Field of the Invention

The present invention relates to an improved saturated soap, which may be used in cosmetics and toiletry applications to replace conventional toiletry soap. Soaps produced by this inventive method are extremely mild, foam well; provide consumer-desired sensory properties and low skin irritation.

Background of the Invention

Soaps are constantly moving towards better formulations that ultimately will provide some enhanced skin care, for example, minimizing levels of skin irritation and enhancing moisturization as well as providing desirable properties such as voluminous creamy lather and not become slimy when left in a soap dish after used.

Conventional toilet soaps are made from oil and fats or their fatty acids from animal or vegetable based sources by saponification or neutralization with an alkali. Some common problems faced by these compositions include poor stability towards oxidation, high tendency of soap mush and swelling when formulated with liquids and in the case of oil saponification, low soap whiteness. Soap manufacturers add preservatives, antioxidants or chelating agents, to preserve the quality of the soap noodle against oxidation; whereas the soap whiteness can be increased with appearance enhancing additives such as fluorescent whitening agents or optical brighteners. However, the problem of swelling and mush tendencies of soaps with high liquid additives has yet to be solved satisfactorily. But the principal disadvantages of preservatives and appearance enhancing additives are additional cost and environmental and health restrictions. Saturated soaps virtually eliminate the need for preservatives, possess whiteness superior than conventional soap noodles and show less mush and swelling tendencies. However, most saturated soap formulations suffer from high skin irritation, having HIE (Human Irritation Equivalent) values of above 2.0, as tested by the In vitro Dermal Irritection Assay. This improved saturated soap base has been tested to be a non-irritant (HIE value less than 2.0). Conventional toilet soaps are made from blends of oil and fats or their equivalent distilled fatty acids from animal or vegetable based sources. Fatty acids are produced by the hydrolysis of the oil under high pressure and temperature in the presence of water to yield a crude mixture of fatty acids and glycerol. This process is commonly referred to as splitting. The crude fatty acids are then purified to the required purity through the process of distillation, and the valuable by-product of glycerol is processed separately to yield pharmaceutical grades of glycerine with purity of 99.5 - 99.7%.

The desired blend of distilled fatty acids, obtained either by blending different oil and fats before the splitting process or after the splitting process in which the individual fatty acid components are blended to form the desired fatty acid composition, shall then be reacted with an alkali to form soap and water. Such reactions are termed according to their raw material used, in the case of oil and fats is saponification and in terms of fatty acid is neutralization.

The manufacture of the saturated soap is based on neutralization of the saturated fatty acid with an alkali, usually potassium and sodium hydroxide mixtures. The saturated fatty acids are obtained by fractionation of fatty acids.

Further, the applicants of the subject invention saturated soap uses only saturated fatty acids therefore it has superior heat and light stability, as well as having less tendency to oxidized or discoloration and less tendency to swell.

Summary of the Invention

One embodiment of the present invention relates to soap compositions comprising substantially saturated fatty acid metal salts at least 98% by weight of these substantially saturated fatty acid radicals containing from 12 to 18 carbons.

A further embodiment of the present invention, fatty acid composition of alkyl fatty acid radical is C12 15% - 35%, C14 30% - 60%, C16 25% - 45% and C18 0 - 10% with the preferable range being Cj2 15% - 25%, C14 45% - 55%, Ci6 25% - 40% and C18 0% - 5%.

The salts of the fatty acid used in the present invention may be selected from the group consisting of alkali-metal salt such as potassium and sodium, organic basic salt or ammonium salt. In the preferred embodiment of the present invention, alkali-metal salt is selected and preferably sodium and potassium salt is used.

In one embodiment of the invention, the fatty acid radicals being partially neutralized as mixed sodium and potassium soaps, the ratio of sodium to potassium expressed as a weight ratio of sodium hydroxide (NaOH) to potassium hydroxide (KOH) being from 9:1 to 2:1, preferably the weight ratio is from 7:1 to 3:1.

Another embodiment of the invention, the amount of neutralized fatty acid radicals being such that the soap composition contains from zero to 7% of free fatty acids by weight of the soap's composition.

A further embodiment of the invention, the soap composition contains as low as 1% or more than 12% of water by weight of the soap composition at the time of manufacturing

A further embodiment of the invention, the soap composition contains less than 3%, preferably less than 1%, of sodium chloride by weight of the soap composition.

A further embodiment of the invention, the total fatty acid composition has iodine value of less 2g/100g.

A further embodiment of the invention, the soap does not need addition of preservatives in order to preserve its quality.

Detailed Description of the Invention

The Fatty Acid Feedstock The present invention involves the manufacturing of soap with trace amounts of unsaturated fatty acids by fractionating the split oil and fats to high purity saturated fatty acids. The fatty acid composition may be derived from any one or combination of vegetable or animal based fatty acids. The desired fatty acids components will be blended to produce the improved saturated soap according to the present invention.

The present invention is chemically a blend of alkali salt of fatty acid to form the improved saturated soap. It has high contents of salt of saturated fatty acids such as lauric, myristic, palmitic and very low contents of unsaturated fatty acids (oleic, linoleic and linolenic acid) as measured by gas chromatography.

The Soap Base Formulation According to the present invention, there is provided a soap composition in which substantially all the fatty acid radicals are substantially saturated fatty acid radicals, at least 98% by weight of these substantially saturated fatty acid metal salts containing from 12 to 18 carbon atoms. The % weight of Ci2 - Ci4 to Cj6 - Ci 8 fatty acid radicals is approximately 7:3 of the soap respectively. The fatty acid composition of alkyl fatty acid metal salt is C,2 15% - 35%, Ci4 30% - 60%, C,6 25% - 45% and C18 0% - 10%, preferably C12 15% - 25%, C14 45% - 55%, C16 25% - 40% and C18 0% - 5%. The fatty acid radicals being partially neutralized as mixed sodium and potassium soaps, the ratio of sodium to potassium expressed as a weight ratio of sodium hydroxide (NaOH) to potassium hydroxide (KOH) being from 9:1 to 2:1, the amount of neutralized fatty acid radicals being such that the toilet soap noodles composition contains from zero to 7% of free fatty acids; the toilet soap composition contains as low as 1% or more than 12% of water by weight of a soap noodle composition at the time of manufacturing and less than 3% by weight of a soap noodle composition of sodium chloride.

The C12 - C14 fatty acids is preferably derived from coconut and/or palm kernel oil where the C6, C8 and ClO fatty acids are preferably removed with fractionation as both is known to cause slight skin irritation. The Cl 6 and Cl 8 acids are obtainable from fractionation of tallow or palm oil. The iodine value of the total fatty acid content is less than 2g/100g. The ratio of sodium to potassium soap in the composition is also expressed as a weight ratio of sodium hydroxide to potassium hydroxide. If this ratio is above 7:1, the soap base lack solubility but below the ratio of 3:1, the soap becomes too soft, sticky and has high mush tendency. The recommended working ratio of sodium to potassium soap in the composition is 7: 1 to 3 : 1.

The neutralization is done such that the final soap composition contains from 2% to 7% of free fatty acids. Below 2% superfatting, the soap does not lather well but above 7% superfatting the soap's stability towards oxidation is reduced. The soap products containing free fatty acids have a greater tendency to undergo auto-oxidation. The presence of fatty acids in fats and oils also tends to show a similar effect; the presence of a free carboxylic group is necessary for this catalytic effect. Therefore, the recommended working range of superfatting is 2% to 6%.

The moisture content of the soap may be as low as 1% or more than 12%. At moisture contents below 1%, the soap tends to be hard and difficult to process on conventional plodders whereas moisture above 18% causes the soap to be too soft to be plodded.

The sodium chloride content of the soap is less than 3%, preferably less than 1%. With dosages below 0.3%, the soap tends to be soft whereas dosages above 3% will cause plodding difficulties.

The need for a soap that does not contain preservative and appearance enhancing additives for the Japanese additive-free soap is fully met by the improved saturated soap base of the present invention. Moreover, this saturated soap has been improved to have lower skin irritation that other saturated soaps.

Advantages of the Invention: 1. Superior natural rich, creamy and copious foam. Consumers perceive rich, creamy and copious foam as premium and luxurious soap properties. Although lathering does not necessarily equate with detergency, consumers associate quick, copious foam with quality and cleaning. Foaming characteristics can be influenced by many factors. Among them are fats and oils type and ratio. Many additives that are oily in nature will tend to act as defoamers if incorporated at high levels. Undoubtedly this property has been capitalized in many facial cleansers by the incorporation of foam boosters.

This improved saturated soap of the present invention is a natural soap that has good intrinsic foaming capability. Due to the high composition of laurate and myristate salt in the soap, this soap produces more foam than conventional soap without the need to add foreign chemicals such as foam boosters. Studies indicated that although foam boosters work well to increase the foaming capability of a particular soap, it also causes defects to the soap - notably the incorporation of most foam boosters will inevitably cause an increase in the mush and smear tendencies of the soap.

Soaps of C6 - C 10 fatty acids give soft, large and plentiful foam. However, these soaps possess strong odor and are known to be skin irritants. Thus, the best fatty acid chain lengths to work with are the C12 -14 soaps. These soaps own the same foaming properties as the lower chain length soaps but they are free of pungent odor and do not cause skin irritation. Thus, for conventional soaps, the foaming capability increases with the increase in the coconut oil and/or palm kernel fatty acids (major contributor of Cl2- 14 soaps) portion in the soap blend. Foaming characteristics can be influenced by many factors.

2. Additive free In another embodiment of the present invention, the improved saturated soap does not need addition of preservatives (notably chelating agents, sequestrants and antioxidants) in order to improve the quality (particularly the stability) of the soap. The absence of bleaching agents and the non-requirement of optical brighteners, fluorescent whitening agents and chelating agents (EDTA), contribute towards environmental protection as well as reduction in processing cost and resources.

3. Low skin irritation A further embodiment of the present invention, the soap has lower skin irritation expressed as the HIE value as compared to some saturated soaps (HIV values of above 2.0). This has been confirmed via the In-vitro Dermal Irritection Assay, where the final HIE value is less than 2.0.

4. Heat stability and the fatty acid composition of fatty acid feedstock. Soaps produced according to this invention will have superior heat and light stability without the need for preservatives such chelating agents or antioxidants. The soaps are thus more natural as it does not contain preservatives. Unsaturated fatty materials will be prone to auto-oxidation than its saturated counterpart, as the free radical intermediates generated in such fatty materials are resonance stabilized by unsaturation.

5. The measurement oxidation A great number of tests have been developed to measure and monitor the development of rancidity in bar soap and other fatty matter containing products. There is no ideal chemical or physical method, which correlates well with changes in organoleptic properties of a product during the entire course of autoxidation. The ultimate test of the suitability of any procedure remains in its agreement with sensory perception of product discoloration and formation of rancid odors.

Due to the absence of unsaturated fatty acids, this superior saturated soap is inherently stable and does not require supplement of additives such as antioxidants or chelating agents. This soap noodles also addresses the problem of EDTA usage in Japan and other EU countries.

6. Whiteness consistency Whiteness appearance of the superior saturated soap is measured in the Hunter Lab Whiteness scale using the Hunter Lab Color Quest 45/0 with DP9000 (related to ASTM E313-73). Conventional white soaps (without appearance enhancing additives) have HWI range from 50 - 75, however, saturated soaps of the present invention have found to have whiteness indices above 75. This superior whiteness permits the production of visually attractive white soap without the need of optical brighteners and/or opacifiers to "whiten" the color of the finished soap and the use of color pigments to beautify the soap. Good soap whiteness is of paramount importance for additive-free soap (due to its tendency to discoloration) and syndets/combars especially when it needs to be formulated with dark color additives such as LABS.

In another embodiment of the present invention, saturated fatty acid feedstock show less tendency to oxidize (and discoloration) during storage and during the neutralization process allowing consistent and small batch-to-batch whiteness of soap to be produced from different production runs. Due to unsaturated fatty acids, conventional soap feedstock will deteriorate with storage (even in nitrogen-blanketed tanks) and this results in a gradual increase in the feedstock color (eventually reducing the whiteness of the soap produced from it). For this reason, it is not advisable to keep feedstock for more than one week for making white soap. Moreover, it is also not advisable to keep feedstock in large quantity as this may result in gradual decrease in whiteness of the soap produced when the tank is full to emptying of the tank. Chemically, saturated fatty acids do not show the tendency to oxidize as compared to conventional soap feedstock containing unsaturated and saturated fatty acids. This enables longer storage of fatty acid feedstock for soap production and reduces batch-to-batch whiteness variation of the feedstock. The stability of saturated fatty acids allow for consistent soap whiteness within and beyond a production batch.

7. Mush and Smear Behavior In another embodiment of the present invention, the soaps produced according to this formulation shows lower tendency to mush and smear. The soap mush and swelling tests measures the consumer-perceived bar economy. It gives an indication on the tendency of the soap to form unsightly mushy soap paste in dish. In the case of saturated soap, the absence of unsaturated soap is the most probable cause for the reduction in mush and swelling tendency. Additives for the Superior Saturated Soap Effects of Unsaturation Due to the absence of preservatives (chelating agents/antioxidants) in the improved saturated soap of the present invention, care must be exercised in the selection of additives to be added at the finishing line. Although the improved saturated soap itself is stable towards oxidation, addition of unsaturated fatty matter in the form of super fatting oils or fatty acids or certain perfume type may spark the initiation of oxidation. In the case where such unsaturated matter is added to this improved saturated soap, preservatives in the form of chelating agents or antioxidants can be added in the additives prior incorporation to the soap base.

It is to be understood that the present invention may be embodied in other specific forms and is not limited to the sole embodiment described above. However modification and equivalents of the disclosed concepts such as those which readily occur to one skilled in the art are intended to be included within the scope of the claims which are appended thereto.