US3043778A

US3043778A - Soap bar compositions

Info

Publication number: US3043778A
Application number: US716273A
Authority: US
Inventors: William A Kelly
Original assignee: Lever Brothers Co
Current assignee: Lever Brothers Co
Priority date: 1958-02-20
Filing date: 1958-02-20
Publication date: 1962-07-10
Anticipated expiration: 1979-07-10
Also published as: FR1231063A; GB844918A

Description

United States Patent 3,043,778 SOAP BAR COMPOSITIONS William A. Kelly, Teaneck, N.J., assignor to Lever This invention relates to a novel soap bar which will disperse a soap scum when used in hard water. More particularly, it relates to a soap bar comprising certain proportions of alkali metal salt of fatty acid methyl taurate, free fatty acid, and coconut soap.

' For many years it has been known that alkali metal salts of fatty acid methyl taurate possess the property of dispersing the precipitate formed when soap is used in hard water. This fact was disclosed as early as 1933 in US. Patent No. 1,932,180. Examples 31-34, 37, 38 and 42 of this patent disclose the preparation of sodium, potassium, and amine salts of fatty acid methyl taurates and their use as wetting agents in solutions which are not rendered turbid by the presence of insoluble calcium salts. Despite the fact that this property has been known for many years, until the present invention, no one has succeeded in making a commercially acceptable soap bar wherein this property of dispersing soap scum has been utilized.

In order to be commercially acceptable in the present day market, a soap bar must meet many requirements. It must give good detergency in both cold and hot water. It must have good lathering properties, but not be irritating or injurious to the skin. It must have pleasant appearance, odor and feel, and maintain these characteristics during and after use. In addition, it must be capable of being formulated and compacted with equipment that would make the product commercially practical. Until the present invention, no one has succeeded in making a bar of soap which contains enough taurate to disperse hard water soap precipitate and which meets all of the above necessary requirements for commercial usefulness.

These and other problems are solved by the present invention which pertains to a bar of soap comprising from 5 to 25% alkali metal salt of fatty acid methyl taurate, from 2 to 25% free fatty acids, and from 15 to 60% coconut soap. The above percentages are by weight andv are based on the weight of the entire bar. The pH of the bar as measured in 10% solutions is between 8.6-9.4. The properties of a bar are mutually dependent functions of the type and amounts of the ingredients present. A change in the composition or amount of any one ingredient may improve one property, but generally only at the expense of one or more of the other properties. Thus, if there is serious departure from the above stated ranges of compositions, the resulting bar will be deficient in one or more respects. Within the ranges stated, it is possible to design bars for various desired characteristics. For example when a bar is to be used in relatively soft water, i.e., up to 50 -p.p.m., a bar containing tallow soap with only 5% of taurate, about 20% coconut soap and 3% free fatty acid will have good lime soap dispersing properties, lather well, and be mild.

When the bar is to be used in 300 p.p.m. hard water, at

least about 18% taurate would be required, along with higher coconut soap and free fatty acid contents to disperse the lime soap scum, lather well and be mild.

It is not economically feasible to go above 25% taurate concentration, since optimum dispersion effects are obtained below that figure, and since the taurate is the most expensive ingredient.

The soap bar should contain at least 15% coconut soap in order to have good lathering action, and may contain up to 60% coconut soap when suflicient free fatty acid is incorporated. The preferred range of coconut soap content is between 15% and because bars containing more than 40% coconut soap tend to develop sand-like granules upon aging for about six weeks. These granules do not interfere with the useful properties of the bar, but they are aesthetically objectionable.

It has been discovered that in order to obtain satisfactory lathering properties it is not only necessary that the bar contain 15 to 60% of coconut soap, but also from 2 to 25% free fatty acids. Fatty acid overcomes the suds depressing effect of taurate on soap, even though it replaces soap in a finished bar formula. Surprisingly, the inclusion of at least 2% free fatty acids'greatly increases the lathering ability of the bar. Compositions containing more than 25% free fatty acids tends to be soft and mushy, especially when used. The free fatty acid reduces the pH of the bar from about 10 to 10.5 to 8.6 to 9.4. It has been discovered that in this range the lathering, mildness and scum dispersing properties of the bar are improved. Free fatty acid also improves the feel and slip qualities. This is especially noticeable in cool water. A soap taurate mixture tends to drag and be rough when rotated in the hands during washing, whereas the taurate, soap, fatty acid mixtures are smooth and slip easily in the hands during use.

One of the most surprising discoveries concerning the soap, taurate, free fatty acid combinations was that the fatty acid improves the lather without contributing to scum formation in hard water.

It is advantageous to use free fatty acids which have been hydrogenated to a very lowiodine value, preferablytoluene or butylated hydroxy anisol at .02 to 0.5%.

The remaining portions of the bar may comprise soap of chain length longer than that in coconut soap, e.g. tallow soap, moisture, and ingredients such as perfume, pigment, preservatives and germicides in minor amounts. Of course, small amounts of various substances such as methyl taurine, dimethyl taurine, glycerol, salt, etc. are present in the taurate or soap, and are carried through to the finished bar.

3,4,S-trihalosalicylanilide having like halogens (e.g. 3,4,5-tribromosalicylanilide), and tetrahalosalicylanilides having like halogens, three of which are in the 3,4',5-posi tions, have been found to be effective germicideswhen incorporated in the bar at levels of about 0.1% to 1.0%, preferably about 0.5

Taurates from fatty acids of 12 to 20 carbon atoms such as described in the aforementioned US. Patent No. 1,932,- may be used, but it has been discovered that in order to have maximum soap curd dispersing action, it is preferable to use relatively long chain fatty acid taurates, e.g. the C16 and C18 compounds from tallow, which have considerably greater dispersing action than the corresponding compounds from coconut oil. It has also been discovered that the occurrence of sand like granules is minimized by the use of taurate made from tallow which has not been hydrogenated below an iodine value of 10.

fatty acid methyl taurate can be made by either of two reactions. One involves reacting a fatty acid chloride with the sodium salt of N-methyl taurine in the presence of caustic. The product of this reaction contains one mole of salt for every mole of taurate formed, and unless this salt is removed, for example by ion exchange, a bar containing the product will be extremely rough when used after an aging period. The preferred method of manufacture of the taurate involves reacting an excess of fatty acid with N-methyl taurine. The product of this reaction contains free fatty acid and taurate but no salt, and can be used to produce a bar having the desired properties.

The soap portion of the bar will normally be sodium soap, although minor amounts of potassium soap may be incorporated.

It has been stated above thatfrom to 60% of the weight of the soap bar should be coconut soap. It is to be understood, however, that soaps derived from other sources, but having approximately the same composition as coconut soap,'are also acceptable. As is well known in the art, the fatty acids of coconut oil comprise about 9% caprylic acid, 10% capric acid, 45% lauric acid, and myristic acid. Thus about. 84% of the fatty acids are those of relatively short (C8 to C14) chain length. Soaps can be made from palm kernel oil, babassu oil and/ or ucuhuba fat which approximate this composition, and

which are equivalent to coconut soap.

A preferred embodiment of the present invention comprises 33% sodium coconut soap, 18% sodium tallow (40 I.V.) methyl taurate, and 6% saturated free fatty acids of C14 to C18 chain length. Water comprises about 6% of the Weight of the bar, and the remaining portions are fallow soap (about and minor amounts of additives such as germicide, tallow alcohol, perfume, pigment and the like, along with the minor amounts of salt and miscellaneous materials present as a result of the chemical reactions involved in the preparation of the soap bar. Soap bars of the above composition give satisfactory scum dispersion even in very hard water, and also have all the other desirable properties of good quality soap.

Example N0. 1

This is an example of a preferred embodiment of the inventiom Kettle soap, taurate, caustic and free fatty acid were charged to a cnltcher in the proper proportions so that :when dried and mixed with perfumes, pigment etc., and milled and plodded, a bar was produced having the following composition:

. Percent Tallow methyl taurate from tallow fatty acids having an iodine value of 41 18 Na coconut oil soap 33 Na tallow soap 29 Miscellaneous impurities associated with the above 7 components 5 H 0 6 Free stearic acid (a commercial grade comprising palrnitic-45% stearic) 6 Perfume, pigments 1.5 3,4,5-tribromosalicylanilide .5 Fatty alcohol (62.0% cetyl, 34.1% stearyl 3.9%

(C14 and C20)) -h. 1

The crutcher mix as made contained about 32-34% water. The batch was tubular dried to 7% water, chilled and formed into ribbons on a chill 'roll, mixed with dyes,

' Example N0. 2

This is an example of embodiments of the invention at lower levels of taurate in bars containing coconut soap and free fatty acid Within the ranges stated in the specification. Bars were made containing 5, 10, 15 and 18% tallow (40 I. V.) methyl taurate by mixing the taurate, kettle soap and stearic acid in a heavy duty jacketed Paterson'mixer and heating until dried to about 7% moisture. The complete compositions of the bars are as follows:

Percent 40 I.V. Tallow methyl taurate 0 5 10 l5 18 Na Coco Soap 16 50 5O 33 38 Na Tallow Soap 70 22 16 35 29 Misc. salts, pigments, H2O, etc 14 13 14 13 14 Free Stearic Acid (Grade used in ex ample 1) 0 10 10 4 6 Water Hardness, p.p.m. Percent Taurate Heavy scum N0 scum Heavy scum Slight scum-.. Heavy scum N0 sc Slight scum..- Heavy scum. 18 do do No scum No scum.

Example N0. 3

This is an example showing the effect of free fatty acid on the sudsing of taurate and soap combinations. For this test solutions were made so that the ingredients would bein the same proportion to each other as in the preferred embodiment of the invention as shown in Example No. l. the proportion of 33 parts sodium coconut soap to 29 parts of sodium tallow soap in 100 ml. of water of about 110 ppm. hardness. Thus when the lathering of taurate and soap was tested 5 gms. of soap, and 1.46 gms. of taurate were dissolved in 100 ml. of water, and the relationship of taurate to soap would be 18 parts'of taurate to 62 parts of soap, or the same as in finished bar product in Example No. l.

For the tests, 100 ml. of solution was placed in a 500 ml. graduated cylinder and agitated by inverting the s'toppered cylinder 10 times in succession, then waiting 10 seconds to allow any large bubbles to break, and then inverting twice more. The volume of the foam was read using the calibration on the cylinder. The following results were obtained:

These results show the foam depressing action of taurate on soap, and indicate that the use of free fatty acid in combination with the taurate and soap improves the sudsing to a point almost equal to the soap alone and greater than the taurate alone.

Example N0. 4 This is an example showing the degrees of improve- The basis used was 5 gms. of soap in miscellaneous perfume, pigments etc. was prepared. Var-' ious percentages of lauric fatty acid were added to 100 ml. aliquots of the solution and these were tested for lathering using the cylinder test described in Example No. 3. The results were as follows:

Percent fatty acid: Height of foam, ml.

Example N0. 5

This is an example to show the effect of free fatty acid on lime soap dispersion. Two bars were made by the processes described both containing 18% stearic taurate and 50% sodium coconut soap. The first bar contained 20% free stearic acid (grade used in Example No. 1) and the balance sodium soap with small amounts of perfume and dyes. The second 'bar was the same except the fatty acid was replaced by sodium tallow soap. These bars were tested for the amount of lime soap scum by a titration method published in J .A.O.C.S., vol. 33, No. 3, pages ll3-1l6. The 'bar containing the free acid produced only 1.3% scum in 300 ppm. hard water while the bar containing no free fatty acid produced 4.7%

scum.

whereas the bar with no free fatty acid, pH 9.8, Was

quite harsh. The bar with the fatty acid was also much Example No. 6

This is an example showing'the dispersing effect of tallow methyl taurate on a fixed weight of soap and fatty acid. Solutions were made so that ml. contained 0.0035 gm. of Na coco soap, 0.0025 gm. of tallow soap and 0.0010 gm. of stearic acid. Tallow methyl taurate was added to each solution so that a specific percentage of taurate based on the weight of the soap and fatty acid was obtained. The concentration of the combination was equal to 0.1%. These percentages were 0, 2, 5, 10, 14 and 18. These were tested in 300 p.p.m. water for dispersing ability by the titration method used in Example No. 5. The following results were obtained.

Percent of bar as This test shows that the first five percent of taurate is the most effective per unit in dispersing lime soap scum, and that at least 5% taurate should be included in a bar to get maximum dispersing per unit of taurate.

Example N0. 7

A bar containing 17% palmitic-oleic methyl taurate (POMT), made by reacting fatty acid chloride with N- aoaa'rvs The bar with the free fatty acid pH 8.8, was mild methyl taurine in the presence of caustic soda, was made in a Paterson mixer; The composition of the bar was as follows: 17% POMT, 12% myristic acid, 40% Na coco soap, 5% sodium stearate, about 2% NaCl, 11% sodium tallow soap and about 13% water. This bar lathered well anddispersed lime soap scum. However, on aging the bar became rough textured when used, due to the high salt content.

The fact that salt tends to induce a sandy feel was demonstrated by making two bars of the approximately same composition as in Example No. 1, but including 1% NaCl in one. The bar with the salt became sandy after aging about 6 weeks, whereas the bar with no salt remained smooth.

Example N0. 8

A bar containing 18% unhardened 51 LV. tallow methyl taurate, 10% free stearic acid (as in Example No. 1), 33% Na coco soap, 26% Na tallow soap and the balance miscellaneous materials, pigments, dyes, perfume, water, etc. was made by mixing in a Paterson mixer and milling and plodding. This bar lathered well, dispersed lime soap and had a smooth texture when used.

Example N0. 9

A bar containing 21.0% tallow methyl taurate, 2.5% Na coco soap, 37.0% K-coco soap, 7.5% Na tallow soap, 4.0% stearic acid (grade used in Example No. l), 20% Attasorb (a diatomaceous earth) and 8.0% Water was made by blending the ingredients in a small heavy duty mixer (Readco) and then milling and plodding. The finished bar was smooth, lathered well and dispersed lime soap scum.

Example N0. 10

A bar containing 18% tallow methyl taurate (40 I.V.),

15% Na coco soap, 6% stearic acid (grade used in Example No. 1), 46% Na tallow soap and the balance miscellaneous salts, pigments, perfume, and water was made by mixing the ingredients in a Paterson mixer and then milling and plodding. The bar lathered well, and dispersed lime soap scum.

What is claimed is:

1., A bar of soap which disperses soap scum in hard water and consists essentially of, by weight based on the weight of the entire "bar, (a) from 5 to 25% of an alkali metal salt of a fatty acid methyl taurate, said fatty acid containing from 12 to 20 carbon atoms and the cationic portion of said alkali metal salt being selected from the group consisting of sodium and potassium; (b) from 15 to 60% of a water soluble alkali metal coconut soap, and (c) from 2 to 25% of free fatty acid containing from 12 to 20 carbon atoms, said bar having a pH as measured in a 10% aqueous solution of about 8.6 to 9.4.

2. The bar of soap of claim 1 wherein the fatty acid portion of the tau-rate contains 16 to 18 carbon atoms.

3. The bar of soap of claim 1 wherein the fatty acid portion of the taurate has an iodine value greater than 10.

4. The bar of soap of claim 1 wherein the free fatty acid has an iodine value no greater than 5.

5. The bar of soap of claim 1 which also contains from 0.1 to 1.0% of 3,4,5-tribromosalicylanilide.

6. The bar of soap of claim 1 wherein the alkali metal salt of a fatty acid methyl taurate is substantially free of sodium chloride. 7

7. A bar of soap which disperses soap scum in hard water and consists essentially of, by weight based on the weight of the entire bar, (a) from 5 to 25% of the sodium salt of unhydrogenated tallow fatty acid methyl taurate; (b) from 15 to 40% of a water soluble alkali metal coconut soap, and ('c) from 2 to 25% of free fatty acid containing from 14 to 18 carbon atoms and having aniodine value no greater than 5, said bar having a pH as measured in a 10% aqueous solution of about 8.6 to

8. A'bar of soap which disperses soap scum in hard water and consists essentially of, by weight based on the I weight of the entire bar, (a) about 18% of sodium fatty acid methyl taurate, said fatty acid containing 16 to 18 carbon atoms and having an iodine value of about 40; (b) about 33% of sodiumtcoconut soap; (0) about 6% of free fatty acid containing from '14 to 18 carbon atoms and having an iodine value no greater than 5 and (d) about 29% of sodium tallow soap, said bar having a pH as measured in a 10% aqueous solution of about 8.6 to 9.4.

9. The bar of soap of claim 8 which also contains about 0.5% of 3,4,S-tribromosalicylanilide.

References Cited in the file of this patent UNITED STATES PATENTS Neusslein May 2, 1933 Malkemus Feb. 22, 1949 Jelinek et a1." Feb. 12, 1957 Schuler Aug. 6, 1957 Henderson et a1 Jan. 13, 1959 Geitz July 14, 1959 FOREIGN PATENTS France Nov. 10, 1953

Claims

1. A BAR OF SOAP WHICH DIPERSES SOAP SCUM IN HARD WATER AND CONSISTIS ESSENTIALLY OF , BY WEIGHT BASED ON THE WEIGHT OF THE ENTIRE BAR, (A) FROM 5 TO 25% OF AN ALKALI METAL SALT OF A FATTY ACID METHYL TAURATE, SAID FATTY ACID CONTAINING FROM 12 TO 20 CARBON ATOMS AND THE CATIONIC PORTION OF SAID ALKALI METAL SALT BEING SELECTED FROM THE GROUP CONSISTING OF SODIUM AND POTASSIUM; (B) FROM 15 TO 60% OF A WATER SOLUBLE ALKALI METAL COCONUT SOAP, AND (C) FROM 2 TO 25% OF FREE FATTY ACID AND CONTAINING FROM 12 TO 20 CARBON ATOMS, SAID BAR HAVING A PH OF MEASURED IN A 10% AQUEOUS SOLUTION OF ABOUT 8.6 TO 9.4.

5. THE BAR OF SOAP OF CLAIM 1 WHICH ALSO CONTAINS FROM 0.1 TO 1.0% OF 3,4'' 5-TRIBROMOSALICYLANILIDE.