Polyester filament acid and alkali resistant sewage filtering bag and preparation method thereof

Abstract

The application discloses a polyester filament acid and alkali resistant sewage filtering bag and a preparation method thereof, and relates to the technical field of sewage treatment filtering materials, which comprises a coarse filtering layer, a metal wire mesh layer, a fine filtering layer and a supporting protection layer, the metal wire mesh layer is arranged on the inner side of the coarse filtering layer, the fine filtering layer is arranged on the inner side of the metal wire mesh layer, and the supporting protection layer is fixedly connected to the inner side of the fine filtering layer, wherein the supporting protection layer comprises a polyester fiber layer and a PTFE microporous membrane layer, and the PTFE microporous membrane layer is fixedly connected to the inner side of the polyester fiber layer. The coarse filtering layer on the outer layer first intercepts large-particle impurities, the middle fine filtering layer captures fine particles, the inner PTFE membrane realizes fine filtering, the metal wire mesh layer is matched with the coarse filtering layer, the fine filtering layer and the supporting protection layer to uniformly disperse fluid pressure and avoid excessively high local load, the large-particle interception capacity is improved, and the filtering efficiency is ensured.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sewage treatment filter materials, in particular to a polyester filament acid-alkali-resistant sewage filter bag and a preparation method thereof. BACKGROUND

[0002] The sewage generated by chemical industry, metallurgy, electroplating, printing and dyeing, pharmaceutical industry and the like often contains corrosive substances such as strong acid, strong alkali, salt and organic solvent. If the sewage is directly discharged, the environment will be seriously polluted. Therefore, the suspended solids, colloids and part of the dissolved pollutants need to be removed through a filtering process to meet the discharge standard or recycling requirement. The sewage filter bag as a terminal filter element has a wide application in sewage treatment.

[0003] In the prior art, the traditional filter bag materials such as nylon and polypropylene are prone to hydrolytic degradation, fiber strength attenuation and pore size deformation when being in contact with strong acid and alkali solution for a long time, which leads to the decrease of filtering efficiency, the shortening of filter bag service life and even the triggering of equipment failure. SUMMARY

[0004] The application aims to provide a polyester filament acid-alkali-resistant sewage filter bag and a preparation method thereof to solve the problems that the traditional filter bag materials such as nylon and polypropylene are prone to hydrolytic degradation, fiber strength attenuation and pore size deformation when being in contact with strong acid and alkali solution for a long time, which leads to the decrease of filtering efficiency, the shortening of filter bag service life and even the triggering of equipment failure.

[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme: a polyester filament acid-alkali-resistant sewage filter bag, comprising a coarse filter layer, a metal wire mesh layer, a fine filter layer and a support protection layer, the metal wire mesh layer is arranged on the inner side of the coarse filter layer, the fine filter layer is arranged on the inner side of the metal wire mesh layer, the support protection layer is fixedly connected to the inner side of the fine filter layer, the support protection layer comprises a polyester fiber layer and a PTFE microporous membrane layer, the PTFE microporous membrane layer is fixedly connected to the inner side of the polyester fiber layer, the top edges of the coarse filter layer, the metal wire mesh layer, the fine filter layer and the support protection layer are fixedly connected with an edge sealing strip, and a stainless steel ring is arranged in the edge sealing strip.

[0006] Preferably, the coarse filter layer and the fine filter layer are both made of modified polyester filaments, the fiber fineness of the coarse filter layer is 200-300D, and the fiber fineness of the fine filter layer is 100-150D.

[0007] Preferably, the filter hole size of the metal wire mesh layer is 20-40 mesh, the polyester fiber layer is made of thick denier polyester filaments, the fiber fineness of the thick denier polyester filaments is 300-400D, and the thickness of the PTFE microporous membrane layer is 4-6 mu.

[0008] A preparation method of the polyester filament acid-alkali-resistant sewage filter bag comprises the following steps:

[0009] S1, modifying the polyester chip material, preparing modified polyester filaments by melt spinning;

[0010] S2, weaving the modified polyester filaments by a plain loom to weave a coarse filter layer, the weft density is 40-50 roots / cm, and a pore size of 50-80 μm is formed;

[0011] S3, pretreating the metal wire mesh to obtain a metal wire mesh layer, and coating the treated metal wire mesh layer and the coarse filter layer with a high-temperature-resistant silicone rubber adhesive, the adhesive dosage is 15-20 g / m², and the room temperature curing time is 24 h;

[0012] S4, stretching the expanded PTFE film into a hole and performing plasma treatment to obtain a PTFE microporous membrane, the average pore size is 10-20 μm, and the PTFE microporous membrane is compounded to the surface of the polyester fiber layer by a hot melt roller pressing process;

[0013] S5, weaving 100-150D modified polyester filament base fabric to prepare a fine filter layer by a twill loom, the density is 80-120 needles / cm 2 Then, the coarse filter layer, the metal wire mesh layer, the fine filter layer and the support protection layer are compounded by a laminating machine to obtain a composite filter material, the temperature is 180-200 ℃, the pressure is 0.2 MPa, and the speed is 5 m / min;

[0014] S6, immersing the composite filter material in an acid and alkali resistant coating liquid, controlling the wet coating thickness by a roller to be 50-80 μm, pre-drying at 120 ℃ for 10 min, sintering at 280-300 ℃ for 15 min, and forming a dense coating layer with a thickness of 5-10 μm on the outer surface of the filter material;

[0015] S7, cutting and sewing the filter material according to the preset size to obtain a filter bag product, and packaging and storing after detection.

[0016] Preferably, in step S1, the polyester chip material modification treatment comprises the following steps:

[0017] S11, after the polyester chip is dried at 120 ℃ for 4 hours and the isophthalic acid and adipic acid are sieved through a 200 mesh sieve, the polyester chip, isophthalic acid and adipic acid are added to a reaction kettle, and the polyester chip, isophthalic acid and adipic acid are added according to a molar ratio of 8:1:1;

[0018] S12, N2 is introduced into the reaction kettle, the flow rate is 5-8 m³ / h, the pressure is maintained at 0.3 MPa, the temperature is raised to 250-260 ℃, and the stirring and mixing occur to generate a co-condensation reaction, and the reaction time is 2-3 hours;

[0019] S13, after the reaction is completed, the pressure in the reaction kettle is gradually reduced to ≤100Pa by a vacuum pump, and the ethylene glycol generated by the polycondensation reaction is volatilized by maintaining for 2-3 hours; the temperature is increased to 280-285 DEG C during the pressure reduction stage, and the ethylene glycol is recovered by condensation; the pressure reduction polymerization reaction is carried out in the reaction kettle by using a composite catalyst of tetrabutyl titanate and antimony trioxide, and the stirring reaction is carried out for 3-4 hours;

[0020] S14, obtaining the modified polyester melt and extruding by using a twin-screw extruder, underwater pelletizing and drying treatment, the drying temperature is 140-150 DEG C, and the time is 6-8 hours.

[0021] Preferably, in step S3, the metal wire mesh pretreatment process is: first, the metal wire mesh is electrolytic polished, then pickling and passivation treatment is carried out, the treated metal wire mesh surface is sprayed with a 5 mu m polyimide insulating layer, and finally immersed in nano-SiO2 dispersion liquid and dried for standby.

[0022] Preferably, in step S7, the cutting and sewing forming of the filter material according to the preset size comprises the following steps:

[0023] S71, cutting the filter material according to the preset size specification, reserving 10-15 mm sewing edge, and using aramid / PTFE blended thread for double-thread overlock sewing;

[0024] S72, aligning the stainless steel ring and the edge strip with the edge of the filter material, and forming continuous sealing by ultrasonic welding;

[0025] S73, coating the surface of the sewing line with silicone sealant, room temperature vulcanization for 24 hours, and the thickness is 1-2 mm.

[0026] Compared with the prior art, the beneficial effects of the present application are:

[0027] 1、In the present application, the outer coarse filter layer first intercepts large particle impurities, the middle fine filter layer captures fine particles, and the inner PTFE membrane realizes fine filtration, and the metal wire mesh layer uniformly disperses the fluid pressure, avoids excessive local load, improves the large particle interception capacity, and guarantees the filtration efficiency;

[0028] 2、In the present application, the coarse polyester fiber layer in the support protection layer provides mechanical support to prevent the filter bag from deforming under high pressure difference; the PTFE microporous membrane layer covers the inner side, which not only blocks the direct erosion of sewage on the polyester fiber, but also cooperates with the fine filter layer to improve the filtration precision through the 10-20 mu m pore size, and at the same time reduces the risk of filter bag blockage;

[0029] 3、In the present application, the polyester chip is modified by blending isophthalic acid and adipic acid, flexible groups and acid and alkali resistant structures are introduced into the molecular chain, and after catalytic polymerization, the acid and alkali resistance strength retention rate is effectively solved, which solves the problems of easy hydrolysis and strength attenuation of traditional polyester in strong acid and alkali environment. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A polyester filament acid and alkali resistant sewage filter bag structure schematic diagram of the present application;

[0031] Figure 2 A polyester filament acid and alkali resistant sewage filter bag support protective layer structure schematic diagram of the present application.

[0032] Legend: 1, coarse filter layer; 2, metal mesh layer; 3, fine filter layer; 4, support protective layer; 41, polyester fiber layer; 42, PTFE microporous membrane layer; 5, stainless steel ring; 6, edge sealing strip. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0034] The present application will be further described below in conjunction with the embodiments.

[0035] Embodiment 1: as shown in Figure 1 and Figure 2 The present embodiment provides a polyester filament acid and alkali resistant sewage filter bag, which comprises a coarse filter layer 1, a metal mesh layer 2, a fine filter layer 3 and a support protective layer 4. The metal mesh layer 2 is arranged on the inner side of the coarse filter layer 1, the fine filter layer 3 is arranged on the inner side of the metal mesh layer 2, and the support protective layer 4 is fixedly connected to the inner side of the fine filter layer 3. The support protective layer 4 comprises a polyester fiber layer 41 and a PTFE microporous membrane layer 42, and the PTFE microporous membrane layer 42 is fixedly connected to the inner side of the polyester fiber layer 41. The top edges of the coarse filter layer 1, the metal mesh layer 2, the fine filter layer 3 and the support protective layer 4 are fixedly connected with an edge sealing strip 6, and the inside of the edge sealing strip 6 is provided with a stainless steel ring 5. The coarse filter layer 1 and the fine filter layer 3 are both made of modified polyester filament, the fiber fineness of the coarse filter layer 1 is 200D, the fiber fineness of the fine filter layer 3 is 100D, the filter hole size of the metal mesh layer 2 is 20 mesh, the polyester fiber layer 41 is made of thick denier polyester filament, the fiber fineness of the thick denier polyester filament is 300D, and the thickness of the PTFE microporous membrane layer 42 is 4μm.

[0036] A polyester filament acid and alkali resistant sewage filter bag preparation method, comprising the following steps:

[0037] Step one, modification treatment of polyester chip material, modified polyester filament is prepared by melt spinning;

[0038] The polyester chip material modification process is as follows: polyester chips are dried at 120 DEG C for 4 hours under vacuum, and isophthalic acid and adipic acid are sieved through a 200 mesh sieve, then polyester chips, isophthalic acid and adipic acid are added into a reaction kettle, and the polyester chips, isophthalic acid and adipic acid are fed at a molar ratio of 8:1:1; N2 is introduced into the reaction kettle, the flow rate is 5-8 m3 / h, the pressure is maintained at 0.3 MPa, the temperature is raised to 250-260 DEG C, and the co-condensation reaction is carried out by stirring and mixing; after the reaction is completed, the pressure in the reaction kettle is gradually reduced to ≤100 Pa by a vacuum pump, and the temperature is raised to 280-285 DEG C to recover the ethylene glycol by condensation, a titanium tetrabutyl titanate and antimony trioxide composite catalyst is used for the vacuum polymerization reaction in the reaction kettle, and the stirring reaction is carried out for 3-4 hours; finally, the modified polyester melt is obtained and extruded by a double screw extruder, underwater pelletizing and drying treatment are carried out, the drying temperature is 140-150 DEG C, and the time is 6-8 hours;

[0039] Step two, weaving the modified polyester filament to weave the coarse filter layer 1 by the plain weave machine, the weft density is 40-50 roots / cm, and a 50 μm pore size is formed;

[0040] Step three, the metal wire mesh is pretreated to obtain the metal wire mesh layer 2, and the treated metal wire mesh layer 2 is compounded with the coarse filter layer 1 by spot coating of high-temperature-resistant silicone rubber adhesive, the adhesive dosage is 15-20 g / m2, and the room temperature curing is carried out for 24 hours;

[0041] The metal wire mesh pretreatment process is as follows: first, the metal wire mesh is electrolytically polished, then it is pickled and passivated, the surface of the treated metal wire mesh is sprayed with a 5 μm polyimide insulating layer, and finally it is immersed in a nano-SiO2 dispersion liquid and dried for standby use;

[0042] Step four, the expanded PTFE membrane is stretched into a hole and subjected to plasma treatment to obtain a PTFE microporous membrane, the average pore size is 10-20 μm, and the PTFE microporous membrane is compounded to the surface of the polyester fiber layer 41 by a hot melt roller pressing process;

[0043] Step five, the 100D modified polyester filament base fabric is prepared by weaving the fine filter layer 3 by the twill weave machine, and the density is 80-120 needles / cm 2 Then, the coarse filter layer 1, the metal wire mesh layer 2, the fine filter layer 3 and the support protection layer 4 are compounded by a laminating machine to obtain a composite filter material, the temperature is 180-200 DEG C, the pressure is 0.2 MPa, and the speed is 5 m / min;

[0044] Step six, the composite filter material is immersed in an acid and alkali resistant coating liquid, the wet coating thickness is controlled to be 50-80 μm by a roller, pre-drying is carried out at 120 DEG C for 10 min, sintering is carried out at 280-300 DEG C for 15 min, and a dense coating with a thickness of 5 μm is formed on the outer surface of the filter material;

[0045] Step seven, according to the preset size of the filter material cutting and sewing forming to obtain filter bag finished product, after detection qualified for packaging storage; wherein, cutting and sewing forming process is: cutting filter material according to the preset size specification, 10-15mm reserved sewing edge, using aramid / PTFE blended thread for double thread overlock sewing; The stainless steel ring 5 and the edge strip 6 are aligned with the edge of the filter material, and the continuous sealing is formed by ultrasonic welding; The surface of the sewing line is coated with silicone sealant, and the room temperature vulcanization is 24h, and the thickness is 1-2mm.

[0046] Embodiment 2: as shown in Figure 1 and Figure 2 The embodiment provides a polyester filament acid and alkali resistant sewage filter bag, which comprises a coarse filter layer 1, a metal wire mesh layer 2, a fine filter layer 3 and a support protection layer 4. The metal wire mesh layer 2 is arranged on the inner side of the coarse filter layer 1. The fine filter layer 3 is arranged on the inner side of the metal wire mesh layer 2. The support protection layer 4 is fixedly connected to the inner side of the fine filter layer 3. The support protection layer 4 comprises a polyester fiber layer 41 and a PTFE microporous membrane layer 42. The PTFE microporous membrane layer 42 is fixedly connected to the inner side of the polyester fiber layer 41. The top edges of the coarse filter layer 1, the metal wire mesh layer 2, the fine filter layer 3 and the support protection layer 4 are fixedly connected with an edge sealing strip 6. The inside of the edge sealing strip 6 is provided with a stainless steel ring 5. The coarse filter layer 1 and the fine filter layer 3 are both made of modified polyester filaments. The fiber fineness of the coarse filter layer 1 is 250D. The fiber fineness of the fine filter layer 3 is 130D. The filter hole size of the metal wire mesh layer 2 is 30 meshes. The polyester fiber layer 41 is made of thick denier polyester filaments. The fiber fineness of the thick denier polyester filaments is 350D. The thickness of the PTFE microporous membrane layer 42 is 5μm.

[0047] A preparation method of a polyester filament acid and alkali resistant sewage filter bag, comprising the following steps:

[0048] Step one, modifying the polyester chip material, and preparing modified polyester filaments by melt spinning;

[0049] The modification process for polyester chips is as follows: Polyester chips are vacuum dried at 120℃ for 4 hours, and isophthalic acid and adipic acid are passed through a 200-mesh sieve. Then, polyester chips, isophthalic acid, and adipic acid are added to a reaction vessel in a molar ratio of 8:1:1. N2 is introduced into the reaction vessel at a flow rate of 5–8 m³ / h, maintaining a pressure of 0.3 MPa. The temperature is raised to 250–260℃, and the mixture is stirred to induce a copolymerization reaction for 2–3 hours. Once the reaction is complete... The pressure inside the reactor was then gradually reduced to ≤100Pa using a vacuum pump and maintained for 2–3 hours to allow the ethylene glycol generated by the polycondensation reaction to evaporate. During the depressurization stage, the temperature was raised to 280–285℃ and the ethylene glycol was recovered by condensation. A composite catalyst of tetrabutyl titanate and antimony trioxide was used in the reactor for depressurization polymerization, and the reaction was stirred for 3–4 hours. Finally, the modified polyester melt was obtained and extruded using a twin-screw extruder. The melt was then pelletized underwater and dried at a temperature of 140–150℃ for 6–8 hours.

[0050] Step 2: Weave the coarse filter layer 1 by weaving modified polyester filaments on a plain weave loom with a weft density of 40-50 filaments / cm to form a pore size of 50-80μm.

[0051] Step 3: Pre-treat the metal wire mesh to obtain metal wire mesh layer 2. Then, apply the treated metal wire mesh layer 2 to the coarse filter layer 1 by dot coating with high-temperature resistant silicone rubber adhesive. The amount of adhesive is 15-20 g / m², and the mixture is cured at room temperature for 24 hours.

[0052] The metal wire mesh pretreatment process is as follows: first, the metal wire mesh is electrolytically polished, then acid pickling and passivation treatment is performed, a 5μm polyimide insulating layer is sprayed onto the surface of the treated metal wire mesh, and finally, it is impregnated with nano-SiO2 dispersion and dried for later use.

[0053] Step 4: Stretch the expanded PTFE membrane into pores and perform plasma treatment to obtain a PTFE microporous membrane with an average pore size of 10-20 μm. Then, laminate the PTFE microporous membrane onto the surface of the polyester fiber layer 41 using a hot melt roll pressing process.

[0054] Step 5: Prepare the fine filter layer 3 by weaving a 130D modified polyester filament base fabric on a twill loom, with a density of 80-120 needles / cm. 2 Then, the coarse filter layer 1, the metal wire mesh layer 2, the fine filter layer 3 and the support and protective layer 4 are laminated together to obtain the composite filter material at a temperature of 180-200℃, a pressure of 0.2MPa and a speed of 5m / min.

[0055] Step 6: Immerse the composite filter material in an acid and alkali resistant coating solution, control the wet coating thickness to 50-80μm using rollers, pre-bake at 120℃ for 10min, and sinter at 280-300℃ for 15min to form a dense coating of 5-10μm on the surface of the filter material.

[0056] Step seven, according to the preset size of the filter material cutting and sewing forming to obtain filter bag finished product, after detection qualified for packaging storage; wherein, cutting and sewing forming process is: cutting filter material according to the preset size specification, 10-15mm reserved sewing edge, using aramid / PTFE blended thread for double thread overlock sewing; The stainless steel ring 5 and the edge strip 6 are aligned with the edge of the filter material, and the continuous sealing is formed by ultrasonic welding; The surface of the sewing line is coated with silicone sealant, and the room temperature vulcanization is 24h, and the thickness is 1-2mm.

[0057] Embodiment 3: as shown in Figure 1 and Figure 2 The embodiment provides a polyester filament acid and alkali resistant sewage filter bag, which comprises a coarse filter layer 1, a metal wire mesh layer 2, a fine filter layer 3 and a support protection layer 4. The metal wire mesh layer 2 is arranged on the inner side of the coarse filter layer 1. The fine filter layer 3 is arranged on the inner side of the metal wire mesh layer 2. The support protection layer 4 is fixedly connected to the inner side of the fine filter layer 3. The support protection layer 4 comprises a polyester fiber layer 41 and a PTFE microporous membrane layer 42. The PTFE microporous membrane layer 42 is fixedly connected to the inner side of the polyester fiber layer 41. The top edges of the coarse filter layer 1, the metal wire mesh layer 2, the fine filter layer 3 and the support protection layer 4 are fixedly connected with an edge sealing strip 6. The inside of the edge sealing strip 6 is provided with a stainless steel ring 5. The coarse filter layer 1 and the fine filter layer 3 are both made of modified polyester filaments. The fiber fineness of the coarse filter layer 1 is 300D. The fiber fineness of the fine filter layer 3 is 150D. The filter hole size of the metal wire mesh layer 2 is 40 mesh. The polyester fiber layer 41 is made of thick denier polyester filaments. The fiber fineness of the thick denier polyester filaments is 400D. The thickness of the PTFE microporous membrane layer 42 is 6μm.

[0058] A preparation method of a polyester filament acid and alkali resistant sewage filter bag, comprising the following steps:

[0059] Step one, modifying the polyester chip material, and preparing modified polyester filaments by melt spinning;

[0060] The modification process for polyester chips is as follows: Polyester chips are vacuum dried at 120℃ for 4 hours, and isophthalic acid and adipic acid are passed through a 200-mesh sieve. Then, polyester chips, isophthalic acid, and adipic acid are added to a reaction vessel in a molar ratio of 8:1:1. N2 is introduced into the reaction vessel at a flow rate of 5–8 m³ / h, maintaining a pressure of 0.3 MPa. The temperature is raised to 250–260℃, and the mixture is stirred to induce a copolymerization reaction for 2–3 hours. Once the reaction is complete... The pressure inside the reactor was then gradually reduced to ≤100Pa using a vacuum pump and maintained for 2–3 hours to allow the ethylene glycol generated by the polycondensation reaction to evaporate. During the depressurization stage, the temperature was raised to 280–285℃ and the ethylene glycol was recovered by condensation. A composite catalyst of tetrabutyl titanate and antimony trioxide was used in the reactor for depressurization polymerization, and the reaction was stirred for 3–4 hours. Finally, the modified polyester melt was obtained and extruded using a twin-screw extruder. The melt was then pelletized underwater and dried at a temperature of 140–150℃ for 6–8 hours.

[0061] Step 2: Weave the coarse filter layer 1 by weaving modified polyester filaments on a plain weave loom with a weft density of 40-50 filaments / cm to form a pore size of 50-80μm.

[0062] Step 3: Pre-treat the metal wire mesh to obtain metal wire mesh layer 2. Then, apply the treated metal wire mesh layer 2 to the coarse filter layer 1 by dot coating with high-temperature resistant silicone rubber adhesive. The amount of adhesive is 15-20 g / m², and the mixture is cured at room temperature for 24 hours.

[0063] The metal wire mesh pretreatment process is as follows: first, the metal wire mesh is electrolytically polished, then acid pickling and passivation treatment is performed, a 5μm polyimide insulating layer is sprayed onto the surface of the treated metal wire mesh, and finally, it is impregnated with nano-SiO2 dispersion and dried for later use.

[0064] Step 4: Stretch the expanded PTFE membrane into pores and perform plasma treatment to obtain a PTFE microporous membrane with an average pore size of 10-20 μm. Then, laminate the PTFE microporous membrane onto the surface of the polyester fiber layer 41 using a hot melt roll pressing process.

[0065] Step 5: Prepare the fine filter layer 3 by weaving a 150D modified polyester filament base fabric on a twill loom, with a density of 80-120 needles / cm. 2 Then, the coarse filter layer 1, the metal wire mesh layer 2, the fine filter layer 3 and the support and protective layer 4 are laminated together to obtain the composite filter material, with a temperature of 180-200℃, a pressure of 0.2MPa and a speed of 5m / min.

[0066] Step 6: Immerse the composite filter material in an acid and alkali resistant coating solution, control the wet coating thickness to 50-80μm using rollers, pre-bake at 120℃ for 10min, and sinter at 280-300℃ for 15min to form a dense coating of 5-10μm on the surface of the filter material.

[0067] Step seven, according to the preset size of the filter material cutting and sewing forming to obtain the filter bag finished product, after detection qualified for packaging storage; wherein, cutting and sewing forming process is: cutting filter material according to the preset size specification, reserving 10-15mm sewing edge, using aramid / PTFE blended thread for double thread overlock sewing; the stainless steel ring 5 and the edge strip 6 are aligned with the edge of the filter material, and a continuous seal is formed by ultrasonic welding; the surface of the sewing line is coated with silicone sealant, and the room temperature vulcanization is 24h, and the thickness is 1-2mm.

[0068] Comparative example 1: the polyester filament acid and alkali resistant sewage filter bag and the preparation method provided by the embodiment are basically the same as those of example 1, the main difference is that the coarse filter layer 1 and the fine filter layer 3 are not modified.

[0069] Comparative example 2: the polyester filament acid and alkali resistant sewage filter bag and the preparation method provided by the embodiment are basically the same as those of example 1, the main difference is that the metal wire mesh is replaced by nylon mesh.

[0070] Comparative example 3: the polyester filament acid and alkali resistant sewage filter bag and the preparation method provided by the embodiment are basically the same as those of example 1, the main difference is that the outer layer is not treated by acid and alkali resistant coating.

[0071] Performance test and result analysis: the polyester filament acid and alkali resistant sewage filter bag prepared by example 1-3 and comparative example 1-3 is tested respectively;

[0072] I. Acid and alkali resistance test:

[0073] Test method: each filter bag sample is respectively placed in pH=2 sulfuric acid solution and pH=14 sodium hydroxide solution, and soaked at 60℃ for 72 hours.

[0074] Performance index: the tensile strength of the filter bag before and after soaking is tested by using universal material testing machine, and the strength retention rate is calculated; the surface morphology change of the filter material is observed by using scanning electron microscope, and the corrosion degree is evaluated.

[0075] Record the relevant data in table 1;

[0076] Table 1: test data record table

[0077] Group Sulfuric acid solution strength retention rate (%) Sodium hydroxide solution strength retention rate (%) Surface corrosion condition Example 1 92 91 Mild corrosion, fiber structure intact Example 2 95 89 Outstanding acid resistance, slight swelling in lye Example 3 93 90 Good protection of PTFE film, no obvious corrosion of fiber Comparative Example 1 65 60 Severe corrosion of fiber, rough surface Comparative Example 2 70 68 Swelling of nylon net, overall structure deformation Comparative Example 3 75 70 No PTFE film, fiber directly eroded

[0078] II. Filtration efficiency test:

[0079] Test method: using simulated sewage (containing 5μm silicon carbide particles, concentration 1000mg / L), the filter bag is filtered at 0.1MPa filtration pressure, and the particle concentration in the sewage before and after filtration is detected by using laser particle size analyzer.

[0080] Performance index: Calculate the filtration efficiency of 5 μm particles, and record the initial pressure difference and the pressure difference change after 10 hours of filtration.

[0081] Record the relevant data in Table 2;

[0082] Table 2: Test data recording table

[0083] Group 5 μm particle filtration efficiency (%) Initial pressure difference (MPa) Pressure difference after 10 hours (MPa) Example 1 96 0.05 0.08 Example 2 95 0.05 0.07 Example 3 97 0.04 0.06 Comparative Example 1 75 0.04 0.12 Comparative Example 2 80 0.04 0.10 Comparative Example 3 85 0.04 0.09

[0084] III. Backwashing performance test:

[0085] Test method: After 10 hours of operation, the filter bag is backwashed (backwashing water pressure 0.2 MPa, time 30 s), and the weight of the pollutants trapped on the filter bag before and after backwashing is measured by weighing method, and the removal rate of pollutants is calculated.

[0086] Performance index: Measure the backwashing performance by the removal rate of pollutants, and observe the appearance integrity of the filter bag after backwashing.

[0087] Record the relevant data in Table 3;

[0088] Table 3: Test data recording table

[0089] Group Pollutant removal rate (%) Appearance after backwashing Example 1 92 No damage, clean surface Example 2 90 No damage, slight residue Example 3 94 No damage, high cleanliness Comparative Example 1 70 Loose fiber, partial damage Comparative Example 2 75 Deformation of nylon net, residue Comparative Example 3 80 Fiber surface with dirt, partial wear

[0090] From Table 1, Table 2 and Table 3, it can be seen that compared with the comparative examples, the acid and alkali resistant polyester filament filter bag prepared in Examples 1-3 has an acid and alkali resistance improvement of 30%-50% by modifying polyester + multi-layer protection structure (PTFE film + coating), the single structure optimization effect is limited, the multi-layer composite structure (coarse filtration → fine filtration → membrane filtration) improves the 5 μm filtration efficiency, and the long-term stability is better than that of single structure, the metal wire mesh cooperates with the coarse filtration layer to improve the interception capacity, the surface coating and the structure support jointly improve the backwashing efficiency, which is the key to reduce maintenance cost.

[0091] Acid and alkali resistance: In the examples, the modified polyester filament cooperates with the PTFE film for protection, effectively resisting acid and alkali corrosion, and the strength retention rate is much higher than that of the comparative examples; Comparative Example 1 has the worst acid and alkali resistance due to unmodified; Comparative Example 2 has nylon mesh that is not resistant to strong alkali, and Comparative Example 3 has no PTFE film, resulting in direct corrosion of the fiber.

[0092] Filtration efficiency: The multi-layer composite structure of the examples realizes efficient fractional filtration, and the filtration efficiency of 5 μm particles is all ≥95%; Comparative Example 1 has low filtration precision due to unmodified polyester filament; Comparative Examples 2 and 3 have structural defects, resulting in penetration of some particles.

[0093] Backwashing performance: the low adsorption of the oil-repellent and water-repellent coating of the surface of the example and the PTFE film makes the pollutants easy to fall off, and the removal rate is greater than or equal to 90%; the counterexamples 1-3 have poor backwashing effect due to material or structural problems, and the filter bag is easy to be blocked and damaged.

[0094] In the present application, the coarse filter layer 1 preferentially intercepts large particle pollutants, the metal mesh layer 2 assists in supporting and preliminary filtering, and the fine filter layer 3 realizes fine filtering, forming a three-stage filtering system of coarse filtering-supporting-fine filtering, and improving efficiency and capacity through staged filtering. The polyester chip is modified by blending isophthalic acid and adipic acid, flexible groups and acid and alkali resistant structures are introduced into the molecular chain, and after catalytic polymerization at 280-285 DEG C, the acid and alkali resistance strength retention rate is still more than 90% after soaking in pH2-14 solution for 24 hours, effectively solving the problem of easy hydrolysis and strength attenuation of traditional polyester in strong acid and alkali environment. Each layer is combined with a dense coating of 5-10 microns on the surface through point coating and lamination of high-temperature silicone rubber, forming an oil-repellent and water-repellent surface, and the backwashing efficiency recovery rate is more than 95%, reducing the adsorption of pollutants and the cleaning frequency, and prolonging the service life of the filter bag. The stainless steel ring 5 and the sealing strip 6 are ultrasonic welded, combined with aramid / PTFE sewing thread and silicone sealant treatment, to avoid bag leakage; 10-15 mm of the reserved suture edge is double-thread locked, enhancing the joint strength, and suitable for high-pressure filtration scenarios.

[0095] The use of the polyester filament acid and alkali resistant sewage filter bag of the present application: the stainless steel ring 5 at the top of the filter bag needs to be matched with the suspension bracket of the filtration equipment, and is usually used in terminal filtration equipment such as bag filter and pressure filter, and the sealing strip 6 is aligned with the equipment interface, and is pressed tightly through flange or clamp to ensure that there is no leakage at the sealing position.

[0096] Filtering process: sewage flows in from the outside of the filter bag, passes through the coarse filter layer 1, the metal mesh layer 2 and the fine filter layer 3 in turn, and finally flows out from the inside after being filtered by the PTFE film of the support protection layer 4.

[0097] Staged filtration: the coarse filter layer 1 intercepts large particles; the metal mesh layer 2 assists in filtering medium particles; the fine filter layer 3 and the PTFE film of the support protection layer 4 capture fine particles.

[0098] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an acid and alkali resistant wastewater filter bag made of polyester filament, characterized in that, Includes the following steps: S1. Modify polyester chip material and prepare modified polyester filaments by melt spinning; The modification treatment of the polyester chip material includes the following steps: S11. After the polyester chips are vacuum dried at 120°C for 4 hours and the isophthalic acid and adipic acid are passed through a 200-mesh sieve, the polyester chips, isophthalic acid and adipic acid are added to the reaction vessel in a molar ratio of 8:1:

1. S12. Introduce N2 into the reactor at a flow rate of 5-8 m³ / h, maintain a pressure of 0.3 MPa, raise the temperature to 250-260℃, stir and mix to induce a copolymerization reaction, and the reaction time is 2-3 hours. S13. After the reaction is completed, the pressure in the reactor is gradually reduced to ≤100Pa by a vacuum pump and maintained for 2-3 hours to allow the ethylene glycol generated by the polycondensation reaction to volatilize. During the depressurization stage, the temperature is raised to 280-285℃ and the ethylene glycol is recovered by condensation. Tetrabutyl titanate and antimony trioxide composite catalyst are used in the reactor to carry out the depressurization polymerization reaction and the reaction is stirred for 3-4 hours. S14. Obtain the modified polyester melt and extrude it using a twin-screw extruder. Then, pelletize it underwater and dry it at a temperature of 140-150°C for 6-8 hours. S2. A coarse filter layer (1) is prepared by weaving modified polyester filaments with a fiber fineness of 200-300D on a plain weave loom, with a weft density of 40-50 threads / cm, forming a pore size of 50-80μm. S3. Pre-treat the metal wire mesh to obtain a metal wire mesh layer (2). Then, apply the treated metal wire mesh layer (2) and the coarse filter layer (1) together with a high-temperature resistant silicone rubber adhesive. The amount of adhesive is 15-20 g / m², and the mixture is cured at room temperature for 24 hours. S4. The expanded PTFE membrane is stretched into pores and subjected to plasma treatment to obtain a PTFE microporous membrane with an average pore size of 10-20 μm. The PTFE microporous membrane is then composited onto the surface of the polyester fiber layer (41) through a hot melt roll pressing process to obtain a support and protective layer (4) including a PTFE microporous membrane layer (42) and a polyester fiber layer (41). The polyester fiber layer (41) is made of coarse denier polyester filaments with a fiber fineness of 300-400D, and the thickness of the PTFE microporous membrane layer (42) is 4-6 μm. S5. A fine filter layer (3) is prepared by weaving a modified polyester filament base fabric with a fiber fineness of 100-150D on a twill loom, with a density of 80-120 needles / cm. 2 Then, the coarse filter layer (1), the metal wire mesh layer (2), the fine filter layer (3) and the support and protective layer (4) are laminated together to obtain composite filter material at a temperature of 180-200℃, a pressure of 0.2MPa and a speed of 5m / min. S6. Immerse the composite filter material obtained in step S5 into an acid and alkali resistant coating liquid, control the wet coating thickness to 50-80μm by using rollers, pre-bake at 120℃ for 10min, and sinter at 280-300℃ for 15min to form a dense coating of 5-10μm on the surface of the filter material. S7. Cut and sew the filter material obtained in step S6 according to the preset size to obtain the finished filter bag. After passing the inspection, package and store it.

2. The method for preparing a polyester filament acid and alkali resistant wastewater filter bag according to claim 1, characterized in that, In step S3, the metal wire mesh pretreatment process is as follows: first, the metal wire mesh is electrolytically polished, then acid pickling and passivation treatment is performed, a 5μm polyimide insulating layer is sprayed onto the surface of the treated metal wire mesh, and finally, it is impregnated with nano-SiO2 dispersion and dried for later use.

3. The method for preparing a polyester filament acid and alkali resistant wastewater filter bag according to claim 1, characterized in that, In step S7, the process of cutting and sewing the filter material processed in step S6 according to the preset dimensions includes the following steps: S71. Cut the filter material according to the preset size and specifications, leaving a 10-15mm seam edge, and use aramid / PTFE blended thread for double-line overlock stitching. S72. Align the stainless steel ring (5) and the sealing strip (6) with the edge of the filter material and form a continuous seal by ultrasonic welding; S73. Apply silicone rubber sealant to the surface of the suture and cure at room temperature for 24 hours to a thickness of 1-2 mm.

4. The polyester filament acid and alkali resistant wastewater filter bag prepared by the method according to any one of claims 1-3 is characterized in that: The filter includes a coarse filter layer (1), a metal mesh layer (2), a fine filter layer (3), and a support and protective layer (4). The metal mesh layer (2) is disposed inside the coarse filter layer (1), the fine filter layer (3) is disposed inside the metal mesh layer (2), and the support and protective layer (4) is fixedly connected to the inside of the fine filter layer (3). The support and protective layer (4) includes a polyester fiber layer (41) and a PTFE microporous membrane layer (42). The PTFE microporous membrane layer (42) is fixedly connected to the inside of the polyester fiber layer (41). A sealing strip (6) is fixedly connected to the top edge of the layer (4). A stainless steel ring (5) is provided inside the sealing strip (6). Both the coarse filter layer (1) and the fine filter layer (3) are made of modified polyester filaments. The fiber fineness of the coarse filter layer (1) is 200-300D, and the fiber fineness of the fine filter layer (3) is 100-150D. The filter pore size of the metal wire mesh layer (2) is 20-40 mesh. The polyester fiber layer (41) is made of coarse denier polyester filaments. The fiber fineness of the coarse denier polyester filaments is 300-400D. The thickness of the PTFE microporous membrane layer (42) is 4-6μm.

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