JPS6020404B2 - Method for removing vinyl chloride monomer remaining in polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing and recovering pinyl chloride monomer (hereinafter referred to as VCM).

More specifically, V remaining attached to vinyl chloride polymer or vinyl chloride copolymer (hereinafter referred to as polymer) after polymerization
The present invention relates to a method for removing and recovering CM from a polymer.

In recent years, the toxicity of VCM has become a problem.

Therefore, in order to prevent environmental pollution in places where vinyl chloride is handled, the process should be made into a closed system to minimize the escape of VCM emitted from the process into the atmosphere, and to prevent VCM from remaining in the polymer. Efforts are being made to reduce this as much as possible. However, conventionally, unreacted VCM after polymerization
VCM that still remains attached to the polymer after being collected is
It has been difficult to remove and recover efficiently. As a method for removing and recovering such VCM, there is a method in which the polymer is heated to increase the vapor pressure of the VCM remaining attached to the polymer, thereby making it easier to disperse the VCM and removing it.

However, this method results in deterioration of the polymer due to heating,
This is not preferable since it deteriorates various properties such as initial coloration, thermal stability, and fish eye properties during processing of this polymer. There is also a method of removing and recovering VCM by keeping the polymer in a reduced pressure system.

This method also has equipment limitations in maintaining a necessary and sufficient degree of vacuum, and when treating a polymer slurry obtained by suspension polymerization, for example, coexisting water is evaporated at the same time, making it inefficient. The present inventors investigated various methods for removing and recovering VCM adhering to polymers, and found that by scattering the polymer slurry after polymerization in a reduced pressure system in the form of a thin film or in the form of droplets, VCM adheres to the polymer efficiently. The present invention was completed by discovering that VCM can be removed. That is, the present invention is characterized in that the vinyl chloride monomer remaining in the polymer is dispersed in the form of a thin film and/or droplets by bringing the polymer slurry into contact with a rotary blade in a dispersion tank under normal pressure or reduced pressure. The purpose of this article is to explain how to remove .

An embodiment of the present invention will be explained in detail with reference to the drawings.

In Fig. 1, a polymer slurry is introduced from a slurry intake port 1 into a dispersion tank 4 maintained in a reduced pressure system, and the centrifugal force causes the slurry to be transferred between the rotary blade surface and between the rotary blades via a rotary blade rotated by a motor 3. The slurry is dispersed in the form of a thin film and/or droplets. The rotor is rotated to the extent that the slurry becomes a sufficiently thin film or provides sufficient centrifugal force to disperse the slurry into droplets. Usually 500~2000R
Preferably, the rotation is performed at a speed of pm. The polymer slurry scattered from the rotor in the form of a thin film or droplets collides with the wall surface of the dispersion tank and becomes further into a thin film.

During this time, the VCM remaining attached to the polymer moves to the gas phase and is recovered into the VCM recovery tank via the VCM vacuum suction port. V
VCM can be removed more effectively by circulating the polymer slurry from which CM has been removed again through the slurry intake port and passing through the rotary blade. Also,
VCM is produced by heating the polymer slurry while contacting it with water vapor or to an extent that does not cause deterioration of the quality of the polymer.
Removal efficiency can be increased.

These can also be used in combination, and it is preferable to use them, for example, when circulating the polymer slurry. The polymer that can be treated in the present invention is a vinyl chloride homopolymer or copolymer slurry obtained by conventional polymerization methods. The present invention can efficiently remove monomers remaining in vinyl chloride or vinyl chloride-based polymers.

Processed products using polymers treated with the method of the invention have good properties.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 In a batch polymerization reactor, vinyl chloride was polymerized until the average degree of polymerization reached 1000, and then the polymerized product was maintained at 60°C and the internal pressure of the polymerization reactor was reduced to lk9/kg to recover unreacted vinyl chloride monomer. did.

The polymerized material was transferred to a blowdown tank equipped with an air conditioner, and a 10.3 to 0.8 k9/c tsumugi vacuum suction was carried out from the bottom of the blowdown tank through a sealed joint. The slurry was sent to the tank via a slurry pump and brought into contact with a dispersion tank rotating at high speed within the dispersion tank.

The vinyl chloride monomer removed from the polymer was recovered from the vacuum suction port. The polymer slurry from which the vinyl chloride monomer was removed was returned to the blowdown tank.

Furthermore, the polymer slurry was circulated through the circulation system described above. After 2 hours of circulation, the monomer concentration in the polymer was 65
100 urigako decreased from 0 gofu.

The treated polymer was dried in a conventional manner and processed under the following formulation and conditions.

The results are shown in Table 1.

Compounding conditions Polymer 150% Tin stabilizer (N-200 fertilizer) 3% (E-101) 3% Processing conditions Roll temperature 1560 Take-out thickness
1m/d Pressure 175o01 Correct Example 2 The procedure of Example 1 was followed except that the polymer slurry was heated to 800°C at the inlet of the dispersion tank, and the VCM in the polymer was reduced by 30Q.

Further, the polymer was processed according to Example 1. Results first
Shown in the table. Example 3 At the inlet of the dispersion tank, the polymer slurry was
Example 1 except that it was heated to 0qo and further steam was blown into it.
When the polymer was treated according to the same procedure, the VCM in the polymer was reduced to 150 Yanagi.

Further, the polymer was processed according to Example 1.

The results are shown in Table 1. Example 4 When a vinyl chloride-vinyl acetate copolymer slurry containing about 5% by weight of vinyl acetate was treated according to Example 1, the monomer concentration in the polymer was reduced by 75 points from 6150 points.

Example 5 When a graft copolymer slurry of about 10% by weight of ethylene monoacetate pinyl copolymer (vinyl acetate content 26%) and vinyl chloride was treated according to Example 1, the pinyl chloride monopolymer in the polymer was removed. The mass concentration decreased from 560 to 60.

Comparative Example 1 The polymer slurry was treated in the same manner as in Example 1 except that it was not passed through a dispersion tank and was sucked under reduced pressure for 2 hours using only a blowdown tank at 60 pm at 0.3 to 0.8 kg/kg. The VCM concentration inside was 500cm.

Comparative Example 2 The procedure of Comparative Example 1 was followed except that the temperature of the polymer slurry in the flow down tank was set at 7.0 psi, and the VCM concentration in the polymer was 350 psi.

Further, the polymer was processed according to Experimental Example 1. The results are shown in Table 1. Comparative Example 3 When treated according to Comparative Example 2 except that the temperature was 80 qC in Comparative Example 2, the VCM concentration in the polymer was 30 qC.
It became 0 blood.

Further, the polymer was processed according to Experimental Example 1. The results are shown in Table 1. Table 1 * Thermal stability test was performed using a roll sheet of 1st grade at 180℃, 9
The number of o** fins that are processed for 0 minutes is the number that exists in the sheet 25.

[Brief explanation of the drawing]

FIG. 1 shows a longitudinal cross-sectional view of an example of an apparatus for scattering polymer slurry in the form of a thin film and/or droplets. In the figure, 1 is a polymer slurry inlet, 2 is a rotor, 3 is a motor for rotating the rotor, 4 is a dispersion tank, 5 is a polymer slurry outlet, and 6 is a VCM vacuum suction port. Figure 1

Claims (1)

[Claims] 1 Residual in a polymer characterized by dispersing a vinyl chloride polymer or a vinyl chloride copolymer slurry into a thin film and/or droplet by contacting it with a rotary blade in a dispersion tank under normal pressure or reduced pressure. A method for removing vinyl chloride monomer.