US 2941950 A
Description (OCR text may contain errors)
June 21, 1960 E.'o. KORPI ETAL CONCENTRATED LIQUID DETERGENT Filed Sept. 30, 1954 WMUIL'U .mvrwULw NZFQJDQDU mafia as ua ms nu m6 mm 8 8 on 0w on a Onan 8 n N a IN VENTURE. [aw/1v 0. flaz l BY "fiaaz'er Rpm 1.5; a111 1 M AT T 0 R N EYS,
United States Patent CONCENTRATED LIQUID DETERGENT Edwin O. Korpi and Robert P. Davis, Cincinnati, Ohio,
assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Sept. 30, 1954, Ser. No. 459,240
Claims. (Cl. 252-153) This invention relates to liquid synthetic detergent compositions, and particularly to those that are intended primarily for washing dishes, glassware, etc. in a dishpan or in a kitchen sink.
Such detergents, to be accepted by the user, should have certain characteristics-pourability, chill point well below normal room temperature, short reliquefaction time at room temperature after having been congealed by storage at low temperatures, good sudsing and detergent qualities; and above all, mildness to the hands of the user. While possessing all of these characteristics, the liquid detergent should be concentrated enough so that a moderate sized bottle or can of the liquid will provide detergent mileage for about as many dishwashings as a package of soap flakes or of synthetic detergent.
Many of the previously made liquid detergents were deficient in sudsing. The housewife is accustomed to having a sudsing detergent in the dishpan, and a low sudsing or non-sudsing detergent is handicapped.
For most housewives washing the dishes constitutes the longest exposure of the hands to a detergent solution.
It is an object of this invention to provide a liquid sulfated anionic detergent composition having characteristics desirable in such compositions and having, particularly, outstanding mildness to the hands of the user, and improved freeze recovery.
We have discovered that when the anionic sulfuric reaction product in a liquid detergent of the dishwashing type is composed of the sulfated and ammonia or substituted ammonia neutralized reaction product of about 3 moles of ethylene oxide and one mole of high molecular weight monohydric alcohol having from to 16 carbon atoms in the molecule there is an unexpected improvement in freeze recovery and mildness to the hands. The high molecular weight alcohol used can be the middle cut produced in distilling the fatty alcohols derived from reducing coconut oil, coconut fatty acids, or their alkyl esters. Such middle cut fatty alcohols are the normal primary alcohols having 10 to 1 6 carbons in the molecule and obviously may be produced from other oils of the coconut group such as palm kernel and babassu.
After the approximately 3 moles of ethylene oxide have been reacted with the high molecular weight alcohol to produce the alkyl ethers the product is sulfated and the sulfuric half ester neutralized with ammonia or alkylol substituted ammonia. The alkylol substituted ammonias we prefer are mono-, di-, and triethanol, mono-, di-, and tripropanol, mono-, di-, and triisopropanol and mono-, di-, and triglyceryl amines, those in which the alkylol group is of 2 to 3 carbon chain length.
The compound that makes the compositions of the present invention differ from those previously known is the sulfated and neutralized reaction product of about three I Patented June 21, 1960 middle cut fatty alcohol from coconut oil was carried out in an autoclave, equipped with an agitator, an internal cooling coil, and an external electric heater. 23.45 parts of fatty alcohol were placed in the autoclave and sodium hydroxide pellets (0.25% based on the alcohol) were added. The cover was bolted onto the autoclave. The agitator was started and the external heater turned on. The autoclave was scavenged with nitrogen during the heating period which continued until a temperature of 270 F. was reached, At this point the heating coil was turned off, and 5.25 parts of ethylene oxide (1 mole per mole of alcohol) from a nitrogen blanketed Weigh tank was allowed to flow into the autoclave. The reaction between the fatty alcohol and the ethylene oxide is exothermic, hence the cooling water was turned on through the internal cooling coil, and the flow of ethylene oxide wascontrolled so' that the temperature did not rise above 305 F. and the pressure was held in the range of 60-80 p.s.i. After the ethylene oxide was all in the autoclave, the reaction was allowed to proceed to completion as indicated by the pressure drop levelling off. After scavenging with nitrogen to remove the dissolved gases, and cooling, the autoclave was opened and the product removed. I
Analysis indicates that this reaction product between 1 mole of ethylene oxide and 1 mole of middle cut fatty alcohol has the approximate following composition molar percents.
Molar percent where n'is more than 2, and R is a mixture of alkyls from middle cut alcohol.
The reaction product of the above example was sulfated with 105% of the theoretical amount of chlorosulfonic acid at a temperature of to F.
Analysis indicated a 98% completeness of sulfation.
The product was neutralized with ammonia. For convenience, the sulfated mixture of reaction products produced by reacting 1 mole of fatty alcohol with 1 mole of ethylene oxide is called alkyl (Et O) sulfate, although it should be noted that the unreacted alcohol (56%) appeers in ths product as alkyl sulfate.
The product was suitable for use in the preparation of liquid detergent compositions in accordance with our invention. t 1
Example 2 .'Using the equipment and operating conditions described in Example 1, 18.35 parts of middle cut fatty-alcohol,"to which caustic soda pellets were added to the amount of 0.25% on the Weight of the alcohol, were reacted with 12.35 parts of ethylene oxide. This is 3 moles of ethylene oxide to 1 mole of fatty alcohol. In this reaction the; temperature went to 315 F. After scavenging with nitrogen and cooling, 2. portion of this product was analyzed. Its composition was approxiwhere n is more than 3 and R is a mixture of alkyls from middle-cut CNO alcohol. e e a The reaction product was sulfated with 'of the theoretical amount of chlorosulfonic" acid. Analysis indicated a completeness of approximately 98%. .'The product was neutralized with ammonia. For'convenience the product is '"eaned'an i (Hi0); sulfate althoiigh ap- V plex, for convenience.
. sures. catalysts and the extra steps, such aswater washing, re
iii-bxinnatelyhalf of it is alkyl sulfate plus alkyl ethylene 1 to 305 F. After scavenging with nitrogen and cooling, 1 the product was removed from the autoclave.
A portion was analyzed and found to have the follow- -ing approximate composition in molar percents.
Molar percent ROH 9 'R(C H O) H 9 R(C H O) H 12 R(C H O) H 13 2 4 )4 11 R(C H O) H R(C H O) H 36 where n is more than 5 and R is a mixture of alkyls from middle cut fatty alcohols.
This is evidence that n may be as high as 12 in this preparation since the data and calculations as presented in Figure 1 show that n is 11 or less in only 90% of the composition.
The reaction product was sulfated with 105% of the theoretical chlorosulfonic acid, and was determined to beabout 98% sulfated.
The product was neutralized with ammonia. For convenience, this reaction product is called alkyl (EtO) -s'ulfate although the actual molar percent of the condensation product of fatty alcohol with 5 moles of ethylene oxide is only about 10%. I The product may be used'in liquid. detergent preparations meeting the objects set forth above.
In contrast with the foregoing uses of an alkaline catalyst, we have also carried out the condensations of high molecular alcohol with alkylene oxide using stannic chloride as the catalyst and boron trifluoride as the catalyst. The boron trifluoride was used as the ether com- These two acid catalysts have some advantages, particularly in their being workable at lower temperatures and correspondingly lower pres- However, the corrosive character of these acid quired to remove the catalysts from the reaction product, have led us to prefer sodium or potassium hydroxide as the catalyst, which only needs neutralization with acid for its inactivation. However, we do not wish to limit ourselves to the use of sodium or potassium hydroxide as the catalyst.
The alkyl ethylene oxide ammonium sulfate products made according to themethods set forth in Examples 1, 2, and 3 were tested for dishpan sudsing against a commercial liquid dishwashing detergent in which the anionic sulfuric reaction product was ammonium alkyl sulfate, the alkyl being middle cut coconut alcohol.
The series of tests was carried out with amide builder.
In all four bf the preparations the composition was:
37.5 parts by wt. of the neutralized anionic sulfuric re -No ethyl or propyl alcohol was added'as prior work *showed these alcohols do not aliect sudsing.
The coconut amide was made by reacting monoethanol amine with coconut fatty acids. The active builder por- 'tion of these amides is comprised essentially of the with one of high molecular alcohol.
amides of the C C and C fatty acids. Other alkylol amines may be used in place of monoethanol amine, for example, diethanol amine, and monoand dipropanol and isopropanol amines and monoand diglyceryl amine may be considered substantial equivalents for the present purpose, thus producing alkylolamides with not more than three carbon atoms in each alkylol radical.
The dishpan sudsing test used in this composition determines the amount of detergent required to wash a standard number of soiled plates and have a definite suds level after theplates are washed. The plates are soiled with a mixture of tallow, salad oil, flour and powdered gelatin. Successive trials with varying amounts of detergent are made until the amount required to wash the plates and have a definite levelof suds at the finish is determined. The tests on the preparations of Examples 1, 2, and 3 were made in water of 7 grains per gallon hardness.
According to thistest, the performance of the compositionsmade by reacting 1 mole of ethylene oxide, and
3'moles of ethylene oxide, with one mole of fatty alcohol, were equal or better than a commercial product, Joy, *a liquid detergent, containing ammonium neutralized fatty alcohol sulfate, built with coconut amide. The composition containing the reaction product of 5 moles of ethylene oxide with one mole of fatty alcohol was" only slightly less efficient than "the other compounds shown, and was also a satisfactory preparation.
If the choice of the number of moles of EtO to react with one mole of alcohol were based solely on the sud'sing test, above, one or two moles of EtO per mole of high molecular alcohol would probably be chosen. However, the mildness to the hands of the user is the principal object of this composition. Mildness increases with the number of moles of EtO reacted with one mole of the high molecular alcohol. 'If mildness were our sole 'objectivewe would probably settle on 5 moles of EtO. This composition, however, when sulfated and neutralized does not suds quite as well as the one with 3 moles of EtO per mole of high molecular alcohol. Our choice therefore taking both mildness and detergency into consideration is the one made by reacting 3 moles of EtO However, the desirable qualities do not peak sharply at 3 EtO but spread out to include 2 and 4 EtO, and if a slight decrease in mildness is tolerated, would include 1 EtO and if a slight decrease in sudsing is tolerated, include 5 EtO.
The reason for these several preparations being ap proximately alike in their qualities may be inferred from Figure 1. In this is shown the molecular percentages of the various alkyl ethers when 1, 3, and 5 moles respectively of ethylene oxide are reacted with the fatty alcohol. In this presentation, the unreacted fatty alcohol has been taken out and only the mol percent of the several ethers shown on an alcohol free basis. Even the alkyl (EtQ) contains more than 5 'mol percent of'alkyl ethers containing five or more ethylene oxide groups. Each of the three condensation products represented by the three curves is a mixture of low and high polymers, the maximum amount of high polymers increasing of course, as more ethylene oxide is condensed with the fatty alcohol. The characteristics, obviously, blend from one preparation to another.
It may be stated that the val-uesin Figure 1 were not obtained by direct analysis of the preparations shown in Examples 1, 2, and 3. When the alcohol used is theapproximately C alcohol used in the examples and preparations, fractional distillation is only possible to about alkyl (EtO) The data, in Figure l were obtained largely with preparations made by condensing ethylene oxide with C alcohol. These were found to have the same molar percentage distribution as the C alcohols in the ranges where they could be checked and it is assumed that this holds in the upper ranges. Even using the C alcohols some of the upper values are extrapolationsbilt Ammonium alkyl (EtO) sulfate 37.5 Coconut monoethanol amide 9.0 Ethyl alcohol 22.0 Citric acid 1.0 Water 30.5
This was tested against an alkyl sulfate liquid detergent, the alkyl radical being derived from a similar middle cut alcohol as used in the alkyl (EtO) sulfate.
The formula was:
. Parts by weight Ammonium alkyl sulfate 37.5 Coconut monoethanol amide 12.0v Ethyl alcohol 18.0 Citric acid 1.0 Water 31.5
312 women who washed their own dishes were supplied the alkyl (EtO) sulfate liquid detergent and 317 women who likewise did their own dishes were supplied the alkyl sulfate liquid detergent. The women used the liquid detergents for a period of two weeks, and then were examined by physicians. Neither the women nor the physicians knew which liquid detergent was used.
The physicians scored the condition of the skin of the "hands of the users on a 1 to scale. On this scale 10 is perfect and is only attained by a few persons who seem immune to the effects of detergents and water. On this scale, 1 is rather severe irritation, deep cracks appearing in the skin. 7.5 is thehighest value ever obtained as the average of a clinical survey. At a value of 7.5 a superficial glance would lead to the conclusion that the skin was unaffected,
but. closer and particularly microscopic examination :Alkyl Bio sulfate liquid detergent 69.9 Alkyl sulfate liquid detergent 65.3
On a scale where 75 represents the average of a clinical test of the mildest detergent ever tested, this difference is, significant. Statistical analysis shows that a difference of only 2.7 gives a 95% assurance of a difference when i rated on a scale of'values according to which 100 rep- ;resents unattainable perfection as an average and 75 represents :the 2 average of the mildest detergent ever tested.
One of the unexpected advantages of the alkyl (EtO) sulfate liquid detergent is rapid freeze recovery. This test is made by holdingthe product in a test tube, about insidediameter, at a low temperature for 4 days at V which the composition clouds and/or freezes. It is then brought into a room at about 75 F. and the time to reach clarity is noted. Clarity is defined as the condition lwherenoobservable solid or congealed matter exists.
. [..For comparison the freeze recovery time of a comammonium alkyl sulfate is 24 hours. e
Alkyl (-EtO) sulfate 36 Coconut monoethanol amide 8.6 Ethyl alcohol 19.5
Water to make 100 parts 35 .9
Portions of this wererplaced in test tubes and held for five days at 50 F. No clouding occurred. Four test tubes were filled with portions and held for 4 days at 0 F., F.,\30 F., and 40 -F. respectively. They were then brought into a space maintained at 75 F. and
they all regained their clarity in less than 4 hours.
Monoethanolamine, diethanolamine and triethanolamine or the corresponding isopropanolamines may be used in place of ammonia, to neutralize the sulfate with *no significant change in the characteristics of these comcleared in less than 4 hours.
Example 5 .--Another preparation was made from the materials of Example 4, but the proportions were as follows:
Parts by weight Alky-l'(EtO) sulfate 37.5 Coconut monethanol amide 9.0 Ethyl alcohol 20.5 Water to make 100 parts 33.0
Portions of this preparation were placed in test tubes,
7 and four of them were placed in spaces held at 0 F.,
20 F., 30 F., and 40 F. respectively. After four days, the tubes were moved to a space held at 75 F. All One tube was held at F. for 5 days and it remained clear.
a Another consideration affecting the amounts of ethyl or propyl or isopropyl alcohol used as a solvent, is the effect of these alcohols on the viscosity of the liquid detergent. Increasing the alcohol content-the water being correspondingly decreasedlowers the viscosity.
With the preparations of our invention, the ethyl or propyl-alcohol used as a solvent will be about 15% to I 25% by weight ofthe liquid detergent as it is ready for ammonia.
use andv enough to maintain the amide and detergent in solution but not enough to cause precipitation or cloudivHESS.
While we speak of the alkyl (EtO) sulfates, and the I coconut amides as if they were pure compounds, this is not exactly true. There are unreacted alcohols, salts of sulfuric and hydrochloric acid (from chlorosulfation) amine soaps and other extraneous substances, which may total 5% on the whole composition.
It is important to control the ammonium and substituted ammonium salts of sulfuric and hydrochloric acid, called for convenience electrolyte salts. After chlorosulfation, the hydrochloric acid not driven off during the process is there as free acid. This is driven off by aeration to, preferably, the amount that will produce not over 0.5% NH CI (finished product basis) when neutralized with Up to 1% NH Cl may be tolerated but a limit of 0.5 NH Cl is preferable. If substituted ammonias are used, the amine chlorides should be held down to the s'toichiornetric equivalents of the above values for NI-LiCl.
H in the reacted mix. This will produce about 0.6
' be tolerated.
. (NHQ SOJ, in the finished product. It-will be appreciated that the determination of the amount of ammonium or amine sulfates in the presence ofsuch large amounts of ammoniumor amine alkyl '(EtO) sulfates-is not precise.
The values for sulfate electrolyte salts given, are our best festimates'. Experiments with added sulfate have indicated that about 1% ammonium sulfate bas'isisall that can If these electrolyte salts are not held at the low levels indicated, the product will have a poor chill test and freeze recovery, and with high sulfates may separate into two layers. The'tolerance of the preparations of our invention-for electrolyte salts depends upon the amount of alcohol present. For this reason the electrolyte salts are held to a-practical Obviously the electrolyte salts are present in direct proportion to the alkyl (EtO) sulfate. Our electrolyte salts are therefore present preferably in the amount of (.6+.5)/37 .5% or just under 3% of the alkyl (EtO), sulfate and the maximum tolerated would be about (1+1)/37.5 or 5.4% of a the alkyl (EtO) sulfate.
Since a liquid detergent is poured in small amounts into a dishpan or sink. containing a large amount ofwater it will be perceived that the concentration of the detergent materials in the bottle or can may be varied. The lower limit of concentration is set by the requirementsthat the container ought to contain about as many washes as a box of soap or synthetic detergent without being so large as to be expensive or clumsy. About 25% ,of the sulfated and neutralized condensationproduct of higher fatty alcohol and ethylene oxide is a satisfactory'lower limit. The upper limit is set by considerations of the pourability of the alcohol-water solution of the active ingredients. With alkyl (EtO) sulfates this limit is at about 40%.
'With the overlapping of species of polymers as shown on Figure 1, it is also evident that the number of moles of ethylene oxide reacted Withl mole of fatty alcohol may be varied over a rather wide range. While 3 moles of ethylene oxide seems a good optimum. value for mildness andsudsing, it is evident that 2 moles or 4 moles will give results differing very little from 3 moles, and even 1 to '5 moles have significant advantages of mildness and freeze recovery over other anionic detergents; in liquid detergent compositions. Since the distribution of species is so wide, in the ethylene oxide fatty alcohol condensation, there is no point in having an integral number of moles of ethylene oxide per mole of fatty alcohol. I 4 3 moles is optimum, one can approximate these results For example, it.
with any amount between 2 and 4 moles. To show the allowable variation in composition the following examples were made from middle cut coconut alcohol with ammonia neutralization of the sulfate.
Example Example Example 6 7 8 Alkyl (Et)a sulfate 36 39 40%, Ethyl alcohol 19% 21% 23 Coconut ethanol amide 8.7 9. 35 V 9. 75 Clcuding days at -50 F none none none Freeze recovery after 4 days at 0 F... .K. 0K. 0K.
dency of the electrolyte salts to interfere with clarity and freeze recovery. The alcohol has to be adjusted to the point where it holds the amide in solution, but'doesnot cause the electrolyte salts to interfere with clarity. n j
- of ethanol, normal propanol and iso propanol;
product including unreacted alcohol and otherwise consisting essentially of'a mixture of fatty alcohol-ethylene oxide ethers of the general formula of moc zcanoa where R represents an alkyl chain of 10 to 16 carbon atoms in the alkyl radical, x is a plurality of Whole numbers within the range from 1 to 12 inclusive, said unreacted alcohol and mixed alkyl ethers being sulfated,.and then neutralized with a neutralizing agent selected from the group consisting of ammonia and alhylol-substituted ammonia having from 2 to 3 carbon atoms in the alkylol group;
a (b) 'An organic builder substance consisting essentially of alkylolamide of saturated fatty acids having 10, 12 and 14 carbon atoms and an alkylol amine, said alkylol amide having not more than'3 carbon atoms in each alkylol radical and the amount thereof being from 6 to 12% of the composition;
(0) 15 to 2.5% of alcohol from the group consisting of ethanol, normal propanol and isopropanol;
(d) Not over 5% of extraneous substances (such as sulfates and chlorides of the ammonia or substituted ammonia used, plus unsulfated alkyl ethers and other reaction products);
(a) Water to make said composition being stable against clouding, precipitation of solids, andgelling at temperatures as low as 50 F and with a freeze recovcry of 4 hours or less.
2'. A single phase concentrated liquid detergent composition consisting essentially of a solution of (a) 25 to 40% of a sulfated and neutralizedreaction product obtained from condensing 2 to 4 moles of ethylene oxide and one mole of. monohydric alcohol of-from -10 to 16 carbon atoms in the molecule, said, reaction product including unreacted alcbhol and otherwise consisting essentially of a mixture'of fatty alcohol-ethylene oxide ethers of the general formula of V mocn cnp on v where R represents an alkyl chain of 10 to 16 carbon atoms in the alkyl radical, x is a plurality of Whole numbers within the range from 1 to 12 inclusive, said unreacted alcohol and mixed alkyl ethers being sulfated,
'in the alkylol group;
. (b) An organic builder, substance consisting essentially of alkylol amide of saturatedfatty acidshaving 1t), 12 and 14 carbon atoms and an alkylol amine,, sa d alkylolamide having not more than 3 carbon atoms in each alkylol radical and the amount thereof beingfrom 6 to 12%'of the composition; 7 v
(c) 15 to 25% of alcohol from the group cons sting (d) Not over 5% of extraneous substances tsuchas sulfates and chlorides ofthe ammonia or. substituted ammoni'a used, plus unsulfated alkylethers and other reaction products);
' stable against clouding,.precipitation of solids, andf' ling; at temperatures as low as 56 F.,-and with a freeze recovery of 4 hours or less.. I
3. A single phase concentrated liquid detergent composition consistingessentially of a solution of (a) 25 to 40% of a sulfated and neutralized reaction product obtained from condensing 1 to 5 moles of ethylene oxide and 1 mole of fatty alcohol, said fatty alcohol being a Straight chain primary alcohol of 10 to 16 carbons and having a terminal hydroxyl group, said reaction product including unreacted alcohol and otherwise consisting essentially of a mixture of fatty.alcohol-ethylene oxide ethers of the general formula of mocri cnp on where R represents an alkyl chain of 10 to 16 carbon atoms in the alkyl radical, x is a plurality of whole numbers within the range from 1 to 12 inclusive, said unreacted alcohol and mixed alkyl ethers being sulfated, and then neutralized with a neutralizing agent selected from the group consisting of ammonia and an alkylol substituted ammonia having from 2 to 3 carbon atoms in the alkylol group;
(b) An organic builder substance consisting essentially of alkylol amide of unsaturated fatty acids having 10, 12 and 14 carbon atoms and an alkylol amine, said alkylol amide having not more than 3 carbon atoms in each alkylol radical and the amount thereof being from 6 to 12% of the composition;
15 to 25% of alcohol from the group consisting of ethanol, normal propanol and iso propanol;
(d) Not over of extraneous substances (such as sulfates and chlorides of the ammonia or substituted ammonia used, plus unsulfated alkyl ethers and other reaction products);
(e) Water to make 100%, said composition being stable against clouding, precipitation of solids, and gelling, at temperatures as low as 50 F., and with a freeze recovery of 4 hours or less.
4. A single phase concentrated liquid detergent composition consisting essentially of a solution of (a) 25 to 40% of a sulfated and neutralized reaction product obtained from condensing 2 to 4 moles of ethylene oxide and 1 mole of fatty alcohol, said fatty alcohol being a straight chain primary alcohol of to 16 carbons and having a terminal hydroxyl group, said reaction product including unreacted alcohol and otherwise consisting essentially of a mixture of fatty alcoholethylene oxide ethers of the general formula of where R represents an alkyl chain of 10 to 16 carbon atoms in the alkyl radical, x is a plurality of whole numbers Within the range from 1 to 12 inclusive, said unreacted alcohol and mixed alkyl ethers being sulfated, and then neutralized with a neutralizing agent selected from the group consisting of ammonia and an alkylol substituted ammonia having from 2 to 3 carbon atoms in the alkyl group;
(b) An organic builder substance consisting essentially of alkylol amide of saturated fatty acids having 10, 12 and 14 carbon atoms and an alkylol amine, said alkylol amide having not more than 3 carbon atoms in each alkylol radical and the amount thereof being from 6 to 12% of the composition.
(c) 15 to 25% of alcohol from the group consisting of ethanol, normal propanol and iso propanol;
(d) Not over 5% of extraneous substances (such as sulfates and chlorides of the ammonia or substituted ammonia used, plus unsulfated alkyl ethers and other reaction products);
(2) Water to make 100%, said composition being stable against clouding, precipitation of solids, and gelling, at temperatures at low as F., and with a freeze recovery of 4 hours or less.
5. The liquid detergent composition of claim 4 in which the straight chain primary alcohol constituent is a middle cut coconut alcohol mixture and in which the number of moles of ethylene oxide per mole of fatty alcohol is approximately 3.
References Cited in the file of this patent UNITED STATES PATENTS Re. 23,840 Vitale et al. June 15, 1954 1,970,578 Schoeller et al. Aug. 21, 1934 2,508,035 Kosmin May 16, 1950 2,758,977 Knowles et al. Aug. 14, 1956 FOREIGN PATENTS 501,145 Belgium Feb. 28, 1951 674,896 Great Britain July 2, 1952 149,977 Australia v Feb. 10, 1953 OTHER REFERENCES Synthetic Detergents, by McCutcheon (1950), page 171, pub. by MacMair-Dorland Co., New York.
Procter, Oflicial Journal of Patents, Trade Marks of Australia, February 26, 1953, pages 383, 384.