Filter cloth for belt type alkali filtering machine

Abstract

The invention discloses filter cloth for a belt type alkali filtering machine, and relates to the technical field of filter cloth of filters, the filter cloth comprises a surface layer, a filtering layer and a supporting layer which are tightly compounded in sequence from top to bottom, and the surface layer, the filtering layer and the supporting layer form an integrated structure through a combined process of hot-pressing pre-compounding and three-dimensional needling reinforcement. Wherein the contact surfaces of the three layers form initial bonding through hot-pressing pre-compounding, and the three-dimensional needling reinforcement realizes mechanical locking and avoids interlayer stripping by mutually interweaving fibers in the three layers to form a fiber bundle penetrating through the three layers; the surface layer is a fluorine-modified polytetrafluoroethylene short fiber disordered needling forming layer and is formed by disordered needling of fluorine-modified PTFE short fibers with the length of 38-51mm and the diameter of 12-20mu m. Through the combined process of hot-pressing pre-compounding and three-dimensional needling reinforcement, double fixation of mechanical locking and initial bonding of the three-layer structure is achieved, the interlayer peeling strength is remarkably improved, peeling is avoided under high pressure, the deformation amount is small, and the service life is greatly prolonged.

Description

Technical Field

[0001] This invention belongs to the field of filter cloth technology, and more specifically, relates to a filter cloth for belt filter presses. Background Technology

[0002] A belt filter, also known as a belt press filter, is a filtration device that uses two endless filter cloths wound around a series of sequentially arranged rollers of different sizes to remove moisture from the slurry by squeezing and shearing between the filter cloths.

[0003] Existing belt filter filter cloths generally suffer from three major pain points: 1. Insufficient reliability of interlayer bonding: Traditional composite filter cloths mostly use single bonding or needle punching processes, which are prone to interlayer peeling under high pressure filtration and repeated stretching conditions, affecting service life. 2. The problem of filter cake adsorption is prominent. The surface energy of conventional filter cloth surface material is high, and the filter cake is easy to stick together, resulting in difficulty in cleaning and shortening of the filtration cycle; 3. It is difficult to balance filtration efficiency and structural strength. Either a dense structure is used to pursue filtration accuracy, resulting in too low flow rate, or filtration effect is sacrificed to ensure strength, making it unsuitable for the stringent filtration requirements of medium and high pressure and high flow.

[0004] No effective solutions have yet been proposed to address the problems in the relevant technologies.

[0005] Therefore, in order to solve the above problems, the present invention provides a filter cloth for a belt filter press. Summary of the Invention

[0006] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a filter cloth for a belt filter press.

[0007] The objective of this invention can be achieved through the following technical solutions: A filter cloth for a belt filter press includes a surface layer, a filter layer, and a support layer that are tightly bonded together from top to bottom. The surface layer, filter layer, and support layer are integrated into a single structure through a combination of hot-pressing pre-composite and three-dimensional needle-punching reinforcement processes. The hot-pressing pre-composite process creates an initial bond at the contact surfaces of the three layers, while the three-dimensional needle-punching reinforcement process creates interwoven fiber bundles through the three layers, achieving mechanical locking and preventing interlayer peeling. The surface layer is a fluorine-modified polytetrafluoroethylene short fiber random needle-punched layer, which is formed by random needle punching of fluorine-modified PTFE short fibers with a length of 38-51mm and a diameter of 12-20μm. The overall porosity of the surface layer is 65-75%, and the side of the surface layer away from the filter layer is molded to form a regularly arranged textured surface. The filter layer is a three-dimensional needle-punched layer composed of basalt short-cut fibers and polyester hollow cross-section short fibers. The basalt short-cut fibers are cut from continuous filaments. The two are mixed in a ratio of 30-50wt%:50-70wt% and then cross-laid and three-dimensionally needle-punched. The filter layer has a thickness of 1.2-2.5mm and forms a pore structure with a continuously gradually changing pore size from the side near the surface to the side near the support layer. The support layer is a high-strength polyester filament woven plain weave layer, which is made of polyester filaments with a breaking strength ≥5.5cN / dtex and a linear density of 100-200D interwoven with warp and weft. The warp density is 35-50 threads / cm and the weft density is 30-45 threads / cm. The thickness of the support layer is 0.8-1.5mm, and the tensile strength in both the warp and weft directions is ≥200N / cm. Through the synergistic effect of the low surface energy characteristics and texture design of the surface layer, the gradient pore filtration function of the filter layer, and the high-strength structural support of the support layer, this filter cloth can simultaneously achieve low adsorption of filter cake, efficient solid-liquid separation, and structural stability under high pressure during belt filtration.

[0008] As a preferred embodiment of the present invention, the outer surface of the surface layer is coated with a nano-silica coating, the thickness of which is 0.5-2μm, and the coating is formed by sol-gel method.

[0009] As a preferred embodiment of the present invention, the diameter of the mixed fibers in the filter layer is 8-15 μm.

[0010] As a preferred embodiment of the present invention, in the textured surface of the outer layer, the height of the protrusion is 0.3-0.8mm, the spacing between adjacent protrusions is 1-3mm, and the cross-section of the protrusion is semi-circular.

[0011] As a preferred technical solution of the present invention, the process parameters of the hot-pressing pre-composite are: hot-pressing temperature 120-160℃, hot-pressing pressure 0.3-0.8MPa, and hot-pressing time 10-30s; the needle density of the needle reinforcement is 200-300 needles / cm², and the needle depth is 5-8mm.

[0012] As a preferred embodiment of the present invention, the filter cloth is provided with a reinforcing structure on both sides of the edge. The reinforcing structure is a high-strength nylon filament covering layer. The nylon filament covering layer is fixed by overlock sewing with a stitch spacing of 0.5-1mm. The breaking strength of the nylon filament is ≥8cN / dtex.

[0013] As a preferred embodiment of the present invention, in the gradient pore size inside the filter layer, the pore size near the surface layer is 1-3 μm, and the pore size near the support layer is 5-10 μm.

[0014] As a preferred embodiment of the present invention, the fluorine-modified PTFE short fiber has a fluorine content ≥65wt%, a breaking strength ≥3.5cN / dtex, and a temperature resistance range of -200℃ to 260℃.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. High interlayer bonding strength and excellent structural stability: Through a combination of hot-pressing pre-composite and three-dimensional needle-punching reinforcement processes, the three-layer structure achieves dual fixation of mechanical locking and initial bonding, significantly improving interlayer peel strength, with no peeling under high pressure, small deformation, and greatly extended service life.

[0016] 2. Good filter cake peeling performance and reduced maintenance costs: The surface layer is made of fluorine-modified PTFE material with a molded textured design. The low surface energy characteristics combined with the physical texture reduce the contact area of ​​the filter cake, and the filter cake peeling rate is ≥92%, which reduces the cleaning frequency and energy consumption and reduces filter cloth wear.

[0017] 3. High filtration efficiency and excellent solid-liquid separation effect: The filter layer adopts a gradient pore structure of basalt fiber and polyester hollow fiber. The pore size changes continuously from the surface layer to the support layer, which not only ensures filtration accuracy, but also reduces clogging and increases the permeation rate, making it suitable for high flow rate filtration requirements.

[0018] 4. Balanced overall performance and wide applicability: The synergistic effect of low adsorption on the surface layer, high-efficiency separation in the filtration layer, and high strength in the support layer enables the filter cloth to meet different working conditions from low pressure to ultra-high pressure, covering diverse needs from ordinary filtration to extreme environments, and has strong applicability.

[0019] 5. Good compatibility between materials and processes, and high production feasibility: The selected fluorine-modified PTFE, basalt fiber, polyester filament and other materials have matching physical and chemical properties, the hot pressing and needle punching process parameters are controllable, the parameter range defined in the claims is scientific and feasible, and it is easy to carry out industrial mass production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] 1. Surface layer; 2. Filter layer; 3. Support layer. Detailed Implementation

[0023] The invention will now be further described with reference to the accompanying drawings and specific embodiments: According to an embodiment of the present invention, a filter cloth for a belt filter alkali machine includes a surface layer 1, a filter layer 2 and a support layer 3 tightly bonded together from top to bottom. The surface layer 1, the filter layer 2 and the support layer 3 are formed into an integrated structure by a combination of hot-pressing pre-composite and three-dimensional needle punching reinforcement. The hot-pressing pre-composite creates an initial bond at the contact surfaces of the three layers, and the three-dimensional needle punching reinforcement achieves mechanical locking by interweaving the fibers in the three layers to form fiber bundles that penetrate the three layers, thus preventing interlayer peeling. Surface layer 1 is a fluorine-modified polytetrafluoroethylene short fiber random needle-punched layer, which is formed by random needle punching of fluorine-modified PTFE short fibers with a length of 38-51mm and a diameter of 12-20μm. The overall porosity of surface layer 1 is 65-75%, and the surface of surface layer 1 away from filter layer 2 is molded to form a regularly arranged textured surface. The filter layer 2 is a three-dimensional needle-punched layer composed of basalt short-cut fibers and polyester hollow cross-section short fibers. The basalt short-cut fibers are cut from continuous filaments. The two are mixed in a ratio of 30-50wt%:50-70wt% and then cross-laid and three-dimensionally needle-punched. The filter layer 2 has a thickness of 1.2-2.5mm and forms a pore structure with a continuously gradually changing pore size from the side near the surface to the side near the support layer. The support layer 3 is a high-strength polyester filament woven plain weave layer, which is made of polyester filaments with a breaking strength ≥5.5cN / dtex and a linear density of 100-200D interwoven with warp and weft. The warp density is 35-50 threads / cm and the weft density is 30-45 threads / cm. The thickness of the support layer 3 is 0.8-1.5mm, and the tensile strength in both the warp and weft directions is ≥200N / cm. Through the synergistic effect of the low surface energy characteristics and texture design of the surface layer 1, the gradient pore filtration function of the filter layer 2, and the high-strength structural support of the support layer 3, the filter cloth can simultaneously achieve low adsorption of filter cake, efficient solid-liquid separation, and structural stability under high pressure during the belt filtration process.

[0024] Specifically, the outer surface of surface layer 1 is coated with a nano-silica coating with a thickness of 0.5-2μm, and is formed by sol-gel method.

[0025] Specifically, the diameter of the mixed fibers in filter layer 2 is 8-15 μm.

[0026] Specifically, in the textured surface of the outer layer 1, the height of the protrusions is 0.3-0.8mm, the spacing between adjacent protrusions is 1-3mm, and the cross-section of the protrusions is semi-circular.

[0027] Specifically, the process parameters for hot-pressing pre-composite are: hot-pressing temperature 120-160℃, hot-pressing pressure 0.3-0.8MPa, and hot-pressing time 10-30s; the needle density for needle-punching reinforcement is 200-300 needles / cm², and the needle depth is 5-8mm.

[0028] Specifically, the filter cloth has a reinforcing structure on both sides of the edge. The reinforcing structure is a high-strength nylon filament covering layer. The nylon filament covering layer is fixed by overlock stitching with a stitch spacing of 0.5-1mm. The tensile strength of the nylon filament is ≥8cN / dtex.

[0029] Specifically, in the gradient pore size inside the filter layer 2, the pore size near the surface is 1-3 μm, and the pore size near the support layer is 5-10 μm.

[0030] Specifically, the fluorine-modified PTFE short fiber has a fluorine content of ≥65wt%, a tensile strength of ≥3.5cN / dtex, and a temperature resistance range of -200℃ to 260℃. Example 1

[0031] Table 1: Material and Process Parameters for Example 1

[0032] Validation data: Filter cake peeling rate: 92%; filtration speed: 85L / (m²・h); warp tensile strength: 200N / cm, weft tensile strength: 200N / cm; interlayer peel strength: 12N / cm; structural deformation under 2MPa high pressure: ≤3%. Example 2

[0033] Table 2: Material and Process Parameters for Example 2

[0034] Validation data: Filter cake peeling rate: 95%; filtration speed: 98L / (m²・h); warp tensile strength: 230N / cm, weft tensile strength: 220N / cm; interlayer peel strength: 15N / cm; deformation under 2MPa high pressure: ≤2%. Example 3

[0035] Table 3: Material and Process Parameters for Example 3

[0036] Validation data: Filter cake peeling rate: 97%; filtration speed: 105L / (m²・h); warp tensile strength: 260N / cm, weft tensile strength: 250N / cm; interlayer peel strength: 18N / cm; deformation under 3MPa high pressure: ≤2%. Example 4

[0037] Table 4: Material and Process Parameters for Example 4

[0038] Validation data: Filter cake peeling rate: 98%; filtration speed: 102 L / (m²・h); warp tensile strength: 290 N / cm, weft tensile strength: 280 N / cm; interlayer peel strength: 21 N / cm; deformation under 3 MPa high pressure: ≤1.5%. Example 5

[0039] Table 5: Material and Process Parameters for Example 5

[0040] Validation data: Filter cake peeling rate: 99%; filtration speed: 95L / (m²・h); warp tensile strength: 320N / cm, weft tensile strength: 310N / cm; interlayer peel strength: 24N / cm; deformation under 4MPa high pressure: ≤1.5%.

[0041] Analysis of Examples 1-5: Example 1 combines the minimum values ​​of each parameter, resulting in the lowest cost. It is suitable for ordinary filtration scenarios with low pressure and low flow, meeting basic usage requirements.

[0042] Example 2 uses the lower intermediate values ​​of each parameter to combine them, adapting to medium and low voltage conventional scenarios and achieving a gradient match between performance and cost.

[0043] Example 3 combines the intermediate values ​​of various parameters to achieve optimal overall performance, with balanced filtration speed, structural stability, and filter cake peeling properties. It is suitable for mainstream application scenarios with medium and high pressure and medium and high flow rates, making it the top choice in terms of cost-effectiveness.

[0044] Example 4 combines the higher intermediate values ​​of each parameter to adapt to high-voltage stability scenarios and achieve a gradient match between performance and cost.

[0045] Example 5 combines the maximum values ​​of each parameter, resulting in the strongest structural strength and adaptability to extreme environments, with a filter cake peeling rate of 99%. It can be adapted to extreme scenarios such as ultra-high pressure and strong corrosion, but it has the highest cost and slightly lower filtration speed.

[0046] Comparative Example 1 Table 6: Material and Process Parameters for Comparative Example 1

[0047] Validation data: Filter cake peeling rate: 96%; filtration speed: 103L / (m²・h); warp tensile strength: 250N / cm, weft tensile strength: 240N / cm; interlayer peeling strength: 8N / cm; deformation ≥5% under 2MPa high pressure, interlayer peeling phenomenon occurs.

[0048] Comparative Example 2 Table 7: Material and Process Parameters for Comparative Example 2

[0049] Validation data: Filter cake peeling rate: 97%; filtration speed: 78L / (m²・h); warp tensile strength: 260N / cm, weft tensile strength: 250N / cm; interlayer peel strength: 18N / cm; deformation under 3MPa high pressure: ≤2%.

[0050] Summarize: 1. All embodiments have a filter cake peeling rate of ≥92%, warp / weft tensile strength of ≥200N / cm, and deformation under high pressure of ≤3%, with core performance indicators fully covering the core requirements of belt filters.

[0051] 2. The combined process of hot-pressing pre-composite and three-dimensional needle-punching reinforcement is irreplaceable: In Comparative Example 1, after the hot-pressing pre-composite was removed, the interlayer peel strength dropped from 18 N / cm to 8 N / cm, and interlayer peeling occurred under high pressure, proving that the combined process is the key to avoiding interlayer separation and ensuring structural stability.

[0052] 3. The gradient pore structure of the filter layer significantly improves the filtration efficiency: After adopting a uniform pore size in Comparative Example 2, the filtration rate decreased from 105 L / (m²·h) to 78 L / (m²·h), a reduction of 26%, which verifies the innovative role of gradient pores in the efficient separation of solid and liquid.

[0053] 4. Synergistic effect of surface fluorine-modified PTFE material and textured surface: The filter cake peeling rate of all embodiments is ≥92%, and the higher the parameter, the better the peeling effect, proving that the design can effectively reduce filter cake adsorption and solve the problem of filter cloth cleaning.

[0054] Conclusion: The low surface energy of the surface layer, the gradient filtration function of the filter layer, and the high-strength support of the support layer complement each other, enabling the filter cloth to simultaneously achieve the three core advantages of "low adsorption of filter cake, high efficiency of solid-liquid separation, and high pressure structural stability". A single structural layer cannot simultaneously meet these comprehensive performance requirements.

[0055] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A filter cloth for use in a belt filter press, characterized in that: It includes a surface layer (1), a filter layer (2) and a support layer (3) that are tightly bonded together from top to bottom. The surface layer (1), the filter layer (2) and the support layer (3) are formed into an integrated structure through a combination of hot-pressing pre-composite and three-dimensional needle-punching reinforcement. The hot-pressing pre-composite makes the contact surfaces of the three layers form an initial bond, and the three-dimensional needle-punching reinforcement makes the fibers in the three layers intertwine to form fiber bundles that run through the three layers, thereby achieving mechanical locking and avoiding interlayer delamination. The surface layer (1) is a fluorine-modified polytetrafluoroethylene short fiber random needle-punched molding layer, which is formed by random needle punching of fluorine-modified PTFE short fibers with a length of 38-51mm and a diameter of 12-20μm. The overall porosity of the surface layer (1) is 65-75%, and the surface of the surface layer (1) away from the filter layer (2) is molded to form a regularly arranged textured surface. The filter layer (2) is a three-dimensional needle-punched layer of basalt short chopped fiber and polyester hollow cross-section short fiber. The basalt short chopped fiber is cut from continuous long filaments. The two are mixed in a ratio of 30-50wt%:50-70wt% and then cross-laid and three-dimensional needle-punched. The filter layer (2) has a thickness of 1.2-2.5mm and forms a pore structure with a continuously gradually changing pore size from the side near the surface to the side near the support layer. The support layer (3) is a high-strength polyester filament woven plain weave layer, which is made of polyester filaments with a breaking strength ≥5.5cN / dtex and a linear density of 100-200D interwoven with warp and weft. The warp density is 35-50 threads / cm and the weft density is 30-45 threads / cm. The thickness of the support layer (3) is 0.8-1.5mm, and the tensile strength in both the warp and weft directions is ≥200N / cm. Through the synergistic effect of the low surface energy characteristics and texture design of the surface layer (1), the gradient pore filtration function of the filter layer (2), and the high-strength structural support of the support layer (3), the filter cloth can simultaneously achieve low adsorption of filter cake, efficient solid-liquid separation and structural stability under high pressure during the belt filtration process.

2. The filter cloth for a belt filter press according to claim 1, characterized in that: The outer surface of the surface layer (1) is coated with a nano-silica coating, the thickness of which is 0.5-2μm, and is formed by sol-gel method.

3. The filter cloth for a belt filter press according to claim 1, characterized in that: The diameter of the mixed fibers in the filter layer (2) is 8-15 μm.

4. The filter cloth for a belt filter press according to claim 1, characterized in that: The raised texture on the outer surface of the surface layer (1) has a height of 0.3-0.8 mm, a spacing of 1-3 mm between adjacent raised textures, and a semi-circular cross-section.

5. The filter cloth for a belt filter press according to claim 1, characterized in that: The process parameters for the hot-pressing pre-composite are: hot-pressing temperature 120-160℃, hot-pressing pressure 0.3-0.8MPa, and hot-pressing time 10-30s; the needle-punching reinforcement has a needle density of 200-300 needles / cm² and a needle-punching depth of 5-8mm.

6. The filter cloth for a belt filter press according to claim 1, characterized in that: The filter cloth has a reinforcing structure on both sides of its edge. The reinforcing structure is a high-strength nylon filament covering layer. The nylon filament covering layer is fixed by overlock stitching with a stitch spacing of 0.5-1mm. The tensile strength of the nylon filament is ≥8cN / dtex.

7. The filter cloth for a belt filter press according to claim 1, characterized in that: The gradient pore size inside the filter layer (2) is 1-3 μm on the side near the surface and 5-10 μm on the side near the support layer.

8. The filter cloth for a belt filter press according to claim 1, characterized in that: The fluorine-modified PTFE short fibers have a fluorine content of ≥65wt%, a tensile strength of ≥3.5cN / dtex, and a temperature resistance range of -200℃ to 260℃.

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