JPS5828283B2 - Method for producing vinyl chloride or vinylidene chloride polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that the unreacted monomers remaining in the polymerization vessel are completely collected after the completion of the polymerization reaction without being released into the atmosphere, and then polymerization is carried out. The present invention relates to a new and improved method for producing vinyl chloride or vinylidene chloride polymers, which allows the vessel to be exposed to the atmosphere.

Generally, when vinyl chloride, vinylidene chloride, or a mixture of monomers containing these as main components is polymerized in an aqueous medium in a polymerization vessel, the polymerization cycle is carried out with the polymerization vessel kept in a closed state. Even in such a polymerization vessel, it is necessary to periodically inspect the interior of the polymerization vessel.

Conventionally, when a worker needs to enter the polymerization vessel to inspect the inside of the polymerization vessel, the gas inside the polymerization vessel is replaced with air after the polymer slurry inside the polymerization vessel is discharged after the polymerization reaction is completed. However, since a considerable amount of unreacted monomer gas still remained in the polymerization vessel after the polymer slurry was discharged, it was necessary to release the gas inside the vessel to the atmosphere. It is undesirable to release the unreacted monomer gas into the atmosphere as it is by air replacement due to the problem of air pollution, and on the other hand, even with the above air replacement, it is difficult to completely discharge the unreacted monomer gas remaining in the polymerization vessel. It is not desirable for workers to enter the polymerization vessel in such a state from the viewpoint of occupational health and environment due to the toxicity of unreacted monomers.

The present invention provides a new and improved method for producing vinyl chloride or vinylidene chloride-based polymers that solves the problems in the conventional methods. After polymerizing the monomers to be used in an aqueous medium in a polymerization vessel, the internal pressure of the polymerization vessel and a slurry tank connected thereto is equalized, and the polymer slurry in the polymerization vessel is transferred to the slurry tank. After cleaning the inside of the polymerization vessel, when opening the polymerization vessel, the gas remaining in the polymerization vessel is suctioned and discharged, unreacted monomers contained therein are recovered, and the pressure is reduced. The method is characterized by introducing an inert gas into the polymerization vessel which has become evaporated, and then opening the polymerization vessel after passing through a step of introducing air into the polymerization vessel which has become under reduced pressure after suctioning and discharging the inert gas. It is something.

According to the method of the present invention described above, most of the unreacted monomers and other gases remaining in the polymerization vessel after discharging the polymer slurry are collected in a gas holder, and then replaced with an inert gas. The monomers are completely extruded from the inside of the polymerization vessel and then adsorbed using, for example, a known activated carbon adsorption device, so there is no risk of unreacted monomers being discharged into the atmosphere when the polymerization vessel is opened. Moreover, even when an operator enters the polymerization vessel as necessary, there is an excellent effect in that there is no harm caused by unreacted monomers.

Next, the method of the present invention will be explained in detail according to its steps based on a system diagram of a vinyl chloride polymer manufacturing apparatus illustrated in the accompanying drawings.

In carrying out the method of the present invention, vinyl chloride or a monomer mixture containing vinyl chloride as a main component is first polymerized in an aqueous medium in a polymerization vessel 1 according to a conventional method.
During this polymerization reaction, the polymerization vessel 1 is completely sealed.

Upon completion of the polymerization reaction, the polymer slurry produced in the polymerization vessel 1 is transferred to the slurry tank 3 below via the slurry discharge valve 2; This is done after equalizing the pressure inside the vessel.

This equalization of the pressure inside the vessel is done in order to smoothly transfer the polymer slurry from the polymerization vessel 1 to the slurry tank 3. This is done by opening the valve 4 of the pipe in which the gas is located, and if necessary the valve 6 leading to the gas holder 5, and then by opening the valve 2 the polymer slurry is allowed to flow down into the slurry tank under the action of gravity, and The gas pushed out from the slurry tank as the slurry flows down is sent to the polymerization vessel or to the gas holder 5 through the above piping.

Although it is not shown in the drawing, when discharging the slurry from the polymerization vessel, for example, by spraying high-pressure water onto the inner wall of the polymerization vessel from an automatic cleaning device installed inside the polymerization vessel, slurry or water-based water adhering to the interior wall of the polymerization vessel can be removed. Flushing of the medium is performed.

The polymer slurry thus transferred into the slurry tank is then dehydrated and dried according to a conventional method, and then taken out as a product.

After the slurry is discharged from the polymerization vessel 1, in preparation for the next polymerization, the inner wall of this polymerization vessel is coated with, for example, nigrosine black to prevent scale adhesion, and then the inner wall of the polymerization vessel is cleaned again by the cleaning device described above. However, the water used for this second cleaning is led to a drain tank 8 via a drain valve 7.

Note that the cleaning water led to the drain tank 8 still contains a considerable amount of unreacted monomer dissolved therein, so if necessary, this water can be passed through a known stripper, for example, although it is not shown in the drawing. The unreacted monomers separated there are sent to the above-mentioned gas holder 5, and the purified water is discharged outside the system or is recycled.

In the method of the present invention, after the series of polymerization cycles described above or after a certain number of polymerization cycles have been completed, the gas remaining in the polymerization vessel is first pumped by the vacuum pump 9 before opening the polymerization vessel. When actuated, it is collected into the gas holder 5 via the valve 10.11.

Note that the unreacted monomers collected in the gas holder 5 can be used for the next polymerization reaction through a purification process if necessary.

Most of the unreacted monomer remaining in the polymerization vessel is recovered into the gas holder by the above operation, but since it is impossible to completely vacuum the inside of the polymerization vessel, there are still some unreacted monomers in the polymerization vessel. A small amount of unreacted monomer remains.

Therefore, in the present invention, the valve 10.1 is then
1 is closed, the operation of the vacuum pump 9 is stopped, and an inert gas such as nitrogen gas, carbon dioxide gas, or helium is introduced from the tank 13 through the valve 12 into the polymerization vessel under reduced pressure. Return the internal pressure to normal pressure.

After the inside of the polymerization vessel returns to normal pressure, the inert gas supply valve 12
Close the exhaust valves 10, 14, and 15 and operate the vacuum pump 9 again to exhaust the mixed gas in the polymerization reactor. This mixed gas passes through the activated carbon adsorption device 16 to remove the small amount contained therein. Unreacted monomers are adsorbed onto activated carbon, and only the inert gas is discharged out of the system via valve 15.

Note that this discharged inert gas is returned to the inert gas tank 13 through a purification process if necessary, and is used for circulation.

In addition, when the activated carbon adsorption device reaches the saturated adsorption amount, the valve 14 is closed, the valves 17 and 11 are opened, and the vacuum pump 9 is operated to perform desorption and regeneration.

The dilution operation of the gas inside the polymerization vessel with the above-mentioned inert gas is as follows:
It is difficult to completely remove unreacted monomers remaining in the polymerization vessel by performing this process only once, so this operation is necessary to ensure that the concentration of unreacted monomers in the polymerization vessel is within the standard value of the working environment, for example, 5p. , p, and m.

In the method of the present invention, after completing the final dilution operation with inert gas as described above and exhausting the mixed gas in the polymerization vessel, it is sufficient to open the valve 18 and introduce outside air into the polymerization vessel. , After this, the polymerization vessel can be opened.

As explained above, according to the method of the present invention, by simple operation, when the residual gas in the polymerization vessel is simply replaced with air according to the conventional method, 0.2 to 0.25 Most of the unreacted monomers that were released into the atmosphere can be recovered, and as a result, for example, when inspecting the inside of the vessel after each polymerization reaction,
20,000 tons/year in a polyvinyl chloride manufacturing plant
Since it is possible to prevent and recover 0 to 250 tons of unreacted monomer per year, the method of the present invention is extremely effective in contributing to improving unit consumption and preserving the working environment and natural environment. .

[Brief explanation of drawings]

The drawing is a system diagram of a vinyl chloride polymer manufacturing apparatus for carrying out the method of the present invention. 1... Polymerization vessel, 2, 4, 6, 7, 10, 11
. 12.14,15,17.18... Valve, 3
...Slurry tank, 5 ...Gas holder 8 ...Drain tank, 9 ...Vacuum pump, 13 ...Inert gas tank, 16・
...Activated carbon adsorption device.

Claims (1)

[Claims] 1. After polymerizing vinyl chloride, vinylidene chloride, or a monomer containing these as main components in an aqueous medium in a polymerization vessel, equalize the internal pressure of the polymerization vessel and a slurry tank connected thereto, After transferring the polymer slurry in the polymerization vessel to a slurry tank and then cleaning the interior of the polymerization vessel, when opening the polymerization vessel, the gas remaining in the polymerization vessel is suctioned and discharged to remove any unused substances contained therein. The reaction monomer was collected, an inert gas was introduced into the polymerization vessel under reduced pressure, and then this inert gas was sucked out and air was introduced into the polymerization vessel under reduced pressure. A method for producing a vinyl chloride or vinylidene chloride polymer, which method comprises subsequently opening a polymerization vessel.