CA1232495A - Microcapsules and process for producing same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The invention provides microcapsules and to a process for producing same. The process permits the encapsulation of sensitive materials in a technically simple manner and under careful conditions. The capsules are produced in the form of preshaped spherical particles in the aqueous solution of an oppositely charged polyelectrolyte or of an oppositely charged low-molecular organic compound. The products produced by means of this process can be used for separating processes and sub-stance-conversion processes in preparative and analytical chemistry and biochemistry as well as in pharmacy and in medi-cine.

Description

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The present invention relates to micro capsules having semipermeable or permeable capsule walls and liquid cores and to a process for producing same. By means of this process sensitive materials can be encapsulated under physiological conditions. The products thus obtained can be used for swooper-lion and substance conversion-processes, in preparative and analytical chemistry and biochemistry, in pharmacy and medicine as well as in agriculture and in the food industry.
r~icrocapsules having semipermeable or permeable capsule walls are known in the most varied forms ED Solodov-nix: Mikrokapselung, Chimija, Moscow 1980; J. R. Nixon: Micro-encapsulation Marcel Decker Inc., New York-Basel, 1976; J. E.
Vandegaer: Micro encapsulation Processes and Applications.
Plenum Press, Jew York-London 1974; M. Gulch: Capsule Tahitian-logy and Micro encapsulation. Notes Data Corp., Park Ridge, 1972).
However, in many cases the polymers or polymer come binations used for the capsule walls have disadvantages regard-in -their permeation properties, their elasticity and motion-teal stability, for example, at high osmotic pressure within the capsule. The liquid core usually consists of an oily organic liquid which is not miscible with water. This has a disadvantageous effect on the properties of sensitive materials to be encapsulated and on the passage of material - when using micro capsules in aqueous systems.
Numerous mechanico-physical and chemical processes for the production of microcàpsules are known. The principle of the mechanico-physical encapsulation processes usually lies in that the material for the core is sprayed and enveloped with the wall material in a gas space. The wall material may already be dissolved in the core material (spray drying) or sub-sequently be brought into contact with the particles or droplets of the core material as occurs in for example, immersion -- 1 -- ' ~,~

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processes, multi component nozzle processes, and fluidized bed processes.
Disadvantages of these processes lie primarily in the application of elevated temperatures, the use of organic solvents or the impermeability of the capsule sheath. The chemical processes usually operate in liquid phase and the wall is -formed by interracial polymerization or condensation or by deposition of a specified wall material. The use of usually reactive monomers and organic solvents usually constitutes substantial disadvantages of the encapsulation processes by interracial reactions.
Most of the chemical processes using a specified polymer wall material have in common the fact that the core material emulsifies or is suspended in the continuous phase and that the polymer dissolved in the continuous phase precip states at the phase boundary between core and continuum, for example, by variation of the pi value, temperature and additions of salts or solvents.
When encapsulating sensitive materials these condo-lions easily result in damage to said materials.
In the case of the very frequently applied complex coalescence the wall material is precipitated by two oppositely charged polymers (W. Slick: Anger. Chum. 87 (1975) page 556 to 567). The use of organic liquids, which are not Messiah-bye with water, as the core material and the usually still ; necessary solidification of the capsule wall requiring some-times very drastic reaction conditions are the most important disadvantages of this process.
A relatively careful inclusion process comprises the production of mixtures of the material to be encapsulated and an aqueous polyelectrolyte solution and feeding this mixture into a precipitating bath containing low-molecular ions. As a

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result of diffusion of ions structures having natural stability and a permeable gel network are formed (J. Klein, U. Hackle, P.
Sahara and P. Erg: Anger. Makromol. Chum. 76/77 (1977), page 329 to 350; German Auslegeschrift 19 17 733).
Because of the required pit variations nor the presence of polyvalent metal ions this process also causes some damage to sensitive materials. Furthermore, structures of this kind have no permeable or semipermeable capsule wall and no liquid nucleus.
process for immobilizing sensitive biological soys-terms which is based on these gel particles and has been further developed is described in the German Offenlegugnsschrift No.

3,012,233. In this process the bead-like particles are encom-passed with a polyelectrolyte complex diaphragm by subsequent treatment with a suitable polyelectrolyte solution and the gel is reliquefied by ion exchange with corresponding buffer solutions. The micro capsules thus obtained have the disadvan-tare that they are very sensitive to external influences during their production and when being handled since the capsule walls have only a very low mechanical strength. The process does not exclude the possibly harmful effect of polyvalent metal ions.
Furthermore, the required reliquefaction of the gel core by ion exchange constitutes an additional interference with the entire system.
The present invention provides micro capsules having improved properties and a process for producing same in order to provide fresh possibilities for the micro encapsulation of sensitive substances and to open up new fields of application for the products thus obtained.
The present invention thus provides micro capsules and a process for producing same, attempting and/or assuring at the ~232~9~
same time the encapsulation owe sensitive materials. It is possible to carry out the production of the capsules under con-dictions as careful as possible, for example, under physiologic eel conditions, and the capsule wall must be an elastic, per-Mobil or semi-permeable diaphragm, which must be sufficiently stable against chemical influences and mechanical s-tresses.
The inside of the capsule must be liquid and must not cause any damage to the ma tori at to be encapsulated.
According to the present invention the process coy proses passing the aqueous solution of a polyelectrolyte for encapsulation in the form of reshaped preferably spherical particles into the aqueous solution of an oppositely charged polyelectrolyte or of an oppositely charged low-molecular or-genie compound as a precipitating bath. The material -to be encapsulated can be contained in the solution of the polyelec-trolyte used as the core material. By mutual precipitation of the oppositely charged polyelectrolyte components or of the polyelectrolyte with the oppositely charged low-molecular or-genie compound an insoluble diaphragm consisting of the cores-pounding pol.yelectrolyte complex immediately forms on the sun-: face of contact of the two solutions, said diaphragm enclosing the material to be encapsulated, which is in the liquid core material.
When using the process according to the present in-mention said sheath constitutes a very thin but mechanically stable diaphragm which is impermeable to dissolved high-molecular compounds and encloses the polyelectrolyte solution used as the core material and the substance to be encapsulated when required. The nature of the polyelectroly-tes used or of the low molecular organic ions, the precipitating conditions, the concentration conditions in -the boundary layer and the viscosity of the solution used as the core material determine

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the structure and properties of the diaphragm sheath formed.
It has been found that the thickness of the capsule wall in a radial direction towards the inside of the capsule can be con-trolled by varying residence times of the polyelectrolyte solution droplets in the precipitating bath. With regard to temperature and pi value of the polyelectrolyte solutions the encapsulation conditions can be varied within wide limits.
however, for an encapsulation of sensitive materials as care-fur as possible temperatures of 237 to 323 K and pi values off

5 to 9 are preferred.
Pure water can be used as a solvent for the polyp electrolyte components concerned and for the low-molecular organic ions.
In addition, the use of buffer mixtures, as for example, 0.001 to 1 M phosphate buffer, or of solutions of low-molecular electrolytes permits the controlled adjustment of specific pi values and of varying ion strengths.
With regard to the polyelectrolytes to be used as the core material in accordance with the present invention polysaccharides or polysaccharide derivatives containing sulk plate or carboxylate groups, as for example, cellulose sulk plate, dextran sulfite, starch sulfite, carboxy-methyl eel-lulls or allegiant, in the form of their sodium salts, alone or in mixture have been found to be particularly suitable.
However, synthetic polymers containing carboxylate or sulphonate groups, as for example, polyp or copoly-acrylates, maleinates or polystyrene sulphonate are also suitable. The polyelectrolyte concentration in the aqueous solution of the core material can be varied between 0.5 and 20% by weight as a function of the nature of the polyelectroltye used and of the degree of polymerization ~1.232~

kite the degree of substitution of the polysacchar-ire sulfites and polysaccharide carboxylates can be varied within wide limits, for example, between 0.3 and 2.5, the de-grew of polymerization should not be too low since a certain minimum viscosity is required for the stability of the micro-capsules in the stage of mousiness. The viscosity of the finish-Ed core material mixture should preferably be maintained within the limits of 0.1 and 10 Pa-s and should be ten to a hundred times that of the precipitating bath.
lo according to the present invention aqueous solutions of polycations containing qua ternary ammonium groups, as for example, polydimethyl-diallyl ammonium chloride and polyvinyl-bouncily trim ethyl ammonium chloride, or of low-molecular organic cations, particularly cation surfactants and/or cat ionic dyes containing qua ternary nitrogen groupings are used for the precipitating bath.
amongst the cation surfactants qua ternary ammonium salts, as for example, lauryl-dimethyl-benzyl ammonium chloride, pyridinium salts, as for example, stearamido-methylene pardon-I'm chloride, and imidazolium salts, as for example, heptadecylimidazolium chloride, have been found to be suitable. The hydrophylic long-chain alkyd or aralkyl radical of the surface lent can be interrupted by hotter atoms or hotter atom groups, for example, diisobutyl-phenoxy-ethyoxy-ethyl-dimethyl-benzyl ammonium chloride, dodecyl carbamyl methyl bouncily dim ethyl ammonium chloride.
For example, amino-triaryl-methane dyes, acridine dyes, methane dyes, thiamine dyes, oXazinR dyes or ago dyes can be used as cat ionic dyes. The concentration of polycation, cation surfactant and/or cat ionic dye in the precipitating bath should be 0.1 to 20% by weight, preferably 0.2 to 10% by weight.

The process according to the present invention is

- 6 -" '~232~L9Si extremely simple to carry out. The aqueous polyelectrolyte solution intended for the core material is first mixed with the material to be encapsulated at the optimal pi value for the Metro at to be encapsulated and at a suitable temperature.
The material to be encapsulated can already be present as an aqueous solution, dispersion or in a solid form. The mixture thus obtained is then mounded to spherical droplets by allowing it to drip from a capillary tube or by blowing off the droplets forming with elf or an inert gas for example, by using a con-centric nozzle, and feeding them into the precipitating bath which is stirred or kept in motion in some other way and, when required, is tempered and buffered. The capsule sheath forms immediately upon mutual contact of core material droplets and precipitating bath. For this reason the micro capsules can be separated directly after being fed into the precipitating bath.
However, it is advantageous to leave the micro capsules in the precipitating bath for another 10 seconds to 120 minutes or longer. In this manner the thickness of the wall layer and its properties are readily reproducible for identical material and constant encapsulation conditions. In this case the wall thickness is of the order of 0.1 to 50 em, but when low-molecu-far ions of opposite charge are used it can be substantially larger. The size of the micro capsules can be varied by a eon-responding condition of the molding process and the viscosity of the core-material solution can be varied within the limits of 50 and 5,000 em. In order to attain homogeneous spherical micro capsules, a gap of 5 to 200 cmj preferably 10 to 100 cm is maintained between the discharge opening of the capillary tube or of the nozzle and the surface of the precipitating bath.
The actual micro encapsulation is usually followed by the separation of the micro capsules formed from the precipitate in bath by filtering or decanting or rinsing the excess ad-

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honing precipitating bath with water or buffer solution.
For solidifying the capsule wall and reducing its permeability the micro capsules can be treated with a diluted, e.g., 0.01 to 1% aqueous solution of the polyelectrolyte used as the core material. This treatment is suitably followed by a further treatment in the precipitating bath.
The micro capsules produced according to the present invention are very stable against deformation and increased osmotic pressure. However, when subjected to intense mechanic eel stress they burst and release the capsule content.
They can be frozen without damaging the capsule wall upon thawing. They are also stable against chemical action, as for example, 0.1 N Noah, 0.1N Hal, ethanol, acetone. For low-molecular inorganic and organic substances, as for example, protons, hydroxyl ions, water, dissolved salts and sugar the diaphragm constitutes no substantial barrier to diffusion.
The process according to the present invention will be explained in greater detail by means of the examples here-after.
The present invention will be further illustrated, by way of the following Examples.
Example 1 0.5 g of Na-cellulose sulfite having a degree of sub-stitution of 2.0 is dissolved in 10 ml of 0.01N phosphate buff for (pi 7.0). The solution thus obtained is forced at room temperature through a capillary tube having an inside diameter of 0.2 mm and after a height of drop of 30 cm it is fed drop-wise into a stirred precipitating bath of 2 g of polydimethyl-Delilah ammonium chloride (relative molecular weight 40,000) 30 and 100 ml of 0.01N phosphate buffer (pi 7.0). Immediately upon entering the precipitating bath the drops become coated with a film of the complex of the two oppositely charged polyelectro-~232~9S
lyres. After 30 minutes the micro capsules obtained are separate Ed from the precipitating bath by decanting and washed with 0.01N phosphate buffer (pi 7.0). The spherical micro capsules have a diameter of 2 to 3 mm and are transparent. They contain the applied cellulose sulfite solution as the core material.
The capsule wall formed is free from defects and con-statutes a diaphragm permeable to low-molecular substances.
On suspending the micro capsules in 0.01N Noah dyed with phenol phthalein and decolonizing the dispersing medium with 0.lN Hal after approximately three minutes the capsules still retain, for several minutes, their red color, which then fades slowly.
When salt is added to the dispersing medium the particles shrink at first while being deformed. When subsequently washed with water they again assume their spherical shape.
Example 2 0.2 g of Na-cellulose sulfite having a degree of substitution of 0.3 is dissolved in 10 ml of water. The soul-lion thus obtained is forced through a capillary tube having an inside diameter of 0~2 mm and so blown off via a concentric nozzle with the aid of a stream of nitrogen that individual liquid droplets having a diameter of 100 to 500 em are formed.
After a drop height of 15 cm the spherical droplets enter a stirred precipitating bath of 2 g of polydimethyl-dialkyl ammonium chloride and 100 ml of water. Immediately upon contact with the precipitating bath the droplets become coated with a film of the complex formed from the two opposite-lye charged polyelectrolytes. After 30 minutes the microcopy-sulks obtained are separated from the precipitating bath by decanting and washed with water. Transparent spherical par tides having a diameter of 100 to 500 em are obtained. Their capsule wall thickness is 1 to 5 em.

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Example 3 1.5 g of Na-dextran sulfite having a degree of sub-stitution of 0.8 are dissolved in 10 ml of water. The solution thus obtained is tempered to 277 K and, as in Example 1, it is fed into a precipitating bath tempered to 277 K and consisting of 10 g of polydimethyl-diallyl ammonium chloride and 100 ml of water. After 60 minutes the micro capsules formed are spear-axed from the precipitating bath by decanting, mixed with 100 ml of a 0.1% dextrane~sulphate solution and then treated with the precipitating bath for further 30 minutes. Micro capsules having a diameter of 3 to 4 mm and a wall thickness of approx-irately 20 em are obtained.
Example 4 0.3 g of Na-carboxy-methyl-cellulose sulfite having a degree of substitution of carboxyl groups of 0.6 and of sulk plate ester groups of 0.3 is dissolved in 10 ml of water. The solution thus obtained is tempered to 313 K and, as in Example 1, fed into a precipitating bath tempered to 313 K and consist-in of 3 g of polyvinyl-benzyl trim ethyl ammonium chloride and 100 ml of water. After 60 minutes the capsules are separated from the precipitating bath by decanting and washed with water.
Transparent micro capsules having a diameter of approximately 3 mm are obtained.
Example 5 0.3 g of Na-cel]ulose-acetate sulfite is dissolved in 100 ml of water. As in Example 1, the solution thus obtain-Ed is fed drops into a precipitating bath obtained by disk solving 3 g of polydimethyl-diallyl ammonium chloride in 100 ml of dilute Hal having a pi value of 4. After 60 minutes the capsules are separated from the precipitating bath by decanting and washed with water. Transparent micro capsules having a diameter of approximately 3 mm are obtained.

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Example 6 0.3 g of Na-polystyrene sulphonate is dissolved in 100 ml of water. As in Example 1, the solution thus obtained is fed drops into a precipitating bath of 3 g of pulled-methyl-diallyl ammonium chloride and 100 ml of water. After 30 minutes the capsules are separated from the precipitating bath by decanting and washed with water. Whitish-turbid microcopy-sulks having a diameter of approximately 2 mm and a liquid core are obtained.
Example 7 .

0.2 g of Na-cellulose sulfite having a degree of substitution of 0.4 is dissolved in 9.8 ml of water. At room temperature the solution thus obtained is forced through a cap-illary tube having an inside diameter of 0.2 mm and after a drop height of 30 cm it is fed drops into a stirred precip-stating bath of 1 g of ethylene blue and 99 ml of water.
Immediately upon entering the precipitating bath the capsules become coated with a film. After 30 minutes the capsules form-Ed are separated from the precipitating bath by decanting and washed with water. Spherical capsules having a deep blue color and a diameter of 3 to 5 mm are obtained.
example 8 0.3 g of Na-carboxy-methyl cellulose having a degree of substitution of 0.6 is dissolved in 9.7 ml of water. the solution thus obtained is forced through a capillary tube have in an inside diameter of 0.2 mm and is so blown off via a concentric nozzle with the aid of a nitrogen stream that India visual liquid droplets having a diameter of 100 to 300 em are formed. The droplets are blown into a stirred precipitating bath of 2 g of dodecyl-carbamyl-methyl-benzyl-dimethyl ammonium chloride and 98 ml of water. After 120 minutes the microcopy-sulks formed are separated from the precipitating bath with the 1;~3~
aid of a fine polyamide sieve and thoroughly washed with water.
White, nontransparent spherical particles having a diameter of 100 to 300 em are obtained.
Example 9 0.2 g of Na-carboxy-methyl cellulose having a degree of substitution of carboxyl groups ox 0.6 and of sulfite ester groups of 0.3 is dissolved in 9.8 g of water. As in Example 7 the solution thus obtained is mounded to spherical droplets and fed into a precipitating bath of 1 g of crystal violet (C. J.
Basic Violet 3) and 99 ml of water. After 10 minutes the cap-sulks formed are separated from the precipitating bath by de-canting and thoroughly washed with water until the water no-mains colorless. The capsules have a dark violet color and a diameter of 3 to 5 mm.
Example 10 0.2 g of Na-cellulose sulfite having a degree of substitution of 0.4 is dissolved in 9.8 ml of water. The soul-lion obtained is molded to spherical particles as in Example 8 and fed into a precipitating bath of 2 g of safranine (C. J.
Basic Red 2) and 98 ml of water. After 30 minutes the micro-capsules are sieved from the precipitating bath and thoroughly washed with water. Dark red spherical particles having a diameter of 100 to 300 em are obtained.
Example 11 0.2 g of Na-alginate is dissolved in 9.8 ml of water and the solution is molded to spherical particles as in Example 7. Said particles are fed into a stirred precipitating bath of 1 g of safranine (C. J. Basic Red 2), 1 g of polydimethyl-Delilah ammonium chloride and 98 ml of water. After 60 minutes the capsules are sieved and washed with water. Dark red sphere teal particles having a diameter of 3 to 5 mm are obtained.

glue Example 12 0.2 g of Na-cellulose sulfite having a degree of substitution of 0.4 is dissolved in 9.8 ml of water. As in Example 7 the solution thus obtained is forced through a cap-Lowry tube and fed drops into a precipitating bath of 1 g of acridine orange (C. J. Basic Orange 14) and 99 ml of water.
After 60 minutes the capsules are sieved and washed with water until the draining wash water is colorless. Spherical particles having an intense orange color and a diameter of 3 to 5 mm are obtained.
Example 13 0.2 g of Na-polystyrene sulphonate is dissolved in 9.8 ml of water. The solution thus obtained is forced through a capillary tube as in Example 7 and fed drops into a pro-cipitating bath of 2 g of benzethonium chloride and 98 ml of ; water. After 2 hours the capsules formed are sieved and thoroughly washed in water. White, nontransparent spherical particles having a diameter of 3 to 5 mm are obtained.
Example 14 0.2 g of Na-cellulose sulfite is dissolved in 9.8 ml of water and the solution thus obtained is forced through a capillary tube as in Example 7, whereupon it is fed drops into a precipitating bath of 2 g of lauryl-dimethyl-benzyl ammonium chloride and 98 ml of water. After two hours the capsules thus formed are sieved and thoroughly washed with water. White, nontransparent spherical particles having a diameter of 3 to 5 mm are obtained.

Claims (40)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing microcapsules having semi-permeable or permeable walls and a liquid core for the encapsulation of dissolved, emulsified or suspended materials by precipitating polyelectrolytes, in which an aqueous solu-tion of at least one polyelectrolyte in the form of preshaped particles is fed into an aqueous solution of an oppositely charged polyelectrolyte or of an oppositely charged low-molec-ular organic compound forming a precipitating bath.

2. A process according to claim 1, in which the material to be encapsulated is added to the polyelectrolyte solution which forms the liquid core material.

3. A process according to claim 1 or 2, in which the particles are pre-shaped by dripping from a capillary tube.

4. A process according to claim 1 or 2, in which the particles are pre-shaped by spraying.

5. A process according to claim 1 or 2, in which after having been pre-shaped the particles travel a path of 5 to 200 cm the surface of the precipitating bath.

6. A process according to claim 1 or 2, in which after having been pre-shaped the particles travel a path of 10 to 100 cm the surface of the precipitating bath.

7. A process according to claim 1 or 2, in which the concentration of the polyelectrolyte solution to form the liquid core material is 0.5 to 20% by weight.

8. A process according to claim 1 or 2, in which the concentration of the polyelectrolyte solution to form the liquid core material is 1 to 10% by weight.

9. A process according to claim 1 or 2, in which the concentration of polyelectrolyte or low-molecular organic ion of opposite charge in the precipitating bath is 0.1 to 20%
by weight.

10. A process according to claim 1 or 2, in which the concentration of polyelectrolyte or low-molecular organic ion of opposite charge in the precipitating bath is 0.5 to 10%
by weight.

11. A process according to claim 1, in which water or 0.001 to 1 molar aqueous solution of low-molecular elec-trolytes, are used as solvents for the polyelectrolyte or for polyelectrolyte and low-molecular organic ion of opposite charge.

12. A process according to claim 11, in which the aqueous solutions are buffer solutions.

13. A process according to claim 1 or 2, in which the encapsulation is carried out at pH values from 5 to 9.

14. A process according to claim 1 or 2, in which the microcapsules are left in the precipitating bath for 10 seconds to 24 hours, at temperatures from 273 to 323°K.

15. A process according to claim 1 or 2, in which the microcapsules are left in the precipitating bath for 5 to 120 minutes, at temperatures from 273 to 323°K.

16. A process according to claim 1, in which the capsule wall is formed from a member selected from the group consisting of a complex of polysaccharides containing sulphate groups, polysaccharide derivatives containing sulphate groups, synthetic polymers containing sulphonate groups and polymers containing quaternary ammonium groups and the liquid core is formed of the aqueous solution of a member selected from the group consisting of the sulphate-groups-containing poly-sac-charide used for the formation of -the capsule, the poly-sac-charide derivative and the sulphonate-groups-containing syn-thetic polymer.

17. A process according to claim 1, in which the capsule wall is formed from a member selected from the group consisting of a complex of sulphate- or carboxylate-groups-containing polysaccharides, polysaccharide derivatives, sulphonate- or carboxylate-groups-containing synthetic poly-mers and cation surfactants of cationic dyes and the liquid core is formed from the aqueous solution of a member selected from the group consisting of the sulphate- or carboxylate-groups-containing polysaccharide used for the formation of the capsule wall, the polysaccharide derivative and the sulphonate- or carboxylate-groups-containing synthetic poly-mer.

18. A process according to claim 16 or 17, in which the sulphate-groups-containing polysaccharides or polysaccha-ride derivatives are cellulose sulphate, cellulose-acetate sulphate, carboxy-methyl cellulose sulphate, dextran sulphate or starch sulphate in the form of their sodium salts.

19. A process according to claim 16 or 17, in which the degree of substitution of the sulphate-groups-containing polysaccharides or polysaccharide derivatives with sulphate-ester groups is 0.3 to 2.5.

20. A process according to claim 16 or 17, in which the sulphonate-groups-containing synthetic polymer is sodium polystyrene sulphonate.

21. process according to claim 17, in which the carboxylate-groups-containing polysaccharides or polysaccha-ride derivatives are carboxy-methyl cellulose, carboxy-methyl cellulose sulphate or alginate in the form of their sodium salt.

22. A process according to claim 16, in which the polymers containing quaternary ammonium groups are poly-dimethyl-diallyl ammonium chloride or polyvinyl-benzyl trimethyl ammonium chloride.

23. A process according to claim 17, in which the cation surfactants are quaternary ammonium, pyridinium or imadazolium salts and the cationic dyes are amino-triaryl-methane dyes, acridine dyes, methine dyes, phenozine dyes, thiazine dyes, oxazine dyes or azo dyes.

24. A process according to claim 16 or 17, in which the capsules have outside diameters of 50 to 5,000 µm.

25. A process according to claim 16 or 17, in which the thickness of the capsule walls is 0.1 to 50 µm.

26. A process according to claim 16 or 17, in which the thickness of the capsule walls is 1 to 20 µm.

27. A process according to claim 16 or 17, which contains further materials in the dissolved, emulsified or suspended form.

28. Microcapsules having semi-permeable or perme-able capsule walls and liquid cores, the capsule wall consist-ing of a polyelectrolyte complex formed by oppositely charged polyelectrolytes or by polyelectrolyte and low-molecular organic ions of opposite charge, the liquid core consisting of an aqueous solution of polyelectroltye.

29. Microcapsules according to claim 28, in which the capsule wall consists of a member selected from the group consisting of a complex of polysaccharides containing sulphate groups, polysaccharide derivatives, containing sulphate groups, synthetic polymers containing sulphonate groups and polymers containing quaternary ammonium groups and the liquid core consists of the aqueous solution of a member selected from the groups consisting of the sulphate-groups-containing polysaccharide used for the formation of the capsule, the polysaccharide derivative and the sulphonate-groups-containing synthetic polymer.

30. Microcapsules according to claim 28, in which the capsule wall consists of sulphate- or carboxylate-groups-containing polysaccharides, polysaccharide derivatives, sulphonate- or carboxylate-groups-containing synthetic poly-mers and cation surfactants of cationic dyes and the liquid core consists of the aqueous solution of a member selected from the group consisting of the sulphate- or carboxylate-groups-containing polysaccharide used for the formation of the capsule wall, the polysaccharide derivative and the sulphonate- or carboxylate-groups-containing synthetic poly-mer.

31. Microcapsules according to claim 29 or 30, in which the sulphonate-groups-containing polysaccharides or polysaccharide derivatives are cellulose sulphate, cellulose-acetate sulphate, carboxy-methyl cellulose sulphate, dextran sulphate or starch sulphate in the form of their sodium salts.

32. Microcapsules according to claim 29 or 30, in which the degree of substitution of the sulphate-groups-con-taining polysaccharides or polysaccharide derivatives with sulphate-ester groups is 0.3 to 2.5.

33. Microcapsules according to claim 29 or 30, in which the sulphonate-groups-containing synthetic polymer is sodium polystyrene sulphonate.

34. Microcapsules according to claim 29 or 30, in which carboxylate-groups-containing polysaccharides or polysaccharide derivatives are carboxy-methyl cellulose, car-boxy-methyl cellulose sulphate or alginate in the form of their sodium salt.

35. Microcapsules according to claim 29, in which the polymers containing quaternary ammonium groups are poly-dimethyl-diallyl ammonium chloride or polyvinyl-benzyl trimethyl ammonium chloride.

36. Microcapsules according to claim 30, in which the cation surfactants are quaternary ammonium, pyridinium or imadazolium salts and the cationic dyes are amino-triaryl-methane dyes, acridine dyes, methine dyes, phenozine dyes, thaizine dyes, oxazine dyes or azo dyes.

37. Microcapsules according to claim 28, 29 or 30, in which the capsules have outside diameters of 50 to 5,000 µm.

38. Microcapsules according to claim 28, 29 or 30, in which the thickness of the capsule walls is 0.1 to 50 µm.

39. Microcapsules according to claim 28, 29 or 30, in which the thickenss of the capsule walls is 1 to 20 µm.

40. Microcapsules according to claim 28, 29 or 30, which contain further materials in the dissolved, emulsified or suspended form.