JP6625916B2 - Semipermeable membrane support - Google Patents

Description

  The present invention relates to a semipermeable membrane support.

  BACKGROUND ART Semipermeable membranes are widely used in fields such as desalination of seawater, water purifiers, food concentration, wastewater treatment, production of ultrapure water for medical use represented by blood filtration, and semiconductor cleaning, and the like. The semipermeable membrane is made of a synthetic resin such as a cellulose resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, a polyester resin, a polyamide resin, and a polyimide resin. However, since the semipermeable membrane alone has poor mechanical strength, it is used as a filtration membrane in which a semipermeable membrane is provided on one surface of a semipermeable membrane support made of a fiber base material such as a nonwoven fabric or a woven fabric. . Hereinafter, the surface of the semipermeable membrane support on which the semipermeable membrane is provided may be referred to as “coated surface”. Further, the surface opposite to the coated surface may be described as “non-coated surface”.

  As a method for producing a filtration membrane, there is a method in which a synthetic resin such as the above-mentioned polysulfone-based resin is dissolved in an organic solvent to prepare a semipermeable membrane solution, and then the semipermeable membrane solution is coated on a semipermeable membrane support. Widely used. Then, for efficient filtration, a spiral type semipermeable membrane element is formed, and a semipermeable membrane module is further assembled (for example, see Patent Document 1).

  In order to obtain high filtration flux and filtration performance, there are few irregularities on the semipermeable membrane surface, there is no lateral curvature or wrinkles when forming the semipermeable membrane, and the semipermeable membrane is uniform on the semipermeable membrane support It must be provided with an appropriate thickness. In order for the semipermeable membrane to be provided with a uniform thickness, the coated surface of the semipermeable membrane support must have excellent smoothness. And 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 bonding the non-coated surfaces to each other using an adhesive, so that it is also required that the non-coated surfaces have excellent adhesion. Further, it is required that the semipermeable membrane liquid does not strike through to the non-coated surface. This is because, when strike-through occurs, problems occur in that the thickness of the semipermeable membrane becomes uneven and the adhesiveness between the non-applied surfaces decreases.

  As a semipermeable membrane support, there has been proposed a nonwoven fabric which includes a main fiber made of synthetic fiber and a binder fiber, is produced by a wet papermaking method, and is subjected to a hot-press processing. For example, a non-woven fabric having a multilayer structure based on a double structure of a surface layer having a large surface roughness (thick fiber layer) using thick fibers and a back layer having a dense structure using fine fibers (thin fiber layer). (See, for example, Patent Document 2). Specifically, a semi-permeable membrane support having a thick fiber layer as a coating surface and a thin fiber layer as a non-coating surface, and a thin fiber layer sandwiched between thick fiber layers, and having both a coating surface and a non-coating surface as a thick fiber A semipermeable membrane support as a layer is described. However, since the thick fibers are used on the application surface, the adhesiveness between the semipermeable membrane and the semipermeable membrane support is improved. There is a problem that the fluff breaks through the semipermeable membrane and the semipermeable membrane does not have a uniform thickness. In addition, when the pressure during hot pressing is increased to suppress the generation of fuzz, the surface density of the semipermeable membrane support increases too much, and the adhesiveness between the semipermeable membrane and the semipermeable membrane support decreases. There was a case. Then, during the cutting process after the formation of the semipermeable membrane support or during the semipermeable membrane liquid coating process, the friction is caused by friction between the application surface and a transport roll such as an expander roll or a metal roll arranged in each process. No consideration is given to fluffing. In addition, the fluff is referred to as a `` loose fiber '' in which one of the fluff fibers is fused to the support, and a `` loop fiber '' in which both ends of the fluff fibers are fixed by fusion and the middle part is raised. There are two types. The loose fiber and the loop fiber tend to cause defects when the semipermeable membrane liquid is applied, and there is a problem that the membrane performance is reduced. In particular, since the fluffed fibers were fused at both ends, the loop fibers were less likely to fall off from the semipermeable membrane support and were more likely to be defective.

JP 2008-238147 A Japanese Patent Publication No. Hei 4-21526

  An object of the present invention is to provide a semipermeable membrane support having less fuzz on a surface on which a semipermeable membrane is provided and having few defects due to fluff of main fibers when applying a semipermeable membrane liquid.

  The problem has been solved by the following means.

(1) In a semipermeable membrane support containing a main fiber composed of synthetic fibers and a binder fiber, a degree of fiber orientation of a surface on which a semipermeable membrane is provided is 10 to 30 °, and an average single fiber of the main fiber A semipermeable membrane support having a strength of 5.0 cN / dtex or less.

  The semipermeable membrane support of the present invention has a fiber orientation degree of 10 to 30 ° on the surface on which the semipermeable membrane is provided, and an average single fiber strength of the main fiber of 5.0 cN / dtex or less. When the transfer roll and the surface of the semipermeable membrane support on which the semipermeable membrane is provided come into contact during the cutting step or the semipermeable membrane liquid coating step after the formation of the permeable membrane support, it is possible to suppress the generation of fluff. It has become possible.

  The semipermeable membrane support of the present invention is a semipermeable membrane support containing a main fiber composed of synthetic fibers and a binder fiber, the degree of fiber orientation of the surface on which the semipermeable membrane is provided is 10 to 30 °, and The average single fiber strength of the main fiber is 5.0 cN / dtex or less.

  In the present invention, the fiber orientation on the application surface of the semipermeable membrane support is longitudinal orientation. The occurrence of fluffing is reduced as compared with the case where the fiber orientation is horizontal orientation, and coating defects derived from fluffing can be suppressed. Although the reason is not clear, when the fiber orientation of the application surface is longitudinal orientation, during the cutting process or semi-permeable membrane liquid coating process, the coating surface and each step, such as an expander roll or a metal roll, etc. It is presumed that the resistance between the transport roll and the semipermeable membrane support decreases, and that fluffing is suppressed. Further, it is presumed that since the average single fiber strength of the main fibers is as low as 5.0 cN / dtex or less, the entanglement between the fibers is increased, and the fuzz is suppressed even when resistance is received from a transport roll or the like. ing.

  Next, a method for adjusting the degree of fiber orientation of the fibers in the semipermeable membrane support will be described. As the semipermeable membrane support of the present invention, a nonwoven fabric such as a spunbonded nonwoven fabric, a meltblown nonwoven fabric, a dry short-fiber nonwoven fabric, and a wet-laid nonwoven fabric, or a composite nonwoven fabric obtained by laminating a plurality of nonwoven fabrics selected from these nonwoven fabrics can be used. Further, the nonwoven fabric is subjected to hot-press processing by a hot roll. The fiber orientation degree can be adjusted by controlling the manufacturing conditions of the nonwoven fabric and the processing conditions when the nonwoven fabric is subjected to hot-press processing by a hot roll. As described below, the semipermeable membrane support of the present invention is preferably a wet-laid nonwoven fabric. Adjust the fiber orientation by adjusting the jet / wire ratio of the raw material (raw material ejection speed / paper machine wire speed) in the wet part of the machine, optimizing the dewatering process in the wire part, and adjusting the tension balance in the dryer part can do. As the processing conditions for the hot-press processing, the degree of fiber orientation can be adjusted by adjusting the type of roll used, the arrangement of the rolls, the temperature of the hot roll, and the balance of tension.

  In the present invention, the degree of fiber orientation on the application surface of the semipermeable membrane support is 10 to 30 °, more preferably 10 to 25 °, and further preferably 10 to 20 °. When the fiber orientation degree exceeds 30 °, during the cutting step or the semipermeable membrane liquid coating step, the resistance between the main fiber on the application surface and the transport roll increases, and the main fiber between the binder fibers via the binder fiber The bond is easily broken, and as a result, fluff such as loose fiber and loop fiber is generated on the application surface. When the fiber orientation degree is less than 10 °, the fiber entanglement between the main fibers is reduced, the adhesiveness between the fibers is reduced, and the generation of fluff is caused.

  In the present invention, the average single fiber strength of the main fibers contained in the semipermeable membrane support is 5.0 cN / dtex or less, preferably 4.7 cN / dtex or less, more preferably 4.5 cN / dtex or less. is there. When the average single fiber strength exceeds 5.0 cN / dtex, the rigidity of the fiber is high, so that the main fiber on the application surface receives resistance from the transport roll during the cutting process or the semipermeable membrane liquid coating process. At this time, the adhesion between the fibers is easily cut, and as a result, fluffs such as loose fibers and loop fibers are generated. The lower limit of the average single fiber strength is preferably 4.2 cN / dtex.

  In the present invention, the main fibers and the binder fibers are made of synthetic fibers. The main fibers are fibers that form the skeleton of the semipermeable membrane support, and even at the temperature at which the binder fibers soften or melt, the main fibers are hardly softened or melted, and although the cross-sectional shape may change, the shape of the fibers is changed. Is a fiber that is not impaired. Examples of the main fiber include, for example, polyolefin-based, polyamide-based, polyacryl-based, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, benzoate-based, polyclar-based, and phenol-based fibers. High 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 main fibers. Due to a fiber network formed by entanglement of two or more types of main fibers having different fiber diameters, complicated and fine irregularities are generated on the application surface, so that the adhesiveness between the semipermeable membrane and the semipermeable membrane support can be improved. it can. Further, the smoothness of the application surface can be improved by the fiber network, and a uniform semipermeable membrane can be obtained. When the main fiber contains one kind of fiber diameter and the binder fiber contains two or more kinds of fibers having different fiber diameters, the binder fiber is softened or melted by a drying process or a hot pressing process. In some cases, the smoothness of the semipermeable membrane support may be too high, and may not be able to contribute to the fiber network for improving the adhesiveness between the semipermeable membrane and the semipermeable membrane support.

  The average fiber diameter of the main fibers is preferably from 7.0 to 20.0 µm, more preferably from 8.0 to 16.0 µm. When the fiber diameter of at least one type of main fiber is 13.0 μm or less, the smoothness of the coated surface can be further improved, and a semipermeable membrane having a uniform thickness can be easily obtained. When the average fiber diameter of the main fiber is less than 7.0 μm, the peel strength between the coated surface and the semipermeable membrane may be reduced, or the adhesiveness between the non-coated surfaces may be deteriorated. When the average fiber diameter of the main fibers exceeds 20.0 μm, not only the smoothness of the surface of the semipermeable membrane support is lost and it becomes difficult to obtain a semipermeable membrane having a uniform thickness, but also the air permeability of Frazier (FG) May be too high, and strikethrough may occur at the time of applying the semipermeable membrane liquid.

  In the present invention, the average fiber diameter of the main fiber is determined by the following equation. N is a positive integer.

Average fiber diameter = (fiber diameter of main fiber 1 (μm) × mass% of main fiber 1 + fiber diameter of main fiber 2 (μm) × mass% of main fiber 2 + fiber diameter of main fiber 3 (μm) × main +% By mass of main fiber N + mass% of main fiber 3 + mass% of main fiber 3 + mass% of main fiber 3 + ... fiber diameter (μm) of main fiber N × mass% of main fiber N ... + mass% of main fiber N)

  The single fiber strength is a value measured based on the tensile strength of JIS L1015.

  In the present invention, the average single fiber strength of the main fiber is obtained by the following equation. N is a positive integer.

Average single fiber strength = (Single fiber strength of main fiber 1 (cN / dtex) × mass% of main fiber 1 + single fiber strength of main fiber 2 (cN / dtex) × mass% of main fiber 2 + mass% of main fiber 3 Single fiber strength (cN / dtex) × mass% of main fiber 3+... + Single fiber strength of main fiber N (cN / dtex) × mass% of main fiber N) / (mass% of main fiber 1 + main body) (Mass% of fiber 2 + mass% of main fiber 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. When the fiber length is less than 1 mm, a three-dimensional network of fibers is not easily formed in the papermaking process, and the releasability from the papermaking wire may be deteriorated. On the other hand, if the fiber length exceeds 12 mm, the uniformity of the semipermeable membrane support and the smoothness of the semipermeable membrane may be adversely affected by the occurrence of entanglement or entanglement between the fibers. The cross-sectional shape of the main fiber is preferably circular, but fibers having irregular cross-sections such as T-type, Y-type, and triangular can also be contained within a range that does not hinder other properties for preventing strike-through and smoothness of the coated surface. .

  Although the semipermeable membrane support of the present invention contains binder fibers, the step of raising the temperature to around the temperature at which the binder fibers are softened or melted is incorporated into the production process of the semipermeable membrane support, whereby the binder fibers are produced. Improves the mechanical strength of the semipermeable membrane support. For example, a semipermeable membrane support can be produced by a wet papermaking method, and the binder fibers can be softened or melted in a subsequent drying step.

  Examples of the binder fibers 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 conjugate fiber does not easily form a film, the mechanical strength can be improved while maintaining the space of the semipermeable membrane support. More specifically, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), a combination of high-melting polyester (core) and low-melting polyester (sheath), polyester, etc. Undrawn fiber. In addition, a single fiber (all-fused type) composed only of a low melting point resin such as polyethylene or polypropylene, or a hot water-soluble binder such as a polyvinyl alcohol-based resin can easily form a film in a drying process of a semipermeable membrane support. However, it can be used as long as the properties are not impaired. In the present invention, a combination of a high-melting polyester (core) and a low-melting polyester (sheath) and undrawn polyester fibers 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 main fiber and the fiber diameter are different, the binder fiber has a role of improving the mechanical strength of the semipermeable membrane support, and also has a role of forming a uniform three-dimensional network together with the main fiber and the small diameter fiber. In a Yankee dryer or hot air drying, in the step of raising the temperature to a temperature near the temperature at which the binder fibers soften or melt, the smoothness of the coated surface can also be improved.

  The fiber length of the binder fiber is not particularly limited, but if the fiber length exceeds 20 mm, the formation tends to be deteriorated. The cross-sectional shape of the binder fiber can include a fiber having a circular or irregular cross-section such as T-shape, Y-shape, and triangle.

  The content ratio of the main fiber and the binder fiber is preferably 60:40 to 80:20, more preferably 60:40 to 75:25, and more preferably 65:35 to 75:25 on a mass basis. More preferably, the ratio is particularly preferably 65:35 to 70:30. When the content ratio of the main fiber is less than 60% by mass with respect to the total amount of the main synthetic fiber and the binder synthetic fiber, the permeation flux may decrease. When the content ratio of the main fiber exceeds 80% by mass, the mechanical strength of the semipermeable membrane support is reduced, and the semipermeable membrane support may be easily broken.

  The semipermeable membrane support of the present invention can contain acetate, triacetate, and promix of semi-synthetic fibers and rayon, cupra, and lyocell fibers of regenerated 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 subjecting a nonwoven fabric produced by a wet papermaking method (wet papermaking nonwoven fabric) to hot pressing with a hot roll.

  In the wet papermaking method, first, a main fiber and a binder fiber are uniformly dispersed in water, and then, through a process such as a screen (removal of foreign matters, lumps, etc.), the final fiber concentration is reduced to 0.01 to 0.50% by mass. Is prepared by a paper machine to obtain wet paper. During the process, a chemical such as a dispersant, an antifoaming agent, a hydrophilic agent, an antistatic agent, a polymer tackifier, a release agent, an antibacterial agent, and a bactericide may be added.

  As the paper making method, for example, a long net, a circular net, an inclined wire method, or the like can be used. A paper machine having one kind of paper making method selected from these paper making methods may be used, or a combination paper machine in which two or more kinds of paper making methods of the same kind or different kinds are installed online may be used. . Further, when the semipermeable membrane support has a multilayer structure of two or more layers, a laminating method of laminating wet papers made by each papermaking method, forming one layer, and then forming Can be manufactured 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 layers in a dry state can be thermally fused to form a multilayer structure.

  The wet paper produced by the paper machine is dried by a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, or the like to obtain a wet nonwoven fabric. When the wet paper is dried, the wet paper is brought into close contact with a hot roll such as a Yankee dryer and dried under hot pressure, thereby improving the smoothness of the contact surface. Hot-press drying refers to pressing wet paper against a hot roll with a touch roll or the like to dry. The surface temperature of the heat roll is preferably from 100 to 180C, more preferably from 100 to 160C, and still more preferably from 110 to 160C. When the surface temperature of the hot roll is lower than 100 ° C., the moisture of the wet paper web produced by the paper machine does not sufficiently evaporate, and the thickness uniformity of the semipermeable membrane support may be deteriorated. If it exceeds 180 ° C., the wet paper web produced by the paper machine may adhere to the heat roll, and the formation of the semipermeable membrane support may be poor. The pressure is preferably 5 to 100 kN / m, more preferably 10 to 80 kN / m. When the pressure is lower than 5 kN / m, the moisture of the wet paper manufactured by the paper machine may not be sufficiently released, and the thickness uniformity of the semipermeable membrane support may be deteriorated. In some cases, the wet paper produced in step (1) sticks to the heat roll, and the formation of the semipermeable membrane support deteriorates.

  In the hot-press processing, the wet nonwoven fabric is passed between the hot rolls while nipping between the hot rolls of the hot-press processing apparatus. Examples of the combination of the heat rolls include two metal rolls, a metal roll and a resin roll, and a metal roll and a cotton roll. One or both heat rolls are heated. Further, if necessary, the number of times of passing through the nip may be two or more by reversing the front and back of the nonwoven fabric.

  The surface temperature of the hot roll used for the hot-press processing is preferably lower than the melting point of the main fiber measured by differential thermal analysis, and is preferably −70 to −20 ° C. with respect to the melting point of the binder fiber, and −60 to −30. C. is more preferable. If the surface temperature of the hot roll 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 heat roll is increased beyond a temperature lower by 20 ° C. than the melting point, a melted portion of the fibers may adhere to the heat roll, and the semipermeable membrane support may become non-uniform. Is difficult to obtain. The melting point of the fiber was determined by DSC (differential scanning calorimetry) under the conditions of a temperature range of 25 to 300 ° C. and a heating rate of 10 ° C./min.

  The nip pressure of the hot roll used for the hot pressing is preferably 50 to 250 kN / m, and more preferably 70 to 180 kN / m. The processing speed is preferably 5 to 100 m / min, and more preferably 10 to 50 m / min.

  The semipermeable membrane support of the present invention may have a multilayer structure in which the fiber composition of each layer is the same, or may have a multilayer structure in which layers having different fiber compositions are laminated. In this case, as the basis weight of each layer is reduced, the fiber concentration of the slurry can be reduced, so that the formation of the semipermeable membrane support is improved, and as a result, the smoothness and uniformity of the coated surface are improved. Even if the formation of each layer is not uniform, it can be compensated by laminating. Further, the paper making 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, when it exceeds 150 g / m ² , the liquid permeation resistance may be increased, or the thickness may be increased, so that a predetermined amount of the semipermeable membrane cannot be stored in the unit or module.

Further, 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 is large, so that the area of the semipermeable membrane that can be incorporated in the unit becomes small, and as a result, the life of the semipermeable membrane becomes short. Sometimes. On the other hand, if it exceeds 1.2 g / cm ³ , the liquid permeability may be low, and the life of the semipermeable membrane may be short.

  The thickness of the semipermeable membrane support is preferably from 60 to 150 μm, more preferably from 70 to 130 μm, even more preferably from 80 to 120 μm. When the thickness of the semipermeable membrane support exceeds 150 μm, the area of the semipermeable membrane that can be incorporated into the unit becomes small, and as a result, the life of the semipermeable membrane may be shortened. On the other hand, when it is less than 60 μm, sufficient tensile strength may not be obtained, or liquid permeability may be reduced, and 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. More preferably, it is 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 solution is applied. In addition, the smoothness of the coated surface may decrease.

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

(Example 1)
As a main fiber, a drawn polyester fiber (main fiber A) having a fiber diameter of 7.9 μm, a single fiber strength of 4.6 cN / dtex, and a fiber length of 5 mm is 60 mass%, and a fiber diameter of 10.5 μm and a fiber length of 5 mm is used as a binder fiber. The unstretched polyester binder fiber having a melting point of 260 ° C. was 40% by mass. These fibers were mixed and dispersed in water and stored separately in two stock tanks having a stirrer. Using a combination machine of an inclined wire paper machine and a mesh paper machine, forming a wet paper web of 40 g / m ² in each layer by using an inclined wire paper machine on the coated side and a mesh paper machine on the non-coated side. After that, drying was performed with a Yankee dryer having a surface temperature of 130 ° C. so that the coated surface side was in contact with the Yankee dryer to obtain a wet nonwoven fabric having a basis weight of 80 g / m ² . At this time, the ratio (jet / wire ratio) between the ejection speed of the raw material and the wire speed of the paper machine was adjusted to adjust the degree of fiber orientation on the coated surface.

  The obtained wet nonwoven fabric is subjected to a first roll nip by using a hot-press processing apparatus in which first and second roll nips comprising a metal roll (heating) and a resin roll (non-heating) are continuously installed. The surface temperature of the roll was 220 ° C., the surface temperature of the metal roll at the time of the second roll nip was 225 ° C., 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 surface in contact with the metal roll was defined as a coating surface.

(Examples 2 to 4)
A semipermeable membrane support was obtained in the same manner as in Example 1, except that the jet / wire ratio was adjusted and the degree of fiber orientation on the coated surface was changed.

(Example 5)
As the main fiber, a fiber diameter of 9.4 μm, a single fiber strength of 5.1 cN / dtex, a fiber length of 6 mm, 50% by mass of a drawn polyester fiber (main fiber B), a main fiber A of 10% by mass, and a binder fiber as fiber The unstretched polyester binder fiber having a diameter of 10.5 μm, a fiber length of 5 mm, and a melting point of 260 ° C. was 40% by mass. These fibers were mixed and dispersed in water and stored separately in two stock tanks having a stirrer. Using a combination machine of an inclined wire paper machine and a mesh paper machine, forming a wet paper web of 40 g / m ² in each layer by using an inclined wire paper machine on the coated side and a mesh paper machine on the non-coated side. After that, drying was performed with a Yankee dryer having a surface temperature of 130 ° C. so that the application surface side was in contact with the Yankee dryer to obtain a wet nonwoven fabric having a basis weight of 80 g / m ² . At this time, the jet / wire ratio was adjusted to adjust the degree of fiber orientation on the application surface.

  The obtained wet nonwoven fabric is subjected to a first roll nip by using a hot-press processing apparatus in which first and second roll nips comprising a metal roll (heating) and a resin roll (non-heating) are continuously installed. The surface temperature of the roll was 220 ° C., the surface temperature of the metal roll at the time of the second roll nip was 225 ° C., 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 surface in contact with the metal roll was defined as a coating surface.

(Example 6)
As the main fiber, 30% by mass of the main fiber A, a fiber diameter of 12.5 μm, a monofilament strength of 4.4 cN / dtex, 20% by mass of a drawn polyester fiber (main fiber C) having a fiber length of 5 mm, and a fiber diameter of 17.5 μm 10% by mass of a drawn polyester fiber (main fiber E) having a single fiber strength of 4.1 cN / dtex and a fiber length of 5 mm, and an undrawn polyester fiber having a fiber diameter of 10.5 μm, a fiber length of 5 mm and a melting point of 260 ° C. as a binder fiber. The binder fiber was 40% by mass. After forming a single layer wet paper using an inclined wire paper machine, it is hot-press dried with a Yankee dryer having a surface temperature of 130 ° C. so that the application side is in contact with the Yankee dryer, and a wet nonwoven fabric having a basis weight of 80 g / m ² is obtained. Obtained. At this time, the jet / wire ratio was adjusted to adjust the degree of fiber orientation on the application surface.

  The obtained wet nonwoven fabric is subjected to a first roll nip by using a hot-press processing apparatus in which first and second roll nips comprising a metal roll (heating) and a resin roll (non-heating) are continuously installed. The surface temperature of the roll was 220 ° C., the surface temperature of the metal roll at the time of the second roll nip was 225 ° C., the nip pressure was 100 kN / m, and the processing speed was 20 m / min. Obtained. In the first roll nip, the surface in contact with the metal roll was defined as a coating surface.

(Comparative Example 1)
As a main fiber, 25% by mass of a main fiber B, a fiber diameter of 13.0 μm, a monofilament strength of 5.9 cN / dtex, a fiber length of 6 mm, 45% by mass of a drawn polyester fiber (main fiber D), and a binder fiber as a fiber The unstretched polyester binder fiber having a diameter of 10.5 μm, a fiber length of 5 mm, and a melting point of 260 ° C. was 30% by mass. These fibers were mixed and dispersed in water and stored separately in two stock tanks having a stirrer. Using a combination machine of an inclined wire paper machine and a mesh paper machine, forming a wet paper web of 40 g / m ² in each layer by using an inclined wire paper machine on the coated side and a mesh paper machine on the non-coated side. After that, drying was performed with a Yankee dryer having a surface temperature of 130 ° C. so that the application surface side was in contact with the Yankee dryer to obtain a wet nonwoven fabric having a basis weight of 80 g / m ² . At this time, the jet / wire ratio was adjusted to adjust the degree of fiber orientation on the application surface.

  The obtained wet nonwoven fabric is subjected to a first roll nip by using a hot-press processing apparatus in which first and second roll nips comprising a metal roll (heating) and a resin roll (non-heating) are continuously installed. The surface temperature of the roll was 220 ° C., the surface temperature of the metal roll at the time of the second roll nip was 225 ° C., 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 surface in contact with the metal roll was defined as a coating surface.

(Comparative Examples 2-3)
A semipermeable membrane support was obtained in the same manner as in Example 1, except that the jet / wire ratio was adjusted and the degree of fiber orientation on the coated surface was changed.

(Comparative Example 4)
A semipermeable membrane support was obtained in the same manner as in Comparative Example 1, except that the jet / wire ratio was adjusted and the degree of fiber orientation on the coated surface was changed.

(Comparative Example 5)
A semipermeable membrane support was obtained in the same manner as in Example 6, except that the jet / wire ratio was adjusted and the degree of fiber orientation on the coated surface was changed.

  The obtained wet nonwoven fabric is subjected to a first roll nip by using a hot-press processing apparatus in which first and second roll nips each including a metal roll (heating) and a resin roll (non-heating) are continuously installed. Was processed at a surface temperature of 220 ° C., a surface temperature of the metal roll at the time of the second roll nip at 225 ° C., a nip pressure of 100 kN / m, and a processing speed of 20 m / min to obtain a semipermeable membrane support of Comparative Example 5. Was. The surface in contact with the first metal roll was defined as a coating surface.

Measurement 1 (Fiber orientation)
From the semipermeable membrane supports obtained in Examples and Comparative Examples, 10 small sample pieces were randomly sampled, photographed at a magnification of 100 to 1000 with a scanning electron microscope, and 10 photographs were taken from each sample. For the fibers of the present invention, the angle was determined when the longitudinal direction (longitudinal direction) of the semipermeable membrane support was 0 ° and the width direction (horizontal direction) of the nonwoven fabric was 90 °, and the average value thereof was calculated. The degree of fiber orientation was determined by rounding off the first decimal place.

Measurement 2 (basis weight)
The grammage was measured according to JIS P8124.

Measurement 3 (thickness)
The thickness was measured according to JIS P8118.

Measurement 4 (air permeability)
The air permeability was measured according to JIS L1096.

Evaluation (Fuzziness evaluation)
From the semipermeable membrane supports obtained in Examples and Comparative Examples, a sample of 40 mm in width direction × 60 mm in longitudinal direction was sampled, attached to the center of a support paper of 100 mm in width × 700 mm in longitudinal direction, and one end of the support paper was attached. The sample adhered to the fixed and mirror-finished φ140 mm metal roll was brought into contact with the roll, the other end was fixed so that the support paper did not sag, and the metal roll was rotated at 65 mm / sec for 1 minute. Thereafter, the sample is removed, the surface is observed with a stereoscopic microscope at a magnification of 40 to 100, and the number of loose fibers and loop fibers is counted. The measurement was performed at n = 4, and the average value is shown. The following evaluation was performed.

"○" The number of loose fibers and loop fibers is less than 5. Practically no problem level.
"△" The number of loose fibers and loop fibers is 5 or more and less than 10. Practically usable level.
“×” The number of loose fibers and loop fibers is 10 or more. Practically impossible level.

  In the semipermeable membrane supports of Examples 1 to 6, the degree of fiber orientation on the application surface is 10 to 30 °, and the average single fiber strength of the main fibers is 5.0 cN / dtex or less. Thus, it has become possible to provide a semipermeable membrane support having less fluff on the surface of the application surface.

  The semipermeable membrane support of Comparative Example 1 had a fiber orientation degree of 10 to 30 °, but had an average single fiber strength of more than 5.0 cN / dtex, so that fluffing was at a practically unacceptable level. The semipermeable membrane supports of Comparative Examples 2 and 3 have an average single fiber strength of 5.0 cN / dtex or less, but the fiber orientation degree is out of the range of 10 to 30 °, and fuzzing is at a practically unacceptable level. Was. The semipermeable membrane support of Comparative Example 4 had a fiber orientation degree of more than 30 ° and an average single fiber strength of more than 5.0 cN / dtex. The semi-permeable membrane support of Comparative Example 5 had an average single fiber strength of 5.0 cN / dtex or less, but had a fiber orientation degree of less than 10 °, so that fuzzing was at a practically unacceptable level.

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

Claims (1)

  In a semipermeable membrane support comprising a main fiber composed of synthetic fibers and a binder fiber, a degree of fiber orientation of a surface of the semipermeable membrane support on which a semipermeable membrane is provided is 10 to 30 °, and the main fiber is Characterized by having an average single fiber strength of 5.0 cN / dtex or less.