Polymer Dissolver

The present invention relates to a method and apparatus for dissolving solid polymers.

The object of the present invention is to provide ways and means by which a water-soluble polymer can be dissolved rapidly in water or an aqueous solution, to provide a solution of polymeric flocculating agent, or a solution of polymers for further reaction by addition of further components.

It is known to dissolve solid polymers in water, by finely dividing the solid polymer and introducing it into water while agitating the water bath. It has been found, however, that some polymers such as polyethylene oxide, used in the cellulose industry as an auxiliary flocculating agent, take a very long time to dissolve, which presents a problem to the achievement of rational procedures.

Consequently, there is a need for a method or an apparatus with which the time taken to dissolve not-readily dissolved polymers can be shortened to one tenth or less of the time taken at present.

It has surprisingly now been found possible to satisfy this need by means of the present invention, which is characterized by bringing the solid polymer in a finely particulated state into contact with a jet of dissolving agent at substantially right angles thereto such that the polymer is captured by said jet; and by subsequently projecting the jet of solvent and captured polymer forcibly onto an oblique surface such as to cause the jet to change direction and to break-up.

Further characteristic features of the invention are set forth in applicable claims.

By polymer is meant here and in the following organic polymers such as polyethylene oxides, in particular those of high molecular weight polymers, and polyacrylamide, although not-readily solvable inorganic salts, such as polyaluminum hydroxide-complexes of the chloride and sulphate type are also included. In the present context, the word "polymer" is also meant to include starch and starch derivatives.

The jet of solvent--which is in the main a jet of water--together with the polymer is preferably inclined to a plane which extends substantially at right angles to the oblique surface, such that it impinges on the oblique surface at an angle of 30.degree.-60.degree. thereto, preferably 30.degree.-45.degree..

Subsequent to the jet having struck against the oblique surface and breaking-up as a result thereof, the droplets of solvent-polymer are thrown down against an agitated collecting-dissolving body of solvent.

The invention will now be described in more detail with reference to the accompanying drawing, the sole FIGURE of which illustrates schematically and in cross-section an apparatus for carrying out the method according to the invention.

The reference 1 identifies a cylindrical container, which is provided with a stirrer or agitator 2. Arranged above the container 1 is a supply hopper 3 which is intended to receive solid polymeric material in finely particulated form and to which there is connected a feed screw 4. The exit orifice 6 of the screw 4 is located at a short distance from the top of the container 1. Arranged on one side of the container 1 is a horizontal water-supply pipe 5 which is aligned with a point vertically beneath the exit orifice 6 of the feed screw 4. An inclined plate 7 is located immediately beneath the upper edge of the container 1, in the geometric extension of the pipe 5 through the aforesaid point. A plane extending substantially at right angles to the plate 7 falls through said point and the geometric extension of the water-supply pipe 5. The container 1 is also equipped with a water-intake 8 and an outlet 9 through which the finished product is removed.

In preparing a polymer solution the hopper 3 is filled with a relevant, finely particulated polymer, such as a polyethylene oxide, the polymer particles measure roughly between 0.2 and 1 mm in diameter. The container 1 is filled to a third of its volumetric capacity with water, entering through the water-intake 8, whereafter the agitator or stirrer 2 is set into motion. Water is then ejected through the pipe 5 towards the plate 7 at a force which ensures that it strikes the obliquely positioned plate. Subsequent to trimming the water jet issuing from the pipe 5, so that the jet strikes the plate 7 in the manner intended, the solid polymer is fed down over the water jet by the feed screw 4, so that individual polymer particles are captured by the jet and carried against the obliquely positioned plate 7. As the jet of water and particulate polymer strikes the plate 7, it is initially deflected downwards, and then breaks-up into a large number of droplets, which are thrown obliquely down into the underlying container.

Thus, as a result of this procedure, each polymer particle is thoroughly wetted and separated from each other particle, or at least substantially from each other polymer particle, and brought down into the underlying aqueous solution, in which the discrete polymer particles rapidly dissolve, as experiments have shown to be the case.

The water and polymer are dispensed in quantities adapted to provide a polymer concentration suitable for the field of application in question, normally 0.01-5% by volume, more often 1-4% by volume.