JPH0468968B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel ultrafiltration membrane made from a curdlan (β-1,3-glucan) derivative. In the field of ultrafiltration, various synthetic polymer membranes have been developed over the past ten years, and molecular weight
Products with various separation performances ranging from 1,000,000 to 500 are commercially available and in use. Ultrafiltration is generally used to separate high- and medium-molecular solutes from low-molecular solutes and ions, and it fractionates solutes at the molecular level and according to molecular size without applying heat.・Since it can be separated, concentrated, and purified, it is particularly suitable for separating and concentrating solutes that are sensitive to heat, pH, chemicals, etc., and have a large gel concentration (e.g., enzymes, proteins, physiologically active substances, etc.). Pharmaceutical industry, food industry, polymer industry, paint/
It is widely used in various fields such as the painting industry, dairy farming, fisheries, and livestock sectors. In general, the advantages of separation methods using these membranes are (1) low energy, (2) simple equipment and operation, and (3)
No phase change (no need to apply heat),
(4) Continuous operation is possible. Polymer membranes for ultraviolet rays currently in practical use include, for example, polysulfone systems, cellulose acetate ester systems, vinyl polymer systems, and polymer electrolyte complex systems. It is difficult to say that the film is still completely satisfactory. For example, in the case of polysulfone-based or polyvinyl alcohol-based membranes, the selectivity of fractionation is poor and sharp fractionation according to the difference in molecular weight is not possible, and solutes with molecular weights of about 10 ⁴ to 10 ⁵ However, it does not show sharp fractionation performance for lower molecular weight solutes. On the other hand, the polymer electrolyte complex membrane is somewhat better in molecular weight fractionation than the above membranes. However, although this membrane is capable of fractionating solutes with a molecular weight of about 10 ³ to ^{10 4} , it is not effective enough to separate solutes with a molecular weight in the range of several hundred to 1000, especially those with a molecular weight of less than 500. It is almost impossible to separate things. Furthermore, a common drawback of various polymer electrolyte complex membranes is that they are weak. That is, all polymer electrolyte complex membranes have physical,
Chemically weak, easily contaminated, and sensitive to electrolytes. In view of this situation, the present inventors have conducted extensive research in search of a new material that has excellent molecular weight fractionation, is physically and chemically stable, and is resistant to pollution and electrolytes. As a result of stacking, it was obtained from a curdlan derivative obtained by modifying the hydroxyl group of curdlan (β-1,3-glucan), a water-insoluble polysaccharide, which has never been used as a material for separation membranes. The present inventors have discovered that a separation membrane has excellent performance in separating and fractionating solutes, has high strength as a membrane, and is fully suitable for the above purpose, and has completed the present invention. That is, the present invention provides curdlan (β-1,3-glucan) having the following structure. General formula [1] obtained by chemically modifying the _hydroxyl group of [C _{6 H 7 O} 2 ₍ OR) group or an acyl group represented by R'CO- (wherein R' represents a lower alkyl group having 1 to 4 carbon atoms), and x represents 1 to 3. Also, n is about 200~
Represents an integer of 2000. ] This is a separation membrane made from a curdlan derivative shown in the following. In the present invention, R of the curdlan derivative represented by the above general formula [1] used as a material for the separation membrane
Examples of the lower alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, iso
-propyl group, n-butyl group, tert-butyl group, etc., and examples of the acyl group represented by R'CO- include acetyl group, propionyl group, butanoyl group, pentanoyl group, etc. Also,
x, which represents the degree of substitution of the modifying group, is usually 1 to 3, more preferably 2 to 3. Further, n is usually about 200 to 2000, more preferably 300 to 2000.
It is 700. The curdlan derivative represented by the general formula [1] is usually easily obtained by alkylating or acylating the hydroxyl group of curdlan. That is, the alkylation of the hydroxyl group of curdlan, for example, follows the conventional method of alkylating the hydroxyl group of polysaccharides, using benzene, toluene, xylene, ether, N,N
- This can be easily carried out using an alkylating agent such as an alkyl halide or a dialkyl sulfate in the presence of an alkali in a solvent such as dimethylformamide. Furthermore, acylation of the hydroxyl groups of curdlan can also be easily carried out, for example, according to the conventional method of acylating the hydroxyl groups of polysaccharides. For example, in the case of acetylation, in the presence of a dehydrating agent such as p-toluenesulfonic acid, curdlan is added to a theoretical amount of 1
Using ~3 times the mole of acetic anhydride, at 40~50°C,
Let the acetylation reaction take place for 5 hours (adjust the amount of acetic anhydride, reaction temperature, reaction time, etc. as appropriate depending on the desired degree of substitution), and then pour this into a large amount of water using a conventional method to crystallize. Acetyl curdlan can be easily obtained by removing, washing with water, and drying. The separation membrane of the present invention can be produced by casting a cast solution prepared by dissolving a curdlan derivative in a formic acid solvent, or by casting the cast solution onto a porous membrane or support, and then applying a solvent to the membrane. It can be easily manufactured by a normal film forming method such as film forming by a gelling method. Moreover, it is of course possible to mold it into a hollow fiber shape. The fractional separation properties of membranes vary depending on the type of solvent used, and the molecular weight fractionation properties differ between formic acid alone and when mixed with water, methylene dichloride, N,N-dimethylformamide, etc. Furthermore, it is also possible to adjust the molecular weight fractionation by adding an inorganic salt or the like. The molecular weight fractionation property also changes depending on the concentration of the curdlan derivative in the solvent, as well as the molecular weight, degree of hydrolysis, degree of substitution of substituents, etc. of the curdlan derivative. The separation membrane of the present invention made from a curdlan derivative is preferably used for fractionating substances having a molecular weight within the range of about 200 to 20,000, and is particularly excellent in the region of small molecular weight cutoff (1,000 or less). Demonstrates fractional separation. The separation membrane of the present invention is capable of separating, for example, organic acids and saccharides with similar molecular weights, such as glucose and lactic acid, sucrose and malic acid (or tartaric acid), and ruffinose (or saccharide). Citric acid, etc. can be effectively separated. Therefore, the present invention can be used to separate and purify organic acids from a mixture of organic acids and saccharides in the production of lower organic acids by fermentation of saccharides, and to remove organic acids contained as impurities in saccharides. This can be done very effectively using a separation membrane. Unlike, for example, polymer electrolyte complex membranes, the separation membrane of the present invention has high physical and chemical strength as a membrane, is resistant to pollution, is resistant to electrolytes, and has good stability, so it can be used repeatedly. It is extremely easy to use from both a device and an operational standpoint, and is extremely economical. As described above, the present invention provides a novel separation membrane made of a novel material, which has excellent fractional separation properties, especially in the region of low molecular weight cutoff, has great strength as a membrane, and has good stability. It is a great contribution to this industry. Examples and reference examples will be shown below, but the present invention is not limited to these examples and reference examples in any way. In addition, the permeation flux (water flux) in the examples
is a batch-type ultrafiltration device (effective membrane area 1213
cm ² ), water permeation was measured using distilled water at 20° C. under an operating pressure of 4 Kg/cm ² , and calculated using the following formula. Permeation flux [/m ² hr] = Water permeation rate [ml] / Effective membrane area [cm ² ] x 60 / Required time (minutes) x 10 In addition, the rejection rate is calculated using the following formula (a). It was expressed using the true rejection rate obtained by correcting the concentration factor using equation (b) from the rejection rate (Rj). Apparent rejection rate (Rj) = 1 - solute concentration in permeated water / solute concentration in stock solution... (a) True rejection rate = log [Rj (A-1) + 1] / logA x 100... (b) Here , A is the concentration ratio (=volume of stock solution [ml]/
Represents the volume of concentrated liquid (ml). Reference Example 1 308 g (1.85 glucose units) of curdlan (β-1,3-glucan, n = approx. 500) and 48 g (0.252 mol) of p-toluenesulfonic acid were dissolved in 1.88 acetic acid and heated at 45 to 50°C. Acetic anhydride 1.08 (11.42
mol) was added dropwise over a period of 1 hour. Approximately 50℃ after dropping
After carrying out the acetylation reaction for 4 hours at
It was diluted with water and filtered by suction. The liquid was poured into 60 g of water to cause crystallization, and the precipitate was collected, washed with water, and dried to obtain 376 g (yield: 72.4%) of acetyl curdlan.
Acetyl content: 43.4%, viscosity (1.8% formic acid solution,
20℃): 12.8cps. Reference Example 2 308 g (1.85 glucose units) of curdlan (β-1,3-glucan, n = approx. 500) and 48 g (0.252 mol) of p-toluenesulfonic acid were dissolved in 1.88 acetic acid and heated at 45 to 50°C. Acetic anhydride 1.08 (11.42
mol) was added dropwise over a period of 1 hour. Approximately 50℃ after dropping
After carrying out the acetylation reaction for 1 hour, Reference Example 1
380 g of acetyl curdlan was obtained in the same manner as above. Acetyl content: 44.65%, viscosity (1.8% formic acid solution, 20℃): 59cps. Reference Example 3 308 g (1.85 glucose units) of curdlan (β-1,3-glucan, n = approx. 500) and 48 g (0.252 mol) of p-toluenesulfonic acid were dissolved in 1.88 acetic acid and heated at 45 to 50°C. Acetic anhydride 1.08 (11.42
mol) was added dropwise over a period of 2 hours. Approximately 50℃ after dropping
After carrying out the acetylation reaction for 4 hours at
It was diluted with water and filtered by suction. Next, 78.9 g of concentrated sulfuric acid and 1.26 g of water were added to the solution, and the mixture was treated at 50° C. for 8 hours to partially hydrolyze the acetyl groups. After the reaction, add 60 g of water to crystallize, collect the precipitated crystals, wash with water and dry to obtain 328 g of acetyl curdlan.
I got it. Acetyl content: 37.3%, viscosity (1.8% formic acid solution, 20°C): 27cps. Example 1 Two parts of the acetyl curdlan synthesized in Reference Example 1 were dissolved in 11.3 parts of formic acid, and the prepared casting solution was cast onto a horizontally held glass plate to a thickness of 0.2 mm, and then cast at 20°C for 40 minutes. The solvent was partially evaporated for minutes. Next, a membrane was obtained by immersing it in water at 20°C. Membrane performance is shown in Table 1.

[Table] Example 2 A cast solution prepared by dissolving 2 parts of the acetyl curdlan synthesized in Reference Example in a mixed solvent of 8.2 parts of formic acid and 1.7 parts of dimethylformamide was placed on a glass plate held horizontally to a thickness of 0.2 mm. After passing away, 30
The solvent was partially evaporated for 3 minutes at °C. Thereafter, the membrane was immersed in ice water to form a gel, thereby obtaining a separation membrane. Membrane performance is shown in Table 2.

[Table] Example 3 2 parts of acetyl curdlan synthesized in Reference Example 1,
A cast solution consisting of 8.2 parts of formic acid and 3.4 parts of methylene dichloride was cast onto a horizontally held glass plate to a thickness of 0.2 mm, and the solvent was partially evaporated at 20° C. for 2 minutes. Next, it was immersed in water at 20°C to form a gel, thereby obtaining a separation membrane. Membrane performance is shown in Table 3.

[Table] Example 4 A casting solution prepared by dissolving 2 parts of acetyl curdlan synthesized in Reference Example 2 in 18 parts of formic acid was cast onto a horizontally held glass plate to a thickness of 0.2 mm. The solvent was partially evaporated for 5 minutes at 20°C. Next, a separation membrane was obtained by immersing it in water at 20°C. Membrane performance is shown in Table 4.

[Table] Example 5 Two parts of the acetyl curdlan synthesized in Reference Example were dissolved in 18 parts of formic acid, and the prepared casting solution was cast to a thickness of 0.2 mm on a horizontally held glass plate.
The solvent was partially evaporated for 1 minute at 20°C. Then 20
A separation membrane was obtained by immersing it in water at ℃ and gelling it. Membrane performance is shown in Table 5.

[Table] Example 6 2 parts of acetyl curdlan synthesized in Reference Example 1,
A cast solution consisting of 8.2 parts of formic acid and 3.4 parts of methylene dichloride was cast onto a horizontally held glass plate to a thickness of 0.2 mm, and the solvent was partially evaporated at 20° C. for 2 minutes. Next, it was immersed in water at 20°C to form a gel, thereby obtaining a separation membrane. The water permeation flux of the resulting separation membrane at an operating pressure of 4 kg/cm ² was 4.26/m ² ·hr. This membrane was used to treat a 1:1 mixture of 1000 ppm lactic acid and 1000 ppm glucose. The results are shown in Table 6.

[Table] However, the degree of separation was calculated using the following formula. Degree of separation = lactic acid concentration in permeated liquid / glucose concentration in permeated liquid / lactic acid concentration in stock solution / glucose concentration in stock solution Example 7 Prepared by dissolving 2 parts of acetyl curdlan synthesized in Reference Example 1 in 11.3 parts of formic acid. The resulting casting solution was cast onto a horizontally held glass plate to a thickness of 0.2 mm, and the solvent was partially evaporated at 20° C. for 4 minutes. Next, a separation membrane was obtained by immersing it in water at 20°C. The permeation flux of water through this separation membrane at an operating pressure of 4 kg/cm ² was 6.6/m ² ·hr. Using this membrane, 1000ppm malic acid and 1000ppm
A 1:1 mixture with sucrose was treated. The results are shown in Table 7.

[Table] Example 8 2 parts of acetyl curdlan synthesized in Reference Example 1,
A cast solution consisting of 8.2 parts of formic acid and 3.4 parts of methylene dichloride was cast onto a horizontally held glass plate to a thickness of 0.2 mm, and the solvent was partially evaporated at 20° C. for 2 minutes. Next, it was immersed in water at 20°C to form a gel, thereby obtaining a separation membrane. The permeation flux of water through this separation membrane at an operating pressure of 4 kg/cm ² was 4.26/m ² ·hr. When this membrane was used as an ultrafiltration membrane, the rejection rates of various solutes were as shown in Table 8.

【table】

Claims (1)

[Claims] 1 Curdlan (β-1,3-
glucan) General formula [1] obtained by chemically modifying the _hydroxyl group of [C _{6 H 7 O} 2 ₍ OR) group or an acyl group represented by R'CO- (wherein R' represents a lower alkyl group having 1 to 4 carbon atoms), and x represents 1 to 3. Also, n is about 200~
Represents an integer of 2000. A separation membrane made from a curdlan derivative shown in ].