DE69705496T2 - CLEANING AGENT, CONTAINING COLOR STABILIZER (S) AND SURFACTANT (S) - Google Patents

Description

Since ancient times, soap has been used to cleanse human skin. Solid and liquid compositions containing soap have been used to deliver the surfactant to the skin for cleaning purposes. As with virtually any composition used for end-use purposes, the stability of the composition for proper use and/or extended storage before use is very important.

It is well known that free radical reactions affect the stability of soap-containing compositions. Free radicals start chain reactions that lead to the degradation of long-chain hydrocarbon materials such as soaps, free fatty acids, synthetic surfactants and the like present in cleaning compositions. These reactions can lead to other perceptible effects, color changes in the cleaning composition and ultimately rancidity of the formulation caused by degradation products that are very odorous.

The degradation of the long chain hydrocarbon containing materials can be substantially altered by using known materials that either hinder the catalysis of certain free radical mechanisms or act as a free radical sink to terminate the free radical chain reaction by rendering the free chain radical harmless. Examples of materials of the former type are agents that form chelates with metals such as copper and iron, which are known catalysts of the free radical initiation stages, particularly at points of unsaturation in the hydrocarbon chain. Such agents include ethylenediaminetetracarboxylic acid and its salts, as well as various salts of phosphonic acid derivatives. Exemplary free radical sinks are various aromatic compounds that appear to function as a sink for the free radicals generated, regardless of what their initial growth mode may have been. A good example of this type of compound, which has been used for several decades is butylated hydroxytoluene (commonly known by its abbreviation BHT).

However, even when using BHT, there are known stability problems. In general, discoloration of cleaning bars occurs from time to time, and at specific points discoloration also occurs, usually to an intense yellow. After longer periods of time, odors may also develop from a soap bar, although this is unusual. There is therefore a need for a better, especially solid, stability-enhancing additive for cleaning formulations.

Summary of the invention

According to the invention, there is provided a cleaning composition comprising a cleaning-effective amount of a long-chain alkyl or alkenyl-containing surfactant or mixtures thereof, where long-chain means at least 8 carbon atoms, and a color-stabilizing amount of a compound selected from the group consisting of

in which R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are the same or different and are isopropyl or tert-butyl,

in which R�9 and R₁₀ are the same or different and are isopropyl or tert-butyl and n is 8 to 20, or

in which R₁₁, R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆ are the same or different and are isopropyl or tert-butyl.

In a preferred composition, the surfactant is a soap.

A further preferred composition is a solid, particularly in bar form.

Detailed description of the invention

Any surfactant that removes soil from the skin and is susceptible to degradation during prolonged storage, particularly degradation that results in discoloration and/or undesirable odors, may be used in the cleaning composition. Therefore, any surfactant that has a long chain alkyl or alkenyl group or mixtures thereof may be susceptible to this By long chain is meant at least about 8, preferably 10 carbon atoms, and usually a normal chain or chains with minor branching. Generally, the maximum number of carbon atoms is insignificant, but usually more than 20 is not preferred. Small amounts of olefinic bond(s) may be present in the predominantly alkyl portions, particularly when the source of the "alkyl group" is obtained from a natural product such as tallow, coconut oil, or the like.

Soap, a salt of a branched or normal long chain alkyl or alkenyl carboxylic acid, such as a sodium, potassium or substituted ammonium salt, may be present in the composition and is preferred.

Examples of these surfactants are the anionic, amphoteric, non-ionic and cationic surfactants. Examples of anionic zwitterionic surfactants include alkyl sulfates, anionic acyl sarcosinates, methyl acyl taurates, N-acyl glutamates, acylisethionates, alkyl sulfosuccinates, alkyl phosphate esters, ethoxylated alkyl phosphate esters, trideceth sulfates, protein condensates, mixtures of ethoxylated alkyl sulfates and the like.

Examples of anionic surfactants that are not soaps are the alkali metal salts of organic sulfates which have in their molecular structure an alkyl radical containing from about 8 to about 22 carbon atoms and a sulfonic acid or sulfuric acid ester radical (the term alkyl includes the alkyl portion of higher acyl radicals). Preferred are the sodium, ammonium, potassium or triethanolamine alkyl sulfates, especially those obtained by sulfating the higher alcohols (C₈ to C₁₈ carbon atoms), sodium coconut oil fatty acid monoglyceride sulfates and sulfonates, sodium or potassium salts of sulfuric acid esters of the reaction product of 1 mole of higher fatty alcohol (e.g. tallow or coconut oil alcohols) and 1 to 12 moles of ethylene oxide, sodium or potassium salts of alkylphenol ethylene oxide ether sulfate with 1 to 10 ethylene oxide units per molecule and in which the alkyl radicals contain 8 to 12 carbon atoms, sodium alkyl glyceryl ether sulfates, the reaction product of fatty acids with 10 to 22 carbon atoms which are reacted with isethionic acid esterified and neutralized with sodium hydroxide, water-soluble salts of condensation products of fatty acids with sarcosine and others known in the art.

Examples of zwitterionic surfactants are those generally described as derivatives of aliphatic quaternary ammonium, phosphonium and sulfonium compounds in which the aliphatic radicals may be straight chain or branched and wherein one of the aliphatic substituents contains about 8 to 18 carbon atoms and one of the aliphatic substituents contains about 8 to 18 carbon atoms and one of the substituents contains an anionic water-solubilizing group, e.g. carboxy, sulfonate, sulfate, phosphate or phosphonate. A general formula for these compounds is:

wherein R2 contains an alkyl, alkenyl or hydroxyalkyl radical containing from about 8 to about 18 carbon atoms, 0 to about 10 ethyleneoxy moieties, and 0 to 1 glyceryl moiety, Y is selected from the group consisting of nitrogen, phosphorus and sulfur atoms, R3 is an alkyl or monohydroxyalkyl group containing from 1 to about 3 carbon atoms, · is 1 when Y is a sulfur atom, and 2 when Y is a nitrogen or phosphorus atom, R4 is alkylene or hydroxyalkylene containing from 0 to about 4 carbon atoms, and Z is a radical selected from the group consisting of carboxylate, sulfonate, sulfate, phosphonate and phosphate groups.

Examples include: 4-[N,N-Di(2-hydroxyethyl)-N-octadecylammonio]butane-1-carboxylate, 5-[S-3-hydroxypropyl-S-hexadecylsulfonio]-3-hydroxypentane-1-sulfate, 3-[P,PP-Diethyl-P-3,6,9- trioxatetradecylphosphonio]-2-hydroxypropane-1-phosphate, 3-[N,N-Dipropyl-N-3-dodecoxy-2-hydroxypropylammonio]-propane- 1-phosphonate, 3-(N,N-dimethyl-N-hexadecylammonio)propane-1-sulfonate, 3-(N,N-dimethyl-N-hexadecylammonio)-2-hydroxypropane-1-sulfonate, 4-(N, N-Di(2-hydroxyethyl)-N-(2-hydroxydodecyl)ammonio]-butane-1-carboxylate, 3-[S-Ethyl-S-(3-dodecoxy-2-hydroxypropyl)sulfonio]- propane-1-phosphate, 3-(P,P-dimethyl-P-dodecylphosphonio)-propane-1-phosphonate and 5-[N,N-di(3-hydroxypropyl)-N-hexadecylammonio]-2-hydroxypentane-1 -sulfate.

Examples of amphoteric surfactants that can be used in the compositions of the invention are those that can be generally described as derivatives of aliphatic secondary and tertiary amines in which the aliphatic moiety can be straight chain or branched and one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one substituent contains an anionic water-solubilizing group, e.g., carboxylate, sulfonate, sulfate, phosphate or phosphonate. Examples of compounds falling within this definition are sodium 3-dodecylaminopropionate, sodium 3-dodecylaminopropanesulfonate, N-alkyltaurines such as that prepared by reacting dodecylamine with sodium isethionate according to the teachings of US-A-2,658,072, N-higher alkyl aspartic acids such as those prepared according to the teachings of US-A-2,438,091, and the products sold under the trade designation "Miranol" and described in US-A-2,528,378. Other amphoteric materials such as betaines are also useful in the present invention.

Examples of betaines useful herein include the higher alkyl betaines such as coco dimethyl carboxymethyl betaine, lauryl dimethyl carboxymethyl betaine, lauryl dimethyl-α-carboxyethyl betaine, cetyl dimethyl carboxymethyl betaine, lauryl bis(2-hydroxyethyl)carboxymethyl betaine, stearyl bis(2-hydroxypropyl)carboxymethyl betaine, oleyl dimethyl-γ-carboxypropyl betaine, lauryl bis(2-hydroxypropyl)-α-carboxyethyl betaine, etc. The sulfobetaines may be represented by coco dimethyl sulfopropyl betaine, stearyl dimethyl sulfopropyl betaine, amido betaines, amido sulfobetaines and the like.

Many cationic surfactants are known in the art. Examples include the following: stearyldimenthylbenzylammonium chloride, dodecyltrimethylammonium chloride, nonylbenzylethyldimethylammonium nitrate, tetradecylpyridinium bromide, laurylpyridinium chloride, cetylpyridinium chloride, laurylpyridinium chloride, laurylisoquinolinium bromide, ditallow(hydrogenated)dimethylammonium chloride, Dilauryldimethylammonium chloride and stearalkonium chloride.

Additional cationic surfactants are disclosed in US-A-4,303,543, see column 4, line 58, and column 5, lines 1 to 42, which are incorporated herein by reference. See also CTFA Cosmetic Ingredient Dictionary, 4th edition 1991, pages 509 to 514, for various long chain alkyl cationic surfactants, which are incorporated herein by reference.

Non-ionic surfactants can be broadly defined as compounds produced by condensation of alkylene oxide groups (hydrophilic in nature) with organic hydrophobic compound, which may be aliphatic or alkylaromatic in nature. Examples of preferred classes of non-ionic surfactants are:

1. The polyethylene oxide condensates of alkylphenols, e.g. the condensation products of alkylphenols with an alkyl group containing about 6 to 12 carbon atoms in a straight-chain or branched arrangement with ethylene oxide, the ethylene oxide being present in amounts corresponding to 10 to 60 moles of ethylene oxide per mole of alkylphenol. The alkyl substituent in such compounds can be derived from, for example, polymerized propylene, diisobutylene, octane or nonane.

2. Those derived from the condensation of ethylene oxide with the product resulting from the reaction of propylene oxide and ethylenediamine products, and which may vary in composition depending on the desired balance between the hydrophobic and hydrophilic elements. For example, compounds containing from 40% to 80% by weight of polyoxyethylene and having a molecular weight of from 5,000 to 11,000 are satisfactory and result from the reaction of ethylene oxide groups with hydrophobic base consisting of the reaction product of ethylenediamine and propylene oxide in excess, having a base having a molecular weight of the order of 2,500 to 3,000.

3. The condensation product of aliphatic alcohols having 8 to 18 carbon atoms in straight-chain or branched configuration with ethylene oxide, e.g. coconut alcohol-ethylene oxide condensate having 10 to 30 moles of ethylene oxide per mole of coconut alcohol, the coconut alcohol fraction having 10 to 14 carbon atoms. Other ethylene oxide condensation products are ethoxylated fatty acid esters of polyhydric alcohols (e.g. Tween-20 polyoxyethylene(20)sorbitan monolaurate),

4. Long-chain tertiary amine oxides corresponding to the following general formula

R₁R₂R₃N→O

in which R₁ contains an alkyl, alkenyl or monohydroxyalkyl radical with 8 to 18 carbon atoms, 0 to 10 ethylene oxide moieties and 0 to 4 glyceryl moieties, and R₂ and R₃ contain 1 to 3 carbon atoms and 0 to 1 hydroxy groups, e.g. methyl, ethyl, propyl, hydroxyethyl or hydroxypropyl radicals. The arrow in the formula is a conventional representation of a semipolar bond. Examples of amine oxides suitable for use in the invention include dimethyldodecylamine oxide, oleyldi(2-hydroxyethyl)amine oxide, dimethyloctylamine oxide, dimethyldecylamine oxide, dimethyltetradecylamine oxide, 3,6,9-trioxyheptadecyldiethylamine oxide, di(2-hydroxyethyl)tetradecylamine oxide, 2-dodecoxyethyldimethylamine oxide, 3-dodecoxy-2-hydroxypropyldi(3-hydroxypropyl)amine oxide, dimethylhexadecylamine oxide:

5. Long-chain tertiary phosphine oxides corresponding to the following general formula:

RR'R"P→O

in which R contains an alkyl, alkenyl or monohydroxyalkyl radical in the range of 8 to 20 carbon atoms chain length, 0 to 10 ethylene oxide moieties and 0 to 1 glyceryl moieties, and R' and R" each contain alkyl or monohydroxyalkyl groups which contain 1 to 3 carbon atoms. The arrow in the formula is a conventional representation of a semipolar bond. Examples of suitable phosphine oxides are dodecyldimethylphosphine oxide, tetradecylmethylethylphosphine oxide, 3,6,9-trioxaoctadecyldimethylphosphine oxide, cetyldimethylphosphine oxide, 3-dodecoxy-2-hydroxyethyl)phosphine oxide, stearyldimethylphosphine oxide, cetylethylpropylphosphine oxide, oleyldiethylphosphine oxide, dodecyldiethylphosphine oxide, tetradecyldiethylphosphine oxide, dodecyldipropylphosphine oxide, dodecyldi(hydroxymethyl)phosphine oxide, dodecyldi(2-hydroxyethyl)phosphine oxide, tetradecylmethyl-2-hydroxypropylphosphine oxide, oleyldimethylphosphine oxide, 2-hydroxydodecyldimethylphosphine oxide.

6. Long chain dialkyl sulfoxides containing a short chain alkyl or hydroxyalkyl radical having 1 to 3 carbon atoms (usually methyl) and a long hydrophobic chain containing alkyl, alkenyl, hydroxyalkyl or ketoalkyl radicals containing 8 to 20 carbon atoms, 0 to 10 ethylene oxide moieties and 0 to 1 glycerin moieties. Examples include: octadecylmethyl sulfoxide, 2-ketotridecylmethyl sulfoxide, 3,6,9-trioxyoctadecyl-2-hydroxyethyl sulfoxide, dodecylmethyl sulfoxide, oleyl-3-hydroxypropyl sulfoxide, tetradecylmethyl sulfoxide, 3-methoxytridecylmethyl sulfoxide, 3-hydroxytridecylmethyl sulfoxide, 3-hydroxy-4-dodecoxybutylmethyl sulfoxide.

Any amount of surfactant or mixture of surfactants that results in a skin cleansing effect can be used in the composition of the invention. Generally, at least about 1% by weight of the composition should be surfactant. Preferred minimum amounts of 3, 5, 7, 10, 20 and 30% by weight of surfactant(s) can be present in the composition. The maximum amounts of surfactant(s) depend on the physical nature of the composition used. Generally, no more than 95 to 97% by weight of surfactant(s) will be present, especially no more than about 90% by weight of surfactant(s). Maximum amounts of 20, 30, 40, 50, 60, 70, 80 or 85 wt% surfactant(s) can also easily be used.

The anionic surfactant may be present in various preferred amounts, in addition to those general amounts previously discussed for all surfactants, from 1 to 96%, especially 5 to 85%, by weight of the composition. With respect to liquid, preferably aqueous compositions, the anionic surfactant(s) is/are present in 2 to 20%, especially 5 to 15%, by weight of the composition. In a solid composition, the anionic surfactant(s) may be present in 5 to 90%, preferably 10 to 50%, by weight for a "syndet" bar, 55 to 80%, by weight for a "combar" and 70 to 90%, especially 75 to 85%, by weight in a solid composition in which there is only an anionic surfactant, such as soap.

Specifically, the antioxidant of the formula is one in which all of the "R" groups in each group a, b, and c are the same or different, and preferably the same, and most preferably all are tert-butyl. When all of the "R" groups are tert-butyl, the compound in group a is available from Ciba-Geigy as Irganox 1010. The CAS number is 6683-19-8 and its chemical name is tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane. In group b, when the "R" groups are each tert-butyl and n is 18, the compound is available from Ciba-Geigy as Irganox 1076. The CAS number is 2082-79-3 and its chemical name is octaclecyl(3,5-di-tert-butyl-4-hydroxyhydrocinnamate). In group c, when all "R" groups are tert-butyl, the compound is available from Ciba-Geigy as Irganox 3114. The CAS number is 2767-62-6 and its chemical name is tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate. The amount of antioxidant present in the composition(s) of the invention is an effective amount to impart color stability to the composition upon prolonged storage. The upper limit appears to depend primarily on the cost of the material. In solid compositions, generally 25 to 500 ppm of the composition may be used, preferably 50 to 300 ppm of the composition. In liquid compositions, generally 10 to 300 ppm of the antioxidant may be used, preferably 25 to 250 ppm of the composition.

The physical nature of the composition is not critical and it may be a solid, a liquid or a gel. The process for preparing such a composition is according to the usual procedures used in the surfactant industry. The antioxidant is added at the usual antioxidant addition point in the process.

Standard liquid and solid compositions are given below as illustrative examples of the composition(s).

Solid Soap bar formula Component wt.%

Mixture of sodium tallow, coconut, palm and palm kernel soaps 80-87

Water 8-10

Glycerine 0.5-1.5

Fragrance/colorant as required

Versenex 80-DTPA (40%) 0.2

Titanium dioxide 0.2

Citric acid (50%) 0.25

Sodium chloride 0.05-1.3

Antioxidant (Irganox 101 or Irganox 1076 or Irganox 3114) 0.0025-0.1

liquid Component wt.%

α-olefin sulfonate (40%) 10.0

Ammonium lauryl sulfate (28%) 25.0

Cocoamidopropylhydroxysultaine (50%) 3.5

Versene 100 (Dow) EDTA (39%) 0.2

Propylene glycol 1.0

Lauryldiethanolamide 0.5

Chloroxylenol 1.0

Citric acid as needed to pH 5.5 to 6.5

Fragrance, colorant(s), preservatives as required

Sodium chloride 0.05 to 0.50

Water 58.5

Antioxidant (Irganox 101 or Irganox 1076 or Irganox 3114) 0.001 to 0.05

The compounds of the invention are not limited to personal cleansing and care compositions. These compositions may also be useful in oral care compositions intended for cleaning teeth.

Organic surfactants are used in oral care compositions to achieve enhanced prophylactic action, to assist in achieving thorough and complete distribution of any active material such as anti-tartar agents in the oral cavity as well as to increase the cosmetic acceptance of the compositions. The organic surfactant material is preferably of anionic, non-ionic or ampholytic nature and it is preferred to use as surfactant material cleaning material which imparts cleaning and foaming properties to the composition. Suitable examples of anionic surfactants are water-soluble salts or monoglyceride monosulfates of higher fatty acids such as the sodium salt of the monosulfated monoglyceride of hydrogenated coconut oil fatty acids, higher alkyl sulfates such as Sodium lauryl sulfate, alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, higher alkyl sulfoacetates, higher fatty acid esters of 1,2-dihydroxypropanesulfonates, and the substantially saturated higher aliphatic acyl amides of lower aliphatic aminocarboxylic acid compounds such as those having 12 to 16 carbon atoms in the fatty acid, alkyl or acyl radicals, and the like. Examples of the latter amides are N-lauroylsarcosine and the sodium, potassium and ethanolamine salts of N-lauroyl, N-myristoyl or N-palmitoylsarcosine, which should be substantially free of soap or similar higher fatty acid material. The use of these sarcosinate compounds in certain oral care compositions is particularly advantageous because these materials exhibit a prolonged and pronounced effect of inhibiting acid formation in the oral cavity due to carbohydrate degradation, as well as resulting in some reduction in the solubility of tooth enamel in acid solutions.

Examples of water-soluble non-ionic surfactants are condensation products of ethylene oxide with various reactive hydrogen-containing compounds that are reactive with ethylene oxide and have long hydrophobic chains (e.g. aliphatic chains with 12 to 20 carbon atoms), where the condensation products ("ethoxamers") contain hydrophilic polyoxyethylene moieties, such as condensation products of poly(ethylene oxide) with fatty acids, fatty alcohols, fatty amides, polyhydric alcohols (e.g. sorbitan monostearate) and polypropylene oxide (e.g. Pluronic materials).

Generally, surfactants are present in the paste, gel or typical tooth cleaning composition at 1 to 15% by weight of the composition. The antioxidant of the present invention can also impart stabilizing properties to oral care compositions containing peroxide such as hydrogen peroxide or calcium peroxide and the like. The amount of antioxidant used is that amount sufficient to stabilize the composition, for example as a free radical scavenger. Exemplary of such antioxidant amounts are 50 to 5000 ppm, preferably 100 to 2000 ppm of the composition.

The following examples of the invention are intended to illustrate the scope of the invention and are not intended to be unnecessarily limiting.

The following test system was initially used to evaluate materials that might be stable in an oxidizing environment and might be suitable for the preservation of cleaning products, particularly soap-containing systems.

Test procedure:

An equal amount of the potential antioxidant Irganox 1010 and benzoyl peroxide (weight basis) to be evaluated were dissolved in an inert organic solvent such as chloroform to form a 1% solution (each). 10 mL of the solution was transferred to a round bottom flask and heated to boiling under a water-cooled condenser. The contents were refluxed for 15 hours. After removing the heat source and allowing it to cool to room temperature, the solution was visually inspected for discoloration. This system should induce yellowing and discoloration normally observed with cleaning systems containing BHT.

Test result:

The following materials evaluated showed varying degrees of color instability:

Irganox 1010, Irganox 1076 and Irganox 3114 were all more stable than Irganox 1330, which was more stable than Casamine OTB, which was more stable than BHT.

a. Irganox 1330 is 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

b. Casamine OTB is ortho-tolylbiguanide.

The BHT was bright yellow after the test period. The Irganox 1330 and Casamine OTB showed different colorations. Neither Irganox 1010 nor Irganox 1076 showed any discoloration after the test period. Irganox 3114 showed no significant discoloration after the test period.

A technique described below was used to evaluate the color stability of antioxidants in soap formulations.

Test procedure

250 ppm of each antioxidant, Irganox 1010 and benzoyl peroxide and 0.2% TiO2 were homogeneously ground into soap base. The homogeneous mixture was extruded through an extruder to produce an ingot which was then pressed into a box-shaped mold to yield 90 mg of bars. The test bars were flash aged in an oven maintained at 43ºC for 4 weeks and one bar was removed each week to evaluate the color change. The color change of the soap bars was measured with a reflectance type colorimeter using the C.I.E. LAB color space scale (L*a*b) where L* indicates the degree of lightness (white, black), a* is the red/green defining color space coordinate and b* is the yellow/blue defining color space coordinate. Freshly made bars were pre-measured to obtain the initial or standard value. Every seven days, the bars were read to determine the change in brightness and color. The DL*, Da* and Db* values are the color differences between the initial samples and the aged samples. The DE* value is a number calculated from the color difference equation that represents the total color difference (i.e., includes brightness and color). Both the Db* and DE* values were recorded to examine the color stability of a specific antioxidant in the soap bars. A positive Db* value indicates an increase in yellowing, or poor color stability of the antioxidant. A positive DE* value indicates an increase in the darkness and color of the soap. A more positive value for this measurement indicates a decrease in the antioxidant's oxidation resistance.

The color difference equation (DE*) is as follows:

DE* = (DL*2 + Db*2 + Da*2)1/2

Results:

Irganox 1010 compared with the control bar containing BHT showed the following trend:

DE*-value: Irganox 1010 < < < BHT

Db* value: Irganox 1010 < < < BHT

Irganox 1010 showed good color stability when exposed to strongly oxidizing environments.

Test procedure:

The stability of Irganox 1010 was investigated under hydrolysis conditions. When boiled as an ethanolic solution in the presence of strong inorganic base such as sodium hydroxide, Irganox 1010 can be easily hydrolyzed to the corresponding alcohol and carboxylic acid.

To evaluate the hydrolytic stability of Irganox 1010, three soap-based formulations were prepared.

(A) - Control: Soap shavings from typical kettle soap with 10 to 13% moisture and 0.02 to 0.10% free alkalinity as Na₂O.

(B) - Experiment 1 - Addition of 0.25% citric acid to the above soap shavings and mixing thoroughly by passing through a laboratory mill.

(C) - Experiment 2 - Addition of 7% fatty acid mixture, such as a 50:50 weight mixture of stearic acid and hydrogenated coconut fatty acids to the above soap chips and thorough mixing by passing through a laboratory mill.

Irganox 1010 was then intimately mixed with each batch of soap at a level of 200 ppm. The mixtures were passed through a laboratory mill several times to ensure homogeneity and were processed into thin ribbons. Each batch of soap ribbon was sealed in three separate glass jars and stored in an oven maintained at 43ºC for 4 weeks. Each week a 2 gram sample of each batch of soap was removed from the jars and analyzed for Irganox 1010 concentration using an HPLC method. Results: (Expressed in ppm Ireanox 1010)

The addition of free fatty acid increased the amount of easily oxidizable material in the system and was therefore an additional burden on the antioxidant. Depending on the amounts of free fatty acid used, the use of a slightly stronger acid such as citric acid is preferred when using free fatty acid.

Irganox 1010 is quite sensitive to the pH of soap and retains its structural integrity only in soaps that are substantially free of free alkali. A similar case arises with group b compounds. The excess alkali in soap formulations can be effectively neutralized by in situ "superfatting" with strong acids or with free fatty acids. Any amount of acid that results in at least substantial neutralization of the free alkali can be used. Effectively, amounts of free acid such as citric, acetic and tartaric acids as low as about 0.1% by weight can be used. The amount of free fatty acid can also vary considerably, although generally at least about 3 or 5% by weight of free fatty acid such as stearic, coco, myristic and the like is used, preferably in at least about 7% by weight of the composition. The final pH of the composition, measured as 1% by weight of solid composition in water, is generally from about 6.5 to about 10.3. A pH that is too acidic should also be avoided, as cleavage of the compound may also occur.

Claims (20)

1. A cleaning composition comprising a cleaning effective amount of a long-chain alkyl or alkenyl-containing surfactant, where long-chain is understood to mean at least 8 carbon atoms, or mixtures thereof and a color-stabilizing effective amount of a compound selected from the group consisting of in which R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ are the same or different and are isopropyl or tert-butyl, in which R�9 and R₁₀ are the same or different and are isopropyl or tert-butyl and n is 8 to 20, or in which R₁₁, R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆ are the same or different and are isopropyl or tert-butyl. 2. The composition of claim 1, wherein each R is the same in each group a, the same in each group b, and the same in each group c. 3. The composition of claim 2 wherein each R is tert-butyl . 4. The composition of claim 3, wherein the cleaning composition is a solid. 5. A composition according to claim 4, wherein the solid can be held in the hand. 6. A composition according to claim 5, wherein the solid is in a bar form. 7. The composition of claim 3, wherein the compound is present in the composition at about 25 to about 500 ppm of the composition. 8. A composition according to claim 6 or claim 7, wherein the compound is present in the composition at about 50 to 300 ppm. 9. A composition according to claim 3 or claim 6, wherein substantially all of the free alkali in the composition is neutralized. 10. A composition according to claim 3 or claim 6, wherein sufficiently strong acid, free fatty acid or mixtures thereof is present to substantially overcome the hydrolytic effects of free alkali on the compound. 11. The composition of claim 6, wherein the pH of the bar, as measured in a 1% solution in water, is 6.5 to 10.3. 12. A composition according to claim 6, wherein the surfactant is soap. 13. The composition of claim 12 wherein the compound is present in 25 to 500 ppm of the composition. 14. A composition according to claim 13, wherein sufficient acid is present to substantially neutralize any free alkali present. 15. A composition according to claim 14, wherein the pH of the solid, as measured in a 1% solution in water, is 6.5 to 10.3. 16. The composition of claim 3, wherein the cleaning composition is suitable for cleaning teeth. 17. A cleaning composition according to claim 1, which is suitable for cleaning the oral cavity. 18. A cleaning composition according to claim 17, which is suitable for cleaning teeth present in the oral cavity. 19. A composition according to claim 9, claim 10 or claim 14, wherein the compound in the composition is selected from group a or b. 20. Composition according to any one of claims 1 to 3, 5, 7, 9, 10 to 12 and 14, wherein the compound in the composition is selected from group a.