JPS6213972B2 - - 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 aligned with the external boundaries of a pair of shafts, said shafts having a number of interlocking ellipses. Polymerization reactors have been proposed that have shaped plates 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 little effect on removing the scale of the polymerization product adhering to the inner surface of the shell, but rather The polymerization products adhering to the inner surface or the scale surface are compressed by the flat end and become fixed as scale, and from an industrial perspective, it is difficult to carry out the continuous bulk polymerization of trioxane in a stable state for a long time in such a reactor. It seemed almost impossible to do. 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 having a convex lens-shaped or pseudo-polygonal plate-shaped paddle with a sharp tip, it is possible to solve the problem of scale adhesion and the resulting deflection and eccentricity of the stirring shaft. Relatively low L/D
The present invention was achieved by completing a method for stably producing high-quality polyacetal at a high conversion rate over a long period of time. The objects and advantages of the present invention are as follows: 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 parallel to the longitudinal direction of the shell at the center of each of the above circles, and a plurality of plate-shaped paddles are fixed to the stirring shaft so as to be in contact with each other. The plate-shaped paddle has a cross section perpendicular to the stirring axis direction that is a convex lens shape or a pseudopolygon inscribed in a virtual circle at each apex angle, and the apex corner of the cross section has a symmetrical shape. It has a sharp scraper without a face; one paddle faces at least one of the other paddles fixed to the other stirring shaft, and the one paddle has a sharp scraper with its sharp scraper. A continuous stirring mixer is used as a reactor, which is positioned so as to rotate while maintaining a small clearance from the inner surface of the paddle and the side surface of the other paddle, and molten trioxane and a catalyst, if desired, are supplied from the feed port of the reactor. Then, a liquid raw material mixture containing a comonomer is continuously supplied, and the polymerization reaction is carried out while moving the raw material mixture to the discharge port by rotation of the paddle, and the reaction product is released from the discharge port as a powder. This is achieved by a method for producing a polyacetal homopolymer or copolymer, which is characterized by taking out the polyacetal. 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 three or more circles, two or more shapes of overlapping parts, that is, parts that are actually missing, are formed.
In this case, the shape of the missing portion needs 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' is a sharp scraper whose cross section perpendicular to the stirring axis direction is a convex lens shape or a pseudopolygon inscribed in a virtual circle at each apex angle, and whose cross section has no plane of symmetry at the apex corner. Paddle 4,4' with
Many have been fixed. Sharp literally means not flat. There are two types of paddles: one with a flat side as shown in Figure 2A, and one with a helical side as shown in Figure 2B.The combination of these paddles 4 and 4' can react to phase changes in 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 constantly touches the side surface of the paddle 4' of the other stirring shaft 1' and the barrel 2.
rotates while maintaining a slight clearance with the inner surface of the Therefore, the reaction mixture is constantly compressed and expanded due to the constant volume change of the space formed between the paddles 4, 4' and the barrel 2, and is intensively mixed. 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 intersection of the two It is preferable that the angle between the two is about 80° to about 100°, particularly preferably 85° to 90°. By doing so, 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 diameter of the circumscribed circle of the paddles, and the clearance between the tips of the paddles of one stirring shaft and the other The clearance between the paddle and the side surface of the shaft is 5 times or less, preferably 2 times or less. If the clearance is larger than this, it is not possible to obtain a finely ground polymerization product, and thick scale adhering to the inner surface of the shell impedes heat transfer to the jacket, making it often difficult to control the reaction temperature. This is not preferable because it may occur. As shown in FIG. 2, the tip of the paddle is sharply machined. 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. FIG. 3 shows an external view of an example of the paddle according to the present invention. In the paddle 4 shown in FIG. 3, 41 is a scraper, and 42 is a side surface of the paddle. Further, FIG. 4 shows another example of the paddle according to the present invention. FIG. 4A is a plan view, and FIG. 4A' is a side view. As shown in the figure, the paddle in FIG. 4 has scrapers at both ends of different shapes. This paddle has a structure in which scale is scraped off with one scraper 43 or 44, and then the remaining scale is scraped off with the other scraper 44 or 43. Further, another example of the paddle according to the present invention is illustrated in FIG. This paddle has a pseudo-triangular cross section and has scrapers at its three apex portions. If the paddle is a pseudo-polygon that is more than a pseudo-triangle, it will generally become increasingly difficult to sharpen the apex portion, but since the paddle in the present invention has a scraper, it is not a pseudo-polygon. Even if there is, it is relatively easy to sharpen the apex portion. In the present invention, a convex lens-shaped or pseudo-triangular paddle is preferably used. Furthermore, the present inventors have developed a continuous bulk polymerization machine using trioxane and/or a comonomer copolymerized with trioxane, which can industrially advantageously produce high-quality oxymethylene polymers or copolymers. In the design, the reactor's L/D (the ratio of the length L of the shell to the inner diameter of the cross-section of the shell where circles of different centers and the same diameter overlap) and the rotation speed, as well as a large number of By establishing a method of combining paddles, we succeeded in producing a reactor that was inexpensive and capable of stable continuous operation. The appropriate L/D, rotation speed, paddle combinations, etc. of these reactors have not been clarified at all in the past. In the continuous bulk polymerization of trioxane, a liquid reaction mixture with a viscosity of several centipoises changes from a slurry to a solid in a few minutes at the beginning of the reaction.
In order to mix the reaction mixture and move it from the supply port to the discharge port in response to such a severe 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. In the case of convex lens shaped paddles, the feeding effect is greatest when the next paddle is offset by 45 degrees in the direction opposite to the rotation direction of the stirring shaft from the supply port to the discharge port, and when installed offset by 90 degrees. The feeding effect is smaller than this, and the feeding effect is the smallest when the stirring shaft is installed offset by 45 degrees in the direction of rotation. If the paddles are pseudo-triangular, the feed effect is 30 degrees in the direction opposite to the direction of rotation of the stirring shaft from the supply port to the discharge port.
The feeding effect is the greatest when it is mounted at an offset of 60°, the feeding effect is smaller when it is mounted at an offset of 60°, and the feeding effect is the smallest when it is mounted at an offset of 90°. In addition, a helical type paddle can also be used, in which the side surface is twisted so that the rotation of the stirring shaft pushes out the contents toward the discharge port. The feeding effect is greater than when both are combined at the same angle. Furthermore, as a helical type, it is also possible to use a reverse helical type in which the side surface is twisted so that the contents are returned to the supply port when the stirring shaft rotates in the opposite direction to the feed type, and a combination of these can be used. In some cases, the feeding effect will be smaller than that of flat types 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, it acts as a kind of roller between the paddles and between the paddles and the inner surface of the shell, thereby preventing contact between the paddles and the metals on the inner surface of the shell. 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 centipoises;
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 method of the present invention is industrially inexpensive and has a clearance between the paddle tip and the body of 2% or less of the diameter of the circumscribed circle of the paddle, preferably 1% or less of the diameter of the circumscribed circle of the paddle.
% or less, L/D is 30 or less, preferably 15 or less, but usually L/D is 5 to 30, preferably 6.
~15, selected in the range. 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 having a sharp scraper at the tip is used, a relatively high rotational peripheral 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 150°C, it will be difficult to obtain sufficiently high quality polyacetal through depolymerization etc. becomes difficult. As described above, according to the present invention, the scale on the inner surface of the cylinder can be efficiently scraped off, and the rotating shaft does not bend due to being pushed by the scale. In other words, in a cross section perpendicular to the stirring shaft, the angle between the tangent line drawn from the apex of the paddle tip in the rotational direction of the circle drawn by the apex and the line representing the side surface of the paddle tip from which scale is to be scraped. When we define the scraping angle as the scraping angle, the paddle having the scraper of the present invention has a larger scraping angle than a convex lens-type or pseudo-polygonal paddle that simply has a sharp tip. According to the research of the present inventors,
If this scraping angle is large, the angle between the scale-scraping side of the paddle and the inside surface of the shell is large, so the tendency to entrain and compress the reaction mixture is very small, and the sharp blade-like tip It was found that the contact area with the scale was also reduced because the scale was scraped off. Therefore, the resistance when scraping off scale is reduced, and not only the power required for rotation is reduced, but also the deflection of the stirring shaft is reduced. Therefore, the clearance of the paddle tip on the inner surface of the reactor shell is made smaller than in the case of a conventional paddle, so that the paddle tip and the inner surface of the shell do not come into contact during operation. In addition, this allows the scale layer to be thin and efficiently remove the heat generated during the polymerization reaction, and furthermore, the powder is rolled up and compressed between the tip of the paddle and the inner surface of the barrel. Since the tendency is small, so-called frictional heat is generated little when the paddle is rotated, and the reaction mixture is not locally heated, so that a high-quality polymer can be obtained. 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. Furthermore, 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 high heat transfer effect and stable continuous operation. A continuous polymerization method for trioxane using a reactor 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. As described above, the present invention is used for homopolymerization or copolymerization of trioxane. The copolymer has a content of 0.4 to 40 mol%, preferably 0.4 to 40 mol%, in the oxymethylene main chain.
It contains 10 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 from 0 to 3], or furthermore, (-CH ₂ ―) _n OCH ₂ ―, (―O―CH ₂ ―CH ₂ ―) _n O―
CH ₂ - means a divalent group represented by [in this case, n is equal to 1 and m is an integer from 1 to 4]. 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-
Also suitable are cyclic formals of diols, 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, especially boron trifluoride diethyl etherate [BF ₃ O
(C ₂ H ₅ ) ₂ ] or boron trifluoride dibutyl etherate are preferred catalysts. Such 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, for example aliphatic or cycloaliphatic hydrocarbons such as hexane, heptane, cyclohexane; benzene, toluene, etrobenzene. Aromatic hydrocarbons such as; petroleum light distillates; halogenated hydrocarbons such as ethane dichloride and carbon tetrachloride are used. 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 or 5, the 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 FIG. 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 Figure 7,
8 is a trioxane inflow path, 9 is a comonomer supply nozzle, 10 is a polymerization catalyst supply nozzle, 11 is an orifice portion, and 12 is an outlet for the reaction mixture. At the orifice, the flow of the reaction mixture is
It is preferable to flow at a linear velocity of cm/sec or higher. By using such a raw material mixing device, a raw material mixture containing an inert medium of 10% by weight or less of trioxane can be smoothly fed into the reactor without causing troubles such as the tip of the supply port being blocked by scale. can be supplied to 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
It is discharged from the discharge port 6 at the other end of the cylinder. 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 as necessary. The residence time in this reactor is usually 0.5 to 30 minutes, preferably 1 to 10 minutes. The polymerization product discharged as a 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, it may be introduced into the second-stage continuous mixer immediately as the case may be to further increase the conversion rate until the unreacted material becomes 5% by weight or less. Second
As the stage mixer, a continuous stirring mixer of the same type as the above-mentioned first stage reactor, or a horizontal continuous mixer which similarly has a high heat transfer surface but has low self-cleaning performance, etc. 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 mixture 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. The connection between the first stage reactor and second stage mixer is as follows:
For example, it is also possible to connect in a crosshead manner. In this case, at the discharge port of the first stage reactor,
It is also possible to provide a feeding screw or a reverse screw having approximately the same diameter as the reaction cylinder. Further, it is desirable that the supply port of the second stage mixer is provided with a normal feed screw. Of course, the respective screws at the first stage reactor discharge port and the second stage mixer supply port can be installed substantially close to each other. 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. The thermal formation of the reaction drives the polymerization product to completion. The first product obtained as described above by the method of the present invention
The polymerization product discharged from the stage mixer or the second
When a stage mixer is used, the polymerization product with a high conversion rate discharged from 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. And the stop agent mixer is
It is preferable to have a supply port for the polymerization product, a discharge port for the crude polymer, 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 explained using Examples and Comparative Examples. Example 1 Using the reactor shown in Fig. 5 having a pseudo-triangular paddle with a sharp scraper at the tip as shown in Fig. 6, 2 kg/hour of trioxane and 70 g/hour of 1,3-dioxepane were added. Then, 0.18 mmol of boron trifluoride diethyl etherate per mol of trioxane was supplied while being mixed using the raw material mixing device shown in FIG. The inner diameter D of the reactor shell was 50 mm, and L/D was 15. Immediately below the raw material feed port, interlocking feed screws with a length of 2D were installed.
In the next 4D reaction zone, the next paddle is attached with its tip shifted by 30 degrees from the supply port to the discharge port in the opposite direction to the direction in which the stirring shaft rotates.
Furthermore, the next 4D reaction zones were installed with a similar offset of 60°, and the remaining 5D reaction zones were installed with a similar offset of 90°. A discharge port was provided at the bottom of the tip of the reactor. The rotation speed of the stirring shaft was adjusted to 200 rpm. This means that the rotational circumferential speed of the scraper at the top of the paddle is approximately
The rotation speed was 3100cm/min. Reaction temperature The reaction temperature was adjusted to 75°C, and the residence time inside the reactor was about 6 minutes. The powder discharged from the discharge port was a copolymer containing 40% of unreacted substances. This copolymer was immediately sent to the second stage mixer under an inert gas atmosphere. The second-stage mixer is a so-called pin mixer, which has a reaction shell with a jacket on the outside and a single shaft with a large number of pins fixed thereon as mixing blades inside. The stirring shaft rotation speed of this mixer is 300 rpm, and the reaction temperature is 60
It was warm at ℃. After a residence time of 1 hour, a fine powder polymerization product containing less than 2% of unreacted monomer was obtained from the outlet. Triphenylphosphine was added to the produced polymer in an amount twice the mole of the polymerization catalyst used to deactivate the catalyst. During approximately 500 hours of continuous operation, the first
No abnormal noises such as metal-to-metal contact were observed in the stage reactor. Yield of the produced polymer obtained by continuous operation for about 500 hours, intrinsic viscosity of the polymer [η] (in p-chlorophenol containing 2% α-pinene at 60°C)
) are 98.5% to 99.5% and
It was 1.43-1.45 dl/g. That is, such a polymer was constantly obtained during continuous operation. 0.5 parts by weight of the antioxidant 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 polymer, and the mixture was melt-kneaded as it was (unwashed) in a small scale. The mixture was stabilized by melt-kneading in a machine at 200°C for 20 minutes. The intrinsic viscosity of the stabilized polymer is 1.45 dl/g,
The weight loss rate K ^air ₂₂₂ due to thermal decomposition at 222° C. in air was 0.02% by weight/min. Example 2 Using the reactor shown in Fig. 1 having a convex lens-shaped paddle with a sharp scraper at the tip as shown in Fig. 2, trioxane was added at a flow rate of 80 kg per hour, and liquefied ethylene oxide was added at a flow rate of 2.0 kg per hour. and 0.13 mmol of boron trifluoride diethyl etherate per mole of trioxane were mixed in advance in the polymerization raw material mixing device shown in FIG. 7 and charged into the feed port. The reactor had an inner diameter of 200 mm and an L/D of 12. Immediately below the raw material feed port, there are interlocking feed screws with a length of 1D, followed by
In the 4D reaction zone, the tip of the next paddle runs in the opposite direction of the shaft rotation from the supply port to the discharge port.
It had a helical-type feed paddle and a flat-type paddle offset by 45 degrees. Then the next
In the 3D reaction zone, the next paddle is installed with its tip offset by 90° or 45° in the opposite direction to the rotation direction of the stirring shaft, and in the subsequent 3D reaction zone, the paddle is installed in the same direction as the rotation direction. It was installed with a 45° offset. Furthermore, a 1D-long inverted screw was attached to the tip of the reactor, and a discharge port was provided at the bottom of the other end. During the polymerization reaction, the shaft was rotated such that the peripheral speed of the scraper at the tip of the paddle was approximately 2500 cm/min. The reaction temperature of the feed section was adjusted to 80℃, and the temperature of all other reaction zones other than the feed section was adjusted so that the temperature of the reaction mixture was 80℃.
The temperature was adjusted by changing the temperature of the heat medium in the jacket so that the temperature was between 110°C and 110°C. The residence time inside the reactor was approximately 4 minutes. The powder discharged from the discharge port was a copolymer containing 20% of unreacted substances. This copolymer was immediately fed into the second stage mixer under an inert gas atmosphere. This second stage mixer has a reaction cylinder with a jacket on the outside, and has a pair of shafts with a large number of mixing blades fixed inside, and as the shafts rotate in different directions, the contents are mixed. This is a type of reactor that mixes. The connection between the first stage reactor and the second stage mixer is connected to a close head, and the vertical distance between the reverse screw at the discharge port of the first stage reactor and the tip of the screw at the supply port of the second stage mixer. were close together. 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, and the mixture was aged until the polymerization was completed. After a residence time of 30 minutes, a fine powder polymerization product containing less than 1% of unreacted monomer was obtained from the outlet. This polymerization product was led to a terminator mixer directly connected to this second stage mixer.
This stopper mixer has a polymer powder supply port on one end, a powder discharge port on the other end, a vent port for collecting waste gas directly above it, and a cooling jacket on the outside. It has a body and a pair of shafts with many mixing blades fixed inside.
This type of mixer mixes the contents while the shafts rotate in different directions. In this terminator mixer, triphenylphosphine in an amount twice the mole of the polymerization catalyst used was added to the polymerization product discharged from the second stage mixer and mixed to deactivate the catalyst. The waste gas generated during the polymerization reaction was collected from the vent port of the terminator mixer. The polymerization product containing this deactivated catalyst is further pulverized by a feather mill in which knives rotate at high speed to shear and pulverize the powder to obtain a coarse copolymer with finer particle size. was ground until it could pass through a 10 mesh sieve. The intrinsic viscosity (measured at 60°C in p-chlorophenol containing 2% α-pinene) of the crude copolymer obtained after approximately 500 hours of operation was 1.41-
The polymerization yield was 1.46 dl/g, and the polymerization yield was stable at 99.2 to 99.8%. During this operation, the first stage reactor did not generate any abnormal noise due to metal-to-metal contact. When the inside of the reactor was inspected after the polymerization reaction was completed, it was found that there were no scratches on the inner surface of the shell, the side surface of the paddle, or the tip of the paddle, and the scale on the inner surface of the shell was maintained at the thickness of the clearance between the scraper and the inner surface of the shell. To 100 parts by weight of the obtained crude copolymer were added and mixed 0.5 parts by weight of the antioxidant Irganox 259 (trade name), 0.2 parts by weight of polyvinylpyrrolidone, and 0.1 parts by weight of calcium hydroxide. The mixture was heated and melted at 210°C in a vented single-screw extruder. The molten resin was immediately supplied to a fully intermeshing co-rotating deep groove twin screw extruder. The temperature of this extruder was controlled so that the resin temperature was 210°C. The resin was stabilized by heating and melting under reduced pressure of 40 Torr and residence for 20 minutes. The unstable oxymethylene terminal was decomposed and recovered from the vent port as formaldehyde gas along with some solvent and unreacted substances. From the die head, stabilized white resin is extruded as a strand.
It was then pelletized and commercialized. The intrinsic viscosity of this copolymer is 1.43 dl/g, and the rate of weight loss due to thermal decomposition at 222°C in air K ^air _2
22
was 0.01% by weight/min, and the physical properties of the molded product were as follows.

[Table] Example 3 Using the same type of reactor as used in Example 2, L/D=
7 was used. Immediately below the raw material supply port, there are interlocking feed screws with a length of 1D, and then in the next 2D reaction zone, from the supply port to the discharge port, the next paddle has its tip on the shaft. A flat paddle is attached to the next 2D with a 45° shift in the opposite direction to the rotational direction, and a flat paddle is attached in the same way to the next 2D with a 90° or 45° shift in the opposite direction to the rotational direction. It was attached in the same way, shifted by 45 degrees. The outlet is the last
2D, installed at the bottom of the tip of the reaction zone. In this reactor, 80 kg of trioxane per hour, 2.0 kg of liquefied ethylene oxide per hour and 1 mole of trioxane were added.
0.13 mmol of boron trifluoride diethyl etherate was mixed and fed in a raw material mixer as shown in FIG. During the polymerization reaction, the shaft was rotated such that the peripheral speed of the paddle tip was approximately 2500 cm/min. The temperature of the heat medium in the jacket was adjusted so that the reaction temperature was 80 to 110°C. The powder discharged from the discharge port contains 30% unreacted materials.
It was a copolymer containing The operating conditions of the continuous reactor were extremely stable for about 500 hours. The intrinsic viscosity of the obtained crude polymer is
It was stable at 1.40-1.44 dl/g. During the polymerization reaction,
There was no abnormal noise caused by contact between the paddles or the tip of the paddle and the inner surface of the body. Comparative Example 1 A jacket having a jacket capable of heating or cooling the reaction mixture on the exterior of the shell, a pair of shafts fixed substantially horizontally along the reaction shell, each of said shafts comprising a number of interlocking elliptical plates. A reactor is used which has a paddle with a flat end that engages with the long axis of the paddle to stroke the other surface, and this is done every hour.
trioxane at a flow rate of 80Kg, liquefied ethylene oxide and trioxane at a flow rate of 2.0Kg per hour
0.13 mmol of boron trifluoride diethyl etherate was mixed in advance in a polymerization raw material mixing device shown in FIG. 7 and charged into the feed port. The reactor had an inner diameter D of 200 mm and a ratio L/D of 12. The combination of many paddles suspended inside the reactor was the same as in Example 2. The rotational speed of the shaft was set so that the rotational circumferential speed of the flat end of the paddle was approximately 2500 cm/min. The reaction temperature in the feed section was adjusted to 80°C, and the internal temperature in all reaction zones other than the feed section was adjusted to be 80-110°C. The powder discharged from the discharge port was a copolymer containing 30% of unreacted substances. This copolymer was prepared in Example 2.
It is sent to the same second stage mixer as used in
In the stage mixer, the reaction temperature was maintained at 60°C, and the polymerization was completed by gentle stirring at a stirring shaft rotation speed of 25 rpm. After a residence time of 30 minutes, a fine powder polymerization product containing less than 1% of unreacted monomer was obtained from the outlet. Twice the mole of triphenylphosphine as the polymerization catalyst used was added and mixed to this polymerization product in the same manner as in Example 2. After about 10 hours of continuous operation, an unusual noise, which appeared to be metal-on-metal contact, was generated from the first stage reactor. Also,
The internal temperature of the first stage reactor also began to rise rapidly, and although the temperature in the jacket part was partially lowered to 30°C, it was not possible to stop the internal temperature from rising. After about 100 hours of continuous operation, the abnormal noise in the first stage reactor became louder and louder, and the polymerization machine suddenly stopped rotating due to shear pin precipitation, so the operation had to be stopped. When the first stage reactor was disassembled and the inside inspected, scars due to metal-to-metal contact were found on the inner surface of the lower part of the reactor in the area around the center of the shaft and on the tip of the paddle. Furthermore, hard scale of the polymerization product was observed on the inner surface of the upper part of the reaction shell, which was more than twice the value of the clearance between the inner surface of the shell and the tip of the paddle measured before the start of polymerization. From this observation, hard scale of the polymerization product adhered to the inner surface of the upper part of the reaction vessel, exceeding the normal clearance.
It became clear that this scale layer pressed down on the shaft, causing the shaft to rotate eccentrically, causing the inner surface of the lower body part to come into contact with the tip of the paddle. It has also become clear that the formation of an extremely thick scale layer impairs the heat transfer effect, making it impossible to remove heat sufficiently. The polymerization product obtained during about 100 hours of continuous operation was subjected to deactivation of the catalyst in the same manner as in Example 2, and was further subjected to pulverization, mixing with a heat stabilizer, and heat stabilization to produce a product. The intrinsic viscosity [η] of the obtained copolymer was 1.15
dl/g, and the polymerization reduction rate K ^air ₂₂₂ due to thermal decomposition at 222° C. in air was 0.09% by weight/min. Comparative Example 2 A reactor of the same type as that used in Comparative Example 1 with a shell inner diameter D of
A reactor of 50 mm and L/D=15 was used. The paddle inside the reactor was an elliptical plate with a flat end at its tip. Immediately below the raw material supply port, feeding screws with a length of 2D and interlocking with each other are attached to the stirring shaft, and in the remaining 13D, from the supply port to the discharge port, the tip of the next paddle is set so that the shaft rotates in the opposite direction. The paddles were attached at a 45° angle. This reactor was charged with 2 kg of trioxane per hour.
For 70 g of 1,3-dioxepane and trioxane, 0.18 mmol of boron trifluoride diethyl etherate was fed. The reaction temperature was maintained at 50 to 60°C, and the rotation speed of the stirring shaft of the reactor was such that the rotational peripheral speed of the paddle tip was approximately
The speed was set to 3100cm/min. However, the raw material mixture was discharged from the discharge port in a liquid state, and the polymerization reaction hardly progressed.
On the other hand, in order to increase the reaction rate, polymerization was carried out by increasing the temperature of the heat medium in the jacket so that the reaction temperature reached 80°C, but in the end, a slurry of crude polymer containing 70% unreacted monomer came out of the discharge port. Ejected.
In addition, this product was further introduced into a non-self-cleaning mixer, but the polymer stuck to the inner surface of the cylinder and the shaft, or formed lumps, making it completely impossible to operate. Furthermore, polymerization was carried out by rotating the stirring shaft of the reactor at a relatively low rotational speed such that the circumferential rotational speed of the paddle tip was 300 cm/min, and by maintaining the reaction temperature at 60°C. The resulting crude polymer powder was so coarse that 40% by weight of the total could not pass through a 10-mesh sieve, and furthermore contained 50% by weight of unreacted monomer. This was ground, washed with benzene containing triethylamine, and then washed repeatedly with acetone to remove unreacted monomers, and then dried. To this polymer, 0.2% by weight of dianoguanidine and 0.5% by weight of Irganox 259 were added, and the mixture was stabilized by kneading at 200° C. for 20 minutes in a small kneader.
The intrinsic viscosity of the stabilized polymer was 1.21 dl/g, and the weight loss rate K ^air ₂₂₂ at 222° C. in air was 0.05% by weight/min. Comparative Example 3 Polymerization was carried out using the same reactor as in Comparative Example 2. The paddle inside the reactor is an elliptical plate with a flat end at its tip, and a 2D long interlocking screw is attached to the stirring shaft just below the raw material supply port. The tip of the next paddle toward the outlet was attached with a 90° offset in the opposite direction to the rotational direction of the stirring shaft. This reactor was charged with 2 kg of trioxane per hour.
For 70 g of 1,3-dioxepane and trioxane, 0.18 mmol of boron trifluoride diethyl etherate was fed. The reaction temperature was maintained at 50 to 60°C, and the rotation speed of the reactor was such that the peripheral speed of the paddle tip was approximately 3100 cm/
It was made to be min. However, 10 minutes after the start of polymerization, the shear pin suddenly broke, making it impossible to rotate the shaft of the reactor. When the reactor was opened and examined, it was found that the polymerization zone from the position 2D from the supply port to the position 8D from the supply port was filled with polymer at a filling rate that filled 100% of the free space. As a result, the shaft could not rotate at all, and it was discovered that the shear pin, which was attached to the shaft to prevent damage to the driving part, had also broken. Comparative Example 4 Same as Example 1 except that the first stage reactor used was a reactor in which the paddle of the first stage reactor of Example 1 was replaced with a pseudo-triangular paddle without a scraper.
The polymerization reaction was carried out in exactly the same manner. As a result, in the first stage reactor, the reaction temperature
In order to make the proportion of unreacted substances contained in the powder discharged from the discharge port 40% at 75°C, the temperature of the jacket cooling water needs to be about 10°C lower than in Example 1. It was hot.

[Brief explanation of the drawing]

FIG. 1 and FIG. 5 are partially sectional side views schematically showing a reactor used in the present invention. Second
A and B in the figures and FIG. 6 are partially sectional front views showing the shape of the paddle in the present invention, and FIG.
Figure A shows a convex lens type flat paddle, Figure 2B shows a convex lens type helical paddle, and Figure 6 shows a pseudo triangular flat paddle. FIG. 3 is an overview diagram showing the shape of the paddle in the present invention. FIG. 4 illustrates another example of the paddle according to the present invention. FIG. 4A is a front view, and FIG. 4B is a side view thereof. 7th
The figure is a sectional view of the raw material mixing device. 1, 1'... Stirring shaft, 2... Body, 3... Jacket, 4, 4'... Paddle, 41, 43, 44...
...Scraper, 42...Side of paddle, 5...
Raw material supply port, 6... Polymer 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 with different centers and the same diameter. When there are multiple missing parts that overlap each other, the shapes of the missing parts are almost congruent; a temperature control jacket is provided on the outer periphery of the 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 body, and each of the stirring shafts has a plurality of plate-shaped paddles fixed to the stirring shaft so as to touch each other. The plate-shaped paddle has a cross section perpendicular to the stirring axis in the shape of a convex lens or a pseudopolygon inscribed in a virtual circle at each apex angle, and the apex corner of the cross section has a plane of symmetry. No sharp scrapers;
One paddle faces at least one of the other paddles fixed to the other stirring shaft, and the one paddle slightly scrapes with its sharp scraper 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 a clearance, is used as a reactor, and a liquid raw material mixture containing molten trioxane, a catalyst, and optionally a comonomer is supplied from the feed port of the reactor. A polyacetal homopolymer or a polyacetal homopolymer characterized in that it is continuously supplied, a polymerization reaction is carried out while the raw material mixture is moved to the discharge port by rotation of the paddle, and the reaction product is taken out as powder or granules from the discharge port. Method for producing copolymer. 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 of 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 in parallel to the longitudinal direction of the cylinder, 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 shaped paddle is a sharp scraper whose cross section in the direction perpendicular to the stirring axis is a convex lens shape or a pseudopolygon inscribed in a virtual circle at each apex angle, and the apex corner of the cross section does not have a plane of symmetry. one paddle faces at least one of the other paddles fixed to the other stirring shaft, the one paddle scraping with its sharp scraper the inner surface of the shell to which it belongs and the other paddles; A continuous stirring mixer is used as a reactor, which is positioned so as to rotate with a slight clearance from the side surface of the reactor, and molten trioxane, a catalyst, and optionally a comonomer are supplied from the feed port of the reactor. A reaction product containing more than 5% by weight of unreacted materials and less than 40% by weight by continuously supplying a liquid raw material mixture and carrying out a polymerization reaction while moving the raw material mixture to the discharge port by rotating the paddle. The product 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 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 the same. The polymerization reaction is continued by introducing the mixture into a horizontal continuous mixer with a non-crowded structure, and the polymerization product containing 5% by weight or less of unreacted substances and having substantially completed polymerization is taken out as a powder. A method for producing a polyacetal homopolymer or copolymer. 3. The plate-shaped paddle has a convex lens-shaped cross section or a pseudo-triangle inscribed in a virtual circle at each apex angle,
3. The method according to claim 1, wherein the apex corner of the cross section is provided with a sharp scraper having no plane of symmetry. 4. In the continuous stirring mixer, from the supply port to the discharge port, the next paddle adjacent to one paddle is sequentially attached to the stirring shaft so as to be 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. 5. 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. 6 In the continuous stirring mixer, the clearance between the tip of the paddle and the inner surface of the barrel is 2% or less of the diameter of the circumscribed circle 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 2% or less of the diameter of the circumscribed circle of the paddle. 3. The method according to claim 1 or 2, wherein the clearance is 5 times or less than the above-mentioned clearance. 7. 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 diameter of the circumscribed circle 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 1% or less of the diameter of the circumscribed circle of the paddle. 3. The method according to claim 1 or 2, wherein the clearance is less than twice the clearance. 8. 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 5 to 30. or the method described in paragraph 2. 9. 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. 10 In the continuous stirring mixer, the rotational speed of the stirring shaft is set so that the rotational peripheral speed of the paddle tip is 800 to 5000.
3. The method according to claim 1 or 2, wherein the method is adjusted to a rate of cm/min. 11. 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. 12. The method according to claim 1 or 2, wherein the polymerization reaction temperature is in the range of 60 to 150°C. 13. The method according to claim 1 or 2, wherein the polymerization reaction temperature is in the range of 65 to 115°C. 14. The method according to claim 1 or 2, wherein boron trifluoride etherate is used as a catalyst. 15. The method according to claim 1 or 2, wherein ethylene oxide is used as the comonomer.