cosmetics

Chapter 3

Formulation of Toilet, Combo, andSynthetic Cleansing Bars

Edmund D. George

Bradford Soap Works Inc., West Warwick, Rhode Island, USA

Introduction

This chapter discusses soap-based compositions, a brief historical perspective ontraditional soap, and any matrix effects that may affect the formulation process.Traditional soap is the sodium or potassium salt of triglycerides and fatty acids,notably from beef tallow, coconut oil, and palm kernel oil and to a lesser extentsuch oils as grape seed, sweet almond oil, or rice bran oil. Soap varieties includetransparent, opaque, translucent, and specialty bases, such as shavings, nonmarringopaque soaps, cream/paste, and powdered soaps. Since the production of thesebases is well documented in the literature (1–15), they will not be discussed.

Synthetic soap bases are basically detergents plasticized with other ingredientsto yield a solid composition that can be formed into a bar (16–24). They are oftencombined in various ratios with traditional soaps to form combination or combosoaps that have similar properties of both bases. Synthetic bases in particular canbe made using one of two methods. The cold method involves the addition ofingredients into a mixer or blender with no heat. Meltable compounds are meltedseparately and added to the mixer with other ingredients. After proper mixing, thematerials are released to the production line. The hot method involves blending theingredients, in proper sequence in a melt tank at an elevated temperature and mix-ing until uniform. The batch is then flaked or chill rolled. The resulting flakes orpellets are then processed as any other soap base. The mode of the manufacturer’slogic depends on the formulation and the availability of equipment.

Over the years, soap bar formulation has become more complex with the needto incorporate more additives into an ever increasing number of soap bases.Consumers have become accustomed to multifunctional products that are oftenfound in the cosmetics industry, such as conditioning shampoos, antiperspirants,sunscreens, lotions, and creams. Traditional soaps were designed to clean skin andclothes; as time passed, soaps were used as a delivery system for perfumes andsuperfatting agents. Today, the cleaning aspect almost seems secondary to theeffects of various types and amounts of additives that are delivered by the soapsystem. The 2002 CTFA International Cosmetic Dictionary (25) lists over 12,000monographs of INCI names as well as 1,600 suppliers and 28,000 trade namesreportedly used in cosmetic applications.

Copyright © 2004 AOCS Press

As with any drug or cosmetic, matrix effects must be considered when devel-oping soap formulas, such as base-additive interactions, pH effects, additive-addi-tive interactions, fragrance effects, and processing effects. Any combination ofthese effects may influence the physical and aesthetic characteristics of the finalproduct. Sometimes it is difficult to predict the consequences of matrix effects, andonly with time and experience can the formulator begin to understand these inter-actions.

Base-Additive Interactions

The base-additive interactions include addition of acidic compounds that mayinteract with the soap base by changing the physical or chemical characteristics ofthe base. Alkaline soap bases may break down into fatty acids if enough acidicmaterial is added; this would basically render the soap ineffective. The reactionmay not be immediately noticeable since the soap base does not have sufficientwater to behave like a solution, but it can occur with time after processing and stor-age. The opposite may occur with a synthetic base, especially if the base containsfatty acids (such as stearic acid) that could be neutralized by alkaline additives, andcould affect the processing characteristics of the formula.

pH Effects

Many of the stability problems due to pH seem to lie with traditional soaps, sincethe majority of soap additives found in cosmetic and personal care products areacidic. Certain compounds, such as some quaternary compounds and some fra-grance ingredients, are unstable under the pH conditions found in traditional soaps.Also, some over the counter (OTC) active ingredients, such as salicylic acid andbenzoyl peroxide, have the greatest stability in combo systems, which have neutralto acid pH.

Additive-Additive

Additive-additive interactions are similar to the interactions discussed with addi-tive-base interactions and should be handled in the same manner (see the sectionon base-additive interactions).

Fragrance Effects

Fragrance effects can develop from fragrance compounds, such as aliphatic andaromatic acids, esters, ketones, and glycols. They can profoundly affect the pro-cessing characteristics by increasing the softness and tackiness of the soap, or inthe case of translucent or transparent soap influence the clarity of the system. Forinstance, fragrance diluents or solvents (such as certain glycols) appear to softenand/or cloud transparent soaps, making an already difficult base to run more diffi-cult. Some of these include diethyl phthalate (DEP) and dipropylene glycol (DPG).


Vanillin is known to cause severe browning of soaps due to chemical reactions inthe alkaline pH range. Some newer ingredients on the market can be added to theformulation or fragrance to retard this effect. Therefore it is recommended thatformulators work closely with suppliers to optimize fragrance selections prior toformula finalization. Fragrance suppliers must be briefed on the type of base thatfragrances will be incorporated in to ensure proper delivery and stability of thefragrance.

Processing Considerations

Processing considerations must be included when formulating a product. Processparameters, such as temperature, shear, scrap recycle, viscosity, vacuum, dierefrigeration and shape, type of equipment, milling versus refining, and plodderspeed must be monitored or controlled. Although this subject is beyond the scopeof this chapter, its consideration is essential for a successful product.

Properties of Soap Bases

Chemical Properties

Chemical properties are often influenced by variations in starting materials in thebase formulas. For instance, transparent bases can be made from detergents and fatsand oils using combinations of sodium hydroxide, potassium hydroxide, and alka-nolamines (such as triethanolamine). Synthetic systems can be plasticized with satu-rated fatty acids, fatty alcohols, or a combination of the two. The ratio of fats and oils(i.e., 80% tallow/20% coconut vs. 70% tallow/30% coconut oil) as well as the manu-facturing process (full-boiled vs. semi-boiled, etc.) will also influence the chemicalproperties. The choice of the preservation system is critical to the long-term chemicalstability of the cleansing system. As can be seen in Table 3.1, virtually all of thecompounds are chelators. It has been found through work at Bradford Soap Works,West Warwick, RI, that chelators provide better protection than antioxidants in thepreservation of traditional soap systems at a pH around 10. This is due to the extremenegative effect of pro-oxidant metals, such as iron, copper, and magnesium, onchemical stability. Pentasodium pentetate and tetrasodium etidronate are particularlyeffective preservatives for color and odor stability in these systems, often at levelsunder 0.10% each. The formulator must be familiar with these properties whendeveloping additive packages that are stable and functional.

Physical Characteristics

Physical characteristics will also influence the amount and type of additives thatwill be incorporated into the final formula. It must be noted that the followingcharacteristics should be established with each formulation to generate completeproduct profiles. Wear rate, crack resistance and sloughing, wash down, foaming,


color, and odor are important physical characteristics that should be noted. Additiveswill tend to influence one or all of these particular aspects of the soap bar, and itmust be determined prior to production if it negatively impacts these particularcharacteristics.

Wear Rate. Wear rate essentially describes the lasting power of the soap barunder use conditions. It is influenced by the various solubilities of the bases, whichis determined by the titer of the fat and oils, the type of alkali used, and the amountof water for traditional soap to the type of plasticizer and solubility of the detergentin syndet systems. For instance, transparent soaps have relatively high wear ratesdue to the use of high level solvents, such as glycols, water, and alcohols, that areneeded to maintain clarity. These soaps may also contain a surfactant system witha high solubility that aids in maintaining clarity. This combination tends to let thebar “melt away.” On the other hand, syndet systems need plasticizers and bindersto hold the bar together. They are typically waxes, starches, fatty acids, and fattyalcohols that have very limited water solubility, and make the system less sensitiveto wear rate than other soap types.

TABLE 3.1Typical Soap Preservatives

INCI name Abbreviation Trade name Supplier

ChelatorsDiphosphonic acid HEDP Dequest 2010 SolutiaTertasodium etidronate Sodium HEDP Dequest 2016 Solutia

(Na4HEDP)Etidronic acid EHDP Turpinal SL SolutiaTetrasodium etidronate Sodium HEDP Briquest ADPA- Albright and

(Na4HEDP) 21SW WilsonEDTA and salts Dissolvine E series Akzo NobelDPTA and salts Dissolvine D series Akzo NobelHEDTA and salts Dissolvine H series Akzo Nobel

Pentasodium pentetate Na5DPTA (DPTA) Versenex 80 DowTetrasodium EDTA Na4EDTA Versene 100 DowTrisodium EDTA Na3EDTA Versenol 120 Dow

NaLED3A (surfactant- NaLED3A Hampshirechelator compound) Chemical (Dow)

Tetrasodium etidronate Sodium HEDP Mayoquest 1530M Vulcan(Na4HEDP)

Tetrasodium etidronate Sodium HEDP Mayoquest 1545M Vulcanand (Na4HEDP) andPentasodium pentetate NA5DPTA (DPTA)Tetradibutyl pentaerythrityl Tinogard TT Ciba

hydroxyhydrocinnamate

AntioxidantsBHT BHT Tenox BHT Eastman Chemical


Crack Resistance. Crack resistance relates to the tendency of soap bars to crackand/or disintegrate when subjected to repeated wet-dry cycles. This is achieved inthe laboratory by submersion of one-half of the bar in ambient water from 4 to 24h, then air drying until completely dry. Cracks will appear if the system is prone tocracking. Also the amount of sloughing can be determined by a similar method ofsubmersion and calculating the weight loss after drying.

Industry experience indicates that translucent soaps traditionally have poorcrack resistance. One theory suggests that translucent systems lack the “grain” orinternal structure that traditional opaque soaps have. This grain or crystallinity,allows the soap to hydrate and dehydrate uniformly, whereas translucent soap lackssufficient structure to stabilize the effect. Additives, such as sucrose, can promotecracking as well as certain solvents in fragrances. Syndet systems appear to be lessprone to cracking but can produce a high rate of sloughing. This is the tendency toform a gel-like material (mush) when hydrated; it depends on the formulation andis a major drawback of syndet-combo systems.

Wash Down. The feel of a bar during use can be determined by a wash downtest. This is usually performed at a lower temperature, 85–90°F in order to deter-mine if there is any grit, drag, or sandiness present in the bar. Traditionally, syn-thetic and combo systems are prone to this problem. Some of the causes includeimproper processing at the base- and bar-making stage or hard particles in the sur-factant system. Formulas containing sodium cocoyl isethionate appear to be proneto this problem. Concern arises when the bar is cold; before use the grit may feelunpleasant to the user in spite of the fact that the grit disappears at a normal usetemperature. Sandiness may occur in a traditional opaque soap base by excessivelydry particles formed during the vacuum-drying process. Various soaps with a high-er water range of 12–14% will typically reduce this problem.

Lathering. While lathering does not necessarily equate to detergency, consumersperceive quick, copious foam with quality and cleaning. In reality, foam may be avisual aid to the consumer, allowing the user to see where the product has beenapplied. Foaming characteristics can be influenced by many factors, including fatand oil type and ratio, or in the case of synthetics, the types of surfactants and plas-ticizers. Many additives that are oily in nature will tend to act as defoamers ifincorporated at high levels, such as in superfatted bars. Traditional soaps will lath-er poorly in hard water and seawater while synthetics, if properly formulated, willfoam well. Standard foam height tests should be performed as part of the productprofile.

Color. Soap bases tend to yellow so that the color of the final bar formulationswill also change. This, coupled with additive and fragrance instability, can producecolor variations in a short period of time. Accelerated stability testing in oven, sun-light, or fluorescent light can help predict the stability of this system. A reflectance


colorimeter is useful to record the color of a sample in a computer database. Thisinstrument mathematically calculates the color as the human eye sees it and allowsthe computer to recall the color any time in the future as a reference standard. Thismethod can be used for all soap types, including translucent and transparent soapsto determine the yellowness of soap bases. It is a particularly reliable tool to char-acterize color. Other, more sophisticated color-measuring devices can be employedthat not only measure color, but also formulate and correct soap batches allowingfor more precise and efficient color matching.

Odor. Olfactory evaluation of a soap base and finished product is as important as anyother physical characteristic. Consumers tend to view the fragrance perception asbeing as important as any other characteristic. Therefore, it is important that the soapfragrances are formulated to ensure as much stability as possible. Evaluation for chem-ical stability can be carried out under similar conditions as color stability. Trained tech-nicians and odor evaluation panels usually perform an olfactory evaluation.

Colorants

Colorants can essentially be divided into three categories: certified, those coloradditives subject to certification; noncertifiable, those color additives not subject tocertification; and noncertified, those color additives not certified. The use of col-orants depends on the type of product that is being produced and the governmentregulations that govern the product. In the U.S., the distinction usually lies in theapplication of the Federal Food, Drug, and Cosmetic (FD&C) Act (26) and the FairPackaging and Labeling (FP&L) Act where the definition and labeling require-ments for drugs and cosmetics are made, and soap is exempt. Drugs must use certi-fied colors, while cosmetics can use certified and noncertifiable colors. Any soapthat makes drug and/or cosmetic claims must have its ingredients labeled accord-ingly, with the appropriate colorants. Soaps however can use any combination ofcolors as long as it meets the definition of soap and is claimed as such. Resources,such as the CTFA dictionary, can be consulted to determine acceptable andapproved colorants in other countries.

Tables 3.2 and 3.3 list some of the more common certified and noncertifiablecolorants. Certified colors are common for drugs and cosmetics, while noncertifi-able colors are primarily used in cosmetic type soaps.

Certified Colorants. Certified colorants (Table 3.4) may be water soluble, oil sol-uble, or oil dispersible. They also include the corresponding metal lakes. The solu-tions or dispersions are typically made at the 1–2% level; higher loads of 30–50%may be obtained from vendors that have specialized equipment for grinding anddispersion. Solubility and dispersion tables should be consulted to determine theoptimum concentrations in dispersing. It is recommended that sufficient concentra-tion strengths be used to maintain relatively low levels of additives and reduce the


amount of dispersant needed for the soap batch. Certified colorants tend to havethe lowest stability of the three categories. Factors include pH, day and fluorescentlight, heat, and additive interactions. For instance FD&C Green 3 renders a greencolor below a pH of 7 but a royal blue above pH 7. Stability stations should be uti-lized to determine overall stability in the surfactant system.

Noncertifiable Colorants. Noncertifiable colorants (Table 3.4) tend to be verystable compounds and are used extensively in cosmetics, eye shadows, mascaras,

TABLE 3.2Color Additives Subject to Certification (March 1990)

Color indexColor additives number Use in cosmetics

FD&C Blue 1 42090FD&C Green 3 42053 Except in eye areaFD&C Red 4 14700 Externally except in eye areaFD&C Red 40 16035FD&C Yellow 5 19140FD&C Yellow 6 15985 Except in eye areaD&C Blue 4 42090 Externally except in eye areaD&C Brown 1 20170 Externally except in eye areaD&C Green 5 61570D&C Green 6 61585 Externally except in eye areaD&C Green 8 59040 Externally except in eye area (0.01% max.)D&C Orange 4 15510 Externally except in eye areaD&C Orange 5 45370 Externally except in eye area

Lip products (5% max.), mouthwashes, dentifrices (GMP)D&C Orange 10 45425 Externally except in eye areaD&C Orange 11 45425 Externally except in eye areaD&C Red 6 15850 Except in eye areaD&C Red 7 15850 Except in eye areaD&C Red 17 26100 Externally except in eye areaD&C Red 21 45380 Except in eye areaD&C Red 22 45380 Except in eye areaD&C Red 27 45410 Except in eye areaD&C Red 28 45410 Except in eye areaD&C Red 30 73360 Except in eye areaD&C Red 31 15800 Externally except in eye areaD&C Red 33 17200 Externally except in eye area

Lip products (3% max.), mouthwashes, dentifrices (GMP)D&C Red 36 12085 Externally except in eye area

Lip products (3% max.)D&C Violet 2 60725 Externally except in eye areaD&C Yellow 7 45350 Externally except in eye areaD&C Yellow 8 45350 Except in eye areaD&C Yellow 10 47005 Externally except in eye areaD&C Yellow 11 47000 Externally except in eye area


and facial makeup. In some products they can be used as primary and secondarycolorants; they tend to stabilize color drifting due to certified color use. Thesecompounds should be dispersed or wet-out before use to maximize their colorvalue. A dispersion aid, such as a 30–40% potassium cocoate solution, gives agood dispersability to these colorants. The formulator can develop a color byapproximating the amount of dry pigment then dispersing the powder in thecocoate solution. A “blooming” effect, where large pigment particles cause a slowmigration of color into the soap system, can occur if the colorant is not dispersed

TABLE 3.3Color Additives Exempt from Certification (March 1990)

Color indexColor additives number Use in cosmetics

Aluminum powder Externally including the eye areaAnnetto No restrictionsBismuth citrate Scalp hair dye onlyBismuth oxychloride 77163 No restrictionsBronze powder No restrictionsCaramel No restrictionsCarmine 75470 No restrictionsCarotene, beta No restrictionsChromium hydroxide green 77289 Externally including the eye areaChromium oxide greens 77288 Externally including the eye areaCopper powder No restrictionsDihydroxyacetone Externally including the eye areaDisodium EDTA-copper Cosmetic shampoo onlyFerric ammonium ferrocyanide Externally including the eye areaFerric ferrocyanide 77510 Externally including the eye areaGuanine No restrictionsGuaiazulene Externally except in the eye areaHenna Scalp hair dye onlyIron oxides 77489 No restrictions

774917749277499

Lead acetate Scalp hair dye only (0.6% Pb w/v max.)

Manganese violet 77742 No restrictionsMica 77019 No restrictionsPotassium sodium, copper Cosmetic dentifrices (0.1% max.)

chlorophyllin (chlorphyllin-copper complex)

Pyrophyllite Externally except in the eye areaSilver Nail polish only (1% max.)Titanium dioxide 77891 No restrictionsUltramarines (blue, green, pink, violet) 77007 Externally except in the eye areaZinc oxide 77497 No restrictions


properly or becomes dried-out before use. Unfortunately this can occur withinhours or days of production and causes a blotched color in the finished product.Newer materials on the market however contain predispersed colorants for ease ofuse. Opacifiers, such as titanium dioxide, zinc oxide, and bismuth oxychloride, arealso used to give uniformity to the color system. Without them the soap mayappear to have light- and dark-colored areas caused by various compression areasfrom processing and pressing operations. Titanium dioxide is offered in both rutileand anatase forms with the water-dispersible anatase USP grade being used mostoften. Traditionally, rutile types typically do not give the brightness or the hidingpower that anatase types give. However there are newer rutile versions that appearto be comparable to the anatase type that give equal opacity, better stability, andsomewhat superior brightness.

Noncertified Pigments. In the U.S., noncertified pigments are often used in barsoaps, as long as the soaps conform to the definition and labeling requirements ofsoap. These colors tend to be very stable, less sensitive to pH, and provide a widerange of brightness and hues. They often are supplied as dispersions with concen-trations of 25–50%. Also, only small amounts of these pigments are required toachieve dark colors in most soap bases. Table 3.5 highlights some of the morecommon noncertified colorants that are used in soaps.

Fragrances

Virtually any scent can be created to fit a product profile and marketing concept.All fragrances should be developed to ensure stability and robustness for use in aparticular soap matrix. Use levels will vary depending on the composition, but atypical low range is 0.25–0.50% for masking purposes and 3–4% for prestige fra-grance bars. At high usage levels, it is important to use vacuum in the extrusion

TABLE 3.4 Common Soap Colorants

Certified Noncertifiable

FD&C Green 3 CaramelFD&C Red 4 Chromium hydroxide greenFD&C Red 40 Chromium oxide greensFD&C Yellow 5 Iron oxidesD&C Green 5 MicaD&C Green 6 Titanium dioxideD&C Green 8 Ultramarines (blue, green, pink, red, violet)D&C Orange 4 Zinc oxideD&C Red 17D&C Red 33D&C Violet 2D&C Yellow 10


process to minimize surface bubbling or blistering caused by the fragrance compo-nents. A very small amount of fragrance will be lost with a vacuum system, but theoverall effect will be a uniform extrusion. As mentioned previously, fragranceswill affect soap processing to the extent that they will not extrude or press (stamp)within the desired process rates. This is seen in synthetic and combo systems, but itis more dramatic in translucent systems where clarity and firmness are critical. Asindicated earlier, two particular fragrance additives used as solvents cause prob-lems in translucent soaps. Dipropylene glycol (DPG) and diethylphthalate (DEP),tend to make translucent soaps sticky to the point where the soap does not extrudeor press at all. When these solvents are removed from fragrance formulations, anoticeable increase in productivity can be seen. Certain resinoid compounds usedin fragrances may cloud translucent systems due to solubility and particulate con-cerns. Other components may produce similar effects and should be investigatedthrough experimentation.

Additives

Most soap products include the addition of compounds to achieve a desired func-tional and/or marketing position. This has become the prime focus of soap formu-lators. The CTFA Cosmetic Handbook (27) and McCutcheon’s FunctionalMaterials (28) contain many of these functional materials. Several important cate-gories will be discussed:

• Emollients

• Humectants/Moisturizers

• Occlusive agents

• Dermabrasive agents

• Drug components

• Anti-irritants

• Secondary surfactants

• Miscellaneous compounds.

TABLE 3.5 Common Noncertified Colorants in Soap

Pigment name Pigment type Color index number

Pthalo blue RS Blue 15 74160Pthalo blue Blue 15:1 74250Pthalo blue GS Blue 15:3 74160Pthalo green Green 7 74260Quinacridone magenta Red 122 73915Napthol red ITR Red 5 12490Carbazole violet Violet 23 51319Hancock yellow G Yellow 1 11680


A difficult task for the formulator is the evaluation of additive benefits in soapbases. Most often expert panels are used to evaluate performance and aesthetic per-ceptions. More sophisticated and highly technical techniques can be employed,such as transepidermal water loss or TEWL, skin elasticity, tracer studies for resid-ual ingredients after rinsing, spectroscopic and florescence studies, and human skinmodels. Kajs and Garstein (29) review the use of these methods for evaluatingcleansing products.

Emollients. Emollients are compounds that are used to impart and maintain soft-ness and pliability of the skin and generally improve the skin’s overall appearance.Fatty esters, alkoxylated ethers, and alkoxylated alcohols comprise the bulk of theingredients in this category (Table 3.6). Typical use levels are 1–3%. These com-pounds are stable under normal bar-soap conditions, however care should be takento review the physical properties of each of these materials to determine the bestway to incorporate the ingredients into the base, as well as any stability considera-tions, such as pH and temperature.

Humectants/Moisturizers. Humectants and moisturizers (Table 3.7) are skin-conditioning agents that increase the moisture in the skin. Their effectivenessdepends on the humidity in the environment they operate in. Typical use levelsvary widely from 0.1 to 10%. Dahlgren et al. (30) describes the results of instru-mental methods and perceived skin benefits of glycerine in various surfactant sys-tems. The results indicate that high levels of glycerine provide improved skin feeland softness. It should be noted that monosaccharides or simple sugars, such as fruc-tose and glucose, darken under alkaline conditions and accelerate by the smallamount of free alkaline present in traditional soap bases. The neutralization of thefree alkali by the addition of a fatty acid, such as coconut or stearic acid, will helpreduce the darkening effect. The discoloration will vary, and depends on the type andamount of sugar. Disaccharides, such as sucrose, are relatively stable under mildalkaline conditions. Water-droplet formation or sweating may occur with high levels(10% or more) of glycols and alcohols, such as glycerine, sorbitol, and propyleneglycol, under humid conditions. This is a persistent problem with transparent soapsthat employ high levels of multiple humectants that also serve as solvents and solubi-lizers. This hygroscopic effect appears to be less of a problem with other types ofsoap systems that employ lower levels (under 5%) of these materials.

Occlusive Agents. Occlusive agents (Table 3.8) include ingredients that aredesigned to prevent moisture evaporation from the skin, and thus help maintainsoft and smooth skin. They typically are lipid in nature and are added to achieve adesired effect in so-called dry-skin products. Use levels are in the 1–10% range.The higher levels may cause extrusion and pressing problems by making the soapexcessively soft and sticky, but this may be reduced by incorporating the ingredi-ents in the base-making stage or pre-milling/refining stage prior to extrusion.


TABLE 3.6 General Emollient Groupings and Common Ingredients

Esters Ethers Alcohols Oils and oil type Glycols Lanolin derivatives Silicone derivatives

Butyl myristate Methyl gluceth-1 Cetearyl alcohol Castor oil Glycerine Acetylated lanolin Dimethicone copolyol

Cetyl palmitate Methyl gluceth-20 Cetyl alcohol Jojoba oil Propylene glycol Lanolin slicone fluids

Glycerol stearate PPG-10 methyl Stearyl alcohol Mineral oil Diglycerine Lanolin esters glucose ether

Isopropyl myristate PPG-20 cetyl ether Mink oil Lanolin alcohols

Isopropyl palmitate PPG-20 lanolin PEG-glycerides Lanolin fatty alcohol alcohol ether

Octyl palmitate PPG-20 methyl Petrolatum PEG-lanolin glucose ether

Tridecyl neopentanoate PPG-20 oleyl ether Shea butterPPG-20 myristyl Cocoa butter

ether Sweet almond oil, wheat germ oil, olive oil, grapeseed oil


Dermabrasive/Exfoliating Agents. Dermabrasive agents work in conjunctionwith a cleanser to remove the outermost layer of stratum cornea by scrubbing, thusproducing a smoother feel to the skin. Loden et al. (31) describes a method to mea-sure the effects of dermabrasive cleansers and has determined that there is a per-ception of improving skin smoothness. Natural components, such as bran, loofa,oatmeal, jojoba beads, and various seeds, are popular since they can be blended toachieve a desired look in the cleanser and a desired feel on the skin in addition to anatural claim. Polyethylene beads of various sizes and colors are also used effec-tively where a natural component is not needed. With some precautions, theseagents can be added to the amalgamator process under normal conditions. Whenusing refiners, the screen sizes should be large enough to allow the scrub agents topass through. Otherwise they will be filtered out. When using mills, the milling

TABLE 3.8 Occlusive Agents

Castor oilCoconut oilDimethiconeHydrogenated oilsJojoba oilJojoba waxMineral oilNatural and synthetic waxesOlive oilPetrolatumShea butterCocoa butterSweet almond oilTallowWheat germ oil

TABLE 3.7 Common Humectants and Moisturizers

MiscellaneousSaccharides Ethers Alcohols Glycols compounds

Fructose Methyl gluceth-10 Mannitol Glycerine Acetamide MEAGlucose starch Methyl gluceth-20 Sorbitol Propylene glycol Hydrogenated

hydrosylateHoney PPG-10 propylene glycol Diglycerine PCALactose Sodium PCASucrose UreaXylitolTridecyl

neopentanoate


action should not break the component down into fines, which will reduce thescrubbing effect. Proper gapping of the roller mills and the use of low shear millswill reduce the problem. If this is not possible, then a scrub agent can be added in apost-milling step or possibly in the finish extruder with no screens. This problemoccurs mostly with the larger size natural components, such as loofa and oatmeal,and too a much lesser extent with the polyethylene beads. It should be noted thatmild exfoliation could be achieved using spherical exfoliants, such as polyethyleneand jojoba beads, since they tend to roll over the skin. Irregularly shaped material,such as crushed seeds, leaves, and shells, tend to provide a more aggressive effect.

Drug Components. The most common drug categories that bar soaps areinvolved in are antimicrobial and acne. In the U.S., each drug category is governedby a monograph published by the federal Food and Drug Administration (FDA).Organizations, such as CTFA, SDA, and others, have been working diligently withthe FDA over the last several years to finalize the antimicrobial monograph toinclude personal care antimicrobial cleansers as a separate category. Each mono-graph sets the conditions under which a product that is claimed in a particular cate-gory may be sold. The formulator should consult the monograph to obtain specificinformation of a category prior to development work; all of these products shouldbe manufactured or controlled according to good manufacturing procedures, sincethe drugs are subject to FDA auditor inspections.

The antimicrobials, Triclosan and Triclocarban are the two compounds mostwidely used in antimicrobial bar soaps. Typical use levels are 0.3–1% for Triclosanand 1–1.5% for Triclocarban. They are incorporated at the amalgamator stage and maybe predispersed or dissolved in a suitable solvent, such as a fragrance, prior to addition.As with all drug products, the soap line should be validated to ensure that the finishedproduct is homogenous, and that the proper level of the antimicrobial is in the soap.

The most commonly approved acne ingredients used in bar soap are salicylicacid, at 0.5–2%, and sulfur at 3–10%. They have been formulated both in traditionaland synthetic or combo bases. Sulfur is stable in both alkaline and acid bases.Salicylic acid however is stable with acid bases but may destabilize traditional alka-line bases. Therefore a mild alkali, such as triethanolamine, is sometimes added to sta-bilize the salicylic acid. Iron contamination should be avoided, since both ingredientswill remove iron from the equipment. This will result in the iron particles blooming inthe soap. This will cause soap discoloration and can potentially lead to rancidity in tra-ditional soaps. Both of these ingredients are normally added in the amalgamator stageand processed under normal conditions. As stated previously, good manufacturingprocedures for this product category need to be enforced.

Anti-irritants. There are several ingredients on the market that claim to have anti-irritant properties. Among these are sucrose esters, α-bisabolol, lactylates, andethoxylated vegetable oils. Also, it is known that surfactant mixtures incorporatingsuch materials as amphoterics, sarcosinates, ethoxylated surfactants, and isethionates


can reduce the overall irritancy of the product. Most of these compounds have beenevaluated in shampoo systems in which skin and eye irritation levels are reportedlyreduced, but it can also be effective in bar soaps.

The overall mechanisms are not fully understood but are believed to involveseveral factors, including binding or complexation of irritants, blocking sites thatare prone to irritation, and prophylaxis that covers the skin thus reducing or pre-venting irritant contact. When adding anti-irritants, a baseline test should be run todetermine the effectiveness on the irritant. This can be achieved by several differ-ent methods that are currently on the market. The so-called soap chamber test wasdeveloped by Frosch and Kligman (32); the Zein test, as described by Gotte (33), isan in vitro method that measures the ability of surfactants to solubilize the veg-etable protein Zein. Newer, in vitro methods continue to be developed that utilizehuman skin factors in bench-top assays that will benefit the formulator in quicklyscreening various additive packages. There does not appear to be one single testthat is an adequate predictor of irritancy potential. Rather, several testing protocolsmay be needed to evaluate a product or surfactant.

Secondary Surfactants. Secondary surfactants are often used to increase the perfor-mance of the bar resulting in improved skin feel, reduced irritancy from the primarysurfactant, improved solubility, or improved quality and quantity of the foam.Typically they are added at low levels, under 5%, as an adjunct to the primary surfac-tant. Theoretically most surfactants found in shampoos and liquid soaps may be usedin bar soap systems as long as they are compatible with the system and are stableunder a given pH. However, most of them are pastes and liquids that tend to makesoap systems tacky and result in increased processing problems. This may be due notonly to their physical state, but also to their tendency to lower the viscosity of the soapsystem and soften the system. Furthermore, additives and fragrances may complicatethe formulation.

Table 3.9 lists several of the more common surfactants that are used: acylisethionates, amphoterics, sarcosinates, sulfosuccinates, and sulfoacetates. Theseingredients may be added to the amalgamator and processed under normal conditions.In particular, sodium coco glyceryl sulfonate has good foam boosting, after-feel,

TABLE 3.9 Secondary Surfactants

Type Example Chemical type Form

Acyl isthionates Sodium cocoyl isethionate Anionic SolidAmphoterics Disodium cocoamphodiproprionate Amphoteric PasteSarcosinates Sodium cocoyl sarcosinate Anionic Liquid-solidSulfosuccinates Disodium lauryl sulfosuccinate Anionic Liquid-solidSulfoacetates Sodium lauryl sulfoacetates Anionic SolidAlkyl glyceryl sulfonate Sodium cocoglyceryl ether sulfonate Anionic Paste


and processing characteristics. When handling powders, care should be taken tosafely handle dust associated with the surfactants. An alternate method to introducethese extra surfactants would be to include them in the base-making process so thatthey become an integral part of the base. For synthetic and combo bases, these sur-factants may be added during the normal compounding process. Additionally,Rigger (34) has developed an excellent list and overview of surfactant types avail-able to the formulator.

Miscellaneous Compounds. Several miscellaneous compounds are commonlyused in soap formulations. Optical brighteners are sometimes used to shift theappearance of a product from a yellow tone to a bluer tone. One ingredient, disodi-um distyrlbiphenyl disulfonate, is particularly effective, requiring approximately0.3% in traditional soap base for soap products. Currently this compound is viewedas a noncertified colorant in the U.S. and is not acceptable in products labeled ascosmetics or drugs. However, it is approved in the EC for use in cosmetics. Colorstabilizers have recently been introduced that help reduce color fading from pho-tolytic effects. Sodium benzotriazolyl sulfonate, sodium benzotriazoyl butylphenolsulfonate and buteth-3, tributyl citrate, and bumetrizole are a few examples of suchcompounds. They can be added to the amalgamator.

Encapsulated products can be useful to the formulator. The challenge of using anencapsulated product in soap products is capsule survival during processing while hav-ing a small enough particle size to minimize drag or grit feel after washing. Thisallows the delivery of process- and formula-sensitive materials during washing; thisresults in enhanced effectiveness and stability. More recently, U.S. Patent 6,403,543(35) demonstrates the suspension of microencapsulated beads in clear glycerine soap.The beads can contain many of the functional materials that have been discussed. Thissystem not only provides an interesting visual effect, but it also isolates the functionalmaterial from the surrounding soap matrix and offers additional stability.

Herbal extracts have increased in popularity recently due to heightened aware-ness of the environment and the subsequent “natural” themes in many product cat-egories. Aromatherapy, spa, and fragrance-free products are included in these cate-gories. Extracts of rosemary, chamomile, sage, and aloe, among others, are oftenused as masking agents to replace fragrances while imparting whatever skin bene-fits they may claim to have. The current CTFA dictionary has an extensive crossindex of botanicals that are powders, oils, and extracts. As with any naturallyderived material, specifications should be developed to ensure acceptable purityand consistency with every shipment. Many botanicals are offered in a standard-ized version, giving the formulator some degree of confidence as to the strength ofthe material. Since some of the components in a natural product are unknown, ade-quate stability studies on all formulations need to be performed to determine ifthere are any color or fragrance issues. For instance, certain phenols and tanninsmay unacceptably discolor the soap. A recent publication (36) outlines many of thenatural and botanical ingredients available today.


Cream soaps and cleansing grains are other types of non-bar cleansing systemsthat can be developed. The cream products can be viewed as modified combo barsthat have a paste-like consistency. The formulations include a combination of tra-ditional soap with synthetic detergents, plus structuring agents and benefit addi-tives. Colorants and fragrances can be added as well as special ingredients, such asclays and botanicals. The resulting product is paste-like generating excellent foam-ing, cleansing, and after-feel. They can be dispensed from a variety of containers,and when pressurized will provide an excellent mousse product. Cleansing grainsare formulated with a powdered soap and/or detergent cleanser, benefit additives,colorants, and fragrances. Liquid additives should be kept at a minimum to ensurethat the product flows and dispenses properly. Encapsulating the liquid material ina solid matrix whereby the liquid is delivered when the product is used allowshigher amounts of liquids to be used. These products offer an additional way thatthe consumer can utilize advances in personal care skin-cleansing additives.

Alternative soap bases can be made from nontraditional oils. These include,but are not limited to, grapeseed, olive, sweet almond, and rice bran oils. Whensaponified, these oils yield a finished soap that can be extruded and pressed. Theresulting soap bars are slightly softer than traditional soap from tallow or palm oil,but are extremely smooth when used and provide excellent lather and a nice after-feel. The all vegetable oil components may be attractive for market sectors in spa,aromatherapy, and natural lines. Standard soap additives, as well as botanicals, canbe incorporated into these bases.

Conclusion

The formulator is urged to take a balanced approach in developing surfactant sys-tems. Consideration must be given to the base type and function; these will dictateacceptable additives for the product category. In turn, process considerations mustbe addressed in order to manufacture a quality product. Surfactant systems can beoverwhelmed trying to achieve higher and higher functionality for a world of ever-changing cultures.

References

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2. Davidsohn, J., E.J. Better, and A. Davidsohn, Soap Manufacture, Interscience, NewYork, 1953, Vol. 1.

3. Swern, D., ed., Bailey’s Industrial Oil and Fat Products, 4th ed., J. Wiley & Sons, NewYork, 1979, Vol. 1.

4. Woolatt, E., The Manufacture of Soaps, Other Detergents and Glycerine, HalsteadPress, New York, 1985.

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6. Chambers, J., T. Instone, and B. Stuart, Eur. Patent Appl. 385,796 (1990).


7. Chambers, J., and T. Instone, Eur. Patent Appl. 350,306 (1990).8. Verite, C., and A. Caudet, Eur. Patent Appl. 336,803 (1981).9. Wood-Rethwill, J., R. Jaworski, and G. Myers, U.S. Patent 4,897,063 (1989).

10. Jungennan, E., T. Hassapis, R. Scott, and M. Wortzman, U.S. Patent 4,758,370 (1988).11. Dawson, G., and G. Ridley, Eur. Patent Appl. 311,343 (1989).12. Joshi, D., U.S. Patent 4,493,786 (1985).13. Nagashima, T., Y. Usuba, T. Ogawa, and M. Takehara, U.S. Patent 4,273,684 (1981).14. O’Neill, J., J. Komor, T. Babcock, R. Edmundson, and E. Shay, U.S. Patent 3,793,214

(1974).15. Deweever, E., and T. Carroll, U.S. Patent 3,903,008 (1975).16. Crudden, J.J., U.S. Patent 5,186,855 (1993).17. Kutny, Y., F. Osmer, I. Podgorsky, D. Richardson, and K. Rys, U.S. Patent 5,041,233

(1991).18. Lee, R., T. Instone, and J. Chambers, Eur. Patent Appl. 434,460 Al (1989).19. Hollstein, M., and L. Spitz, Manufacture and Properties of Synthetic Toilet Soaps, Soap

Cosm. Specialties 59: 29–34, 51 (1983).20. Barker, G., L. Safrin, and M. Barabash, U.S. Patent 4,335,025 (1981).21. Kamen, M., and I. Ugelow, U.S. Patent 3,562,167 (1971). 22. Chemical Services (Proprietary) Ltd., UK Patent 1,153,303 (1969).23. Geitz, R., U.S. Patent 2,894,912 (1959).24. Dederen, I.C., Skin Cleansing and Mildness: A Comparison, Cosmetics and Toiletries

Manufacture Worldwide, 1993, pp. 110–124. 25. Pepe., R.C., J.A. Wenninger, and G.N. McEwen, CTFA International Cosmetic Dictionary,

9th ed., The Cosmetic, Toiletry, and Fragrance Association, Washington, D.C., 2001.26. Title 21, U.S. Code of Federal Regulations (2ICFR).27. Pepe., R.C., J.A. Wenninger, and G.N. McEwen, CTFA International Cosmetic Dictionary,

9th ed., The Cosmetic, Toiletry, and Fragrance Association, Washington, D.C., 2001.28. McCutheon’s Vol. 2: Functional Materials, North American ed., The Manufacturing

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