Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1999-08-30
2001-10-02
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...
C570S146000, C570S147000, C570S153000, C570S155000
Reexamination Certificate
active
06297205
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to transparent bar soaps, and more particularly to moisturizing transparent bar soaps essentially free of monohydric alcohol and having a high humectant content.
A personal bar soap is characterized as “moisturizing” if the bar soap contains an agent that helps retain moisture in the skin (i.e., a “humectant”). Humectants (such as glycerin) help prevent the skin from excessively drying during the wash process. Excessive skin drying can result in raw, red, chapped, irritated, itchy, or cracked skin—especially for those with sensitive skin or during the winter months when indoor air heating can create very dry air that contributes to skin drying. Generally, the more humectant that is present in the bar soap, the better the moisturizing attributes of the soap.
Consumers consider a transparent bar soap having a high humectant content as a premium bar soap, not only because of the enhanced moisturizing properties, but also because the humectant content significantly increases the cost of the bar soap. However, increasing the amount of glycerin humectant to provide better moisturization for a transparent bar soap generally decreases the desirable hardness, resistance-to-wear, and foaming attributes of the bar. For example, U.S. Pat. No. 5,786,311 issued Jul. 28, 1998 to Zyngier entitled “Monohydric Alcohol-Free Process for Making a Transparent Pour Molded Personal Cleansing Bar” states that the amount of humectant (such as glycerin and propylene glycol) in the transparent bar soap should not exceed about 37%. (Column 7, lines 6-9.) Further, although the hardness and detergency of a bar soap can be improved by increasing the fatty acid soap content, that component also tends to negatively affect the transparency of the bar soap.
Soap formulators have addressed these problems by adding significant amounts of monohydric alcohol (e.g., ethanol) to dissolve the fatty acid soap. However, monohydric alcohols contribute to skin dryness. Also, bars containing monohydric alcohol typically display increased weight loss due to evaporation of the volatile alcohol. Specialized and expensive explosion-proof process equipment is also required with monohydric alcohol-containing soap formulations, due to the volatile and explosive nature of monohydric alcohols.
The fatty acid soap component of a bar soap can be made in situ by the well-known saponification process—that is, the reaction of triglyceride with caustic to produce fatty acid soap and glycerin. However, the high temperature associated with the saponification process frequently causes undesirable discoloration of soap bars.
SUMMARY OF THE INVENTION
The aforementioned problems are overcome in the present invention wherein a monohydric alcohol-free transparent bar soap formulation includes a high level of humectant solvent, yet has good hardness and wear characteristics. More specifically, the inventive soap formulation includes from about 38% to about 96% of one or more humectant solvents, such as glycerin and propylene glycol. The formulation also includes from about 3% to about 20% of insoluble and/or soluble fatty acid soaps, so that the amount of insoluble fatty acid soap is at least about 3%. The weight ratio of humectant solvent to insoluble fatty acid soap ranges from about 3:1 to about 23:1. The formulation is substantially free of monohydric alcohol, and produces a transparent solid bar soap having a standardized wear rate of less than about 15% and a hardness of from about 30 to about 100 hardness units, or about 3 mm to 10 mm, where each hardness unit is 1/10 mm penetration into the bar.
The transparent solid bar soap may be manufactured by: (i) forming a liquid homogenous bar soap mixture that includes the above-described amounts of components and that is substantially free of monohydric alcohol, (ii) transferring the homogeneous liquid mixture to a mold or tray, and (iii) cooling the transferred mixture to form a transparent solid bar soap having a standardized wear rate of less than about 15% and a hardness of from about 30 to about 100 hardness units or about 3 mm to 10 mm where each hardness unit is 1/10 mm penetration into the bar.
The inventive soap formulation provides several advantages. The formulation includes high amounts of humectant solvent to provide superior skin moisturization characteristics; yet, the formulation produces transparent—even clear—bar soaps having wear rates and hardnesses comparable to opaque bar soaps. The formulation produces very light yellow to water-white bar soaps that provide a wide range of color options. During storage, the finished bar soap maintains its transparency without crystallization of the fatty acid soap molecules that can cloud the bar soap. During use, the bar soap formulation does not leave a drying film or greasy residue on the skin.
PARAGRAPH A1
The inventive process of forming the transparent bar soap also has several advantages. The process uses relatively short batch times and moderate temperatures, thus avoiding the discoloration problems associated with longer batch times and higher temperatures, such as those required for the saponification process of soap manufacture. The process can use a conventional batch mixing tank that is lower in operating, installation, and equipment costs than the specialized explosion proof equipment associated with making soap from saponification processes using alcohol formulations. Further, the process reduces the safety hazard that is a part of processing mixtures above their flashpoint. The soap formulation can be “hot poured” directly to a mold for cooling to form a solid bar. Since the soap may be poured at a relatively low temperature, the mold can be constructed of relatively less expensive materials such as plastic, high density polyethylene (HDPE), polyethylene terephthalate (PET), or polypropylene (PP). Advantageously, using the low temperature molding techniques, and such low cost molds, it is possible to use the mold in which the soap is actually manufactured as the final packaging apparatus marketed to consumers. Further, because the molten soap can be packaged before it actually congeals, the additional congealing time is eliminated from the manufacture of finished product soap bars. Unlike monohydric alcohol-containing soaps, the forming of fatty acid soap crystals is relatively independent of the cooling rate; thus, the inventive formulation does not need to cool slowly to maintain transparency. Also, the bar soap scrap material from the bar soap finishing process can be recycled to the next batch for continuous processing.
These and other objects, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description of the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The attributes of the bar soap formulation of the present invention can be characterized by reference to several categories, such as transparency, hardness, and wear rate, which are described below. The inventive bar soap formulation also includes one or more of the following components: (i) fatty acid soaps, (ii) humectant solvents, (iii) water, (iv) fatty acid soap solubilization aids, and (v) lathering synthetic surfactants, which are also described below. Further, the transparent bar soap can be manufactured using a “hot pour” method without the need for in situ saponification.
Bar Soap Characteristics
It is desirable that a transparent moisturizing bar soap have good performance in the following categories: (1) transparency, (2) hardness, (3) wear rate, (4) foaming, (5) weight loss, (6) stability, and (7) pH.
A bar soap is considered “transparent” if one can read 14 point type font through a ¼ inch thickness of the bar. A bar soap is considered “clear” if one can read 6 point type font through a half-inch thickness of the bar.
The hardness of a bar soap is expressed in “hardness units,” which are measured by a Penetrometer at room temperature. Each hardness unit is 1/10 mm. The hardness is represented by t
Luke William M.
Saxena Rahul
Amway Corporation
Ogden Necholus
Warner & Norcross & Judd LLP
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