Toilet soap bars superfatted with branched chain fatty acids having from about 8 to 12 carbon atoms and where the branching occurs at the carbon position alpha to the carboxyl group.

BACKGROUND OF THE INVENTION 
This invention relates to superfatted soaps and more particularly to soaps 
which have been superfatted by the use of certain fatty acids whereby the 
lathering of the superfatted soap is enhanced and the tendency of the soap 
to become rancid is reduced. The superfatted soap is preferably of toilet 
quality in the form of bars. 
Soaps employing superfatting agents of many kinds are known in the art and 
are commercially available. Such superfatting agents can include lanolin, 
higher fatty alcohols, mineral oils and higher fatty acids. The use of 
free fatty acids as a superfatting agent in soap is described in U.S. Pat. 
No. 3,576,749 to Megson. According to this patent, the presence of free 
fatty acids such as lauric, palmitic, stearic, oleic and others in the 
soap product improves the volume and quality of lather, causing it to be 
more stable with smaller air bubbles which give a lather characterized as 
richer and creamier, and is also alleged to tend to soften skin. Thus the 
incorporation of free fatty acids into a soap bar is desirable in that it 
helps eliminate free alkali, lowers the pH and may make the soap milder. 
It is also indicated to improve the lathering characteristics of the bar. 
Our studies indicate that the customary free fatty acids added to soaps as 
a superfatting agent and the soap molecules reach an equilibrium 
distribution by migration. This migration tends to be in the direction of 
the free fatty acid portion having a composition similar to that of the 
total soap. For example, consider a soap base consisting of 70 parts 
sodium tallowate and 30 parts sodium cocoate to which has been added 10% 
by weight of coco fatty acids as a superfatting agent. The coco fatty 
acids normally contain about 50% of lauric acid (C.sub.12). After the soap 
was processed and allowed to stand for a period, analysis of the free fat 
portion of the soap showed that the lauric acid content had dropped from 
about 50% to about 17.6% which is about the lauric acid content of the 
entire soap product. Analysis of the free fat of this same soap base also 
showed that the unsaturated fatty acid portion (oleic acid) had increased 
from an initial 5% to about 42.3%. The tallow portion of such a 70/30 
ratio tallow/coco base contains about 42% of oleic acid. 
Thus, by migration, the free fat portion of a soap made with tallow fatty 
acids, when superfatted with a fatty acid such as coco, could contain a 
large amount of unsaturated fatty acids such as oleic, linoleic and 
linolenic, all of which are particularly prone to rancidity. 
We have also found that with a soap base consisting of 90 parts by weight 
sodium laurate soap and 10 parts by weight oleic acid as the superfatting 
agent, an analysis of the superfatting agent after a period of time shows 
a mixture of free lauric and free oleic acid in about a 9:1 ratio. This 
shows that by virtue of migration, the ratio of free oleic and free lauric 
acid in the superfatting agent is about the same as in the original 
mixture, that is, 90 parts of sodium laurate with 10 parts of oleic acid. 
Thus, migration causes a distribution of fatty acid chains similar to that 
of the overall soap product even though the acid used to superfat the soap 
has a different distribution. This migration is about the same whether the 
free fatty acid is added to the finished soap pellets or to the neat soap. 
This migration of fatty acids can be a problem. Since tallow fatty acids 
are a prime acid source for producing soaps and tallow fatty acid is 
composed mainly of oleic, linoleic and linolenic acid which are 
unsaturated acids, through migration there will be a greater proportion of 
oleic acid in the superfatting agent, and this can lead to rancidity 
problems. 
SUMMARY OF THE INVENTION 
We have discovered that the problems associated with the migration of fatty 
acids in a soap containing free fatty acids as an additive or as a 
superfatting agent may be substantially reduced or eliminated entirely by 
employing as the superfatting agent organic acids which have a lower 
acidity, or higher pK.sub.a, than the acids used to form the soaps 
themselves. For this purpose we have discovered that branched chain fatty 
acids having from about 8 to 20 carbon atoms and where the branching 
occurs at the carbon position alpha to the carboxyl group are suitable. 
Examples of such branched chain fatty acids include ethyl octanoic, ethyl 
decanoic and ethyl hexanoic as well as the rosin acids such as abietic, 
dehydroabietic and dihydroabietic acid, all of which work well as 
superfatting agents in soap products. We also find that the presence of 
such branched chain acids seems to enhance lathering of the finished soap 
product. 
Thus the incorporation of such branched chain fatty acids in soaps made 
from tallow and/or coco fatty acids provides an excellent superfatting 
agent which does not migrate and thus will not become rancid through 
oxidation; that is, liberation of unsaturated acids such as oleic, 
linoleic or linolenic is greatly reduced or eliminated. 
It is known from U.S. Pat. Nos. 3,793,214 and 3,926,828 that branched chain 
C.sub.5 -C.sub.18 saturated aliphatic monocarboxylic acids including 
2-ethyl hexanoic acid, can be employed in transparent soap products to aid 
in maintaining the transparency and glossy surface appearance of such 
soaps. These references disclose that from about 10 to 20 parts by weight 
based on the total weight of the soap base comprises such a branched chain 
C.sub.5 -C.sub.18 saturated acid. However, these references do not 
disclose the use of similar branched chain fatty acids in free form as a 
superfatting agent for soaps, the branched chain acids as used in 
accordance with the teachings of these two patents being neutralized 
preferably through the use of a combination of sodium hydroxide and 
triethanolamine. 
In addition, U.S. Pat. Nos. 2,628,195 and 2,628,202 disclose the use of 
2-ethyl hexanoic acid as an additive to a stearic or other oil-soluble 
soap to be used as a lubricating grease. As with the two previously 
mentioned patents dealing with the production of transparent soaps, these 
patents use the salt form of 2-ethyl hexanoic acid and the acid itself is 
not in a free form in the lubricating composition. 
The amount of the aforesaid branched chain fatty acids to be used in soap 
products according to our invention will range from about 2% to about 15% 
by weight of the soap with about 5% to about 10% by weight being 
preferred. These branched chain acids may be added to the soap base in the 
same manner and at the same stages as is recommended by the art with 
respect to the customary long chain acids such as coco or tallow. We 
prefer to add the acids to the soap pellets.

The following soap formulations were evaluated. 
EXAMPLE I 
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SOAP BASE 
BAR % Tallow % Coco SUPERFATTING AGENT 
% 
______________________________________ 
A 55.0 45.0 Stripped Hydrogenated 
8.0 
Coco* 
B 42.4 57.6 Tallow Fatty Acid 
10.0 
C 55.0 45.0 2-Ethyl Hexanoic 
8.0 
D 49.6 50.4 C.sub.8 -C.sub.10 Fatty Acid 
5.8 
______________________________________ 
*C.sub.8 to C.sub.10 fatty acids have been removed 
After all bars had been stored at room temperature for a period of 7 days, 
the free acid portion of all bars was extracted and analyzed by gas 
chromatography with the following results. 
______________________________________ 
BAR 
FATTY ACID A B C D 
#C % % % % 
______________________________________ 
8 4.4 
10 2.8 
12 19.3 20.9 20.7 
14 11.2 11.4 13.2 
16 8.5 8.7 8.1 
16-1 4.6 5.4 3.7 
18 6.7 4.2 5.7 
18-1 35.9 37.3 30.2 
18-2 10.4 7.3 4.8 
17 1.5 
2-EthylHexanoic 91.3 
Misc. 3.2 4.6 8.0 1.6 
______________________________________ 
It will be seen from the above that Bar C which was superfatted with 
2-ethyl hexanoic acid showed almost no migration although the straight 
chain C.sub.8 -C.sub.10 fatty acid used as the superfatting agent in Bar D 
showed considerably more migration. 
EXAMPLE II 
To evaluate the lathering performance of a soap containing 2-ethyl hexanoic 
acid, the following soap formulations were prepared and stamped into bars. 
______________________________________ 
SOAP BASE 
BAR % Tallow % Coco SUPERFATTING AGENT 
% 
______________________________________ 
E 55 45 Stripped hydrogenated Coco 
8 
F 55 45 2-Ethyl hexanoic acid 
8 
______________________________________ 
In evaluating the foregoing bar soaps, 8 panelists washed their hands with 
each of bars E and F and evaluated the bars for: 
Lather speed: how quickly lather accumulates on hands. 
Lather thinness: thin lather will be watery or "soupy". Thick lather will 
be stiff and compact; staying in a mound. 
Creaminess: creamy lather has a lotion-like quality. 
Bubble size: are bubbles large and fragile or small and dense? 
Lather amount: quantity of lather. 
Each panelist was asked to indicate which bar was preferred with respect to 
each characteristic. 
The results of the test are as follows: 
______________________________________ 
PREFERENCE CONFIDENCE 
BAR E BAR F LEVEL 
______________________________________ 
Lather Speed 
0 8 95% 
Lather Thinness 
8 0 95% 
Creaminess 
0 8 95% 
Bubble Size 
6 2 Not significant 
Lather Amount 
0 8 95% 
______________________________________ 
As seen above, all of the panelists found that the soap bar superfatted 
with 2-ethyl hexanoic acid was significantly superior in lathering 
characteristics (excepting bubble size) to a soap bar superfatted with 
stripped hydrogenated coco fatty acids. In evaluating lather 
characteristics of soap we consider lather speed, creaminess and the 
quantity of lather to be the most important criteria. 
EXAMPLE III 
Bars A, B, C and D were also subjected to color stability tests. Such tests 
involve separately subjecting the bars to a mercury vapor light for 6 
hours and ultra-violet light for 16 hours. The bars were then evaluated 
for color at various time intervals with the following results. 
______________________________________ 
REFLECTOMETER RATING** 
BAR 2 Week 4 Week 8 Week 13 Week 
______________________________________ 
A 7.3 6.6 5.9 5.4 
B 7.2 6.4 5.7 5.2 
C 7.9 7.5 7.1 6.5 
D 7.2 6.2 5.5 5.0 
______________________________________ 
**Higher numbers indicate better color stability 
It will be observed that Bar C, which contained 2-ethyl hexanoic acid as 
the superfatting agent, has better color stability than the other 
formulations tested. 
EXAMPLE IV 
Soap bars were prepared having the following formula 
______________________________________ 
Soap Base sodium tallowate 
85% 
sodium cocoate 
15% 
Superfatting agent 
abietic acid*** 
16% 
______________________________________ 
***Available as "DR20" from Arizona Chemical Company 
After the bars had been stored at room temperature for a period of 3 days, 
the free acid portion of the soap was extracted and analyzed by gas 
chromatography. The analysis did not detect the presence of C.sub.8 
-C.sub.18 acids, including the unsaturated oleic, linoleic and linolenic 
acids. 
The soaps to be employed in our invention can be characterized as water 
soluble salts of higher fatty acids, particularly the alkali metal salts, 
for example, the sodium and potassium salts, thereof. Such fatty acids in 
general have chain lengths comprising from 8-20 carbon atoms and 
predominantly from 10-18 carbon atoms. The soaps are conventionally 
prepared by the saponification of alkaline materials of a mixture of 
tallow-class fats and oils. Sodium and potassium soaps can be prepared by 
direct saponification of fats and oils or by the neutralization of the 
free fatty acids which are prepared in a separate manufacturing process. 
Particularly useful are the sodium and potassium salts of mixtures of 
fatty acids derived from coconut oil and tallow, i.e., sodium and 
potassium tallowate and/or cocoate. The invention is particularly useful 
in soaps which contain a proporation of sodium tallowate since the 
tallowate has a higher percentage of unsaturated fatty acids. That is, the 
problem of migration is greater in sodium tallowate soaps. 
The amount of alpha branched fatty acid used as the superfatting agent in 
soaps can range from 2 to 15 percent. Preferably from about 5 to 10 
percent. 
From the foregoing examples we see that the incorporation of alpha branched 
fatty acids having from about 8 to 20 carbon atoms into soap increases 
both its stability and lathering.