JP3470368B2 - Method for producing polyacetal resin - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a self-cleaning type twin-screw reaction mixer suitable for producing a polyacetal resin, more specifically for continuously polymerizing trioxane and a cyclic ether. a manufacturing method of using polymerization equipment of the polyacetal resin obtained by connecting in series the polyacetal copolymer.

[0002]

2. Description of the Related Art In bulk polymerization of trioxane, a polymer is rapidly precipitated with a temperature rise due to heat generated by polymerization in a reactor, and a polymerization product is changed from a slurry form to a paste form.
Finally it solidifies. Several proposals have been made so far in order to remove the heat of polymerization and carry out a polymerization reaction involving a phase change without causing problems such as deterioration due to heat generation and torque out due to solidification.

For example, in the manufacturing method described in Japanese Examined Patent Publication No. 57-44690, two or more biaxial polymerization reactors are connected in series, and the tip of the paddle of one shaft is always slightly the inner surface of the body or the paddle of the other shaft. Taking out a polymerization product having a conversion rate of 40 to 60 mol% with a front-stage polymerization machine having a shape of turning while keeping a large gap, and then using a second-stage polymerization machine which is a horizontal stirring device without mutual scraping action. Is proposed. However, in this method, since the reaction mixture adheres to the inner surface of the body at a later stage, the reaction heat generated is insufficiently removed, and a polymer polyacetal preferable as a product cannot be obtained.

In the production method described in JP-A-59-159812, it is proposed that the raw material monomer and the polymerization catalyst are uniformly mixed and then the reaction mixture is supplied to the polymerization reactor while maintaining the liquid state. It is stated that the exothermic heat of initial polymerization from the mixer to the liquid state is efficiently removed with the mixing. However, in this method, since the conversion rate of the reaction mixture in the liquid state is extremely low, the heat generation amount up to the liquid state is a small part of the total heat generation amount, and only by increasing the heat removal efficiency of the initial polymerization heat generation, high quality polyacetal Can't get

Further, in the production method described in Japanese Patent Publication No. 47-629, since the self-cleaning function of the reactor used is insufficient, the screw member is clogged with the rapid phase change of the polymerization reaction mixture, and In order to avoid falling into a loaded state, it has been proposed to reduce the filling rate of the polymerization reaction mixture and increase the grinding efficiency by providing a gap between the screw member and the casing. However, in this method, since the polymerization mixture adheres to the gap between the screw member and the casing, heat removal is insufficient, and high quality polyacetal cannot be obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to connect two or more self-cleaning type twin-screw reaction mixers in series so as to suppress the temperature rise in the reactor due to the heat of polymerization and to provide a high quality polymer. It is intended to provide a method for producing a high yield.

[0007]

[Means for Solving the Problems] That is, according to the present invention, a trioxane, a cyclic ether and a polymerization catalyst are used in a polymerization reaction system.
The polyacetal which is supplied from the supply port of the reactor and is subjected to continuous polymerization reaction to obtain the polyacetal copolymer from the discharge port as a granular material.
A method of manufacturing a Lumpur resin, and the polymerization reactor
Te, connecting two or more reactors in series, anti of its first stage
The reactor and the second-stage reactor each have a cross-section of two overlapping concentric circles with the same diameter, and a pair of parallel stirring shafts inside the reactor and one mounted on the shafts. A self-cleaning type that has multiple paddles of at least one kind and has a mechanism in which the tip of one paddle rotates with a slight clearance from the inner surface of the body or the paddle of the other shaft to scrape the reaction mixture from each other. use of continuous stirring mixing machine
Then, the filling rate of the reaction mixture of the first stage reactor is set to 2 to 60.
%, The filling rate of the reaction mixture of the second stage reactor is 15 to 90
% Is a method for producing a polyacetal resin .

In the present invention, two or more reactors are connected in series, and as the reactor, a self-cleaning continuous stirring mixer is used as the first-stage reactor and the second-stage reactor. And the effects of the present invention can be obtained.

The reactor used in the present invention has a cross section of two overlapping concentric circles of the same diameter, and a pair of parallel stirring shafts and a pair of parallel stirring shafts are mounted inside the reactor. Self-cleaning that has a plurality of paddles of one or more types, and the tip of one paddle rotates with a slight clearance from the inner surface of the body or the paddle of the other shaft to scrape the reaction mixture from each other. It is a continuous stirring mixer of the type. This self-cleaning type continuous stirring mixer (reactor) usually has a jacket on the outer periphery of the cylinder that can heat or cool the reaction mixture, and the raw material supply port and the discharge of the polymerization product are provided at both ends of the reactor. It is equipped with an exit.

The temperature of the cooling water or hot water flowing through the jacket of the reactor used in the present invention is usually 0 to 95 ° C., preferably 5 to 7 from the viewpoint of balance with heat removal and polymerization reaction rate.
The temperature is 0 ° C, more preferably 10 to 50 ° C.

Reactor barrel length (L) and barrel inner diameter (D)
The ratio, that is, L / D, is usually 20 or less, and preferably 3 to 15, in consideration of machining precision, clearance variation due to deflection of the shaft, and operational stability.

The shape of the paddle of the reactor used in the present invention is a convex lens type whose cross section perpendicular to the longitudinal direction of the stirring shaft is a convex lens type,
It is possible to preferably use an oval type or a pseudo-polygonal plate-shaped paddle inscribed in a virtual circle at each apex angle, further, each side surface of the tip portion of the paddle is symmetrically twisted, and the side surface is A helical type which is rotationally symmetrical about the stirring shaft can also be used. The twisted helical type in which the side surface of the paddle pushes the contents to the discharge port by rotating 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 may be provided with a sharp scraper.

Such a paddle is used by being attached to a pair of parallel stirring shafts provided in the reactor. The feeding effect is different depending on the paddle used, as described above, and the paddle patterns can be combined according to the purpose. .

In the reactor used in the present invention, the tip of one paddle rotates with the inner surface of the body or the paddle of the other shaft with a slight clearance to scrape the reaction mixture from each other (self-cleaning). In order to obtain a good self-cleaning effect, the clearance between the tip of the paddle and the inner surface of the body is preferably 2% or less of the diameter of the paddle circumscribing circle, and 1% or less. Is more preferable. If the clearance is within 2% of the diameter of the paddle circumscribed circle, a sufficient self-cleaning effect can be obtained, and the heat removal effect is sufficient because the scaling of the polymer or unreacted monomer on the inner surface of the body or paddle surface does not become thick. can get.

In the present invention, two or more reactors are connected in series to form a polymerization reactor. It is preferable that the connecting portion between the reactors is subjected to buffing inner surface processing or lining, and It is preferred to use short tubes with / or jackets. The number of reactors to be connected is set according to the amount of polyacetal resin to be produced, and is not particularly limited as long as it is 2 or more. When three or more reactors are connected in series to form a polymerization reactor, the reactor used in the third and subsequent stages is not particularly limited, and may be a self-cleaning type continuous stirring mixer. A different reactor may be used.

In the polymerization reactor having two or more reactors of the present invention, the polymerization reaction mixture is removed by controlling the filling rate in the first-stage reactor and the filling rate in the second-stage reactor. The heat can be carried out efficiently. The first-stage and second-stage reactors are self-cleaning type continuous stirring mixers, and the filling rate in the first-stage reactor is preferably 2 to 60%, more preferably 5 to 60%.
50% is preferable. When the filling rate is in this range, the heat removal effect by using the self-cleaning type continuous stirring mixer is sufficiently obtained, and the polymerization degree is lowered by the evaporation of the monomer and the chain transfer reaction of the monomer caused by the temperature rise is caused. An increase in the number of unstable terminals generated can be suppressed, and a polymer having excellent thermal stability can be obtained. Further, it is within a practical range in terms of residence time and yield.

The filling rate in the second-stage polymerization machine is 15 to 9
0% is preferable, and 30-80% is more preferable. When the filling rate is within this range, the heat removal effect by using a self-cleaning type continuous stirring mixer can be sufficiently obtained, and the yield decreases due to the formation of unstable terminals due to the decomposition reaction and the vaporization of the monomer. It is also practical in terms of residence time and yield. on the other hand,
Even if the filling rate is 15 to 90%, if it is not a self-cleaning type continuous stirring and mixing machine, heat removal will be insufficient and the yield will decrease for the same reason as described above.
Not preferable. The filling rate in each reactor can be controlled by adjusting the paddle type, paddle pattern recombination, rotation speed, etc., and the effect of sending the polymerization reaction mixture to the front of the reactor (feeding When the effect) is large, the filling rate is low, and when the feeding effect is small, the filling rate is high. In the present invention, it is preferable to set the feeding effect of the reaction mixture in the first-stage reactor to be larger than the feeding effect of the reaction mixture in the second-stage reactor, and this setting is the kind of paddle and / or It is possible by selecting the paddle pattern or adjusting the rotation speed of the stirring shaft. Paddle type and / or paddle
An example of the relationship between the pattern and the feeding effect is as described above. Further, the feeding effect can be increased by increasing the rotation speed of the stirring shaft.

The polyacetal resin produced by the present invention is
The main raw material is trioxane and a cyclic ether, and a polyacetal resin is polymerized by adding a polymerization catalyst.

The cyclic ether used in the present invention has the formula (I)

[Chemical 1] Means a compound represented by. (However, Y1 to Y in the formula
4 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom
6 to 6 represent halogen-substituted alkyl groups, which 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, and m represents an integer of 0 to 3. Or X is _{- (CH 2) p -O-} CH 2 - or _{-O-CH 2 - (CH 2} ) p -O-CH 2 - is a even better, in this case a m = 1, p = 1 to 3 is an integer. )

Among the cyclic ethers represented by the above general formula, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3,5-trioxepane are particularly preferable compounds. , 1,3,6-trioxocane, epichlorohydrin and the like.

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 includes boron trifluoride, boron trifluoride hydrate and a coordination compound of boron trifluoride with an organic compound containing an oxygen atom or a sulfur atom. It is used in the form of a gas, 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 with boron trifluoride is preferable, and particularly boron trifluoride / diethyl ether complex, boron trifluoride / di (n
-Butyl) ether complex and boron trifluoride / phenol complex are preferable.

As the solvent for the polymerization catalyst, aromatic hydrocarbons such as benzene, toluene and xylene, n-
Hexane, aliphatic hydrocarbons such as n-heptane and cyclohexane, alcohols such as methanol, ethanol and isopropanol, halogenated hydrocarbons such as chloroform, dichloromethane, 1,2-dichloroethane and carbon tetrachloride, acetone and methyl ethyl ketone. Ketones such as are used.

The addition amount of the polymerization catalyst is preferably 0.000005 to 0.1 mol, and particularly preferably 0.00001 to 0.01 mol, based on 1 mol of trioxane.

The polymerization temperature is 50 to 140 ° C., especially 65 to 1
25 ° C is preferred.

In the present invention, after deactivating the polymerization catalyst, it is stabilized by blocking or removing unstable terminals, which is suitable for practical use. In this case, as a method for deactivating and stabilizing the catalyst, generally known methods are adopted.

An amine compound, a tertiary phosphine compound, and a hindered amine compound are used as the terminator for the boron trifluoride-based catalyst used in the present invention. Among them, the tertiary phosphine compound and the hindered amine compound are extremely advantageous in terms of process because it is not necessary to remove the deactivated catalyst. In particular, the hindered amine compound is more preferably used because it gives a polymer having excellent thermal stability.

It is also possible to supply an appropriate degree of polymerization regulator and other additives to the polymerization reactor.

In the present invention, a high-quality polymer can be produced by polymerizing the polyacetal resin using the above-mentioned polyacetal resin polymerization reactor, and the polyacetal resin produced by the production method of the present invention is Various molded products can be obtained by molding by a usual molding method.

[0030]

EXAMPLES 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.

MI value: pellets obtained by stabilizing the powdery crude polymer obtained in the polymerization step by a known method are dried in a hot air oven at 80 ° C. for 3 hours, and then ASTM D12
According to No. 38, the temperature was 190 ° C. and the load was 2160 g.

Polymerization yield: 100 g of the powdery crude polymer discharged from the latter-stage polymerization machine was mixed in 500 ml of benzene to obtain 3
After stirring for 0 minutes at room temperature, the polymer was filtered off and dried under vacuum. The crude polymer weight after drying was measured to determine the polymerization yield (%).

Filling rate: The filling rate is controlled by the type of paddle,
It was performed by recombination of the pattern and the number of rotations. That is, a low filling rate was obtained by using a pattern with strong feed. The filling rate is measured by forming a predetermined paddle pattern, then sending the powdery crude polymer obtained by the polymerization reaction in advance to the reactor, and then measuring the inside of the reactor at the stage where the powder pad is in a steady state at the predetermined paddle rotation speed. The filling powder amount is calculated and the bulk density is 0.8
(G / cm ³ ) and the volume of the reactor space were calculated by the following formula.

[0034]

[Formula 1]

Thermal decomposition rate Kx (y): Kx means the decomposition rate when left to stand at x ° C. for a certain period of time, and about 10 mg of a sample was left to stand at x ° C. in an air atmosphere using a thermobalance device. It was calculated by the following formula.

Kx (y) = (Wo−Wy) / Wo × 100 (%) Wo: sample weight before heating Wy: sample weight after heating for y minutes The thermobalance device is TG / DTA20 manufactured by Seiko Instruments Inc.
0 was used, and measurement was performed at x = 240 ° C. and y = 60 minutes.

Example 1 The self-cleaning type twin-screw reaction mixer shown in FIG. 1 was used as a front stage (first stage) reactor and a rear stage (second stage) reactor, and 30 k of trioxane melted at 70 ° C. was used.
g / h, 0.15 kg / benzene solution containing 2.4% by weight of boron trifluoride / diethyl etherate as a catalyst
The time and 1,3-dioxolane as cyclic ether were fed at 1.1 kg / h. FIG. 1 is a partially cutaway side view of a self-cleaning twin-screw reaction mixer used as a front-stage reactor and a rear-stage reactor. The reactor is a stirring shaft 1, 1 ',
Multiple paddles 2, 2 ', and temperature control jacket 3
It is a twin-screw self-cleaning continuous mixer having a. Feed port 4 for trioxane, cyclic ether and catalyst
The polymer supplied and polymerized is discharged from the discharge port 5. 6 indicates a screw. Further, 0.024 kg / hour of methylal was supplied as a molecular weight regulator.

The inner diameter and L / D of the reactor are 100 mm for the former reactor, L / D = 7.2, and 200 m for the latter reactor.
m, L / D = 5. The paddle is a convex lens type paddle in cross section as shown in FIG.
m and 20 mm were used. FIG. 2 is a cross-sectional view of a convex paddle having a self-cleaning function.
Sequences were arranged in a staggered and 90 degree staggered combination. The paddle of the latter-stage reactor was arranged so that the feeding effect was small. Especially in the latter half part, a paddle with a thickness of 10 mm was incorporated in the reverse direction to enhance the returning effect. The stirring shaft was rotated in the same direction, and the front stage was set to 75 rpm and the rear stage was set to 30 rpm. The filling rate at this time was 20% in the former stage and 50% in the latter stage. For the jacket of the polymerization machine, cooling water of 15 ° C. was used in both the first and second stages.

29.5 of white powdery crude polymer was discharged from the discharge port.
Obtained in kg / hour. Polymerization yield at this time is 95.0%
Met.

With respect to 100 parts by weight of the obtained white powdery polymer, bis (1,2,2,6,6) was used as a catalyst deactivator.
-Pentamethyl-4-piperidinyl) sebacate (Sankyo "Sanol" LS765) 0.18 parts by weight 9% by weight
After adding as a benzene solution, triethylene glycol bis {3- (3-t-butyl-5-methyl-4) was further added.
-Hydroxyphenyl) propionate} (Ciba Geigy "Irganox" 245) 0.5 part by weight, calcium stearate 0.1 part by weight, benzobuanamin 0.1.
23 parts by weight, and continuously fed to an ordinary twin-screw extruder,
The unstable terminal was melt-stabilized at 0 ° C. and 10 mmHg, discharged into water and cut to obtain a pellet-shaped polyacetal copolymer. The MI value of the obtained pellets was 9.1 g / 10 minutes. The thermal decomposition rate of the pellets was K240 (60) = 1.2%. The results are shown in Table 1.

[0041]

[Table 1]

Example 2 The same reactor as in Example 1 was used, the same paddle pattern was used, and the number of rotations was changed to control the filling rate. That is, the paddle rotation speed of the former-stage polymerization machine is set to 75
20% filling rate by changing from 90 rpm to 90 rpm
From 30 rpm to 2%
It was increased from 50% to 70% by setting it to 0 rpm. The polymerization yield of the obtained crude polymer was 93%.
Further, after subjecting this crude polymer to the same treatment as in Example 1, the MI value of the obtained polymer was 8.9 g / 10 minutes, and the thermal decomposition rate was 1.2%.

Comparative Example 1 Using the same reactor as in Example 1, the filling rate was controlled by changing the paddle pattern and the rotation speed of the reactor. That is, the paddle pattern of the former polymerization machine is set to 4
The pattern was made only for feeding, which was shifted by 5 degrees, and the filling rate was set to 1.5% by increasing the number of revolutions from 75 rpm to 100 rpm. The subsequent paddle pattern, rotation speed and treatment of the crude polymer were carried out in the same manner as in Example 1. Polymerization yield is 71%, MI is 9.8 g / 10 minutes,
The thermal decomposition rate was 2.9%.

Comparative Example 2 Using the same reactor as in Example 1, the filling rate was controlled by changing the paddle pattern and the rotation speed of the reactor. That is, the paddle pattern of the latter-stage reactor was removed by removing the returning pattern part, and the feed was shifted by 45 degrees and the kneading pattern was shifted by 90 degrees.
The filling rate is 50 by increasing from 40 rpm to 40 rpm.
% To 10%. The subsequent paddle pattern, rotation speed, and treatment of the crude polymer were carried out in the same manner as in Example 1. Polymerization yield is 62%, MI value is 10.1 g / 10
The heat decomposition rate was 3.3%.

Comparative Example 3 The same procedure as in Example 1 was carried out in the former reactor. on the other hand,
In the latter-stage reactor, the types of the reactor main body and the paddle were changed to the stirring type shown in FIG. 3 so that the pattern had no self-cleaning action. FIG. 3 is a partially cutaway perspective view of a stirring reactor having no self-cleaning function.
Reference numerals 1 and 11 'denote stirring shafts and reference numerals 7 and 7' denote stirring blades. The filling rate was set to 50% by lowering the rotation speed from 30 rpm to 20 rpm. The treatment of the crude polymer was carried out in the same way as in Example 1. At this time, the polymerization yield was 70%, the MI value was 10.4 g / 10 minutes, and the thermal decomposition rate was 4.0%.

Comparative Example 4 The latter reactor was carried out in the same manner as in Example 1. on the other hand,
As for the former reactor, the kind of paddle was changed to the reactor shown in FIG. 3 and the paddle for stirring as in the latter reactor of Example 3,
The pattern has no self-cleaning effect. However, in order to make the filling rate 20%, the screw was incorporated only in the portion corresponding to the initial L / D = 1 to strengthen the feeding. The paddle rotation speed of the latter-stage reactor was 90 rpm. The treatment of the obtained crude polymer was carried out in the same manner as in Example 1. Polymerization yield is 76%, MI value is 13.7 g / 10
The heat decomposition rate was 4.5%.

Comparative Example 5 In the same manner as in Comparative Example 4, the former reactor and the latter reactor were modified in the same manner as in Comparative Example 3, except that the paddles for stirring were changed to polymerize as a pattern having no self-cleaning action. The reaction was carried out. Polymerization yield was 68%, MI value was 14.
It was 1 g / 10 minutes and the thermal decomposition rate was 5.8%.

[0048]

According to the present invention, two or more twin-screw reaction mixers having a self-cleaning function are connected in series,
By controlling the filling rate in each polymerization machine, it is possible to obtain a high-quality polymer having a predetermined degree of polymerization and excellent thermal stability in a high yield.

[Brief description of drawings]

1 is a partially cutaway side view of a reactor used in the present invention in Examples.

FIG. 2 is a sectional view of a convex paddle having a self-cleaning function used in an example.

FIG. 3 is a partially cutaway perspective view of a stirring reactor having no self-cleaning function.

[Explanation of symbols]

1, 1 ': stirring shaft 2, 2 ': Paddle 3: Temperature control jacket 4: Supply port 5: Discharge port 6: Screw 7: Stirring blade 11, 11 ': stirring shaft

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-38313 (JP, A) JP-A-56-59824 (JP, A) JP-A-53-86794 (JP, A) JP-A-2- 283709 (JP, A) JP-A-3-109411 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 2/00 -2/38

Claims (8)

(57) [Claims] 1. A continuous polymerization reaction in which trioxane, a cyclic ether and a polymerization catalyst are supplied from a supply port of a polymerization reaction apparatus.
In the method for producing a polyacetal resin, the polyacetal copolymer is obtained as a powder or granules from a discharge port , wherein two or more reactors are connected in series as the above-mentioned polymerization reactor,
As the first-stage reactor and the second-stage reactor, the cross-sections of the reactors have the shape of two overlapping concentric circles with the same diameter, and a pair of parallel stirring shafts inside the reactor and on the shafts. It has a plurality of one or more attached paddles, and has a mechanism in which the tip of one paddle rotates with a slight clearance from the inner surface of the body or the paddle of the other shaft to scrape the reaction mixture from each other. Using a self-cleaning continuous stirring mixer , filling the reaction mixture of the first stage reactor
2-60%, the filling rate of the reaction mixture in the second stage reactor
Of 15 to 90% is a polyacetal.
Resin manufacturing method . 2. A reactor having a jacket capable of heating or cooling the reaction mixture on the outer circumference of the cylinder, and having a raw material supply port and a polymerization product discharge port at both ends of the reactor. 1. The method for producing the polyacetal resin according to 1. 3. The paddle according to claim 1 or 2, wherein the paddle is a plate-shaped paddle having a convex lens shape, an elliptical shape, or a pseudo-polygonal shape inscribed in a virtual circle at each apex angle in a cross section perpendicular to the longitudinal direction of the stirring shaft. Method for producing polyacetal resin. 4. The first-stage reactor and the second-stage reactor are
Production side of the polyacetal resin according to any one of claims 1 to 3 fixed to one of the stirring shaft paddle is continuous stirring mixer is a paddle relative fixed to the other of the stirring shaft
Law . 5. A polymerization reactor is one in which a short tube having a jacket and / or a buffed inner surface or a lining is applied to a connecting portion between the reactors, and / or a short tube having a jacket is used. Made in the polyacetal resin according to any one to 4 of
Build method . 6. The feeding effect of the reaction mixture in the first stage reactor is set to be larger than the feeding effect of the reaction mixture in the second stage reactor.
6. The method for producing the polyacetal resin according to any one of to 5 . 7. A claim, wherein the adjustment of the feeding effects in reactor those subjected by the rotation speed of the adjustment of the kind and / or selection of the paddle pattern, or the stirring shaft of the paddle 1-6 6. The method for producing a polyacetal resin according to any one of 1. And paddle 8. A reactor of one paddle tip barrel inner surface or the other shaft, claims, characterized in that it is intended to rotate while maintaining the 2% of the clearance of the diameter of the paddle circumcircle Production of polyacetal resin according to 1 to 7
Way .