US3897362A

US3897362A - Stabilized surfactants and their preparation

Info

Publication number: US3897362A
Application number: US299964A
Authority: US
Inventors: David Ross Mccoy
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-10-02
Filing date: 1972-10-24
Publication date: 1975-07-29
Anticipated expiration: 1992-07-29

Abstract

This invention relates to a process for stabilizing solubilized Schiff bases normally unstable in alkaline aqueous environment, and the stabilized products produced therein. The solubilized Schiff bases are stabilized with methyl alkyl ketone selfcondensates having an average molecular weight of 350-450 and a nitrogen content of 3-4% by weight, said methyl alkyl ketone self-condensates being derived from heating a reaction mixture consisting essentially of inert solvent, ethanolamine and at least one methyl alkyl ketone containing 10 to 15 carbon atoms at temperatures ranging from 50*C. to the boiling point of the reaction mixture until water of reaction is formed, and removing the water of reaction. The stabilized products are useful as surfactants or as components of detergent compositions.

Description

States Elite *5 McCoy [451 July 29,1975

[ STABILIZED SURFACTANTS AND THEIR [21] Appl. N0.: 299,964

Related US. Application Data [63] Continuation-in-part of Ser. No. 863,368, Oct. 2,

1969, abandoned.

[52] US. Cl. 252/357; 252/106; 252/110; 252/118; 252/403; 252/524; 252/529; 252/542; 252/548; 260/566 R FOREIGN PATENTS OR APPLICATIONS 414,712 8/1934 United Kingdom 252/357 Primary Examiner-Richard D. Lovering Attorney, Agent, or Firm--T. H. Whaley; C. G. Ries; B. Marlowe [57] ABSTRACT This invention relates to a process for stabilizing solubilized Schiff bases normally unstable in alkaline aqueous environment, and the stabilized products produced therein. The solubilized Schiff bases are stabilized with methyl alkyl ketone self-condensates having an average molecular weight of 350-450 and a nitrogen content of 3-4% by weight, said methyl alkyl ketone self-condensates being derived from heating a reaction mixture consisting essentially of inert solvent, ethanolamine and at least one methyl alkyl ketone containing 10 to 15 carbon atoms at temperatures ranging from 50C. to the boiling point of the reaction mixture until water of reaction is formed, and removing the water of reaction. The stabilized products are useful as surfactants or as components of detergent compositions.

7 Claims, No Drawings STABILIZED SURFACTANTS AND THEIR PREPARATION This application is a continuation-in-part of Ser. No. 863,368 filed Oct. 2, 1969 (now abandoned).

This invention relates to stabilizing solubilized condensates of aliphatic ketones with amino-containing re actants and the utilization of these stabilized products as surfactants or as components of detergent compositions.

More particularly, this invention concerns a process of stabilizing the above solubilized Schiff bases which are normally unstable to neutral or alkaline aqueous environment.

The terms surfactant or surface-active, which are used throughout this disclosure, are synonymous and refer to substances which, in solution, are used by themselves or in conjunction with cleaning adjuvants such as additives or builders to form cleaning compositions. Solutions of surfactants, particularly aqueous solutions are widely used to wet surfaces, remove soil, penetrate porous materials, disperse particles, emulsify oils and greases, etc, dependent upon the particular characteristics of the surfactant or surfactants used.

Desirably surfactants are inexpensive. light colored materials which function at low concentration levels in aqueous solutions and which can be produced in good yield from readily available low cost starting materials, free from deleterious contaminants, preferably as easily handled, free-flowing liquids or powders.

For many applications such as heavy duty industrial applications for metal scouring and dishwasher detergent compositions, the compositions necessarily include highly alkaline materials such as alkali metal hydroxides, alkoxides and phosphates. In the aqueous media that these detergents function, the pH of the cleaning solution frequently will be from to 13. For this reason a prerequisite of heavy duty detergency compositions is stability at elevated pHs in aqueous solutions.

Recently with the advent of a large supply of potentially inexpensive aliphatic ketones from petrochemical sources, various derivatives of ketones were explored as surfactants and as detergent components.

The solubilized Schiff bases derived from the prod ucts formed from the condensation of aliphatic ketones with amine-containing reactants were particularly of interest in view of the disclosure of British Pat. No. 414,712 (1933) which states that solubilized (ethoxylated or sulfonated, etc.) Schiff bases prepared by condensing aliphatic aldehydes or ketones of more than 6 carbon atoms with aliphatic amines or amino alcohols produce high foaming detergents stable to hard (alkaline) water. Unfortunately the applicant has found that solubilized condensation products as exemplified by the ethoxylated condensate of Schiff bases prepared from the reaction of C C ketone mixtures (or methyl nonyl ketone) with amino-containing reactants such as ethanolamine are extremely unstable in aqueous solutions ranging from pH 5.6 to 13. Inasmuch as this pH range includes most cleaning applications, the unstabilized condensate products of the British Patent are practically of no value as detergent components.

Quite unexpectedly it has been found that the use of either or both of two treatment processes can substantially improve the stability of the heretofore unstable product.

In practice an alkoxylated Schiff base believed to have the formula below:

wherein R and R, are alkyl groups containing at least 2 carbon atoms whose sum totals at least 6 carbon atoms, A is an alkoxy radical containing from 2 to 4 carbon atoms and n which represents the average degree of alkoxylation is between 3 and 25, normally unstable in aqueous solution, is treated so that upon exposure to aqueous media the pH of a 1% by weight aque ous solution will be 2 10.

In the favored practice, the methyl alkyl ketone stel' condensate content of the above described alkoxylated Schiff base product is adjusted to be between 2 and 35% of its weight, prior to its exposure to mildly acid or to strongly alkali aqueous solutions.

In the preferred practice, an ethoxylated Schiff base within the formula:

wherein R and R are alkyl radicals containing at least 2 carbon atoms whose sum contains from 9 to 14 carbon atoms, and n, the average degree of ethoxylation is from 7 to 13, is treated as follows:

a. its pH is adjusted so that a 1% by weight aqueous solution will have a pH between about 10 and 13. and

b. the content of methyl alkyl ketone selfcondensation products is adjusted to be between 2 to 35% by weight.

In order to better describe the workings of this invention in greater detail, the following supplemental disclosure is submitted:

A. Schiff Bases The Schiff bases which, when alkoxylated and stabilized are the surfactant mixtures of this invention, are derived from the condensation at elevated temperatures of equi-molar or near equi-molar quantities of aliphatic ketones containing 6 or more carbon atoms with ethanolamine, either in the presence or absence of inert solvent.

The Schiff bases fall within the formula:

= N (A) H NCH CH OH 1. Aliphatic Ketones The ketones which are employed as reactants in the formation of the abovedescribed Schiff bases are aliphatic ketones of the formula:

wherein R and R are alkyl radicals of 2 or more carbon atoms, whose sum totals at least 6 carbon atoms. The ketones having a total of 6 to 30 carbon atoms are favored, with the most favored ketones being those containing 10 to carbon atoms. The preferred ketones are those mixtures containing from 10 to 15 carbon atoms derived from the dehydrogenation of secondary alcohols from the boric acid-directed oxidation of linear hydrocarbon containing 10 to 15 carbon atoms. The preparation of these alcohols is disclosed in US. Pat. No. 3,410,913 among other places. The ketones derived from these secondary alcohols may be prepared from the alcohols using standard methods of oxidation or catalytic hydrogenation, i.e., over copper chromate at 150275C. This mixture of ketones, prepared as described, represents the preferred ketone source since it ordinarily contains as an impurity at least 2% but less than 35% by weight of aliphatic ketones in which one of the alkyl groups of the ketone, R and R are methyl. These ketones, when reacted with lower alkanolamines such as ethanolamine, produce Schiff bases containing thedesired methyl alkyl ketone self-condensation products. These products are the primary cause for the substantially improved stability of the alkoxylated product to water. It should be noted that even when the ketone reactant is free from, or contains less than the required methyl alkyl ketone content it can be enriched to the desired degree by adding a sufficient amount of methyl alkyl ketones prior to preparation of the Schiff base.

2. Alkoxylated Schiff bases The alkoxylated Schiff bases which are stabilized to form the surfactant mixtures of this invention comprise the ethoxylated, propoxylated, butoxylated and the mixtures of these alkoxylated Schiff bases. These alkoxylated derivatives as typified by the ethoxylated derivatives can be prepared by methods well described in the technical and patent literature. Generally speaking these alkoxylations are carried out between 50 and 175C in the presence of strongly alkaline catalysts such as the alkali metals, i.e., elemental sodium, as well as the strongly alkali metal salts such as sodium and potassium hydroxides and alkoxides. The reaction is carried out by passing the free alkylene oxide into the reaction mixture until 1 to or more alkoxy groupings, preferably 7 to 13 alkoxy groups are placed in the molecule. Ordinarily the reaction mixture is neutralized by the addition of acidic materials to the alkaline alkoxylation reaction mixture. However since one mode of improving the water stability of the alkoxylated Schiff base is to adjust the pH on the alkaline side, the neutralization step may be omitted. The alkoxylation may be carried out on purified Schiff base or preferably on Schiff base containing the methyl alkyl self-condensation product, since the latter has been shown to be unreactive to alkoxylation conditions and obviate the need for tedious and costly separations.

3. Methyl alkyl ketone self-condensates As previously alluded to, in addition to pH adjustment, the water stability of the alkoxylated Schiff bases can be upgraded substantially by incorporating into the alkoxylated Schiff base at least 2% by weight and up to 35% by weight of said alkoxylated bases as methyl alkyl ketone self-condensates. These materials (methyl alkyl ketone self-condensate products) as described herein refers to the mixture of lower alkanolamine (where the alkanol moiety can be propanol, butanol or preferably ethanol) addition products to ketonic dimers. Probably these addition products consist of one or more of the following classes of compounds (ethanolamine addition compounds only are given as illustrative examples):

l L o e-g NH where R, R H or n-alkyl and R-l-R= C -C said condensates having an average molecular weight of 350-450 and a nitrogen content of 3-4 weight percent and arising from the reaction of a single methyl alkyl ketone or preferably a mixture of methyl alkyl ketones in the C -C range with ethanolamine at elevated temperatures (50C to the boiling point of the reaction mixture) in the presence or absence of inert solvents or internal C C ketones 1n the overall preferred practice, the mixture of C -C methyl alkyl ketones and internal ketones obtained from the oxidation of n-paraffins as described in Section 1 is treated with ethanolamine at elevated temperature while removing the water of reaction through the addition of appropriate inert solvent followed by azeotropic distillation. This offers the advantage of forming both the desired Schiff base and the methyl alkyl ketone self condensate in the same step. This mixture of bases and condensate may be alkoxylated directly or after optionally removing any solvent present by distillation.

B. Utilization of Stabilized Alkoxylated Schiff bases (1) Concentration The alkoxylated Schiff bases exhibit long lasting surfactant properties in aquous solution in concentrations ranging from 0.01 wt. percent* and higher depending upon the mode of application. The minimal concentration of ethoxylated product usually employed is about 0.1 by weight while the upper concentration, which is limited almost entirely by cost, for all but special purposes seldom exceeds by weight. Usually the range of concentration is between about 1% to 15% by weight with the residuum being detergent adjuvants described below. In all instances the lower or minimal concentration (0.01% by weight) is referred to as a surfactant amount of an effective quantity of surfactant.

*Since from 2 to 35% by wt. of the alkoxylated Schiff Bases are methyl alkyl ketone self-condensate, the concentration of said condensate in the final detergent solution will vary from 0.002 to 0.035% by weight.

C: Utilization of the Stabilized Alkoxylated Schiff bases as detergent components When these stabilized products are employed as detergents they ordinarily are present in at least the minimal concentrations disclosed supra accompanied by one or more of the following classes of materials which are generically referred to as detergent adjuvants:

1. Inorganic salts, acids and bases. These are usually referred to as builders. These salts usually comprise alkalies, phosphates and silicates of the alkali metals as well as their neutral soluble salts. These materials constitute from about 40 to 80 weight percent of the composition in which they are employed.

2. Organic builders or additives These are substances which contribute to characteristics such as detergency, foaming power, emulsifying power or soilsuspending effect. Typical organic builders include sodium carboxymethyl cellulose, sequestering agents such as ethylenediaminetetraacetic acid and the fatty monoethanolamides, etc.

3. Special purpose additives These include solubilizing additives such as lower alcohols, glycols and glycol ethers, bleaches or brighteners of various structures which share in common that they are dyestuffs and they do not absorb or reflect light in the visible range of the spectrum.

D. Testing and Evaluation Procedures In order to accurately gauge the value of the solubilized dioxolanes as wetting, detergent and surfactant agents, carefully standardized procedures must be used.

1. Standard Launder-Ometer Test.

Ten standard wash solutions ranging in detergent content from 0.05 to 0.30 weight percent (they are 0.05, 0.10, 0.10, 0.10, 0.20, 0.20, 0.20, 0.30, 0.30, 0.30) and ten standard wash solutions ranging in sodium sulfate content from 0.075 to 0.70 weight percent (they are 0.075, 0.067, 0.15, 0.233, 0.133, 0.30, 0.466, 0.20, 0.45, 0.70) are prepared in 3,000 ppm hard water. The hard water was previously prepared by dissolving 26.43 grams of CaC1 .2H O in 600 ml of distilled water and mixing this solution with a solution of 29.58 grams of MgSO .7l-l O in 600 ml of distilled water and making up the admixed solutions to 10 liters with distilled water.

Standard soiled cloths containing the same amount of soil are placed in each solution and washed in a Launder-Ometer* for 10 minutes at 60 C. The cloths are removed from the wash solutions, rinsed, dried and the degree of whiteness measured by a Photovolt Reflectometer**. The data obtained are plotted and expressed as Average Detergency Coefficient. This term is derived by expressing the soil removal properties of the experimental detergent as a percentage of a known standard detergent at 0.25 weight percent concentration.

*The apparatus used is designated Model B-S. Type LHD-HT by its distributor, Atlas Electric Devices Co., Chicago 13, Ill. **Photovolt Reflectometer The apparatus used is the Photovolt Reflection Meter 670, Search Unit 6l0-W sold by Photovolt Corporation. New York City, NY.

2. Standard Foam Test This is the procedure described in ASTM procedure No. D1 173-53.

EXAMPLE 1 Preparation of An Ethoxylated Schiff Base in which R R C ,C with Neutralization of Final Product.

To a reaction vessel equipped with heating, cooling and stirring means and means of stripping of a water azeotrope, are added 25 parts by weight of ethanolamine, parts by weight to toluene and 37 parts by weight of an alkyl C C ketone mixture having an average molecular weight of 185. The ketone mixture contains about 20% by weight of methyl alkyl ketones (as determined by gas chromatographic analysis). The ketones are derived from the dehydrogenation of a C, C, secondary alcohol mixture at 200250 C. over copper chromite catalyst. The alcohol in turn is obtained from the boric acid-directed air oxidation of a C C normal paraffin.

The mixture of ketones, amine and toluene is refluxed for 2 hours while removing water of formation. Solvent and excess starting materials are removed by distillation leaving 33 parts by weight of Schiff base shown below with about 22% by weight of methyl alkyl ketone self-condensates.

wherein RCR C C To 50 parts by weight of the above Schiff base containing about 22% by weight of methyl alkyl ketone self-condensates is charged to an appropriate reaction flask and 0.5 parts of elemental sodium is dissolved in the solution. Ethylene oxide is passed into the reaction flask at atmospheric pressure at a flow rate of 0.25 g. per minute while maintaining the temperature between and C. After 2 hours 1.76 moles of ethylene oxide is added which amounts to about 8 moles of ethylene oxide on the Schiff base. At this time the addition of ethylene oxide is discontinued, and the ethoxylated product is neutralized with 2 parts by weight of concentrated hydrochloric acid, and the inorganic material is removed by filtration.

EXAMPLE 2 Preparation of Ethoxylated Schiff Base of Example 1 containing Self Condensation Products but without Neutralization of Final Product.

Utilizing the same quantity of materials and the identical preparative procedure, a 37 parts by weight portion of the C -C aliphatic ketone mixture (containing the same amount of methyl alkyl ketone as Example 1 and derived from the same source) is condensed with 25 parts by weight of ethanolamine to form the Schiff base of Example 1. The Schiff base is ethoxylated to the same extent using the procedure of Example 1, but in this instance the highly basic ethoxylation reaction mixture is not neutralized. The alkaline ethoxylated product has a good cotton detergency coefficient (168) when compared to a standard comparably ethoxylated oxo alcohol.

EXAMPLE 3A Preparation of Ethoxylated Schiff Base from which Methyl Alkyl Ketone Self-Condensation Contaminant Originally Present is Removed Prior to Ethoxylation.

A. Using the quantities, reactants and procedure of Example 1, Schiff base containing 22% by weight of methyl alkyl ketone self-condensation product as contaminant is prepared by condensing a mixture of C C aliphatic ketone, molecular weight 185, with cthanolamine in the presence of toluene. After refluxing 2 hours and stripping off toluene solvent the Schiff base of Example 1 is prepared containing 22% by weight of the total mixture as the methyl alkyl ketone selfcondensation products. This material is separated by vacuum distillation from the self-condensation products by collecting at 129141 C. under 1.6 mm of mercury pressure. yielding the purified Schiff base. This purified material is ethoxylated as in Example 1 in the presence of sodium until an average of 8 moles of ethylene oxide are substituted to the Schiff base molecule. The product is isolated without neutralization. The self-condensation products contained by analysis 3.7 wt.% nitrogen and had an average molecular wt. of 419.

EXAMPLE 38 Effect of Ethoxylation on Methyl Alkyl Ketone Selfcondensates.

B. The cut of methyl alkyl ketone self-condensation product from (A) is treated with ethylene oxide at a rate of 0.25 g of ethylene oxide in the presence of potassium hydroxide catalyst for 8 hours. At the end of this time, the volatiles are stripped off under vacuum and the methyl alkyl ketone self-condensation cut is examined for evidence of ethoxylation. IR and molecular weight analyses indicate that no ethoxylation has taken place. This appears to establish that under these ethoxylation conditions the methyl alkyl ketone selfcondensation contaminants are inert to ethoxylation.

EXAMPLE 4 Preparation of Ethoxylated Schiff Base free from Methyl Alkyl Ketone Self-Condensation Contaminant with Neutralization of Final Product.

The procedure of Example 3A is repeated except that the final (ethoxylated) product is neutralized with 2 parts by weight of concentrated hydrochloric acid and filtered.

EXAMPLE 5 Effect of Addition of Methyl Alkyl Ketone Self- Condensation Products with or without Neutralization on the Stability of Ethoxylated Schiff Base Derived from a Carbon having an Alkyl Radical of less than two Carbon Atoms.

1n this example, 340 parts by weight of reagent grade methyl nonyl ketone, 140 parts by weight of ethanolamine and 522 parts by weight of toluene are refluxed for 2 hours, removing water through the formation of the toluene-water azeotrope. The mixture is vacuum distilled to obtain parts by weight of the uncontaminated Schiff base boiling at l00122C at 0.22 mm pressure. The residuum or non-distillable material is methyl alkyl ketone self-condensate having an average molecular weight of 363 and containing 3.4 weight nitrogen. The distillate free from methyl alkyl ketone self-condensate is ethoxylated as in Example 1 to produce a Schiff base in which 8 moles of ethylene oxide are added to 1 mole of Schiff base.

The ethoxylated Schiff base, free from selfcondensate contaminant, is divided into 4 parts treated as follows: One sample (5A) is neutralized by the addition of concentrated hydrochloric acid. A second sample (5B) is left in the alkaline state. A third sample (5C) has sufficient residuum self-condensate added to it so that self-condensate content is 35% by weight but it is left in the alkaline state. The fourth sam' ple (5D) also has its self-condensate content adjusted to 35% by weight but is neutralized with concentrated hydrochloric acid.

As can be seen by the table which follows Example 6, neither the addition ofself-condensate" nor leaving the ethoxylated Schiff base in the alkaline (unneutralized) state substantially increases the stability of the ethoxylated product because the Schiff base is derived from a ketone in which one of the alkyl groups contains less than 2 carbon atoms.

EXAMPLE 6 TABLE 1 TlME 1N MlNUTES FOR DECOMPOSITION OF PRODUCTS PREPARED IN THE VARIOUS EXAMPLES pH PRODUCT FROM EXAMPLE 1 2 3A 4 5A 5B 5C 5D As the test results of the preceding table indicate, unneutralized ethoxylated Schiff base of Example 2, containing the requisite methyl alkyl self-condensate, is the most stable of all the products upon exposure to slightly acid to alkaline aqueous solutions. The neutralized product from Example 1, which contains the required self-condensate product, has the second best stability showing the advantage to be gained in leaving the ethoxylated Schiff base unneutralized in the highly alkaline state. The product of Example 3A, originally contained the desired amount of the self-condensate product, but had it removed prior to ethoxylation. This example demonstrates the value of the methyl alkyl ketone self-condensate to the final product. The product from Example 4 shows that while the stability of the neutralized, ethoxylated Schiff base derived from a suitable ketone which has had the desired selfcondensates removed prior to ethoxylation is relatively poor, the product has slightly better stability compared to samples from Example 5. The samples from Example 5 confirm that even when the desired self-condensates are present and the material is left in the alkaline state, if the Schiff base is derived from a methyl alkyl ketone the stability of the product is completely unsatisfactory.

EXAMPLE 7 Illustrative Detergent COmpositions ammonium bromide As the preceding specification indicates, the novel invention is advantageous and gives rise to unexpected results, particularly in reference to its compositional aspects. For example, the novel stabilized, alkoxylated products as illustrated by the ethoxylated Schiff bases, are superior surfactants and detergent components in an aqueous environment. This has been demonstrated by their superior detergency when compared to commercially utilized ethoxylated fatty alcohols of comparable molecular weight. In addition, the alkoxylated condensates are inexpensively prepared in relatively good yield, from readily available ketones, amines and the lower alkylene oxides. In addition, the light colored materials show a surprising stability in aqueous media at pH ranges from 6 to 13. That the ethoxylated condensates even require stabilization in alkaline aqueous media is most surprising in view of British Pat. No.

414,712 1944) which discloses the preparation of seemingly similar ethoxylated Schiff bases and their use as surfactants. Inasmuch as the British Patent teaches (col. 2, lines 55-68) that these solubilized Schiff bases are stable to hard (alkaline) water, it was unexpected to find:

1. that the compounds prepared as described in the British Patent are very unstable in the presence of water, and

2. that adjusting the methyl alkyl ketone selfcondensates present and/or an adjustment of the pH of the solution substantially increase the stability of these products to water.

As the specification including the several examples clearly establish, numerous changes. modifications and substitutions in materials, proportions and temperatures can be made without departing from the inventive concept. The true metes and bounds of the inventive concept are best determined from the claims which follow, taken in conjunction with the specification.

What is claimed is: i

l. A substantially water soluble or water dispersible surfactant mixture having good stability in aqueous solution in the pH range of about 5.6 to 13, consisting essentially of, as its surfactant component:

a. at least 0.1% by weight of said surfactant mixture as ethoxylated Schiff base of the structure:

N(CH CH 0) H wherein R and R are alkyl groups where each of said groups contain at least two carbon atoms, the sum of said alkyl groups totaling from 9 to 14 carbon atoms and n which represents the average degree of ethoxylation varies between 7 to 13, and

b. at least 0.002% by weight of the methyl alkyl ketone self-condensates obtained from the condensation of ethanolamine with ketonic dimers, said condensates having an average molecular weight of 350-450 and a nitrogen content of 34% by weight, the methyl alkyl ketone condensates being present in a concentration of at least 2% by weight and up to 35% by weight of the ethoxylated Schiff base condensates, the condensates being derived from the reaction of at least one methyl alkyl ketone containing l0 to 15 carbon atoms with ethanolamine, at temperatures ranging from 50C and up, said surfactant mixture having a pH in a 1% by weight aqueous solution of about 10 to 13.

2. The surfactant mixture of claim 1 wherein the R and R alkyl groups in said ethoxylated Schiff base are in the form of a mixture.

3. The surfactant mixture of claim 2 wherein the alkyl groups in the Schiff base mixture contain 10 to 12 carbon atoms.

4. The surfactant mixture of claim 1 wherein n the average degree of ethoxylation is about 8.

5. A process for substantially improving the stability of ethoxylated Schiff bases to the exposure of aqueous solutions in the pH range between about 5.6 to 13, said Schiff bases being of the structure wherein R and R are alkyl groups each group containing at least 2 carbon atoms, the sum of said alkyl groups totaling from 9 to 14 carbon atoms and n which represents the average degree of ethoxylation varies between 7 and 13, consisting essentially of adjusting the alkalinity of the Schiff bases whose stability in water is to be improved so that the pH of a 1% by weight aqueous solution of said bases will be between about to 13, and adjusting the content of methyl alkyl ketone selfcondensate in the Schiff bases to be between 2% by weight to 35% by weight, said self-condensate having an average molecular weight of 350-450, a nitrogen content of 3%4% by weight, the methyl alkyl-ketone self condensate being derived from heating a reaction mixture consisting essentially of inert solvent, ethanolamine and at least one methyl alkyl ketone containing 10 to carbon atoms, at temperatures ranging from 50C to the boiling point of the reaction mixture until the water of reaction resulting from the condensations of said ethanolamine and said methyl alkyl ketone is formed, and removing the water of reaction contained therein.

6. The process of claim 5 wherein the ethoxylated Schiff bases consist essentially of a mixture of Schiff bases wherein the sum of the R and R alkyl radicals total from about 9 to 14 carbon atoms and n is about 8.

7. A process for substantially improving the stability 'of ethoxylated Schiff bases to the exposure of aqueous solutions in the pH range between about 5.6 to 13, said Schiff bases being of the structure wherein R and R are alkyl groups each group containing at least 2 carbon atoms, the sum of said alkyl groups totaling from 9 to 14 carbon atoms and n which represents the average degree of ethoxylation varies between 7 and 13, said consisting essentially of first adjusting the content of the methyl alkyl ketone self-condensate of the Schiff base whose stability in water is to be improved to be between 2% by weight to 35% by weight,

'then adjusting the alkalinity of said Schiff bases so that the pH ofa 1% by weight aqueous solution of said bases will be between about 10 to l3,-self-condensate having an average molecular weight of 350-450, a nitrogen content of 3%4% by weight, said methyl alkyl ketone self-condensate being derived from heating a reaction mixture consisting essentially of inert solvent, ethanolamine and at least one methyl alkyl ketone containing 10 to 15 carbon atoms, at temperatures ranging from 50C to the boiling point of the reaction mixture until the water of reaction resulting from the condensation of said ethanolamine and said methyl alkyl ketone is formed, and removing the water of reaction contained therein.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CURRECTIUN PATENT NO. 3,8 7,362 DATED :July 29, 1975 V 0 1 David Ross McCoy it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Name of Assignee, Texaco Inc., New York, N.Y. should be printed on the patent.

Col. 6, line 32: "to" should read --of-- Col. 12, line 12: "said" should be deleted.

Col. 12, line 18, "said" should be inserted before --self-condensate-- Signed and Scaled this Y Sixteenth D y 0% November 1976 I [SEAL] Arrest."

RUTH C. MASON Arresting ()jfirer C. MARSHALL DANN Commissioner nfPalenls and Trademark DATED Name UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 13 897 362 July 29, 1975 David Ross McCoy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

of Assignee, Texaco Inc., New York, N..Y. should be printed on the patent.

6, line 32: "to" should read --of--=- 12, line 12: "said" should be deleted.

Signed and Sealed this Sixteenth D y of November 1976 A nes r:

RUTH C. MASON Allesling Officer C. MARSHALL DANN Commissioner uj'PaIenis and Trademarks

Claims

1. A SUBSTANTIALLY WATER SOLUBLE OR WATER DISPERSIBLE SURFACTANT MIXTURE HAVING GOOD STABILITY IN AQUEOUS SOLUTION IN THE PH RANGE OF ABOUT 5.6 TO 13, CONSISTING ESSENTIALLY OF, AS ITS SURFACTANT COMPONENT: A. AT LEAST 0.1% BY WEIGHT OF SAID SURFACTANT MIXTURE AS ETHOXYLATED SCHIFF BASE OFTHE STRUCTURE:

2. The surfactant mixture of claim 1 wherein the R and R'' alkyl groups in said ethoxylated Schiff base are in the form of a mixture.

5. A process for substantially improving the stability of ethoxylated Schiff bases to the exposure of aqueous solutions in the pH range between about 5.6 to 13, said Schiff bases being of the structure

6. The process of claim 5 wherein the ethoxylated Schiff bases consist essentially of a mixture of Schiff bases wherein the sum of the R and R'' alkyl radicals total from about 9 to 14 carbon atoms and n is about 8.

7. A process for substantially improving the stability of ethoxylated Schiff bases to the exposure of aqueous solutions in the pH range between about 5.6 to 13, said Schiff bases being of the structure

13.