OLEUM SULPHONATION PROCESS

Abstract: A process is provided for obtaining sulphophenyl quaternary ammonium or phosphonium substituted carbonic acid esters. The important step in this process involves reacting a phenyl quaternary ammonium or phosphonium substituted carbonic ester with oleum that contains from 0.5 up to 33% sulphur trioxide. Amounts in excess of 33% sulphur trioxide lead to increased reaction times and, eventually, unacceptable product conversions.

Description: 1. Field of the Invention The invention relates to a process for preparing sulphonated phenyl carbonic acid esters having a quaternary group, which esters are useful as bleach precursors in detergent compositions. 2. The Prior Art Detergent compositions that rely upon sodium perborate as a bleach normally require a precursor to activate the oxygen-releasing compound where wash-water temperatures are below 60°C. A recently issues patent, U.S. 4,751,015 (Humphreys et al.), reported an exceptionally effective bleach precursor family of compounds identified as quaternary ammonium or phosphonium substutited peroxy carbonic acid esters. These precursors were reported synthesized in a two-step procedure. Illustrative is 2-(N,N,N-trimethylammonium)ethyl sodium 4-sulphophenyl carbonate chloride (SPCC) which was synthesized by first preparing choline chloroformate chloride through reaction of phosgene with choline chloride in a chloroform solution. The choline chloroformate chloride was then isolated as a crystalline solid. In a second step, the solid choline chloroformate chloride was added to an aqueous solution of sodium 4-phenol sulphonate containing an equimolar amount of sodium hydroxide. A number of problems are associated with this process. For instance, there are handling problems with choline chloroformate chloride, a highly hygroscopic material. Spontaneous crystallization of the chloroformate from solution has been noted. This presents a challenge in commercial production to avoid pipeline constriction. Furthermore, yields of the final product, SPCC, are variable, sometimes being even quite poor (40-85%). Instability of the final product is a still further problem. Final bleach precursor product, e.g. SPCC, resulting from this process normally contains a very substantial amount of sodium chloride. This by-product is undesirable for several reasons. Sodium chloride promotes corrosion of certain metallic parts of washing machines. Further, sodium chloride takes up valuable space within a detergent formulation without contributing any useful functionality. Consequently, it is an object of the present invention to provide an improved process for the synthesis of quaternary ammonium or phosphonium substituted carbonic acid esters. A more specific object of the present invention is to provide an improved process for obtaining the aforementioned carbonic acid esters which limits the amount of sodium chloride present in the final product. A further object of the present invention is to provide a synthesis of carbonic acid esters that results in a high and relatively reproducible product yield. SUMMARY OF THE INVENTION A process is provided for preparation of sulphophenyl quaternary ammonium and phosphonium carbonate esters of the formula: wherein: R₁, R₂ and R₃ are each a radical selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, alkaryl, aryl, phenyl, hydroxyalkyl and polyoxyalkylene; or two or more of R₁, R₂ and R₃ together form an alkyl substituted or unsubstituted nitrogen-containing heterocyclic ring system; or at least one of R₁, R₂ and R₃ is attached to R₄ to form an alkyl substituted or unsubstituted nitrogen-containing heterocyclic ring system; R₄ is selected from a bridging group consisting of alkylene, cycloalkylene, alkylenephenylene, phenylene, arylene and polyalkoxylene; and wherein the bridging group can be unsubstituted oor substituted with C₁-C₂₀ atoms selected froom alkyl, alkenyl, benzyl, phenyl and aryl radicals; Q is nitrogen or phosphorus; R₅ is C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy, carboxy, hydroxy, C₁0C₁₂ alkyl carboxy group and mixtures thereof; and n ranges from 0 to 4; comprising the steps of: (i) reacting a phenyl quaternary ammonium or phosphonium carbonate of the formula: wherein Z⁻ is a monovalent or multivalent anion leading to charge neutrality when combined in the appropriate ratio with Q⁺; with a sulphonation reagent consisting of oleum wherein the percent sulphur trioxide ranges from about 0.5 up to 33%; and (ii) recovering from the reaction said quaternary ammonium or phosphonium carbonate ester of formula I. DETAILED DESCRIPTION OF THE INVENTION The present invention describes an oleum sulphonation process that provides sulphophenyl esters of quaternary ammonium or phosphonium substituted carbonic acids containing no more than small amounts of halide counterion. These sulphophenyl esters are useful adjuncts in fabric-washing powders. They provide excellent low temperature stain bleaching when formulated with peroxygen compounds such as those of sodium perborate or sodium percarbonate. There are a whole variety of sulphonation agents known in the art. These include sulphur trioxide, chlorosulphonic acid and concentrated sulphuric acid. Each of these presents problems in that they require large stoichiometric excesses to achieve good yields of the subject carbonic acid esters. Although not wishing to be bound by any theory, it is believed the excess sulphonation agent is required because of the normally present chloride counterion associated with the reactant quaternary ammonium or phosphonium substituted carbonic acid ester (II). Halide ion reacts with the electrophilic sulphonating agent and is now believed to be the cause of reducing its reactivity. This is represented in equation 1 and 2 for the cases of sulphur trioxide and chlorosulphonic acid, respectively. Only after the addition of a second equivalent of sulphur trioxide according to equation 1 does the reaction of the present invention proceed to completion. Further, the fact that the reaction must be performed in an organic solvent, e.g. 1,2-dichloroethane, at reflux means that work-up of the product involves the extra step of solvent stripping. Most importantly, since the chloride ion is still bound with the first equivalent of sulphur trioxide, neutralization of the reaction mixture results in sodium chloride in the finished product. With concentrated sulphuric acid at room temperature, the sulphonation reaction was not observed. When the temperature of the reaction medium was raised to 90°C, only hydrolysis was observed. Sulphophenol was the only sulphonated product found. Presumably, the activity of the hydronium ion in concentrated (95-100%) sulphuric acid was high enough to promote acid catalyzed hydrolysis. According to the present invention, it has been found that the strength of the oleum is an important factor in determining the reaction time for quantitative conversion to the sulphonated product. As the mole fraction of sulphur trioxide in oleum increases, the rate of reaction decreases. Thus, it has been found that the oleum strength in terms of percent sulphur trioxide must range from about 0.5 up to 33%, preferably no higher than 25%. Amounts greater than 33% result in a very substantial, unacceptable increase in reaction time. This unexpected result is believed to be due to the decrease of the H₂SO₄/SO₃ ratio as the oleum strength increases. In other words, the actual sulphonating agent in this reaction is sulphuric acid, whereas the sulphur trioxide serves only to bind the chloride counterion. Further, as the sulphuric acid sulphonates the phenyl ring, water is produced as a by-product and, instead of promoting hydrolysis of the quaternary alkyl ammonium sulphophenyl carbonate product, the water reacts with the chlorosulphate anion too form hydrogen chloride and bisulphate. Although the sulphonation reaction is quite facile at lower oleum strength, an advantage in performing the reaction at the higher oleum strength is that the amount of sodium sulphate formed on neutralization is minimized. With less sodium sulphate in the finished product, one has even more flexibility in terms of formulating the material into a finished fabric-washing powder. Advantageously, the reaction is conducted at a temperature of less than 200°C, preferably between 40°C and 150°C, optimally between 75°C and 125°C. Although phosphonium groups where Q is phosphorus are within the scope of this invention, for economic reasons it is most preferred that Q be nitrogen. Furthermore, the precursor should preferably contain a quaternary ammonium carbon surrounded by R₁, R₂ and R₃ each the same oor different and having C₁-C₂₀ atom radicals selected from the group consisting of alkyl, alkylaryl, benzyl, hydroxyalkyl, heterocyclic rings containing the quaternary nitrogen groups where R₁ and R₄ or R₁ and R₂ are joined together, and mixtures of groups thereof. In particular, it is desirable that R₁ be a short-chain C₁-C₄ alkyl radical, preferably methyl, while R₂ and R₃ be a longer chain C₇-C₂₀ alkyl or alkylaryl, such as stearyl, lauryl or benzyl group. With regard to the R₄ bridge between the quaternary nitrogen and carbonate groups, it is desirable that R₄ be a bridging group selected from C₂-C₂₀ alkylene, C₆-C₁₂ phenylene, C₅-C₂₀ cycloalkylene and C₈-C₂₀ alkylenephenylene groups. Preferably, the alkylene groups should have carbon 2 atoms. Further, the bridging group can be unsubstituted or substituted with C₁-C₂₀ alkyl, alkenyl, benzyl, phenyl and aryl radicals. Within the context of this invention, there may be compounds having the general structure (I) where R₁ and R₄ together or R₁ and R₂ together form an alkyl substituted or unsubstituted nitrogen-containing heterocyclic ring system. Representative of these systems are rings defining pyridine, morpholine, pyrrolidine, piperidine and piperazine. More specific compounds are listed in U.S. Patent 4,751,015. The process is described generally as comprising the steps of: (i) reacting a phenyl quaternary ammonium or phosphonium carbonate of the formula: wherein Z⁻ is a monovalent or multivalent anion leading to charge neutrality when combined in the appropriate ratio with Q⁺; with a sulphonation reagent consisting of oleum wherein the percent sulphur trioxide ranges from about 0.5 up to 33%; and (ii) recovering from the reaction said quaternary ammonium or phosphonium carbonate ester of formula I. The following examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise illustrated. EXAMPLE 1 A typical oleum sulphonation was performed as follows. In a three-necked 100 ml round bottom flask equipped with a mechanical stirrer and drying tube were placed 12.3 gms (3.08 gms, 38.5 mmoles of "free" sulphur trioxide) of 25% oleum. This reaction vessel was chilled in an ice bath. Thereinto was rapidly added 10.0 gms (38.5 mmoles of cholyl phenyl carbonate chloride. A highly viscous beige-coloured solution resulted. The solution was heated in an oil bath at 100°C for 70 minutes. During the reaction, hydrogen chloride outgassing was noted as soon as the reaction solution was heated. NMR analysis of the reaction mixture revealed quantitative conversion to sulphonated product at the end of the heating period. To the above solution was added 12 ml of water so as to decrease the viscosity. Anhydrous sodium carbonate was slowly added to the reaction solution until the pH rose to 4-5. The resultant thick slurry was allowed to dry in air. The solid product was 44% active, the remainder being sodium sulphate and sodium chloride. Residual sodium chloride was 15% of the theoretical amount as determined by a potentiometric chloride titration. Yield of 2-(N,N,N-trimethylammonium)ethyl 4-sulphophenyl carbonate was 95%. EXAMPLE 2 Illustrated herein is the effect of varying the oleum strength used for the sulphonation reaction. All of the experiments were run in accordance with the reaction as outlined in Example 1. Each of the entries in the Table was calculated for 90% conversion. Evident from the Table is that at 26% oleum strength there is greater than a ten-fold increase in reaction time relative to the 21% oleum strength level. The foregoing description and examples illustrate selected embodiments of the present invention.

Claims: 1. A process for preparation of sulphophenyl quaternary ammonium and phosphonium carbonate esters of the formula: wherein: R₁, R₂ and R₃ are each a radical selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, alkaryl, aryl, phenyl, hydroxyalkyl and polyoxyalkylene; or two or more of R₁, R₂ and R₃ together form an alkyl substituted or unsubstituted nitrogen-containing heterocyclic ring system; or at least one of R₁, R₂ and R₃ is attached to R₄ to form an alkyl substituted or unsubstituted nitrogen-containing heterocyclic ring system; R₄ is selected from a bridging group consisting of alkylene, cycloalkylene, alkylenephenylene, phenylene, arylene and polyalkoxylene; and wherein the bridging group can be unsubstituted oor substituted with C₁-C₂₀ atoms selected froom alkyl, alkenyl, benzyl, phenyl and aryl radicals; Q is nitrogen or phosphorus; R₅ is C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy, carboxy, hydroxy, C₁OC₁₂ alkyl carboxy group and mixtures thereof; and n ranges from 0 to 4; comprising the steps of: (i) reacting a phenyl quaternary ammonium or phosphonium carbonate of the formula: wherein Z⁻ is a monovalent or multivalent anion leading to charge neutrality when combined in the appropriate ratio with Q⁺; with a sulphonation reagent consisting of oleum wherein the percent sulphur trioxide ranges from about 0.5 up to 33%; and (ii) recovering from the reaction said quaternary ammonium or phosphonium carbonate ester of formula I. 2. A process according to claim 1, wherein Q is nitrogen and R₁, R₂ and R₃ are each the same or different and selected from C₁-C₂₀ atom radicals selected from the group consisting of alkyl, alkylaryl, benzyl, hydroxyalkyl and heterocyclic rings containing the quaternary nitrogen where R₁ and R₄ or R₁ and R₂ are joined together, and mixtures of groups thereof. 3. A process according to claim 2, wherein R₁ is selected from short-chain C₁-C₄ alkyl radicals. 4. A process according to claim 2 or 3, wherein R₂ and R₃ are each a longer chain C₇-C₂₀ alkyl or alkylaryl radical. 5. A process according to claim 4, wherein said longer chain radical is selected from the group consisting of benzyl, lauryl and stearyl groups. 6. A process according to claim 1, wherein R₄ is selected from a bridging group consisting of C₂-C₂₀ alkylene, C₆-C₁₂ phenylene, C₅-C₂₀ cycloalkylene and C₈-C₂₀ alkylenephenylene groups. 7. A process according to claim 6, wherein the R₄ bridging group is a C₂-C₆ alkylene or C₆-C₁₂ phenylene group. 8. A process according to claim 2, wherein said heterocyclic ring is selected from pyridine, morpholine, pyrrolidone, piperidine and piperazine. 9. A process according to claim 1, wherein the ester product is 2-(N,N,N-trimethylammonium)ethyl 4-sulphophenyl carbonate salt.

Inventors: ILARDI, LEONORA MARIE, MADISON, STEPHEN ALAN
Applicants: UNILEVER N.V., UNILEVER PLC
Application year: 1989
Main classification: C07C303
IPC codes: C11D3, C07C303, C07F9, C07C309