Chitosan preparation process

FIELD: natural compounds technology.

SUBSTANCE: chitosan preparation process comprises breaking naturally occurring chitin-containing material, charging it into reactor, demineralization with 6-7% aqueous hydrochloric acid, deproteination with sodium hydroxide solution at 85-95°C, deacetylation with sodium hydroxide solution on heating, decoloration, and washing with water after each stage to pH 6.5. Process is characterized by that chitin-containing material broken to achieve fraction 0.5-6 mm is fed simultaneously into a number of reactors, wherein demineralization is effected with aqueous hydrochloric acid stream at 85-95°C for 1.5 h while controlling pH in each reactor exit to achieve acid concentration in each reactor exit the same as concentration of the initial acid by way of feeding it in a continuous manner. In addition, deproteination is carried out with 6-7% sodium hydroxide solution stream for 1.5 h followed by discharging treated material into autoclave to perform deacetylation simultaneously with decoloration using 50% sodium hydroxide solution at 130-140°C in inert gas environment and in presence of 3-5% hydrogen peroxide solution used in amount 3-5% of the total volume of mixture.

EFFECT: enhanced process efficiency.

1 dwg

 

The invention relates to the chemical industry, in particular to the technology of chitosan, which can be used as a sorbent, filler for polymer composites, as well as in the textile, food, paper industry, agriculture and medicine.

A method of obtaining chitosan from chitin-containing raw material, namely shell crab crushed to obtain at least 90% particle fraction 5±0.5 mm, holding deproteinization 1-5%sodium hydroxide solution, decalcomania 1-5%solution of hydrochloric acid and deacetylation 46-47%sodium hydroxide solution at a temperature of 80-85°C. Before deacetylation spend additional stage of deproteinization and decalcomania respectively. The first stage of deproteinization are 1-3 hours and the first stage of decalcomania are 0.5-1.5 h; the second stage of deproteinization are 1-3 h, the second stage of decalcomania are 0.5-1.5 h; the third stage of deproteinization are 1-3 hours, decalcomania 0.5 to 1.5 hours All stages of decalcomania conducted at 35-55°and deproteinization at 60-85° (RF Patent No. 2087483).

The process is carried out at the facility, consisting of 8 reactors connected in series. Each reactor equipped with a paddle mixer and two siphons, one of which is executed with the set is ATiM filter, to remove the mother liquor, and the second is designed to handle in the subsequent reactor. The disadvantage of this method is the large number of stages, the long duration of the process, as a result, insufficiently high deacetylation 78%.

Also known is a method of obtaining chitosan from chitin-containing raw materials, in particular shell crab, which consists in grinding the feedstock to fraction 49-2000 μm, the discoloration it using a 0.1 N solution of sodium hypochlorite, double demineralization 6-7%hydrochloric acid at a temperature of 15-35°C for 1 hour under stirring. Module baths is 7-8. When this is added a small amount of butanol as a non. At the end of the process of demineralization of acid is drained through the false bottom of the device. Next is stage 2 of deproteinizovana, after each of them also produce expression of the mother liquor. The first stage is 15-20%solution of sodium hydroxide at a temperature of 85-95°and the second 5-6%sodium hydroxide solution. To reduce the degradation of added sodium borohydride. The deacetylation spend 43-45%sodium hydroxide solution at initial temperature 113-115°With that in 15-30 minutes is reduced to 105-108°C. After each process (demineralization, deproteinized is s, the deacetylation) rinse raw water to pH 6.5 (RF Patent No. 2172744).

The process is carried out on the unit for the production of chitosan, including three reactors and tanks for acid and alkaline solutions. All reactors have grills and anchor stirrer and connected in series. Each reactor has a false bottom and a diagram of the valves, which allows you to remove the mother liquor from the solid phase, and then to translate aqueous suspension of the product in the next reactor.

The disadvantage of this method is the large number of stages, the use of additional reagents, such as sodium hypochlorite and sodium borohydride and butanol, which are toxic and expensive chemicals. In addition, chitosan, obtained in this way has a high enough degree of deacetylation, which is 82%.

The objective of the proposed method of chitosan was to eliminate the disadvantages of the above methods, the simplification of the technology, reducing the cost of the final product and improve its quality.

This is achieved in that in the method of producing chitosan, including grinding of natural chitin-containing raw material, loading it into the reactor, the demineralization 6-7% solution of hydrochloric acid, deproteinizovana sodium hydroxide at a temperature of 85-95°, deacetylation solution hydro is sid sodium when heated, bleaching and washing with water after each stage to pH 6.5, spend a load of chitin-containing raw material is crushed to obtain a fraction (0.5-6 mm, while in several reactors. The demineralization spend a stream of hydrochloric acid at 85-95°C for 1.5 h with pH control at the exit of each reactor to equalize the acid concentration at the outlet of each reactor concentration of the original acid by continuous filing, deproteinizovana conduct the flow of 6-7% sodium hydroxide for 1.5 h, then carry out the unloading of the processed raw materials in the autoclave, where the deacetylation simultaneously with the discoloration of 50% sodium hydroxide solution at 130-140°C in an atmosphere of inert gas of nitrogen and in the presence of a 5%solution of hydrogen peroxide in the amount of 3-5% of the total the volume of the mixture.

The drawing shows a diagram of chitosan. It shows the following items: 1 - up, 2, 3, 4, reactors for demineralization and deproteinizovana (diffusers), 5 - reactor for deacetylation (autoclave), 6 - drying unit, 71-712- control valves.

The method of obtaining semi-continuous, without manual unloading and loading. The process is carried out on the unit for the production of chitosan, which includes the grinder 1, the battery of the three cones, 2, 3, 4, autoclave 5, su is safe installation of 6 and control valves 7 1-712. Diffusers 2-4 and autoclave 5 is equipped with heating jackets and anchor agitators, they have a grating to separate the substrate from the mother liquor and folding the bottom, through which is unloading the processed raw materials. Battery diffusers 2-4 is intended for carrying out the processes of demineralization and deproteinizovana that run continuously. A feature of this technological solution is that after loading the chitin-containing raw material in all three of the diffuser acid (demineralization) and alkali (deproteinizovana) of a given concentration continuously flows through the battery diffusers, and not poured into the apparatus at a certain time. Due to this constantly maintained a high driving force of the process (the difference of concentrations). The flow rate should be such that the concentration of acid at the outlet of each of the diffuser was not zero. Changing the acid concentration at the outlet of each of the cone is measured pH meters. When the concentration of acid at the outlet of the diffuser is equal to the original valve system disables the battery, and the reagent with the initial concentration begins to flow through the next cone. The solution is fed from the bottom of the device and exits through the top.

The process of demineralization spend 6-7%hydrochloric acid, which is fed continuously with the achala in 2 diffuser, from 2nd to 3rd, 3rd to 4th and from 4th to regeneration. The flow of the acid passes through the open valves 71, 74, 75, 76, 77and 78. The rest of the valves when closed. Because in the 2nd cone, the difference between the concentration of acid in such a scheme of maximum flow, the demineralization process ends in it in the first place. And through the valves 72, 74, 711given the rinse water to pH 6.5. The flow of the acid passes through the 3-d cone in 4-th and 4-th regeneration through the open valves 71, 79, 76, 77,78. At the end of the process in the 3rd cone and also carry out the washing with water through the valves 72, 79, 76, 712. The stream of acid passes through the 4th cone regeneration. At the end of the process it also carry out the washing with water through the valves 72, 710, 78. At the end of the washing process alternately in each cone valves, engaged in the movement of water flow in the directions indicated above, are disabled. The process of deproteinizovana carried out in the same way, only through the valve 73instead of 71.

The obtained chitin of the three diffusers is loaded into the autoclave 5, which is the deacetylation under the action of a 50%aqueous sodium hydroxide solution for 1-2 h at t is mperature 130-140° C in an atmosphere of inert nitrogen gas, which makes possible the production of chitosan with a high degree of deacetylation and molecular weight by preventing oxidative degradation of the polymer chain. In the autoclave also served hydrogen peroxide for bleaching of the obtained chitosan. The obtained chitosan washed with water to pH 6.5 and dried at a temperature of 60-70°in the drying unit 6.

Thus, the proposed method is less stages. The method has a higher efficiency, lower labor and energy costs (the process can be easily automated). The method allows to increase the degree of deacetylation to 87-91%, and also provides for the use of more accessible and affordable, in regions remote from the sea, raw - shell crayfish.

The obtained chitosan has the following properties:

Solubility in 2-3%acetic acid - 99.9%of the

The deacetylation 87-91%

Molecular weight of from 250,000 to 350,000

Viscosity - 5,5-7,5 DL/g

Humidity 8-10%

Such chitosan can be used as a sorbent, filler for polymeric materials, as well as in the textile, food, paper industry, agriculture and medicine.

A method of producing chitosan, including grinding of natural chitin-containing raw material, is the recalls it in the reactor, the demineralization 6-7%solution of hydrochloric acid, deproteinizovana sodium hydroxide at a temperature of 85-95°, deacetylation with sodium hydroxide solution by heating, bleaching and rinsing with water after each stage to a pH of 6.5, characterized in that are loaded chitin-containing raw material is crushed to obtain a fraction (0.5-6 mm, while in several reactors, where the demineralization flow of hydrochloric acid at 85-95°C for 1.5 h with pH control at the exit of each reactor to equalize the acid concentration at the outlet of each reactor concentration of the original acid by continuous filing, deproteinizovana conduct the flow of 6-7%sodium hydroxide for 1.5 h, followed by the unloading of the processed raw materials in the autoclave, where the deacetylation simultaneously with the bleaching of 50%sodium hydroxide solution at 130-140°C in an atmosphere of inert gas of nitrogen and in the presence of 3-5%solution of hydrogen peroxide in the amount of 3-5% of the total volume of the mixture.



 

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FIELD: organic chemistry of natural compounds, chemical technology, medicine.

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EFFECT: valuable medicinal properties of modified chitosan.

1 tbl, 1 dwg, 3 ex

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EFFECT: enhanced process efficiency.

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