JP7102572B1 - Method for manufacturing semipermeable membrane support and semipermeable membrane support - Google Patents

Abstract

An object of the present invention is to provide a semipermeable membrane support in which the peel strength between the semipermeable membrane and the semipermeable membrane support is improved. In a semipermeable membrane support made of a wet-laid nonwoven fabric containing main synthetic fibers and binder synthetic fibers, the fiber orientation strength of the coating surface on which the semipermeable membrane is provided is 1.00 or more and 1.30 or less, and the semipermeable membrane support is not coated. The fiber orientation strength of the surface is 1.00 or more and 1.50 or less, and the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. A semipermeable membrane support, wherein the average area of the permeable membrane is 500 μm 2 or less, and the residual rate of the semipermeable membrane is 2.5% or more and 5.0% or less. [Selection figure] None

Description

The present invention relates to a semipermeable membrane support and a method for manufacturing a semipermeable membrane support.

Semipermeable membranes are widely used in fields such as seawater desalination, water purifiers, food concentration, wastewater treatment, medical use represented by hemofiltration, and ultrapure water production for semiconductor cleaning. The semipermeable membrane is composed of a synthetic resin such as a cellulosic resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, and a polyester resin. However, since the semipermeable membrane alone is inferior in mechanical strength, it is used as a separation 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. Has been done. The surface of the semipermeable membrane support on which the semipermeable membrane is provided is referred to as a "coated surface", and the surface on the opposite side is referred to as a "non-coated surface".

As the semipermeable membrane support, a non-woven fabric containing synthetic fibers is mainly used. In particular, polyester-based wet non-woven fabrics are often used (see, for example, Patent Documents 1 and 2). Conventionally, antimony compounds typified by antimony trioxide have been widely used as polymerization catalysts for polyester fibers constituting these semipermeable membrane supports. Antimony trioxide is inexpensive and has excellent catalytic activity, but in recent years, environmental problems have been pointed out in various countries including Europe and the United States.

Further, as the performance required for the semipermeable membrane support, the adhesion between the semipermeable membrane and the semipermeable membrane support is good, and in order to provide the semipermeable membrane, the semipermeable membrane solution is a semipermeable membrane. When applied to the support, the semipermeable membrane solution does not strike through to the non-coated surface, the semipermeable membrane has few defects, and the semipermeable membrane does not peel off from the semipermeable membrane support.

When separating using a semi-transparent membrane, if impurities contained in water accumulate on the surface of the semi-transparent membrane and the semi-transparent membrane is clogged or the permeation flux is reduced, the membrane may be washed with a high-pressure water stream. If the peeling strength between the semitransparent film and the semitransparent film support is low, the semitransparent film is peeled off from the semitransparent film support and the semitransparent film is damaged, so that sufficient membrane performance cannot be obtained. Further, when the semipermeable membrane is stopped during high-pressure operation and the semipermeable membrane is peeled off from the semipermeable membrane support due to the backflow of permeated water, the semipermeable membrane performance is deteriorated.

In the step of wet-making a fiber slurry in which synthetic fibers are dispersed in water to form a non-woven fabric, for the purpose of improving the uniformity of the semi-transparent film support so that the semi-transparent solution does not strike through, the said at the time of paper making. The fiber content concentration of the fiber slurry is 0.01 to 0.1% by mass, and a water-soluble polymer having a molecular weight of 5 million or more is added to the fiber slurry as a polymer viscous agent from 3 to 3 based on the fiber content mass. A method of making paper with a content of 15% by mass has been proposed (see, for example, Patent Document 3). However, since the polymer viscous agent is excessively added, the uniformity is improved, but the viscosity of the fiber slurry on the papermaking net is increased, the dehydration property from the papermaking net is lowered, and the production rate cannot be increased. There was a possibility that the problem would occur. In addition, there is also a problem that the polymer viscous agent remains on the surface of the fiber forming the semipermeable membrane support after papermaking.

Also, from a multilayer structure non-woven fabric based on 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 semi-transparent membrane support has been proposed (see, for example, Patent Document 4). Specifically, a semipermeable membrane support having a thick fiber layer as a coated surface and a thin fiber layer as a non-coated surface, and a thin fiber layer sandwiched between thick fiber layers, and both the coated surface and the non-coated surface are thick fiber layers. A semipermeable membrane support is described. However, since thick fibers are used on the coated surface, the uniformity of the semipermeable membrane support becomes low, and the permeation of the semipermeable membrane becomes non-uniform, so that sufficient film peeling strength cannot be obtained. There is a problem that membrane peeling occurs when the separation membrane using the above semipermeable membrane support is operated at high pressure. In addition, there is a problem that the smoothness is low and the semipermeable membrane tends to have defects.

Further, in order to solve the problem that a non-uniform semipermeable membrane is produced by bending the semipermeable membrane support in the width direction when the semipermeable membrane solution is applied, the paper flow direction and width are used. A semipermeable membrane support in which the tensile strength ratio in the direction is 2: 1 to 1: 1 and the fibers are in a disoriented state has been proposed (see, for example, Patent Document 1). Further, Patent Document 1 proposes a method of adjusting the air permeability and pore size of the semipermeable membrane support for the purpose of improving the adhesiveness between the semipermeable membrane and the semipermeable membrane support and preventing strike-through. .. However, the air permeability according to JIS L1096 is calculated based on the amount of air that passes from one side of the semipermeable membrane support through the inside of the semipermeable membrane support and permeates to the other side, and is calculated based on the amount of air that permeates the other side. It does not accurately reflect the strike-through of the semipermeable membrane solution applied to the surface to the non-applied surface. Therefore, when the semipermeable membrane solution is applied to the semipermeable membrane support having the air permeability in the range shown in Patent Document 1, the semipermeable membrane solution may strike through.

In order to provide a composite semipermeable membrane having both strength and water permeability, the sum of the weight A per unit of the semipermeable membrane support and the weight B (permeation amount) of the dope permeating the semipermeable membrane support. A composite of a semipermeable membrane and a semipermeable membrane support having (A + B) of 30 to 100 g / m ² and a ratio B / A of the weight A to the weight B of 0.10 to 0.60. (Composite semipermeable membrane) is provided (for example, Patent Document 5) However, since the void ratio of the semipermeable membrane support is 65% or more, the semipermeable membrane solution is applied at the time of forming the semipermeable membrane. In some cases, strike-through may occur from the front surface to the back surface (non-coated surface).

JP-A-2002-95937 Japanese Unexamined Patent Publication No. 10-225630 Japanese Unexamined Patent Publication No. 2008-238147 Tokuho 4-21526 Gazette International Publication No. 2014/192883 Pamphlet

An object of the present invention is to provide a semipermeable membrane support in which there are few defects of the semipermeable membrane, the semipermeable membrane solution is difficult to strike through, and the membrane peeling strength between the semipermeable membrane and the semipermeable membrane support is improved. be.

As a result of diligent studies to solve the above problems, the present inventors have been able to solve the problems by the following inventions.

(1) In a semipermeable membrane support made of a wet non-woven fabric containing a main synthetic fiber and a binder synthetic fiber, the fiber orientation strength of the coated surface on which the semipermeable membrane is provided is 1.00 or more and 1.30 or less, and is not. The fiber orientation strength of the coated surface is 1.00 or more and 1.50 or less, and remains on the coated surface of the semipermeable membrane support when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. A semipermeable membrane support characterized in that the average area of the semipermeable membrane is 500 μm ² or less, and the residual rate of the semipermeable membrane is 2.5% or more and 5.0% or less.
(2) The semipermeable membrane support according to (1), wherein the amount of antimony element eluted from the semipermeable membrane support is less than 1.5 μg / g.
(3) In the method for producing a semipermeable membrane support for producing the semipermeable membrane support according to (1) or (2), from the fiber dispersion obtained by dispersing the main synthetic fiber after dispersing the binder synthetic fiber. A method for producing a semipermeable membrane support, which comprises producing a semipermeable membrane support by a wet fabrication method.

According to the present invention, it is possible to obtain a semipermeable membrane support in which there are few defects of the semipermeable membrane, the semipermeable membrane solution is difficult to strike through, and the membrane peeling strength between the semipermeable membrane and the semipermeable membrane support is improved. ..

The semipermeable membrane support of the present invention is a semipermeable membrane support made of a wet non-woven fabric containing a main synthetic fiber and a binder synthetic fiber, and the fiber orientation strength of the coated surface on which the semipermeable membrane is provided is 1.00 or more. .30 or less, the fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less, and the semipermeable membrane support when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. The average area of the semipermeable membrane remaining on the coated surface of the body is 500 μm ² or less, and the residual rate of the semipermeable membrane is 2.5% or more and 5.0% or less.

The "fiber orientation strength" in the present invention is expressed by the tensile strength ratio in the MD direction and the CD direction in that the fiber orientation (anisotropic) of only the fibers existing on the surface layer is emphasized instead of the entire semitransparent film support. It is very different from the fiber orientation. Further, as a method for confirming the fiber orientation existing on the surface layer of the semipermeable membrane support, there is a method of measuring the orientation angle of each fiber existing on the surface layer with the MD direction set to 0 °. The "fiber orientation strength" in the present invention measures the degree of anisotropy and is significantly different from the orientation angle.

As a method of setting the fiber orientation strength of the coated surface on which the semipermeable membrane of the semipermeable membrane support is provided to be 1.00 or more and 1.30 or less and the fiber orientation strength of the non-coated surface to be 1.00 or more and 1.50 or less.
(I) Optimization of main synthetic fiber (fiber diameter, fiber length, cross-sectional aspect ratio)
(II) Improvement of fiber dispersibility by two-step dispersion (III) Optimization of base paper fabrication conditions (IV) Adjustment of thermal pressure processing conditions (thermal roll temperature, processing speed), etc. As (III), more specifically
(III-1) Adjustment of concentration (water extraction amount) during wet papermaking (III-2) Adjustment of papermaking speed (III-3) Adjustment of slurry flow velocity and wire relative speed (J / W ratio) (III-4) Adjustment of dehydration pressure in the wire part (III-5) It can be controlled by performing the tension balance in the dryer part alone or in combination.

In the method for manufacturing a semipermeable membrane support of the present invention in which the semipermeable membrane support is manufactured by a wet fabrication method, when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support after the semipermeable membrane is formed. The method for adjusting the average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support of the above to 500 μm ² or less and the residual rate of the semipermeable membrane to 2.5% or more and 5.0% or less will be described. Average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support and the residual ratio of the semipermeable membrane when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support after the semipermeable membrane is formed. In order to control the above, it is important to disperse the main synthetic fiber and the binder synthetic fiber in water in a fiber disperser (palper) to loosen the fiber bundle into a single fiber. Examples of the method of unraveling into single fibers include addition of a dispersant, optimization of the shape of blades in the pulper, optimization of the clearance between the bottom surface of the pulper and the blades, installation of a weir plate on the wall surface of the pulper tank, and the like. Next, in the step of defibrating into single fibers, diluting the fiber dispersion with white water (diluted water), and sending the liquid to the papermaking net, the diluted fiber dispersion is dispersed by a stirrer to obtain single fibers. The degree of dilution can be increased. Further, by adding an aqueous solution of a water-soluble polymer having a molecular weight of 5 million or more as a polymer viscous agent after fiber dispersion with pulper and / or after dilution of the fiber dispersion liquid, the degree of monofiber formation is further increased.

Then, in the method for producing a semipermeable membrane support of the present invention, a semipermeable membrane support is dispersed by a wet fabrication method from a fiber dispersion obtained by two-step dispersion in which binder synthetic fibers are dispersed and then main synthetic fibers are dispersed. It is characterized by manufacturing. When the fibers are put into the pulper, the binder synthetic fibers are put in first and dispersed, and then the main synthetic fibers are put in and dispersed, so that even if the monofilament of the main synthetic fibers is insufficient, it is sufficient. Since the binder synthetic fiber that has been made into a single fiber can cover the main synthetic fiber and a semitransparent film support having fine and uniform pores can be produced, the fiber orientation strength of the coated surface of the semitransparent film support can be increased. The fiber orientation strength of the non-coated surface is 1.00 or more and 1.30 or less, and the fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less. The average area of the semitransparent film remaining on the coated surface of the semitransparent film support when peeled off is 500 μm ² or less, and the residual rate of the semitransparent film is 2.5% or more and 5.0% or less. It becomes easier to obtain a support.

Further, in the wet papermaking method, the fiber dispersion is supplied on the papermaking net, and in the process of squeezing excess water to obtain wet paper, a sheet-like wetness is placed on the papermaking net in which metal threads or plastic threads are woven. As the paper is formed, water is gradually squeezed under the papermaking net. The formation of wet paper on the papermaking net proceeds by depositing fibers on the surface of the papermaking net, and the formation of wet paper is completed when water is squeezed. At the start of wet paper formation, the fibers are deposited in the dispersed state of the fiber dispersion liquid supplied on the papermaking net, so that the surface in contact with the papermaking net (hereinafter, the "surface in contact with the papermaking net" is referred to as the "papermaking net surface". The loosened state of the fibers (sometimes referred to as) becomes uniform. On the other hand, the fiber dispersion still exists on the wet paper being formed on the paper net, and the wet paper formation is completed depending on the position of water extraction by suction, the strength of suction, the paper net speed, the flow velocity of the fiber dispersion, and the like. It is possible to adjust the loosened state of the fibers on the surface opposite to the papermaking net surface (hereinafter, the "surface opposite to the papermaking net surface" may be referred to as the "papermaking felt surface"). However, as compared with the papermaking net surface, the uniformity of the fibers in the loosened state is reduced on the papermaking felt surface. Further, in the middle to the latter half of the wet paper formation, when the thickness and length of the main synthetic fiber and the binder synthetic fiber are different, the same kind of fibers may gather together due to suction, and the uniformity may be further lowered. The gathering of the binder synthetic fibers may lead to a partial shortage of the binder synthetic fibers. Therefore, the fiber orientation strength of the paper-making net surface of the wet non-woven fabric is lower than the fiber orientation strength of the paper-making felt surface. Therefore, when the paper-making net surface is the coated surface, the average area of the remaining semipermeable membrane becomes small and the semipermeable membrane becomes semipermeable. Since the residual rate of the membrane is high, the peeling strength between the semipermeable membrane and the semipermeable membrane support is high.

The base paper obtained by drying the wet paper obtained by the wet papermaking method is preferably subjected to thermal pressure processing (thermal calendar) treatment with a thermal roll. In the thermal pressure processing device (thermal calendar device), the base paper is passed between the rolls that are nipped, and the base paper is thermally processed to melt and soften the binder synthetic fiber and fix the main synthetic fiber. do. If there is a place where the binder synthetic fiber does not exist in the base paper, large pores are formed in the semipermeable membrane support, and when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support after the semipermeable membrane is formed. Since the average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support of No. 1 becomes large and it becomes difficult to obtain the anchoring effect for improving the membrane peeling strength, the binder synthetic fiber in the base paper by the wet manufacturing method It is important to make the semipermeable membrane and the dispersibility of the binder synthetic fiber and the main synthetic fiber.

By taking the above measures, it is possible to control the fiber orientation strength of the coated surface and the non-coated surface of the semipermeable membrane support, the residual area and the residual ratio of the semipermeable membrane after the semipermeable membrane is peeled off.

In the present invention, the fiber orientation strength of the coated surface on which the semipermeable membrane is provided is 1.00 or more and 1.30 or less, more preferably 1.00 or more and 1.25 or less, and further 1.00 or more and 1.20 or less. preferable. When the fiber orientation strength is 1.00 or more and 1.10 or less, it means that the fibers are in a state close to non-orientation. When the fiber orientation strength of the coated surface of the semipermeable membrane support exceeds 1.30, the distance between the fibers on the surface of the semipermeable membrane support is narrowed, so that the penetration of the semipermeable membrane is inhibited and the membrane peeling strength is increased. It may decrease. The fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less, more preferably 1.00 or more and 1.40 or less, and further preferably 1.00 or more and 1.30 or less. If the fiber orientation strength of the non-coated surface of the semipermeable membrane support exceeds 1.50, the penetration of the semipermeable membrane solution from the coated surface side to the non-coated surface side may be hindered and the film peeling strength may decrease. ..

In the present invention, the average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support is 500 μm ² or less, and 450 μm ² The following is more preferable, and 400 μm ² or less is further preferable. If it exceeds 500 μm ² , the permeation of the semipermeable membrane into the semipermeable membrane support becomes non-uniform, and the anchoring effect is lowered, so that the membrane peeling strength may be lowered. Further, the residual rate of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support is 2.5% or more and 5.0% or less. It is more preferably 2.7% or more and 5.0% or less, and further preferably 3.0% or more and 5.0% or less. If the residual rate of the semipermeable membrane exceeds 5.0%, the semipermeable membrane excessively permeates the semipermeable membrane support, which may cause strike-through of the semipermeable membrane. If the residual rate of the semipermeable membrane is less than 2.0%, a sufficient anchoring effect cannot be obtained, the membrane peeling strength is lowered, and the semipermeable membrane may be peeled.

In the present invention, the amount of antimony element eluted from the semipermeable membrane support is preferably less than 1.5 μg / g, and more preferably the amount of antimony eluted from the semipermeable membrane support is less than 1.0 μg / g. .. When the amount of antimony element eluted from the semipermeable membrane support is less than 1.5 μg / g, the fiber dispersibility during fabrication of the semipermeable membrane support is improved, and the film peeling strength after the semipermeable membrane is formed is improved. The effect of doing is obtained.

The "antimon element elution amount" in the present invention means an antimonate obtained by immersing a fiber or a semitransparent film support in ultrapure water having a specific resistance of 18.2 MΩ · cm and a temperature of 25 ° C. for 24 hours and eluting it in ultrapure water. The amount of the element was calculated by using <Equation 1> from the value quantitatively analyzed by ICP-MS (Inductively Coupled Plasma-Mass Spectro-metery).

<Equation 1>
Antimony element elution amount (μg / g) of fiber or semipermeable membrane support = Antimony element content (μg / L) of eluent x volume of ultrapure water used in elution test (L) / fiber or semipermeable membrane Support mass (g)

In the present invention, the main synthetic fiber is a fiber that forms the skeleton of the semipermeable membrane support, and is difficult to soften or melt in the step of raising the temperature to near the softening point or melting temperature (melting point) of the binder synthetic fiber, and the fiber. A fiber that maintains its shape. Examples of the main synthetic fiber include polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, benzoate-based, polyclaral-based, and phenol-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 fiber diameter of the main synthetic fiber is preferably 30 μm or less. When the fiber diameter of the main synthetic fiber exceeds 30 μm, the fiber orientation strength of the coated surface exceeds 1.30, the orientation strength of the non-coated surface exceeds 1.50, or the semipermeable membrane and the semipermeable membrane support. When the semipermeable membrane is peeled off at the interface of the above, the average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support may exceed 500 μm ² , or the semipermeable membrane solution may strike through. In addition, the main synthetic fibers on the surface of the wet non-woven fabric tend to stand up, which may penetrate the semipermeable membrane and become a defect of the semipermeable membrane, or the film performance may deteriorate. It is more preferably 2 to 20 μm, further 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.

In the present invention, the fiber diameter is the diameter of the fiber converted into a perfect circle by measuring the area of the fiber cross section forming the semipermeable membrane support by observing the cross section of the semipermeable membrane support with a scanning electron microscope. The fiber cross section is a cross section when the fiber is cut perpendicularly to the length direction of the fiber.

The fiber length of the main synthetic fiber is not particularly limited, but is preferably 1 to 15 mm, more preferably 3 to 10 mm, and further preferably 4 to 6 mm. If the fiber length is less than 1 mm, the strength of the semipermeable membrane support becomes insufficient, and the semipermeable membrane support may be torn. When the fiber length exceeds 15 mm, the fiber dispersibility tends to decrease, the formation of the semipermeable membrane support becomes non-uniform, and when the fiber orientation strength of the coated surface exceeds 1.30, the orientation of the non-coated surface If the strength exceeds 1.50, or the film forming property of the semipermeable membrane may be impaired.

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 is lowered, and the fibers are entangled or entangled, which adversely affects the uniformity of the semipermeable membrane support and the smoothness of the coated surface. Semipermeable membrane when the fiber orientation strength of the surface exceeds 1.30, the orientation strength of the non-coated surface exceeds 1.50, or when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. The average area of the semipermeable membrane remaining on the coated surface of the membrane support may exceed 500 μm ² . 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 characteristics such as fiber dispersibility in order to prevent strike-through and surface smoothness.

The aspect ratio (fiber length / fiber diameter) of the main synthetic fiber is preferably 200 to 1000, more preferably 220 to 900, and further preferably 280 to 800. When the aspect ratio is less than 200, the dispersibility of the fibers is good, but when the fibers fall off from the papermaking net during papermaking, or when the fibers are stuck in the papermaking net, the peelability from the papermaking net deteriorates. In some cases. On the other hand, if it exceeds 1000, it contributes to the formation of a three-dimensional network of fibers, but the occurrence of entanglement and entanglement of fibers adversely affects the uniformity of the semipermeable membrane support and the smoothness of the coated surface. Detachment fibers may be generated, and film defects may occur during the formation of a semipermeable membrane.

The content of the main synthetic fiber is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and even more preferably 60 to 75% by mass with respect to the wet nonwoven fabric related to the semipermeable membrane support of the present invention. If the content of the main synthetic fiber is less than 40% by mass, the liquid permeability may decrease. Further, when it exceeds 90% by mass, when detached fibers occur frequently, or when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support, the half remaining on the coated surface of the semipermeable membrane support. If the average diameter of the permeable membrane exceeds 30 μm, or the semipermeable membrane support may be torn due to insufficient strength.

The semipermeable membrane support of the present invention contains a binder synthetic fiber. By incorporating the step of raising the temperature to near the softening point or the 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 fabrication 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 (zen'yu 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 semitransparent film support. However, it can be used as long as the characteristics are not impaired. In the present invention, polyester undrawn fibers can be preferably used.

The fiber diameter of the binder synthetic fiber is not particularly limited, but is preferably 2 to 20 μm, more preferably 5 to 15 μm, and even more preferably 7 to 13 μm. Further, it is preferable that the fiber diameter is different from that of the main synthetic fiber. Since the fiber diameter is different from that of the main synthetic fiber, it 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 1 to 12 mm, more preferably 3 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 adhesion between 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 200 to 1000, more preferably 300 to 800, and further preferably 400 to 700. When the aspect ratio is less than 200, the dispersibility of the fibers is good, but there is a risk that the fibers may fall off from the papermaking net during papermaking, or the fibers may stick into the papermaking net, resulting in poor peelability from the papermaking net. There is a fear. 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 adversely affects the uniformity of the wet non-woven fabric and the smoothness of the coated surface. , Withdrawal fibers may occur and film defects may occur during semipermeable membrane film formation.

The content of the binder synthetic fiber is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and even more preferably 25 to 40% by mass with respect to the wet nonwoven fabric related to the semipermeable membrane support of the present invention. In the above range, by increasing the content of the binder synthetic fiber, the fluffing of the desorbed fiber and the main synthetic fiber can be suppressed. If the content of the binder synthetic fiber is less than 10% by mass, it may be torn due to insufficient strength, and the number of fibers for covering the main synthetic fiber may be insufficient to generate detached fibers. On the other hand, if it exceeds 60% by mass, the liquid permeability may be lowered and the adhesiveness between the semipermeable membrane and the semipermeable membrane support may be deteriorated.

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 base paper is produced by a wet papermaking method, the base paper is thermally pressure-processed by a heat roll.

In the wet papermaking method, first, the binder synthetic fiber or the like is uniformly dispersed in water by a disperser such as a pulper, and then the main synthetic fiber is charged and dispersed, so that the binder synthetic fiber is uniformly mixed with the main synthetic fiber. do. After that, through steps such as screen (removal of foreign matter, lumps, etc.), a slurry diluted with white water (diluted water) and prepared to have a final fiber concentration of 0.01 to 0.50% by mass is made with a paper machine. Raised to obtain wet paper. Stirring the diluted slurry with a stirrer is preferable because it promotes monofilament of the fiber bundle. In order to make the dispersibility of fibers uniform, chemicals such as dispersants, defoamers, hydrophilic agents, antistatic agents, polymer viscous agents, mold release agents, antibacterial agents, and bactericidal agents may be added in 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 with one paper machine selected from these paper machines, or a combination paper machine with two or more paper machines of the same type or different types selected from these paper machines online. can do. Further, in the case of producing a wet non-woven fabric having a multi-layer structure of two or more layers, a "slurry method" in which wet papers made by each paper machine are laminated, or after forming one layer, the layer is formed. A "casting method" or the like can be used in which a slurry in which fibers are dispersed is cast on top to form another layer.

The fiber orientation strength of the coated surface of the semipermeable membrane support is 1.00 or more and 1.30 or less, the fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less, and the semipermeable membrane and the semipermeable membrane support The average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane is peeled off at the interface is 500 μm ² or less, and the residual rate of the semipermeable membrane is 2.5% or more and 5.0%. In order to make the following, in any paper making machine, it is preferable to adjust so that the difference between the flow velocity and the wire speed when the slurry lands on the paper making wire from the head box becomes small. Furthermore, it is important to draw water and dehydrate the slurry as soon as it comes into contact with the papermaking wire to immobilize the fibers. For this purpose, the concentration during wet papermaking (water extraction amount), the papermaking speed, the slurry flow velocity and the relative speed of the papermaking wire (J / W ratio), the dehydration pressure at the wire part, and the tension balance adjustment at the dryer part are adjusted individually or in combination. By doing so, it can be controlled.

The wet paper produced by the paper machine is dried with a Yankee dryer, an air dryer, a cylinder dryer, a suction drum type dryer, an infrared type dryer, or the like to obtain a base paper. 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 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

Next, thermal pressure processing using a thermal roll will be described, but the present invention is not limited to the following description. In the thermal pressure processing device (thermal calendar device), the base paper is thermally processed by passing the base paper between the nipped rolls. Examples of the combination of rolls include two metal rolls, a metal roll and a resin roll, a metal roll and a cotton roll, and the like. At least one of the two rolls is heated and used as a heat roll. Mainly, metal rolls are used as thermal rolls. The thermal pressure processing by the thermal roll can be performed twice or more, and in that case, two or more sets of the above roll combinations arranged in series may be used, or one set of roll combinations may be used. It may be processed twice. If necessary, the front and back of the base paper may be reversed. The desired semipermeable membrane support can be obtained by controlling the surface temperature of the thermal rolls, the nip pressure between the rolls, and the processing speed of the base paper.

In addition, even if fluffing of the main synthetic fibers occurs on the base paper, the binder synthetic fibers are optimally melted and softened during thermal pressure processing with a hot roll to hold the fluffing, so that detached fibers are generated and the film is applied. It is possible to prevent it from becoming a drawback later. For that purpose, it is important to raise the thermal roll temperature to near the melting point of the binder synthetic fiber and to raise the nip pressure. Further, by controlling the processing speed, the hold of fluffing by the binder synthetic fiber can be adjusted to some extent. Further, by increasing the content of the binder synthetic fiber, the degree of holding by the fluffy binder synthetic fiber can be increased.

The temperature of the heat roll 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 −30 ° C. to −15 ° C. When the temperature of the thermal roll in the thermal pressure processing is lower than -50 ° C with respect to the melting point of the binder synthetic fiber, the temperature of the binder synthetic fiber does not rise sufficiently and poor adhesion with the main synthetic fiber occurs, so that the semipermeable membrane support The strength may decrease or detached fibers may occur. On the other hand, when the temperature exceeds -10 ° C, the binder synthetic fiber is inactivated, the adhesion between the binder synthetic fiber and the main synthetic fiber becomes insufficient, and detachment fiber is generated, or the semipermeable membrane support becomes a thermal roll. The surface of the semipermeable membrane support may become non-uniform due to sticking, the fiber orientation strength of the coated surface may exceed 1.30, or the fiber orientation strength of the non-coated surface may exceed 1.50. ..

The nip pressure of the roll in the hot pressure processing is preferably 19 to 180 kN / m, more preferably 45 to 140 kN / m. When the nip pressure is less than 19 kN / m, the adhesion between the thermal roll and the base paper becomes low, causing fluffing of the fibers and causing detachment fibers, or the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. The average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support may exceed 500 μm ² . On the other hand, when it exceeds 180 kN / m, the density of the semipermeable membrane support becomes high, the penetration of the film-forming solution decreases, the adhesiveness between the semipermeable membrane and the semipermeable membrane support decreases, or the excess on the roll. The increased load may shorten the roll life.

The processing speed in the hot pressure processing is preferably 4 to 100 m / min, and more preferably 10 to 80 m / min. When the speed is less than 4 m / min, the productivity is inferior, the density of the semipermeable membrane support is increased, the air permeability is lowered, the semipermeable membrane solution is difficult to permeate, and the adhesiveness between the membrane and the support is lowered. In some cases. On the other hand, when it exceeds 100 m / min, heat transfer to the base paper becomes insufficient and fluffing of the main synthetic fiber occurs, so that detached fibers are generated or the fiber orientation strength of the coated surface is 1.30. When the alignment strength of the non-coated surface exceeds 1.50, or when the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support, it remains on the coated surface of the semipermeable membrane support. The average area of the semipermeable membrane may exceed 500 μm ² .

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 and the semipermeable membrane support may be torn. 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, when it exceeds 1.0 g / cm ³ , it becomes difficult for the semipermeable membrane solution to permeate into the semipermeable membrane support, and the adhesiveness between the semipermeable membrane and the semipermeable membrane support deteriorates, or the semipermeable membrane becomes semipermeable. The liquid permeability during film formation may be reduced, 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.

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

≪Main synthetic fiber≫
PET fiber 1: A stretched polyester fiber made of polyethylene terephthalate, having a fiber diameter of 7.5 μm, a fiber length of 5 mm, and an Sb element elution amount of 0.12 μg / g.

PET fiber 2: A stretched polyester fiber made of polyethylene terephthalate, having a fiber diameter of 7.5 μm, a fiber length of 5 mm, and an Sb element elution amount of 0.01 μg / g.

PET fiber 3: A stretched polyester fiber made of polyethylene terephthalate, having a fiber diameter of 7.5 μm, a fiber length of 6 mm, and an Sb element elution amount of 10.3 μg / g.

PET fiber 4: A stretched polyester fiber made of polyethylene terephthalate, having a fiber diameter of 12.5 μm, a fiber length of 5 mm, and an Sb elution amount of 11.9 μg / g.

≪Binder synthetic fiber≫
PET fiber 5: An undrawn polyester fiber made of polyethylene terephthalate, having a fiber diameter of 10.5 μm, a fiber length of 5 mm, and an Sb element elution amount of 0.04 μg / g.

PET fiber 6: An undrawn polyester fiber made of polyethylene terephthalate, having a fiber diameter of 13.6 μm, a fiber length of 5 mm, and an Sb element elution amount of 0.01 μg / g.

PET fiber 7: An undrawn polyester fiber made of polyethylene terephthalate, having a fiber diameter of 11.8 μm, a fiber length of 5 mm, and an Sb element elution amount of 2.3 μg / g.

(Manufacturing of base papers 1 to 19, 21 and 22: with two-step dispersion)
After water is poured into a 2 m ³ dispersion tank, the binder synthetic fiber is first charged into the dispersion tank and dispersed for 3 minutes with the fiber composition shown in Table 1, and then the main synthetic fiber is charged into the dispersion tank and mixed and dispersed for 7 minutes ( Dispersion concentration is 2.0%), and after laminating the wet paper formed on the inclined wire and the wet paper formed on the circular net wire using an inclined wire / circular net composite paper machine, the surface temperature is 130 ° C. The base papers 1 to 19, 21 and 22 having a target basis weight of 70 g / m ² were obtained by hot pressure drying with the Yankee dryer of the above. The fiber composition of the inclined wire and the circular net is the same.

(Manufacturing of base paper 20: No two-step dispersion)
After pouring water into a 2 m ³ dispersion tank, the binder synthetic fiber and the main synthetic fiber are simultaneously put into the dispersion tank with the fiber composition shown in Table 1, mixed and dispersed for 7 minutes (dispersion concentration 2.0%), and the inclined wire. / Using a circular net composite paper machine, the wet paper formed on the inclined wire and the wet paper formed on the circular net wire are laminated, and then hot-pressure dried with a Yankee dryer with a surface temperature of 130 ° C. A base paper 20 having an amount of 70 g / m ² was obtained. The fiber composition of the inclined wire and the circular net is the same.

(Thermal calendar processing)
For the obtained base paper, use a thermal calendar device with a combination of a metal roll (heat roll) and an elastic roll, or a thermal calendar device with a combination of a metal roll (heat roll) and a metal roll (heat roll). The semitransparent film supports of Examples 1 to 20 and Comparative Examples 1 to 8 were obtained under the thermal calendar conditions described in 1. In the first stage where the thermal pressure processing is performed first, the surface (processed surface) where the base paper is in contact with the metal roll (thermal roll) is set as the coating surface, and the treated surface in the second stage where the thermal pressure processing is performed second is , The opposite side of the first stage. Further, the semipermeable membrane support subjected to the thermal calendar treatment by the combination of the metal roll (heat roll) and the metal roll (heat roll) has a circular mesh surface as a coating surface.

The semipermeable membrane supports obtained in Examples 1 to 20 and Comparative Examples 1 to 8 were measured and evaluated as follows, and the results are shown in Table 3.

[Basis weight]
Basis weight was measured according to JIS P8124: 2011.

[Thickness and density of semipermeable membrane support]
The thickness was measured and the density was calculated according to JIS P8118: 2014.

[Fiber orientation strength]
Using a scanning electron microscope (product name: JSM-6610LV, manufactured by JEOL Ltd.), the non-coated surface opposite to the coated surface on which the semi-transparent film of the semi-transparent film support is provided is subjected to secondary electrons at a magnification of 50 times. The image was taken with an acceleration voltage of 20 kV and a spot size of 30. At the time of shooting, the top and bottom were in the MD direction (flow direction), and the left and right were in the CD direction (width direction). Ten measurement points were photographed on the coated surface and the non-coated surface of one semipermeable membrane support.

The program "FiberOrientation Analysis Ver.8.13 single (FiberOri8s03)" was used. In this program, an image of 1024 pixels x 1024 pixels is extracted from the original image → binarization by moving average → FFT conversion → calculation of orientation angle and altitude distribution by two axes mode, and the degree of anisotropy "Orientation" "Intensity" was measured. Ten points were measured on the coated surface and the non-coated surface of each semipermeable membrane support, and the average value was taken as the "fiber orientation strength" in the present invention.

[Separation film formation]
Using a constant-speed coating device (trade name: TQC fully automatic film applicator, manufactured by Cortec) with a constant clearance, a solution of N, N-dimethylformamide (DMF) of polysulfone resin was applied to the coated surface of the semipermeable membrane support. Concentration: 18%) was applied to a thickness of 125 μm and phase-separated in a coagulation bath to prepare a porous polysulfone membrane. An aqueous solution A containing 2% by mass of m-phenylenediamine and 0.15% by mass of sodium lauryl sulfate was brought into contact with the porous polysulfone film, and then the excess aqueous solution A was removed to form a coating layer of the aqueous solution A. .. Next, a solution B containing 0.3% by mass of trimesic acid chloride was brought into contact with the surface of the coating layer of the aqueous solution A, and the excess solution B was discharged. Then, it was dried at 120 ° C. to form a separation functional layer, and a separation membrane in which a composite semipermeable membrane composed of a porous polysulfone membrane and a separation functional layer was provided on a coating surface of a semipermeable membrane support was obtained. The obtained separation membrane was used in the following measurement of the average area of the remaining semipermeable membrane, measurement of the residual ratio of the semipermeable membrane, evaluation of defects of the semipermeable membrane, and evaluation of membrane peeling strength.

[Average area of remaining semipermeable membrane]
After air-drying the separation film, cut it into strips of 25 mm x 150 mm with the MD direction as the long side, and attach double-sided tape (trade name: Nystack (registered trademark) NW-25, manufactured by Nichiban Co., Ltd.) to the separation film surface. , A sample for measuring the peeling strength of the film was obtained. Using a constant speed tension type tensile tester "single column type material tester, model number: STB-1225S" (manufactured by A & D Co., Ltd.), the distance between chucks is set to 20 mm, and the chuck movement speed is 50 mm / min. , The semipermeable membrane was peeled off from the semipermeable membrane support.

Using a scanning electron microscope (product name: JSM-6610LV, manufactured by JEOL Ltd.), the coated surface of the semitransparent film support from which the semitransparent film has been peeled off has secondary electrons at a magnification of 100 times, an acceleration voltage of 20 kV, and a spot size. At 70, a mapping analysis of the sulfur (S) element (observation size: 1285 μm × 970 μm) was performed. A mapping analysis of 5 measurement points was performed on the coated surface of one semipermeable membrane support.

A transparent sheet is placed on the copy of the obtained mapping image, the detected portion of the sulfur (S) element is painted black using a black pen or the like, and then the transparent sheet is copied to a blank sheet to obtain the sulfur (S) element. The detected part was clearly distinguished from black, and the non-detected part was clearly distinguished from white. When the sulfur (S) element detection portion touched the boundary of the mapping image, it was not considered as a measurement target.

Using the image analysis software "ImageJ", binarization was performed, the area (individual area) of the sulfur (S) element detection portion having one measurement point was obtained, and the average value of each area was calculated. Similarly, the average value of the individual areas of the sulfur (S) element detection portions at each measurement point was calculated, and the average value of the five measurement points was defined as the "average area of the remaining semipermeable membrane".

[Residual rate of semipermeable membrane]
Using a scanning electron microscope (product name: JSM-6610LV, manufactured by JEOL Ltd.), the coated surface of the semitransparent film support from which the semitransparent film has been peeled off has secondary electrons at a magnification of 100 times, an acceleration voltage of 20 kV, and a spot size. At 70, a mapping analysis of the sulfur (S) element (observation size: 1285 μm × 970 μm) was performed. A mapping analysis of 5 measurement points was performed on the coated surface of one semipermeable membrane support.

A transparent sheet is placed on the copy of the obtained mapping image, the detected portion of the sulfur (S) element is painted black using a black pen or the like, and then the transparent sheet is copied to a blank sheet to obtain the sulfur (S) element. The detected part was clearly distinguished from black, and the non-detected part was clearly distinguished from white. When the sulfur (S) element detection portion touched the boundary of the mapping image, it was not considered as a measurement target.

Using the image analysis software "ImageJ", binarization is performed, the area (individual area) of the sulfur (S) element detection part with one measurement point is obtained, and the total area and mapping image obtained by adding the individual areas. From the area (image area: 1246450 μm ² , observation size: 1285 μm × 970 μm), the occupancy rate of the sulfur element in the mapped image was calculated. Similarly, the occupancy rate of sulfur elements in the mapping image is calculated from the total area of each sulfur (S) element detection portion and the mapping image area at each measurement point, and the average value of 5 measurement points is "semipermeable membrane". Residual rate ”.

[Measurement of antimony element elution amount]
1.6 g of fiber or semi-transparent film support was immersed in 0.20 L of ultrapure water having a specific resistance of 18.2 MΩ · cm and a temperature of 25 ° C. for 24 hours, and 30 mL of the eluate was collected. Co., Ltd., for precision analysis, concentration 60%) After adding 1 μL, it is contained in the eluate by an inductively coupled plasma mass spectrometer (ICP-MS) (device name: iCAP-Qc, manufactured by Thermo Fisher Scientific). After measuring the antimony element content, it was quantified by the calibration linear method. Further, the amount of antimony element eluted was calculated by the following formula. The lower limit of antimony quantification of the ICP-MS was 0.1 ppb, and the antimony content of the ultrapure water used for the measurement was equal to or less than the lower limit of quantification.

<Equation 1>
Antimony element elution amount (μg / g) of fiber or semipermeable membrane support = Antimony element content (μg / L) of eluent x volume of ultrapure water used in elution test (L) / fiber or semipermeable membrane Support mass (g)

[Semipermeable membrane defect evaluation]
The separation membrane was cut into 14 cm × 19 cm and set in a flat membrane test device (trade name: SEPA CFII, SUEZ). An aqueous solution containing a 200 ppm dye (Direct Blue 1, molecular weight: 993) was passed at 25 ° C. at a differential pressure of 1.5 MPa between the membrane supply side and the permeation side. Then, the dye accumulated on the surface of the composite semipermeable membrane was washed away with pure water, the separation membrane was dried, and the number of dyed portions (membrane defect portions) was measured.

"0 to 1 place": Very good level.
"2 to 3 places": Good level.
"4 to 6 places": Usable level.
"7 or more places": Membrane performance is inferior and cannot be used.

[Semipermeable membrane strike through]
Using a constant-speed coating device with a certain clearance (trade name: Automatic Film Applicator, manufactured by Yasuda Seiki Seisakusho Co., Ltd.), set the semipermeable membrane support on the mount, and black on the coated surface of the semipermeable membrane support. Apply a DMF solution (concentration: 18%) of polysulfone resin mixed with the oil-based ink of the above, and after application, visually observe the amount of polysulfone resin reflected on the mount through the semipermeable membrane support, and observe the amount of polysulfone resin reflected in the semipermeable membrane. A strike-through evaluation was performed.

"1": No strike-through. Very good level.
"2": Small dots, very slightly strike-through. Good level.
"3": It is a small dot and strikes through. Practically usable level.
"4": Large dots, many strike through. Practically unusable level.

[Membrane peeling strength]
After air-drying the separation film, cut it into strips of 25 mm x 150 mm with the MD direction as the long side, and attach double-sided tape (trade name: Nystack (registered trademark) NW-25, manufactured by Nichiban Co., Ltd.) to the separation film surface. , A sample for measuring the peeling strength of the film was obtained. Using a constant speed tension type tensile tester "single column type material tester, model number: STB-1225S" (manufactured by A & D Co., Ltd.), set the distance between chucks to 20 mm and set the chuck movement speed to 50 mm / min. , T-type peeling test was performed, and the peeling strength was obtained by calculating the average peeling strength of the moving amount of 20 mm to 80 mm from the start of the test. Table 3 shows the average value of the 10 peel strengths obtained for each sample.

The semipermeable membrane supports of Examples 1 to 20 are made of a wet non-woven fabric containing a main synthetic fiber and a binder synthetic fiber, and the fiber orientation strength of the coated surface on which the semipermeable membrane is provided is 1.00 or more and 1.30 or less. On the coated surface of the semipermeable membrane support when the fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less and the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. Since the average area of the remaining semipermeable membrane is 500 μm ² or less and the residual rate of the semipermeable membrane is 2.5% or more and 5.0% or less, there are few defects of the semipermeable membrane and the semipermeable membrane strikes through. It was difficult to do so, and it was found that the semipermeable membrane and the semipermeable membrane support had high peeling strength.

From the comparison of Examples 1 and 5 to 8 and the comparison of Examples 9 and 11 to 12, the fiber orientation strength of the coated surface and the non-coated surface of the semipermeable membrane support is adjusted according to the papermaking conditions and the fiber composition. It turns out that it is possible.

Comparing the semipermeable membrane supports of Example 1 and Comparative Example 1, Example 3 and Comparative Example 2, Example 7 and Comparative Example 4, and Example 10 and Comparative Example 5, the fabrication speed was increased and the amount of water extracted was increased. When the J / W ratio is lowered, the fiber orientation strength of the permeable membrane coated surface exceeds 1.30, the fiber orientation strength of the non-immediate surface exceeds 1.50, the semipermeable membrane permeation area exceeds 500 μm ² , and the semipermeable membrane is semipermeable. Since the residual rate of the film was less than 2.0%, the result was that the peeling strength of the film was low.

The content of the semipermeable membrane support of Example 1 in which the content of the binder synthetic fiber is 35%, the semipermeable membrane support of Example 9 in which the content of the binder synthetic fiber is 30%, and the content of the binder synthetic fiber. Comparing the semipermeable membrane supports of Example 13 in which the content is 25%, it can be seen that the membrane peeling strength increases as the content of the binder synthetic fiber increases. On the other hand, in Comparative Example 7 in which the PET fiber 1 of Example 13 was changed to the PET fiber 3 having a large amount of Sb element elution, the defects of the semipermeable membrane and the semipermeable membrane strike-through were deteriorated, and the film peeling strength was lowered. I understand.

The fiber orientation strength of the coated surface is 1.00 or more and 1.30 or less, the fiber orientation strength of the non-coated surface is 1.00 or more and 1.50 or less, and the semipermeable membrane is formed at the interface between the semipermeable membrane and the semipermeable membrane support. The average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane was peeled off was 500 μm ² or less, the residual rate of the semipermeable membrane was 2.5% or more and 5.0% or less, and the semipermeable membrane. With respect to the semipermeable membrane support of Example 1 in which the amount of Sb element eluted from the support is less than 1.5 μg / g, the fiber orientation strength of the coated surface is 1.00 or more and 1.30 or less, and the fiber orientation of the non-coated surface is The average area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support when the strength is 1.00 or more and 1.50 or less and the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. Is 500 μm ² or less, the residual rate of the semipermeable membrane is 2.5% or more and 5.0% or less, and the amount of Sb element eluted from the semipermeable membrane support exceeds 1.5 μg / g. It can be seen that the support is at a usable level, but the semipermeable membrane defects increase and the membrane peeling strength decreases.

In Examples 3, 4 and 10 in which the coating surface is an inclined wire surface with respect to the semipermeable membrane supports of Examples 1, 2 and 9 in which the coating surface is a circular mesh surface, Examples 1 and 3 are carried out. Comparing Example 2 and Example 4, and Example 9 and Example 10, it can be seen that the fiber orientation strength of the coated surface of the circular mesh surface is lower than that of the inclined wire surface, so that the defects of the semipermeable membrane are reduced.

The semipermeable membrane support of Comparative Example 6 in which the two-step dispersion was not performed has a fiber orientation strength of 1 on the semipermeable membrane-coated surface, as opposed to the semipermeable membrane support of Example 1 in which the two-step dispersion was performed during the production of the base paper. The half remaining on the coated surface of the semipermeable membrane support when the semipermeable membrane was peeled off at the interface between the semipermeable membrane and the semipermeable membrane support, exceeding .30 and the non-immediate fiber orientation strength exceeded 1.50. Since the average area of the permeable membrane exceeds 500 μm ² and the residual rate of the semipermeable membrane is less than 2.5%, the result is that the membrane peeling strength is low.

From the comparison between Examples 1 and 2 and Comparative Example 3, in Comparative Example 3 in which the temperature of the heat roll in the second stage was low, the residual rate of the semipermeable membrane was high, the semipermeable membrane strike-through occurred, and the membrane was formed. The peel strength was also low.

In Comparative Example 8 in which PET fibers 3 and 4 having a large amount of Sb element eluted were blended and the roll combination of the first stage was changed to a metal roll-metal roll, the residual rate of the semipermeable membrane was lower than 2.5%. It can be seen that the film peeling strength is low.

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

Claims (3)

In a semipermeable membrane support made of a wet non-woven fabric containing a main synthetic fiber and a binder synthetic fiber, the fiber orientation strength of the coated surface on which the semipermeable membrane is provided is 1.00 or more and 1.30 or less, and the fiber orientation of the non-coated surface. The average of the semipermeable membranes remaining on the coated surface of the semipermeable membrane support when the strength is 1.00 or more and 1.50 or less and the semipermeable membrane is peeled off at the interface between the semipermeable membrane and the semipermeable membrane support. A semipermeable membrane support having an area of 500 μm ² or less and a semipermeable membrane residual rate of 2.5% or more and 5.0% or less. The semipermeable membrane support according to claim 1, wherein the amount of antimony element eluted from the semipermeable membrane support is less than 1.5 μg / g. In the method for producing a semipermeable membrane support for producing the semipermeable membrane support according to any one of claims 1 and 2, the fiber dispersion obtained by dispersing the main synthetic fiber after dispersing the binder synthetic fiber is used. A method for producing a semipermeable membrane support, which comprises producing a semipermeable membrane support by a wet fabrication method.