PROCESS FOR THE PRODUCTION OF ACYL LACTAMS

Abstract: Acyl lactam is made by reacting an acyl halide with a lactam in a substantially non-aqueous, substantially solvent free, reaction mixture containing an inorganic base.

Description: Process for the Production of Acyl Lactams Technical Field The present invention relates to a process for the production of acyl lactams. Such products are useful as bleach activators in detergent compositions. Background of the Invention The production of acyl lactams of good purity and in an economic manner can be difficult because many of the processes give a poor yield and/or a poor quality product and/or involve relatively costly or difficult reaction and recovery procedures. It would be desirable to provide a process that overcomes one or more of these disadvantages. In particular, it would be desirable to provide such a process that does not involve the use of water (thereby eliminating hydrolysis problems and subsequent costly treatments of waste water) or the use of organic solvents (thereby avoiding the need for additional equipment to recover solvent). A process is described in U.S. 2,877,220, issued March 10, 1969, for making N-benzoyl caprolactam by reacting caprolactam with benzoyl chloride in the presence of an acid acceptor, and it is stated that this is preferably a tertiary amine such as pyridine or dimethyl aniline. In each of the examples, the amount of tertiary amine is greater than the amount of caprolactam. It would be desirable to avoid the use of these large volumes of expensive organic solvent. Summary of the Invention The present invention relates to a process for making an acyl lactam and comprises reacting an acyl halide with a lactam in a substantially non-aqueous, substantially solvent-free, mixture containing an inorganic base. Description of Preferred Embodiments The acyl lactam is made by heating a reaction mixture consisting essentially of the acyl halide, the lactam and the inorganic base. The reaction mixture is substantially non-aqueous and substantially free of organic solvent and generally contains no significant volumes of other materials that would need to be separated from the end products. Generally the reaction mixture consists solely of the acyl halide, the lactam and the inorganic base or it consists of this mixture together with a minor amount of a quaternary ammonium compound. The acyl halide is usually an acyl chloride, but any other suitable halide that will react satisfactorily in the reaction could be used. The acyl group generally has the formula RCO- where R is generally an aryl group or a Cι-20 linear or branched, saturated or unsaturated, fatty aliphatic group. The aryl group is preferably phenyl while the aliphatic group is preferably selected from C7-12 alkyl or alkenyl groups. Any of these groups may be optionally substituted with non-interfering substituents. The preferred acyl halide is benzoyl chloride. The lactam usually is a compound of the formula where n is an integer from zero to 8. Preferred lactams are selected from the group consisting of caprolactams (n=2), valerolactams (n= l), 2-azacyclooctanone, 2-azacyclotridecanone and pyrrolidone (n=o), with caprolactam being particularly preferred. The lactam can be substituted by one or more non-interfering substituents. The inorganic base can be any inorganic base that will act as an acid halide acceptor in the process. It is generally a compound of a metal of groups 1 or 2 of the periodic table. In particular it is preferably a compound of an alkali metal or a metal of groups 2a or 2b of the periodic table. Preferred metals are potassium, magnesium, calcium and zinc. The compound is preferably capable of being introduced as a finely divided paniculate solid. Preferred compounds are oxides and carbonates, for instance potassium carbonate, magnesium oxide or carbonate, calcium oxide or carbonate or zinc oxide or carbonate. Zinc oxide is particularly preferred. The amount of caprolactam or other lactam in the mixture is usually at least about 1 mole but not more than about 4 moles per mole of benzoyl chloride or other acyl halide. Generally it is at least about 1.3 moles and preferably at least about 1.7 moles. Generally the amount is not more than about 3 moles and preferably it is not more than about 2.3 moles. An amount of about 2 moles caprolactam per mole benzoyl chloride is generally preferred. The amounts of inorganic base usually at least about 80% but usually not more than about 150% of the stoichiometric amount required for neutralising all the hydrogen halide formed by reaction from the acyl halide. Generally the amount is at least 100% of the stoichiometric amount. Generally it is not more than about 110 or 120% of the stoichiometric amount. When the inorganic base is the oxide of a divalent metal or the salt of a divalent anion, the base can neutralise two equivalents of the hydrogen halide. Accordingly the molar proportion of the base is usually at least about 0.5 moles, often 0.55 moles inorganic base per mole acyl halide. This applies to, for instance, inorganic bases such as ZnO, MgO, CaO, K2CO3 and CaCOβ. When the base can neutralise only one equivalent of the hydrogen halide then the amount of the inorganic base is preferably at least about 1.0, often about 1.1, moles per mole acyl halide. This applies to bases such an NaHC03, NaH and KOH. In some instances it is desirable to include a small amount of a tertiary or quaternary ammonium compound. The amount is, per mole acid halide, generally below 0.1 moles, for instance in the range about 0.003 to about 0.05 moles, typically about 0.01 moles. The purpose of including the tertiary or quaternary ammonium compound is to activate the acyl halide. The ammonium compound appears to act as a catalyst. Suitable compounds that can be incorporated for this purpose include tetra alkyl ammonium halides wherein the alkyl group can contain from 1 to 12 carbon atoms. A suitable compound is tetra ethyl ammonium bromide. Other ammonium compounds that can be used include pyridine, triethylamine, and N,N-dimethylaniline and other tertiary amines that may form a quaternary ammonium or acid addition salt in the reaction mixture. Other components that can be included in the reaction mixture include water absorbing material in amounts of not more than necessary to react with traces of water introduced initially into the reaction mixture or formed during the neutralisation of the acid formed during the reaction. Although the reaction mixture may include other components that do not interfere undesirably with the process or with the recovery of the reaction products, it is generally preferred that the reaction mixture should contain only the materials named above, namely the acyl halide, the lactam, the inorganic base, the optionally catalytical and ammonium compound and the optional water absorbent compound. The reaction is best conducted at a temperature of at least about 75° C and more usually at least about 85°C. The reaction temperature can be as high as, for instance, 130°C but preferably it is not more than about 110°C for most or all of the reaction. Best results are generally obtained when the reaction temperature is in the range about 85 to 100°C, most preferably around 90 to 95°C. The reaction mixture can be formed by forming a mixture of paniculate inorganic base with a melt or other fluid mixture of heated acyl halide and lactam. Usually the lactam is introduced into the reaction vessel first and is heated to a temperature at which it is fluid or molten. The acyl halide and the paniculate inorganic compound can then be added in either order but it is usually preferred to add the inorganic compound before the acyl halide. If desired, the inorganic compound can be introduced into the reaction vessel before the lactam or can be present during the melting of the lactam. The reaction is usually conducted for at least about one hour and it can be for as long as about 3 or 4 hours, but often the reaction time is around 1.5 to 2 hours. The reaction vessel is preferably stirred throughout the reaction and may be fitted with a condenser open to the atmosphere. At the end of the reaction, the mixture may be cooled to near ambient temperature and the desired acyl lactam recovered by conventional techniques. Preferably, however, the recovery is performed by a method comprising the addition of an aqueous base, generally aqueous sodium bicarbonate. This may be conducted by first diluting the mixture with a large excess of distilled water (for instance 3 to 10 parts by weight water per part by weight mixture) and sufficient sodium bicarbonate to make the mixture slightly alkaline, for instance about pH 8. The resultant precipitate contains the desired end product and zinc hydroxide or other insoluble material derived from the inorganic compound. Separation of the reaction product from the zinc hydroxide or other inorganic compound can be conducted by solvent extraction (for instance using acetone or methylene chloride) or by treatment with a mineral acid such as HC1 in order to solubilise the inorganic compound as, for instance, zinc chloride. In other processes, the recovery may be performed by treating the initial reaction product with aqueous hydrogen chloride or other mineral acid in order to solubilise inorganic compound present in the reaction mixture (for instance zinc oxide and zinc chloride). The aqueous acid phase will then be separated from the water insoluble organic phase or water insoluble precipitate. The water insoluble phase or precipitate will be rendered alkaline by the addition of base (for instance, aqueous sodium hydroxide) in order to precipitate the desired reaction product. By the invention it is possible to obtain precipitated acyl lactam having a high purity level, for instance at least 95% and most preferably at least 96 or 97%. This recovery can be in a satisfactory yield, for instance at least 60% by weight based on the acyl halide. The following are examples of the invention. Example 1 226g (2 moles) caprolactam is melted at 90 to 100°C in a 1.5 litre reaction vessel. 45g zinc oxide (0.55 moles) and 2.1g tetra ethyl ammonium bromide (0.01 moles) in paniculate form are mixed into the melt to form a low to medium viscous dispersion. 141g benzoyl chloride (1 mole) is added to the mixture over a period of about half an hour while maintaining the temperature in the range 90 to 103°C. The reaction mixture is then held at 90°C for 1.5 hours to allow the reaction to proceed. 900ml water is then added and results in the production of an emulsion having a temperature of about 35°C. 60g solid sodium bicarbonate is added portionwise to precipitate both the acyl caprolactam and the zinc salts. The white precipitate is filtered, washed neutral and dried. Benzoylcaprolactam is separated from the Zn salts by solubilisation in an organic solvent such as acetone, or methylene chloride. Evaporation of the solvent leaves 142g of 97% pure (by gas chromatography) N-benzoylcaprolactam having a melting point of 58.3° to 63.5°C. The yield is 65.4%. Altei natively, the benzoylcaprolactam can be separated from the Zn salts by treatment with dilute hydrochloric acid so as to solubilise selectively the Zn salts. Example 2 The process of Example 1 is repeated but without the tetra ethyl ammonium bromide and with the addition of benzoyl chloride being conducted over a period of 0.75 hours and the reaction being continued for 2.75 hours. A yield of 62.1 % is obtained of a benzoyl caprolactam product having a melting point 53.1 to 59.7°C. Example 3 The process of Example 1 is repeated but without the tetra ethyl ammonium bromide and the zinc oxide is replaced by 76g (0.55 moles) anhydrous potassium carbonate. The addition of the benzoyl chloride is conducted over one hour at 90 to 140°C and then the reaction is performed for 2 hours at 90 to 130°C. Although the yield is only 33.2% , the obtained product is extremely pure benzoyl caprolactam and has melting point 69 to 69.9°C. Example 4 The process of Example 1 is repeated using 0.5 moles magnesium oxide in place of the zinc oxide and tetra ethyl ammonium bromide. The addition of the benzoyl chloride is conducted over quarter of an hour at 80 °C and the reaction is conducted for 3 hours at 95 °C. A yield is obtained of about 38.6% of a product containing about 96.5% benzoyl caprolactam and having a melting point of 58.6 to 62.9°C. Example 5 Example 1 is repeated except that 0.6 moles calcium oxide is used in place of the zinc oxide and tetra ethyl ammonium bromide. The benzoyl halide is added over a period of 0.5 hours at 90°C and the reaction is conducted at 90°C for 2 hours. A yield is obtained of 60%, based on benzoyl chloride, of a product having a melting point of 44.6 to 52.8°C and which contains 93.6% benzoyl caprolactam.

Claims: WHAT IS CLAIMED IS: 1. A process for making an acyl lactam comprising reacting acyl halide with a lactam in a non-aqueous, substantially solvent-free, reaction mixture containing an inorganic base as acid halide acceptor. 2. A process according to claim 1 in which the acyl halide is an acyl chloride wherein the acyl group has the formula RCO where R is an aryl group or a Cj-20 linear or branched saturated or unsaturated fatty aliphatic group. 3. A process according to claim 2 in which R is phenyl or C7-12 alkyl or alkenyl. 4. A process according to claim 1 in which the acyl halide is benzoyl chloride. 5. A process according to any preceding claim in which the lactam has the formula O HN - CH2 - (CH2)n where n is an integer from zero to 8. 6. A process according to claim 5 in which n is 1 or 2. 7. A process according to any preceding claim in which the inorganic base is selected from paniculate oxides and carbonates of a metal which is selected from alkali metals and metals of groups 2a or 2b of the periodic classification. 8. A process according to any preceding claim in which the inorganic base is zinc oxide. 9. A process according to any preceding claim for making benzoyl caprolactam comprising reacting benzoyl chloride with caprolactam in the presence of paniculate zinc oxide as acid halide acceptor. 10. A process according to any preceding claim in which the reaction mixture comprises 1 mole acyl halide, 1.7 to 2.3 moles lactam and inorganic base in an amount of 100 to 150% of stoichiometric. 11. A .process according to any preceding claim conducted at a temperature of 80 to 100°C for 1 to 3 hours. 12. A process according to any preceding claim in which the reaction mixture contains up to 0.1 moles, per mole acyl halide, of a teniary amine or a quaternary ammonium salt. 13. The use of acyl lactams prepared according to the process of any one of Claims 1 to 12 as bleach activators in detergent compositions.

Inventors: BELLMANN GUNTER GERD ULRICH, GUEDIRA NOUR-EDDINE, BELLMANN, GUNTER, GERD, ULRICH, GUEDIRA, NOUR-EDDINE
Applicants: BELLMANN GUNTER GERD ULRICH, GUEDIRA NOUR EDDINE, PROCTER & GAMBLE, BELLMANN, GUNTER, GERD, ULRICH, GUEDIRA, NOUR-EDDINE, THE PROCTER & GAMBLE COMPANY
Application year: 1995
Main classification: C07D211
IPC codes: C07D223, C11D3, D06L3