JP2018130689A - Semipermeable membrane support - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semipermeable membrane support showing less defects such as pinholes after performing semipermeable membrane coating.SOLUTION: In a semipermeable membrane support made of a nonwoven fabric including a main synthetic fiber and a binder synthetic fiber, the average value of small aperture permeability is 0.3-5.0 cm/cms, the maximum value-minimum value of the small aperture permeability is 3.0 cm/cms or less and a liquid droplet penetration diameter is less than 15 mm (where, the small aperture permeability is permeability obtained by converting permeation resistance measured by a permeability test machine with a small aperture permeation hole (permeation hole area is 0.2π cmand aperture diameter is 8.94 mm) to the permeability of a Frazier type method of JIS L 1913 (2010); the average value of the small aperture permeability is the arithmetic mean value of the small aperture permeability at 10 places of measuring regions being continuous in a width direction and having a diameter of 8.94 mm on center lines of each divided region in a longitudinal direction by uniformly performing X division of the semipermeable membrane support cut so as to have a width of 10×X cm and a length of 10 cm in a width direction; X is a positive integer; the maximum value-minimum value of the small aperture permeability is the maximum value-minimum value of the small aperture permeability at the 10 places; and the liquid droplet penetration diameter is the spreading diameter of a solution permeated into the semipermeable membrane support passing 15 seconds after dropping a solution dissolved with a dye in pure water by 0.035±0.005 milliliter to the semipermeable membrane support).SELECTED DRAWING: None

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, or a polyamide resin. However, since the semipermeable membrane itself is inferior in mechanical strength, it is used in a form in which a semipermeable membrane is provided on one side 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 “application surface”, and the opposite surface may be referred to as “non-application surface”.

  The performance required for the semipermeable membrane support is that the semipermeable membrane is uniformly formed (semipermeable membrane uniformity), and that there are few defects such as pinholes in the semipermeable membrane (pinhole suppression ability) ) And the like. In addition, a phenomenon that the semipermeable membrane support turns brown after the formation of the semipermeable membrane (hereinafter, this phenomenon may be referred to as “yellowing”) does not occur. Controlling the air permeability of a semipermeable membrane support for semipermeable membrane uniformity and pinhole suppression ability is disclosed (for example, see Patent Documents 1 to 4).

Patent Document 1 describes that the fragile air permeability (JIS L 1079-1966) of the nonwoven fabric constituting the semipermeable membrane support is required to be 0.2 to 10.0 cm ³ / cm ² · s. Has been. When the air permeability is less than 0.2 cm ³ / cm ² · s, the semipermeable membrane liquid for forming the semipermeable membrane does not sufficiently penetrate into the nonwoven fabric even when the concentration is low and the viscosity is low. When the air permeability exceeds 10.0 cm ³ / cm ² · s, even if the semipermeable membrane liquid has a high concentration and high viscosity, the membrane exudes to the back surface of the nonwoven fabric. It is described that pinholes are likely to occur in the film structure by entraining air existing in the voids of the nonwoven fabric at that time.

Patent Document 2 discloses a fragile air permeability (JIS L 1096) in a semipermeable membrane support, which is a non-woven fabric made of synthetic resin fine fibers and binder fibers, and is manufactured by heat-pressing after papermaking. ) Is preferably 0.5 to 7.0 cm ³ / cm ² · s. And when the air permeability of the semipermeable membrane support is 0.5 cm ³ / cm ² · s or less, the penetration of the semipermeable membrane liquid into the semipermeable membrane support is hindered, The problem of lowering the adhesive strength with the semipermeable membrane support tends to occur, and conversely, when the air permeability of the semipermeable membrane support is 7.0 cm ³ / cm ² · s or more, It is described that there is too much permeation into the permeable membrane support and the problem that the semipermeable membrane liquid partially penetrates easily occurs.

Patent Document 3 describes that the semipermeable membrane support has an air permeability (JIS L 1913) of preferably 0.1 to ⁵ cm ³ / cm ² · s. Then, 0.1 cm ³ / cm is less than ² · s, there is a possibility that film air permeability is too low is reduced processability becomes difficult to adhere to the nonwoven fabric, on the contrary, air permeability ^5cm 3 / ^cm 2 · s It is described that, when the amount exceeds 50%, the semipermeable membrane liquid tends to exude to the back surface of the nonwoven fabric, and pinholes are likely to be generated in the membrane structure.

  The diameter of the fragile type tester used in the fragile type method in JIS L 1079-1966, JIS L 1096 and JIS L 1913 is 70 mm. The Frazier type testing machine is intended to quantify the average air permeability in the entire plane of a fabric such as a nonwoven fabric, a woven fabric, or a knitted fabric, and measures it with a large measurement area of 70 mm in diameter. Even if the air permeability measured with this Frazier type tester is within a specific numerical range, pinholes may be formed in the semipermeable membrane.

Patent Document 4 discloses a laminate dry thermoplastic long-fiber nonwoven fabric of three or more layers including at least a melt bron fiber layer as an intermediate layer and a spunbond fiber layer on both sides of the intermediate layer, and the average value of the airflow resistance is 2. A composite membrane support that is 0 to 30.0 kPa · s / m and that has a difference between an average value of airflow resistance and a standard deviation of 0.6 or less is described. In patent document 4, the local variation is detected using the ventilation resistance meter by the KES method which can be measured with a measurement area of 0.2πcm ² (diameter 8.94 mm). And in the portion where the ventilation resistance value is locally high and the density is high, the bubbles existing near the interface between the semipermeable membrane liquid and the nonwoven fabric stay in the vicinity of the coating surface without being pulled out to the nonwoven fabric layer side opposite to the coating surface. The problem that a film may be formed in a state is solved by a composite membrane support that achieves uniform ventilation resistance in a minute region. However, Patent Document 4 does not describe anything about yellowing.

In Patent Document 5, conforming to JIS P 8140-1976, Cobb when pure water was 5sec contact as a sample (Cobb) method water absorbency 3.0 g / ^{m 2} or more, is less than 11.0 g / ^{m 2} It is described that the semipermeable membrane support is excellent in adhesiveness with the semipermeable membrane, and can prevent the semipermeable membrane liquid from getting through and preventing a minute leak of permeated water. Moreover, in patent document 6, when manufacturing a semipermeable membrane with the semipermeable membrane support body whose Cobb method water absorption is 11.0-40.0 g / m < ² > when it contacts 30 seconds using pure water as a sample. It is described that the back-through of the semipermeable membrane liquid is suppressed, good adhesiveness between the non-coated surfaces of the semipermeable membrane support is obtained, and a semipermeable membrane excellent in adhesiveness is obtained. However, yellowing could not be solved even by a semipermeable membrane support having a Cobb method water absorption in a specific range.

Japanese Patent Laid-Open No. 10-225630 JP 2002-95937 A Japanese Patent Laying-Open No. 2015-73946 International Publication No. 2010/126113 Pamphlet JP2013-188712A JP2013-139030A

  It is an object of the present invention to provide a semipermeable membrane support that is less susceptible to pinholes and the like after the semipermeable membrane is formed, and at the same time, the semipermeable membrane support is less likely to turn brown after the semipermeable membrane is formed. is there.

  The above problems have been solved by the following means.

(1) In a semipermeable membrane supporting body made of a nonwoven fabric containing at least a main synthetic fiber and a binder synthetic fiber, the average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s. A semipermeable membrane support, wherein the maximum value-minimum value of the small-diameter air permeability is 3.0 cm ³ / cm ² · s or less, and the droplet permeation diameter is less than 15 mm.
Small-diameter air permeability: Ventilation resistance measured with an air permeability tester provided with small-diameter air holes (vent hole area 0.2πcm ² , diameter 8.94 mm) was changed to JIS L 1913: 2010 air-permeable fragile form method. Air permeability obtained by conversion.
Average value of small-diameter air permeability: a semipermeable membrane support cut into a width of “10 × X” cm and a length of 10 cm is divided into X evenly in the width direction, and on the center line in the length direction of each divided area, Arithmetic mean value of small-diameter air permeability at 10 measurement areas having a diameter of 8.94 mm that are continuous in the width direction. X is a positive integer.
Maximum value-minimum value of small-diameter air permeability: Maximum value-minimum value of small-diameter air permeability at the above 10 locations.
Droplet penetration diameter: The spread diameter of the solution which was dropped into a semipermeable membrane support after dropping 0.035 ± 0.005 ml of a dye dissolved in pure water to the semipermeable membrane support.

In the present invention, the average value of the small-diameter air permeability in the semipermeable membrane support is 0.3 to 5.0 cm ³ / cm ² · s, and the maximum value-minimum value of the small-diameter air permeability is 3.0 cm ³ / By being below cm ² · s, it is possible to provide a semipermeable membrane support with few defects such as pinholes after semipermeable membrane application. Furthermore, when the droplet permeation diameter is less than 15 mm, it is possible to provide a semipermeable membrane support with little yellowing after the semipermeable membrane is formed.

It is the microscope picture which image | photographed and applied transmitted light to the surface of the filtration membrane in which the pinhole generate | occur | produced. With respect to the pinhole generating portion of FIG. 1, the surface of the semipermeable membrane is peeled off from the semipermeable membrane support, and transmitted light is applied to the pinhole generating portion of the semipermeable membrane from the surface that is in contact with the semipermeable membrane support. It is the photographed micrograph. A semipermeable membrane support cut into a width of “10 × X” cm and a length of 10 cm is equally divided into X in the width direction, and is continuous in the width direction on the center line in the length direction of each divided area. It is the graph which showed the small-diameter air permeability in the 1st division area-the X-th division area when the small-diameter air permeability of 10 measurement area | regions of .94 mm was measured (X = 6). A semipermeable membrane support cut out to a width of “10 × X” cm and a length of 10 cm is equally divided into X in the width direction, and a Frazier type tester (caliber diameter: 70 mm) is used at the center of each divided area. It is the graph which showed the measured fragile air permeability. A semipermeable membrane support having a width of 31 cm and a length of 10 cm is equally divided into three in the width direction, and 10 measurement areas having a diameter of 8.94 mm are continuously provided on the center line in the length direction of each divided area. It is the figure which showed the measurement location in the case of measuring small aperture air permeability. It is the photograph which image | photographed the semipermeable membrane support 15 seconds after dripping 0.035 +/- 0.005 milliliters of the solution which dissolved the dye in the pure water, and a droplet penetration diameter is less than 11.0 mm. It is the photograph which image | photographed the semipermeable membrane support 15 seconds after dripping 0.035 +/- 0.005 milliliters of the solution which dissolved the dye in the pure water, and a droplet penetration diameter is more than 15.0 mm. It is the photograph which showed the method of measuring a droplet penetration diameter. It is the graph which showed the relationship between the Cobb method water absorption, a droplet penetration diameter, and yellowing.

  The semipermeable membrane support of the present invention can be used in the fields of seawater desalination, water purifier, food concentration, wastewater treatment, medical filtration represented by blood filtration, production of ultrapure water for semiconductor cleaning, and the like. it can. Examples of the semipermeable membrane include a semipermeable membrane made of a synthetic resin such as a cellulose resin, a polysulfone resin, a polyacrylonitrile resin, a fluorine resin, or a polyester resin. A semipermeable membrane solution in which a synthetic resin, which is a raw material for the semipermeable membrane, is applied to one surface (application surface) of the semipermeable membrane support, gelled in a coagulation bath, washed with water, and microporous membrane Is formed, and a composite form in which a semipermeable membrane is provided on the coating surface of the support for semipermeable membrane (filtration membrane) is obtained.

  Conventionally, it has been considered that a pinhole generated in a semipermeable membrane becomes a pinhole when the semipermeable membrane liquid falls into a gap existing in the semipermeable membrane support. However, as a result of investigating the semipermeable membrane support at many pinhole occurrence locations, the semipermeable membrane support at the pinhole occurrence portion has no voids such as depressions, cuts, cavities, etc. It was confirmed that the film was in a state close to film formation.

  The semipermeable membrane support of the present invention comprises a nonwoven fabric containing at least main synthetic fibers and binder synthetic fibers. It is thought that the state close | similar to film formation with clogging is a location (melting location) where melting | fusing of the binder synthetic fiber in a semipermeable membrane support is advancing. When the semipermeable membrane liquid is applied to the melted portion, bubbles remaining between the melted portion and the semipermeable membrane liquid cannot escape to the back side of the semipermeable membrane support in the coagulation / water washing process. It is considered that pinholes are generated because they try to escape toward the film side. It is thought that the melted portion is in a state where the gap between the main fibers is filled with a melted binder to form a film, which is why the bubbles remaining at the time of coating the film component cannot be degassed.

  FIG. 1 is a photomicrograph taken by applying transmitted light to the surface of a filtration membrane in which pinholes have occurred. It can be seen that the semi-permeable membrane of the pinhole generating portion becomes thin and can be seen through.

  FIG. 2 shows the pinhole generating part of FIG. 1, the surface of the semipermeable membrane is peeled from the semipermeable membrane support, and is transmitted from the surface in contact with the semipermeable membrane support to the pinhole generating portion of the semipermeable membrane. It is the microscope picture which image | photographed and applied light. It can be seen that the pinhole generating part has no semipermeable membrane component and contains transmitted light. In addition, minute bubbles can be seen in portions other than the pinhole generating portion. From this, it is considered that the pinhole is generated when it is a large bubble and cannot be degassed to the semipermeable membrane support side.

  If the film-like state at the melted portion can be quantified, the occurrence of pinholes can be prevented. In order to obtain a semipermeable membrane support that is unlikely to generate pinholes, it has been practiced to control the air permeability of the semipermeable membrane support. As the air permeability, fragile air permeability measured mainly by the fragile method defined in JIS L 1079 (1966), JIS L 1096, JIS L 1913, etc. is used. The diameter of the fragile type tester used in the fragile type method is 70 mm. The Frazier type testing machine is intended to quantify the average air permeability in the entire plane of a fabric such as a nonwoven fabric, a woven fabric, and a knitted fabric, and thus measures with a large measurement area of 70 mm in diameter. Therefore, it is difficult to grasp the presence / absence of a melted part causing a pinhole when a Frazier type tester is used.

In the present invention, for example, a breathability tester (KES-F8-AP1) manufactured by Kato Tech Co., Ltd. can be used as an apparatus used for small-diameter air permeability measurement. A small-diameter vent hole (the cross-sectional area of the vent hole is 0.2πcm ² , the caliber diameter is 8.94 mm) is used. The small-diameter air permeability in the present invention is obtained by quantifying the air permeability of each small measurement area with an aperture diameter of 8.94 mm. Can be grasped more accurately.

  FIG. 3 shows a semipermeable membrane support cut to a width of “10 × X” cm and a length of 10 cm, which is equally divided into X in the width direction and continuous in the width direction on the center line in the length direction of each divided area. It is the graph which showed the small-diameter air permeability in the 1st division area-the X-division area when the small-diameter air permeability of 10 measurement area | regions of diameter 8.94mm is measured. It can be seen that the fluctuations in the small-diameter air permeability at 10 locations in each divided area are large.

  FIG. 4 is a graph showing the fragile air permeability measured using a fragile type tester (caliber diameter 70 mm) at the central portion of each divided region with respect to the same semipermeable membrane support as in FIG. One fragile air permeability is measured in one divided area, and it can be seen that the fluctuation of the fragile air permeability in each divided area is small and stable as compared with the small-diameter air permeability.

  That is, a semipermeable membrane support cut out to a width of “10 × X” cm and a length of 10 cm is divided into X evenly in the width direction, and continuous in the width direction on the center line in the length direction of each divided area. When the semi-permeable membrane support after removing the semipermeable membrane of the filtration membrane in which pinholes were generated with a solvent when measuring the small-diameter air permeability of 10 measurement regions having a diameter of 8.94 mm, It was found that the runout was large, and pinholes occurred in the small-diameter portion with low air permeability. According to the present invention, since the small-diameter air permeability is obtained by quantifying the air permeability for each small measurement area having a diameter of 8.94 mm, the presence or absence of a melted part that causes a pinhole is determined. It can be grasped more accurately than the Frazier type testing machine. Further, by managing the air permeability for each small measurement area, it is possible to reduce the poor air permeability and to suppress the occurrence of pinholes.

  For example, in the case of a semipermeable membrane support having a width of 106 cm, the measurement of the small-diameter air permeability is performed with respect to the semipermeable membrane support cut out to a width of 106 cm and a length of 10 cm, except for each 3 cm at both ends in the width direction. The remaining width of 100 cm is divided into 10 parts every 10 cm (X = 10), and the small-diameter air permeability of 10 measurement areas having a diameter of 8.94 mm that are continuous in the width direction on the center line in the length direction of each divided area. taking measurement. In the case of a semipermeable membrane support having a width of 31 cm, the semipermeable membrane support having a width of 31 cm and a length of 10 cm is cut from the semipermeable membrane support having the remaining width of 30 cm except for 0.5 cm at both ends in the width direction. The small-diameter air permeability in the membrane support is measured. FIG. 5 is a diagram specifically showing a part where the small-diameter air permeability is measured in a semipermeable membrane support having a width of 31 cm. Except for the width of 0.5 cm at both ends in the width direction, the remaining 30 cm wide and 10 cm long semipermeable membrane support is equally divided into three for every 10 cm in the width direction, and on the center line in the length direction of each divided area, The small-diameter air permeability of 10 measurement regions having a diameter of 8.94 mm that are continuous in the width direction is measured.

The semipermeable membrane support of the present invention is a semipermeable membrane support composed of a nonwoven fabric containing at least main synthetic fibers and binder synthetic fibers, and the average value of small-diameter air permeability is 0.3 to 5.0 cm. ³ / cm ² · s, and the maximum value-minimum value of the small-diameter air permeability is 3.0 cm ³ / cm ² · s or less. The average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s, preferably 0.3 to 4.0 cm ³ / cm ² · s, and more preferably 0.00. 4 to 3.0 cm ³ / cm ² · s. When the average value of the small-diameter air permeability is less than 0.3 cm ³ / cm ² · s, when the semipermeable membrane liquid is applied to the semipermeable membrane support, the semipermeable membrane liquid is introduced into the semipermeable membrane support. The degree of permeation is low, and the anchor effect between the semipermeable membrane and the semipermeable membrane support cannot be obtained, resulting in a problem of semipermeable membrane peeling. On the other hand, when it exceeds 5.0 cc / cm ² · s, the semipermeable membrane liquid penetrates too much into the semipermeable membrane support, and the semipermeable membrane liquid reaches the back surface of the semipermeable membrane support. “Back-through” occurs, and a sufficient amount of semipermeable membrane is not formed on the coated surface side, leading to a reduction in membrane performance.

In the present invention, the maximum value-minimum value of the small-diameter air permeability is 3.0 cm ³ / cm ² · s or less, more preferably 2.5 cm ³ / cm ² · s or less, more preferably 2 0.0 cm ³ / cm ² · s or less. When the maximum value-minimum value of the small-diameter air permeability exceeds 3.0 cm ³ / cm ² · s, since the fluctuation of the small-diameter air permeability in the divided area is large, a film is formed by melting the binder synthetic fiber. It is highly likely that this is happening locally, and at the part where the small-diameter air permeability is considered to be filming, bubbles cannot smoothly escape to the back side of the semipermeable membrane support, The probability that a pinhole will occur increases.

  Based on the average value of the small-diameter air permeability and the maximum-minimum value of the small-diameter air permeability, it is possible to grasp whether the degree of melting of the binder synthetic fiber by hot pressing and the degree of clogging by the binder synthetic fiber are uniform and appropriate. it can.

As a method of setting the average value of the small-diameter air permeability of the semipermeable membrane support to 0.3 to 5.0 cm ³ / cm ² · s, selection of the fiber diameter of the main synthetic fiber, the main synthetic fiber and the binder synthetic fiber Adjustment of a compounding ratio, adjustment of hot press processing conditions by a hot roll, etc. are mentioned. Moreover, as a method of setting the maximum value-minimum value of the small-diameter air permeability of the semipermeable membrane support to 3.0 cm ³ / cm ² · s or less, the hot roll temperature during hot pressing with a hot roll is set to a binder synthetic fiber. The method of lowering the melting point, the method of lowering the nip pressure during hot pressing, the combination of a hot roll, a resin roll, a cotton roll, etc. are important. In addition, the degree of melting of the binder synthetic fiber can be adjusted to some extent by controlling the processing speed during hot pressing. It can also be adjusted by lowering the blending ratio of the binder synthetic fiber.

  In the semipermeable membrane support, in addition to the occurrence of defects due to pinholes, there are cases where the commercial value and performance are reduced due to yellowing. Yellowing occurs in the process of forming a composite membrane on a semipermeable membrane support. As a method for forming a composite film, there are [1] polymer coating method, [2] cross-linked polymer coating method, and [3] monomer polymerization method. In the interfacial polymerization method, which is one of the [3] monomer polymerization methods in this, yellowing occurs after forming a support membrane layer such as a polysulfone resin on the coated surface of the semipermeable membrane support, and then the surface of the support membrane layer. This occurs in the step of forming a polyamide resin layer to form a composite film.

  In the step of forming a polyamide resin layer by the interfacial polymerization method, first, an aqueous solution is formed by applying an aqueous amine solution by a coating method or an impregnation method on the support membrane layer formed on the coating surface of the semipermeable membrane support. To do. Next, an acid chloride organic solvent solution such as acid chloride is applied to the aqueous phase of the amine to cause interfacial polymerization. Yellowing is a phenomenon that occurs after the completion of interfacial polymerization, when the excess amine cannot be removed in the water washing step and remains on the semipermeable membrane support or the composite membrane, the amine turns brown.

For example, in JP2013-188712A (Patent Document 5) and JP2013-139030A (Patent Document 6), the Cobb method water absorption of the semipermeable membrane support is measured. The Cobb water absorption test method based on JIS P8140-1976 is used as a means for measuring the amount of water penetrating into paper or nonwoven fabric. The Cobb method water absorption test method is to measure the mass of pure water that permeates the sample in 30 seconds by placing a cylindrical jig with a diameter of 51.2 mm on the sample and pouring a certain amount of pure water into the sample in the cylinder. It is a method to do. However, there is a drawback that the area to be measured is large and the degree of penetration of pure water cannot be observed visually. In the graph of FIG. 9, the Y-axis indicates the Cobb method water absorption when pure water is used as a sample for 5 seconds, but for example, the point A where the Cobb method water absorption is 17 to 18 g / m ^2. And point B, it was found that yellowing occurred at point A, but only slightly at point B. That is, as in the past, even when measuring the amount of water penetrating into the semipermeable membrane support by the Cobb method water absorption test method, it is not possible to clarify the relationship between the Cobb method water absorption and the occurrence of yellowing. could not.

  As a result of the study, it was found that the amine residue that causes yellowing is closely related to the droplet permeability of the semipermeable membrane support, and the present invention has been achieved. When water droplets of pure water are dropped on a semipermeable membrane support that is not coated with a polysulfone membrane after the polysulfone membrane liquid is applied to one side of the semipermeable membrane support, the water droplets are likely to spread (highly penetrating droplets). It was found that the permeable membrane support was easily yellowed. This droplet permeability is obtained by applying an aqueous amine solution to the support membrane surface in the interfacial polymerization step of the membrane by a coating method or an impregnation method, and forming a water phase to a semipermeable membrane support other than the support membrane surface. It shows the degree of penetration. When the droplet permeability is high, the penetration from the non-coated surface, which is the opposite surface of the semipermeable membrane support, increases, and the amine enters the interface between the polysulfone membrane and the semipermeable membrane support. Therefore, excessive amine remains in the semipermeable membrane support even in the washing step after completion of interfacial polymerization, and yellowing occurs.

  In the present invention, 0.035 ± 0.005 ml of a colored solution obtained by dissolving a dye in pure water is dropped on the non-coated surface of the semipermeable membrane support, and the solution droplets permeate the semipermeable membrane support. The diameter (unit: mm) of the spread part is determined as the “droplet penetration diameter”. Measurement is made 15 seconds after the drop is dropped. In the graph of FIG. 9, when the droplet penetration diameter where the X axis indicates the droplet penetration diameter is less than 15 mm, the occurrence of yellowing is small, and the commercial value and performance are not reduced. Moreover, when it is less than 11 mm, yellowing does not occur. FIG. 6 is a photograph 15 seconds after dropping the droplet, and the droplet penetration diameter is less than 11 mm. The droplet penetration diameter at the moment when the droplet was dropped was about 6 mm. FIG. 7 is a photograph 15 seconds after the droplet was dropped, and the droplet penetration diameter significantly exceeded 15 mm. When the droplet penetration diameter is 15 mm or more, the probability of yellowing increases.

  As a method of making the droplet penetration diameter of the semipermeable membrane support less than 15 mm, selection of the fiber diameter of the main synthetic fiber, adjustment of the blending ratio of the main synthetic fiber and the binder synthetic fiber, adjustment of the hot press processing conditions by the hot roll Etc. This can be achieved by adjusting the hot roll temperature during hot-pressing with a hot roll, adjusting the nip pressure during hot-pressing, optimizing the combination of hot roll, resin roll, and cotton roll, and controlling the processing speed during hot-pressing. . In order to reduce the droplet permeation diameter, the surfactant attached to the surface of the main synthetic fiber and binder synthetic fiber used in the semipermeable membrane support by increasing the amount of heat applied to the semipermeable membrane support It is necessary to reduce the hydrophilic group of the oil equalizing agent.

  In the present invention, the main synthetic fiber is a fiber that forms the skeleton of the semipermeable membrane support. Examples of the main synthetic fiber include polyolefin-based, polyamide-based, polyacrylic-based, vinylon-based, vinylidene-based, polyvinyl chloride-based, polyester-based, benzoate-based, polychral-based, and phenol-based fibers. Polyester fibers having high heat resistance are more preferable. 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.

The fiber diameter of the main synthetic fiber is not particularly limited, but is 30 μm or less. Preferably it is 2-25 micrometers, More preferably, it is 5-20 micrometers, More preferably, it is 7-20 micrometers. When the diameter is less than 2 μm, the maximum value-minimum value of the small-diameter air permeability is small, but the average value of the small-bore air permeability is less than 0.3 cm ³ / cm ² · s, or the semipermeable membrane liquid is a semipermeable membrane It may be difficult to penetrate the support, and the adhesion between the semipermeable membrane and the semipermeable membrane support may be deteriorated. When the fiber diameter of the main synthetic fiber exceeds 30 μm, the average value of small-diameter air permeability exceeds 5.0 cm ³ / cm ² · s, the case where the droplet penetration diameter becomes 15 mm or more, In order to obtain the thickness of the film, there may be a problem that a large amount of semipermeable membrane liquid is required, or there may be a case where the semipermeable membrane liquid is breached. In addition, the main fibers tend to stand on the surface of the nonwoven fabric, and the performance of the semipermeable membrane may be reduced by penetrating the semipermeable membrane.

  The fiber length of the main synthetic fiber is not particularly limited, but is preferably 1 to 12 mm, more preferably 3 to 10 mm, and still more preferably 4 to 7 mm. The cross-sectional shape of the main synthetic fiber is preferably circular, and the cross-sectional aspect ratio (fiber cross-section major axis / fiber cross-section minor axis) of the fiber before dispersion in water in the wet papermaking process is 1.0 to less than 1.2. preferable. When the fiber cross-sectional aspect ratio is 1.2 or more, the fiber dispersibility may be deteriorated, or the non-uniformity of the nonwoven fabric and the smoothness of the coated surface may be adversely affected by the entanglement and entanglement of the fibers. However, fibers having irregular cross-sections such as T-type, Y-type, and triangle can also be contained within a range that does not hinder other properties such as fiber dispersibility for preventing back-through and surface smoothness.

  The aspect ratio (fiber length / fiber diameter) of the main synthetic fiber is preferably 200 to 2000, more preferably 200 to 1500, and still more preferably 280 to 1000. When the aspect ratio is less than 200, the dispersibility of the fiber is good, but the fiber may fall off the paper making wire during paper making, or the fiber may be stuck in the paper making wire and the peelability from the wire may deteriorate. is there. On the other hand, when it exceeds 2000, although it contributes to the formation of a three-dimensional network of fibers, the occurrence of entanglement and entanglement of the fibers may adversely affect the uniformity of the nonwoven fabric and the smoothness of the coated surface.

40-90 mass% is preferable, as for content of the main synthetic fiber with respect to the nonwoven fabric concerning the semipermeable membrane support body of this invention, 50-80 mass% is more preferable, and 60-75 mass% is still more preferable. When the content of the main synthetic fiber is less than 40% by mass, the liquid permeability may be lowered. Moreover, when it exceeds 90 mass%, there is a possibility that the droplet penetration diameter becomes 15 mm or more, the average value of the small-bore air permeability exceeds 5.0 cm ³ / cm ² · s, or may be broken due to insufficient strength. .

  The semipermeable membrane support of the present invention contains a binder synthetic fiber. The binder synthetic fiber can improve the strength of the semipermeable membrane support by incorporating the process of raising the temperature to the softening point or the melting temperature (melting point) or higher of the binder synthetic fiber into the method for producing the semipermeable membrane support. . In the process of raising the temperature, the main synthetic fiber is difficult to soften or melt and the cross-sectional shape may change, but the shape as a fiber is not impaired, and the skeleton of the semipermeable membrane support is used as the main fiber. Form. For example, the binder synthetic fiber can be softened or melted during the drying process or thermal calendering process after the nonwoven fabric is produced by the wet papermaking method.

  Examples of the binder synthetic 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.

  Although the fiber diameter of a binder synthetic fiber is not specifically limited, Preferably it is 2-20 micrometers, More preferably, it is 5-15 micrometers, More preferably, it is 7-12 micrometers. Moreover, it is preferable that it is a fiber diameter different from a main synthetic fiber, and it is especially preferable that it is a fiber diameter thinner than a main synthetic fiber. Since the fiber diameter is different from that of the main synthetic fiber, the binder synthetic fiber plays a role of forming a uniform three-dimensional network together with the main synthetic fiber in addition to improving the mechanical strength of the semipermeable membrane support. Furthermore, in the step of raising the temperature to the softening temperature or melting temperature of the binder synthetic fiber, the smoothness of the semipermeable membrane support surface can be improved, and in this step, it is more effective when accompanied by pressurization. is there.

  Although the fiber length of a binder synthetic fiber is not specifically limited, Preferably it is 1-12 mm, More preferably, it is 3-10 mm, More preferably, it is 4-7 mm. The cross-sectional shape of the binder synthetic fiber is preferably circular, but fibers having irregular cross-sections such as T-type, Y-type, and triangle can also be used for preventing back-through, smoothness of coated surfaces, and adhesion between non-coated surfaces. In the range which does not inhibit the characteristic of this.

  The binder synthetic fiber has an aspect ratio (fiber length / fiber diameter) of preferably 200 to 2000, more preferably 200 to 1500, and still more preferably 300 to 1000. When the aspect ratio is less than 200, the dispersibility of the fiber is good, but the fiber may drop off from the papermaking wire during papermaking, or the fiber may pierce the papermaking wire and the peelability from the wire may deteriorate. is there. On the other hand, when it exceeds 2000, the binder synthetic fiber contributes to the formation of the three-dimensional network, but the fiber may be entangled or the tangle may adversely affect the uniformity of the nonwoven fabric and the smoothness of the coated surface. .

10-48 mass% is preferable, as for content of the binder synthetic fiber with respect to the nonwoven fabric concerning the semipermeable membrane support body of this invention, 20-45 mass% is more preferable, and 25-40 mass% is still more preferable. When the content of the binder synthetic fiber is less than 10% by mass, when the droplet permeation diameter is 15 mm or more, when the average value of the small-bore air permeability exceeds 5.0 cm ³ / cm ² · s, or due to insufficient strength There is a risk of tearing. Moreover, when it exceeds 48 mass%, when the average value of a small-bore air permeability will be less than 0.3 cm < ³ > / cm < ² > / s, liquid permeability may fall or film formation may advance at the time of a hot press process There is.

  The method for producing the semipermeable membrane support of the present invention will be described. In the semipermeable membrane supporting material of the present invention, after a sheet is produced by a wet papermaking method, the sheet is hot-pressed by a hot roll.

  In the wet papermaking method, first, at least the main synthetic fiber and the binder synthetic fiber are uniformly dispersed in water, and then passed through a process such as screen (removal of foreign matters, lump etc.), and the final fiber concentration is 0.01-0. Slurries prepared to 50% by weight are made up with a paper machine to obtain 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 papermaking method, for example, a papermaking method such as a long mesh, a circular mesh, or an inclined wire method can be used. Use a paper machine with at least one paper machine selected from the group of these paper machines, or a combination machine with two or more same or different paper machines selected online from these paper machine groups can do. In addition, when manufacturing a nonwoven fabric having a multilayer structure of two or more layers, a wet paper made by each paper machine is laminated, or one sheet is formed and then formed on the sheet. A method of casting a slurry in which fibers are dispersed can 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 the wet paper is pressed against the heat 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.

Next, although hot press processing by a hot roll is demonstrated, this invention is not specified to the following. The sheet is passed through the hot pressing process while niping between the rolls of the sheet hot pressing apparatus (calendar apparatus). Examples of the combination of rolls include two metal rolls, a metal roll and a resin roll, and a metal roll and a cotton roll. One or both of the two rolls is heated and used as a hot roll. At that time, a desired semipermeable membrane support is obtained by controlling the surface temperature of the hot roll, the nip pressure between the rolls, and the sheet processing speed. The surface temperature of the hot roll is preferably 150 to 260 ° C, more preferably 180 to 240 ° C. When the temperature is lower than 150 ° C., the droplet permeation diameter may be 15 mm or more, and the average value of the small mouth air permeability may exceed 5.0 cm ³ / cm ² · s. The roll nip pressure is preferably 190 to 1800 N / cm, more preferably 390 to 1500 N / cm. If it is less than 190 N / cm, the droplet permeation diameter may be 15 mm or more, and the average value of the small mouth air permeability may exceed 5.0 cm ³ / cm ² · s. The processing speed is preferably 4 to 100 m / min, and more preferably 10 to 80 m / min. In the case of less than 4 m / min, the average value of the small mouth air permeability may be less than 0.3 cm ³ / cm ² · s. It is also possible to perform the hot pressing with a hot roll two or more times. In that case, two or more sets of rolls arranged in series may be used, or one set of rolls may be used. You may process twice or more. If necessary, the front and back of the sheet may be reversed. In order to set the maximum value-minimum value of the small-diameter air permeability to 3.0 cm ³ / cm ² · s or less, the combination of rolls is preferably a metal roll and a resin roll, or a metal roll and a cotton roll.

Although the basic weight of a semipermeable membrane support body is not specifically limited, 20-150 g / m < ² > is preferable, More preferably, it is 50-100 g / m < ² >. If it is less than 20 g / m ² , sufficient tensile strength may not be obtained. Moreover, when it exceeds 150 g / m < ² >, a liquid flow resistance may become high, thickness may increase, and a predetermined amount of semipermeable membrane may not be accommodated in a unit or a module.

The density of the semi-permeable membrane support is preferably 0.5 to 1.0 g / cm ^3, more preferably 0.6~0.95g / cm ^3. When the density of the semipermeable membrane support is less than 0.5 g / cm ³ , the thickness increases, and the area of the semipermeable membrane that can be incorporated into the unit is reduced. As a result, the life of the semipermeable membrane is shortened. May end up. On the other hand, when it exceeds 1.0 g / cm ³ , the liquid permeability may be lowered, and the life of the semipermeable membrane may be shortened.

  The thickness of the semipermeable membrane support is preferably 50 to 150 μm, more preferably 60 to 130 μm, and still more preferably 70 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 is reduced, and as a result, the life of the semipermeable membrane may be shortened. On the other hand, when the thickness is less than 50 μm, sufficient tensile strength may not be obtained or liquid permeability may be reduced, and the life of the semipermeable membrane may be shortened.

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

Example 1
Main body synthetic fiber (stretched polyester fiber, fiber diameter 12.5 μm, fiber length 5 mm), binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) 70:30 After mixing and dispersing in water at a ratio and forming wet paper with a circular paper machine, it was hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having a basis weight of 80 g / m ² .

  The obtained sheet was heated using a calender device comprising a combination of a heated metal roll (JR) and a resin roll (bullet) in the first stage, a heated metal roll surface temperature of 225 ° C., a nip pressure of 1000 N / cm, and a processing speed of 30 m / min. Of the combination of the second stage resin roll and the heated metal roll so that the surface of the sheet in contact with the heated metal roll of the first stage is in contact with the second stage resin roll. Using a calender device, hot pressing was performed under the conditions of a heated metal roll surface temperature of 225 ° C., a pressure of 1000 N / cm, and a processing speed of 30 m / min to obtain a semipermeable membrane support.

(Example 2)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the temperatures of the heated metal rolls of the first stage and the second stage were changed to 230 ° C. and 230 ° C., respectively.

(Example 3)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 7.4 μm, and a fiber length of 5 mm.

Example 4
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 12.5 μm, and a fiber length of 10 mm.

(Example 5)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 17.5 μm, and a fiber length of 5 mm.

(Example 6)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 7.4 μm, and a fiber length of 10 mm.

(Example 7)
Main synthetic fiber 1 (stretched polyester fiber, fiber diameter 12.5 μm, fiber length 5 mm), main synthetic fiber 2 (stretched polyester fiber, fiber diameter 24.7 μm, fiber length 5 mm), binder synthetic fiber (unstretched polyester system) Fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) are mixed and dispersed in water at a mixing ratio of 35:35:30, and wet paper is formed with a circular net paper machine. It was hot-pressure dried with a dryer to obtain a sheet having a basis weight of 80 g / m ² .

  Using the calender device of the combination of the heated metal roll and heated metal roll of the first stage, the obtained sheet was heated under the conditions of both heated metal roll surface temperature of 225 ° C., pressure of 1000 N / cm, and processing speed of 40 m / min. Processed to obtain a semipermeable membrane support.

(Example 8)
A semipermeable membrane support was obtained in the same manner as in Example 1 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 240 ° C.

Example 9
A semipermeable membrane support was obtained in the same manner as in Example 3 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 235 ° C.

(Example 10)
A semipermeable membrane support was obtained in the same manner as in Example 3 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 240 ° C.

(Example 11)
Semi-permeable membrane support in the same manner as in Example 3 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 240 ° C. and the processing speed of the first stage and the second stage was changed to 40 m / min. Got the body.

(Example 12)
Semi-permeable membrane support in the same manner as in Example 3, except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 245 ° C. and the processing speed of the first stage and the second stage was changed to 50 m / min. Got the body.

(Example 13)
The blending ratio of the main synthetic fiber (stretched polyester fiber, fiber diameter 12.5 μm, fiber length 5 mm) and binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) is 80: A semipermeable membrane support was obtained in the same manner as in Example 8, except that the number was changed to 20.

(Example 14)
The blending ratio of the main synthetic fiber (stretched polyester fiber, fiber diameter 12.5 μm, fiber length 5 mm) and binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) is 60: A semipermeable membrane support was obtained in the same manner as in Example 8 except that the number was changed to 40.

(Example 15)
A semipermeable membrane support was obtained in the same manner as in Example 8 except that the nip pressure of the first stage and the second stage was changed to 700 N / cm.

(Example 16)
A semipermeable membrane support was obtained in the same manner as in Example 8 except that the nip pressure of the first stage and the second stage was changed to 1300 N / cm.

(Comparative Example 1)
50:50 blend of main synthetic fiber (stretched polyester fiber, fiber diameter 17.5 μm, fiber length 10 mm), binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) mixture was dispersed in water at a ratio, after forming the wet paper in the cylinder paper machine, and hot pressing dried by a Yankee dryer having a surface temperature 130 ° C., to obtain a sheet having a basis weight of 80 g / m ^2.

  Using the calender device of the combination of the heated metal roll and heated metal roll of the first stage, the obtained sheet was heated under the conditions of both heated metal roll surface temperature of 235 ° C., pressure of 1000 N / cm, and processing speed of 30 m / min. Processed to obtain a semipermeable membrane support.

(Comparative Example 2)
A semipermeable membrane support was obtained in the same manner as in Comparative Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 12.5 μm, and a fiber length of 10 mm.

(Comparative Example 3)
A semipermeable membrane support was obtained in the same manner as in Comparative Example 1 except that the main synthetic fiber was changed to a stretched polyester fiber, a fiber diameter of 24.7 μm, and a fiber length of 10 mm.

(Comparative Example 4)
Semi-permeable membrane support in the same manner as in Example 1 except that the temperature of the heated metal roll of the first stage and the second stage was changed to 220 ° C. and the processing speed of the first stage and the second stage was changed to 40 m / min. Got the body.

(Comparative Example 5)
Semi-permeable membrane support in the same manner as in Example 1 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 220 ° C. and the processing speed of the first stage and the second stage was changed to 50 m / min. Got the body.

(Comparative Example 6)
Semi-permeable membrane support in the same manner as in Example 1 except that the temperature of the heated metal rolls of the first stage and the second stage was changed to 220 ° C. and the processing speed of the first stage and the second stage was changed to 60 m / min. Got the body.

(Comparative Example 7)
50:50 blend of main synthetic fiber (stretched polyester fiber, fiber diameter 7.4 μm, fiber length 5 mm), binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) After mixing and dispersing in water at a ratio and forming wet paper with a circular paper machine, it was hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having a basis weight of 80 g / m ² .

  The obtained sheet is subjected to hot pressing under the conditions of a heated metal roll surface temperature of 235 ° C., a nip pressure of 1000 N / cm, and a processing speed of 20 m / min, using a calendar device that is a combination of a heated metal roll and a resin roll in the first stage. Then, using the calendar device of the combination of the second stage resin roll and the heated metal roll so that the surface in contact with the heated metal roll of the first stage of the sheet is in contact with the second stage resin roll, Hot pressing was performed under the conditions of a heated metal roll surface temperature of 235 ° C., a pressure of 1000 N / cm, and a processing speed of 20 m / min to obtain a semipermeable membrane support.

(Comparative Example 8)
85:15 blend of main synthetic fiber (stretched polyester fiber, fiber diameter 17.5 μm, fiber length 5 mm), binder synthetic fiber (unstretched polyester fiber, fiber diameter 10.5 μm, fiber length 5 mm, melting point 260 ° C.) After mixing and dispersing in water at a ratio and forming wet paper with a circular paper machine, it was hot-pressure dried with a Yankee dryer having a surface temperature of 130 ° C. to obtain a sheet having a basis weight of 80 g / m ² .

  The obtained sheet is hot-pressed using a calender device that combines a heated metal roll and a resin roll in the first stage under the conditions of a heated metal roll surface temperature of 220 ° C., a nip pressure of 1000 N / cm, and a processing speed of 50 m / min. Then, using the calendar device of the combination of the second stage resin roll and the heated metal roll so that the surface in contact with the heated metal roll of the first stage of the sheet is in contact with the second stage resin roll, Hot pressing was performed under the conditions of a heated metal roll surface temperature of 220 ° C., a pressure of 1000 N / cm, and a processing speed of 50 m / min to obtain a semipermeable membrane support.

  The following measurements and evaluations were performed on the semipermeable membrane supports obtained in Examples and Comparative Examples, and the results are shown in Table 1.

Measurement 1 (average value of fragile air permeability at small diameter)
Ventilation resistance was measured with an air permeability tester (KES-F8-AP1) manufactured by Kato Tech Co., Ltd. equipped with a small-diameter ventilation hole (cross-sectional area of the ventilation hole 0.2πcm ² , diameter 8.94 mm). The value was converted into JIS L 1913: 2010 breathable fragile form method to obtain small-diameter air permeability.

  For a semipermeable membrane support cut to a width of 106 cm and a length of 10 cm from a semipermeable membrane support having a width of 106 cm, the remaining width of 100 cm is equally divided into 10 parts every 10 cm, except for 3 cm at both ends in the width direction. Then, on the center line in the length direction of each divided area, the small-diameter air permeability of 10 measurement areas having a diameter of 8.94 mm that are continuous in the width direction is measured, and the arithmetic average value of the 10 small-diameter air permeability values is calculated as “ Average value of small-diameter air permeability ”. The results are shown in Table 2.

  In the definition of the breathable fragile type method in JIS L 1913: 2010, when the pressure difference is 125 Pa, the flow rate passing therethrough is defined as Q, and the air permeability is defined.

Air flow rate (air permeability): Q = (cm ³ / cm ² · s)

In the KES-F8-AP1 air permeability tester used in Test 1, a constant flow rate V (m ³ / m ² · s) was passed and the pressure difference ΔP (KPa) at this time was measured. Ventilation resistance R (KPa · s / m) is obtained.

R = △ P / V

  The flow rate when the pressure difference is 125 Pa = 0.125 KPa is obtained.

The diameter in the cylinder of the KES-F8-AP1 air permeability tester is 4 cm, its cross-sectional area is 4πcm ² , and the speed of piston movement is 2 cm / s, so the volume is 4πcm ² × 2 cm / sec = 8πcm. ³ / s.

The diameter of the vent hole in the small-diameter vent hole is 8.94 mm (radius 4.47 mm), and its cross-sectional area is 0.2πcm ² .

Since Q is the flow rate per unit area and unit time,
Q = (8πcm ³ /sec)/(0.2πcm ² ) = 40 (cm ³ / cm ² · s)

When the unit is combined with the flow rate V (m ³ / m ² · s), the following formula is obtained.
V = 40 (cm ³ / cm ² · s) = 40 cm / s = 0.4 (m ³ / m ² · s)

Therefore, the ventilation resistance R is expressed by the following formula.

R = ΔP / V = 0.125 / 0.4 (KPa · s / m)

If Q = K / R and K is a constant, K is 125 from the following equation.

K = RQ = 0.125 / 0.4 (KPa · s / m) × 40 (cm ³ / cm ² · s) = 125

  Therefore, Q = 125 / R, and using this equation, the air flow rate (air permeability) Q was obtained from the value of the air flow resistance R measured by the air permeability tester.

Measurement 2 (maximum value-minimum value of small-diameter air permeability)
The maximum value-minimum value of the small-diameter air permeability at 10 locations in each divided area measured in Measurement 1 was defined as “maximum value-minimum value of small-diameter air permeability”. The results are shown in Table 3.

Evaluation 1 (number of pinholes)
An N, N-dimethylformamide (DMF) solution of polysulfone resin on the coated surface of the semipermeable membrane support using a constant speed coating device (trade name: Automatic Film Applicator, manufactured by Yasuda Seiki Co., Ltd.) having a certain clearance ( (Concentration: 18%), solidified, washed with water, and dried to form a semi-permeable membrane by forming a polysulfone membrane on one side of the semi-permeable membrane support. In each divided area, the width is 10 cm and the length is 10 cm. The number of pinholes existing in the square was observed and measured with a magnifying glass having a magnification of 10 times. The results are shown in Table 4.

Number of pinholes: 0: good level: 1 level where problems may occur 2 or more: level where problems occur

Measurement 3 (Droplet penetration diameter)
Dissolve the dye (food color, edible blue No. 1, manufactured by Beni Fuji Chemical Co., Ltd.) in pure water to 0.01% by mass, prepare a light-colored solution, and use a dropper to support the semipermeable membrane 0.035 ± 0.005 ml of the solution is dropped on the non-application surface of the body, and after 15 seconds, the excess solution that has not penetrated is sucked off. FIG. 8 is a photograph showing a method for measuring the droplet penetration diameter. The length L1 of the longest straight line passing through the center in the region where the colored solution has permeated is measured (unit: mm). Next, a straight line L2 that perpendicularly crosses the center of the measured straight line L1 is drawn, and the length is measured (unit: mm). The average value of these two lengths is defined as the droplet penetration diameter (mm). Similar to the measurement of small-diameter air permeability, the semipermeable membrane support is divided into 10 parts, and the average value is calculated by measuring the droplet penetration diameters at 5 locations in each divided area that is 10 cm wide and 10 cm long. did. The results are shown in Table 5.

Evaluation 2 (Evaluation of yellowing)
Using a constant speed coating apparatus (trade name: Automatic Film Applicator, manufactured by Yasuda Seiki Co., Ltd.) having a certain clearance, a DMF solution of polysulfone resin (concentration: 18% by mass) is applied to the coated surface of the semipermeable membrane support. Then, coagulation, washing with water and drying were carried out to form a support membrane layer of polysulfone resin on one side of the semipermeable membrane support. m-Phenylenediamine and sodium lauryl sulfate were mixed and dissolved in pure water so as to be 2% by mass and 0.1% by mass, respectively, and impregnated on the coated surface. Next, an acid chloride solution in which acid chloride (1,3,5-benzenetricarboxylic acid chloride) is dissolved in n-hexane so as to be 0.1% by mass is applied to the coated surface of the semipermeable membrane support. Worked. After the acid chloride solution had evaporated, it was washed with pure water and dried with a warm air dryer to form a polyamide resin layer to obtain a composite membrane. Yellowing was evaluated by observing the color of the back surface of the composite membrane (non-coated surface of the semipermeable membrane support). The results are shown in Table 6.

Degree of yellowing: Good level with no yellowing.
(Triangle | delta): There exists a location discolored slightly yellowish brown. A practically usable level.
×: Almost entire surface is yellowish brown. Unusable level for practical use.

In the semipermeable membrane supports of Examples 1 to 7, the average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s, and the maximum value-minimum value of the small-diameter air permeability is 3. Since it was 0 cm ³ / cm ² · s or less, there were few pinholes, and good results were obtained. Further, in the semipermeable membrane supports of Examples 1 to 7, since the droplet permeation diameter was more than 11 mm and less than 15 mm, yellowing slightly occurred, but it was a practically usable level. .

In the semipermeable membrane supporting materials of Examples 8 to 16, the average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s, and the maximum value-minimum value of the small-diameter air permeability is 3. Since it was 0 cm ³ / cm ² · s or less, there were few pinholes, and good results were obtained. Further, in the semipermeable membrane supports of Examples 8 to 16, since the droplet permeation diameter was less than 11 mm, there was no yellowing and good results were obtained.

On the other hand, since the semipermeable membrane support of Comparative Examples 1 to 3 has a high blending ratio of the binder synthetic fiber and a high temperature of the heated metal roll at the time of hot pressing, a local film formation of the binder synthetic fiber is achieved. And there was a divided region where the maximum value-minimum value of the small-diameter air permeability exceeded 3.0 cm ³ / cm ² · s. As a result, pinholes occurred. In particular, the semipermeable membrane support of Comparative Example 3 has a poor texture because the fiber diameter of the main synthetic fiber is as thick as 24.7 μm, and the maximum value-minimum value of the small-diameter air permeability is 4.0 cm ³ / cm ^2.・ Since there was a division area exceeding s, there was a division area where two or more pinholes occurred, and the problem occurred.

In the semipermeable membrane supports of Comparative Examples 4 to 6, the average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s, and the maximum value-minimum value of the small-diameter air permeability is 3. Since it was 0 cm ³ / cm ² · s or less, there were few pinholes. However, since the heated metal roll temperature at the time of hot pressing was low and the processing speed was high, the amount of heat given to the semipermeable membrane support was insufficient, and there was a divided region where the droplet permeation diameter was 15 mm or more. It was bad and practically unusable.

In the semipermeable membrane support of Comparative Example 7, since the droplet permeation diameter was less than 11 mm, there was no yellowing and good results were obtained. However, since there was a divided region where the average value of the small-diameter air permeability was less than 0.3 cm ³ / cm ² · s, the anchor effect between the semipermeable membrane and the semipermeable membrane support was not obtained, and the semipermeable membrane was peeled off. Problem happened.

In the semipermeable membrane support of Comparative Example 8, since the average value of the small-diameter air permeability exceeded 5.0 cm ³ / cm ² · s and the droplet permeation diameter was 15 mm or more, yellowing was bad and practical use. It was unusable.

  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.

Claims (1)

In the semipermeable membrane support made of a nonwoven fabric containing at least a main synthetic fiber and a binder synthetic fiber, the average value of the small-diameter air permeability is 0.3 to 5.0 cm ³ / cm ² · s, and the small-diameter A semipermeable membrane supporting material having a maximum value-minimum value of air permeability of 3.0 cm ³ / cm ² · s or less and a droplet permeation diameter of less than 15 mm.
Small-diameter air permeability: Ventilation resistance measured with an air permeability tester provided with small-diameter air holes (vent hole area 0.2πcm ² , diameter 8.94 mm) was changed to JIS L 1913: 2010 air-permeable fragile form method. Air permeability obtained by conversion.
Average value of small-diameter air permeability: a semipermeable membrane support cut into a width of “10 × X” cm and a length of 10 cm is divided into X evenly in the width direction, and on the center line in the length direction of each divided area, Arithmetic mean value of small-diameter air permeability at 10 measurement areas having a diameter of 8.94 mm that are continuous in the width direction. X is a positive integer.
Maximum value-minimum value of small-diameter air permeability: Maximum value-minimum value of small-diameter air permeability at the above 10 locations Droplet penetration diameter: 0.035 ± 0.005 ml of a solution of dye dissolved in pure water is semi-permeable membrane The spread diameter of the solution dropped on the support and penetrating the semipermeable membrane support after 15 seconds.