WO2017172597A1

WO2017172597A1 - Personal cleansing compositions and methods of making same

Info

Publication number: WO2017172597A1
Application number: PCT/US2017/024271
Authority: WO
Inventors: Darren Wei-Bun TANG; Edward Dewey Smith, Iii; Jason Edward COOK
Original assignee: The Procter & Gamble Company
Priority date: 2016-03-30
Filing date: 2017-03-27
Publication date: 2017-10-05
Also published as: PH12018502081A1; CN108697910A

Abstract

Personal cleansing compositions include zinc pyrithione and a soluble zinc salt where the composition has an acid pH. Methods of making the personal cleansing compositions and for improving stability of ZPT at acid pH are also provided.

Description

PERSONAL CLEANSING COMPOSITIONS AND METHODS OF MAKING SAME

TECHNICAL FIELD

The present disclosure generally relates to personal cleansing compositions having zinc pyrithione and a soluble zinc salt; and methods of making personal cleansing compositions and for improving stability of zinc pyrithione.

BACKGROUND

To help promote hygiene, humans cleanse their skin. Cleansing of the skin can help prevent odor and can also help prevent the spread of germs and disease. Some of these cleansing compositions can be formulated at an acid pH which can give rise to some interesting formulation challenges. Accordingly, it would be desirable to provide a personal cleansing composition and methods for making such a composition.

SUMMARY

A personal cleansing composition comprising: a surfactant; from about 0.01% to about 2.0%, by weight of the personal cleansing composition, of zinc pyrithione; from about 0.00762% to about 2.0%, by weight of the personal cleansing composition, of a soluble zinc salt; and a structurant; wherein the personal cleansing composition has a pH of about 4.0 to about 6.0.

A skin cleansing composition, comprising: a) from about 7% to about 20%, by weight of the composition, of a surfactant; b) from about 0.4% to about 1.0%, by weight of the skin cleanser, of zinc pyrithione; c) from about 0.04% to about 1.0%, by weight of the skin cleanser, of a soluble zinc salt; and d) from about 0.05% to about 1.0%, by weight of the skin cleanser, of a structurant, wherein the skin cleanser has a pH of about 4.0 to about 5.0.

These and other formulations and methods will be described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting the zinc pyrithione level over time of compositions with zinc pyrithione and no soluble zinc salt (nil ZnS0₄), a composition with a 1:1 mol ratio of a soluble zinc salt to zinc pyrithione (1:1 mol ZnS0₄:ZPT), and a composition with a 10:1 mol ratio of a soluble zinc salt to zinc pyrithione (1:1 mol ZnS0₄:ZPT) when aged in an oven at 50°C, where the level of perfume is 0.70%, by weight of the composition; FIG. 2 is a graph depicting the zinc pyrithione level over time of a composition with zinc pyrithione and no soluble zinc salt (nil ZnS0₄), a composition with a 1:1 mol ratio of a soluble zinc salt to zinc pyrithione (1:1 mol ZnS0₄:ZPT), and a composition with a 10:1 mol ratio of a soluble zinc salt to zinc pyrithione (1:1 mol ZnS0₄:ZPT) when aged in an oven at 50°C, where the level of perfume is 0.35%, by weight of the composition;

FIG. 3 is a graph depicting the zinc pyrithione level over time of a composition with zinc pyrithione and no soluble zinc salt (nil ZnS0₄) and a composition with 0.0762%, by weight of the composition, of a soluble zinc salt to zinc pyrithione (0.0762% ZnS0₄) when aged in an oven at 50°C;

FIG. 4 is a graph depicting the zinc pyrithione level over time of a composition with zinc pyrithione and no soluble zinc salt (nil ZnS0₄) and a composition with 0.0762%, by weight of the composition, of a soluble zinc salt to zinc pyrithione (0.0762% ZnS0₄) when aged in an oven at 50°C;

FIG. 5 is a graph depicting the zinc pyrithione level over time of a composition with zinc pyrithione and no soluble zinc salt (nil ZnS0₄) and a composition with 0.0762%, by weight of the composition, of a soluble zinc salt to zinc pyrithione (0.0762% ZnS0₄) when aged in an oven at 40°C; and

FIG. 6 is a graph depicting the zinc pyrithione level over time of a composition with zinc pyrithione and no soluble zinc salt (nil ZnS0₄) and a composition with 0.0762%, by weight of the composition, of a soluble zinc salt to zinc pyrithione (0.0762% ZnS0₄) when aged in an oven at 40°C.

DETAILED DESCRIPTION

I. Definitions

As used herein, the following terms shall have the meaning specified thereafter:

"Personal cleansing composition" refers to compositions intended for topical application to skin. Personal cleansing compositions can be rinse-off formulations, in which the product can be applied topically to the skin and then subsequently rinsed within seconds to minutes from the skin with water. The product could also be wiped off using a substrate. Personal cleansing compositions can also be used as shaving aids. Examples of personal cleansing compositions can include but are not limited to body washes, liquid hand soap, moisturizing body washes, shower gels, skin cleansers, cleansing milks, pet shampoos, shaving preparations, and cleansing compositions used in conjunction with a disposable cleansing cloth. "Rinse-off means the intended product usage includes application to skin and/or hair followed by rinsing and/or wiping the product from the skin and/or hair within a few seconds to minutes of the application step.

"Soluble zinc salt" refers to a salt of zinc which has a solubility in water at 20°C and at 1 atm of pressure of greater than 1 g salt / 100 mL water.

"Structurant" refers to a substance/ingredient that helps to structure a personal cleansing composition so that it is physically stable, i.e., so that particles do not settle and droplets do not float. Structurants can include materials which may be, for example, insoluble gellants or polymers. Insoluble gellants can form a network, while polymer gellants may confer structure by filling space or by forming a network.

"Structured" refers to having a rheology that can confer stability on the personal cleansing composition. Generally, a personal cleansing composition can be considered to be structured if particles or groups of particles (e.x. floes) that are more dense than the continuous phase and large enough to exhibit insignificant Brownian motion do not settle; or if the particles are less dense than the continuous phase, the particles do not rise, or cream, during the product lifetime.

"Viscosity" refers to the viscosity of a cleansing composition, where the viscosity is measured by using a cone and a plate rheometer and applying a shear rate of 2 s^"1 to the cleansing composition.

Levels of materials are by active weight percentage unless otherwise noted.

II. Personal cleansing Compositions

It has been suggested in the literature that compositions containing zinc pyrithione can provide cosmetic benefits to skin, thus improving skin health. For example, it is believed that zinc pyrithione can provide an antimicrobial effect on the skin. It can be desirable to provide an antimicrobial effect on the skin using zinc pyrithione from a composition that has an acidic pH, for example to provide a combination of rapid germ kill or even enhanced product preservation from the low pH, with residual antimicrobial activity from the zinc pyrithione. However, acidic pH environments (6.0 and below) can be harsh toward components in a composition and can contribute to chemical instability. In addition, perfume can compound the stability issues at an acidic pH. To ensure optimum benefits over the life of a product, personal cleansing compositions should maintain zinc pyrithione at optimum levels throughout the product's shelf life, even in relatively acidic pH environments. To look at the levels of zinc pyrithione in a cleansing composition over time, accelerated aging can be used. Accelerated aging generally involves placing a product in a lidded container in an oven at an elevated temperature (like 40°C or 50°C). Accelerated aging can indicate how a product will age, including the stability of components in the product, such as zinc pyrithione. When looking at zinc pyrithione in a cleansing composition utilizing accelerated aging, the present inventors discovered that including a soluble zinc salt with zinc pyrithione can improve the stability of zinc pyrithione in such an acidic pH composition over time.

FIGS. 1 and 2 show the results of testing a cleansing composition, a hand wash, at a pH of about 6.0, with zinc pyrithione without a soluble zinc salt (nil ZnS0₄) and with a zinc salt (1:1 mol ZnS0₄:ZPT and 10:1 mol ZnS0₄:ZPT) in a 50°C oven for 10 days. The difference in the compositions tested between FIGS. 1 and 2 is the perfume and level of the perfume. The zinc pyrithione level in the compositions was about 0.015% in each to start (data are normalized to precisely 0.015% in order to easily see relative differences.) As can be seen from FIGS. 1 and 2, regardless of the perfume or perfume level tested, the zinc pyrithione stability was improved (i.e. more zinc pyrithione was present at day 10) in all of the compositions with the combination of zinc pyrithione and the soluble zinc salt over the composition with zinc pyrithione with no soluble zinc salt. In addition, the compositions with the 10:1 mol ratio showed more stability improvement than the 1:1 ratio.

FIGS. 2 and 3 show the results of testing a cleansing composition, a hand wash, at a pH of about 4.5, with zinc pyrithione without a soluble zinc salt (nil ZnS0₄) and with a soluble zinc salt (0.0762% ZnS0₄) in a 50°C oven for 10 days. The difference between the compositions tested between FIGS. 2 and 3 is the perfume. The zinc pyrithione level in the compositions was about 0.020% in each to start (data are normalized to precisely 0.020% in order to easily see relative differences). As can be seen from FIGS. 2 and 3, regardless of the perfumes tested, the zinc pyrithione stability was improved in both compositions where the combination of zinc pyrithione and the soluble zinc salt had more zinc pyrithione present at day 10.

The compositions were also tested at a lower temperature (40°C), but over a longer period of time, 30 days. At day 30, again, zinc pyrithione stability was improved in both of the compositions with the combination of zinc pyrithione and a soluble zinc salt at day 30, as shown in FIGS. 5 and 6.

While certain zinc salts, like zinc carbonate, have been taught to be a zinc pyrithione potentiator by improving the bioavailability of the zinc pyrithione, especially for use in shampoo, zinc carbonate is not a soluble zinc salt. Therefore, it will not provide a significant source of zinc ions to assist with the chemical stability of zinc pyrithione.

Personal Cleansing Compositions

Personal cleaning compositions can include a surfactant, zinc pyrithione, a soluble zinc salt, and a structurant, wherein the composition is at a pH of about 4.0 to about 6.0, or at a pH of about 4.0 to about 5.0, or at a pH of about 4.5. The cleansing compositions are structured. Personal cleansing compositions can include rinse-off personal cleansing compositions. Personal cleansing compositions can have a yield stress of from about 10^"3 Pa to about 10 Pa, or from about 10^"2 Pa to about 1.0 Pa. Yield stress can be measured in accordance with the method below. In addition, a personal cleansing composition can maintain at least about 97% of the weight percent of zinc pyrithione originally present after aging at 40°C for 30 days.

Zinc pyrithione, also known as zinc omadine, or a zinc salt of l-hydroxy-2- pyridinethione, for example, a mercaptopyridine-N-oxide zinc salt is included in a cleansing composition. Zinc pyrithione can be included, for example, at a level of about 0.01% to about 2.0%, by weight of the cleansing composition. Zinc pyrithione can also be present at a level from 0.05%, 0.075%, 0.10%, 0.15%, 0.20%, 0.5%, 1.0% to about 1.5%, 2.0%, or any combination thereof, by weight of the composition. Thus, levels of 0.05% to about 2.0%, 0.075% to about 2.0%, 0.10% to about 2.0%, 0.15% to about 2.0%, 0.20% to about 2.0%, 0.5% to about 2.0%, from about 0.4% to about 1.0%, etc. of zinc pyrithione by weight of the cleansing composition are envisioned.

Zinc pyrithione can be, for example, made by reacting l-hydroxy-2-pyridinethione (i.e., pyrithione acid) or a soluble salt thereof with a zinc salt (e.g. zinc sulfate) to form a zinc pyrithione precipitate as illustrated in U.S. Patent No. 2,809,971 and the zinc pyrithione can be formed or processed into a platelet form using, for example, sonic energy as illustrated in U.S. Patent No. 6,682,724.

Zinc pyrithione can take the form of particulates, which can be shaped, for example, as platelets, rods, needles, cubes, sheets, or a combination thereof. For example, where the zinc pyrithione is introduced as particulate, such particulates may have an average particle size (i.e. diameter) from about 0.1 μιη to about 20 μιη; such particulates may also have an average particle size from about 0.2 μιη to about 10 μιη, or from about 0.3 μιη to about 1.5 μιη.

The composition also comprises a soluble zinc salt. Soluble zinc salt is defined above. Zinc salt can be present, for example, from about 0.00762% to about 2%, by weight of the cleansing composition. A soluble zinc salt can also be present at a level from 0.01%, 0.025%, 0.04%, 0.05%, 0.07%, 0.0762% to about 0.5%, 1.0%, 1.5%, 2.0%, or any combination thereof, by weight of the composition. Thus, levels of about 0.01% to about 2.0%, about 0.025% to about 2.0%, about 0.04% to about 2.0%, about 0.05%, to about 2.0%, about 0.07% to about 2.0%, about 0.07% to about 2.0%, about 0.04% to about 1.0%, etc. of a soluble zinc salt by weight of the cleansing composition is envisioned.

In addition, the soluble zinc salt may be present as a mol ratio by weight with the zinc pyrithione. For example, the composition may have a mol weight ratio of soluble zinc salt to zinc pyrithione of about 1:1 to about 10:1. Soluble zinc salts can include, for example, zinc sulfate, zinc acetate, zinc bromide, zinc chloride, zinc citrate, zinc fluoride, zinc gluconate, zinc iodide, zinc phosphate, or combinations thereof.

A cleansing composition may also comprise a structurant. A structurant helps to modify the viscosity of a composition. A structurant can be present in an amount of 0.01 % to about 5%, by weight of the composition. A structurant can also be present at a level from 0.05%, 0.10%, 0.30%, 0.50%, 1.00%, 1.50% to about 1.00 %, 2.00%, 3.00%, 4.00%, 5.00%, or any combination thereof, by weight of the composition. Thus, levels of 0.05% to about 5.0%, 0.10% to about 5.0%, about 0.30% to about 4.0%, about 0.5% to about 2.0%, about 0.05% to about 1.0%, etc. of structurant by weight of the cleansing composition are envisioned.

Examples of suitable structurants can include lipid structurants, naturally derived structurants, mineral structurants, synthetic structurants, ionic structurants, or a combination thereof. Examples of suitable lipid structurants can include cetyl alcohol, stearyl alcohol, carnauba wax, stearic acid, trihydroxystearin, hydrogenated castor oil, ethylene glycol distearate, cellulose, or a combination thereof. Examples of suitable mineral structurants can include silica, bentonite, magnesium aluminum silicate, or a combination thereof. Examples of suitable naturally derived structurants can include cellulose, guar gum, locust bean gum, xanthan gum, gellan gum, pectin, gelatin, or a combination thereof. Examples of suitable synthetic structurants can include acrylic acid polymers, acrylamide polymers and copolymers, acrylates copolymers and acrylates/vinyl isodecanoate crosspolymer, or a combination thereof. Examples of suitable ionic structurants can include salts, like sodium chloride.

A structurant can include, for example, trihydroxystearin, ethylene glycol distearate, a structuring polymer, or a combination thereof. The structurant can be, for example, trihydroxystearin.

Structurants can be used to ensure a composition has a viscosity which falls within a particular range. Personal cleansing compositions can have a viscosity of, for example, from about 500 cP to about 100,000 cP, from about 1,500 cP to about 20,000 cP, from about 3,000 cP to about 15,000 cP; or from about 500 cP, 1,500 cP, 3,000 cP, to about 10,000 cP; about 20,000 cP; about 30,000 cP; about 40,000 cP; or about 50,000 cP, or any combination thereof.

A personal cleansing composition can include a surfactant. A personal cleansing composition can include, for example, from about 1.0% to about 50%; from about 5% to about 40%; from about 10% to about 35%, or from about 7% to about 20%, by weight of the composition of surfactant. Surfactants can include anionic, amphoteric, zwitterionic, nonionic, or mixtures thereof. A wide variety of anionic surfactants are potentially useful herein. Non- limiting examples of anionic lathering surfactants include those selected from the group consisting of alkyl and alkyl ether sulfates, sulfated monoglycerides, sulfonated olefins, alkyl aryl sulfonates, primary or secondary alkane sulfonates, alkyl sulfosuccinates, acyl taurates, acyl isethionates, alkyl glycerylether sulfonate, sulfonated methyl esters, sulfonated fatty acids, alkyl phosphates, acyl glutamates, acyl sarcosinates, alkyl sulfoacetates, acylated peptides, alkyl ether carboxylates, acyl lactylates, anionic fluorosurfactants, and mixtures thereof.

Specific examples of alkyl sulfates which may be used in the cleansing compositions are sodium, ammonium, potassium, magnesium, or TEA salts of lauryl or myristyl sulfate. Examples of alkyl ether sulfates which may be used can include ammonium, sodium, magnesium, or TEA, laureth-n sulfate. The n may be 1-3.

Non-limiting examples of acyl isethionates include ammonium cocoyl isethionate, sodium cocoyl isethionate, sodium lauroyl isethionate, and mixtures thereof.

An exemplary list of anionic surfactant can include sodium lauryl sulfate, sodium laureth(n) sulfate (where n is 1-3), ammonium lauryl sulfate, ammonium laureth(n) sulfate (where n is 1-3).

Anionic surfactants can include, for example, sodium lauryl sulfate, sodium laureth(n) sulfate, ammonium lauryl sulfate, ammonium laureth sulfate, sodium cocoyl isethionate, ammonium cocoyl isethionate, or a combination thereof.

Amphoteric surfactants can include those that can be broadly described as derivatives of aliphatic secondary and tertiary amines in which an aliphatic radical can be straight or branched chain and wherein an aliphatic substituent can contain from about 8 to about 18 carbon atoms such that one carbon atom can contain an anionic water solubilizing group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. Examples of compounds falling within this definition can be sodium 3-dodecyl-aminopropionate, sodium 3-dodecylaminopropane sulfonate, sodium lauryl sarcosinate, N-alkyltaurines such as the one prepared by reacting dodecylamine with sodium isethionate according to the teaching of U.S. Patent No. 2,658,072, N-higher alkyl aspartic acids such as those produced according to the teaching of U.S. Patent No. 2,438,091, and products described in U.S. Patent No. 2,528,378. Other examples of amphoteric surfactants can include sodium lauroamphoacetate, sodium cocoamphoacetate, disodium lauroamphoacetate disodium cocodiamphoacetate, and mixtures thereof. Amphoacetates and diamphoacetates can also be used.

Zwitterionic surfactants suitable for use can include those that are broadly described as derivatives of aliphatic quaternary ammonium, phosphonium, and sulfonium compounds, in which aliphatic radicals can be straight or branched chains, and wherein an aliphatic substituent can contain from about 8 to about 18 carbon atoms such that one carbon atom can contain an anionic group, e.g., carboxy, sulfonate, sulfate, phosphate, or phosphonate. Other zwitterionic surfactants can include betaines, including cocamidopropyl betaine (CAPB).

Nonionic surfactants suitable for use can include those selected from the group consisting of alkyl ethoxylates, alkyl glucosides, polyglucosides (e.g., alkyl polyglucosides, decyl polyglucosides), polyhydroxy fatty acid amides, alkoxylated fatty acid esters, sucrose esters, amine oxides, or mixtures thereof.

A personal cleansing composition can also include water. Water can be included, for example, in a level of about 40% to about 75%, by weight of the composition.

Other non-limiting optional additives can be included in a personal cleansing composition, including for example pH adjuster. These are used to adjust the pH of the composition to the desired target or range and/or provide a buffering effect to the composition. Exemplary pH adjusters can include any suitable organic acid or base, such as citric acid, hydrochloric acid, sodium hydroxide, or a combination thereof. Another optional additive can include an antimicrobial. Suitable antimicrobials can include, for example, chloroxylenol, sodium salicylate, and salicylic acid. Preservatives can also be included in the personal cleansing composition. Exemplary preservatives can include sodium benzoate, benzyl alcohol, methylchloroisothiazolinone, methylisothiazolinone. Perfume can also be included in a personal cleansing composition. Perfume can be included at a level of 0.05% to about 3%, or 0.5% to about 1%, by weight of the composition.

Other optional ingredients can be most typically those materials approved for use in cosmetics and that are described in the CTFA Cosmetic Ingredient Handbook, Second Edition, The Cosmetic, Toiletries, and Fragrance Association, Inc. 1988, 1992. Such optional ingredients as described herein can be categorized or described by their cosmetic and/or therapeutic benefit or their postulated mode of action or function. However, it can be understood that actives and other materials useful herein can, in some instances, provide more than one cosmetic and/or therapeutic benefit or function or operate via more than one mode of action. Therefore, classifications herein can be made for convenience and cannot be intended to limit an ingredient to particularly stated application or applications listed. A precise nature of these optional materials, and levels of incorporation thereof, will depend on the physical form of the composition and the nature of the cleansing operation for which it is to be used.

Personal cleansing compositions can be applied by a variety of means, including by rubbing, wiping or dabbing with hands or fingers, or by means of an implement and/or delivery enhancement device. Non-limiting examples of implements can include a sponge or sponge- tipped applicator, a mesh shower puff, a swab, a brush, a wipe (e.g., wash cloth), a loofah, and combinations thereof. Non-limiting examples of delivery enhancement devices can include mechanical, electrical, ultrasonic and/or other energy devices. A personal cleansing composition may be sold together with such an implement or device. Alternatively, an implement or device can be sold separately but contain indicium to indicate usage with a personal cleansing composition. Implements and delivery devices can employ replaceable portions (e.g., the skin interaction portions), which can be sold separately or sold together with the personal cleansing composition in a kit.

Also included herein are methods for preserving zinc pyrithione in a cleansing composition at a pH of about 4.0 to about 6.0, or a pH of about 4.0 to about 5.0, or a pH of about 4.5. This method includes incorporating a soluble zinc salt into a cleansing composition with zinc pyrithione.

The components discussed above with respect to the personal cleansing composition can be employed in such methods and can contain any combination of components as described herein.

Procedures

A. Iodine-Based Titration Method

The content of a pyrithione material, such as zinc pyrithione, in personal cleansing compositions can be measured by an iodine-based titration method. For example, a mercapto group in zinc pyrithione (ZPT) can be titrated by iodine, which can oxidize it to a disulfide-2,2' dithiobispyridine-l-oxide. If zinc pyrithione has already been oxidized or undergone transformation otherwise so that it no longer possesses the mercapto group, it will not be detectible by the iodine-based titration method described hereinafter.

First, a standardized 0.04 N iodine solution is prepared as follows. Anhydrous sodium thiosulphate (with a minimum purity of 99%) is oven-dried for 2 hours at 105 °C and then stored in a desiccator. Then, 0.05 g (+/-0.0001 g) of the anhydrous sodium thiosulfate is weighed and placed into the 100 mL polypropylene beaker of an autotitrator, and 50 mL of deionized water is added to form a standard solution. The autotitrator used herein is preferably a Mettler DL25 or Mettler DM140-SC titrator with a platinum ring electrode, which is commercially available from Mettler Toledo International, Inc. (Switzerland), or an equivalent thereof. The autotitrator is set up to titrate the standard sodium thiosulfate solution with the iodine solution that is being standardized. Bubbles are eliminated from the burette of the autotitrator, and titration is commenced. Such procedure is repeated twice more, and the results are averaged to obtain a standardized 0.04 N iodine solution. The % relative standard deviation (RSD) should be less than 1 % of the average.

Next, standardized 0.01 N and 0.006 N iodine solutions are prepared. Specifically, standardized 0.0 IN iodine solution is prepared using 0.10 g (+/-0.0001 g) sodium thiosulphate dissolved in 100 mL deionized water, using 10.0 mL pipetted into the 100 mL autotitrator breaker with 50 mL additional deionized water followed by the titration procedure. Standardized 0.006 N iodine solution is prepared using 3.0 mL of a 0.01 M sodium thiosulphate solution and 40 mL of a solvent (containing 13% v/v hydrochloric acid in 6% v/v butanol), followed by addition of 40 mL of 1:1 hexane/isopropanol. The auto titration procedure is subsequently carried out. The standardized solutions are prepared daily.

4.00 g of the personal cleansing composition is weighed and put into a clean, dry beaker of an autotitrator. 75 mL of hot 6% v/v butanol (which was heated in a boiling- water bath) and 5 mL of concentrated HC1 (provided at room temperature) are then added into the beaker. The mixture is agitated vigorously for a few minutes so as to fully dissolve all soluble components. The beaker is subsequently placed in the autotitrator, and bubbles are completely eliminated from the burette.

The titration is then initiated and analyzed while the mixture is still warm. The mixture is vigorously agitated during the titration procedure. For compositions with less than 0.2% of ZPT by weight of the personal cleansing composition, titration is carried out using the 0.006N iodine solution. For compositions with higher ZPT concentrations, the initial starting sample weight can be reduced. Titration can be done either manually or by using auto titration procedi those with skill in the art.

The ZPT content in the personal cleansing composition is calculated as follows:

Volume of Iodine Solution (mL)x N x 15.88%

ZPT Content (%) =

Sample Weight (g) wherein N is the normality of the standardized iodine solution, and wherein 15.88% is a constant that is derived from:

Molecular Weight of ZPT x 100% 371.6 x 100%

15.88% =

No. of Pyrithione per Molecule x 1000 mL/L 2 x 1000

The above-described procedure is repeated three times for each personal cleansing composition whose ZPT content is to be measured, and the results are averaged to obtain a final ZPT content in percentage (%) for the specific personal cleansing composition.

All chemical reagents employed hereinabove are high-purity reagents obtained from VWR Scientific (Batavia, Illinois, USA) or other scientific chemical suppliers.

Examples

Tables 1-4 below illustrate formulations for personal cleansing compositions.

Table 1

As added Active in

RM RM Activity

(wt. %) FP (wt. %) water 1.00 59.845 59.845

Zinc Pyrithione (Premix ZPT

dilution (24%) <50% 96338895 0.24 0.8330 0.2000

(48% ZPT) and 50% water>)

zinc sulfate (solid) 1.00 0.0762 0.0762

Sodium Salicylate 1.00 0.2500 0.2500

Sodium Benzoate 1.00 0.4500 0.4500

Benzyl Alcohol 1.00 0.2500 0.2500

Sodium laureth3 sulfate 0.28 23.21 6.500

Sodium Lauryl Sulfate 0.29 8.621 2.500

Cocamidopropyl Betaine 0.30 3.333 1.000

Citric acid 1.00 0.4000 0.4000

Trihydroxystearin 1.00 0.1320 0.1320

Sodium Chloride 1.00 2.000 2.0000

Perfume 1.00 0.6000 0.6000

total 100.0 Table 2

As added Active in

RM RM Activity

(wt. %) FP (wt. %) water 1.00 60.62 60.62

Zinc Pyrithione (Premix ZPT

dilution (24%) <50% 96338895 0.24 0.0625 0.0150 (48% ZPT) and 50% water>)

zinc sulfate (solid) 1.00 0.0762 0.0762

Sodium Salicylate 1.00 0.2500 0.2500

Sodium Benzoate 1.00 0.4500 0.4500

Benzyl Alcohol 1.00 0.2500 0.2500

Sodium laureth3 sulfate 0.28 23.21 6.499

Sodium Lauryl Sulfate 0.29 8.621 2.500

Cocamidopropyl Betaine 0.30 3.333 0.9999

Citric acid 1.00 0.4000 0.4000

Trihydroxystearin 1.00 0.1320 0.1320

Sodium Chloride 1.00 2.000 2.000

Perfume 1.00 0.6000 0.6000 total 100.0

Table 3

As added Active in

RM RM Activity

(wt. %) FP (wt. %) water 1.00 58.66 58.66

Zinc Pyrithione (Premix ZPT

dilution (24%) <50% 96338895 0.24 2.083 0.5000 (48% ZPT) and 50% water>)

zinc sulfate (solid) 1.00 0.00762 0.00762

Sodium Salicylate 1.00 0.2500 0.2500

Sodium Benzoate 1.00 0.4500 0.4500

Benzyl Alcohol 1.00 0.2500 0.2500

Sodium laureth3 sulfate 0.28 23.21 6.499

Sodium Lauryl Sulfate 0.29 8.621 2.500

Cocamidopropyl Betaine 0.30 3.333 0.9999

Citric acid 1.00 0.4000 0.4000

Trihydroxystearin 1.00 0.1320 0.1320

Sodium Chloride 1.00 2.000 2.000

Perfume 1.00 0.6000 0.6000 total 100.0 Table 4

The personal cleansing compositions are prepared by the following process. A ZPT premix is made by adding equal parts of 48% aqueous ZPT (Fine Particle Size ZPT obtained from Lonza, Inc, USA) and DI water to a beaker while stirring. A main mix is prepared by heating sodium laureth-3 sulfate and sodium lauryl sulfate to 91 + 3°C in a jacketed mixing vessel while mixing. The main mix is then pH adjusted with citric acid. Then, cocamidopropyl betaine is added to the mixing vessel followed by sodium benzoate. The mixture is then transported to a final mixing vessel through a heat exchanger with an inlet temperature of 91 + 3°C and an outlet temperature of 70 + 3°C. Remaining DI water is added to the mixing vessel. Sodium laureth-3 sulfate, sodium lauryl sulfate, and cocamidopropyl betaine are added to the mixing vessel as necessary, followed by mixing until homogeneous. The zinc salt is added to the mixing vessel, followed by mixing until fully dissolved and homogeneous. Perfume is added and mixed for at least 10 minutes. Sodium benzoate is then added as necessary and allowed to dissolve into the mixture for at least 2 minutes. Citric acid is used to titrate the mixture until a pH of about 4.5 was reached, followed by the addition of benzyl alcohol, zinc sulfate, and sodium salicylate until well-mixed. Then the zinc pyrithione premix is added. The mixture is mixed for at least 5 minutes to allow full dispersion of the zinc pyrithione. Sodium chloride is then added and allowed to dissolve into the mixture for at least 2 minutes. DI water and/or sodium chloride are then added to adjust the viscosity of the mixture, which had a target range of 1,500-4,500 cP.

Yield Stress Method

Using a controlled stress rheometer such as AR G2, AR2000, Discovery series, or rheometer of equivalent low stress capability, the following procedure is used to measure yield stress, which determines the robustness of a network or any other structurant used. A consistent amount is added to the lower plate to start and the edge is not trimmed (thus no trim needed), and geometry is locked prior to moving into position. A steady state flow test is implemented to ramp shear stress from 10^"5 Pa to 10 Pa in "log" mode taking three points per decade at a temperature of 25°C using a 40 mm diameter, 1 degree cone upper geometry (parallel plate can be substituted if large particles are present). The percentage tolerance is set to 5% with three consecutive points within tolerance and a maximum point time of 50 seconds. In order to reduce edge drying artifacts, only a few data points are taken on the log scale. Therefore, when analyzing the data set, interpolation is required from the two data points that encompass the area on the plot that intersects the "shear stress" axis (zero shear rate). In the event that a negative shear rate point is not achieved, the first two points at a stress having positive shear rates are used to calculate the intercept on the stress axis where the shear rate is zero. The data points are plotted with linear shear rate vs. linear shear stress for this analysis. A personal cleansing composition can have a yield stress of, for example, from about 10^"3 Pa to about 10 Pa, or from about 10^"2 Pa to about 1.0 Pa.

Examples/Combinations

A. A personal cleansing composition comprising: a surfactant; from 0.01% to 2.0%, by weight of the personal cleansing composition, of zinc pyrithione; from 0.00762% to 2.0%, by weight of the personal cleansing composition, of a soluble zinc salt; and a structurant; wherein the personal cleansing composition has a pH of 4.0 to 6.0.

B. Use of a soluble zinc salt to stabilize zinc pyrithione in an acidic personal cleansing composition, wherein the personal cleansing composition comprises a surfactant; from 0.01% to 2.0%, by weight of the personal cleansing composition, of zinc pyrithione; from 0.00762% to 2.0%, by weight of the personal cleansing composition, of the soluble zinc salt; and a structurant; wherein the personal cleansing composition has a pH of about 4.0 to about 6.0.

C. The use or personal cleansing composition of paragraphs A and B, wherein the personal cleansing composition further comprises a perfume. D. The use or personal cleansing composition of paragraphs A-C, wherein the composition maintains at least 97% of the weight percent of zinc pyrithione originally present after aging at 40°C for 30 days.

E. The use or personal cleansing composition of paragraphs A-D, wherein the soluble zinc salt is comprises sulfate, zinc acetate, zinc bromide, zinc chloride, zinc citrate, zinc fluoride, zinc gluconate, zinc iodide, zinc phosphate, zinc-containing layered materials, or a combination thereof.

F. The use or personal cleansing composition of paragraphs A-E, wherein the structurant comprises trihydroxystearin, ethylene glycol distearate, structuring polymers, or a combination thereof.

G. The use or personal cleansing composition of paragraphs A-F, wherein the composition comprises from 0.1% to 5.0%, by weight of the composition, of the structurant.

H. The use or personal cleansing composition of paragraphs A-G, wherein the structurant comprises trihydroxystearin and is present in an amount of 0.05% to 1.0%, by weight of the composition.

I. The use or personal cleansing composition of paragraphs A-H, wherein the composition has a pH of 4.0 to 5.0, or 4.5.

J. The use or personal cleansing composition of paragraphs A-I, wherein the soluble zinc salt comprises zinc sulfate.

K. The use or personal cleansing composition of paragraphs A-J, wherein the soluble zinc salt is present at an amount of 0.04% to about 2.0%, by weight of the composition.

L. The use or personal cleansing composition of paragraphs A-K, wherein the cleansing composition further comprises from 40% to 75%, by weight of the cleansing composition, of water.

M. The use or personal cleansing composition of paragraphs A-L, wherein the cleansing composition comprises from 7% to 20%, by weight of the cleansing composition, of the surfactant.

N. The use or personal cleansing composition of paragraphs A-M, wherein the cleansing composition further comprises citric acid.

O. The use or personal cleansing composition of paragraphs A-N, wherein the cleansing composition is a rinse-off composition.

P. The use or personal cleansing composition of paragraphs A-O, wherein the composition is structured. Q. A hand wash, comprising: a surfactant; from 0.05% to 2.0%, by weight of the hand wash, of zinc pyrithione; from 0.05% to 2.0%, by weight of the hand wash, of a soluble zinc salt; and a structurant; wherein the hand wash has a pH of 4.0 to 5.0.

R. The hand wash of paragraph Q, wherein the composition maintains at least 97% of the weight percent of zinc pyrithione originally present after aging at 40°C for 30 days.

S. The hand wash of paragraphs Q-R, wherein the soluble zinc salt is selected from the group comprising zinc sulfate, zinc acetate, zinc bromide, zinc chloride, zinc citrate, zinc fluoride, zinc gluconate, zinc iodide, zinc phosphate, or a combination thereof.

T. The hand wash of paragraphs Q-S, wherein the structurant is comprises trihydroxystearin, ethylene glycol distearate, a structuring polymer, or a combination thereof.

U. The hand wash of paragraphs Q-T, wherein the hand wash comprises from 0.1% to 5%, by weight of the hand wash, of the structurant.

V. The hand wash of paragraphs Q-U, wherein the hand wash further comprises sodium salicylate or salicylic acid.

W. The hand wash of paragraphs Q-V, wherein the hand wash further comprises from 40% to 75%, by weight of the hand wash, of water.

X. The hand wash of paragraphs Q-W, wherein the hand wash comprises from 7% to about 20%, by weight of the hand wash, of the surfactant.

Y. A skin cleansing composition, comprising: a) from 7% to 20%, by weight of the composition, of a surfactant; b) from 0.4% to 1.0%, by weight of the skin cleanser, of zinc pyrithione; c) from 0.04% to 1.0%, by weight of the skin cleanser, of a soluble zinc salt; and d) from 0.05% to 1.0%, by weight of the skin cleanser, of a structurant, wherein the skin cleanser has a pH of 4.0 to 5.0.

Z. The skin cleansing composition of paragraph Y, wherein the skin cleanser further comprises a pH adjuster.

AA. The skin cleansing composition of paragraph Z, wherein the pH adjuster comprises citric acid.

BB. The skin cleansing composition of paragraphs Y-AA, wherein the structurant comprises trihydroxystearin.

CC. The skin cleansing composition of paragraphs Y-BB, further comprising sodium salicylate, salicylic acid, or a combination thereof.

DD. The skin cleansing composition of paragraphs Y-CC, wherein the soluble zinc salt comprises zinc sulfate. EE. The skin cleansing composition of paragraphs Y-DD, wherein the cleansing composition is a rinse-off composition.

FF. The skin cleansing composition of paragraphs Y-EE, wherein the composition is structured.

GG. The skin cleansing composition of paragraphs Y-FF, wherein the composition further comprises a perfume.

It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

The products and methods/processes of the present disclosure can comprise, consist of, and consist essentially of the essential elements and limitations of the invention described herein, as well as any of the additional or optional ingredients, components, steps, or limitations described herein.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm."

Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

CLAIMS What is claimed is:

1. A personal cleansing composition comprising: a surfactant; from 0.01% to 2.0%, by weight of the personal cleansing composition, of zinc pyrithione; from 0.00762% to 2.0%, by weight of the personal cleansing composition, of a soluble zinc salt; and a structurant; wherein the personal cleansing composition has a pH of 4.0 to 6.0.

2. The personal cleansing composition of claim 1, wherein the personal cleansing composition further comprises a perfume.

3. The personal cleansing composition of claims 1 and 2, wherein the composition maintains at least 97% of the weight percent of zinc pyrithione originally present after aging at 40°C for 30 days.

4. The personal cleansing composition of claims 1-3, wherein the soluble zinc salt comprises zinc sulfate, zinc acetate, zinc bromide, zinc chloride, zinc citrate, zinc fluoride, zinc gluconate, zinc iodide, zinc phosphate, zinc-containing layered materials, or a combination thereof; preferably zinc sulfate.

5. The personal cleansing composition of claims 1-4, wherein the structurant comprises trihydroxystearin, ethylene glycol distearate, a structuring polymer, or a combination thereof; preferably trihydroxystearin.

6. The personal cleansing composition of claims 1-5, wherein the composition comprises from 0.1% to 5.0%, preferably 0.05% to 1.0%, by weight of the composition, of the structurant.

7. The personal cleansing composition of claims 1-6, wherein the composition has a pH of 4.0 to 5.0, preferably 4.5.

8. The personal cleansing composition of claims 1-7, wherein the soluble zinc salt is present at an amount of 0.04% to about 2.0%, by weight of the composition.

9. The personal cleansing composition of claims 1-8, wherein the cleansing composition further comprises from 40% to 75%, by weight of the cleansing composition, of water.

10. The personal cleansing composition of claims 1-9, wherein the cleansing composition comprises from 7% to 20%, by weight of the cleansing composition, of the surfactant.

11. The personal cleansing composition of claims 1-10, wherein the cleansing composition is a rinse-off composition.

12. The personal cleansing composition of claims 1-11, wherein the composition is structured.

13. Use of a soluble zinc salt to stabilize zinc pyrithione in an acidic rinse-off personal cleansing composition, wherein the personal cleansing composition comprises a surfactant; from 0.01% to 2.0%, by weight of the personal cleansing composition, of zinc pyrithione; from 0.00762% to 2.0%, by weight of the personal cleansing composition, of the soluble zinc salt; and a structurant, preferably trihydroxy stearin; wherein the personal cleansing composition has a pH of 4.0 to 6.0.

14. The use of claims 13, wherein the soluble zinc salt comprises zinc sulfate, zinc acetate, zinc bromide, zinc chloride, zinc citrate, zinc fluoride, zinc gluconate, zinc iodide, zinc phosphate, zinc-containing layered materials, or a combination thereof; preferably zinc sulfate.

15. The use of claims 13-14, wherein the composition comprises from 0.05% to 1.0%, by weight of the composition, of the structurant, and further comprises from 40% to 75%, by weight of the composition, of water.