DE1226308B - Device for the continuous separation of cis-1,4-polybutadiene - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C08d

German class: 39 c - 25/05

Number:
File number:
Registration date:
Display day:

M 52593 IV d / 39 c
April 21, 1962
October 6, 1966

The invention relates to a device for the continuous separation of the solvent from a cis-1,4-polybutadiene solution with recovery of the solvent.

It is known that the polybutadiene solution coming from the polymerization plant is at room temperature a liquid mass with a viscosity of the order of 10,000 cP that is highly sticky and is thread-forming, this viscosity value corresponds to a solution with an intrinsic viscosity of 2.05, a molecular weight of 146,000 and a dry residue of 15%. The viscosity was at 20 ° C. with a Broockfield viscometer equipped with a hat rotor rotating at 50 rpm was determined.

It is known that the viscosity of such masses changes with the molecular weight and the temperature; above all, it changes considerably with concentration, and the material is already taking that Property of a gummy mass when the dry residue is of the order of about 30%.

It is already a work-up process for polymer solutions known in which a pre-concentrated polymer solution in a heated dry extruder is freed from the last residues of solvent under vacuum. This is where the concentration takes place the polymer solution in two stages, namely initially at temperatures above the Melting point of the polymer and then at a lower temperature in vacuo. The second process step, which is carried out to protect the polymer, can only be used successfully with such Perform polymers whose viscosity is still relatively low even after concentration is. In the separation of cis-1,4-polybutadiene occur in the removal of the solvent direct evaporation using this known method using conventional equipment a Number of difficulties, particularly related the heat transfer, the mixing of the mass and the renewal of the evaporation surface. As a result of high viscosity and the rubbery character that the cis-1,4-polybutadiene in relatively concentrated Solution assumes an effective evaporation of the solvent in the known devices not reach.

The invention is based on the object of eliminating the aforementioned difficulties. This is achieved by means of the device according to the invention for the continuous separation of cis-1,4-polybutadiene in two successive stages from a device for the continuous separation
of cis-1,4-polybutadiene

Applicant:

MONTECATINI Societä Generale per l'Industria Mineraria e Chimica, Milan (Italy)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald,

Dr.-Ing. Th. Meyer

and Dipl.-Chem. Dr. rer. nat. J. F. Fues,

Patent attorneys, Cologne 1, Deichmannhaus

Named as inventor:

Idisoro Ronzoni,

Arturo Werthhammer, Milan (Italy)

Claimed priority:

Italy April 24, 1961 (7660)

Solution in which the polymerization has been carried out and which is characterized by a preheater, which consists essentially of a right-angled tub, along the bottom of which largest length extension two screw conveyors are arranged, which in their middle part one into the other intervene and the thread pitch of which is lower in the last part than in the first part, as well as through one Conveyor funnel and a drying extruder, consisting of a cylindrical container, inside a screw conveyor with constant thread pitch in all parts for transporting the solution from the pre-concentrator is arranged to the extrusion head from which the dried polymer is squeezed.

The device according to the invention is used to evaporate the solvent from the polymer solution carried out in two separate, consecutive steps. In the first stage, in the solution is relatively liquid, the heat of evaporation of the solution by conduction over heating surfaces supplied, and the evaporation area is enlarged and continuously renewed by the Solution is spread on a series of rotating metal surfaces that are partially immersed in the solution; while in the second stage in which the solution assumed the properties of a rubbery mass has (for polymer concentrations of more than

609 669/431

3 4

50 ° / o) and the heat transfer is therefore difficult. During this passage the thread is The heating of the mass is achieved by the action of the snails and having a threefold effect acts in the mass through an extrusion mechanism

The mechanical energy introduced was partly in _{a) the further transfer of the loos through the pre} .

Warm is transferred. The 5 direction can be used in both stages

Removal of the solvent can be facilitated, _{b) the constant} renewal of the solution

if you put the affected part of the device to _{the heating walls of the tub u} * _d

/ ^m T -α ν ■ u < τ ·· «* · i. c) at their upper part, which leaves the solution, the

. Fil device according to the invention can be _BM ^ ^ _{n Lös hic} ^g _{ht with e} ' _iner

a gleichmaßige and continuous heating of the _"big SEN evaporation surface,

already relatively concentrated rubbery mass r β

reach so that the solvent is evenly The tub is completely closed and insulated and

and can be driven out completely. This can be done via a funnel with nozzle 6, which is connected to

a considerable advantage over the previously associated with a capacitor not shown,

known working methods and devices are kept under vacuum at 15,

which the heating by simple heat transfer- The solution that leaves the pre-concentrator and

supply, but not, as in the case of the inventive concept, the properties of a rubber-like mass

direction, by converting mechanical energy, is via a feed hopper 7, which is closed

is made. It is surprising that through sen and is isolated from any condensation

To prevent use of the device according to the invention with a 20 of solvent vapors, and with

conveyor provided with a constant thread pitch is connected to the condenser via a connector 6 '

this even heating of the mass is screwed to the drying extruder 8, which consists of a

by converting mechanical energy achieved screw extruder 9, the length of which is approximately

and the previous disadvantages of 50 times the diameter,

Processing of cis-1,4-polybutadiene switched off in the upper part of the extruder cylinder

could become. a right-angled in the direction of the screw axis

On the basis of the drawing, the opening 10 according to the invention is approximately three square meters in length Device below, for example, closer tel the total length of the cylinder. This opening explained. It is closed by a discharge funnel 11, which shows

1 shows a longitudinal section through an embodiment 30 two inspection openings (not shown) for observation

form of the invention and respect for the operation of the machine

F i g. 2 shows a cross-section through an invention held under vacuum via the nozzle 6 ″,

proper device. The cylinder 8 carries an outer jacket 12 for

The preconcentrator (Fig. 1 and 2) consists in the circulation of heating fluid in three zones

essentially of a right-angled tub 1, at 35 is divided.

whose correspondingly shaped bottom has two conveyor The screw 9 of the extruder has constant

worms 2, 2 along the longest extension and a profile with a constant shape, whereby

are ordered. a strong mechanical effect on the

Each screw consists of a shaft 3, which can be reached around traded polymers. the

its periphery around a thread with a very 40 screw is also pierced along the axis,

low slope and large surface, which allows the circulation of heating fluid,

almost forms a series of slices. The two screws The solution from the pre-concentrator enters the

ken interlock in their middle part, rotary extruder and is through the whole cylinder

ren in the opposite direction and point to the extrusion head 13 transported. While the-

through a self-cleaning effect. Those in the polymer can still do 45 this run

The last part 4 of the snails extends with existing amounts of solvent still evaporating,

unchanged diameter from the right-angled and the vapors are through the collecting funnel

gen tub out in a section with double 11 and the nozzle 6 "fed to the condenser,

circular cross-section in which the screws are located at the outlet end of the extruder

completely closed. 50 extrusion head 13 with a right-angled opening

In this last part 4 (FIG. 1) the con of 30 × 2.5 mm, and the dried polymer is

constant pitch of the worm thread less than pressed out in the form of a band,

the also constant slope of the first part. In the following, the data that are available at

The tub 1 has over the part that is caused by the operation of the device described above Snails ingested resulted in a coat 5 to 55, for example given: Circulation of heating fluid, which is divided into three zones; furthermore, the shafts 3 also have the pre-concentrator Screws 2 have a hole for the inner circulation of the rotation of the two screws .. 6 rpm (in the Heat exchange fluid. contrary

The 60th direction coming from the polymerization plant)

Polymer solution flows through a jacket tube 5 ', in which the vapor pressure in the heating chamber is 2.9 kg / cm ²

it can be heated, and in the preheater at the residence time of the solution 14 minutes

Beginning of the part with a right-angled cross-section. Vacuum 500 mm Hg

The inflow of the solution is adjusted so that the solution supplied 100 kg / hour

Screw shaft 3 just remains covered. 65 Concentration of the supplied

As a result of the rotation of the screws, the solution becomes 8%>

Solution transported through the whole tub and in concentration of the discharged

the opposite side emptied. Solution 56.4%

Claims (1)

5 6 Dry extruder (1) consists, at the bottom along the largest Rotation of the screw 20 rpm linear expansion two conveyor screws (2, 2) Steam pressure in the heating jacket 2.9 kg / cm ² are arranged, which in their middle part Dwell time of 4 minutes intervene and their thread pitch in Vacuum 500 mm Hg 5 last part is less than the first part, as well Concentration during the supply. 56.4% through a feed hopper (7) and a drying Concentration during discharge .. 99% kenextruder (8), consisting of a cylindrical Container (12), inside of which a conveying Claim: the screw (9 ') with constant thread pitch ίο in all parts for transporting the solution from Device for the continuous separation of the preconcentrator for the extrusion head (13) arranged by cis-1,4-polybutadiene in two on top of each other, from which the dried polymer in the following stages from the solution in which the poly is pressed,
merization has been carried out, characterized by a preheater, which in the 15 publications considered: essentially from a rectangular tub British Patent No. 824 240. 1 sheet of drawings 609 669/431 9.66 © Bulldesdruckerei Berlin