JP2001261709A - Production of vinyl chloride polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing vinyl chloride polymers that gives vinyl chloride polymers of high quality and can largely shorten the polymerization time with no occurrence of scaling. SOLUTION: Vinyl chloride polymers are produced as the ratios of the diameter of the polymerization reactor to the vertical distance from the surface of the polymerization reaction liquid mixture to the top end of the agitation blade is maintained in a specific range, when the temperature reaches the polymerization one and the specified periods during the polymerization, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vinyl chloride monomer or a mixture of a vinyl monomer and a copolymerizable vinyl monomer of the vinyl chloride monomer (hereinafter referred to as vinyl chloride monomer). In the method for producing a vinyl chloride polymer by suspension polymerization of a monomer), the temperature from the surface of the polymerization reaction solution to the top of the stirring blade with respect to the tank diameter of the polymerization reactor when the polymerization temperature is reached and at a specific time during the polymerization reaction. By maintaining the vertical distance ratio within a specific range, foaming of the polymerization reaction solution can be prevented even if the rate of heat removal by the reflux condenser is increased. The present invention relates to a method for producing a vinyl chloride polymer, which can improve the properties and prevent the adhesion of scale, and can also improve the fisheye of the vinyl chloride polymer obtained.

[0002]

2. Description of the Related Art Generally, a vinyl chloride polymer is produced in a batch system. When producing a vinyl chloride polymer, an aqueous medium, a suspending agent, a polymerization initiator and After the additives are charged, the inside of the polymerization reaction system is degassed, vinyl chloride monomers are charged, and warm water circulation or steam is passed through the jacket of the polymerization reactor with stirring, and the temperature is raised to the polymerization temperature to perform polymerization. Initiate the reaction. Thereafter, from the point when the heat of the polymerization reaction comes out, cooling is performed to keep the polymerization reaction temperature constant by passing cooling water through the jacket of the polymerization reactor, and the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer is reduced. The polymerization reaction is continued until a predetermined polymerization conversion is reached. After the completion of the polymerization reaction, a series of polymerization operations for recovering the unreacted vinyl chloride monomer and discharging the vinyl chloride polymer from the reactor are performed.

In recent years, in order to improve the productivity of vinyl chloride-based polymers, attempts have been made to increase the size of polymerization reactors and shorten the polymerization time. However, when the polymerization reactor is enlarged, the heat transfer area of the jacket per internal volume of the reactor decreases, and when the polymerization time is shortened, the heat removal per unit time increases. There is a limit in cooling the polymerization reaction system.

Therefore, as a method of increasing the heat removal efficiency in the polymerization reaction system, there is a method of lowering the temperature of cooling water flowing through the jacket by using a refrigerator or the like to increase the heat removal efficiency by the jacket.
A method of using an inner jacket having a jacket in the polymerization reaction system, a method of removing heat with a reflux condenser, and the like have been proposed.Among them, particularly, heat removal by a reflux condenser has a large heat removal ability, The equipment cost and running cost are low.

However, in the method of removing heat with a reflux condenser, when the heat removal efficiency with a reflux condenser is increased, the amount of unreacted vinyl chloride-based monomer evaporated increases, and as a result, heavy polymerization occurs in the polymerization reactor. The phenomenon in which the combined slurry foams or the polymer slurry flows into the reflux condenser due to the foaming is likely to occur. Here, when the polymer slurry foams, not only a problem such as adhesion of scale on the inner wall surface of the polymerization reactor, the inside of the reflux condenser, and the like occurs, but also the chloride obtained by mixing the scale into the vinyl chloride polymer. Roll fish eye of vinyl polymer deteriorates, quality such as particle size distribution widens, and in the worst case,
It becomes difficult to control the heat removal of the reflux condenser, and it becomes difficult to stably and safely produce a vinyl chloride polymer.

As a method for preventing foaming of a polymer slurry when heat is removed by a reflux condenser, Japanese Patent Application Laid-Open No.
-26908 and JP-B-3-38283, a method of breaking bubbles by a rotating blade installed in a gas phase portion,
JP-A-180908 and JP-A-3-212409 propose a method of adding an antifoaming agent and the like, and JP-A-7-25909 discloses a method in which a liquid level sensor is installed in a polymerization can and the liquid level is measured. A control method using a reflux condenser has been proposed.

[0007]

However, the above-mentioned Japanese Patent Application Laid-Open No. 56-26908, Japanese Patent Publication No. 3-38283.
In the method proposed in Japanese Patent Laid-Open Publication No. H07-187, it is possible to break the foam bubbles, but since the scattered bubbles adhere to the wall surface of the polymerization reactor and cause scale, the resulting vinyl chloride polymer There is a problem that the roll fish eye deteriorates.

In the methods proposed in JP-A-2-180908 and JP-A-3-212409, although the foaming can be suppressed by adding an antifoaming agent, the thermal stability of the obtained vinyl chloride-based polymer is reduced. There is a problem that the roll fish eye deteriorates.

Further, the method described in Japanese Patent Application Laid-Open No. 7-25909 is capable of suppressing the rise in the liquid level due to foaming by adjusting the amount of heat removed by the reflux condenser. It is difficult to increase the heat efficiency, and when the heat removal efficiency in the reflux condenser is increased, foaming of the polymer slurry cannot be fundamentally suppressed.

Accordingly, an object of the present invention is to prevent the foaming of the polymer slurry even if the heat removal efficiency in the reflux condenser is increased, to improve the productivity of the polymerization step in the production of a vinyl chloride polymer, and to further improve the scale. It is an object of the present invention to provide a method for producing a vinyl chloride polymer in which the adhesion of water can be prevented and the fisheye of the obtained vinyl chloride polymer is improved.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, when the polymerization temperature is reached and at a specific time during the polymerization reaction, the polymerization reaction solution surface is measured from the polymerization reaction solution surface to the top of the stirring blade. By maintaining the ratio of the vertical distance to each within a specific range, foaming can be prevented even if the heat removal efficiency by the reflux condenser is increased, and the productivity of the polymerization process during the production of vinyl chloride polymer can be improved. Of the vinyl chloride-based polymer obtained was improved, and the present invention was completed.

That is, the present invention relates to a method for producing a vinyl chloride monomer in an aqueous medium, in the presence of a polymerization initiator and a dispersion stabilizer, by using a polymerization reactor equipped with a reflux condenser to carry out suspension polymerization. In the method for producing a polymer, a vinyl chloride monomer, an aqueous medium, a polymerization initiator, and a dispersion stabilizer were charged, the temperature was increased, and the tank diameter of the polymerization reactor at the time when the temperature reached a predetermined polymerization temperature was measured. H / D, which is the ratio of the vertical distance (H) from the polymerization reaction solution surface to the top of the stirring blade to (D)
Is 0.30 to 0.60, and the H / D is 0.10 to 0.20 when the polymerization conversion of the vinyl chloride monomer to the vinyl chloride polymer is in the range of 65% to 80%. The present invention relates to a method for producing a vinyl chloride-based polymer, characterized by being maintained within the range.

Hereinafter, the present invention will be described in more detail.

[0014] The present invention provides a vinyl chloride polymer in which a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of a polymerization initiator and a dispersion stabilizer using a polymerization reactor equipped with a reflux condenser. In the production method of the coalescing, a vinyl chloride monomer, an aqueous medium, a polymerization initiator, and a dispersion stabilizer are charged, the temperature is increased, and the tank diameter of the polymerization reactor (D The ratio H / D, which is the ratio of the vertical distance (H) from the surface of the polymerization reaction solution to the top of the agitating blade, to 0.30 to 0.60, is set to 0.30 to 0.60, and the vinyl chloride monomer is converted into a vinyl chloride polymer. Rate is in the range of 65% to 80%, while maintaining the H / D in the range of 0.10 to 0.20, the suspension polymerization is carried out, and the vinyl chloride-based weight with good production efficiency and improved roll fish eye is obtained. It is for producing a united product.

Here, H / D, which is the ratio of the vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade to the tank diameter (D) of the polymerization reactor in the present invention, means H / D from the bottom of the polymerization reaction tank. H, which is a distance obtained by subtracting the vertical distance from the bottom of the polymerization reactor to the upper end of the stirring blade from the vertical distance to the flat polymerization reaction liquid surface in a stationary state at the time when the predetermined polymerization temperature is reached, that is, in a state where the stirring is not performed, It is a value obtained by dividing by D, which is the tank diameter of the polymerization reactor. Further, D, which is the tank diameter of the polymerization reactor, refers to the inner diameter of the body of the polymerization reaction tank, and the upper end of the stirring blade refers to the uppermost end of the stirring blade. In the present invention, it is preferable that at least two or more stages of stirring blades are installed as the stirring blades installed in the polymerization reaction tank. Refers to the upper end.

In the present invention, a vinyl chloride monomer, an aqueous medium, a polymerization initiator and a dispersion stabilizer are charged, and the temperature is increased,
H / D, which is the ratio of the vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade to the tank diameter (D) of the polymerization reactor at the time when the temperature reaches the predetermined polymerization temperature, is 0.30 to 0.60. Range. Here, when the H / D is less than 0.30, the suspension polymerization solution is liable to be scattered due to agitation, the scale adherence after the polymerization reaction is intensified, and the agitation is difficult because the agitation becomes difficult. The vinyl polymer is coarsened, and the fisheye deteriorates. On the other hand, when the H / D exceeds 0.60, it becomes difficult to stir to the surface of the polymerization reaction solution, and scale is attached, and the obtained vinyl chloride polymer becomes coarse particles.

As a method of controlling the H / D at the time when the temperature reaches a predetermined polymerization temperature, for example, a method of changing a position of a stirring blade, an aqueous medium charged in a polymerization reactor, a vinyl chloride monomer or the like It can be performed by appropriately selecting a method of changing the charged amount or the like. An aqueous medium,
Since the specific gravity of a vinyl chloride-based polymer or the like changes with temperature, the volume may be calculated from the specific gravity at a predetermined polymerization temperature, and the charged amount may be adjusted to a predetermined polymerization reaction solution surface level.

In the present invention, the polymerization conversion of the vinyl chloride monomer to the vinyl chloride polymer is in the range of 65% to 80%, and the H / D is in the range of 0.10 to 0.20. To maintain. Here, when the H / D is less than 0.10, the suspension polymerization solution is scattered sharply, scale adherence after the polymerization reaction is severe, and the roll fish eye of the obtained vinyl chloride polymer deteriorates. . On the other hand, H / D is 0.1.
If it exceeds 20, the suspension polymerization liquid having a polymerization conversion rate in the range of 65% to 80% has a very high viscosity, and it is difficult to sufficiently stir. As a result, when the heat is removed by the reflux condenser, the foaming becomes intense, causing not only problems such as adhesion of scale on the inner wall of the polymerization reactor, the inside of the reflux condenser, and the like, but also the resulting vinyl chloride polymer. Roll fish eyes deteriorate, and in the worst case, it becomes difficult to control the heat removal of the reflux condenser, making it impossible to produce a stable vinyl chloride polymer.

As a method for maintaining and controlling the H / D in the range of 65% to 80% of the polymerization conversion rate in the range of 0.10 to 0.20, for example, a vinyl chloride monomer is converted into a salt by a polymerization reaction. The method can be controlled by appropriately selecting a method utilizing volume shrinkage at the time of conversion to a vinyl polymer, a method of purging a vinyl chloride monomer, a method of adding injection water, and a method of combining these.

Here, the volume shrinkage when a vinyl chloride monomer is converted into a vinyl chloride polymer by a polymerization reaction is as follows.
Since the specific gravity of the vinyl chloride polymer is larger than the specific gravity of the vinyl chloride monomer and the specific gravity of the vinyl chloride polymer, the difference in specific gravity indicates that the volume of the polymerization reaction system shrinks as the polymerization reaction proceeds. Say. And such volume shrinkage can be measured by any method,
For example, it can be calculated from the following equation (1).

V = weight of charged vinyl chloride monomer * C / 100 * (1 / ρ1-1 / ρ2) (1) (where V is the volume shrinkage due to the polymerization reaction, and C is the vinyl chloride monomer) Conversion of the polymer to vinyl chloride polymer, ρ
1 is the specific gravity of the vinyl chloride monomer, and ρ2 is the specific gravity of the vinyl chloride polymer. The polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer in the present invention is determined, for example, by adding the integrated value of the heat removal amount when the inside of the polymerization reaction system is removed. The theoretical calorific value when a vinyl polymer is obtained (the theoretical calorific value per kg of vinyl chloride monomer is 374.4).
kcal / kg) and can be calculated by showing the value as a percentage.

The vinyl chloride monomer referred to in the present invention includes a vinyl chloride monomer or a mixture of a vinyl monomer copolymerizable with a vinyl chloride monomer and a vinyl chloride monomer. Any vinyl monomer copolymerizable with a vinyl chloride monomer may be used as long as it is a vinyl monomer copolymerizable with a vinyl chloride monomer, such as ethylene and propylene. Olefins, vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate and propyl acrylate, and maleic acid And vinyl esters of fumaric acid, fumaric acid, aromatic vinyl compounds such as styrene, and acrylonitrile. Vinyl monomers known as if possible monomer. And the copolymerizable vinyl monomer is usually 2 to vinyl chloride monomer.
It is preferable to use it in a proportion of 0% by weight or less.

As the aqueous medium referred to in the present invention, any one can be used as long as it belongs to the category of the aqueous medium. Among them, deionized water is preferable. Alternatively, heating may be performed in advance to shorten the heating time, or may be performed during charging in the polymerization reactor.

As the polymerization initiator referred to in the present invention, those generally known as polymerization initiators for vinyl chloride monomers can be used. For example, diisopropyl peroxy dicarbonate, di-2-ethylhexyl peroxy Percarbonate compounds such as dicarbonate and diethoxyethyl peroxydicarbonate; t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, t-hexyl peroxy vivalate;
Peroxyester compounds such as t-amyl peroxy neodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxy neodecanoate, t-hexyl peroxy diglycolate, α-cumyl peroxy neodecanoate Peroxides such as acetylcyclohexylsulfonyl peroxide, azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile); and hydrogen peroxide; These can be used alone or in combination of two or more. These polymerization initiators are used in an amount of 0.00 parts by weight based on 100 parts by weight of the vinyl chloride monomer.
It is preferable to use it in the range of 1 to 1 part by weight.

The dispersion stabilizer referred to in the present invention may be any of those generally used as suspension stabilizers in suspension polymerization, for example, cellulose derivatives such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose. Water-soluble polymers such as partially saponified polyvinyl alcohol (hereinafter, referred to as PVA), acrylic acid polymer, and gelatin; nonionic surfactants, anionic surfactants, and the like; and these may be used alone or in combination of two or more. It is also possible to use these dispersion stabilizers, and it is preferable to use these dispersion stabilizers in the range of 0.01 to 1 part by weight based on 100 parts by weight of the vinyl chloride monomer.

The polymerization reactor used in the present invention is a polymerization reactor provided with a reflux condenser. The polymerization reactor is a large-sized reactor having an inner volume of 40 m ³ or more, particularly 80 m ³ or more. Preferably, there is.

As the predetermined polymerization temperature in the present invention, a polymerization temperature generally used in the production of a vinyl chloride polymer may be appropriately selected, and in particular, it is preferably from 30 to 80 ° C.

As the stirring blade used in the present invention, it is possible to use a stirring blade generally used as a stirring blade for a polymerization reaction. Among them, it is particularly preferable to stir a suspension polymerization solution uniformly. Thus, a multi-stage blade having two or more stages is preferable. Examples of such a blade include a paddle blade, a turbine blade, a Faudler blade, and a blue margin blade.

The polymerization reactor for carrying out the present invention may be equipped with a baffle. As such a baffle, for example, a plate type, a cylindrical type, a D type, a loop type, a finger type and the like can be used. It is also possible to provide a heating and cooling jacket, as a heating and cooling jacket,
For example, an outer jacket, an inner jacket or the like can be used.

Further, in the present invention, if necessary, a chain transfer agent, an antioxidant, an antistatic agent, a pH adjusting agent, a scale adhesion inhibitor, a lubricant, etc., which are appropriately used in the production of a vinyl chloride polymer. May be added.

[0031]

EXAMPLES The present invention will be described below based on examples and comparative examples, but the present invention is not limited to these examples.

The evaluation of the vinyl chloride polymers obtained in Examples and Comparative Examples was measured by the following method.

-Foaming State-The movement of the surface of the polymerization reaction solution was visually observed through an observation window attached to the upper part of the polymerization reactor, and the foaming state was observed.

；: No foaming was observed in the polymerization reaction system.

X: Foaming was observed in the polymerization reaction system.

[Average Particle Size] The obtained vinyl chloride polymer is sieved through a 45-mesh sieve according to JIS Z 8801, and a sample passed through the sieve is used. 50% by weight of the sample is a vinyl chloride polymer. The size (μm) of the sieve mesh through which the particles pass is expressed as the average particle size.

-45 mesh on- The obtained vinyl chloride polymer is sieved through a 45 mesh sieve according to JIS Z 8801, and the weight of the sample not passing through the sieve is determined by the weight of the obtained vinyl chloride polymer. Expressed as a percentage by weight based on weight.

Roll Fish Eye 100 parts by weight of the obtained vinyl chloride polymer, Ca-Zn
A mixture of 1.5 parts by weight of a base powder composite stabilizer, 0.5 parts by weight of an organic phosphorus-based stabilizing aid, 3 parts by weight of ultramarine blue and 50 parts by weight of a polyester plasticizer was used. The mixture was kneaded for 9 minutes at 0.35 mm, a 0.35 mm sheet was taken out, and the number of transparent particles in 50 cm ² of the sheet was indicated.

-Scale adhesion state-The scale adhesion state on the polymerization reactor wall was visually evaluated.

○: good ×: bad (severe scale adhesion) Example 1 A reflux condenser, an observation window through which the inside of a polymerization reactor can be observed, and the upper end of the uppermost paddle blade 1.60 m from the bottom of the reactor. A tank diameter (D) of 1.00 m and an internal volume of 1.80 provided with three stages of paddle blades as stirring blades so that
100 parts by weight (586 kg) of a vinyl chloride monomer, PVA having a degree of saponification of 80 mol% and an average degree of polymerization of 2600 as a dispersion stabilizer were placed in a polymerization reactor having a polymerization reaction vessel of m ^3.
0.050 parts by weight, 0.030 parts by weight of PVA having a saponification degree of 40 mol% and an average degree of polymerization of 550, 0.020 parts by weight of cumyl peroxy neodecanoate as a polymerization initiator, and t-butyl peroxy neodecano Eat 0.045
105 parts by weight (615 kg) of 40 parts by weight of water at 40 ° C. were charged and the temperature was raised to 57 ° C., which is the polymerization temperature. When the temperature reached 57 ° C., the surface of the polymerization reaction solution was 1.92 m from the bottom of the polymerization reaction tank, and the vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade was 0.32 m. H / D, which is the ratio of the vertical distance (H) from the polymerization reaction liquid surface to the upper end of the stirring blade to the tank diameter (D) of 1.00 m (H) 0.32 m, was 0.32.

The polymerization reaction was continued for 140 minutes after the temperature reached 57 ° C. At that time, the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer was 50%, and the volume shrinkage during that time was 141 liters, the surface of the polymerization reaction solution was reduced by 0.20 m, and H / D = 0. It was 12. Thereafter, water was injected into the polymerization reaction tank, and the polymerization reaction was continued for 4 hours from when the temperature reached 57 ° C. while maintaining H / D = 0.12. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total polymerization calorific value was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.

During the production of the vinyl chloride polymer, no foaming occurred, the obtained vinyl chloride polymer had no 45 mesh on, the average particle diameter and the roll fish eye were good, and No scale adhesion was observed.

Example 2 A vinyl chloride monomer, a suspension stabilizer, a polymerization initiator and water were charged into the same polymerization reactor as in Example 1 under the same charging conditions as in Example 1, and the temperature was raised to 57 ° C. did.

The polymerization reaction was continued for 90 minutes after the temperature reached 57 ° C. At that time, the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer was 32%, the volume shrinkage during that time was 90 liters, and the surface of the polymerization reaction solution was 0.1%.
It decreased by 5 m, and H / D became 0.17. Thereafter, water was injected into the polymerization reaction tank, and the polymerization reaction was continued for 4 hours from when the temperature reached 57 ° C. while maintaining H / D = 0.17. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total heat generated by polymerization was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.

No foaming occurred during the production of the vinyl chloride polymer. The obtained vinyl chloride polymer had no 45 mesh on, had an average particle diameter and a good roll fish eye. No scale adhesion was observed.

Example 3 A vinyl chloride monomer 10 was placed in the same polymerization reactor as in Example 1.
0 parts by weight (621 kg), saponification degree 8 as dispersion stabilizer
0 mol%, PVA 0.050 having an average degree of polymerization of 2600
Parts by weight, 40 mol% of saponification degree, 0.030 parts by weight of PVA having an average degree of polymerization of 550, 0.020 parts by weight of cumyl peroxy neodecanoate as polymerization initiator and 0.1 part by weight of t-butyl peroxy neodecanoate. 045 parts by weight, 4
105 parts by weight (652 kg) of water at 0 ° C. were charged, and the temperature was raised to 57 ° C., which is a polymerization reaction temperature. The vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade at that time is 0.40 m, and the vertical distance (H) 0 from the surface of the polymerization reaction solution to the top of the stirring blade with respect to the tank diameter (D) of 1.00 m. The H / D, which was a ratio of .40 m, was 0.40.

The polymerization reaction was continued for 160 minutes from the time when the temperature reached 57 ° C. At that time, the polymerization conversion rate of the vinyl chloride monomer into the vinyl chloride polymer was 57%, and the volume shrinkage was 170 liters during the conversion, the surface of the polymerization reaction solution was reduced by 0.22 m, and H / D = 0. It was 18. Thereafter, water was injected into the polymerization reaction tank, and the polymerization reaction was continued for 4 hours from when the temperature reached 57 ° C. while maintaining H / D = 0.18. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total polymerization calorific value was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 1 shows the evaluation results of the obtained vinyl chloride polymers.

During the production of the vinyl chloride polymer, no foaming occurred, the obtained vinyl chloride polymer had no 45 mesh on, the average particle diameter and the roll fish eye were good, No scale adhesion was observed.

Comparative Example 1 A vinyl chloride monomer, a suspension stabilizer, a polymerization initiator and water were charged into the same polymerization reactor as in Example 1 under the same charging conditions as in Example 1, and the temperature was raised to 57 ° C. did.

Then, water was injected into the polymerization reaction tank when the temperature reached 57 ° C., and the polymerization reaction was continued for 4 hours from the time when the temperature reached 57 ° C. while maintaining H / D = 0.32. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total polymerization calorific value was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

When the H / D is higher than 0.20 in the range of 65% to 80% of the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer, the foaming becomes extremely severe, and after the polymerization, the inside of the polymerization reactor is The scale adhered to the wall surface and the inside of the reflux condenser, and the obtained vinyl chloride polymer had poor roll fish eye.

Comparative Example 2 The same polymerization reactor as in Example 1 was charged with a vinyl chloride monomer, a suspension stabilizer, a polymerization initiator and water under the same charging conditions as in Example 1, and the temperature was raised to 57 ° C. did.

The polymerization reaction was continued for 170 minutes after the temperature reached 57 ° C. At that time, the polymerization conversion rate of the vinyl chloride monomer to the vinyl chloride polymer was 63%, the volume shrinkage was 177 liters during the conversion, the surface of the polymerization reaction solution was reduced by 0.25 m, and H / D = 0. 07. Thereafter, water was injected into the polymerization reaction tank, and the polymerization reaction was continued for 4 hours from when the temperature reached 57 ° C. while maintaining H / D = 0.07. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total heat generated by polymerization was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

If the H / D is lower than 0.10 in the range of 65% to 80% of the polymerization conversion ratio of the vinyl chloride monomer to the vinyl chloride polymer, the scattering of the polymer slurry is extremely severe.
After the polymerization, the scale adhered to the inner wall surface of the polymerization reactor in a lump, and the obtained vinyl chloride polymer had poor roll fish eye.

Comparative Example 3 A vinyl chloride monomer 10 was placed in the same polymerization reactor as in Example 1.
0 parts by weight (551 kg), saponification degree 8 as dispersion stabilizer
0 mol%, PVA 0.050 having an average degree of polymerization of 2600
Parts by weight, 40 mol% of saponification degree, 0.030 parts by weight of PVA having an average degree of polymerization of 550, 0.020 parts by weight of cumyl peroxy neodecanoate as polymerization initiator and 0.1 part by weight of t-butyl peroxy neodecanoate. 045 parts by weight, 4
105 parts by weight (579 kg) of water at 0 ° C. were charged, and the temperature was raised to 57 ° C., which is the polymerization temperature. The vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade is 0.18 m, and the vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade for the tank diameter (D) of 1.00 m is 0.18 m. The ratio H / D was 0.18.

Water was poured into the polymerization reaction tank when the temperature reached 57 ° C., and the polymerization reaction was continued for 4 hours from the time when the temperature reached 57 ° C. while maintaining H / D = 0.18. At that time, the polymerization conversion rate from the vinyl chloride monomer to the vinyl chloride polymer was 85%.

Regarding heat removal during the polymerization reaction, heat removal by the reflux condenser was started after the temperature reached 57 ° C., and 60% of the total polymerization calorific value was removed by the reflux condenser.

After 4 hours at 57 ° C., the polymerization reaction was terminated, the unreacted vinyl chloride monomer was recovered, the polymer slurry was taken out, and dehydrated and dried to obtain a vinyl chloride polymer.
Table 2 shows the evaluation results of the obtained vinyl chloride polymer.

When the ratio H / D, which is the ratio of the vertical distance (H) from the surface of the polymerization reaction solution to the top of the stirring blade to the tank diameter (D) when the polymerization temperature is reached, falls below 0.30, the suspension at the beginning of polymerization is reduced. In addition to vigorous scattering of water and severe adhesion of scale to the polymerization vessel wall after the polymerization, the obtained vinyl chloride polymer was coarsened and the roll fish eye was inferior because it was not possible to stir well at the beginning of polymerization. Was.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

According to the present invention, even if the heat removal efficiency by the reflux condenser is increased, foaming does not occur during the production of the vinyl chloride polymer, and the obtained vinyl chloride polymer is coarsened and the roll fish eye deteriorates. The polymerization time can be greatly shortened without accompanying scale, and the productivity of the vinyl chloride-based polymer can be greatly increased, and its industrial value is very large.

Claims (1)

[Claims] 1. A method for preparing a vinyl chloride polymer by subjecting a vinyl chloride monomer to suspension polymerization in an aqueous medium in the presence of a polymerization initiator and a dispersion stabilizer using a polymerization reactor equipped with a reflux condenser. In the production method, vinyl chloride monomer,
An aqueous medium, a polymerization initiator, and a dispersion stabilizer were charged, the temperature was increased, and the vertical temperature from the surface of the polymerization reaction solution to the top of the stirring blade with respect to the tank diameter (D) of the polymerization reactor when the temperature reached a predetermined polymerization temperature. H / D which is a ratio of the distance (H) is set to 0.30 to 0.3.
60, wherein the H / D is maintained in the range of 0.10 to 0.20 when the polymerization conversion ratio of the vinyl chloride monomer to the vinyl chloride polymer is in the range of 65% to 80%. For producing a vinyl chloride polymer.