JP5413243B2 - Stirring apparatus and stirring method - Google Patents

Description

  The present invention relates to a stirring device and a stirring method used for suspension polymerization.

  Usually, in suspension polymerization, water containing a monomer (oil), a dispersant, and a stabilizer is supplied to a reaction vessel, mixed by stirring to form a monomer / water emulsion, and then heated to the polymerization start temperature. Thus, polymerization is performed.

  Conventionally, turbine blades that generate a radiant flow, inclined paddle blades that generate an axial flow, and the like have been used in suspension polymerization agitators. These are systems in which a turbulent flow is generated in the reaction tank, and the monomer phase is mixed and dispersed in the aqueous phase to form a monomer / water emulsion. However, these stirring blades are prone to stagnation and overdispersion because the balance between the shear flow and the circulation flow required for uniform dispersion of the monomer phase in suspension polymerization cannot be well achieved.

  As a result, massive polymer or small-diameter resin particles are generated. In addition, the upward flow generated by the stirring blade installed at the lower part of the reaction tank is blocked by the monomer phase / water phase interface. For this reason, it is necessary to stir at a high stirring speed to break the monomer phase / water phase interface. However, when the stirring speed is high, there is a problem that the product resin particle size becomes small.

  Therefore, when a large resin particle size is desired, a method such as stirring at high speed to form a monomer / water emulsion and then reducing the stirring speed to coalesce oil droplets has been taken. It was.

  However, systems such as vinylpyridine / divinylbenzene are unlikely to cause coalescence of oil droplets and require long-time treatment, so that part of the monomer phase dissolves in the aqueous phase and has a uniform droplet size. There was a problem that dispersion could not be performed.

  Furthermore, in order to perform stirring at a high speed, a transmission or the like is required, and a high-output stirrer motor is required. Therefore, there is a problem that the apparatus is increased in size and cost is increased. Further, in order to obtain the effect of stirring and mixing, when a large upward flow is formed, the liquid level rises, a vortex flow is generated, and bubbles are entrained. Thereby, there also exists a problem that a bubble becomes a nucleus and shell particles (cavity particles) generate.

  The present invention has been made in view of such circumstances, and a stirring device and a stirring device that can efficiently disperse a monomer in water by applying a shearing force to the monomer phase / water phase interface to subdivide the monomer. It is an object to provide a method.

  In order to solve the above problems, the stirring device according to claim 1 is provided with a bottomed cylindrical reaction vessel to which monomers and water are supplied, and is rotatably provided at the center of the reaction vessel by a driving device. A rotating pad, a bottom paddle provided at the lower end of the rotating shaft, and a pair of side paddles standing along the inner wall of the reaction tank from both ends of the bottom paddle, In the stirring device provided with a U-shaped stirring blade that forms a stirring flow in the vertical direction of the monomer and water, the stirring device is disposed at the interface between the monomer phase and the water phase and is driven to rotate by the rotating shaft. A middle paddle is provided.

  According to a second aspect of the present invention, in the stirring device according to the first aspect, the middle paddle is provided such that the height position in the vertical direction can be adjusted.

  According to a third aspect of the present invention, in the stirring device according to the first or second aspect, a vortex breaker extending toward the rotating shaft is integrally provided at each upper end of the side paddle. It is characterized by being.

  Furthermore, the invention described in claim 4 is the stirring device according to any one of claims 1 to 3, wherein the middle paddle has a vertical width of 20 to 60% of a vertical width of the bottom paddle. It is characterized by being formed.

  The invention according to claim 5 is the stirring method using the stirring device according to any one of claims 1 to 4, wherein the aqueous phase is raised by an upward flow, and the monomer phase and the aqueous phase are A shearing force is applied to the interface to disperse the monomer into the aqueous phase while being subdivided, and to prevent entrainment of bubbles due to vortices generated at the gas-liquid interface.

  According to the first to fifth aspects of the present invention, the bottom of the rotating shaft provided at the center of the bottomed cylindrical reaction tank is respectively connected to the bottom paddle and both ends of the bottom paddle. A U-shaped stirring blade comprising a pair of side paddles erected along the inner wall is provided, and a middle paddle disposed at the interface between the monomer phase and the water phase and driven to rotate by the rotating shaft is provided. Therefore, a shear force is applied to the interface between the monomer phase and the water phase to form a shear flow, and the monomer can be subdivided by the shear flow and uniformly dispersed in the water phase. Thereby, while suppressing the production | generation of the block polymer by the stagnation of the said monomer, the underproduction | generation of the resin particle size by overdispersion can be suppressed, and the yield of product resin can be raised.

  Further, since the middle paddle provided rotatably together with the rotating shaft can efficiently apply a shearing force to the interface between the monomer phase and the aqueous phase, the monomer phase and the aqueous phase can be provided at a high stirring speed. There is no need to destroy the interface. As a result, a large agitator motor and transmission are not used, and the amount of power and cost can be reduced.

  According to the second aspect of the present invention, since the middle paddle is provided such that the height position in the vertical direction can be adjusted, the monomer phase and the water phase are adjusted in accordance with the ratio of the monomer and water. The middle paddle can be easily arranged on the interface. Thereby, even when the ratio of the monomer to water is changed, it is possible to respond quickly and to apply a shearing force to the interface between the monomer phase and the water phase with certainty.

  According to the third aspect of the present invention, since the vortex breaker extending to the rotating shaft side is integrally provided at the upper end of each of the side paddles, Swelling of the gas-liquid interface caused by the formation of a stirring flow in the vertical direction of the monomer and water can be suppressed. As a result, the vortex flow caused by the rise of the gas-liquid interface can be suppressed to prevent entrainment of bubbles, and the formation of shell particles (cavity particles) in which these bubbles are the core can be prevented.

  According to the fourth aspect of the present invention, since the vertical width of the middle paddle is formed to be 20 to 60% of the vertical width of the bottom paddle, The hindrance to the stirring flow can be minimized. Thereby, the flow of the whole reaction vessel can be made uniform.

  According to this invention of Claim 5, while using the stirring apparatus as described in any one of Claims 1-4, while raising the said aqueous phase by an upward flow, the said monomer phase and an aqueous phase In order to disperse the monomer in the water phase while applying a shearing force to the interface, and to prevent entrainment of bubbles due to vortices generated at the gas-liquid interface, shear required for uniform dispersion of the monomer A balance between the flow and the circulation flow can be obtained, and a monomer / water emulsion with a high yield can be formed.

It is sectional drawing which shows the outline of one Embodiment of the stirring apparatus of this invention. It is a top view which shows the outline of one Embodiment of the stirring apparatus of this invention. (A)-(c) is explanatory drawing which showed adjustment of the position of a middle paddle corresponding to the interface of a monomer phase and an aqueous phase. It is a particle size distribution map in the stirring apparatus of this invention and another stirring apparatus.

1 to 3 show an embodiment of the stirring device of the present invention.
As shown in FIG. 1, the stirring device 1 of the present invention includes a bottomed cylindrical reaction tank 2 to which a monomer m and water w are supplied, and is rotatable by a driving device at the center of the reaction tank 2. A rotating shaft 3 provided, a bottom paddle 4 provided at a lower end portion of the rotating shaft, and a pair of side paddles 5 erected along the inner wall of the reaction tank 2 from both ends of the bottom paddle 4 And a U-shaped stirring blade 6.

  Here, the U-shaped stirring blade 6 is formed of flat stainless steel or the like. The stirring blade 6 is integrally attached to the lower end portion of the rotating shaft 3 with a screw at the horizontal center portion of the bottom paddle 4. The bottom paddle 4 is formed in an arc shape on the bottom side of the reaction tank 2. In addition, a pair of side paddles 5 that are erected in parallel to the inner wall of the reaction tank 2 are integrally formed at both ends of the bottom paddle 4. The side paddles 5 are formed so that each horizontal width dimension is smaller than the vertical width dimension of the bottom paddle 4. Thereby, the vertical stirring flow of the monomer m and the water w flows smoothly and circulates in the reaction tank 2.

  Between the side paddles 5, a middle paddle 8 disposed at the interface 7 between the monomer m-phase and the water w-phase is horizontally mounted. The middle paddle 8 is formed such that the vertical width dimension is smaller than the vertical width dimension of the bottom paddle 4, and is formed at a ratio of 20 to 60% of the bottom paddle 4 width dimension. The middle paddle 8 is attached to a slit 5b formed in the vicinity of the center portion in the vertical direction of each side paddle 5 so as to be slidable in the vertical direction by screws, and the center of the middle paddle 8 in the horizontal direction. The part and the rotary shaft 3 are provided so as to be able to be engaged with each other by screws.

  Further, a flat plate-like vortex breaker 9 is integrally provided at the upper end portion 5a of the side paddle 5 so as to extend at a right angle toward the rotating shaft 3 side. In this vortex breaker 9, each plate surface is arranged perpendicularly to the gas-liquid interface 11, and each of the vortex breakers 9 is arranged opposite to each other with the rotation shaft 3 sandwiched therebetween. Yes.

  Moreover, the bottomed cylindrical reaction tank 2 has a bottom formed in an arc shape. A baffle plate 10 that protrudes from the inner wall surface and extends in the vertical direction is provided on the inner wall of the reaction tank 2. As shown in FIG. 2, the baffle plates 10 are provided at four locations at equal intervals in the circumferential direction of the reaction tank 2.

  In order to stir monomer m and water w to form a monomer / water emulsion using the stirring device of the present embodiment having the above-described configuration, first, monomer m and water w are placed in a bottomed cylindrical reaction tank 2. Supply. Here, the monomer m having a specific gravity smaller than that of the water w is positioned above the reaction tank 2 as the monomer m phase, and the water w is positioned below the reaction tank 2 as the water w phase and separated from each other. Therefore, the position of the middle paddle 8 that is fixed and screwed between the side paddles 5 of the stirring blade 6 at the interface between the monomer m phase and the water w phase is adjusted.

  Here, a method of adjusting and arranging the position of the middle paddle 8 at the interface 7 formed by the monomer m phase and the water w phase supplied to the reaction tank 2 will be described with reference to FIG. In FIG. 3A, a middle paddle 8 is arranged at the position of the interface 7 between the monomer m phase and the water w phase. By supplying monomer m and water w in a ratio different from that shown in FIG. 3 (a), the position of the interface 7 between the monomer m phase and the water w phase is changed to that shown in FIG. 3 (b) or FIG. 3 (c). When the position shown in FIG. 2 is reached, the screws fixed to the slits 5b of the side paddles 5 are loosened, and the screws fixing the rotary shaft 3 and the middle portion of the middle paddle 8 are loosened, 8 is slid in the vertical direction and arranged at the interface 7 between the monomer m phase and the water w phase shown in FIG. 3B or FIG. 3C, and the three loosened screws are tightened and fixed.

  Next, the driving device is operated to rotate the rotating shaft 3. Along with the rotation of the rotating shaft 3, the stirring blade 6 provided integrally with the rotating shaft 3 rotates in the reaction tank 2. Due to the rotation of the stirring blade 6, as shown in FIG. 1, the water w phase discharged by the bottom paddle 4 moves up the baffle plate 10 formed on the wall surface of the reaction tank 2, and the monomer m phase and the water w phase. The interface 7 is reached. At this time, the interface 7 between the monomer m phase and the water w phase is disturbed by the middle paddle 8 whose height is adjusted by the slit 5b of the side paddle 5, and the monomer m is dispersed in the water w phase while being subdivided. A monomer m / water w emulsion is produced.

  The produced monomer m / water w emulsion reaches the vicinity of the gas-liquid interface 11 by upward flow, descends from the vicinity of the center of the reaction tank 2 and circulates in the entire reaction tank 2. At this time, the horizontal width dimension of the side paddle 5 formed to be smaller than the vertical width dimension of the bottom paddle 4 forms a gentle horizontal flow that does not inhibit the upward flow. The flow of the entire tank 2 is made uniform and the downward flow is promoted.

  Further, the vortex breaker 9 forms a circumferential flow in the vicinity of the gas-liquid interface 11 and suppresses the rising of the liquid formed by the upward flow. Thereby, the entrainment of bubbles due to the generation of vortex flow is prevented, and the generation of shell particles in which these bubbles are the core is suppressed.

  According to the stirring device and the stirring method according to the above-described embodiment, the bottom paddle 4 and the bottom paddle 4 are respectively connected to the lower end 3a of the rotating shaft 3 provided at the center of the bottomed cylindrical reaction tank 2 from the both ends. A U-shaped stirring blade 6 composed of a pair of side paddles 5 erected along the inner wall of the reaction tank 2 is provided, and is disposed at the interface 7 between the monomer m phase and the water w phase, and the rotating shaft 3 Since the middle paddle 8 that is driven by rotation is provided, a shear force is applied to the interface 7 between the monomer m phase and the water w phase to form a shear flow. Can be uniformly dispersed. Thereby, while suppressing the production | generation of the block polymer by the stagnation of the monomer m, the underproduction | generation of the resin particle size by overdispersion can be suppressed, and the yield of product resin can be improved.

  In addition, since the middle paddle 8 that is rotatably provided with the rotating shaft 3 can efficiently apply a shearing force to the interface 7 between the monomer m phase and the water w phase, the monomer m phase It is not necessary to destroy the interface 7 with the water w phase. As a result, a large agitator motor and transmission are not used, and the amount of power and cost can be reduced.

  And since the middle paddle 8 is provided so that the height position of the vertical direction can be adjusted by the slit 5b formed in each side paddle 5, according to the ratio of the monomer m and the water w, the monomer m phase The middle paddle 8 can be easily disposed at the interface 7 between the water and the water w phase. Thereby, even when the ratio of the monomer m and the water w changes, it can respond rapidly and can apply a shear force to the interface 7 of the monomer m phase and the water w phase reliably.

  Furthermore, since the vortex breaker 9 extending integrally with the rotary shaft 3 is integrally provided at the upper end portion 5a of each side paddle 5, the rotation of the stirring blade 6 causes the monomer m and water w to move in the vertical direction. Swelling of the gas-liquid interface 11 due to the formation of the stirring flow can be suppressed. As a result, the vortex flow caused by the rising of the gas-liquid interface 11 can be suppressed to prevent entrainment of bubbles, and the formation of shell particles with the bubbles as nuclei can be prevented.

  Further, since the vertical width of the middle paddle 8 is formed to be 20 to 60% of the vertical width of the bottom paddle 4, the hindrance of the monomer m and the water w to the vertical stirring flow is minimized. Can be suppressed. Thereby, the flow of the whole reaction tank 2 can be made uniform.

  And by using the stirrer of this invention, while the water w phase rises by an upward flow, shear force is added to the interface 7 of the monomer m phase and the water w phase, and the monomer m is subdivided and the water w phase. In addition, bubbles are prevented from being entrained by vortices generated at the gas-liquid interface 11 and uniform circulation mixing is performed, so that a balance between shear flow and circulation flow required for uniform dispersion of the monomer m can be obtained. And a uniform monomer / water emulsion can be formed.

<Experimental example>
Here, effects obtained by experiments conducted by the inventors will be described.
In the experiment, the stirring blade 6 (blade diameter 115 mm) used in the stirring device 1 of the present invention, the disc turbine blade (blade diameter 120 mm, 6 sheets) that is a conventional stirring blade for suspension polymerization, and the gate and anchor type A vinylpyridine / divinylbenzene copolymer was synthesized in a reaction vessel 2 having a diameter of 230 mm and a liquid depth of 270 mm using a blade (blade diameter 130 mm). In this experiment, the stirring speed was set to the lowest dispersible speed, and the same speed was maintained until the polymerization was completed.

  From the above experiment, the minimum dispersible stirring speed for each stirring blade of the stirring blade 6, the disk turbine blade, and the gate & anchor type blade used in the stirring device 1 of the present invention, and the average of the resins obtained at this speed Table 1 shows the particle diameter, bulk polymer and shell particle ratio. The particle size distribution is shown in FIG.

  From this experiment, the stirring blade 6 used in the stirring device 1 of the present invention can perform polymerization at a low stirring speed and can easily obtain a product having a large particle size without any special operation. In addition, bulk polymer due to stagnation can be completely eliminated, and generation of shell particles due to entrainment of bubbles caused by vortex flow can be reduced.

  In the above embodiment, only the case where the side paddle is provided with a slit so that the middle paddle can be adjusted in the vertical direction has been described. However, the present invention is not limited to this. It is possible to fix even if it is fixed and slid in the vertical direction of the rotating shaft 3.

  It can be used for suspension polymerization of monomers.

DESCRIPTION OF SYMBOLS 1 Stirring apparatus 2 Reaction tank 3 Rotating shaft 3a Lower end part 4 Bottom paddle 5 Side paddle 5a Upper end part 6 Stirring blade 7 Interface 8 Middle paddle 9 Vortex breaker 10 Baffle plate 11 Gas-liquid interface m Monomer w Water

Claims (5)

A bottomed cylindrical reaction vessel to which monomer and water are supplied, a rotary shaft rotatably provided by a driving device at the center of the reaction vessel, a bottom paddle provided at a lower end of the rotary shaft, and A U-shape that has a pair of side paddles erected from both ends of the bottom paddle along the inner wall of the reaction tank, and forms a stirring flow in the vertical direction of the monomer and water in the reaction tank In a stirring device equipped with a stirring blade of
A stirrer provided with a middle paddle disposed at an interface between the monomer phase and the aqueous phase and driven to rotate by the rotating shaft.   The stirring device according to claim 1, wherein the middle paddle is provided so that a height position in a vertical direction can be adjusted.   The stirrer according to claim 1 or 2, wherein a vortex breaker extending to the rotating shaft side is integrally provided at an upper end portion of each of the side paddles.   The stirring device according to any one of claims 1 to 3, wherein the middle paddle is formed so that a vertical width thereof is 20 to 60% of a vertical width of the bottom paddle.   While stirring the aqueous phase by an upward flow with the stirrer according to any one of claims 1 to 4, applying shearing force to the interface between the monomer phase and the aqueous phase to subdivide the monomer An agitation method characterized by being dispersed in the aqueous phase and preventing entrainment of bubbles by vortices generated at a gas-liquid interface.

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