Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-07-25
2002-03-19
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S159000, C510S417000, C510S458000, C510S481000
Reexamination Certificate
active
06358898
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to soap stabilized emulsions and to the methods of manufacture of such emulsions, and in particular to silicone emulsions useful in personal care products.
BACKGROUND OF THE INVENTION
Traditionally, soap in the form of bars or flakes has been used as the preferred cleaning agent in personal care. In recent years, personal cleaning agents in the form of gels have become increasingly popular. These gels are sometimes referred to as shower gels. Such shower gels are extremely popular with consumers.
These shower gels commonly contain:
Detergents or surfactants which can be synthetic or natural soap.
Humectants such as glycerine and propylene glycol.
Chelating agents such as EDTA.
Buffers such as citrate or citric acid.
Pearlisers such as EGMS and mica.
Perfumes and Colours.
Thickeners such as hydroxy ethyl cellulose.
Water.
It is believed that the addition of silicones (commonly polydimethylsiloxane) to these gel formulations adds beneficiary sensory effects to the skin which may be observed during or after the use of the gel.
The proportions of each ingredient are selected to provide good clearing ability and also to result in a product with a texture pleasant to the consumer. Shower gels can be classified according to the type of surfactants present e.g. all-synthetic surfactant, blend of soap with synthetic surfactant and all natural soap with no synthetic surfactant.
A “Soap” as herein defined is composed of one or more carboxylates of long chain fatty acids in combination with one or more cations.
Consumer tests in markets where shower gels are most popular have shown that consumers can detect the difference between a shower gel containing synthetic surfactants and one containing all natural soap, and clearly prefer the 100% soap based gel.
All-synthetic surfactant based products are generally more stable and more easily prepared than soap based products. A number of silicone based compounds give suitably stable emulsions in conjunction with these all-synthetic surfactant products. While these emulsions are relatively easy to manufacture, and have good stability, they suffer from the drawback that consumers can detect a reduction in agreeable skin-feel of the product when compared with a 100% soap based gel. All-synthetic surfactant based products are also less attractive from a marketing point of view as they are not perceived by consumers as having the desirable property of being derived from natural sources. Shower gels containing a 100% soap (that is to say substantially exclusively soap as the surfactant), typically contain around 25% soap in total. As mentioned above, 100% soap based gels are preferable from a marketing point of view, because of their good skin-feel properties and their being perceived as more “natural” than synthetic surfactant based gels.
When manufacturing 100% soap based gels, the key raw materials are the long chain fatty acids which form the soaps. These tend to be low melting solids or waxes which are difficult to process. Heating may be required when preparing the soap.
An even greater problem of the 100% soap based shower gels comprised of a silicone oil-in water emulsion is that such a combination of the soap based shower gel and the silicone oil is not stable. Currently no stable silicone emulsion with a 100% soap is known. Typically, the product begins to separate and exhibit distinct layers ie. a clear, lower water layer and an opaque layer containing components which are not water soluble or water miscible. This can happen quite rapidly, in some cases overnight. Such separated products are generally unacceptable to consumers.
Some silicone compounds provide limited stability for emulsions based on a blend of soaps and synthetic surfactants, with typically more than 5% synthetic surfactant being required. Shower gels which contain a synthetic surfactant/soap blend typically contain around 5 to 15% soap therein. Two types of synthetic surfactant can be used in combination with the soap, namely amphoteric surfactants (for example betaines) or non-ionic surfactants (for example CDEA (coconut diethanolamines)). These surfactants are generally added at a level of 5% into the synthetic/soap surfactant blend. Generally silicone oil-in-water emulsions prepared using synthetic surfactants are stable in synthetic surfactant and soap/synthetic surfactant blend (generally provided that the synthetic surfactant level in the blend is greater than or equal to 5%) based shower gels, but such emulsions are not stable in soap surfactant shower gels.
The present invention seeks to overcome at least some of the disadvantages of the prior art or at least provide a commercial alternative thereto.
DESCRIPTION OF THE INVENTION
According to a first aspect the present invention relates to a silicone oil emulsion stabilized with soap, wherein the soap includes:
one or more carboxylates of a fatty acid having from 8 to 18 carbon atoms; and
a cation of a base, the soap being formed in situ from the fatty acid and the base during formation of the emulsion.
Preferably, the one or more carboxylates is a mixture having a similar distribution to that found in vegetable oils. More preferably, the distribution is that found in coconut oil or palm kernel oil. Most preferably, the mixture is derived from coconut oil. Table 1 shows typical compositions of Coconut and Palm oil which are suitable for use in the present invention.
It will be appreciated by those skilled in the art that compositions of coconut and palm kernel oil vary somewhat depending on the geographical origin, soil composition etc. The average compositions are summarised for the purposes of information only in the Table. The average compositions must be understood such that they may contain other fatty acids which have more or less carbon atoms than those described in the table. The compositions described in the table do not show any particular oil available from a single supplier, but rather give representative compositions. If it is desired to know the exact composition of the oil, this must be examined prior to production of the silicone emulsion.
These oils are available commercially, or may be obtained as precursors which may be converted into the desired fatty acids by chemical treatment such as hardening, cracking, saponification etc depending on the necessity thereof.
TABLE 1
Composition of Coconut Oil and Palm Kernel Oil (% by weight)
Coconut Oil
Palm Kernel Oil
Caprylic Acid (C8)
less than 10
1-7
Capric Acid (C10)
less than 10
1-10
Lauric Acid (C12)
40-60
40-60
Myristic Acid (C14)
10-25
10-20
Palmitic Acid (C16)
5-15
5-15
Stearic Acid (C18)
1-20
1-5
Oleic Acid (C18:1)
less than 10
5-20
The base is one which may be reacted with the above fatty acids to form a soap. Preferably, the base is a trialkanolamine species, most preferably [HN(CH
3
CH
2
OH)
3
]. However, mineral caustics, such as sodium hydroxide and potassium hydroxide may also be used.
Preferably the silicone oil is a “silicone fluid”, and more preferably a polydiorganosiloxane. Such a polydiorganosiloxane is a linear polymer where the organo radical may be hydrogen, an alkyl group such as methyl, ethyl, propyl, butyl, an aryl group such as phenyl, an alkenyl group such as vinyl and the like. Preferably, the polymer terminates with —Si(CH
3
)
3
(“trimethyl endcapped”) or —Si(CH
3
)
2
OH (“hydroxy endcapped”) moieties. Preferably, the silicone oil used has a viscosity below 1,000,000 cps and more preferably below 100,000 cps. The oil may contain other functional groups, such as carboxy, halo etc. or any combination thereof.
The silicone oils of this invention are well known to those skilled in the art, with the most highly preferred compound being trimethylsilyl terminated polymethylsiloxane having the viscosity range described above.
As discussed below, the mean particle size of the emulsion is critical to provide a stable emulsion for use in a 100% soap based shower gel. Preferably the emulsion of the present invention is a “submicro-emulsion” with a
Dow Corning Australia Pty. Ltd.
Duane Morris & Heckscher LLP
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