Mixtures of alkylphosphoric esters and use thereof as...

Details Mixtures of alkylphosphoric esters and use thereof as... Mixtures of alkylphosphoric esters and use thereof as...

1998-02-26

2003-04-01

Travers, Russell (Department: 1617)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

C516S056000, C516S199000, C548S180000, C548S182000

Reexamination Certificate

active

06541016

ABSTRACT:

This application claims the foreign priority of FED REP GERMANY application 197 07800-1, filed Feb. 27, 1997
This invention relates to mono-, di- and, in small amounts, also trialkylphosphoric esters or salts thereof, which are preferably based on &bgr;-branched fatty alcohols, particularly preferably on Guerbet alcohol, and which are very effective in lowering the surface tension of both polar and also nonpolar liquids, and have high stability, even at elevated temperatures, and low sensitivity to electrolytes and acids.
The invention further relates to the use of such mixtures as emulsifiers in cosmetic and pharmaceutical formulations, and also to the resulting products.
The use of emulsifiers in the preparation of creams, lotions, ointments etc., which comprise two or more immiscible substances (e.g. water, oil, organic and inorganic constituents), has been known for some time. The emulsifiers used are surfactants, e.g. soaps of alkali metals and alkanolamines, mono- and diglyceryl esters of fatty acids, but also certain naturally occurring substances (e.g. lecithins and waxes) and inorganic substances (e.g. bentonites).
EP-B-0 553 241 discloses the use of mixtures of alkyloligoglucosides, fatty alcohols and, if desired, polyglucose for the preparation of emulsions. WO-92/07543 discloses the use of alkyloligoglucosides with fatty alcohols and partial glycerides as cosmetic emulsifiers.
EP-B-0 201 040 describes the emulsifying power of metal salts of dialkyl phosphates, and EP-B-0 227 012 describes that of monophosphoric esters.
GB-A-2 139 112 discloses an emulsifier mixture of mono- and diesters of phosphoric acid, some of which are also ethoxylated, in a ratio of from 100:0 to 70:30 and also a nonionic surfactant.
The use of &bgr;-branched monoalkylphosphoric esters as emulsifiers is disclosed in EP-A-0 265 702.
The specified emulsifiers do, however, also have unfavorable properties, such as low stability at elevated temperatures, limited miscibility with or solubility in aqueous or organic media and they reduce the emulsifying power on addition of salt-like components.
The object was thus to develop high-performance stable emulsifiers which are insensitive to salt-like components, for example electrolytes. For applicational reasons, they should be liquid at room temperature and, to ensure good tolerability by theskin, have a pH of from about 5 to 7.
Surprisingly, it has been found that mixtures of mono-, di- and trialkylmonophosphoric esters have the required properties.
The invention relates to mixtures of mono-, di- and trialkylmonophosphoric esters of the formulae I, II and III
in which
R, R
1
, R
2
and R
3
, which may be identical or different, are straight-chain or branched alkyl groups having from 8 to 36 carbon atoms, and
X and Y, which may be identical or different, are hydrogen, alkali metal or alkaline earth metal, substituted or unsubstituted ammonium or basic organic groups.
Basic organic groups under the meaning of X and Y are, for example, basic amino acids, such as arginine, ornithine and lysine, and also alkanolamines, e.g. triethanolamine or monoethanolamine. Examples for substituted ammonium include C
8
-C
22
-alkylammonium.
The invention further relates to the use of these mixtures of alkylphosphoric esters as emulsifiers in cosmetic or pharmaceutical formulations and also to cosmetic or pharmaceutical formulations which comprise these esters.
The mixtures according to the invention comprise the monoesters of the formula I and also the diesters of the formula II, in each case in amounts of from about 30 to 60% by weight, in particular from about 40 to 50% by weight. The triesters of the formula IlI are present in the mixtures according to the invention in amounts of between about 0.5 and 5% by weight, preferably about 1 to 2% by weight.
The phosphoric ester mixture is normally used in amounts of from 0.1 to 5 percent by weight, preferably in amounts of from 0.3 to 3 percent by weight, based on finished formulations.
It has been found that mixtures of phosphoric esters, comprising mono-, di- and triesters of the formulae I, II and III, have excellent emulsifier properties when R, R
1
, R
2
and R
3
are &bgr;-branched alkyl groups having from 16 to 20 carbon atoms. The parent alcohols of these radicals are referred to as Guerbet alcohols. Alkylphosphoric esters in which R, R
1
, R
2
and R
3
are &bgr;-branched alkyl groups having from 16 to 20 carbon atoms are a preferred embodiment of this invention.
The alkylphosphoric esters are synthesized by reacting tetraphosphorus decaoxide and alkyl fatty alcohols to form mono- and diesters in an approximate molar ratio of 1:1, with small amounts of triester, as shown in the reaction equation (R is used here for all the R, R
1
, R
2
and R
3
radicals):
The alkylphosphoric ester mixtures are yellowish to white, in some cases solid or waxy, or viscous, liquid substances having melting points of between −5° C. and 80° C. and iodine color numbers of from <4 to <0.5.
P
4
O
10
reacts with C
16
/C
20
-Guerbet alcohol to give a phosphoric ester mixture in which R, R
1
, R
2
and R
3
=C
16
-C
20
-&bgr;-branched alkyl which has particularly advantageous physicochemical characteristics. The pale yellow, liquid mixture, comprising about 40-60% by weight of the monoester, about 30-50% by weight of the diester and up to 10% by weight of the triester, has a melting point of <−5° C., an iodine color number of <1.0 and has good solubility both in polar and also in nonpolar organic substances, such as paraffin, soybean oil and isopropyl palmitate.
The phosphoric ester mixtures according to the invention, preferably those in which R, R
1
, R
2
and R
3
are &bgr;-branched C
16
-C
20
-alkyl, are suitable, in particular, for the preparation of oil-in-water emulsions, but also for water-in-oil emulsions preferably for the preparation of alcohol-free emulsions.
The performance of an emulsifier is correlated with the reduction in surface tension. Phosphoric esters having the composition described above are notable for their surface tension-lowering effect. Surprisingly, it has been found that phosphoric esters based on Guerbet alcohols drastically reduce the surface tension which the performance as an emulsifier reflects.
TABLE 1
The effect of a variety of phosphoric esters on the surface tension of
oils of varying polarity
Phosphoric ester
Paraffin oil
Cetearyl isononanoate
Soybean oil
Lauryl
28
16.5
16
Stearyl
16
15.8
15.5
Isostearyl
11
8.5
9.0
Isooctadecyl
1.5
2.5
3.0
Oleyl
13
11
9.0
Behenyl
36
24
17.5
Surface tension in mN/m
Temperature 25° C., concentration 1.5 g of phosphoric ester in 1 liter of water, pH 7, Na salt
“Cetearyl” refers to a mixture of cetyl and stearyl.
The surface tension was determined using a Lauda drop volume tensiometer.
The term “phosphoric ester” in this table means a novel mixture of approximately equal parts of mono- and diesters and also a small amount of triesters.
Stability tests with a variety of oils, such as squalene, soybean oil, cetearyl isononanoate and isopropyl palmitate, showed that emulsions which comprise the phosphoric esters based on Guerbet alcohols show no cracking whatsoever in the 30-day storage test at 40, 45 and 50° C. Comparable results were obtained in the centrifuge test at different emulsifier concentrations.
The emulsifiers according to the invention are notable for being very effective in lowering the surface tension, even at elevated temperatures, of polar and nonpolar constituents. The emulsifiers, some of which are liquid, have improved stability to electrolyte additives and acids and a long shelf life. They have a pH in the range from 5 to 7 and can thus be used as emulsifiers which are very kind to the skin, preferably in skincare products.
The nonaqueous part of the emulsions, which largely comprises the emulsifier and oily substances and usually corresponds to the solids content, is usually from 5 to 95% by weight and preferably from 15 to 75% by weight. This means that the emulsions may contain from 5 to 95% by weight, and preferably

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