DE69203507T2 - Detergent composition. - Google Patents

Description

This invention relates to soap bars, in particular for personal cleaning, and their manufacture.

A number of publications report that it is desirable to incorporate skin-beneficial oils, e.g. so-called bath oils or emollient oils, into soap bars. A number of proposals exist for this. However, US Patent 3,941,712 explains that the simple incorporation of such oils into milled soap is not possible because it results in an overly soft bar with an oily feel.

A well-known method for producing soap bars is to prepare an isotropic melt containing the soap and various organic solvents and to cast the resulting melt directly into bars. This method has the advantage that it leads in only one step from a shapeless melt of the ingredients to cast bars having the desired shape. The cast bars naturally contain solvent as well as soap and can be transparent or translucent.

Surprisingly, it has now been found that by observing certain formulation restrictions, it is possible to incorporate a skin-beneficial oil into the bars produced by this so-called melt-cast route. It is surprising that the presence of the skin-beneficial oil does not prevent the formation of an isotropic solution of the soap in the solvent.

According to a first aspect of the present invention, a soap composition is provided which, in addition to any non-detergent macroparticles

25 to 60% anionic, nonionic, zwitterionic or amphoteric active detergent containing soap of saturated C₁₆₋₂₂ fatty acids in an amount of 8 to 32%,

10 to 50% of one or more alcohols, including one or more solvent alcohols selected from ethanol, propanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, ethanolamines and propanolamines, the amount of solvent alcohol being 5 to 30%,

not more than 30% water, and

1 to 20% of an oily skin benefit agent, the percentages given above being based on the weight of the composition, excluding any dispersed non-detergent macroparticles.

The present invention also provides a process for the manufacture of soap bars comprising forming an isotropic melt of the composition as set forth above and casting the molten composition into solid bars.

The various components of the soap composition will now be discussed one by one.

An essential ingredient is soap of saturated C16-22 fatty acids. The term "fatty acid" means monocarboxylic acids. Generally more than half of these, probably substantially all of them, will be soap of saturated C16 and C18 fatty acids, which are palmitic acid and stearic acid respectively. Soaps of these saturated C16-22 fatty acids are often classified as insoluble soaps because of their poor solubility in water. These provide structural strength in the final soap bars. Blends of these chain lengths are preferred.

The remainder of the active anionic detergent may consist of soap from other fatty acids which are more soluble and thus provide a foam when brought into contact with water. In this case it is preferred that from 4% up to 30%, or the remainder of the active detergent if this is less than 30% consists of soap of C₁₀₋₁₄ fatty acids and/or unsaturated C₁₆₋₂₄ fatty acids. Soap of these acids usually refers to a soluble soap. Significant chain lengths which can contribute at least a majority of the soluble soap and at least 4% of the composition are C₁₂, C₁₄ and unsaturated C₁₆ and C₁₈ chain lengths.

Since the saturated C16-22 soaps contribute to structural strength and hardness, whereas the other detergents, i.e. shorter chain soaps, unsaturated soaps and/or non-soap detergents contribute to foam generation, it is preferred that both are present and that the saturated C16-22 soap and the other detergent are present in a weight ratio of 3:1 to 1:3, more preferably in a weight ratio of 2:1 to 1:2 and more preferably in a weight ratio of 1.5:1 to 1:1.5.

The active detergent may also contain any non-soap detergent which provides foam on contact with water. This may be anionic, non-ionic, zwitterionic or amphoteric. In particular, it may be any of the non-soap detergents known for use in combination with soap in individual laundry bars. These include fatty acyl isethionates, acyl taurides, alkyl sarcosinates, mono- and dialkyl sulphosuccinates, alkane sulphonates, alkyl ether sulphates, alkyl benzene sulphonates, alkyl sulphates and α-olefin sulphonates, each of which has an alkyl or acyl chain containing from 8 to 18 carbon atoms.

It is preferred that nonionic, zwitterionic or amphoteric detergent, if present, be used in conjunction with anionic non-soap detergent. Examples of nonionic detergents are alkyl ethoxylates, alkyl polyglutamates, alkyl ethanolamides and amine oxides. Examples of zwitterionic compounds are betaines and amido betaines. Such materials can act as at least partial replacements for soluble soap. Therefore, the amount of detergent active selected from the group consisting of C₁₂₋₁₄ fatty acids, C₁₆₋₂₂ unsaturated fatty acids and non-soap detergent active, generally within a range of 4 to 30% (but not exceeding the balance of the active detergent).

Anionic non-soap detergent may be present along with soluble soap. The amount of non-soap detergent, if present at all, may be in the range of 1 to 30% by weight of the composition, excluding any dispersed non-soap macroparticles.

On cooling from the molten state, any active non-soap detergent will solidify into opaque particles. This may be acceptable, but preferably such detergent has a Krafft point not significantly above 40°C.

The soap which is present, both the insoluble soap of saturated C16-18 fatty acids and any other soap present, may be entirely or substantially entirely sodium soap, so that at least 90% by weight of even 95 or 97% by weight of the soap counterions are sodium. On the other hand, however, any other counterions such as potassium and trialkanolammonium may be present. If other counterions are present, they will usually constitute a minor proportion, up to 30 or 40% by weight of the soap counterions present.

The soap may be derived from fats and oils as conventionally used in soap making. The fats and oils and the amounts used must be selected to provide the required amounts of C16-18 and other soap. A mixture of chain lengths meeting the requirements of this invention may be provided by a conventional soap such as conventional 80:20 tallow:coconut soap or by a mixture of conventional soaps such as 80:20 soap enhanced with additional soap made from coconut oil as the sole triglyceride source. Any other alcohol present is preferably a polyalcohol. As previously mentioned, the alcohol must be at least

contain a solvent alcohol selected from a small group of short-chain monohydric alcohols, short-chain diols and short-carbon alkanolamines. These materials are good solvents for insoluble soap.

Preferred within this group are ethanol, isopropanol, 1,2-propanediol, triethanolamine and triisopropanolamine.

Various polyalcohols are available and can be used. One possibility is glycerin. Another possibility is a sugar such as sucrose or glucose and yet another possibility is a sugar derivative such as sorbitol.

Another possibility is polyethylene glycol of fairly low molecular weight, such as a molecular weight of about 400. It is believed that the presence of polyalcohol(s) helps to reduce the shrinkage of the bar as it is poured from a melt.

The skin benefit agent is a compound or a mixture of compounds which is an oil at room temperature. In general, they will contain at least one saturated aliphatic C8-22 hydrocarbon chain. In particular, the oily skin benefit agent may be a hydrocarbon oil such as petrolatum, mineral oil or nujol; alternatively it may be an ester of a C8-22 fatty acid and/or a C8-22 fatty alcohol. Such an ester could be a triglyceride.

The oil beneficial to the skin can be, in particular, a known emollient, and specific possibilities include:

Natural oils such as jojoba oil, coconut oil, mink oil, sesame oil, arachis oil, sunflower seed oil, primrose oil and castor oil;

Hydrocarbons such as nujol, mineral oil and petrolatum; Lanolin and lanolin alcohols;

C₁₂₋₂₄ alcohols such as stearyl alcohol, cetyl alcohol, octadecan-2-ol;

Esters of C₈₋₂₂ acids and C₂₁₋₂₄ alcohols (including diacids, diols, triacids and triols, not necessarily esterified with all acid hydroxy groups), such as glyceryl monoricinoleate, Glyceryl monostearate, mink oil, isopropyl isostearate, isobutyl palmitate, isocetyl stearate, isopropyl laurate, hexyl laurate, decyl oleate, cetyl palmitate, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate and myristyl myristate.

The amounts of the ingredients of a soap bar according to this invention are interrelated. The amount and nature of the solvents must be such as to enable dissolution of the soaps while at the same time being sufficiently limited that the solidification temperature is reasonably high, such as at least 50°C.

Increasing the proportion of saturated C16-18 soaps increases the hardness and reduces the rate at which the bar will dissolve in water during use, therefore improving the wear rate, but increases the demand on the ability of the organic solvents in the composition to dissolve the soap during manufacture. Consequently, when high levels of saturated C16-18 soaps are present, it will be desirable to make use of the most effective solvents, most particularly triethanolamine and ethanol.

In particular, the amounts of the constituent materials may fall within any of the following three sets of ranges, which represent preferred options with various levels of saturated C₁₆₋₁₈ soap. Saturated C₁₆₋₁₈ Soap Other Detergent Total Detergent Ethanol/Isopropanol Triethanolamine Polyalcohol WaterIn In each of these range sets, the weight percent range for the total detergent urges an additional limitation on the amounts of saturated C₁₆₋₁₈ soap and other detergent. For example, if 12% saturated C₁₆₋₁₈ soap was present in the middle range set, at least 18% of other detergent is necessary to achieve the minimum of 30% total detergent.

Soap bars according to this invention may contain various other materials, particularly if the amount of the same is limited so as not to exceed 10% or even 5%. In particular, a soap composition may contain small amounts of conventional additives, e.g. electrolytes, perfume, preservatives, colorants and pearlizing agents.

Bars according to this invention may contain any free fatty acid. However, this provides little benefit and may not be adequately soluble. It is therefore preferred that the amount of free fatty acid in a bar is less than 10%.

A soap composition according to this invention may well be transparent or at least translucent. However, if this property is not required, then the soap composition may contain a particulate filler which is insoluble in both water and the alcohols mentioned. It is possible to add moderate amounts of such a filler without it having any significant effect on the behavior of the rest of the composition, to form a melt with the filler dispersed therein and then solidify it, nor with the filler dispersed therein. Accordingly, the composition percentages given above are based on the weight of the composition excluding any solid dispersed non-soap macroparticles. Possible fillers include kaolin, silica and starch. The amount of any macroparticle filler included will usually not exceed 20% by weight of the total composition. Particle sizes are desirably in the range of 1.0 to 20 microns. As mentioned above, any non-soap detergents will render a bar opaque.

As also briefly mentioned above, a second object of the present invention is a process for the manufacture of soap bars comprising forming a melt of the composition and pouring the melt into solid bars, e.g. by pouring the melt into molds and allowing the melt to solidify.

In order to achieve an isotropic, homogeneous and transparent melt, the composition is preferably heated to a temperature of between 70º and 90ºC, more preferably between 80º and 85ºC, and maintained below the boiling point of the solution at such an elevated temperature until all solids present have dissolved, which typically occurs between 30 and 60 minutes, e.g. 45 minutes. Suitably, cooling may be at a rate determined by the ambient temperature. However, accelerated cooling may be used if desired.

Suitably the ingredients are added in the form in which they will be present in the final product. However, if a particular composition contains a trialkanolamine soap, then the starting materials to be added are preferably the equivalent fatty acids and their stoichiometric equivalent of trialkanolamine, which will preferably be present as a proportion of the total trialkanolamine required by the composition with the relationship to the solvent system. Sodium soaps can either be added ready for use or prepared in situ from fatty acids and sodium hydroxide.

Conveniently, any perfume and thermally degradable fatty acids may be added after any heating stage and immediately before pouring the melt into molds.

Once the composition has at least partially settled, it can be removed from the molds and any be subjected to the necessary post-processing, including, if necessary, cutting and/or pressing to the desired final shape, followed by packaging.

Preferably, however, the melt is poured into individual molds which additionally serve as a means of packaging the resulting soap bars. Removal of the bars from the mold will occur when the consumer opens the package immediately prior to use. Such an arrangement has the advantage that no removal of the mold or a separate packaging step is necessarily required during manufacture. Suitably, the mold may be completely filled with the melt and sealed hermetically. The resulting bar may thus have a pleasing shape and surface appearance determined by the shape and internal surface of the mold. By providing an hermetically sealed closure, any tendency for any volatile components of the bar to escape during storage is additionally prevented.

Examples of articles which can act both as a mold and as a package are rigid or semi-rigid plastic cans such as those described, for example, in US Patent 3,149,188 and FR Patent 910,256. Alternatively and preferably, the melt is poured into packages according to the invention described in published European Patent Application EP-A-321 179. In this application the use of a flexible film as the material from which the package is made is described. The melted soap composition is poured directly into the package which is then hermetically sealed. The flexible film is preferably molded or thermoplastic so that the heat present in the melt causes the film package to adjust to a wrinkle-free fit around the composition which, if desired, can be easily molded during the settling period. The film is preferably transparent so that the resulting product reveals the soap bar.

Embodiments of the present invention will now be described by the following examples.

EXAMPLE 1

Bars were prepared with the following two formulations in which the percentages are by weight of the final composition. The bars were prepared by the method indicated above, which involved heating the ingredients to a temperature of 70º to 90ºC until everything was melted, adding perfume after the other ingredients had melted and then pouring the melt into molds. Ingredients (comparison) % by weight Sodium coco-isethionate (75%) Hydrogenated tallow soap Propane-1,2-diol Technical denatured alcohol Perfume Water Isopropyl myristate

Hardened tallow soap contains almost completely insoluble soap with a small percentage of soluble short-chain soap. Technically denatured alcohol is 90% ethanol, 10% methanol.

All formulations produced an isotropic transparent melt but opaque bars.

The mildness of the bars of Examples 1A and 1B on human skin was determined by a flex-wash procedure performed on a panel of volunteers. One such test is described in J. Society of Cosmetic Chemists, 40, P297-306, September/October 1989, by D.D. Strube, S.W. Koontz, R.I.

Murahata and R.F. Thieler. In summary, this test, which differs from the test described, consists in washing the inside of the elbow (bend area) for 2 minutes 3 times per day (for 1 week). Each "bend area" was checked for erythema 4 times per day and scored from 0 (none) to 3 (very severe). When a score reached a value of two, the subject stopped washing the bend area. Scores are based on the average cumulative erythema over 5 days. (Discontinued sites were assigned scores of 2 for each subsequent scoring period, after interruption, until the end of the trial period).

Cumulative erythema scores were:

Example 1B...20

Example 1A (Comparison)...27

This difference exceeds the value (of 5) which was the required number for statistical significance at a 95% confidence level.

The bars were also used to wash the volunteers' skin, after which the effect of moisture content was determined by a test instrument. This used a probe with two concentric metal disks, 1.5 mm apart, placed on the skin at the test area. The instrument measures conductivity at an applied voltage at high frequency (3.5 MHz). Higher values indicate more moisture on the skin. Measurements were taken before washing and after (20 min) and performance calculated based on the percentage difference between readings. Normally, washing with soap will result in a significant reduction in conductivity once the skin has been equilibrated (e.g. 20 minutes after washing).

The results, i.e. the percentage decrease in conductivity, were:

Example 1A (comparison)...59%

Example 1B...72%

Example 1C...64%

EXAMPLE 2

Soap bars were prepared with the following two formulations using the same general procedure as in Example 1. Ingredients (comparison) % by weight Sodium coconut soap Sodium tallow soap Palmitic/stearic acid mixture Glycerin Ethanol Triethanolamine Perfume Water Isopropyl palmitate

The fatty acids were neutralized by the triethanolamine to form triethanolammonium soap. The amount of saturated C16-18 soap in the bars was approximately 20% by weight. The amount of free triethanolamine in the formulation would therefore be reduced by about 3 to 5% from the amount originally incorporated.

Bars with both formulations were translucent.

The mildness of the bars was determined in a similar manner as in Example 1, but using the forearm of the subjects instead of using the bending area.

The skin was evaluated by an evaluator who assessed both dryness and erythema (the latter as in Example 1) and determined by the subject against a standard scale for overall skin condition. The cumulative results were: Specific dryness Rating Erythema Perceived by the subject Condition of the entire skin Example 2A (Comparison) Difference of importance

The bars of Example 28 were also evaluated by panelists in a sensory evaluation comparing them to conventional 80/20 tallow/coconut toilet soap and to the melt cast bars of Example 5A below which did not contain oil but contained coco isethionate, which is considered a mild detergent.

The test involved 20 panelists using each product in turn to wash their face once a day and evaluating product performance against a range of attributes. Average ratings for each property Property 80/20 Soap Example a) Properties in use Greasy lather Product feels greasy when used b) Skin feel 10 min after use Face feels tight Moisturized Irritated

Therefore, the soap bar containing the oil does not feel greasy when used, but reduces the negative feeling of hardness after use.

EXAMPLE 3

Soap bars of the following two formulations were prepared using the same general procedure as above. Ingredients (comparison) % by weight Sodium tallow/coconut soaps 80/20 Sodium coconut soap Palmitic/stearic acid Ethanol Triethanolamine Isopropyl palmitate Glycerin Water

The amount of saturated C16-18 soap in these bars was approximately 20%. The amount of free triethanolamine in the formulation was thus reduced by approximately 3 to 5% from the amount originally incorporated.

The bars were used to wash the skin of volunteers and the effect on moisture content was determined by a test instrument as in Example 1.

The percentage decreases in conductivity were:

Example 3A (Comparison) 66

Example 3B...85

These bars and the 80/20 tallow/coconut soap bars were tested for soap bar properties by the following procedure:

The test bars were weighed, then washed 8 times a day for 4 days. This involves a panelist turning the bar 18 times with (plastic) gloved hands, and immersing it in water at 30ºC before and after turning. The bars are stored on drained soap dishes between washes. They are left overnight before being evaluated. The softness of the bottom of the bar, referred to as "mush", is determined on a scale ranging from no softness, rated as 0, to completely softened, rated as 10. The bars are left for two days and then weighed, from which the percentage weight loss is determined (expressed as "% wear rate").

The bars were also examined using a procedure in which samples were left partially immersed in water under standardized conditions, the soft material was then scraped off the sample surface and the percentage weight loss was determined.

The results were: 80/20 Soap Subjective Slurry Percent Durability Rate Immersion Weight Loss (g)

These results show that the soap bars produced by the melt/pour route produce more slurry, but that the inclusion of isopropyl palmitate makes very little difference to these properties studied in use.

EXAMPLE 4

Soap bars were prepared using the same general procedure with the formulations given below.

All the compositions produced isotropic transparent melts and the soap bars were translucent.

The decrease in conductivity was determined as in Example 1 and the results are given below. Component Weight Percent Sodium Tallow/Coconut Soap 82/18 Sucrose Ethanol Propane-1,2-diol Perfume Water Isopropyl Myristate Mineral Oil Percent Decrease in Conductivity

(40% of 82/18 tallow/coconut soap yields approximately 16% C₁₆₋₁₈ saturated soap).

EXAMPLE 5

Soap bars were prepared using the same general procedure with the formulations given below.

All the compositions produced isotropic transparent melts; the soap bars were opaque.

The decrease in conductivity was determined as in Example 1 and the results are given below. Ingredients (comparison) % by weight Sodium Coco-Isethionate (75 %) Hydrogenated Tallow Soap Sorbitol Technical Denatured Alcohol Water Isopropyl Myristate Percent decrease in conductivity

Claims (10)

1. Soap composition containing: 25 to 60% anionic, nonionic, zwitterionic or amphoteric active detergent containing soap of saturated C₁₆₋₂₂-monocarboxylic acids in an amount of 8 to 32%, 10 to 50% of one or more alcohols, including one or more solvent alcohols selected from ethanol, propanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, ethanolamines and propanolamines, the amount of solvent alcohol being 5 to 30%, not more than 30% water, and 1 to 20% of an oily skin benefit agent, the percentages given above being based on the weight of the composition, excluding any dispersed non-detergent macroparticles. 2. A composition according to claim 1, containing soap of C₁₀₋₁₄monocarboxylic acids and/or of unsaturated C₁₆₋₂₂monocarboxylic acids in an amount ranging from 4% to 30%, based on the weight of the composition, excluding any dispersed non-detergent macroparticles. 3. A composition according to claim 1 or claim 2, containing non-soap detergent in an amount of from 1% to 30%, by weight of the composition, excluding any dispersed non-detergent macroparticles. 4. A composition according to any one of claims 1 to 3, wherein said solvent alcohol is selected from the group consisting of ethanol, isopropanol, 1,2-propanediol, triethanolamine and triisopropanolamine. 5. A composition according to any one of claims 1 to 4, wherein said oily skin benefit agent is a hydrocarbon, a triglyceride or other ester of a C8-22 monocarboxylic acid and/or a C8-22 monohydric alcohol. 6. Composition according to one of claims 1 to 5, wherein the composition contains: (i) 8 to 12% soap of saturated C₁₆₋₁₈-monocarboxylic acids, (ii) 5 to 20% of other anionic detergent, (iii) 5 to 15% ethanol or isopropanol, (iv) 15 to 30% polyalcohol, (v) 20 to 30 % water, wherein the total amount of (i) and (ii) is from 17 to 32% and the above percentages are based on the weight of the composition excluding any dispersed non-detergent macroparticles. 7. Composition according to one of claims 1 to 5, wherein the composition contains: (i) 12 to 25% soap of saturated C₁₆₋₁₈ monocarboxylic acids, (ii) 10 to 30% of other anionic detergent, (iii) 7 to 20% ethanol or isopropanol, (iv) 10 to 30% polyalcohol, (v) 10 to 20 % water, wherein the total amount of (i) and (ii) is from 30 to 50% and the above percentages are based on the weight of the composition excluding any dispersed non-detergent macroparticles. 8. Composition according to one of claims 1 to 5, wherein the composition contains: (i) 20 to 32% soap of saturated C₁₆₋₁₈-monocarboxylic acids, (ii) 20 to 30% of other anionic detergent, (iii) 5 to 15% ethanol or isopropanol, (iv) 6 to 15% triethanolamine, (v) 5 to 20% polyalcohol, (vi) 2 to 15 % water, wherein the total amount of (i) and (ii) is from 45 to 60% and the above percentages are based on the weight of the composition excluding any dispersed non-detergent macroparticles. 9. A molded bar of a composition according to any one of the preceding claims. 10. Process for producing a soap bar containing forming an isotropic melt of a composition according to any one of claims 1 to 8 and pouring the molten composition into solid bars.