POROUS SUPPORT, COMPOSITE SEMIPERMEABLE MEMBRANE AND SPIRAL WOUND SEPARATION MEMBRANE ELEMENT

Abstract

The objective of the present invention is to provide a porous support that is unlikely to curl (the incidence of MD curling is low). This porous support has a polymer porous layer on one surface of a nonwoven cloth layer, the nonwoven cloth layer having an MD bend stiffness of 1.2 to 2.1 g.Math.cm.sup.2/cm, and an MD bend recovery of 0.3 to 0.6 g.Math.cm/cm. The nonwoven cloth layer is impregnated with a polymer that is the material for forming the polymer porous layer, the impregnation ratio of the polymer impregnated in the nonwoven cloth layer being 25 to 34% by weight of the total weight of the polymer in the polymer porous layer and the polymer impregnated in the nonwoven cloth layer.

Claims

1. A porous support having a polymer porous layer on one surface of a nonwoven cloth layer, wherein the nonwoven cloth layer has an MD bend stiffness of 1.2 to 2.1 g.Math.cm.sup.2/cm and an MD bend recovery of 0.3 to 0.6 g.Math.cm/cm, a polymer that is a material for forming the polymer porous layer is impregnated in the nonwoven cloth layer, and the impregnation ratio of the polymer impregnated in the nonwoven cloth layer is 25 to 34% by weight of the total weight of the polymer in the polymer porous layer and the polymer impregnated in the nonwoven cloth layer.

2. The porous support according to claim 1, wherein the polymer is a polysulfone.

3. A composite semipermeable membrane having a skin layer on the surface of the porous support according to claim 1.

4. A spiral wound separation membrane element using the composite semipermeable membrane according to claim 3.

5. A composite semipermeable membrane having a skin layer on the surface of the porous support according to claim 2.

6. A spiral wound separation membrane element using the composite semipermeable membrane according to claim 5.

Description

EXAMPLE

[0062] The present invention will, hereinafter, be described with reference to Examples, but the present invention is not limited at all by these Examples.

[0063] [Evaluation and Measurement Method]

[0064] (Measurement of MD Bend Stiffness of Nonwoven Cloth Layer)

[0065] KES test method; Using a pure bending tester (KES-FB2, manufactured by Kato Tech Co., Ltd.), a repulsive stress was measured when a nonwoven cloth layer having a length of 10 cm and a width of 10 cm was bent in the longitudinal direction, and the stress when the bending curvature was 2.5 was defined as a bend stiffness (g.Math.cm.sup.2/cm).

[0066] (Measurement of MD Bend Recovery in Nonwoven Cloth Layer)

[0067] KES test method; Using a pure bending tester (KES-FB2, manufactured by Kato Tech Co., Ltd.) repulsive stresses when bending a nonwoven cloth layer having a length of 10 cm and a width of 10 cm in the longitudinal direction and when returning the bent nonwoven cloth layer were measured, respectively, and the stress difference when the bending curvature was 2.5 was defined as a bend recovery (g.Math.cm/cm)

[0068] (Measurement of Air Permeability of Nonwoven Cloth Layer)

[0069] In accordance with the method described in JIS L 1096, the air permeability of the nonwoven cloth layer was measured using a Frazier type tester.

[0070] (Measurement of Viscosity of Polysulfone Solution)

[0071] The viscosity of the polysulfone solution was measured at a measurement temperature of 30° C. using an E type viscometer (RE-85 type viscometer, manufactured by Toki Sangyo Co., Ltd.).

[0072] (Calculation of impregnation Ratio of Polysulfone Impregnated in Nonwoven Cloth Layer)

[0073] The weight A of the dried porous support was measured. Thereafter, the polysulfone porous layer was peeled off from the porous support with a tape, and the weight B of the nonwoven cloth layer was measured. Then, the nonwoven cloth layer was impregnated in DMF, and the polysulfone impregnated in the nonwoven cloth layer was dissolved in DMF. Subsequently, the nonwoven cloth layer was taken out from the DMF, washed, and dried. Then, the weight C of the nonwoven cloth layer was measured.

[0074] The weight D of the polysulfone porous layer was calculated by the following formula:

Weight D=Weight A−Weight B

[0075] The weight E of the polysulfone impregnated in the nonwoven cloth layer was calculated by the following formula:

Weight B=Weight B−Weight C

[0076] The impregnation ratio (% by weight) of the polysulfone impregnated in the nonwoven cloth layer was calculated by the following formula:

Impregnation ratio (% by weight)=[Weight E/(Weight D+Weight E)]×100

[0077] (Measurement of Salt-Rejection)

[0078] The prepared flat shape composite semipermeable membrane was cut into a predetermined shape and size, and was set to a cell for flat shape evaluation. An aqueous solution containing 0.15 wt % NaCl and being adjusted to pH 6.5 was allowed to contact to a supply side and permeation side of the membrane at a differential pressure of 1.5 MPa at 25° C. An electric conductivity of the permeated water obtained by this operation was measured, and a salt-rejection (%) was calculated. The correlation (calibration curve) of the NaCl concentration and electric conductivity of the aqueous solution was made beforehand, and the salt-rejection was calculated by the following equation.

Salt-rejection (%)={1−(NaCl concentration in permeated liquid [mg/L])/(NaCl concentration in supply solution) [mg/L]}×100

[0079] (Evaluation of MD Curling of Porous Support)

[0080] The prepared porous support was unwound from the supply roll and cut into a size of 1 m in width and 1 m in length to obtain a sample. The sample was placed on a flat table and the warpage height from the table at the end portion in the MD direction was measured and the MD curling of the porous support was evaluated in accordance with the following criteria:

⊙: The warpage height is 20 mm or less.
◯: The warpage height is from more than 20 mm to 26 mm or less.
x: the warpage height is more than 26 mm.

Example 1

[0081] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 20 μm was formed to prepare a porous support, and the produced porous support was wound around a supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.6 seconds.

[0082] Then, an amine solution was prepared by dissolving 3% by weight of metaphenylene diamine in water. In addition, 0.25% by weight of trimesic acid chloride was dissolved in hexane to prepare an organic solution. While delivering the produced porous support from the supply roll, the amine solution was coated on the porous support, and then the excess amine solution was removed to form an amine solution coating layer. Next, the organic solution was coated on the surface of the amine solution coating layer. Thereafter, the excessive solution was removed and the coating layer was further kept in a hot air dryer at 140° C. for 3 minutes to form a skin layer containing a polyamide-based resin on the porous support, thereby to prepare a composite semipermeable membrane.

Example 2

[0083] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 20 μm was formed to prepare a porous support, and the produced porous support was wound around the supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.5 seconds.

[0084] Then, a composite semipermeable membrane was prepared in the same manner as in Example 1.

Example 3

[0085] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 20 μm was formed to prepare a porous support, and the produced porous support was wound around the supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.4 seconds.

[0086] Then, a composite semipermeable membrane was prepared in the same manner as in Example 1.

Example 4

[0087] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 30 μm was formed to prepare a porous support, and the produced porous support was wound around the supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.3 seconds.

[0088] Then, a composite semipermeable membrane was prepared in the same manner as in Example 1.

Comparative Example 1

[0089] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 15 μm was formed to prepare a porous support, and the produced porous support was wound around the supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.7 seconds.

[0090] Then, a composite semipermeable membrane was prepared in the same manner as in Example 1.

Comparative Example 2

[0091] A polysulfone solution (dope) containing 18.3% by weight of polysulfone and dimethylformamide was coated on the surface of a nonwoven cloth layer shown in Table 1, and then the nonwoven cloth layer having the doped membrane was impregnated in a water bath to be coagulated, so that a polysulfone porous layer having a thickness of 30 μm was formed to prepare a porous support, and the produced porous support was wound around the supply roll. The time from the application of the polysulfone solution to the completion of the coagulation treatment was 3.2 seconds.

[0092] Then, a composite semipermeable membrane was prepared in the same manner as in Example 1.

TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 1 Example 2 Material for nonwoven cloth layer Polyester Polyester Polyester Polyester Polyester Polyester MD bend stiffness of nonwoven cloth layer (g .Math. cm.sup.2/cm) 1.80 1.89 1.61 1.32 1.80 1.44 MD bend recovery of nonwoven cloth layer (g .Math. cm/cm) 0.52 0.45 0.32 0.4 0.52 0.27 Basis weight of nonwoven cloth layer (g/m.sup.2) 77 81 80 83 77 74 Air permeability of nonwoven cloth layer (cm.sup.3/cm.sup.2 .Math. s) 3.1 1.5 2.1 2.0 3.1 1.7 Thickness of nonwoven cloth layer (μm) 120 103 102 101 120 96 Viscosity of polysulfone solution (mPa .Math. s) 600-850 600-850 600-850 600-850 600-850 600-850 Impregnation ratio of polysulfone (% by weight) 34 30 28 25 37 23 Salt-rejection (%) 99.8 99.8 99.7 99.7 99.5 99.7 MD curling ○ ⊙ ⊙ ○ ○ ×

INDUSTRIAL APPLICABILITY

[0093] The composite semipermeable membrane and spiral wound separation membrane element of the present invention are suitably used for production of ultrapure water, desalination of brackish water or sea water, etc., and usable for removing or collecting pollution sources or effective substances from pollution, which causes environment pollution occurrence, such as dyeing drainage and electrodeposition paint drainage, leading to contribute to closed system for drainage. Furthermore, the element can be used for concentration of active ingredients in foodstuffs usage, for an advanced water treatment, such as removal of harmful component in water purification and sewage usage etc. Moreover, the element can be used for waste water treatment in oil fields or shale gas fields.