SU1759445A1 - Method of producing encapsulated hydrophobic substances - Google Patents

Abstract

Use: in engineering, agriculture, and medicine for the production of adhesives, pesticides, pharmaceuticals, and the like. drugs in capsules. SUMMARY OF THE INVENTION: Particles of a hydrophobic substance are dispersed in an aqueous acidic solution containing 2-6% by weight of chitosan and 5-50 May, including at 100 May. including chitosan salts of the transition metal and monobasic acid. Selected capsules are treated with a dilute aqueous solution of alkali, washed with water and dried. Capsules have a high mechanical strength of the membranes. 1 tab.

Description

The invention relates to the field of chemical technology, in particular to the preparation of products in capsules.

It can be used in engineering, agriculture and medicine to obtain encapsulated adhesives, pesticides, pharmaceuticals, etc.

A known method of encapsulating substances that are not miscible with water is by applying a shell of an aqueous solution of chitosan to the surface of the particles and making it insoluble by the action of an inorganic salt, followed by washing and drying the resulting capsules (1).

The method is as follows: a finely powdered inorganic salt of sodium polyphosphate is preliminarily added to the encapsulated material which is not miscible with water, and a weakly acidic chitosan solution is added to this mixture under stirring conditions. As a result, a homogeneous film of chitosan cross-linked by polyphosphate is formed on the surface of the particles of the encapsulated compound. The resulting capsules are washed with water and dried.

The disadvantage of this method is the low mechanical strength of the chitosan polyphosphate shell at the time of its formation, i.e. in a swollen condition. The tensile strength of a chitosan film swollen in water, crosslinked with 5-10% sodium polyphosphate, is 1-3 MPa. The low strengths of the sheath films lead to partial destruction of the capsules and their collapse.

The purpose of the invention is to increase the mechanical strength of capsule shells.

In the proposed method of producing encapsulated hydrophobic substances, including applying a mixture of chitosan and an acid salt to the particle particles, separating the mixture of capsules from the reaction mixture, washing them with water and drying, using a salt of a monobasic acid while the substance is dispersed in an aqueous acidic solution containing 2-6 wt.% chitosan and the specified salt in the amount of 5-50 wt.h. on May 100th. including chitosan, and in the selected capsules are treated with a dilute aqueous solution of alkali.

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As substances that are not miscible with water, oils, liquid oly, omerl, pastes, solids can be used, for example, nitrates, chlorides, bromides, copper acetates, nickel of iron, cadmium, zinc, cobalt, chromium. , lead and aluminum.

The method is carried out as follows.

In the process of dispersion, microparticles of a substance with a diameter of 0.3–3 mm are coated with an aqueous solution of chitosia, taken at a concentration of 2–6% and containing a transition metal salt and a monobasic acid. Then the particles are treated with a 2-10% aqueous solution of alkali for 3-5 minutes with further washing and drying. The tensile strength of the water-swelled films of which the capsule shells are molded is 6-50 MPa. Dried capsules are spheres with a diameter of 0.3-3 mm, a wall thickness of 20-100 µm and a useful substance content of 80-90%, having different colors of the shells (depending on the selected transition metal). The contents of the capsules, if necessary, can be easily released either mechanically (by crushing) or by dissolving the membranes in aqueous acidic media.

A significant difference of the invention is the use for strengthening of chitosan shells of salts of transition metals and monobasic acids in combination with alkaline treatment. In this case, a new mechanism is implemented to make the chitosan shells insoluble, causing a sharp increase in strength.

In a known method, anionic crosslinking takes place: the amino groups of chitosan interact with the polybasic anion (polyphosphate) to form cross-linked insoluble chitosan salts. In the proposed method, the cationic crosslinking mechanism works. Amino groups of chitosan form strong coordination bonds with cations of transition metals. At the same time, the introduction of these salts into the chitosan solution does not in itself lead to the formation of shells, since the solution is acidic, but after alkaline treatment, the shells are successfully crosslinked with transition metals. The alkaline treatment value is that the acid is neutralized, necessary for the dissolution of chitosan, and the amino groups of the polymer can interact with metals. Use only alkaline treatment, i.e. without the introduction of salt into the solution of chitosan, does not give a noticeable

increase the strength of films (3-5 MPa). Thus, the use of salts of transition metals and monobasic acids in combination with alkaline treatment allows one to achieve the goal of the inventions.

Use of salts in the amount of

5-50 ma.ch. on 100 ma.ch. chitosan is explained by the fact that when going beyond the lower limit, a sufficient increase in strength is not provided, and when going beyond the upper limit, it is not

salt compatibility with polymer is ensured.

The invention is exemplified. Example 1. Use 4% solution of chitosan in a 2% aqueous solution.

acetic acid containing 12 ma.ch. C (MOZ) 2 per 100 ma.ch. chitosan. Particles of epoxy oligomer ED-20 with a diameter of 2 mm are forced through a layer of polymer solution and salt into a precipitation bath with

4% aqueous solution of caustic soda and stirred for 5 minutes The strength of the shells in the swollen state is 10-13 MPa. Then the encapsulated mass is washed with water on the filter and dried. Get the encapsulated product in the form of blue spheres with a diameter of 2 mm, a wall thickness of 50 μm and with a useful substance content of 90%.

The following examples are performed analogously to example 1, the data are given in the table,

From the above it can be seen that the implementation of the proposed method can significantly increase the strength of chitosan

shells.

Claims (1)

Claims A method of obtaining encapsulated hydrophobic substances, comprising applying a chitosum and an acid salt to the particle particles, separating the capsules from the reaction mixture, washing them with water and drying, characterized in that, to increase the mechanical strength of the capsule shells, the acid salt is used salt of the transition metal and monobasic acid, while the substance is dispogey in an aqueous solution containing 2-6 wt.% chitosan and the specified salt in the amount of 5-50 ma.h, 100 May hours chitosan, and the selected capsules are treated with a dilute aqueous solution of alkali, -J ate ie L .Ј. " Note. In Example 7, the oil was dispersed in an aqueous medium.