US2271619A

US2271619A - Process of making pure soaps

Info

Publication number: US2271619A
Application number: US268820A
Authority: US
Inventors: Bradshaw George Burt; Walter C Mealy
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1939-04-19
Filing date: 1939-04-19
Publication date: 1942-02-03
Anticipated expiration: 1959-02-03
Also published as: FR865045A; GB543604A

Description

Patented Feb. 3, 1942 PROCESS OF MAKING PURE SOAPS George Bart Bradshaw, Wilmington, Del and Walter C. Manly. New

lignon to I. I. do Pont de Nemoarol Oomnony, W aware No Drawing. Application Serial No. 268,82

19 Claims.

This invention relates to methods for the preparation of soaps and soap compositions. More particularly it relates to a novel process of making soaps from glycerides. Still more particularly it relates to a process of making soap from glycerides of higher open chain aliphatic carboxylic acids. The invention also pertains to the separation of glycerine from the fatty acid components of natural glycerides and to novel improvements in the soap making arts.

This invention hasfor an object the provision of a rational process for producing soap and soap compositions which can be carried out in an economical manner. A further object is to provide a novel process for making soap which is applicable to any natural glyceride. A further object is to provide a process for making soap in which the glycerine may be recovered in a substantially anhydrous and concentrated condition. A further object is to furnish a process for making hard soap from oils which have hitherto yielded soft soap. A still further object is to provide a low temperature process for making soaps. Another object is to furnish a process for making hard potash soaps. Another object is to furnish a process for making high melting point wax-like materials. Another object is to furnish a process for making lighter colored and more brilliant soaps than formerly possible from a given grade of oil or fat. A further object is to furnish a process for a soap containing a new superfatting agent. A further object is to provide a fatty acid mono ester from a natural glyceride which can be easily and completely saponified to form either a pure dry soap or soap modified at will. A still further object is to furnish a process for a new composition of matter consisting of dry crystalline sodium and/or potassium salts of mixed natural fatty acids.

In the usual process for manufacture of soap, naturally occurring oils and fats from both animal and vegetable sources are treated stepwise with dilute caustic soda or potash solutions and salt solutions to effect separation of the glycerine; as complete as possible conversion of the fatty material to soap and to isolate the soap in a condition as free from water and as pure as possible. By this procedure there is incompletely recovered a very impure glycerine of from to strength containing both impurities from the original oils and dissolved salt and lye. The soap resulting contains about 35% of water and salt, free caustic and unsaponified fat, depending on the skill with which the operation has been carried out and also the economics of ilmington. Del., a corporation of Del- Agril 19, 1989,

the-situation. The dilute glycerine is purified and recovered by intricate processes and when sold, often represents the only profit in the whole soap operation. The soap must generally be dried so as to be marketable. This is dimcult because of the gelatinous nature of the material. Often the whole operation of making soap lasts from 4 to 6 days.

Many eitorts have been made to simplify and rationalize the above procedure. The merely simplified methods so far result in a poor quality of soap. Some of the better methods are scientifically more rational than the usual process, but are too expensive. The commonest of these processes is to separate the glycerine by a fat splitting process not involving the use of caustic soda or potash. The free fatty acid is then neutralized with soda to produce a soap. In one process this involves producing a lime soap which is double decomposed with soda to form a soda soap. All these processes have been in existence for many years, but can only compete under very specialized conditions against the usual procedure first described above.

It has now been found that the above disadvantages can be obviated, the above objects attained and that soaps can be prepared by reacting a glyceride with an alcohol, preferably a monohydric aliphatic alcohol, in the presence of a small amount oi an alkali metal base, separating the esters of the alcohols with fatty acids from the glycerine and reacting the resulting esters with a saponii'ying agent. In a more limited sense the objects of the invention are accomplished by reacting a glyceride with a saturated aliphatic monohydric alcohol which boils at a temperature below C. and preferably is miscible with water, in the presence of a small amount of an alkali metal hydroxide, separating the alkyl esters from the glycerine and reacting the resulting esters with a basic saponifying agent.

To obtain all the benefits of the invention it is desirable to use all the novel steps herein described. However. some of the benefits are obtainable by using only one or two steps of the complete invention. The invention will first be described in one of its more complete aspects. A natural fat such as coconut oil which contains some glycerides of lower fatty acids which do not make good soap. and which are irritating to the skin, first is selected. It is more economical of materials if an oil is used which has been refined. such as Cochin type refined coconut oil. This oil should be nearly dry and substantially free from free fatty acids and mucilaginous vegetable matter. The ester value of this oil is obtained by well known means. The oil is heated to a moderate temperature, e. g., about 80 centigrade more or less, depending on the time apparatus can be held up. There is then mixed into the oil about 1.6 equivalents of commercially anhydrous methyl alcohol, containing from 0.1 to 0.5% caustic soda or potash calculated on the oil used. The amount of caustic depends on the dryness and acidity of the oil being treated and of alcohol used, and the speed of reaction desired. The glycerine begins to separate in a very short time, for instance, within ll minutes. The conversion to methyl ester is about 98% complete generally in less than one hour. The oil tests alkaline at this stage. The lower layer of anhydrous glycerine which is first developed or formed consists of at least about 90% of the glycerine content of the original oil and may contain a small amount of methanol. The

glycerine because of its high degree of purity may be used directly in many chemical processes, for example, in the manufacture of glyptal resins. The alcohols can be washed out of the formed esters with two or three washes of a small amount of water each time, which settles and can be drawn off each time from the bottom. This operation also purifies and lightens the color of the original oil.

The oily layer formed consisting of the methyl ester of the coconut oil acids is now fractionally distilled. As the oil is non-corrosive and distills on an average 30 to 50 lower than the free acids, the distillation is much simpler than the distillation of fatty acids. The distillation may be effectively conducted under 3 mm. pressure and with 110 lbs. of steam in the heating coils, first the Cu and then the C methyl ester is driven or topped off through a column packed with 1 inch rings. The residue in the still consisting of methyl esters of C12, C14, Cu and saturated and unsaturated C1: acids can be drawn off and worked up to soap, or can be further separated by distillation or hydrogenated and separated by crystallization and other known processes.

To make substantially anhydrous soaps. there is added to the mixed methyl esters which are preferably still warm, a solution and/or suspension of the equivalent quantity of caustic soda or potash in a commercially anhydrous alcohol, e, g. methyl alcohol. This should be mixed in quickly so that it is uniformly admixed before the mass thickens due to soap formation. This mixture may be made into soap flakes by one of the usual processes and allowed to stand until the neutral soap is formed and most of the evolved methyl alcohol dissipated by evaporation, or the still fluid mixture is sprayed into the top of a tower in which there is an ascending current of hot air, and recovered at the bottom as neutral soap powder. The alcohol can be recovered if desired and re-used. By using very finely ground caustic alkali and suitabl mixing device, all or nearly all the alcohol solvent for the saponifying alkali can be dispensed with. The soap so produced by the process Just described is an anhydrous pure alkali salt of mixed natural fatty acids. It is crystalline in nature and much harder, brighter, more transparent, and of higher melting point than soaps made by any of the known processes from the same materials and is apparently a new product. It is also more stable. This is probably because no incipient rancidity has been caused by excessive or prolonged heating as in the usual soap processes.

The process just described might be outlined as follows: A g'lyceride is reacted with a substantially anhydrous alcohol, preferably a lower volatile, saturated aliphatic primary alcohol, e. g. methyl or ethyl alcohol in small excess in the presence of a small amount of a dry alkali metal hydroxide; the resulting alkyl esters are separated from the glycerine and then subjected to fractional distillation to remove the lower boiling esters: the mixture of higher esters is then reacted with an alkali metal hydroxide, preferably in the substantial absence of water to form soaps.

The amount of alcohol required for the liberation of the glycerine is not limited to the proportions above stated, but may be varied somewhat. Furthermore, the amount can be reduced substantially by working in steps. For instance, if the theoretical quantity of methyl alcohol is used the conversion will be about The glycerine can then be removed and more alcohol and catalyst added. If the alcohol is added in three steps the amount required can be reduced, for instance, from one and six tenths times theory to one and two tenths times theory. Amounts of methyl alcohol above 1.75 equivalents tend to prevent the gravity separation of the glycerine, thus adding useless expense to the separation. Amounts of alcohol from 1.20 to 1.75 equivalents represent a practical range.

If a concentrated caustic soda solution, e. g. 50% strength is used. as the saponifying agent, it preferably is emulsified by means of soap or otherwise with the methyl esters to a homogeneous emulsion befor the reaction causes muck thickening. The emulsion may be treated as described above, and will produce a neutral soap containing about 12% water which is the usual amount in fine soaps. If sodium carbonate is used, high heating or autoclaving will be necessary to effect the reaction. If a deficiency of saponifying alkali is employed the finished soap will still be neutral and will contain a valuable superfatting material that is the mono ester or esters of the fatty acids from the glycerides with the alcohol used.

A somewhat narrower but important use of the invention is involved in making valuable products including soaps, from cotton seed and similar unsaturated oils. Preferably refined oil is employed because of saving in chemicals. The ester value is determined and about one and six tenths equivalents of methyl alcohol and 0.5% caustic soda are admixed. The mixture is warmed to about 80 C. and after three hours the glycerine is drawn oil and the oil washed free of glycerine and alcohol. The methyl esters of the cotton seed oil acids are treated with saponlfying agent to produce an anhydrous soap. The soap is found to be hard like the ordinary soap made from saturated fats and has the above described properties.

The mixed esters of the unsaturated acids, e. g. the methyl esters from the cotton seed oil may be hydrogenated and distilled to form fractions of nearly pure methyl palmitate and methyl stearate. If the methyl stearate, for instance, is converted into an anhydrous soap as sodium stearate, there is obtained a crystalline waxy material melting at about 260 C. It is useful as an ingredient of waxy coatings, for instance of use in coating paper, producing paper from which later printing ink can be easily removed.

The invention will be further illustrated, but isnetintendedtobelimitedbythefollowing examplesinwhichthepartsstatedareparts by weight.

Ensues I One thousand parts of refined Cochin type coconut oil are heated to about 80 C. and then isaddedfipartsofdrycausticsodaandm parts of commercial anhydrous (99.7%) methanol. The mixture is stirred for a few minutes and allowed to stand three hours. The lower layerisdrawnollandthefioatinloil (consisting of methyl esters) is washed three time with a small amount of water each time. Conversion is found to be 98.0%. The wash waters are removed by allowing the washed oil (mixture of methyl esters) to fioat and drawing of! the bottom watery layer. The unreacted methanol and a small amount of soap and oil are recovered from the glycerine plus wash water by neutralizing with acid, adding about 50% water, distilling oi! the methanol, separating the oil and soap by gravity. The glycerine is distilled under vacuum to concentrate it.

The floating oils, that is the methyl esters of the coconut oil acids, are subjected to vacuum fractional distillation to top of! or remove the lower esters, e. g. the Cs. Cs, and Cu methyl esters. The mixture remaining in the still of 830 parts consists of higher methyl esters, e. g. esters of 01:, Cu, Cm and C1: acids, and is then treated by one of the following procedures:

Procedure A To 120 parts of the above-described higher methyl esters at temperature C. was admixed parts of a solution and suspension of caustic soda in methanol containing 20 parts caustic soda. The temperature of the mass immediately began to rise, reaching 37' C. The mass was pulverized and warmed to C. and held to constant weight. A neutral pure anhydrous soap of mixed fatty acids which was crystalline in nature was produced.

Procedure B Approximately 20 parts of 99% caustic soda as a fine powder was mixed with 120 parts of the above-described higher dry methyl esters of coconut oil acids. The mixture was warmed under agitation and then pulverized and heated to constant weight. An anhydrous soap was obtained.

Procedure C To 237 parts of the above-described hot higher methyl esters (temperature about 50 C.) was admixed parts of a 50% water solution of caustic soda to a homogeneous emulsion. In 2% hours 9'! of the caustic soda had reacted and a fairly hard mass was formed. This was reduced to particles, dried so as to contain very little alcohol, and about 10% water, and formed into cakes of practically neutral soap.

Procedure D To 120 parts of the esters at temperature 30 C. was admixed 50 parts of a solution and suspension of caustic soda in methanol containing 20 parts caustic soda. This mixture was sprayed into the top of a tower against a current of rising hot air. The hot air from the top of this tower was washed with water to recover the methyl alcohol. From the bottom of the tower was recovered a pure anhydrous soap of mixed higher fatty acids of coconut oil.

lumen solution and suspension of caustic soda in methanol containing 114.5 parts caustic soda. The mixture was masticated in 9. Werner and Pfieiderer type masticator with, initially, steam in the Jacket of the masticator. The temperature was not allowed to rise above 100 C. As soon as the greater part of the alcohol had evaporated off there was added 5 parts of powdered titanium white and 50 parts of a mixture of glyceryl mono oleate and glyceryl mono stearate. When complete admixture had been effected the mixture was formed into hard cakes under hydraulic pressure. There resulted a white neutral soap comparable in hardness to soaps ordinarily made I from hard fats.

The range of glycerides available for producing soap directly by this process is greater than that available for the old processes because harder soaps can be made from liquid glycerides. In place of the specific glycerides described above may be substituted other animal and vegetable fats and oils which have been used for the production of soap. As examples of additional suitable materials, mention is made of olive oil, palm oil, sardine oil, castor oil, whale oil, linseed oil, stearin, tallow, cocoa butter, etc.

The preparation of the esters of the fatty acids preparatory to making soap from them as taught herein is not limited to the specific alcohols above named, but other alcohols may be used. Thus, saturated aliphatic alcohols having from 1 to 5 carbon atoms have utility. The preferred alcohols are saturated aliphatic monohydric alcohols boiling below about 100 C. and especially below about C. As examples of additional suitable alcohols mention is made of propyl, isopropyl, the butanols and the pentanols. Of these those which are water miscible and most volatile are preferred. An amount of alcohol above 1.75 equivalents or use of an alcohol with great intersolubility powers with glycerine such as methylpropylcarbinol will tend to prevent or prevent the glycerine from settling to the bottom and separating as an easily removable phase.

One important embodiment of the invention is concerned with the use of caustic potash as the saponifying agent in the above procedures, whereby hard potash soaps are formed. These soaps are believed to be new mixtures and have great utility in the arts. The potassium soaps of the more highly unsaturated glycerides, e. g. those prepared from cottonseed, linseed, sardine, etc. oils being hard, light colored and crystalline in nature are quite valuable and have many uses in the arts.

The invention has a number of decided advantages, among which are:

(l) The starting material may be any glyceride,

(2) The glycerine may be removed in a very pure and highly concentrated form,

(3) There are very small amounts of by-products formed, for instance, the small amount of lower alcohols does not require recovery to make the process economical,

(4) The catalysts used are very cheap and do not have to be recovered,

(5) The lower alkyl esters of the fatty acids from the glycerides readily admix with the saponifying agent and allow the saponification to proceed rapidly,

(6) The reaction starts and completes at low temperatures,

(7) The soaps are not subjected to prolonged or excessive temperatures at any stage,

(8) The initial and final products are non-corrosive to metals,

(9) Large amounts of caustic soda do not have to be recovered.

It is possible to produce soaps different from those of the prior art. For example. they can be made lighter in color, non-irritating, and con-' taining a neutral superfatting agent. They may be obtained in a pure anhydrous form having less than of electrolyte content. However, various amounts of water may be contained in the final products.

Fats and inorganic or organic diluents, as soap builders and cake formers, solubility modifying agents, preservatives, bleaching agents, may be compounded with the soaps, as lanolin, stearyl alcohol, methyl stearate, sodium carbonate, sodium silicate, sodium phosphate, sodium perborate, cyclonol, cyclohexanol, glue, glyceryl mono oleate, glyceryl mono stearate, bentonite, perfume.

The anhydrous pure soap which consists of a mixture of salts or higher fatty acids has great utility and may be substituted in a great many arts in the same way that soap and the newer soap-substitutes have been used.

The properties of these soaps described above make them suitable for use in a large number of processes. The following uses are suggested as being indicative of the manner in which the products may be employed: scouring raw wool, fulling, sizing, desizing, impregnating, bleaching, mordanting, lime soap dispersing, mercerizing, improvement of absorption, delustering, degumming, kier boiling, felting, oiling and lubricating, dyeing cellulose acetate fibers with insoluble dyes, dyeing of leather, dye printing pastes, pastes of dyes or dye components, preparation of lakes, preparation of inorganic pigments, emulsification and dispersion, treatment of oil wells, air foam and chemical foam fire extinguishers, cooking wood pulp, radiator cleaners, stripping, dyeing in neutral, or alkaline dye baths, dyeing of animal fibers with vat dyes, cleansing agents, fat liquoring, washing paper mill felts, improving absorbency of paper products, household dye preparations, metal cleaning, removal of fibrous layers from surfaces, shampoo, insecticides and agricultural sprays, flotation, breaking petroleum emulsions, food preparations, scouring rayon, creping assistant, flooding oil bearing sands, ceramic assistant, polishing, abrasive and bufling compositions, dentifrices, agents to prevent rubber and other plastics from sticking to molds, in adhesives such as starch, glue and casein and in compositions containing degraded proteins.

Thus, the herein described sodium and potassium soaps may be substituted in equal amounts for the alkyl betaines in Examples 16, 18 to 31 inelusive, 34, 36 to 53 inclusive, 55 to 59 inclusive, and 61 to 66 inclusive of Downing and Johnson application, Serial No. 200,530, filed April 8, 1938.

by other processes or with soap substitutes such as alkyl naphthalene sulfonic acids, Turkey red oil, higher aliphatic alcohol sulfates, higher alkyl betaines both of the C- and N- type, mineral oil sulfonates, etc.

As many apparently widely diiferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein except as defined by the appended claims.

We claim:

1. The process which comprises reacting a higher fatty acid glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrous conditions, said hydroxide being added in an amount of 0.1 to 0.5% by weight based upon the glyceride and the amonut of alcohol employed being not more than 1.75 equivalents of the glyceride.

2. A process as defined in claim 1 wherein the alkali metal hydroxide is added to the reaction zone from an alcohol of the character defined containing said hydroxide.

3. The process which comprises reacting a natural glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon The soaps may be mixed with soaps produced atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrous conditions, said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being not more than 1.75 equivalents of the glyceride and separating the glycerine from the alkyl esters formed.

4. The process which comprises reacting a natural glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrous oonditions, said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being not more than 1.75 equivalents of the glyceride, separating the glyceride from the alkyl esters formed and saponifying the latter.

5. The process which comprises reacting a natural glyceride with a saturated aliphatic monohydric alcohol boiling below C. in the presence of a small amount of an alkali metal hydroxide under substantially anlurdrous conditions, by heating to a moderate temperature, said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being not more than 1.75 equivalents of the glyceride, separating the alkyl esters from the glycerine and saponifying the same, said process being carried out in the substantial absence of water.

6. A process as set forth in claim 4 wherein the alkali metal hydroxide is added to the reaction zone from an alcohol of the character defined containing said hydroxide.

7. The process which comprises reacting a higher fatty acid glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrous conditions, said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being not more than 1.75 equivalents of the glyceride, separating the glycerine from the alkyl esters formed, purifying the esters by distillation and saponifying the same.

8. A process as set forth in claim 4 wherein one of the products of the reaction of each step 5 is removed as formed.

9. The process which comprise reacting a higher fatty acid glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrou condltions until conversion to the monoester is substantially complete, removing a substantially anhydrous glycerine and reacting the resulting monoesters with a saponifying agent,

said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the g yceride and the amount ofaicohol employed being not more than 1.75 equivalents of the glyceride.

10. The process which comprises reacting a higher fatty acid glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of av small amount of an alkali metal hydroxide under substantially anhydrous conditions, removing a substantially as anhydrous glycerine and reacting the resulting monoesters with a saponifying agent, said by droxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being from 1.2 to 80 1.75 equivalents of the glyceride.

l1. A-cyclic process for the productionof soaps and glycerine' which comprises reacting a natural glyeeride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the Z presence of a small amount ofan alkali metal hydroxide under substantially anhydrous conditions, said hydroxide being added in anamount. of 0.1% to 0.5% by weight based upon the glyceride and the amount of alcohol employed being not more than 1.75 equivalents of the gLvceride, separating the esters formed, saponifying the esters and returning the evolved alcohol to the first step of the process.

12. The process which comprises reacting a glyceride with a saturated aliphatic monohydric alcohol having less than 5 carbon atoms in the presence of a small amount of an alkali metal hydroxide under substantially anhydrous conditions, said hydroxide being added in an amount of 0.1% to 0.5% by weight based upon the glyceride, adding the alcohol in successive portions the total amount employed being not more than 1.75 equivalents of the glyceride and removing the glycerine as formed.

13. A process as set forth in claim 12 wherein 3 portions of about 0.4 equivalent each of alcohol is used. I

14. A'process a set forth in claim 3 wherein methyl alcohol is used.

15. A process as set forth in claim 7 wherein said glyceride is cocoa butter.

16. A process as set forth in claim 7 wherein said glyceride is fish oil.

17. A processa set forth in claim 4 wherein thesaponiflcation is carried out by forming an emulsion of said alkyl esters with a concentrated alkali metal ydroxide solution.

18. A process as set forth in claim 5 wherein potassium hydroxide is used as the saponifying agent.

19. A' process asset forth in claim 4 wherein the saponificatlon iscarried out with a concentrated alkali metal hydroxide solution of at least strength at a temperature of to C.

' and most of the alcohol is driven off.

GEORGE BURT BRADSHAW. WALTER C. LIEULY.