JPH0549884A - Polyphenylene sulfide sulfone hollow fiber membrane and its production - Google Patents

Abstract

PURPOSE:To provide a porous hollow fiber membrane having smooth inner surface and excellent heat resistance, chemical resistance and org. solvent resis tance. CONSTITUTION:This porous hollow fiber membrane is obtd. by spinning a polymer comprising polyphenylene sulfide sulfone essentially containing a recurring structural unit expressed by formula (Ar-S-Ar-SO2)n(wherein Ar is a phenylene group). During spinning, it is specified that the line speed ratio of a liquid injected from the center of an annular nozzle to the polymer above described is 0.85 to 2.0 and the draft ratio of 0.7-1.1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a porous hollow fiber membrane, and more particularly to a porous hollow fiber membrane useful as an ultrafiltration membrane or a composite membrane supporting membrane having a pore size level equivalent to that of the ultrafiltration membrane. is there.

[0002]

2. Description of the Related Art Conventionally, ultrafiltration membranes produce pure water for the electronic industry, collect electrodeposition paints, treat sewage in yarn mills and pulp mills, treat oil-containing wastewater, treat wastewater from buildings, clarify juice, and drink sake. Production, concentration and desalting of tea whey, production of concentrated milk, concentration of egg white, treatment of soybean protein, concentration and recovery of enzyme, utilization for bioreactor, concentration and separation of biproducts, concentration in gas The application to various fields such as removal of fine particles, removal of fine particles in organic liquid, water treatment of nuclear power plant, etc. has been studied and put into practical use. Further, a porous membrane having a pore size level equivalent to that of the ultrafiltration membrane used for such an application is also used as a support membrane for a composite membrane in the fields of reverse osmosis composite membrane and gas separation membrane. In such application fields, heat resistance that can withstand hot water cleaning, steam sterilization, or steam sterilization, chemical cleaning,
Characteristics such as sterilization and acidic or basic use conditions, chemical resistance to withstand organic solvents and chemicals, and stain resistance (fouling resistance) are required. However, a porous membrane satisfying all such required characteristics has not yet been developed, and there is a strong demand for the development of a porous hollow fiber membrane having excellent durability, especially a porous membrane.

As an example of the porous film, for example, cellulose acetate is a film material having good workability and excellent performance, but it is not satisfactory in heat resistance and chemical resistance.
Polyacrylonitrile, polyvinylidene fluoride, etc. are materials superior in solvent resistance and heat resistance to cellulose acetate, and practical porous membranes have come to be provided, but they are still sufficiently satisfactory properties. It cannot be said that it is a membrane material. Since polysulfone has excellent heat resistance and good processability, ultrafiltration membranes including hollow fiber membranes with various fractionation characteristics have been developed and put into practical use, but in terms of solvent resistance and fouling resistance. I have a problem. If the chemical resistance and the organic solvent resistance are excellent, it is possible to recover the membrane performance by washing, and this can be a solution to the durability. The polyimide membrane is very excellent in solvent resistance and heat resistance, and a hollow fiber membrane of a practical level has been developed, but it has a drawback of poor alkali resistance.

As a film having excellent heat resistance, chemical resistance and solvent resistance, a polyphenylene sulfide (PPS) film has been proposed (JP-A-58-67733 and JP-A-60-202).
659), a method for producing a hollow fiber membrane has also been studied (JP-A-59-59917, JP-A-60-44404, Kaikai).
60-248202 publication). However, there is an inherent problem with workability, and it is difficult to control the pore size of the membrane. When the stretching method is used, it becomes a microporous membrane at the level of a microfiltration membrane, and it dissolves in a special solvent under severe conditions, and even if it is formed by the solution method, it exhibits high permeability as an ultrafiltration membrane. It is considered difficult to realize a film structure. Of course, it can be said that it is difficult to put it into practical use as a porous film for a supporting film, because it has problems with the pore shape and the inner and outer surface structures. There has been proposed a method of further improving heat resistance and chemical resistance by oxidizing a PPS porous body to convert a sulfide bond into a sulfone bond (JP-A-63-225636). Since the porous body itself relates to a method of selectively oxidizing sulfide bonds after processing by the various methods described above,
Problems remain in the control of fractionation performance and permeability.

In addition to the above, studies have been conducted on forming an ultrafiltration membrane from heat-resistant and chemical-resistant engineering plastics such as polyetheretherketone, but no membrane of practical level has been developed.

[0006]

Among these polymers, polyphenylene sulfide sulfone is extremely excellent in heat resistance, chemical resistance and organic solvent resistance, and is expected to be applied to porous hollow fiber membranes. However, it is known that it is difficult to adjust the viscosity to a high viscosity, and thus spinning is extremely difficult. It is also possible to add polyethylene glycol or polyvinylpyrrolidone to increase the viscosity, but such additives reduce the excellent heat resistance, chemical resistance, organic solvent resistance, etc. inherent to polyphenylene sulfide sulfone. There is a risk of

Therefore, the object of the present invention is to provide a porous hollow fiber membrane having excellent heat resistance, chemical resistance and organic solvent resistance, and a method for producing the same, by solving such problems. It is what

[0008]

In order to achieve the above object, the present invention has the following constitution. (1) General formula - (Ar-S-Ar- SO 2) n - ( wherein Ar represents a phenylene group) consisting mainly comprising polyphenylene sulfide sulfone repeating structural unit represented by the inner surface smooth and macrovoids Porous hollow fiber membrane without defects.

(2) General formula- (Ar-S-Ar-SO
₂ ) In the spinning of polyphenylene sulfide sulfone mainly containing a repeating constitutional unit represented by _n − (where Ar represents a phenylene group), the linear velocity of the injected liquid discharged from the central pipe of the annular die and the annular orifice The ratio of the linear velocity of the polyphenylene sulfide sulfone solution to the range of 0.85 to 2.0, and the take-up speed of the hollow fiber in the coagulation bath and the linear speed of the solution discharged from the annular orifice. The method for producing a porous hollow fiber membrane, wherein the ratio, that is, the draft ratio, is in the range of 0.7 to 1.1.

(3) General formula- (Ar-S-Ar-SO
₂ ) _n- (wherein Ar represents a phenylene group), wherein polyphenylene sulfide sulfone mainly containing a repeating constitutional unit is an n-methylpyrrolidone solution to which triethylene glycol is added,
The method for producing a porous hollow fiber membrane according to claim 2.

The porous hollow fiber membrane of the present invention shows almost no change in permeation performance and fractionation performance even after repeated steam sterilization, is resistant to many organic solvents, and is sterilized by sodium hypochlorite sterilization. The characteristics do not change even if repeated. It is also useful as a porous membrane for ultrafiltration that can be used in a wide pH range, and has excellent properties as a support membrane for composite membranes. Further, the present invention can stably spin a wide range of hollow fiber membranes, and can economically provide a hollow fiber membrane having a smooth inner and outer surface, particularly an inner surface where irregular wrinkles are likely to occur. it can.

The porous hollow fiber membrane composed of polyphenylene sulfide sulfone according to the present invention has the general formula-(A
r-S-Ar-SO 2 ) n - ( wherein Ar consists of polyphenylene sulfide sulfone containing mainly a repeating structural unit represented by a phenylene group), a smooth porous hollow fiber membrane of the inner surface.

The phenylene group (Ar) is usually a paraphenylene group in a preferred embodiment, but may be a metaphenylene group or an orthophenylene group, or these groups may coexist. Furthermore, this phenylene group is a hydroxyl group, a hydroxyethyl group, a hydroxymethyl group,
Although it may be substituted with a sulfonic acid group, a carboxylic acid group, or the like, an unsubstituted phenylene group is preferable in consideration of the characteristics of the film. The proportion of the polyphenylene sulfide sulfone repeating constitutional unit in the whole polymer composed of polyphenylene sulfide sulfone mainly containing this repeating constitutional unit needs to be about 70 mol% or more. When the proportion of the structure other than the repeating constitutional unit is more than 30%, the properties may be deteriorated in heat resistance, chemical resistance or solvent resistance.

It is difficult to strictly specify the range of n indicating the degree of polymerization because many factors are involved, but the approximate range is about 80 to 400, and the weight average molecular weight is 11
Polymers in the range 600 to 93000 can be preferably used. The molecular weight distribution is also an important factor, but the range of polymers obtained by a usual method, that is, the weight average molecular weight / number average molecular weight value of 1.2 to 3.5, and the workability of 2.0 to 3 Polymers in the range of 0.0 are preferred. 3.
When it is 5 or more, the spinnability may lack stability. Since it is time-consuming to directly measure the molecular weight or the degree of polymerization of a polymer, it is usually evaluated by the diluted solution viscosity. The preferred range of the intrinsic viscosity number measured at 25 ° C. with n-methylpyrrolidone (hereinafter abbreviated as NMP) as a solvent is 0.1 to 1.0 dl / g, and a particularly preferred range is 0.3 to 0. It is 0.6 dl / g. Further, as a simpler method for evaluating the degree of polymerization, there is evaluation by melt viscosity.
This is represented by the number of grams of polymer discharged in 10 minutes under the following conditions using a melt flow measuring device. That is, diameter 0.0825 ± 0.002 inches, length 0.3
343 with 15 ± 0.001 inch orifice installed
It is measured by applying a load of 5 kg at ° C. This value is the MF value. There are factors other than molecular weight as factors that affect the melt viscosity, and it is generally difficult to specify the measured value of the melt viscosity, but it is empirically known that an approximate suitable range can be shown. There is. Therefore, in terms of MF value, a range of 2 to 1500, preferably a range of 5 to 40,
More preferably, a polymer in the range of 5 to 30 is preferable for carrying out the present invention.

When the viscosity is lower than the above range, it is difficult to spin, and when the viscosity is high, it is impossible or extremely difficult to obtain such a highly viscous polyphenylene sulfide sulfone, and it is practical. Not.

Such a polymer can be produced by a known method, for example, according to Japanese Patent Laid-Open No. 63-270736.

The porous hollow fiber membrane of the present invention is a porous membrane having a smooth inner surface and a hollow fiber having a circular cross section.
Here, the hollow fiber having a smooth inner surface refers to a state in which wrinkle-like deformation or unevenness is not observed on the inner surface at a level observed with an optical microscope and a scanning electron microscope at a magnification of 500 times. When the inner surface is smooth, when a fluid to be treated is poured into the inside of the hollow fiber, it is possible to suppress the deposition of foreign matters on the membrane surface, and when pressure is applied from the outside, the hollow fiber may not be concentrated due to stress concentration. It is advantageous in preventing deformation or buckling.
A true circular hollow fiber means that the degree of deformation of the circles of the outer circumference and the inner circumference of the hollow fiber having a cross section perpendicular to the fiber axis of the hollow fiber is considered to be elliptical, and the major axis is a _o , a _i , and the minor axis is _bo. , B _i , the hollow fibers are such that b _o / a _o and b _i / a _i are 0.9 or more, preferably 0.95 or more and can be visually regarded as a perfect circle. When the center of the outer circumference and the center of the inner circumference of the hollow fiber are deviated, the ratio WT _min / WT _max between the maximum film thickness WT _max and the minimum film thickness WT _min of the hollow fiber is 0.8. As described above, the hollow fiber is preferably 0.9 or more. In such a hollow fiber membrane, deformation and buckling of the hollow fiber due to stress concentration when pressure is applied from the outside is unlikely to occur.

The porous membrane has a volume porosity of 20% to 80% and an ultrafiltration rate coefficient of pure water of 1.0 to 300.
It refers to a porous membrane in the range of mlm ⁻² h ⁻¹ mmHg ⁻¹ . The average pore diameter of the pores is in the range of 1 to 30 nm. When the inner and outer surfaces of such a porous film are observed with a scanning electron microscope at a magnification of 50,000 to 100,000, an open-portion-like structure of pores of 1 nm or more is found. Such a membrane is useful as a supporting membrane for ultrafiltration membranes or composite membranes for reverse osmosis, composite membranes for gas separation, and other functional composite membranes, depending on the combination of properties of water permeability and molecular weight cutoff. ..

The membrane structure having a cross section perpendicular to the fiber axis of the hollow fiber has a dense layer at least on the outer surface side. It may have a dense layer on the inner surface side. The structure of the outer surface layer is composed of a dense layer having no surface microvoids, and a porous layer in which microvoids are arranged tangentially to the circumference supporting the layer. The microvoid porous layer is further supported by the macrovoid porous layer which is developed tangentially to the circumference. The structure on the inner surface side may be the same as the structure on the outer surface side, or may be a structure in which a dense layer having no microvoids is supported by a macrovoid porous layer. Between the inner surface layer and the outer surface layer, there may be an intermediate layer made of microvoids without macrovoids. In that case, the shape of the microvoids in the intermediate layer must have a cellular structure, and the walls between the microvoids must be connected by pores. Such a structure is a structure that avoids the permeation rate resistance of the porous layer as much as possible because the fractionation characteristics are determined by the dense layer, and is also a durable structure against external force that is applied when the hollow fiber membrane is used.

However, a huge macrovoid having a void diameter reaching 80% of the film thickness of the hollow fiber membrane or having an opening on the outer or inner surface of the hollow fiber membrane is a hollow fiber membrane. And the hollow fiber membrane is likely to be deformed or buckled due to stress concentration when pressure is applied from the outside.

The above general formula-(Ar--S--Ar)
A preferred embodiment for producing a porous hollow fiber membrane having a smooth inner surface, which is composed of polyphenylene sulfide sulfone mainly containing a repeating structural unit represented by —SO ₂ ) _n- ,
The ratio of the linear velocity of the injected liquid discharged from the central pipe of the annular die to the linear velocity of the polymer solution discharged from the annular orifice is in the range of 0.85 to 2.0, and the hollow fiber in the coagulation bath. That is, the ratio of the take-up speed to the linear velocity of the polymer solution discharged from the annular orifice, that is, the draft ratio is in the range of 0.7 to 3.0.

A generally known method for producing a hollow fiber membrane from a polymer solution is a wet method or a dry-wet method in which a spinning solution prepared by dissolving a polymer in a predetermined solvent is used with a spinneret having a central pipe in the center of an annular orifice. It is introduced into the coagulation bath by the method, and is subjected to coagulation, washing with water, and post-treatment steps to make yarn. The spinning solution is discharged from the annular orifice, and a predetermined amount of gas or liquid is introduced from the central pipe. It is often difficult to inject a gas in the solution spinning method, and a liquid is usually used, and more generally, a liquid having a coagulating power is used. Non-coagulating liquids can be used provided that the spinning solution has a sufficiently high viscosity. However, as in the case of polyphenylene sulfide sulfone, when the viscosity of the spinning solution is low, a coagulating liquid is used to obtain spinnability expressed by the gel layer formed by coagulation on the inner surface of the hollow fiber. Hollow fibers need to be formed. In this case, a solution of a solvent used for the spinning solution is generally used as the injection liquid after adjusting the concentration.
Since it is practically advantageous to use an aqueous solution for the coagulation bath, an aqueous solution is often used for the injection solution. In order to produce a hollow fiber membrane suitable for various purposes by widely controlling the water permeability and the fractionation characteristics of the porous hollow fiber membrane, the polymer concentration and coagulation conditions of the spinning dope are changed. Therefore, depending on the characteristics of the target hollow fiber membrane, the viscosity of the spinning dope may be low and the spinnability may be insufficient. Furthermore, the coagulation force of the injected liquid may be low or the liquid may be easily deformed in the coagulation bath. It may be a condition. Moreover, when a coagulable injection liquid is used, wrinkle-shaped irregularities are generated on the inner surface depending on the inner diameter and outer diameter of the hollow fiber, and when the hollow fiber membrane is used, fine particles and foreign substances in the treatment liquid are deposited and the membrane module is -This will cause the performance of the cable to deteriorate. Also, it causes stress concentration of external force applied when the membrane module is used, and causes buckling or rupture of the hollow fiber membrane. Therefore, the inner surface is required to be as smooth as possible. The outer surface tends to be relatively smooth, but the inner surface tends to be wrinkled.
Further, as a general spinning technique, the thickness of the yarn is adjusted by adjusting the ratio of the drawing speed of the hollow fiber in the coagulation bath to the linear velocity of the polymer solution discharged from the annular orifice, that is, the draft ratio. To do. However, as in the case of polyphenylene sulfide sulfone, it is generally difficult to adjust the draft ratio when a hollow fiber membrane is produced from a spinning stock solution having low viscosity and low spinnability.

The general formula of the present invention-(Ar-S-Ar
In the case of producing a hollow fiber membrane from a solution of polyphenylene sulfide sulfone mainly containing a repeating structural unit represented by —SO ₂ ) _n −, the above-mentioned low viscosity, low spinnability,
A smooth porous hollow fiber membrane with an inner surface that has water permeability and molecular weight cut-off characteristics within the range required for ordinary porous membranes for ultrafiltration due to various causes such as wrinkle-like deformation and low coagulation of the inner surface. Was very difficult to make. However, when the present inventors design and manufacture an annular spinneret for a hollow fiber having desired dimensional characteristics so as to satisfy the conditions in the above range,
It has been found that a porous hollow fiber membrane having a smooth inner surface can be produced in a good state.

In the case of a spinning dope having a solution viscosity of several tens of poise or more, the difference in speed between the polymer solution discharged from the annular orifice and the injection liquid discharged from the central pipe is not a serious problem. However, in the case of a spinning dope having a solution viscosity of several tens poise or less, the surface shape inside the hollow fiber is significantly impaired, and in some cases, the injected liquid is entrained in the polymer solution,
The inventors have found that macrovoids are formed in the membrane wall of hollow fibers. This phenomenon can improve the shape of the inner surface to some extent by lowering the coagulability of the injecting liquid, but it causes the increase in the inclusion of macrovoids in the membrane wall and causes the leakage of the hollow fiber membrane. Become. Increasing the coagulability deteriorates the shape of the inner surface, and it is not possible to completely prevent the inclusion of macrovoids.Soluble viscosities of a dozen or less poise make it possible to produce hollow fiber membranes free from the above defects under a wide range of spinning conditions. It was extremely difficult to make the yarn below.

However, the ratio of the linear velocity of the injection liquid discharged from the central pipe of the annular die to the linear velocity of the polymer solution discharged from the annular orifice is in the range of 0.85 to 2.0, and The spinneret size is designed so that the ratio of the drawing speed of the hollow fiber in the coagulation bath to the linear speed of the polymer solution discharged from the annular orifice, that is, the draft ratio is in the range of 0.7 to 1.1, and spinning is performed. It was found that by adjusting the conditions, a hollow fiber in a good condition can be produced under a wide range of spinning conditions without causing the inner surface of the hollow fiber to be smooth and the macrovoids to be caught in the membrane wall. When the ratio of the linear velocity of the injected liquid and the linear velocity of the polymer solution discharged from the annular orifice is 0.85 or less, it becomes difficult to adjust the hollow fiber membrane to a predetermined thickness, and wrinkles are formed on the inner surface. Upper streak or deformation is likely to occur. When it is 2.0 or more, the macro voids are likely to be involved, the circularity of the cross section is changed, and the variation of the film thickness in the fiber axis direction is increased. More preferably 0.
It is advisable to design the spinneret size so that spinning can be performed in the range of 9 or more and 1.5 or less. The lower limit of the draft ratio is also regulated by the viscosity of the spinning dope, so it is difficult to specify it in a straightforward manner. The range is preferably 7 or more, more preferably 0.8 or more. The upper limit of the draft ratio is regulated by the spinnability of the polymer solution, and the spinnability is influenced by not only the viscosity but also the coagulation force of the injection liquid and the conditions of the dry part atmosphere, so it is difficult to specify exactly, but it is approximately 3 .0
In order to spin a defect-free hollow fiber having a smooth inner surface and a roundness of 0.8 or more with good spinnability, 1.5 is required.
The following is a more preferable condition.

A more preferred embodiment for producing a defect-free hollow fiber membrane from the polyphenylene sulfide sulfone polymer of the present invention is to add triethylene glycol (hereinafter abbreviated as TEG) in preparing a spinning dope. Spinning from the NMP solution described above by a dry-wet method. When manufacturing a hollow fiber membrane by a solution spinning method, an additive is often recommended conventionally. The additive is used as a pore-opening agent or for the purpose of improving spinnability, but in the case of a low-molecular organic compound, the phase separation function is used, so it is necessary to add a large proportion of 10% or more. is there. In the case of a high molecular compound, it is washed out in the step after coagulation and the remaining pores are utilized. As with the case of a low molecular organic compound, it is added to the spinning dope in a proportion of 10% or more. There is a need. In many cases, it may also have the function of phase separation.
A polymer compound is added for the purpose of improving spinnability while keeping the die size and structure unchanged. In this case, the effect is to increase the viscosity of the spinning dope, and the effect can be expected with a relatively small amount, but it is necessary that the additive has a high molecular weight. The purpose of the addition of TEG of the present invention is not any of these, but the aim is to have a rectifying effect to improve the flow state of the polymer solution in the vicinity of the die. Even under unexpected conditions, it is effective in smoothing the inner surface, preventing macrovoids, and improving spinnability. It is not clear for what reason such an effect appears, but TEG is added to the spinning solution in a range of 2.5% by weight to 10% by weight, more preferably 3.5% by weight to 7.5% by weight. When added in the following range, the effect of further improving the spinnability is exhibited even in the range of the optimum conditions of the linear velocity ratio and draft ratio of the spinning solution. If the amount is 2.5% by weight or less, the effect is small, and if the amount is 10% by weight or more, the stability of the NMP solution of the polyphenylene sulfide sulfone polymer of the present invention is lost and gelation or solidification is likely to occur, which makes spinning difficult. .. As substances other than TEG, ethylene glycol, glycerin, diethylene glycol, tetraethylene glycol, and their monoesters or diesters have the same effect as TEG, and low molecular weight polyhydric alcohols and these And monoesters or diesters thereof. It is TEG that is easy to spin because the range of gelling or solidification, especially the upper limit, is different.

The spinning stock solution was placed in a dissolution tank equipped with a stirrer, and a predetermined amount of dried polymer was added to the solution. Then, NMP was weighed and heated to 150 ° C. while stirring and dissolving, and after dissolving at 150 ° C. for 1 hour or more, Further, the temperature is raised to 180 ° C. or higher to dissolve for 1 hour or longer. After dissolution, defoaming is performed to prepare a spinning dope. Then, the liquid is transferred to a stock solution tank of a generally known hollow fiber spinning device, and the yarn is produced. When an additive such as TEG is added, it is melted at 180 ° C., and after reaching 150 ° C. or lower and 120 ° C. or higher, a predetermined amount of the additive is added and further stirred to uniformly mix.

Even if the viscosity of the spinning dope thus prepared is 50 poise or less at 50 ° C., if the conditions of the spinneret and the spinning draft are selected within the above-mentioned preferred ranges, the methods and spinning conditions are generally known. The hollow fiber membrane in good condition can be spun. That is, the temperature around the spinneret during spinning is 20 to
The temperature is adjusted to 100 ° C, more preferably 30 to 60 ° C. When the spinning temperature is high, the viscosity is lowered and spinning becomes difficult. If the spinning temperature is too low, the undiluted solution is likely to solidify and continuous stable spinning becomes difficult.

The fluid to be injected into the hollow portion of the hollow fiber membrane is preferably a coagulating liquid in the case of the polyphenylene sulfide sulfone of the present invention. This is because the solution of the polymer has a very low viscosity and is inferior in spinnability, so that it is necessary to promote some filamentous formation in the dry section until it is introduced into the coagulation bath. The injection liquid is preferably an aqueous solution of the solvent used for the spinning dope, 30 to 90% by weight, particularly preferably 50 to
A solution with a concentration of 70% by weight is preferred. When the concentration is high, the coagulability is low, the filament formation is delayed, the spinnability is insufficient, the filament is easily cut right under the spinneret, and in a severe state, it becomes a droplet and cannot be spun. If the concentration is too low, the coagulability is too strong, and wrinkles or streaks are formed on the inner surface and the inner surface is smooth, making it difficult to spin a perfect circular hollow fiber membrane.

The concentration of the coagulation bath is preferably an aqueous solution of the solvent used in the spinning dope with a concentration in the range from 0 to 40% by weight. From the viewpoint of recovering the solvent, a high concentration is economically advantageous, but in the case of the polyphenylene sulfide sulfone of the present invention, the coagulation is relatively slow, so a low concentration is preferable. The temperature is 0 to 70 ° C., more preferably 2
It is 0 to 60 ° C. The coagulation conditions are selected in consideration of the coagulability and the performance characteristics of the hollow fiber membrane.

The water washing step can be carried out in the same manner as a normal dry-wet spinning method. As a post-treatment after washing with water, heat treatment is preferable. Usually, hot water at 50 to 95 ° C., preferably 70 to 95 ° C., is used for 1 after the washing step.
By continuously treating for 0 to 60 seconds, the performance and dimensions of the hollow fiber membrane can be stabilized. Of course, there is no particular problem even if the batch processing is performed for 1 minute or more. After the heat treatment, the hollow fiber membrane may be processed into a membrane module, and may be impregnated and dried with an appropriate amount of a surfactant so that water can be easily replaced during use.

The present invention will be specifically described below with reference to examples, but it goes without saying that the present invention is not limited to the following examples.

The characteristic value evaluation / measurement method of the present invention is as follows.

(1) The viscosity of the spinning dope was measured by using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd.
o. It measured at 30 rpm or 60 rpm using the rotor of 2.

(2) Form and size of hollow fiber (inner diameter (I
D), outer diameter (OD), roundness, inner surface smoothness)
The measurement was performed using a Nihon Kogyo metal microscope Nikon VMS type.

The roundness was calculated by the following formula.

Roundness = minor axis of outer diameter (a _o ) / major axis of outer diameter (b _o ) × 100 Further, the smoothness of the inner surface is about 500 times with the above-mentioned optical microscope or scanning electron microscope. And observed according to the following procedure.

Good smoothness of inner surface ○ Wrinkle, few streaks △ Wrinkle, many streaks × (3) Volume of hollow fiber The porosity is calculated from the dimensions of the hollow fiber, and the polymer absolute dry weight and the hollow fiber volume are calculated. Calculated from

(4) Regarding the pressure resistance of the hollow fiber, a leak was observed by making a glass mini-module having a length of about 25 cm. The number of hollow fibers was about 10 to 20, the hollow fibers were inserted into glass so that the effective length was 20 cm, and both ends were sealed with an adhesive. Close one end of the hollow fiber sealed with an adhesive, connect a rubber tube to the other end, and with nitrogen gas,
A pressure of about 100 mmHg was applied from the inside of the hollow fiber. The module was filled with water, air bubbles from the hollow fiber were observed, and evaluated according to the following procedure.

No air bubbles are generated. 0-1 air bubbles are generated / m △ Air bubbles are generated at least 1 air / m × (5) The water permeability of the hollow fiber is about 25 cm long glass. Was prepared by measuring the ultrafiltration rate using purified water. The number of hollow fibers is about 10 to 20
A book was inserted into glass so that the effective length of the hollow fiber was 20 cm, and both ends were sealed with an adhesive. The filtered water was collected from a nozzle of a branch pipe attached to a glass tube, and the weight of the filtered water was measured at a certain time. Purified water was supplied while filtering with a hollow fiber type ultrafiltration membrane, and measured at 25 ° C. The water permeability UFRS was calculated by the following formula.

UFRS = Wd ⁻¹ A ⁻¹ t ⁻¹ P ⁻¹ (mlm ⁻² h ⁻¹ mmHg ⁻¹ ) where W: weight of filtered water d: density of water at 25 ° C. (g / ml) A: Effective membrane area of hollow fiber membrane (m ² ) t: Time of collecting filtered water (h) P: Applied pressure (mmHg) (6) Linear velocity of injection liquid discharged from the central pipe of the annular die The ratio of the linear velocity of the polymer solution discharged from the annular orifice to the specific gravity of the polymer solution is about 1.15, and the specific gravity of the injected liquid is about 1.00. The discharge weight per unit time (g / min) And the discharge area of the orifice.

[0042]

EXAMPLES The present invention will be described with reference to examples.

Examples 1 to 7, Comparative Examples 1 to 15 Polyparaphenylene sulfide sulfone (PPS) obtained from Toray Phillips Petroleum Co., Ltd.
Using S), a hollow fiber membrane spinning test was performed. 320 parts by weight of PPSS polymer having an MF value of 28, 80 parts by weight of TEG, and 1200 parts by weight of n-methylpyrrolidone (NMP) are weighed in a separable flask having a volume of 2 l, heated from room temperature, and heated at 130 ° C. for 1 hour. Subsequently, it was dissolved by stirring at 180 ° C. for 6 hours. The viscosity was 2.98 poise at 50 ° C. and 1.60 poise at 70 ° C. This polymer solution was filtered through a 400-mesh stainless mesh and subjected to a spinning test. Tests were conducted by changing the die size and the polymer discharge amount, and the results are shown in Table 1. The temperature of the spinneret during spinning was 55 ° C, 60% NMP aqueous solution was used as the injection liquid, and 40 ° C water was used as the coagulation bath. Wash with water 30
It was performed in a tray-type washing bath at ℃.

[0044]

[Table 1]

As can be clearly seen from Table 1, the ratio of the linear velocity of the injection liquid discharged from the central pipe of the annular orifice to the linear velocity of the spinning dope discharged from the annular orifice is 0.85 to 2.0. When the spinning draft ratio is in the range of 0.7 to 1.1, the inner surface of the hollow fiber is smooth, and there is no leak due to macrovoids in the membrane wall of the hollow fiber. A yarn film can be spun.

Table 2 shows the evaluation results of the circularity of the cross section, the water permeability, the volume porosity, and the puncture pressure of the hollow fiber membrane in a good state.

[0047]

[Table 2]

Examples 8 to 12 A spinning dope was prepared in the same manner as in Example 1 using PPSS having an MF value of 40 obtained from Toray Phillips Petroleum Co., Ltd. However, the amounts of TEG added were 2.5 and 5.0% by weight. TEG0
The viscosity of the spinning dope of 10% was 2.0 poise at 50 ° C and 1.2 poise at 70 ° C. The stock solution with TEG 2.5% was slightly higher than that with TEG 0%, and the viscosity of the stock solution with TEG 5.0% was 2.2 poise at 50 ° C. and 1.3 poise at 70 ° C., respectively. However, it is judged that the viscosity does not increase to the extent that improvement in spinnability is expected. The dimensions of the spinneret used were: slit outer diameter 1.4, slit inner diameter 1.1, injection pipe inner diameter 0.7 (mm), spinning draft 0.83, discharge linear velocity ratio 1.36, spinning temperature 30.
~ 50 ° C, dry length 10 ~ 50mm, injection liquid concentration 60
%, Injection liquid temperature 25 ° C., coagulation bath concentration 10%, coagulation bath temperature 20 ° C., washing bath temperature 30 ° C., heat treatment bath 95 ° C.,
Spinning was performed while changing the spinning temperature and the range of dry length. Table 3 shows the examined spinning conditions and the results.

[0049]

[Table 3]

It has been shown that the addition of TEG enables stable spinning from a low-viscosity spinning dope.

Examples 13 to 16 Using PPSS obtained from Toray Phillips Petroleum Co., Ltd. and having an MF value of 33, 5% of TEG was added in the same manner as in Example 1 to prepare spinning dope. The intrinsic viscosity of the polymer measured with NMP as a solvent at 30 ° C. was about 0.35 dl / g, and the weight average molecular weight was about 30,000. The viscosity of the spinning dope was 2.1 poise at 50 ° C and 1.4 poise at 70 ° C. The dimensions of the die used are: slit outside diameter 1.4, slit inside diameter 1.1, injection pipe inside diameter
At 0.7 (mm), spinning draft 0.79, discharge linear velocity ratio 0.88, spinning temperature 50 ° C, dry length 30 mm, injection liquid concentration 40 to 80%, injection liquid temperature 50 ° C, coagulation bath concentration 0
%, Coagulation bath temperature 30 ° C., washing bath temperature 30 ° C., heat treatment bath 9
The spinning was performed under the condition of 0 ° C. while changing the concentration range of the injection liquid.
The results are shown in Table 4.

[0052]

[Table 4]

In the spinneret with dimensional accuracy that can be usually manufactured,
The concentration of the injection liquid is preferably in the range of 40 to 65%, and it was determined that spinning can be performed up to about 80% by selecting the size of the die.

Examples 17 to 27 Using PPSS having a MF value of 8 obtained from Toray Philippe Petroleum Co., Ltd., TEG 5% was added in the same manner as in Example 1 to prepare spinning dope. The viscosity of the spinning dope was 4.1 poise at 50 ° C and 2.7 poise at 70 ° C. The dimensions of the die used are the outer diameter of the slit 1.
4, slit inner diameter 1.1, injection pipe inner diameter 0.7 (mm)
Then, spinning draft 0.83, discharge linear velocity ratio 1.36, spinning temperature 60 ° C., dry length 50 mm, injection liquid concentration 60%,
The spinning temperature is changed to 55 ° C, the coagulation bath concentration is 0 to 40%, the coagulation bath temperature is 10 to 50 ° C, the washing bath temperature is 30 ° C, and the heat treatment bath is 95 ° C. did. The results are shown in Table 5.

[0055]

[Table 5]

When the concentration of the coagulating bath is increased, the water permeation rate tends to decrease, and when it is 60% or less, particularly preferable inner surface smoothness is obtained.

When the temperature of the coagulation bath is high, the water permeation rate tends to be high, and when it is 50 ° C. or lower, leak-free and particularly preferable characteristics are obtained.

Examples 28 to 36 Using PPSS having an MF value of 7 obtained from Toray Phillips Petroleum Co., Ltd., a spinning dope was prepared in the same manner as in Example 1 without adding TEG. The weight average molecular weight of the polymer was about 30,000. The viscosity of the spinning dope was 80 poise at 50 ° C and 49 poise at 70 ° C. The dimensions of the die used were: slit outside diameter 1.5, slit inside diameter 1.1, injection pipe inside diameter 0.7 (mm), spinning draft 1.04, discharge linear velocity ratio 1.82, spinning temperature 70.
~ 100 ℃, dry length 50 ~ 450 mm, injection liquid concentration 6
Changing the coagulation bath concentration and coagulation bath temperature range under the conditions of 0%, injection liquid temperature 65 to 85 ° C, coagulation bath concentration 0%, coagulation bath temperature 30 ° C, washing bath temperature 30 ° C, and heat treatment bath 95 ° C. Spun The results are shown in Table 6.

[0059]

[Table 6]

It is understood that in the case of a spinning dope having a high molecular weight and a high viscosity, spinning can be carried out at a relatively high temperature and a long dry length can be obtained.

Example 37 Using PPSS having an MF value of 31 obtained from Toray Philippe Petroleum Co., Ltd., 5% of TEG was added in the same manner as in Example 1, and the polymer concentration of the spinning solution was 22%.
A spinning dope of was prepared. Viscosity of spinning dope at 50 ° C 7.
It was 8 poise and 3.7 poise at 70 ° C. The dimensions of the die used are: slit outside diameter 1.4, slit inside diameter
1.1, injection pipe inner diameter 0.7 (mm), spinning draft 0.75, discharge linear velocity ratio 1.20, spinning temperature 80 ° C., dry length 50 mm, injection liquid concentration 60%, injection liquid temperature 65
℃, coagulation bath concentration 0%, coagulation bath temperature 30 ℃, washing bath temperature 3
Spinning was performed under the conditions of 0 ° C. and a heat treatment bath of 95 ° C. When the spinning draft and the discharge linear velocity ratio were set within a suitable range, a hollow fiber membrane with no leak and a smooth inner surface and UFRS = 55 could be spun.

Example 38 Using PPSS having an MF value of 31 obtained from Toray Philippe Petroleum Co., Ltd., 5% of TEG was added in the same manner as in Example 1 to prepare a spinning solution having a polymer concentration of 18%.
A spinning dope of was prepared. The viscosity of the spinning dope is 50 ° C. 2.
It was 1 poise and 1.2 poise at 70 ° C. The dimensions of the die used are: slit outside diameter 1.4, slit inside diameter
1.1, injection pipe inner diameter 0.7 (mm), spinning draft 0.79, discharge linear velocity ratio 0.88, spinning temperature 30 ° C., dry length 10 mm, injection liquid concentration 60%, injection liquid temperature 20
℃, coagulation bath concentration 0%, coagulation bath temperature 30 ℃, washing bath temperature 3
Spinning was performed under the conditions of 0 ° C. and a heat treatment bath of 95 ° C. When the spinning draft and the discharge linear velocity ratio were set in a suitable range, a hollow fiber membrane of UFRS = 156, which had no leak and had a smooth inner surface, could be spun although it was a low-viscosity stock solution.

[0063]

INDUSTRIAL APPLICABILITY According to the present invention, a hollow fiber membrane having excellent heat resistance and solvent resistance, a smooth inner surface and no defects such as macrovoids can be economically produced by a stable technique. It can be provided in an advantageous way. Application of such a hollow fiber membrane having excellent heat resistance and solvent resistance to various separation / purification processes contributes to resource and energy saving, and economically manufactures high-quality products to provide to society. Contribute to that.

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[Procedure amendment]

[Submission date] June 5, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

The above general formula-(Ar--S--Ar)
A preferred embodiment for producing a porous hollow fiber membrane having a smooth inner surface, which is composed of polyphenylene sulfide sulfone mainly containing a repeating structural unit represented by —SO ₂ ) _n- ,
The ratio of the linear velocity of the injected liquid discharged from the central pipe of the annular die to the linear velocity of the polymer solution discharged from the annular orifice is in the range of 0.85 to 2.0, and the hollow fiber in the coagulation bath. The ratio of the take-up speed to the linear velocity of the polymer solution discharged from the annular orifice, that is, the draft ratio is in the range of 0.7 to 1.1.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

However, the ratio of the linear velocity of the injection liquid discharged from the central pipe of the annular die to the linear velocity of the polymer solution discharged from the annular orifice is in the range of 0.85 to 2.0, and The spinneret size is designed so that the ratio of the drawing speed of the hollow fiber in the coagulation bath to the linear speed of the polymer solution discharged from the annular orifice, that is, the draft ratio is in the range of 0.7 to 1.1, and spinning is performed. It was found that by adjusting the conditions, a hollow fiber in a good condition can be produced under a wide range of spinning conditions without causing the inner surface of the hollow fiber to be smooth and the macrovoids to be caught in the membrane wall. When the ratio of the linear velocity of the injected liquid and the linear velocity of the polymer solution discharged from the annular orifice is 0.85 or less, it becomes difficult to adjust the hollow fiber membrane to a predetermined thickness, and wrinkles are formed on the inner surface. Upper streak or deformation is likely to occur. When it is 2.0 or more, the macro voids are likely to be involved, the circularity of the cross section is changed, and the variation of the film thickness in the fiber axis direction is increased. More preferably 0.
It is advisable to design the spinneret size so that spinning can be performed in the range of 9 or more and 1.5 or less. The lower limit of the draft ratio is also regulated by the viscosity of the spinning dope, so it is difficult to specify it in a straightforward manner. The range is preferably 7 or more, more preferably 0.8 or more. The upper limit of the draft ratio is regulated by the spinnability of the polymer solution, and the spinnability is influenced by not only the viscosity but also the coagulation force of the injection liquid and the conditions of the dry part atmosphere, so it is difficult to specify exactly, but it is approximately 1 .1
In order to spin a defect-free hollow fiber having a smooth inner surface and a roundness of 0.8 or more with good spinnability, 1.0 is required.
The following is a more preferable condition.

Claims (3)

[Claims] 1. A general formula - (Ar-S-Ar- SO 2) n
A porous hollow fiber membrane composed of a polyphenylene sulfide sulfone mainly containing a repeating structural unit represented by (wherein Ar represents a phenylene group) and having a smooth inner surface and no defects due to macrovoids. 2. A general formula - (Ar-S-Ar- SO 2)
_In the spinning of polyphenylene sulfide sulfone mainly containing a repeating constitutional unit represented by _n − (where Ar represents a phenylene group), the linear velocity of the injected liquid discharged from the central pipe of the annular die and the annular orifice The ratio with the linear velocity of the polyphenylene sulfide sulfone solution is in the range of 0.85 to 2.0, and the ratio of the take-up velocity of the hollow fiber in the coagulation bath to the linear velocity of the solution discharged from the annular orifice, that is, A method for producing a porous hollow fiber membrane, characterized in that the draft ratio is in the range of 0.7 to 1.1. 3. The general formula:-(Ar-S-Ar-S
O ₂ ) _n − (where Ar represents a phenylene group), wherein the polyphenylene sulfide sulfone mainly containing a repeating constitutional unit is an n-methylpyrrolidone solution to which triethylene glycol is added. Item 3. A method for producing a porous hollow fiber membrane according to item 2.