US2383630A - Production of soap - Google Patents

Description

' Patented Aug. 28, 1945 PRODUCTION or soar Walter Russell Trent, North Arlington, N. J., as-

signor to Coigate-Palmolive-Peet Company, Jersey City, N. J a corporation of Delaware No Drawing. Application March 25, 1942, Serial No. 436,098

7 Claims.

The present invention relates to processes for making soaps and, more particularly, to processes of preparing soaps from mono-fatty acid esters.

Soaps have been made from time immemorial by saponification of fats and oils. The saponification is generally carried out by intimately mixing such fats and oils with alkaline agents in such proportions as are readily determinable by those skilled in the art. The mixture is heated with agitation, forming soap and glycerine. After completion of the reaction, the soap is salted out, leaving glycerine in solution which is thus separated from the soap. If more of the glycerine is to be removed, successive washings, resulting in considerable aqueous dilution of the glycerine,

must be employed. The soap is put in a crutcher, where it is mixed with any desired adjuvant material, and may then be framed or plodded and cut, or run in a plastic condition to steel rolls for flaking. The flakes may be left in this condition or may be ground. The plastic soap may also be forced through a nozzle in a spray tower to form beads or other finely divided particles. Continuous or semi-continuous processes of soap-making have been provided, but high temperatures and/ or numerous washings are also employed in these for removing 'glycerine from the soap.

Recently, it has been taught to split fats or oils by hydrolysis with water to obtain free fatty acids, and then to saponify these acids. Free acids react very quickly and vigorously with alkaline agents, as compared with the long process of saponifying fats and oils, but it is diflicult to control the reaction and the condition of the product at this speed. Contact of free fatty acids, particularly unsaturated acids, with air, even at moderate temperatures, causes the formation of dark oxidation products which tend to discolor soaps. Furthermore, the use of free acids requires that expensive, corrosion-resistant equipment be employed.

It is an object of the present invention to provide a rapid and economical process for making soaps, wherein lower alkyl mono-fatty acid esters are employed.

It is another object of the invention to provide a novel process of manufacturing soap of controlled water content.

It is also an object of this invention to provide a novel and improved method for the continuous manufacture of soap from fatty acid esters of lower monohydric alcohols.

The invention also contemplates the provision of a novel process for the preparation of soap in granular, globular or other comminuted' forms. 4

According to this invention, soap is prepared by mixing a fatty acid ester of a lower monohydric alcohol with an alkaline or saponifying agent, the ensuing reaction being carried out at reduced pressures to remove alcohol from the product as the alcohol is liberated in the reaction. The reaction is preferably carried out as a continuous process, operating from a continuous method of producing monoesters by alcoholysis of fats and fatty oils, using a measuring or proportioning device for mixing the monoesters with the alkaline agent in such proportions as are determined by the operator, and then continuously passing them to a saponifier, as will be described in more detail infra.

In selecting fatty acid esters for use in the present invention, it is preferred to employ fatty acid esters of short chain monohydric alcohols, especially" of alcohols having a boiling point in the presence of excess water of lower than C.

at atmospheric pressure,.and preferably the lower alcohols having 1 to about 6 carbon atoms to the molecule. By excess water is meant water in excess of the azeotropic composition of the alco hol with water. The fatty acids are preferably those having about 12 to about 20 carbon atoms, and mixtures of the esters may also be used.

Mono-fatty acid esters of polyhydric alcohols may also be present in admixture with monohydric alcohol esters. Esters satisfactory for use in the process of the present invention include ethyl laurate, methyl stearate, ethyl margarate, propyl oleate, ethyl esters of coconut oil fatty acids, isopropyl esters of tallow fatty acids, methyl esters of tall oil fatty acids, :butyl palmitate, tertiary butyl laurate, methyl arachidate, amyl myristate, isobutyl esters of cottonseed oil fatty acids, benzyl palmitate, and other monohydric alcohol esters. Among the monoesters of polyhydric alcohols which may be present in admixture with the esters of monohydric alcohols are ethylene glycol monostearate, propylene glycol monolaurate, trimethylen-e glycol monoesters of olive oil fatty acids, glyceryl alpha- (or beta-) monostearate, mannitol monoesters of coconut oil fatty acids, sorbtol monopalmitate, erythritol mono-oleate, etc.-

Any of these monoesters may be mixed with di-, tri-, or polyesters for treatment in accordance with this invention, although such modification is not preferred.

The alkaline or saponifying agents which may be used for saponifyingthese esters include sodium and potassium hydroxides, carbonates, silicates, etc., pyridine, methyl morpholine, piperidine, alkyl amines, alkanolamines and other organic and inorganic bases and alkaline materials, and mixtures of these. The alkaline agent may be introduced in aqueous solution, in alcoholic solution, or in'solutions of other solvents, or may be substantially anhydrous and/or substantially undiluted. The amount of solvent introduced with the alkaline or saponifying agent has may alone be sufilcient to raise the mixture to the desired temperature, depending upon the materials employed and subsequent operating conditions, or heat from external sources may be supplied. Either or both of the reactants may be preheated by steam or other means before being run into the vessel and/or the mixture may be heated during and/or after admixture. Soap and alcohol are thereby formed, and the alcohol is volatilized at the temperature and reduced pressure within the vessel and is withdrawn.

The operation 'of this process can be carried out continuously by contacting a monoester with a saponifying agent under conditions of temperature and subatmospheric pressure adapted for saponification of the ester and removal of the liberated alcohol. The temperature of the saponification mixture may bevaried over a Wide range, depending upon the type of ester to be saponified, the amount of water and/or other solvent present, and the type of product desired. Even at only slightly elevated temperatures, the reaction rates are relatively high, as compared with polyesters, such as fats and oils. The temperature employed is partially controlled by the degree of vacuum used, and both temperature and pressure are influenced by ,the boiling point of the alcohol to be liberated in the reaction. Thus, depending upon the ester to be saponified and the pressure employed, elevated tempera tures of about 20 to about 100 C. can be used. At these temperatures, products of very light color are obtainable. Moreover, the reaction may be carried out in the presence of air, as the neutral esters are substantially undarkened by this treatment.

The monoester and alkali, preferably preheated to a desired temperature, are automatically proportioned and delivered, preferably continuously, to a mixing vessel where the ester is saponified under reduced pressure. The mixing vessel may be supplied with heat transfer means, such' as a jacket, for heating or cooling, as required, and the solvent for the alkali, as well as the alcohol liberated by the reaction, is vaporized under the reduced pressure and is removed from the mixing vessel. Regulation of the temperature of the reaction mass is a factor in determining the amount of solvent and/or alcohol remaining in the product. The soap, dried or partially dried, can be removed from the mixing vessel and cooled.

Various means may be employed for facilitating the reaction of the saponifying agent with the ester. Thus, it has been found convenient to jet the alkaline solution into the liquid ester and to employ a size and shape of reaction vessel which provides a high degree of turbulence for contacting the materials. The vessel may be in the form of a conduit and may be equipped with a screw conveyor to displace solid material formed when using plastic or viscous mixtures.

The reaction vessel may also be operated in conjunction with a spray tower 01! other. means for obtaining substantially granular and/or hollow particles, the material from the reaction v ssel being forced in plastic form to a spirmer bowl or spray nozzle, and, upon atomization, coming in contact in the tower with a current of inert gas, preferably air. The air current may be heated and it is preferably passed through the tower countercurrent to the sprayed material, although concurrent passage of the air is also contemplated.

In vaporizing the hydroxylated products of the reaction, the saponification of the monoesters afiords great advantage over saponification of the glycerides or other natural esters, since the alcohols liberated can be vaporized for recovery at much lower temperatures and with far less difficulty than is possible with glycerine. Where the reactants employed are nearly anhydrous, considerably lower temperatures can be used for removal of solvent than are possible with soap made from even free fatty acids, as the lower alcohols, including methyl, ethyl, propyl and isopropyl alcohols, can be vaporized below the temperature required at a given pressure for the vaporization of either water or glycerine. Since the lower alcohol liberated is lower boiling in the presence of sufilcient water than glycerin and/or water and requires less heat to volatilize, lower temperatures may be used, and lighter colored products are consequently obtainable.

Another advantage of the present process is that, wherethe reaction is not carried to completion, there is no rancidity problem arising from the presence of unreacted mono-fatty acid esters in the soap products, as is the case with unreacted fats or fatty acids. A proportion of the mono-fatty acid ester can be left unreacted in the product to provide a superfatting agent therein, and such unreacted residues provide superior, more stable and sweeter-smelling superfatting materials than are the fats and oils disclosed by the prior art. By operating at low temperatures, the excess fatty acid ester can be left in the soap, even though substantially all of the liberated alcohol is volatilized.

The moisture or solvent content of the finished I product can be modified by regulating the heat the reactants and/or furnishing heat to the reaction vessel from an external source, or otherwise. The temperature required is far below that necessary for glycerine recovery in saponi-fying glycerides. Therefore, although possible, it is unnecessary and less desirable to go to the temperature of molten anhydrous soap or higher in order to vaporize the monohydric alcohols liberated, as they or their aqueous azeotropes are lower boiling than water. Furthermore, it is possible to recover the soap in hydrated form, but free from the alcohol, without additional hydrating equipment, as required with anhydrous soap obtained in certain methods of saponifying glycerides. Moreover, shorter periods of heating, with consequently diminished danger of local overheating and decomposition, can be employed.

Soap builders, inert materials, anti-oxidants, etc., may be added to the monoester and/or to the saponifying agent before contacting. Since the washing steps, in general use in prior art' practice, need not be employed, these modifying agents, even if water-soluble, are found in the product of the present process. Converse it is also possible to employ, if desired, vol e, waterinsoluble materials, such as low-boi g petroleum hydrocarbons, the presence of w ch in the final product might be disadvantageous for some uses,

and of the pressure upon the condensers.

since they do not appear in' the finished product.

Certain saponification accelerators, while not ordlnarily required for saponifyirig monohydric al cohol esters, fall in this category and may be added, if desired.

The vaporized water or other solvent and the vaporized alcohol liberated in the reaction are withdrawn at the top of the reaction vessel and together pass to a condensation system. The temperature of the vessel and of the passage to the condensers is maintained above the dew point of the vapors. v condensed, but it is'preferred to provide at least one condenser for each material to be condensed or to employ a fractionating column. The condensers may be of reflux, jet or other suitable type. The recovery of solvent and/or alcohol in relatively pure condition is facilitated by this means.

The pressure within the vessel is easily regulated by control of the condenser temperatures The pressure within the reaction vessel is preferably low enough to provide rapid vaporization of the highest boiling material to be withdrawn as a vapor.

In practice, temperature and pressure conditions can be so regulated that a dry product or a hydrated product can be produced. The product may be made in a moreor less finely divided condition, which permits its ready transformation into flakes or other physical forms, for example, by passing between a pair of properly spaced rolls, or by pressing into cakes, or by other means, with or without addition agents.

Adjuvant materials may be admixed with the soaps thus formed by mixing them with the mono.- esters and/or the saponifying agents before contacting, by simultaneously passing into the reaction vessel a solution containing such adjuvant materials, and/or by mixing the final product therewith. Such adjuvant materials may include fatty acid soaps prepared b the same or other methods, resin acid soaps, naphthenic and alkylated naphthenic acid soaps, sulphated and sulphonated organic compounds, alkaline Soap builders, water-soluble, water-softening compounds of the acids of phosphorus, and other salts, including sodium carbonate, sodium silicates, trisodium phosphate, borax, sodium tetraphosphate,

sodium bicarbonate, sodium sulphate, sodium chloride, sodium acetate, sodium hypochlorite, sodium thiosulphate, sodium penborate, sodium tartrate, sodium citrate and sodium oxalate, and the corresponding ammonium, substituted ammonium and potassium salts of the corresponding acids; insecticidal, germicidal, styptic and me- I dicinal agents, including aluminum chloride, mercuric chloride and various copper and lead salts; coloring agents, abrasives, fillers, and water-dispersible gums, including dyes, lakes, pigments, silica, kieselguhr, silica gel, feldspar, precipitated chalk, pumice, infusorial earth, bentonite, talc, starch, Irish moss, sugar, methyl cellulose, agar, gum tragacanth, gum'arabic and polyvinyl alcohol; liquids, such as ethyl alcohol, glycerol, cyclohexanol, naphtha, benzene, kerosene, turpentine, pine oil, decalin and tetralin and the like. The type of addition agent will depend upon the ultimate use of the new composition. Y v

The reaction mixture from the s'aponification vessel may be discharged therefrom into a cooling element or conduit, where it is partially cooled, thus partly solidifying the soap. It maythen be passed to an extrusion orifice, where it ma be cut into bars. During the cooling operation but The vapors may be conjointly while the soap product is still liquid due to the presence of water and/or other solvents, any desired modifiers oradjuvant materials, as aforesaid, including builders, abrasives, perfumes, coloring principles, germicides, liquids, air or other gas, etc., may b injected into the soap. The regulation of the supply of cooling fluid, both in amount and temperature, is also desirable for controlling the amount of solvent (including water) remaining in the soap. Solvent vapors (and any remaining alcohol) produced in the re action vessel are condensed, wholly or in part, in the cooling element.

In practice, when producing bars and cakes of soap, it is preferred so to control the cooling of the soap in the cooling element that the soap is at least partially liquid upon passing to the extrusion element. This element, having an orifice of cross section approximating that of the desired soap cake; is preferably of extended length and jacketed for carrying a cooling fluid for further cooling of the soap The cooling of the soap may thus be substantially completed in the extrusion orifice during its passage therethrough.

Where a fatty acid ester of an alcohol having a boiling point above that of water and/or where a solvent for the saponifying agent having a boiling point above that of water is employed in the material under treatment, it will be understood from the foregoing that at'least part of such alcohol and/or solvent can be retained, if desired, in a substantially anhydrous soap. The temperature (or vacuum) in the reaction vessel, for example, can be lowered enough so that all of such alcohol and/or solvent is not vaporized but a portion falls out with the soap. The temperature selected is higher than the boiling point of water at the particular pressure in the vessel but lower than the boiling points of the alcohol and/or solvent. Similarly, where the fatty acid ester of a low-boiling alcohol is used, the temperature and pressure conditions in the reaction vessel can be regulated so as to remove substantially all of the liberated low-boiling alcohol,'

while retaining at least part of the water or other solvent.

The soap may be passed to drum dryers to produce flakes and ribbons. Since drying can be accomplished by other means, as set forth herein, chilling rolls may instead be provided. Where it is desired to form a friable soap, sudden chilling has been found to be advantageous. The dryer soaps are more friable than those containing considerable amounts of water, and very dry soaps are frequently self-disintegrating,

breaking up into small grains upon cooling.

Thus, after removal of alcohol and water or other solvent in the saponification vessel, the soap may be withdrawn by means of scaled conveyors, preferably operated under subatmospheric pressure. The conveyors may be jacketed, and a plurality of jackets may be employed, so that a heating fluid may be passed through the first part of the jacket (to aid in maintaining a sufficiently high temperature within the saponification vessel), while the second part carries a cooling fluid to give the soap a sudden chill. Another and/or additional means of suddenly cooling may be employed by injecting water directly into the soap while in the conveyor, preferably at a part of the conveyor non-contiguous to the outlet of the reaction vessel.

While the removal of alcohol formed with the soap acts to cool the soap by the evaporation of the alcohol in the reaction vessel, additional wa- .the condensers.

ter or other liquid may be injected into the soap at temperatures above the boiling point of such injected liquid at the reduced pressure in the reaction vessel, the vapors being removed as formed so as not to hydrate the soap. For example, water introduced into the soap in the conveyor is immediately vaporized at the temperature of the soap, cooling the soap at a low pressure and in the absence of air, and the water vapor may be passed into the reaction vessel, if desired, for removal with the vapors therein to If it is desired to hydrate the soap to any degree, additional water may be injected into the soap, either while in the conveyor or farther along, controlling th amount injected. The cooling jacket can be employed for condensing vapors before discharge. Even where considerable hydration is desired and sufllcient cooling can be obtained by circulating a cooling fluid in a conveyor jacket, it may nevertheless be advantageous to vaporize part of the injected water for the purpose of obtaining. uniform distribution of the water added. Such uniformity may also be obtained by agitation in the conveyor. Economy of operation may be achieved by using one of the reactants, preferably the monoester, as the cooling fluid in the jacket. This serves to preheat the reactant before its passage to the saponification vessel.

The following examples described herein are merely illustrative of the present invention, and it will be understood that thisinvention is not limited thereto.

Example 'I About 200 gallons per hour of the ethyl esters of coconut oil fatty acids are continuously contacted with about 106 gallons per hour of 30 B. sodium hydroxide solution, and at the same time process steam is injected to raise the temperature of the mixtureto about 60 C. The mixture is passed through a short length of pipe with reverse bends to provide good mixing and into a 1 reaction vessel undera vacuum of 20 inches of mercury. The temperature is maintained at about 80 C., and the ethyl alcohol formed is withdrawn at the top of the vessel. The resultin soap product is continuously removed through a sealed port at the bottom.

Example II About 350 pounds per hour of the amyl esters of garbage grease fatty acids are preheated to about 50 C. and passed into a reaction vessel having efficient agitating means and under a vacuum of about 20 inches of mercury. About 230 pounds per hour of a 28 B. solution of caustic potash at about 60 C. is fed into the vessel concurrently with the esters. Amyl alcohol is liberated by the reaction and comes off as its aqueous azeotrope. The soap formed is removed by a sealed conveyor. v

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modiflcations'of this invention can be made and that equivalents can be substituted therefor without departing from the principles and true spirit of the invention. Such variations and modifications are believed to be within the scope of the present speciflcation and within the purview of the appended claims.

I claim:

aasaoso 3. The process for producing soap which comprises reacting a fatty acid ester of an alcohol having a boiling point in the presence of water in excess of the azeotropic composition of lower than 100 C. at atmospheric pressure with an aqueous solution of a saponifying agent under reduced pressure and at a temperature above the vaporization point at said pressure of the free monohydric alcohol in the presence of water in excess of the azeotropic composition to produce a reaction mixture comprising a soap and a free monohydric alcohol, thereby removing at least part of the monohydric alcohol and at least part of the water therefrom during the reaction.

4. The process for producing soap which comprises preheating at least one of a fatty acid ester of a lower alkyl monohydric alcohol and a saponifying agent, and reacting said ester with said saponifying agent to produce a soap and a free monohydric alcohol, said reaction being carried out under sufficiently reduced pressure to remove the alcohol as it is liberated in the reaction.

5. The process for producing soap which comprises preheating at least one of a fatty acid ester of a lower alkyl monohydric alcohol and a saponifying agent to a predetermined temperature, re:-

.acting said ester with said saponifying agent under reduced pressure and at a temperature above the vaporization point at said reduced pressure of the free monohydric alcohol whereby a reaction mixture comprising a soap and a free monohydric alcohol is produced and the monohydric alcohol is removed from said mixture as it is liberated in the reaction.

6. The process for producing soap of predetermined moisture content which comprises reacting a fatty acid ester of a lower alkyl monohydric alcohol with an aqueous solution of a saponifying agent under reduced pressure to produce a reaction mixture comprising water, soap and free monohydric alcohol, maintaining the temperature of the mixture during reaction above the vaporization point at said reduced pressure of the free monohydric alcohol in the presence of water in excess of the azeotropic composition to volatilize free monohydric alcohol therefrom, and regulating the heat supplied to the reaction mixture, to

produce a soap containing a predetermined proportion of moisture.

7. The process for producing soap. which comprises continuously passing a fatty acid ester of a lower alkyl'monohydric alcohol and a saponifying agent through a zone at subatmospheric pressure and at a temperature above the vaporization Pint' at said pressure of the free monohydric alcohol to produce soap and free monohydric alcohol, continuously removing volatilized monohydric alcohol from said zone, and continuously withdrawing soap from said zone.

WALTER RUSSELL TRENT.