NO131663B - - Google Patents

Description

Procedure for encapsulation of

substances that are finely divided in a liquid.

The invention relates to a method for encapsulation

of substances, especially dyes or pesticides, which are finely divided in a liquid, by means of reactive surfactants, formed on the basis of aminoplast precondensate, where the substance to be encapsulated is dispersed in a dispersing agent in the presence of the reactive surfactant capable of forming an insoluble compound in the dispersing agent, transfers the surfactant in this dispersion to the irreversibly insoluble state while forming a primary capsule suspension, the method being characterized by adding the suspension of

the capsules a solution of aminoplast precondensates with low surface activity, and transfer these aminoplast precondensates in suspension to the irreversibly insoluble state as they are precipitated on.

the capsule wall and hardens to form capsules with reinforced capsule walls.

Here, surfactants are generally understood as substances which are soluble in water or also in organic solvents and which lower the solvent's surface tension and thus act as emulsifiers or dispersants. Surfactant molecules thus have both hydrophobic and hydrophilic groups and have the property of being enriched at the phase boundaries (e.g. oil-water). They form voluminous and stable foams when shaken together with the solvent. In dilute solution, the compounds can reduce the solvent's surface tension considerably. Reactive surfactants are furthermore able under certain conditions, preferably in an acidic environment or at high temperature, to polymerize or to form a network, so that insoluble resinous condensates are formed which no longer have surfactant properties. Particularly reactive surfactants of this type are derived from aminoplasts, preferably urea or melamine-formaldehyde compounds which are substituted with both hydrophobic and hydrophilic groups.

Such reactive surfactants used according to the invention are known, e.g. from French patents 1,065,686, 1,381,811, 1,470,103 and 1,581,989.

Reactive surfactants of this type are excellently suited for the production of finely dispersed systems, including emulsions and dispersions, where the particle diameter is usually on average l^u, preferably even below l^u. Diluted in a suitable way, such dispersions pass through ordinary filters without filter residues, possibly also through hardened filters. Even poorly dispersible substances such as e.g. viscous adhesive solutions can be fine-distributed in suitable devices using such surfactants.

The general property of surfactants to be enriched at the phase boundaries and their ability, especially in an acidic environment, to polymerise, make the surfactants suitable for the encapsulation technique. A method in which finely divided substances are encapsulated using reactive surfactants is known from French patent 1,487,905.

This method has the disadvantage for certain purposes that the capsule walls are not particularly strong, i.e. that they are relatively easily penetrated or mechanically damaged.

It is also known to encapsulate water-insoluble, solid or liquid substances, i.e. to surround them with a resin shell, by dispersing these substances with the aid of a fast-running stirrer in a solution of a primary condensate produced in the usual way by e.g. urea and formaldehyde, which mixture is acidified and stirred continuously while the resin is being formed, whereby the dispersed particles are constantly kept in distribution or confluent and agglomerated particles are constantly torn apart. This known method leads to an unsatisfactory result for several reasons.

Firstly, the dissolution of such primary condensates has a modest dispersing effect so that only relatively coarse particles with at least a few microns in diameter can be produced.

In many cases, however, you want to make the capsules as small as possible because the contents can then be made to work better and more evenly. It should be remembered that already a doubling of the diameter from approx. 1 ^u to 2 ju gives capsules with approx. 8 times as much content, in other words that a capsule with a diameter of 2 yu corresponds to eight capsules with a diameter of 1 yu. The distribution of the active ingredient is thus eight times better with the small capsules.

Secondly, the necessary vigorous stirring required to maintain the distribution of the particles, e.g. when encapsulating specific lighter organic liquids, a smooth and tight surrounding capsule. It is thus difficult and for many purposes impossible to produce capsules with sufficient density and strength.

Thirdly, substances that are relatively difficult to disperse, such as e.g. viscous adhesives, not distributed at all in the usual primary condensate solutions. If one tries to force such substances to disperse by adding emulsifiers of the usual type, one finds that no encapsulation can then be achieved as the emulsifier has occupied the surface of the particles.

However, these disadvantages of the known encapsulation methods are avoided according to the present method, as it has surprisingly been shown that a combination of the known and individually partially unsatisfactory methods leads to a new method that offers unexpected and advantageous results.

According to the invention, one proceeds so that a primary emulsion or dispersion is first prepared, after which this is hardened, i.e. that the reactive surfactant used for the dispersion is transferred to an insoluble resin, after which a secondary resin layer is applied to the relatively thin-walled capsules produced in this way, i.e. reinforces the first capsule wall by adding a solution of a common aminoplast pre-condensate to the formed capsule dispersion and polycondensing the latter. For the production of the first emulsion or dispersion, a powerful mixer is required, while the actual encapsulation, i.e. curing of the reactive surfactant as well as the formation of the secondary second layer can take place practically without stirring, since the particles formed are so small that they are subjected to Brownian movements so that the suspension remains homogeneous even without stirring. This applies in particular when the specific gravity of the encapsulated substance is not very different from the specific gravity of the surrounding solvent.

These are preferably highly surface-active aminoplast precondensates for use as reactive surfactants according to the invention.

Particularly suitable reactive surfactants are methylol group-containing aminoplast precondensates which

a) contains residues of monohydroxy compounds with at least 4 C atoms, and

b-^) residues of a hydroxyl group-containing amine or

bg) residues of a polyethylene glycol or

b^) residues of an alcohol containing at least two hydroxyl groups and residues of Me-O^S groups bound to carbon atoms, where Me

denotes an alkali metal atom or

b^) residues of aliphatic hydrocarbon acids which are bound with the hydroxyl group of the aminoplast precondensate, as well as possibly an amine containing a hydroxyl group,

By aminoplast precondensates from which present reactive surfactants are derived, is meant addition products of formaldehyde and methylolable nitrogen compounds. As such aminoplast formers are highlighted here: 1,3,5-aminotriazines such as N-substituted melamines, of the type N-butylmelamine, N-trihalomethylmelamines as well as ammeline, guanamines such as benzoguanamine, acetoguanamine or also diguanamines. Furthermore, alkyl or aryl urea compounds and -thiourea compounds, alkyleneureas or -diureas, e.g. ethyleneurea, propyleneurea, acetylenediurea or 4,5-dihydroxyimidazolidone-2 and derivatives thereof, e.g. 4,5-dihydroxyimidazolidone-2 which is substituted in the 4-position on the hydroxyl group with the residue -CF^CHgCO-NH-CHg-OH. Preferably, the methylol compound of urea and melamine is used. Particularly valuable products are generally obtained from the most highly methylated products. Both mainly mono-molecular and higher pre-condensed compounds are suitable as starting materials. The aminoplast precondensates that are used as starting products for the production of the reactive surfactants can also be present as ethers of alkanols with 1 -

3 G atoms, especially as methyl ethers.

Highly surface-active etherified methylolmelamines or methylolurea compounds are thus preferred as reactive surfactants.

Among the many reactive surfactants which are suitable for the method according to the invention are non-ionic, anionic and cationic surfactants.

Particularly suitable non-ionic reactive surfactants are e.g. aminoplast precondensates containing curable etherified methylol groups, where the methylol groups are partially etherified with hydroxy compounds of the formula

where n denotes an integer from 2 to 115>°g is partially etherified with a monoalcohol containing 4 ~ 7 C atoms.

Compounds of formula (1) are preferably polyethylene glycols. The monoalcohols are e.g. amyl alcohols, hexanol-(1), 2-ethylbutanol-(1), dodecanol, benzyl alcohol, stearyl alcohol or above all n-butanol.

Of particular interest as reactive surfactants are curable ethers of methylolurea compounds or methylol melamines where the methylol group is partially etherified with a polyethylene glycol with an average molecular weight of 1000 - ^ 000 and partially with an alkanol with 4 - 7 C atoms. Reactive surfactants of this type are described in French patent I.38I.8H.

As reactive surfactants with an anionic character, e.g. aminoplast precondensates which contain etherified methylol groups where the methylol groups are partly reacted with monohydroxy compounds containing at least 4 C atoms and partly with alcohols containing at least 2 hydroxyl groups, and which contain Me-O^S groups which are bound to carbon atoms, where Me denotes an alkali metal atom. Me can therefore be a sodium, potassium or lithium atom, e.g. Particularly suitable surfactants of this type are particularly etherified methylolurea compounds or methylolmelamines where the methylol group is partially etherified with alkanols containing 4 - 18

C atoms and partly with alcohols of the formula H-(0-CH2-CH2)-0H,

where m is an integer of at most 25, and which contains Me-O^S groups bonded to carbon atoms, where Me is an alkali metal atom. Such anionic reactive surfactants are described in French patent no.

I.47O.IO3.

Other interesting reactive surfactants with an anionic character are e.g. aminoplast precondensates containing etherified methylol groups where the methylol groups are etherified partly with monohydroxy compounds containing 4 - 22 C atoms, and partly with aliphatic hydroxycarboxylic acids containing 2 - 4 C atoms, and optionally partly with an alkanolamine containing 2 - 6 C atoms. Among these reactive surfactants, particularly preferred are etherified methylolurea compounds or methylol melamines where the methylol groups are etherified partly with alkanols containing 4-22 C atoms, partly with saturated hydroxyalkanecarboxylic acids containing 2-4 C atoms and optionally partly with ethanol, diethanol or triethanolamine. Such anionic reactive surfactants are described in French Patent No. I.58I.989.

Aminoplast precondensates are preferred as so-called cationic reactive surfactants where the methylol groups are partially reacted with an alkanol or a fatty acid each of which contains at least 4 C atoms and partially with an alkanolamine containing 2-6 C atoms. Particularly suitable representatives for surfactants of this type are methylol melamines where the methylol groups are partially etherified with an alkanol containing 4 - 22 C atoms and partially with ethanol, diethanol or triethanolamine. Cationic reactive surfactants of this type are described in French patent I.065.686.

The production of the primary capsule emulsion is now carried out using a reactive surfactant of the specified type according to the method in French patent 1.487.9^5'

For the production of aminoplast precondensates with low surface activity, one can start from the same aminoplast formers as specified for the reactive surfactants. As an aminoplast precondensate with low surface activity, a methylolmelamine and/or a corresponding methylolurea compound which has been etherified or etherified with alcohols containing no more than 3 C atoms is preferred. Of particular interest are di- to hexa-methylol melamines. In contrast to the reactive surfactants, the aminoplast precondensates with low surface activity form practically no stable foam after mixing and shaking with a solvent. As a rule, such aminoplast precondensates in dilute solution only have an insignificant effect on the surface tension of the solvent.

The production of such aminoplast precondensates is known and takes place in an aqueous medium, e.g. by dissolving 1 mol of urea or melamine in as much water, approx. 37 $ig formaldehyde solution that per 1 mole of urea takes approx. 1.2 - 2 mol, and per 1 mole of melamine approx. 3 ~ 6 m°l formaldehyde. Optionally, the solutions formed are diluted somewhat with water and precondensed at a pH above 8 and a slightly elevated temperature for some time. The aminoplast precondensate solutions prepared in this way are added to the already prepared primary capsule suspensions, taking care to keep the suspension dispersed. Each individual capsule must be freely movable, which is achieved by adding a sufficient amount of water. The secondary resin coating is formed within a few hours at a pH which for urea-formaldehyde is approx. 2.0 and with melamine-formaldehyde is approx. 4>0- Stirring is usually not necessary, but the resin formation can be accelerated by increasing the temperature to 40 ~ 60°C.

When the encapsulation is finished, the pH value can be adjusted to a desired value by adding a base such as ammonia or alkali hydroxide. The capsule masses and suspensions produced contain larger or smaller lumps by combining smaller capsules with mostly less than 1 yu in diameter. Depending on the amount of added aminoplastic precondensates with low surface activity, capsules with different wall thicknesses, different specific gravity and different mechanical strength are obtained.

The added amounts of reactive surfactant, aminoplast precondensate and the type of encapsulated substance can be very different, depending on the purpose of the capsules and the type of encapsulated substance. For encapsulation of liquids, it has proven beneficial per 100 parts by weight of liquid to use 5 to 50 parts by weight of reactive surfactant and 10 to 50 parts by weight of aminoplast precondensate. For encapsulation of solid substances, the lower limit for these amounts is usually somewhat higher, that is, per 100 parts by weight of solid substance is used, e.g. 30 to 50 parts by weight reactive surfactant and 30 to 50 parts by weight aminoplast precondensate. The weight parts reactive surfactant and aminoplast precondensate are naturally calculated here on the basis of dry product.

With the method according to the invention, the transfer of the reactive surfactants or aminoplast precondensates with low surface activity to the irreversibly insoluble state can be started and ended by means of various precautions. Particular mention should be made of raising the temperature, setting specific pH values, adding substances that react with the surfactants and aminoplast precondensates to form high molecular weight products, but in particular the addition of so-called curing catalysts which react acidly.

If the encapsulation is carried out in an aqueous medium, the pH of the preparation is advantageously between 2 - 5 - For setting the pH value, aliphatic low molecular weight carboxylic acids such as formic acid, acetic acid or citric acid, or inorganic acids such as hydrochloric acid or phosphoric acid, further acidic or hydrolysable salts are suitable above all such as aluminum sulphate, titanium oxychloride, magnesium chloride, ammonium salts of strong acids such as ammonium chloride, nitrate, sulphate or dihydrogen phosphate. You can also use oxidizing agents that can oxidize formaldehyde to formic acid, such as e.g. hydrogen peroxide. The acids have proven most beneficial for the purpose.

As already mentioned, water is preferred. as a distribution agent, using a water-insoluble and water-inert substance as a finely divided substance. Conversely, however, you can use organic solvents that are not miscible with water as a dispersing agent and water-soluble substances or aqueous solutions of these as finely divided substances.

Examples of such distribution agents are aliphatic and aromatic hydrocarbons and halogenated hydrocarbons such as benzene, toluene, chlorobenzene, tetra- and deca-hydronaphthalene, trichloroethylene or tetrachlorocarbon.

The quantity ratio of encapsulated compound in relation to the weight of the entire capsule mass can be very different. The amount ratio can be as low as 20% by weight or up to 99% by weight. Preferably, the amount ratio is 70 ~ 95% by weight. Depending on the use, the primary capsule walls can be made more or less strong. The walls can be made harder or softer. The porosity of the capsule walls can also be adjusted as desired.

The finished capsules can, if they are to be used as such, be freed from moisture by filtration and/or drying (e.g. spray drying). The dry capsules form a fine free-flowing powder. They can further be used as suspensions in a liquid, as molded bodies, pressed into tablets, as a coating on a surface or processed in any other way where the capsules are initially retained as such. '■

The capsules are very durable.. Even temperatures of approx. 100°C does not have a destructive effect on the quality of the capsules, provided that no heat-sensitive substances are encapsulated.

The encapsulated, finely divided substances can be released from the capsules in different ways. As a rule, this happens mechanically by breaking the capsule wall as it is pressed into pieces. Furthermore, the substance, above all if it is not volatile, can also be released by dissolving the capsule wall with a suitable solvent, or released by means of shear forces, rubbing, heat, ultrasound, enzymes or slow diffusion through a partially intact capsule wall.

The substances to be finely divided in the capsules according to the invention can be solid, liquid or gaseous substances.

Solid substances must be dispersed in the presence of a reactive surfactant and possibly finely ground so that a stable dispersion occurs.

If the substance to be encapsulated is a liquid, this must not be soluble in the distribution medium, i.e. not be soluble or at least not miscible with the external phase. In general, one can say that the outer and inner phase must be chosen so that significant amounts of one phase are not dissolved by the other, and that unwanted chemical reactions do not take place either. A wide variety of materials can be used as dispersed solids such as pigments, fillers, pesticides, fragrances, fats, waxes, paraffin, fertilizers or pharmaceuticals. Liquid substances to be emulsified can be undiluted, liquid materials, such as e.g. paraffin oil or solutions of liquid or solid substances in suitable solvents. One generally prefers liquid substances that have a high boiling point, i.e. are highly volatile. Phthalic acid dibutyl ester and phosphoric acid tricresyl ester, or chlorinated diphenyl, are mentioned as examples. Furthermore, other water-insoluble solvents, which are less volatile, come into consideration, such as e.g. gasoline, toluene or xylene. Organic solvents that are poorly soluble in water can thus be used for the present invention in two different ways, firstly as a dispersing agent for an internal aqueous phase (water in oil emulsion) or as the internal phase, since the solvent generally contains in dissolved form at least one other substance, e.g. a fat dye, a color former, an adhesive, etc. (oil-in-water emulsion). Similarly, water and aqueous solutions can be considered both as external and internal phases. In an internal aqueous phase, e.g. dissolve salts, dyes or adhesives. It may also be the case, as is the case with fats, waxes or paraffins, that the internal phase that makes up these substances is initially liquid due to a higher working temperature so that an emulsion is present, and then after cooling turns into a solid state. In a similar way, dissolved substances can also crystallize from aqueous solutions in the capsules if the substances are emulsified in a non-aqueous external phase, during or after the process.

Capsules produced according to the invention are particularly suitable for the production of pressure-sensitive copying paper. The dye formers are then optionally encapsulated together with antioxidants or UV absorbers and applied or incorporated into the paper pulp. The color formers, which are usually encapsulated as an organic solution, can e.g. applied to the back of a paper. When pressed, the capsules burst and the color former solution is transferred imagewise to the upper side of an underlying paper which is coated with developer. This procedure is also called the "Chemical-Transfer method.

In the so-called "self-contained" or "Chemical-Self-Contained" method, the encapsulated dye former and the developer are applied to the paper in a single layer so that the upper side of each sheet is permanently active. With so-called "Monoform" papers, the capsules and the developer are incorporated into the paper stock together.

As a developer, e.g. acid-reactive kaolins.

Such papers coated with capsules produced according to the invention are distinguished by great storage stability. After storage for more than 10 hours at 100°C, good, unchanged copies with sharp font edges were obtained.

Quantities and percentages in the following manufacturing regulations and examples are based on weight.

Manufacturing regulations for reactive surfactants.

I. 206 parts 36.5% ±g aqueous formaldehyde, 170 parts n-butanol and 60 parts urea are added to 8 parts 25% ±g ammonia and heated in a stirring flask with an attached cooler for 2 hours at 96°C, whereby all is distilled off 32 parts n-butanol-water mixture..

It cools to approx. 50°C °g one adds 1 part 85% ±g. phosphoric acid dissolved in 20 parts of n-butanol. It is heated in a vacuum at 80°C whereby water and n-butanol distil. The water is separated from the distillate and the n-butanol is fed back into the reaction vessel. After 4 hours the product is practically anhydrous and "miscible with benzene in any proportion. It is neutralized by the addition of 5 parts of triethanolamine and evaporated in vacuo to 212 parts, to a product hereafter called varnish resin A.

212 parts of urea-formaldehyde-butanol-varnish resin A (equivalent to 1 mol of urea) are heated together with 177 parts of polyethylene glycol with an average molecular weight of 1540 at 120 - 130°C until the product is clearly water-soluble. during this, approx. 24 parts butanol. 35 parts of triethanolamine are added and further heated for one hour at 120°C. The formed condensation product is added to so much distilled water that a 50 µg faint yellow clear solution is formed which can be diluted with water in the desired ratio. The product proves to be an excellent emulsifier in an alkaline environment (pH = 9>0) or slightly acidic solution (pH = 5>0)> in a strongly acidic environment it polymerizes, especially at high temperature.

Out of 100 parts, 50 due to surfactant dissolution are formed approx. 6 parts insoluble resin. II. 390 parts of hexamethylolmelamine hexamethyl ether, corresponding to 1 mole of melamine, is heated with 372 parts (2 moles) of dodecanol and 1540 parts (1 mole) of polyethylene glycol of average molecular weight 1540 in the presence of 3'35 parts of 85 $ig phosphoric acid, for 1 hour at 115 - 130° C, and 97 parts of methanol were distilled off in this way. The reaction product was neutralized with 10 parts of triethanolamine.

A waxy, slightly water-soluble surfactant was obtained. The aqueous solutions foam and have an excellent emulsifying and dispersing effect.

III. 212 parts of urea-formaldehyde-butanol-varnish resin A from regulation I (equivalent to 1 mol of urea) are heated with 70 parts of glycolic acid butyl ester and 4 parts of glacial acetic acid in a vacuum at 85 - 90°C until 42 parts of n-butanol have distilled off - Stir for 1 hour further at 100°C under reflux. Finally, the reaction product is diluted with 140 parts of ethanol, 35 parts of solid potassium hydroxide are added and heated for 15 minutes at reflux so that the ester groups are saponified. After evaporation in a vacuum, you have 225 parts of a solid, slightly brownish, slightly water-soluble compound. If some acid is added to the strongly foaming solution, a polymerized product is precipitated which is insoluble in lye. IV. 126 parts melamine is dissolved while adding 18 parts 25 flg ammonia at 59° parts 36.5% aqueous formaldehyde containing methanol at 60°C. It is heated to 80°C and 132 parts of a mixture of methanol and water are distilled in vacuum over the course of 20 minutes. 490 parts of n-butanol are added and further distilled in vacuum whereby the mixture of water and n-butanol that passes through is separated, the n-butanol is returned to the reaction flask while 118 parts of the aqueous layer are discarded. 3 parts of 85% formic acid dissolved in 5 parts of n-butanol are added, and a total of 452 parts of n-butanol are distilled off, removing the last remnants of water. You get 532 parts of a viscous, colorless resin that can be mixed with benzene in any ratio, and is referred to in the following as varnish resin B.

532 parts of melamine-n-butanol lacquer resin B (containing 1 mole of melamine) are heated with 104 parts of triethanolamine with stirring for 1 1/2 hours at 120°C and then for 1'1/2 hours at 135-140°C, and 76 parts n-butanol distills off. After cooling, you have 560 parts of product that is clear and viscous. and easily soluble in 10 flg of acetic acid. The acidic solutions have excellent emulsifying properties. At pH = §, 0 and a somewhat elevated temperature, an insoluble resin is formed. These properties characterize the product as a reactive surfactant. The product has a solids content (solids content) of 80 to 85 f. In 5 volumes of aqueous solution, the reactive surfactant lowers the surface tension of water from 72.75 dyne/cm to 37.6 dyne/cm.

V. 445 parts varnish resin B from regulation IV is added

50 parts polyethylene glycol with average molecular weight §. 000. Heat at 95 - 100°G and add 3 parts glacial acetic acid. The mixture is heated further at 95 ~ 100°C until a sample of the reaction product dissolves until clear in water. 70 parts of trialkanolamine are now added, stirred and heated for 2 hours at 120°C. After cooling, you have a colourless, waxy compound which is easily mixed with water at 60°C. By adding the same amount of water and some acetic acid, you get a 50 flg slightly cloudy surfactant solution with a pH value of 8.1 to 8.2. 15 following aqueous solution, this reactive surfactant causes a reduction of the surface tension in water from 72.75 dyne/cm to §1.0 dyne/cm.

Example 1

1.1 Preparation of the primary emulsion

Dissolve 20.0 g of reactive surfactant from regulation IV in a mixture of 9^.0 g of water and 2.0 g of glacial acetic acid. 200 g of dye solution consisting of 3.6 g of crystal violet lactone is emulsified,

2.4 g of benzoyl-leuco-methylene blue in 97.0 g of chlorinated diphenyl and 97.0 g of paraffin oil, using a rapid stirrer and reactive surfactant solution. The emulsion is set with 400 ml of water and with 6 ml of 85 flg phosphoric acid to a pH value of 2.1. The emulsion's particle size is approx. 1 y-u.

1.2 Curing of the primary emulsion

The primary emulsion is kept for 3 hours at room temperature and 2 hours at 60°C. Adjust with 24 flg of ammonia to pH = 6.0.

1.3 Preparation of the secondary suspension

50.0 g of primary capsule suspension (from 1.2) is diluted with 30 ml of water and, while stirring, a solution of 10 ml of water and 7.0 g of aminoplast precondensate prepared by stirring 2.38 g of melamine and 4.62 g of 37 folg formaldehyde at 60°G is added for 30 minutes. In 5 flg aqueous solution, this aminoplast precondensate lowers the water's surface tension from 72.75 dyne/cm to 57.5 dyne/cm. The foam volume of such a solution after shaking for one minute is practically zero. The suspension is formed for 30 minutes at room temperature.

1.4 Reinforcement of the primary capsules

0.5 ml of 85 flg phosphoric acid is added, the temperature is increased to 40°C and stirred for 30 minutes at this temperature. The mixture is stirred for 1 hour at 60°C and cooled to 20°C. The suspension is adjusted to pH 9>0 with 24% ammonia. The size of the capsules is still approx. 1 yo.

By drying the capsule mass, a very fine powder is obtained. This powder can be redispersed in water and coated on paper. The capsules have practically unchanged quality after more than 300 hours of storage at 100°C, and can be used for the production of copying paper.

In addition to the aminoplast precondensates described under point 1.3, under the same conditions, the following condensates can be used with equal success.

Instead of reactive surfactant according to regulation IV, reactive surfactant according to regulations I to III or V can be used with equally good results.

Example 2

100.0 g of primary capsule suspension after 1.2 is diluted with 55 ml of water and a solution of 20 ml of water and 18.0 g of aminoplast precondensate is added while stirring. The suspension is heated to 40°C, acidified with 0.9 ml of 85% ± g phosphoric acid and stirred for 30 minutes at this temperature. Stir for 1 hour at 65°C and cool to 20°C. With 24% ammonia, the suspension is adjusted to pH 9>°« The particle size of the capsules is approx. 1 yo. These capsules are also gas-tight and can be isolated as powder.

The aminoplast precondensate is produced from the following components:

The individual components are stirred together for 30 minutes at 60°C.

Example 3

75g of primary capsule suspension according to 1.2 is diluted with 45 ml of water and a solution of 15 ml of water and 14.0 g of aminoplast precondensate is added while stirring. The suspension is stirred for 15 minutes at room temperature. 0.7 ml of 85% phosphoric acid is now added, the temperature is increased to 40°C and stirred for 30 minutes at this temperature. Stir for 1 hour at 60°C and cool to 20°G. The suspension is adjusted to pH 8.5 with 24 µg of ammonia. The particle size of the capsules is also this time 1 µm. The capsules are practically gas-tight and can be isolated as powder.

The aminoplast precondensate is produced while stirring.

for 30 minutes at 60°C.

Example 4

4.1 Manufacturing; of primary silt. the ion

30.0 g of reactive surfactant according to regulation V is dissolved in

30 ml water and 0.5 ml 85 flg phosphoric acid. Now 100.0 g of dye solution consisting of 3>6 g of crystal violet lactone, 2.4 g of benzoyl-leuco-methylene blue, 37.0 g of Aroclor and 97 g of paraffin oil is emulsified with a rapid stirrer using reactive surfactant solution. 100 ml of water and 2.5 ml of 85% phosphoric acid are added to the emulsion.

4.2 Curing of the primary emulsion

The primary emulsion is left for 2 hours at room temperature and 1 1/2 hours at 60°C. During curing, a further 100 ml of water is added. Finally, pH = 6.0 is adjusted with 24% ammonia.

4.3 Preparation of the secondary suspension

50.0 g of primary capsule emulsion from 4-2 is diluted with JO ml of water and a solution of 10 ml of water and 10.0 g of aminoplast precondensate (prepared by stirring for 3 minutes of 15.1 g of melamine and 29.25 g of 37 % ig formaldehyde at 60°G). The suspension is stirred for JO minutes at room temperature.

4.4 Reinforcement of the primary capsules

0.5 ml of 85% phosphoric acid is added, the temperature is increased to 40°C and the mixture is stirred for 1 hour at this temperature and for 1 hour at 60°C. The suspension is then cooled to 20°G and adjusted with 24 flg of ammonia to pH 9.0. The particle size of the capsules is approx.

1 yo.

Example 5

50.0 g of primary capsule suspension after 1.2 is heated to 40 C, 30 ml of water and 0.5 ml of 85 fols phosphoric acid are added. A solution of 10 ml of water and 10.0 g of aminoplast precondensate a) is then added dropwise and stirred for 30 minutes at 40°G. A solution of 10 ml of water and 10.0 g of aminoplast precondensate b) is then added and it is stirred for JO minutes at 40° G and 1 hour at 60° C. One cools down

to room temperature and the suspension is adjusted with 24% ammonia to pH 3.0. The capsules' particle size is approx. 1 yo.

Production of the aminoplast precondensate

a) 45>0 g urea and 91.0 g 37 $ig formaldehyde are stirred at pH approx. 7.9 to 8.0 for 1 hour at 80 - 85°C. b) 15.0 g urea, 8l.0 g 37 flg formaldehyde and 5 ml 20 flg triethanolamine are stirred for 30 minutes at 60°G.

Example 6

l80 g 40 flg solution in acetic acid ethyl ester of an adhesive of acrylic acid-n-butyl ester, vinyl acetate and acrylic acid are mixed with 70 g tricresyl phosphate and emulsified with the aid of a high-speed stirrer in a solution of 100 g 50 flg reactive surfactant according to regulation I in 150 g distilled water. The emulsion is then diluted with 500 g of water. The emulsion contains particles of approx. 1px diameter. By evaporation in a vacuum, the emulsion is freed from acetic acid and adjusted to 1100 g of distilled water. By adding 10 g of 85 folg phosphoric acid in 140 g of water, the emulsion's pH value drops to pH 2.0 to 2.5. It is heated to 35°c and the emulsion is kept for 18 hours at this temperature with gentle movement. A solution of 1755 g of urea in 35 g of 37% formaldehyde and 197 > 5 g of distilled water is now added to the formed primary capsule mass, and the mixture is stirred for 30 minutes. The secondary capsule mass reinforced in this way is neutralized by the addition of ammonia. The mass is transferred to paper and a smooth, non-sticky surface is obtained. If the coated paper is pressed against a substrate, the capsules are crushed, and an intense adhesive effect is quickly formed. The capsules consist of approx. 88 f adhesive and 12 f resin coating.

Example 7.

30 g of styrene-butadiene copolymer is dissolved in 70 g of toluene and 44 g of dioctyl phthalate and 6 parts of Sudan Black G are added to the solution. The viscous dye solution produced is emulsified in a solution of 110 g of 50 flg of reactive surfactant according to regulation V and 80 g of water which is with the help of 85 flg of phosphoric acid have adjusted to pH 5>5 to 6.0. The emulsion is formed using a rapid stirrer and adjusted with 450 g of distilled water and a further 85 g of phosphoric acid at pH 2.0. It is gradually heated with stirring to 60 to 65°G and the emulsion is kept for 1 1/2 hours at this temperature, during which the surfactant "hardens". It is cooled to 20°C and a further 1600 g of water and 40 g of a solution prepared by dissolving 13.8 g of melamine in 26.2 g of 37% formaldehyde at 60°C are added. Stir slowly for 3 hours, during which the temperature rises from 20 to 60°C. Cool to 20°C, filter off the capsule mass and disperse the filter cake in enough 3% polyvinyl alcohol solution to obtain 1000 g of thin paste. When the paste is applied to paper, a dark-coloured rub-resistant coating is obtained which has a black copying effect on all other types of paper.

Example 8.

100 g of pigment dye of diazotized 1-amino-2-methyl-4-chlorobenzene, coupled with 2-hydroxy-naphthalene-3-carboxylic acid-2'-methyl-4'-chlorophenylamide, finely divided in a ball mill in 400 g of 10% solution of reactive surfactant according to regulation II, in such a way that the dispersion, after dilution with water to 1250 g, passes through filter paper. So much phosphoric acid or formic acid is added to the diluted pigment suspension that the pH value drops to 2.5. The mixture is allowed to stand for 2 hours at room temperature and then stirred at 60°C for 2 hours. Cool to 20°C and add a solution of 22.5 g of melamine in 56 g of 37% formaldehyde, as well as 171.5 g of water, and set the pH, which has been increased to 5.0 by the addition, back to the value 4.0 with acid. With careful stirring, heat to 60°C and hold for 3 hours at this temperature. The encapsulated pigment suspension can be neutralized with ammonia before it is filtered off, washed and dried. You get approx. 140 g of fine-grained pigment powder with strong colour, which, compared to the raw pigment, has a clearly improved oil fastness (insolubility in organic solvents). You get a similar result if you use reactive surfactant according to regulation III instead of reactive surfactant according to regulation II, and proceed as indicated in the example.

Example 9.

Dissolve 30.0 g of reactive surfactant according to regulation IV (80 to 85%) in 143.0 g of water and 3.0 g of glacial acetic acid. The aqueous solution is emulsified with 2000 g of 3% dye solution (prepared from 36.0 g of crystal violet lactone, 24.0 g of benzoyl methylene blue, 970.0 g of "Arochlor" and 970.0 g of paraffin oil). During the emulsification, care must be taken that the temperature does not rise above 25°C

400 ml of water and 10.1 g of 85% phosphoric acid are then added to the emulsion. The emulsion is allowed to stand at room temperature for 2 hours and then it is stirred for 1 1/2 hours at 60°G. Finally, the pH is adjusted to 6.0 with 24 µg of ammonia and the suspension is diluted with 480 ml of water.

Production of aminoplast precondensate

54)6 g of melamine and 105.0 g of formaldehyde (37% strength) are stirred for 30 minutes at 60°G. The clear solution is diluted with 160 ml of water.

The condensate solution is now dripped over the course of 10 minutes to the primary suspension, stirred for JO minutes at room temperature and acidified with 8 ml of 85 µg phosphoric acid. The suspension is stirred for 10 minutes at 40°C and 1 hour at 60°C. It is cooled to room temperature and the pH is adjusted to 9>0 with 24% ammonia. The suspension is filtered off and the filter residue is dried overnight at 65°C in a vacuum drying cabinet.

Yield: 267.8 g capsule powder.

Hence are:

200.0 g dye solution = 74.7%

67.8 g capsule mass = 25.3%.

Example 10

With capsules prepared as in example 1, a coating compound with the following composition is made:

1000 g capsule mass according to example 1

60 g denatured starch (as binding agent)

200 g of water

10 g of sodium carboxymethyl cellulose (thickening agent).

The viscosity of the coating mass is 150 centipoise.

In a laboratory coating machine, cellulose paper is applied to this mass in a coating weight of 6 g/m .

You get a pressure-sensitive paper according to the "Chemical Transfer" method with good storage stability, which gives through printing on a base paper coated with acid-reactive. kaolin, and the writing edges become precise and sharp. Even after storage at 110°G for over 60 hours, the quality of the copy print is not significantly affected. With the same coating mass, pressure-sensitive paper of good quality can also be produced for the so-called "Ghemical-Self-Contained" method.

With consistently good results, you can use prepared capsules

according to example 5'

Example 11

a) Dissolve 15 g of reactive surfactant according to regulation IV in 72 g of water and 1.5 g of glacial acetic acid. The aqueous solution is emulsified with a

solution of 15 g of 2,4>4'-trichloro-2'-hydroxydiphenyl ether in 85 g of "Arochlor". The emulsion is diluted with 200 ml of water and acidified with 3 ml of phosphoric acid (85%). The emulsion is allowed to stand for 2 hours at room temperature and then stirred for 2 hours at 60°C. Finally, pH is adjusted to 6.0 with 24% ammonia. b) 100 g of the above primary suspension is diluted with 100 ml of water and a solution of 20 g of aminoplast precondensate according to 1.3 in 60 ml of water is added while stirring at room temperature. The suspension is stirred for 1/2 hour at room temperature and the pH is adjusted to 4.6 by adding 0.5 ml of phosphoric acid (85% ig) • The reaction is terminated by stirring for 1 hour at 40°C and a further 1 hour at 60°C . The capsule suspension is then cooled to room temperature and adjusted to pH = 7 with concentrated ammonia. By filtering the suspension, a capsule mass is obtained which is dried in a vacuum cabinet at 60°C. Under the same conditions, a solution of 5 g of hexachlorophene can be encapsulated in 95 g of "Arochlor".

Example 12

a) Dissolve 30 g of reactive surfactant from regulation IV in 160 g of water and 1.5 g of glacial acetic acid. The aqueous solution is emulsified with JO g

tri-n-butyl phosphate. The emulsion is diluted with 35 ml of water and adjusted with a solution of 6 ml of concentrated phosphoric acid in 5 ml of water at pH 3.1. The emulsion is then stirred for 1/2 hour at room temperature and 1 1/2 hours at 4°C>°g and finally 2 hours at 60°C. The mixture is allowed to cool to 25°C and adjusted to pH 6.0 with

12 ml of concentrated ammonia.

b) To 200 g of primary suspension prepared according to a), add 7 g of aminoplast precondensate according to 1.2 in 10 ml of water during 5 minutes at room temperature and stirring. The mixture is stirred for 1/2 hour at room temperature, adjusted to pH = 3)4 with 3.4 ml of concentrated phosphoric acid (85%) and stirred for 1 hour at 40°C and finally 2 hours at 60°C. The reaction mixture is then cooled to approx. 25 - 30°C, and adjusted with 12.6 ml of concentrated ammonia at pH = 8.0.

After filtering the suspension, a capsule mass is obtained

which is dried in a vacuum cabinet at 60°C.

In the same way, one can also encapsulate a solution of 0.9 g of crystal violet lactone in 29.1 g of tri-n-butyl phosphate, or a solvent mixture of trichloroethyl phosphate and trichlorobenzene.

Example 13

a) Dissolve 25 g of reactive surfactant according to Regulation IV in 125 g of water and 2.5 g of glacial acetic acid. The aqueous solution is emulsified with 100 g

tris-(2,3-dibromopropyl)-phosphate. The emulsion is diluted with 500 ml of water, stirred for 1/2 hour at room temperature and adjusted with 10 ml of concentrated phosphoric acid (85%) to pH 3.2. The emulsion is then stirred for 1/2 hour at 25°G, 3/4 hour at 40 °C and 2 hours at 60°C. After cooling to 25°C, the suspension is adjusted to pH = 6.0 with 18.0 ml of concentrated ammonia. b) 800 g of primary suspension according to a) is diluted with 100 ml of water and 100 g of aminoplast precondensate according to 1.3 in 100 ml of water is added within 10 minutes, at room temperature and while stirring.

The suspension is stirred for 1/2 hour at room temperature and adjusted with concentrated phosphoric acid to pH 3.0. It is then stirred for 1/2 hour at 25°C, 1 hour at 40°C and 1 hour at 60°C. After cooling the suspension to 25 C, the pH is adjusted to 6.0 with concentrated ammonia. The suspension is filtered and a capsule mass is obtained which is dried in a vacuum cabinet at 60°G.

Example 14

100 g of reactive surfactant according to regulation I is diluted with 100 g of water and 260 g of oil is emulsified in this using a high-speed stirrer. The emulsion is diluted with further water to 2500 g. The diameter of the oil droplets is at most 1 µU. By adding 85% ±g H^PO^, the emulsion's pH value is set to 3>5°g, heating for 2 hours at 60°C, whereby stirring is done rather weakly or not at all. A solution of 33 g of urea and 87.5 g of 37% formaldehyde is then added, the pH value is set by adding more acid to 3>0 and the emulsion is stirred for 4 ~ 6 hours at 60°G. The capsule mass is filtered off and washed with distilled water. No free oil can be detected in either the filtrate or the wash water, so that the encapsulation has been practically complete. The capsule mass is then dried at normal or slightly elevated temperature, e.g. 60°C. You get a solid, colorless powder that contains over 80% oil and e.g. can be used as solid fuel.

Claims (1)

Process for encapsulating substances, especially dyes or pesticides, which are finely divided in a liquid, by means of reactive surfactants formed on the basis of aminoplast precondensate, where the substance to be encapsulated is dispersed in a distribution medium in the presence of the reactive surfactant which is able to form an insoluble compound in the distribution medium, the surfactant in this dispersion transfers to the irreversibly insoluble state while forming a primary capsule suspension, characterized by adding a solution of aminoplast precondensates with low surface activity to the suspension of the capsules, and transferring these aminoplast precondensates in the suspension to the irreversibly insoluble state, as they precipitate on the capsule wall and harden while forming capsules with reinforced capsule walls.