Extruded soap bar with high water content

Abstract

The present invention relates to an extruded soap bar composition. It more particularly relates to a soap bar composition which comprises low amount of soap where high amount of water can be incorporated. This is achieved by including selective amount of a mixture of sodium or calcium silicate and an acrylic/acrylate polymer, wherein the soap bar comprises 0.01 to 0.7 wt % of the polymer. The soap bars of the invention are easy to extrude and has acceptable product hardness.

Claims

1. An extruded soap bar comprising: (i) 40 to 60 wt % total fatty matter; (ii) 21 to 40 wt % water; (iii) 0.5 to 5 wt % electrolyte; and (iv) 0.1 to 10 wt % of a structuring system comprising a mixture of sodium silicate and an acrylic/acrylate polymer, wherein said soap bar comprises 0.01 to 0.7 wt % of said polymer, wherein said soap bar comprises 0.5 to 3 wt % sodium silicate.

2. The soap bar as claimed in claim 1, comprising 45 to 55 wt % total fatty matter.

3. The soap bar as claimed in claim 1, comprising 25 to 40 wt % water.

4. The soap bar as claimed in claim 1, comprising 0.5 to 3 wt % electrolyte.

5. The soap bar as claimed in claim 1, wherein said electrolyte is selected from sodium chloride, sodium sulphate, sodium citrate or a mixture thereof.

6. The soap bar as claimed in claim 1, comprising sodium silicate.

7. The soap bar as claimed in claim 1, wherein said polymer is a hydrophobically modified, a homo polymer, a copolymer, or a cross polymer.

8. A process to prepare a soap bar as claimed in claim 1, comprising the step of including the polymer during the step of saponification to form the soap.

9. The soap bar as claimed in claim 7, wherein the sodium silicate is alkaline sodium silicate with a Na.sub.2O:SiO.sub.2 weight ratio of about 1:2.

10. The soap bar as claimed in claim 7, wherein the polymer is an acrylic polymer, a partially neutralized acrylic polymer, or an acrylate polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description and claims indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about”. Numerical ranges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y”, it is understood that all ranges combining the different endpoints are also contemplated.

(2) The present invention relates to a soap bar composition. By a soap bar composition is meant a cleansing composition comprising soap which is in the form of a shaped solid. The soap bar of the invention is especially useful for personal cleansing. The soap bar of the present invention comprises 40 to 60% total amount of TFM from soap, preferably 40 to 55%, more preferably 45 to 55 wt % TFM from soap. The term soap means salt of fatty acid. Preferably, the soap is soap of C8 to C24 fatty acids. The cation may be an alkali metal, alkaline earth metal or ammonium ion, preferably alkali metals. Preferably, the cation is selected from sodium or potassium, more preferably sodium. The soap may be saturated or unsaturated. Saturated soaps are preferred over unsaturated soaps for stability. The oil or fatty acids may be of vegetable or animal origin.

(3) The soap may be obtained by saponification of oils, fats or fatty acids. The fats or oils generally used to make soap bars may be selected from tallow, tallow stearins, palm oil, palm stearins, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, and palm kernel oil. The fatty acids may be from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed or soyabean.

(4) The fatty acid soaps may also be synthetically prepared (e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process). Resin acids, such as those present in tall oil, may also be used. Naphthenic acids may also be used.

(5) The soap bar may additionally comprise synthetic surfactants selected from one or more from the class of anionic, non-ionic, cationic or zwitterionic surfactants, preferably from anionic surfactants. These synthetic surfactants, as per the present invention, are included in less then 8%, preferably less then 4%, more preferably less then 1.5% and sometimes absent from the composition.

(6) The composition of the present invention is in the form of a shaped solid for example a bar. The cleaning soap composition is generally a wash off products have sufficient amounts of surfactants included therein that it is used for cleansing the desired topical surface e.g. the whole body, the hair and scalp or the face. It is applied on the topical surface and left thereon only for a few seconds or minutes and washed off thereafter with copious amounts of water.

(7) The soap bars of the present invention preferably includes low molecular weight soaps (C8 to C14 soaps) which are generally water soluble, which are in the range of 2 to 20% by weight of the composition. It is preferred that the soap bar includes 15 to 55 wt % of the soap of C16 to C24 fatty acid, which are generally water insoluble soaps. Unsaturated fatty acid soaps preferably at 15 to 35% may also be included in the total soap content of the composition. Unsaturated soaps are preferably oleic acid soaps. The composition of the invention comprises a silicate compound preferably sodium silicate or calcium silicate, more preferably sodium silicate. Sodium silicate includes compounds having the formula (Na.sub.2O).sub.x.SiO.sub.2. The weight ratio of Na.sub.2O to SiO.sub.2 could vary from 1:2 to 1:3.75. Grades of sodium silicate with ratio from about 1:2 to 1:2.85 are called alkaline silicate and with ratios from 1:2.85 to about 1:3.75 are called neutral silicate. Forms of sodium silicate that are available include sodium metasilicate (Na.sub.2SiO.sub.3), sodium pyrosilicate (Na.sub.6Si.sub.2O.sub.7), and sodium orthosilicate (Na.sub.4SiO.sub.4). It is preferred as per this invention that alkaline sodium silicate is used. Especially preferred is alkaline sodium silicate with a ratio of 1:2. It is preferred that the soap bar comprises 0.01% to 3 wt % sodium silicate, on dry weight basis.

(8) The composition of the invention includes a polymer of the acrylic/acrylate class. The polymer may be hydrophobically modified, a homo polymer, a copolymer, or a cross polymer which may be an acrylic polymer, a partially neutralized acrylic polymer or an acrylate polymer. Commercially available polymer of these classes which may be used include Carbopol Aqua SF polymer from Lubrizol, Carbopol SC-200 polymer also from Lubrizol, or Acusol 445 G-polymer from Dow. The polymer is included in 0.01 to 0.7%, preferably from 0.1 to 3%, furthermore preferably 0.2 to 2% by weight of the soap bar.

(9) The soap bar of the invention is capable of stably retaining high amount of water as compared to conventional soap bar. The amount of water in the soap composition ranges from 21 to 40%, preferably 25 to 40%, more preferably 25 to 35%, furthermore preferably 25 to 33 by weight of the soap bar.

(10) The soap bar composition generally comprises electrolyte and water. Electrolytes as per this invention include compounds that substantially dissociate into ions in water. Electrolytes as per this invention are not ionic surfactants. Suitable electrolytes for inclusion in the soap making process are alkali metal salts. Preferred alkali metal salts for inclusion in the composition of the invention include sodium sulfate, sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium sulfate, sodium carbonate and other mono or di or tri salts of alkaline earth metals, more preferred electrolytes are sodium chloride, sodium sulfate, sodium citrate, potassium chloride and especially preferred electrolyte is sodium chloride, sodium citrate or sodium sulphate or a combination thereof. For the avoidance of doubt, it is clarified that the electrolyte is a non-soap material. Electrolyte is included in 0.5 to 5%, preferably 0.5 to 3%, more preferably 1 to 2.5% by weight of the composition. It is preferred that the electrolyte is included in the soap bar during the step of saponification to form the soap. The soaps bar composition may optionally comprise 0.1 to 15%, preferably 0.1 to 12% by weight of free fatty acids. By free fatty acids is meant a carboxylic acid comprising a hydrocarbon chain and a terminal carboxyl group. Suitable fatty acids are C8 to C22 fatty acids. Preferred fatty acids are C12 to C18, preferably predominantly saturated, straight-chain fatty acids. However, some unsaturated fatty acids can also be employed.

(11) The composition preferably comprises a polyhydric alcohol (also called polyol) or mixture of polyols. Polyol is a term used herein to designate a compound having multiple hydroxyl groups (at least two, preferably at least three) which is highly water soluble, preferably freely soluble, in water. Many types of polyols are available including: relatively low molecular weight short chain polyhydroxy compounds such as glycerol and propylene glycol; sugars such as sorbitol, manitol, sucrose and glucose; modified carbohydrates such as hydrolyzed starch, dextrin and maltodextrin, and polymeric synthetic polyols such as polyalkylene glycols, for example polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG). Especially preferred polyols are glycerol, sorbitol and their mixtures. Most preferred polyol is glycerol. In a preferred embodiment, the bars of the invention comprise 0 to 8%, preferably 1 to 7.5% by wt. polyol.

(12) The various optional ingredients that make up the final soap bar composition are as described below:

(13) Organic and Inorganic Adjuvant Materials

(14) The total level of the adjuvant materials used in the bar composition should be in an amount not higher than 50%, preferably 1 to 50%, more preferably 3 to 45% by wt. of the soap bar composition.

(15) Suitable starchy materials which may be used include natural starch (from corn, wheat, rice, potato, tapioca and the like), pre-gelatinzed starch, various physically and chemically modified starch and mixtures thereof. By the term natural starch is meant starch which has not been subjected to chemical or physical modification—also known as raw or native starch.

(16) The raw starch can be used directly or modified during the process of making the bar composition such that the starch becomes gelatinized, either partially or fully gelatinized.

(17) The adjuvant system may optionally include insoluble particles comprising one or a combination of materials. By insoluble particles is meant materials that are present in solid particulate form and suitable for personal washing. Preferably, there are mineral (e.g., inorganic) or organic particles.

(18) The insoluble particles should not be perceived as scratchy or granular and thus should have a particle size less than 300 microns, more preferably less than 100 microns and most preferably less than 50 microns.

(19) Preferred inorganic particulate material includes talc and calcium carbonate. Talc is a magnesium silicate mineral material, with a sheet silicate structure and a composition of Mg.sub.3Si.sub.4(OH).sub.22 and may be available in the hydrated form. It has a plate-like morphology, and is essentially oleophilic/hydrophobic, i.e., it is wetted by oil rather than water.

(20) Calcium carbonate or chalk exists in three crystal forms: calcite, aragonite and vaterite. The natural morphology of calcite is rhombohedral or cuboidal, acicular or dendritic for aragonite and spheroidal for vaterite.

(21) Examples of other optional insoluble inorganic particulate materials include aluminates, phosphates, insoluble sulfates, borates and clays (e.g., kaolin, china clay) and their combinations.

(22) Organic particulate materials include: insoluble polysaccharides such as highly crosslinked or insolubilized starch (e.g., by reaction with a hydrophobe such as octyl succinate) and cellulose; synthetic polymers such as various polymer lattices and suspension polymers; insoluble soaps and mixtures thereof.

(23) Bar compositions preferably comprise 0.1 to 25% by wt. of bar composition, preferably 5 to 15 by wt. of these mineral or organic particles.

(24) An opacifier may be optionally present in the personal care composition. When opacifiers are present, the cleansing bar is generally opaque. Examples of opacifiers include titanium dioxide, zinc oxide and the like. A particularly preferred opacifier that can be employed when an opaque soap composition is desired is ethylene glycol mono- or di-stearate, for example in the form of a 20% solution in sodium lauryl ether sulphate. An alternative opacifying agent is zinc stearate.

(25) The product can take the form of a water-clear, i.e. transparent soap, in which case it will not contain an opacifier.

(26) The pH of preferred soaps bars of the invention is from 8 to 11, more preferably 9 to 11.

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

(28) Other optional ingredients like anti-oxidants, perfumes, polymers, chelating agents, colourants, deodorants, dyes, emollients, moisturizers, enzymes, foam boosters, germicides, additional anti-microbials, lathering agents, pearlescers, skin conditioners, stabilisers, superfatting agents, sunscreens may be added in suitable amounts in the process of the invention. Preferably, the ingredients are added after the saponification step. Sodium metabisulphite, ethylene diamine tetra acetic acid (EDTA), borax or ethylene hydroxy diphosphonic acid (EHDP) are preferably added to the formulation. The composition of the invention could be used to deliver antimicrobial benefits. Antimicrobial agents that are preferably included to deliver this benefits include oligodynamic metals or compounds thereof. Preferred metals are silver, copper, zinc, gold or aluminium. Silver is particularly preferred. In the ionic form it may exist as a salt or any compound in any applicable oxidation state. Preferred silver compounds are silver oxide, silver nitrate, silver acetate, silver sulfate, silver benzoate, silver salicylate, silver carbonate, silver citrate and silver phosphate, with silver oxide, silver sulfate and silver citrate being of particular interest in one or more embodiments. In at least one preferred embodiment the silver compound is silver oxide. Oligodynamic metal or a compound thereof is preferably included in 0.0001 to 2%, preferably 0.001 to 1% by weight of the composition. Alternately an essential oil antimicrobial active may be included in the composition of the invention. Preferred essential oil actives which may be included are terpineol, thymol, carvacol, (E)-2(prop-1-enyl) phenol, 2-propylphenol, 4-pentylphenol, 4-sec-butylphenol, 2-benzyl phenol, eugenol or combinations thereof. Further more preferred essential oil actives are terpineol, thymol, carvacrol or thymol, most preferred being terpineol or thymol and ideally a combination of the two. Essential oil actives are preferably included in 0.001 to 1%, preferably 0.01 to 0.5% by weight of the composition.

(29) The soap composition may be made into a bar by a process that first involves saponification of the fat charge with alkali followed by extruding the mixture in a conventional plodder. The plodded mass may then be optionally cut to a desired size and stamped with a desirable indicia. An especially important benefit of the present invention is that, notwithstanding the high amount of water content of the soap bar, compositions thus prepared by extrusion are found to be easy to stamp with a desirable indicia.

(30) The present invention also relates to a process to prepare the soap bar of the invention comprising the step of including substantially all of the structuring system to the soap when it is being produced during the saponification step. Preferably, at least, the polymer is included during the saponification stage.

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

EXAMPLES

Example A-D and 1-2: Effect of Soap Bars Outside and within the Invention on Extrudability and Product Hardness

(32) The following four soap bar compositions as shown in Table-1 were prepared.

(33) The following method was used to measure the product hardness:

(34) Hardness Testing Protocol

(35) Principle

(36) A 30° conical probe penetrates into a soap/syndet sample at a specified speed to a pre-determined depth. The resistance generated at the specific depth is recorded. There is no size or weight requirement of the tested sample except that the bar/billet be bigger than the penetration of the cone (15 mm) and have enough area. The recorded resistance number is also related to the yield stress and the stress can be calculated as noted below. The hardness (and/or calculated yield stress) can be measured by a variety of different penetrometer methods. In this invention, as noted above, we use probe which penetrates to depth of 15 mm.

(37) Apparatus and Equipment

(38) TA-XT Express (Stable Micro Systems)

(39) 30° conical probe—Part #P/30c (Stable Micro Systems)

(40) Sampling Technique

(41) This test can be applied to billets from a plodder, finished bars, or small pieces of soap/syndet (noodles, pellets, or bits). In the case of billets, pieces of a suitable size (9 cm) for the TA-XT can be cut out from a larger sample. In the case of pellets or bits which are too small to be mounted in the TA-XT, the compression fixture is used to form several noodles into a single pastille large enough to be tested.

(42) Procedure

(43) Setting Up the TA-XT Express

(44) These settings need to be inserted in the system only once. They are saved and loaded whenever the instrument is turned on again. This ensures settings are constant and that all experimental results are readily reproducible.

(45) Set Test Method

(46) Press MENU

(47) Select TEST SETTINGS (Press 1)

(48) Select TEST TPE (Press 1)

(49) Choose option 1 (CYCLE TEST) and press OK

(50) Press MENU

(51) Select TEST SETTINGS (Press 1)

(52) Select PARAMETERS (Press 2)

(53) Select PRE TEST SPEED (Press 1)

(54) Type 2 (mm s.sup.−1) and press OK

(55) Select TRIGGER FORCE (Press 2)

(56) Type 5 (g) and Press OK

(57) Select TEST SPEED (Press 3)

(58) Type 1 (mm s.sup.−1) and press OK

(59) Select RETURN SPEED (Press 4)

(60) Type 10 (mm s.sup.−1) and press OK

(61) Select DISTANCE (Press 5)

(62) Type 15 (mm) for soap billets or 3 (mm) for soap pastilles and press OK

(63) Select TIME (Press 6)

(64) Type 1 (CYCLE)

(65) Calibration

(66) Screw the probe onto the probe carrier.

(67) Press MENU

(68) Select OPTIONS (Press 3)

(69) Select CALIBRATE FORCE (Press 1)—the instrument asks for the user to check whether the calibration platform is clear

(70) Press OK to continue and wait until the instrument is ready.

(71) Place the 2 kg calibration weight onto the calibration platform and press OK

(72) Wait until the message “calibration completed” is displayed and remove the weight from the platform.

(73) Sample Measurements

(74) Place the billet onto the test platform.

(75) Place the probe close to the surface of the billet (without touching it) by pressing the

(76) UP or DOWN arrows.

(77) Press RUN

(78) Take the readings (g or kg) at the target distance (Fin).

(79) After the run is performed, the probe returns to its original position.

(80) Remove the sample from the platform and record its temperature.

(81) Calculation & Expression of Results

(82) Output

(83) The output from this test is the readout of the TA-XT as “force” (R.sub.T) in g or kg at the target penetration distance, combined with the sample temperature measurement. (In the subject invention, the force is measured in Kg at 40° C. at 15 mm distance)

(84) The force reading can be converted to extensional stress, according to the equation given below.

(85) The equation to convert the TX-XT readout to extensional stress is

(86) $\sigma =\frac{1}{C}\frac{R_T{g}_c}{A}$

(87) where: σ=extensional stress C=“constraint factor” (1.5 for 30° cone) G.sub.c=acceleration of gravity A=projected area of cone=π(d tan ½θ).sup.2 d=penetration depth θ=cone angle

(88) For a 30° cone at 15 mm penetration, Equation 2 becomes
σ(Pa)=R.sub.T(g)×128.8

(89) This stress is equivalent to the static yield stress as measured by penetrometer. The extension rate is:

(90) $\stackrel{.}{\mathrm{.Math.}}=\frac{V}{d\tan \left(\frac{1}{2}\theta \right)}$
where {dot over (ε)}=extension rate (s.sup.−1)

(91) V=cone velocity

(92) For a 30° cone moving at 1 mm/s, {dot over (ε)}=0.249 s.sup.−1

(93) Temperature Correction

(94) The hardness (yield stress) of skin cleansing bar formulations is temperature-sensitive. For meaningful comparisons, the reading at the target distance (R.sub.T) should be corrected to a standard reference temperature (normally 40° C.), according to the following equation:
R.sub.40=R.sub.T×exp[α(T−40)]
where R.sub.40=reading at the reference temperature (40° C.)
R.sub.T=reading at the temperature T
α=coefficient for temperature correction
T=temperature at which the sample was analyzed.

(95) The correction can be applied to the extensional stress.

(96) Raw and Processed Data

(97) The final result is the temperature-corrected force or stress, but it is advisable to record the instrument reading and the sample temperature also.

(98) A hardness value of at least 1.2 kg (measured at 40° C.), preferably at least 2.7 kg is acceptable.

(99) TABLE-US-00001 TABLE 1 Ingredient (wt %) A B C D 1 2 TFM 52 53 54 53 54 51 Talc 3.0 3.0 3.0 3.0 3.0 3.0 AOS 1.0 1.0 1.0 1.0 1.0 1.0 Sodium sulphate 1.2 1.2 1.2 1.2 1.2 1.2 Sodium chloride 0.9 0.9 0.9 0.9 0.9 0.9 Alkaline sodium silicate 2.0 1.0 — — 1.5 1.5 Glycerin 4.0 4.0 4.0 4.0 4.0 5.0 Free Fatty acid 0.15 0.15 0.15 0.15 0.15 0.15 Carbopol ® SC200 — — 0.5 1.0 0.4 0.5 Water 30.8 30.6 29.6 29.6 28.1 29.8 Extrudability Poor Poor Poor Poor Good Good Product hardness (kg) 2.59 2.28 1.84 2.34 3.57 3.35 Note: AOS: Synthetic anionic surfactant Alpha olefin sulphonate

(100) The data in the above table indicates that compositions within the invention (Examples 1 and 2) are easy to extrude and have good product hardness. Example A to D are outside the invention (either does not contain sodium silicate or polymer) and have low product hardness and are difficult to extrude.