JPH0525204A - Suspension polymerization method of vinyl chloride monomer - Google Patents

Abstract

PURPOSE:To provide an improved method for producing a vinyl chloride polymer within a time period as short as 6 hours or less without causing polymer particle size enlargement, increasing the number of fisheyes, or lowering the bulk specific gravity by using a large-sized polymerization vessel equipped with a reflux condenser and having a capacity of 40m<3> or more. CONSTITUTION:A vinyl chloride monomer is polymerized by suspension polymerization in an aqueous medium in the presence of an oil-soluble initiator using a large-sized polymerization vessel which is equipped outside with a reflux condenser and inside with a stirrer, has an internal jacket for heating/cooling disposed inside the vessel, and has a capacity of 40m<3> or more. This polymerization is conducted while regulating the net stirring power, Pv, which is the stirring power required per m<3> of the contents in the polymerization vessel, at 1.2-3.0kW/m<3>, and is terminated within 6 hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an improvement of a mixture of vinyl chloride monomer and vinyl chloride monomer or vinyl chloride monomer (hereinafter referred to as vinyl chloride monomer). The present invention relates to a suspension polymerization method, and more specifically, using a large-scale polymerization vessel equipped with a reflux condenser, a vinyl chloride-based polymer is produced without causing coarsening of particles, lowering of bulk specific gravity, and increase of fish eyes. The present invention relates to a method for producing a high efficiency.

[0002]

BACKGROUND OF THE INVENTION Vinyl chloride resin is industrially equipped with a polymerization vessel equipped with a jacket for heating and cooling and a stirrer.
It is produced by batchwise suspension polymerization. In order to improve the productivity of the resin, increase the heat removal capacity of the polymerization vessel, increase the polymerization rate to the limit of heat removal capacity to complete the polymerization in a short time,
It is important to increase the size of the polymerization vessel and increase the production amount per batch.

In order to shorten the polymerization time, a highly active initiator is selected according to the polymerization temperature (Japanese Patent Laid-Open No. 53-73280).
No.), and by increasing the amount of addition thereof, and by homogenizing the polymerization rate by combining initiators having different activities (JP-A-56-149407), the heat removal capacity of the polymerization vessel is limited. It is possible to increase the polymerization rate.

Increasing the size of the polymerization vessel reduces the jacket area per internal volume and reduces the heat removal capacity. Therefore, it is possible to greatly improve the heat removal capacity by attaching a reflux condenser outside the polymerization vessel to remove the reaction heat, and even in a large-scale polymerization vessel of 40 m ³ or more, short-time polymerization of 6 hours or less is possible. It becomes possible (Japanese Patent Publication No. 1-18082). However, when polymerization is carried out for a short time using a reflux condenser, coarsening of polymer particles,
There are quality problems such as increase in fish eyes (especially when using polymer plasticizers with relatively low plasticizing ability and high viscosity such as polyester) and decrease in bulk specific gravity, especially after the middle stage of polymerization. There is a problem that a foaming phenomenon occurs and the normal operation of the condenser and the polymerizer becomes difficult due to the adhesion of the polymer to the condenser.

In order to solve such a problem, a polymerization prescription,
Various methods have been proposed for the device and the operation method. For example, as for a polymerization formulation, nonionic surfactants are selected and added to suppress foaming and increase in fish eyes (JP-A-61-207410).
No.), a suspension agent is selected to obtain a resin having a high bulk specific gravity and rapid gelation (JP-A-1-268702), and a resin having a high bulk specific gravity and a small fish eye is obtained by polymerizing while adding water ( JP-A-61-111307) and the like.

Further, regarding the apparatus and the operating method, foaming is suppressed by devising a method of applying a load to the condenser to reduce adverse effects on quality (Japanese Patent Laid-Open No. 57-1460).
No. 8), a bubble cutting blade is provided in the gas phase part of the polymerization vessel to mechanically break the cells (Japanese Patent Laid-Open No. 58-49710), but there is no complete one, and a condenser is used. At present, it is inferior in terms of quality and operation compared to the case where it is not.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to coarsen polymer particles in a short time within 6 hours using a large-scale polymerizer having an internal volume of 40 m ³ or more equipped with a reflux condenser. It is an object of the present invention to provide a method for producing a vinyl chloride polymer without causing an increase in fish eyes and a decrease in bulk specific gravity.

[0008]

The object of the present invention is to provide a mixture of a vinyl chloride monomer copolymerizable with vinyl chloride and a vinyl chloride monomer in the presence of an oil-soluble initiator in an aqueous medium. When the suspension polymerization is carried out in 6 hours and the polymerization is completed within 6 hours, the inner volume is equipped with a reflux condenser on the outside, a stirrer on the inside, and an inner jacket for heating / cooling enclosed inside the polymerization vessel. This can be achieved by using a large-sized polymerization vessel of 40 m ³ or more and controlling the net stirring power Pv (kW / m ³ ) per 1 m ³ of the content liquid in the polymerization vessel in the range of 1.2 to 3.0.

The present invention will be described in detail below. In the present invention, a polymerization vessel having an internal volume of 40 m ³ or more, which is provided with a reflux condenser outside the polymerization vessel, is used. If the inner volume is 40 m ³ or less, the reflux condenser is not always necessary because the heat transfer area of the jacket per inner volume is large. However, in this case, since the production amount per batch is small, a large number of polymerization reactors are required, which is not economical.

The reflux condenser used in the present invention is a condenser connected to the gas phase portion of the polymerization vessel by a conduit. The structure is not particularly limited as long as it has a heat removal ability corresponding to a desired polymerization rate. Generally, a multi-tube reflux condenser is used.

In the present invention, JP-A-57-14750
The present invention can be more advantageously carried out by using the inner jacket type polymerization vessel described in No. 2 in which the jacket for heating / cooling is included in the inner surface of the polymerization vessel body to improve the heat transfer performance. can do. That is, since the heat removal capacity is larger than that of a normal external jacket polymerization device, the polymerization can be completed in a shorter time, and the load on the reflux condenser can be reduced.

As the stirring blades of the stirring device used in the present invention, there are a Faudler blade, a bull margin blade, a turbine blade, a fan turbine blade, a paddle blade, and the like, which can be more preferably implemented in the Faudler blade. As the baffle, pipe (bar type) baffle, D type baffle, and E type (finger type) baffle are preferable. These stirring blades and baffles are generally used, and for example, “Koji Saeki: Polymer Manufacturing Process, 157-1.
P. 59, 1971, Industrial Research Board ".

Examples of the monomer copolymerizable with vinyl chloride in the present invention include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-monoolefins such as ethylene and propylene, and acrylic acid. Examples thereof include (meth) acrylic acid alkyl esters such as methyl and methyl methacrylate, but are not limited thereto.

Examples of the dispersant such as a suspending agent and a surfactant used in the present invention include partially saponified polyvinyl acetate, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hiro which are usually used for suspension polymerization of vinyl chloride. Water-soluble cellulose ethers such as doxypropylmethyl cellulose, acrylic acid polymers, water-soluble polymers such as gelatin, sorbitan monolaurate,
Sorbitan monostearate, glycerin monostearate, oil-soluble emulsifiers such as ethylene oxide propylene oxide block copolymer, polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, water-soluble emulsifiers such as sodium laurate are exemplified, These are used alone or in combination of two or more. All of these may be used from the beginning of the polymerization, or a part thereof may be added during the polymerization.

The polymerization initiator used in the present invention is di-2
-Ethylhexyl peroxydicarbonate, di- (2
-Ethoxyethyl) peroxydicarbonate-based initiator such as peroxydicarbonate, diacyl peroxide-based initiator such as 3,5,5-trimethylhexanoyl peroxide, 2,2'-azobis (2,4 -Dimethylvaleronitrile) and other azo-based initiators, and 2,4,4-trimethylpentylperoxy-2-neodecanoate, (α, α'-bis-decanoylperoxy) diisopropylbenzene, tertiary butylper Examples thereof include perester-based initiators such as oxyneodecanoate and tert-hexyl peroxypivalate, but are not limited to these initiators. The type and amount of these initiators are selected so that the polymerization time is 6 hours or less at a predetermined polymerization temperature, and one type or a combination of two or more types is used.

The term "polymerization time" as used herein means that, after the time when the internal temperature reaches a predetermined polymerization temperature due to heating / heating after the completion of charging, the pressure in the polymerization vessel is allowed to change for a while under the spontaneously generated pressure at the reaction temperature, It is defined as the time until the pressure drop starts with the decrease of unreacted monomer and the width of the drop reaches 2 kg / cm ² . In the case of the present invention, the polymerization conversion is usually 83 to 86%.

In the present invention, a chain transfer agent such as mercaptoalkanol and thioglycolic acid alkyl ester, and a pH adjusting agent such as sodium polyphosphate can be added, if necessary.

In the present invention, the net stirring power Pv (kW / m ³ ) per 1 m ³ of the content liquid in the polymerization vessel is controlled within the range of 1.2 to 3.0, preferably 1.5 to 2.5. There is a need. The net stirring power is shown by Pv = (Pt-Pe) / V,
Is the stirring power (kW) during polymerization, Pe is the stirring power (kW) when there is no load (the polymerization vessel is empty), and V is the content liquid amount (m ³ ) of the polymerization vessel.

Conventionally, the net stirring power Pv in the suspension polymerization of vinyl chloride has been less than 1 (kW / m ³ ). However, when a reflux condenser is used under this stirring condition, there are problems in quality such as an increase in fish eyes and an increase in particle diameter as the polymerization reaction speed is increased and the polymerization time is shortened. Further, after the middle stage of the polymerization, the adhesion of the polymer to the condenser, which is considered to be due to the rise of the polymer slurry due to foaming, not only reduces the heat removal capacity of the condenser, but also makes the temperature control of the polymerization vessel impossible. Become.

As a result of earnest studies on this problem, the inventors of the present invention found an appropriate condition for the net stirring power Pv (kW / m ³ ) in setting the polymerization time to 6 hours or less, and arrived at the present invention. is there. That is, in order to shorten the polymerization time and obtain a high-quality polymer, it is necessary to increase the net stirring power, using a large-scale polymerizer of 40 m ³ or more equipped with a reflux condenser, and Pv of 1.2 to It was found that there was no problem in granulation when it was within the range of 3.0, the quality was good, and the polymer did not adhere to the condenser. The value of Pv is 1.5-2.
More preferably, it is within the range of 5.

When Pv is less than 1.2, the particles become coarse and the bulk specific gravity decreases, and the plasticizer absorbability of the obtained polymer is poor and fish eyes increase. This is because the stirring strength is low, the frequency of dispersion and coalescence of monomer suspension oil droplets is low, the porosity of the generated polymer particles is small, and the monomer liquefied in the condenser is refluxed and polymerized. When absorbed by the polymer particles in the vessel, the gas generated from the monomer droplets is included in the polymerization suspension, which reduces the uniformity of stirring and tends to agglomerate into coarse particles. It is presumed that particles having a small porosity are partially generated because they are not uniformly dispersed in the particles, and the surface smoothness of the particles is impaired due to the polymerization of the non-uniformly adhered monomers, especially at the final stage of the polymerization. Also P
If v is less than 1.2, polymer deposition on the condenser occurs. It is considered that this is because the foaming phenomenon in which the polymer particles float as a cream layer above the polymerization suspension becomes more prominent particularly after the middle stage of the polymerization.

On the other hand, when Pv is larger than 3.0, not only the particles become coarse and fish eyes increase, but also the adhesion of the polymer to the condenser occurs. This is because the frequency of dispersion / coalescence of suspended oil droplets becomes too high, and the oil droplets and polymer particles tend to agglomerate due to collisions with each other, resulting in coarse particles, and the stirring strength is large, causing entrainment of bubbles. It is presumed that the foaming phenomenon in the polymerization vessel increases and the polymer adheres to the condenser. This Pv is 1.2-from start to end of reaction
It is necessary to control to 3.0, preferably 1.5 to 2.5.

In the polymerization of vinyl chloride by using a reflux condenser, it is known that the load factor (the ratio of heat removal in the condenser to the total amount of heat generated by the polymerization) has a great influence on the quality and stable operation. There is. That is, when the load factor is increased, the amount of heat removed is improved and polymerization in a shorter time is possible, but coarsening of the polymer particles, increase of fish eyes, reduction of the bulk specific gravity, and adhesion of the polymer to the condenser Increase. However, according to the present invention, the above problems can be solved even with a relatively large load factor.

As a method for adjusting the stirring power of the polymerization vessel, for example, "Chemical Engineering Association, edited by Chemical Engineering Handbook, 3rd edition,"
As described in detail in "Maruzen Co., Ltd., 1968", use an empirical formula or a diagram showing the relationship between the Reynolds number Re and the power number Np of the stirring system for the stirring devices of various shapes, or By measuring the power, Np can be obtained and the stirring power can be adjusted. That is, the density of the contents of the polymerization vessel is ρ (kg / m ³ ), the viscosity coefficient is μ (kg / msec), the rotation speed of the stirring blade is n (1 / sec), the blade length d (m), and the gravity. If the conversion coefficient is g _C (kg · m / Kg · sec ² ), and the net agitation power that does not include loss in the speed reduction mechanism or shaft seal is P (Kg · m / sec), then Re and Np are Each is defined by Re = ρnd ² / μ Np = P · g _C / ρn ³ d ⁵ , and Np can be easily obtained by known literature or experiments.

The Np of the agitator of a large-scale polymerization vessel which is generally employed in the suspension polymerization of vinyl chloride type monomers is in the range of about 0.3 to 1.5. Once Np is obtained, the net stirring power Pv per unit volume of the polymerization vessel can be calculated from the following equation. ^{Pv = Np · ρn 3 d 5} /102 · V · g C where V is the liquid volume in the polymerization vessel (m ^3). When the power is adjusted using a specific stirring device, the power is proportional to the cube of the number of revolutions, and therefore the stirring power can be arbitrarily adjusted by changing the number of revolutions. Usually, at a constant stirring rotation speed, Pv increases with the increase in the viscosity of the system after the initiation of polymerization, and then becomes constant, but the increase is slight. The stirring speed may be constant during the reaction period or may be changed during the reaction, but the Pv (kW / m ³ ) is 1.2 to 3.0, preferably 1.5 to Must be in the range of 2.5.

In the present invention, water, vinyl chloride type monomer,
As a method for charging the suspending agent, the initiator, and other auxiliary agents, any method used in ordinary suspension polymerization can be adopted. For example, a method of sequentially adding water, a suspending agent, an initiator, and a vinyl chloride-based monomer to a polymerization vessel, or a method of continuously charging these at the same time, a vinyl chloride-based single solution in which an aqueous suspension agent and an initiator are dissolved. Any method such as a method of charging the monomers sequentially or simultaneously is possible.

The weight ratio of water to vinyl chloride monomer is generally about 1: 1 to 2: 1. Polymerization is usually 3
It is performed at a temperature of 0 to 80 ° C.

[0028]

As described above, according to the present invention, a large-sized polymerizer having an inner jacket with a reflux condenser attached to the outside and an internal volume of 40 m ³ or more is used to coarsen polymer particles and increase fisheyes. Since the polymerization can be completed in a short time of 6 hours or less without lowering the bulk specific gravity,
The operating rate of the polymerization vessel is greatly improved, which is extremely useful industrially.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples, comparative examples and reference examples, but the present invention is not limited to these examples. In the Examples, Comparative Examples and Reference Examples,% and parts are based on weight unless otherwise specified. The physical properties of the vinyl chloride-based polymers shown in each of the examples, comparative examples and reference examples were measured by the following methods.

(1) Coarse Grain Content The ratio of residual coarse particles in a 60-mesh wire mesh was shown by a sieve analysis using a JIS-standard wire mesh. (2) Average particle size (Dp50) The particle size was determined to be 50% by sieve analysis using a JIS standard wire mesh. (3) Bulk specific gravity It was measured according to the method specified in JIS K6721-1977. (4) Fish eye vinyl chloride polymer 100 g, lead stearate 1.0
g, barium stearate 1.0 g, dibasic lead stearate 0.5 g, polyester plasticizer (manufactured by Mitsubishi Kasei Vinyl, D-409) 50 g, and carbon black 0.8.
g and kneading on a roll at 150 ° C. for 7.5 minutes, and then pulling out a sheet of about 0.6 mm. 1 from that sheet
Two test pieces of 5 cm × 30 cm are cut out, placed on the same roll, preheated for 30 seconds, and then kneaded for 20 seconds to form a sheet having a thickness of 0.6 mm. The number of fish eyes observed at 5 points on a 5 cm square was divided by 5 by shining light from the back surface of the sheet.

Example 1 A shell-and-tube reflux condenser having a heat transfer area of 100 m ² and a blade length of 1.7
m Faudler type 4 retreating blades and 4 pipe baffles with an outer diameter of 0.22 m, diameter 3.2 m, internal volume 4
After degassing a 5 m ³ inner jacketed stainless steel polymerization vessel, vinyl chloride monomer 100 parts (16.5 tons), water 130 parts, saponification degree 80 mol% and average degree of polymerization 2500.
Partially saponified polyvinyl acetate 0.055 parts, saponification degree 33
0.03 part of partially saponified polyvinyl acetate having an average degree of polymerization of 300 in mol%, 0.015 part of di- (2-ethoxyethyl) peroxydicarbonate (EEP), 2,4,4-trimethylpentyl-2 -0.050 parts of peroxyneodecanoate (TMPND) were charged.

After the temperature was raised, stirring was carried out at a rotation speed of 112 rpm so that the net stirring power Pv at the start of polymerization was 1.5 kW / m ^3, and then the internal temperature was raised to 57 ° C. to start the polymerization and the reflux condenser. To the total heat value of 40
The polymerization was promoted by adjusting the loading rate so that it became%. When the internal pressure dropped by 2.0 kg / cm ² , unreacted monomer was recovered and the content was dehydrated and dried. Pv gradually increased with the lapse of time after the temperature was raised, and was 1.9 kW / m ³ at the end of the polymerization. The polymerization reaction time was 3.1 hours. After the polymerization was completed, adhesion of the polymer to the reflux condenser and the conduit was not seen.

Example 2 Polymerization was carried out under the same conditions as in Example 1 except that 0.055 parts of 2-ethylhexyl peroxydicarbonate (OPD) was used as the polymerization initiator and the load factor of the reflux condenser was 30%. did. Net stirring power Pv is 1.5kW / m at the start of polymerization
^3, was polymerized at the end of 1.9kW / m ^3. The reaction time was 3.9 hours. After the polymerization was completed, adhesion of the polymer to the reflux condenser and the conduit was not seen.

Example 3 Polymerization was carried out under the same conditions as in Example 2, except that the polymerization initiator OPD was 0.042 part and the load factor of the reflux condenser was 20%. Net stirring power Pv is 1.5kW / m at the start of polymerization
^3, was polymerized at the end of 1.9kW / m ^3. The reaction time was 5.2 hours. After the polymerization was completed, adhesion of the polymer to the reflux condenser and the conduit was not seen.

Example 4 Polymerization was carried out under the same conditions as in Example 2 except that the stirring rotation speed was 120 rpm and the net stirring power Pv at the start of polymerization was 1.8 kW / m ³ . Pv at the end of polymerization is 2.3 kW /
m ³ , reaction time was 4.0 hours. After the polymerization was completed, neither adhesion to the reflux condenser nor conduit was observed.

Example 5 Polymerization was carried out under the same conditions as in Example 2, except that the stirring speed was 125 rpm and the net stirring power Pv at the start of polymerization was 2.1 kW / m ³ . Pv at the end of polymerization is 2.6 kW /
m ³ , and reaction time was 4.1 hours. After the polymerization was completed, adhesion of the polymer to the reflux condenser and the conduit was not seen.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 2 except that the stirring speed was 91 rpm and the net stirring power Pv at the start of polymerization was 0.8 kW / m ³ . Pv at the end of polymerization is 1.1 kW / m ³ ,
The reaction time was 4.0 hours. After the polymerization was completed, many polymer deposits due to foaming were observed in the reflux condenser and the conduit.

Comparative Example 2 Polymerization was carried out under the same conditions as in Example 2 except that the stirring rotation speed was 145 rpm and the net stirring power Pv at the start of polymerization was 3.3 kW / m ³ . Pv at the end of polymerization is 4.0 kW /
m ³ , reaction time was 4.0 hours. After the polymerization was completed, many polymer deposits due to foaming were observed in the reflux condenser and the conduit.

Reference Example The stirring speed was 91 rpm, the net stirring power Pv at the start of polymerization was 0.8 kW / m ^3, and the initiator was di- (2-ethoxyethyl) peroxydicarbonate (EEP).
Polymerization was carried out under the same conditions as in Example 1 except that the content was 0.022 part and water was not passed through the reflux condenser. At the end of the polymerization, Pv was 1.1 kW / m ³ , and reaction time was 9.0 hours.

Table 1 shows a summary of the polymerization conditions of Examples 1 to 5, Comparative Examples 1 and 2 and Reference Example, the properties of the obtained polymer, and the adhesion of the polymer to the reflux condenser. The vinyl chloride-based polymer according to the present invention has an appropriately small particle size as compared with the comparative example, has no coarse particles, has less fish eyes, and has no reduction in bulk specific gravity. In addition, compared to the vinyl chloride-based polymer by the long-term polymerization of Reference Example, a polymer of comparable quality can be obtained in a short time of polymerization, and further, the adhesion of the polymer to the reflux condenser was not observed, and stable operation was achieved. It was possible.

[0041]

[Table 1]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideki Wakamori             16 Ochiai, Nishiki-cho, Iwaki-shi, Fukushima Prefecture Kureha Chemical Industry             Within the corporation (72) Inventor Isao Ouchi             16 Ochiai, Nishiki-cho, Iwaki-shi, Fukushima Prefecture Kureha Chemical Industry             Within the corporation (72) Inventor Yamato Tamio             No. 1-2 Harumi-cho, Tokuyama City, Yamaguchi Prefecture             -Chemical Co., Ltd. (72) Inventor Yasumichi Ishii             2767 Shiohama, Niihama, Kojima, Kurashiki, Okayama Prefecture             Inside Zeon Corporation (72) Inventor Masahisa Okawa             Sumitomo Chemical 5-1, Soukai-cho, Niihama-shi, Ehime             Industry Co., Ltd.

Claims (2)

[Claims] 1. A mixture of a monomer copolymerizable with vinyl chloride and a vinyl chloride monomer or a vinyl chloride monomer is polymerized in an aqueous medium in the presence of an oil-soluble initiator within 6 hours. When completing the polymerization, a large-scale polymerization vessel having an internal volume of 40 m ³ or more, which has a reflux condenser on the outside, a stirrer on the inside, and an internal jacket for heating and cooling, which is encapsulated inside the polymerization vessel, is used. A suspension polymerization method of a vinyl chloride-based monomer, characterized in that the net stirring power Pv (kW / m ³ ) per 1 m ³ of the content liquid in the vessel is controlled in the range of 1.2 to 3.0. 2. A stirrer mounted on the polymerizer is a Faudler type retreating blade, and the baffle is a pipe baffle, E
The method for suspension polymerization of a vinyl chloride-based monomer according to claim 1, wherein the method is a type baffle or a D type baffle.