US3397227A - Ester production - Google Patents

Description

United States Patent 3,397,227 ESTER PRODUCTION Igor Sobolev, Grinda, Calif., assignor to Shell Oil Cornpany, New York, N.Y., a corporation of Deiaware No Drawing. Continuation-impart of application Ser. No. 405,858, Oct. 22, 1964. This application Nov. 9, 1967, Ser.'N0. 681,932

11 Claims. (Cl. 250-486) ABSTRACT OF THE DISCLOSURE Reaction of acyclic hydrocarbon monoalkene monocarboxylic acid, epihalohydrin and a reaction-limiting amount of trialkylamine produces 2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide, useful in the production of polymeric wet end additives.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continua-tiondn-part of applicants copending application Ser. No. 405,858, filed Oct. 22, 1964, now abandoned.

BACKGROUND OF THE INVENTION Compounds incorporating quaternary nitrogen atoms and ester linkages within the molecule are known in the art, being produced, for example, by acylation of ethanolamine derivatives. Such materials have established utility as surface active agents and the like, particularly when the acid moiety of the cationic acid is derived from a long-chain alkanoic acid. In part because of the method of production, it is difficult to prepare esters of this type with additional reactive functional groups, and in general, the cationic esters of the art contain only the ester linkage and the quaternary ammonium moiety as active reaction sites. In the U.S. Patent 3,329,706, issued July 4, 1967, to Sobolev, there is described a process for the production of cationic esters containing a free hydroxyl group and also ethylenic unsaturation. Such esters are characterized as 2-hydroxy-3-alkenoyloxy-propyltrialkylammonium halides and are prepared from reaction of the free acid and a glycidyltrialkylammonium halide. Although this process offers a method for the production of such cationic esters in high yield and purity, it does require the pre-formation of the glycidyltrialkylammonium halide. It would be of advantage to provide a'method for the production of these cationic esters from simpler and more readily available starting materials.

SUMMARY OF THE INVENTION It has now been found that an improved process of producing 2-hydroxy-3-alkenoyloxypropyl-trialkylammonium halides comprises the process of directly reacting an alkenoic acid, an epoxyhaloalkane and a tertiary amine in an inert polar solvent. In contrast with somewhat related processes of the prior art, the success of the present process is determined by the use of selected reactant ratios, without the use-of which little production, or at least a substantially lessened production, of the desired cationic ester is observed.

DESCRIPTION OF PREFERRED EMBODIMENTS The alkenoic acid employed in the process of the invention is a hydrocarbon carboxylic acid possessing at least one canboxy group and at least one e-thylenic link- 3,397,227 Patented Aug. 13, 1968 age, i.e., non-aromatic carbon-carbon double bond, which ethylenic linkage(s) constitutes the only carbon-carbon unsazturation present within the molecule. Preferred acids are acyclic lower monoalkene monocarboxylic acids con,- taining from 3 to- 8 canbon atoms, especially those acids wherein the ethylenic linkage is conjugated with the carboxy group. Thus, lower monoalkene monocarboxylic acids such as cr-otonic acid, 3-b-uten0ic acid, S-hexenoic acid, 5-methyl-6-heptenoic acid and the like are operable in the process of the invention. Best results areobtained, however, when the ethylenic linkage, in addition to being conjugated with the carboxy group, is also terminal. One class of acids of this type is represented by the formula CH2=CCO2H wherein a is a whole number from O to 5 inclusive. These a-(nonto monoalkyl)acrylic acids are illustrated by acrylic acid, methacrylic acid, ethacrylic acid and a-amylacrylic acid. A particularly preferred class of lower monoalkene monocarboxylic acids, principally because of the desirable properties of the products produced therefrom, comprises acrylic acid and methacrylic acid, generically designated (meth)acrylic acid.

The tertiary amine reactant comprises a trivalent nitrogen atom, each valence of which is satisfied with an alkyl substituent of from 1 to 20 carbon atoms. Such amines are represented by the formula NR wherein each R group independently is alkyl of from 1 to 20 carbon atoms. Preferred tertiary amines have at least two, and more preferably three, lower alkyl substituents, that is, alkyl of from 1 to 4 carbon atoms, and best results are obtained When the nitrogen atom of the tertiary amine possesses at least two methyl SllllJStltLlCl'liS. Suitable amine reactants include trimethylarnine, triethylamine, tributylamine, dimethyloctylarnine, diethyldecylamine, dimethyllaurylamine, dimethylstearylamine, dibutyltridecylamine, methylamyldecylam-ine, trilaurylamine and the like.

The epoxyhaloalkane is an m,n-epoxy-o-haloalkane wherein m, n and 0 represent adjacent atoms in a continuous carbon chain. Although epoxyhaloalkanes of greater chain length are operable, the preferred epoxyhaloalkanes comprise the epihalohydrins, that is, the 2,3-epoxy-1-halopropanes. The halogen moiety of the epihalohydrin reactant is suitably fluorine, chlorine, bromine or iodine, although the preferred epihalohydrins are those wherein the atomic number of the halogen is from 17 to 35, Le, the middle halogens chlorine and bromine, and particularly preferred as the epoxyhaloalkane reactant is epichlorohydrin.

It has been found that the ratio of reactants present in the reaction mixture exerts a substantial influence upon the conversion of reactants and the yield of the desired 2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide. The stoichiometry of the reaction process would predict the desirability of employing equimolar amounts of each of the three reactants. However, when equimolar amounts of reactants are employed, reduced yields of the desired cationic ester product are obtained. The relative molar amounts of alkenoic acid and epoxyhaloalkane does not appear to be critical, and molarratios of alkenoic acid to epoxyhaloalkane from about 3:1 to about 1:3 are satisfactorily utilized. Generally, no great excess of either the alkenoic acid .or the epoxyhaloalkane is required and no substantial advantage is gained by the use thereof. Molar ratios of alkenoic acid to epoxyhaloalkane that are substantially stoichiometric, that is, ratios from about 1.521 to about 1:15 are preferred. It is highly desirable, however, to employ a reaction-limiting amount, i.e., an amount less than the stoichiometric amount, of the trialkylamine reactant in order to obtain the optimum yield of the desired cationic ester product, and the number of moles of trialkylamine per mole of limiting other reactant, that is, mole of alkenoic acid or mole of epoxyhaloalkane, whichever is smaller, should desirably not exceed about 0.95. The use of less than stoichiometric amounts of the amine reactant results, of course, in incomplete conversion of the alkenoic acid and epoxyhaloalkane, but these reactants may be recovered and recycled to improve the overall conversion. Although the selectivity for production of the desired cationic ester not infrequently increases with lessened proportions of the trialkylamine, the use of too small an amount of trialkylamine relative to the other reactants unnecessarily increases the operating expense, because of the required increase in recycle operation, without obtaining any compensating advantage. From practical considerations, the relative amount of trialkylamine should be at least about 0.5 mole per mole of limiting other reactant. Relative amounts of trialkylamine from about 0.5 mole to 0.85 mole, especially amounts from about 0.6 mole to about 0.8 mole, per mole of limiting other reactant are satisfactory.

The process of the invention is conducted in liquid phase solution in an inert polar solvent. Suitable solvents are liquid at reaction temperature and pressure, are capable of dissolving the reactants and are inert to the reactants as well as the products produced therefrom. Illustrative solvents include sulfones such as dimethyl sulfone and sulfolane; N,N-disubstituted lower alkyl amides, e.g., dimethylformamide and N,N-dimethylacetamide; and sulfoxides such as dimethylsulfoxide. Preferred solvents, however, largely for economic reasons, comprise certain alcohols. It has been found that primary alcohols, such as methanol and ethanol, are not inert and are therefore not satisfactory as solvents in the present process, apparently because of a promotion of trans-esterification processes leading to substantially decreased yield of the desired cationic ester. However, when the alcohol possesses at least two non-hydrogen substituents on the carbon to which the hydroxyl group is attached, that is, the alcohol is a secondary or a tertiary alcohol, such trans-esterification processes do not take place extensively and high yields of the desired product are obtained. The preferred alcohol solvents therefore comprise a carbon atom to which is attached one hydroxyl group and from two to three hydrocarbyl substituents which are alkyl of from 1 to -6 carbon atoms or are aryl of 6 carbons, i.e., phenyl, and any unsatisfied valences of the central carbon atom are satisfied by hydrogen substituents. Such alcohols, characterized as dito trihydrocarbyl carbinols wherein the hydrocarbyl substituents are :as defined above, preferably have from 3 to 10 carbon atoms and are illustrated by isopropanol, secbutanol, tert-butanol, tert-amyl alcohol, triethylcarbinol, dimethyl phenyl carbinol and methyl ethyl phenyl carbinol. More preferred are the dito trialkyl carbinols wherein the alkyls are alkyl of 1 to 6 carbon atoms and particularly preferred are the dito trialkyl carbinols having a total of from three to four carbon atoms, i.e., sec-butanol, tert-butanol and isopropanol. The alcohols employed as solvents are preferably substantially anhydrous, as the presence of water appears to be detrimental to the reaction process. The presence of small amounts of water, e.g., up to about of the reaction mixture, may be tolerated without losing the advantages of the invention, but the yield of desired cationic ester will be somewhat lowered.

The method of mixing the reactants and solvent is not critical. Although it is frequently desirable to maintain the concentration of the trialkylamine reactant at a minimum, as by adding the amine in increments to a mixture of the other reactants and solvent, it is also suitable to initially mix the entire amount of reactants and solvent. The reaction is preferably conducted at somewhat elevated temperatures. Reaction temperatures from about 30 C. to about 125 C. are satisfactory, although reaction temperatures from about 50 C. to about C. are preferred. The process may be conducted at atmospheric, subatrnospheric or superatmospheric pressure so long as the reactants are maintained in the liquid phase. Little apparent advantage is gained by the use of reaction pressures considerably different than atmospheric, and the use of substantially atmospheric reaction pressures, e.g., from about 0.5 atmosphere to about 5 atmospheres, is preferred.

It is generally desirable to make some provision in the reaction procedure for the inhibition of alkenoic acid polymerization, particularly when the alkenoic acid is readily polymerizable, e.g., as acrylic acid, methacrylic acid or the like. Surprisingly, it is not necessary to rigorously exclude oxygen from the reaction environment and the process of the invention is conveniently conducted under an atmosphere of air. Prevention of alkenoic acid polymerization is customarily accomplished by the inclusion within the reaction mixture of an inhibitor. Conventional polymerization inhibitors capable of trapping organic free radicals formed during the reaction process are satisfactory, provided that the inhibitor is inert toward the reactants and the products produced therefrom. Preferred inhibitors therefore contain no active hydrogen atoms. Illustrative of suitable inhibitors are the quinones, particularly monoto dinuclear quinones, e.g., 1,4- benzoquinone, 1,2-benzoquinone, 1,4-naphthoquinone and a1- kylated or halogenated, particularly chlorinated, derivatives thereof such as chloranil, duroquinone, 2-ethylbenzoquinone and the like; as well as hindered phenols, i.e., phenols wherein the phenolic hydroxyl group is hindered by the presence of branched alkyl substituents on each ring position ortho relative to the hydroxyl group. Illustrative of the class of hindered phenolic inhibitors are 2,6- di-tert-butylphenol, 2,6-di tert-butyl-4-methylphenol, 2,6- diisopropylphenol and 2,4,6-tri-tertbutylphenol. The inhibitor, if employed, is added in comparably small amounts. Amounts of inhibitor from about 0.001 to about 5 molar percent based on the alkenoic acid reactant are suitable, while amounts from about 0.01 to about 3 molar percent on the same basis are preferred.

Subsequent to reaction the product is separated and recovered by conventional methods such as precipitation through the addition of a non-solvent, crystallization through a cooling procedure, by selective extraction or the like.

The products of the invention are 2-hydroxy-3-alkenoyloxypropyltrialkyl-ammonium halides. Illustrative of such products are 2 hydroxy-3-acrylyloxypropyltrimethylammonium chloride; 2 hydroxy-3-methacrylyloxypropyltrimethylammonium chloride, 2 hydroxy-3-ethacrylyloxypropyltrilaurylammonium bromide, 2 hydroxy-3-methacrylyloxypropylmethyldibutylammonium chloride and 2- hydroxy-3-(2 ethylacrylyloxy)propyldimethylstearylammonium chloride.

The products of the invention are suitable for use in numerous applications. As cationic materials they exhibit surface activity and are further useful as biocidal chemicals, particularly germicides. The number and variety of reactive functional groups present allow wide usage as chemical intermediates, wherein, for example, the hydroxyl group may be esterfied or etherified, other useful quaternary ammonium salts prepared by anion exchange, or alternatively the unsaturated linkage can be epoxidized to form useful epoxy resin precursors. A particularly important utility for the products of the invention is in the formation of polymeric materials, useful, for example, as wet end additives in paper manufacture.

To further illustrate the improved process of the invention, the following examples are provided. It should be understood that the details thereof are not to be regarded as limitations, as they may be varied as will be-understood by one skilled in this art.

Example -I r A solution was prepared from 200 gr tert-butyl alcohol, 60 g. (0.80 mole) methacrylic acid, and 4g. 2, .6-di-tertbutyl-4-methylphenol inhibitor. The solution was maintained at approximately C. while gaseous trimethylaminewas bubbled into the solution until the solution weight had increased 38 g. (which represents 0.64rnole of the amine). To the mixture was added 74 g. (0.80 mole) of epichlorohydrin. A -180 -200ml. aliquot of this solution was placed in a separate container and shaken for 72 hours while maintained at55' C. To the product'mixture, which contained appreciable quantities of crystalline precipitate when cooled to room temperature, was added six times its weight of acetone and the product mixture was allowed to stand for one hour. Filtration afforded crystals which were washed with acetone and dried under vacuum at 30-40 C. The yield of 2-hydroxy-3-methacrylyloxypropyltrimethylammonium chloride was 66% based upon the trimethylamine charged.

Example II By procedures similar to that of Example I, trimethylamine, epichlorohydrin and methacrylic acid were reacted, employing a variety of solvents. The results are shown in Table I wherein the yield represents yield of Z-hydroxy- 3 methacrylyloxypropyltrimethylamrnonium chloride based on the trimethylamine charged.

Example III By a procedure similar to that of Example I a series of reactions employing varying molar ratios of epichlorohydrin, trimethylamine and methacrylic acid was conducted. The results are shown in Tabe II, wherein the yield represents yield of 2 hydroxy 3 methacrylyloxypropyltrimethylammonium chloride based on the amine charged. The solvent in all cases was tert-hutyl alcohol, and each reaction mixture was heated at 60 C. for 48 hours with the exception of Experiment 4 wherein the reaction mixture was heated at 60 C. for 6 hours and then at 75 C. for 24 hours.

TABLE II Experiment 1 2 3 4 Tn'rnethylamine, moles/100 g. solution. 0.179 0. 168 0.206 0. 186 Methacrylic acid, moles/mole amine. 1.15 1.03 1. 28 Epichlorohydrin, moles/mole amine- 1. 35 0. 95 1. 28 Conversion of trimethylamine 100 55 85 Yield, percent 46 83 24 79 When dimethyllaurylamine is reacted with acrylic acid and epibromohydrin in isopropanol solution, the molar ratio of reactants being -O.7:1:1, a good yield of 2-hydroxy 3 acrylyloxypropyldirnethyllaurylammonium bromide is obtained.

6 f Example V 1 When the prodcedure of Exampe I'is-repeated, except that an equivalent amount of crotonicacid is employedis place of the methacrylic'acid, a good yield of Z-hydroxy- 3 crotonyloxypropyltrimethylammonium' chloride is obtained. v l

' Example' VI Several experiments were conducted -by procedures similar to that of Example 1,, except that other alcohol solvents were employed and the :2 l 1ydroxy 3v methacrylyloxypropyltrimethylammonium chloride was obtained by cooling the product mixture at -18 C. for 24 hours before filtration. The reaction mixture had been maintained at 60 C. for 48 hours. The results are shown I claim as my invention:

1. The process of producing 2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide by intimately contacting (a) acyclic hydrocarbon 'monoalkene monocarboxylic acid of from 3 to 8 carbon atoms;

('b) epihalohydrin wherein the halogen is halogen of atomic number from 17 to 35, the molar ratio of epihalihydrin to said monocarboxylic acid being from about 3 :1 to about 1:3, and

(c) an amount greater than about 0.5 mole per mole of limiting other reactant but less than stoichiometric of trialkylamine wherein each alkyl independently is alkyl of from -1 to 20 carbon atoms; in liquidphase solution in inert polar solvent, at a temperature from about 30 C. to about 125 C.

2. The process of claim 1 wherein the monocarboxylic acid is a-(nonto mono-alkyDacrylic acid wherein any alkyl is alkyl of from 1 to 5 carbon atoms, and said inert polar solvent is dito trihydrocarbyl carbinol of 3 to 10 carbon atoms.

3. The process of claim 2 wherein the epihalohydrin is epichlorohydrin.

4. The process of claim 3 wherein the amine is dimethylalkylamine wherein the alkyl is alkyl of from 1 to 20 carbon atoms present in an amount from about 0.5 mole 0t about 0.95 mole per mole of limiting other reactant, and the dito trihydrocarbyl carbinol is dito trialkyl carbinol.

5. The process of claim 4 wherein the amine is trimethylamine.

6. The process of claim 4. wherein the monocarboxylic acid is acrylic acid or methacrylic acid, the dito trialkyl carbinol is a dito trialkyl carbinol of from 3 to 4 carbon atoms, and said contacting is conducted in the presence of from about 0.001 to about 5 molar percent based on said monocarboxylic acid of a polymerization inhibitor having no active hydrogen atoms and at a temperature from about 50 C to about C.

7. The process of claim 6 wherein the amine is trimethylamine.

8. The process of claim 7 wherein the acid is methacrylic acid and the molar ratio of epichlorohydrin to said methacrylic acid is from about 1.5 :1 to about 1:15.

9. The process of claim 8 wherein the carbinol is secbutyl alcohol.

10. The process of claim 8 wherein the carbinol is isopropyl alcohol.

11. The process of claim 6 wherein the acid is acrylic acid.

(References on following page) Referencs Cited 3,075,999 1/1963 June ef al 260-348.6 UNITED STATES PATENTS 3,170,901 2/1965 Melamed et a1. 260-486 XR 3/1937 stfaub et a1 6 3,272,712 9/1966 Kalopissis et a1. 260404 10/1949 Caldwell 260-486 6 OTHER REFERENCES 10/19 50 Dorough 260-348 1/1951 Edwards 260 348 Kakvlchu et a1.: Chenucal Abstracts, vol. 61: 777 (g), 4/1951 Oli n 260-567.6 July 1964- 'f g LORRAINE A. WEINBERGER, Primary Examiner. 1/1959 shokal et a1. 260-408 A. P. HALLUIN, Assistant Examiner.