DE1519925B - Method for encapsulating droplets with a polymer skin by means of a condensation reaction - Google Patents

Description

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There are methods of encapsulating droplets of a first liquid, which by a second, with the first immiscible liquid are surrounded, known, at the interfaces of the droplets and the second liquid, a condensation reaction between first and second monomers Respondents, one in the first and the other in the second Liquid is contained and interconnected at the interfaces of the droplet and the second liquid react to form a polymer that creates a skin around the droplets.

Thus, droplets of an organic solvent containing a chloride of a dibasic acid became sprayed into an aqueous liquid containing, for example, ethylene glycol to thereby to achieve an encapsulation of the organic liquid or the oil in polyester capsules. For this However, special devices are required for experiments. In addition, the reactants merge and liquids easily become a heterogeneous mass, the capsule size that is supposed to be uniform difficult to adjust and the process is limited to certain types of reactions and products.

These disadvantages can be avoided if, according to the invention, the droplets of the first liquid, containing the first reactant, are formed in the second liquid as the latter second liquid does not yet contain a reactant, and if only then does the second reactant is introduced into the second liquid and the polymer skin is created.

The intermediate compounds which undergo condensation to form the polycondensate are preferred organic reactants that react with one another to form the polycondensate, it does not matter whether any group is removed or not.

Preferably, the droplets of the first liquid are in a larger amount of the other liquid formed by mixing with or without a dispersant.

One of the practically immiscible liquids is water and the other one with Water immiscible organic solvent used.

In this way completely satisfactory separate capsules are formed, which form a skin from the Have formed polycondensate and contain the first liquid. Then the Perform separation of the capsules for any purpose in a simple manner, for example by allowing the capsules to settle, filtering or skimming them, which are then washed - and if so desired - be dried. The first carried out dispersion of one liquid in the others can be promoted with the help of a suitable emulsifying or dispersing agent, and the Regulation of the size and uniformity of the capsules finally obtained can be done in the initial Easily achieve the dispersion stage, for example by changing the strength of the movement through which Choice of optionally used dispersants and by adjusting the proportions of the Liquids. Capsules of microscopic size up to dimensions can be produced without difficulty on the order of millimeters. With the appropriate setting of the strength the agitation during the addition of the second intermediate compound to the continuous phase there is no undesired agglomeration or fusion of the capsules.

There are a wide variety of uses for capsules produced by such processes, for example for holding inks, paints, chemical reagents, pharmaceutical substances, flavoring agents Substances, pesticides, herbicides, peroxides and practically everything Substances that are dissolved, suspended or otherwise

can be introduced or transferred into a liquid enclosed by the capsule and the are to be preserved in liquid or other form until they are released by a means that the capsule skin breaks open, crushed, melts, loosens or otherwise removed or down to under for it Under suitable conditions, a release takes place by diffusion. Such an encapsulation is used mainly for the preservation of very small droplets in a liquid state, but the process can can also be used to contain liquid bodies that are inside the capsule in a other state, e.g. B. the solid form, can be converted, creating entrapped solid particles Formed for special uses as a granulated protected form of the enclosed Substance are available.

The claimed process can be carried out using the known condensation reactions used for Formation of polymers lead to be carried out.

In the practical implementation of the procedure, the usual precautionary measures are applied, with which undesired reactions or changes in the substances used can be avoided. For example, it is beneficial to ensure that the organic phase containing the diacid chloride or contains equivalent intermediate compounds, kept as dry as possible and isolated from the atmosphere to avoid hydrolysis. If the organic phase is to be encapsulated and therefore first in an aqueous liquid (preferably a dilute aqueous solution of the dispersant) Is dispersed before the diamine, diol or the like. Adds, then is used to prepare the Dispersion time applied kept as short as possible in order to hydrolyze the diacid chloride as far as possible as possible to prevent. For example, when adding the solution of the diacid chloride in the organic solvent to the aqueous liquid through a dropping funnel on the latter Pressure can be applied to accelerate the addition and thus the dispersion of the organic phase. If the aqueous phase is to be encapsulated and, for example, an aqueous diamine solution initially dispersed in the form of droplets in a mass of the organic solvent then the diacid chloride is then added in a further portion of this solvent. The latter solution of the acid chloride should of course also be as dry as possible held until added for reaction.

In all cases, the formation of the dispersion of the droplets of one phase in the motion used by others is diminished, and usually rather greatly diminished, while the second complementary intermediate compound is added to the continuous phase and after this addition is complete. At this stage of the process there is reduced or barely noticeable or no movement at all to prevent the capsules from rupturing during their formation, the main requirement being only that there is good circulation for the flow of the Reaction is achieved.

Tests have shown that according to the invention Process manufactured capsules are used for the same purposes and in the same way like the products of other encapsulation or microencapsulation processes. For example One can use encapsulated inks or dyes in coatings for transfer purposes Release by mechanical pressure or similar effects at the desired locations or locations bring in. In the same way, other substances can be caused by mechanical action or by the actions released by heat or chemicals or by prolonged exposure to moisture on the capsule wall. Special meaning comes to the encapsulation of organic peroxides, especially liquid peroxides, which in used as reagents in many cases.

The encapsulation prevents premature volatilization or other impairment of the Avoided peroxide. The encapsulation can also serve to increase the effect of such a peroxide delay if desired for a particular use.

example 1

In this and the following Examples 2 and 5, the basis of the encapsulation process was the same the formation of an oil-in-water suspension, d. H., the organic phase was encapsulated in a polyamide skin. Following this first example, the substances listed below are brought into the flask together; this is the aqueous solution of the suspending agent, the organic solvent and the ingredients introduced into the latter; the suspending agent had previously been dissolved in the water with the aid of a mixer.

100 ml of 0.5% solution of polyvinyl alcohol, in

water
100 ml mineral oil,

0.2 g red dye,

4.8 g of sebacoyl chloride (0.02 mole).

The following solution was prepared in one of the dropping funnels:

6.7 g of 70% strength hexamethylenediamine solution

(0.04 moles),

8 g sodium carbonate,
50 ml of distilled water.

The mineral oil, the diacid chloride and the aqueous solution of the dispersant (polyvinyl alcohol) were dispersed by rapid stirring, creating a dispersion of droplets of the organic phase (Mineral oil) was formed. Then the further aqueous solution of the diamine was added from the funnel, and the contents of the flask were gently stirred for 20 minutes, thereby encapsulating the mineral oil droplets was effected in polyamide capsules. After diluting the mixture with distilled water, the separated became very small capsules in directly usable condition separated on a suction filter. There was no red color in the filtrate Contain dye.

Example 2

In this case, an organic solvent, which in turn contained a red dye, encapsulated with a polyamide skin, but with an additional trifunctional amine and a trifunctional Acid chloride as a crosslinking agent to improve the properties of the capsule skin

were applied. The flask and funnel were loaded with the following materials:

Pistons

300 ml of 0.5% aqueous solution of polyvinyl alcohol.

1. funnel

75 ml xylene,

0.2 g red dye,

12 g of sebacoyl chloride (0.05 mol),

3 ml of trimesoyl trichloride.

2. funnel

50 ml of distilled water, 12 g of ethylenediamine (0.2 mol), 4.65 g of 1,3,5-benzenetriamine trihydrochloride

(0.02 moles),
2.4 g sodium hydroxide (to neutralize

Hydrogen chloride in the trifunctional

Amine),
10 g sodium carbonate monohydrate.

During the rapid addition from the first funnel, the mixture was formed to form visible droplets stirred vigorously. After this first addition was complete, the stirring was slowed down. Slow stirring was maintained during the second, equally rapid addition, and the contents of the flask were then left to stand for two hours, which solidified the skin would. Then the mixture was filtered off and the resulting capsules were washed with acetone and dried. The product consisted of capsules about 1 mm in diameter and solid Walls.

Example 3

In this case, monomeric styrene was used as the organic phase and encapsulated in polyamide. This was followed by a treatment to polymerize the styrene, which resulted in polyamide solid polystyrene particles were obtained. The starting materials given below were used applied. The mixture of styrene and the acid chloride and the other ingredients included of the benzoyl peroxide, which was used as the organic phase, was first flushed with nitrogen, to prevent premature reactions:

50 pistons

100 ml styrene,

8 ml divinylbenzene,

1 g benzoyl peroxide,

4.8 g of sebacoyl chloride (0.02 mol), 100 ml of 0.5% strength aqueous solution of polyvinyl alcohol.

Dropping funnel

6.7 g of 70% hexamethylene diamine solution (0.04 mol),

8 g sodium carbonate,
50 ml of distilled water.

The solution containing the styrene and the diacid chloride was by rapid stirring in the aqueous Elvanol solution dispersed. Then the aqueous diamine solution was introduced into the flask. It was

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60 stirred slowly for 10 minutes. The contents of the flask were diluted with distilled water and filtered through a suction filter. The capsules were then introduced with 500 ml of distilled water in a flask equipped with a stirrer, reflux condenser and thermometer sealed resin reaction flask with a capacity of one liter and held for 5 hours at 8O ⁰ C. The product was filtered through a suction filter, washed and dried at 60.degree. The particles were spherical and ranged in diameter from 250 microns to less than 75 microns. Following the encapsulation, the styrene was polymerized with the aid of the benzoyl peroxide contained therein, the capsule walls remaining intact. This illustrates the applicability of the method according to the invention to the encapsulation of solid substances.

Example 4

The following solutions were placed in the flask and the dropping funnels:

Pistons

300 ml of 0.33% aqueous solution of polyvinyl alcohol.

1. Dropping funnel

100 ml carbon disulfide,
12 g sebacoyl chloride (0.05),
4 ml trimesoyl trichloride (for crosslinking).

2. Dropping funnel

50 ml of distilled water,
12 g ethylenediamine (0.5 mol),
2.3 g of 1,3,5-benzenetriamine trihydrochloride
(0.01 mol) for crosslinking,

1.2 g sodium hydroxide,

10 g sodium carbonate monohydrate.

The encores came one after the other and quickly. The agitation was adjusted so that visible droplets were formed and slowed down after the first addition. Thereafter, the flask contents V was stirred for ₂ hours, allowed to stand for further IV ₂ hours, filtered, washed with water and acetone and dried in air. The size of the polyamide capsules filled with carbon disulfide was 1 to 2 mm in diameter.

Example 5

Di-tert-butyl peroxide was encapsulated as the organic phase. It was locked in a Reaction flask with a capacity of 500 ml and the following loads:

Pistons

100 ml of 0.5% aqueous solution of polyvinyl alcohol.

1. Dropping funnel

6 g di-t-butyl peroxide,

4 g sebacoyl chloride,
ImI trimesoyl trichloride.

2. Dropping funnel

6 g ethylenediamine,

2.3 g 1,3,5-benzoyltriamine 3HCl,
1.2 g sodium hydroxide,

5 g sodium carbonate monohydrate,
75 ml of distilled water.

An ice bath was used. The additions were made one after the other and quickly. The agitation was adjusted so that visible droplets were formed and was slowed down after the first addition. The flask contents were stirred for _^3/4 hour. The product was then washed by decanting with acetone, filtered and air dried. The small capsules formed consisted of the aforementioned liquid peroxide enclosed in a polyamide skin. This product is particularly suitable for storing and handling this highly reactive chemical substance in the form of a commercial reagent.

Example 6

This example illustrates the encapsulation of an aqueous liquid, i. H. the aqueous phase with a suitable polycondensation skin, e.g. B. polyamide. The following batches were made used:

Pistons

200 ml carbon tetrachloride,
100 ml of pentane.

1. Dropping funnel

10 ml of distilled water,
5 g ethylenediamine,
2.0 g 1,3,5-benzoyltriamine hydrochloride,
0.7 g sodium hydroxide.

2. Dropping funnel

50 ml carbon tetrachloride,
12 g sebacoyl chloride,

3 grams of trimesoyl trichloride.

It should be noted that in this case the organic liquid in relatively large Amount was present and the aqueous phase containing the amine before the addition of the acid chlorides to the continuous organic phase was introduced and dispersed. Stirring during and immediately after the addition of the aqueous phase from the first dropping funnel was adjusted so that visible Droplets were formed. Then it was slowed down, and the solution from the second dropping funnel was added, causing the reaction to form the desired capsules to occur. After filtering of the contents of the flask were polyamide capsules with a diameter that are separated from one another of about 1 mm containing an aqueous liquid.

Example 7

In this example, the organic phase was namely as an oil-in-water suspension with a Polyester skin encapsulates the reaction of di- and trifunctional acid chlorides with a trihydroxy compound was produced. The following solutions were made:

Pistons

300 ml of 0.5% solution of polyvinyl alcohol.
1. Dropping funnel

12 g of sebacoyl chloride (0.05 mol),

4 ml trimesoyl trichloride,
50ml xylene,

0.2 g of red dye.

2. Dropping funnel

12.6 g pyrogallol (1,2,3-benzenetriol) (0.1 mol),
2 g sodium hydroxide,
50 ml of distilled water.

The additions are made quickly and one after the other. As before, the stirrer was used to start the first Addition started and stirring adjusted so that visible droplets were formed. To ίο the first addition, the stirring was slowed down. The polyester capsules formed were on a suction filter filtered off and had a diameter of about 0.5 to 1 mm up to about 5 mole percent.

Examples

In this case, the organic liquid was encapsulated with a polyurea skin, namely by Reaction of phosgene with a diamine with formation

—HNRNHC

The following batches were prepared: Flasks

3TOmI 0.5% aqueous solution of polyvinyl alcohol.

1. Dropping funnel
50 ml of 12.5% phosgene in benzene.

2. Dropping funnel
18 g ethylenediamine,

2.4 g sodium hydroxide,
10 g sodium carbonate monohydrate,
100 ml of distilled water.

The addition and the cessation of stirring were carried out as in the previous examples. The visible droplets formed were encapsulated by the polyurea skin, the contents of the flask being gently stirred for _{2 hours after the addition of the diamine solution IV.} Small capsules were formed.

Example 9

Using an oil-in-water suspension the organic liquid was encapsulated with a polycarbonate skin; this is the reaction of phosgene with a diol to form

Γ — OROC— |

L ο J

The following solutions were prepared:
Pistons

300 ml of 0.5% aqueous solution of polyvinyl alcohol.

1. Dropping funnel

50 ml of 12.5% phosgene in a benzene solution.

109583/359

2. Dropping funnel

12.1 g of 2,2-bis [4-hydroxyphenyl] propane (0.075 mol),

6.3 g pyrogallol (0.05 mol),
10 g NaOH,
200 ml of distilled water.

Again the additions were sequential and rapid and the stirring became visible Droplets stopped and slowed down after the first additions. After that the contents of the flask Stirred moderately for an hour. Small polycarbonate capsules containing benzene were formed.

Example 10

It is another example of the encapsulation of the oil; H. the organic phase with a polycarbonate skin. In this case the reaction proceeded between a bis-chloroformate and a diol to form

2. Dropping funnel

20th

—OROCOR'OC

Il Il L ο o_

The following batches were prepared:

Pistons
300 ml aqueous solution of polyvinyl alcohol

1. Dropping funnel

11 ml ethylene-bis-chloroformate, 100 ml xylene.

30th

35

2. Dropping funnel

11.4 g of 2,2-bis [4-hydroxyphenyl] propane, 2 g phloroglucinol dihydrate (trifunctional alcohol),

10 g NaOH (all substances dissolved in a mixer at low speed).

The procedure given in the previous examples was used, resulting in small Capsules with a polycarbonate wall were obtained.

Example 11

In this example the organic liquid (xylene) was encapsulated with a polyurethane skin; here a bis-chloroformate was reacted with a diamine to form

Γ— NHRNHCOR'OC — Ί

Il Il L ο ο J

The following solutions were prepared:

Pistons

300 ml of 0.5% aqueous solution of polyvinyl alcohol.

1. Dropping funnel

11ml ethylene-bis-chloroformate, 100 ml xylene.

18 g ethylenediamine,
5 g diethylenetriamine,
10 g sodium carbonate monohydrate,
100 ml of distilled water.

Again, the additions were made quickly in the order given. The agitation was adjusted so that visible droplets of the xylene component were formed in the water and was slowed down after the first addition. After the second addition, the contents _^3/4 hour, it was stirred and then filtered. Capsules with a polyurethane wall with diameters in the range from 0.5 to 1.5 mm were obtained.

B e i s ρ i e1 12.

Using the example of oil-in-water encapsulation with A polyurea-polyamide skin will result in the formation of a copolymer (which is also made by crosslinking is reinforced) by interfacial polycondensation illustrated. The following feed mixtures were prepared:

Pistons

300 ml of 0.5% aqueous solution of polyvinyl alcohol.

1. Dropping funnel

100 ml xylene,

15 ml toluene-2,4-diisocyanate,
2 ml of trimesoyl trichloride.

2. Dropping funnel

18 g ethylenediamine,

5 g diethylenetriamine,

10 g sodium carbonate monohydrate,

100 ml of distilled water.

The encores came quickly and one after the other. The agitation was adjusted so that droplets were visible were formed and slowed down after the first addition. The contents of the flask were stirred for 1 hour and then filtered. Capsules with xylene were obtained.

Example 13

In this example an oil-in-water encapsulation was used forming a copolymer skin (polyamine-polyurea) effected, the crosslinking was achieved with polymethylene polyphenyl isocyanate. The encapsulated organic liquid was a pesticide, namely O, O-dimethyldithiophosphate of diethyl mercaptosuccinate. The reaction was carried out in a one-capacity flask of 500 ml, which was equipped with a high-speed stirrer (20,000 rpm). There were the following loads are used:

Pistons

300 ml of 0.5% solution of polyvinyl alcohol with 6 drops of silicone defoamer.

1. Dropping funnel

28.8 g Ο, Ο-dimethyldithiophosphate of diethyl mercaptosuccinate,
13 g azelaoyl chloride,
2 g of polymethylene polyphenyl isocyanate.

2. Dropping funnel

20 g diethylenetriamine,
10 g sodium carbonate monohydrate,
100 ml of distilled water.

The contents of the first and second dropping funnels were added one by one with stirring added at high speed. Then the speed was reduced and another 1 hour touched. The contents of the flask were left to stand for a further 1 hour and filtered through a suction filter the residue at room temperature in vacuo

dried. Small capsules (less than 1 mm) were obtained. When used in preparations For pest control, these capsules can use the pesticide they contain by gradual diffusion or by a leaching effect, such as occurs during prolonged periods Time in the presence of moisture is released.

As used herein, the term "polyfunctional reagent" means reagents which are im In contrast to the bifunctional reagent groups with the intended function on more than two Carry places in the molecule.

Claims (5)

Patent claims: 1. A method of encapsulating droplets of a first liquid released by a second, with the first immiscible liquid are surrounded, at the interfaces of the droplet and the second liquid a condensation reaction between the first and second monomeric! Respondents is carried out, one of which is contained in the first and the other in the second liquid and which are connected to each other the interfaces of the droplets and the second liquid react to form a polymer, which creates a skin around the droplets, characterized in that the droplets the first liquid containing the first reactant in the second liquid be formed while this second liquid does not yet contain a reactant, and that only then is the second reactant introduced into the second liquid and the polymer skin is produced. 2. The method according to claim 1, characterized in that the droplets of the first liquid in a larger amount of the other liquid by mixing with or without a dispersant be formed. 3. The method according to claim 1 or 2, characterized in that as one of the practically not Miscible liquids are water and, as the other, a water-immiscible organic Solvents can be used. 4. The method according to any one of the preceding claims, characterized in that for generation a skin made of a crosslinked polymer as at least one of the two reactants a polyfunctional reactant or a reactant is used • who is used together with a bifunctional Reactant contains a polyfunctional reactant who is involved in the implementation between the first and second reactants in a significant number of places capable of producing crosslinks in the polymer chains formed by this reaction. 5. The method according to any one of the preceding claims, characterized in that first and second reactants are used, which together form a polyamide, polysulfonamide, Polyester, polyureas, polycarbonate or polyurethane skin react.