Field of the invention

The present invention relates to a laundry composition in a solid shaped form for direct application to fabric. More particularly, it relates to soap composition in the form of bars or tablets which are suitable for use in the handwashing of fabrics.

Background of the invention

Laundry detergent compositions, such as laundry bars, powders, gels and tablets, are used for hand laundering clothes at ambient temperatures. Laundry bars designed for hand-washing fabrics are formulated to provide effective cleaning of fabrics, acceptable lather characteristics, slow wear rates, good hardness, durability and low smear properties. Laundry bar compositions may include soap, synthetic detergent or a combination of soap and synthetic detergent as the main detersive surfactant. In some regions of the world soap-based laundry bars are preferred for laundering fabrics.

Soap is typically produced from animal and vegetable-based fats and oils as the raw materials which contain relatively high level of water associated with it. Laundry bars which incorporate soap as the sole or predominant surfactant in them typically also contain a relatively high level of water. This high levels of water in laundry soap bars makes such laundry bars soft and difficult to use.

Consumers of laundry bars generally desire a firm bar to permit the bar to be rubbed vigorously across the surface of clothes without excessively abrading the material from the surface of the bar. Soap bars employed for the purpose of laundering fabrics require to be firmer than those used for cosmetic purpose in order to effectively remove soil from fabrics during the scrubbing action using the bar.

To achieve desired firmness, the laundry soap bar manufacturers dry the excess water from the soap raw material, which is costly, and often less efficient technique. Drying of excess water from the finished laundry bars is time consuming and costly when bars are manufactured on a large scale. As soap-based laundry compositions are typically employed in emerging world economies, reducing cost becomes a significant consideration in formulating these bars.

Typically, laundry soap bar compositions include soap at a level of 60 wt.% or more to provide a suitable combination of cleaning performance, foaming and firmness. Soaps are derived from triglycerides which are becoming increasingly expensive.

Consequently, manufacturer have sought ways to use soaps more efficiently in soap bars.

It is particularly desirable to reduce the soap content of laundry soap bar compositions without altering the cleaning performance, firmness and sensorial properties. Several different technologies have been tried in the past to lower soap content in a laundry soap bar composition.

One strategy towards reducing overall soap content would be to increase the water content. However, attempts at increasing the water content in the soap bar has resulted in bars which are soft and have a sticky texture and the composition is extremely difficult to be processed into bars using conventional equipment. In general, increasing the water content of laundry bars has the consequence that the bars tend to shrink on storage, leading to stress cracking.

Another possible way of reducing soap content is to include fillers. However, use of soluble and insoluble fillers in the laundry soap bar composition may cause several adverse effects. Use of soluble fillers (eg. polyols) tends to negatively impact lather, bar hardness and increases rate of wear. On the other hand, use of insoluble fillers tends to increase the viscosity of the composition leading to processing difficulties.

When soap content is minimized, use of synthetic (e.g., anionic) surfactant is yet another way to make up for the loss in the bar user properties and lathering.

One such laundry soap bar composition is disclosed in WO 96/35772 A1 (P&G, 1996) in which the bar composition includes a combination of soap and synthetic anionic surfactant to provide desired bar firmness. Alternately, soap bar composition with lower soap content may be prepared by incorporating a structuring system in laundry soap bars.

One such example includes the laundry bar composition disclosed in WO 2008/071561 A1 (Unilever) which discloses a low TFM soap bar which has improved firmness. The soap bar composition includes 30 wt.% to 70 wt.% soap and a structuring system prepared by mixing soap with sodium silicate and water-soluble calcium compound to produce calcium silicate formed in-situ.

IN 187129 (Hindustan Lever Ltd. 1997) discloses to a detergent bar for laundry washing with lowered soap content, having alumino-silicate structuring agent formed in-situ. It discloses that the structuring agent alumino-silicate is formed in-situ from soluble aluminum salt and a silicate salt or sodium aluminate and alkaline silicate.

Although several approaches at providing laundry soap bars with lower soap content which provide desired firmness, good cleaning performance while maintaining desired sensorial properties have been known, it is still desired to provide improved laundry soap bar composition with high water content which is maintained in the finished bar composition and which also has good firmness and cleaning performance when such compositions have lower soap content and with minimal levels or no synthetic surfactant, while maintaining good user properties.

It is thus an object of the present invention to provide a laundry soap bar composition with lower soap content while maintaining good user properties and bar firmness.

It is a further object of the subject invention to provide laundry soap bar composition with good cleaning performance.

It is yet another object of the invention to provide a laundry soap bar composition having lower soap content and with higher water content in which the relatively high- water content is maintained in the finished bar composition and the bar composition retains its shape and integrity and is suitable for consumer use. It is also an object of the present invention to provide a process for preparing a laundry soap bar composition with lower soap content and higher water levels.

It is another object of the present invention to provide for a low TFM laundry soap bar composition which in addition to being conveniently extrudable and stamp-able does not compromise on the bar integrity and delivers the desired sensorial properties like high lather and low mush.

Summary of the invention

The present inventors have found that by incorporating a balanced combination of silica gel preferably generated in-situ and a silicate structuring agent selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof, it is possible to provide a laundry soap bar composition with lower fatty acid soap content and higher water content while still maintaining satisfactory bar hardness and sensorial properties. The laundry soap bar composition also provides good cleaning performance, good foam performance and good fragrance delivery.

According to a first aspect, present invention discloses a laundry soap bar composition comprising: i) 30 wt.% to 55 wt.% fatty acid soap; ii) 10 wt.% to 15 wt.% silica gel having a specific surface area of at least 25 m ² /g; iii) a silicate structuring agent wherein the silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof; and, iv) 30 wt.% to 45 wt.% water.

According to the second aspect of the present invention disclosed is a process for preparing the laundry soap bar composition of the first aspect comprising the steps of: i) neutralizing one or more fatty acid or fat with an alkaline neutralizing agent to obtain a fatty acid soap; ii) acidulating an alkaline silicate salt with an acid to form in-situ silica gel; iii) adding a silicate structuring agent and water to form a dough mass; and, iv) converting the resulting dough mass into a shaped laundry soap bar composition. wherein the laundry soap bar composition comprises from 30 wt.% to 55 wt.% fatty acid soap and 30 wt.% to 45 wt.% water.

According to a third aspect, the present invention discloses the use of a silica gel having a specific surface area of at least 25 m ² /g, silicate structuring agent wherein the silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof and 30 wt.% to 45 wt.% water in a laundry soap bar composition having 30 wt.% to 55 wt.% fatty acid soap for providing improved bar properties.

According to a further aspect, the present invention discloses the use of a silica gel having a specific surface area of at least 25 m ² /g, silicate structuring agent selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof and 30 wt.% to 45 wt.% water in a laundry soap bar composition having 30 wt.% to 55 wt.% fatty acid soap for providing improved fragrance delivery.

According to a yet another aspect, the present invention discloses the use of a silica gel having a specific surface area of at least 25 m ² /g, silicate structuring agent wherein the silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof and 30 wt.% to 45 wt.% water in a laundry soap bar composition having 30 wt.% to 55 wt.% fatty acid soap for providing improved lather characteristics.

By the term “bar” it is meant that the laundry composition in in the form of a shaped solid. The soap bar is in solid form which retains its shape after manufacture and during transport and storage. The term bar also includes other shaped laundry bar composition such as cake form or tablet form. The shaped solid is preferably formed either by a casting route or an extrusion route, more preferably the extrusion route.

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. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized 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 and claims 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.

Detailed description of the invention

According to a first aspect of the present invention disclosed is a laundry soap bar composition comprising 30 wt.% to 55 wt.% fatty acid soap, a silicate structuring agent; a silica gel; and 15 wt.% to 45 wt.% water.

Fatty acid soap

According to the first aspect of the present invention disclosed laundry soap bar composition includes 30 wt.% to 55 wt.% fatty acid soap.

The term fatty acid soap denotes the salts of the carboxylic fatty acids. This class of compound includes ordinary alkali metal soaps such as sodium, potassium and ammonium salts of carboxylic fatty acids. Soaps can be made by direct saponification of fats and oils or by the neutralization of free fatty acids. Particularly useful are the sodium and potassium salts of the mixtures of fatty acids derived from coconut oil, tallow, fish oil, soya oil, palm oil e.g. sodium and potassium tallow soap. In general, sodium soaps are used in the compositions of the invention, but the soap may also be selected from 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 from 8 to 22 carbon atoms, preferably from 10 to 18 carbon atoms. They may be described as alkali metal carboxylates of saturated or unsaturated hydrocarbons having from 8 to 22 carbon atoms. The fatty acids may be synthetically prepared example by oxidation of petroleum stocks or by the Fischer-Tropsch process.

The fatty acid soap according to the present invention preferably includes lauric soap. The lauric soap preferably include fatty acid soap having 8 carbon atoms to 14 carbon atoms. Preferably these encompass soaps which are derived predominantly from C ₈ to C12 saturated fatty acid, i.e. lauric acid, but can contain minor amounts of soaps derived from shorter chain fatty acids, e.g., Cw. Preferably lauric soaps are generally derived in practice from the hydrolysis of nut oils such as coconut oil and palm kernel oil. Lauric soap having short chain fatty acid molecules with 8 carbon atoms to 12 carbon atoms lather quickly. They are the saponification products of fatty acids or lauric oils (that is C ₈ to C12 palm kernel oil, coconut oil) with selected alkali (Na ⁺ and/or K ⁺ ). The lauric soaps are predominantly saturated.

The fatty acid soap may also include soaps with carbon chain length of Cu or greater. The long chain fatty acid soap molecules preferably include fatty acid soap having 14 carbon atoms to 22 carbon atoms, still preferably from 16 to 22 carbon atoms, further preferably from 16 to 20 carbon atoms. They may be classified as follows:

"Stearics" soaps which encompass soaps which are derived predominantly from C to Ci ₈ saturated fatty acid, i.e. palmitic and stearic acid but can contain minor level of saturated soaps derived from longer chain fatty acids, e.g., C ₂ o. Stearics soaps are generally derived in practice from triglyceride oils such as tallow, palm oil and palm stearin.

“Oleics" soaps which encompass soaps which are derived from unsaturated fatty acids including predominantly oleic acid (Ci _8: i), linoeleic acid( (Ci _8:2 ), myristoleic acid (C141) and palmitoleic acid (Cwi) 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 of various triglyceride oils and fats such as tallow, palm oil, sunflower seed oil and soybean oil. Fatty acid soaps with C to C22 carbon atoms, more preferably the saturated soaps with C14 to C22 carbon atoms is insoluble in water and help maintain the structure of the bar, but the long chain fatty acid soap do not readily generate lather. Long chain fatty acid soap molecules are the saponification products (typically with sodium counterions) of primarily non-lauric oils (such as stearic and oleics) with sodium hydroxide. By non- lauric it is meant to include long saturated (C16 and Cu) and unsaturated (C181 , C182, C183) fatty acids found in palm oil, palm oil stearine, tallow.

In the laundry soap bar composition according to the present invention, preferably the weight ratio between the long chain soap molecules having Cu or greater number of carbon atoms to the short chain soap molecules having C12 or lesser number of carbon atoms is from 85:15 to 98:2, preferably the ratio is 80:20 to 90:10.

Preferably the laundry soap bar composition according to the present invention comprises from 30 wt.% to 55 wt.% fatty acid soap. Preferably the laundry soap bar composition comprises at least 32 wt.%, preferably at least 33 wt.%, still preferably at least 34 wt.% and most preferably at least 35 wt.%, but typically not more than 50 wt.%, still preferably not more than 45 wt.%, still further preferably not more than 43 wt.%, and most preferably not more than 40 wt.% fatty acid soap in the laundry soap bar composition.

Silica gel

According to a first aspect of the present invention disclosed is a laundry soap bar composition having silica gel. By the term “silica gel” it is herein meant to include an amorphous form of silica having a specific surface of at least 25 m ² /gm.

Silica gel may be pre-formed silica gel, or the generation of silica gel may be in-situ during the manufacturing process. It is understood that silica gel is a porous form of silicon dioxide. Silica gels are amorphous solids. The partial dipole in the Si-0 bond allows silica gel to hydrogen bond with water molecules while the porous nature and large surface area of silica gel enables the material to readily adsorb water. In accordance with embodiments of the present invention, metal silicates can form silica gel in-situ during the manufacture of laundry soap bar composition. More preferably the silica gel has a specific surface area in the range from 100 m ² /g to 1000 m ² /gm, more preferably 300 to 750 m ² /g. Still preferably the specific surface area is at least 200 m ² /g, preferably at least 300 m ² /g, still preferably at least 400 m ² /g, still more preferably 500 m ² /g and most preferably at least 700 m ² /g, but typically not more than 950 m ² /g, still preferably not more than 900 m ² /g, still further preferably not more than 850 m ² /g, still more preferably not more than 800 m ² /g and most preferably not more than 750 m ² /g. The specific surface area of the silica gel may be determined by known method to determine the specific surface area such as BET (Brunauer-Emmett-Teller) nitrogen absorption method.

Preferably the silica gel is formed in-situ by acidulation of an alkaline metal silicate salt. Any metal silicate that can convert to silica gel is suitable for the present invention. For example, alkali metal silicates such as sodium silicate, potassium silicate, lithium silicate, or any combination thereof are suitable for the present invention. The alkaline metal silicate can be added by itself (in a solid form) or in a wet form, such as a slurry or solution. The alkaline metal silicate component is preferably sodium silicate or alternatively, sodium silicate in combination with another metal silicate. Sodium silicate is a basic inorganic compound which is readily soluble in water, sodium silicate is often sold as an aqueous solution.

The sodium silicates are frequently referred to or characterized by their alkaline oxide to silica ratio, such as their ratio of Na2O to SiC>2. Orthosilicate, having the formula Na ₄ SiO ₄ , is the most alkaline having a Na ₂ O to SiO ₂ ratio of 2:1. Metasilicate, Na ₂ SiO ₃ has a Na ₂ O to SiO ₂ ratio of 1 :1. The so-called “water glass” silicates, which are soluble in water, have a Na ₂ O to SiO ₂ ratio in the range of about 1 : 1 .5 to 1 :3.8. Preferably the Na2O to SiO2 ratio used in the present invention is from 1 :1 .5 to 1 :3.0. In preparing the silica gel in accordance with this invention commercially available alkali metal silicates may be employed in which the ratio of sodium oxide to silicon dioxide may range from 1 :0.48 to 1 :3.75, preferably the range from 1 :1 .5 to 1 .3.75 and more preferably 1 :3.0 to 1 :3.5. Examples of silicates which may be used for purposes of this invention are sodium silicate (Na ₂ O to SiO ₂ , ratio of 1 :3.0), sodium ortho silicate (Na ₂ O to SiO ₂ , ratio of 2:1) and potassium silicate (K ₂ O to SiO ₂ , ratio of 1 :2.50). Preferably the alkali metal silicate is alkaline.

Preferably the generation of silica gel is in-situ by acidulation of alkaline silicate with a reactant selected from the class consisting of carbon dioxide, alkali metal bicarbonates or mixtures thereof. The carbon dioxide gas employed may be full strength or may be diluted with air or other inert gases, example such as the dilute carbon dioxide gas produced by the combustion of hydrocarbons such as propane or butane. Preferably the bicarbonate salt is an alkali metal salt, more preferably sodium bicarbonate. Preferably the alkaline silicate is water-soluble or water dispersible. Preferably the silica gel is formed in-situ by acidulating an alkaline silicate salt with bicarbonate salt. Preferably the alkaline silicate salt is sodium silicate, and the bicarbonate salt is sodium bicarbonate. Preferably the weight ratio of sodium bicarbonate to sodium silicate is in a range from 1 :5 to 1 :7.

It is within the scope of the present invention to form in-situ silica gel by reacting the water soluble or water-dispersible silicates with organic acids. Preferably the organic acids are anionic, detergent-forming acids. Non-limiting examples of the acids are saturated and unsaturated fatty acids, having a carbon chain containing from about 8 to 22 carbon atoms, exemplified by lauric, stearyl, oleic and linoleic acid. Non-soap detergent forming acids such as alkyl aryl sulfonic acids, wherein the alkyl group (both linear and branched) has a carbon chain length of at least 4 carbon atoms, preferably from 10 to 12 carbon atoms in the chain which are capable of forming water-soluble non-soap detergents upon neutralization wit alkali such as sodium or potassium hydroxide.

The degree of silicate polymerization to silica gel is preferably 50% or more (i.e., a ratio of 1 :1), more preferably 60% or more, further preferably 70% or more, still further preferably 80% or more, still further preferably 90% or more, further more preferably 95% or more, and most preferably 99%, or more. Preferably the alkali metal silicate is fully polymerized to silica gel. Preferably the silica gel has a pore volume from 0.4 to 4.4 mL/gm preferably 0.5 to 1.4 mL/g. The pore volume may be determined using mercury porosimeter and measured as the volume of pores of diameter greater than 25 millimicrons.

Preferably the laundry soap bar composition according to the present invention comprises from 10 wt.% to 15 wt.% silica gel. Preferably the laundry soap bar composition comprises at least 10 wt.%, preferably at least 10.5 wt.%, still preferably at least 11 wt.% and most preferably at least 11 .5 wt.%, but typically not more than 15 wt.%, still preferably not more than 14.5 wt.%, still further preferably not more than 14 wt.%, and most preferably not more than 13 wt.% silica gel in the laundry soap bar composition.

Silicate structuring agent

According to the first aspect of the present invention disclosed laundry soap bar composition includes a silicate structuring agent. The silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof.

The silicate structuring agent is preferably pre-formed or is present by in-situ generation during the process of preparing the laundry soap bar composition. The silicate structuring agent is preferably formed in-situ.

Preferably the composition includes a further silicate structuring agent selected from sodium silicate, potassium silicate, magnesium silicate or mixtures thereof. Most preferably the further silicate structuring agent is sodium silicate, magnesium silicate, or mixtures thereof.

Most preferably the further silicate structuring agent is sodium silicate. Sodium silicate includes compounds having the formula (Na2O) _x SiO2. The weight ratio of Na2O to SiC>2 could vary from 1 :1 .5 to 1 .3.8. Grades of sodium silicate with ratio from about 1 : 2 to 1 :2.85 are called alkaline silicate and with ratios from 1 :2.85 to about 1 .3.75 are called neutral silicate. Forms of sodium silicate that are available include sodium metasilicate (Na2SiC>3), sodium pyrosilicate (Na6Si2O?), and sodium orthosilicate (Na4SiO4) It is preferred as per this invention that alkaline sodium silicate is used. Especially preferred is sodium silicate with a ratio of Na ₂ O to SiO ₂ of 1 :2. The sodium silicate is generally available as a solution in water having a solid content of 40 % to 50%, the balance being water. It is preferred that the soap bar comprises from 0.01 wt.% to 20 wt.% sodium silicate, more preferably from 2 wt.% to 20 wt.%, still more preferably from 2 wt.% to 15 wt.%, further preferably 3 wt.% to 10 wt.% on dry weight basis.

The further silicate structuring agent may also be a magnesium silicate, preferably a hydrated magnesium silicate preferably in an amount from 0 wt.% to 10 wt.% preferably 1 wt.% to 5 wt.%, still preferably 1 wt.% to 3 wt.% in the composition. Preferably the further silicate structuring agent is a mixture of sodium silicate and hydrated magnesium silicate.

The further silicate structuring agent may also be selected from in-situ formed borosilicate, boro-aluminosilicate or combinations thereof. The in-situ generation of borosilicate structuring agent may be prepared as discussed in WO 02/46341 A2 (Unilever, 2002). The in-situ generation of aluminosilicate may be prepared as described in GB-A-209 013 and WO 03/040283 A1 (Unilever, 2003).

Preferably the silicate structuring agent is selected from calcium silicate, silicate, aluminium silicate, sodium aluminosilicate combinations thereof.

Preferably the laundry soap bar composition according to the present invention comprises from 1 wt.% to 30 wt.% silicate structuring agent, preferably the laundry soap bar composition comprises from 1 wt.% to 10 wt.% silicate structuring agent. Preferably the laundry soap bar composition comprises at least 2 wt.%, preferably at least 5 wt.%, still preferably at least 8 wt.% and most preferably at least 10 wt.%, but typically not more than 25 wt.%, still preferably not more than 20 wt.%, still further preferably not more than 18 wt.%, and most preferably not more than 15 wt.% silicate structuring agent in the laundry soap bar composition.

Water

According to the first aspect, disclosed laundry soap bar composition includes from 30 wt.% to 45 wt.% water, preferably from 33 wt.% to 40 wt.%. The soap bar composition of the invention is capable of stably retaining high amount of water in the range from 30 wt.% to 40 wt.%, still preferably at least 32 wt.%, further preferably at least 33 wt.%, still more preferably at least 34 wt.% furthermore preferably at least 35 wt.% but the amount of water in the laundry soap bar composition is preferably not more than 38 wt.%, still preferably not more than 36 wt.%, most preferably not more than 35.5 wt.%.

The preferred water content levels quoted above refers to freshly made laundry soap bars where water content is measured within 8 hours. This quantity is designated as the "initial water level" or "initial water content" of the freshly prepared laundry soap bar composition and is also known as the "nominal water content" or "nominal water level" of the composition. The water present in the bar at room temperature (approximately 25°C) includes "free" water and bound water of crystallisation.

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 and 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 differ from the nominal water content of the bar immediately after manufacture.

Optional ingredients

Laundry soap bar composition:

In addition to the components described above, the laundry soap bar composition of the present invention can contain a wide variety of optional ingredients. These optional ingredients include but are not limited to, synthetic surfactants, water-soluble fillers, water-insoluble fillers, organic and inorganic adjunct materials, alkaline materials, processing aids, minor additives, dyes, electrolytes, chelating agents.

Synthetic surfactants:

Optionally the laundry soap bar composition of the present invention includes a synthetic surfactant. Preferably the synthetic surfactant is a non-soap anionic surfactant including but not limited to alkali metal and alkaline earth metal salts of higher alkyl aryl sulphonate surfactant, higher alkyl sulphate surfactant, higher fatty acid monoglyceride sulphate surfactant or mixtures thereof. Examples of mild synthetic surfactants include alkyl glyceryl ether sulfonates (AGS), anionic acyl sarcosinates, methyl acyl taurates, N-acyl glutamates, alkyl glucosides, acyl isethionates, alkyl sulfosuccinates, alkyl phosphate esters, ethoxylated alkyl phosphate esters, ethoxylated alkyl alcohols, alkyl sulfates, alkyl ether sulfates, methyl glucose esters, protein condensates, mixtures of alkyl ether sulfates and alkyl amine oxides, betaines, sultaines, and mixtures thereof. Included in the synthetic surfactants are the alkyl ether sulfates with from about 1 to about 12 ethoxy groups, especially ammonium and sodium lauryl ether sulfates. Alkyl chain lengths for these surfactants are about Csto C22, preferably Cwto Cis.The alkyl portion of such synthetic surfactants are often derived from natural sources of fatty acids which are the same as for the fatty acid soaps.

The composition of the present invention includes less than 5 wt.%, preferably less than 3 wt.%, still preferably less than 1 wt.%, still more preferably less than 0.1 wt.% of the synthetic surfactant. Preferably the composition of the present invention is substantially free of the synthetic surfactant. By “substantially free” it is meant that there is no deliberately added synthetic surfactant in the laundry soap bar composition of the present invention. Preferably the composition of the present invention comprises less than 5 wt.%, preferably less than 1 wt.% non-soap anionic surfactant, most preferably the soap bar composition is substantially free of the non-soap anionic surfactant. By “substantially free” it is meant that there is no deliberately added non- soap anionic surfactant in the soap bar composition of the present invention.

Soluble fillers:

Optionally the composition of the present invention includes a soluble filler. The soluble fillers consist of a polyhydric alcohol (also called 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 but not limited to relatively low molecular weight short chain polyhydroxy compounds such as glycerol and propylene glycol; sugars such as sorbitol, mannitol, sucrose and glucose; modified carbohydrates such as hydrolyzed starch, dextrin and maltodextrin, and polymeric synthetic polyols such as polyalkylene glycols, for example polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG). Especially preferred polyols are glycerol, sorbitol, mannitol and their mixtures. Most preferred polyol is glycerol. Preferably the soap bar composition of the present invention comprises from 0 wt.% to 10 wt.%, preferably 0.5 wt.% to 7.5 wt.%, still preferably from 1 wt.% to 7 wt.%, most preferably less than 6 wt.% soluble fillers by weight of the composition. Preferably the soap bar composition includes from 0.5 to 5.5 wt.% polyol, preferably glycerol.

Organic and inorganic adjunct materials:

Non-limiting examples of organic adjunct material may include suitable starchy materials such as natural starch (from corn, wheat, rice, potato, tapioca and the like), pre-gelatinized starch, various 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. The organic adjunct material may also be particulate materials which include insoluble polysaccharides such as crosslinked or insolubilized starch and cellulose, synthetic polymers or mixtures thereof. The composition of the present invention includes less than 5 wt.%, preferably less than 3 wt.%, still preferably less than 1 wt.%, still more preferably less than 0.1 wt.% of the organic adjunct materials. Preferably the composition of the present invention is substantially free of the water-soluble organic adjunct material. By “substantially free” it is meant that there is no deliberately added organic adjunct material in the laundry soap bar composition of the present invention.

Non-limiting examples of the inorganic adjunct material includes particulate zeolite, calcite, dolomites, feldspars, silica, other carbonates, bicarbonates, and talc. Most preferred are calcium carbonate (as calcite), kaolin, silica, talc. Talc is a magnesium silicate mineral, with a sheet silicate structure and a composition Mg3Si ₄ (OH) ₂ 2 and may be available in the hydrated form. Examples of other optional insoluble inorganic particulate adjunct material includes aluminates, phosphates, insoluble sulfates, borates, sodium carbonate, calcium carbonate, magnesium sulphate, clay and combinations thereof. Preferably the composition is substantially free of starch, talc and clay such as kaolin.

The composition of the present invention includes from 0 wt.% to 12 wt.% of the inorganic adjunct material, preferably 2 wt.% to 10 wt.% of the inorganic adjunct material by weight in the laundry soap bar composition. Still preferably the inorganic adjunct material is less than 5 wt.% of the composition.

Alkaline neutralizing agent:

The alkaline material used for neutralization of the acid precursor of the fatty acid soap active is selected from a silicate, carbonate, hydroxide, alkaline aluminium-containing compounds such as aluminates phosphate and mixtures thereof. Preferably the amounts of alkaline materials used is at least equal to stoichiometric amount required for the neutralization of the precursor of soap active. For the purpose of the invention the especially preferred alkaline material used for the neutralization of the detergent active is sodium silicate, sodium hydroxide, sodium aluminate, sodium carbonate.

Minor additives:

Non-limiting examples of optional minor additives which may be included in the laundry soap bar composition of the present invention includes colorants, preservatives, perfumes, other polymers which may be incorporated up to 10 wt.% in the composition. Perfumes may be optionally present at a level of from about 0.1 wt.% to 1.5 wt.% of the composition. Any perfume known to the person skilled in the art may be used and not limiting to perfume oil, encapsulated perfume oil.

Electrolytes:

Optionally the composition of the present invention includes electrolytes. Electrolytes as per this invention include compounds that substantially dissociate into ions in water. Electrolytes as per this invention are not ionic surfactants. Suitable electrolytes for inclusion in the soap making process are alkali metal salts. Preferred alkali metal salts for inclusion in the composition of the invention include sodium sulfate, sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium sulfate, sodium carbonate and other mono or di or tri salts of alkaline earth metals, more preferred electrolytes are sodium chloride, sodium sulfate, sodium citrate, potassium chloride and especially preferred electrolyte is sodium carbonate, sodium chloride, sodium citrate or sodium sulphate or a combination thereof. Preferably the electrolyte is sodium carbonate or sodium chloride. For the avoidance of doubt, it is clarified that the electrolyte is a non-soap material. The composition of the present invention includes from 0.5 wt.% to 5 wt.%, preferably 0.5 wt.% to 3 wt.%, more preferably 1 wt.% to 2.5 wt.% electrolytes by weight of the composition. More preferably the composition of the present invention has less than 4.2 wt.% electrolytes, still preferably less than 3 wt.% further preferably less than 2 wt.% electrolytes. Most preferably the composition of the present invention does not require any electrolytes.

Chelating agents:

Optionally the composition of the present invention includes a chelating agent, the chelating agents may be selected from but not limited to ethylene diamine tetra acetic acid (EDTA), ethylene hydroxy diphosphonic acid (EHDP) or mixtures thereof. The chelating agent is preferably present in an amount ranging from 0.01 wt.% to 1 wt.%. Non-phosphate chelating agents like methylglycinediacetic acid and salts thereof are also preferred.

Polymers:

Optionally the composition of the present invention includes polymers, preferably cationic polymers selected from the group of cationic polysaccharides, cationic copolymers of saccharides and synthetic cationic monomers, homopolymers of dimethyldiallyl ammonium chloride, copolymers of dimethyldiallyl ammonium chloride and acrylamide, quaternized vinylpyrrolidone acrylate or methacrylate copolymers of amino-alcohol, cationic homopolymers and copolymers derived from acrylic acid and/or methacrylic acid, polyalkylene imines and ethoxy polyalkylene imines and mixtures thereof. The cationic polymer includes naturally and synthetically derived cationic polymers. Preferably the cationic polymer is a polymer of dimethyldiallyl ammonium chloride (DMDAAC) which includes both the homopolymers and copolymers dimethyldiallyl ammonium chloride (DMDAAC) or mixtures thereof. Preferably the copolymers of dimethyldiallyl ammonium chloride and acrylamide. Non-limiting examples of polymers suitable for the laundry soap bar composition of the present invention includes Merquat S and Merquat 550 and Merquat 100 by Lubrizol., Inc. and acrylic acid copolymers such as Noverite™ GP250. The laundry soap bar composition according to the present invention comprises from 0.01 wt.% to 5 wt.% by weight of cationic polymer.

Personal wash soap bar composition:

The soap bar composition according to the present invention may be a personal wash soap bar composition. In addition to the above disclosed optional ingredients the composition for personal wash soap bar composition may include an opacifier, when opacifiers are present, the soap composition in a bar form is generally opaque. Examples of opacifiers include titanium dioxide, zinc oxide and the like. A particularly preferred opacifier that can be employed when an opaque soap composition is desired is ethylene glycol mono- or di-stearate, for example in the form of a 20% solution in sodium lauryl ether sulphate. An alternative opacifying agent is zinc stearate.

The pH of preferred personal wash soap composition of the invention is from 8 to 11 , more preferably 9 to 11 .

A preferred composition may additionally include up to 30 wt.% benefit agents. Preferred benefit agents include moisturizers, emollients, sunscreens, skin lightening agents and anti-ageing compounds. The agents may be added at an appropriate step during the process of making the bars. Some benefit agents may be introduced as macro domains.

Soap bar composition

The laundry soap bar composition according to the present invention is a low TFM soap bar composition having a high-water content. The soap bar composition retains the high-water content in the bar during storage and delivers excellent feel, hardness, cleaning and lathering properties. Preferably the laundry soap bar composition of the present invention is prepared in the form of a bar by any conventional methods which includes frame cooling method (cast bar route) or milled and plodded route (extrusion route). Preferably the composition is an extruded laundry soap bar composition with a high level of water which is still easy to extrude and stamp. pH:

The laundry soap bar composition according to the present invention has a pH from 9 to 13, preferably from 9 to 11 , more preferably from 9.5 to 10.5 when measured using a 4 wt.% solution in deionised water at 25°C. A bar composition according to the first aspect wherein the composition has a pH when measured in a 4% solution with distilled water at 25°C in the range from 9 to 13.

Total fatty matter:

The term “Total Fatty Matter” or TFM is used to denote the percentage by weight of fatty acid and triglyceride residues present in soap excluding the accompanying cations. The soap bar composition according to the present invention has a TFM in the range from 30% to 55%, more preferably the TFM is in the range from 30% to 50%, further preferably 35% to 50%, still preferably from 40% to 55%.

Shape:

The laundry soap bar composition according to the present invention may take any shape. The bars according to the present invention have low rates of water loss, by which it is meant the bar typically has excellent water retention and relatively low amounts of shrinkage both upon stamping and upon storage and use.

Hardness:

The laundry soap bar composition of the present invention has a hardness expressed as Kg force required to move the probe for a prespecified distance. The hardness is measured by a Taxtmeter. The bar whose hardness is to be measured is placed onto the testing platform. Then the probe of the measuring instrument is placed close to surface of the bar composition without touching it. Next the instrument is started, and the force required to reach a preset target distance is measured and the observation is recorded. Preferably the instrument reading is from 1300 to 3000 force (RT) in Kg at the target penetration distance of around 10 to 40. Density:

The laundry soap bar composition according to the present invention has a density ranging from 0.8 to 1.3, preferably from 1.01 to 1.15 grams per cubic metre. One significant advantage of the present invention is that it allows for incorporation of water without significantly affecting the bar density. The bar density of the present invention is similar to the density of a conventional laundry soap bar composition having a higher amount of fatty acid soap.

Iodine Value:

It is preferred that the laundry soap composition according to the present invention includes soap having an Iodine Value in the range of 30 to 70, more preferably in the range of 30 to 60 and most preferably in the range of 35 to 45. The Iodine values of the composition of the present invention is measured by Wijs 20 Method, The American Oil Chemists' Society (AOCS) Official Method Cd 1-25, Revised 1988.)

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. The more iodine is attached, the higher is the iodine value.

Process for preparing the laundry soap bar composition

According to the second aspect of the present invention disclosed is a process for preparing a laundry soap bar composition of the first aspect comprising the steps of: i) neutralizing one or more fatty acid or fat with an alkaline neutralizing agent to obtain fatty acid soap; ii) acidulating an alkaline silicate salt with an acid to form in-situ silica gel; iii) adding a silicate structuring agent and water to form a dough mass; and, iv) converting the resulting dough mass into a shaped laundry soap bar composition. wherein the laundry soap bar composition has from 30 wt.% to 55 wt.% fatty acid soap and from 30 wt.% to 45 wt.% water and wherein the silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof.

The laundry soap bar composition according to the present invention may be produced on a commercial scale by any of the processes known to a person skilled in in the art. Preferably the soap bar composition of the present invention is prepared using the extrusion route. Preferably using a Sigma mixer process (Post dosing route) or a crutcher/Mazzonni/spray drier process.

Neutralizing fatty acid or fats to form fatty acid soap:

The fatty acids used for neutralization may be of a single type or a mixture of different fatty acids. Preferably the fatty acids are a mixture of different fatty acids. The fats used are a combination of those which provide the preferred amounts of short chain fatty molecules and long chain fatty molecules. As used herein the term fats also includes oils as is generally known to the person skilled in the art. The neutralization step is achieved by using an alkaline neutralizing agent preferably selected from silicate, carbonate, hydroxide, alkaline aluminium-containing material such as aluminate, a phosphate or mixtures thereof to form fatty acid soap, preferably the alkaline neutralizing agent is a hydroxide or silicate. Still preferably the alkaline neutralizing agent used for neutralization is sodium hydroxide or potassium hydroxide.

Adding a silicate structuring agent:

The silicate structuring agent may be pre-formed or generated in-situ. More preferably the present invention relates to a process to prepare a soap bar composition according to the present invention comprising the step of in-situ generation of silicate structuring agent before or after the saponification step (step i). When the silicate structuring agent is calcium silicate, it is preferably generated in-situ by mixing a sparingly water-soluble calcium compound with the alkaline metal silicate to form calcium silicate in-situ. The alkaline metal silicate is preferably sodium silicate. The sparingly water-soluble calcium compound has a water solubility less than 2 g/litre at a temperature of 25°C. The source of calcium is preferably chosen from calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride, calcium sulphate and combinations thereof., more preferably the calcium compound is calcium hydroxide, calcium sulphate or mixtures thereof. Preferably the sparingly water-soluble calcium compound is chosen from calcium hydroxide or calcium sulphate, most preferably calcium hydroxide.

Preferably the process may include incorporation of a further silicate structuring agent. By further silicate structuring agent it refers to those additional structuring agents which are included in addition to the calcium silicate, aluminium silicate and sodium aluminosilicate. When the further silicate structuring agent is magnesium silicate, it is preferably generated in-situ by mixing a source of magnesium with the alkaline metal silicate to form magnesium silicate in-situ. The alkaline metal silicate is preferably sodium silicate. The source of magnesium is a magnesium compound, preferably a sparingly water-soluble magnesium compound has a water solubility less than 2 grams /litre at a temperature of 25°C. The magnesium compound is preferably chosen from chosen from magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium chloride, magnesium sulphate and combinations thereof. Preferably the magnesium compound is magnesium sulphate.

The silicate structuring agent may be aluminium silicate or sodium aluminium silicate (also referred herein as sodium aluminosilicate). Preferably the in-situ generation of aluminium silicate structuring agent is by reacting precursor material selected from (a) soluble aluminium salt and silicate salt or (b) sodium aluminate and alkaline silicate. It is preferably generated in-situ using a source of monomeric aluminium to condense with silicate anion. The preferable source of monomeric aluminium is aluminium sulphate and the generation of the silicate structuring agent is by reacting aluminium sulphate and alkaline sodium silicate to form sodium alumino-silicate into the formulation. The sodium aluminosilicate structuring agent is preferably present in an amount in the range of 0.5 wt.% to 10 wt.% % by weight of the laundry soap bar composition. Preferably the sodium aluminosilicate structuring agent may be formed in- situ by reacting aluminium sulphate with alkali metal carbonate and then alkaline silicate to form sodium aluminosilicate. Preferably the alkali metal carbonate is sodium carbonate, and the alkaline silicate is sodium silicate.

In one embodiment of the invention, during the addition of the silicate structuring agent an excess of the alkaline silicate salt preferably sodium silicate is used during the step of in-situ forming of the silicate structuring agent. This is followed by the silica gel formation in-situ by reacting the remaining alkaline silicate salt with an acid.

The step of neutralizing the fatty acids or fats with an alkaline neutralizing agent may be precede or follow the step of formation of silicate structuring agent. Alternately the preformed soap may be added in the reaction.

Process for preparing in-situ silica gel:

The next step involves acidulating an alkaline silicate salt with an acid to form in-situ silica gel. Preferably the silicate salt is an alkali metal silicate, still preferably sodium silicate and the acid are selected from an inorganic acid (preferably sodium bicarbonate) or organic acid. Preferably the acid is selected from carbon dioxide, organic acid, bicarbonate salt or mixtures thereof. Preferably the bicarbonate salt is sodium bicarbonate. During the step of acidulating, desired concentrations, approximately stoichiometric proportions or slight excess of silicate salt is mixed with the acid. The silicate salt may be added at room temperature or a further step of heating to a temperature within the range of about 45°C to 80°C preferably around 60°C may be performed separately prior to mixing. Preferably the silica gel is formed in-situ by acidulating an alkaline silicate salt with bicarbonate salt. Preferably the alkaline silicate salt is sodium silicate, and the bicarbonate salt is sodium bicarbonate. Preferably the weight ratio of sodium bicarbonate to sodium silicate is in a range from 1 :5 to 1 :7.

Reactants are introduced simultaneously into the reaction vessel at or substantially at atmospheric pressure in a closed vessel condition and the reaction mass is subjected to agitation to uniformly mix. The reaction is allowed to proceed to completion which generally takes around 20 to 30 minutes. After this, the pH of the silica gel is adjusted to the desired levels by the addition of the acid or silicate. The pH of the final dough mass is preferably adjusted to within the range of 7.2 to 10.0 pH.

The preparation of the laundry soap bar composition involves preferably acidulating an excess of alkaline metal silicate with an acid source selected from bicarbonate salt, carbon dioxide or organic acid to form a silica gel. Preferably bicarbonate salt is reacted with an alkaline metal silicate salt to form a silica gel. Preferably the bicarbonate salt is sodium bicarbonate and the alkaline metal silicate salt is sodium silicate.

In one embodiment of the present invention, the step for preparing the laundry soap bar composition involves the step of preparing silica gel in-situ followed by preparing the silicate structuring agent in-situ. In this, the step of acidulating an excess of silicate salt with an acid preferably bicarbonate salt to form in-situ silica gel is followed by the step of contacting the remaining silicate salt with a source of calcium to form calcium silicate or a source of aluminium to form sodium aluminium silicate and waterto provide a dough mass.

Crutcher process:

Step (i): This is one of the well-known process for preparing a laundry soap bar composition. In the crutcher process the step of neutralizing one or more fatty acid or fat with an alkaline neutralizing agent to obtain fatty acid soap is carried out by adding the fatty acid or fats with the preferred ratio ranges of fatty acid with shorter chain length of C12 or below and fatty acids with longer chain length of Cu or higher in the crutcher which is maintained at a temperature of 50°C to 90°C. The oils used may be selected from distilled fatty acids or neutral oils. Next an alkaline neutralizing agent preferably sodium hydroxide or potassium hydroxide is added in an amount required for achieving complete saponification of the fatty acids or fat. Thereafter the temperature of crutcher is increased to a range from 75°C to 120°C. Preferably during the neutralizing step a desired amount of sodium carbonate or sodium chloride solution is added to the neutralizing mixture to obtain the fatty acid soap. Sufficient amounts of free water is added at this stage that is required to provide a final bar composition with 15 wt.% to 45 wt.% water. During the step of neutralizing the fatty acid or soap or immediately thereafter preferably a chelating agent is also added. Non-limiting examples of the chelating agent includes the EHDP and EDTA. step (ii) : The next step involves adding silicate structuring agent or generating silicate structuring in-situ. Preferably the silicate structuring agent is generated in-situ. Preferably the silicate structuring agent is aluminium based. Preferably the aluminium compound (example aluminium sulphate) is added in solid form or in the form of a solution into the crutcher and mixed for 5 to 10 minutes to form a homogeneous mixture with the fatty acid soap. This is followed by the addition of the alkaline silicate salt preferably sodium silicate in an excess to the stochiometric proportions in either ambient temperature conditions or slightly heated before addition to the crutcher. After addition the contents in the crutcher are mixed for around 5 to 10 minutes to completely react the aluminium compound with the alkaline silicate salt to form the silicate structuring agent. As discussed above, preferably the aluminium compound is aluminium sulphate and the alkaline silicate salt is sodium silicate which react to form sodium aluminosilicate. Preferably sodium carbonate is also present in the reaction mixture.

Step (iii): Next step involves acidulating silicate salt with an acid to form the silica gel in-situ. Firstly, an acid preferably sodium bicarbonate is added to the crutcher. The sodium bicarbonate is preferably in the solid form. Thereafter an alkaline silicate salt is added in stoichiometric proportion is added to the mixture to and the mass is mixed for 5 to 10 minutes to form a dough mass with the silica gel formed in-situ. The silica gel holds the excess amount of the water.

Preferably at this stage cationic polymer may added to the dough mass. The addition of desired cationic polymer at the end of the process avoids any complex formation with the anionic soap. Other optional ingredients that may be added to the laundry soap bar includes the electrolytes, dyes, acrylic polymer and colorants, glycerine, chelating agents, soluble fillers, inorganic fillers, alkaline materials (carbonates) are added to form a dough mass. The soap bar composition may preferably include a cationic polymer which is preferably a homopolymer of dimethyldiallyl ammonium chloride. An example of a homopolymer of dimethyldiallyl ammonium chloride (DMDAAC) is that sold under the registered trademark MERQUAT by Lubrizol., Inc. Nonlimiting example includes Merquat™ 100, which is a highly charged cationic dimethyl diallyl ammonium chloride homopolymer. Commercially available example of highly preferred polyquaternium-6 polymer include, for example, that having a tradename Merquat™ 100 available from Lubrizol, has a molecular weight of about 150,000 g/mol. The laundry soap bar composition according to the present invention preferably comprises from 0.01 wt.% to 5 wt.% by weight of cationic polymer. The dough mass at this stage preferably has a moisture content in the range from 30 to 45 wt.%.

Drying: The dough mass formed is preferably dried in the next step. In this drying step, the dough mass is dried to reduce the moisture content of the mix to 30 wt.% to 45 wt.%. The drying step on a commercial basis may be achieved by several different methods. One procedure employs a water-chilled roll in combination with a second feed roll to spread molten, neutralized soap into a thin, uniform layer. The cooled dough mass is then scraped from the roll to form chips and dried to a specific moisture level in a tunnel dryer. A modern technique for the drying is known as spray drying. This process directs molten dough mass to the top of a tower via spray nozzles. The dough mass sprayed to form dried soap mix hardens and then dries in the presence of a current of heated air. Vacuum may be applied to facilitate removal of water, preferably the vacuum of at least 50 mm Hg absolute pressure is provided. The dried soap mix is then extruded to form soap noodles having a water content of 30 wt.% to 45 wt.%. During the drying step generally 4 wt.% to 7 wt.% of the moisture is removed from the dough mass. Preferably the drier is a mazzoni vacuum spray drier which is maintained at a temperature of 85°C to 90°C and the vacuum is maintained at 700 mm Hg and the flow rate is around 3 to 8 tonnes per hour.

Plodding: Preferably after drying, in dough mass is subjected to a plodding step, the dried soap noodles are transferred to a plodder. In the plodding, the step involves converting the soap noodles into a shaped laundry soap bar composition. A conventional plodder is set up with the barrel temperature at about 90°F. (32°C.) and the nose temperature at about 110°F. (43°C.). The plodder used is a dual stage twin screw plodder that allows for a vacuum of about 40 to 65 mm Hg between the two stages. Preferably the perfume may be added at this stage. The soap log extruded from the plodder is typically round or oblong in cross-section and is cut into individual plugs. These plugs are then preferably stamped on a conventional soap stamping apparatus to yield the finished shaped laundry soap bar composition. After stamping the finished soap bar is packaged in desired packaging material which may be selected from laminate, films, paper or combinations thereof.

In a preferred process, prior to plodding the dried soap noodles may be subjected to an amalgamating step carried out in a simple paddle-type mixer where the noodles are added to an amalgamator in which adjunct ingredients such as colorants, preservatives, perfume are added and mixed thoroughly to combine all the ingredients together. Further to this, the mix from the amalgamator may be preferably subjected to a milling step. In the three-roll soap mill the amalgamated mixture is passed through the rolls set at a temperature from 29°C to 41 °C to obtain a homogenous mix, This, is an intimate mixing step where the soap mix is subjected to compression and an intense shearing action. After mixing in the mill the mix is transferred to the plodder.

Sigma mixer (Post dosing) process:

Another well known process for preparing the laundry soap bar composition is known as the post dosing process or a sigma mixer process. The sigma mixer process involves the preparation of the soap noodles using the crutcher or a ploughshear mixer.

The step of neutralizing the fatty acid or the fat with the alkaline neutralizing agent is carried out in the crutcher mixer or a ploughshare mixer where the fatty acids or oils/fats with the desired levels of the fatty acid molecules with shorter chain length of C12 or below and fatty acid molecules with longer chain length of Cu or higher are added along with the alkaline neutralizing agent, preferably sodium hydroxide. This step is continued i.e. sodium hydroxide is added until the fatty acid or fats/oils is completely neutralised. Preferably during the neutralizing step, a desired amount of sodium carbonate or sodium chloride solution is added to the neutralizing mixture to obtain the fatty acid soap. Sufficient amounts of free water is added at this stage that is reguired to provide a final bar composition with 30 wt.% to 45 wt.% water. During the step of neutralizing the fatty acid or soap or immediately thereafter preferably a chelating agent is also added. Non-limiting examples of the chelating agent includes the EHDP and EDTA. In the next step the neutralized fatty acid soap is dried as described above in the crutcher process preferably in a vacuum spray drier. The soap noodles are formed with a moisture content of 30 wt.% to 45 wt.%.

In the next step 30 wt.% to 55 wt.% of dried fatty acid soap and desired levels of water to obtain a final laundry bar composition with 30 wt.% to 45 wt.% water are added into the sigma mixer and the mixer is operated for preferably 10 to 15 minutes to homogenize.

Preferably in the next step the silicate structuring agent and the silica gel is formed as is described above in reference to the crutcher process to form a dough mass. The dough mass is thereafter subjected to a plodding step as described above. The dough mass is subjected to a plodding step, in which the dough mass is transferred to a plodder which involves converting the dough mass into a shaped laundry soap bar composition.

According to a third aspect, the present invention discloses the use of a silica gel, silicate structuring agent wherein the silicate structuring agent is selected from calcium silicate, aluminium silicate, sodium aluminosilicate or mixtures thereof and 30 wt.% to 45 wt.% water in a laundry soap bar composition having 30 wt.% to 55 wt.% fatty acid soap for providing good user properties, improved bar properties or lather characteristics or improved fragrance delivery.

The invention will now be illustrated by means of the following non-limiting examples.

Examples

Example 1

Laundry soap bar composition (Ex 1) according to the present invention was prepared using the formulation as shown in Table 1 . The fatty acids/fats according to the required blend was weighed and neutralized using sodium hydroxide. Thereafter the other cationic polymer and water and other ingredients as shown in the table 1 were added, and the mixture was plodded and thereafter extruded to form a shaped laundry bar composition. The silica gel was formed during the process of preparing the laundry bar by reacting sodium silicate with sodium bicarbonate to form silica gel in-situ. The silicate structuring agent was formed in-situ by mixing aluminium sulphate with sodium carbonate followed by sodium silicate to form sodium aluminosilicate.

Measurement of the bar parameters: a) Bar Hardness

Bar hardness refers to the hardness of the bar after manufacture which gives an indication of the processability, strength and retention of structural integrity during handling, transport and use.

Bar hardness was determined by using a TA-XT Express Texture Analyser has a 30° conical probe which penetrates into a soap bar sample at a specified speed to a predetermined depth. The resistance generated at the specified depth is recorded. The bar whose hardness is to be measured is placed onto the testing platform. Then the probe of the measuring instrument is placed close to surface of the bar composition without touching it. Next the instrument is started, and the force required to reach a preset target distance is measured and the observation is recorded (force in g, g _f ).

This number can be related to the yield stress (ref 2), which has long been known to be an important determinant of processability and is also related to in-use performance.

The hardness of the bar was measured of the freshly prepared bars and after 24 hours of storage. b) Measurement of the pH of the laundry soap bar composition

The pH of the laundry soap bar composition was measured in a 4% solution with distilled water at 25°C. c) % rate of wear measurement:

Rate of wear refers to the amount of the bar loss during use which is measured by its weight.

Step 1 : Preconditioning step

The laundry soap bar was cut into a piece with the following dimension, 8.5cm x 5 cm. A damp cloth was placed in a soap dish, the working face of the cut soap bar was placed on this soap dish touching the damp cloth and was transferred into a sealed polyethylene pouch. The soap bar was left undisturbed for 1 hour.

After an hour the soap bar placed on the soap dish was removed from the pouch and the soap dish was kept aside. A cotton cloth piece measuring 65cm x 60 cm was immersed in water with a hardness of 15 FH and after the cloth piece was fully soaked it was removed from water and the water allowed to drip out. Once no more water dripped from the cloth piece, the cloth piece was placed on a flat metal or plastic tray and the surface of the cloth was flattened and any trapped bubbles were smoothened out.

Next the laundry soap bar was removed from the soap dish and fixed to the bar holder. The working face of the laundry soap bar was now applied onto the damp cotton cloth piece resting on the plastic or a flat metal tray along the length of the damp cotton cloth (length 60 cm) by moving the holder from one edge of the cotton cloth to the other edge of the cotton cloth in each stroke. Two such strokes were applied such that the strokes were non overlapping along the length of the damp cotton cloth. This completes the preconditioning step. At this stage, the weight of the bar was measured and the weight of the bar along with the holder was recorded (W _o ).

Step 2: Rate of wear evaluation

After the weight of the bar is determined, the working face of the bar is rubbed again in 5 non-overlapping strokes along the length of the damp cloth piece by moving the holder from one edge of the cloth piece to the other edge of the cloth piece covering a distance of 60 cm. After 5 strokes the weight of the bar along with the holder is measured and recorded (W). The % rate of wear is then calculated as follows:

Weight loss over 3 metres (60cm x 5 strokes) = W _o - W

6. Note: The average weight loss over five (5) times the effective cloth length corresponds to weight loss over three metres (3 m) for a given product - and can be expressed as weight loss per 10 metres of application to the fabric as:

7. Weight loss per 10 metres = weight loss over 3 metres x 10 d) Determination of the sog and mush

Sog mush refers to the ingress of water from the atmosphere into the bar and relates to the cause of sogginess of the bar.

To measure the sog mush of the prepared laundry bar composition the following process was followed.

Step 1 : preconditioning step

A cloth piece was placed in a soap basin and 10 mL water was added. Thereafter the laundry bar composition was placed in the soap basin and the soap basin along with the laundry soap bar composition was placed in a sealed pouch and left undisturbed for a period of 1 hour.

Step 2: Mush evaluation

At the end of the 1 hour the laundry soap bar composition was removed from the sealed pouch. A fresh cloth piece (measuring 40 cm x 25 cm) was taken and immersed in water to wet the cloth piece. Thereafter the cloth piece was removed and allowed to drip. The cloth piece was next placed on a flat surface and spread and smoothened on the surface. Any excess water was dabbed and removed. The preconditioned laundry soap bar composition was placed in the holder at one end of the wet cloth piece and gently pulled to the other end of the cloth piece. This procedure was repeated twice once on the top surface of the cloth piece and then on the other surface of the cloth piece. Thereafter the weight of the laundry soap bar was measured and recorded (W1). Next the laundry soap bar was again placed in the soap basin and transferred to a sealed pouch and left undisturbed for 4 hours.

Step 3: Mush evaluation

At the end of 4 hours the laundry soap bar was removed from the sealed pouch. The weight of the laundry soap bar was measured and recorded (W2). Next the soft mush layer on the laundry soap bar was gently scrapped across the surface of the bar and along the sides of the bar using a spatula. Now, the weight of the laundry soap bar was measured and recorded (W3) for the third time. After this the laundry soap bar was left undisturbed and any cracking of the bar is assessed visually after a day.

The sog mush was calculated using the following formula Weight loss over 30cm ² = [(W1 - W3)*30]/Area (40cm ² ) Mush over 30cm ² = [(W2 - W3)*30]/Area (40cm ² ) e) Measurement of the lather

Soil lather refers to foam generated during wash by which the consumer controls the product dosage.

Step 1 : preconditioning step

A cloth piece was placed in a soap basin and 10 mL water was added. Thereafter the laundry bar composition was placed in the soap basin and the soap basin along with the laundry soap bar composition was placed in a sealed pouch and left undisturbed for a period of 1 hour.

Step 2: lather evaluation

A white terry towel measuring 40 cm x 25 cm was immersed in water with a hardness of 15FH and when it is fully soaked, the terry towel was removed from water and allowed to drip out until no further drops come out. The terry towel was next placed on a flat metal tray and any wrinkles and bubbles were removed and the surface of the towel was smoothened.

Laundry bar was taken, and the test face of the bar was placed in the holder. The bar was moved from an edge of the towel towards the other edge of the towel such that the bar covers the entire length of the towel. This process was repeated twice. The strokes were non-overlapping.

Next 100 ml of water (15°FH hardness) was poured over the fabric and the towel was rubbed 8 times at each corner. The towel was then squeezed to remove all the water and lather out of the towel into a measuring cylinder. Another 20mL of water was added onto the towel and any lather and water remaining on the towel was scrapped and transferred into the measuring cylinder. The amount of lather generated was calculated as follows -

Volume of lather (in mL) = T otal volume of water and lather - volume of water. Leave the lather to stand for 10 minutes undisturbed and the reading of the lather volume was calculated again and recorded.

Table 1

The data in Table 1 demonstrates that a laundry soap bar composition having low levels of fatty acid soap (43 wt.%) and higher than normal levels of water (36 wt.%) in the composition provides good bar properties like hardness and wear rate and also good lather in the water with varying hardness levels.

Example 2: Evaluation of the cleaning performance of laundry soap bar composition according to the present invention.

The cleaning performance of the soap bar composition according to the present invention (Ex2, Ex 3) and a control composition (Ex C1) as shown in Table 2 was evaluated by using the Stain removal index value (SRI). SRI was measured using swatches having different stain types as shown in table 2. A FRU Precision Colorimeter WF32 was used for the measurement, the colorimeter has integrated software which measures colours in LAB scale and equipped to calculate the colour difference in CIELAB AE* which is the difference between stained sample and unstained fabric. The absolute color difference is given by the following equation, Af* ₌ ^Ai'**Aa*Z2**' where L is reflectance, a is redness, b is yellowness. The colour difference was calculated for both unwashed stain and washed stain using in both cases the difference between the stained area and unstained fabric before washing. From the two values obtained stain removal index (SRI) was calculated using the formulae here, “US” refers to unwashed stain area, “WS” is washed stain area, UF is unwashed unstained fabric area, AE ₍ US-UF) denotes the colour difference between unwashed stain and unstained fabric, AE(WS-UF) denotes the colour difference between washed stain and unstained fabric. SRI is the measure for the change in the stain intensity after washing or how effective is washing for stain removal. Index 0 means no stain removal, whereas SRI = 100 corresponds to fully removed stain. The higher the SRI value, the greater is the stain removal potential. The colorimeter was used with a light source denoted as D65 corresponding to 6500K.

For the determination of the SRI, a standard protocol was used, called the Tergometer (also called Tergotometer) wash protocol. Said Tergometer wash protocol has the following steps: 1 . Measurement of the colour of the stain on the textile cloth (unwashed stain area). 2. Switch on the Tergometer and set to a temperature of 25°C. 3. Add water of required hardness, leave to heat to 25°C for 10 minutes. 4. Add formulation to each pot and then agitate at 100 rpm for 1 minute 5. Add the stained swatches and ballast into each pot. 6. Start the wash, agitate at 100 rpm and leave to wash for 12 minutes. 7. Rinse with fresh water (24°FH) for 2 minutes. 8. Repeat rinse. 9. Dry overnight in the dark. 10. Read stains after wash.

The details of the soap bar composition that were prepared and subjected to SRI studies thereafter, is shown in table 2. The silica gel in the composition according to the present invention (Ex 2, Ex 3) was prepared in-situ by reacting sodium silicate and sodium bicarbonate. The silicate structuring agent in Ex 2 was sodium aluminosilicate which was prepared in-situ by reacting aluminium sulphate with sodium carbonate followed by sodium silicate. The silicate structuring agent in Ex 3 was calcium silicate which was formed in-situ by reacting sodium silicate with calcium silicate. Table 2

The data given in table 2 indicates that the SRI values of compositions outside the invention (Ex C1) are lower than the SRI provided by composition inside the invention (Ex 2, Ex3). Thus, it demonstrates that the composition according to the present invention having a combination of silicate structuring agent and silica gel at higher levels of water and lower soap concentration gives better stain removal performance on tough to remove stains (such as fatty-oily stains like the red curry stain, motor oil stain and bleachable stains like the black coffee stain) when compared to soap bar composition with higher soap content but without the silicate structuring agent and silica gel.

Example 3: Evaluation of the perfume delivery performance and perfume quality of the soap bar composition according to the present invention. A control soap bar composition (Ex C1) and the composition according to the present invention (Ex 2, Ex 3) having formulation as provided in Table 2 were prepared and 0.14 wt.% of citronella perfume was incorporated into each soap bar composition. Test fabrics were washed under similar conditions using each of the soap bar composition (Ex C1 , Ex 2 and Ex 3). A group of trained panellists, then evaluated the perfume performance under following conditions (a) perfume delivery of the soap bar composition as is immediately after opening the pack, (b) the perfume delivery in wash and (c) the perfume delivery on the damp fabric after rinsing, the evaluation details are provided in table 3.

Table 3

As seen from the data provided in table 3, the perfume performance was better in Ex 2 and Ex 3 as compared to the comparative composition Ex C1 .

Example 4: Determination of the surface properties of the soap bar composition: The dynamic surface tension was measured at a temperature of 25°C on a BP100 Tensiometer (Kriiss GmbH, Germany) using the maximum bubble pressure method between 10 and 50 000 ms surface age. From the kinetic curves showing the time evolution of the surface tension the value at 100 ms was chosen, because typically it correlates well with the characteristic time of air entrapment and bubble formation in hand washing. The dynamic surface tension in mN/m was reported at 100 ms interval.

The dynamic surface tension of soap solution prepared using 24° FH water was recorded and is provided in table 4 below.

Table 4

As shown in table 4, the dynamic surface tension of an aqueous solution of the soap bar composition according to the present invention (Ex 2, Ex 3) is lower than that of the control composition (Ex C1) under similar conditions. A lower dynamic surface tension indicates that the cleaning action of the soap bar composition according to the present invention (Ex 2, Ex 3) is better than the control composition (Ex C1). Further a lower dynamic surface tension also indicates better foam volume.