IE47125B1 - Toilet soap bars - Google Patents

Abstract

Superfatted toilet soap bars are prepared from compositions comprising predominantly sodium soap of higher fatty acids and minor proportions of superfatting higher fatty acids, high molecular weight poly(ethylene oxide) and water. A process for making such compositions includes blending the polymer with the superfatting acids and some of the water, and mixing the blend with the soap.

Description

This invention relates to superfatted toilet soap bar compositions, to toilet soap bars prepared from such compositions, to a process for preparing such compositions, and to blends of certain components of such compositions.

Superfatted toilet soap bars (such as those sold as cosmetic or complexion bars) are well known in the art and are described, for instance, in U.S. Patent to Megson et al No. 3,576,749. As pointed out in the Megson et al Patent, such bars are unlike bars made of synthetic detergents which, according to that Patent, give a very soft, slimy, messy type of smear which is unacceptable in soap bars. According to the Megson et al Patent, free acids in the bar improve the volume and quality of the lather, causing it to be more stable with small air bubbles which gives the user a lather which is characterised as “richer and creamier, and the fatty acids also tend to soften the skin. The Megson et al Patent teaches that with such superfatted bars large amounts of sodium chloride and high milling temperatures are required in order to attain firmness of the bar and smear resistance. - 2 4712S This invention makes it possible to produce superfatted toilet soap bars, substantially and preferably entirely devoid of synthetic detergents which form a rich creamy lather and which give a pleasant feel both in use and after use; when compared with commercial superfatted toilet soap bars which are believed to be made according to the teachings of Megson et al it is found that the bars made in accordance with this invention are greatly preferred by users, with respect to the nature of the lather and other characteristics. The bars are firm and have high resistance to sloughing or smear without the need for incorporation of added sodium chloride and without the need for using high milling temperatures.

The invention makes it possible to produce toilet soap bars which give a rich and creamy, but only moderately slippery, lather and which are firm and resistant to sloughing and cracking in use.

According to one aspect of this invention a toilet soap bar composition comprises 15 predominantly sodium soap of higher fatty acids as substantially the sole detergent, from 6% to 15%, such as from 8% to 10%, of superfatting higher fatty acids, from 0.5% to 4%, typically from 1% to 4%, preferably from 1.5% to 3%, of polyethylene oxide) having a molecular weight in the range from 100,000 to 5,000,000, and from 5% to 18% of water, 2θ All percentages and other ratios, and parts, given herein are by weight.

Molecular weights are approximate as exact determinations are not practicable, The term higher used in relation to fatty acids means that they contain from 8 to 20 carbon atoms per molecule.

It has also been found that poly (ethylene oxide)-containing superfatted bars 25 which have particularly good slough - resistant or smear - resistant properties comprise a sodium soap of about equal proportions of coco fatty acids and tallow - 3 47125 fatty acids superfatted with about equal amounts of coco fatty acids and stearic acid, as can be seen, for instance, in the data tabulated in Example 1 below.

Soap is conveniently manufactured by the saponification of fatty acids or esters (e.g. fats and oils) by either a kettle process or a continuous saponification technique, as discussed in the Kirk-Othmer Encyclopedia of Chemical Technology (2nd edition) Vol. 18 pages 415-425, which states that the end product of both the kettle and continuous saponification procedures is a neat soap containing approximately 30% water...... The 30% water content of neat soap must be reduced to 10-15% before shaping into bars.........

Soap bars have been made commercially by adding powdered polyethylene oxide) to soap chips in a soap amalgamator; such addition requires special precautions in order to avoid formation of specks in the final bar. The use of high molecular weight polyethylene oxide) (Polyox resin1' Polyox is a trade mark) in synthetic detergent bars, which may contain some soap, has been described and it has been suggested that the resin may be melted in combination with soap, detergent base, or other ingredients and then other material incorporated into the melt (Davidson and Sitting Water Soluble Resins pub. 1962, pages 197-8). When it was attempted to incorporate about 2% powdered polyethylene oxide) into a neat soap containing about 30% water (kettle soap), a mixture was obtained which was lumpy and poorly dispersed and not pumpable.

It has now been found that a superior blend is obtained by incorporating the polyethylene oxide), desirably in powder form, into a melt of all, or a portion of, the higher fatty acids which are to be used for superfatting the soap.

Best results are obtained when this blend also contains a minor amount of water. As will be seen in Example 3 below, the presence of the water has a marked effect on the nature of the blend of fatty acid and high molecular weight - 4 47135 polyethylene oxide), significantly decreasing its viscosity; the presence of the water also tends to opacify the blend which may indicate that a waterin-oil type of dispersion is formed. The water-containing blend can be pumped readily; its viscosity is well below the upper viscosity limit (which is about 7,000 or 8,000 centipoises) of materials that can be handled readily by ordinary reciprocating pumps. It can thus be easily pumped into admixture with the kettle soap. The polyethylene oxide)-containing soap bars made by this procedure have outstanding properties; they lather well, have an especially pleasant feel during and after use, have good slough resistance and resistance to wet-cracking.

The following Examples illustrate the invention.

EXAMPLE 1. (a) 4.5 parts of stearic acid and 4.5 parts of coco fatty acids are melted together at a temperature of 80°C in a vessel equipped with a stirrer. 1.8 part of high molecular weight polyethylene oxide) (Polyox WSR N-750 sold in U.S.A. by Union Carbide Company, having an average molecular weight of about 300,000, a viscosity [when measured in a 5% solution in water] in the range from about 550 to about 900 cps at 250°C, and a melting point of about 65°C) are added thereto with stirring while maintaining the blend at about 8D°C. 2Q This blend is then mixed with a kettle soap (at 70°C) in such proportions that the resulting mixture contains about 75 parts of the sodium soap (expressed as anhydrous soap), 4.5 parts of the added stearic acid, 4.5 parts of the added coco fatty acids and 1.8 parts of the poly(ethylene oxide). The kettle is made by saponifying a 50-50 mixture of coconut oil and tallow with sodium hydroxide solution, extraction of resultant glycerine, washing with electrolyte solution and removal of high electrolyte nigre soap layer all as is conventional in the manufacture of kettle soaps; it contains from about 27% to about 32% (e.g. 30%) water, up to about 1% (e.g. 0.5%) glycerol, up to about 0.3% (e.g. 0.1%) - 5 47125 sodium hydroxide and up to about 1% (e.g. 0.7%) sodium chloride. The ingredients are stirred together for a few minutes and the mixture is then formed into dried soap chips containing about 10% moisture, as by pumping the hot soap mixture onto a chilled roll, forming a thin film on the roll, slicing the film into chips or ribbons and then drying the chips or ribbons. The chips are then blended with colour and perfume (e.g. 0.7% titanium dioxide and i.5% perfume) in a conventional manner in a soap amalgamator at about room temperature, then milled to homogenize them (e.g. at a temperature from about 15 to about 35°C), then extruded into a bar form by means of a conventional soap plodder (e.g. at a temperature from about 20 to about 50°, e.g. 40°C), then cut into cakes; the surfaces of the cakes are cooled and the cakes are pressed into the desired shapes (e.g. in a pin-die press). (b) Part (a) is repeated except that instead of using 4.5 parts stearic acid and 4.5 parts coco fatty acids there is employed 9 parts stearic acid. (c) Part (a) is repeated except that instead of using 4.5 parts stearic acid and 4.5 parts coco fatty acids there is employed 9 parts coco fatty acids.

On testing the soap bars (after aging at least 3 days) the following results are obtained; % Erosion Sponge Lather No. of Strokes Slough (17 hr.) % loss 95°F - Hydration 100°F (2 hr.) % gain Cracking Index (a) 60 1.5 2.6 16.1 12.5 18 (b) 80 3.5 2.2 18.8 11.6 15 (0 68 5.2 18.7 19.6 IQ.8 0 In the sponge lather test, which measures the quickness of lather formation, the bar's flat surface is alternately rubbed against a sponge and dipped in a pan of water (with a hardness level of 125 ppm and a temperature of 95°F). The up- 6 4712S and-down motion of the lather machine produces a lather and the number of strokes required to form a continuous ring of foam in the pan is counted.

The less the number of strokes, the quicker the lather. In the slough test, the bars are placed flat with one side immersed in a Petri dish for seventeen hours, after which time the soft, mushy soap is removed by fingers.

The percent weight lost as slough is repoured. In the erosion test the bar is immersed in water for 260 strokes (about 10 minutes) of the lather machine, and the amount of soap lost is measured. In the hydration test the bars are completely immersed in tap water for two hours and the increase in weight is determined. The cracking index is an evaluation based on number and severity of cracks in a test in which the bars are shaved on one side at half their original sizes then placed under tap water (about 100 ppm hardness) for one hour, taken out and hung to dry in air until no sign of free water remains on their surfaces (usually overnight).

The bar of part (a) shows unexpectedly high lather quickness, unexpectedly low slough loss and erosion loss and acceptable cracking behaviour.

EXAMPLE 2.

Bars are made as in Example 1(a) except that they also contain 0.5% lanolin with and without 0.5% sodium caseinate solids, these ingredients being incorporated with the hot fatty acid~poly(ethylene oxide) blend before mixing it with the kettle soap.

EXAMPLE 3.

Example 1(a) is repeated except that the following procedure is employed in making the blend mixed with the kettle soap. 5 parts of commercial stearic acid (m.p. 54°C) and 5 parts of coco fatty acids (m.p. 25°C) and 5 parts of coco fatty acids (m.p. 25°C; iodine value 6) are melted together at a temperature of about 102°C. One part of powdered high molecular weight polyethylene oxide) - 7 47125 (''Polyox WSR N-750 as in Example 1) is added thereto with stirring. The viscosity of the mixture at 102°C is about 750 cps, at 88°C it is about 4,000 cps and at 54°C it is about 5,000 cps (as determined with a Brookfield viscosimeter).

One more part of the same Polyox is then added with stirring. The viscosity of the mixture is about 18,000 cps at 94°C, and 19,000 cps at 88°C, about 33,500 cps at 66°C and about 42,500 cps at 54°C, Then 0.5 part of lanolin is added with stirring. The resulting blend now has a viscosity of about 15,000 cps at 94°C and a similar viscosity at 70°C.

Next, 1 part of water is added. As a result, the formerly clear blend becomes cloudy or opaque. Its viscosity is about 5,000 cps at 77°C, about 4,000 cps at 71°C and about 3,250 cps at 50 to 63°C.

Thereafter an additional 1 part of water is added with stirring. The resulting blend has a viscosity of about 2,250 cps at 84°C, 1500 cps at 81°C, 930 cps at 71°C, 470 cps at 67°C, 234 cps at 60°C and 114 cps at 52°C.

Next 2.5 parts of a solution of sodium caseinate (containing 20% casein) is added. The resulting blend is white. Its viscosity is about 2,900 cps at 81°C, 2520 cps at 71 °C, 1,700 cps at 66°C and 1,800 cps at 60°C.

It will be seen that the addition of the water gives a blend whose viscosity at, say, 70°C is greatly decreased (e.g. to well below half its value before the addition of the water). Also the blends containing water show a remarkable decrease in viscosity with decrease in temperature (e.g. when temperature is reduced, from 70°C or 80°C, by 10°C the viscosity drops by well over 10%). The above resulting blend is pumped at a temperature of from about 60 to about 85°C into a mixing vessel containing kettle soap (at 70°C) in such proportions that the resulting mixture contains about 75 parts of the sodium soap (expressed as - 8 47125 anhydrous soap), 4.5 parts of the added stearic acid, 4.5 parts of the added coco fatty acids and 1.8 parts of the polyethylene oxide).

EXAMPLE 4.

Example 1(a) is repeated except that in making the blend, 10 parts of stearic acid are melted and 2 parts of the polyethylene oxide) of Example 1 are added thereto, followed by 1.5 parts of water, while the mixture is stirred and maintained at from about 70 to about 90°C.

EXAMPLE 5.

Example 4 is repeated except that coco fatty acids are used in place of stearic acid.

In the water-containing blend of polyethylene oxide) and higher fatty acids there are preferably 2 to 20 (more preferably from 4 to 8) parts of the fatty acids per part of polyethylene oxide) and from 0.5 to 5 (more preferably from 1 to 2) parts of water per part of poly(ethylene oxide).

It is preferred that the amount of moisture in the ingredients added to the kettle soap be such that the moisture:soap ratio be maintained below 33:67 (such as from 27:73 to 32:68) to minimize formation of less desirable gel soap phase.

It is desirable, particularly in the formulations containing relatively large amounts of coco fatty acids (such as in Example 1a) to dry to a moisture content below about 18%, preferably to from 5% to 18%, e.g., from 5% to 12%, in order to reduce the tendency for stickiness during later blending (e.g. in the amalgamator) or processing. To the same end it is desirable to use relatively low plodding temperatures, pre-cool and pre-dry the outer surfaces of the bars before pressing in the dies, and lubricate the dies (e.g. with an aqueous solution containing 16% sodium chloride and 25% glycerol, which is then air- 9 47135 blown off the surfaces of the pressed bars).

The high molecular weight polyethylene oxide) has an average molecular weight in the range from 100,000 to 5,000,000. Examples of such compounds are those sold in U.S.A. by Union Carbide Company under the trademark Polyox. These polymers are nonionic materials soluble in water. It is preferred to employ polymers having average molecular weights below 1,000,000, more preferably not above 600,000 such as in the range from 300,000 to 600,000 e.g. 300,000 to 400,000. For the material having an average molecular weight of about 300,000 a proportion in the neighbourhood of 2% has given excellent results. 300,000 molecular weight material (sold as Polyox WSR N-750) has a viscosity at 25°C, for a 2% aqueous solution, of about 40 centipoises (Brookfield Spindle No. 1 at 10 rpm); for a 5% solution the viscosity is from about 600 to about 1000 centipoises. Use of, say 2% of extremely high molecular weight polyfethylene oxide), e.g. of about 4,000,000 average molecular weight, causes the lather to be pituitous, which is less desirable. According to the manufacturer the Polyox materials typically have a pH of about 10 (e.g. in 5% solution). Soap typically'has a pH in 1% aqueous solution of about 10 (e.g. 10.2), while the superfatted soaps of this invention generally have lower pHs such as about 9.5.

The polyethylene oxide) is generally supplied as a powder and typically has thejollowing particle size distribution when a sample thereof is screened through a series of sieves, expressed as weight percent retained on the indicated Sieve No. screen (U.S. Sieve Series); No. 20-5.2%; No. 40-31.2%; No. 60-20.7%; No. 100-16.7% and through No. 100-balance. It is often preferable to use a finer particle size polyethylene oxide) having the following distribution as measured above : No. 20-5%; No. 40-13%; No. 50-13%; No. 100-13.9% and through No. 100-balance. - 10 47125 Best results have been obtained by using a soap made by saponifying a blend of about equal parts of tallow and coconut oil. Generally it is preferred to use a tallow-coco ratio within the range from 2:1 to 1:2 such as 3:2 or 2:3.

Before mixing it with the various ingredients, the kettle soap is preferably stabilized, as by incorporating into it about 0.06% stannic chloride and about 0.024% tetrasodium salt of ethylene-diamine-tetraacetic acid, these being added as aqueous solutions.

With respect to the superfatting acid, best results have been obtained when this comprises about equal proportions of stearic and coco fatty acids. Generally it is preferred to use these acids in a ratio within the range from 2:1 to 1:2 such as 3:2 or 2:3. The total amount of superfatting acids in the bar does not exceed 15%.

It will be understood that cation-exchange of Na and H may occur during processing of the soap-fatty acid mixture and that it is most convenient to express the distribution of chain lengths in the mixture in terms which lump together the saponified and unsaponified fatty acids. Typical distributions, so expressed, in bar compositions of this invention are tabulated below: Number of carbon atoms in fatty acid (fatty acid is saturated unless otherwise noted) a Percent b 8 3.1 2.8 10 2.9 2.6 12 24.3 21.5 14 11.0 10.5 14 monounsaturated 0.2 0.5 15 0.2 0.3 15 monounsaturated - - 16 19.0 18.6 16 monounsaturated 1.0 1.7 - 11 47125 Number of carbon atoms in fatty acid (fatty acid is saturated unless otherwise noted) a Percent b 17 0.6 0.4 17 monounsaturated 0.3 - 18 13.4 12.6 18 monounsaturated 21.6 25.9 18 diunsaturated 2.1 2.1 18 triunsaturated 0.3 0.3 Summary up to 30.3 26.9C16 - C14 31.4 31.6C18 - C17 38.3 41.3 With respect to the moisture content below 12# during processing, it should be noted that in use, or in storage, after processing the moisture content may increase (see, for instance, the hydration data in Example 1); preliminary results indicate, however, that the bars have a significantly lower tendency to hydrate than known commercially available superfatted bars.

Conventional kettle soap contains up to about 1# (e.g. 0.7%) sodium chloride.

The bars of this invention have good smear resistance without the need for addition of sodium chloride, although such additions are not excluded. The bars of this invention have good hardness, comparable to or greater than that of ordinary toilet soap at 90°F, when the milling is carried out at conventional relatively low temperatures (that is , their Dietert hardness at 90°F is above about 85, e.g. 90 to 92); there is no need to use the higher milling temperatures set forth in the Megson et al Patent although the use of such milling temperatures is not excluded. - 12 47125 The fatty acids in the soap and the superfatting acids, and the relative proportions of the various acids, may be described in the Megson et al Patent. The superfatting acid may contain fatty acids having an odd number of carbons; thus one may employ a fatty acid mixture containing equal proportions (one third each) of C^, and C^3 saturated fatty acids (Monsanto CR-1157).

The soap bars of this invention may contain conventional ingredients such as opacifiers (e.g. 0,4% titanium dioxide added in the amalgamator), lanolin (e.g. 0.5% added to the neat soap, preferably in admixture with the superfatting acid), glycerine (e.g. 1% added in the amalgamator or to the neat soap), soap perfume (e.g. from 1% to 3%, such as from 1.5% to 2%, added in the amalgamator), antioxidants (e.g. 0,02% di-t-butyl p-cresol or BHT added to the neat soap), protein (e.g. 0.5% sodium caseinate, added to the neat soap or, as an aqueous solution, in the amalgamator). Antibacterials or germicides such as those mentioned in the Megson et al Patent and Kaniecki U.S. Patent No. 3,598,746 may be included. The bars may be aerated in a manner well known in the art, to give lower density (floating) soaps, such as those having a specific gravity of about 0.8.

Toilet soap bars range in size from the small hotel size (weighing from about 20 to about 30 grams) through the regular size (about 100 grams) and the bath size (about 150 grams) to the extra large size (about 200 grams). The bars of this invention may be of such sizes, particularly in the range from 100 to 200 grams.

As mentioned above, the polyethylene oxide) may be incorporated in two stages, one portion (such as about half or two thirds of the total polymer), being incorporated into the neat soap and the other portion being added to the soap chips in the amalgamator. In order to reduce the tendency to form specks when the latter addition is made in the amalgamator, it is desirable to add the polymer there in the form of very finely ground material (such as material of - 13 47125 which 98% passes through a No. 100 screen (U.S, Sieve series) and to distribute the powdered polymer thoroughly over the surfaces of the chips in the amalgamator prior to adding the other ingredients such as pigment. When a significant portion of the total polymer is incorporated into the neat soap, the soap is less sticky during the incorporation of the balance of the polymer in the amalgamator and the amalgamation process may be accomplished more easily and with the use of less power.

Claims (14)

1. A toilet soap bar comprising predominantly sodium soap of higher fatty acids as substantially the sole detergent, from 6% to 15% of superfatting higher fatty acids, from ¢5% to 4% of polyethylene oxide) having a molecular weight in the range from 100,000 to 5,000,000, and from 5% to 18% of water.

2. A toilet soap bar as claimed in Claim 1 in which the polyethylene oxide) has a molecular weight in the range from 300,000 to 600,000 and is present in a proportion in the range from 1.5% to 3%.

3. A toilet soap bar as claimed in Claim 1 or Claim 2 in which the sodium soap is a mixture of tallow soaps and coconut oil soaps in a ratio in the range from 1:2 to 2:1.

4. A toilet soap bar as claimed in Claim 1 or Claim 2 in which the sodium soap is a mixture of approximately equal parts of tallow soaps and coconut oil soaps,

5. A toilet soap bar as claimed in any of the preceding claims in which the superfatting acids comprise a mixture of stearic acid and coco fatty acids in a ratio in the range from 2:1 to 1:2.

6. A toilet soap bar as claimed in any of Claims 1 to 4 in which the superfatting acids comprise a mixture of approximately equal parts of stearic acid and coco fatty acids. - 14 47125

7. A toilet soap bar substantially as described in any of the Examples.

8. A process for preparing a toilet soap bar as claimed in any of the preceding claims which comprises mixing neat soap comprising the said sodium soap and about 30% moisture with a blend of the polyethylene oxide) in a melt 5 of the superfatting higher fatty acids and subjecting the resulting mixture to drying conditions, and thereafter shaping the mixture into a bar.

9. A process as claimed in Claim 8 in which the blend contains from 2 to 20 parts of superfatting fatty acids per part of polyethylene oxide).

10. A process as claimed in Claim 8 or Claim 9 in which the blend contains 10 a minor proportion of dispersed water sufficient to decrease the viscosity of the blend.

11. A process as claimed in any of Claims 8 to 10 in which the blend contains from 0.5 to 5 parts of water per part of polyethylene oxide).

12. A process as claimed in any of Claims 8 to 11 in which the blend 15 contains from 4 to 8 parts of superfatting fatty acids and from 1 to 2 parts of water per part of poly(ethylene oxide).

13. A process for preparing a toilet soap bar substantially as described in any of the Examples.

14. A toilet soap bar which has been prepared by a process as claimed in an.· 20 of Claims 8 to 12.