US2974154A - Process of preparing salt-free n-acyl taurines - Google Patents

Description

United States Patent PROCESS OF PREPARING SALT-FREE N-ACYL TAURINES Leslie M. Schenck, Mountainside, NJ assignor'to General Aniline & Film Corporation, New York, N.Y.,,a corporation of Delaware No Drawing. Filed Dec. '30, 1958, Ser; No. 783,681"

12 Claims. (Cl. 260-401) U-.S; Patent No; 1,932,180, severalprocesses are-described' for the preparation of suchsurface active materialsbut the only process which hasup tothe presentbeen employed commercially is that wherein an acid-chloride is reacted in aqueous medium with a Z-aminoalkane sulfonic acidin thepresence of an acid neutralizer such asv caustic soda.

salt, eig; sodium chloride (or potassium chloride if caustic potash is used as acid neutralizer) as awby-product'.

Thepresence of such salts with the N-higher acyl taurine is highly undesirable and disadvantageous-forj a num'ber'of reasons. Not only do such salts have asubstantial corrosive efiect inthe packaging and handling of detergents and'other surface active-compositionscon taining such acyl taurines, but theyalso exert a strong adverse effect on the lathering; detergent and other surface active properties of mixtures of such acyl taurines with soap. The acyl taurines' are verygood'lime soapdispersants and the combination of minor amounts thereof with ordinary fatty acid soaps in detergent andbuilt-soap formulations results in highly effective-detergent properties; particularly in hard'water. However, for such com binations to'have optimum properties, the' N-higher-acyl taun'n'epresent therein should-have a low salt content.

The'presence'of this salt in' a number of. commerciallyavailable N-acyl taurines, has'been identified as amajor reason for the unduly high hygroscopicityof such products: Thepresence of such salt is also undesirable when theN-acyl taurine is to be employed in certainemulsion' polymerization reactions and in other uses.

A numb'er of proposals have been made in the prior art" for the production of salt-free N-liigher acyl taurines,

some of which involvethe use ofa' differentmethod of reaction or of different reactants in'the produ'cti'onof such tauri'nes, and others ofwhich involve expensive an'cl'ditficult separation methods,

Itis an object of this invention to providea process for producing a salt-free N higher acyl taurine which will not be subject to" the above disadvantages. An-

other objectof this invention is the provision of' a proc-- ess-for'p'roducing wsalt-free N-higher acyl taurinefrom.

an aqueous slurry containingisuch: taurine in combination with a water soluble salt.- va'nt'ages will appear as the description proceeds;

The attainment: of the aboveobjectsis madepossible by the present invention which includes a process com- This inherently produces;v in addition tothe N-higher'acyl taurine, a considerable quantity of Other objectsan'claadsprising addingto an aqueousslurry containing (A) N-higher. acyltaurine of the formula R'CONR"CHR--CHRSO M wherein one R is selected from the group consistingof i H and methyl and the other R is H, R is selectedfromv the group consisting of H and hydrocarbon radicals of the group consisting of H, alkali metal, alkaline earth metal, ammonium. and amino, and (B) a water soluble salt selected from the group consisting of the alkali metal chlorides and sulfates, a water insoluble compound;

C selected from the group consisting of aliphatic and alicyclic monocarboxylic acids of 8 to 24 carbon atoms and their esters in an amount sufficient to form a compatible solvent systemwith said taurine (A),-heating the resulting mixture to distill off the water, and then separating the crystallized salt B from the mixture at a temperature above the solidification point of the A and C solvent: system;

An outstanding advantage of the process of this invention is that it is operable on the commercially avail able N-higher acyl taurines produced by the Schotten- Baumann reaction between a higher fatty acid chloride and a taurine, and may be carried out by soap manufacturers themselves in readily available equipment. The product produced by the above process is a mixture of the acyl taurine Withthe higher molecular Weight can boxylic acid or ester which may be employed as such to saponify the carboxylic acid and produce its soap-in. Such soa'p compositions are useful directly as Sill]; toilet soaps and other cosmetic applications in liquid or solid form and can readily be formulated into bars or'cakes. If desired, the resulting combination of soap and N-higher acyl taurine may be spray dried or drain dried to produce a flake or powder detergent and may be combined before or after such drying with common. builders, stabilizers and thelike for the production of heavy'duty built detergent compositions. Common compon'ents of such built compositions include alkali metalphosphates and polyphosphates, silicates, carbonates, and sodium -ca'rboxyinethyl cellulose.

Since the-present process is performed at moderatetemperatures; no discoloration of product or reactants is experienced and the original purity of the intermedi ates "is representative of the final product, excluding those impurities that are insoluble in the dehydrated solution and? thereby; removed during the; processing. Highly specialized equipment required by the prior art to maintain the necessary reaction conditions for'the production of the desired salt-free N-higher acyl taurines is no longer'necessary. The operability of the present process is surprising and unexpected in view of the anticipated foamingwhich would normally be expected to occur in a fatty acid-synthetic detergent-soap and water formulation of'the type involved in the present process. t

If a final product is desired which must be not only salt-free but also substantially pure, the higher carboxylic acid employed to form a compatible solvent system with theacyl taurine maybe conveniently removed by distillation.

The process of this invention is applicable for'the treatment of any aqueous slurry containing the N-higher. acyl taurine and a water soluble salt, regardless of its manner of production. The N-higher acyl taurines which are produced in salt-free form in accordance with this.

invention may in general be ascribe'd'tlie formula givti" Patented Mar. 1-, 1-961 above. Such acrylated taurines may be prepared by reaction of a taurine salt containing at least one N-bonded hydrogen atom with a higher molecular weight acylating agent of the formula R'COOH or R'COCl. Those acylating agents particularly preferred are the higher free fatty acids of 12 to 18 carbon atoms (R' is 7 to 17 carbon atoms). As generally representative of higher aliphatic and alicyclic carboxylic acids operative in the instant invention, there may be mentioned caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, linoleic acid, undecylenic acid, tall oil acid, acid mixtures from various natural plant and animal oils such as olive, tallow, castor, peanut, coconut, soybean, cotton seed, ucahuba, linseed, cod, herring, menhaden, neatsfoot, sperm, palm, corn, butter, babassu, kapok, hempseed, mustard, rubberseed, rape, sunflower, sesame, acids from the oxidation fractions of petroleum, and from oxoaldehydes, naphthenic acids, abietic acids, and the hydrogenated derivatives of such acids and acid mixtures. Other acids which may be employed include alkyl benzoic acids such as dodecyl benzoic acid, nonyl bcnzoic acid, octyl benzoic acid, alkyl naphthoic acids such as nonyl naphthoic acid, and the like.

The above described carboxylic acid acylating agents are accordingly representative of the aliphatic, alicyclic and aromatic hydrocarbon radicals of 7 to 23 carbon atoms which may be employed as R in the above formula. Such carboxylic acid acylating agents (e.g. RCOCl) are reacted with taurines of the formula to produce the acylated taurines treated in accordance with the present process. In this formula, R" may represent hydrogen, methyl, ethyl, isopropyl, butyl, hexyl, cyclohexyl, phenyl and the like, and M may represent hydrogen or a salt-forming cation such as an alkali metal, e.g. sodium, potassium or lithium, an alkaline earth metal such as calcium, magnesium or barium, ammonium, or an amine such as mono-, dior triethanolamine, cyclohexylamine, guanidine or the like. Thus, by way of example only, the following specific Z-aminoalkane sulfonic acids may be employed as such or in the form of their salts for reaction with the above defined carboxylic acid acylating agents: taurine, N-methyl taurine, N-ethyl taurine, N-propyl taurine, N-isopropyl taurine, N-butyl taurine, N-amyl taurine, N-hexyl taurine, N-cyclohexyl taurine, N-phenyl taurine, N-methyl-Z- methyl taurine, N-methyl-l-methyl taurine, and the like.

The aqueous slurries treatest in accordance with the present process, should in general be sufiiciently fluid to be readily workable. In general, in such slurries, the acylated taurine would be present in concentrations of about 15 to 40% by weight, 35% slurries being those most readily available on the market. In such slurries, the water soluble salts usually present as a result of the method manufacturing the acylated taurine may be present in proportions as high as 30 to 35% of the weight of the acylated taurine, 20 to 25% being common. It will of course be understood that the present process is also operative for removing smaller proportions of salt, e.g. as little as 5% or less or higher proportions, e.g. up to 50% or more, of the weight of the acylated taurine. The salt most commonly present in such slurries is sodium chloride, usually accompanied by smaller proportions of sodium sulfate. However, potassium chloride and potassium sulfate may also be present for other reasons or because potash was employed in the reaction for producing the acylated taurine. The acylated taurine slurries commonly available normally have a pH of about 7 to 8, but the process of this invention is operative not only on these slurries but on those of a much higher acidity or alkalinity.

As stated above, the process of this invention requires the addition to an aqueous slurry as above described of 4 a water insoluble compound (component C) selected from the group consisting of aliphatic and alicyclic monocarboxylic acids of 8 to 24 carbon atoms and their esters in an amount sufficient to form a compatible solvent system with the acylated taurine (component A).

The preferred component C for use in the present process is a free higher fatty acid of 12 to 18 carbon atoms which may be saturated or unsaturated, branched but preferably straight. Other aliphatic and alicyclic monocarboxylic acids which may be employed as component C in the present process include those disclosed above as operative acylating agents (R'COOH) with the exception of the alkyl benzoic and alkyl naphthoic acids since component C and component A (acylated taurine) must be mutually soluble to form a compatible solvent system melting belowthe boiling point of water and boiling above the boiling point of water under the conditions of the distillation required in the present process. The methyl, ethyl, propyl or glyceryl esters of such acids may also be employed. It will be generally found that the amount of component C necessary to form a compatible solvent system with component A at the temperature of separation of the crystallized salt from the mixture above the solidification point of such system will be at least twice theweight of said component A (acylated taurine), and will in general range from about 2 to 6 parts per part by weight of component A. Higher porportions may be employed but are uneconomical except where a larger proportion of soap is desired in the final product as obtained by saponification of component C in situ following removal of the water and salt in accordance with the present process.

After addition of the required amount of component C to the aqueous slurry containing the acylated taurine and water soluble salt, the slurry is heated to the boiling point to distill off the water. The distillation maybe carried out at super or sub-atmospheric pressure but it is preferred, in the interests of simplicity and economy to operate at atmospheric pressure. Surprisingly, the boiling proceeds without the anticipated foaming. At normal atmospheric pressures, temperatures of about to C. are preferred for optimum simplicity, economy and rate of dehydration. A small flow of air or inert gas over the surface of the boiling slurry is desirable but not essential to aid in removal of water vapor. An inert gas such as nitrogen or carbon dioxide is in such case preferred to prevent possible discoloration of the acylated taurine. Lower temperatures of boiling may be em ployed at sub-atmospheric pressures.

The distillation is continued until substantially no more water is removed, as indicated by substantial cessation of loss of weight of the distillation vessel. The duration of the distillation process will of course in any particular instance depend upon the amount of slurry being treated, the temperatures and pressures employed, and the like. Under usual conditions and batch sizes, a duration of about 1 to 3 hours is sufficient. At the completion of this distillation step, substantially all of the salt has been precipitated in the distillation vessel which may still contain a small amount of occluded water.

During the boiling operation and as the water is removed from the aqueous slurry, the water soluble salts crystallize out and may, after completion of the distillation step, be readily separated from the remaining mixture at a temperature above the solidification point of the compatible solvent system of components A and C contained in the mixture. system is maintained in liquid form to permit removal of the crystallized water soluble salt originally dissolved in the aqueous slurry. The separation of the salt may be carried out in any desired manner as by filtration, centrifugation, decantation, or the like. In practice, it would be desirable to filter or centrifuge the mixture immediately after all the water has been removed and while it is still hot and in liquid condition. Generally, the separa- Stated otherwise, such solvent.

abraded.

tio nfwould be carried out; at about-130 '6. although any temperature would *be suitable provided it is above the solidification point of the system throughout the separating operation.

By the present process, there is thusobtained :from the original .aqueous :slurry asusbtantially homogeneous mixture or solution of component Aand component .C. This Product is advantageouslysubjected to saponification with caustic soda or potash to produce the soap of component C insitu together-with the acylated'taurine. However, if desired, component C may beseparated from the acylated taurine bydistillation or the like.

The following examples, in which parts are byweight, unless otherwise indicated, are only illustrative of the instant invention and are not to .be regarded as limitative. In these examples, all parts and proportions of fatty acid amides are determined by the methylene blue analytical method described in Nature, 160, '759 (1947) and Trans. Faraday Soc. 44, 226- 23911948). The tallow fatty acid contains, by weight, approximately myristic, 43% 'palmitic, 9% stearic, 30% oleic, and 8% linoleic acids, and the coconut fatty acid contains, approximately, 8% caprylic, 7% capric, 49% lauric, 17% myristic, 9% palmitic, 2% stearic, 6% oleic, and 2% linoleic acids.

Example 1 Twelve hundred grams of an aqueous commercial slurry containing 300 g. of sodium N-methyl-N-coconut fatty acid taurate and 69 g. sodium chloride is admixed with 900 g. commercial coconut fatty acid and gradually heated to 130 C. with agitation in an open vessel with a loss of 685 g. water, after which crystallized salts are immediately removed by filtration. The filtrate contains by analysis 300 g. of said taurate, 0.63 g. sodium chloride, and 17.3 g. water, in addition to the fatty acid.

Upon saponifying the fatty acid with caustic to convert same to the sodium soap in situ, the resultant detergent-soap mixture can be converted to bars with excellent detergent properties.

Example 2 One hundred fifty grams of an aqueous commercial slurry containing 52.5 g. sodium N-methyl-N-oleoyl taurate and 10.2 g. sodium chloride is admixed with 100 g. coconut fatty acid and heated to 135 C. to remove 71 g. water by atmospheric distillation, after which the inorganic suspension is immediately removed by filtration, and the filtrate analyzed as containing 52.0 g. of said taurate, 0.1 g. sodium chloride, and 3.0 g. water in addition to the fatty acid.

Example 3 One hundred fifty grams of an aqueous commercial slurry containing 52.5 g. of sodium-N-methyl-N-oleoyl taurate and 10.2 g. sodium chloride is admixed with 100 g. coconut fatty acid and dehydrated at 55 C. by heating under reduced pressure of about 150 mm. of Hg until no more water distills over. The crystallized salts are then immediately removed by centrifuging, and the clear oil effluent found by analysis to contain in addition to said fatty acid 52.5 g. of said taurate, and substantially no sodium chloride or water.

Example 4 Two hundred forty grams of an aqueous commercial slurry containing 24.6% by weight sodium-N-methyl-N- coconut fatty acid taurate and 5.75% by weight sodium chloride is added to 160 g. tallow fatty acid and the mixture dehydrated by heating to 140 C. under a stream of nitrogen until substantially no more water distills over The inorganic suspension is then immediately removed by filtration, and the product, 235 g. analyzed as containing, in addition to the tallow fatty acid and some water, 25.1% by weight of said taurate and 0.291% by weight sodium chloride.

g I Example 5 p Four'hundred parts by weight of an aqueous commas cial ,slurry containing 25% by weight of ,sodiumeN- methyl-N-ftallow fatty acid. taurate and 6.82% by weight sodium chloride are admixed at 60 C. with 200 parts by weight of commercial tallow fatty acid. The resultant slurryis fed into a continuous evaporator .opcratingat 1:25 to 135 .,C., at a rate allowing substantially complete dehydration and .the essentially anhydrous fluid effluent immediately freed ofsuspended inorganic salts 'by continuousfiltration:toyield a product containing parts .by weight of said taurate, 1 part by weight of sodium chloride and 19 parts by weight of water, in ad. dition :to ,the vtallow fatty :acid.

V Example -6 The process of Example 2 is repeated, except that the initial slurry contains the corresponding potassium taurate salt and potassium chloride. Similar results are obtained.

Example 8 Six hundred parts by weight of an aqueous commercial slurry containing by weight 25% of sodium-N-methyl-N- coconut fatty acid taurate and 5.75 by weight of sodium chloride is admixed with 450 parts by weight of coconut fatty acid and heated to C. to distill out sub stantially all the water originally contained in the slurry, after which the precipitated salts are immediately removed by filtration, and the coconut fatty acid is removed from the filtrate by distillation in vacuo to leave a residue analyzing parts by weight of said taurate and 0.3 parts by weight of sodium chloride. V

Example 9 The process of Example 6 is repeated except that the taurate in the initial slurry is sodium-N-butyl-N-palmitoyl taurate. Similar results are obtained.

This invention has been disclosed with respect to certain preferred embodiments, and various modifications and variations thereof will become obvious to the person skilled in the art. It is to be understood that such modifications and variations are to be included within the spirit and purview of this application and the scope of the appended claims.

I claim:

1. A process comprising adding to an aqueous slurry containing (A) an N-higher acyl taurine of the formula of the alkali metal chlorides and sulfates, a water insoluble compound C selected from the group consisting of aliphatic and alicyclic monocarboxylic acids of 8 to 24 carbon atoms and their esters in an amount sufficient to form a compatible solvent system with said taurine A, heating the resulting mixture to distill off the water, and

then separating the crystallized-salt B from the mixture at a temperature above the solidification point of the A and C solvent system.

' 2. A process as defined in claim 1 wherein component A is sodium-N-methyl-N-coconut fatty acid taurate.

3. A process as defined in claim 1 wherein component A is sodium-N-methyl-N-tallow fatty acid taurate.

4. A process as defined in claim 1 wherein component A is sodium-N-oleoyl taurate.

5. A process as defined in claim 1 wherein compm nent A is sodium-N-cyclohexyl-N-palmitoyl taurate.

6. A process as defined in claim 1 wherein component C is a free fatty acid of 12 to 18 carbon atoms.

7. A process as defined in claim 1 wherein said component C is added to said slurry in an amount at least twice the weight of said component A.

8. A process comprising adding to an aqueous slurry containing an N-higher fatty acid taurine compound and an alkali metal chloride, an amount of higher fatty acid of 12 to 18 carbon atoms sufiicient to form a compatible solvent system with the said taurine compound, heating the resulting mixture to distill off the water, and then separating the crystallized alkali metal chloride from the mixture at a temperature above the solidification point of the solvent system containing the said taurine compound and the higher fatty acid.

9. A process as defined in claim 8 wherein said higher fatty acid is coconut fatty acid.

- 10. A process as defined in claim 8 wherein said higher fatty acid is tallow fatty acid.

11. A process as defined in claim 8 wherein said higher fatty acid is palmitic acid.

12. A process as defined in claim 8 wherein said higher fatty acid is added to said slurry in an amount ranging from about 2 to 6 parts by weight per part of the said taurine compound in the slurry.

No references cited.

Claims (1)

1. A PROCESS COMPRISING ADDING TO AN AQUEOUS SLURRY CONTAINING (A) AN N-HIGHER ACYL TAURINE OF THE FORMULA