JPS6043846B2 - Method for producing vinyl chloride resin using a reflux condenser - Google Patents

Description

[Detailed description of the invention] The present invention is a vinyl chloride based tree using a reflux condenser.

Regarding the method for producing fat, in more detail, the polymerization reaction of vinyl chloride monomer is carried out while the vinyl chloride monomer is charged from the upper part of the reflux condenser, and the adhesion of scale to the inner surface of the reflux condenser is prevented. The present invention relates to a manufacturing method for producing uniform polymer particles. In recent years, large-sized polymerization reactors equipped with reflux condensers have come to be used in the production of vinyl chloride resins in order to improve productivity.

Although this has greatly improved the production capacity of vinyl chloride resins, the vinyl chloride monomer attached to the inner surface of the reflux condenser in the polymerization reactor, or the monomer that can be copolymerized with vinyl chloride monomer, A phenomenon occurs in which a mixture of polymer and vinyl chloride monomer undergoes a polymerization reaction to form a thin polymer layer (hereinafter sometimes referred to as scale) and adhere to it, resulting in a decrease in the heat removal ability of the reflux condenser. In even more extreme cases, the connection with the polymerization reactor may become clogged and the function of the reflux condenser may be impaired. 1 In order to prevent scale adhesion on the inner surface of the reflux condenser, there has been a method to prevent scale adhesion by bringing water into contact with the inner surface of the reflux condenser.
-30105), a method for preventing scale adhesion by bringing a sulfite aqueous solution into contact with a reflux condenser (JP-A-50-17398)
G, 50-73990) and a method of preventing scale adhesion by injecting demineralized water from a nozzle into a connecting pipe between a polymerization reactor and a reflux condenser (Japanese Patent Laid-Open No. 51-84887).

However, although these methods using water or water and other substances all have a considerable improvement effect on preventing scale adhesion, they have the side effect of coarsening the resulting polymer and widening the particle size distribution. This is a major drawback of this method, as it results in reduced productivity in the molding process of the final product.
In view of these drawbacks of the conventional methods, the present inventors
The results of various studies aimed at providing a method for preventing scale from adhering to the connection between the reflux condenser and the polymerization reactor and on the inner surface of the reflux condenser and for obtaining polymer particles with a uniform particle size distribution. , we have completed the present invention. That is, the present invention involves suspending vinyl chloride monomer or a monomer mixture mainly consisting of vinyl chloride monomer using a polymerization reactor equipped with a reflux condenser in the gas phase of the polymerization reactor or outside the polymerization reactor. When carrying out a turbid polymerization reaction, a portion of the monomers is charged in advance into a polymerization reactor to start polymerization, and after the polymerization conversion rate per total monomer reaches 5% by weight, heat removal using a reflux condenser is started. On the other hand, a method for producing a vinyl chloride resin characterized in that the remaining monomer is continuously or intermittently charged from the upper part of the reflux condenser before the start of heat removal by the reflux condenser. be.

In the present invention, the amount of monomer charged in advance into the polymerization reactor is usually 5% or more of the total amount used.

If the amount is less than 5%, the number of monomer droplets present in the polymerization reaction system at the beginning of the polymerization reaction is small, so some of the monomers tend to become droplets with small diameters, and the particle size of the resulting polymer particles decreases. The distribution tends to be wider.

Incidentally, the monomers to be charged into the polymerization reactor in advance may be charged from the upper part of the reflux condenser. In the present invention, the heat removal using the reflux condenser is carried out after the polymerization conversion reaches 5% by weight, preferably from about 2% by weight, more preferably from about 2% by weight. If it is carried out from less than 5% by weight, the final polymer particles obtained will be coarse and the particle size distribution will be wide. In the present invention, the remaining monomers are charged from the upper part of the reflux condenser continuously or intermittently, but preferably continuously.

The time to start charging the monomer can be determined as appropriate, but since heat removal in the reflux condenser starts after the polymerization conversion rate is 5% by weight or later, it is necessary to start removing heat in the reflux condenser at least by the time you start removing heat in the reflux condenser. It is necessary to start charging the monomer, and it is preferable to start charging the monomer before the contents of the polymerization reaction system are heated to the polymerization reaction temperature, that is, before the start of polymerization. In addition, the amount of the remaining monomer charged, the charging speed, and the timing of stopping the charging should be determined in order to determine the timing and extent of scale adhesion, the connection between the polymerization reactor and the reflux condenser, and the necessity for washing out the inner surface of the reflux condenser. It can be arbitrarily determined by considering the amount per unit time, the size and shape of the reflux condenser, etc.

The monomer charged from the upper part of the reflux condenser is not necessarily limited to vinyl chloride monomer alone, but may include other monomers, mainly vinyl chloride, that can be copolymerized with vinyl chloride. It may be a mixture of

In the present invention, other monomers that can be copolymerized with the vinyl chloride monomer include, for example, olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, methyl acrylate, and methyl methacrylate. acrylic acid esters such as maleic acid or fumaric acid, esters and anhydrides of acids such as maleic acid or fumaric acid, nitrile compounds such as acrylonitrile, and vinylidene compounds such as vinylidene chloride. It is included in the range of 20 vol.% or less out of 10 vol.% of the mass mixture.

Examples of the polymerization initiator used in the present invention include initiators commonly used in vinyl chloride suspension polymerization, such as lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxypivalate,
Organic peroxides such as diisopropyl peroxydicarbonate and acetylcyclohexylsulfonyl peroxide, and azo compounds such as α·α″-azobisisobutyronitrile and α·α″-azobis2,4-dimethylvaleronitrile. One or a mixture of two or more species can be crushed.

The suspending agent used in the present invention may be a known suspending agent, such as partially saponified polyvinyl alcohol, vinyl acetate-maleic anhydride copolymer, styrene-maleic anhydride copolymer, polyvinylpyrrolidone, gelatin, starch, methyl Cellulose, hydroxypropyl cellulose, etc. are commonly used.

In the present invention, a molecular weight regulator may be used if necessary.

Further, before the start of the polymerization reaction, suspending agents, molecular weight regulators, etc. can be added all at once to the polymerization reaction system, or they can be added in portions during the polymerization reaction.

The polymerization reaction temperature range in the present invention is usually 40 to 75°C.
However, there is no particular limitation.

By using the method of the present invention, it is possible to completely prevent scale adhesion on the connection between the polymerization reactor and the reflux condenser and on the inner surface of the reflux condenser, prevent coarse particles, and create uniform particles with a narrow particle size distribution. Polymer particles can be obtained.

The present invention will be specifically explained below using examples.

Parts and percentages are by weight unless otherwise specified. Example experiment no. l (Example 1 of the present invention) As shown in Figure 1, a multi-tubular reflux condenser was attached to the center of the upper part of a stainless steel polymerization reactor, and vinyl chloride monomer and water were charged to the top of this reflux condenser. A polymerization reactor equipped with piping for each reaction was used.

After charging 1 (1) part of water, 0.05 part of partially saponified polyvinyl alcohol, and 0.03 part of di-2-ethylhexyl peroxydicarbonate into the above polymerization reactor and degassing it,
Of the 1 (1) part polymerization prescription amount of vinyl chloride monomer, 88 parts were charged from a pipe directly attached to the polymerization reactor.

While stirring, the temperature begins to rise, and the remaining vinyl chloride monomer (liquid) is poured from the pipe installed at the top of the reflux condenser.
began charging. Two hours after completing the temperature rise to 58°C and starting the polymerization reaction (polymerization conversion rate: 15% by weight), the charging of vinyl chloride monomer was stopped, and at the same time, water was passed through the reflux condenser to remove heat. I started.

The polymerization reaction was stopped one hour after the start (polymerization conversion rate of 96% by weight). After recovering the unreacted vinyl chloride monomer, the contents of the polymerization reactor were extracted from the polymerization reactor, a portion of which was dehydrated and washed, and dried in a ventilation dryer for 2 hours.
The resin powder was dried at 60'C for $f and the particle size distribution was measured. Furthermore, when the inside of the reflux condenser was observed, no scale was observed.

As a result of repeating the polymerization reaction 10 times in the same manner as above, no scale was observed at all at the connection between the polymerization reactor and the reflux condenser and on the inner wall of the tube of the reflux condenser. Experiment No. 2 (Example 2 of the present invention) Experiment No. 1, an initial charge of 75 parts of vinyl chloride monomer was carried out through a pipe provided at the top of the reflux condenser.

At the same time as the temperature started to rise, the remaining 25 parts were started to be charged through the pipe, and this charging was continued until 4 hours and 4 hours after the start of the polymerization reaction. Heat removal using the reflux condenser was started 2 hours after the start of the polymerization reaction (polymerization conversion rate: 15% by weight). After the polymerization reaction was completed, the state of scale adhesion to the reflux condenser was observed, but no scale was observed.

As a result of repeating the polymerization reaction 10 times in the same manner as above, no scale was observed at all at the connection between the polymerization reactor and the reflux condenser and on the inner wall of the tube of the reflux condenser. Furthermore, after the first polymerization reaction and the subsequent 10 repeated polymerization reactions, the state of scale adhesion to the vessel wall in the gas phase portion of the polymerization reactor was also observed, and no scale was found to have adhered thereto.

Experiment No. 3 (Example 3 of the present invention) Experiment No. In 1, vinyl chloride monomer 3 was first charged, and at the same time as the temperature started to rise, the remaining vinyl chloride monomer was started to be charged from the pipe provided at the top of the reflux condenser, and this charging was carried out to complete the polymerization reaction. After 1 hour and 3 minutes had passed since the start (polymerization conversion rate of 1%), the process was terminated and at the same time, heat removal using a reflux condenser was started.

After the polymerization reaction was completed, the state of scale adhesion to the reflux condenser was observed, but no scale was observed.

As a result of repeating the polymerization reaction 10 times in the same manner as above, no scale was observed at all on the connection between the polymerization reactor and the reflux condenser and on the inner wall of the tube of the reflux condenser.

Experiment No. 4 (Comparative Example 1) Experiment No. 1, 100 parts (total amount) of vinyl chloride monomer was initially charged, and thereafter charging was not performed from the upper part of the reflux condenser.

Further, heat removal using a reflux condenser was not performed during the polymerization reaction.
When the reflux condenser was observed after the polymerization reaction was completed, scale was observed at the connection between the reflux condenser and the polymerization/reactor. As a result of performing the polymerization again without removing the attached scale, the connection portion was blocked by scale. Experiment N
O. 5 (Comparative Example 2) Experiment No. In step 4, heat removal using a reflux condenser was started 2 hours after the start of the polymerization reaction (polymerization conversion rate: 15% by weight).

When the reflux condenser was observed after the polymerization reaction was completed, a slight amount of scaling was observed at the connection between the reflux condenser and the polymerization reactor and on the inner wall of the tube of the reflux condenser. As a result of repeating the polymerization reaction five times in the same manner as described above without removing the attached scale, a large amount of scale was observed to be attached to the connection between the polymerization reactor and the reflux condenser and the inner wall of the tube.

Experiment No. 6 (Comparative Example 3) Experiment No. In step 4, 145 parts of 160 parts of water were initially charged through a pipe directly attached to the polymerization reactor.

At the same time as the temperature started to rise, the remaining water was started to be charged through a pipe installed at the top of the reflux condenser. After 2 hours have passed since the polymerization reaction started with the end of temperature rise (polymerization conversion rate 15% by weight)
The charging of water was stopped, and at the same time, heat removal using the reflux condenser was started. When the reflux condenser was observed after the completion of the polymerization reaction, almost no scale was observed inside the reflux condenser. As a result of repeating the polymerization reaction 10 times in the same manner as above,
Scale adhesion was observed at the connection between the polymerization reactor and the reflux condenser and on the inner wall of the tube of the reflux condenser.

Experiment No. 7 (Comparative Example 4) Experiment No. 1, 3 parts of vinyl chloride monomer were first charged through a pipe provided at the top of the reflux condenser.

Simultaneously with the start of temperature rise, the remaining vinyl chloride monomer was started to be charged through the piping, and when the temperature rise was finished and the reaction was started, the charge was also stopped, and heat removal was started using the reflux condenser. After the polymerization reaction was completed, the inside of the reflux condenser was observed, and scale adhesion was observed.

As a result of repeating the polymerization reaction 10 times in the same manner as above, no scale was observed at all on the connection between the polymerization reactor and the reflux condenser and on the inner wall of the tube of the reflux condenser.

At the same time, the inner wall surface of the gas phase portion of the polymerization reactor was also observed, and no scale was found attached.

The results of the particle size distribution of the resin powder obtained in each of the above experiments are shown in Table 1 below. The particle size distribution was determined by measuring the passage rate using a JIS Z88Ol sieve.

From the above experimental examples, the example of the present invention is clearly superior in preventing scale adhesion to the connection between the polymerization reactor and the reflux condenser and the inner wall of the tube in the reflux condenser, and the particle size of the vinyl chloride resin is uniform. Yes, it is excellent.

However, in Comparative Example 3 in which water was charged from the upper part of the reflux condenser, although an improvement effect in preventing scale adhesion was observed compared to Comparative Examples 1 and 2 in which nothing was charged in the reflux condenser, polymerization continued for a long period of time. By repeating the reaction, scale adhesion is observed, and the resulting polymer particles become coarse and have a wide particle size distribution, an undesirable phenomenon. It can also be seen that in Comparative Example 4, in which heat removal was started in the reflux condenser before the polymerization conversion rate reached 5%, the particles became coarser and the particle size distribution became wider.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a polymerization reactor equipped with a reflux condenser used in experiments of examples of the present invention, in which reference numeral 1 is the polymerization reactor, and 2 and 7 are vinyl chloride monomer charging pipes. , 3 and 4 are cooling water inlet and outlet pipes, respectively, 5 is a reflux condenser, and 6 is a water charging pipe.

Claims (1)

[Claims] 1. Vinyl chloride monomer or a monomer mixture mainly consisting of vinyl chloride monomer using a polymerization reactor equipped with a reflux condenser in the gas phase of the polymerization reactor or outside the polymerization reactor. Considering that a suspension polymerization reaction will be carried out, some monomers are charged in advance into a polymerization reactor to start polymerization, and after the polymerization conversion rate per total monomer reaches 5% by weight, removal is carried out using a reflux condenser. Heat is started, while the remaining monomer is continuously or intermittently charged from the upper part of the reflux condenser from before the start of heat removal by the reflux condenser. Production method. 2. The manufacturing method according to claim 1, in which the remaining monomer is charged from the upper part of the reflux condenser before the start of polymerization. 3. The manufacturing method according to claim 1, wherein the monomers previously charged to the polymerization reactor are charged from the upper part of the reflux condenser.