Method of preparation of sodium aluminum lactate

The present invention is directed to a method of preparing sodium aluminum lactate by reacting aluminum lactate with sodium hydroxide is an aqueous medium. The reaction is carried out within the temperature range of about 20.degree. C. to about 80.degree. C. The weight ratio of aluminum lactate to sodium hydroxide is about 5.0:1 to about 8.0:1. The weight ratio of water to sodium hydroxide is about 0.8:1 to about 2.3:1.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to a method of making sodium aluminum 
lactate. More specifically, this invention involves preparation of sodium 
aluminum lactate by reaction of aluminum lactate with sodium hydroxide in 
an aqueous medium. 
2. Prior Art Statement 
Sodium aluminum lactate powder is well known as a non-irritating deodorant 
ingredient. Previously, manufacturing of this material had accomplished by 
reacting sodium aluminate, lactic acid and sodium hydroxide in batch 
process, however, this process was limited due to pH and viscosity 
instability of its liquid intermediate. The liquid intermediate has a pH 
drift and viscosity increase to the point of a semisolid gel after one to 
two days from the date of manufacture. The pH variation results in product 
quality variation, and an unstable viscosity means that only small 
quantities of liquids are prepared and used almost immediately. 
SUMMARY OF THE INVENTION 
The present invention is directed to a method of preparing sodium aluminum 
lactate by reacting aluminum lactate with sodium hydroxide is an aqueous 
medium. The reaction is carried out within the temperature range of about 
20.degree. C. to about 80.degree. C. The weight ratio of aluminum lactate 
to sodium hydroxide is about 5:1 to about 8:1. The weight ratio of water 
to sodium hydroxide is about 8:1 to about 2.3:1.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
A new method of preparation has been found that eliminates the pH and 
viscosity instability of liquid solutions of sodium aluminum lactate 
discussed above. This new method is useful in that a stable pH and 
viscosity allows commercial quantities of the liquid sodium aluminum 
lactate to be prepared and dried over several days. The stable pH of this 
new method means a constant liquid resulting in constant product quality. 
The new method of preparation uses aluminum lactate, sodium hydroxide and 
water to prepare the pH and viscosity stable liquid intermediate. The use 
of aluminum lactate is new and useful. When aluminum is reacted with 
lactic acid, it forms a stable molecular species, aluminum lactate. The 
stability of the aluminum lactate prevents the formation of aluminum 
hydroxide when the sodium hydroxide is added to the solution. It is the 
formation of aluminum hydroxide that causes the pH shifts and viscosity 
increase. This method produces a liquid that has a constant pH and 
viscosity for greater than 45 days. When spray dried, a white free flowing 
powder is produced with an analysis such as the following: 
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Percent Al 7.9 
Percent Na 14.1 
Percent lactic acid 
78.0. 
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The reaction may be conducted in stepwise bulk fashion or on a continuous 
flow basis. The temperature range within which the process takes place is 
about 20.degree. C. to about 80.degree. C. Lower temperatures may work but 
would be too sluggish for commercial purposes. Higher temperatures shift 
the stoichiometry and are not cost effective from the standpoint of yield 
and from the standpoint of energy consumption. 
In general, solid (powder) sodium hydroxide and aluminum lactate may be 
used. In preferred embodiments, the sodium hydroxide is first added to 
water and then the aluminum lactate is mixed into the sodium hydroxide 
solution. In other embodiments, aqueous sodium hydroxide (e.g. 50% aq.) is 
combined with additional water and then aluminum lactate is mixed in until 
dissolved. In any of the previous embodiments, aluminum lactate may be in 
aqueous solution and combined with the water and sodium hydroxide. 
About 5.0:1 to about 8.0:1 of aluminum lactate to sodium hydroxide, based 
on weight, is used. Also, about 0.8:1 to about 2.3:1 of total water 
content to sodium hydroxide, based on weight is used. 
The aluminum lactate may be formed by reacting aluminum with lactic acid. 
This process may, for example, be carried out as follows: 
EQU 2Al+6 C.sub.3 H.sub.6 O.sub.3 +10H.sub.2 O.fwdarw. 
EQU 2 Al (C.sub.3 H.sub.5 O.sub.3).sub.3 +3H.sub.2 +10H.sub.2 O. 
The constituents are reacted at room temperature and them maintained in 
aqueous form or dried and used in solid form and either is subsequently 
used in the present invention process. Alternatively, aluminum lactate 
product may be obtained from commercial suppliers. 
The sodium aluminum lactate resulting from the present invention method is 
an aqueous product with stability and relatively constant, reliable 
viscosity. Thus, the present invention method consistently yields a 
product with a pH of about 3.0-3.2 up to about 7.4-7.6 dependent on water 
in the formulation. The viscosity is dependent in part upon the water 
content, but is stable for at least a month and a half to two months. On 
the other hand, prior art products of sodium aluminum lactate have 
drifting or varying pH results from as low as 7 to as high as 10, with 
changes in pH of as much as 2.0 over a one to two day period. 
The following examples of the present invention are illustrative: 
EXAMPLE I--SOLID REACTANTS 
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Formulation: 
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Aluminum Lactate (Powder) 
35.0% 
Sodium Hydroxide (Powder) 
10.0% 
Water 55.0% 
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Charge water to vessel. While mixing, slowly add sodium hydroxide and mix 
until a uniform solution is produced. While mixing, slowly add aluminum 
lactate and mix until all dissolved. 
The resulting product was subsequently spray dried with the following 
assay: 
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Powder - Assay, Percentage 
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Aluminum 
7.9 
Sodium 14.1 
Lactic acid 
78.0 
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EXAMPLE II--AQUEOUS SODIUM HYDROXIDE 
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Formulation: 
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Aluminum lactate 35.0% 
Sodium hydroxide (50% aq.) 
16.0% 
Water 49.0% 
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The same procedure as Example I ws used, except that aqueous sodium 
hydroxide instead of powder was added to the water. 
The results of the spray dried product assay are: 
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Aluminum 
7.9 
Sodium 12.4 
Lactic acid 
79.7 
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