US2485205A - Method for the continuous production of soap - Google Patents

Description

F. L. LACHAMPT METHOD FOR THE CONTINUOUS PRODUCTION OF SOAP Filed May 24, 1946 l wwm %MZMW 7 WATER Patented Oct. 18, 1949 UNITED STATES PATENT OFFICE METHOD FOR THE CONTINUOUS PRODUCTION OF SOAP Application May 24, 1946, Serial No. 672,083 In France August 2'7, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires August 27, 1963 4 Claims.

The present invention has for its object a novel process which is based on increasing the rate of saponification by increasing the contact area between the fatty materials to be saponified-and the alkaline lye by producing an emulsion of the water-in-oil type between said reagents.

By a study of the conditions of stability in such emulsions, the applicant has been able to restrict the operative conditions of the above-mentioned process between narrower limits. In particular, the novelty of the improved continuous process, lies in the fact that the starting temperature of the saponification reaction is the lowest possible consistent with the necessity of melting the fat to be saponified. Practically, such temperature is, within a 2 Comargin, the same as the solidifying temperature of the fats used.

Experimental work carried out by the applicant has further brought to light the fact that it is preferable, for the fats employed, to be free of any natural or artificial saponifying catalyst, such as fatty acids, phenols and the like, so as to avert a premature release of the reaction. It has been recognized that it is preferable to start the saponifying process only after a maximum amount of diffusion has occurred in the emulsion. Lastly, a study of the equilibrium conditions between the soap phases has brought the applicant to the conclusion that best results may be obtained by so determining the concentration of the alkali used that the water of the soap produced at the termination of the saponifying process will be such that said soap will occur in the liquid phase thereof which has the highest soap concentration i. e. in the so-called neat soap phase.

By carrying out the various steps in such manner as to obtain, after saponification, a neat soap, it is possible to substitute, forthe lengthy salting out operation habitually used in soapmaking in the old Marseilles method, a washing process by means of an electrolytical solution having a concentration approximating and preferably above the critical concentration, i. e. the concentration below which the electrolytical washing solution still may dissolve soap. Such washing operation, which likewise is carried out in a continuous and methodical manner, is of the type described in the copending patent application Ser. No. 672,082 filed by the applicant on May 24, 1946 for Novel soap purifying process.

The novel process, which forms an object of this invention, comprises also a continuous and automatic control of the progress of the saponifying reaction. To that end, there is provided means for continuously checking the absence of any non-saponified fats in the soap, on one hand, and means for continuously checking that the finished soap produced at the end of the operation is free of any alkaline content, on the other hand.

The first control is achieved by continuously dissolving a small portion of the soap in 4 to 7 parts of boiling distilled water. The accidental presence of free glycerides or of non-saponifiable materials is enough to cause cloudiness, the appearance of which detected by optical means is operative through the action of a photo-electric cell to stop the operation of the saponifying apparatus.

The second control mentioned above is obtained by means of an indicator, the colourchange in which controls the stopping of the saponifying apparatus through the medium of a photoelectric. cell responsive to such colour change.

The advantages resulting from the process according to this invention are mainly the following:

(1) Uniformity of the finished product.

(2) Elimination of oxidizing products.

(3) Recovery of glycerol.

This first set of advantages is obtained in common with the conventional process.

The process according to the invention further brings about the following advantages:

(1) Complete continuousness of the process.

(2) High rate of operation. The total duration of the manufacturing process from the beginning to the cutting of the cake of soap may be within 5 hours.

(3) The control of non-saponifiable material and of neutrality are automatic and continuous.

(4) All tricks of the trade are eliminated and replaced by complete automaticity.

(5) Steam consumption is greatly reduced.

Lastly, all the operations are carried out in a condition where the product under treatment is screened from the air except the final drying of the soap phase.

In order to make the organization of the process according to the invention more clearly understandable, a preferred embodiment thereof will now be described, in a purely informative and nonrestrictive sense, reference being had to the annexed drawing wherein:

Fig. 1 is a general diagrammatic view of the plant;

Fig. 2 is a diagrammatic side-view of the de- 3 vice for controlling the presence of non-saponified products;

Fig. 3 is a front view of the device of Fig. 2.

It is assumed that it is desired to produce a tallow and cocoa-nut oil soap.

The previously melted tallow is introduced into a tank I which may be heated by means of a steam coil. The tallow is kept at a temperature of 45 C., slightly in excess of its solidification temperature.

In another tank 2, the alkaline lye is introduced at a concentration which is sufiicient to obtain, after saponification, a soap which is present in the liquid phase thereof having the highest soap concentration, such concentration of the lye being for example 40% NaOH.

Conducts 3 and 4 respectively lead the melted tallow and the alkaline lye to a feeding and metering device 5. This feeder comprises two volumetric pumps 6 and I having an adjustable It will be understood that the 7 feed of lye and tallow could be efiected by any length of stroke.

, tions that the quantity of alkali will be by 1 to 2% in excess over the theoretical quantity. In

this chamber 8, there occurs a first rough mixing of the product, the proportions thereof being approximately the following.

. Grams Tallow 715 Lye 260 the lye having 39.7% NaOH by weight and the mix being maintained at a temperature of 45 C. An agitator 9 makes it possible to make the mix sufliciently homogeneous without however permitting the saponification reaction to set in be- V fore the following homogenizing operation.

-The homogeneous mix thus obtained is sent,

by means of a pressure pump, into the saponifying apparatus proper, which comprises a homogenizer l0 and a reaction chamber ll provided With an agitator and heating means. The homogenizer is constituted by a colloidal mill of the Premier Mill type. It is in this colloidal mill that the desired emulsion of the water-in-oil type. is formed. It should be noted that this emulsion is formed at a low temperature (45 C.) and that it is homogenized before the saponification reaction sets in. This reaction is only brought about in the chamber ll after the very finely subdivided emulsion obtained at the discharge of the colloidal mill has entered said chamber. 7

The start of the reaction is brought about in this chamber by contact with the hot portion l2 of the walls thereof. The walls are heated to a temperature approximating 100 C. by indirect heat generated by steam circulating around the chamber without penetrating into it.

Once the reaction has set in, it will proceed without the necessity of supplying heat from an external source as a result of the exothermic character thereof. The emulsion, which is initially whitish in colour, is converted into an homogeneous translucid mass while the temperature throughout said mass rises to 100 C. Saponification is then completed and the soap is discharged in the form of neat soap at the lower; end of chamber H to the washing ma- 4 chines which are to free it of the glycerol contained therein.

It will be seen from the drawing that the soap is first washed in two stages with brine containing 12% salt for instance, during which stages the soap, the path of travel of which through the apparatus is indicated by arrows in full lines, encounters in contaminated condition, a salty solution loaded with glycerol, The path of the salty solution from C to D is indicated by dotted arrows. Each washing stage comprises a tank such as tanks 7'0, r1, T2, and m, a mixing and metering device such as me, m1, m2, and m3 and a static separator or settling device such as $0, s1, s2, and 83.

The soap discharged from the separator 52 is already purified and almost entirely free of glycerol but is still strongly salted. The salt content of the soap in equilibrium with the brine depends on the salt content of the brine; practically, said salt content also depends on the conditions in which the continuous separation of the soap from the lye is operated. Experimental runs have shown that, after two washing steps carried out with a 12% crude sodium chloride solution, the tallow soap contains about 2.5% salt.

Said soap is freed from the salt by effecting, for example, two washing operations by means of a 12% NaOH lye, which frees said soap from its salt but adds sodium hydrate thereto, so that the soap discharged from the separator 80 is practically free of salt but rich in sodium hydrate.

The path of travel of the lye from F to a sodium hydrate storage tank G is indicated by arrows drawn in dashes.

During the above mentioned experiments, it

' has been found, in the case of a tallow soap washed twice with brine and twice with 12% hydrate amounting to 2.8

In the preferred embodiment of the invention given solely by way of illustration and not of limitation, four washing stages have been used,

1 namely two stages adapted for brine washing and two for lye washing.

The alkaline soap thus obtained is treated by a certain amount of cocoa-nut fat, for example, contained in a tank 6 and sufficient to take up,

during saponification thereof, the major portion of the free alkali contained in the soap. This fresh saponification progresses rapidly at 100 C. in an apparatus I3 similar to the apparatus II and likewise comprising a mill and a reaction chamber.

This saponification may be effected at a high temperature without there being cause to fear a breaking up of the emulsion because of the high soap content of this emulsion. During the above mentioned experiment seven parts of the soap containing 2.8% NaOI-I for one part of copra fat were treated, the alkaline content of the soap thereby being reduced to 0.2%.

The soap thus produced is completely or partly neutralized either by a buffer mixture contained in a tank 6 or by a fatty acid in free or emulsified condition, or by free or dispersed rosin or by silica or by any other neutralizing product or mixture of products enabling a suitable soap product to be obtained.

In the above mentioned example, 65 parts of soap still containing 0.2% NaOH were treated by one part of a mixture made up in equal parts of lauric acid and acidic triethylolamin sulphoricinate.

The soap discharged from the apparatus is,

after having passed through an homogenizer l4, received on cooling rollers I5 and is then ready to be subjected to drying, milling, forming and so on, or any other treatment required for obtaining the commercial soap product.

The output of the apparatus is adjusted in such a way as to provide, at the discharge end B,- a continuous discharge of completely treated soap.

The continuous and automatic control is twofold: both the presence of the non-saponified fats and the presence of free alkali are detected,

The control for non-saponified fat is effected, for example, at s at the discharge from the saponification chamber 1 I.

Such control is made by detecting any cloudiness, which may appear'in a continuously formed solution of the soap to be controlled, provided in the ratio of one part soap for four parts boiling water. in said solution, is caused by the presence of non-saponified glycerides or of non-saponifiable products. In this connection, it has been observed that such a solution made from a satisfactorily saponified soap is perfectly clear, but that a detectable cloudiness or haze appears whenever a quantity of non-saponified matter in excess of 0.05% is present in the soap. Accordingly, in order to achieve saponification control, a continuous stream of soap is drawn out and dissolved in four to seven'parts of boiling distilled water. This solution is continuously carried out in a bent tube forming a sinuous path, the length of which is selected so as to provide sufilcient time for the solution to form (see Fig. 2). The length of the tube and the rate of flow of the soap and f the water are determined in such a way as to complete the solution in one minute, for example. This solution enters a cylindrical glass tank l6 havin two lateral pipe connections I! and I8, one being provided as a fluid inlet and the other as a fluid outlet. This tank has walls, shown hatched in the drawing, which are outwardly blackened or covered with a dark material and is laterally lighted from a source of light S and a photoelectric cell P is juxtaposed to the control tank l6 so that, if the solution is optically clear, no light ray can reach the cell, whereas the slightest amount of difiusion of light within the liquid, such as may be caused by any haze, is sufilcient to cause the cell to be illuminated and may therefore, by means of a suitable device, cause the colloidal mills of the saponifying apparatuses to stop operating.

Automatic alkalinity control of the mixture is accomplished at 'y at the discharge of the apparatus upon the cooling rollers l themselves; a brush coated with an alcoholic phenol phthaleine solution is made continuously to wipe a Such cloudiness, when it appears ing the scope of the invention; for example, the fatty mix could be directly saponifie'danda final lye could be used having the accurate critical concentration, so as to obtain a smaller proportion of alkali requiring neutralization at the end of the treatment.

The brine washing operation (the object of which is to provide an economic process for reclaiming the glycerol) could also be eliminated and the alkali washing treatment could directly be resorted to. In the same way, the washing stages could be varied or other devices than those shown could be conceived therefor. The brines and lyes used for the various washing operations could have their concentrations variable within very wide limits depending upon the fats used but ranging from concentrations slightly below the critical concentration defined above (in which case however leading to loss ofsoap) up to concentrations such that the soap in equilibrium with the electrolyticalsolutions would become partially dehydrated, thus causing solid curds to' appear and forming what sometimes is known as curd soap. To sum up, the concentrations which may be used for theelectrolytical solutions in carrying out this invention are those for which the soap, in equilibrium with said solutions, will be found in the state of the liquid phase having the higher concentration or neat soap.

The control of non-saponified matter could also be carried out by means of a photo-electric cell serving to detect the absorption, as caused by any haze, of a light ray passing through a tube filled with a soapy solution which is prepared as described above.

What I claim is:

1. An improved process for the continuous ,manufacture of soap comprising forming an Gil narrow band across the sheet of soap spread upon the rollers; a pencil of light rays falls on the thus moistened area of the soap and is refiected thereby into a photo-electric cell provided with a monochromatic blue screen, and this cell is operative to stop the operation of the colloidal mills in the event a red colouring should appear and thereby cause a substantial amount of absorption in the light normally incident into the cell.

It will of course be understood that various changes, improvements and additions could be made in the process and the apparatus for carrying out said process, as described hereinabove, without departing from the spirit nor exceedemulsion of the type "water in oil between fatty glyceridic materials and an alkaline lye having a concentration of caustic soda to produce soap in the neat phase wherein the quantity of soda placed in reaction is slightly above the quantity necessary for a complete saponification of said fatty materials, said emulsion being formed at a temperature slightly above the melting temperature of said fatty materials, then homogenizing said emulsion to fine particles, conducting said homogenized emulsion continuously through a saponification chamber, starting the saponification at the entrance of said chamber by heating said emulsion momentarily to about C. and then relying upon the exothermic heat developed to complete the reaction to form neat soap and then washing the neat soap obtained at the exit from said chamber with a solution formed from a substance taken from a class consisting of sodium chloride and sodium hydroxide solutions and a mixture thereof at a temperature of about 100 C. having a concentration approximating the critical concentration below which the soap may be dissolved whereby glycerine is quickly eliminated from the soap.

2. An improved process for the continuous manufacture of soap comprising forming an emulsion of the type Water in oil between fatty glyceridic materials and an alkaline lye having a concentration of caustic soda to produce soap in the neat phase so that the quantity of soda placed in reaction is about 1 to 2% above the quantity necessary for complete saponification of said fatty materials, said emulsion being formed at a temperature slightly above the melting temperature of said fatty materials, homogenizing said emulsion into fine particles, conducting said homogenized emulsion continuously through a saponification chamber, starting the saponification at the entrance of said chamber by heating said emulsion momentarily to about 100 C. and

' then relying upon the exothermic heat developed to complete the reaction to form neat soap,

washing the neat soap obtained at the exit from said chamber at a temperature of about 100 C. in two stages in countercurrent using a brine in the first stage and caustic soda lye in the second stage, the concentration of said brine andthe concentration of said lye approximating thecritical concentration below which said brine or said lye may still dissolve the soap.

3. An improved process for the continuous manufacture of soap comprising forming an emulsion of the type water in oil between fatty glyceridic materials and an alkaline lye concentrated to about 40% of caustic soda and containing a quantity of soda slightly above that which is necessary for a complete saponification of said fatty materials, said emulsion being formed at a low temperature, homogenizing said em'ulsion into fine particles, starting the saponification reaction by a momentary heating of said emulsion and then relying upon the exothermic heat developed to complete the reaction to form neat soap, circulating the neat soap thus obtained continuously, washing said neat soap with a solution formed from a substance taken from a class consisting of sodium chloride and sodium hydroxide solutions and a mixture thereof at about 100 C., said solution having a concentration approximating the critical concentration below which said solution may still dissolve the soap, and then finally neutralizing the free alkali contained in the soap by a neutralizing agent.

8 4; An improved process for continuously manufacturing soap comprising forming an emulsion of the type water in oil between fatty glyceridic materials and an alkaline lye concentrated to about 40% caustic soda containing a quantity of soda slightly above that necessary for complete saponification of said fatty materials, said emulsion being formed at low temperature and then homogenized to fine particles, starting the saponification reaction by amomentary heating of said emulsion and then relying upon the exothermic heat to form neat soap circulating the neat soap obtained continuously, -washing said neat soap with a solution formed from a substance taken from a class consisting of sodium chloride and sodium hydroxide solutions and a mixture thereof of about C., said solution having a concentration approximating the critical concentration below which said solution may still dissolve the soap and then mixing with the soap a fat to be saponified by the free alkali.

FELIX LUCIEN LACHAMPT.

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

UNITED STATES PATENTS Number Name Date 1,831,610 Schuck Nov. 10, 1931 1,905,251 Styer Apr. 25, 1933 1,994,768 Holven et al Mar. 19, 1935 2,146,661 Thurman 1 Feb. 7, 1939 2,190,592 Clayton Feb. 13, 1940 2,295,366 Stout Sept. 8,1942 2,321,947 Sender et al June 15, 1943 2,335,457 Sender 1- Nov. 30, 1943 2,401,756 Gunther June 11, 1946

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