JPH0832757B2 - Polymerization method of trioxane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention is a continuous polymerization method, and more specifically, bulk polymerization of trioxane and cyclic ether using a self-cleaning biaxial mixer to produce a polyacetal copolymer. On how to do.

<Prior Art> In bulk polymerization of trioxane, a polymer is rapidly precipitated in a reactor, a polymerization product changes from a slurry state to a paste state, and finally solidifies. In order to prevent torque out of the reactor due to this solidification and to obtain a polymer having a desired particle size in the deactivation step of the catalyst following the polymerization step, it is necessary to provide a sufficiently large stirring force in the reactor. However, on the other hand, in order to obtain a high polymerization conversion rate, it is necessary to allow the polymer to stay in the reactor as much as possible.

Therefore, as a polymerization reactor, it has a strong stirring ability,
A twin-screw self-cleaning mixer having a jacket whose reaction temperature can be controlled is particularly preferably used.

Many proposals have been made so far, for example, a method using an elliptical paddle in JP-A-51-84890 and a convex-lens paddle having a sharp tip in JP-A-56-38313. A method using a convex lens-shaped or pseudo-polygonal paddle with a sharp scraper has been proposed.

When the paddle arrangement method is inappropriate, for example, when the retention amount is small, the polymerization conversion rate hardly increases, or when the retention amount is excessive, the stirring shaft of the reactor is torqued out and steady operation is performed. If you can't
Various paddle arrangement methods have been proposed. For example, Japanese Unexamined Patent Publication No. 56-59824 discloses a method of arranging the feeding effect so that the feeding effect is reduced in sequence. Arrangement methods have been proposed.

However, a sufficient retention amount cannot be secured only by the paddle arrangement method, and in order to obtain a high polymerization conversion rate, the method disclosed in Japanese Patent Laid-Open No.
In Japanese Laid-Open Patent Publication No.-44690, a method of connecting two or more reactors in series is proposed.

<Problems to be Solved by the Invention> An object of the present invention is to provide a method for increasing the amount of residence in a reactor and obtaining a high polymerization conversion rate without causing torque-out of the reactor.

<Means for Solving the Problems> That is, the present invention has a heating or cooling jacket on the outer circumference of the body of a reactor, and the cross section thereof has the shape of two overlapping eccentric circles having the same diameter. Each end of the machine is provided with a raw material supply port and a discharge port for the polymerization product, and inside thereof, a pair of equilibrium stirring shafts and a plurality of plate-shaped paddles mounted on the shafts are provided. The cross section in the direction perpendicular to the longitudinal direction is a convex lens shape, an elliptical shape, or a pseudopolygon inscribed in a virtual circle at each apex angle, and the paddle fixed to one stirring shaft is the paddle fixed to the other stirring shaft. On the other hand, one paddle is a continuous stirring mixer that rotates at the tip with the inner surface of the barrel and the opposing paddle with a slight clearance used as a reactor, and trioxane, cyclic ether and catalyst are fed from the supply port. Supply and polymerize, In the method for polymerizing trioxane in which the reacetal copolymer is taken out from the discharge port as a powder or granular material, the thickness of the paddle is more than 0.2 times and 1.0 times or less of the major axis of the paddle. It is a method for polymerizing trioxane, which is characterized by being used in combination within a range of 100%.

The reactor used in the present invention is a continuous stirring mixer having a plurality of paddles attached to two parallel shafts,
In order to obtain good self-cleaning effect and stirring effect, the clearance between the tip of the paddle and the inner surface of the body is preferably 2% or less, especially 1% or less of the diameter of the paddle circumscribing circle.
Further, the clearance between the opposing paddles is preferably 5 times or less, particularly preferably 2 times or less.

And considering the fluctuation of clearance due to the work precision and the deflection of the shaft and the operation stability, L / D (where L is the length of the reactor cylinder and D is the inner diameter of the cylinder) is usually 20 or less,
It is preferably 6 to 15.

The shape of the paddle of the reactor used in the present invention is a convex lens shape, an elliptical shape, or a pseudopolygon inscribed in a virtual circle at each apex angle, and further, each side surface of the tip portion of the paddle is symmetrically twisted. It is also possible to use a helical type whose side surfaces are rotationally symmetrical with respect to the stirring axis. That is, the twisted helical type whose side surface pushes the contents to the discharge port by the rotation of the stirring shaft has a larger feeding effect than the normal flat type, and the helical type twisted in the opposite direction has a large reverse feeding effect. Indicates.
The tip of the paddle may have a circumferential surface, a flat surface, an acute angle, or a sharp scraper may be provided on these.

On the other hand, as for the paddles, it is preferable to combine and arrange the ones having a large thickness, rather than combine and arrange the plurality having a small thickness. This means that due to the nature of the polymer particles, the amount of particles held on the surface of a large paddle is larger than on the surface of a paddle that is divided into smaller parts with the same length. To do.

Therefore, the thickness of the paddle used in the present invention is preferably more than 0.2 times the paddle major axis and 1.0 times or less, rather than 0.05 to 0.2 times the conventional paddle major axis. If it is 0.2 times or less, the amount of polymer held on the paddle surface is small, but if it is about 0.21 times, a sufficient effect can be obtained. On the other hand, if it is 1.0 times or more, there is no effect of increasing the amount of polymer any more, and conversely, the stirring force applied to the polymer is reduced, and a polymer having a desired particle size cannot be obtained. Also, stack multiple paddles with small thickness,
The same effect can be obtained even when the paddle is used as one thick paddle.

Further, as a method of arranging the paddles in the present invention, when a convex lens-shaped or elliptical paddle is used, the paddles adjacent in the longitudinal direction of the stirring shaft are arranged with respect to the rotation direction of the stirring shaft.
The method of arranging the combination deviated by 90 ° and the combination deviated by 45 ° is particularly preferable because the feeding effect is small and a large amount of retained polymer can be obtained.

In addition, the screw used at the lower part of the supply port of the reactor is of a type that meshes with each other, and between the upper part of the discharge port and the tip part of the reactor, in order to efficiently push out the polymer,
A reverse feed screw can be used.

In the present invention, the rotation speed of the stirring shaft is preferably adjusted so that the peripheral speed at the tip of the paddle is 800 to 4000 cm / min. If it is less than 800 cm / min, the stirring force is insufficient, there is a risk of torque out, and it is not possible to obtain a desired particle size. On the other hand, when it is 4000 cm / min or more, the amount of polymer staying is decreased, which is not preferable.

The average residence time in the reactor is preferably 2 to 20 minutes. Setting the time to 20 minutes or more is inferior in productivity and is not industrially desirable, and there is no difference from that in which a reactor suitable for each of a plurality of polymer phases is directly connected. Two
If it is less than the minute, a high polymerization conversion cannot be obtained.

The cyclic ether used in the present invention is represented by the following general formula (I
It means a compound represented by I).

(However, Y _{1 to} Y _{4 in the} formula represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen-substituted alkyl group having 1 to 6 carbon atoms, and they may be the same or different. X
Represents a methylene or oxymethylene group, which may be substituted with an alkyl group or a halogen-substituted alkyl group,
m represents an integer of 0 to 3. Alternatively, X is - (CH ₂₎ p
It may be —O—CH ₂ — or —O—CH ₂ — (CH ₂ ) p—O—CH ₂ —, in which case m = 1 and p is 1-3.
Is an integer. ) Among the cyclic ethers represented by the general formula (II), as particularly preferable compounds, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane, 1,
3-dioxepane, 1,3,5-trioxepane, 1,3,6-trioxocane, epichlorohydrin and the like can be mentioned.

The copolymerization amount of the cyclic ether of the present invention is 0.1 to 10 mol%, particularly preferably 0.2 to 6 mol% based on trioxane.

The polymerization catalyst used in the present invention is at least one selected from the group consisting of boron trifluoride, boron trifluoride hydrate and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. A compound, which is used in the form of a gas, a liquid or a suitable organic solvent. Examples of the organic compound having an oxygen atom or a sulfur atom which forms a coordination compound with boron trifluoride include alcohol, ether, phenol and sulfide. Among these catalysts, a coordination compound of boron trifluoride is particularly preferable, and particularly boron trifluoride / diethyl ether complex, boron trifluoride / di (n-butyl) ether complex, boron trifluoride / phenol complex. Is preferred.

Further, as the solvent for the polymerization catalyst, benzene, toluene,
Aromatic hydrocarbons such as xylene, n-hexane, n-heptane, aliphatic hydrocarbons such as cyclohexane, alcohols such as methanol, ethanol and isopropanol, chloroform, dichloromethane, 1,2-dichloroethane, carbon tetrachloride. Halogenated hydrocarbons such as, acetone, ketones such as methyl ethyl ketone are used.

The addition amount of the polymerization catalyst was 0.
000005-0.1 mol is preferable, and particularly preferably 0.00001-
It is 0.01 mol.

The polymerization method in which the polymerization catalyst is merged with the cyclic ether before entering the polymerization reactor to activate the catalyst, and then contacted with trioxane is a polymerization method in which the polymerization time is high and the polymerization conversion is high with a short residence time in the polymerization machine. Since the rate can be realized, it can be particularly preferably used in the present invention.

The polymerization temperature is preferably 50 to 140 ° C, particularly preferably 65 to 125 ° C. 50
If the temperature is lower than ° C, the polymerization rate is slow because trioxane is a solid, and if it is higher than 125 ° C, the depolymerization reaction becomes predominant, and a polymer having a high degree of polymerization cannot be obtained.

The polyacetal copolymer obtained according to the present invention is stabilized by deactivating the polymerization catalyst and then blocking or removing unstable terminals, and is put to practical use. In this case, as a method for deactivating and stabilizing the catalyst, generally known methods are adopted.

In the present invention, it is also possible in some cases to supply a terminating agent that deactivates the polymerization catalyst to stop the polymerization reaction to the latter half of the polymerization reactor to carry out the polymerization and catalyst deactivation steps in one reactor. is there.

As the terminating agent for the boron trifluoride-based catalyst used in the present invention, an amine compound, a tertiary phosphine compound or a hindered amine compound is used. Among them, the tertiary phosphine compound and the hindered yne compound do not require the removal of the deactivated catalyst, and are therefore extremely advantageous in terms of process. In particular, the hindered amine compound is more preferably used because it gives a polymer having excellent thermal stability.

Further, it is also possible to supply an appropriate polymerization degree adjusting agent and other additives to the polymerization reactor.

Next, an example of a method for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a reactor used in the present invention. The reactor is a biaxial self-cleaning type mixer having a stirring shaft 1, a plurality of plate-shaped paddles 2 and a temperature adjusting jacket 3.
The trioxane, the cyclic ether and the catalyst are supplied from the supply port 4, and the polymerized polymer is discharged from the discharge port 5.

Various sectional shapes of the paddle 2 are shown in FIG. 2A is a convex lens type, FIG. 2B is a helical type with a twisted tip, and FIG. 2C is a pseudo-triangular type.

The lower part of the supply port 4 and the upper part of the discharge port 5 of the reactor are constituted by ordinary screws 6.

Further, FIG. 3 schematically shows an example of an array in which convex lens paddles are combined. In the figure, F is a forward screw, R is a reverse screw, N and n are combinations of 90 ° offset from adjacent paddles, and B and b are combinations of 45 ° offset from adjacent paddles in the reverse traveling direction. In addition, uppercase letters represent thicker paddles, and lowercase letters represent smaller paddles.

<Operation> According to the method of the present invention, the amount of residence in the reactor can be increased without causing torque out of the reactor, and a high polymerization conversion rate can be obtained.

<Example> Next, the present invention will be described with reference to Examples and Comparative Examples. The physical properties and the like shown in Examples and Comparative Examples were measured as follows.

[Relative viscosity ηr] p-chlorophenol containing 2% α-pinene 10
0.5 g of polymer was dissolved in 0 ml and measured at 60 ° C. using an Ostwald viscometer.

[Polymerization conversion rate] 100 g of the polymer discharged from the polymerization machine was stirred in 500 ml of benzene for 30 minutes at room temperature, and then the polymer was separated and vacuum dried. The polymer weight after drying was measured, and the polymerization conversion rate (%)
I asked.

[Thermal decomposition rate Kx] Kx means the decomposition rate when left for a certain time at x ° C,
Using a thermobalance device, about 10 mg of polymer under air atmosphere,
It was left at x ° C. and calculated by the following formula.

Kx = (W ₀ −W ₁ ) / W _0x 100% W ₀ ; pre-heating polymer weight W ₁ ; post-heating polymer weight The thermal balance device used was a thermal analyzer 1090/1091 manufactured by DuPont.

[Mechanical Properties] A tensile test piece and an Izod impact test piece were injection-molded using an injection molding machine having an injection capacity of 5 ounces, setting a cylinder temperature of 200 ° C., a mold temperature of 60 ° C., and a molding cycle of 50 seconds. Using these molded products, the tensile strength and Izod impact value were measured according to ASTM D-638 and D-256, respectively.

Example 1 A self-cleaning twin-screw mixer as shown in FIG. 1 was used as a polymerization reactor, and 0.10 kg of a benzene solution containing 20 kg / h of trioxane and 3.70% by weight of boron trifluoride / diethyl etherate as a catalyst. / h and 0.64 kg / h of 1,3-dioxolane as cyclic ether.

The inner diameter of the reactor was 100 mm, and the L / D was 10. The paddle is a paddle with a convex lens section as shown in FIG. 2 (A).
One sheet alone had a thickness of 20 mm, and two sheets were stacked and used as a sheet having a thickness of 40 mm. The paddle arrangement is the third
As shown in the figure, 45 °
With the combination of 90 ° offset, the thick one was 40 mm and the thin one was 20 mm. The lower part of the supply port and the upper part of the discharge port are ordinary screws.

The stirring shaft was set to 60 rpm by rotating in the same direction. The reactor jacket was adjusted to 60 ° C with warm water.

The average residence time at this time was 4 minutes, and a white powdery polymer was obtained from the discharge part at 19.4 kg / h. The polymer ηr is
It was 2.00 and the conversion rate was 90%.

Example 2 The polymerization was carried out in the same manner as in Example 1 except that the catalyst and the cyclic ether were previously activated at 30 ° C. for 2 minutes by mixing in the pipe and the catalyst was supplied to the reactor.

The average residence time at this time was 4 minutes, and a white powdery polymer was obtained from the discharge part at 19.8 kg / h. The polymer ηr is
It was 2.10 and the conversion rate was 98%.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the thickness of each paddle was 20 mm, which was a single sheet, and the paddles were mounted in a combination of shifted by 45 ° and 90 ° in the traveling direction.

The average residence time at this time was 2 minutes. The polymer obtained was still a paste and the conversion was low at 60%.

Comparative Example 2 Except that the rotation speed of the stirring shaft was 20 rpm, Example 1 was carried out at all.
It polymerized similarly.

The average residence time at this time was 4 minutes, and a powdery polymer was obtained, but the torque was out 2 hours after the initiation of polymerization.

From Example 1 and Comparative Examples 1 and 2 described above, it can be seen that by using a paddle having a large thickness, the retention amount can be increased without torque-out, and a high polymerization conversion rate can be obtained.

Furthermore, it can be seen that by combining with the method of mixing and supplying the catalyst and the cyclic ether in advance in Example 2, it is possible to obtain a sufficiently high polymerization conversion rate industrially even with one reactor.

Example 3 40 kg / h of trioxane was prepared in the same reactor as in Example 1.
Supplied. As a catalyst, 0.20 kg / h of a benzene solution containing 3.70% by weight of boron trifluoride / diethyl etherate and 1.28 kg / h of 1,3-dioxolane as a cyclic ether were preliminarily mixed at 30 ° C in a reactor for 1 minute. Supplied to.

Rotation speed of stirring shaft is 60 rpm, reactor jacket is 60 ° C
I drove in.

The average residence time of the polymer at this time was 3 minutes, and a white powdery polymer was obtained at 39 kg / h. Polymer ηr is 2.
It was 09, and the yield was 96%.

With respect to 100 parts by weight of the obtained polymer, 0.18 parts by weight of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate as a catalyst stopper, and further triethylene glycol-bis [3- ( 3-t-butyl-5-methyl-4
-Hydroxyphenyl) propionate] 0.50 parts by weight,
Calcium hydroxide (0.10 parts by weight) and melamine (0.10 parts by weight) were added and continuously fed to a conventional vented twin-screw extruder.
It was melt-stabilized at ℃ and 50 torr.

Injection molding was performed using this polymer, and the mechanical properties and heat stability of the molded product were measured. The results are shown below.

Tensile strength; 64MPa Tensile rupture elongation; 62% Izod impact value; 66J / m (1/2 ″ notch) Thermal decomposition rate K ₂₄₀ (60min); 3.0% It can be seen that it shows a very good value.

<Effects of the Invention> By using the polymerization method of the present invention in the polyacetal copolymer manufacturing process which is used for a wide range of applications such as mechanical mechanism parts and electric / electronic parts, the process can be simplified or the productivity can be improved. .

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a polymerization reactor for carrying out the present invention, FIGS. 2 (A), (B), and (C) are partial cross-sectional views of a paddle in the polymerization reactor, and FIG. FIG. 4 is a schematic diagram showing a method of arranging paddles in a polymerization reactor. 1, 1 '... stirring shaft, 2 2' ... paddle, 3 ... jacket, 4 ... supply port, 5 ... discharge port, 6 ... screw.

Claims (5)

[Claims] 1. A heating or cooling jacket is provided on the outer circumference of a reactor body, and its cross section has a shape of two overlapping concentric circles having the same diameter. Raw material supply ports are provided at both ends of the reactor. And a pair of equilibrium stirring shafts and a plurality of plate-shaped paddles mounted on the shafts, the paddles having a convex section in the direction perpendicular to the longitudinal direction of the stirring shaft. Shape, ellipse, or pseudo-polygon inscribed in a virtual circle at each apex angle, the paddle fixed to one stirring shaft faces the paddle fixed to the other stirring shaft, and one paddle is the tip Using a continuous stirring mixer that rotates while maintaining a slight clearance with the inner surface of the barrel and the facing paddle, the trioxane, the cyclic ether and the catalyst are fed from the feed port and polymerized to give a polyacetal copolymer. From the discharge port In the method of polymerizing trioxane to be taken out as a body, the paddle is used in combination in a range of 20 to 100% of the total paddle excluding the screw such that the thickness of the paddle is more than 0.2 times and not more than 1.0 times the major axis of the paddle. Method for polymerizing trioxane. 2. The method according to claim 1, wherein in the reactor, an average residence time obtained by dividing a residence amount of the polymer in the reactor by an ejection amount of the polymer per hour is 2 to 20 minutes. 3. In the above reactor, the convex lens-shaped or elliptical paddles adjacent to each other in the longitudinal direction of the stirring shaft are arranged in a combination of 90 ° and 45 ° with respect to the rotation direction of the stirring shaft. The method of claim 1. 4. The method according to claim 1, wherein in the reactor, the ratio of the length of the cylinder to the inner diameter D of the cylinder, that is, L / D is 6 to 15. 5. The method according to claim 1, wherein in the reactor, the rotation speed of the stirring shaft is adjusted so that the peripheral speed at the tip of the paddle is 800 to 4000 cm / min.