JPS6392604A - Production of alkali chitin - Google Patents

Abstract

PURPOSE:To obtain an alkali chitin by using a small amount of an alkali, by mixing chitin containing an organic solvent with an aqueous alkali solution and kneading the mixture. CONSTITUTION:Powdery or flaky chitin (A) is brought to a wet state by adding thereto 0.5-10pts.wt., per pt.wt. component A, organic solvent (B) (e.g., isopropanol) and mixed with 0.5-20pts.wt., per pt.wt. component A, aqueous alkali solution (C) (e.g., aqueous NaOH solution) of a concentration of 10-60wt%, preferably, 40-50wt%. The obtained mixture is kneaded, or alternatively after the addition of component C, component A is mixed with component B, and the mixture is kneaded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing alkaline chitin.

(Prior art) As is well known, chitin is present in abundance in crustaceans, insects, and cell walls of fungi. is excluded.

Chitin is a linear homopolysaccharide with N-7 cetyl-D-glucosamine as a constituent sugar and has (1→4)-β-glycosidic bonds.
It has a structure in which the hydroxyl group at the -2 position is substituted with an acetamido group.

There are various derivatives of chitin.

Examples include acetyl chitin, nitrated chitin, methyl chitin, ethyl chitin, carboxymethyl chitin, hydroxyethyl chitin, hydroxypropyl chitin, and the like.

Various uses of these derivatives have been investigated, including wound healing promoters, admixtures for cosmetics and creams, food additives, substrates for enzymes such as chitinase and lysozyme, and antibacterial agents.

In the production of the chitin derivatives mentioned above, especially carboxymethyl chitin, hydroxyethyl chitin, hydroxypropyl chitin, etc., chitin is first treated with an alkaline aqueous solution to make alkaline chitin, and then monochloroacetic acid is added in the case of carboxymethyl chitin, and hydroxyethyl chitin is In the case of chitin, ethylene oxide is reacted, and in the case of hydroxypropyl chitin, propylene oxide is reacted.

Therefore, in the production of these derivatives, the quality of the alkali chitin greatly influences the reactivity and reaction yield.

However, unlike cellulose, chitin has a crystalline structure due to the strong intermolecular attraction of aminoacetyl groups within the molecule, so it is stable against chemicals, and good alkaline chitin cannot be obtained just by mixing an aqueous alkaline solution and chitin powder. I can't do it.

Therefore, after mixing chitin and aqueous alkaline solution, vacuum treatment is performed.
Alkaline chitin is produced by performing pressure treatment, freezing treatment, etc., or by performing swelling treatment with dimethyl sulfoxide as a pretreatment.

(Problems to be Solved by the Invention) The above method requires an excessive amount of alkali to immerse chitin in an aqueous alkaline solution, and has the following problems.

■Because a large amount of concentrated alkaline aqueous solution is used, chitin molecules may be cut or deacetylation reactions may occur.
The quality of the chitin derivatives produced deteriorates due to coloring.

■Because there is an excess amount of alkali in alkaline chitin, neutralization may be required during the subsequent production of derivatives, or the effective utilization rate of chemicals may be poor.For example, in the case of carboxymethyl chitin, an excess amount of Since a large amount of monochloroacetic acid is consumed by alkali neutralization, the effective utilization rate of monochloroacetic acid is extremely poor.

(Means for Solving the Problems) The present inventors have conducted extensive research based on these findings, and as a result, have come to provide the present invention. That is, in producing alkaline chitin from chitin, after adding an organic solvent to chitin, then adding an alkaline aqueous solution and kneading, or after adding an alkaline aqueous solution to chitin, then adding an organic solvent and kneading. This is a method for producing alkaline chitin characterized by the following.

Chitin used in the present invention includes commonly used powder or flake chitin.

Examples of organic solvents include alcohols such as ethanol, propatool, impropatol, butanol, imbutanol, amyl alcohol, and isoamyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; Examples include halogenated alkylenes such as methylene chloride and ethylene chloride, mixtures thereof, and further examples include mixed solvents of the above-mentioned solvents and methanol.

Examples of the alkaline aqueous solution include aqueous solutions of alkali hydroxides, such as sodium hydroxide and potassium hydroxide.

The method for producing alkaline chitin according to the present invention includes the chitin (
The organic solvent was added to the chitin (powder or flakes) to make it wet, and then the alkali aqueous solution was added and kneaded, or the alkali aqueous solution was uniformly added to the chitin (powder or flakes) by spraying or the like. After that, the organic solvent is added and kneaded.

The amount of organic solvent used is 0.5 to 10 times the amount of chitin.

The concentration of the alkaline aqueous solution is 10 to 60% (by weight), preferably 40 to 50% (by weight), and the amount thereof is 0.5 to 20 times the amount of chitin.

Furthermore, when kneading chitin (powder or flakes) by adding an organic solvent, aqueous alkaline solution, etc., a normal kneading machine,
For example, a meat chopper or the like is used.

(Effects of the Invention) The method for producing alkaline chitin of the present invention is as follows: (1) Since an organic solvent is added, extremely smooth kneading is possible even with a small amount of alkali. (2) The state of dispersion of alkali in chitin is extremely high. (3) Since the amount of alkali is the minimum necessary, cutting of chitin molecules, deacetylation reactions of chitin molecules, coloring, etc. are unlikely to occur. (4) ) When producing chitin derivatives, it is an excellent production method, as there is little surplus alkali, so the effective utilization rate of chemicals is greatly improved.

(Example) Next, the present invention will be explained in detail with reference to Examples.

Example 30 g of a 7=3 mixture of Improper Tool and methanol was added to 15 g of powdered chitin and stirred.

Next, 50% (by weight) aqueous sodium hydroxide solution.

After adding 30 g and stirring, the mixture was kneaded 10 times at room temperature using a meat chopper to obtain alkaline chitin.

Reference Example After adding 300 g of Impropatool to 75 g of alkaline chitin obtained in Example, while stirring at room temperature, 916.5 g of monochlorine vinegar dissolved in Impropatool was added.
was added dropwise, and the reaction was further carried out at 80° C. for 1 hour. The reaction product was washed with water-containing methanol and then dried to obtain 16.2 g of crude carboxymethyl chitin.

The obtained crude carboxymethyl chitin is a water-soluble white powder with a low content of by-product sodium glycolate, the degree of carboxymethyl etherification of the purified product is 1.15, and the effective utilization rate of monochloroacetic acid is 49%. Met.

Comparative Example 1 100 g of a 50% (by weight) aqueous sodium hydroxide solution was added to 15 g of powdered chitin, stirred, and kneaded 10 times using a meat chopper at room temperature to obtain alkaline chitin.

Next, after adding 300g of Impropa Tool.

55 g of monochloroacetic acid dissolved in Impropatol was added dropwise while stirring at room temperature, and the same procedure as in Example was repeated to obtain 55.7 g of crude carboxymethyl chitin.

The obtained crude carboxymethyl chitin contains a large amount of by-product sodium glycolate and is colored grayish brown.The degree of carboxymethyl etherification of the purified product is 1.14, and the effective utilization rate of monochloroacetic acid is 12%. This was a low value.

Comparative Example 2 30g of 50% (by weight) sodium hydroxide aqueous solution was added to 15g of powdered chitin and stirred.Next, when I tried to knead it using a meat chopper at room temperature, the amount of aqueous solution was too small. Unable to knead, we gave up on producing alkaline chitin'.

Comparative Example 3 To 15 g of powdered chitin was added 30 g of a 7:3 mixture of Improper Tool: methanol and stirred.

Next, 30 g of a 50% (weight) sodium hydroxide aqueous solution was added and stirred, and then left at room temperature for 2 hours to obtain alkali chitin.

Next, 24.4 g of crude carboxymethyl chitin was obtained in the same manner as in the reference example.

The degree of carboxymethyl etherification of the purified product and the effective utilization rate of monochloroacetic acid were the same as in the reference example, but
Because no kneading operation was performed during the production of alkaline chitin,
Water-soluble carboxymethyl chitin could not be obtained because the alkali did not penetrate sufficiently into the chitin.

Claims (1)

[Claims] In producing alkaline chitin from chitin, an organic solvent is added to chitin and then an alkaline aqueous solution is added and kneaded, or an alkaline aqueous solution is added to chitin and then an organic solvent is added. A method for producing alkaline chitin, which is characterized by kneading it by mixing.