JPS6012327B2 - Processing method for vinyl chloride polymer slurry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and recovering unreacted monomers from a vinyl chloride polymer slurry obtained by suspension polymerization.

Vinyl chloride polymers produced by the suspension polymerization method are porous granular materials, so they retain adsorbed monopolymers in their micropores, and usually contain several thousand legs immediately after polymerization. There is.

The vinyl chloride polymer slurry is generally dehydrated using a centrifugal separator, supplied to a ventilation dryer, and dehydrated and dried to produce a product, but according to this method, a large amount of monomer is This not only significantly worsens the working environment but also reduces the quality of the product.

On the other hand, effectively recovering the monomers contained in the slurry after polymerization is not only effective in improving the working environment, but also provides excellent benefits such as improving product quality. Various studies have been made regarding this, but nothing that is technically satisfactory has yet been found.

For example, a method has been adopted in which a water-containing slurry after centrifugal dehydration is forcibly heated in a dryer with rotary blades to produce the monomer contained therein, but there is a risk of air entering through the seal mechanism of the rotating part. There are also problems with monomer recovery.

The present inventors studied how to effectively eliminate monomers in polymers and to recover them advantageously, and as a result, they completed the method of the present invention.

That is, the present invention is characterized in that a pinyl chloride polymer slurry obtained by suspension polymerization is brought into direct contact with steam in a flooded tray column to separate and recover the reactive monomers in the slurry. This is a method for treating vinyl chloride polymer slurry.

The method of the present invention will be explained as follows with reference to the drawings.

In FIG. 1, a slurry to be treated obtained by suspension polymerization is supplied from a tank 1 to a plate column 3 via a pump 2.

The shelves* are equipped with partition plates made of perforated plates, etc., and steam is blown into them through piping 4 from the bottom of the tower. The inside of the column is maintained at reduced pressure by an ejector 6, and the monomer emitted from the slurry passes through a condenser 5, reaches a separator 7, and is recovered through a pipe 8.

The slurry is sent from the falling part to a centrifugal separator (not shown) via piping 9. In the pinyl chloride polymer slurry that is the subject of the method of the present invention, some of the residual monomers therein are usually adsorbed onto the polymer and the rest are dissolved in water.

Therefore, in order to recover these monomers, it is necessary to heat the slurry directly with steam, preferably at normal pressure to reduced pressure, particularly preferably under reduced pressure, and to maintain the liquid temperature as high as possible for a long time. The temperature is preferably maintained at 80°C.
~100 qo, particularly preferably from 90 to 100 pm, and the treatment time is preferably from 10 to 30 minutes, particularly from 10 to 15 minutes.

Excessively high temperature or long-time treatment may cause a change in the quality of the polymer, and low temperature or too short treatment time may not produce sufficient treatment effects. The liquid-filled plate column used in the method of the present invention is a column that is equipped with one or more shelves inside, and is filled with the liquid in the system without back-mixing. In the method of the present invention, the number of shelves can be arbitrarily set to one or more than two, but generally the greater the number of shelves, the better the effect of single island removal.

In addition, in the method of the present invention, back mixing can be prevented.
Treatment can significantly enhance the monomer removal effect compared to methods such as a complete mixing system. For example, in a complete mixing system, the average residence time of the charged slurry in the system is 5.
If the operating conditions are changed to piston flow at a monomer residual rate of 23% (expressed as (monomer concentration after treatment/initial monomer concentration) x 100) after 10 minutes, the monomer residual rate will theoretically decrease to 3%. You can.

In addition, steam is advantageous in terms of thermal efficiency, concentration effect, etc. by bringing it into direct contact with the slurry, compared to external heating using a jacket or the like.

As described above, the method of the present invention can efficiently separate and recover unreacted monomers using simple processing equipment, and it is an invention with high utility value in that it can sufficiently avoid health and safety hazards such as contamination of the working environment. It is.

．． The present invention will be described with reference to Examples above.

Examples 1 to 9 Vinyl chloride polymer slurries obtained by suspension polymerization were treated under various conditions using the apparatus shown in FIG.

The results are shown in Table 1 below. Comparative Examples 1 and 2 Table 1 also shows the results of processing in the same manner as in Example 1, except that the slurry was spread in portions from the upper part of each tray of the tray column in Example 1 to form a non-full bale shape.

Table 1 (Note) 1 Slurry concentration was 35mm2.The number of shelves was 5 by removing one from each of the 9 shelves.

Approximately 600 rows apart. As for the number of shelves, only the top shelf was left and the others were removed.

[Brief explanation of drawings]

FIG. 1 is a process diagram illustrating the treatment method of the present invention. 1...Tank, 2...Pump, 3...
Shelf row, 5...Condenser, 6...Ejector, 7
...Separator. Figure 1

Claims (1)

[Claims] 1. A vinyl chloride polymer slurry obtained by suspension polymerization, which is characterized in that the unreacted monomers in the slurry are separated and recovered by directly contacting the vinyl chloride polymer slurry with steam in a flooded tray column. processing method.