WO1999056721A1

WO1999056721A1 - Liquid compositions comprising high levels of alkyl aryl sulfonates

Info

Publication number: WO1999056721A1
Application number: PCT/EP1999/003235
Authority: WO
Inventors: Judith Lynne Kerschner; Robert Stanley Lee; Joanna Dawson; Prathiba Bhat
Original assignee: Unilever Plc; Unilever N.V.; Hindustan Lever Limited
Priority date: 1998-05-07
Filing date: 1999-05-05
Publication date: 1999-11-11
Also published as: AU4141699A

Abstract

The present invention provides personal wash liquid detergent compositions comprising relating high levels ( > 1 %) of linear alkyl aryl sulfonate. This ingredient provides desired enhanced foaming while the composition is formulated to retain overall mildness. The composition is also stable to salt and results in low temperature clouding.

Description

LIQUID COMPOSITIONS COMPRISING HIGH LEVELS OF ALKYL ARYL SULFONATES

This invention relates to personal wash liquid detergent compositions (e.g., shower gels or shampoos) which contain relatively high levels of linear alkyl aryl sulfonate (in order to provide consumer desirable lathering properties) while retaining equally desired mildness properties. The compositions also have desirable viscosity (for shower gel functions) while maintaining clarity (stability) even at low temperature (for example, less than 10°C) .

Liquid personal wash compositions containing a mixture of anionic and other surfactants are known. Typically the anionic surfactants will be selected to be as mild as possible since mildness is an obviously desired consumer attribute .

U.S. Patent No. 5,661,189 to Grieveson et al., for example, teaches liquid personal washing compositions (i.e., shower gels) . A typical shower gel composition is set forth at column 7, and may comprise an anionic surfactant such as sodium lauryl ether sulfate in combination with betaine and alkylpolyglucoside (APG) .

The art is replete with examples of such shower gel or shampoo compositions comprising such linear alkyl sulfates. Use of surfactants such as alkyl benzene sulfonate is, however, generally avoided (see U.S. Patent No. 5,661,189 to Grieveson discussed above, column 4, lines 37-38). Such compounds are not readily chosen in personal wash compositions at levels above, 1% because these surfactants are generally not viewed to be mild enough for use in such formulations .

In addition, use of LAS is difficult because the LAS is generally introduced as salt (e.g. Na or triethanolamine

LAS) and these salts can precipitate causing low temperature clouding of the formulation.

Unexpectedly, the applicants have now discovered it is possible to use alkyl benzene sulfonate surfactants at levels above 1%, preferably at levels 2% to 20%, preferably 3% to 15% and more preferably 4% to 10% by wt . of total composition. In doing so, it is possible to obtain higher foaming, lower cost compositions while retaining mildness benefits. Further, by using preferred surfactant combinations, LAS can be introduced while avoiding precipitation and clouding problems.

The key is to provide compositions comprising a mixture of at least 1% linear alkyl aryl sulfonates with another surfactant selected from the group consisting of anionic surfactants, amphoteric surfactants, nonionic surfactants and mixtures thereof such that the ratio of linear alkyl aryl sulfonate (LAS) to other surfactant is at least 1:25 (e.g., 1:25 up to 100:1, preferably 1:25 to 25:1). By combining LAS with various less irritant surfactants, superior performance can be obtained while maintaining mildness .

In preferred embodiments, LAS should be used with another anionic (preferably an alkali metal alkyl ether sulfate, e.g., sodium lauryl ether sulfate) and an amphoteric/zwitterionic (e.g., in a ternary surfactant system). Further, the LAS (introduced as salt, for example, of alkali metal or triethanolamine) should comprise no more than 70%, preferably 5-60% of surfactant system and, when alkali metal LAS is used, it should comprise no more than 50% of surfactant system. Preferably, the compositions should also comprise cationic polymer and have viscosity of about 2000 to 25,000 centipoises measured at 10s^"1, more preferably about 2000 to 20,000.

The invention will now be further described by way of example only with reference to the accompanying drawing, in which:

- Figure 1 is a ternary graph showing preferred ternary surfactant system wherein percentage of LAS salts should be minimized.

The present invention relates to liquid personal cleansing compositions which contain relatively high levels of linear alkyl aryl sulfonate surfactant, particularly alkyl benzene sulfonate (LAS) , and hence provide enhanced lather properties. The liquid personal cleansing compositions of the present invention comprise one percent or greater (preferably above 1%) linear alkyl aryl sulfonates of various salts (e.g., alkali metal, preferably sodium, salt and triethanolamine salts) , and at least one other surfactant selected from anionic surfactant other than LAS, nonionic surfactants, amphoteric surfactants and mixtures thereof; and water.

Preferably, the compositions are ternary compositions containing LAS; a second anionic which is preferably a milder anionic such as alkali metal ether sulfate (e.g., sodium CIQ-C20_Λ preferably C]_2~ χ8 alkyl ether sulfates having average 0.5 to 10 moles of ethoxylation; a preferred compound is sodium lauryl ether sulfate (e.g., having about 1 to 4 EO units) ; and an amphoteric/zwitterionic surfactant (e.g., betaine) .

As noted in the examples, the "mild" anionic (e.g., alkali metal ether sulfate) and amphoteric should preferably be used such that LAS salts comprise no more than 70%, preferably 1 to 60% of surfactant system. Further, where LAS salt is alkali metal salt (e.g., sodium LAS), such salt should comprise no more that 50%, preferably 1-45% of surfactant system. Excessive LAS salt will lead to precipitation (instability) causing low temperature (below 10°C, especially below 5°C) clouding.

As used herein, "personal cleansing compositions" refers to any cleansing composition which can be used on the human body including, for example, shower gel compositions, hand soaps and shampoos.

The invention is set forth in greater detail below.

The liquid personal cleansing compositions of the present invention comprise from above about 1% to about 20%, preferably above 1% to about 15% linear alkyl aryl sulfonate. A preferred alkyl aryl sulfonate is a linear alkyl benzene sulfonate having the formula below:

where Ri is an alkyl or alkenyl group of 6 to 24 carbon atoms substituted at any position on the benzene ring and substituted to the ring at any carbon atoms in R_]_ and mixtures thereof; and M is a cation selected from ammonium and substituted ammoniums such as alkanolamines; monovalent metals, such as sodium and potassium; and polyvalent metal cations, such as magnesium and calcium and mixtures thereof. The cation M of the anionic detersive surfactant should be chosen such that the detersive surfactant component is soluble in water, or in combination with the surfactant blend of the composition over normal range of product use (e.g. 0-50°C) .

As noted, LAS salts should preferably comprise no more than 70% of total surfactant system and alkali metal LAS salt should comprise no more than 50% of total surfactant system.

Compositions according to the invention will also comprise additional surfactants.

The liquid cleansing formulation of the present invention also contains from 0-30%, preferably 1-20% and most preferably 1-15% of an additional anionic surfactant. A highly preferred anionic surfactant for use in the compositions herein is alkyl ether sulfate of the formula:

R²0(CH₂CH₂)nS0₃M

2 where R is an alkyl or alkenyl group of 8 to 24 carbon atoms, n ranges from about 0.5 to about 10 especially about 1.5 to about 8, and is a cation as previously described. The cation M of the anionic detersive surfactant should be chosen such that the detersive surfactant component is soluble in water or in combination with the surfactant blend of the composition over normal range of product use (e.g. 0- 50°C) . Solubility will depend upon the particular anionic detersive surfactants and cations chosen.

Other anionic detersive surfactants which can be used in the compositions herein are the water soluble salts of organic, sulfuric acid reaction products of the general formula

3 3

[R SO3M] where R is selected from a straight or branched chain, saturated aliphatic hydrocarbon radical having from about 8 to about 24, preferably about 10 to about 18 carbon atoms; and M is a cation previously described. Examples of such detersive surfactants are the salts of an organic sulfuric acid reaction product of a hydrocarbon of the methane series, including iso-, neo-, and n-paraffins, having about 8 to about 24 carbon atoms, preferably about 12 to about 18 carbon atoms and a sulfonating agent, e.g., SO3,

H₂SO₄, obtained according to known sulfonation methods, including bleaching and hydrolysis. Preferred are alkali metal and ammonium sulfonated Cio-₁8 n-paraffins.

Still other suitable anionic detersive surfactants are the reaction products of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil or palm kernel oil; sodium or potassium salts of fatty acid amides of methyl tauride in which the fatty acids, for example, are derived from coconut oil or palm kernel oil. Other similar anionic surfactants are further described in U.S. Patent No. 2,486,921; U.S. patent No. 2,486,922; and U.S. Patent No. 2,396,278. Other anionic detersive surfactants suitable for use in the personal cleansing compositions are the succinates, examples of which include disodium N-octadecylsulfosuccinate; disodium lauryl sulfosuccinate; diammoniumlauryl sulfosuccinate; tetrasodium N- (1, 2-dicarboxyethyl) -N- octadecylsulfosuccinate; diamyl ester of sodium sulfosuccinic acid.

Other suitable anionic detersive surfactants include olefin sulfonates having about 10 to about 24 carbon atoms. The term olefin sulfonates' is used herein to mean compounds which can be produced by the sulfonation of alpha-olefins by means of uncomplexed sulfur trioxide, followed by neutralization of the acid reaction mixture in conditions such that any sulfones which have been formed in the reaction are hydrolyzed to give the corresponding hydroxy- alkanesulfonates . The SO3 can be liquid or gaseous, and is usually, but not necessarily, diluted by inert diluents, for example by liquid SO₂, chlorinated hydrocarbons, etc., when used in the liquid form, or by air, nitrogen, gaseous S0₂, etc. when used in the gaseous form.

The alpha-olefins from which the olefin sulfonates are derived are mono-olefins having about 10 to about 24 carbon atoms, preferably about 12 to about 16 carbon atoms. Preferably, they are straight chain olefins.

In addition to the true alkene sulfonates and a proportion of hydroxyl-alkanesulfonates, the olefin sulfonates can contain minor amounts of other materials, such as alkene disulfonates depending upon the reaction conditions, proportion of reactants, the nature of the starting olefins 8

and impurities in the olefin stock and side reactions during the sulfonation process.

A suitable specific alpha-olefin sulfonate mixture of the above type is described more fully in the U.S. Patent No. 3,332,880.

Another class of anionic detersive surfactants suitable for use in the personal cleansing compositions are the beta- alkyloxy alkane sulfonates. These compounds have the following formula:

R⁴CH(OR⁵)CH₂S0₃M,

4 where R is a straight chain alkyl group having from about 6

5 to about 20 carbon atoms, R is a lower alkyl group having from about 1 to about 3 carbon atoms, and M is a water soluble cation as hereinbefore described.

Another class of anionic detersive surfactants suitable for use in the personal cleansing compositions are fatty acid soaps of the formula:

R⁶C0₂M

where R is a straight chain alkyl or alkenyl group having from about 6 to about 20 carbon and M is a water soluble cation as hereinbefore described.

Preferred additional detersive anionic surfactants for use in the personal cleansing composition include ammonium lauryl sulfate, alkali metal cocoyl isethionate, ammonium laureth sulfate, triethylamine lauryl sulfate, sodium laureth sulfate, potassium lauryl sulfate, potassium laureth sulfate, sodium lauryl sarcosinate, cocoyl sarcosine, sodium cocoyl sulfate, potassium cocoyl sulfate sodium laurate, sodium myristate, sodium stearate, triethanolamine laurate, triethanolamine stearate, triethanolamine myristate and combinations thereof.

In the preferred embodiment of the present invention, the liquid personal cleansing compositions containing from about

0% to about 30%, preferably 1% to about 20%, most preferably

1% to about 10% of an amphoteric or zwitterionic surfactant.

When such surfactant is employed in the compositions herein, the ratio of the total anionic to total amphoteric/zwitterionic surfactant is preferably greater than 1:1.

Suitable amphoteric surfactant components for use in the liquid personal cleansing compositions herein include those which are known for use in personal cleansing compositions or other personal care cleansing compositions, and which contain a group that is anionic at the pH of the personal cleansing composition. Concentration of such surfactant components in the personal cleansing composition preferably ranges from 0% to about 20%, most preferably 0% to about 10% by weight of composition. Examples of amphoteric ^■ surfactants suitable for use in the personal cleansing composition herein are further described in U.S. Patents No. 5,104,646 (Bolich Jr. et al.), U.S. Patent No. 5,106,609 (Bolich Jr. et al. ) .

Examples of amphoteric detersive surfactants which can be used in the compositions of the present invention are those which are broadly described as derivative of aliphatic 10

secondary and tertiary amines in which the aliphatic substituents contains from about 8 to about 18 carbon atoms and once contains an anionic water solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate or phosphonate. Examples of compounds falling within this definition are sodium 3-dodecylaminopropionate and sodium 3- dodecylaminopropane sulfonate.

Suitable zwitterionic detergents have an alkyl or alkenyl group of 7 to 18 carbon atoms and comply with an overall structural formula:

O ¥ -M;—NH(CH2>„-t «Ψ -X—Y

R⁹

where R⁷ is alkyl or alkenyl of 7 to 18 carbon atoms; R⁸ and R⁹ are each independently alkyl, hydroxyalkyl or carboxylalkyl of 1 to 3 carbon atoms; m is 2 to 4; n is 0 or 1; X is alkylene of 1 to 3 carbon atoms optionally substituted with hydroxyl, and Y is CO2 or SO3 .

Zwitterionic detergents within the above general formula include simple betaines of formula:

R⁷—N⁺—CH₂CO₂ ^"

R⁹

and amido betaines of formula 11

R⁸

R⁷—CONH(CH₂)_m—N⁺—CH₂CO₂ ^"

R⁹

wherein m is 2 or 3.

7 8 9 7

In both formulae R , R and R are as defined previously. R may, in particular, be a mixture of Cι₂ and C alkyl groups derived from coconut so that at least half, preferably, at

₇ least three quarter of the groups R has 10 to 14 carbon

8 9 atoms. R and R are preferably methyl.

A further possibility is a sulphobetaine of formula:

R⁸ R⁸

R⁷— N⁺ (CH₂)₃SO₃- or R⁷ — CONH(CH₂)mN⁺ — (CH₂)₃SO₃ ^"

R⁹ R⁹

where m is 2 or 3, or variants of these in which

(CH₂)₃S0₃

is replaced by

OH -CH₂CHCH₂SO₃ ^"

7 8 9 R , R and R in these formulae are as defined previously. 12

In a preferred embodiment of the present invention the liquid personal cleansing compositions may contain from about 0% to about 30%, preferably 0% to about 20%, most preferably 1% to about 10% of a nonionic surfactant. When a nonionic surfactant is employed in the compositions herein, the ratio of the total anionic to total nonionic surfactant is preferably greater than 1:1.

The nonionic which may be used includes in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Specific nonionic detergent compounds are alkyl (C6-C22) phenols-ethylene oxide condensates, the condensation products of aliphatic (Cg-Cι_g) 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 sugar amide, such as a polysaccharide amide. Specifically, the surfactant may be one of the lactobionamides further described in U.S. Patent No. 5,389,279 to Au et al., or it may be one of the sugar amides described in Patent No. 5,009,814 to Kelkenberg.

Other surfactants which may be used are described in U.S.

Patent No. 3,723,325 to Parran Jr. and alkyl polysaccharide nonionic surfactants as disclosed in U.S. Patent No. 4,565,647 to Llenado. 13

Preferred alkyl polysaccharides are alkylpolyglycosides of the formula:

R 0(C_nH_2nO)_t(glycosyi;

2 wherein R is selected from alkyl, alkylphenyl, hydroxyalkyl, hydroxyalkylphenyl, and mixtures thereof in which alkyl groups contain from about 10 to about 18, preferably from about 12 to about 14, carbon atoms; n is 0 to 3, preferably 2; t is from 0 to about 10, preferably 0; and x is from 1.3 to about 10, preferably from 1.3 to about 2.7. The glycosyl is preferably derived from glucose.

To prepare these compounds, the alcohol or alkylpolyethoxy alcohol is formed first and then reacted with glucose, or a source of glucose, to form the glucoside (attachment at the 1-position) . The additional glycosyl units can then be attached between their 1-position and the preceding glycosyl units 2-, 3-, 4- and/or 6-position, preferably predominantly the 2-position.

The nonionic surfactant can also be a water soluble polymer chemically modified with hydrophobic moiety or moieties. For example, EO-PO block copolymer, hydrophobically modified PEG such as POE (200) -glyceryl-stearate can be included in the formulations claimed by the subject invention.

A preferred surfactant system is a ternary system comprising LAS salt, alkali metal ether sulfate and amphoteric (e.g., mixture of sodium/triethanolamine LAS; SLES; and betaine) wherein LAS salt comprises no more than 70% of surfactant system. 14

The liquid personal cleansing compositions of the present invention also contain 20% to about 98%, preferably from about 40% to about 95% and more preferably from about 55% to about 95% and most preferably from about 70% to about 95% water by weight of the composition.

Examples of optional ingredients which can desirably be employed in the liquid personal cleansing compositions of the present invention include, for example, compatibly salt and salt hydrates as viscosity adjusting agents. Some preferred salts include sodium chloride, sodium sulfate, ammonium sulfate, ammonium chloride, disodium hydrogen phosphate.

Generally, compatible salts and salt hydrates include the sodium, potassium magnesium, calcium, aluminum lithium and ammonium slats of inorganic acids and small (6 carbons or less) carboxylic or other organic acids, corresponding hydrates ad mixtures thereof and are applicable. The inorganic salts include chloride, bromide, sulfate, metasilicate, orthophosphate, pyrophosphate, polyphosphate, metaborate, tetraborate and carbonate. The organic salts include acetate, formate, methyl sulfate, and citrate.

Water soluble amine salts can also be used. Monoethanolamine, diethanolamine, and triethanolamine chloride salts are preferred.

Thickening agents may be selected from inorganic clays, including aluminosilicates, zeolites, kaolinite, montmorillonite, attapulgite, illite, bentonite halloysite and kaolin. Polymeric carboxylates consisting of the set including modified and unmodified starches, substituted and 15

unsubstituted guar gums, agars, alginates, xanthan gum, carrageenan, cellulose derivatives, exudate gums, gellan gum, gelatin, pectins and seed gums are also useful thickening agents.

Other thickening agents include synthetic polymers such as carbomers and PEG distearate. Still other thickeners include fumed silica, polyethylene, alkyl silicone wax, lanosterol, natural and synthetic waxes, fatty acid and derivatives thereof, in particular fatty acid monoglyceride polyglycol fatty alcohols, petrolatum, narogel, polyammonium stearate, hydrotalcites and mixtures thereof.

Another optional ingredient which may be used is cationic polymers.

In principle, the cationic polymers used in the process and compositions of the invention may be any polymer of the polyamine, polyaminoamide, or quaternary polyammonium type, with the amine or ammonium group constituting part of the polymer chain or being bonded thereto. Examples of these are any of the cationic polymers further described in U.S. Patent No. 4,438,095.

Preferred polymers are derivatives of cellulose ethers entailing quaternary ammonium groupings such as those described in French Patent No. 1,492,597 such as, for example, polymers sold under the designation JR (e.g., JR 125, JR 400, JR 30M) and LR (e.g., LR 500 and LR 30M) by Union Carbide under the designation CELQUAT by National

Starch Company; and cationic polysaccharides such as those further described in U.S. Patent No. 3,509,978 or U.S. Patent No. 4,031,307. 16

Specific examples of cationic polymers which may be used in the invention are a glycidyltrimethylammonium chloride ether of hydroxyethylcellulose (Polymer JR-400, Union Carbide), a quaternary ammonium salt of a polyvinylpyrrolidone derivative (Gafcoat 734, GAF) , polydimethylmethylenepyrellidinium chloride (Merquat 100, Merck) , a quaternary ammonium derivative of hydroxy propyl guar (Jaguar C-13-S, Meyhall) , and a quaternary ammonium salt of hydrolyzed gelatin (Crodine Q, Croda) .

If used, the polymer will generally be used in the compositions of the invention in an amount ranging from about 0.01 to 2.0% by wt . , preferably 0.05 to 0.5% by wt .

The liquid personal cleansing compositions of the present invention can contain also other additives commonly included in personal cleansing compositions such as sanitizing or antimicrobial reagents, dyes, conditioning/moisturizing agents including oils, glycerine, preservatives, perfumes, opacifiers/pearlescers and the like.

The liquid personal cleansing compositions of the present invention have a viscosity ranging from about 100 to about 100,000 centipoise, preferably from about 1,000 to about 50,000 centipoise and most preferably from about 2000 to about 15,000 centipoise at a shear rate of 10/sec.

Minimizing LAS salt as percentage of surfactant system is important because too much LAS salt may lead to viscosities outside desired range (e.g., they are generally too low for acceptable consumer benefit) and to salt intolerance (precipitation/instability) which in turn causes clouding. 17

The liquid personal cleansing compositions of the present invention contain greater than at least one percent by weight of linear alkyl aryl sulfonate in combination with other detersive surfactant materials to produce an overall formulation that contains about 2% to about 50% surfactant ingredients, preferably about 3% to about 30% surfactant ingredients and most preferably about 4% to about 20% surfactant ingredients by weight.

Without being bound by theory, it is believed that the addition of other surfactants to that of linear alkyl benzene sulfonate will lower the overall critical micelle concentration (CMC) of the formulation and the resulting personal cleansing composition will be milder to the skin. Therefore it is preferred that this formulation contain at least one other surfactant than the linear alkyl benzene sulfonate (LAS) in a ratio of LAS to other surfactant of at least 1:25 (preferably 1:25 to 100:1, more preferably 1:25 to 25:1), most preferably at least 1:10.

Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts or ratios of materials or conditions or reaction, physical properties of materials and/or use are to be understood as modified by the word " about" .

Where used in the specification, the term "comprising" is intended to include the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more features, integers, steps, components or groups thereof. 18

The following examples are intended to further illustrate the invention and are not intended to limit the invention in any way.

Unless indicated otherwise, all percentages are intended to be percentages by weight.

Formulations

The following liquid shower gel formulations #1-10 were prepared and found suitable for topical application:

19

Form. #1 For . #2 Form #3 Form. #4 Form. #5

Active Material % Active % Active % Active % Active % Active

Sodium Linear 5.0 0.0 5.5 5.5 5.5

Alkylbenzene

Sulfonate

Triethanolamine 2.9 10.0 4.4 4.4 2.9 Linear Alkylbenzene Sulfonate

Sodium Laureth 2.5 2.5 2.5 2.5 2.5 Sulfate

Cocoamidopropyl 2.5 2.5 2.5 2.5 2.5 Betaine

Ethyl Glycol Monostearate

PEG 6000 Distearate 1.5 4.0 3.0 4.0

Guar Gum

Polyquaterium 10 0.2

Corn Starch

Sodium Chloride 0.5

Perfume 0.5 0.5 0.5 0.5 0.5

Formaldehyde 0.04 0.04 0.04 0.04 0.04

Glycerine 4.0 4.0

Water to 100% to 100% to 100% to 100% to 100%

Form. #6 Form. #7 Form #8 Form. #9 Form. #10

Active Material % Active % Active % Active % Active % Active

Sodium Linear 5.0 0.0 5.0 5.0 5.0

Alkylbenzene

Sulfonate

Triethanolamine 1.8 10.0 2.9 2.9 2.9 Linear

Alkylbenzene Sulfonate

Sodium Laureth 3.5 2.5 2.5 2.5 2.5 Sulfate

Cocoamidopropyl 2.5 2.5 2.5 2.5 2.5 Betaine

Ethyl Glycol 4.0 1.0 Monostearate

PEG 6000 Distearate

Cationic Guar 0.2

Guar Gum 0.5

Polyquaterium 10

Corn Starch 0.25

Sodium Chloride 0.55 0.25 0.25

Perfume 0.5 0.5 0.5 0.5 0.5

Formaldehyde 0.04 0.04 0.04 0.04 0.04

Glycerine 4.0 4.0 2.0 2.0

Water to 100% to 100% to 100% to 100% to 100%

Comparative Example and Examples 1-5 20

Selected formulations from those listed above were examined for viscosity and lather volume using an in-house designed pouf (polymeric mesh sponge) test. Viscosities was measured on a Haake RV20 Rotovisco Rheometer with the recorded value as the viscosity at a shear rate of 10 sec-1 at 25°C. The pouf test was performed by 21 panelists and an average of the results of those panelists is listed in the following table.

Each panelist was required to wet a pouf (polyethylene sponge) for 10 seconds and then 0.5 g of product was added to the pouf. The panelist then massaged the pouf for 30 seconds generating lather. The lather was extracted from the pouf by immersion and trapped inside an inverted funnel with a graduated neck. The volume generated was recorded in ml. The lather and viscosity of the LAS containing products are compared to a non-LAS product.

The skin irritancies of the various formulations were measured by the so-called Zein test. This in-vitro test method makes use of the correlation between binding ability of surfactants to proteins to the damage the surfactant causes to the skin. The denaturation of epidermal protein structures is a key mechanism in the development of observable damage to the skin by surfactants.

Zein protein, an insoluble protein extracted from corn kernel, is used as a model for epidermal protein and the solubility of the Zein protein in surfactant solutions is a reliable guide for the skin irritancy caused by the surfactant. The test involves establishing the amount of Zein protein which can be solubilized by surfactant. 5g of Zein protein is dispersed in 40g of example shower gel 21

formulation diluted by five times. The mixture is shaken for one hour at 35°C, and immediately centrifuged to remove any non-solubilized Zein. The amount solubilized is estimated from the nitrogen content of the supernatent solution using a Macro-N nitrogen analyzer (making allowance for any nitrogen in the surfactant solution) .

Active Material Comparative Example 1 Example 2 Example 3 Example 4 Example 5 % Active % Active % Active % Active % Active % Active v©

Sodium Linear 5.0 5.0 0.0 5.5 5.5 Alkylbenzene Sulfonate as

-4

Triethanolamine Linear 2.9 2.9 10.0 4.4 4.4 Alkylbenzene Sulfonate

Ammonium Lauryl Sulfate 5.0

Sodium Laureth Sulfate 5.0 2.5 2.5 2.5 2.5 2.5

Cocoamidopropyl Betaine 2.5 2.5 2.5 2.5 2.5 2.5

Ethyl Glycol Monostearate

60000S Silicon Oil

PEG 6000 Distearate 1.5 4.0 3.0

Cationic Guar

Guar Gum 0.25

Polyquaterium 10 0.2 0.2

Corn Starch 0.25

Sodium Chloride 0.25 0.25

Perfume 0.5 0.5 0.5 0.5 0.5 l\5

Formaldehyde 0.05 0.04 0.04 0.04 0.04 0.04

Glycerine 2.0 4.0 4.0

Water to 100% to 100% to 100% to 100% to 100%

Lather volume (ml) 390* 554 560 566 525 527

Zein 0.522 0.490 0.490 0.635

Viscosity (mPas) 9349 3500 4000 3450 2300 3520

o

|H

M T) v -© o-

1*1 w in

23

* This lather volume measurement is statistically significantly different from the others with a 0.5% confidence level .

As can be seen from Examples 1-5 versus the Comparative Example, a consistently higher lather was obtained using LAS. In addition, the formulations have similar mildness attributes based on the Zein measurements and are significantly milder than conventional toilet soaps which typically have a Zein measurement of greater than one.

Example 6

LAS shower gel formulations were found to incur two basic problems during large scale processing. First, the formulation had low tolerance to salt levels for controlling the viscosity. Secondly, there was low temperature clouding of the formulations. Both of these issues were enhanced by increasing the level of perfume in the formulation. To overcome these issues, mainly derived from the need to have reasonably viscous formulations for shower liquids and the presence of high levels of NaLAS in the formulation, a mixture of surfactants were used within the formulation. One possible mixture is a ternary system containing LAS/SLES/CAPB (linear alkyl sulfate/sodium lauryl ether sulfate/cocoamido propyl betaine) .

In an attempt to resolve some of these issues or at least understand the limitations of this ternary formulation, it was decided to prepare a series of LAS/SLES/CAPB products to determine the optimum formulation that meets self imposed viscosity specifications and maintain clarity even at low temperatures. An experimental design approach was taken to 24

define the formulations that should be tested within an agreed formulation range. These products were then subjected to a series of physical tests to determine their viscosities and stability under the desired conditions.

The first step in approaching a statistical design for this study was to agree on the requirements of the formulation space. It was decided to maintain the level of CAPB in all formulations at 2.5%, since this amount is desired to maintain the mildness claims. Also, the perfume level was maintained at 0.7%.

This left three surfactants available for manipulation in this design. It was decided to vary the levels of NaLAS, TEALAS and SLES in the products, and the maximum level of each surfactant allowed in the formulation was set by a price constraint. This study can be performed with any number of restraints to limit the amount of the various surfactants in the formulations, but the final ratio of surfactants will most likely be consistent to maintain the optimum processing and final product performance.

Initially, the formulations designated from the experimental design to adequately cover the formulation space were prepared. Each product was prepared by adding the appropriate amounts of TEALAS, NaLAS and/or SLES, 2.5% CAPB and 0.7% Larissa perfume. When all of the samples were prepared, it was quite obvious that those formulations with high levels of NaLAS or TEALAS or combinations thereof would either be cloudy, or not viscous enough to meet the targeted specifications. The actual formulations and results of the salt thickening experiments are shown in Tables 1-3. The 25

viscosity measurements are presented in mPas at a shear rate of 10/S .

Table 1 : Experimental Results of 7-Point Design

Ingredients Form. Form. Form. Form. Form. Form. Form.

1 2 3 4 5 6 7

NaLAS 14.4 7.2 0 7.2 0 4.8 0

TEALAS 0 4.6 9.2 0 0 3.06 4.6

SLES 0 0 0 3.8 7.6 2.53 3.8

CAPB 2.5 2.5 2.5 2.5 2.5 2.5 2.5

Perfume 0.7 0.7 0.7 0.7 0.7 0.7 0.7

Water To To To To 100 To 100 To 100 To 100 100 100 100

Best Not Not 2500 Not 8725 4325 8760 viscosity clear clear No clear 3.5% 0.35% 1.5% with clarity salt salt salt salt

Table 2: Experimental Results of 13-Point Design

Ingredients Form. Form. Form. Form. Form. Form.

1 3 7 8 10 13

NaLAS 2.76 1.24 1.24 11.9 2.76 8.87

TEALAS 1.76 7.6 0.79 0.79 5.66 1.76

SLES 4.68 0.65 0.65 0.65 1.46 1.46

CAPB 2.5 2.5 2.5 2.5 2.5 2.5

Perfume 0.7 0.7 0.7 0.7 0.7 0.7

Water To To 100 To To To 100 To 100 100 100 100

Best viscosity 11520 Not 10610 Not 3310 Not with clarity 0.75% clear 1.75% clear 0.25% clear salt salt salt

26

Table 3: Experimental Results of 16-Point Design

Ingredients Form. Form. Form. Form. Form. Form. Form. Form. Form.

1 3 5 8 9 10 11 13 16

Na Las 1.44 11.52 4.8 1.44 4.8 1.44 1.44 8.16 8.16

TEA Las 7.36 0.92 0.92 0.92 5.21 5.21 3.1 3.1 0.92

SLES 0.76 0.76 4.31 6.08 0.76 2.53 4.31 0.76 2.53

CAPB 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5

Perfume 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7

Water To To To To 100 To 100 To 100 To To To 100 100 100 100 100 100

Best Not Not 8000 10000 Not 6000 10000 Not Not viscosity Clear Clear 0.75% 2.0% Clear 0.65% 1.0% Clear Clear with Salt Salt Salt Salt clarity

The results of all of the tests from the experimental design including the low temperature stability studies can be graphed on the triangle diagram to show a summary of the experiments. This graph is shown in Figure 1. It is clear from this diagram where the optimal formulation space for this multi-component mixture is contained. The lower right corner of the triangle contains the formulation range that is acceptable for this product, again remembering in the initial price constraints and the fact that the CAPB and perfume level are held constant. Other constraints on the formulations would open other acceptable formulation ranges.

Analysis of the formulation space from Figure 1 gives a representation of how to balance a multi-component surfactant formulation to process shower liquids containing LAS. When preparing a LAS containing shower liquid which require viscosities >2000 cp and clarity, many multicomponent systems can be utilized as long as the total 27

NaLAS is maintained below 50% of total surfactant or the combination of NaLAS and TEALAS is maintained below 70% of the total formulation.

Claims

28CLAIMS

1. A liquid personal cleansing composition which comprises :

(a) from 1% to 20% of a linear alkyl aryl sulfonate;

(b) from 0.5% to 30% of at least one other surfactant selected from anionic surfactant other than alkyl aryl sulfonate, nonionic surfactant and mixtures thereof;

(c) from 1 to 10% amphoteric or zwitterionic surfactant; and

(d) water,

wherein the compositions contain at least two different detersive surfactants and has a linear alkyl aryl sulfonate to other surfactant ratio of at least 1:25;

wherein linear alkyl aryl sulfates comprises no more than 70% of total surfactant; and

wherein viscosity is from about 2000 to 25,000 cps measured at 10s^"1.

2. A composition according to claim 1, wherein the alkyl sulfonate is alkyl benzene sulfonate.

3. A composition according to claim 1 or claim 2 wherein at least one other surfactant (b) is alkali metal alkyl ether sulfate.

4. A composition according to claim 3, wherein surfactant is sodium lauryl ether sulfate. 29

5. A composition according to any of the preceding claims, wherein ratio of alkyl aryl sulfonate to other surfactant (b) is at least 1:10.

6. A composition according to any of the preceding claims, additionally comprising cationic polymer.

7. A liquid cleansing composition comprising

(a) from 1% to 20% of a linear alkyl aryl sulfonate;

(b) from 0.5% to 30% sodium lauryl ether sulfonate;

(c) from 1 to 10% cocoamidopropyl betain; and

(d) water,

wherein linear alkyl aryl sulfates comprises no more than 60% of total surfactant;

wherein viscosity is from about 2000 to 25,000 cps measured at 10s