Preparation method of low-leakage-point filtering framework convenient for membrane compounding and filter element of filter

Abstract

The invention relates to the technical field of filtering materials, and discloses a preparation method of a low-leakage-point filtering framework convenient for membrane compositing and a filter element of a filter.According to the method, polypropylene is used as a raw material to prepare the filtering framework through a spunbond method, the filtering framework comprises a supporting layer and a composite layer, and the fiber diameter of the supporting layer is larger than that of the composite layer; the supporting layer is used as a supporting framework to improve the stiffness and strength of the filtering layer, the composite layer is used for being compounded with the polymeric membrane, the fiber diameter of the composite layer is smaller than that of the supporting layer, and the flatness uniformity of the filtering layer compounded with the polymeric membrane is improved; the combination firmness of the filter layer and the filter framework is improved through the gradually-changed filter framework structure, and the leakage points of the filter layer are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of filter materials, and in particular to a preparation method of a low-leakage point filter skeleton which is convenient for membrane composite and a filter element. Background Art

[0002] The filter element is a component that plays a filtering role in the filter. Its structure mainly includes end covers, a frame, filter materials and seals. According to needs, bypass valves, handles, nylon tie straps, clamps, winding belts and other structures will be added; the filter material in the filter element is the filter element component used for filtration, and the component that plays a filtering role in the filter element is the filter layer; currently, the filter layer of the filter element mainly adopts the form of pleats to increase the filtration area. The more pleats, the larger the surface of the filter layer per unit volume. Therefore, in the prior art, the pleat form of the filter layer is usually designed to increase the filtration area of ​​the filter layer, such as a pleated high-efficiency filter element disclosed in publication number CN218686895U. The filter material of the filter element adopts fan-shaped pleats and half-height pleats are added to the fan-shaped pleats, which significantly increases the filtration area and increases the pollution holding capacity.

[0003] When the number of pleats in the filter layer increases, higher requirements are placed on the structural strength of the filter layer. When the number of pleats is too many, the structure of the filter layer will be destroyed, resulting in leakage in the filter layer. Therefore, the strength of the filter layer needs to be enhanced. Therefore, in the prior art, the filter skeleton is compounded with the filter layer to increase the structural strength of the filter layer. Currently, the filter skeleton material mainly includes metal mesh and acid- and alkali-resistant polyester fiber. For example, a polyolefin skeleton filter material and a preparation method and use thereof disclosed in publication number CN111206292A, wherein the filter material adopts a polyolefin skeleton to provide additional strength and stiffness to the filter layer. In actual use, the present application has found that when the filter skeleton is compounded with the filter layer, the composite strength is low, and the filter layer may separate from the filter skeleton during use, resulting in leakage in the filter layer. Summary of the invention

[0004] In order to overcome the problems in the prior art of low composite strength between the filter skeleton and the filter layer, separation of the filter layer and the filter skeleton, and leakage points in the filter layer, the present invention provides a method for preparing a low leakage point filter skeleton that is easy for membrane composite and a filter element. The method uses polypropylene as a raw material and adopts a spunbond method to form a filter skeleton. The filter skeleton includes a support layer and a composite layer. The fiber diameter of the support layer is larger than the fiber diameter of the composite layer. The support layer is used as a support skeleton to improve the stiffness and strength of the filter layer. The composite layer is used to be composited with a polymer membrane. The fiber diameter of the composite layer is smaller than that of the support layer. After composited with the polymer membrane, the flatness uniformity of the filter layer is improved. The gradual filter skeleton structure is used to improve the bonding strength between the filter layer and the filter skeleton, and reduce the leakage points of the filter layer.

[0005] The specific technical scheme of the present invention is: A method for preparing a low leakage point filter skeleton which is convenient for membrane composite, wherein the filter skeleton is made of polypropylene as raw material by a spunbond method, and comprises a support layer and a composite layer, wherein the fiber fineness of the support layer is 10-15 dtex, and the fiber fineness of the composite layer is 5-7 dtex.

[0006] Preferably, the surface density of the support layer is 25-50 warp threads / 10 cm, and the surface density of the weft threads is 25-50 threads / 10 cm.

[0007] Preferably, the weight of the support layer is ≥100 g / m 2 .

[0008] Preferably, the surface density of the composite layer is 15-25 warp threads / 10 cm, and the surface density of the weft threads is 15-25 threads / 10 cm.

[0009] Preferably, the composite layer has a gram weight of 15 to 30 g / m 2 .

[0010] The invention provides a method for preparing a low leakage point filter skeleton which is convenient for membrane composite. The method uses polypropylene as a raw material and adopts a spunbond method to prepare the filter skeleton. The filter skeleton comprises a support layer and a composite layer. The fiber wire diameter of the support layer is larger than the fiber wire diameter of the composite layer. The support layer is used as a support skeleton to improve the stiffness and strength of the filter layer. The composite layer is used to be composited with a polymer membrane. The fiber wire diameter of the composite layer is smaller than that of the support layer. After composited with the polymer membrane, the flatness uniformity of the filter layer is improved. The gradual filter skeleton structure is used to improve the bonding strength between the filter layer and the filter skeleton, and reduce the leakage point of the filter layer.

[0011] Preferably, the surface of the filter skeleton is modified with organosilicon-modified polyether, which is prepared by hydrogenation reaction of polyoxyethylene ether and hydrogen-containing silicone oil under catalyst conditions, and has a viscosity of 300 to 500 mPa·s.

[0012] Preferably, the hydrogen-containing silicone oil is polymethyl hydrogen siloxane.

[0013] Preferably, the hydrogenation reaction conditions include: the stirring and heating temperature is 50 to 130° C., the reaction time is 2 to 4 hours, and the molar ratio of polyoxyethylene ether to hydrogen in hydrogen-containing silicone oil is 1 to 3:1.

[0014] Preferably, the number of chain links of the hydrogen-containing silicone oil is 10-30.

[0015] Preferably, the polyester material is polypropylene.

[0016] Preferably, the catalyst is a platinum catalyst, and the platinum catalyst is selected from a complex of platinum and an alcohol solution, a complex of platinum and tetramethyldivinyldisiloxane, a complex of platinum and methylvinylcyclotetrasiloxane, and a silica-supported platinum catalyst.

[0017] Preferably, the amount of the catalyst used is 1 to 100 ppm of the total reaction system.

[0018] The present invention composites the organosilicon-modified polyether on the fiber of the filter skeleton made of polyester material, so that the organosilicon-modified polyether forms a membrane structure on the filter skeleton fiber. When the filter skeleton is composited with the polymer membrane, the membrane structure can significantly improve the interface compatibility between the polyester material and the polymer membrane, significantly improve the composite strength of the filter skeleton and the polymer membrane, significantly improve the composite uniformity of the filter skeleton fiber and the polymer membrane, and significantly reduce the frequency of leakage problems in the filter element. For the above technical effects, the polymer membrane used in the filter material usually adopts a filter membrane with poor interface compatibility such as polytetrafluoroethylene resin and polysulfone sulfide resin. These filter membranes have poor interface compatibility with polyester materials, and the composite strength of the polyester material and the filter membrane is low, resulting in the separation of the filter membrane and the polyester material during use, thereby causing the filter membrane to be damaged and the filter material to leak.

[0019] The organosilicon-modified polyether in the present invention is a compound having long-chain alkyl and polyoxyethylene groups synthesized from polyoxyethylene and hydrogen-containing silicone oil. The organosilicon-modified polyether can be compounded on the fiber surface and form a membrane structure. When the polyester material is compounded with the polymer membrane, the long-chain alkyl and polyoxyethylene groups in the organosilicon-modified polyether have high compatibility with the polymer membrane and can serve as a bridge connecting the polyester fiber and the polymer membrane, significantly improving the interface compatibility between the polyester fiber and the polymer membrane, and significantly increasing the composite strength of the filtration skeleton and the polymer membrane. In addition, since there is a requirement for the wire diameter of the filtration skeleton fiber, the thickness of the formed membrane structure needs to be controlled within a certain range. The present invention controls the thickness of the membrane formed by the organosilicon-modified polyether on the surface of the filtration skeleton fiber by controlling the viscosity of the organosilicon-modified polyether. The present invention can control the viscosity of the finally formed organosilicon-modified polyether by controlling the number of chain segments of the hydrogen-containing silicone oil.

[0020] A filter element comprises a filter element, wherein the filter element comprises a filter layer and a filter skeleton compounded with the filter layer, and the filter skeleton is made by adopting the preparation method of the low leakage point filter skeleton which is convenient for membrane compounding.

[0021] Preferably, the material of the filter layer includes one of polytetrafluoroethylene resin and polyethersulfone resin.

[0022] Preferably, each large pleat of the filter element is provided with a plurality of small pleats.

[0023] Preferably, the number of the small folds is 1 to 3.

[0024] Preferably, the filter element further comprises an end cover, a gasket and a frame sleeved on the outside of the filter element.

[0025] The present invention also provides a filter element, in which the filter skeleton support layer is made by the above-mentioned preparation method of the low leakage point filter skeleton that is convenient for membrane composite. The filter skeleton includes a support layer and a composite layer. The fiber wire diameter of the support layer is larger than the fiber wire diameter of the composite layer. The support layer is used as a support skeleton to improve the stiffness and strength of the filter layer. The composite layer is used to be composited with a polymer membrane. The fiber wire diameter of the composite layer is smaller than that of the support layer. After composited with the polymer membrane, the smoothness uniformity of the filter layer is improved.

[0026] Compared with the prior art, this application has the following technical effects: The invention provides a method for preparing a low leakage point filter skeleton which is convenient for membrane composite. The method adopts a spunbond method to prepare the filter skeleton using polypropylene as a raw material. The filter skeleton comprises a support layer and a composite layer. The fiber diameter of the support layer is larger than that of the composite layer. The support layer is used as a support skeleton to improve the stiffness and strength of the filter layer. The composite layer is used to composite with a polymer membrane. The fiber diameter of the composite layer is smaller than that of the support layer. After composited with the polymer membrane, the flatness uniformity of the filter layer is improved. The gradual filter skeleton structure is used to improve the bonding strength between the filter layer and the filter skeleton, thereby reducing the leakage point of the filter layer. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the embodiments.

[0028] Embodiment 1: A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 300 parts of polyoxyethylene ether (propylene glycol polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (trimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 10) into a reaction container, introduce nitrogen, heat to 90°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, and heat to 130°C for reaction for 1 hour; after the reaction is completed, stop heating and cool the material to 50°C, add a catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain a silicone-modified polyether (viscosity is 298mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0029] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0030] Embodiment 2: A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 250 parts of polyoxyethylene ether (polyethylene glycol polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (trimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 18) into a reaction container, introduce nitrogen, heat to 90°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, heat to 100°C and react for 1.5 hours; after the reaction is completed, stop heating and cool the material to 50°C, add catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain silicone modified polyether (viscosity is 340mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0031] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0032] Embodiment 3: A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 100 parts of polyoxyethylene ether (dodecyl polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (dimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 25) into a reaction container, introduce nitrogen, heat to 90°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, heat to 100°C and react for 1 hour; after the reaction is completed, stop heating and cool the material to 50°C, add catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain silicone modified polyether (viscosity is 483mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0033] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0034] Embodiment 4: A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 120 parts of polyoxyethylene ether (octadecylamine polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (dimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 38) into a reaction container, introduce nitrogen, heat to 90°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, and heat to 70°C for reaction for 3 hours; after the reaction is completed, stop heating and cool the material to 50°C, add catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain silicone modified polyether (viscosity is 502mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0035] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0036] Embodiment 5: A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 150 parts of polyoxyethylene ether (isooctanol polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (dimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 25) into a reaction container, introduce nitrogen, heat to 50°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, and heat to 80°C for reaction for 2 hours; after the reaction is completed, stop heating and cool the material to 50°C, add a catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain a silicone-modified polyether (viscosity is 367mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0037] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0038] Comparative Example 1: (without silicone-modified polyether) In Comparative Example 1, no silicone-modified polyether was used.

[0039] A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: After adding polyester material (polypropylene) slices into the hopper, the polyester slices are fed into the screw extruder to be melted and extruded. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form fibers, and then enters the drawing device for drawing and elongation. After drawing, the fibers are laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fibers made of the front spinning piece are used to make a supporting layer, and the fibers of the rear spinning piece are used to make a composite layer. The supporting layer and the composite layer constitute a fiber skeleton.

[0040] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0041] Comparative Example 2: (Excessive Viscosity of Silicone Modification) The viscosity of the silicone-modified polyether in Comparative Example 2 is 800 mPa·s.

[0042] A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: 300 parts of polyoxyethylene ether (propylene glycol polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (trimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 95) are injected into a reaction vessel, nitrogen is introduced, the temperature is raised to 90° C. and dehydrated for 30 minutes; platinum catalyst is dropped into platinum-isopropanol catalyst, and the temperature is raised to 130° C. for reaction for 1 hour; after the reaction is completed, heating is stopped and the material is cooled to 50° C., a catalyst stabilizer (tetramethyldiethylamine) is added, and the mixture is stirred to room temperature to obtain a silicone-modified polyether (viscosity is 800 mPs); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0043] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0044] Comparative Example 3: (Viscosity of silicone modification is too low) The viscosity of the silicone-modified polyether in Comparative Example 3 is 100 mPa·s.

[0045] A method for preparing a low leakage point filter skeleton that is convenient for membrane composite comprises the following steps: Step 1: inject 100 parts of polyoxyethylene ether (methanol polyoxyethylene ether) and 100 parts of polymethylhydrogensiloxane (trimethylsilyl-terminated polymethylhydrogensiloxane, the number of chain segments is 10) into a reaction container, introduce nitrogen, heat to 90°C and dehydrate for 30 minutes; drop platinum catalyst into platinum-isopropanol catalyst, and heat to 130°C for reaction for 1 hour; after the reaction is completed, stop heating and cool the material to 50°C, add a catalyst stabilizer (tetramethyldiethylamine), and stir to room temperature to obtain a silicone-modified polyether (viscosity of 100 mPa·s); Step 2: After adding polyester material (polypropylene) slices into a hopper, feed them into a screw extruder to melt and extrude the polyester slices. The filtered melt is transported to the spinning assembly by a metering pump according to the flow rate. The melt flows out from multiple small holes of the spinneret of the spinning assembly and forms a thin stream. The melt thin stream is cooled by blowing cold air to form a fiber, and then enters the drawing device for drawing and elongation. After drawing, the fiber is laid on a mesh curtain with a blowing device. The spinning assembly is provided with two spinning pieces arranged before and after spinning. The fiber fineness of the spinning piece at the front end is 10dtex to 15dtex, and the fiber fineness of the spinning piece at the rear end is 5dtex to 7dtex. The fiber made of the front spinning piece is used to make a support layer, and the fiber of the rear spinning piece is used to make a composite layer. The support layer and the composite layer constitute a fiber skeleton; Step 3: soak the fiber skeleton prepared in step 2 in the organosilicon-modified polyether solution prepared in step 1, and after soaking, send the fiber skeleton into a roller to squeeze out excess organosilicon-modified polyether solution, and then dry the fiber skeleton attached with organosilicon-modified polyether at 80°C for 2 hours, and then dry at room temperature for 3 days to prepare a low leakage point filtration skeleton that is easy to composite with membrane.

[0046] A filter element comprises a hollow cylindrical filter element, end caps arranged at both ends of a filter layer, a gasket arranged on the filter element, and a frame sleeved on the outside of the filter element; the filter layer is a pleated filter medium in which each large pleat is provided with one small pleat, the filter element comprises a filter skeleton located on the outer surface and a polymer membrane (polytetrafluoroethylene membrane) located on the inner surface, and the filter skeleton is prepared by the above-mentioned method for preparing a low leakage point filter skeleton that is convenient for membrane composite.

[0047] Comparative Example 4: Compared with the embodiment, the filtering skeleton in comparative example 4 is only a skeleton layer, and the other conditions are the same as those of the embodiment.

[0048] Comparative Example 5: Compared with the embodiment, the filtration skeleton in comparative example 5 is only a composite layer, and the other conditions are the same as those of the embodiment.

[0049] The composite strength and filtration performance of the filter elements prepared in the above Examples 1 to 5 and Comparative Examples 1 to 4 were tested.

[0050] The composite strength test method uses a constant speed tensile testing machine, and the automatic recorder of the constant speed tensile testing machine records the value at least once every 1mm of the sample peeled off. The two fixtures equipped with the testing machine are calibrated on the same center line, aligned in parallel, and in the same plane in the moving direction. The entire clamped sample is moved at a constant speed of 5.0±0.2mm / s, and the load reading is recorded to obtain the peel strength. The sample width is 20±0.5mm and the length is 300mm.

[0051] The filtration performance test method adopts the pressure difference method. A pressure tester is used to test the pressure on both sides of the clean filter layer, and the pressure difference of the clean filter layer is calculated. The pressure difference is used as the initial filtration resistance of the filter layer. After multiple uses, the filter layer is tested to see if there are leaks. The above test results are shown in Table 1.

[0052] Table 1 Composite strength and filtration performance test results As shown in Table 1, the peel strengths of Examples 1 to 5 are between 4.83 N / cm and 4.91 N / cm, and the peel strength of Comparative Example 1 is 3.26 N / cm. The peel strengths of Examples 1 to 5 are significantly improved compared with Comparative Example 1. The above results show that the composite strength of the support skeleton and the filter membrane of the filter layer of the present invention is significantly improved after being treated with silicone-modified polyether. In addition, the initial filtration resistance of Examples 1 to 5 is between 28 Pa and 29 Pa, and the initial filtration of Comparative Example 1 is 30 Pa. The above results show that the initial filtration resistance of the filter layer of the present invention does not change significantly after being treated with silicone-modified polyether, and the filtration performance is not affected; compared with Comparative Example 2, the peel strength of Comparative Example 2 does not change significantly in Examples 1 to 5, but the initial filtration resistance of Comparative Example 2 is significantly lower than that of Examples 1 to 5, which shows that when the viscosity of the silicone-modified polyether is too large, the composite strength of the filter skeleton and the polymer filter membrane is not significantly improved, but the excessive viscosity will cause the internal pore size of the filter layer to change, resulting in a significant increase in the initial filtration resistance of the filter layer.

[0053] Compared with Examples 1 and 3, the peel strength of Example 3 of Examples 1 to 5 is higher than that of Example 1, but the improvement is not significant. This shows that the composite strength of the filter skeleton and the polymer filter membrane can be improved after treating the filter skeleton with silicone modified polyether, but the composite strength improvement is not significant when the viscosity of the silicone modified polyether is too small. Only within a fixed viscosity range can the composite strength of the filter skeleton and the polymer filter membrane be significantly improved while ensuring that the initial filtration resistance of the filter layer is not affected.

[0054] Comparative Examples 4 and 5 are technical solutions of using only the skeleton layer and only the composite layer respectively. The results show that when only the skeleton layer is used, leakage problems occur in the filter layer of the filter element after use, and when only the composite layer is used, the filter element structure is prone to collapse without the support of the skeleton layer, and effective filtration cannot be carried out and cannot be used.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a low leakage point filter skeleton that is convenient for membrane composite, characterized in that: The filter skeleton is made of polypropylene as raw material by a spunbond method. The filter skeleton comprises a support layer and a composite layer. The fiber fineness of the support layer is 10-15 dtex, and the fiber fineness of the composite layer is 5-7 dtex.

2. The method for preparing a low leakage point filtration framework for easy membrane composite according to claim 1, characterized in that: The surface density of the support layer is 25-50 warp threads / 10 cm, and the surface density of the weft threads is 25-50 threads / 10 cm.

3. The method for preparing a low leakage point filtration framework for easy membrane composite according to claim 1 or 2, characterized in that: The weight of the support layer is ≥100 g / m 2 .

4. The method for preparing a low leakage point filtration framework for easy membrane composite according to claim 1, characterized in that: The surface density of the composite layer is 15-25 warp threads / 10 cm, and the surface density of the weft threads is 15-25 threads / 10 cm.

5. The method for preparing a low leakage point filtration framework for easy membrane composite according to claim 1 or 4, characterized in that: The composite layer has a gram weight of 15-30 g / m 2 .

6. A filter element, characterized in that: The invention comprises a filter element, wherein the filter element comprises a filter layer and a filter skeleton compounded with the filter layer, and the filter skeleton is made by the preparation method of a low leakage point filter skeleton convenient for membrane compounding as claimed in any one of claims 1 to 5.

7. The filter element according to claim 6, characterized in that: The material of the filter layer includes one of polytetrafluoroethylene resin and polyethersulfone resin.

8. The filter element according to claim 6, characterized in that: A plurality of small folds are arranged on each large fold of the filter element.

9. The filter element according to claim 8, characterized in that: The number of the small folds is 1 to 3.

10. The filter element according to claim 6, characterized in that: The filter element also includes an end cover, a gasket and a frame sleeved on the outside of the filter element.

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