Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2001-08-06
2003-09-09
Delcotto, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S127000, C510S130000, C510S137000, C510S138000, C510S158000, C510S159000, C510S503000, C510S506000, C510S509000
Reexamination Certificate
active
06617293
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid soap and particularly to a liquid soap specifically formulated to thicken upon dilution.
BACKGROUND OF INVENTION
There has been a trend in the commercial care cleaning and personal care industries to supply concentrated products that can be diluted with water either manually or by a dispenser to provide “ready-to-use” (RTU) products for the end user. This approach reduces the costs associated with the bulk packaging, handling, transportation, and storage of such products.
Liquid soap manufacturers can purchase concentrated surfactant blends and typically these concentrate blends are very viscous liquids or semi-solids. These concentrated surfactant blends are commonly a blend of anionic surfactants, amphoteric surfactants, and alkanolamide type surfactants. Appropriate amounts of water, fragrance, and dye are later added to these surfactant blends in the soap manufacturing plant to make a finished product.
Typically, upon dilution with water, the concentrated liquid soap become thinner, that is, a soap with reduced viscosities. This results in a RTU liquid soap having a viscosity that is generally equal to or less than the viscosity of the concentrate surfactant blend. Thus, the concentrate surfactant blends offer little benefit or convenience to the soap manufacturer or end-users due to the low dilution ratio (about 2:1 or 3:1 water:concentrate).
Unfortunately, higher dilution ratios result in low viscosity solutions that are undesirable for liquid hand soap, shampoo, or body wash type product applications. It is often necessary to add thickening agents when diluting the concentrate to increase the viscosity of the RTU soap.
European patent application (EP 0724013 A1) discloses a detergent concentrate of two or more surfactants having differing resistance to electrolytic salting out in the form of micellar solutions, thus, lower viscosity in the concentrate state. Upon dilution with water, the micellar phase transforms into a lamellar phase that leads to an increase in viscosity. However, the concentrate described in this application still has rather higher viscosity (about 2500 cps), and the diluted concentrate has a viscosity equal or less than that of the undiluted concentrates (200 to 2500 cps). Generally for RTU liquid hand soaps, the desired viscosity should range from about 1000 to about 15000 cps.
As disclosed in WO95102664, a liquid concentrate is described, which when diluted with water to gives a liquid composition, having the same viscosity or increase in viscosity. The concentrate contains a thickening component described as (1) a surfactant consisting of an ether sulfate or a mixture with another anionic surfactant or nonionic or amphoteric, or a cationic surfactant, and an electrolyte. The levels of electrolyte disclosed in the examples are all exceedingly high (13-17%). The dilution ratio is typically 3:1 or 4:1. However, the reference failed to recognize the instability of diluted liquid caused by pH drift, ultimately influencing the viscosity of the final product.
It is known that nonionic surfactants such as amine oxides will spontaneously form rod-like micelles upon the addition of solvent (e.g. water), thereby forming a thickened solution, and this thickening-on-dilution property does not require the presence of electrolytes. In U.S. Pat. No. 6,150,320, a concentrated hand soap composition is disclosed that gives the same or higher viscosity when diluted with water. Unfortunately, the viscosity of the diluted liquid soaps was not very high.
There has been a commercial liquid soap that utilizing the synergistic thickening mechanisms of amine oxide and anionic surfactants-electrolytes interactions to achieve thickening-on-dilution property. However, the thickened solution is sensitive to the pH of the solution.
Certain anionic surfactants such as alkyl alcohol sulfates or alkyl ether sulfates are known to be unstable in acidic condition, thus it is common practice to add pH adjusters such as citric acid or NaOH to shift the pH of the liquid soap to about 7. However, those pH adjusters do not have the capacity to maintain constant pH, so when the pH of the soap solution drift to a lower pH (acid) over time, the surfactants will be hydrolyzed and soap performance is lost.
There exists a need for low viscosity concentrate surfactant blends such that the soap concentrate can be diluted with water, preferably using a gravity feed type fluid dispensing system, where the diluted RTU soap has a significantly higher viscosity without exhibiting significant phase separation or crystallization, and is pH stable.
SUMMARY OF INVENTION
Briefly, in one aspect of the present invention, a liquid soap composition is provided comprising:
(a) about 5% to 20% by weight of an amine oxide surfactant or mixture thereof having the general formula R1R2 R3N→O, where R1 and R2 are the same or different and are selected from methyl or ethyl and R3 is a straight or branched chain saturated or unsaturated alkyl group having from about 6-24 carbon atoms;
(b) about 10% to 40% by weight of an anionic surfactant or mixture thereof;
(c) about 2% to 5% by weight of an electrolyte;
(d) a water content of about 10% to 40% by weight; and
(e) about 0.5% to 5% by weight of a buffering agent, sufficient to maintain the pH of the composition between about 8 and about 10.
concentrated liquid soap composition which readily increases in viscosity upon dilution with water, the concentrated liquid soap composition comprising
Advantageously, the formulations of the present invention thicken upon dilution and are pH stable. In the present invention, the pH of the diluted soaps is maintained between 8 and 10. While not intending to be bound by theory, it is believed that this pH range facilitates the formation of microstructure of the surfactants, which in turn “thickens” the RTU soap. Generally, a pH drift below 8 will turn amine oxides into a cationic surfactant which is incompatible with the anionic surfactants in the composition. A tradition pH adjuster is not sufficient to maintain long-term stability of the RTU liquid soaps.
Advantageously, the buffer system used in the present invention will not disrupt or interfere the formation of the microstructure of the soap surfactant in the diluted state and provides the improved RTU soap stability.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
This invention describes a low viscosity concentrate surfactant system that readily increases in viscosity upon dilution with water to give a ready-to-use liquid soap that is pH stable over time. The concentrate comprises an amine oxide surfactant, an anionic surfactant, an electrolyte, and a buffering agent.
The viscosity of the concentrate is sufficiently low (less than about 300 cps) so it is easily pumpable or easily gravity feedable so that it can be dispensed by a variety of dispensing systems, including gravity feed type dispensing systems such as the 3M Twist 'n Fill™ dispenser. The dilution ratio of water to concentrate (weight of water to weight of concentrate) for the soap applications ranges from 5:1 to 15:1. This produces ready-to-use soaps with a viscosity range of from about 500 to 15,000 cps.
Particularly useful classes of anionic surfactants in the present invention include sodium lauryl sulfates, ammonium lauryl sulfates, and lauryl ether sulfates having various degree of ethoxylation to build the viscosity. Examples of these classes of anionic surfactants include those sold under the tradename “EMPICOL”, available from Rhodia, Cranbury, N.J. Preferably, the total amount of anionic surfactant (the active ingredient) in the concentrate is about 10% by weight and not greater than approximately 40% by weight of the total composition, more preferably from about 10% to 25% by weight.
The electrolyte used in the compositions of the present invention will typically be sodium chloride. However, other water soluble electrolytes, such as ammonium chloride, may also be used. Preferably, the total amount of electrolyte (the active ingredient)
3M Innovative Properties Company
Delcotto Gregory
Peters Carolyn V.
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