CN109316974B - Semipermeable membrane supporting material - Google Patents
Semipermeable membrane supporting material Download PDFInfo
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- CN109316974B CN109316974B CN201811407003.1A CN201811407003A CN109316974B CN 109316974 B CN109316974 B CN 109316974B CN 201811407003 A CN201811407003 A CN 201811407003A CN 109316974 B CN109316974 B CN 109316974B
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- 239000000463 material Substances 0.000 title claims abstract description 136
- 239000012528 membrane Substances 0.000 title claims abstract description 82
- 239000004745 nonwoven fabric Substances 0.000 claims abstract description 111
- 238000010438 heat treatment Methods 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 10
- 238000010030 laminating Methods 0.000 claims abstract description 3
- 239000000835 fiber Substances 0.000 claims description 50
- 229920002647 polyamide Polymers 0.000 claims description 4
- 239000004952 Polyamide Substances 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
- 229920006231 aramid fiber Polymers 0.000 claims description 3
- 229920000728 polyester Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 239000004760 aramid Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 abstract description 45
- 239000011248 coating agent Substances 0.000 abstract description 44
- 238000007731 hot pressing Methods 0.000 abstract description 44
- 229920006254 polymer film Polymers 0.000 abstract description 15
- 238000012545 processing Methods 0.000 abstract description 12
- 230000035699 permeability Effects 0.000 abstract description 5
- 238000000034 method Methods 0.000 description 29
- 239000002002 slurry Substances 0.000 description 21
- 229920002492 poly(sulfone) Polymers 0.000 description 17
- 229920000139 polyethylene terephthalate Polymers 0.000 description 15
- 239000005020 polyethylene terephthalate Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 239000006185 dispersion Substances 0.000 description 9
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 7
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- -1 polyethylene terephthalate Polymers 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 6
- 238000001223 reverse osmosis Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 238000005345 coagulation Methods 0.000 description 5
- 230000015271 coagulation Effects 0.000 description 5
- 238000001035 drying Methods 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000000108 ultra-filtration Methods 0.000 description 3
- XRASRVJYOMVDNP-UHFFFAOYSA-N 4-(7-azabicyclo[4.1.0]hepta-1,3,5-triene-7-carbonyl)benzamide Chemical compound C1=CC(C(=O)N)=CC=C1C(=O)N1C2=CC=CC=C21 XRASRVJYOMVDNP-UHFFFAOYSA-N 0.000 description 2
- KKEYFWRCBNTPAC-UHFFFAOYSA-N benzene-dicarboxylic acid Natural products OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001728 nano-filtration Methods 0.000 description 2
- 229920005597 polymer membrane Polymers 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001631 haemodialysis Methods 0.000 description 1
- 230000000322 hemodialysis Effects 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
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- 229910001220 stainless steel Inorganic materials 0.000 description 1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
Abstract
The invention discloses a semipermeable membrane support material, which is a sheet material obtained by laminating two non-woven fabrics with different aspect ratios k and then heating and pressurizing, wherein the k value of the non-woven fabric layer of the sheet material close to the coating surface side is more than 1.5, and the k value of the non-woven fabric layer close to the non-coating surface side is less than 1.0. The support material can not curl after hot pressing while ensuring excellent performances such as air permeability, tensile strength and fluffiness, and can not curl after coating a polymer film on a coating surface, thereby effectively avoiding the condition of being unfavorable for processing in the production process.
Description
Technical Field
The invention belongs to the field of wet-process non-woven fabrics, and particularly relates to a semipermeable membrane support material and a preparation method thereof.
Background
In the fields of seawater desalination, deep purification of drinking water, domestic sewage treatment, drug concentration, hemodialysis, food concentration and the like, a semipermeable membrane is taken as a high-efficiency filter material, and gradually receives more and more attention, application and popularization with higher efficiency and lower use cost. Generally, a semipermeable membrane is made of synthetic resins such as cellulose-based resins, polyester-based resins, polysulfone-based resins, polyamide-based resins, and fluororesins, and these materials have low bulk strength when used as a semipermeable membrane, and are difficult to stably operate for a long period of time under rated operating conditions of the semipermeable membrane, and cannot be used alone. As a solution, the semipermeable membrane needs a support material to provide strength when used, i.e., a manner of combining it with a nonwoven fabric as a support material.
US6919026 discloses a method for preparing a reverse osmosis membrane support material, which utilizes chemical fiber and conventional paper making methods including cylinder mould, fourdrinier and inclined net to prepare the support material. Although this patent proposes a method for supporting a reverse osmosis membrane, it does not solve many problems in the actual use of the support material.
Chinese patent CN 102574070 discloses a preparation method of a reverse osmosis membrane supporting material. The patent proposes a support material that distinguishes between a coated side and a non-coated side, wherein the ratio of the smoothness of the non-coated side to the coated side is from 5.0:1.0 to 1.1: 1.0. The adhesive property between the semipermeable membrane and the supporting material is ensured through the different smoothness of the coated surface and the non-coated surface, and the condition of the infiltration of the semipermeable membrane solution is prevented. However, simply defining the properties of the support material by the ratio of coated to uncoated side smoothness is not a reliable way to direct the product.
Chinese patent CN 102413909 discloses a semipermeable membrane support material with a three-layer structure. The invention provides a non-woven fabric which is composed of a low-melting-point melt-blown layer as a middle layer and spunbond layer long fibers on two sides. And the long fiber spun-bonded non-woven fabric on the two sides is bonded through hot-pressing and melting of the middle layer. The material obtained by the process has the advantages that the process is complicated, and the low-melting-point fibers of the intermediate melt-blown layer cannot be subjected to higher-temperature treatment in the subsequent processing process of the semipermeable membrane, so that the performance of the final product is greatly influenced.
Chinese patent CN103429327 discloses a semipermeable membrane support material prepared by using a mode of hot pressing together of upper and lower sheet layers with different stretching ratios, which can avoid the phenomenon of middle warping after coating polysulfone solution. Although the invention patent tries to solve the problem of warping after coating the polysulfone solution by using an upper and lower layer structure asymmetric treatment mode, the warping phenomenon of the coating surface is negatively acted by enabling the support material to warp in the opposite direction of the coating surface in advance, the support material has warping when not coated, and a plurality of problems are caused in the next processing. In addition, the problem of too large a stretch ratio of one of the layers, which affects the strength of the final product, is not effectively solved.
From the prior art, the proven and approved scientific method for preparing semipermeable membrane support materials by adopting a multilayer structure still cannot provide a better solution to the problem of warping of the support materials after heat treatment.
The support material has a ratio of MD (machine direction, i.e. the direction of production of the device) tensile strength E1 to CD (cross direction, i.e. perpendicular to the direction of production) tensile strength E2 of k, i.e. the aspect ratio k ═ E1/E2. The aspect ratio k represents the ratio of the MD tensile strength to the CD tensile strength, and a larger value of k indicates a larger increase in the MD tensile strength to the CD tensile strength. The smaller the k value, the closer the MD tensile strength is to the CD tensile strength. For a certain fiber raw material determined and formulated supporting material, the orientation of the fiber in the MD and CD directions determines the tensile strength of the fiber in the MD and CD directions, and more orientation of the fiber in the MD direction leads to more tensile strength in the MD direction. That is, a larger k value represents more MD direction fiber orientation, while a smaller k value represents less MD direction fiber orientation.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a semipermeable membrane support material and a preparation method thereof, when the semipermeable membrane support material prepared by the method is applied to support materials of reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes and the like, the method and the material can ensure that the semipermeable membrane cannot be curled in the preparation process of the semipermeable membrane and effectively avoid the influence of the curling of the support material on processing and use except that excellent mechanical strength can be provided, the semipermeable membrane solution is prevented from being penetrated, and the sufficiently strong bonding strength between the semipermeable membrane and the semipermeable membrane is ensured.
The purpose of the invention is realized by the following technical scheme: a semipermeable membrane support material which is a sheet-like material obtained by laminating two nonwoven fabric layers having different aspect ratios k and subjecting the laminate to heat and pressure treatment, wherein the k value of the nonwoven fabric layer on the coated surface side of the sheet-like material is more than 1.5, and the k value of the nonwoven fabric layer on the non-coated surface side is less than 1.0. The non-woven fabric is formed by gathering short fibers, k is E1/E2, E1 is the tensile strength of the non-woven fabric in the equipment production direction, and E2 is the tensile strength of the non-woven fabric in the direction perpendicular to the equipment production direction.
Further, the k value of the nonwoven fabric layer of the sheet-like material on the coated surface side is preferably 1.5 to 3, and the k value of the nonwoven fabric layer of the sheet-like material on the non-coated surface side is preferably 0.3 to 1.0.
Further, the k value of the nonwoven fabric layer of the sheet-like material on the coated surface side is more preferably 1.5 to 2.5, and the k value of the nonwoven fabric layer of the sheet-like material on the non-coated surface side is more preferably 0.5 to 1.0.
Further, the temperature of the heating and pressurizing treatment is 120-400 ℃, and the pressure is 200-5000N/cm.
Furthermore, the short fiber is selected from polyester fiber, polyamide fiber, aramid fiber and polyimide fiber. The diameter of the short fiber is 0.5-20 μm, and the length is 3-15 mm.
Further, the short fiber preferably has a diameter of 3 to 15 μm and a length of 3 to 10 mm.
Compared with the prior art, the invention has the following beneficial effects:
1. the semipermeable membrane supporting material is compounded through a multilayer structure and has a coating surface and a non-coating surface, wherein the coating surface is used for coating a semipermeable membrane solution, so that the fibers of the coating surface and the semipermeable membrane form stronger bonding force.
2. The semipermeable membrane support material of the present invention has a smaller non-coated aspect ratio k, i.e., greater CD-direction tensile strength. Heat treatment at less than 250 c does not produce MD or CD curl. Such a property ensures that the support material will not unnecessarily curl during subsequent processing, particularly in the CD direction. It is well known that the MD direction, even if curling occurs, will cancel out under traction force due to the traction force. However, CD is not stressed during processing or use, and if curl is produced, the effect cannot be eliminated. The semipermeable membrane support material provided by the invention has the advantages that the formed semipermeable membrane support material is not curled due to the reasonable k value, and the formed semipermeable membrane support material is not curled in the processing process, so that the performance is ensured, and the processing is greatly facilitated.
Drawings
FIG. 1 is a schematic diagram of a semipermeable membrane support material according to an embodiment of the present invention;
FIG. 2 is a flow diagram of a process for coating a polymeric membrane with a semipermeable membrane support material;
in the figure, a sheet material 100, a coated surface 101, a non-coated surface 102, a nonwoven fabric layer 001A of the sheet material on the coated surface side, a nonwoven fabric layer 001B of the sheet material on the non-coated surface side, an unwinding roller 200, a winding roller 201, a guide roller 220, a coating roller 210, a coating device 230, a guide roller 240, a coagulation tank 250, a first washing tank 251, and a second washing tank 252.
Detailed Description
The semipermeable membrane support material of the present invention will be further described with reference to specific examples. It should be noted that the described embodiments are only intended to enhance the understanding of the present invention, and do not have any limiting effect on the present invention.
As the semipermeable membrane support material disclosed by the patent of the invention, a polymer membrane layer formed by a polymer is coated on one side of the semipermeable membrane support material, and a proper separation membrane, such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane, is prepared through necessary subsequent processing processes. In general, a polymer film is formed by preparing a polymer into a solution with a certain concentration, coating the solution on the surface of a support material, and then removing a solvent through a drying process. During the drying process, the solvent is volatilized to generate stress concentration, and simultaneously, the polymer is gradually separated out from the solvent and becomes solid again, and the stress generated by the two causes the whole film to curl towards the side of the polymer film layer. The curled membrane can affect subsequent processing and needs to be solved. The invention enables the coating surface to have a larger k value and the non-coating surface to have a smaller k value by purposefully controlling the aspect ratio k value of the non-woven fabric layer constituting the support material, namely the ratio E1/E2 of the MD tensile strength E1 and the CD tensile strength E2, so that the non-coating surface has a larger CD tensile strength, and even if stress is generated after the coating surface is coated with a polymer film, the larger CD tensile force of the non-coating surface can avoid the phenomenon of curling.
As shown in fig. 1, the semipermeable membrane support material is formed by stacking a plurality of layers of nonwoven fabrics formed by collecting short fibers and then heating and pressurizing the stacked layers. The non-woven fabric layer is 2 layers. The support material is a sheet material 100 formed by stacking a plurality of short fiber-gathered nonwoven fabric layers 001 and then heating and pressurizing the stack. The sheet material 100 remains uncrimped after heat treatment at a temperature of from room temperature to 250 ℃. The coated surface 101 of the sheet-like material 100 does not curl even in the heat treatment after the coating of the separation film.
The coated side 101 of the sheet material 100 is used to coat the semipermeable membrane solution to create sufficient adhesion between the semipermeable membrane and the sheet material 100 to allow the semipermeable membrane to be securely attached to the sheet material 100. The coated side 101 has better uniformity than the non-coated side 102, as indicated by the higher porosity and pore size distribution of the coated side 101 than the non-coated side 102. Meanwhile, the smoothness of the coated side 101 is superior to the smoothness of the non-coated side 102. To obtain better porosity and pore size distribution, the nonwoven layer near the coated side 101 is often made with lower dispersion and wire concentration by selecting fibers with finer diameters, and the side is set at a higher hot pressing temperature during hot pressing. If more than two different specifications of fibers are selected, it is necessary to ensure that the specification difference between the fibers is not too large, and the large difference can increase the pore size distribution and the porosity.
In fig. 1, MD denotes machine direction, i.e., the device production direction, and CD denotes cross direction, i.e., perpendicular to the device production direction. The nonwoven fabric layer 001A of the sheet material on the coated surface side has a higher k value than the nonwoven fabric layer 001B of the sheet material on the non-coated surface side. The k value of the nonwoven fabric layer 001A of the sheet-like material on the side closer to the coating surface is greater than 1.5, preferably 1.5 to 3, more preferably 1.5 to 2.5. The k value of the nonwoven fabric layer 001B of the sheet-like material on the side closer to the non-coated surface is less than 1.0, preferably 0.3 to 1.0, more preferably 0.5 to 1.0. A larger k value indicates a higher tensile strength of the nonwoven layer in the MD, indicating that the staple fibers are more prone to MD orientation. A lower k value indicates a greater tensile strength of the nonwoven layer in the CD direction, and a k value less than 1 indicates a greater tensile strength of the nonwoven layer in the CD direction. For the sheet-shaped supporting material obtained by stacking a plurality of non-woven fabric layers, when the k value difference between the layers is more than 0.5, the obtained sheet-shaped supporting material has excellent MD and CD strength, and the higher CD strength of the non-coating surface can ensure that the whole sheet-shaped supporting material can still maintain flat appearance after being subjected to processes such as hot pressing, high-temperature treatment and the like.
The non-woven fabric layer 001 constituting the semipermeable membrane support material is prepared by a wet papermaking method or a dry papermaking method. The wet paper making equipment is generally produced by a fourdrinier wire, a cylinder mould, an inclined wire, a clamping wire and a side wave type paper machine, and the dry paper machine carries out lapping by conveying fibers through air flow. Among them, in order to make the nonwoven fabric have better uniformity, it is preferable to use a wet papermaking method. Different k values can be obtained by optimizing the papermaking process and setting different fiber dispersion concentrations, upper wire concentration, pulp speed, vehicle speed and vehicle/pulp speed ratio.
The heating and pressurizing treatment method of the semipermeable membrane support material has the hot pressing temperature of 120-400 ℃, the pressure of 200-5000N/cm and the treatment time of 0.01-60 seconds.
The short fibers are polyester fibers, polyamide fibers, aramid fibers and polyimide fibers. The staple fibers used have a diameter of 0.5 to 20 μm, preferably 3 to 15 μm. The staple length used is 3 to 15mm, preferably 3 to 10 mm.
As shown in fig. 2, in the semipermeable membrane support material according to the present invention, a polymer membrane is coated on the coated surface 101 side of the sheet material 100 in the subsequent processing process, for example, a reverse osmosis membrane or an ultrafiltration membrane is prepared, a polysulfone solution is coated on the coated surface side of the support material, i.e., a polysulfone solution is prepared by dissolving a certain amount of polysulfone resin in N, N-Dimethylformamide (DMF), the mass fraction of the polysulfone solution is 30 wt%, the sheet material 100 is unreeled from the unreeling roller 200, and enters the coating roller 210 through the guide roller 220, the polysulfone solution is coated on the coated surface 101 from the coating device 230, and is scraped by the scraper to ensure that the amount of the polysulfone solution coated on the coated surface 101 is constant, and then the sheet material 100 enters the coagulation tank 250 through the guide roller 240, water exists in the coagulation tank 250 as a poor solvent for polysulfone, and after the polysulfone solution coated on the coated surface 101 contacts with water in the coagulation tank 250, polysulfone will slowly precipitate out of the solution and eventually solidify on the coated surface 101, forming a denser polymer film layer with smaller pore sizes. In the actual production line, the branch sheet material 100 is also continuously guided by the guide roller 240 into the first washing tank 251 and the second washing tank 252 because the precipitation of water in the coagulation tank is not fast enough and further precipitation of the washing tank is required, while the washing tank has another greater function of removing the solvent DMF in the coating film and the support material. And then wound on a wind-up roll 201. The formation of the polymer film during the coating process creates internal stresses, and the treatment with the solvents DMF and water and the subsequent desolventizing process create internal stresses, which can cause the product to curl toward the side of the polymer film. If the degree of curling is too great, it will obviously affect the transport, receipt and subsequent processing of the product, as is often seen in the previous patents of the same type. There are also patents which teach the preparation of a support material that first curls toward the uncoated side to counteract the curling that occurs when coating a polymer film. Although this method can offset the curling phenomenon to some extent, it is obviously not a scientific solution. The present inventors have found that when the difference in k value between the nonwoven fabric layer 001A on the coated surface side of the sheet-like material and the nonwoven fabric layer 001B on the non-coated surface side of the sheet-like material is 0.5 or more and the k value of the nonwoven fabric layer 001B on the non-coated surface side of the sheet-like material is 1.0 or less, excellent lateral support force can be obtained and a certain degree of internal stress can be generated in time, and the occurrence of lateral shrinkage can be prevented by this lateral support force. Further, the combination of the nonwoven fabric layer 001A on the side of the sheet-like material closer to the coated surface and the nonwoven fabric layer 001B on the side of the sheet-like material closer to the non-coated surface ensures that the overall strength is balanced even when the two layers have variations in the longitudinal and transverse strengths. In order to ensure a good overall strength of the sheet-like material 100, the k value of the nonwoven fabric layer 001A on the coated side of the sheet-like material should not be too large, the k value of the nonwoven fabric layer 001B on the non-coated side of the sheet-like material should not be too small, and both too large and too small values of k would result in too low a strength in one direction, which would affect the MD and CD strengths of the final product.
In the embodiment of the patent, the reference standards of the related technical indexes of the semipermeable membrane supporting material are as follows:
the "gram weight" of the semipermeable membrane support material is determined according to the method of GB/T451.2-2002.
The "thickness" of the semipermeable membrane support material is determined according to the method of GB/T451.3-2002.
The "tensile strength" of the semipermeable membrane support material was determined according to GB/T12914-.
The "fuzz" property of the semipermeable membrane support material was measured according to the method described in chinese patent CN 103429327A. The method comprises the following specific steps: a nonwoven fabric having a width of 30cm was folded in half, and the number of fluffs of the fibers produced at the fold was counted by visual observation or a microscopic method by rolling a cylindrical roller made of stainless steel and having a diameter of 5cm and a length of 40cm three times back and forth at the fold. At least three different positions were tested and the average calculated.
0-10: the fuzz was low and was very good.
11-20: at a good level.
21-30 pieces: the lower level of use.
More than 31: at an unusable level.
The "permeability" of the semipermeable membrane support material was determined according to the method mentioned in chinese patent CN 103429327A. The method comprises the following specific steps: and (3) coating the DMF solution of polysulfone on the coating surface of the support material by using a constant-speed coating device, and then washing and drying. SEM testing of the sections of the support material coated with polysulfone was performed, and polysulfone was observed and measured through a ruler to permeate the support material to calculate the permeation thickness as a percentage of the total thickness of the support material and is reported as permeability.
The melting point in the present invention patent is measured by a differential thermal scanner (DSC), and it should be noted that the melting point generally corresponds to the temperature corresponding to the melting peak, and in the case of a melting peak having a large peak width, the melting point also refers to the temperature corresponding to the peak position of the melting peak.
"air permeability" of the semipermeable membrane support material was measured in cc/cm using a Frazier-type testing machine in accordance with JIS L10962s。
The semipermeable membrane support material was tested for permeability while observing whether it would bend toward the coated side.
The crimpability of the semipermeable membrane support material was visually observed, and it was marked as "●" when the crimp occurred, and as "o" when no crimp was observed.
The effects of the invention will be explained in more detail by the following examples, before which different nonwoven layers are first prepared.
[ non-woven fabrics layer I ]
60% by mass of drawn polyethylene terephthalate (PET) fibers having a diameter of 6 μm and a length of 5mm, and 40% by mass of undrawn PET fibers having a diameter of 8 μm and a length of 3 mm. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 240 ℃ and the pressure is 3000N/cm. Thus, a sample base paper I after hot pressing of the nonwoven fabric layer I is obtained.
The base paper I was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio E1/E2 is the aspect ratio k of the base paper I, i.e. the nonwoven layer I. The grammage of the base paper I was also measured to be 35g/m2。
The gram weight of the non-woven fabric layer I is 35g/m2The aspect ratio k is 1.5.
[ non-woven fabrics layer II ]
69% by mass of drawn polyethylene terephthalate (PET) fibers having a diameter of 5 μm and a length of 8mm, and 31% by mass of undrawn PET fibers having a diameter of 12 μm and a length of 10 mm. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 250 ℃, and the pressure is 1800N/cm. Thus, the sample base paper II after the non-woven fabric layer II is hot-pressed is obtained.
The base paper II was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio E1/E2 is the aspect ratio k of the base paper II, i.e. the non-woven fabric layer II. The grammage of the base paper I was also measured to be 38g/m2。
The gram weight of the non-woven fabric layer II is 38g/m2And the aspect ratio k is 2.
[ non-woven fabric layer III ]
69% by mass fraction of poly (phenylene terephthalamide) fibers, 1 μm in diameter, 15mm in length, and 31% by mass fraction of a partial terephthalic acid phenylene diamine pulp. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 320 ℃, and the pressure is 2500N/cm. This gave a sample base paper III after hot pressing of the nonwoven fabric layer III.
The base paper III was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio E1/E2 is the aspect ratio k of the base paper III, i.e. the nonwoven layer III. While measuring the grammage of the base paper III to be 33g/m2。
The gram weight of the non-woven fabric layer III is 33g/m2And the aspect ratio k is 3.
[ non-woven fabrics layer IV ]
70% by mass of drawn polyethylene terephthalate (PET) fibers having a diameter of 6 μm and a length of 5mm, and 30% by mass of undrawn PET fibers having a diameter of 8 μm and a length of 3 mm. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 240 ℃ and the pressure is 3000N/cm. This gave a sample base paper IV after hot pressing of the nonwoven fabric layer IV.
The base paper IV is cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio E1/E2 is the aspect ratio k of the base paper IV, i.e. the nonwoven layer IV. The basis paper IV was also measured to have a grammage of 35g/m2。
The gram weight of the non-woven fabric layer IV is 35g/m2The aspect ratio k is 0.8.
[ non-woven fabrics layer V ]
70% by mass of drawn polyethylene terephthalate (PET) fibers having a diameter of 6 μm and a length of 5mm, and 30% by mass of undrawn PET fibers having a diameter of 8 μm and a length of 3 mm. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 240 ℃ and the pressure is 3000N/cm. This gave a sample base paper V after hot pressing of the nonwoven fabric layer V.
The base paper V was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. Edge ofThe tensile strength of the specimens cut in the MD direction was E1, and the tensile strength of the specimens cut in the CD direction was E2. The ratio E1/E2 is the aspect ratio k of the base paper V, i.e. the nonwoven layer V. The grammage of the base paper V was measured at the same time to be 42g/m2。
The gram weight of the non-woven fabric layer V is 42g/m2The aspect ratio k is 1.0.
[ non-woven fabrics layer VI ]
69% by mass fraction of poly (phenylene terephthalamide) fibers, 1 μm in diameter, 15mm in length, and 31% by mass fraction of a partial terephthalic acid phenylene diamine pulp. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 320 ℃, and the pressure is 2500N/cm. This gave a sample base paper VI after hot pressing of the nonwoven layer VI.
The base paper VI was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio E1/E2 is the aspect ratio k of the base paper VI, i.e. the nonwoven layer VI. The grammage of the base paper III was simultaneously measured to be 45g/m2。
The gram weight of the non-woven fabric layer VI is 45g/m2The aspect ratio k is 0.3.
[ non-woven fabrics layer VII ]
70% by mass of drawn polyethylene terephthalate (PET) fibers having a diameter of 20 μm and a length of 10mm, and 30% by mass of undrawn PET fibers having a diameter of 12 μm and a length of 3 mm. After dispersion in the tank, an aqueous slurry of 0.01% concentration was prepared. After the slurry is conveyed to the inclined wire paper machine, the paper machine travelling speed and the flow velocity of the slurry are adjusted to regulate and control the k value of the aspect ratio. The hot pressing temperature is 240 ℃ and the pressure is 3000N/cm. This gave a sample base paper VII after hot pressing of the nonwoven fabric layer V.
The base paper VII was cut into a size of 20mm in width and 100mm in length, and subjected to a tensile strength test. The tensile strength of the sample strips was E1 when cut in the MD direction and E2 when cut in the CD direction. The ratio of the two is E1/E2VII, i.e. the aspect ratio k of the nonwoven layer VII. While measuring the grammage of the base paper VII to be 42g/m2。
The gram weight of the non-woven fabric layer VII is 42g/m2The aspect ratio k is 0.7.
Example 1
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And superposing a non-woven fabric layer I and a non-woven fabric layer IV, and hot-pressing at the temperature of 240 ℃ and under the pressure of 3000N/cm. Obtaining the semipermeable membrane support material. The gram weight is 70g/m2The aspect ratio k is 1.32. Wherein, the surface of the non-woven fabric layer I is a coating surface.
Example 2
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And (3) overlapping the non-woven fabric layer II and the non-woven fabric layer IV, wherein the hot pressing temperature is 240 ℃, and the pressure is 2300N/cm. Obtaining the semipermeable membrane support material. The gram weight is 73g/m2The aspect ratio k is 1.73. Wherein, the surface of the non-woven fabric layer II is a coating surface.
Example 3
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And a non-woven fabric layer III and a non-woven fabric layer VI are superposed, and the hot pressing temperature is 320 ℃ and the pressure is 2500N/cm. Obtaining the semipermeable membrane support material. The gram weight is 78g/m2The aspect ratio k is 2.62. Wherein, the surface of the non-woven fabric layer III is a coating surface.
Example 4
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And (3) superposing the non-woven fabric layer I and the non-woven fabric layer V, and carrying out hot pressing at the temperature of 240 ℃ and the pressure of 1800N/cm. Obtaining the semipermeable membrane support material. The gram weight is 77g/m2The aspect ratio k is 1.63. Wherein, the surface of the non-woven fabric layer I is a coating surface.
Example 5
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And a non-woven fabric layer I and a non-woven fabric layer VII are superposed, and the hot pressing temperature is 240 ℃ and the pressure is 2200N/cm. Obtaining the semipermeable membrane support material. The gram weight is 77g/m2The aspect ratio k is 1.46. Wherein, the surface of the non-woven fabric layer I is a coating surface.
Comparative example 1
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And (3) superposing a non-woven fabric layer IV and a non-woven fabric layer I, and hot-pressing at the temperature of 240 ℃ and under the pressure of 2500N/cm. Obtaining the semipermeable membrane support material. The gram weight is 70g/m2The aspect ratio k is 1.32. Wherein, the surface of the non-woven fabric layer IV is a coating surface.
Comparative example 2
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And (3) overlapping the non-woven fabric layer I and the non-woven fabric layer II, and hot-pressing at the temperature of 240 ℃ and under the pressure of 2500N/cm. Obtaining the semipermeable membrane support material. The gram weight is 73g/m2The aspect ratio k is 1.68. Wherein, the surface of the non-woven fabric layer I is a coating surface.
Comparative example 3
When the supporting material is prepared, the non-woven fabric layers which are not subjected to hot pressing are combined and overlapped in pairs, and then hot pressing is carried out.
And (3) superposing a non-woven fabric layer V and a non-woven fabric layer VII, and carrying out hot pressing at the temperature of 240 ℃ and under the pressure of 2700N/cm. Obtaining the semipermeable membrane support material. The gram weight is 84g/m2The aspect ratio k is 0.91. Wherein, the surface where the non-woven fabric layer V is positioned is a coating surface.
As shown in fig. 2, the support materials according to the examples and comparative examples were sequentially coated, wherein the concentration of the polysulfone solution, i.e., the mass fraction of polysulfone was 15%. After coating the resulting polymer film, it was dried at 110 ℃. The complex was observed for crimpability.
The results of the tests and evaluations carried out on the semipermeable membrane support materials of examples 1 to 5 and comparative examples 1 to 3 are shown in the following table.
In examples 1 to 5, the aspect ratio k of the upper and lower nonwoven fabric layers of the semipermeable membrane support material was set in accordance with the requirements of the present invention, i.e., the k value of the coated-side nonwoven fabric layer was large, the k value of the non-coated-side nonwoven fabric layer was small, and the difference between them was larger than 0.5. It was found by testing that the support material did not develop curl after preparation, and also did not develop curl after coating with the polymer film. Achieving the performance required by the present invention.
Comparing comparative example 1 with examples 1 to 5, it was found that when the k value of the nonwoven fabric layer on the coated side was smaller than that on the non-coated side by a difference of less than 0.5, no curling occurred after the support material was prepared, and curling occurred after the polymer solution was applied. It can be seen that comparative example 1 is substantially the same as example 1 except that example 1 has a large k value as the coated surface, and comparative example 1 has a small k value as the coated surface. From the above analysis, it is found that although the coated surface of comparative example 1 also has a high CD strength, the stress is generated on the whole because the side is coated with the polymer film, and the non-coated surface side has a high k value and a low CD strength, and cannot generate enough force to balance the stress generated on the side of the polymer film, which finally results in curling after coating the polymer film.
Comparing comparative example 2 with examples 1 to 5, it was found that when the k value of the coated-side nonwoven fabric layer was smaller than that of the non-coated-side nonwoven fabric layer by a difference of less than 0.5, the support material still developed curl after coating the polymer film. Meanwhile, the high aspect ratio of the two non-woven fabric layers indicates that the CD-direction strength is low, and no non-woven fabric layer can provide enough CD-direction tensile force, so that the support material can be curled after being hot-pressed.
Comparing comparative example 3 with examples 1 to 5, it can be seen that when the nonwoven fabric layers on both sides of the support material have an aspect ratio of less than 1.0, the occurrence of curling phenomenon is also prevented after the polymer film is coated. However, it is noted that since the aspect ratios of both nonwoven fabric layers are less than 1.0, the MD strength is low, and sufficient MD tensile force cannot be generated after drying, the support material may curl in the MD.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the claims.
Claims (6)
1. A semipermeable membrane support material, which is a sheet-like material obtained by laminating two nonwoven fabric layers having different aspect ratios k and then subjecting the laminate to heat and pressure treatment, wherein the k value of the nonwoven fabric layer on the side of the sheet-like material closer to the coated surface is greater than 1.5, and the k value of the nonwoven fabric layer on the side closer to the non-coated surface is less than 1.0; the non-woven fabric is formed by gathering short fibers, k is E1/E2, E1 is the tensile strength of the non-woven fabric in the equipment production direction, and E2 is the tensile strength of the non-woven fabric in the direction perpendicular to the equipment production direction.
2. The semipermeable membrane support material according to claim 1, wherein the sheet material has a k value of 1.5-3 in the non-woven fabric layer on the coated side and a k value of 0.3-1.0 in the non-woven fabric layer on the non-coated side.
3. The semipermeable membrane support material according to claim 2, wherein the sheet material has a k value of 1.5-2.5 in the non-woven fabric layer on the coated side and a k value of 0.5-1.0 in the non-woven fabric layer on the non-coated side.
4. The semipermeable membrane support material according to claim 1, wherein the temperature of the heating and pressurizing treatment is 120-2 。
5. The semipermeable membrane support material according to claim 1, wherein the short fibers are selected from polyester fibers, polyamide fibers, aramid fibers, and polyimide fibers; the diameter of the short fiber is 0.5-20 μm, and the length is 3-15 mm.
6. The semipermeable membrane support material according to claim 5, wherein the short fibers have a diameter of 3-15 μm and a length of 3-10 mm.
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