JPS6311361B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an acylated chitin film. Chitin is a natural polymeric substance that is the main organic component that makes up the exoskeleton of crustaceans such as shrimp and crabs, and insects, and is also present in the cell walls of lower plant mushrooms and fungi. They are widely and abundantly distributed in the animal and plant kingdoms. Its chemical structure is β-1,4 whose basic unit is N-acetyl-D-glucosamine.
-A bonded polysaccharide with a structure similar to cellulose. As can be inferred from this structure, chitin is chemically stable and does not react with most reagents under mild conditions. Furthermore, since no suitable solvent for dissolving chitin has been found so far, chitin is extremely difficult to handle, and as a result, it is hardly used at present. Chitin is also a naturally occurring harmless polymer substance with excellent mechanical strength, heat resistance, and chemical resistance.
There is no risk of causing any environmental pollution even when disposed of, and it has the great feature of natural purification through microbial decomposition.If it can be molded into an appropriate solution state, it can be used in a wide range of applications such as films and fibers. It has promising uses. The present inventors have conducted various studies on a solvent that can make chitin into a moldable solvent solution without impairing its characteristics, with the aim of effectively utilizing the above-mentioned chitin, and in the process, trichloroacetic acid 20-70% by weight and 80% halogenated hydrocarbons
According to a specific mixed solvent consisting of ~30% by weight,
Chitin can be easily dissolved without polymer collapse or depolymerization, and the resulting chitin solution can be used as packaging films, magnetic tape films, semipermeable membranes, etc. by casting, etc. He discovered that films could be produced and completed inventions related to them. However, the present inventors continued their research and found that if an acylating agent is added to a chitin solution dissolved in the above-mentioned specific mixed solvent and reacted, an arbitrary degree of acylation can be achieved depending on the amount of the acylating agent added. The present inventors have discovered that a homogeneous acylated chitin solution can be obtained, and that an acylated chitin film can be easily prepared from this solution, thereby completing the present invention. That is, the present invention uses 20 to 70% by weight of trichloroacetic acid.
and 80 to 30% by weight of at least one halogenated hydrocarbon selected from dichloromethane, chloroform, bromoform, 1,2-dichloroethane, and 1,2-dibromoethane, and chitin and an acylating agent. The present invention provides a method for producing an acylated chitin film, which comprises reacting the acylated chitin with the acylated chitin and then casting the obtained acylated chitin solution. According to the method of the present invention, the acylation reaction of chitin can proceed extremely easily using the above-mentioned specific mixed solvent, and the addition of the acylating agent can be carried out without substantially causing polymer breakdown of chitin itself. A desired target product having an arbitrary degree of acylation can be obtained by simply adjusting the amount, and the solvent solution of acylated chitin obtained by the above acylation reaction has excellent film-forming ability, so that By casting, it is possible to produce a film with excellent properties such as a tensile strength of 4 kg/mm ² or more in a standard environment (temperature 20°C, relative humidity 60%). In particular, the film produced from the above-mentioned acylated chitin solution exhibits excellent elasticity and soft feel depending on the degree of acylation or the type of acylating agent, and also has less hydrophobicity than chitin film. The wet strength is improved. Therefore, like chitin film, the film can be used for packaging, as recording tape, magnetic tape, etc., and as semipermeable membranes such as reverse osmosis membranes and ultrafiltration membranes, and is equivalent to or even better than the chitin film mentioned above. It exhibits excellent characteristics. The chitin used as a raw material in the present invention can be commercially available chitin as it is or pulverized if necessary. It is preferable to dry and use purified chitin powder obtained by pulverizing and repeating treatment with dilute hydrochloric acid and dilute aqueous sodium hydroxide solution. Chitin dissolves in the mixed solvent described below regardless of its particle size, but usually the particle size is
It is appropriate to grind it into a fine powder of 50 mesh or more. Trichloroacetic acid, which is one component of the mixed solvent used in the present invention, may be either commercially available JIS standard reagent grade 1 or reagent grade reagent, but it is preferable to use one with as little water content as possible. Examples of halogenated hydrocarbons that are other components of the solvent include dichloromethane, chloroform, bromoform, 1,2-dichloroethane, and 1,2-dibromoethane. These halogenated hydrocarbons can be used alone or in combination with the trichloroacetic acid. The mixing ratio of trichloroacetic acid and halogenated hydrocarbon is such that trichloroacetic acid accounts for 20 to 70% by weight of the total. This is
If it is less than 20% by weight, the solubility of chitin will be significantly reduced and it will take a long time to dissolve, so that the molecular breakdown of chitin will proceed simultaneously with dissolution. On the other hand, if it exceeds 70% by weight, the solubility of chitin at room temperature becomes poor and it takes time to dissolve the chitin, and the film-forming properties when forming a chitin film from this solution are significantly deteriorated. The most preferable content of trichloroacetic acid in the mixed solvent is 30 to 40% by weight. Within this range, it usually takes 30 minutes to several hours at room temperature to dissolve chitin, and at most 24 hours.
Dissolves completely within hours. As the acylating agent used in the present invention, carboxylic anhydride is used, and examples of such agents include acetic anhydride, propionic anhydride, butyric anhydride, n-valeric anhydride, isovaleric anhydride, caproic anhydride, Examples include caprylic anhydride, capric anhydride, lauric anhydride, palmitic anhydride, stearic anhydride, acrylic anhydride, methacrylic anhydride, succinic anhydride, and maleic anhydride. In the present invention, in order to cause the acylating agent to act on chitin, the acylating agent may be mixed and dissolved in the above-mentioned specific mixed solvent in advance, and then the acylating agent may be added and mixed into the chitin solution. After adding the agent in advance, chitin may be mixed and dissolved in this mixture and the acylation reaction may be carried out at the same time. Of course, you can mix the three at the same time, or you can mix or dissolve chitin and acylating agent separately in a mixed solvent and then mix them together. It is also possible to add chitin to this and then further add the remainder of the acylating agent. In either method, the reaction temperature between chitin and the acylating agent is -5°C to +50°C.
It is preferable to adopt temperature conditions in the range of . In particular, if this temperature is too high than 50° C., the molecular breakdown of chitin tends to occur, and the obtained acetyl chitin may deteriorate, which is not preferable. In one preferred embodiment of the method of the present invention, chitin powder is first poured into a mixed solvent of trichloroacetic acid and a halogenated hydrocarbon while stirring. According to this addition, the chitin powder smoothly dissolves in about 30 minutes at 25°C, and completely dissolves in about 2 hours at 0°C to form a viscous homogeneous solution. Next, an appropriate amount of an acylating agent is added to the chitin solution obtained above, and the temperature of the solution is maintained in the range of -5°C to +50°C for several hours to several days. As a result, chitin is acylated and the above-mentioned solvent solution of acylated chitin is obtained. According to another preferred embodiment of the present invention, acylated chitin is produced by first adding an appropriate amount of acylating agent to a mixed solvent consisting of trichloroacetic acid and a halogenated hydrocarbon, and then lowering the temperature of the resulting mixture to -5. It can also be produced by mixing chitin powder at a temperature of 10°C to +50°C. In this case, acylation proceeds simultaneously with dissolution of the chitin powder in the solvent. In each of the above embodiments, the amount of chitin added to the mixed solvent is appropriately determined depending on the intended use of the acylated chitin obtained, and is usually preferably about 0.5 to 15 parts by weight per 100 parts by weight of the solvent.
The amount of the acylating agent to be used can be arbitrarily selected depending on the desired degree of acylation of the target product, and is preferably 0.1 to 25 times the molar ratio of acetylglucosamine units, which are usually a constituent of chitin. The solvent solution of acylated chitin obtained by each of the above methods has a homogeneous solution form, and in order to obtain the desired acylated chitin from the solution,
For example, after the acylated chitin is coagulated and recovered by adding water or a suitable organic solvent to the solution, it may be treated with an alkaline aqueous solution such as an aqueous sodium carbonate solution or aqueous ammonia as necessary, washed with water, and dried. In addition, in producing a film of acylated chitin, a solvent solution of acylated chitin having the above-mentioned homogeneous solution form is cast onto a smooth metal support surface, glass support surface, or plastic support surface. After the film formed on the surface is coagulated with water or a suitable organic solvent, it may be treated with an alkali if necessary. Furthermore, by discharging the acylated chitin from the solvent solution through the pores into a coagulation bath consisting of a suitable organic solvent,
Acylated chitin having a fibrous morphology can be obtained. In any of the above cases, the solvent solution of acylated chitin may be used as it is, or may be used after being filtered through a filter cloth such as a glass sintered plate, glass fiber, or cotton cloth. Examples of suitable organic solvents that can be used to coagulate acylated chitin from the solution include alcohols, ketones, esters, and ethers, and among these, methanol, ethanol, 2-propanol, and acetone are particularly suitable. , dioxane, tetrahydrofuran, ethyl acetate and the like are suitable. As a result of infrared absorption spectrum analysis, the acylated chitin produced by the method of the present invention shows that the carbonyl group of the ester bond (>
An absorption band in the 1720-1750 cm ^-1 region due to C=0) is observed, and the intensity of this absorption band increases in proportion to the increase in the degree of acylation. From this, it is considered that the acylation of chitin in the present invention occurs to the hydroxyl group bonded to the 6-position carbon of the acetylglucosamine unit, which is a component of chitin, and further extends to the hydroxyl group bonded to the 3-position carbon. Further, the degree of acylation of acylated chitin can be calculated by determining the composition ratio of nitrogen element to the composition ratio of carbon element (N/C value) from the elemental analysis value. For example, the degree of acetylation (DA, %) of acetylated chitin is calculated by the following formula. DA (%) = {[0.5831/(N/C)] -4}×100 In addition, the acylated chitin film obtained by the method of the present invention shows that as the degree of acylation increases, and the acylation with higher fatty acids It has improved elasticity and a soft feel. Acylation generally increases the hydrophobicity of the film and increases its wet strength. Therefore, the acylated chitin film can be effectively used as a selective membrane for metal ions, an organic compound or a polymer compound, etc. by reverse osmosis. Examples will be given below to explain the present invention in more detail. In each example, "center" indicates parts by weight. Example 1 35 parts of trichloroacetic acid and 1,2-dichloroethane
2.03 parts of purified chitin that had passed through a 120-mesh sieve was added to a mixed solvent consisting of 65 parts while stirring while maintaining the temperature at 15°C. After half an hour, it became a viscous solution. Acetic anhydride 1.5 hours after chitin addition
10.8 parts (molar ratio 1:10) was added dropwise and stirring was continued for another half hour to form a homogeneous solution. This solution was allowed to stand at 4° C. for 20 hours, filtered through a glass filter, and a portion of the solution was poured into acetone to precipitate acetylated chitin. After washing with water and treating with a 0.2% ammonia aqueous solution for 1 hour, washing with water was repeated and drying to obtain acetyl chitin with a degree of acetylation of 108% (N/C = 0.1147). The remainder of the solution was spread on a glass plate and left to stand in the air for half an hour, then placed in acetone and treated for 20 minutes to solidify, and the film peeled off. This film was treated with 0.2% aqueous ammonia, thoroughly washed with water, and then dried to obtain an acetylated chitin film. The infrared absorption spectrum of this film showed strong absorption at 1745 cm ^-1 . The moisture content of this film was 12% at 20° C. and 55% relative humidity (the moisture content of chitin film was 16% under the same conditions). Example 2 35 parts of trichloroacetic acid and 1,2-dichloroethane
2.00 parts of purified powdered chitin was added and dissolved in a mixed solvent consisting of 71 parts while stirring while maintaining the temperature at 15°C, and then 13.0 parts of propionic anhydride was added and stirring was continued for an additional 2 hours. The reaction solution became viscous and homogeneous. This solution was allowed to stand at 4° C. for 18 hours, then cast onto a glass plate, dried for half an hour, and then poured into acetone to solidify the film, which was peeled off from the glass plate. Wash this film with water and add 0.2% ammonia water to
1740 when processed for a period of time, repeatedly washed with water, and then dried.
A propionylated chitin film with strong absorption in cm ^-1 was obtained. Example 3 35 parts of trichloroacetic acid and 1,2-dichloroethane
2.12 parts of purified chitin powder was added to 65 parts of a mixed solvent and stirred at 15°C for 1 hour, resulting in a viscous solution. To this solution, 2.6 parts of propionic anhydride was added while stirring, and the reaction was continued for an additional hour.
The reaction solution was kept at 4°C for 18 hours. This reaction solution was cast onto a glass plate, dried for half an hour, then soaked in an acetone bath for half an hour to solidify the film, washed with water, treated with 0.2% ammonia water, washed with water, dried, and propionylated. A chitin film was obtained. In the infrared absorption spectrum of this film, weaker absorption than that of the film produced in Example 2 was observed at 1738 cm ^-1 . Example 4 36 parts of trichloroacetic acid and 1,2-dichloroethane
Add 2.02 parts of purified chitin powder to a mixed solvent consisting of 62 parts, stir at 15°C for 20 minutes, and when the solution becomes viscous, add 4.6 parts of n-caproic anhydride to the solution.
The reaction was carried out for 2.5 hours. This reaction solution was stored in a refrigerator at 4°C for 20 hours. Thereafter, the reaction solution was cast onto a glass plate, dried for half an hour, then put into an acetone bath to solidify the film, washed with water, treated with 0.2% ammonia water, washed with water, dried, and made water repellent. A caproylated chitin film with a soft touch was obtained. In the infrared absorption spectrum of this film, strong absorption was observed at 1740 cm ^-1 . Example 5 36 parts of trichloroacetic acid, 1,2-dichloroethane
When 2.03 parts of purified chitin powder that has passed through an 80-mesh sieve is added to a mixed solvent consisting of 64 parts of acetic anhydride and 2.16 parts of acetic anhydride (molar ratio 1:2) at 15°C while stirring, the chitin dissolves and after 2 hours It turned into a viscous solution. After storing this solution in a refrigerator at 4°C for 24 hours, the solution was cast onto a glass plate and dried for half an hour.
The film was coagulated in an acetone bath. After that, the film was washed with water, treated with 0.2% ammonia water, washed with water, and then dried. An acetylated chitin film with strong absorption at 1745 cm ^-1 was obtained.
This film had an N/C=0.1285 and a degree of acetylation of 53.5%. Example 6 35 parts of trichloroacetic acid and 1,2-dichloroethane
Keep 65 parts of the mixed solvent at 15℃, add 0.20 parts of acetic anhydride while stirring, and then add 2.04 parts of purified chitin powder.
After 2 hours of reaction, the mixture was stored in a refrigerator at 4°C for 20 hours. Thereafter, the reaction solution was cast onto a glass plate, treated according to the method of Example 5, and dried to obtain a transparent film. Example 7 35 parts of trichloroacetic acid and 1,2-dichloroethane
2.03 parts of purified chitin that had passed through a 120-mesh sieve was added to a mixed solvent consisting of 65 parts while stirring while maintaining the temperature at 15°C. After half an hour, it became a viscous solution. Acetic anhydride 1.5 hours after chitin addition
10.8 parts (molar ratio 1:10) was added dropwise and stirring was continued for another half hour, resulting in a homogeneous solution. This solution was spread on a glass plate and allowed to stand in the air for half an hour, then placed in acetone and treated for 30 minutes to solidify, and the film peeled off. This film was thoroughly washed with water and then dried to obtain an acetylated chitin film. The infrared absorption spectrum of this film showed the same strong absorption as in Example 1 at 1745 cm ^-1 . Equivalent acetylated chitin films were obtained even when methanol was used as the coagulation solution instead of acetone. In addition, a chitin-added product containing 35 parts of trichloroacetic acid, 65 parts of 1,2-dichloroethane, and 2.03 parts of chitin.
After 1.5 hours had passed, 16.2 parts of acetic anhydride was added to the chitin solution and stirred for 2 hours, resulting in a homogeneous solution. When 21.6 parts of acetic anhydride was added, a homogeneous solution was obtained by stirring at 15°C for 2 hours and then storing at 4°C for 24 hours. Example 8 35 parts of trichloroacetic acid and 1,2-dichloroethane
1.47 parts of purified chitin powder dried at 105°C for 2 hours was added to a mixed solvent consisting of 65 parts of chitin, uniformly dispersed, and stirred at 15°C for 2 hours to obtain a viscous solution. 2.30 parts of distilled acetic anhydride was added to this solution, stirred at 15°C for 1 hour, and then stored in a refrigerator adjusted to 4°C for 20 hours to carry out the reaction. When a film was prepared from the reaction solution thus obtained according to the method of Example 6, a film with a degree of acetylation of 97% was obtained, which showed strong absorption at 1745 cm ^-1 in the infrared absorption spectrum. Example 9 35 parts of trichloroacetic acid, 1,2-dichloroethane
1.50 parts of purified chitin powder was added to 65 parts of a mixed solvent, stirred at 15°C to disperse and dissolve the chitin, and then stored overnight in a refrigerator adjusted to 4°C for ripening. Next, predetermined amounts of various carboxylic acid anhydrides were added to this solution, stirred at 15°C for 2 hours, and then stored in a refrigerator adjusted to 4°C for 20 hours to carry out the reaction. Table 1 shows the results of producing acyl chitin using 12 types of carboxylic acid anhydrides. In the table, the addition ratio of carboxylic acid anhydride is expressed as the molar ratio of acid anhydride to the acetylglucosamine unit, which is a component of chitin, and this addition ratio is calculated from the amount of carboxylic anhydride added. Ta. The degree of acylation of the produced acylated chitin was calculated from the N/C value of a film prepared from the reaction solution in the same manner as in Example 6. In addition, from the infrared absorption spectrum of the produced film, the ratio of the absorbance of the absorption peak of about 1745 cm ^-1 to the absorbance of the absorption peak of about 1658 cm ^-1
I asked for D ₁₇₄₅ / D ₁₆₅₈ . This value is another measure of the degree of acylation and is also listed in Table 1.

【table】

[Table] Reference Example 1 Acetylated chitin with acetylation degrees of 0.35%, 0.58% and 1.02%, respectively, was prepared in exactly the same manner as in Example 9, and a film was also prepared in the same manner. Properties were measured using a Tensilon universal tensile tester. The results are shown in Table 2.

[Table] Reference Example 2 5 parts of acetylated chitin (degree of acetylation 108%) produced by the method of Example 1 was mixed with 70% of trichloroacetic acid.
and 130 parts of 1,2-dichloroethane, stirred at 15°C for 2 hours, and then heated to 5°C.
When kept for 20 hours, the acetylated chitin dissolved. When a film was prepared from this acetylated chitin solution according to the method of Example 5, a film having substantially the same quality as that of Example 1 was obtained.

Claims (1)

[Scope of Claims] 1. 20 to 70% by weight of trichloroacetic acid and at least one halogenated hydrocarbon selected from dichloromethane, chloroform, bromoform, 1,2-dichloroethane, and 1,2-dibromoethane.
1. A method for producing an acylated chitin film, which comprises reacting chitin with an acylating agent in a mixed solvent containing 80 to 30% by weight, and then casting the resulting acylated chitin solution. 2 The temperature at which chitin is reacted with the acylating agent is -5
The method according to claim 1, wherein the temperature is in the range of .degree. C. to +50.degree. 3. The method according to claim 1, wherein the acylating agent is a carboxylic anhydride. 4. The method according to claim 1, wherein the acylating agent is used in an amount of 0.1 to 25 times the amount of acetylglucosamine units that are constituents of chitin.