JPH0763590B2 - How to remove colored components - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing a coloring component from a solution containing the coloring component by a film treatment.

(Prior Art) In the production of foods and pharmaceuticals, it is often necessary to remove the coloring components dissolved in the solution in order to improve the quality of the product or treat the waste liquid. Conventionally, as a method for removing the coloring component in such a solution, for example, a method using an adsorption resin and a method using a semipermeable membrane such as an ultrafiltration membrane or a reverse osmosis membrane are known.

However, the method using the adsorbent resin requires regeneration of the adsorbent resin after the adsorption treatment, while the method by the membrane treatment has a pH resistance because the membrane which is generally used in the past is composed of cellulose acetate. Low, for example, soy sauce with a pH of about 4,
Furthermore, vinegar having a low pH cannot be stably decolorized over a long period of time. Further, since the chlorine resistance and the heat resistance are poor, the method for cleaning the film after the decolorization treatment is limited. For example, it is not possible to use hypochlorite, which is an effective cleaning agent, for the recleaning of membranes which have been contaminated by colored components. Further, the semipermeable membrane cannot be heat-sterilized when necessary.

On the other hand, an ultrafiltration membrane made of polysulfone is known as a semipermeable membrane having excellent pH resistance, chlorine resistance, heat resistance, etc. However, conventional polysulfone ultrafiltration membranes are all fractionated. Since the molecular weight is large, it is difficult to effectively remove the coloring component having a relatively low molecular weight. For example, the coloring component in soy sauce is gel permeation chromatography (GPC).
According to, it is about 1000.

Furthermore, in the case of an aqueous solution having a high salt concentration such as soy sauce, its osmotic pressure is very high, and high pressure is required for the membrane treatment. On the other hand, since the water permeation rate of the membrane is remarkably low, it is not practical to industrially remove the coloring component.

(Object of the Invention) As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a skin layer having a solute separation activity composed of a sulfonated polyaryl ether is integrated on an ultrafiltration membrane as a supporting membrane. According to the composite semipermeable membrane having a sulfonic acid group laminated on, it has a high removal rate even for a coloring component having a relatively low molecular weight, and is based on the sulfonic acid group even at a relatively low processing pressure. Since the membrane water permeation rate is remarkably high due to its hydrophilicity, it has been found that the coloring component can be effectively removed while ensuring a practical water permeation rate even for a high salt concentration colored aqueous solution, such as soy sauce. ,
The present invention has been achieved.

(Structure of the Invention) The method for removing a coloring component according to the present invention comprises a repeating unit A A sulfonated polyaryl ether obtained by sulfonation of a polyaryl ether comprising: or a repeating unit A and a repeating unit B (However, R represents —CO— or —SO ₂ —, R ′ represents a carbon-carbon bond or a divalent group.) A sulfonated polyaryl ether obtained by sulfonation of a linear polyaryl ether copolymer. And 0.5 g of N-methyl-2-
A skin having solute separation activity consisting of a sulfonated polyaryl ether having a logarithmic viscosity of 0.2 or more measured at a temperature of 30 ° C. and an ion exchange capacity of 2.3 meq / g or less for a solution dissolved in 100 ml of pyrrolidone. A solution containing a coloring component is treated with a composite semipermeable membrane having a sulfonic acid group in which layers are integrally laminated on an ultrafiltration membrane as a supporting membrane.

The composite semipermeable membrane used in the method of the present invention is preferably prepared by sulfonation of the polyaryl ether comprising the repeating unit A or the linear polyaryl ether copolymer comprising the repeating unit A and the repeating unit B, respectively. , A sulfonated polyaryl ether, which may contain a small amount of aprotic polar organic solvent, an alkylene glycol alkyl ether such as ethylene glycol monomethyl ether, and a water-soluble and low volatility additive An organic compound or an inorganic salt of is applied as a film-forming solution containing an additive onto a dried support film,
Then, it can be obtained by evaporating the organic solvent from this film forming solution.

The above-mentioned sulfonated polyaryl ether can be obtained by treating the corresponding polyaryl ether with concentrated sulfuric acid. In the present invention, 0.5 g thereof is dissolved in 100 ml of N-methyl-2-pyrrolidone. About 3
The logarithmic viscosity measured at a temperature of 0 ° C is 0.2 or more,
In addition, a sulfonated polyaryl ether having an ion exchange capacity of 2.3 meq / g or less is used. When the ion exchange capacity exceeds 2.3 meq / g, the sulfonated polyaryl ether has water solubility and is unsuitable as a material for a semipermeable membrane for treating an aqueous solution.
This is because when the logarithmic viscosity is smaller than 0.2, it is difficult to form a uniform skin layer without defects such as pinholes.

When a skin layer is formed by using a sulfonated polyaryl ether obtained by sulfonation of the linear polyaryl ether copolymer, the linear polyaryl ether copolymer is repeatedly used at 10 mol% or more. It is preferably composed of the unit A and 90 mol% or less of the repeating unit B.

The sulfonic acid group contained in the sulfonated polyaryl ether is represented by the formula —SO ₃ M, where M represents hydrogen, alkaline metal or tetraalkylammonium.

For example, after sulfonation of a polyaryl ether, the sulfonated polyaryl ether is washed with water and dried to obtain a sulfonated polyaryl ether having a free sulfonic acid group. Further, the sulfonic acid group can be converted to an alkali metal salt by suspending the sulfonated polyaryl ether in an aqueous solution of an alkali metal hydroxide or an alkali metal alcoholate, a methanol solution, an ethanol solution, or the like. Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like, and examples of the alkali metal alcoholate include sodium methylate, potassium methylate, potassium ethylate and the like. Further, if the sulfonated polyaryl ether is treated in the same manner with a solution of tetraalkylammonium, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. The acid group can be the corresponding tetraalkylammonium salt.

The composite semipermeable membrane used in the method of the present invention preferably contains the above-mentioned sulfonated polyaryl ether, a water-soluble and low-volatile compound as an additive, and a small amount of an aprotic polar organic solvent. It can be obtained by dissolving and containing it in an alkylene glycol alkyl ether which may be used to form a film-forming solution, coating the solution on a dried support film, and then evaporating an organic solvent from the film-forming solution.

As the organic solvent for preparing the film forming solution, an alkylene glycol alkyl ether having an alkylene group having 2 to 4 carbon atoms and an alkyl group having 1 to 4 carbon atoms is particularly preferably used. This solvent has excellent solubility in the sulfonated polyaryl ether and is highly volatile, while, as will be described later,
This is because it does not dissolve the polysulfone ultrafiltration membrane that can be suitably used as the support membrane in the composite semipermeable membrane used in the present invention.

Specific examples of such alkylene glycol alkyl ethers include, for example, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol dimethyl ether, ethylene. Glycol methyl ethyl ether,
Mention may be made of alkylene glycol dialkyl ethers such as ethylene glycol diethyl ether. In particular, ethylene glycol monomethyl ether is preferably used because it has excellent solubility in sulfonated polyaryl ether and high volatility.

However, depending on the sulfonated polyaryl ether used, it may be difficult to dissolve it in the above alkylene glycol alkyl ether, or it may simply swell. It has been found that it dissolves well in a mixed solvent prepared by adding an aprotic polar organic solvent. As such an aprotic polar organic solvent,
For example, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like are preferably used. In such a mixed solvent, the proportion of the aprotic polar organic solvent is preferably 5 parts by weight or less, particularly 3 parts by weight or less with respect to 100 parts by weight of the alkylene glycol alkyl ether. In the mixed solvent, when the aprotic polar organic solvent is more than 5 parts by weight with respect to 100 parts by weight of the alkylene glycol alkyl ether, a dry polysulfone ultrafiltration membrane as described below is used as a supporting membrane to form a membrane-forming solution. This is because, when this is applied onto this support film, this support film dissolves or swells, so that a composite semipermeable membrane with good performance cannot be obtained.

Further, as the solvent of the film forming solution, using a mixed solvent of alkylene glycol alkyl ether or a small amount of the aprotic polar organic solvent, as described later, after applying the film forming solution to the support film, In the step of evaporating and removing the solvent from the film-forming solution, it is possible to remove substantially all the solvent by heating at room temperature to a little.
Moreover, it is advantageous because a uniform thin film without defects can be obtained.

The concentration of the sulfonated polyaryl ether in the membrane forming solution is also related to the thickness of the semipermeable membrane made of these polymers in the obtained composite semipermeable membrane, but usually in the range of 0.05 to 10% by weight, particularly preferably , 0.1 to 5% by weight is preferable.

In producing the composite semipermeable membrane used in the method of the present invention, the above-mentioned membrane forming solution contains a specific additive. Among such additives, as the organic compound, polyhydric alcohols, polyalkylene glycols, carboxylic acids, salts thereof,
At least one selected from the group consisting of hydroxycarboxylic acids and salts thereof is used. The organic compounds as these additives are water-soluble and have low volatility, and are required to be dissolved in the film-forming solution. Therefore, a polyhydric alcohol having 2 to 5 carbon atoms and a low molecular weight are required. The polyalkylene glycol, carboxylic acid, salt thereof, hydroxycarboxylic acid or salt thereof are preferably used. As a specific example,
As polyhydric alcohol, ethylene glycol, propylene glycol, glycerin, 1,4-butanediol, etc.
Diethylene glycol, triethylene glycol, dipropylene glycol and the like as polyalkylene glycol, citric acid, oxalic acid and the like as carboxylic acid, lactic acid, hydroxybutyric acid and the like as hydroxycarboxylic acid,
Further, examples of salts of carboxylic acid and hydroxycarboxylic acid include sodium salt and potassium salt.

Further, an inorganic salt which is water-soluble and is soluble in the film-forming solution can also be used as an additive. Examples of such inorganic salts include lithium chloride, lithium nitrate, magnesium perchlorate, and the like.

The concentration of these additives in the film forming solution is usually 0.1 to 8
It is in the range of 0% by weight. Although the effect of these additives on the formation of a composite semipermeable membrane is not always clear, it is related to the micropore size of the semipermeable membrane formed from the sulfonated polyarylether, and the membrane forming solution is used as a support membrane. When applied on a certain ultrafiltration membrane, the solvent and additives of the membrane-forming solution appear to modify the surface of the ultrafiltration membrane, thus
By selecting the type and amount of the additive to be used, the performance of the obtained composite semipermeable membrane, in particular, the removal rate for the solute containing the coloring component and the membrane permeated water amount can be controlled in a wide range.

The membrane forming solution prepared as described above is then applied onto a dry ultrafiltration membrane as a supporting membrane. The dry ultrafiltration membrane, as is well known, heats a wet ultrafiltration membrane prepared by a wet method to an appropriate temperature to evaporate the water contained in the micropores of the membrane, It can be obtained by substantially drying.

In the above method, the ultrafiltration membrane as the support membrane for applying the membrane-forming solution is not particularly limited, but is preferably an ultrafiltration membrane made of polysulfone, for example, the repeating formula C: unit An ultrafiltration membrane consisting of is preferably used.

As described above, when a mixed solvent containing an alkylene glycol alkyl ether or a small amount of the aprotic polar organic solvent is used as the solvent for the film-forming solution, usually,
It is possible to evaporate virtually all the solvent at room temperature without the need for heating, however, in order to evaporate the solvent after applying the film-forming solution onto the supporting film, it is necessary to evaporate the solvent. You may heat. The heating temperature may be appropriately selected depending on the solvent used, but a temperature of 150 ° C. or lower is usually sufficient. In addition, in order to accelerate evaporation of the solvent after applying the film forming solution on the support film, the film forming solution may be heated in advance and applied on the support film.

The film thickness of the thin film semipermeable membrane based on the sulfonated polyaryl ether in the composite semipermeable membrane thus obtained depends on the concentration of these polymers in the membrane forming solution and the coating thickness of the membrane forming solution on the supporting membrane. Depending on the method, it is preferable that the composite semipermeable membrane be thin in order to increase the water permeation rate, and thicker in order to increase the strength. Therefore, although not particularly limited, the semipermeable membrane having solute separation activity based on the sulfonated polyaryl ether preferably has a membrane thickness of usually 0.01 to 5 μm.

As described above, the skin layer having a thickness of 10 μm or less and having a sulfonic acid group and having separation performance is made of a sulfonated polyaryl ether, and the skin layer is integrally laminated on the support membrane. A sulfonated polyaryl ether composite semipermeable membrane can be obtained.

In the composite semipermeable membrane thus obtained, the additive may remain in the membrane depending on the kind of the additive used, but the obtained composite semipermeable membrane is treated in water. Soak in
These additives are removed from the film by passing water or immediately subjecting the aqueous solution containing the direct color component to decolorization.

As described above, the composite semipermeable membrane made of the sulfonated polyaryl ether and having the skin layer having a thickness of 10 μm or less is stable over the pH range of 1 to 14 even at 80 ° C. In addition, the removal rate of the coloring component in the aqueous solution is high, and the water permeation rate is high even when the aqueous solution contains a high concentration of salt.

Therefore, the method of the present invention is not particularly limited as long as it is an aqueous solution containing a coloring component, and can be applied to the removal of the coloring component of any of those aqueous solutions. According to the permeable membrane, it has a high water permeation rate even for an aqueous solution having a high salt concentration, and even if the salt concentration is increased with the treatment of the aqueous solution, the water permeation rate is less likely to decrease and is relatively low. The method of the present invention can be suitably applied to decolorization of a coloring aqueous solution having a high salt concentration such as soy sauce because it has a high removal rate even for a low molecular weight coloring component.

In the method of the present invention, the treatment conditions of the aqueous solution containing the coloring component are the properties of the aqueous solution and the properties of the semipermeable membrane used.
It is appropriately selected in consideration of the types and concentrations of coloring components and salts contained therein, and such conditions can be generally and easily selected in the technical field of aqueous solution membrane treatment. However, in the method of the present invention, the processing temperature is usually in the range of 0 to 95 ° C. The higher the temperature, the higher the water transmission rate. Further, the higher the treatment pressure, the higher the water permeation rate, but it is usually in the range of 0.1 to 100 kg / cm ² .

Since the composite semipermeable membrane used in the method of the present invention is excellent in chlorine resistance and heat resistance, when washing the composite semipermeable membrane after the decolorization treatment, an aqueous sodium hypochlorite solution can be used. . Especially, sodium hypochlorite concentration 50
An aqueous solution of 00 ppm or less can be preferably used. Further, the above-mentioned composite semipermeable membrane can be heat-sterilized if necessary, if the temperature is up to 95 ° C.

(Effects of the Invention) As described above, in the method of the present invention, an ultrathin film skin layer having a solute separation activity made of a sulfonated polyaryl ether is integrally laminated on an ultrafiltration membrane as a supporting membrane. Is used to treat an aqueous solution containing a coloring component, wherein the composite semipermeable membrane has a sulfonic acid group and has high hydrophilicity. It has a sufficiently high water permeation rate even for aqueous solutions with high salt concentration, and exhibits a high removal rate for relatively low-molecular weight colored solute components. The coloring component can be practically separated and removed. Furthermore, since the above-mentioned composite semipermeable membrane has excellent pH resistance, it is suitable for decolorizing treatment of seasonings such as soy sauce and vinegar. Of course, it can be applied to other decolorization such as waste sugar density.

Therefore, the method of the present invention is not particularly limited in its mode of application, but can be effectively applied, for example, for the removal of coloring components in the production of foods and pharmaceuticals.

(Examples) Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In the examples, the solute removal rate and the water permeation rate were calculated by the following equations.

Example 1 (1) Production of sulfonated polysulfone Repeating unit A ₁ Polysulfone (10 g) was added to 97% concentrated sulfuric acid (80 ml), and the mixture was gently stirred and reacted at room temperature for 4 hours to obtain a blackish brown viscous reaction solution. This was put into an ice bath to solidify the sulfonated polysulfone. After washing with water, the mixture was left overnight in 800 ml of 0.5N aqueous sodium hydroxide solution. Then, the polymer was washed until the washing solution became neutral, and then at 30 ° C. for 7 hours.
Vacuum dried for an hour. The pale yellow granular sulfonated polysulfone thus obtained had an inherent viscosity of 3.00, sulfonic acid groups of 100% of all ion exchange groups, and an ion exchange capacity of 1.92 meq / g.

(2) Preparation of Composite Semipermeable Membrane An anisotropic ultrafiltration membrane consisting of repeating units of the above formula C and having a removal rate of 10% for polyethylene glycol having an average molecular weight of 20,000 is dried at a temperature of 60 ° C., A dry ultrafiltration membrane for the support membrane was obtained.

The polymer solution obtained by dissolving 0.8 g of the sulfonated polysulfone obtained above in 79.2 g of ethylene glycol monomethyl ether, adding 20 g of lactic acid, and filtering with 10 μm filter paper was used as a film forming solution.

This membrane-forming solution was applied on the above dry ultrafiltration membrane, and most of the solvent was volatilized at room temperature and then heat-treated at a temperature of 60 ° C. for 5 minutes to obtain a composite semi-layer having a skin layer of 0.5 μm in thickness. A permeable membrane was obtained.

The performance of this composite semipermeable membrane is that the removal rate is 50% when treated with 0.2% sodium chloride solution at 25 ° C and 20 kg / cm ^2.
%, The water permeability rate was 2.5 m ³ / m ² / day.

(3) Decolorization treatment of soy sauce A commercially available soy sauce having a sodium chloride concentration of 18.8%, a total nitrogen concentration of 1.6%, and a pH of 4.6 is used as a stock solution, and the composite semipermeable membrane obtained above is used to treat a temperature of 25 ° C and a treatment pressure of 20 kg. The soy sauce was subjected to membrane permeation treatment at / cm ² , and the membrane permeate was measured for the removal rate of the coloring component from the change in absorbance at 450 nm.

As a result, the removal rate of coloring components was 97%, the removal rate of sodium chloride was 0%, and the removal rate of total nitrogen was 60%. The average permeation rate was 0.1 m ³ / m ² / day.

Example 2 (1) Production of Sulfonated Polysulfone Copolymer 57 mol% of the repeating unit of the formula A ₁ and repeating unit of the formula B ₁ 97 g of linear polysulfone copolymer consisting of 43 mol%
80% concentrated sulfuric acid was added and dissolved, and the mixture was stirred and reacted at room temperature for 4 hours to obtain a blackish brown viscous reaction liquid. This was put into an ice bath to solidify the sulfonated polysulfone copolymer. After washing with water, 800m of 0.5N sodium hydroxide solution
l left in overnight. Next, this polymer was washed until the washing liquid became neutral, and then vacuum dried at 60 ° C. for 5 hours.

The sulfonated polysulfone copolymer thus obtained had an inherent viscosity of 0.84, sulfonic acid groups were 100% of all ion exchange groups, and an ion exchange capacity of 1.2 meq / g.

(2) Preparation of composite semipermeable membrane Obtained by dissolving 0.8 g of the linear sulfonated polysulfone copolymer obtained above in 79.2 g of ethylene glycol monomethyl ether, adding 20 g of glycerin, and filtering with 10 μm filter paper. The polymer solution was used as a film forming solution.

This membrane forming solution was applied on the same polysulfone dry ultrafiltration membrane as in Example 1, and most of the solvent was volatilized at room temperature,
Heat treatment was performed for 5 minutes at a temperature of 60 ° C. to obtain a composite semipermeable membrane having a skin layer having a thickness of 0.5 μm.

The performance of this composite semipermeable membrane is a removal rate of 6.3% when treated with a 0.2% aqueous sodium chloride solution at 25 ° C and 20 kg / cm ^2.
%, The permeation rate was 6.5 m ³ / m ² / day.

(3) Decolorization treatment of soy sauce The same commercial soy sauce as used in Example 1 was subjected to a membrane permeation treatment at a treatment temperature of 25 ° C and a treatment pressure of 20 kg / cm ² using the composite semipermeable membrane obtained above. Regarding the permeated liquid, in the same manner as in Example 1,
The removal rate of the coloring component in the membrane permeate was measured.

As a result, the removal rate of coloring components was 96.4%, the removal rate of sodium chloride was 0%, and the removal rate of total nitrogen was 31.3%. The average water permeation rate was 0.1 m ³ / m ² / day.

Example 3 (1) Production of sulfonated polyaryl ether ketone) Repeating unit A ₂ Polyaryletherketone consisting of (ICI PEEK45
G) (10 g) was added to 97% concentrated sulfuric acid (80 ml), and the mixture was reacted at room temperature for 8 hours and then left at room temperature for 17 hours to obtain a concentrated sulfuric acid solution of the above polymer.

The above solution was thinly poured onto pure water cooled in an ice bath so as to pull a thread to solidify the polymer, which was collected by filtration and washed with pure water.
Washed twice. 1N sodium hydroxide solution 60 in this polymer
After adding 0 ml, the mixture was left standing for 3 hours, and then washed until the pH of the washing liquid reached 7. Then, the polymer was dried at 60 ° C. for 16 hours to obtain 11.6 g of a sulfonated polyaryl ether ketone. That this polymer is sulfonated. It was confirmed by its infrared absorption spectrum and nuclear magnetic resonance spectrum.

The ion exchange capacity of this polymer is 1.5 meq / g,
A solution of 0.5 g of N-methylpyrrolidone in 100 ml had an inherent viscosity of 1.30 measured at 30 ° C.

(2) Preparation of composite semipermeable membrane 9 g of the sulfonated polyaryl ether ketone obtained above was dissolved in 89.1 g of ethylene glycol monomethyl ether, 10 g of glycerin was added, and the solution was obtained by filtering with 10 μm filter paper. It was a membrane solution.

The above membrane-forming solution was applied on the same dry polysulfone ultrafiltration membrane as used in Example 1, and most of the solvent was volatilized at room temperature and then heat-treated at a temperature of 60 ° C. for 5 minutes,
A composite semipermeable membrane was obtained.

The performance of this composite semipermeable membrane is that the removal rate is 20% when treated with 0.2% sodium chloride aqueous solution at 25 ° C and 20 kg / cm ^2.
%, The water permeability rate was 4 m ³ / m ² / day.

(3) Decolorization treatment of soy sauce The same commercial soy sauce as used in Example 1 was subjected to a membrane permeation treatment at a treatment temperature of 25 ° C and a treatment pressure of 20 kg / cm ² using the composite semipermeable membrane obtained above. Regarding the permeated liquid, in the same manner as in Example 1,
The removal rate of the coloring component in the membrane permeate was measured.

As a result, the removal rate of coloring components was 97%, the removal rate of sodium chloride was 0%, and the removal rate of total nitrogen was 40%. Also,
The average permeation rate was 0.1 m ³ / m ² / day.

Claims (1)

[Claims] 1. Repeating unit A A sulfonated polyaryl ether obtained by sulfonation of a polyaryl ether comprising: or a repeating unit A and a repeating unit B (However, R represents —CO— or —SO ₂ —, R ′ represents a carbon-carbon bond or a divalent group.) A sulfonated polyaryl ether obtained by sulfonation of a linear polyaryl ether copolymer. And 0.5 g of N-methyl-2-
A skin having solute separation activity consisting of a sulfonated polyaryl ether having a logarithmic viscosity of 0.2 or more measured at a temperature of 30 ° C. and an ion exchange capacity of 2.3 meq / g or less for a solution dissolved in 100 ml of pyrrolidone. A method for removing a coloring component, which comprises treating a solution containing a coloring component with a composite semipermeable membrane having a sulfonic acid group in which layers are integrally laminated on an ultrafiltration membrane as a supporting membrane.