US 2324348 A
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Watented July 13, 1943 PRESERVATION F SOAPS AND FERFUMES Carl N. Andersen, Wellesley Hills, Mass assignor to Lever Brothers Company, a corporation of Maine No Drawing. Application May 28, 1938, Serial No. 210,779
This invention relates to a method of preventing or greatly inhibiting thedevelopment of undesirable odors and colors in soap, perfume, and compositions containing the same; the invention relates also to the resulting compositions.
It is an object of my invention to provide a practical method of preserving perfumed soaps by preventing the development therein of undesirable odors and colors that result from changes in the soap or perfume or both.
In accordance with my invention, I achieve the above objects by adding to the perfume used in the soap, a small quantity of an ascorbic acid or a similar compound of the type hereinafter described. These compounds, I believe, function primarily as antioxidants, thus preventing or arresting the oxidation that would otherwise take place and cause the formation of undesirable odors and colors.
Naturally occurring oils and fats comprise glyceride esters of saturated and unsaturated fatty acids. These oils and fats are used as a primary ingredient in making soap, and soaps produced from such fats contain salts of unsaturated fatty acids.
It is well known in the chemistry of oils and fats that the glycerol esters of unsaturated fatty acids decompose by oxidizing, resulting in the splitting up of the fats into products of lower molecular Weight. Upon exposure of the oil or fat to oxygen or air the oxygen is usually first adsorbed or dissolved in the oil or fat; this is followed by a chemical process in which the oxygen reacts to form peroxides. This is the first chemical step in the development of rancidity and is in turn followed by the formation of aldehydes and other compounds that have an undesirable odor and impart the rancidity to the oil or fat.
In the formation of soap from unsaturated oils and fats, the unsaturated portions of the oil and fat molecules are contained in the soap. Consequently, the soap so formed is unsaturated. The process of reaction with oxygen, which is characteristic of oils and fats, is also characteristic to a marked degree of soaps formed from such oils and fats. As a result, a soap that is exposed to the air gradually assumes a foreign or rancid odor.
Naturally occurring oils and fats often contain ingredients that enable the oil or fat to resist this oxidizing action. During the refining and purifying process to which the oils and fats are normally subjected, however, certain of these naturally occurring constituents are often removed whereby the oxidation of the oil or fat is enabled to take place more readily. In the making of soaps, many naturally occurring antioxidant conremoved during the formation and processing of the soap.
The development of rancidity in either an oil or soap is accelerated by the presence of either light or moisture or both. Therefore, since water is a compound naturally associated with soap and since soap is often exposed to light in its normal use, the development of undesirable and foreign odors in an ordinary soap, due to changes resulting from reactions with oxygen, is favored by conditions that ordinarily cannot be avoided. For this reason it is important that a soap be treated so as to inhibit such oxidation reactions. The oxidizing tendencies of oil and soap are usually progressive, that is, the rate of the oxidation is accelerated as the process continues. For this additional reason it is desirable that oxidation reactions be retarded as much as possible.
In accordance with my invention, I incorporate in soap 9, small amount of ascorbic acid or similar compound which I have found prevents or greatly retards the oxidation reactions and therefore prevents or materially reduces the development of oxidation products and undesirable odors in the soap.
The odor of soap is readily apparent, and the prevention of these oxidation reactions, therefore, is of great importance in the development of an acceptable soap product.
,In addition to the development of undesirable odors, the oxidation reactions in soap usually cause a change in color. This is particularly noticeable in the case of a. white soap, which turns yellow or brown upon oxidation. The change in color usually accompanies the development of rancidity.
Inasmuch as it is the surface of soap, particularly in the cake form, that is exposed to air and light and usually also to water, conditions that accelerate the oxidation, the undesirable odor and color develop primarily at the surface of the soap. But it is also the surface of the soap which is visible to the eye; changes in color at the surface, even though such changes may not be uniform throughout a bar of soap, are particularly undesirable. The quality of a soap is judged largely by the appearance and the odor of the outer portion of the soap cake and it is important, therefore, that even the exposed surface be protected against oxidation.
In accordance with my invention, not only is the development of undesirable odors inhibited, but the formation of undesirable colors that are visible on the surface of the soap is also prevented or retarded.
The compound I employ is effective in very small quantities, and therefore does not materially increase the cost of the soap.
Ascorbic acid is ordinarily believed to be affected adversely by the presence of water and alkali. Inasmuch as soap contains moisture and yields alkali on hydrolysis it might have been expected that ascorbic acid would be unsuitable for any use under such conditions. Contrary to what might have been expected, however, I have found it to be a very effective antioxidant in soap.
It has been proposed heretofore to add antioxidants to soap,but most of these are undesirable for one reason or another. A great many of the antioxidants are toxic or have other harmful actions on the body and are therefore undesirable in a product that is to contact human tissue.
Ascorbic acid is a substance naturally occurring in vegetable materials and also occurs in various parts of the human anatomy; in fact, it contributes to normal metabolism and body health. In employing ascorbic acid in soap as an antioxidant, therefore, I not only obtain advantages from the inhibition of undesirable color and odor formation, but in addition the soap so treated is not rendered harmful because there is no inclusion of any substance that is in the least injurious to human tissue.
I have also discovered that perfumes can be treated in accordance. with my invention to prevent deleterious changes in odor and color.
Most perfumes consist of a mixture of chemical compounds. As a rule, each of these chemical compounds by itself has a rather harsh odor. The delightful aroma, characteristic of flowers, is usually developed only when a number of chemical compounds are present in the proper combination and in the proper proportion, as they exist in nature, or as the skill of the chemist can combine them. i
It is known that many of the compounds that are comprised in.- perfume are unsaturated or contain chemical groups that render them easily capable of oxidation. Geranium bourbon, ionine, heliotropine, aubepine, buxine, and limonene are but a few of many examples that could be named. The products of oxidation are compounds such as peroxides, ozonides, aldehydes and acids. The
- oxidation products in some cases are odorless and in many cases they possess undesirable odors. As the result of oxidation of perfume some of the compounds are decomposed to give odorless or unpleasant smelling compounds; the delicate balance of the compounds in the perfume is de-- stroyed, and the fragrance is materially altered. This can be readily demonstrated by exposing a sample of perfume to light and air and then comparing the exposed sample with an original sealed sample. In some instances the initial exposure to air results in a sweeter odor, due probably to the formation of terpenes, but this condition is only temporary and is followed by the development of rancidity.
The oxidation products of perfume are often dark colored and upon standing exposed to air, a perfume will darken in color. For example, a synthetic perfume prepared from a variety of compounds in proper combination and proportion will have an original color of 11.7 red and 55 yellow. After one month of exposure to air it will have a color of 47 red and 80 yellow.
In accordance with my invention, I have found that ascorbic acid or a similar compound may be added to perfume to prevent or materially reduce the loss of fragrance and the development of undesirable odors, along with a reduction in the darkening of the color. In some instances the addition of the ascorbic acid not only results assassin in an inhibition in color change but produces a slight bleaching of the perfume, unattended by any undesirable change in odor.
I am not aware that it has heretofore been proposed to include an antioxidant in perfume. I am of the opinion that most substances here-- tofore suggested as antioxidants for use in other materials would probably be regarded as unsuitable for inclusion in perfume because of the delicate nature of the aroma and the possibility of the antioxidant reacting or otherwise modifying one or more of the constituents of the per-- fume, thereby altering the delicate balance of the ingredients and modifying the odor. I have discovered, however, that in addition to the ad-- vantage heretofore noted. no deleterious action can be attributed to the inclusion of ascorbic acid in perfume.
In the manufacture of soap, it is quite common to include a perfume. The undesirable re sults of oxidation in a perfumed soap are particularly apparent because oxidation of both the soap and the perfume yield undesirable odors and colors from both these sources.
My invention relates particularly to perfumed soap and the prevention of the development of rancidity and the prevention of the simultaneous development of undesirable odors due to the oxidation of both the soap and the perfume.
The preservation of perfume in soap presents an unusual problem because the presence of even a small amount of free alkali in soap deleteriously afiects the perfume. Tests have shown that soaps containing as little as .0002 part of alkal greathv depreciate the fragrance of the perfume and render constituent compounds in the perfume unstable. Just as certain aromatic substances can be affected by soap. so the latter can be affected by aromatics. It is well known that colorchanges in a neutral white soap can be accelerated by certain perfumes. This is particularly true in the case of artificial musirs and eugenol containing perfumes.
I have found that the. incorporation of as' corbic acid markedly arrests the decomposition by oxidation of both the soap and the perfume and results in a soap that has a much fresher odor after exposure to light and air. The soapylilze rancid odor is absent and the perfume has a much more fragrant and flowery odor than a sample not containing the ascorbic acid.
Tests have shown'that the odor of perfumed soap to which ascorbic acid has been added is far superior to that of soap otherwise identical but not containing ascorbic acid. In the sample not containing ascorbic acid there is a gradual loss of the odor and strength of the perfume, which is replaced by the development of undesirable odors due to oxidation products of both the soap and the perfume. In the sample of soap containing the ascorbic acid, however, the perfume retains its original identity.
Ascorbic acid is more completely identified as B(or 3) -keto 1 gulonogamma lactone. This compound is composed of carbon. hydrogen and oxygen and contains hydroxyl and carbonyl groups, depending on whether or not it exists in the tautomeric enol" or "keto" form. Ascorbic acid is a white crystalline substance hav-' ing the formula Cal-1410a and has a melting point of 192 C.
It may be obtained by isolating it from many vegetable materials in which it occurs naturally or it may be formed by synthesis from glucose or sorbitol by processes well lmown and fully described in chemical literature. Material from either source may be used in practicing the invention.
In practicing my invention in the treatment of perfumes, one-half gram of ascorbic acid may be added to 50 grams of perfume. Much smaller quantities, however, may be employed and the percentage may be as low as .1 quantities may be used, no particular advantage appears to accrue therefrom.
Amounts of ascorbic acid greater than 1 part of the acid to 1000 parts soap may be employed but in general any improved results obtainedby using a larger quantity are not economic. Much smaller amounts may be used and proportions as low as 1:25,000 and 1:500,Q00 give noticeably improved results.
in themanufa'cture oi perfumed soap, the ascorbic acid may be dissolved in the perfume that is to be added to the soap; the perfume and the ascorbic acid may be added during any ordinary While larger process employed for introducing perfume into the soap. This method'is particularly desirable and feasible inasmuch as no additional steps are necessaryin the soap making operation. This method also assures that the ascorbic acid is intimately mixed with both the perfume and the soap and therefore has an opportunity to exert its maximum antioxidant effect. The addition of the ascorbic acid to theperfume and the addition of this mixture to the soap appears to give forms, the l and .the "(1" form. The l-ascorbic acid also exists in two tautomeric forms, namely, the lreto and "enol forms, which have the following formulae, respectively:
It is believed that both compounds exist tautomcrically.
The other form of ascorbic acid, namely, the d-ascorbic acid, has the following formula:
This also exists in similar tautoeric Other ascorbic acids and their empcal iormulae, are: a
d-erythro-ascorblc acid, n
o l ol-con -c on-ca-cmon dand l-arabo-ascorbic acid,
the sum of the improvements in the perfume and the soap, is greater than the cumulative elffect. Apparently there is some synergism be tween the soap, perfume and ascorbic acid, which produces the markedly improved results.
As additional illustrations of the invention, I may employ iso-ascorbic acid, reductic acid, and other compounds mentioned hereinafter in'a manner and in an amount similar to that described previously. Tests show these compounds to be particularly effective in inhibiting the formation of undesirable odors and colors in soaps and perfume.
The ascorbic acids and similar compounds may also be used in combination with other antioxiin soaps in which only the previously known antioxidant is used.
It will be understood that my invention is appllcable to perfumed soap in many forms. The soap may be in a solid cake form, or it may be in a powdered or flake form. The compositions dand l-gluco-ascorhic acid, ti galacto-ascorbie acid, and l-gulo-ascorbic acid,
. 0 ocon=oon-n-cnon-cnom-onlcn l-rhamno-ascorbic acid, and l-iuco-ascorhic acid,
and d-gluco-hcpto ascorhic acid,
It will be understood t all these compounds may exist in both 61- andl-iorms andintautomeric keto and enol forms. Reference to ascorbic acid is intended to include any taummere and optical isomers.
My invention is applicable to various ascorbic acids of the type herein generally disclosed and and laundry soaps in solid form, the steps which may be used for a variety of purposes. Examples are toilet soaps and laundry soaps.
I have previously referred to compounds similar to ascorbic acid as included in my invention. In amplifying the meaning of this expression it should be noted that ascorbic acid exists in two comprise adding a small amount of pure crystal line ascorbic acid to perfume subject to deterioration by oxidation, anddntimately admg the ascorbic acid treated perfume with a solid soap to be perfumed, whereby the original character of the perfume in the soap is preserved for a long time and the development of 1; it
CARL N. me.