JPH08134107A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE: To produce vinyl chloride polymer of the quality stabilized every batch-with scaling reduced because the amount of the heat removed by the reflux condenser is stably maintained, even when a polymerization vessel of a large scale is operated for a prolonged period of time. CONSTITUTION: Using a polymerizer provided with a polymerization vessel 1 having more than 100m<3> capacity and 1.5 or more L/D ratio, and having the uppermost stirring blade 2 arranged so that it comes in the range of from 150 to 300cm down from the top end (TL) of the straight cylinder of the vessel, the reaction mixture in the polymerization vessel is raised up near the polymerization temperature, then a non-condensing gas in the refluxing condenser is exhausted at a rate of 10-100Nm<3> /hour so that the exhaustion time becomes more than 20% of the total polymerization time, and the cooling with the reflux condenser is started at or after the start of the exhaustion.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer.

[0002]

2. Description of the Related Art Conventionally, as a polymerization apparatus used for suspension polymerization of vinyl chloride type monomers, a reflux condenser in a polymerization vessel, a heating / cooling jacket, an agitator, a raw material charging nozzle, and a polymer withdrawing nozzle. There is known a polymerization apparatus including the above. These polymerization apparatuses are mainly provided with a reflux condenser and a heating / cooling jacket for the purpose of removing heat of polymerization reaction. The reflux condenser is generally disposed above the polymerization vessel, introduces the vapor generated in the polymerization vessel, cools it with a coolant such as cooling water to condense it, and causes the condensed liquid to flow back into the polymerization vessel. To cool the temperature of the liquid contents. The heating / cooling jacket is arranged around the polymerization container and introduces cooling water or the like into the jacket to cool the contents in the polymerization container. Among them, the reflux condenser has a large cooling capacity and is attracting attention in terms of improving productivity or saving energy.

By the way, in recent years, for the purpose of improving productivity, the polymerization container itself has been increased in size and the polymerization time has been shortened. However, if the polymerization time is shortened, the amount of heat generated per unit time increases, and therefore there is a limit to cooling the polymerization container with only the heating / cooling jacket, and it is necessary to increase the rate of heat removal by the reflux condenser. On the other hand, in order to keep the quality of the polymer obtained in each batch constant by repeating the polymerization, it is necessary to maintain good reproducibility of the heat removal amount for each batch by the reflux condenser. However, generally, when the heat removal load of the reflux condenser is increased, the slurry foams in the polymerization container, and the slurry easily flows into the reflux condenser. Therefore, not only problems such as polymer scale adhering to the condenser occur, but also the heat removal capacity of the reflux condenser decreases, making it difficult to control the heat removal amount by the reflux condenser of each batch with good reproducibility. Is.

Further, in a large-sized polymerization vessel, when multi-stage continuous operation of 100 batches or more is carried out, the deposition of scale becomes remarkable on the portion of the inner wall of the polymerization vessel which is in contact with the gas phase part and near the interface between the gas phase and the liquid phase. As a result, the cooling capacity of the reflux condenser is lowered, and the scale is mixed, so that the quality of the obtained polymer is lowered.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to keep the amount of heat removed from the reflux condenser stable even if a long-term operation is carried out in a large-sized polymerization vessel. It is an object of the present invention to provide a method for producing a vinyl chloride polymer, which has stable quality and is less likely to cause scale adhesion.

[0006]

Means for Solving the Problems As a result of diligent studies, the present inventor has found that nitrogen, oxygen, etc., which are mixed in a polymerization container during the manufacturing process,
In addition, so-called non-condensable gases such as nitrogen, carbon monoxide, and carbon dioxide (which are usually dissolved in the contents of the polymerization vessel) generated by the decomposition of the polymerization initiator evaporate during the reaction, and especially in a large size. It has been found that in a vertically long polymerization vessel, the condensation and condensation of the evaporated and concentrated monomer inside the reflux condenser can be prevented, and the heat removal by the reflux condenser cannot be maintained. Therefore, at least before the cooling by the reflux condenser is started, that is, before the cooling by the reflux condenser is started, the non-condensable gas is exhausted from the reflux condenser under a predetermined condition to enhance the heat removal efficiency of the reflux condenser, and The present invention has been achieved by finding that the above problems can be solved by using a specific stirring blade.

According to the present invention, there is provided a substantially cylindrical polymerization container comprising a cylindrical straight body part and a substantially hemispherical top and bottom parts for sealing the upper and lower parts thereof, and a rotary shaft arranged on the center line of the polymerization container. A plurality of stages of stirring blades each having a blade, and a reflux placed in the upper part of the polymerization container to condense the monomer vapor generated in the polymerization container and to reflux the condensed liquid in the polymerization container. In a polymerization apparatus equipped with a condenser and a heating / cooling jacket which is arranged around the polymerization vessel and heats and cools the liquid content in the polymerization vessel, a vinyl chloride monomer or a vinyl-based monomer mainly containing the vinyl chloride monomer is used. Chlorination, which comprises suspension polymerization of the monomer mixture in an aqueous medium in the presence of an oil-soluble polymerization initiator while stirring with the stirring blade and exhausting the non-condensable gas that evaporates from the contents. Method for producing vinyl polymer Oite, as the polymerization vessel, internal volume 1
In 00m ³ or more, and the ratio of the length of the straight body portion to the inner diameter (D) (L) (L / D) is, is 1.5 or more, a stirring blade uppermost stage, the center line of the vertical width of the blade At a height of 1, the polymerization apparatus is arranged so that it falls within the range of 150 to 300 cm from the upper end position of the straight body part of the polymerization container, and the contents in the polymerization container are heated to near the polymerization temperature and then refluxed. Exhaust flow rate of non-condensable gas entering the condenser is 10-100N
m ³ / hour, exhausting under conditions such that the exhausting time is 20% or more of the total polymerization time, and cooling with a reflux condenser is started at the same time as or after the start of exhausting the non-condensable gas It is a method for producing a vinyl chloride polymer.

The present invention will be described in detail below. As shown in FIG. 1, the polymerization container to which the production method of the present invention is applied is basically a substantially cylindrical polymerization container including a cylindrical straight body portion and a substantially hemispherical top and bottom portions that seal the upper and lower portions thereof. 1 and the internal volume is 100 m ³ or more, preferably 100 to 200 m ³
And the length (L) of the straight body part with respect to the inner diameter (D) of the polymerization container
Ratio (L / D) is 1.5 or more, preferably 1.5 to
It is 2.5. As shown in FIG. 1, the stirring blade used in the present invention has a plurality of stages, preferably 3 or more stages, more preferably 3 to 5 stages along the rotary shaft 7 arranged on the center line A of the polymerization container 1. For example, as shown in FIG. 2, the uppermost stirring blades 2 are arranged at a height of the center line C of the vertical width of the blades from the upper end position (TL) of the straight body portion of the polymerization container 1 to 150 to downward. Install it so that it is within 300 cm. Further, as shown in FIG. 3, when the height of the upper end of the vertical width of the blade is H ₁ , the stirring blade 2 in the uppermost stage has H ₁ = 1.3D to
It is preferably installed at 1.85D (where D is as described above). In this case, the material charged into the polymerization vessel is (10/9) H ₁ ≦ when the height of the liquid surface of the content before the reaction is H ₀ and the height of the upper end of the straight body portion is H _2. H ₀ ≤ (100
/ 65) H ₁ (where H ₁ is as described above) and H ₀ <H ₂
It is preferable to prepare so as to satisfy the above conditions.

In the production method of the present invention, by using the stirring blades 2 arranged in this way, especially when 100 batches or more are continuously operated using a constant-flow reflux condenser, foam-like substances that stay at the gas-liquid interface are formed. It is possible to significantly reduce the scale growth by reducing the slurry and adding the cleaning effect of the interface portion. In addition, when this arrangement position is above the position of 150 cm downward from the upper end position (TL), the bulk specific gravity of the obtained vinyl chloride polymer is lowered,
The particle size distribution becomes broad, the number of fish eyes increases, and scale easily adheres to the interface in the polymerization container. When this arrangement position is below the position 300 cm below the upper end position (TL), the fish eyes of the vinyl chloride polymer obtained increase, and the scale easily adheres to the interface in the polymerization container. .

Known types of stirring blades can be preferably used, and examples thereof include paddle blades, pitched paddle blades, bull margin blades, Faudler blades, turbine blades,
A propeller blade or the like can be used. Among them, as shown in FIG. 2, a paddle blade provided with a plurality of plate-like substantially rectangular blades 4 in a radial shape around the rotation axis B is preferable.
The number of blades 4 is usually 2 to 6, preferably 2. The size of the blade 4 is not particularly limited as long as it does not affect the rotation, but one satisfying the following relational expression is preferable. 0.35 ≦ d / D ≦ 0.55 and 0.10 ≦ n
W / D≤0.16 (wherein D is as defined above, d is the blade diameter of the paddle blade, w is the vertical width of the blade 4, and n is The number of paddle wings 2)

It is also preferable to combine these paddle blades with other stirring blades. For example, as shown in FIG. 4, paddle blades 2a and 2c and pitched paddle blades 2b and 2d (the pitch angle of the blades of the pitched paddle blade is the rotation axis). On the other hand, a combination of, for example, 45 degrees) is included. In this case, the positional relationship between the paddle blade and the other stirring blades is not particularly limited and may be appropriately determined so that the contents are uniformly mixed.

The stirring blade 2 as described above is fixed to a rotary shaft 7, and the rotary shaft 7 is driven by an electric motor 8 installed above or below the polymerization container 1. Electric motor 8
The rotation speed of the stirring blade 2 is 7 to 15 m.
A speed of / s is preferred. For that purpose, the driving force of the electric motor 8 (stirring power of the stirring blade) is 1 t of the content of the polymerization container 1.
On the other hand, 80 to 170 kg · m / s is preferable.

As the reflux condenser used in the present invention, as shown in FIG.
A direct coupling condenser for condensing the monomer vapor generated in the polymerization vessel 1 through one conduit at the lower end of the condenser and for returning the condensed liquid to the polymerization vessel 1 through the same conduit,
As shown in FIG. 4, the same monomer vapor is condensed through the lateral conduit of the two conduits at the lower end of the condenser, and the condensed monomer is condensed through the central conduit into the polymerization vessel 1. An example is a separate condenser that refluxes. Therefore, the reflux condenser 6 may be a known one having a structure in which one or a plurality of conduits are connected to the main body of the polymerization vessel and vapor and condensate move in the conduit, for example, a coil type, a spiral type, a multi-tube type. Formula, shell-and-tube type, and the like. Among them, the shell-and-tube type is preferable. The heat transfer area of the reflux condenser is 60 ~ 300m ²
Is preferred. Reference numeral 9 is a non-condensable gas outlet.

In the production method of the present invention, after the temperature of the polymerization vessel is raised to near the polymerization temperature, the non-condensable gas in the reflux condenser is started to be exhausted and the cooling by the reflux condenser is started. The polymerization temperature may be a known polymerization temperature in suspension polymerization of vinyl monomers, and is usually 35 to 60 ° C.

The non-condensable gas is exhausted after the temperature of the polymerization vessel is raised to near the polymerization temperature, and when the polymerization temperature is t ° C., it is usually (t-5) ° C. to t ° C., preferably Is after reaching (t-2) ° C to t ° C. If the exhausting time is too early, foaming will occur in the polymerization container, and the foam containing the polymerization initiator will be mixed into the gas phase part and the inside of the condenser to increase the generation of scale or foamy polymer. May be mixed with a target polymer, and a vinyl chloride product obtained from this polymer may have fish eyes.

The heating is usually carried out by passing hot water or steam through a heating / cooling jacket 5 arranged around the polymerization vessel 1 as shown in FIG. 1 for heating and cooling the contents in the polymerization vessel 1. To do. Further, by raising the temperature within the above temperature range, the non-condensable gas dissolved in the contents of the polymerization container is evaporated from the liquid phase and accumulated in the gas phase part. Since this non-condensable gas has a lower specific gravity than the vinyl chloride monomer, it is concentrated in the gas phase portion of the polymerization container and the inside of the reflux condenser.

As a method for exhausting the non-condensable gas,
There is no particular limitation, and for example, a method of exhausting from a discharge port 9 provided at the top of the reflux condenser 6 with a pump or the like (not shown) can be mentioned.

The flow rate of the non-condensable gas discharged from the reflux condenser is usually 10 to 100 Nm ³ / hour,
It is preferably 10 to 60 Nm ³ / hour. If this flow rate is less than 10 Nm ³ / hour, it will be difficult to keep the heat removal amount of the reflux condenser constant for each batch, and it will be difficult to control the polymerization temperature constant.
Scale easily adheres to the interface in the polymerization container, and the resulting vinyl chloride has a lot of fisheyes. When the flow rate exceeds 100 Nm ³ / hour, the foaming in the polymerization container becomes vigorous, so that the scale easily adheres to the interface part in the polymerization container and the obtained vinyl chloride has a lot of fisheye, and also has a heavy weight. The yield of coalescence is reduced.

Evacuation of the non-condensable gas takes 20 minutes during the total polymerization time.
% Or more, preferably 20 to 80%, more preferably 2
It is continued for 0 to 60% or more. If the exhaust time is less than 20% of the total polymerization time, it becomes difficult to keep the heat removal amount of the reflux condenser constant, and it becomes difficult to control the polymerization temperature constant. The scale easily adheres to the interface part of, and the obtained vinyl chloride has a lot of fisheyes.

In the production method of the present invention, the cooling by the reflux condenser is started at the same time as or after the start of the exhaust of the non-condensable gas, and the monomer is polymerized while controlling the heat removal amount. As a method of controlling the amount of heat removed from the reflux condenser, for example, a method of adjusting the temperature and flow rate of the cooling water (see JP-A-57-8206)
Etc., specifically, the heat removal amount is 500,000 to 2,
It is preferable to appropriately control in the range of, 000,000 kcal / hour.

The polymerization apparatus used in the production method of the present invention includes
In addition to the polymerization vessel, stirring blade, reflux condenser, and heating / cooling jacket, as shown in FIG.
May be provided. As the baffle 3, a well-known one can be preferably used, and for example, a flat plate-shaped or pipe-shaped baffle 3 can be vertically installed along the inner wall of the polymerization container.

In the production method of the present invention, vinyl chloride may be used alone as a monomer, or a monomer mixture containing vinyl chloride as a main component and a comonomer copolymerizable with vinyl chloride ( Usually, vinyl chloride (containing 50% by weight or more) can also be used. Such comonomers include, for example, vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid esters and methacrylic acid esters such as methyl acrylate and ethyl acrylate; olefins such as ethylene and propylene; maleic anhydride; Acrylonitrile; styrene;
α-Methylstyrene; vinylidene chloride and the like can be mentioned.
These may be used alone or in combination of two or more.

The amount of the aqueous medium (water) used to suspend and disperse the polymer component of the monomer is the same as that in the conventional method, and the charging ratio of the monomer (water / monomer) is 1. .0-1.
It may be about 5 (weight ratio), and if necessary, water may be added during the polymerization.

In order to stabilize the polymerization system (contents of the suspension dispersion), for example, polyvinyl alcohol, water-soluble and oil-soluble methyl cellulose, ethyl cellulose,
Water-soluble cellulose ethers such as hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose, water-soluble polymers such as polyacrylic acid and gelatin, sorbitan monolaurate, sorbitan trioleate, sorbitan monostearate, glycerin tristearate, ethylene oxide, propylene Oil-soluble emulsifiers such as oxide block copolymers; for example, water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene gucerine oleate, sodium laurate; calcium carbonate, calcium phosphate, sodium dodecylbenzene sulfonate, etc. It can be used in a small amount within a range that does not impair the object of the invention. These may be used alone or in combination of two or more. The amount of these suspending agents added is 0.01 to 5 parts by weight with respect to 100 parts by weight of the charged monomers.

Examples of the oil-soluble polymerization initiator used in the present invention include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl peroxide. Perester compounds such as oxypivalate, t-hexyl peroxypivalate, t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethyl Pentyl-2-peroxyphenoxyacetate,
Examples include peroxides such as 3,5,5-trimethylhexanoyl peroxide; azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile). These can be used alone or in combination of two or more. The addition amount of these oil-soluble polymerization initiators is usually 0.01 to 3 parts by weight with respect to 100 parts by weight of the charged monomers.

Deionized water is usually used as the aqueous medium. Further, in this polymerization system, if necessary, a polymerization regulator, a chain transfer agent, and a pH that are appropriately used for vinyl chloride-based polymerization.
Regulator, gelation improver, antistatic agent, crosslinking agent, stabilizer,
Addition of fillers, antioxidants, buffers, etc. is also optional.

In carrying out the production method of the present invention, a scale adhesion preventing agent may be applied to the inner wall of the polymerization container or the like in advance. The scale adhesion preventive agent may be a known one, for example, a self-condensate of polyhydric phenols and polyhydric naphthols (JP-A-54-7487); a condensate of 1-naphthol and formaldehyde (special (JP-A-57-164107); a condensate of a phenol compound and an aldehyde (JP-A-54-36389); a mixed solution of a quinone-amine compound and an organic silica sol (JP-A-1-135802); Naphthols, sulfide compounds (JP-A-4-311702); a mixture of an electron-donating dye and an arylsulfonic acid and / or a reaction product (JP-A-5-70505); a phenothiazine derivative (JP-A-5-70505). 501892); quinone compounds and / or reduction products thereof (JP-A-5-279404); reaction products of ketone resins and phenolic compounds (JP-A-62-236804); dyes, pigments, Conjugate π bond to 5 Aromatic compounds having the above, heterocyclic compounds having five or more conjugated π bonds (USP-4,757,124); Polyaromatic amines (USP-4,024,330); Salts of cationic compounds and anionic compounds (GB-2,170,604); Polyvinyl alcohol Reaction product of benzoic acid and aminobenzoic acid (EP-0498142A1); initial condensation modified product of phenols and aldehydes
6-501884) and the like.

In the production method of the present invention, other conditions for polymerization, an aqueous medium to the polymerization vessel, vinyl chloride monomer,
Depending on the case, other comonomers, suspending agents, polymerization initiators and the like may be charged in the same manner as in the past, and these charging conditions may also be the same. , 80 to 90% of the volume of the polymerization container, preferably 82 to 87%. With such a charging amount, the liquid surface comes to almost the vicinity of the upper end position TL of the straight barrel portion of the polymerization container while stirring with the stirring blade.

[0029]

【Example】

(Embodiment 1) As shown in FIG. 1, it is a substantially cylindrical shape having a cylindrical straight body part and a substantially hemispherical top part and a bottom part that seal the upper and lower parts thereof, the inner volume is 130 m ³ , and the inner diameter (D: 4,200 mm). Of the length of the straight body part (L: 7,900 mm) to ()
D) 1.88 polymerization vessel 1, heating / cooling jacket 5, stirring paddles 2 in which paddle blades are arranged in three stages along the rotary shaft 7 (the stirring blade at the top stage is the center line C of the vertical width of the blade). 250 from the upper end position TL of the straight body part of the polymerization container at the height of
cm)), baffle 3, and reflux condenser 6 with a discharge port 9 on the top (shell and tube type,
A polymerization apparatus equipped with a heat transfer area of 150 m ² ) was used.

Deionized water 57,500k in the polymerization vessel
g, partially saponified polyvinyl alcohol 13.8 kg and hydroxypropylmethyl cellulose 9.2 kg were charged as an aqueous solution into a polymerization vessel. Then, it was evacuated by a vacuum pump until the internal pressure of the polymerization container reached 60 mmHg. Next, 46,000 kg of vinyl chloride monomer was charged, 25.3 kg of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator was press-fitted with stirring, and hot water was passed through the jacket to start the temperature rise. The stirring power (driving force of the electric motor) at this time is the weight (t) of the contents of the polymerization container.
The hit rate was 130 kg / s. The static liquid level H ₀ of the contents of the polymerization container at this time was 853 cm. The height H _{1 of the} upper end of the vertical width of the uppermost stirring blade is 655 cm, and the height H _{2 of the} upper end of the straight body is 895 cm.
(10/9) H ₁ ≤ H ₀ ≤ (100/65) H ₁ and H ₀
The formula of <H ₂ was simultaneously satisfied, and it was 1.56D.

Next, the temperature of the mixture in the polymerization vessel is 57 ° C.
At that time, the non-condensable gas was exhausted at a flow rate of 50 Nm ³ / hour for 3 hours from the outlet provided at the top of the reflux condenser. At the same time when the discharge of the non-condensable gas is started, water is passed through a reflux condenser to cool it, and the polymerization reaction is carried out while maintaining the polymerization temperature at 57 ° C., and the internal pressure of the polymerization vessel is 6.0 kg / m ² ( Polymerization was stopped when the pressure reached (gauge pressure), unreacted monomer was recovered, and the obtained polymer was withdrawn out of the vessel in a slurry form, and the scale adhesion state inside the vessel was observed and obtained. The polymer was dehydrated and dried and subjected to a test by the following method. Table 1 shows the results.

Adhesion of scale in the polymerization vessel: The evaluation was performed according to the following criteria after repeating 100 batches of polymerization by each production method. O: Almost no scale adhered. △: Scale is partially observed at the vapor-liquid interface. ×: Scale is observed all around the gas-liquid interface. -Measurement of bulk specific gravity: JIS K-6721 for the obtained polymer
Was measured according to.・ Measurement of particle size distribution (distribution under the sieve): The obtained polymer is sieved using each sieve of # 60, # 100, and # 200 according to JIS Z-8801, and the passing amount is measured and weighted. Expressed in%.・ Measurement of fish eye number; 100 parts by weight of the obtained polymer, 50 parts by weight of DOP, 0.1 part by weight of barium stearate, 0.1 part by weight of cadmium stearate, cetanol
0.8 parts by weight, tin stabilizer 2.0 parts by weight, titanium dioxide 0.5
Parts by weight and carbon black 0.1 parts by weight at 140 ° C.
The mixture was kneaded and kneaded with an inch roll mill for 5 minutes and separated as a sheet having a thickness of 0.3 mm, and the number of white transparent particles in 100 cm ^{2 of} this sheet was counted.

(Comparative Example 1) Polymerization was carried out in the same manner as in Example 1 except that the exhaust time of the non-condensable gas was changed to 45 minutes after the end of the temperature rise of the polymerization. During the polymerization, the heat removal amount of the reflux condenser was set to 1.3 × 10 ⁶ kcal
/ Hour was not reached, the temperature of the contents of the polymerization container increased by 1.5 ° C from the set temperature of 57 ° C. The obtained polymer was tested in the same manner as in Example 1. The results are shown in Table 1. The relationship among H ₁ , H ₀ , H ₂ and D is shown in Example 1.
Is the same as

(Comparative Example 2) In Example 1, except that the exhaust flow rate of the non-condensable gas was 150 Nm ³ / hour.
Polymerization was carried out in the same manner as in Example 1. The obtained polymer was tested in the same manner as in Example 1. The results are shown in Table 1. The relationship among H ₁ , H ₀ , H ₂ and D is the same as in the first embodiment.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that the exhaust flow rate of the non-condensable gas was changed to 5 Nm ³ / hour. During the polymerization, the amount of heat removed from the reflux condenser did not reach the set value of 1.3 × 10 ⁶ kcal / hour.
The temperature rose by 1.5 ° C. The obtained polymer was tested in the same manner as in Example 1. The results are shown in Table 1. In addition, H
The relationship among ₁ , H ₀ , H ₂ and D is the same as in the first embodiment.

(Comparative Example 4) Polymerization was carried out in the same manner as in Example 1 except that the position of the uppermost stirring blade was changed to 100 cm below the upper end position TL of the straight body of the polymerization container. The obtained polymer was tested in the same manner as in Example 1. The results are shown in Table 1. H ₁ is 805 cm, and (10/9) H ₁ ≦ H ₀
The expressions of ≦ (100/65) H ₁ and H ₀ <H ₂ were not satisfied at the same time, and the relationship with D was 1.92D.

(Comparative Example 5) Polymerization was carried out in the same manner as in Example 1 except that the position of the uppermost stirring blade was changed to 400 cm below the upper end position TL of the straight body of the polymerization container. The obtained polymer was tested in the same manner as in Example 1. The results are shown in Table 1. H ₁ is 505 cm, and (10/9) H ₁ ≦ H ₀
The expressions of ≦ (100/65) H ₁ and H ₀ <H ₂ were not simultaneously satisfied, and the relationship with D was 1.20D.

[0038]

[Table 1]

(Embodiment 2) As shown in FIG. 1, a cylindrical straight body portion and a substantially hemispherical top portion and a bottom portion which seal the upper and lower portions thereof are substantially cylindrical and have an inner volume of 100 m ³ and an inner diameter (D: 3,8
Length of straight body part for 50 mm (L: 7,240 m
m) the ratio (L / D) of 1.88, the polymerization vessel 1, the heating / cooling jacket 5, the paddle blades along the rotary shaft 7,
The stirring blades 2 arranged in three stages (the uppermost stirring blade is at the height of the center line C of the vertical width of the blade and is at the upper end position T of the straight body portion of the polymerization container).
A polymerization device equipped with a baffle 3 and a reflux condenser 6 (shell-and-tube type, heat transfer area 120 m ² ) having a discharge port 9 at the top was used.

Ion-exchanged water 44,300k in the polymerization vessel
g, 10.6 kg of partially saponified polyvinyl alcohol and 7.1 kg of hydroxypropylmethyl cellulose were charged as an aqueous solution into a polymerization vessel. Then, it was evacuated by a vacuum pump until the internal pressure of the polymerization container reached 60 mmHg. Next, 35,400 kg of a vinyl chloride monomer was charged, 19.5 kg of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator was press-fitted with stirring, hot water was passed through the jacket to start the temperature rise. The stirring power (driving force of the electric motor) at this time is the weight (t) of the contents of the polymerization container.
The hit rate was 130 kg / s. The static liquid level H ₀ of the contents of the polymerization container at this time was 782 cm. The height H ₁ at the upper end of the vertical width of the uppermost stirring blade is 590 cm, and the height H _{2 at the} upper end of the straight body is 820 cm,
(10/9) H ₁ ≤ H ₀ ≤ (100/65) H ₁ and H ₀ <
The formula for H ₂ was satisfied at the same time, and it was 1.53D.

Next, the temperature of the mixture in the polymerization vessel was 57 ° C.
At that time, the non-condensable gas was exhausted from the outlet provided at the top of the reflux condenser at a flow rate of 40 Nm ³ / hour for 3 hours. At the same time when the discharge of the non-condensable gas is started, water is passed through a reflux condenser to cool it, and the polymerization reaction is carried out while maintaining the polymerization temperature at 57 ° C., and the internal pressure of the polymerization vessel is 6.0 kg / m ² ( Polymerization was stopped when the pressure reached (gauge pressure), unreacted monomer was recovered, and the obtained polymer was withdrawn out of the vessel in a slurry form, and the scale adhesion state inside the vessel was observed and obtained. The polymer was dehydrated and dried and subjected to the same test as in Example 1. The results are shown in Table 2.

(Embodiment 3) As shown in FIG. 4, a substantially cylindrical shape having a cylindrical straight body portion and a substantially hemispherical top portion and a bottom portion which seal the upper and lower portions of the cylindrical body portion has an inner volume of 100 m ³ and an inner diameter (D: 3,8
Length of straight body part for 50 mm (L: 7,240 m
m) the ratio (L / D) of 1.88, the polymerization vessel 1, the heating / cooling jacket 5, the paddle blades along the rotary shaft 7,
The stirring blades 2 arranged in three stages (the uppermost stirring blade is at the height of the center line C of the vertical width of the blade and is at the upper end position T of the straight body portion of the polymerization container).
A polymerization device equipped with a baffle 3 and a reflux condenser 6 (shell-and-tube type, heat transfer area 120 m ² ) having a discharge port 9 at the top was used. The relationship among H ₁ , H ₀ , H ₂ and D is shown in Example 2.
Is the same as

Hereinafter, Example 2 was repeated except that this polymerization apparatus was used.
Polymerization reaction similar to the above was carried out, the obtained polymer was taken out of the vessel in the form of a slurry, and the scale adhesion state in the vessel was observed, and the obtained polymer was dehydrated and dried and subjected to the same test as in Example 1. I served. The results are shown in Table 2.

[0044]

[Table 2]

[0045]

EFFECTS OF THE INVENTION According to the present invention, the heat removal amount of the reflux condenser can be stably maintained even when a long-term operation is carried out in a large-sized polymerization vessel, so that a polymer of good quality and stable can be obtained. And, it is possible to prevent the scale from adhering to the inside of the polymerization container.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating a polymerization apparatus used in the present invention.

FIG. 2 is a side view illustrating a stirring blade used in the present invention.

FIG. 3 is an explanatory view of the installation position of the uppermost stirring blade used in the present invention.

FIG. 4 is a schematic view illustrating another polymerization apparatus used in the present invention.

[Explanation of symbols]

 1 ... Polymerization container 2 ... Stirring blade 4 ... Blade 5 ... Heating / cooling jacket 6 ... Reflux condenser

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitaka Okuno No. 1 Towada, Kamisu-cho, Kashima-gun, Ibaraki Prefecture Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A substantially cylindrical polymerization container comprising a cylindrical straight body part and a substantially hemispherical top part and a bottom part which seal the upper and lower parts of the cylindrical body part, and a plurality of them along a rotary shaft arranged on the center line of the polymerization container. A stirrer having stages, each having a blade, and a reflux condenser disposed above the polymerization vessel for condensing the monomer vapor generated in the polymerization vessel and refluxing the condensed liquid in the polymerization vessel. Disposed around the polymerization vessel,
A vinyl chloride monomer or a vinyl-based monomer mixture mainly containing the same in a polymerization apparatus equipped with a heating / cooling jacket for heating and cooling the liquid content in the polymerization container, in an aqueous medium,
While stirring with the stirring blade in the presence of an oil-soluble polymerization initiator,
In addition, in a method for producing a vinyl chloride-based polymer, which comprises suspension-polymerizing while evaporating a non-condensable gas that evaporates from the contents, a polymerization container has an inner volume of 100 m ³ or more and an inner diameter (D) The ratio (L / D) of the length (L) of the straight body portion is 1.5 or more, and the stirring blade at the uppermost stage is at the height of the center line of the vertical width of the blade, Using a polymerization apparatus arranged so as to be in the range of 150 to 300 cm downward from the upper end position, the exhaust flow rate of the non-condensable gas entering the reflux condenser is increased after the contents in the polymerization vessel are heated to near the polymerization temperature. The exhaust gas is exhausted under the conditions of 10 to 100 Nm ³ / hour and the exhaust time is 20% or more of the total polymerization time, and the cooling by the reflux condenser is started at the same time as or after the start of the exhaust of the non-condensable gas. Vinyl chloride to be Method for producing a system polymer.