US 3539518 A
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Patented Nov. 10, 1970 3,539,518 LOW FOAM SURFACTANTS George C. Feighner, Franklin Lakes, N.J., and Dean R. W e1mer, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Filed Feb. 21, 1968, Ser. No. 707,326 Int. Cl. Clld N66 US. Cl. 252-89 10 Claims ABSTRACT OF THE DISCLOSURE Low foam, nonionic surfactant compositions consisting essentially of lower (C straight chain acyl group capped alcohol ethoxylates. More specifically, the surfactant compositions consist essentially of an alkoxypolyethenoxycarboxylate compound of the general structural formula 0 Rr-o oH2oH2o d-R2 where R, is a C -C n-alkyl group attached to the oxygen atom through a primary or secondary carbon atom, n is a number from 5 to 25, inclusive, and R is selected from the group consisting of hydrogen and n-alkyl groups containing from 1 to 5 carbon atoms.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to nonionic surfactants having low foaming power, and thus benig useful in cleaning applications where excessive foam is undesirable.
Brief description of the prior art In some industrial and household cleaning operations, it is very desirable or necessary to maintain a low level of foam during the cleaning operation. For example, in the industrial field, conventional nonionic surfactants usually produce foaming to an extent rendering them unsuitable in spray metal cleaning formulations. In the household, conventional nonionic surfactants give too high a foam level for satisfactory use as the active ingredient in detergents and rinse aids for mechanical dishwashers. Excessive foam is objectionable here because it may cause overflow of the machine, and even moderate amounts of foam will interfere with proper rinsing. Low foaming can often be achieved by the addition of defoaming agents, but this approach generally does not give adequate wetting or detergency properties.
A type of nonionic surfactant which has been previously proposed includes the fatty acid esters of alcohol ethoxylates, which esters are produced by condensing ethylene oxide with detergent range alcohols, and then reacting such ethoxylated alcohols with fatty acids containing from 8 to 18 carbon atoms, or with the chlorides of such acids. Esters produced in this manner are described in US. Pat. 1,970,578 to Schoeller, issued Aug. 21, 1934, as possessing excellent wetting, foaming and cleansing powers. The Schoeller patent thus indicates that these C -C fatty acid derivatives are actually good foam producers, and thus provides no suggestion that they would have any utility whatsoever in a cleaning usage where suppression of foam is important. Further than this, I have determined that the fatty acid capped alcohol ethoxylates described by Schoeller are of low water solubilitya characteristic which effectively prevents their being practical for use in applications where an aqueous solution of the surfactant is required, and specifically, in the dishwashing and industrial metal cleaning operations described.
OBJECTS OF THE INVENTION The present invention has as its basic objective, the provision of new low foam, nonionic, surfactant compositions. Subsidiary to this basic objective, further objectives of the invention are to demonstrate:
(a) That these compositions produce relatively low foam over a wide temperature range, and compare well in this respect with presently used, commercially available, 10W foam nonionic surfactants;
(b) That these compositions compare well with commercially available, low foam, noninic surfactants in wetting characteristics; and
(c) That the alkoxypolyethenoxycarboxylate compounds constituting the active surfactant compounds used in the compositions are characterized by relatively high water solubility, and have better cloud point properties than similar carboxylates derived from higher molecular weight carboxylic acids, and also commercially available nonionic, how foam, surfactants.
SUMMARY OF THE INVENTION The present invention is broadly directed to new surfactant cleaning compositions, and more specifically, to surfactant compositions consisting essentially of water and acyl group capped alcohol ethoxylates of the structural formula where R, is a C -C n-alkyl group bonded to the oxygen atom through a primary or secondary carbon atom, n is a number from 5 to 25, inclusive, and R is selected from the group consisting of hydrogen and n-alkyl groups containing from 1 to 5 carbon atoms.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The acyl group capped alcohol ethoxylates of the invention which have the structural Formula (1) set out above are prepared by initially reacting primary or secondary monohydric n-alkanols with ethylene oxide in the presence of an acidic or basic catalyst. Catalysts suitable for this reaction are well known in the art and include, for example, alkali metal oxides and hydroxides, boron trifluoride, stannic chloride and sulfuric acid. Preferably, a basic catalyst is used in this ethoxylation reaction, and most referably, from about 0.1 to about 0.3 weight percent of NaOH is utilized, based on the weight of the alcohol. The ethoxylation reaction is carried out under anhydrous conditions to avoid formation of by-products, and at a temperature which is preferably in the range of from about 310 C. to about 390 C. The reaction may be carried out at substantially atmospheric pressure, although it is preferably carried out in an autoclave at pressures of from about 10 p.s.i.g, to about p.s.i.g. The amount of ethylene oxide introduced to the reaction zone, and the duration of reaction time, determines the number of moles of ethylene oxide added to the alcohol.
The alcohol ethoxylates can be capped with a suitable acyl group by reacting them with C -C straight chain alkanoic acids, or with the acyl halides or the anhydrides of such acids. Suitable acids include formic, acetic, propanoic, butyric, pentanoic, and hexanoic acids, and typical halides and anhydrides include acetyl chloride and acetic anhydride. A conventional esterification reaction of the acid, or acid derivative with the alcohol ethoxylate is carried out.
As previously indicated, the alkyl group (R in the structural Formula 1 contains from four to twenty carbon atoms, and is thus derived from alcohols ranging from n-butanol to n-eicosanol. Preferably, the alkyl group of the capped ethoxylate contains from 8 to 16 carbon atoms, and most desirably from 8 to 12 carbon atoms, depending, however, to some extent, upon the character of the remaining portion of the molecule as hereinafter explained. The surfactant compositions of the invention may very conveniently contain a mixture of acyl group capped ethoxylates derived from the ethoxylation of mixtures of C to C n-alkanols of even carbon number, since alcohol mixtures of this type are readily available starting materials.
The number of moles (designated n in the structural formula) of ethylene oxide which are incorporated in the alkoxypolyethenoxycarboxylate compounds during ethoxylation can range from to 25, but is preferably from about 5 to about 12, and most desirably from about 5 to about 10. In order to achieve the requisite degree of water solubility in the surfactant compounds, the carboxyl group of the compound should contain from 1 to 6 carbon atoms and preferably contains from 2 to 4 carbon atoms.
The overall molecular structure which is most suitable for the capped ethoxylate compounds of the invention is dictated by the interaction of the several functional groups in the molecule, and the effect of each group on such properties as water solubility, foaming characteristics, product color and biodegradability. With respect to water solubility, it is desirable that a 1 weight percent aqueous solution of the acyl group capped ethoxylates have a cloud point of at least 75 F., and most perferably 100 F., with a higher cloud point being indicative of greater solubility. Lengthening of the alcohol chain (in structural Formula 1, the R group) decreases water solubility whereas increasing the number of ethenoxy groups in the molecule increases solubility. Increasing the chain length of the carboxylic acid used in the esterification reaction so that the group R in the structural formula contains more carbon atoms also has the effect of decreasing solubility. Increasing the number of carbon atoms in the R alkyl group derived from the alcohol also has the effect or increasing the foam developed or sustained by the surfactant, whereas an increase in the number of incorporated ethenoxy groups to much above 12 groups tends to lessen the biodegradability of the compounds.
Considering these criteria, an optimum balance of water solubility, low foaming, and biodegradability properties is attained in capped ethoxylate compounds in which the R n-alkyl group contains from 8 to 12 carbon atoms, from 6 to ethenoxy groups (55 to 65 weight percent) are included, and the R group contains from 1 to 3 carbon atoms (that is, it is derived from acetic, propanoic or butyric acid). An increase in the number of carbon atoms in either R or R is preferably accompanied by an increase in the number of ethenoxy groups in the molecule.
EXAMPLE 1 In order to provide a more complete appreciation of the product evaluation test data hereinafter appearing, the manner in which the tested compounds were prepared will be described. An alcohol mixture containing 85 weight percent normal l-decanol, about 8.3 weight percent normal l-dodecanol, and about 6.7 weight percent normal l-tetradecanol was ethoxylated in the manner hereinbefore described, using a sodium hydroxide catalyst. A product was yielded which contained about 60 weight percent ethylene oxide (an average value of 5.7 moles of ethylene oxide per mole of alcohol). The sodium hydroxide catalyst was then neutralized with glacial acetic acid, and the ethoxylated alcohols isolated.
196.4 grams (0.5 mole) of the mixture of ethoxylated alcohols prepared in the manner described in the preceding paragraph were then charged to a 3-necked, creased flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. 39.2 grams /2 mole) of acetyl chloride were charged to the dropping funnel. The acetyl chloride was dripped into the ethoxylate, maintaining a maximum temperature in the flask of 45 C. After the acetyl chloride addition, the product was poststirred and blown with nitrogen for 25 minutes to remove the residual hydrogen chloride. The product ester was a cloudy, viscous liquid with a melting point below 36 F.
The following examples demonstration the properties of the acyl capped ethoxylates which make them excellent surfactants for incorporation in compositions used for cleaning applications which require minimum foam, good water solubility and good wetting ability.
EXAMPLE 2 The product made in Example 1 was evaluated for foam properties in a Hamilton Beach mixer test, conventionally used in the art to evaluate surfactant foam characteristics. For purposes of comparison, several commercially available, widely used, low foam, nonionic surfactants were subjected to the same malt mixer foam test. 200 ml. of a 0.1 weight percent aqueous solution of the surfactants to be tested were placed in a 1000 ml. tall form beaker, and the solution subjected to high speed stirring for three minutes. The tested solution was then allowed to settle for two minutes, and the height of the foam was then measured. The tests were run at temperatures of F. and 140 F. The results of the tests are shown in Table I.
TABLE I Foam height at- 75 F., 140 F., Surfactant in cm. in cm.
Example 1 product 1. 2 0. 5 Commercial product A 1.0 0, 6 Commercial product B 2 2. 7 0.8
l A chlorine capped ethoxylated n-decanol containing 73 weight percent ethylene oxide.
2 A chlorine capped ethoxylated n-decanol containing Weight percent ethylene Oxide.
The data in Table I show that the surfactant product of Example 1 compares favorably with the commercial, low foam, nonionic surfactants tested. In the Hamilton Beach test, foam heights of less than 5 cm. are considered low.
EXAMPLE 3 The product prepared in Example 1 was subjected to a cotton skein wetting test to obtain the 25 second wetting concentration, and the wetting time required to wet he skein to a 0.1 percent concentration. Data on one commercially available, low foam, nonionic surfactant is included for purposes of comparison. The results obtained are set forth in Table II.
TABLE II 25 second wetting Wetting concentime tration, to 0.1%, Surfactant percent sec.
Example 1 product 0. 063 9. 8 Commercial product A from Example 2 0. 068 12. 3
The data appearing in Table II show that the product made in Example 1 is a better wetting agent than the low foaming, nonionic, commercially available surfactant compared therewith.
EXAMPLE 4 ing capped ethoxylates were then evaluated for water solubility by preparing 1 percent aqueous solutions of each of the products, and running cloud point tests upon each of the aqueous solutions. The results of the cloud point tests are set forth in Table III.
TABLE III Cloud point of Surfactant: 1% solution, F. Acetyl capped ethoxylate 137 Butyryl capped ethoxylate 81 Octanoyl capped ethoxylate 34 The solubility evaluation of the three products showed, as evidenced by the data in Table III, that the octanoyl capped ethoxylate had very poor solubility and thus would be undesirable for use as a low foam, nonionic employed in aqueous solutions. The acetyl capped ethoxylate, on the other hand, demonstrated excellent water solubility.
Although certain preferred embodiments of the invention have been herein described and illustrated by example, various departures from the specific uses mentioned, and compound structures described, may be effected without a consequent departure from the basic principles of the invention. Changes and innovations of this type are therefore deemed to be within the spirit and scope of the invention except as they may necessarily be excluded therefrom by the appended claims or reasonable equivalents thereof.
What is claimed is:
1. A low foam, nonionic, surfactant composition consisting essentially of an acyl group capped alcohol ethoxylate having the structural formula where R is a C -C n-alkyl group attached to the oxygen atom through a primary or secondary carbon atom, n is a number from 5 to 25, inclusive, and R is selected from the class consisting of hydrogen and n-alkyl groups containing from 1 to 5 carbon atoms.
2. A low foam, nonionic, surfactant composition as defined in claim 1 wherein said composition contains an aqueous solution of said capped ethoxylates.
3. A low foam, nonionic, surfactant composition as defined in claim 1 wherein the capped ethoxylates in said composition are characterized in having a water solubility such that a 1 Weight percent aqueous solution of each of said capped ethoxylates has a cloud point of at least F.
4. A low foam, nonionic, surfactant composition as defined in claim 2 wherein said composition consists essentially of a plurality of said capped ethoxylates, and wherein R contains from 8 to 16 carbon atoms.
5. A low foam, nonionic, surfactant composition as defined in claim 2 wherein R contains 1 to 3 carbon atoms.
6. A low foam, nonionic, surfactant as defined in claim 2 wherein n is not greater than 12.
7. A low foam, nonionic, surfactant composition as defined in claim 4 wherein R contains from 8 to 12 carbon atoms,
8. A low foam, nonionic, surfactant composition as defined in claim 7 wherein R contains from 1 to 3 carbon atoms,
9. A low foam, nonionic, surfactant composition as defined in claim 8 wherein n is a number from about 6 to about 10.
10. A low foam, nonionic, surfactant composition as defined in claim 7 wherein n is a number from about 6 to about 10.
References Cited UNITED STATES PATENTS 5/1938 Graves. 5/1963 Guest et al.
US. Cl. X.R. 260488, 496