The invention relates to low TFM personal washing bars that are made by high speed extrusion and stamping and are suitable for the mass market. The personal washing bars include a polysaccharide-polyol structuring system and fatty acids soaps which have a limited level of unsaturated soaps relative to their content of saturated soluble soaps.

Personal washing bars such as soap bars have played an important role in hygiene and their routine use has been critical in reducing the spread of communicable diseases. Manufacturers have continuously sought ways to improve the in-use sensory properties and skin compatibility of personal washing bars and to increase their affordability to consumers around the world.

Fatty acid soaps derived from triglycerides still remain the predominant surfactant used in the majority of personal wash bars. With the growing demands for triglycerides as foods and recently as alternative fuels, the costs of these materials are increasing. Consequently manufacturers have sought ways to use fatty acid soaps more efficiently in personal washing bars. When the predominant surfactant in the personal washing bar is fatty acid soap, a reduction in surfactant is commonly expressed as a reduction in "Total Fatty Matter" or TFM. The term TFM is used to denote the percentage by weight of fatty acid and triglyceride residues present in soaps without taking into account the accompanying cations. The measurement of TFM is well known in the art.

One strategy that has been used to reduce the soap content in bars is to replace part of the fatty acid soap by inorganic fillers and/or higher levels of water.

However, the use of high levels of inorganic fillers and/or high water levels leads to several negative properties which includes a significant shrinkage of the bar during storage by evaporation of water and to a smaller bar volume because of the higher density of inorganic fillers.

Another approach that has been used to lower the surfactant content of bars is the use of coagels formed in a melt-cast process. Here a molten surfactant solution is poured into a mold and cooled. The surfactant solution forms a highly extended three-dimensional network. Although melt-cast technology yields bars that have lower surfactant content, the process is less efficient than high-throughput extrusion. Furthermore, melt-cast bars have substantial levels of water and solvents, are subject to drying out and their rate of wear is much higher than milled toilet soaps. Consequently such bars are less economical in use than milled soaps.

Examples of approaches based on the above concepts include the following.

WO 01/42418 to Chokappa et al discloses a detergent bar containing 0.5 to 30% amorphous alumina, one alkali metal salt of carboxylic/sulfonic acid, 5-70% detergent active and 10-55% water.

WO 2006/094586 to Gangopadhayay et al discloses a low TFM detergent bar including soap (15 % to 30 % TFM); 25 % to 70 % inorganic particulates including talc and calcium carbonate; 0.5 % to 10 % of alumino-silicate; and 3 % to 20 % water.

US 6,440,908 to Racherla discloses high moisture containing bar compositions that includes a borate compound which enables the retention of high amounts of moisture without compromising bar properties.

WO 96/35772 to Wise et al discloses laundry bar compositions including from about 20 % to about 70 % surfactant; from about 12 % to about 24 % water; from about 6.25 % to about 20 % calculated excess alkali metal carbonate; from about 2 % to about 20 % water-soluble inorganic strong-electrolyte salt; and various optional ingredients including whole-cut starch.

WO98/18896 to Rahamann et al discloses laundry bar composition including structured soap composition; from about 5 % to about 50 % starch; and about 25 % to about 45 % moisture.

US 2007/0021314 and US 2007/0155639 to Salvador et al disclose cleansing bar compositions that include (a) at least about 15%, water; (b) from about 40% to about 84% soap; and (c) from about 1 % to about 15%, inorganic salt. The bar compositions further comprise a component selected from the group consisting of carbohydrate structurant, humectants, free fatty acid, synthetic surfactants, and mixtures thereof.

U.S. 6838420B2 to Sachdev et al discloses a translucent or transparent composition comprising a. about 3 to about 40 wt. % soap, b. about 4 to about 40 wt. % of at least one synthetic surfactant, c. about 14 to about 45 wt. % water, d. from 0 to about 3 wt. % lower monohydric alcohol, e. about 5 to about 60 wt. % of a humectant, f. from 0 to about 5 wt. % of a structurant, g. from 0 to about 10 wt. % of a gellant with the proviso that the structurant and gellant are not 0 at the same time.

US 4,808,322 to James McLaughlin discloses a non-foaming skin cleansing- conditioning bar consisting essentially of 14% to 18% of specific anionic surfactant materials; about 40% to 72% of specific water-insoluble emollients; 0% to 25% of a starch-derived filler; and 2% to 12% of water.

WO08055765 to Jagdish Gupta discloses soap prepared from fatty matter having 8 to 22, carbon atoms, 30 to 60%, total fatty matter (TFM). Of the total fatty matter it is preferred that 70 to 90% of the total fatty matter by weight is unsaturated. The soap bar has less than 30%, saturated fatty matter by weight of total fatty matter. Previous work described in Patent Application GB 806340.6 identified lower TFM extrudable soap bar compositions that included starch, specific polyols and optionally water insoluble particles that did not require high levels of water and inorganic fillers. However, this technology was limited to compositions having a total level of fatty acid soap no lower than 45%. It was found that when the fatty acid soap level fell below about 45%, especially below 40%, the processing and in-use properties became progressively more sensitive to small changes in composition. This sensitivity increased as the total fatty acid soap level was reduced towards 20% soap made large scale production problematic.

Further extensive experimentation has revealed that the increased sensitivity of physical properties of compositions structured with polysaccharides such as starch and cellulose, polyols and optionally water insoluble particulate material at a soap level below 45% is surprisingly related to the types and relative proportions of the more water soluble and lower melting soap components which are present in the soap mixture.

It was surprisingly found that the ratio of unsaturated soluble soaps such as oleate soap to the more water soluble and lower melting saturated soaps such as laurate soap and myristate soap was a key parameter in controlling the relative levels of starch and polyol required to achieve extrudable compositions with acceptable bar properties. Furthermore, the optimal value of this ratio and its relationship to the optimal composition of the structuring system were found to depend upon the total fatty acid soap level in the composition and to some extent on the detailed composition of the structuring system which added additional levels of complexity to the composition. This understanding has now allowed the definition of a composition space for soap bars having much lower soap content, e.g., 20-40% soap, which have highly acceptable in-use properties and can be manufactured by high speed extrusion. This technology is the subject of the present invention. The personal washing bars of the invention are extruded and preferably stamped bars suitable for mass market applications. One embodiment of the invention is a personal washing bar that has a continuous phase that includes:

a) 20% to less than 45% fatty acid soap, preferably 20% to less than

40% fatty acid soap, in which the fatty acid soap comprises at least 30% saturated fatty acid soaps based on the total weight of the soap and wherein the fatty acid soap has a ratio R _OL , defined as the total weight of oleics fatty acids soaps divided by the total weight of the laurics fatty acid soaps which satisfies the inequality given in Eq (1 );

ROL ≤ ( -0.00063(TS ² )+0.297(TS)-1 .95) ± (15%) (1 )

where TS is the weight % of the total fatty acid soap in the continuous phase;

b) a structuring system comprising: i) from 10% to 40% by weight of continuous phase of a polysaccharide structurant selected from the group consisting of starch, cellulose and a combination thereof, ii) from 8.0% to 30% by weight of continuous phase of a polyol selected from the group consisting of glycerol, sorbitol and their mixtures, and iii) 0 to 15% by weight of continuous phase of water insoluble particulate material; and

wherein the weight of polysaccharide structurant divided by the weight of polyol, designated Rsp, is in the range from 0.3 to 5.0, preferably 0.5 to 4.5, and wherein the continuous phase composition is an extrudable mass having a penetrometer hardness of 3 to 8 Kg and a yield stress of 350 to 2000 kPa measured at a temperature of 40° C. In one embodiment, the polysaccharide structurant is starch and the weight ratio of starch and polyol structuring components lies within a range which depends upon the weight % of the total fatty acid soap present in the continuous phase. Specifically, the weight of starch component divided by the weight of polyol component, designated Rsp, satisfies the inequality expressed by Eq (2)

(0.0053(TS ² ) - 0.44(TS) + 9.55) ± 15% < Rsp < (5.98 - 0.087(TS)) ± 15% (2)

In another embodiment, the optional insoluble particulate material is present at a level of about 3 to 15%, preferably 5% to 10%. In this embodiment the insoluble material is preferably an inorganic particulate material.

In another embodiment, the bar composition includes a synthetic surfactant at a level of up to about 10% by weight of the bar, preferably between 2% and 8% by weight.

In yet another embodiment, the continuous phase includes a slip modifier which greatly improves the feel of the wet bar when it is rubbed on the skin especially when the polysaccharide and/or insoluble particles are present in the bar at levels approaching the upper limits of their useful concentration ranges.

In still another embodiment, the continuous phase has a nominal water content of no more than 20% by weight, preferably between 14% and about 18% by weight when the bar is initially manufactured, i.e., immediately after it is extruded and stamped.

In still another embodiment the continuous phase of the bar comprises 25% to 35% soap by weight, the polysaccharide is starch and Rsp is in the range from 0.5 to 3.7. These and other embodiments are described more fully below in the following written description and various embodiments that are illustrated in the examples.

As used herein % or wt % refers to percent by weight of an ingredient as compared to the total weight of the composition or component that is being discussed (generally the composition of the continuous phase or the composition of the fatty acid soap).

Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about." All amounts are by weight of the final composition, unless otherwise specified. Unless otherwise specified the term composition will refer to the composition of the continuous phase of the bar.

For the avoidance of doubt the word "comprising" is intended to mean "including" but not necessarily "consisting of or "composed of." In other words, the listed steps, options, or alternatives need not be exhaustive.

The present invention relates to extruded personal washing bars in which the continuous phase of the bar comprises specific levels of fatty acid soaps, hereinafter designated simply as "soap"; from about 30% to about 60% of a structuring system; and various optional ingredients. The compositions used to prepare the continuous phase of bars of the invention and the methods used to manufacture and evaluate the compositions and bars made from the compositions are described below.

The term "continuous phase of the bar" is used in a macroscopic sense to describe the predominant soft solid phase into which various macroscopic solid domains, the "dispersed phase" may be optionally dispersed or distributed. The continuous phase is generally not a single phase in the microscopic sense but rather is a substantially uniform mixture (i.e., dispersion) of microscopic soap crystals and liquid crystalline or gel and liquid materials, components of the structuring system (e.g., starch, polyol, insoluble particulate material), and various optional ingredients. The continuous phase generally comprises from 65% to 100% by weight of the personal washing bar. In the majority of applications, the continuous phase comprises 90% to 100% of the personal washing bar.

The optional dispersed phase can be in the form of stripes or variegations, bits (e.g., pieces or chunks of solid), plate like inclusions, veins, the like and mixtures thereof. The dispersed phase generally has a different overall composition from the continuous phase but may only differ in the level or type of colorant.

The bar compositions of the invention are capable of being manufactured at high production rates by processes that generally involve the extrusion forming of ingots or billets, and stamping or molding of these billets into individual tablets, cakes, or bars.

By the term "capable of high manufacturing rates" is meant that the mass formed from the continuous phase composition and any dispersed phase is capable of being extruded at a rate in excess of 9 kg per minute, preferably at or exceeding 27 kg per minute and ideally at or exceeding 36 kg per minute.

Personal washing bars produced from compositions according to the invention in addition to being capable of being processed at high production rates also possess a range of desirable physical properties that make them highly suitable for every day use by mass market consumers.

Test method to assess various physical properties of the composition that provide objective criteria for bars manufacture and in-use properties are described below in the TEST METHODOLOGY section. Composition of the continuous phase

Fatty acid soap

The fatty acid soaps, optional surfactants and in fact all the components of the bar should be suitable for routine contact with human skin and preferably yield bars that are high lathering.

The preferred type of surfactant is fatty acid soap. The term "soap" is used herein to mean an alkali metal or alkanol ammonium salts of aliphatic, alkane-, or alkene monocarboxylic acids usually derived from natural triglycerides. Sodium, potassium, magnesium, mono-, di- and tri-ethanol ammonium cations, or combinations thereof, are the most suitable for purposes of this invention. In general, sodium soaps are used in the compositions of the invention, but from about 1 % to about 25 wt% of the soap may be potassium, magnesium or triethanolamine soaps. The soaps useful herein are the well known alkali metal salts of natural or synthetic aliphatic (alkanoic or alkenoic) acids having about 8 to about 22 carbon atoms, preferably about 10 to about 18 carbon atoms. They may be described as alkali metal carboxylates of saturated or unsaturated hydrocarbons having about 8 to about 22 carbon atoms.

Soaps having the fatty acid distribution of coconut oil and palm kernel oil may provide the lower end of the broad molecular weight range. Those soaps having the fatty acid distribution of peanut or rapeseed oil, or their hydrogenated derivatives, may provide the upper end of the broad molecular weight range.

It is preferred to use soaps having the fatty acid distribution of coconut oil or tallow, or mixtures thereof, since these are among the more readily available triglyceride fats. The proportion of fatty acids having at least 12 carbon atoms in coconut oil soap is about 85%. This proportion will be greater when mixtures of coconut oil and fats such as tallow, palm oil, or non-tropical nut oils or fats are used, wherein the principle chain lengths are Ciβ and higher. Preferred soap for use in the compositions of this invention has at least about 85% fatty acids having about 12 to 18 carbon atoms.

The preferred soaps for use in the present invention should include at least about 30% saturated soaps, i.e., soaps derived from saturated fatty acids, preferably at least about 40% saturated soaps by weight of the soap.

Soaps can be classified into three broad categories which differ in the chain length of the hydrocarbon chain, i.e., the chain length of the fatty acid, and whether the fatty acid is saturated or unsaturated. For purposes of the present invention these classifications are:

"Laurics" soaps encompass soaps which are derived predominantly from C12 to Ci ₄ saturated fatty acid, i.e. lauric and myristic acid, but can contain minor amounts of soaps derived from shorter chain fatty acids, e.g., Ci ₀ . Laurics soaps are generally derived in practice from the hydrolysis of nut oils such as coconut oil and palm kernel oil

"Stearics" soaps encompass soaps which are derived predominantly from C16 to C18 saturated fatty acid, i.e. palmitic and stearic acid, but can contain minor levels of saturated soaps derived from longer chain fatty acids, e.g., C2o- Stearics soaps are generally derived in practice from triglyceride oils such as tallow, palm oil and palm stearin.

Oleics" soaps encompass soaps which are derived from unsaturated fatty acids including predominantly oleic acid (Ci ₈ 1), linoeleic acid( (Ci ₈ 2), myristoleiic acid (Ci _{4 1} ) and palmitoleic acid (Ci _{6 1} ) as well as minor amounts of longer and shorter chain unsaturated and polyunsaturated fatty acids. Oleics soaps are generally derived in practice from the hydrolysis various triglceride oils and fats such as tallow, palm oil, sunflower seed oil and soybean oil. Coconut oil employed for the soap may be substituted in whole or in part by other "high-lauhcs" or "laurics rich" oils, that is, oils or fats wherein at least 45% of the total fatty acids are composed of lauric acid, myristic acid and mixtures thereof. These oils are generally exemplified by the tropical nut oils of the coconut oil class. For instance, they include: palm kernel oil, babassu oil, ouhcuri oil, tucum oil, cohune nut oil, murumuru oil, jaboty kernel oil, khakan kernel oil, dika nut oil, and ucuhuba butter.

When a solid mass which comprises a mixture of laurics, stearics and oleics soaps is heated, the laurics and oleics soaps which are more water soluble and have lower melting points than stearics soaps, combine with water and other components present in the composition to form a more or less fluid liquid crystal phase depending on water content and temperature. This transformation of laurics and oleics soaps from a solid to a liquid crystal phase provides plasticity to the mass which allows it to be mixed and worked under shear, i.e. the mass is thermoplastic.

It has been found critical when using a structuring system comprising a mixture of starch and/or cellulose, polyol and optional insoluble particulate material, to control the relative proportions of oleics and laurics soaps in the compositions of the present invention in order to achieve acceptable lower TFM bars, e.g., bars containing 20% to 40% soap. Specifically, it has been found that the ratio of Oleics soaps to Laurics soaps, designated R ₀ L, must be below a threshold value which depends on the total weight percent (%) of soap present in the continuous phase composition, designated TS. This threshold ratio can be expressed by the inequality set forth in Eq (1 ) which has been determined empirically.

RO _L ≤ (-0.00063(TS ² ) + 0.297(TS) -1.95) (± 15%) (1 ) Examples of these limits at several representative values of the weight % total soap (TS) are shown in the Table 1 below.

Table 1 Approximate Maximum Oliecs/Laurics Soap Ratios

A preferred soap is a mixture of about 10% to about 40% derived from coconut oil, palm kernel oil or other laurics rich oils and about 90% to about 60% tallow, palm oil, palm stearin or other stearics rich oils or a combination thereof provided the ratio of oleics and laurics soaps, R ₀ L, satisfies the above criteria.

Soaps may be made by the classic kettle boiling process or modern continuous soap manufacturing processes wherein natural fats and oils such as tallow, palm oil or coconut oil or their equivalents are saponified with an alkali metal hydroxide using procedures well known to those skilled in the art. Two broad processes are of particular commercial importance. The SAGE process where triglycerides are saponified with a base, e.g., sodium hydroxide, and the reaction products extensively treated and the glycerin component extracted and recovered. The second process is the SWING process, where the saponification product is directly used with less exhaustive treatment and the glycerin from the triglyceride is not separated but rather included in the finished soap noodles and/or bars.

Alternatively, the soaps may be made by neutralizing fatty acids (e.g., distilled fatty acids), such as lauric (Ci ₂ ), myristic (Ci ₄ ), palmitic (Ci ₆ ), stearic (Ci ₈ ) and oleic acid (Cis i) acids and their mixtures with an alkali metal hydroxide or carbonate. The level of fatty acid soap in the continuous phase of the bar (generally a mixture of different chainlengths and/or isomers) can range from 20% to less than 45%, preferably 20% to about 40% and more preferably about 25% to 35% based on the total weight of the continuous phase composition.

Surfactants other than soap (commonly known as "synthetic surfactants" or "syndets") can optionally be included in the bar at levels generally up to and including about 10%, preferably at levels between about 2% to about 7% by weight of the bar. Examples of suitable syndets are described below under OPTIONAL INGREDIENTS.

Structuring system

The structuring system includes one or more polysaccharide structurants selected from the group consisting of starch, cellulose and their mixtures; one or more polyols; and optionally, water insoluble particulate material.

The total level of the structuring system used in the composition should be greater than 30% by weight, preferably 30% to 70% and most preferably 35% to about 55% based on the total weight the continuous phase. By total level of the structuring system is meant the sum of the weights of the starch/cellulose, polyol, and optional insoluble particle material.

Suitable starch materials include natural starch (from corn, wheat, rice, potato, tapioca and the like), pregelatinzed starch, physically and chemically modified starch and mixtures thereof. By the term natural starch is meant starch which has not been subjected to chemical or physical modification - also known as raw or native starch.

A preferred starch is natural or native starch from maize (corn), cassava, wheat, potato, rice and other natural sources of it. Raw starch with different ratio of amylose and amylopectin include: maize (25% amylose); waxy maize (0%); high amylose maize (70%); potato (23%); rice (16%); sago (27%); cassava (18%); wheat (30%) and others. The raw starch can be used directly or modified during the process of making the bar composition such that the starch becomes either partially or fully gelatinized.

Another suitable starch is pre-gelatinized which is starch that has been gelatinized before it is added as an ingredient in the present bar compositions. Various forms are available that will gel at different temperatures, e.g., cold water dispersible starch. One suitable commercial pre-gelatinized starch is supplied by National Starch Co. (Brazil) under the trade name FARMAL CS 3400 but other commercially available materials having similar characteristics are suitable.

Suitable cellulose materials can come from various sources for example wood, cotton, and various grasses such as switch grass and sugar cane (Bagasse). The plant biomass can be processed by a range of physico-chemical techniques and purified as required. Particularly suitable cellulose have a particle size less than 100 microns, preferably less than 50 microns and preferably 45 microns or less.

Examples of suitable celluloses include microcrystalline cellulose, hydroxyalkyl alkylcellulose ether and mixture thereof.

A preferred cellulose material is microcrystalline cellulose which is generally made from alpha cellulose and is highly crystalline particulate cellulose made primarily of crystalline aggregates. This is typically done with a strong mineral acid (e.g., hydrogen chloride). Such an acid hydrolysis process produces microcrystalline cellulose of predominantly coarse particulate aggregates, typically of mean size range 10 to 40 microns. A suitable commercial microcrystalline cellulose is supplied by FMC Biopolymer (Brazil) under the trade name AVICEL GP 1030 but other commercially available materials having similar characteristics are suitable.

A preferred polysaccharide structurant is starch, most preferably a natural starch (raw starch), a pre-gelatinized starch, a chemically modified starch or mixtures thereof. The amount of the polysaccharide (e.g., starch and/or cellulose) component in the continuous phase can range from about 10% to about 40%, preferably 20% to 40% and more preferably 30% to 40% by weight of the composition.

A second critical component of the structuring system is a polyol or mixture of polyols. Polyol is a term used herein to designate a compound having multiple hydroxyl groups (at least two, preferably at least three) which is highly water soluble, preferably freely soluble, in water.

Many types of polyols are available including: relatively low molecular weight short chain polyhydroxy compounds such as glycerol and propylene glycol; sugars such as sorbitol, manitol, sucrose and glucose; modified carbohydrates such as hydrolyzed starch, dextrin and maltodexthn, and polymeric synthetic polyols such as polyalkylene glycols, for example polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG).

Preferred polyols are relatively low molecular weight compound which are either liquid or readily form stable highly concentrated aqueous solutions, e.g., greater that 50% and preferably 70% or greater by weight in water. These include low molecular weight polyols and sugars.

Especially preferred polyols are glycerol, sorbitol and their mixtures.

The level of polyol is critical in forming a thermoplastic mass whose material properties are suitable for both high speed manufacture (27 - 36 Kg/min) and for use as a personal washing bar. It has been found that when the polyol level is too low, the mass is not sufficiently plastic at the extrusion temperature, typically 4O ⁰ C to 45 ⁰ C. Conversely, when the polyol level is too high, the mass becomes too soft to be efficiently formed into bars by extrusion at normal process temperatures. The level of polyol should be between 8% and 30%, preferably 10 to 20% and preferably about 10% to about 15% by weight of composition.

The weight ratio of starch and/or cellulose to polyol in the continuous phase is critical to forming compositions that can be extruded at high speed and provide bars having good in-use properties such as a low level of mush and a low rate of wear.

The weight of polysaccharide structurant to the weight of polyol, designated Rsp, should be in the ranged from about 0.3 to about 5, preferably 0.7 to about 4.5 based on the total weight of the continuous phase. It has been found that the exact ratio required to achieve acceptable compositions depends primarily on the total level of soap employed in the continuous phase and to some extent on R ₀ L-

It has been found through extensive experimentation that when the polysaccharide structurant is starch and/or cellulose, Rsp, should approximately satisfy the inequality set forth in Eq (2):

(0.005(TS ² ) - 0.4(TS) + 9.5) ± 15% < Rsp < (6.0 - 0.09(TS)) ± 15% (2)

An example of the minimum and maximum starch/glycerin ratios computed from the inequality in Eq (2) as a function of the weight % total soap (TS) is shown as a function of total soap TS in Table 2 below.

Table 2 Approximate Limits for Starch/Polyol Ratios

The structuring system may optionally include one or a combination of insoluble particulate materials. By insoluble particulate material is meant materials that are present in the continuous phase as finely divided solid particles and are suitable for personal washing applications. The particulate material can be inorganic or organic or a combination as long as it is insoluble in water. The insoluble particulate material should not be perceived as scratchy or granular and thus should have a particle size less than 300 microns, more preferably less than 100 mircons and most preferably less than 50 microns.

Preferred inorganic particulate material include talc and calcium carbonate. Talc is a magnesium silicate mineral material, with a sheet silicate structure represented by the chemical formula Mg ₃ Si ₄ (O)i ₀ (OH) ₂ , and may be available in the hydrated form. Talc has a plate-like morphology, and is substantially oleophilic/hydrophobia

Calcium carbonate or chalk exists in three crystal forms: calcite, aragonite and vaterite. The natural morphology of calcite is rhombohedral or cuboidal, acicular or dendritic for aragonite and spheroidal for vaterite.

Commercially, calcium carbonate or chalk (precipitated calcium carbonate) is produced by a carbonation method in which carbon dioxide gas is bubbled through an aqueous suspension of calcium hydroxide. In this process the crystal type of calcium carbonate is calcite or a mixture of calcite and aragonite.

Examples of other optional insoluble inorganic particulate materials include alumino silicates, aluminates, silicates, phosphates, insoluble sulfates, borates and clays (e.g., kaolin, china clay) and their combinations.

Organic particulate materials include: insoluble polysaccharides such as highly crosslinked or insolubilized starch (e.g., by reaction with a hydrophobe such as octyl succinate); synthetic or natural polymers such as various polymer lattices and suspension polymers and mixtures thereof. The structuring system can comprise up to and including about 15% insoluble particulate material, preferably 4% to about 10%, based on the total weight of the composition.

In should be noted that the limitations on the ratios of oleics to laurics soaps and on polysaccharide to polyol recited in Equations 1 and 2 are meant as targets to greatly reduce experimentation. However, the equations are approximate as they relate to compositions at the boundary values of the inequalities (i.e., the end points of each equation). As the composition gets close to the boundary, other components such as perfumes, emollient oils, electrolytes as well as the variability in the fatty acid distribution and starch/cellulose component can affect the material properties of the composition (e.g., yield stress and hardness). It is preferable to target the ratios to be within the boundaries. In setting the error limits in the Eq 1 and Eq 2 we have tried to capture the variability we have typically encountered at the boundary limits. However, the overriding limitation on composition is that the composition be an extrudable mass having a penetrometer hardness of 3 to 8 Kg and a yield stress of 350 to 2000 kPa measured at a temperature of 40° C.

Water content

The bar compositions of the invention do not comprise an especially high level of water compared to typical extruded and stamped soap bars which typically can range from about 13 to about 18% water when freshly made, i.e., after extrusion and stamping. In fact, it is preferable that the water content of the freshly made bar should be less than 20%, and preferably be between 14% and 18% based on the total weight of the bar. Thus, in preferred embodiments, the water level of the freshly made bars of the invention is lower than the water content of freshly made melt and pour or melt-cast bars, i.e., the nominal water content based on the formulation as made in a factory, which typically exceeds 25% by weight in melt- cast compositions. It is stressed that the preferred water levels quoted above refers to freshly made bars. This quantity "initial water level" or "initial water content" of the freshly made bar" is also designated as the "nominal water content" or "nominal water level" of the composition. As is well known, soap bars are subject to drying out during storage, i.e., water evaporates from the bar when the relative humidity is lower than the partial vapor pressure of water in equilibrium with the bar composition although the amount of evaporation depends on the rate of diffusion of water from the bar. Hence, depending upon how the bar is stored (type of wrapper, temperature, humidity, air circulation, etc) the actual water content of the bar at the moment of sampling can obviously differ significantly from the nominal water content of the bar immediately after manufacture.

Optional Ingredients

Added soluble salts

By the term "added" soluble salt is meant one or more salts that are introduced in the bar in addition to the salts which are present in the bar as a result of saponification and neutralization of the fatty acids, e.g., NaCI generated from saponification with sodium hydroxide and neutralization with hydrochloric acid.

A variety of water soluble salts could potentially be used. The preferred salts are water soluble salts that do not contain cations which precipitate with soap, i.e., which form insoluble precipitates with fatty acid carboxylates. Thus, water soluble salts containing divalent ions such as calcium, magnesium and zinc and trivalent ions such as aluminum should be avoided. Of course highly insoluble calcium salts such as calcium carbonate may be used as optional insoluble particulate material as part of the structuring system as discussed above.

Especially preferred soluble salts comprise monovalent cations that form soluble fatty acid soaps (such as sodium, potassium, alkylanolammonium but not lithium) and divalent anions (e.g., sulfates, carbonates, and isethionates), trivalent anions (e.g., citrates, sulfosuccinates, phosphates) and multivalent anions (e.g., polyphosphates and polyacylates).

Especially preferred salts are sodium and potassium sulfates, carbonates, phosphates, citrates, sulfosuccinates and isethionates and mixtures thereof.

The added salts have been found to be useful in reducing wear rate and mush. Without wishing to be bound by theory, it is believed that a limited amount of the one or more water soluble salts reduces the level of liquid crystal phase (e.g., lamellar phase) in the bar and therefore allow the bar to accommodate a composite structuring system that itself comprises some liquid. However, the incorporation of too much salt reduces the liquid crystal phase to a level where the bar becomes insufficiently pliable and may exhibit excessive cracking.

The level of added salt (i.e., excluding salts generated during saponification like NaCI) should be less than 2.0% (e.g. 1.5% to 2%), preferably less than 1.5%, preferably up to about 1.0%, preferably up to and including 0.8%. In some circumstances a level of salt from about 0.3% to about 0.8% is useful.

It should be noted that salts are not used in the present invention to lower water activity so as to accommodate very high levels of water in the bar which are characteristic of some low TFM bars described in the prior art, i.e. the use of electrolytes to prevent or slow the drying out of the bar. In fact, the bars of the current invention have water levels that are not especially high (up to about 20%) compared with normal commercial soap bars which can range from about 13 to about 15-18% nominal water content. Thus, levels of salts in the range of 2.5 to 8% typical of the high water content bars of the prior art, would be detrimental to the bars described herein. Free Fatty acid and triglycerides

A useful optional ingredient is fatty acid and /or triglycerides which are useful for improving lather, as well as modifying the rheology at low levels incorporated in composition to increase plasticity.

Potentially suitable fatty acids are C ₈ -C ₂₂ fatty acids. Preferred fatty acids are Ci ₂ - Ci8, preferably predominantly saturated, straight-chain fatty acids. However, some unsaturated fatty acids can also be employed. Of course the free fatty acids can be mixtures of shorter chain length (e.g., C10-C14) and longer chain length (e.g., Ci ₆ -Ci ₈ ) chain fatty acids. For example, one useful fatty acid is fatty acid derived from high-lauhcs triglycerides such as coconut oil, palm kernel oil, and babasu oil.

The fatty acid can be incorporated directly or they can be generated in-situ by the addition of a protic acid to the soap during processing. Examples of suitable protic acids include: mineral acids such as hydrochloric acid and sulfuric acid, adipic acid, citric acid, glycolic acid, acetic acid, formic acid, fumaric acid, lactic acid, malic acid, maleic acid, succinic acid, tartaric acid and polyacrylic acid.

The level of fatty acid having chain lengths of 14 carbon atoms and below should generally not exceed 5.0%, preferably not exceed about 1 % and most preferably be 0.8% or less based on the total weight of the continuous phase.

Synthetic surfactants

The bar compositions can optionally include non-soap synthetic type surfactants (detergents) - so called "syndets". Syndets can include anionic surfactants, nonionic surfactants, amphoteric or zwitterionic surfactants and cationic surfactants. The level of synthetic surfactant present in the bar is generally not greater than about 10% in the continuous phase although inclusion of higher levels in the bar may be advantageous for some applications. Some embodiments of the invention include syndets at a level of about 2% to 10%, preferably about 4% to about 10%.

Especially preferred syndets include anionic surfactants (non-soap), amphoteric surfactants and nonionic surfactants.

Advantageously, the toilet bar compositions of the present invention may contain one or more non-soap anionic syndet surfactants (simply designated "anionic syndets") at a level up to about 20%, preferably 0 to 10% and more preferably 2% to 5% based on the total weight of the continuous phase. Suitable anionic syndets may be, for example, an aliphatic sulfonate, such as a primary alkane (e.g., C8-C22) sulfonate, primary alkane (e.g., C8-C22) disulfonate, C8-C22 alkene sulfonate, C ₈ -C ₂₂ hydroxyalkane sulfonate or alkyl glyceryl ether sulfonate (AGS); or an aromatic sulfonate such as alkyl benzene sulfonate. Alpha olefin sulfonates are another suitable anionic surfactant.

The anionic syndet may also be an alkyl sulfate (e.g., Ci ₂ -Ci ₈ alkyl sulfate), especially a primary alcohol sulfate or an alkyl ether sulfate (including alkyl glyceryl ether sulfates).

The anionic syndet can also be a sulfonated fatty acid such as alpha sulfonated tallow fatty acid, a sulfonated fatty acid ester such as alpha sulfonated methyl tallowate or mixtures thereof.

The anionic syndet may also be alkyl sulfosuccinates (including mono- and dialkyl, e.g., C ₆ -C ₂₂ sulfosuccinates); alkyl and acyl taurates, alkyl and acyl sarcosinates, sulfoacetates, C ₈ -C ₂₂ alkyl phosphates and phosphates, alkyl phosphate esters and alkoxyl alkyl phosphate esters, acyl lactates or lactylates, C ₈ -C ₂₂ monoalkyl succinates and maleates, sulphoacetates, and acyl isethionates. Another class of anionic syndets is Cs to C20 alkyl ethoxy (1 -20 EO) carboxylates.

Another suitable anionic syndet is Cs-Cis acyl isethionates. These esters are prepared by reaction between alkali metal isethionate with mixed aliphatic fatty acids having from 6 to 18 carbon atoms and an iodine value of less than 20. At least 75% of the mixed fatty acids have from 12 to 18 carbon atoms and up to 25% have from 6 to 10 carbon atoms. The acyl isethionate may also be alkoxylated isethionates

Frequently, the anionic syndet will comprise a majority of the synthetic surfactants used in the composition.

Amphoteric surfactants which may be used in this invention include at least one acid group. This may be a carboxylic or a sulphonic acid group. They include quaternary nitrogen and therefore are quaternary amido acids. They should generally include an alkyl or alkenyl group of 7 to 18 carbon atoms. Suitable amphoteric surfactants include amphoacetates, alkyl and alkyl amido betaines, and alkyl and alkyl amido sulphobetaines.

Amphoacetates and diamphoacetates are also intended to be covered in possible zwittehonic and/or amphoteric compounds which may be used.

Suitable nonionic surfactants include the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols or fatty acids, with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Examples include the condensation products of aliphatic (C ₈ - Cis) primary or secondary linear or branched alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long chain tertiary amine oxides, long chain tertiary phosphine oxides and dialkyl sulphoxides.

The nonionic may also be a carbohydrate or sugar based, ethers, esters or amides, such as alkyl (poly)sacchahdes and alkyl (poly)sacchahde amides.

Examples of cationic detergents are the quaternary ammonium compounds such as alkyldimethylammonium halides.

Other surfactants which may be used are described in U.S. Pat. No. 3, 723,325 to Parran Jr. and "Surface Active Agents and Detergents" (Vol. I & II) by Schwartz, Perry & Berch, both of which is also incorporated into the subject application by reference.

Slip Modifier

Very useful optional ingredients are slip modifiers. The term "slip modifier" is used herein to designate materials that when present at relatively low levels (generally less than 1.5% based on the total weight of the bar composition) will significantly reduce the perceived friction between the wet bar and the skin. The most suitable slip modifiers are useful at a level of 1 wt% or less, preferably from 0.05 to 1 % and more preferably from 0.05% to 0.5%.

Slip modifiers are particularly useful in bar compositions which contain starch/ cellulose and/or insoluble particles whose levels approach the higher end of the useful concentration range for these materials, e.g., 30-40% for starch with 5-10% insoluble particulate material. It has been found that the incorporation of higher levels of starch and/or insoluble particles increases the wet skin friction of the bar and the bars are perceived as "draggy" (have a high perceived level of fhctional "drag" on the skin). Although some consumers do not mind this sensory quality, other dislike it. In general, consumers prefer bars that are perceived to glide easily over their skin and are perceived as being slippery.

It has been found that certain hydrophobic materials incorporated at low levels can dramatically reduce the wet skin frictional drag of bars containing higher levels of starch and/or insoluble particles to improve consumer acceptability.

Suitable slip modifier include petrolatum, waxes, lanolines, poly-alkane, -alkene, - polyalkalyene oxides, high molecular weight polyethylene oxide resins, silicones, poly ethylene glycols and mixtures thereof.

A particularly suitable slip modifier is high molecular weight polyethylene oxide resin. Preferably the molecular weight of the polyethylene oxide resin is greater than 80,000, more preferably at least 100,000 Daltons and most preferably at least 400,000 Daltons. Examples of suitable high molecular weight polyethylene oxide resins are water soluble resins supplied by Dow Chemical Company under the trade name POLYOX. An example is WSR N-301 (molecular weight 4,000,000 Daltons).

Adjuvants

Adjuvants are ingredients that improve the aesthetic qualities of the bar especially the visual, tactile and olefactory properties either directly (perfume) or indirectly (preservatives). A wide variety of optional ingredients can be incorporated in bars of the current invention. Examples of adjuvants include but are not limited to: perfumes; opacifying agents such as fatty alcohols, ethoxylated fatty acids, solid esters, and TiO ₂ ; dyes and pigments; pearlizing agent such as TiO ₂ coated micas and other interference pigments; plate like mirror particles such as organic glitters; sensates such as menthol and ginger; preservatives such as dimethyloldimethylhydantoin (Glydant XL1000), parabens, sorbic acid and the like; anti-oxidants such as, for example, butylated hydroxytoluene (BHT); chelating agents such as salts of ethylene diamine tetra acetic acid (EDTA) and thsodium etidronate; emulsion stabilizers; auxiliary thickeners; buffering agents; and mixtures thereof.

The level of pearl izing agent should be between about 0.1 % to about 3%, preferably between 0.1 % and 0.5% and most preferably between about 0.2 to about 0.4% based on the total weight of the composition.

Adjuvants are commonly collectively designated as "minors" in the soap making art and frequently include at a minimum, colorant (dyes and pigments), perfume, preservatives and residual salts and oils from the soap making process, and various emotive ingredients such as witch-hazel. Minors generally constitute 4 to 10% by weight of the total continuous phase composition, preferably 4 to 8%, and often about 5-7% of the continuous phase.

Skin benefit agents

A particular class of optional ingredients highlighted here is skin benefit agents included to promote skin and hair health and condition. Potential benefit agents include but are not limited to: lipids such as cholesterol, ceramides, and pseudoceramides; antimicrobial agents such as TRICLOSAN; sunscreens such as cinnamates; exfoliant particles such as polyethylene beads, walnut shells, apricot seeds, flower petals and seeds, and inorganics such as silica, and pumice; additional emollients (skin softening agents) such as long chain alcohols and waxes like lanolin; additional moisturizers; skin-toning agents; skin nutrients such as vitamins like Vitamin C, D and E and essential oils like bergamot, citrus unshiu, calamus, and the like; water soluble or insoluble extracts of avocado, grape, grape seed, myrrh, cucumber, watercress, calendula, elder flower, geranium, linden blossom, amaranth, seaweed, gingko, ginseng, carrot; impatiens balsamina, camu camu, alpina leaf and other plant extracts such as witch-hazel, and mixtures thereof. The composition can also include a variety of other active ingredients that provide additional skin (including scalp) benefits. Examples include anti-acne agents such as salicylic and resorcinol; sulfur-containing D and L amino acids and their derivatives and salts, particularly their N-acetyl derivatives; anti-wrinkle, anti-skin atrophy and skin-repair actives such as vitamins (e.g., A, E and K), vitamin alkyl esters, minerals, magnesium, calcium, copper, zinc and other metallic components; retinoic acid and esters and derivatives such as retinal and retinol, vitamin B3 compounds, alpha hydroxy acids, beta hydroxy acids, e.g. salicylic acid and derivatives thereof; skin soothing agents such as aloe vera, jojoba oil, propionic and acetic acid derivatives, fenamic acid derivatives; artificial tanning agents such as dihydroxyacetone; tyrosine; tyrosine esters such as ethyl tyrosinate and glucose tyrosinate; skin lightening agents such as aloe extract and niacinamide, alpha-glyceryl-L-ascorbic acid, aminotyroxine, ammonium lactate, glycolic acid, hydroquinone, 4 hydroxyanisole, sebum stimulation agents such as bryonolic acid, dehydroepiandrosterone (DHEA) and orizano; sebum inhibitors such as aluminum hydroxy chloride, corticosteroids, dehydroacetic acid and its salts, dichlorophenyl imidazoldioxolan (available from Elubiol); anti-oxidant effects, protease inhibition; skin tightening agents such as terpolymers of vinylpyrrolidone, (meth)acrylic acid and a hydrophobic monomer comprised of long chain alkyl (meth)acrylates; anti-itch agents such as hydrocortisone, methdilizine and trimeprazine hair growth inhibition; 5-alpha reductase inhibitors; agents that enhance desquamation; anti-glycation agents; anti-dandruf agents such as zinc pyhdinethione; hair growth promoters such as finasteride, minoxidil, vitamin D analogues and retinoic acid and mixtures thereof.

OPTIONAL DOMAINS DISPERSED IN THE CONTINUOUS PHASE

The extruded bars according to the invention can include various types of optional macroscopic domains generally having a different composition from the continuous phase which are dispersed or distributed either uniformly or non- uniformly in the continuous phase of the bar. The composition of domains can differ from the composition of the continuous phase in for example colorant, surfactant level and type, benefit agents, structurants or matrix.

Optional dispersed domains can include one or a combination of stripes or variegations such as described in U.S. Patents 4,634,564, 3,673,294, 3,884,605 and 6,383,999, chucks or bits as described in U.S. Patent 6,730,642, veins as described in U.S. Patent Application no. 2008/214430, plate like inclusions, and surface inclusions such as is described in U.S. Patent Application no. 2008/188388.

The domains can be included during extrusion by injection, co-extrusion, dispersion and post-extrusion by surface impaction.

MATERIAL PROPERTIES OF AN EXTRUDED MASS

The personal washing bars described herein are extruded masses. By the term "extruded mass" is meant that the bars are made by a process which involves both the intensive mixing or working of the soap mass while it is in a semi-solid plastic state, and its forming into a cohesive mass by the process of extrusion.

The intensive mixing can be accomplished by one or more unit operations known in the art which can include roller milling, refining, and single or multistage extrusion. Such processes work (shear) the composition at a temperature between about 3O ⁰ C and about 5O ⁰ C to form a homogeneous network of insoluble solid materials dispersed in a viscous liquid and/or liquid crystalline phase containing the lower melting, more soluble surfactants (e.g., laurics and oleics soaps and other water soluble/dispersible materials).

An extruded mass must be thermoplastic within the process temperature of extrusion which is generally between about 30 ⁰ C and about 45°C, preferably at a temperature between about 33°C to about 42°C. Thus, the material must soften within this process temperature window but remain highly viscous, i.e., the material should not soften excessively to form a sticky mass. The material must regain its structure and harden quickly as the temperature is lowered below its softening point. This means that the internal structure must reform quickly generally by re-solidification of structure forming units, e.g., crystals.

Furthermore, the softened mass although pliable must be sufficiently viscous so that it does not stick to the surfaces of the extruder in order to be capable of conveyance by the extruder screws but not bend excessively when exiting the extruder as a billet. However, if the mass is too viscous it will not be capable of extrusion at reasonable rates. Thus, the hardness of the mass should fall within limits within the process temperature window to be capable of high rates of production as defined above.

Personal washing bars formed by extrusion (also commonly known as milled soaps) have physical-chemical properties and an internal structure which are quite different from soaps that are made by a melt-cast process wherein the bar composition is first melted at high temperature (e.g., 7O ⁰ C) to form a liquid phase which is then poured into molds to solidify by quiescent cooling.

These differences in internal structure, composition and physical-chemical characteristics provide extruded personal washing bars with overall in-use properties which are better suited for the mass market than cast soaps. These properties include: much lower wear rates, more resistance to scuffing and denting, and a richer, more creamy opaque lather.

The one or more key properties that serve as characteristic "finger-prints" of an extruded mass are structural anisotropy, the level of high melting point materials such as stearics soaps, high melting point and thermal reversibility, and rapid recovery of hardness after heating and shear. These characteristics are briefly described below.

Structural anisotropy

Bars made by extrusion typically have a characteristic anisotropic internal structure both with respect to the alignment of crystals and overall macro- structure.

One important element of the macro-structure is the "candle structure", disclosed for example by Schonig et al in US patent 4,720,365 which is produced in the plodder and modified in the stamper. Shear forces generated at the eyeplate and subsequent extensional forces in the plodder cone produce marked alignment within the candles and thus influence the colloidal structure of the extruded mass. Although there is some modification of alignment after stamping, the resultant bar usually has a characteristic macroscopic alignment of the crystallites and domains relative to the bar surface and some residual candle structure.

The liquid (crystalline) phase generated at the extrusion temperature has a relatively lower viscosity and is expected to preferentially flow to the surface of the candles during the plodder compression stage.

In contrast, melt-cast bars have a predominantly isotropic structure because crystallization occurs during quiescent cooling and thus the alignment of crystals is minimal and there is no candle structure.

The differences in internal structure between extruded and melt-cast bars can be visualized by a simple ethanol extraction procedure. In this procedure bars are shaven, for example with a plane or mandolin to reveal inside surfaces (the bars can be shaved in several orthogonal directions). These shaved sections are then immersed overnight in anhydrous alcohol. After removal from the alcohol, the bars are allowed to dry by standing whereupon a pattern of small cracks become apparent. These cracks are indicative of the orientated micro-structure of the bar. The alcohol extracts the more soluble soaps in extruded bars, thus exposing the candle structure interface and the lines of flow. In melt-cast bars flow lines and the candle structure are absent and fine cracks are much less pronounced or absent after alcohol emersion.

Level of high melting materials

In order to achieve the rheological properties required for milling and extrusion, an extruded mass must have a sufficient level of solid particles to adequately structure the mass at the process temperature, i.e., the bar contains materials whose melting point is above the extrusion temperature.

For bars that are comprised predominantly of soap, these high melting solids are provided in at least part by the stearic soaps which include the C16 and C18 saturated soaps.

The level of high melting solids (e.g. melting point greater than the extrusion temperature) found in extruded bars is generally greater than 20%, and typically greater than 30% based on the total level of fatty acid soap present in the continuous phase. For compositions of the instant invention which are predominantly comprised of soaps, the level of stearics soaps is generally between about 25% and about 60%, preferably between 30% to about 45% based on the total weight of the fatty acid soap. Other sources of solid particles are also present in the bars described herein.

Melting point and thermal reversibility

Because of the presence of significant high melting solids (e.g. stearics-hch soaps) and the lower levels of liquids relative to cast soaps, extruded masses have melting points that are generally above 8O ⁰ C, typically above 9O ⁰ C and usually above 100 ⁰ C. In contrast, cast soaps generally melt at temperature between 7O ⁰ C and 8O ⁰ C.

Furthermore, an extruded mass regains its structure and harden quickly as the temperature is lowered below its softening point. This means that the internal structure reform quickly, generally by re-solidification of structure forming units, e.g., soap crystals. This rapid re-solidification is generally observed as thermal reversibility in differential scanning calohmetry (DSC). By the term thermal reversibility is meant that increasing and decreasing temperature sweeps tend to be superimposible albeit offset by a temperature difference characteristic of the composition. In contrast, cast soaps require much longer periods of time to reform the solid structural units and exhibit lower thermal reversibility, e.g., increasing-decreasing temperature sweeps are either not super-imposable or are offset by much larger temperatures than is found with an mass.

Recovery of hardness after heating and shear

An extruded mass must soften when it is heated to the extrusion process temperature, which is typically in the range of about 35° C to about 45° C.

However, at this temperature it must retain sufficient hardness. It has been found experimentally that to achieve the desired rates of production, the hardness of the mass should generally be at least about 3 Kg, preferably at least 4 Kg but generally not greater than about 8 Kg, preferably between 4.5 Kg and 6.5 Kg when measured by the Hardness Penetration Test described in the TEST

METHODOLOGY section, said measurement being carried out at a temperature in the range of about 4O ⁰ C.

An extruded mass also remains cohesive after its has been subjected to shear at the extrusion temperature without exhibiting excessive pliability or stickiness. By the term "remain cohesive" is meant when compacted under pressure the mass should be capable of sintering together to form a single cohesive unit that has mechanical integrity.

Finally, it has been found that an extruded mass quickly recovers its yield stress (as measured by its penetrometer hardness) when it is subjected to shear at the extrusion temperature (e.g., 4O ⁰ C) and allowed to cool. For example when the extrudate is cooled after extrusion to 25 ⁰ C, the mass should recover at least about 75%, preferably at least about 85% and more preferably at least about 95% of the initial hardness before it was sheared, by for example, extrusion through an "orifice" extruder.

The influence of shear on cohesivity, stickiness, pliability and recovery of yield stress can be assessed utilizing an "orifice" extruder which provides a controlled extensional flow similar to that encountered by the mass during extrusion through an eye plate. This device comprises a thermal jacketed barrel (e.g. 350 mm length by 90 mm in diameter) ending in a narrow opening (typically 2-4 mm) and a plunger which is coupled to a drive unit e.g., lnstron Mechanical Tester. The plunger forces the mass through the orifice to form an extrudate. The extrudate can be assessed at the process temperature.

The extrudate can be placed in the barrel of the orifice extruder, compressed under different loads and removed to determine its cohesivity or extent of cohesion, its stickiness and its ability to recover its hardness after it has been sheared at the extrusion temperature (e.g., 4O ⁰ C) and cooled (e.g., 25 ⁰ C).

Based on the above extrudability criteria, so called melt and pour compositions such as those used to make glycerin soaps that require casting in molds in order to form bars are not extrudable masses when they are initially formed from the melt and are not suitable. Thus, after a cast melt composition is melted and allowed to solidify in a mold for several hours, the composition does not form a cohesive non-sticky mass after extrusion through an orifice extruder and the extrudate does not exhibit the required recovery of hardness after cooling.

In addition to the requirement of being suitable for extrusion, the bar mass should also be sufficiently hard to be stamped with conventional soap making dies. The stamping process involves placing a billet or ingot of the extruded mass into a split mold comprised of generally two moveable halves (the dies). These dies when closed compress the billet ("stamp" the billet), squeezing out excess mass and defining the ultimate shape of the bar. The mold halves meet at a parting line which becomes visible as a line on the edge perimeter of the molded finished bar (stamped bar). Thus, a stamped personal washing bar can be characterized as comprising top and bottom stamped faces meeting at a parting line.

Experience has shown that stamping can be achieved by ensuring that an extruded billet of the bar mass (also known as an ingot) has a minimum hardness of at least about 3.0 Kg at the stamping temperature which is typically in the range 25° to 45 ⁰ C.

The one or more key characteristics of an extruded mass are summarized below.

Table 3 - Properties of Compositions Suitable for Extrusion

TEST METHODOLOGY

Rheological Properties (Hardness and Yield Stress)

The general properties of an extrudable mass were discussed above. However, for a soap composition to be capable of being extruded and stamped at high speeds requires that its rheological properties meet certain criteria. Specifically the hardness of the mass and its yield stress should fall within certain limits.

A variety of methods are known in the art to measure the hardness and yield stress of soft solids such as toilet soaps. The techniques used in the current work, is the Penetration Test which measures the penetration of a needle or tapered rod under load. The distance traveled (penetration of the needle into the test mass) under a constant load or the load required to produce a given distance of penetration can be measured. In the test method used in the present work, the latter measurement approach is employed, i.e., variable load to achieve fixed penetration depth.

Although the invention is described by parameters that are measured by the Penetration Test, various other rheological methods can be used and inter- correlated with the methods used herein.

Hardness penetration measurements were made using finished toilet soap bars using the TA-XT Plus Texture Analyzer supplier by Stable Micro Systems.

The rheological parameters of the finished bars were determined by measuring the weight necessary for the test probe to penetrate the sample to a distance of 15 mm (see table below). The 30° conical test probe is made from X2 stainless steel and the dimensions are: Length, 60.4 mm; Diameter 30 mm. The instrument parameters used in hardness analyses with TA-XT Express are given in the table below

Table 4

Parameters Value

Load cell capacity (kg) 10

Pre-speed (mm/s) 2

Return speed (mm/s) 10

Conical Probe Angle (°) 30

Trigger Force (g) 5

Test speed (mm/s) 1

Distance of penetration (mm) 15

The TA-XT Plus Texture Analyser allows for various preset probe speeds. In the examples described herein, the rheological parameters other then hardness were carried out at various speeds (minimum 10), ranging from 0.01 to 10 mm/sec and the forces measured accordingly. Shear stresses and shear rates were calculated and rheological charts were built. The rheological parameters were finally calculated by least-squares utilizing the Herschel-Bulkley equation:

σ = σ ₀ + κγ ⁿ

where σ is the shear stress, σo is the yield stress, k stands for the consistency index, n is the flow index and γ is the shear rate.

Stickiness was measured using the TA-XT Plus Texture Meter using the compression mode and by acquiring the peak reading when a 45° conical probe left the sample. The other parameters were: penetration distance 10mm, pre-test speed (10 mm.s ^"1 ), test speed (1 mm.s ^"1 ), and post-test speed (10 mm.s ^"1 ). Soap bar compositions suitable for the present invention should have a yield stress and penetrometer hardness (or simply "hardness") which falls within the following ranges:

Yield stress: from 350 to 2000 kPa when measured at a temperature of 4O ⁰ C, preferably from 500 to 1000 kPa.

Hardness: from 3 to 8 Kg when measured at a temperature of 4O ⁰ C, preferably from 4.5 Kg to 6.5 Kg

The rheological properties of a thermoplastic soap composition not only depend upon the soap composition (e.g., oleics to laurics ratio), the structuring system and water content but also upon the optional ingredients that are included in the bar composition. For example, inclusion of excessive amounts of low melting point emollients, e.g., mineral oil and/or liquid nonionic surfactants can lead to excessive softening of the bar composition at temperatures within the extrusion process window. Conversely, the inclusion of excessive levels of electrolyte(s) or particulate material can produce a mass which is highly brittle and non-cohesive.

Measurements of yield stress and hardness provide a means for determining whether particular optional ingredients at the levels contemplated can be included in the bar composition without excessively compromising the extrusion and stamping rates of the composition. Thus, optional ingredients can be incorporated in the continuous phase composition provided that the mass has a penetrometer hardness of 3 to 8 Kg and a yield stress of 350 to 2000 kPa measured at a temperature of between 35 and 45, preferably around 4O ⁰ C.

Wear Rate Test

The wear rate of the bar was measured by the following procedure. Four weighed samples of each test bar are placed on soap trays. Two types of soap trays are employed: those that have drainers or raised grids so the water left on the bar after rinsing is drained away; and no drainers so that water can be added to the tray to allow the bars to become "water-logged". The trays are coded as follows:

With drainers? Wash temperature ( ⁰ C)

Yes 25

Yes 40

No 25

No 40

10 ml of distilled water (ambient temperature) are poured into the undrained tray (25° and 40 ⁰ C).

Each tablet of soap treated as follows:

- Fill washing bowl with about 5 litres of water, at the desired temperature (20 ⁰ C or 40°C). - Mark the tablet to identify top face (e.g. make small hole with a needle).

- Wearing waterproof gloves, immerse the tablet in the water, and twist 15 times (180° each time) in the hands above water.

- Repeat the above step

- Briefly immerse tablet in the water to remove lather. - Place tablet back on its soap tray, ensuring that the opposite face is uppermost (i.e. the unmarked face).

The above procedure is carried out 6 times per day for 4 consecutive days, at evenly spaced intervals during each day. Alternate face of each bar is placed in the downward position (facing the bottom of the tray) after each washdown. Between washdowns the soap trays should be left on an open bench or draining board, in ambient conditions. After each washdown cycle, the position of each soap tray/tablet is changed to minimize variability in drying conditions.

At the end of each day each soap tray with drainer is rinsed and dried. Soap trays without drainers are refilled with 10 ml distilled water (ambient temperature). After the last washdown (4 ^th day), all soap trays are rinsed and dried. Each washed bar is placed in its tray and allowed to dry for up to a period of 9 days. On the 5 ^th day afternoon, the samples are turned so that both sides of the tablet dry. On the 8 ^th day, each tablet is weighed.

The rate of wear is defined as the percent weight loss as follows:

%Wear = (initial weight - final weight) *100 initial weight

Bar Mush Test

Mush is a paste or gel of soap and water, formed when soap is left in contact with water as in a soap-dish. Soluble components of the soap move into solution, and water is absorbed into the remaining solid soap causing swelling, and for most soaps, also recrystallization. The nature of the mush depends on the balance of these solution and absorption actions. The presence of a high level of mush is undesirable not only because it imparts an unpleasant feel and appearance to the soap, but also especially because the mush may separate from the bar and leaves a mess on the wash basin. Residual mush or soap residue is a known consumer negative.

The Mush Immersion Test described herein gives a numerical value for the amount of mush formed on a bar. The test is carried out as follows: A rectangular billet from the soap tablet is cut to the required dimensions using a plane, knife or cutting jig. The width and depth of the cut billet are accurately measured (+/- 0.1 cm). A line is drawn across the billet 5 cm from the bottom of the billet. This line represents the immersion depth.

The billet is attached to a sample holder and suspend in an empty beaker. Demineralised (or distilled) water at 20 ⁰ C is added to the beaker until the water level reaches the 5 cm mark on the billet. The beaker is placed in a water bath at 20 ⁰ C (+/- 0.5°C) and left for exactly 2 hours.

The soap-holder + billet is removed, the water emptied from the beaker, and the soap-holder + billet is replaced on the beaker for 1 minute so that excess water can drain off. Extraneous water is shaken off, the billet is removed from the soap- holder, and the weight of the billet standing it on its dry end is recorded (W _M ).

All the mush from all 5 faces of the billet is carefully scraped off, and any remaining traces of mush are removed by wiping gently with a tissue. The weight of the billet within 5 minutes of scraping is recorded (W _R ).

The quantitative amount of mush is calculated as follows:

Mush( _g l5Qcm ² ) = ^ W -W Lx ₅₀

A where A is the surface area:

Surface area (cm ² ) = A = 10 (width + thickness) + (width x thickness)

Accelerated Bar Cracking Test

The potential of bars to crack in use is assessed by washing the bars in a controlled manner 6 times per day for 4 days, storing the bars between washes under different conditions to simulate different consumer habits and then allowing the bars to dry for different periods of time to induce cracking. The procedure is as follows: Four weighed of each test bar are placed on soap trays in an identical arrangement as described above in the Wear Rate Test. 10 ml of distilled water (ambient temperature) are poured into the undrained tray (25° and 40 ⁰ C).

Each tablet of soap then treated in an identical manner as described above for the Wear Rate Test.

After the last washdown (4 ^th day), all soap trays are rinsed and dried and each washed bar is placed in its tray and allows to dry for up to a period of 9 days.

A subjective assessment of the degree of cracking is carried out on each bar. Some cracking may occur during the first 5 days of the test, but for maximum sensitivity and realism it is best to assess the cracking after drying out (i.e. on the 8th or 9th day).

A trained assessor examines the tablets and records separately the degree of cracking in each of the following areas: Both faces - all types of tablets; both ends - band-type tablets; both sides - band-type tablets periphery - capacity die tablets

The degree of cracking is graded using the following 0-5 scale:

0 - No cracking

1 - Small and shallow cracking: 2 - Small and medium deep cracking:

3 - Medium and deep cracking:

4 - Big and deep cracking:

5 - Very big and very deep cracking: It is advantageous to use photographic standards representing each of these grades, produced from typical local soap samples. This gives greater consistency of assessment between technicians.

EXAMPLES

The following non-limiting examples illustrate various aspects of the invention and preferred embodiments. Examples of the invention are designated with the prefix "E" while comparative examples are designated with the prefix "C".

Examples 1-3

These examples illustrates exemplary bar compositions according to the invention.

The compositions used to prepare the personal washing bars of examples Ex 1 - Ex 3 are set forth in Table 5 and contain about 33-43% soap (about 30-40% TFM). Ex1 and Ex2 include starch (native corn starch) as the polysaccharide while Ex3 is based on cellulose (microcrystalline). The continuous phase compositions and bars were prepared at pilot plant scale using conventional equipment used in the manufacture of extruded soap. In summary, the compositions were prepared by combining soap noodles with the remaining ingredients in Table 5 in a Z-blade mixer and passing the mixture through a 3-roll mill and a refiner. The compositions of the soap noodles are given in the second row of the table and were composed of a mixture of fatty acids derived from palm kernel oil (PKO - laurics-rich soap) and a mixture derived from of palm oil (PO) and palm stearin (POS), sources of stearics-rich and oleics soaps, using the weight ratios set forth in the table. The compositions so processed were added to the hopper of a two stage extruder and extruded at a temperature of 35 ⁰ C to 45 ⁰ C at an extrusion rate of 1.2 - 4.0 Kg/min through an eyeplate having a 3.5 x 3.5 cm cross section to form billets that were cut to about 12 cm in lengths. The billets were then transferred to a manual soap stamper and stamped to form the finished personal washing bar utilizing a die set defining a mold having a volume of approximately 79 to 80 cm ³ .

The physical and overall user properties are included in the bottom part of the Table 5.

The polyol used in these examples was glycerin and no insoluble particulate material was used in the structuring system.

The limiting values for the oleics soaps to laurics soaps ratio, R _OL , computed from Eq 1 and the starch/polyol ratio or cellulose/polyol ratio, Rsp computed from Eq. 2 are given in the table.

The second column from the left under physical properties provides the "ideal range" for these properties to achieve a bar that combines excellent manufacturability (high throughput extrusion and stamping on a commercial scale) and highly acceptable overall in-use properties.

The results in Table 5 indicate that the exemplary compositions have both a ratio of Oleics soap to Laurics soap, R ₀ L and a starch (or cellulose) to polyol ratio, R _S p which are within the limits required by Eq (1 ) and (2) at the soap level employed in each composition subject to the error limits at the boundary values as described above. The compositions not only exhibit hardness and yield stress that allows high throughput manufacture (e.g., 36 Kg per minute) but also provides excellent in-use properties as judged from acceptably low values of bar cracking, wear rate and mush. Table 5. Soap compositions of Examples 1-3 (TFM)

Example 4 and Comparative Examples 1 -3 (25% TFM)

The compositions used to prepare the personal washing bars of example Ex 4 and comparative examples C1 -C3 are shown in Table 6 and contain about 27% soap (25% TFM). The bars were prepared according to the methods described in Examples 1 -3. The organization and form of the Table 6 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The first point to note from Table 6 is that only the Ex 4 composition has both a Oleics soap to Laurics soap ratio and a starch to polyol ratio within the limits required by Eq 1 and 2 at this TFM level. This composition not only provides a hardness and yield stress that allows high throughput manufacture (e.g. 36 Kg per minute) but also provides excellent in-use properties as judged from acceptably low values of bar cracking, wear rate and mush.

In contrast, the comparative composition C1 to C3 which have either one or both of the critical ratios outside the required ranges, do not provide bars that either allow high throughput extrusion and/or have optimal in-use properties.

Table 6. Soap compositions having approximately 25% Total Fatty Matter (TFM)

Example 5 and Comparative Examples 4-6 (35% TFM)

The compositions of example Ex 5 and comparative examples C4-C6 are set forth in Table 7 and correspond to bars having 37.5% soap by weight (35% TFM). The bars were prepared according to the methods used to produce the bars of

Examples 1 -3. The organization and form of the Table 7 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The first point to note from Table 7 is that only the Ex 5 composition has both an Oleics soap to Laurics soap ratio (R ₀ L.) and a starch to polyol ratio (Rps) within the limits required by Eqs 1 and 2 at the soap content employed. This composition not only provides hardness and yield stress that allows high throughput manufacture (e.g. 36 Kg per minute) but also provides excellent in-use properties as judged from acceptably low values of bar cracking, wears rate and mush.

In contrast, the comparative composition C4 to C6 which have either one or both of the ratios outside the optimal ranges, do not provide bars that either allow high throughput extrusion and/or have optimal in-use properties.

Table 7. Soap compositions having approximately 35% Total Fatty Matter (TFM)

Example 6 and Comparative Examples 7-9 (40% TFM)

The compositions of example Ex 6 and comparative examples C7-C9 are set forth in Table 8 and contain about 42% soap by weight (40% TFM). The bars were prepared according to the methods used to produce the bars of Examples 1 -3. The organization and form of the Table 8 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The Ex 6 composition has both an Oleics soap to Laurics soap ratio (R _OL ) and a starch to polyol ratio (Rps) within the limits required by Eqs 1 and 2 at the total soap content employed. This composition not only provides hardness and yield stress that allows high throughput manufacture (e.g. 36 Kg per minute) but also provides excellent in-use properties as judged from acceptably low values of bar cracking, wears rate and mush.

In contrast, the comparative composition C7 to C9 which have either one or both of the ratios outside the optimal ranges, do not provide bars that either allow high throughput extrusion and/or have optimal in-use properties.

Table 8. Soap compositions having approximately 40% Total Fatty Matter (TFM)

Example 7 and Comparative Examples 10-12 (20% TFM)

The compositions of example Ex 7 and comparative examples C10-C12 are set forth in Table 9 and contain about 22.5% soap by weight (20%TFM). The bars were prepared according to the methods used to produce the bars of Examples 1 - 3. The organization and form of the Table 9 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The Ex 7 composition has both an Oleics soap to Laurics soap ratio (R _OL ) and a starch to polyol ratio (Rsp) within the limits required by Eqs 1 and 2 at the soap content employed. This composition not only provides hardness and yield stress that allows high throughput manufacture (e.g., 36 Kg per minute) but also provides acceptably low values of bar cracking, wears rate and mush.

In contrast, the comparative composition C10 to C12 which have either one or both of the ratios outside the optimal ranges, do not provide bars that either allow high throughput extrusion and/or have optimal in-use properties.

Table 9. Soap compositions having approximately 20% Total Fatty Matter (TFM)

Example 8 and Comparative Examples 13-15 (30% TFM)

The compositions of example Ex 8 and comparative examples C13-C15 are set forth in Table 10 and contain about 32 % soap by weight (30%TFM). The bars were prepared according to the methods used to produce the bars of Examples 1 - 3. The organization and form of the Table 10 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The Ex 8 composition has both an Oleics soap to Laurics soap ratio (R _OL ) and a starch to polyol ratio (Rps) within the limits required by Eqs 1 and 2 at the soap content employed. This composition not only provides a hardness and yield stress that allows high throughput manufacture (e.g. 36 Kg per minute) but also provides acceptably low values of bar cracking, wear rate and mush.

In contrast, the comparative composition C13 to C15 which have either one or both of the ratios outside the optimal ranges, do not provide bars that either allow high throughput extrusion and/or have optimal in-use properties.

Example 9-11 and Comparative Example 16-18

The compositions of Examples Ex 9-11 and comparative examples C16-C18 are set forth in Table 11. The bar compositions have 20% to 30% TFM. The bars were prepared according to the methods used to produce the bars of Ex 1 and C1 -C3. The organization and form of the Table 11 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The Ex 9-11 composition have both an Oleics soap to Laurics soap ratio (R _OL ) and a starch to polyol ratio (Rps) within the limits required by Eqs 1 and 2 at the soap content employed. These compositions provided bars having hardness and yield stress in the desired range for high speed extrusion and also provide bars that were acceptable in terms of cracking, wear rate and mush generation.

In contrast, the comparative composition C16 to C18 had a starch/polyol ratio that was above the maximum range, i.e., they contained too much starch relative to the polyol component. Although the bars could be extruded they were too hard and brittle (above the ideal hardness limit of about 8). All of these bars exhibited to high a level of cracking, rate of wear and mush generation.

Table 11. Soap compositions of Examples 9-11 and Comparative Examples 16-18

Example 12 and Comparative Example 19-20

The compositions of example Ex 12 and comparative examples C19-C20 are set forth in Table 12. The polysaccharide in this case is microcrystalline cellulose. The bar compositions have about 30% TFM. The bars were prepared according to the methods used to produce the bars of Ex 1 and C1 -C3. The organization and form of the Table 11 and the meanings of the various parameters are the same as described above in Examples 1 -3.

The Ex 12 composition has both an Oleics soap to Laurics soap ratio (R _OL ) and a polysaccharide to polyol ratio (Rsp) within the limits required by Eqs 1 and 2 at the soap content employed. This composition provides bars having the hardness and yield stress in the desired range for high speed extrusion and also provides bars that were acceptable in terms of cracking, wear rate and mush generation.

In contrast, the comparative composition C19 and C20 had either an R ₀ L or an Rsp ratio that was outside the preferred ranges. Although the bars could be extruded they were too soft for high throughput extrusion. All of these bars exhibited to high a rate of wear and mush generation.

Table 12. Soap compositions of Examples 12 and Comparative Examples 19-20

Example 13

Especially preferred personal washing bars are extruded bar consisting essentially of the ingredients listed in Table 13 with the constraints that: i) the sum of the ingredients can not exceed 100% so that all or some of the individual ingredients can not be simultaneously present at their maximum levels; ii) the ratio of oleic soaps to lauric soaps satisfies Eq 1 within the error limits of about 15% and iii) the composition is an extrudable mass having a penetrometer hardness of 3 to 8 Kg and a yield stress of 350 to 2000 kPa measured at a temperature of 40°; and iv) the finished bars have physical properties close to the ideal values as set forth in preceding tables (e.g. Table 5).

In the above context the term "essentially" is used to encompass ingredients that can be included to confer benefits to soap bars provided the ingredients are safe for routine contact with skin and do not cause the composition to exhibit physical properties outside the boundaries set forth under item iii) and iv) above which insure high speed manufacturing and acceptable in-use properties.

Table 13: Preferred continuous phase compositions for extruded bars of the invention