JP2021146248A - Semipermeable membrane support body - Google Patents

Abstract

To provide a semipermeable membrane support body that can suppress contraction after the membrane is coated to form a uniform semipermeable membrane that is not curled.SOLUTION: A semipermeable membrane support body includes a main body fiber and a binder fiber made of a synthetic fiber, and has a two-layer structure constituted of a layer on a semipermeable membrane forming face side and a layer on a semipermeable membrane non-forming face side. An average thermal shrinkage ratio of the main body fiber in the layer on the semipermeable membrane non-forming face side is 1.3-3.0 times an average thermal shrinkage ratio of the main body fiber in the layer on the semipermeable membrane forming face side. It is preferable that an average of floating heights of four corners of the semipermeable membrane support body, which is cut out into a size of 10 cm times 10 cm, is still placed horizontally on a flat base, and is subjected to humidity conditioning for 24 hours under the condition of 23°C and 50% R.H. is in a range of 5-20 nm.SELECTED DRAWING: None

Description

The present invention relates to 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 semitransparent film is composed of a synthetic resin such as a cellulose-based resin, a polysulfone-based resin, a polyacrylonitrile-based resin, a fluorine-based resin, a polyester-based resin, a polyamide-based resin, or a polyimide-based resin. However, since the semipermeable membrane alone is inferior in mechanical strength, it is used as a "filter membrane" 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. ing. The "surface on which the semipermeable membrane of the semipermeable membrane support is provided" may be referred to as a "semipermeable membrane forming surface". Further, the "opposite surface of the semipermeable membrane forming surface" may be described as a "non-semipermeable membrane forming surface".

As a method for producing a filter membrane, a method is obtained in which a synthetic resin such as the above-mentioned polysulfone resin is dissolved in an organic solvent to prepare a semipermeable membrane liquid, and then the semipermeable membrane liquid is applied onto a semipermeable membrane support. Widely used. Then, in order to efficiently perform filtration, a spiral type semipermeable membrane element is formed, and a semipermeable membrane module is further assembled (see, for example, Patent Document 1).

In order to obtain high filtration flux and filtration performance, the surface of the semipermeable membrane has few irregularities, there is no lateral curvature or wrinkles during formation of the semipermeable membrane, and the semipermeable membrane is uniform on the semipermeable membrane support. It is necessary to be provided with a sufficient thickness. In order for the semipermeable membrane to be provided with a uniform thickness, excellent smoothness is required on the semipermeable membrane-forming surface of the semipermeable membrane support. Further, in order to obtain good filtration performance, it is necessary to have excellent adhesiveness between the semipermeable membrane and the semipermeable membrane support. In addition, when assembling the semipermeable membrane module, there is a step of adhering the non-semipermeable membrane forming surfaces to each other using an adhesive, so that the non-semipermeable membrane forming surfaces are also required to have excellent adhesiveness. Has been done. Further, it is required that the semipermeable membrane liquid does not strike through to the non-semipermeable membrane forming surface. This is because when strike-through occurs, the thickness of the semipermeable membrane becomes non-uniform, and the adhesiveness between the non-semipermeable membrane forming surfaces decreases.

As a semipermeable membrane support, a support has been proposed in which non-woven fabrics having different tensile strength aspect ratios are laminated, the support is curved in a convex shape, and the shrinkage curl of the semipermeable membrane liquid is suppressed (Patent Document 2). .. However, in this method, when thermal pressure bonding is performed, layers having different tensile strength aspect ratios are laminated, so that the number of fiber binding points between the layers is reduced, the interlayer strength is lowered, and delamination may occur. there were. In addition, the aspect ratio of tensile strength correlates with the fiber orientation, and the fiber orientation is greatly affected by the water temperature in the papermaking and the viscosity of the slurry in which the fibers are dispersed, and it is difficult to control the fiber orientation. Had difficulty in stable productivity.

Japanese Unexamined Patent Publication No. 2008-238147 Japanese Patent No. 5739154

An object of the present invention is to provide a semipermeable membrane support capable of suppressing shrinkage after application of a semipermeable membrane liquid and forming a uniform semipermeable membrane without curl.

The above problem was solved by the following means.

(1) A non-semipermeable membrane support having a two-layer structure including a main fiber made of synthetic fibers and a binder fiber and a layer on the semipermeable membrane forming surface side and a layer on the non-semipermeable membrane forming surface side. The feature is that the average heat shrinkage rate of the main fiber in the layer on the permeable membrane forming surface side is 1.3 to 3.0 times the average heat shrinkage rate of the main fiber in the layer on the semipermeable membrane forming surface side. Semipermeable membrane support.
(2) A semipermeable membrane support cut out to a size of 10 cm × 10 cm was placed horizontally on a smooth table with the non-semipermeable membrane forming surface side facing up, and the temperature was 23 ° C., 50% R. H. The semipermeable membrane support according to (1), wherein the average height of the raised heights at the four corners is in the range of 5 to 20 mm after humidity control for 24 hours under the above conditions.

The semipermeable membrane support of the present invention has a two-layer structure including a main fiber made of synthetic fibers and a binder fiber, and a layer on the semipermeable membrane forming surface side and a layer on the non-semipermeable membrane forming surface side. The average heat shrinkage rate of the main fiber in the layer on the non-semipermeable membrane forming surface side is 1.3 to 3.0 times the average heat shrinkage rate of the main fiber in the layer on the semipermeable membrane forming surface side. , The semipermeable membrane support is curled toward the non-semipermeable membrane forming surface side, and has the effect of suppressing curling due to membrane contraction.

The semipermeable membrane support of the present invention contains a main fiber made of synthetic fibers and a binder fiber, and in the layer on the semipermeable membrane forming surface side, the average heat shrinkage rate of the main fiber in the layer on the non-semipermeable membrane forming surface side. However, it is characterized in that it is 1.3 to 3.0 times the average heat shrinkage rate of the main fibers in the layer on the semipermeable membrane forming surface side. "The average heat shrinkage rate of the main fiber in the layer on the non-semipermeable membrane forming surface side with respect to the average heat shrinkage rate of the main fiber in the layer on the semipermeable membrane forming surface side" is "the average heat shrinkage rate of the main fiber (non-semipermeable membrane). Membrane-forming surface / semipermeable membrane-forming surface) ”may be described.

In the semipermeable membrane support, the content ratio of the binder fiber to the total amount of the main fiber and the binder fiber is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, and 30 to 40% by mass. Is more preferable. When the content ratio of the binder fiber is less than 20% by mass, the binding between the fibers becomes insufficient, and problems such as deterioration of the film performance due to the occurrence of fiber dropout and breakage due to the decrease in mechanical strength may occur. When the content ratio of the binder fiber exceeds 50% by mass, the semipermeable membrane support becomes dense, the penetration of the semipermeable membrane liquid is reduced, a sufficient anchor effect cannot be obtained, and the semipermeable membrane support is formed on the semipermeable membrane support. There may be a problem that the semipermeable membrane is easily peeled off.

In the present invention, the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber is 1.3 to 3.0 times, and 1.6 to 2.7 times. More preferred. Since the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber is 1.3 to 3.0 times, the semipermeable membrane support is curled toward the non-semipermeable membrane forming surface side. The effect of suppressing curl due to membrane contraction can be obtained. When the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber is less than 1.3 times, the curl toward the non-semipermeable membrane forming surface side is reduced, and the curl due to the membrane shrinkage is sufficient. Can no longer be suppressed. When the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber exceeds 3.0 times, the curl toward the non-semipermeable membrane forming surface side becomes too large, and the transport process and the coating process In the above, a transport trouble occurs, and the productivity of film production deteriorates.

In the present invention, the semipermeable membrane support cut out to a size of 10 cm × 10 cm is placed horizontally on a smooth table with the non-semipermeable membrane forming surface side facing up, and the temperature is 23 ° C., 50% R. H. After controlling the humidity for 24 hours under the above conditions, the average height of the raised corners (hereinafter, may be referred to as "average curl height") is preferably 5 to 20 mm, preferably 7 to 17 mm. More preferably, it is more preferably 9 to 15 mm. If the average curl height is less than 5 mm, when the semipermeable membrane is formed on the semipermeable membrane forming surface side, the film contraction toward the semipermeable membrane forming surface side may not be sufficiently suppressed. If the average curl height is higher than 20 mm, the curl toward the non-semipermeable membrane forming surface side becomes too large, and there is a high possibility that transfer troubles will occur in the transfer process and the coating process, and the productivity of film production will deteriorate. ..

In order to make the average curl height 5 to 20 mm, the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber needs to be 1.3 to 3.0 times. Further, in the thermal pressure treatment step, it is preferable that the number of passes through the nip is twice and the surface temperature of the thermal roll at the time of the second nip is higher than the surface temperature of the thermal roll at the time of the first nip. The temperature difference is preferably within 10 ° C, more preferably within 5 ° C.

As the semitransparent film support of the present invention, non-woven fabrics such as spunbonded non-woven fabrics, melt-blown non-woven fabrics, dry short-fiber non-woven fabrics and wet-made non-woven fabrics, and composite non-woven fabrics obtained by laminating a plurality of non-woven fabrics selected from these non-woven fabrics can be used. Further, the non-woven fabric is preferably heat-pressed by a heat roll.

In the present invention, the main fiber and the binder fiber are composed of synthetic fibers. The main fiber is a fiber that forms the skeleton of the semipermeable membrane support, and even at the temperature at which the binder fiber softens or melts, the main fiber is difficult to soften or melt, and the cross-sectional shape may change, but the shape as a fiber. Is a fiber that is not impaired. Examples of the main 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 preferably used.

In the semipermeable membrane support of the present invention, it is preferable that two or more kinds of fibers having different fiber diameters are contained as the main fibers. The fiber network formed by entwining two or more types of main fibers with different fiber diameters causes complex and fine irregularities on the semipermeable membrane forming surface, thus improving the adhesiveness between the semipermeable membrane and the semipermeable membrane support. Can be made to. Further, by this fiber network, the smoothness of the semipermeable membrane forming surface can be improved, and a uniform semipermeable membrane can be obtained.

The average fiber diameter of the main fiber is not particularly limited, but is preferably 7 to 20 μm, and more preferably 8 to 16 μm. Further, when the fiber diameter of at least one of the main fibers is 13 μm or less, the smoothness of the semipermeable membrane forming surface can be further enhanced, and a semipermeable membrane having a uniform membrane thickness can be easily obtained. When the average fiber diameter of the main fiber is less than 7 μm, the adhesiveness between the semipermeable membrane forming surface and the semipermeable membrane may decrease. Further, when assembling the semipermeable membrane module, there is a step of bonding the non-semipermeable membrane forming surfaces to each other by using an adhesive, but the adhesiveness between the non-semipermeable membrane forming surfaces may be deteriorated. When the average fiber diameter of the main fiber exceeds 20 μm, the smoothness of the surface of the semipermeable membrane support is lost, which makes it difficult to obtain a semipermeable membrane having a uniform thickness, and also has high Frazier (FG) air permeability. It may become too large and strike-through may occur during semipermeable membrane coating.

The heat shrinkage rate of the main fiber is a value measured in accordance with the dry heat dimensional change rate of JIS L1015: 2010. The heat shrinkage rate of the main fiber is preferably 2.0 to 8.0%, more preferably 3.0 to 7.0%. When the heat shrinkage rate of the main fiber is less than 2.0%, the fiber dispersibility deteriorates, the undissolved fiber bundle remains on the semipermeable membrane forming surface side of the semipermeable membrane support, and coating defects occur. Membrane performance may deteriorate. If it exceeds 8.0%, wrinkles may occur during the drying process or thermal pressure processing in the manufacture of the semipermeable membrane support.

In the present invention, the average heat shrinkage rate of the main fiber is calculated by the following formula. N is a positive integer.

Average heat shrinkage rate = (heat shrinkage rate of main fiber 1 (%) x mass% of main fiber 1 + heat shrinkage rate of main fiber 2 (%) x mass% of main fiber 2 + heat shrinkage rate of main fiber 3 ( %) × Mass% of main fiber 3 + ・ ・ ・ + Heat shrinkage of main fiber N (%) × Mass% of main fiber N) / (Mass% of main fiber 1 + Mass% of main fiber 2 + Main fiber Mass% of 3 + ... + Mass% of main fiber N)

The fiber length of the main 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. If the fiber length is less than 1 mm, it is difficult to form a three-dimensional network of fibers in the papermaking process, and the peelability from the papermaking wire may deteriorate. On the other hand, when the fiber length exceeds 12 mm, the uniformity of the semipermeable membrane support and the smoothness of the semipermeable membrane may be adversely affected due to the occurrence of entanglement and entanglement between the fibers. The cross-sectional shape of the main fiber is preferably circular, but fibers having irregular cross-sections such as T-shaped, Y-shaped, and triangular are also within a range that does not impair other characteristics in order to prevent strike-through and smoothness of the semipermeable membrane forming surface. Can be contained within.

The semipermeable membrane support of the present invention contains the binder fiber, but by incorporating the step of raising the temperature to near the temperature at which the binder fiber softens or melts into the manufacturing process of the semipermeable membrane support, the binder 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 fibers can be softened or melted in a subsequent drying step or thermal pressure processing.

Examples of the binder 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 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 fibers of polyester can be preferably used.

The fiber diameter of the binder fiber is preferably different from that of the main fiber, but is not particularly limited. Since the fiber diameters of the main fiber and the binder fiber are different, the binder 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 fiber, and further. In a step of raising the temperature to near the temperature at which the binder fiber is softened or melted, such as a drying step or a thermal pressure processing, the smoothness of the semipermeable membrane forming surface can also be improved.

The fiber length of the binder fiber is not particularly limited, but is preferably 1 to 12 mm, more preferably 3 to 10 mm, and further preferably 4 to 7 mm. If the fiber length is less than 1 mm, the fiber binding points may be reduced, and the strength as a semipermeable membrane support may not be obtained. When the fiber length exceeds 12 mm, the texture tends to deteriorate. The cross-sectional shape of the binder fiber can include fibers having a circular shape and a deformed cross section such as T-shaped, Y-shaped, and triangular.

The semipermeable membrane support of the present invention can contain semi-synthetic fibers such as acetate, triacetate and promix, and regenerated fibers such as rayon, cupra and lyocell fibers as long as the performance is not impaired.

The semipermeable membrane support of the present invention is preferably a semipermeable membrane support produced by hot-pressing a non-woven fabric (wet-made non-woven fabric) produced by a wet-making method with a thermal roll.

In the wet papermaking method, first, the main fiber and the binder fiber are uniformly dispersed in water, and then the final fiber concentration is 0.01 to 0.50% by mass through steps such as a screen (removal of foreign matter, lumps, etc.). The slurry adjusted to the above is made by a paper machine to obtain wet paper. In the process, chemicals such as dispersants, antifoaming agents, hydrophilic agents, antistatic agents, polymer thickeners, mold release agents, antibacterial agents, and bactericidal agents may be added.

As the papermaking method, for example, a long net, a circular net, an inclined wire type or the like can be used. A paper machine having one type of papermaking method selected from these papermaking methods may be used, or a combination paper machine in which two or more types of papermaking methods of the same type or different types are installed online may be used. .. Further, since the semipermeable membrane support of the present invention has a two-layer structure, a "papermaking method" in which wet papers made by each papermaking method are laminated, after forming one layer, the layer is used. It can be produced by a "casting method" or the like in which a slurry in which fibers are dispersed is cast. In the casting method, the previously formed layer may be in a wet paper state or in a dry state. Further, two or more dried layers may be heat-sealed to form a two-layer structure.

A wet paper made by a paper machine is dried with a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, or the like to obtain a wet paper making non-woven fabric. 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 170 ° C, and even more preferably 100 to 160 ° C. If the surface temperature of the heat roll is lower than 100 ° C., the moisture content of the wet paper produced by the paper machine may not be sufficiently evaporated, and the thickness uniformity of the semitransparent film support may be deteriorated. If the temperature exceeds 180 ° C., the wet paper produced by the paper machine may stick to the heat roll and the texture of the semitransparent film support may be deteriorated. The pressure is preferably 5 to 100 kN / m, more preferably 10 to 80 kN / m. If the pressure is less than 5 kN / m, the moisture of the wet paper produced by the paper machine may not be sufficiently removed, and the thickness uniformity of the semipermeable membrane support may be deteriorated. If the pressure exceeds 100 kN / m, the paper machine may not be sufficiently drained. The wet paper produced in (1) may stick to the heat roll and the semipermeable membrane support may become poorly formed.

In the thermal pressure processing, the wet papermaking nonwoven fabric is passed between the thermal rolls while nipating between the thermal rolls of the thermal pressure processing apparatus. Examples of the combination of the heat rolls include two metal rolls, a metal roll and a resin roll, a metal roll and a cotton roll, and the like, and one or both of the heat rolls are heated. Further, if necessary, the front and back sides of the non-woven fabric may be reversed so that the number of passes through the nip may be two or more.

The surface temperature of the thermal roll used for the thermal pressure processing is lower than the melting point of the main fiber measured by differential thermal analysis, preferably −70 to −20 ° C. with respect to the melting point of the binder fiber, and preferably −60 to −30. More preferably, it is ° C. If the surface temperature of the thermal roll temperature is lower than the melting point of the binder fiber by more than 70 ° C., fluffing may easily occur, and it becomes difficult to obtain a semipermeable membrane having a uniform thickness. On the other hand, if the surface temperature of the thermal roll is raised beyond a temperature 20 ° C. lower than the melting point, the melted content of the fibers may adhere to the thermal roll, and the semipermeable membrane support may become non-uniform, resulting in a uniform thickness. It becomes difficult to obtain a semipermeable membrane.

The semipermeable membrane support of the present invention has a two-layer structure in which the fiber composition of each layer is different. In this case, by lowering the basis weight of each layer, the fiber concentration of the slurry can be lowered, so that the formation of the semipermeable membrane support is improved, and as a result, the smoothness and uniformity of the semipermeable membrane forming surface are improved. improves. Further, even if the formation of each layer is uneven, it can be compensated by laminating. Furthermore, the papermaking speed can be increased, and the operability is improved.

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 1.2 g / cm 3} , and more preferably 0.6 to 1.0 g / cm ³ . When 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 1.2 g / cm 3} , the liquid permeability may be lowered and the life of the semipermeable membrane may be shortened.

The thickness of the semipermeable membrane support is preferably 60 to 150 μm, more preferably 70 to 130 μm, and even more preferably 80 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 60 μm, a 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.

Air permeability of the semipermeable membrane support is preferably from 0.5~5.0cm ³ / ^cm 2 · ^sec, more preferably from ^{1.0~4.5cm 3 / cm 2 · sec,} 1. It is more preferably 5 to 4.0 ^{cm 3} / cm ^{2 · sec.} If it is smaller than 0.5 cm ³ / cm ² · sec, the adhesiveness between the semipermeable membrane and the semipermeable membrane support may be poor. If it is ^{larger than 5.0 cm 3} / cm ² · sec, strike-through may easily occur when the semipermeable membrane liquid is applied. In addition, the smoothness of the semipermeable membrane forming surface may decrease.

The present invention will be described in more detail by way of examples.

(Example 1)
The composition of the layer on the semitransparent film forming surface side is 70 mass of the main fiber (fiber diameter 8.1 μm, fiber length 6 mm, heat shrinkage rate 4.5%, drawn polyester fiber, hereinafter referred to as “main fiber A”). %, Binder fiber (fiber diameter 11.8 μm, fiber length 5 mm, unstretched polyester-based binder fiber having a melting point of 260 ° C., hereinafter referred to as “binder fiber”) is 30% by mass, and the layer on the non-semi-transparent film forming surface side. The main fiber (fiber diameter 7.5 μm, fiber length 6 mm, heat shrinkage rate 6.0%, drawn polyester fiber, hereinafter referred to as “main fiber B”) is 70% by mass, and the binder fiber is 30% by mass. Then, the slurry in which these fibers were mixed and dispersed in water was separately stored in two stock tanks having a stirrer. Using a combination machine of an inclined wire paper machine and a circular net paper machine, the layer on the semipermeable membrane forming surface side is an inclined wire paper machine, and the layer on the non-semipermeable membrane forming surface side is a circular net paper machine, and each layer is 35 g / after forming the paper making combined wet paper m ^2, by a Yankee dryer having a surface temperature 130 ° C., the semipermeable membrane forming surface is hot pressure drying so as to be in contact with the Yankee dryer to obtain a wet papermaking nonwoven.

The obtained wet-made non-woven film is used at the time of the first roll nip by using a thermal pressure processing apparatus in which the first and second roll nip composed of a metal roll (heated) and a resin roll (non-heated) are continuously installed. The surface temperature of the metal roll was 220 ° C., the surface temperature of the metal roll at the time of the second roll nip was 225 ° C., and processing was performed under the conditions of a nip pressure of 100 kN / m and a processing speed of 20 m / min to obtain a semipermeable membrane support. In the first roll nip, the semipermeable membrane-forming surface is in contact with the metal roll, and in the second roll nip, the non-semipermeable membrane-forming surface is in contact with the metal roll.

(Example 2)
The composition of the layer on the semitransparent film forming surface side is 70 mass of the main fiber (fiber diameter 7.5 μm, fiber length 5 mm, heat shrinkage 5.4%, drawn polyester fiber, hereinafter referred to as “main fiber C”). %, The binder fiber is 30% by mass, and the layer on the non-semi-transparent film forming surface side is blended with the main fiber (fiber diameter 8.1 μm, fiber length 6 mm, heat shrinkage rate 8.0%, drawn polyester fiber, hereinafter “ A semi-transparent film support was obtained in the same manner as in Example 1 except that the main fiber D) was 70% by mass and the binder fiber was 30% by mass.

(Example 3)
The composition of the layer on the semipermeable membrane-forming surface side is 70% by mass of the main fiber A and 30% by mass of the binder fiber, and the composition of the layer on the non-semipermeable membrane-forming surface side is 70% by mass of the main fiber D and the binder. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the fibers were made 30% by mass.

(Example 4)
The composition of the layer on the semipermeable membrane forming surface side is 70 mass of the main fiber (fiber diameter 8.1 μm, fiber length 5 mm, heat shrinkage rate 2.0%, drawn polyester fiber, hereinafter referred to as “main fiber E”). %, The binder fiber was 30% by mass, and the layer on the non-semipermeable membrane forming surface side was blended in the same manner as in Example 1 except that the main fiber A was 70% by mass and the binder fiber was 30% by mass. A semipermeable membrane support was obtained.

(Example 5)
The composition of the layer on the semipermeable membrane-forming surface side is 70% by mass of the main fiber E and 30% by mass of the binder fiber, and the composition of the layer on the non-semipermeable membrane-forming surface side is 70% by mass of the main fiber B and the binder. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the fibers were made 30% by mass.

(Example 6)
At the time of the first roll nip, using the thermal pressure processing apparatus in which the first and second roll nip consisting of the metal roll (heated) and the resin roll (non-heated) are continuously installed in the same composition as in Example 1. The surface temperature of the metal roll was 220 ° C. and the surface temperature of the metal roll at the time of the second roll nip was 220 ° C., and processing was performed under the conditions of a nip pressure of 100 kN / m and a processing speed of 20 m / min to obtain a semipermeable membrane support. ..

(Example 7)
At the time of the first roll nip, using the thermal pressure processing apparatus in which the first and second roll nip consisting of the metal roll (heated) and the resin roll (non-heated) are continuously installed in the same composition as in Example 1. The surface temperature of the metal roll was 220 ° C. and the surface temperature of the metal roll at the time of the second roll nip was 230 ° C., and processing was performed under the conditions of a nip pressure of 100 kN / m and a processing speed of 20 m / min to obtain a semipermeable membrane support. ..

(Comparative Example 1)
The composition of the layer on the semipermeable membrane-forming surface side and the composition of the layer on the non-semipermeable membrane-forming surface side were the same as in Example 1 except that the main fiber A was 70% by mass and the binder fiber was 30% by mass. , A semipermeable membrane support was obtained.

(Comparative Example 2)
The composition of the layer on the semipermeable membrane-forming surface side is 70% by mass of the main fiber E and 30% by mass of the binder fiber, and the composition of the layer on the non-semipermeable membrane-forming surface side is 70% by mass of the main fiber D and the binder. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the fibers were made 30% by mass.

<Preparation of semipermeable membrane>
Using a constant-speed coating device (trade name: Automatic FilmApplicator, manufactured by Yasuda Seiki Co., Ltd.) having a constant clearance on the semipermeable membrane-forming surfaces of the semipermeable membrane supports of Examples 1 to 7 and Comparative Examples 1 and 2. A semipermeable membrane solution which is a dimethylformamide (DMF) solution (concentration: 18% by mass) of polysulfone (manufactured by SIGMA-ALDRICH Corporation, mass average molecular weight Mw <35,000, number average molecular weight Mn <16,000, product number 428302). Was applied, washed with water, and dried to form a semipermeable membrane made of polysulfone having a thickness of 50 μm on the semipermeable membrane-forming surface of the semipermeable membrane support to obtain a filtered membrane.

Measurement 1 (basis weight)
Basis weight was measured according to JIS P8124: 2011.

Measurement 2 (thickness)
The thickness was measured according to JIS P8118: 2014.

Measurement 3 (air permeability)
The air permeability was measured according to the Frazier method of JIS L1096: 2010.

Measurement 4 (average curl height)
From the semipermeable membrane supports obtained in Examples and Comparative Examples, a sample of 10 cm in the width direction × 10 cm in the longitudinal direction was taken, and placed horizontally on a smooth table with the non-semipermeable membrane forming surface facing up. , 23 ° C., 50% R. H. After controlling the humidity for 24 hours under the above conditions, the raised heights of the four corners were measured, and the average value of the values was defined as the "average curl height".

Evaluation (curl evaluation after coating)
From the filtration membrane in which the semipermeable membrane was formed using the semipermeable membrane supports obtained in Examples and Comparative Examples, a sheet sample of 200 mm in the width direction × 300 mm in the longitudinal direction was collected, and the semipermeable membrane forming surface was turned up. Then, the sheet sample was placed horizontally on a smooth table, and the curl state of the sheet sample was evaluated according to the following criteria.

◯: No curl was seen and it was good.
Δ: Slight curl is seen, but there is no problem in practical use.
×: The sheet sample is curled and is at a level that is practically impossible.

The semipermeable membrane supports of Examples 1 to 7 include a main fiber made of synthetic fibers and a binder fiber, and have a two-layer structure including a layer on the semipermeable membrane forming surface side and a layer on the non-semipermeable membrane forming surface side. Since it is a semipermeable membrane support of the above and the average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) of the main fiber is 1.3 to 3.0 times, after semipermeable membrane coating The curl of was also at a level where there was no problem in operation.

Further, comparing Examples 1, 6 and 7 having the same fiber composition, the semipermeable membrane support of Example 1 having an average curl height in the range of 5 to 20 mm has an average curl height of less than 5 mm. Compared with the semipermeable membrane support of No. 6, there is no curl after semipermeable membrane coating, the film is flatter, and even when compared with the semipermeable membrane support having an average curl height of more than 20 mm. There was no curl after semipermeable membrane coating, and the result was excellent in coatability.

The semipermeable membrane support of Comparative Example 1 is a flat semipermeable membrane support having the same average heat shrinkage rate of the main fibers in each layer and an average curl height of 0 mm, but after coating with the semipermeable membrane liquid. , Curled due to shrinkage derived from the semipermeable membrane liquid, and became a practically impossible level. The semipermeable membrane support of Comparative Example 2 has an average heat shrinkage rate (non-semipermeable membrane forming surface / semipermeable membrane forming surface) exceeding 3.0 times, and curls toward the non-semipermeable membrane forming surface side, but the curl does not occur. It was too strong to apply evenly.

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 (2)

Non-semipermeable membrane formation in a semipermeable membrane support having a two-layer structure including a main fiber made of synthetic fibers and a binder fiber, and a layer on the semipermeable membrane forming surface side and a layer on the non-semipermeable membrane forming surface side. The semipermeable membrane is characterized in that the average heat shrinkage rate of the main fiber in the surface side layer is 1.3 to 3.0 times the average heat shrinkage rate of the main fiber in the semipermeable membrane forming surface side layer. Membrane support. A semipermeable membrane support cut out to a size of 10 cm × 10 cm was placed horizontally on a smooth table with the non-semipermeable membrane forming surface side facing up, and the temperature was 23 ° C., 50% R. H. The semipermeable membrane support according to claim 1, wherein the average height of the raised heights of the four corners is in the range of 5 to 20 mm after humidity control for 24 hours under the above conditions.