Process for the Manufacture of Alkyl Ketene Dimers by Dimerization With

Office europeen des brevets (fi) Publication number: 0 619 289 A1 @ EUROPEAN PATENT APPLICATION @ Application number : 94302165.9 @ Int. CI.5 : C07C 45/89, C07C 49/88 (22) Date of filing : 25.03.94 (30) Priority : 26.03.93 US 37203 @ Inventor : Zhang, Jian Jian (NMN) 10.05.93 GB 9309603 508 Waterford Drive, Gateway Farms Hockessin, Delaware 19707 (US) @ Date of publication of application : 12.10.94 Bulletin 94/41 (74) Representative : De Minvielle-Devaux, Ian Benedict Peter et al @ Designated Contracting States : CARPMAELS & RANSFORD AT BE DE ES FR GB IT NL PT SE 43, Bloomsbury Square London WC1A 2RA (GB) @ Applicant : HERCULES INCORPORATED 1313 N. Market Street, Hercules Plaza Wilmington, Delaware 19894-0001 (US) (54) Process for the manufacture of alky I ketene dimers by dimerization with tertiary amines. (57) A process is disclosed for the synthesis of alkyl ketene dimers by the dehydrohalogenation of a Cg - C22 saturated or unsaturated linear fatty acid halide, comprising reacting the fatty acid chloride with a cyclic tertiary amine in an inert solvent at a temperature of up to 75°, separating tertiary amine hydrochloride salts from alkyl ketene dimer dissolved in the solvent, and recovering the alkyl ketene dimer from the solvent. < 00 CM o> S o Q_ LU Jouve, 18, rue Saint-Denis, 75001 PARIS 1 EP 0 619 289 A1 2 This invention relates to a process for the synthe- German OLS 29 27 118 discloses a process to sis of alkyl ketene dimers by thedehydrohalogenation make diketenes using of a mixture of amines, which of Cs - C22 saturated or unsaturated linear fatty acid includes trimethylamine and at least one other terti- chlorides with tertiary amines in an inert solvent. ary amine. The trimethylamine is said to avoid the 5 high viscosity in the reaction mixtures with fatty acid BACKGROUND OF THE INVENTION halides that higher-substituted trialkylamines were found to cause. The other amine or amines may in- It is well known to react reaction of saturated lin- clude 1-methylpiperidine or 1-methylpyrrolidene. The ear fatty acid chlorides with linear tertiary amines in solvents used include alkanes and cyclo alkanes, as a variety of inert solvents to make disubstituted etha- 10 well as aromatic hydrocarbons, the reaction temper- nones, such as alkyl ketene dimers, which are useful ature is between 60 and 90°C, and the post-reaction as constituents of paper sizes as well as for other ap- heating is at 80°. Separation of LTEA-HCI precipitate plications in industry. For instance, U.S. Patents from the dimerization slurry involves liquid/liquid wa- 2,238,826 and 2,369,919, and an article by J. C. Sa- ter extraction of the LTEA-HCI salt, which introduces uer, Ketene Dimers from Acid Hal ides, in the Journal 15 moisture that is likely to cause hydrolysis of the alkyl of the American Chemical Society, 69 2444-8 (1947) ketene dimer and lessening of product yield. Yields of describe such reactions. Among the known useful 87 to 92% are obtained and presumably cannot be im- solvents are benzene, toluene, xylene, ligroin, chlor- proved further because of the inherent nature of the obenzene, dichlorobenzene, diethyl ether, dibutyl reaction. ether, chloroform, carbon tetrachloride, and trichloro- 20 There is a need for an alkyl ketene dimerization ethylene. The known families of solvents can be clas- process that avoids excessive viscosity and small sified as: amine-hydrochloride crystals in the dimerization slur- 1. alkanes and alkane petroleum fractions; ry, to facilitate the separation of amine-hydrochloride 2. cycloalkanes such as cyclohexane and methyl- precipitates in consistently high yields by such mech- cyclohexane; 25 anical separation methods as filtration, sedimenta- 3. aromatic hydrocarbons such as benzene, tol- tion and decantation, and without using uneconomic uene, and xylene; volumes of solvent, as disclosed in U.S Patent 4. chlorinated solvents such as chlorobenzene, 2,369,919. dichlorobenzene, chloroform, carbon tetrachlor- Also, because the conventional dimerization sol- ide, and trichloroethylene; and 30 vents used in present industrial applications are eith- 5. ethers such as diethyl ether. er unacceptably toxic, particularly benzene, diethyl The reaction in the said solvents to produce alkyl ether and toluene, used in the said U.S Patent ketene dimer (AKD) in solution also produces linear 2,369,91 9), or are known to be environmentally objec- tertiary amine hydrochloride (LTEA-HCI) as a finely tionable, including the whole class of the chlorinated divided precipitate. For some of the known solvent 35 solvents. There is therefore a need for a alkyl ketene families, problems encountered in the alkyl ketene di- dimerization process that uses a solvent with less merization reaction are low AKD selectivity (<80%), health and environmental problems than aromatic hy- an excessively viscous dimerization mixture, or very drocarbons, such as benzene and toluene or halogen- small amine-hydrochloride crystals in the dimeriza- ated solvents as used in the German OLS. tion slurry that are hard to separate by mechanical 40 procedures such as filtration and/or centrifugation Summary of the Invention and decantation. U.S. Patents 2,238,826 and 2,369,919 indicate According to the invention, a process for the syn- that saturated acyclic amines free of active hydrogen thesis of alkyl ketene dimers by reacting a C8 - C22 are preferred for the said reaction, although they in- 45 saturated or unsaturated linear fatty acid chloride dicate that suitable amines include 1-methylpiperi- with a cyclic tertiary amine in an inert solvent at a tem- dine, 1-isopropylpiperidine, and 1-methylpyrrolidene. perature of up to 75°C, mechanically separating ter- From the disclosure, of the '919 Patent it is apparent tiary amine hydrochloride salts from the alkyl ketene that the use of the preferred linear amines requires a dimer in the solvent, and recovering the alkyl ketene very dilute reaction mixture (100-200 parts solvent 50 dimer by evaporation of the solvent, characterized in per tenth mol of each reactant to obtain a yield of 60 that the tertiary amine has the structure: to 97%. That degree of dilution appears to be necessary to prevent the dimerization reaction slurry from becoming highly viscous, which would make separa- f tion of a linear tertiary amine hydrochloride (LTEA- HCI) precipitate from the reaction mixture extremely difficult and filtration disclosed in impossible by as (CH2)n the patent. 2 3 EP 0 619 289 A1 4 in which R represents a CrC7 substituted or unsub- It is possible to add the fatty acid chloride to the stituted alkyl group and n is an integer from 2 to 10. tertiary amine solution in the aliphatic hydrocarbon Preferably the alkyl group R contains one to three solvent, or to add the tertiary amine to the fatty acid carbon atoms and n is four or five, and more prefer- chloride solution in aliphatic hydrocarbon, orsimulta- ably the tertiary amines for use in the invention are N- 5 neously to add both fatty acid chloride and tertiary methylpyrrolidine, N-methylpiperidine, or N-ethylpi- amine to the solvent. However, the preferred method peridine. The most preferred cyclic tertiary amine is is dropwise addition of the fatty acid chloride, either N-methylpyrrolidine. as is or dissolved in aliphatic hydrocarbon solvent, to The preferred solvents are cycloalkanes or al- a tertiary amine solution, also in aliphatic hydrocar- kanes, preferably containing from 5 to 10 carbon 10 bon solvent. atoms. The cycloalkanes may be either unsubstituted The reaction of the dehydrochlorination of fatty or substituted by an alkyl group having one to four car- acid chloride by tertiary amine is exothermic. The ad- bon atoms, and the alkanes may be either linear or dition of fatty acid chloride to the tertiary amine sol- branched. The more preferred solvents are cycloalk- ution in aliphatic hydrocarbon solvent is preferably anes. 15 carried out at a temperature ranging from room tem- The amount of solvent used for the reaction is perature to 70°C, if necessary accompanied by cool- preferably between about 30% and 100% by mass of ing to prevent the temperature from exceeding 70°C. the solvent, based upon the mass of the fatty acid In order to complete the dehydrochlorination re- chloride or mixture of fatty acid chlorides. More pre- action of the fatty acid chloride and the dimerization ferably, the amount of solvent is just above the 20 reaction of ketene monomer, the complete reaction amount needed to avoid the saturation concentration mixture is preferably maintained at an elevated tem- of alkyl ketene dimer in the solvent at the reaction cy- perature of up to 70°C for at least 30 minutes and up cle temperatures, namely, to provide an alkyl ketene to 5 hours, preferably at a temperature of at least dimer concentration in the reaction slurry in the range 50°C and more preferably between 55 and 65°C for of 1 .0 molar to 3.65 molar. 25 between 2 and 3 hours. This post-reaction heat treat- ment generally lowers the viscosity of the reaction DETAILED DESCRIPTION OF THE INVENTION slurry and improves the alkyl ketene dimer quality. As indicated above, the amount of solvent used Among the cycloalkanes, the best results are se- for the reaction is preferably at least sufficient and cured by use of cyclohexane or methylcyclohexane, 30 preferably in excess of the amount necessary to in particular methylcyclohexane. The preferred al- maintain the alkyl ketene dimer in solution at the re- kane is heptane. The most preferred combination of action mixture. In some circumstances it may be de- cyclic tertiary amine and solvent is methylpyrrolidine sired to add additional solvent during the course of the and methylcyclohexane reaction to avoid the precipitation of the alkyl ketene In the process according to the invention, long- 35 dimer along with the tertiary amine hydrochloride chain carboxylic acid halides with 12 to 22 carbon salt.

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