DE2453852A1 - METHOD OF ENCAPSULATING SUBSTANCES NOT MIXABLE WITH WATER - Google Patents

Description

CIBA-GEIGY AG. CK-4002 Basel

CIBAR GEIGY

Case 5-9107 / + ■ Germany

■ Dr.-F, Zumstein sen. - Dr. E. Assmann Dr.R.Koenigsberger - Dipl. Phys. R. Holzbauer

Dr. F. Zumsisin jun.

Patent attorneys

8 Munich 2, Bräuhausstraße 4 / III

Process for the encapsulation of water immiscible

Substances

The invention relates to a method for encapsulating substances immiscible with water, characterized in that the substance to be encapsulated is present in a distribution means

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a) a water-soluble, surface-active, polymeric, polyfunctional compound, which has primary amino, imino, hydroxyl and / or thiol groups,

dispersed and component a) of this dispersion with

b) an aqueous compound capable of forming a compound which is insoluble in the distribution agent Solution of a polyacrolein or acrolein copolymer present as a hydrate or bisulfite adduct and

c) optionally additionally with a hardening agent or an aminoplast precondensate

reacted to form an insoluble capsule material.

The present method uses a two-phase system, consisting of a liquid outer phase, which is referred to as the distribution agent, and a fine to be distributed, immiscible with the outer phase, encapsulated substance, which represents the inner phase,

and a surface-active, polymeric /
/ polyfunctional compound a), which serves the state.

to produce and maintain the fine distribution.

The preferred distribution agent is an aqueous one Medium, so for example water, used in which the surface-active compound a) and optionally other Substances are dissolved.

Substances to be finely distributed according to the process according to the invention are solid, liquid or gaseous substances as well as substance solutions into consideration,

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which are insoluble in water and with water as well as with the the substances that make up the capsule wall do not react. Solids must be in the presence of the surfactant compound a) dispersed and optionally comminuted by grinding to such an extent that a stable dispersion is produced can be.

A wide variety of active ingredients can be used as dispersible solids, for example pharmaceutical products including growth hormones and vitamins, cosmetics, pigments, dyes, color formers, optical brighteners, textile auxiliaries, textile protection or finishing agents, fillers, waxes, fertilizers, plant regulators, pesticides such as insecticides, fungicides, Antimicrobials, bio-oids, such as, for example, tick-killing agents, also synthetic polymers, fragrances and aromas, photochemicals, water-insoluble metal oxides, such as magnetic iron oxide ^ water-insoluble salts, etc., which can be used as adhesives.

If the substance to be encapsulated, i.e. the inner phase, is a liquid, including? Substance solutions are understood, they may, as already mentioned, in the distribution medium, i.e. in the outer phase, not soluble or at least not miscible with it. . In general it can be said that the outer and the inner Phase should be chosen so that neither substantial amounts

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the one phase detached from the other is still undesirable chemical reactions take place.

As liquid substances to be emulsified, undiluted liquid active ingredients or solutions can be used solid active ingredients in suitable organic solvents come into consideration. In general, liquids are preferred Substances that have a high boiling point or are of low volatility. However, the process also allows low-boiling points Encapsulate liquids.

Examples of liquid substances are petroleum fractions such as kerosene and naphtha, unbranched and branched, optionally halogenated paraffins, aromatic, optionally halogenated hydrocarbons such as benzene and alkylbenzenes, e.g. toluene, xylene, chlorobenzene, dichlorobenzene, Trichlorobenzene, benzyl chloride, benzal chloride and analogous bromine compounds, alkylated di- and polyphenyls, hydrogenated terphenyls such as hexa- and dodecahydro-terphenyl, halogenated di- and polyphenyls such as chlorinated diphenyls and polyphenyls, diphenyl diphenyl ether mixtures such as diphenyl diphenyl oxide mixtures, Methylenediphenyl, alkyl and hydronaphthalenes, phosphoric acid esters such as tributyl and tricresyl phosphate, alkylated, optionally halogenated cycloaliphatics, esters of higher fatty acids such as ethyl myristate, Ethyl oleate, ethyl palmitate, vegetable oils such as corn oil, soybean oil, Olive oil, coconut oil, palm oil, castor oil, peanut

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oil, rapeseed oil, sunflower oil, hemp oil, linseed oil, cottonseed oil, animal oils such as fish and whale oil, mineral oils, Silicone oils or sperm oil,

Component (a) is suitably a polymerizate with protective colloid character, which is made with polyacrolein can react. These polymers, which are surface-active and water-soluble, are opposed to carbonyl functions reactive by having hydroxyl, thiol, imino or primary amino groups.

Accordingly, proteins, cellulose, cellulose derivatives or synthetic polymers with protective colloid properties are preferably used as component (a); " ¹ ""

The synthetic polymers are e.g. polyvinyl alcohol, polyallyl alcohol, polyhydroxycarboxylic acids (e.g. by Cannizzaro reaction from polyacrolein available), polyalkylenimines, polyvinylamine hydrochloride or poly-p-aminostyrene hydrochloride.

Suitable polyalkyleneimines are polymers of an alkyleneimine having 2 to 4 carbon atoms that have a molecular weight from 500 to 80,000, preferably 10,000 to 40,000. These polymers usually have a Brookfield viscosity at 20 ° C from 500 to 20,000 centipoise (cp). ' Polyethyleneimines, in particular, are used as polyalkyleneimines, Polypropyleneimine, poly-1,2-butyleneimine and poly-2,3-butyleneimine into consideration. Of all polyalkyleneimines, polyethyleneimine is preferred.

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Cellulose and cellulose derivatives such as partially etherified or esterified cellulose also come into play Consider, e.g. cellulose acetate, methyl or ethyl cellulose.

Components a) used with preference, however, are protein substances, in particular ski protein such as gelatin or gelatin-like products, for example gelatin glue, glutin, tendon collagen, collagen breakdown products, Albumins such as blood albumin, egg albumin, serum albumin, globulins, catalase, casein, isinglass such as isinglass " glue and fish glue obtained from fish bones and cartilage, protamines such as salmin and clumps; these polymers can be used as such or chemically modified, e.g. cross-linked with azetidinium compounds. the named polymers contain both free amino and carboxyl groups. This is how they react with gelatine, for example and gelatin-like products, the c-amino group of lysine, the amide flu of an asparagine building block and / or the guanidine group an arginine unit with the carbonyl functions of the polyaciolein component. As far as the polymers are difficult are water-soluble as in the case of casein, solutions in the presence of alkali, e.g. alkali metal hydroxides or carbonates or of tertiary amines and these are used as such. In the protein-polyacrolein system, especially gelatine-polyacrolein, are highly

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hardened but not fragile capsule materials. Gelatin and gelatin-like products are therefore in the foreground of interest.

Component b) is preferably an aqueous solution of a bisulfite adduct Polyacrolein or an acrolein copolymer.

It is particularly advantageous to use the polyacrolein component the solutions of polyacrolein in aqueous sulphurous acid or in aqueous bisulphite solution, in particular Sodium bisulfite solution.

The polyacrolein bisulfite solutions used in the process according to the invention are expediently prepared by introducing sulfur dioxide into aqueous suspensions of polyacrolein, preferably at room temperature, for 1 to 12 hours. However, polyacrolein bisulfite solutions obtained by dissolving polyacrolein in aqueous sodium hydrogen sulfite solution are also suitable for producing the emulsions. In the bisulfite solutions polyacroleins is weight usually the sulfurous acid adduct with the hydrated form of Polyacroleins in equilib->. '

If the presence of sulphurous acid interferes with reactions with sensitive hydrophilic compounds, this can be removed by dialysis, ion exchange or oxidation with air. The polyacrolein does not work here

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in the insoluble state, but remains as reactive, stable polyacrolein hydrate in solution.

A suitable polyacrolein is, for example, the disacryl known from the article by J. Redtenbacher, Liebigs Ann., Chem. 47 (1943) 113, a polymer formed on destabilized acrolein under the action of light, heat or catalytic amounts of oxygen with average molecular weights between 60,000 and 300,000. In particular, however, radical polymers of acrolein with average molecular weights between 500 and 300,000, preferably between 15,000 and 100,000, are used, which are produced in particular by redox polymerization of acrolein in an aqueous medium - depending on the desired molecular weight in the absence or presence of emulsifiers such as For example sodium oleate, polyethylene oxide, sodium polyvinyl sulfonic acid or polyacrolein bisulfite can be obtained.

In the absence of emulsifiers, average molecular weights between and 100,000 can be achieved, depending on the reaction conditions, while in the presence of the abovementioned emulsifiers, average molecular weights between; 100000 and 300000 are available.

In the process according to the invention it is also possible to use copolymers of acrolein with other copolymerizable vinyl compounds. Acrylamide, vinyl acetate, styrene and acrylonitrile, for example, are suitable as comonomers.

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The component ratio in these copolymers can be chosen as desired, provided that the copolymers are still in aqueous sulphurous acid or in alkali metal bisulphite solution with adduct formation are soluble.

Preferred copolymers obtained by copolymerizing acrolein with the comonomers mentioned Redox systems are obtained in an aqueous medium E.g. the following compositions:

63 mole percent acrolein / 37 mole percent acrylamide 80 mole percent acrolein / 20 mole percent vinyl acetate 53 mole percent acrolein / 47 mole percent acrylonitrile 66 mole percent acrolein / 34 mole percent acrylonitrile

The carbonyl group content of the invention usable polyacrolein or acrolein copolymer solutions is 20 to 100 mol percent, preferably 50 to 80 mol percent, based on the dissolved polyacrolein.

The capsule material obtained as a dispersion can optionally be post-cured with component c) or else be strengthened by re-encapsulation. Halogenated aliphatic compounds can optionally be used for additional post-curing Carbonyl compounds with preferably 1 to 6 carbon atoms can be used as curing agents. Suitable carbonyl compounds are, for example, monoaldehydes such as formaldehyde, Acetaldehyde, propionaldehyde, acrolein and dialdehydes such as

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Glyoxal, methylglyoxal, glutaraldehyde and mucochloric acid.

Ketone compounds, e.g. dihydroxy ketones such as dihydroxyacetone, can also be used as hardening agents. 1,2- and 1,4-diketones such as cyclohexanedione-1,2, also quinones, Trioxane, tetroxane, hexamethylenetetramine, dianhydrides of tetracarboxylic acids, multifunctional methanesulfonic acid esters, Compounds with several reactive vinyl groups, such as Vinyl sulfones, acrylamides, compounds with at least two easily cleavable heterocyclic rings such as ethyleneimine and ethylene oxide and the azetidinium compounds described in U.S. Patent No. 3,634,399. One can the effect of the low molecular weight hardeners mentioned can be increased by adding known hardening accelerators, as described, for example, in German Patent No. 837 955.

In addition to the low molecular weight hardeners listed above, high molecular weight e.g. polyaldehydes can also be used like the periodic acid oxidation products of starch, as well as Metal salts such as chromium aluminum and zirconium salts are used. Hardening with metal salts leads to a certain brittleness and reduced stickiness of the capsule materials.

The capsule material present in aqueous dispersion can, if desired, be reinforced. For this aminoplast precondensates are suitable, especially urea-formaldehyde or melamine

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Formaldehyde condensates. .

The production of such aminoplast precondensates is known and takes place, for example, by dissolving 1 mole of urea or melamine in an aqueous, approximately 37% formaldehyde solution, that for 1 mole of urea 1.2 to 2 moles, for 1 mole of melamine about 3 up to 6 moles of formaldehyde are not required. If necessary, the resulting solutions are slightly diluted with water and precondensed for some time at a p "value above 8.0 and a slightly elevated temperature. The aminoplast precondensate solutions obtained in this way are added to the component (a) -substrate emulsion or the already pre-formed primary capsule suspension, it being important to ensure that the dispersity of the suspension is retained. Each capsule must be able to move freely, which is ensured by adding a sufficient amount of water. The resin shell is formed within a few hours at a p "value, which is around 2.0 for urea-formaldehyde and between 4 and 6 for melamine. As a rule, stirring is not necessary. Resin formation can be accelerated by increasing the temperature to 40 to 60 ^{° C.}

The amounts used in the present process ■

required substances can vary within wide limits, depending on Purpose and the requirements placed on the capsule material as well as the type of substances to be encapsulated.

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For the encapsulation of liquid substances, it has proven to be expedient to add to 100 parts by weight of liquid 33.5 to 335 parts by weight, preferably 67 to 200 parts by weight of 15% strength aqueous solution of component (b) to be used. Dias corresponds, for example, to an amount of solid polyacrolein from 5 to 50 parts by weight, preferably 10 to 30 parts by weight per 100 parts by weight of the encapsulating Liquid.

Under 15% polyacrolein bisulfite solution is understood a solution that is 15 percent by weight of polyacrolein, not counting the one used to make the Solution required SO ^ amount, which should be dosed in such a way that clear solutions are created. Generally moved this amount is between 1 and 16 percent by weight SO2 in the solution. However, it is preferably between 2 and 10 percent by weight.

The amount of component (a) is also expediently 5 to 50 parts by weight, preferably 10 to 30 parts by weight to 100 parts by weight of the liquid to be encapsulated. In the case of solid substances to be encapsulated, the lower limits of the quantities used for components (a) and (b) are generally somewhat higher than specified for liquids. For 100 parts by weight of solid there are, for example, etx ^ a 35 to 335 parts by weight, preferably 80 to 200 parts by weight of the 15% solution of component (b), which is e.g. a polyacrolein solids amount of 6 to 50 weight

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share, preferably 12 to 30 parts by weight. the The amount of component (a) ranges between 6 and 50 parts by weight, preferably 8 and 30 parts by weight per 100 Parts by weight of solid. The proportion of the to be encapsulated Substance in the total capsule mass can be 50 to 95 percent by weight, preferably 60 to 90 percent by weight.

For encapsulation, the substrate provided as the capsule content is emulsified in the solution of component (a), diluted with water and then mixed with an aqueous solution of component (b). Encapsulation takes place advantageously at p "values in the range from 2 to 10, but preferably at p" values between 5 and 8. The polyacrolein (bisulfite) gelatine system is preferably encapsulated in the p "range of 8 to 10 In this case, the polyacrolein bisulfite solution is expediently adjusted to the specified value with triethylamine and this solution is preferably used immediately. The erfindungsgem'äss usable polyacrolein bisulfite solutions are stable at p "values below 10, and up to 80 ⁰ C. The reaction temperature is generally between 5 and 80 ° C. Preferably, the encapsulation is to be performed at 20 to 60 ⁰ C.

The polyacroleine-Bisülfitlösungen are made with sulfur dioxide, kept closed, virtually indefinitely and have, depending on the SO ^ content, a p _H 1 to 4 to set the for encryption

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encapsulation desired p "values" are particularly suitable Alkali metal hydroxides, bicarbonates and carbonates. In particular, however, tertiary bases, e.g. tertiary amines such as triethylamine, triethanolamine and pyridine, etc. used. . · '

The capsule material is formed immediately after component (a) - substrate emulsion has been combined and component (b), the order of the union being irrelevant. The capsule formation is Result of a precipitation reaction in which the polyacrolein bisulfite or hydrate [crosslinker component b)] with component (a) to one in the external as well as internal Phase insoluble polymers' compound is reacted, with co-crosslinking a capsulex ^ and forming Composite polymer is formed. By adding small amounts of aliphatic carboxylic acids with 1 to 6 carbon atoms such as formic acid, acetic acid, oxalic acid or citric acid can catalyze the crosslinking reaction will. Acid hydrolyzing salts are also suitable.

<■ The finished capsules are isolated by filtering and drying or by spray or freeze drying. The dry capsules form a fine, free-flowing powder.

Depending on the starting materials used, in particular the hydrophilic, polyfunctional emulsifier

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component (a) can be gas-tight or capsules with microporous and thus made a permeable capsule wall. will. In the latter case, the capsules are liquid-tight, but not gas-tight. The gas tightness can be obtained by adding the encapsulation of hardening agents. By setting the specific gravity of the substance to be encapsulated, for example by adding suitable solvents, non-sedimenting microcapsules can be produced which can be of great importance for certain application purposes.

The capsules obtained can be dispersed in a liquid, compressed into tablets, as surface coatings or processed in any other way in which the capsules are initially received as such stay.

The capsules are usually colorless and have a very long shelf life. Even temperatures of about. 10O ⁰ C do not have a disruptive effect on the capsule quality, provided that no heat-sensitive substances have been encapsulated. The encapsulated substance can be released from the capsules in a number of ways. Usually this is done mechanically by breaking the capsule wall by applying pressure to it. Destruction of the capsule wall and

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thus release of the contents can also be achieved by shear forces, friction, heat, ultrasound or enzymes. If the capsule wall has a microporous structure, the encapsulated substrate can also move by diffusion released outside.

Those produced by the process according to the invention Microcapsules usually have a particle diameter of 1 to 500 μ, preferably 1 to 20 μ. They are particularly suitable for the production of heat- and pressure-sensitive copier papers and recording materials. Color former solutions, if necessary together with * antioxidants and / or UV absorbers, encapsulated and the capsule mass applied to paper or incorporated into the paper mass. Capsules with color former solutions can e.g. be applied to the back of a paper. The capsules are ruptured by pressure and the color former solution is image-wise transferred onto the top of an underlying paper covered with a Developer is coated. This process is called "chemical transfer".

In the so-called "chemical self-contained process" the encapsulated color former and the developer are applied in one layer on the paper, so that the top of each sheet is permanently active. In the case of so-called "monoform" papers, the capsules and the

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Developer incorporated together into the paper pulp. For example, acidic kaolins are used as developers. Papers of this type coated with the capsules produced according to the invention are distinguished by excellent properties Storage stability. After storage for more than 5 Hours at 100 ° C., copies of good quality with sharp, non-smeared edges are obtained.

Percentages in the following manufacturing instructions and examples relate to weight.

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example 1

8 g of edible gelatin are dissolved in 70 ml of distilled water while heating to 50 ^° C. until clear. In this solution, 50 g of a 4% color former solution, consisting of 1.2 g of crystal violet lactone, 0.8 g of benzoyl-leukomethylene blue, 24 g of chlorinated biphenyl and 24 g of paraffin oil (low viscosity) are emulsified up to an oil droplet size of about 1 to 6 μ in diameter is achieved. The emulsion is then diluted with 1 liter of water. The p “value of the solution is 5.3. 48 g of a 14.6% polyacrolein bisulfite solution (average molecular weight of the polyacrolein: 23400; SOr, content: 7.1%) which have been made to Pu 5.3 with 41.5 ml of 5% aqueous sodium hydroxide solution now stirred in and the batch is precured for one hour at room temperature with stirring. Then it is adjusted to p "7.5 with 10 ml of 5% strength aqueous sodium hydroxide solution and post-cured at 40 ° C. for 22 hours.

After spray drying at an inlet temperature of 150 ° C., 59 g of a discrete microcapsules are obtained existing capsule preparation with a particle diameter between 2 and 10 μ, which is excellent for Carbonless and copier papers are suitable.

Example 2

12 g of casein are pre-swelled in 70 ml of distilled water for 12 hours and then heated to 50 ° C while stirring, with the occasional addition of a little triethylamine, until a solution is formed that no longer contains any gel particles. Then 60 g of a 3% color former solution, prepared by dissolving 10.8 g of crystal violet lactone and 7.2 g of benzoyl leukomethylene blue in 582 g of chlorinated biphenyl are emulsified in a high-speed mixer and then the emulsion is emulsified with 400 ml of distilled water of 40 ° C diluted. In a beaker, 68.5 g of a 14.6% strength Polyacroleinbisulfit solution (average molecular weight of the Polyacroleins: 23400; S0 ₂ content: 7.1%) were charged, diluted with 400 ml of distilled water at 40 ⁰ C and the solution then adjusted to p "7.4 with 70 ml of 5% strength aqueous sodium hydroxide solution. The color former emulsion is then allowed to run in rapidly while stirring and it is cured for 22 hours at 60 ^° C., the p n value being kept at 7.5. After spray drying at an inlet ^{temperature of 150 °} C., 82 g of a colorless, free-flowing capsule preparation consisting of discrete microcapsules with a particle diameter between 2 and 15 μg, which is well suited for the production of carbonless and copier papers.

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Example 3

11 g of commercially available isinglass glue are pre-swollen in 60 ml of distilled water for 12 hours and then dissolved with stirring and heating to 50 ^° C. with the addition of a little 5% aqueous sodium hydroxide solution. Insoluble residues and impurities, which are present in small amounts, are separated off by filtration under reduced pressure. The p “value of the solution is 7.4. Then 60 g of a 4% color former solution, prepared by dissolving 18 g of crystal violet lactone and 12 g of benzoylleuco-methylene blue in 360 g of chlorinated biphenyl and 360 g of paraffin oil (thin), emulsified in the glue solution with the aid of a high-speed stirrer and dilute the emulsion with 400 ml of distilled water at 40 ° C. Then, while stirring, 67.5 g of a 14.8% polyacrolein bisulfite solution (average molecular weight of the polyacrolein: 15,000; SO ₂ content: 6.1%), which was previously increased to pH 7.5 with 5% sodium hydroxide solution admitted. After 20 hours of curing at 50 ⁰ C is spray-dried at an inlet temperature of 150 ⁰ C, whereby 76g of a colorless, pulverulent capsule preparation consisting ju from discrete microcapsules having a particle diameter of between 2 and 10, be obtained for the production of write-through and Copy papers

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Example 4

30 g of commercially available isinglass made from fish bones and cartilage with a dry content of 58% are diluted with 20 ml of distilled water. Then 50 g of a color former solution consisting of 24 g of chlorinated biphenyl, 24 g of paraffin oil (low viscosity), 1.2 g of crystal violet lactone and 0.8 g of benzoyl leukomethylene blue are emulsified therein. After diluting the emulsion with 600 ml of distilled water, 68.5 g of a 14.6% polyacrolein bisulfite solution (average molecular weight of the polyacrolein: 23,400; SO ₂ content: 7.1%), the one with 5% aqueous sodium hydroxide solution is adjusted to p _H 5.9 and is diluted with 400 ml of distilled water were stirred in. While stirring is precured for one hour at 40 ⁰ C, then treated with 5% aqueous sodium hydroxide solution to Pu provided 7.5 and postcured this p "during 22 hours at ·. After spray drying at an inlet temperature of 150 ^° C., 73 g of a capsule preparation consisting of discrete microcapsules with a particle diameter between 4 and 15 p., Which is particularly suitable for copy and copy paper, is obtained.

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Claims (13)

Claim 1. A method for the encapsulation of water-immiscible substances, characterized in that one the substance to be encapsulated in a distribution means in the presence a) a water-soluble, surface-active ", polymeric, polyfunctional compound, which has primary amino, imino, hydroxyl and / or thiol groups, dispersed and component a) of this dispersion with b) an aqueous compound capable of forming a compound which is insoluble in the distribution agent Solution of a polyacrolein or acr'olein copolymer present as a hydrate or bisulfite adduct and c) optionally additionally with a hardening agent or an aminoplast precondensate reacted to form an insoluble capsule material. 2. The method according to claim 1, characterized in that that as component a) proteins, cellulose, cellulose derivatives or synthetic polymers with protective colloid properties used. 509822/0877 3. - The method according to claim 2, characterized in that as component a) gelatin or gelatin-like Products used. 4. The method according to any one of claims 1 "to 3, characterized characterized that one has as component t>) a aqueous solution of a bisulfite adduct of a polyacrolein or an Acroleiiicopqlymerisates used. 5. The method according to claim 4, characterized in that that as component b) a bisulfite solution of a polyacrolein with an average molecular weight of 500. to 300,000, preferably 15,000 to 100,000 are used. 6. The method according to claim 4, characterized in that a bisulfite solution of a copolymer is used as component b) used by acrolein with another copolymerizable vinyl compound. 7. The method according to any one of claims 1 to 6, characterized in that a carbonyl compound is used as component c) or an aminoplast precondensate is used. 509822/0877 8. The method according to any one of claims 1 to 7, characterized in that as component c) aliphatic Carbony! Compounds with a maximum of 6 carbon atoms used. 9. The method according to any one of claims 1 to 7, characterized characterized in that urea-formaldehyde or melamine-formaldehyde condensates are used as component c). 10. The method according to any one of claims 1 to 9, characterized characterized in that water is used as the distribution medium. 11. The method according to any one of claims 1 to 10 _}, characterized in that liquid or solid active ingredients or active ingredients dissolved in organic solvents are used as the substance to be encapsulated. 12 .. The capsule masses obtainable by the process of one of claims 1 to. 13. Use of water-soluble, surface-active, Imino / polyfunctional compounds which have primary amino, / hydroxyl and / or thiol groups in combination with aqueous solutions of a polyacrolein or acrolein copolymer present as a hydrate or bisulfite adduct, and optionally 509822/0877 . - 25 - additionally with hardeners or an aminoplast precondensate For encapsulating substances that are immiscible with water. · ·. ^;: - _; 50 9 822/0877