JP3309641B2 - Method for producing oxymethylene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to a method for producing an oxymethylene copolymer having a high crystallization rate in a high yield.

[0002]

2. Description of the Related Art Oxymethylene polymers have excellent mechanical and thermal performances, and in particular, oxymethylene copolymers have better thermal stability and moldability than oxymethylene homopolymers. , Has been used as an engineering plastic. Regarding the method for producing the oxymethylene copolymer, trioxane is copolymerized with a cyclic ether represented by ethylene oxide or 1,3-dioxolane using a Lewis acid catalyst represented by boron trifluoride to form an oxymethylene copolymer. A method for obtaining a polymer is already known from JP-B-36-14640. In this publication, a catalyst is used in an amount of 0.001 to 1.0 with respect to trioxane.
A method for producing a copolymer using 0.1% to 15% by weight of a cyclic ether is disclosed. However, differences in the thermal stability and crystallization rate of the copolymer due to differences in copolymer components such as cyclic ethers and cyclic formals have been hardly clear until now.

[0003] Oxymethylene copolymers produced by the prior art using ethylene oxide as the copolymer component, which is the most common, have a considerable amount of unstable parts, which has caused poor thermal stability. For this reason, it was necessary to decompose and remove unstable parts and stabilize them.However, decomposing and removing unstable parts lowers the product yield, requires complicated post-processing steps and a large amount of energy, and is economically disadvantageous. there were. For this reason, development of a production method for suppressing generation of an unstable portion during polymerization has been desired.

On the other hand, the present inventors have studied and found that 1,
It has been found that the oxymethylene copolymer produced by the prior art using 3-dioxolane as a copolymer component has less unstable parts causing poor thermal stability than when ethylene oxide is used as a copolymer component. Was. More specifically, the unstable portion was treated with base instability (2.5 g of oxymethylene copolymer subjected to post-polymerization termination treatment in 25 ml of benzyl alcohol containing 1% by volume of tri-n-butylamine). Decomposition rate by heat treatment at 2 ° C. for 2 hours), the base instability of the copolymer obtained when 1,3-dioxolane is used as the copolymerization component is as follows. It has been clarified that the reduction can be reduced to about half of the case of the above. However, on the other hand, it was also found that the crystallization rate of a copolymer containing 1,3-dioxolane as a copolymer component was reduced to about half that of a copolymer containing ethylene oxide as a copolymer component.

Furthermore, even when 1,3-dioxolane is used as a copolymer component, the amount of unstable parts depends on the amount of 1,3-dioxolane and the amount of catalyst used, and the formation of unstable parts is suppressed. In order to do so, it was necessary to use 1,3-dioxolan in a certain amount or more. However, the present inventors have studied and found that an increase in the amount of 1,3-dioxolane used resulted in a decrease in the polymerization yield, and furthermore, a crystallization rate of the copolymer was significantly reduced. It also became clear.

In the prior art, the method of improving the polymerization yield is to increase the amount of catalyst used. However, when the present inventors also examined this, a simple increase in the amount of catalyst promoted the formation of unstable parts. However, it became clear that it was not preferable.

In general, the crystallization rate is closely related to the moldability of a crystalline resin, particularly to the molding cycle, and is an important factor. It is well known that when the crystallization rate is low, it takes a relatively long time for the molten resin to solidify in the mold, and the molding time per shot, that is, the molding cycle, is long. In addition, a long molding cycle reduces the production amount per molding machine, so that an economic disadvantage cannot be denied. That is, even with the conventional copolymer production technology including 1,3-dioxolane as a copolymer component, the generation of an unstable portion was suppressed as compared with the case where ethylene oxide was used as a copolymer component. Although the production method was obvious, it was not known according to the prior art how to simultaneously suppress the generation of unstable parts, achieve a high crystallization rate and a high polymerization yield.

[0008]

An object of the present invention is to provide an oxymethylene copolymer having a small number of unstable parts, easy stabilization in the subsequent steps, and a short molding cycle. To get in. More specifically, trioxane is used with a Lewis acid catalyst typified by boron trifluoride or its coordination compound, and is copolymerized with 1,3-dioxolane to obtain an oxymethylene copolymer having a small number of unstable parts. An object of the present invention is to find a continuous production method which does not decrease the crystallization rate and polymerization yield of the oxymethylene copolymer.

[0009]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide a method for producing an oxymethylene copolymer having a small amount of unstable parts and a high crystallization rate in a high yield of 90% or more. In a method for continuously polymerizing a methylene copolymer, trioxane and 1,3 are used by using a continuous polymerization apparatus in which a continuous polymerization machine and a terminator mixer connected thereto are connected in series.
In copolymerizing dioxolane with boron trifluoride or a coordination compound thereof, 1,3-dioxolane is used in an amount of 3 to 7 mol% based on trioxane, and the catalyst is used in a molar ratio relative to 1,3-dioxolane. , 0.0
008 ≦ [catalyst] / [1,3-dioxolane] ≦ 0.0
03, the polymerization oxymethylene copolymer and the polymerization terminator are brought into contact with each other in the terminator mixer when the polymerization yield is at least 90%.
The focus is stopped is obtained found to be achieved by Rukoto.

In the production method of the present invention, 1,3-dioxolan is used in an amount of 3 to 7 mol%, preferably 3 to 6 mol%, and most preferably 4 to 6 mol% based on trioxane. When the amount of 1,3-dioxolane used is larger than this, the polymerization yield and the crystallization rate decrease, and when it is small, the unstable portion increases.

In the production method of the present invention, the catalyst comprises 1,3
An amount satisfying 0.0008 ≦ [catalyst] / [1,3-dioxolane] ≦ 0.003 in a molar ratio to dioxolane is preferably 0.0008 ≦ [catalyst] / [1,3-dioxolane] ≦ An amount satisfying 0.002, more preferably 0.0008 ≦ [catalyst] / [1,3-dioxolane] ≦ 0.0018, most preferably an amount satisfying 0.001 ≦ [catalyst] / [1 , 3-dioxolane] ≦ 0.0018. When the amount of the catalyst used is larger than this, the unstable portion increases, and when the amount is small, the polymerization yield decreases.

The catalyst used in the present invention is boron trifluoride or a coordination compound thereof. Examples of the coordination compound of boron trifluoride include a coordination compound with an organic compound having an oxygen atom or a sulfur atom. As the organic compound, alcohol, phenol,
Examples include acids, ether anhydrides, esters, ketones, aldehydes, dialkyls, and sulfides.
The Above all coordination compounds boron trifluoride, preferably etherate trifluoride boric Preferred examples
And ethyl etherate and butyl etherate . The catalyst is used alone or in the form of a solution.
When used in a solution, examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; benzene,
Aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene dichloride and ethylene dichloride.

In the practice of the present invention, the intrinsic viscosity of the copolymer is adjusted to 0.5 to 5 dl / g, preferably 0.7 to 3 dl / g, more preferably 0.8 to 2 dl / g.
/ G.

To control the intrinsic viscosity of the copolymer, a molecular weight modifier (chain transfer agent) is added to trioxane in an amount of 0.01%.
~ 0.3 mol% can be used. Examples of the chain transfer agent include carboxylic acids, carboxylic anhydrides, esters, amides, imides, phenols, and acetal compounds. In particular, phenol, 2,6-dimethylphenol, methylal, and polyoxymethylene dimethoxide are preferably used. Most preferred is methylal. The chain transfer agent is used alone or in the form of a solution.
When used in a solution, examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as methylene dichloride and ethylene dichloride.

In the practice of the present invention, it is important to control the polymerization temperature before and after a polymerization yield of 60-90% (defined as the boundary yield). The boundary yield is preferably between 65 and 90%, more preferably between 70 and 90%, and most preferably between 80 and 90%.
%. The polymerization temperature is 60-115 ° C, preferably 60-110 ° C, until the polymerization yield reaches the boundary yield.
More preferably at 60-100C, most preferably at 60-100C.
It should be kept in the range of ９０90 ° C. In addition, the polymerization yield should be maintained at 0 to 100 ° C, preferably 0 to 80 ° C, more preferably 0 to 70 ° C, and most preferably 0 to 60 ° C, at or above the boundary yield. It is. If the polymerization temperature until the polymerization yield reaches the boundary yield is higher than this, the unstable portion increases and the polymerization yield also decreases.
When it is low, the generation of unstable parts is suppressed, but the polymerization yield also decreases in this case. If the polymerization temperature at or above the boundary yield is higher than this, the unstable portion increases, and if it is lower, inconvenience such as an increase in the torque of the stirring power of the polymerization machine occurs. Also, the polymerization temperature above the boundary yield must not be higher than the polymerization temperature until the boundary yield is reached. If this were reversed, the instability would increase.

In the practice of the present invention, the polymerization time is generally from 0.25 to 120 minutes, preferably from 1 to 60 minutes, more preferably from 1 to 30 minutes, and most preferably from 2 to 15 minutes. is there. If the polymerization time is longer than this, the unstable portion increases, and if the polymerization time is shorter, the polymerization yield decreases.

The impurities such as water, formic acid, methanol and formaldehyde contained in the trioxane used in the practice of the present invention are unavoidably generated when industrially producing trioxane. The content is preferably 100 ppm or less, more preferably 70 ppm or less, and most preferably 50 ppm or less. In particular, water is preferably at most 50 ppm, more preferably at most 20 ppm, most preferably at most 10 ppm. Also, with respect to 1,3-dioxolane, similarly to trioxane, the total amount of impurities such as water, formic acid, and formaldehyde present in 1,3-dioxolane is preferably 1,000 ppm or less, more preferably 200 ppm or less. Particularly preferably below 100 ppm, most preferably 50 ppm
It is as follows. Further, since water reduces the activity of the catalyst, it is preferable to employ a method for preventing water from entering the polymerization apparatus from the outside. Examples of the method include a method of constantly replacing the polymerization apparatus with an inert gas such as nitrogen gas during the polymerization reaction.

In the practice of the present invention, the polymerization reaction can be carried out in the presence of an inert solvent, but it is preferable to conduct the polymerization substantially in the absence of a solvent. When using a solvent,
Aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; and halogenated hydrocarbons such as methylene dichloride and ethylene dichloride.

In the practice of the present invention, the polymerization reaction is continuous
This is done in a formula manner. At that time, a method of implementing connecting two or more continuous polymerization machine in series, is suitable. As a continuous polymerization machine, it has at least two horizontal rotation axes,
A kneading machine having a wing in which a screw or a paddle is incorporated in the rotation shaft can be mentioned as a preferable one.

In the present invention, usually, when the polymerization yield reaches 90% or more, preferably 95% or more, more preferably 97% or more, the catalyst is deactivated to terminate the polymerization. Termination of the polymerization reaction is performed by bringing a terminator into contact with the polymer. The terminator is used as it is or in the form of a solution or suspension. The contact method is to continuously add a small amount of a terminator, a solution or suspension of the terminator to the polymer, and to form a substantially bulky or In order to promote the contact with the polymerization catalyst, the polymer is introduced into a large amount of a solution or suspension of a terminator and brought into contact in a slurry state. The contact in the slurry state requires a solvent recovery step or a solvent removal step at a later stage, which complicates the process and leads to an increase in utilities. Industrially more preferred is the method of adding a small amount to the polymer. When adding to a polymer, it is preferable to mix with a mixer after addition. As the mixer, a continuous mixer such as a single or twin screw or paddle type mixer can be used.

As the terminator, primary amines, secondary amines, tertiary amines, trivalent organic phosphorus compounds, hydroxides of alkali metals and alkaline earth metals are used. Primary amines include n-propylamine, isopropylamine, n-butylamine and the like; secondary amines include diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, piperidine, morpholine and the like; As the amine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine and the like are preferably used. Among them, tertiary amines and trivalent organic phosphorus compounds are preferable, and tri-n-butylamine is most preferably used as the tertiary amine, and triphenylphosphine is most preferably used as the trivalent organic phosphorus compound. When the terminator is used in the form of a solution or suspension,
The solvent used is not particularly limited, but water, alcohols, acetone, methyl ethyl ketone,
Various aliphatic and aromatic organic solvents such as hexane, cyclohexane, heptane, benzene, toluene, xylene, methylene dichloride, and ethylene dichloride can be used. Preferred among these are water, alcohols, and aliphatic and aromatic organic solvents such as acetone, methyl ethyl ketone, hexane, cyclohexane, heptane, benzene, toluene, and xylene.

According to the present invention, the copolymer after termination of the polymerization contains 10% by weight of an unstable portion as measured by the method described below.
Hereinafter, it usually has 0.9 to 8% by weight, and its ratio is small.

Further, the copolymer after the termination of the polymerization can be sent to the subsequent stabilization step as it is because it can be obtained in high yield. However, if further purification is necessary, washing and recovery of unreacted monomer are performed. And drying processes. In the stabilizing step, the stabilizing methods described in the following (1) and (2) can be adopted. (1) A method of heating and melting the oxymethylene copolymer obtained above to remove unstable portions. (2) A method of hydrolyzing the oxymethylene copolymer obtained above in an aqueous medium to remove unstable portions. After stabilization by these methods, pelletization is performed to obtain a stabilized moldable oxymethylene copolymer.

Of the above methods, the method (1) is the method (2)
The process is simpler than that of the above method, and is preferable as an industrial method. That is, when the method (1) is adopted,
It is preferable that the oxymethylene copolymer is melt-kneaded in a temperature range from its melting temperature to 100 ° C. higher under a pressure of 760 to 0.1 mmHg. When the treatment temperature is lower than the melting temperature of the oxymethylene copolymer, the decomposition reaction of the unstable portion becomes insufficient, and the effect of stabilization cannot be obtained. On the other hand, when the temperature is higher than the melting temperature by 100 ° C., the yellowing occurs, the main chain of the polymer is decomposed by heat, and at the same time, an unstable portion is generated to impair the thermal stability, which is not preferable. A more preferred range is 170 to 250 ° C, and a most preferred range is 18 to 250 ° C.
0-235 ° C. The pressure during the treatment is 7
When the pressure is higher than 60 mmHg, the effect of removing the decomposition gas generated by decomposition of the unstable portion out of the system is low, and a sufficient stabilizing effect cannot be obtained. When the pressure is lower than 0.1 mmHg, an apparatus for obtaining such a high degree of decompression is expensive, not only causing industrial disadvantages but also causing the molten resin to easily flow out of the suction vent, resulting in operational trouble. It is not preferable because it is easy to cause a problem. A more preferred range is 7
40 to 10 mmHg, most preferably 400 to 50 mm
Hg. Further, the processing time is appropriately selected in the range of 5 minutes to 1 hour.

In the present invention, a single-screw or two-screw or more extruder with a vent can be used as an apparatus used for the stabilization treatment. An extruder is an advantageous method in which two or more extruders are arranged in series in order to obtain a required residence time. As an extruder, Werner Z
A method combining SK extruders, ZDS extruders and the like having a high degassing effect is a more advantageous method. Further, a method of combining a surface-renewal type mixer with the above-described extruder, as shown in Examples described later, is the most effective method.

In the stabilization method (1), a stabilizer such as an antioxidant and a heat stabilizer can be added during the melt-kneading of the oxymethylene copolymer to perform the stabilization treatment.

In the above stabilization treatment, an antioxidant that can be used is triethylene glycol-bis-3.
Sterically hindered phenols such as-(3-t-butyl-4-hydroxy-5-methylphenyl) propionate and pentaerythrityl-tetrakis-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate And the like. Examples of the heat stabilizer include melamine, methylolmelamine, benzoguanamine, cyanoguanidine, N,
Amine-substituted triazines such as N-diarylmelamine,
Examples thereof include polyamides, urea derivatives, urethanes and the like, and sodium, potassium, calcium, magnesium, and barium inorganic acid salts, hydroxides, and organic acid salts.

The oxymethylene copolymer obtained by the method of the present invention described above has the same excellent properties as the oxymethylene copolymer obtained by the conventional method, and can be used for the same purpose. Can be.

The oxymethylene copolymer produced by the method of the present invention includes a coloring agent, a nucleating agent, a plasticizer, a release agent, an antistatic agent such as polyethylene glycol and glycerin, a benzophenone compound, Additives such as light stabilizers such as hindered amine compounds can be added as desired.

[0030]

EXAMPLES Examples and comparative examples of the present invention will be shown below, but the present invention is not limited to these. Further, terms and measurement methods described in Examples and Comparative Examples will be described below.

(1) a continuous polymerization machine having a pair of shafts in a long case having an inner cross section in which two circles partially overlap each other, having a major axis of the inner cross section of 100 mm, and having a jacket around the circumference; Each shaft is fitted with a large number of pseudo-triangular plates that mesh with each other, and the first-stage continuous polymerization machine that can clean the inner surface of the case and the surface of the other pseudo-triangular plate at the tip of the pseudo-triangular plate, As a second-stage polymerization machine, the long diameter of the inner cross section is 200 mm, it has a jacket around it, and it has a pair of shafts in a long case. It is a continuous mixer equipped with suitable stirring blades.

(2) Terminator mixing machine: having a structure similar to that of the second-stage polymerization machine, continuously mixing a solution containing a terminator from a supply port and continuously mixing with the polymer. Machine.

(3) Surface renewal type mixer; having two rotating shafts inside, and a plurality of scraping blades mounted on the shafts. When the shafts rotate in different directions, the blades The blades are staggered so that they do not come into contact with each other, and the blade tips are arranged so as to rotate with a slight gap between the inner surface of the case and the mutual shaft.The rotation of the shaft kneads the polymer and melts the polymer. This is a mixer that has a function to constantly renew the surface of, and make it easier to volatilize volatile components.

(4) Base instability: after termination treatment, 6
Approximately 2.5 grams of the oxymethylene copolymer dried in vacuo at 0 ° C. for 24 hours was accurately weighed and dissolved in 25 ml of benzyl alcohol containing 1% by volume of tri-n-butylamine.
The polymer was heated at 60 ° C. for 2 hours, then cooled, and the precipitated polymer was filtered, washed with acetone three times, and vacuum-dried at 60 ° C. to a constant weight. Thereafter, the mixture was precisely weighed, and the base instability was determined by the following equation. Base instability = [W ₀ −W ₁ ] / W ₀ × 100 W ₀ ; weight before benzyl alcohol treatment W ₁ ; weight after benzyl alcohol treatment and drying

(5) Crystallization time: measured by a polymer crystallization rate measuring device (MK-701 manufactured by Hexa Scientific Co., Ltd.) for optically detecting a change in birefringence due to crystallization.
A film sample having a thickness of about 50 μm produced by a hot press was heated and melted at 200 ° C. for 2 minutes, then immersed in an oil bath at 148 ° C., and light passed through a polarizing plate (polarizer) was transmitted therethrough. The amount of light after passing through the polarizing plate (analyzer) was detected by a light receiving element, and the time required for crystallization was measured based on the time change of the amount of light. Here, the total of the induction period time from the start of measurement at 148 ° C. to the start of crystallization and the half-crystallization time (half the time required from the start of crystallization to the end of crystallization) were measured, and this was defined as the crystallization time. did.

(6) Polymerization yield: 20 g of the terminated oxymethylene copolymer was immersed in 20 ml of acetone, filtered, washed three times with acetone, and then cooled to 60 ° C.
And dried under vacuum until the weight became constant. Thereafter, the mixture was precisely weighed, and the polymerization yield was determined by the following equation. Polymerization yield = M ₁ / M ₀ × 100 M ₀ ; weight before acetone treatment M ₁ ; weight after acetone treatment and drying

(7) Intrinsic viscosity: 0.1% of the copolymer in a p-chlorophenol solvent containing 2% of α-pinene.
(Weight)% dissolved and measured at 60 ° C.

(8) Retention stability;
After drying for 4 hours, the resin for 6 shots is retained in an injection molding machine (IS75E manufactured by Toshiba Machine Co., Ltd.) with a cylinder temperature of 240 ° C., and molded every 7 minutes, and silver (silver strip) caused by foaming of the resin is formed. Evaluation was made based on the time (minutes) until occurrence.

Examples 1 to 7 As the continuous polymerization apparatus, a continuous polymerization apparatus and the above-mentioned terminator mixer connected to the continuous polymerization apparatus were used in series.
Production of the oxymethylene copolymer was carried out. 80 kg / hr (889 kmol / h)
r) trioxane and the amount of 1,3-dioxolane shown in Table 1 and boron trifluoride ethylate as a catalyst.
The rate was fed continuously. In addition, methylal as a molecular weight regulator was continuously supplied in an amount necessary to adjust the intrinsic viscosity to 1.1 to 1.5 dl / g. Boron trifluoride
The ethyl ethyl etherate and methylal were each added as a benzene solution. The total amount of benzene used was 1% by weight or less based on trioxane. In addition, from the inlet of the terminator mixer, triphenylphosphine twice as much as the amount of the catalyst used was continuously supplied with a benzene solution, and the weight of
The combined reaction was stopped, and an oxymethylene copolymer was obtained from the outlet. In the continuous polymerization apparatus, the shaft rotation speed was set to about 40 rpm, and the first-stage jacket temperature was set to 65 ° C.
C., the second-stage jacket temperature was set to 35 ° C., and the jacket temperature of the terminator mixer was set to 15 ° C. to perform the polymerization operation. The polymerization yield, base instability, and crystallization rate of the obtained oxymethylene copolymer were measured, and the results are shown in Table 1.

Comparative Examples 1-2 The catalysts shown in Table 1 ( boron trifluoride ethyl ether
G ) The procedure was repeated in the same manner as in Examples 1 to 7, except that the amount was used. The results are shown in Table 1.

Examples 8 to 14 The amounts of 1,3-dioxolane and the catalyst ( 3
Example 7 was repeated except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 2.

Comparative Examples 3 and 4 The amounts of 1,3-dioxolane and the catalyst ( 3
Examples 8-14 were repeated except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 2.

Examples 15 to 21 The amounts of 1,3-dioxolane and the catalysts ( 3
Example 7 was repeated except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 3.

Comparative Examples 5 to 6 The amounts of 1,3-dioxolane and the catalyst ( 3
Examples 15-21 were repeated except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 3.

Examples 22 to 23 The amounts of 1,3-dioxolane and the catalyst ( 3
Example 7 was repeated except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 4.

Comparative Examples 7 to 8 The amounts of 1,3-dioxolane and the catalyst ( 3
The procedure was repeated in the same manner as in Examples 22 to 23 except that the amount of boron iodide (ethyl etherate ) was used. The results are shown in Table 4.

Example 24 To 100 parts by weight of the oxymethylene copolymer obtained in Example 11, 0.2 parts by weight of melamine and triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5) were added.
-Methylphenyl) propionate 0.5 part by weight, magnesium hydroxide 0.05 part by weight, and calcium stearate 0.015 part by weight were added and mixed, and then the mixture was fed into a vented twin-screw extruder (50 mmφ, L / D = 49). Supply, 160
The mixture was melt-kneaded at 200 ° C. under a reduced pressure of mmHg, subsequently supplied to a surface renewal type mixer, and again stabilized at a reduced pressure of 160 mmHg at 220 ° C. The average residence time from the inlet of the twin screw extruder to the outlet of the surface renewal type mixer was 25 minutes. The stabilized resin was extruded from a die and pelletized. It was 42 minutes as a result of measuring the residence stability of the obtained pellet.

Comparative Example 9 The same operation as in Example 24 was repeated, except that the oxymethylene copolymer obtained in Comparative Example 4 was used. It was 28 minutes as a result of measuring the residence stability of the obtained pellet.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

According to the process for producing an oxymethylene copolymer of the present invention, an oxymethylene copolymer having a small amount of unstable parts and a sufficiently high crystallization rate can be obtained in high yield. That is, this makes it easy to stabilize the latter stage, has high thermal stability during molding, and can produce the copolymer which can be molded in a short time with a high yield. In the production conditions of the present invention, that is, in the method for continuously polymerizing an oxymethylene copolymer, a continuous polymerization machine and a terminator mixer connected thereto were connected using a continuous polymerization apparatus in which 1,3
- dioxolane amount, [catalyst] / [1,3-dioxolane] ratio and the polymerization yield is at least 90%, and the generated the oxymethylene copolymer and the polymerization inhibitor is contacted with the terminating agent mixer improvement of the effect of reducing the polymerization of Ru is stopped, the labile moiety crystallization rate and polymerization yield is truly critical. That is, the unstable part is 1,3-
Dioxolane amount, [catalyst] / [1,3-dioxolane]
Rather than simply decreasing with a decrease in the ratio, it changes abruptly with the amount and ratio forming the boundary of the scope of the present invention. The change in the crystallization rate with respect to the amount of 1,3-dioxolane used is the same.

Continued on the front page (72) Inventor Masahiko Ishikawa 2-4-1-16, Hinagahigashi, Yokkaichi City, Mie Prefecture Inside the Yokkaichi Plant of Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Satoshi Nagai 2-4-2, Hinagahigashi, Yokkaichi City, Mie Prefecture No. 16 Inside the Yokkaichi Plant, Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Daigo Nakatani 2-4-1, Hinagahigashi, Yokkaichi City, Mie Prefecture Inside the Yokkaichi Plant, Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Junichi Abe Yokkaichi, Mie Prefecture No. 4-16, Nagato Mitsubishi Gas Chemical Co., Ltd. Yokkaichi Plant (56) References JP-A-5-17547 (JP, A) JP-A-5-1125 (JP, A) JP-A-7-228649 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 2/00-2/38

Claims (7)

(57) [Claims] In a method for continuously polymerizing an oxymethylene copolymer, trioxane and 1,3-dioxolane are converted into three by using a continuous polymerization apparatus in which a continuous polymerization machine and a terminator mixer connected thereto are connected in series. In the copolymerization using boron fluoride or its coordination compound as a catalyst, 1,3-dioxolane is used in an amount of 3 to 7 mol% based on trioxane, and the catalyst is expressed in a molar ratio of 0.0008 to 1,3-dioxolane. ≦ [catalyst] / [1,3-dioxolane] ≦ 0.003, and when the polymerization yield is at least 90%, the produced oxymethylene copolymer and polymerization terminator are combined with the terminator. mixture is contacted on board by Ru to stop the polymerization, the labile moiety is small and fast crystallization rate oxymethylene copolymer, a method for producing in high yields of 90% or more. 2. When the polymerization yield is at least 95%,
The method according to claim 1, wherein the produced oxymethylene copolymer is contacted with a polymerization terminator. 3. The method according to claim 1, wherein the polymerization terminator is a tertiary amine.
The described method. 4. The method according to claim 1, wherein the polymerization terminator is triphenylphosphine. 5. The method according to claim 1, wherein the obtained oxymethylene copolymer is subjected to a stabilization treatment. 6. The stabilizing treatment is carried out by heating the oxymethylene copolymer in a range from its melting temperature to a temperature higher by 100 ° C.
The method according to claim 5, which is carried out by melt-kneading under a pressure of 60 to 0.1 mmHg. 7. The method according to claim 6, wherein the stabilization treatment is carried out by a combination of a single-screw or two-screw or more vented extruder and a surface-renewal type mixer.