Method of producing chitosan

FIELD: chemistry.

SUBSTANCE: invention relates to producing chitosan from chitin and can be used in medicine, chemical, textile, paper and food industry. The method comprises crushing chitin to particle size of 1-22-3 mm; deacetylation of chitin in a double-neck reactor in 40% NaOH solution with in ratio to chitin of (1-3):(20-60) at 100C, pressure of 300 mm Hg for 1-2 hours, wherein the double-neck reactor is fitted with a reflux condenser and is connected to a vacuum water-jet pump.

EFFECT: invention improves the degree of acetylation of chitosan and preserves the natural structure of the finished product.

2 tbl, 1 dwg

 

The invention relates to the field polymeranalogous transformations of natural macromolecular compounds, in particular the production of chitosan from chitin and can find application in medicine, chemical, textile, paper and food industries.

A method of obtaining chitosan, in which the cuticular chitin shells of insects crushed to particles of 0.2-0.3 mm, treated with 40% solution of caustic alkali at 100-110C, liquid module 1:20, 3-3,5 hours, while the effects of ultrasound with a frequency of 15-35 kHz (Patent No. 2067588, Russia, MKI C08B 37/08. Priority from 17.09.1991,)

The main disadvantage of this method is carrying out the process at elevated temperatures, the use of additional equipment for ultrasound, increased the duration of the process.

A method of obtaining chitosan by adding chitin in 50% alkaline solution prepared by dissolving dry alkali in distilled water and cooled to room temperature 18-22C. Chitin contribute to this solution in small portions in the ratio of chitin : the alkali solution 1:10-1:15 until a homogeneous suspension, the last stand at room temperature with periodic mixing for 5-20 days (Patent No. 2116733, Russia, IPC A23L 1/33. Priority from 07.10.1996).

The main disadvantages of this the method is the use of high alkali concentration (50%), that leads to a significant consumption of alkali and destruction of the target product, increased alkali content in the wastewater, increased time consuming process.

Closest to the present invention is a method, which provides for the grinding of chitin to a particle size of 0.05-0.2 mm, the deacetylation of 50% sodium hydroxide solution for 30-40 minutes at a temperature of 96-98C, the separation of the target product from the alkaline solution by filtration, washing with water and drying (Patent No. 2358553, Russia, IPC A23L /33. Priority on 22.08.2007).

The main disadvantages of this method is the use of high alkali concentration (50%), which leads to a significant consumption of alkali and destruction of the target product, a high degree of pulverizing substances with a low degree of deacetylation.

The task of the invention is to develop more technological process of obtaining chitosan from chitin, a decrease in the degree of comminution of the raw materials, the preservation of the structure of the finished product close to nature, increase the degree of deacetylation (88-92%).

The technical result is an increase in the degree of grinding of the raw materials, the preservation of the natural structure of the finished product, the increase in the degree of deacetylation.

The technical result is achieved by the performance of the process of deacetylation is pre-crushed to a size of 1-22-3 mm of chitin in a two-neck reactor, equipped with thermometer, reflux condenser and connected to a water-jet vacuum pump, a 40% solution of NaOH at a ratio to chitin (1-3):(20-60) at 100C, a pressure of 300 mm RT.article within 1-2 hours

The essence of the proposed method is illustrated by the following example.

Example. In a two-neck reactor equipped with a thermometer and connected to a water-jet vacuum pump, pour the pre-crushed to a size of 1-22-3 mm chitin, then pour a 40% NaOH solution at a ratio to chitin 1:20. The process of deacetylation (Fig.1) is carried out at 100C for 1-2 hours

The process under vacuum water pump contributes to a significant reduction in the oxygen concentration in the reaction zone, which, as is known, increases the degree of degradation of chitin.

After this time the finished product is repeatedly washed with distilled water on a Buechner funnel to neutral pH with subsequent spin cycle.

The washed and filtered chitosan is a highly hydrated, swollen product with a water content of more than 70%. To prevent keratinization chitosan is dried in a heating Cabinet at 35-40C to air-dry state.

The deacetylation installed potentiometric titration of a solution of 0.1 G. hydrochloric acid, is 93% (the prototype 88-92%) (table.2). The composition of the obtained chitosan from shell was determined by the method of elemental analysis. In the result of the analysis, the nitrogen content was 8.6%, hydrogen - 6,46%, carbon - 43,8%, oxygen - 40,9%.

To assess the level of quality of the obtained chitosan were used indicators set out in the technical specifications for food chitosan THAT 9289-067-00472124-03 (see tab.1).

Organoleptic characteristics:

Appearance: flakes size of 1-3 mm

Color: white with cream shade.

Taste: characteristic of the product, without foreign taste. Odour: characteristic of the product, without foreign smell.

Sources of information

1. Patent No. 2067588, Russia, MKI C08B 37/08. Priority from 17.09.1991,

2. Patent No. 2116733, Russia, IPC A23L 1/33. Priority from 07.10.1996,

3. Patent No. 2358553, Russia, IPC A23L 1/33. Priority on 22.08.2007,

pH of 1% solution of chitosan in 2% acetic acid
Table 1
Physico-chemical properties of chitosan
Name of indicatorEd. MEAs.The norm on THE otherThe results of the tests
Mass fraction of moisture%Not more than 10.09,4
Ed. pHNot more than 7.53,85

Table 2
The process conditions and the degree of deacetylation of the finished product.
The placeholderThe proposed method
The degree of crushing of chitin0.05-0.2 mm1-22-3 mm
Temperature96-98C100C
Pressure760 mm RT.article.300 mm RT.article.
Duration30-40 minutes1-2 hours
Mass fraction of NaOH solution50%40%
The deacetylation88-92%93%

A method of producing chitosan, characterized in that the process of deacetylation pre-shredded is about 1-22-3 mm chitin is carried out in a two-neck reactor, equipped with reflux condenser and connected to a water-jet vacuum pump, a 40% solution of NaOH at a ratio to chitin (1-3):(20-60)) at 100C, a pressure of 300 mm RT.article within 1-2 hours



 

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