JPS591722B2 - Apparatus for recovering polymers from dispersions in liquid media - Google Patents

Description

[Detailed description of the invention] Latex and coagulation liquid are supplied to an extruder, the polymer solid content is salted out in the extruder, the separated water is separated, and the remaining water that cannot be squeezed out by compression is removed from the vent part. The method of removing by heating evaporation is the method of removing rubber by emulsion polymerization.
It has been conventionally used in ABS polymers and the like.

In the melting or compounding of such rubbers and plastics, it is preferable that there be uniformity of the thermal history during the process, provided that other conditions are equally satisfied. The extruder has an advantage that other types of extruders do not have, including a self-cleaning effect due to the action of mutually meshing screws.

By the way, when compared to a co-rotating meshing twin-screw extruder like this, there is no tightening action at the meshing part when compared to a counter-rotating meshing extruder, so there is a large backflow when the pressure at the tip is high, and the Although it is superior to a single-screw extruder in terms of generating pressure, it is inferior to a twin-screw extruder with opposite meshing. When latex and coagulation liquid are supplied to an extruder, for example, as shown in JP-A No. 54-50587, about 400J on the supply side! /H liquid is fed, whereas only about 1/3 of the elastomer is extruded.

When such an operation is carried out using a co-rotating intermeshing twin-screw extruder (see TEM50) in the literature Plastic Age, February 1977 issue, p. It is determined by the feed, or supply capacity. Describing such a conventional extruder with reference to FIG. 1, it has a barrel 11 and a screw 12, and a latex liquid and a coagulating liquid are supplied in fixed amounts from inlets 15 and 16 from a latex liquid tank 13 and a coagulating liquid tank 14, respectively.
These liquids are stirred between the inlet 16 and the outlet IT to advance the separated grams, and the separated water is discharged to the outside from the outlet IT.

At the tip of the discharge port IT, a kneading block 18 is provided on the screw 12 to prevent the water separated and remaining in the barrel 11 from moving forward with the grams, and in this part the grams are compressed and directed toward the front end 19. At the same time, the remaining water is squeezed out, flows back, and is discharged to the outside from the discharge port 17. In this way, the terax liquid is mechanically separated into grams and water. In such a system, the solid content is high in the part of the two-daying block 18, and therefore the apparent viscosity rises considerably. Since the screw 12 suspends grams in a low viscosity liquid containing a large amount of water, in order to generate the pressure necessary for passing through the cutting block 18 in this part, It is necessary to increase the length of the screw 12, and if it is short, the slurry transport capacity is reduced.

As a modification of FIG. 1, it is possible to insert a mixing block 18A between the inlet 16 and the outlet 17 as shown in FIG. 2 in order to completely mix the coagulated latex liquid. In some cases, the screw 12A must be able to overcome the resistance generated by the cutting block 18A and ensure a predetermined flow rate.

As another example, ABS polymer powder, which is obtained by salting out and dehydrating latex using separate equipment and separating water using a centrifugal dehydrator, usually has a moisture content of 30 to 50%. When extruding with the device shown in the figure, the wet-ABS powder supplied from the inlet 21 is advanced by the screw 12 and heated by the kneading block 18 and the part 22 of the screw 12. Moisture and some of the steam separated by the compression and shear action in the screw 18 flow backward through the screw 22 and flow out through the drain port 17 to the outside.

At this time, the discharge port 17 is equipped with a necessary filter, for example, JP-A-54.
It is effective to use a device such as that shown in No. 270. Note that 23 is the vent port and secondary block 1.
In step 8, the molten polymer gas is discharged. By the way, the separated water and steam coexist with the ABS powder in equilibrium up to the screw 22 and, depending on the case, up to the screw part below the inlet 21, so if the ABS powder is fine, this part is particularly unstable. The powder tends to form into a slurry, making it difficult to compress and advance the ABS powder over the resistance of the seconding block 18, or reducing transport capacity. In order to solve these problems, for example, it is necessary to make the inlet 21 and the portion of the screw 12 below it larger in diameter, which creates a cost problem.

The present invention eliminates such drawbacks, and the object thereof is to provide an apparatus for recovering a polymer from a dispersion in a liquid medium using a co-intermeshing twin-screw extruder and increasing the feed capacity. . The details of the present invention will be explained in the fourth embodiment, which is one embodiment.
The figure and FIG. 5 will be explained.

Reference numeral 31 denotes a starry unit of a co-meshing type twin-screw extruder, and a screw 31A on one side is provided with a driven gear 32 that meshes with a worm just like a worm gear.

Note that 33 is a shaft of the driven gear 32, and 34 is a casing 35 supporting the shaft 33, which is a barrel.

The gear 32 has a tooth profile created by the profile of the screw 31A and is driven by the rotation of the screw 31A, but if necessary, it can be driven externally via the shaft 33 at a predetermined speed synchronized with the rotation of the screw 31A. It's okay. Further, the rotational axes of the screw 31A and the gear 32 do not need to be perpendicular to each other as shown in the figure, but it is sufficient that they are designed so that they can mesh and rotate with the necessary backlash as a normal gear system. Furthermore, the number of gears 32 is not limited to one per screw 31A. By combining the screw 31 and the gear 32 that meshes with it in this way, the screw groove is almost closed by the gear 32 at this part, which eliminates the flaw in the co-rotating twin-screw extruder. As a result, the feeding of low viscosity materials such as slurry can be ensured. For example, such a gear 32 may be installed between the inlet 16 and the discharge port 17 in FIG. 1, between the inlet 16 and the kneading block 18A in FIG. 2, or between the discharge hole 17 and the kneading block 18B in FIG. Furthermore, by providing it between the outlet 17 and the inlet 21 shown in FIG. 3, it is possible to make the feed capacity extremely high.

[Brief explanation of the drawing]

1 to 3 are conventional examples of different aspects;
5 and 5 show one embodiment of the present invention, and FIG. 4 is a sectional view of the main part. 31... Screw, 32... Gear.

Claims (1)

[Claims] 1. A co-rotating intermeshing type twin-screw extruder, which has a gear that meshes with at least one of the two screws and rotates as a result of the rotation, and the gear is sealed around the screw. Apparatus for recovering polymer from a dispersion in a liquid medium that is interlocked to the extent that smooth rotation is allowed to prevent backflow of the material propelled by the screw in the screw groove. 2. An apparatus for recovering a polymer from a dispersion in a liquid medium according to claim 1, characterized in that the gear is driven by the rotation of a screw. 3. An apparatus for recovering a polymer from a dispersion in a liquid medium according to claim 1, characterized in that a gear is actively rotated. 4. An apparatus for recovering a polymer from a dispersion in a liquid medium according to claim 1, characterized in that a gear is installed downstream of the latex liquid supply section and upstream of the kneading block. 5. An apparatus for recovering a polymer from a liquid dispersion according to claims 1 to 3, characterized in that a gear is installed downstream of the large amount of water-containing powder supply section and upstream of the discharge port. .