REVERSE OSMOSIS MEMBRANE SUPPORT MATERIAL AND PREPARATION METHOD THEREOF

Abstract

The present invention relates to the technical field of filtering materials and provides a reverse osmosis membrane support material. The support material is obtained by hot pressing treatment of a surface layer, a middle layer and a bottom layer which are sequentially disposed from top to bottom. The surface layer and the bottom layer are each a spunbond non-woven fabric layer made of thermoplastic polymer spunbonded fibers, and the middle layer is a polymer nanofiber membrane. In accordance with the invention, the comprehensive mechanical strength of the reverse osmosis membrane support material is improved, and the overall anti-leakage performance is enhanced. A spunbond technology and a nanofiber preparation technology are combined organically, and the method is simple and controllable. The support material can be produced in batches.

Claims

1. A reverse osmosis membrane support material, comprising: a surface layer of a spunbond non-woven fabric of thermoplastic polymer spunbonded fibers; a middle layer of a polymer nanofiber membrane; and a bottom layer of a spunbond non-woven fabric of thermoplastic polymer spunbonded fibers; wherein the reverse osmosis membrane support material is obtained by hot pressing treatment of the surface layer, the middle layer and the bottom layer which are sequentially disposed from top to bottom, respectively.

2. The reverse osmosis membrane support material according to claim 1, wherein the thermoplastic polymer comprises one or more of polyester, polyamide, polylactic acid, polypropylene, polystyrene, polytetrafluoroethylene, polyphenylene sulfide, and cellulose acetate.

3. The reverse osmosis membrane support material according to claim 1, wherein a polymer in the polymer nanofiber membrane comprises one or more of polyester, polysulfone, polyethersulfone, polyamide, polylactic acid, cellulose acetate, polytetrafluoroethylene and polyvinylidene fluoride.

4. The reverse osmosis membrane support material according to claim 1, wherein the support material has an apparent surface density of 0.75-0.95 g/cm.sup.3, a thickness of 35-80 m, a surface layer smoothness of 20-30 s, and a gram weight of 40 g/m.sup.2 to 70 g/m.sup.2.

5. A preparation method of the reverse osmosis membrane support material according to claim 1, comprising: step (1): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers to obtain a spunbond non-woven fabric layer as a bottom layer; step (2): spinning a polymer nanofiber membrane on the surface of the bottom layer in the step (1) by an electrospinning or solution blowing method as a middle layer; step (3): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers on the surface of the middle layer to obtain a spunbond non-woven fabric layer as a surface layer, to obtain a layered material; and step (4): performing hot pressing treatment on the layered material obtained in the step (3) to obtain a reverse osmosis membrane support material.

6. A preparation method of the reverse osmosis membrane support material according to claim 2, comprising: step (1): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers to obtain a spunbond non-woven fabric layer as a bottom layer; step (2): spinning a polymer nanofiber membrane on the surface of the bottom layer in the step (1) by an electrospinning or solution blowing method as a middle layer; step (3): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers on the surface of the middle layer to obtain a spunbond non-woven fabric layer as a surface layer, to obtain a layered material; and step (4): performing hot pressing treatment on the layered material obtained in the step (3) to obtain a reverse osmosis membrane support material.

7. A preparation method of the reverse osmosis membrane support material according to claim 3, comprising: step (1): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers to obtain a spunbond non-woven fabric layer as a bottom layer; step (2): spinning a polymer nanofiber membrane on the surface of the bottom layer in the step (1) by an electrospinning or solution blowing method as a middle layer; step (3): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers on the surface of the middle layer to obtain a spunbond non-woven fabric layer as a surface layer, to obtain a layered material; and step (4): performing hot pressing treatment on the layered material obtained in the step (3) to obtain a reverse osmosis membrane support material.

8. A preparation method of the reverse osmosis membrane support material according to claim 4, comprising: step (1): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers to obtain a spunbond non-woven fabric layer as a bottom layer; step (2): spinning a polymer nanofiber membrane on the surface of the bottom layer in step (1) by an electrospinning or solution blowing method as a middle layer; step (3): melt-spinning a thermoplastic polymer to obtain spunbonded fibers, and separating and laying the spunbonded fibers on the surface of the middle layer to obtain a spunbond non-woven fabric layer as a surface layer, to obtain a layered material; and step (4): performing hot pressing treatment on the layered material obtained in step (3) to obtain a reverse osmosis membrane support material.

9. The preparation method according to claim 5, wherein the spunbonded fiber in the bottom layer in step (1) has a diameter of 7-30 m and a gram weight of 25-40 g/m.sup.2; and the spunbonded fiber in the surface layer in step (3) has a diameter of 7-20 m and a gram weight of 10-20 g/m.sup.2.

10. The preparation method according to claim 6, wherein the spunbonded fiber in the bottom layer in step (1) has a diameter of 7-30 m and a gram weight of 25-40 g/m.sup.2; and the spunbonded fiber in the surface layer in step (3) has a diameter of 7-20 m and a gram weight of 10-20 g/m.sup.2.

11. The preparation method according to claim 7, wherein the spunbonded fiber in the bottom layer in step (1) has a diameter of 7-30 m and a gram weight of 25-40 g/m.sup.2; and the spunbonded fiber in the surface layer in step (3) has a diameter of 7-20 m and a gram weight of 10-20 g/m.sup.2.

12. The preparation method according to claim 8, wherein the spunbonded fiber in the bottom layer in step (1) has a diameter of 7-30 m and a gram weight of 25-40 g/m.sup.2; and the spunbonded fiber in the surface layer in step (3) has a diameter of 7-20 m and a gram weight of 10-20 g/m.sup.2.

13. The preparation method according to claim 5, wherein when step (2) is performed by an electrospinning method, a concentration of a spinning solution for the electrospinning is 8-20 wt %, a voltage of the electrospinning is 5-30 kV, and a receiving distance is 5-25 cm.

14. The preparation method according to claim 6, wherein when step (2) is performed by an electrospinning method, a concentration of a spinning solution for the electrospinning is 8-20 wt %, a voltage of the electrospinning is 5-30 kV, and a receiving distance is 5-25 cm.

15. The preparation method according to claim 7, wherein when step (2) is performed by an electrospinning method, a concentration of a spinning solution for the electrospinning is 8-20 wt %, a voltage of the electrospinning is 5-30 kV, and a receiving distance is 5-25 cm.

16. The preparation method according to claim 8, wherein when step (2) is performed by an electrospinning method, a concentration of a spinning solution for the electrospinning is 8-20 wt %, a voltage of the electrospinning is 5-30 kV, and a receiving distance is 5-25 cm.

17. The preparation method according to claim 5, wherein when step (2) is performed by a solution blowing method, a concentration of a spinning solution for the solution blowing is 8-20 wt %, a drafting air pressure of the solution blowing is 0.2-0.6 MPa, and a receiving distance is 50-120 cm.

18. The preparation method according to claim 6, wherein when step (2) is performed by a solution blowing method, a concentration of a spinning solution for the solution blowing is 8-20 wt %, a drafting air pressure of the solution blowing is 0.2-0.6 MPa, and a receiving distance is 50-120 cm.

19. The preparation method according to claim 5, wherein the polymer nanofiber membrane in step (2) has a gram weight of 2-10 g/m.sup.2, and a nanofiber in the polymer nanofiber membrane has a diameter of 50-900 nm.

20. The preparation method according to claim 5, wherein a hot pressing temperature of the hot pressing treatment in step (4) is lower than the melting point of the polymer nanofiber membrane of the middle layer by 20-60 C., and the pressure of the hot pressing is 500-750 N/cm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic structural view of a reverse osmosis membrane taking polysulfone as a support layer;

[0028] FIG. 2 is a schematic structural view of a reverse osmosis membrane support material according to the present invention;

[0029] FIG. 3 is a schematic flow chart of preparing a polymer nanofiber membrane by a wet laying method according to the present invention; and

[0030] FIG. 4 is a flow diagram of the preparation method of the reverse osmosis membrane support material according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0031] The present invention provides a reverse osmosis membrane support material, which is obtained by hot pressing treatment of a surface layer, a middle layer and a bottom layer which are sequentially disposed from top to bottom. The surface layer and the bottom layer are each a spunbond non-woven fabric layer, and a schematic structural view is shown in FIG. 2. The spunbond non-woven fabric layer is made of thermoplastic polymer spunbonded fibers; and the middle layer is a polymer nanofiber membrane.

[0032] The surface layer and the bottom layer of the reverse osmosis membrane support material according to the present invention are each a spunbond non-woven fabric layer. The spunbond non-woven fabric layers are made of thermoplastic polymer spunbonded fibers. In the present invention, the surface layer and the bottom layer independently use a thermoplastic polymer preferably including one or more of polyester, polyamide, polylactic acid, polypropylene, polystyrene, polytetrafluoroethylene, polyphenylene sulfide, and cellulose acetate. In a specific embodiment of the present invention, one or more thermoplastic polymers may be used in combination. The present invention preferably uses a compound of thermoplastic polymers having eutectic points greater than 160 C. as a raw material for the surface layer and the bottom layer, and more preferably uses a compound of thermoplastic polymers having eutectic points of 180-300 C. In a specific embodiment of the present invention, for example, spun-grade PET and/or spun-grade PA6 may be used as a thermoplastic polymer material for the surface layer and the bottom layer. A purpose of the present invention to limit the eutectic point of the thermoplastic polymer is to select a thermoplastic polymer, which is advantageous for the subsequent hot pressing treatment forming. Those skilled in the art can carry out selection and combination according to the preferred thermoplastic polymer material provided by the present invention in combination with the control of the eutectic temperature. The source of the thermoplastic polymer of the present invention is not particularly limited.

[0033] The middle layer of the reverse osmosis membrane support material of the present invention is a polymer nanofiber membrane. The polymer used in the middle layer preferably includes one or more of polyester, polysulfone, polyethersulfone, polyamide, polylactic acid, cellulose acetate, polytetrafluoroethylene and polyvinylidene fluoride. In the present invention, the eutectic point of the polymer used in the middle layer is preferably slightly lower than the eutectic point of the thermoplastic polymer used in the surface layer and the bottom layer to ensure uniform heating of the three-layer composite structure during hot pressing treatment. This not only satisfies the bonding requirement for hot pressing integration, but also ensures the pore size distribution of the middle layer nanofiber membrane. The sources of the polymers of the present invention are not particularly limited.

[0034] In the present invention, the surface layer and the bottom layer are each a spunbond non-woven fabric layer, where a spunbonded fiber has a large diameter, is in the micron order, and mainly plays a supporting and protecting role. The middle layer is a polymer nanofiber membrane, and the nanofiber in the polymer nanofiber membrane has a relatively small diameter, is in the nanometer order and mainly plays a role of preventing leakage.

[0035] The present invention provides a preparation method of the reverse osmosis membrane support material according to the aforementioned technical solution, including the following steps (See e.g., FIG. 4):

[0036] Step (1): melt-spin a thermoplastic polymer to obtain spunbonded fibers, and separate and lay the spunbonded fibers to obtain a spunbond non-woven fabric layer as a bottom layer.

[0037] Step (2): spin a polymer nanofiber membrane on the surface of the bottom layer in the step (1) by an electrospinning or solution blowing method as a middle layer.

[0038] Step (3): melt-spin a thermoplastic polymer to obtain spunbonded fibers, and separate and lay the spunbonded fibers on the surface of the middle layer to obtain a spunbond non-woven fabric layer as a surface layer to obtain a layered material.

[0039] Step (4): perform hot pressing treatment on the layered material obtained in the step (3) to obtain a reverse osmosis membrane support material.

[0040] According to the present invention, a thermoplastic polymer is subjected to melt-spinning to obtain spunbonded fibers, and the spunbonded fibers are separated and laid to obtain a non-woven material layer as a bottom layer. In a specific embodiment of the present invention, a thermoplastic polymer is subjected to high temperature melt extrusion by using a spunbond method and then is spun, drafted and cooled to obtain spunbonded fibers. In the present invention, the diameter of the spunbonded fiber in the bottom layer is preferably 7-30 m, more preferably 10-25 m, and further preferably 18-22 m.

[0041] In the present invention, the step of separating and laying specifically includes: first separating the prepared spunbonded fibers, laying the separate fibers on a web curtain to form a uniform fiber web, and eliminating static electricity of the fiber web. In the present invention, the separating method is preferably a gas flow, electrostatic or mechanical separating method.

[0042] In the present invention, the gram weight of the bottom layer is preferably 25-40 g/m.sup.2, more preferably 37-42 g/m.sup.2. The present invention uses the spunbond method to prepare the fibers and has fewer steps and a high production speed. The present invention has no special requirements for devices used for preparing the spunbonded fibers and used for separating and laying, and devices well known to those skilled in the art can be used.

[0043] After the bottom layer is obtained, according to the present invention, a polymer nanofiber membrane is spun on the surface of the bottom layer by an electrospinning or solution blowing method as a middle layer.

[0044] In the present invention, when the electrospinning method is adopted, a concentration of a spinning solution for the electrospinning is 8-20 wt %, more preferably 12-16 wt %; a voltage of the electrospinning is preferably 5-30 KV, more preferably 15-20 KV; a receiving distance is preferably 5-25 cm, more preferably 10-20 cm; and the electrospinning method is preferably a multi-needle electrospinning method. According to the present invention, through the control of electrospinning operation parameters, it can be ensured that the spinning process is stable, so that obtained polymer nanofibers have the same morphology, the formed middle layer has good evenness, and the pore distribution is reasonable, which is beneficial to maintaining an anti-leakage function of the middle layer.

[0045] In the present invention, when a solution blowing method is adopted, a concentration of a spinning solution for solution blowing is preferably 8-20 wt %, more preferably 12-16 wt %; a drafting air pressure of the solution blowing is preferably 0.2-0.6 MPa, more preferably 0.4-0.5 MPa, and a receiving distance is preferably 50-120 cm, more preferably 70-90 cm.

[0046] In a specific embodiment of the present invention, the above-mentioned electrospinning or solution blowing method may be used to directly form a middle layer on the surface of the bottom layer, or a large amount of polymer nanofibers may be prepared by using the electrospinning or solution blowing method first, and then the obtained polymer nanofibers are formed into a nanofiber membrane on the surface of the bottom layer by a wet laying method. The wet laying specifically includes: sequentially subjecting the nanofibers to shearing, beating, separation and laying treatment to obtain a nanofiber membrane, and the specific process is shown in FIG. 3.

[0047] In the present invention, a polymer nanofiber membrane of the middle layer preferably has a gram weight of 2-10 g/m.sup.2, more preferably 5-7 g/m.sup.2, and a diameter of a nanofiber in the polymer nanofiber membrane is 50-900 nm, more preferably 100-500 nm, further preferably 200-400 nm. In specific embodiments of the present invention, the diameter of the nanofiber obtained by spinning is controlled to be within the range of 50-900 nm, and the diameters of the nanofibers are not required to be uniform but are required to be in a range of values, and the nanofibers of different diameters fill each other to form a dense polymer nanofiber membrane having a uniform pore size.

[0048] After the middle layer is obtained, in the present invention, a thermoplastic polymer is subjected to melt-spinning to obtain spunbonded fibers, and the spunbonded fibers are separated and laid on the surface of the middle layer to obtain a spunbonded non-woven material as a surface layer. In the present invention, a specific operation method for melt-spinning and separating and laying in the step (3) is the same as the step (1), and details are not described herein again. In the present invention, a diameter of a spunbonded fiber in the surface layer is preferably 7-20 m, more preferably 10-17 m, further preferably 12-15 m; and a gram weight of the surface layer is preferably 10-20 g/m.sup.2, more preferably 13-17 g/m.sup.2. In the present invention, the surface layer can further stabilize the middle layer and coordinate the overall performance of the support material.

[0049] After the surface layer is obtained, in the present invention, the obtained layered material is subjected to hot pressing treatment to obtain a reverse osmosis membrane support material. In the present invention, a hot pressing temperature of the hot pressing treatment is lower than the melting point of the polymer nanofiber membrane of the middle layer by 20-60 C. The present invention controls the hot pressing temperature to be lower than the melting point of the polymer nanofiber membrane, and the purpose is to ensure uniform heat transfer during hot pressing forming of the three-layer support material, satisfy the requirement of bonding each layer of material without affecting the pore size distribution inside the reverse osmosis membrane support material, and maintain the overall functionality. In the present invention, a pressure of the hot pressing treatment is preferably 500-750 N/cm, more preferably 700-750 N/cm; and a hot pressing treatment mode according to the present invention is preferably roller type hot rolling.

[0050] The reverse osmosis membrane support material according to the above technical solution of the present invention or the reverse osmosis membrane support material prepared by using the above preparation method has an apparent surface density of 0.75-0.95 g/cm.sup.3, a thickness of 35-80 m, a surface layer smoothness of 20-30 s, and a gram weight of 40 g/m.sup.2 to 70 g/m.sup.2.

[0051] The reverse osmosis membrane support material and the preparation method thereof provided by the present invention are described in detail below with reference to the embodiments, but the embodiments cannot be understood as limiting the protection scope of the present invention.

Embodiment 1

[0052] A preparation method of a reverse osmosis membrane support material according to one embodiment includes the following steps:

[0053] Step (1): spin spun-grade PET at 300 C. by a spunbond method, and obtain a spunbond non-woven fabric layer having an average fiber diameter of 21 m and a gram weight of 35 g/m.sup.2 by a separating and laying method as a bottom layer of a support material.

[0054] Step (2): use a multi-needle electrospinning technology to spin on the surface of the bottom layer to obtain a copolyester nanofiber membrane having a melting point of 220 C. as a middle layer. The multi-needle electrospinning conditions are as follows: high-voltage static electricity is 22 kV, a spinning solution concentration is 15%, a receiving distance is 22 cm, a gram weight of the nanofiber membrane is 6 g/m.sup.2; and a diameter of a nanofiber in the nanofiber membrane is 260-720 nm.

[0055] Step (3): spin spun-grade PET at 300 C. by a spunbond method, and obtain a spunbond non-woven fabric layer having an average fiber diameter of 18 m and a gram weight of 15 g/m.sup.2 by a separating and laying method as a surface layer of a support material.

[0056] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0057] The reverse osmosis membrane support material obtained in Embodiment 1 was subjected to basic performance measurement, and an apparent surface density was 0.84 g/cm.sup.3 and a thickness was 43 m according to the standard GB/T 24328.2-2009; it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 27 s and the gram weight was 60 g/m.sup.2.

Embodiment 2

[0058] A preparation method of a reverse osmosis membrane support material according to another embodiment includes the following steps:

[0059] Step (1): spin spun-grade PET at 300 C. by a spunbond method and obtain a spunbond non-woven fabric layer having an average fiber diameter of 21 m and a gram weight of 35 g/m.sup.2 by a separating and laying method as a bottom layer of a support body.

[0060] Step (2): use a multi-needle electrospinning technology to spin on the surface of the bottom layer to obtain a polyamide nanofiber membrane having a melting point of 230 C. as a middle layer. The electrospinning conditions are: high-voltage static electricity is 25 KV, a spinning solution concentration is 15%, a receiving distance is 22 cm, a gram weight of the nanofiber membrane is 8 g/m.sup.2; and a diameter of a nanofiber in the nanofiber membrane is 180-680 nm.

[0061] Step (3): spin spun-grade PET at 300 C. by a spunbond method, and obtain a spunbond non-woven fabric layer having an average fiber diameter of 15 m and a gram weight of 20 g/m.sup.2 by a separating and laying method as a surface layer of a support material.

[0062] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0063] The reverse osmosis membrane support material obtained in Embodiment 2 was subjected to basic performance measurement, and an apparent surface density was 0.79 g/cm.sup.3 and a thickness was 51 m according to the standard GB/T 24328.2-2009; and it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 26 s and the gram weight was 63 g/m.sup.2.

Embodiment 3

[0064] A preparation method of a reverse osmosis membrane support material according to a third embodiment includes the following steps:

[0065] Step (1): spin spun-grade PA6 at 286 C. by a spunbond method, and obtain a spunbonded non-woven material having an average fiber diameter of 23 m and a gram weight of 37 g/m.sup.2 by a separating and laying method as a bottom layer of a support material.

[0066] Step (2): use a multi-needle electrospinning technology to spin on the surface of the bottom layer to obtain a copolyester nanofiber membrane having a melting point of 220 C. as a middle layer. The multi-needle electrospinning conditions are as follows: high-voltage static electricity is 22 kV, a spinning solution concentration is 15%, a receiving distance is 22 cm, a gram weight of the nanofiber membrane is 12 g/m.sup.2; and a diameter of a nanofiber in the nanofiber membrane is 220-740 nm.

[0067] Step (3): spin spun-grade PA6 at 240 C. by a spunbond method, and obtain a spunbonded non-woven material having an average fiber diameter of 15 m and a gram weight of 19 g/m.sup.2 by a separating and laying method as a surface layer of a support material.

[0068] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0069] The reverse osmosis membrane support material obtained in Embodiment 3 was subjected to basic performance measurement, and an apparent surface density was 0.87 g/cm.sup.3 and a thickness was 40 m according to the standard GB/T 24328.2-2009; and it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 27 s and the gram weight was 67 g/m.sup.2.

Embodiment 4

[0070] A preparation method of a reverse osmosis membrane support material according to a fourth embodiment includes the following steps:

[0071] Step (1): spin spun-grade PA6 at 286 C. by a spunbond method, and obtain a spunbonded non-woven material having an average fiber diameter of 23 m and a gram weight of 37 g/m.sup.2 by a separating and laying method as a bottom layer of a support body.

[0072] Step (2): use a multi-needle electrospinning technology to spin on the surface of the bottom layer to obtain a polyamide nanofiber membrane having a melting point of 230 C. The electrospinning conditions are as follows: high-voltage static electricity is 25 KV, a spinning solution concentration is 15%, a receiving distance is 22 cm, a gram weight of the nanofiber membrane is 6 g/m.sup.2; and a diameter of a nanofiber in the nanofiber membrane is 210-700 nm.

[0073] Step (3): spin spun-grade PA6 at 240 C. by a spunbond method, and obtain a spunbonded non-woven material having an average fiber diameter of 14 m and a gram weight of 15 g/m.sup.2 by a separating and laying method as a surface layer of a support material.

[0074] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0075] The reverse osmosis membrane support material obtained in Embodiment 4 was subjected to basic performance measurement, and an apparent surface density was 0.83 g/cm.sup.3 and a thickness was 45 m according to the standard GB/T 24328.2-2009; and it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 27 s and the gram weight was 65 g/m.sup.2.

Embodiment 5

[0076] A preparation method of a reverse osmosis membrane support material according to a fifth embodiment adopts a solution blowing method to obtain a middle layer and includes the following steps:

[0077] Step (1): spin spun-grade PET at 300 C. by a spunbond method and obtain a spunbonded non-woven material having an average fiber diameter of 21 m and a gram weight of 35 g/m.sup.2 by a separating and laying method as a bottom layer of a support body.

[0078] Step (2): use a solution blowing technology to spin on the surface of the bottom layer to obtain a polyamide nanofiber membrane having a melting point of 230 C. as a middle layer. The solution blowing conditions are as follows: a spinning solution concentration is 15%, a drafting air pressure is 0.2 MPa, an advance speed is 20 ml/h, a box body temperature is 45 C., and an auxiliary voltage is 4 kV, a receiving distance is 70 cm, a gram weight of the nanofiber membrane is 6 g/m.sup.2; and a diameter of a nanofiber in the nanofiber membrane is 310-820 nm.

[0079] Step (3): mix spun-grade PET with spun-grade PA6 at a proportion of 1:1, spin the mixture at 300 C. by a spunbond method and obtain a spunbonded non-woven material having an average fiber diameter of 17 m and a gram weight of 20 g/m.sup.2 by a separating and laying method as a bottom layer of a support body.

[0080] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0081] The reverse osmosis membrane support material obtained in Embodiment 5 was subjected to basic performance measurement, and an apparent surface density was 0.81 g/cm.sup.3 and a thickness was 49 m according to the standard GB/T 24328.2-2009; and it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 25 s and the gram weight was 65 g/m.sup.2.

Embodiment 6

[0082] A preparation method of a reverse osmosis membrane support material according to a sixth embodiment adopts a wet laying method to obtain a middle layer and includes the following steps:

[0083] Step (1): spin spun-grade PET at 300 C. by a spunbond method and obtain a spunbonded non-woven material having an average fiber diameter of 21 m and a gram weight of 35 g/m.sup.2 by a separating and laying method as a bottom layer of a support body.

[0084] Step (2): obtain polyamide nanofibers with a melting point of 230 C. by using a solution blowing method, where the diameter is 330-900 nm; place the polyamide nanofibers in a beater for shearing, separating the polyamide nanofibers in a dissociator, and then obtain a polyamide nanofiber membrane on the bottom layer by using a wet laying method as a middle layer, where the nanofiber membrane obtained by wet laying has a gram weight of 12 g/m.sup.2.

[0085] Step (3): spin spun-grade PET at 300 C. by a spunbond method and obtain a spunbonded non-woven material having an average fiber diameter of 18 m and a gram weight of 20 g/m.sup.2 by a separating and laying method as a surface layer of a support body.

[0086] Step (4): finally bond the three layers by roller type hot rolling at 180 C. and a pressure of 700 N/cm to obtain a three-layer composite reverse osmosis membrane support material.

[0087] The reverse osmosis membrane support material obtained in Embodiment 6 was subjected to basic performance measurement, and an apparent surface density was 0.88 g/cm.sup.3 and a thickness was 42 m according to the standard GB/T 24328.2-2009; and it was measured according to the standard GB/T 22881-2008 that the surface smoothness was 29 s and the gram weight was 67 g/m.sup.2.

[0088] As can be seen Embodiments 1 to 6, the reverse osmosis membrane support material obtained by a three-layer composite method according to the present invention includes the bottom layer providing main mechanical support, the middle layer for preventing permeation of a casting solution and the surface layer for stabilizing the middle layer and coordinating the overall performance of the support material. The present invention combines a spunbond technology and a nanofiber preparation technology, the method is simple and controllable, and the reverse osmosis membrane support material can be produced in batches. The comprehensive mechanical strength of the reverse osmosis membrane support material is improved, the overall impermeability is enhanced, and the thickness of the support material is effectively reduced.

[0089] The foregoing descriptions are only preferred implementation manners of the present invention. It should be noted that for a person of ordinary skill in the art, several improvements and modifications may further be made without departing from the principle of the present invention. These improvements and modifications should also be deemed as falling within the protection scope of the present invention.