JP2015058411A - Semipermeable membrane support - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semipermeable membrane support having less generation of membrane defects and less fuzz.SOLUTION: Provided is the semipermeable membrane support formed by laminating nonwoven fabric formed into one layer in a wet type sheet making step so as to become two or more layers by hot pressing processing, and having a pinhole size detected by transmitted beam of 10 pixel numbers or less. An average fiber diameter of a main fiber is 7-12 μm and speed in the wet type sheet making step is 30 m/min or less, preferably.

Description

  The present invention relates to a semipermeable membrane support.

  Semipermeable membranes are widely used in the fields of desalination of seawater, water purifiers, food concentration, wastewater treatment, ultrapure water production for medical use and semiconductor cleaning, such as blood filtration. The semipermeable membrane is made of a synthetic resin such as a cellulose resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, or a polyester resin. However, since the semipermeable membrane itself is inferior in mechanical strength, a semipermeable membrane is provided on one side (hereinafter referred to as “semipermeable membrane application surface”) of a semipermeable membrane support made of a fiber base material such as a nonwoven fabric or a woven fabric. (Hereinafter referred to as “filtration membrane”).

  As a method of coating a semipermeable membrane on a semipermeable membrane support, after synthesizing a synthetic resin such as the polysulfone-based resin described above in an organic solvent to prepare a semipermeable membrane coating solution, the semipermeable membrane coating solution is added to the semipermeable membrane coating solution. The method of coating on a permeable membrane support is widely used, and in order to efficiently perform filtration, the surface opposite to the semipermeable membrane support application surface of the semipermeable membrane support constituting the filtration membrane is an adhesive. And filtration is performed by flowing filtered water on the non-coated surface.

  In this method for producing a filtration membrane (see, for example, Patent Document 1), a semipermeable membrane coating solution is applied to a semipermeable membrane support or more and then left in a low humidity atmosphere for a certain period of time, followed by water. Alternatively, a semipermeable membrane layer having a fine pore diameter is formed by being immersed in warm water. In this case, if there is a pinhole having a certain size in the semipermeable membrane support, the semipermeable membrane coating solution penetrates into the semipermeable membrane support from the pinhole and reaches the liquid surface of the semipermeable membrane coating solution. A large dent is generated, and the semipermeable membrane coating liquid surface undulates at the moment of collision with the water surface, which may cause a half-moon-shaped coating defect.

  In order to suppress such coating defects, a method is shown in which long-fiber nonwoven fabrics composed of thermoplastic filaments are bonded together during hot pressing, and then the transmission high luminance variation coefficient is set to 1.0 to 6.0%. (For example, refer to Patent Document 2). However, when long-fiber non-woven fabric is used, the texture of the semipermeable membrane support tends to deteriorate, and there is a problem that the coating amount of the semipermeable membrane is difficult to be uniform. Further, the luminance variation coefficient of transmitted light tends to decrease as the fiber diameter used becomes closer, and it is difficult to say that it reflects the maximum pinhole diameter of the semipermeable membrane support.

  Also, when the amount of the semipermeable membrane coating solution applied on the semipermeable membrane support is increased, the dent of the semipermeable membrane coating solution becomes relatively small, and the occurrence of the above-mentioned moon-shaped membrane defects occurs. Although it tends to be suppressed, increasing the coating amount is economically problematic, and it is a major factor in reducing the water flow rate, so it has not been a fundamental solution.

JP 9-313905 A Japanese Patent No. 5206277

  An object of the present invention is to provide a semipermeable membrane support with less occurrence of membrane defects and less fuzz.

As a result of intensive studies to solve the above problems, the present inventors have
(1) A non-woven fabric composed of one layer in a wet papermaking stage is laminated in two or more layers in hot pressing, and the size of pinholes detected by transmitted light is 10 pixels or less. A semipermeable membrane support,
(2) The semipermeable membrane support according to the above (1), wherein the main fiber has an average fiber diameter of 7 to 12 μm,
(3) The semipermeable membrane support according to the above (1) or (2), wherein the paper making speed in the wet paper making stage is 30 m / min or less,
I found.

  According to the present invention, it is possible to obtain a semipermeable membrane support that hardly causes membrane defects and has less fuzz.

  The semipermeable membrane support of the present invention is composed of a wet nonwoven fabric containing main fibers and binder fibers. In order to obtain a semipermeable membrane support having a uniform texture and air permeability profile, it is necessary to use a wet nonwoven fabric obtained by a wet papermaking method.

  In the present invention, as the wet papermaking method used, for example, a paper machine having a wet papermaking method such as a long-mesh type, a circular net type, a short net type, or an inclined wire type can be used, but is not limited thereto. It is not a thing.

  In the wet papermaking method, first, the main fibers and binder fibers are uniformly dispersed in water, and then passed through processes such as screen (removal of foreign matters, lumps, etc.), and the final fiber concentration is 0.01 to 0.50 mass%. The slurry prepared in (1) is made up with a paper machine to obtain a wet paper. In the process of uniformly dispersing the fiber in water, air is mixed into the dispersion and is pumped, under the normal pressure in the inclined wire type and long net type wet papermaking methods, and under the reduced pressure in the circular mesh type. Since the sheet is formed, bubbles are increased and pinholes appear to be generated. Therefore, by laminating two or more layers in the hot pressing process, a semipermeable membrane supporting body with less fuzzing and hardly causing membrane defects due to pinholes can be obtained.

  In the present invention, in order to uniformly disperse the main fiber and binder fiber in water, a dispersing agent, an antifoaming agent, a hydrophilic agent, an antistatic agent, a polymer viscosity agent, a release agent, an antibacterial agent, and a bactericidal agent are used in the process. In some cases, chemicals such as these are added.

  Sheets are obtained by drying wet paper produced by a paper machine with a Yankee dryer, air dryer, cylinder dryer, suction drum dryer, infrared dryer, or the like. When the wet paper is dried, it is brought into close contact with a hot roll such as a Yankee dryer and dried by heat and pressure to improve the smoothness of the contacted surface. Hot-pressure drying means that the wet paper is pressed against the heat roll with a touch roll or the like and dried. The surface temperature of the hot roll is preferably 100 to 180 ° C, more preferably 100 to 160 ° C, and still more preferably 110 to 160 ° C. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

  The main fiber is a fiber that forms the skeleton of the semipermeable membrane support, and a synthetic fiber is used. For example, polyolefin fibers, polyamide fibers, polyacrylic resins, vinylon resins, vinylidene resins, polyvinyl chloride resins, polyester resins, benzoate resins, polyclar resins, phenol fibers, etc. Is more preferable. Semi-synthetic fibers such as acetate, triacetate, promix, and regenerated fibers such as rayon, cupra, and lyocell fiber may be contained within a range that does not impair the performance.

  In the present invention, the average fiber diameter of the main fibers is preferably 7 to 12 μm. When the average fiber diameter of the main fibers exceeds 12 μm, it is difficult to make the size of the pinhole detected by the transmitted light 10 pixels or less. When the average fiber diameter of the main fibers is less than 7 μm, fuzz is likely to occur.

Here, the average fiber diameter of the main fibers is determined by the following method.
Average fiber diameter = (fiber diameter of main fiber 1 (μm) × mass% of main fiber 1 + fiber diameter of main fiber 2 (μm) × mass% of main fiber 2 + fiber diameter of main fiber 3 (μm) × main body Mass% of fiber 3) /
(Mass% of the main fiber 1 + mass% of the main fiber 2 + mass% of the main fiber 3)

  The fiber length of the main fiber is not particularly limited, but is preferably 10 mm or less. 1-10 mm is more preferable, and 3-6 mm is further more preferable. When the fiber length of the main fibers exceeds 10 mm, the fibers are likely to be localized in the wet papermaking method, and it is difficult to obtain a semipermeable membrane support having a uniform air permeability. Further, when the fiber length is less than 1 mm, there is a drawback that the strength of the semipermeable membrane support is reduced or fluff is likely to occur.

  The cross-sectional shape of the main fiber may be called a modified cross-section fiber having a triangle, a quadrangle, or a polygon other than a circle. In this case, the cross-sectional area of the deformed cross-section fiber may be approximated as a fiber diameter in a circular approximation. it can.

  In the present invention, a binder fiber is used together with the main fiber for the semipermeable membrane support.

  Examples of the binder fibers include core-sheath fibers (core-shell type), parallel fibers (side-by-side type), composite fibers such as radially divided fibers, unstretched fibers, and the like. The binder fiber is added to bind to the main fiber to form a three-dimensional network structure between the fibers, increase the strength of the semipermeable membrane support, and suppress fuzz. Since the composite fiber hardly forms 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 point polyester (core) and low melting point polyester (sheath), polyester, etc. Of undrawn fiber. In addition, a single fiber (fully fused type) composed only of a low melting point resin such as polyethylene or polypropylene, or a hot water-soluble binder such as polyvinyl alcohol easily forms a film in the drying process of the 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 point polyester (core) and a low-melting point polyester (sheath) and unstretched polyester fibers can be preferably used.

  Although the fiber diameter of a binder fiber is not specifically limited, Preferably it is 2-20 micrometers, More preferably, it is 5-15 micrometers, More preferably, it is 7-12 micrometers. The binder fiber has a portion that is not crystallized in the fiber as compared with the main fiber, and plays the role of improving the mechanical strength of the semipermeable membrane support by heating during hot pressing. In addition, the melted and plastically deformed binder fiber also plays a role of forming a uniform three-dimensional network with the main fiber. Further, in the step of raising the temperature to the softening temperature or melting temperature of the binder fiber, the smoothness of the semipermeable membrane application surface can be improved, and it is more effective if pressurization is involved in the step. The pore diameter on the surface of the semipermeable membrane support can be made fine by the binder fiber, and as a result, the fuzz on the surface of the semipermeable membrane support is suppressed, there is no see-through of the semipermeable membrane coating solution, and air permeability A semipermeable membrane support having a uniform profile can be obtained.

  Although the fiber length of a binder fiber is not specifically limited, Preferably it is 1-12 mm, More preferably, it is 3-10 mm, More preferably, it is 4-6 mm. When the fiber length of the binder fiber is less than 1 mm, it may be difficult to contribute to the formation of the main fiber and the three-dimensional network structure, and the mechanical strength of the semipermeable membrane support may be lowered. Further, when the fiber length of the binder fiber exceeds 12 mm, the number of fibers decreases, and the melted portion is localized, making it difficult to obtain a semipermeable membrane support having a uniform air permeability. The cross-sectional shape of the binder fiber is not particularly limited, and a fiber having an irregular cross section such as a circular shape, a T shape, a Y shape, or a triangular shape can also be contained.

  The temperature at the time of hot pressing the non-coated surface is not particularly limited. Moreover, the roll on the side in contact with the non-coated surface is not particularly limited, and can be appropriately selected from a metal roll, a cotton roll, a resin roll, a fine rough surface metal roll, and the like.

  In the present invention, the nonwoven fabric composed of one layer in the wet papermaking stage needs to be laminated in two or more layers in the hot pressing process.

  In the hot-pressing process, metal rolls or a combination of a metal roll and a cotton roll, a resin roll, a fine rough surface metal roll, or the like can be appropriately selected for use. It is preferable that the semipermeable membrane application surface and the semipermeable membrane non-application surface are in contact with the metal roll at least once each because fuzzing of the semipermeable membrane support can be suppressed.

  In the wet papermaking stage, when a nonwoven fabric composed of one layer is laminated by hot pressing to make a single semipermeable membrane support, it is better to bond the surfaces in contact with the Yankee dryer and cylinder dryer. The semipermeable membrane support obtained by bonding can be made to have a lower density. The low density of the semipermeable membrane support is useful in preventing the semipermeable membrane coating solution developed on the semipermeable membrane application surface from penetrating the semipermeable membrane support and escaping to the back surface. is there. Although there is no clear reason for this mechanism, when one side of the wet paper is contacted and dried with, for example, a Yankee dryer, crystallization of the binder fiber strongly occurs on the surface that contacts the Yankee dryer, and the plasticity Therefore, it is expected that this portion maintains a low density even in hot pressing.

  Although the nonwoven fabric laminated | stacked in a hot press process will not be specifically limited if it is two or more layers, When two layers of the nonwoven fabric which reduced the basic weight of the semipermeable membrane support body are laminated | stacked, productivity can be improved most.

  The melting point of the binder fiber can be measured by differential thermal analysis. In the method for producing a semipermeable membrane support of the present invention, the induction exothermic metal roll having a surface temperature of −50 ° C. to + 10 ° C. with respect to the melting point of the binder fiber is in contact with the semipermeable membrane application surface. It is necessary to perform hot pressing. A more preferable surface temperature is −40 to ± 0 ° C. with respect to the melting point of the binder fiber, and a more preferable surface temperature is −30 to ± 0 ° C.

  When the temperature at the time of hot pressing of the semipermeable membrane coated surface is lower than the melting point of the binder fiber by more than 50 ° C., fluffing is likely to occur under any conditions. In addition, the air permeability profile is difficult to be uniform, and as a result, the back-through of the semipermeable membrane coating solution is likely to occur, which is not preferable. On the other hand, if the temperature at the time of hot press processing of the semipermeable membrane coated surface is higher than the melting point of the binder fiber by 10 ° C., the melt of the fiber adheres to the metal roll and the air permeability becomes non-uniform. It is not preferable.

  When performing hot-pressure processing, as a method for adjusting the surface temperature of the metal roll, the metal roll has a multi-layered structure, in which steam or heated oil is circulated, and heated by a heating wire embedded inside Although a system etc. are mentioned, when the metal roll which adjusts temperature by an induction heat generation system is used, the air permeability profile of the width direction and the flow direction of a semipermeable membrane support can be made more uniform.

  The nip pressure of the roll during the hot pressing is preferably 190 to 1800 N / cm, more preferably 390 to 1500 N / cm. The processing speed is preferably 5 to 150 m / min, and more preferably 10 to 80 m / min.

Although the basic weight of a semipermeable membrane support body is not specifically limited, 20-150 g / m < ² > is preferable, More preferably, it is 70-90 g / m < ² >. If it is less than 20 g / m ² , sufficient tensile strength may not be obtained. Moreover, when it exceeds 150 g / m < ² >, a liquid flow resistance may become high, thickness may increase, and a predetermined amount of semipermeable membrane may not be accommodated in a unit or a module.

The density of the semi-permeable membrane support is preferably 0.5 to 1.0 g / cm ^3, more preferably 0.6~0.9g / cm ^3. When the density of the semipermeable membrane support is less than 0.5 g / cm ³ , the thickness increases, and the area of the semipermeable membrane that can be incorporated into the unit is reduced. As a result, the life of the semipermeable membrane is shortened. May end up. On the other hand, when it exceeds 1.0 g / cm ³ , the liquid permeability may be lowered, and the life of the semipermeable membrane may be shortened.

  The thickness of the semipermeable membrane support is preferably 60 to 150 μm, more preferably 70 to 130 μm, and still more preferably 80 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 unit is reduced, and as a result, the life of the semipermeable membrane may be shortened. On the other hand, if the thickness is less than 60 μm, sufficient tensile strength may not be obtained or the liquid permeability may be reduced, and the life of the semipermeable membrane may be shortened.

  In the present invention, as a method for obtaining a semipermeable membrane support having a pinhole maximum value detected by transmitted light of 10 pixels or less, the average fiber diameter of the main fibers used is thinned and laminated during hot pressing. Increase the number of layers and reduce the paper making speed during paper making. Here, the maximum value of the pinhole detected by the transmitted light means the size of the pinhole penetrating in the thickness direction of the semipermeable membrane support, and when this number of pixels is large, the semipermeable membrane support The pinholes that exist in the body are large, meaning that moon-shaped defects are likely to occur. More effectively, when the average fiber diameter of the main fibers is 7 to 12 μm, it is possible to achieve both a semipermeable membrane support with less occurrence of fuzz and hardly causing membrane defects.

  In the present invention, a semipermeable membrane support having a maximum pinhole value detected by transmitted light of 10 pixels or less can also be obtained by slowing the papermaking speed in the wet papermaking stage. The clear mechanism in this case is unknown, but the maximum pinhole diameter is 10 pixels or less by making the paper making speed 30 m / min or less in the inclined wire type, circular net type, and long net type wet paper making methods. It can be.

  The invention is explained in more detail by means of examples. Hereinafter, unless otherwise specified, the parts and ratios described in the examples are based on mass.

Example 1
70% by mass of stretched polyester fiber having a fiber diameter of 7.5 μm as the main fiber (trade name: TA07N, manufactured by Teijin Limited), and 30% by mass of unstretched polyester binder fiber having a melting point of 260 ° C. as the binder fiber (trade name: TA04N) (Manufactured by Teijin Ltd.) was mixed and dispersed in water, and a wet paper was formed at a paper making speed of 30 m / min so that the basis weight after drying was 40 g / m ² with a circular paper machine. It was hot-pressure dried so as to come into contact with a Yankee dryer, and a nonwoven fabric having a basis weight of 40 g / m ² was obtained.

  Next, the surfaces of the obtained non-woven fabric in contact with the Yankee dryer are combined, and the surface temperature of the induction heat generation type metal roll is determined by a calender apparatus having a combination of an induction heat generation type metal roll and a resin roll having a Shore D hardness of 94 degrees. Is 225 ° C, nip pressure is 700 N / cm, and processing speed is 20 m / min. Then, heat treatment is performed again with a calender device having a combination of an induction heating type metal roll and a Shore D hardness of 94 degrees. The second hot pressing was performed under the conditions of a nip pressure of 700 N / cm and a processing speed of 20 m / min so that the surface in contact with the resin roll at the time of pressing was in contact with a metal roll having a surface temperature of 225 ° C. A semipermeable membrane support of Example 1 having an average fiber diameter of 7.5 μm was obtained.

(Example 2)
The fiber blending of the circular net paper machine is 40% by mass of stretched polyester fiber having a fiber diameter of 7.5 μm (trade name: TA07N, manufactured by Teijin Ltd.), and 30% by mass of stretched polyester fiber having a fiber diameter of 17.5 μm ( Product name: TA07N, manufactured by Teijin Limited), and 30 mass% of unstretched polyester binder fiber having a melting point of 260 ° C. as a binder fiber (trade name: TA04N, manufactured by Teijin Limited). A semipermeable membrane supporting material of Example 2 in which the average fiber diameter of the main fibers was 11.7 μm was obtained.

(Example 3)
The fiber blending of the circular paper machine is 10% by mass of stretched polyester fiber (trade name: TA04N, manufactured by Teijin Ltd.) with a fiber diameter of 7.5 μm, and 60% by mass of stretched polyester fiber with a fiber diameter of 12.5 μm (product). Name: TT07N, manufactured by Teijin Ltd.) Mainly the same method as in Example 1 except that 30% by mass of unstretched polyester binder fiber (trade name: TA04N, manufactured by Teijin Ltd.) having a melting point of 260 ° C. was used as the binder fiber. A semipermeable membrane support of Example 3 having an average fiber diameter of 11.8 μm was obtained.

(Comparative Example 1)
The fiber composition of the circular net paper machine is 70% by mass of stretched polyester fiber having a fiber diameter of 12.5 μm (trade name: TT07N, manufactured by Teijin Ltd.), and 30 mass of unstretched polyester binder fiber having a melting point of 260 ° C. as a binder fiber. % (Trade name: TA04N, manufactured by Teijin Ltd.) was obtained in the same manner as in Example 1 to obtain a semipermeable membrane support of Comparative Example 1 in which the average fiber diameter of the main fibers was 12.5 μm.

(Comparative Example 2)
The fiber composition of the circular net paper machine is 70% by mass of a stretched polyester fiber having a fiber diameter of 17.5 μm (trade name: TA07N, manufactured by Teijin Ltd.), and 30 mass of an unstretched polyester binder fiber having a melting point of 260 ° C. as a binder fiber. % (Trade name: TA04N, manufactured by Teijin Ltd.) was obtained in the same manner as in Example 1 to obtain a semipermeable membrane support of Comparative Example 2 in which the average fiber diameter of the main fibers was 17.5 μm.

(Comparative Example 3)
The fiber composition of the circular net paper machine is 70% by mass of a stretched polyester fiber having a fiber diameter of 5.3 μm (trade name: TA04TN, manufactured by Teijin Ltd.), and 30 mass of an unstretched polyester binder fiber having a melting point of 260 ° C. as a binder fiber. % (Trade name: TA04N, manufactured by Teijin Ltd.) was obtained in the same manner as in Example 1 to obtain a semipermeable membrane support of Comparative Example 3 in which the average fiber diameter of the main fibers was 5.3 μm.

(Comparative Example 4)
10% by mass of stretched polyester fiber (trade name: TA04N, manufactured by Teijin Ltd.) and 60% by mass of stretched polyester fiber having a fiber diameter of 12.5 μm (trade name) : TT07N, manufactured by Teijin Ltd.), a non-stretched polyester binder fiber having a melting point of 260 ° C. (trade name: TA04N, manufactured by Teijin Ltd.) as a binder fiber, and a nonwoven fabric having a basis weight of 80 g / m ² A semipermeable membrane support of Comparative Example 4 in which the average fiber diameter of the main fibers was 11.8 μm was obtained in the same manner as in Example 1 except that it was hot-pressed with a single layer.

  The following evaluations were performed on the semipermeable membrane supports obtained in Examples and Comparative Examples, and the results are shown in Table 1.

Test 1 (Measurement of maximum pinhole pixels by transmitted light)
A semipermeable membrane support made with a width of 1 m is cut into a sheet of width 20 cm × flow direction 20 cm × 5, light is applied from the semipermeable membrane application surface side to the opposite surface side, and the size is 50 mm × 50 mm per sheet. Then, a transmitted light image was taken under the following conditions.
・ Film type: Positive film ・ Image quality: 8-bit gray, image quality priority ・ Resolution: 800 dpi

  The luminance histogram of the bitmap (BMP) image taken here is observed with the image processing software Jtrim, and the luminance with the highest luminance histogram is set as the luminance of the peak top. Was implemented. The maximum pinhole diameter was measured from the binarized image using image processing software ImageJ, and the maximum pinhole diameter observed at that time was defined as the maximum number of pinhole pixels. When the maximum number of pinhole pixels is 10 pixels or less, there is no practical problem.

Test 2 (observation of membrane defects)
A polysulfone resin (trade name: Udel P3500, manufactured by Solvay Specialty Polymers) was dissolved in dimethylformamide so as to be 20% by mass, and the viscosity at 60 rpm of a Brookfield viscometer was 1.1 Pa · s. A permeable membrane coating solution was prepared. Twenty sheets of each semipermeable membrane support cut into a width of 20 cm and a flow of 25 cm were collected, the total area was 1 m2, and a semipermeable membrane coating solution was applied with a film applicator so that the final thickness was 50 μm. After coating and leaving for 10 seconds, the film was immersed at an angle of 90 degrees with respect to the water surface to observe whether a film defect occurred. If the generated film defects were 1 piece / m ² or less, there was no problem in practical use.

Test 3 (Observation of the amount of fluffing on the semipermeable membrane application surface)
A semipermeable membrane support made with a width of 1 m was divided into 5 parts in the width direction, and after making 5 test pieces cut into a width direction of 10 cm and a flow direction of 5 cm in an arbitrary place, the diameter was It was wound around an 18 mm paper tube so that the semipermeable membrane application surface was on the outside, the surface was observed with a microscope, and fuzz having a length of 80 μm or more was calculated. If it was 5 / 0.025 cm ² or less, it was regarded as practically no problem.

  Semi-transparent materials of Examples 1 to 3, in which a nonwoven fabric composed of one layer is laminated in two or more layers in the hot papermaking process, and the maximum pinhole value detected by transmitted light is 10 pixels or less. The result was that the membrane support had less fuzz and less membrane defects. In Examples 1 to 3, the average fiber diameter of the main fibers is 7 to 12 μm, the paper making speed in the wet paper making stage is 30 m / min or less, the fuzz is small, and the amount of film defects is small. there were. On the other hand, the semipermeable membrane support of Comparative Example 4 constituted by a single layer in the wet papermaking stage and the hot pressing process, the half of Comparative Examples 1 to 3 in which the average fiber diameter of the main fibers is outside the preferred range of the present invention. The result was that the permeable membrane support had a lot of fuzz or a large amount of membrane defects.

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

Claims (3)

  Semi-transparent, characterized in that a non-woven fabric composed of one layer in the wet papermaking stage is laminated in two or more layers in hot pressing, and the size of pinholes detected by transmitted light is 10 pixels or less. Membrane support.   The semipermeable membrane supporting material according to claim 1, wherein the main fiber has an average fiber diameter of 7 to 12 µm.   The semipermeable membrane support according to claim 1 or 2, wherein the paper making speed in the wet paper making stage is 30 m / min or less.