Patent GB-796556-A (GB)
Title: Process for the production of polyethers
IPC: C07C43/303
Filed: 1956-03-01
Abstract: An a ,b -ethylenically unsaturated ether is reacted with an ortho ester, an acetal or a gem hemi-acetal ester to form an addition compound incorporating at least one molecule of said ether, the compounds boiling at or above the boiling point of the desired addition compound being continuously removed from the reaction zone, and lower boiling compounds being retained in or returned to the reaction zone.  Preferably the concentration within the reaction zone of compounds boiling at or above the boiling point of the addition compound is maintained below 20 per cent by weight.  The removal of the high boilders may be effected by continuously withdrawing from the reaction vessel a stream of the reaction mixture, distilling the mixture under such conditions that the high boilers accumulate in the base of the column, from which they are withdrawn, and the low boilers pass overhead and are returned to the reaction zone. Preferably the volume of low boilers returned should be at least 4 times, preferably at least 10 times, the volume of high boilers separated in the same time. Another method of operation is to introduce the reactants and catalyst into a distillation column operated so that the high boilers accumulate in and are withdrawn from the base of the column while the low boilers remain in the reaction zone. Suitable unsaturated ethers are methyl ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-amyl, isoamyl, dodecyl, octadecyl, stearyl, phenyl, cresyl and benzyl ethers of vinyl, isopropenyl, butenyl, a -phenyl vinyl and b -phenyl vinyl alcohols. b -Methoxyethyl vinyl ether, and dihydropyran or dihydrofuran and their a -methyl derivatives, may also be employed.  Examples of ortho esters are the orthoformates, orthoacetates, orthopropionates, orthobutyrates, orthobenzoates, and orthophenylacetates of alcohols such as methyl, ethyl, propyl, butyl, benzyl or phenylethyl alcohols, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, phenol or cresols. Suitable acetals are dimethyl, diethyl and methyl ethyl acetals, dimethyl butyral or isobutyral, diethyl butyral, dimethyl benzal, dibutyl acetal, butyl methyl acetal, cyclohexanone dimethyl or diethyl acetal, dimethyl propional, the dimethyl acetal of lauraldehyde or stearaldehyde, acetone dimethyl or diethyl acetal, methyl ethyl ketone dimethyl acetal; phenyl acetaldehyde dimethyl acetal, acetophenone dimethyl acetal; the simple and mixed acetals of malonaldehyde, such as the tetramethyl, tetraethyl, ethyl trimethyl, stearyl trimethyl, phenyl triethyl and benzyl trimethyl acetals.  A mixture of an a ,b -ethylenically unsaturated ether and an alcohol may be used to form the acetal in situ.  Gem hemi-acetal esters include a -methoxy ethyl acetate and a -ethoxyethyl propionate.  Good results are obtained when using a 5 to 50 per cent molar excess of the unsaturated ether.  Suitable catalysts are boron trifluoride, zinc chloride, boron trichloride, stannic chloride, titanic chloride, antimony trichloride, bismuth trichloride and sulphuric acid, used in amounts of 0.05 to 0.1 per cent by weight of the total reaction mixture.  Suitable reaction temperatures are between 50 DEG  and 65 DEG  C.  In examples: (1) methanol and methyl vinyl ether are reacted to form dimethyl acetal, the latter is reacted with methyl vinyl ether in the presence of boron trifluoride at 55-65 DEG  C., and a stream of reaction mixture is withdrawn from the reactor and fed to the midpoint of a distillation column in which the high boilers accumulate in the base and the low boiler and catalyst are distilled overhead and fed back to the reactor; 1,1,3,5-tetramethoxyhexane is recovered from the high boilers; (2) similarly, methyl vinyl ether and 3-methoxy-dimethyl butyral give 1,1,3,5-tetramethoxyhexane; (3) methyl vinyl ether and dimethyl acetal give 1,1,3,5,7-pentamethoxy octane; (4) methyl vinyl ether and dimethyl butyral give 1,1,3-trimethoxyhexane; (5) methyl vinyl ether and dimethyl butyral give 1,1,3,5-tetramethoxyoctane.