JPS5845202A - Preparation of acylated chitin - Google Patents

Abstract

PURPOSE:To obtain the titled chitin having desired degree of acylation, without causing the degradation of the polymer, by reacting chitin with an acylating agent in a solvent composed of trichloroacetic acid and a specific halogenated hydrocarbon, and coagulating and recovering the product by adding a non- solvent to the reaction mixture. CONSTITUTION:0.5-15pts.wt. of chitin is made to react with 0.1-25mol, based on 1mol of the acetylglucosamine unit which is a constituent element of chitin, of an acylating agent (e.g. acetic anhydride) in 100pts.wt. of a mixed solvent composed of 20-70(wt)%, preferably 30-40% trichloroacetic acid and 80-30% halogenated hydrocarbon selected from dichloromethane, chloroform, bromoform, 1,2-dichloroethane, and 1,2-dibromoethane. The reaction mixture is mixed with a non-solvent (e.g. acetone) to effect the coagulation of the acylated chitin, which is recovered from the reaction mixture.

Description

[Detailed description of the invention] The present invention relates to a method for producing acylated chitin.

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 a β-1,4-linked polysaccharide whose basic units are N-acetyl to D-glucosamine, and has a structure similar to that of cellulose. As can be inferred from its 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 currently hardly used. Chitin is also a naturally occurring, harmless polymeric substance with excellent mechanical strength, heat resistance, and chemical resistance, and there is no risk of causing any environmental pollution when disposed of, and it can be naturally purified through microbial decomposition. Since it has the great feature of being able to be used as a liquid, if it can be molded into a suitable solution state, it can be expected to have a fairly wide range of uses as films and fibers.

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 According to a specific mixed solvent consisting of 20 to 70% by weight and a certain type of halogenated hydrocarbon, chitin can be easily dissolved without polymer collapse or depolymerization. The inventors discovered that suitable films such as packaging films, magnetic tape films, and semipermeable membranes could be produced from the obtained chitin solution by casting, for example, and completed inventions related to these films.

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. discovered that acylated chitin with
The present invention was made based on this knowledge.

That is, the present invention provides trichloroacetic acid in an amount of 20 to 7゜z
t=tocyclomethane, chloroform, bromoform,
After reacting chitin with an acylating agent in a mixed solvent consisting of 80 to 30% by weight of a halogenated hydrocarbon selected from 1,2-dichloroethane and 1,2-dibromoethane, the reaction mixture is The present invention provides a method for producing acylated chitin, which comprises adding a non-solvent to solidify the acylated chitin, and recovering the coagulated chitin.

According to the method of the present invention, using the above-mentioned specific mixed solvent, the acylation reaction of chitin can proceed extremely easily, without substantially causing the polymer collapse of chitin itself.
A desired product having an arbitrary degree of acylation can be produced simply by adjusting the amount of the acylating agent added. Moreover, the acyl-dissolved solution obtained according to the present invention has excellent film-forming ability, and therefore, films and fibers having excellent properties can be produced from the solution. In particular, the film produced from the above acylated chitin paste exhibits excellent elasticity and soft feel depending on the degree of acylation or the type of acylating agent, and also has a soft feel compared to chitin film. The hydrophobicity of the material is increased and the wet strength of the material 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 ultraviolet osmosis membranes. It exhibits the following 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 is dissolved in the mixed solvent described below regardless of its particle size, but it is usually appropriate to reduce the particle size to 50 mesh or more in terms of efficiency of the dissolution operation (time).

Trichloroacetic acid, which is a component of the mixed solvent used in the present invention, may be either commercially available JIS standard reagent grade or reagent grade, but it is desirable 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,
．． 2-Schiffooxri/Also, HaX+2-dibromoethane is used. These halogenated hydrocarbons can be used alone or in combination with the trichloroacetic acid. The mixing ratio of trichloroacetic acid and halogenated hydrocarbon is 20 to 70% of the total.
Be in charge of weight. If this 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 at the same time as 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 ratio 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 it is completely dissolved within 24 hours at the longest.

The acylating agent used in the present invention is selected from carboxylic acids, carboxylic anhydrides and carboxylic acid chlorides.

Specific examples of these include formic acid, acetic acid, dichloroacetic acid, propionic acid, acetic anhydride, propionic anhydride, butyric anhydride, n-valeric anhydride, isovaleric anhydride, caproic anhydride, caprylic anhydride, capric anhydride, Examples include lauric anhydride, palmitic anhydride, stearic anhydride, acrylic anhydride, methacrylic anhydride, cono-phosphoric anhydride, maleic anhydride, acetyl chloride, acryloyl chloride, methacryloyl chloride, and benzoyl chloride.

In the present invention, when making the acylating agent 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 to and mixed with 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 champion at the same time, mix the saliva and acylating agent separately with the mixed solvent, or mix and dissolve them and then mix them together, or even after premixing a part of the acylating agent with the mixed solvent. It is also possible to add chitin to this and then further add the remainder of the acylating agent.

In employing either method, it is preferable to adopt a temperature condition in the range of -5°C to +50°C as the reaction temperature between chitin and the acylating agent. In particular, if this temperature is too high than 50° C., the molecular breakdown of chitin is likely to occur, and the resulting acetylated chitin may deteriorate, which is not preferable.

In one preferred embodiment of the method of the present invention, chitin powder is first added to a mixed solvent K 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, chitin is acylated with the chitin solution obtained above to obtain the above solvent solution of acylated chitin. According to another preferred embodiment of the invention, acylated chitin is also produced by first mixing a mixed chitin powder consisting of trichloroacetic acid and a halogenated hydrocarbon.

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 use of the obtained acylated chitin, and is usually 0.5 to 1 part by weight per 100 parts by weight of the solvent.
It is preferable to set the area to about 5 points. 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 usually set at a molar ratio of 0.1 to 25 times the acetylglucosamine unit, which is a component of chitin. is preferred.

The reaction mixture of acylated chitin obtained by each of the above methods is in the form of a homogeneous solution, and in order to obtain the desired acylated chitin from the solution, water or a suitable non-alcoholic acid is added to the mixture. After coagulating and recovering the acylated chitin by adding a solvent,
If necessary, this may be treated with an alkaline aqueous solution such as a sodium carbonate aqueous solution or aqueous ammonia, washed with water, and dried.

As the nonsolvent in this case, for example, alcohols, ketones, esters, and ethers are used, and among these, methanol, ethanol, 2-propanol, acetone, dioxane, tetrahydrofuran, ethyl acetate, etc. are particularly suitable. .

Acylated chitin produced by the method of the present invention usually has
It is in powder form, and as a result of infrared absorption spectrum analysis, it was found that the carbonyl group of the ester bond (>
An absorption band in the 1720-1750 cm-' region due to a=O) 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.

The degree of acylation of Ushita acylated chitin can be determined from the elemental analysis value.
The composition ratio of nitrogen element to the composition ratio of carbon element (N/, C
It can be calculated by finding the value).

For example, regarding acetylated chitin, its degree of acetylation (D
AW) is calculated by the following formula.

DA (person in charge) = ([o,,5sal/(N/c)]
-4) X 100 or less Examples will be given to explain the present invention in more detail. In each example, "center" indicates parts by weight.

Example 1 While stirring a mixed solvent consisting of 35 parts of trichloroacetic acid and 65 parts of 1,2-dichloroethane while maintaining it at 15°C,
When 2.03 parts of purified chitin that had passed through a 120-mesh sieve was added thereto, it became a viscous solution after half an hour. 1.5 hours after the addition of chitin, io, s parts of acetic anhydride (molar ratio 1:10) were added dropwise, and stirring was continued for an additional 30 minutes 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 Solution F was poured into acetone to precipitate acetylated chitin. After washing with water,
After being treated with a 0.2% ammonia aqueous solution for 1 hour, repeated washing with water and drying resulted in an acetylation degree of 108% (N10
= 0.1147) was obtained.

The remaining part of Solution F was spread on a glass plate and allowed 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 062 aqueous ammonia, thoroughly washed with water, and then dried to obtain an acetylated chitin film.

The infrared absorption spectrum of this film is 1745 crn
-' showed strong absorption. The moisture content of this film was 12% at 20° C. and a relative humidity of 55 qb (the moisture content of the chitin film was 16% under the same conditions).

Example 2 1.99 parts of purified chitin powder was added to a mixed solvent of 35 parts of trichloroacetic acid and 68 parts of 1,2-dichloroethane, and the mixture was heated at 15°C.
When the solution became viscous after stirring for half an hour, 2.76 parts of benzoyl chloride was carefully and slowly added dropwise. The reaction solution began to increase in viscosity after half an hour, and became difficult to stir after about 1.5 hours.

After maintaining the temperature at 15° C. for an additional 21 hours, 400 parts of ethanol was added, and the coagulated polymer material was washed with water, treated with a dilute ammonia solution, washed with water, and then dried. In the infrared absorption spectrum of the product, weak absorption was observed at 1720 crn-'.

Example 3 4.00 parts of purified chitin powder was carefully added little by little to a mixed solvent consisting of 70 parts of trichloroacetic acid, 30 parts of 1,2-dichloroethane, and 130 parts of formic acid while stirring at 0°C. It gradually dissolved to become a clear solution. When this solution was stored overnight in a refrigerator at 4°C after adding chitin, the contents quickly became gel-like and lost fluidity, but 30
The polymer material precipitated from this solution was purified and showed strong absorption at 1730 crn-', indicating that it was formylated chitin.

Example 4 1.50 parts of purified chitin powder was added to a mixed solvent consisting of 35 parts of trichloroacetic acid and 65 parts of 1,2-dichloroethane,
After stirring at 15℃ to disperse and dissolve chitin,
It was stored overnight in a refrigerator adjusted to ℃ for ripening. Next, a predetermined amount of various carboxylic acid anhydrides was added to this solution,
After stirring at 15°C for 2 hours, the mixture was stored in a refrigerator adjusted to 4°C for 20 hours to carry out the reaction. Table 1 shows the results of producing acylated chitin using 12 types of carboxylic acid anhydrides. In the table, the addition ratio of the carboxylic acid anhydride is expressed as the molar ratio of the acid anhydride to the acetylglucosamine unit, which is a component of chitin. Determined from quantity.

Claims (1)

[Claims] l Trichloroacetic acid 20-70% by weight and a halogenated hydrocarbon selected from dichloromethane, chloroform, bromoform, '1,2-dichloroethane and Q: 1,2-cyfuromoethane 80-30% by weight A method for producing acylated chitin, which comprises reacting chitin and an acylating agent in a mixed solvent consisting of the following: and then adding a non-solvent to the reaction mixture to coagulate the acylated chitin, which is then recovered. 2 The temperature at which chitin is reacted with the acylating agent is 15℃~+
The method according to claim 1, wherein the temperature is in the range of 50°C. 3. The method according to claim 1, wherein the arylizing agent is a carboxylic acid, a carboxylic acid anhydride, or a carboxylic acid chloride. 4. The method according to claim 1, wherein the acylating agent is used in an amount of 1 to 25 times the amount of acetylglucosamine units, which are constituents of chitin.