JP2020049473A - Semipermeable membrane support body - Google Patents

Abstract

To provide a semipermeable membrane support body that resolves a failure due to flexure in a width direction of a membrane filter when transporting a roll in a step of forming a semipermeable membrane and a step of processing an element.SOLUTION: A semipermeable membrane support body is made of a nonwoven fabric obtained by containing at least a main body synthetic fiber and a binder synthetic fiber. The semipermeable membrane support body has a MD directional curl of +0.5 mm or more and +50 mm or less.SELECTED DRAWING: None

Description

The present invention relates to a semipermeable membrane support.

  BACKGROUND ART Semipermeable membranes are widely used in the fields of desalination of seawater, water purifiers, food concentration, wastewater treatment, production of ultrapure water for medical treatment represented by hemofiltration, semiconductor cleaning, and the like. The semipermeable membrane is made of a synthetic resin such as a cellulose resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, a polyester resin, and a polyamide resin. However, since the semipermeable membrane alone has poor mechanical strength, it is used in the form of a "filtration membrane" in which a semipermeable membrane is provided on one surface of a semipermeable membrane support made of a fiber base material such as a nonwoven fabric or a woven fabric. I have. Further, industrially, a semipermeable membrane is continuously formed on a long semipermeable membrane support such as a roll.

  In the semipermeable membrane forming process, when the semipermeable membrane liquid is applied to the semipermeable membrane support, it is curved in the width direction, and then, when processed in a coagulation / washing tank by roll transport, an uneven semipermeable membrane is produced. There was a problem. As a solution to this problem, it has been disclosed that the tensile strength ratio between the papermaking flow direction and the width direction is 2: 1 to 1: 1 (for example, see Patent Document 1).

  Also, after coating the semipermeable membrane liquid on the semipermeable membrane support, the filter membrane is bent in the width direction due to shrinkage during curing of the semipermeable membrane, and when the element is processed, the filter membrane passes through the line well. There has been a problem that such troubles as not being possible occur. As a solution to this, the degree of thermal fusion of the organic synthetic fibers in the middle layer portion of the nonwoven fabric having a one-layer structure and made of one type of polyester-based fiber is determined by the degree of thermal fusion of the organic synthetic fibers in the coated surface portion and the non-coated surface portion. It is disclosed that the distance is made lower (for example, see Patent Document 2).

  In recent years, it has been required to reduce the thickness of the semipermeable membrane support in order to increase the area of the filtration membrane that can be incorporated into the element and increase the amount of permeated water per element. In the techniques of Patent Literature 1 and Patent Literature 2, when the thickness of the semipermeable membrane support is reduced, the curvature in the width direction may increase in the semipermeable membrane forming step, and a problem occurs during element processing. There was a case.

  Patent Literature 3 discloses that, even when the basis weight of the semipermeable membrane support is lightened and reduced, bending in the width direction due to shrinkage of the semipermeable membrane is suppressed, and tension is reduced as a means for reducing defects during element processing. A plurality of nonwoven fabric sheets having different strength aspect ratios are laminated, and in a state of being subjected to heat and pressure treatment, a semipermeable membrane support in which a bonding surface with a semipermeable membrane is curved in a width direction and a convex center is described. ing. However, the inventors of the present invention have studied that, since the semipermeable membrane support is curled in the width direction, even if the tension applied to the roll during the roll conveyance is adjusted, In some cases, the curvature at both ends cannot be suppressed, and the semipermeable membrane liquid cannot be applied uniformly.

Japanese Patent No. 5291274 Japanese Patent No. 5203518 JP 2012-135713 A

  It is an object of the present invention to provide a semipermeable membrane support in which a problem due to a widthwise curvature of a filtration membrane during roll conveyance in a semipermeable membrane forming step or an element processing step is eliminated.

  As a result of intensive studies to solve the above problems, the following invention was found.

  A semipermeable membrane support comprising a nonwoven fabric containing at least a main synthetic fiber and a binder synthetic fiber, and having a curl in a flow direction (MD direction) of +0.5 mm or more and +50 mm or less.

  By using the semipermeable membrane support of the present invention, it is possible to provide a filtration membrane in which a problem due to a curvature in a width direction at the time of roll conveyance is eliminated in a semipermeable membrane forming step or element processing.

The semipermeable membrane liquid was applied to the flat semipermeable membrane support without curl and cured and shrunk in the coagulation bath, causing the filtration membrane to bend in the width direction, with the semipermeable membrane inside and width It is a photograph curled in the direction (CD direction) in a cylindrical shape. The semipermeable membrane liquid is applied to the application surface of the semipermeable membrane support curved in the flow direction with the application surface inside, and the curl component in the flow direction of the semipermeable membrane support is formed by curing and shrinking in the coagulation bath. This is a photograph in which the filtration membrane is rolled into a cylindrical shape in a twisting direction with the semipermeable membrane inside from the balance between the (MD direction curl component) and the width direction curl component (CD direction curl component) of the semipermeable membrane. FIG. 4 is a diagram showing a measurement point 1 (central portion of both sides perpendicular to the flow direction of the semipermeable membrane support) of the semipermeable membrane support in the MD direction. FIG. 9 is a diagram showing the height of the curl in the MD direction of the semipermeable membrane support (the height (distance from the table) at the center of both sides perpendicular to the flow direction of the semipermeable membrane support).

  The semipermeable membrane support of the present invention can be used in the fields of seawater desalination, water purifiers, food concentration, wastewater treatment, medical treatment represented by blood filtration, production of ultrapure water for cleaning semiconductors, and the like. it can. Examples of the semipermeable membrane include semipermeable membranes made of a synthetic resin such as a polyamide resin, a cellulose resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, a polyester resin, and a polyolefin resin. On one surface (coated surface) of the semipermeable membrane support, a semipermeable membrane liquid in which a synthetic resin as a raw material of the semipermeable membrane is dissolved is applied, gelled in a coagulation bath, and then washed with water to form a microporous membrane. It is formed into a composite (filtration membrane) in which a semipermeable membrane is provided on the application surface of the semipermeable membrane support. The surface of the semipermeable membrane support on which the semipermeable membrane is provided is referred to as “coated surface”, and the opposite surface is referred to as “non-coated surface”.

  FIG. 1 shows that the semipermeable membrane liquid was applied to the flat semipermeable membrane support without curl and cured and shrunk in the coagulation bath, whereby the filtration membrane was curved in the width direction and the semipermeable membrane was removed. It is a photograph that is rolled into a tube shape in the width direction (CD direction) on the inside.

  As shown in FIG. 1, if the sheet is rolled into a tubular shape in the width direction, even if the tension applied to the roll by the roll conveyance is adjusted, the curvature at both ends cannot be suppressed, and a problem is likely to occur in the next step.

  FIG. 2 shows the flow of the semipermeable membrane support as a result of the semipermeable membrane liquid being applied to the application surface of the semipermeable membrane support curved in the flow direction with the application surface inside, and cured and contracted in a coagulation bath. From the balance between the curl component in the MD direction (curl component in the MD direction) and the curl component in the width direction of the semi-permeable membrane (curl component in the CD direction), the filter membrane is rolled into a cylindrical shape in the twisting direction with the semi-permeable membrane inside. is there.

  As shown in FIG. 2, the curl of the filtration membrane contains a curl component in the MD direction, and the filtration membrane is twisted or curled in the MD direction. By controlling the tension in roll conveyance, the curving of both ends in the flow direction of the filtration membrane is suppressed. This facilitates the operation and eliminates problems in the next step. For example, in the process of applying another membrane on the filtration membrane, a uniform membrane can be applied to both ends, and in the element processing step, the filtration membrane can smoothly pass through the line, so that yield and work efficiency are reduced. Go up.

  The reason why it is easy to suppress the curvature of both ends of the filtration membrane by the tension control in the roll conveyance is that the curl of the filtration membrane contains a curl component in the MD direction. Providing a curling component in the MD direction to the curling of the filtration membrane by forming a semipermeable membrane on the coating surface of the semipermeable membrane support in which the MD curl of the semipermeable membrane support is +0.5 mm or more and +50 mm or less. Can be. The MD direction curl of the semipermeable membrane support is more preferably +5 mm or more and +50 mm or less, and still more preferably +10 mm or more and +50 mm or less. When the curl in the MD direction is lower than +0.5 mm, the curl of the filtration membrane does not include the curl component in the MD direction. Problems may occur in the film forming process and the element processing process. Conversely, if the MD direction curl exceeds +50 mm, there may be a problem in paper passing properties such as wrinkling of the semi-permeable membrane support when passing through the semi-permeable membrane support, or the film may not be uniform. May not be painted.

  The “MD curl” of the semipermeable membrane support referred to in the present invention means that four samples of 20 cm in the width direction × 20 cm in the flow direction are sampled, and the coated surface of the semipermeable membrane support is placed on a flat table. And as shown in FIGS. 3 and 4, the height (distance to the table) of the central part (measurement point 1) of both sides perpendicular to the flow direction of the semipermeable membrane support is measured in 0.5 mm units. It is the average value. The sign of the average value in this measurement is plus (+) when the measurement point 1 rises to the coating surface side, and minus (-) when the center point of the sample rises higher than the measurement point 1. The center point of the sample refers to the intersection of two diagonal lines of the sample having a width of 20 cm and a flow direction of 20 cm. The average value is rounded to the first decimal place and rounded to the first decimal place.

As a method of making the MD direction curl of the semipermeable membrane support +0.5 mm or more and +50 mm or less,
(I) Adjustment of the blending ratio of the main synthetic fiber and the binder synthetic fiber (II) Adjustment of hot-press processing conditions by a hot roll (III) Implementation of post-treatment and the like. (II) More specifically,
(II-1) Optimization of combination of hot roll, resin roll, and cotton roll (II-2) Hot roll temperature during hot pressing with hot roll (II-3) Semi-permeable membrane support base paper and heat before nip Roll contact length (II-4) This can be achieved by controlling the processing speed during hot pressing.

  In the present invention, the main synthetic fiber is a fiber that forms the skeleton of the semipermeable membrane support. Examples of the main synthetic fibers include polyolefin-based, polyamide-based, polyacryl-based, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, benzoate-based, polychloral-based, and phenol-based fibers. Polyester fibers having high heat resistance are preferred. In addition, cellulose derivatives such as acetate and triacetate of semi-synthetic fibers, or promixes, and regenerated fibers such as rayon, cupra, lyocell fibers, and polylactic acid, polybutyric acid, and polysuccinic acid fibers derived from natural products do not impair the performance. May be contained.

  Although the fiber diameter of the main synthetic fiber is not particularly limited, it is preferably 5 to 20 μm, more preferably 5 to 15 μm, and still more preferably 5 to 13 μm. When the thickness is less than 5 μm, the semipermeable membrane liquid becomes difficult to penetrate the semipermeable membrane support, and the adhesiveness between the semipermeable membrane and the semipermeable membrane support is deteriorated, or a pinhole is easily generated. There is. When the fiber diameter of the main synthetic fiber exceeds 20 μm, the amount of the semipermeable membrane liquid that has slipped through the non-coated surface increases, and the membrane performance may decrease. In addition, the main synthetic fibers tend to stand on the surface of the semipermeable membrane support, and may penetrate the semipermeable membrane to deteriorate the performance of the semipermeable membrane.

  The fiber length of the main synthetic fiber is not particularly limited, but is preferably 1 to 12 mm, more preferably 3 to 10 mm, and still more preferably 4 to 7 mm. The cross-sectional shape of the main synthetic fiber is preferably circular, and the cross-sectional aspect ratio (fiber cross-sectional major axis / fiber cross-sectional minor axis) of the fiber before dispersion in water in the wet papermaking process is preferably less than 1.0 to less than 1.2. preferable. When the fiber cross-sectional aspect ratio is 1.2 or more, the fiber dispersibility may decrease, or the entanglement or entanglement of the fibers may occur, which may adversely affect the uniformity of the nonwoven fabric and the smoothness of the coated surface. However, fibers having irregular cross-sections such as T-type, Y-type, and triangular can also be contained within a range that does not hinder other properties such as fiber dispersibility for preventing strike-through and surface smoothness.

  The aspect ratio (fiber length / fiber diameter) of the main synthetic fiber is preferably from 200 to 2,000, more preferably from 200 to 1500, and still more preferably from 280 to 1,000. When the aspect ratio is less than 200, the dispersibility of the fiber is good, but when the fiber falls off from the papermaking wire during papermaking, or when the fiber is stabbed into the papermaking wire and the peelability from the wire deteriorates. is there. On the other hand, when it exceeds 2,000, although it contributes to the formation of a three-dimensional network of fibers, the entanglement and entanglement of the fibers may adversely affect the uniformity of the semipermeable membrane support and the smoothness of the coated surface. .

  The semipermeable membrane support of the present invention contains a binder synthetic fiber. By incorporating the step of raising the temperature up to or above the softening point or melting temperature (melting point) of the binder synthetic fiber into the method for producing a semipermeable membrane support, the binder synthetic fiber can improve the strength of the semipermeable membrane support. . In the step of raising the temperature, the main synthetic fiber is not easily softened or melted, and the cross-sectional shape may be changed, but the shape of the fiber is not impaired, and the main fiber is formed of the skeleton of the semipermeable membrane support. Form. For example, the binder synthetic fiber can be softened or melted during the drying step or hot pressing after the nonwoven fabric is manufactured by the wet papermaking method.

  Examples of binder synthetic fibers include core-sheath fibers (core-shell type), side-by-side fibers (side-by-side type), composite fibers such as radial split fibers, and undrawn fibers. Since the composite fiber does not easily form a film, the mechanical strength can be improved while maintaining the space of the semipermeable membrane support. More specifically, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), a combination of high-melting polyester (core) and low-melting polyester (sheath), polyester, etc. Undrawn fiber. In addition, a single fiber (all-fused type) composed only of a low melting point resin such as polyethylene or polypropylene, or a hot water-soluble binder such as a polyvinyl alcohol type easily forms a film in a drying step of a semipermeable membrane support. However, it can be used as long as the properties are not impaired. In the present invention, a combination of a high-melting polyester (core) and a low-melting polyester (sheath) and unstretched polyester fibers can be preferably used.

  The fiber diameter of the binder synthetic fiber is not particularly limited, but is preferably 5 to 15 μm, more preferably 6 to 14 μm, and still more preferably 7 to 13 μm. When the thickness is less than 5 μm, the semipermeable membrane liquid becomes difficult to penetrate the semipermeable membrane support, and the adhesiveness between the semipermeable membrane and the semipermeable membrane support is deteriorated, or a pinhole is easily generated. There is. If the fiber diameter of the binder synthetic fiber exceeds 15 μm, the amount of the semipermeable membrane liquid that has slipped through the non-coated surface may increase, and the membrane performance may decrease. In the step of raising the temperature to a temperature equal to or higher than the softening temperature or the melting temperature of the binder synthetic fiber, the smoothness of the surface of the semipermeable membrane support can be improved. In this step, it is more effective if pressure is applied.

  The fiber length of the binder synthetic fiber is not particularly limited, but is preferably 1 to 12 mm, more preferably 3 to 10 mm, and still more preferably 4 to 7 mm. The cross-sectional shape of the binder synthetic fiber is preferably circular. However, fibers having irregular cross-sections such as T-type, Y-type, and triangular are also used for preventing strike-through, smoothness of the coated surface, and adhesion between the non-coated surfaces. Can be contained within a range that does not impair the characteristics of

  The aspect ratio (fiber length / fiber diameter) of the binder synthetic fiber is preferably from 200 to 2,000, more preferably from 200 to 1500, and still more preferably from 300 to 1,000. When the aspect ratio is less than 200, the dispersibility of the fiber becomes good, but the fiber may fall off from the papermaking wire during papermaking, or the fiber may be stabbed into the papermaking wire and the peelability from the wire may deteriorate. is there. On the other hand, when it exceeds 2,000, although the binder synthetic fiber contributes to the formation of the three-dimensional network, the fiber may be entangled or entangled, which may adversely affect the uniformity of the nonwoven fabric and the smoothness of the coated surface. .

  The content of the binder synthetic fiber in the nonwoven fabric related to the semipermeable membrane support of the present invention is preferably 20 to 40% by mass, more preferably 23 to 37% by mass, and more preferably 25 to 35% by mass based on all the fibers constituting the nonwoven fabric. % Is more preferred. If the content of the binder synthetic fiber is less than 20% by mass, the fiber may be broken due to insufficient strength. In addition, the amount of the semipermeable membrane liquid that has slipped through the non-coated surface may increase, and the membrane performance may decrease. If the content exceeds 40% by mass, film formation proceeds during hot-pressing, and air bubbles cannot be smoothly released to the non-coated surface side of the semipermeable membrane support, and pinholes are likely to be generated. There is a possibility that the property is reduced. When the semipermeable membrane support is composed of a nonwoven fabric having a multilayer structure of two or more layers, the ratio of the binder synthetic fibers contained in the layer on the non-coated side is higher than the ratio of the binder synthetic fibers contained in the layer on the coated side. Is preferred.

  The method for producing the semipermeable membrane support of the present invention will be described. In the semipermeable membrane support of the present invention, after a semipermeable membrane support base paper is produced by a wet papermaking method, the semipermeable membrane support base paper is hot-pressed by a hot roll.

  In the wet papermaking method, first, at least the main synthetic fiber and the binder synthetic fiber are uniformly dispersed in water, and then, through a process such as a screen (removal of foreign matters, lumps, etc.), the final fiber concentration is 0.01 to 0.1. The slurry adjusted to 50% by mass is made up by a paper machine to obtain wet paper. Chemicals such as dispersants, defoamers, hydrophilic agents, antistatic agents, polymer thickeners, release agents, antibacterial agents, and bactericides may be added during the process to make the dispersibility of the fibers uniform. is there.

  As the papermaking method, for example, a papermaking method such as a long net, a circular net, or an inclined wire type can be used. Use a paper machine having at least one paper machine selected from the group of these paper machines, or a combination paper machine in which two or more paper machines of the same or different types selected from the group of paper machines are installed online. can do. In the case of producing a nonwoven fabric having a multilayer structure of two or more layers, a laminating method of laminating wet papers made by each paper machine, or forming one sheet, and then forming a sheet on the sheet A method of casting a slurry in which fibers are dispersed can be used.

  The wet paper produced by the paper machine is dried by a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, or the like to obtain a semipermeable membrane support base paper. When the wet paper is dried, the wet paper is brought into close contact with a hot roll such as a Yankee dryer and dried under hot pressure, whereby the smoothness of the adhered surface is improved. Hot-press drying refers to pressing wet paper against a hot roll with a touch roll or the like to dry. The surface temperature of the heat roll is preferably from 100 to 180 ° C, more preferably from 105 to 170 ° C, even more preferably from 110 to 160 ° C. The pressure at which the wet paper web is pressed against the hot roll is preferably from 300 to 1000 N / cm, more preferably from 300 to 800 N / cm.

  Next, a description will be given of hot-press working by a hot roll, but the present invention is not limited to the following. While the nip between the rolls of the hot-press processing device (calender device) is nipped, the hot-press processing is performed by passing through the semi-permeable membrane support base paper.

  Examples of the combination of the rolls include two metal rolls, a metal roll and a resin roll, and a metal roll and a cotton roll. Hot-pressing with a hot roll can be performed two or more times, in which case, two or more sets of the above rolls arranged in series may be used, or one set of rolls may be used. It may be processed twice or more. If necessary, the front and back of the semipermeable membrane support base paper may be reversed. In the combination of rolls, a combination of two metal rolls and a combination of a metal roll and a cotton roll are preferable.

  The contact length between the semi-permeable membrane support base paper before the nip and the hot roll is preferably 0 to 80 cm, more preferably 0 to 70 cm. If it exceeds 80 cm, bubbles may not be able to smoothly escape to the non-coated surface side of the semipermeable membrane support, and pinholes may be easily generated. When manufacturing the semipermeable membrane support, the semipermeable membrane support base paper is subjected to hot-press processing at least twice, and when the first surface to be in contact with the heating roll is the coating surface, the second heating roll is used. Is preferably 10 to 20 cm longer than the contact length of the first heating roll.

  The surface temperature of the heat roll is preferably 150 to 250 ° C., and is appropriately adjusted depending on the type of the fibers constituting the semipermeable membrane support. In polyester fibers mainly used for water treatment membrane applications, the surface temperature of the hot roll is preferably from 200 to 250C, more preferably from 205 to 245C. When the temperature is lower than 150 ° C., the main synthetic fibers tend to stand on the surface of the nonwoven fabric, and when the performance of the semipermeable membrane is reduced by penetrating the semipermeable membrane, or the amount of the semipermeable membrane liquid that has penetrated the uncoated surface. And the film performance may decrease. If the temperature exceeds 250 ° C., bubbles may not be able to smoothly escape to the non-coated surface side of the semipermeable membrane support, and pinholes may be easily generated. When manufacturing the semipermeable membrane support, the semi-permeable membrane support base paper is subjected to the heat-pressure processing for the second time or more, and when the surface in contact with the heating roll for the first time is used as the coating surface, the second heating roll is used. It is preferable that the surface temperature be higher by 10 to 20 ° C. than the surface temperature of the first heating roll.

  The nip pressure of the roll is preferably 500 to 1200 N / cm, more preferably 600 to 1100 N / cm. If it is less than 500 N / cm, the amount of the semipermeable membrane liquid that has penetrated through the non-coated surface may increase, and the membrane performance may decrease. If it exceeds 1200 N / cm, pinholes may easily occur.

  The processing speed is preferably 10 to 150 m / min, and more preferably 20 to 130 m / min. If it is less than 10 m / min, pinholes may easily occur. If it exceeds 150 m / min, the amount of the semipermeable membrane liquid that strikes through the non-coated surface increases, and the membrane performance may decrease. When manufacturing the semipermeable membrane support, the semi-permeable membrane support base paper is subjected to the hot-press processing for the second time or more, and when the surface in contact with the heating roll for the first time is used as the application surface, the second processing speed is set. It is preferable that the processing speed is lower by 5 to 30 m / min than the first processing speed.

The basis weight of the semipermeable membrane support is not particularly limited, but is preferably ²⁰ to 150 g / m ² , and more preferably 50 to 100 g / m ² . If it is less than 20 g / m ² , sufficient tensile strength may not be obtained. Further, when it exceeds 150 g / m ² , the liquid permeation resistance may be increased, or the thickness may be increased, so that a predetermined amount of the semipermeable membrane may not be stored in the element.

Further, the density of the semipermeable membrane support is preferably 0.5 to 1.0 g / cm ³ , and more preferably 0.6 to 0.95 g / cm ³ . When the density of the semipermeable membrane support is less than 0.5 g / cm ³ , the thickness becomes large, so that the area of the semipermeable membrane that can be incorporated in the element becomes small, and as a result, the life of the semipermeable membrane becomes short. Sometimes. On the other hand, if it exceeds 1.0 g / cm ³ , the liquid permeability may be reduced, and the life of the semipermeable membrane may be shortened.

  The thickness of the semipermeable membrane support is preferably from 50 to 150 μm, more preferably from 60 to 130 μm, even more preferably from 70 to 120 μm. When the thickness of the semipermeable membrane support exceeds 150 μm, the area of the semipermeable membrane that can be incorporated into the element becomes small, and as a result, the life of the semipermeable membrane may be shortened. On the other hand, if it is less than 50 μm, sufficient tensile strength may not be obtained, or liquid permeability may be reduced, and the life of the semipermeable membrane may be shortened.

  The post-treatment may adjust the curl in the MD direction of the semipermeable membrane support to at least +0.5 mm and at most +50 mm. Examples of the post-treatment include a decurler treatment and a method of winding in the MD direction with the application surface inside to form a curl.

  As the decurler device, a device using a mechanism such as a blade system, a roll system, or a small-diameter roll system is known, and any of them can be used in the present invention. Is preferred. The blade method presses a blade-shaped (or square) decurler against a web running between two rolls at a constant tension, and has a high curl straightening effect. However, because the fixed body is pressed, static electricity is generated, causing friction. And the web may be broken if operated excessively. In the roll method, a rotating roll (φ40 to 80 mm) is pressed a plurality of times instead of a blade. Since the roll is a rotating body, the occurrence of scratches is greatly reduced compared to the blade method, but the installation space is large. The reality is that the curl correction effect is small. The small-diameter roll system is a decurler developed to have the advantages w of the blade system and the roll system. The small-diameter roll system presses an extremely small-diameter rotating roll (φ12 to 20 mm) to reduce the pressing force of the small-diameter roll and the speed of the rotating spindle roll. The curl is corrected by adjustment. Since the rotating roll is a high-hardness rotating body, there is almost no damage to the web, and the small-diameter roll is supported by backup bearings arranged at a constant pitch, and has a small diameter by permanent magnets arranged with minute clearance. It is devised to prevent the roll from bending. The decurler device used in the present invention is not limited to the above-described mechanism, but it is preferable to use a small-diameter roll system in consideration of the effect of the decurler treatment and damage to the semipermeable membrane support.

  In the method of winding in the MD direction with the coating surface inside, the outer diameter of the paper tube around which the semipermeable membrane support is wound is preferably 30 mm or more and 200 mm or less, more preferably 35 mm or more and 105 mm or less, More preferably, it is 40 mm or more and 70 mm or less. When the outer diameter is less than 30 mm, the semi-permeable membrane support tends to have a curl in the MD direction of more than 50 mm, and the semi-permeable membrane support is wrinkled when paper is passed. In some cases, or the film may not be coated uniformly. If the outer diameter of the paper tube exceeds 200 mm, curling in the MD direction may not be provided.

  The time for winding and storing around a paper tube is preferably 12 hours or more, more preferably 48 hours or more, and further preferably 72 hours or more. Although there is no particular upper limit for the storage time, it is preferably 336 hours or less from the viewpoint of production efficiency. To shorten the storage time, the winding may be heated in an atmosphere of 30 ° C. or higher. The heating temperature is preferably 30 ° C. or higher, more preferably 45 ° C. or higher, and further preferably 55 ° C. or higher. If the temperature is too high, the semipermeable membrane support may cause blocking. Further, when the outer diameter of the paper tube exceeds 105 mm, heating may be necessary in order to form a curl.

  The present invention will be described in more detail by way of examples. Hereinafter, unless otherwise specified, parts and ratios described in Examples are based on mass.

<Stretched PET fiber>
A drawn polyester fiber made of polyethylene terephthalate and having a fiber diameter of 7.4 μm and a fiber length of 5 mm was used as a drawn PET fiber.

<Unstretched PET fiber>
An unstretched PET fiber made of polyethylene terephthalate and having a fiber diameter of 11.8 μm and a fiber length of 5 mm (melting point: 260 ° C.) was used.

  The semipermeable membrane supports of Examples 1 to 12 and Comparative Examples 1 to 6 were produced under the following conditions.

(Manufacture of base paper)
After adding water to a 2 m ³ dispersion tank, the mixture was blended at the raw material blending ratio (%) shown in Table 1, dispersed at a dispersion concentration of 0.2% by mass for 5 minutes, and using a combined gradient / circular mesh paper machine, After forming the wet paper of the first surface layer on the inclined wire, forming the wet paper of the second surface layer on the wire mesh wire, and laminating both wet papers before drying, the surface temperature is 130 ° C. The resultant was dried with a Yankee dryer under a high pressure to obtain semipermeable membrane support base papers of Examples 1 to 12 and Comparative Examples 1 to 6 each having a width of 1000 mm with a target weight as shown in Table 1.

(Heat and pressure processing 1)
The semi-permeable membrane support base papers of Examples 1 to 10 and Comparative Examples 1 to 6 were nipped as shown in Table 2 using a calendar device of a combination of a first stage heated metal roll (JR) and a resin roll (bullet). Hot-press processing under the conditions of the contact length between the heated metal roll before and the base material of the semipermeable membrane support (the JR contact length before the nip), the surface temperature of the heated metal roll (JR temperature), and the processing speed; Using a calendar device of a combination of the second stage resin roll and the heated metal roll, the surface of the permeable membrane support base paper was brought into contact with the second stage resin roll so that the surface in contact with the first stage heated metal roll was in contact with the second stage resin roll. The hot-press processing is performed under the conditions of the contact length between the heated metal roll before the nip and the base material of the semi-permeable membrane support (the JR contact length before the nip), the surface temperature of the heated metal roll (JR temperature), and the processing speed. A permeable support was obtained. The surface that hit the heated metal roll in the first stage treatment was taken as the coating surface, the surface that hit the metal roll in the second stage treatment was taken as the non-coating surface, and the layers of the coating surface are shown in Table 2. The semi-permeable membrane support after the hot-press processing was wound in a flow direction (MD direction) on a paper tube having an outer diameter shown in Table 2 with the surface shown in Table 2 inside.

(Heat and pressure processing 2)
The semi-permeable membrane support base paper of Example 11 was mixed with the heated metal roll before the nip shown in Table 2 using a calendar device of a combination of a first-stage heated metal roll (JR) and a cotton roll (cotton). Heat-press processing is performed under the conditions of the contact length of the membrane support base paper (JR contact length before nip), the surface temperature of the heated metal roll (JR temperature), and the processing speed. Using a calendar device of a combination of the second stage cotton roll and the heated metal roll, the heated metal roll before the nip shown in Table 2 so that the surface of the stage in contact with the heated metal roll is in contact with the second stage cotton roll. The semi-permeable membrane support was subjected to hot-press working under the conditions of a contact length (JR contact length before nip), a heated metal roll surface temperature (JR temperature), and a processing speed to obtain a semi-permeable membrane support. The surface that hit the heated metal roll in the first stage treatment was set as the coated surface, and the surface that hit the metal roll in the second stage treatment was set as the non-coated surface. The results are shown in Table 2. The semi-permeable membrane support after the hot-press processing was wound in a flow direction (MD direction) on a paper tube having an outer diameter shown in Table 2 with the surface shown in Table 2 inside.

(Heat and pressure processing 3)
The semi-permeable membrane support base paper of Example 12 was mixed with the heated metal roll before nip shown in Table 2 by using a calendar device of a combination of a heated metal roll (JR) of the first stage and a heated metal roll (JR). The semi-permeable membrane support was obtained by hot-pressing under the conditions of the contact length of the permeable support base paper (JR contact length before nip), the surface temperature of both heated metal rolls (JR temperature), and the processing speed. The surface that had been in contact with the heated metal roll before the nip in the first stage treatment was the coated surface, and the opposite surface was the non-coated surface. The results are shown in Table 2. The semi-permeable membrane support after the hot-press processing was wound in a flow direction (MD direction) on a paper tube having an outer diameter shown in Table 2 with the surface shown in Table 2 inside.

(Post-processing 1)
The semipermeable membrane supports of Examples 6 to 9 were stored in the temperature atmosphere shown in Table 3 for the time shown in Table 3 as they were obtained after the hot-press processing.

(Post-processing 2)
The semipermeable membrane supports of Example 10 and Comparative Example 6 were rolled into a paper tube having an outer diameter shown in Table 3 from the winding obtained after the hot-press processing in the flow direction (MD direction) with the application surface inside. It was wound and stored under the temperature atmosphere shown in Table 3 for the time shown in Table 3. Note that the post-treatment in an atmosphere of 25 ° C. is based on the assumption of storage at room temperature (rt) without heating.

(Post-processing 3)
The semi-permeable membrane support of Comparative Example 5 was wound in a flow direction (MD direction) with the non-coated surface inward from the winding obtained after the hot-press processing, on a paper tube having an outer diameter shown in Table 3. It was stored under the temperature atmosphere shown in Table 3 for the time shown in Table 3. Note that the post-treatment in an atmosphere of 25 ° C. is based on the assumption that storage is performed at room temperature without heating.

  The following measurements and evaluations were performed on the semipermeable membrane supports obtained in Examples and Comparative Examples, and the results are shown in Table 4.

Measurement 1 (MD direction curl of semipermeable membrane support)
The semi-permeable membrane support cut into a size of 20 cm in the width direction × 20 cm in the flow direction is placed on a flat table with the application side up, and the flow of the semi-permeable membrane support as shown in FIGS. The height (distance to the table) of the central part (measurement point 1) of both sides perpendicular to the direction was measured in units of 0.5 mm, and defined as the height in the plus (+) direction. Four semipermeable membrane support sheets were equally sampled in the width direction except for both ends 5 cm of the semipermeable membrane support, and the average value of the four sheets was defined as “MD direction curl of the semipermeable membrane support”. When the curl in the MD direction of the semipermeable membrane support is 0.0 mm when measured with the coated surface of the semipermeable membrane support sheet facing upward, the non-coated surface of the semipermeable membrane support sheet is oriented upward. Place on a flat table, measure the height at the center of both sides perpendicular to the flow direction of the semipermeable membrane support sheet in units of 0.5 mm, and set the height in the minus (-) direction as the average of the four sheets. The value was defined as "MD direction curl of the semipermeable membrane support". The average value was rounded off to one decimal place and recorded to one decimal place. The results are shown in Table 4.

Measurement 2 (CD direction curl of semipermeable membrane support)
The measurement point 1 of the semipermeable membrane support sheet measured in the measurement 1 was changed to the center (measurement point 2) of both sides parallel to the flow direction of the semipermeable membrane support, and the height of the four measurement points 2 was changed. Was measured in the same manner as in Measurement 1 except that the average value of was set as “curl in the CD direction of the semipermeable membrane support”. The results are shown in Table 4.

Evaluation 1 (MD direction curl of filtration membrane)

(1) Preparation of semipermeable membrane solution Polysulfone (trade name: Cordell (registered trademark) P-3500LCD MB-7, manufactured by Solvay) was added to N, N-dimethylformamide (manufactured by Junsei Chemical Co., special grade) at 140 ° C. After dissolving to a concentration of 16% by mass while heating, the mixture was stirred at a temperature of 25 ° C. for half a day to prepare a semipermeable membrane liquid.

(2) Preparation of Filtration Membrane A mount is set on a constant-speed coating device (trade name: Automatic Film Applicator, manufactured by Yasuda Seiki Co., Ltd.), and a coating width of 100 mm x a coating length of 180 mm is set on the set mount. The semi-permeable membrane support thus cut was fastened with an OPP tape (trade name: BK-24N, manufactured by 3M) with the coated side up. Using a baker-type applicator (manufactured by Yasuda Seiki Co., Ltd., coating width 100 mm) that can adjust 5 to 6 g of the semipermeable membrane liquid to a constant clearance, so that the coating amount (dry mass) is 24 ± 3 g / m ² . Coating was performed at a coating speed of 250 mm / sec, and after 15 seconds from the start of coating, it was immersed in tap water at 20 ° C. to solidify. After washing with water for 3 hours, it was dried to produce a filtration membrane.

(3) Preparation of sample for measurement of “curl in the MD direction of filtration membrane” The center part of the produced filtration membrane was cut into a width direction of 25 mm × a flow direction of 25 mm, and placed on a flat table with the semipermeable membrane surface facing upward. The height (distance to the table) of the center of both sides perpendicular to the flow direction of the semipermeable membrane support was measured in units of 0.5 mm, and defined as the height in the plus (+) direction. The measurement was carried out on the four semipermeable membrane support sheets for which the MD curl of the semipermeable membrane support was measured in Measurement 1, and the average value of the four sheets was defined as "MD curl of the filtration membrane". The average value was rounded off to one decimal place and recorded to one decimal place. The results are shown in Table 4.

Curling of the filtration membrane in the MD direction + 0.5 mm or more: The filtration membrane is curled in the MD direction or torsionally curled, and does not easily cause a problem in the next step, and is practically usable.
0.0 mm or more and less than +0.5 mm: In many cases, the filtration membrane tends to curl in the CD direction, causing problems in the next step, and cannot be used practically.

  As shown in Table 4, in the semipermeable membrane supports of Examples 1 to 12, since the curl in the MD direction of the semipermeable membrane support was +0.5 mm or more and +50 mm or less, the filtration membrane using the semipermeable membrane support was used. Was curled or twisted in the MD direction, and good results were obtained.

  In the semi-permeable membrane support of Comparative Example 1 in which the first stage and the second stage were hot-pressed at the same JR temperature, the curl in the MD direction of the semi-permeable membrane support was less than +0.5 mm, and the semi-permeable membrane support was second to the first stage. Compared with the semi-permeable membrane support of Example 1 in which the JR temperature of the stage was increased and hot-pressed, the MD of the filtration membrane was smaller in the MD direction and less than +0.5 mm.

  The semipermeable membrane supports of Comparative Example 2 and Comparative Example 3 in which the ratio of the binder synthetic fiber contained in the layer on the coated side was higher than that of the layer on the uncoated side, the MD direction curl of the semipermeable membrane support was +0.5 mm, compared with the semipermeable membrane supports of Examples 2 and 3 in which the ratio of the binder synthetic fiber contained in the layer on the non-applied surface side was higher than that of the layer on the coated surface side. The curl in the MD direction of the filtration membrane was small and less than +0.5 mm.

  The semi-permeable membrane support of Comparative Example 4 in which the semi-permeable membrane support was wound around a paper tube with the non-coated side facing inward after the hot-press processing, the MD-direction curl of the semi-permeable membrane support was shifted toward the non-coated side. In comparison with the semi-permeable membrane supports of Examples 1 to 9 in which the semi-permeable membrane support was wound around a paper tube with the coated surface inside after the hot-press processing, The curl in the MD direction of the filtration membrane was small and less than +0.5 mm.

  The semi-permeable membrane support of Comparative Example 5 in which the semi-permeable membrane support was wound around a small-diameter paper tube having an outer diameter of 40 mm with the non-coated surface facing inward after the hot-press processing and stored at room temperature for 72 hours was a semi-permeable membrane. The support is curled in the negative direction so that the curl in the MD direction is lifted to the non-coated side, and after the hot-press processing, the semipermeable membrane support is wound around a small-diameter paper tube with the coated side inside and stored at room temperature for 72 hours. Compared with the semipermeable membrane support of Example 10, the MD of the filtration membrane was small and less than +0.5 mm.

  The semipermeable membrane support of Comparative Example 6, in which the semipermeable membrane support was wound around a small-diameter paper tube having an outer diameter of 20 mm with the coated surface facing inward after the heat-pressure processing and stored at room temperature for 72 hours, was used. Since the MD curl of the body exceeded +50.0 mm, the center of the semipermeable membrane support was lifted during the production of the semipermeable membrane in Evaluation 1, and the film at the center was thinned. Alternatively, the semipermeable membrane became non-uniform, and it was not possible to measure the MD direction curl of the filtration membrane.

  The curl in the CD direction of the semipermeable membrane supports of Comparative Examples 2 to 4 was -1.1 to -0.5 mm, and the curl in the MD direction of the semipermeable membrane supports of Comparative Examples 4 and 5 was -39. 0.8 to -5.3 mm, and even if the semipermeable membrane support is curled toward the non-coated side, the MD direction curl of the filtration membrane may be small (less than +0.5 mm), as in the present invention. In addition, since the semi-permeable membrane support has a curl in the MD direction of +0.5 mm to +50 mm, the filtration membrane using the semi-permeable membrane support has a curl in the MD direction of +0.5 mm or more and a curl shape in the MD direction. Or, it turns out that it becomes a twist curl, and the problem in the next step after the formation of the semipermeable membrane is solved.

  The semipermeable membrane support of the present invention can be used in the fields of seawater desalination, water purifier, food concentration, wastewater treatment, medical treatment represented by blood filtration, production of ultrapure water for semiconductor cleaning, and the like. it can.

Claims (1)

  In a semipermeable membrane support made of a nonwoven fabric containing at least a main synthetic fiber and a binder synthetic fiber, the curl in the flow direction (MD direction) of the semipermeable membrane support is not less than +0.5 mm and not more than +50 mm. Characteristic semipermeable membrane support.