Method and device for the continuous coagulation of aqueous dispersions of graft rubbers
AssigneeBASF SE
InventorsNorbert Güntherberg, Jürgen Hofmann
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Abstract
A process for the continuous coagulation of aqueous dispersions of graft rubbers suitable for toughening thermoplastics is described. In the process, dispersions are transported through an apparatus having at least one shear element with a slotted stator and a rotating of the rotor within the stator, so that said dispersions are passed radially from the inside to the outside as a result of the rotation of the rotor in the shear element and, during or after passage through the slots of the rotor and stator, are subjected to such strong shearing that they coagulate, resulting in graft rubber coagulums which can be readily worked up even at a solids content of more than 50% by weight of elastomers.
Claims7
A process for the continuous coagulation of aqueous dispersions of graft rubbers (P) which
- a) contain, as soft grafting base (P1), elastomeric polymers and/or copolymers of 1,3-dienes or acrylic esters having a glass transition temperature Tg of less than −10° C. in an amount of from 30 to 85% by weight of the amount of graft rubber (P) and
- b) contain a hard one-shell or multishell graft shell (P2) comprising monomer units which form a thermoplastic polymer or copolymer having a glass transition temperature of more than +50° C. and whose content of acrylonitrile or methacrylonitrile monomer units is from 0 to 45% by weight, and
- c) at least in the last stage of the graft polymerization, were prepared by emulsion polymerization of the monomers for the graft shell (P2) in the presence of the grafting base (P1),
- which process comprises transporting the graft rubber through an apparatus (10) having at least one shear element (13, 14, 15) with a stationary circular slotted stator (13a, 14a, 15a) and a slotted rotor (13b, 14b, 15b) which rotates within the stator and is mounted on a rotatably mounted drive shaft (12), so that the graft rubber dispersion introduced into the apparatus (10) is passed radially from the inside to the outside as a result of the rotation of the rotor (13b, 14b, 15b) in the shear element (13, 14, 15) and, during or after passage through the slots of the rotor (13b, 14b, 15b) and stator (13a, 14a, 15a), is subjected to shearing having a shear velocity in the shear element (13, 14, 15) of from 4 to 30 m/second which is so strong that coagulation of the graft rubber dispersion takes place.
Dependencies are inferred from the claim text.