US 3694367 A
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United States Patent US. Cl. 252121 Claims ABSTRACT OF THE DISCLOSURE New superfatted detergent products and processes for making them are provided. A neutral soap in fluid state is mixed with a detergent-type sulfonic acid to liberate fatty acids in suitable proportion to impart desired superfatting properties to the product, neutralizing at the same time the sulfonic acid, and working up the mixture into finished products such as powder, granules, flakes, ribbons, and preferably milled toilet bars. The superfatted products, preferably milled toilet bars, comprise fatty acid salts of a suitable cation, usually sodium, free fatty acids in suitable proportions to impart the desired superfatting properties to the finished product and a detergent-type sulfonate in the intimate relationship characteristic of in situ formation of the sulfonate by reaction of the sulfonic acid with neutral soap in fluid state. Further novelty of the product and its characteristics are attributable to the difference in the distribution of free fatty acids produced in situ vis-a-vis the distribution of the fatty acids in the neutral soap.
This application is a continuation-in-part of application Ser. No. 746,243 filed July 22, 1968 now abandoned.
The present invention relates to a process for producing superfatted detergent product, more particularly to such a process in which a detergent-type sulfonic acid is added to a neutral soap to liberate fatty acids and neutralize the sulfonic acid, and to the soap produced thereby. Additional anionic synthetic detergent may be added to increase the detergent: soap ratio to as high as about 1.5 1 to produce a bar of the synthetic detergent-soap type which has come to be known in this art as a combar.
superfatted soaps of many different kinds have been referred to in prior patents and literature. Generally speaking, experts in this field have advised against the use of free fatty acids as the superfatting agent, whether added or formed in situ by addition of mineral acid, because of the development of odors due to rancidity which perfumes cannot mask. These experts usually recommend superfatting agents such as lanolin, lecithin, casein, higher fatty alcohols, spermaceti, saponifiable oils, mineral oils and sulfated oils. The addition of these recommended materials, however, increased the cost of the finished soap by reason of the cost of the superfatting agent and additional processing costs and in many cases the improvement in performance of the superfatted soap resulting from the addition over a soap of the same composition without the superfatting agents was not observable by users who did not find the more expensive soap worth the added cost.
Another proposal in the art to improve the performance of soap, especially in hard and sea water, is to add a syn- "ice thetic detergent, especially an organic sulfate or sulfonate salt having a long aliphatic chain in the molecule, in suflicient amounts to inhibit or prevent precipitation of soap during use in such water. Many formulas and procedures for making products of this type, including bars, have been suggested but most of them which have been tried have been unsuccessful in the market place. The very few that have had some commercial success, which are usually referred to in the art as combars, have had relatively high proportions of the sulfuric acid reaction product and of other materials in addition to soap and none of these have been superfatted as taught herein.
The present invention is a departure from the prior art in both method of manufacture and composition. The method of manufacture comprises converting fats and oils to a neutral soap by any desired manner. By neutral soap is meant a soap having no free fatty acid and at most a small fraction of 1% of free alkali computed as Na O. While the soap is in sufficiently flowable condition to permit mixing, e.g. in a crutcher, a sulfonic acid as hereinafter defined, is added in sufficient proportion to liberate the desired proportion of fatty acids based on the weight of the final product. In soap bars this proportion is preferably about 2% to 8% but in combars it may be higher, e.g., up to about 25% The sulfonic acid has higher aifinity for the cation of the soap so that the soap itself, and any free alkali present, serves as the neutralizing agent for the sulfonic acid which, in the neutralized or salt form, has detersive properties. Other additives normally introduced into soap formulations at the crutcher, including anionic detergent salts to produce combars, can be added, if desired, and the crutched mass may be worked up into finished products, e.g., bars, by usual process in conventional soap making machinery. The product of this process is a superfatted soap bar having smooth, creamy lather, a cold cream or emollient effect because of the free fatty acids, and improved wetting and curd dispersing properties by reason of the presence of the sulfonate salt. The crutched mass may be framed, solidified and cut into bars but preferably it is dried, amalgamated, milled, plodded, cut, stamped and wrapped like ordinary soap of toilet quality. The bars so formed resist marring, cracking, and sloughing at least as well as conventional milled toilet soap bars. These surprising results are obtained at the low cost of the sulfonic acid and without adding another operation to the process.
Suitable soap making processes that may be used to prepare soap for use in the present process include the usual kettle soap making process, continuous saponification processes in which saponification is elfected with aqueous alkali and heat, the resultant mixture being washed and fitted to obtain a neat soap either continuous- 1y or by use of a kettle for the fitting and optionally one or more washing stages, and neutralization processes for fatty acids derived by hydrolysis of fats and oils.
The kettle process of making soap is well known to those skilled in the soap making art so it will be disclosed here only in general outline since it does not form part of the present invention. A typical kettle process includes the following stages:
(1) Killing or saponification stage. (2) Change stage.
(3) Washing stage.
(4) Fitting or pitching stage.
In the first or saponification stage the fatty material chosen for the particular soap to be produced, e.g., fat and oils which are glyceryl esters of fatty acids, is heated with aqueous caustic solution to effect substantial conversion of the fatty material to glycerine and fatty acid salts of the alkali metal or metals present in the caustic solution. For toilet bars sodium soaps are generally preferred but in some cases caustic potash may be used with caustic solution. Potassium soaps are softer than sodium soaps of the same fatty acid content and therefore the content of potassium fatty acid salts is somewhat limited in proportion to the sodium fatty acid salts in order to have a soap that works up well into bar form in conventional soap making machinery. Generally, the caustic solution used in the killing stage is obtained in whole or in part from the change stage of another batch. The extent of saponification in the killing stage is not critical and may vary from as low as about 80% to almost complete saponification.
In the change stage, which may take place in one or more separate operations, salt is added to the reaction mixture in sufficient concentration to effect precipitation of the soap from the solution. The salt used may be fresh salt or salt recovered from the purification of the glycerine, or a mixture of both. Generally, boiling is continued for a short time after addition of the salt and if the saponification is incomplete in the killing stage caustic may be included with the salt to complete the saponification during this boil. The mass is then settled, during which the less dense soap rises to the top and the spent lye containing the bulk of the glycerine and electrolyte sinks to the bottom. When the settling is complete the lye is drawn off and sent to the glycerine plant for recovery of the glycerine, salt, etc.
The washing stage has as its object the more complete removal of glycerine, which may be as much as 0.5% of the weight of the soap layer left after drawing off the lye, and the complete saponification of the fat charge. In general, a washing operation consists of closing the soap by adding water and boiling vigorously, usually with open steam, and then adding salt and/or caustic to grain the soap and permit settling again into an aqueous lower layer and an upper grained soap layer. Where caustic is used in the washing operation it is sometimes called a strengthening change and the lye settled is not fully spent and may be used as the caustic solution in the killing stage of another batch of fatty material. The washing operation also removes further amounts of impurities that may have been present in the original charge.
The fitting or pitching stage has for its objective the separation of a neat soap phase from a nigre phase and it is effected by again closing the soap by the addition of water and boiling. The water addition is carefully done so as to reach a final stage Where the electrolyte content of the mixture is sufficient to dissolve part of the soap but not all of it. On settling the dissolved soap sinks to the bottom and forms the nigre while the undissolved soap rises to the top as neat soap. The neat soap may then be pumped from the kettle for further processing.
A typical composition of the withdrawn neat soap is approximately 60% total fatty acids, with a maximum of about 0.14% caustic calculated as Na O and a maximum of about 0.6% sodium chloride, with water at about the 30%-32% level.
Soap of similar composition may be obtained by other soap making processes, such as the continuous and neutralization processes referred to above. These processes are also well known to workers of ordinary skill in this artand need not be further described.
The sulfonic acid used in the process and composition of the invention may be any organic sulfonic acid which, in neutralized or salt form, possess desired detergent properties and which is referred to sometimes as a detergent type sulfonic acid. Such detergent type organic sulfonic acids usually have an aliphatic group of at least 8, preferably at least 10, carbon atoms and generally not more than 20, preferably up to 16, carbon atoms in the molecule. The aliphatic group may be straight or branch chain and may be joined at a primary or secondary carbon atom to the sulfonic acid group, either directly or indirectly through an aryl group, by a C-S bond. Exemplary products are the alkyl (C to C benzene and naphthalene sulfonic acids and preferably the C to C alkyl benzene sulfonic acids. A particularly useful example is an alkyl benzene monosulfonic acid in which the alkyl group is derived from propylene tetramers and pentamers, i.e., dodecyl and pentadecyl benzene sulfonic acids. Other useful sulfonic acids include olefine sulfonic acids preferably C to C olefin sulfonic acids wherein the sulfonic acid group is in any position and the unsaturated group is also anywhere in the alkenyl chain, i.e., internal. The most preferred are the l-sulfonic acids derived from aolefins as well as l-sulfonic acids containing the unsaturation in an internal position, (i.e., 2, 3, 4, 5, 6, 7, 8, etc.). Also useful are the alkane (C to C sulfonic acids such as lauryl, myristyl and cetyl sulfonic acids, secondary sulfonic acids produced by the treatment of paraffins with sulfur dioxide and chlorine or oxygen in the presence of actinic light or reaction promoters. Other sulfonic acids which are useful include hydroxyalkane sulfonic acid, e.g., 2, 3, 4, 5, 6, 7, etc. hydroxy (C -C alkane sulfonic acids and specifically 3-hydroxy tetradecane-l-sulfonic acid, 4-hydroxy hexadecane, l-sulfonic acid, etc., olefin disulfonic acids, etc. These organic sulfonic acids are further characterized by the ability to liberate fatty acids from their salts by combining with the cation to form sulfonates. In truly neutral soaps the sulfonates formed on addition of the sulfonic acid will bear a direct stoichiometric relation to the free fatty acid content and even in soaps which are slightly alkaline the relation for all practical purposes is stoichiometric.
It has been proposed heretofore to produce a superfatted soap by adding a mineral acid, e.g., hydrochloric acid, to a fully saponified mixture of coconut fatty acids and colophony or castor oil in a proportion of about parts of fatty acids to 5 parts by weight of colophony or castor oil, the amount of acid being about 7 parts of 30% HCl. The acidified mixture is then worked up in bar form in the usual way, i.e., by crutching, framing and cutting. This process leaves the inorganic salt form in the acidification step in the soap, which can be tolerated in a soap made largely from coconut oil fatty acids but it is uneconomical to make soap of this composition because of its higher cost than tallow. In soaps made from tallow, or mainly from tallow, the relatively high inorganic salt content resulting from the addition of mineral acid cannot be tolerated. A coconut oil soap also has the disadvantage of a high proportion of salts of lower fatty acids having from 6 to 10 carbon atoms per molecule which are known to be irritating to sensitive skin when present in soa While coconut and like acids can be topped to remove these irritating lower acids, the removal operation adds considerably to the cost of soap production. The present invention, on the other hand, permits the use of all soap making fatty acids by forming a beneficial organic salt, i.e., the organic salt in the acidification reaction which liberates the desired proportion of fatty acids.
It has also been proposed to make superfatted soaps by either incomplete neutralization of fatty acids used as the starting material in the soap making process, or by adding free fatty acids to fully saponified fatty material. The partial neutralization process results in a soap that does not contain salt which is a desirable ingredient, within critical limits, in a soap that is to be worked up by milling and plodding because it makes the soap harder and easier to work in the mill, the plodder and the press or stamp. The addition of free fatty acids to fully saponified fatty material produced from fats and oils in a kettle process requires a special preparation of these acids which adds cost to the product compared to the present process which forms the free fatty acids from the fat used in the kettle charge. These disadvantages are avoided by the present invention.
The fat charge used in the present invention is not critical, but it is preferred to use a charge comprising about 50% to 70% tallow and 30% to 50% of the oils of the coconut type, including coconut oil, palm kernel oil, Babassu oil, and the like. A soap made from this combination of raw materials by the process of the invention is a new composition of matter comprising soap, preferably the sodium salts of tallow and coconut oil type fatty acids in the ratio of about 50% to 70% tallow and 30% to 50% coconut oil type fatty acids, an excess of fatty acids, preferably in the range of about 1% to 8% by weight of the total composition, to impart superfatting properties to the product, and a sulfonic acid detergent salt in stoichiometric relation to the free fatty acid content, and is part of the present invention.
Fatty material that may be used in the fat charge to the kettle or other equipment for making the soap include the following:
Coconut oil Palm kernel oil Babassu oil Palm oil Animal fats Olive oil Tall oil Rosin Castor oil Groundnut oil Linseed oil Cottonseed oil Fish oils and hydrogenated versions of these products, but as indicated tallow and coconut type oils are preferred.
The caustic used to saponify the fat charge is preferably sodium hydroxide but it may be replaced in part by potassium hydroxide, e.g., up to about 15% if desired.
It is advantageous to include a preservative in the soap to prevent the rancification of the free fatty acids and among suitable preservatives are the following: 2-6 ditertiary butyl p-cresol, tertiary butyl hydroxyanisole,
Sopanox, triphenyl phosphite.
The usual steps for converting kettle soap into milled toilet bar form may be used for making soap bars of the present invention which include crutching the near soap phase with the predetermined proportion of sulfonic acid and other desired additives such as preservatives and heavy metal sequestrants, e. g., stannic chloride and ethylene diamine tetra-acetate, then drying the soap to a moisture content within the range of about 8% to 15 preferably about 9-l0%, mixing the dried soap in the form of dried ribbons, granules, or the like in an amalgamator with other desired additives such as colors, perfumes, glycerine, lanolin, cold cream, etc., milling the mixture, plodding the milled chips to form a long, continuous bar, cutting the bar into tablet or cake lengths and pressing or stamping the tablet or cake which may then be wrapped or not as desired.
In the following examples parts are by weight unless otherwise indicated.
EXAMPLE 1 This example illustrates the process and product of the invention relating to soap bars: The fat charge consisting of 70 parts tallow and 30 parts coconut oil is fully saponified by boiling with caustic soda in a kettle at a temperature of about 105 C. for about 4 hours. After the customary washing and fitting stages, a neat soap is separated from a nigre. The neat soap is then worked by by crutching it at about 80 C. with about 6% by weight of the crutched batch of dodecyl benzene sulfonic acid which is introduced at about 50 C. During the thorough crutching the sulfonic acid molecules are neutralized by sodium cations of molecules of fatty acid salts immediately adjacent thereto,
Percent Soap 1 84.0 Moisture 8.0
NaCl 1.0 Preservative, color, etc. 0.5
1 Including detergent.
Soaps produced by the process described are greatly superior to the corresponding soaps produced without addition of the sulfonic acid. The volume of lather produced is greater, and the lather tends to be rich, thick and creamy in texture. The concentration of soap in the lather is lower than with a corresponding soap to which sulfonic acid was not added and consequently the amount of soap that need to be used from the bar is less. This makes soap made by the above process more economical in use than the corresponding soap made without sulfonic acid. There is also tendency to form soap curds in hard water.
The content of neutralized anionic sulfonate detergent in the soap bar made as just described is about 6% because the mean molecular weight of the fatty acids is approximately the same as the mean Weight of the sulfonic acid used to liberate the free fatty acids. It is a feature of the present invention that the free fatty acid content of the finished bar is obtained by liberating these fatty acids from neutral soap by addition of sulfonic acids which are converted by the reaction into detergent salts. The proportion of detergent salts, and the cation of these salts, obtained in this way are therefore limited by the proportion of fatty acids desired in the finished bar and the cation of the soap. In some cases it is advantageous to have a larger proportion of detergent salts in a bar than is obtainable by the liberation of fatty acids and/or to have detergent salts present which have a cation different from the cation of the soap. The benefits of the present invention extend to such products, particularly milled tolet bars, which contain either a larger proportion of the same detergent salt or an added quantity of a detergent salt differing from the salt produced in situ either in the anion or cation.
EXAMPLE 2 Example 1 is repeated using as the fat charge 50 parts tallow and 50 parts coconut oil.
EXAMPLE 3 Examples 1 and 2 are repeated employing, in separate runs, 1, 2, 3, 4 and 5% dodecyl benzene sulfonic in place of 6% thereof.
EXAMPLE 4 Examples 1, 2 and 3 are repeated using in place of dodecyl benzene sulfonic the following sulfonic acids:
(A) linear tridecyl benzene sulfonic acid (B) dodecane sulfonic acid (C) hexadecane sulfonic acid Products produced in the manner described above for soap bars, using detergent type sulfonic acids in an amount required to liberate about 1% of free fatty acid will also contain about 89% salts of fatty acids and about 1% salts of the sulfonic acid, the balance being moisture, perfume, preservatives, etc., giving a detergent: soap ratio of about 1:90. A soap bar containing about 8% free fatty acids liberated by sulfonic acid acidification will contain also about 74% fatty acid salts and about 8% salts of the sulfonic acids, giving a detergentzsoap ratio of about 1:9. If the total content of anionic detergent salts is increased to about 15%, e.g., by adding about 7% of such salts to the crutcher after liberation of 8% free fatty acids, the product has a total detergent:soap ratio of about 1:4 which approaches the minimum ratio used in commercial combars. In general the detergentzsoap ratio in commercial combars does not exceed about 1.5 :1 which obtains when a bar is made having about 60 parts detergent and 40 parts soap with other ingredients including free fatty acids, moisture, preservative, etc., as noted above. The present invention contemplates bars having a total anionic synthetic detergent content in relation to soap Within this entire range, i.e., a detergentzsoap ratio of about 1:90 to 1.5 :1, which contains free fatty acids in the desired proportion liberated from neutral soap as described herein. Combars also may tolerate a higher percentage of free fatty acids than the 8% specified above for soap bars, even up to 25% of the total bar content, particularly where anionic synthetic detergents such as parafiin sulfonates and olefin sulfonates are present in major, or at least very substantial, proportions in relation to soap content. These fatty acids are all obtained by acidification of the neutral soap with sulfonic acid as described above.
The anionic detergent salts that may be used as additives to produce combars in accordance with this aspect of the invention include all such detergent salts which have been found useful in combars of the prior art. Generally speaking sodium salts are preferred but other alkali metal, ammonium and amine salts of the sulfonic acids mentioned above may be used. In addition to such salts of the sulfonic acids mentioned hereinabove, the added detergents salt content of bars of the present invention may be selected from alkyl sulfosuccinates, including monoand dialkyl sulfosuccinates such as monolauryl sulfosuccinate and diamyl sulfosuccinate; short chain sulfonates having intermediate ester, ether and arnide linkages to high alkyl and acyl groups such as and RCOOC H SO Na where R has from 8 to 18 carbon atoms; salts of sulfuric acid esters, with or Without intermediate linkages including ester, ether, and amide linkages, such as higher alcohol (including synthetic) sulfates, e.g., sodium lauryl sulfate, sodium C alcohol sulfate, higher fatty acid monoglyceride sulfates such as sodium monococonut oil fatty acid glyceride sulfates; alkane sulfonates with intermediate amide, ester and ether linkages; and alkyl aryl sulfonates having the hydrophobic group joined to the sulfonated aryl group by any suitable intermediate linkage. These classes of detergent salts, which are well known to the ordinary skilled worker in this art, need not be further described.
The process of making superfatted combars in accordance with the invention differs from the process described for soap 'bars only in the addition of the desired amount of synthetic detergent salt to the bar composition no later than the amalgamator and preferably in the crutcher, or earlier in some cases. If the detergent salt used Will not react with the sulfonic acid which is added to liberate the free fatty acids from the neutral soap it may be added to the neutral soap before the sulfonic acid is added to the liquid mass in the crutcher. 0n the other hand, if the detergent salt used would react with the acid it must not be present during the liberation of the fatty acids but must be added subsequently, e.g., in the crutcher or the amalgamator.
The process of acidification with sulfonic acid does not free the various fatty acids in the proportions in which they were present in the original soap. Acidification pushes out preferentially the shorter chain fatty acids in higher proportion than the longer chain fatty acids, and the unsaturated acids in higher proportion than the saturated acids. For these reasons, the process of the present invention produces a soap product of novel composition and properties by the addition of the sulfonic acid as described. Percentages where cited are by weight.
Although the present invention has been described and illustrated with reference to certain specific embodiments, it is to be understood that variations and modifications can be made without departing from the spirit and scope of the invention as defined in the following claims.
What is claimed is:
1. In a process for producing superfatted sodium and potassium soaps of fatty acids obtained from vegetable oils and animal fats in combination with synthetic detergent including the steps of forming the neat soap and subsequently Working the superfatted soap-detergent combination into a toilet bar, the improvement which comprises adding to the neat soap a detergent organic sulfonic acid containing a C -C alkyl group to liberate 1% to 8% fatty acids from the soap to impart superfatting properties thereto and to neutralize the sulfonic acid.
2. A process as defined in claim 1 wherein the sulfonic acid is an alkyl benzene sulfonic acid.
3. A process as defined in claim 2 wherein the alkyl is C12 to C 4. A process as defined in claim 3 wherein the soap is a sodium soap of 30% to 50% coconut oil fatty acids and the balance tallow fatty acids.
5. A process as defined in claim 4 wherein the finished product is a milled toilet bar.
References Cited UNITED STATES PATENTS 3,494,869 2/1970 Armstrong 252-l09 3,247,121 4/1966 Hendricks 252-1 17 3,150,097 9/1964 Kelly 25212l 3,043,778 7/1962 Kelly 252107 2,894,912 7/1959 Geitz 252l2 l 2,749,315 6/1956 Faier 2521 17 FOREIGN PATENTS 723,925 2/ 1955 Great Britain 252l21 LEON D. ROSDOL, Primary Examiner D. L. ALBRECHT, Assistant Examiner US. Cl. X.R.
252117, 132, 368, 369, 370, DIGEST l6