Antidandruff composition and method of use

Abstract

An aqueous anti-dandruff shampoo composition which comprises: (I) a cleansing surfactant selected from the group consisting of anionic surfactant, zwitterionic or amphoteric surfactant and nonionic surfactant; (II) suspended particles of an anti-dandruff agent, (III) an anti-settling, thickening polymer, wherein the anti-settling, thickening polymer, comprises: (a) 40 to 74.5 wt % of structural units of C.sub.1-4 alkyl acrylate; (b) 20 to 50 wt % of structural units of methacrylic acid; (c) 0.2 to <5 wt % of structural units of 2-acrylamido-2-methylpropane sulfonic acid (AMPS); (d) 5 to 25 wt % of structural units of a specialized associated monomer having the following structure wherein R.sup.1 is a linear saturated C.sub.10-24 alkyl group; wherein R.sup.2 is a hydrogen or a methyl group (preferably, wherein R.sup.2 is a methyl group); and wherein n is an average of 20 to 28; with the proviso that the structural units of the specialized associated monomer (d) are derived from one of (i) a single specialized associated monomer (preferably, a single specialized associated monomer wherein R.sup.1 is selected from the group consisting of a linear saturated C.sub.12 alkyl group, a linear saturated C.sub.18 alkyl group and a linear saturated C.sub.22 alkyl group; more preferably, a single specialized associated monomer wherein R 1 is selected from the group consisting of a linear saturated C12 alkyl group and a linear saturated C18 alkyl group); (ii) two specialized associated monomers, wherein R.sup.1 is, respectively, a linear saturated C.sub.12 and a linear saturated C.sub.18 alkyl group; or (iii) two specialized associated monomers, wherein R.sup.1 is, respectively, a linear saturated C.sub.18 alkyl group and a linear saturated C.sub.22 alkyl group; (e) 0 to 1 wt % of structural units of acrylic acid; and (f) 0 to 2 wt % of structural units of multi-ethylenically unsaturated crosslinking monomer or chain transfer agent; and wherein the sum of the weight percentages of structural units (a)-(f) is equal to 100 wt % of the anti-settling, thickening polymer; and the use of such a composition in a method of treating hair or scalp. ##STR00001##

Claims

1. An aqueous anti-dandruff shampoo composition which comprises: (I) 2-40 wt % of a cleansing surfactant selected from the group consisting of sodium lauryl sulphate, sodium lauryl ether sulphate, sodium lauryl ether sulphosuccinate, ammonium lauryl sulphate, ammonium lauryl ether sulphate, sodium cocoyl isethionate and lauryl ether carboxylic acid, coco betaine, cocamidopropyl betaine, sodium cocoamphoacetate and mixtures thereof, (II) 0.01 to 30 wt % suspended particles of an anti-dandruff agent that is zinc pyrithione, (III) 0.05 to 4 wt % an anti-settling, thickening polymer, wherein the anti-settling, thickening polymer, comprises: (a) 50 to 65 wt % of structural units ethyl acrylate; (b) 25 to 40 wt % of structural units of methacrylic acid; (c) 0.75 to 2.0 wt % of structural units of 2-acrylamido-2-methylpropane sulfonic acid; (d) 7.5 to 9 wt % of structural units of a specialized associated monomer having the following structure ##STR00011## wherein R.sup.1 is a linear saturated C.sub.12-14 alkyl group; wherein R.sup.2 is a methyl group; and wherein n is an average of 20 to 28; and wherein the sum of the weight percentages of structural units (a)-(d) is equal to 100 wt % of the anti-settling, thickening polymer.

2. The aqueous anti-dandruff shampoo composition as claimed in claim 1, which further comprises an insoluble conditioning silicone.

3. The aqueous anti-dandruff shampoo composition as claimed in claim 1, which has a pH of 3 to 7.

4. The aqueous anti-dandruff shampoo composition as claimed in claim 1, which further comprises an additional antidandruff agent that is soluble in the aqueous formulation at 15 to 25° C.

5. The aqueous anti-dandruff shampoo composition as claimed in claim 1, which further comprises a fragrance.

6. A method of treating hair comprising applying to the hair, the aqueous anti-dandruff shampoo composition of claim 1.

7. A method as claimed in claim 6, further comprising rinsing the hair with water.

Description

EXAMPLES

Example 1: Polymer for Use in the Compositions of the Invention

(1) The polymer, designated Polymer P1, for use in the compositions of the invention was prepared in accordance with formula 1. The details are given in Table 1 below.

(2) TABLE-US-00001 TABLE 1 Structural Composition of Polymer P1                     Hydrophobe % Hydrophobe Chain Length (n) when conforming to the structure                       Ethyl Acrylate %                     Methacrylic acid %                     AMPS % 9 12 59.5 31.5 1
Polymer P1 Synthesis

(3) A 3 liter, 4 necked round bottom flask equipped with a mechanical stirrer, thermocouple, condenser and nitrogen sparge was charged with 430 g of deionized water and 4.7 g of sodium lauryl sulfate. The flask was then purged with nitrogen and its contents were warmed to 90° C. Then a first initiator solution containing 0.33 g of ammonium persulfate dissolved in 10 g of deionized water was added to the flask. Then a monomer solution was gradually charged to the flask over a period of 107 minutes, wherein the monomer solution contained 633 g deionized water, 18 g of sodium lauryl sulfate and the amounts (as noted in TABLE 1) of each of ethyl acrylate (EA), methacrylic acid (MAA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and a lipophilically modified monomer (LIPO) having the following structure:

(4) ##STR00010##
wherein R.sup.1 was a linear saturated C.sub.12-14 alkyl group; R.sup.2 is selected from hydrogen or methyl; R.sup.2 is selected from hydrogen or methyl, preferably methyl; and n was an average of 20 to 28. Starting simultaneously with the monomer solution charge, a second initiator solution containing 0.33 g of ammonium sulfate in 49 g of deionized water was gradually charged to the flask over a period of 112 minutes. Following the monomer charge and the second initiator solution charge, the transfer lines were rinsed with deionized water followed by a free radical catalyst and activator chase solution. The resulting latex product (Polymer P1) was recovered.

Example 2: Preparation of Antidandruff Shampoo, S1, in Accordance with the Invention and Comparative Antidandruff Shampoos, SA and SB

(5) A comparative antidandruff shampoo, designated SA was prepared by the following method:

(6) 1. Carbomer was added to water.

(7) 2. The Carbomer was then allowed to swell by increasing the pH to pH 5.5-6.5, using a suitable pH modifier.

(8) 3. The cleansing surfactants, cationic polymer, antidandruff active, fragrance and preservatives were then added to the swollen polymer and fully dispersed.

(9) 4. The resulting formulation was adjusted to the desired pH and viscosity using suitable pH and viscosity modifiers.

(10) Antidandruff shampoos, S1, in accordance with the invention and comparative example SB, were prepared by the following method:

(11) 1. Polymer (Polymer P1) was added to water.

(12) 2. The polymer was then allowed to swell by increasing the pH, using a suitable pH modifier, until a clear solution was obtained.

(13) 3. The cleansing surfactants, cationic polymer, antidandruff active, fragrance and preservatives were then added to the swollen polymer and fully dispersed.

(14) 4. The resulting formulation was adjusted to the desired pH and viscosity using suitable pH and viscosity modifiers.

(15) The compositions of Shampoo S1, Comparative Shampoo SA and Comparative Shampoo SB are shown in Table 2 below.

(16) TABLE-US-00002 TABLE 2 Compositions of Shampoo S1, in accordance with the invention and Comparative Shampoo SA Shampoo Shampoo Shampoo SA SB S1 INCI Name % w/w % w/w % w/w Water To 100% To 100% To 100% Carbomer (ex. Lubrizol) 0.6 0 0 Acrylates Co-Polymer 0 0.4 0 (Carbopol Aqua SF1) Polymer 1 0 0 0.4 Sodium Laureth Sulphate 14 14 14 Cocamidopropyl Betaine 1.6 1.6 1.6 Zinc Pyrithione 1 1 1 Fragrance 0.75 0.75 0.75 Guar Hydroxypropyltrimonium 0.20 0.20 0.20 Chloride Preservatives 0.9 0.9 0.9 Viscosity modifiers 0.6 0.36 0.8 pH modifiers 0.4 1.26 0.11 Dimethicone 2 2 2

(17) pH's were in the range of from 5.5 to 6.5 as measured by calibrated pH meter.

Example 4: Thermal Stability and Degree of Particle Aggregation of Shampoo S1, in Accordance with the Invention and Comparative Shampoos SA and SB

(18) Thermal stability and degree of particle aggregation of Shampoo S1, in accordance with the invention and Comparative Shampoos SA and SB were measured using the following procedures:

(19) Thermal stability was tested by placing the shampoo compositions S1, SA and SB in an oven at 45° C. for 12 weeks. The compositions were assessed at frequent intervals over the 12 weeks period for sedimentation of particles.

(20) The degree of particle aggregation was assessed by first diluting the shampoo composition (S1, SA and SB) to a level of 1 in 10 in water. The microstructural appearance of the resulting mixture was captured using an optical microscope at magnification of 20×, using a light polarising filter. Each sample was imaged three times at a consistent exposure. The resulting micrographs were then analysed using ImageJ (an open source and free software for image analysis available at http://imagej.nih.gov/ij/). The micrographs were first converted to a 16-bit image and the visible particles were highlighted using the threshold function at appropriate settings for the analysis. The resulting average particle area was reported in units of μm.sup.2.

(21) The results are given in Table 3.

(22) TABLE-US-00003 TABLE 3 Thermal stability, degree of particle (zinc pyrithione) aggregation and particle size of Shampoo S1, in accordance with the invention and Comparative Shampoo SA Shampoo Shampoo Shampoo SA SB S1 Thermal Stability at 45° C. >12 weeks >12 weeks >12 weeks Degree of particle aggregation High Very high Very Low Lower = better Average Particle Size (μm.sup.2) 22 ± 9 93 ± 20 8 ± 1 determined using ImageJ analysis software

(23) It will be seen that the degree of particle aggregation of the suspended zinc pyrithione is lower in the shampoo of the present invention than in the comparative shampoos SA and SB, which comprise conventional polymers, resulting in a much smaller particle size. The small particles are deposited more onto the scalp, as seen by Example 5 below.

Example 5: Level of Deposition of Antidandruff Active (Zinc Pyrithione) onto Hair and Scalp; and Log Reduction in Malassezia Furfur after Treatment with Shampoo S1, in Accordance with the Invention and Comparative Shampoo SA

(24) The amount of antidandruff active deposited onto the hair and scalp (an artificial skin was used to mimic scalp); and the Log reduction in Malassezia Furfur treated with Shampoo S1 and Comparative Shampoo SA were measured using the following procedures:

(25) Measurement of Zinc Deposition to Hair

(26) Virgin hair switches were treated with the shampoo of interest. Switches were rinsed and dried before the level of zinc was quantified using x-ray fluorescence (XRF).

(27) Measurement of Zinc Pyrithione Deposition to VITROSKIN®

(28) The treatment of VITROSKIN® consisted of adding 0.2 g of the composition (Shampoo S1 or Comparative Shampoo SA) to the VITROSKIN®, followed by 1.8 ml of water. This was rubbed for 30 s using a teflon rod and the solution was then removed. The surface was then rinsed by adding 4 ml of sterile water to the VITROSKIN®, rubbing for 30 s using a teflon rod and then removing the solution. The rinsing step was repeated one more time.

(29) Following the treatment, zinc pyrithione was extracted from the VITROSKIN® into methanol before a DPS (2,2′-dipyridyl disulphide) derivation was conducted. The zinc pyrithione level in the resulting liquor was then quantified using a Waters ACQUITYUPLC System coupled to UV detector at an absorption wavelength of 235 nm.

(30) Measurement of In-Vitro Log Reduction Malassezia Furfur

(31) Malassezia furfur 7019 in Pityrosporum Broth (comprising 10 g Bacteriological Peptone, 0.1 g Yeast extract, 10 g Ox-bile, 2.5 g Taurocholic acid, 10 g Glucose, 1 L Deionised water, 0.5 ml Tween 60, 1 ml Glycerol and 0.5 ml UHT milk; adjusted to pH 6.2) was grown for 2 days and adjusted to a final concentration of 2-6×10.sup.5 cells/ml. 0.2 ml of the above Malassezia was pipetted out onto VITROSKIN® (10.34 cm.sup.2) and left for 30 minutes. The treatment of VITROSKIN® consisted of adding 0.2 g of the composition (Shampoo S1 or Comparative Shampoo SA) to the VITROSKIN®, followed by 1.8 ml of water. This was rubbed for 30 s using a teflon rod and the solution was then removed. The surface was then rinsed by adding 4 ml of sterile water to the VITROSKIN®, rubbing for 30 s using a teflon rod and removing the solution. The rinsing step was repeated one more time.

(32) For the measurement of Log reduction of Malassezia furfur, treated VITROSKIN® was first placed onto a Modified Dixon Agar Plate and incubated at 32° C. for 24 h. Following incubation, each piece of VITROSKIN® was cut off and placed into a vial containing 10 ml of PBS buffer (pH 7.2), 0.1% Triton X-100 and 0.5% Tween-80. The vial containing VITROSKIN® was vortexed for 1 minute. 20 μl of 10.sup.0-10.sup.−3 dilutions were plated onto Modified Dixon Agar Plates, and incubated at 32° C. for 3-4 days. The number of colonies on each plate were then counted, and final numbers determined by multiplying by the appropriate dilution. The Log reduction of Malassezia furfur was then calculated from the measurements.

(33) Each sample was run in triplicate and was tested three times.

(34) The results are presented in Table 4.

(35) TABLE-US-00004 TABLE 4 Level of deposition of Zinc Pyrithione onto hair and scalp; and Log reduction in Malassezia Furfur after treatment with Shampoo S1, in accordance with the invention and Comparative Shampoo SA Test SA S1 Zinc Pyrithione Deposition to Hair 1121 ± 246 310 ± 63 (ppm) (+/−standard deviation) Higher = better Zn from Zinc Pyrithione Deposition  0.19 ± 0.03  0.29 ± 0.03 to Vitro Skin (μg/cm.sup.2) (+/−standard error) Higher = better Log Reduction (Malassezia Furfur) −1.12 ± 0.07 −1.63 ± 0.07 (+/−standard error) Lower = better

(36) It will be seen that the antidandruff active is selectively deposited onto scalp rather than hair when the shampoo of the present invention (S1) is used. This is advantageous because the bioavailability of the antidandruff agent is consequentially increased on the scalp. Further, lower deposition of Zinc Pyrithione onto the hair gives better hair feel, in line with consumer preference. Additionally, the zinc pyrithione is highly disaggregated when used in the shampoo of the present invention (Table 3). This results in a significant reduction in the level of Malassezia Furfur on VITROSKIN® versus the highly aggregated zinc pyrithione in the carbomer structured shampoo (SA).