Process for producing concentrated liquid detergents containing magnesium alkylbenzene sulfonic acid and alkanolamide

Abstract: A process for the manufacture of a concentrated liquid detergent composition containing over 40% solid ingredients including magnesium alkylbenzene sulfonate and an alkanolamide component, offers reduction in viscosity during manufacture and upon cooling of the composition. The addition of salts and hydrotropes to the concentrated liquid detergent composition and the incorporation of alkanolamide prior to the addition of alkylbenzene sulfonic acid sufficiently lowers the viscosity of the mixture to allow processing using conventional low shear mixing equipment.

Description: BACKGROUND OF THE INVENTION Field Of The Invention: The present invention relates to a process for producing concentrated liquid detergent compositions containing the magnesium salt of alkyl benzene sulfonic acid and a suds boosting alkanolamide component, and which compositions have decreased viscosity during manufacture and upon cooling. Description Of The Prior Art: Typical liquid dishwashing detergents contain substantial amounts of anionic surfactants that help provide greasy soil removal. Generally, the grease cutting ability of the composition increases with an increased concentration of surfactants; however, the viscosity of compositions containing concentrations of anionic surfactants of about 30-50% is potentially problematic in the manufacture of such compositions, particularly as the surfactant levels of such compositions approach 50%. The viscosity of a liquid detergent composition is affected by the concentration of anionic surfactant components as well as all other solid ingredients. The word "solid" is used herein to refer to all ingredients other than solvents and thus may include normally liquid ingredients. A viscosity of about 12.000 mPa·s (12,000 cps) renders a composition thick and paste-like and is thus extremely difficult to mix. It is sometimes desirable in manufacturing liquid detergents to make a base composition separately from the finished product. The base composition contains appropriate amounts of the surfactant active ingredients such as, magnesium alkylbenzene sulfonate, alkyl sulfate and alkyl ethoxy sulphate; suds boosting agents such as alkyl mono- or di-alkanolamide; and a liquid carrier such as water, a water soluble solvent or mixtures of water and a water-soluble solvent. The base composition may be diluted to form the desired final liquid detergent product composition with other aqueous or aqueous-alcohol solutions containing ingredients such as hydrotropes, to provide phase stability and lower the viscosity of the composition, alkali metal salts such as magnesium sulfate or sodium sulfate to boost detergency; minor ingredients such as opacifying agents; color stabilizers; dyes; perfumes; heavy metal chelating agents; antioxidants; antimicrobial agents; etc.; and pH modifying bases and acids such as NaOH and HCl. Examples of hydrotropes include urea, C₂-C₄ alcohols, sodium xylene sulfonate, potassium xylene sulfonate, sodium cumene sulfonate and ammonium xylene sulfonate. Such base compositions may contain higher concentrations of surfactants and other solid ingredients than the final liquid detergent product composition and as such, the viscosities of such compositions may require expensive and high energy mixing devices during manufacture and may cause the compositions to gel at ambient temperature. In U.S. patent 4,169,076 a method is disclosed for making a pre-neutralized base solution of the magnesium salt of an anionic active agent which can be directly utilized in the production of liquid detergent. Similarly, U.S. Patent 4,129,515 discloses a process for producing a heavy-duty liquid detergent base composition wherein an anionic surfactant in the free acid form is mixed with magnesium hydroxide to provide an acid solution that is later neutralized with alkanolamine. In prior art techniques for preparing concentrated liquid detergent formulations which contain foam boosting compounds or hydrotropes, it is customary to first add the detergent active compounds to the liquid carrier and then add the foam boosters and hydrotropes. It is also customary to add the detergent active anionic compounds in their neutralized, i.e. salt, form. According to the conventional practice, the viscosity of the formulations with high solids content is generally quite high, often in excess of 15,000 to 20,000 mPa·s (15,000 to 20,000 cps). While these high viscosities might not present a significant problem for manufacturers having, or having access to, existing facilities with high shear mixers, viscosities in excess of about 20,000 mPa·s (20,000 cps), especially above 12,000 mPa·s (12.000 cps), could present a significant problem if such high speed, high shear mixers were not available. In particular, equipment start-up costs could, in some cases, preclude some manufacturers from attempting to make such products or from being competitive in the market place. Moreover, with electrical utility costs on the rise and with worldwide efforts to conserve energy, any means for reducing power consumption during manufacture would be highly beneficial. It is accordingly an object of this invention to provide a process for the manufacture of concentrated liquid detergent base, useful in the manufacture of concentrated liquid detergents, which comprises magnesium alkylbenzene sulfonate and alkanolamide, and in which the base is made separately from the finished product. It is another object of this invention to provide a process for the manufacture of concentrated liquid detergent compositions that contain levels of magnesium alkylbenzene sulfonate suds boosting agent, such as alkanolamide or an ethoxylated alkanolamide and other solid (non-solvent) ingredients that otherwise would result in viscosities above about 12,000 mPa·s (12,000 cps) during manufacture or after cooling and which does not require special heavy duty or high shear mixing devices. Another object of this invention is to provide a process for the manufacture of concentrated liquid detergent compositions containing at least about 40% solid ingredients including magnesium alkylbenzene sulfonate and a suds boosting agent including an alkanolamide or an ethoxylated alkanolamide and that can be stored at ambient temperature without gelling. SUMMARY OF THE INVENTION The present invention encompasses an improvement in the process for preparing a concentrated liquid detergent composition containing (A) the magnesium salt of alkylbenzene sulfonic acid and (B) ethoxylated or non-ethoxylated alkyl mono- or di-substituted alkanolamide as suds boosting agent, (C) alkali metal salts and/or alkaline earth metal salts, and (D) hydrotrope. This invention is based upon the discovery that by (1) first forming an aqueous mixture containing the suds boosting alkanolamide, alkali metal salts and/or alkaline earth metal salts, and hydrotrope and up to the stoichiometric neutralizing amount of an active magnesium compound relative to the alkylbenzene sulfonic acid added in step (2) in a liquid carrier (E) and (2) then adding the alkylbenzene sulfonic acid to the mixture from step (1); the viscosity of the formulation is sufficiently lowered to about 20,000 mPa·s (20,000 cps) or lower to allow mixing with ordinary low shear mixing devices. If the suds booster or hydrotropes are added after the alkylbenzene sulfonic acid, or if excess neutralizing magnesium compound is used, the viscosity of the resulting mixture increases to levels which make mixing with ordinary low shear liquid mixers difficult or impossible. Concentrated liquid detergent compositions prepared according to the foregoing process have decreased viscosity during manufacture and remain pourable upon cooling. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, concentrated magnesium alkylbenzene sulfonate-containing compositions comprising a total detersive active ingredients and solid (non-solvent) ingredients level such that the viscosity of the composition during manufacture would be 12,000 mPa·s) (12,000 cps) or higher if prepared by a process outside the present invention, are prepared by combining suds boosting alkanolamides such as lauric and myristic monoethanolamides with a mixture containing hydrotropes, alkali metal salts and/or alkaline earth metal salts and stoichiometric neutralizing amount of magnesium compound, such as magnesium carbonate, magnesium oxide or magnesium hydroxide in a liquid carrier, and then adding alkylbenzene sulfonic acid in an amount sufficient to produce a composition having a pH in the range of 2 to 5. Although useful concentrated liquid detergent compositions prepared according to this invention of necessity contain a liquid carrier, such as water or mixture of water and water-soluble solvents, it is desirable that the amount of carrier be kept to a minimum, generally less than 60% by weight of the composition. The amount of carrier liquid used herein is preferably chosen to provide a composition containing from 25 to 55%, preferably from 30 to 42%, of carrier liquid by weight of the total detergent composition, and conversely solids contents ranging from 45 to 75% preferably from 58 to 70% by weight. These solid concentrations can be obtained with viscosities below 20,000 mPa·s (20,000 cps), preferably below 17,000 mPa·s (17,000 cps), and especially preferably no more than 12,000 mPa·s (12,000 cps). These viscosities will, in any case, be lower than the viscosity achieved at the same solids content if the alkylbenzene sulfonic acid is added before the hydrotrope, salts or suds boosting agent. Any alcohol containing from 1 to about 5 carbon atoms can be used in the carrier mixture to prepare detergent compositions in the manner of this invention. For example, methanol, n-propanol, ethanol, n-butanol, isopropanol, isobutanol and pentanol may be used. Various liquid or low-melting point, water-soluble poly-ols can also be used in the carriers herein. Such materials include ethylene glycol, polyethylene glycol, glycerins, glycol ethers and the like. Other water-soluble solvents include ketones such as acetone; aldehydes such as propionaldehyde; ethers such as diethyl ether as well as various natural water-soluble oils that contain water-soluble organic solvents. The preferred organic solvent carrier is propylene glycol. The amide suds booster of the compositions prepared in the manner of this invention is preferably added in prill form but may be added in the molten state, alone, or as a blend with another material of the composition such as a sodium xylene sulfonate solution. The amide suds booster is preferably added in amount to provide a composition containing from 5 to 10% of suds booster by weight of the total detergent composition. The amide may contain ethoxylation to increase its solubility. The alkyl group of the amide may be derived from coconut or palm kernel oil. The alkanol group of the amide may have a carbon chain distribution of C₁-C₅ and be either mono- or di-substituted. The preferred amide suds booster is lauric/myristic monoethanolamide. Hydrotrope is added to the composition in the interests of achieving phase stability and decreased viscosity. Hydrotropes such as sodium and potassium toluene sulfonate, sodium and potassium xylene sulfonate, trisodium sulfosuccinate, sodium and potassium cumene sulfonate and related compounds are preferred and can be used indivudually or in combination. In a preferred embodiment, a mixture of sodium cumene sulfonate and sodium xylene sulfonate comprise from 3 to 10 wt % of the total composition. A mixture containing salts, hydrotrope, alkanolamide and, up to or slightly less than the stoichiometric amount of a neutralizing magnesium compound such as magnesium carbonate, magnesium oxide or magnesium hydroxide in a liquid carrier is first formed and while the mixture is continuously agitated alkylbenzene sulfonic acid is added. The alkylbenzene sulfonic acid can be either linear or branched. The alkyl group preferably contains 12 to 18 carbon atoms, most preferably 12 to 14 carbon atoms in a linear chain configuration. However, C₁₁-C₁₄ branched chain alkylbenzene sulfonic acids, which are excellent sudsers, may also be used. The amount of alkylbenzene sulfonic acid added to the mixture is chosen to provide a composition containing from 30 to 50% alkylbenzene sulfonic acid by weight of the total detergent composition. The alkylbenzene sulfonic acid to be added to the mixture can be prepared by sulfonating alkylbenzene in any known procedure. Typical examples of alkylbenzene sulfonic acids include undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid, tridecylbenzene sulfonic acid and mixtures thereof. The acid form of alkylbenzene sulfonic acid is neutralized, i.e. converted, to the magnesium salt form during admixture of the alkylbenzene sulfonic acid with the neutralizing magnesium compound present with the other ingredients in the liquid carrier formed prior to admixture with the acid. The conversion may be accomplished by direct neutralization by the magnesium compound or by ion exchange between, for example, an alkali metal salt or the ammonium salt of the alkylbenzene sulfonate and a water-soluble magnesium compound. Direct neutralization of the acid is preferred. The amount of neutralizing magnesium compound, preferably magnesium oxide or magnesium hydroxide that is added to the composition in molar amount sufficient to neutralize substantially all of the alkylbenzene sulfonic acid. Usually, amounts ranging from 2 to 4 wt % will suffice for this purpose. A source of reactive magnesium ions, such as provided by MgO, Mg(OH)₂ or MgCO₃ is added to the liquid carrier prior to the addition of alkylbenzene sulfonic acid to form the desired salt of alkylbenzene sulfonic acid. Usually, the stoichiometric amount of the magnesium compound required for neutralizing all of the alkylbenzenesulfonic acid is added to the initial mixture in the liquid carrier. However, amounts below the stoichiometric amount, such as at least 85 mol %, preferably 90 to 95 mol % or more, of the reactive magnesium compound is added during the first step, prior to the addition of the alkyl benzene sulfonic acids. Preferably from 98 to 100 mol % of the neutralizing amount of the reactive magnesium compound is added during the first step. If above stoichiometric reactive magnesium compound were to be used in the first step, the unreacted magnesium would increase the pH of the composition resulting in an undesired cloudy appearance. The preferred salt of alkylbenzene sulfonate is m-gnesium alkylbenzene sulfonate and, most preferably, the alkylbenzene sulfonate is the magnesium salt of linear dodecylbenzene sulfonate. The amount of alkali metal salt and/or alkaline earth metal salt (C) is chosen to provide a composition containing from 1 to 3 wt % based upon the weight of the total composition. Suitable salts include the inorganic salts, such as sulfates, chlorides, carbonates, and nitrates and/or organic salts, such as acetates, citrates, propionates, and the like. Sodium sulfate is especially preferred. The order in which the materials are mixed in the liquid carrier affects the viscosity of the composition during manufacture and upon cooling. Significant reductions in viscosity during manufacturing are made by adding reactive magnesium compound, salts and hydrotrope solutions to the liquid carrier prior to the addition of alkylbenzene sulfonic acid. Whereas this modification decreases viscosity of the composition during manufacture, it does not prevent the concentrated composition from gelling upon cooling, however. The addition of the alkanolamide to the liquid carrier mixture containing salt and hydrotrope prior to the addition of the alkylbenzene sulfonic acid further reduces the viscosity of the composition during manufacture and prevents the composition from gelling upon cooling. Thus, a composition in which the alkanolamide, reactive magnesium compound, alkali metal and/or alkaline earth metal, salt and hydrotrope are added to a liquid carrier prior to the addition of alkylbenzene sulfonic acid decreases viscosity of the composition during manufacture and results in a concentrated liquid detergent composition that remains fluid after the temperature of the composition has dropped. These modifications in the process for preparing a concentrated liquid detergent composition are particularly significant in that they eliminate the need for specialized mixing equipment and allow for the manufacture of a concentrated liquid detergent composition that can be stored at ambient temperature without gelling. It is sometimes desirable in the manufacture of concentrated liquid detergent compositions to formulate compositions containing a very high active ingredients content. However, as the level of solid ingredients in the composition increases, the viscosity of the composition also increases. A composition viscosity of over 12,000 mPa·s (12,000 cps) generally requires special mixing equipment during manufacture and generally the composition is not readily pourable at room temperature. The process of this invention allows manufacture of a more concentrated magnesium alkylbenzene sulfonate containing detergent composition than would be possible without mixture of the alkanolamide, salt and hydrotropes prior to the addition of alkylbenzene sulfonic acid. Concentrated detergent compositions prepared according to the process of this invention can optionally contain various other components that contribute to aesthetics or performance. Such components can be added to the mixture containing salts, hydrotrope and alkanolamide in liquid carrier prior to the addition of alkylbenzene sulfonic acid but may also be added together with or after alkylbenzene sulfonic acid has been added to the mixture. Conveniently, the optional ingredients may be added as aqueous or aqueous-alcohol solutions. The optional ingredients will usually, when present, each be used in amounts of no more than 3% by weight of the final composition, such as from 0.01 to 3%, preferably 0.05 to 2.5%, by weight of the final composition. The optional components that may be added to the base compositions prepared herein are well known and include opacifying agents; color stabilizers; dyes; water-soluble pigments; perfumes; heavy metal chelating agents such as EDTA; antioxidants; anti-microbial agents such as bactericides, fungicides, etc., preservatives, sun-screening agents, pH modifiers, pH buffering agents and proteins. Other conventional detergent active compounds may be added, if desired, to the aforementioned concentrated base composition to provide a finished light duty liquid composition. The other detergent active ingredient, when present, will preferably also be anionic in nature or nonionic, but cationic, amphoteric or zwitterionic compounds may also be used. Preferred other anionic sufactants include the alkyl ether sulfates, alkyl sulfate, alkyl sulfosuccinates and paraffin sulfonates. Preferred nonionic surfactants include the ethoxylated and/or propoxylated higher fatty alcohols. Example 1 : Concentrated liquid detergent compositions are prepared by mixing the following components in the order as listed: The concentrated liquid detergent compositions of Example 1 are prepared by mixing all of the ingredients, with the exception of dodecylbenzene sulfonic acid, into the water-propylene glycol carrier mixture. The dodecylbenzene sulfonic acid is then added to the mixture. Compositions 2, 3 and 4 contain a lower solids concentration and a lower level of detersive active ingredients than Composition 1 but which, by adding docecylbenzene sulfonic acid prior to the addition of alkanolamide, are extremely thick and paste-like during manufacture and require special high shear mixing equipment. Compositions 2 and 4, for example, have a viscosity of almost 50,000 mPa · s (50,000 cps) at room temperature. Composition 1, on the other hand, has decreased viscosity during manufacture and remains pourable after the composition has cooled. The viscosity of the composition is less than 10,000 mPa·s (10,000 cps). Composition 5, which is made by the process of this invention and which contains 65% solid ingredients has a high viscosity but shows significant improvement in viscosity and fluidity over Compositions 2 and 4, which contain 8 and 13% less active ingredients, respectively. This example demonstrates the decreased viscosity of a concentrated liquid detergent composition containing magnesium alkylbenzene sulfonate and manufactured by the process of this invention over similar compositions made by mixing the alkylbenze ne sulfonic acid with other ingredients prior to the addition of alkanolamide. Composition 1 is a pourable liquid at 25°C, whereas Compositions 2 and 4 are thick gels at 25°C. Example 2 : Concentrated liquid detergent compositions are prepared by mixing the following components in the order as listed: Composition 1 Composition 2 Deionized water 24.8 37.7 Sodium cumene sulfonate (45% sol.) 4.7 - Sodium xylene sulfonate (40% sol.) 12.0 - Propylene glycol 2.3 2.5 Magnesium oxide 2.7 2.9 Sodium sulfate 1.2 - Lauric/myristic monoethanolamide 8.0 8.7 Dodecylbenzene sulfonic acid 44.3 48.2 Total 100.0 100.0 Consistency at 25 o C Pourable liquid Thick gel After mixing the above listed ingredients, hydrotropes (sodium cumene sulfonate and sodium xylene sulfonate) and sodium sulfate were added to Composition 2 in amounts equal to that in Composition 1. The addition of hydrotropes and salt subsequent to the addition of alkylbenzene sulfonic acid slightly decreased the viscosity of the composition but left it highly aerated and thicker than desirable for manufacture. This example illustrates that the addition of salt and hydrotropes decreases viscosity of a concentrated liquid detergent composition but that the addition of these ingredients must precede the addition of alkylbenzene sulfonic acid in order to exert the full effect on viscosity. The above examples are, of course, merely provided for illustrative purposes and are not intended to limit the invention in any way.

Claims: A process for producing a concentrated liquid detergent composition containing (A) a surfactant compound comprising a magnesium salt of a higher alkylbenzene sulfonic acid, the alkyl group of which contains 12-18 carbon atoms; (B) a suds boosting agent selected from the group consisting of ethoxylated and non-ethoxylated alkyl mono- and di-C₁ to C₅ alkanolamides; (C) alkali metal salt, alkaline earth metal salt or combinations thereof; (D) hydrotrope; (E) a liquid carrier which comprises (1) forming a mixture containing said alkali metal salt, alkaline earth metal salt or combinations thereof (C), said hydrotrope (D), said suds boosting alkanolamide (B) and up to the stoichiometric amount of an active magnesium compound for neutralizing substantially all of the alkylbenzenesulfonic acid to be added in step (2), in liquid carrier (E), and (2) adding an alkylbenzene sulfonic acid to the mixture of step (1) to provide a concentrated liquid detergent composition with a viscosity below 20,000 mPa·s (20,000 cps) during manufacture and which remains pourable upon cooling. A process according to Claim 1 wherein the alkylbenzene sulfonic acid is selected from the group consisting of linear and branched alkylbenzene sulfonic acid containing from 12 to 18 carbon atoms in the alkyl group. A process according to Claim 1 wherein the suds promoting agent is a member selected from the group consisting of C₁₀-C₁₆ alkyl mono- or di C₁-C₅ alkanolamides and ethoxylated C₁₀-C₁₆ alkyl mono- or di C₁-C₅ alkanolamides. A process according to Claim 1 wherein the liquid carrier is selected from the group consisting of water and mixtures of water and a water-soluble organic solvent. A process according to Claim 1 wherein the solids content of the concentrated liquid detergent is at least 50% by weight. A process according to Claim 1 wherein the concentrated liquid detergent composition comprises (A) from 30 to 50 wt %; (B) from 5 to 10 wt %; (C) from 1 to 3 wt %; (D) from 3 to 10 wt %; and (E) from 10 to 50 wt %. The process of claim 6 wherein the solid content is 60% by weight. The process of claim 5 wherein the concentrated liquid detergent composition has a viscosity of no more than 12,000 mPa·s (12,000 cps). A process for producing a concentrated liquid detergent composition containing (A) a surfactant component comprising a magnesium salt of a higher alkylbenzene sulfonic acid, the alkyl group of which contains 12-18 carbon atoms; (B) a suds boosting agent selected from the group consisting of ethoxylated and non-ethoxylated alkyl mono- and di-C₁-C₅ alkanolamides; (C) alkali metal salt; (D) hydrotrope; (E) a liquid carrier, and, optionally (F) one or more additives selected from chelating agents, coloring agents, dyes, perfumes, bactericides, fungicides, preservatives, sunscreening agents, pH modifiers, pH buffering agents, opacifiers, antioxidants and proteins; which comprises (1) forming a mixture containing said alkali metal salt (C), said suds boosting alkanolamide (B), said hydrotrope (D), and a magnesium compound capable of neutralizing acis in a liquid carrier (E), and (2) adding an alkylbenzene sulfonic acid to mixture (1) and optionally (3) adding one or more additives selected from the group (F) before, after or during step (1) or step (2), to provide a concentrated liquid detergent composition with a viscosity below 20,000 mPa·s (20,000 cps) during manufacture and which remains pourable upon cooling, which, if made by adding said magnesium compound after the alkylbenzene sulfonic acid, would result in a composition with a viscosity above 20,000 mPa·s (20,000 cps). A process according to Claim 9 wherein the magnesium compound is selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium carbonate. A process according to Claim 9 wherein the concentrated liquid detergent composition comprises: (A) from 30 to 50 wt %; (B) from 5 to 10 wt %; (c) from 1 to 3 wt %; (D) from 3 to 10 wt %; (E) from 10 to 50 wt %; and (F) from 0 to 3 wt % for each said additive. The process of claim 11 wherein the solids content is 60% by weight of the detergent composition. The process of claim 9 wherein the concentrated liquid detergent composition has a viscosity of no more than 12,000 mPa·s (12,000 cps).

Inventors: JAKUBICKI GARY JOSEPH, SCHWARZ CARL, URAY ALP JOHN, JAKUBICKI, GARY JOSEPH, SCHWARZ, CARL, URAY, ALP JOHN
Applicants: COLGATE PALMOLIVE CO, COLGATE-PALMOLIVE COMPANY
Application year: 1991
Main classification: C11D11
IPC codes: C11D17, C11D11, C11D1, C11D3