JPS6144083B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing particulate chitin. Chitin is a major organic component that participates in the formation of the skeleton and outer skin of living organisms, such as the cell walls of crustaceans such as shrimp and crabs, insects such as beetles and crickets, mushrooms, and fungi, and is widely and abundantly distributed in nature. It is a substance that has This is N-acetyl-D
- It is a polysaccharide consisting of β-1-4 bonds of glucosamine, and is chemically extremely stable, so it does not react with most reagents under mild conditions, and until now it has dissolved chitin in its original form. Since no suitable solvent had been found, it was considered to be extremely difficult to handle. In recent years, the use of chitin as a pharmaceutical, cosmetic, or physiologically active substance has been developed, and it has become clear that it can be effectively used in the form of fine particles or suspension. For example, according to US Pat. No. 3,914,413,
As a substance that promotes wound healing, chitin is said to have a revitalizing and healing effect when applied directly to the wound in the form of fine particles, or when it is dispersed in physiological saline and administered by intramuscular or intravenous injection. Also, US Patent No.
No. 3590126 describes that dogs injected subcutaneously with a suspension of chitin have a detoxifying effect, and the serum of warm-blooded animals containing antibodies produced by chitin can be used to detect parasites of other animals and the parasites caused by them. It has been reported that it has an immunological effect on certain diseases. However, when administering to a wound, it is necessary to make it into fine particles, but especially when administering intramuscular or intravenous injections, the particle size of chitin must be adjusted so that the chitin dispersion or suspension can easily pass through a thin injection needle. It is necessary to have a particle size of 150 microns or less, preferably 50 microns or less. However, it is extremely difficult to obtain such fine chitin particles by conventional grinding methods, and even when freeze grinding is performed, the particle size is limited to 200 microns. Moreover, it has been difficult to obtain highly pure chitin that does not contain impurities. Classic purification methods for obtaining high-purity chitin include the Hackman method and the Offer-alderhalden method, both of which involve repeatedly treating crab shells with acid or alkali. Only the parts soluble in these drugs were extracted and removed, and the impurities insoluble in these drugs remained contained in chitin. Thereafter, in order to remove these impurities, a method of dissolving them in the following solvent was investigated. Namely, concentrated mineral acids, caustic alkalis, caustic soda and carbon disulfide, torchloroacetic acid and halogenated hydrocarbon mixtures, dimethylacetamide containing lithium chloride, trichloroacetic acid and chloral hydrate, chlorides including dichloroacetic acid and methanesulfonic acid, It is known to use solvents such as hexafluoroacetone and hexafluoroisopropyl alcohol, but when these solvents are used, they either cause significant molecular breakdown, change into chitin derivatives and dissolve, or use expensive chemicals. Therefore, it had some drawbacks, such as difficulty in putting it into practical use. For example, when concentrated sulfuric acid with a concentration of 80% or more is applied to chitin, it becomes blackish brown and dissolves uniformly.
-6720, it is sulfated without exception and molecular collapse has also occurred, and it no longer recrystallizes as chitin. Also, a method of recrystallizing by dissolving in concentrated hydrochloric acid (hydrochloric acid method) is also known as a similar technique.
As is clear from the fact that when chitin is treated with concentrated hydrochloric acid, glucosides are cleaved and a deacetylation reaction occurs, producing glucosamine hydrochloride, contamination of the precipitated chitin with polymers or oligomers having free amino groups can be avoided. do not have. A method of recrystallizing chitin by treating chitin with caustic soda to obtain an alkaline chitin solution and diluting it with water is also known (Japanese Patent Application Laid-open No. 122100/1983), but partial deacetylation is still inevitable. Further, fine grain crystals cannot be obtained. Therefore, an object of the present invention is to provide a method for producing a fine particulate chitin suspension having appropriate fineness and high purity under mild conditions without using expensive chemicals and at a high yield. According to the experiments and research conducted by the present inventors, it has been found that crude chitin obtained from natural products can be used at a concentration of 45 to 45°C at a liquid temperature of 40°C or lower.
After dissolving in 75% sulfuric acid to remove impurities, recrystallize by reducing the sulfuric acid concentration to 30% or less, and repeat washing with water to create a stable fine particle suspension of highly pure chitin that does not contain impurities. It has been discovered that it can be obtained as a liquid and that the above object can be achieved. In other words, the present invention uses sulfuric acid, which is an extremely common chemical agent, and achieves high purity using an extremely practical method of simply adjusting the sulfuric acid concentration, without the conventionally accepted reactions such as significant molecular breakdown or sulfation. We were able to obtain a fine-particle chitin suspension in good yield. To explain the present invention in more detail below, chitin used as a raw material of the present invention can be obtained from crustaceans such as shrimp and crabs, insects such as beetles and crickets, mushrooms, and fungi, as described above. However, it is usually obtained from the shells of crabs or shrimps, which are abundant resources and easy to obtain, and are sequentially demineralized and deproteinized using hydrochloric acid and caustic soda in a conventional manner. This crude chitin is preferably pulverized to a particle size of 3 mm or less in view of the rapidity and uniformity of the subsequent reaction. In the present invention, this crude chitin is dissolved in sulfuric acid with a concentration of 45 to 75%. Higher concentrations, especially
At a concentration of 80% or more, the solution becomes blackish brown and dissolves uniformly as described above, but sulfation and low molecular weight chitin occurs, resulting in chitin in its original form even after recrystallization. No precipitation was observed. In this case, the sulfuric acid acts more as a sulfating agent or oxidizing agent than as a solvent. while less than 45%, especially 40
% or less of sulfuric acid, and even when heated to 60°C and treated for 60 minutes, the chitin concentration in the supernatant was only 0.1% or less. On the other hand, surprisingly, 45-75% sulfuric acid acts strongly as a solvent, and especially when treated with 50-70% sulfuric acid, it dissolves well and does not cause molecular collapse. It was discovered that fine particulate chitin can be obtained in good yield by recrystallization. Moreover, this dissolution takes place under mild conditions, i.e. at 40°C.
Hereinafter, the temperature is desirably maintained in the range of 20 to 30°C. The time required for dissolution varies depending on the surrounding conditions, but is usually 10 to 120 minutes, usually about 30 to 60 minutes, and a homogeneous and viscous solution is obtained. The solubility of chitin in sulfuric acid is about 5 under the above conditions.
~15%. After dissolution, it is immediately recrystallized. To do this, first, impurities are quickly removed, and then this liquid is poured into the amount of water calculated to bring the sulfuric acid concentration to 30% or less, and fine particles of chitin are precipitated. When the sulfuric acid concentration during recrystallization exceeds 30%, recrystallization of chitin is incomplete. The precipitated fine particulate chitin is filtered or centrifuged and washed with water repeatedly to form a fine particulate chitin suspension. The chitin concentration of the suspension varies depending on the processing conditions, but is usually 5 to 10%, and the particle size is 100 microns or less. In order to dilute the sulfuric acid solution and produce fine particulate chitin, technical means for producing fine particulate precipitates can be applied when recrystallizing ordinary inorganic substances, but the feature of the present invention is that these In addition to this, a moderate amount of glycosidic bond cleavage is required.
That is, when the cleavage of glucosidic bonds is relatively small and the particles are dissolved in polymers, the particle size tends to increase, and conversely, if the cleavage progresses excessively, recrystallization does not occur upon dilution. However, within the scope of the present invention, particle sizes suitable for the above-mentioned purposes can be obtained. The yield of fine particulate chitin is 60 to 90% of the raw material crude chitin. As mentioned above, impurities are removed by the separation operation after dissolution, but water-soluble impurities such as protein decomposition products are also dissolved in the mother liquor during dilution and recrystallization, and are completely removed by washing with water. So,
The precipitated fine particulate chitin has extremely high purity compared to the raw material chitin. If necessary, it is also easy to obtain purified chitin in the form of a fine powder by pulverizing it in a dispersion state to a size of 10 microns or less or by freeze-drying it. Next, when crude chitin obtained from crab shells is processed as in the present invention to obtain a suspension of fine particulate chitin, the relationship between various processing conditions (within and outside the specified range) and yield or quality. The following is shown. The sulfuric acid concentration during dilution and recrystallization was 30% in both cases. (1) Relationship between sulfuric acid concentration and yield at 25℃

【table】 (2) Relationship between temperature and yield by 60% sulfuric acid treatment

【table】 (3) Relationship between sulfuric acid concentration and yield during recrystallization (Sulfuric acid concentration 65%, liquid temperature 25℃, processing time 50 minutes)

【table】 (4) Quality of particulate chitin

[Table] As is clear from Table 1 above, when the sulfuric acid concentration during sulfuric acid dissolution is within the specified range of the present invention, the yield is good, but when it is outside the range, no recrystallization occurs. , the yield will be 0. On the other hand, it is clear from Table 2 that the temperature at which the sulfuric acid is dissolved is preferably 40°C or less, particularly in the range of 20 to 30°C. Also, from Table 3, it is clear that purified chitin can be obtained at a constant yield virtually all the time if the sulfuric acid concentration during recrystallization is kept at 30% or less. Furthermore, according to Table 4, compared to the conventionally known hydrochloric acid method, the sulfuric acid method of the present invention produces almost no amino nitrogen in both cases 1 and 2. It is clear that there is virtually no generation of free amino groups due to deacetylation. Furthermore, although sulfuric acid is used in the sulfuric acid method of the present invention, since the product contains almost no sulfur, it is unlikely that sulfuric acid esters or sulfates are produced. Thus, as in the present invention, crude chitin obtained from natural sources is dissolved in 45 to 75% sulfuric acid at a temperature of 40°C or lower, impurities are removed, and then recrystallized at a sulfuric acid concentration of 30% or less, and this process is repeated. By washing with water, a suspension of fine particulate chitin can be obtained in good yield. The crude chitin used here, including the following examples, was obtained by decalcifying dried crab shells by immersing them in dilute hydrochloric acid at room temperature using a known method, and then washing them with water.
It is then boiled with dilute caustic soda to remove protein, washed with water, dried, and crushed.
9.5%, ash 1.6%, alkali soluble content 2.4%, and particulate content 86.5%. The present invention will be explained in more detail by the following examples, but they are not intended to limit the invention. Example 1 100 g of sulfuric acid with a concentration of 65% was kept at 20° C., and while stirring, 10 g of the above crude chitin was gradually added thereto, and the mixture was treated at this temperature for 60 minutes. The obtained solution was passed through a glass filter to remove impurities, and the sulfuric acid concentration was
Pour the solution into 117 ml of water to dilute it to 30%, separate the chitin in the precipitated suspension by filtration, repeat the filtration and water washing until the washing solution becomes nearly neutral, and determine the particle size. 100 g of a suspension of fine particulate chitin with a particle size of 80 microns or less and a concentration of 8.3% was obtained. Its quality is ash content 0.2% and alkali soluble content 0.2% on anhydrous basis.
%, chitin content 99.6%, total nitrogen 6.78%, amino nitrogen 0.03%, sulfur 0.05%, and the yield was 83.0%. Example 2 100 g of sulfuric acid with a concentration of 60% was kept at 30° C. and 10 g of the above crude chitin was gradually added thereto while stirring, and the mixture was treated at the same temperature for 50 minutes. After removing impurities from the resulting solution, the solution was poured into 200 ml of water to dilute it to a sulfuric acid concentration of 20%. Hereinafter, Example 1
Treated in the same way as, particle size 50 microns or less, concentration 7.8
115 g of a suspension of finely divided chitin was obtained. The quality is 0.3% ash and 0.2 alkali soluble content in anhydrous terms.
%, chitin content 99.5%, total nitrogen 6.80%, amino nitrogen 0.06%, sulfur 0.05%, and the yield was 89.7%. Example 3 100 g of sulfuric acid with a concentration of 60% was kept at 40°C, and 10 g of the above crude chitin was gradually added to it while stirring.
It was treated at the same temperature for 40 minutes. The resulting solution was then treated in the same manner as in Example 2 to obtain 110 g of a finely divided chitin suspension with a particle size of 20 microns or less and a concentration of 5.1%. The quality was almost the same as Example 1, but the yield was
It was 62.7%. Example 4 100 g of sulfuric acid with a concentration of 70% was kept at 20° C., and 10 g of the above crude chitin was gradually added to it while stirring, and the mixture was treated at the same temperature for 30 minutes. The obtained solution was then treated in the same manner as in Example 2 to obtain a particle size of 15 microns or less and a concentration of
77 g of a 9.0% microparticulate chitin suspension was obtained. The quality was almost the same as in Example 1, but the yield was 69.3%.

Claims (1)

[Claims] 1 Crude chitin obtained from natural products at a concentration of 45 to 75
% sulfuric acid, remove impurities, recrystallize by reducing the sulfuric acid concentration to 30% or less, and wash with water to obtain high purity particulate chitin.