CS253949B1 - Process for preparing hydroxyethyl starch - Google Patents

Abstract

The purpose of the method of preparation of hydroxyethyl starch is to improve its production from the standpoint of product quality and work safety during its preparation. The stated purpose is achieved by alkalizing the starch in an organic solvent suspension with an aqueous solution of sodium or potassium hydroxide and then hydroxyethylation with oxirane at a temperature of 80°C to 120°C. Hydroxyethyl starch has po

Description

4 253949

The invention relates to a process for the preparation of hydroxyethyl starch. According to the method described above for the preparation of hydroxyethyl starch, said derivative is prepared by hydroxyethylation of acid hydrolysed starch with oxirane at temperatures below the starch lubrication point, i.e. at temperatures below 50 ° C for 24 hours by a valical atmosphere [AO 183 272]. A disadvantage of the aforementioned method is that pre-specific hydroxyethylation in the alkaline environment requires acid hydrolysed starch to be pretreated because it contains alkaline substances which impart undesirable properties to the product. Another disadvantage of the aforementioned process is that the temperature of the preparation of hydroxyethyl starch is limited to 70 ° C, since acid hydrolysed starch occurs at higher temperatures.

The above drawbacks are substantially hindered by the preparation of the hydroxyethyl ester of the invention, which is characterized in that it is hydroxyethylated at 80-120 ° C. An advantage of the process according to the invention is that it is necessary to remove the acid hydrolysis of the alkali-labile substances formed. A further advantage is that hydroxyethylation of native starches in an inert solvent (preferably 2-pranol) medium is carried out at elevated temperatures of 80 ° C to 120 ° C, shortening the reaction time (from 24 hours to 1-2 hours). increasing work safety. At elevated temperatures, the oxirane added in portions immediately reacts with the starch to avoid its hazardous accumulation in the reactor. When operating at temperatures below 50 ° C, the accumulation of can occur and the concentration of added oxirane can reach an explosive value. The amount of oxirane added to the starch suspension in the organic solvent (2-propanol or 2-butanol) and in the alkaline medium depends on the desired degree of substitution (0.05 to 1.0), calculated with 90% Alkalization of the starch slurry in the organic solvent is carried out with agar agitation, thereby homogeneously distributing the liquor in the starch grains. EXAMPLE 1 In a 500 ml three-necked flask equipped with a stirrer with a reflux condenser and added dropwise to a suspension of 100 g of native earth starch (dry matter 83%; 0.5 mol) in 100 ml of 2-propanol at a temperature of 82 DEG C. QC and stirring 10 ml of 40 wt. aqueous sodium hydroxide solution. After the addition, boil and stir for a further 1 h. The resulting alkali starch suspension in 2-propanol is transferred to an autoclave, purged with nitrogen, and purged with nitrogen to a pressure of 0.5 MPa. The mixture was heated to 90 ° C with stirring and 22 g (0.5 mol) of oxirane (ethylene oxide) was added in small portions over 2 hours. Each batch is added after a pressure drop of 0.5 MPa. After completion of the reaction, the suspension was neutralized with 10 ml of 37 wt. hydrochloric acid], filtered off and washed with 100 ml of 2-propanol and dried at 40 ° C. Yield: 103 g of hydroxyethyl starch (100% to starch starting point) by 0.9% substitution. Oxirane Recovery 90%; the 10% found in the filter is in the form of ethylene glycol oligomers

The procedure is as in Example 1, except that corn starch is used. The yield of hydroxyethyl starch with a degree of substitution of 0.9 is 100%. Example 3

The procedure is as in Example 1 except that wheat starch is used. The hydroxyethyl starch yield of 0.9 is 100%. Example 4

The procedure is as in Example 1, except that oxirane is added to the autoclave at a temperature of 120 ° C and the reaction time is 1 hour. The hydroxyethyl starch yield is 100% and the degree of substitution is 0.9. Example 5

The procedure is as in Example 4 except that hydroxyethylation is carried out with 2.2 g (0.05 mol) of oxirane and the reaction time is half an hour. This procedure yields hydroxyethyl starch with a degree of substitution of 0.9 in a yield of 100%. Example 6

The procedure is as in Example 1, except that 10 ml of 40 wt. Potassium hydroxide solution. The hydroxyethyl starch yield of 0.9 is 100%. Example 7

The procedure is as in Example 1 except that 2-butanol is used as the organic solvent. The hydroxyethyl starch yield of 0.9 is 100% substitution. The prepared hydroxyethyl starch can be used as a substitute for blood plasma and an acocryoprotective agent.

[E. Rock: Hydroxyethyl starch as surrogate plasma, Central Report, Central Hospital in Prague 1985):

Claims (1)

Example 8 Hydroxyethyl starch having a molecular weight of 200,000 and a degree of substitution of 0.9 is dissolved in 0.15 molar sodium chloride solution to 6% by weight. solution. From this solution, 10 mice are administered intravenously with 0.5 ml at 20 g of body weight (equivalent to 1.5 l per human). Mice were observed for 15 days. During the study period, the mice did not show signs of toxicity or ipyrogenicity, nor did they show any signs of toxicity. Example 9 20 g of human blood marrow were suspended in a solution of 200 ml of 6% w / w. a solution of hydroxyethyl starch having a molecular weight of 200,000 and a degree of substitution of 0.9 and a freezing temperature of -80 ° C. After a week and thawing the cells were biologically alive. Hydroxyethyl starch can find wide use in the paper, textile, food and cosmetic industries, in surfactant preparation, in medical practice as a blood plasma container, and as a cryoprotective agent for tissue storage for transplantation. SUBJECT A method of preparing hydroxyethyl starch by basifying the starch suspension in propan-2-ol or 2-butanol with aqueous sodium hydroxide or potassium hydroxide solution with stirring, and then alkaline starch in the organic solvent-water suspension is hydroxyethylated with an oxirane, by hydroxyethyl at 80-120 ° C.