US2879839A - Concentrating synthetic organic detergent solutions - Google Patents

Description

March 31, 1959 n c. LE ROY CARPENTER ETAL 2,879,839

CONCENTRATING SYNTHETIC ORGANIC DETERGENT SOLUTIONS Filed Aug. 16. 1955 g.. Qu

ATTORNEY United States Patent O t CONCENTRATING SYNTHETIC ORGANIC i DETERGENT SOLUTIONS Clifford Le Roy Carpenter, Belfast, Maine, and Salvatore John Slvis, Brooklyn, N.Y., assignors to Colgate-Palmolive Company, Jersey City, NJ., a corporation of Delaware This invention relates to a process for concentrating a solutionY or dispersion of synthetic organic detergent compounds in a lower aliphatic monohydric alcohol, such as isopropanol, and water. The synthetic organic detergent compounds are those including alkali metal salts, such as sodium salts, of sulfated partial esters of polyhydric alcohols, such as glycerol, with long chain fatty acids having from 8 to 24jcarbon atoms per molecule. Such solutions and dispersions as above mentioned normally result from theA extraction of crude mixtures of these synthetic organic detergent compounds wherein a lower aliphatic monohydric alcohol, such as isopropanol, is ernployed as the solvent extraction agent.

Synthetic organic detergent compounds such as alkali metal salts of sulfated partial glyceryl esters of long chain fatty acids having from 8 to 24 carbon atoms have long since established themselves as standard items of commerce. A very well known example of this class of compounds is the mixture comprising the sodium salts of the sulfated partial "esters of glycerol with the fatty acids derived from coconut oil and having an average of about 12 carbon atoms per molecule, and for brevity and convenience this compound (or rather mixture of cornpounds) will be referred to frequently hereinafter as the prototype of the compounds to which the present invention primarily relates, but without intending any limitation upon the invention by such ellipsis. The partial esters referred to herein are mixtures of the polyhydric alcohol mono-esters and di-esters, with the former generally predominating. l

During the vcourse of manufacture of compounds of this type, it is conventional practice first to manufacture partial esters having the desired configuration such as by an alcoholysis-type reaction after which the partial esters are treated with a suitable sulfating reagent such as oleum, etc., whereupon the desired salt-form of the detergent compound is produced by treating the reaction mixture withia suitable alkali such as sodium hydroxide, carbonate or bicarbonate. Since the sulfating step is invariably carried out with the aid of` excess sulfating agent to insure complete sulfation, the alkali is also employed in excess in order to insure complete neutralization of excess sulfating agent (including the HZSO, of the oleum) and therefore the sulfated partial ester alkali metal salt product is finally obtained in admixture with an alkali metal sulfate such as sodium sulfate.-

For many uses, for example, in the case of dental detergents, shampoos and the like, it is desirable if indeed not essential to obtain the sulfated partial ester organic salt products in a high degree of purity, and especially free or substantially free from inorganic salts such as sodium sulfate, The separation or isolation of the active ingredient (i.e., the alkali metal salts of the sulfated partial esters) of the organic detergent composition from the inorganic salts or other impurities that may be present `may be carried out in a number of ways, but a particuy larly desirable way is by solvent extractionv by means of a lower aliphatic monohydric alcohol, such as ethanol or isopropanol. Isopropanol is especially desirable,v particularly` when the synthetic `detergent compound is-intended for use as a dental detergent.

The alcohol extraction step may be carried out batchwise or in a continuous manner according to procedures per se well known in the art. The net result of such an extraction operation is to effect a separation of the alcoholinsoluble components, including the bulk of the inorganic salts such as sodium sulfate, on the one hand, from the alcohol-soluble components, including the sodium salts of `the sulfated partial esters on the other hand. The

active ingredient of the composition (i.e., the sodium saltsv of the sulfated partial esters), .is thus obtained in the form of an upper extract layer having a relatively low inorganic salts content, say 5% more or less.

However, this extract layer from the alcohol extraction step contains the desired active ingredient in intimate admixture with the alcohol used as extractant and for many purposes it becomes necessary thereafter to separate the active ingredient from the alcohol, especially when the synthetic organic detergent compound is intended for use as a dental detergent or the like. v

The process of this invention is eminently suited tothe treatment of synthetic organic detergents of the sulfated type. Particularly desirable results are obtained in the treatment of lower aliphatic monohydric alcohol extracts of sodium salts of sulfated partial glyceryl esters of long chain fatty acids having from 8 to 24 carbon atoms per molecule. Specific examples of these are sodium salts of sulfated glyceryl partial esters, and especially sulfated glyceryl mono-esters of coco-fatty acids, tallow fatty acids, mixed coco-tallow fatty acids, hydrogenated coco-fatty acids, hydrogenated tallow-fatty acids, hydrogenated cocotallow-fatty acids, etc., etc. While the process is described more particularly in reference to the synthetic organic detergent compounds in the form of their sodium salts, the process is also applicable to other corresponding alkali metal salts such as the potassium salts as well as the ammonium salts.

A phase study of the equilibrium relationships of ternary systems of this type show that with solids concentrations between approximately 39 and 57%, a gel region exists depending for the most part upon the concentration of the alcohol and to a lesser part upon the presence of relatively small amounts of the organic compounds generally present as a result of the reaction and 'neutralization steps. Accordingly, prior attempts to concentrate a dilute solution by the simple -addition of dried detergent chips have in each instance encountered this gel region and for this reason have been unsuccessful. Experiment confirms that in all cases between approximately 3,9% and 57% total solids a thick paste'with absolutely no flow characteristics will be obtained. It has now been found after careful study of the foregoing ternary phase` system, that a way exists by which it is possible to concentrate a detergent solution or dispersion of the above character from approximately below 39% solids to approximately 57% solids and higher without encountering the gel region. The concentrated solution may, as will be appreciated by those skilled in the art, be subjected to a drying operation of a suitable type to enable the production of the desired synthetic organic detergent compound in a dry form. The exact nature and character of the drying operation per se forms no part of the present invention and it is contemplated that any drying operation can be employed. For the sake of illus'- tration, it will be assumed that the synthetic organic detergent compound solution or dispersion concentrated by this process is subsequently converted into the dry state inadrumtypedrier. Y*

Patented Mar. 31,-4 1959 Generally, it is an object of the present invention to provide a process for concentrating a solution or dispersion of a synthetic organic detergent compound in a lower aliphatic monohydric alcohol and water which will function to circumvent or avoid an inoperable region in the ternary phase system.

Further, it is, therefore, an object of the present invention to provide a process for concentrating a solution or dispersion of the sodium salt of monoglyceride higher fatty acid sulfate in a lower aliphatic monohydric alcohol and water in a manner to circumvent or avoid an inoperative gel region occurring between approximately 39% and 57% total solids, thereby to provide a feed to a subsequent drying operation which will materially reduce the evaporation load on the drier and thereby increase the throughput.

It is a still further object of the present invention to provide a process for concentrating a sodium salt of monoglyceride higherfatty acid sulfate in isopropyl alcohol and water which will operate more efficiently and economically than simply introducing said solution to the drying step without initially concentrating same.

Other objects and advantages of the present invention will become apparent from a detailed consideration of the following description when taken in conjunction with the appended drawings in which:

Figure l is a phase diagram of the system; and

Figure 2 shows one form of the apparatus suitable for carrying out the method of this invention.

Generally, the process of the present invention consists in feeding to a long tube vertical evaporator a detergent extract or solution of the kind indicated herein. The evaporator is arranged with a recirculation pipe in which a heel portion of concentrated extract is maintained and recycled to the evaporator. The concentrated product is removed from the recirculation pipe as required. In the operation of the process, a critical operating condition is the percentage evaporation, by which is meant the weight of overhead vapors removed per pound of feed. Thus, the extract feed to the evaporator must be adjusted with respect to the collection and removal of overhead vapors and the removal of concentrated product such that the rate of feed will establish the degree to which the concentration of the detergent is effected. Hence, for example, if a detergent extract containing 30% solids is being fed to the evaporator and it is desired to concentrate the extract to 60% solids, it will be necessary to maintain a vaporization rate of 50% of the extract feed.

Referring now to Figure 2, there is shown a long tube vertical evaporator provided with an overhead takeoff pipe 11 leading to a vapor-liquid separator 12. Vapors are removed from the separator 12 through overhead pipe 13 and directed in the usual manner to a condenser (not shown). A liquid discharge pipe 14 from the separator 12 provides a recirculation pipe by connecting with the bottom of the evaporator 10. Extract feed is introduced to the evaporator through pipe 15 which communicates with the pipe 14 prior to its connection to the bottom of the evaporator 10. Steam is fed into the heating jacket of the evaporator through inlet 16 and steam and condensate are withdrawn through outlet 17. The evaporator 10 shown is a long tube vertical evaporator characterized by `a tubeglength of between 6 and 12 feet. Although the invention is described with specific reference to a long tube vertical evaporator, other types of evaporators may be used, but in general a vaporliquid separator will be required. In the operation of the evaporator, a concentrated heel of relatively high solids content is established in recirculation pipe 14 and is recycled as indicated by the arrows to the bottom of the evaporator 10. Evaporated product or concentrate is removed through pipe 18 connected to the recirculation pipe 14 as indicated.

The use of the recirculation pipe 14 in conjunction with the long tube vertical evaporator 10 prevents the extract feed from gelling during the concentration operation. In effect, the heel portion of the concentrate, maintained in the recirculation pipe 14 and recycled to the evaporator 1t), acts as the medium whereby the concentration of the detergent extract or solution can be accomplished without the formation of a gel phase which would otherwise prohibit such an evaporation directly. The admixed feed and recycled heel entering the bottom of the evaporator form an overall solution whose resultant concentration does not lie within the gel region (the limits of which are shown in Figure l) and whose concentration will not enter the gel region as it is evaporated to the desired solids content. In effect, the process of the present invention permits the gel region to be by-passed, as it were, during the concentration operation, thereby completely avoiding operating diculties that would otherwise occur due to gelling.

The heel can be prepared synthetically using dried detergent solids, such as chips of the same kind of detergent to be processed, and the corresponding solvent, i.e. corresponding to that present in the dilute extract feed to be processed. As an example of the initial preparation of such a heel, pounds of chips may be added to pounds of dilute extract feed (30% solids) to give an approximately 60% solids mixture. This heel can then be placed in the recirculation pipe 14, and the process commenced by introducing dilute extract feed via pipe 15, recirculating the heel in pipe 14, and withdrawing the desired concentrated product via line 18. In making up the heel, any desired order of mixing the ingredients may be employed.

Alternatively, the heel may be prepared by introducing dilute extract feed directly into the evaporator. To do so, it is desirable to dilute even more the initial extract material (30% solids) by adding thereto a sucient amount of 87.7 weight percent isopropanol to give an overall composition of solids 15%, isopropanol 60%, water 25%. This diluted mixture is fed to the evaporator in suicient quantity to make up the amount of evaporation to maintain the normal operating level in the evaporator and recirculation pipe 14. No material is pumped out of pipe 18 during this start-up operation. Hence, the solids concentration continues to increase with continued evaporation. At higher solids concentrations (above about 45%) when the isopropanol concentration becomes too low (indicated by a thickening of the heel) it is necessary to stop the feed of diluted material and to introduce into the evaporator 87.7 weight percent isopropanol to maintain the operating level within the evaporator. This technique enables the mass within the evaporator to retain its fluidity and, hence, to stay out of the gel region the limits of which are shown in Figure 1. When the mass becomes more fluid (i.e., further away from the gel region), then the isopropanol feed is shut olf, and the concentration within the evaporator continues until say 53% solids is reached. Thickening may' again occur, whereupon the dilution procedure just described is again employed. When 60% solids is reached, the desired heel has thus been prepared in recirculation pipe 14 and the concentration process proper according to the invention may be begun.

The following are examples of the operation of the process:

Example I A heel is prepared by adding 95 lbs. of detergent chips (sodium salt of sulfated glyceryl mono-esters of cocofatty acids) dried in a drum drying operation to 130 lbs. of extract feed material (30% sodium salt of sulfated glyceryl mono-esters of coco-fatty acids and 60% isopropyl alcohol and water) to give an approximately 60% solids mixture, The heel so formed is pumped into the l i i i l i evaporator until the normal operating level for'the heel lis attained in the recirculation pipe 14. Qperating level `of heel in the evaporator should be high to insure good wetting of the tubes, rand the heel should be suicient in quantity to absorb the feed without becoming toodiluted by same to cause the resulting mixture to fall within the gel region. System pressure is regulated to,

90 mm. Hg absolute, and the steam pressure used is 6 p.s.i.g. on 10 feet of tube length in the evaporator. The evaporator is operated with a vaporization rate of 50% with a view to concentrating the extract feed (30% solids) to approximately 60% solids. Thus, foreach 100 lbs. of extract material (30% solids) fed .to the evaporator through feed inlet 15 there are removed 50 lbs. of overhead vapors and 50 lbs. of concentrated product through pipe l18. The run is continued for several hours under conditions designed to achieve .a vaporization ratio of 50%. However, vthe actual results of the run indicate that under the conditions given above, a product of 54.5%. solids is made continuously but at such a solids content the isopropanol concentration must be carefully watched since the resulting solution may reach the gel region and become too viscous to handle. The 54.5% solids content obtained in this run apparently results from the inability to maintain the desired ideal operating conditions during the actual run, and most probably a true vaporization rate of 50%. At 54.5% solids content the isopropanol concentrationis critical, as previously mentioned, since as shown by Figure 1 the solution falls in the gel region range lfor certain isopropanol concentrations. A value of approximately 15% isopropanol should be maintained in the heel (and therefore, product) in order to operate satisfactorily when producing a concentrate of 54.5% solids content. Maintaining the required proportion of isopropanol can be readily accomplished either by further dution of the feed with isopropanol or bypumping in isopropanol simultaneously with the given feed.

Example II A- solution of high solids 4concentration of70% is prepared by adding spray dried and rolled detergent chips (same detergent as in Example I) to an extract material (same as in Example I) of initially 30% solids concentration. lsolution and the single mixture is too viscous for use as such. Isopropyl alcohol and water are then added to the mixture to render it more uid, and consequently, the solids concentration is decreased to about 60%. This material is then introduced into the long tube ver-y tical evaporator as a heel. The extract material (30% solids) is diluted with a suicient amount of 87.7 weight percent isopropanol until its overall composition is 16% solids, 59% isopropanol and 25% water. The evaporator is operated with a 77% vaporization rate to concentrate the diluted extract material to 70% solids. As a result of the selection of this vaporization rate, 77 lbs. of solvent are removed for every 100 lbs. of feed. 'Ihe operating conditions for which the apparatus is set are system pressure 120 mm. I-Ig absolute, steam pressure 3 p.s.i.g., steam jacket length 10 ft., and feed temperature 110 to 115 F. A critical operating condition is the percent evaporation or vaporization rate and, during the run, the feed tank and overhead vapor receiver tank are closely watched and the feed carefully adjusted so that 77% by weight of the feed is being collected as overhead vapor. Under the set conditions of the run, however, the maximum vaporization obtained is 71%. The unit produces a concentrate having approximately 55% solids during the run, the isopropanol concentration, however, being sufficiently high to maintain the concentrate well outside the gel region.

The chips are extremely slow in goinginto' Example lll l Since the process of synthesizing the heel by adding dried chips to the extract material until the solids concentration has been built up to the desired value is sometimes diicult and time consuming, the following illustrates the direct production of the heel in the evaporator from the extract material. The extract material (30%v solids), same as in Example I, is diluted with 87.7 weight percent isopropanol, to give an overall composition of solids 15%, isopropyl alcohol 60%, water 25%. This diluted extract material is fed to the evaporator in .Sudicient quantity to maintain the normal operating level in the'evaporator. The conditions set for the run are system pressure mm. Hg absolute, steam pressure .2 p.s.i.g., and steam jacket length 6 feet. As the evaporation progresses, material removed as overhead vapors is replaced by an equivalent weight of diluted extract feed so that the normal operating level is maintained in the evaporator. No material is pumped out of the evaporator during the run so that the solids concentration continues to build up with continued evaporation. At higher solids concentrations (above 45%) when the isopropyl alcohol concentration tends to become too low (indicated by a thickening of the heel), the technique employed to increase the fluidity of the solution in the evaporator and to cause it to stay out of the gel region consists in shutting oi the alcohol-diluted extract feed and introducing into the evaporator 87.7 weight percent isopropyl alcohol to maintain the normal operating level in the evaporator, As a result of the above run, a heel having 59% solids is successfully produced. The heel is found to have a viscosity of 2840 centipoises at F. measured with a Brookield viscosimeter at 60 r.p.m. and a No. 4 spindle.

Example IV A run is made in the evaporator using the heel produced in Example III. The extract material (same as Example I) before being introduced into the evaporator is diluted with isopropyl alcohol until the extract material has a concentration of 15% solids. The conditions for this run are system pressure 120 mm. Hg absolute, steam pressure 2 to 4 p.s.i.g., and steam jacket length from 7 feet to 10 feet. A product is obtained in which the solids concentration is 60.6% with an accompanying isopropyl alcohol content of 13%.

Example V Extract material (same as Example I) is diluted with isopropyl alcohol until it is characterized by a 16.6% solids concentration. At this time, the extract material contains 57.4% isopropyl alcohol and 26.0% water. The isopropyl alcohol employed to dilute the extract material is 87.7 weight percent isopropyl alcohol. This diluted extract material is fed to the evaporator already containing therein a heel of approximately 56% solids. The operating conditions for the run are system pressure 90 to 120 mm. Hg absolute, steam pressure 1 to -6 p.s.i.g., and steam jacket length 6 to l0 feet. centrated product has the following composition-56.2% solids, 13.0% isopropyl alcohol, and 30.8% water. The overhead vapors removed have the following composition: 76.9% isopropyl alcohol, 23.1% water and a trace of solids.

Example VI The extract material concentrated by the process of the present invention is used to produce a dried detergent on a drum drier. The drying operation is conducted with a feed material having between 55 to 56% solids. The production rate using such material is 4.05 #/hour-ft.2 of total drum surface. To alord a basis of comparison and to demonstrate the value of the present process, the ligure of 4.05 #/hour-it.2 compares with 1.2 #/hour-ft.2 from the same drum drier using the extract material undiluted. Thus, the dry product capacity of a The cony'1 given drum drier is increased about 3.4 times by prior evaporation according to this invention to a relatively high solids concentration.

What is claimed is:

1. A process for concentrating a relatively dilute solution having as a solute content thereof a synthetic orgarlic detergent of the sulfated type in a lower aliphatic monohydric alcohol and water, said process involving remaining outside a gel region, the limits of said region being dened such that the alcohol content may not go below 9% when the solids percentage is between about 40-58% and the water percentage is between about 36-60%, said process comprising adjusting the solute to water to alcohol ratio to remain outside the limits of said gel region, said adjustment being accomplished by adding to said dilute solution a concentrated owable mixture having as the solute content thereof a synthetic organic detergent of the sulfated type, charging the resulting mixture into an evaporating zone, and concentrating said resulting mixture to the desired concentration while remaining outside the limits of said gel region.

2. A process as defined in claim l wherein said alcohol is selected from the group consisting of ethyl alcohol and isopropyl alcohol.

3. A process as dened in claim 1 wherein said dilute solution contains between about to about 30% solute concentration.

4. A process as deued in claim 1 wherein said concentrated flowable mixture of a synthetic organic detergent contains more than about 55% solute concentration.

5. A process as defined in claim 1 wherein said synthetic organic detergent is an alkali metal salt of sulfated monoglycerides of higher fatty acids having from 8 to 24 carbon atoms per molecule.

6. A process for concentrating a relatively dilute solution having as a solute content thereof a synthetic organic detergent of the sulfated type in a lower aliphatic monohydric alcohol and water, said process involving remaining outside a `gel region, the limits of said region being dened such that the alcohol content may not go below 9% when the solids percentage is between about 40-58% and the water percentage is between about 36- 60%, said process comprising adjusting the solute to water to alcohol ratio to remain outside the limits of said gel region, said adjustment being accomplished by adding to said dilute solution a concentrated iiowable mixture having as the solute content thereof a synthetic organic detergent of the sulfated type, charging the resulting mixture into an evaporating zone, concentrating said resulting mixture to the desired concentration while remaining Outside lthe limits of said gel region, and thereafter recycling a portion of the concentrate inadmixture with fresh dilute solution prior to a concentrating step.

7. A process for concentrating a relatively dilute solution of less than about 39% solute concentration of a synthetic organic detergent of the sulfated type in a lower aliphatic monohydric alcohol and water, said process involving remaining outside a gel region, the limits of said region being defined such that the alcohol content may not go below 9% when the solids percentage is between about 40-5 8% and the water percentage is between about 36-60%, said process comprises adding to said dilute solution a mixture of more than about solute concentration of a synthetic organic detergent of the sulfated type in a lower aliphatic monohydric alcohol and water in sucient quantity to effect a solute to water to alcohol ratio which remains outside the limits of said gel region, charging the resulting mixture into an evaporating zone and concentrating said resulting mixture to the desired concentration while remaining outside the limits of said gel region.

8. A process 'for concentrating a relatively dilute solution of less than about 39% solute concentration of a synthetic organic detergent of the sulfated type in a lower `aliphatic monohydric alcohol and water, said process involving remaining outside a gel region, the limits of said region being defined such that the alcohol content may not go below 9% when the solids percentage is between about 40-58% and the water percentage is between 36-60%, said process comprises adding to said dilute solution a mixture of more than about 55% solute concentration of a synthetic organic detergent of the sulfated type in a lower aliphatic monohydric alcohol and water in suficient quantity to effect a solute to water to alcohol ratio which remains outside the limits of said gel region, charging the resulting mixture into an evaporating zone, concentrating said resulting mixture to the desired Vconcentration while remaining outside the limits of said gel region, and thereafter recycling a portion of the concentrate in admixture with fresh dilute solution prior to a concentration step.

References Cited in the le of this patent UNITED STATES PATENTS 1,676,277 Mumford July 10, 1928 1,831,121 Kenner Nov. 10, 1931 2,328,931 Steik Sept. 7, 1943 2,343,085 Sevell Feb. 29, 1944 2,673,208 Andrews et al Mar. 23, 1954 2,726,139 Oliver Dec. 6, 1955

Claims (1)

1. A PROCESS FOR CONCENTRATING A RELATIVELY DILUTE SOLUTION HAVING AS A SOLUTE CONTENT THEREOF A SYNTHETIC ORGANIC DETERGENT OF THE SULFATED TYPE IN A LOWER ALIPHATIC MONOHYDRIC ALCOHOL AND WATER, SAID PROCESS INVOLVING REMAINING OUTSIDE A GEL REGION, THE LIMITS OF SAID REGION BEING DEFINED SUCH THAT THE ALCOHOL CONTENT MAY NOT GO BELOW 9% WHEN THE SOLIDS PERCENTAGE IS BETWEEN ABOUT 40-58% AND THE WATER PERCENTAGE IS BETWEEN ABOUT 36-60%, SAID PROCESS COMPRISING ADJUSTING THE SOLUTE TO WATER TO ALCOHOL RATIO TO REMAIN OUTSIDE THE LIMITS OF SAID GEL REGION, SAID ADJUSTMENT BEING ACCOMPLISHED BY ADDING TO SAID DILUTE SOLUTION A CONCENTRATED FLOWABLE MIXTURE HAVING AS THE SOLUTE CONTENT THEREOF A SYNTHETIC ORGANIC DETERGENT OF THE SULFATED TYPE, CHARGING THE RESULTING MIXTURE INTO AN EVAPORATING ZONE, AND CONCENTRATING SAID RESULTING MIXTURE TO THE DESIRED CONCENTRATION WHILE REMAINING OUTSIDE THE LIMITS OF SAID GEL REGION.

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