JP5546992B2 - Method for producing porous hollow fiber membrane, porous hollow fiber membrane, module using porous hollow fiber membrane, filtration device using porous hollow fiber membrane, and water treatment method using porous hollow fiber membrane - Google Patents

Description

  The present invention relates to a method for producing a porous hollow fiber membrane, a porous hollow fiber membrane, a module using the porous hollow fiber membrane, a filtration device using the porous hollow fiber membrane, and a water treatment using the porous hollow fiber membrane. Regarding the method.

  In recent years, porous membranes such as ultrafiltration membranes and microfiltration membranes have been used for electrodeposition paint collection, removal of fine particles from ultrapure water, production of pyrogen-free water, enzyme concentration, sterilization / clarification of fermentation broth, etc. Used in a wide range of fields such as water, sewage and wastewater treatment. In particular, porous hollow fiber membranes are widely used because they have a high membrane packing density per unit volume and are effective in reducing the size of processing equipment. Such a porous hollow fiber membrane is required to have a high balance between actual liquid performance and mechanical and chemical strength from a practical viewpoint. As one solution to this problem, for example, Patent Document 1 discloses a method for producing a porous hollow fiber membrane that exhibits high mechanical strength by adding inorganic fine powder (hydrophobic silica).

JP-A-3-215535

  However, in the manufacturing method described in Patent Document 1, the inorganic fine powder is likely to aggregate, and the inorganic fine powder may not be uniformly kneaded. Thereby, since many independent pores that are not effectively used for filtration are formed, it is not possible to ensure communication, and a membrane having low actual liquid performance may be obtained. Therefore, there is room for further improvement regarding the formation of independent holes.

  The present invention has been made in order to solve the above-mentioned problems. A method for producing a porous hollow fiber membrane capable of ensuring a high communication property and obtaining a porous hollow fiber membrane having a high actual liquid performance, and a high communication property. Porous hollow fiber membrane having high performance and real liquid performance, module using the porous hollow fiber membrane, filtration device using the porous hollow fiber membrane, and water treatment method using the porous hollow fiber membrane The purpose is to provide.

  As a result of intensive investigations to solve the above problems, the present inventors have obtained a porous hollow fiber membrane from a melt-kneaded product containing a thermoplastic resin, an organic liquid, and inorganic fine powder by a thermally induced phase separation method. In the method, it is possible to provide at least one filter between the melt-kneading step and the hollow fiber molding step, and to discharge the melt-kneaded material after passing through the filter. In order to obtain a film, it was found to be extremely important, and the present invention was reached.

That is, the present invention is as follows.
(1) A melt-kneaded material containing a thermoplastic resin, an organic liquid and inorganic fine powder is discharged from an annular discharge port of a hollow fiber molding nozzle to form a hollow fiber-like material, and the hollow fiber-like material is cooled and solidified, and then the organic liquid And a method for producing a porous hollow fiber membrane by extracting and removing inorganic fine powder, from melt-kneading a thermoplastic resin, organic liquid and inorganic fine powder to discharging the melt-kneaded material into a hollow fiber shape to mold A method for producing a porous hollow fiber membrane, characterized in that a filter is provided in at least one place, and the melt-kneaded material is passed through the filter and then discharged and molded into a hollow fiber shape,
(2) The method for producing a porous hollow fiber membrane according to (1), wherein the time from when the melt-kneaded product passes through the filter until it is discharged is within 100 seconds,
(3) The method for producing a porous hollow fiber membrane according to (1) or (2), wherein the slit width of the filter is 1,000 to 120,000 times the primary particle diameter of the inorganic fine powder,
(4) The temperature at which the thermoplastic resin, the organic liquid and the inorganic fine powder are melt-kneaded, and the resin temperature when the melt-kneaded product is discharged from the discharge port are determined from the torque inflection temperature of the melt-kneaded product measured by a plastmill. The method for producing a porous hollow fiber membrane according to any one of (1) to (3), characterized in that it is high,
(5) The method for producing a porous hollow fiber membrane according to any one of (1) to (4), wherein the inorganic fine powder is hydrophobic silica,
(6) A porous hollow fiber membrane produced by the method for producing a porous hollow fiber membrane according to any one of (1) to (5),
(7) A porous hollow fiber membrane made of a thermoplastic resin, wherein a value obtained by dividing the porosity P _wet calculated from the weight of the impregnated liquid by the porosity P _dry calculated from the dry weight is 0.90. A porous hollow fiber membrane, wherein the membrane is 1.00 or less and 1.00 or less,
(8) The porous hollow fiber membrane according to (7), which has an isotropic three-dimensional network structure,
(9) The porous hollow fiber membrane according to (7) or (8), wherein the thermoplastic resin is polyolefin and polyvinylidene fluoride,
(10) A module using the porous hollow fiber membrane according to any one of (6) to (9),
(11) A filtration device using the porous hollow fiber membrane according to any one of (6) to (9),
(12) A water treatment method using the porous hollow fiber membrane according to any one of (6) to (9),
It is.

  According to the present invention, it is possible to obtain a porous hollow fiber membrane having few independent pores and high communication properties, that is, high actual liquid performance.

It is the schematic which shows an example of the porous hollow fiber membrane which concerns on one Embodiment of this invention. It is a figure which shows the structure of the hollow fiber membrane manufacturing apparatus which manufactures a porous hollow fiber membrane. It is sectional drawing which shows the structure of the discharge outlet of the nozzle for hollow fiber shaping | molding. It is a figure which shows the structure of a filter. It is a schematic diagram of an isotropic three-dimensional network structure. It is a microscope picture of an isotropic three-dimensional network structure. It is a schematic diagram of a spherical structure. It is a figure which shows the structure of a hollow fiber membrane module. It is a block diagram which shows an example of the filtration apparatus of a pressure filtration system. It is a table | surface which shows an evaluation result. It is a table | surface which shows an evaluation result.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  The method for producing a porous hollow fiber membrane according to the present invention is a method for producing a porous hollow fiber membrane using a thermally induced phase separation method, and is advantageous for obtaining a porous hollow fiber membrane having high strength. Thermally induced phase separation is a method in which a thermoplastic resin and a latent solvent (organic liquid) that does not dissolve this thermoplastic resin at room temperature but dissolves at high temperature are kneaded at high temperature to dissolve the thermoplastic resin in the potential solvent. And then cooling to room temperature to induce phase separation and further remove the potential solvent to produce a porous body. According to the heat-induced phase separation method, a porous hollow fiber membrane having high mechanical strength is easily obtained because it is rapidly cooled and solidified from a high temperature.

[Configuration of porous hollow fiber membrane]
FIG. 1 is a schematic view showing an example of a porous hollow fiber membrane according to an embodiment of the present invention. Fig.1 (a) is a perspective view of a porous hollow fiber membrane, FIG.1 (b) is the figure which looked at the porous hollow fiber membrane from the longitudinal direction. As shown in each figure, the porous hollow fiber membrane 1 is a porous hollow fiber membrane having a substantially cylindrical shape in which an opening 2 is provided in a central portion. In addition, in FIG. 1, although the outer peripheral part and the inner peripheral part are exhibiting substantially circular shape, the porous hollow fiber membrane 1 may be irregularly shaped. That is, the porous hollow fiber membrane 1 may have irregularities formed along the circumferential direction in the outer peripheral portion, or irregularities formed along the circumferential direction in the inner circumferential portion. The outer peripheral portion means the outer surface portion of the porous hollow fiber membrane 1, and the inner peripheral portion means the inner surface portion of the porous hollow fiber membrane 1.

[Method for producing porous hollow fiber membrane]
The method for producing a porous hollow fiber membrane can be divided into three steps for convenience. The first step is a step of uniformly melting and kneading the thermoplastic resin, organic liquid and inorganic fine powder to produce a melt-kneaded product, and the second step is discharging the melt-kneaded product from a hollow fiber molding nozzle 12 (described later). Thus, the step of obtaining the hollow fiber-shaped molded product, the third step is a step of obtaining the porous hollow fiber membrane 1 by extracting and removing the organic liquid and the inorganic fine powder from the obtained hollow fiber-shaped molded product.

  First, the thermoplastic resin, organic liquid and inorganic fine powder constituting the melt-kneaded product in the step of producing the melt-kneaded product will be described in detail.

(Thermoplastic resin)
Thermoplastic resin (thermoplastic polymer) is not easily deformed at room temperature (20 ° C ± 15 ° C (5-35 ° C)) and does not exhibit plasticity, but it can be molded by appropriate plasticity. It is a resin that undergoes a reversible change back to its original elastic body when it cools down and cools down, and does not cause chemical changes such as molecular structure during that time (edited by the Chemistry Dictionary Dictionary, Dictionary 6 Miniature Edition, Kyoritsu Shuppan, 860 and 867, 1963). Examples of thermoplastic resins include resins described in the pages of thermoplastics (pages 1069 to 1125) of 14705 chemical products (Chemical Industry Daily, 2005), and the Chemical Handbook Application Edition, revised edition 3 (The Chemical Society of Japan) , Maruzen, 1980), pages 809-810.

  Specifically, the thermoplastic resin includes polyethylene, polypropylene, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, polyamide, polyetherimide, polystyrene, polysulfone, polyvinyl alcohol, polyphenylene ether, polyphenylene sulfide, cellulose acetate, poly Such as acrylonitrile. Among these, crystalline polyethylene, polypropylene, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and the like can be suitably used from the viewpoint of strength development. Further, among these crystalline thermoplastic resins, hydrophobic crystalline thermoplastics such as polyolefins such as polyethylene and polypropylene, polyvinylidene fluoride, etc., which have high water resistance due to hydrophobicity and can be expected to be durable in the filtration of ordinary aqueous liquids. The resin can be used more suitably. Furthermore, among these hydrophobic crystalline thermoplastic resins, polyvinylidene fluoride, which is excellent in chemical durability such as chemical resistance, can be particularly preferably used. Examples of the polyvinylidene fluoride include a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer having a vinylidene fluoride ratio of 50 mol% or more. Examples of the vinylidene fluoride copolymer include a copolymer of vinylidene fluoride and one or more selected from ethylene tetrafluoride, propylene hexafluoride, ethylene trifluoride chloride, or ethylene. As the polyvinylidene fluoride, a vinylidene fluoride homopolymer is most preferable.

(Organic liquid)
The organic liquid is a potential solvent for the thermoplastic resin. An organic liquid is an organic compound that has substantially no dissolving power at a normal temperature in a target thermoplastic resin, but has a high concentration of dissolving power at a high temperature. The organic liquid may be liquid at the kneading and melting temperature with the thermoplastic resin, and does not necessarily need to be liquid at room temperature.

  As the organic liquid, for example, when the thermoplastic resin is polyethylene, dibutyl phthalate, diheptyl phthalate, dioctyl phthalate, di (2-ethylhexyl) phthalate, diisodecyl phthalate, ditridecyl phthalate, and the like, sebacin Sebacic acid esters such as dibutyl acid, adipic acid esters such as dioctyl adipate, trimellitic acid esters such as trioctyl trimellitic acid, phosphoric acid esters such as tributyl phosphate and trioctyl phosphate, propylene glycol dicaprate, Examples thereof include glycerin esters such as propylene glycol dioleate, paraffins such as liquid paraffin, and mixtures thereof.

  As the organic liquid, for example, when the thermoplastic resin is polyvinylidene fluoride, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dicyclohexyl phthalate, diheptyl phthalate, dioctyl phthalate, di (2-ethylhexyl) phthalate Phthalates such as methyl benzoate, benzoates such as methyl benzoate, phosphates such as triphenyl phosphate, tributyl phosphate, tricresyl phosphate, γ-butyrolactone, ethylene carbonate, propylene carbonate, Examples include cyclohexanone, acetophenone, isophorone, and mixtures thereof.

(Inorganic fine powder)
Examples of the inorganic fine powder include silica, alumina, titanium oxide, zirconia oxide, and calcium carbonate. Silica fine powder having an average primary particle size of 0.5 μm or less is preferable. Furthermore, hydrophobic silica fine powder which is hard to agglomerate and has good dispersibility is more preferable. More preferably, the powder is completely wetted, and the MW value measured by the methanol wettability (NW) method for measuring the volume% of methanol is 30% by volume. It is the hydrophobic silica which is the above. The MW value mentioned here is the volume% of methanol in the aqueous solution when 50% by weight of silica settles when silica is added to pure water and methanol is added below the liquid level with stirring. It is.

  As for the addition amount of the inorganic fine powder, the mass ratio of the inorganic fine powder in the melt-kneaded product is preferably 5% by mass or more and 40% by mass or less. When the proportion of the inorganic fine powder is 5% by mass or more, the effect of the inorganic fine powder kneading can be sufficiently exhibited, and when it is 40% by mass or less, stable spinning can be performed. The mixing ratio in the melt-kneading is such that the volume ratio obtained by dividing the weight by the specific gravity is in the range of 15 to 50% by volume in the thermoplastic resin, and in the range of 50 to 85% by volume in the total of both the organic liquid and the inorganic fine powder. It is preferable from the viewpoint of the obtained hollow fiber and the balance between water permeability and strength, and the stability of the spinning operation which is a melt extrusion operation. When the volume ratio of the thermoplastic resin is too small, the strength of the porous hollow fiber membrane to be obtained is lowered. On the other hand, when the volume ratio of the thermoplastic resin is too high, the water permeability of the obtained porous hollow fiber membrane is lowered. Further, if the volume ratio of the thermoplastic resin is too low or too high, the spinning stability is lowered. When the inorganic fine powder is added, the weight ratio of the inorganic fine powder in the melt-kneaded product is preferably 5% by weight or more and 40% by weight or less. If the proportion of the inorganic fine powder is too small, the effect to be manifested by the inorganic fine powder kneading is diminished, and if the proportion of the inorganic fine powder is too large, the melt-kneaded product becomes brittle and the spinning stability is lowered.

  Next, molding of the porous hollow fiber membrane will be described. FIG. 2 is a diagram showing a configuration of a hollow fiber membrane production apparatus for producing a porous hollow fiber membrane. As shown in FIG. 2, the hollow fiber membrane manufacturing apparatus 10 includes a melt kneader 11 that melts and kneads a thermoplastic resin, an organic liquid, and inorganic fine powder to extrude a melt kneaded product, and a tip (extrusion) side of the melt kneader 11. A hollow fiber molding nozzle 12 provided in the vacuum, a suction device 13 for generating cooling air to the melt-kneaded material discharged from the hollow fiber molding nozzle 12, and a cooling tank for cooling and solidifying the melt-kneaded part 14 and a take-up roller 15 for winding the solidified hollow fiber-like material.

  In the hollow fiber membrane manufacturing apparatus 10, the melt-kneaded product supplied from the melt-kneader 11 is discharged from the hollow-fiber molding nozzle 12, runs idle while receiving cooling air from the suction machine 13, and then in the cooling tank 14. The melt-kneaded product is cooled and solidified through the cooling bath, and the cooled and solidified hollow fiber is wound up by the winding roller 15.

(Molding method)
The melt-kneader 11 is a part for melt-kneading the above-mentioned thermoplastic resin, organic liquid and inorganic fine powder, and is a conventional melt-kneading means, for example, a continuous kneader such as a twin screw extruder, or a batch type such as a Banbury mixer. A kneader can be used. The melt-kneaded material melt-kneaded by these devices is melt-molded into a hollow fiber shape from a hollow fiber-forming nozzle 12 having discharge ports 16 arranged concentrically, so that the precursor of the hollow hollow fiber membrane 1 (hollow Thread-like material) is preferably obtained.

  The melt-kneading process and the molding process may be continuous or sequential. That is, the thermoplastic resin, the organic liquid, and the inorganic fine powder are respectively put into the melt kneader 11 and may be continuously melted and kneaded and then continuously extruded from the hollow fiber molding nozzle 12, or may be melted and kneaded uniformly. It may be solidified once into a pellet form, and then the pellet form obtained again is melted by the melt kneader 11 or the like and extruded from the hollow fiber molding nozzle 12. When the latter process is employed, a more uniform porous hollow fiber membrane 1 can be obtained by providing a filter before discharge even in the stage of solidifying into a pellet or the like once.

  FIG. 3 is a diagram showing the configuration of the discharge port of the hollow fiber molding nozzle. As shown in FIG. 3, the discharge port 16 includes an interior part 16a and an exterior part 16b arranged so as to surround the interior part 16a. The interior portion 16a is provided with an opening K at the center. As shown in FIG. 3, the shape of the discharge port 16 of the hollow fiber molding nozzle 12 may be an annular shape as shown in FIG. 3 (a) or as shown in FIGS. 3 (b) and 3 (c). It may be an irregular shape with such irregularities. It is also preferable to co-extrude melt-kneaded materials having different compositions from two or more melt-kneaders 11 (extruders).

(Extraction method of organic liquid and inorganic fine powder)
Next, extraction and removal of organic liquid and extraction and removal of inorganic fine powder will be described. The extraction and removal of the organic liquid and the inorganic fine powder can be performed simultaneously as long as they can be extracted and removed with the same solvent, but usually the extraction and removal are performed separately.

  The extraction and removal of the organic liquid can be performed by using an extraction liquid that is miscible with the organic liquid without dissolving or modifying the kneaded thermoplastic resin and contacting the extraction liquid by a technique such as immersion. it can. The extraction liquid is conveniently volatile so that it can be easily removed from the hollow fiber membrane after extraction. Examples of the extraction liquid include alcohols and methylene chloride. If the organic liquid is water-soluble, water can be used as the extraction liquid.

  For example, when the inorganic fine powder is silica, the inorganic fine powder can be extracted and removed by first contacting with an alkaline solution to convert the silica to silicate, and then contacting with water to extract and remove the silicate. it can.

  Either the extraction removal of the organic liquid or the extraction removal of the inorganic fine powder may be performed first. However, since both of them (organic liquid and inorganic fine powder) usually coexist in the organic liquid concentrated partial phase, if the organic liquid is immiscible with water, the organic liquid is first extracted and removed. The extraction and removal of the inorganic fine powder is advantageous because the inorganic fine powder can be smoothly extracted and removed using the aqueous extraction liquid. Thus, the porous hollow fiber membrane 1 can be obtained by extracting and removing the organic liquid and the inorganic fine powder from the cooled and solidified hollow fiber-like material.

  In addition, for the hollow fiber-like material after cooling and solidification, (1) before extraction and removal of organic liquid and inorganic fine powder, (2) after extraction removal of organic liquid and before extraction removal of inorganic fine powder, (3) extraction and removal of inorganic fine powder Before the extraction and removal of the organic liquid, and (4) after the extraction and removal of the organic liquid and inorganic fine powder, the hollow fiber-like material may be stretched in the longitudinal direction within a range of 3 times or less. it can. In general, when the porous hollow fiber membrane 1 is stretched in the longitudinal direction, the water permeability is improved, but the pressure resistance (burst strength and compressive strength) is lowered. Therefore, the membrane does not often have a practical strength after stretching. However, since the molten kneaded material in which the inorganic fine powder is kneaded in addition to the thermoplastic resin and the organic liquid is discharged and molded from at least one annular discharge port 16, the porous hollow fiber membrane 1 is a machine. High strength. Therefore, it can be carried out as long as the stretching is performed at a low magnification within 3 times. By this stretching, the water permeability of the porous hollow fiber membrane 1 can be improved.

  In addition, the draw ratio said here shows the value which divided the hollow fiber length after extending | stretching by the hollow fiber length before extending | stretching. For example, when a hollow fiber having a hollow fiber length of 10 cm is drawn to a hollow fiber length of 20 cm, the draw ratio is 20 cm ÷ 10 cm = 2 (times). Further, if necessary, the stretched film may be subjected to heat treatment to increase the pressure resistance. The heat treatment temperature is usually suitably carried out below the melting point of the thermoplastic resin.

(filter)
Returning to FIG. 2, in the hollow fiber membrane production apparatus 10, the melt-kneaded material is formed between the extrusion port 11 a of the melt-kneader 11 and the discharge port 16 of the hollow-fiber molding nozzle 12, that is, in the melt-kneading step and the hollow fiber shape. The filter 17 is disposed at least at one place (two places in FIG. 2) between the step of discharging the gas. By passing the melt-kneaded material through this filter 17, it is possible to obtain a porous hollow fiber membrane 1 having a small number of independent pores and high communication properties, that is, high actual liquid performance. In general, it is known to use a filter having a relatively large opening (slit width) in order to remove foreign matters such as insoluble matters and scorching. However, the filter 17 of the present embodiment is clear from this purpose. Different.

  In the melt-kneaded product, it is difficult to uniformly disperse the added inorganic fine powder, and it has a portion where the inorganic fine powder is aggregated. This is not a non-uniformity at a macro size (several hundreds of μm) disclosed in conventional literature, but a kneading unevenness at a more microscopic size (several tens to 100 μm). It is difficult to disperse the inorganic fine powder uniformly in this micro size. As a result of intensive studies, the present inventors have many communication holes for discharging the melt-kneaded product through the filter 17 provided between the melt-kneading step and the step of discharging into a hollow fiber and then discharging it into a hollow fiber. It was found to be important for obtaining a porous hollow fiber membrane. This is presumably due to the following two reasons.

(1) Dispersibility improvement of inorganic fine powder Aggregates are dispersed below the slit size by passing the melt-kneaded material through the opening of the filter, that is, the narrow slit. As a result, it is possible to reach the uniformity even higher than that of the dispersion in the melt-kneading step. As a result, the polymer concentration is low (relatively high organic liquid concentration), phase separation proceeds quickly in the cooling process after ejection, and it becomes difficult to form a non-uniform region where independent holes are likely to be formed.

(2) Orientation of aggregate of inorganic fine powder By passing the melt-kneaded material through a narrow slit, the aggregate state of the inorganic fine powder changes. Specifically, a linear aggregated state is created. Thus, the aggregate of the inorganic fine powder is oriented in the hollow fiber film thickness direction by the ballast effect when the aggregate of the inorganic fine powder oriented in the flow direction of the melt-kneaded product is discharged from the discharge port 16. When phase separation occurs in the cooling process after discharge, the start of phase separation occurs from the inorganic fine powder as the base point, and the phase separation proceeds. ) Is oriented. As a result, a porous hollow fiber membrane having high communication is obtained.

  Here, as one index representing the effect of the production method of the present embodiment, variation in physical properties of the obtained porous hollow fiber membrane (standard deviation in terms of statistics) can be mentioned. For example, the physical properties of the obtained porous hollow fiber membrane have a certain standard deviation (variation). According to the manufacturing method of the present embodiment, a film having a small standard deviation, that is, a more uniform distribution can be obtained. A smaller standard deviation is a great advantage in production and in designing the membrane. Normally, when considering a standard (physical property value) in a certain product, the upper limit and the lower limit of the standard are determined in consideration of the distribution of the porous hollow fiber membrane. For example, a standard deviation is obtained by sampling a sufficient number of samples (about 100 points are sufficient for the porous hollow fiber membrane of the present embodiment) for the obtained membrane. It can be calculated by the equation (11) described in “Standard deviation rate”.

  As the filter 17, a commercially available sintered filter, a woven stainless steel wire, or a ceramic filter can be suitably used. What woven the stainless wire which is easy to make the filter which has high durability at high temperature and has a fine slit is preferable. Moreover, when using a thin filter, the structure which superimposes filters can also be used preferably. For example, when the slit width is small, stainless steel wire with a thin wire diameter is used, so it is also possible to apply a double filter by applying a filter with a large wire diameter and a large slit width from the back, in order to avoid risks such as filter breakage. It can be used suitably. Moreover, in order to extend the lifetime until a filter is clogged more, the structure which piles up several sheets from a filter with a large slit width to a small filter can also be used suitably.

  FIG. 4 is a diagram illustrating the configuration of the filter. As shown in the figure, the slit width D of the filter 17 is preferably about 1000 to 120,000 times (1000 to 120,000 times) the primary particle diameter of the inorganic fine powder. If the width D of the filter 17 is 1000 times or more the primary particle diameter of the inorganic fine powder, the filter 17 can be prevented from being clogged, and the pressure increase before and after the filter 17 can be reduced. Can be practically used for the production of the porous hollow fiber membrane 1. Moreover, if the width D of the filter 17 is 12000 times or less of the primary particle diameter of the inorganic fine powder, the above-mentioned inorganic fine powder is sufficiently dispersed and a porous film having high communication can be obtained. The slit width D is, for example, a mesh opening width between wires in the case of a filter woven from stainless steel wires. Further, when the vertical and horizontal slit widths D are different, a value calculated by arithmetic averaging may be used as the slit width D of the filter 17. The value obtained by dividing the slit width D by the primary particle diameter of the inorganic fine powder is preferably 1200 or more and 107000 or less, more preferably 3000 or more and 24000 or less, and most preferably 5000 or more and 1000 or less.

  Further, the time from when the melt-kneaded material passes through the last (lowermost) filter 17 until it is discharged is preferably within 0.1 to 100 seconds. If the time is 0.1 seconds or more, the liquid can be stably discharged without being affected by the flow disturbance occurring in the filter 17. Moreover, if time is less than 100 second, the state (aggregation state, orientation of an aggregate) of the inorganic fine powder produced by letting it pass through the filter 17 can fully be maintained. The time from when the melt-kneaded material passes through the filter 17 until it is discharged is more preferably 75 seconds or less, still more preferably 60 seconds or less, and most preferably 30 seconds or less.

  Moreover, it is also preferable that the installation location of the filter 17 be two or more. For example, a first filter is installed at a position immediately after the melt-kneading step to improve the uniformity of the melt-kneaded product and to remove insoluble matter, scorch and large aggregates in the melt-kneaded product, and further to the discharge port 16. A method of further improving the uniformity of the melt-kneaded material by a second filter installed at the immediately preceding position can be suitably used. The filter 17 only needs to have a slit through which the melt-kneaded material passes, and the shape, thickness, and the like thereof are appropriately selected and are not particularly limited. That is, it may be in the form of a mesh as shown in FIG. 4, may be in the form of a honeycomb as found in a ceramic filter, or may be in the form of a narrow channel such as an orifice. May be. In particular, a mesh shape or a honeycomb shape having a plurality of slits is preferable from the viewpoint of dispersibility, and a thin mesh filter with little pressure loss is most preferable.

(Plastomill temperature)
In producing the porous hollow fiber membrane 1, both the resin temperature Tm at the time of melt-kneading and the resin temperature Ts at the time of discharging from the discharge port (spinning port) may be set to the torque inflection temperature Tp or higher. It is preferable for obtaining a porous hollow fiber membrane 1 having properties. Here, the torque inflection temperature means that the organic liquid bleeds in the melt-kneaded material containing silica (for example, the organic liquid starts to exist independently from the thermoplastic resin and the aggregate of inorganic fine powder during cooling. ) Temperature. This torque inflection temperature can be measured, for example, by the following method. That is, the melt-kneaded product (one melt-kneaded and solidified) is kneaded with a plastmill at a temperature equal to or higher than the melting point (in the case of polyvinylidene fluoride resin, about 190 ° C.) until it melts uniformly, and then heated to increase the organic liquid Is mixed with the thermoplastic resin and the torque is increased. When a certain temperature is exceeded, the organic liquid and the thermoplastic resin become uniform, and thereafter, the decrease in the viscosity of the thermoplastic resin becomes dominant, and the torque decreases conversely. At this time, the temperature at which the torque becomes maximum is defined as a torque inflection temperature.

  As described above, by setting the resin temperature Tm and the resin temperature Ts to be equal to or higher than the torque inflection temperature Tp, a film with higher communication can be obtained. This is because by making the resin temperature Tm at the time of melt-kneading higher than the torque inflection temperature Tp at which the organic liquid begins to bleed, a more uniform melt-kneaded product can be obtained, resulting in higher communication Become a film. Also, the resin temperature Ts at the time of discharge is made higher than the torque inflection temperature Tp, so that bleeding before discharge, that is, phase separation is not started. Thereby, a film having higher communication can be obtained more efficiently by forming a porous structure by phase-separating only the state in which inorganic fine powders are arranged in the film thickness direction after ejection. The resin temperature Tm and the resin temperature Ts are more preferably 5 ° C. or higher, more preferably 10 ° C. or higher than the torque inflection temperature Tp, from the viewpoint of suitably exhibiting the above effects.

(Characteristics of porous hollow fiber membrane)
Next, the structural features of the porous hollow fiber membrane 1 obtained by the method for producing the porous hollow fiber membrane of the present embodiment will be described in detail. The porous hollow fiber membrane 1 is greatly characterized by having many communication holes. The connectivity of the porous hollow fiber membrane 1 is measured by the following method because there is almost no difference in the pure water permeability even if there are some independent bubbles (portions through which liquid does not pass). For the connectivity, the porosity P _wet calculated from the amount of liquid impregnated in the porous hollow fiber membrane 1 is the porosity P _dry calculated from the mass (dry weight) of the porous hollow fiber membrane 1 in the dry state. It can be evaluated by the communication rate, which is the value obtained by dividing. The porosity P _wet and the porosity P _dry can be accurately measured by the method described in Example 7 shown in FIG. As described in the examples below, the connectivity contributes to the actual liquid performance more than the difference (ratio) between the numerical values. This is because the part where the communication is low is concentrated in the central part of the film thickness direction, and the difference is small when viewed from the whole film thickness, but the number of flow paths in the actual filtration greatly affects more than the numerical value. It is inferred that The value obtained by dividing the porosity P _wet calculated from the amount of the liquid impregnated in the porous hollow fiber membrane 1 by the porosity P _dry calculated from the mass of the porous hollow fiber membrane 1 in a dry state is 0. It is preferable that it is 90 or more and 1.00 or less.

  According to the method for producing a porous hollow fiber membrane of the present embodiment, a membrane having a communication rate of 0.90 or more can be suitably obtained, and as a result, a membrane having high actual liquid performance can be obtained. The communication rate is more preferably 0.95 or more, and still more preferably 0.97 or more.

(Isotropic three-dimensional network structure)
Moreover, the porous hollow fiber membrane 1 of the present embodiment has a three-dimensional network structure. Here, the three-dimensional network structure refers to a structure in which a resin is innumerable columnar and is joined to each other at both ends to form a three-dimensional structure. In the three-dimensional network structure, almost all of the resin forms a columnar body, and the innumerable resinous mass that is seen in a so-called spherulite structure is hardly seen. The void portion of the three-dimensional network structure is surrounded by a columnar body of thermoplastic resin, and each portion of the void portion communicates with each other. As described above, since most of the used resin forms a columnar material that can contribute to the strength of the porous hollow fiber membrane 1, a high-strength support layer can be formed. In addition, chemical resistance is improved. The reason why chemical resistance is improved is not clear, but because there are a large number of pillars that can contribute to strength, even if part of the pillars are attacked by chemicals, the overall strength of the layer is not significantly affected. It is thought that.

  On the other hand, in the spherulite structure, since the resin is collected in the lump, the number of columnar objects is relatively small and the strength is low. Therefore, it is considered that when a part of the columnar material is invaded by the chemical, the strength of the entire layer is likely to be affected. Further, the three-dimensional network structure capable of expressing high strength is a structure obtained by liquid-liquid type phase separation. The liquid-liquid type phase separation refers to a phase separation in which both phases are separated in a liquid state when separating into a phase rich in organic liquid and a phase rich in thermoplastic resin during phase separation. Compared with solid-liquid type phase separation (phase separation mode in which a solid thermoplastic resin is rich and a phase in which a liquid thermoplastic resin is rich), which is another phase separation form, this liquid-liquid In mold phase separation, the droplets tend to be independent, and as a result, the resulting porous membrane tends to have independent pores. Therefore, the method for producing the porous hollow fiber membrane 1 of the present embodiment is most effective in producing a membrane having a three-dimensional network structure by liquid-liquid phase separation, which is suitable for obtaining high strength. This is a preferred production method.

  Moreover, it is most preferable that the porous hollow fiber membrane 1 of the present embodiment has an isotropic three-dimensional network structure. Here, isotropic means that the change in the structure (pore diameter) of the porous body is small in both the longitudinal direction of the porous hollow fiber membrane 1 and the direction perpendicular to the longitudinal direction (hereinafter referred to as the film thickness direction). It means a simple structure. If the isotropic three-dimensional network structure is used, the used resin is used for the columnar object without waste, and the columnar object is uniformly distributed over the entire support layer, so that a weak portion is hardly generated, and a high strength is obtained. It is believed that a support layer is obtained. As a result, the mechanical strength of the porous hollow fiber membrane having this support layer is increased, and the chemical resistance is also improved. A schematic diagram of such an isotropic three-dimensional network structure is shown in FIG. As shown in FIG. 5, in the isotropic three-dimensional network structure, it can be seen that the voids b are formed by joining the columnar objects a. FIG. 6 shows a micrograph of an isotropic three-dimensional network structure in an actual porous hollow fiber membrane example obtained in Example 14 described later. For reference, a schematic diagram of a spherical structure is shown in FIG. As shown in FIG. 7, in the spherical structure, it can be seen that the spherulites c are partially dense, and the gaps between the dense parts of the spherulites c are the voids d.

  As a specific isotropic evaluation, it can be measured by the following method. First, a photograph of the cross section of the membrane obtained by cleaving the porous membrane in the longitudinal direction of the hollow fiber is used for measurement. The magnification of the photograph is preferably a size in which a large number of holes can be seen in order to improve the measurement accuracy. For example, if the film has a pore size of about 0.1 μm, a magnification of about 5000 times can be sufficiently measured. In the center of this cross section, using a scanning electron micrograph at a magnification at which the pores of the porous body can be clearly seen, the average pore diameter in the longitudinal direction of the porous hollow fiber membrane is the direction perpendicular to the longitudinal direction (that is, the film thickness direction) The value obtained by dividing by the average hole diameter of the hole is used as the isotropic ratio in the longitudinal direction of the hollow fiber. As a method for measuring the average pore diameter, it may be obtained by binarization by image analysis, or a plurality of lines are drawn on the photograph in the longitudinal direction and the film thickness direction of the hollow fiber, and the lengths of the lines crossing the holes are shown. The average value may be obtained as the pore diameter. If the value of this isotropic rate is 0.3 to 3, it can be said to be isotropic, and high strength can be expressed. More preferably, it is 0.5-2, More preferably, it is 0.75-1.25.

(Module, filtration device and filtration method)
The porous hollow fiber membrane 1 obtained as described above is used for a hollow fiber membrane module, a filtration device to which the hollow fiber membrane module is attached, a water treatment (water treatment method) using the filtration device, and the like.

  Hereinafter, a hollow fiber membrane module, a filtration method and a filtration apparatus using the hollow fiber membrane module will be described. In addition, although various aspects are assumed as a hollow fiber membrane module, in the following description, a membrane type pressure filtration system membrane module will be described as an example.

  FIG. 8 is a diagram showing the configuration of the hollow fiber membrane module. As shown in FIG. 8A, the hollow fiber membrane module 20 includes a bundle (hereinafter referred to as a hollow fiber membrane bundle) 21 of the porous hollow fiber membrane 1 described above. As for the hollow fiber membrane bundle 21, the upper end part and lower end part are being fixed by fixing | fixed part 22a, 22b. Further, the hollow fiber membrane bundle 21 and the fixing portions 22 a and 22 b are accommodated in a pipe-like case 23. In the hollow fiber membrane module 20 having such a configuration, a to-be-filtered liquid L is supplied between the case 23 and the hollow fiber membrane bundle 21 from the lower part (downward in the figure), and a porous hollow fiber membrane is applied by applying pressure. The filtrate L is filtered by 1 and the filtrate is transported through a header pipe or the like disposed above the hollow fiber membrane module 20. As shown in FIG. 8 (b), during filtration, the liquid L to be filtered in the hollow fiber membrane module 20 permeates the porous hollow fiber membrane 1 from the outer surface side to the inner surface side of the porous hollow fiber membrane 1. And filtered. The fixing portions 22a and 22b are provided with through holes 24 for supplying the liquid L and air to be filtered between the case 23 and the hollow fiber membrane bundle 21. In the hollow fiber membrane module 20, the through holes 24 are provided. Air scrubbing of the hollow fiber membrane bundle 21 is performed by supplying air.

  Other aspects are also possible for the module in which the porous hollow fiber membrane 1 described above is integrated. For example, the module is not limited to the above-described casing type, and may be a non-casing type. Further, the cross-sectional shape of the module is not limited to the above-described circular shape (so-called cylindrical module) but may be a square shape (so-called casket type module). Further, the raw water as the liquid to be filtered may be directly filtered through the porous hollow fiber membrane 1 or after the addition of an oxidant such as a flocculant or ozone as a pretreatment, the porous hollow fiber membrane 1 May be filtered. The filtration method (filtration method) may be a total amount filtration method, a cross flow filtration method, a pressure filtration method or a suction filtration method. Further, as an operation method, air scrubbing and back pressure cleaning used for the purpose of removing the filtration target deposited on the membrane surface may be performed separately, or they may be performed simultaneously. Moreover, as a liquid used for back pressure washing | cleaning, oxidizing agents, such as sodium hypochlorite, chlorine dioxide, ozone, etc. can be used suitably.

  Next, a pressure filtration type filtration device will be described. FIG. 9 is a configuration diagram illustrating an example of a pressure filtration type filtration device. As shown in the figure, the filtration device 30 includes a pump 31 for supplying pressure to the hollow fiber membrane module 20, a tank 32 for storing the filtrate, a tank 33 for storing the filtrate, and back pressure washing as necessary. A device equipped with a chemical tank 34 and a liquid feed pump 35, a pump 36 for sending air necessary for air scrubbing, a pipe 37 for draining liquid discharged during air scrubbing and backwashing, and the like can be suitably used.

  In the filtration method according to the present embodiment, low cost can be realized by using the hollow fiber membrane module 20, the filtration device 30, and the filtration method provided with the above-mentioned many porous hollow fiber membranes 1, and the long-term can be realized. Stable operation is possible.

  Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples. In addition, the measuring method used for this Embodiment is as follows. The following measurements were all performed at 25 ° C. unless otherwise specified. Below, after explaining an evaluation method, the manufacturing method and evaluation result of an Example and a comparative example are explained.

<Evaluation method>
(1) Measurement of the inner diameter (mm) and outer diameter (mm) of the porous hollow fiber membrane The hollow fiber membrane is sliced thinly with a razor or the like in the direction perpendicular to the longitudinal direction of the membrane, and the major axis and the minor axis of the inner diameter of the cross section using a microscope The major and minor diameters of the diameter and the outer diameter were measured, and the inner diameter and the outer diameter were determined by the following formulas (1) and (2), respectively.

(2) Pure water permeability (l / m ² /hr/0.1 MPa / 25 ° C.)
Seal one end of a wet hollow fiber membrane about 10 cm long, put an injection needle into the hollow part at the other end, inject pure water into the hollow part from the injection needle at a pressure of 0.1 MPa, and permeate to the outer surface The permeated water amount of the pure water was measured, and the pure water permeability was determined by the following equation (3).

(3) Breaking strength (MPa), elongation at break (%)
Using an Instron type tensile tester (AGS-5D, manufactured by Shimadzu Corporation), the wet hollow fiber membrane was placed at a distance between chucks of 5 cm and a tensile speed of 20 cm / min. The breaking strength and breaking elongation were determined by the following formulas (4) and (5) from the load and displacement at the time of pulling and breaking.


Here, the film cross-sectional area is obtained by the following equation (6).

(4) Measurement of the slit width of the filter The slit width of the filter used was photographed with a microscope at a magnification at which the slit width can be measured sufficiently. Then, 20 slit widths were measured from the photographed photographs, and the average value was taken as the slit width.

  (5) Torque inflection temperature of melt-kneaded product (° C.) 110 g of the solidified melt-kneaded product was placed in a lab plast mill (model 30C150, manufactured by Toyo Seiki Co., Ltd.) and heated to 190 ° C. After the temperature increase, the mixture was kneaded at 50 rpm for about 10 minutes, and then heated to 270 ° C. at a temperature increase rate of 14 ° C./min, and the resin temperature at which the torque reached a maximum was defined as the torque inflection temperature.

(6) Extruder discharge resin temperature Tm (° C.), Spinner discharge resin temperature Ts (° C.)
The extruder discharge resin temperature and the spinneret discharge resin temperature were measured by inserting a K-type thermocouple thermometer.

(7) Communication rate First, using a precision balance (to prevent static electricity from being charged in the membrane), weigh the mass of 20 cm × 20 completely dried porous hollow fiber membranes in the booth where the ionizer was operated. Measured. The obtained mass W _dry and the density ρ _p of the thermoplastic resin (for example, 1.78 g / cm ^{3 in} the case of the polyvinylidene fluoride resin used in the present application), and from the outer diameter and inner diameter measured in (1) to the following P _dry was determined from equation (7).

Furthermore, using the same hollow fiber membrane sample, it is difficult to volatilize and it is easy to impregnate the porous material, this time using propylene, 1, 2, 3, 3, 3, hexafluoride oxide (trade name: Galwick). The liquid was impregnated inside the hollow fiber membrane. Thereafter, the liquid adhering to the outer surface is carefully removed by wiping with a cloth, and the hollow part liquid is removed by capillary action by pressing the hollow part at both ends of the sample against the cloth, and then the mass W _{wet of the} hollow fiber is determined. It measured similarly to the measurement of mass W _dry . From the density ρ _L of the impregnated liquid (Galwick used this time is 1.70 g / cm ³ ), P _wet was obtained by the following equation (8).

Furthermore, the communication rate was calculated by the following formula (9) using the above P _dry and P _wet .

(8) Production of pressurized hollow fiber membrane module A pressurized hollow fiber membrane module having a membrane area of 50 m ² was produced as follows. After bundling a plurality of porous hollow fiber membranes, the hollow portion on one end face of the hollow fiber bundle was sealed, and stored in a polysulfone cylindrical module case having an inner diameter of 150 mm and a length of 2000 mm. Only the bonding jig is attached to the end portion subjected to the sealing treatment, and a total of 24 polypropylene rods having an outer diameter of 11 mm are arranged on the other end portion in parallel with the porous hollow fiber membrane and then liquid-tight. A bonding jig was attached to the.

  The module case with the bonding jig attached on both sides was centrifugally cast with a two-component epoxy resin. After centrifugal casting, the bonding jig and the polypropylene rod are removed, and after the epoxy bonding portion is sufficiently cured, the bonded end portion on the side subjected to the sealing treatment is cut to open the hollow fiber hollow portion. It was. As described above, a pressure-type hollow fiber membrane module comprising a hollow fiber membrane bundle was obtained.

(9) Water permeability measurement experiment 1 of a hollow fiber membrane module (pressurization)
Using the hollow fiber membrane module obtained in (8), river surface water having a turbidity of 5 to 10 degrees and a water temperature of 18 to 25 ° C. was used as raw water. Permeation rate is the limit permeation rate by increasing the permeation rate step-by-step with the external pressure total filtration method by pressurization by the pump, and the transmembrane pressure difference does not increase rapidly (does not exceed 10 kPa / week in terms of 25 ° C). The amount was measured.

  The filtration operation was a cycle operation of filtration / (backwashing and air bubbling). Each cycle is a filtration / (backwash and air bubbling) time cycle: 29 minutes / 1 minute, the backwash flow rate during backwash is 2.3 L / min / module, and the air flow rate during air bubbling is 4.6 NL / min / module.

(10) Maximum pore size (μm)
It measured based on the measuring method (another name: bubble point method) of the maximum hole diameter described in ASTM: F316-86. The measurement was performed on a 5 cm long hollow fiber membrane using ethanol as a liquid and compressed air as a gas for pressurization at 25 ° C. and a pressure increase rate of 0.05 atm / sec. With respect to the obtained bubble point pressure, the maximum pore diameter was calculated by the following formula (10).

When the liquid used is ethanol, the surface tension at 25 ° C. is 21.97 dynes / cm. (Edited by the Chemical Society of Japan, Basic 3rd edition of the Chemical Handbook, II-82, Maruzen, 1984)

(11) Standard deviation rate of maximum pore size (%)
The measurement of the maximum pore diameter described in (10) was carried out for a total of 100 points using samples collected by changing the sampling location. For the measured data, the maximum pore size of one sample is D _i , and the arithmetic average of 100 points is D _ave. As a result, the standard deviation rate (%) of the maximum pore diameter was calculated by the following formula (11).

[raw materials]
The raw materials used in the examples are shown below.
<Plastic resin>
(R-1) Vinylidene fluoride homopolymer (manufactured by Kureha Co., Ltd., trade name: KF # 1000)
(R-2) High density polyethylene resin (Asahi Kasei Chemicals Corporation, trade name: SH800)
(R-3) Polypropylene resin (manufactured by Tokuyama Corporation, trade name: PN110G)
<Organic liquid>
(L-1) Bis (2-ethylhexyl) phthalate (manufactured by CG Esther)
(L-2) Dibutyl phthalate (manufactured by CG Esther)
(L-3) Triacetin (manufactured by Aldrich)
(L-4) Glycerin (Wako Pure Chemical Industries, Ltd.)
<Inorganic fine powder>
(P-1) Fine silica (Nippon Aerosil Co., Ltd., trade name: AEROSIL-R972, average primary particle diameter of about 16 nm)
(P-2) Fine powder silica (manufactured by Tokuyama Corporation, trade name: Fine Seal X-45, primary particle size 15 nm)
<Flocculant>
(S-1) Hexaglyceryl monolaurate (Nikko Chemicals, Hexalglyn lL)
The formulation and production conditions in each example are shown in FIG.

[Example 1]
Vinylidene fluoride homopolymer (made by Kureha Co., Ltd., trade name: KF # 1000) as a thermoplastic resin, a mixture of di (2-ethylhexyl) phthalate and dibutyl phthalate as an organic liquid, and finely divided silica (Nippon Aerosil) as an inorganic fine powder The melt extrusion was performed using a product name: AEROSIL-R972). The melt-kneaded material to be discharged has a composition of vinylidene fluoride homopolymer: bis (2-ethylhexyl) phthalate: dibutyl phthalate: fine powder silica = 25.0: 38.5: 7.7: 28.8 (mass ratio) ), And air was used as the hollow portion forming fluid. In the hollow fiber forming nozzle having two annular discharge ports, the melt-kneaded material is discharged from the outer annular discharge port (“discharge port 16” shown in FIG. 3), and the inner annular discharge port (FIG. The hollow fiber-like molded product was obtained by discharging air from the “opening K” shown in FIG.

  The filter used was a mesh of 150 mesh (plain weave, slit width 109 μm: manufactured by Taiyo Wire Mesh Co., Ltd.) and 40 mesh (plain weave, slit width 390 μm: manufactured by Taiyo Wire Mesh Co., Ltd.) used as a backup. It was installed at a position on the upstream side (extruder side) for 10 seconds in the time for the resin to move from the discharge port. When the torque inflection temperature of this raw material composition was measured with a plast mill, the torque inflection temperature Tp was 235 ° C. Therefore, both the resin temperature Tm during melt-kneading and the resin temperature Ts during spinneret discharge were 250 ° C. It melt-kneaded and discharged under conditions.

  The obtained hollow fiber-like molded product was cooled and solidified by being introduced into a 30 ° C. water bath after running in the air of 30 cm, and wound up skein at a speed of 30 m / min. The resulting hollow fiber extrudate was immersed in methylene chloride to extract and remove bis (2-ethylhexyl) phthalate and dibutyl phthalate, and then dried. Next, after immersing in a 40% by mass ethanol aqueous solution for 30 minutes, it was immersed in water for 30 minutes to wet the hollow fiber membrane. Subsequently, it was immersed in a 20% by mass NaOH aqueous solution at 60 ° C. for 1 hour, and further washed with water to extract and remove finely divided silica.

  By the above-described method, a porous hollow fiber membrane was obtained in which the increase in pressure due to filter clogging was small, the communication property was high, and the actual liquid performance was also high. In addition, there was no defect due to silica aggregates in the spun hollow fiber membrane 15000 m. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane and the evaluation results of the actual liquid performance are shown in FIG.

[Examples 2 to 5]
The final filters on the side near the spout outlet are 635 mesh (twill, slit width 20 μm), 200 mesh (plain weave, slit width 45 μm), 40 mesh (plain weave, slit width 390 μm), 12 mesh (plain weave, slit width). 1720 μm) was used (common in that 40 mesh was overlapped as a backup), and a porous hollow fiber membrane was produced in the same manner as in Example 1.

  The 635 mesh and 200 mesh with small slit widths had a large filter pressure increase compared to Example 1, but a porous hollow fiber membrane having high connectivity and high actual liquid performance was obtained. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane and the evaluation results of the actual liquid performance are shown in FIG.

[Example 6]
A porous hollow fiber membrane was prepared in the same manner as in Example 1 except that the filter immediately after the extruder was removed. Although the pressure increase due to clogging of the filter was slightly larger than that in Example 1, a porous hollow fiber membrane having high communication was obtained. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane and the evaluation results of the actual liquid performance are shown in FIG.

[Example 7]
A porous hollow fiber membrane was produced in the same manner as in Example 1 except that the filter immediately before the discharge part was removed. The resin moving time from the filter to discharge was 75 seconds. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane and the evaluation results of the actual liquid performance are shown in FIG.

[Examples 8 to 10]
Except for adjusting the position in the flow path of the filter (final filter) close to the discharge part, and setting the resin movement time from the final filter to discharge to 15 seconds, 30 seconds, and 60 seconds A porous hollow fiber membrane was produced in the same manner as in Example 1. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 11]
A porous hollow fiber membrane was produced in the same manner as in Example 1 except that the resin temperature Tm and the resin temperature Ts were both 210 ° C. Ten defects due to silica aggregates were generated in the spun hollow fiber membrane 15000 m. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 12]
A porous hollow fiber membrane was produced in the same manner as in Example 1 except that the resin temperature Ts was 210 ° C. Three defects due to silica aggregates were generated in the spun hollow fiber membrane 15000 m. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 13]
A porous hollow fiber membrane was produced in the same manner as in Example 1 except that the resin temperature Tm was 210 ° C. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 14]
The melt-kneaded material to be discharged has a composition of vinylidene fluoride homopolymer: bis (2-ethylhexyl) phthalate: dibutyl phthalate: R972 = 34.0: 33.8: 6.8: 25.4 (mass ratio) A porous hollow fiber membrane was produced in the same manner as in Example 1 except that. A porous hollow fiber membrane was obtained in which the increase in pressure due to clogging of the filter was small, the communication property was high, and the actual liquid performance was also high. In addition, there was no defect due to silica aggregates in the spun hollow fiber membrane 15000 m. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 15]
The melt-kneaded material to be discharged is a high-density polyethylene resin as a thermoplastic resin, dibutyl phthalate as an organic liquid, R972 as an inorganic fine powder, polyethylene resin: dibutyl phthalate: R972 = 18.5: 54.3: 27.2 A porous hollow fiber membrane was produced in the same manner as in Example 1 except that the weight ratio was (mass ratio) and the resin temperature Ts was 230 ° C. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 16]
The melt-kneaded material to be discharged is a polypropylene resin (product name: PN110G, manufactured by Tokuyama Co., Ltd.) as a thermoplastic resin, dibutyl phthalate (produced by CG Ester Co., Ltd.) as an organic liquid, R972 as an inorganic fine powder, polyethylene resin: phthalic acid A porous hollow fiber membrane was produced in the same manner as in Example 1 except that dibutyl: R972 = 34.0: 40.6: 25.4 (mass ratio) and the resin temperature Ts was 230 ° C. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 17]
The melt-kneaded material to be discharged is a vinylidene fluoride homopolymer as a thermoplastic resin, a mixture of triacetin and glycerin as an organic liquid, and R972 as an inorganic fine powder. .2: 6.4: 25.4 (mass ratio) and a porous hollow fiber membrane was produced in the same manner as in Example 1 except that the resin temperature Tm and the resin temperature Ts were 180 ° C. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Example 18]
Vinylidene fluoride homopolymer as a thermoplastic resin (trade name: KF # 1000, manufactured by Kureha Co., Ltd.), hexyl benzoate as an organic liquid, fine silica as an inorganic fine powder (trade name: Fine Seal X-45, manufactured by Tokuyama Corporation), (Primary particle diameter 15 nm), and melt extrusion was performed using hexaglyceryl monolaurate as an aggregating agent. As the melt-kneaded material to be discharged, a melt-kneaded material having a composition of vinylidene fluoride homopolymer: hexyl benzoate: finely divided silica: = 20: 60: 10: 10 (mass ratio) is used. Was used.

  The filter uses 12 mesh (plain weave, slit width 1720 μm: manufactured by Taiyo Wire Mesh Co., Ltd.) immediately after discharge from the extruder and at a position 10 seconds upstream (extruder side) at the time the resin moves from the nozzle outlet. installed.

  The obtained hollow fiber-like molded product was cooled and solidified by being introduced into a 30 ° C. water bath after running in the air of 15 cm, and wound up skeinly at a speed of 5 m / min. Further, the film was stretched approximately twice in the longitudinal direction of the film in hot water at 80 ° C., and heat fixed in hot water at 100 ° C. Both the resin temperature Tm at the time of melt-kneading and the resin temperature Ts at the time of discharge from the nozzle were melt-kneaded and discharged under the condition of 230 ° C. Then, it was immersed in 20 mass% NaOH aqueous solution at 60 degreeC for 1 hour, and also water washing was repeated, and the fine powder silica was extracted and removed. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Comparative Example 1]
A porous hollow fiber membrane was produced in the same manner as in Example 1 except that no filter was installed. The obtained porous hollow fiber membrane was a membrane having low communication properties and low actual liquid performance. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

[Comparative Example 2]
A porous hollow fiber membrane was produced in the same manner as in Example 14 except that no filter was installed. The obtained porous hollow fiber membrane was a membrane having low communication properties and low actual liquid performance. The production conditions of the hollow fiber membrane, the physical properties of the obtained porous hollow fiber membrane, and the evaluation results of the actual liquid performance are shown in FIG.

  DESCRIPTION OF SYMBOLS 1 ... Porous hollow fiber membrane, 12 ... Nozzle for hollow fiber shaping | molding, 16 ... Discharge port, 17 ... Filter, 20 ... Hollow fiber membrane module, 30 ... Filtration apparatus.

Claims (11)

A melt-kneaded material containing a thermoplastic resin, an organic liquid and inorganic fine powder is discharged from an annular discharge port of a hollow fiber molding nozzle to form a hollow fiber-like material, and after cooling and solidifying the hollow fiber-like material, the organic liquid and the above-mentioned A method for producing a porous hollow fiber membrane by extracting and removing inorganic fine powder,
A filter is provided in at least one place between melt-kneading the thermoplastic resin, the organic liquid and the inorganic fine powder and discharging the melt-kneaded product into a hollow fiber shape,
The slit width of the filter is 1000 times to 120,000 times the primary particle diameter of the inorganic fine powder,
A method for producing a porous hollow fiber membrane, wherein the melt-kneaded material is passed through the filter and then discharged and molded into a hollow fiber shape.   The method for producing a porous hollow fiber membrane according to claim 1, wherein the time from when the melt-kneaded material passes through the filter until it is discharged is within 100 seconds. Each of the temperature at which the thermoplastic resin, the organic liquid and the inorganic fine powder are melt-kneaded, and the resin temperature when the melt-kneaded material is discharged from the discharge port are torque changes of the melt-kneaded material measured by a plast mill. The method for producing a porous hollow fiber membrane according to claim 1 or 2, wherein the temperature is higher than the bending temperature. The method for producing a porous hollow fiber membrane according to any one of claims 1 to 3 , wherein the inorganic fine powder is hydrophobic silica. The porous hollow fiber membrane manufactured by the manufacturing method of the porous hollow fiber membrane as described in any one of Claims 1-4 . The porosity according to claim 5, wherein a value obtained by dividing the porosity Pwe calculated from the weight of the impregnated liquid by the porosity Pdry calculated from the dry weight is 0.90 or more and 1.00 or less. Hollow fiber membrane. The porous hollow fiber membrane according to claim 6, which has an isotropic three-dimensional network structure. The porous hollow fiber membrane according to claim 6 or 7 , wherein the thermoplastic resin is polyolefin and polyvinylidene fluoride. Module using a porous hollow fiber membrane according to any one of claims 5-8. Filtration apparatus using a porous hollow fiber membrane according to any one of claims 5-8. Water treatment method using the porous hollow fiber membrane according to any one of claims 5-8.