A SHAPED SOLID CLEANSING COMPOSITION AND PROCESS OF

MANUFACTURE THEREOF

Field of the invention

The present invention relates to a process of preparing a milled soap bar with high moisture levels.

Background of the invention

Conventional cleansing composition based on soap for personal washing usually contain over about 70% by weight total fatty matter, the remainder being water (about 10 to 20%) and other ingredients such as colour, perfume, preservatives, etc.

Structurants and fillers are also present in such compositions in amounts, which replace some of the soap in the composition while retaining the desired hardness of the composition. A few known fillers include starch, kaolin and talc.

In classic bar extrusion technology (i.e., where ingredients are combined and mixed at higher temperatures, chilled to form chips, and chips are plodded and extruded) it is extremely difficult to provide high levels of low melting point emollients and mild, water soluble surfactants (e.g., liquid components). Hard non-milled soap composition containing moisture of less than 35% are also available. These compositions have a TFM of about 30 to 65%. The reduction in TFM is usually achieved by the use of insoluble particulate materials and/or soluble silicates. Milled compositions generally have a water content about 8 to15%, and the hard non-milled compositions have a water content of about 20 to 35%.

It is important to deliver sensory properties such as lather and skin feel, preferably by incorporating benefit agents in the formulation without altering the process, ability and physical properties of the composition.

Compositions of soap are usually manufactured by extrusion or casting. Extrusion involves a plodder or extruder which provides definite and often distinctive shape to compositions. Personal washing compositions formed by extrusion are also commonly known as milled soaps.

Currently most of the extruded soap compositions contain some amount of soluble oil soap content which helps for lathering, and cleansing and insoluble oil soap content for structuring the soap composition. Normally any soap composition contains 5% to 20% of soluble soap and rest is insoluble soap. Essentially any soap composition will have 60 to 95% of insoluble soap used only for structuring the soap composition which does not play any role in cleansing. There are some soap compositions with 40 to 50 TFM, where TFM is compensated by skin beneficiary agents, moisturizers etc. Overall normal soap contains 60-70% of soap which only helps for structuring soap

composition. Generally, cast melt soap compositions available in the market range from with 40 to 60 TFM. The increasing demand for vegetable oils, such as palm oil, (one of the main sources of oils and fatty acids used by soap manufacturers), and consequent soaring prices has led to severe constraints on the sustainability of the soaps and detergents Industry, as it is becoming increasingly difficult to provide high TFM soaps at a competitive cost, while still making reasonable profits. As a result, the trend is towards lower TFM soaps, being a cost-effective measure.

IN 176384 A (Hindustan Lever Limited) discloses a detergent composition with low TFM content having high ratio of water to TFM without affecting hardness, cleaning and lathering properties of the bar by the incorporation of up to 20% colloidal aluminium hydroxide (A-gel). The A-gel/TFM combination enables the preparation of bars with higher water content while using TFM at a lower level.

IN 177828 A (Hindustan Lever Limited) discloses a process wherein, by providing a balanced combination of aluminium hydroxide and TFM, it is possible to prepare a low TFM bar having high water content but with satisfactory hardness. The patent teaches the generation of colloidal aluminium hydroxide in-situ by a reaction of fatty acid/fat with an aluminium containing alkaline material such as sodium aluminate to form bars which are obtained by plodding. WO2003010272 A1 (Unilever) discloses a soap or detergent bar, primarily intended for personal or fabric washing. The bar has relatively low levels of total fatty matter, allowing relatively high levels of water and/or other liquid additives to be present. This is achieved whilst retaining good physical properties in the bar by incorporating aluminium hydroxide and tetra sodium pyrophosphate decahydrate (ka<1 ) into the bar. Methods of producing such bars are also disclosed.

WO 00/36075 A1 (Unilever) discloses a low total fatty matter content detergent bar composition comprising a surfactant 25-70% total fatty matter, 9-16% by weight colloidal aluminium hydroxide and 12-52% water. The invention also comprises a process for preparing a detergent bar comprising a surfactant, 25-70% total fatty matter, 0.5-20% colloidal aluminium hydroxide and 15-52% water, comprising the steps of reacting one or more fatty acids or fats with sodium aluminate with a solid content of 20-55% wherein the AI203 to Na20 ratio is in the region 0.5-1.55:1 to obtain a mixture of aluminium hydroxide and soap at a temperature of between 40 DEG C and 95 DEG C, adding a predetermined amount of water to the mixture of aluminium hydroxide and soap, adding any further minor additives, and converting the product into bars.

WO 2004/063320 A1 (Unilever) discloses multiphase personal washing bars having artisan crafted appearance. In such bars the hardness of the discontinuous phase is greater than 2 times the hardness of the continuous phase. It further relates to processes for making the bar, and methods of using the same.

WO2006/061 144 A1 (Unilever discloses a novel method of incorporating free fatty acid into soap-based bars to minimize or eliminate efflorescence and to compositions made by the process.

US 4574053 A (Kinsman) discloses Soap, combo or syndet bars filled with particulate inorganic filler materials wherein the particles of the filler are coated with fatty acid which has reacted chemically with the filler.

GB916570 A (Kurt) discloses soap bars coated with Alumina or containing Alumina in order to regularize the filamentary growth on soap. Therefore, there is need is to have a low TFM shaped solid cleansing composition with good physical, cleansing and sensorial properties.

There is also a need to provide a shaped solid cleansing composition which is economical and which contributes to sustainability by reducing the amount of natural oil content, such as palm oil.

There is also a need to have a process of manufacturing a shaped solid cleansing composition having low TFM and which is capable of incorporating higher level of moisture content.

Summary of the invention

The present invention provides a process of manufacturing a shaped solid cleansing composition comprising the steps of:

a) neutralizing trivalent salt of a metal with alkali metal hydroxide to obtain a

mixture;

b) adding fatty acids to the mixture of step (a) to obtain a blend; and

c) saponifying the blend of step (c) to obtain the shaped solid cleansing

composition.

These and other aspects features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims.

Detailed description of the invention

For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. 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".

Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated.

The present invention relates to a shaped solid cleansing composition. By the term "cleansing composition" is meant a composition which is used to clean any substrate e.g. skin, hair or other external surfaces of human or animal body, or hard surfaces in homes, offices or any public or industrial location or soft/porous substrates like fabric.

By "shaped solid" is meant a body in solid form which retains its shape after manufacture and during transport and storage. Examples of shaped solids include bars and tablets. It is highly preferred that the shaped solid cleansing composition of the present invention is shaped in bar or tablet form.

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.

The shaped solid cleansing composition 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.

Shaped solid cleansing composition produced from compositions according to the process of 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 everyday use by mass market consumers.

The process of the present invention provides a shaped solid cleansing composition comprising 35 to 75 wt% TFM; 0.5 to 5 wt% hydroxide of trivalent metal ion; and 0.8 to 5 wt% electrolyte; wherein, the electrolyte is a salt of acid having Ka >1. The shaped solid cleansing composition is a milled soap bar. Conventionally, milled soap bars are made by a process comprising drying of soap, forming the dried soap into noodles by passing it through a plodder, mixing the various desired additives such as colorants, perfume, etc., into the soap noodles, passing the mixture formed in through a mill or series of mills ("milling" the soap) thereby forming ribbons of soap, passing the milled soap mixture through a plodder to form billets of soap (i.e., "plodding" the soap, and cutting the billets into segments and stamping the segments into the desired shape.

The present invention provides a process of manufacturing a shaped solid cleansing composition comprising the steps of:

a) neutralizing trivalent salt of a metal with alkali metal hydroxide to obtain a mixture; b) adding fatty acids to the mixture of step (a) to obtain a blend; and

c) saponifying the blend of step (c) to obtain the shaped solid cleansing composition. It is an unexpected finding of the present invention that neutralizing a trivalent salt of a metal with alkali metal hydroxide and in situ generation of hydroxide of trivalent metal ion at a particular step in the process of preparing the composition is important to achieve composition with the desired properties. The term neutralization, in the context of this step of the process according to the invention means reaction of the trivalent salt of a metal with the alkali metal hydroxide. The metal of the trivalent salt and the metal of the alkali metal hydroxide may or may not be same.

Various components (ingredients) of the shaped solid cleansing composition made in accordance with the process of the present invention, are described in detail below.

Fatty acid soap

The term soap denotes salts of carboxylic fatty acids. The soap may be derived from any of the triglycerides conventionally used in soap manufacture. Consequently, the carboxylate anions in the soap may contain from 8 to 22 carbon atoms.

The soap may be obtained by saponifying a fat and/or a fatty acid. The fats or oils generally used in soap manufacture may be such as tallow, tallow stearines, palm oil, palm stearines, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, palm kernel oil, and others. In the above process the fatty acids are derived from oils/fats selected from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed, soybean, castor etc. The fatty acid soaps can also be synthetically prepared (e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process). Resin acids, such as those present in tall oil, may be used. Naphthenic acids are also suitable.

Tallow fatty acids can be derived from various animal sources and generally comprise about 1 to 8% myristic acid, about 21 to 32% palmitic acid, about 14 to 31 % stearic acid, about 0 to 4% palmitoleic acid, about 36 to 50% oleic acid and about 0 to 5% linoleic acid. A typical distribution is 2.5% myristic acid, 29% palmitic acid, 23% stearic acid, 2% palmitoleic acid, 41 .5% oleic acid, and 3% linoleic acid (all percentages by weight). Other similar mixtures, such as those from palm oil and those derived from various animal tallow and lard are also included. Coconut oil refers to fatty acid mixtures having an approximate carbon chain length distribution of 8% Cs, 7% Cio, 48% Ci2, 17% CM, 8% Ci6, 2% Ci ₈ , 7% oleic and 2% linoleic acids (the first six fatty acids listed being saturated). Other sources having similar carbon chain length distributions, such as palm kernel oil and babassu kernel oil, are included within the term coconut oil.

A typical suitable fatty acid blend consists of 5 to 30% by weight coconut fatty acids and 70 to 95% by weight fatty acids ex-hardened rice bran oil. Fatty acids derived from other suitable oils/fats such as groundnut, soybean, tallow, palm, palm kernel,, may also be used in other desired proportions.

Total fatty matter

The term total fatty matter is used very widely and popularly in the field of soaps and detergents. The term Total Fatty Matter, abbreviated to "TFM", is used to denote the soap obtained from fatty acids and triglycerides present in the cleansing composition without taking into account the accompanying cations. For a soap having 18 carbon atoms, an accompanying sodium cation will generally amount to about 8 percent by weight of a mole of soap. Other cations may be employed as desired, for example zinc, potassium, magnesium, alkyl ammonium and aluminium. To calculate the "soap" level in the personal wash composition, the TFM level is to be multiplied by 1 .08.

The TFM content of the shaped solid composition made by the process of the invention is in the range of 35 to 75 wt% more preferably between 40 to 65 wt%, and most preferably 40 to 60 wt%.

It is preferred that 10 to 95 parts by weight of said total fatty matter is made up of soap of Ce to C22 fatty acids. The balance of TFM may include non-soap surfactants.

Hydroxide of trivalent metal ion

It is preferred that the hydroxide of the metal ion is generated in situ by reacting a trivalent salt of a metal with a hydroxide of an alkali. The metals preferred for the invention are trivalent metals and more preferably include but are not limited to

Aluminium and Ferric. It is highly preferred that the hydroxide of the metal ion for the invention is Aluminium hydroxide. It can be generated in situ by reacting an aluminium salt such as a trivalent salt of aluminum to generate aluminum hydroxide. Preferred trivalent salts for the invention include but are not limited to aluminium sulphate, aluminium chlorohydrate, aluminium nitrate, aluminium bromide and aluminium iodide. It is highly preferred to use aluminium sulphate as the trivalent salt for the process of the invention. It is highly preferred that the metal hydroxide is an alkali metal hydroxide and most preferably is sodium hydroxide or potassium hydroxide. . It is preferred that the shaped solid composition obtained by the process of the present invention has water up to 20 wt% and more preferably up to 35 wt% and hardness of at least 3500 grams and more preferably up to 8000 grams.

For the sake of clarity, the hardness values throughout the description are those of fresh shaped solid cleansing compositions (soap bars), measured within five hours and most preferably within three hours of making.

It is a surprising finding of the present invention that in situ generation of hydroxide of a trivalent metal ion by addition of a trivalent salt of a metal and a hydroxide of an alkali metal results in shaped solid compositions, i.e. milled soap bars, of significantly better sensory properties such as lather, average wear rate and mush.

Iodine Value

Iodine Value is the measure of degree of unsaturation of oils. Iodine value, also called Iodine Number is the measure of the degree of unsaturation of an oil, fat, or wax, i.e., the amount of iodine, in grams, that is taken up by 100 grams of the oil, fat, or wax. Saturated oils, fats, and waxes take up no iodine; therefore, their iodine value is zero; but unsaturated oils, fats, and waxes take up iodine. (Unsaturated compounds contain molecules with double or triple bonds, which are very reactive toward iodine.) The more iodine is attached, the higher is the iodine value, and the more reactive, less stable, softer, and more susceptible to oxidation and rancidification is the oil, fat, or wax. The compositions made by the process of the present invention have Iodine value in the range of 30 to 70, more preferably in the range of 30 to 50 and most preferably in the range of 35 to 45.

The Iodine values of the composition of the present invention is measured by Wijs Method, The American Oil Chemists' Society (AOCS) Official Method Cd 1 -25, Revised 1988.)

Electrolyte and K _a value It is preferred that the electrolyte content of the shaped solid compositions made by the process of the present invention is in the range of 1 to 5 wt%, more, preferably in the range of 0.8 to 4 wt% and most preferably in the range of 1 to 3.5 wt%. It is preferred that the electrolyte, in the context of the present invention, is a salt of acid having K _a >1 or pK _a <1 .

The term acid dissociation constant (K _a ) is a quantitative measure of the strength of an acid in solution. The dissociation constant is usually written as a quotient of the equilibrium concentrations (in mol/L): Ka= [A-] [H+] / [HA] . It is known to express Ka value by using the pK _a , which is equal to -log-io(K _a ) . The larger the value of pK _a , the smaller is the extent of dissociation. A weak acid has pK _a in the approximate range of -2 to 12 in water. Acids with a pKa less than about -2 are said to be strong acids.

Given below is a table of acids having Ka >1 or PKa<1.

TABLE A: Table of Acids with Ka and pKa Values ^* CLAS

Electrolytes that are preferably present in the shaped solid compositions obtained by the process of the currentinvention include sodium sulfate, sodium chloride, potassium chloride, potassium sulfate, more preferred electrolytes are sodium chloride, sodium sulfate, potassium chloride and especially preferred electrolytes are sodium chloride, sodium sulfate, and combinations thereof. For the avoidance of doubt is clarified that the electrolyte is a non-soap material.

Water content The compositions obtained by the process of the invention comprises water in the range of 20 to 35 wt%, more preferably 22 to 35 wt%, and most preferably 20 to 30 wt%.

The process of the present invention enables incorporation of water to at least 20 wt%, more preferably to at least 30 wt% and most preferably to at least 35 wt% based on the total weight of the shaped solid cleansing composition, i.e. milled soap bars. The preferred water levels quoted above refers to freshly made soap bars where water content is measured within 8 hours. This quantity "initial water level" or "initial water content" of the freshly made shaped solid cleansing composition" is also designated as the "nominal water content" or "nominal water level" of the composition. As is well known, soap bars are subject to dry out (lose moisture) during storage, i.e., water evaporates from the shaped solid cleansing composition when the relative humidity is lower than the partial vapor pressure of water in equilibrium with the shaped solid cleansing composition although the amount of evaporation depends on the rate of diffusion of water from the shaped solid cleansing composition. Hence, depending upon how the soap bar is stored (type of wrapper, temperature, humidity and air circulation) the actual water (moisture) content of the shaped solid cleansing composition at the moment of sampling can obviously differ significantly from the nominal water content of the shaped solid cleansing composition immediately after manufacture. βΗ

The pH of shaped solid cleansing compositions made by the process of the present invention is 9 to 1 1 , more preferably 9.5 to 10.5. (Measured as 1 % solution of the soap bar at 25 °C).

The present invention provides a process for making a shaped solid cleansing composition comprising: 35 to 75 wt% TFM, 0.5 to 5 wt% hydroxide of trivalent metal ion, 0.8 to 5 wt% electrolyte wherein, the electrolyte is a salt of acid having Ka >1 .

It is preferred that the composition further comprises water in the range of 20 to 35 wt%, more preferably 22 to 35 wt%, and most preferably 20 to 30 wt%. It is preferred that the shaped solid compositions made by the process of the present invention have TFM to water ratio in the range of 3.5:1 to 1 .33:1 , more preferably from 3:1 to 1 .5:1 and most preferably from 2.3 :1 to 1.8:1.

It is preferred that the hydroxide of trivalent metal ion is aluminium hydroxide. The shaped solid cleansing composition is a milled soap bar.

It is preferred that the composition has Iodine Value in the range of 30 to 70, more preferably in the range of 30 to 50 and most preferably in the range of 35 to 45.

The present invention provides a process of manufacturing a shaped solid cleansing composition comprising the steps of:

a) neutralizing trivalent salt of a metal with alkali metal hydroxide to obtain a

mixture;

b) adding fatty acids to the mixture of step (a) to obtain a blend; and

c) saponifying the blend of step (b) to obtain the shaped solid cleansing

composition.

It is preferred that the saponifying step (c) is followed by a plodding step in which the soap mixture is extruded as soap billets and then cut into smaller shaped solid cleansing composition.

The solid shaped cleansing composition obtained after the plodding step is followed by stamping step in which tit is stamped to yield the finished shaped solid cleansing composition.

It is preferred that saponification in step (c) is achieved by addition of an alkali metal hydroxide, e.g. NaOH. Neutralization (i.e. reaction) of trivalent salt of a metal with alkali metal hydroxide in step (a) can either be done in the mixer in which the rest of the process is carried out or it may be done in an external mixer and added back to the mixer in which the main process steps are carried out. It is preferred that the trivalent salt of a metal is neutralized with alkali metal hydroxide in the molar ratio of 1 :1 to 1 :10, more preferably 1 :2 to 1 :8 and most preferably 1 :4 to 1 :8. It is most preferred that the trivalent salt of metal is neutralized with alkali metal hydroxide such that there is free alkali is in the range of 0.01 to 0.05 %wt by weight of the composition. It is also preferred that the mixture of step (a) is solubilized in water to obtain a solubilized mixture. It is particularly preferred that 0.1 to 10 wt%, more preferably 0.3 to 8% and most preferably 0.3 to 6% of electrolyte by weight of the composition is added during the saponifying step (c).

It is preferred that the trivalent salt of metal is trivalent salt of aluminium, and more preferably the trivalent salt of metal is aluminium sulphate.

In a preferred aspect of the present invention the mixture of step (a) comprises hydroxide of trivalent metal ion, more preferably the hydroxide of trivalent metal ion is generated in situ and most preferably it is preferred that the hydroxide of trivalent metal ion is aluminium hydroxide.

It is preferred that the temperature of the process is controlled in the range of 50 °C to 95 °C, more preferably in the range of 55 °C to 90 °C and most preferably in the range of 70°C to 85 °C. Process of The Invention

Of the various types of shaped solid cleansing compositions of the invention, the bar form is most preferred. Shaped solid cleansing composition may be prepared by many methods, of which the milled and plodded bars and cast bars are most commonly used. The process of the present invention preferably involves a crutching/mixing step where aqueous solution of Aluminium sulphate is added in the crutcher and neutralized with sodium hydroxide to attain a pH of 7. This reaction leads to the in situ generation of sodium sulphate and aluminium hydroxide. Subsequently, i.e., in the next step, the fatty acid blend containing, e.g, a mixture of Palm Kernel oil & distilled palm fatty acid is added slowly to the crutcher/mixer and neutralised with sodium hydroxide solution while preferably maintaining temperature of 85 to 90 °C. It is preferred that

preservatives and electrolytes are also added in this step during or after saponification. Soap noodles are obtained from this step. It is preferred that the soap noodles are then added to a suitable mixer, such as sigma mixer (Z- shaped blades) and crushed. It is most preferred that thereafter additives such as polyols, filler, actives, colourant, perfume and other minors are added and mixed to obtain a soap mass. It is further preferred that this soap mass is milled in triple roll mill for uniform mixing and then extruded through a twin worm plodder to obtain shaped solid cleansing composition which were cut then placed moulds & stamped. It is highly preferable that in the process of manufacturing a shaped solid cleansing composition Aluminium sulphate is added and neutralized before the saponification step.

The invention further relates to a composition obtainable by a process according to the invention.

Optional Ingredients in the soap bars

The shaped solid compositions, i.e., soap bars made by process of the invention, may preferably, contain one or more of the following ingredients.

Added soluble salts

By the term "added" soluble salt is meant one or more salts that are introduced in the shaped solid cleansing composition in addition to the salts which are present in the shaped solid cleansing composition 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, alkylanol ammonium 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 water soluble salts reduces the level of liquid crystal phase (e.g., lamellar phase) in the shaped solid cleansing composition and therefore allow the shaped solid cleansing composition 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 shaped solid cleansing composition 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.

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 C8-C22 fatty acids. Preferred fatty acids are C12-C18, 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., C16-C18) chain fatty acids. For example, one useful fatty acid is fatty acid derived from high- laurics 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 cleansing compositions can optionally include non-soap synthetic type surfactants (detergents) - so called "syndets"which can include anionic surfactants, nonionic surfactants, amphoteric or zwitterionic surfactants and cationic surfactants.

The level of synthetic surfactant present in the shaped solid cleansing composition is generally not greater than about 15% in the continuous phase although inclusion of higher levels in the shaped solid cleansing composition may be advantageous for some applications. Some embodiments of the invention include syndets at a level of about 2% to 15%, preferably about 4% to about 10%. Especially preferred syndets include anionic surfactants (non-soap), amphoteric surfactants and nonionic surfactants.

Advantageously, the shaped solid cleansing composition 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, C8-C22 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., C12-C18 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 dialkyi, e.g., C6-C22 sulfosuccinates); alkyl and acyl taurates, alkyl and acyl sarcosinates, sulfoacetates, C8-C22 alkyl phosphates and phosphates, alkyl phosphate esters and alkoxyl alkyl phosphate esters, acyl lactates or lactylates, C8-C22 monoalkyi 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 to C18 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 zwitterionic 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 (Cs-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)saccharides and alkyl (poly)saccharide 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.

The invention will be further described by the following illustrative non-limiting examples. All parts therein are by weight% unless otherwise specified.

Examples

Control milled shaped solid cleansing composition were made by the usual process. The preferred shaped solid cleansing composition of the present invention in the form of bars, were prepared by the following process: Example 1 - Process

Of the various types of shaped solid cleaning compositions of the invention, the bar form is most preferred. Shaped solid cleansing composition may be prepared by many methods, of which the milled and plodded bars and cast bars are most commonly used. The process involves a crutching step where aqueous solution of Aluminium sulphate is added in the crutcher and neutralized with sodium hydroxide to attain a pH of 7. This reaction leads to the in situ generation of sodium sulphate and aluminium hydroxide. Subsequently fatty acid blend containing a mixture of Palm Kernel oil and distilled palm fatty acid was added slowly to the crutcher and neutralised with sodium hydroxide solution while maintaining a temperature of 85 to 90°C. Preservatives and electrolytes are also added in this step during or after saponification. Soap noodles are obtained from this step. The soap noodles are then added to a suitable mixer, such as sigma mixer (Z- shaped blades) crushed for two minutes. Thereafter polyols, filler, actives, colourant, perfume and other minors are added and mixed for 10 minutes to obtain a soap mass. This soap mass is milled in triple roll mill for uniform mixing and then extruded through a twin-worm plodder to obtain elongated shaped solid cleansing composition which were cut then placed moulds and stamped.

Composition of the soap bars is shown in Table 1 .

TABLE 1 : Composition of the soap bars

Compositions E1 and E2 are the examples of soap bars made according to the process of the present invention, whereas Control 1 falls outside the scope of the invention for the reasons as provided in the second row of the table. Addition of Aluminium Sulphate is a critical step of the process of the invention. As shown in the Table 2, when Aluminium sulphate is added at stages/steps other than that at which it is added in the process of the invention, i.e., added and neutralized before saponification, the resultant bars had some drawbacks as explained hereinafter.

TABLE 2

Test Methods Example 1 : Hardness analysis

Hardness of soap bars is an important measure of quality control. The lower the penetration value, the higher the hardness. Hardness of soaps has direct relation with their formulation. Yet another important point about hardness is that it can vary from time to time. Freshly made soap or detergent bars are slightly softer and accordingly their hardness as expressed in terms of penetration values is on the lower side.

However, as time progresses, the bars generally tend to lose moisture or other volatile components which makes them harder. Therefore, the penetration value is seen to drop (reduce) over a period of time. In high liquid phase bar edges of bar are soft hence hardness measurement in this area will give better reflection of hardness of cleansing bar. Hardness penetration measurements were made using fresh (within 0.5 to 2.5 hours) finished cleansing bars using the TA-XT Plus Texture Analyzer supplier by Stable Micro Systems TM. Force measured for depressing/ cracking 2 mm edge of a cleansing bar to a depth of 3 mm indicates the hardness of soap. A 30 ^° cone plunger with penetration depth of 15 mm and speed of penetration 1 mm/sec was used for the penetration measurements. The measurements were done at an ambient temperature of 28 to 30 ^° C. A force of more than 6000 g indicates the bar is hard enough to be taken up for even for stamping. TAXT meter (Model- Taxt express enhanced texture analyzer - 10 kg capacity) machine was used for controlled force application for measuring hardness of cleansing bar.

TABLE 3

Table 3 shows that bars made by the process of the present invention, (E1 & E2) even though with higher water content, have hardness similar to the Control 1 bar with lower water content and higher TFM.

Example 2: Sensory analysis

Testing the rate of wear of bars

The wear-rate of the soap bars was measured by the following procedure. Four pre-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 (°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 °C). Each tablet of soap is treated as follows:

- A washing bowl is filled with about 5 litres of water, at the desired temperature (20 °C or 40 °C).

- The test tablets (bars of fixed mass and dimensions) are marked to identify top face (e.g. by making a small hole with a needle).

- Wearing waterproof gloves, the tablets are immersed one at a time in the water, and twisted 15 times (180° each time) in the hands above water.

- The tablet is immersed again in the water and twisted again 15 times (180° each time) in the hands above water.

- The treated tablet is briefly immersed in the water to remove lather.

- The tablet is placed back on its soap tray, ensuring that the opposite face is

uppermost (e.g., the unmarked face).

The above procedure is carried out six times per day for four 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 afternoon of the 5 ^th day, the samples are turned so that both sides of the tablet is allowed to 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) X 100

initial weight

Testing the volume of lather

The amount (volume) of lather generated by a shaped solid cleansing composition is an important parameter affecting consumer preference. The lather volume test described herein gives a measure of lather generation under standard conditions, thus allowing objective comparison of different soap formulations.

Lather is generated by trained technicians using a standardised method. The lather is collected and its volume measured.

Washing up bowl 1 per operator capacity 10 litres Soap drainer dishes 1 per sample Surgeons' rubber gloves Tall cylindrical glass beaker 400 ml_, 25 ml_ graduated (Pyrex® nQ1000) Thermometer glass rod. Tablet pre-treatment:

Wearing the surgeon's glove previously washed in plain soap, wash down all test tablets at least 10 minutes before starting the test sequence. This is best done by twisting them about 20 times through 180° under running water. Place about 5 litres of water of known hardness and at a specified temperature in a bowl. Change the water after each bar of soap has been tested. Take up the tablet, dip it in the water and remove it. Twist the tablet 15 times, between the hands, through 180°. Place the tablet on the soap dish. The lather is generated by the soap remaining on the gloves.

Stage 1 : Rub one hand over the other hand (two hands on same direction) 10 times in the same way.

Stage 2: Grip the right hand with the left, or vice versa, and force the lather to the tips of the fingers. This operation is repeated five times. Repeat Stages 1 and 2. Place the lather in the beaker. Repeat the whole procedure of lather generation from paragraph iii, twice more, combining all the lather in the beaker. Stir the combined lather gently to release large pockets of air. Read and record the volume.

Data analysis is carried out by 2-way analysis of variance, followed by Turkey's Test.

Assessment results are summarised in Table 4.

TABLE 4

The data indicates that even though E1 and E2 contain higher amount of water, the bars perform at least equal to Control bars with respect to lather volume, mush amount and rate of average wear,