JPH041015B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a regenerated cellulose large pore membrane. More specifically, it relates to a method for producing a regenerated cellulose large-pore membrane, which is characterized by casting a cellulose cuprammonium solution in an organic solvent atmosphere to cause microphase separation, and then horizontally immersing it in a mixed solution containing an organic solvent. It is something. In recent years, membrane separation technology has been attracting attention among materials separation and purification technologies. Unlike distillation, polymer membranes are used in a wide range of fields, taking advantage of the characteristics of the membrane separation process: no temperature change is required for separation, little energy is required for separation, and the process is compact. ing. For example, dairy farming, fisheries, livestock farming, food processing, pharmaceuticals,
These include chemical industry, textile dyeing processing, steel, machinery, surface treatment, water treatment, and nuclear power industry. In the future, fields where membrane separation systems may become central are fields that require concentration, purification, and recovery at low temperatures (food and biochemical industries), and fields that require sterility and dust-free conditions (pharmaceuticals, etc.). (therapeutic institutions, electronics industry), concentrated recovery of trace amounts of expensive substances (nuclear power, heavy metal fields), special small quantity separation field (pharmaceutical field), and energy-intensive separation field (distillation substitute). As membranes used in these fields, there is an increasing need for hydrophilic membranes with large pores and easy handling. The large pore membrane in the present invention means a membrane with an average pore diameter (twice the pore radius ₃ described below) of 0.4 μm or more. One method for producing a porous membrane made of cellulose, which is a typical example of a hydrophilic polymer, is to obtain a porous membrane by mixing an emulsion such as kerosene into a cellulose copper ammonia solution. The porous membrane obtained by this method has an average pore diameter of 1 μm or more, but the pores are non-circular and the pores form a layered structure, making it extremely brittle. Furthermore, the casting solution is mixed with the emulsion. It is unstable and difficult to produce a film from this solution industrially with good reproducibility. In addition, in a method of manufacturing a porous membrane by mixing a non-coagulating liquid into a cupric ammonia solution and immersing it in a coagulating solution to solidify it, the resulting porous membrane has a pore diameter of 0.01 μm or less and has poor permeability.
Furthermore, a method for producing a regenerated cellulose porous membrane by saponifying a cellulose acetate derivative porous membrane with an alkaline aqueous solution is known. Although the average pore size of the porous membrane obtained by this method may be in the range of 0.01 to 2 μm, the pore size distribution is wide. The average molecular weight of the cellulose molecules that make up this membrane is usually 3.5×
10 ⁴ or less. Possibly due to such a low molecular weight, the mechanical properties (particularly the strength) of the porous membrane in the dry state are extremely low and brittle. For example, the porosity of a porous membrane is Pr
(%), the elastic modulus of the porous membrane is approximately 10 ² (100
-Pr) ³ dyn/ ^cm2 . Since the strength in a wet state with water is lower than that in a dry state, conventional regenerated cellulose porous membranes obtained from cellulose derivatives were sometimes damaged during handling.
Furthermore, the manufacturing process is long and the cost is high. The inventors of the present invention have completed the present invention as a result of intensive research to eliminate these conventional drawbacks. That is, the gist of the present invention is that in the film forming process of casting, coagulating, regenerating, washing, and drying a cellulose cuprate solution having an average molecular weight of 5×10 ⁴ or more, the cellulose concentration in the cellulose cuprate solution is 2. ~5% by weight, and after casting, microphase separation is caused in an organic solvent atmosphere before coagulation, and then the cast product undergoing microphase separation is immersed in an organic solvent atmosphere in a horizontal position to solidify. A method for producing a regenerated cellulose large-pore membrane characterized by: The present invention will be explained in detail below. In the present invention, there are two types of organic solvent atmospheres: gas (vapour) and liquid atmospheres. In addition, a horizontal state means an inclination angle of 0° (horizontal) ±10°, casting means extruding the cellulose copper ammonia solution onto a horizontal surface with a constant thickness, and coagulation means that the cellulose copper ammonia solution is solid. It is to become
At this time, the viscosity of the solution is 10 ⁴ poise or more, and regeneration means removing copper from the coagulated cellulose copper ammonia solution and changing it to cellulose solid. is usually 1% or less. Washing with water means washing off various treatment liquids used in the regeneration process from the cellulose membrane with water, and drying means that the moisture content in the cellulose membrane becomes 10% or less. In addition, the copper ammonia solution in the present invention is a solution whose main components are copper and ammonia, and is a dark blue solution called Schuweitzer's reagent, which means a solvent system that can substantially dissolve cellulose. . It also includes some mixture of cations other than copper or solvents other than ammonia. The first feature of the production of the present invention is that a cuprate ammonia solution having an average molecular weight of cellulose molecules of 5×10 ⁴ or more is used. As the molecular weight increases, the strength of the porous membrane increases, the brittleness improves, the handling of the porous membrane becomes easier, and the breakage of the porous membrane decreases. With the conventional method of dissolving cellulose derivatives (such as cellulose acetate) in an organic solvent and then forming a porous membrane, it is almost impossible to increase the molecular weight to 5×10 ⁴ or more. By using a cupric ammonia solution, a regenerated cellulose membrane of high molecular weight can be produced. The elastic modulus of the membrane obtained by the method of the present invention is 1.5×10 ⁸ (100−Pr) dyn/cm ² or more.
The larger the average molecular weight of cellulose molecules, the lower the breakage rate when compared at the same porosity. As for the influence of the average molecular weight on the physical properties of the film, it is recognized that as the average molecular weight increases, it tends to become saturated. Therefore, an average molecular weight of 5×10 ⁴ or more and 50×10 ⁵ or less is acceptable from the point of view of practical ease of handling. Preferably 55×
10 ⁴ or more and 3×10 ⁵ or less. Next, the second feature of the present invention is that the cellulose concentration in the casting solution is 2% by weight or more and 5% by weight or less. When the cellulose concentration is less than 2% by weight, the viscosity of the cuprammonium solution decreases, making it difficult to control the film thickness even when immersed horizontally in a coagulation solution containing an organic solvent, which will be described later. The strength of the membrane is significantly lower than when the amount is 2% by weight or more, and it is difficult to obtain a porous membrane with good manufacturing reproducibility. When the amount exceeds 5% by weight, it is difficult to obtain the large pore size porous membrane of the present invention. Therefore, if the cellulose concentration is less than 5% by weight and 2% by weight or more, the performance as a large-pore porous membrane is sufficiently satisfied. Preferably the cellulose concentration is 3-4% by weight. However, the cellulose concentration here means the weight concentration of cellulose in the copper ammonia solution. The third feature of the method of the present invention is that after casting and before solidification, the cast product undergoing microphase separation in an organic solvent atmosphere is horizontally immersed in an organic solvent liquid atmosphere and solidified. . The solution immediately after microphase separation has high fluidity. The present invention was completed by discovering that when the cellulose concentration is low, a lot of unevenness occurs due to this fluidity. That is, as the cellulose concentration decreases, the viscosity of the cellulose copper ammonia solution decreases, and the viscosity of the solution after microphase separation decreases. Therefore, when a cast product obtained from a solution with a cellulose concentration of 5% by weight or less is vertically immersed in the organic solvent liquid atmosphere, the viscosity of the solution decreases after microphase separation and it becomes difficult to control the film thickness. As a result, film formation becomes impossible. By immersing the cast material horizontally in an organic solvent liquid atmosphere and solidifying it, it is possible to control the film thickness, and the pore diameter of the porous film increases, the number of pores increases, and the number of through holes increases, making it even easier to reproduce. Porous membranes can be obtained with good properties. The fourth feature of the method of the present invention is that microphase separation occurs before solidification in an organic solvent atmosphere. What is microphase separation here?
It means a state in which a concentrated phase or a dilute phase of cellulose is dispersed and stabilized as particles with a diameter of 0.01 to several μm in a solution. The above-mentioned principle feature (occurrence of microphase separation) of the method of the present invention is evident from the fact that the film becomes devitrified during film formation in the organic solvent atmosphere.
That is, the method of the present invention is characterized in that it undergoes microphase separation in an organic solvent atmosphere, and then undergoes solidification and regeneration treatment. In order to cause such microphase separation solely by the action of an organic solvent, it is necessary that the organic solvent has no hydroxyl group and has a solubility in water of 10% by weight or more. Another method for causing microphase separation is to utilize temperature changes after casting. There are two specific methods for causing microphase separation using only the action of an organic solvent: the organic solvent atmosphere is a gas (vapour) or a liquid. In the method of the present invention, the boiling point of the organic solvent is important in determining whether the organic solvent can be used in an organic solvent vapor atmosphere. In an organic solvent vapor atmosphere with a boiling point of 100°C or higher, no microphase separation occurs, and either a transparent film or a skin layer forms on the membrane surface, and the surface pore size becomes 0.01 μm or less. Therefore, the lower the boiling point, the better, but from the viewpoint of manufacturing conditions, it is usually 0° C. or higher. If the organic solvent atmosphere is liquid, the boiling point is not important. First, a case where the organic solvent atmosphere is a gas will be explained. When forming a film from a cellulose copper ammonia solution with a cellulose concentration of 2% by weight or more and 5% by weight or less, an organic solvent with a boiling point of 100°C or less, a solubility in water of 10% by weight or more, and no hydroxyl group is used. Casting is carried out under a vapor atmosphere containing at least one organic solvent. After the cellulose cuprammonium solution undergoes microphase separation and before the dilute phase after microphase separation leaches onto the membrane surface,
An organic solvent/ammonia/water mixed solution containing an organic solvent that does not have hydroxyl groups, has a solubility in a 28% ammonia aqueous solution of 10% by weight or more, and does not swell cellulose (hereinafter referred to as the coagulation mixed solution) ) The cast material is immersed in a horizontal state. The resulting porous membrane has larger pore diameter, pore density, and porosity than porous membranes produced by conventional methods. When the concentration of organic solvent vapor becomes 50% or less of the saturated vapor pressure, the pore diameter becomes smaller, the pore density also decreases, and the abundance ratio of through-holes decreases. By forming the film in an organic solvent vapor atmosphere, the skin layer that normally forms on the evaporation surface of the porous membrane disappears, and the pore size is reduced on the evaporation surface.
Pores of 0.01 μm or more are formed. As the concentration of the organic solvent in the film forming atmosphere increases, the pore diameter of the porous membrane increases, the number of pores increases, and the number of through holes increases. Therefore, it is desirable that the partial pressure of the organic solvent vapor is 50% or more of the saturated vapor pressure. Furthermore, when the cellulose concentration in the casting solution is less than 2% by weight, the viscosity of the cuprammonium solution decreases, making it difficult to control the film thickness even when immersed horizontally in a mixed solution containing an organic solvent. It is difficult to obtain porous membranes with good reproducibility. When the cellulose concentration exceeds 5% by weight, it is difficult to obtain a porous membrane with large pores by the method of the present invention. Therefore, if the cellulose concentration is 2% by weight or more and 5% by weight or less, the performance as a large-pore porous membrane is sufficiently satisfied. In addition, after casting in an organic solvent atmosphere, the cellulose cuprammonium solution causes microphase separation, but before the dilute phase is leached onto the membrane surface, it is poured horizontally into a coagulation mixed solution containing an organic solvent. By immersing the film in this state, the pore diameter becomes larger, the number of pores increases, the number of through holes increases, and the unevenness of film formation increases compared to when the material is not immersed in the coagulation mixed solution or when it is not immersed in the horizontal state. The yield also increases. Therefore, the concentration of ammonia with respect to water in the coagulation mixed solution is 0.2% by weight or more and 5% by weight or less, and the concentration of organic solvent with respect to water is 10% by weight or more.
It is desirable that the amount is at least 70% by weight and not more than 70% by weight. Furthermore, by adding the organic solvent to the cellulose cupric ammonia solution up to the gel point or a concentration of 30% by weight or less, the film forming time can be shortened and a porous film with better reproducibility can be obtained. The occurrence of microphase separation is confirmed by direct visual observation of the devitrification phenomenon during membrane formation, or by the presence of particles with a diameter of 1 μm or more by electron microscopic observation of the membrane after membrane formation. It is also possible to promote such microphase separation with a mixed solvent for coagulation. Organic solvents that do not have hydroxyl groups and
It is necessary that the solubility in a 28% by weight ammonia aqueous solution at 20°C is 10% by weight or more and that the cellulose is not swollen. Here, an organic solvent that does not swell cellulose is an organic solvent that, when a cellulose porous membrane measuring 1.00 cm long and 1.00 cm wide is immersed in the organic solvent for 10 minutes at 20°C, the size will be 1.05 to 0.97 cm long and 1.05 to 0.97 cm wide. means solvent. Further, it is important whether or not the organic solvent of the mixed solution for coagulation containing the organic solvent has a hydroxyl group. In a mixed solution containing an organic solvent with hydroxyl groups, microphase separation does not occur, and a transparent film is formed, a skin layer is formed on the membrane surface, or it solidifies into a gel-like state, resulting in a surface pore size of 0.01 It becomes less than μm. Specific examples of organic solvents that cause microphase separation in a solvent vapor atmosphere include ketones and amines. For example, there are acetone, methyl ethyl ketone, trimethylamine, etc., and these are preferable because the smaller the molecular weight, the shorter the time for microphase separation to occur and the workability in post-processing steps (coagulation, regeneration, washing, drying steps, etc.). The film was formed in an acetone vapor atmosphere, and after the cellulose copper ammonia solution caused microphase separation, it was immersed in a horizontal state in a mixed solution for coagulation of acetone/ammonia/water, and then an acid (for example, 2% by weight After regenerating with dilute sulfuric acid) and washing with water, if the water is replaced with an organic solvent with a boiling point of 70°C or less (this organic solvent is abbreviated as an organic solvent for water replacement), the number of pores and porosity will increase. However, it is more preferable. In addition, the concentration of ammonia relative to water in the acetone/ammonia/water coagulation mixed solution is 0.2% by weight or more and 3% by weight or less, and the concentration of acetone relative to water is 15% by weight or more and 65% by weight or less. is the most desirable. Furthermore, when water is replaced using acetone as an organic solvent for water replacement with a boiling point of 70°C or less, the production time is further shortened, the number of pores in the obtained porous membrane increases, and the porosity also increases. The porous membrane provides good overperformance. The acid for regeneration is not particularly limited, but dilute sulfuric acid is used in consideration of recovery, corrosion, etc. In particular, the porous membrane obtained by the method of the present invention is notable for the fact that the polymer chains effectively create pores, and the number of free ends that do not create pores is small. Therefore, the strength of the obtained porous membrane is much greater than that of conventional membranes. Next, a case where the organic solvent atmosphere is a liquid will be explained. When forming a film from a cellulose copper ammonia solution with a cellulose concentration of less than 5% by weight and 2% by weight or more, it does not have hydroxyl groups, has a solubility in a 28% by weight ammonia aqueous solution of 10% by weight or more, and does not swell the cellulose. The cellulose copper ammonia solution after casting is horizontally immersed in a mixed solution for microphase separation containing at least one type of organic solvent to cause microphase separation, coagulated in the mixed solution, and then regenerated using an acid. . The obtained porous membrane has larger pore diameter, pore number, and porosity than those obtained by conventional methods. The amount of immersion of the cellulose copper ammonia solution into the microphase separation mixed solution is such that the weight ratio of [mixed solution/cellulose copper ammonia solution] is 1 to 1000, preferably 50 to 750, and the film forming time is becomes shorter and the pore size, pore number, and porosity increase. In addition, if the cellulose concentration in the casting solution is less than 2% by weight, the viscosity of the copper ammonia solution decreases, making it difficult to control the film thickness even when immersed horizontally in the organic solvent mixed solution. It is difficult to obtain porous membranes with good reproducibility. If the amount exceeds 5% by weight, it is difficult to obtain a porous membrane with large pores according to the method of the present invention. Therefore, similar to the method in which cellulose is cast in an organic solvent vapor atmosphere to cause microphase separation of the cellulose copper ammonia solution, it is immediately immersed in a coagulating mixed solution containing an organic solvent. Weight% or more, 5
If it is less than % by weight, the properties as a porous membrane with large pores are sufficiently satisfied. Further, the composition of the mixed solution for microphase separation is an organic solvent/ammonia/water system, and the concentration of ammonia with respect to water is 5% by weight or less, preferably 3% by weight or less, and the concentration of organic solvent with respect to water is 10% by weight or less.
At least 70% by weight, preferably 25% by weight
As mentioned above, if it is 60% by weight or less, the pore diameter becomes large, the number of pores increases, and the abundance ratio of through holes also increases. By immersing the cellulose copper ammonia solution after casting in the mixed solution for organic solvent microphase separation in a horizontal state and forming a film, the skin layer that normally forms at the interface of the porous membrane surface disappears, and the skin layer that normally forms on the interface of the porous membrane surface disappears. pore size
Pores of 0.01 μm or more are formed. In addition, the organic solvent is added to the cellulose copper ammonia solution to the gel point or to a concentration of 30% by weight or less.
By adding it in advance, the film forming time can be shortened and a porous film with good reproducibility can be obtained. In the method of the present invention, when the cast material is horizontally immersed in the mixed solution for microphase separation after casting, the cast material becomes devitrified. That is, like the above method, this method also undergoes microphase separation. moreover,
After forming a film, it was immersed in a mixed solution for microphase separation consisting of acetone and aqueous ammonia in a horizontal state.
Then, by regenerating with acid (for example, 2% dilute sulfuric acid), washing with water, and then replacing the water with acetone, the film forming time is further shortened and the number of pores in the obtained porous film is increased. Moreover, the porosity also increases, and the overperformance of the porous membrane becomes better. The porous membrane obtained by the method of the present invention can be used to separate and remove target components in liquid or gas mixtures containing water, such as artificial kidneys, artificial livers, and artificial pancreatic membranes. A strong porous membrane that is hydrophilic and has excellent mechanical properties is particularly suitable for bio-related fields (medicine, biochemical industry) or food fermentation fields. Typical examples of microstructural features and various physical property values of films obtained by the method of the present invention are shown. The average molecular weight of cellulose molecules is 5.8×10 ⁴ , the dynamic elastic modulus at 30°C at a measurement frequency of 110 Hz is 8.0×10 ⁹ dyn/cm ² , and the peak value (tan δ) of mechanical loss tangent (tan δ) is 0.28.
Above, the average pore diameter is 1.5μm, the porosity is 78%, and the number of pores is
It is 4.4× ¹⁰⁷ pieces/ ^cm2 . Prior to Examples, methods for measuring various physical property values used in the detailed description of the invention are shown below. Average molecular weight: The average molecular weight (viscosity average molecular weight) Mv is calculated by substituting the intrinsic viscosity number [η] (ml/g) measured in a cupric ammonia solution (20°C) into the following formula (1). Mv [η] × 3.2 × 10 ³ (1) (tan δ) max, dynamic elastic modulus: A strip-shaped sample with a width of 1 mm and a length of 5 cm was cut from the porous membrane and
Using Vibron DDV-c type, measurement frequency 110
Hz, tanδ at an average heating rate of 10°C/min under dry air
- Measure the temperature curve and the dynamic modulus-temperature curve. From the measured tanδ-temperature curve and dynamic elastic modulus-temperature curve, the peak value of tanδ (tanδ) max
and the dynamic elastic modulus at 30℃. Average pore radius ₃ and number of pores: If the number of pores with a pore radius of r to r + dr per 1 cm ² of porous membrane is expressed as N(r) dr (N(r) is the pore radius distribution function), then the average pore radius is ₃ and the number of holes per cm ² N are given by equations (2) and (3), respectively. ₃ = ∫ ^∞ / ₀ r ³ N(r) dr / ∫ ^∞ / ₀ r ² N(r) dr (2) N = ∫ ^∞ ₀ N(r) dr (3) Porous membrane using a scanning electron microscope Take electron micrographs of the front and back sides of the A pore size distribution function N(r) is calculated from the photograph by a known method and substituted into equation (2). In other words, take a scanning electron micrograph of the area where you want to find the pore size distribution and take it to an appropriate size (for example,
20cm x 20cm) and draw 20 test lines (straight lines) at equal intervals on the resulting photo. Each straight line crosses a number of holes. Measure the length of the straight line that exists within the hole when it crosses the hole, and find this frequency distribution function. Using this frequency distribution function,
For example, N(r) is determined by the method of "stereorosi"("QuantitativeMorphology" by Norio Suwa, published by Iwanami Shoten). Porosity Pr: Cut a planar porous membrane into a circular shape with a diameter of 47 mm, dry the porous membrane in vacuum, and reduce the moisture content to 0.5%.
The following shall apply. When the thickness of the porous membrane after drying is d (cm) and the weight is W (g), the porosity Pr (%) is given by equation (4). Pr (%) = (1-W/1.5 x 17.34 x d) x 100 (4) Strength elongation: A strip-shaped sample with a width of 2.5 cm and a length of 5 cm was cut out from the porous membrane, and the sample was manufactured by Toyo Baldwin Co., Ltd.
Using a TENSILONUTM-20 type tensile tester, the tensile speed was 50m/ under the conditions of 20℃ and 60%RH.
Measured in min. The present invention will be explained below with reference to Examples. Examples 1 to 3 Cellulose linter (average molecular weight 2.33×10 ⁵ )
were dissolved in a cupric ammonia solution prepared by a known method at various concentrations shown in Table 1. The solution was cast onto a glass plate at a speed of 0.2 m/min using a 500 μm thick applicator in an acetone vapor atmosphere at 30° C. with a concentration of 80% of the saturated vapor pressure.
The cast film was left in this atmosphere for 8 minutes to confirm that microphase separation had occurred and that no dilute phase had leached onto the membrane surface. , the ammonia/water ratio is
It was immersed horizontally in a 0.8% by weight coagulation mixed solution (20°C) for 120 minutes, then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes, washed with water, and then the moisture was absorbed with paper. The film was immersed in acetone (100% by weight) at 20°C for 15 minutes to replace the moisture in the film with acetone, then sandwiched between paper and air-dried at 30°C. Table 1 shows the properties of the obtained porous membrane. Example 4 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of 75% by weight, the solution was heated to a methyl ethyl ketone vapor atmosphere at 30°C with a concentration of 75% by weight.
% atmosphere on a glass plate with a 500 μm thick applicator at a speed of 0.2 m/min and left in this atmosphere for 8 minutes to cause microphase separation and to cause the dilute phase to form on the membrane surface. Within a period of time without leaching to the top, the cast material was mixed with a methyl ethyl ketone/water ratio of 33.6% by weight and an ammonia/water ratio of 33.6% by weight.
Immersed horizontally in a 0.8% by weight coagulation mixed solution (20°C) for 120 minutes, then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes, rinsed with water, then blotted the moisture with paper, and placed it at 20°C. in acetone (100% by weight)
Soak for 15 minutes, replace water in the membrane with acetone,
It was sandwiched between paper and air-dried at 30°C. Table 1 shows the properties of the porous membrane obtained. Examples 5-6 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of % by weight, the solution was cast at a speed of 0.2 m/min with a 500 μm thick applicator on a glass plate in an acetone vapor atmosphere at 30°C with a concentration of 80% of the saturated vapor pressure. The cast film was then left in this atmosphere for 8 minutes to confirm that microphase separation had occurred and that the dilute phase had not leached onto the membrane surface. /
In a mixed solution for coagulation of water and ammonia/water (20
℃) for 120 minutes in a horizontal state, then 20℃ 2
After immersing the membrane in a sulfuric acid aqueous solution for 15 minutes, washing it with water, absorbing the moisture with paper, and immersing it in acetone (100% by weight) at 20°C for 15 minutes, replacing the moisture in the membrane with acetone, and placing it on paper. It was sandwiched and air-dried at 30°C. Table 1 shows the properties of the porous membrane obtained. Comparative example 1 Cellulose linter (average molecular weight 2.33×10 ⁵ )
in a cupric ammonia solution prepared by a known method.
After dissolving at a concentration of 5.5% by weight, the solution was poured onto a glass plate at a speed of 0.2 m/min with a 500 μm thick applicator in an acetone vapor atmosphere at 30°C with a concentration of 80% of the saturated vapor pressure. It was extended. The cast film was left in this atmosphere for 8 minutes, and it was confirmed that microphase separation had occurred and that the dilute phase had not leached onto the membrane surface.
In weight%, the ammonia/water ratio is 0.8% by weight
It was immersed horizontally in a mixed solution for coagulation (20℃) for 120 minutes, and then in a 2% by weight sulfuric acid aqueous solution at 20℃.
After soaking for 15 minutes, rinse with water, then absorb the moisture with paper, immerse in acetone (100% by weight) at 20℃ for 15 minutes, replace the moisture in the membrane with acetone, sandwich between paper and heat at 30℃. Air dried. Table 1 shows the properties of the obtained porous membrane. Comparative example 2 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
Dissolved at a concentration of % by weight. The solution was applied to a glass plate using a 500 μm thick applicator in an acetone vapor atmosphere at 30°C with a concentration of 80% of saturated vapor.
Casting was carried out at a speed of 0.2 m/min. The cast film was left in this atmosphere for 8 minutes to confirm that microphase separation had occurred and that no dilute phase had leached onto the membrane surface, and the resulting cast film had an acetone/water ratio of 33.6% by weight.
Then, it was immersed for 120 minutes in a mixed solution for coagulation (20°C) with an ammonia/water ratio of 0.8% by weight. At this time, the film surface was approximately perpendicular to the horizontal plane. After that, the obtained film was immersed horizontally in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes, washed with water, then the moisture was absorbed with paper, and the film was immersed in acetone (100% by weight) at 20°C for 15 minutes. The water in the membrane was replaced with acetone, and the membrane was sandwiched between sheets of paper and air-dried at 30°C. Table 1 shows the properties of the obtained porous membrane.
The porous membrane thus obtained has many streak-like irregularities and cannot be used as a porous membrane for ultra-precision scanning. Comparative example 3 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of % by weight, the solution was cast at a speed of 0.2 m/min with a 500 μm thick applicator on a glass plate in a methanol vapor atmosphere at 30°C with a concentration of 75% of the saturated vapor pressure. 8 in the same atmosphere.
Leave it for a minute. At this time, no microphase separation occurred. The resulting membrane was mixed with methanol/water ratio
33.6% by weight and ammonia/water ratio of 0.8% by weight in a mixed solution (20°C) for 120 minutes in a horizontal state, then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes, and then washed with water. After that, the moisture was absorbed with paper, immersed in acetone (100% by weight) at 20°C for 15 minutes, the moisture in the membrane was replaced with acetone, and the film was sandwiched between paper and air-dried at 30°C. The properties of the obtained film are
Shown in the table. Examples 7-11 Cellulose linter (average molecular weight 2.33×10 ⁵ )
in a copper ammonia solution prepared by a known method,
After dissolving at various concentrations shown in Table 2, it was cast onto a glass plate using an applicator with a thickness of 500 μm, and poured into a microphase separation solution composed of acetone/aqueous ammonia at the concentrations shown in Table 2 for 120 minutes. , immersed in a horizontal state (microphase separation occurs at this time), and then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes.
Wash with water, then absorb the moisture with paper, immerse in acetone (100% by weight) at 20℃ for 15 minutes, replace the moisture in the membrane with acetone, and sandwich it between paper at 30℃.
It was air-dried. Table 2 shows the properties of the porous membrane obtained. Example 12 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of % by weight, it was deposited on a glass plate to a thickness of 500 μm
The mixture was cast using an applicator to form a mixed solution of methyl ethyl ketone and aqueous ammonia at the concentrations shown in Table 2.
After being immersed horizontally for 120 minutes (at this time, microphase separation has occurred), immersed in a 2% by weight sulfuric acid aqueous solution for 15 minutes at 20°C, washed with water, then absorbing moisture with paper, and soaking at 20°C. 15 in acetone (100% by weight)
After soaking for a minute, the water in the membrane was replaced with acetone.
It was sandwiched between paper and air-dried at 30°C. Table 2 shows the properties of the porous membrane obtained. Comparative example 4 Cellulose linter (average molecular weight 2.33×10 ⁵ )
in a cupric ammonia solution prepared by a known method.
After dissolving at a concentration of 5.5% by weight, the thickness is deposited on a glass plate.
It was cast with a 500 μm applicator and immersed in a mixed solution for chromophase separation consisting of acetone and aqueous ammonia at the concentrations shown in Table 2 in a horizontal state for 120 minutes (at this time, microphase separation occurred). ),after that
After immersing in a 2% by weight sulfuric acid aqueous solution at 20℃ for 15 minutes, washing with water, absorbing the water with paper, and immersing in acetone (100% by weight) at 20℃ for 15 minutes, the water in the membrane was replaced with acetone. , sandwiched between paper and air-dried at 30°C. Table 2 shows the properties of the porous membrane obtained. Comparative example 5 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of % by weight, it was deposited on a glass plate to a thickness of 500 μm
The sample was cast using an applicator and immersed vertically in a mixed solution for microphase separation consisting of acetone and aqueous ammonia at the concentrations shown in Table 2 for 120 minutes (at this time, microphase separation occurred). ), immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 15 minutes, rinsed with water, then blotted the moisture with paper, immersed in acetone (100% by weight) at 20°C for 15 minutes, and removed the moisture in the membrane with acetone. It was replaced, sandwiched between paper and air-dried at 30°C. Table 2 shows the properties of the porous membrane obtained. The obtained porous membrane had film formation irregularities that were visible to the naked eye and could not be used as a porous membrane for precision separation. Comparative example 6 Cellulose linter (average molecular weight 2.33×10 ⁵ )
4 in a copper ammonia solution prepared by a known method.
After dissolving at a concentration of % by weight, it was deposited on a glass plate to a thickness of 500 μm
Using an applicator, the mixture was poured into a methanol-ammonia water mixture solution with the concentration shown in Table 2 for 120 minutes.
After immersion in a horizontal state (at this time, a thin film is formed on the membrane surface before microphase separation occurs), at 20℃.
After immersing in a 2% by weight sulfuric acid aqueous solution for 15 minutes, washing with water,
After that, the moisture was absorbed with paper, immersed in acetone (100% by weight) at 20°C for 15 minutes, the moisture in the membrane was replaced with acetone, and the film was sandwiched between paper and air-dried at 30°C. Table 2 shows the properties of the obtained membrane.

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【table】 [Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph of a porous membrane obtained by the production method of the present invention, where A is a surface photograph and B is a back surface photograph.

Claims (1)

[Claims] 1. From a copper ammonia solution of cellulose with an average molecular weight of 5×10 ⁴ or more, casting, coagulation, regeneration, water washing,
In the film forming step of drying, the cellulose concentration in the cellulose cuprammonium solution is 2 to 5% by weight, and after casting and before coagulation, microphase separation is caused in an organic solvent atmosphere, and then microphase separation is caused. A method for producing a large-pore regenerated cellulose membrane, which comprises immersing the cast material in a horizontal state in an organic solvent atmosphere and solidifying it. 2 The cellulose concentration in the cellulose copper ammonia solution is 2 to 5% by weight, the boiling point is 100°C or less,
A copper ammonia solution of the cellulose is cast in an organic solvent vapor atmosphere containing at least one organic solvent vapor that satisfies the conditions of having a solubility in water of 10% by weight or more and having no hydroxyl group. After the solution undergoes microphase separation and before the dilute phase after the phase separation leaches onto the membrane surface, it does not have hydroxyl groups and has a solubility of 10% by weight or more in a 28% by weight ammonia aqueous solution. and
Claim 1, wherein the microphase-separated cast product is horizontally immersed in a coagulating mixed solution containing at least one organic solvent that does not swell cellulose. Method for producing regenerated cellulose large pore membrane. 3. The method according to claim 2, characterized in that an organic solvent is added in advance to the copper ammonia solution for casting before casting to a concentration below the gelling point or below 30% by weight. Method for producing regenerated cellulose large pore membrane. 4 When forming a film from a cellulose cupric ammonia solution having an average molecular weight of 5 x 10 ⁴ or more, the cellulose cupric ammonia solution is cast in an acetone vapor atmosphere, and after the cellulose cupric ammonia solution has caused microphase separation. Before the dilute phase generated during phase separation leaches onto the membrane surface, the cast material is immersed in a horizontal state in a mixed solution for coagulation of acetone/ammonia/water,
Then, after re-treatment with acid and washing with water, the boiling point is 70℃
4. A method for producing a regenerated cellulose large-pore membrane according to claim 2 or 3, which comprises replacing water in the porous membrane with the following organic solvent and then drying it. 5. The method for producing a regenerated cellulose large-pore membrane according to claim 4, wherein the organic solvent for water replacement having a boiling point of 70° C. or lower is acetone. 6 The cellulose concentration in the copper ammonia solution is 2 to 5% by weight, has no hydroxyl group, and has 28
Solubility in aqueous ammonia solution is 10% by weight
As described above, the cellulose copper ammonia solution after casting is immersed in a horizontal state in a mixed solution for microphase separation that satisfies the conditions of a mixed solution containing one or more types of organic solvents that do not swell cellulose to cause microphase separation.
2. The method for producing a regenerated cellulose large-pore membrane according to claim 1, which is then coagulated in the mixed solution for microphase separation. 7. The composition of the mixed solution for microphase separation consists of an organic solvent/ammonia/water system, and the concentration of ammonia relative to water is 5% by weight or less, and the concentration of organic solvent relative to water is 10 to 70% by weight. A method for producing a regenerated cellulose large-pore membrane according to claim 6. 8. Claim 6 or 7, characterized in that an organic solvent is added to the copper ammonia solution to a concentration below the gelling point or below 30% by weight.
The method for producing a regenerated cellulose large-pore membrane as described in 2. 9. The method for producing a regenerated cellulose large-pore membrane according to claim 6, 7, or 8, wherein the organic solvent is acetone. 10 Characterized by immersing in a mixed solution for micro phase separation in a horizontal state, regenerating with acid, then washing with water, then replacing the water with an organic solvent with a boiling point of 70°C or less to remove water and drying. A method for producing a regenerated cellulose large-pore membrane according to claim 6 or 7. 11. The regenerated cellulose bulk according to claim 10, which is immersed horizontally in a mixed solution for microphase separation, then regenerated with acid, then washed with water, and then replaced with acetone. Method for manufacturing porous membranes.