Patent GB-731871-A (GB)
Title: Drying granular particles of polyvinyl acetate by azeotropic distillation
Inventor: GERMAIN LEO MARCEL
IPC: C08J3/12
Filed: 1953-04-09
Abstract: Residual surface moisture and absorbed water are removed from granules of polyvinyl acetate by suspending the granules in a water-immiscible liquid (an entrainer), which is a non-solvent for the polymer, containing a small amount (0.2 to 0.5 per cent by weight of the granules) of a detergent soluble in the entrainer, and subjecting the mixture to azeotropic distillation whereby the water is distilled off with the entrainer; the vapours are condensed and the entrainer, which separates from the condensate as a separate liquid layer, is returned to the still.  The detergent prevents the coalescence of the granules into lumps.  A petroleum fraction boiling below 150 DEG  C. is preferably used as entrainer.  Suitable detergents are alkyl sulphonates, substituted oxazolines, and condensation products of glycerol or glycols with long chain fatty acids.  It is generally expedient, prior to the azeotropic distillation, to soak the granules for a few minutes in an aqueous medium containing a water-soluble dispersing agent of the type made by condensing sulphonic acids of aromatic hydrocarbons with formaldehyde, and neutralizing to obtain a salt. Specification 662,351, [Group IV (a)], is referred to.ALSO:Residual surface moisture and absorbed water are removed from granules of polyvinyl acetate by suspending the granules in a water-immiscible liquid (an entrainer), which is a non-solvent for the polymer, containing a small amount (0.2 to 0.5 per cent by weight of the granules) of a detergent soluble in the entrainer, and subjecting the mixture to azeotropic distillation whereby the water is distilled off with the entrainer; the vapours are condensed and the entrainer, which separates from the condensate as a separate liquid layer, is returned to the still.  The detergent prevents the coalescence of the granules into lumps.  A petroleum fraction boiling below 150 DEG  C. is preferably used as entrainer.  Suitable detergents are alkyl sulphonates, substituted oxazolines and condensation products of glycerol or glycols with long chain fatty acids.  It is generally expedient, prior to the azeotropic distillation, to soak the granules for a few minutes in an aqueous medium containing a water-soluble dispersing agent of the type made by condensing sulphonic acids of aromatic hydrocarbons with formaldehyde, and neutralizing to obtain a salt.  In an example, a small quantity of the polymerized sodium salts of alkyl naphthalene sulphonic acid was added to an aqueous suspension of freshly-prepared polyvinyl acetate granules.  After ten minutes the mixture was centrifuged, and granules containing 18 per cent total water were obtained.  The granules (172 lb.) were slurried in 350 lb. of a petroleum fraction, which boiled under total reflux at 90 DEG  C., containing 0.35 lb. of a mixture of alkyl sulphonates. The mixture was then subjected to azeotropic distillation for four hours, water being withdrawn from the condensed distillate, and the petroleum oil layer being returned to the still.  The granules obtained as product contained 3 per cent by weight of residual moisture. Specification 662,351 [Group IV (a)], is referred to.