JP3774291B2 - Solution polymerization equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solution polymerization apparatus. More specifically, the present invention relates to a solution polymerization apparatus having a plurality of columnar bodies and stirring blades.
[0002]
[Prior art]
Conventionally, various polymerization apparatuses have been developed, and a polymerization tank in which the stirring blade is particularly devised has been proposed. The types of agitating blades are roughly classified into a paddle type, a radial type represented by a turbine type, and an axial type represented by a propeller type (separate volume chemical industry "design and operation of a stirring device" ( 1970) vol.14, No.7 Chemical Industries, Ltd. p.4-11).
[0003]
When a radiating type stirring blade is used for the mixing vessel, a strong flow is generated in the rotating direction of the blade due to the centrifugal action of the blade rotation. Accordingly, the liquid level is lowered and bubbles are entrained by the spiral flow generated by the horizontal rotating flow. In addition, since the center of the vortex rotates in a rod shape, there are disadvantages such as weak stirring action. In order to overcome such drawbacks, baffle plates have been introduced, whereby vertical stirring is promoted, and an improvement in stirring effect accompanying an increase in stirring power is observed. However, this effect is manifested with respect to a low-viscosity liquid, and in the case of a high-viscosity liquid, there are problems such as liquid retention behind the baffle plate, and it is difficult to say that the effect is high.
[0004]
On the other hand, when an axial flow type stirring blade is used, a strong flow is generated in the direction of the rotation axis. In particular, when a baffle plate or the like is used, this tendency appears remarkably, and the flow in the tank becomes a clear circulation flow. The axial flow type can generate liquid flow in a much wider range than the radial flow type, and relatively small blades can be used in large tanks, but this effect is sufficient only for low viscosity liquids. Is not demonstrated.
[0005]
In these stirring blades described above, the blade position in the vertical direction is fixed in most cases. Therefore, the effect of stirring varies greatly depending on whether or not the stirring blade is immersed in the reaction solution, that is, where the stirring blade is located with respect to the liquid surface, and as a result, the quality of the product is greatly affected.
[0006]
Furthermore, these stirring blades have a drawback that the stirring action is weakened unless a baffle plate is used. However, introducing a baffle plate into the device can compensate for these drawbacks, but a stagnant part is generated, and if the operation is continued for a long time, a block is generated and grows in the stagnant part, and the operation gradually becomes difficult. Become.
[0007]
A screw blade or a helical ribbon blade is used for stirring the high viscosity liquid. For example, Japanese Patent Publication No. 61-14853 discloses an example in which a helical stirring machine is used, and Japanese Patent Publication No. 1-3444 discloses a plurality of double helical types on a rotating shaft. An example of use in which a stirring blade is disposed is disclosed, and in Japanese Patent Publication No. 58-51962, a rotating shaft to which a stirring blade is fixed is provided, and an annular support plate is fixed to each rotating shaft. An example using a stirring blade formed by fixing a scraping plate to the tip of the annular support plate is disclosed. Japanese Patent Publication No. 6-55269 discloses an example in which two meshed screw screw blades are provided, and the screw screw blades are meshed with each other and stirred. However, these have a complicated structure, generally have a large stirring power, and have a limited liquid viscosity.
[0008]
By the way, the liquid flows generated by the stirring blades described so far are all in the vertical direction, and when batch processing is performed, the same residence time can be obtained. In the case of carrying out, a product having a residence time distribution, that is, a mixture of those having various reaction rates in microscopic view is obtained. There has also been proposed a polymerization reaction apparatus directed to a so-called piston flow type in which no stagnant portion is generated in a polymerization system using a high-viscosity liquid. For example, in Japanese Patent Publication No. 58-3481, A polymerization reaction apparatus is disclosed in which a shaft for agitating blades is eccentric and a blade for scraping off the polymer adhering to the inner wall surface of the tank and a perforated plate are attached.
[0009]
[Problems to be solved by the invention]
According to this polymerization reaction apparatus, the above object can be achieved to some extent, but the structure is still complicated and it is quite difficult to adopt industrially. Accordingly, an object of the present invention is to provide a solution polymerization apparatus which can be applied to both batch and continuous systems, which has a simple structure, does not generate blocks, and has a wide applicable viscosity range.
[0010]
[Means for Solving the Problems]
The inventors of the present invention have made extensive studies in order to obtain a solution polymerization mixing apparatus that satisfies the above object, and have reached the present invention. That is, the present invention is a solution polymerization apparatus comprising a substantially cylindrical mixing vessel and a stirring blade, and the stirring blade has an outer diameter of 15 to 20% of the inner diameter of the polymerization tank, and has a rotational trajectory. It is a solution polymerization apparatus characterized by comprising at least two columnar bodies that do not coincide with each other and at least one connecting member for connecting them.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The solution polymerization apparatus of the present invention has the greatest feature in using a plurality of columnar bodies. The shape of the columnar body is not particularly limited, and various forms such as a solid columnar body, a hollow cylindrical body, a solid or hollow prismatic body can be used. The cross-sectional shape perpendicular to the axis of the columnar body is not particularly limited, and may be a polygon such as a circle, an ellipse, a triangle, a rectangle, and a hexagon. When the columnar body is a columnar body or a cylindrical body, the outer diameter is 15 to 20%, preferably 17 to 18% of the inner diameter of the polymerization tank. If the columnar body is not circular, an equivalent diameter may be used instead of the diameter.
[0013]
The ratio of the outer diameter to the length of the columnar body is preferably 1/5 to 1/20, more preferably 1/9 to 1/18. Also, in the case of a prismatic object, it is almost the same. The columnar body is usually made of metal, but other materials may be used as long as the strength is safe. Each columnar body is usually the same length and is usually used in two, but may be three or more as required.
[0014]
The columnar bodies are connected in the lateral direction by connecting members at the ends of the columnar bodies. The connecting member is not particularly limited in shape, material and the like, and may be any member that can connect the columnar bodies. Usually, the upper end portions and / or the lower end portions of the columnar bodies are connected to each other. Thus, the stirring blade of this invention is comprised from what the columnar body was connected with the connection member in the horizontal direction. A plurality of columnar bodies are used, and each is connected by a connecting member. Preferably, all of the columnar bodies are connected in parallel so that the end portions of the columnar bodies coincide with the respective connecting members by two connecting members.
[0015]
The columnar bodies are connected so as to be vertical by at least one connecting member. There is no restriction | limiting in particular in a connection member, There is no restriction | limiting in particular also about the position where a connection member couple | bonds a columnar body. Usually, the connecting member is combined with the columnar body so as to have an optimum strength. For example, when there is one connecting member, it is preferable to join the central portions of the columnar bodies. In the case where there are two connecting members in the normal form, it is preferable to join the upper and lower parts of the columnar body. In the stirring blade used in the present invention , it is preferable that both ends of each connecting member are coupled to the columnar body. Although the number of connecting members may be one, two are usually used so that a weak portion does not occur in the stirring blade. When many connecting members are used, both ends of the columnar body are connected by two connecting members, and the remaining connecting members are connected to each other so that the lengths of the columnar bodies between the two members are equal.
[0016]
The at least one connecting member includes a connecting mechanism that makes the agitating blade and the mixing vessel asymmetric. When there is one connecting member, the connecting member is coupled to the columnar body at both ends of the connecting member, and the connecting mechanism is provided to be eccentric from the center of the member. When a plurality of connecting members are used, the connecting member is connected to the columnar body at both ends of the connecting member, but at least one member (usually the uppermost member) is provided to be eccentric from the center of the member. Have
[0017]
Therefore, the stirring blade used in the present invention includes at least two columnar bodies arranged at intervals from each other, and at least one connecting member that couples the columnar bodies in the lateral direction, preferably so that the columnar bodies are vertical. Composed. And since at least 1 connection member has a connection mechanism, a stirring blade can be fixed to the shaft rotated at the center of the circular cross section of a mixing container. As a result, the trajectories formed by the columnar bodies do not match each other.
[0018]
The columnar body may be inclined as long as it does not hinder rotation, but the columnar body that rotates on the outermost periphery, that is, the columnar body that is located farthest from the axis of the mixing vessel, in other words, the most The columnar body rotating with a large cylindrical trajectory exhibits the effect of preventing the polymer from adhering to the inner wall of the polymerization tank when the gap, which is the distance between the inner wall of the container and the outermost part of the columnar body, is sufficiently small. In order to exhibit the effect of scraping off the polymer adhering to the inner wall of the container, it is preferably provided vertically. In other words, it can be said that the polymerization apparatus of the present invention has a self-cleaning mechanism.
[0019]
The gap between the inner wall of the container and the columnar body rotating on the outermost periphery of the tank depends on the system to be mixed, but is preferably 0.1 to 0.5% of the inner diameter of the container, more preferably 0.2 to 0.4%. The smaller the gap is, the higher the self-cleaning effect is, but the shearing force generated in the gap is increased and the stirring power is increased. Conversely, when the gap is increased, the stirring power is reduced, but the effect of self-cleaning is reduced. As for the gap described above, when the connecting member is located at the bottom of the columnar body and the bottom surface is flat, the same applies to the gap between the connecting member and the container bottom surface.
[0020]
In a preferred embodiment of the present invention, when the stirring blade rotates around the axis of the container, the trajectories of the columnar bodies do not coincide with each other, that is, the mutual shape, size and position are not the same. Is installed in the container so that the central axis of the two columnar bodies is eccentric from the axis of the container, and is fixed to a rotating shaft by a driving mechanism such as a motor. The case where there are two columnar bodies will be described with reference to FIG. 2. The distance a between the center of the container and the center of the outermost columnar body is not equal to the distance b between the center of the container and the center of the innermost columnar body. Means that.
[0021]
The distance (ab) / 2 between the axis of the container and the center of the innermost and outermost columnar bodies is preferably 6 to 12% of the inner diameter of the container, so that the effects of the present invention can be sufficiently exhibited. Preferably it is 8 to 10%. By installing the stirring blade in this manner, the stirring blade rotates eccentrically with the rotation axis of the container body, and coupled with the fact that the outer diameter of the columnar body is 15 to 20% of the inner diameter of the container, The cross-sectional area of the rotation locus drawn by the body in the container occupies about 90% or more of the cross-sectional area of the container, and the liquid in the container can be sufficiently stirred.
[0022]
The upper lid of the mixing vessel is equipped with a nozzle for introducing the liquid vaporized by the polymerization heat into the heat exchanger and a nozzle for introducing a polymerization inhibitor in the event of an abnormal reaction. However, the uppermost part of the stirring blade is preferably 100 mm to 1000 mm lower than the uppermost part of the polymerization tank, and more preferably 300 mm to 600 mm lower so as not to block these nozzles. .
[0023]
The solution polymerization apparatus of the present invention essentially comprises a mixing vessel and a stirring blade, but the ratio (H / D) between the height H of the vessel and the inner diameter D of the vessel is practically 0.5 ≦ H / D. ≦ 5.0, preferably 1.0 ≦ H / D ≦ 3.5. The ratio L / D between the height of the liquid level and the inner diameter of the container is practically 0.2 ≦ L / D ≦ 4.0, preferably 0.5 ≦ H / D ≦ 2.0. . Usually, the mixing container is provided with a jacket for heating and cooling. In addition, a polymerization inhibitor charging device and a rupturable plate for safety are provided as necessary. In order to prevent the raw material liquid which is the monomer composition from reacting with the upper surface of the upper connecting plate, the monomer composition supply port to the container has an uppermost portion from the top of the stirring blade. 10-50 mm, preferably 20-30 mm lower. Further, the extraction port is installed on the bottom surface of the container, but it is preferable to install it as far as possible from the center of the container so that the extraction port is exposed for as long as possible.
[0024]
The ratio L / l between the height L of the liquid level of the container and the length l of the columnar body including the thickness of the connecting member is preferably 0.10 to 0 so that stirring is not incomplete in the container. .95, more preferably 0.70 to 0.90. The ratio 1 / H between the length l of the columnar body and the height H of the container is preferably 0.70 to 0.95, more preferably 0.80 to 0.90.
[0025]
Monomers applicable to the polymerization apparatus of the present invention can be basically applied to all monomers capable of solution polymerization. For example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate, pivalin. And vinyl esters such as vinyl acid. There is no particular limitation on the solvent for solution polymerization, for example, alcohols such as methanol, ethanol and propanol, esters such as ethyl acetate and methyl acetate, organic acids such as acetic acid, Acetone, benzene, toluene and the like can be exemplified. The viscosity range of the monomer solution is not particularly limited, but practically 50 to 5000 poise, preferably 100 to 3000 poise is used.
[0026]
As can be seen from FIG. 3, the stirring blade made of a columnar body in the present invention has the same shape at any position except the connecting members at the upper and lower ends when the horizontal cross section is viewed. That is, since the stirring effect does not change regardless of the height of the columnar body of the reaction liquid, the production amount and the reaction time can be arbitrarily set while maintaining the same stirring effect. Furthermore, since the efficiency of stirring does not change even when the liquid level is low as at the start of operation, the same stirring state can be obtained until a certain liquid level is reached, and the transition to the steady state can be easily performed in a short time. It can be carried out.
[0027]
Since the baffle plate is not used in the polymerization apparatus of the present invention, there is no liquid retention portion and no block is generated. In the polymerization apparatus of the present invention, since the gap between the wall surface of the container and the columnar body rotating on the outermost periphery of the tank is small, it has a self-cleaning effect and has a structure in which blocks are not easily generated.
[0028]
In the polymerization apparatus of the present invention, stirring occurs when the columnar body rotates in the tank, but the liquid flow by stirring is only in the horizontal direction, and is hardly stirred in the vertical direction. For this reason, the stirring power is small. When the monomer composition is continuously charged and the polymer solution as the reaction product is withdrawn, the flow of the reaction liquid in the tank becomes a piston flow. Therefore, the residence time distribution of the reaction liquid is narrowed, and a reaction product having uniform physical properties can be obtained.
[0029]
As described above, since the polymerization apparatus of the present invention has the above-described characteristics, it can be easily scaled up with a substantially similar shape. Moreover, even if the liquid level of the reaction liquid in the container changes, the stirring efficiency does not fluctuate. Therefore, the liquid level in the container can be freely set, and is suitable not only for batch systems but also for continuous systems such as a polymerization apparatus. Further, according to the polymerization apparatus of the present invention, the generation of blocks can be eliminated, so that stable operation can be achieved for a long time, which is industrially advantageous.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a conceptual diagram showing an example of the solution polymerization apparatus of the present invention, and FIG. 2 is an elevation view. As apparent from FIG. 2, the solution polymerization apparatus 10 includes a stirring blade 12 and a cylindrical mixing container 14. The stirring blade 12 has two columnar bodies 16 and 17 parallel to each other, and the upper and lower sides thereof are vertically connected at both ends of the connecting members 18 and 19. The connecting members 18 and 19 connect the columnar bodies 16 and 17 at both ends, and as is apparent from FIG. 1 or 2, the connecting members 18 and 19 protrude slightly from the upper and lower ends of the columnar body 16, Since the self-cleaning effect occurs on the columnar body 17 side, the self-cleaning effect is not hindered.
[0031]
The container 14 has a rotation shaft 20, which is connected to a drive mechanism (not shown) through the center of the upper lid and rotates. Reference numeral 42 denotes a rotating shaft. As can be seen from FIG. 1 or 2, the upper connecting member 18 is connected to the shaft 20 eccentrically from the center of the member. The lower connecting member 19 is rotatably connected to the bottom wall 24 by a connecting member 26 provided at the center of the bottom wall 24. If the upper mechanism is sufficient to support the stirring blade, the connecting member 26 is not necessarily required.
[0032]
As the shaft 20 rotates, the columns 16 and 17 rotate about the shaft 20, i.e. the vessel axis 42, and as shown in FIG. 3, the column 17 draws a large cylindrical trajectory 44, and the column 16 is A smaller cylindrical trajectory 46 is drawn and the trajectories do not match. The columnar bodies 16 and 17 are provided in parallel to the axis 42 of the container 14 so that the gap 34 between the inside of the container and the outermost surface of the columnar body 17 is constant in the length direction of the columnar body 17. Further, the mixing container 14 is provided with a nozzle 48, from which, for example, vapor generated from the liquid in the container is led to a condenser or a polymerization inhibitor is added.
[0033]
3 is a cross-sectional view taken along the line AA ′ of FIG. For ease of understanding, two trajectories 44 and 46 formed by the rotating columnar bodies 16 and 17 are indicated by broken lines. Of course, the locus formed by these columnar bodies is a concentric circle. FIG. 4 shows another embodiment of the solution polymerization apparatus of the present invention. This embodiment is similar to FIG. 2, but differs from FIG. 2 in that three columnar bodies are used, that is, a columnar body 16 ′ is used between the columnar bodies 16 and 17. Hereinafter, the polymerization apparatus of the present invention will be described.
[0034]
First, the system inside the polymerization apparatus 10 is replaced with nitrogen, and a monomer solution composed of a monomer and a solvent is first charged from the supply port 30 of the mixing container 14 to a predetermined liquid level. Next, the mixture is stirred while paying attention to the viscosity of the reaction solution, and heated to the set temperature. Heating is performed by supplying steam or hot water from an inlet 40 to a jacket 36 provided on the outer periphery of the container, and the steam or hot water is extracted from an outlet 38. The number of rotations of the stirring blade may be appropriately determined according to the desired viscosity state of the reaction product, but if it is too slow, the mixing state of the reaction solution is not perfect, and conversely if too fast, the stirring power increases rapidly. Usually, it is carried out at 2 to 20 revolutions per minute, preferably at 5 to 15 revolutions per minute.
[0035]
In the case of the continuous type, when the desired polymerization rate is reached, the monomer composition is continuously fed and sampling is started at the same time. The extraction is performed from the outlet 32 by, for example, a gear pump (not shown). If necessary, a flow meter such as an oval may be installed. The level of the liquid level may be controlled by controlling the extraction, but in order to keep the liquid level constant, the extracted liquid may be circulated to the polymerization tank according to the change in the liquid level. In order to stop the polymerization, it is preferable to provide a polymerization inhibitor charging device or to install a safety device such as a rupturable plate in case of emergency. EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these.
[0036]
【Example】
Example 1
Polymerization of vinyl acetate was carried out using the polymerization apparatus 10 shown in FIG. 1 comprising a stirring blade 12 and a cylindrical mixing vessel having an inner diameter of 2300 mm and a height of 6000 mm. The stirrer blade has two vertical columnar bodies 16 and 17 having a diameter of 5500 mm including two 400 mm diameters and thicknesses of upper and lower connecting members (each 300 mm), and a connecting connection in which the upper and lower ends of the columnar bodies are connected at the ends. It consists of members. The stirring blade was installed in the container so that the distance a from the center of the container to the center of the outer columnar body 17 was 943 mm, and the distance b from the center of the container to the center of the inner columnar body 16 was 510 mm.
[0037]
The inside of the system was replaced with nitrogen, and 83 wt% vinyl acetate, 17 wt% methanol and a polymerization initiator were supplied. The monomer solution was heated with a heat exchanger, and the temperature was raised by passing warm water through a jacket provided in the container. The reaction temperature was set to 65 ° C., the liquid level was set to 4200 mm (liquid level height / polymerization tank inner diameter = 1.8 / 1), and a continuous polymerization reaction of vinyl acetate was performed at a stirring speed of 10 revolutions / minute. The polymerization rate was adjusted by the addition rate of the polymerization catalyst calculated from the composition of the charged monomer and the residence time. Although the polymerization rate was kept at 64% and the operation was continued for one year, no block formation was observed, and a vinyl acetate resin having a degree of polymerization of about 1700 could be obtained.
[0038]
Example 2
The polymerization operation was performed in the same manner as in Example 1 except that the ratio of the liquid surface height to the inner diameter in the polymerization tank was 1.3 / 1. Although continuous operation was conducted for 1 year at a polymerization rate of 64%, no block formation was observed, and a vinyl acetate resin having a degree of polymerization of about 1700 could be obtained.
[0039]
Example 3
The polymerization operation was carried out in the same manner as in Example 1 except that the ratio between the liquid surface height and the inner diameter in the polymerization tank was 0.75 / 1 and the methanol concentration was 16 wt%. Although continuous operation was conducted for 1 year at a polymerization rate of 62%, no block formation was observed, and a vinyl acetate resin having a degree of polymerization of about 2000 could be obtained.
[0040]
Comparative Example When a mixing vessel 14 having an inner diameter of 2400 mm and a height of 3600 mm, in which the paddle type stirring blade 12 and baffle plate 50 shown in FIG. 5 were installed, was used for polymerization for 10 days in the same manner as in Example 1. The block grew gradually and the stirring power increased. In addition, since the effect of stirring varies greatly depending on the position of the liquid level, stable continuous operation is extremely difficult.
[0041]
【The invention's effect】
The solution polymerization apparatus of the present invention has a simple structure, there is no fluctuation in the stirring effect associated with the change in the liquid level in the container, there is no adhesion of polymer to the wall surface of the container, and there is no block generation, so long time Polymerization can be carried out stably. Furthermore, since the liquid flow in the container is essentially a piston flow, it is possible to obtain a reaction product having uniform physical properties, easy to scale up, and various batch or continuous solution polymerizations. Can be widely used as a device.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an example of a polymerization apparatus of the present invention.
FIG. 2 is an elevation view showing an example of the polymerization apparatus of the present invention.
FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 4 is a conceptual diagram showing another example of the polymerization apparatus of the present invention.
FIG. 5 is an example of a mixing container used for comparison.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Polymerization apparatus 12 Stirring blade 14 Mixing container 16 Columnar body 16 'Columnar body 17 Columnar body 18 Upper connection member 19 Lower connection member 20 Rotating shaft 22 Top cover 24 Bottom wall 26 Connection member 28 Connection mechanism 30 Monomer supply port 32 Product extraction Mouth 34 Gap 36 Jacket 38 Heating / cooling water outlet 40 Heating / cooling water inlet 42 Rotating shaft 44 Trajectory 46 Trajectory 48 Nozzle 50 Baffle plate

Claims (3)

A solution polymerization apparatus comprising a substantially cylindrical mixing vessel and a stirring blade, wherein the stirring blade has an outer diameter of 15 to 20% of the inner diameter of the polymerization tank, and the rotation trajectories do not substantially coincide with each other. A solution polymerization apparatus comprising two columnar bodies and at least one connecting member for connecting them. The solution polymerization apparatus according to claim 1 , wherein the gap between the inner wall of the mixing vessel and the outermost columnar body closest to the inner wall is 0.2 to 0.4% of the inner diameter of the mixing vessel. 3. The solution polymerization apparatus according to claim 1, wherein the solution polymerization is polymerization of a vinyl ester monomer selected from vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate and vinyl pivalate.

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