JP2006273896A - Polymerization vessel having reflux condenser and method for producing polymer by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a further high quality polymer in a high productivity by preventing troubles accompanying with foaming in a polymerization vessel having a reflux condenser in advance and enabling the stable operation even in the case of increasing a heat removal ratio by the reflux condenser. <P>SOLUTION: This polymerization vessel having the reflux condenser is provided by installing a device for spraying a monomer condensed in the reflux condenser and returning into the polymerization vessel over the surface of the content liquid, at the outside of the polymerization vessel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polymerization vessel provided with a reflux condenser and a method for producing a polymer using the polymerization vessel. Specifically, the heat removal rate by the reflux condenser can be stably increased, and the polymerizer with the reflux condenser and the polymerizer capable of producing a high-quality polymer with high productivity and stability can be used. The present invention relates to a method for producing a polymer.

  In the production of general-purpose polymers, it is important for those skilled in the art to reduce production costs and improve polymerization productivity. For example, as a measure for improving the polymerization productivity of a vinyl chloride polymer produced mainly in a batch system, the pursuit of the merit of scale using a large-sized polymerizer has been made in recent years. Although the yield per batch increases due to the use of a large polymerization vessel, the heat removal area per unit volume of the content liquid decreases with the increase in the polymerization vessel size and the associated reaction heat, that is, removal by a normal external jacket. Eliminating the reduction in heat capacity has become an important issue for those skilled in the art, and it has become extremely difficult to remove the total reaction heat with only the outer jacket.

  As measures to compensate for the reduction in heat removal capacity due to the increase in the size of the polymerization vessel, an internal jacket system and a water flow baffle that can have high heat transfer efficiency by reducing the thickness of the partition wall, a reflux condenser, In view of the fact that a significant improvement in heat removal capability can be expected, a method using a reflux condenser is particularly preferred.

  Heat removal by a reflux condenser is a method using latent heat of vaporization of the monomer, and is generally used in combination with heat removal by an external jacket. The rate of heat removal by the external jacket and reflux condenser in the total heat removal requirement varies, but the rate of heat removal by the reflux condenser is higher than the heat removal by the external jacket, especially in large-sized polymerizers. There is a tendency, and ultimately it is possible to remove all the heat with only a reflux condenser.

  On the other hand, as the rate of heat removal by the reflux condenser increases in this way, troubles due to foaming of the content liquid have become a problem among those skilled in the art. In other words, an increase in the amount of heat removed by the reflux condenser means that the amount of monomer evaporation from the content liquid increases, and the monomer gas that evaporates and the polymerization product form bubbles to form an upper part of the polymerization vessel In such a case, there is a problem of so-called splash entrainment that scatters into the reflux condenser. If the polymerization product scattered by this phenomenon deposits on the upper part of the polymerization vessel or inside the reflux condenser to form a scale, not only does it take a lot of effort to remove it, but also the polymerization inside the reflux condenser may cause clogging. It is difficult to remove heat and the internal temperature rises abnormally, resulting in uncontrollable operations. Furthermore, the problem that quality deteriorates when the generated scale is mixed in the final product is likely to occur.

  There are two types of countermeasures for foaming: chemical methods and mechanical methods. As an example of a vinyl chloride polymer as a typical general-purpose polymer, a chemical method is obtained by using a partially saponified polyvinyl alcohol (hereinafter abbreviated as PVA) having a high saponification degree as a dispersant. A method of making the inside itself difficult to foam, a method of suppressing foaming by using an antifoaming agent or the like in combination, and a mechanical method include a method of mechanically breaking the generated bubbles.

  For example, a method using PVA having an average saponification degree of 85 mol% or more is disclosed (Patent Document 1). However, in this method, generation of coarse particles and fine particles due to high protective colloid properties of high saponification degree PVA, that is, The expansion of the particle size distribution is inevitable, and the deterioration of the quality of fish eyes and the like due to coarse particles and the deterioration of water quality due to the mixing of fine particles into the wastewater were serious problems.

  Moreover, although the method of using an antifoamer together is disclosed (patent document 2) (patent document 3), in these methods, an antifoamer brings about the deterioration of the color tone of a final product, transparency, and an electrical property. There was a problem.

  Furthermore, a method is disclosed in which bubbles that are generated are broken by a rotating blade provided in a gas phase portion in the polymerization vessel (Patent Document 4). By mechanically dispersing the foam containing particles, the scale adheres to the upper part of the polymerization vessel and the rotating blade cover. It was.

In addition, as a general defoaming means, there is a method of spraying a foam with a lower alcohol such as methanol or ethanol, or a liquid hydrocarbon such as hexane or heptane, that is, a low surface tension substance. Although this method certainly has a high defoaming effect, it has a problem that the influence on the polymerization reaction is large, and the COD of the wastewater becomes high, and the processing requires a great deal of labor and cost, and is difficult to apply.
JP 61-115908 A Japanese Patent Laid-Open No. 02-180908 Japanese Patent Laid-Open No. 03-212409 JP 58-49710 A

  The problem of the present invention is to prevent troubles associated with foaming in the reflux condenser-attached polymerizer as described above, and to enable stable operation even when the heat removal rate by the reflux condenser is increased. The object is to provide a method for producing a high-quality polymer with high productivity.

As a result of intensive studies on the above problems, the present inventors have come up with an idea that the same effect as the defoaming effect by spraying the lower alcohol or liquid hydrocarbon is exhibited in the monomer. Therefore, the present invention was completed by discovering that a remarkable defoaming effect was recognized by condensing with a reflux condenser and atomizing the monomer refluxed into the polymerization vessel and spraying and contacting the generated bubbles. It came to do.
That is, the present invention is provided with 1) a reflux condenser, and 2) an apparatus for spraying the monomer condensed in the reflux condenser and refluxed into the polymerization vessel on the surface of the polymerization content liquid. A polymerization vessel characterized in that (Claim 1);
A reflux condenser and a device for spraying the monomer condensed in the reflux condenser and refluxed into the polymerization vessel onto the surface of the polymerization content liquid are obtained by using a polymerization vessel provided outside the polymerization vessel. A method for producing a vinyl chloride polymer, characterized by polymerizing a monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the monomer and a vinyl chloride monomer (claim) 2),
The production method (claim 3) of the vinyl chloride polymer according to claim 2, characterized in that the polymerization method is suspension polymerization.

  According to the present invention, foaming of the content liquid can be stably suppressed even if the heat removal rate by the reflux condenser is increased. In addition, the process can be stably operated while maintaining high productivity. Furthermore, polymerization is possible without deteriorating the quality of the resulting polymer such as fish eyes.

  The reflux condenser referred to in the present invention is attached to the outside of the polymerization vessel, and cools and condenses the monomer gas that evaporates from the polymerization content liquid during the polymerization reaction, and returns it to the polymerization content liquid in a liquid state. Is. The reflux condenser has a role of removing reaction heat by latent heat generated when the monomer evaporates from the content liquid.

  The polymerization apparatus of the present invention is provided with an apparatus for spraying the monomer condensed in the reflux condenser and refluxed in the polymerization apparatus on the surface of the polymerization liquid. Here, spraying the refluxing monomer onto the surface of the polymerization liquid means that the refluxing monomer does not drop or pour onto only one part of the surface of the liquid, but forms a mist and has a large area. It means to pour into. It is preferable that spraying is performed uniformly on the polymerization liquid surface. In a normal reflux condenser, the refluxing monomer is free-falling, and the place where it falls is only one place on the surface of the polymerization content liquid. The foam generation rate is higher than the foam suppression rate, and the foam suppression as a whole cannot be expected. The larger the area where the monomer comes into contact with the content liquid surface by spraying the refluxing monomer, the higher the effect, and the more the surface of the content liquid, that is, the same area as the cross-sectional area of the polymerization vessel Is desirable. Hereinafter, the polymerization apparatus of the present invention and the apparatus used in the present invention will be briefly described with reference to the drawings.

  FIG. 1 shows an example of a polymerization apparatus according to claim 1 of the present invention. In a polymerization apparatus with a reflux condenser, a monomer condensed by the reflux condenser and refluxed in the polymerization apparatus is sprayed on the surface of the polymerization content liquid. The apparatus for providing is equipped with the apparatus for the exterior of the polymerization apparatus, The polymerization apparatus characterized by the above-mentioned is shown. In FIG. 1, reference numeral 1 denotes a polymerization vessel body, 2 denotes a polymerization vessel outer jacket, 3 denotes a stirring shaft, and 4 denotes a polymerization stirring blade. A reflux condenser 7 is attached to the upper part of the polymerization vessel 1, and the monomer gas evaporated from the polymerization content liquid 6 is led into the reflux condenser through the monomer gas flow path 8 and cooled. Condensed. This condensed monomer is led to the monomer spraying device 5 provided outside the polymerization vessel through the monomer spraying device introduction pipe 9 and is atomized from the pores 11 of the discharge nozzle 10 to form a polymerization content liquid. Sprayed on the surface. It should be noted that the mounting position of the discharge nozzle 10 in the polymerization vessel must always be located above the surface of the polymerization content liquid during polymerization, that is, in the gas phase portion. If this nozzle is attached at a position where it is immersed in the solution in the polymerization even for a short time during polymerization, the effect of suppressing the generated foam is not only impaired, but there is a problem that the nozzle is clogged with resin and normal spraying cannot be performed. To do. Therefore, it is desirable that the discharge nozzle is mounted above the vicinity of the center between the uppermost part of the upper mirror part of the polymerization vessel and the liquid surface position at the start of polymerization.

  The monomer spraying device 5 includes a storage tank for storing the introduced condensed monomer, and a pump for loading the condensed monomer with a pressure higher than the internal pressure of the polymerization vessel and discharging the pressure into the polymerization vessel. Composed. The pump that discharges the condensed monomer is preferably a reciprocating pump such as a piston pump, a plunger pump, or a diaphragm pump.

  FIG. 2 shows an example of the detailed structure of the discharge nozzle. At the tip of the discharge nozzle, a large number of fine holes are provided for spraying the condensed monomer to be sprayed into the polymerization vessel. The number and diameter of the pores are not particularly limited as long as this purpose can be achieved, but the pore diameter is set so that the droplet diameter of the condensed monomer to be sprayed is 0.5 mm or less. It is desirable to do. If the droplet diameter of the condensed monomer to be sprayed is 0.5 mm or less, a sufficient foaming suppression effect can be obtained.

  The polymerizer of the present invention can be suitably used for all polymer production processes using a reflux condenser, and is particularly a water-soluble or water-dispersible polymer suspension dispersion stabilizer and oil-soluble polymerization in an aqueous medium. It is suitable for producing a vinyl chloride polymer that undergoes suspension polymerization in the presence of an initiator.

  Examples of the vinyl chloride polymer in the present invention include vinyl chloride homopolymers and vinyl chloride copolymers. Examples of the monomer copolymerizable with the vinyl chloride monomer for producing the vinyl chloride copolymer include, for example, alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, ethylene, propylene and the like. Examples include α-olefins, alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate, and vinylidene compounds such as vinylidene chloride.

  Next, the water-soluble or water-dispersible polymer suspension dispersion stabilizer used in the present invention includes partially saponified polyvinyl acetate, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid, and vinyl acetate-malein. Examples thereof include acid copolymers, styrene-maleic acid copolymers, gelatin, starch, and polyethylene oxide, and these can be used alone or in combination of two or more.

  The oil-soluble polymerization initiator in the present invention is not particularly limited as long as the object of the present invention can be achieved, but one or two of these initiators having a 10-hour half-life temperature of 30 to 65 ° C. It is preferable to use the above. Examples of polymerization initiators include acetylcyclohexylsulfonyl peroxide, 2,4,4 trimethylpentyl-2-peroxyneodecanoate, di-2-ethylhexyl peroxydicarbonate, di (2-ethoxyethyl) peroxy Organic peroxide initiators such as dicarbonate, t-butylperoxypivalate, 3,5,5-trimethylhexanoyl peroxide, azobisisobutyronitrile, azobis-2,4, -dimethylvaleronitrile, etc. These azo initiators can be used, and these can be used alone or in combination of two or more.

  Furthermore, polymerization degree regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, emulsifiers, stabilizers, scale inhibitors, etc. that are conventionally used for the polymerization or copolymerization of vinyl chloride monomers. These charging methods are not particularly limited as long as the object of the present invention can be achieved.

  In the present invention, the ratio of heat removal by the reflux condenser out of the total heat removal amount is simply referred to as the heat removal ratio by the reflux condenser.

  The heat removal rate by the reflux condenser during the polymerization reaction may be set arbitrarily, and as an ultimate example, the cooling water may not be passed through the polymerization jacket, and the total heat removal may be performed only by the reflux condenser. .

  Specific examples of the present invention will be described in detail below, but the present invention is not limited by the following examples unless it exceeds the gist. In the following examples, “parts” represents parts by weight and “%” represents percent by weight unless otherwise specified. Moreover, all the water of the present Example used ion exchange water.

  Furthermore, the polymerization apparatus used in the following examples was provided with an apparatus (hereinafter abbreviated as a liquid level gauge) for monitoring the liquid level position of the content liquid during the polymerization. The liquid level gauge is set so that the liquid level at the time when the set temperature is raised to the predetermined polymerization temperature after charging the set filling amount, that is, all the main and auxiliary raw materials, is 40%. The value increases as the liquid level increases. Moreover, the standard of the liquid surface position where the polymerization starts to be hindered by the entrainment of droplets as described above is 45% or more. Furthermore, the measurement limit of the liquid level position with the liquid level gauge is 60%.

The characteristic value of the obtained vinyl chloride polymer was measured by the following method.
(1) Fisheye After adding 6 parts of dioctyl phthalate, 2 parts of butyltin maleate stabilizer, and 1 part of liquid paraffin lubricant to 100 parts of vinyl chloride polymer, the mixture was stirred and mixed. Extrusion was performed using a pipe die at a screw rotation number of 35 rpm in a 40 mm extruder adjusted to a die temperature of 165 ° C. A small amount of nitrogen gas was blown from the discharge tip of the extruded tube, and the thickness of the tube was adjusted to 0.2 mm. The number of fish eyes generated on the tube surface due to the unmelted portion of the vinyl chloride polymer was counted with the naked eye and evaluated as the number of fish eyes per 10 g of the polymer.
(2) Amount of coarse particles The obtained vinyl chloride polymer was sieved with a 42 mesh sieve in accordance with JIS / K-6721, the weight of the polymer remaining on the mesh was measured, and the polymer used The percentage of the original total weight was calculated.

Example 1
As shown in FIG. 1, in a 1500-liter stainless steel polymerization vessel equipped with a stirring blade, an external jacket and a reflux condenser, a single quantity condensed outside the polymerization vessel with a reflux condenser and refluxed into the polymerization vessel A monomer spraying device for spraying the body onto the surface of the polymerization content liquid was installed. A plunger pump was used as a discharge device for the monomer spraying device. Further, a discharge nozzle for spraying the monomer from the monomer spraying device to the upper part of the polymerization vessel through a pipe was installed. 3 and 4 show the detailed structure of the discharge nozzle used in this embodiment. FIG. 3 is a view of the discharge nozzle as viewed from the side, and FIG. 4 is a view of the discharge nozzle as viewed from directly below. As shown in FIG. 4, the discharge nozzle was provided with 2500 pores having a diameter of 0.3 mm. The attachment position of the discharge nozzle was always above the polymerization content liquid during the polymerization reaction. In this polymerization vessel, 100 parts of water (the same applies to 100 parts of vinyl chloride monomer), 0.08 part of partially saponified polyvinyl acetate having an average polymerization degree of 900 and a saponification degree of 78% as a dispersion stabilizer, As an oil-soluble initiator, 0.015 part of tert-butylperoxyneodecanoate and 0.02 part of 3,5,5-trimethylhexanoyl peroxide were charged and the pressure was reduced with a vacuum pump to remove oxygen. Subsequently, after stirring was started, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using the outer jacket 2 of the polymerization vessel, and polymerization was started, followed by polymerization at a constant 63 ° C. When the polymerization conversion rate reaches about 5%, the operation of the reflux condenser and the monomer spraying equipment is started, the heat removal rate by the reflux condenser is gradually increased, and the reflux rate is reached when the conversion rate is about 20%. The heat removal rate by the condenser was adjusted to be 70% of the total heat removal amount, and thereafter the heat removal rate by the reflux condenser was kept constant at 70% until the polymerization was completed at a conversion rate of 75%. The remaining heat removal amount used was a polymerizer outer jacket. When the liquid level position during the polymerization was examined by a liquid level gauge, the liquid level position started to rise at a conversion rate of about 60%, but the liquid level position was 35% even when the highest value was subsequently shown. It was confirmed that foaming was suppressed. Moreover, as a result of observing the inner wall of the polymerization vessel after polymerization, the scales at the upper portion of the polymerization vessel and the gas-liquid interface were not adhered. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were 190 and 0.02%, respectively.

(Comparative Example 1)
In the same polymerization apparatus as in Example 1, the discharge nozzle was removed, and the condensed monomer introduced into the monomer spraying device was discharged to one place on the surface of the polymerization content liquid via the pipe. In this polymerization vessel, 100 parts of water, 0.08 part of partially saponified polyvinyl acetate having an average degree of polymerization of 900 and a saponification degree of 78% as a dispersion stabilizer, and tert-butyl peroxyneodecanoate as an oil-soluble initiator 0.015 part and 0.02 part of 3,5,5-trimethylhexanoyl peroxide were charged and the pressure was reduced with a vacuum pump to remove oxygen. Subsequently, after stirring was started, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using the outer jacket of the polymerization vessel to start the polymerization, and then polymerization was carried out at a constant 63 ° C. When the polymerization conversion rate reaches about 5%, the operation of the reflux condenser and the monomer spraying equipment is started, the heat removal rate by the reflux condenser is gradually increased, and the reflux rate is reached when the conversion rate is about 20%. The heat removal rate by the condenser was adjusted to be 70% of the total heat removal amount, and thereafter the heat removal rate by the reflux condenser was kept constant at 70% until the polymerization was completed at a conversion rate of 75%. The remaining heat removal amount used was a polymerizer outer jacket. Furthermore, when the position of the liquid surface during the polymerization was traced by a liquid level gauge, the liquid surface position gradually decreased with the volume shrinkage of the polymerization content liquid 7 as the polymerization progressed, and showed 25% at the lowest. The liquid surface position started to rise at about 60%, and the liquid surface position at the time of showing the highest value showed 52%, indicating that foaming of the polymerization content liquid was remarkable. After the polymerization was completed, the unreacted monomer was recovered and the polymerization vessel was opened. As a result, a scale was attached to the gas-liquid interface portion of the inner wall of the polymerization vessel, and some scale was also attached to the upper portion of the polymerization vessel. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were about 1900 and 2.0%, respectively.

(Comparative Example 2)
In the same polymerization vessel as in Example 1, 0.08 part of partially saponified polyvinyl acetate having an average polymerization degree of 900 and a saponification degree of 78% as a dispersion stabilizer, and tert-butyl peroxyneodecanoate as an oil-soluble initiator Was added to 0.015 part and 0.05 part of 3,5,5-trimethylhexanoyl peroxide, and the pressure was reduced with a vacuum pump to remove oxygen. Subsequently, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using an outer jacket of the polymerization vessel, and polymerization was started, and then polymerization was carried out at a constant 63 ° C. However, in this comparative example, the reflux condenser was not operated, and therefore, the total heat removal was performed by the outer jacket of the polymerization vessel. When the liquid level position during the polymerization was examined by the liquid level gauge, the liquid level position started to rise at the time of about 60% conversion as in the above-mentioned Examples and Comparative Examples, but the highest value was shown thereafter. Even at that time, the liquid level was 35%. When the conversion rate was about 60%, the temperature of the cooling water in the outer jacket of the polymerization vessel suddenly decreased and it was difficult to keep the temperature of the polymerization content liquid constant, so the polymerization was terminated when the conversion rate was about 68%. . This indicates that the heat removal capability by the outer jacket of the polymerization vessel is insufficient. When the same amount of oil-soluble polymerization initiator as in the above-mentioned Examples and Comparative Examples is used, polymerization control is not possible. It shows that it is possible. As a result of observing the inner wall of the polymerization vessel after polymerization, the scales at the upper portion of the polymerization vessel and the gas-liquid interface were not attached at all. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were 138 and 0.03%, respectively. The result of this comparative example shows that foaming is very small when a reflux condenser is not used, and it is not necessary to use the polymerization apparatus of the present invention, but the heat removal capability is insufficient compared with the case where a reflux condenser is used. However, this indicates that the productivity must be lowered, for example, the polymerization time has to be extended, or the water / monomer weight ratio has to be increased.

(Comparative Example 3)
In the same polymerization vessel as in Comparative Example 1, 0.08 part of partially saponified polyvinyl acetate having an average polymerization degree of 900 and a saponification degree of 78% as a dispersion stabilizer, and tert-butyl peroxyneodecanoate as an oil-soluble initiator Was added to 0.015 part and 0.05 part of 3,5,5-trimethylhexanoyl peroxide, and the pressure was reduced with a vacuum pump to remove oxygen. Subsequently, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using an outer jacket, and polymerization was started. Polymerization was then continued at a constant 63 ° C. However, in this comparative example, the total heat removal was performed with a reflux condenser. The method for adjusting the reflux capacitor load factor was as follows. After finishing the preparation of all the main and auxiliary materials, the content liquid is heated using an external jacket, and when the internal temperature reaches 63 ° C., the heat removal rate by the reflux condenser is adjusted to 100%. Thereafter, the rate of heat removal by the reflux condenser was kept constant at 100% until the polymerization was completed at a conversion rate of 75%. During this time, the outer jacket was not flushed. When the liquid level position during the polymerization was examined by a liquid level gauge, the liquid level position started to rise at a conversion rate of about 60% as in the comparative examples and examples described above, and then the liquid level position decreased to 60%. It became impossible to measure. Furthermore, as a result of observing the inner wall of the polymerization vessel after polymerization, a large amount of scale adhered not only to the gas-liquid interface but also to the upper portion of the polymerization vessel, and much effort was required to remove the scale. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were 5000 or more and 3.5%, respectively.

(Example 2)
In the same polymerization vessel as in Example 1, 0.08 part of partially saponified polyvinyl acetate having an average polymerization degree of 900 and a saponification degree of 78% as a dispersion stabilizer, and tert-butyl peroxyneodecanoate as an oil-soluble initiator Was added to 0.015 part and 0.05 part of 3,5,5-trimethylhexanoyl peroxide, and the pressure was reduced with a vacuum pump to remove oxygen. Subsequently, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using an outer jacket of the polymerization vessel, and polymerization was started, and then polymerization was carried out at a constant 63 ° C. However, in this example, the total heat removal was performed with a reflux condenser. The method for adjusting the load factor of the reflux condenser was the same as in Comparative Example 3. When the liquid level position during the polymerization was examined by the liquid level gauge, the liquid level position started to rise at the time of about 60% conversion as in the comparative examples and examples described above, but the highest value was shown thereafter. Even at that time, the liquid surface position was 39%, that is, the liquid surface position comparable to that at the start of polymerization. Moreover, as a result of observing the inner wall of the polymerization vessel after polymerization, the scale adhesion state at the upper portion of the polymerization vessel and the gas-liquid interface was about the same as in Example 1. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were 230 and 0.08%, respectively.

(Comparative Example 4)
In the same polymerization vessel as in Example 1 except that the diameter of the pores of the discharge nozzle was 1.0 mm and the number of pores was 1000, partial saponification with an average polymerization degree of 900 and a saponification degree of 78% was used as a dispersion stabilizer. Charged with 0.08 parts of poly (vinyl acetate), 0.015 parts of tert-butylperoxyneodecanoate and 0.02 parts of 3,5,5-trimethylhexanoyl peroxide as an oil-soluble initiator, and vacuum pump Under reduced pressure to remove oxygen. Subsequently, 100 parts of vinyl chloride monomer was charged, the content liquid was heated to 63 ° C. using an outer jacket of the polymerization vessel, and polymerization was started, and then polymerization was carried out at a constant 63 ° C. When the polymerization conversion rate reaches about 5%, the operation of the reflux condenser and the monomer spraying equipment is started, the heat removal rate by the reflux condenser is gradually increased, and the reflux rate is reached when the conversion rate is about 20%. The heat removal rate by the condenser was adjusted to be 70% of the total heat removal amount, and thereafter the heat removal rate by the reflux condenser was kept constant at 70% until the polymerization was completed at a conversion rate of 75%. The remaining heat removal amount used was a polymerizer outer jacket. Further, the liquid level position during the polymerization was traced by a liquid level meter. As a result, the liquid level position started to rise when the conversion rate was about 60%, and the liquid level position when the highest value was shown showed 47%. This indicates that when the reflux monomer is sprayed, if the diameter of the monomer droplets to be sprayed is about 1.0 mm, the ability to suppress foaming of the polymerization content liquid is insufficient. After the polymerization was completed, the unreacted monomer was recovered and the polymerization vessel was opened. As a result, a scale was attached to the gas-liquid interface portion of the inner wall of the polymerization vessel, and some scale was also attached to the upper portion of the polymerization vessel. When the fish eye and the amount of coarse particles were examined using the obtained polymer, they were about 970 and 1.4%, respectively.

1 is a schematic view of a polymerization vessel used in the present invention. It is the schematic which shows the structure of the discharge nozzle used for this invention. FIG. 2 is a schematic diagram illustrating a detailed structure of a discharge nozzle used in Example 1. FIG. 2 is a schematic diagram illustrating a detailed structure of a discharge nozzle used in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymerizer main body 2 Polymerizer outer jacket 3 Stirring shaft 4 Polymerization stirring blade 5 Monomer spray device 6 Polymerization content liquid 7 Reflux condenser 8 Monomer gas flow path 9 Monomer spray device introduction pipe 10 Discharge nozzle 11 Fine Hole

Claims (3)

  1. Polymerization characterized in that an apparatus for spraying the monomer that is condensed in the reflux condenser and refluxed into the polymerization vessel onto the surface of the polymerization liquid is provided outside the polymerization vessel. vessel.   A reflux condenser and a device for spraying the monomer condensed in the reflux condenser and refluxed into the polymerization vessel onto the surface of the polymerization content liquid are obtained by using a polymerization vessel provided outside the polymerization vessel. A method for producing a vinyl chloride polymer, comprising polymerizing a monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the monomer and a vinyl chloride monomer.   The method for producing a vinyl chloride polymer according to claim 2, wherein the polymerization method is suspension polymerization.

Images