US 2860151 A
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2,860,151 METHOD FOR THE MANUFACTURE OF SOAP Edward Robert Larnson, Sewell, N. J., and Theodore A. Renshaw, Glenolden, Pa.
N Drawing. Application January 20, 1954 Serial No. 405,263
6 Claims. (Cl. 260-413) (Granted under Title 35, U. S.-Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purpose without the payment of any royalties thereon or therefor.
This invention relates to the art of soaps, soap making and grease making with soaps. More specifically, this invention contemplates making unusual efficiency in the formation of gels and greases without requiring the addition of heat. The soap is initially produced in its active form directly from the soapmaking raw materials and in this respect, the invention constitutes an improvement over the disclosure of a copending application, Serial No. 386,411, filed October 15, 1953 by the same inventors in which there is taught a method for improving the gelling characteristics of an existing soap.
Some of the known grease or gel forming methods are as follows:
A selected soap and the desired oil are mixed in the proportions required to produce a grease or gel of the nature desired. The mixture is heated to a temperature high enough to cause the formation of a gel and then cooled. Generally, the temperature must be raised to about the melting point of the soap and in the case where, for example, a lithium soap is used, the required temperature is about 400 F.
Stearic acid or l2-hydroxystearic acid is mixed with lubricating oil and to the mixture is added a solution of the hydroxide or carbonate of the desiredmetal; The temperature is raised to about 350 F. to aid the gelling process and toremove water or other solvent in which the metal hydroxide or carbonate was dissolved.
In each of these methods, the heating step adds to the cost of the process and in addition exposes the finished product to possible degradation or discoloration.
Therefore, it is a basic advantage of the instant invention that the entire soap and grease making processes are performed in most cases entirely without the addition of any external heat.
Another method for making a desired grease is to extract the liquid fraction from an existing grease and substitute therefor the desired oil. This method has the obvious disadvantage of requiring that the grease making process be performed twice. If it is assumed that extraction of the original grease leaves a soap similar to that produced by the instant invention, there are still the disadvantages of duplication and complexity. That is, to produce an active soap by solvent extraction of grease,
there is required the performance of a process for making a conventional soap, then a grease making process which would be one of those suggested above and then an additional process for extracting the oil. Obviously, the direct production from raw materials of a soap which will combine, readily atroom temperatures with an oil to form a grease would be preferred.
It is an object of this invention to disclose a novel soap having unusual qualities in its ability to form gels -without requiring the addition of heat.
2,860,151 Patented Nov. 11, 1958 Another object of this invention is to teach a new and novel method for manufacturing a soap so that the resulting soap displays unusual activity in the formation of gels or greases.
This invention also has for an object the production of an active soap directly from soap-making raw materials without employing external heat in any step of the process.
Another object is to produce an active soap by combining soap-making materials at temperatures well below,
the melting point of the soap.
A further object lies in the teaching of various means for obtaining the active soap in a dry, powdered form for easier storage and handling.
Still another object of this invention is to add to the knowledge in the field of grease making the disclosure of a novel and efiicient method for the production of greases by a continuous process.
Another object is the production of a grease by mixing together a lubricating oil and a dry active soap at room temperature without exposing the grease to the posibility of degradation caused by heat. i i
The development of a method for making a grease in the field from a lubricating oil and a soap in dry or slurry form without requiring the use of heat is also an object of this invention.
These and other objects and advantages of the present invention will become apparent from the following description and claims.
Other objects and many of the attendant advantages of this invention will 'be readily appreciated as the same becomes better understod by reference to the following detailed description:
The soap which is the subject of this invention is readily produced by combining soap-making ingredients in the presence of a hydrocarbon carrier. Under ordinary circumstances the ingredients will combine at room temperatures and by choosing a hydrocarbon of suitable properties, it can be removed to leave a dry soap merely by permitting the carrier to evaporate. A liquid hydrocarbon suitable for a carrier in this process should have the following qualities: less viscous than a lubricating oil, volatile, a lighter hydrocarbon and have a boiling point below the melting point of soap. Such hydrocarbons are described in greater detail on page 5 and 6 of our copending application Serial No. 386,411.
Because of the comparative ease of handling a relatively volatile carrier in performing the active-soap making process and because of the usually lower cost of such materials as opposed to the more viscous hydrocarbons, it is preferred to employ a relatively light carrier.
Similarly, although the soap can be retained in slurry form in the carrier, it is preferred to dry it to a powder form because it is more readily handled and transported. Drying can be accomplished in several ways, for example, by simple evaporation mentioned above. A low bulkdensity soap which more easily combines with various liquids to form gels is produced when the active soap is dried by a spray drying method or by sublimation of a high vapor pressure carrier from the solid state.
soap by neutralization or saan oxide, hydroxide or carbonate of the v tate out of solution by adding acetone. "hydroxide was then dried and reacted with stearic by causing reaction between "benzene solution and solid lithium hydroxide. "made" an excellent grease containing 20% milled with an oil at room temperature.
desired soap-making metal is reacted with a stearic or hydroxystearic acid or stearic or hydroxystearic acid ester which will provide the desired radical.
"lI nfthe double decomposition method, a compound of the desired metal is reacted with a compound which will provide the desired soap radical. Examples of this reaction are those between lithium acetate and stearic acid toform lithium stearate and acetic acid and between lithium chloride and sodium stearate to form sodium chloride 5 and *lithium stearate.
V In each of the neutralization, saponification and double decomposition reactions, the'reaction may be induced in the presence of a hydrocarbon carrier which will cause the soap to precipitate as it forms, or may be carried on inasolvent for the soap and then added to a hydrocarbon to cause precipitation of the soap.
The preferred hydrocarbons include naphthas, light petroleum distillates, terpenes and aromatic hydrocarbons which, in each case, have boiling points lower than the melting point of the soap to be formed as well as hydrocarbons which have boiling points higher than the meltin'g point of the soap but which can be extracted with one of the llower boiling point hydrocarbons defined above.
The simplest method for carrying out the process of this invention consists of neutralizing an acid, such as stearic acid, l2-hydroxystearic acid, with a hydroxide, oxideor carbonate of the desired metal. The reaction is carried on in the presence of a hydrocarbon taken from the group outlined above and the soap precipitates uponformation and is removed from the carrier. The metallic compound may be in dry form or in a solution. When used in a dry or solid form, it may be desirable to reduce the particle size to promote the reaction.
Example I solution of stearic acid in petroleum ether was prepared and combined with a solution of lithium hydroxide in water. The stearic acid solution was stirred rapidly while the lithium hydroxide solution was added thereto and neutralization, as evidenced by formation of a thick, heavy gel, took place without the addition of any heat. When it. appeared that the reaction had ceased, the stirring was stopped and a water phase became separated from the saponified mass. Some of the soap formed in this manner was retained as a slurry in the petroleum ether and the remainder was dried to a powder.
Both the slurry form and the dry form of the soap combinedwith a lubricating oil to form a satisfactory grease containing 25% soap without requiring any heatmg. Example 11 The particle size of solid lithium hydroxide was reduced by dissolving it in water and causing it to precipi- The lithium acid dissolved in benzene. The mixture was stirred during the-neutralization reaction and an additional quantity of lithium hydroxide was introduced to neutralize the excess stearic acid. A portion of the soap thus produced was dried from the soap-benzene slurry and the remainder 'left in the slurry form.
A good grease containing 20% soap could be produced by; combining an oil with either the dry soap or thesoap in slurry form at room temperatures.
Example III Hydroxystearic acid was substituted for the stearic acid in the process of Example II and an active soap produced the hydroxystearic acid- This soap soap when Example IV Hydroxystearic acid dissolved in petroleum ether was A benzene solution of stearic acid was combined with a water solution of lithium hydroxide to produce a reaction. The benzene was evaporated leaving a dry, active soap. 7
This soap could be readily milled into a grease containing 20% soap with white mineral oil.
Example VI Thirty grams of double pressed stearic acid was dissolved in 200 cubic centimeters of aromatic naphtha and wit was added slowly a solution of 5 grams lithium hydroxide dissolved in 40 cubic centimeters of water. The mixture was stirred during the process of adding the lithium hydroxide. This was all done at room temperature. A slurry resulted which was dried.
Di-2-ethyl-hexyl sebacate was added slowly to soap produced in Example VI while working with a spatula on a flat surface to form a grease containing 20% soap.
Soaps which had the active grease forming qualities were made by reacting stearic acid dissolved in petroleum ether with the following metallic compounds which were in solid form: sodium hydroxide, barium hydroxide, calcium hydroxide, sodium carbonate, lithium carbonate and zinc carbonate. In the case of the carbonates, it was found that the reaction proceeded more rapidly if a trace of water was added to the petroleum ether solution.
It was discovered that, when the soap-making reaction took place in a hydrocarbon, washing the slurry with an alcohol or a mixture of alcohol and a hydrocarbon greatly improved the gelling qualities of the soap. This phenomenon may be due to the fact that the alcohol aids the removal of excess water from the soap.
Example Vll A solution of stearic acid in benzene was neutralized with a water solution of lithium hydroxide and a thick slurry resulted. The slurry was washed with a solution of benzene and ethyl alcohol and then dried leaving an active soap.
Di-Z-ethyl-hexyl sebacate could be worked into the dry "soap with a spatula'to form a good grease containing 20% soap.
Example VIII The method of Example VII was repeated using isopropyl alcohol in place of the ethanol with equally satisfactory results.
The lower molecular weight alcohols containing from 1 to 5 carbon atoms compose the group of alcohols which can be satisfactorily employed in the process.
Example IX a hydrocarbon solvent and a slurry formed. An active soap was dried from this slurry.
Example X The method of Example IX was repeated but the washing step was performed using a mixture of hydrocarbon solvents and low molecular weight alcohols.
The dried soap was worked into an oil to a concentration of 30% with a spatula to form a 'stiif'grease.
Example XI 25 grams of stearic acid were dissolved in aboutl'50 c ic centimeters of an aromatic naphtha fraction and neutralized with 6 grams of calcium oxide stirred into the solution. A thick paste resulted from the reaction. A slurry was produced by washing with a hydrocarbon solvent and an active soap was dried from this slurry.
Example XII The steps of Example XI were repeated but a mixture of hydrocarbon solvents and low molecular alcohols was substituted for the washing solvent.
The dry active soap produced a grease by milling it into a lubricating oil. The soap solvent slurry also was made to produce a grease by the addition of some lubricating oil and subsequent evaporation of the volatile solvent.
The gelling propensity of the soap also appeared to improve when a quantity of a low molecular weight alcohol was added to the reactive materials rather than in the washing stepor where alcohol was present both during the reaction and in the washing.
Example XIII 30 grams of double pressed stearic acid was dissolved in 275 cubic centimeters of aromatic naphtha to which had been added cubic centimeters of isopropyl alcohol. A solution of 5 grams of lithium hydroxide in cubic centimeters of water was slowly stirred into the acid-naphtha solution at room temperature to produce a slurry. An additional 1 part of isopropyl alcohol was added for each 6 parts of the slurry and the solution stirred, filtered and dried. A grease composed of 20% soap and 80% di-2ethyl-hexyl sebacate was made by working the oil into the soap with a spatula on a flat surface.
In the above quoted examples, no heat was required to carry on the soap making reaction.
In the methods of preparing the active soap where the soap is formed in a material which is a solvent for the soap, it is usually necessary to supply external heat to some degree. However, this disadvantage is offset by the apparently increased activity of the soap in forming gels and greases water and of excess reactants. In practice, the method to be employed will probably depend to a considerable degree on the suitability of the available equipment.
Example XIV A solution of stearic acid in methyl alcohol was reacted with dry sodium hydroxide to form a clear solution of sodium stearate in methyl alcohol. This last solution was stirred into a quantity of petroleum ether to form a thick slurry composed of soap, petroleum ether and alcohol. The petroleum ether-alcohol solution was filtered off leaving a dry soap.
Soap prepared by the method of Example XIV was mixed with a petroleum lubricating oil at room temperature and a satisfactory grease containing 20% soap resulted.
A grease containing 20% soap Was made by mixing a petroleum lubricating oil with the slurry formed in Example XIV and evaporating the alcohol-petroleum ether solution.
Example XV Stearic acid was dissolved in hot methyl alcohol and reacted with dry sodium hydroxide to form a solution of sodium stearate in alcohol. When the solution cooled, a stiff gel formed which was dried, leaving the active soap.
Soap formed in Example XV made a good 20% soap grease when worked into a petroleum lubricating oil with a spatula.
A good grease containing 10% soap was made by pouring the alcohol-soap solution of Example XV into a petroleum lubricating oil and removing the solvent.
plus greater ease in the removal of excess of stearic acid for the 6 Example XVI One part solid lithium hydroxide containing one mole of water per mole of lithium hydroxide was added slowly to approximately 15 parts of double pressed stearic acid which was at about 12 C. The temperature was then raised to about 150 C. for about 15 minutes to allow the reaction to proceed to completion producing a clear solution. The warm solution was stirred into some benzene and a thick slurry resulted. The slurry was filtered and washed several times with benzene. The slurry was dried on a steam bath and then in an oven at about C. An extremely soft, dry, powdery soap remained which which was unusually active in gelling oils and had a melting point approximating 3 C. above the melting point of high grade commercial lithium stearate.
The soap of Example XVI produced a 20% soap grease when mixed with a spatula on a flat surface with di-2- ethyl-hexyl sebacate which was added slowly to the dry soap. The grease produced had a dropping point of 379 F. and a micropcnetration of 96.
It will be noted that Example XVI merely employs an reaction to supply the solvent for the soap which forms.
In connection with this point, it was found that contamination of the solvent with a hydrocarbon would not change the character of the soap produced as long as the concentration of the solvent was sufiicient to keep the soap in solution. This would be of importance where a continuous process involving recovery of the solvent is employed since it reduces the cost of recovery by not requiring difiicult separation of small percentages of contaminating hydrocarbon.
As was previously stated, the active soap may be produced by a saponification reaction with a fatty acid ester.
Example XVII Solid sodium hydroxide reacted readily with glycerin tri-stearate which was dissolved in petroleum ether to form a soap displaying the active grease making qualities described above.
Because of the substantially instantaneous gelling of an oil by the active soap produced by this invention and the absence of the requirement of heating, it may readily be seen that the method of this invention may be practiced as a continuous process with an end product of grease or other desired gel.
The soap formed by the methods of this invention would be useful in gelling various low boiling hydrocarbons and other liquids such as petroleum ether, naphtha and gasoline. It is also particularly efiective in gelling oils and other liquids in which normal soaps cannot be thermally dispensed; for example, glycerin and silicone oils. Of added importance is its ability to produce gels of these liquids as Well as other. lubricants and hydrocarbons readily at room temperature.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than a specifically described.
What is claimed is:
1. A method for preparing a soap displaying unusual activity in the formation of gels and greases comprising dissolving an alpihatic carboxylic acid from'the group consisting of stearic and IZ-hydroxystearic acids, which acid when neutralized yields the desired soap constituent, in a liquid hydrocarbon having a boiling point below the melting point of the soap, said hydrocarbon being one from the group consisting of naphtha, light petroleum distillates, terpenes and aromatic hydrocarbon; neutralizing said acid with a metal base from the group consisting of the oxides, hydroxides and carbonates of lithium, calcium, sodium, barium and zinc causing precipitation of the soap form in the liquid hydrocarbon; and evaporating the hydrocarbon.
2. The method of claim 1 in which the metal base is in a Water solution.
3. The method of claim 1 in which all of the steps of the process are performed at room temperature.
4. A method for preparing an insoluble active soap comprising dissolving stearic acid in petroleum ether, neutralizing said acid with a water solution of lithium hydroxide causing precipitation of the lithium stearate in the petroleum ether, and evaporating the ether.
5. The method of claim 4- in Which the steps of the process are performed at room temperature.
6. A method for preparing an insoluble active soap comprising dissolving 12-hydroxystearic acid in benzene, neutralizing said acid with lithium hydroxide causing precipitation of the lithium 12hydroxystearate in the benzene, freezing the benzene-lithium 12'-hydroxystea'rate mixture and removing the benzene by sublimation.
'References Cited in the file of this patent UNITED STATES PATENTS 2,157,767 Long May 9, 1939 2,444,720 Bell a- July 6, 1948 2,480,564 Forney Aug. 30, 1949 2,616,850 Browning Nov. 4, 1952 2,636,001 Browning et al Apr. 21, 1953