US2539889A

US2539889A - Method of manufacturing soap

Info

Publication number: US2539889A
Application number: US754949A
Authority: US
Inventors: Bradford Purdy
Original assignee: Swift and Co Inc
Current assignee: JBS USA LLC
Priority date: 1947-06-16
Filing date: 1947-06-16
Publication date: 1951-01-30
Anticipated expiration: 1968-01-30

Description

im. 30, 12951 P. BRADFORD METHOD OF MANUFACTURING SOAP Filed June 16, 1947 ness and purity in the finished product.

Patented Jan. 30, 1951 UNITED STATES ATENT OFFICE METHOD OF MANUFACTURING SOAP of Illinois Application .lune 16, 1947, Serial No. 754,949

2 Claims.

The present invention relates to a method of manufacturing soap. More particularly, the invention has to do with a continuous soap-,making process wherein the saponii-iable material is subjected to a purification treatment before saponification, whereby the resulting soap Vis of improved quality and may be employed in the preparation of high-grade toilet soaps.

Important steps in the art of soapmaking involve the selection of the saponiiiable raw material and the treatment thereof to producel a soap having the desired characteristics. For example, a high degree of purity, as evidenced by the whiteness of the soap, is highly desirable in high-grade toilet soaps. Crude saponiable fatty material contains color bodies which, if not removed from the fatty material, are often carried into the finished soap product, thus making it impossible to obtain a high degree of white- In producing a superior toilet soap, it is often the practiceto select superior raw material relatively color free, and to subject the said material to a bleaching operation before saponication.

The quality of whiteness possessed by the high-grade soap is not only due to the nature of raw material treated, but is also partly due to the soapmaking process employed. When the so-called full-boiled process of making soap is employed, a series of operations are involved, as

a result of which the color characteristics of the iinished soap are improved. In the full-boiled soap-making process, saponication is carried out in successive stages, which involve boiling of -the soap in water, graining -or salting out the soap, removing the aqueous layer containing various impurities and glycerine, and settling.

In other soapmaking processes, such as the semi-boiled and cold processes, the operations of boiling, graining and settling are omitted. Consequently, any improvement in color in the iin- `ished product due to these omitted operations is lacking. For these reasons, the soap product obtained from the aforesaid soapmaking processes is usually inferior in color characteristics to that obtained from the full-boiled process. Because it is desirable that a high-grade toilet soap possess a high degree of whiteness, the fullboled process of making soap is generally employed in the manufactureof vthe superiorv white soap.

More recently, in the art of soaprnaking, there have been developed processes for the continuous saponication of fats. The continuous saponiication process generally involves a careful mixing of the fat or fatty acids, often inthe presence of a diluent with the correct ramount of caustic, saponifying the mixture, then spraying the resulting` soap into a spray or flash chamber, wherein the volatile products of saponication are flashed off, and the soap is recovered as a dry product.

The washing effects of the various operations of the full-boiled process are lacking in continuous saponiiication processes. The degree of whiteness in the finished product, therefore, is inferior to that of the full-boiled soap, and is about equivalent to that possessed by the soap obtained by the semi-boiled or cold process.

An object of the invention is to produce soap of improved color characteristics, employing a continuous saponication process.

Another object of the invention is to produce soap of improved color characteristics by means of a continuous saponiiication process, which soap is superior to or equivalent to full-boiled soap.

Afurther object of the invention is to provide a continuous saponification process, wherein purication of the saponiable fat is continuously effected.

crine.

Yet another object of the invention is to provide a continuous saponication process, wherein the diluent for the fat employed in thecontinuous saponification of the fat is utilized in the purification of the fat before the continuous saponification thereof.

A stillfurther object of the invention is to provide a process wherein the diluent is recovered from the soap, is employed in the purification of the fat, and is simultaneously purified with the fat.

Other objects and' advantages of the invention will be apparent from the foliowing description.

The invention contemplatesl broadly a continuous soapmaking process, wherein a solution of the fat to be saponified is effected with the diluent or solvent, such as kerosene, employed in the saponiiication operations, the resulting solution bleached and then subjected to saponification conditions of temperature and pressure, whereby the fat is converted into soapl and glyc- The productsV ofsaponication are then discharged into a Vaporization zone maintained under reduced pressure, wherein the volatile materials, including' diluent, are separated from the soap by vaporization.

More particularly the invention contemplates forming the fat to be saponied into a solution with the diluent employed inthe continuous saponication of the fat. The solution is treated with a bleaching agent, for example, fullers earth, at elevated temperatures. After bleaching of the fat solution, the solution is filtered and the earth-free solution mixed with a caustic saponifying reagent. The resulting mixture is charged to a saponirlcation zone to eiIect the saponification reaction, following which the soap is separated from the volatile products of saponication, including the diluent. The diluent is recycled and is used to form a solution with new fat. The solution is treated with a bleaching agent, whereby both the fat and the recovered solvent may be decolorized.

In carrying out the invention," it is contemplated to employ a continuous saponication process, wherein a diluent is employed for the saponication reagents and the products of saponification. It is also understood that the diluent exhibits solventaction for the yfat to be saponiiied. A suitable saponifcation process for accomplishing the purposes of the present invention is shown, for example, in Patent No. 2,401,756 to Gunther, issued June l1, 1946.

The aforesaid patent discloses a continuous saponication process, employing a relatively dilute caustic alkali solution and an amount of diluent or solvent for the saponifiable material in "excess of 50 -per cent, and-preferably at least about '75 per cent, based on the saponiable matter. The relative large amounts of diluent make it possible to effect the saponication reaction at lower temperatures than would be possible were the diluent not present and to maintain the soap product fluid at temperatures below the melting point thereof.

In accordance with the Gunther patent, the caustic alkali solution, saponiii-able material, and diluent, formed into an emulsion, are subjected to conditions of saponifcation in a zone of restrcted cross-section, under pressure, to prevent Avaporization of any of the reactants and products o f saponicaton. Upon completion ofthe saponification reaction, the mixture lis heated and then sprayed into a low-pressure zone wherein, by partial pressure distillation, the volatile products of saponication and the diluent are vaporized and continuously removed, leaving the soap product, which may also bev kcontinuously removed. The invention will `be more fully understood from the followingA description read in connection with the accompanying drawing which shows diagrammatically a form of apparatus which can be employed for carrying out the process. v

vReferring more particularly to the drawing, the numeral I indicates a tank for holding saponiable fat, for example, tallovv. Another tank II is provided for the storage of the diluent, or solvent, for the fat, such as kerosene. The fat and diluent are introduced through conduits I3 and I4, respectively, into a bleaching tank I6. Bleaching tank I6 may be provided with a hopper I1 for the introduction therein of bleaching material, such as fullers earth, and means, such as an agitator I8, to effect intimate yadmixture of the solution and earth. The bleaching tank may also be provided with means for supplying heat to the contents thereof, since it is vpreferred to carry out the bleaching operation at temperatures above 212 F. Following the bleaching operation, the bleached fat solution is withdrawn from the bleaching tank through line 22 and,` in the form of a slurry, is pumped by means'of pump 23 into a lter press 25. J'Ihe filtered f at 4 solution is collected through line 21 in feed tank 29.

'Ihe solution of saponiable fat in the solvent and aqueous caustic soda of the desired strength held in tank 3l are drawn in the proper ratio through

conduits

33 and 35, respectively, by proportioning pump 31, driven by motor 38. From the proportioning pump 31, the saponiiication reactantsvow in a commonv stream through conduit 40 to homogenizer 4 I. rThe homogenizer may be any suitable apparatus wherein the fat solvent solution and the caustic may be thoroughly mixed. A suitable homogenizer may comprise a container and an agitator 43 driven by any suitable source of power through a pulley 44. In the homogenizer an emulsion is formed comprising microscopic globules of caustic soda solution dispersed in the solution of saponiable material. The emulsion usually contains a soap formed by the instantaneous neutralization of the free fatty acids-contained in thev fat, which functions to stabilize the dispersion of the aqueous caustic phase in the inert medium.

From the homogenizer the emulsion is pumped by means of pump 46 through conduit 41 into saponcation coil 48, which is provided with any suitable heating means to raise the temperature of the emulsied mixture to that necessary for substantially complete saponification. Thetemperature of reaction will vary inversely with the length of time the mixture remains in the coil, being about 400 F. for a l-minute reaction Period .and lower for longer, periods offresidencein the coil. The pressurein the saponication'coil is sufficiently -high to prevent substantial evaporation of the diluent. This pressure may be approximately pounds per square inch. Upon completion of the saponification reaction, vthe fatty mixture passes from the saponification coil through conduit 58 into a relatively short preheating coil 52. The temperature of the reaction mixture maybe raised in coil 52 high enough, for example, to about 480 F., to supply sufcient sensible heat to facilitate flash evaporation of the inert diluent and glycerine from the soap product when the pressure is reduced. The pressurefin the preheating coil is maintained suilicientlyhigh to avoid vaporization which might interfere with keepingr thev saponication reactionvproductsin a fluid state. 4

The reaction-mixture passes through conduit 54 to a nozzle 56, from which it is continuously sprayed into a vaporizing, or flash, zone 58. The chamber 58 is held at relatively low pressure, preferably less than 40 mm. of mercury absolute, whereby a substantially complete separation-,of water, glycerine, and other volatiles from'the soapproduct usually occurs. the heating coils and flash chamber are preferably controlled so that the temperature'of the soap and vapors after flashing is reduced to about 320 F. to 350 F., or to a temperaturejust above the boiling-point of the highest boiling volatile constituent at the existing conditions. In some cases, particularly where it is desired to `producea soap product having a high glycerine content Aor where glycerine recovery is not' material, the preheating coil may be eliminated. In the latter case, the reaction mixture passes directly from the saponification coil and through. the spray nozzle into the flash chamber. In such cases, more volatile ldiluent is preferably employed and/or heat supplied through the jacket ofthe vaporization chamber in order toilashY the.:diluent. The preheating coil is preferred, however,

The conditions in `charged 'into 'vfractio'nating @armrest Aby' YanVE expeller ft. The"?expel1erfmayr'be'f-any suitable ftype' i of conveyor for l"continuously vkiremo'v'ing thesoap whilepreserving?fthevacuumvin the-'flash chamber j' `f or `e"x`ample ,fia lscreizt/Sandi shell arrangement L"which 'compacts'f. thefsoapY particles as-jthy are 'advanced'by the scr'wcenveyor'has beenfound" satisfactory. 'is' arewcontinuoiisly withdravvn from tll flash *chamber Vby means 'off lin 62,1' and racti Vtils therefrm.

settling tanlg'wvherein a Sparation of Water A Lafnd solvent iiitoil'ayers'j of diffrent specicfgravi- The i glyceri-ne :may be lwitlfidrawn from @the fractionating columnf 63 .-atfi one for more2 levelsiTheLdi-luentf iusedllin'` lthef; process` may l lbefany substancefwhich :is f'substantially-f inert.. to fthereactantsf; and fthe` products Pof saponicati'on-'' but whieh isha slv'entffor Sthe' fat @to2-*be saponid. In" carrying outffthe' processA` of the inventiong'fit is'llpreie'rred1'Lto 'employ-f an inert, organic Ihydrocarbon-diluent .which boilsv not greatly' excess `offabout- 2100l`]i..fat the pressure in the low-pressureflzonef and which is substantially irnrniscible Withwater andthe.glycerine formed in the "reaction, and substantially miscible with the fsoa'p at the temperature inthe saponi'cation zone. Solvents; su'chlascertainV alcohols which aremiscible Withf water 'Jandglycerine,l maybe Q utilized providedthey possessfithe other requisite V'physi- 'calo properties. `A .prefer-red inert -di-luentf'fissia hydrocarbon i petroleum il fraction 'Which hasf a boiling rang'effoffrom 450 Reto-500 F. Other linertrv'fdiluents'Fwhichmayf bei-:employed nin the processincludekerosene, nap'thaV gas oil, toluene, and l xylene. In vs'oine cases 'noninflammable- Atype diluents, suchA as trcliloroberizeneors-tetrachloroetha'ney 4may `be used.

*FT-hei saponifyifng reagenti may ,consist i *of Aany materialcapable offconverting an ester 'intoan alcohol and a salt'with thek fatty acid,- sucnl'fas caustic'"l's'oda @realistic-potash Thesaponifying reagent is preferably a Vrelatively ldilute aqueous Solutionof -a concentration of about 50 percent 'or lss by lWeight of thecaustic.

Inl1 accomplishing"saponication in the ipres- "ence'of a lisolve'nt, :itf is"des'irable to employran cludefanirnal andvegetable `fats Aand-oils, such as 'tallowfand coconut oil, Aor :any organic4 ester'susceptible tosapon'ication.v It is understoodtl'iat the 'quality of vthe nal soap' producttwill depend 't'oafg'reatextent on the selectionof the'raw'rna- "vteri'al. "f Ihusfin4 'ordento' "produce a' high-'grade White toi-let` soap, it i is important toV employ lsaponiableV materials lof good quality.Y However, fats of low"q'uality maylalso be employed which, because `'ofthe- `bleaching step, may "be productive of a soapproduct having `improved.

cent to'15o Yper'cent-based on the Saponiabie material, produce `.satisfactory results. .The

'amountlof bleachingv agentV empoyed may range `from about 0.5 percent to about 5 per cent, based 'on' thesapon'iable material, and may be any suitable bleaching earthy or clay or acid-activated' `clay or activatedcarbon orv charcoal.

'L Allietemperaturesemployed .in` bleaching f the fat 'in the presence of the solvent are .preferably above 212 F., for example, between Vabout 215fF. and 220 F., in order to evaporate moisture, the presence of which seems to render the bleaching operation less effective. In the absence of water the bleaching step may be accomplished at lower temperatures, a temperature as low as 140 F. having been found satisfactory.

I have found that bleaching of fat in the presence of a solvent prior to charging the resulting bleached solution to a saponication process requiring the presence of a diluent, as hereinabove illustrated, produces a soap of superior color characteristics. The soap produced in this manner may be used in the preparation of high-grade white toilet soaps which heretofore have generally required the full-boiled process for the manufacture thereof. I have found that if the fat is rst separately bleached prior to being formed into a mixture with the diluent and then saponied, the resulting soap does not possess the degree of whiteness characteristic of soap produced by the full-boiled process or the process herein disclosed.

In soapmaking processes heretofore practiced it has not been customary to bleach a solution of the fat, for such a process used in connection therewith would have no particular utility. For example, if the aforesaid process were applied to the full-boiled process of soap manufacture, the solvent would require removal after the bleaching operation, an expensive operation and one which would tend to discolor the fat, thus rendering the whole operation useless. For these reasons, bleaching of the fat has heretofore been accomplished in the absence of a solvent.

In accordance with the present invention, however, the bleaching of thefat in the presence of V.the diluent employed in the continuous saponication process has many advantages. For exam- ;ple, the heat imparted to the fat in effecting the .solution thereof may be advantageously utilized :in the saponication reaction. In addition, by virtue of the combination of the bleaching step :with the steps in the continuous saponication process, it is not required to remove theso-lvent .after bleaching. The solvent is removedl after :saponication from the soap, an operation which is inherent in the continuous saponiilcation process. For this reason no discoloration of the fat occurs through distillation of the solvent therefrom, and the process is rendered economical. By using fat immediately after decolorizing and without removing solvent there is no opportunity for fat to deteriorate and afbetter colored soap is obtained. Moreover, I have found that the solvent distilled from the products of thesaponication reaction is often discoored, but that in reusing the solvent in the bleaching of additional fat, the solvent is decolorized along with the fat and may thus be used indefinitely. l

As an example of the invention, 100 parts of prime tallow, not darker than 17 F. A. C., havv`ing a free fatty acid content of 2.5 per cent, and 125 parts of a petroleum fraction boiling between about 450 F. and 500 F. were formed-into a solution. The solution was then agitated in the presence of about l per centfullers earth for about .one-half hour and at a temperature of about 215 to bleach the fat. Following the bleaching operation, the mixture was filtered and the resultant earth-free solution was formed into a common stream with a 50 per cent caustic solution in the ratio of 28 parts of the caustic to 100 parts pf fat.V The fat solution and caustic were intimately mixed in the homogenizer to form arl emulsion. The emulsion was continuously passed through a saponiflcation coil at a temperature .of about 415 F., under a pressure of about 100 pounds per square inch. The time of ow of the reaction mixture through the saponication coil was about seven minutes, after which time the saponication reaction was completed. Following saponication, the mixture was passed through a preheating coil and the temperature thereof raised to about 480 F. in about 25 sec= onds, while maintaining the pressure of about pounds per square inch.` The mixture was then sprayed through a restricted nozzle into the ilash chamber, which was maintained at about 400 F. and at a reduced pressure of about 20 mm. of mercury absolute. Solid soap in the form of a white powder settled to the bottom of the flash chamber and was continuously removed therefrom. The vapors were continuously discharged into a fractionating tower, also maintained at a pressure of about 20 mm., wherein the -vapors were separated by rectification. The temperature of the vapors coming off the top of the tower was about 100 F., at which temperature the major portion of the solvent condensed as a reflux condensate and was taken off of an upper plate of the column and recycled to the system. The volatile materials, including the small proportion of uncondensed diluent, passed into a condenser, wherein water and the diluent were condensed and separated by stratification in a settling tank.

Employing portions of the same tallow used in accordance with the foregoing process, saponication of one portion of the tallow was effected by following the full-boiled process, and the other portion according to a continuous process, substantially -as hereinabove described, except that bleaching of the tallow was effected in the absence of solvent. Three Ll-gram samples of soap, representing each of the three methods, were separately dissolved in 100 ml. of specially denatured ethyl alcohol, and the three solutions measured for color on the Lovibond scale. Soap from the continuous process, wherein bleaching was performed without the solvent, gave a read.- ing of 2.3 R., while the full-boiled soap gave a value of 1.2 R., and soap prepared in accordance with the present invention, 1.0R. The results show that the present invention is productive of a soap of a higher degree of whiteness than lsoap prepared by priorA art methods.

As another illustrative example of the invention, a second lot of tallow was substituted for the fat used in the preceding example. Bleaching and saponification conditions were the same as in the first example. Color tests were then performed by comparing, for color, the alcohol solution of the resulting soap with the solutions of soap made from portions of the same tallow by the full-boiled process and the continuous soap process wherein the tallow had not been .bleached in the presence of the diluent. The colors of the three solutions were as follows: 3.6 R. forsoap obtained by the continuous process wherein bleaching of the fat was effected in the absence of solvent; 2.6 R. for full-boiled soap, and 2.5 R. for soap obtained in accordance with the invention.

While the present invention has been der scribed as being particularly adapted to the soapmaking process described in the Gunther `patent aforementioned, `itis understoodthat the invention is not to be construed as being limited thereto, but may be appliedy to other soapmaklng tions shouldbe imposed as are indicated in theV appended claims.

I claim:

1. In a continuous process of manufacturing soap, the improvement which comprises: forming an intimate mixture of a saponiiable material containing objectionable color bodies, a solid adsorbent bleaching agent, and an inert hydrocarbon boiling between about 230 and 500 F., said hydrocarbon having a property of forming a solution with both the saponiable material and the soap subsequently formed therefrom; separating the bleaching agent and objectionable color bodies from the solution of saponiiiable material; subjecting the bleached saponiliable material while dissolved in the said hydro- 1 carbon to a saponiication temperature and pressure in the presence of an alkaline saponication reagent to convert the saponiable material into glycerin and soap, said soap substantially free of objectionable color bodies being I dissolved in said hydrocarbon; and discharging the products of saponication and the hydrocarbon into a fractionation Zone to individually recover the said products of saponicationand the hydrocarbon.

2. In a continuous process of manufacturing soap, the improvement which comprises: forming in a mixing zone an intimate mixture of a saponiiiable material containing objectionable color bodies, a solid adsorbent bleaching agent and an inert hydrocarbon boiling between about 230 and 500o F., said hydrocarbon having the property of forming a solution with both the saponiable material and the soap subsequently formed therefrom, and being present in an amount at least between 100 and y150 per cent by Weightv of the saponifiable material; separating the bleaching agent and objectionable color bodies from the solution of saponiable material; subjecting the bleached saponiiiable material While dissolved in the said hydrocarbon to a saponii-lcation temperature and pressure in the presence of an alkaline saponication reagent to convert the saponiable material into glycerin and soap, said soap substantially free of objectionable color bodies being dissolved in the said hydrocarbon; discharging the products of .saponication including dissolved soap, vglycerin, and hydrocarbon into a fractionation zone maintained at subatmospheric pressure to individually separate the soap, glycerin, and hydrocarbon; and recycling the said hydrocarbon without further processing to the mixing zone where it is bleached simultaneously with the saponii'lable material.

PURDY BRADFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,100,146 Schmidt-Nielsenetal. NoV. 23, 1937 2,255,875 Buxton et al Sept. 16, 1941 2,318,748 Buxton et al May 11, 1943 2,383,630 Trent Aug. 28, 1945 2,401,756 Gunther June 11, 1946 FOREIGN PATENTS Number Country Date 251,290 Great Britain July 25, 1947

Claims

1. IN A CONTINUOUS PROCESS OF MANUFACTURING SOAP, THE IMPROVEMENT WHICH COMPRISES: FORMING AN INTIMATE MIXTURE OF A SAPONIFIABLE MATERIAL CONTAINING OBJECTIONABLE COLOR BODIES, A SOLID ADSORBENT BLEACHING AGENT, AND AN INERT HYDROCARBON BOILING BETWEEN ABOUT 230* AND 500* F., SAID HYDROCARBON HAVING A PROPERTY OF FORMING A SOLUTION WITH BOTH THE SAPONIFIABLE MATERIAL AND THE SOAP SUBSEQUENTLY FORMED THEREFROM; SEPARATING THE BLEACHING AGENT AND OBJECTIONABLE COLOR BODIES FROM THE SOLUTION OF SAPONIFIABLE MATERIAL; SUBJECTING THE BLEACHED SAPONIFIABLE MATERIAL WHILE DISSOLVED IN THE SAID HYDROCARBON TO A SAPONIFICATION TEMPERATURE AND PRESSURE IN THE PRESENCE OF AN ALKALINE SAPONIFICATION REAGENT TO CONVERT THE SAPONIFIABLE MATERIAL INTO GLYCERINE AND SOAP, SAID SOAP SUBSTANTIALLY FREE OF OBJECTIONABLE COLOR BODIES BEING DISSOLVED IN SAID HYDROCARBON; AND DISCHARGING