JP2019013914A - Hollow fiber membrane, and manufacturing method for hollow fiber membrane - Google Patents

Abstract

To provide a hollow fiber membrane capable of attaining compatibility between chemical resistance and mechanical durability.SOLUTION: A hollow fiber membrane in one embodiment includes a hollow support medium organized from one or a plurality of string bodies, a porous joint layer laminated on an outer surface of the support medium, and having at least a part deposited on the support medium, and a porous filter sheet laminated on a reverse side to a support medium side of the joint layer, on which at least a part of the joint layer is deposited.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hollow fiber membrane and a method for producing the hollow fiber membrane.

  Conventionally, hollow fiber membranes are known as filtration membranes for water treatment. The hollow fiber membrane is an elongated tubular filtration membrane whose one end is closed, and it filters the water to be treated coming into contact from the outside to obtain filtered water on the inside.

  As a hollow fiber membrane, for example, a porous stretch tube made of polytetrafluoroethylene is used as a support, and a filtration layer is provided on the outer surface of this support layer (Patent Document 1), and knitted with a plurality of resin fine wires A hollow braid is used as a support, and a porous membrane layer is provided on the outer surface of this support (Patent Document 2).

  In the hollow fiber membrane of Patent Document 1, a belt-like porous resin sheet (filtration layer) is spirally wound around the outer surface of a porous stretched tube (support) made of polytetrafluoroethylene, and the support and the filtration layer are attached. They are welded at a temperature equal to or higher than these melting points (350 ° C.) to integrate them, and have improved mechanical durability and chemical resistance.

  Moreover, the hollow fiber membrane of patent document 2 apply | coats the film-forming stock solution of a porous membrane layer to the outer surface of the hollow braid (support) knitted with the thread | yarn which consists of several resin fine wires, and forms a film in a support body The film-forming stock solution is solidified with the stock solution entering to form a porous membrane layer, and the adhesive strength between the support and the porous membrane layer is improved.

JP 2004-141753 A Japanese Patent No. 5341760

  The hollow fiber membrane for water treatment is required to have a certain water permeability and mechanical durability and chemical resistance. The hollow fiber membrane of Patent Document 1 uses a stretched porous body that does not have a very high tensile strength as a support, and has a configuration in which a filtration layer is directly joined to this support. Further improvement is necessary to improve mechanical durability. Moreover, since the hollow fiber membrane of patent document 2 needs to select the membrane-forming stock solution which can be solidified as a material of a porous membrane layer, polytetrafluoroethylene etc. with high chemical resistance are made into a porous membrane layer. The material of the porous membrane layer is limited.

  This invention is made | formed based on the above situations, and it aims at providing the manufacturing method of this hollow fiber membrane which can make chemical resistance and mechanical durability compatible, and this hollow fiber membrane. .

  A hollow fiber membrane according to an aspect of the present invention made to solve the above problems is knitted with one or a plurality of strings, and is laminated on a porous hollow support and an outer surface of the support. A porous bonding layer in which at least a portion is welded to the support, and a porous filtration sheet that is laminated on the opposite side of the bonding layer to the support, and at least a portion of the bonding layer is welded. Prepare.

  The method for producing a hollow fiber membrane according to another aspect of the present invention made to solve the above problems includes a step of thermally laminating a porous bonding layer and a porous filtration sheet, and one or a plurality of strings. A step of contacting the outer surface of the hollow support having a porosity and the bonding layer side of the sheet after the heat laminating step, and thermally laminating the support and the sheet after the heat laminating step. Have.

  The present invention can provide a hollow fiber membrane that can achieve both chemical resistance and mechanical durability.

It is typical sectional drawing which shows a part of cross section which cut | disconnected the hollow fiber membrane which concerns on one Embodiment of this invention along the longitudinal direction. It is a typical perspective sectional view showing a hollow fiber membrane concerning one embodiment of the present invention.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  A hollow fiber membrane according to one embodiment of the present invention is knitted with one or a plurality of string bodies, and is laminated on a porous support body having porosity and an outer surface of the support body, and at least a part of the hollow support film is formed on the support body. A porous bonding layer to be welded and a porous filter sheet that is laminated on the opposite side of the bonding layer to the support side and to which at least a part of the bonding layer is welded.

  The hollow fiber membrane includes a bonding layer between the support and the filtration sheet, and since the bonding layer is welded to the support and the filtration sheet to join them, the support and the filtration sheet can be strongly bonded to each other. And the material of the filter sheet can be selected relatively freely. Moreover, since the support body of the hollow fiber membrane is knitted with one or a plurality of string bodies, it has high tensile strength and moderate flexibility. For this reason, since the hollow fiber membrane uses a support having a high tensile strength as a base, and the filter sheet is bonded to the support through a bonding layer, the filter sheet peels off from the support even during bending deformation. Difficult and has high pressure resistance during filtration or backwashing. In other words, the hollow fiber membrane can be selected from materials having high chemical resistance as a material for the support and the filtration sheet, and structurally improves mechanical durability. Both durability can be achieved.

  The support is formed in a cylindrical shape, the filtration sheet is formed in a strip shape, and the filtration sheet is wound spirally and in a stripe shape around the outer surface of the support via the bonding layer. It should be turned. Thereby, a support body and a filtration sheet are joined easily and reliably via a joining layer.

  It is good for the said string to be knitted with 8 or more and 32 or less resin fine wires. The string body for knitting the support is knitted with 8 or more and 32 or less resin fine wires, so that the mechanical strength of the support is further improved.

  The bonding layer may be a nonwoven fabric or a porous resin. Thereby, when the hollow fiber membrane is bent and deformed, the bonding layer is appropriately deformed to disperse the stress, so that the filtration sheet is more difficult to peel from the support.

  The main component of the filter sheet is preferably polytetrafluoroethylene. The hollow fiber membrane is improved in chemical resistance by being used in a filtration sheet in which polytetrafluoroethylene having high chemical resistance is disposed on the outer surface. Here, the main component indicates a component having the largest content, for example, a component having a content of 50% by mass or more.

  The average thickness of the filtration sheet is 12 μm or more and 100 μm or less, the average pore diameter of the filtration sheet is 0.01 μm or more and 0.45 μm or less, and the bubble point of the hollow fiber membrane is 80 kPa or more and 200 kPa or less. Thereby, the water permeation performance and impurity removal performance of the hollow fiber membrane are adjusted in a well-balanced manner. Here, the average pore diameter is a value obtained by observing 10 or more holes with a microscope and averaging the average value of the maximum diameter of the holes and the diameter in the direction perpendicular to the maximum diameter over the entire sample. Moreover, a bubble point shows the value measured using isopropyl alcohol based on JIS-K3832 (1990).

  A method for producing a hollow fiber membrane according to another aspect of the present invention is a method for producing a hollow fiber membrane, the step of thermally laminating a porous bonding layer and a porous filter sheet, and one or more The outer surface of the hollow support body that is knitted with a string and is porous is brought into contact with the bonding layer side of the sheet after the thermal laminating process, and the support body and the sheet after the thermal laminating process are thermally laminated. Process.

  In the manufacturing method of the hollow fiber membrane, since the bonding layer is welded to the support after the bonding layer is welded to the filtration sheet, the support and the filtration sheet are relatively easy to connect via the bonding layer. Can be joined. In other words, the hollow fiber membrane production method can relatively easily produce a hollow fiber membrane having both chemical resistance and mechanical durability.

[Details of the embodiment of the present invention]
Hereinafter, a hollow fiber membrane and a method for producing the hollow fiber membrane according to an embodiment of the present invention will be described with reference to the drawings as appropriate.

[Hollow fiber membrane]
The hollow fiber membrane 1 shown in FIGS. 1 and 2 is knitted with one or a plurality of string bodies, and is laminated on a hollow support body 2 having porosity and an outer surface of the support body 2, and at least a part of the support body 2. A porous bonding layer 3 that is welded to the substrate, and a porous filtration sheet 4 that is laminated on the side opposite to the support 2 side of the bonding layer 3 and to which at least a part of the bonding layer 3 is welded.

  The string for knitting the support 2 is knitted with 8 to 32 resin fine wires, and the support 2 is formed in a cylindrical shape. The bonding layer 3 is a nonwoven fabric or a porous resin. The filter sheet 4 is formed in a band shape. The main component of the filter sheet 4 is polytetrafluoroethylene, the average thickness of the filter sheet 4 is 12 μm or more and 100 μm or less, and the average pore diameter of the filter sheet 4 is 0.01 μm or more and 0.45 μm or less. The filtration sheet 4 is wound spirally and in a striped manner on the outer surface of the support 2 via the bonding layer 3. The bubble point of the hollow fiber membrane 1 is 80 kPa or more and 200 kPa or less.

  The hollow fiber membrane 1 is a hollow fiber membrane used for water treatment, and is laminated so that the bonding layer 3 and the filter sheet 4 overlap in this order on the outer surface of the support 2 as shown in FIG. . As shown in FIG. 2, the hollow fiber membrane 1 is configured in a cylindrical shape so as to filter the water to be treated coming into contact with the filtration sheet 4 and obtain the filtered water in the hollow portion 5 inside the support 2. .

  As a minimum of a bubble point of hollow fiber membrane 1, 80 kPa is preferred, 100 kPa is more preferred, and 120 kPa is still more preferred. On the other hand, the upper limit of the bubble point of the hollow fiber membrane 1 is preferably 200 kPa, more preferably 180 kPa, and even more preferably 160 kPa. If the bubble point of the hollow fiber membrane 1 is less than the lower limit, the water to be treated may not be sufficiently filtered. On the other hand, when the bubble point of the hollow fiber membrane 1 exceeds the above upper limit, the water flow resistance increases, and the filtration efficiency may decrease.

<Support>
The support 2 is a member that becomes a base of the hollow fiber membrane 1 and is formed in a cylindrical shape. The support body 2 is knitted with one or a plurality of string bodies, and has a porosity that allows filtered water to pass through the gaps between the string bodies. A hollow portion 5 is formed inside the support 2.

  As a minimum of average thickness (average thickness) of support 2, 0.1 mm is preferred, 0.3 mm is more preferred, and 0.5 mm is still more preferred. On the other hand, the upper limit of the average thickness of the support 2 is preferably 2 mm, more preferably 1.7 mm, and even more preferably 1.5 mm. If the average thickness of the support 2 is less than the lower limit, the mechanical strength of the support 2 may be insufficient. Conversely, when the average thickness of the support 2 exceeds the above upper limit, the hollow fiber membrane 1 becomes too thick, so that when the plurality of hollow fiber membranes 1 are used, the number density of the hollow fiber membranes 1 decreases. There is a possibility that the filtration efficiency is lowered.

(String)
The string body for knitting the support body 2 is knitted with a plurality of fine resin wires in order to improve the mechanical strength. Although it does not specifically limit as a material of a resin fine wire, For example, polyester, such as a polyethylene terephthalate, resin which has polyethylene or a polypropylene as a main component is used.

  As a minimum of the number of the resin fine wires which knit a string object, 8 are preferred, 10 are more preferred, and 12 are still more preferred. On the other hand, the upper limit of the number of resin fine wires knitting the string is preferably 32, more preferably 28, and even more preferably 24. If the number of resin fine wires knitting the string is less than the lower limit, the mechanical strength of the string may be insufficient. Conversely, if the number of resin fine wires knitting the string exceeds the upper limit, the manufacturing cost of the string may increase.

<Junction layer>
The bonding layer 3 is an intermediate layer that bonds the support 2 and the filter sheet 4 by welding the surface contacting the support 2 to the support 2 and welding the surface contacting the filter sheet 4 to the filter sheet 4. And laminated between the outer surface of the cylindrical support 2 and the inner surface of the filter sheet 4. The bonding layer 3 is dissolved by a predetermined thickness from the surface in contact with the support 2, is bonded to the support 2 in the dissolved thickness region, and is dissolved by a predetermined thickness from the surface in contact with the filtration sheet 4, It joins with the filtration sheet 4 in this melt | dissolved thickness area | region. As the bonding layer 3, a porous resin or a nonwoven fabric obtained by heat-treating resin powder is used. The material of the porous resin or the nonwoven fabric is not particularly limited, and for example, a porous resin mainly composed of polyester such as polyethylene terephthalate, polyethylene, or polypropylene is used. The bonding layer 3 is preferably made of the same material as the support 2 from the viewpoint of improving the affinity in bonding with the support 2.

  The lower limit of the average thickness of the bonding layer 3 is preferably 10 μm, more preferably 20 μm, and even more preferably 30 μm. On the other hand, the upper limit of the average thickness of the bonding layer 3 is preferably 200 μm, more preferably 150 μm, and even more preferably 100 μm. If the average thickness of the bonding layer 3 is less than the lower limit, the welding to the support 2 and the filter sheet 4 may be insufficient, and the bonding force of the bonding layer 3 may be insufficient. Conversely, when the average thickness of the bonding layer 3 exceeds the above upper limit, the hollow fiber membrane 1 becomes too thick, so that when the plurality of hollow fiber membranes 1 are used, the number density of the hollow fiber membranes 1 decreases. There is a possibility that the filtration efficiency is lowered.

  Since the bonding layer 3 is welded to the support 2 and the filter sheet 4 when the hollow fiber membrane 1 is manufactured, it is preferable that the melting point is not more than the melting point of the support 2 and not more than the melting point of the filter sheet 4. For example, when polytetrafluoroethylene (melting point: about 327 ° C.) is used as the filter sheet 4 and polyethylene terephthalate, polyethylene, or polypropylene (melting point: about 110 ° C. to 260 ° C.) is used as the support member 2, the support member 2 is used as the bonding layer 3. It is preferable to use the same material as that described above or a material having a melting point lower than that of the support 2.

<Filtration sheet>
The filtration sheet 4 is a belt-like porous sheet that is disposed on the outer surface of the bonding layer 3 and has a function of filtering water to be treated. As the filter sheet 4, a porous resin having chemical resistance is preferably used, and a porous resin mainly composed of polytetrafluoroethylene is used. The filtration sheet 4 is disposed so as to cover the outer surface of the hollow fiber membrane 1 by being wound in a spiral shape and a stripe shape around the outer surface of the cylindrical support 2. Moreover, the filtration sheet 4 is wound around the outer surface of the support 2 without a gap so that the side portions overlap. That is, the hollow fiber membrane 1 has an overlapping portion 6 in which the filtration sheet 4 is overlapped in a spiral shape and a stripe shape. In addition, in the superimposition part 6, the support body 2, the joining layer 3, the filtration sheet 4, the joining layer 3, and the filtration sheet 4 are joined in this order.

  As a minimum of average thickness of filter sheet 4, 12 micrometers is preferred, 15 micrometers is more preferred, and 18 micrometers is still more preferred. On the other hand, the upper limit of the average thickness of the filter sheet 4 is preferably 100 μm, more preferably 80 μm, and even more preferably 60 μm. If the average thickness of the filtration sheet 4 is less than the lower limit, the water to be treated may not be sufficiently filtered. On the contrary, if the average thickness of the filtration sheet 4 exceeds the upper limit, the water flow resistance may increase and the filtration efficiency may decrease.

  The lower limit of the average pore diameter of the filter sheet 4 is preferably 0.01 μm, more preferably 0.05 μm, and still more preferably 0.10 μm. On the other hand, the upper limit of the average pore diameter of the filter sheet 4 is preferably 0.45 μm, more preferably 0.40 μm, and still more preferably 0.35 μm. If the average pore diameter of the filter sheet 4 is less than the above lower limit, the water flow resistance may increase and the filtration efficiency may decrease. Conversely, if the average pore diameter of the filter sheet 4 exceeds the above upper limit, the water to be treated may not be sufficiently filtered.

[Method for producing hollow fiber membrane]
The method for producing the hollow fiber membrane is a method for producing the hollow fiber membrane 1, and includes a first laminating step of thermally laminating the porous bonding layer 3 and the porous filter sheet 4, and one or a plurality of strings. The outer surface of the hollow support body 2 that is knitted and has a porosity is brought into contact with the bonding layer 3 side of the sheet after the first laminating step, and the support body 2 and the sheet after the first laminating step are thermally laminated. 2 laminating process.

<First laminating step>
In the first laminating step, the bonding layer 3 and the filtration sheet 4 are thermally laminated in a state where the bonding layer 3 is laminated on one surface of the filtration sheet 4 so as to overlap with each other in plan view. To weld. As the bonding layer 3, one having a melting point lower than that of the filter sheet 4 is used.

  The method of thermal lamination is not particularly limited. For example, after one surface side of the bonding layer 3 is dissolved by a predetermined thickness, the filtration sheet 4 is cooled in a state in which the filter sheet 4 is brought into contact with the dissolution surface. In a state where the bonding layer 3 is welded to 4 and the bonding layer 3 and the filtration sheet 4 are laminated, the bonding layer 3 in the vicinity of the filtration sheet 4 is dissolved by a predetermined thickness by heating from the filtration sheet 4 side, A method of welding the bonding layer 3 to the filter sheet 4 by cooling is used. The bonding layer 3 is preferably dissolved by a predetermined thickness at a temperature that is higher by about 10 ° C. to 50 ° C. than the melting point of the bonding layer 3.

  The laminated sheet after the first laminating step is processed into a band shape using a method such as cutting before the second laminating step. In addition, since the shape of the lamination sheet after a 1st lamination process should just be a strip | belt shape, it replaces with the method of processing the lamination sheet after a 1st lamination process, and uses a 1st lamination process using the strip | belt-shaped filtration sheet 4, for example. A method of obtaining a belt-like laminated sheet by executing may be adopted.

<Second laminating step>
In the second laminating step, the laminated sheet and the support 2 are thermally laminated in a state where the bonding layer 3 side of the laminated sheet after the first laminating step and the outer surface of the cylindrical support 2 are brought into contact with each other. Thereby, the bonding layer 3 is welded to the support 2. As the support 2, the same material as the bonding layer 3 may be used, or a material having a melting point higher than that of the bonding layer 3 may be used.

  When the belt-like laminated sheet and the support 2 are laminated, as shown in FIG. 2, the belt-like laminated sheet is wound spirally and in a striped manner on the outer surface of the cylindrical support 2. Thus, the bonding layer 3 and the filter sheet 4 are laminated on the outer surface of the support 2 in this order. Since the outer surface of the manufactured hollow fiber membrane 1 needs to be covered with the filtration sheet 4 without a gap, the belt-like laminated sheet is spiral and striped with respect to the support 2 so that the side portions overlap. Wound around.

  The heat laminating method is not particularly limited. For example, after the bonding layer 3 side of the belt-like laminated sheet is dissolved by a predetermined thickness, the outer surface of the support 2 and the upper surface of the side portion of the laminated sheet are attached to the dissolved surface. A method is used in which the bonding layer 3 is welded to the support 2 by winding the belt-shaped laminated sheet spirally and in a stripe shape around the support 2 while making contact. The bonding layer 3 is preferably dissolved by a predetermined thickness at a temperature that is higher by about 10 ° C. to 50 ° C. than the melting point of the bonding layer 3.

(advantage)
The hollow fiber membrane 1 includes a bonding layer 3 between the support 2 and the filtration sheet 4, and the bonding layer 3 is welded to and bonded to the support 2 and the filtration sheet 4. 4 is strongly joined. Since the support 2 of the hollow fiber membrane 1 is knitted by a string knitted with 8 or more and 32 or less resin fine wires, it has high tensile strength and moderate flexibility. Since the bonding layer 3 of the hollow fiber membrane 1 is a non-woven fabric or a porous resin, the hollow fiber membrane 1 is appropriately deformed and disperses stress when the hollow fiber membrane 1 is bent and deformed. For this reason, the hollow fiber membrane 1 uses the support 2 having a high tensile strength as a base, and the filtration sheet 4 is joined to the support 2 via the joining layer 3. And the joining layer 3 is hard to peel from the support body 2, and the pressure resistance at the time of filtration or backwashing is high. Moreover, since the polytetrafluoroethylene with high chemical resistance is used for the filtration sheet 4 of the hollow fiber membrane 1, the hollow fiber membrane 1 achieves both chemical resistance and mechanical durability. Further, since the hollow fiber membrane 1 has a bubble point of 80 kPa or more and 200 kPa or less, the water permeability performance and the impurity removal performance are adjusted in a well-balanced manner.

  In the manufacturing method of the hollow fiber membrane, since the joining layer 3 is welded to the filter sheet 4 and then the joining layer 3 of this sheet is welded to the support 2, The filter sheet 4 can be joined relatively easily. Moreover, since the manufacturing method of the said hollow fiber membrane winds the strip | belt-shaped filtration sheet 4 helically and in stripes so that a side part may overlap with the outer surface of the cylindrical support body 2, an outer surface is The hollow fiber membrane 1 covered with the filtration sheet 4 without gaps can be produced, and the support 2 and the filtration sheet 4 can be easily and reliably bonded via the bonding layer 3.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  Although the said embodiment demonstrated what the support body 2 was formed in a cylinder shape, the support body 2 should just be formed with the hollow part 5 inside, and the shape of the support body 2 is not limited to a cylinder shape.

  In the above embodiment, the belt-shaped filtration sheet 4 is spirally and striped around the outer surface of the cylindrical support 2. However, the filtration sheet 4 is supported via the bonding layer 3. If it is a laminated structure joined to the outer surface of the body 2, the support body 2, the joining layer 3, and the filtration sheet 4 may be joined by other procedures.

  The hollow fiber membrane produced by the hollow fiber membrane of the present invention and the hollow fiber membrane production method of the present invention can achieve both chemical resistance and mechanical durability.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane 2 Support body 3 Bonding layer 4 Filtration sheet 5 Hollow part 6 Overlapping part

Claims (7)

A hollow support body knitted with one or a plurality of string bodies and having porosity;
A porous bonding layer laminated on the outer surface of the support, at least a portion of which is welded to the support;
A hollow fiber membrane comprising: a porous filtration sheet that is laminated on a side opposite to the support side of the bonding layer and to which at least a part of the bonding layer is welded. The support is formed in a cylindrical shape,
The filtration sheet is formed in a strip shape,
The hollow fiber membrane according to claim 1, wherein the filtration sheet is wound in a spiral shape and a stripe shape around the outer surface of the support via the bonding layer.   The hollow fiber membrane according to claim 1 or 2, wherein the string is knitted with 8 to 32 fine resin wires.   The hollow fiber membrane according to claim 1, wherein the bonding layer is a nonwoven fabric or a porous resin.   The hollow fiber membrane according to any one of claims 1 to 4, wherein a main component of the filtration sheet is polytetrafluoroethylene. The average thickness of the filtration sheet is 12 μm or more and 100 μm or less,
The average pore size of the filtration sheet is 0.01 μm or more and 0.45 μm or less,
The hollow fiber membrane according to any one of claims 1 to 5, wherein a bubble point is 80 kPa or more and 200 kPa or less. A method for producing a hollow fiber membrane comprising:
Heat laminating a porous bonding layer and a porous filter sheet;
An outer surface of a hollow support body that is knitted with one or a plurality of cords and has porosity, and the bonding layer side of the sheet after the thermal laminating step are brought into contact, and the support body and the sheet after the thermal laminating step are contacted A method for producing a hollow fiber membrane, comprising a step of heat laminating.

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