JP2021107053A - Semipermeable membrane support for membrane separation active sludge treatment - Google Patents

Abstract

To provide a semipermeable membrane support for membrane separation active sludge treatment which makes a semipermeable membrane solution less likely to strike through a non-coating surface.SOLUTION: A semipermeable membrane support for membrane separation active sludge treatment is formed of a non-woven fabric including at least a main body synthetic fiber and a binder synthetic fiber as synthetic fibers. The semipermeable membrane support for membrane separation active sludge treatment includes a synthetic fiber having a fiber length of 0.2 mm or shorter.SELECTED DRAWING: None

Description

The present invention relates to a semipermeable membrane support for membrane separation activated sludge treatment.

Semipermeable membranes are widely used in fields such as desalination of seawater, water purifiers, food concentration, wastewater treatment, medical use represented by hemofiltration, and ultrapure water production for semiconductor cleaning. The separating functional layer of the semipermeable membrane is composed of a porous resin such as a cellulose-based resin, a polysulfone-based resin, a polyacrylonitrile-based resin, a fluorine-based resin, and a polyester-based resin. However, since these porous resins alone are inferior in mechanical strength, a filtration membrane in the form of a composite in which a semipermeable membrane is provided on one side of a semipermeable membrane support made of a fiber base material such as a non-woven fabric or a woven fabric. Is used. In the semipermeable membrane support, the surface on which the semipermeable membrane is provided is referred to as a "coated surface".

One of the usage forms of these semipermeable membranes and filtration membranes is a membrane separation activated sludge treatment method (Membrane Bioreactor, MBR). The membrane separation activated sludge treatment method is widely used because the treated water quality is stable and maintenance is easy when treating organic sewage. Membrane separation In the activated sludge treatment method, after removing impurities in the sewage, organic substances in the sewage are decomposed and removed by the activated sludge in the biological treatment tank (aeration tank), and the immersion type membrane separation installed in the biological treatment tank. The mixed solution is solid-liquid separated by the device, and the permeated filtered solution is discharged as treated water. The membrane separation part in such a membrane separation device is subjected to an aeration operation performed to prevent clogging and supply of oxygen to activated sludge, as well as violent collision of inorganic substances such as sand, sludge, and other solid substances during use. Since air bubbles violently collide with the membrane surface, it is necessary to secure the thickness of the semipermeable membrane provided on the semipermeable membrane support.

The performance required for the semipermeable membrane support for membrane separation active sludge treatment is that it has excellent adhesion to the resin frame and smoothness of the coated surface, there are few irregularities in the semipermeable membrane after film formation, and the semipermeable membrane solution. It is possible to secure a certain thickness as a semipermeable membrane on the semipermeable membrane support without strike-through to the non-coated surface (the surface opposite to the coated surface).

In order to solve the above problems, the basic structure is a double structure consisting of a surface layer with a large surface roughness using thick fibers (thick fiber layer) and a back layer with a dense structure using fine fibers (thin fiber layer). A semipermeable membrane support made of a non-woven fabric having a multi-layer structure (see, for example, Patent Document 1) has been proposed. With this configuration, it is possible to maintain good adhesion between the semipermeable membrane and the semipermeable membrane support, but strike-through of the semipermeable membrane solution to the non-coated surface occurs, and the semipermeable membrane There is a problem that the component hinders the adhesiveness with the resin frame.

A semipermeable membrane support made of a non-woven fabric using polyester fibers having specific birefringence and heat shrinkage stress (see, for example, Patent Document 2), and a semipermeable membrane having a specific tensile strength ratio in the papermaking flow direction and the width direction. Membrane supports (see, for example, Patent Document 3) and the like have been proposed. However, when used for membrane separation activated sludge treatment, there is a problem that the semipermeable membrane solution strikes through to the non-coated surface.

A semipermeable membrane support (see, for example, Patent Document 4) in which a main fiber made of polyester fiber and a binder fiber made of core-sheath type polyester composite fiber are blended in a specific ratio has been proposed. Although the semipermeable membrane support having this structure is excellent in texture and strength, there is a problem that the semipermeable membrane solution strikes through to the non-coated surface when used for membrane separation activated sludge treatment.

Tokuho 4-21526 Gazette Japanese Patent No. 3153487 JP-A-2002-95937 JP-A-2010-194478

An object of the present invention is to provide a semipermeable membrane support for membrane separation active sludge treatment in which a semipermeable membrane solution does not easily strike through to a non-coated surface.

As a result of diligent studies to solve the above problems, the following inventions were found.

(1) As the synthetic fiber, a semipermeable membrane support for film separation active sludge treatment, which is made of a non-woven fabric containing at least a main synthetic fiber and a binder synthetic fiber, contains a synthetic fiber having a fiber length of 0.2 mm or less. A semipermeable membrane support for membrane separation active sludge treatment.

The semipermeable membrane support for membrane separation active sludge treatment of the present invention is made of a non-woven fabric containing at least a main synthetic fiber and a binder synthetic fiber as synthetic fibers, and contains synthetic fibers having a fiber length of 0.2 mm or less. This made it possible to produce a semipermeable membrane support for membrane separation active sludge treatment in which the semipermeable membrane solution does not easily strike through to the non-coated surface.

It is a fiber length distribution figure of the slurry containing the main synthetic fiber, the binder synthetic fiber, and the synthetic fiber of a fiber length 0.2 mm or less. It is a microscope photograph of a main synthetic fiber and a synthetic fiber of a fiber length of 0.2 mm or less.

The semitransparent film support for film separation active sludge treatment of the present invention is made of a non-woven fabric containing at least a main synthetic fiber and a binder synthetic fiber as synthetic fibers, and contains synthetic fibers having a fiber length of 0.2 mm or less. It is characterized by that. In the present specification, "semipermeable membrane support for membrane separation activated sludge treatment" may be abbreviated as "semipermeable membrane support". Further, "synthetic fiber having a fiber length of 0.2 mm or less" may be abbreviated as "short fiber".

The semipermeable membrane support of the present invention is preferably produced by producing a sheet by a wet papermaking method and then hot-pressing the sheet with a thermal roll. The raw material fibers for producing a sheet by the wet papermaking method include a main synthetic fiber, a binder synthetic fiber, and a synthetic fiber having a fiber length of 0.2 mm or less.

FIG. 1 shows the fiber length of a fiber slurry containing a main synthetic fiber, a binder synthetic fiber, and a synthetic fiber having a fiber length of 0.2 mm or less. It is a fiber length distribution map measured by the fiber quality analyzer (FQA-360) manufactured by the company. It can be seen that synthetic fibers having a fiber length of 0.2 mm or less are contained.

FIG. 2 is a photograph of a main synthetic fiber and a synthetic fiber having a fiber length of 0.2 mm or less taken with a microscope at a magnification of 200 times. The fibers in the circle are synthetic fibers having a fiber length of 0.2 mm or less, and the other fibers are main synthetic fibers.

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 fiber include fibers such as polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, polybenzoate-based, polyclaral-based, and polyphenol-based fibers, which are heat-resistant. Polyester-based fibers having high properties are more preferable. In addition, semi-synthetic fibers such as acetate, triacetate and promix, and regenerated fibers such as rayon, cupra and lyocell fibers may be contained within a range that does not impair the performance.

The diameter of the main synthetic fiber is not particularly limited, but is preferably 30 μm or less. It is more preferably 2 to 20 μm, still more preferably 4 to 20 μm, and particularly preferably 6 to 20 μm. If it is less than 2 μm, the semipermeable membrane solution may not easily penetrate into the semipermeable membrane support, and the adhesiveness between the semipermeable membrane and the semipermeable membrane support may be deteriorated. If the diameter of the main synthetic fiber exceeds 30 μm, there may be a problem that a large amount of semipermeable membrane solution is required to obtain the desired thickness of the semipermeable membrane, or strike-through of the semipermeable membrane solution may occur. May occur. In addition, the main synthetic fibers on the surface of the non-woven fabric tend to stand up and penetrate the semipermeable membrane, which may reduce the performance of the semipermeable membrane.

The fiber length of the main synthetic fiber is not particularly limited, but is preferably 0.2 to 12 mm, more preferably 1 to 10 mm, and further preferably 4 to 6 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 papermaking process is preferably 1.0 to less than 1.2. .. When the fiber cross-sectional aspect ratio is 1.2 or more, the fiber dispersibility may decrease, or the uniformity of the semipermeable membrane support and the smoothness of the coated surface may be adversely affected due to the occurrence of fiber entanglement and entanglement. be. However, fibers having irregular cross sections such as T-type, Y-type, and triangular can also be contained within a range that does not impair other properties such as fiber dispersibility in order to prevent strike-through and surface smoothness.

The aspect ratio (fiber length / diameter) of the main synthetic fiber is preferably 10 to 1000, more preferably 20 to 900, and further preferably 40 to 800. When the aspect ratio is less than 10, the dispersibility of the fibers is good, but the fibers may fall off from the papermaking wire during papermaking, or the fibers may stick into the papermaking wire and the peelability from the wire may deteriorate. be. On the other hand, if it exceeds 1000, although it contributes to the formation of a three-dimensional network of fibers, the uniformity of the semipermeable membrane support and the smoothness of the coated surface may be adversely affected by the occurrence of entanglement and entanglement of the fibers. ..

The content of the main synthetic fiber is preferably 38 to 89.9% by mass, more preferably 48.4 to 79.8% by mass, and 58.6 to 58.6% by mass with respect to the nonwoven fabric related to the semipermeable membrane support of the present invention. 74.7% by mass is more preferable. If the content of the main synthetic fiber is less than 38% by mass, the liquid permeability may decrease. If it exceeds 89.9% by mass, it may be torn due to insufficient strength.

The semipermeable membrane support of the present invention contains a binder synthetic fiber. By incorporating a step of raising the temperature above the softening point or melting temperature (melting point) of the binder synthetic fiber into the manufacturing process of the semipermeable membrane support, the binder synthetic fiber improves the mechanical strength of the semipermeable membrane support. For example, the semipermeable membrane support can be manufactured by a wet papermaking method, and the binder synthetic fiber can be softened or melted in a subsequent drying step.

Examples of the binder synthetic fiber include core-sheath fibers (core-shell type), parallel fibers (side-by-side type), composite fibers such as radial split fibers, and undrawn fibers. Since the composite fiber is difficult to 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 point polyester (core) and low melting point polyester (sheath), polyester, etc. Undrawn fibers can be mentioned. In addition, single fibers (total fusion type) composed only of low melting point resins such as polyethylene and polypropylene, and hot water-soluble binders such as polyvinyl alcohols tend to form a film in the drying process of the semipermeable membrane support. However, it can be used as long as the characteristics are not impaired. In the present invention, a combination of a high melting point polyester (core) and a low melting point polyester (sheath), and undrawn polyester fibers can be preferably used.

The diameter of the binder synthetic fiber is not particularly limited, but is preferably 2 to 20 μm, more preferably 5 to 15 μm, and further preferably 7 to 12 μm. Further, the diameter is preferably different from that of the main synthetic fiber, and particularly preferably the diameter is larger than that of the main synthetic fiber. Since the diameter is different from that of the main synthetic fiber, the binder synthetic fiber not only plays a role of improving the mechanical strength of the semipermeable membrane support, but also plays a role of forming a uniform three-dimensional network together with the main synthetic fiber. Further, in the step of raising the temperature to the softening temperature or the melting temperature or higher of the binder synthetic fiber, the smoothness of the surface of the semipermeable membrane support can also be improved, and it is more effective when the step is accompanied by pressurization. be.

The fiber length of the binder synthetic fiber is not particularly limited, but is preferably 0.2 to 12 mm, more preferably 1 to 10 mm, and further preferably 4 to 6 mm. The cross-sectional shape of the binder synthetic fiber is preferably circular, but fibers having irregular cross-sections such as T-type, Y-type, and triangular are also used for preventing strike-through, smoothness of coated surfaces, and adhesiveness between non-coated surfaces. Can be contained within a range that does not impair the characteristics of.

The aspect ratio (fiber length / diameter) of the binder synthetic fiber is preferably 10 to 1000, more preferably 20 to 800, and further preferably 40 to 700. When the aspect ratio is less than 10, the dispersibility of the fibers is good, but there is a risk that the fibers may fall off from the papermaking wire during papermaking, or the fibers may stick into the papermaking wire and the peelability from the wire may deteriorate. be. On the other hand, if it exceeds 1000, the binder synthetic fiber contributes to the formation of the three-dimensional network, but the fibers may be entangled or entangled, which may adversely affect the uniformity of the non-woven fabric and the smoothness of the coated surface. ..

The content of the binder synthetic fiber is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and further preferably 25 to 40% by mass with respect to the nonwoven fabric related to the semipermeable membrane support of the present invention. If it is less than 10% by mass, it may be torn due to insufficient strength. On the other hand, if it exceeds 60% by mass, the liquid permeability may decrease.

In the present invention, the synthetic fiber having a fiber length of 0.2 mm or less is a fiber that supplements the skeleton formation of the semipermeable membrane support. Examples of short fibers include polyolefin-based, polyamide-based, polyacrylic, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, polybenzoate-based, polyclaral-based, and polyphenol-based fibers, which are heat-resistant. Higher polyester fibers are more preferred. In addition, semi-synthetic fibers such as acetate, triacetate and promix, and regenerated fibers such as rayon, cupra and lyocell fibers may be contained within a range that does not impair the performance.

The diameter of the short fibers is not particularly limited, but is preferably 30 μm or less. It is more preferably 2 to 20 μm, still more preferably 4 to 20 μm, and particularly preferably 5 to 20 μm. If it is less than 2 μm, it will often fall off from the papermaking net during wet papermaking. On the other hand, if the diameter of the fiber exceeds 30 μm, the short fibers on the surface of the non-woven fabric tend to stand up and penetrate the semipermeable membrane, which may deteriorate the performance of the semipermeable membrane.

The fiber length of the short fibers is 0.2 mm or less, preferably 0.05 to 0.2 mm, and more preferably 0.1 to 0.2 mm. The cross-sectional shape of the short fibers is preferably circular, but short fibers having irregular cross sections such as T-shaped, Y-shaped, and triangular can also be contained for the purpose of preventing strike-through and surface smoothness. The short fibers are fibers that are in contact with the binder synthetic fibers in the sheet and control the voids of the semipermeable membrane support. By being present in the voids between the binder synthetic fibers and at the contact points between the main synthetic fibers and the binder synthetic fibers, the voids are subdivided to prevent strike-through of the semipermeable membrane solution and improve the surface smoothness.

The short fibers are formed by cutting the main synthetic fibers and the binder synthetic fibers at the clearance between the stirring blade and the container, which are rotated by a device such as a pulper that disperses in water, in the wet papermaking process. In addition, the fibers are cut into short pieces and formed during the manufacturing process of the main synthetic fiber and the binder synthetic fiber.

In the semipermeable membrane support of the present invention, the content ratio of the short fibers is not particularly limited, but is preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.6% by mass. More preferably, it is 0.3 to 1.4% by mass. If it is less than 0.1% by mass, the effect of preventing strike-through of the semipermeable membrane may not be obtained. On the other hand, if it exceeds 2.0% by mass, short fibers may be desorbed from the semipermeable membrane support and the membrane performance may deteriorate. The content ratio of the short fibers in the present invention is such that the fiber length of the pulper-dispersed slurry is measured in the measurement range of 0.07 to 20 mm and the cutoff value is 0.20 mm. It is a "fine ratio (length-weighted average value)" obtained by measuring with a fiber quality analyzer (FQA-360) manufactured by the company, and is the ratio of short fibers having a fiber length of 0.2 mm or less to the fibers contained in the slurry. ..

The method for producing the semipermeable membrane support of the present invention will be described. In the semipermeable membrane support of the present invention, it is preferable that the sheet is thermally pressure-processed by a thermal roll after the sheet is produced by a wet papermaking method.

In the wet papermaking method, the fibers were first uniformly dispersed in water, and then the final fiber concentration was adjusted to 0.01 to 0.50% by mass through steps such as a screen (removal of foreign matter, lumps, etc.). The slurry is made with a paper machine to obtain wet paper. In order to make the dispersibility of fibers uniform, chemicals such as dispersants, defoamers, hydrophilic agents, antistatic agents, polymer thickeners, mold release agents, antibacterial agents, and bactericides may be added during the process. be.

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 making method selected from these paper making methods, or a combination paper machine in which two or more paper machines of the same type or different types selected from these paper making methods are installed online. can do. Further, in the case of producing a non-woven fabric having a multi-layer structure of two or more layers, a laminating method in which wet papers made by each paper machine are laminated, or after forming one sheet, the sheet is placed on the sheet. A method of casting a slurry in which fibers are dispersed can be used.

A sheet is obtained by drying the wet paper produced by the paper machine with a Yankee dryer, an air dryer, a cylinder dryer, a suction drum type dryer, an infrared type dryer, or the like. When the wet paper is dried, it is brought into close contact with a heat roll such as a Yankee dryer and heat-pressure dried, so that the smoothness of the adhered surface is improved. Hot pressure drying means drying by pressing wet paper against the hot roll with a touch roll or the like. The surface temperature of the heat roll is preferably 100 to 180 ° C, more preferably 100 to 160 ° C, and even more preferably 110 to 160 ° C. The pressure is preferably 5 to 100 kN / m, more preferably 10 to 80 kN / m.

In the present invention, it is preferable that the sheet is further subjected to a thermal calendar treatment. In the thermal calendar processing, a calendar unit having a roll structure such as a metal roll-metal roll, a metal roll-elastic roll, a metal roll-cotton roll, and a metal roll-silicon roll can be used alone or in combination. At least one metal roll of the calendar unit is heated. In the present invention, it is preferable to use a metal roll-elastic roll calendar unit because a sufficient amount of heat can be applied to the non-woven fabric and a high-strength semipermeable membrane support can be obtained.

The metal roll temperature during the thermal calendar treatment is preferably in the range of −50 ° C. to −10 ° C. with respect to the melting point of the binder synthetic fiber. More preferably, it is in the range of −40 ° C. to −15 ° C., and even more preferably, it is in the range of −35 ° C. to −20 ° C.

For example, when the melting point of the binder synthetic fiber is 260 ° C., the surface temperature of the semipermeable membrane support is preferably 210 to 250 ° C., more preferably 220 to 245 ° C. When the temperature is lower than −50 ° C. with respect to the melting point of the binder synthetic fiber, the strength of the semipermeable membrane support may not be sufficiently obtained.

The nip pressure during the thermal calendar treatment is preferably 19 to 180 kN / m, more preferably 39 to 150 kN / m. The processing speed is preferably 3 to 150 m / min, more preferably 5 to 80 m / min.

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, if it exceeds 150 g / m ² , the liquid passage resistance may increase or the thickness may increase and a specified amount of semipermeable membrane may not be stored in the unit or module.

The density of the semipermeable membrane support ^{is preferably 0.5 to 1.0 g / cm 3} , and more preferably 0.6 to 0.9 g / cm ³ . If the density of the semipermeable membrane support is ^{less than 0.5 g / cm 3} , the thickness becomes thicker, so that the area of the semipermeable membrane that can be incorporated into the unit becomes smaller, and as a result, the life of the semipermeable membrane becomes shorter. It may end up. On the other hand, ^{if 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 50 to 150 μm, more preferably 60 to 130 μm, and even more preferably 70 to 120 μm. If the thickness of the semipermeable membrane support exceeds 150 μm, the area of the semipermeable membrane that can be incorporated into the unit 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 the liquid permeability may be lowered, so that the life of the semipermeable membrane may be shortened.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the present examples.

(Example 1)
Main synthetic fiber (stretched polyester fiber, diameter 8 μm, fiber length 6 mm), binder synthetic fiber (unstretched polyester fiber, diameter 11.8 μm, fiber length 5 mm, melting point 260 ° C) solid content at 70:30 4 kg of fiber was ^{put into a 2 m 3} pulper (dispersion container) ^{together with 1 m 3} of dispersed water and dispersed for 10 minutes to prepare a slurry. The fiber length of the slurry was determined by OpTest Equipment Inc. When measured with a fiber quality analyzer (FQA-360) manufactured by the same company, the content ratio of short fibers was 1.5% by mass. A wet paper was formed from the slurry with a circular net paper machine and then hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having ^{a target basis weight of 78 g / m 2.}

The obtained sheet is hot-press processed under the conditions of a heated metal roll surface temperature of 225 ° C., a pressure of 80 kN / m, and a processing speed of 30 m / min, using a calendar device that is a combination of a heated metal roll and a resin roll in the first stage. Using a calendar device that combines the resin roll and the heated metal roll of the second stage so that the surface of the sheet in contact with the heated metal roll is in contact with the resin roll, the surface temperature of the heated metal roll is 230 ° C. and the pressure is 80 kN. Thermal pressure processing was performed under the conditions of / m and a processing speed of 30 m / min to obtain a semitransparent film support. The surface that first came into contact with the heated metal roll was used as the coated surface.

(Example 2)
Main synthetic fiber (stretched polyester fiber, diameter 8 μm, fiber length 6 mm), binder synthetic fiber (unstretched polyester fiber, diameter 11.8 μm, fiber length 5 mm, melting point 260 ° C) solid content at 70:30 4 kg of fiber was ^{put into a 2 m 3} pulper (dispersion container) ^{together with 1 m 3} of dispersed water and dispersed for 10 minutes to prepare a slurry. The slurry 18 strained with a net mesh was removed leaving only the dispersed water fibers, new water 1 m ³ added was recreate dispersed slurry and adjusting construed the fibers. The fiber length of the redispersion slurry was determined by OpTest Equipment Inc. FIG. 1 shows a fiber length distribution diagram measured by a fiber quality analyzer (FQA-360) manufactured by the same company. The content ratio of short fibers was 0.9% by mass. A wet paper was formed from the redispersed slurry with a circular net paper machine and then hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having ^{a target basis weight of 78 g / m 2.}

The obtained sheet is hot-press processed under the conditions of a heated metal roll surface temperature of 225 ° C., a pressure of 80 kN / m, and a processing speed of 30 m / min, using a calendar device that is a combination of a heated metal roll and a resin roll in the first stage. Using a calendar device that combines the resin roll and the heated metal roll of the second stage so that the surface of the sheet in contact with the heated metal roll is in contact with the resin roll, the surface temperature of the heated metal roll is 230 ° C. and the pressure is 80 kN. Thermal pressure processing was performed under the conditions of / cm and a processing speed of 30 m / min to obtain a semitransparent film support. The surface that first came into contact with the heated metal roll was used as the coated surface.

(Example 3)
Main synthetic fiber (stretched polyester fiber, diameter 8 μm, fiber length 6 mm), binder synthetic fiber (unstretched polyester fiber, diameter 11.8 μm, fiber length 5 mm, melting point 260 ° C) solid content at 70:30 4 kg of fiber was ^{put into a 2 m 3} pulper (dispersion container) ^{together with 1 m 3} of dispersed water and dispersed for 10 minutes to prepare a slurry. The slurry 18 strained with a net mesh was removed leaving only the dispersed water fibers, new water 1 m ³ was added made a re-dispersed slurry tone construed the fibers. Leaving only fibers to remove dispersed water strained then redispersed slurry 18 mesh net, were forms regulating the retrocession dispersed slurry construed fibers newly water 1 m ³ was added. When the fiber length of the redispersed slurry was measured, the content ratio of the short fibers was 0.2% by mass. A wet paper was formed from the redispersed slurry with a circular net paper machine, and then hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having ^{a target basis weight of 78 g / m 2.}

The obtained sheet is hot-press processed under the conditions of a heated metal roll surface temperature of 225 ° C., a pressure of 100 kN / m, and a processing speed of 30 m / min, using a calendar device that is a combination of a heated metal roll and a resin roll in the first stage. Using a calendar device that combines the resin roll and the heated metal roll of the second stage so that the surface of the sheet in contact with the heated metal roll is in contact with the resin roll, the surface temperature of the heated metal roll is 230 ° C. and the pressure is 100 kN. Thermal pressure processing was performed under the conditions of / m and a processing speed of 30 m / min to obtain a semitransparent film support. The surface that first came into contact with the heated metal roll was used as the coated surface.

(Comparative Example 1)
Main synthetic fiber (stretched polyester fiber, diameter 8 μm, fiber length 6 mm), binder synthetic fiber (unstretched polyester fiber, diameter 11.8 μm, fiber length 5 mm, melting point 260 ° C) solid content at 70:30 4 kg of fiber was ^{put into a 2 m 3} pulper (dispersion container) ^{together with 1 m 3} of dispersed water and dispersed for 10 minutes to prepare a slurry. The slurry is strained with an 18-mesh net to remove the dispersed water, leaving only the fibers, and 1 m ³ of water is newly added to dissolve the fibers to prepare the redispersed slurry, and then the redispersed slurry is made into an 18-mesh net. and strained by leaving only the fiber to remove the dispersion water to form regulating the retrocession dispersed slurry construed fibers newly water 1 m ³ was added. The redispersed slurry was strained with an 18-mesh net to remove dispersed water leaving fibers, and the operation of adding fresh water was performed twice more to prepare the final slurry. When the fiber length of the final slurry was measured, the content ratio of the short fibers was 0.0% by mass. A wet paper was formed from the final slurry with a circular net paper machine and then hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having ^{a target basis weight of 78 g / m 2.}

The obtained sheet is hot-press processed under the conditions of a heated metal roll surface temperature of 225 ° C., a pressure of 80 kN / m, and a processing speed of 50 m / min, using a calendar device that is a combination of a heated metal roll and a resin roll in the first stage. Using a calendar device that combines the resin roll and the heated metal roll of the second stage so that the surface of the sheet in contact with the heated metal roll is in contact with the resin roll, the surface temperature of the heated metal roll is 230 ° C. and the pressure is 80 kN. Thermal pressure processing was performed under the conditions of / m and a processing speed of 50 m / min to obtain a semitransparent film support. The surface that first came into contact with the heated metal roll was used as the coated surface.

The semipermeable membrane supports obtained in Examples and Comparative Examples were evaluated for basis weight, thickness, air permeability, and semipermeable membrane penetration, and the results are shown in Table 1.

(Basis weight)
Basis weight was measured according to JIS P8124: 2011.

(Thickness)
The thickness of the semipermeable membrane support was measured according to JIS P8118: 2014.

(Breathability)
The air permeability by the Frazier method was measured according to JIS L 1096: 2010.

(Semipermeable membrane penetration)
A semipermeable membrane support is set on the mount using a constant-speed coating device (trade name: Automatic Film Applicator, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) with a certain clearance, and is applied to the coated surface of the semipermeable membrane support. An N, N-dimethylacetamide solution (concentration: 26% by mass) of polyvinylidene fluoride (PVDF) is applied, washed with water and dried to form a PVDF film on the surface of the semipermeable membrane support to prepare a semipermeable membrane. , A cross-sectional SEM photograph of the semipermeable membrane was taken to evaluate the degree of penetration of PVDF into the semipermeable membrane support.

⊚: PVDF has penetrated only to the vicinity of the center of the semipermeable membrane support. Very good level.
◯: PVDF does not exude to the non-coated surface of the semipermeable membrane support. Good level.
Δ: PVDF partially exudes to the non-coated surface of the semipermeable membrane support. Available level.
X: PVDF exudes to the non-coated surface of the semipermeable membrane support. Unusable level.

The semipermeable membrane penetration evaluation of the semipermeable membrane of the semipermeable membrane support of Example 1 and Example 2 was ◯, which was a good level. The evaluation of the semipermeable membrane support of Example 3 was Δ, which was a usable level. On the other hand, the evaluation of the semipermeable membrane support of Comparative Example 1 containing no short fibers was x, which was a practically unusable level.

Claims (1)

As a synthetic fiber, a semipermeable membrane support for film separation active sludge treatment, which is made of a non-woven fabric containing at least a main synthetic fiber and a binder synthetic fiber, is characterized by containing a synthetic fiber having a fiber length of 0.2 mm or less. Semipermeable membrane support for membrane separation active sludge treatment.

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