DE1256195B - Manufacture of capsules with walls made of gelatinized, polymeric materials - Google Patents

Description

GERMAN

PATENT OFFICE

EDITORIAL

German class: 12 c-3

number
File number:
Registration date:
Display day:

1256195
N22076IVc / 12c
September 11, 1962
December 14, 1967

t-t-

U ₄₁ ,

In British patent 751600, the Manufacture of microscopic capsules with walls made of gelatinized and hardened polymers described by coacervation However, the method described there is not suitable for Production of thick-walled macroscopic capsules, since the deposition of the capsule wall-forming Substance is carried out in a manufacturing liquid that is kept in motion by stirring to a temperature above the gelation temperature of the The temperature of the deposited capsule wall-forming substance is due to this high temperature the deposited substance is kept very liquid, which means together with the shear forces generated by the agitation of the carrier liquid and the simultaneous reduction in the viscosity of the non-deposited polymeric substance, which thereby causes that the denser fractions of the complex substance in the carrier liquid come first deposit, the effective wall thickness of the capsules after gelatinization is limited to about 5 μ Such thin walls hold microscopic droplets of the core-forming substance securely enclosed, but no large droplets

It is also known that the carrier liquid can be added by adding reactivate a large amount of polymer to allow a greater amount of capsule wall-forming Substance is deposited This reactivation causes a new formation of denser fractions which then precipitate on the first deposit, making the capsule core a thicker one Wall preserved than was previously possible Due to the greater thickness of the capsule wall achieved in this way can even then use the capsules in a fur size visible to the naked eye, however, if they have a liquid content In this process too, the deposition of the capsule wall-forming substance at a temperature performed well above the gelation temperature this substance lies. As a result, there is also a limitation in this method final capsule wall thickness due to the shear forces caused by the agitation of the system.

The subject matter of the invention is a method of production of capsules with walls made of gelatinized, complex, hydrophilic, film-forming, polymeric Substances that are essentially immiscible with water Contain substances by coacervation and lowering the temperature of the capsule wall forming Substance with stirring up to the gelatimerungsbereich

Manufacture of capsules with walls
gelatinized, polymeric substances

Applicant

The National Cash Register Company,

Dayton, Ohio (V StA.)

representative

Dr. A. Stappert, lawyer,

Dusseldorf, Feldsti 80

Claimed priority
V. St v. America September 14, 1961
(137992)

The inventive method is characterized in that the temperature is so long in this temperature range is maintained until the desired capsule wall thickness is reached, and only then

a ₅ cools below this temperature range

In the preferred method according to the invention the lowering of the tempeiatur is started, once coacervation has been initiated, the temperature gradually increasing as the progression the coacervation is reduced. The substance to be encapsulated can preferably be lowered the temperature m be introduced into the system

In the preferred exemplary embodiment of the invention the substances are selected so that the pH of the system by performing the Coacervation need not be set below 6.8. Of course he can take this value can be reduced if this is expedient even after the liquid has been imported or solid core-forming substance, the pH does not need to be set to a certain value to become. This makes the use of both alkali-sensitive and acid-sensitive core-forming substances possible

Complexes of film-forming hydrophilic, polymeric Substances can be in a warm aqueous solution (30 to 45 ° C) of gelatine and complex-forming, negatively and positively charged polymers Substances at a pH of the carrier liquid between 6.8 and 4 depending on the normal relative charges of the molecules of the individual components are generated in many cases ^

709 708

3 4

it is desirable to encapsulate such substances as well, after which 250 ecm of toluene under rest

that can be introduced with the capsule wall-forming substance at ren and the system for so long

react at a certain pH value. This can continue to be stirred until the toluene drops to a drop

by choosing such polymeric substances avoided size of 500 μ is dispersed. After achieving this

the complex coacervate phases under other 5 states, which only take a few minutes

pH conditions should take place during which complex coacervate

The invention is well suited for the production of units on the toluene droplets m one thickness

Capsules, with a diameter of about 100 to about 5 μ, are deposited, the temperature of the sy-

15 000 μ, with the upper diameter limit due to stems within a period of about 20 minutes

the thick and viscous coatings are achieved, the io utes reduced to room temperature (25 ± 5 ⁰ C),

in turn arise from the fact that the temperature caused by the deposition of the remaining fractions of the

temperature effect gelatinizable complex polymer complex, polymeric, liquid, capsule wall-forming

units begins to be deposited on the particles of the substance and continues until one

core-forming substance, the Gioße mainly relatively thick wall of about 150 to 200 μ around each

Determine the final capsule size on which 15 toluene droplets have formed while stirring further

be kept at a relatively low temperature. The system is cooled to about 10 ° C, whereby

it has been shown that coacervate units are higher than the liquid deposits of the polymeric, composite

Viscosity form the thicker walls, as they gelatinize for the plexy substance

Holding on to large liquid cores is necessary, capsules ready, unless they are to be replaced by

since the viscous deposit is still less than it was when the 20 nets were stirred in the

To be resisted to the shear forces caused by the carrier liquid,
The capsules can be separated as usual.

Example 1 Example 2

In this preferred example, the em- 25 In this example, only one of two poly-

encapsulation of toluene as a typical complex that does not contain water, namely gelatin and

Miscible, volatile liquid described, gum arabic, gelatin and ethylene maleic acid

all the difficulties encountered with bulk anhydride mixed polymers, gelatin and vinyl

production of large, liquid-containing methylämer-maleic anhydride polymerizate,

Capsules in emem liquid carrier can occur, 30 Gelatme and pectin, gelatin and styrene-Malem-

holds in itself. In this and the other examples, acid anhydride copolymer or gelatin and

the amounts are given in which the use of a phthalated gelatin used Each of these combi-

Two-liter container is based. nations delivers a positive and emen negative

The capsule wall-forming polymeric substances are polymeric substances

Black skin gelatin with an isoelectric point 35 The gelatin-gum arabic

of about 8.9, gum arabic and ethylene-maleic system similar to that described in the British patent

acid anhydride copolymer with two different systems disclosed 751600 comes closest,

molecular weights. During the first part there the gum arabic only at a pH of

During the process, the pH will drop to around 6.8 and 4.5 has the ability to quickly complex with

set and the temperature to form over the gelatinization 40 of the gelatin, Schntt for Schntt described,

temperature raised ^ by a coacervation However, in the method according to the invention

between the "" fractions of the polymers, the deposition of the coacervate at room temperature

whereby the gelatmolecules carry a positive net charge, creating a thick coating

and the other polymeric molecules give a negative, which allows the encapsulation of large liquid

Have network charge. 45 drops possible.

The following substances are filled into a 2-nl beaker The following substances are filled ^{into a} 2-1 beaker:

Water .... 1000 ecm of water. 700 ecm

ll weight percent aqueous solution of 2 weight percent solution of gel

Gelatine (pig ^{skin gelatine with a 5} ° tine of the aforementioned type 180 ecm

isoelectric point of 8.9) 180 ecm 2 percent by weight of rubber

ll weight percent aqueous solution of arabic solution. . 180 ecm

Gum arabic 180 ecm whereby the system is adjusted to a temperature of 40 to ethylene-maleic anhydride mixed poly- ₅₅ 45 ° C and a pH value of 4.5 Viscosity) as a 2 percent by weight uniform stirring to the desired core aqueous solution with a pH value drop-sized. Then the system is brought from 9. .40 ecm with constant stirring within a period of ethylene-maleic anhydride mixed poly 60 of one hour to 25 ⁰ C cooled. The finished mensat (molecular weight 100,000 - capsules are hardened in the same way and solute viscosity) are obtained as 2 percent by weight from the carrier liquid residue, as described in Example 1 as aqueous solution with a pH value

of 9 40 ecm In the previous examples, the

65 storage of the polymeric, capsule wall-forming substance

The system is then stirred and the temperature is maintained at a moving liquid

38 ° C increased and the pH of the system to 6.8 temperatures near the gelatinization point of the

'-set. This brings about a complex coacemic coacervate phase.

Volatile and non-volatile oils and insoluble oils Solid materials of a kind can be encapsulated in the manner described, whereby by the invention creates the possibility of cores from substances of microscopic or macroscopic particle size that are sensitive in the acidic pH range at a pH of up to 6.8 and off in alkaline pH-value range sensitive substances at a pH-value of 4.5 with thick polymer walls to surround

The invention is not intended to be limited to the m of the description These substances are limited. Any other complex-forming, hydrophilic, film-forming material can also be used Polymer can be used, provided that at least some of the polymers used gelatinized when exposed to a certain temperature and crosslinked and hardened by other means The mentioned artificial copolymers with large negative charges are everywhere useful where the production of the capsules is carried out in the vicinity of the neutral pH value range will. If a low pH system is required, it should be used to achieve complex coacervation negative polymeric substances with a low negative charge are used in the acidic range will

Claims (2)

Claims. 1. Process for the production of capsules with walls made of gelatinized, complex, hydrophilic, film-forming, polymeric substances that are essentially water-immiscible by coacervating and lowering the temperature of the substance forming the capsule wall with stirring up to the gelation area, characterized in that the temperature is so long in this temperature range hold until the desired capsule wall thickness is reached, and that one then only cools below these temperature ranges. 2. The method according to claim 1, characterized in that after the initiation of the Coacervation begins to lower the temperature and as coacervation progresses gradually continues Considered publications:
British Patent No. 751600 709 708/340 12 67 ® Bundesdruckerei Berlin