JPH11255810A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Particularly in the case of long-term continuous operation, the quality of the obtained vinyl chloride-based polymer in each batch is stable, and the scale is less likely to adhere to the scale in the polymerization reactor. It is intended to provide a method for producing a polymer. SOLUTION: A non-condensable gas is exhausted from the top of the reflux condenser by using a polymerization apparatus equipped with a reflux condenser, so that the temperature at the top of the reflux condenser is lower than the polymerization temperature by 10 ° C. or higher. A method for producing a vinyl chloride-based polymer, wherein suspension polymerization of a vinyl chloride-based monomer is performed while controlling the amount of the vinyl chloride-based monomer to be within the range below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer, and more particularly to a method for producing a vinyl chloride polymer in which the quality of a vinyl chloride polymer obtained in each batch is stable even after long-term continuous operation. The present invention also relates to a method for producing a vinyl chloride polymer in which scale does not easily adhere in a polymerization reactor.

[0002]

2. Description of the Related Art Conventionally, a polymerization apparatus used for producing a vinyl chloride polymer is provided with a reflux condenser and a heating / cooling jacket for the purpose of removing the heat of the polymerization reaction during the polymerization reaction. The reflux condenser is generally located at the top of the polymerization vessel, and introduces the vapor generated in the polymerization vessel, cools it with a coolant such as cooling water, condenses it, and refluxes the condensed liquid into the polymerization vessel. It cools the temperature of the liquid contents. The heating / cooling jacket is disposed around the polymerization vessel, and guides cooling water or the like to the heating / cooling jacket to cool the contents in the polymerization vessel.

[0003] In recent years, in order to improve productivity in the production of a vinyl chloride polymer, it has been attempted to increase the size of the polymerization vessel itself and to shorten the polymerization time. However, when the polymerization vessel itself is enlarged and the polymerization time is shortened, the amount of heat generated per unit time increases.Therefore, there is a limit to cooling the polymerization vessel only with a heating / cooling jacket, and the cooling capacity is limited. The use of reflux condensers, which are said to be effective in improving productivity and saving energy, has attracted attention.

[0004] However, if the heat removal load on the reflux condenser is increased, the slurry foams in the polymerization vessel or the slurry easily flows into the reflux condenser, so that the polymer scale (hereinafter referred to as scale) is placed in the condenser. Not only causes problems such as adhesion of
Since the heat removal capability of the reflux condenser decreases, there arises a problem that it becomes difficult to control the amount of heat removed by the reflux condenser in each batch with good reproducibility.

[0005] In the production of a vinyl chloride polymer, in particular, nitrogen and oxygen mixed in a polymerization vessel during the production process, and nitrogen, carbon monoxide, and carbon dioxide generated by decomposition of a polymerization initiator. Since the condensable gas has a lower specific gravity than the vinyl chloride-based monomer, the condensable gas evaporates during the polymerization reaction and is concentrated and accumulated in the reflux condenser arranged at the top of the polymerization vessel, and the evaporated vinyl chloride-based monomer is evaporated. Of the vinyl chloride monomer is hindered, and there is a problem that stable production cannot be performed using the reflux condenser. In addition, since the non-condensable gas has an uneven gas concentration in the reflux condenser, it has been difficult to accurately determine the amount of the non-condensable gas.

Japanese Patent Publication No. 51-29196 discloses a method for improving the heat transfer capability by forcibly circulating a gas into a condenser. Japanese Patent Application Laid-Open No. 8-134107 discloses a method.
A method has been proposed in which a non-condensable gas evaporating from the contents in a polymerization apparatus provided with a reflux condenser is exhausted at a constant flow rate under conditions that the exhaust time is 20% or more of the total polymerization time.

[0007]

[Problems to be solved by the invention]
The method proposed in US Pat. No. 29196 requires an expensive circulation blower. On the other hand, JP-A-8-13
In the method proposed in Japanese Patent No. 4107, the amount of non-condensable gas differs for each production batch when a long-term continuous operation is performed. Therefore, the amount of heat removed by the reflux condenser for each production batch is controlled with good reproducibility. Is difficult,
It is not efficient to use a specific polymerization vessel and to attach a stirring blade to a specific position.

Accordingly, an object of the present invention is to eliminate the need to use a specific polymerization vessel or a stirring device, and to control the heat removal by the reflux condenser with good reproducibility even when a long-term continuous operation is performed. It is an object of the present invention to provide a method for producing a vinyl chloride polymer in which the quality of the vinyl chloride polymer obtained for each production batch is stable and scale does not easily adhere to a polymerization reactor.

[0009]

Means for Solving the Problems As a result of diligent studies on the above problems, the present inventor has found that the temperature of the top of the reflux condenser within a specific range can be controlled by discharging non-condensable gas from the top of the reflux condenser. It was found that the above problems could be solved by controlling the temperature within the range, and the present invention was completed.

That is, the present invention provides a method for producing a vinyl chloride polymer in which a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of a suspending agent. The non-condensable gas is exhausted from the top of the reflux condenser to control the temperature of the top of the reflux condenser within a range from a temperature lower than the polymerization temperature by 10 ° C. to a temperature lower than the polymerization temperature. The present invention relates to a method for producing a vinyl chloride polymer, which comprises performing suspension polymerization of a polymer.

Hereinafter, the present invention will be described in detail.

The polymerization apparatus provided with a reflux condenser in the present invention may be any polymerization apparatus provided with a reflux condenser, and may be a stirrer used in the polymerization apparatus or a stirring apparatus such as a baffle used if desired. There is no particular limitation, and a known stirring device generally used in a suspension polymerization method of a vinyl chloride-based monomer can be used. Examples of such stirring blades include a paddle blade and a pitched paddle. Examples include a blade, a bull margin blade, a Faudler blade, a turbine blade, and a propeller blade. These stirring blades may be used alone or in combination with another stirring blade. Also, as a baffle,
For example, a plate type, a cylindrical type, a D type, a loop type, a finger type and the like are exemplified. Further, a heating / cooling jacket may be used in the polymerization apparatus, and examples of such a heating / cooling jacket include an outer jacket and an inner jacket.

Although the capacity of the polymerization vessel in the present invention is not particularly limited, a large-sized polymerization vessel having a size of 40 m ³ or more is used because a vinyl chloride polymer can be produced with high production efficiency. Is preferred.

As the reflux condenser used in the present invention, a known reflux condenser connected to the polymerization vessel main body by one or more conduits and having a structure in which vapor and condensate move therein can be used. Examples of such a reflux condenser include a coil type, a spiral type, a multi-tube type, a shell-and-tube type, and the like, and a shell-and-tube type is particularly preferable because of its excellent removal efficiency of heat of polymerization.

According to the present invention, the non-condensable gas is exhausted from the top of the reflux condenser to control the temperature of the top of the reflux condenser within a range from 10 ° C. lower than the polymerization temperature to less than the polymerization temperature. is there. The non-condensable gas referred to here is a gas having a lower specific gravity than the vinyl chloride monomer used for purging during the production of the vinyl chloride polymer or a vinyl chloride monomer generated during the production of the vinyl chloride polymer. It is a gas having a lower specific gravity, for example, nitrogen, oxygen, carbon monoxide, carbon dioxide, and the like.In the present invention, the non-condensable gas is exhausted from the top of the reflux condenser to form a tower in the reflux condenser. The temperature at the top is controlled in a range of 10 ° C. or lower to lower than the polymerization temperature, preferably 10 to 5 ° C. lower than the polymerization temperature, to efficiently cool and condense the vinyl chloride monomer which has become a vapor. This effectively removes heat generated by polymerization during polymerization.

When the temperature at the top of the reflux condenser is lower than the polymerization temperature by 10 ° C. or less, the non-condensable gas is not exhausted more efficiently than the reflux condenser. Of vinyl chloride monomer which has been concentrated, accumulated and vaporized inside
Condensation is significantly hindered, and the heat removal by the reflux condenser cannot be maintained. On the other hand, when the temperature at the top of the reflux condenser reaches the polymerization temperature, the gas exhausted from the reflux condenser is not only the non-condensable gas, but also the vinyl chloride monomer that has been vaporized, and the reaction yield is reduced. In addition to lowering the productivity, the vinyl chloride polymer slurry in the polymerization reactor foams and flows into the reflux condenser, which makes it difficult to control the reflux condenser and scale adheres to the polymerization reactor. In some cases, fish eyes are generated due to the scale and the quality of the obtained vinyl chloride polymer is deteriorated.

In the present invention, the method of exhausting the non-condensable gas from the top of the reflux condenser is not particularly limited. For example, a method of exhausting the non-condensable gas from a discharge port provided at the top of the reflux condenser with a pump, etc. And the like, and a method of exhausting and collecting the vinyl chloride monomer in a collecting container.

In the present invention, there is no particular limitation on the timing at which the exhaust of the non-condensable gas is started from the top of the reflux condenser. Since the heat transfer efficiency of the reflux condenser can be set to a high value from the start of heat removal by the reflux condenser, it can be kept constant, and the amount of heat removed by the reflux condenser can be controlled with good reproducibility. It is particularly preferable to start evacuation of the non-condensable gas from the top of the column before the start of the reaction, so that the internal temperature of the reflux condenser is in a range of 10 ° C. lower than the polymerization temperature to lower than the polymerization temperature.

In the present invention, when operating the reflux condenser, the amount of heat removed by the reflux condenser may be constant, or the amount of heat removed from the reflux condenser may be controlled so as to control the internal temperature of the reactor. As a method of controlling the heat removal amount of the reflux condenser, a known method such as adjusting the temperature and flow rate of the cooling water may be used.

As described above, in the present invention, the non-condensable gas is exhausted from the top of the reflux condenser so as to control the temperature at the top of the reflux condenser within a range from 10 ° C. lower than the polymerization temperature to less than the polymerization temperature. By doing
Even if the amount of non-condensable gas in the polymerization system changes for each batch during the production of the vinyl chloride-based polymer, the heat transfer efficiency of the reflux condenser can always be kept at a high value and constant, and Because there is no sudden change in heat removal,
The slurry does not foam and flow into the reflux condenser, and the heat removal amount of the reflux condenser can be controlled with good reproducibility even when the long-term operation is performed in a large polymerization vessel. The quality of the system polymer is stable, and the scale is less likely to adhere.

The aqueous medium used in the present invention includes:
Water or a medium containing water as a main component, and may contain any medium without departing from the object of the present invention. It is preferable that the temperature of the aqueous medium is 30 ° C. or higher, since a vinyl chloride polymer having excellent production efficiency and excellent quality can be obtained.

In the present invention, the ratio of the aqueous medium to the vinyl chloride monomer (weight ratio) is in the range of aqueous medium / vinyl chloride monomer = 0.7 to 2.0. Is preferred. In addition, in order to keep the fluid state of the suspension at the time of polymerization constant, it is desirable to continuously or intermittently add an aqueous medium having the same volume as the volume shrinkage accompanying the polymerization.

As the suspending agent used in the present invention, known suspending agents are used. Examples of such suspending agents include partially saponified polyvinyl acetate, cellulose derivatives, polyvinylpyrrolidone, and vinyl acetate-maleic anhydride. Water-soluble polymers such as polymers, starch, gelatin, nonionic surfactants, and anionic surfactants, and mixtures thereof can be used. These suspending agents may be partially or continuously added to the polymerization system before or during the polymerization.

In the present invention, if necessary, a scale inhibitor, a chain transfer agent, an antifoaming agent, a pH adjuster, an antistatic agent, an antioxidant, a crosslinking agent, etc. may be added to the polymerization system before or after the polymerization. It may be added, or a part thereof may be dividedly or continuously added to the polymerization system during the polymerization.

Examples of the antifoaming agent include polysiloxane,
Silicone oils such as dimethylpolysiloxane and diphenylpolysiloxane; fatty acids having 10 to 30 carbon atoms or aromatic alcohols; ethylene oxide;
Polyoxyalkylene glycols such as propylene oxide, alkylene oxide homopolymers such as butylene oxide and the like, random copolymers and block copolymers; sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and the like, acetylene glycols and the like. These are exemplified, and these can be used alone or in combination of two or more. These antifoaming agents may be added to the polymerization system as it is, or in a state of being dissolved or dispersed in a solvent such as water, before or after the initiation of polymerization. Parts may be added to the polymerization system in portions or continuously.

In the present invention, the vinyl chloride monomer is
It contains a mixture of a vinyl chloride monomer or a vinyl monomer which is mainly composed of a vinyl chloride monomer and a copolymerizable vinyl monomer,
Examples of the vinyl monomer copolymerizable with the vinyl chloride monomer include olefin compounds such as ethylene and propylene; vinyl esters such as vinyl acetate and vinyl propionate; and acrylic acid and α-alkylacrylic acid. Unsaturated monocarboxylic acids and alkyl esters and amides thereof; unsaturated nitriles such as acrylonitrile; unsaturated dicarboxylic acids such as maleic acid and fumaric acid; alkyl esters and anhydrides thereof; N-substituted maleimides; Examples include vinyl alkyl ethers such as methyl ether and vinyl ethyl ether; various vinylidene compounds.

As the oil-soluble polymerization initiator used in the present invention, for example, acetylcyclohexylsulfonyl peroxide, isobutyryl peroxide, (α, α-
(Bisneodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, diisopropylperoxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-butyl Organic peroxides such as peroxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, lauryl peroxide; azobis-2,4-dimethylvaleronitrile, azobis- (4-methoxy- 2,4
-Azo compounds such as dimethylvaleronitrile and azobisisobutyronitrile, and other known compounds can be used alone or in combination of several kinds.

[0028]

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 vinyl chloride polymers obtained in Examples and Comparative Examples were evaluated by the following methods.

-Bulk specific gravity-According to JIS K6721.

~ Fisheye ~ 100 parts by weight of the obtained vinyl chloride polymer is
Roll forming in which 1.5 parts by weight of a Zn-based 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) are adjusted to 150 ° C. Kneading for 5 minutes with a machine, thickness 0.35mm
And the number of transparent particles in 50 cm ^{2 of the} sheet is shown.

-Scale adhesion state-The scale attached to the inner wall of the polymerization vessel was visually observed to determine the adhesion state.

Example 1 A 100 m ³ reactor equipped with a reflux condenser having a thermometer at the top was used to pass 70 ° C. hot water through the reflux condenser, followed by 450 ° C. deionized water at 450 ° C.
An aqueous solution was charged with 15.1 kg of 00 kg, partially saponified polyvinyl alcohol having a saponification degree of 80 mol% and an average degree of polymerization of 2600. Thereafter, the pressure in the reactor was reduced by a vacuum pump. Next, 36,000 kg of a vinyl chloride monomer and 19.8 kg of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator were charged into a reactor and stirring was started, and the temperature was raised to 57 ° C. to start a polymerization reaction. that time,
When the temperature reaches 57 ° C., the evacuation of non-condensable gas is started from the top of the reflux condenser, and the evacuation is continued until the temperature at the top of the reflux condenser reaches from 35 ° C. to 49 ° C. The jacket temperature of the reflux condenser was controlled so that the jacket temperature of the reactor became constant. Thereafter, the jacket temperature of the reflux condenser was controlled while intermittently evacuating the non-condensable gas so as to control the temperature at the top of the reflux condenser to 49 ° C., and the polymerization reaction was continued for 5 hours.

After the completion of the polymerization reaction, the unreacted vinyl chloride monomer is recovered, the vinyl chloride polymer slurry is taken out, the state of scale adhesion in the reactor is observed, and the vinyl chloride polymer is dehydrated and dried. A coalescence was obtained.

Further, the production of the vinyl chloride polymer shown above was continuously performed for 200 batches, and the obtained vinyl chloride polymer was evaluated, and continuous productivity was evaluated.

Table 1 shows the results.

The obtained vinyl chloride polymer had a high bulk specific gravity of 0.550 ± 0.010 g / cc, its dispersion was small, fish eyes were small, and the quality was excellent. Further, as a result of continuously producing 200 batches, almost no scale adhesion was observed in the reactor.

Example 2 When the temperature in the reactor reached 57 ° C., the evacuation of non-condensable gas was started from the top of the reflux condenser, and the evacuation was started when the temperature of the top in the reflux condenser was 34 ° C. 52
° C, and thereafter the vinyl chloride was produced in the same manner as in Example 1 except that the non-condensable gas was intermittently exhausted while controlling the temperature at the top of the reflux condenser at 52 ° C. A polymer was produced and evaluated.

Table 1 shows the results.

The obtained vinyl chloride polymer had a high bulk specific gravity of 0.553 ± 0.008 g / cc, its dispersion was small, and it was excellent in quality with few fish eyes. In addition, as a result of performing continuous 200 batch production, almost no scale adhesion was observed in the reactor.

Example 3 Ten minutes after the temperature in the reactor reached 57 ° C., the evacuation of non-condensable gas was started from the top of the reflux condenser, and the exhaust was cooled to 35 ° C. in the top of the reflux condenser. To 49 ° C., and thereafter, while controlling the temperature at the top of the reflux condenser at 49 ° C., except that the non-condensable gas was intermittently exhausted, the same method as in Example 1 was used. Production and evaluation of a vinyl chloride polymer were performed.

Table 1 shows the results.

The obtained vinyl chloride polymer had a high bulk specific gravity of 0.555 ± 0.006 g / cc, its dispersion was small, fish eyes were small and the quality was excellent. In addition, as a result of performing continuous 200 batch production, almost no scale adhesion was observed in the reactor.

Comparative Example 1 When the temperature in the reactor reached 57 ° C., the evacuation of the non-condensable gas was started from the top of the reflux condenser, and the evacuation was started when the temperature of the top in the reflux condenser was 33 ° C. 49
° C, and thereafter, the exhaust was continued at an exhaust flow rate of 50 Nm ³ / hour for 3 hours from the start of the exhaust. A vinyl chloride polymer was produced and evaluated in the same manner as in Example 1 except that the temperature at the top of the tower in the reflux condenser after evacuation for 3 hours was 57 ° C.

Table 1 shows the results.

During the production of the vinyl chloride polymer, the cooling by the reflux condenser was not stabilized due to foaming of the vinyl chloride polymer slurry, and the resulting vinyl chloride polymer had a low bulk specific gravity of 0.514 ± 0.025 g / cc. Furthermore, the variation was large, and there were many fish eyes and the quality was poor. Further, as a result of producing 200 batches continuously, the scale adhesion in the reactor was remarkable.

COMPARATIVE EXAMPLE 2 When the temperature in the reactor reached 57 ° C., the evacuation of non-condensable gas was started from the top of the reflux condenser, and the exhaust was cooled to 42 ° C. in the top of the reflux condenser. And thereafter, while controlling the temperature at the top of the reflux condenser at 42 ° C., and intermittently evacuating the non-condensable gas, in the same manner as in Example 1 to obtain a vinyl chloride polymer. Production was attempted, but during the polymerization reaction, the amount of heat removed by the reflux condenser did not reach the set value, and the reaction was stopped because the temperature in the reactor rose above the set temperature of 57 ° C.

Comparative Example 3 When the temperature in the reactor reached 57 ° C., the non-condensable gas was exhausted from the top of the reflux condenser at an exhaust flow rate of 50N.
³ hours at m ³ / hour. A vinyl chloride polymer was produced and evaluated in the same manner as in Example 1 except that the temperature at the top of the reflux condenser 3 hours after the start of evacuation was 57 ° C.

Table 1 shows the results.

During the production of the vinyl chloride polymer, the cooling by the reflux condenser was not stabilized due to foaming of the vinyl chloride polymer slurry, and the resulting vinyl chloride polymer had a bulk specific gravity of 0.552 ± 0.020 g / cc. The variation was large, the fish eyes were many, and the quality was inferior. Further, as a result of producing 200 batches continuously, the scale adhesion in the reactor was remarkable.

Comparative Example 4 When the temperature in the reactor reached 57 ° C., the non-condensable gas was exhausted from the top of the reflux condenser at an exhaust flow rate of 120
It lasted 3 hours at Nm ³ / hour. A vinyl chloride polymer was produced and evaluated in the same manner as in Example 1 except that the temperature at the top of the reflux condenser 3 hours after the start of evacuation was 57 ° C.

Table 1 shows the results.

During the production of the vinyl chloride polymer, the cooling by the reflux condenser was not stabilized due to foaming of the vinyl chloride polymer slurry, and the obtained vinyl chloride polymer had a low bulk specific gravity of 0.503 ± 0.023 g / cc. Furthermore, the variation was large, and there were many fish eyes and the quality was poor. Further, as a result of producing 200 batches continuously, the scale adhesion in the reactor was remarkable.

[0054]

[Table 1]

[0055]

According to the method of the present invention, even when a long-term continuous operation is carried out, the quality of the obtained vinyl chloride-based polymer for each batch is stable, and scale is hardly adhered to the reactor. Its industrial value is high.

Claims (1)

[Claims] 1. A method for producing a vinyl chloride polymer in which a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of a suspending agent, wherein the polymerization is carried out by using a polymerization apparatus equipped with a reflux condenser. By discharging the non-condensable gas from the top of the condenser, the temperature of the top of the reflux condenser in the reflux condenser is controlled at a temperature lower than the polymerization temperature by 10 ° C. or more and lower than the polymerization temperature to suspend the vinyl chloride monomer. A method for producing a vinyl chloride polymer, which comprises conducting polymerization.