JP2012161725A - Semipermeable membrane support, semipermeable membrane for water treatment, and method for manufacturing semipermeable membrane support - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semipermeable membrane support having a high tensile modulus of elasticity in a width direction and high tear strength in the width direction, and a semipermeable membrane for water treatment using the support.SOLUTION: The semipermeable support is mainly composed of synthetic fibers and subjected to heating and pressurizing treatment after wet papermaking. The semipermeable support is formed by laminating at least a first layer and a second layer with different fiber orientation. The fiber orientation ratio of the first layer surface to a papermaking flow direction is 6.0 or less, and the fiber orientation ratio of the second layer surface to the papermaking flow direction is 12.0 or less.

Description

  The present invention relates to a semipermeable membrane support, a water treatment semipermeable membrane, and a method for producing a semipermeable membrane support. More specifically, it relates to a semipermeable membrane support for supporting a semipermeable membrane used under high pressure.

  Currently, water shortages are progressing on a global scale, and attention has been focused on technologies for desalinating seawater, technologies for reusing wastewater, technologies for producing pure water for semiconductor applications, and technologies for concentrating raw materials for food applications. Yes. The technologies for desalinating seawater mainly include a flash system that evaporates seawater at low temperature and a reverse osmosis system that pressurizes at normal temperature to generate fresh water.

  A semipermeable membrane is used for the filtration membrane used in the reverse osmosis system, but when a functional membrane having the function of a semipermeable membrane is used alone, the durability against mechanical pressure is low, so it is fixedly supported on a nonwoven fabric support. Is used in the form. Such a semipermeable membrane is manufactured by casting a polymer solution containing a membrane material on a support to form a functional membrane.

  The semipermeable membrane is required to be strong and difficult to break because it obtains fresh water by pouring seawater under high pressure conditions. As described above, the semipermeable membrane itself does not have sufficient strength, so it is sufficient for the support. High strength is required.

  In order to increase the amount of water treated by the reverse osmosis membrane, recently, there is a demand for a high-pressure type semipermeable membrane support that can be used in a high-pressure environment from 4 MPa to 10 MPa, which is a higher pressure than the conventional pressure of 1 MPa to 4 MPa. .

  However, if the current semipermeable membrane support is used for the high pressure type, the semipermeable membrane and the support will be deformed by the pressure, and the semipermeable membrane will be dented. A method such as a structure in which a seat is installed is employed. When the semipermeable membrane having such a structure is used, the feed water can be filtered without causing dents even under a high pressure environment. On the other hand, the semipermeable membrane having such a structure is increased in thickness of the entire semipermeable membrane as the pressure-resistant sheet is added. As a result, the semipermeable membrane provided with such a pressure-resistant sheet has a problem that the area of the semipermeable membrane that can be accommodated in the element is lower than that without the pressure-resistant sheet, and the amount of water treatment is reduced. In addition, the semipermeable membrane having such a structure requires a manufacturing process in which a pressure-resistant sheet is installed on the semipermeable membrane supporting member, which causes problems such as a decrease in productivity and an increase in manufacturing cost. . For this reason, there is a need for a semipermeable membrane support that does not require a pressure-resistant sheet and has a strength that does not cause dents even in a high-pressure environment.

  For example, Patent Document 1 discloses a semipermeable membrane support having longitudinal and lateral tear lengths and air permeability within a predetermined range when stretched by 5%, and Patent Document 2 discloses a width direction and a flow direction. A semipermeable membrane support having a tensile strength ratio in a direction within a specific range is disclosed.

Japanese Patent Laid-Open No. 10-225630 JP 2002-95937 A

  However, since these semipermeable membrane supports cannot provide sufficient strength, dents are generated under high pressure and a pressure-resistant sheet is actually required.

  For example, when a semipermeable membrane support is manufactured with a circular paper machine, the fibers can be easily arranged in the flow direction, the tensile strength in the width direction is low, and the tear strength in the flow direction is low. A semipermeable membrane support having sufficient strength cannot be obtained. In addition, if the fiber orientation is manufactured with a short paper machine that can be adjusted within a certain narrow range, the fiber orientation is adjusted, and the longitudinal and transverse strength of the semipermeable membrane support is uniform, the flow direction and width direction The tensile strength in the width direction is made uniform and the tensile strength in the width direction is improved, but troubles such as paper breaks due to a decrease in the tear strength in the width direction occur, and there is a problem that a semipermeable membrane cannot be produced continuously, Moreover, it was not able to withstand use under a high pressure environment. That is, at present, a semipermeable membrane support having a tear strength in the width direction that can withstand use under high-pressure conditions and can withstand the production of a continuous semipermeable membrane has not been obtained.

  The present invention has been made in view of the above problems, has a high tensile modulus in the width direction that does not generate dents even under a high pressure environment, has a high tear strength in the width direction, and is continuous. An object of the present invention is to provide a semipermeable membrane support that can withstand the production of such a semipermeable membrane. Furthermore, the present invention provides a semipermeable membrane support and a semipermeable membrane for water treatment using the support, which have high penetration of the coating solution during film formation and excellent adhesion between the support and the semipermeable membrane. With the goal.

  In order to solve the above problems, the present application adopts the following configuration. That is, the first aspect of the present invention is a semipermeable membrane support mainly composed of synthetic fibers and subjected to heat and pressure treatment after wet papermaking, and the semipermeable membrane support is different in the fiber orientation. 1 layer and 2nd layer are laminated | stacked at least, The fiber orientation ratio of the 1st layer surface is 6.0 or less, The fiber orientation ratio of the 2nd layer surface is 12.0, The half A permeable membrane support.

  The second aspect is that, in the first aspect, the semipermeable membrane support includes two types of polyester main fibers having an average single fiber fineness of 1.0 dtex or more and polyester main fibers having an average single fiber fineness of less than 1.0 dtex. It is characterized by containing polyester main fibers having different finenesses as at least main components.

  According to a third aspect, in any one of the first to second aspects, the semipermeable membrane support is made by separately making wet paper as the first layer and the second layer individually in different paper making processes. The first layer and the second layer are laminated by being combined in a wet state.

According to a fourth aspect, in any one of the first to third aspects, the first layer is made by an inclined short paper machine, the second layer is made by a circular paper machine, and the inclined short paper machine The paper making speed is 20 m / min or more and less than 60 m / min, the inclination angle of the short net provided in the inclined short net paper machine is 5 ° or more and 20 ° or less. Is V (m / min) and the inclination angle is ω (degrees), the parameter G obtained by the equation (1) is 1.0 or more and 5.0 or less. One layer is made of paper.
G = V / ω (1)

  A fifth aspect is a semipermeable membrane for water treatment comprising the semipermeable membrane support according to any one of the first to fourth aspects and a thin film layer formed on the surface of the semipermeable membrane support.

  A sixth aspect is a method for producing a semipermeable membrane support, in which a first paper making process using a first layer having a fiber orientation ratio of 6.0 or less as wet paper, and a fiber orientation ratio of 12.0. The second paper making process for making the second layer as a wet paper, the first layer sent from the first paper making process, and the second layer sent from the second paper making process are kept in a wet state. A method for producing a semipermeable membrane support, comprising: a lamination step of forming a semipermeable membrane support by performing heat and pressure treatment after the sheets are laminated together.

In a seventh aspect, in the sixth aspect, the first papermaking process is to make the first layer with an inclined short net paper machine, and the second papermaking process is to make the second layer with a circular paper machine, The paper making speed of the short net paper machine is 20 m / min or more and less than 60 m / min, the inclination angle of the short net provided in the inclined short paper machine is 5 ° or more and 20 ° or less, and the inclined short paper machine Is a condition in which the value of the parameter G obtained by the equation (1) is 1.0 or more and 5.0 or less when the paper making speed is V (m / min) and the inclination angle is ω (degrees). Originally, the first layer is made of paper.
G = V / ω (1)

  According to the first aspect, a semipermeable membrane support excellent in tensile modulus in the width direction and durability can be obtained by laminating two layers having different fiber orientations. According to such a semipermeable membrane support, no dent is generated even in a high-pressure environment. Moreover, such a semipermeable membrane support body has high adhesiveness with a semipermeable membrane layer, and it is difficult for a semipermeable membrane layer to peel from the said semipermeable membrane support body. Therefore, according to such a semipermeable membrane support, it can be used for the production and use of a continuous semipermeable membrane for water treatment.

  According to the second aspect, a gap is appropriately generated between the fibers by combining two or more kinds of materials having different finenesses. Therefore, the penetration of the coating liquid at the time of film formation becomes high, and the adhesiveness between the semipermeable membrane support and the semipermeable membrane can be made superior to the conventional one.

  According to the third and sixth aspects, the first layer and the second layer having different fiber orientations can be manufactured by using a paper machine of a suitable system according to each fiber orientation. Since the first layer and the second layer are made together in a wet state, a dense layer is not formed between the first layer and the second layer. Therefore, it is possible to obtain a semipermeable membrane support excellent in the permeability and liquid permeability of the membrane liquid during film formation.

  According to the fourth and seventh aspects, the fiber orientation angle ratio of the first layer can be more reliably maintained at a predetermined value. Therefore, it is possible to improve the tensile elasticity and tear strength of the semipermeable membrane support more reliably.

  According to the fifth aspect, the pressure-resistant sheet is not required, and the semipermeable membrane support can be formed thinner than the conventional one. Therefore, the entire semipermeable membrane including the semipermeable membrane layer and the semipermeable membrane support is combined. The thickness can be reduced as compared with the conventional case. Therefore, for example, when the semipermeable membrane layer is accommodated in the element in an overlapping manner, the total area of the semipermeable membrane that can be accommodated in the element can be increased as compared with the conventional case. That is, the filtration capacity per element can be increased as compared with the conventional one.

Sectional drawing which shows an example of a structure of the semipermeable membrane 100 for water treatment Image of manufacturing process of semipermeable membrane support 1

  Hereinafter, the semipermeable membrane support 1 according to the embodiment of the present invention and the water treatment semipermeable membrane 100 using the same will be described.

  The semipermeable membrane 100 for water treatment which concerns on embodiment of this invention is used as a filtration membrane which desalinates seawater, for example. For example, the water treatment semipermeable membrane 100 is housed inside a cylindrical element in a folded and laminated state. Hereinafter, the process of bending the semipermeable membrane for water treatment 100 so as to be housed in the element is referred to as element processing, and the process of performing the process is referred to as the element processing process. By allowing the supply water to pass through the element configured as described above, a permeated liquid in which the supply water is purified can be obtained.

  The semipermeable membrane for water treatment 100 is formed using the semipermeable membrane support 1. Specifically, the semipermeable membrane for water treatment 100 is formed by applying a membrane liquid that is a raw material of the semipermeable membrane layer 2 (thin film layer described in claims) on the surface of the semipermeable membrane support 1. Is done. Specifically, the semipermeable membrane for water treatment 100 has a layer shape as shown in FIG. FIG. 1 is a cross-sectional view showing a configuration of a water treatment semipermeable membrane 100. The semipermeable membrane layer 2 is a thin film layer having a function of removing impurities from the supply water, and is typically a reverse osmosis membrane layer. In addition, the conventionally well-known arbitrary materials and methods may be used for the raw material and formation method of the semipermeable membrane layer 2. For example, a polysulfone solution is applied to the surface of the semipermeable membrane support 1 (on the first layer 11 side) and solidified to form a microporous membrane. Further, an aqueous solution containing a polyfunctional amine and an organic solvent solution of a polyfunctional acid halide are sequentially applied on the surface, whereby the cross-linked polyamide semipermeable membrane layer 2 is formed. Hereinafter, the process of coating and forming the semipermeable membrane layer 2 on the semipermeable membrane support 1 in this way is referred to as film formation, and the step of forming the film is referred to as a film formation step.

  Next, the structure, composition, and manufacturing method of the semipermeable membrane support 1 will be described in detail. As shown in FIG. 1, the semipermeable membrane support 1 of the present invention is a sheet-like member having a first layer 11 and a second layer 12 made of synthetic fibers and having at least different fiber orientations. As described above, since the semipermeable membrane support 1 has a two-layer structure, it is possible to obtain a higher tensile elastic modulus and tear strength in the width direction as compared with the prior art. It is not necessary to use a sheet, and the amount of water treatment can be greatly increased.

  The tensile elastic modulus is a value indicating the ratio of the load change amount to the elongation change amount of the semipermeable membrane support 1. Hereinafter, unless otherwise specified in the flow direction (longitudinal direction) and the width direction (lateral direction), the tensile elastic modulus in the width direction is indicated. The tear strength indicates the amount of load necessary for tearing the semipermeable membrane support 1. Hereinafter, the tear strength in the width direction is shown unless otherwise specified in the flow direction (longitudinal direction) and the width direction (lateral direction). The tensile modulus and tear strength are both indices that indicate the strength of the semipermeable membrane support 1. Details of these indices will be described later.

<Main fiber>
The semipermeable membrane support 1 has a synthetic fiber as a main component as a main fiber. As synthetic fiber used for manufacture of semipermeable membrane support 1, what is generally used for manufacture of a nonwoven fabric can be used. Specifically, synthetic fibers such as polyester fiber, polypropylene fiber, polyethylene fiber, acrylic fiber, aramid fiber, and nylon fiber can be used as the main component of the semipermeable membrane support 1. In particular, it is preferable to use polyester fibers as the main component of the semipermeable membrane support 1. By using polyester fiber as a main component, the semipermeable membrane supporting body 1 having high water resistance and high tear strength can be obtained. The fiber length of the synthetic fiber is not particularly limited as long as papermaking is possible. For example, the fiber length is preferably about 3 to 10 mm.

  Further, in the production of the semipermeable membrane support 1, a synthetic fiber (α) having an average single fiber fineness of 1.0 dtex or more and a synthetic fiber (β) having an average single fiber fineness of less than 1.0 dtex are different. It is preferable to use a kind of synthetic fiber as a raw material. The average single fiber fineness is an index of the thickness of the fiber, and 1 dtex means the fiber thickness when the weight of the fiber per 10,000 m is 1 g. High tear strength by combining relatively thick synthetic fibers (α) with an average single fiber fineness of 1.0 dtex or more and relatively thin synthetic fibers (β) with an average single fiber fineness of less than 1.0 dtex A support having excellent holding, smoothness and air permeability can be obtained. In addition, as above-mentioned, if both synthetic fiber ((alpha)) and synthetic fiber ((beta)) are polyester fibers, it is still more preferable. The average single fiber fineness of the synthetic fiber (α) is preferably 1.0 dtex or more and less than 7.0 dtex, and more preferably 1.0 dtex or more and less than 3.0 dtex. The average single fiber fineness of the synthetic fiber (β) is preferably 0.1 dtex or more and less than 0.9 dtex, and more preferably 0.3 dtex or more and less than 0.7 dtex.

  On the other hand, when the average single fiber fineness of the synthetic fiber is made only with fibers having a density of less than 1.0 dtex, the gap in the semipermeable membrane support is reduced, and the permeability of the membrane liquid during film formation is reduced. Cause peeling. In addition, when the average single fiber fineness is made only with fibers having 1.0 decitex or more, the gap in the semipermeable membrane support increases, and the membrane liquid during film formation easily leaks through the semipermeable membrane support 1. Thus, the semipermeable membrane layer 2 having a uniform thickness is hardly formed. That is, when the average single fiber fineness is made of only fibers having 1.0 dtex or more, the service life of the water treatment semipermeable membrane is shortened. Thus, a semipermeable membrane support composed of only a single synthetic fiber is not preferred because of its low durability.

  Moreover, it is preferable that the compounding quantity of the thick synthetic fiber ((alpha)) whose average single fiber fineness is 1.0 dtex or more shall be 10-50 mass%. Furthermore, the blending amount of the thick synthetic fiber (α) having an average single fiber fineness of 1.0 dtex or more is more preferably 15 to 40% by mass.

  On the other hand, when the blending amount of the synthetic fiber (α) is less than 10% by mass, the gap in the support is reduced, and the permeability of the membrane liquid during film formation is reduced. Cause. Moreover, when the compounding quantity of a synthetic fiber ((alpha)) exceeds 50 mass%, the clearance gap in a semipermeable membrane support body will increase, and the film | membrane liquid at the time of film forming will become easy to leak through. Therefore, the semipermeable membrane layer 2 having a uniform thickness is hardly formed, and the service life of the water treatment semipermeable membrane is shortened, which is not preferable.

  In addition, the binder fiber mentioned later is not contained in the main fiber of this invention.

<Binder fiber>
As a raw material for the semipermeable membrane support 1, not only the above two types of main fibers but also binder fibers for bonding the main fibers can be used. As a binder fiber, what is generally used for manufacture of a nonwoven fabric can be used. For example, as the binder fiber, polyester fiber, polypropylene fiber, polyethylene fiber, polyvinyl alcohol fiber, or the like having a binder function can be used. Among these, it is preferable to use a polyester fiber as the binder fiber. By using polyester fiber as the binder fiber, it is possible to obtain the semipermeable membrane supporting body 1 having excellent adhesive strength and high tear strength. The fiber length of the binder fiber is not particularly limited as long as papermaking is possible. For example, the fiber length is preferably about 3 to 15 mm.

  Moreover, it is preferable that the average single fiber fineness of a binder fiber is 0.2-5.0 dtex. More preferably, the average single fiber fineness of the binder fiber is preferably 0.2 to 2.5 dtex.

  On the other hand, when the average single fiber fineness of the binder fiber is less than 0.2 decitex, the semipermeable membrane support tends to be densely packed only as the fiber becomes thin. Therefore, although the smoothness of the semipermeable membrane support 1 is improved, the air permeability of the semipermeable membrane support 1 is deteriorated and the permeability of the membrane liquid during film formation is lowered. Therefore, the semipermeable membrane layer 2 is easily peeled from the semipermeable membrane support 1. In addition, when the average single fiber fineness of the binder fiber is relatively small, fine fibers are bound to each other, so that a bound fiber (so-called “dama”) is easily generated. Generation | occurrence | production of such a binding fiber not only worsens the appearance of the semipermeable membrane support 1, but also causes a decrease in adhesiveness with the semipermeable membrane around the binding fiber. When the average single fiber fineness exceeds 5.0 dtex, the number of fibers decreases and the main fibers become difficult to adhere to each other as the fibers become thicker. Therefore, not only the tensile elastic modulus and tear strength in the width direction are lowered, but also the surface of the support becomes rough and the smoothness tends to be lowered.

<Dispersant>
The dispersant for dispersing the main fiber and the binder fiber in water is not particularly limited, and conventionally used dispersants can be used. For example, a modified polyester dispersant, a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like can be used. In particular, when a modified polyester dispersant is used during the production of the semipermeable membrane support 1, good dispersibility can be obtained. That is, since the main fiber and the binder fiber can be uniformly dispersed, unevenness of the texture of the semipermeable membrane supporting body 1 can be reduced, and high tensile elastic modulus and tear strength can be obtained.

  If the dispersibility is insufficient, a portion having a weak tensile elastic modulus and tear strength is locally generated due to uneven dispersion of the fiber, and the tensile elastic modulus and tear strength tend to be lowered. In particular, as in the case of the semipermeable membrane support 1 of the present invention, when it is used for a long time under a high pressure environment of 4 MPa to 10 MPa, not only the tensile elastic modulus and tear strength are high, but also local texture unevenness. It is necessary to prevent the tearing after long-time use. For this reason, the dispersibility of the synthetic fiber is an important factor in the production process of the semipermeable membrane support 1, and among the above-mentioned dispersants, it is preferable to use a modified polyester dispersant.

  About the addition amount of a dispersing agent, it is preferable to set it as 1-7,000 ppm in conversion of solid content with respect to a total of 100 mass% of a main fiber and a binder fiber, and it is more preferable to set it as 150-3,000 ppm. When the amount added is less than 1 ppm, poor dispersion of the synthetic fiber is likely to occur, and bundling fibers (dama) may occur when the support is produced. When the added amount exceeds 7,000 ppm, gaps in the support increase, and the membrane liquid during film formation is likely to leak through, making it difficult to form a functional film having a uniform thickness. The years may be shortened.

<Manufacturing method>
Next, a method for producing the semipermeable membrane support 1 will be described. FIG. 2 is an image diagram of a manufacturing process of the semipermeable membrane support 1. As shown in FIG. 2, the manufacturing process of the semipermeable membrane support 1 includes an inclined short net paper machine 31, a circular net paper machine 32, a paper making process 33, and a heating and pressing process 34.

<Paper making process>
The inclined short net paper machine 31 produces the first layer 11. The inclined short net paper machine 31 includes a short net wire 311 for paper making the first layer 11. The inclined short net paper machine 31 has a characteristic that the fiber orientation of the paper made by changing the inclination angle of the short net wire 311 can be arbitrarily adjusted. Therefore, the fiber orientation of the first layer 11 can be adjusted. It can be easily and arbitrarily adjusted. In addition, the circular net paper machine 32 papers the second layer 12 described above. The circular net paper machine 32 has a characteristic of aligning and orienting the fibers of the paper that has been made in the flow direction. In this way, the first layer 11 and the second layer 12 are made by different paper machines so as to have different fiber orientations.

<Fiber orientation>
The fiber orientation of the first layer 11 and the second layer 12 constituting the semipermeable membrane support 1 can be adjusted by adjusting a paper machine for making each layer by a conventionally known method.

  For example, when the first layer 11 is made using the inclined short net paper machine 31, the fiber orientation of the first layer 11 can be changed by changing the paper making speed, the inclination angle of the short net wire 311, or the like. it can. More specifically, since the gravity resistance acting on the fibers in the slurry increases as the inclination angle of the short mesh wire 311 increases, the direction of the fibers can be changed from the flow direction to the width direction by the action of the gravity resistance. It can be done. The inclination angle of the short wire 311 is preferably 5 to 20 degrees upward, more preferably 5 to 15 degrees with respect to the horizontal plane.

  In addition, when the inclination angle is 0 degree, the fibers are easily arranged in the flow direction, the tensile elastic modulus in the width direction is lowered, and the fiber cannot be used in a high pressure environment, which is not preferable. Also, if the inclination angle exceeds 20 degrees, the fibers are likely to be lined up in the width direction and the tear strength in the width direction is lowered and easily torn in the width direction. is there.

Here, in the inclined short net paper machine 31, if the paper making speed is high and the inclination angle is small, the fiber orientation is difficult to be dispersed on the short net wire 311, and therefore the orientation angle of the first layer 11 with respect to the second layer 12. Is small, and the tensile elastic modulus in the width direction tends to decrease, which is not preferable. On the other hand, if the paper making speed is slow and the inclination angle is large, the fiber orientation is too scattered on the short mesh wire 311 and the orientation angle of the support becomes large, so that the tear strength in the width direction is liable to decrease. Therefore, it is preferable that the inclined short net paper machine 31 produces the first layer 11 satisfying the following conditions. Specifically, the paper making speed of the inclined short paper machine 31 is preferably 20 m / min or more and less than 60 m / min. Moreover, it is preferable that the inclination angle of the short net wire 311 provided in the inclined short net paper machine 31 is 5 ° or more and 20 ° or less. Further, in the inclined short net paper machine 31, the value of the parameter G obtained by the equation (1) is 1 when the paper making speed is V (m / min) and the inclination angle of the short net wire 311 is ω (degrees). It is preferable to make the first layer 11 under the condition of 0.0 or more and 5.0 or less.
G = V / ω (1)

  In addition, when the first layer is made using a long paper machine, the fiber orientation of the first layer 11 can be adjusted by changing the jet wire ratio (raw material ejection speed ratio).

In the semipermeable membrane supporting body 1 obtained through the heating and pressurizing process described later, the fiber orientation ratio of the surface on the first layer 11 side is 6.0 or less. Further, the fiber orientation ratio of the surface on the second layer 12 side is 12.0 or less.
The fiber orientation ratio in the present invention is a numerical value of how the pulp fibers are arranged. The fiber orientation ratio can be measured, for example, with an optical orientation tester (FOT) manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a laser beam with a wavelength of 685 nm is irradiated at a certain angle to the paper surface fixed on the sample table, and the reflection intensity is measured when the sample table is rotated by 360 degrees and rotated 360 degrees. The ratio between the maximum value and the minimum value of the reflection intensity is defined as the fiber orientation ratio. That is, if the numerical value is large, the fiber is oriented along the flow direction, and if the numerical value is small, it means that the fiber is also oriented along the width direction.

  The fiber orientation ratio of the first layer 11 is preferably 6.0 or less, and more preferably 1.0 or more and 4.0 or less. When the fiber orientation ratio of the first layer 11 is more than 6.0, the arrangement of the fibers is easily oriented in the flow direction, the tensile modulus in the width direction is greatly reduced, and cannot be used in a high pressure environment (described later). , See Comparative Example 3 in Tables 1 to 4).

  The fiber orientation ratio of the second layer 12 is preferably 12.0 or less, and more preferably 1.0 or more and 10.0 or less. When the fiber orientation ratio of the second layer 12 is more than 12.0, the fibers are easily aligned in the flow direction, the tensile elastic modulus in the width direction is greatly reduced, and cannot be used in a high pressure environment. In addition, when the fiber orientation ratio of the second layer 12 is higher than that of the first layer 11, since the fibers in the flow direction and the width direction are appropriately arranged, the tensile elastic modulus and tear strength in the flow direction and the width direction are appropriately increased. preferable.

  That is, the above-mentioned semipermeable membrane supporting body 1 in which the fiber orientation ratio of the first layer 11 is 6.0 or less and the fiber orientation angle ratio of the second layer 12 is 12.0 or less has the tensile modulus and tear. It can be said that it is excellent in strength.

  The paper making method of the first layer 11 and the second layer 12 is an example, and as described above, if the first layer 11 and the second layer 12 having different fiber orientations can be made, it is not limited to the above. Other methods may be used. For example, the first layer 11 and the second layer 12 may be made by using other known paper machines such as a short net paper machine or a long net paper machine conventionally used for manufacturing nonwoven fabrics.

<Making process>
The first layer 11 and the second layer 12 having different fiber orientations made as described above are brought into the making process 33 in a wet state, and are made together in the process. Usually, there are two methods for laminating a nonwoven fabric. The first method is a method in which the first layer 11 and the second layer 12 are individually made and dried, and then bonded and subjected to heat and pressure treatment. The second method is a method in which the first layer 11 and the second layer 12 after wet paper making are stacked in a wet paper state and combined as a single sheet, and then dried and heated and pressed. Here, when the first method is used, a dense layer is easily formed between the first layer 11 and the second layer 12. Therefore, at the time of film formation, there is a possibility that the permeation of the membrane liquid into the semipermeable membrane support 1 may be inhibited or the liquid permeability may be reduced. On the other hand, when the second method is used, it is difficult to form a dense layer between the first layer 11 and the second layer 12. Therefore, good liquid permeability can be obtained without impeding the permeation of the membrane liquid into the semipermeable membrane support 1 during film formation. For this reason, in this invention, it is preferable to use the 2nd method, ie, the method of laminating | stacking the 1st layer 11 and the 2nd layer 12 in a wet state, and making it one sheet.

  Thus, according to the manufacturing process of the semipermeable membrane supporting body 1 shown in FIG. 2, the fiber orientation is achieved by combining the first layer 11 and the second layer 12 respectively made by different types of paper machines. Can be stacked. It is preferable to laminate two layers having greatly different fiber orientations because a semipermeable membrane support 1 having excellent tensile modulus in the width direction and durability can be obtained (Examples in Tables 1 to 4 below). 1-23). In the semipermeable membrane supporting body 1 manufactured by the above-described method, the ratio of the tensile elastic modulus in the width direction to the tensile elastic modulus in the flow direction is 30 to 80%, preferably 35 to 75%. The semipermeable membrane supporting body 1 having such an elastic ratio is particularly preferable because of excellent tensile modulus in the width direction and tear strength. In order to obtain the semipermeable membrane supporting body 1 having the tensile modulus ratio as described above, it is preferable that the rice basis ratio of the first layer 11 to the second layer 12 is 1.0 to 6.5.

  When a semipermeable membrane support is produced with only one layer, there are the following problems. When a single-layer semipermeable membrane support is produced using only a short net paper machine, although the fiber orientation in the flow direction and the width direction can be adjusted within a certain narrow range, the tear strength in the width direction decreases. (See Comparative Example 1 in Tables 1 to 4 below). Therefore, there is a problem that when the semipermeable membrane support is continuously produced, paper breakage is likely to occur, and dents and the like are likely to occur in a high-pressure environment. In addition, when a single-layer semipermeable membrane support is manufactured using only a circular paper machine, the fiber orientation of the semipermeable membrane support is a constant direction of flow. Therefore, it is not possible to obtain a tensile modulus and tensile strength in the width direction sufficient as a semipermeable membrane support (see Comparative Example 2 in Tables 1 to 4 below).

<Heating and pressing process>
The first layer 11 and the second layer 12 that have been combined in the above-described combining step 33 are subjected to a heating and pressing process in a heating and pressing step 34. In the heating and pressing step 34, the heating and pressing process may be executed by any conventionally known heating and pressing apparatus. For example, a calender device combining a metal roll and a metal roll or a calender device combining a metal roll and an elastic roll can be used in the heating and pressing step 34. In addition, the heat and pressure treatment apparatus can be used even if one or more heat and pressure units are installed.

  In addition, it is preferable that the heating temperature at the time of the heating and pressing in the heating and pressing step 34 is 190 ° C. to 230 ° C., and the pressing amount is 100 kg / cm to 170 kg / cm of the linear pressure. Here, when the heat and pressure treatment is performed on the first layer 11, the tensile elastic modulus in the width direction of the semipermeable membrane support 1 can be improved. As described above, since the fibers of the first layer 11 are relatively large in the width direction compared to the second layer 12, by performing the heat and pressure treatment on the first layer 11, More fibers oriented in the width direction can be fixed. As a result, the tensile elastic modulus in the width direction of the semipermeable membrane support 1 can be improved. In addition, when the heat and pressure treatment is performed on the second layer 12, the tear strength in the width direction of the semipermeable membrane support 1 can be improved. Therefore, it is more preferable to heat and press the second layer 12 on both sides of the semipermeable membrane support 1.

<US tsubo and US tsubo ratio>
As described above, by forming the first layer 11 and the second layer 12 using different paper machines, it is possible to produce the semipermeable membrane support 1 having different fiber orientations on the front and back surfaces. In addition, the ratio of the width direction with respect to the flow direction of the tensile elastic modulus and tear strength can be set to a specific range by setting the rice basis weight of the first layer 11 and the second layer 12 to a specific ratio. Specifically, the rice basis ratio of the first layer 11 to the second layer 12 is preferably 1.0 to 6.5, and more preferably 1.0 to 2.0. The ratio of the width direction with respect to the flow direction of the tensile elastic modulus of the semipermeable membrane supporting body 1 is 30 to 80%, preferably 35 to 35 by making the rice tsubo of the first layer 11 and the second layer 12 within the above-mentioned range. It can be 75%. That is, the semipermeable membrane support 1 excellent in the tensile modulus in the width direction and the tear strength can be obtained.

  In addition, when the rice basis ratio of the 1st layer 11 and the 2nd layer 12 is less than 1.0, when making the 1st layer 11 and the 2nd layer 12 into a support body, the tear strength of a flow direction will fall. It becomes easy to do. That is, the ratio of the tensile modulus of the semipermeable membrane support 1 to the width direction with respect to the flow direction is reduced, and the semipermeable membrane support 1 is liable to tear in the flow direction. In addition, when the ratio of rice basis weight between the first layer 11 and the second layer 12 exceeds 6.5, the ratio of the tensile modulus of the semipermeable membrane support 1 to the width direction with respect to the flow direction increases excessively, and the semipermeable The membrane support 1 is not preferable because it easily tears in the width direction.

In addition, the whole rice tsubo of the semipermeable membrane supporting body 1 may be arbitrary. Moreover, the rice weight of the 1st layer 11 and the 2nd layer 12 is not specifically limited as long as the above-mentioned rice weight ratio is satisfy | filled, For example, the rice weight of each layer should adjust suitably in the range of 10-100 g / m < ² >. Can do.

However, although the tensile elastic modulus and tear strength of the semipermeable membrane supporting body 1 are improved as the rice floor is increased, the cost is increased. Moreover, since the thickness of the semipermeable membrane support 1 increases as the rice tsubo increases, the area of the semipermeable membrane that can be accommodated in the element is reduced, so that the amount of filtration treatment is likely to decrease, which is not preferable. Here, in the conventional semipermeable membrane support, when the basis weight is 60 to 90 g / m ² , the tensile elastic modulus and the tear strength are reduced. It becomes necessary. On the other hand, in the semipermeable membrane support 1 according to the present invention, even if it is 60 to 90 g / m ² , the predetermined tensile elastic modulus, tear strength, etc. defined in the present invention can be satisfied. It can be used without cost. Further, as a result of using the pressure-resistant sheet as described above, the thickness of the conventional water treatment permeable membrane is about 230 to 260 μm. On the other hand, the permeable membrane 100 for water treatment manufactured using the semipermeable membrane support 1 according to the present invention can have a thickness of about 130 to 160 μm. That is, according to the semipermeable membrane supporting body 1 according to the present invention, the water treatment permeable membrane 100 having sufficient function and strength when used under high pressure can be formed thinner than the conventional one.

  As described above, the semipermeable membrane support 1 obtained through each of the steps described above has the semipermeable membrane layer 2 formed on the surface of the first layer in the film forming step, and the semipermeable membrane for water treatment 100. Is manufactured. Moreover, the semipermeable membrane for water treatment 100 manufactured in the film forming process is processed in the element processing process and stored in the element.

<Performance>
The semipermeable membrane support 1 produced by the above-described method has an unprecedented tensile elastic modulus and tensile elastic modulus ratio (width / flow) as follows, and has the following tear strength, air permeability, and smoothness. Have degrees and so on. Therefore, the semipermeable membrane supporting body 1 according to the present invention does not dent in the semipermeable membrane even under a high pressure environment, and can withstand continuous production of the semipermeable membrane. In addition, the semipermeable membrane support 1 according to the present invention is superior in performance to conventional products in terms of the permeability of the coating liquid during film formation and the adhesion between the semipermeable membrane support 1 and the semipermeable membrane layer 2. Demonstrate.

<Tensile modulus>
The tensile elastic modulus refers to a tensile elastic modulus obtained in accordance with JIS P8113. The tensile elastic modulus is the ratio of the load change amount to the elongation change amount of the subject. According to the present inventors, it has been found that the strength of the semipermeable membrane support 1 under high pressure cannot be sufficiently evaluated only by an index such as tensile strength, tear strength, or elongation. As a result of the trial and error by the inventors, it was revealed that the tensile modulus is a suitable index for evaluating the strength of the semipermeable membrane support 1 under high pressure.

  The tensile elastic modulus in the width direction of the semipermeable membrane support 1 is preferably 900 MPa or more, and more preferably 1,100 MPa or more. On the other hand, when the tensile modulus in the width direction of the semipermeable membrane support 1 is less than 1,000 Mpa, the semipermeable membrane support 1 is easily stretched and deformed in a high-pressure environment, and can withstand long-term use. I can't. Further, the tensile elastic modulus in the flow direction of the semipermeable membrane support 1 is preferably 1,600 MPa or more, and more preferably 1,700 MPa or more. On the other hand, when the tensile elastic modulus in the flow direction of the semipermeable membrane support 1 is less than 1,600 MPa, it cannot be used in a high-pressure environment.

<Tension modulus ratio>
The tensile modulus ratio is a value indicating the magnitude of the tensile modulus in the width direction with respect to the tensile modulus in the flow direction. The tensile modulus ratio (width / flow) of the semipermeable membrane support 1 is preferably 30 to 80%, and more preferably 35 to 75%. When the tensile elastic modulus ratio of the semipermeable membrane support 1 is less than 30%, it is possible to improve the tensile elastic modulus in the flow direction, but on the other hand, the tensile elastic modulus in the width direction is lowered. Unbearable to use under. In addition, when the tensile modulus ratio of the semipermeable membrane support 1 is 80% or more, the semipermeable membrane support 1 is easily torn in the width direction, and paper breakage is likely to occur during film formation or element processing. It is not preferable.

<Tear strength>
The amount of load necessary for tearing the semipermeable membrane support 1 is shown. The tear strength shown in the present invention refers to the tear strength measured in accordance with JIS P 8116. The tear strength in the width direction of the support is preferably 1,100 mN or more, and more preferably 1,300 mN or more. When the tear strength in the width direction is 1,100 mN or less, it is easy to tear in the width direction, tearing occurs during film formation or element processing, and troubles such as paper breakage are likely to occur.

<Air permeability>
The air permeability is a value indicating the gas permeability to the semipermeable membrane support 1. In the present invention, air permeability is used as a means for evaluating the permeability of the membrane liquid. The air permeability shown in the present invention refers to a value measured according to JIS L 1096. That is, the larger the numerical value of the air permeability, the higher the air permeability (membrane fluid permeability) of the semipermeable membrane support 1. The air permeability of the semipermeable membrane support 1 is preferably 0.1 to 1.0 cc / cm ² / second, more preferably 0.2 to 0.8 cc / cm ² / second. The semipermeable membrane supporting body 1 having such air permeability characteristics is suitable for manufacturing the semipermeable membrane for water treatment 100 because the membrane liquid has good permeability and is difficult to cause back-through.

<Smoothness>
The smoothness is a value indicating the smoothness of the surface of the semipermeable membrane support 1. In the present invention, smoothness is used as a means for evaluating the adhesion of the semipermeable membrane layer 2 to the semipermeable membrane support 1. In addition, the smoothness in this invention says the value measured based on JISP8119. That is, it is shown that the smaller the smoothness value, the less the irregularities on the surface of the semipermeable membrane support 1. The smoothness of the surface on the first layer 11 side of the semipermeable membrane support 1 is preferably 15 to 35 seconds, and more preferably 20 to 30 seconds. When the surface of the semipermeable membrane support 1 on the first layer 11 side has such smoothness, the adhesion of the semipermeable membrane layer 2 becomes good, and the semipermeable membrane layer 2 is peeled off from the semipermeable membrane support 1. It becomes difficult to do.

<Experimental result>
Specific examples of the present invention will be described below. Tables 1 to 4 are tables showing the implementation conditions of each example and the evaluation results of the semipermeable membrane support 1 obtained in each example.

<Example 1>
In Example 1, as a raw material, a polyester short fiber having a fineness of 1.6 dtex and a fiber length of 5 mm (Unitika Ester N801 manufactured by Unitika Ltd.) (synthetic fiber α as a main fiber) is 24%, and the fineness is 0.00. Polyester short fiber with 6 decitex and 5 mm fiber length (Unitika Ester 521 manufactured by Unitika Ltd.) (synthetic fiber β as the main fiber) 39%, polyester unstretched short fiber with fineness of 1.2 decitex and fiber length of 5 mm ( Unitika Ltd. 84V) (binder fiber) 37%, and dispersant A (MDP-048 made by Takemoto Yushi Co., Ltd.) whose active ingredient is a modified polyester is 100% by mass of the main fiber and binder fiber in total. The amount was added so that the solid content was 180 ppm. Subsequently, the raw material was dispersed with a pulper. Next, the above-mentioned raw material which has been subjected to dispersion treatment by adjusting the inclined short net paper machine 31 so that the short net weight is 41 g / m ² and the circular paper machine 32 so as to be 30 g / m ² The wet semipermeable membrane support 1 was prepared using Subsequently, the obtained semipermeable membrane supporting substrate 1 in a wet state was subjected to heat and pressure treatment with a combination of a metal roll and an elastic roll using a calender device having one set of heat and pressure units. In the heating and pressurizing treatment, first, the surface in contact with the metal roll is in the order of the second layer 12 side and the first layer 11 side under the conditions that the temperature of the metal roll is 200 ° C., the pressure is 150 kg / cm, and the speed is 6 m / min. Double-sided processing was performed. Thereafter, the same calender apparatus was used to process the metal roll at a temperature of 225 ° C., a pressure of 150 kg / cm, and a speed of 6 m / min so that the surface in contact with the metal roll was on the first layer 11 side.

On the surface on the first layer side of the semipermeable membrane support obtained by the above method, a 15.3% polysulfone N, N-dimethylformamide (DMF) solution is 200 μm in thickness at room temperature (25 ° C.). The microporous support membrane was produced by casting and immediately immersing in pure water and allowing to stand for 5 minutes. The microporous support membrane (thickness 130 to 160 μm) thus formed was immersed in a 3.4% by weight aqueous solution of metaphenylenediamine for 2 minutes, then slowly pulled up in the vertical direction, and nitrogen from an air nozzle. Excess solution was removed from the support membrane surface by exposure to an air stream. Thereafter, an n-decane solution containing 0.15% by weight of trimesic acid chloride was applied so that the surface was completely wetted, and held for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 2 minutes and drained. Thereafter, this was washed with hot water at 90 ° C. for 2 minutes and immersed in an aqueous sodium hypochlorite solution adjusted to pH 7 and a chlorine concentration of 200 mg / l for 2 minutes, and then the sodium bisulfite concentration was 1,000 mg / l. Then, excess sodium hypochlorite was reduced and removed. Furthermore, this membrane was rewashed with hot water at 95 ° C. for 2 minutes. The composite semipermeable membrane thus obtained was evaluated, and its membrane permeation flux was 1.05 m ³ / m ² / d and the salt removal rate was 99.88%.

<Example 2>
The semi-permeable membrane support 1 was changed in the same manner as in Example 1 except that the dispersant was changed to Dispersant B (Baruo M-20 manufactured by Maruhishi Oil Chemical Co., Ltd.) whose active ingredient was polyoxyethylene nonylphenyl ether. And production of the semipermeable membrane 100 for water treatment was implemented.

<Examples 3 to 4>
The concentration of the dispersant was changed as described in Table 1, and production of the semipermeable membrane support 1 and the water treatment semipermeable membrane 100 was carried out in the same manner as in Example 1 except that.

<Examples 5-8, 10-11, 13-18>
The fineness and mixing ratio of the raw materials were changed as shown in Table 1, and production of the semipermeable membrane support 1 and the water treatment semipermeable membrane 100 was carried out in the same manner as in Example 1 except that.

<Examples 9 and 12>
The main fiber of the raw material was changed to only synthetic fiber α or synthetic fiber β, and production of semipermeable membrane support 1 and water treatment semipermeable membrane 100 was carried out in the same manner as in Example 1 except that.
<Examples 19 to 23>
The production of the semipermeable membrane support 1 and the water treatment semipermeable membrane 100 under the same conditions as in Example 1 except that the inclination angle and the paper making speed of the inclined short net paper machine were changed as shown in Table 1. Carried out.

<Examples 24-27>
The basis weight of the first layer 11 and the second layer 12 was changed as described in Table 1, and the production of the semipermeable membrane support 1 and the water treatment semipermeable membrane 100 was otherwise performed in the same manner as in Example 1. Carried out.

<Example 28>
The angle of inclination of the slanted short web paper machine 31 and the rice squares of the first layer 11 and the second layer 12 were each changed as described in Table 1, except that the semipermeable membrane support 1 and Production of a semipermeable membrane 100 for water treatment was carried out.

<Comparative Example 1>
The semipermeable membrane support 1 and the semipermeable membrane 100 for water treatment were produced in the same manner as in Example 1 except that the circular paper machine 32 was not used and only the inclined short paper machine 31 was used.

<Comparative example 2>
The semipermeable membrane support 1 and the water treatment semipermeable membrane 100 were produced in the same manner as in Example 1 except that the inclined short net paper machine 31 was not used and only the circular net paper machine 32 was used.

<Comparative Examples 3-6>
The production of the semipermeable membrane support 1 and the water treatment semipermeable membrane 100 under the same conditions as in Example 1 except that the inclination angle and the paper making speed of the inclined short net paper machine were changed as shown in Table 1. Carried out.

<Evaluation method>
The following evaluation was performed about the semipermeable membrane support obtained in each of the above examples. The results of the following evaluation are shown in Table 3 and Table 4.
1) Fiber orientation angle ratio The fiber orientation ratio was measured with an optical orientation tester manufactured by Toyo Seiki Seisakusho, and the fiber orientation ratio was described.
2) Tensile modulus Measured according to the Japanese Industrial Standard (JIS P 8113).
3) Tear strength Measured according to Japanese Industrial Standard (JIS P 8116).
4) Smoothness Measured according to Japanese Industrial Standard (JIS P 8119).
6) Air permeability In accordance with Japanese Industrial Standard (JIS L 1096), measurement was performed using a Frazier type air permeability tester so that the differential pressure was 127 Pa.
8) Bundling fibers The post-paper base paper according to each example was subjected to 30 m ² inspection, and the number of bundling fibers (so-called “dama”) having a size of 6 mm ² or more was counted. Specifically, when the number of bundling fibers of 6 mm ² or more per 1 m ² of the base paper is less than 0.1, ○, and when it is 0.1 or more and less than 0.5, Δ Is 0.5 or more, x is shown in the table.

From the results of the above evaluation, the semipermeable membrane support 1 produced under the production conditions shown in Examples 1 to 24 has sufficient strength (tensile modulus, tear strength), smoothness and ventilation. It was also confirmed that it has good characteristics with respect to the degree. Specifically, it was confirmed that the semipermeable membrane support 1 obtained in these examples had a tensile modulus in the paper making width direction (lateral direction) of 900 MPa or more. Moreover, it was confirmed that the ratio of the tensile elastic modulus in the paper making width direction (lateral direction) to the tensile elastic modulus in the paper making flow direction (longitudinal direction) of the semipermeable membrane support 1 is 30 to 80%. Moreover, it was confirmed that the tear strength in the papermaking width direction (transverse direction) of the semipermeable membrane supporting member 1 is 1,100 mN or more. In addition, it was confirmed that the smoothness of the surface on the first layer 11 side of the semipermeable membrane support 1 was 15 to 35 seconds, and the smoothness of the surface on the second layer 12 side was 5 to 35 seconds. Moreover, it was confirmed that the air permeability of the semipermeable membrane supporting body 1 is 0.1 to 1.0 cc / cm ² / sec.

  In contrast, the semipermeable membrane supports obtained in Comparative Examples 1 to 3 and 5 have a tensile modulus in the papermaking width direction (lateral direction) of 900 MPa or less and do not have sufficient strength. there were. In addition, the semipermeable membrane supports obtained in Comparative Examples 1, 4, and 6 have a tear strength in the paper width direction (lateral direction) of 1,100 mN or less and do not have sufficient strength. It was.

  Here, the semipermeable membrane support according to Comparative Examples 1 and 2 is different from Examples 1 to 24 in that the production conditions do not include a two-layer structure. Moreover, the semipermeable membrane support according to Comparative Example 3 is different from Examples 1 to 24 in that the inclination angle is low. Moreover, the semipermeable membrane support according to Comparative Example 4 differs from Examples 1 to 24 in that the tilt angle is high.

  Therefore, in order to obtain the semipermeable membrane supporting body 1 having durability characteristics even under a high pressure environment as shown in the above Examples 1 to 24, at least the first layer 11 and the first layer 11 having different fiber orientations are used. Two layers 12 are laminated, and the fiber orientation ratio of the first layer 11 surface measured by an optical orientation tester (FOT) is 6.0 or less, and the fiber orientation angle ratio of the second layer 12 surface is 12. It became clear that it was necessary to make it 0.0 or less. In addition, as long as these conditions are satisfied, the semipermeable membrane supporting body 1 according to the present invention is not limited to the above-described embodiments.

  In addition, as in Example 5, when the average single fiber fineness of the polyester main fiber (α) as a raw material is less than 1.0 dtex, the semipermeable membrane support 1 has sufficient performance, but has air permeability. There was a tendency to decrease slightly compared to other examples. Further, as in Example 11, when the average single fiber fineness of the polyester main fiber (β) is 1.0 or more, although it has sufficient performance as the semipermeable membrane support 1, it has a tensile modulus in the width direction. There was a tendency to decrease compared to other examples. Therefore, as a more preferred embodiment of the present invention, as a raw material, a polyester main fiber (α) having an average single fiber fineness of 1.0 dtex or more and a polyester main fiber (β) having an average single fiber fineness of less than 1.0 dtex are used. It has become clear that it is good to combine polyester-based fibers of different finenesses.

  According to the semipermeable membrane supporting body 1 obtained as described above, no dent is generated even under a high pressure environment, and it can be used for the production of a continuous semipermeable membrane for water treatment.

  The semipermeable membrane support, the semipermeable membrane for water treatment, and the method for producing the semipermeable membrane support according to the present invention include a semipermeable membrane support that can withstand use in a high pressure environment, a semipermeable membrane for water treatment, and the like. Useful as.

DESCRIPTION OF SYMBOLS 1 Semipermeable membrane support body 11 1st layer 12 2nd layer 2 Semipermeable membrane layer 31 Inclined short net paper machine 311 Short net wire 32 Circular net paper machine 33 Making process 34 Heating and pressing process 100 Semi-permeable for water treatment film

Claims (7)

Synthetic fiber as a main component, after wet paper making, a heat-pressed semipermeable membrane support,
The semipermeable membrane support is formed by laminating at least a first layer and a second layer having different fiber orientations,
The fiber orientation ratio of the first layer surface is 6.0 or less,
The semipermeable membrane support, wherein the fiber orientation ratio of the second layer surface is 12.0 or less.   As the synthetic fiber, polyester main fibers having two or more different finenesses of polyester main fibers having an average single fiber fineness of 1.0 dtex or more and polyester main fibers having an average single fiber fineness of less than 1.0 dtex are used as at least the main component. The semipermeable membrane support according to claim 1, which is contained.   In the semipermeable membrane support, after the first layer and the second layer are individually made as wet paper in different paper making processes, the first layer and the second layer are put together in a wet state. The semipermeable membrane supporting material according to claim 1, wherein the semipermeable membrane supporting material is laminated. The first layer is made by an inclined short netting machine,
The second layer is made with a circular paper machine,
The paper making speed of the inclined short paper machine is 20 m / min or more and less than 60 m / min,
The inclination angle of the short mesh provided in the inclined short paper machine is 5 ° or more and 20 ° or less,
In the inclined short paper machine, the value of the parameter G obtained by the equation (1) when the paper making speed is V (m / min) and the inclination angle is ω (degrees) is 1.0 or more, and The semipermeable membrane support according to any one of claims 1 to 3, wherein the first layer is made under a condition of 5.0 or less.
G = V / ω (1) The semipermeable membrane support according to any one of claims 1 to 4,
A semipermeable membrane for water treatment comprising a thin film layer formed on the surface of the semipermeable membrane support. A method for producing a semipermeable membrane support,
A first paper making step of making a first layer having a fiber orientation ratio of 6.0 or less as a wet paper;
A second paper making step of making a second layer having a fiber orientation ratio of 12.0 or less as a wet paper;
The first layer sent out from the first paper making process and the second layer sent out from the second paper making process are laminated together in a wet state and then subjected to heat and pressure treatment. And a laminating step for forming the semipermeable membrane support. In the first paper making process, the first layer is made with an inclined short net paper machine,
In the second paper making process, the second layer is made with a circular paper machine,
The paper making speed of the inclined short paper machine is 20 m / min or more and less than 60 m / min,
The inclination angle of the short mesh provided in the inclined short paper machine is 5 ° or more and 20 ° or less,
In the inclined short paper machine, the value of the parameter G obtained by the equation (1) when the paper making speed is V (m / min) and the inclination angle is ω (degrees) is 1.0 or more, and 7. The method for producing a semipermeable membrane support according to claim 6, wherein the first layer is made under a condition of 5.0 or less.
G = V / ω (1)

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