BAR COMPOSITIONS COMPRISING NOVEL CHELATING SURFACTANTS AND RELATED PROCESS FOR MANUFACTURE OF SUCH BARS

Abstract: A personal washing bar composition comprises: 1 to 40 % by wt. of hydrophobically modified salt(s) of ethylenediaminetriacetic acid of formula (I), wherein n is from 1 to 40. A process of manufacturing such bars is also disclosed.

Description: BAR COMPOSITIONS COMPRISING NOVEL CHELATING SURFACTANTS AND RELATED PROCESS FOR MANUFACTURE OF SUCH BARS FIELD OF THE INVENTION The present invention relates to personal wash beauty bar compositions, particularly compositions comprising (1) novel EDTA-derived chelating anionic surfactants, preferably in combination with other types of anionic surfactants; and (2) one or more amphoteric surfactants. The invention relates to the incorporation of the novel EDTA-derived chelating surfactants into specific bar skin cleansing formulation bases. Through careful balancing of the anionic, amphoteric and optional nonionic surfactants, and through specific handling of the novel chelating surfactants during processing, ultra formulation mildness to skin is achieved without sacrificing other desired user properties, such as rich and creamy lather. BACKGROUND OF THE INVENTION Hydrophobically modified ethylenediaminetriacetic acid (EDTA) chelating surfactants, salts thereof, and methods for making these compounds are taught, for example, in U.S. Patent Nos. 5,177,243, 5,191,081 and 5,191,106 (all assigned to Hampshire Chemical Corp. ) U.S. Patent No. 5,250,728 to B. A. Parker et al . , (assigned to Hampshire Chemical Corp.), teaches a novel route of synthesizing the hydrophobically modified ethylenediaminetriacetic acid. U.S. Patent No. 5,284,972 to B. A. Parker et al . (assigned to Hampshire Chemical Corp.) teaches a synthetic route leading to the salts of the hydrophobically modified ethylenediaminetriacetic acid which are the novel chelating surfactants applied by the subject invention. Inform, Vol. 6, No. 10 (October, 1995, J. Crudden and B. Parker) teaches the physical and physiological properties of the novel chelating surfactants. Mild skin cleansers and mild shampoos are among the potential applications, as discussed in the articles. Although these novel EDTA-derived surfactants are ultra-mild to skin, inclusion of the surfactants into a personal washing bar is fraught with difficulties. For example, the lather produced by the chelating surfactant alone is not as satisfactory as that of a conventional anionic detergent (e.g., sodium lauryl ether sulfate) . Further, aqueous solutions of the EDTA surfactants at the concentrations relevant to the personal washing have a viscosity which is too low to deliver the desired sensory cues . By this invention, applicants have formulated these chelating surfactants into specific skin cleansing formulations using specific routes of processing such that lather performance and other desired user properties are not sacrificed. BRIEF SUMMARY OF THE INVENTION The present invention comprises personal wash bar compositions comprising: (1) 1 to 40% by wt . of hydrophobically modified salt(s) of ethylenediaminetriacetic acid (I) (2) 1 to 40% by wt . of one or more synthetic (non- soap) anionic surfactants other than the EDTA derived anionics described in (1) (for lather enhancement ) ; (3) 1 to 20% by w . of one or more amphoteric and/or zwitterionic surfactants (to reduce skin irritation and enhance lather) (4) 0 to 10% by wt . of one or more nonionic surfactants; (5) 20 to 85% by wt . total composition of a structurant selected from the group consisting of alkylene oxide components having a molecular weight of from about 2,000 to about 25,000; C 8 to C 22 free fatty acids; C 2 to C 20 alkanols; paraffin waxes; and water soluble starches; (6) 0 to 20% by wt. of fatty acid soaps; wherein no more than 1% of composition comprises inorganic salts with multivalent counterions (e.g., aluminum chloride) . The addition of 1 to 40% by wt . total composition of the novel EDTA-derived surfactants will lead to significantly enhanced mildness in such compositions without sacrificing the surfactancy of the EDTA-derived surfactants. In a second embodiment, the application relates to a process for making the composition mentioned above by (1) dispersing an acid form of EDTA into the structurant (s) at a temperature between about 80° to 120°C; (2) adding sufficient caustic (e.g., NaOH) to neutralize the EDTA acid surfactant (molar ratio of caustic to EDTA acid from about 1:1 to 1:3); and (3) mixing the EDTA/structurant solution with remaining compounds at temperature of 80° to 120°C. DETAILED DESCRIPTION OF THE INVENTION In one embodiment, the present invention relates to novel personal washing bar compositions, particularly compositions in which the surfactant system comprises 1 to 40% wt . total composition of the salt or salts of hydrophobically modified ethylenediaminetriacetic acid, and additionally comprises one or more anionic surfactants and one or more amphoteric surfactants, wherein no more than 1% of said compositions comprise salts with multivalent counterions (high levels are associated with lather depression). Using precise formulation windows, it is possible to incorporate EDTA-derived surfactants into bar compositions retaining the benefits of mildness and without sacrificing latherability . In a second embodiment, the invention relates to a process for forming such bar compositions while retaining mildness and lathering, and acceptable bar properties by ensuring that EDTA acid is first dispersed into structurant and subsequently adding sufficient caustic to neutralize the EDTA acid. The compositions and processing are defined in greater detail below: In the first embodiment of the invention, the personal wash bar compositions comprise: (1) 1 to 40% by wt . total composition salt or salts of hydrophobically modified ethylenediaminetriacetic acid; the hydrophobically modified ethylenediaminetriacetic acids have general structure as follows: where n is from 1 to 40. If unsaturation occurs, the hydrophobically modified group may be C H 2n _ 1 where n is 2 to 40 and if further unsaturation occurs, the group may be C n H 2n _ 3 where n is 3 to 40 and so forth. The salts are the salts of one or more of the carboxylic acid groups. These compounds and methods of their preparation are described, for example, in U.S. Patent No, 5,284,972 to Parker et al . , hereby incorporated by reference into the subject application; (2) 0 1% to 40% by wt . total composition one or more anionic surfactants other than the hydrophobically modified EDTA-derived compounds described above; inclusion of the such anionic surfactants (i.e., lathering surfactants) is preferred because the EDTA-derived surfactants alone do not deliver satisfactory lather performance; (3) 1 to 20% by wt. total composition one or more amphoteric and/or zwitterionic surfactants; inclusion of the amphoteric and zwitterionic surfactants is a criticality and required because the amphoteric surfactants reduce the skin irritation potential of the anionic surfactants in (2) and enhance the lather performance; and (4) 0 to 10% by wt . total composition one or more nonionic surfactants. Finally the formulations of the invention preferably comprise no more than 1% wt . total composition of inorganic 2+ . 2 + and organic salts of Calcium (Ca ) , Magnesium (Mg ) , 3+ Alum um (Al ) and other multivalent metal counterions, and mixtures thereof; preferably said salts are excluded from the total composition; the restriction on the concentration of said salts is important because such salts tend to diminish the lather performance of the EDTA-derived surfactants. Examples of the multi-valence salts include, but are not limited to, Calcium Chloride, Magnesium Chloride, Aluminum Chloride, Magnesium sulfate, Magnesium Stearate, Calcium Laurate, etc. By using these specific formulation ingredients in specific formulation windows (e.g., 1% to 40% EDTA-derived surfactants), it is possible to make a composition comprising the mild surfactants without sacrificing lathering ability. To further insure this, the formulations should be made using the process encompassed by the second embodiment of the invention described in more detail below. The various formulation components are described in greater detail below: The EDTA-Deriv d Anioni c Surfactants (Component (1)) The salt and/or salts of the hydrophobically modified ethylenediaminetriacetic acid (EDTA) are salts (s) of the N- acyl EDTA surfactants described in US Patent No. 5,177,243, 5,191,081, 5,191,106, 5,250,728, and 5,284,972, all of which are incorporated by reference into the subject application. The synthesis, physical and physiological properties of the EDTA-derived surfactants are also summarized in an article published recently (Inform, Vol. 6 no. 10, Oct. 1995). The hydrophobically modified ethylenediaminetriactive acids have general structure as follows: where n is from 1 to 40 If unsaturation occurs, the hydrophobically modified group may be C H where n is 2 to 40 and if further unsaturation occurs, the group may be C H 3 where n is 3 to 40 and so forth. The salts are the salts of one or more of the carboxylic acid groups. These compounds and methods of their preparation are described, for example, in U.S. Patent No, 5,284,972 to Parker et al . , hereby incorporated by reference into the subject application. The counterions which may be used for the EDTA derived surfactants of the subject invention include but are not limit to Sodium (Na ) , Potassium (K ) , ammonium (NH 4 ) , monoethanolamine, diethanolamine, triethanolamine, N- Propylamine, isopropylamine, and tris (hydroxymethyl aminomethane) . As noted, multivalent counterions should be avoided. Examples of the N-acyl EDTA surfactants used by the current invention include, under the names given by B. Parker et al. (Inform, Vol. 6 no. 10, Oct. 1995), sodium lauroyl ED3A, Potassium cocoyl ED3A, triethanolamine myristoyl ED3A, and sodium Oleoyl ED3A. The EDTA-derived surfactants comprise 1% to 40% of the total composition. In addition, the surfactant should comprise at least 5%, preferably 8%, more preferably $ 10% of the total anionic surfactants in the composition. Other Ani oni c Surfactants (Component (2)) The anionic surfactant other than EDTA-derived surfactant may be any such anionic surfactant well known to the person skilled in the art. In general, the anionic component will comprise from 1 to 40% by weight of the composition, preferably 5 to 30%, most preferably 8 to 25% by weight of the composition. Zwi t terioni c and Amphoteri c Surfactants (Component (3)) Any zwitterionic or amphoteric surfactant well known to the person skilled in the art may be used. The amphoteric/ zwitterionic generally comprises 0.1 to 20% by weight, preferably 0.5% to 15%, more preferably 1.0 to 10% by wt . of the composition. Optional Nonionic Surfactants (Component (4) ) In addition to one or more anionic and amphoteric and/or zwitterionic, the surfactant may optionally comprise any nonionic surfactant well known by the person skilled in the art. Nonionic comprises 0 to 10% by wt . of the composition. Other Optional Ingredients In addition, the compositions of the invention may include optional ingredients as follows: Organic solvents, such as ethanol; auxiliary thickeners, such as carboxymethylcellulose, magnesium aluminum silicate, hydroxyethylcellulose, methylcellulose, carbopols, glucamides, or Antil from Rhone Poulenc; perfumes; sequestering agents, such as tetrasodium ethylenediaminetetraacetate (EDTA) , EHDP or mixtures in an amount of 0.01 to 1%, preferably 0.01 to 0.05%; and coloring agents, opacifiers and pearlizers such as zinc stearate, magnesium stearate, Ti0 2 , EGMS (ethylene glycol monostearate) or Lytron 621 (Styrene/Acrylate copolymer) ; all of which are useful in enhancing the appearance or cosmetic properties of the product. The compositions may further comprise antimicrobials such as 2-hydroxy-4, 2 ' 4 ' trichlorodiphenylether (DP300); preservatives such as dimethyloldimethylhydantoin (Glydant XL1000), parabens, sorbic acid etc. The compositions may also comprise coconut acyl mono- or diethanol amides as suds boosters, and strongly ionizing salts such as sodium chloride and sodium sulfate may also be used to advantage. Antioxidants such as, for example, butylated hydroxytoluene (BHT) may be used advantageously in amounts of about 0.01% or higher if appropriate. Cationic conditioners which may be used include Quatrisoft LM-200 Polyquaternium-24, Merquat ©-polymer; and ( R ) Jaguar type conditioners from Rhone-Poulenc; and Salcare®-type conditioners from Allied Colloids. Polyethylene glycols which may be used include: Polyox SR-205 PEG 14M, Polyox WSR-N-60K PEG 45M, or Polyox WSR-N-750 PEG 7M. PEG with molecular weight ranging from 300 to 10,000 Dalton, such as those marketed under the tradename of CARBO AX SENTRY (R> by Union Carbide. Another ingredient which may be included are exfoliants such as polyoxyethylene beads, walnut shells and apricot seeds The structurant of the invention can be a water soluble or water insoluble structurant. Water soluble structurants include moderately high molecular weight polyalkylene oxides of appropriate melting point (e.g., 40° to 100°C, preferably 50° to 90°C) and in particular polyethylene glycols or mixtures thereof. Polyethylene glycols (PEG'S) which are used may have a molecular weight in the range 2,000 to 25,000, preferably 3,000 to 10,000. However, in some embodiments of this invention it is preferred to include a fairly small quantity of polyethylene glycol with a molecular weight in the range from 50,000 to 500,000, especially molecular weights of around 100,000. Such polyethylene glycols have been found to improve the wear rate of the bars. It is believed that this is because their long polymer chains remain entangled even when the bar composition is wetted during use. If such high molecular weight polyethylene glycols (or any other water soluble high molecular weight polyalkylene oxides) are used, the quantity is preferably from 1% to 5%, more preferably from 1% to 1.5% to 4% or 4.5% by weight of the composition. These materials will generally be used jointly with a large quantity of other water soluble structurant such as the above mentioned polyethylene glycol of molecular weight 2,000 to 25,000, preferably 3,000 to 10,000. Water insoluble structurants also have a melting point in the range 40-100°C, more preferably at least 50°C, notably 50°C to 90°C. Suitable materials which are particularly envisaged are fatty acids, particularly those having a carbon chain of 12 to 24 carbon atoms. Examples are lauric, myristic, palmitic, stark, arachidic and behenic acids and mixtures thereof. Sources of these fatty acids are coconut, topped coconut, palm, palm kernel, babassu and tallow fatty acids and partially or fully hardened fatty acids or distilled fatty acids. Other suitable water insoluble structurants include alkanols of 8 to 20 carbon atoms, particularly cetyl alcohol. These materials generally have a water solubility of less than 5 g/litre at 20°C. Soaps (e.g., sodium stearate) can also be used at levels of about 1% to 15%. the soaps may be added neat or made in situ by adding a base, e.g., NaOH, to convert free fatty acids. The relative proportions of the water soluble structurants and water insoluble structurants govern the rate at which the bar wears during use. The presence of the water-insoluble structurant tends to delay dissolution of the bar when exposed to water during use and hence retard the rate of wear. Another optional ingredient is oil/emollient which may be added as a benefit agent to the bars compositions. Various classes of oils are set forth below. Vegetable oils: Arachis oil, castor oil, cocoa butter, coconut oil, corn oil, cotton seed oil, olive oil, palm kernel oil, rapeseed oil, safflower seed oil, sesame seed oil and soybean oil. Esters: Butyl myristate, cetyl palmitate, decyloleate, glyceryl laurate, glyceryl ricinoleate, glyceryl stearate, glyceryl isostearate, hexyl laurate, isobutyl palmitate, isocetyl stearate, isopropyl isostearate, isopropyl laurate, isopropyl linoleate, isopropyl, myristate, isopropyl palmitate, isopropyl stearate, propylene glycol monolaurate, propylene glycol ricinoleate, propylene glycol stearate, and propylene glycol isostearate. Animal Fats: Acytylated lanolin alcohols, lanolin, lard, mink oil and tallow. Fatty acids and alcohols: Behenic acid, palmitic acid, stearic acid, behenyl alcohol, cetyl alcohol, eicosanyl alcohol and isocetyl alcohol. Other examples of oil/emollients include mineral oil, petrolatum, silicone oil such as dimethyl polysiloxane, lauryl and myristyl lactate. The emollient/oil is generally used in an amount from about 1 to 20%, preferably 1 to 15% by w . of the composition. Generally, it should comprise no more than 20% of the composition. Preferably, the compositions of the invention should comprise no more than 1%, and should more preferably be free of inorganic or organic salts of multivalent metal counterions. Such metal counterions are defined as having valence of +2 or higher and include counterions such as calcium, magnesium and aluminum. Examples of such salts include, for example, aluminum chloride, magnesium chloride, calcium chloride and magnesium laurels. While not wishing to be bound by theory, it is believed essential to keep the amount of such counterions low or absent so that they don't interfere with lather performance of EDTA-derived anionic surfactant . In a second embodiment of the invention, the invention relates to a process of making the composition of the invention to ensure that EDTA-derived surfactant is incorporated, provides desired mildness characteristics and that latherability is not at the same time compromised. More specifically, process comprises: (a) dispersing an acid form of EDTA into molten structurant system at temperature between 80°C and 120°C; and (b) adding sufficient caustic to neutralize the EDTA surfactant . This in situ neutralization process is necessary to avoid gelling of the EDTA derived surfactant. The gelling, which occurs in an aqueous solution, prevents a homogeneous mixing of the ingredients. The following examples are intended to illustrate further the invention and are not intended to limit the invention in any way. All percentages are intended to be percentages by weight unless stated otherwise. EXAMPLES Protocol of Skin Mildness Evaluation Mildness Assessments: Zein dissolution test was used to preliminary screen the irritation potention of the formulations studied. In an 8 oz. jar, 30 mLs of an aqueous dispersion of a formulation were prepared. The dispersions sat in a 45°C bath until fully dissolved. Upon equilibration at room temperature, 1.5 gms of zein powder were added to each solution with rapid stirring for one hour. The solutions were then transferred to centrifuge tubes and centrifuged for 30 minutes at approximately 3,000 rpms . The undissolved zein was isolated, rinsed and allowed to dry in 60°C vacuum oven to a constant weight. The percent zein solubilized, which is proportional to irritation potential, was determined gravimetrically . The Lather Volume Measurement : The lather performance was studied by a cylinder shaking test. Forty grams of a test solution was put in a 250 ml PYREX cylinder with cap. Foam was generated by shaking the cylinder for 0.5 minute. After the foam settled for 2.5 minutes, the foam height was measured. Example 1 An In-Vitro Test of the Skin Mildness of Na-LED3A The skin irritation potential of Na-LED3A was investigated by the zein dissolution test. As shown in Table 1, Na-LED3A dissolved significantly less amount of zein than commonly used anionic surfactants, such as sodium cocoyl isethionate and sodium lauryl ether (3EO) sulfate. The result indicates that the sodium lauroyl EDTA is an ultra-mild anionic surfactant to skin. When Na LED3a is incorporated in typical bar formulations (Example 5), the percent zein dissolved is also significantly reduced as shown below in Table 2. Example 2 Formulation Processing The Preparation of the EDTA Derived Surfactants: Sodium lauroyl EDTA (named as Na-LED3A) was obtained through neutralizing N-lauroyl-N, N'N' -ethylenediaminetriacetic (Hampshire, under the trade name of LED3A) using 50% sodium hydroxide (NaOH) solution. LED3A was first dispersed and mixed in molten polyethylene glycol 8000 at a temperature between 80°C and 120°C. A precalculated amount of sodium hydroxide solution (50%) was slowly added to neutralize the LED3A. After adequate mixing, the remaining ingredients were added. This in-situ process was used to avoid the gelling of EDTA-derived surfactants in an aqueous solution (gelling occurs at concentrations between 40% and 79% by weight in water) which prevents a homogeneous mixing of the bar material. Formulation Processing: Formulations shown in the examples of this invention were prepared in 400 mL beakers in a 100°C oil bath. Mixing was accomplished with a variable speed overhead motor. Batch size was varied from 100-250 gms. All chemicals used except the EDTA derived surfactants were commercial materials and used as supplied. Example 3 The Lather of Na-LED3A The lather performance of the Na-LED3A aqueous solution is not as satisfactory as those commonly used anionic surfactants, such as sodium lauryl ether (3EO) sulfate. As shown in Table 3, the lather volume of the 2.5% Na-LED3A is significantly less than that of SLES. However, by adding relatively low levels of SLES and Cocoamidopropyl betaine as coactives to the Na-LED3A solution, the lather performance was greatly improved. This example demonstrates the necessity of inclusion of anionic and amphoteric surfactants into an EDTA-derived surfactant based skin cleanser. * An EDTA-derived anionic surfactant defined in Example 1. Table 4 shows the lather volumes of bar formulations which are composed of Na-LED3A. This example demonstrates that acceptable lather performance is achieved when the chelating surfactant is incorporated in bar formulations. Example 4 The Defoaminσ Effect of Multi-Valence Salts to the EDTA- Derived Surfactants Organic and inorganic salts containing multi-valence salts, such as Aluminum Chloride, Magnesium Chloride, Calcium Chloride, Calcium stearate, Magnesium laurate, etc. are often used in personal washing products. However, these multi-valence salts can interact with the EDTA-derived surfactants and cause defoaming if the salt concentration is above 1% wt. total composition. As shown in Table 2, 2.5% salts significantly defoamed the EDTA-derived surfactant. Therefore, preferably, these multi-valence salts are excluded from the skin cleansing compositions claimed by this invention. * An EDTA-derived anionic surfactant defined in Example 1. Example 5 Skin Cleansing Composition All amounts are given in percentage of weight. Formulations (A) , (B) and (C) used sodium cocoyl isethionate and Na-LED3A as the major anionic detergent with amphoteric cocoamidopropyl betaine as a coactive. The formulations provide rich, creamy, and slippery lather that was rinsed off easily. *DEFI: directly esterified fatty acid isethionate, which is a mixture containing about 74% by weight of sodium acyl isethionate, 23% stearic-palmitic acid and small amounts of other materials, manufactured by Lever Brother Co. , U.S. *Na-LED3A: an EDTA-derived surfactant defined by Example 1.

Claims: CLAIMS 1. A personal washing bar composition comprising: (a) 1 to 40% by wt . of hydrophobically modified salt(s) of ethylenediaminetriacetic acid (I) wherein n is from 1 to 40; (b) 1 to 40% by wt . of one or more synthetic (non- soap) , anionic surfactants other than the EDTA derived anionics described in (1) ; and (c) 1 to 20% by wt. of one or more amphoteric and/or zwitterionic surfactants; (d) 0 to 10% nonionic; (e) 20 to 85% by wt . of a structurant selected from alkylene oxide components having a molecular weight of from 2,000 to 25,000; C 8 to C 22 free fatty acids; C 2 to C 20 alkanols; paraffin waxes; and water soluble starches; and (f) 0 to 20% by wt. of fatty acid soap; wherein no more than 1% wt . total composition comprises inorganic and organic salts of Calcium (Ca2+) , Magnesium (Mg2+) and Aluminum (A13+) and other multi-valence metal counterions, and mixtures thereof. 2. A composition according to claim 1, wherein the hydrophobically modified salt(s) of ethylenediaminetriacetic acid is greater or equal to 50% by wt . of the total anionic surfactant system; 3. A composition according to either claim 1 or claim 2, wherein the multi-valence salt is selected from calcium chloride, magnesium chloride, aluminum chloride, magnesium sulfate, magnesium stearate and calcium laurate. 4. A process for making a bar detergent composition as claimed in any preceding claim comprising: (i) dispersing an acid form of EDTA into the structurant (s) at a temperature between about 80°C to 120°C; (ii) adding sufficient caustic, for example NaOH, to neutralise the EDTA acid surfactant, such that the molar ratio of caustic to EDTA acid is from 1:1 to 1:3; and (iii) mixing the EDTA/structurant solution with remaining compounds at a temperature of 80°C to 120°C.

Inventors: FAIR MICHAEL JOSEPH, HE MENGTAO, MASSARO MICHAEL, FAIR, MICHAEL, JOSEPH, HE, MENGTAO, MASSARO, MICHAEL
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1998
Main classification: C11D1
IPC codes: C11D1, C11D17