US2529537A - Sulfonation of allyl esters - Google Patents

Description

Nov. 14, 1950 BROD 2,529,537

SULFONATION or-' ALLYL ESTERS Filed July is, 1948 am E L? z afizm 4; 6 w I mm 2 LL.

2 3 Mn 5 O 2 iii % Free 50 in Oleum IN V EN TOR.

JOHN S. B4 oa ATTORNEYS.

Patented Nov. 14, 1950 S'ULFONATION F ALLYL ESTERS John S. Brod, Wyoming, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio,

a corporation of Ohio Application July 13, 1948, Serial No. 38,405

This invention relates to a process of sulfonating allyl esters of soap-forming acids in the production of monoglyceride sulfonates and detergents containing monoglyceride sulfonates.

Sulfonated monoglycerides are known to possess wetting, sudsing and washing power and to have advantages over soap in their resistance to the soap-precipitating action of calcium and magnesium compounds present in hard water and in their non-alkaline reaction, but heretofore no suiliciently economical or commercially practicable method of preparing sulfonated monoglycerides has been known, and hence their commercial exploitation has not been feasible. It is true that methods of preparation have been described, as for example in U. S. Letters Patent 2,006,309 and 2,289,391. Thus an alkali metal soap may be heated with a soluble salt of 1- halogen-2-hydroxy-propane-3-sulfonic acid, or free fatty acid may be heated with a soluble salt, of 1,2-dihydroxy-propane-3-sulfonic acid, or a fatty acid chloride may be reacted with such a salt. But in addition to the high cost of some of these reactants (especially the halogen derivatives), these processes are slow and require high temperatures, and none of them gives entirely satisfactory yields of the desired product. Purification of the products is therefore commonly required both in order to improve color and to separate the active mo'noglyceride sulfonate from unreacted constituents or undesired by-products. Improved yields are obtained if the 1halogen-2- hydroxy-propane-3-sulfonate is heated with soap in the presence of certain amides which act as a solvent medium, but both the halogen hydroxy propane sulfonate and the amide are expensive, and the subsequent removal and recovery of the amide involve a costly manufacturing step which has discouraged the industrial application of this rocess.

Another way of producing the desired monoglyceride sulfonate is to react fatty acids with allyl alcohol and to sulfonate the resulting allyl esters. Although this procedure has been proposed in the past, it too has not hitherto been commercially practicable because of the difficulties encountered in the sulfonation reaction Thus if the allyl esters are treated with sulfuric acid or with oleum which is low in its content of free $03, sulfuric esters rather than the less readily hydrolyzable sulfonic acids are obtained, while oleum high in free S0: has commonly caused discoloration and objectionable side reactions. The use of sulfuric acid in the presence of acetic anhydride has been suggested for reactions of a 13 Claims. (Cl. 260-400) similar nature (for example, in U. S. Letters Patent 2,341,060) but it is my experience that in the case of allyl esters this process, even when carried out in the presence of an inert solvent such as ethylene dichloride, does not give good yields of sulfonated monoglyceride and that the reaction product must be free fromimpurities in order to be comparable inefliciency with other synthetic detergents, and furthermore, the removal of sodium acetate from the reaction product is especially difi'icult and the cost of acetic anhydride is so high as to make this process industrially uneconomical and impracticable.

Chlorsulfonic acid can be used as a sulfonat- 4 ins agent for the allyl esters, but in factory scale operation the removal of the hydrochloric acid produced by the reaction is troublesome, requiring special equipment fabricated of acid-resistant material, and furthermore, the degree of sulfonation obtainable with chlorsulfonic acid is notably less than is obtainable by the process of my invention. Thus it is my experience that unless a lar e excess of chlorsulfonic acid is used (in which case color is harmed and costs rise), a

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maximum of only about per cent of the allyl ester can be sulfonated thereby, whereas by my process to be described hereinafter, this figure rises to about per cent or more.

It will be seen from the above discussion that, so far as I am aware, there has not existed in the past any truly satisfactory or commercially attractive method of producing monoglyceride sulfonate detergents, despite their known value as wetting, sudsing and washing agents in hard wa- It is an object of the present invention to provide such a process, and-more particularly to provide'a process whereby high molecular carboxylic acid esters of allyl alcohol may be sulfonated at low cost to yield products of high sudsing, wetting and washing efliciency, which products are suitable for use without further purification.

Further objects will become apparent in the description which follows.

I have found that, in sulfonating high molecular allyl esters, oleum is outstandingly satisfactory as a sulfonating agent, provided both the strength and the amount of oleum are controlled as herein described, since both strength and amount are critical with respect to the yield, emciency and color of the fesulting product. More particularly, I have found that under certain conditions to be set forth hereinafter, sulfonation products which are suitable asv wetting, sudsinl and washing agents without prior purification may be obtained, provided the oleum contains at least 30 per cent but not substantially more than 60 per cent free sulfur trioxide. Allyl esters, so treated and subsequently neutralized, are converted chiefly into hydroxy sulfonates, or monoglyceride sulfonates, such as:

or mixtures of this with smaller proportions of sulfated sulfonate:

RCOOCHz CHOSOJNB. CI-IzSOzNa Small amounts of other sulfonates and sulfuric esters are also probable, but analytical methods for isolating, identifying and quantitatively estimating their amounts are not entirely satisfactory.

Oleum containing less than about 30 per cent free sulfur trioxide is not satisfactory for this reaction since it gives low yields of sulfonated product, and even the character of the product is different. Thus with oleum of per cent or per cent free sulfur trioxide content, marked splitting of the carboxylic linkage of the allyl ester is evident, the monoglyceride sulfonate content of the product is lower, and sulfated products appear in larger amount. With still weaker oleum, these trends become more marked, until with no free sulfur trioxide (i. e. with 100% sulfuric acid), splitting of the ester is extensive and the remaining allyl ester is converted chiefly into RCOOCHz-CHz-CHzOSOsN and/ or RCOOCHz CHOSOaNfl'CH:

which products are less stable than the true sulfonates with respect to hydrolysis caused by heat and acid.

Increasing the strength of the oleum from about 30 per cent to about 60 per cent free $03 increases somewhat (i. e. from about 85 per cent to about 90 per cent) the extent of sulfonation of the allyl esters without essential change in the character of the products formed. Whereas great discoloration commonly results from using such oleum in sulfonatlng other materials such as high molecular alcohols or olefines, discoloration is to a large extent absent in the case of allyl esters, provided highly efllcient mixing is employed and provided overheating and more especially localized overheating and localized excesses of acid are avoided. When, however, the strength of the oleum much exceeds 60 per cent free S03, even these precautions do not prevent excessive discoloration, oxidation, evolution of sulfur dioxide and other evidences of side reactions, and oleum containing more than 65 per cent free S0: is impractical on this account.

While products of good color and of good wetting, sudsing and washing power have been obtained from allyl esters using oleum of 30 per cent strength, yet I prefer to use oleum containing from about 55 per cent to 60 per cent free sulfur trioxide, since such strengths give the highest degree of sulfonation consistent with reasonably good color and practical absence of undesirable side reactions.

It is important to control the amount as well as the strength of the oleum. The sulfonation procedure should conform with the general principles that reaction may be initiated by a small proportion of acid; that a large excess of acid over ester is to be avoided, especially in the early stages of the reaction; and that some excess acid must finally be present in order to bring the reaction to a high degree of completion. However, if the proportion of acid exceeds certain critical limits, extensive splitting of the allyl ester at the ester linkage occurs and the completeness of sulfonation decreases markedly. The critical relationships which I have found between the strength of the oleum and the total amount of oleum that should be used for the sulfonation are shown in tabular form below:

Strength oi Oleum 0 timum Proportion of leum (Molar ratio of ggggg; free so;: Ally] Ester) 30 From 1.321 to 1.721 60 From 1.7:1 to 2.3:1

In batchwise operation, adding the ester to the oleum is to be avoided, lest an initial large excess of acid be present. Instead, oleum may be added slowly to the ester, or the two reactants may be mixed with each other in the desired proportions, or the ester may be added to a batch of pro-formed acid reaction mixture into which the required amount of additional oleum may then be slowl introduced. Prompt as well as thorough mixing is necessary to prevent l0cal excess of acid, local overheating and consequent discoloration and side reactions. Alternatively, a continuous system may be employed, concurrently flowing streams of ester and of oleum in the desired proportions being mixed with one another. If desired, additional amounts of ester and oleum may then be added to this acid reaction mixture, before neutralization thereof. Thus the concurrently flowing streams of ester and oleum may be so proportioned that less than the desired amount of oleum is mixed with the fresh stream of ester, and one or more supplementary streams of oleum may then be introduced after the initial reaction has taken place, thereby increasing the total added oleum to the desired proportion. Other modifications of procedure are permissible provided they conform with the hereinbefore enunciated principles as to amounts and ratios of ester and oleum, namely:

Oleum should be added to the ester in such manner and amount that (a) in the case of oleum containing about 30% free S03, the molar ratio of free S03 addedrallyl ester should be at least 1.3:1 when all of the oleum has been added, although during the course of the addition this ratio may vary from 0: 1 to not substantially more than 1.7:1, and (b) in the case of oleum containing about 60% free S03, this ratio should be at least 1.7:1 when all of the oleum has been added, although during the course of the addition it may vary from 0:1 to not substantially more than 2.3 1. With oleums of intermediate strengths, the

allowable ratios will vary correspondingly.

These facts are graphically shown in Fig. 1, wherein the molar ratio of free S03 addedzallyl ester is plotted on the ordinate scale, and the strength of the oleum, expressed as the per cent free $03 therein, is plotted on the abscissa scale. The oleum should be added to the ester in such manner and amount that this molar ratio shall be between lines A and B when all of the oleum has been added, although during the course of the addition it is required only that this rati hall not be above line A.

Using oleum of the concentrations and in the amounts hereinbefore described, temperature should be maintained within certain limits in order to obtain good results. If the temperature substantially exceeds 60 C. during sullfonation,

discoloration, charring, oxidation and excessiveside-reactions commonly occur, while at temperatures below about C. viscosity becomes great,

-eflicient stirring is difficult, and localized overv the reactants may be added slowly in order to facilitate dissipation of the heat of reaction.

Under these conditions sulfonation proceeds rapidly. Usually only a few minutes, rarely exceeding 10 or 15, are allowed after mixing the reagents before the reaction is completed. Thereafter the acid sulfonation mixture may be used for some purposes without neutralization, or if desired the excess free $03 and H2804 may be eliminated and the free sulfonic acid which has been formed may be neutralized. This may be done in several ways, the simplest of which is direct neutralization of the acid mixture with an alkali. Neutralization may be with alkali hydroxides, alkaline salts, oxides or hydroxides of alkaline earths or of heavy metals, ammonia or organic bases. For most purposes, the neutralizing agent should be such as to form a watersoluble monoglyceride sulfonate, and sodium hydroxide or its alkaline salts are commonly used for this purpose. Since high temperature and an alkaline reaction favor splitting of the ester or .its sulfonated product at the carboxylic linkage, it is advisable to keep the neutralization batch at a temperature not substantially above 50C., and preferably below C., and to add the alkali to the acid mixture with eflicient mixing so that at no time during neutralization is the mixture substantially alkaline. Temperature control may be effected in various ways, such for example as by external or artificial cooling. or by neutralizing in the presence of a large proportion of previously neutralized material, or by coupling such procedure with artificial cooling. The pH of the neutralized product should not substantially exceed 7.0. Satisfactory stability of the product has been obtained within a preferred pH range from about 4.5 to about 6.5.

The following examples illustrate in greater detail ways in which I practice my invention, but it will be understood that these examples are illustrative only and that the invention is not limited to the details thereof except as indicated in the appended claims. In the examples, all parts are by weight, and all materials were initially at room temperature.

Example 1.The allyl ester of mixed fatty acids from coconut oil was sulfonated in a vessel which was externally cooled with ice water and which was equipped with an efllcient stirrer having blades which scraped the sides of the vessel. One hundred parts of the ester and 160 parts of oleum were added to this vessel simultaneously, with continuous stirring, at such rates that the weight ratio of oleumzester was not substantially more than 1602100 at any time, and that the temperature of the acid mixture was between and C. throughout the major portion of the reaction. The molar ratio of free SOa:ester was 1.5:1. Within a few minutes after all of the reactants were added, neutralization was commenced by adding a portion of the acid reaction mixture to 8 times its own weight of-ice water and then neutralizing with 28% caustic soda solution until alkaline to methyl orange, whereupon further increments of acid mixture were added to the neutralized portion and neutralized in like manner, until all of the acid mixture was neutralized. The temperature during neutralization was kept below 10 C. Analysis of the resulting tan-colored paste showed that 77.8% of the allyl ester had been converted to sulfonated ester. On drying, a cream-colored powder was obtained The product possessed high wetting, sudsing and washing power.

Example 2.One hundred parts of allyl laurate were sulfonated in equipment similar to that of Example 1 by adding 122.5 parts of 60% oleum thereto over a 15 minute period, with constant stirring, the weight ratio of oieum:ester being not substantially more than 122.5: 100 at any time and the temperature during this addition being held between 30. and 40 C. The molar ratio of free SOazallyl ester was 2.221. The mixture was then neutralized until alkaline to methyl orange by adding ice and caustic soda solution thereto. Analysis showed that of the ester was converted into sulfonated ester. The product possessed high sudsing, washing, wetting an emulsifying power.

added to the sulfonation mixture in order to make the reaction less drastic, reduce viscosity, facilitate mixing, and improve color. The thinn agent should be substantially inert to oleum, and should preferably be readily volatile, with a boiling point below that of water, in order to facilitate subsequent removal. Saturated aliphatic ethers, hydrocarbons and chlorinated hydrocarbons, such for example as di-isopropyl ether, hexane, carbon tetrachloride, chloroform, perchorethylene, tetrachlorethane and the like are serviceable. In general, I find ethylene dichloride to be the most effective thinning agent. It may be used as a medium to which oleum and allyl ester are added, or allyl ester may first be dissolved in ethylene dichloride before oleum is added, or a portion of the ethylene dichloride may be introduced into the vessel in which the reaction is to take place (thereby insuring effective stirring at the beginning of th reaction) and the oleum and a solution of the allyl ester in the remainder of the ethylene dichloride may then be added. In order to reduce viscosity effectively and make the reaction less drastic, the amount of ethylene dichloride should as a rule be at least one-third by weight of the amount of allyl ester. The following example illustrates how I practice this modification of the invention.

Example 3.One hundred 'parts of the allyl ester of mixed fatty acids from coconut oil were dissolved in 51 parts of ethylene dichloride and the mixture was sulfonated and neutralized as in Example 1, using 93 parts of 58% oleum and maintaining at all times a weight ratio of oleumzallyi ester solution of not substantially more than 93:151. The maximum temperature during the suifonation was about 40 C. The molar ratio of free SOuester was about 1.7:1.

The resulting product was light in color and posgroup is that of soap-forming monocarboxylic acids having from about 8 to about 22 carbon atoms, and particularly the fatty acids derived from natural fatty esters or from their wholly or partially hydrogenated derivatives. Either individual soap-formin fatty acids such as eaprylic, capric, lauric, myristic, palmitic, stearic, arachidic and behenic acids, or mixtures of fatty acids such as occur in natural oils, fats and waxes may be used. The mixed fatty acids from tallow, lard, marine oils, palm oil, or various vegetable seed oils may be used, but I find the acids of oils of the coconut oil group to be especiallysuitable, this being a group of tropical nut oils, such as coconut, babassu and palm kernel oils, characterized by their high lauric and myristic acid content, and described by Lewkowitsch in "Chemical Technology and Analysis of Oils, Fats and Waxes," sixth edition, volum 2, pages 500 and 617. Other acids of from about 8 to about 22 carbon atoms may be used, such as the acids of rosin and of tall oil, naphthenic acids and the soap-forming acids prepared by oxidation of petroleum or paraflin hydrocarbons or by hydrogenating carbon monoxide (sometimes called the Flscher-Tropsch process) or by oxidizing the saturated or unsaturated hydrocarbons resulting from this process.

Oxidation and discoloration frequently occur when esters of highly unsaturated acids are used, hence substantially saturated acids are preferred. Hydrogenation of highly unsaturated acids, oils, fats or waxes is advised before making the allyl esters therefrom. Good results have in general been obtained when the iodine value of the fatty 1 acid is less than 25.

Following neutralization, the sulfonated products may be treated in conventional manner to remove unsulfonated organic matter, inorganic salts, water, etc., or they may if desired be used without drying or further purification.

Conventional modifications in procedure to make the sulfonation and neutralization processes continuous lie of course within the scope of my invention.

Products of high wetting, sudsing and washing power are also produced when the process of my invention is applied to fatty acid amides of unsaturated amines, such as the lauric acid amide of allyl amine. I am uncertain as to the exact constitution of the final products, which appear in most cases to be mixtures of sulfated and sulfonated fatty acid amides, or to have both sulfate and sulfonate groups introduced into the same molecule.

Having thus described'my invention, what I claim and desire to secure by Letters Patent is:

l. The process of preparing substantially neutral wetting, sudsing and washing agents which comprises admixing an allyl ester of soap-forming monocarboxylic acids containing about 8 to about 22 carbon atoms with oleum containing 30 per cent to 60 per cent by weight of free sulfur trioxide to effect reaction between allyl ester and oleum thereby forming a sulfonic acid, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide addedzallyl ester lies above line B of Figure 1 when all of the oleum has been added but at no time during the addition lies substantially above line A, maintaining the temperature between 10 C. and 60 C. while the reaction takes place, and thereafter eliminating excess free $03 andsulfurlc acid and neutralizing the sulfonic acid at a temperature not substantially above 50 C. to a pH above 4.5 to form a water-soluble salt and in such a manner that the mixture is at no time substantially alkaline.

2. The process of preparing wetting, sudsing and washing agents which comprises admixing a high molecular fatty acid ester of allyl alcohol with oleum containing about 60 per cent by weight of free sulfur trioxide to effect reaction between allyl ester and oleum thereby forming a sulfonic acid, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide addedmllyl ester is at least 1.7:1 when all of the oleum has been added but at no time during the addition substantially exceeds 2.3:1, and maintaining the temperature between 30 C. and 50 C. while the reaction takes place.

3. The process of preparing substantially neutral wetting, sudsing and washing agents which comprises admixing an allyl ester of soap-forming monocarboxylic acids containing about 8 to about 22 carbon atoms with oleum containing 30 per cent to 60 per cent by weight of free sulfur trioxide to effect reaction between allyl ester and oleum, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide addedzallyl ester lies above line B of Figure 1 when all of the oleum has been added but at no time during the addition lies substantially above line A, maintaining the temperature between 10 C. and 60 C. while the reaction takes place, and neutralizing the acid reaction mixture at a temperature not substantially above C. to a final pH between 4.5 and 'l to form a water-soluble salt and in such a manner that the mixture is at no time substantially alkaline.

4. The process of claim 12 in which the ester is an ester of allyl alcohol with fatty acids of natural fatty esters.

5. The process of claim 12 in which the ester is an ester of allyl alcohol with high molecular fatty acids of iodine value less than 25.

6. The process of claim 12 in which the ester is an ester of allyl alcohol with substantially saturated soap-forming acids.

7. The process of claim 12 in which the ester is an ester of allyl alcohol with the fatty acids of an oil of the coconut oil group.

8. The process of claim 12 in which the esteris essentially the lauric acid ester 'of allyl alcohol.

9. The process of preparing substantially neutral monoglyceride sulfonate detergents which comprises admixing a high molecular ester of allyl alcohol, in the presence of a thinning agent selected from the group consisting of saturated aliphatic ethers, saturated aliphatichy'dro'carbons and saturated chlorinated aliphatic hydrocarbons, with oleum containing about, per cent free sulfur trioxide by weight, thereby to effect reaction between the allyl ester and oleum, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide addedzallyl ester is at least 1.7:1 when all of the oleum has been added but at no time during the addition substantially exceeds 2.3:1, restraining the temperature from rising substantially above 60 C. while the reaction takes place, and neutralizing the acid reaction mixture at a temperature not substantially above 50 C. to a pH above 4.5 to form a watersoluble salt and in such a manner that the mixture is at no time substantially alkaline.

10. The process of claim 9 in which the thinning agent is ethylene dichloride.

11. The process of claim 9 in which the thinning agent is ethylene dichloride, the weight thereof being at least one third the weight of the allyl ester.

12. The process of preparing wetting, sudsing and washing agents which comprises admixing an allyl. ester of soap-forming monocarboxylic acids containing about 8 to about 22 carbon atoms with oleum containing 30 per cent to 60 per cent by weight of free sulfur trioxide to effect reaction between allyl ester and oleum thereby forming a sulfonic acid, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide added:al1yl ester lies above line B of Figure 1 when all of the oleum has been added but at no time during the addition lies substantially above line A, and maintaining the temperature between 10 C. and 60 C. while the reaction takes place.

13. The process of preparing monoglyceride sulfonate detergents which comprises admixing a high molecular ester of allyl alcohol, in the presence of a thinning agent selected from the group consisting of saturated aliphatic ethers, saturated aliphatic hydrocarbons and saturated chlorinated aliphatic hydrocarbons, with oleum containing about 60 per cent free sulfur trioxide by weight, thereby to effect reaction between the allyl ester and oleum, the oleum being added to the allyl ester in such manner and amount that the molar ratio of free sulfur trioxide added: allyl ester is at least 1.7:1 when all of the oleum has been added but at no time during the addition substantially exceeds 2.3 :1, and restraining the temperature from rising substantially above 60 C. while the reaction takes place.

JOHN S. BROD.

REFERENCES CITED FOREIGN PATENTS Country Date Great Britain Sept. 26, 1929 Number

Claims (1)

1. THE PROCESS OF PREPARING SUBSTANTIALLY NEUTRAL WETTING, SUDSING AND WASHING AGENTS WHICH COMPRISES ADMIXING AN ALLYL ESTER OF SOAP-FORMING MONOCARBOXYLIC ACIDS CONTAINING ABOUT 8 TO ABOUT 22 CARBON ATOMS WITH OLEUM CONTAINING 30 PER CENT TO 60 PERCENT BY WEIGHT OF FREE SULFUR TRIOXIDE TO EFFECT REACTION BETWEEN ALLYL ESTER AND OLEUM THEREBY FORMING A SULFONIC ACID, THE OLEUM BEING ADDED TO THE ALLYL ESTER IN SUCH MANNER AND AMOUNT THAT THE MOLAR RATIO OF FREE SULFUR TRIOXIDE ADDED:ALLYL ESTER LIES ABOUT LINE

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