JP2504031B2 - Method for producing homo- or copolymer of polyoxymethylene - Google Patents

Description

Description: TECHNICAL FIELD 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.

[Prior art and its problems]

Conventionally, various proposals have been made regarding the method and apparatus for bulk polymerization of trioxane. Most of them are mixers having a single shaft or two or more shafts for stirring, and apply a shearing force to the polymerization mixture during the polymerization reaction to take out the reaction product as a pulverized powder or granular material. For example, in JP-A-57-40520, there are two mutually rotating shafts, a large number of paddles mounted on each shaft, and a barrel close to the outer periphery of the paddle,
A reactor in which the long axis end of the paddle is periodically arranged close to the short axis end of the other paddle is also proposed.

In this counter-rotating type reactor, since the reaction mixture is not completely self-cleaning in the reaction region where it rapidly solidifies from a slurry state, scale adheres to the paddle, which prevents heat transfer by the scale and scale. Is mixed in the reaction product and deteriorates the quality, which is not preferable. Further, the shearing force applied to the reaction mixture is insufficient, and the polymer is not sufficiently finely divided.

On the other hand, as a completely self-cleaning polymerization reaction material, JP-A-51-84890 discloses that the polymerization reaction material consists of a long case substantially extending along the outer boundary of a pair of stirring shafts. A polymerization reactor has been proposed, in which a shaft has multiple elliptical plates that mesh with each other, and the elliptical plates have flat ends that mesh with each other at the long axis end of the plates so as to stroke the surface of the mating member. The present inventors have also proposed a reactor incorporating a convex lens-shaped paddle having a sharp tip or a pseudo-polygonal plate-shaped paddle. (JP-A-56-38312
Further, it is characterized in that both ends of the convex lens type paddle or the pseudo polygonal paddle are provided with scrapers each having a shape cut with an arcuate circumferential surface so as to have an asymmetrical cross section with respect to the cross section long axis. I also suggest something to do. (JP-A-56-38313) These inventions have an object to efficiently scrape off the scale adhering to the inner surface of the body and grind the reaction mixture.

However, when performing continuous bulk polymerization of trioxane,
The polymerization raw material is liquid, and the reaction mixture rapidly changes from a slurry state to a lump state as the reaction progresses. The reaction mixture is efficiently stirred and mixed in response to such a phase change,
In order to take out the polymer as pulverized fine particles while maintaining the piston flow from the supply port to the discharge port, it is not sufficient to have the self-cleaning property as seen in the above invention and to improve the cross-sectional shape of the paddle. Is.

Therefore, the present inventors changed the shape of the paddle so that the feed of the reaction mixture became gradually smaller from the raw material supply port toward the discharge port, or changed the arrangement of the paddles continuously or stepwise. I'm proposing that first. (JP-A-56
By this method, the reaction mixture can be transported while maintaining the Biston flow in response to the phase change of the reaction mixture, and local overfilling can be prevented, so that the desired conversion rate and stability can be obtained. The reaction product can be taken out. However, according to the present invention as well, in the reactor of the type in which the stirring shafts rotating in the same direction are horizontally installed on the left and right, since the reaction mixture is filled only in one side shaft, the whole reactor is not effectively utilized. Have

That is, in a state where the reaction mixture is present at a filling rate of 50% by volume or more with respect to the effective volume of the reactor, the reaction mixture is filled on both sides, but at such a filling rate, shear heat generation in the powder zone occurs. Occurs and makes it difficult to control the polymerization temperature. This means that when the average filling rate is 50% by volume, the filling rate in the one-sided axial space reaches 80 to 100% by volume, and heat is generated due to powder compression. For this reason, it is impossible to operate at a filling rate of 50% by volume or more with respect to the effective volume of the reactor, and therefore, it is generally necessary to operate at less than 30% by volume.

[Means for solving problems]

The present invention has been made in order to solve the problems of the above-mentioned conventional methods, and has a hollow cylinder having a raw material supply port and a reaction product discharge port at distant positions. It has a cross-section with overlapping circles of the same diameter, and has a jacket for temperature control on the outer circumference of the cylinder.The inside of the hollow cylinder is parallel to the longitudinal direction of the cylinder at the center of each circle. And a plurality of plate-shaped paddles fixed so as to be in contact with each other, the plate-shaped paddles being perpendicular to the direction of the stirring axis. The cross section in the direction is a convex lens shape, an elliptical shape, or a pseudo-polygon inscribed in a virtual circle at each apex angle, and one paddle faces one of the other paddles fixed to another stirring shaft, The paddle maintains a slight clearance at its tip with the inner surface of its torso and other paddles. The stirring shaft is positioned so as to rotate so that the left stirring shaft is at the right when the rotation direction is clockwise when the discharge port side is viewed from the raw material supply port side, and the right side is at the top when the rotation direction is counterclockwise. In addition, the straight line connecting the centers of the two stirring shafts should be installed at an angle of 30 to 45 ° from the horizontal when the plate-shaped paddle has a convex lens shape or an elliptical shape, and 15 to 30 ° from the horizontal when the paddle is a pseudo triangle. Using a continuous stirring mixer as a reactor,
Molten trioxane and a catalyst, optionally a comonomer, and a molecular weight modifier are continuously supplied from a raw material supply port of the reactor, and a polymerization reaction is carried out while a raw material mixture is moved to a discharge port by rotation of a paddle, A method for producing a homopolymer or copolymer of polyoxymethylene, in which a reaction product is taken out as a powder or granules from a discharge port.

Furthermore, it is desirable to carry out the present invention such that the feed of the reaction mixture in the reactor becomes gradually smaller from the raw material supply port toward the discharge port.

The feeding ability can be adjusted by continuously or stepwise changing the shape or arrangement of the paddles attached to the stirring shaft, and more specifically, a paddle having a convex lens shape or an elliptical cross section can be used. In this case, from the material supply port toward the discharge port, the paddle adjacent to the one paddle on the discharge side is displaced by 45 °, 90 °, or 135 ° in the negative direction with respect to one paddle, so that the paddle has a pseudo-triangular cross section. In the case of,
This can be achieved by shifting the paddle adjacent to the one paddle on the discharge side in the negative direction by 30 °, 60 ° or 90 °. In addition, the side surface of the paddle is flat, or a feed helical type machined by twisting so that the contents are pushed toward the discharge port by the rotation of the stirring shaft,
On the contrary, there is a reverse helical type in which the side surface is twisted so as to return the content to the supply port, and by combining these, the feeding ability of the reaction mixture can be adjusted.

Next, the reactor used for carrying out the present invention will be described with reference to the drawings. FIG. 1 schematically shows an example in which a convex lens paddle is used in the reactor used in the present invention in which two circles having the same eccentricity and the same diameter are overlapped with each other to form an 8-shaped cross section. . 2 (A) and 2 (B) show A of FIG.
Fig. 4 is a schematic view of the inside 4 of the reactor barrel in the A line cross section. The shaft rotates counterclockwise, the straight line connecting the centers of both shafts is horizontal, and the right side is the upper part. It is tilted by an angle θ. Further, as shown in FIG. 3, the convex lens type paddle can be sharpened at its tip,
Further, the side surface is flat as shown in FIGS. 2 (A) and 3 (A), and FIGS. 2 (B) and 3 (B) show a helical type machined by twisting the side surface. The paddle is illustrated.

 In the example of FIG. 3, the shaft rotates clockwise.

That is, the reactor used in the present invention is, as schematically illustrated in FIG. 1 and FIG. 2, a continuous stirring mixer having a self-cleaning action on the inner surface upon rotation of the shafts 1, 1 ′. The outer circumference of the body 2 has a heating or cooling jacket 3 which is divided into one piece or a plurality of pieces and whose temperature can be controlled independently. Further, the inside of the stirring shafts 1, 1'in the barrel 2 may be structured so that a medium for heating or cooling can be passed through. A large number of paddles 4, 4 '... Each of which has a convex lens shape and has a cross-section with a plane including the long axis as a plane of symmetry, are fixed to the two stirring shafts 1, 1'. There are two types of paddles, one with a flat side as shown in Fig. 2 (A) and the other with a helical side as shown in Fig. 2 (B). The paddles 4, 4 '... It is possible to perform feed corresponding to the phase change of the system. Two
The stirring shafts 1, 1'of the book rotate in the same direction, and in the same cross section, one of the paddles fixed to the stirring shaft 1 is the stirring shaft 1 '.
The tip of the paddle 4 of the one stirring shaft 1 is constantly facing the other paddle fixed to the paddle 4'of the other stirring shaft 1 '.
Rotate while maintaining a slight clearance with the side surface of the body and the inner surface of the body 2. Therefore, the reaction mixture is paddle 4,4 '…
Due to the constant volume change of the space formed between the body 2 and the body 2, it undergoes constant compression and expansion and vigorous mixing.

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 exterior circle of the paddle, and the tip of the paddle of one stirring shaft and the other are The clearance from the side surface of the paddle attached to the shaft is 5 times or less, preferably 2 times or less. If the clearance is larger than this, a finely pulverized polymerization product cannot be obtained, and the thick scale attached to the inner surface of the cylinder hinders heat transfer with the jacket, making it difficult to control the reaction temperature. However, it is not preferable.

Further, as the paddle, as shown in FIG. 4, an elliptical plate having a flat end at its long axis end may be used. Further, as shown in FIG. 5, a pseudo-triangle paddle whose cross section in the direction perpendicular to the stirring axis direction of the paddle is inscribed in a virtual circle at each vertex can also be used. A sharp scraper can be attached to the apex of the pseudo-triangle paddle.

The stirring shaft with these paddles attached is shown in Figs.
As shown in Fig. 4, Fig. 5 and Fig. 5, rotation of the stirring shaft when the straight line connecting the centers of the two stirring shafts is installed with an inclination of θ and the discharge port side is viewed from the raw material supply port side If the direction is clockwise, the left shaft is installed, and if it is left, the right shaft is installed at the top.

The inclination angle θ of the left and right axes differs depending on the major axis diameter of the reactor paddle, the number of rotations, the axial thickness of the paddle, the shape of the paddle, etc., but an oval plate or convex lens type paddle is used for the cross-sectional shape. When used, it is suitable to set the temperature to 30 to 45 °, and to set the temperature to 15 to 30 ° C. when using a pseudo-triangle or a pseudo-polygonal paddle whose vertices are in contact with a virtual circle.

Below these inclination angles, the reaction mixture is unevenly distributed, and above these inclination angles, only the lower stirring shaft space is filled, which is not preferable.

Usually, in order to obtain a polymerized product as a completely pulverized granular material, the rotation speed of the stirring shaft is set to the rotation speed of the paddle tip.
It is preferably in the range of 800 to 5000 cm / min, 1600 to 40
More preferably, it is 00 cm / min.

Generally, when the rotation speed is high, it is preferable to make the inclination angle large, and it is preferable to make the inclination angle large even in a reactor in which the major axis diameter of the paddle is large.

The thickness of the plate-shaped paddle is 1/20 of the diameter of the circumscribed circle of the paddle.
It is desirable to set it to about 1/5.

According to the research by the present inventor, in the bulk polymerization method of trioxane using a continuous stirring mixer, in response to the change of the state of the reaction mixture, from the raw material supply port toward the discharge port of the reaction product, the reaction mixture It was revealed that it is desirable to gradually reduce the feeding effect.

Also in the present invention, it is preferable that the feeding effect of the reaction mixture is gradually reduced from the raw material supply port toward the discharge port, because the filling rate of the entire reactor becomes uniform.

In particular, in the region where the content of the unreacted monomer is about 70 to 40% by weight and the reaction mixture exhibits a creamy or sticky fine powdery state, the moving speed of the reaction mixture is extremely small and overfilling easily occurs, Therefore, in this region, especially in the region where the amount of unreacted monomer is 50% by weight or more, and especially 60% by weight or more, the deviation angle of one paddle in the negative direction of the other paddles adjacent to this on the discharge side is In the case of a convex lens type or elliptical paddle, it is desirable that the angle is about 90 ° or less.

Further, even in a region where the reaction mixture having an unreacted monomer content higher than that is in the form of liquid or slurry, it is desirable that the deviation angle is about 90 ° or less. An angle of about 90 ° or more is not preferable because creamy or tacky fine powder is likely to be generated in this region.

In the most preferred embodiment of the present invention, in a region where the reaction mixture contains unreacted monomer in an amount of about 50% by weight or more, first, a paddle arrangement having only a negative shift angle of 45 ° is used in the area near the feed port, and then, Alternate arrangements of 45 ° and 90 ° negative displacement angles and / or 45 ° negative displacement angles in subsequent areas
It is preferable to use a 90 °, 90 ° repeating sequence.

Further, in the region following the above region where the unreacted monomer content is less than about 50% by weight, the negative shift angle 45
Alternate arrangement of ° and 90 ° and / or offset angle 45 in the negative direction
It may be a repeating arrangement of °, 90 ° and 90 °, but as the content of unreacted monomer becomes lower, it becomes easier for underfilling to occur, so to prevent underfilling as it approaches the discharge port of the reaction product. If desired, use a paddle arrangement with a negative displacement angle of only 90 °, an arrangement of only 135 °, an alternating arrangement of 90 ° and 135 °, and / or a repeating arrangement of 90 °, 90 °, 135 °. You can

In this way, by using a combination of paddles having different feeding effects depending on each reaction zone, the filling rate of the contents in the reactor is further maintained in the whole reactor, and shear heat generation due to overfilling in some regions is caused. Is prevented, and the effective heat transfer area on the inner surface of the body can be made large, so that the reaction temperature can be easily controlled.

Reactor used in the method of the present invention which is industrially inexpensive and can be manufactured so that the clearance between the tip of the paddle and the body is 2% or less, preferably 1% or less of the diameter of the circumscribed circle of the paddle. As L / D is 30 or less, preferably 15
Below are the ones. Usually, L / D is selected in the range of 5 to 30, preferably 6 to 15. By using such a reactor, a sufficient residence time can be obtained, and a polyacetal of high quality with a sufficiently high conversion can be obtained. L / D
Is less than 5, it is difficult to obtain a sufficiently high conversion rate.

Further, in order to suitably carry out the method of the present invention, a reaction temperature of 60 to 150 ° C., preferably 65 to 115 ° C., that is, a relatively high temperature range in which the trioxane is kept in a liquid state is selected. High-quality polyacetal can be obtained without causing a runaway reaction even at such a high temperature. If the reaction temperature is lower than 60 ° C, the reaction rate will be slow, and it will be difficult to obtain a sufficiently high conversion rate.If the reaction temperature is higher than 150 ° C, a sufficiently high quality polyacetal will be obtained by depolymerization and the like. Becomes difficult.

The present invention is used for homopolymerization or copolymerization of trioxane as described above. The copolymer has 0.4 to 40 mol%, preferably 0.4 to 10 mol%, of 2 carbon atoms in the oxymethylene main chain.
It contains the above oxyalkylene units. The cyclic ether or cyclic acetal which is a copolymer giving an oxyalkylene unit is, for example, of the general formula (1).

Here, in the formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different and each represents a hydrogen atom, an alkyl group or a halogen-substituted alkyl group. R ₅ represents a methylene group, an oxymethylene group, a methylene group substituted by an alkyl group, a halogenated alkyl group, or an oxymethylene group, in which n is an integer of 0 to 3, or CH _{2 m} −. OCH ₂ —, O—CH ₂ —CH _{2 m} O—CH ₂ — means a divalent group represented by [where n is equal to 1 and m is an integer of 1 to 4]. The above alkyl groups have 1 to 5 carbon atoms, the hydrogen atoms of which may be replaced by 0 to 3 halogen atoms, in particular chlorine atoms.

Specific examples of cyclic acetals or cyclic ethers include ethylene oxide, glycol formal or diglycol formal. Furthermore, for example, propylene oxide and epichlorohydrin may be used. Also suitable are long-chain α, ω-diol cyclic formal, such as butanediol formal, ie 1,3-dioxepane, or hexanediol formal.

As the polymerization catalyst, a general cationic polymerization catalyst is used, but in particular, boron fluoride, borohydride 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 etherate [BF ₃ · O (C
₂ H ₅ ) ₂ ] is a preferred catalyst. Boron trifluoride etherate is usually 0.01 to 1 per mol of trioxane.
It is used in an amount of mmol, preferably 0.05 to 0.2 mmol.

In the present invention, the polymerization may be carried out using a relatively small amount of anhydrous inert medium. The use of an inert medium controls reaction heat and shear exotherm directly with the latent heat of evaporation of this medium,
Make the reaction smooth. The inert medium may or may not dissolve the trioxane, the comonomer or the catalyst, and may be an aliphatic or cycloaliphatic hydrocarbon such as hexane, heptane or cyclohexane;
Aromatic hydrocarbons such as benzene, toluene and nitrobenzene; light petroleum fractions; halogenated hydrocarbons such as ethane dichloride and carbon tetrachloride are used. Generally, these inert media should be used in an amount of 10% by weight or less based on the amount of trioxane used.

Further, in the present invention, the polymerization degree of the product can be adjusted by using a chain transfer agent as in a conventional method. As the chain transfer agent, alcohols, for example, methanol, ethanol,
Various known chain transfer agents such as phenols such as phenol, 2,6-dimethylphenol and acetals such as methylal and bis [methoxymethyl] ether are used.

In FIG. 1, the raw material supply port 5 of the reactor used in the present invention is provided at one end of the barrel. Each component of the raw material, namely trioxane, catalyst and optionally comonomer,
The chain transfer agent and / or the inert medium may be mixed immediately before being introduced into the supply port 5, or may be separately introduced. In particular, in a continuous reaction in which trioxane is copolymerized with a cyclic ether or a cyclic acetal to obtain a polyacetal copolymer, as shown in FIG. 6, the tip of the comonomer supply nozzle and the tip of the polymerization catalyst supply nozzle are connected to each other. Advantageously, the nozzles are opened in close proximity, the tips of the two nozzles are flushed with a stream of trioxane to mix and the reaction mixture thus obtained is immediately fed to the reactor. In FIG. 6, 8 is a trioxane inflow path, 9 is a comonomer supply nozzle, 10 is a polymerization catalyst supply nozzle, 11 is an orifice part, and 12 is an outlet of the reaction mixture. In the orifice section, 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, a raw material mixture containing 10 wt% or less of an inert medium of trioxane can be smoothly reacted without causing trouble such as clogging of the feed port tip with a scale. Can be supplied to. After being supplied to the reactor, the raw material mixture undergoes transport and mixing, and polymerizes in a short 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 polymerized product in the form of powder or granules, but a damper 7 may be provided as necessary to adjust the amount of residence in the reactor. The residence time in this reactor is usually 0.5 to 30 minutes, preferably 1 to 10
It's a minute. The polymerized product discharged as granules is 40
It contains less than 5% by weight of unreacted material, for example, and can be sufficiently post-treated as it is. However, if it contains more than 5% by weight of unreacted material, it may be immediately It may be introduced into the second-stage continuous mixer to further increase the conversion rate until the unreacted material becomes 5% by weight or less. Second
As the stage mixer, a self-cleaning continuous stirring mixer in which the left and right stirring shafts are tilted and installed, or a similar continuous stirring mixer in which the left and right stirring shafts are horizontally installed, is used. To be Although not completely self-cleaning, it has shafts that rotate in opposite directions, a large number of paddles mounted on each shaft, and a barrel that is close to the outer periphery of the paddles, and the long ends of the paddles are periodically aligned with each other. A reactor configured to be close to the side paddle minor axis end can also be used. The horizontal continuous mixer has a plurality of stirring shafts and stirring blades attached to the shafts, and the clearance between the outer surface of the stirring blade and the inner surface of the hollow cylinder or the clearance between the outer surfaces of the stirring blades is not necessarily narrow. A cleaning structure can also be used.

Therefore, according to the present invention, the polymerization reaction is carried out in the above-mentioned continuous stirring and mixing machine under the conditions as described above, and the unreacted matter is reduced to 5%.
The reaction product containing more than 40% by weight but not more than 40% by weight is taken out as a granular material, and then this reaction product is introduced into the above-mentioned second-stage mixer directly connected to the continuous stirring and mixing machine for further polymerization. A method for producing a homopolymer or a copolymer of polyacetal, which comprises conducting a reaction and extracting a polymerization product containing unreacted material in an amount of 5% by weight or less and substantially completing the polymerization as a granular material. Offered as well.

In the reaction in the second stage mixer, the reaction temperature is 20 to 13
0 ℃, preferably 40 ~ 80 ℃, residence time 5 ~ 120
Min, preferably 10-100 min. Upon the aging of the reaction, the polymerization product is brought to completion of the polymerization.

The high conversion polymerization product discharged from the first-stage mixer or the second-stage mixer obtained as described above by the method of the present invention is immediately quenched by addition and mixing of a polymerization terminator. Done. As the polymerization terminator, various known polymerization terminators are used. For example, as a basic neutralizing agent,
Amine compounds such as triethylamine, tributylamine, triethanolamine or sodium hydroxide,
An alkaline inorganic compound such as potassium hydroxide or calcium hydroxide is used. These basic neutralizing agents can be used by dissolving them in water or an organic solvent such as alcohol, cyclohexane, benzene or toluene. The mixing of the solvent containing the basic neutralizing agent and polyoxymethylene homopolymer or copolymer is carried out in a tank equipped with a rotary stirrer or a slurry circulation pump. In this case, it is preferable from the viewpoint of handling that the concentration of the slurry is 5% by weight to 30% by weight. After the deactivating step, the copolymer is separated from the solvent by centrifugation or filtration and sent to the next stabilizing step.

The present inventors previously, in a method of terminating a polymerization reaction using a tertiary phosphine and an amine compound as a terminating agent, the crude oxymethylene copolymer was pulverized after adding a terminating agent or an organic solvent solution thereof, and 10 mesh (ASTM) sieve, 20 mesh (ASTM) sieve and 600 mesh (ASTM)
M) Sieve passing rate is 100%, 90% or more, and 60 respectively
It proposes the method of making powder which is more than%. According to this method, the amount of the terminating agent or the organic solvent solution added is 0.01 to 1 wt% of the crude oxymethylene polymer, so that the polymerization reaction can be stopped. Will be extremely advantageous to.

That is, it is preferable to continuously add the terminating agent by a continuous horizontal mixer directly connected to the reactor or a cone type hopper having a rotary blade inside. In this way, the crude polymer whose polymerization has been stopped can be continuously taken out from the stopper mixer. In this case, the polymerization reaction system formed by the reactor and, if necessary, the second-stage mixer directly connected to the reactor is a closed system having no opening other than the raw material supply port and the discharge port, and stopped. The agent mixer preferably has a supply port for the polymerization product, a discharge port for the crude polymer, and a vent port provided immediately above this. Waste gas generated during the polymerization reaction is collected from the vent port of the stopper mixer.

The crude oxymethylene polymer whose polymerization has been stopped is sent to a pulverizer and finely pulverized. As the crushing machine, it is also possible to use a gyro crusher, a rotary mill, a hammer mill, a pin mill, a rotary cutter mill, a jet mill or a combination of these in several stages.

In the case of a polyoxymethylene homopolymer, the end of the molecular chain is stabilized by acetylation, etherification and urethane conversion. In the case of a copolymer of polyoxymethylene and a cyclic acetal or a cyclic ether, the copolymer is heated at 160 to 240 ° C in the presence of a hydrolysis solvent selected from the group consisting of water, alcohols and a mixture thereof. , It is possible to take a method to decompose the unstable part. The crude polymer, which has been terminated by the addition of a tertiary phosphine compound, is mixed with a known heat stabilizer, and the mixture is heated and kneaded as it is in the temperature range from the melting point of the polymer to 100 ° C higher than the melting point, resulting in unstable parts. By further decomposing and removing the polyacetal, a further stabilized polyacetal copolymer can be obtained.

[Operation and effect of the invention]

As described above, in the conventional method using the reactor in which the two stirring shafts are positioned horizontally, the reaction mixture is unevenly distributed on one side, so that the inside of the cylinder of the reactor is not effectively used as a whole, and particularly the powder is Control of the polymerization temperature is disadvantageous because shear heat generation is likely to occur in the zone, and the other inner surface of the cylinder, which is less filled with the reaction mixture, does not contribute to heat transfer.

On the other hand, in the method of the present invention, since the reaction mixture is evenly filled in the barrel, the reactor is effectively used, the heat transfer from the jacket is efficiently performed, and the control of the polymerization temperature is easy. When compared with the reactor, the throughput is 1.5 to 2.0 times that of the horizontal case.

This difference in the effect on the processing capacity has an extremely great industrial significance.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 FIG. 2 (A) shows a reactor as shown in FIG.
A paddle as shown in (B) was attached and used. The inner diameter D of the barrel was 200 mm and the L / D was 10. The stirring shaft was rotated counterclockwise when the discharge port 6 side was viewed from the raw material supply port 5 side, and the straight line connecting the centers of the left and right stirring shafts was installed at an angle of 35 ° with respect to the horizontal. The 1D area directly below the supply port is the feed screw, and in the 2D area from the raw material supply port to the discharge port, the feed helical paddles are arranged in the direction opposite to the rotation direction (negative direction) by 45 °. In the next 5D area, the flat paddles are alternately shifted by 90 ° or 45 ° in the negative direction. In the final 3D, the flat paddles are alternately shifted by 90 ° or 135 ° in the negative direction. Was done. The paddles had a thickness of 40 mm. The tip of the paddle was sharpened and the clearance with the inner surface of the body was 2 mm or less, and the clearance with the paddle side surface of the opposite shaft was 4 mm or less. The stirring peripheral speed of the reactor is 25 at the peripheral speed of the paddle tip.
It was rotated to be 00 cm / min.

Liquid trioxane (350 kg / hr), liquefied ethylene oxide (10.5 kg / hr), boron trifluoride etherate as a catalyst, a concentration of 10 wt% in benzene, 0.10 mmol per mol of trioxane, methylal as a molecular weight regulator, concentration of 400 ppm based on trioxane. Used in.
These polymerization raw materials were premixed by the raw material mixing apparatus shown in FIG. 6 and immediately continuously introduced into the reactor through the supply port. Hot water was flown into the jacket 3, and the internal reaction temperature was adjusted to 95 ° C on average.

The average residence time of the reaction mixture in the reactor was 4.5 minutes. A polymerized product containing 8 wt% of unreacted material was obtained from the discharge port as a granular material. This polymerization product was immediately introduced into water containing 1 wt% of triethylamine and stirred to form a slurry liquid. The slurry concentration was set to 20 wt%. The crude oxymethylene copolymer whose polymerization reaction has been stopped in this way is separated by a centrifuge and then separated from the copolymer.
5 wt% water and 1 wt% methanol and 0.01 wt% triethylamine, 0.4 wt% 2,2'-methylenebis (4-methyl-6-t-butylphenol) and 0.2 wt% cyanoguanidine, 0.01 wt% Melamine was added, and the mixture was extruded at a reaction temperature of 180 to 190 ° C. in a single-screw two-vent type screw extruder. Unstable moieties were removed by melt hydrolysis and the cracked gas was recovered from the vent with added solvent and excess triethylamine.

The stabilized resin was extruded from a die and pelletized. Its MI value (according to ASTM D-1230) is 9.5.
g / 10 min, TGA has a decomposition rate of 0.018 in air at 222 ° C
% / Min.

Comparative Example 1 A polymerization reaction was performed in the same manner as in Example 1, except that the left and right stirring shafts of the reactor were horizontally installed, the paddle arrangement, the rotation speed, the raw material supply amount, the supply method, and the like. However, 10 minutes after the start of the reaction, the reactor torqueed out, and the operation became impossible. When inspecting the inside of the reactor, 5D from the raw material supply port
It was found that the free space of the right shaft was almost 100% filled from the raw material supply port to the discharge port in the ~ 7D reaction zone.

Example 2 A reactor having a pseudo-triangular paddle as shown in FIG. 5 and having a barrel inner diameter of 100 mm and L / D = 7.0 was used. The reactor rotates counterclockwise from the supply port to the discharge port,
The straight line connecting the centers of the left and right stirring shafts was tilted at 20 °, and the right shaft was installed at the top.

The paddle arrangement of this reactor was designed so that the feed ability gradually decreased from the raw material supply port toward the discharge port.

Next, at the discharge port of this reactor, the two rotating in opposite directions
It has a stirring shaft of a book, a large number of paddles mounted on each shaft, and a barrel close to the paddle, and the long paddle end of the paddle is configured to be close to the short shaft end of the mating paddle.
The reactor with the oval cross section of the paddle was directly connected.
The left and right stirring shafts of this downstream reactor were installed horizontally, the inner surface of the cylinder was 127 mm, and L / D = 10. The reactor on the upstream side and the reactor on the downstream side were connected by a closed shout.

80 Kg of molten trioxane per hour in the upstream reactor,
2.4 kg of liquefied ethylene oxide and boron trifluoride etherate were supplied as a benzene solution having a concentration of 10 wt% in an amount of 0.10 mmol per mol of trioxane, and methylal as a molecular weight regulator was added at a concentration of 400 ppm based on trioxane. The internal temperature of the upstream reactor is 90 on average.
The polymerization product containing 15 wt% of unreacted material was discharged from the discharge port, which was adjusted by warm water flowing through the jacket so that the temperature became ℃, and sent to the downstream side polymerization machine.

In the downstream side reactor, the internal temperature was adjusted to be 70 ° C on average. 0.05 wt% unreacted material from the downstream polymerization machine
A crude oxymethylene copolymer containing, was removed. This was immediately put into a mixer equipped with a screw that revolves in a cone type hopper while rotating internally, and a 0.8 mol / tribenzene solution of triphenylphosphine was used in the polymerization in an amount of triphenylphosphine. It was added so as to be twice the molar amount of the catalyst. Next, the crude oxymethylene copolymer has a large number of pins on a disk that rotates at high speed and is introduced into a pin mill that impacts and shears and pulverizes the powder between it and a fixed pin, and the particle size of the powder passes through 98% by weight of 20 mesh. Was crushed to become. Add 5 wt% water, 1 wt% methanol and 0.005 wt% ammonia to the pulverized powder, and add 0.4 wt%
2,2'-Methylenebis (4-methyl-6-t-butylphenol) and 0.5 wt% of polyamide were added, and the mixture was extruded at a reaction temperature of 180 to 190 ° C with a single-screw two-vent screw extruder. The stabilized resin was extruded from a die and pelletized. The MI value (ASTM D-1230) of this product is 9.
Decomposition rate in air at 222 ℃ by TGA is 0.020
% / Min.

Comparative Example 2 A polymerization reaction was performed in the same manner as in Example 2 except that the left and right stirring shafts of the reactor were horizontally installed.

However, the internal temperature of the reactor on the upstream side could not be controlled to 115 ° C or lower even if cooling water of -20 ° C was used for the jacket.

This was introduced into the same downstream reactor as in Example 2,
Similarly, triphenylphosphine was added, pulverized, and a molten hydrolyzing agent was added for heat stabilization.

The MI value of the obtained pellet was 37 g / 10 min, and the decomposition rate in air at 222 ° C. by TGA was 0.085% / min. This product vigorously evolved gas during molding, and many silver strips were found on the molded pieces.

In order to produce a polyacetal resin having the same physical properties as in Example 2 with this reactor, 50 kg of trioxane and 1.5 kg of ethylene oxide fed to the upstream reactor were used.
However, the total throughput must be reduced so that the supply ratio of the other auxiliary raw materials becomes the same as in Example 2.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view schematically showing a reactor used in the present invention. 2 (A) and 2 (B) are cross-sectional views schematically showing only the inside of the reactor barrel taken along the line AA in FIG. 1, and FIG. 2 (A) shows the flat paddle. ,
FIG. 2B illustrates a helical paddle. FIG. 3 is a partial sectional front view showing an example of the shape of a convex lens type paddle with scraper, and FIG. 3 (A) shows a flat paddle.
FIG. 3B illustrates a helical paddle. Similarly, the fourth
The figure illustrates an elliptical paddle and FIG. 5 illustrates a pseudo triangle paddle. FIG. 6 is a sectional view showing a raw material mixing apparatus. In FIGS. 2, 3, 4, and 5, arrows indicate the directions of rotation when the reactor is viewed from the raw material supply port toward the discharge port. The angle θ indicates the inclination of a straight line connecting the centers of both the left and right axes. Also, the display of the wall thickness of the body is omitted.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP 62-156116 (JP, A) JP 62-96515 (JP, A) JP 61-238812 (JP, A) JP 61- 209215 (JP, A) JP 60-101108 (JP, A) JP 58-32621 (JP, A) JP 58-32619 (JP, A) JP 57-40520 (JP, A) JP-A-56-59824 (JP, A)

Claims (2)

(57) [Claims] 1. A hollow cylinder provided with a raw material supply port and a reaction product discharge port at distant positions, and the cylinder has a cross section in which two circles having the same eccentricity and the same diameter are overlapped with each other. A jacket for temperature control is provided on the outer periphery of the cylinder, and two stirring shafts located parallel to the longitudinal direction of the cylinder are provided in the center of each of the circles inside the hollow cylinder. The stirring pad has a plurality of plate-shaped paddles fixed so as to be in contact with each other, and the plate-shaped paddle has a convex lens shape, an elliptical shape, or an imaginary circle at each vertex in a direction perpendicular to the stirring axis direction. A tangent pseudo-polygon, one paddle facing one of the other paddles fixed to the other stirring shaft, the one paddle being at its tip the inner surface of the barrel to which it belongs and the other paddle. It is positioned so that it rotates with a slight clearance, and the agitation shaft is It left stirring shaft when the rotational direction is clockwise when viewed outlet side, so that the right agitation shaft when the left around is the top, is a straight line connecting the centers of the two stirring shaft,
If the plate-shaped paddle has a convex lens shape or an elliptical shape, it is 30
~ 45 °, in the case of a pseudo-triangle, a continuous stirring mixer installed at an angle of 15 to 30 ° from the horizontal is used as a reactor, and molten trioxane and a catalyst and, if necessary, a comonomer amount from a raw material supply port of the reactor. It is characterized in that a polymer and a molecular weight modifier are continuously supplied, a polymerization reaction is carried out while the raw material mixture is moved to the discharge port by the rotation of the paddle, and the reaction product is taken out from the discharge port as a granular material. Method for producing homo- or copolymer of polyoxymethylene 2. A patent in which the shape of the paddle is changed so that the feed of the reaction mixture from the raw material supply port toward the discharge port of the reaction product becomes gradually smaller, or the arrangement of the paddles is continuously or stepwise changed. Method according to claim 1.