Method for preparing chitosan polyethylene glycol ester

FIELD: chemistry and technology of derivatives of polysaccharides, chemical technology.

SUBSTANCE: invention relates to methods for preparing chitosan esters. Invention describes a method for preparing chitosan polyethylene glycol ester that involves dissolving chitosan in acetic acid followed by alkalization. Then the reaction mixture is subjected for effect of ethylene oxide under pressure 1-3 atm and temperature 60-100°C, and the concentration of reaction mass is corrected by addition of distilled water up to the density value of solution 1.030-1.032 g/cm3. Then the reaction mass is purified by electrodialysis at the rate value of solution in treatment chambers 3.0 cm/s, not less, temperature 20-45°C, the current density value 0.25-0.75 A/dm2 and the constant volume of the reaction mass. Method provides enhancing the effectiveness of purification by electrodialysis due to reducing energy consumptions. Chitosan esters can be used in medicine, cosmetics, food and chemical industry.

EFFECT: improved preparing method.

5 ex

 

The invention relates to the field of chemistry and technology of derivatives of polysaccharides, in particular to methods of producing esters of chitosan, which can be used in medicine, cosmetics, food and chemical industries.

Chitosan is a product of the saponification of natural carbohydrate-containing biopolymer - chitin, which, along with cellulose is the most abundant in nature organic substance and belongs to the group of hydrocolloids. In contrast to most hydrocolloids, which in the biological pH values have a negative charge, chitosan in these conditions represents the cationic polymers of biological origin. Positively charged chitosan can interact with oppositely charged surfaces, which makes their use in cosmetics hair care and body (patent RF 2159253, class 08 In 37/08, A 61 K 31/722, 2001). In addition, the ability of chitosan to heal wounds and strengthen the immune system is of interest for creation on their basis of drugs for medical purposes.

The chitosans are much more chemically active than chitin. They do not dissolve in water, but soluble in dilute acids and in some organic solvents. Chemical properties of chitosan significantly affect the cash is Chiyo in glycoside residue of an amino group, which is easily alleroed with the formation of N-acetylcytosine, alkiliruya with the formation of N-alkyl - or N,N-dialkylamino, and with aromatic aldehydes to form Schiff bases, which is used for its protection during the synthesis of derivatives of chitosan.

Chemical modification of chitosan allows for a wide variety of properties of the drug, while preserving its useful characteristics. However, as the chitosan, these derivatives do not dissolve in water, which complicates their use in the pharmaceutical and cosmetic industries. For pharmaceuticals and cosmetics the desired product of high purity, which is soluble in water at pH from 5.5 to 7.8.

In patent literature known method of obtaining water-soluble chitosan (RF patent 2099351, class 08 In 37/08, 1997), namely that spend degradation of the polymer chains of chitosan by swelling oncodispensary fraction of chitosan in a highly polar solvent in acid medium followed by the addition of the appropriate reagent. When using acetic acid have the chitosan acetate, hydrochloric acid hydrochloride, chitosan, succinic acid - N-succinylcholine.

The disadvantage of this method is that under this treatment chitosan loses its inherent hydrophilicity, i.e. the ability to retain water.

Also known is a method of obtaining vodorastvorimogo the carboxymethylchitosan (RF patent 218 5387, CL 08 In 37/08, And 61 To 31/722, 2002), including the dispersion of chitosan in the medium of organic solvent, the mercerization in alkaline medium, followed by carboxyethylgermanium chitosan monochloracetic acid at a temperature of 60°C for 3-4 hours, then the reaction mixture is stored at a temperature of 25°C for 12-20 hours and then neutralized to pH 7 by addition of a solution of glacial acetic acid in anhydrous ethanol. The disadvantage of this method is the multistage and the long duration of the process, and the solubility product in water is only 85-92%.

In patent literature mainly provides information on improved methods of obtaining water-soluble chitosan in the direction of the search conditions of its chemical transformations and very limited data on the methods of cleaning the resulting reaction mass of chitosan. However, for the pharmaceutical and cosmetic preparations, the development of effective methods and treatment technologies is an actual task.

Closest to the proposed invention is a method of obtaining water-soluble polietilenglikoli ether chitosan (RF patent 2199716, CL 7 08 In 37/08, And 61 To 31/772, 2002), including the dissolution of chitosan in acetic acid, alkalization, the impact on the reaction mixture of ethylene oxide at a pressure of 1-3 and the m and a temperature of 60-100° With, purification of the reaction mass by electrodialysis and distillation of the solvent.

This method does not provide conditions for the process of cleaning reaction mass of chitosan by electrodialysis and basic technological parameters of the process: the current output, energy intensity and degree of demineralization, characterizing the efficiency of electrodialysis purification method. The only indicator of the process described in the patent is the specific conductivity of the pure solution, the value of which is 2·10-4Cm/m, But this value can be achieved due to the high energy process, low current and is not valid. Thus, when the impurity concentration of sodium acetate 0.0005 g/l in 17%of the first solution polietilenglikoli ether chitosan value of conductivity is 16·10-4Cm/m, and the degree of demineralization when such residual concentration of the organic salt is 99.99%. These disadvantages of this method was the basis for improvement of this process.

The task of the invention is to increase the efficiency of electrodialysis purification reaction mass polietilenglikoli ether chitosan.

The problem is solved by the fact that before electrodialysis carry out the adjustment of the concentration of the reaction mass polietileno olevaga ether chitosan by adding distilled water to the density of a solution of 1.03-1,032 g/cm 3and purification of the target product from sodium acetate and hydroxide sodium carried out by means of electrodialysis when the linear velocity of the reaction mass in the cells of cleaning at least 3 cm/s, a temperature of 20-45°and a current density of 0.25 to 0.75 a/DM2at constant volume of the purified solution.

Before electrodialysis reaction mass of polyoxyethylene chitosan is adjusted with distilled water to a density of the solution 1,030-1.032 g/cm3. The reaction mass without dilution (density 1,037-1,040 g/cm3) to be subjected to electrodialysis is impractical because it leads to a significant increase in the intensity of the cleaning process. So, electrodialysis, the reaction mixture diluted to a density 1.030 g/cm3at the current density of 0.75 A/DM2flows with the intensity of the cleaning process 170 W·h/l and the current output to 53.0%and without dilution 520 W·h/l and 17.3%, respectively. Greater dilution of the reaction mass (density of solution <1.03 g/cm3) is undesirable, as the energy intensity of electrodialysis decreases slightly, and will significantly increase energy costs when Parke larger volume of solvent.

During electrodialysis, the volume of the reaction mixture decreases due to the passage of water through the membrane, resulting in increased viscosity of the solution, which causes a decrease in podi the property transferred across the membrane of organic anions of acetic acid, therefore, to increase the intensity of electrodialysis. This requires maintaining a constant volume of reaction solution by adding distilled water.

The reaction mass is purified from sodium acetate and sodium hydroxide at a current density of 0.25 to 0.75 a/DM2. A further increase in current density is impractical because it leads to increased energy consumption. So. with increasing current density from 0.25 to 1.0 A/DM2the current output decreases with 59,5% to 12.0%, and the consumption of the process increases with 70,0 to 755,0 W·h/L. in Addition, with increasing current density is difficult for the temperature control.

At the current density below 0.25 a/DM2decreases the performance of electrodialyzer.

Temperature (20-45° (C)at which carry out the electrodialysis process in accordance with the invention, should not exceed 45°due to thermal instability anion-exchange membranes, resulting in reduced service life of the latter, and at a temperature below 20°With increasing viscosity of the solution, which leads to increased energy consumption for the cleaning process.

With greater efficiency purification of the reaction mixture ethoxylated chitosan occurs when the linear velocity of the solution in the chambers of cleaning at least 3 cm/sec. At a linear speed Rast is ora 2 cm/s and a current density of 0.75 a/DM 2the consumption of the process increases to 270 W·h/l against 170 W·h/l at a linear velocity of 3 cm/S.

For implementing the method of the reaction mass polietilenglikoli ether chitosan with density solution 1,037-1,040 g/cm3obtained by dissolving chitosan in acetic acid and exposed to ethylene oxide in an alkaline medium at a pressure of 1-3 atmospheres and a temperature of 60-100°C, diluted with distilled water to a density of the solution 1,030-1,032 g/cm3and sent for electrodialysis purification to achieve the concentration of sodium acetate 0,0005-0,0007 g/l and absence of sodium hydroxide, as indicated by the pH of the solution is not more than about 7.8. The process of electrodialysis is carried out at a linear velocity of the solution in the chambers clean not less than 3.0 cm/s, a temperature of 20-45°C, current density of 0.25-0.75 a/DM2at constant volume of the solution. After removal of the solvent receive polietilenglikolya ether chitosan in the form of a gel-like transparent liquid light yellow color with a specific conductivity 14-16-10-6Cm/m at a temperature of 25°C.

If all these conditions, the yield polietilenglikoli ether chitosan substance is 95,7-96.4%, degree of purification from sodium acetate and sodium hydroxide and 99.8-99.9%, the output current to 53.0 59.5 per cent, and the energy of 70-170 W·h/l

Thus, thanks to the combination of conditions is electrodialysis and techniques can increase the efficiency of electrodialysis reaction mass polietilenglikoli ether chitosan by increasing the current output and reducing energy intensity of the process.

The proposed method is illustrated by the following examples, but is not limited to them.

Example 1

In a flask equipped with a stirrer, was loaded with 20 g of chitosan and 1667 1%acetic acid, stirred at room temperature for 1 hour, filtered and transfer the solution in the autoclave, add 167 g of a 10%aqueous solution of sodium hydroxide, heated the reaction mass to a temperature of 50°and served With ethylene oxide, adjusting its supply so that the temperature of the reaction mass does not exceed 100°and the pressure is 3 ATM. After adding 400 g of ethylene oxide (weight ratio of chitosan ethylene oxide 1:20), the reaction mass is then cooled and filtered. Resulting in getting 2260 g of the reaction mass with the density of the solution 1,037 g/cm3. The resulting reaction mass is adjusted to the density of the solution 1,030 g/cm3by adding distilled water and transfer to clean electrodialysis method.

The reaction mass polietilenglikoli ether chitosan with the density of a solution of 1.03 g/cm3the number 2280 ml, containing 10.2 g/l sodium acetate and 2.5 g/l of sodium hydroxide, subjected to electrodialysis purification in a multi-chambered apparatus - electrodialyzer filter presnogo type consisting of ion-exchange membranes of the type MA-40 and MK-40 with the intermediate part of paronite and separators-energizers. The cathode is a plate of arabeya steel HOT with the working surface 4 DM 2, the anode platinized titanium with the same surface. Electrodialyzer consists of 8 anion-exchange membranes and 7 cation-exchange membranes, forming a 7 chambers purification and 8 cameras concentration, and two electrode chambers. The working surface of each membrane 4 DM2and the distance between them is 1.5 mm

The reaction mass polietilenglikoli ether chitosan with impurities of organic and inorganic nature of the pump is passed through the camera demineralization of electrodialyzer with a linear speed of 3 cm/s, at the same time through the camera concentrating and electrode chambers of the pump is pumped 0,1%solution of sodium hydroxide in a closed loop.

At a temperature of 20°through electrodialyzer miss DC power which corresponds to a current density of 0.25 A/DM2. During electrodialysis maintain a constant volume of the reaction mass by adding distilled water in the amount of 80 ml. Process is considered complete when reaching in a purified solution concentration of sodium acetate 0,00045 g/l and sodium hydroxide 0.0004 g/l, which corresponds to the magnitude of the conductivity 14·10-4Cm/m and the pH value of the solution to 7.4. While the current output is 59.5%, the intensity of the cleaning process 70 W·h/l, and the degree of demineralization of 99.9%.

During electronial isney cleaning which are square-2280 ml of purified solution polietilenglikoli ether chitosan, from which the solvent is distilled off and get 403 g of the desired product in the form of a gel-like transparent mass of light yellow color. The substance is 96,0% of theoretical.

Product feature:

UV-spectrum, solvent - water, λ max = 206 nm;

Conductivity χ25=14-10-6Cm/m;

Viscosity - 88,20 SP;

The refractive index of nD23.5=1,4440.

Product feature the patent of the Russian Federation 2199716:

UV-spectrum, solvent - water, λ max = 206 nm;

Viscosity - 88,14 SP;

The refractive index of nD23.5=1,4435.

Example 2

The reaction mass polietilenglikoli ether chitosan. is obtained analogously to example 1, is subjected to electrodialysis purification similar to example 1, but at the current density of 0.75 A/inch While the current output is 53,0%, the energy of 170 W·h/l, and the degree of demineralization 99,8%.

In the process of electrodialysis purification receive 2270 ml of purified solution polietilenglikoli ether chitosan containing sodium acetate 0,0006 g l and sodium hydroxide 0.0005 g/l, which corresponds to the magnitude of the conductivity 16·10-4Cm/m and pH of 7.8. The selection of the target product from the solution as in example 1. Get 405 g polietilenglikoli ether chitosan in the form of a gel-like transparent light weight-altago color out of the substance 96,4% of theory and characteristics, similar to example 1.

Example 3

The reaction mass polietilenglikoli ether chitosan obtained analogously to example 1, is subjected to electrodialysis purification similar to example 1 at a temperature of 45°and a current density of 0.75 a/DM2. While the current output is 58.8 per cent, the consumption of the process 140 W·h/l, and the degree of demineralization 99,8%.

In the process of electrodialysis purification receive 2270 ml of purified solution polietilenglikoli ether chitosan containing sodium acetate 0.0005 g/l and sodium hydroxide 0,0045%, which corresponds to the conductivity of a solution of 15.5·10-4Cm/m and pH of solution to 7.5 Selection of the target product from the solution as in example 1. Receive 402 g polietilenglikoli ether chitosan in the form of a gel-like transparent mass of light yellow color out of the substance or 95.7% of theory and characteristic similar to that of example 1.

Example 4 (comparative)

The reaction mass polietilenglikoli ether chitosan obtained analogously to example 1, is subjected to electrodialysis purification similar to example 1 at a current density of 1 A/DM2and without density correction solution (1,037 g/cm). While the current output is 8.3% and the energy consumption of the process 1080 W·h/l

In the process of electrodialysis purification receive 2290 ml purified solution polietilene celevogo ether chitosan with the value of the specific conductivity of a solution of 2· 10-4Cm/m and the value of pH was 7.45. The selection of the target product from the solution as in example 1. Receive 402 g polietilenglikoli ether chitosan in the form of a gel-like transparent mass of light yellow color out of the substance or 95.7% of theory and characteristic similar to that of example 1.

Example 5 (comparative)

The reaction mass polietilenglikoli ether chitosan obtained analogously to example 1, is subjected to electrodialysis purification similar to example 2, but when the linear velocity of the solution in the chambers clean 2 cm/sec. While the current output is 35.5%, the energy of 270 W·h/l, and the degree of demineralization 99,8%.

In the process of electrodialysis purification receive 2270 ml of purified solution polietilenglikoli ether chitosan containing sodium acetate 0.0005 g/l and sodium hydroxide 0,0006 g/l, which corresponds to the value of the specific conductivity of the solution 16,8·10-4Cm/m and the value of pH of 7.7. The selection of the target product from the solution as in example 1. Get 404 g polietilenglikoli ether chitosan in the form of a gel-like transparent mass of light yellow color out of the substance of 96.2% of theory and characteristic similar to that of example 1.

Thus, the proposed method for polietilenglikoli ether chitosan improves the efficiency of electronial the heat cleaning reaction mass polietilenglikoli ether chitosan by reducing energy consumption.

The method of obtaining polietilenglikoli ether chitosan, which consists in the fact that chitosan is dissolved in acetic acid, then alkalinized and the reaction mixture is subjected to the action of ethylene oxide at a pressure of 1-3 atmospheres and a temperature of 60-100°C, the resulting reaction mass is distilled electrodialysis and the solvent is distilled off, characterized in that before the electrodialysis are adjusting the concentration of the reaction mass by adding distilled water to the density of the solution 1,030-1,032 g/cm3the reaction mass is passed through chamber cleaning with a speed of not less than 3.0 cm/s, and the electrodialysis is carried out at a temperature of 20-45°C, current density of 0.25-0.75 a/DM and constant volume of the reaction mass.



 

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