JP2013248589A - Method for producing fiber reinforced porous hollow fiber membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fiber reinforced porous hollow fiber membrane which is excellent not only in permeation performance and separation membrane performance but also in mechanical characteristics.SOLUTION: In a method for producing a fiber reinforced porous hollow fiber membrane, a spinning solution for forming a porous membrane is made to adhere to the outer peripheral surface of a cylindrical support made of a fiber material and a porous membrane layer is provided on the outer surface of the support made of the fiber material by solidifying an adhered material. In the method for producing the porous hollow fiber membrane, the spinning solution for forming the porous membrane is applied onto the outer peripheral surface of the support made of the fiber material in a state where a heat shrinkable tube is inserted in the cylindrical part of the support made of the fiber material, is solidified and then is heated and a heat-shrinked tube is removed.

Description

  The present invention relates to a method for producing a fiber-reinforced porous hollow fiber membrane. More specifically, the present invention relates to a method for producing a fiber-reinforced porous hollow fiber membrane having excellent water permeability.

  Water purification treatment and membrane wastewater treatment by membrane filtration are easier to maintain and manage operation than conventional coagulation sedimentation filtration methods, and the quality of the treated water is also good. For this reason, the filtration operation using a porous membrane such as a precision filtration membrane or an ultrafiltration membrane is used for water treatment in the sewerage field for the purpose of sterilization and turbidity, and in the water supply field for the purpose of sterilization. Widely used in the field. In recent years, the use of porous membranes has expanded, such as humidification of fuel cell stack membranes using porous membranes.

  The porous membrane is required not only to have permeation performance and separation membrane performance but also to have mechanical properties because it is used continuously without breaking for a long period of time. For example, when used in the membrane separation activated sludge method in the sewerage field, the membrane is vigorously shaken during aeration for removing clogged filtrate and supplying oxygen to the activated sludge. When it is used as a humidifying membrane for a fuel cell stack diaphragm, it must be able to withstand a large amount of air humidification of about 4000 NL / min.

  As a method for increasing the mechanical characteristics, there is a method for increasing the film thickness. However, as the film thickness is increased, the transmission performance is decreased.

  In addition, as a film that satisfies the requirements of mechanical properties, in Patent Documents 1 and 2, spinning is performed by dissolving a thermoplastic resin in a good solvent on the outer surface of a fiber material support that is meshed in a hollow fiber shape. A fiber-reinforced porous hollow fiber membrane obtained by applying or impregnating as a stock solution and coagulating with a coagulating liquid composed of a poor solvent of a thermoplastic resin has been proposed.

  Generally, a fiber-reinforced porous hollow fiber membrane is made to pass through a fiber material support from a nozzle (inner nozzle) at the center of a double annular spinning nozzle and discharge a spinning stock solution for forming a porous membrane from an outer nozzle. It is obtained by applying or impregnating the spinning solution on the outer surface of the fiber material support and solidifying it.

  However, when a constant tension is not applied to the support, the outer diameter of the support is not determined, and as a result, the gap between the inner peripheral surface of the film forming stock solution discharge part of the annular nozzle and the outer peripheral surface of the support changes. Therefore, the film-forming stock solution cannot be applied with a uniform thickness. On the other hand, when a constant tension is applied to the support, the support usually has an elastic property and therefore shrinks in the inner diameter direction, and the stitches Since the density increases, there may be a problem that the permeation performance of the hollow fiber membrane is lowered.

JP 2008-126199 A JP 2008-168224 A

  An object of the present invention is to provide a method for producing a fiber-reinforced porous hollow fiber membrane having excellent mechanical properties as well as permeation performance and separation membrane performance.

The object of the present invention is to provide a porous membrane layer on the outer surface of the fibrous material support by attaching the spinning solution for forming the porous membrane to the outer peripheral surface of the cylindrical fibrous material support and solidifying the adhered material. In the method for producing a porous hollow fiber membrane,
The spinning solution for forming a porous membrane was applied to the outer peripheral surface of the fiber material support with the heat-shrinkable tube inserted into the tubular part of the fiber material support, solidified, and then heat-shrinked. This is accomplished by removing the tube.

  According to the method of the present invention, a heat-shrinkable tube is inserted into the cylindrical interior of a cylindrical fiber material support, and the outer surface is coated or impregnated with a spinning stock solution, then solidified, and then heated to heat. Since the contracted tube is removed, it is possible to obtain a fiber-reinforced porous hollow fiber membrane in which the shrinkage rate of the inner diameter of the hollow fiber membrane is reduced and the cylindrical portion has no closed portion.

  The obtained fiber-reinforced porous hollow fiber membrane is not easily increased in the stitch density of the support due to shrinkage of the support made of fiber material that supports the cylindrical portion even if the support made of fiber material is flexible. Hollow fiber membranes can withstand aeration during water filtration, easily remove clogged filtration materials, and have a high permeation performance, making it possible to form membrane filtration modules with a compact module shape. It has excellent effects.

It is a cross-sectional enlarged photograph of the porous hollow fiber membrane obtained in the Example. It is a cross-sectional enlarged photograph of the porous hollow fiber membrane obtained by the comparative example.

  The method for producing a fiber-reinforced porous hollow fiber membrane according to the present invention includes spinning a porous membrane on the outer peripheral surface of a fiber material support in a state where a heat-shrinkable tube is inserted into a tubular part of the fiber material support. After applying the undiluted solution and solidifying it, the tube that has been heat-shrinked by heating is removed to produce a porous hollow fiber membrane in which a porous membrane layer is provided on the outer surface of the fiber material support. Since a heat-shrinkable tube is inserted into the cylindrical interior of the fiber material support and the spinning solution is applied or impregnated on the outer surface and then solidified, it is possible to suppress radial shrinkage of the support Thus, it is possible to obtain a fiber-reinforced porous hollow fiber membrane in which the cylindrical portion does not have a blocking portion.

  As the hollow fiber material support, any conventionally used fiber material support can be used without particular limitation, and preferably braided support, braided support, such as monofilament, multifilament, Cylindrical nets such as spun yarn are used.Specifically, the thickness is 0.15 to 0.5 mm, the yarn fineness is 200 to 600 dtex, the number of batting is 16 to 40, polyester, polypropylene, polyethylene, rayon, vinylon, polyamide, Examples thereof include organic fiber base materials such as polyimide and aramid, and polyester is preferably used.

  As the heat-shrinkable tube, a tube having an outer diameter before shrinkage of 50% or more, preferably 60% or more of the inner diameter of the support is used from the viewpoint of suppressing shrinkage of the fiber material support. From the viewpoint of workability, it is preferable that the outer diameter after shrinkage is 80% or less, more preferably 70% or less of the inner diameter of the support.

  Examples of such heat-shrinkable tubes include those made of polyolefin resin, silicone resin, polyvinyl chloride resin, polyvinylidene fluoride resin, polyethylene terephthalate resin, polytetrafluoroethylene resin, and preferably made of hollow fiber membranes. A silicone resin that shrinks around 100 ° C., which is the drying temperature during film formation, is used. Further, as its properties, those having a smooth surface and having elasticity are preferably used from the viewpoint of ease of insertion into the support and ease of removal from the support.

  The method for disposing the heat-shrinkable tube inside the support is not particularly limited as long as the heat-shrinkable tube can be disposed on the cylindrical portion of the fiber material support, but is supported around the heat-shrinkable tube. Examples thereof include a method of knitting a body and a method of directly inserting a heat-shrinkable tube into a cylindrical portion of a support.

  The spinning solution for forming the porous hollow fiber membrane is attached to the outer peripheral surface of the fiber material support in which the heat-shrinkable tube is inserted into the cylindrical portion. The spinning stock solution is adhered to the outer peripheral surface of the fiber material support. The spinning stock solution discharged from the outer nozzle of the double annular spinning nozzle is discharged to the outer surface of the fiber material support that passes through the inner nozzle of the double annular spinning nozzle. Examples thereof include a method of coating, a method of immersing the fiber material support in a container containing the spinning stock solution for a certain period of time, and a method of continuously spraying and spraying the spinning stock solution on the surface of the fiber material support. Is a method in which a spinning solution is applied to the outer surface of a fiber material support that passes through the inner nozzle together with a heat-shrinkable tube using a double annular spinning nozzle. Here, when the fiber material support is passed through the inner nozzle of the double annular spinning nozzle, generally a tension of about 4 to 50 N is applied to the support.

  The spinning dope contains a material for producing a hollow fiber membrane and a solvent. As the hollow fiber membrane production material, any of the known hollow fiber membrane-forming materials (polymers) can be used. For example, cellulose-based materials such as cellulose acetate, cellulose propionate, cellulose butyrate, regenerated cellulose, or a mixture thereof. Examples thereof include hydrophobic polymers such as materials, hydrophilic polymers such as polyvinyl alcohol, polysulfone resins, polyethersulfone resins, polyvinylidene fluoride resins, polyacrylonitrile resins, polyimide resins, polyaramid resins, polypropylene resins, and polyethylene resins. As the solvent, alcohols and aprotic polar solvents such as dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone are preferably used.

  The support made of fiber material to which the spinning solution for forming the porous hollow fiber membrane is adhered is preferably coagulated with a coagulating liquid by a dry-wet spinning method or a wet spinning method, and after washing and drying, A fiber-reinforced porous hollow fiber membrane is formed by removing the shrinkable tube. As a method for removing the heat-shrinkable tube, for example, a method in which it is cut to a predetermined length and then heated to the shrinkage temperature of the heat-shrinkable tube to reduce the outer diameter of the heat-shrinkable tube and then pulled out, a hollow fiber membrane is used. Examples include a method of performing heat drying in a state of being wound around a bobbin, and then cutting to a predetermined length and drawing out from the inside.

  Next, the present invention will be described with reference to examples.

Example Heat-shrinkable tube made of silicone resin (outer diameter 1.3 mm, heat-shrinking temperature: 80 to 80 mm) on the cylindrical portion of a polyester sleeve (strand assembly, outer diameter 2.4 mm, inner diameter 2.0 mm) which is a support made of tubular fiber material 250 ° C) is passed through the inner nozzle of a 2.5 mm inner diameter double annular spinning nozzle under a moving speed of 1.5 m / min with 5 N tension applied, and double annular spinning. Apply the spinning stock solution pumped and discharged from the outer nozzle of the double ring spinning nozzle to the outer surface of the support that passed through the inner nozzle of the nozzle using a gear pump, and coagulate with the coagulation liquid (40 ° C hot water) Then, cutting to a predetermined length was performed. Next, it was washed in 100 ° C. water for 1 hour, dried in an oven at 80 ° C., and removed by pulling out the heat-shrinkable silicone tube to obtain a porous polyphenylsulfone resin hollow fiber membrane. Here, as the spinning dope, a polyphenylsulfone resin (Amoco product RADEL R5000) 20% by weight, polyvinylpyrrolidone (ISP product K-30G) 15% by weight and dimethylacetamide 65% by weight was used.

The obtained hollow fiber membrane has an outer diameter of 1.9 mm, an inner diameter of 1.2 mm, an inner diameter shrinkage of 40%, no defects are observed in the spinning solution application part, and the water vapor transmission rate is 0.40 g / cm ² / min / MPa.

Comparative Example In the examples, a support without a heat-shrinkable tube was used. The obtained porous polyphenylsulfone resin hollow fiber membrane has an outer diameter of 1.6 mm, an inner diameter of 0.8 mm, an inner diameter shrinkage of 60%, and no defects were observed in the spinning solution application part, but the water vapor transmission rate was It was 0.14 g / cm ² / min / MPa.

  The porous hollow fiber membrane produced by the production method according to the present invention is excellent in permeation performance and mechanical properties, so that it can be used for various purposes such as from humidification, dehumidification, sewage treatment, water purification treatment to fuel cell. It can be effectively used as a functional film over a wide range of fields.

Claims (5)

A porous hollow fiber membrane in which a porous membrane layer is provided on the outer surface of a fibrous material support by adhering a spinning solution for forming a porous membrane to the outer peripheral surface of a cylindrical fibrous material support and solidifying the deposit. In the manufacturing method,
The spinning solution for forming a porous membrane was applied to the outer peripheral surface of the fiber material support with the heat-shrinkable tube inserted into the tubular part of the fiber material support, solidified, and then heat-shrinked. A method for producing a fiber-reinforced porous hollow fiber membrane, wherein the tube is removed.   The method for producing a fiber-reinforced porous hollow fiber membrane according to claim 1, wherein the spinning solution for forming a porous membrane is a dry-wet method or a wet-method spinning solution.   The method for producing a fiber-reinforced porous hollow fiber membrane according to claim 1 or 2, wherein the heat shrinkable tube has an outer diameter before heat shrinkage of 50% or more of a fiber material support inner diameter.   The method for producing a fiber-reinforced porous hollow fiber membrane according to claim 1, 2, or 3, wherein the heat-shrinkable tube has an outer diameter after heat shrinkage of 80% or less of the inner diameter of the fiber material support.   A fiber-reinforced porous hollow fiber membrane produced by the method for producing a fiber-reinforced porous hollow fiber membrane according to any one of claims 1 to 4.