JPH11209409A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Problem] To provide a production method in which the productivity of a vinyl chloride polymer having a sharp particle size distribution and excellent roll fish eye is greatly improved. SOLUTION: In a method for producing a vinyl chloride monomer by suspension polymerization, 50.
Circulating warm water of not less than 80 ° C. and less than 80 ° C., and adjusting the pressure in the reaction vessel to 0 Mpa or more, charging the aqueous medium and the dispersion stabilizer at 40 ° C. or less into the polymerization reactor under stirring, and using the charged amount of the aqueous medium. When the amount reaches 30% by weight or more of the vinyl chloride monomer to be charged, the vinyl chloride monomer is charged.
The method of manufacturing, characterized in that the temperature is raised with warm water of 80 ° C. or more and less than 100 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer (hereinafter referred to as vinyl chloride monomer). In the suspension polymerization method, the time required for the polymerization to reach the polymerization temperature of the aqueous medium and the vinyl chloride-based monomer is shortened, thereby increasing the productivity of the polymerization step in the production of the vinyl chloride-based polymer. To improve fish eye of the vinyl chloride polymer obtained and to prevent scale adhesion.
The present invention relates to a method for producing a vinyl chloride polymer having a sharp particle size distribution.

[0002]

2. Description of the Related Art Generally, a suspension polymerization of a vinyl chloride monomer is carried out in a batch system.
After charging the aqueous medium, the suspending agent, the polymerization initiator, and the additives into the polymerization reactor, deaerate the polymerization system, charge the vinyl chloride monomer, etc., and stir with warm water into the jacket of the polymerization reactor. The polymerization reaction is started by circulating or passing steam to raise the temperature to the polymerization temperature. Thereafter, from the point when the polymerization reaction heat is generated, cooling water is passed through the jacket of the polymerization reactor to keep the polymerization temperature constant, and the reaction is continued until a predetermined polymerization rate is reached. After the completion of the polymerization reaction, an unreacted monomer such as a vinyl chloride-based monomer is recovered, and a series of polymerization operations for discharging the vinyl chloride-based polymer from the polymerization reactor are performed.

However, in such a conventional method, it takes a long time to raise the temperature in a large-sized polymerization reactor having a small heat transfer area with respect to the internal volume, which causes a decrease in productivity of the vinyl chloride polymer. It has contributed.

[0004] In order to solve such a problem, various methods have been proposed.

[0005] For example, Japanese Patent Publication No. 58-50603 discloses a method of shortening the heating time by using heated water. A method in which monomers are charged and stirred and mixed, and then heated water is charged to start polymerization.
JP-A-248804 discloses a method in which an aqueous medium at normal temperature and a suspending agent are charged, stirring is started, and then a vinyl chloride monomer, a polymerization initiator and heated water are charged to start polymerization.
Japanese Patent Application No. 0-47007 proposes a method of uniformly mixing a vinyl chloride-based monomer, a polymerization initiator, a dispersion stabilizer, and the like at a temperature of 40 ° C. or lower, and then adding heated water.

Further, as a method combining the shortening of the heating time using heated water and the shortening of the charging time for simultaneously charging the heated water and the vinyl chloride monomer, Japanese Patent Publication No. Sho 60-26
No. 488 discloses that a vinyl chloride monomer in which the polymerization initiator is completely dissolved and heated water in which the dispersion stabilizer is completely dissolved are mixed with 50.
No. 7-119247, a vinyl chloride monomer and warming water are simultaneously charged at 70% or more, and at least 20% of a dispersion stabilizer is charged during the vinyl chloride monomer charging. A method has been proposed in which the polymerization initiator is charged in an amount of 30 to 100% of the total amount of the vinyl chloride-based monomer and when the weight ratio of the monomer to the water in the polymerization vessel is 1.5 or less. .

Further, Japanese Patent Application Laid-Open No. 6-93006 discloses that
There has been proposed a method of shortening a heating time in which steam is supplied into a polymerization reactor.

[0008]

[Problems to be solved by the invention]
No. 50603, JP-A-4-2488
In the method described in Japanese Patent Application Publication No. 04-204, the heating time can be shortened by using heated water, but the operation of the manufacturing process is complicated because two types of water having different temperatures, such as low-temperature water and high-temperature water, are used. In addition, in order to shorten the heating time, it is necessary to use high-temperature hot water inevitably because the low-temperature water is previously prepared compared to the case of using one kind of hot water, and the temperature of the hot water is high. Since the polymerization reaction is rapidly started, there are problems such as generation of scale on the inner wall of the polymerization reactor and generation of coarse particles of the obtained vinyl chloride polymer.

On the other hand, as a method using one kind of hot water, a method described in Japanese Patent Application Laid-Open No.
Since the vinyl chloride monomer containing the polymerization initiator is charged before the heated water, the vinyl chloride monomer is in direct contact with the wall of the polymerization reactor, and the polymerization is started when the heated water is charged therein. As a result, the vinyl chloride polymer adheres to the wall surface of the polymerization reactor to form a scale, which causes fisheye to deteriorate. In addition, in this method, since the warming water is charged after the vinyl chloride monomer is charged, the state in which the warming water is dispersed in the vinyl chloride monomer (the vinyl chloride monomer is a continuous phase)
Phase transition to a state in which the vinyl chloride monomer is dispersed in the heated water (the vinyl chloride monomer is in the dispersed phase) occurs, so that coarse particles are formed and the particle size distribution of the obtained vinyl chloride polymer is widened. Quality problems. Furthermore, if the phase transition does not occur, the vinyl chloride-based polymer becomes a lump in the polymerization reactor and cannot be discharged from the polymerization reactor, which causes a serious problem in production.

[0010] Further, shortening of the heating time using heated water,
Japanese Patent Application Laid-Open No. 60-2648 discloses a method combining the shortening of charging time for simultaneously charging warmed water and a vinyl chloride monomer.
In the method described in JP-A No. 8 (1996) -1989, a polymerization initiator is dissolved in a vinyl chloride-based monomer and charged, so that the temperature of the vinyl chloride-based monomer is kept low or a polymerization initiator having a low polymerization activity is used. It is necessary to use, because when the temperature of the vinyl chloride monomer is kept at a low temperature, the time required for raising the temperature cannot be shortened, and when a polymerization initiator having low polymerization activity is used, the polymerization time cannot be shortened. The effect of improving productivity is small. In order to further reduce the temperature rise time, it is necessary to use higher-temperature water because of the lower temperature of the vinyl chloride monomer, which causes problems such as adhesion of scale to the inner wall of the polymerization reactor and formation of coarse particles. Becomes In addition, when the dispersion stabilizer is dissolved in warm water and charged, if the temperature of the heated water exceeds the cloud point of the dispersion stabilizer, the dispersion stabilizer precipitates and adheres to the charging pipe or the like, making the charging difficult. It is necessary to use a dispersion stabilizer having a high water content or to take measures to prevent adhesion to the piping.

The method described in Japanese Patent Publication No. 7-119247 is based on the fact that at least 20% of a dispersion stabilizer is charged during the preparation of a vinyl chloride monomer, and the concentration of the dispersion stabilizer can be uneven. There is a problem that the particle size distribution of the system polymer is widened. Furthermore, in the simultaneous charging of the vinyl chloride monomer and the heating water, the phase transition between the vinyl chloride monomer and the aqueous medium may occur unless the charging ratio of the vinyl chloride monomer and the heating water is controlled. Yes, especially when the amount of vinyl chloride monomer charged per batch is increased to improve productivity, the ratio of heated water to vinyl chloride monomer decreases, It is necessary to finely control the charging timing and charging speed of the heating water.

Further, in the method described in Japanese Patent Application Laid-Open No. Hei 6-93006, although the time for raising the temperature is shortened by blowing steam, the temperature of the contact portion with steam rises sharply, so that the polymerization starts locally. However, there is a problem that the roll fish eye of the obtained vinyl chloride polymer is greatly deteriorated.

Accordingly, an object of the present invention is to provide a vinyl chloride polymer which is excellent in productivity in solving the above-mentioned problems, has a sharp particle size distribution of the obtained vinyl chloride polymer, and has an improved fish eye. To provide a method for producing a vinyl chloride polymer.

[0014]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems and to shorten the cycle time of the polymerization step. As a result, a vinyl chloride polymer is produced under specific conditions. By shortening the heating time, the cycle time of the polymerization step can be shortened, and the fish eye and particle size distribution of the obtained vinyl chloride polymer are not impaired and there is no scale adhesion. Was completed.

That is, the present invention relates to a method for producing 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. Circulating warm water of 50 ° C. or more and less than 80 ° C. in the jacket, and in a polymerization reactor of an aqueous medium and a dispersion stabilizer at 40 ° C. or less under stirring with the pressure in the reaction vessel set to 0 MPa or more by gauge pressure. When the amount of the aqueous medium reaches 30% by weight or more with respect to the vinyl chloride monomer to be used, the charging of the vinyl chloride monomer is started. The present invention relates to a method for producing a vinyl chloride polymer, which comprises circulating hot water at a temperature of 80 ° C. or higher and lower than 100 ° C. through a polymerization reactor jacket after completion of charging of the system monomer.

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

The vinyl chloride monomer used in the present invention is a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer.

As the monomer copolymerizable with the vinyl chloride monomer, any monomer can be used as long as it is a monomer copolymerizable with the vinyl chloride monomer. Olefins, vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, acrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate and propyl acrylate, maleic acid, Esters or anhydrides of fumaric acid, aromatic vinyl compounds such as styrene, and monomers conventionally known as monomers copolymerizable with vinyl chloride monomers, such as acrylonitrile, may be mentioned. The copolymerizable monomer is preferably used at a ratio of usually 20% by weight or less based on the vinyl chloride monomer.

The aqueous medium used in the present invention is preferably deionized water. When the aqueous medium is used, it may be at room temperature or may be heated beforehand.
It is charged into a polymerization reactor at a temperature of 40 ° C. or less.

As the polymerization initiator used in the present invention, those generally known as polymerization initiators can be used. For example, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl Peroxy carbonate compounds such as peroxy dicarbonate; t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, t-hexyl peroxy vivalate, t-amyl peroxy neodecanoate, 1 , 1-dimethyl-3
-Hydroxybutyl peroxy neodecanoate, t-
Peroxyester compounds such as hexylperoxydiglycolate and α-cumylperoxyneodecanate; peroxides such as acetylcyclohexylsulfonyl peroxide; azobis (2,4-dimethylvaleronitrile);
An azo compound such as azobis (4-methoxy-2,4-dimethylvaleronitrile); hydrogen peroxide; and the like, and these can be used alone or in combination of two or more.

The polymerization initiator is preferably used in an amount of 0.001 to 1 part by weight based on 100 parts by weight of the vinyl chloride monomer.

The dispersion stabilizer used in the method of the present invention is not particularly limited, and those generally used as suspension stabilizers for suspension polymerization may be used. Examples thereof include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and the like. Examples include cellulose derivatives such as hydroxypropylmethylcellulose, partially saponified polyvinyl alcohol, acrylic acid polymers, water-soluble polymers such as gelatin, nonionic surfactants, anionic surfactants, and the like. These may be used alone or in combination of two or more. It is also possible to use.

The dispersion stabilizer is preferably used in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the vinyl chloride monomer.

In the production method of the present invention, hot water of 50 ° C. or more and less than 80 ° C. is circulated in advance in the polymerization reactor jacket. The purpose of this is to warm the aqueous medium charged in the polymerization reactor during the charging, and the present invention improves the productivity by this operation. Here, the aqueous medium is circulated through the polymerization reactor jacket. When the temperature of the hot water is lower than 50 ° C., the temperature of the aqueous medium cannot be increased when the aqueous medium is charged into the polymerization reactor, and as a result, the productivity cannot be improved. On the other hand, when the temperature of the hot water circulated through the jacket of the polymerization reactor is 80 ° C. or higher, the temperature in the polymerization reactor rises sharply, which makes it difficult to control the temperature in the polymerization reactor, and also makes it difficult to control the vinyl chloride weight. At the time of production of the union, the scale is strongly attached, which is not preferable.

Further, when the production method of the present invention is carried out, it is preferable to use a polymerization reactor having a baffle plate, since the vinyl chloride polymer is obtained as particles having a particularly small particle size distribution. In this case, since the temperature of the aqueous medium can be efficiently increased, the baffle plate is formed as a double tube, and the baffle plate is also heated to 50 ° C. in advance in order to heat the aqueous medium during preparation. It is preferable to circulate warm water having a temperature of at least 80 ° C.

In the production method of the present invention, the charging of the aqueous medium and the dispersion stabilizer at a temperature of 40 ° C. or less is started under stirring with the pressure in the polymerization reaction vessel kept at 0 MPa or more by gauge pressure. It is. The gauge pressure in the present invention is:
A value measured using a general commercially available pressure gauge.

Here, when the charging of the aqueous medium and the dispersion stabilizer at 40 ° C. or less is started under stirring with the pressure in the polymerization reaction vessel set to a gauge pressure of less than 0 MPa, the dissolved oxygen in the aqueous medium is Since the concentration is reduced, the obtained vinyl chloride polymer is coarsened. In particular, as the aqueous medium used in the present invention, it is preferable to use an aqueous medium having a dissolved oxygen concentration of 2 ppm or more and a saturation concentration of +2 ppm or less.

When the charging of the aqueous medium and the dispersion stabilizer at 40 ° C. or higher is started without stirring, it is difficult to control the temperature of the aqueous medium. Furthermore, when the cloud point of the dispersion stabilizer is exceeded, the dispersion stabilizer adheres to the wall of the polymerization reactor, causing scale during the polymerization reaction, and the vinyl chloride-based polymer obtained due to a decrease in the concentration of the dispersant is reduced. It becomes coarse.

In the present invention, the method of setting the pressure in the polymerization reaction vessel to 0 MPa or more at a gauge pressure may be any method as long as the pressure in the polymerization reaction vessel can be set to 0 MPa or more at a gauge pressure. For example, a method in which a small amount of vinyl chloride-based monomer is charged to 0 MPa or more after degassing of the polymerization reactor, or a method in which unreacted monomers of the previous batch are left in the polymerization reactor to be 0 MPa or more. In the present invention, there are a method in which the pressure in the polymerization reactor is increased to 0 MPa or more by a system monomer, and a method in which the pressure in the polymerization reactor is increased to 0 MPa or more by an inert gas such as nitrogen, helium, or argon. Since the pressure in the polymerization reaction vessel can be increased to 0 MPa or more by a gauge pressure without complicating the polymerization process, these methods, particularly, a vinyl chloride monomer, The pressure in the reactor it is preferable to use a method of the above 0 MPa.

Further, according to the production method of the present invention, the charging of the vinyl chloride-based monomer is started when the charged amount of the aqueous medium reaches 30% by weight or more based on the vinyl chloride monomer to be used. Things. Here, when the charging of the vinyl chloride monomer is started at a stage where the amount of the aqueous medium charged is less than 30% by weight based on the vinyl chloride monomer to be used, the vinyl chloride monomer and the aqueous medium Phase transition may occur, and there is a problem that scale adheres during the polymerization reaction and the roll fish eye of the obtained vinyl chloride polymer deteriorates. Further, there is a possibility that the vinyl chloride-based polymer becomes a lump in the polymerization reactor and cannot be discharged from the polymerization reactor, causing a serious problem in production.

The production method of the present invention comprises the steps of:
By circulating warm water of less than 00 ° C., the temperature is raised to a predetermined polymerization temperature. Here, the temperature of the hot water is 8
When the temperature is lower than 0 ° C., the temperature in the polymerization reactor rises slowly, so that it takes a long time to raise the temperature to a predetermined polymerization temperature, and improvement in productivity during the production of a vinyl chloride polymer cannot be achieved. On the other hand, when the temperature of the hot water is 100 ° C. or higher, the temperature in the polymerization reactor rapidly rises, and not only becomes difficult to control the temperature in the polymerization reactor, but also the scale of the vinyl chloride polymer adheres violently. And a vinyl chloride polymer having excellent quality cannot be obtained.

[0032]

EXAMPLES Hereinafter, the production method of the present invention will be described based on examples and comparative examples, but the present invention is not limited to these.

The evaluation and measurement of the vinyl chloride polymers obtained in Examples and Comparative Examples were performed by the following methods.

Particle Size Distribution The obtained vinyl chloride polymer is sieved through a 45-mesh sieve according to JIS Z 8801, and the sample passing through the sieve is further subjected to 60-mesh, 80-mesh, and 100-mesh according to JIS Z 8801. , 140 mesh,
The sample was sieved with a 200-mesh sieve, and the size of the sieve through which 85% by weight of the vinyl chloride polymer particles of the sample passed (A
(Μm)), the sieve size (B (μm)) through which 15% by weight of the vinyl chloride polymer particles passed, and the sieve size (C (C) through which 50% by weight of the vinyl chloride polymer particles passed) (Μ
m)) was measured, and the particle size distribution was calculated by inserting the result into the following equation.

Particle size distribution = (AB) / C ~ average particle size ~ The obtained vinyl chloride polymer is passed through a 45 mesh sieve according to JIS Z8801, and a sample passed through the sieve is used. The size (μm) of the sieve through which 50% by weight of the vinyl chloride polymer particles pass is expressed as the average particle size.

-45 mesh on- The obtained vinyl chloride polymer is passed through a 45 mesh sieve according to JIS Z8801, and the weight ratio (percentage) of the sample remaining on the sieve to the total amount of the sample passed through the sieve is calculated. Expressed as 45 mesh on.

-Bulk specific gravity-According to JIS K6721.

~ Fisheye ~ 100 parts by weight of the obtained vinyl chloride polymer, Ca-Zn
1.5 parts by weight of a composite 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 DOP (dioctyl phthalate) were mixed and rolled at 150 ° C. to a thickness of 0.1 part. The mixture was kneaded at 35 mm for 5 minutes, and a 0.35 mm sheet was taken out and indicated by the number of transparent particles in 50 cm ^{2 of} the sheet.

-Scale adhesion-The amount of scale attached to the polymerization reactor wall was visually evaluated.

○ good × bad (heavy adhesion) Example 1 As a polymerization reactor, a 1.6 m ³ backflow condenser was installed, and a polymerization reactor having a pipe type baffle plate having a double pipe structure was used. Was. First, hot water of 60 ° C. was circulated through the jacket of the polymerization reactor and the baffle plate having the double tube structure. After that, the inside of the polymerization reactor was degassed, and 10 kg of vinyl chloride monomer was used.
Was charged. At that time, the pressure in the polymerization reactor was 0.1 MPa in gauge pressure.

Then, under stirring, 576 kg of deionized water having a dissolved oxygen concentration of 7 ppm at 35 ° C., 7,800 g of a 3.5% solution of partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and an average polymerization degree of 2,600 as a dispersion stabilizer were charged. At the same time, charging was completed in 10 minutes for deionized water and 2 minutes for the dispersion stabilizer. After the preparation of deionized water, 2
Start charging 536 kg of vinyl chloride monomer at 0 ° C,
The charging of the vinyl chloride monomer was completed in 6 minutes. In addition,
At the stage of charging 380 kg of vinyl chloride monomer (about 70% by weight of the total charged amount of vinyl chloride monomer), 368 g of cumyl peroxy neodecanoate having a purity of 70% by weight previously charged in a pot and a purity of 70% 368 g of t-butyl peroxy neodecanoate was charged in the polymerization reactor.
The temperature in the polymerization reactor after the completion of the charging was 45 ° C.

After the vinyl chloride monomer was charged, hot water of 90 ° C. was circulated through the jacket of the polymerization reactor and the baffle plate having a double tube structure to raise the temperature in the polymerization reactor to 57.5 ° C. The heating required 18 minutes, and the heating time from the start of the charging to the polymerization temperature was 34 minutes.

The polymerization was terminated when the pressure in the polymerization reactor decreased by 0.2 MPa from the saturated vapor pressure at 57.5 ° C., and the unreacted vinyl chloride monomer was recovered and stirred. The obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 1 shows the results.

The powder characteristics and fisheye of the obtained vinyl chloride polymer were good, and no adhesion of scale during the production of the vinyl chloride polymer was observed.

Example 2 75 ° C. was applied to a polymerization reactor jacket and a baffle plate having a double tube structure.
Of warm water was circulated, and charging of 35 ° C. deionized water and a dispersion stabilizer was simultaneously started with stirring. The pressure inside the polymerization reactor at the start of charging was 0.2 MPa.

After the completion of the deionized water charging, the charging of the vinyl chloride monomer at 20 ° C. was started, and the charging of the vinyl chloride monomer was completed in 6 minutes. After the vinyl chloride monomer was charged, the temperature in the polymerization reactor was 50 ° C.

Subsequently, hot water of 90 ° C. was circulated through the jacket of the polymerization reactor and the baffle plate having a double tube structure to raise the temperature in the polymerization reactor to 57.5 ° C. It takes 11 minutes to raise the temperature.
The polymerization of the vinyl chloride monomer was carried out in the same manner as in Example 1 except that the polymerization was continued for 1 minute.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 1 shows the results.

The powder characteristics and fisheye of the obtained vinyl chloride polymer were good, and no scale adhesion was observed during the production of the vinyl chloride polymer.

Example 3 A polymerization reactor jacket and a baffle plate having a double tube structure were set at 75 ° C.
Of warm water was circulated, and charging of 35 ° C. deionized water and a dispersion stabilizer was simultaneously started with stirring. The pressure inside the polymerization reactor at the start of charging was 0.2 MPa.

Five minutes after the start of the charging of deionized water, 268 kg of deionized water (corresponding to 50% by weight of the vinyl chloride monomer to be used) was charged. Was started, the vinyl chloride monomer was charged in 6 minutes, and after the vinyl chloride monomer was charged, the temperature in the polymerization reactor was 45 ° C.

Then, hot water of 90 ° C. was circulated through the jacket of the polymerization reactor and the baffle plate having the double tube structure to raise the temperature in the polymerization reactor to 57.5 ° C. It takes 18 minutes to raise the temperature.
The polymerization was carried out in the same manner as in Example 1 except that the polymerization was carried out for 1 minute.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 1 shows the results.

The powder characteristics and fisheye of the obtained vinyl chloride polymer were good, and no adhesion of scale during the production of the vinyl chloride polymer was observed.

COMPARATIVE EXAMPLE 1 60 was added to the jacket of the polymerization reactor and
Circulating hot water at a temperature of -0.0 ° C.
After degassing to 6 MPa, polymerization of vinyl chloride monomer was carried out in the same manner as in Example 1 except that charging of deionized water at 35 ° C. and a dispersion stabilizer was simultaneously started under stirring in that state.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 1 shows the results.

The obtained vinyl chloride polymer is coarsened,
The roll fish eye was greatly deteriorated, and the scale adhered severely.

COMPARATIVE EXAMPLE 2 90 was added to the jacket of the polymerization reactor and
After circulating warm water at ℃, the temperature in the polymerization reactor after charging the vinyl chloride monomer is 55 ℃, it takes 5 minutes to raise the temperature to the polymerization temperature, and the temperature rise from the start of charging to the temperature reaches the polymerization temperature A vinyl chloride polymer was polymerized in the same manner as in Example 1 except that the time was 21 minutes.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 2 shows the results.

The obtained vinyl chloride polymer is coarsened,
The roll fish eye was greatly deteriorated, and the scale adhered severely.

Comparative Example 3 Pure water at 50 ° C. was used as deionized water. The temperature in the polymerization reactor after the completion of the vinyl chloride monomer charging was 50 ° C., and the temperature was raised to the polymerization temperature for 11 minutes. The polymerization of the vinyl chloride polymer was carried out in the same manner as in Example 1 except that the time from the start of the charging to the polymerization temperature was 27 minutes.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 2 shows the results.

The obtained vinyl chloride polymer is coarsened,
The roll fish eye was greatly deteriorated, and the scale adhered severely.

Comparative Example 4 Deionized water and a vinyl chloride monomer were charged in the same manner as in Example 1 without circulating warm water through the jacket of the polymerization reactor and the baffle plate having the double tube structure. The temperature in the polymerization reactor after the completion of charging the vinyl chloride monomer was 30 ° C. After the vinyl chloride monomer charging is completed, circulate hot water at 90 ° C through the jacket of the polymerization reactor and the baffle plate of the double tube structure, and it takes 40 minutes to raise the temperature to the polymerization temperature, and from the start of charging to the polymerization temperature Example 1 except that the time required for the temperature rise was 56 minutes.
The vinyl chloride polymer was polymerized in the same manner as in the above.

The obtained vinyl chloride polymer was evaluated and measured by the above evaluation method. Table 2 shows the results.

The heating time from the start of the charging until the polymerization temperature was reached had a long time, and the productivity was low.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

According to the production method of the present invention, a vinyl chloride polymer having a sharp particle size distribution and excellent roll fish eyes can be drastically shortened without increasing the adhesion of scale, and the temperature rise time for charging can be greatly reduced. The polymer can be produced by a method for greatly increasing the productivity of the polymer, and the industrial value of the present invention is very large.

Claims (2)

[Claims] 1. A method for producing 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. Circulating hot water at a temperature of at least 80 ° C. and setting the pressure in the reaction vessel to 0 MPa or more by gauge pressure,
Start charging the aqueous medium and the dispersion stabilizer at 40 ° C. or lower into the polymerization reactor under stirring, and the charged amount of the aqueous medium reaches 30% by weight or more based on the vinyl chloride monomer to be used. At that point, start charging the vinyl chloride monomer,
A method for producing a vinyl chloride polymer, comprising circulating hot water at a temperature of 80 ° C. or more and less than 100 ° C. through the polymerization reactor jacket after the completion of the charging of the vinyl chloride monomer. 2. A polymerization reactor having a double-tube baffle plate is used as the polymerization reactor, and the baffle plate also has a temperature of 50.degree.
The method for producing a vinyl chloride-based polymer according to claim 1, wherein less than less warm water is circulated.