SU605398A1 - Method of obtaining films from carboxylcellulose - Google Patents

Description

The invention relates to the production of modified cellulosic films, in particular to the preparation of films of oxidized cellulose, which can be used as cation exchangers and hemostatic agents. A known method for producing cellulosic films is by dissolving cellulose in dimethylformamide in the presence of nitrogen oxides, followed by deposition of the films in methanol fj. However, this method does not receive carboxyl-containing films. A known method of producing transparent films and sheets from oxidized nitrogen tetroxide (nitrogen dioxide) of cellulose by dissolving it in aqueous solutions of alkali metal bases, ammonia, pyridine and triethylamine with the formation of the corresponding salts soluble in water and subsequent drying 2. The water-soluble film obtained in this way can be made insoluble by treating with an aqueous acid solution. However, as the degree of oxidation decreases, the solubility of monocarboxylic cellulose In a dilute solution, for example, sodium hydroxide decreases. With increasing concentration of sodium hydroxide, the degree of destruction of oxidized cellulose sharply increases. It should be noted that preparations of monocarboxyl cellose are characterized by a significant decrease in the stability of the glycosidic bond only to the action of alkaline, but not to the action of acids. Therefore, the action on monocarboxycellulose even dilute solutions of alkalis or other bases at normal temperature leads to an intensive process of destruction. To improve the quality of the films and reduce the loss of oxidized cellulose, cellulose with a carboxyl group content of 0.2-25.5% in H or salt form is dissolved in an organic solvent mixture selected from the group containing dimethylformamide, dimethyl acetamide, dimethyl sulfoxide, methyl ester of acetic acid, ethyl ester of acetic acid, methyl propionic ester, acetonitrile, or their mixture and nitrogen tetroxide with a ratio of the components of the mixture (2.8-13): 1. Moreover, the formation of the foam is carried out by evaporation of the solvent or precipitation with acetone, methanol, ethanol, isopropanol, propanol, butanol, water or their mixture with dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetic acid methyl ester, ethyl acetate, methyl ester, ethyl acetate, acetonite rilom. Any cellulosic material, such as wood pulp, cotton, sulphate, sulfate or regenerated cellulose, as well as its low substituted derivatives, is used as a raw material for the production of oxidized cellulose. Nitrogen dioxide (nitrogen dioxide) in gaseous, liquid or dissolved (in solvents that do not react to form chemical compounds or any other oxidant oxidizing hydroxyl groups of cellulose to carboxyl) is used as an oxidizing agent. when it is treated with aqueous and aqueous organic solutions of the corresponding salt or base, for example, alkali or alkaline earth metals, as well as ammonia or organic compounds. electron-donor plants are used in monocarboxylic cellulose solvents in H- or saline form; the donors listed above can be used separately or mixed with each other to dissolve the oxidized cellulose or its salt with the addition of a small amount of nitrogen tetroxide. Nitrogen tetroxide with electron donor solvents forms complex compounds that dissolve monocarboyl sildellulose or its salt, with no further oxidation of monocarboxy cellulose. This is due, on the one hand, to the binding of nitrogen tetroxide molecules with an electron-donor solvent to the complex compounds, and on the other hand, to solvation; organic solvent molecules of reactive centers of unoxidized units of monocarboxylic cellulose macromolecules. The dissolution of monocarboxylic cellulose or its salt occurs at normal temperature and pressure. Temperature rise to. 40–50 ° C accelerates the dissolution process, however, this causes additional destruction of the dissolved, as well as loss of the organic solvent. Intensive mixing and a high degree of grinding of the initial samples speed up the dissolution process. The procedure for producing films is as follows. To the oxidized cellulose add a mixture of an organic solvent with nitrogen tetroxide and mix. The dissolution time is acidified by the electron-donating properties of the organic solvent, the intensity of the NIN mixing, the degree of polymerization of the oxidized cellulose, and its concentration in the solution. The oxidized cellulose is introduced into an already prepared mixture of an organic solvent — nitrogen tetroxide, or an organic solvent is added to the oxidized pulp, followed by nitrogen tetroxide. Nitrogen oxide (in the form of a gas) saturates the organic solvent or is poured in the required amount (if liquid). The resulting solution of oxidized cellulose is applied in a thin layer on a hard surface (polyethylene, teflon, glass, etc.), a. then, by evaporating the organic solvent and nitrogen tetroxide or by treating an oxidized cellulose precipitator, a transparent film of a given thickness is obtained. Under prolonged conditions, concentrated film solutions of oxidized cellulose can be obtained by pressing through a spinneret and followed by stretching (similar to the production of cellophane). The following are specific examples of the preparation of solutions of oxidized cellulose and films from them, which, naturally, does not limit the applicability of the claimed invention. Example 1.6 g of crushed 20% cotton monocarboxycellulose is placed in a mixture consisting of 29 g of dimethylformamide and 4 g of nitrogen tetroxide (nitrogen dioxide). After 30 minutes with constant stirring, a viscous homogeneous solution of oxidized cellulose is obtained. The solution is then applied in a thin layer onto the glass surface and regenerated as a film with isopropyl alcohol. After drying in air, a transparent film is obtained. Example2. 3 g of fluffed 15% monocarboxycellulose sulphate in the form of a calcium salt is dispersed in 33 f of dimethylsulfroxide. Then 2.5 g of nitrogen peroxide (nitrogen dioxide) are added and stirred for 3 hours. A homogeneous homogeneous solution of the oxidized cellulose is obtained, it is poured onto the surface of Teflon and distilled with distilled water. After drying under vacuum, a clear film is obtained. Froze 8 g of 10% sulphite monocarboxyl cellulose in the form of sodium salt are sutured with 27 g of dimethylformamide and 5 g of nitrogen tetroxide (nitrogen dioxide). After 26 hours of constant stirring, a homogeneous, homogeneous

solution of oxidized cellulose, deposited on a glass surface and planted with a mixture of ethyl alcohol and water (70:30). Get a transparent film.

Example4. 4g of 22.5% monocarboxylcellulose as viscose fiber is placed in 27 g of dimethylformamide; gaseous nitrogen tetroxide (nitrogen dioxide) is passed through the mixture. After vigorous stirring at 2Q ° C, the resulting solution is applied to a hard surface and treated with a mixture of water and dimethylformamide (60:40), dried in a drying cabinet, then: soaked in a 5% glycerol bath. As a result, a transparent flexible film was obtained.

Example 5, 2 g of crushed 6% monocarboxylic cellulose (sulphate) as a strontium salt is dissolved in 27 g of ethyl acetate and 5 g of nitrogen tetroxide (nitrogen dioxide) for 6 hours of constant stirring at 20 s. The resulting solution is poured onto stretched polyethylene and dried in air. Get a thin transparent film.

Example 6. 1 g of chromatographic paper with a degree of oxidation of 0.5% is dissolved in 24 g of acetonitrile and 2 g of nitrogen tetroxide (nitrogen dioxide) at 20 ° C for 5 hours with constant stirring. The resulting solution is regenerated with a mixture of acetone and acetonitrile (80:20 as a film.

Example7. 8 g of fluffed 3.4% sulfite monocarboxycellulose is dissolved in 10 g of dimethylformamide and 30 g of methyl acetate with the addition of 8 parts of nitrogen tetroxide (nitrogen dioxide). The resulting solution was applied to a glass surface and dried at 50 ° C. The result is a transparent, uniform film.

Example8. 2 g of crushed pulp with an oxidation state of 1.5% is dissolved in 30 g of propionic acid methyl ester and 5 g of nitrogen tetroxide (nitrogen dioxide) at. for 7 hours with constant stirring. The resulting solution is regenerated with methyl propionate as a thin transparent film, and then dried under vacuum.

Sample 4 g of fluffed 4.5% sulfate monocarboxycellulose in the form of potassium salt was dissolved in 30 g of methyl acetate and 7.5 g of nitrogen tetroxide. (nitrogen dioxide) with constant stirring. The resulting solution was applied to a glass surface and treated with a mixture of methyl acetate.

ester of acetic acid with methyl alcohol (40:60). At. This formed a transparent elastic film. According to chemical analysis and IR spectra, the film does not contain free carboxyl groups and bound nitrogen,

Example 10. 6 g of ground monocarboxycellulose with an oxidation state of 21% based on cotton cellulose are filled in with 25 g of dimethylacetamide and 4 g of nitrogen tetroxide (nitrogen dioxide). After 28 hours of constant stirring, a homogeneous, homogeneous solution of oxidized cellulose is obtained, which is applied to the glass surface and

Planted with a mixture of n-propyl alcohol and dimethylacetamide (70:30), then washed with acetone and dried the resulting film. On the uniform distribution of carboxyl groups in

the volume of the film was judged by the uniform staining of the film with methylene blue. The content of carboxyl groups in the cast film was 20.5%.

PrimerI.Zg fluff

monocarboxylic cellulose with an oxidation state of 15% in the form of a calcium salt based on sulphate cellulose was dissolved in 8 g of dimethylacetamide and 20 g of acetonitrile with the addition of 10 g of nitro tetroxide (nitrogen dioxide). The resulting solution was applied to a hard surface and treated with a mixture of acetonitrile and isopropyl alcohol (30:70), and then dried at 40 s. A uniformly oxidized transparent ion exchange film was obtained.

The advantage of this method of producing oxidized cellulosic films is as follows.

1. Films based on monocarboxycellulose obtained by the proposed method can contain any theoretically possible amount of carboxyl groups.

2. Uniform distribution of carboxyl groups in the volume of the film, since the films differ from homogeneous homogeneous solutions of oxidized cellulose. This solves the problem of obtaining fully absorbable hemostatic agents, as well as

uniform dyeing task

oxidized cellulosic materials. In addition, waste disappears due to uneven and insufficient oxidation of certain areas of cellulosic

materials.

3. Liquidation of cellulosic material losses in the process of obtaining oxidized films (in contrast to the known, where, during the regeneration of dissolved monocarboxylic cellulose with an increase in the content of carboxyl groups

losses reach 90%).

4. The ability to use oxidized cellulose with a higher degree of polymerization than oxidized cellophane for the production of film materials; (practically the only oxidized cellulosic material in the form of a film).

5. The proposed method of producing cellulosic films containing carboxyl groups using organic solvents, in particular at the dissolution stage, is much less harmful and safer, since there are no explosive and toxic carbon disulfide used in modern cellophane production, and the accompanying impurities, as well as salt waste precipitation bath. (Nitrogen oxide is almost completely absorbed by precipitation and flushing baths containing water or low molecular weight alcohols, while removal of carbon disulfide and hydrogen sulfide from production areas is carried out only with the help of exhaust ventilation, suction of gassing air from the places of emission of gases)

6. The proposed method of obtaining film materials by dissolving and subsequent regeneration of oxidized cellulose is much more economical due to the reduction of a number of technological stages preceding the dissolution (mercerization, pre-ripening, xanthogenesis), as well as through the use of cheap non-aqueous solvents and their almost complete regeneration or recycling (for example, obtaining nitrogen fertilizers from nitric acid).

The method for producing film materials from oxidized celluloses can also be used to obtain fibers in both dry and wet forming processes.

Thus, the production of films containing carboxyl groups

The proposed method will practically solve the problem of obtaining hemostatic agents and cation exchangers in the form of film materials on an industrial scale.

Claims (2)

1. A method of producing carboxycellulose films by dissolving oxidized cellulose in a solvent and then forming films, characterized in that, in order to improve the quality of the films and reduce the loss of oxidized cellulose, cellulose containing carboxyl groups 0.2-25.5% in n-or salt form dissolved in a mixture of nitrogen tetroxide and an organic solvent selected from the group consisting of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetic acid methyl ester, acetic acid ethyl ester, propionic acid methyl ester, acetonitrile, or a mixture of the mixture components (2.8- 13): 1. 2. Method POP1, characterized in that the films are formed by precipitation with acetone, methanol, ethanol, n- and isopropyl alcohol, water or their mixture with dimethylformamide, dimethyl acetamide, dimethyl sulfoxide, ethyl acetate, ethyl acetate acetic acid ester, propionic acid methyl ester, acetonitrile. Sources of information taken into account in the examination p ,, L.P.BendesP Walter fight10 tte ceetuEoee derwatwes prepared Hz {.he action oi soBtitions of nitfotfer oEivxTde n dtmelhytfoumamide J.Pofiirr 6ce 197 Pont Ae, io, NPu, i669-167r. 3 2. US patent 2232.990, cl. 260-212,1941.