AU609477B2

AU609477B2 - Stirring apparatus and stirring tower type apparatus for polymerization reactions

Info

Publication number: AU609477B2
Application number: AU16101/88A
Authority: AU
Inventors: Kazuto Kobayashi; Hidetaro Mori; Hiroaki Ogasawara; Setsuo Omoto; Takafumi Shimada; Takao Yamazaki
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1987-05-19
Filing date: 1988-05-12
Publication date: 1991-05-02
Anticipated expiration: 2008-05-12
Also published as: MX167571B; KR910005676B1; KR880013980A; AU1610188A; AR242124A1; BR8802423A; DE3817380C2; DE3817380A1

Description

S;I A U131 ALIA .ENTS.ACT 1952 r I COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Class Lodgcd: Int. Class Complete Specification Lodged: Accepted: Published: 00,099 Piorit'; 044 9 Rtlated Art: 0 0 0 goo* 609477 IThis docttmmiit cmti'n'7 the zvdvi,2al~ts ls pac trnd,,x Sectiorn 4i9 mid is currcwt for Prm U3 Nitqreeif Applicant(s): MITSUBISHI JUKOGYO KABUSHIII KAISHA 04 0 Address ofApplicant(s); 5-1, Marunouchi 2-chorkie, Chiy.ada-ku, Tokyo, JAPAN 0 ActualInventor(s): Takafumin Shimada, Hiroaki Ogasawara, Hidetaro Moi, Setsuo Omotc Kazuto Kobayashi and Takao Yawazak:L.

Address for Service: Kelvin Lord Co., 4 Douro Place, WEST PERTH:, Western AUstralia 6005.

Complete Specification for the inventioiz cntitlcd' STIRRING APPARATUS AND STIRRING TOWER TYPE APPARATUS FOR POLYMERIZATION REACTIONS.

Ile following statement isa full description otthiz inventian including thec best me-had ofpcrformingitknob 'Y.to Y c> \r DECLARED at Tokyo, Japan this 10th ay of June 188 MITSUBISHI TUKQGYO.KAP TIT STTT ATUAu Ts i

SPECIFICATION

1. TITLE OF THE INVENTION: STIRRING APPARATUS AND STIRRING TOWER TYPE APPARATUS FOR POLYMERIZATION REACTIONS 2. FIELD OF THE INVENTION AND RELATED ART STATEMENT: 0 0 o001o First, the present invention relates to a stirring apparatus that is used as a reaction apparatus in which 0 00 a. reactions of highly viscous materials, for example viscous S liquids or slurry, take place, with the intention of obtaining uniform products by stirring.

0 00° Secondly, the present invention relates to a high 00 "0 performance apparatus for polymerization reactions in S0a manufacturing high molecular compounds continuously.

More Specifically, the present invention relates to 0o o an apparatu,' for continuous polymerization reactions which is used particularly for solution polymerization and bulk polymerization in a highly viscous and homogeneous system.

As stirring apparatuses for highly viscous materials, large paddle wings, anchor type wings, helical ribbon wings, and helical screw wings have beer often used as discussed in Mixing Principles and Applications by Shinji NAGATA (Kodansha, 1976).

j la 1 i

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Large paddle wings and anchor type wings are structurally simple and easy to clean and manufacture. However, they are not effective in stirring highly viscous materials.

Particularly, when the stirring Raynolds number, Re (=pnd 2 /p, where p is the density, n the number of rotation, d the radius of wings, V the viscosity), is less than or equal to the order of ten, they show significantly inferior j up-and-down stirring performances.

o°'o Helical ribbon wings and helical screw wings with 10 draft tubes, on the other hand, work well with highly o o Sao° viscous materials and show a sufficiently good performance o even at low Reynolds numbers. Since they have a very complicated structure, however, they are difficult and expensive S" to manufacture, and cleaning them is troublesome.

Also, as polymerization reactions for manufacturing I o" high molecular compounds, solution and bulk polimerization methods have been widely used. In these solution and bulk oo polymerization methods, when polymers dissolve in monomers a aa and solvent, the system becomes homogeneous and highly 4 4 viscous as polymerization reactions progress.

As examples for such polymerization reactions, the following can be cited: bulk polymerization of polymethyl methacrylate, solution and bulk polymerization of acrylonitrile-styrene resin, solution polymerization of acrylonitrile-butadiene-styrene resin, solution polymerization S-2 1 of polybutadiene, solution polymerization of styren-butadiene rubber, condensation polymerization (particularly in its final stage) of nylon 6 in which e-caprolactam is used as an ingredient, condensation polymerization (particulary in its intermediate stage) of nylon 66 in which adipic acid and hexamethylenediamine are used as ingredients. Solutioln polymerization of polyvinyl acetate, etc.

go General requirements for a continuous polymerization reactor for highly viscous reaction fluids are discussed in detail in Jugohannosochi No Kiso To Kaiseki (Basics and Analysis of Polymerization Reaction Apparatus in Japanese) 4 qo by Yasuhiro MURAKAMI, pnblisher Baifuukan, 1976. From the this reference the following list of requirements 4*4a may be extracted.

They stay time distribution is sharp; the piston "o oflow characteristics are required.

Stirring efficiency is high so that the temperature Sand concentration distribution in every part in the flow direction is uniform.

There is no "dead space," space in which flow is obstructed, anywhere in the reaction apparatus.

Power required for stirring is small.

Heat transferring areas and heat transfer coefficients are large so that heat of reaction can be removed quickly.

-3f i 4 The structure of the apparatus is simple and easy to clean.

Efforts have been made to satisfy these requirements as much as possible, and there have been proposed numerous polymerization apparatuses. However, no single apparatus has been truly satisfactory.

3. OBJECTIONS AND SUMMARY OF THE INVENTION: It is an object of the present invention to solve the above problems of the conventional stirring apparatus and provide a new stirring apparatus having a simple structure whose performance for highly viscous materials is high.

It is another object of the present invention to @044 0** o 0 0 •O 0 t t 0<' 6 fl provide an stirring tower type apparatus for polymerization reactions which has a sharp stay time distribution the piston flow characteristics), high mixing efficiency in every stirring area along the flow, higher heat transfer coefficients, a simple structure, and no obstructed flow areas and requires small power for stirring, in order to solve the problems in polymerization reactions discussed above.

o The present invention provides a stirring apparatus vYr \icoN 10 comprising a container, a rotational shaft inserted into the container, and a flat wing whose area is nore than .0 0 of the sectional area encircled by the center of the rotational shaft, an inner wall of the container and the surface 0 Ok of materials being stirred in the container, This flat o""15 wing is fixed in a sufficiently parallel fashion to the 0 o rotational shaft.

By rotating the above large flat wing and a slanted S0 wing in the container, a stirring apparatus of the present invention is capable of: 4 4 Producing, with the large wing, two types of flow, a fast outer flow and a slow inner circulation; Producing, with the slanted wing disposed in either one or both of the two types of flow, another up-anddown flow; With the effects of and above, introducing %/7 l better circulation covering every part of the container, and thus making fast and efficient stirring possible.

Utilizing the principle of the above stirring apparatus, the present invention also provides a stirring tower type apparatus for polymerization reactions that comprises a cylidrical container having a fluid supply inlet and a Vert' cc\ fluid outlet; a4rotational shaft coaxially inserted into S the container; stirring means comprising a plurality of flat wings attached to the rotational shaft with their 30 face being substancially parallel to the center axis of the rotational shaft, and slanted wings attached to the S above rotational shaft at a certain angle from the center axis forming sets with the flat wings; and partitioning S* means to divide the above container in the longitudinal S400015 direction between the above stir-ring means.

SO I, the reaction apparatus of the above structure, fluid is supplied into the container from the fluid supply inlet and introduced into stirring areas divided by the these stir ing areas, as in the stirring apparatus above, patitining mans in th n a d the flat wings and slanted wings which serve as stirring means and are attached to the rotational shaft, are rotated to create circulating flows such as up, down and horizontal flows with the combined effects of the two types of wings above. The supplied fluid is stirred and mixed sufficiently, 6i F. sent from one stirring area to another to be stirred and mixed further and finally discharged from the fluid outlet of the container out of the system.

4. BRIEF DESCRIPTION OF THE DRAWINGS: These and other objects as well as advantage of the present invention will become clear by the following description of preferred embodiments of the present invention with reference to the accompanying drawings:

S

t FIG. 1 is a vertical section of a first embodiment of InO the present invention; FIG. 2 is a section of FIG. 1 along the I-I line; oFIG. 3 is a schematic view of a flow pattern of the above embodiment; FIGS.4 and 5 are flow patterns near the circumference t15 and in the inner part of the container, respectively, observed from the A-A plane of FIG. 3; FIG. 6 is an elevational view of a second embodiment of the present invention; FIG. 7 is a plan view of the above second embodiment; 8 FIG. 8 is an elevational view of a third embodiment of the present invention; FIG. 9 is a plan view of the above third embodiment; FIG. 10 is an elevational view of a fourth.embodiment of the present invention; FIG. 11 is a plan view of the above fourth embodiment.

I-7i, f A 3 i FIG. 12 is a vertical section of an embodiment of the reaction apparatus of the present invention; FIG. 13 is a horizontal section along the II-II line in FIG. 12; FIG. 14 is a vertical section of another embodiment of the reaction apparatus of the present invention; FIG. 15 is a horizontal section along the IV-IV line in FIG. 14; a.s. FIG. 16 is a vertical section of still another embodia 10 ment of the reaction apparatus of the present invention; 0" FIG. 17 is a horizontal section along the VI-VI line in FIG. 16; and FIG. 18 shows experimental results obtained for the ona stay time distribution for Comparative Examples Bl and B2 o,",p 1 5 and Experimental Examples Bl to B3 of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS: Several embodiments of the stirring apparatus of the present invention will be first explained in the following 4a a with reference to FIGS. 1 to 11. Next, three embodiments of the apparatus for polymerization reactions of the present invention will be described with reference to the FIGS. 12 to 18.

FIGS. 1 and 2 show an embodiment of the stirring apparatus of the present invention. A rotational shaft 2 is inserted in a containe: 1, and a flat wing 3 and a slanted -8 i wing 4 are fixed to the rotational shaft. The flat wing 3 is disposed substantially parallel to the center axis of the rotational shaft 2. The area of the flat wing is more than 60% of the sectional area encircled by the center axis 5 of the shaft, the inner wall of the container 6 and the fluid surface 7. If this area is less than 60% a high stirring performance that will be discussed below can not be attained. Also, the slanted wing 4 is fixed to the st*, rotational shaft 2 with a certain angle against the center axis.

s FIG. 3 shows a flow pattern along the horizontal section of the container (the section indicated by II-II in FIG. 1) while stirring highly viscous materials using the wings of FIGS. 1 and 2. When the flat wing 3 is moving 15 at a speed (indicated by Arrow 10), the outer portion of the fluid is pushed by the flat wing 3 and moves in the same direction. With the effect of the viscous resistance 0 4 between the wing and the wall 6, however, the velocity a 0 (indicated by Arrow 11) of the fluid near the circumference oQ#444 is less than the speed 10 of the flat wing 3.

As a result, the displaced volume of the fluid due to this movement of the wing 3 becomes different from that of the fluid near the circumference, and this difference causes a flow in the radial direction, appearing as a flow velocity (indicated by Arrow 12) in the radia 'ection i I 1. near the flat wing 3. This radial flow toward the center changes its direction as it reaches the center and becomes an inner circulating flow with an inner flow velocity (indicated by Arrow 13).

The inner circulating flow thus generated is strong, and the inner flow velocity 13 becomes much greater than the velocity (indicated by Arrow 14) of the surface of the rotational shaft 2 and the velocity of the slanted wing 4 at its inner portion, 0 On the other hand, the velocity of the fluid near ,o the circumference 11 is much smaller than the Velocity (indicated by Arrow 16) of the slanted wing 4 at its outer portion.

FIG. 4 shows a flow pattern near the circumference observed from the A-A plane in the pointed direction.

B o, Because the velocity 11 of the fluid near the circumference is small compared to the veloc 4 ty (indicated by Arrow 16) of the slanted wing 4, the fluid moves downward as indicated by arrow 17.

FIG. 5 shows a flow pattern of the inner part observed from the A-A plane. In this part of the apparatus of the present invention, quite contrary to the situation near the circumference shown in FIG. 4, the inner flow velocity 13 becomes large compared to the velocity (indicated by Arrow 15) of the slanted wing 4, and the fluid

I

moves upward as indicated by arrow 18.

Since the large flat wing 3 is intended to genet' the two types of flow as described above, certain restrictions on its size have to be observed. In FIG, 3, a positive pressure is generated at the front of the flat wing 3 because the fluid is being displaced by the moving flat wing 3: a negative pressure is generated at the rear as the space created by the motion of the flat wing is being filled up by the inner circulating flow of the fluid. Because of this pressure difference, a shortcut flow is generated in o* the space between the tip of the flat wing 3 and the inner wall 6 of the container, Because the inner circulating flow decreases as the shortcut flow increases, this shortcut flow has to be 15 minimized, From the various experimental results obtained So, by the inventors of the present invention it has been found that the area encircled by the center axis 5 of the Sa rotational shaft and the outer edge of the flat wing 3 o a needs to be more than 60%, preferably more than 80%, of the area enclosed by the center axis 5, the fluid surface, and the wall 6 of the container.

Also, tne angle at which the slanted wing is attached can be selected rather freely, While in FIGS. 1 to 3 an up flow near the circumference and a down flow in the inner part are shown to be generated, reversed flows canl be 11

~I-

created if the above angle is flipped.

While an embodiment of the present invention has been described in terms of its structure, functions and effects, the present invention is by no means -restricted to the above stirring apparatus and naturally includes the examples discussed below.

FIG. 6 is an elevational view of a second embodiment of the present invention. FIG. 7 is a plan view of the stir- 4i ,*93 ring apparatus shown in FIG. 6 having two flat wings 3(a), 9949 04#,,010 3(b) and two slanted wings and shows that the qtiring apparatus of the present invention is not t restricted by the number oi the flat and slanted wings.

FIG. 8 is an elevational view of a third embodiment t of the present invention. FIG. 9 is a plan view of the 15 stirring apparatus shown in FIG. 8 having one flat wing 3 and a screw type slanted wing 4, and shows that the stirring apparatus of tile present invention is not restricted to flat slanted wings.

FIG, 10 is an elevated view of a fourth embodiment of tit[ 4 the present invention, IG. 1.1 is a plan view of the stirring apparatus of the present invention having one slanted wing 3 and three slanted wings 4 4 4 attached at different angles from the flat wing, and shows that the stirr4nq apparatus of the present invention is not restricted by the number of the slanted wings and their direction of 12 12 attac,..rint.

In the second or the third embodiment above, the flat wings and slanted wings are capable of achieving similar effects and results as explained for the first embodiment and generate "lows in every part of the container to attain fast and efficient stirring.

Further, while, in any of the above embodiments, the S slanted wings are disposed in the slow flow near the 9 a *oB circumference and the fast inner circulating flow in the .aon", 10 inner part, the slanted wings can be made to generate 0 o a up-and-down flow cnly in one of the above two types of g flow.

i'he following are experimental results to show some o 4 9 effects of the stirring apparatus of the present invention in comparison to the conventional stirring apparatus.

o Comparative Example Al Inside a transpherent container of acrylic resin whose inner diameter and height are both 200 mm, an anchor type o wing whose diameter is 190 mm was disposed. Each of I2 and NazS 2 03 was dissolved into a starch syrup solution which has the viscosity of 200 poise to make two different solutions. The two solutions were supplied to the container separately, and the wing was rotated at n 15 (rpm).

Subsequentlyt the time necessary for the dark brown color of I2 to vanish due to the effect of NazSo0 3 t(min), was 13 1 measured, and the required number of rotation N =n-t was calculated.

As a result, it was found that even with values of N over 200 the color of 12 remained in the upper and center parts of the container.

Comparative Example A2 In the same container as used in Comparative Example Al, a helical ribbon wing whose diameter is 190 mmt was disposed and N =n-t was obtained by measuring t(min) in 01l0 the same manner as the above.

Asa eslt it was found that at N =35 the 12 color disappered everywhere ex<cept for the vicinity of the rotational shaft, and at N =60 the color disappeared from the entire container.

Experimental Examples Al to A4 In the same container as used in Comparative Example Al, each of four sets of new wings of the present invention whose corresponding diameter' of' a flat wing is 19 0 mm was 4 OJO 0disposed, and N =n-t was obtained by measuring the time t(min) for the disappearance of the 12 color in the entire container in the same manner as in Comparative Example Al.

The results are shown in TABLE 1 below.

144 TABLE 1 41441

I

I a 4 4

I

'#44 '4444 4 4 a,

I

14-4 Ii *41

I

4 4 4*

II

a 4*4 4 altI 4 4 4441 Exp. Example Wing shapes used N =n-t .3 FIGS. 8 and 9 42 4 FIGS. 10 and 11 a From TABLE I. it is clear that the stirring apparatus '10 of the present invention is superior, despite its simple structure, even to the helical ribbon wing, which is said, to mix highly viscous fluids in the shortest time.

The ent invention comprises a large flat wing whose area is more than 60% of the sectional area encircled by 15 the center axis of a rotational shaft, the inner wall of a container and the surface of supplied fluid, and this large flat wing is attached to the, rotational shaft in a substancially parallel fashion. Therefore, a slow flow near the. circumference of the container and a fast inner ciroulating flow inside are generated because of rotation of this flat wing. Also, a slanted wing dttached to the rotational shaft at a certain angle from the center axis is disposed and rotated in either one of the above two flows or in both of them to generated an up-and-down flow in order to ensure the complete flow of fluid in every part is 28 between said stirring means to divide said container in the 2 i i 1131 r~of the container and efficient stirring.

Consequently, the present invention achieves a fast and efficient stirring performance in treating highly viscous liquids or slurry by quickly forming a complete flow pattern covering the entire container.

In the following, embodiments of the stirring tower type apparatus for polymerization reactions of the present application are explained in detail with reference to FIGS. 12 to 18.

10 FIG. 12 is a vertical section of an embodiment of the t So"* reaction apparatus of the present invention.

In FIGS. 12 and 13, a rotatio -l shaft 25 is inserted into a container 24 having a fluid supply inlet 21, a o° fluid outlet 22 and a jacket 23. This rotational shaft is sealed rotatably by a shaft sealing means 26. The con- S* tainer 24 is devided by a number of obstructing plates 27 serving as partioning means, and the piston flow characteristics are secured in the direction of flow. Porous plates with a certain opening ratio are used as obstructing plates.

In stirring chambers 28 partitioned by the obstructing plates, stirring means are attached to the rotational shaft 25. The stirring means in each of the stirring chambers comprise the center axis 50 of the rotational shaft a flat wing parallel to it, and slanted wings 30(b), 30(c) wnich form a set with one of the flat wings 16 i above. These three slanted wings, whose shape is close to a rectangular plate, are attached to the rotational shaft at 900 apart from the flat wing and other slanted wings with their vertical position on the shaft shifted from each other, and their slanting angle and direction are the same with respect to the center axis 50 as shown in the figure.

FIG. 13 is a horizontal section along the II-II line in FIG. 12. As the rotational shaft rotates, the flat wing 29 moves in the direction of Arrow 31, and the fluid displaced by this motion forms a large circulation flow in *a the inner part as indicated by Arrow 32. Since the velocity of this circulating flow is greater than that of the slanted wings 3 30(b), 3C0c), the flow takes over the wings in effect, and the fluid in the circulating t.

flow is pushed up by the slanted wings 30 and moves upward.

40, On the other hand, since the fluid near the container wall is under the influence of viscous resistance from the wall and moves slowly in the direction along the wall as indicated by Arrow 33 in FIG. 13, it is pushed down by the slanted wings 30 and moves downward. Thus, an up flow in the center part and a down flow near the wall are generated to form an overall up-and-down circulating flow.

Also, if the slanted wings are tilted in the opposite direction of the wings shown in the figures, a down flow in the center part and an up flow near the wall are generated.

I? .,t i As described above, circulating flows in both of the horizontal and up-and-down directions are generated at the same time in the stirring chamber 28, and thus efficient mixing can be achieved.

Also, since the stirring effect of the flat wing reaches even to the corners of the container, there is no room for "dead space." In the case of normal stirring wings, flow near the rotational shaft tends to be insufficient, and gelled material a l0 or the like attaches to the shaft. In the reaction apparatus of this embodiment of the present invention, however, D a strong circulation flow is formed around the rotational shaft 25, and the attachment of gelled material is prevented.

As described above, since the large flat wing 29 plays the role of generating a horizontal circulating flow, its size is subject to certain restrictions. In FIG. 13, in the front of the flat wing 29 in the direction of rotation, a positive pressure is generated because of the displacement of fluid: in the rear, a negative pressure results as the space created by the motion of the wing is being filled up by circulating flow. Thus, a pressure difference appears between the front and rear of the flat wing, and a shortcut flow occurs in the gap between the inner wall 51 of the container and the tip of the flat wing 29. Because as this shortcut flow increases the overall circulating flow 18 f' decreases, the shortcut flow has to be minimized. The inventors of the present invention, from various experimental results, have found that the area encircled by the center axis 50 of the rotational shaft and the outer edge of the flat wing 29 should be more than 60%, preferably more than 80%, of the area enclosed by the center axis the inner wall 51 of the container and the obstructing plate 27.

Also, the power required for stirring in the present C.10 invention is similar to that for the conventional large 4 0 S paddle wings, and belongs to the category of low power requirement as stirring wings for highly viscous fluids.

The heat transfer coefficients of the container walls are better in the present embodiment than the conventional stirring wings for highly viscous materials because of the scraping effect of the large flat wing ard the exchange of fluid by the up-and-down circulating flow.

Furthermore, the structure of the present invention is as simple as the paddle and anchor wings; it is sampler than the helical ribbon wing often used for highly viscous fluids and the stirring wings of the previous patent applications discussed above.

As discussed above, this embodiment of the present invention satisfies all the requirements listed above for a reaction apparatus for continuous polymerization reactions.

19 Also? althopgh porous plates are used as obstructing plates in the above as an example, annular rings or any other types of structures and shapes may be used instead.

FIG. 14 is a vertical section of another embodiment of the reaction apparatus of the present invention, and FIG. 15 is a horizontal section along the IV-IV line in FIG. 14.

In this embodiment, two flat wings 29 29 are attached to the rotational shaft 25 at 1800 apart from 1110 each other in a parallel fashion to the center axis 50 of (11,1 0 the rotational shaft 25. Togetherl with these flat wings, four slanted wings 30(a), 30(b), 30(c), 30(d), two in a high positiQn and the other two in a low position, are attached to the rotational shaft 25 at 9 0 apart from the ilat wings. They are tilted with respect to the center axis 0 50 of the rotational shaft 25 at the same angle and in the same direction as shown in the figures.

9,4 As this emboDdiment indicates, there exist no restrictions as to the number of flat and slanted wings for the reaction apparatus of the present invention. Also, partitioning means that are also a heat exchanger comlprising tube plates a shell 41 and tubes 42 are disposed between stirring chambers so that the highly viscous fluid passing through the tubes 42 can be cooled or heated by heat conducting oil or the like outside the tubes and insid~e the shell.

The tubes 42 act as obstructing plates as well as a heat exchanger.

FIG. 16 is a vertical section of still another embodiment of the reaction apparatus of the present invention, and FIG. 17 is a horizontal section along the VI-VI line in FIG. 16.

In this embodiment, stirring means comprise a combinas. :tion of one flat wing 29 and a spiral slanted wing o0 This embodiment shows that the reaction apparatus of the 1 010 present invention is by no means restricted to flat slanted wings. Also, a coiled tube 42 is inserted into a partitioning means between stirring chambers 28 so that the highly viscous fluid passing through this part can be S: 1 cooled or heated by letting heat conducting oil or the like o0 flow in the tube. This coiled tube also acts as a partia 9 so tioning means.

In the following, experimental results for the stay o timi distribution for reaction apparatuses of the present 0 00 invention and of conventional types.

In this experiment, a test apparatus comprising a long cylindrical container of clear acrylic resin whose inner diameter is 200 mm was used, and this container was divided into 28 stirring chambers and 27 heat exchanging parts.

The experiment was carried out for different stirring wings attached to the test apparatus in turn.

21- I-I I i i -a~ The height of the stirring chamber was 100 mm, and four acrylic tubes whose inner diameter is 23 mm were disposed in the heat exchanging part whose height was also 100 mm. This combination is almost identical to the apparatus in FIG. 14.

Starch syrup of 200 poise was used and supplied from the bottom of the container using a gear pump. While the starch syrup was being supplied continuously, red ink was injected as a pulse and watched by the eye as it flowed, and the concentration at the outlet was continuously *9 09" measured to find the stay time distribution.

TABLE 2 summarizes the observation of flow and the wings used. In the table, the comparative examples are 0 O* S0* for the case of conventional reaction apparatuses, and the experimental examples are as described above.

t4 0 t9 0 0 o *(ic 22 L TABLE 2 t Li it t tifr tIii ii t t w- LI t t: i Wings used Flow in the stirring chamber Comparative Two large Almost no up-and-down flow Example Bl paddles insufficient flow areas in the center Comparative Helical ribbon Up-and-down flow observed Example B2 Insufficient flow areas between the ribbon wings Experimental FIGS. 12 Up-and-down flow observed Example Bl and 13 No insufficient flow areas Experimental FIGS. 14 Ditto Example B2 and Experimental FIGS. 16 Ditto Example B3 and 17 I- i4I--,- From TABLE 2, the following becomes clear: There exist insufficient flow areas for large paddle 9 o* and helical ribbon wings which are conventional stirring methods.

In Experimental Examples Bl to B3, in which the wing configurations of the present invention were used, no insufficient flow areas were observed.

FIG. 18 shows results obtained for the stay time distribution of starch syrup in the cylindrical container for Comparative Examples B1 and B2 and Experimental Examples 23 Bl to B3. In FIG. 18, E(f) on the ordinate is the stay time distribution as a function of the dimensionless time which is on the abscissa- In the case of Comparative Example Bl, the peak height and position are shifted considerably from the perfect mixing chamber array model, and the amount of fluid staying for a long time is quite large, which is not a desirable 4:44. situation, In the case of Comparative Example B2, the peak height is low, and the corresponding number of chamers a in lhe perfect mixing chamber array model is also small 4 S O indicating that the situation is away from the piston flow.

o g The reason for this can be that part of the fluid tends to a 04 4 0 11 bypass toward the outlet because the up-and-down circulation 4 44 flow is too strong.

44 The stay time distributions of Experimental Examples B1 to B3 are close to the perfect mixing7 chamber array model and are indeed what is desired.

.The reaction apparatus of the present invention shows the following desirable effects, and present invention is to provide a stirring tower type apparatus for polymerization reactions which is useful industrially, The reaction apparatus of the present invention can achieve the piston flow characteristics and, together with special mixing effects, may control the temperature 1 24 i 't of each stirring area independently as a polymerition reaction progresses because partitioning means are disposed between the stirring areas. Also, tubes for heat exchange can be inserted into the partitioning means to make indepe dent temperature control in the each stirring area still easier.

Since, in the reaction apparatus of the present invention, two types of stirring wings, slanted and flat, are attached to the rotational shaft, up, down, horizontal tL circulation flows are formed, and a high mixing efficiency is achieved for highly viscous liquid and slurry type materials without areas in which flow is obstructe,.

In conventional reaction apparatuses, gelled material often attaches to the rotational shaft because the flow around the shaft is not sufficient, while in the i reaction apparatus of the present invention no attachment of gelled material occurs because of its high mixing performance, Since the reaction apparatus of the present invention has two types of wings, slanted and flat, it requires less power to stir than the one with flat wings only.

The scraping effect of the flat wings and the exchange of fluid due to the generation of an up-and-down flow help to improve the heat transfer coefficients, II i

E

,resulting in superior heat conductance.

()The reaction apparatlis has a stmple structure.

ii' 4 ~4 44 4 4 #4*4 4 4 4 4 4 4 4* ~4"4 4 4 4 ~4 *4 4 44 .4 *4 1 4 *1 4 44 4 1 *44 4 4* 4 44 *1 *444, 4 26 L

Claims

4. 4 .454 *4 5* a I 444445 4 4 The claims defining the invention are as follows:- 1. A stirring apparatus comprising a container, a vertical rotational shaft inserted into said container, a flat wing whose area is more than 60% of the sectional area encircled by the center of said rotational shaft, an inner wall of said container and the surface of materials being stirred in said container, said flat wing being attached to the side of said rotational shaft in a sufficiertly pare. 1-1l fashion to the center axis of said :cotational shaft, and a slanted wing attached to the side of said rotational shaft at a certain slanting angle with respect to said center axis of said rotational shaft. 2. A stirring apparatus as claimed in Claim 1, characterized in that at least one flat wing and a 15 plurality of said slaited wings are attached to said rotational shaft. 3. A stirring apparatus as claimed in Claim 1, wherein said slanted wing has a screw like shape. 4. A stirring tower type apparatus for polymerization 20 reactions comprising a cylindrical container having a fluid supply inlet and a fluid outlet, a vertical, rotational shaft coaxially inserted into said container, stirring means having a plurality of flat wings attahced to the side of said rotational shaft in a parallel fashion to the center axis of said rotational shaft and a plurtality of slanted wings attached to the side of said rotational shaft in a tilted fashion with respect to said center axis forming sets with said flat wings, and partitioning means S throu~gh which materials being stirred may flow dispose6 I I 15 c I 28 between said stirring means to divide said container in the V longitudinal direction. A stirring tower type apparatus as claimed in Claim 4, wherein said partitioning means comprise porous plates.
6. A stirring tower type apparatus as claimed in Claim 4, wherein said partitioning means comprise tubes, tube plates and a shell such that materials being stirred may flow in the space between the tubes.
7. A stirring tower type apparatus as claimed in Claim 4, wherein said partitioning means comprise a coiled tube, such that materials being stirred can flow around the tube. 4
8. A stirring tower type apparatus as claimed in any one of Claims 4 to 7, wherein said slanted wing has a screw S like shape. 15 9. A stirring apparatus substantially as hereinbefore described with reference to Figures 1 to 5, Figures 6 and 7, Figures 8 and 9 or Figures 10 and 11 of the accompanying So drawings.
10. A stirring tower type apparatus for polymerization 20 reactions substantially as hereinbefore described with 4*9941 S° reference to Figures 12 and 13, Figures 14 and 15 or Figures 16 and 17 of the accompanying drawings. DATED JANUARY 31 1991 MITSUBISHI JUKOGYO KABUSHIKI KAISHA By their Patent Attorneys KELVIN LORD AND COMPANY PERTH, WESTERN AUSTRALIA. V \i' 1