Europaisches Patentamt J European Patent Office Qy Publication number: 0 267 662 Office europeen des brevets A2 EUROPEAN PATENT APPLICATION © Application number: 87301384.1 © mt. ci.< C11D 1/75 © Date of filing: 18.02.87 ® Priority: 14.11.86 US 931398 © Applicant: ECOLAB INC. Ecolab Center © Date of publication of application: Saint Paul Minnesota 55102(US) 18.05.88 Bulletin 88/20 @ Inventor: Copeland, James L © Designated Contracting States: 12729 Pheasant Run AT BE CH DE ES FR GB IT LI LU NL SE Burnsville Minnesota 55337{US) Inventor: Donovan, Daniel J. 435 Bay Street St. Paul Minnesota 55102(US) © Representative: Bond, Bentley George et a I Haseltine Lake & Co. 28 Southampton Buildings Chancery Lane London WC2A 1AT(GB) © Detersive systems and low foaming aqueous surfactant solutions containing a mono (C1-4 alkyl)-di (C6-20 alkyl)-amine oxide compound. © A C1.4 alkyl-di C6.2o alkylamine oxide surfactant composition can be used in detersive systems. The amine oxide can be used in effective surfactant concentrations in aqueous alkaline solutions (pH about 7 or greater) producing an aqueous solution having halogen stability, reduced surface tension and low foaming properties. The surfactants have properties that are useful in detersive systems for hard surfaces, warewashing, laundry, clean-in-place, and other applications. CM < CM CO CO 1^ CO CM a. LU Xerox Copy Centre 0 267 662 DETERSIVE SYSTEMS AND LOW FOAMING AQUEOUS SURFACTANT SOLUTIONS CONTAINING A MONO (Ci-4 ALKYL)-DI(C6-20 ALKYL)-AMINE OXIDE COMPOUND Field of the Invention The invention relates to a novel class of surfactant compounds, to aqueous solutions containing an 5 effective surface active amount of the novel surfactants and to detersive systems containing the surfactant as an active detergent ingredient. More particularly the invention relates to a class of low-foaming surfactants that, depending on pH can have both cationic and nonionic properties, can be stable in the presence of halogen bleaches, and can be used generally in detersive systems such as particulate, liquid and solid household and institutional warewashing detergents, laundry detergents, hard surface cleaners, io clean-in-place agents, and others. Background of the Invention 15 Commonly a surfactant is an organic compound having at least one functional group that tends to be hydrophilic or water-seeking and at least one other functional group that tends to be hydrophobic or water hating. These functional groups can be assembled in surfactant molecules wherein the solubility, properties, location and relative sizes of the functional groups determines the surfactant properties of the compound. The practical application of surfactants generally depends upon the properties of the surfactant in 20 aqueous solution. Important properties of surfactants include the wetting power of aqueous solutions of surfactants, the ability of surfactants to dissolve normally water insoluble substances, the ability of surfactants to stabilize dispersed systems such as emulsions or suspensions, the ability of detersive systems (systems containing a detergent) to clean, the ability of surfactants to foam or resist foaming in aqueous solutions, the ability of surfactants to sanitize and others. Many types of surfactant molecules are 25 known and are broadly classified as anionic, cationic, nonionic and amphoteric. Surfactant molecules can contain one or more of a variety of hydrophilic functional groups such as hydroxyl groups, ether linkages, groups derived from alkylene oxides such as ethylene oxide and propylene oxide; quaternary amines, ester linkages, amino groups, amido groups, carboxylic acid groups, sulfonic acid groups, and can contain one or more of hydrophilic groups such as alkyl groups, unsaturated alkenyl or alkynyl groups, aromatic groups, 30 fatty acid residues, and many others. Such functional groups can easily be classified by the skilled artisan into groups that tend to be hydrophilic and groups that tend to be hydrophobic. However, the properties of the resulting surfactant molecules are not directly predictable since the contribution of each functional group is not fully quantifiable. In general, high molecular weight tertiary amine oxide compounds have been recognized in the art. The 35 prior art is primarily directed to two classes of surfactants which have been examined in great detail and have useful high-foaming surfactant properties. These compounds are typically the mono-(C8.i8 alkyl)di- (methyl) amine oxide compounds of the formula: CH-, - - 40 I O R- N ->O I . CH3 45 wherein R is a C8-i8 alkyl group and the mono-(C8.i8alkyl)di(C2-3 alkanol) amine oxide compounds of the formula: R I 50 HO-alkylene- N -alkylene-OH 0 0 267 662 The commercial use of such amine oxide classes are discussed in Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 1, pp. 32-47, Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 19, pp~. 556-559. See also Burton, U.S. Pat. No. 4,421,740, Ando et al, U.S. Pat. No. 4,337,165, Yoshikawa, U.S. Pat. No. 4,320,033, Russell, U.S. Pat. No. 3,843,395, Olson et al, U.S. Pat. No. 3,808,311, Morton, U.S. Pat. No. 3,686,025, Heinz, U.S. Pat. No. 3,470,102, Drew, U.S. Pat. No. 3,441,612, Wakeman et al, U.S. Pat. No. 3,270,060, Lang, U.S. Pat. No. 3,086,943, Drew et al, U.S. Pat. No. 3,001,945, Pilcher et al, U.S. Pat. No. 2,999,068, and British Pat. No. 1 ,294,642. 10 Brief Description of the Invention We have found a novel surfactant class that comprises at least one compound or a mixture of compounds of the formula: 75 R-L R- N -K) Rl 20 wherein R is a C1.4 alkyl and each Ri is independently a branched or unbranched aliphatic hydrocarbon group having more than 6 carbon atoms, and less than 20, preferably less than 14 carbon atoms. The novel aqueous compositions of this invention comprise an effective amount, typically about 5 wt-% 25 or less, of a mono-(C1^t alkyl)di(C6.20 alkyl)-amine oxide compound sufficient to produce surfactant properties in an aqueous solution. We have found that such solutions have chlorine stability, substantially reduced surface tension, have low foaming properties, defoaming properties and antimicrobial sanitizing activity in specific pH ranges. We have also found novel detersive systems that contain the novel surfactants of this invention in 30 combination with other components. The unique properties of the surfactants of this invention provide warewashing detergents, hard surface cleaners and laundry detergents, clean-in-place compositions and other systems having novel and surprising properties. 35 Detailed Description of the Invention The mono-(d.4 alkyl)-di-(C6.20 alkyl)amine oxide surfactant compounds of the invention comprise a compound according to the formula: 40 Rx R- N +O I Rl 45 X wherein R comprises an alkyl group of 1 to 4 carbon atoms and Ri comprises a linear, branched or cyclic aliphatic group having 6 to 20, preferably 6 to 12 carbon atoms. Specific examples of C6.20 linear or branched alkyl groups include hexyl, heptyl, 2-ethylhexyl, n-octyl, 2,2,4-trimethyipentyl, cyclohexyl, methyl- 50 cyclohexyl, decyl, dodecyl, tetradecyl, hexadecyi, octadecyl, etc. The C iJt alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl. Specific examples of the preferred amine oxide surfactants for use in the novel aqueous solutions of the invention include dihexylmethyiamine oxide, dioctyimethylamine oxide, didecylmethylamine oxide, octyldecylmethylamine oxide, decyldodecyl- methyiamine oxide, dodecyltetradecylmethylamine oxide, decyltetradecylmethylamine oxide, didodecyl- 55 methylamine oxide, dipentadecylmethylamine oxide, dihexadecylpropylamine oxide, dihexylisopropylamine oxide, dioctylethylamine oxide, didecylethylamine oxide, didodecylethylamine oxide, dipen- tadecylethylamine oxide, dihexadecylethylamine oxide, dioctyiisopropylamine oxide, didecylisopropylamine oxide, didodecylisopropylamine oxide, dipentadecylisopropylamine oxide, dihexadecylisopropylamine oxide, 0 267 662 and others. The most preferred amine oxide surfactants are compounds of the formulae I wherein either (1) Ri is octyl, decyl or mixtures thereof, (2) Ri is octyl, (3) Ri is decyl, or (4) Ri is a mixture of decyl, dodecyl and tetradecyl. The mixtures of the surfactant compositions comprise a mixture of dioctyl methylamine oxide 5 and didecyl amine oxide or a mixture of compounds wherein Ri can be either octyl, decyl or a mixture of octyl and decyl. We have found, surprisingly in comparison with dimethyl higher (C18.24) alkylamine oxide that the aqueous solutions of the compounds of this invention exhibit excellent surfactant properties as shown in a substantial reduction in surface tension, surprising low foaming properties in view of the high foaming nature 10 of the alkyl dimethylamine oxide surfactants, chlorine stability, excellent detersive properties and have a number of other properties not recognized in the prior art. Amine oxides are typically formed from tertiary amines by an oxidative reaction creating the amine oxide functional group. Typically amine oxides are made by oxidizing a tertiary amine with hydrogen peroxide or other oxygen source. Such preparatory methods are discussed by Lake and Hoh in ± Am. OH 75 Chemist Society , 40, 628 (1963), The higher alkyl C6.18 dimethylamine oxides were first developed as foam builders in liquid handwashing formulations. In addition to foam boosting, the higher alkyl dimethylamine oxides have been shown to be effective in high foaming shampoos and other end uses where foaming is important, We have found that the amine oxide compounds of this invention are preferably made by oxidizing the 20 di-C 6-2oalkyl-Ci.4 alkylamine with hydrogen peroxide or other common oxidant (oxygen yielding substance) at elevated temperature. The tertiary amine compound is typically placed in a reaction flask and heated to an elevated temperature. Into the heated tertiary amine is slowly added an aqueous solution of oxidant (30 to 50 wt-%) over an extended period, At the end of the addition of the hydrogen peroxide, the reaction mixture is typically treated to dispel remaining hydrogen peroxide.