JP5809583B2 - Semipermeable membrane support - Google Patents

Description

  The present invention relates to a semipermeable membrane support.

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

  The semipermeable membrane is provided on the semipermeable membrane support by dissolving the above-mentioned synthetic resin such as polysulfone resin in an organic solvent, preparing a semipermeable membrane solution, and then adding the semipermeable membrane solution to the semipermeable membrane. A method of coating on a support is widely used. And in order to perform filtration efficiently, a spiral type semipermeable membrane element is formed, and a semipermeable membrane module is further assembled (for example, refer to patent documents 1).

  In order to obtain a high filtration flux and filtration performance, the semipermeable membrane surface has few irregularities, there is no occurrence of lateral bending or wrinkles when forming the semipermeable membrane, and the semipermeable membrane is uniform on the semipermeable membrane support It is necessary to be provided with an appropriate thickness. Therefore, excellent smoothness is required for the application surface of the semipermeable membrane support. And in order to obtain favorable filtration performance, it is necessary to be excellent also in the adhesiveness of a semipermeable membrane and a semipermeable membrane support body. In addition, when assembling the semipermeable membrane module, there is a step of bonding the opposite surfaces (hereinafter referred to as “semipermeable membrane non-coated surface” or “non-coated surface”) to each other using an adhesive. It is also required that the adhesion between the non-coated surfaces is excellent. Furthermore, it is required that the semipermeable membrane solution does not penetrate the non-coated surface. This is because if the back-through occurs, the thickness of the semipermeable membrane becomes non-uniform and the adhesion between the non-coated surfaces decreases.

  In recent years, in order to increase the area of a semipermeable membrane that can be incorporated into a semipermeable membrane element and increase the amount of permeated water per element, it is required to reduce the thickness of the semipermeable membrane support. By reducing the thickness of the semipermeable membrane support, the amount of permeated water per element can be increased. However, the basis weight is also likely to decrease with a decrease in the thickness of the semipermeable membrane support. Demerits such as a decrease in strength of the membrane support and a decrease in bending resistance of the semipermeable membrane support occur. In particular, if the bending resistance of the semipermeable membrane support is too low, wrinkles are generated in the semipermeable membrane support during the formation of the semipermeable membrane, making it difficult to form a uniform semipermeable membrane.

  As a method for preventing the semipermeable membrane support from being bent in the width direction when the semipermeable membrane liquid is applied, it is disclosed that the tensile strength ratio between the papermaking flow direction and the width direction is 2: 1 to 1: 1. (For example, refer to Patent Document 2). Although this method has a certain effect in preventing the bending in the width direction, when the thickness and basis weight of the semipermeable membrane support are small, there arises a problem that wrinkles are generated when the semipermeable membrane is applied.

  Moreover, in the separation membrane support, a method is disclosed in which the fibers arranged on the membrane-forming surface side of the separation membrane are set in a lateral direction relative to the fibers arranged on the non-membrane-forming surface side of the separation membrane (for example, (See Patent Document 3). According to this method, it is described that the separation membrane support can be prevented from curling on the separation membrane surface side during the formation of the separation membrane, and the separation membrane support excellent in workability during the production of the liquid separation element can be obtained. ing. However, no consideration is given to wrinkle generation during semipermeable membrane application when the thickness and basis weight of the semipermeable membrane support are small. In addition, there is a problem that the desalination performance after film formation tends to be inferior because of the poor uniformity of the semipermeable membrane.

JP 2001-252543 A JP 2002-95937 A JP 2011-161344 A

  An object of the present invention is to provide a semipermeable membrane support that is excellent in desalting performance with less generation of wrinkles during the formation of the semipermeable membrane and less coating failure on the semipermeable membrane application surface.

As a result of intensive studies to solve the above problems,
(1) The fiber orientation degree of the fiber arranged on the semipermeable membrane application surface side is 15 to 30 °, the fiber orientation degree of the fiber arranged on the non-application surface is 30 to 90 °, and specified by JIS L1913. Ri der lateral bending resistance is 5.5mN · cm or more by 41.5 ° cantilever method is the aspect ratio of the stiffness by 41.5 ° cantilever method specified in JIS L1913 is 1.00 1.80, the thickness of the semipermeable membrane support is 60-100, semipermeable membrane support basis weight of semipermeable membrane support and said 50 to 100 g / ^{m 2} der Rukoto,
I found.

  In the semipermeable membrane support of the present invention, the fiber orientation degree of the fibers arranged on the semipermeable membrane application surface side is 15 to 30 °, and the fiber orientation degree arranged on the non-application surface is 30 to 90 °, In addition, it is characterized in that the bending resistance in the transverse direction according to the 41.5 ° cantilever method defined in JIS L1913 is 5.5 mN · cm or more. By adopting such a configuration, it is possible to provide a semipermeable membrane support excellent in desalting performance with less generation of wrinkles during the formation of the semipermeable membrane and less application failure on the semipermeable membrane application surface.

In this invention, it is the schematic showing the combination and arrangement | positioning of the roll used by a hot-pressing process, and the paper passing state of a sheet | seat. In this invention, it is the schematic showing the combination and arrangement | positioning of the roll used by a hot-pressing process, and the paper passing state of a sheet | seat.

  In the semipermeable membrane support of the present invention, the fiber orientation degree of the fibers arranged on the semipermeable membrane application surface side is 15 to 30 °, and the fiber orientation degree of the fibers arranged on the non-application surface is 30 to 90 °. In addition, the transverse bending resistance according to the 41.5 ° cantilever method defined in JIS L1913 is 5.5 mN · cm or more. In the present invention, the semipermeable membrane coated surface side is longitudinally oriented more than the semipermeable membrane noncoated surface. By setting it as this structure, the desalination performance at the time of seawater filtration can be improved rather than the case where a semipermeable membrane application surface is laterally oriented rather than a semipermeable membrane non-application surface. The reason is not clear, but when the fibers on the semipermeable membrane application surface are in the longitudinal orientation, the direction of the semipermeable membrane application and the fiber orientation on the semipermeable membrane application surface are almost the same. It is presumed that the resistance to the semipermeable membrane support is reduced, and fine coating failure is less likely to occur. In addition, even if there are fine markings on the semipermeable membrane support, if the semipermeable membrane application surface is in the vertical orientation, the orientation of the markings is made opposite to the coating direction, so that the coating is smoothed and the coating defects It is also possible to suppress the occurrence of.

  In this invention, the fiber orientation degree of the fiber arrange | positioned at a semipermeable membrane application surface side is 15-30 degrees. When the fiber orientation degree is less than 15 °, the curl at the time of coating the semipermeable membrane is large, and the processability at the time of manufacturing the semipermeable membrane element (liquid separation element) is poor. When the fiber orientation degree is larger than 30 °, the desalting rate is lowered. The fiber orientation degree is more preferably 20 to 28 °, and particularly preferably 23 to 28 °.

  The degree of orientation of the fibers arranged on the non-coated surface is 30 to 90 °. When the fiber orientation degree is less than 30 °, the curl when the semipermeable membrane is applied is large, and the processability during the production of the semipermeable membrane element is poor. The fiber orientation degree is more preferably 35 to 60 °, and particularly preferably 35 to 55 °.

  The absolute value of the difference between the fiber orientation degree of the fibers arranged on the semipermeable membrane application surface side and the fiber orientation degree arranged on the non-application surface is preferably 5 ° or more, more preferably 8 ° or more. is there.

  Here, the degree of fiber orientation is an index indicating the direction of the fibers of the nonwoven fabric constituting the semipermeable membrane support. The longitudinal direction of the nonwoven fabric, that is, the longitudinal direction of the nonwoven fabric is 0 °, and the transverse direction of the nonwoven fabric, that is, the nonwoven fabric. The average angle of the fibers constituting the nonwoven fabric when the width direction is 90 °. Accordingly, the closer to 0 ° the fiber orientation, the longer the orientation, and the closer to 90 °, the lateral orientation.

  Next, a method for adjusting the fiber orientation degree of the fibers in the nonwoven fabric will be described. As the nonwoven fabric constituting the semipermeable membrane support of the present invention, nonwoven fabrics such as spunbond nonwoven fabrics, melt blown nonwoven fabrics, dry short fiber nonwoven fabrics and wet papermaking nonwoven fabrics, and composite nonwoven fabrics obtained by laminating these can be used. The degree of fiber orientation can be adjusted by controlling the manufacturing conditions of the nonwoven fabric and the processing conditions when the nonwoven fabric is hot-pressed with a hot roll. The semipermeable membrane support of the present invention preferably uses a wet papermaking nonwoven fabric, but when the nonwoven fabric is produced by the wet papermaking method, the selection of the paper machine to be used and the adjustment of the operating conditions, for example, the wet part of the paper machine Can be achieved by adjusting the jet / wire ratio (raw material jet speed / paper machine wire speed), optimizing the dehydration process in the wire part, and adjusting the tension balance in the dryer part. Moreover, as a processing condition at the time of carrying out a hot press processing, it can aim at adjustment of the kind of roll to be used, arrangement | positioning of a roll, a hot roll temperature, and tension balance.

  The translucent membrane support of the present invention has a lateral bending resistance of 5.5 mN · cm or more according to the 41.5 ° cantilever method specified in JIS L1913. If the bending resistance in the transverse direction is less than 5.5 mN · cm, wrinkles are generated on the semipermeable membrane support when the semipermeable membrane is applied. The bending resistance in the transverse direction is more preferably 6.0 mN · cm or more, and particularly preferably 6.5 mN · cm or more. It is preferable that the aspect ratio of the bending resistance according to the 41.5 ° cantilever method defined in JIS L1913 is 1.00 to 1.80. More preferably, it is 1.00-1.60, Most preferably, it is 1.00-1.50. If the aspect ratio of the bending resistance is greater than 1.80, wrinkles are likely to occur when the semipermeable membrane is applied, and the curl of the sheet after forming the semipermeable membrane tends to be large. If it is smaller than 1.00, the effect of suppressing wrinkles is saturated and it is difficult to manufacture the product.

  The bending resistance of the semipermeable membrane support depends on the thickness and basis weight of the semipermeable membrane support, and as the thickness and basis weight decrease, the bending resistance of the semipermeable membrane support also tends to decrease. Increasing the thickness and basis weight of the semipermeable membrane support increases the bending resistance of the semipermeable membrane support, but the thickness of the membrane, including the semipermeable membrane support, is increased. The area of the semipermeable membrane that can be incorporated tends to be small, and the amount of permeated water of the element tends to decrease. In the present invention, the thickness of the semipermeable membrane support is preferably 60 to 100 μm, more preferably 65 to 90 μm, and further preferably 70 to 85 μm. If the thickness is smaller than 60 μm, sufficient tensile strength may not be obtained.

The basis weight of the semipermeable membrane support is preferably 50 to 100 g / m ² , and more preferably 60 to 80 g / m ² . If it is less than 50 g / m ² , sufficient tensile strength may not be obtained. Further, when it exceeds 100 g / m ² , the area of the semipermeable membrane that can be incorporated into the element tends to be small when the liquid flow resistance becomes high or the thickness increases.

The density of the semi-permeable membrane support is preferably 0.50~1.10g / cm ^3, more preferably 0.60~0.90g / cm ^3. When the density of the semipermeable membrane support is less than 0.50 g / cm ³ , the thickness increases, and the area of the semipermeable membrane that can be incorporated into the element may be reduced. On the other hand, when it exceeds 1.10 g / cm ³ , the liquid permeability may be lowered, and the life of the semipermeable membrane may be shortened.

  As a method for adjusting the bending resistance by the 41.5 ° cantilever method defined in JIS L1913, a method similar to the method for adjusting the fiber orientation degree of the fibers in the nonwoven fabric can be employed. In particular, the processing conditions when the non-woven fabric is hot-pressed with a hot roll are important. Adjustment to increase the bending resistance in the transverse direction to 5.5 mN · cm or more, or adjust the bending aspect ratio to 1.00 by a method of heat-treating the nonwoven fabric before the nip during hot pressing or a method of reducing the tension. Easy adjustment to ˜1.80.

  The heat treatment temperature is preferably −50 ° C. to + 10 ° C., more preferably −30 ° C. to ± 0 ° C. with respect to the melting point or softening point of the binder fiber used in the nonwoven fabric. Examples of the method of heat-treating the nonwoven fabric before the nip at the time of hot pressing include a method of non-contact such as hot air and far infrared rays, a method of contacting a heat medium such as a hot roll and a hot plate. Among these, as shown in FIGS. 1 (A) and (D), the method of passing through the nip portion after being held in the metal roll (heating) 1 at the time of hot pressing does not require any new equipment. It is preferable because stable heat treatment is possible. 1 (A) and 1 (D), the nonwoven fabric shows a path of 180 ° held by the metal roll (heating) 1, but this angle can be appropriately selected and should be 10 to 350 °. More preferably, it is 30 to 330 °, and particularly preferably 50 to 300 °. By heat-treating the nonwoven fabric before the nip at the time of hot pressing, it is presumed that the crystallization of the binder fiber proceeds, the bending resistance of the entire nonwoven fabric increases, and the bending resistance in the lateral direction also improves.

  The method of decreasing the tension is effective for adjusting the aspect ratio of the bending resistance to 1.00 to 1.80. As the tension increases, the aspect ratio of the bending resistance tends to increase, and wrinkles tend to occur during the formation of the semipermeable membrane. By reducing the tension, it becomes easy to adjust the aspect ratio of the bending resistance to 1.00 to 1.80, and it becomes possible to suppress wrinkles at the time of forming the semipermeable membrane. If the tension becomes too weak, it may loosen and wrinkle during winding, and it is necessary to set the tension so weak that these problems do not occur.

  In the semipermeable membrane support of the present invention, the fiber orientation degree of the fibers arranged on the semipermeable membrane application surface side is 15 to 30 °, and the fiber orientation degree arranged on the non-application surface is 30 to 90 °. is there. In order to provide a difference in the degree of fiber orientation between the front and back, a nonwoven fabric in which two or more layers are laminated is preferable. When the semipermeable membrane support is composed of three or more layers of nonwoven fabric, the fiber orientation degree of the intermediate layer other than the surface layer is not particularly defined, but from the semipermeable membrane application surface side toward the semipermeable membrane non-application surface side. It is preferable that the degree of fiber orientation increases sequentially. A multilayer structure in which the fiber blending of each layer is the same may be used, or a multilayer structure in which layers having different fiber blending are laminated may be used.

  It is preferable that the semipermeable membrane support of the present invention is formed into a sheet by a wet papermaking method and then subjected to a hot pressing process with a hot roll. The nonwoven fabric in the wet papermaking method is composed of at least main fibers and binder fibers. The main fiber is a fiber that forms the skeleton of the semipermeable membrane support. The main fiber contains synthetic fiber. For example, polyolefin fiber, polyamide fiber, polyacrylic resin, vinylon fiber, vinylidene fiber, polyvinyl chloride fiber, polyester fiber, benzoate fiber, polychlore fiber, phenol fiber, etc., high heat resistance polyester fiber Is more preferably used. Semi-synthetic fibers such as acetate, triacetate, promix, and regenerated fibers such as rayon, cupra, and lyocell fiber may be contained within a range that does not impair the performance.

  In the semipermeable membrane supporting material of the present invention, it is preferable to contain two or more kinds of fibers having different fiber diameters as main fibers. The fiber network formed by intertwining two or more main fibers having different fiber diameters causes complex and fine irregularities on the coated surface, so that the adhesion between the semipermeable membrane and the semipermeable membrane support can be improved. it can. Further, the smoothness of the coated surface can be improved by this fiber network, and a uniform semipermeable membrane can be obtained.

  The average fiber diameter of the main fibers is preferably 2.0 to 20.0 μm, and more preferably 5.0 to 20.0 μm. In addition, when the fiber diameter of at least one main fiber is 10.0 μm or less, the smoothness of the coated surface can be further improved, and a semipermeable membrane having a uniform film thickness can be easily obtained. When the average fiber diameter of the main fibers is less than 2.0 μm, the adhesion between the non-coated surfaces may deteriorate. When the average fiber diameter of the main fibers exceeds 20.0 μm, the semipermeable membrane support is likely to have a mark on the surface, making it difficult to obtain a semipermeable membrane having a uniform thickness.

  Although the fiber length of a main fiber is not specifically limited, Preferably it is 1-12 mm, More preferably, it is 3-10 mm, More preferably, it is 4-6 mm. When the fiber length is less than 1 mm, a three-dimensional network of fibers is hardly formed in the wet papermaking process, and the peelability from the papermaking wire may be deteriorated. On the other hand, when the fiber length exceeds 12 mm, entanglement of fibers and occurrence of twisting may adversely affect the uniformity of the semipermeable membrane support and the smoothness of the semipermeable membrane. The cross-sectional shape of the main fiber is preferably circular, but fibers having an irregular cross-section such as T-type, Y-type, and triangle can also be contained within a range that does not hinder other characteristics in order to prevent back-through and smooth the coated surface. .

  Examples of the binder fiber include core-sheath fibers (core-shell type), parallel fibers (side-by-side type), composite fibers such as radially divided fibers, unstretched fibers, and the like. Since the composite fiber hardly forms a film, the mechanical strength can be improved while maintaining the space of the semipermeable membrane support. More specifically, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), a combination of high melting point polyester (core) and low melting point polyester (sheath), polyester, etc. Of undrawn fiber. In addition, a single fiber (fully fused type) composed only of a low melting point resin such as polyethylene or polypropylene, or a hot water-soluble binder such as polyvinyl alcohol easily forms a film in the drying process of the semipermeable membrane support. However, it can be used as long as the properties are not impaired. In the present invention, a combination of a high-melting point polyester (core) and a low-melting point polyester (sheath) and unstretched polyester fibers can be preferably used.

  The fiber diameter of the binder fiber is preferably different from that of the main fiber, but is not particularly limited. Because the fiber diameter is different from the main fiber, the binder fiber plays a role of forming a uniform three-dimensional network together with the main fiber and the thin fiber, in addition to the role of improving the mechanical strength of the semipermeable membrane support, In the process of raising the temperature to the softening temperature or melting temperature of the binder fiber in the Yankee dryer or hot air drying, the smoothness of the semipermeable membrane support coated surface can be improved.

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

  The content ratio of the main fiber and the binder fiber of the present invention is preferably 10:90 to 90:10 on a mass basis. When the content ratio of the main fiber is less than 10% by mass, the permeation flux of the filtration membrane may decrease. When the content ratio of the main fiber exceeds 90% by mass, the mechanical strength of the semipermeable membrane supporting member may be lowered and easily broken.

  In the wet papermaking method, first, the main fibers and binder fibers are uniformly dispersed in water, and then passed through processes such as screen (removal of foreign matters, lumps, etc.), and the final fiber concentration is 0.01 to 0.50 mass%. The slurry prepared in (1) is made up with a paper machine to obtain a wet paper. In order to make the dispersibility of the fibers uniform, chemicals such as dispersants, antifoaming agents, hydrophilic agents, antistatic agents, polymer thickeners, mold release agents, antibacterial agents, bactericides, etc. may be added during the process. is there.

  As the paper machine, for example, a long net paper machine, a circular net paper machine, or an inclined wire type paper machine can be used. These paper machines can be used alone, or a combination paper machine in which two or more same or different types of paper machines are installed online may be used. In addition, when the semipermeable membrane support has a multilayer structure of two or more layers, a sheeting method in which wet papers made by each paper machine are laminated, or after forming one sheet, Any method of casting a slurry having fibers dispersed thereon may be used.

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

  The semipermeable membrane support of the present invention performs hot-pressure processing by passing a sheet produced by a wet papermaking method while niping between the rolls of a hot-pressure processing apparatus. 1 and 2 are schematic views showing the combination and arrangement of rolls used in the hot pressing process and the sheet passing state of the sheet. 1 and 2, reference numeral 1 is a metal roll (heating), reference numeral 2 is any roll (heating or non-heating) such as metal, resin, and cotton, and reference numeral 3 is non-metal such as resin and cotton. It is a roll (heating or non-heating), and the code | symbol 4 is a conveyance roll (non-heating). Examples of the combination of rolls in the hot pressing process include two metal rolls, a metal roll and a resin roll, a metal roll and a cotton roll, and one or both rolls are heated. Further, if necessary, the sheet may be reversed so that the number of passes through the nip is two or more. The combination of rolls is not limited to FIGS. 1 and 2 show a combination of two rolls, but three or more rolls can be combined, and a plurality of such roll combinations can be provided in a plurality of stages so that a plurality of hot pressing processes can be performed in one pass. Processing can also be performed.

  The surface temperature of the roll used in the hot pressing process is lower than the melting point of the main fiber measured by differential thermal analysis, and is preferably −50 ° C. to + 10 ° C. with respect to the melting point or softening point of the binder fiber, and −30 ° C. More preferably, the temperature is ˜ ± 0 ° C. In the present invention, the differential thermal analysis is performed at a heating rate of 10 ° C. per minute according to JIS K7121. If the surface temperature of the roll temperature is lower than the melting point or softening temperature of the binder fiber contained in the sheet by more than 50 ° C., fuzzing may occur easily, and it becomes difficult to obtain a semipermeable membrane having a uniform thickness. On the other hand, when the surface temperature of the roll is increased to exceed 10 ° C., the melted portion of the fibers adheres to the metal roll, and the semipermeable membrane support may become non-uniform. It becomes difficult to obtain.

  The nip pressure of the roll is preferably 190 to 3000 N / cm, more preferably 390 to 2000 N / cm. The processing speed is preferably 5 to 200 m / min, and more preferably 10 to 100 m / min.

  The radii of the two rolls constituting the roll nip may be the same or different. The roll radius is preferably 50 to 2000 mm, more preferably 100 to 1500 mm. When the roll radius is less than 50 mm, it is difficult to obtain a desired thickness. On the other hand, when the roll radius exceeds 2000 mm, it becomes difficult to control the surface temperature.

The invention is explained in more detail by means of examples. Hereinafter, unless otherwise specified, the parts and ratios described in the examples are based on mass. Examples 7 and 13 are reference examples.

(Example 1)
The semi-permeable membrane coated surface side and the non-coated surface side are each blended with 50% by mass of a stretched polyester fiber having a fiber diameter of 7.9 μm and a fiber length of 5 mm as a main fiber, a fiber diameter of 12.1 μm and a fiber length of 5 mm. The polyester fiber was 20% by mass and the binder fiber was 30% by mass of unstretched polyester binder fiber having a fiber diameter of 10.5 μm, a fiber length of 5 mm, and a melting point of 260 ° C. These fibers were mixed and dispersed in water and stored separately in two stock tanks having a stirring device. Using a combination machine of an inclined wire paper machine and a circular net paper machine, the semipermeable membrane coating surface side is an inclined wire paper machine, the non-coating surface side is a circular net paper machine, and 35 g / m ² of each layer is combined. After forming the paper, it was hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. so that the semipermeable membrane application surface side was in contact with the Yankee dryer, and a sheet having a basis weight of 70 g / m ² was obtained. At this time, the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) is adjusted, the fiber orientation degree on the semipermeable membrane application surface side is 26 °, and the fiber orientation degree on the non-application surface is 38 °. It adjusted so that it might become.

  The obtained sheet is contacted with the metal roll (heating) 2 by using a hot-pressure processing apparatus in which each roll (reference numerals 1 and 2) is a metal roll in FIG. 1A. Pass through, and heat and pressure processing is performed under the conditions that the surface temperature of both metal rolls (heating) 1 and 2 is 220 ° C., the nip pressure is 800 N / cm, the tension is 0.15 kN / m, and the processing speed is 20 m / min. A semipermeable membrane support was obtained.

(Example 2)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 29 ° and the fiber orientation degree on the non-application surface is 38 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Example 3)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 22 ° and the fiber orientation degree on the non-application surface is 38 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

Example 4
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 16 ° and the fiber orientation degree on the non-application surface is 38 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Example 5)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 26 ° and the fiber orientation degree on the non-application surface is 31 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Example 6)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 26 ° and the fiber orientation degree on the non-application surface is 58 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Example 7)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 26 ° and the fiber orientation degree on the non-application surface is 78 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Example 8)
In FIG. 2 (E), except that each roll (reference numerals 1 and 2) uses a calender device (an angle at which the metal roll (heating) 1 before the nip 1 holds the nonwoven fabric) made of a metal roll (heating). In the same manner as in Example 1, a semipermeable membrane support was obtained.

Example 9
In FIG. 1B, a semipermeable membrane support was obtained in the same manner as in Example 1 except that a calender device comprising metal rolls (heating) was used for each roll (reference numerals 1 and 2).

(Example 10)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the tension during hot pressing was 0.25 kN / m.

(Example 11)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the tension during hot pressing was 0.30 kN / m.

(Example 12)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the tension during hot pressing was 0.40 kN / m.

(Example 13)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the tension during hot pressing was 0.45 kN / m.

(Example 14)
In Example 1, using a calender device in which the roll 2 in FIG. 2 (E) is a resin roll (non-heated), a pass-through is performed so that the semipermeable membrane application surface side is in contact with the metal roll (heating). The metal roll (heating) 1 was hot-pressed under the conditions of a surface temperature of 220 ° C., a nip pressure of 800 N / cm, a tension of 0.15 kN / m, and a processing speed of 20 m / min. Subsequently, using the same calender device, a pass was made so that the semipermeable membrane application surface side was in contact with the resin roll (non-heated) 2, and hot pressing was performed under the same conditions to obtain a semipermeable membrane support.

(Comparative Example 1)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 12 ° and the fiber orientation degree on the non-application surface is 38 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Comparative Example 2)
Adjust ratio of jet speed of raw material and wire speed of paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 32 ° and the fiber orientation degree on non-application surface is 38 ° A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Comparative Example 3)
Adjust the ratio of the jet speed of the raw material and the wire speed of the paper machine (jet / wire ratio) so that the fiber orientation degree on the semipermeable membrane application surface side is 26 ° and the fiber orientation degree on the non-application surface is 28 °. A semipermeable membrane support was obtained in the same manner as in Example 1 except that the adjustment was made.

(Comparative Example 4)
A semipermeable membrane support was obtained in the same manner as in Example 7 except that the nip pressure was changed to 1600 N / cm.

(Comparative Example 5)
In Example 1, the semipermeable membrane coating surface was used as the non-coating surface, and the non-coating surface was used as the coating surface to obtain a semipermeable membrane support of Comparative Example 5.

  The following evaluation was performed with respect to the semipermeable membrane support obtained in Examples and Comparative Examples. The results are shown in Table 1.

Test 1 (Fiber orientation (°))
Ten small sample samples are taken at random from the nonwoven fabric, photographed 100 to 1000 times with a scanning electron microscope, and the longitudinal direction (longitudinal direction) of the nonwoven fabric is measured for a total of 100 fibers, 10 from each sample. The angle when the width direction (transverse direction) of the nonwoven fabric was 90 ° was measured, the average value thereof was calculated, and the first degree after the decimal point was rounded off to obtain the fiber orientation degree.

Test 2 (bending softness by cantilever method)
In accordance with JIS L1913, the longitudinal and lateral bending resistances were measured.

Test 3 (basis weight)
The basis weight was measured according to JIS P8124.

Test 4 (thickness)
The thickness was measured according to JIS P8118.

Test 5 (Wrinkle during semipermeable membrane formation)
Using a comma coater having a certain clearance (200 μm), polysulfone (manufactured by SIGMA-ALDRICH Corporation, mass average molecular weight M _W <35,000, number average molecular weight M _n <16,000 is applied to the coating surface of the semipermeable membrane support. , Product number 428302) was coated with an NN-dimethylacetamide solution (concentration: 18%), washed with water and dried to form a polysulfone membrane on the coated surface of the semipermeable membrane support. The state of occurrence of sheet wrinkles was evaluated according to the following criteria.

A: No wrinkle is generated and good.
○: One spot was generated during coating of 2,000 m. Good level.
(Triangle | delta): The wrinkle generate | occur | produced in 2-4 places during the coating of 2,000 m. Practical upper and lower limit level.
×: Wrinkles frequently occur, practically unusable level.

Test 6 (curl)
In Test 5, after coating and washing the polysulfone membrane, a 30 cm square sample was cut out from the center of the sheet before drying. Place this sample on a flat desk with the side facing up,
The curl value was set to the maximum value among the four raised heights. If the curl value is 30 mm or less, it is good, if it is more than 30 mm and 50 mm or less, there is no practical problem, and if it exceeds 50 mm, handling becomes complicated and impossible.

Test 7 (Desalination rate, Permeated water amount)
After immersing the surface of the polysulfone membrane prepared in Test 5 in an aqueous solution containing 2% by mass of m-phenylenediamine and 0.15% by mass of sodium lauryl sulfate for 30 seconds, the polysulfone membrane was slowly pulled up, and an excess aqueous solution from the surface of the polysulfone membrane. Removed. Next, the surface of the polysulfone membrane was brought into contact with an n-hexane solution containing 0.1% by weight of trimesic acid chloride for 10 seconds to cause an interfacial polycondensation reaction to form a polyamide membrane (thickness 1 μm) on the polysulfone membrane. Then, a composite semipermeable membrane was obtained by drying for 3 minutes in a hot air dryer set at 120 ° C.

  The composite semipermeable membrane thus obtained was allowed to permeate 0.15 mass%, pH 6.5 saline for 1 hour at an operating pressure of 1.5 MPa and a temperature of 25 ° C. The flux was measured. The salt concentration in the permeate and the salt concentration in the feed solution were determined by measuring the electrical conductivity of each solution, and the desalting rate was determined by the following formula. The larger the value of the desalination rate and the amount of permeated water, the better the performance.

  Desalination rate (%) = (1- (solute concentration in permeate / solute concentration in feed solution)) × 100

  In the semipermeable membrane supports of Examples 1 to 14, the fiber orientation degree of the fibers arranged on the semipermeable membrane application surface side is 15 to 30 °, and the orientation degree of the fibers arranged on the non-application surface is 30 to 30 °. It is 90 ° and the bending resistance in the lateral direction according to the 41.5 ° cantilever method defined in JIS L1913 is 5.5 mN · cm or more. By adopting such a configuration, it is possible to provide a semipermeable membrane support that is less likely to cause wrinkles during the formation of the semipermeable membrane and has excellent desalting performance.

  From the comparison of Examples 1 to 4, Examples 1 and 3 in which the degree of fiber orientation on the semipermeable membrane application surface side is 20 to 28 ° have a high desalting rate and the curl of the sheet after the semipermeable membrane is formed. Since it is small, it is particularly preferable. From the comparison of Examples 1 and 5 to 7, Examples 1 and 6 in which the fiber orientation degree on the non-application surface side is 35 to 60 ° are free from wrinkles during the formation of the semipermeable membrane, and the semipermeable membrane is formed. Since the curl of the later sheet is small, it is particularly preferable. From a comparison of Examples 1, 8, and 9, Example 1 having a lateral bending resistance of 6.5 mN · cm or more is satisfactory because no wrinkles are generated when the semipermeable membrane is formed. From the comparison of Examples 1 and 10 to 13, Examples 1 and 10 to 12 in which the aspect ratio of the bending resistance is 1.00 to 1.80 are less likely to cause wrinkles when the semipermeable membrane is formed. The curl of the sheet after film formation is small, which is preferable. In Examples 1 and 10 in which the aspect ratio of the bending resistance is 1.00 to 1.60, these characteristics are particularly good.

  On the other hand, Comparative Example 1 in which the fiber orientation degree on the semipermeable membrane application surface is less than 15 ° and Comparative Example 3 in which the fiber orientation degree on the non-application surface is less than 30 ° have a large curl of the sheet after forming the semipermeable membrane. Inferior to sex. Comparative Examples 2 and 5 in which the fiber orientation degree of the semipermeable membrane application surface is larger than 30 ° are inferior in desalination rate. Although the degree of fiber orientation on each surface is within the scope of the present invention, Comparative Example 4 in which the lateral bending resistance is smaller than 5.5 mN · cm causes frequent wrinkles during the formation of the semipermeable membrane, and the desalination rate. Was also inferior.

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

1 Metal roll (heating)
2 Roll of metal, resin, cotton, etc. (heated or non-heated)
3 Non-metallic rolls such as resin and cotton (heated or non-heated)
4 Transport roll (non-heated)

Claims (1)

The fiber orientation degree of the fiber arranged on the semipermeable membrane application surface side is 15 to 30 °, the fiber orientation degree of the fiber arranged on the non-application surface is 30 to 90 °, and 41 defined in JIS L1913. .5 ° Ri der lateral bending resistance is 5.5mN · cm or more by cantilever method, the aspect ratio of the stiffness by 41.5 ° cantilever method specified in JIS L1913 is 1.00 to 1.80 , and the thickness of the semipermeable membrane support is 60-100, semipermeable membrane support basis weight of semipermeable membrane support and said 50 to 100 g / ^{m 2} der Rukoto.

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