JPH0286821A - Cellulose-base laminated membrane and production thereof - Google Patents

Abstract

PURPOSE:To increase the separation factor of a cellulose-based laminated membrane and the rate of permeation by integrating a chitosan membrane with a membrane of a cellulose deriv. obtd. by introducing carboxyl groups into cellulose to produce the laminated membrane. CONSTITUTION:A chitosan soln. is film casted and solidified on a substrate, and an aq. alkali soln. or an aldehyde compd. is brought into contact with the resulting chitosan membrane. A soln. of a cellulose deriv. obtd. by introducing carboxyl groups into cellulose is film casted and solidified on the chitosan membrane and the resulting cellulose deriv. membrane is integrated with the chitosan membrane to produce a laminated membrane. Ammonia or an aq. acid soln. may be brought into contact with the chitosan membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cellulose-based composite membrane used as a separation membrane for separating a liquid mixture into individual components by a pervaporation method, and a method for producing the same.

(Background of the Invention) As a technology for producing a specific component from a liquid mixture (a technology for selectively separating water from a mixture of water and an organic solvent), there is a separation method using a membrane. A liquid mixture is placed on one side of the separation membrane, and reduced pressure or an inert carrier gas such as nitrogen gas is passed through the other side of the separation membrane, and the difference in permeation rate when each component of the liquid mixture permeates through the membrane The pervaporation method is about separation! Research has been underway since the 1950s.

This pervaporation is suitable for separating azeotropic mixtures that are difficult to separate by distillation, mixtures of liquids with close boiling points, etc., and is said to be a method that is more energy-saving and cost-effective than distillation. In the current industrial production of ethanol by alcohol fermentation, distillation is used to recover ethanol from the fermentation liquid, but energy costs are high due to the large amount of heat that is applied during distillation. On the other hand, the pervaporation method can be said to be energy-saving in that it does not require such heating.

As described above, the pervaporation method has recently attracted attention as a separation technique that enables concentration of alcohol at low cost.

(Prior Art) Many studies have been made in the past regarding the separation of liquid mixtures by the pervaporation method, which has the characteristics described above.

For example, a polymaleimide acrylonitrile membrane was used to separate a mixture of water and ethanol (separation coefficient: 7.5.
Transmission rate 0.107kg/rrs” + h) (Jo
urnalof Po1y＋＊er 5cienc
e; Po1y+*er ChemistryE
dition, Vol, 22.2159-2168 (1
984)), an example using an N-substituted phenylmaleimide/styrene copolymer membrane (separation coefficient 20, permeation rate 0.004
kg/ni'-h) (Polymer Journa
l, Shio1.17.36:1-368 (1985)),
Example using cellulose acetate membrane (separation membrane a5.9゜permeation rate 04kg/m"I h) (Journ, al o
f Applied Polya+er 5science
, Vol. 16.1061 (1972) Example using chitosan membrane (separation coefficient 0.47-4.4, if
i overspeed 4.9-20 kg/h) (Kobunshi Papers, Vol. 42.

1.39-142 (19,85), JP-A-60-31
Publication No. 803), etc. have been reported. The separation coefficient here is a numerical value representing the difference in permeability between water and ethanol, and is determined by the following formula.

(However, in the above formula, water, 7. represents the weight fraction of water and X ethanol on the mixed liquid supply side, and Y water, Y eta/-7) represents the weight fraction of water and ethanol on the permeation side. ) (Problems to be Solved by the Invention) However, the conventional separation membranes mentioned above have insufficient overall membrane performance, such as a large separation coefficient but a slow permeation rate, so it is difficult to put these membranes into practical use as is. It is not possible.

For example, a separation coefficient of 50 or more and a permeation rate of 0.5 kg are considered practical guidelines for this type of membrane.
/n?・No existing membrane is known to have a performance of more than h or more than 25 in terms of the product of separation coefficient and permeation rate used for comprehensive evaluation of membrane performance.

In view of the fact that single membranes such as cellulose derivative membranes or chitosan membranes used in conventional pervaporation methods do not exhibit sufficient performance for separating liquid mixtures by pervaporation methods, the present inventors have developed several As a result of considering the idea of compositing the membrane materials of the present invention and adding various ideas to film formation, we have developed the composite membrane of the present invention.

In other words, the present inventors conducted intensive research on various composite membranes, and found that a composite membrane made by laminating a thin film of a cellulose derivative with carboxyl groups introduced therein and a thin film of chitosan was able to selectively permeate water. It was discovered that it has excellent performance as a membrane.

The present invention was made based on this knowledge, and its purpose is to provide a composite membrane having the characteristics of a high separation coefficient and a high permeation rate.

Another object of the present invention is to remove hemicellulose and lignin solubilized by the process from wood raw materials that have been subjected to the steaming and blasting process in a pre-extraction process, and to convert the remaining cellulose into succinoylation in methanesulfonic acid. By combining a succinoylated cellulose membrane into which carphoxyl groups have been introduced by esterification with succinic anhydride and a chitosan membrane, a pervaporation membrane with particularly excellent separation coefficient and permeation rate! The present invention provides a composite membrane for use as 11R1.

(Means for Solving the Problems) The composite membrane A used in the pervaporation method according to the present invention, which was made to achieve the above object, is characterized by a chitosan membrane and a cellulose with carboxyl groups. It has a laminated integral structure with the introduced cellulose derivative membrane.

The present invention further provides a cellulose derivative membrane into which a carboxyl group has been introduced by esterification, typically a cellulose derivative membrane into which a carboxyl group has been introduced by succinoylation (particularly succinoylation in methanesulfonic acid). It has the feature that it can provide the above-mentioned composite membrane which is particularly excellent in terms of membrane uniformity and the like.

Here r! The term "It layer-separated" typically means that the layers are adhered together by the casting method described below, and does not include those that are simply mechanically joined.

Cellulose generally refers to IA fibrous substances derived from plant cell walls, and may also refer to cellulose or lignocellulose in a narrow sense, but the present invention also includes derivatives thereof.

The composite membrane of the present invention is characterized by having a chitosan membrane as one layer of a laminated, integrally fixed structure.

Chitosan is a substance obtained by deacetylating chitin, which is one of the outer shell components of crustaceans such as crabs and shrimp.
It is a polysaccharide in which 0-glucosamine monomers are bonded through β-1,4 bonds, and dissolves in dilute aqueous solutions containing formic acid, acetic acid, hydrochloric acid, etc. by forming a salt with the acid. The degree of deacetylation of chitin to obtain chitosan used in the present invention is 70% or more, preferably 85% or more, more preferably 9
It is preferable to set it to 0% or more. Chitosan with a low degree of deacetylation has a problem of low solubility and a large amount of insoluble matter, so the above range is set. This chitosan film in the present invention also serves as a reinforcing material for the cellulose derivative film to be laminated. Furthermore, chitosan can be blended with a number of polymers, such as neutral water-soluble polymers such as polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate, or basic water-soluble polymers such as polyethyleneimine and polyarylamine.

The composite membrane of the present invention is characterized in that it has a cellulose derivative membrane in which carboxyl groups are introduced into cellulose as another layer laminated to the chitosan membrane, and as a cellulose derivative membrane in which carboxyl groups are introduced into cellulose. Specifically, the following items (1) to (2) can be exemplified.

■Cellulose ether derivatives ■Cellulose ester derivatives ■Cellulose oxides ■Cellulose graft copolymers ■Cellulose derivatives having the structure of m numbers from ■ to ■ Above Examples of the cellulose derivatives mentioned in ■ above include carboxyalkyl cellulose such as carboxymethyl cellulose and carboxyethyl cellulose. Examples include cellulose and their sodium and potassium salts.

Examples of the cellulose ester derivatives in (2) above include cellulose succinate (succinoylated cellulonis), cellulose phthalate acetate, cellulose acetate maleate, and their sodium and potassium salts.

Examples of the cellulose oxide mentioned in (■) above include monocarboxycellulose, which is the oxidation product of cellulose with nitrogen dioxide, the oxidation product of cellulose with sodium periodate, periodic acid, lead tetraacetate, and chromic acid, and the oxidation product of cellulose with chlorite. Alternatively, dicarboxycellulose or tricarboxylcellulose, which is a product oxidized with sodium chlorate, and their sodium and potassium salts can be used.

Examples of the cellulose graft copolymer described in (2) above include:
Copolymers in which vinyl monomers containing carboxyl groups such as acrylic acid and methacrylic acid, and their sodium salts, potassium salts, or lower alkyl esters are graft-bonded to the hydroxyl groups of cellulose molecular chains or cellulose derivative molecular chains, or in cellulose derivatives. Examples include copolymers in which active groups other than hydroxyl groups are graft-bonded.

In the present invention, a cellulose derivative containing a carboxyl group is dissolved in water or an aqueous solution or an organic solvent containing an inorganic (alkali, etc.)↓organic compound to form a solution,
A substance that solidifies again when the solvent (or water) is removed. The solubility is influenced by the size of the atomic group containing the carboxyl group, the content of the carboxyl group, the distribution, etc. The cellulose derivative used in the present invention is generally 0.5 to 1.0 g/g. It is desirable to have carboxyl groups of Qmeq or higher and have a uniform distribution in terms of solubility, film formability, membrane performance, etc. For example, cellulose in methanesulfonic acid used as a cellulose solvent smoke catalyst Succinoylation of is particularly preferred as it provides carboxyl group-containing cellulose derivatives having such properties. In addition to the above methanesulfonic acid, cellulose solvents include
For example, dinitrogen tetroxide-dimethyl sulfoxide (DMSO
), nitrosyl chloride-DMSO, dinitrogen tetroxide-dimethylformamide (DMF), dinitrogen tetroxide-dimethylacetamide (DMAc), paraformaldehyde-D
Examples include cellulose solvent systems such as MSO1 lithium chloride-DMAc.

The composite membrane of the present invention in which a cellulose derivative membrane and a chitosan membrane are laminated can be typically produced, for example, as follows.

For example, in the first step, chitosan is dissolved in a dilute aqueous solution of chitosan (e.g., 0.5 to 1 t of acetic acid aqueous solution) to give a chitosan concentration of 0.1 to 1.0 mm. A predetermined amount (e.g. 20~zoog) is cast onto a resin substrate (hereinafter referred to as a resin plate), and the resin plate is held horizontally at a constant temperature of 20~60°C, preferably 30°C. At a constant humidity of 20 to 90*, preferably 4091, moisture is evaporated for several hours to one day, thereby forming acid and salt on the resin plate to form a solidified chitosan film. Instead of acetic acid as the dilute acid, organic acids such as formic acid, lactic acid, and ascorbic acid, and inorganic acids such as hydrochloric acid can also be used. Note that as a solvent for chitosan, water-methanol containing the above-mentioned dilute acid, formic acid, dichloroacetic acid, trichloroacetic acid, etc. can also be used.

Next, as a second step, a cellulose derivative containing a carboxyl group is dissolved in a solvent to form a solution with a polymer concentration of O11-2t, and this solution is placed on the chitosan film formed in the first step. quantitative (e.g. 20-2
The solvent is evaporated for several tens of seconds to one day at a constant temperature of 20 to 70°C, preferably 30°C, and a constant humidity of 2O-9ON, preferably 40X. A composite membrane is formed by laminating the chitosan membrane and a cellulose derivative membrane thereon on the plate.

In the production of the above-described composite membrane, the resin plate on which the chitosan solution is cast in the first step is a resin plate that is not affected by the chitosan solution and has a suitable affinity for the resin plate. It has the property of being able to spread uniformly on the
In addition, a chitosan film formed by casting is not easily peeled off in its natural state, but it is preferably selected to exhibit adhesion to the extent that it can be easily peeled off by hand, for example, by an operator in a dry state.

Specifically preferred materials for such a resin plate include polyacrylic resin, polystyrene resin, polyvinyl chloride resin, and the like. For example, Teflon resin, which has high water repellency, is often not suitable for forming a large film. In addition, for example, for glass plates, etc., which have good compatibility with the chitosan solution and have too high adhesion with the formed chitosan film, it is difficult to peel the film from the substrate in a dry state, so this is done in a wet state. Since this is necessary, the above-mentioned resin plate is preferable.

In the first step, the dilute acid (acetic acid) type chitosan film formed on the resin plate is brought into contact with a dilute alkaline aqueous solution and washed with water to convert it into a free amino group type chitosan film. It is also preferred to carry out a contact treatment with an aldehyde compound such as ~5% formaldehyde. If the cellulose derivative solution is cast in the second step without this treatment, the chitosan membrane will swell and wrinkles will occur, and the flatness of the manufactured composite membrane may not be obtained. The contact treatment with the dilute alkali aqueous solution is usually carried out for several seconds, preferably for 5 seconds or more, and typically 1%
Examples of dilute alkaline aqueous solutions include sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, and aqueous ammonia of about 3%. The above-mentioned aldehyde compound is brought into contact with the chitosan membrane by adding 10% to 5% formaldehyde aqueous solution to the aldehyde compound, for example.
This can be carried out by contacting for more than a minute at room temperature, or by contacting with formaldehyde vapor for one to several hours at 20 to 50'C.

The thickness of the chitosan film formed in the first step of the present invention can be adjusted by adjusting the chitosan concentration of the chitosan aqueous solution, the casting amount, and the area of the resin plate (i.e., the casting area).
In terms of M, it is 1~lo.

It is preferable that the thickness is about μm, preferably 2.5 to 90 μm.

In the second step of the present invention, in some cases, in order to insolubilize the film, the formed film of cellulose derivative or the like is brought into contact with ammonia vapor at 20 to 50°C for several hours to one day, and then washed with water, or Weakly acidic aqueous solutions such as acetic acid and hydrochloric acid (
For example, after contacting with 983-4), if necessary, the cellulose derivative film may be made insolubilized by washing with water and evaporating water under the same conditions as above.

In manufacturing the composite membrane of the present invention, the first and second steps typically described above may be performed in reverse order. In this case as well, it is necessary to select the resin plate in consideration of the relationship in which the formed cellulose derivative film can be peeled off.

When manufacturing a composite film by reversing this order, for the same purpose as wrinkle prevention 1 mentioned above, the cellulose derivative film formed in the first step is It is preferable to contact with ammonia or with acid water 78 liquid. The contents of the process may be the same as described above.

Furthermore, the chitosan film formed in the second step can be insolubilized as necessary.

As mentioned above, the composite membrane having a laminated integrated structure of the present invention refers to a membrane having a laminated structure of a cellulose derivative membrane containing carboxyl groups and a chitosan membrane, and the carboxyl group and amino It is not limited to those in which the groups form a so-called polyion complex (polymer electrolyte complex) through electrostatic ionic bonding.

Furthermore, the composite membrane of the present invention is not limited to two layers;
It can also be formed as a composite membrane having three or more layers. In this case, the above-mentioned first step and second step
Membranes may be manufactured by repeating the steps alternately.Furthermore, a membrane made of a third component, such as an organic synthetic resin membrane or an inorganic polymer membrane, may be laminated on these membranes.

The composite membrane according to the present invention preferably has a thickness of at least about 3 μm or more. This is because if the film is too thin, the film strength will be weakened. Furthermore, if the membrane is too thick, the permeation rate will be slow, so it is often appropriate to set the membrane thickness to about 5 to 100 .mu.m.

The ratio of the thickness of the chitosan membrane to the cellulose derivative membrane may be selected appropriately depending on the strength, separation performance, permeation rate, etc. of the membrane, but is generally 100:1 to t:1GG, preferably 10:1. It is preferable to set it to about 1 to 1:1O.

The composite membrane of the present invention can be implemented in existing pervaporation equipment, and is preferably implemented in the novel pervaporation equipment proposed in the present invention as shown in FIG. 2 of the drawings.

In other words, known pervaporation devices have a relatively small ratio between the actual volume on the feed liquid side and the effective permeation area of the membrane.
・Journal of Applied Polym
er 5science, vol, 14.2341-2
35B (1970) is 500411/83.3c
m+2-6.0, same vo1.16゜1061~107
110 mj in B (1972)! / 20.0cm
2=5.5, same vol, 30. 179-188
(1985), 80 m115.7c+a2=14,
Journal of Polymer 5cienc
e, Polymer Chemistry E
ditlon, vol, 22. 2159-2
168 (1984) is 200a+ft/t2.8c
m2 = 15.8, but in the pervaporation device used in the present invention, the actual capacity of the supply side container is 400 mA, and the effective permeation area of the attached composite membrane is 9.62 cm'. The ratio of the side volume to the effective area of the membrane was set to 41.6 in order to minimize changes in the composition of the feed liquid due to permeation.

This is done using the composite membrane of the present invention! In this operation, the pressure on the raw material supply side is preferably around normal pressure, and the pressure on the permeate side is preferably 5 mmHg or less, preferably 1
It is preferable to set it to below mmHg.

Furthermore, the pervaporation device shown in FIG. 2 is characterized in that it can be used both as a pressure reduction method and as a carrier gas method on the permeation side.

The composite membrane of the present invention can be used in a pervaporation method, for example, for concentration of ethanol by alcohol fermentation of agricultural and forestry biomass, for dialysis, for gas separation, for reverse osmosis, etc.

Typical examples of liquid mixtures separated by the composite membrane of the present invention having the above configuration include liquid mixtures containing at least an organic liquid as one of its constituents, such as water/methanol, water/ethanol, water/propertool, etc. water/alcohols, water/acetone, water/methyl ethyl ketone,
liquid mixtures of water and water-compatible organic liquids such as water/dioxane, water/ethylene glycol, water/glycerin;
Acetone/alcohols, acetone/carbon tetrachloride, acetone/benzene, ethanol/benzene, ethanol/
Examples include mutually compatible binary organic liquid mixtures such as ethylbenzene and chloroform/benzene, binary or ternary azeotropic mixtures, and mixtures of constituent components thereof.

(Examples) The present invention will be described below based on Examples, but the present invention is not limited to these Examples.

Examples 1 to 3 5 g of chitosan powder with a degree of deacetylation of 89% and a molecular weight of approximately 700,000 was added to 990 g of water, and 5 g of acetic acid was added while stirring to prepare a 0.5% chitosan aqueous solution. Acrylic resin board (vertical 30
160g was cast onto a resin plate (30cm wide, 1cm thick), and the resin plate was held horizontally at a temperature of 30°C and a humidity of 35%.
The water was evaporated for 20 hours to form a chitosan film on the acrylic resin plate. Next, the chitosan film on the resin plate was
After contact treatment with 200 mL of % sodium hydroxide aqueous solution for 3 minutes, the sample was washed with water and water was evaporated for 3 hours under the same conditions as above.

Next, carboxyl base ff13.2 meq/g, carboxymethylcellulose sodium salt with a molecular weight of 620,000 5
160 g of a carboxymethylcellulose aqueous solution with a concentration of 0.5%, prepared by dissolving 1.5 g of carboxymethylcellulose in 995 g of water, was cast onto the chitosan membrane, and the resin plate was held horizontally, and water was evaporated for 20 hours under the same conditions as above. Then, the composite film on the acrylic resin plate was peeled off to obtain a transparent film with a thickness of 19 μm.

This @1 is placed in the barbecuing cell 2 shown in FIG. 2, with the carboxymethylcellulose membrane facing the feed liquid 3 side and the chitosan membrane facing the permeate side 4 as shown in the figure. P
Set on A board 5, initial concentration of ethanol 19.8
wt% (Example 1), 49.9wt% (Example 2)
), and 83.2 wt% (Example 3) of 300 g of the feed liquid (water-ethanol mixed liquid), the feed pressure of the raw material liquid was normal pressure, the feed liquid temperature was 40°C, and the permeation side pressure was 0.
Pervaporation was performed while stirring the feed liquid with a stirring blade 7 at 45 mmHg. The inside of the apparatus was kept at a constant temperature (40° C.) by passing hot water through the jacket 6.

The results are shown in Table 1.

The molecular weights of the chitonsan and cellulose derivative membranes used in this example were measured by gel fA chromatography.

Examples 4 to 6 In this example, birch was first steamed and exploded, and part of the hemicellulose and lignin were removed by extraction, and the remaining lignocellulose was used as a raw material to produce Die Ma
kromolekrale Chemie, Vol.

185.2371-2376 (1985), and collection of research presentation abstracts of the 35th Japan Wood Society Conference, I) 255
(1985), an aqueous succinoylated lignocellulose solution was synthesized.

That is, birch beetles were treated with steam at 15 J/cm' for 15 minutes, and the dry residue fibers (8.0 g), which had been extracted with hot water and dioxane, were put into methanesulfonic acid (100 mj2) at 25°C. After stirring for a minute, it was cooled to about lθ℃, and further succinic anhydride (25g
) dissolved in methanesulfonic acid was poured into the mixture, stirring was continued, and the reaction temperature was maintained at 25° C. by cooling appropriately. 10 minutes after immersing the succinic anhydride solution, the reaction solution was poured into ice-water (
1.5ft) with stirring, the precipitated product was collected by centrifugation, and this product was added to 0.1N-HCIL.
(1.5°C), suspended in water (500 mJZ), neutralized and dissolved with IOM-NaOH aqueous solution, purified by dialysis, and insoluble matter was removed by filtration with a glass fiber membrane. Out of bounds? The product was concentrated using a PA membrane and dried under vacuum. The same synthetic operation was performed three times to obtain a total of 17 g of the same product, ie, succinoylated lignocellulose.

Next, 40 g of the 0.5% chitosan aqueous solution prepared in Examples 1 to 3 was placed on an acrylic resin plate (height 15 cm, width 15 cm, thickness 1 cm) with vinyl tape.
) and held the resin plate horizontally at a temperature of 30°C.
Water was allowed to evaporate for 20 hours at a humidity of 35%, and then the chitosan film on the acrylic resin plate was diluted with 1% sodium hydroxide solution.
&50+nfL for 3 minutes, washed with water, and evaporated water for 3 hours under the same conditions as above.

Next, the carboxyl group content 2.3me synthesized as above
q/g, 40 g of a succinoylated lignocellulose aqueous solution with a molecular f of 1.25 million was cast onto the above chitosan membrane, the resin plate was held horizontally, and water was evaporated for 20 hours under the same conditions as above to form an acrylic resin plate. A composite membrane was formed on top. Further, the acrylic resin plate with this composite membrane attached was placed in a desiccator containing 50 ff1il of 29% ammonia water at the bottom and exposed to ammonia vapor for 16 hours at a room temperature of 23°C, then washed with water and treated in the same manner as above. The moisture was evaporated for 3 hours under the conditions, and the composite film on the resin plate was peeled off to a thickness of 16 μm.
A pale yellow transparent composite film (measured with a screw micrometer) was obtained.

Figure 1 shows the obtained composite film under a scanning electron microscope (200
A cross section observed at 0x magnification is shown. This figure shows the torn cross section of the composite membrane prepared above, viewed diagonally from the chitosan membrane side.

This IN! 1 was set in the pervaporation cell 2 shown in FIG. 2, with the succinoylated lignocellulose membrane facing the feed liquid 3 side and the chitosan membrane facing the permeation side 4 as shown in the figure, and an initial concentration of ethanol of 21.8 wt. % (Example 4), 51.4 Yoi t% (Example 5), and 83.2
+vt% (Example 6) of 300 g of each feed liquid (water-ethanol mixed liquid) was pervaporized while stirring the feed liquid at normal pressure of raw material liquid, feed liquid temperature of 40°C, and permeate side pressure of 0.45 mmHg. ration was conducted.

The results are shown in Table 1.

Comparative Example As in the example, 80 g of a 0.5% chitosan aqueous solution was placed on an acrylic resin plate (vertically 15
cm, width 15cI11. 1 cm thick),
The resin plate was held horizontally and water was evaporated for 20 hours at a temperature of 30°C and a humidity of 35% to form a chitosan film on the resin plate. Next, the chitosan film on the acrylic resin plate was oxidized with 1% hydroxyl. After contact treatment with 50 ttrJl of sodium aqueous solution for 3 minutes, the sample was washed with water, and water was evaporated for 3 hours under the same conditions as above.

The chitosan film was peeled off from the resin plate to obtain a transparent film with a thickness of 16 μm.

This membrane was set in the Barbe Pepsicon cell shown in FIG. 2 in the same manner as in the example, and the initial concentration of ethanol was 20.0.
wt% feed liquid (water-ethanol mixture) 300g
Regarding, the supply pressure of raw material liquid is normal pressure, the supply liquid temperature is 40℃,
Pervaporation was performed while stirring the feed liquid at a permeate side pressure of 0.45 mml (g).

The results are shown in Table 1.

(Effects of the Invention) According to the present invention, pervaporation can be performed with a higher separation coefficient and higher permeation rate than conventional membranes, increasing processing capacity and lowering costs, resulting in industrial scale. This has the effect that a predetermined component in the mixed liquid can be suitably separated. Particularly in the field of alcohol production by alcohol fermentation, it is characterized by its extremely usefulness in terms of energy conservation.

Furthermore, in the present invention, when a composite membrane having a structure in which a succinoylated lignocellulose membrane and a chitosan membrane are laminated is used, a particularly excellent high separation coefficient and a large permeation rate can be obtained, and the effects are extremely impressive. There is.

[Brief explanation of drawings]

Figure 1 is an electron micrograph (2000x magnification) of a cross section of a composite membrane made by laminating succinoylated lignocellulose membranes and chitosan membranes produced in Examples 4 to 6 of the present invention. This figure shows a torn cross section of the prepared composite membrane viewed diagonally from the chitosan membrane side. FIG. 2 shows the structure of a cell that performs pervaporation using the separation membrane of the present invention. 1... Separation membrane 2... Cell 3... Feed liquid side 4... Permeate side and 4 other people

Claims (1)

[Scope of Claims] 1. A cellulose-based composite membrane used for pervaporation, which has a structure in which a chitosan membrane and a cellulose derivative membrane in which carboxyl groups are introduced into cellulose are laminated and integrated. 2. The cellulose composite membrane used for pervaporation according to claim 1, wherein the cellulose derivative membrane has carboxyl groups introduced through etherification. 3. The cellulose composite membrane used for pervaporation according to claim 1, wherein the cellulose derivative membrane has carboxyl groups introduced through esterification. 4 The cellulose derivative membrane into which carboxyl groups have been introduced is
The cellulose-based composite membrane according to claim 3, which is a succinoylated cellulose membrane obtained by succinoylating cellulose in methanesulfonic acid. 5. A first step of casting and solidifying the chitosan solution;
A second step of casting and solidifying a cellulose derivative solution in which a carboxyl group has been introduced into cellulose is sequentially performed on a substrate, in a method for producing a composite film. 5. The method for producing a cellulose-based composite membrane according to any one of claims 1 to 4, characterized in that the chitosan membrane formed in the step is brought into contact with an alkaline aqueous solution or an aldehyde compound. 6 The first step of casting and solidifying a cellulose derivative solution in which carboxyl groups have been introduced into cellulose, and the second step of casting and solidifying a chitosan solution into a film are sequentially performed on a substrate to form a composite. 2. A method for producing a film, wherein, prior to the second step, the cellulose derivative film formed in the first step is brought into contact with ammonia or an acid aqueous solution. 4. A method for producing a cellulose-based composite membrane according to any one of Item 4.