JPH07233201A - Polymerizer effective for preventing polymer scale deposition and preparation of polymer by using the same - Google Patents

Abstract

PURPOSE:To obtain a polymer of a high quality in high productivity through prevention of the deposition/growth of polymer scale by locating the tip of a pipe for returning a condensate into a polymerizer to project into the vapor phase from the inner wall surface of the polymerizer. CONSTITUTION:In a polymerizer 1 equipped with a reflux condenser for heat removal and having a pipe 2 which is for returning a condensate formed in the condenser into the polymerizer 1, and is piped to a vapor phase section 5 in the polymerizer from the outside thereof, the tip 2a of the pipe 2 opening in the polymerizer 1 is located to project into the vapor phase section 5 from the inner wall surface 1a of the polymerizer. By using this equipment, the condensate flowing down from the reflux condenser does not come in direct contact with the inner wall of the polymerizer but falls down from the opening at the tip 2a as shown by an arrow 6, getting to the liquid surface 4a of the reaction mixture. Therefore, no polymer scale deposits and grows on the inner wall 1a, and then a polymer of a high quality with little fisheye can be produced with high productivity even in a long-term operation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymerization vessel useful for polymerization of a monomer having an ethylenically unsaturated double bond and a method for producing a polymer using the polymerization vessel.

[0002]

BACKGROUND ART Suspension polymerization of a monomer having an ethylenically unsaturated double bond such as vinyl chloride in an aqueous medium is usually carried out by introducing water and a monomer from a charging pipe provided in a polymerization vessel. , A polymerization initiator, a dispersant, and other various additives added as necessary, and then the polymerization reaction is started. During the polymerization reaction, in order to keep the reaction system at a predetermined temperature, cooling heat is removed by passing cooling water through a jacket, and optionally a reflux condenser, a baffle and a coil.

By the way, in the polymerization of vinyl chloride or the like, there is a problem that the polymer scale is apt to adhere to the inside of the polymerization vessel.
Conventionally, as a method of preventing the adhesion of polymer scale, dye, pigment, water-soluble polymer, nitrite, nitrogen-containing aromatic compound, hetero compound, iodine, in the portion where the inner wall of the polymerization vessel and other monomers come into contact. There is known a method of forming a coating film composed of a chemical compound, a pyrogallol derivative, a phenolic compound, an aromatic amine compound or the like, which has an agent having an action of preventing adhesion of polymer scale. Such agents are known from the publications mentioned below.

In recent years, from the viewpoint of occupational health and environmental measures, efforts have been made to open the polymerization vessel and reduce the frequency of inspecting and cleaning the inside of the polymerization vessel. Therefore, there is a demand for an effective method for preventing polymer scale from adhering and growing in the polymerization vessel even if the polymerization is repeated for 100 batches or more, or even after long-term operation. However, with only a coating film consisting of the polymer scale anti-adhesion agent, when the long-term operation as described above is carried out, the polymer scale grows on the inner wall of the polymerization vessel or the like, and peels off from the inner wall. However, there is a problem in that the fish eye of the resulting product polymer increases and the quality of the product polymer tends to deteriorate.

Further, in recent years, the size of the polymerization vessel has been increased in order to improve the productivity, the heat removal capacity by the jacket is relatively decreased, and the heat removal rate by the reflux condenser is increasing more and more. Therefore, heat removal by a reflux condenser is essential for a polymerization vessel having an internal volume of 40 m ³ or more, particularly 80 m ³ or more. The reflux condenser is provided outside the polymerization vessel, and the monomer condensed in the condenser is returned to the inside of the polymerization vessel through a liquid return pipe connected to a gas phase portion inside the polymerization vessel.
The tip of this liquid return pipe, which is open in the polymerization vessel, is processed to form a surface that is substantially flush with the inner wall of the polymerization vessel. When it comes out of the opening, it usually flows down the inner wall surface and flows into the reaction mixture. In a polymerization vessel having an internal volume of 40 m ² or more, the amount of the monomer condensed in the reflux condenser also returns to the polymerization vessel as the amount of heat removed by the reflux condenser increases. Under these circumstances, even if the polymer scale adhesion inhibitor is applied to the inner wall surface of the polymerization vessel,
It is difficult to prevent the adhesion of the polymer scale, and the liquid is likely to adhere to the inner wall surface, and the adhesion of the scale is likely to occur remarkably in the portion located below the opening of the pipe. Once the scale adheres to the coating of the polymer scale anti-adhesion agent, its scale preventing effect is impaired.

In addition, in addition to the liquid return pipe from the reflux condenser, various pipes such as raw material preparation pipes and exhaust gas pipes are usually connected to the gas phase portion inside the polymerization reactor from outside the polymerization reactor. There is. The monomer gas also enters these pipes during the polymerization and is condensed on the inner wall of the pipes to become a liquid.
The monomer condensed in this way also returns to the inside of the polymerization vessel after exiting from the inside of the polymerization vessel of these pipes, but since the opening at the tip of the pipe has the same structure as that of the above-mentioned liquid return pipe, that opening also Scale is likely to adhere to the lower side of the.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a polymerizer equipped with a reflux condenser, and a liquid return pipe from the reflux condenser even when a long-term operation in which the polymerization is repeated for about 100 batches or more is repeated. It is an object of the present invention to provide a polymerization vessel in which adhesion of polymer scale is less likely to occur in the lower part of an opening, and a method for producing a polymer using the polymerization vessel to obtain a high-quality polymer.

[0008]

As a means for solving this problem, the present invention comprises a reflux condenser for heat removal, and a pipe for returning the condensate produced by the condenser to the inside of the polymerization vessel is external to the polymerization vessel. From the polymerization vessel connected to the gas phase section inside the polymerization vessel, the polymerization vessel characterized in that the tip opening into the polymerization vessel of the pipe projects from the inner wall surface of the polymerization vessel to the gas phase section. To provide.

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic vertical cross-sectional view showing the structure of a polymerization vessel 1 of the present invention. In FIG. 1, the tip 2a of a liquid return pipe 2 from a reflux condenser (not shown) is an inner wall surface of the polymerization vessel 1. It projects from the gas phase portion 5 in the polymerization vessel from 1a.
Therefore, the condensate flowing down from the reflux condenser does not come into direct contact with the inner wall 1a of the polymerization vessel, but drops from the opening at the tip 2a as shown by the arrow 6, and reaches the liquid surface 4a of the reaction mixture. Therefore, the polymer scale does not adhere and grow on the inner wall 1a. Wall surface 1a of the polymerization vessel
When a coating film composed of a polymer scale anti-adhesive is formed on the surface of the polymer scale, the effect of the coating film is not impaired even after long-term operation by repeating the polymerization, so that the adhesion and growth of the polymer scale is prevented. Can be prevented.

In a preferred embodiment of the present invention, the polymerization vessel has at least one other pipe connected to the gas phase portion inside the polymerization vessel from outside the polymerization vessel, other than the liquid return piping from the reflux condenser, The tip of the pipe that opens into the polymerization vessel also projects from the inner wall surface of the polymerization vessel into the gas phase portion, similarly to the liquid return piping described above. Most preferably, all such pipes project from the inner wall surface of the polymerization vessel to the gas phase portion. As such other piping, piping for charging various raw materials, piping for exhaust gas collection, piping for water washing device in polymerization vessel, scale application agent coating device pipe, safety valve pipe, emergency stop polymerization inhibitor pipe Etc.

In the polymerization vessel of the present invention, the pipe leading to the gas phase portion in the polymerization vessel may be projected to such an extent that the condensate does not reach the inner wall of the polymerization vessel.
It may be 1 cm or more, preferably 1 to 10 cm.
The shape of the protruding tip of the pipe is not particularly limited, and for example, the tip may be cut obliquely to improve drainage.

The pipe may be inserted into the gas phase portion in the polymerization vessel by penetrating the wall of the polymerization vessel, or the conventional polymerization vessel may be used so that the conventional polymerization vessel can be used. A short tubular lip may be attached to the tip of the tubing provided in the vessel. FIG. 2 shows a pipe 2 leading to the gas phase section 5.
It is the figure which showed the outline around the tubular lip of the superposition | polymerization machine which attached the tubular lip 7 to the front-end | tip of FIG. The tip of the pipe member 2 is formed so as to be flush with the inner wall surface 1a, to which the tubular lip 7 is joined. In order to improve drainage, the tip of the tubular lip 7 shown in FIG. 2 is cut obliquely to form an acute angle. As the material of the tubular lip attached to the tip, from the viewpoint of corrosion resistance, 18-8 austenite type, 13 chromium ferrite type, martensite type, 18 chromium ferrite type, high chromium ferrite type, which is usually used for the inner surface of the polymerization vessel, Duplex austenitic / ferritic stainless steel is preferable.

The polymerization vessel of the present invention may be of a known type, and in addition to the above-mentioned charging pipe, exhaust gas recovery pipe and reflux condenser, for example, a stirrer,
It is equipped with baffles, jackets and coils. As the stirrer, for example, there is a stirrer having a stirrer of a type such as a paddle, a Fowler, a bull margin, a propeller, and a turbine, and it is used in combination with a baffle such as a flat plate, a cylinder, a hairpin coil, etc., if necessary.

There are no particular restrictions on the type of the reflux condenser, and a normal shell-and-tube type may be used. For a polymerization vessel having an internal volume of 40 m ³ or more, particularly 80 m ³ or more, a heat transfer area of 60 m ² or more is required. Those are preferable. As shown in Fig. 4, there are two types of installation to the polymerization reactor, one is directly connected with a pipe and the other is a gas-liquid separation type with two connected pipes. Is preferred. In the direct connection type reflux condenser, the gaseous monomer moving from the inside of the polymerization vessel to the inside of the condenser and the liquid monomer condensed and returning to the inside of the polymerization vessel pass through the same pipe. In the gas-liquid separation type reflux condenser, the passage pipe for the gaseous monomer moving into the condenser and the liquid return pipe for returning the liquefied monomer to the inside of the polymerization vessel are separate.

Further, in the case of polymerizing a monomer having an ethylenically unsaturated double bond using the polymerization vessel of the present invention, various known polymer scale adhesion preventing techniques can be used in combination. However, preferably, a conventionally known polymer scale adhesion preventive agent is applied in advance to form a coating film. Adhesion of the polymer scale can be prevented by forming a coating film of the polymer scale anti-adhesive agent on the inner wall surface of the polymerization vessel, and in some cases, at other places where the monomer contacts during the polymerization.

Examples of the polymer scale adhesion preventive agents include dyes, pigments, water-soluble polymers, nitrites, nitrogen-containing aromatic compounds, heterocyclic compounds, iodo compounds, pyrogallol derivatives, phenolic compounds, aromatic amines. Compounds and the like, specifically, JP-B-46-16084 and 45-303.
43, 46-4753, 45-37988, 46-20821,
45-30835, 48-29795, 51-21672, 51-37306
No. 51, No. 51-37308, No. 51-24953, No. 53-6023, No. 53
-6024, 53-6025, 53-6026, 53-21908
No. 53, No. 53-28347, No. 53-28348, No. 53-46235, No. 59
-1413, 58-13564, 56-5442, 56-5443
No. 56, No. 56-5444, No. 59-34721, No. 58-11884, No. 60
-6361, 59-31522, 60-48522, 60-48523
No. 51-1471, No. 51-1472, No. 57-59243, No. 55-
5523, 56-22445, 56-22447, 57-31730
No. 57, No. 57-47922, No. 60-59246, No. 61-25730, No. 52
-24070, 55-4327, 58-12893, 58-14444
No. 58, No. 58-14445, No. 58-14446, No. 58-14447, No. 60
-42245, 61-21247, 61-842, 61-843,
49-2992, 53-36509, 57-34286, 60-40444
No. 60-59247; JP-A Nos. 57-195702 and 57-198710.
No. 58, No. 58-11504, No. 58-180509, No. 58-180510,
59-78210, 60-20909, 54-50089, 54-101
889, 55-21436, 55-73709, 55-98207,
55-112209, 58-8709, 58-61104, 58-1
68607, 58-180511, 58-204006, 60-716
No. 14, No. 55-54305, No. 55-54317, No. 57-192413,
57-192414, 59-129207, 61-7309, 53
-108187, 59-184202, 59-202201, 59-2
No. 10902, No. 60-47002, No. 60-71601, No. 60-72902
No. 60, No. 60-96603, No. 60-233103, No. 61-31406, No.
61-34006, 61-51001, 61-51002, 55-15500
No. 1, No. 55-155002, No. 56-112903, No. 58-69203
Issue 58-101103, Issue 58-103503, Issue 58-210902
No. 59-11303, No. 59-170102, and the like.

The present invention also provides a method for producing a high-quality polymer while effectively preventing the adhesion of polymer scale by using the above-mentioned polymerization vessel. That is, the present invention is
A method for producing a polymer, which comprises polymerizing a monomer having an ethylenically unsaturated double bond in an aqueous medium in the above-mentioned polymerization vessel, wherein the reflux condenser removes the polymerization after the initiation of the polymerization. Provided is a method for producing a polymer, characterized in that the reflux condenser removes 20% or more of the total heat of polymerization reaction generated during the entire polymerization process by increasing the amount of heat stepwise or continuously. . In the present specification, the average heat generation rate is the following formula: Average heat generation rate (kcal / hr) =
It is defined as the total heat of polymerization reaction (kcal) / polymerization time (hr).

In the above method, the amount of heat removed by the reflux condenser is preferably increased at an average of 30% or less of the average heat generation rate per unit time, more preferably at 10 to 25%. Further, it is preferable to continuously increase the amount of heat removed. When the amount of heat removed from the reflux condenser is rapidly increased from the beginning of the polymerization, bubbles of the suspension polymerization solution containing a large amount of polymerization initiator are generated by bumping and rise to the vapor phase part of the polymerization vessel, so scale adheres to the inner wall surface of the polymerization vessel. Is more likely to occur. In addition, for example, in the case of suspension polymerization of vinyl chloride, since the specific gravity of the monomer is smaller than that of water at the initial stage of polymerization, oil droplets of the monomer easily carry over, and a polymer having a large specific gravity as the polymerization proceeds. Carryover is relatively unlikely to occur because it is converted to. Therefore, the operation according to the method of the present invention is effective in preventing the adhesion of polymer scale, and the scale is more effectively prevented in combination with the above-mentioned structure of the polymerization vessel.

The method of the present invention is particularly effective in the case of a polymerization vessel having an internal volume of 80 m ³ or more, in which heat removal is highly dependent on the reflux condenser. In such a polymerization vessel, the amount of heat removed by the reflux condenser is 10% of the average heat generation rate when the polymerization conversion rate is less than 5%.
The following is more preferable: 0%, a polymerization conversion rate of 5% or more and less than 30% is controlled to less than 28% of the average heat generation rate, and a polymerization conversion rate of 30% or more is controlled to 28% to 80% of the average heat generation rate. A method of increasing the amount of heat continuously or stepwise is preferable. The amount of heat removed by the reflux condenser is 20% or more, preferably 20% or more of the total heat of polymerization reaction throughout the whole process of the polymer.
Controlled to ~ 50%.

Examples of the monomer having an ethylenically unsaturated double bond which is polymerized by using the polymerization vessel of the present invention include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate. Acrylic acid, methacrylic acid, and their esters or salts; maleic acid, fumaric acid, and their esters or anhydrides; diene-based monomers such as butadiene, chloroprene, isoprene; styrene, acrylonitrile, vinylidene halide, vinyl ether Etc. These are used alone or in combination of two or more.

When a monomer having an ethylenically unsaturated double bond is polymerized using the polymerization vessel of the present invention, vinyl chloride alone is used among the monomers having an ethylenically unsaturated double bond exemplified above. Besides, it is particularly effective to polymerize a monomer mixture containing vinyl chloride as a main component and a comonomer which can be copolymerized with this (usually 50% by weight or more of vinyl chloride).
The comonomers copolymerized with vinyl chloride include vinyl acetate, vinyl propionate and other vinyl esters; methyl acrylate, ethyl acrylate and other acrylate or methacrylic acid esters; ethylene, propylene and other olefins, maleic anhydride, Acrylonitrile,
Examples are styrene and vinylidene chloride.

When a vinyl chloride polymer is produced using the polymerization vessel of the present invention, a method for charging an aqueous medium, a monomer such as vinyl chloride, a polymerization initiator and a dispersant into the polymerization vessel,
The charging ratio, other polymerization reaction conditions and the like may be the same as those in the conventionally known method. Also, in the polymerization,
If necessary, a polymerization regulator, a chain transfer agent, a pH regulator, a gelation improver, an antistatic agent, a cross-linking agent, a stabilizer, a filler, an antioxidant, which is appropriately used in the production of a vinyl chloride polymer. It is also optional to add a buffer or the like.

[0023]

【Example】

Example 1 A stainless steel jacket having an internal volume of 80 m ³ , a reflux condenser, a charging pipe, an exhaust gas recovery pipe, a stirrer, and a baffle-equipped polymerization vessel were used. Various pipes for charging etc. provided in the polymerization vessel are processed so that the end surface of the tip end thereof is substantially flush with the inner wall surface of the polymerization vessel,
It was a conventional type. At the tip of the reflux condenser, the charging pipe and the exhaust gas recovery pipe of the polymerization vessel, FIG.
Attached the tubular lip shown in. 10 g of CI Direct Blue 1 and 2 g of C as a polymer scale adhesion preventive agent.
I. Basic Blue 12 was dissolved in 10 liters of deionized water, and an aqueous solution containing 17 g of phytic acid was applied to the entire inner wall of the polymerization vessel, stirring blades, baffles, and pipes, and at 50 ° C.
After drying for 10 minutes, it was washed with water.

Thereafter, 37,000 deionized water was added to the polymerization vessel.
An aqueous solution of 9200 g of partially saponified polyvinyl alcohol and 3900 g of cellulose ether was added as an aqueous solution. 50 inside
After exhausting to mmHg, vinyl chloride monomer 29000kg
Was charged, and 17400 g of di-2-ethylhelyl peroxydicarbonate was further press-fitted with a pump while stirring. Hot water was passed through the jacket of the polymerization vessel to raise the temperature to 57 ° C. After the reaction was started, cooling water was passed through the jacket and cooling water was passed through the condenser to continue the polymerization while removing heat. The reflux condenser was operated under the conditions shown in Table 1. The internal pressure of the polymerization vessel
It was judged that the polymerization was completed when it fell to 6.5 kg / cm ² G.
At this point, the polymerization conversion rate was 85% and the polymerization time was 5 hours. After the completion of the polymerization, unreacted monomers were recovered, the polymer was taken out of the reactor in a slurry form, and the inside of the polymerization reactor was washed with water.
The operation from application of the polymer scale anti-adhesion agent to polymerization and washing with water in the polymerization vessel was repeated 100 batches continuously, and then the state of adhesion or growth of the polymer scale in the polymerization vessel was examined. . The results are shown in Table 1.

The average heat generation rate in this polymerization is [vinyl chloride monomer total loading amount] × [vinyl chloride monomer 1 kg
Heat of polymerization reaction per unit] x [polymerization conversion rate] / [polymerization time] = 2
It was calculated as 1.81 × 10 ⁶ kcal / hr by the calculation of 9,000 kg × 368 kcal / kg × 0.85 ÷ 5 hr.

The bulk specific gravity, particle size distribution and fish eye of the polymer obtained after 100 batches were measured by the following methods. The results are shown in Table 1. (1) Bulk Specific Gravity: Measured according to JIS K 6721. (2) Particle size distribution: # 48, # 60, # 80 according to JIS Z 8801,
Each of the sieves # 100, # 150, and # 200 was used for sieving, and the passing amount (% by weight) was measured. (3) Fish eye: 100% of the obtained vinyl chloride polymer
Parts by weight, 1 part by weight of tribasic lead sulfate, lead stearate
1.5 parts by weight, titanium oxide 0.2 parts by weight, carbon black 0.1 part by weight, and dioctyl phthalate were mixed at a ratio of 50 parts by weight. The resulting mixture is rolled 145
After kneading at ℃ for 5 minutes, form a sheet with a thickness of 0.2 mm,
The number of fish eyes contained in 100 cm ^{2 of the} sheet was counted.

Comparative Example 1 In Comparative Example 1, a polymer was prepared in the same manner as in Example 1 except that a polymerization vessel was used without a tubular lip attached to the tips of the charging pipe, the reflux condenser and the exhaust gas collecting pipe. Was produced, and the scale adhesion state in the polymerization vessel and the bulk specific gravity, particle size distribution and fish eye of the obtained polymer were examined in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 In Comparative Example 2, the operating conditions of the reflux condenser are shown in Table 1.
A polymer was produced in the same manner as in Example 1 except that the changes were made as shown in Example 1, and in the same manner as in Example 1, the scale adhesion state in the polymerization vessel and the bulk specific gravity, particle size distribution and fish eye of the obtained polymer were obtained. I checked. The results are shown in Table 1.

[0030]

[Table 1] Note) The ratio of the heat removal amount of the condenser to the average heat generation rate in Table 1 is as follows. 0.5 × 10 ⁶ kcal / H ── 28% 1.0 × 10 ⁶ kcal / H ── 55% 1.25 × 10 ⁶ kcal / H ── 69%

[0031]

[Effect of the Invention] When a monomer having an ethylenic double bond is polymerized by using the polymerization vessel of the present invention, the adhesion of polymer scale in the polymerization vessel is observed even after a long-term operation of about 100 batches or more. / Growth can be effectively prevented. Therefore,
A high quality polymer with less fish eyes can be produced with high productivity.

In the polymerization vessel equipped with the reflux condenser of the present invention, even if the polymerization is repeated for 100 batches or more, and the liquid is returned from the reflux condenser, the adhesion of the polymer scale is effective at the lower side of the pipe opening. Be prevented. Further, according to the method for producing a polymer of the present invention, polymer scale is effectively prevented, so that a high quality polymer can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a polymerization reactor, which is a simplified illustration of the polymerization reactor of the present invention.

FIG. 2 is a cut end view showing a state in which a tubular lip is attached to the tip of a pipe communicating with a gas phase portion of a conventional polymerization vessel.

[Explanation of symbols]

 1a Inner wall of polymerization vessel 2 Piping leading to gas phase section in polymerization vessel 2a Tip of piping leading to gas phase section in polymerization vessel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toshiaki Maruyama, Toshiaki Maruyama, Iwaki, Kashima-gun, Kamisu-cho, Higashiwada, No. 1 Kashin Plant, Shin-Etsu Chemical Co., Ltd. No. 1 Shin-Etsu Chemical Co., Ltd.

Claims (5)

[Claims] 1. A polymerization vessel comprising a reflux condenser for removing heat, and a pipe for returning the condensate produced by the condenser to the inside of the polymerization vessel is connected from the outside of the polymerization vessel to the gas phase part inside the polymerization vessel. The polymerizer, wherein the end of the pipe opening in the polymerizer projects from the inner wall surface of the polymerizer to the gas phase portion. 2. The polymerization vessel according to claim 1, further comprising at least one other pipe connected from the outside of the polymerization vessel to a gas phase portion inside the polymerization vessel, and the inside of the polymerization vessel of the piping. A polymerization vessel in which a tip opening to the inside projects from the inner wall surface of the polymerization vessel to the gas phase portion. 3. The polymerizer according to claim 1, wherein the inner wall has a coating film of a polymer scale anti-adhesive agent. 4. The polymerizer according to claim 1, 2 or 3, which has an inner volume of 40 m ³ or more. 5. A method for producing a polymer, which comprises polymerizing a monomer having an ethylenically unsaturated double bond in an aqueous medium in the polymerization vessel according to claim 1, 2, 3 or 4. By increasing the amount of heat removed by the reflux condenser stepwise or continuously after the start of polymerization, the total heat of polymerization reaction generated during the whole process of polymerization is increased.
A method for producing a polymer, wherein 20% or more of the heat is removed by the reflux condenser.