US2653958A - Method for the continuous purification of soap - Google Patents

Description

Sept. 29, 1953 F. L. LACHAMPT" METHOD FOR THE CONTINUOUS PURIFICATION OF SOAP Filed July 8, 1949 Patented Sept. 29, 1953 UNITED STATES PATENT OFFICE METHOD FOR THE CONTINUOUS PURIFICATION OF SOAP Morocco Applicationluly 8,1949, Serial No.1:03g637 In Morocco July 11",. 1am

f Claims; 1

This invention is concerned with. improvements in the methods of continuous purificationofsoap, and with an apparatus for use in applying said improvements.

An object of my invention is to provide a methd of continuously and. automatically purifying the reaction. roducts obtained. when a mixture of fatty substances and/or acids or the like is mixed with a; caustic alkali. such as caustic soda- Another object of" my present. invention is to provide a method of continuously purifying, a soap obtained in. a. concentrated. anisotrope phase, such as neat soap or kettle Wax.

A. further object of my inventionisto. provide an arrangement for' applying my improved. method.

A number of methods have been designed already to purify continuously a soapmixture. Thus, in the U. S patentto Scott, No. 2,300,749, filed". May 6*, 19 0, a. method has been described wherein purification achieved simultaneously with saponi fication'. Also, in my copending patent' applications 6721082 and 6721083" both. filed May 24, 1946, a method has been described wherein a soap}. after having been. saponifi'ed completely, is purified by washing with a. solution of an alkaline chloride; thereafter washing iseffect'ed by a solution of an alkali for eliminating the chloride in excess, and. then the purifies.

titon is completed by neutralising the. mixture with an acid", according to any convenient means adapted to lower the alkalinity ot a commercial soap to a; permissible value. I

it is well-known, in the conventional method of. kettle production, that after the soap. has been. washed by a brine and the used brinehas; been removed, the last purifying step consistsof adding water in a convenient amount. This is. the conventional fitting or finishing step,wherein the soap separates into two layers or phases; anupper" layer consisting of a. neat soap which is transformed thereafter into a. commercial product, and a' lower layer. consisting of the nigre, that is a solution of soap inan alkaline the leng-th. of. time required. for the decantation would. counterbalance. completely theadvantages resulting. from the continuity of the preceding operations. 'Ihatis" the reason why many attempts have: been made'to design methods and processes: of continuous fitting: or finishing of soap usable with a method. of continuous prepation of. soap. As far as I am aware; however, none of. these methods has been successful.

I have now designed a. novel and improved. method of continuous finishing. of soap, derived from the conventional method used inthe kettle soap preparation, and have determined accurately' the various parameterswhich act to change the: conditions of. the fitting or finishing. operation.

According to myinventiom the soap is continuously washed in a tower comprising a series of separated. stagesand the nigresolution drawn ofithe last washing stage: is treated with a brine causing. said. nigre solution.- toseparate into a poorer brine: and: into neat soap, bothof which are recycled.

Preferably the: soap isobtained previously by reacting a mixture of. fatty substances, of fatty substancesacids; or fatty substances and. resinic acids, or else fatty or resinic acids. and soapstock, with a caustic alkali, particularly caustic soda the concentration of. which is: preferablyhigher than 30%.. a. completely saponified: soap; that is asoap in which. no free fatty substance remains present.

More generally, the invention. has for one object, to purify a soapobtained: ina concentrated anisotrope: phase, such: asneat soap: or kettle: wax.

In practice, the concentration; of: such: a soap is comprised within. to in. some particular cases, however, for. instance in the: case of sodium stearate; the diagram.- 015 which. was given by McBain. and: Lee, the: concentration may be as low asabout48-%..

According to my invention, the soap-is continuously and methodically washed by a salt brinehaving a concentration slightly higher'than the limitconcentration corresponding to the composition of; thepurified soap under consideration, ina tower comprisingjias series-oi stages each pro-- videdwith both atmixin gr and a; decanting zone"; then, the soap--' is; continuously "finished by continuous decantatim oi neat soap at'the top of 2:

Such a reaction; gives kettle, while the mixture in the lower part of said kettle is drawn off the bottom thereof, means being provided for controlling the rate of flow of the drawn oif mixture. The quantity of the portion thus drawn off is chosen to comprise some of the neat soap from the upper part of the kettle with the whole nigre deposited at the lower part thereof and this portion is treated with a brine having a concentration higher than that of the first-mentioned washing solution, said concentration being so determined, that said portion be separated completely into neat soap and a poorer brine, the concentration of which precisely equals that of said first-mentioned brine; the neat soap and the brine so obtained are recycled separately in the washing stage which immediately precedes the finishing stage, whereby the neat soap is added to that previously formed and separated, while the poorer brine obpresent in the cycle must be maintained within the range 80 to 90 C., for instance 85 C. It is desirable indeed that no vaporisation of the water takes place, and thus the temperature must be kept far below 100 C. taking in account the fact that the structural transformation of the soap during the water addition is exothermic.

Obviously the concentration of the chloride solution used for the washing must be slightly greater than that of the limit brine corresponding to the purified soap, and that concentration must be chosen in such a way that the chloride solution only dissolves the oxyacidic soap, which may cause growing, and the low molecular weight soaps, the existence of which is undesirable. In the present specification, a limit brine with respect to a soap is defined as a brine having such a concentration that said soap is not dissolved thereby, although said soap could be dissolved by a brine having a lesser concentration.

The ratio of the volume of the washing solution used to the volume of the fatty acids present in the soap to be washed must be to parts washing solution to every parts fatty acids, and generally said ratio equals 40/70.

The washing is effected by methodical counterfiow of the soap and the brine with respect to each other, and must be carried out in a number of succeeding stages, preferably four; in each stage the soap and the brine are intimately mixed, then the mixture is directed to a decantation zone, wherein to of the washing solution separates to be recycled in the immediately preceding stage for use in that stage.

When leaving the last washing stage, therefore, the soap contains substantially 10% of brine and for the finishing operation, 10 to 20 parts water must be added to parts of soap, that is an average amount of 15%.

The occluded gases are removed from the washing brine and from the finishing water, respectively, before the use thereof, in order to avoid bubbling out and foaming which would be detrimental both to the washing and the finishing operations.

Preliminarily a small quantity of a caustic alkali is added to the finishing water, preferably in an amount comprised between 0.2% and 2%. As a matter of fact it has been found that the free alkali content of the liquid soap is a function of the free alkali content of the finishing water.

TABLE Percent alkalinity gg gg soap nigre Therefore, the addition of some alkali to the finishing water permits the obtention of a soap having a perdetermined free alkali content; said addition further prevents a carbonic foaming due to the possible action of a carbonated alkali contained in the soap on the fatty acids, said action being caused to manifest itself by the fact that the soap becomes hydrolysed by a neutral brine; the resultant washing with an alkaline water is completed to such a point that, starting from a very alkaline soap, a completely neutral soap, or even a partially acid soap may be obtained.

The washed soap and the finishing water are mixed during a time amounting to a maximum of ten minutes, generally two minutes.

The soap is introduced in the kettle at a level below the middle-height thereof, for instance at a fifth of the kettle height, as measured from the bottom of the kettle, through a flared-out opening, in such a way that the flowing rate of the soap be less than one centimeter per second, in order to prevent the formation of any eddy current detrimental to the decantation.

The volume of solution drawn off the decantation kettle is greater than the volume of nigre theoretically formed in said kettle, by about 20%. Thus the drawing off of the whole nigre present in the kettle is secured, said nigre being mixed with some neat soap, which has no importance since the total volume drawn off is recycled thereafter into the last washing stage.

The drawn off liquid must undergo a change of structure and be separated into neat soap and poorer brine before it is recycled in the mixer of the last washing stage; this is obtained by increasing the salt content of the mixture. Preferably the salt content is increased by adding fresh brine having such a concentration that the neat soap thus separated from the mixture be in equilibrium with the poorer brine thus obtained, the concentration of which is very near the limit concentration below which the soap may be dissolved thereby.

If, for instance, the limit concentration for the brine corresponding to a given soap is 13.5%, the nigre will be separated by means of such a brine that, after separation, the nigre mixture presents a layer of neat soap and a layer of brine having a concentration of 13.5%. Experiments have shown that, in such a case, one part of the nigre is to be treated with one part of a brine having a 15% concentration. More generally, I have found that the concentration of the brine used for the separation of the nigre mixture must be higher than the concentration of the limit brine by 1% to 5%.

An arrangement for use in conjunction with the method according to my invention comprises aesaoss in combination; a series. oiv interccmmunico ihs washing stages, each of said stages includin a mixer, a settling compartm nt, a. p pe between said mixer and said settling com artment and pipes for circulating the soap and the brine n. counterfiow with respect to each other from. said settling compartments respectively in the mixer of the next h g stage and. in the m xer of th ne t o r a e; mea for admitt n so p.- into the mixer of one end stage oi said series; m ans for admittingwashing brine into th mix r the; opposite. end sta e in said series; a hamber provided with mixer means and. for d mitting water and flowin soon out; the s ttlin compartment of said. opposite end stage respectively; a finishing kettle; a tube connected to said mixer means and opening in said finishing kettle at a level below the middle-height thereof through downwardly directed, outwardly flared end portion; an upper pipe for removing the neat soap from said finishing kettle; a lower pipe for removing the mixture in the lower part of said finishing kettle; a variable flow volumetric pump inserted in said lower pipe; a mixer tankfed from said lower pipe; a pipe for introducing a brine in said mixer tank, said pipe being connectable successively to two sources of supply of brines having difierentconcentrations respectively'; a second variable flow volumetric pump inserted in saidlast-mentioned pipe; a third pipe connecting said mixer tank with the mixer in the last washing stage immediately preceding said chamber with mixer means; means for removing preliminarily the occluded gases from the liquids present, and means for maintaining the temperature of the fluids and apparatus within the range 80 to 90 Q.

The arrangement of such a device will be best understood from the following; description of an illustrative embodiment theerof, taken in connection with the annexed sheet or drawing, wherein the single figure schematically shows such an arrangement in vertical cross-section.

The described purifying arrangement illustrated in the figure is. a part oi. a. plant. for the continuous preparation of soap, which has not been shown for the sake of clarity. The arrangement comprises a four-stage washing tower I including a chamber 2 provided with mixing or stirring means 2' at the upp r end f sa tower- Each washing stage in said tower ompr s a mixer c mpartm nt 3 an dec ntat n omartment 4 connected, toge her throu h. a pip 5. The mixers 3 each are driven from respective electrical motors A pipe 5 connec s he mixe compartment in every stagei except the uppermost one, with the mixer 3 in the n xt preceding t Another pipe it connects the ecantati n compartment 4 in each. stage with the mixer 3 in the next following stage, except for the lowermost stage. The soap to be washed is caused to flow in the lowermost sta e through a p p I, and the water for finishing or fitting the soap is supplied in the uppermo t stage in the tower I through a pipe 9, to which a. thermostat I0. is connected, the function of. which will be discussed hereafter.

When the soap has been washed, the used brine is eliminated to waste through the tube l. The liquid soap flows off the chamber 2 through a pipe l2 which terminates in a flared out, downwardly directed mouthpiece l2 within a decanting kettle l3.

Through an upper tube II, the kettle it is connected with a kettle l5 for receiving the pun 6 fled soap; said soap may be taken of through h lower pipe It at the-bottomof the kettle IS.

A variable flow volume ric. pump P is inserted in nice 20. pass ng thr ugh the ttom Wall. of the.- kettle B at. one end nd op n ng, in a mixer tank ll at. th oth r nd The m x re i th kettle l3 be taken oft from sa d pump. B-

The mixer tank i1 s con ec e t a suitable supply of br ne thr ugh nin I8 prov d, it a pump P2 The, mixture contained in the tank 11 may low to the m x r ii the upp rmos washin sta e in the tow r through a pipe Th purificat on is carri out as follows:

when startin he s mo P stopped! whereas the pu p P is operated and ur cshroush the conduct la. the H and the p pe s n th mixer 3 of: the hi hest. washin sta a sa t solution. havin a coh ehtra n s htly hi he than the. prev ously d fined m t ncentration, for. instance a 1.35% chloride solu on aid chloride solution (or brine) further flows irom the. mixer 3. of sci hi hest sta into he setthus: compartm nt 4. f. this sta e h ou h the pipe. 5.- This brine th reaite f ows hrou h h nice 8. into the mixer 3 of; the next; sta e which i located el w, and then rom his mixer into hcsc tl n comp rtment. 4. of same sta e h ou h he pipe 5-; so. the rine is f owin from a sta to he nex and lowe on to finally reach the mix r 3 of the. l w s ta e wher in it, ome into contact with the soap to be purified. The latter is driven back into the washing tower I by a vol metric rump (not shown). thr u h the conduct a then. reaches the mix r 3 of the. lowest st e. wh re n. it omes in ontact with the brine; the scan and brine mix ng is firstly f med within, the mi er 3 o h s ow age and th mixtur flows out throu h. pipe 5 and. reach s the lower settlin com ar ment The rin ho s, down into the low r part i th s. compartment 4 of the lowest sta e a d i dra n ofi throu h the c n uct H y a vo ume c hum (not. showh Th s an accumula es at h h hest part of the compartment 4 of the lowest stage, an flow he f om. through a pip 6 in the mixer 3 o he ne t an hi r sta wh e n it comes into contact with the brine flowing from the comp rtmen 4 of he n t l w g and higher stage throu h, p pe 8. Soap is so flowing p o sta e o state un i the h hest co partment 4 is full; it then flows into the vat 2, wherein a slightly alkaline water is urged through a pipe 9 and a volumetric pump (not shown); the temperature of this water is regulated by a thermostat l0 which acts upon the heating device (not shown) for the water; the mixer 2 makes the fitting easier by performing a close mixing of water with the soap previously treated with brine.

As already mentioned, the temperature of the arrangement and of the fluids flowing therethrough is maintained at O. by any wellknown suitable means, and. the gases in the water as well as in the washing brine are removed pre- 3 liminarily by any convenient means, not shown.

The tower l and the auxiliary devices may have a double outer wall within which a liquid at the temperature of 85 C; will be caused to flow; said qu d mo r may be conv n the finishns wate he finished so p fl ws thr gh the p ne into the kett e 13 which progr v ly fills up. The kettle i3 is indrical in shap nd has frusto-conical bottom well for d with an an le of about. the heigh f a kettle is made slightly greater than its diameter and the opening I4 is arranged substantially at one fifth of the height of the kettle I3 below the top end thereof. Preferably the volume of the kettle I3 is substantially twenty times greater than the volume of soap produced by hour, whereby the finished soap becomes perfectly decanted in the upper part of the kettle I3 before reaching the pipe I4. Since in practice six hours only are required for the phases of the liquid soap to be separated, due to the physico-chemical conditions existing following the washing of said soap, it is thus apparent that in this manner a very large security is given for the obtention of a neat soap having good qualities.

When the kettle I3 becomes filled up, the pump P is started and an amount of mixture is drawn off the kettle l3 from the bottom thereof, which corresponds to a volume greater by 20% than the volume of nigre theoretically formed in th kettle I3.

At the same time, a more concentrated brine must be fed in the mixer tank 11; therefore the pipe I8 will be connected now with a source of more concentrated brine, having for instance a 15% concentration. Said more concentrated brine causes the mixture in the tank ll to separate into neat soap and a poorer brine; according to my invention, the concentration of said poorer brine must be equal to 13.5% in the example described in order that it can be used for washing.

The arrangement is very easily controlled, by controlling the amount of finishing water which is added; said amount may be varied within a substantially large range, while giving yet sufficiently good results. Indeed, only the respective volumes of the phases in contact are changed, which is of no importance, since the volume of liquid drawn oif the kettle I3 is maintained greati er than the volume of nigre formed by about Generally speaking, a volume of 15 parts finishing water to every 100 parts soap gives satisfactory results.

As has been mentioned already, it is desirable to use a finishing water which has been made slightly alkaline by adding a caustic alkali in an amount of 0.2 to 2% by weight, according to the desired alkalinity for the finished product.

It is to be clearly understood that the embodiment shown and described has been given by way of illustration only, and that many changes could be made thereto without departing from the scope of my invention as defined in the appended claims.

What I claim is:

I. In a method for continuously purifying a totally saponified glycerinated soap obtained in the most concentrated liquid phase known as the neat soap, including washing said soap in counter-current with a first brine constituted by an alkaline metal chloride having a concentration slightly above the critical concentration below which said purified soap dissolves, the steps comprising, mixing said soap with water after Washing with said first brine, circulating said mixture of soap with water in a settling zone where separation into neat soap and nigre takes place, drawing off continuously from said settling zone, at the bottom thereof a quantity of liquid greater than the quantity of said nigre, and at the .top thereof the surplus of the purified neat soap, circulating said drawn off liquid containing nigre through a supplementary mixing zone with a second brine having a concentration 8 greater than that of said first brine and adjusted to produce after mixing a change of structure resulting in a mixture of deglycerinated neat soap and of a brine constituting said first brine and circulating said mixture of said first brine and deglycerinated neat soap for the washing of said glycerinated neat soap.

2. In a method for continuously purifying a totally saponified glycerinated soap obtained in the most concentrated phase known as the neat soap hase, including washing said soap in counter-current at a temperature between about and about C. with a first brine constituted by an alkaline metal chloride solution having a concentration slightly above the critical concentration below which said purified soap dissolves, the steps comprising, mixing said soap with water after washing with said first brine, circulating said mixture of soap with water in a settling zone to separate the neat soap at the top from the nigre at the bottom, continuously drawing from the bottom of the settling zone a quantity of liquid greater than the quantity of the nigre and continuously drawing from the surplus of said purified neat soap, mixing said drawn off liquid from the bottom of said settling zone with a second brine having a concentration greater than that of said first brine, the concentration of said second brine being so adjusted to produce in the mixture a change of structure to form deglycerinated soap and residual brine of the same concentration as said first brine and circulating the last named mixture for the first brine washing of the glycerinated neat soap.

3. In a method for continuously purifying a totally saponified glycerinated soap obtained in the most concentrated phase known as the neat soap phase including washing said soap in counter-current at a temperature between about 80 and about 90 C. with a first brine constituted by an alkaline metal chloride solution having a concentration slightly above the critical concentration below which said purified soap dissolves, the ratio of the volume of said first brine to the fatty acids in said soap being within the range of 30/70 to 50/70, the steps comprising, mixing said soap with water after washing with said first brine, circulating said soap in admixture with water in a settling zone, continuously separating the neat soap from the top of the settling zone and continuously drawing off a quantity of liquid from the bottom of the settling zone which is greater than the quantity of nigre at the bottom of the settling zone, mixing the drawn off liquid from the bottom of the settling zone with a second brine having a concentration greater than that of said first brine, the concentration of said second brine being so adjusted to produce a change in structure in the mixture to form deglycerinated soap and a residual brine of the same concentration as said first brine, and circulating the last named mixture for the first brine washing of the glycerinated neat soap.

4. In a method for continuously urifying a totally saponified glycerinated soap obtained in the most concentrated phase known as the neat soap phase including washing said soap in counter-current at a temperature between about 80 and about 90 C. with a first brine constituted by an alkaline metal chloride solution having a concentration slightly above the critical concentration below which said purified soap dissolves, the steps comprising, mixing said soap with a dilute aqueous solution containing from about 0.2 to about 2% of caustic alkali after washing with said first brine, circulating said soap in admixture with said dilute aqueous solution of caustic alkali in a settling zone, continuously separating the neat soap from the top of the settling zone and continuously drawing off a. quantity of liquid from the bottom of the settling zone which is greater than the quantity of nigre at the bottom of the settling zone, mixing the drawn oif liquid from the bottom of the settling zone with a second brine having a concentration greater than that of said first brine, the concentration of said second brine being so adjusted to produce a change in structure in the mixture to form deglycerinated soap and a residual brine of the same concentration as said first brine, and circulating the last named mix- 15 2,485,205

10 ture for the first brine washing of the glycerinated neat soap.

FELIX LUCIEN LACHAMPT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 783,196 Hatschek Feb. 21, 1905 889,664 Crozier June 2, 1908 1,367,973 Ittner Feb. 8, 1921 2,300,751 Scott et al Nov. 3, 1942 2,485,204 Lachampt Oct. 18, 1949 Lachampt Oct. 18, 1949

Claims (1)

1. IN A METHOD FOR CONTINUOUSLY PURIFYING A TOTALLY SAPONIFIED GLYCERINATED SOAP OBTAINED IN THE MOST CONCENTRATED LIQUID PHASE KNOWN AS THE NEAT SOAP, INCLUDING WASHING SAID SOAP IN COUNTER-CURRENT WITH A FIRST BRINE CONSTITUTED BY AN ALKALINE METAL CHLORIDE HAVING A CONCENTRATION SLIGHTLY ABOVE THE CRITICAL CONCENTRATION BELOW WHICH SAID PURIFIED SOAP DISSOLVES, THE STEPS COMPRISING, MIXING SAID SOAP WITH WATER AFTER WASHING WITH SAID FIRST BRINE, CIRCULATING SAID MIXTURE OF SOAP WITH WATER IN A SETTING ZONE WHERE SEPARATION INTO NEAT SOAP AND NIGRE TAKES PLACE DRAWING OFF CONTINUOUSLY FROM SAID SETTLING ZONE, AT THE BOTTOM THEREOF A QUANTITY OF LIQUID GREATER THAN THE QUANTITY OF SAID NIGRE, AND AT THE TOP THEREOF THE SURPLUS OF THE PURIFIED NEAT SOAP, CIRCULATING SAID DRAWN OFF LIQUID CONTAINING NIGRE THROUGH A SUPPLEMENTARY MIXING ZONE WITH A SECOND BRINE HAVING A CONCENTRATION

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