The utility model discloses a porous film. The porous membrane comprises N filtering units which are sequentially overlapped and connected into a whole, wherein N is more than or equal to 2; each filter unit comprises a porous support and a filter structure distributed on the outside of the material constituting the porous support. The porous film has a multi-layer structure, and thus has stronger strength than a conventional single-layer film material. Because the thickness of the porous film is increased, the deep filtration can be realized, and the filtration precision is greatly improved. Meanwhile, the pore diameter of the porous film can be controlled by controlling the sintering temperature, thereby ensuring higher gas flux.

Description

Porous film

Technical Field

The utility model relates to a filtering material's technical field particularly, relates to porous film.

Background

At present, a single-layer metal screen (plain weave) is mainly adopted as a porous support body of the flexible porous film, and the preparation process comprises the following steps: filling the pores of the porous support body, spraying a layer of film material on the outer surface of the porous support body in a mechanical spraying mode, and sintering to form the flexible porous film filter material.

The flexible porous film filter material prepared by the process is influenced by the strength of the matrix, and the strength is low.

SUMMERY OF THE UTILITY MODEL

A first object of the present invention is to provide a porous membrane having a strength significantly higher than that of the existing porous membrane but still having high filtering accuracy and high gas flux.

A second object of the present invention is to provide a method for preparing a porous membrane, so as to prepare a porous membrane with high strength, high filtration precision and high gas flux.

In order to achieve the first object, the present invention provides a porous film. The porous membrane comprises N filtering units which are sequentially overlapped and connected into a whole, wherein N is more than or equal to 2; each filter unit comprises a porous support and a filter structure distributed on the outside of the material constituting the porous support.

The porous film has a multi-layer structure, and thus has stronger strength than a conventional single-layer film material. Because the thickness of the porous film is increased, the deep filtration can be realized, and the filtration precision is greatly improved. Meanwhile, the pore diameter of the porous film can be controlled by controlling the sintering temperature, thereby ensuring higher gas flux.

Further, the filter structure comprises a filling filter layer and a side filter layer, wherein the filling filter layer is mainly filled in pores of the porous support body, and the side filter layer is attached to the windward side or the leeward side of the porous support body. From this, set up the side filter layer again after filling filter layer and porous supporter combine, can promote the apparent mass of filter unit, reduce defects such as hole, unevenness, fracture, increase of service life.

Further, the filling and filtering layer fills the pores of the porous support; and/or the thickness of the filling and filtering layer is larger than that of the porous support body. Therefore, the structure of the filtering unit is more stable, and the strength is higher.

Further, the pore diameter of the porous membrane changes in a gradient manner along the filtering direction. When the aperture is gradually increased along the filtering direction, the surface filtration can be carried out, which is beneficial to forming a filter cake and simultaneously reduces the filtering resistance; when the aperture is gradually reduced along the filtering direction, the back flushing regeneration is facilitated.

Further, the thickness of the porous support body is 0.4-0.45 mm, and the pore diameter is 50-80 meshes; the average pore diameter of the porous film is less than or equal to 23 mu m. By adopting the parameter setting, the porous film with high strength, high filtering precision and high gas flux is easy to obtain.

Further, when N is 2, the gas flux of the porous film is more than or equal to 500m³/m²Kpa · h, the warp-wise tensile strength of the porous film is more than or equal to 2kN, and the weft-wise tensile strength is more than or equal to 2.5 kN.

Further, the porous membrane also comprises a supporting net which is overlapped and connected with the leeward side of the filter unit on the leeward side or the windward side of the filter unit on the windward side into a whole. The pore size of the support net is preferably 80-120 meshes, if the pore size is less than 40 meshes, the support net and the filter unit are not firmly combined due to too small contact area, and if the pore size is more than 500 meshes, the gas flux is remarkably reduced.

In order to achieve the first object, the present invention provides a method for preparing a porous film. The preparation method of the porous film comprises the following steps:

1) preparing green bodies of N filtering units, wherein N is more than or equal to 2;

A. the porous support body carrying the first slurry penetrates between the two scrapers, and the precursor is obtained after drying;

B. spraying second slurry on the windward side or the leeward side of the first blank body, and drying to obtain a blank body of the filtering unit;

2) preparing a sintered blank: sequentially overlapping the green bodies of the N filtering units, and pressing the green bodies into a whole to obtain a sintered green body;

3) sintering the sintered blank to obtain a porous film;

the first slurry and the second slurry respectively comprise a dispersing agent, a bonding agent and raw material powder, and the raw material powder is converted into a filtering structure after being sintered.

The method comprises the steps of preparing a blank of the filtering unit separately, pressing the blank into a whole, and sintering the whole to obtain the porous film, so that materials forming the filtering structure can be distributed more uniformly, the binding force of adjacent filtering units in the obtained porous film is very strong, and the stripping phenomenon cannot be generated. Through pressing before sintering as an organic whole, can also promote raw materials powder bulk density in the porous supporter to promote the homogeneity that raw materials powder distributes, reduce porous film's aperture.

Further, the viscosity of the first slurry > the viscosity of the second slurry; the viscosity of the first slurry is preferably 12000-18000 mPa & s, at the moment, the first slurry is in a paste shape and is easy to be carried by a porous support body for movement, the pores of the porous support body can be fully filled under the extrusion action of a scraper, and the uniformity of the distribution of the first slurry cannot be reduced due to flowing; meanwhile, the viscosity of the second slurry is preferably 80-120 mPa · s, and at the moment, the second slurry has good fluidity, so that the good product quality can be ensured, the defects of holes, unevenness, cracking and the like can be reduced, and the service life can be prolonged.

Further, the first slurry employs a multi-component binder; the second slurry employs a one-component binder. When the same binder is used, the higher the viscosity of the slurry is, which means that the higher the binder is used, the less the raw material powder is used; when a multi-component adhesive is used, for example, a multi-component adhesive composed of an adhesive which is expensive but has a good bonding effect and an adhesive which is inexpensive but has a poor bonding effect is helpful for controlling the usage amount of raw material powder, controlling the cost and maintaining high filtration accuracy. The binder is preferably selected from the group consisting of CMC (sodium carboxymethylcellulose), SBR (styrene butadiene rubber) and PVA (polyvinyl alcohol), which do not adversely affect the properties of the porous film.

Furthermore, the thickness of the porous support body is 0.4-0.45 mm, and the distance between the two scrapers is 0.46-0.49 mm. Therefore, the first slurry layer can be attached to the outer surface of the porous support body, so that the spraying quality of the second slurry can be controlled more easily when the surface of the first slurry is sprayed, and a porous film without holes and with a smooth surface can be obtained more easily.

Further, the pressing in the step 2) is rolling, and the rolling pressure is 0.3-0.5 MPa. Thereby, the green bodies of adjacent filter units are firmly bonded without damage. The rolling is a processing method in which a billet is passed through a gap (various shapes) between a pair of rolls so that the billet is compressed by the rolls to reduce the thickness of the billet.

The present invention will be further described with reference to the accompanying drawings and the detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The accompanying drawings, which form a part of the disclosure, are included to assist in understanding the disclosure, and the description provided herein and the accompanying drawings, which are related thereto, are intended to explain the disclosure, but do not constitute an undue limitation on the disclosure.

In the drawings:

fig. 1 is a schematic structural view of the porous film according to embodiments 1 to 6 of the present invention.

Fig. 2 is a schematic structural diagram of a porous film according to embodiment 7 of the present invention.

The relevant references in the above figures are:

100-filtration unit, 200-support mesh, 10-porous support, 20-filtration structure, 201-fill filtration layer, 202-side filtration layer.

Detailed Description

The present invention will be described more fully with reference to the accompanying drawings. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. Before the present invention is described with reference to the accompanying drawings, it is to be noted that:

the technical solutions and features provided in the present invention in each part including the following description may be combined with each other without conflict.

Moreover, references to embodiments of the invention in the following description are generally only to be considered as examples of the invention, and not as all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the protection scope of the present invention.

With respect to the terms and units of the present invention. The terms "comprising," "having," and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions.

The filter structure 20 of the porous membrane is made of solid solution alloy, a metal simple substance with a face-centered cubic structure or a metal porous material with a body-centered cubic structure as a matrix phase. The solid solution may be, but is not limited to, Ni-Cu solid solution, Ag-Au solid solution, Ti-Zr solid solution, Mg-Cd solid solution, Fe-Cr solid solution, Cu-Al solid solution, Cu-Zn solid solution or Fe-C-Cr solid solution; the metal simple substance of the face-centered cubic structure may be, but is not limited to, Al, Ni, Cu, or Pb; the simple metal of the body-centered cubic structure may be, but is not limited to, Cr, W, V, or Mo. The composition of the filter structure 20 and the corresponding raw powder can refer to the flexible porous metal foil and the preparation method thereof disclosed in chinese patent CN 104588651A.

The porous membrane having high strength, high filtration accuracy and high gas flux can be obtained by the following parameters and methods. The preparation method of the porous film taking Ni-Cu solid solution as an example comprises the following steps:

1) preparing N green bodies of the filter units 100, wherein N is more than or equal to 2;

A. taking Ni powder and Cu powder as raw material powder, taking CMC and SBR as binders and water as a dispersing agent to prepare first slurry with the viscosity of 12000-18000 mPa & s; a plain screen with the thickness of 0.4-0.45 mm and the aperture of 50-80 meshes is used as a porous support body 10; then, enabling the porous support body 10 carrying the first slurry to pass through between two scrapers with a gap of 0.46-0.49 mm at a speed of 3-5 m/min, and drying to obtain a precursor;

B. taking Ni powder and Cu powder as raw material powder, taking PVA as a binder and water as a dispersing agent, preparing second slurry with the viscosity of 80-120 mPa & s, spraying the second slurry to the windward side or the leeward side of a precursor with the moving speed of 2.5-3.5 m/min by a spray gun with the flow rate of 190-210 g/10s, and drying to obtain a blank of the filtering unit 100;

2) preparing a sintered blank: sequentially overlapping the green bodies of the N filtering units 100, and pressing the N filtering units 100 into a whole under the pressing force of 0.3-0.5 MPa to obtain a sintered green body;

3) sintering the sintering blank: in the first stage, the temperature is increased to 120-250 ℃ from room temperature and is kept for 60-90 min, in the second stage, the temperature is continuously increased to 450-600 ℃ and is kept for 60-120 min, in the third stage, the temperature is continuously increased to 900-1150 ℃ and is kept for 90-180 min, and then the porous film is obtained; the heating rate of the whole sintering stage is less than or equal to 5 ℃/min.

To verify the advantageous effects of the present invention, the following examples 1 to 7 were carried out.

Example 1

The preparation process of the porous membrane in this example is as follows:

1) preparing two green bodies of filter unit 100, i.e., N-2;

A. taking Ni powder and Cu powder as raw material powder, wherein the mass of the Cu powder is 30% of that of the raw material powder, and the particle sizes of the Ni powder and the Cu powder are-400 meshes; CMC and SBR are used as binding agents, and the mass ratio of the CMC to the SBR is 0.6: 2; water is used as a dispersant, so that a first slurry with the viscosity of 15000 +/-10 mPa & s can be prepared; in order to disperse the adhesive more uniformly, the adhesive is prepared into colloidal liquid with solid content of 2% in advance and used; a plain screen with the thickness of 0.41mm and the aperture of 50 meshes is taken as a porous support body 10; then, the porous support body 10 carrying the first slurry passes through the space between two scrapers with the gap of 0.47mm at the speed of 4m/min, and is dried to obtain a precursor;

B. taking Ni powder and Cu powder as raw material powder, wherein the mass of the Cu powder is 30% of that of the raw material powder, and the particle sizes of the Ni powder and the Cu powder are-400 meshes; preparing a second slurry with the viscosity of 100 +/-5 mPa & s by using PVA as a binder and water as a dispersing agent; in order to disperse the adhesive more uniformly, the adhesive is prepared into a colloidal liquid with a solid content of 3% in advance and is used; then spraying the second slurry to the windward side of the precursor with the moving speed of 3m/min by a spray gun with the flow rate of 200g/10s, and drying to obtain a green body of the filtering unit 100;

2) preparing a sintered blank: sequentially overlapping the green bodies of the two filter units 100, enabling the side filter layer 202 obtained by sintering the second slurry in each filter unit 100 to be positioned on the windward side during overlapping, and then pressing the two filter units 100 into a whole under the pressing force of 0.3MPa to obtain a sintered green body;

3) sintering the sintering blank: in the first stage, the temperature is increased from room temperature to 180 ℃ and is kept for 80min, in the second stage, the temperature is continuously increased to 550 ℃ and is kept for 100min, in the third stage, the temperature is continuously increased to 1150 ℃ and is kept for 150min, and then the porous film is obtained; the heating rate of the whole sintering stage is less than or equal to 5 ℃/min.

Example 1 was repeated 5 times to obtain 5 porous films, a1#, a2#, A3#, a4# and a5 #.

The structure of the resulting porous membrane is shown in FIG. 1. As can be seen from fig. 1, the porous membrane comprises two filter units 100 overlapped and connected into a whole, each filter unit 100 comprising a porous support 10 and a filter structure 20, said filter structure 20 being distributed on the outer side of the material constituting the porous support 10. The filter structure 20 comprises a filling filter layer 201 and a side filter layer 202, wherein the filling filter layer 201 is formed by converting first slurry and mainly filled in pores of the porous support 10, the side filter layer 202 is attached to the windward side of the porous support 10, and the side filter layer 202 is formed by converting second slurry. The filling and filtering layer 201 fills up the pores of the porous support 10, and the thickness of the filling and filtering layer 201 is greater than that of the porous support 10.

Example 2

The sintered compact of this example consists of a green body of one filter unit 100, i.e., the green body of one filter unit 100 prepared in step 1) of example 1 is directly subjected to the sintering of step 3), and the obtained porous membrane is numbered B #.

Using standard ISO 4003: the bubble test in 1977 measures the pore diameters of the porous membranes of examples 1-2, the strength of the porous membranes of examples 1-2 was measured by the method in GB/T228-2002, and the gas flux of the porous membranes of examples 1-2 was measured by the method in GB/T14295-2008. The test results are shown in Table 1.

TABLE 1

As can be seen from Table 1, the porous membranes of example 1 had a reduced flux of gas as compared to that of example 2, but they were still > 500m³/m²Kpa · h. The average pore diameter of the porous membrane of example 1 was reduced from that of example 2, indicating that the filtration accuracy was improved. The strength of example 1 was greatly improved as compared with example 2. Therefore, the porous film provided by the invention has the advantages of high strength, high filtering precision and high gas flux. The porous films with the numbers of A1#, A2#, A3#, A4# and A5# have very close pore diameter, gas flux and strength, which shows that the preparation method of the porous film has high repeatability and can be produced in batch.

Example 3

This example differs from example 1 in that: the granularity of Ni powder and Cu powder adopted for preparing the filtering unit 100 close to the windward side is-400 meshes, and the granularity of Ni powder and Cu powder adopted for preparing the filtering unit 100 far away from the windward side is 200-300 meshes; the pore size of the filter unit 100 near the windward side in the porous membrane thus obtained is smaller than that of the filter unit 100 far from the windward side, i.e., the pore size gradually increases in the filtration direction. The porous membrane can not only obtain higher filtering precision (small pore size can also accelerate the formation of filter cakes) by the filtering unit 100 close to the windward side, but also ensure higher air flux by the filtering unit 100 far away from the windward side.

Example 4

This example differs from example 1 in that: the granularity of Ni powder and Cu powder adopted for preparing the filtering unit 100 close to the windward side is 200-300 meshes, and the granularity of Ni powder and Cu powder adopted for preparing the filtering unit 100 far away from the windward side is-400 meshes; the pore diameter of the porous membrane is gradually reduced along the filtering direction, so that the back flushing regeneration is favorably carried out when the porous membrane is seriously blocked.

Example 5

This example differs from example 1 in that: in the preparation of each filtering unit 100, the granularity of the Ni powder and the Cu powder adopted in the step A is 200-300 meshes, and the granularity of the Ni powder and the Cu powder adopted in the step B is-400 meshes; thus, in each filter unit 100, the pore size of the side filtration layer 202 is smaller than that of the filling filtration layer 201.

Example 6

This example differs from example 1 in that: in the preparation of each filtering unit 100, the granularity of the Ni powder and the Cu powder adopted in the step A is-400 meshes, and the granularity of the Ni powder and the Cu powder adopted in the step B is 200-300 meshes; thus, in each filter unit 100, the pore size of the side filtration layer 202 is larger than that of the filling filtration layer 201.

Example 7

This example differs from example 1 in step 2). The step 2) of this embodiment is specifically as follows:

2) preparing a sintered blank: sequentially overlapping the supporting net 200 with the aperture of 200 meshes and the green bodies of the two filtering units 100, enabling the supporting net 200 to be positioned on the leeward side during overlapping, and then pressing the supporting net 200 and the two filtering units 100 into a whole under the pressing force of 0.3MPa to obtain a sintered blank; as shown in fig. 2, the resulting porous membrane further comprises a support mesh 200 overlapping and integrally connected to the leeward side of the leeward side filter unit 100. It is verified that the support net 200 does not have a great influence on the pore size and the air flux of the porous membrane after being arranged, but the pore size of the porous membrane is significantly improved.

The contents of the present invention have been explained above. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. Based on the above-mentioned contents of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A porous membrane characterized by: comprises N filtering units (100) which are sequentially overlapped and connected into a whole, wherein N is more than or equal to 2; each filter unit (100) comprises a porous support (10) and a filter structure (20), said filter structure (20) being distributed on the outside of the material constituting the porous support (10).

2. The porous membrane of claim 1, wherein: the filter structure (20) comprises a filling and filtering layer (201) and a side filtering layer (202), wherein the filling and filtering layer (201) is mainly filled in pores of the porous support body (10), and the side filtering layer (202) is attached to the windward side or the leeward side of the porous support body (10).

3. The porous membrane of claim 2, wherein: the filling and filtering layer (201) is filled in the pores of the porous support body (10); and/or the thickness of the filling and filtering layer (201) is greater than the thickness of the porous support (10).

4. The porous membrane of claim 1, wherein: the pore diameter of the porous membrane is changed in a gradient manner along the filtering direction.

5. The porous membrane of claim 1, wherein: the thickness of the porous support body (10) is 0.4-0.45 mm, and the aperture is 50-80 meshes; the average pore diameter of the porous film is less than or equal to 23 mu m.

6. The porous membrane of claim 5, wherein: when N is 2, the gas flux of the porous film is more than or equal to 500m³/m²Kpa h, the warp-wise tensile strength of the porous film is more than or equal to 2kNAnd the weft tensile strength is more than or equal to 2.5 kN.

7. The porous membrane of claim 1, wherein: the porous membrane also comprises a supporting net (200) which is overlapped and connected with the leeward side of the filter unit (100) on the leeward side or the windward side of the filter unit (100) on the windward side into a whole.