JPS6213974B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyacetal.
More specifically, the present invention relates to a method for producing a polyacetal homopolymer or copolymer by homopolymerizing or copolymerizing trioxane by a so-called bulk polymerization method. Various proposals have been made regarding methods and apparatus for bulk polymerization of trioxane. For example, regarding the continuous bulk polymerization of trioxane, JP-A-51-84890 discloses that the polymerization reactor consists of a long case substantially along the outer boundary of a pair of shafts, the shafts having a large number of intertwined shafts. A polymerization reactor has been proposed that has an elliptical plate with flat ends that interlock so that the elliptical plate strokes the mating surface at the long axis end of the plate. This reactor is characterized by having a flat end at the long axis end of an elliptical plate that engages with the surface of the other elliptical plate. However, according to the research conducted by the present inventors, as shown in the comparative example described later, in such a reactor, the flat end has almost no effect in removing the scale of the polymerization product adhering to the inner surface of the cylinder.
Rather, the polymerization products adhering to the inner surface of the shell or the scale surface are compressed at the flat end and become fixed as scale, and from an industrial perspective, continuous bulk polymerization of trioxane cannot be stabilized for a long period of time in such a reactor. It seemed almost impossible to do so under such conditions. The present inventors solved the drawbacks of the above conventional method, and
As a result of intensive research to develop a method for industrially performing continuous bulk polymerization of trioxane stably over a long period of time,
By using a so-called highly self-cleaning reactor that has a convex lens-shaped plate paddle with a sharp tip, it is possible to solve the problems of scale adhesion and the accompanying deflection and eccentricity of the stirring shaft, and also to achieve a relatively low L. The present invention was achieved by completing a method for producing high-quality polyacetal at a high conversion rate and stably for a long period of time. The objects and advantages of the present invention are that, according to the present invention, a hollow shell is provided with a raw material supply port and a reaction product discharge port at separate positions, and this shell has a plurality of eccentric circles of the same diameter. It has a cross section with an overlapping shape, and when there are multiple overlapping and missing parts, the shapes of the missing parts are almost congruent with each other; The inside of the hollow shell is equipped with a stirring shaft located in the center of each of the above circles in parallel to the longitudinal direction of the shell,
The stirring shaft has a plurality of plate-shaped paddles fixed to the stirring shaft so as to touch each other,
The plate-shaped paddle has a convex lens-shaped cross section in a direction perpendicular to the stirring axis, and both ends of the convex lens-shaped cross section in the long axis direction are sharp, and a plane containing the long axis is a plane of symmetry. one paddle faces at least one of the other paddles fixed to the other stirring shaft, and the one paddle faces with its sharp tip the inner surface of the barrel to which it belongs and the other paddle. A continuous stirring mixer, which is positioned so as to rotate while maintaining a small clearance with the side surface of the paddle, is used as a reactor, and here the first
clearance is 2% or less of the major diameter of the paddle, and a second clearance between the tip of the paddle on one shaft and the side surface of the paddle on the other shaft is no more than 5 times the first clearance, and the reactor A liquid raw material mixture containing molten trioxane, a catalyst, and optionally a comonomer is continuously supplied from the supply port, and the polymerization reaction is carried out while the raw material mixture is moved to the discharge port by rotation of the paddle. This is achieved by a method for producing a polyacetal homopolymer or copolymer, characterized in that a reaction product containing more than 5% by weight and less than 40% by weight of unreacted substances is taken out as powder from a discharge port. Ru. The reactor used in the present invention is a continuous stirring mixer, and has a hollow shell having a cross section in the shape of a plurality of overlapping circles of different centers and the same diameter. The plurality is most typically two, but may also be three or four. There is only one way of overlapping two circles, but in the case of three or more circles, various ways of overlapping can be considered. In the case of three circles, for example, they can be arranged in a straight line and stacked on top of each other, or they can be stacked on top of each other in a triangular shape. In the case of 3 or more yen,
Two or more shapes of overlapping parts, that is, actually missing parts, are formed, but in this case, the shapes of the missing parts need to be approximately congruent. The reactor used in the present invention will be explained with reference to FIGS. 1 and 2. FIGS. 1 and 2 schematically show an example of a reactor used in the present invention, in which two circles with different centers and the same diameter overlap to form a figure-eight cross section. That is, the reactor used in the present invention, as schematically illustrated in FIGS. 1 and 2, has shafts 1,
It is a continuous stirring mixer with a self-cleaning effect on the internal surface per rotation of 1', and the outer periphery of the cylinder 2 is divided into one or more parts for heating or cooling that can independently control the temperature. It has a jacket 3. Further, the inside of the stirring shafts 1, 1' in the shell 2 can be structured to allow a heating or cooling medium to pass therethrough. Two stirring shafts 1,
1′ each has a convex lens shape,
A paddle 4 whose both ends in the long axis direction are sharp and which has a cross section with a plane of symmetry including the long axis;
4'... are fixed in large numbers. Sharp literally means not flat. There are two types of paddles, one with a flat side as shown in Figure 2A, and the other with a helical side as shown in Figure 2B.The combination of these paddles 4, 4'... corresponds to the phase change of the reaction system. It is possible to perform the following transfers. The two stirring shafts 1 and 1' rotate in the same direction, and in the same cross section, one of the paddles fixed to the stirring shaft 1 faces the other paddle fixed to the stirring shaft 1'; The tip of the paddle 4 of the stirring shaft 1 rotates while constantly maintaining a slight clearance with the side surface of the paddle 4' of the other stirring shaft 1' and the inner surface of the barrel. Therefore,
The reaction mixture is constantly compressed and expanded due to the constant change in volume of the space formed between the paddles 4, 4', . . . and the shell 2, and is intensively mixed. paddle 4
The distance between the stirring shaft 1 that fixes the paddle 4' and the stirring shaft 1' that fixes the paddle 4', in other words, the overlap of the two circles in the cross section of the hollow shell is the center of the circle and the two intersection points. The angle between the two is preferably about 80° to about 100°, particularly preferably 85° to 90°. By doing so, the mutual cleaning of the paddles 4 and 4' can be advantageously performed. The clearance between the tips of the paddles 4, 4'... and the body 2 is preferably 2% or less, particularly preferably 1% or less of the major axis (diameter in the long axis direction) of the paddles, and the clearance between the paddles of one stirring shaft The clearance between the tip and the side surface of the paddle attached to the other shaft is 5 times or less, preferably 2 times or less. If the clearance is larger than this, it will not be possible to obtain a finely pulverized polymer product, and the thick scale adhering to the inner surface of the shell will impede heat transfer to the jacket.
This is not preferred because it often becomes difficult to control the reaction temperature. As shown in FIG. 2, the paddle, which has a convex lens-shaped cross section, has a sharp tip. A particularly hard material can also be welded to the tip. This sharp tip has the effect of scraping away scale attached to the inner surface of the barrel. The thickness of the plate-shaped paddle is approximately 1/20 to 1/5 of the length of the paddle in the longitudinal direction. In the continuous bulk polymerization of trioxane, a liquid reaction mixture with a viscosity of several centipoises at the beginning of the reaction changes from a slurry state to a solid state in a few minutes.
In order to mix the reaction mixture and move it from the supply port to the discharge port in response to such a drastic phase change, it is necessary to appropriately change the paddle combination described above from the supply port to the discharge port. is desirable. The present inventors have found that it is preferable to use a paddle combination with a large feeding effect near the raw material supply port of the reactor, and sequentially use paddle combinations with a small feeding effect toward the discharge port. The feeding effect referred to here is an effect of moving the contents from the supply port to the discharge port. The feeding effect is greatest when the next paddle is shifted from the supply port to the discharge port by 45 degrees in the direction opposite to the direction in which the stirring shaft rotates.
The feeding effect is smaller when the stirring shaft is mounted at a 90° offset, and the smallest feeding effect is when the stirring shaft is mounted at a 45° offset in the direction of rotation of the stirring shaft. In addition, a helical type paddle can be used, in which the side surface is twisted so that the rotation of the stirring shaft pushes the contents toward the discharge port. The feeding effect is greater than when both are combined at the same angle. In addition, as a helical type, it is also possible to use a reverse helical type in which the feeding mold and the side are twisted so that the contents are returned to the supply port when the stirring shaft rotates, and when using a combination of these In this case, the feeding effect is smaller than that of the flat type combined at the same angle. Furthermore, interlocking screws can be placed before and after the area formed by such paddles. Further, paddles of different thicknesses can also be used in combination.
In this way, various combinations of screws and paddles can be varied to correspond to the phase change of the reaction mixture from the supply port to the discharge port, and combinations having arbitrary feeding effects can be created. In this way, by using a combination of paddles with different feeding effects for each reaction zone, the filling rate of the contents in the reactor can be kept almost uniform in all reaction zones, and the contents can be When the stirring shaft rotates,
In order to function as a kind of roller between the paddles and between the paddles and the inner surface of the shell, contact between the paddles and the metals on the inner surface of the shell is prevented. This is one of the reasons why the reactor can operate stably for a long time. In a preferred embodiment of the present invention, a feed screw is installed in a part of the raw material supply port directly below the raw material supply port, and when the stirring shaft rotates, the reaction mixture is immediately transferred to the paddle through the screw. You will be led to a realm of combinations. The reaction mixture is initially a liquid with a viscosity of a few inches;
In the area immediately after the introduction of the reaction mixture, a feed screw or paddle combination with the greatest feed effect is used. Next, the paddle combination is gradually changed to a smaller feeding effect toward the region where the reaction mixture turns into a slurry, and the paddle combination is changed to an even smaller feeding effect in the region where the reaction mixture turns into powder. The degree of reduction in the feeding effect is controlled by reaction conditions such as reaction temperature, raw material supply amount, and catalyst amount. The reactor used in the method of the present invention is industrially inexpensive and can be manufactured so that the clearance between the paddle tip and the barrel is 2% or less, preferably 1% or less of the paddle major axis: Torso length L
The ratio of the inner diameter of the overlapping body cross-section of circles with different centers and the same diameter, that is, L/D, is 30 or less, preferably
15 or less, but usually L/D is 5~
30, preferably from 6 to 15. By using such a reactor, a sufficient residence time can be achieved, and a high quality polyacetal can be obtained with a sufficiently high conversion rate. When L/D is less than 5, it is difficult to obtain a sufficiently high conversion rate. In addition, in order to obtain a polymerization product as a completely pulverized powder, it is preferable that the rotational speed of the stirring shaft is such that the rotational circumferential speed of the paddle tip is in the range of 800 to 5000 cm/min. 1600~4000cm/
It is more preferable to set it to min. In the present invention, since a paddle with a sharp tip is used, a relatively high peripheral rotational speed such as 5000 cm/min can be selected. Furthermore, in order to carry out the method of the present invention suitably, the reaction temperature is 60 to 150°C, preferably 65 to 115°C.
A relatively high temperature is chosen, ie, in the temperature range in which the trioxane remains in liquid form. Even at such high temperatures, high quality polyacetal can be obtained without causing a runaway reaction. If the reaction temperature is lower than 60°C, the reaction rate will be low and it will be difficult to obtain a sufficiently high conversion rate, and if the reaction temperature is higher than 450°C, it will be difficult to obtain sufficiently high quality polyacetal through depolymerization etc. becomes difficult. As described above, in the present invention, a convex lens-shaped plate-shaped paddle with a sharp tip is used, and by using such a paddle, it is possible to efficiently scrape off the scale on the inner surface of the body, and the scale can be pressed against the scale. There is no possibility that the stirring shaft will bend. In addition, by changing the paddle combination to change the feeding effect according to the phase change of the reaction mixture, it is possible to keep the internal filling rate in the reactor almost constant in each region, and the rotational torque due to overfilling It is also possible to prevent the occurrence of wasted space in the reaction region due to an abnormal rise in the amount of gas or underfilling. The present invention has such various advantages, and for the first time, industrially advantageous continuous bulk polymerization of trioxane has become possible. moreover,
According to the present invention, it is possible to easily satisfy the L/D and rotational circumferential speed of the continuous bulk polymerization reactor within a predetermined range, thereby achieving a reaction with high heat transfer effects and stable continuous operation. A continuous polymerization method for trioxane using a machine was established. Knowledge regarding the appropriate paddle combination, L/D, and rotational peripheral speed of such a continuous bulk polymerization reactor for trioxane has not been clarified in the past. Therefore, the present invention is a novel and industrially It provides useful technology. The present invention is used in the homopolymerization or copolymerization of trioxane as described above. The copolymer is present in the oxymethylene main chain in an amount of 0.4 to 40 mol%, preferably 0.4 to 10
It contains mol % of oxyalkylene units having 2 or more carbon atoms. The cyclic ether or cyclic acetal which is a comonomer providing an oxyalkylene unit is, for example, one of general formula (1). Here, in the formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different, and represent a hydrogen atom, an alkyl group, or an alkyl group substituted with a halogen.
R ₅ means a methylene group or an oxymethylene group, or a methylene group or an oxymethylene group each substituted with an alkyl group or a halogenated alkyl group [n is an integer of 0 to 3], or furthermore, (-CH ₂ )― _n OCH ₂ ―, (―O―CH ₂ ―CH ₂ )― _n O―
CH ₂ - [In this case n is equal to 1 and m is 1 to 4
means a divalent group represented by an integer of . The alkyl groups mentioned above have 1 to 5 carbon atoms, the hydrogen atoms of which may be replaced by 0 to 3 halogen atoms, especially chlorine atoms. As a cyclic acetal or cyclic ether,
Particular mention may be made of ethylene oxide, glycol formal or diglycol formal. Additionally, for example propylene oxide or epichlorohydrin can be used. Furthermore, long chains α, ω-
Cyclic formals of diols are also suitable, such as butanediol formals, ie 1,3-dioxepane, or hexanediol formals. As the polymerization catalyst, a general cationic polymerization catalyst is used, and in particular, boron fluoride, boron fluoride hydrate, or a coordination compound of an organic compound having an oxygen atom and boron fluoride is used. Coordination compounds of boron fluoride with ethers, particularly boron trifluoride etherate [BF ₃ .O(C ₂ H ₅ ) ₂ ], are preferred catalysts. The boron trifluoride etherate is usually used in an amount of 0.01 to 1 mmol, preferably 0.05 to 0.2 mmol, per mole of trioxane. In the present invention, the polymerization may be carried out using relatively small amounts of anhydrous inert medium. The use of an inert medium directly controls the reaction heat and shear exotherm with the latent heat of vaporization of this medium, making the reaction smooth. The inert medium may or may not dissolve the trioxane, comonomer or catalyst, e.g. aliphatic or cycloaliphatic hydrocarbons such as hexane, heptane, cyclohexane; benzene, toluene, nitrobenzene, etc. aromatic hydrocarbons; petroleum light fractions; halogenated hydrocarbons such as ethane dichloride and carbon tetrachloride. These inert media should generally be used in amounts up to 10% by weight of the amount of trioxane used. Furthermore, in the present invention, the degree of polymerization of the product can be adjusted using a chain transfer agent as in the conventional method. There are no particular restrictions on the chain transfer agent, and alcohols such as methanol, ethanol, phenols such as phenol, 2,6-dimethylphenol,
and acetals, such as methylal, bis[methoxymethyl]ether, and various other known chain transfer agents. In FIG. 1, a raw material supply port 5 of the reactor used in the present invention is provided at one end of the shell. The components of the feedstock, namely trioxane, catalyst and optionally comonomer, chain transfer agent and/or inert medium, may be mixed immediately before being introduced into the feed port 5 or may be introduced separately. Good too. In particular, in the continuous reaction to copolymerize trioxane and cyclic ether or cyclic acetal to obtain a polyacetal copolymer, as shown in Figure 3, the tip of the comonomer supply nozzle and the tip of the polymerization catalyst supply nozzle are Advantageously, the nozzles are opened in close proximity, the tips of both nozzles are flushed with a flow of trioxane, mixed, and the reaction mixture thus obtained is immediately fed to the reactor. In FIG. 3, 8 is a trioxane inflow path, 9 is a comonomer supply nozzle, 10 is a polymerization catalyst supply nozzle, 11 is an orifice part,
12 is the outlet of the reaction mixture. In the orifice part, it is preferable to flow the reaction mixture at a linear velocity of 20 cm/sec or more. By using such a raw material mixing device, trioxane can be
A raw material mixture containing not more than 10% by weight of inert medium,
It is possible to smoothly supply the reactor to the reactor without causing problems such as the tip of the supply port being blocked by scale. After being supplied to the reactor, the raw material mixture undergoes transport and mixing, and polymerizes within a short period of time. The polymerization product is discharged from the discharge port 6 at the other end of the barrel. The discharge port 6 is a normal opening for discharging the polymerization product in the form of powder or granules, but a damper 7 may be provided to adjust the amount of retention in the reactor, if necessary. The residence time in this reactor is usually 0.5 to 30 minutes, preferably 1 to 10 minutes. The polymerization product discharged as powder contains 40% by weight or less, for example, 5% by weight of unreacted substances, and can be sufficiently post-treated as it is, but if 5% by weight of unreacted substances are If the content exceeds 5% by weight, the conversion may be further increased by immediately introducing it into the second-stage continuous mixer, as the case may be, until the unreacted material becomes 5% by weight or less. As the second stage mixer, a continuous stirring mixer of the same type as the above-mentioned first stage reactor, or a horizontal continuous mixer having a similar high heat transfer surface but with low self-cleaning properties is used. That is, the horizontal continuous mixer used has a structure in which the clearance between the outer surface of the stirring blade and the inner surface of the hollow body or the clearance between the outer surfaces of the stirring blades is not necessarily narrow. Therefore, according to the present invention, the polymerization reaction is carried out in the above-mentioned continuous stirring mixer under the above-mentioned conditions,
The reaction product containing more than 5% by weight and less than 40% by weight of unreacted substances is taken out as powder, and then this reaction product is transferred to the second stage mixer as described above, which is directly connected to the continuous stirring mixer. A homopolymer or copolymer of polyacetal, which is characterized in that the polymerization reaction is further carried out by conducting a polymerization reaction, and the polymerization product containing unreacted substances in an amount of 5% by weight or less and having substantially completed polymerization is taken out as a powder or granule. A method of manufacturing a coalescence is also provided. In the reaction inside the second stage mixer, the reaction temperature is
The temperature is 20 to 130°C, preferably 40 to 80°C, and the residence time is maintained at 5 to 120 minutes, preferably 10 to 100 minutes. Upon aging of the reaction, the polymerization product is guided to completion of the polymerization. The first product obtained as described above by the method of the present invention
The high conversion polymerization product discharged from the stage mixer or the second stage mixer is then immediately subjected to reaction termination by addition and mixing of a polymerization terminator. Various known polymerization terminators can be used as the polymerization terminator, but the tertiary phosphine compound previously proposed by the present inventors is particularly advantageous. The addition of the terminator is preferably carried out continuously using a continuous horizontal mixer directly connected to the reactor. When using a second-stage mixer, it is preferable to carry out the same process using a horizontal mixer directly connected to the second-stage mixer. In this way, the terminated crude polymer can be continuously taken out from the terminator mixer. In this case, the polymerization reaction system formed by the reactor and, if necessary, a second-stage mixer directly connected to it, is a closed system with no openings to the atmosphere other than the raw material supply port and discharge port. Preferably, the terminator mixer has a polymerization product supply port, a crude polymer discharge port, and a vent port provided directly above these ports. The waste gas generated during the polymerization reaction is recovered from the vent port of the terminating agent mixer. It is also possible to immediately pulverize this polymerized coarse polymer to obtain a coarse polymer with finer particle size. As the crusher, a geo crusher, a rotary mill, a hammer mill, a feather mill, a rotary cutter mill, a turbo mill, a classification type impact crusher, etc. are used. In the case of copolymerization of trioxane and a cyclic acetal or a cyclic ether, a known heat stabilizer is added and mixed to the crude polymer that has been polymerized by adding a tertiary phosphine compound, and then the mixture is heated from above the melting point of the polymer to 100°C below the melting point. A more stabilized polyacetal copolymer can be obtained by heating and kneading in a temperature range up to a high temperature and decomposing and removing unstable portions. The intrinsic viscosity of this copolymer (measured at 60°C in p-chlorophenol containing 2% by weight of α-pinene) can be adjusted to a desired value by adjusting the polymerization reaction conditions, that is, practically 1.0 to 2.0.
It can be done. Next, embodiments of the present invention will be described with reference to Examples and Comparative Examples. Example 1 A reactor as shown in FIG. 1 was used. The inner diameter D of the barrel was 200 mm, and L/D was 12. Immediately below the supply port 5 is a feed screw with a length of 1D, and then, in the next 1D area, a feed screw whose tip is sequentially shifted by 45 degrees in the opposite direction to the rotational direction of the stirring shaft from the supply port to the discharge port. A helical paddle, in the next 1D area, a flat paddle that is sequentially shifted by 45 degrees in the opposite direction of rotation, and in the next 6D area, a flat paddle that is alternately shifted by 90 degrees or 45 degrees in the opposite direction of rotation, and then In the 2D area, flat type paddles are alternately shifted by 90° or 45° in the same direction of rotation, and in the last 1D area, that is, directly above the discharge port 6, the flat type paddles are sequentially shifted by 45° in the same direction of rotation. I used a paddle. The thickness of each paddle was 40 mm. The clearance between the sharply machined tip of the paddle and the inner surface of the barrel is less than 2mm, and the clearance between the opposing paddle side of the other shaft is 4mm.
It was below. 80 kg of liquid trioxane per hour, 2 kg of liquefied ethylene oxide per hour, and 0.13 mmol of boron trifluoride etherate per mole of trioxane were prepared as a benzene solution with a concentration of 10% by weight.
The raw materials were mixed in advance in the raw material mixing device shown in the figure and immediately introduced continuously into the supply port 5. The jacket 3 is divided into four equal parts in the length direction of the shell, and the reaction temperatures are 80°C, 85°C, and 95°C in order from the supply port side.
The temperature of the heating medium was adjusted to be 110°C and 110°C. The rotational peripheral speed of the paddle tip is approximately 2500cm/
min, the residence time of the contents was approximately 5 minutes. At this time, the driving energy per 1 kg of trioxane is
It was 0.30KWH. A polymerization product containing 5% by weight of unreacted substances was obtained from the discharge port 6 in the form of powder. This polymerization product is
Immediately introduced into the stopper mixer. This terminator mixer has a polymerization product supply port at one end, a crude polymer discharge port at the other end, a vent port directly above it, a cooling jacket on the outer periphery, and a body with a cooling jacket inside. It was a continuous horizontal mixer that had a pair of shafts equipped with many stirring blades, and the shafts rotated in different directions to mix the contents, and its supply port was directly connected to the discharge port of the reactor. . From the supply port of the stopper mixer, twice the molar amount of triphenylphosphine relative to the boron trifluoride etherate used was continuously supplied as a benzene solution with a concentration of 20% by weight. The waste gas generated during the polymerization reaction was collected from the vent port of the terminator mixer. The crude polymer discharged from the stopper mixer is pulverized by a feather mill in which a knife rotates at high speed to shear and pulverize the powder to make it even finer, and the entire material passes through a 10-mesh sieve. was made possible. After approximately 500 hours of continuous operation, the intrinsic viscosity of the crude polymer obtained (measured at 60°C in p-chlorophenol supplemented with 2% by weight of α-pinene) was:
The polymerization yield was stable at 1.41 to 1.46 dl/g and about 95%. During this period, there was no abnormal noise caused by metal-on-metal contact in the reactor, and when the inside of the reactor was inspected after the operation was completed, there were no scratches on the inner surface of the shell, sides or tip of the paddle, and there was no scale on the inner surface of the shell. The thickness of the clearance was kept. 0.5 parts by weight of the antioxidant Irganox 259 per 100 parts by weight of the crude polymer thus obtained.
(trade name), 0.2 parts by weight of polyvinylpyrrolidone and 0.1 parts by weight of calcium hydroxide were added and mixed. The mixture is produced in a vented single-screw extruder.
It was heated and melted at 210℃. The molten resin is immediately transferred to two deep-groove types that are completely intermeshing and rotate in the same direction.
It was fed into a screw extruder. This extruder is temperature controlled so that the internal temperature is 210℃, and the pressure is
The crude polymer was stabilized at 40 Torr and a residence time of 20 minutes. The unstable oxymethylene terminals were decomposed by this treatment and recovered as formaldehyde gas from the vent port along with some solvent and unreacted substances. A stabilized white resin was extruded as a strand from the die head. This pellet was cut to obtain a product. The intrinsic viscosity of this stabilized copolymer is 1.43 dl/g, and the weight loss rate K ^air ₂₂₂ due to thermal decomposition in air at 222°C is 0.001.
weight%/min, and the physical properties of molded articles obtained using this copolymer were as follows.

[Table] Comparative Example 1 A case having a jacket capable of heating or cooling a reaction mixture on the outer periphery of the case, a pair of shafts being fixed horizontally within the case, each of the shafts having a number of interlocking oval plates, A continuous mixer was used as the reactor, with the flat end of the elliptical plate interlocking with the other elliptical plate so that its long axis end stroked the surface of the other elliptical plate. Liquid trioxane at a flow rate of 80 kg/hour, liquefied ethylene oxide at a flow rate of 2.0 kg/hour, and 0.13 mmol of boron trifluoride etherate per 1 mole of trioxane were mixed in advance in the raw material mixing device in the same manner as in Example 1. and introduced it into the raw material supply port. The case inner diameter D of this reactor is
It was 200mm and L/D was 12. The combination of multiple oval plates installed inside the reactor was the same as the paddle combination of Example 1. The same was true for clearance. The reaction temperature was also the same. The rotational speed of the shaft was such that the rotational circumferential speed of the flat end of the elliptical plate was approximately 2500 cm/min. At this time, the driving energy per 1 kg of trioxane is
It was 0.37KWH. The polymerization product discharged from the discharge port contained 7% by weight of unreacted substances. To this polymerization product, twice the mole of triphenylphosphine as the polymerization catalyst used was added and mixed in the same manner as in Example 1. After approximately 10 hours of continuous operation, the reactor produced an abnormal sound that appeared to be caused by metal-on-metal contact. Furthermore, since the reaction temperature started to rise, the temperature of the jacket part was lowered, but the reaction temperature could not be controlled immediately. After about 100 hours of continuous operation, the abnormal noise from the reactor became louder and louder, and the shear pin suddenly broke and the shaft stopped rotating, forcing the operation to stop. Disassemble the reactor,
Upon inspecting the inside, we found scratches caused by metal-to-metal contact on the inner surface of the lower part of the case near the center of the shaft and on the tip of the oval plate. In addition, hard scale of polymerization products was observed on the inner surface of the upper part of the case, which was more than twice the value of the clearance between the inner surface of the case and the tip of the oval plate measured before the start of polymerization. This observation revealed that a hard scale of polymerization products adhered to the inner surface of the upper part of the case to an extent greater than the normal clearance, and this scale layer pushed down the shaft, and as the shaft rotated eccentrically, the inner surface of the lower part of the case and the flat end of the oval plate It became clear where they had come into contact. It was also revealed that the formation of an extremely thick scale layer deteriorated the heat transfer effect, making it impossible to remove heat sufficiently. The crude polymer produced during about 100 hours of continuous operation was pulverized, mixed with a stabilizer, and thermally stabilized in the same manner as in Example 1, and was turned into a product. The intrinsic viscosity of this stabilized copolymer is 1.35 dl/g in air.
Rate of weight loss due to thermal decomposition at 222°C K ^air _22
2 is
It was 0.04% by weight/min. Example 2 Using the same type of reactor as used in Example 1, L/D=
7 was used. In the 3D area from the supply port 5 side, a flat paddle is installed in which the next paddle is sequentially shifted by 45 degrees in the opposite direction of the shaft rotation direction from the supply port toward the discharge port. The 2D area is equipped with flat paddles that are alternately shifted by 90° or 45° in the direction of rotation and the opposite direction, and the remaining 2D area is equipped with paddles that are shifted in the direction of rotation and vice versa.
Flat paddles were installed that were shifted sequentially by 45 degrees. The discharge port 6 was provided at the bottom of the tip of the last 2D region. To this reactor, 80 kg of trioxane per hour, 2.0 kg of liquefied ethylene oxide per hour, and 0.13 mmol of boron trifluoride etherate per 1 mole of trioxane are mixed in a raw material mixing device as shown in Figure 3 and fed. It was done. The stirring shaft was rotated such that the peripheral speed of the paddle tip was approximately 2500 cm/min. The residence time of the contents was approximately 3 minutes. The jacket is divided into three equal parts, and the reaction temperature is 80℃, 90℃ and 110℃ in order from the supply port side.
The temperature of the heat medium in the jacket was adjusted so that the temperature was ℃. The polymerization product discharged from the discharge port 6 contains unreacted materials.
It was a powder containing 30% by weight. This polymerization product was immediately fed into a second mixer under a nitrogen gas atmosphere. This second mixer has a barrel with a jacket on the outer periphery, and a pair of shafts equipped with a large number of stirring blades inside, and the shafts rotate in different directions to mix the contents continuously. This is a type horizontal mixer. The supply port of this second-stage mixer was directly connected to the discharge port 6 of the reactor, and the discharge port was directly connected to the supply port of the same termination agent mixer as in Example 1. In this second-stage mixer, the reaction temperature was maintained at 60° C., and the mixture was slowly stirred at a stirring shaft rotation speed of 25 rpm to complete polymerization. The residence time in the second stage mixer was 30 minutes. The polymerization product taken out from the discharge port of the second-stage mixer was a granular material containing only 1% by weight or less of unreacted substances. To this product, twice the molar amount of triphenylphosphine as that of boron trifluoride etherate was added and mixed in the same manner as in Example 1 to obtain a crude polymer. The operating condition of the reactor was extremely stable throughout the continuous operation of about 500 hours, and the intrinsic viscosity of the obtained crude polymer was stable in the range of 1.40 to 1.44 dl/g. During continuous operation, there was no abnormal noise caused by contact between the paddles of the reactor or between the paddle tip and the inner surface of the shell. Example 3 A reactor similar to that used in Example 1 with a shell inner diameter D of 50 mm and L/D of 15 was used. Immediately below the supply port 5 is a feed screw with a length of 2D, and then in the next 4D area, a flat screw whose tip is sequentially shifted by 45 degrees in the opposite direction to the rotational direction of the stirring shaft from the supply port to the discharge port. In the next 4D area, we used a flat paddle that was sequentially shifted by 90 degrees in the opposite direction of rotation, and in the last 5D area, we used a flat paddle that was sequentially shifted by 45 degrees in the same direction of rotation. The thickness of each paddle was 10 mm. The clearance between the sharply machined tip of the paddle and the inner surface of the barrel, and the clearance between the opposing paddle side surface of the other shaft were both 1 mm or less. 2 kg of liquid trioxane per hour, 70 g of 1,3-dioxepane per hour, and 0.18 mmol of boron trifluoride etherate per mole of trioxane were continuously introduced into the feed port 5. The reaction temperature was adjusted to 75°C. The rotation speed of the stirring shaft is
It was hot at 200rpm. This was a rotational speed at which the rotational circumferential speed of the paddle tip was about 3100 cm/min. The residence time of the contents was approximately 6 minutes. At this time, the driving energy per 1 kg of trioxane was 0.6 KWH. A polymerization product containing 35% by weight of unreacted substances was obtained from the discharge port 6 in the form of powder. This polymerization product was immediately and continuously introduced into the second stage mixer under a nitrogen gas atmosphere. The second stage mixer is a so-called pin mixer, which has a shell with a jacket around its outer periphery and a single shaft inside which is equipped with a number of pins as an agitator. The supply port of the second stage mixer was directly connected to the discharge port 6 of the reactor. This device had a shaft rotation speed of 300 rpm. The reaction temperature in the second stage mixer was 60°C and the residence time was 1 hour. The polymerization product taken out from the second stage mixer was a fine powder containing less than 2% by weight of unreacted materials. To this polymerization product, triphenylphosphine was added in an amount twice the mole of the polymerization catalyst used to deactivate the catalyst. No. 1 after approximately 500 hours of continuous operation
No abnormal sounds such as metal-to-metal contact were observed in the stage reactor. After approximately 500 hours of continuous operation, the yield and intrinsic viscosity were 98.5% to 99.5% and 1.43 to 1.43, respectively.
1.45 dl/g of crude polymer was consistently obtained. 0.5 parts by weight of Irganox 259 (trade name), 0.2 parts by weight of dimer acid polyamide, and 0.1 parts by weight of calcium hydroxide were added to 100 parts by weight of the obtained crude polymer, and the mixture was melt-kneaded at 200°C for 20 minutes using a small melt-kneader. and stabilized. The intrinsic viscosity of this stabilized copolymer is 1.45
dl/g, and the weight loss rate K ^air ₂₂₂ due to thermal decomposition in air at 222° C. was 0.02% by weight/min. Comparative Example 2 A reactor similar to that used in Comparative Example 1 with a case inner diameter D of 50 mm and L/D of 15 was used. Immediately below the raw material supply port, interlocking feed screws with a length of 2D are attached to the shaft, and in the remaining 13D area, an elliptical plate with a flat end rotates the shaft from the supply port to the discharge port. They were installed at 45° shifts in the opposite direction. The clearance was similar to Example 3. This reactor was charged with 2 kg of trioxane per hour and 70 kg per hour.
For each g of 1,3-dioxepane and trioxane, 0.18 mmol of boron trifluoride etherate was fed. The reaction temperature is maintained at 50 to 60℃, and the rotational speed of the shaft is approximately 3100.
cm/min. However, it was found that the reaction mixture was discharged from the discharge port in the form of a liquid or slurry, indicating that the polymerization reaction was hardly progressing. Therefore, in order to increase the reaction rate, polymerization was carried out by increasing the temperature of the heat transfer medium in the jacket so that the reaction temperature reached 80°C, but in the end, the polymerization product containing 70% by weight of unreacted materials was released from the discharge port as a slurry. It was only discharged as a result. When this product was fed to a non-self-cleaning second-stage mixer, it stuck to the inner surface of the cylinder and shaft.
Or it could form into a mass, making it completely impossible to drive. Next, the shaft rotational speed of the reactor was set to a relatively low rotational speed such that the rotation peripheral speed of the flat end was 300 cm/min, and the reaction temperature was maintained at 60°C. The particles were so coarse that 40% by weight of the total could not pass through a 10-mesh sieve, and furthermore, it contained 50% by weight of unreacted substances. Comparative Example 3 Polymerization was carried out using the same reactor as in Comparative Example 2. Immediately below the raw material feed opening, interlocking feed screws with a length of 2D were attached to the shaft, and in the remaining 13D area, oval plates with flat ends were attached sequentially at 90° offset. The clearance was similar to Example 3. 2Kg of trioxane per hour is added to this reactor, and
For 70 g of 1,3-dioxepane and trioxane, 0.18 mmol of boron trifluoride etherate was fed. The reaction temperature is maintained at 50 to 60℃, and the rotational speed of the shaft is approximately 3100.
cm/min. However, 10 minutes after the start of operation, the shear pin suddenly broke, making it impossible for the reactor shaft to rotate. When the reactor was opened and examined, it was found that the polymer filled the free space at a filling rate of 100% in the region from 2D from the supply port to 8D from the supply port. As a result, the shaft was unable to rotate at all, and it was discovered that the shear pin, which was attached to the drive unit to avoid damage, had broken.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view schematically showing a reactor used in the present invention. FIG. 2 is a partially sectional front view showing the shape of the paddle; FIG. 2A shows a flat paddle, and FIG. 2B shows a helical paddle. FIG. 3 is a sectional view showing the raw material mixing device. 1, 1'... Stirring shaft, 2... Cylinder, 3... Jacket,
4, 4'...paddle, 5...supply port, 6...discharge port, 7
...Damper, 8...Trioxane inflow path, 9...Comonomer supply nozzle, 10...Catalyst supply nozzle, 11...
Orifice part, 12...Mixture outlet.

Claims (1)

[Claims] 1. A hollow shell equipped with a raw material supply port and a reaction product discharge port at separate locations, and this shell has a cross section in the shape of a plurality of overlapping circles of different centers and the same diameter. When there are multiple overlapping missing parts, the shapes of the missing parts are almost congruent with each other; a temperature control jacket is provided on the outer periphery of the hollow shell; The inside is provided with a stirring shaft located parallel to the longitudinal direction of the body at the center of each of the circles, and each of the stirring shafts has a plurality of plate-shaped paddles fixed to the stirring shaft so as to be in contact with each other. The plate-shaped paddle has a convex lens-shaped cross section in a direction perpendicular to the stirring axis, and the convex lens-shaped cross section has sharp ends in the long axis direction, and a plane including the long axis. It has a shape that is a plane of symmetry;
One paddle faces at least one of the other paddles fixed to the other stirring shaft, and the one paddle has a sharp tip that makes a slight clearance with the inner surface of the barrel to which it belongs and the side surface of the other paddle. A continuous stirring mixer, which is positioned to rotate while maintaining rinsing, is used as the reactor, where the first clearance between the tip of the paddle and the inner surface of the barrel is 2% of the long diameter of the paddle.
and the second clearance between the tip of the paddle on one shaft and the side surface of the paddle on the other shaft is five times or less than the first clearance, and molten trioxane and catalyst are supplied from the supply port of the reactor. ,
If desired, a liquid raw material mixture containing a comonomer is continuously supplied, and the polymerization reaction is carried out while the raw material mixture is moved to the discharge port by rotation of the paddle, and unreacted materials are removed from the discharge port. Weight% over 40
1. A method for producing a polyacetal homopolymer or copolymer, characterized in that a reaction product containing less than % by weight is taken out as powder. 2. It has a hollow shell equipped with a raw material supply port and a reaction product discharge port at separate positions, and this shell has a cross section in the shape of a plurality of overlapping circles with different centers and the same diameter. When there are multiple missing parts, the shapes of the missing parts are almost congruent with each other; a temperature control jacket is provided on the outer periphery of this shell; and each of the above-mentioned parts is provided inside the hollow shell. A stirring shaft is provided in the center of the circle and is located parallel to the longitudinal direction of the body, and the stirring shaft has a plurality of plate-shaped paddles fixed to the stirring shaft so as to touch each other. The shaped paddle has a convex lens-shaped cross section in a direction perpendicular to the stirring axis, and the convex lens-shaped cross section has a shape in which both tips in the long axis direction are sharp and the plane containing the long axis is a plane of symmetry. have;
One paddle faces at least one of the other paddles fixed to the other stirring shaft, and the one paddle has a sharp tip that makes a slight clearance with the inner surface of the barrel to which it belongs and the side surface of the other paddle. A continuous stirring mixer, which is positioned to rotate while maintaining rinsing, is used as the reactor, where the first clearance between the tip of the paddle and the inner surface of the barrel is 2% of the long diameter of the paddle.
and the second clearance between the tip of the paddle on one shaft and the side surface of the paddle on the other shaft is five times or less than the first clearance, and molten trioxane and catalyst are supplied from the supply port of the reactor. ,
If desired, a liquid raw material mixture containing a comonomer is continuously supplied, and the polymerization reaction is carried out while the raw material mixture is moved to the discharge port by rotation of the paddle, and unreacted materials are reduced to 5% by weight. The reaction product containing more than 40% by weight or less is taken out from the discharge port in the form of powder and granules, and then the reaction product is transferred to a continuous stirring mixer of the same type directly connected to the reactor or a combination between the outer surface of the stirring blade and the inner surface of the hollow body. The polymerization reaction is continued by introducing a horizontal continuous mixer with a structure in which the clearance or the clearance between the outer surfaces of the stirring blades is not necessarily narrow.
1. A method for producing a polyacetal homopolymer or copolymer, which comprises taking out a substantially completed polymerization product containing 5% by weight or less of unreacted substances as powder or granules. 3. In the continuous stirring mixer, the stirring shafts are sequentially attached from the supply port to the discharge port so that the next paddle adjacent to the first paddle is shifted in the direction of rotation of the paddle or in the opposite direction. 3. A method according to claim 1 or 2, characterized in that the feeding effect of the reactant is adjusted. 4. The method according to claim 1 or 2, wherein in the continuous stirring mixer, a feed screw is attached to a part of the supply port side of the stirring shaft to which a paddle is fixed. 5 In the continuous stirring mixer, the clearance between the tip of the paddle and the inner surface of the barrel is 1% or less of the major diameter of the paddle, and the clearance between the tip of the paddle on one shaft and the side surface of the paddle on the other shaft is 3. The method according to claim 1 or 2, wherein the clearance is not more than twice the clearance. 6 In the continuous stirring mixer, the length L of the shell and the inner diameter D of the overlapping circles with the same diameter and the same cross-section
3. The method according to claim 1 or 2, wherein the ratio of L/D to L/D is 5 to 30. 7. In the continuous stirring mixer, the ratio of the length L of the shell to the inner diameter D of the cross-section of the shell where the eccentric circles overlap with each other, that is, L/D, is 6 to 15. or the method described in paragraph 2. 8 In the above-mentioned continuous stirring mixer, the rotational speed of the stirring shaft is adjusted so that the rotational circumferential speed of the paddle tip is 800 to 5000 cm/
3. The method according to claim 1 or 2, wherein the method is adjusted to a minimum value. 9. The method according to claim 1 or 2, wherein in the continuous stirring mixer, the barrel has a cross section in the shape of two overlapping circles of different centers and the same diameter. 10. The method according to claim 1 or 2, wherein the polymerization reaction temperature is in the range of 60 to 150°C. 11. The method according to claim 1 or 2, wherein the polymerization reaction temperature is in the range of 65 to 115°C. 12. The method according to claim 1 or 2, wherein boron trifluoride etherate is used as a catalyst. 13. The method according to claim 1 or 2, wherein ethylene oxide is used as the comonomer.