Encapsulation

Details Encapsulation Encapsulation

2000-02-14

2001-09-11

Gitomer, Ralph (Department: 1623)

Drug, bio-affecting and body treating compositions

Dentifrices

C424S417000

Reexamination Certificate

active

06287542

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for treating a mixture of an oil and a copper chlorophyll extract with a solvent to render such mixture e.g. suitable for making microcapsules which contain a liquid core material comprising a mixture of oil and copper chlorophyll, said microcapsules e.g. being particularly suitable for use in oral care products.
2. The Related Art
It has already been previously suggested in the art to include microcapsules which contain an oily core and colouring agent in oral care products, primarily to impart a “speckled” or “spotty” colouring effect thereto. Thus, for example, GB-A-1,381,444 (Blendax) describes microcapsules having a transparent shell material encapsulating a solution or suspension of colouring matter in a physiologically inert solvent such as paraffin oil. These microcapsules can be included in toothpastes to impart a speckled colouring effect thereto. The colouring materials are colouring agents or pigments such as various C-reds, C-blues, and C-greens, the latter including C-green 8 which is a mixture of a copper chlorophyll complex and a copper chlorophyllin complex. These microcapsules can be made by well-known encapsulation processes, such as coacervation, using e.g. gelatine as the encapsulating material.
However, we have found that it is not possible to obtain acceptable microcapsules according to this prior proposal when using copper chlorophyll as the colouring agent. Dissolving copper chlorophyll in the paraffin oil gave a precipitate of small, blackish particles when added to water, thus making the mixture unsuitable for obtaining acceptable microcapsules by means of coacervation.
In EP-A-0,711,544 (Kao) microcapsules for use in dentifrice compositions are described, which contain agar as the coat-forming material, and core material which may consist of a great variety of dentifrice ingredients and vehicles therefor. Among these dentifrice ingredients copper chlorophyll is also mentioned, and among the vehicles natural fats and oils as well as minerals oils are mentioned. While various production methods, including coacervation, are mentioned, a double nozzle dropping method is preferred to make the microcapsules.
In some of the working examples, microcapsules are described which contain as core material a medium chain triglyceride and sodium copper chlorophyllin.
However, sodium copper chlorophyllin is water-soluble, and we have found that it is not possible to obtain acceptable microcapsules which contain a core of an oil and sodium copper chlorophyllin by means of coacervation according to this prior proposal. A green sludge was formed at the oil/water interface during the emulsification step, which prevented capsule wall formation. The same was found when using copper chlorophyll instead of the sodium copper chlorophyllin.
Chlorophyll extracts are usually obtained by suitable extraction of plant leaves such as alfalfa, grass, nettles.
The extracts normally contain chlorophyll a and b, as well as a number of other ingredients such a pigments, carbohydrates, waxes, fats, oils, salts, proteins and xanthophyll.
Copper chlorophyll extracts are usually obtained by replacing in the chlorophyll extract the magnesium ion at the centre of the porphyrin ring by copper.
Commercial grades of copper chlorophyll extract (INCI name: Chlorophyllin-Copper Complex or CI 75810; EINECS No. 234-242-5) are usually mixtures of copper chlorophyll extract and a vegetable oil, containing up to 15% copper chlorophyll.
SUMMARY OF THE INVENTION
We have now found, quite unexpectedly, that by treating a mixture of a copper chlorophyll extract and an oil with a mixture of at least 90% by weight of a C
2
-C
4
monohydric alcohol, which is miscible with water in all proportions, the balance of the mixture being water, and subsequently separating the resulting alcoholic and oily layers, an oil- and copper chlorophyll-containing mixture is obtained which is quite suitable for making quite acceptable microcapsules containing a liquid core material comprising said mixture by means of coacervation methods. These microcapsules contain a green liquid core, and a translucent or transparent, outer shell, thus providing for a speckled appearance to the oral care products in which they may be included, without causing the presence of unsightly burst capsule skins upon use of such oral care products. Preferably, a mixture of at least 96% by weight of a C
2
-C
4
monohydric alcohol which is miscible with water in all proportions, the balance being water, is used. Suitable examples of the C
2
-C
4
monohydric alcohols are ethanol, propanol, isopropanol, butanol, isobutanol, tertiary butanol, and mixtures thereof. Preferred are ethanol and isopropanol, and particularly preferred is ethanol. We have found that optimum results are obtained, when using 97.5% absolute ethanol/2.5% water; up to 10% copper chlorophyll extract in the oil can thereby successfully treated.
The aforementioned commercial grades of copper chlorophyll are suitable starting materials for the process of the present invention. Naturally, it is also possible to mix a required amount of copper chlorophyll, obtained from other sources, with an oil to obtain the required starting material.
DETAILED DESCRIPTION OF THE INVENTION
Although it is possible to first treat the commercial grades of copper chlorophyll extract, containing an oil, with the alcohol/water mixture and subsequently recovering the oil- and copper chlorophyll-containing oily layer, and mixing said layer with an oil, it is preferred to first admix such commercial grades with an appropriate oil, and then treat said admixture with the process according to the present invention.
Thus, typically, the copper chlorophyll/oil mixture is mixed with the alcohol/water mixture in a ratio of 2:1 to 1:4 (expressed as parts of the copper chlorophyll/oil mixture to parts of the alcohol/water mixture), preferably 1 part of the copper chlorophyll/oil mixture to 2 parts of the alcohol/water mixture, preferably under vigorous agitation. The resulting mixture is then allowed to stand until the phases have separated, usually for at least 12 hours. The resulting green oil-phase is then separated from the alcohol-containing phase, mixed again with the alcohol/water mixture in the same ratio, and allowed to stand until the phases have separated, usually for at least 6 hours. The resulting green oil-phase is then washed with water to remove traces of alcohol.
The thus-obtained green oil is subsequently admixed with a liquid oil to form the liquid core material for the microcapsules to be formed by a coacervation process. The liquid oil can be selected from well-known liquid vegetable or animal edible oils, such as soybean oil, rapeseed oil, cottonseed oil, coconut oil, palm oil, palm kernel oil, sunflower oil, groundnut oil, safflower oil, fish oil, whale oil and the like, as well as synthetic analogues thereof, as well as fatty acid mono- and/or -diglycerides. The liquid oil can also be an inert, physiologically acceptable mineral oil such as paraffin oil. The liquid oil should be liquid or liquefiable at the encapsulating temperature or below, usually at 60° C. or below, and preferably at 25° C. or below. Mixtures of the various oils can also be used. A particularly preferred oil is sunflower oil. The resulting mixture should not have too high or too low a viscosity, as otherwise the coacervation process would not yield acceptable microcapsules. The viscosity should in general not be higher than 5 Pa.s and not lower than 0.004 Pa.s. If required, the viscosity can be adjusted by inclusion of a small amount of a thickening agent, e.g. up to 5% of beeswax or beeswax ester or a thickening silica.
The oil/copper chlorophyll mixture and the liquid core oil are usually admixed in a weight ratio of 1:5 to 1:1000, preferably 1:10 to 1:50 to form the liquid core material for the microcapsules.
The liquid core material may also contain small amounts of gum health agents such as antimicrobial agents like Triclosan;

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