A flat sheet membrane element and its preparation method

Abstract

The present invention relates to the field of ultra-microfiltration membranes, and discloses a flat membrane element, which includes two layers of flat composite membranes superimposed on each other, and a plurality of hot-melt resins intersecting each other are arranged between the two layers of flat composite membranes. A small opening for water outlet is left around the two superimposed layers of flat composite membranes, and the rest are sealed and connected. The present invention also discloses a method for preparing a flat membrane element, which includes the following steps: S1, coating the surfaces of two rolls of flat composite membranes with hot-melt resin. S2, subjecting the two rolls of flat composite membranes coated with hot-melt resin to double-roll extrusion, so that the hot-melt resins on the flat composite membranes are fused into one in the shape of a "cross" to obtain an initial flat membrane element; S3, cutting the initial flat membrane element obtained in step S2 into the required size, welding the surroundings, leaving a small opening for water outlet, and obtaining a flat membrane element. The flat membrane element and the preparation method thereof of the present invention are simple and easy to operate, convenient for industrial production, and have good application prospects and economic value.

Description

Technical Field

[0001] The invention relates to the field of ultra-microfiltration membranes, and in particular to a flat membrane element and a preparation method thereof. Background Art

[0002] Membrane separation technology has been widely used in many fields such as water treatment, and ultrafiltration membrane plays an important role in the field of membrane water treatment. According to the different shapes and component forms, ultrafiltration membranes can be divided into rolled membranes, hollow membranes and flat membranes. Flat membranes have become one of the important ultrafiltration products in the field of water treatment due to their good pressure resistance, high mechanical strength and high pollution tolerance.

[0003] Traditional flat membranes for water treatment generally have three layers, the outer layer is a flat composite membrane layer, the middle is a support plate, which is generally made of ABS material, and there is a lining net or lining cloth between the membrane layer and the support plate for diversion. This type of flat membrane is durable and has good stability, but due to the presence of the support plate and the diversion mesh, the membrane element is bulky, inconvenient to install and transport, and the production cost is higher than that of hollow membranes and roll membranes, which limits its application. For this reason, flat membrane elements with low R&D costs and convenience are increasingly valued.

[0004] Patent CN 102512963 B discloses a flat membrane element for water treatment. The surface of the membrane element support plate has a boss. Adjacent membrane elements rely on the boss as a spacing support, which not only reduces membrane pollution, but also reduces the cost of the support plate by 30%. Patent CN 104014246 B discloses a double-membrane cross-flow filtration flat membrane assembly. The support plate is provided with a permeate guide groove, which increases the effective area of ​​the membrane and makes the replacement of the membrane simple and convenient. Patent CN 104226119 A discloses a split flat membrane. The support plate can be reused, reducing the cost of the flat membrane. The above patents are all focused on improving the support plate and water flow channel. In order to further reduce the cost to a level similar to that of hollow membranes and roll membranes, and to ensure that the performance of the membrane elements is not reduced, while simplifying the production process and improving production efficiency, it is particularly important to invent a new form of flat membrane. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a flat membrane element and a method for preparing the same. The filtering performance of the prepared flat membrane element is similar to that of a traditional flat membrane with a support plate, but the cost is only about one-third of that. In addition, the manufacturing specifications of the membrane element are not limited by the size of the support plate and the welding machine, and can be adjusted at any time, which greatly simplifies the production equipment and improves production efficiency.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a flat membrane element, which comprises two layers of superimposed flat composite membranes, wherein a plurality of intersecting hot-melt resins are arranged between the two layers of flat composite membranes; a small opening for water outlet is left around the two superimposed flat composite membranes, and the rest are sealed and connected.

[0008] Furthermore, the flat composite membrane comprises an organic polymer membrane layer and a non-woven fabric support layer, the organic polymer membrane layer is attached to the non-woven fabric support layer, and the hot melt resin is arranged on the non-woven fabric support layer.

[0009] Furthermore, the hot melt resin is ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer or acrylonitrile-butadiene-styrene copolymer.

[0010] Furthermore, the mutually intersecting hot-melt resins are in a cross shape.

[0011] Furthermore, the hot melt resin is spaced 75-150 mm in parallel and 25-50 mm in vertical spacing.

[0012] Furthermore, the length of the hot-melt resin is 50-100 mm, the width of the hot-melt resin is 8-12 mm, and the thickness of the hot-melt resin is 2.5-10 mm.

[0013] The present invention discloses a method for preparing a flat membrane element, which comprises the following steps:

[0014] S1. Two rolls of flat composite film are passed through rollers at the same speed at the same time, and a vertical "1"-shaped hot-melt resin is coated on the upper surface of one roll, and a horizontal "1"-shaped hot-melt resin is coated on the upper surface of the other roll.

[0015] S2. Two rolls of flat composite membranes coated with hot-melt resin are subjected to double-roll extrusion, so that the vertical hot-melt resin and the horizontal hot-melt resin on the flat composite membrane are fused into one in the shape of a "cross" to obtain an initial flat membrane element.

[0016] S3, cutting the initial flat membrane element obtained in step S2 into the required size, welding it around, leaving a small opening for water to flow out, and then obtaining the flat membrane element.

[0017] The flat composite membrane in step S1 has two layers, one layer is an organic polymer membrane layer, and the other layer is a non-woven fabric support layer, the organic polymer membrane layer is attached to the non-woven fabric support layer; and the hot melt resin is coated on the non-woven fabric support layer.

[0018] The hot melt resin in step S1 is ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer or acrylonitrile-butadiene-styrene copolymer. Depending on the non-woven fabric material (PP, PET, etc.) of the flat composite membrane, a hot melt resin material that can be firmly bonded can be used.

[0019] Furthermore, the hot melt resin in step S1 has a parallel spacing of 75-150 mm and a vertical spacing of 25-50 mm.

[0020] Furthermore, in step S1, a vertical "1"-shaped hot-melt resin is applied by a vertical hot-melt resin extruder, and a horizontal "I"-shaped hot-melt resin is applied by a horizontal hot-melt resin extruder; the hot-melt resin interval can be adjusted by the outlet interval of the hot-melt resin extruder.

[0021] Furthermore, the length of the hot-melt resin is 50-100 mm, the width of the hot-melt resin is 8-12 mm, and the thickness of the hot-melt resin is 2.5-10 mm.

[0022] Furthermore, the temperature of the hot melt resin during extrusion is 100-200°C, and the temperature of the hot melt resin during double-roll extrusion is 50-100°C.

[0023] Furthermore, the double rollers in step S2 are round stainless steel rollers, and the extrusion gap between the double rollers is 4-15 mm.

[0024] Furthermore, the welding in step S3 is hot melt welding or ultrasonic welding, and corresponding welding methods can be adopted according to different hot melt resins to ensure excellent airtightness of the membrane element.

[0025] Furthermore, the two rolls of flat composite films are made of the same material, and the material and temperature of the hot melt adhesive extruded from the two rolls of flat composite films are consistent.

[0026] The benefits of the present invention are:

[0027] 1. The flat membrane element prepared by the present invention utilizes the mechanical strength of the flat composite membrane itself as support, and does not require any support plate or other support material, thereby greatly reducing the cost. The membrane sheets are welded together by hot-melt resin, which increases the mechanical strength of the membrane element. The intervals between the hot-melt resins serve as water channels, and the membrane element no longer requires any lining cloth or lining mesh for diversion, thereby further significantly reducing the cost.

[0028] 2. The flat membrane element preparation method of the present invention is simple and easy to implement, convenient for industrial production, and has good application prospects and economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the preparation method of the present invention.

[0030] Figure 2 It is a flat composite film coated with a longitudinal hot-melt resin in the present invention.

[0031] Figure 3It is a flat composite film coated with a horizontally placed hot-melt resin in the present invention.

[0032] Figure 4 It is the finished product of the flat membrane element of the present invention.

[0033] Main component symbols:

[0034] 1-flat composite membrane, 2-roller, 3-vertical "1" shaped hot melt resin, 4-horizontal "I" shaped hot melt resin, 5-round stainless steel roller, 6-initial flat membrane element, 7-flat membrane element, 8-small mouth, 9-vertical hot melt resin extruder, 10-horizontal hot melt resin extruder. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Embodiment 1:

[0037] like Figure 1-4 As shown, two rolls of flat composite film 1 of the same material are taken. The flat composite film 1 has two layers, one layer is an organic polymer film layer, and the other layer is a non-woven fabric support layer. The organic polymer film layer is attached to the non-woven fabric support layer. One roll is placed at the front end of the vertical hot melt resin extruder 9, and the other roll is placed at the front end of the horizontal hot melt resin extruder 10. The two rolls of flat composite film 1 pass through the roller 2 at the same speed and reach the extruder. Ethylene-vinyl acetate copolymer is added to the two hot melt resin extruders, and the hot melt temperature is set to 100°C. The air is isolated to heat and melt the ethylene-vinyl acetate copolymer into a liquid state, and then it is applied in strips on the non-woven fabric support layer of the flat composite film 1. The parameters of the hot melt resin extruder are set, and the hot melt resin is adjusted to have a parallel interval of 75mm, a vertical interval of 25mm, a length of 50mm, a width of 10mm, and a thickness of 2.5mm. A vertical "1"-shaped hot melt resin 3 film is applied, as shown Figure 2 As shown, a film of a horizontal "I"-shaped hot-melt resin 4 is applied, such as Figure 3 As shown, two rolls of flat composite membrane 1 coated with hot-melt resin are sent to the extrusion place of round stainless steel roller 5 through roller 2, the hot-melt resin is cooled to 50°C in the air, and the extrusion gap of round stainless steel roller 5 is adjusted to 4mm. After being extruded by round stainless steel roller 5, the hot-melt resins at two places are fused together in a "cross" shape, so that the two rolls of flat composite membrane 1 are made into initial flat membrane element 6. The initial flat membrane element 6 is cut and then welded around by hot-melt welding machine, leaving a small opening 8 for water discharge, and the finished flat membrane element 7 can be obtained, as shown in FIG. Figure 4The total mass of the flat membrane element per square meter is only 500g, which is about one-third of the mass of the conventional flat membrane supported by the same support plate. Its sewage flux is equivalent to that of the conventional flat membrane, and its manufacturing cost is about one-third of that of the conventional flat membrane.

[0038] Embodiment 2:

[0039] like Figure 1-4 As shown, two rolls of flat composite film 1 of the same material are taken. The flat composite film 1 has two layers, one layer is an organic polymer film layer, and the other layer is a non-woven fabric support layer. The organic polymer film layer is attached to the non-woven fabric support layer. One roll is placed at the front end of the vertical hot melt resin extruder 9, and the other roll is placed at the front end of the horizontal hot melt resin extruder 10. The two rolls of flat composite film 1 pass through the roller 2 at the same speed and reach the extruder. Ethylene-vinyl alcohol copolymer is added to the two hot melt resin extruders, and the hot melt temperature is set to 180°C. The air is isolated to heat and melt the ethylene-vinyl alcohol copolymer into a liquid state, and then it is applied in strips on the non-woven fabric support layer of the flat composite film 1. The parameters of the hot melt resin extruder are set, and the hot melt resin is adjusted to have a parallel interval of 150mm, a vertical interval of 50mm, a length of 100mm, a width of 10mm, and a thickness of 10mm. The film coated with the vertical "1"-shaped hot melt resin 3 is as shown in the attached Figure 2 As shown, the film of the horizontal "I"-shaped hot-melt resin 4 is coated as shown in FIG. Figure 3 As shown, two rolls of flat composite membrane 1 coated with hot-melt resin are sent to the extrusion place of round stainless steel roller 5 through roller 2. The hot-melt resin is cooled to 90°C in the air. The extrusion gap of round stainless steel roller 5 is adjusted to 15mm. After being extruded by round stainless steel roller 5, the hot-melt resins at two places are fused together in a "cross" shape, so that the two rolls of flat composite membrane 1 are made into initial flat membrane element 6. The initial flat membrane element 6 is cut and then welded around by hot-melt welding machine, leaving a small opening 8 for water discharge, and the finished flat membrane element 7 can be obtained. Figure 4 The total mass of the flat membrane element per square meter is only 300g, which is about one-fifth of the mass of the conventional flat membrane supported by the same support plate. Its sewage flux is equivalent to that of the conventional flat membrane, and its manufacturing cost is about one-third of that of the conventional flat membrane.

[0040] Embodiment 3:

[0041] like Figure 1-4As shown, two rolls of flat composite film 1 of the same material are taken. The flat composite film 1 has two layers, one layer is an organic polymer film layer, and the other layer is a non-woven fabric support layer. The organic polymer film layer is attached to the non-woven fabric support layer. One roll is placed at the front end of the vertical hot melt resin extruder 9, and the other roll is placed at the front end of the horizontal hot melt resin extruder 10. The two rolls of flat composite film 1 pass through the roller 2 at the same speed and reach the extruder. Add acrylonitrile-butadiene-styrene copolymer into the two hot melt resin extruders, set the hot melt temperature to 200°C, isolate the air to heat and melt the acrylonitrile-butadiene-styrene copolymer into a liquid state, and then apply it in strips on the non-woven fabric support layer of the flat composite film 1. Set the parameters of the hot melt resin extruder, adjust the parallel spacing of the hot melt resin to 100mm, the vertical spacing to 40mm, the length to 80mm, the width to 10mm, and the thickness to 5mm. The film coated with the vertical "1"-shaped hot melt resin 3 is as shown Figure 2 As shown, the film of the horizontal "I"-shaped hot-melt resin 4 is coated as shown in FIG. Figure 3 As shown, two rolls of flat composite membrane 1 coated with hot-melt resin are sent to the extrusion position of the round stainless steel roller 5 through the roller 2. The hot-melt resin is cooled to 100°C in the air, and the extrusion gap of the round stainless steel roller 5 is adjusted to 8mm. After being extruded by the round stainless steel roller 5, the hot-melt resins at two places are fused together in a "cross" shape, so that the two rolls of flat composite membrane 1 are made into an initial flat membrane element 6. The initial flat membrane element 6 is cut and then welded around by an ultrasonic welding machine, leaving a small opening 8 for water discharge, and a finished flat membrane element 7 can be obtained. Figure 4 The total mass of the flat membrane element per square meter is only 400g, which is about a quarter of the mass of the conventional flat membrane supported by the same support plate. Its sewage flux is equivalent to that of the conventional flat membrane, and its manufacturing cost is about one-third of that of the conventional flat membrane.

[0042] In summary, the flat membrane element prepared by the present invention uses the mechanical strength of the flat composite membrane itself as support, and does not require any support plate or other support, thereby greatly reducing the cost. The membrane sheets are welded together by hot-melt resin, which increases the mechanical strength of the membrane element. The intervals between the hot-melt resins serve as water channels, and the membrane element no longer requires any lining cloth or lining mesh for flow diversion, thereby further significantly reducing the cost. In addition, the manufacturing specifications of the membrane element are not limited by the size of the support plate and the welding machine, and can be adjusted at any time, which greatly simplifies the production equipment and improves production efficiency.

[0043] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a flat membrane element, characterized in that: The steps include: S1, passing two rolls of flat composite film through rollers at the same speed at the same time, coating the upper surface of one roll with a vertical "1"-shaped hot melt resin, and coating the upper surface of the other roll with a horizontal "1"-shaped hot melt resin; S2, subjecting two rolls of flat composite membranes coated with hot-melt resin to double-roll extrusion, so that the vertical hot-melt resin and the horizontal hot-melt resin on the flat composite membrane are fused into one in the shape of a "cross" to obtain an initial flat membrane element; S3, cutting the initial flat membrane element obtained in step S2 into the required size, welding it around, leaving a small opening for water to flow out, and then obtaining the flat membrane element.

2. The method for preparing a flat membrane element according to claim 1, characterized in that: The flat composite membrane in step S1 has two layers, one layer is an organic polymer membrane layer, and the other layer is a non-woven fabric support layer. The organic polymer membrane layer is attached to the non-woven fabric support layer; and the hot melt resin is coated on the non-woven fabric support layer.

3. The method for preparing a flat membrane element according to claim 1, characterized in that: The hot melt resin in step S1 is ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer or acrylonitrile-butadiene-styrene copolymer.

4. The method for preparing a flat membrane element according to claim 1, characterized in that: The hot melt resin in step S1 is spaced 75-150 mm in parallel and 25-50 mm in vertically; In the step S1, a vertical "1"-shaped hot-melt resin is applied by a vertical hot-melt resin extruder, and a horizontal "I"-shaped hot-melt resin is applied by a horizontal hot-melt resin extruder; the hot-melt resin interval can be adjusted by the discharge port interval of the hot-melt resin extruder; The length of the hot melt resin is 50-100 mm, the width of the hot melt resin is 8-12 mm, and the thickness of the hot melt resin is 2.5-10 mm; The temperature of the hot melt resin extrusion is 100-200°C, and the temperature of the hot melt resin reaching the double roll extrusion is 50-100°C; The double rollers in step S2 are round stainless steel rollers, and the extrusion gap between the double rollers is 4-15 mm; The welding in step S3 is heat-melt welding or ultrasonic welding; The two rolls of flat composite films are made of the same material, and the material and temperature of the hot melt adhesive extruded from the two rolls of flat composite films are consistent.

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