CA1184342A - Method of continuous polymerization - Google Patents
Method of continuous polymerizationInfo
- Publication number
- CA1184342A CA1184342A CA000384397A CA384397A CA1184342A CA 1184342 A CA1184342 A CA 1184342A CA 000384397 A CA000384397 A CA 000384397A CA 384397 A CA384397 A CA 384397A CA 1184342 A CA1184342 A CA 1184342A
- Authority
- CA
- Canada
- Prior art keywords
- paddles
- shafts
- polymerization
- reactor
- action
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B7/00—Mixing; Kneading
- B29B7/30—Mixing; Kneading continuous, with mechanical mixing or kneading devices
- B29B7/34—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices
- B29B7/38—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary
- B29B7/46—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with more than one shaft
- B29B7/48—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with more than one shaft with intermeshing devices, e.g. screws
- B29B7/482—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with more than one shaft with intermeshing devices, e.g. screws provided with screw parts in addition to other mixing parts, e.g. paddles, gears, discs
- B29B7/483—Mixing; Kneading continuous, with mechanical mixing or kneading devices with movable mixing or kneading devices rotary with more than one shaft with intermeshing devices, e.g. screws provided with screw parts in addition to other mixing parts, e.g. paddles, gears, discs the other mixing parts being discs perpendicular to the screw axis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/60—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
- B01F27/73—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with rotary discs
- B01F27/731—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis with rotary discs with two or more parallel shafts provided with perpendicularly mounted discs, e.g. lens shaped, one against the other on each shaft and in circumferential contact with the discs on the other shafts, e.g. for cleaning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
- B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
- B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
- B29C48/405—Intermeshing co-rotating screws
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
- B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
- B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
- B29C48/41—Intermeshing counter-rotating screws
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/02—Polymerisation in bulk
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
- C08G2/10—Polymerisation of cyclic oligomers of formaldehyde
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)
- Polymerisation Methods In General (AREA)
- Other Resins Obtained By Reactions Not Involving Carbon-To-Carbon Unsaturated Bonds (AREA)
Abstract
ABSTRACT
A method of continuous polymerization of a liquid polymerization medium to obtain fire particles of polymer product, the reaction being continuously effected in a polymerization reactor wherein mixing is effected by the action of a plurality of paddles mounted on each of dual rotating shafts, characterised in that the said dual shafts rotate in reverse directions to each other, and the said paddles are enclosed by walls of the said reactor the inside surface of the said walls closely defining the surface generated by the rotation of the ends of both sets of paddles; the ends of major axes of the said paddles on one rotating shaft periodically approaching the ends of minor axes of the corresponding paddles on the other rotating shaft to effect a mixing action as well as a longitudinal shearing action across a notional interface between said two shafts. The method is particularly useful for the polymerization of trioxan.
A method of continuous polymerization of a liquid polymerization medium to obtain fire particles of polymer product, the reaction being continuously effected in a polymerization reactor wherein mixing is effected by the action of a plurality of paddles mounted on each of dual rotating shafts, characterised in that the said dual shafts rotate in reverse directions to each other, and the said paddles are enclosed by walls of the said reactor the inside surface of the said walls closely defining the surface generated by the rotation of the ends of both sets of paddles; the ends of major axes of the said paddles on one rotating shaft periodically approaching the ends of minor axes of the corresponding paddles on the other rotating shaft to effect a mixing action as well as a longitudinal shearing action across a notional interface between said two shafts. The method is particularly useful for the polymerization of trioxan.
Description
3~ .
This invention re~a-tes to a method of continuous polymerization of a liquid polymerization medium to obtain fine particles of polymer product? the reaction being continuously effected in a polymerization reactor wherein rnl~ing is effected by the action of a plurality of paddles mounted on each of dual rotating shafts~
The ho~o- or co-polymerization of molten trioxan is wid~ly practised. Thus the production o~ poly-o~ymethy-lene (co-) polymer, is industrially ~ery important in the production of polyacetal resin.
The present in~ention is particularly suitable to such continuous polymerization of trioxan, although it can be used for other processes wherein a phase change takes place and in which a desired granulating step is re-quirsd.
When moltQn trio~an ~if desired containingmaterial comonomer for example one or more o~ the monomers ethylene o~ide, dioxolan, butanediol, formal and diethylene glycol formal) ls polymerized in the presence of a strong acid e.g, phosphorous penta~luoride or pQrchloric acid or tin chloride or boron trifluoridQ, to giVQ for example poly-oxym~thylene, the vQry rapid reaction rate changes the liquid phase of ~e poly~lerization medium into a solid phase through a short intermediatQ slurry phase.
If the reaction is e~fected without a comminuting step large blocks of stiff p~oduct will be obtained resul-tlng in difficult handling, a deterioration in quality due to accumulated polymerization heat, and lowered polymerization , ., , '"~''~.
This invention re~a-tes to a method of continuous polymerization of a liquid polymerization medium to obtain fine particles of polymer product? the reaction being continuously effected in a polymerization reactor wherein rnl~ing is effected by the action of a plurality of paddles mounted on each of dual rotating shafts~
The ho~o- or co-polymerization of molten trioxan is wid~ly practised. Thus the production o~ poly-o~ymethy-lene (co-) polymer, is industrially ~ery important in the production of polyacetal resin.
The present in~ention is particularly suitable to such continuous polymerization of trioxan, although it can be used for other processes wherein a phase change takes place and in which a desired granulating step is re-quirsd.
When moltQn trio~an ~if desired containingmaterial comonomer for example one or more o~ the monomers ethylene o~ide, dioxolan, butanediol, formal and diethylene glycol formal) ls polymerized in the presence of a strong acid e.g, phosphorous penta~luoride or pQrchloric acid or tin chloride or boron trifluoridQ, to giVQ for example poly-oxym~thylene, the vQry rapid reaction rate changes the liquid phase of ~e poly~lerization medium into a solid phase through a short intermediatQ slurry phase.
If the reaction is e~fected without a comminuting step large blocks of stiff p~oduct will be obtained resul-tlng in difficult handling, a deterioration in quality due to accumulated polymerization heat, and lowered polymerization , ., , '"~''~.
2 ~ 3~
yield. Reaction under a high shearing action is a particularly preferred technique for the prevention of large blocks of product and for providing e~ective removal of polymeri~ation heat of which various detailed methods have bee~ proposed. A reactor which ls a mixer extruder having dual shafts supporting paddles is a useful apparatus I because it imparts a high shearing ac-tion to the contents.
¦ For example published Japane~e Paten-t specification No.
¦ 84890/76 discloses a dual shaft mlxer co!nprising a combina-tion of elliptical paddles. Such features have a disad-I vantage however when used for polymerization reactions ! in that the dual shafts all rotate in the same direction~
The features of this system are the strong shearing action ~ on the contents, a self clsaning action, the ability to fully I 15 granulate the conten-ts of a polymeriæing apparatus, and paddles free from polymer adhering thereto. Howe~er such - advantages are offset by -the higher loads that are applied to the rotating shafts, and for safe operation the contents of the vessel must be restricted. For the solutlon of this problem published Japanese Patent specification No.
86794/78 discloses a method which restrlcts the degree of high shearlng actior. to a lower value and provides a second reactor of lower shearing action. Such two-stage reaction techniques however restrict the conversion obtained to a specif`ied range, and if it increases too much the load on the final vessel providing high shearing becomes too high, and i~ the conversion is too low the degree of filling of the 4econd reactor increases so as to cause agglomeration of solid particles leading to a deterioration o~ quality.
Thus the method according to the said Japanese Patent specifica-tion No. 86794/78 is limited in adaptability to change of material quality and product grade. It is therefore desirable to provide an optimum shearing action in the same reactor in accordance with the progress of reaction, While it is possible in dual shaft apparatuses using shafts rotatlng in the same direction to vary the 1' .
'
yield. Reaction under a high shearing action is a particularly preferred technique for the prevention of large blocks of product and for providing e~ective removal of polymeri~ation heat of which various detailed methods have bee~ proposed. A reactor which ls a mixer extruder having dual shafts supporting paddles is a useful apparatus I because it imparts a high shearing ac-tion to the contents.
¦ For example published Japane~e Paten-t specification No.
¦ 84890/76 discloses a dual shaft mlxer co!nprising a combina-tion of elliptical paddles. Such features have a disad-I vantage however when used for polymerization reactions ! in that the dual shafts all rotate in the same direction~
The features of this system are the strong shearing action ~ on the contents, a self clsaning action, the ability to fully I 15 granulate the conten-ts of a polymeriæing apparatus, and paddles free from polymer adhering thereto. Howe~er such - advantages are offset by -the higher loads that are applied to the rotating shafts, and for safe operation the contents of the vessel must be restricted. For the solutlon of this problem published Japanese Patent specification No.
86794/78 discloses a method which restrlcts the degree of high shearlng actior. to a lower value and provides a second reactor of lower shearing action. Such two-stage reaction techniques however restrict the conversion obtained to a specif`ied range, and if it increases too much the load on the final vessel providing high shearing becomes too high, and i~ the conversion is too low the degree of filling of the 4econd reactor increases so as to cause agglomeration of solid particles leading to a deterioration o~ quality.
Thus the method according to the said Japanese Patent specifica-tion No. 86794/78 is limited in adaptability to change of material quality and product grade. It is therefore desirable to provide an optimum shearing action in the same reactor in accordance with the progress of reaction, While it is possible in dual shaft apparatuses using shafts rotatlng in the same direction to vary the 1' .
'
3~
shearing force by changing the pitch of the screws or by changing the clearance inside the apparatus, since the progress of the reaction depends upon slight changes of the reaction conditions and material quality, such apparatus is not readily adaptable. Thus there is a need for apparatus in which shearing action ch~m ges according to the progr0ss of reaction.
Hitherto a paddle-type dual shaft mixer the shafts of which rotate in reverse directions to each other has not been considered as a polymerization apparatus because it effects only low shearing force and is not self-cleaning.
~lowever it has now been found that in such a mixer the shearing force automatical-ly changes in the desirable direction corresponding to changes in phase occurring in liquid phase polymerization reactions.
The invention provides a method of continuous polymerization of a liquid polymerization medium to obtain fine particles of polymer product by conducting the reaction in a polymerization reactor wherein ~.ixing is effected by the action of a plurality of elliptical paddles mounted on each of dual rotating shafts, characterised in that the shafts are rotated in reverse directions to each other~ and the paddles are enclosed by walls of the reactor with the inside surface of major axes of the elliptical paddles on one rotating shaft periodically approaching the ends of the minor axes of the corresponding elliptical paddles Oll the other rotating shaft to effect a mixing action as well as a longitudinal shearing action across a notional interface between said two shafts.
'l'he method according to this invention can expeditiously be used for polymerization reactions in which a liquid-to-solid phase-change occurs, particularly for the continuous polymerization of trioxan.
This invention is hereinafter described and illustrated in the accompanying drawings, of which Figure 1 is a schematic elevation of the mixer reactor 1 used in the method of the invention, the broken portion showing the position of the shafts;
Figure 2 is a cross-sectional view on line A-A
in Figure 1, and Figure 3 is a partial elevation of a shaft of the mixer.
The mixer 1 includes a closed long narrow space 2 having a cross-section as shown in ~igure 2. The space 2 accommodates two shafts 3 and 40 On the flrst shaft 3 and second shaft 4 are mounted a plurality of paddles 5, 6, 7, 8, ,.. in an arrangement whereby corresponding paddles on both the shafts engage with each other alternately.
Successive paddles on the same shaft are,displaced for example by 90 or 60 , to vary the mixing characteristics~
Skewed feed paddles 7, 8 are also included in the paddles, Around the periphery of the paddles an enclosing wall 9 ' is provided with its lnside surfaces in close contact with 20 ' the paddles. The mixer 1 has an inlet port for charging the liquid poly~leri~ation medium and an outlet port 11 ~or discharging the solid product. The liquid medium e.g.
trioxan ls charged from the charging port 10 into one end of the Mixer reactor 1, and the catalyst is introduced through the 'catalyst inlet 12 and mixed with the liquid medium, and,the solid product is discharged from the discharging port 11 provided at the other end. The position of the catalyst inlet 12 is not limited to the upper portion of the mixer, and the catalyst ca,n be introduced from any direction. The catalyst can be charged also together with the starting material e.gO
trioxan. As shown in Figure 3 a feed screw 13 is positioned near the charging port and pushes forward the contents. The skewed feed paddles 7 arranged between the adjacent non-skewed paddles help to push the contents forward.
The relationship of the movements of paddles and contents when the dual shafts rotate in the same direction or in reverse directions is shown in Figure 4 and Figure ~5. ~igure 4 shows the movement of the contents when the shafts rotate in the same direction, and Figure 5, when the shafts rotate in reverse directions, the contents sho~n in hatched outline. In ~igure 4 the paddles rotate by 90 in the stages (a~ (b) -~ (c). With respec-t to the space (B) enclosed by the paddles 5~, 6~ and walls 9, the space volume, while undergoing some change, is merely moved Prom right to left. Thus, only a small mixing effect is obtained in this process, while the large resistance increases the load applied on the apparatus. In contrast to this in ~igure 5, which lllustratss the invention, the space (E) in the stage (a) is decreased by compression when moving from stage (b) to (c), the space (G) being gradually expanded. Therefore the contents move in the arrowed direction (F) through the clearance bet~een the paddles 5 and 6, and longitudinal mixing and adequate shearing ! 20 are effected. There is thus a significant difference between po:Lymerization processes using co-directional rotation of the shafts and by the reverse-directional rotation, as hereafter further described.
As set forth in published Japanese Patent specification No. 86794/78, the polymerization of trioxan is divided into three stages:
In the first stage rapid ~eaction has not yet occurred I or the reaction is 1Q~ than 20% completed~ the contents still being in liquid state~ The requirements for the reactor mixer i~ this stage is merely a good mixing ability, In the second stage, reaction proceeds with a rapid phase change from liquid to solid. The reaction proce~ds in the range from 20 to 600/o completion. The re~uired properties of the reactor mixer are strong shearing effects and good removal of heat. The third stage results in the formation of fine particles of solid (providing ~ull shearing force 6 ~ qL2 has been applied in the preceding stage), the liquid not remaining as a continuous phase~ Requirements for th~
reactor in this stage are slow agitation which is enough to pr~vent adhesion between solid particles, heat removal, S and a retention time to allow for completion of the poly-merization. Shearing effects are not required.
A feature of the dual shaft reactor described in the said Japanese Paten-t specifica-tion No. 84890/76 with elliptical paddles rotating in the same direction, which had been considered best before the advan-t of the pres~nt in~ention, is such that two corresponding paddles rotate always in contact with each othsr (with self-cleaning effect) and rotate the space deflned by the I paddles and the walls of the mixer, while changing its 1 15 volume and shape to effect substantial deformation of the contents. This feature has favourable effect in the first stage of reaction, but the effect arising from the -fact that the paddles are always in contact ~ith each other, is aalall because o~ the low ~iscosity of the contents at -this stage. These features are favourable also in ths second stage where a strong shearing force is re-¦ quired; a reason why the same directional rotation systemhas been eo;nsidered desirable. In the third stage, thQ
contents are in substantially the form of solid particles, the ~olume of which and the interstitial spaces aredifficult to change. If such contents are forced to change ~olume and form, they show a strong resistance and j impose a very high load, and therefore the apparatus should be operated at a lower degree of filling. Howe~er a low fllling degree leads to sinking of solid par-ticles and uneven - force exerted on the shafts resulting in bent shafts and increased load. Thus the operztive range is extremely linlited~ To increase the retention time, in addition, the length/diameter ratio must be increased, which will further increase shipping of the rotating shafts.
In contrast, in the dual shaft reactor with 7 ~ 3~2 paddles rotating in reverse directions used according to this invention, though coupled elliptical paddles contact at the end of the major axis of a paddle wlth the end of the minor axis of the other paddle, other parts of the paddles do not contact each other on rotation.
Thus the reactor is not self-cleaning in the usual sense.
In the first stage of reaction, the problem of mixing low viscosity liquids has little correspondence with the direction of rotation, and th~ apparatus of this invention has a similar function to the same direction rotation apparatus.
In the second ~tage of reaction high shearing force is roquired9 and the reverse directional rotation apparatus7 which is not a self-cleaning type, at first sight appears to be disadvantageous with weak shearing force~ In fact however the contents at this stage, having a strong tendency to stick to each other, hardly move from the clearance between the paddles, and good shearing action is effected by the reverse directional rotation apparatus, like the same directional rotation apparatus. The clearance between paddles has little significance. In the third stage wherein solid particles have relatively weak adhesion9 the clearance between paddles is of significance in that it allo~s the particles to move into another space through it. Therefore the resistance and load are kept lower even at higher filling degrees. In addition, since the paddle surface is alwayq rubbed by solid particles, undesirable sticking of polymer hardly occurs in spite of the paddles not being self cleaning. Thus the reverse directional rotation apparatus has such characteristics that the exertion of the shearing force, that is the load on the apparatus, automatically changes in a desirable direc-tion as the reaction stage proceeds9 namely according to the phase change of the contents.
For the above reason~, the sa~e directional , 3~;2 ~3 rotation reactor and re~erse directional rotation reactor cannot be operated under the sqme conditions. In the conditions that attain enough filling and keep sufficient retention time for the reverse directional rotation reactor9 the same directional rotation reactor cannot operate because of greatly raised resistance of the solid filling and the maximum filling degree in the operative range for the same directional rotation reaotor is half that for the reverse directional reactor. Even in this range however the shafts of the same directional rotation reactor can be ben* during agitation Because of this whipping effect the clearance between the paddles and the barrel must be made large enough to prevent their contact. This results in a thick layer on the barrel walls leading to poor heat removal and lowered product quality. The operation at lower filling degree extends retention -time and also causes lowered quality.
In the reverse directional rotation apparatus used in the method of this invention, the automatic change of characteristics in the same reactor fully responds to the change of reaction rate due to the change of reaction conditions, material quality and grade Thus the reactor used according to this invention per~its reaction at a rate from zero to nearly 100% and can be used also as the prirnary or secondary reactor in a two-stage reaction method.
This invention will be further described with-reference to the examples.
Exam~le 1 One hundred par-ts by weigh-t o-f trio~an, 2.5 parts by weight of ethylene oxide, and 100 pprn boron trifluoride were charged into a reactor shown in ~igure 1. Water at 25 C was passed through the jacket. The shafts were rotated in reverse directions at 45 rpm. After a residence time of about 8 min. a finely powdered product was obtained from the discharge port. Unreacted monomer content in the product was about 2%.
3~
S
Exa~ple 2 Materials of the same composition as Example 1 were reacted in the apparatus shown in Figure 1, with a residence time of 2 min. The conversion at the discharge port was 600/o. This reactant was further fed into an agitator having paddles inside a cylinder which was water-cooled and agitated for 10 min. The unreacted monomer content in the product taken out of the agitator was 2%.
Comparative Experiment Sirnilar polymerization was tried in the same reactor as in Example 1, with the shafts rotated in the same direction. Upon the start of polymerization, the load on the apparatus increased substantially and the shafts whipped so muc~ that tho paddles contacted the ¦ barrel and stopped the motor. Thus the e~periment could ¦ not be continued.
shearing force by changing the pitch of the screws or by changing the clearance inside the apparatus, since the progress of the reaction depends upon slight changes of the reaction conditions and material quality, such apparatus is not readily adaptable. Thus there is a need for apparatus in which shearing action ch~m ges according to the progr0ss of reaction.
Hitherto a paddle-type dual shaft mixer the shafts of which rotate in reverse directions to each other has not been considered as a polymerization apparatus because it effects only low shearing force and is not self-cleaning.
~lowever it has now been found that in such a mixer the shearing force automatical-ly changes in the desirable direction corresponding to changes in phase occurring in liquid phase polymerization reactions.
The invention provides a method of continuous polymerization of a liquid polymerization medium to obtain fine particles of polymer product by conducting the reaction in a polymerization reactor wherein ~.ixing is effected by the action of a plurality of elliptical paddles mounted on each of dual rotating shafts, characterised in that the shafts are rotated in reverse directions to each other~ and the paddles are enclosed by walls of the reactor with the inside surface of major axes of the elliptical paddles on one rotating shaft periodically approaching the ends of the minor axes of the corresponding elliptical paddles Oll the other rotating shaft to effect a mixing action as well as a longitudinal shearing action across a notional interface between said two shafts.
'l'he method according to this invention can expeditiously be used for polymerization reactions in which a liquid-to-solid phase-change occurs, particularly for the continuous polymerization of trioxan.
This invention is hereinafter described and illustrated in the accompanying drawings, of which Figure 1 is a schematic elevation of the mixer reactor 1 used in the method of the invention, the broken portion showing the position of the shafts;
Figure 2 is a cross-sectional view on line A-A
in Figure 1, and Figure 3 is a partial elevation of a shaft of the mixer.
The mixer 1 includes a closed long narrow space 2 having a cross-section as shown in ~igure 2. The space 2 accommodates two shafts 3 and 40 On the flrst shaft 3 and second shaft 4 are mounted a plurality of paddles 5, 6, 7, 8, ,.. in an arrangement whereby corresponding paddles on both the shafts engage with each other alternately.
Successive paddles on the same shaft are,displaced for example by 90 or 60 , to vary the mixing characteristics~
Skewed feed paddles 7, 8 are also included in the paddles, Around the periphery of the paddles an enclosing wall 9 ' is provided with its lnside surfaces in close contact with 20 ' the paddles. The mixer 1 has an inlet port for charging the liquid poly~leri~ation medium and an outlet port 11 ~or discharging the solid product. The liquid medium e.g.
trioxan ls charged from the charging port 10 into one end of the Mixer reactor 1, and the catalyst is introduced through the 'catalyst inlet 12 and mixed with the liquid medium, and,the solid product is discharged from the discharging port 11 provided at the other end. The position of the catalyst inlet 12 is not limited to the upper portion of the mixer, and the catalyst ca,n be introduced from any direction. The catalyst can be charged also together with the starting material e.gO
trioxan. As shown in Figure 3 a feed screw 13 is positioned near the charging port and pushes forward the contents. The skewed feed paddles 7 arranged between the adjacent non-skewed paddles help to push the contents forward.
The relationship of the movements of paddles and contents when the dual shafts rotate in the same direction or in reverse directions is shown in Figure 4 and Figure ~5. ~igure 4 shows the movement of the contents when the shafts rotate in the same direction, and Figure 5, when the shafts rotate in reverse directions, the contents sho~n in hatched outline. In ~igure 4 the paddles rotate by 90 in the stages (a~ (b) -~ (c). With respec-t to the space (B) enclosed by the paddles 5~, 6~ and walls 9, the space volume, while undergoing some change, is merely moved Prom right to left. Thus, only a small mixing effect is obtained in this process, while the large resistance increases the load applied on the apparatus. In contrast to this in ~igure 5, which lllustratss the invention, the space (E) in the stage (a) is decreased by compression when moving from stage (b) to (c), the space (G) being gradually expanded. Therefore the contents move in the arrowed direction (F) through the clearance bet~een the paddles 5 and 6, and longitudinal mixing and adequate shearing ! 20 are effected. There is thus a significant difference between po:Lymerization processes using co-directional rotation of the shafts and by the reverse-directional rotation, as hereafter further described.
As set forth in published Japanese Patent specification No. 86794/78, the polymerization of trioxan is divided into three stages:
In the first stage rapid ~eaction has not yet occurred I or the reaction is 1Q~ than 20% completed~ the contents still being in liquid state~ The requirements for the reactor mixer i~ this stage is merely a good mixing ability, In the second stage, reaction proceeds with a rapid phase change from liquid to solid. The reaction proce~ds in the range from 20 to 600/o completion. The re~uired properties of the reactor mixer are strong shearing effects and good removal of heat. The third stage results in the formation of fine particles of solid (providing ~ull shearing force 6 ~ qL2 has been applied in the preceding stage), the liquid not remaining as a continuous phase~ Requirements for th~
reactor in this stage are slow agitation which is enough to pr~vent adhesion between solid particles, heat removal, S and a retention time to allow for completion of the poly-merization. Shearing effects are not required.
A feature of the dual shaft reactor described in the said Japanese Paten-t specifica-tion No. 84890/76 with elliptical paddles rotating in the same direction, which had been considered best before the advan-t of the pres~nt in~ention, is such that two corresponding paddles rotate always in contact with each othsr (with self-cleaning effect) and rotate the space deflned by the I paddles and the walls of the mixer, while changing its 1 15 volume and shape to effect substantial deformation of the contents. This feature has favourable effect in the first stage of reaction, but the effect arising from the -fact that the paddles are always in contact ~ith each other, is aalall because o~ the low ~iscosity of the contents at -this stage. These features are favourable also in ths second stage where a strong shearing force is re-¦ quired; a reason why the same directional rotation systemhas been eo;nsidered desirable. In the third stage, thQ
contents are in substantially the form of solid particles, the ~olume of which and the interstitial spaces aredifficult to change. If such contents are forced to change ~olume and form, they show a strong resistance and j impose a very high load, and therefore the apparatus should be operated at a lower degree of filling. Howe~er a low fllling degree leads to sinking of solid par-ticles and uneven - force exerted on the shafts resulting in bent shafts and increased load. Thus the operztive range is extremely linlited~ To increase the retention time, in addition, the length/diameter ratio must be increased, which will further increase shipping of the rotating shafts.
In contrast, in the dual shaft reactor with 7 ~ 3~2 paddles rotating in reverse directions used according to this invention, though coupled elliptical paddles contact at the end of the major axis of a paddle wlth the end of the minor axis of the other paddle, other parts of the paddles do not contact each other on rotation.
Thus the reactor is not self-cleaning in the usual sense.
In the first stage of reaction, the problem of mixing low viscosity liquids has little correspondence with the direction of rotation, and th~ apparatus of this invention has a similar function to the same direction rotation apparatus.
In the second ~tage of reaction high shearing force is roquired9 and the reverse directional rotation apparatus7 which is not a self-cleaning type, at first sight appears to be disadvantageous with weak shearing force~ In fact however the contents at this stage, having a strong tendency to stick to each other, hardly move from the clearance between the paddles, and good shearing action is effected by the reverse directional rotation apparatus, like the same directional rotation apparatus. The clearance between paddles has little significance. In the third stage wherein solid particles have relatively weak adhesion9 the clearance between paddles is of significance in that it allo~s the particles to move into another space through it. Therefore the resistance and load are kept lower even at higher filling degrees. In addition, since the paddle surface is alwayq rubbed by solid particles, undesirable sticking of polymer hardly occurs in spite of the paddles not being self cleaning. Thus the reverse directional rotation apparatus has such characteristics that the exertion of the shearing force, that is the load on the apparatus, automatically changes in a desirable direc-tion as the reaction stage proceeds9 namely according to the phase change of the contents.
For the above reason~, the sa~e directional , 3~;2 ~3 rotation reactor and re~erse directional rotation reactor cannot be operated under the sqme conditions. In the conditions that attain enough filling and keep sufficient retention time for the reverse directional rotation reactor9 the same directional rotation reactor cannot operate because of greatly raised resistance of the solid filling and the maximum filling degree in the operative range for the same directional rotation reaotor is half that for the reverse directional reactor. Even in this range however the shafts of the same directional rotation reactor can be ben* during agitation Because of this whipping effect the clearance between the paddles and the barrel must be made large enough to prevent their contact. This results in a thick layer on the barrel walls leading to poor heat removal and lowered product quality. The operation at lower filling degree extends retention -time and also causes lowered quality.
In the reverse directional rotation apparatus used in the method of this invention, the automatic change of characteristics in the same reactor fully responds to the change of reaction rate due to the change of reaction conditions, material quality and grade Thus the reactor used according to this invention per~its reaction at a rate from zero to nearly 100% and can be used also as the prirnary or secondary reactor in a two-stage reaction method.
This invention will be further described with-reference to the examples.
Exam~le 1 One hundred par-ts by weigh-t o-f trio~an, 2.5 parts by weight of ethylene oxide, and 100 pprn boron trifluoride were charged into a reactor shown in ~igure 1. Water at 25 C was passed through the jacket. The shafts were rotated in reverse directions at 45 rpm. After a residence time of about 8 min. a finely powdered product was obtained from the discharge port. Unreacted monomer content in the product was about 2%.
3~
S
Exa~ple 2 Materials of the same composition as Example 1 were reacted in the apparatus shown in Figure 1, with a residence time of 2 min. The conversion at the discharge port was 600/o. This reactant was further fed into an agitator having paddles inside a cylinder which was water-cooled and agitated for 10 min. The unreacted monomer content in the product taken out of the agitator was 2%.
Comparative Experiment Sirnilar polymerization was tried in the same reactor as in Example 1, with the shafts rotated in the same direction. Upon the start of polymerization, the load on the apparatus increased substantially and the shafts whipped so muc~ that tho paddles contacted the ¦ barrel and stopped the motor. Thus the e~periment could ¦ not be continued.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of continuous polymerization of a liquid polymerization medium to obtain fine particles of polymer product by conducting the reaction in a polymerization reactor wherein mixing is effected by the action of a plurality of elliptical paddles mounted on each of dual rotating shafts, characterised in that the shafts are rotated in reverse directions to each other, and the paddles are enclosed by walls of the reactor with the inside surface of major axes of the elliptical paddles on one rotating shaft periodical-ly approaching the ends of the minor axes of the corresponding elliptical paddles on the other rotating shaft to effect a mixing action as well as a longitudinal shearing action across a notional interface between said two shafts.
2. A method according to claim 1 for the continuous polymerization of trioxane.
3. A method according to claim 1 for the continuous polymerization of trioxane with a comonomer selected from a group comprising ethylene oxide, dioxolane, butanediol, formal and diethylene glycol formal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55115423A JPS5740520A (en) | 1980-08-22 | 1980-08-22 | Continuous polymerization |
| JP115423/80 | 1980-08-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1184342A true CA1184342A (en) | 1985-03-19 |
Family
ID=14662196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000384397A Expired CA1184342A (en) | 1980-08-22 | 1981-08-21 | Method of continuous polymerization |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5740520A (en) |
| KR (1) | KR840001754B1 (en) |
| AU (1) | AU547770B2 (en) |
| BE (1) | BE890030A (en) |
| BR (1) | BR8105183A (en) |
| CA (1) | CA1184342A (en) |
| DE (1) | DE3132453A1 (en) |
| FR (1) | FR2488896B1 (en) |
| GB (1) | GB2082597B (en) |
| HK (1) | HK85784A (en) |
| NL (1) | NL188290C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59115318A (en) * | 1982-12-21 | 1984-07-03 | Ube Ind Ltd | Production of formaldehyde copolymer |
| JPS61238812A (en) * | 1985-04-17 | 1986-10-24 | Polyplastics Co | Continuous polymerization |
| FR2647693B1 (en) * | 1989-06-02 | 1992-03-27 | Japan Storage Batterie Cy Ltd | DEVICE FOR PREPARING A PASTE OF ACTIVE MATERIAL FOR A BATTERY |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE813154C (en) * | 1949-09-29 | 1951-09-06 | Bayer Ag | Mixing and kneading device |
| DE2020935A1 (en) * | 1970-04-29 | 1971-11-18 | Bayer Ag | Process for the continuous production of stereospecific elastomers from 1,3-dienes |
| DE2321854A1 (en) * | 1973-04-30 | 1974-11-14 | Werner & Pfleiderer | KNEADING AND MIXING MACHINE |
| DE2362791C2 (en) * | 1973-12-18 | 1982-07-01 | Hoechst Ag, 6000 Frankfurt | Process for the preparation of copolymers of trioxane |
| JPS518489A (en) * | 1974-07-10 | 1976-01-23 | Hitachi Electronics | SETSUTEICHI SEIGYOHOSHIKI |
| US4105637A (en) * | 1974-10-11 | 1978-08-08 | Celanese Corporation | Process for producing a polyacetal polymer |
| DE2550969C2 (en) * | 1975-11-13 | 1982-12-16 | Josef 7120 Bietigheim Blach | Screw machine for homogenizing solid, liquid and viscous materials |
| JPS5386794A (en) * | 1976-11-29 | 1978-07-31 | Mitsubishi Gas Chem Co Inc | Continuous polymerization |
| US4136251A (en) * | 1977-09-12 | 1979-01-23 | E. I. Du Pont De Nemours And Company | Extrusion process for recovery of polymers from their dispersions in liquids |
-
1980
- 1980-08-22 JP JP55115423A patent/JPS5740520A/en active Granted
-
1981
- 1981-05-30 KR KR1019810001928A patent/KR840001754B1/en active
- 1981-06-03 GB GB8116942A patent/GB2082597B/en not_active Expired
- 1981-08-12 BR BR8105183A patent/BR8105183A/en not_active IP Right Cessation
- 1981-08-17 DE DE19813132453 patent/DE3132453A1/en active Granted
- 1981-08-20 AU AU74376/81A patent/AU547770B2/en not_active Expired
- 1981-08-21 NL NLAANVRAGE8103900,A patent/NL188290C/en not_active IP Right Cessation
- 1981-08-21 BE BE2/59305A patent/BE890030A/en unknown
- 1981-08-21 CA CA000384397A patent/CA1184342A/en not_active Expired
- 1981-08-25 FR FR8115997A patent/FR2488896B1/en not_active Expired
-
1984
- 1984-11-08 HK HK857/84A patent/HK85784A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| HK85784A (en) | 1984-11-16 |
| FR2488896A1 (en) | 1982-02-26 |
| BE890030A (en) | 1981-12-16 |
| NL8103900A (en) | 1982-03-16 |
| DE3132453C2 (en) | 1993-01-14 |
| JPS6213969B2 (en) | 1987-03-30 |
| AU7437681A (en) | 1982-02-25 |
| AU547770B2 (en) | 1985-11-07 |
| KR840001754B1 (en) | 1984-10-19 |
| GB2082597A (en) | 1982-03-10 |
| FR2488896B1 (en) | 1985-09-13 |
| KR830006334A (en) | 1983-09-24 |
| DE3132453A1 (en) | 1982-06-24 |
| NL188290B (en) | 1991-12-16 |
| JPS5740520A (en) | 1982-03-06 |
| BR8105183A (en) | 1982-04-27 |
| GB2082597B (en) | 1983-11-02 |
| NL188290C (en) | 1992-05-18 |
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