US2567381A - Process for manufacturing soap - Google Patents

Description

Patented Sept. II, 1951 PROCESS FOR MANUFACTURING SOAP Hans George Kirschenbauer, Allendale, N. .L, and

Joseph Henry Percy, deceased, late of Woodmere, N. Y., by Constance L. Percy, executrix, New York, N. Y., assignors to Colgate-Palmolive-Peet Company, Jersey City, N. J a corporation of Delaware No Drawing. Application September 9, 1947, Serial No. 773,069

13 Claims. (Cl. 260419) This invention relates in general to the manufeature of soaps, and more particularly to a process for improving the color and odor of soap by the removal of undesirable materials during manufacture.

Common soap, an alkali metal (usually sodium) salt of fatty acids, is made by the treatment of fatty esters and/or free fatty acids with alkali. The esters generally used are glyceride type, and are predominantly combinations formed by the union of a molecule of glycerine and three molecules of fatty acids. When glyceride oils or other fatty acid esters are heated with alkaline hydroxide, the ester molecule splits, forming glycerinc and soap. Similarly, when fatty acids are heated with alkaline hydroxide, water and soap are formed.

The soap boiling process, as carried out according to general kettle room practice in the manufacture of soap from glyceride oils and fats, usually comprises five stages, or changes, as follows:

Killing, in which aqueous alkali is added to molten fat in a kettle, and the mixture boiled with the aid of open and closed steam coils;

Graining, in which an inorganic alkali metal salt is added to the mixture until the soap previously formed is thrown out of solution and, upon settling, forms a top surface layer, the aqueous spent lye phase being withdrawn from the bottom of the kettle;

Washing, in which the soap is brought into solution, or closed by the addition of water of a successive boiling;

F ttin i which wa r is aref ly "a ed to the boiling soap to reduce the solute concentration so that, upon settling, the lye will dissolve a fraction of the soap, the several layers formed, including the undissolved neat soap, the partially dissolved nigre fraction and the remaining lye solution, being drawn oil separately. The nigre fraction, comprising that portion of the soap which has gone back into solu- 7,

tion, usually contains heavy metal soaps, hydrox a s a d o er mpu ities wh h m a a poor color to th fin shed s p odu i o removed.

Af er set lin t e bo led s ap is. usually dr off and agitated in a mixing device, called a crutcher, where additional elements are introduced, such as talc, starch, silicates, coloring, etc. From this stage the soap may be cooled and worked mechanically, as in the milling process, allowed to settle and harden as in the framing process, be spray dried or otherwise treated, perfume added where desired and ultimately packed and shipped.

In the milling process, the soap is drawn from the crutcher, cooled and converted into ribbons by deposition in molten form on chilled rolls, and subsequent scraping therefrom, whence it is dried, mixed in an amalgamator with perfume and other agents, made homogeneous by processing on milling rolls, and extruded in bar form from a worm-operated compacting device called a plodder.

Modifications of the boiling process described are known to be widely practiced with respect to each of the changes. For example, in the killing change, saponification may be carried out to an extent of from to almost complete saponification. Occasionally the washing and strengthening steps are omitted. Fitting may be accomplished by first closing the soap completely and thereafter subjecting the solution to partial graining. In still other processes the soap may be subjected to a half-finish, in which Water is added in the mixture containing the undissolved, grained soap, but added only in amounts insufiicient to separate any nigre. The solution is then withdrawn from the mixture, and the soap finished by the further addition of Water to separate the nigre.

When soaps are manufactured by the neutralization of substantially pure fatty acids, the kettle boiling processes generally used are much the same as in saponillcation. The fatty acid is mixed with alkaline hydroxide and the mixture grained, settled out and separated.

Washing, which is employed in saponification for removing alcohol formed in the reaction, such as 'glycerine in the saponification of glycerides; is less necessary in neutralization, as the reaction products comp-rise mainly water and soap. The soap is usually closed into solution after graining by the addition of water to the boiling mixture, strengthened with alkali and fitted. The proportion of nigre necessary to be separated to insure good color in soap resulting from neutralization is generally less than that required in soap manufactured by saponification, which condition seems best accounted for by the prior refining of free fatty acids which is usually incident to th ei r manufacture.

The fatty materials and the alkali used in malt.-

ing soaps often contain heavy metals, such as iron, manganese, copper and others. The presence of such metals contributes to poor color and lack of stability in the soap product, and also form heavy metal soaps, that the metals ortheir soaps may catalyze oxidation of the fatty materials, either during the processing of the soap or 4 ous mass into solution by the addition of water, and subsequently partially graining by addition of electrolyte such as lye, salt or a mixture thereof.

. In such a process the phosphate-yielding substances may also be added before, with or after the addition of water.

after the product has been finished and marketed,

that the metals themselves may undergo oxidation, and that these and other deleterious effects may occur, singly or in combination, to cause the soap product to exhibit oor and/or unstable color and odor:

In the past, it has been practice to remove impurities from fatty materials by subjecting them to a sulfuric or phosphoric acid wash prior to saponification. Washes, as so applied, are conventionally carried out in vessels lined with inert substances, and large or substantial quantities are usually washed at one time. Fatty material, when acid-washed, generally requires a subsequent water washing to attain the desired degree of purification and particularly to remove the acid from the material. Thus, when fats intended for soap making are pretreated by an acid wash,- undesirable inconvenience and added expense accompany the improvement in the final product.

Methods other than acid-washing have been used previously also. Some of these which comprise incorporating organic antioxidants in the soap so as to prevent oxidation, however, do not provide for removal of the harmful metals. Still other methods have been proposed, comprising the addition in a reaction mixture of sulphiding materials, such as sodium thiosulphate so as to incorporate them with the soap and to remove undesirable materials such asmetals therefrome This has the disadvantage, however, that remnants of sulfur-containing materials carried 4 in the finished soap have a deleterious eifect upon the odor thereof.

It has now been found that soap of good color, odor and stability can be manufactured by the conventional soap boiling process by adding in the mixture, prior to fitting, a small proportion of a substance capable of yielding phosphate ions. It is believed that the addition of phosphate ions in the mixture causes undesirable metals to form relativelyinsoluble phosphate salts which, upon settling of the mixture, remain largely in the lower or denser lye or .nigre layer, and are thereby substantially eliminated from the less dense or upper layer of finished soap. This treatment has no deleterious effect on the perfume which is later added to the soap.

Phosphates have previously been added to soap and soap mixtures after the completion of the ,boiling process, for example, in the crutching operation. Their presence per se has not been observed to exert any harmful effect on the mixture, and in many cases phosphates are desirable ingredients in soap products.

While fitting is carried out by adding water to partially close a heterogeneous system of undissolved soap and dissolved electrolyte, the phos- .phates may be effectively added before, with or after the addition of the Water. Similar fiexi- ,bility is afforded where fitting is accomplished by completely closing, or dissolving, a heterogene- In carrying out the process, for example in the kettle saponification of fats, molten fat may be killed and boiled with alkali in an ordinary manner, grained, washed, strengthened and phosphating material added in an amount of from 0.10 to 5.0% of the weight of the fat. The mixture may then be boiled further, subjected to fitting and, upon settling, the neat soap drawn off for further processing according to the framing, milling, spray drying or other method of finishing.

The phosphating materials may be added-in the soap mixture while the soap is in or outof solution, however it is generally desirable that they be added after the removal of any solutions which may later be treated for purification of glycerine contained therein. The spent lye removed from the mixture after the first graining is generally so treated, and where the unspent lye of a previous strengthening change is used as a killing lye, these considerations make it somewhat desirable that the phosphating materials be added after the strengthening change.

In the case of neutralization of fatty acids, more liberty is possible because of absence of the glycerine removal problem. Addition of the phosphating materials, when performed while the soap is in solution, appears to have a quicker action, however not to constitute any great difference in the ultimate result of the treatment.

The process of soap making in its manifold variations may be carried out using the process of the invention herein disclosed. Soaps made by modified boiling processes, and particularly those already mentioned in which steps such as washing and strengthening are omitted, may be improved in quality and appearance by the use of the present invention.

The process may be carried out in the preferred form by the addition of phosphoric acid or any of the soluble alkali metal phosphates and polyphosphates, including sodium orthophosphate,

- sodium monohydrogen orthophosphate, sodium dihydrogen orthophosphate, sodium pyrophosphate, sodium hexametaphosphate, potassium orthophosphate, potassium monoand dihydrogen orthophosphate, potassium pyrophosphate, sodium and potassium tripolyphosphates and tetraphosphates, etc., and mixtures thereof.

While substances which yield phosphate ions, other than free phosphoric acid and its soluble alkali metal salts, are operative in the process in some degree, it is preferred to use substances from the classes mentioned, because of the known harmlessness of small proportions of hydrogen and alkali metal ions in a soap kettle mixture.

The method of the present invention may be employed in any conventional soapboiling process, including those wherein soap is made from free fatty acids, fattyglycerides and other fatty acid esters, such as the fatty acid esters of the lower aliphatic monoand polyhydric alcohols. Typical starting materials include coconut oil, palm oil, palm kernel oil, cottonseed oil, tallow, menhaden oil, olive oil, corn oil, tung oil, soya bean oil, whale oil, etc., and the split fatty acids and lower monoand polyhydric alcohol esters derived from these.

The process of the invention, hereinbefore described :as applied hip-conventional kettlefind pan-boiling soap manufacture, is not limited to .these methods and is profitably extendedrinto other techniques of soap making, for example the continuous method.

Where'soap is made continuously by progressively intermingling a source of fat-and aqueous 'oaustic alkali, and the reaction products are later separated mechanically, as in conventional fitting-and-settling or centrifugation, or by other physical methods, such as flash distillation, the phosphating materials may be added in the mixture at a convenient point prior tomsuch separation.

The manner and method of separating the soap from the mixture has apparently negligible influence upon the reaction of the 'phosphating .materials with any portion of the mixture, however, thoseprocesses in which the final mixture is separated by settling, centr-ifugation or otherwise, possess added advantage in regard tothis invention in that any harmful materials precipitated are removed permanently from the product and retained by the aqueouslayer, i. .e., the lye or nigre.

Typical instances of application of the inven- -tion in soap boiling processes are described in the following examples, which are included to illustrate but not to limit the invention:

Example I Fatty acids, obtained by hydrolyzing a low grade palm oil, are converted into soap in a kettle boiling process. After one lye wash, 0.25%

of trisodium phosphate (basis free fatty acid) is added to the boiling curd soap. The kettle contents are next given a half finishing treatment, then finally finished off by closing to a medium fit, and settling until Stratification had taken place.

distinctly lighter than those made without the treatment and show, after two months aging, a difference in color which is even more pronounced, and, in addition, a difference in'odor which is in favor of'the phosphate-treated sample.

Exampl II 280 parts by weight of commercial Red 011 are boiled with an aqueoussolution of 55 parts of caustic soda in a soap kettle. The. soap is subjected to one lye wash and divided into two equal portions. Four parts of trisodium phosphate are added to one portion, while no such addition is made to the other. ..A n ere i p rated ro each fra t on by addin Water n oiling wit open steam. After settling, the neat soaps are separately crutched with addition of D fume and poured into molds. Upon examination, the soap which had been treated with the phosphate is found to have a light color, whilethe untreated soap is quite dark, having a reddish brown hue. On aging for three months, the diference in color has become even more pronounced, and the untreated soap-has'a poorer odor than the treated sample.

40 The neat soap is converted into chips ,by chilling on cooling rolls andby processing in Example III A good grade of tallow, such as is'generally used in the manufacture of toilet soap, is converted into sodium soap in a conventional boiling process. After the customary lye-changes have been made, and the lye fromthe final change, or half-finish, has been withdrawn, a proportion of technical ortho-phosphoric acid is added in the .amount of 0.2% of the tallow, together with an amount of water necessary to obtain separation of a nigre. After the kettle contents are allowed to settle, the neat soap is withdrawn and converted into toilet soap by conventional processing including cooling on chill rolls, drying, amalgamating, milling, plodding, etc. In the amalgamator 0.75% perfume is incorporated into the soap. The product of this process. is considerably lighter in color than another sample prepared in identical manner from the same stock except that nophosphoric acid was added during processing. On aging the difference in color becomes more pronounced and the original scent is considerably better preserved in the sample which had been subjected to the phosphoric acid treatment.

Example IV I A soap prepared from cottonseed foots is treated, prior to settling, with .tetrasodium pyrophosphate in the amount of 0.75% of the fat used. The neat soap obtained is converted into powder form by drying on steam heated rolls and 0.60% ,neri'ume added in an amalgamator. For comparative purposes, a second portion of the same stock is prepared in a corresponding manner, except that no phosphate was used. There is a striking difierence in the color of the two prod- .ucts and, on aging, the color and odor of the untreated product becomes progressively worse while the treated product showed onlya very moderate darkening and not so pronounced *a change in aroma.

Example V Three samples of sodium soap are prepared from tallow, using conventional soap-boiling procedure, consisting of killing.- ll'fiwhangirIg and fitting. Prior to settling, trisodium phosphate is added in one mixture in the amount of 0.25% of the tallow, in another in the amount-of3% of the tallow, and in the third, no addition of phosphate is made. On settling, the neat soaps are poured into molds and when examined, good color is manifested in the order of most phosphate treatment, the sample in which 3% phosphate had been used being a very good color, the 0.25% sample a slightly darker hue, and the untreated sample the poorest of the three. On aging, at the end of two months, the color differences have magnified, the untreated sample being appreciably darker than previously, and the sample which was treated with 3% phosphate showing the least change.

Example. VI

-' of 1% of the coconut oil is added in the mixture.

'The mixture is closed with water to a medium fit, and after settling, the neat soap is withdrawn, 1% perfume added and poured into molds. Upon cooling, the sample is seen to be of very good color, while anuntreated sample, made under otherwise identical conditions, is of a darker shade. On aging, the color difference between Example VII .A charge of cottonseed oil is subjected to a soap boiling process for conversion into sodium soap. After a final lye-wash has been performed, and the-lye withdrawn, the mixture is closed completely into solution by the addition of water with open steam. To the boiling solution is added a proportion of potassium pyrophosphate in the amount of 2% of the cottonseed oil. .The soap is partially grained to a medium lit by the addition of electrolyte, and permittedto settle. The

neat soap is drawn off, crutched, 1% of perfume added and a sample preserved in molded form for observation. The sample has good color, while a similar sample, made from the same stock by identical processing except for the phosphate treatment, shows a poorer color, which difference between the samples is more striking after an aging period of two months, in addition to which the untreated sample has lost more of its odor upon aging.

Example VIII A charge of coconut oil is converted into sodium soap in a conventional soap-boiling process. After a final lye-wash has been performed, and the lye withdrawn, tetraphosphate of sodium is added in the amount of 1% of the coconut oil in the boil, and the resulting mass then closed to a medium .fit. After settling, the neat soap is Withdrawn,

crutched, 1% perfume added and poured into molds. The molded samples have good color and stability, while similar samples, made from the same stock by identical treatment except for the addition of phosphate, show a poorer color which becomes increasingly worse with aging.

Example IX The process of Example VIII is carried out using sodium tripolyphosphate in place of tetraphosphate. The resulting molded samples show good color and stability as compared with a control made without benefit or phosphate, which deteriorated rapidly upon aging.

- While the description herein is limited to certain specific forms of the invention, it should be understood that the invention is limited only as defined in the appended claims.

What is claimed is: 1 1. In the making of soap from fatty glycerides by a process which includes a fitting operation in which the soap is settled into layers including neat soap, nigre and lye, the improvement which comprises adding to and mixing with the soap,

prior to settling, a water soluble material yielding phosphate ions in the resulting mixture, settling the soap to form layers, and separating the neat soap from the other layers which contain the major portion of the phosphate material including impurities removed from said neat soap. 1

. 2. The process as set forth in claim 1 in which the soluble material is phosphoric acid.

3. The process as set forth in claim 1 in which the'soluble material is an alkali metal phosphate salt.

- 4. The process as set forth in claim 1 in which the soluble material is sodium orthophosphate.

5.'Theprocess which comprises saponifying 'fatty iglycerides with aqueous alkaline saponifier,

phosphate ions in the resulting mixture; and

separating a less dense soap phase from a denser phase containing a major proportion of the phosphate material including impurities removed from said less dense soap phase. e

6. The process as set forth in claim 5 in'which the soluble'material is phosphoric acid. a

'7. The process as set forth in claim 5 in which the soluble material is an alkali metal phosphate salt.

8. The process which comprises saponifying fatty glycerides with aqueous alkali metal hydroxide, graining out the soap and separating the grained soap from an aqueous phase, adding to saidseparated grained soap water an electrolyte including soluble material yielding phosphate ions in the resulting mixture, said Water and electrolyte being added in sufficient amount to effect phase formation, and separating a less dense. soap phase from a denser aqueous phase. 9. The process as set forth in claim '8' in which the soluble material is phosphoric acid. I

10. The process as set forth in claim 8 in which the soluble material is an alkali metal phosphate.

11. The process of making soap of improved color. and stability which comprises saponifying fatty glycerides with an alkali metal. saponifier, adding, an inorganicelectrolyte and separating a soap phase from an aqueous phase, adding to said soap phase sufficient aqueous electrolyte solution containing a soluble material yielding phosphate ions'in the resulting mixture to effect phase formation, and separating a less dense soap phase from a denser aqueous phase.

12. The process as set forth in. claim 11 in which the saponifier is sodium hydroxide and the soluble material is sodium phosphate.

13. In the process of making sodium soap from fatty-glycerides by the kettle process, the improvement which comprises adding, to the soap after graining but prior to fitting a minor amount of alkali metal phosphate and separating a less dense soap phase from atdenser aqueous phase containing the major portion of said phosphate combined with impurities removed from said HANS GEORGE 'KIRSCHENBAUER.

CONSTANCE L. PERCY, I

Executrix of the Last Will and Testament of Joseph Henry Percy, Deceased.

REFERENCES CITED The following references are of ,record in the file of this patent!- 1 UNITED STATES PATENTS Number Name a Date 2,383,630 Trent Aug. 28, 1945 2,383,631 Trent Aug. 28,1945 2,391,019 Hirsch Dec. '18, 1945 FOREIGN PATENTS Number 3 Country Date 1 494,056 Great Britain Oct. 19, 1938 OTHER REFERENCES Kirschenbauer: Fats and Oils. (1 944) Reinzhold Pub.Co., pa es 47 and 4s.

Claims (1)

1. IN THE MAKING OF SOAP FROM FATTY GLYCERIDES BY A PROCESS WHICH INCLUDES A FITTING OPERATION IN WHICH THE SOAP IS SETTLED INTO LAYERS INCLUDING NEAT SOAP, NIGRE AND LYE, THE IMPROVEMENT WHICH COMPRISES ADDING TO AND MIXING WITH THE SOAP, PRIOR TO SETTLING, A WATER SOLUBLE MATERIAL YIELDING PHOSPHATE IONS IN THE RESULTING MIXTURE, SETTLING THE SOAP TO FORM LAYERS, AND SEPARATING THE NEAT SOAP FROM THE OTHER LAYERS WHICH CON TAIN THE MAJOR PORTION OF THE PHOSPHATE MATERIAL INCLUDING IMPURITIES REMOVED FROM SAID NEAT SOAP.