JPH0441913B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for encapsulating a reactant solution of a color-forming reaction system by a conventional encapsulation method, a capsule made by such a method, and its use in carbonless paper. It is about use.

Commercially available carbonless paper, such as German patent no.
2151178 and US Patent Nos. 3418250 and 3016308
For example, crystal violet lactone is used to provide color markings by means of acidic reactants during the printing process.
A coloring agent is encapsulated within the microcapsules in the form of lactone. If the acidic reactant is also soluble,
It may also be encapsulated. The purpose of encapsulation is to prevent the two reactants from undergoing an unexpected and premature color reaction. Known color formers are typically aromatic systems. They are therefore also encapsulated in aromatic solvents, producing relatively hard capsule walls. Known aromatic solvents for aromatic color formers, such as alkylated biphenyl, especially butyl biphenyl,
isopropylbiphenyl, amylbiphenyl, hexylbiphenyl and diisopropylphenyl,
Also, alkylated naphthalenes, terphenyls and their derivatives, particularly partially hydrogenated terphenyls, diallylmethane and its derivatives, and diallylethane and its derivatives are relatively difficult to make and expensive. Many attempts have been made to overcome this difficulty. For example, when isopropyl biphenyl, a combination of polyisopropyl biphenyl and biphenyl in arbitrary proportions is used as a readily soluble solvent for an aromatic color former, the resulting color former solution may contain, for example,
A high-boiling saturated aliphatic hydrocarbon oil having a boiling point range of 160-288°C and being an inexpensive aliphatic solvent is mixed as a diluent.

The use of aliphatic diluents is therefore generally done because they are much cheaper than aromatic solvents such as isopropylbiphenyl. Addition of a diluent reduces the solubility of the color former in the solvent mixture. If crystal violet lactone is used as a coloring agent, for practical needs (proper solubility, optimal color development, etc.), isopropyl biphenyl and inexpensive aliphatic hydrocarbon oil should be used in a weight ratio of approximately 2:1. Can be used in mixtures. Therefore, the proportion of inexpensive aliphatics in the total mixture is at most about 33%.

Attempts to increase the proportion of inexpensive aliphatic non-solvents in readily soluble mixtures have been shown to be problematic since increasing the proportion of non-solvent always brings at least a portion of the dissolved color former into an undesirable solid state. These dispersions (with suspended solid particles) are no longer able to be encapsulated by conventional encapsulation methods, and are therefore a complete failure. It has been found that when such suspensions are encapsulated, the capsules obtained do not exhibit the desired effect in the color system and in particular do not produce the desired color intensity. Tests have shown that a solution of crystal violet lactone in a mixture of 15% aromatic solvents such as diisopropylnaphthalene, partially hydrogenated terphenyl or isopropyl biphenyl and 85% insoluble aliphatic hydrocarbons forms a color former within a very short time. Almost all of it had precipitated. Furthermore, when carbonless paper capsules are made using such a dispersion medium, the precipitated main component of the coloring agent is removed from the coloring mechanism during the subsequent printing process, resulting in unsatisfactory color intensity. I found out that I can't get it.

For this reason, attempts in the prior art to use large quantities of inexpensive non-aromatic, non-solvents in conjunction with aromatic solvents in the encapsulation of color former solutions have been unsuccessful. In fact, it was considered that research in this direction would not be successful.

Surprisingly, however, even when using an inexpensive non-solvent or color former or its acidic reactant in such amounts that a fairly highly saturated solution of the reactant results,
Immediately after the preparation of such a supersaturated solution, if it is allowed to proceed without delay to emulsification and encapsulation while still in fresh form, the desired color reaction of the color former and its acidic reactants in the color reaction system will occur to the desired degree. I found out what happens. If such capsules are used in a color reaction system, the color reaction occurring during the printing process will be surprising, in the same way as if a pure unsaturated aromatic system were encapsulated instead of a supersaturated system. It hasn't been damaged that much.

Therefore, the object of the present invention is to first dissolve the reactant in a solvent with excellent solubility, and then immediately before emulsification and encapsulation, add a non-solvent that dissolves only a trace amount of the reactant to a supersaturated system. The present invention provides a method for encapsulating a solution of the reactants of a color-forming reaction system by conventional microencapsulation methods, by mixing with a fresh solution thereof in a controlled amount.

The method according to the invention includes encapsulation of a color-forming reaction system;
In particular, carbonless papers are of special importance, i.e., in carbonless papers, the color former and the acidic reactant are applied either on the surface of each of the two mutually contacting papers or on the surface of one paper (self-coloring). paper) are placed on the same surface in a spatially separated manner.

The basic color former may be, for example, a compound such as diallylphthalide, such as 3,
3-bis-(p-dimethylaminophenyl)-6-
Dimethylaminophthalide (crystal violet lactone) and 3,3-bis-(p-dimethylaminophenyl)-phthalide (malachite green lactone), leucoalamines such as N-halofenyl, especially N-(2,5-dichlorophenyl) enyl)−
Leucoalamines, acylouramines, e.g. N-
Benzoyluramine and N-acetyloramine, N-phenyluramine, α,β-unsaturated allyl ketones such as dianicylideneacetone, dibenzylideneacetone and anisylideneacetone, basic monoazo dyes such as p-dimethylaminoazobenzene. -O-carboxylic acids (methyl red), 4-aminoazobenzene and 4-phenylazo-1-naphthalenamine, rhodamine-β-lactam, e.g. N-(p-nitrophenyl)-rhodamine-B-lactam-polyallylcarbinol, e.g. -bis-(p-dimethylaminophenyl)-methanol, crystal violet carbinol, fluorans such as monoaminofluorane, diaminofluorane and their derivatives, and spiranes such as benzo or naphtose spiropyran derivatives. These are so-called primary color formers, which develop color almost instantaneously by reaction with an acidic reactant during a desired color development reaction. It is also possible to additionally use a secondary color former, which slows down the color development reaction and prevents the rapid browning of the color produced by the primary color former. An example is N-
There is benzoylleucomethylene blue.

In color reaction technology, in particular in carbonless paper technology, it is also desirable in individual cases to encapsulate the reactants of the color former in dissolved form. In the case of conventional acidic reagents, aromatic solvents are used. The reactant is acidic phenolic resin,
In particular, it includes phenylaldehyde resins, such as phenol formaldehyde resins. Preferred are p-alkylphenol resins, e.g.
Described in DE-OS1934457. The p-alkyl group preferably has 1 to 12 carbon atoms. However, it is also possible to encapsulate so-called "chelated" or "zinc-modified" phenolic resins, ie those in which the phenolic protons are replaced by zinc. Phenolic resins of this type are described, for example, in US Pat. No. 3,732,120. Compounds such as the following can also be used, and these also include compounds with acidic carboxyl groups (also in the form of anhydride structures): phenolic acetylene polymers, maleic resins, partially or completely styrene-maleic anhydride copolymers and ethylene-maleic anhydride copolymers hydrolyzed to type of resin. Furthermore, for example bis-(p-hydroxyphenyl)-propane, naphthol derivatives, p
Special acidic monomeric phenolic compounds such as -hydroxybenzoic acid esters and salicylic acid derivatives are also suitable.

The acidic reagents of the abovementioned color formers are particularly preferred within the scope of the invention for the following color formers: crystal violet lactone, orange, red and green/
Fluoranes and benzo and naphthospiran compounds that develop an olive or black color.

When within the scope of the present invention we refer to "solvents with good solvent power", this solvent power refers to the particular reactants to be encapsulated. If the reactants are dissolved by such a solvent to form an encapsulatable solution of satisfactory thickness, the expression "excellent solvency" is then made. Obviously, such a solvent must have the property of being inert to the system to be prepared, i.e. it must not undergo chemical changes itself and must not alter the dissolved chemicals. This is not the case. Any changes that occur should be negligible. “Non-solvent” used for the purposes of the present invention
are of course inert in the sense described above, but alone do not produce a suitably concentrated solution of the particular reactants to be dissolved. In fact, it dissolves the reactant only in very small amounts, for example with a solubility of 0.1-0.3% or less, which is of little significance with respect to the concentration of the reactant in the solution to be encapsulated. For example, in the case of most well-known color formers and their acidic reactants, which are generally particularly soluble in aromatic systems, this means that from a practical point of view the term "non-solvent" refers to these This means that it is a nonpolar aliphatic compound that does not dissolve the reactant. Thus, the terms "non-solvent" and "solvent with good solvent power" should always be taken into account with respect to the compounds to be dissolved in the form of the reactant with respect to their solvent power. It is true that their dissolving power differs from the current definition to such an extent that the definition currently in use is also justified from this point of view.

For the purposes of the present invention, aromatic solvents have been found to be particularly advantageous as solvents having excellent dissolving power for the reactants of color reaction systems. More specific of these are alkylbiphenyl, alkylnaphthalene, preferably containing 3 to 10 carbon atoms in the alkyl group, especially isopropyl, butyl, amylhexyl and diisopropyl groups, dialkyl phthalates, especially dioctyl. phthalates, but also simple aromatic compounds such as benzene, alkylbenzenes (e.g. methylbenzene, ethylbenzene, propylbenzene,
isopropylbenzene, amylbenzene and hexylbenzene), and halobenzenes such as chlorobenzene. Particular mention may be made of chlainated paraffins as an example of non-aromatic compounds, which also constitute solvents with good solvent power within the meaning of the invention.

For example, the chlorinated paraffins described in GB 1296477 have special significance in this respect. According to the latter, chlorinated linear paraffins having 6 to 18 carbon atoms and a degree of chlorination of 20 to 60% by weight are suitable as solvents for color formers. Particular preference is given to chlorinated paraffins having 12 to 14 carbon atoms and a degree of chlorination of 40 to 42% by weight.

According to the present invention, large amounts of non-solvents can be used for specific reactants, and in particular non-aromatic solvents are available in large quantities and inexpensively, or have simple properties and are therefore inexpensive to produce. can do. When specified as having these compounds, it includes aliphatic and cycloaliphatic compounds. Aliphatic and cycloaliphatic petroleum constituents
plays a special role, especially its partial fraction in the form of crude gasoline or petroleum ether, light gasoline, ligroin, heavy naphtha, kerosene, i.e. with 9 to about 20 carbon atoms. a second main fraction of fractionated petroleum containing paraffinic hydrocarbons;
and gas oils (diesel oils, heating oils) resulting from paraffins with 12 to 19 carbon atoms as the third main distillation fraction and used for diesel engines or heating purposes. Natural gasoline is also suitable and represents the gasoline fraction present in natural gas and removed from it by compression or absorption of oil.

The aforementioned aliphatic petroleum fractions are primarily based on petroleum containing linear paraffins. in cyclic hydrocarbons (naphthenes) (such as Soviet naphtha)
Some oils are made up of up to 80%. Naphthene fractions are also usefully used for the purposes of the present invention,
The most important representatives of them are cyclopentane and cyclohexane (as well as their alkyl derivatives).

It is also possible to use petroleum fractions of petroleum which are intermediate in composition between "paraffinic" and "naphthenic" petroleum.

The following commercially available products are exemplified as particularly inexpensive non-aromatic solvents. Exol D80, Exol
D180/210, Exol D140/170, Isopar L,
Isopar M, Solvent OP (all Eso products),
Shellsol TD: Shellsol K: Shellsol H:
Sinarol II: Risella oil GO5 (all Shell products) with Flavex oil 909, Catenex oil 913, particularly preferred are Exol D80 or Exol
There is D100.

The non-solvent of the present invention and a solvent having excellent dissolving power,
It is particularly useful if the mixing ratio between the solvent and the solvent, especially in the form of an aromatic solvent, is greater than or equal to 1:1 (by weight), in particular greater than 2:1 or even greater than 3:1. Surprisingly, it has been found that the non-solvent proportion can be as high as 85% by weight and in individual cases even exceed 85% by weight of the complete dissolved system. This means that the price of the entire system is largely determined by the inexpensive non-solvent, which constitutes the essence of the invention.
What is crucial for the process according to the invention is that the preparation of the dissolution system constituted by a non-solvent and a solvent with good solvent power is carried out as early as possible and that this freshly prepared supersaturated or even highly The supersaturated solution should undergo emulsification or encapsulation immediately, and at least before crystallization, which has undesirable and even deleterious effects, takes place significantly. If encapsulation is carried out from such dissolution systems, capsules are obtained that are comparable with known capsules not made from supersaturated systems with respect to their stability in color reaction systems.

The invention is not limited to any particular encapsulation method. In fact, in general, known encapsulation methods can be used which ensure suitably rapid encapsulation of a freshly supersaturated dissolved system of the color former or its acidic reactant in emulsified form. Generally, capsule coating takes place within seconds to minutes, even in liquid form. However, encapsulation can be roughly completed within just two minutes.

The following methods, such as hardening of the capsule wall, are not essential for the purpose of the invention.

For the purposes of the present invention, it is advantageous to use a coacervation process to encapsulate the solution of the reactants of the color-forming reaction system described above. However, other methods not based on the principle of coacervation are equally effective. I will explain the appropriate method in detail later.

The coacervation method is usually performed as follows. First, an aqueous solution is prepared from an ionizable hydrophilic colloid material (particularly gelatin, gum arabic, CMC, alginate or casein) at about 50°C by selecting at least two types of colloids that can be electrically charged with opposite signs. . If you use gelatin on one side and gum arabic on the other,
Electronegatively charged colloidal ions are obtained above the isoelectric point of gelatin (eg, pH 8). When a solution of the color former to be encapsulated is emulsified in the aqueous colloid solution, an oil-in-water type emulsion is formed. Then lower the pH to about 3.8,
At the same time, water is added to dilute the emulsion, into which extremely dilute aqueous acetic acid or hydrochloric acid is added at 50°C. This reverses the charge of the gelatin molecules to positive, causing the deposition of liquid complex coacervate and forming the walls of the capsule. When the mixture is cooled from 50°C to 6-8°C, gelatinization or setting of the capsule walls occurs. Additionally, crosslinking of gelatin with formaldehyde or glutaraldehyde hardens the capsule walls and creates a stable capsule dispersion. This method is described in US Patent No.
It is described in detail in issue 2800457. It can similarly be used to encapsulate the acidic reactant of the color former.

However, as already mentioned, by simply mixing a solution of a water-immiscible oil-based substance, at least one thermoplastic resin, and water, a color-forming agent for a color-forming reaction system can be produced without relying on coacervation. Another method is to prepare microcapsules by encapsulating a solution of . The water serves to separate the resin from the solution in the form of solid particles surrounding the core of the oily substance mentioned above. This method is described in US Pat. No. 3,418,250. Other suitable encapsulation methods for the present invention include DOS2940786 and
Can be collected from DOS2652875.

In the case of the process known from DOS 2940786, the melamine-formaldehyde precondensate or its C ₁
The condensation of ~ _C4 alkyl ethers in water has been used in which a nearly water-insoluble substance is dispersed and then forms the core of the microcapsule. Condensation takes place in the presence of dissolved polymers containing negatively charged ionic groups at pH values of 3 to 6.5 and temperatures of 20 to 100°C. The characteristic feature of this method is that the polymer dissolved in water is a homopolymer or copolymer with sulfonic acid groups and no phenyl or sulfophenyl groups;
The K value is 100-170, and the shear gradient is 489s ^-1 (20
Viscosity (measured on a 20 wt% solution at °C)
The melamine-formaldehyde precondensate is added continuously or in portions at 200-5000 mPas and as a function of the condensation. This method is easy to control. Therefore, it is easy to determine the optimum amount of water-soluble polymer required by simple routine testing.

It is also advantageous according to the invention to use the method described in EP 0016366, which relates in particular to the production of microcapsules containing a solution of a color former. A solution of color former is encapsulated in an organic solvent in capsules from polyaddition products of specific diicyanates and diamines. First, a suitable diisocyanate is added to a solution of a color former in an aromatic solvent while heating and stirring. This organic layer is then added to an aqueous polyvinyl alcohol solution and emulsified on an ultrasonic blowpipe. A dilute aqueous amine solution is added to this emulsion and stirred. The amounts of amine and diisocyanate are in stoichiometric proportions. Following the addition of the amine, the temperature is raised at room temperature with stirring.

It is clear that the method described above can be subjected to modifications known to the expert without impairing its suitability for the purposes of the invention. Other methods, hitherto undescribed, also suggest that more or less supersaturated fresh solutions of reactants in those color-forming systems, especially carbonless papers, can lead to harmful premature crystallization of dissolved reactants prior to encapsulation. Anything suitable for the purposes of the present invention can be used as long as it is certain that it will be encapsulated or encapsulated within a sufficiently short period of time that it is almost certain that it will not be present. A guideline for the time between the preparation of the supersaturated solution and the formation of individual media droplets upon initiation of encapsulation is a period of about 1 to 60 seconds. If the process is carried out under optimal conditions, it can be reduced to less than this time, which is advantageous.
For example, in the mixing of the starting materials, an optimally concentrated solution of a particular reactant on the one hand, and its non-solvent on the other hand, this can occur in a high speed mixer, such as a stationary tubular mixer placed directly above the emulsifier. , the shorter the processing time, the better. Therefore, it is the encapsulation method that next controls the overall process time. Conventional encapsulation methods generally ensure rapid operation of the process. Coacervation is the preferred method.

The unexpected advantageous effects obtained with the method according to the invention can be explained as follows. Through rapid emulsification with subsequent encapsulation of a fresh supersaturated solution of high non-solvent proportions of reactants, especially carbonless paper color formers, the development of crystallization within the capsules is substantially prevented. This is due, for example, to the fact that the nucleation forces within the capsule or on its inner wall are not sufficient. However, it is conceivable that crystallization also occurs, resulting in microcrystalline or colloidal precipitates that actually correspond to molecular dispersion. In subsequent practical applications, such as capsules containing solutions of color formers in carbonless paper, this dispersion does not cause any disadvantages during the printing operation. However, I would like to emphasize that this is only an explanation of one possibility and not a conclusive explanation of the mechanism of action. Other mechanisms of action may also be at work. However, the important fact is that, apart from established expert opinion, a technically advantageous and especially economically favorable approach has been taken for the use of inexpensive non-solvents according to the invention.

The invention will be explained in more detail with reference to the figures and some embodiments. The figure schematically shows a plant in which the method of the invention can be carried out.
The encapsulation of a coloring agent for carbonless paper will be described. Obviously, this also applies to acidic reactants of color formers. However, in principle the method according to the invention can be used for other substances to be dissolved and encapsulated. According to the figure, a solution of crystal violet lactone in isopropylphenyl (an aromatic solvent) is placed in container 1, while kerosene (an aliphatic or non-aromatic solvent) is placed in container 2. Container 3 contains an aqueous colloidal solution of gelatin, which in turn becomes the capsule wall material. Container 4 contains an aqueous solution of a second colloidal component, gum arabic. The color former solution in the container 1 enters the pump head 13 of the charge system 29 (feed pump) via the pipe 6. In addition to the pump head 13, the charging system 29 has further pump heads 14, 15 and 16. container 2
The non-solvent within is sent via line 7 to pump head 14. From pump heads 13 and 14, the aforementioned substances of containers 1 and 2 enter via lines 17 and 18 into a stationary tubular mixer 19, which constitutes a flow tube. The feed rate of the pump head 13 is set such that the mixing ratio of kerosene to color former solution in the fresh solvent mixture is 3:1 (by weight). This mixture is passed via line 21 to another stationary tubular mixer 22. At the same time, line 20 is connected to pump head 1 of charging system 29.
5 to the stationary tubular mixer 22 with capsule wall material. This is the gelatin and gum arabic solution from containers 3 and 4 which enters container 10 through lines 8 and 9 and is mixed uniformly. The mixture is then passed in the manner described above.

The coarse emulsion produced in the high speed mixer 22 is then passed through line 23, fine emulsifier 24 and line 2.
6 and is supplied to a coacervation container 28. At the same time, the additives necessary for coacervation are transferred from container 5 to line 12 and pump head 1.
6 and a charging system 29 and a line 25 to a coacervation container 28. It consists of an acidic aqueous solution that initiates coacervation. Initially, the capsule wall material in the system created in the coacervation container 28 with the stirrer 27 is still in liquid form, but has already become a liquid surrounding the droplets to be encapsulated.
The time required to create a liquid capsule coating is on the order of seconds at most, eg 15 seconds.

After exiting the coacervation container 28 via outlet 31, the effluent cools from 50°C to approx.
Cooled to 8°C. As a result of this cooling, the capsule wall material solidifies. Approximately 3 of the capsules produced
In order to irreversibly achieve the desired hardness of the walls with a diameter of ~10 μm (microns), the capsule dispersion obtained is subjected to a hardening treatment, for example using a formalin solution in a manner known per se. The means for cooling and hardening are not shown in the figures since they are known.

Methods of the aforementioned type are known and described many times in the literature, see for example US Pat. No. 2,800,457.

The invention will now be described in more detail with reference to embodiments. The materials mentioned herein are processed according to the method previously described in the figures.
That is, the examples merely give the composition of the solution to be encapsulated in oil form.

Example 1 Oils to be encapsulated: 2% crystal violet lactone 0.6% N-benzoylleucomethylene blue 28% partially hydrogenated terphenyl (Santosol 340) 69.4% aliphatic hydrocarbon oil (Shell Shellsol H) 100% Example 2 Oils to be encapsulated: 2% Crystal Violet Lactone 0.6% N-benzoylleucomethylene Blue 40% Diisopropyl Naphthalene 57.4% Industrial White Oil (Paraffinic Process Oil Type - Energol WT 1) 100% Example 3 To be Encapsulated Oil: 2.2% 3-methylspirodinatophthopyran 0.5% N-benzoylleucomethylene blue 25.0% isopropyl biphenyl (Tanacol)
PSG) 72.3% dearomatized, synthetic hydrocarbon oil (Shell
Exsol D 200/240) 100% Example 4 Oils to be encapsulated: 5% color former mixture, reacts to black (Note) 15% isopropyl biphenyl (Tanacol PSG) 80% synthetic hydrocarbon oil (Shell Exsol D 240/
270) 100% (Note) 2-octylamino-6-diethylaminofluorane 3.0% N-benzoylleucomethylene blue 1.2% Crystal violet lactone 0.3% 2-isobutyl-6-diethylaminofluoran bis-[N-octyl-2- Methyl-indolino-(3)]-phthalide 0.2% 5.0%

[Brief explanation of drawings]

The drawing schematically shows a plant in which the invention is implemented. 1, 2, 3, 4 and 5... In the container, 1 is an aromatic solvent, 2... Non-solvent, 3... First colloid solution, 4... Second colloid solution, 5... Addition for coacervation. Agent, 29... Preparation system, 19,2
2... Stationary tubular mixer, 28... Core cell basin container, 31... Outlet.

Claims (1)

[Scope of Claims] 1. A method of encapsulating a coloring agent of a coloring reaction system or a reactant of the coloring agent in an aqueous emulsion by a normal microencapsulation method, the method comprising: first immersing the reactant in a solvent; by dissolving in the solution obtained as described above a non-solvent that dissolves only 0.1 to 0.3% of the color former or the reactant of the color former, and mixing the solution with the liquid phase. The microencapsulation process is carried out by converting into an aqueous emulsion, in which the non-solvent is rapidly mixed into the solution obtained with the solvent in an amount to prepare a supersaturated solution, and immediately thereafter the dissolved color former or A process characterized in that, before the reactant crystallizes, the supersaturated solution is emulsified in a liquid phase and then encapsulated. 2. The method according to claim 1, wherein an aromatic solvent or a chlorinated paraffin is used as the solvent. 3. Process according to claim 2, in which alkylated biphenyl, alkylated naphthalene, alkylated terphenyl or diallylalkane compound is used as aromatic solvent. 4. A method according to one of claims 1 to 3, in which a non-aromatic solvent is used as the non-solvent. 5. Process according to claim 4, in which an aliphatic or cycloaliphatic solvent is used as the non-aromatic solvent. 6. A process according to one of claims 2 to 4, wherein the aromatic solvent or chlorinated paraffin and the non-solvent are used in the form of a non-aromatic solvent in a mixed weight ratio of 1:1 or less. 7. A process according to one of claims 1 to 6, wherein the reactant is encapsulated in the form of a basic color former of a color-forming reaction system. 8. The method according to claim 7, wherein a lactone derivative, a fluoran derivative, a phthalide derivative, a diphenylmethane derivative, a triphenylmethane derivative, or a spiropyran derivative is used as a color former. 9 N-benzoylleucomethylene blue or N
-Alkyl-carbazolyl-diphenylmethane derivatives are additionally used, claim 7
or the method according to paragraph 8. 10. A method according to one of claims 1 to 6, wherein the acidic color-forming reactant of the basic color-forming agent of the color-forming reaction system is encapsulated. 11. The method according to claim 10, wherein an acidic phenolic compound is encapsulated as the acidic reactant. 12. Claims 1 to 11, wherein a coacervation method is used for encapsulation.
One method up to the term. 13. Capsules obtainable by the method according to one of claims 1 to 12. 14. Use of the capsule according to claim 13, which uses an encapsulated solution of a basic color former that develops color by reacting with an acidic color former in a colored reaction paper.