JPS6213975B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a thermally stable polyacetal polymer. More specifically, polyoxymethylene having a number average molecular weight of 10,000 or more is reacted with a compound selected from the group consisting of alkylene oxides and cyclic formals in the presence of a coordination compound of a Lewis acid and a cyclic ether,
The present invention relates to a method for producing a stabilized polyacetal polymer having excellent stability such as thermal stability and base stability. Japanese Patent Publication No. 43-26872 describes a method of reacting polyoxymethylene with 1,3-dioxolane, and Japanese Patent Publication No. 48-3711 describes a method of reacting polyoxymethylene with 1,3,6-trioxokene. It has been stated. In these methods, side reactions frequently occur and the main chain of polyoxymethylene is cleaved, making it difficult to obtain stabilized polyoxymethylene with a constant molecular weight. Furthermore, Japanese Patent Publication No. 52-9230 describes the reaction of polyoxymethylene with ethylene glycol or diethylene glycol. In this method, the reaction produces a large amount of water. The water produced acts as a chain transfer agent before being removed from the system.
Lowers the molecular weight of the polymer. In addition, this method also makes it difficult to control the reaction. Japanese Patent Publication No. 44-27667 discloses a method in which polyoxymethylene and ethylene oxide are reacted in an acidic reaction medium. Further, in this invention, for example, an acetic acid compound of Lewis acid is used as a catalyst. When reacting polyoxymethylene and ethylene oxide using a dialkyl ether acetic acid compound of a Lewis acid such as a boron trifluoride diethyl ether acetate compound (boron trifluoride diethyl etherate), an acetylating agent is used. ionization occurs. As a result, the polyoxymethylene main chain is cleaved by the fragments of the acetylating agent, and a decrease in molecular weight is unavoidable. Furthermore, the activity of the dialkyl ether acetic acid compound of a Lewis acid as a catalyst is somewhat low, making it necessary to increase the amount of catalyst and use an excessive amount of ethylene oxide during the reaction. By increasing the amount of catalyst, the reduction in molecular weight becomes even greater. Further, the use of an excessive amount of ethylene oxide is disadvantageous in terms of industrial production. As a result of extensive studies on the stabilization reaction of polyoxymethylene, the present inventors have discovered that a coordination compound of a Lewis acid and a cyclic ether can be formed by combining polyoxymethylene with a compound selected from the group consisting of alkylene oxides and cyclic formals. When reacted in the presence of
The present inventors have discovered that a stabilized polyacetal polymer having both good stability and desired molecular weight can be obtained in high yield, leading to the completion of the present invention. The present invention comprises 100 parts by weight of polyoxymethylene having a number average molecular weight of 10,000 or more;

[Formula] (R ₀ ; hydrogen, alkyl group, substituted alkyl group, aryl group, substituted aryl group, each of which may be the same or different; m = 2 to 6); alkylene oxide; 0.01-200 parts by weight and general formula

【formula】

【formula】

[Formula] 0.01 to 200 parts by weight of a compound selected from the group consisting of cyclic formals represented by (R ₁ ; alkyl group, aryl group), a Lewis acid and the general formula

【formula】

【formula】

[Formula] (R ₁ ; alkyl group, aryl group)

【formula】

[Formula] (R ₃ alkyl group, aryl group)

Coordination compound with a compound selected from the group consisting of cyclic ethers represented by [Formula], 0.0005 to 2 parts by weight when using no solvent, 1 x 10 ^-7 based on Lewis acid when using an organic medium Provided is a method for producing a stabilized polyacetal polymer, characterized in that the reaction is carried out in the presence of ~1×10 ⁻¹ mol/l at a temperature of −20° C. to 230° C. for a time of 5 seconds to 300 minutes. That is, the first object of the present invention is to create a stabilized polyacetal polymer having a desired molecular weight and excellent stability such as thermal stability and base stability by inserting an oxyalkylene bond into the polyoxymethylene main chain. The purpose is to provide a method for manufacturing. The second object of the present invention is to provide a production method that causes less decrease in the molecular weight of the polymer during the reaction, and the third object of the present invention is to provide a production method that reduces the decrease in the molecular weight of the polymer during the reaction. The objective is to provide a rational manufacturing method that uses less alkylene oxide and cyclic formal. The present invention will be specifically explained below. The polyoxymethylene used in the present invention is a polymer having repeating oxymethylene units (-CH ₂ O-), and is a polymer in which both ends of the polymer are hydroxyl groups, or one or both ends of the polymer are This is a polymer blocked using a known method. Esterification methods, urethanization methods, etherification methods, etc. are known as methods for blocking polymer terminals. In addition, the molecular weight (number average molecular weight) of polyoxymethylene used as a starting material is at least 10,000.
Although it is necessary that the number is above 30,000, it is more preferable from the viewpoint of the practical performance of the stabilized polyacetal polymer. The upper limit of the molecular weight is mainly determined by the molecular weight of the desired stabilized polyacetal polymer and, if a molecular weight regulator is used, the amount of the molecular weight regulator used, but it is more preferably 500,000 or less. The compound to be reacted with polyoxymethylene in the present invention is selected from alkylene oxides and cyclic formals. As alkylene oxide, the general formula (Ro: hydrogen, alkyl group, substituted alkyl group,
They are selected from allyl groups and substituted aryl groups, and may be the same or different. The first example is a compound having a structure represented by m=2 to 6). For example, ethylene oxide, propylene oxide, butylene oxide, trans-2,3-epoxybutane, cis-2,3-epoxybutane, isobutylene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, 2-methyltetrahydrofuran, oxepane , styrene oxide, p-chlorostyrene oxide, epichlorohydrin, etc. are included in this group. In addition to these compounds, cyclohexene oxide and the like can also be used. Among these alkylene oxides, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and cyclohexene oxide are particularly preferred. As a cyclic formal, the general formula The first examples include cyclic alkylene glycol formals having the structure represented by (p=2 to 10), including ethylene glycol formal, 1,3-propanediol formal, 1,4-butanediol formal, and 1,5-pentanediol formal. Formal, 1,6-hexanediol formal,
1,7-heptanediol formal, 1,8-
Octanediol formal and 1,10-decanediol formal are included in this group. Among these cyclic formals, ethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal and 1,6-hexanediol formal are particularly preferred. As a cyclic formal, the general formula The second example is cyclic polyethylene glycol formal having a structure represented by (g=2-15), such as diethylene glycol formal,
This group includes triethylene glycol formal, tetraethylene glycol formal, hexaethylene glycol formal, decaethylene glycol formal, and polyethylene glycol-200 formal. Among these cyclic formals, diethylene glycol formal, triethylene glycol formal and tetraethylene glycol formal are particularly preferred. In addition, in the present invention, the general formula A cyclic formal having a structure represented by (R ₁ :alkyl group, aryl group) can also be used. For example, propylene glycol formal, butylene glycol formal, styrene glycol formal, etc. are included in this group. In the present invention, a coordination compound of a Lewis acid and a cyclic ether is used as a catalyst. Here, the coordination compound is defined as a compound in which the oxygen of the cyclic ether serves as an electron donor, and the Lewis acid serves as an electron acceptor. The formation of coordination compounds is
Infrared absorption spectrum, ultraviolet absorption spectrum,
Confirmation can be performed using means such as nuclear magnetic resonance spectroscopy. Further, the coordination compound used in the present invention can be synthesized by adding a Lewis acid to an organic solvent containing a cyclic ether. However, when synthesizing a coordination compound using a ring-opening polymerizable cyclic ether such as ethylene oxide or tetrahydrofuran, measures such as keeping the concentration of the cyclic ether in the organic solvent as low as possible are taken to synthesize the cyclic ether polymer. It is necessary to avoid the generation of The first group of Lewis acids that can form coordination compounds with cyclic ethers include tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, phosphorus pentafluoride, Examples include Friedel-Crafts type compounds such as antimony chloride, antimony pentafluoride, boron trifluoride, and boron tribromide. The second group of Lewis acids includes perchloric acid, acetyl perchlorate, t-butyl perchlorate, hydroxyacetic acid, trichloroacetic acid,
There are inorganic acids and organic acids such as trifluoromethanesulfonic acid and p-toluenesulfonic acid. The third group of Lewis acids includes complex salt compounds such as triphenylmethylhexafluoroantimonate, allyldiazonium hexachlorophosphate, and triethyloxonium tetrafluoroborate. A fourth group of Lewis acids includes organometallic compounds such as triethylaluminum, diethylaluminum chloride, aluminum isopropoxide, diethylzinc, and triethoxyboron. In addition to these four groups, molybdenum oxide acetylacetonate and the like can also be used as Lewis acids. Among these Lewis acids, Friederu-Crafts type compounds and complex salt compounds are more preferable, but inorganic acids, organic acids, and organometallic compounds can also be added in increasing amounts to form Friederu-Crafts type compounds and complex salt compounds. can produce the same effect. Among these Lewis acids, boron trifluoride is particularly preferably used. As a source of boron trifluoride, gaseous boron trifluoride is preferred, and boron trifluoride complexes such as boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride triethylamine complex, etc. It can also be used in some cases. The first group of cyclic ethers that can form coordination compounds with Lewis acids include the general formula Examples include compounds having a structure represented by (s=2-6). Ethylene oxide, oxetane, tetrahydrofuran, tetrahydropyran and oxepane are included in this group. The second group of cyclic ethers has the general formula Examples include compounds having a structure represented by (R ₃ :alkyl group, aryl group). For example, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, etc. are included in this group. The third group of cyclic ethers includes cyclic formals, such as ethylene glycol formal, propylene glycol formal, diethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, and the like. In addition to these cyclic ethers, cyclic polyethers collectively referred to as dioxane, furan, 2-methylfuran, cineole, and crown ether can also be used. Among these cyclic ethers, ethylene oxide, tetrahydrofuran, tetrahydropyran, epichlorohydrin, ethylene glycol formal, diethylene glycol formal,
1,4-butanediol formal and dioxane are most preferred. In the present invention, the molecular weight of the stabilized polyacetal polymer can also be arbitrarily adjusted using a molecular weight regulator. Molecular weight regulators that can be used in the present invention include acetal compounds, orthoformates, alcohols, carboxylic acids, carboxylic anhydrides, and water. The first group of acetal compounds is
There are formal compounds and hemiformal compounds represented by R ₂ OCH ₂ OR ₂ and HOCH ₂ OR ₂ . here
_R2 is a _C1 - _C8 alkyl group. Specific examples include methylal, diethoxymethane, di-iso-propoxymethane, di-n-butoxymethane, and butoxyhydroxymethane. The second group of acetal compounds are:
There is a polyacetal compound represented by _R2O ( _CH2O ) _nR2 . Here, R ₂ is a C ₁ to C ₈ alkyl group, and n is an integer of 2 to 20. Specific examples include dioxymethylene dimethoxide, tetraoxymethylene dioctoxide, decaoxymethylene diisopropoxide, dioxymethylene diethoxide, and the like. These compounds are often difficult to isolate as single substances and are usually used as mixtures. The degree of polymerization n of these compounds is
It can be determined using methods such as nuclear magnetic resonance spectroscopy, gas chromatography, and liquid chromatography. The third group of acetal compounds is

There is an acetal compound represented by the formula: Here, _R2 is a _C1 - _C8 alkyl group.
Specifically, dimethyl acetal, diethyl acetal, di-iso-propyl acetal, di-t-
Examples include butyl acetal, dihexyl acetal, dioctyl acetal, and the like. Orthoformate is a compound represented by HC( _OR2 ) ₃ , where _R2 is a _C1 to _C4 alkyl group,
It is a group selected from aryl groups. in particular,
Examples include methyl orthoformate, ethyl orthoformate, diethylpropyl orthoformate, propyl orthoformate, and phenyl orthoformate. Alcohol is a compound represented by R ₂ OH, where R ₂ is a group selected from a C ₁ to _{C 20} alkyl group and an aryl group. Specifically, methanol, ethanol, n-propanol, iso-butanol,
Examples include aliphatic alcohols such as lauryl alcohol and stearyl alcohol, and aromatic alcohols such as benzyl alcohol and 2-phenylethanol. Carboxylic acid is a compound represented by R ₂ COOH, where R ₂ is a group selected from hydrogen, a C ₁ to C ₂₀ alkyl group, and an aryl group. Specifically, formic acid,
These include aliphatic carboxylic acids such as acetic acid, propionic acid, lauric acid, and stearic acid, and aromatic carboxylic acids such as benzoic acid and iso-phthalic acid. Carboxylic acid anhydride is

【formula】 【formula】

【formula】

It is a compound represented by the formula: Here, _R'1 is a _C1 - _C20 alkyl group, _R'2 is hydrogen or a _C1 - _C20 alkyl group, and _R'3 is hydrogen or a _C1 - _C3 alkyl group. Specifically, acetic anhydride, propionic anhydride, stearic anhydride,
Examples include aliphatic carboxylic anhydrides such as succinic anhydride, dodecenylsuccinic anhydride, and maleic anhydride, and aromatic carboxylic acid anhydrides such as phthalic anhydride and 4-methylphthalic anhydride. Among these molecular weight modifiers, formal compounds represented by R ₂ OCH ₂ OR ₂ , R ₂ O (CH ₂ O) nR A polyacetal compound represented by ₂ , and

An acetal compound represented by the formula is preferable, and methylal and diethyl acetal are particularly preferable from the viewpoint of ease of purification and availability. The reaction between polyoxymethylene and alkylene oxide is carried out without a solvent or in an organic medium.
The reaction without a solvent is usually carried out by adding a catalyst to a mixture of polyoxymethylene, an alkylene oxide, and a cyclic formal, using the raw material polyoxymethylene in a solid powder state or a molten state. The reaction in an organic medium is usually carried out by adding a catalyst to the organic medium containing the raw material polyoxymethylene, alkylene oxide, and cyclic formal. Examples of the organic medium that can be used in the present invention include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, and cyclopetane; aromatic hydrocarbons such as benzene, toluene, and xylene; Examples include halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, and trichloroethylene, and halogenated aromatic hydrocarbons such as chlorobenzene and o-dichlorobenzene. These organic media may be used alone or in combination of two or more. When using a molecular weight regulator, the molecular weight regulator is uniformly dissolved or dispersed in the reaction system. The concentration of the molecular weight regulator in the system is
Depending on the requirements, the molecular weight of the desired stabilized polyacetal polymer can be easily determined by experiment. The alkylene oxide and cyclic formal are used in an amount of 0.01 to 200 parts by weight, more preferably 0.05 to 100 parts by weight, per 100 parts by weight of raw material polyoxymethylene. The blended compound of Lewis acid and cyclic ether is 0.0005 to 2.0 parts by weight per 100 parts by weight of raw material polyoxymethylene in the case of no solvent, and 1 x 10 ^-7 based on Lewis acid in the case of using an organic medium. ~1×10 ^-1
Used in moles/-concentration of organic medium. The reaction temperature is usually set between -20 and 230°C, but preferably between 20 and 210°C in the case of no solvent, and more preferably between 0 and 120°C when using an organic medium. . There is no particular limit to the reaction time, but from 5 seconds
Set between 300 minutes. In the case of no solvent, a basic substance such as sodium hydroxide, ammonia, amine, or quaternary ammonium salt is added to the system after a predetermined period of time has passed, and the reaction is completed. It is also possible to add stabilizers, etc. to the stabilized polyacetal polymer and put it into practical use.
Furthermore, after heating the stabilized polyacetal polymer with water, alcohol, etc., a stabilizer etc. can be added to the polymer for practical use. When an organic medium is used, the polymer is separated from the organic medium after a predetermined period of time, and a basic substance such as sodium hydroxide, ammonia, amine, or quaternary ammonium salt is added to complete the reaction. It is also possible to add a stabilizer to the stabilized polyacetal polymer as it is for practical use. Alternatively, after heating the stabilized polyacetal polymer with water, alcohol, etc., a stabilizer etc. can be added for practical use. By using the method of the present invention described in detail above, it has become possible to obtain a good stabilized polyacetal polymer. The features of the present invention are listed as follows:
It is as follows. It is possible to produce a stabilized polyacetal polymer with excellent stability such as thermal stability and base stability. There is little decrease in molecular weight during reaction. The reaction proceeds easily at low catalyst concentrations. The molecular weight of the stabilized polyacetal polymer can be controlled arbitrarily by using a molecular weight regulator. By using a specific molecular weight regulator, it is possible to simultaneously control the molecular weight and improve stability such as thermal stability and base stability. Measured values in the following examples are based on the following measurement method. Molecular weight (number average molecular weight): Based on terminal group determination method. That is, the terminal methoxy group (-OCH ₃ ) was quantified using the modified Zeisel method. Terminal hydroxyl group (-OH)
convert this group to an acetyl group (-
OCOCH ₃ ) and then quantified using infrared absorption spectroscopy. Also, the terminal carboxyl group (−
OCOR.R: Hydrogen, alkyl groups) are also quantified using infrared absorption spectroscopy. Reduced viscosity: 0.5gr/in p-chlorophenoltetrachlorethylene (1:1 weight ratio) solution
Polymer concentration of dl, measured at 60℃. Base stability yield: at 5% polymer concentration in benzyl alcohol containing 1% tributylamine
Polymer recovery rate when heat treated at 150℃ for 60 minutes.
It is a measure of stability. Rv222: The amount of polymer remaining after heating at 222°C under vacuum for 50 minutes. It is a measure of stability. The present invention will be explained below with reference to some examples.
The present invention is not limited to these examples. Example 1 (1) Preparation of catalyst After 55 mg of ethylene oxide was blown into 100 ml of sufficiently dehydrated n-hexane, 85 mg of boron trifluoride diethyl etherate was added to this solution and stirred for 2 minutes. After stirring for 2 minutes, stirring was stopped and a small amount of the polymer formed was allowed to precipitate. The supernatant n-hexane solution was gently collected and analyzed for fluorine and diethyl ether, and it was found to be 0.334g/ml of fluorine.
, 0.423 gr/diethyl ether was detected. In this solution, 98% of boron trifluoride
is a boron trifluoride ethylene oxide coordination compound, 2
As a result of the above analysis, it was found that % was boron trifluoride diethyl etherate. (2) Reaction between polyoxymethylene and ethylene oxide 50g of polyoxymethylene dihydroxide sufficiently dried under reduced pressure with a number average molecular weight of 61,500 and a reduced viscosity of 3.08, and 500ml of substantially anhydrous toluene distilled over metallic sodium. and 4 mg of methylal as a molecular weight regulator were charged into the flask.
After charging 3.8g of ethylene oxide into the flask, the contents of the flask were heated to 60°C. (1)
The reaction was started by adding the entire amount of the catalyst solution prepared above to the flask. The internal temperature of the flask is 60℃.
After maintaining the temperature for 65 minutes, the reaction was stopped by adding 5 ml of tributylamine. After separating the polymer, it was washed 5 times with methanol and vacuum dried at 60°C for 5 hours to obtain 49g of polymer. This polymer had a desired molecular weight, with a molecular weight of 34,200 and a reduced viscosity of 1.76. The base stabilization yield of this polymer was 92%, and the Rv of the polymer after base stabilization was 98.8.
%, and had good stability. Example 2 200 gr of polyoxymethylene diacetate with a molecular weight of 65,700 and a reduced viscosity of 3.30, styrene oxide 14
gr, and 1000 ml of cyclohexane were charged into a flask. A catalyst solution was prepared by blowing 14 mg of boron trifluoride into 200 ml of cyclohexane containing 45 mg of tetrahydrofuran, and then the reaction was started by adding the entire amount of this catalyst solution to the flask. After maintaining the contents of the flask at 75 °C for 35 minutes,
The reaction was stopped by adding 10 ml of 1NKOH ethanol solution. Separately, wash and dry the polymer to 197gr.
I got it. The molecular weight of this polymer was 59500, the reduced viscosity was 2.90, the base stabilization yield was 91%, and the Rv of the polymer after base stabilization was 98.4%, indicating that a stable polyacetal polymer with good properties was obtained. Ta. Examples 3 to 13 200 gr of polyoxymethylene with a molecular weight of 52,700 and a reduced viscosity of 2.45 (53% of all terminals are blocked with acetyl groups and 47% with methoxy groups), alkylene oxide shown in Table 1, cyclic formal, molecular weight regulator When using molecular weight regulator and n-hexane
Pour 1000ml into a flask. In 200 ml of methylene chloride containing the cyclic ether shown in Table 1,
A catalyst solution was prepared by adding the Lewis acid shown in the table, and the reaction was started by adding the entire amount of this catalyst solution to the flask. After maintaining the contents of the flask at 60 °C for 45 minutes,
The reaction was stopped by adding 15 ml of 10% ammonia aqueous solution. The sample was then separated, washed and dried, and the results shown in Table 1 were obtained. In all Examples, stabilized polyacetal polymers having the desired molecular weight and excellent thermal stability and base stability were obtained. Comparative Example 1 A sample obtained by operating in the same manner as in Example 2 except that an increased amount of boron trifluoride diethyl etherate was used in place of the boron trifluoride tetrahydrofuran coordination compound used in Example 2. The results are also shown in Table 1. The catalytic activity of boron trifluoride diethyl etherate was slightly lower than that of the coordination compound used in Example 2, and a decrease in molecular weight due to scission of the polyoxymethylene main chain was observed. Comparative Example 2 All operations were performed in the same manner as in Example 2, except that titanium tetrachloride was used in place of the boron trifluoride tetrahydrofuran coordination compound used in Example 2, and the obtained results are summarized in Table 1. It was shown. In the case of titanium tetrachloride, the molecular weight also decreases significantly due to side reactions. Example 14 Polyoxymethylene diacetate with a molecular weight of 46100 and a reduced viscosity of 2.21 with both ends capped with acetic anhydride.
350gr and 15gr of propylene oxide were charged into the autoclave. The contents are then stirred at high speed,
The temperature was raised to 80℃. 21 mg of titanium tetrachloride was added to 150 ml of methylene chloride in which 2.30 g of dioxane was dissolved to prepare a catalyst solution. The reaction was started by adding 120 ml of catalyst solution to the autoclave using a metering pump (the time required to add the catalyst solution was 23 seconds). 15 minutes after the start of the reaction, dioctylamine 6
ml was added using a metering pump to stop the reaction. The polymer was washed with acetone and dried to recover 338g of polymer. This polymer had a molecular weight of 40,800 and a reduced viscosity of 1.85, and the decrease in molecular weight was surprisingly small. 0.5 part of cyanoguanidine to 100 parts of this polymer,
2,2-methylene-bis(4-methyl-6-t-
When 0.15 parts of butylphenol was added and subjected to molding, a molded product with strong physical properties was obtained. Example 15 After mixing 1500 gr of polyoxymethylene with a molecular weight of 55,000 and a reduced viscosity of 2.87 (42% of all terminals are capped with methoxy groups, 58% are hydroxyl groups), 40 gr of styrene oxide, and 75 mg of diethyl acetal in a sufficiently dried hopper, 30 of L/D=35 with vent port
It was extruded using a mmφ extruder. The time required for extrusion was 26 minutes, and the temperature of the molten resin at the die exit was 198°C. boron trifluoride
100ml of toluene containing 120mg and 890mg of dioxane
In addition, it was made into a catalyst solution. This catalyst solution is
ml was forcibly added from the vent port using a metering pump over the 26 minutes required for extrusion. The average residence time of the resin from the vent port to the die exit was 25 seconds. The molten resin coming out of the die
A total of 1462 gr of polymer was recovered as strands by introducing into a 1.1% NaOH aqueous solution. This polymer had a desired molecular weight, with a molecular weight of 36,200 and a reduced viscosity of 1.73.

【table】

【table】

Claims (1)

[Scope of Claims] 1. 100 parts by weight of polyoxymethylene having a number average molecular weight of 10,000 or more; Each may be the same or different. 0.01 to 200 parts by weight of alkylene oxide represented by m = 2 to 6) and general formula [Formula] [Formula] [Formula] (R ₁ ; alkyl group, aryl group ) 0.01 to 200 parts by weight of a compound selected from the group consisting of cyclic formals represented by Lewis acid and the general formula [Formula] [Formula] [Formula] (R ₁ : alkyl group, aryl group) [Formula] [ Formula] (R ₃ Alkyl group, aryl group Coordination compound with a compound selected from the group consisting of cyclic ethers represented by [Formula], 0.0005 to 2 parts by weight in the case of no solvent, 0.0005 to 2 parts by weight in the case of using an organic medium) is 1 based on Lewis acid standards.
A method for producing a stabilized polyacetal polymer, which comprises reacting in the presence of ×10 ^-7 to 1 ×10 ^-1 mol/l at a temperature of -20°C to 230°C for a time of 5 seconds to 300 minutes.