US2846402A

US2846402A - Alkyl sulfate detergent compositions

Info

Publication number: US2846402A
Authority: US
Publication date: 1958-08-05
Anticipated expiration: 1975-08-05

Description

United States Patent C ALKYL SULFATE DETERGENT COMPOSITIONS Henry Y. Lew, San Francisco, Calif., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application December 28, 1953 Serial No.- 400,765

4 Claims. (Cl. 252-152) The present invention relates to anionic synthetic detergent compositions. More particularly, it applies to detergent compositions, which contain an alkyl sulfate as their active organic detergent ingredient and which are capable of producing dense, stable and persistent foams when dissolved in water to form conventional household or commercial laundering solutions.

Small scale users of synthetic anionic detergents prefer that the detergent products be capable of producing substantial lather or foam when used in dilute aqueous solutions, and that this foam be persistent (maintain its volume) throughout the washing process.

A number of otherwise efficient synthetic anionic detergents, and, in particular, those of the alkyl sulfate and alkylbenzene sulfonate type, when employed to form dilute aqueous solutions for washing purpose in the house and in commercial laundries, produce an unstable foam having a lacy texture, as contrasted to the small-sized bubbles and dense cream-like consistency of conventional soapsuds. Moreover, in the presence of soil and under conditions of agitation in a washing machine, the foam of these detergents lacks the desired persistence, and rapidly collapses and disappears before the completion of the washing operation.

The various additives suggested in the art for the purpose of improving the foam characteristics of the aforementioned alkyl sulfate detergents, for instance, C C saturated aliphatic alcohols, are often found to be incapable of insuring formation of persistent foam without impairing at the same time the detergency of the composition, or without adversely affecting some other properties thereof. Thus, while the addition of lauryl alcohol improves the sudsing preformance, a fatty odor is imparted by the presence of this alcohol to the finished dried detergent particles and, furthermore, a considerable proportion of the alcohol additive is lost in spray-drying 'of the neutralized slurries of alkyl sulfates to the desired particle-form. Likewise, it is known that certain alkylolamides of lauric acid, e. g., lauric isopropanolamide and lauric ethanolamide, upon being added to alkyl sulfates derived from coconut oil C -C fatty acids, improve the foam persistence of corresponding aqueous wash solutions; however, the foam heights and the static foam stability achieved by the use of these additives, are definitely inadequate.

I have found that by adding to an alkyl sulfate containing from '8 to 18 carbon atoms in the alkyl chain from 3 to 75% by weight thereof of a monoalkylolamide of a saturated fatty acid, in which the alkylol portion contains 2 to 3 carbon atoms and the fatty acid portion contains 16 to 18 carbon atoms, a detergent com-' position having improved foam characteristics is obtained. Such a detergent composition, when employed to make up dilute aqueous solutions or baths for washing purposes, produces foams of excellent quality, adequate volume and good static stability. The foam of these compositions possesses a remarkable degree of persistence under agitation in the presence of soil in the wash solutions.

tub or bowl of a washing machine. For all practical purposes an addition of from 20 to 30% of the aforementioned fatty acid monoalkylolamides, based on the weight of alkyl sulfate, secures the desirable foam properties atconventional concentrations of the detergent composition, namely, from 0.1 to 0.4%, in the aqueous Any of the C C alkylolamides of the C C saturated fatty acids can be employed to obtain the desired improvement of foam, properties, for instance, C -C monoalkylolamides of palmitic acid and C -C monoalkylolamides of mixtures of G -C fatty acids known in the market under the name of pressed stearic acid and containing 67% by weight of palmitic, 29% by weight of stearic and 4% by weight of oleic acid. Palrnitic ethanolamide is found to be particularly effective as an additive for the improvement of foam characteristics.

Salts of alkyl sulfuric acids suitable for the preparation of the detergent compositions of my invention include water-soluble salts of straight-chain alkyl sulfuric acids, ,H-hydroxyalkyl sulfuric acids and 'y-hydroxyalkyl sulfuric acids which contain from 8 to 18 carbon atoms in the hydrophobic alkyl group and in which the hydrophilic group occupies the terminal position on the carbon chain. These salts include among their number sodium, potassium, magnesium, ammonium, alkyl ammonium and alkylol ammonium salts. As a practical matter, however, sodium salts of C -C straight-chain alkyl sulfuric acids (sodium C -C n-aliphatic alcohol sulfates) are usually employed. These C -C alkyl sulfates may be prepared by any known suitable method, e. g., by any of the methods of sulfation of aliphatic alcohols described at pages 53 to 58 of the book Surface-Active Agents, by A. M. Schwartz and I. W. Perry (I'nterscience Publishers, 1949, New York), followed by neutralization of the resulting C C alkyl sulfuric acids to the corresponding water-soluble salts.

The fatty acid alkylolamide additive responsible for the improvement of foam properties may be prepared by any of the known methods of the art, e. g., by reacting. an ester of a suitable O -C saturated fatty acid with a C -C alkylolamine; or by reacting the fatty acid directly with the alkylolamine and heating the resulting amine salt; or by reacting a fatty acid chloride with an excess of alkylolamine; or yet by reacting the fatty acid chloride with a stoichiometrical amount of the alkylolamine, but in the presence of a suitable base such as sodium hydroxide or pyridine to neutralize the hydrogen chloride being formed. Pure fatty acids, such as palimitic, or,

stearic, as well as hydrogenated tallow fatty acids and their esters and chlorides, may be thus employed. The C -C alkylolamides of palmitic acid, and particularly palmitic ethanolamide, represent the most effective additives for the improvement of foam characteristics in accordance with my invention.

It is noted, however, that the addition of a C -C alkylolamide of a O -C saturated fatty acid, such as palmitic ethanolamide, to the compositions having as their active detergent component a C -C alkyl sulfate which may have been derived from hydrogenated fatty acids of tallow, cottonseed oil, soybean oil, and other. similar organic fatty materials, fails to secure an adequate foam height and foam volume, and, consequently, does not result in the formation of a persistent foam under conditions of agitation.

I found that by replacing up to by weight of the active alkyl sulfate in a detergent composition containing a C -C alkylolamide of a C -C saturated fatty acid in accordance with my invention with detergent 0 -0 monoalkyl benzene sulfonates, good foam stability, qnality and persistence are obtained not only where the alkyl sulfate component is derived from the lower molecular weight C -C hydrogenated coconut oil fatty acids, but also where the alkyl sulfate component is derived from the higher molecular weight hydrogenated tallow fatty acids, or the like. Notwithstanding the presence of up to 85% by weight of C -C alkyl benzene sulfonate, the foam of the wash solutions of the aforementioned detergent composition attains adequate heights, has good stability and quality and is persistent, even though the wash solutions are made up with hard water (300 p. p. m. Ca-Mghardness).

' Considering the fluctuating prices of the coconut oil, which tend to increase excessively the cost of alkyl sulfate detergents derived therefrom, the discovery that C -C alkyl sulfates derived from tallow, a much cheaper and readily available raw material, may be employed in combination with the inexpensive Cg-C1 alkyl benzene sulfonates to satisfy the washing needs of the housewife and of the commercial laundry operator constitutes an important-advance in the detergent art.

The terms C -C alkyl sulfate and C -C monoalkyl benzene sulfonate, as employed in this specification to describe detergent compositions containing a mixed active organic component, designate in accordance with the established usage of the detergent art, water-soluble salts of C C alkyl sulfuric acids and C9-C18 monoalkyl benzene sulfonic acids, respectively, Because of their lesser cost and availability, sodium salts of the aforementioned organic sulfuric and sulfonic acids are usually employed, although water-soluble salts other than those of sodium may be employed whenever required by the particular washing or cleaning application.

The water-soluble salts of monoalkyl benzene sulfonic acids, employed in the preparation of the detergent compositions of my invention, are those containing from 9 to 18 carbon atoms, and preferably from 12 to 15 carbon atoms, in the alkyl chain. These salts are prepared by any of the several methods disclosed in the art, e. g., by starting with the condensation of propylene polymers and benzene as shown in U. S. Patent No. 2,477,383, issued to A. H. Lewis, or with the chlorination of a kerosene fraction boiling from 205 to 245 (3., followed by the reaction of the resulting keryl chloride with benzene as shown in the U. S. patent issued to Kyrides. The resulting alkyl benzene stock produced by either technique is then sulfonated, and the sulfonic acid in the sulfonation reaction mixture is separated from the unreacted sulfuric acid and neutralized. Thereupon, the neutralized slurry may be reduced to the particle form by conventional drying techniques (spray-drying or drum-drying). When aqueous solutions of detergent compositions containing detergent -0 alkyl sulfates or a mixture of detergent C -C alkyl sulfates and C C monoalkyl benzene sulfonates in weight ratios ranging from 1:1 to 1:6, and, furthermore, containing from about 3 to about 75% by weight of an alkylolamide of a C -C fatty acid, in which the alkylol portion contains from 2 to 3 carbon atoms (based on the weight of the C -C alkyl sulfate), are employed to wash fabrics in dilute concentrations in water (from 0.1 to 0.4%), in accordance with the conventional laundering practice, they produce a rich cream-like foam of densely agglomerated small bubbles. This foam retains its stability for relatively long periods of time, both under static conditions and under conditions of agitation in the presence of soil in the washing machine throughout the length of the washing cycle, i. e., as long as 20 minutes and frequently longer. Furthermore, the detergency of the wash solutions containing these improved detergent compositions is not adversely affected by the presence of the foam-improving alkylolamide additive.

It is well known that the detergent action of alkyl aryl sulfonates and alkyl sulfates is generally improved by the addition of water-soluble inorganic electrolyte salts or builders. These detergency builders added to detergent compositions exert a number of beneficial effects on the properties and actions of the detergent composition. For instance, they neutralize the acid soil, deflocculate (suspend) the soil and prevent its redeposition, sequester magnesium and calcium ions from hard water, aid micelle formation, etc. Whatever be the particular effect of a specific detergent builder on the properties of alkyl benzene sulfonates and alkyl sulfates i-n detergent compositions, all builders contribute to enhance the over-all washing efliciency of detergent compositions.

I have found that the presence of water-soluble, alkaline, electrolyte salts of weak inorganic acids, e. g., carbonates, silicates, phosphates and borates, and of watersoluble, neutral, electrolyte salts of strong inorganic acids, e. g., sulfates and chlorides, as detergent (detergency) builders in the aforedescribed mixtures of alkyl sulfates and alkyl benzene sulfonates, in amounts ranging fiom 60 to 90% by weight of the total solids in a particular detergent composition, does in no way interfere with the improvement in foam characteristics thereof, brought about by the introduction of a C -C alkylolamide of a Gig-C13 saturated fatty acid in accordance with my invention. Although any of the water-soluble alkaline and neutral inorganic electrolyte salt builders may be used in the detergent formulations prepared in accordance with the present invention, inorganic sodium salt builders are usually employed, particularly in view of the general preference due to economic reasons for sodium salts of alkyl sulfuric and alkyl benzene sulfonic acids as active components of detergent formulations. These inorganic sodium salt detergent builders for alkyl sulfates and alkyl benzene sulfonates include sodium sulfate, sodium carbonates, sodium silicates, sodium polyphosphates, sodium pyrophosphates, borax, sodium chloride, etc.

The additives other than the detergent builders coma prise various compatible anti-caking compounds, optical bleaches, perfume, coloring agents (if required) and skin emollients such as various N-alkyl glycines and diglycines. Sodium carboxymethyl cellulose and sodium celluronates may be also employed and act not only as extenders,

but also exert a marked action in preventing redeposition of the soil. These various additives are employed in amounts readily determinable by those skilled in the art to suit the requirements of each particular application without interference with the improvement of foam characteristics, brought about by the introduction of the alkylolamide additive. Usually they constitute not more than 5% of the total weight of solids in the final detergent formulation.

Whether the detergent compositions of my invention are to contain only the C -C alkyl sulfates as the detergent ingredient or the alkyl sulfates are to be used with an admixture of (l -C monoalkyl benzene sulfonates, it is preferred to prepare these compositions by blending (mixing) the active ingredients with the alkylolamide foam-improving additive, detergent builders and other additives in the solution or slurry stage, and then to dry the resulting mixture. When aliphatic alcohols derived from hydrogenated tallow c c fatty acids are available for the production of the alkyl sulfate detergent ingredient of mixed alkyl sulfate-alkyl benzene sulfonate detergent compositions of my invention, it is preferred to sulfonate a suitable alkyl benzene stock with an excess of concentrated (98100 sulfuric acid, or

Y 22% oleum, and then to add molten or flaked aliphatic alcohols derived from C C tallow fatty acids into the 'sulfonation reaction mixture to produce the desired alkyl sulfuric acid. Details of sulfonation of alkyl benzene stocks are described in the bulletin entitled Alkane- Product and Processingv Information, published by Oronite Chemical Company of San Francisco, California, in 1950. In all events, the quantity of the sulfonating agent'required for the preparation of a particular mixture of alkyl benzene sulfonic and alkyl sulfuric acid is governed by the desired weight ratio of detergent alkyl sulfate to alkyl benzene sulfonate in the ultimate neutral ized product. The mixture of alkyl benzene sulfonic and alkyl sulfuric acids is neutralized with aqueous NaOH, Na CO or other suitable neutralizing agent. The resulting neutralized slurry is then blended with the alkylolamide foam-improving additive, detergent builders and other additives, and the blend is dried to the desired solid-particle form and size.

In introducing the alkylolamide foam-improving additive such as palmitic ethanolamide into the aqueous slurry of neutralized alkyl sulfuric and alkyl benzene sulfonic acids, it may be necessary to dissolve the alkylolamide in some ethanol or isopropanol to insure a uniform distribution of the additive within the slurry. The introduction of the alkylolamide additive is effected simultaneously with the blending of the detergent builders and other additives with the neutralized slurry of alkyl sulfates and alkyl benzene sulfonates. After spray-drying or drum-drying of the slurry, the product contains all ingredients uniformly distributed within each solid particle.

If desired, instead of drying the slurry to the dry particle-form, it may be processed into a paste, or, yet, it may be diluted to form a salable liquid concentrate.

A number of foam-evaluation bench tests were carried out in the laboratory, employing dilute aqueous solutions of dried particulate detergent formulations prepared in accordance with the invention in concentrations ranging from 0.1 to 0.4%. In a particular representative test series, each 100 parts by weight of the built detergent formulation employed for making up test solutions contained in its active organic portion a total of from 20 to 22 parts by Weight of a composition consisting of detergent sodium alkyl sulfate and sodium monoalkyl benzene sulfonate, including the alkylolamide foam-improving additive. The weight ratio of the alkyl sulfate component to the monoalkyl benzene sulfonate component ranged from 1:1 to 1:6, the foam-improving alkylolarnide additive was present in amounts from 1 to 3 parts by weight in each 22 parts of the organic active component. The sodium alkyl sulfate component for these tests was prepared by neutralizing sulfated fatty alcohols derived from hydrogenated tallow fatty acids by conventional reduction procedures. The alkyl chains in these organic sulfates contain from 14 to 18 carbon atoms, the major proportion (65-70%) being C alkyl sulfates.

The sodium monoalkyl benzene sulfonate component for the tests was prepared by alkylating benzene with a mixture of pentamers and tetramers of propylene, sulfonating the resulting C -C monoalkyl benzene product and neutralizing in accordance with the aforementioned disclosure of U. S. Patent 2,477,383. Various alkylolamides of fatty acids were employed in combination with the detergent organic sulfates and sulfonates in order to observe the effects of these additives on foam properties.

Detergent builders were present in the following amounts: 30 parts by weight of sodium tripolyphosphate; 20 parts by weight of tetrasodium pyrophosphate; parts by weight of liquid sodium silicate (known as N grade in the trade and characterized by a soda to silica ratio of 123.2); the remainder of the builder portion of the composition being tested was essentially sodium sulfate.

The solid particle-form detergent formulations were dissolved in soft water (50 p. p. m. of Ca-Mg hardness) at 120 F. to make up 500 ml. of 0.15% solution in a 2-liter beaker. The test solutions were agitated with the aid of a propeller-type stirrer for 1 minute and then allowed to stand for 1 minute, whereupon foam heights in millimeters were measured. minutes after the agitation was terminated, the foam heights were measured again and the stability and quality of the foam were ascertained. Foam stability was rated by observing the rate of foam decay under mechanical stress, as by blowing on a small volume of foam gently with air. In the case of unstable foam this procedure resulted in a rapid collapse of foam'bubbles. Quality of the foam,fi. e, the size of its bubbles, and the feel or the body thereof, was also observed and rated. Foam of Good quality have uniformly small-sized bubbles and a high bulk viscosity. They are white and opaque. Poor quality is manifested by uniformly large-sized foam bubbles, a low bulk viscosity, and a tendency towards laciness. These foams are more transparent and gray in color. Ratings of Fair were assigned to foams of intermediate stability and quality.

A parallel series of Washing machine test runs, using the same dilute aqueous solutions of detergent formulations as employed in the bench tests, was carried out to ascertain persistence of the foam under the conditions of operation, prevailing in the commonly used non-automatic agitator-type domestic washing machines. After adding to the bowl of the machine a quantity of the wash solution, normally required for the operation, a load of soiled cotton towels was placed in the bowl of the machine. The contents were agitated in each test run under substantially identical conditions of operation and temperature, approximating the conditions and temperature of the regular laundering practice. The foam was observed at regular intervals and its persistence was rated as follows:

When the sud-s disappeared in less than 5 minutes after starting the operation of the washing machine, the foam persistence was given a rating of 1. When the suds disappeared in an interval of time equal from 5 to 10 minutes, the foam persistence was assigned a rating of 2. When the suds disappeared in a period of time from 10 to 20 minutes, its persistence was assigned a rating of 3. Whenever the suds lasted 20 minutes under the conditions of agitation, but the height of the suds on the surface of the liquid in the bowl of the machine was lower than 1 inch, a rating of 4 was assigned to the foam persistence. When, after 20 minutes of operation, the height of the suds above the surface of the liquid was from 1 to 3 inches, a rating of 5 was assigned to the foam persistence. A rating of 6 was given to the persistence of the suds which stayed at a height of 3 to 6 inches after 20 minutes of operation. Finally, a maximum rating of 7 was assigned to the persistence of studs which remained higher than 6 inches above the surface of the liquid after 20 minutes of operation.

Thetable presented hereinafter, contains results of the aforedescribed series of test runs, illustrating the advantages attained by the employment of the improved detergent formulations of the present invention.

The results shown in the table clearly point out that foam persistence is improved by the presence of a C -C alkylolamide of a C C saturated fatty acid. The foam of solutions, formed with hard water (300 p. p. m., Ca-Mg hardness) and containing a detergent composition, the organic active component whereof consisted of a mixture of an alkyl sulfate detergent derived from hydrogenated tallow fatty acid and a monoalkyl benzene sulfonate detergent is more persistent in the presence of the alkylolamide additive (runs #1, 2 and 7) than the foams of similar hard water solutions containing either the alkyl sulfate alone (run #18) or the alkyl benzene sulfonate alone (run #5), both notoriously deficient (runs #19 and 20) as regards foam persistence. The results of the bench tests show that the C C alkylolamides of C -C saturated fatty acids, and, in particular, palmitic ethanolamide, improve foam heights, foam stability and foam quality, whereas alkylolamides of lower molecular weight fatty acids, e. g., of lauric acid, are incapable of Y promoting the formation of stable, good-quality foam.

7 whidhresembles that of the foams ofthe better fatty acid soaps. They-are light in color, made up of small-sized bubbles agglomerated to a cream-likeconsistency and impart to thehands the same creamy,-dense-bodied feeling -8 are normally present in sulfated alcohol compositions, does' not adversely affect the performance improvement achieved by the alkylola mides employedsin the detergent compositions of my invention. I

It is to be understood that the aforegiven description as the conventional soap suds familiar to housewives. o

* Bench Tests Parts by Foam Persistence in whet Parts by Washing Machine Run hydrowt. of Parts by Foam Height Tests genated alkyl Additive Wt.'of inmin. tallow benzene additive Foam Foam alkyl sulfonate Stability Quality sulfate After After 1 Soft Hard 1 min. 15 min. Water Water 10 10 Palmitio ethanolamide 2 84 70 1o 10 -..-.do 1 s 67 1'0- 10 a so 74 5. 15 2 87 77 o 20 2 7s 50 10 10 Palmitie n-propanolamide-.- 2 82' 65. 10 10 Hydrogenated tallow fatty.-- 2 68 58 acid ethanolamide. -10 to d 1 72 62 15 2 78 e5 '0 17 2 s5 12 1O Stearic dlethanolamide 2 60 15 5 15 Stearie isopropanolamide.-.. 1 83 68 10 10 Laurie ethanolamide..- 2 83 41 10 10 Laurie n-propauolamid 2 81 33 10 1O Lauricisopropanolamide. 2 82 43 10 10 Laurie diethanolamide. 2 70 24 10 10 None 0 as 17 20 0 Palmitle ethanolamide 2 60 48 20 0 None 0 28 8 d 0 20 ..do 0 85 75 do.- Poor.... 1 10 10 Ethanolamide of pressed 1 '2 85 64 Good... Good... 7

stearic acid."

An important advantage of the alkylolamide additives and examples are only illustrative of the invention, and of any invention, as exemplified by palmitic ethanolamide that any modification thereof consistent with its spirit and resides in the low volatility and a very low odor as comscope areto be included in the terms of the following pared with lauryl alcohol and other similar foam-improvclaims. ing additives. Detergency of the wash solutions conta-in- I claim: I ing the improved detergent compositions of my inven- 1. A detergent composition consisting essentially, by tion, particularly the removal of soil from cotton fabrics weight, of a normal aliphatic alcohol sulfate detergent soiled with an oily vsoil, favorably compares with the derived from hydrogenated tallow fatty acids predominatdetergency of good-quality domestic laundry fatty acid 40 ing in C n-alkyl sulfate, about 1 to 6 parts per part of soaps. sulfate detergent of C C monoalkyl benzene sulfonate 'In another series of test runs, sodium alkyl sulfate obdetergent, and, as a foam-improving agent, about 3 to tained by sulfating aliphatic alcohols derived from hydro- 75%, based on the sulfate detergent, of a C C; monogenated cocoanu-t oil fatty acids was employed as the alkylolamide of a c -c saturated fatty acid. essential active organic constituent of the detergent for- 2. A detergent composition according to claim '1 mulations containing the C -C alkylolamides of wherein the sulfate and sulfonate detergents are sodium C -C saturated fatty acids in accordance with the insulfate and sodium sulfonate detergents. vention. The foam performance (foam quality, stability 3. A detergent composition according to claim 1 in and persistence) and the detergency observed in these which the C n-alkyl sulfate is present in an amount series of test runs were substantially the same as those from about to 7 observed in test runs Nos. 1, 2 and 3.of the foregoing 4. A built detergent composition consisting essentially table. of 10 to 40%, by weight, of the detergent composition It may be mentioned, in addition, that alkyl'olamides defined in claim 1 and 60 to of essentially watercommonly employed in the art as foam promoters and soluble inorganic electrolyte salt builders. stabilizers, e. g., lauric isopropanolamide or lauric ethanol- 55 amide, may be employed, if desired, in the detergent References Clted the file of thls P119311t compositions prepared in accordance with my invention. UNITED STATES PATENTS Their presence enhances the soil tolerance without inter- 2,342,562 Tucker Fab. 22, 1944 fering in any way With the beneficial efffiCts 0f the C -C 2 333 737 i h d A 2 1945 .alkylolarnides of C C saturated fatty acids on foam 60 2 477 3 3 Lewis July 2 1.949 characteristics of the dishwashing and laundering so-lu- 2,519,052 i k 1 15, 0 tions prepared by using these concentrates. Also, the 2,733,214 vitale Jan, 31, 1956 presence of small amounts of unsulfated alcohols, which 2,757,143 Katzman July 31, 1956

Claims

1. A DETERGENT COMPOSITION CONSISTING ESSENTIALLY, BY WEIGHT, OF A NORMAL ALIPHATIC ALCOHOL SULFATE DETERGENT DERIVED FROM HYDROGENATED TALLOW FATTY ACIDS PREDOMINATING IN C18 N-ALKYL SULFATE, ABOUT 1 TO 6 PARTS PER PART OF SULFATE DETERGENT OF C12-C15 MONOALKYL BENZENE SULFONATE DETERGENT, AND, AS A FOAM-IMPROVING AGENT, ABOUT 3 TO 75%, BASED ON THE SULFATE DETERGENT, OF A C2-C3 MONOALKYLOLAMIDE OF A C15-C18 SATURATED FATTY ACID.