Abstract: The present invention relates to a process for the forming of a powdered composition of a sulfonated EPDM terpolymer, having less than 1.25 wt. % ENB wherein the powder has a particle size distribution of from about 500 to about 3,000 microns, a water content of less than 2 wt. %, and a sulfonate content of less than 250 meq./100 g polymer.

Abstract: Described herein is an improved process for preparing a polyarylate having a reduced viscosity of from about 0.5 to greater than 1.0 dl/gm which process comprises the following steps:(a) reacting an acid anhydride derived from an acid containing from 2 to 8 carbon atoms with at least one dihydric phenol to form the corresponding diester; and(b) reacting said diester with at least one aromatic dicarboxylic acid at a temperature sufficient to form the polyarylate, wherein the improvement comprises removing residual acid anhydride, after formation of the dihydric phenol diester, so that its concentration is less than about 1500 parts per million. The novel polyarylates produced by the improved process of this invention are melt stable and low in color.

Abstract: A process is disclosed for recovering polymer from a solution of the polymer in a solvent by high temperature phase separation in which a low molecular weight hydrocarbon is added to the solution, the solution and the added hydrocarbon are subjected to a temperature and pressure so that one liquid phase is formed and the pressure is reduced to form three phases, namely, a vapor phase rich in the hydrocarbon, a polymer-lean liquid phase and a polymer-rich liquid phase. The polymer-rich liquid phase is separated from the vapor phase and the polymer-lean liquid phase, and the polymer is then recovered from the polymer-rich liquid phase.

Abstract: This invention relates to a distillation column for removing vinyl chloride monomer or other volatile material from an emulsion, suspension or dispersion containing such material. The apparatus comprises a column in which a series of inverted cones are mounted. The dispersion or emulsion is pulled downwardly over the cones and steam is fed into the column through sparges and flows upwardly against the descending stream of material. The low boiling materials are distilled out and recovered for reuse. The strips emulsion or dispersion are collected at the bottom of the column.

Abstract: A process for recovering a rubbery polymer from a rubber-in-solvent solution by steam-stripping the solution to produce rubber crumb in aqueous phase using a low molecular weight lactone copolymer as stripping aid.

Abstract: In aqueous dispersions on the basis of polyvinyl chloride the content of residual monomers is reduced by the countercurrent method by contacting the rapidly moved surface of the dispersion with secluded intensely mixed gas atmospheres in several successive chambers. To carry out the process a device is used which permits to obtain under mild conditions residual monomer contents of 10 ppm and therebelow.

Abstract: Latex is shear coagulated to form a paste, the paste heated and sheared to form a desired crumb; the crumb is mechanically dewatered and ground to a desired particle size. Relatively low energy consumption is a feature of the process.

Abstract: The present invention relates to a process for the reduction of the vinyl chloride content of aqueous dispersions of vinyl chloride polymers and copolymers by counter-current stripping with steam in a perforated plate column, by (1) adjusting the amount of steam introduced at the bottom of the column in such relation to the perforated area of an individual plate that the pressure drop across one plate gives a steam space between two adjacent plates of not more than 50 mm in height, such that the steam space is established just underneath the upper perforated plate and whereby the liquid layer is maintained above the lower perforated plate, and the liquid by bubbling steam therethrough, flushes the wall (surfaces) of the column in the steam space and said perforated plates to become clear of polymer particles; (2) the amount of dispersion fed to the top of the column and the amount of outgoing, stripped dispersion are adjusted in such relation to each other that at any time, the liquid layer is maintained well

Abstract: The invention relates to the production of vinyl dispersion or paste resins by means of the emulsion polymerization process and the recovery of the resins from the polymer latices produced thereby. In the process, the polymer latex is first carefully coagulated to yield a fast filtering sludge, the sludge is passed to a pressure filter to separate a high solids, friable polymer wetcake from the serum, the wetcake is rinsed with proper agents to neutralize the same and remove undesirable residues, pressure in the filter is applied to the rinsed wetcake to increase the solids content thereof, the wetcake is then broken into particles and friable agglomerates, and thereafter said particles and agglomerates are dried and ground to proper size in one step in a fluid energy mill. Thus the spray drying and the subsequent harsh grinding steps are eliminated producing a superior product for plastisols.

Abstract: A method of continuously treating an aqueous latex of a synthetic polymer which contains unreacted residual monomer from the polymerization reaction used for the production of the polymer, which method comprises feeding the aqueous latex as a spray into a vessel defining a chamber so that all or a substantial quantity of the droplets of spray avoid contact with the side wall of the chamber, and contacting the falling spray with steam flowing counter-current thereto whereby residual monomer is removed with the flow of steam leaving the chamber. Apparatus for carrying out the method is also claimed. The method is advantageously employed for the removal of residual vinyl chloride monomer from a latex of a vinyl chloride polymer.

Abstract: In an improved process for preparing discrete particles from solution polymers in which water and neutralizing agent are added to the polymer to form a suspension, the organic solvent is removed therefrom, and the particles are collected by filtration, washing and drying, the suspension is formed by co-feeding the flowable polymer and the aqueous phase containing neutralizing agent into a reactor vessel under specified conditions; stirring the reactants; and discharging the resultant suspension from the reactor vessel, with all steps being carried out in a continuous manner. In one embodiment of the process, additional neutralizing agent, which is preferably sodium hydroxide, is added to the suspension during removal of the solvent therefrom.

Abstract: Unreacted residual monomer is removed from an aqueous slurry of a vinyl chloride polymerizate by a method, according to which the monomer-containing aqueous slurry continuously fed to a plate column from its top runs down by way of a cyclone-type mist separator and through a plurality of perforated plates, coming into counter-current contact with steam which is blown into the column from its bottom and ascends through the same perforated plates, to dissipate the monomer in the form of vapors, and the steam carrying the dissipated monomer vapors having entered the mist separator is subjected to mist separation and heat exchange with the slurry fed, and the resulting steam is discharged out of the column, followed by condensation to recover the monomer. The slurry having reached the bottom of the column is transferred to a flush tank where it is quenched to generate steam which is then blown into the column for recycling.

Abstract: A procedure is disclosed for the removal of alkali metal halide from phosphazene rubber crumb swollen in water. The crumb is pressed whereby a large proportion of the alkali halide is discharged from the crumb.

Abstract: An improved method is provided for the recovery of a friable crumb-form of resinous compositions comprising polyphenylene ethers. The method comprises polymerization of a monohydric phenol, removal of the catalyst employed, heating, I.V. stabilization, optionally, capping, and product recovery.

Abstract: A continuous process for simultaneously drying, thickening and increasing the flowability and processibility of polycarbonate powders is disclosed. The powders are fed to a tubular drier equipped with a mechanical stirrer in which they are fluidized with the aid of a stream of heated inert gas or vapor flowing counter-currently to the powders.

Abstract: Process for the polymerization of vinyl chloride in aqueous suspension in the presence of dialkyl peroxydicarbonates in which the polymer is treated with a monobasic hydroxide at the end of polymerization and before the unreacted vinyl chloride is removed. The alkaline treatment is advantageously applied to polymers that are subsequently subjected to steam stripping.The treatment improves the initial heat stability of vinyl chloride polymers.

Abstract: The apparatus proposed herein relates to mass-exchange apparatus for isolating polymers from hydrocarbon solutions. The apparatus comprises a vertical column provided with a device for producing polymer crumb and an aqueous suspension, a device for feeding live steam, and contact trays which divide the column into compartments as for height. The device for producing polymer crumb and aqueous suspension is accommodated in the top portion of the vertical column and is essentially a chamber established on at least one side by the overflow baffle. The chamber accommodates the water supply nozzle and a conventional injector-type polymer crumb former. Such an arrangement of the device for polymer crumb formation and producing aqueous suspension results in a simplified construction of the entire apparatus and diminished overall dimensions thereof, as well as to a simpler attendance of the apparatus.

Abstract: In a process for removing monomeric impurities from an aqueous dispersion of homopolymers or copolymers of vinyl chloride having a surface tension below 60 dyn/cm. by treatment with steam while avoiding foam formation by a rapid lowering of the pressure at high flow velocities, the improvement which comprises:(a) continuously mixing said dispersion in a flow pipe with steam at a steam pressure of 800-4660 millibars for an average residence time of about 0.01-5 seconds;(b) continuously passing the resultant admixture from said flow pipe at a velocity of at least 30 meters per second directly to a degasification vessel having a pressure of 133-660 millibars; and(c) continuously recovering a polymer product containing less than 20 p.p.m. residual monomer impurities therefrom.

Abstract: The unreacted gaseous vinyl chloride monomer still remaining in a polymerization reactor from which the polymerizate has been removed can be discharged by blowing steam into the reactor from its top so that the gaseous monomer is pushed downward and moved out from the bottom of the reactor, followed by a conventional treatment for condensation. This method of discharge serves to put the reactor open to the ambient atmosphere without the emission of the unreacted monomer and, as such, solve the problems of the workers' health and environmental pollution.

Abstract: Vinyl chloride is removed from an aqueous dispersion that contains 5%-50% by weight of a vinyl chloride resin and 1000-15,000 ppm of vinyl chloride by a process in which the aqueous dispersion is contacted first with steam and vinyl acetate to remove at least 90% of the vinyl chloride from it and then, after a short conditioning period, with steam to reduce its monomer content to less than 10 ppm.

Abstract: In the process for steam-stripping residual monomer from an aqueous polymer dispersion comprising injecting steam into an aqueous polymer dispersion containing residual monomers and the customary amounts of emulsifiers and/or protective colloids, said dispersion having a solids content of from 15% to 55% by weight with simultaneous evacuation of the gas space above the dispersion whereby said gas space is maintained at a subatmospheric pressure and said residual monomers are volatilized, the improvement consisting of injecting a sufficient volume of steam into said aqueous polymer dispersion whereby from 5% to 50% by weight of the injected steam passes through said dispersion uncondensed, thereby substantially preventing formation of foam above said dispersion.

Abstract: Solid polycarbonate is recovered continuously from solutions thereof in organic solvents by a process consisting of:(a) subdividing the polycarbonate solution by steam (water vapor) at either sonic or ultra-sonic speed by means of a De Laval type nozzle;(b) conveying the dispersion thus obtained into a tubular heat exchanger having an increasing cross-section, preferably spirally-shaped or with elbow stretches having a thermal exchange coefficient of 500-1500 Kcal/h.m.sup.2 .degree.C., in which the heat dispersion is kept at 100.degree.-140.degree. C. for periods of time comprised between 0.05 and 5 seconds;(c) separating the solid from the vapors in a cyclone;(d) drying of the solid in a water vapor fluid bed.

Abstract: Process for the removal of unconverted monomers from a copolymer of acrylonitrile with one or more monomers copolymerizable therewith by a treatment with steam whereina latex of said copolymer obtained from a polymerization stage is subjected to a continuous treatment with steam comprisingatomizing said latex to form a gas-liquid-mixture consisting of latex droplets dispersed in a gasphase and passing the said gas-liquid-mixture through a gas-liquid contacting device,the gasphase is separated from the mixture,this gasphase is at least partially condensed,the condensate is separated into an organic and an aqueous phase,the thus separated organic phase is returned to the polymerization stage, andthe latex is further processed.This process is especially suitable to remove non-converted monomers from latices of copolymers of (.alpha.-methyl) styrene and acrylonitrile or graft copolymers thereof on a rubbery polymer.

Abstract: A process for the preparation of chlorinated aliphatic polymers wherein chlorine-free polymers are chlorinated by using gaseous chlorine in chlorinated hydrocarbons as solvents and the chlorinated aliphatic polymers are recovered from the chlorinating solution by steam distillation in which process from 15 to 50% by weight of a lacquer resin is added to the chlorinating solution before steam distillation. The chlorinated polymers contain less residual solvent.

Abstract: The present invention relates to an improvement in a process for polymerization of polyvinyl chloride, particularly in a suspension polymerization process which provides for removal of residual vinyl chloride monomer, such as by employing a step in which the PVC suspension resin slurry is passed through a column in which it is subjected to a combination of stream and pressure/vacuum conditions. In the improved process of the present invention, the PVC suspension resin slurry feed to the stripping column is first passed through the cold feed side of a spiral hat exchanger, and the PVC suspension slurry outflow from the stripping column is passed through the hot feed side of the heat exchanger, whereby the feed stream to the stripping column acts as a cooling medium for the outlet stream from the stripping column, and the outlet stream from the stripping column serves as a preheating medium for the feed stream.

Abstract: In order to remove monomer residues from an acrylonitrile polymer which has been produced in the form of particles, for the purpose of reducing the residual monomer content to virtually negligible values, the particles are subjected to a removal process which includes raising the temperature of the particles to a value between the glass transition temperature and the melting point of the polymer.

Abstract: Process for removing the residual vinyl chloride monomer present after polymerisation in vinyl chloride polymers in the form of an aqueous dispersion which is heated to a temperature at least equal to the glass transition temperature of the polymer and subjected to stripping by an inert fluid while being maintained at a temperature at least equal to the glass transition temperature of the polymer.

Abstract: Styrene and acrylic acid or methacrylic acid copolymers can be devolatilized at a temperature above 200.degree. C. and below the decomposition temperature of the copolymer under vacuum in the presence of a monohydric compound such as alcohol or water without significant increase in molecular weight or the formation of undesirable and insoluble gels.

Abstract: A method for stripping residual monomer from acrylonitrile copolymers which have been prepared in aqueous suspension by steam stripping acrylonitrile monomer from the suspension at a temperature of from 100.degree. C. up to 135.degree. C. and at a pressure of from about 5 to 30 psig is described.

Abstract: A dispersion or solution of a polymer or a coaguable protein (such as blood) and a coagulating or desolventizing agent for the dispersion or solution (such as an electrolyte or steam) are introduced into a localized turbulent zone of liquid, preferably formed at the tip of a high shear agitator blade operating at a tip speed of 1500 feet per minute or above, where they mix under conditions of highly efficient heat and mass transfer to produce a flowable slurry of polymer or protein particles. When the dispersion is a polymeric latex, anionic surfactant beyond that normally present in the latex is also introduced to the turbulent zone.

Abstract: An apparatus for reducing the vinyl chloride monomer content of polyvinyl chloride resins suspended as a slurry in an aqueous medium. The polyvinyl chloride-water slurry as produced in a conventional suspension resin autoclave, or a resin-water slurry prepared subsequent to suspension polymerization, is placed in a vessel and heated to a suitable temperature for removal of vinyl chloride monomer from the resin. In this operation, the polyvinyl chloride-water slurry is agitated in a vessel and steam is injected directly into the slurry to rapidly heat the slurry up to a minimum temperature of at least about 180.degree. F. The slurry is cooled immediately, or optionally it can be maintained for a period of time at the selected maximum temperature and then rapidly cooled by applying vacuum to the vessel and condensing the vapor phase removed from the vessel. Dried polyvinyl chloride resin produced by this process has been found to have a vinyl chloride monomer content below a detectable limit of 0.5 ppm.

Abstract: Volatile substances are removed from styrene resin by introducing steam into styrene resin suspended in hot water, while agitating the suspension, to maintain the suspension at a temperature of 120.degree. to 150.degree. C. and a pressure of 1.4 to 4 kg/cm.sup.2 G whereby to remove the volatile substances.

Abstract: Monomeric matter is removed from an aqueous dispersion of a polymer containing at least 50 weight % of polymerized vinyl chloride. To this end, the dispersion is introduced into the upper portion of a column provided with sieve plates and contacted therein for 10 seconds up to 20 minutes, under 600 up to 1200 mm Hg, with hot steam at 100.degree. up to 150.degree. C. flowing countercurrently with respect to the dispersion. The polymer dispersion so treated is removed from the column base portion; and a vaporous matter mixture issuing at the head of the column is condensed stagewise so as to recover an aqueous phase and the monomeric matter.

Abstract: An improved process for reducing the amount of residual vinyl chloride monomer in polyvinyl chloride latex to acceptable levels is provided. Carefully controlled sparging and defoaming removes the monomer without affecting physical properties of the latex.

Abstract: Polymer dispersions are subject to a spray treatment to reduce the monomer content thereof. The dispersions are sprayed against the wall of the vessel by means of at least one spray nozzle.The residual monomer content of polymer dispersions is further reduced by spraying them in at least two series connected vessels, conducting the escaping gaseous constituents in one direction and the dispersion in opposite direction from one vessel to the next. The process is little liable to troubles and ensures a very effective monomer removal without thermal damage of the polymer.

Abstract: In a process wherein an acrylonitrile polymerization slurry made up of polymer solids, unreacted monomers and water is passed downward through a column containing a plurality of perforated trays for the purpose of removing unreacted monomers from the slurry, the improvement comprising: sequentially applying sprays of water to that portion of the inner wall of the column above each of the trays, with each such wall portion being sprayed by at least two sprays positioned to substantially cover that wall portion and with the sprays being operated intermittently in such a sequence that only one of the sprays is in operation at a given time and all sprays in the column are operated within a period of less than about 15 minutes, preferably less than five minutes. In the sequence, each spray is operated for a time period of at least about five seconds.

Abstract: An aqueous polymer dispersion containing approximately 1 to 60 weight % of solid polymer particles with an average size of 20 to 500 microns and 5000 to 15,000 ppm of monomer(s), is freed from monomeric material. More specifically, the aqueous dispersion is preheated to 60.degree. to 90.degree. C. and introduced continuously into an upper portion of a column accommodating a plurality of apertured trays disposed one above another of which each has at least one eccentric aqueous dispersion descent shaft. The aqueous dispersion is introduced at a rate of a 5 to 35 m.sup.3 per m.sup.2 of tray area per hour and contacted countercurrently with steam at 80.degree. to 150.degree. C., under 0.5 to 5 bars, and in a proportion of 30 to 100 kg of steam per m.sup.3 of dispersion, for a mean period of 1 to 30 minutes; the pressure drop for steam ascending through one tray in the column being lower than that which would occur upon the undesirable passage of steam through one of the said shafts.

Abstract: A process for the preparation of a chlorinated aliphatic polymer which comprises chlorinating a chlorine-free aliphatic polymer in a chlorinated hydrocarbon solvent using gaseous chlorine as the chlorinating agent; adding from 2 to 25% by weight, based on the chlorinated polymer, of at least one plasticizer and/or at least one lacquer resin, to the chlorination solution; and isolating the chlorinated aliphatic polymer from the chlorination solution by steam distillation.

Abstract: Residual unreacted monomer, such as vinyl chloride monomer, is removed from an aqueous latex of polymer, such as polyvinyl chloride, by allowing the latex to flow as a thin liquid film down the inner surface of a substantially vertical column at subatmospheric pressure countercurrent to an ascending flow of steam. If desired, packing may be inserted in the column to enhance the removal of residual monomer.

Abstract: An apparatus and method for the continuous or semi-continuous removal of unreacted monomers from polymer suspension slurrys or latices to produce polymers with the least possible distribution of heat history.A polymer suspension liquor or latex is supplied to a vessel having open topped compartments positioned on a vertical shaft for rotation. A feed inlet for the polymer suspension liquor is mounted on the shaft to permit introduction of the polymer into each of the open topped compartments. A steam and/or inert gas is introduced at the bottom portion of each compartment to strip a monomer from the polymer.

Abstract: An apparatus and process for removing undesired monomers and oligomers from polyamide melt at subatmospheric pressure by passing steam through the melt to absorb the undesired components and carry them away. Various constructions are disclosed for vigorously intermixing the gas with the melt in which the gas is passed through a foraminous surface over which a thin film of melt flows, and a rotating agitator, spaced less than 50 mm from the surface, mixes the gas with the melt film. In a preferred form of the invention the rotating shaft comprising the agitator carries screw threads and serves as a conveyor for discharging treated melt from the pressure vessel in which the process is carried out.

Abstract: This process relates to the preparation of stable aqueous latices from solvent dispersions of elastomers and other high polymer compositions. The process in common with that of earlier applications is characterized, inter alia, by the establishment of a flow of gas comprising steam as a continuous phase into which an emulsion of a cement of the polymer is dispersed as an aerosol of latex droplets in a solvent-vapor continuum, followed by coalescence of the latex droplets and separation of the resulting coalesced liquid phase from the resulting solvent-vapor phase.In the present disclosure, special provisions are made for generating from recovered water saturated with solvent (and possibly contaminated with carry-over of macromolecular material and/or emulsifier and/or latex droplets) the gas comprising steam employed in forming the initial continous phase.

Abstract: Isolating thermoplastic or thermoelastic polymers in the form of a powder of limited water and precipitant content and uniform grain size from their aqueous dispersions wherein(i) a polymer dispersion and a precipitant are intensively mixed at an uptake of mechanical energy of 0.2 to 0.6 KWh per m.sup.3 of dispersion thus causing high turbulence,(ii) the polymer is precipitated while in this state of high turbulence at a temperature below the sintering temperature of the polymer,(iii) the precipitated polymer particles are agglomerated and hardened while still in contact with the aqueous liquor either in one or in several stages, and(iv) the aqueous liquor and agglomerated polymer particles are separated from one another.

Abstract: A process for the continuous production of indene resins comprising the steps of continuously pre-heating an indene-containing hydrocarbon mixture, continuously adding a boron trifluoride-adduct catalyst and the pre-heated indene-containing mixture to a reaction tube, continuously isothermally reacting the indene-containing mixture with the catalyst at the temperature of the pre-heated mixture to form an indene-containing resin, continuously decomposing the catalyst, and continuously separating the indene-containing resin from the decomposed catalyst and unreacted substances.

Abstract: A process for sulfonating polymers which are prepared by solution polymerization using a Friedel-Crafts or Ziegler-type catalyst is disclosed. The reactor effluent containing polymer, unreacted light monomers, diluent-solvent and active catalyst is first treated to remove substantially all unreacted light monomer, e.g. by flashing. The effluent is then treated with a sulfonating agent (e.g. acetyl sulfate and acetic acid) which simultaneously deactivates catalyst. Thereafter, the sulfonated polymer is neutralized, e.g. by exposure to metal salts, organic amines, etc., and subjected to normal finishing operations, e.g. deashing, steam stripping, stabilizing and drying.

Abstract: Polypropylene is recovered from a dilute solution in spent organic polymerization medium in a process comprising: (1) partial steam stripping of volatile components from said medium to form an aqueous phase and a concentrated, water-insoluble phase containing the soluble polypropylene: (2) separating said concentrated water-insoluble phase and leading it into an evaporator: (3) evaporating the remaining volatile components from the separated said water-insoluble phase leaving fluidized polypropylene which when drawn off and solidified is suitable for commercial use.

Abstract: A method for reducing the vinyl chloride monomer content of polyvinyl chloride resins suspended as a slurry in an aqueous medium. The polyvinyl chloride-water slurry as produced in a conventional suspension resin autoclave, or a resin-water slurry prepared subsequent to suspension polymerization, is placed in a vessel and heated to a suitable temperature for removal of vinyl chloride monomer from the resin. In this operation, the polyvinyl chloride-water slurry is agitated in a vessel and steam is injected directly into the slurry to rapidly heat the slurry up to a minimum temperature of at least about 180.degree. F. The slurry is cooled immediately, or optionally it can be maintained for a period of time at the selected maximum temperature and then rapidly cooled by applying vacuum to the vessel and condensing the vapor phase removed from the vessel. Dried polyvinyl chloride resin produced by this process has been found to have a vinyl chloride monomer content below a detectable limit of 0.5 ppm.

Abstract: Sulfur vulcanizable elastomers comprise interpolymers of a major proportion of (a) one or more olefinic or haloolefinic hydrocarbons; (b) one or more esters of acrylic acid in which the acyclic or alicyclic radical moiety of the ester is free of olefinic unsaturation; and (c) a minor proportion, of about 0.10 to 10 mol percent of the total monomers present in the interpolymer, of an acyclic conjugated diolefin, prepared with a catalyst system comprising a Lewis acid, a vanadium compound and a source of free-radicals such as an organic peroxide. The polymer chain consists of segments of alternating olefin and acrylic ester monomer units of variable length interconnected by randomly distributed diolefin units and the sum of the olefin and diolefin monomers in moles is substantially equal to the sum of the acrylic esters in moles present in the interpolymer.

Abstract: A composition which comprises a mixture of (a) an unvulcanized elastomeric block copolymer having the general configuration A -- B -- A, where A is a non-elastomeric styrene polymer block and B is an elastomeric diene polymer block of 1,3-butadiene and (b) a tackifying resin containing carbon-to-carbon unsaturation, characterized by having a softening point of about 60.degree. C. to about 110.degree. C. and comprising about 30 to about 55 weight percent units derived from piperylene, about 20 to about 45 weight percent units derived from 2-methyl-2-butene, about 15 to about 30 weight percent units derived from dicyclopentadiene and about 20 to about 35 weight percent units derived from .alpha.-methyl styrene. The composition has particular utility as a pressure-sensitive adhesive.

Abstract: in accordance with the invention, a method of continuously treating an aqueous latex of a synthetic polymer contaminated with unreacted residual monomer used in the production of the polymer, comprises feeding the aqueous latex as a spray into a vessel defining a chamber so that all or a substantial quantity of the droplets of spray avoid contact with the side wall of the chamber, and contacting the falling spray with steam flowing counter-current thereto, whereby residual monomer is separated from the latex and is removed with the flow of steam leaving the chamber. Preferably at least 80% by weight of the droplets of spray avoid contact with the side wall of the chamber. Apparatus which includes the vessel and means to provide a flow of steam up the chamber to contact the falling spray is also disclosed.In this method all or most of the spray falls directly to the bottom of the chamber without touching the side wall of the chamber. In this way foaming difficulties are avoided.