RU2564824C1 - Biodegradable film - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: biodegradable film contains glycerine, a structure-forming agent - 10% aqueous gelatine solution and additionally as a crosslinking agent - transglutaminase enzyme, mixed with milk whey in ratio of 1:4, with a given ratio of components.

EFFECT: high strength and stretching, faster biodegradation while preserving properties which match polyethylene films.

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Description

The invention relates to compositions of biodegradable films and can be used in pharmaceuticals, medicine, veterinary medicine, food and cosmetic industries, as well as for the manufacture of wrapping food film, capsules, packaging materials.

The known composition of a biodegradable laminated film containing chitosan and pectin. Glycerin may be added as a plasticizer. To the pectin or chitosan solution used for the manufacture of the film, starch can be added (US, No. 5919574, IPC C08L 5/06, publ. 06.07.1999).

A disadvantage of the known solution is the significant complexity of the manufacture of a layered film, since it is necessary to separately produce a layer of pectin and a layer of chitosan films. In addition, the layering of these films on each other can be associated with the appearance of air bubbles between the layers, which are almost impossible to remove, since the layers of the film adhere sufficiently tightly to each other.

Known non-adhesive elastic gelatin matrix, which is a lyophilized mixture of protein, polymer, a crosslinking agent and possibly a plasticizer. As a protein, a group consisting of collagen, denatured collagen and mixtures thereof was selected; as a polymer, a group consisting of polyethylene glycol, poly-L-lysine, alginate, chitosan, hyaluronic acid, chondroitin sulfate and mixtures thereof was selected; as a crosslinking agent, a group consisting of 1- [3- (dimethylamino) propyl] -3-ethylcarbodiimide (EDC), N-hydroxysuccinimide (NHS), formaldehyde, glutaraldehyde, polyaziridines, diglycidyl ethers and mixtures thereof (EP, No. 016776, IPC A61L 15 32, publ. 2012.07.30).

The disadvantage is inelasticity, relatively low strength, as well as the use of a crosslinking agent of chemical origin.

A biodegradable film based on chitosan and pectin is known. Pectin is dissolved in distilled water at a temperature of 37-38 ° C. Chitosan is dissolved in 1 H (one-normal) hydrochloric acid at a temperature of 37 ° -38 ° C. Then, the resulting solutions of pectin and chitosan in equal proportions are drained and mixed until complete dissolution of the resulting clots. Then add a plasticizer - glycerin and a structurant - 3% methylcellulose solution. The film is formed on a glass substrate for 20-24 hours at a temperature from 0 to 25 ° C (RU, No. 2458077, IPC C08L 5/18, C08L 5/06, C08L 5/08, C08L 101/16, publ. 10.08. 2012).

The disadvantages are the complexity of manufacturing the film, the relatively low strength and brittleness when dried, not allowing to produce packaging materials, as well as the relatively high cost of pectin.

The technical result consists in increasing the strength and stretching, as well as in accelerating the biodegradability, while maintaining characteristics not inferior to plastic films.

The technical result is achieved by the fact that the biodegradable film includes glycerin, the structuring agent is a 10% aqueous solution of gelatin. Additionally, as a crosslinking agent, it contains the transglutaminase enzyme mixed with whey in a ratio of 1: 4, in the following ratio of components, wt. %:

glycerol 11.7-14.6 10% aqueous gelatin solution 26.9-31.5 transglutaminase enzyme, mixed with dairy serum in a ratio of 1: 4 53.9 61.4

Whey is a secondary raw material (by-product) in the production of cheeses, cottage cheese and casein. It is separated after coagulation of milk as a result of lowering the pH to 4.6 units. under the influence of lactic acid. The main plasma proteins are alpha-lactalbumin (65%), beta-lactoglobulin (25%) and serum albumin (8%). Proteins make up 0.7-1.1% of the total mass of serum. Liquid whey contains lactose, vitamins and minerals, as well as traces of fats [Processing and use of whey / A.G. Khramtsov and others, - M .: Agropromizdat, 1989. - 271 p.]. Whey proteins have a high affinity for transglutaminase [Sharma, R .; Lorenzen, P.C .; Qvist, C.V. / International Dairy Journal, Volume 11, Number 10, 2001, pp. 785-793 (9)] and therefore its presence in the composition improves the physical and mechanical properties of the resulting films.

Gelatin, as a product of the processing of collagen, a protein substance that is common in nature, forms the main component of the connective tissue of vertebrates, especially in the skin, bone ossein and tendons. In terms of amino acid and elemental composition, gelatin is close to collagen. The main acids: glycine (about 27%), proline (about 16%), hydroxyproline (about 14%), glutamic acid (about 12%), arginine (about 9%), lysine (about 5%). Gelatin swells in water and dissolves when heated from 30 to 60 ° C; upon cooling, the gelatin solution forms jelly (gel), which when heated again passes into the solution. The optimal proportion of dissolution of gelatin in water in the claimed solution is 1:10. The pour point and jelly strength depend on the concentration of the solution and the quality of the gelatin. The main quality criteria for gelatin are the viscosity of the solution, the strength of the jelly, its melting point and gelation, measured under certain conditions [Artemenko A.I. Reference Guide to Chemistry / A.I. Artemenko, V.A. Malevanny, I.V. Tikunova - M :. Graduate School. 1990. 124 p.]. Due to the function of the gelling agent, it can be used in the preparation of biodegradable polymers. With a lack of gelatin, the strength of the films decreases.

The transglutaminase enzyme has unique properties - it binds simple and complex proteins, forms covalent bonds between free amino groups (free or from the lysine side chains) and gamma-carboxamide groups of glutamine, contributing to the intra- and intermolecular crosslinking of protein molecules. Covalent bonds of transglutaminase are resistant to proteolysis.

The optimal concentration of a mixture of transglutaminase enzyme with whey should be 1: 4. At a higher concentration (for example, 1: 3), the strength of the films increases, but they become brittle even with an increase in the amount of plasticizer (glycerin).

Glycerin is responsible for the plasticity and flexibility of the films. With its deficiency, the films do not stretch, they easily break when bent. With an excess of glycerol, films poorly separate from the surface, become sticky, viscous.

Biodegradable film is prepared as follows. Gelatin is dissolved in water in proportions of 1:10 at a temperature of 60 ° C. Then it is mixed with glycerin, and the transglutaminase enzyme mixed with whey in a ratio of 1: 4 is added last (Table 1). The enzyme cross-links the components of the film very quickly, so after applying it, the suspension is stirred on a magnetic stirrer for no more than 2 minutes. The temperature of the mixture should be 45-55 ° C, as this is the optimum effect of transglutaminase. The resulting mass is carefully poured into dishes with a horizontal bottom. The amount of mass depends on the required thickness. The film is formed within 20-24 hours at room temperature. The result is a uniform, slightly cloudy film. The film is flexible - when bent, cracks do not form, when unbent, the film takes its initial state. The film is odorless, can take various forms depending on the shape of the vessel into which the solution is poured.

The strength and tensile strength of biopolymer films in MPa (N / mm ² ) were determined in accordance with GOST 17035-86 and ASTM using a universal testing machine with electromechanical drive XLW (PC) Auto (GOST 7855-84; ASTM). The film thickness was determined on a CHY-C2 automatic high-resolution thickness gauge (Table 2).

Table 1 shows the composition of the obtained film; table 2 shows the comparative characteristics when testing the obtained films.

Evaluation of the biodegradation of the films was carried out in a soil environment. Freshly prepared films were completely biodegradable in 6 days (a prototype of freshly prepared film decomposes in 8 days). After three months of storage, the film decomposes in 12 days (the prototype after three months of storage decomposes in 15 days), after six months in 23 days.

Compared with the known solutions, the proposed composition of the biodegradable film can increase its strength by 10-15%, stretching by 20-30%. The film becomes biodegradable and can be used to make biodegradable packaging and dressing materials. In addition, its cost is reduced by 1.5 times due to the use of cheaper whey.

Claims (1)

Biodegradable film, including glycerin and a structure-forming agent, characterized in that it contains 10% aqueous gelatin solution as a structure-forming agent, and also, as a cross-linking agent, the transglutaminase enzyme mixed with whey in a ratio of 1: 4, in the following ratio of components, wt .%:
glycerol 11.7-14.6 10% aqueous gelatin solution 26.9-31.5 transglutaminase enzyme, mixed with dairy serum in a ratio of 1: 4 53.9-61.4