US2395665A - Agents for protecting against light of short wave length - Google Patents

Description

' Patented Feb. 26, 1946 AGENTS FOR PROTECTING AGAINST LIGHT OF SHORT WAVE LENGTH Samuel Isermann, Tucson, Ariz., and Ernst. Ohlsson, Short Hills, N. J.

No Drawing. Application April 1, 1943. Serial No. 481,434

4 Claims. (01. 167-90) This invention relates to improvements in compositions for use as coatings or films for protection of the skin against light of short wave length. It more particularly relates to novel compositions of matter containing substances having the property of absorbing light of short wave length or transforming its wave length to non-burning length; and to substances comprising the active ingredients of these compositions.

The compounds described and claimed herein are particularly characterized by their insolubility in water. so that they are preferably to be applied to the point of use in the form of lotions. emulsions, creams and the like, as distinguished from pure solutions, and the invention also is directed to the formation of such compositions and the compositions themselves.

The application is a continuation in part of our copending application, Serial No. 303,536, filed November 9, 1939.

It is well known that over-exposure of the body to direct radiation from the sun is apt to cause acute and chronic dermatitis, blisters, severe burns, as well as such disagreeable minor effects as mottling of the skin, pigment anomalies, freckles, etc. Th development of a pleasin tan coloration of the skin is much sought after but can be obtained only by allowing the skin gradually to develop its own protective pigmentation by even deposits of melanin. I

The basis of approach in preventing solar or light wave dermatitis is that it is desirable to provide a screen which will affect impinging rays in a manner to render their contact with the surface of the skin harmless.

which actually intercepts or absorbs the harmful rays, or by the use of a screen which modifies the wave lengths of the harmful rays to render them harmless, and is preferably obtained by use of a This desirable re- .sult may be obtained either by the use of a screen.

screen which simultaneously achieves both of these desirable objects.

The rays to which this treatment is paiticularly directed are themselves of a wave length of talline form, since crystallization will tend materially to interrupt the film formation, and solubility in convenient and non-toxic carriers. In addition such materials must themselves be of a completely non-toxic character, the-term nontoxic being meant to include the elimination of any undesired efiect upon the skin, including irritation, infection and anesthesia. In addition it is desirable that the compound used may be effective in relatively small concentrations, both from the standpoint of expens of. the product and from the general undesirability of applying high concentrations of foreign substances to the surface of the skin. In addition the materials used are desirably colorless and tasteless and more particularly, since they are intended for cosmetic use, are preferably entirely without odor. In fact not only must unpleasant odors be eliminated from consideration, but since the type of compound used is commonly employed by both sexes, particularly by soldiers operating in tropical or arctic climates, the presence of perfumery type odors is quite as undesirable as those which are unpleasant to the sense of smell.

It has been found that many substances heretofore' proposed for the purpose mentioned possess one or more of the various difficulties and disabilities outlined above. Such materials as benzyl cinamate, benzyl salicylate, menthol salicylate. aesculetine and the like, though apparently capable on theoretical grounds of absorbing a substantial amount of ultra-violet light must be used, in order to be eifective at all, in concentrations as high as 10%, in which concentrations they are expensive and liable to cause serious physiological disturbances when applied to the body. Such substances as ethyl, propyl, butyl, and amyl esters of para amino benzoic acid have been suggested for the purpose but are found to cause-so high an anesthetic effect (they are in fact indicated as local anesthetics), that they are substantially useless for ultra-violet ray interception purposes. Decyl and lauryl alcohols when condensed with para amino benzoic acid are also unavailable because'of substantial odors which these compounds have even when present in very small concentrations.

Our present compounds have been found to be highly effective in the interception and transformation of light of short wavelength, particularly when applied to the skin of a human being. These compounds comprise higher fatty acid esters of para amino benzoic acid, characterized by an essential lack of anesthetic effect, ready emulsifiability. naturally rendering their incorporation in creams and lotions relatively easy, waxy as opposed to crystalline composition, also contributing to ease of combination into lotions and creams, a complete lack of odor or any other undesired physical property when spread on the surface of the skin. and high screening properties in small concentrations in thin films.

More particularly our invention includes the fatty alcohol esters of para amino benzoic acid containing fourteen or more carbon atoms in the fatty alcohol carbon chain, especially desirable compounds being myristyl, cetyl. oleyl and stearyl alcohols. as well as mixed alcohols obtained from hydro enated natural oil which can be esterified with the formation of waxes of varying hardness.

A particular advantage of this group of compounds over the esters of the lower fatty acids of the same series lies in the fact that they are completely non-anesthetic. as opposed to ethyl, propvhbutyl, and amyl compounds. They are substantially completely insoluble in water as opposed to the compounds of the series from methyl to amyl. which is a very desirable property. particularly when used in tropical countries where the probl m of pers iration must be consi ered. and in use by swimmers, and they are completely without odor, as opposed to the capryl. decyl and lauryl com ounds. It will a so be seen t at since it is the purpose of this invention to provide materials of a generally waxy charact r which may suitably be incorporated into creams. lotions or the like. derivatives or com ounds of this class, substituted either in the fatty acid portion or in the amino benzoate ortion of the compound which are of a normally cr stalline nature. may not be used as effectively as the compounds them selves.

Our compounds may preferably be repared by alcoholosis. an exam le of which follows. though it is not intended to be limitin in any respect.

Exam le I. 105 gm. of cetvl alcohol and 2.3

am. of 50% solution of potassiu hydroxide are heated under vacuum with d stillation of water until no more water distills. 66 m, of ethyl para. amino benzoate are added /and the mixture heated to a temperature of ap roximately 135 C. Distillation of ethyl alcohol be ins and continues wi h radual increase in temperature to about 200 C. or until approximately 15 cc. of ethyl alcohol have distilled over, potassium hydroxide remaining may be neutralized in any suitable manner. Addition of a hi her fatty acid. such as stearic acid. until the neutral point is reached. leaves the final product in a form readily emulsifiable with water. due to the presence of potassium stearate which acts as an emulsifier. In the process of this example a proximat ly molecular ro ortions of myristyl. oleyl. stearyl, or such mixed alcohols obtained from hydrogenated natural oil, such as cocoanut and whale oils, which are free of the undesired lower fatty components. can be substituted with the formation of waxes of varying hardness. all of which may be emulsified directly with water and have valuable light absorbing properties.

As pointed out above. it is desirable to incorporate the compounds of our invention into various form more suitable for direct action to the skin; one of such forms is a liquid lotion which The r si ue of the I may suitably be made by combining with the finished product from the example above. dl-ethyl amino stearyl lactate as an emulsifying agent and boiling water. whereby the combination takes place at a temperature near the boiling point of water. On cooling this mixture is awhite creamy lotion which will pour readily and is suitable for bottling, for storage or shipment purposes. An example of such a lotion and the method of making it is as follows:

Example II .-5 parts of para amino cetyl benzoate are melted together with 4 parts of di-ethyl amino stearyl lactate and the mixture is heated to approximately C. To this is added, while stirring, 91 parts of boiling water. The mixture is allowed to cool to room temperature and when so cooled is ready for use by application directly to the skin, -or may be bottled for shipment and storage.

In some cases it is desirable to provide the ma terial in the form of a cream adapted for application to the skin. The cream may preferably be obtained by addition of a thickening agent 'to the composition of the lotion, and further if it is desired to provide a cream of oily character. the addition of small quantities of mineral or vegetable oils will achieve this end. An example of a cream is as follows:

Example III .-5 parts para amino cetyl benzoate, 4 parts of di-ethyl amino stearyl lactate, and 3 parts of monoglyceryl stearate are melted together and heated to 90 C. To this is added. while stirring, 88 parts of boiling water. The mixture when cooled to room temperature is a non-greasy. stable cream.

The addition of one part or more of any desired mineral or vegetable oil suitable for application to the skin while the above mixture is hot will change the character of the cream from non-greasy to more or less oily.

An advantage of the compounds described containing the higher fatty alcohol carbon chains is that such compounds, and particularly the cetyl compound, have a very desirable healing and emollient action upon the skin. This action helps to protect the skin from the irritating effects of the sun. These compounds are thus especially suitable in the making of creams. it is also characteristic of the compounds described that they do not tend to turn rancid.

We claim:

1. A preparation for protecting the skin against light of short wave length containing as its active ingredient a non-crystalline, odorless. nonanesthetic. substantially water insoluble ester of para amino benzoic acid and a ,fatty alcohol chosen from the class consisting of myristyl. cetyl, and stearyl alcohols.

2. A composition for protecting the skin against light of short Wave length containing as its active ingredient myristyl para amino benzoate.

3. A composition for protecting the skin against light of short Wave length containing as its active ingredient cetyl para amino benzoat-e.

4. A composition for protecting the skin against light of short wave length containing as its active ingredient stearyl para amino benzoate.

SAMUEL ISERMANN. ERNST OHLSSON.