JPH10330405A - Continuous polymerization method for styrenic polymer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When producing a styrene-based polymer by a continuous bulk polymerization reaction, the heat generated in the tank in the initial and middle polymerization steps is efficiently removed, and the high viscosity in the late polymerization step is reduced. To provide a method that solves the difficulties of the agitation work and meets the requirements of mass productivity, high conversion, high molecular weight, narrow molecular weight distribution, and the like. SOLUTION: At the time of production through a continuous bulk polymerization step consisting of each step of initial polymerization, middle-stage polymerization and late-stage polymerization, at least one complete mixing tank-type latent heat latent polymerization tank is used in the initial and middle-stage polymerization steps. The late polymerization step is a continuous polymerization method of a styrene-based polymer using at least one tubular reactor under the condition that the final conversion is maintained at 80% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a styrenic polymer by a continuous bulk polymerization reaction. More specifically, the present invention relates to a method for producing a high molecular weight styrene-based polymer having a narrow molecular weight distribution width by a continuous bulk polymerization reaction.

[0002]

2. Description of the Related Art Conventionally, in the case of producing a styrene-based polymer by a continuous bulk polymerization reaction consisting of initial polymerization, middle-stage polymerization, and late-stage polymerization, a jacket heat removal method is employed for all heat removal. In addition, a complete mixing type polymerization tank has been used for the middle stage polymerization, and a mechanical stirring type tower type polymerization tank has been used for the latter stage polymerization. However, in response to the demand for increased production, simply increasing the size of a conventional complete-mixing polymerization tank using a jacket heat removal system results in a small heat transfer area per unit volume, which makes it difficult to sufficiently remove heat. Do you get it.

[0003] On the other hand, in a mechanically stirred tower polymerization tank used in the latter stage polymerization, in addition to demands for mass production, high conversion, high molecular weight, and a demand for narrowing the molecular weight distribution, the viscosity of the system is increased. Can not respond. To solve this problem, Japanese Patent Application Laid-Open No. Sho 64-70507 has already proposed a tubular reactor having a circulation line in which at least one tubular reactor having a structure for static mixing is incorporated. However, there are disadvantages that the equipment cost is high and the production efficiency is low because the equipment is special.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for producing a styrenic polymer by a continuous bulk polymerization reaction, which efficiently removes heat generated in a polymerization tank in an initial polymerization process and a middle-stage polymerization process. To provide a method for producing a styrene-based polymer which solves the difficulty of stirring work due to the increase in viscosity in the polymerization step, and satisfies requirements such as mass productivity, high conversion, high molecular weight, and narrow molecular weight distribution. The purpose is to:

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve this problem, and as a result, at least the complete polymerization tank type evaporative latent heat type polymerization tank is used for the initial polymerization step, and the latter is used for the latter polymerization step. Obtained the knowledge that can be solved by using a tubular reactor while maintaining the final conversion of the styrene raw material at a predetermined value, and completed the present invention. The gist of the present invention is as follows.

(1) In a method for producing a styrenic polymer through a continuous bulk polymerization reaction process comprising an initial polymerization, a middle polymerization and a late polymerization, at least one of the steps comprising the initial polymerization and the middle polymerization is required. A styrene-based system using at least one tubular reactor under the condition that the final conversion of the styrene raw material is maintained at 80% or more in the latter polymerization step using a complete mixing tank type evaporative latent heat polymerization tank. A method for continuous polymerization of a polymer. (2) In a method for producing a styrenic polymer through a continuous bulk polymerization reaction process comprising initial polymerization, middle polymerization and late polymerization processes, each of the initial polymerization and the middle polymerization has one complete group. A mixed tank type evaporative latent heat type polymerization tank was used, and the final conversion of the styrene raw material was 8
A method for continuously polymerizing a styrenic polymer using at least one tubular reactor under the condition of maintaining 0% or more. (3) The continuous polymerization method for a styrene-based polymer according to the above (1) or (2), wherein the ratio L / D of the length L and the diameter D of the complete mixing tank type evaporation latent heat polymerization tank is 1.5 or more. (4) The continuous polymerization method for a styrene-based polymer according to the above (1) or (2), wherein the gas phase portion in the complete mixing tank type evaporative latent heat type polymerization tank is reacted while cooling with air or water. (5) The continuous polymerization method for a styrene-based polymer according to the above (1) or (2), wherein a vertically circulating flow generating type stirring blade is used as a stirring blade of the complete mixing tank type evaporation latent heat polymerization tank. (6) The method for continuous polymerization of a styrene-based polymer according to the above (5), wherein the up-and-down circulation flow generating type stirring blade is a helical ribbon blade or an inclined paddle blade. (7) The method for continuous polymerization of a styrene-based polymer according to the above (1) or (2), wherein the tubular reactor has at least one static mixing structural section comprising a large number of mixing elements therein. (Eighth) The method for continuous polymerization of a styrene-based polymer according to the seventh aspect, wherein the tubular reactor is provided with at least two structural parts for static mixing comprising at least four mixing elements. (Ninth) The viscosity of the system in the reaction process of continuous bulk polymerization is as follows:
The viscosity is 0.5 to 2,000 poise in the complete mixing tank type evaporative latent heat type polymerization tank, and the viscosity at the outlet of the tubular reactor is 2,000.
3. The continuous polymerization method for a styrene-based polymer according to the first or second aspect, wherein the styrene-based polymer exceeds poise.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the continuous bulk polymerization method according to the present invention, a polymerization tank used in the steps of initial polymerization and middle polymerization uses a latent heat of evaporation of a solvent for a styrene-based polymer such as styrene. This is an evaporation latent heat type complete mixing tank that controls the temperature by removing the heat of polymerization. In the evaporating latent heat type complete mixing tank, a large amount of gas is generated due to evaporation of styrene, a copolymerizing monomer or a solvent, and the liquid expands 1.2 to 1.4 times. ) Is preferably considerably large with respect to the diameter D. By keeping L / D at 1.5 or more, it becomes easy to prevent the polymerization product from adhering to the top of the tank, and it is also necessary to provide sufficient air in the tank. Liquid separation becomes possible, which is preferable.

The temperature control jacket of the polymerization tank used in the above-mentioned initial polymerization and middle-stage polymerization according to the present invention is attached so as to cover only the liquid phase in the tank, and the wall of the gas phase is cooled (air cooled). Or water-cooled) or uncontrolled temperature. By setting the temperature distribution of the entire tank in such a state, the wall can be used for condensation of the vaporized liquid and can be maintained in a wet wall state, and as a result, polymerization reaction of styrene or the like on the wall surface can be achieved. It is also possible to prevent this, or to wash away the attached matter on the wall surface, which is a preferable embodiment.

The stirring blade used in the above-mentioned polymerization tank according to the present invention has a high mixing function of well circulating and stirring the reaction solution in the vertical direction in order to promote the evaporation of the solvent for the styrene polymer such as styrene. A helical ribbon blade (FIG. 1), a (multistage) inclined paddle blade (FIG. 2) and the like are particularly preferably used. The Max Blend wing (Fig. 3),
Turbine blades (FIG. 4) and anchor blades (FIG. 5) are not preferred. When the reaction solution has a high viscosity, a helical ribbon blade with a draft tube is suitable.

Next, preferred polymerization conditions for achieving the intended purpose will be described. In the initial polymerization step, the viscosity in the polymerization tank is maintained at 0.5 to 100 poise, the liquid temperature is maintained at 100 to 150 ° C., and the gas linear velocity is maintained at 0.01 to 0.2 m / sec. 2,000 poise, liquid temperature 120-170
° C, the gas linear velocity is maintained at 0.01 to 0.2 m / sec, and in the latter stage polymerization step, the molecular weight distribution is narrowed in order to increase the molecular weight, and further, the final conversion rate is 80% or more. It is preferable to maintain the liquid temperature at 120 to 200 ° C. and the viscosity at 2,000 poise or more. In the latter polymerization step, it is necessary to maintain the condition that the final conversion is 80% or more and use at least one known tubular reactor incorporating one or more static mixing structures. Among them, a tubular reactor incorporating at least one static mixing structure composed of a large number of mixing elements is preferable. As the tubular reactor, a Sulzer type static mixer, a Kenix type static mixer, a Toray type static mixer is preferable. A mixer and a Noritake type static mixer can be exemplified, but those having four or more mixing elements are particularly preferable, and
Those having 20 are more preferred. The number of static mixers is preferably two or more, more preferably 3 to 1
Those having zero are used.

The main raw materials for polymerization used in the continuous bulk polymerization according to the present invention are usually (A) a styrene-based monomer and (B) a half-life having a half-life temperature of 75 to 130 ° C.
The organic peroxide is used for a time, and known additives such as a plasticizer, an antioxidant, and a chain transfer agent are appropriately added as needed. Here, when the above-mentioned specific organic peroxide is not used as (B), for example, it is difficult to control the molecular weight and molecular weight distribution of the polymer, and the amount of oligomer increases, and furthermore, the production decreases rapidly, which is not preferable. .

The usage ratio of the main raw materials (A) and (B) is such that the concentration of the main raw material (B) is 50 to 500 p.
pm, preferably 100
~ 300 ppm is preferred. The method of adding the other raw materials to the main raw material (A) is not particularly limited, and the main raw material (B) and the above additives may be added to the main raw material (A) at one time.
Moreover, you may add sequentially. However, 2,2 bis (4,4-
With respect to dibutylperoxycyclohexyl) propane, the formation of oligomers such as dimers and trimers can be remarkably suppressed by adding about 200 ppm in the initial polymerization step and about 100 ppm in the latter polymerization step. This is a preferred embodiment.

The (A) styrene monomer as the main raw material for polymerization used in the present invention includes styrene, α
In addition to -methylstyrene, styrene derivatives in which the hydrogen atom of these aromatic rings is substituted with a halogen atom or an alkyl group having 1 to 4 carbon atoms, and the like, may be mentioned. Are styrene, o-
Methyl styrene, p-methyl styrene, 2,4-dimethyl styrene, pt-butyl styrene and the like.

(B) as a main raw material for polymerization used in the present invention has a half-life of 75 to 130 at a half-life temperature.
Organic peroxides at 10 ° C. for 10 hours are preferred, such as benzoyl peroxide, t-butyl benzoate, diisopropyl peroxide, dicumyl peroxide, and t-butyl peroxide.
Butyl-peroxyisopropyl carbonate, 1,3-
Bis (t-butyl-peroxyisopropyl) benzene, 2,2-di-t-butylperoxybutane, 1,1-bis (t-butylperoxy) -3,3,5 trimethylcyclohexane, di-t- Butyl peroxyhexahydroterephthalate, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2,2-bis (4,4-di-t-butyl-peroxylcyclohexyl) propane, etc. Although these may be used alone,
Two or more kinds may be used in combination. The polymer exiting the polymerization vessel is pelletized after removing unreacted monomer and solvent.

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The units “parts”, “ppm” and “%” of the added amount are all based on weight. Example 1 As a polymerization apparatus, apparatuses arranged as shown in a flow sheet in FIG. 6 were used. Raw styrene is fed by a plunger pump arranged in a supply unit (1) (not shown), and organic peroxide is sent by a diaphragm type pump arranged in a supply unit (2) (not shown). . The polymerization tank is composed of a first polymerization tank for initial polymerization, a second polymerization tank for medium-term polymerization, and a third polymerization vessel for final polymerization, and is connected to a series. First polymerization tank: a complete mixing tank in which only the liquid portion in the tank is provided with a temperature control jacket A, and styrene vapor is guided from the top B to a condenser C outside the tank, condensed and returned into the tank. As the stirrer D, a double helical ribbon blade is used. 35-40% styrene polymerization conversion
It has become. The polymerization liquid is sent to the second polymerization tank by the gear pump E at the bottom of the tank. Second polymerization tank: The structure is the same as the first polymerization tank. The polymerization conversion of styrene is 58-63%. The polymerization liquid is sent to a stationary mixing type third polymerization vessel by a gear pump E at the bottom of the tank. Third polymerization vessel: A tubular reactor using a static mixing type Sulzer type static mixer is installed, and the mixer has eight SMXs as mixing elements arranged in series. The operation is performed while maintaining the polymerization conversion at 80% or more. The polymerization liquid is supplied to the next step by an extraction gear pump E provided to reduce the pressure loss to 20 kg / cm ² or less. The residual monomer is treated in a degassing tank, and the polymerization conversion is set to 99.9% or more. In addition, sampling lines were provided at the outlets of the first and second polymerization tanks and the third polymerization vessel to measure the results of the polymerization, and the polymerization conversion was measured, and the weight was measured by gel permeation chromatography. The average molecular weight Mw and the number average molecular weight Mn were measured to calculate Mw / Mn, which was used as a value indicating the molecular weight distribution. For the polymerization, the above three polymerization tanks and polymerization vessels were used, while 95 parts of styrene and 5 parts of ethylbenzene were used.
And a polymerization solution comprising 300 ppm of 2,2-bis (4,4-di-t-butyl-peroxycyclohexyl) propane (based on 95 parts of styrene) was continuously prepared under the conditions shown in Table 1. Bulk polymerization was performed to obtain a styrene-based polymer. Table 2 shows the measured values of the results accompanying the polymerization.

Example 2 Using the polymerization tank and the polymerization vessel shown in Example 1, styrene 9
8 parts, ethylbenzene 2 parts and 2,2-bis (4,4-di-
t-butyl-peroxylcyclohexyl) propane 2
A polymerization solution comprising 00 ppm (based on 98 parts of styrene) was prepared, and continuous bulk polymerization was performed under the conditions shown in Table 1 to obtain a styrene-based polymer. The results of the polymerization were measured in the same manner as in Example 1, and the results are shown in Table 2.

Example 3 Using the polymerization vessel and the polymerization vessel shown in Example 1, styrene 1
00 parts and 1,1-bis (t-butylperoxy) -3,3,
A polymerization solution comprising 130 ppm of 5 trimethylcyclohexane (based on 100 parts of styrene) was prepared.
Was performed under the conditions shown in (1) to obtain a styrene-based polymer. The results of the polymerization were measured in the same manner as in Example 1, and the results are shown in Table 2.

Example 4 Using the polymerization tank and the polymerization vessel shown in Example 1, styrene 9
8 parts, ethylbenzene 2 parts and 2,2-bis (4,4-di-
t-butyl-peroxycyclohexyl) propane 18
A polymerization solution consisting of 0 ppm (based on 98 parts of styrene) was prepared, and 50 ppm of the same organic peroxide was further added to the third polymerization vessel, and continuous bulk polymerization was carried out under the conditions shown in Table 1. Thus, a styrene polymer was obtained. The results of the polymerization were measured in the same manner as in Example 1, and the results are shown in Table 2.

COMPARATIVE EXAMPLE 1 Using the polymerization tank and the polymerization vessel shown in Example 1, styrene 9
Prepare a polymerization solution consisting of 8 parts and 2 parts of ethylbenzene,
Continuous bulk polymerization was performed under the conditions shown in Table 1 to obtain a styrene polymer. The results of the polymerization were measured in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 2 Using the polymerization vessel and the polymerization vessel shown in Example 1, styrene 9
8 parts, ethylbenzene 2 parts and 2,2-bis (4,4-di-
t-butyl-peroxycyclohexyl) propane 60
A polymer solution containing 0 ppm (based on 98 parts of styrene) was prepared, and continuous bulk polymerization was performed under the conditions shown in Table 1 to obtain a styrene polymer. The viscosity increased, the gas amount also increased, the liquid level was not stabilized, and stable operation was not possible. In addition, the result accompanying polymerization was measured in the same manner as in Example 1 and shown in Table 2.

[0021]

[Table 1]

[0022]

[Table 2]

Example 5 and Comparative Example 3 A styrene-based polymer was produced by continuous bulk polymerization.
For initial polymerization, the viscosity of the evaporation latent heat type complete mixing tank (first polymerization tank) is used.
0.5 to 100 poise, temperature of 100 to 150 ° C., gas linear velocity in the tank of 0.01 to 0.2 m / sec, and the same tank (second polymerization tank) for medium-term polymerization, having a viscosity of 100 to 2, 000 poise, temperature 120-170 ° C, gas linear velocity in the tank 0.01-0.2m
/ Second, the late-stage polymerization using a tubular reactor (third polymerization reactor) with a viscosity of 2,000 poise or more, a temperature of 120 to 200 ° C., and a flow rate of polymer in a pipe of 0.2 m / hour or more, First and second
The type of the stirring blade in the polymerization tank was changed to various types (using helical blades, inclined paddle blades (Example 5), turbine blades, anchor blades, and Max blend blades (Comparative Example 3)), and the viscosity of the second polymerization tank was changed to 130. ~ 2,000 poise, gas linear velocity in the tank (superficial velocity) according to the type of stirring blade and viscosity in the tank
The relationship between hold-up (liquid expansion = H / H ₀ = [liquid level with evaporation] / [liquid level without evaporation]) was examined. 7 and 8 show the relationship. FIG. 7 shows that the helical blade and the inclined paddle blade are more preferable than the turbine blade, the anchor blade, and the max blend blade, and FIG. The presence of conditions in the tank was confirmed.

[0024]

According to the present invention, a styrene-based polymer is produced by a continuous bulk polymerization method under the condition that a complete latent heat evaporation type mixing tank is used for the initial and middle-stage polymerization and the final conversion is 80% or more for the latter polymerization. By using a tubular reactor incorporating a static mixing structure, a styrene-based polymer having a high degree of polymerization and a narrow molecular weight distribution can be efficiently obtained.

[Brief description of the drawings]

Fig. 1 Double helical wing

FIG. 2 Inclined paddle wing

Fig. 3 Max blend wing

FIG. 4 Turbine blade

FIG. 5 Anchor wing

FIG. 6 is a flow sheet of a process used in Examples and Comparative Examples.

FIG. 7 is a diagram showing the relationship between the type of stirring blade, the superficial velocity, and the holdup (liquid expansion)

FIG. 8 is a diagram showing a relationship among viscosity in the second polymerization tank, superficial velocity, and hold-up (liquid expansion).

[Explanation of symbols]

 A: Temperature control jacket B: Top of tank C: Condenser D: Stirrer E: Gear pump Fig. 6 (1)-Feeding device for raw styrene Fig. 6 (2)-Feeding device for organic peroxide

Claims (9)

[Claims] 1. A method for producing a styrenic polymer through a continuous bulk polymerization reaction step comprising an initial polymerization, a middle-stage polymerization and a late-stage polymerization. A complete mixing tank type evaporative latent heat type polymerization tank is used, and in the latter polymerization step, at least one styrene raw material under a condition that the final conversion of the raw material is maintained at 80% or more.
A continuous polymerization method for a styrenic polymer, comprising using a tubular reactor. 2. A process for producing a styrenic polymer through a continuous bulk polymerization reaction step comprising an initial polymerization, a middle polymerization and a late polymerization, wherein each of the initial polymerization and the middle polymerization includes one group. A complete mixing tank type evaporative latent heat type polymerization tank is used, and at least one tubular reactor is used in the latter polymerization step under the condition that the final conversion of the styrene raw material is maintained at 80% or more. Continuous polymerization method for styrenic polymers. 3. The continuous polymerization method for a styrene-based polymer according to claim 1, wherein the ratio L / D of the length L and the diameter D of the complete mixing tank type evaporation latent heat type polymerization tank is 1.5 or more. 4. The continuous polymerization method for a styrene-based polymer according to claim 1, wherein the reaction is carried out while air-cooling or water-cooling the gas phase portion in the complete-mixing-tank type evaporative latent heat polymerization tank. 5. The continuous polymerization method for a styrene-based polymer according to claim 1, wherein a vertically circulating flow generating type stirring blade is used as a stirring blade in the complete mixing tank type evaporation latent heat type polymerization tank. 6. The continuous polymerization method for a styrenic polymer according to claim 5, wherein the up-down circulating flow generating type stirring blade is a helical ribbon blade or an inclined paddle blade. 7. A continuous polymerization method for a styrene-based polymer according to claim 1, wherein at least one static mixing structure comprising a plurality of mixing elements is provided inside the tubular reactor. . 8. The tubular reactor has at least two static mixing structures comprising at least four mixing elements.
The continuous polymerization method for a styrenic polymer according to claim 7, wherein a plurality of the styrenic polymers are provided. 9. The viscosity of the system in the reaction step of continuous bulk polymerization is from 0.5 to 2,000 in a complete mixing tank type evaporative latent heat type polymerization tank.
0 poise and the viscosity at the outlet of the tubular reactor is 2.0
3. The continuous polymerization method for a styrenic polymer according to claim 1 or 2, wherein the number of the styrene polymers exceeds 00 poise.