US2704279A - Toilet soap and process of preparing same - Google Patents

Description

United States Patent TOILET SOAP AND PRISIgESS F PREPARING Robert Franklin Heald, Nutley, N. J., assignor to Colgate- Palmolive Company, Jersey City, N. J., a corporation of Delaware No Drawing. Application February 24, 1950, Serial No. 146,153

7 Claims. (Cl. 252-121) This invention relates to a new milled and essentially unbuilt toilet soap in bar and cake form containing a minor proportion of water soluble salts of higher fatty acid monoglyceride monosulfates, and to a novel process of preparing such a combination bar.

It has been suggested that soap and various synthetic detergents may be compounded together such that certain desirable characteristics may be attained, such as lime soap dispersion. More particularly, it has been known that laundry bars of soap and synthetic detergent, generally the higher alkyl aryl sulfonate type, may be prepared for use in salt water. Such mixtures have not attained any practical acceptance in the art in view of the many obstacles encountered in the production of a satisfactory product in bar form due to the basic physical and chemical differences between the synthetic detergent and the soap stocks.

In the consideration of the acceptability of a toilet soap designed for personal use on the hands, face, and body of the user, it is necessary to consider a multitude of both 1 objective and subjective considerations. Such objective factors as scum dispersion and soil removal must be integrated with the many personal considerations of appearance, feel, effect on skin, etc.

The preparation of a toilet bar containing a mixture of soap and synthetic detergent of the character of water soluble higher fatty acid monoglyceride monosulfate salts, as described more particularly hereinafter, has been fraught with many obstacles. The fundamental differences in properties between the monoglyceride sulfates on the one hand and toilet soap stocks on the other, such as the greater solubility, higher specific gravity, greater opaqueness and comparative lack of luster in solid form of the synthetic detergent as compared to soap created such problems that a suitable combination toilet bar was believed impracticable for some time. Other vital considerations will be apparent from the following description.

Representing the culmination of years of research, it has now been discovered that a combination toilet bar of soap and the higher fatty acid monoglyceride sulfate detergent may be prepared which has in its unitary effect the desirable attributes of each detergent to a maximum beneficial degree, and comprises an essentially unbuilt milled toilet soap in the form of bars and cakes having above about 60% of anhydrous water soluble higher fatty acid soaps, with a minor proportion of water soluble salts of higher fatty acid monoglyceride monosulfates uniformly dispersed throughout and effective to substantially disperse the lime soaps generated during use as a toilet soap, the ratio of said sulfate salt to soap being less than about 0.5.

For the sake of simplicity, the criticality of the various essential ingredients and necessary processing details will be discussed individually to some extent. It is to be noted, however, that the combination bar of the present invention does exert its beneficial effects in a unitary manner due to the conjoint action of the essential ingredients and their mutual compatibility in the relationship set forth, which result from the processing techniques inter-related with and necessarily productive of such characteristics.

The combination bar has as the major ingredient above about 60% of water soluble metallic salts of higher fatty acids. These soaps may be produced by the saponification of fatty materials suitable for use in soap making. Among suitable fatty materials are the fats, oils, and waxes of animal, vegetable, and marine origin, and the 'ice fatty acids derived therefrom or of synthetic origin. More specifically, the fatty acids may be derived from tallow, cotton seed oil, coconut oil, palm oil, palm kernel oil, grease, fish oils, fatty acids derived therefrom by hydrolysis, etc. It is preferred ordinarily to use in the present invention the sodium salts of the fatty acids derived from tallow, coconut oil and mixtures thereof.

As indicated, the specific synthetic detergent suitable for the manufacture of the combination bar of the present invention is the water soluble salts of the monosulfuric acid esters of higher fatty acid monoglycerides such as the alkali metal (e. g. sodium, potassium), ammonium and amine salts. The higher fatty acid radicals are also derived from natural fats, oils, and waxes or fatty acids of natural or synthetic origin. It is a more specific feature of this invention that these water soluble monoglyceride sulfates may be derived more particularly from hydrogenated fatty materials since a higher proportion of more saturated fatty acid radicals tends to equalize the solubility of the soap and synthetic detergent and to produce a harder and less soluble toilet bar. These products may be prepared in any convenient manner. A suitable process cited by way of illustration only involves the interaction of such components as glycerine, fatty oils or fatty acids, and a substantial excess of a strong sulfonating agent. The resulting acidic products may be neutralized with a neutralizing agent and may be dried in any conventional manner. Such procedures and the like are well known in the art, as illustrated by Muncie, U. S. Patent Nos. 2,130,361; 2,130,362; 2,242,979; etc.

As a result of such processing, the final reaction mass comprises primarily about 30 to 35% of the organic sulfate salt, and the remaining per cent of sulfates (about 65 to 70%) being inorganic salts such as sodium sulfate. This detergent base containing major proportions of inorganic salts is generally unsuitable for the production of a successful combination bar. While these inorganic salts are generally neutral in solution and would appear to have utility as filling or diluent material, it has been found that the detergent base must be essentially saltfree in order to attain maximum beneficial effects. A combination bar made from the crude salt-containing detergent base exhibits to a marked degree many undesirable physical and chemical characteristics, such as chalky appearance, gritty feel, poor lathering qualities, formation of crystalline type material on the bar surfaces after drying, relatively poor scum dispersion and dirt removal, and a general irritative effect upon the skin.

Accordingly, it is essential that the bulk of these inorganic salts be separated from the synthetic detergent base. This result may be accomplished in any suitable manner, preferably by solvent extraction processes, such as illustrated by Russell et al., U. S. Patent No. 2,303,582; Russell U. S. Patent No. 2,316,719, etc., which have been developed for such purposes primarily. It is not necessary that the synthetic detergent base be completely free of these inorganic salts, since the presence of minor amounts of inorganic salts which do not substantially adversely affect the desired characteristics for the combination bar may be tolerated herein. After purification of the synthetic detergent base by the solvent extraction process indicated above, the base will contain generally about 80 to synthetic detergent with the remainder being sodium sulfate. This material is highly suitable for use in formation of the combination bar. The minor amounts of sodium sulfate and the like are not detrimental to the product and are embraced within the phrase essentially unbuilt as used herein. Generally up to about 10% sodium sulfate and similar inorganic salts may be tolerated before an adverse effect on the properties of the combination bar is encountered to a significant degree. The addition of minor amounts of coloring agents, perfumes, preservatives, super-fatting agents, antiseptics, and the like may, and usually are, to be added to the combination mix for their individual elfects.

The amount of monoglyceride sulfate salt in the combination bar should be usually up to about 30% uniformly dispersed throughout, and effective to substantially disperse the lime soaps generated during use as a toilet soap, with the ratio of the sulfate salt to soap less than about 0.5. The particularity of such specifications is necessitated by the unique conditions encountered during use of a toilet soap. Under laundering washing conditions wherein a detergent mixture in particulate form may be used, the concentration of active ingredients (soap and detergent) may be controlled during use by the addition, if necessary, of large quantities of materials. In this way, sufficient scum dispersion may be had by the presence of large quantities of synthetic detergent and usually various alkaline builders also. On the other hand, however, the combination toilet bar does not possess any significant amount of alkaline builders and the concentration of detergent composition during use in bathing and rinsing is relatively minute, and controlled only to a limited extent by the amount of washing by the user and solubility of the bar. It is evident, therefore, that during use in the bath tub and the like the total concentration of active ingredients is of an extremely small order, probably of the order of about 0.10%. In view of the minute amount of synthetic detergent in solution during bathing using a combination bar, it is required that its dispersing power be of the highest possible order. In this respect it is to be noted that the monoglyceride sulfate detergent salt possesses remarkable properties on scum dispersion in comparison to other known synthetic detergent salts. For example, solutions of soap and monoglyceride salt in selected ratios may be tested at selected concentrations in hard water of 300 parts per million (p. p. m. hardness calculated as calcium carbonate) and room temperature to determine the point of complete scum dispersion, and compared to the action of other known detergents under like conditions. At a total concentration in solution of 0.05%, the per cent synthetic detergent in a coconut soap-monoglyceride sulfate detergent mixture which achieves complete dispersion is approximately 2%, and at 0.01% concentration only about 4% of this synthetic detergent in the detergent mixture is required. The remarkable effectiveness of the monoglyceride salt in this respect is evident when the well known higher alkyl aryl sulfonate salts are tested in comparison thereto. Using the dodecyl benzene sulfonate salt as the synthetic detergent under identical conditions, it may be noted that substantial dispersion is achieved with about 40 to 50% synthetic detergent at 0.05% total concentration of the soap-synthetic detergent solution, and about 70 to 80% of alkyl aryl salt is required at 0.01% total concentration. It is highly significant that the monoglyceride sulfate salt in the relationship set forth is about times more effective than the alkyl aryl sulfonate salts and the like. For a combination bar possessing substantial dispersing properties using an alkyl aryl sulfonate as the synthetic detergent, it would be necessary to use such large quantities of synthetic detergent as to change the entire character of the product as a toilet soap bar.

As indicated, moreover, about 2% and about 4% monoglyceride sulfate salt in the soap monoglyceride mixture are required for complete dispersion under the specified testing conditions. These represent an approxi mation of the minimum amounts of synthetic detergent in solution required to achieve the necessary scum dispersion under such representative hard Water conditions. In soft or medium hard water, the amount required for dispersion would be less of course. In actual practice however, it has been found that at least about twice the minimum amount of monoglyceride sulfate salt as determined by the described test is required in the bar in order to achieve any substantial degree of dispersion under varying conditions of use. Such amount is requisite because, in natural use of the toilet bar, some curd or scum is formed prior to solution of the necessary amount of synthetic detergent, and the amount of dispersal power required to breakup an initially formed curd is greater than the amount required for inhibition of the formation of any such curd. Accordingly, it is preferred that the amount of monoglyceride sulfate salt be from about 10 to about 30% and preferably about 10 to about of the weight of total solids.

The ratio of monoglyceride sulfate salt to soap is rather critical and should be less than 0.5 in general. It has been found that within such proportions the desired properties are attained to a maximum degree. Thus, using a synthetic detergent to soap ratio of about 1:3, marked improvement may be noted in such properties as soil removal, better lather at first, better lather after using, greater scum dispersion, and less irritation to the skin, in comparison to the use of a white high grade toilet soap. In contradistinction, however, a combination bar prepared with approximately a 1:1 ratio of the active ingredients under similar conditions proves to be highly inferior to the all-soap bar, particularly on such qualities as initial and sustained lathering, appearance, feel on hands, general irritative effect, and with no marked improvement in scum dispersion.

The combination bar of the present invention may be made by a modified soap milling and plodding process. In the manufacture of soap bars there are two methods in wide commercial use, namely, the framing method and the milling method.

In the framing method, molten kettle soap is crutched with various addition agents and cast while still molten into frames or molds for cooling and settling. After setting. the solidified mass may be cut into bars or cakes of desired size and shape. Cakes of soap made by this process have a high moisture content (at least about 30% moisture) and in general are unsuitable for manufacture of the combination toilet bar. Combination bars made by this framing technique are quite soft because of the relatively high moisture content and wear away comparatively rapidly in use. They are subject to warping and distortion on aging, due to evaporation of the moisture content. It is difficult to incorporate perfume into the mix satisfactorily in view of the high temperatures established prior to framing. Moreover, by this procedure the combination bar does not have a uniform composition and fine texture.

In the milling process, however, kettle soap is cooled and dried to chip or granular form. The soap particles are then mechanically mixed with various addition agents such as perfume, coloring materials, whitening agents, etc., and then milled to produce chips of homogeneous composition. The milled particles are compacted under pressure in a plodder from which the soap is extruded as a continuous bar having a cross section approximating that of the finished cake. The continuous bar is then cut into individual cakes which usually are pressed to give a smooth and polished appearance to the finished cake, and, when desired, to impress upon the cake a trade name, trade mark etc.

The combination soap-monoglyceride sulfate bars of the present invention may be made by the milling process provided the moisture content of the mix is kept within rather narrow and critical limits and correlated with the temperature of the mixture during plodding. Generally speaking, the process comprises milling a mixture of the water soluble soap and monoglyceride sulfate detergent, plodding the resulting chips and severing the bar extruded from the plodder into convenient lengths for use. The moisture content of the mixture is to be maintained within the rather critical limits of 5 to 15%. This moisture content refers to the free moisture i. e., the moisture which is not combined as water of crystallization. The composition may, and preferably does, include preservatives, perfume, coloring agents etc. with the inorganic salts, if any, being kept to a minimum as described supra.

If the moisture content is below about 5%, it cannot be plodded satisfactorily. The internal friction is so great that the temperature of the mixture rises so high that the extruded bar cannot be handled satisfactorily. If the moisture content exceeds about 15%, apart from the moisture present as water of crystallization, the material cannot be plodded to produce an extruded bar capable of maintaining its shape.

The temperature of the material being plodded must be correlated with the moisture content and the temperature of the extruded bar will vary within the range of about to 135 F. With a moisture content of about 10%, the temperature of the extruded bar for best results should be about F. If the moisture content is lower than 10%, a higher temperature should be used for satisfactory operation. Thus, with a water content approximating 5%, the temperature of the extruded bar should be about for best results. If the moisture content is higher than about 10%, the temperature of the extruded bar should be less than 120 for best results. Consequently, with a moisture content approximating 136%; tlgie extruded bar should have a temperature of about The loss in moisture content in manufacture generally is nil, or in any event not in excess of more than a few per cent, such that the final composite bar product does not have a moisture content in excess of about 15%, and usually within the range of about 5-15%.

The finished bars and cakes have a fine texture, firmness, appearance, shape stability, and wearing qualities requisite to a high grade toilet soap. The most striking improvements appear in better lathering qualities, significant and substantial scum dispersion and greater mildness.

With regard to the latter factor, the emollient properties of soap are retained with the improved detersive and dispersal power of the toilet bar in soft and hard water.

It has been found moreover that the combination of active ingredients as set forth herein possesses a satisfactory intermediate alkaline pH value in solution. The monoglyceride sulfate is particularly liable to hydrolysis upon the alkaline side. In the composite bar however, hydrolysis of the synthetic detergent is not encountered to any significant degree. In addition, the monoglyceride sulfate itself is substantially neutral in character, and therefore has a reduced tendency to change the normal pH of the skin in comparison to the use of more alkaline cleansing agents. In commercial manufacture of the synthetic detergent base, it is customary to control the product so that solutions are slightly acidic (e. g. pH of about 5.5-7) and as a result, when such detergent base is used, it has been found that the pH value of the mixed detergent is below the normal value of an equivalent all-soap solution. In general, the pH of the combination bar in 0.5% concentration in hard water is less than 10, and usually not substantially in excess of about 9.5. At such a pH there is no substantial hydrolysis of the soap, nor a high degree of alkalinity which has a deleterious effect on the s The following examples are additionally illustrative of the present invention and it is to be understood that the invention is not restricted thereto.

Example I Kettle soap is prepared from refined and bleached No. 2 tallow and refined babassu nut oil in a 3:1 ratio to the following specifications: about 31% moisture, about 62.5% T. F. A. & U., about 0.1% free alkali as NazO, chlorides as NaCl about 0.5% maximum, and glycerine about 0.3% maximum. This soap is granulated to chip form and dried to 12.5% moisture.

The synthetic detergent is prepared completely from hydrogenated, refined and bleached coconut oil by interaction with oleum and glycerine. The reaction mixture is neutralized with caustic soda solution to a pH of about 6 to yield about 35% sodium hydrogenated coconut oil monoglyceride sulfate salts, the remainder of total solids being essentially sodium sulfate.

This synthetic detergent base is extracted with isopropyl alcohol to recover essentially inorganic salt-free monoglyceride sulfate salt. About a 25% solution of the extract is spray dried such that the final product has a moisture content of about 1.5%.

72.3 parts by weight of the soap chips are thoroughly mixed with about 25 parts of the monoglyceride sulfate base with minor amounts of whitening agents, perfume and perservative incorporated therein. This mixture contains about 63.4% anhydrous soap, about 23.15% monoglyceride sulfate salt and a moisture content about 9.5%. The mixture is milled twice in a soap mill. The milled chips are fed into an unheated soap plodder (85 F.) having an extrusion nozzle temperature of 120-125 F. where they are compacted and extruded as a finished bar which is tough, strong, and of uniform color and texture. The bar is cut and pressed in dies to cake form. The pH of an 0.55% solution of the product at 25 C. in water of 300 p. p. m. is about 9.1.

In the above processing, no additional moisture was needed to produce a satisfactory product. If desired, additional water may be added in the mixing stage prior to milling, with appropriate adjustment of the extrusion temperature.

The composite bar prepared above and tested under normal conditions of use exhibits markedly improved properties over a high grade toilet soap. The combination bar exhibits better initial and sustained lathering, marked improvement in soil removal and scum dispersion, increased mildness on the skin, etc., as compared to the soap toilet bar. Moreover, the combination bar is to be preferred for use in both hard and soft water.

Example 11 not to the same extent as the product of Example I.

Combination bars similar to that of Example H having about 10% monoglyceride sulfate prove also to he satisfactory.

Example 11! Following the general procedure of Example I, a combination bar is prepared from 73 parts soap chips derived from mixed tallow and coconut oil in a 3:1 ratio and 25 parts monoglyceride sulfate base prepared from mixed hydrogenated tallow and hydrogenated coconut oils in a 2:1 ratio, with minor amounts of perfume, etc. The moisture content is about 12% and an extrusion temperature of about 1l5 F. produces a satisfactory combination toilet bar with good lathering and scum dispersion properties.

The term consisting essentially of as used in the definition of the ingredients present in the composition claimed is intended to exclude the presence of other materials in such amounts as to interfere substantially with the properties and characteristics possessed by the composition set forth but to permit the presence of other materials in such amounts as not substantially to aifect said properties and characteristics adversely.

Although the present invention has been described and illustrated with a reference to specific examples, it is understood that modifications and variations of composition and procedure are contemplated within the scope of the appended claims.

Having described the invention, what is desired to be secured by Letters Patent is:

1. An improved and essentially unbuilt milled toilet soap in bar or cake form consisting essentially of at least about 60% of anhydrous water-soluble metallic salts of higher fatty acids with about 4 to about 30% of watersoluble higher fatty acid monoglyceride monosulfate detergent uniformly dispersed throughout, and about 5 to about 15% moisture.

2. A toilet product in accordance with claim 5 containing sodium hydrogenated coconut oil monoglyceride monosulfate detergent.

3. A toilet product in accordance with claim 5 which contains sodium higher fatty acid soap selected from the group consisting of sodium tallow and coconut oil soaps.

4. A milled and essentially unbuilt toilet soap in bar or cake form consisting essentially of at least about 60% water-soluble metallic soap of higher fatty acids, about 10 to about 30% of hydrogenated higher fatty acid monoglyceride monosulfate detergent uniformly dispersed throughout, and about 5 to about 15% moisture.

5. A milled and essentially unbuilt toilet soap in bar or cake form consisting essentially of at least about 60% sodium higher fatty acid soap, about 10 to about 30% of sodium higher fatty acid monoglyceride monosulfate detergent uniformly dispersed throughout, and about 5 to about 15% moisture.

6. A process of making an essentially unbuilt toilet soap in bar or cake form which comprises forming a mixture of at least about 60% water-soluble metallic salts of higher fatty acids, a minor proportion of about 4 to about 30% of water-soluble higher fatty acid monoglyceride monosulfate detergent and from about 5 to about 15 moisture, milling said mixture to uniformly disperse said monoglyceride monosulfate salt therein and form homogeneous particles thereby, plodding the resulting milled mixture and extruding the same as a bar at a temperature of about 100 to about F., and forming the resulting extruded bar into bar or cake form suitable for toilet use.

7. A process of making an essentially unbuilt toilet soap in bar or cake form which comprises forming a mixture of at least about 60% sodium higher fatty acid soap, about 10 to about 30% of sodium higher fatty acid monoglyceride monosulfate detergent and about 5 to about 15% moisture, milling said mixture to uniformly disperse said monoglyceride monosulfate detergent therein and form homogeneous particles thereby, plodding the resulting milled mixture and extruding the same in bar form, the temperature of extrusion being from about 100 to about 135 F. and correlated with the amount of moisture in said mixture, and forming the resulting extruded bar into bar or cake form suitable for toilet use.

References Cited in the file of this patent UNITED STATES PATENTS Colgate Aug. 25, 1942 Safrin Nov. 13, 1945 Bodman Sept. 17, 1946 Hoyt Mar. 23, 1948 Preston Oct. 24, 1950 FOREIGN PATENTS Great Britain Dec. 28, 1937

Claims (1)

1. AN IMPROVED AND ESSENTIALLY UNBUILT MILLED TOILET SOAP IN BAR OR CAKE FORM CONSISTING ESSENTIALLY OF AT LEAST ABOUT 60% OF ANHYDROUS WATER-SOLUBLE METALLIC SALTS OF HIGHER FATTY ACIDS WITH ABOUT 4 TO ABOUT 30% OF WATERSOLUBLE HIGHER FATTY ACID MONOGLYCERIDE MONOSULFATE DETERGENT UNIFORMLY DISPERSED THROUGHOUT, AND ABOUT 5 TO ABOUT 15% MOISTURE.