US3070547A - Soap-synthetic bar - Google Patents

Description

Unite States Patent ()filice 3, li7h,54i7 Patented Dec. 25, 1962 3,ti7ti,547 SQAr-SYNTHE'HC BAR Robert H. Qhatfee, Cclcrain Township, Hamilton County, (iiiio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, in corporation of @illit) No Drawing. Qontinnation of application Ser. No. 367,769, July 13, 1953. This application Dec. 12, 1951, er. No. 159,431

2 Ciaims. (Qt. 252-421) The present invention relates to detergent bars, more particularly to bars containing substantial amounts of synthetic detergent, and methods of making same.

The shortcomings of sulfonated and sulfated synthetic detergents in the manufacture of bars are many. if the attempt is made to form a straight synthetic detergent into a bar, it will not stick together in a firm mass like soap does, but will become smeary, slushy, fall apart, and rapidly dissolve when exposed to water in a soap dish. Various materials have been used to add plasticity and water resistance to synthetic detergents and allow the formation of a bar of satisfactory quality. These include, for example, the monoglycerides of saturated fatty acids and the monoestcrs of fatty acids of coconut oil and ethylene glycol. Such compositions have not produced commercially successful bars. These esters are of no help in reducing smeariness and slushiness and they are relative'y expensive for an ingredient that not only is of no help in detergency, but actually adds to the load. By load is meant the using up of the detergent, such as is done by oily matter in clothes or on the hands.

Soap is a good plasticizer and has the property of absorbing a limited amount of water from a soap dish without disintegration, so its use with synthetics is advantageous. Moreover, when soap is added to synthetic detergents, coherent bars may be formed from the composition by conventional soap making methods and machinery. However, although the mixed soap-synthetic deiergent bar will not dissolve in Water as readily as the straight synthetic detergent, it does, without further modification, get slushy in a soap dish containing a layer of water. In addition, such mixtures have at least two other disadvantages. During use in hard Water the soap forms a curd, especially at rinsing concentrations, thus negativing part of the advantages of the synthetic detergent, and the bars crack badly when exposed to conditions of alternate wetting and drying.

An object of this invention is to provide a detergent bar in which the active detergent ingredient is mainly a synthetic detergent, but which shows a minimum tendency to slush, crack, and form curd during use in medium or hard water. Another object of the invention is to produce a composition which, when formed into a bar in the equipment employed to form soap into bars-such as mils, plodders and stamps-has a soap-like rather than a sticky, smeary or greasy feel as used.

I have discovered that detergent bars, made from a suitably proportioned mixture of a water-soluble synthetic detergent, a water-soluble alkali metal soap, a hydrated water-insoluble alkaline earth metal soap, and a salting-out electrolyte, are desirably plastic and have many advantages over synthetic detergent-soap bars previously prepared, especially in resistance to excessive penetration of water and resulting development of slushiness or smeariness, in resistance to cracking when alternately wetted and dried, and in resistance to formation of curd in hard water.

I am not certain why the detergent bar compositions of my invention possess their improved characteristics, but it has been observed on microscopic examination of a portion of a bar after exposure to water, that a liquid crystalline phase of the active ingredients at the bar surface exists at least in part as middle phase or gum phase, which is difficultly soluble in water. The formation of this water resistant layer on the bar surface, in association with other ingredients of my composition, apparently reduces Water penetration and the tendency to form a slushy or smeary surface which ultimately develops cracks on alternate wetting and drying.

The presence of a hydrated water-insoluble alkaline earth metal soap in the compositions of my invention appears to have the functional advantage not only of improving the lathering properties of the bar and of reducing tendencies toward curd formation when the bar is used in hard water, but also of having binding and plasticizing properties. As more fully hereinafter explained, the alkaline earth metal soaps may be added as such in the compounding of ingredients or may be formed in situ in this operation by reaction of a water-soluble alkaline earth metal salt with Water-soluble alkali metal soap in suitable proportions. Moreover, it is to be understood that in the present invention the term alkaline earth metal is intended to include magnesium as well as calcium, barium, and strontium.

The salting-out electrolyte in my compositions has the function of reducing smear or slushiness and is regulated in amount so as to slow up the solubility of the bar without preventing the formation of middle phase. The salting-out electrolytes may be any of the chlorides, sulfates, or carbonates of the alkali metals, but in practicing my invention it should be borne in mind that the salts of bivalent anions such as the sulfates of sodium and potassium have only about half the salting-out power of the chlorides of these alkali metals.

In the preferred method of preparing bars of the present invention, the synthetic detergent, neutralized with a solution of an alkali metal hydroxide or carbonate, to which the salting-out electrolyte has been added (if insufiicient electrolyte will be formed in situ during the neutralization step and in other steps of the process), is introduced into a suitable mixer, such as a soap crutcher. Some water may then be added to improve fiuidIty, and a sodium or potassium soap, preferably as kettle soap containing about 30% Water, is added. These ingredients are mixed and then an appropriate amount of water-soluble aTkaTine earth metal salt, such as magrzesfurn su'fate or chloride, or calcium chloride, is added to convert a portion of the water-soluble soap to water-insoluble soap, sodium or potassium salting-out electrolyte being formed as by-product. Mixing is then continued to insure the equilibrium in the formation of the alkaline earth metal soap is attained. Desirable adjustments in water-soluble soap content may, of course, be made after the waterinsoluble soap has been formed.

The resulting mix is then dried either by drum drying, screen drying, or spray drying, to a Water content of /2 to 12 percent, and the dried product is transferred to an amalgamator where perfume, coloring matter or other minor ingredients may be added and mixed to achieve uniformity. From the amalgamator, the material is milled, plodded and stamped, in accordance with procedures well known in the art of soapmaking.

It is not essential that the calcium and magnesium soaps be formed in the crutcher; they may be produced separately and then added to the other ingredients. If so added, they should contain enough water to be plastic or they should be mixed with the other ingredients in the presence of water so that they may absorb water sufiiciently to become plastic and enable thorough incorporation and homogeneous distribution throughout the entire mass, thereby assisting in binding together the constituents of the finished bar. If this is not done, the binding power of the alkaline earth metal soaps is lost and it becomes necessary to add a binder or gum to stick the mass together.

The following examples illustrate the present invention, but it is understood that details relating to ingredients, proportions, and methods of processing are given merely for exemplification purposes and are not to be construed as limiting the scope of the appended claims. In all instances, the proportions are expressed as parts by weight.

Example 1.50 parts of a mixture consisting essentially of lauryl and myristyl alcohols derived from coconut oil by sodium reduction and subsequent fractional distillation (sometimes referred to as middle cut alcohols) were sulfated with chlorosulfonic acid to a completeness of 96%. The monosulfuric acid ester thus produced was neutralized with a 45% aqueous solution of potassium hydroxide. The resulting preparation was a paste containing 78 parts of the potassium salt of the sulfuric acid esters of the alcohols described above.

62.5 parts of this neutralized mix, containing 54 parts of the potassium alkyl sulfates of the middle cut alcohols and about 0.4 part potassium chloride, were mixed with 5 parts of sodium chloride and 51 parts of kettle sodium soaps (containing about parts of water) derived from a mixture of coconut oil and 80% tallow. To this were added 10.6 parts of epsom salts, the latter being equivalent to 5 parts of magnesium sulfate. This amount of magnesium sulfate was sufficient to convert 24 of the 36 parts of sodium soap (dry basis) to magnesium soap, forming also 5.9 parts sodium sulfate which has the salting-out effect of about 2.9 parts sodium chloride. The ingredients were thoroughly mixed in a crutcher to enable reaction to equilibrium, and the mixture was thereafter dried on an atmospheric drum drier. The dried product was transferred to an amalgamator where 1% of perfume and suificient water to bring the total water content to about 8% were thoroughly incorporated. The amalgamator charge was milled, plodded and stamped. The bars were satisfactory with respect to cracking and development of smear.

In this example the ratio of synthetic detergent to total soap was 1.5 to 1, the ratio of magnesium soap to sodium soap was 2:1, and the sodium chloride salting-out electrolyte equivalent was about 12.5% of the sum of the synthetic detergent and alkali metal soap.

By comparison, a product prepared similarly from a mixture of 54 parts of the same potassium alkyl sulfate and 36 parts of same soda soap as used in Example 1, but Without addition of sodium chloride or magnesium sulfate, was definitely inferior.

The potassium salt of the coconut oil fatty acid monoester of 1,2-dihydroxy-propane-3-sulfuric acid may be substituted for the alkyl sulfate in this example with satisfactory results.

Example 2.--In this example three products were prepared, the potassium alkyl sulfate and the sodium soap being identical with those of Example 1 and the procedure for making the bars being substantially the same. The total parts of soap and alkyl sulfate (finished product basis) was held at but the ratio was varied. The other ingredients on a finished product basis were:

Moisture 8 parts. Sodium chloride 5.4 parts. Magnesium sulfate 5 parts per 30 parts soap.

Miscellaneous (unsulfated fatty alcohol, whitener, preservative, perfume) 7 parts.

Relative amounts of synthetic detergent, water-soluble All three samples were satisfactory with respect to cracking and smear and were not substantially affected by the change in ratio of potassium alkyl sulfate to total soap from 1.5:1 to .6621, the ratio of magnesium soap to alkali metal soap remaining constant at 4: 1.

Example 3.--30 parts (dry basis) of potassium alkyl sulfate made from middle cut alcohol as described in Example 1 were mixed with 19 parts of a commercial synthetic detergent containing 15 parts of sodium coconut fatty acid monoglyceride sulfonate (sodium salt of coconut fatty acid monoester of 1,2-dihydroxy-propane-3-su1- fonic acid) and about 3 parts of sodium chloride and about 1 part of sodium sulfate. To this mixture were added 43 parts of kettle sodium soap of 20 coconuttallow mix containing 13 parts water. An amount of epsom salts equivalent to 2.1 parts of magnesium sulfate and sufficient to convert one-third of the soap to the magnesium form and 4.3 parts of NaCl were added. In the reaction of the magnesium sulfate with the soap about 2.5 parts of sodium sulfate, equivalent to about 1.3 parts sodium chloride, were formed, the total sodium chloride salting-out electrolyte equivalent being about 14% of the synthetic plus alkali metal soap. After thorough crutching, drum drying, and mixing in an amalgamator with perfume, whitener, etc., the product was milled, plodded and stamped into bars. The bars were satisfactory from the standpoint of smear and wet crack and also formed no visible curd when used in hard water, although the sodium soap content was greater than in Examples 1 and 2. We believe this is due to the good curd dispersing effect of this monoglyceride sulfonate used. The ratio of synthetic to soluble soap was 2.25:1.

Example 4.As another example coming within the scope of my invention, 60.0 parts of Santomerse #3 paste, containing 45 parts of sodium alkyl benzene sulfonate (having predominantly 12-15 C. in the alkyl radical), substantially all of the remaining 15 parts being water, are put into the crutcher. 5 parts of sodium chloride is added. Then add 43 parts of kettle potassium soap derived from a 20 coconut-80 tallow fat mix and containing about 30 parts of potassium soap and about 13 parts water. Crutch the mixture, and to it add an amount of epsom salts equivalent to 5 parts of magnesium sulfate and sufficient to convert 24 parts of sodium soap to magnesium soap. After further adequate crutching, the mix is dried on a drum drier. In the reaction, salting-out electrolyte equivalent to about 2.9 parts sodium chloride is formed, making the total sodium chloride salting-out electrolyte equivalent equal to about 15.5% of the sum of the synthetic and alkali metal soap. The dried mix is mixed with perfume, color, and antioxidant in an amalgamator, and then milled, plodded and stamped into bars.

An equivalent amount of calcium chloride can be substituted for the magnesium sulfate in this Example 4 without material change in the characteristics of the bar.

It will be observed that in selecting the ingredients for compounding the products in the above examples, soaps and synthetic detergents in the form of sodium and/or potassium salts were employed in the admixture. It is well known that the firmness and solubilities of these materials vary depending on the alkali metal salt, and the relative proportion of each may be adjusted so that the desired firmness and solubility of the ultimate mixture may be achieved. Potassium salts or sodium salts exclusively or other proportions than those specifically used in the examples may, of course, be employed, especially with change in type of synthetic or soap, without departing from the spirit of the invention. Those versed in the art will also recognize that by virtue of ionization during processing, the alkali metal ions may become redistributed in establishing chemical equilibrium in the mix.

The water-soluble soap which is used in the practice of the invention may be of any form-retaining type suitable for preparing soap bars. These will ordinarily be sodium and/ or potassium soaps of tallow, grease, palm oil, palm kernel oil, coconut oil, hydrogenated vegetable oils, hydrogenated marine oils, and mixtures thereof, as is well known in the art of bar soap making.

A wide range of ratios of synthetic detergent to total soap is permissible in the practice of my invention, ratios from 6:1 to 0.3 :1 giving satisfactory bars, ratios from 4:1 to .5 :1 being preferred. Likewise the ratio of alkaline earth metal soap to alkali metal soap can vary from 6:1 to 0.l76:1, those of 4:1 to .4:1 being preferred. In the choice of ratios as outlined, it is preferable to select those that maintain the ratio of synthetic detergent to alkali metal soap between 15:1 and 1.521; similarly the ratio of synthetic detergent to alkaline earth metal soap should be maintained between 5:1 and 1 /2:1. As more fully explained below, the salting-out electrolyte calculated as sodium chloride equivalent can vary from 5% to 30% of the sum of synthetic detergent and soluble soap, 7 to 25% usually being sufiicient in mixtures of preferred formulation. Percentagewise the compositions normally comprise 20 to 60% synthetic detergent, 10 to 50% of total soap, said soap being about to 85% alkaline earth metal soap, the remainder of the soap being alkali metal soap, and the sodium chloride salting-out electrolyte equivalent being 5 to 30% of the sum of the synthetic detergent and the alkali metal soap in the finished bar.

Variations in the salting-out electrolyte can, of course, be made, depending on the primary ingredients of the composition. The minimum amount is that required to repress the rate of solubility of the synthetic detergent and the maximum amount is that which will change the middle phase of active ingredients at the surface of the bar to the curd phase. The actual amounts used vary with the character of the components. If the water-soluble soap is coconut soap more salting-out electrolyte will be required than in the case of the 80 tallowcoconut soap of the examples. If a straight tallow soap is used, less electrolyte will be required than in the case of the 80 tallow-20 coconut Soap of the examples. In a like manner, the choice of synthetic detergent will affect the amount of salting-out electrolyte, since it is known that synthetic detergents exhibit phases similar to those exhibited by soap. However, in any case the amount of such electrolyte is such as to slow up the rate of solution of the synthetic and to allow the formation of middle phase on the surface when the bar is placed in contact with water.

The synthetic detergent constituent of the present detergent bar composition may be broadly designated as a detergent of the class consisting of water-soluble salts of organic sulfonic acids and of aliphatic sulfuric acid esters, that is, water-soluble salts of organic sulfuric reaction products having in the molecular structure an alkyl radical of 10 to 22 carbon atoms and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals. As indicated above in the designation of the soaps which may be used in compounding the bars of the present invention, those versed in the art will appreciate that normally solid synthetic detergents are used.

Synthetic detergents of the following types can be used substantially as set forth in the above examples, suitable choice of alkali metal hydroxides, and adjustment of ratios of synthetic detergent, soluble and insoluble soaps and electrolytes being made as those versed in the art will recognize.

Synthetic detergents of special interest are the normally solid alkali metal salts of sulfuric acid esters of normal primary aliphatic alcohols having 10 to 18 carbon atoms. Thus the sodium and potassium salts of alkyl sulfuric acids obtained from the mixed higher alcohols derived by the reduction of tallow or by the reduction of coconut oil, palm kernel oil, babassu oil or other oils of the coconut group which are characterized by a content of more than 50 percent combined lauric and myristic acids, may be used.

Other aliphatic sulfuric acid esters which may be employed in the preparation of detergent bars of the present invention include appropriate water-soluble salts of sulfuric acid esters of polyhydric alcohols incompletely esterified with high molecular weight soap forming carboxylic acids. Such synthetic detergents include the water-soluble alkali metal salts of sulfuric acid esters of higher molecular weight fatty acid monoglycerides such as the sodium and potassium salts of the coconut oil fatty acid monoester of l,2-hydroxy-propane-3-sulfuric acid ester, sodium and potassium monomyristoyl ethylene glycol sulfate, and sodium and potassium monolauroyl diglycerol sulfate.

There may be employed also the synthetic detergents having a true sulfonate group, such as water-soluble salts of higher molecular weight monofatty acid esters of lower molecular weight hydroxy alkyl sulfonic acids, for example the sodium salt of the coconut oil fatty acid monoester of 1,2-dihydroxy-propane-3-sulfonic acid, and the coconut fatty acid ester of the potassium salt of isethionic acid. Included also are the water-soluble salts of the higher molecular weight alcohol esters of sulfocarboxylic acids, for example the sodium salt of the lauryl alcohol ester of sulfo acetic acid, as well as the alkylated aryl sulfonic acid, including the sodium and potassium salts of the sulfonic acid derived from the condensation products of benzene and either a chlorinated kerosene fraction containing predominantly 10 to 14 carbon atoms per molecule, or a polypropylene having 12 to 15 carbons, both of such compositions being represented by the formula where R is the alkyl group.

The materials which may be added in the am-algamator, in addition to coloring matter, perfume, and antioxidants, may include water or other liquids to improve the plasticity of the mix.

In some cases it is helpful to add 2 to 5 percent of a non-ionic or anionic liquid synthetic detergent. The nonionics are practically all liquid, so any one with the desired plasticizing qualities may be used. Among the anionic detergents, the substituted amine salts, made liquid with a small amount of water, for instance triethanolamine alkyl sulfate with 10 percent of water, are satisfactory plasticizing detergents.

As is well known in the art, cold creams and similar emollients may be added in the amalgamator.

This application is a continuation of application Serial No. 367,769, now abandoned.

Having thus described my invention, what I claim and desire to secure by Letters Patent is: 1. A milled detergent bar characterized by good lathering performance and a reduced tendency to crack and smear during use, consisting essentially of a homogeneous mixture of 7 8 (l) a water-soluble, normally solid synthetic detergent 2. The detergent composition of claim 1 in which the that is a potassium salt of an alkyl sulfuric acid conpotassium salt of the alkyl sulfuric acid is a mixture of taining an alkyl radical of from 10 to 22 carbon alkyl sulfates of lauryl and myristyl alcohols. atoms, (2) a water-soluble, normally solid alkali metal soap, 5 References Cited in the file of this patent (3) a. hydrated magnesium soap, and UNITED STATES PATENTS (4) an alkali metal salting-out electrolyte selected from the group consisting of chloride, sulfate and car- 1,906,484 Nuesslem May 1933 bonate salts 2,390,295 Flett Dec. 4, 1945 10 2,438,169 Hoyt Mar. 23, 1948 the who of synthetic detergent to total soap being about 2,673,921 Tm-ck May 18 1954 6:1 to 0.321, the magneslum soap constitutmg from 15% 2,781,320 jelinek at al F611 12, 1957 to 85% of the total soap, the remainder of the soap being 2,731,321 Maybe, et a1 p 12 1957 alkali metal soap, and the amount of salting-out electrolyte, calculated as sodium chloride, being from about FOREIGN PATENTS 5% to 30% of the sum of synthetic detergent plus alkali 15 9 5 9 Great Britain Apr, 1, 953

metal soap, and such that a water resistant phase is formed at the surface of the bar when said bar is contacted with OTHER REFERENCES Water, the moisture content of the finished bar immediately Surface Active Agents, Schwartz et al., Interscience after milling being about 8%. Publ. Inc, 1949, pp. 236 and 335.

Claims (1)

1. A MILLED DETERGENT BAR CHARACTERIZED BY GOOD LATHERING PERFORMANCE AND A REDUCED TENDENCY TO CRACK AND SMEAR DURING USE, CONSISTING ESSENTIALLY OF A HOMOGENEOUS MIXTURE OF (1) A WATER-SOLUBLE, NORMALLY SOLID SYNETHIC DETERGENT THAT IS A POTASSIUM SALT OF AN ALKYL SULFURIC ACID CONTAINING AN ALKYL RADICAL OF FROM 10 TO 22 CARBON ATOMS, (2) A WATER-SOLUBLE, NORMALLY SOLID ALKALI METAL SOAP, (3) A HYDRATED MAGNESIUM SOAP, AND (4) AN ALKALI METAL SALTING-OUT ELECTROLYTE SELECTED FROM THE GROUP CONSISTING OF CHLORIDE, SULFATE AND CARBONATE SALTS, THE RATIO OF SYNTHETIC DETERGENT TO TOTAL SOAP BEING ABOUT 6:1 TO 0.3:1, THE MAGNESIUM SOAP CONSTITUTING FROM 15% TO 85% OF THE TOTAL SOAP, THE REMAINDER OF THE SOAP BEING ALKALI METAL SOAP, AND THE AMOUNT OF SALTING-OUT ELECTROLYTE, CALCULATED AS SODIUM CHLORIDE, BEING FROM ABOUT 5% TO 30% OF THE SUM OF SYNTHETIC DETERGENT PLUS ALKALI METAL SOAP, AND SUCH THAT A WATER RESISTANT PHASE IS FORMED AT THE SURFACE OF THE BAR WHEN SAID BAR IS CONTACTED WITH WATER, THE MOISTURE CONTENT OF THE FINISHED BAR IMMEDIATELY AFTER MILLING BEING ABOUT 8%.