KR101644199B1 - A method for preparing vinyl chloride based polymers by suspension polymerization and an apparatus used thereof - Google Patents

Abstract

The present invention relates to a process for producing a vinyl chloride polymer by suspension polymerization and a device used therefor, wherein a reactor equipped with a reflux condenser is used and the non-condensable gas generated during the reaction is exhausted to efficiently control the heat of the reflux condenser Thereby improving the productivity. However, it is possible to effectively solve the problem that the non-condensable gas is scaled inside the reflux condenser due to the back flow of the foam during the discharge, and consequently the quality of the product is deteriorated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a vinyl chloride polymer by suspension polymerization,

The present invention relates to a process for producing a vinyl chloride polymer by suspension polymerization and a device used therefor, wherein a reactor equipped with a reflux condenser is used and the non-condensable gas generated during the reaction is exhausted to efficiently control the heat of the reflux condenser The problem is that the scale is generated inside the reflux condenser due to the back flow of the foam when the non-condensable gas is exhausted, and as a result, the properties of the product of the product can be deteriorated by using a foam detector To a process for producing a vinyl chloride polymer and a device used therefor.

The vinyl chloride polymer refers to an interpolymer obtained by polymerizing a mixture of a vinyl chloride monomer and a copolymerizable monomer. The polymerization method of the vinyl chloride polymer is largely a suspension polymerization method and an emulsion polymerization method. The double suspension polymerization method is a method of polymerizing particles of about 150 μm using water, a vinyl chloride monomer, a suspension stabilizer and an initiator. It has excellent electrical insulation and chemical resistance and is used for various purposes such as pipe, window frame, wire covering.

The emulsion polymerization method is a method of polymerizing particles of about 0.1 to 2 탆 using water, an emulsifier, a vinyl chloride monomer, and an initiator. The vinyl chloride polymer produced by the emulsion polymerization method has good flowability during processing and is excellent in foaming properties and is widely used as a flooring material.

The polymerization of the vinyl chloride monomer is carried out by maintaining a constant temperature by providing a heating and cooling jacket on the outside of the reaction vessel to control the heat generated during the reaction in the exothermic reaction. However, since the reactor is enlarged to improve the productivity, there is a limitation in controlling the heat generated by the reaction of the jacket alone. Therefore, a reflux condenser is installed on the upper part of the reaction vessel to effectively heat the reactor.

However, since the non-condensable gas generated by decomposition of nitrogen, oxygen and initiator which can be introduced from the outside is less dense than the vinyl chloride monomer, it accumulates on the reflux condenser and obstructs the condensation of the vinyl chloride monomer, Lt; / RTI >

In addition, the vinyl chloride monomer condensed in the reflux condenser is scaled to produce a scale, so that it is difficult to reproduce a constant heat removing ability for each polymerization, and the characteristics of the fish eye deteriorate due to scale generation.

In order to solve these problems, Japanese Patent Application Laid-Open No. 1996-134107 proposes a method of discharging a non-condensable gas generated during polymerization for a predetermined time by installing a gas discharge line on the reflux condenser. However, since the amount of gas generated for each batch can not be accurately known, it is difficult to maintain the heat-releasing capacity of the reflux condenser at a constant level.

Japanese Unexamined Patent Application Publication No. 1999-255810 discloses a method of discharging non-condensable gas by controlling the temperature of the upper portion of the reflux condenser within a specific temperature range in order to solve such a problem. However, if foam is generated during the reaction, if the temperature of the upper part of the reflux condenser is controlled only in a specific range, foam may flow back into the reflux condenser during overdischarging and scale may be generated therein, And it is difficult to expect a stable heat-retaining ability for each batch.

On the other hand, the polymerization reaction of the vinyl chloride polymer may exert an influence on the physical properties if the heat removal is not stable during the reaction due to the exothermic reaction, and furthermore, the pressure inside the reaction vessel rises due to the increase of the temperature.

However, the scale, which can be generated by the back flow of the foam due to the generation of the accumulated gas and the exhaust of the gas, does not fall off easily on the inner wall of the reflux condenser, The vinyl chloride monomer in the gaseous phase is condensed by the cooling water flowing into the reflux condenser and must be supplied to the reactor again.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a suspension polymerization method which improves the heat-removing ability per unit time of the reflux condenser to improve productivity and produce stable quality.

Another object of the present invention is to provide a polymerization apparatus suitable for use in the suspension polymerization method.

In order to solve the above problems, the inventors of the present invention conducted researches to improve the heat-releasing effect by discharging the non-condensable gas accumulated in the upper part of the reflux condenser, but by installing a foam detector at the upper part of the reactor, it is possible to prevent the backflow of foam that may occur in the reflux condenser due to exhaust of the non-condensable gas, and as a result, to prevent scale formation inside the reflux condenser, And the polymerization time can be shortened to improve productivity. The present invention has been accomplished on the basis of this finding.

That is, according to the method for producing a vinyl chloride polymer of the present invention, in suspension polymerization of an initiator, a suspension stabilizer and a vinyl chloride monomer,

The upper temperature of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is controlled so that the temperature difference from the polymerization temperature in the polymerization reactor becomes 4 ° C or less.

Further, according to the method for producing a vinyl chloride polymer of the present invention, in suspension polymerization of an initiator, a suspension stabilizer and a vinyl chloride monomer,

The upper temperature of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is controlled to the polymerization temperature in the polymerization reactor

And the foam level height in the polymerization reactor satisfies 70% or less.

Further, according to the method for producing a vinyl chloride polymer of the present invention, in suspension polymerization of an initiator, a suspension stabilizer and a vinyl chloride monomer,

The upper temperature of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is adjusted so that the temperature difference from the polymerization temperature in the polymerization reactor is 2 ° C or lower

And has a technical characteristic in that the foam level height in the polymerization reactor is adjusted to satisfy 50% or less.

Hereinafter, the present invention will be described in detail.

In the present invention, the reactor equipped with the reflux condenser is used, and the non-condensable gas generated during the reaction is exhausted to efficiently control the heat of the reflux condenser, thereby improving the productivity. In the reflux condenser, A problem arises in that a scale is generated in the product and the deterioration of the heat-generating ability of the product may result in deterioration of the product's characteristics of the product, using a foam detector.

First, the present invention polymerizes a vinyl chloride monomer in a reactor equipped with a reflux condenser, and starts polymerization in the presence of a suspension stabilizer, a polymerization initiator, and a vinyl chloride monomer. From the start of the polymerization, a line of the reflux condenser connected to the reactor was opened. It is possible to prevent the backflow of the reactant due to the pressure difference by preventing the pressure difference between the inside of the reflux condenser and the inside of the reactor.

Further, in the present invention, the polymerization temperature is not limited to a specific temperature but can be used. Therefore, the polymerization temperature is preferably set within the range of 40 to 80 ° C.

Particularly in the present invention, the problem is that, in the suspension polymerization of the initiator, the suspension stabilizer and the vinyl chloride monomer, the temperature of the upper part of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is set to 4 Lt; 0 > C or less.

The vinyl chloride polymer includes not only a resin made of a pure vinyl chloride monomer but also a mixture of a vinyl monomer mainly composed of a vinyl chloride monomer and a vinyl monomer copolymerizable therewith (content of the vinyl chloride monomer in the resin composition is 50% by weight or more) .

Examples of the vinyl monomer copolymerizable with such a vinyl chloride monomer include olefin compounds such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, vinyl methyl ether and vinyl ethyl ether Unsaturated fatty acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid, and anhydrides of these fatty acids, can be used alone or in admixture of two or more kinds of monomers copolymerizable with vinyl chloride monomers.

Examples of the polymerization initiator usable in the present invention include diacyl peroxides such as dicumyl peroxide, dipentyl peroxide, di-3,5,5-trimethylhexanoyl peroxide and diaryl peroxide, diisopropyl peroxide Butyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneodecanoate, Peroxyesters such as amyl peroxyneodecanoate, cumyl peroxyneodecanoate, cumyl peroxyneoheptanoate, and 1,1,3,3-tetramethylbutyl peroxyneodecanoate, azobis -2,4-dimethylvaleronitrile, and sulfates such as potassium persulfate and ammonium persulfate, and they may be used alone or in combination of two or more thereof. The amount of the initiator to be used may be in the range of 0.02 to 0.2 part by weight based on 100 parts by weight of the total charged monomers and most preferably in the range of 0.04 to 0.12 parts by weight The use of parts is preferable.

Examples of the antioxidant that can be used before the reaction is stopped in the present invention include a triethylene glycol-bis- [3- (3-t-butyl Methyl-4-hydroxyphenyl) propionate], hydroquinone, p-methoxyphenol, t-butylhydroxyanisole, n-octadecyl- Di-t-butylphenyl) propionate, 2,5-di-t-butylhydroquinone, 4,4-butylidenebis (3-methyl- Phenol compounds such as 4,4, -thiobis (6-t-butyl-m-cresol) and tocopherol, N, N-diphenylp-phenylenediamine, 4,4-bis (dimethylbenzyl) diphenylamine , Dodecyl mercaptan, sulfur compounds such as 1,2-diphenyl-2-thiol, triphenyl phosphite, diphenyldecyl phosphite, phenyl isodecyl phosphite, tri (nonylphenyl) phosphite, Trirallyl tree A phosphoric acid-based antioxidants such as O phosphite may be used either alone or in mixture of two or more.

Also, the non-condensable gas generated during the polymerization accumulates in the upper part of the reflux condenser, and the temperature of the upper part of the reflux condenser is lowered. When the temperature difference between the upper temperature of the reflux condenser and the polymerization temperature in the polymerization reactor exceeds 4 ° C, a large amount of non-condensable gases accumulate in the reflux condenser, while the upper temperature of the reflux condenser is maintained through the exhaust of non-condensable gas. And the heat-releasing capacity of the reflux condenser is reduced due to the non-condensable gas, which is not preferable.

On the other hand, the non-condensable gas is exhausted from the upper part of the reflux condenser. The specific kind of the non-condensable gas is not limited thereto, but means a mixed gas accumulated in the upper part of the polymerization reactor as the polymerization reaction is performed.

On the other hand, when the height of the foam measured by the foam detector is higher than the set value, the exhaust is stopped to prevent the scale from being generated inside the reflux condenser by the foam.

More preferably, the problem is that, in the suspension polymerization of the initiator, the suspension stabilizer and the vinyl chloride monomer, the upper temperature of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is controlled to the polymerization temperature in the polymerization reactor The foam level height in the polymerization reactor is adjusted to satisfy 70% or less.

At this time, the foam level height in the polymerization reactor is characterized by stopping and controlling the process of discharging the non-condensable gas for the temperature control on the reflux condenser. Such disadvantages of the backflow of the foam in the polymerization reactor and the formation of scale in the reactor can be prevented in advance through the stop of the exhaust process.

When the foam level height is lowered to a predetermined level, the exhaust process is regenerated to continuously regulate the temperature in the reflux condenser. The 'predetermined level' means that the upper temperature of the reflux condenser When the polymerization temperature is maintained, it is preferable that the maximum is 70%.

As shown in FIG. 2, the 'foam level height' of the present invention represented by 70%, 50% or the like indicates the foam height from the bottom edge of the foam detector to the foam height of the foam detector based on the length (c) foam means the measured height in%. For example, if the foam detector inside the reactor is 110 mm and the height measured from the bottom of the foam detector is 11 mm, it is referred to as 10%.

Further, the foam level height can be measured by using a foam detector separately mounted on a polymerization reactor with a reflux condenser. For a detailed description related to the foam detector, refer to the explanation with reference to the following drawings.

Most preferably, the problem is that, in suspension polymerization of the initiator, the suspension stabilizer and the vinyl chloride monomer, the upper temperature of the reflux condenser provided on the top of the polymerization reactor used in the suspension polymerization is set to a temperature difference with the polymerization temperature in the polymerization reactor Of not more than 2 DEG C and at the same time, adjusting the foam level in the polymerization reactor to 50% or less.

At this time, the foam level in the polymerization reactor is adjusted so as to stop the process of discharging the non-condensable gas for controlling the temperature of the upper part of the reflux condenser, and the foam in the polymerization reactor flows back into the reactor through the stop of the exhaust process, It is possible to prevent the drawbacks of forming the light emitting diode.

Here, when the foam level height falls to a predetermined level, the exhaust process is recovered. In this case, when the upper temperature of the reflux condenser is maintained at a temperature difference of 2 ° C or lower from the polymerization temperature in the polymerization reactor, As described in the example, it is preferable that the standard is 50%.

Further, the foam level height can be measured using a foam detector separately mounted on a reflux condenser on a polymerization reactor, and a detailed description related to a foam detector is also referred to the following description with reference to the following drawings .

The vinyl chloride polymer slurry prepared by the process of the present invention can be dried to remove the water using a fluidized bed drier under the usual reaction conditions, to obtain a final vinyl chloride polymer.

According to the present invention, since the scale generation is prevented, the vinyl chloride polymer can be produced while shortening the polymerization time without significantly changing the properties of the produced polyvinyl chloride.

In the meantime, the production apparatus used in the vinyl chloride polymer production method of the present invention is not limited thereto, but it is preferable to use the apparatuses shown in Figs. 1 and 2.

First, the production apparatus used in the present invention is a device for suspension polymerization of a vinyl chloride monomer, which comprises a polymerization reactor (1) and a reflux condenser (2) provided on the top of the polymerization reactor (1) And a foam detector 3 separately mounted from the reflux condenser 2 at the top of the reactor 1.

In the foam detector 3, the length of the lowermost end of the foam detector 3 measured from the uppermost end of the polymerization reactor 1 is 8 to 14% of the height of the reactor. In the double polymerization reactor 1, The length of the lowermost end of the foam detector 3 measured from the uppermost end of the polymerization reactor 1 is 11% of the height of the reactor and the height of the reactor 1 in the double polymerization reactor 1 It is most preferable that the device is mounted so that 9% of it is mounted in consideration of the reaction efficiency .

In addition, the form detector 3 is not limited thereto, but it is possible to use an inversion type, a conduction type, a potential difference type, an ultrasonic type, and an optical type, and it is more preferable to use a laser type Do.

The capacity of the polymerization reactor (1) used in the polymerization in the present invention is not particularly limited and is applicable to a large reactor. And a generally used stirring device may be used. Specifically, the wing type may be a paddle type, a pitched paddle type, a turbine type, a bluemagine type, a pfaudler type, And a baffle can be a cylindrical type, a D type, a loop type, a finger type, or the like.

Further, as the reflux condenser (2), any known reflux condenser connected to the main body of the polymerization reactor by one or more conduits and having a structure in which the steam and the condensate move inside can be used. For example, a coil type, Tubular type, shell-and-tube type, and the like, and it is particularly preferable to use a shell-and-tube type having excellent efficiency of removing polymerization heat.

According to the suspension polymerization method of the vinyl chloride polymer of the present invention, the non-condensable gas accumulated in the upper part of the reflux condenser is exhausted within a specific temperature range, and the problem that the foam can flow back while the non-condensable gas is exhausted, it is possible to prevent the generation of scales inside the reflux condenser by adjusting the amount of exhaust gas using a foam detector, thereby improving the heat-removing efficiency of the reflux condenser, producing stable quality for each batch, and improving productivity.

1 is a schematic view of a production apparatus used in an embodiment of the present invention having a foam detector 3 at the top of a polymerization reactor 1 equipped with a reflux condenser 2.
2 is a detailed view of the foam detector shown in a circle in FIG. 1, wherein the distance a from the upper part of the polymerization reactor 1 to the lower end of the foam detector 3 is 130 mm (11% of the height of the reactor) As shown in Fig. 2 (c), the length of the length of the detector 3 entering the polymerization reactor 1 in the entire length is 110 mm (9% of the height of the reactor).
* Explanation of simple codes for main parts of the drawing *
1: Reactor
2: reflux condenser
3: foam detector
4: R / CN phase thermometer
5: On / off valve and flow meter
6: B / D tank

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Manufacturing example  One

An example of a device used in the present invention is shown in Fig.

A foam detector 3 was installed at the top of the polymerization reactor 1 provided with the shell and tubular reflux condenser 2. The length from the uppermost stage of the polymerization reactor 1 to the lowermost end of the polymerization reactor 1 shown in Fig. 1 is 11% (in this experiment, from the top of the reactor 1 to the bottom of the foam detector 3) The length of the entire length of the foam detector 3 into the polymerization reactor 1 was 110 mm (9% of the height of the reactor) as shown in Fig. 2 (c) Respectively.

At this time, a device for detecting by laser irradiation was used as the form detector 3.

A line through which the non-condensable gas is discharged is installed at the upper part of the reflux condenser 2 so that the exhausted gas can go to the B / D (Blow Down) tank.

Example  One

130 parts by weight (390 kg) of polymerization water and a degree of hydration of 88 (weight) were added to a stainless polymerization reactor (1) having an internal volume of 1 m ³ and equipped with a reflux condenser (2), a foam detector (3) and a stirrer 0.0256 parts by weight of polyvinyl alcohol, 0.0410 parts by weight of polyvinyl alcohol having a hydration degree of 72%, 0.0320 parts by weight of polyvinyl alcohol having 55% of hydration degree, 0.064 parts by weight of hydroxypropyl methylcellulose, 0.07 part by weight of peroxyneodecanoate (BND) and 0.018 part by weight of? -Cumylperoxyneodecanoate (CND) were added. Then, the inside was degassed with a vacuum pump and 100 parts by weight (300 kg) of vinyl chloride monomer was added thereto. Respectively. Further, the valve of the reflux condenser 2 was opened in addition to the start of the polymerization so that the pressure was not changed.

The temperature of the polymerization reactor (1) was maintained at 58 캜 during the prepolymerization process. During the reaction, the temperature of the upper portion of the reflux condenser (2) was adjusted within the range of 54 to 58 ° C to discharge the non-condensable gas. The polymerization was then stopped when the polymerization reactor pressure had changed by 1.0 kg / cm ² .

Then, 0.05 part by weight of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] was added as an antioxidant to recover unreacted monomers, Was recovered in the polymerization reactor (1). The slurry thus obtained was dried in a fluid bed drier (not shown) and a vinyl chloride polymer was obtained.

Example  2

The polymerization was carried out under the same conditions as in Example 1 except that the amount of exhaust gas was adjusted so that the upper temperature of the reflux condenser (2) could be kept at 55 to 58 캜 in Example 1.

Example  3

Polymerization was carried out under the same conditions as in Example 1 except that the amount of exhaust was adjusted so that the upper temperature of the reflux condenser (2) in Example 1 could be maintained at 56 to 58 占 폚.

Example  4

The polymerization was carried out under the same conditions as in Example 1 except that the amount of exhaust gas was adjusted so that the upper temperature of the reflux condenser (2) could be maintained at 58 캜 in Example 1.

Example  5

The exhaust amount is adjusted so that the upper temperature of the reflux condenser 2 can be maintained at 58 占 폚 in the first embodiment. And measured by a foam detector 3, the non-condensable gas is stopped when the foam level height indicated on the monitor is 70%, and once the foam level height is reduced to 70%, the non- Polymerization was carried out under the same conditions as in Example 1 except for exhausting and evaluation.

Example  6

When the foam level height measured by the foam detector 3 in Example 5 is 60%, the non-condensed gas is stopped and when the foam level height is lowered to 60%, the non-condensed gas Polymerization was carried out under the same conditions as in Example 5 and evaluated.

Example  7

When the foam level height measured by the foam detector 3 in Example 5 is 50%, the non-condensing gas is stopped and when the foam level height is lowered to 50%, the non- Polymerization was carried out under the same conditions as in Example 5 and evaluated.

Example  8

When the foam level measured by the foam detector 3 in Example 5 is 40%, the non-condensed gas is stopped and when the foam level height is lowered to 40%, the non-condensed gas Polymerization was carried out under the same conditions as in Example 5 and evaluated.

Example  9

When the upper temperature of the reflux condenser 2 in Example 1 is 56 캜, the discharge amount of the non-condensable gas is started and the upper temperature of the reflux condenser 2 is maintained at 56 to 58 캜. When the foam level height measured by the foam detector 3 is 50%, the non-condensable gas is stopped and when the foam level height is reduced to 50%, the non-condensable gas is again exhausted The polymerization was carried out under the same conditions as in Example 1 and evaluated.

Example  10

0.05 parts by weight of polyvinyl alcohol having a degree of hydration of 88% in Example 1, 0.02 part by weight of polyvinyl alcohol having a degree of hydration of 72%, 0.015 part by weight of polyvinyl alcohol having a degree of hydration of 55%, hydroxypropyl methylcellulose 0.01 By weight, and the amount of exhaust is adjusted so that the upper temperature of the reflux condenser (2) can be maintained at 55 to 57 占 폚.

Except that when the foam level height measured by the foam detector 3 is 50%, the non-condensed gas is stopped and the non-condensed gas is exhausted again when the foam level height is lowered to 50% The polymerization was carried out under the same conditions as in Example 1 and evaluated.

Comparative Example  One

Polymerization was conducted and evaluated under the same conditions as in Example 1, except that the amount of exhaust was adjusted so that the upper temperature of the reflux condenser (2) in Example 1 could be maintained at 52 to 58 캜.

Comparative Example  2

Polymerization was conducted and evaluated under the same conditions as in Example 10, except that the exhaust amount was adjusted so that the upper temperature of the reflux condenser (2) in Example 10 could be maintained at 51 to 57 占 폚.

The properties of the vinyl chloride polymer prepared in each of Examples 1 to 10 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Tables 1 and 2 below. The specific measurement method is as follows:

* Average particle size: Measured according to ASTM D 1243-79.

* Apparent Specific Gravity (B.D.): Measured according to ASTM D1895-89.

* Plasticizer Absorption Rate (wt%): The amount of DOP absorbed in the sample according to ASTM D3367-95 was measured in terms of weight% based on the sample weight before absorption.

* Scale generation: The internal state of the reflux condenser and the state of sieving after slurry drying were determined visually during the reactor cleaning stage after polymerization.

?: Scale generation at the same level as Comparative Examples 1 and 2.

&Amp; cir &: Scale generation was slightly increased based on Comparative Examples 1 and 2.

X: Scale generation is remarkably large based on Comparative Examples 1 and 2.

Fish-eye number: 45 parts by weight of DOP, 0.1 part by weight of barium stearate, 0.2 part by weight of tin stabilizer, and 0.1 part by weight of carbon black were added to 100 parts by weight of the vinyl chloride polymer prepared, And mixed / kneaded for 4 minutes to form a sheet having a thickness of 0.3 mm and expressed by the number of white transparent particles in 100 m ² of the sheet.

Metrics Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Average particle diameter (占 퐉) 139 141 144 138 142 137 Apparent Specific Gravity (g / cc) 0.522 0.519 0.524 0.520 0.521 0.516 Plasticizer absorption rate (%) 26.8 27.5 27.3 27.3 26.9 27.1 Polymerization time (minutes) 225 221 217 218 217 214 Fishy Eye (Dog) 4 5 7 8 7 5 Scale occurrence ○ ○ X X X X

Metrics Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Average particle diameter (占 퐉) 139 144 142 173 144 171 Apparent Specific Gravity (g / cc) 0.520 0.524 0.517 0.579 0.523 0.581 Plasticizer absorption rate (%) 27.0 27.3 26.9 16.2 27.1 15.9 Polymerization time (minutes) 211 213 207 203 229 221 Fishy Eye (Dog) 3 3 3 - 3 - Scale occurrence ◎ ◎ ◎ ◎ ◎ ◎

As shown in Tables 1 and 2, when the temperature of the upper portion of the reflux condenser 2 is controlled within a specific temperature range, the results of Examples 1 to 4 show that the polymerization time of Comparative Example 1 is decreased. This is because the larger the difference between the polymerization temperature in the polymerization reactor 1 and the upper temperature of the reflux condenser 2, the greater the amount of non-condensable gas accumulated on the reflux condenser 2, It was confirmed that the reaction time was affected because the content of the vinyl chloride monomer was reduced.

Also, it was found that the case of Example 3 in which the temperature of the reflux condenser (2) regulates the discharge of the non-condensable gas within the range of 56 to 58 ° C, which is different from the reaction temperature by 2 ° C, is effective in shortening the polymerization time. In addition, as the temperature of the upper part of the reflux condenser (2) is adjusted to a range similar to the polymerization temperature, the amount of gas discharged increases, and the foam generation increases due to the pressure difference, and scale is generated thereby deteriorating the fish eye characteristics See Example 4).

In Examples 5 to 8 in which the non-condensable gas was stopped depending on the foam level measured by the foam detector 3, it was confirmed that the lowering of the foam level height to determine the non-condensable gas exit time gradually improved the fishy eye And the exhaustion of the non-condensable gas was stopped when the foam level height was 50%, it was confirmed that the characteristic of the fish eye was maintained at the same level as that of the conventional product.

In the case of Example 9 in which the improved conditions were applied in consideration of all of these conditions, it was confirmed that the polymerization time was shortened by about 10% while maintaining the same level as that of the existing quality. Comparing Example 10, which was carried out under different polymerization conditions, with Comparative Example 2, it was confirmed that the polymerization time was shortened without significant change in the characteristic of the phosphorous ion, which was similar to Example 9.

Therefore, it can be confirmed that the examples 9 and 10 according to the present invention are most effective for shortening the polymerization time without greatly changing the characteristics of the conventional vinyl chloride polymer while improving the heat capacity per unit time of the reflux condenser.

Claims (12)

In suspension polymerization of an initiator, a suspension stabilizer and a vinyl chloride monomer,
1) The temperature of the upper part of the reflux condenser provided on the top of the reactor used in the suspension polymerization is controlled by controlling the temperature of the reactor and the temperature of the reflux condensation period under the continuous exhaust of non-condensable gas, A suspension polymerization step in which the polymerization temperature is adjusted to
2) a suspension polymerization process for controlling the temperature difference between the reactor temperature and the reflux condensation period under the stoppage of exhaust of the non-condensable gas,
2-1) Exhaust stop point of the non-condensable gas in the above 2) is based on when the height of the foam level in the reactor exceeds 70%
2-2) When the height of the foam level drops to 70% or less, continuous evacuation of the non-condensable gas of 1) is performed. In suspension polymerization of an initiator, a suspension stabilizer and a vinyl chloride monomer,
1) The temperature of the upper part of the reflux condenser provided on the top of the reactor used in the suspension polymerization is controlled by controlling the temperature of the reactor and the temperature of the reflux condensation period under the continuous exhaust of non-condensable gas, A suspension polymerization step in which the temperature difference between the polymerization temperature and the polymerization temperature is controlled to be 2 DEG C or less;
2) a suspension polymerization process for controlling the temperature difference between the reactor temperature and the reflux condensation period under the stoppage of exhaust of the non-condensable gas,
2-1) Exhaust stop point of the non-condensable gas in the above 2) is based on when the height of the foam level in the reactor exceeds 50%
2-2) When the height of the foam level drops below 50%, the continuous evacuation of the non-condensable gas of 1) is performed. delete delete delete delete delete The method according to claim 1 or 2, wherein the foam level height is measured using a foam detector separately mounted on a polymerization reactor with a reflux condenser,
The foam detector is a device for detecting a foam level by laser irradiation. The distance (a) from the top of the reactor to the bottom of the foam detector is within 8 to 14% of the height of the reactor. Is used in a range of 7 to 11% of the height of the reactor. delete delete delete delete

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