content_image/931074.jpg content_image/931073.jpg content_image/931072.jpg
[0041] Per the preferred embodiments, lactic acid, pKa of 3.86, and monoethanolamine, pK$_{6 }$ of 4.56, the pH at the equivalence point should be 6.65. This is experimentally verified in FIG. 2. Because of the spontaneity of the reaction the ratio of acid to base can be in any proportion, although near equivalence is most desired. 

[0042] The resulting solution varies slightly in appearance depending on the reaction conditions. If the reaction is carried out slowly and the heat is allowed to dissipate the solution can be colorless, but if the reaction is done quickly and heat builds up, then the solution will tum to an amber color because of the oxidation of monoethanolamine. The solution also has a slightly honey-like odor. One inherent observation is an increase in the viscosity of the solution. Starting from two water thin liquids, the final solution has a viscosity of about 1500 to 3000 centipoise. 

[0043] Although there are numerous antimicrobial agents, the most preferred embodiment contains halogenated diphe› nylether. Most specifically, the use of pcmx and/or triclosan is most desired. These two compounds, and most specifi› cally triclosan, interact with the amine salt to produce a more efficacious hand wash. The hypothesis governing this trend is described as charge interaction between the negatively charged triclosan substitutents, chlorines and the hydroxyl group, and the positive charge found on the amine group. Triclosan has a pKa value of 7 .4, so, at the desired pH of the hand wash, the triclosan will be disassociated and have a negative charge. The positive charge on the amine is attracted to the negative charge on the triclosan and, thus, the triclosan is chelated and prevented from precipitating. 

[0044] The antimicrobial properties of the hand wash containing an amine salt are improved compared to hand washes without. This improvement is seen both in the broad spectrum inhibition and the quick inhibition. A log reduction of 2 on hard to kill organisms, specifically Staphylococcus aureus (MRSA) ( ATCC#335 91) at 30 second exposure time, is desired and, as such, this hand wash provides greater than 2 log reduction of both the Gram positive Staphylococcus aureus (MRSA) (ATCC#33591) and Shigella dysenteriae (ATCC#l3313). 

[0045] While making soap through a saponification reac› tion of a primary nitrogenous base with a primary fatty acid, the addition of excess base was examined. Because the high pH resulting from excess base would be irritating and detrimental to the skin care properties of the hand wash, the excess base was neutralized with a second water soluble acid. For a first control (Control 1), a hand wash made without excess base was tested along side the hand wash containing excess base neutralized with the second acid. A second control (Control 2) excess base is present, but is not subsequently neutralized with the second acid. The hand washes included antimicrobial agent, namely triclosan. The base was monoethanolamine. The first acid was !auric acid, and the second was lactic acid. 

[0046] The triclosan was dissolved in dipropylene glycol, to make an "active premix." The monoethanolamine was added to the water and then the !auric acid was added. After allowing the saponification process to complete, lactic acid was added to neutralize the excess base, and was added until the solution was brought to a pH of 9 .25. The active premix 

## EXPERIMENTAL 

## Example 1 

was then added to the solution to create the antimicrobial hand wash. The ingredient amounts were as follows: 

<img src='content_image/931074.jpg'>

A log reduction test was performed for each formulation. The samples were tested by placing a loopful (approx 10 microliters) of the formulation into a microbial broth (Staph. Aureus ATCC#6538) for 15 seconds. A sample was then taken from the broth and plated. The bacteria was grown and then counted resulting in a quantitative reduction value, as shown below. 

<img src='content_image/931073.jpg'>

There is a dramatic increase in the log reduction for the antimicrobial hand wash employing excess base subse› quently neutralized with a second acid. This suggests that the neutralized excess base improves the antimicrobial prop› erties of the hand wash. 

[0047] Because there is a boost in the efficacy of the product due to the use of excess primary nitrogenous base and a secondary neutralizing acid, alternate bases were tested. The focus was to find suitable weaker bases that might be used, because weaker bases should further reduce the degree of skin irritation experienced when using a resultant antimicrobial hand wash. Samples were made using the same procedure as in Example 1, but with alternate bases. Because the bases had different molecular masses, the percentage used in each sample was different. This was done in order to ensure that the same number of moles were present in each sample, thus allowing for the same concen› tration of amine salt in the final hand wash. As mentioned the same formulation was used as in Example 1, but with the base, monoethanolamine, replaced with the following: 

<img src='content_image/931072.jpg'>

## Example 2 

