DE69031193T2 - Mild, liquid or gel detergent containing an alkyl ethoxy carboxylate as a surfactant - Google Patents

Abstract

A light-duty liquid or gel dishwashing detergent composition containing an alkyl ethoxy carboxylate surfactant and little or no alcohol ethoxylate and soap by-product contaminants. The compositions exhibit good grease removal while manifesting mildness to the skin. A preferred type of dishwashing detergent composition is in the liquid form. High pH and magnesium ion containing versions of the compositions increase grease removal properties while maintaining mildness.

Description

Technical area

The present invention relates to dishwashing with a mild, liquid or gel dishwashing detergent composition containing alkyl ethoxycarboxylate surfactants (alternatively labeled alkylpolyethoxycarboxymethylates, alkylpolyethoxyacetates, alkylpolyethercarboxylates, etc.) of the type described in U.S. Patent Nos. 2,183,853; 2,653,972; 3,003,954; 3,038,862; 3,741,911; and 3,941,710; British Patent Nos. 456,517 and 1,169,496; Canadian Patent No. 912,395; French Patent Nos. 2,014,084 and 2,042,793; Dutch Patent Application Nos. 7,201,735-Q and 7,406,336; and Japanese Patent Application Nos. 96,579/71 and 99,331/71 disclosed.

Background of the field

There has been a significant demand for mild liquid or gel dishwashing detergent compositions capable of providing good grease removal. These compositions are well known in the art and are described, for example, in U.S. Patent Nos. 4,316,824 (Panchen), 4,681,704 (Bemardino et al.), 4,133,779 (Hellyer et al.), and 4,615,819 (Leng et al.). Although they are good grease and dirt removers, these compositions can be aggressive to the skin under certain conditions, particularly when used during the dry winter months.

Likewise, the art offers a wide variety of detergent compositions that are gentle to the skin. These mild compositions often contain sulfates of highly ethoxylated alcohols. See, for example, U.S. Patent No. 3,743,233 to Rose and Thiele. Betaines have also been suggested for use in improving the mildness of a liquid dishwashing composition. See, for example, U.S. Patent No. 4,555,360 (Bissett et al.). Alkyl ethoxycarboxylates are also known as mild surfactants for use in liquid detergent compositions. See Japanese Patent Applications 48-60706 and 48-64102. However, these alkyl ethoxycarboxylate surfactants have been reported to be inadequate in grease removal ability and to require the use of other surfactants to achieve the desired cleaning ability.

Seldom have these two important characteristics of mildness and grease removal ability been combined in one product. It has been generally believed that one must be sacrificed for the benefit of the other. An object of this invention is therefore to provide a detergent composition which exhibits good grease removal while being gentle to the skin.

Summary of the invention

The present invention relates to a method for dishwashing with a mild, liquid or gelatinous, preferably liquid dishwashing detergent composition which comprises about 5 to 70% of a surfactant mixture comprising:

(a) about 80 to 100% alkyl ethoxycarboxylates of the formula:

RO(CH2CH2O)xCH2COO-M+

wherein R is a C12-C16 alkyl group, x ranges from 0 to about 10, and the ethoxylate distribution is such that on a weight basis the amount of material where x is 0 is less than about 20% and the amount of material where x is greater than 7 is less than about 25%, with an average of x being about 2 to 4 when R is on average C13 or less and an average of x being about 3 to 6 when R is on average greater than C13, and M is a cation;

(b) 0 to about 10% alcohol ethoxylates of the formula:

RO(CH2CH2O)xH

wherein R is a C₁₂-C₁₆ alkyl group and x ranges from 0 to about 10, and x is on average less than about 6; and

(c) 0 to about 10% soaps of the formula:

RCOO⊃min;M⊃plus;

wherein R is a C₁₁-C₁₅ alkyl group and M is a cation;

wherein a 10 wt.% aqueous solution of the composition has a pH of about 7 to 11.

Detailed description of the invention

The mild liquid or gel, preferably liquid, dishwashing detergent compositions used in the process of the present invention contain a surfactant mixture comprising a significant amount of an alkyl ethoxycarboxylate surfactant and low or no alcohol ethoxylate and soap by-product impurities. These and other supplemental, optional ingredients commonly present in liquid or gel dishwashing compositions are set forth below.

Surfactant mixture containing alkyl ethoxycarboxylate

The liquid compositions used in the process of the invention contain about 5 to 50% by weight, preferably about 10 to 40%, and more preferably about 12 to 30% of a surfactant mixture having limited amounts of impurities. Gel compositions contain about 20 to about 70%, preferably about 25 to about 45%, and more preferably about 28 to about 35% of the surfactant mixture.

The surfactant mixture contains about 80 to 100%, preferably about 85 to 95% and more preferably about 90 to 95% alkyl ethoxycarboxylates of the general formula RO(CH2CH2O)xCH2COO-M+, wherein R is a C₁₂-C₁₆ alkyl group, x ranges from 0 to about 10, and the ethoxylate distribution is such that on a weight basis the amount of material wherein x is 0 is less than about 20%, preferably less than about 15%, and more preferably less than about 10%, and the amount of material wherein x is greater than 7 is less than about 25%, preferably less than about 15%, and more preferably less than about 10%, where x is on average about 2 to 4 when R is on average C₁₃ or less, and x is on average about 3 to 6, when R is on average greater than C₁₃, and M is a cation which is preferably selected from alkali metal, alkaline earth metal, ammonium, mono-, di- and triethanolammonium, and most preferably from sodium, potassium, ammonium and mixtures thereof with magnesium ions. The preferred alkyl ethoxycarboxylates are those wherein R is a C₁₂-C₁₄ alkyl group.

Suitable alcohol precursors of the alkyl ethoxycarboxylates are primary aliphatic alcohols having from about 12 to about 16 carbon atoms. Other suitable primary aliphatic alcohols are the linear primary alcohols obtained from the hydrogenation of vegetable or animal fatty acids, such as coconut, palm kernel and tallow fatty acids, or by ethylene enrichment reactions and subsequent hydrolysis, such as in Ziegler-type processes. Preferred alcohols are n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl and n-hexadecyl. Other suitable alcohol precursors include primary alcohols having a branching portion at the β or 2 carbon atoms, with the alkyl branch containing 1 to 4 carbon atoms. In such alcohols, at least 30% of the alcohol of any specific chain length is preferably linear and the branching preferably comprises about 50% methyl groups with minor amounts of ethyl, propyl and butyl groups. These alcohols are conveniently prepared by reacting linear olefins of about 11 to 17 carbon atoms with carbon monoxide and hydrogen. Both linear and branched alcohols are produced by these processes and the mixtures can either be used as such or can be separated into individual components and then recombined to obtain the desired mixture.

Common processes for preparing "oxo" halides which are then used to prepare alcohols are disclosed in U.S. Patent Nos. 2,564,456 and 2,587,858, and the direct hydroformylation of olefins to prepare alcohols is disclosed in U.S. Patent Nos. 2,504,682 and 1,581,988. All of these patents are incorporated herein by reference.

The corresponding secondary alcohols can also be used. It is obvious that using a single chain length olefin as starting material will result in a corresponding single chain length alcohol, but it is generally more economical to use mixtures of olefins with a range of carbon chain lengths around the desired mean. This will of course give a mixture of alcohols with the same distribution of chain lengths around the mean.

Primary aliphatic alcohols derived from vegetable oils and fats and from other petroleum starting materials and having alkyl or alkylene groups as part of their structure also contain a range of chain lengths. Since the range of chain lengths includes lengths from C8 to C20 and beyond, it is therefore a normal procedure to separate the product from such starting materials into various chain length ranges which are selected with reference to their intended use.

The desired average ethoxy chain length of the alcohol ethoxylate can be obtained using a catalyzed ethoxylation process, wherein the molar amount of ethylene oxide reacted with each equivalent of fatty alcohol corresponds to the average number of ethoxy groups of the alcohol being ethoxylated. It is known that the addition of ethylene oxide to alkanols is promoted by a catalyst, usually a catalyst having either a strongly acidic or strongly basic character. Suitable basic catalysts are the basic salts of the alkali metals of Group I of the Periodic Table, e.g. sodium, potassium, rubidium and cesium, and the basic salts of certain alkaline earth metals of Group II of the Periodic Table, e.g. calcium, strontium, barium and in some cases magnesium. Suitable acid catalysts generally include the Lewis acid of Friedel-Crafts catalysts. Specific examples of these catalysts are the fluorides, chlorides and bromides of boron, antimony, tungsten, iron, nickel, zinc, tin, aluminium, titanium and molybdenum. The use of complexes of such halides with, for example, alcohols, ethers, carboxylic acids and amines has also been reported. Other examples of known acidic alkoxylation catalysts are sulphuric and phosphoric acids; perchloric acid and the perchlorates of magnesium, calcium, manganese, nickel and zinc; metal oxalates, sulphates, phosphates, carboxylates and acetates; alkali metal fluoroborates, zinc titanate; and metal salts of benzenesulphonic acid. The type of catalyst used determines the distribution range of the ethoxy groups. Stronger catalysts give a very narrow or narrow distribution of ethoxy groups around the mean value. Weaker catalysts result in a broader distribution.

The surfactant mixture used in the compositions in the process of the invention may also contain from 0 to about 10%, preferably less than about 8%, and more preferably less than about 5%, of alcohol ethoxylates of the formula RO(CH2-CH2O)xH, where R is a C12-C16 alkyl group and x ranges from 0 to about 10 and x is on average less than 6. The surfactant mixture may also contain from up to about 10%, preferably less than about 8%, and more preferably less than about 5%, of soaps of the formula RCOO-M+, where R is a C11-C15 alkyl group and M is a cation as described above.

The noncarboxylated alcohol ethoxylates set forth above have disadvantages with respect to the alkyl ethoxycarboxylate surfactant mixture, particularly with respect to the performance benefits provided thereby. Therefore, it is important that the alkyl ethoxycarboxylate-containing surfactant mixture used in the process of the present invention contain less than about 10% by weight of the alcohol ethoxylates from which they are derived. Although commercially available alkyl ethoxycarboxylates contain 10% or more alcohol ethoxylates, there are known methods to obtain the preferred alkyl ethoxycarboxylates in high purity. For example, unreacted alcohol ethoxylates can be removed by steam distillation, see U.S. Patent No. 4,098,818 (Example 1), or by recrystallization of the alkyl ethoxycarboxylate, see British Patent No. 1,027,481 (Example 1). Other methods for preparing the desired carboxylates include reacting sodium hydroxide or sodium metal and monochloroacetic acid or its salt with alcohol ethoxylates at specific combinations of pressure and temperature as described in U.S. Patent Nos. 3,992,443 and 4,098,818; and in Japanese Patent Application No. 50-24215, all of which are incorporated herein by reference.

Alternatively, a perturbed base such as potassium tert-butoxide can be substituted for the sodium hydroxide in the above-cited patents, thus obtaining alkyl ethoxycarboxylates of high purity with less stringent temperature and pressure requirements. In particular, a perturbed base of the formula RO⊃min;M⊃plus is used, which generally consists of an alkyl group, a reactive oxygen center and a cation. The structure of this perturbed base is secondary or tertiary and contains a non-linear alkyl group with at least one branching point within 3 carbon atoms of the reactive center, the oxygen atom and an alkali metal or alkaline earth metal cation. The process comprises reacting the alcohol ethoxylates with the perturbed base described above and either anhydrous chloroacetic acid in a molar ratio of the perturbed base to the anhydrous chloroacetic acid of 2:1 or an alkali metal salt or alkaline earth metal salt of the anhydrous chloroacetic acid in a molar ratio of the perturbed base to the alkali metal salt or alkaline earth metal salt. of chloroacetic acid of 1:1, wherein the molar ratio of the ethoxylated fatty alcohol to the anhydrous chloroacetic acid or alkali metal or alkaline earth metal salt thereof is about 1:0.7 to about 1:1.25, the temperature is about 20 to 140°C, and the pressure is about 1 to 760 mm Hg.

Other methods for preparing high purity alkyl ethoxycarboxylates include reacting an alcohol ethoxylate with oxygen in the presence of platinum, palladium or other precious metals as disclosed in U.S. Patent No. 4,223,460 (Example 1-7); U.S. Patent No. 4,214,101 (Example 1); U.S. Patent No. 4,348,509; German Patent No. 3,446,561; and Japanese Patent Application No. 62,198,641. One of the byproducts of such reactions is soap, the amount of which should be limited as described above to avoid adversely affecting the cleaning and mildness benefits provided by the present compositions. This can be achieved by using an alcohol ethoxylate starting material which contains small amounts of non-ethoxylated fatty alcohol and by choosing catalysts which preferentially oxidize the terminal methylene in the alcohol ethoxylate in at least 90% of cases, preferably about 95% of cases. Oxidation of the non-terminal methylene groups in the alcohol ethoxylate produces a soap from ethoxylated fatty alcohol components.

The compositions used in the process of the invention have a pH of about 7 to 11, which is preferably determined as the pH of a 10% by weight aqueous solution using a pH meter. The preferred detergent compositions have a pH of about 8 to 10.5, and most preferably about 8.5 to 10. Typically, liquid dishwashing compositions have a pH of about 7. For the detergent compositions used in the process of the invention, it has been found that a more alkaline pH of about 9 greatly improves the cleaning performance compared to a product having a pH of 7. This cleaning benefit appears to be unique to compositions containing the present alkyl ethoxycarboxylates. Surprisingly, the compositions of the invention are also gentler to the hands at this alkaline pH than at a pH of 7.

If a composition having a pH greater than 7 is to be particularly effective in improving performance, it should contain a buffering agent capable of maintaining the alkaline pH in the composition and in dilute solutions, i.e., about 0.1 to 0.2% by weight of an aqueous solution of the composition. The pKa of this buffering agent should be about 0.5 to 1.0 pH units below the desired pH of the composition (determined as described above).

The dishwashing compositions used in the process of the invention are subjected to acid stress caused by food soils when used, i.e., diluted and applied to soiled dishes. To maintain the performance benefits of the compositions in use, a buffering agent having a pKa of about 0.5 to 1.0 pH units below the desired pH of the composition should be present. Under these conditions, the buffering agent is particularly effective in regulating pH as long as the minimum amount thereof is used.

The buffering agent may itself be an active cleaning agent or it may be a low molecular weight organic or inorganic material used in the composition solely to maintain an alkaline pH. Preferred buffering agents for the compositions used in the process of the invention are nitrogen-containing materials. Some examples are glycine or other amino acids or lower alcohol amines such as mono-, di- and triethanolamine. Other preferred nitrogen-containing buffering agents are 2-amino-2-ethyl-1,3-propanediol, tris-(hydroxymethyl)-aminomethane and disodium glutamate. Boric acid is also preferred. These buffering agents are usually present in an amount of about 0.1 to 10% by weight, preferably about 1 to 7% and most preferably about 1.5 to 5%.

The cations for the present alkyl ethoxycarboxylates can be alkali metals, alkaline earth metals, ammonium and lower alkanolammonium ions. The cation source for the alkyl ethoxycarboxylates results from the neutralization of the alkyl ethoxycarboxylic acid and additional components, e.g. performance-enhancing salts containing a divalent ion.

Preferred cations for the compositions used in the process of the invention are ammonium, sodium and potassium. For compositions having a pH between about 7 and 8, ammonium is particularly preferred, but at pH values above about 8 it is undesirable due to the release of small amounts of ammonia gas resulting from the deprotonation of the ammonium ions in the composition.

For liquid compositions, potassium is preferred over sodium because it makes the compositions more resistant to precipitate formation at low temperatures and provides improved solubility to the composition. On the other hand, for gel compositions, sodium is preferred over potassium because it makes gelling of a composition easier. Mixtures of the cations may be present in any of the compositions.

It has also been found that the presence of divalent cations greatly improves the cleaning power of the alkyl ethoxycarboxylates present against fatty soils. This is particularly true when the compositions are used in softened Water containing few divalent ions may be used. Liquid dishwashing compositions containing alkyl ethoxycarboxylates not meeting the narrow definition of this invention benefit little from the addition of divalent ions, in fact in many cases they exhibit reduced cleaning performance upon the addition of divalent cations. Divalent ions are believed to increase the density of the alkyl ethoxycarboxylates present at the oil/water interface, thereby reducing interfacial tension and improving grease cleaning.

Preferably, the divalent ions are added as a chloride or sulfate salt to compositions containing an alkali metal or ammonium salt of the alkyl ethoxycarboxylate, and most preferably the sodium salt, after the composition has been neutralized with a strong base. The proportion of the divalent ion in the composition is from 0 to about 1.5% by weight, preferably from about 0.2 to 1% by weight, and most preferably from about 0.3 to 0.8% by weight. Particularly preferred divalent ions are magnesium ions.

If both divalent ions and an alkaline pH are combined with the surfactant mixture, a grease cleaning superior to that obtained by either an alkaline pH or divalent ions alone is achieved. Preferably, the divalent ion is magnesium, which is present in the composition in an amount of about 0.1 to 1 wt.%, and more preferably about 0.3 to 0.8 wt.%, while the pH is preferably about 8 to 9.5, and most preferably about 8.5 to 9.5. Compositions containing larger amounts of magnesium and having a pH much above about 9.5 are not preferred because of the tendency to form precipitates.

The amount of magnesium ions present depends on the total amount of anionic surfactant present therein, including the amount of alkyl ethoxycarboxylates. If magnesium ions are present in the compositions, the molar ratio of magnesium ions to total anionic surfactant is from about 0.25:1 to about 0.5:1.

Co-surfactants

The compositions used in the process of the invention contain certain co-surfactants to enhance foaming ability, cleaning action and/or mildness.

Included in this category are several anionic surfactants that are commonly used in liquid or gel dishwashing detergents. The cations associated with these anionic surfactants may be the same as the cations previously described for the alkyl ethoxycarboxylates. Examples of anionic co-surfactants useful in the present invention include the following classes:

(1) Alkylbenzenesulfonates, wherein the alkyl group contains 9 to 15 carbon atoms, preferably 11 to 14 carbon atoms, in a straight or branched chain configuration. A particularly preferred linear alkylbenzenesulfonate contains about 12 carbon atoms. U.S. Patent Nos. 2,220,099 and 2,477,383 describe these surfactants in detail.

(2) Alkyl sulfates obtained by the sulfatization of an alcohol having 8 to 22 carbon atoms, preferably 12 to 16 carbon atoms. The alkyl sulfates have the formula ROSO₃⁻M⁺, in which R is a C₈₋₂₂ alkyl group and M is a mono- and/or divalent cation.

(3) Paraffin sulfonates containing 8 to 22 carbon atoms, preferably 12 to 16 carbon atoms, in the alkyl moiety. These surfactants are commercially available as Hostapur SAS from Hoechst Celanese.

(4) Olefin sulfonates having 8 to 22 carbon atoms and preferably 12 to 16 carbon atoms. US Patent No. 3,332,880 contains a description of suitable olefin sulfonates.

(5) Alkyl ether sulfonates derived from the ethoxylation of an alcohol having 8 to 22 carbon atoms, preferably 12 to 16 carbon atoms, with less than 30 moles, preferably less than 12 moles, of ethylene oxide. The alkyl ether sulfates have the formula:

RO(C2H4O)xSO3-M+

wherein R is a C8-C22 alkyl group, x is 1 to 30 and M is a mono- or divalent cation.

(6) Alkyl glyceryl ether sulfonates having 8 to 22 carbon atoms, preferably 12 to 16 carbon atoms, in the alkyl moiety.

(7) Dialkyl sulfosuccinates of the formula:

wherein each R₁ and R₂, which may be the same or different, represents a straight or branched chain alkyl group having from about 4 to 10 carbon atoms, and more preferably from about 6 to 8 carbon atoms, and M+ represents a mono- or divalent cation. A more detailed description of suitable dialkyl sulfosuccinates can be found in GB-2,105,325 and GB-2,104,913.

(8) Fatty acid ester sulfonates of the formula:

R₁-CH(SO₃⊃min;M⁺)CO₂R₂

wherein R₁ is a straight chain or branched alkyl having about 8 to 18, preferably 12 to 16 carbon atoms and R₂ is a straight chain or branched alkyl having about 1 to 6 carbon atoms and preferably mainly 1 carbon atom, and M represents a mono- or divalent cation.

(9) Mixtures thereof.

The anionic surfactants described above are all commercially available. It should be noted that, although both dialkyl sulfosuccinates and fatty acid ester sulfonates are effective at a neutral to slightly alkaline pH, they are not chemically stable in a composition having a pH much greater than about 8.5.

Other useful cosurfactants for use in the compositions are the nonionic fatty acid alkyl polyglucosides. These surfactants contain straight chain or branched C8 -C15, preferably about C12 -C14 alkyl groups and have an average of about 1 to 5 glucose units, with an average of 1 to 2 glucose units being preferred. U.S. Patent Nos. 4,393,203 and 4,732,704, which are incorporated by reference, describe these surfactants.

The co-surfactants for the compositions may also contain mixtures of anionic surfactants with alkyl polyglucosides. The co-surfactants are present in the composition in an amount of from 0 to about 35% by weight, preferably from about 5 to 25% by weight, and most preferably from about 7 to 20% by weight.

Foam improver

Another component that may be included in the composition is a foam stabilizing surfactant (foam improver) in an amount of less than about 15%, preferably about 0.5 to 12%, and more preferably about 1 to 10%. Optional foam stabilizing surfactants useful in the present composition include five basic types: betaines, ethylene oxide condensates, phenolic acid amides, semipolar nonionic amine oxides, and cationic surfactants.

The composition may contain betaine detergent surfactants of the general formula:

wherein R is a hydrophobic group selected from the group consisting of alkyl groups having about 10 to about 22 carbon atoms, preferably about 12 to about 18 carbon atoms, alkylaryl and arylalkyl groups having a corresponding number of carbon atoms, where a benzene ring corresponds to about 2 carbon atoms, and similar structures interrupted by amido or ether bonds;

each R¹ is an alkyl group having 1 to about 3 carbon atoms; and R² is an alkylene group having 1 to about 6 carbon atoms.

Examples of preferred betaines are dodecyldimethylbetaine, cetyldimethylbetaine, dodecylamidopropyldimethylbetaine, tetradecyldimethylbetaine, tetradecylamidopropyldimethylbetaine and dodecyldimethylammoniumhexanoate.

Other suitable amidoalkyl betaines are disclosed in U.S. Patent Nos. 3,950,417; 4,137,191; and 4,375,421; and British Patent GB-2,103,236, all of which are incorporated herein by reference.

It is known that the alkyl (and acyl) groups for the above betaine surfactants can be derived from either natural or synthetic sources, e.g., they can be derived from naturally occurring fatty acids; olefins such as those produced by the Ziegler or oxo synthesis processes; or from olefins separated from petroleum either with or without a cracking process.

The ethylene oxide condensates are generally defined as compounds prepared by the condensation of ethylene oxide groups (hydrophilic) with an organic hydrophobic compound, which may be aliphatic or alkyl aromatic. The length of the hydrophilic group or the polyoxyalkylene group condensed with any single hydrophobic group can be easily adjusted to obtain a water-soluble compound with the desired balance between hydrophilic and hydrophobic elements.

Examples of such ethylene oxide condensates suitable as foam stabilizers are the condensation products of aliphatic alcohols with ethylene oxide. The alkyl chain of the aliphatic alcohol can be either straight or branched and generally contains from about 8 to about 18, preferably from about 8 to about 14, carbon atoms for best performance as foam stabilizers, with the ethylene oxide being present in amounts of from about 8 to about 30 moles, preferably from about 8 to about 14 moles, of ethylene oxide per mole of alcohol.

Examples of amide surfactants useful herein include the ammonia, monoethanol and diethanol amides of fatty acids having an acyl moiety of about 8 to about 18 carbon atoms represented by the general formula:

R1-CO-N(H)m-1(R2OH)3-m

wherein R is a saturated or unsaturated aliphatic hydrocarbon radical having about 7 to 21, preferably about 11 to 17 carbon atoms; R₂ represents a methylene or ethylene group; and m is 1, 2 or 3 and preferably 1. Specific examples of the amides are monoethanol coconut fatty acid amide and diethanolamine dodecyl fatty acid amide. These acyl units can be derived from naturally occurring glycerides, e.g. coconut oil, palm oil, soybean oil and tallow, but they can also be derived synthetically, e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process. The monoethanolamides and diethanolamides of C₁₂₋₁₄ fatty acids are preferred.

Semipolar nonionic amine oxide surfactants include compounds and mixtures of compounds of the formula:

wherein R₁ is an alkyl, 2-hydroxyalkyl, 3-hydroxyalkyl or a 3-alkoxy-2-hydroxypropyl radical, the alkyl or alkoxy radical containing about 8 to about 18 carbon atoms, R₂ and R₃ are each methyl, ethyl, propyl, isopropyl, 2-hydroxyethyl, 2-hydroxypropyl or 3-hydroxypropyl, and n is 0 to about 10. Particularly preferred are amine oxides of the formula:

wherein R1 is C12-16 alkyl and R2 and R3 are methyl or ethyl. The above ethylene oxide condensates, amides and amine oxides are described in more detail in U.S. Patent No. 4,316,824 (Panchen), which is incorporated herein by reference.

The composition may also contain certain cationic, quaternary ammonium surfactants of the formula:

[R1(OR2)y][R3(OR2)y]2R4N+X-

or amine surfactants of the formula:

[R19OR2)y][R3(OR2)y]R4N

wherein R¹ is an alkyl or alkylbenzyl group having from about 6 to about 16 carbon atoms in the alkyl chain; each R² is selected from the group consisting of -CH₂CH₂-, -CH₂CH(CH₃)-, -CH₂- CH(CH₂OH)-, -CH₂CH₂CH₂-, and mixtures thereof; each R is selected from the group consisting of C₁-C₄ alkyl, C₁-C₄ hydroxyalkyl, benzyl and hydrogen when y is not 0; R⁴ has the same meaning as R³ or is an alkyl chain, the total number of carbon atoms of R¹ plus R⁴ being from about 8 to about 16; each y is 0 to about 10 and the sum of the y values is 0 to about 15; and X is any compatible anion.

Of the foregoing, the alkyl quaternary ammonium surfactants are preferred, particularly the single long chain alkyl surfactants described in the above formula when R4 is selected from the same groups as R3. The most preferred quaternary ammonium surfactants are the chloride, bromide and methyl sulfate C8-16 alkyltrimethylammonium salts, C8-16 alkyldi(hydroxyethyl)methylammonium salts, C8-16 alkylhydroxyethyldimethylammonium salts, C8-16 alkyloxypropyltrimethylammonium salts and the C8-16 alkyloxypropyldihydroxyethylmethylammonium salts. Of the foregoing, the -C₁₀₋₁₄alkyltrimethylammonium salts are preferred, e.g., decyltrimethylammonium methylsulfate, lauryltrimethylammonium chloride, myristyltrimethylammonium bromide, and coconut trimethylammonium chloride and methylsulfate.

The foam improvers used in the compositions may contain any or a mixture of the foam improvers listed above.

Other optional components

In addition to the ingredients described above, the compositions may comprise other conventional ingredients suitable for use in liquid or gel dishwashing compositions.

Optional ingredients include drainage-promoting ethoxylated nonionic surfactants of the type disclosed in U.S. Patent 4,316,824 to Pancheri (February 23, 1982), incorporated herein by reference.

Others include detergent builders, either of the organic or inorganic type. Examples of water-soluble inorganic builders, which may be used alone or in admixture with themselves or with organic alkaline sequestrant builder salts, are alkali metal carbonates, phosphates, polyphosphates and silicates. Specific examples of such salts are sodium tripolyphosphate, sodium carbonate, potassium carbonate, sodium pyrophosphate, potassium pyrophosphate, potassium tripolyphosphate and sodium hexametaphosphate. Examples of organic builder salts which may be used alone or in admixture with any other or with the foregoing inorganic alkaline builder salts are alkali metal polycarboxylates, e.g., water-soluble citrates such as sodium and potassium citrate, sodium and potassium tartrate, sodium and potassium ethylenediaminetetraacetate, sodium and potassium N-(2-hydroxyethyl)ethylenediaminetriacetates, sodium and potassium nitrilotriacetates (NTA), sodium and potassium N-(2-hydroxyethyl)nitrilodiacetates, sodium and potassium oxydiscuccinates, and sodium and potassium tartrate mono- and disuccinates as described in U.S. Patent No. 4,663,071 (Bush et al., issued May 5, 1987), which is incorporated herein by reference. Other organic detergent builders such as water-soluble phosphates may find use in the compositions of the invention. In general, however, detergent builders in dishwashing detergent compositions have limited effect and their use in amounts above about 10% may limit formulation flexibility. with regard to the present liquid or gel compositions due to considerations regarding solubility and phase stability.

Alcohols such as ethyl alcohol and propylene glycol and hydrotropes such as sodium and potassium toluene sulfonate, sodium and potassium xylene sulfonate, trisodium sulfosuccinate and related compounds (as disclosed in U.S. Patent No. 3,915,903, which is incorporated herein by reference) and urea may be used in the interest of achieving a desired product phase stability and viscosity. Alcohols such as ethyl alcohol and propylene glycol in an amount of 0 to about 15%, potassium or sodium toluene, xylene or cumene sulfonate in an amount of 0 to about 10%, urea in an amount of 0 to about 10% and trisodium sulfosuccinate in an amount of 0 to about 15% are particularly useful in liquid compositions.

Gel compositions usually do not contain alcohols. These gel compositions may contain larger amounts of potassium or sodium toluene, xylene or cumene sulfonate and urea in larger amounts, i.e. about 10 to about 30%, as gelling agents (see US Patent No. 4,615,819 and GB-2,179,054A).

Other desirable ingredients include diluents and solvents. The diluents can be inorganic salts such as sodium sulfate, ammonium chloride, sodium chloride, sodium bicarbonate, etc., and the solvents include water, low molecular weight alcohols such as ethyl alcohol, isopropyl alcohol, etc. The present compositions typically contain up to about 80%, preferably about 30 to about 70%, and most preferably about 40 to about 65% water.

Unless otherwise stated, all percentages, parts and ratios are by weight.

The following examples illustrate the invention and facilitate its understanding.

Example I

The following three liquid compositions useful for use in the method of the invention are prepared according to the descriptions given below.

Formulation A is prepared by adding ethanol, sodium chloride and sodium xylene sulfonate to the surfactant mixture containing alkyl ethoxycarboxylate. The remaining surfactants are then added and mixed in. Then glycine is added and the pH is adjusted to about 10 with sodium hydroxide. Finally the magnesium chloride is added which reduces the pH to about 9.5. At this point final adjustments of viscosity and pH can be made followed by the addition of the fragrance and colorant. The remainder is water.

Formulation B is prepared by adding ethanol, sodium chloride and sodium xylene sulfonate to the sodium alkyl ethoxycarboxylate. The remaining formula ingredients are added in the order given in the table.

Formulation C is prepared by adding ethanol, sodium chloride and sodium xylene sulfonate to the sodium salt of the alkyl ethoxycarboxylate. The alkyl glucoside is mixed in and the temperature of the mixture is raised to about 40ºC. The coconut monoethanolamide is heated to about 65ºC and mixed in. Minor adjustments of pH and viscosity are made at this time, followed by the addition of the colorant and fragrance and water to bring the formulation to 100% volume.

*: The surfactant mixture containing sodium alkyl ethoxycarboxylate and alkyl ethoxy alcohol is prepared according to the procedure described below:

1. A C12-13 alkyl ethoxy (avg. 3.0) alcohol is reacted with potassium t-butoxide and sodium chloroacetate in a ratio of 1:1.1:1.1 by first mixing the alkyl ethoxylate with the potassium t-butoxide at about 60°C and a pressure of about 2666.4 Pa (20 mm Hg) for about 1 hour. Then t-butanol is continuously removed from the reaction mixture by distillation. Then the vacuum is released and sodium chloroacetate is added with mixing. The pressure is re-established at about 2400.0-2666.4 Pa (18-20 mm Hg) and the reaction is allowed to continue for about 3 hours. Then the reaction pressure is brought to atmospheric level with nitrogen and the steam heating coils are turned off. The reaction mixture is allowed to stand in this state overnight. The next day, the temperature of the reaction mixture is increased and the pressure reduced to remove more t-butanol from the system. The reaction mixture is then added to an aqueous solution of hydrochloric acid containing 105% of the theoretical amount required to neutralize the initially added t-butoxide. The acidic, aqueous reaction product is heated to accelerate phase separation of the organic and aqueous materials. The organic phase is recovered.

2. Step 1 above is performed using a C12-13 alkyl ethoxy (avg. 2.7) alcohol and a ratio of this ethoxy alcohol to potassium t-butoxide and sodium chloroacetate of 1:1.3:1.3. The potassium t-butoxide is added to the alkyl ethoxylate which is at a temperature of about 32.2°C and the temperature of the reaction mixture is then raised to about 76.7°C. The vacuum pump is then turned on to achieve reduced pressure. The reaction temperature is raised to about 104.4°C and the t-butanol is stripped and collected over a period of 30 minutes. The sodium chloroacetate is then added to the reaction mixture which has been slightly cooled to about 66°C. The reaction mixture is mixed for about 1.5 hours, cooled and added to an aqueous solution containing a sufficient amount of hydrochloric acid to achieve a pH of 3.4. Water is added to increase the volume of the reaction mixture to about 50% and the mixture is then heated to about 49°C. The upper organic layer is recovered and the washing process repeated.

3. The surfactant mixtures prepared in steps 1 and 2 above are mixed in a ratio of 40.4 to 59.6, respectively. A major portion of this combined surfactant mixture is neutralized with 50% sodium hydroxide to a pH of about 8 and diluted to about 50% with a 25/75 mixture by volume of water and ethanol. The resulting solution is continuously extracted with hexanes at room temperature for about 4 days. The The lower aqueous phase is recovered and traces of ethanol and water are removed by heating to obtain a paste containing the alkyl ethoxycarboxylate-containing surfactant mixture described below.

According to the foregoing, the surfactant portion of the foregoing mixture contains about 93.9% alkyl ethoxycarboxylates of the formula RO(CH2CH2O)xCH2COO-Na+, wherein R is a C12-13, on average a C12,5 alkyl; x ranges from 0 to about 10, and the ethoxylate distribution is such that the amount of material in which x is 0 is about 2.8% and the amount of material in which x is greater than 7 is less than about 2%, based on the weight of the alkyl ethoxycarboxylates. On average, x has a distribution of 2.8. The surfactant blend also contains about 6.1% alcohol ethoxylates of the formula RO(CH2CH2O)xH, where R is C12-13, on average C12,5 alkyl, and x is on average 2.8. The surfactant blend contains 0% soap materials.

The above formulations provide an excellent combination of grease cleaning and mildness benefits. Using the alkyl ethoxycarboxylate containing surfactant blend as a modular component, a range of good grease cleaning is achieved, the order being Formulation A > Formulation B > Formulation C. These same formulations provide a range of mildness benefits, the order being Formulation C > Formulation B > Formulation A.

Example II

The liquid formulations in Example 1 can also be successfully prepared by replacing the alkyl ethoxycarboxylate-containing surfactant mixture with a surfactant mixture (described below) prepared by an oxidation process wherein alcohol ethoxylates are reacted with oxygen in the presence of a noble metal catalyst, as generally disclosed in U.S. Patent Nos. 4,223,460; 4,214,101; and 4,348,509; and German Patent No. 3,446,561; and Japanese Patent Application No. 62,198,641. The surfactant mixture comprises 92.4% alkyl ethoxycarboxylates of the formula RO(CH2CH2O)xCH2COO-Na+, wherein R is C12-14, on average C12,7 alkyl, and wherein x ranges from 0 to about 12. According to the ethoxylate distribution, the weight percent of component x = 0 is about 10% and the amount of materials wherein x is greater than 7 is less than about 3% by weight. On average, x has a distribution of 2.5. The surfactant mixture also contains about 6.4% alcohol ethoxylates of the formula RO(CH2CH2O)xH, wherein R is C12-14, on average C12,7 alkyl, and x averages about 3.7. In addition, the surfactant mixture contains about 1.2% by weight of soaps of the formula RCOO-Na+, where R is C₁₁₋₁₃, on average C₁₁,₇ alkyl. This formulation would contain 15% by weight of the alkyl ethoxycarboxylates, 1.04% by weight of alcohol ethoxylates and 0.20% by weight of soaps. The other components in the formulations are identical. Minor modifications to the amounts of ethanol and sodium xylene sulfonate may be made. to adjust the viscosity and stability of the preparation to match the preparations of Example I.

These preparations provide approximately the same grease cleaning and mildness benefits as observed in Example I.

Example III

The following liquid preparation containing the surfactant mixture used in Example I comprising the same alkyl ethoxycarboxylates provides excellent grease cleaning and hand mildness, with somewhat less foaming power than Preparations A, B and C.

Example IV

A gel composition suitable for use in the process of the present invention can be prepared using the general procedure described in U.S. Patent No. 4,615,819. The composition contains 35.0 wt.% sodium C12-14 alkyl ethoxy (avg. 3.0) carboxylate and 2.3 wt.% C12-14 alkyl ethoxy (avg. 3.0) alcohol. If urea is used as a gelling "additive," the pH of a 10 wt.% aqueous solution should be kept below about 8.0 to prevent an ammonia odor in the composition resulting from degradation of the urea.

This gel composition exhibits good grease release ability and excellent hand mildness properties compared to currently available gel compositions (e.g., US Patent No. 4,615,819).

Example V

The following three liquid compositions suitable for use in the process of the invention are prepared according to the procedure given below.

Ethanol is added to the acid form of the alkyl ethoxycarboxylate mixture. A slight excess over the stoichiometric amount of sodium hydroxide required to neutralize the acid is then added and mixed in. After neutralization, the alkyl sulfate, cumene sulfonate, trisodium sulfosuccinate, betaine and amine oxide are added, if desired. The appropriate buffering agents (glycine and/or tris(hydroxymethyl)aminomethane) are then added as an aqueous solution at or in the case of formulations X and Y slightly above the target pH of the composition. If required for the formulation, the magnesium chloride is added at this time to the mixture at a pH between 9.5 and 10. If the magnesium is added to a mixture at a pH greater than about 10, precipitation of the magnesium may occur. Finally, the fragrance and colorant are added, the viscosity is adjusted using ethanol, and water is added to complete the formula.

*: The surfactant mixture containing sodium alkyl ethoxycarboxylates and alcohol ethoxylate is prepared by neutralizing the acid form of the alkyl ethoxycarboxylate mixture with sodium hydroxide. After neutralization, the surfactant portion of the mixture contains about 94.3% alkyl ethoxycarboxylates of the formula RO(CH2CH2O)xCH2C00-Na+, where R is C12-13, on average C12,5 alkyl, x ranges from 0 to about 10, and the ethoxylate distribution is such that the amount of material where x is 0 is about 0.5% and the amount of material where x is greater than 7 is less than about 6%, based on the weight of the alkyl ethoxycarboxylates. On average, x has a distribution of 3.5. The surfactant blend also contains about 5.7% alcohol ethoxylates of the formula RO(CH2CH2O)xH, where R is C12-13, on average C12,5 alkyl and x is on average 3.5. The surfactant blend contains 0% soap materials.

The above formulations provide an excellent combination of grease cleaning and mildness benefits. Using the alkyl ethoxycarboxylate containing surfactant blend as a modular component, a range of good grease cleaning is achieved, the order being Formulation X > Formulation Y » Formulation Z. These same formulations provide both a range of mildness benefits, the order being Formulation X > Formulation Z > Formulation Y, and a range of foaming benefits, the order being Formulation Y > Preparation Z » Preparation X.

Claims (7)

1. A method of dishwashing with a mild liquid or gel dishwashing detergent composition comprising 5 to 70% by weight of a surfactant mixture, characterized in that the surfactant mixture comprises on a weight basis: (a) 80 to 100%, preferably 90 to 95%, alkyl ethoxycarboxylates of the formula: RO(CH2CH2O)xCH2COO-M+ wherein R is a C12-C16, preferably a C12-C14 alkyl group, x is in the range of 0 to 10, and the ethoxylate distribution is such that on a weight basis the amount of material in which x is 0 is less than 20% and the amount of material in which x is greater than 7 is less than 25%, with an average of x being 2 to 4 when R is on average C13 or less, and an average of x being 3 to 6 when R is on average greater than C13, and M is a cation; (b) 0 to 10%, preferably less than 5%, alcohol ethoxylates of the formula: RO(CH2CH2O)xH wherein R is a C₁₂-C₁₆ alkyl group and x is in the range of 0 to 10, and x is on average less than 6; and (c) 0 to 10%, preferably less than 5%, of soaps of the formula: RCOO-M&spplus; wherein R is a C₁₁-C₁₅ alkyl group and M is a cation; wherein a 10 wt.% aqueous solution of the composition has a pH of 7 to 11. 2. The method of claim 1, wherein the composition is a liquid and comprises 12 to 30% of the surfactant mixture. 3. The method of claim 1, wherein the composition is a gel and comprises 28 to 35% of the surfactant mixture. 4. A method according to any one of the preceding claims, wherein the composition has a pH of 8.5 to 10. 5. A method according to any one of the preceding claims, wherein the composition comprises 0.3 to 0.8% magnesium ions. 6. A method according to any one of the preceding claims, wherein the composition further comprises a co-surfactant selected from alkylbenzenesulfonates, alkyl sulfates, paraffinsulfonates, olefinsulfonates, alkyl ether sulfates, fatty acid ester sulfonates, alkylpolyglucosides and mixtures thereof. 7. A method according to any one of the preceding claims, wherein the composition further comprises a foam improver selected from betaines, ethylene oxide condensates, fatty acid amides, semipolar nonionic amino xylene compounds, cationic surfactants and mixtures thereof.