RU2458077C1 - Pectin- and chitosan-based biodegradable film - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: biodegradable film contains pectin, chitosan, water, 1N hydrochloric acid, a plasticiser - glycerine and a structure-forming agent - 3% methyl cellulose solution.

EFFECT: obtaining a uniform biodegradable film without structural defects, which similar to household packaging polyethylene films on homogeneity, plasticity and strength.

2 dwg, 1 tbl

Description

The invention relates to compositions of biodegradable films containing pectin for use in pharmaceuticals, medicine, veterinary medicine, the food or cosmetic industry, as well as for the manufacture of wrapping food film capsules.

Known for the prototype is a highly elastic laminated film made from chitosan and pectin. Glycerin or lactic acid may be added as a plasticizer, and starch may be added to the pectin or chitosan solution used to make the film. The resulting laminated film is biodegradable and is made from renewable agricultural raw materials (US patent No. 5919574).

The disadvantage of the prototype is the significant complexity of manufacturing a layered film, since it is necessary to separately produce a pectin layer and a layer of chitosan film, 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 stick together quite tightly.

The objective of the invention is to simplify and accelerate the process of manufacturing a film of pectin and chitosan, obtaining a biodegradable film with characteristics similar to packaging polyethylene films.

The technical result of the invention is to obtain a homogeneous biodegradable film based on pectin and chitosan without the disadvantages of a structure similar in homogeneity, ductility, and strength to packaging polyethylene films for domestic use.

The technical result is achieved by the fact that in a biodegradable film obtained from pectin, water, chitosan, monoform hydrochloric acid and a plasticizer, glycerin is used as a plasticizer, as well as a film-forming agent, a three percent methylcellulose solution in the following ratio, wt.%:

pectin 35-37 chitosan 35-37 water 7-8 normal hydrochloric acid 7-8 glycerol 5-6 three percent methyl cellulose solution rest.

The figure 1 shows photographs of a biodegradable film based on pectin and chitosan according to the invention. The figure 2 shows photographs of the decomposition of the proposed films for 8 days.

In the biodegradable film according to the invention, the optimum ratio of pectin and chitosan should be approximately 1: 1. This ratio allows the films according to the invention to be strong (pectin gives the geliness to the films), with a lack of pectin, the film structure becomes too loose and liquid, the films may not freeze. And with an excess of pectin, the film becomes inflexible, and the decomposition period of the film increases, due to the higher density of the films.

Chitosan is responsible for compatibility with animal tissue. When exposed to natural fungi, films containing chitosan have an integrated nitrogen source to increase biodegradation. Those. with a lack of chitosan, the decomposition time of the films increases significantly, their degree of harmlessness to the body decreases. With an excess of chitosan, the film will be opaque, will have a cloudy white tint.

Glycerin is responsible for the plasticity and flexibility of the films. With its lack of film does not stretch, when bent, cracks appear. With an excess of glycerol, films poorly separate from the surface, become sticky, viscous.

A three percent solution of methyl cellulose makes the films more durable. With an excess of this component, the films become brittle, brittle. With a lack - easily torn, fragile.

The biodegradable film according to the invention is prepared as follows. Pectin is dissolved in distilled water. Then, for better dissolution of the components, the solution is placed in a thermostat for 1 minute at a temperature of 37-38 ° C. Chitosan is dissolved in 1 N. (one-normal) hydrochloric acid. To better dissolve the components, the solution is also placed in a thermostat for 1 minute at a temperature of 37-38 ° C. Then, the resulting solutions of pectin and chitosan are preferably poured and mixed in equal proportions until the resulting clots are completely dissolved. In order for the film to be strong and evenly separate from the substrate, after mixing the clots, a plasticizer and a structurant are added to the resulting solution.

The resulting mass is carefully poured into a Petri dish. The film is formed on a glass substrate (in a Petri dish) for 20-24 hours at a temperature of 0 to 25 ° C.

The result is a uniform, transparent (depending on the thickness of the film will be transparent or slightly cloudy) film. The film is flexible - when bent, cracks do not form, when unbent, the film takes its initial state. The film has no color, no smell. It can be dyed with various dyes, for example food colors, as they are harmless to humans. The film can take various forms depending on the shape of the vessel into which the solution is poured: round films in the Petri dishes (Fig. 1), square films in a square container. Changes in the color and shape of the films did not affect their properties.

The strength of biopolymer films was determined in accordance with GOST 17035-86 using a universal testing machine with an electromechanical drive (GOST 7855-84). Strength σ _r , MPa (H / mm ² ) was calculated by the formula:

,

,

where σ _r is the tensile strength (MPa, N / mm ² ),

F _r - tensile force (N),

And ₀ is the cross-sectional area (mm ² ).

The strength indicators of the obtained film are shown in table 1, which also shows the values of the indicators of the film according to the invention in comparison with similar indicators of polyethylene. Since one of the main objectives of the invention was to obtain a worthy analogue of plastic bags, the most important properties of the obtained polymer films are shown in the table with similar properties of plastic films for household use (packaging). Based on these data, it can be concluded that the strength of polymer films is close to the strength of polyethylene, but their safety and ability to quickly undergo biodegradation expands the scope of their application.

Table 1 shows the composition of the film obtained according to the invention: its thickness is h, the circumference of the taken fragment is 1, the elongation of the material in width to one side is σ _{in width} , the elongation of the material in length to the other side is σ _{in length} .

Table 1 h mm l ₀ mm σ _{in width} , MPa σ _{in length} , MPa The composition of the obtained film: cellulose 0.06 fifteen 12,2 13.8 pectin chitosan glycerol water 1 n Hcl Polyethylene film 0.04 fifteen 13.7 14.7

Film thickness was measured using an ELECTRO MS DIGITAL MICROMETER micrometer. It amounted to 0.074 mm. For different copies of the films made, the thickness ranged from 0.075 to 1 mm.

Evaluation of the biodegradation of the films was carried out in a soil environment. Freshly prepared films based on a mixture of chitosan - pectin were completely biodegradable in 8 days (figure 2). After three months of storage, the film decomposes in 15 days, after six months - in 23 days.

The invention is illustrated by example.

10 mg of apple petin is dissolved in 2 ml of distilled water. For better dissolution, place the solution in a thermostat for 1 minute at a temperature of 37-38 ° C.

10 mg of polyfractional chitosan from the crustacean shell (manufacturer - JSC Bioprogress) is dissolved in 2 ml of 1 N. (normal) HCL. For better dissolution, place the solution in a thermostat for 1 minute at a temperature of 37-38 ° C.

Then the resulting solutions of pectin and chitosan are poured. During the pouring of a pectin solution with an equal volume of chitosan solution, clots form at the interface between two liquids. The clots have a gel-like structure. During sedimentation, clots are slowly deposited on the bottom of the vessel without the formation of a homogeneous mass. Clots are either removed from the solution or stirred until a homogeneous mass is formed. In order for the film to be strong and evenly separate from the substrate, after mixing the clots, a plasticizer and a structurant are added to the resulting solution. To give plasticity add 1.5 ml of plasticizer - glycerol. To give the film strength, a structurant is added - 2 ml of a 3% methylcellulose solution (3 g of methylcellulose + 100 ml of water).

The film is formed on a glass substrate (in a Petri dish) for 20-24 hours at a temperature of 20-25 ° C. After drying, the film is separated from the substrate. The film thickness was measured using an ELECTRO MS DIGITAL MICROMETER micrometer; it was 0.074 mm.

Claims (1)

A biodegradable film obtained from pectin, water, chitosan, monoform hydrochloric acid and a plasticizer, characterized in that it contains glycerin as a plasticizer, as well as a structurant - a three percent solution of methyl cellulose in the following ratio, wt.%:
pectin 35-37 chitosan 35-37 water 7-8 normal hydrochloric acid 7-8 glycerol 5-6 three percent methyl cellulose solution rest

Images