GB2316088A - Lotion Bar - Google Patents

Abstract

A lotion bar comprises from 5 to 40% by weight of surfactant material, from 10 to 80% by weight of water-insoluble material and from 5 to 45% by weight of a blend of at least two polyethylene glycol (PEG) materials in a ratio in the range from 1:10 to 10:1, a first of said PEG materials having a molecular weight in the range from 500-3000 and a second of said PEG materials having a molecular weight in the range from 3000 to 20,000.

Description

LOTION BAR The present invention relates to a lotion bar; i.e. a bar which produces a lotion when subjected to pressure and friction, for example by rubbing, in the presence of water.

Traditional cleansing can be broadly divided between the use of liquid products such as shower gels, liquid soaps and facial washes, and the use of solid products, for example soap and syndet bars. Although bars have traditionally been the main cleansing product used by the consumer, a trend is now very apparent in many of the more developed countries towards the use of liquid products. Much of this is down to the convenience aspect, for example of shower gels, and also to the perceived image of soap bars, soap having a reputation for drying the skin.

This trend is particularly highlighted by the growth of facial cleansing products as replacements for soap for facial washing. Although bars based on synthetic detergents, such as sodium cocoylisethionate, instead of soap have been developed and are proven to be milder than soap, the perception of these products is that they are still soap (albeit milder) and thus they have not stopped this trend for facial washing.

The alternative to this is the development of lotion bars wnich produce a lotion of composition similar to commercial cleansing lotions. Such products do exist and are best exemplified by Patent Application No. WO 89/08444. Although these bars are obviously formulated to give gentler cleansing, the key performance criteria must still remain that the skin is cleansed. With their usage being in a large part for the face, the removal of make-up is obviously a key factor. The problem with this technology is that cleansing is compromised as compared to standard toilet bars.

WO 89/08444 cites the use of dextrin materials along with glucose polymers for improving processability. Dextrin, however, is not particularly effective as a processing aid.

Furthermore, both of these materials are supplied as a powder which requires mixing with water separately before adding to the rest of the product.

WO 94/21778 relates to a syndet bar and as such produces a foam lather on washing as opposed to a lotion bar which produces a lotion when in use. Syndet bars do not produce a lotion. WO 94/21778 is concerned with improving processing solely at the molten stage of the process. A single polyethylene glycol (PEG) is generally used in the bar for improving processing at the molten stage with the PEG material used as a structurant to obtain a solid/rigid bar.

The present invention seeks to provide a lotion bar which can be processed using standard finishing lines, and which will rapidly produce a creamy lotion when rotated in the hands in the presence of water.

According to the present invention there is provided a lotion bar comprising from 1 to 50% by weight of the total composition of surfactant material, from 10 to 80% by weight of the total composition of water-insoluble material and from 5 to 45% by weight of the total composition of a blend of at least two polyethylene glycol materials (hereafter called "PEG" materials) in a ratio in the range from 1:10 to 10:1, the said PEG materials having different molecular weights, a first of said PEG materials having a molecular weight in the range from 500-3000 and a second of said PEG materials having a molecular weight in the range from 3000 to 20,000 in a ratio of 1:10 to 10:1, and wherein the bar does not comprise quaternised dihydroimidazole detergent.

The use of the said PEG blend provides increased rate of wear and superior lotion characteristics in the final bar.

The lotion of the bars of these inventions can be easily produced in-use and is of a cream-like consistency.

Preferably only two PEG materials are included in the blend.

The PEG blend further acts as a processing aid in the finishing stage of the process for making the lotion bars of the invention. It is noted that the PEG materials are water soluble and thus do not present the same processing problems as solid materials. In fact the selected blend of PEG optimises the balance between providing good processing of the lotion bar on standard soap finishing lines with optimum bar properties such as bar aesthetics, in-use skin feel, dry skin feel and in particular good lotion quality.

Preferably the PEG blend comprises PEG material of MW 1000-2000 in combination with PEG material of MW 4000 - 8000 in a ratio of 1:5 - 5:1. Most preferably, the PEG blend comprises PEG material of MW 1000 - 2000 in combination with PEG material of MW 4000 - 6000 in a ratio of 1:1 - 1:3.

The lower MW weight PEG is used primarily for increasing the rate of production of lotion when the bar is in contact with water, and for building the lotion viscosity. The higher MW weight PEG material is used primarily for binding the product together during process, and for increasing bar hardness.

The lower MW weight PEG also helps bind the product together, but if used alone the product could not be produced using a standard finishing line (due to the 'creaming effect'). Likewise the higher MW PEG also helps build the lotion structure in-use but if used alone the bar would be difficult to work with and a thinner lotion would be the result. Using a single PEG material of MW balanced between the higher and lower Mws mentioned above is unsatisfactory as the PEG materials mentioned above have the particular benefits - a compromised MW would likewise compromise bar properties (more difficult to process, poorer lotion characteristics).

Although each of the two classes PEG materials bring their own benefits to the formulation, it appears from the structural investigations that these two classes are also interacting in such a way as to give the structure observed which in turn is an integral part of the process characteristics, and thus an important part of the invention.

The preferred surfactant material includes at least one soap, alone or in combination with other surfactants such as anionic, amphoteric and/or nonionic surfactants. Preferred surfactants include any of the following either alone or in combination: Soap - alkali metal, alkaline earth metal or triethanolamine salts of monocarboxylic acids; such mono carboxylic acids preferably containing a carbon backbone of 12 to 18 carbons. The amount of soap incorporated is 1-50%, preferably 5-35%, most preferably 10 - 30%.

Other anionic surfactants which may be used include C8-18 sulphates, isethionates, sulphonates, alkylbenzene sulphonates, ether carboxylates, sarcosinates, taurates, sulphosuccinsates, phosphate esters, and sulphofatty acid esters. Although the carbon chain on all of these is essentially C8-18, any of the above may also be further substituted with other chemical groups e.g. ether and amide groups.

Preferred nonionic surfactants are selected from alcohol ethoxylates, alkyl polyglucosides and fatty acid esters.

In a preferred embodiment of the invention, the composition does not include a fatty acid dialkanolamide.

Preferred amphoteric surfactants are selected from betaine and glycinate type materials.

The water insoluble material preferably comprises C12/20 fatty alcohol and/or C12/20 fatty acid and/or their derivatives. The bar preferably comprises from 10 to 80% by weight, more preferably from 20 to 70% by weight and most preferably from 30 to 70% by weight of the water insoluble material.

The lotion bar described imparts excellent mildness to the skin, in comparison to traditional soaps and soap/synthetic detergent mixtures.

The bar of the invention technically cannot be transparent or translucent. It is noted that the compositions of the invention do not contain quaternised dihydromidazoles which have previously been used in such prior art transparent or translucent bars.

The lotion bar of the invention may additionally include any of the following minor ingredients: a) from 0% to 5 % by weight of titanium dioxide, optical brightener or other materials known to improve the appearance of cleansing bars; b) from 0% to 20% by weight of additives known within the art to be effective for helping processing. Of particular note are silicone materials (dimethicones and dimethiconols) which help reduce the tackiness of the base and thus assist in throughput during plodding. These materials also assist in die release during stamping; c) from 0% to 10% by weight of emollient materials used to change the skin feel in some way. These may include silicones, benzoate esters, talc, mineral oils, polymeric materials (charged or uncharged) and various waxes. It should be noted, however, that the skin feel from the lotion bars of the invention is excellent and thus in most instances, addition of these materials is unnecessary; d) from 0% to 10% by weight of active materials used to impart some specific benefit to the skin (e.g.

vitamins, natural extracts) may be added. The nature of the lotion bars of the invention is such that they are very effective at depositing material onto the skin; e) from 0% to 5% by weight of inorganic salts were found to be of use for further improving processability, bar hardness and reducing mush.

Blends of these materials were found to be particularly effective, for example, an addition of a blend of magnesium sulphate and sodium chloride; f) preservative materials, such as trisodium ethylenediamine-tetraacetate (EDTA); g) from 0% to 20% of water; h) from 0% to 30% of filler materials, such as talc and starch; i) antimicrobial materials, such as triclocarban; and/or j) perfume.

A number of methods are available for the manufacture of the lotion bars of the present invention, the most desirable of which use standard soap finishing lines. The preferred method may be summarised as follows: The water-insoluble material (if solid) and PEG are melted. The surfactant material is then added to this molten mix. This mix is then cooled and milled to produce the base. Other materials may be added at the molten stage or to this milled base for example perfume and/or titanium dioxide.

At this stage the base may also be passed through a plodder to be extruded as noodle. The base is then finished on a standard soap-type finishing line; that is it is compressed in a plodder, extruded as a billet, and is cut and stamped into bars.

In order to process those formulations where the "creaming effect" is more pronounced, lower plodding temperatures are required; i.e. temperatures in the range from 5"C to 35"C. However, this is not necessary with the optimised blends of PEG.

One aspect of this invention is that it is milder to skin than conventional soap or soap/synthetic detergent mixtures, which are traditionally milder than conventional soap bars.

A bar of the present invention was tested using the Frosch and Kligman soap chamber test (reference Frosch, PJ and Kligman, AM, Journal of the American Academy of Dermatology, 1, 35-41). In the same test a conventional soap bar and a soap/synthetic detergent bar (Soap and Sodium Cocoyl Isethionate surfactant blend) were placed. The sum of overall scores for Erythema, scaling and fissuring score over the duration of the test are presented in the table below. It is evident that the bar of this invention is significantly milder than both soap and soap/synthetic detergent type bars.

Sample Lotion Bar Soap Soap/Synthetic detergent Total Sum of Scores (Erythema, Scaling and Fissuring) 4 121 56 Considerable investigations were carried out to determine the structural changes which were taking place in the formulation during and after process. The following points summarise these studies: 1) Differential Scanning Calorimetry (DSC) was used to investigate structural changes taking place when temperature is increased (compared to standard soap and syndet bars). These studies highlighted a number of "melts" (structural rearrangements) which occur, indicating a structure which is considerably more complex than that of soap.

2) Observation of the behaviour of the product backed up these studies. The product became considerably softer with increasing mechanical stress and/or temperature. This effect was seen to be exaggerated when lower molecular weight PEG materials were used.

This "creaming" effect resulted in the product being difficult to plod. In the optimised formulations, this effect was small and did not cause problems in processing the bars.

3) All of the formulations were shown to be considerably harder after 24 hours than when first plodded - indicating structural rearrangement to a more stable conformation and XRD traces on fresh and aged bars confirms this an increase in crystallinity was observed as the bars cooled and aged.

4) Xray diffraction studies carried out indicated a number of crystalline phases are present in these bars. These studies confirmed the structure to be unique from other bars. As such, it is concluded that the structure of the plodded bars is integral in optimising the technology and is thus contained within the uniqueness of this invention.

In particular, more phases were shown to be present using XRD (differentiated by line spacings) and these phases were seen to more distinct (greater intensity in the rings).

In order that the present invention may be more readily understood specific embodiments thereof will now be described by way of example only with reference to Table 1 attached hereto.

Referring to Table 1.

1) by comparing formulation A with formulation B the effect of changing the molecular weight of the constituent PEG material of the bar on bar properties is illustrated.

2) Formulation C was found to have considerably worse skin feel due to the replacement of stearic acid with palmitic acid. The skin feel was shown to be unique to those formulations where total replacement of the stearic acid with palmitic acid had occurred.

Blends of stearic acid and palmitic acid were seen to work best.

Incorporation of the PEG 6000, i.e. PEG of molecular weight 6000, was shown to help with processing of the bars.

3) Formulation D showed that the level of starch could be reduced and the ease-of-use improved by incorporation of some PEG 1000. A blend of PEG materials (including PEG 6000) was necessary to retain processability.

4) A blend of fatty acid was found to be better than stearic acid or palmitic acid alone (formulation E), particularly in terms of lotion quality.

5) Formulation F is based on an optimised blend of fatty acids. By incorporating PEG 2000 and 3000, the PEG 1000 could be removed from the formulation without any compromise in bar characteristics. Thus the process was significantly improved.

6) Formulation G represents an optimised formulation and demonstrates the need for a blend of PEG materials. The PEG 2000 is primarily used for improving ease-of-use and lotion quality. The PEG 6000 is used for optimum processability whilst also improving bar hardness.

7) The use of a high level of glucose polymer (formulation H) resulted in a product which could not be processed down a standard finishing line.

The product did not bind together. This clearly demonstrates the inferiority of glucose polymer in comparison to PEG as a binder for the lotion bar.

8) When a lower level was used (formulation I) the quantity of PEG 6000 remaining in the bar was sufficient to ensure the product could be processed - albeit with some difficulty (careful monitoring of plodding temperature was required). A further problem with this technology is that the properties of the resulting lotion itself (ease-of-use, lotion quality) was adversely affected by replacing the PEG 2000 with the glucose polymer. This demonstrates the importance of using the PEG 2000 material as well as the fact that there is no real benefit gained from the incorporation of the glucose polymer.

Thus the benefit of using the blend is exemplified in table 1 herein. Only those formulations incorporating a blend of PEG material resulted in bars which could be processed down a standard finishing line and which had good performance properties, such as ease-of-use and lotion quality.

It is to be understood that the examples of the invention which are shown in Table 1 are by way of illustration only.

Many modifications and variations are possible.

TABLE 1

A B C D E F G H I SOAP 21.5 21.5 18.5 18.5 18.5 17.5 17.5 17.5 17.5 STARCH 0 0 17 8 8 7 7 7 7 CETYL ALCOHOL 21.5 21.5 17 17 17 18 18 18 18 STEARIC ACID 19.5 19.5 0 0 8.5 10.5 10.5 10.5 10.5 PALMITIC ACID 0 0 17 17 8.5 6.5 6.5 6.5 6.5 PEG 1000 25 0 0 5 5 0 0 0 0 PEG 2000 0 0 0 0 0 5 10 10 0 PEG 3000 0 0 0 0 0 5 0 0 0 PEG 4000 0 25 19 19 19 14 0 0 0 PEG 6000 0 0 6 10 10 10 24 0 24 MALTRIN M150* 0 0 0 0 0 0 0 24 10 PROCESSABILITY 0 2 3 3 3 4 5 0 3.5 EASE-OF-USE 5 2 2 3 3 4 5 N/A 5 LOTION QUALITY 4 2 2 2 4 5 5 N/A 3.5 SKIN FEEL 4 4 2 2 4 5 5 N/A 5 * - glucose polymer In all the above scales, the higher the number, the better the formulation is against that parameter.

Further experimental results exemplifying the superior properties of the products of the invention are set out below.

These results give an indication of the differences and improvements arising through using a blend of PEG material.

Structural investigations have also been included.

The formulations tested are those detailed in Table 2 hereinafter.

Processing The soap processing consists of the following stages.

Each formulation was made up using identical manufacturing methods, as set out below, and observations were recorded at each stage. The formulation containing PEG blends was by far the easiest to process.

Manufacturing Method Mixing: Simple mixing of all ingredients using a heated vessel and mixer with a Z-blade configuration.

Milling: Passing the mixed ingredients through a chilled 3 roll mill and produce ribbons of lotion bar formulation.

Plodding: Compresses the ribbons into a "billet" of lotion bar which can then be moulded into the required bar shape.

i) No PEG [D] No problems were encountered mixing or milling the product. However the product could not be plodded at any temperature. No bars could be produced.

ii) Lower PEG 2000 [B] Mixing was not a problem. Milling of the base caused some problems when the formulation began to cream. On plodding the base was observed to be sticky and stuck to the sides of the hopper. When the billet is first formed feathering occurred (the outside of the billet broke away from the main bulk). This continued much longer than for soap and could not be prevented by adjusting the cone temperature or recycling. A few bars were produced from the split billets.

iii) Higher PEG 6000 [C] Mixing and milling was not a problem. Some stickiness observed and no billets were produced due to separation of the outer layers from the core of the billet similar to the observations with the lower PEG 2000. A few bars were produced from the split billets.

iv) PEG blends (2000 and 6000) [A] No problems were encountered and 30 finished bars were easily produced.

TABLE 2

STANDARD [A] LOWER PEG [B] HIGHER PEG [C] NO PEG * [D] % % % % SOAP BASE 17.4 17.4 17.4 17.4 CETYL ALCOHOL 18 18 18 18 STEARIC ACID 10.5 10.5 10.5 10.5 PALMITIC ACID 6.5 6.5 6.5 6.5 PEG 6000 24 0 34 0 PEG 2000 10 34 0 0 STARCH 7 7 7 7 WATER 2.8 2.8 2.8 2.8 MgSO4 0.7 0.7 0.7 0.7 EDTA 0.1 0.1 0.1 0.1 T102 1 1 1 1 PERFUME 1 1 1 1 ABIL B8814 1 1 1 1 MALTODEXTRIN 0 0 0 34 (ALTERNATIVE BINDER) * Alternative binder needed to be in placed due to large gap in formulation without the PEG materials.

Evaluation of the bars of Table 2 The bars were evaluated using standard evaluation tests.

The blend of PEG [A] gave a better lotion quality than the single PEG formulations [B] and [C]. In addition the bar without the lower PEG 2000 [C] gave a lower rate of wear and hence a poorer lotion quality. The bar without the higher PEG 6000 [B] gave a softer bar.

Details of the bar evaluation are set out below.

Standard evaluation methods were used for, Rate Of Wear, Hardness and Mush Values and Lotion Quality.

For the Lotion Quality Test, the bars are washed in a random order and rated for the quality of lotion that they produced.

Results Rate of Mush (g/50cm2) Hardness Lotion Product Wear at 200C (mm) Quality Standard [A] 11.6% 10.2 1.7 4-5 Higher PEG [C] 9.3% 10.8 1.4 3 Lower PEG [B] 12.0% 10.5 2.2 3-4 Key to Lotion Ouality Results 1 - Water Thin - Very Thin lotion.

2 - Fairly Thin - Thin lotion but has a very slight viscosity.

3 - Moderate - Definite feel of thickness to the lotion.

4 - Fairly Thick - Noticeable viscosity, thick, quite creamy etc.

5 - Rich, Thick & Creamy - Very rich, thick and creamy lotion.

Structural Investigation of the Bars DSC DSC measures the heat change that occurs when a product undergoes a phase change and also the temperature at which this occurs. The bar with the PEG blend [A] undergoes a phase change at a different temperature to that of the individual materials [B], [C], indicating the possibility of formation of a different structure.

Sample Temperature of the main phase change observed deg C PEG 2000 + 6000 [A] 57 PEG 2000 [C] 45 PEG 6000 [B] 52 XRD analysis supports the view that the Lotion Bar is highly crystalline.

It is to be understood that the examples of the invention which are shown herein are by way of illustration only. Many modifications and variations are possible.

Claims (11)

1. A lotion bar comprising from 1 to 50% by weight of the total composition of surfactant material, from 10 to 80% by weight of the total composition of water-insoluble material and from 5 to 45% by weight of the total composition of a blend of at least two polyethylene glycol materials (hereafter called "PEG" materials) in a ratio in the range from 1:10 to 10:1, the said PEG materials having different molecular weights, a first of said PEG materials having a molecular weight in the range from 500-3000 and a second of said PEG materials having a molecular weight in the range from 3000 to 20,000, and wherein the bar does not comprise quaternised dihydroimidazole detergent.

2. A lotion bar as claimed in claim 1, wherein the lotion bar comprises only two PEG materials.

3. A lotion bar as claimed in claim 1 or claim 2, wherein the lotion bar comprises a PEG blend of a first PEG material having a molecular weight in the range from 10002000 in combination, in a ratio of 1:5 to 5:1, with a second PEG material having a molecular weight in the range from 4000-8000.

4. A lotion bar as claimed in any preceding claim, wherein the lotion bar comprises a PEG blend of a first PEG material having a molecular weight in the range from 1000 2000 in combination, in a ratio of 1:1 to 1:3, with a second PEG material having a molecular weight in the range from 4000-6000.

5. A lotion bar as claimed in any preceding claim, wherein the surfactant material includes at least one soap.

6. A lotion bar as claimed in claim 5, wherein the soap comprises any of the following either alone or in combination: alkali metal, alkaline earth metal or triethanolamine salts of monocarboxylic acid.

7. A lotion bar as claimed in any preceding claim, wherein the bar comprises from 1 to 50% by weight of the total composition of soap.

8. A lotion bar as claimed in any preceding claim, wherein the bar comprises either alone or in combination anionic, amphoteric or nonionic surfactant.

9. A lotion bar as claimed in any preceding claim, wherein the water insoluble material comprises C12/20 fatty alcohol and/or C12/20 fatty acid and/or derivatives of C12/20 fatty alcohol and/or C12/20 fatty acid.

10. A lotion bar as claimed in any preceding claim, wherein the bar comprises from 10 to 80% by weight of water insoluble material.

11. A lotion bar as claimed in any preceding claim, wherein the bar comprises from 20 to 70% by weight of water insoluble material.