JPH08245703A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PURPOSE: To produce a high-quality vinyl chloride-based polymer in a temperature-controlled element type reaction tank container whose structure is to mutually connect a main chamber and a gap chamber by a piping via a communicating tube or a pressure-leveling device. CONSTITUTION: Vinyl chloride or a copolymerizable monomer mixture predominant in vinyl chloride is polymerized in an aqueous medium using a reaction tank container has the following scheme: partition plates are spacedly arranged in parallel with one another rectangularly to the outer surface of an inner cylinder, each outer strip is set astride between the tips of a pair of the partition plates adjacent to each other to spacedly fix, inside the container body, temperature-controlled elements each having a heat transfer medium channel partitioned by the partition plates between the inner cylinder and the outer strip in such a manner as to face the outer strip side against the inner surface of the container body, and both the upper and lower parts of the gap between the temperature-controlled elements and the inner surface of the container body are sealed to form a gap chamber, and the gap chamber and the container body are mutually connected by a communicating tube or a piping via a pressure-leveling device.

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 in particular to a high quality vinyl chloride polymer,
The present invention relates to a method for producing a vinyl chloride polymer that can be produced with high productivity.

[0002]

2. Description of the Related Art Generally, a tank container used for a polymerization reaction of vinyl chloride or a mixture of vinyl chloride-based copolymerizable monomers (hereinafter collectively referred to as "vinyl chloride-based monomer") is a container. The main body 1'is formed of a pressure-tight sealed container in which dish-shaped end plates are welded to both ends of a cylindrical body, and a jacket 18 for removing heat generation or heating contents is provided.
An external jacket type tank container (Fig. 4) attached to the outside of the container body 1'is used.

In this type of tank container, since the container body retains pressure resistance, the plate thickness of the container is generally large, the coefficient of heat transfer through the wall of the container body is low, and a vinyl chloride-based simple substance that is an exothermic reaction. It was difficult to obtain high productivity in the polymerization of monomers. Also, when enlarging the tank container,
It is necessary to increase the wall thickness of the container body from the viewpoint of strength,
Further, there is a disadvantage that the heat transfer coefficient is lowered.

Therefore, in order to solve this inconvenience in heat conduction, partition plates 19 are arranged side by side at a right angle to the inner surface of the container body 1 ', as shown in FIG. By straddling the inner strip 20 on the inner wall of the container body 1 ', a partition plate 19 is provided between the inner strip 20 and the inner surface of the container body 1'.
A vessel container of the internal jacket type (JP-A-57-147502) in which a spiral flow path 21 partitioned by the above is formed is proposed. In this type of tank container, the pressure resistance strength is increased by making the interval between the partition plates 19 smaller than the body length of the container body 1 ′, the inner strip 20 is made thin, and the heat transfer coefficient is made high. You can

However, while the inner jacket type tank container has excellent thermal conductivity, there are many welded portions between the inner strips 20 on the inner surface of the tank container where the contents come into contact during the polymerization reaction of the vinyl chloride monomer. There is a disadvantage due to being exposed on the surface. That is, the welded portion has a rough surface roughness due to its construction, and there is a weld defect portion, but in the polymerization reaction of the vinyl chloride-based monomer, the contacted portion of the reaction mixture (hereinafter, referred to as "wetted portion") If the surface roughness is rough, the polymer scale tends to adhere, and if the generated scale peels and mixes into the product, the quality deteriorates (especially when processed into a film, an unmelted product remains in the film, Causes so-called fish eye (FE). Also, when trying to prevent the adhesion of polymer scale that causes quality deterioration,
There are disadvantages that the cost of manufacturing and maintaining the equipment becomes large, because it is necessary to extremely smooth a large number of welding lines and to introduce special adhesion prevention / removal technology.

Further, in the polymerization reaction of vinyl chloride-based monomer, stainless steel is usually used as the material of the inner surface of the tank because of the corrosiveness caused by hydrogen chloride generated as the reaction proceeds. The residual stress due to welding is concentrated in the container, and when the polymerization reaction of vinyl chloride monomer is carried out using an internal jacket type tank container with many welding lines adjacent to the inner surface of the container, the reaction progresses. There is a concern of stress corrosion cracking due to hydrogen chloride (chlorine ion) that is generated along with it. Therefore, it is necessary to carefully and continuously inspect the degree of deterioration of the welding line, and maintenance is complicated and inspection costs increase.

In order to solve the inconvenience while taking advantage of the advantage of this inner jacket type tank container, the present inventors have previously described, as a method for producing a vinyl chloride-based polymer in an aqueous medium without such a problem, Partition plates are arranged side by side at a right angle to the outer surface of the cylinder, and an outer strip is laid between the ends of the partition plate so that the heat separated by the partition plate between the inner cylinder and the outer strip. A flow path wall (hereinafter referred to as "temperature control element") having a flow path of the medium is formed, and the temperature control element is fixed in the container body with the outer strip side facing the inner surface of the container body with a space therebetween. In a tank container having a structure in which a gap chamber is formed by sealing the upper and lower portions of the gap between the outer strip side of the temperature control element and the inner surface of the container body (hereinafter referred to as "temperature control element type tank container") , The internal pressure of the gap chamber and While the difference between the internal pressure of the vessel main body inner surface and a space surrounded by the inner cylinder of the temperature control element (hereinafter referred to as "main body chamber") kept small by communicating pipe or the like has proposed a method of performing a polymerization reaction.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a vinyl chloride type unit amount in a temperature control element type vessel container having a structure in which a main body chamber and a gap chamber are connected by a communication pipe or a pipe via a pressure equalizer. In carrying out the polymerization reaction of the body, it is intended to prevent clogging of the pipe due to scale, to produce a high-quality vinyl chloride polymer, and to provide a method capable of safe and stable operation. .

[0009]

That is, the gist of the present invention is as follows.
Polymerization of vinyl chloride-based monomer in an aqueous medium is carried out by arranging partition plates side by side at a right angle to the outer surface of the inner cylinder, and by straddling an outer strip between the tips of the partition plates. A temperature control element having a flow path for a heat medium partitioned by a partition plate is formed between the cylinder and the outer strip, and the temperature control element is provided inside the container body with the outer strip side facing the inner surface of the container body. And has a structure in which a gap chamber is formed by sealing the upper and lower parts of the gap between the outer strip side of the temperature control element and the inner surface of the container body while fixing
In addition, the space (main body chamber) surrounded by the inner surface of the container body and the inner cylinder of the temperature control element and the gap chamber are connected by a pipe through a communication pipe or a pressure equalizer (hereinafter collectively referred to as "pressure equalizing pipe"). When carrying out in a connected tank container, the pressure equalizing pipe projects into the gas phase portion on the main chamber side, and the end portion of the tank container is of a structure having an upward structure. A method for producing a vinyl chloride polymer, characterized in that a liquid is supplied into the main body chamber through a pipe.

Hereinafter, the present invention will be described in detail. <Bath container> Bath container main body The temperature control element type bath container used in the method of the present invention has the following structure. That is, as shown in FIGS. 1 to 3, the partition plates 7 are arranged side by side at right angles to the outer surface of the inner cylinder 6, and the outer strip 8 is spanned between the tips of the partition plates 7, thereby The temperature control element 5 having the flow path 9 for the heat medium partitioned by the partition plate 7 is formed between the inner cylinder 6 and the outer strip 8. The outer diameter of the temperature control element 5 is made smaller than the inner diameter of the tank container, and the outer strip 8 side of the temperature control element is fixed to the inner surface of the container body 1 with a space therebetween.

The temperature control element 5 is preferably fixed so that the center line of the temperature control element and the center line of the container substantially coincide with each other. At this time, the inner surface of the container body and the outer surface of the temperature control element (that is, the outer strip side). And a gap corresponding to the difference in radius between the two are formed, and this is almost uniform in the circumferential direction.
The lower end of the temperature control element may be directly sealed to the bottom end plate 3 around the tank container nozzle 12 by continuous welding or the like as shown in FIG. 1, or may be sealed via a partition wall.

At the upper end of the temperature control element, a partition wall 13 is usually attached to the cylindrical body portion 2 or the top end plate 4 of the container and sealed. In this way, a gap chamber is formed between the outer surface of the temperature control element 5 fixed inside the container body 1 and the inner surface of the container body 1. This makes it possible to prevent the reaction mixture from penetrating into the gap and the consequent formation of scale deposits.

It is preferable that the partition wall or the like for sealing the upper part and / or the lower part of the gap is provided with an expansion / contraction absorbing part capable of absorbing expansion / contraction of the temperature control element due to heat. It is necessary to have a strength that can withstand the temperature and pressure normally used during the polymerization of the system monomer. Further, in order to prevent the temperature control element and the welding for sealing the upper and lower portions of the gap between the temperature control element and the container body and the partition wall from being destroyed by reaction pressure or the like, the inner surface of the container body (usually,
For safety, it is preferable to minimize the difference between the internal pressure of the space (main body chamber) surrounded by the top end plate and bottom end plate) and the inner cylinder of the temperature control element and the internal pressure of the gap chamber. The pressure resistance of the partition walls is not necessary.

In the method of the present invention, as a method for reducing the difference between the internal pressure of the main body chamber and the internal pressure of the interstitial chamber, the main chamber and the interstitial chamber are connected, for example, to the communicating pipe 15 or a pressure equalizer as shown in FIG. Use a method of connecting with piping (equal pressure piping) through. Examples of the pressure equalizer that can be used in the method of the present invention include a balance piston type and a diaphragm type. For example, as a balance piston type pressure equalizer as shown in FIG. 3, there are an air cylinder type and a cylinder type one for mechanical seal liquid pressurization (for example, a pressure equalizer manufactured by Nippon Pillar Industry Co., Ltd.). Further, examples of the diaphragm type pressure equalizer include a diaphragm type and a bellows type. These pressure equalizers use a sliding piston or a pressure resistant film such as a diaphragm or bellows to adjust the differential pressure on both sides of the pressure equalizer to, for example, 3 kg / c.
The structure is such that the pressure can be kept below a predetermined pressure, such as m ² or below.

The material of the pressure equalizer is preferably made of stainless steel, but a material having strength and corrosion resistance capable of withstanding the pressure change during the polymerization reaction of the vinyl chloride type monomer may be used. Further, when liquid is sealed in the gap chamber side portion of the pressure equalizer, the gap chamber, and the pipe portion connecting the both, it is possible to reduce the displacement amount of the movable portion of the pressure equalizer, and therefore the pressure equalizer is small in scale. It is preferable that it is sufficient.

The liquid to be enclosed is preferably the same type as the liquid to be supplied into the main body chamber described later, but is not particularly limited. Also, in the case of considering mixing with the contents inside the main body due to a leak or the like, it is recommended to use water, vinyl chloride-based monomers, or those to which a polymerization inhibitor such as a radical scavenger is added. It is suitable.

For the above reason, the temperature control element type vessel container used in the method of the present invention should be connected to each other via a pressure equalizing pipe in order to reduce the difference between the internal pressure of the main chamber and the internal pressure of the gap chamber. However, it is important for stable production, but in the case of polymerization reaction of vinyl chloride monomer, the reaction mixture containing vinyl chloride monomer enters the pressure equalizing pipe and polymerizes there. Or, the polymer or the reaction mixture scattered by foaming adheres to the inner wall of the pressure-equalizing pipe, and the scale gradually grows, eventually causing the pressure-equalizing pipe to be blocked, resulting in a pressure difference between the two. May not be maintained within a predetermined pressure range.

In the method of the present invention, as shown in FIG.
The pressure equalizing pipe has a structure protruding toward the gas phase portion on the main chamber side, and the tip of the pipe is formed in a U shape so as to face upward, and at least the polymerization reaction is performed through the pressure equalizing pipe. During the period, supplying liquid to the main chamber side prevents the reaction mixture of vinyl chloride monomer from entering and adhering to the pressure equalizing pipe due to foaming, etc., preventing scale formation and blocking the pressure equalizing pipe. Prevent.

The length of the pressure-equalizing pipe projecting to the main chamber side is preferably short in order to reduce the possibility of scale adhesion to the outside of the pipe, and is usually 20 cm or less, preferably 10 cm or less. . The connection position of the pressure equalizing pipe to the main body chamber side may be anywhere as long as it is in the vapor phase portion, but from the viewpoint of preventing scale adhesion, the liquid of the reaction mixture of the vinyl chloride monomer in the main body chamber where foaming occurs It is preferable to provide the position as far as possible from the surface, and in the tank container in which the reflux condenser is provided in the vapor phase portion of the tank container, the top of the reflux condenser is most preferable.

By forming the U-shaped end of the pressure-equalizing pipe projecting into the gas phase portion on the side of the main body chamber so as to face upward, and by supplying the liquid through the pressure-equalizing pipe during the polymerization reaction period. The liquid always stays in the vicinity of the end of the pressure equalizing pipe, and the reaction mixture that overflows from the liquid and scatters in the pressure equalizing pipe can be washed away to prevent scale from adhering and forming.

When a pressure equalizing pipe is inserted from the top of the reflux condenser and a liquid is supplied from the pressure equalizing pipe, the liquid cleans the surface of the reflux condenser on the process fluid side, whereby the reflux condenser is cooled. It has the effect of preventing scale from adhering to the inside. As the liquid supplied during the polymerization reaction period, water used as a dispersion medium for the polymerization reaction is preferable, and examples thereof include deionized water and an aqueous solution of a dispersant, but there is no adverse effect on the quality of the vinyl chloride polymer. If it is a thing, it will not be specifically limited.

The inlet 16 for the liquid to be supplied may be anywhere on the gap chamber side relative to the connection position on the body chamber side of the pressure equalizing pipe, and may be provided in the gap chamber as shown in FIG. 1 or in the pressure equalizer. Alternatively, the pressure equalizing pipe may be provided. The supply amount of the liquid is not particularly limited as long as it does not adversely affect the polymerization reaction and the quality and there is no adverse effect due to overfilling, etc., but the supply liquid including the amount of the liquid supplied from other parts to the main chamber is also included. It is preferable that the total amount does not exceed the volume shrinkage due to the polymerization of the vinyl chloride-based monomer.

The liquid is preferably supplied continuously or intermittently at least during the polymerization reaction period. The flow path of the heat medium in the temperature control element 5 may be spiral as shown in FIG. 1, the bottom end plate may be spiral, and the body of the container body may be serpentine in the circumferential direction. Not limited. As the heat medium flowing in the flow path, steam, hot water or the like is used for heating, normal temperature water such as industrial water for cooling, water cooled by a separate refrigerator, refrigerant such as ethylene glycol, CFC, etc. The low-temperature boiling point refrigerant can be used, but is not particularly limited.

The plate thickness of the inner cylinder 6 depends on the required strength and the space between the partition plates 7. However, since the space between the partition plates 7 is smaller than the body length of the container body 1, The plate thickness can be reduced to obtain a high heat transfer coefficient.

As described above, the material of the inner cylinder 6 is made of stainless steel (solid stainless steel, stainless steel, etc.) in consideration of the corrosion resistance of the portion in contact with the reaction mixture of the vinyl chloride type monomer.
A carbon steel clad material, particularly SUS316L is preferable), a glass lining material, or the like is used, but the material is not particularly limited as long as it is a material resistant to stress corrosion cracking due to chlorine ions.

The surface of the inner cylinder 6 is preferably smooth in order to prevent adhesion of scale, and in order to smooth the surface, buffing, electrolytic polishing, etc. which are usually carried out industrially are used. The method can be used without particular limitation. The surface roughness is usually 10 in Rmax.
μm or less, preferably 3 μm or less, more preferably 1 μm
m or less is preferable. Rmax is measured according to JIS B060
The method specified in 1 may be used.

Since the proportion of the welded portion on the content surface of the main body chamber side of the tank container manufactured in this manner is significantly smaller than that of the internal jacket type tank container, the adhesion formation of polymer scale is small and the product obtained is The quality is also good,
Since there is little concern about stress corrosion cracking, the degree of maintenance / inspection (so-called maintenance) may be the same as that of a normal outer jacket type tank container.

Equipment attached to tank container The type, material, etc. of the reflux condenser used in the method of the present invention are not particularly limited, and generally, such as a multi-tube heat exchanger having stainless steel as the material for the liquid contact portion, etc. What is used for the polymerization of vinyl chloride-based monomers may be used.
The heat transfer area of the reflux condenser may be determined according to the required quality of the product type, the degree of heat removal load, the load control method, and the like. The load control method may be a generally used method, and examples thereof include a method of controlling by the flow rate and temperature of the refrigerant passed through the reflux condenser.

The reflux condenser is installed in the gas phase part of the tank container, but as described above, it is installed vertically on the upper mirror part of the tank container body so that the adhered reaction mixture and the scale It is suitable for preventing generation. The shape of the stirring blades and baffles that are the auxiliary equipment of other tank containers (polymerization tanks)
It is not particularly limited, and the equipment and equipment generally used in the conventional suspension polymerization method, emulsion polymerization method or fine suspension polymerization method can be used.

<Polymerization prescription> The vinyl chloride-based polymer referred to in the present invention is a polymer containing vinyl chloride as a main constituent unit, which is obtained by polymerizing a vinyl chloride-based monomer in an aqueous medium. Say. Further, the polymerization reaction period according to the present invention, after the reaction system reaches a predetermined polymerization temperature, the internal pressure of the polymerization tank is reduced by a predetermined pressure from the saturated pressure of the vinyl chloride-based monomer at the temperature of the reaction system, It refers to the time when the collection of unreacted monomers is started.

The polymerization method of the vinyl chloride type monomer in an aqueous medium generally includes a suspension polymerization method, an emulsion polymerization method and a fine suspension polymerization method. Suspension polymerization of a vinyl chloride monomer is usually carried out by polymerizing a vinyl chloride monomer in an aqueous medium containing a dispersant in the presence of an oil-soluble polymerization initiator.

Emulsion polymerization of a vinyl chloride monomer is carried out in an aqueous medium in the presence of an emulsifier and a water-soluble polymerization initiator, and fine suspension polymerization is carried out by a vinyl chloride monomer. It is carried out by polymerizing the monomer in an aqueous medium in the presence of an emulsifier and an oil-soluble polymerization initiator, followed by homogenization treatment.

Monomer The vinyl chloride monomer used in the method of the present invention includes a vinyl chloride monomer alone and a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer. As the other monomer copolymerizable with the vinyl chloride monomer, those generally used in the related art can be used and are not particularly limited. Examples of the above-mentioned other monomers include vinyl acetates such as vinyl acetate, vinyl propionate and vinyl stearate, alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, lauryl vinyl ether and cetyl vinyl ether, ethylene and the like. Α-olefins, acrylic acid,
Mono-unsaturated acids such as methacrylic acid, alkyl esters of these mono-unsaturated acids such as methyl ester and ethyl ester, di-unsaturated acids such as maleic acid, fumaric acid, itaconic acid, etc. One or a mixture of two or more of alkyl esters such as methyl ester and ethyl ester of saturated acid, vinylidene compound such as vinylidene chloride, unsaturated nitrile such as acrylonitrile and the like can be mentioned. These other monomers are usually 3
It is used in an amount of 0% by weight or less, preferably 20% by weight or less, but there is no particular limitation.

Dispersant The dispersant which can be used in the method of the present invention may be any one conventionally used in the suspension polymerization method of vinyl chloride monomers and is not particularly limited. Examples of the dispersant include partially saponified polyvinyl acetate (so-called polyvinyl alcohol), cellulose derivatives such as hydroxypropylmethyl cellulose, and water-soluble polymers such as gelatin. In addition, anionic surfactants such as sodium lauryl sulfate and nonionic surfactants such as sorbitan fatty acid esters and glycerin fatty acid esters may be used as a dispersion aid. These dispersants or dispersion aids can be used alone or in combination of two or more. The amount of these dispersants used is not particularly limited, and its type, stirring strength, polymerization temperature,
Depending on the type and composition of other monomers to be copolymerized with the vinyl chloride monomer and the particle size of the intended vinyl chloride polymer, etc. 0.001-2% by weight, preferably 0.03-1
Used in the range of wt%.

Emulsifiers Examples of emulsifiers used in the emulsion polymerization method and the fine suspension polymerization method include higher alcohol sulfate ester salts (alkali metal salts and ammonium salts), alkylbenzene sulfonates (alkali metal salts and ammonium salts), and higher salts. Examples include fatty acid salts (alkali metal salts, ammonium salts) and other anionic surfactants, nonionic surfactants, and / or cationic surfactants. These surfactants may be used alone or in combination of two or more. The amount of the emulsifier used is usually 0.1 to 3% by weight (preferably 0.3 to 1% by weight) based on the vinyl chloride-based monomer, but is not particularly limited. In addition, these emulsifiers may be additionally used for adjusting the foamability during processing, and at this time, separately from the emulsifier for polymerization, they may be added after the completion of the polymerization reaction.

Polymerization Initiator The polymerization initiator used in the method of the present invention is not particularly limited and may be one that has been conventionally used generally in each polymerization method of vinyl chloride type monomers.

As the polymerization initiator used in the suspension polymerization method, for example, t-butylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-hexylperoxyneodecanoate, Perester compounds such as α-cumyl peroxy neodecanoate, diacyl or dialkyl peroxide compounds such as dilauroyl peroxide, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, azobis (2,4 -Dimethylvaleronitrile), azo compounds such as azobisisobutyronitrile, and the like. These polymerization initiators can be used alone or in combination of two or more. Although the amount of the polymerization initiator used varies depending on the type of the initiator, the polymerization temperature, the desired reaction time, etc., it is generally in the range of 0.01 to 1% by weight based on the total amount of the vinyl chloride monomer.

The polymerization initiator used in the emulsion polymerization method is a water-soluble peroxide such as persulfate (sodium salt, potassium salt, ammonium salt), hydrogen peroxide, or the like. Examples of the water-soluble redox-based initiators include a combination of a water-soluble reducing agent (eg, sodium sulfite, sodium pyrosulfite, sodium bisulfite, ascorbic acid, sodium formaldehyde sulfoxylate, etc.).

The polymerization initiator used in the fine suspension polymerization method is azobisisobutyronitrile or azobis (2,4-
Dimethyl valeronitrile), lauroyl peroxide,
Examples thereof include a monomer-soluble (oil-soluble) initiator such as t-butylperoxypivalate, or a redox-based initiator composed of a combination of these oil-soluble initiators and the above water-soluble reducing agent.

Other Auxiliary Agents Further, in the method of the present invention, if necessary, a polymerization degree adjusting agent (chain transfer agent, crosslinking agent) used for the polymerization of vinyl chloride-based monomers, an antioxidant, a pH Various polymerization aids such as regulators and activators of redox type initiators can be appropriately added, and the charging amount of each of these components is generally the same as that conventionally used for polymerization of vinyl chloride monomers. It does not matter under normal conditions.

As the polymerization degree regulator used for the polymerization of vinyl chloride type monomers, trichlorethylene, carbon tetrachloride, chain transfer agents such as 2-mercaptoethanol and octyl mercaptan, diallyl phthalate and triallyl isocyanurate. Examples thereof include cross-linking agents such as ethylene glycol diacrylate and trimethylolpropane trimethacrylate.

<Polymerization Method> Preparation Method In carrying out the method of the present invention, an aqueous medium, a vinyl chloride monomer, a polymerization initiator, a suspension polymerization method in a vessel (hereinafter sometimes referred to as “polymerization vessel”) The dispersant, the emulsifier in the emulsion polymerization method and the fine suspension polymerization method, and the charging ratio and charging method of other various polymerization aids are not particularly limited.

Polymerization temperature : The polymerization temperature employed in the method of the present invention includes the type of polymerization initiator used, the polymerization method, the presence or absence of a polymerization degree modifier,
Generally, it varies from 0 to, although it varies depending on the target degree of polymerization and the like.
90 ° C., especially 40 to 70 ° C. is often used.
Further, in the reaction, even if the polymerization is carried out at a constant temperature,
Alternatively, the polymerization temperature may be changed during the polymerization.

Polymerization Termination Method In the method of the present invention, examples of the method for terminating the polymerization reaction include a method of adding a so-called polymerization inhibitor or a polymerization terminator, a method of recovering unreacted monomers from the polymerization tank, and the like. .

<Post-Treatment Method> As operations for dehydration / drying of the slurry of the vinyl chloride polymer produced by the suspension polymerization method, generally-used dehydration such as centrifugal dehydration / fluid drying
Drying means may be used and is not particularly limited. Operations such as drying of the latex of the vinyl chloride polymer produced by the emulsion polymerization method and the fine suspension polymerization method can be performed by spray drying using a conventionally used rotating disk or a spray nozzle such as a two-fluid nozzle. Means may be used, and there is no particular limitation.

Before the drying treatment, a part of the water content in the latex may be removed in advance to increase the concentration of the vinyl chloride polymer in the latex, or a concentration operation may be carried out. You may perform the operation.

[0047]

EXAMPLES Next, specific embodiments of the method of the present invention will be described with reference to Examples, but the present invention is not limited as long as the gist thereof is not exceeded.
The present invention is not limited to the examples below. Example 1 With an internal volume of 400 liters, a stirrer and a multi-tube reflux condenser with a vertical heat transfer area of 1 m ² on the upper mirror part were provided, and the inner wall of the tank container (that is, the surface of the inner cylinder of the temperature control element) was electrolyzed. The Rmax is about 1.2 μm by polishing, and a communicating pipe as shown in FIG. 1 is installed in a stainless steel temperature control element type tank container divided into a gap chamber and a main chamber, and a water inlet is provided at the bottom of the gap chamber. The liquid is supplied from the gap chamber through the communication pipe.

In this tank container, vinyl chloride monomer 100 k
g, deionized water 150 kg, partially saponified polyvinyl acetate 60 g as a dispersant, and dioctyl peroxydicarbonate 48 g as an initiator, and then warm water was circulated through the temperature control element to heat up to 57 ° C. to start polymerization. did. From the start of the polymerization reaction (when the internal temperature of the polymerization tank reaches the specified reaction temperature is defined as the polymerization reaction start) to the end of the recovery of unreacted vinyl chloride monomer, the tank container is opened from the gap chamber. Deionized water was supplied into the main body through a communication pipe by a plunger pump at a flow rate of 2.5 liter / hr.

Polymerization was carried out while maintaining this temperature until a predetermined polymerization rate was reached. After that, unreacted vinyl chloride monomer was recovered, the produced slurry was extracted, ventilated, and the tank container was opened to observe the scale-adhered condition of the tank-side connection port of the pressure equalizing pipe and the lower part of the reflux condenser. After observing the scale adhesion state, the inner wall of the tank container was washed with low-pressure ion-exchanged water, and the test of the next batch was repeated under the same conditions. Table 1 shows the results of observation of the scale adhesion state.

[0050]

[Table 1]

[0051]

EFFECTS OF THE INVENTION In a temperature control element type tank container,
The upper and lower parts of the gap between the element and the container body are sealed to form a gap chamber, and a pressure equalizing pipe is provided between the gap chamber and the main body chamber to reduce the difference between the internal pressure of the gap chamber and the internal pressure of the container body. In the temperature control element type tank container with the structure connected by
As a structure in which the pressure equalizing pipe projects toward the main body chamber side and the end portion thereof faces upward, a vinyl chloride monomer while supplying a liquid to the main body chamber side through the pressure equalizing pipe during the polymerization reaction period. By adopting the method of the present invention in which the polymerization is carried out, it is possible to prevent the generation and growth of scale in the pressure equalizing pipe and the clogging of the pressure equalizing pipe due to this.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a tank container used for carrying out the method of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a vertical cross-sectional view showing another example of a tank container used for carrying out the method of the present invention.

FIG. 4 is a vertical sectional view showing an example of a conventional tank container.

FIG. 5 is an enlarged vertical sectional view of an essential part showing an example of a conventional tank container.

[Explanation of reference numerals] 1 container body 2 cylindrical body 3 bottom mirror plate 4 top mirror plate 5 temperature control element 6 inner cylinder 7, 19 partition plate 8 outer strip 9, 21 heat medium flow passage 10 heat medium flow passage inlet 11 heat medium Flow path outlet 12 Tank container nozzle 13 Partition wall 14 Gap chamber 15 Communication pipe 16 Liquid inlet 17 Balance piston 18 (External) jacket 20 Inner strip 21 Reflux cooler H Gap

Claims (5)

[Claims] 1. Polymerization of vinyl chloride or a mixture of vinyl chloride-based copolymerizable monomers in an aqueous medium is carried out by arranging partition plates side by side at right angles to the outer surface of the inner cylinder. A flow path wall (hereinafter referred to as a "temperature control element") having a flow path for the heat medium partitioned by the partition plate between the inner cylinder and the outer strip by straddling an outer strip between the ends of the partition plate. The temperature control element is fixed in the container body with the outer strip side facing the inner surface of the container body with a gap and the gap between the outer strip side of the temperature control element and the inner surface of the container body. It has a structure in which the upper and lower parts are sealed to form a gap chamber, and the space surrounded by the inner surface of the container body and the inner cylinder of the temperature control element (hereinafter referred to as "main body chamber") and the gap chamber are , Piping through a communication pipe or pressure equalizer (below Collectively referred to as "equalizing pipes"), when using in a vessel container that is connected by the pressure equalizing pipes projecting to the gas phase part of the main chamber side, and the end part of which is upward A method for producing a vinyl chloride polymer, characterized in that a liquid is supplied into the main chamber through the pressure equalizing pipe at least during a polymerization reaction period. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein a reflux condenser is attached to the vapor phase portion, and a tank container having a structure in which a pressure equalizing pipe is connected to the top of the reflux condenser is used. 3. The method for producing a vinyl chloride polymer according to claim 1, wherein the liquid supplied is water. 4. The method for producing a vinyl chloride polymer according to claim 1, wherein a balance piston type pressure equalizer is used as the pressure equalizer. 5. The method for producing a vinyl chloride polymer according to claim 1, wherein a diaphragm type pressure equalizer is used as the pressure equalizer.