JP2000119356A - Raw material for producing stabilized polyoxymethylene copolymer and production of the copolymer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain practically applicable crude polyoxymethylene(POM) copolymer powdery granules as a raw material of stabilized POM copolymers through economically advantageous and simple process, and to provide a method for producing such a stabilized POM copolymer using the above crude powdery granules. SOLUTION: The crude POM copolymer is such one as to be discharged from a polymerizer, and after ground, gives granules which have the particle size distribution characteristics and surface pore size characteristics specified in (1) and (2) as described below, respectively: (1) the fraction >1.0 mm in particle size accounts for 10-50 wt.% of the whole granules, (1-a) having the average diameter of the surface pores of >=4 μm, wherein (1-b) the total volume of the pores <=4 μm in diameter accounts for <=50% of the total volume of the surface pores, and (2) the fraction <0.18 mm in particle size accounts for <=30 wt.% of the whole granules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyoxymethylene copolymer (hereinafter referred to as POM) having excellent stability, especially heat stability.
Crude POM as a raw material for the copolymer)
The present invention relates to a copolymer powder and an economical production method of the stabilized POM copolymer using the powder.

[0002]

2. Description of the Related Art POM copolymers are excellent in mechanical properties, heat resistance, chemical resistance, electrical properties, slidability, etc., and are also excellent in molding processability. It is used for a wide range of applications, such as parts, automobile parts, and electric / electronic equipment parts. Practically stabilized POM copolymers are generally produced by the following process. First, a cyclic acetal such as trioxane is used as a main monomer, a cyclic acetal containing a structure adjacent to carbon atoms or a cyclic ether is used as a comonomer, and a chain transfer agent for adjusting the degree of polymerization is added according to the purpose. A crude POM copolymer is obtained by copolymerization using

[0003] Generally, such crude POM copolymers have a significant amount of unstable terminal moieties. Further, the polymerization catalyst remains in an active state, and easily causes depolymerization of the copolymer and causes an increase in unstable terminal portions. Therefore, the crude POM copolymer, which is a polymerization product, is converted into an organic or inorganic basic compound such as an alkylamine, an alkoxyamine, a hindered amine or a hydroxide of an alkali metal or an alkaline earth metal in a catalyst. After performing the summation or deactivation treatment, the resultant is subjected to the step of decomposing and removing the unstable terminal portion, and is heated in the presence of a basic compound, for example, the compound as described above, and optionally water, alcohol or the like used in combination. As a result, the unstable terminal portion is decomposed and removed. The POM copolymer from which the unstable terminal portion has been decomposed and removed in this manner is then blended with various stabilizers to impart stability, especially heat stability, as well as long-term stability. Thus, various additives, reinforcing agents, and the like are added to impart properties according to the purpose, and the mixture is melt-kneaded to obtain a stabilized POM copolymer that can be practically used.

There is a strong demand for simplifying such complicated multi-step processes from the viewpoint of cost reduction. Therefore, for example, improvement of a polymerization machine and a polymerization catalyst in a polymerization step, improvement of a deactivator in a deactivation step of a residual catalyst, a deactivation method, and the like, a decomposition accelerator and a decomposition removal device in a decomposition and removal step of an unstable terminal, etc. Improvements have been proposed. However, all of them focus on only a specific process, and there is naturally a limit in achieving the object of the present invention by the improvement, and the synthesis from the polymerization process to the final stabilization process of the POM copolymer is comprehensive. More economically stabilized POM
There has been a demand for a method for producing a copolymer. In particular, among the above-mentioned steps, the step of decomposing and removing the unstable terminal portion requires the most complicated processing operation, and requires a large amount of energy for the processing.
If the copolymer can be subjected to the final stabilization step (stabilizer compounding step), it becomes extremely advantageous economically to produce a stabilized polyoxymethylene copolymer. It is necessary to obtain a high quality crude POM copolymer in the step and / or the residual catalyst deactivation step.

[0005] Among them, as a method for improving the deactivation of the residual catalyst, from the viewpoint of the efficiency of deactivating the residual catalyst and the subsequent efficiency of decomposing and removing the unstable terminal, the crude POM copolymer, which is a polymerization product, is used. It has been known that the combined product is finely pulverized and deactivated, and it is considered that the smaller the particle size of the pulverized product is, the more preferable it is (JP-A-57-80414, JP-A-58-34)
No. 819). However, when the particle size is excessively small, handling problems such as poor penetration of the pulverized material into the kneader in the subsequent steps such as kneading have occurred. Therefore, by producing a crude POM copolymer in which the particle size distribution is appropriately adjusted, it is possible to substantially eliminate the unstable partial decomposition removal step, and to produce a stable additive-added compound. Has been proposed (JP-A-10-101756).

The present inventor has further studied this technique. As a result, there is a great technical limitation in grinding the crude POM copolymer so that the average particle size or the particle size distribution falls within a prescribed range. However, coarse polyoxymethylene flakes that deviate from this condition are liable to be formed, and if the particle size distribution shifts excessively to the small particle size side, it becomes difficult to handle the powdery granules. Was difficult. Thus, by subjecting the polyoxymethylene copolymer to a final stabilization step without going through a simplified process, in particular, a step of decomposing and removing unstable terminal portions, an economically stabilized polyoxymethylene copolymer can be obtained. There was a need for a solution for producing the coalescence.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention is to provide a crude POM copolymer powder which is a raw material for a stabilized POM copolymer which can be put to practical use in a very economically advantageous and simple process. An object of the present invention is to provide a method for producing a stabilized POM copolymer using the coarse POM copolymer powder.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have comprehensively studied the entire process from the polymerization step of the POM copolymer to the stabilization step. The characteristics of the particles of the coarse POM copolymer particles, which are the particles of the coarse POM copolymer, are the key factors, specifically, the particle size distribution and the pores on the surface of the particles. By specifying the state of the powder in an appropriate range, and by using the specified granular material,
It has been found that it is possible to produce a stabilized POM copolymer having excellent extruder operability while maintaining the above-mentioned quality target even if a component having a large particle size is larger than the particle size distribution proposed in Japanese Patent No. 1756, The present invention has been completed. The gist of the present invention is as follows.

The first invention is a crude polyoxymethylene copolymer discharged from a polymerization machine, and has a particle size distribution characteristic and a surface pore characteristic defined by the following (1) to (2) after being pulverized. The present invention relates to a coarse polyoxymethylene copolymer powder having the same. (1) 10 to 50% by weight of a component having a particle size exceeding 1.0 mm
(1-a) the average diameter of the surface pores of the above component is 4 μm
(1-b) in the total volume of the surface pores of the above component, the total volume of the pores having a diameter of 4 μm or less is 50% or less,
(2) The component having a particle size of less than 0.18 mm is 30% by weight or less. According to a second aspect of the present invention, there is provided a stabilized polyoxymethylene compound, comprising subjecting the crude polyoxymethylene copolymer powder according to the first aspect to a melt kneading treatment together with a stabilizer after deactivating the residual polymerization catalyst. The present invention relates to a method for producing a methylene copolymer.
In the third invention, after the residual polymerization catalyst of the crude polyoxymethylene copolymer powder is deactivated, 0.1 to 0.8% by weight of an unstable terminal is contained in the polyoxymethylene copolymer component. The present invention relates to a method for producing the stabilized polyoxymethylene copolymer according to the second invention. A fourth invention relates to the method for producing a stabilized polyoxymethylene copolymer according to the second or third invention, wherein the crude polyoxymethylene copolymer is obtained using an acid catalyst as a polymerization catalyst. Fifth
The stabilized polyoxymethylene according to any one of the second to fourth inventions, wherein the crude polyoxymethylene copolymer is obtained by polymerization in the presence of a hindered phenol compound. The present invention relates to a method for producing a copolymer. According to a sixth aspect, the crude polyoxymethylene copolymer is 10 pp.
The present invention relates to the method for producing a stabilized polyoxymethylene copolymer according to any one of the second to fifth aspects of the present invention, which is obtained by polymerization using a raw material monomer containing water of m or less. According to a seventh invention, a deactivating agent for a residual polymerization catalyst is added to a crude polyoxymethylene copolymer between immediately before discharge from a polymerization machine and before input to a pulverizer, followed by pulverization. The present invention also relates to a method for producing a stabilized polyoxymethylene copolymer, characterized by obtaining the coarse polyoxymethylene copolymer powder according to the first aspect of the present invention, and then subjecting the powder to melt kneading with a stabilizer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the coarse POM copolymer powder according to the present invention is:
It is obtained by pulverizing the crude POM copolymer obtained and discharged by the polymerization machine. Here, the crude POM copolymer is a polymer produced using a polymerization catalyst, and more specifically,
A cyclic acetal such as trioxane as a main monomer,
It is obtained by copolymerizing a cyclic ether or cyclic formal as a comonomer in the presence of a cationically active catalyst. Here, the cyclic ether or cyclic formal used as a comonomer is a cyclic compound having at least one pair of a linking carbon atom and an oxygen atom, such as ethylene oxide, 1,3-dioxolan,
Examples include 3,5-trioxepane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, propylene oxide and the like. Among these, preferred comonomers are ethylene oxide, 1,3-dioxolan, diethylene glycol formal, 1,4
-Butanediol formal. The amount used is 0.1 to 20 mol%, preferably 0.2 to 10 mol%, based on trioxane as the main monomer.

As the polymerization catalyst used for the copolymerization of the main monomer and the comonomer, a general cationic polymerization catalyst is used, and specific examples thereof include Lewis acids and derivatives thereof. Halides such as tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride and antimony pentafluoride, and salts thereof Compounds and their complex compounds, such as coordination compounds of boron trifluoride and organic compounds, are preferred. Further, besides Lewis acids, protonic acids and derivatives thereof can be mentioned, and more specifically, trifluoromethanesulfonic acid,
In addition to perchloric acid and the like, these esters, for example, perchloric acid tertiary butyl ester, protonic acid anhydride,
For example, acetyl perchlorate is suitable. In addition, polyacids such as heteropolyacid and isopolyacid can also be mentioned, and specifically, phosphomolybdic acid is preferable. In addition, an ion-pair catalyst is also preferable, and examples thereof include triethyloxonium hexaphosphate and triphenylmethylhexafluoroarsenate.

Among them, boron trifluoride or a coordination compound of boron trifluoride and an organic compound (eg, ethers) is the most common. In addition, protonic acids such as heteropolyacids and isopolyacids have a high activity as a catalyst, and it is easy to obtain a high-quality crude POM copolymer with a small amount of a catalyst, and it is easy to deactivate the catalyst. Such a crude POM copolymer is preferably obtained by polymerizing one or a mixture of two or more selected from such compounds as a catalyst. Also,
When a Lewis acid such as boron trifluoride is used as a catalyst, its addition amount is preferably 10 to 25 ppm based on the raw material monomer. In order to obtain a high quality crude polyoxymethylene copolymer, it is preferable to use a monomer having a water content of 10 ppm or less.

In order to control the molecular weight of the crude POM copolymer obtained by copolymerization, if necessary, an appropriate chain transfer agent, for example, an acetal compound such as methylal or dioxymethylene dimethyl ether is added in an appropriate amount for polymerization. You can also. Further, the production of the crude POM copolymer obtained by such copolymerization can be carried out in the presence of a hindered phenol-based compound which is an antioxidant. It is effective in suppressing the oxidative decomposition and the like of the POM copolymer at a high temperature in the subsequent step and providing the POM copolymer having high quality to the final stabilization step. It is suitable as a methylene copolymer.

The production of the crude POM copolymer by copolymerization is as follows:
Conventionally known equipment and methods can be used. That is, any of batch type, continuous type, etc. is possible, and may be any of melt polymerization, melt bulk polymerization, etc., but using a liquid monomer,
A continuous bulk polymerization method for obtaining a solid powdery polymer as the polymerization proceeds is industrially common and particularly preferred.
In this case, an inert liquid medium can coexist as necessary. Further, as a polymerization apparatus, a co-kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle type continuous mixer, or the like can be used.

The crude polyoxymethylene copolymer powder according to the present invention is obtained by pulverizing the crude POM copolymer obtained as described above to give a specific particle size distribution and surface structure. However, before or after the pulverization, it is necessary to deactivate the polymerization catalyst contained therein. Next, the POM
The method is characterized in that the copolymer particles are melt-kneaded together with a stabilizer and stabilized. Here, it is necessary that the pulverized crude POM copolymer satisfies the particle size distribution characteristics and surface pore characteristics specified in the following (1) and (2). (1) 10 to 50% by weight of a component having a particle size exceeding 1.0 mm
(1-a) the average diameter of the surface pores of the above component is 4 μm
(1-b) in the total volume of the surface pores of the above component, the total volume of the pores having a diameter of 4 μm or less is 50% or less,
(2) The component having a particle size of less than 0.18 mm is 30% by weight or less.

In the above particle size distribution characteristics and the pore characteristics of the surface of the granular material, components having a particle size of more than 1.0 mm
50% by weight, and 30 components having a particle size of less than 0.18 mm
Deactivation of the catalyst when the condition that the average diameter of the surface pores is 4 μm or more and the total volume of the pores with a diameter of 4 μm or less is 50% or less is not satisfied, even if the content is not more than 50% by weight. Is not performed sufficiently, the amount of unstable parts in the polymer increases,
Also, the thermal stability is reduced. Further, even if the above-mentioned surface pore characteristics are satisfied, if the amount of the component having a particle size of more than 1.0 mm is more than 50% by weight, the same quality deterioration is brought about. On the other hand, even if the above-mentioned specification of surface pore characteristics is satisfied,
When the amount of the component having a particle diameter of more than 1.0 mm is less than 10% by weight or the amount of the component having a particle size of less than 0.18 mm exceeds 30% by weight, the ability of the raw material to bite into the extruder is reduced, resulting in stable operation. Cannot be performed, and a problem that workability is remarkably reduced occurs.

The combination of the particle size distribution characteristics and the surface pore characteristics is determined by performing the deactivation treatment of the catalyst by pulverization or the pulverization of the coarse POM copolymer powder obtained by pulverization after the deactivation treatment. From the viewpoint of satisfying both the quality, particularly the amount of unstable terminals thereof, and the operability of a stabilizing step of stabilizing the pulverized crude POM copolymer by melt-kneading and stabilizing the same together with a stabilizer, the inventors of the present invention have made earnest efforts. It is something that has been examined and found. That is, when the particle size of the coarse POM copolymer particles exceeds 1.0 mm, a phenomenon in which the efficiency of the deactivation reaction is remarkably reduced has been confirmed so far, and it has been necessary to limit the average particle size. -a)
And the conditions of (1-b) are satisfied at the same time, the particle size dependence of the quality is reduced, and even if a large particle size is present, the catalyst can be successfully deactivated. This reduces the burden and restrictions imposed on the vehicle, which can lead to improved drivability. Relaxation of the restriction of the presence of the large particle diameter also suppresses the reduction in the overall particle diameter, and leads to an improvement in the operability of the extruder in the stabilization step. The deactivation of the catalyst is not a quick reaction, and a sufficient effect can be obtained even if the catalyst is pulverized after the start of the deactivation treatment.

In the pulverizing step, there are cases where pores on the surface of the flakes are crushed as the polymer pieces (flakes) are destroyed. As a result, pores on the flake surface, which originally had a large pore diameter, are reduced. In an extreme case, the pore distribution becomes bimodal. Therefore, in performing the above-mentioned pulverization, it is necessary to almost eliminate the abrasion and blockage of the surface pores by selecting a pulverizer and adjusting the operation conditions, and any pulverizer capable of almost eliminating the abrasion and blockage. It is not particularly limited. For example, a pin mill, a rotary mill, a hammer mill, a jaw crusher, a feather mill, a rotary cutter mill, a turbo mill, or a classifying impact crusher are used. ,
It can be controlled by a screen mesh provided in the pulverizer and / or a sieve provided separately as required.

Taking the case where a pin mill is used as a preferred pulverizer as an example, the particle size distribution characteristics and the surface pore characteristics specified by the present invention can be obtained, for example, by the following pulverization method. A large number of pins attached to a plurality of disks fixed to a single rotating shaft are rotated at high speed in a grinding chamber to strike flakes, and to strike the flakes against a plate provided around Pulverizing with powerful and powerful force. The flakes are repeatedly hit and crushed until they are large enough to pass through a screen mounted on the wall. The surface of the powder obtained in this way hardly wears the pores obtained from the fine voids inside the flakes, and the number of pins, pin shape, disk rotation speed, screen mesh size, pin and screen of the device. By appropriately adjusting the gap, a powder having the desired shape can be obtained.
In particular, it is important to adjust the screen mesh size and the gap between the pins and the screen. Although the numerical value varies depending on the device used, the screen mesh size mainly affects the particle size distribution characteristics, and the particle size distribution can be controlled by setting the screen mesh size in an appropriate range. Also, the gap between the pin and the screen mesh mainly affects the pore characteristics. The smaller the gap, the smaller the average diameter of the surface pores, and the larger the gap, the larger the average diameter of the surface pores. The properties of (1-b) on the surface of the large particle size component having a particle size exceeding 1.0 mm are determined by an appropriate relationship between the screen mesh size and the gap between the pin and the screen mesh. Note that the relationship between the characteristic (1-b), the screen mesh size, and the gap between the pin and the screen mesh varies depending on the type of the crusher. Therefore, it is preferable to set these in advance so that the target characteristics can be obtained by trial.

In order to deactivate the residual catalyst contained in the crude POM copolymer or the coarse POM copolymer powder discharged from the polymerization machine, a known method can be used as the deactivation method. For example, any of a method using a large or small amount of an aqueous solution or a solvent solution containing a basic compound, a method using a basic gas and bringing into contact therewith, and the like can be used. As the deactivator usable as an aqueous solution or a solvent solution, any of known basic substances is effective, for example, ammonia, various amine compounds, or alkali metal or alkaline earth metal oxides, hydroxides, Organic acid salts or inorganic acid salts, trivalent phosphorus compounds and the like can be mentioned. Among them, a particularly suitable deactivation treatment agent is, for example, an aqueous solution of an organic or inorganic basic compound such as triethylamine, triethanolamine, sodium carbonate, and calcium hydroxide. It is preferable to obtain More preferably, such a deactivating agent is added between immediately before the outlet of the crude POM copolymer of the polymerization machine and the inlet of the pulverizer, and pulverization is carried out in the presence of the deactivator. A coarse POM copolymer powder and granules of high quality can be obtained.

The crude POM copolymer powder particles which have been deactivated and pulverized or deactivated after pulverization are subjected to washing, drying and the like as necessary. In the present invention, the crude POM copolymer is subjected to the catalyst deactivation treatment as described above and crushed into a powder having a specific particle size distribution characteristic and a surface structure, whereby a high-quality unstable terminal is obtained. Less coarse P
Although an OM copolymer powder can be obtained, it is particularly preferable that the powder having an unstable terminal content of 0.1 to 0.8% is subjected to the next stabilization step. The amount of unstable terminal of the crude POM copolymer powder particles specified here is determined by putting 1 g of the powder particles together with 100 ml of a 50% aqueous methanol solution containing 0.5% by weight of ammonium hydroxide in a pressure-resistant closed container. 45 at 180 ° C
After heat treatment for a minute, the mixture was taken out by cooling, and the amount of formaldehyde decomposed and eluted in the liquid was quantitatively analyzed, and the result was shown in terms of% by weight with respect to the granular material.

As described above, the coarse POM copolymer powder which has been pulverized so as to have specific particle size distribution characteristics and surface pore characteristics, and which has been subjected to a deactivation treatment of the residual catalyst, is subjected to a usual unstable terminal portion. Is immediately melt-kneaded together with a stabilizer without substantially undergoing a decomposition removal step to obtain a stabilized polyoxymethylene copolymer.

The stabilizer used here is not particularly limited, and any known stabilizer can be used. Generally, an antioxidant and a heat stabilizer are used in combination. Examples of the antioxidant include 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityltetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis ( 3,5-di-t-butyl-4-hydroxy-cinnamamide) and the like.

Examples of the heat stabilizer include triazine compounds such as melamine and melamine-formaldehyde condensate;
Polyamides such as nylon 12, nylon 6,10, etc., and hydroxides, carbonates, phosphates, acetates, oxalates and the like of alkali metals or alkaline earth metals, and higher fatty acids such as stearic acid or substituents such as hydroxyl groups. Metal salts of higher fatty acids having the formula

In addition, the stabilized polyoxymethylene copolymer according to the present invention may contain other various additives depending on the purpose. Examples thereof include a weather (light) stabilizer, a lubricant, and a lubricant. , A nucleating agent, a release agent, an antistatic agent, a dye, a pigment, other organic polymer materials, inorganic and organic fibrous, plate-like, and powder-like fillers. Melt kneading with a stabilizer or the like is generally performed using an extruder.

[0026]

(Powder characteristics)

・ Particle size distribution characteristics The sample is separated by a plurality of metal sieves with different openings,
It was evaluated by weight fraction. -Characterization of pores The pore volume and pore diameter distribution were measured by a general mercury intrusion method. On the measurement, when the pore diameter is 0.1 μm or less, the sample can be compressed and pulverized, and when the pore diameter is 100 μm or more, the sample gap is measured.
The evaluation was made by the pore diameter distribution curve obtained for the region of m or less. [Thermal Stability of Stabilized Polyoxymethylene Copolymer] 5 g of stabilized polyoxymethylene copolymer was placed in air at 220
The weight loss at the time of heating at 45 ° C. for 45 minutes was measured, and the weight loss rate per minute (%) is shown. [Extrusion property]-Raw material biting property When a stabilizer is mixed with the coarse polyoxymethylene copolymer powder and melted and kneaded with an extruder, the raw material bites into the extruder and the stabilized polyoxygen from the extruder. The state of methylene emission was observed, and evaluated on the following four grades A to D. A: Both biting and discharging strands are stable. B: Occasionally, biting failure occurs and the thickness of the strand fluctuates, but sufficiently stable operation is possible. C: The fluctuation of the bite is slightly large, the fluctuation of the thickness of the strand is large, and the strand is occasionally cut. D: The bite fluctuates greatly, the amount of bite is generally low, and the strand cannot be drawn normally.・ Motor load amplitude Difference between maximum and minimum values of motor current during extrusion (unit: Ampere) ・ Resin pressure fluctuation range Difference between maximum and minimum values indicated by a resin manometer installed immediately after the screw tip of the extruder (Unit is kg / cm ² )

[0027]

[Table 1]

[0028]

EFFECT OF THE INVENTION Crude POM of the polymer discharged from the polymerization machine
When given predetermined particle size distribution characteristics and surface pore characteristics,
It was found that a stabilized POM copolymer can be obtained efficiently regardless of the average particle size and without the need for terminal treatment.

Continuation of the front page (72) Inventor Hajime Serizawa 973 Miyajima, Fuji-shi, Shizuoka Prefecture F-term in Polyplastics Co., Ltd. AD47 AD51 AE14 AF00

Claims (7)

[Claims] 1. A crude polyoxymethylene copolymer discharged from a polymerization machine, which is pulverized and has the following properties (1) and (2):
A coarse polyoxymethylene copolymer powder having a particle size distribution characteristic and a surface pore characteristic specified in (1). (1) 10 to 50% by weight of a component having a particle size exceeding 1.0 mm
(1-a) the average diameter of the surface pores of the component is 4 μm or more, and (1-b) the total volume of the pores having a diameter of 4 μm or less is 50% of the total volume of the surface pores of the component. % Or less, and (2) a particle size of 0.1
The component of less than 8 mm is 30% by weight or less. 2. A stabilized polyoxymethylene copolymer, comprising subjecting the crude polyoxymethylene copolymer powder according to claim 1 to melt kneading together with a stabilizer after deactivating the residual polymerization catalyst. A method for producing a polymer. 3. After the residual polymerization catalyst of the crude polyoxymethylene copolymer powder is deactivated, 0.1 to 0.8% by weight of unstable terminal is present relative to the polyoxymethylene copolymer component. A method for producing a stabilized polyoxymethylene copolymer according to claim 2. 4. The method for producing a stabilized polyoxymethylene copolymer according to claim 2, wherein the crude polyoxymethylene copolymer is obtained using an acid catalyst as a polymerization catalyst. 5. The stabilized polyoxymethylene copolymer according to claim 2, wherein the crude polyoxymethylene copolymer is obtained by polymerization in the presence of a hindered phenol compound. Manufacturing method of coalescence. 6. The crude polyoxymethylene copolymer is 10 p
The method for producing a stabilized polyoxymethylene copolymer according to any one of claims 2 to 5, which is obtained by polymerization using a raw material monomer containing water of pm or less. 7. A deactivating agent for a residual polymerization catalyst is added to the crude polyoxymethylene copolymer between immediately before discharge from the polymerization machine and before input to the pulverizer, followed by pulverization. A method for producing a stabilized polyoxymethylene copolymer, comprising obtaining the crude polyoxymethylene copolymer powder according to claim 1, followed by melt-kneading with a stabilizer.