摘要:
A process is described for effectively reducing the residual monomer content of an aqueous polymer dispersion by aftertreatment at atmospheric pressure or above with an initiator system comprising a) a hydroperoxide, hydrogen peroxide or a peracid, and b) an &agr;-hydroxy carboxylic acid, such as tartaric acid, or with a salt thereof.
摘要:
A process is described for reducing the residual monomer content in a liquid solution, mixture, melt, suspension or dispersion of a polymer by postpolymerization with addition of a redox initiator system at a reaction temperature appropriate to it and with an extremely short mixing time of the liquid system in the production reactor by metering—gradually, in portions or continuously—at least one of the redox initiator components required to initiate polymerization of the residual monomers over a period (metering time) which is from about 10 to 250 times the mixing time of the liquid system in said reactor.
摘要:
A process for deodorizing and subsequently cooling dispersions or liquids comprisinga) passing steam through the dispersion or liquid to be cooled and held in a vessel (1), said dispersion or liquid being caused to foam up as a result,b) discharging the foam from the top section of the vessel via a nozzle (5) into an evacuated separation vessel (4), the foam being broken in the process,c) condensing the water vapor formed from the foam in a heat exchanger (8) and removing volatile organic components at the same time, andd) returning the broken foam to the vessel (1),in which the steps a) to d) are performed until the dispersion or liquid has been deodorized to the desired extent, wherein, after completion of the deodorization (in accordance with steps a) to d)), the hot dispersion or liquid is discharged from the bottom section of the vessel (1) through the nozzle (5) into the evacuated separation vessel (4), so that the dispersion or the liquid is cooled, the nozzle (5) and the evacuated separation vessel (4) also being used beforehand for performing step b), wherein the water vapor held in the separation vessel (4) is condensed at the heat exchanger (8) which was also employed beforehand in step c), and wherein the cooled dispersion or liquid is discharged from the bottom of the separation vessel (4).
摘要:
At least one single-stage or multistage stirrer which produces not only a tangential flow component but also an axial flow field is used in a stirred-vessel reactor in connection with the preparation of polymers by liquid phase polymerization.
摘要:
A polymer which contains from 50 to 99.98% by weight of a C1-C12 alkyl (meth)acrylate a), from 0.02 to 10% by weight of a vinylaromatic compound b), from 0 to 10% by weight of an ethylenically unsaturated acid or of an ethylenically unsaturated acid anhydride c), and from 0 to 40% by weight of further monomers d), the percentages by weight being based on the polymer and the polymer being obtainable by polymerizing the monomers a) to d) in at least two stages which differ in their content of vinylaromatic compounds in such a way that the content of vinylaromatic compounds in the vinylaromatics-rich stage is at least 5 times as great as in the low-vinylaromatics stage.
摘要:
A process for reducing the amount of residual monomer in aqueous polymer dispersions operates by aftertreatment with an initiator system essentially comprising a) from 0.001 to 5% by weight, based on the total monomer amount used to prepare the polymer dispersion, a1) of an oxidizing agent R1OOH, where R1 is hydrogen or a C1-C8-alkyl or a C6-C12-aryl group, and/or a2) of a compound which in aqueous medium releases hydrogen peroxide, and b) from 0.005 to 5% by weight, based on the total monomer amount used to prepare the polymer dispersion, of a reducing agent prepared from b1) an aldehyde R2CH═O, where R2 is a C1-C12-alkyl group which may contain functional groups and/or may be olefinically unsaturated, and b2) an inorganic dithionite, and c) catalytic amounts of a polyvalent metal ion which is able to exist in a plurality of valence states.
摘要:
Polymer prepared by anionic polymerization and having a number average molecular weight of from 300,000 to 10,000,000 contain, as components,from 10 to 100% by weight of an ethylenically unsaturated vinyl-aromatic a),from 0 to 90% by weight of an aliphatic diene having two conjugated double bonds b) andfrom 0 to 30% by weight of further ethylenically unsaturated monomers c).
摘要:
The process of the present invention for removing residual volatiles from polymer dispersions by performing first chemical deodorization using an initiator to remove residual monomers and then physical deodorization to remove volatile constituents comprises conducting the chemical deodorization for as long as the decrease in monomers is greater than the increase in secondary components introduced into the dispersion by the initiator, to result reliably in polymer dispersions having a residual volatiles content of less than or equal to 100 ppm.
摘要:
A polymer composed overall of from 50 to 99.98 % by weight of C1-C12 alkyl (meth)acrylate a), from 0.02 to 10 % by weight of a vinylaromatic compound b), from 0 to 10 % by weight of an ethylenically unsaturated acid or of an ehtylenically unsaturated acid anhydride c), and from 0 to 40% by weight of further monomers d), the percentages by weight being based on the polymer and the polymer being obtainable by polymerizing the monomers a) to d) in at least two stages which differ in their content of vinylaromatic compounds in such a way that the content of vinylaromatic compounds in the vinylaromatics-rich stage is at least 5 times as great as in the low-vinylaromatics stage.
摘要:
Binder formulations based on aqueous polymer dispersions having a minimum film-forming temperature of below 10° C. and comprising at least one binder polymer P in the form of an aqueous dispersion comprising at least one anionic emulsifier and at least one nonionic emulsifier.