JPH05310815A - Method of recovering vinyl monomer - Google Patents

Abstract

PURPOSE:To prevent scale deposition or clogging within a monomer-recovery system in the recovery of a vinyl monomer remaining unreacted after vinyl- monomer polymerization in an aqueous medium by recovering the monomer (a) while introducing a spray of a water-soluble polymerization inhibitor into the system. CONSTITUTION:The recovery of a vinyl monomer remaining unreacted after polymerization in an aqueous medium is conducted while introducing a spray of a water-soluble polymerization inhibitor into the system. A preferred inhibitor is one having a solubility in water of 1g/100g-water or higher under use conditions. The spray preferably has droplet diameters of 100mum or smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering unreacted monomers after polymerization of vinyl monomers (hereinafter referred to as "monomers") using an aqueous medium. The present invention relates to a method for recovering a monomer that prevents a decrease in productivity due to scaling and blockage in a recovery facility).

[0002]

BACKGROUND OF THE INVENTION Polymerization of monomers is usually carried out with an aqueous medium.
It is carried out in the presence of an emulsifier or suspending agent, a polymerization initiator and the like. And when the conversion rate of the monomer reaches a predetermined value,
After the polymerization reaction is stopped and the unreacted monomer is recovered, the polymerization product is dried through a blowdown tank, a demonomer tower and a dryer to obtain a dried polymer.

In this process, the unreacted monomer is recovered from the polymerization vessel, the blowdown tank and the demonomer column or continuously, and is recovered by the gas holder, the direct compression liquefaction apparatus or the cooling liquefaction apparatus. This recovered monomer is reused in the polymerization vessel directly or after removing unnecessary components or after separating specific components.

However, during this series of monomer recovery steps, a polymerization reaction of the monomers occurs, resulting in a decrease in productivity due to scaling or blockage in the recovery facility, an increase in maintenance costs, and a decrease in safety. Etc. became a big problem in manufacturing.

In order to solve such a problem, a substance having a polymerization initiating ability may be removed or conditions may be avoided, but not only the effect is not perfect, and a large amount of equipment cost is required, which is not practical.

Further, Japanese Patent Application Laid-Open No. 51-90381 discloses N-nitrosophenylhydroxyamine or a salt thereof as a vinyl chloride polymerization inhibitor. Among them, the water-insoluble polymerization inhibitor is However, it is not useful for inhibiting polymerization of unreacted monomers in the monomer recovery device, which is the object of the present invention.

In addition, Japanese Patent Laid-Open No. 48-89990,51-
61591, 52-3681, 58-17106, 64
-66206 and other methods for stopping or inhibiting polymerization in a polymerization vessel, and JP-A-47-34584, 50-729.
84,50-73990, etc.
The method for preventing the adhesion of the polymer is not effective and is unsuitable as the method for preventing the polymerization reaction which occurs during the recovery of the unreacted monomer, which is the object of the present invention.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to carry out recovery of an unreacted monomer after polymerization of a monomer using an aqueous medium without causing scaling or clogging in a recovery facility. To provide.

[0009]

Means for Solving the Problems The inventors of the present invention have made diligent studies to solve these problems and prevent polymerization in the recovery facility. As a result, the presence of a water-soluble polymerization inhibitor in the recovery facility. Then, they have found that the above problems can be completely solved, and have reached the present invention. That is, the present invention is a method for recovering an unreacted monomer after polymerization of a monomer using an aqueous medium, which is characterized in that a recovery operation is performed while injecting droplets of a water-soluble polymerization inhibitor in a mist state. It is a method of recovering a monomer. Hereinafter, the present invention will be described in more detail.

It is sufficient for the polymerization inhibitor used in the present invention to be water-soluble, and 1 g / 100 under the conditions of use.
It is preferred that it has a solubility of at least g-water. Further, it is preferable that the droplets of the water-soluble polymerization inhibitor at the time of injection have a mist shape of 100 μm or less. Specific examples of the water-soluble polymerization inhibitor include hydroquinone and P-methoxypheno-
Such as phenol, quinones such as P-benzoquinone,
Examples thereof include nitroso compounds such as ammonium salt of N-nitrosophenylhydroxyamine.

A polymerization inhibitor having a low solubility in water has a polymerization inhibition effect in a polymerization reaction in a liquid monomer or in a usual polymerization vessel, but a recovery device in which a recovery monomer gas or a part thereof is condensed. Within, the effect of inhibiting polymerization is low.

The method of injecting the water-soluble polymerization inhibitor is as follows:
In the unreacted monomer recovery apparatus after the polymerization reaction, it is sufficient to inject 1 ppm-1% by weight with respect to the unreacted monomer on the upstream side of the place where the unreacted monomer is easily polymerized. Further, in order to inject it in a mist state, it is preferable to pressurize the polymerization inhibitor and spray it with a spray nozzle or a water vapor ejector, and further to make the spray droplets 100 μm or less. As an injection place, for example, an outlet of an unreacted monomer such as a polymerization vessel, a blowdown tank or a demonomer tower, and an upstream side of a place where a scale due to a polymerization reaction is likely to be generated is preferable.

The vinyl-based monomer in the present invention includes
In addition to vinyl chloride, vinyl halides such as vinylidene chloride and vinyl fluoride, vinyl esters such as vinyl acetate and vinyl propionate, acrylic acid, methacrylic acid and their esters or salts, styrene derivatives such as styrene and α-methyl styrene. Further, it may contain one or more of the above vinyl-based monomers or may contain a diene-based monomer such as copolymerizable butadiene, chloroprene, or isoprene containing a vinyl-based monomer as a main component.

In addition to using the above vinyl-based monomer and an aqueous medium, an emulsifying agent or suspending agent to be added to the polymerization reaction,
There are no particular restrictions on the raw materials used such as the polymerization initiator, the conditions for monomer recovery, and the equipment materials used.

[0015]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 150 parts of deionized water in a polymerization vessel, 95 parts of vinyl chloride as a monomer, 5 parts of vinyl acetate, 0.02 parts of t-butyl peroxynedecaneate as a polymerization initiator, partially saponified polyvinyl alcohol. 0.1 part was charged, and after stirring and heating,
Polymerization reaction is carried out at 57 ° C and the internal pressure of the can is 2.0 kg / cm ^2.
At the time of decrease, the polymerization reaction was terminated, unreacted monomers were recovered, and when the internal pressure of the can reached 2 kg / cm ² G, after transferring the produced polymerization liquid (slurry) to the blowdown tank,
The produced polymerization liquid was continuously sent to a demonomer column, a centrifugal dehydrator, and a drying to obtain a dry polyvinyl chloride.

On the other hand, the unreacted monomer was continuously recovered from the blowdown tank and the demonomer column in a batch mode from the polymerization reactor.

At the outlet of the unreacted monomer of the polymerization vessel, hydroquinone as a water-soluble polymerization inhibitor was recovered in an amount of 10 with respect to the recovered monomer.
The solution was pressurized with a 2 wt% aqueous solution so as to have a ppm and was injected by a spray nozzle in a mist state of 100 μm or less.

After 10 batches after continuing this operation, the pipe at the outlet of the unreacted monomer of the polymerization vessel was disassembled and the amount of the attached scale was measured. 101 is shown.

Example 2 The results obtained by the same method as in Example 1 except that the type of monomer charged to the polymerization vessel, the type of polymerization inhibitor or the addition amount thereof were changed are shown in Experiment No. 1 of Table 1. 102 to No. Shown at 104.

Comparative Example 1 The results obtained by the same method as in Example 1 except that the polymerization inhibitor was not injected are shown in Table 1. Shown at 201.

The results obtained in the same manner as in Example 1 except that the water-insoluble polymerization inhibitor was used and the solution was changed to an acetone solution. Shown at 202-203.

Table 1 shows the results obtained by the same method as in Example 1 except that injection was performed without using a spray nozzle.
Experiment No. Shown at 204.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, the unreacted monomer can be recovered in the recovery facility without causing scaling or blockage. The coalescence can be manufactured with high productivity.

Claims (3)

[Claims] 1. A method for recovering an unreacted vinyl monomer after polymerization of a vinyl monomer using an aqueous medium, wherein a recovering operation is carried out while injecting water-soluble polymerization inhibitor droplets in a mist state. A method for recovering vinyl monomers, which is characterized in that 2. The method for recovering a vinyl monomer according to claim 1, wherein the solubility of the water-soluble polymerization inhibitor in water under the conditions of use is 1 g / 100 g-water or more. 3. The method for recovering a vinyl-based monomer according to claim 1, wherein the droplets of the water-soluble polymerization inhibitor are in a mist state of 100 μm or less.