JPH0730150B2 - Method for producing stable oxymethylene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention is a method of copolymerizing trioxane and a cyclic ether in the presence of a catalyst, followed by addition of a metal sulfite for deactivation,
The present invention relates to a method for producing a stable oxymethylene copolymer by adding a stabilizer and an alkali metal or alkaline earth metal salt and heating the mixture to remove unstable terminals, and further adding a formaldehyde absorbent.

<Prior Art> It is known, for example, from JP-B-44-5234 to obtain a polyacetal homopolymer or copolymer by bulk polymerization of trioxane alone or trioxane and a cyclic ether.

Since the obtained polymer is thermally unstable as it is, in the case of a homopolymer, the terminal group is blocked by esterification or the like, and in the case of a copolymer, the unstable terminal portion is decomposed and removed. Although stabilized, it is necessary to deactivate the catalyst and stop the polymerization reaction prior to the stabilization.

That is, oxymethylene homopolymers and copolymers obtained by cationically polymerizing trioxane, etc., gradually depolymerize unless a catalyst remaining in them is deactivated, and a remarkable decrease in molecular weight occurs, or thermal It becomes an extremely unstable polymer.

Regarding the deactivation of boron trifluoride-based polymerization catalyst, see Japanese Patent Publication 55
JP-A-45087 and JP-B-55-50485 disclose a method of bulk polymerization of trioxane or the like with a boron trifluoride-based catalyst and then adding a trivalent phosphorus compound.

<Problems to be Solved by the Invention> However, even when the boron trifluoride-based polymerization catalyst is deactivated with a trivalent phosphorus compound, the deactivating effect is not sufficient, and depolymerization still occurs when the polymer is melted. Occurs and a decrease in molecular weight is seen. Particularly when the polymer is melted at a high temperature of 230 ° C. or higher, the molecular weight is remarkably reduced.

Therefore, the inventors of the present invention have achieved the present invention as a result of solving the above-mentioned problems of the prior art and earnestly examining a method for producing an oxymethylene copolymer having excellent thermal stability.

<Means for Solving the Problems> That is, the present invention provides a mixture of trioxane and a cyclic ether with boron trifluoride, a boron trifluoride hydrate, and an organic compound containing boron trifluoride and an oxygen atom or a sulfur atom. In the presence of at least one polymerization catalyst selected from the group consisting of a coordination compound with a compound, in bulk polymerization, to produce an oxymethylene copolymer containing an oxymethylene unit and another oxyalkylene unit, a sulfite metal salt after completion of the polymerization To deactivate the boron trifluoride-based catalyst, and further heat resistance stabilizer and alkali metal hydroxide, alkaline earth metal hydroxide, inorganic weak acid alkali metal salt, inorganic weak acid alkaline earth metal salt, organic acid Alkali metal salts, organic acid alkaline earth metal salts, alkali metal alkoxides, alkaline earth metal alkoxides, alkali metal powders Noxide, at least one selected from alkaline earth metal phenoxide is added, after heating the temperature range of 100 ~ 260 ℃ to remove the unstable terminal, formaldehyde absorbent is added, characterized by heating and kneading The present invention provides a method for producing a stable oxymethylene copolymer, preferably the above method for inactivating a boron trifluoride-based catalyst by adding a metal sulfite and a phosphine oxide represented by the following general formula (I). It is a thing.

(However, R ¹ , R ² , and R ³ are organic residues having 1 to 20 carbon atoms,
They may be the same or different, and R ¹ , R
² may form a cyclic structure between R ³ ) The cyclic ether used in the present invention is represented by the following general formula (I
It means a compound represented by I).

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

The copolymerization amount of the cyclic ether of the present invention needs to be in the range of 0.1 to 10 mol%, particularly preferably 0.2 to 5 mol% with respect to trioxane, and if it is 0.1 mol% or less, unstable terminal parts are decomposed. When removed and stabilized, the polymer yield is low and productivity is reduced, which is not preferable. Also, 10 mol%
The above is not preferable because the melting point and crystallinity of the polymer are lowered and the mechanical strength and moldability are deteriorated.

The polymerization catalyst of the present invention comprises one or more compounds selected from the group consisting of boron trifluoride, a boron trifluoride hydrate and a coordination compound of an organic compound having an oxygen or sulfur atom and boron trifluoride, a gas. It is used in the form of a liquid, a liquid or a suitable organic solvent.

Examples of the organic compound having an oxygen or sulfur atom which forms a coordination compound with boron trifluoride include alcohol, ether, phenol and sulfide.

Among these catalysts, a coordination compound of boron trifluoride is particularly preferable, and boron trifluoride / diethyl etherate and boron trifluoride / dibutyl etherate are particularly preferably used.

Examples of the solvent for the polymerization catalyst of the present invention include benzene, toluene, aromatic hydrocarbons such as xylene, n-hexane,
Aliphatic hydrocarbons such as n-heptane and cyclohexane, alcohols such as methanol and ethanol, halogenated hydrocarbons such as chloroform, dichloromethane, 1,2-dichloroethane, ketones such as acetone and methyl ethyl ketone are used. .

The amount of the polymerization catalyst added is 5 with respect to 1 mol of trioxane.
It is in the range of × 10 ^-6 to 1 × 10 ^-1 mol, particularly preferably 1
It is in the range of × 10 ^-5 to 1 × 10 ^-2 mol.

Various devices for polymerizing trioxane alone or trioxane and cyclic ether in a bulk are known, but the bulk polymerization used in the present invention is not particularly limited by the device, and 10% by weight or less based on trioxane. Then,
It can also be applied to a polymerization reaction carried out in the presence of an organic solvent such as cyclohexane.

In the bulk polymerization, an apparatus having a strong stirring ability and controlling the reaction temperature is particularly preferably used because rapid solidification and heat generation occur during the polymerization.

As the bulk polymerization apparatus of the present invention having such performance, a kneader having a sigma type stirring blade, a cylindrical barrel as a reaction zone, and a screw having coaxial and a large number of interrupted peaks in the barrel are provided. A mixer that operates so that the interruption portion and the teeth protruding on the inner surface of the barrel mesh with each other,
In a long case having a jacket for heating or cooling, a normal screw extruder having a pair of mutually parallel parallel screw screws, two horizontal stirring shafts having a large number of paddles,
A self-cleaning mixer or the like that rotates when the shaft is simultaneously rotated in the same direction while maintaining a slight clearance between the mating paddle surface and the inner surface of the case.

Also, in bulk polymerization, a strong stirring ability is required because it solidifies rapidly in the initial stage of the polymerization reaction, but once pulverized, a large stirring ability is not required thereafter, so the bulk polymerization step is not performed. It may be divided into stages.

The bulk polymerization reaction temperature is preferably in the temperature range from the melting point to the boiling point of trioxane, that is, in the range of 60 to 115 ° C, particularly preferably in the range of 60 to 90 ° C.

At the initial stage of the polymerization, the temperature in the polymerization reaction apparatus tends to rise particularly due to the reaction heat or the frictional heat caused by solidification, so it is desirable to control the reaction temperature by passing cooling water through the jacket. .

Examples of the metal sulfite used in the present invention include sodium sulfite, potassium sulfite, calcium sulfite, barium sulfite, and the like, and sodium sulfite is particularly preferably used.

The phosphine oxides represented by the general formula (I) used in the present invention include triphenylphosphine oxide, tri-n-butylphosphine oxide and di-
Examples thereof include n-butylbenzyl phosphine oxide, dicyclohexyl phenyl phosphine oxide and tritolyl phosphine oxide, with triphenyl phosphine oxide being preferred.

The polymerization terminator of the present invention may be added as it is, but may be added as a solution or suspension of an organic solvent in order to promote contact with the polymerization catalyst. Examples of the organic solvent at that time include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as n-hexane, n-heptane and cyclohexane, alcohols such as methanol and ethanol, chloroform, dichloromethane and the like. Examples thereof include halogenated hydrocarbons such as 1,2-dichloroethane, ketones such as acetone and methyl ethyl ketone.

The addition amount of the terminating agent of the present invention is not limited to the equimolar amount with respect to the boron trifluoride-based catalyst of the polymerization catalyst used. It is effective.

Examples of the heat resistance stabilizer used in the present invention include antioxidants, and specific examples thereof include triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate]. , Pentaerythrityl-
Tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) (Enyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3 , 5-Di-t-butyl-4-hydroxybenzyl) benzene, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4 -Bis- (n-octylthio) -6- (4-
Hydroxy-3,5-di-t-butylanilino) -1,3,5-
Triazine, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2-
Thiobis (4-methyl-6-t-butylphenol),
3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-tris (4-
t-Butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-t-butylphenyl) butane, 1,1
-Bis (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2'-methylene-bis (4-methyl-6-t-butylphenol), N, N'-bis [3-
(3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and other hindered phenol compounds, tetrakis (2,4-di-t-butylphenyl)-
4,4'-biphenylene phosphonite, tris (2,4-di-
t-Butylphenyl) phosphite, tetrakis (2,4
-Di-t-butylphenyl) -4,4'-biphenylenediphosphonite, distearyl pentaerythritol diphosphite, ditridecyl pentaerythritol diphosphite, dinonylphenyl pentaerythritol diphosphite, tris (nonylphenyl) phosphite ,
Bisphenol A pentaerythritol phosphite,
Trilauryltrithiophosphite, tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite, hydrogenated bisphenol A phosphite polymer, tris (2,4-di-t-butylphenyl) phosphite,
Phosphorus compounds such as diphenyl monodecyl phosphite, didecyl monophenyl phosphite, tridecyl phosphite, dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, 4,4'- Thio-bis (3-methyl-5-t-
Butylphenol) and an ester of tridecylthiopropionic acid, and a sulfur-based compound such as an ester of pentaerythritol and dodecylthiopropionic acid.

These antioxidants include triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (4-
t-Butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl)
Benzene, N, N'-hexamethylenebis (3,5-di-t-
The effect of the present invention is sufficiently realized by adding a hindered phenol compound such as butyl-4-hydroxy-hydrocinnamide), but the hindered phenol compound and the phosphorus compound and / or the sulfur compound are When used together, the action of a hindered phenol compound as a trapping agent for radicals generated during oxidative decomposition of oxymethylene copolymer and a phosphorus compound as a peroxide decomposing agent,
The effects of the sulfur compounds are synergistic and the effect is increased.

The amount of the antioxidant added as a stabilizer is 0.01 to 5% by weight, particularly preferably 0.05, based on the oxymethylene copolymer.
Must be in the range of ~ 3% by weight, 0.01% by weight
In the following, the effect of improving heat resistance is not sufficient, and in the case of 5% by weight or more, the antioxidant is deposited in the form of white powder on the surface of the oxymethylene copolymer and the commercial value is reduced, which is not preferable.

Examples of the alkali metal, alkaline earth metal hydroxide, inorganic weak acid salt, organic acid salt, alkoxide or phenoxide used in the present invention include lithium, sodium,
Salts of potassium, cesium, magnesium, calcium, strontium, barium and the like can be mentioned, but sodium, potassium, magnesium and calcium salts are preferable. Inorganic weak acid salts and organic acid salts include carbonates, bicarbonates, phosphates, borates, silicates, acetates, oxalates, formates, benzoates, terephthalates, isophthalates. Examples thereof include salts and phthalates. As alkoxide, methoxide, ethoxide, isopropoxide, n-
Butoxide, sec-butoxide, tert-butoxide and the like can be mentioned. One or more of these compounds are added, but the addition amount is usually 0 to oxymethylene copolymer.
It is 001 to 5% by weight, preferably 0.005 to 2% by weight.
If it is less than 0.001% by weight, decomposition and removal of unstable terminals are insufficient, and if it is more than 5% by weight, impact resistance and hydrolysis resistance decrease, which is not preferable.

The formaldehyde absorbent used in the present invention is a compound capable of reacting with formaldehyde to absorb formaldehyde, and examples thereof include amide compounds, urethane compounds, pyridine derivatives, pyrrolidone derivatives, urea derivatives, triazine derivatives and hydrazine. Derivatives, amidine compounds and the like, specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N, N
-Diphenylformamide, N, N-diphenylacetamide, N, N-diphenylbenzamiode, N, N, N ', N'-
Homopolymers or copolymers of lactams such as tetramethyl adipamide, oxalic acid dianilide, adipic acid dianilide, α- (N-phenyl) acetanilide, nylon 6, nylon 11, nylon 12, adipic acid, sebacic acid, Polyamide homopolymers or copolymers derived from divalent carboxylic acids such as decanedicarboxylic acid and dimer acid and diamines such as ethylenediamine, tetramethylenediamine, hexamethylenediamine and metaxylylenediamine, lactams and dicarboxylic acids And a polyamide copolymer derived from diamine, polyacrylamide, polymethacrylamide, N, N-bis (hydroxymethyl) sveramide, poly (γ-methylglutamate), poly (γ-ethylglutamate), poly (N-
Amide compounds such as vinyl lactam) and poly (N-vinylpyrrolidone), diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate, and
Polyurethanes derived from glycols such as 4-butanediol and polymeric glycols such as poly (tetramethylene oxide) glycol, polybutylene adipate, polycaprolactone, melamine, benzoguanamine, acetoguanamine, N-butylmelamine, N-phenylmelamine , N, N'-diphenylmelamine, N, N ', N "
-Triphenyl melamine, N-methylol melamine, N,
N'-dimethylolmelamine, N, N ', N'-trimethylolmelamine, 2,4-diamino-6-benzyloxytriazine, 2,4-diamino-6-butoxytriazine, 2,4
-Diamino-6-cyclohexyltriazine, melem,
Triazine derivatives such as melam, N-phenylurea, N,
N'-diphenylurea, thiourea, N-phenylthiourea, N, N'-diphenylthiourea, urea derivatives such as nonamethylene polyurea, phenylhydrazine, diphenylhydrazine, benzaldehyde hydrazone, semicarbazone, 1-methyl-1 -Phyenylhydrazone, thiosemicarbazone, hydrazone of 4- (dialkylamino) benzaldehyde, hydrazine derivatives such as 1-methyl-1-phenylhydrazone, thiosemicarbazone, dicyandiamide, guanzidine, guanidine, aminoguanidine, guanine, Guanacrine, guanoclor, guanoxan, guanosine, amiloride, N-amidino-
Amidine compounds such as 3-amino-6-chloropyrazinecarboxamide, poly (2-vinylpyridine), poly (2-methyl-5-vinylpyridine), poly (2-ethyl-5-vinylpyridine), 2-vinyl Pyridine-2-
Examples include pyridine derivatives such as methyl-5-vinylpyridine copolymer and 2-vinylpyridine-styrene copolymer.

Among these formaldehyde absorbents, dimer acid polyamide, melamine, guanamine, benzoguanamine,
N-methylolated melamine, N-methylolated benzoguanamine, thermoplastic polyurethane resin, dicyandiamide, guanidine, poly (N-vinylpyrrolidone), poly (2-vinylpyridine), polyurea, melem, and melam are oxy containing them. Methylene copolymer is particularly preferable because it has excellent thermal stability.

The amount of formaldehyde absorbent added is 0.01 to 5% by weight, particularly preferably 0.05 to 5% by weight, based on the oxymethylene copolymer.
It is necessary to be in the range of 3% by weight, and if it is 0.01% by weight or less, the heat resistance is not sufficiently improved, and if it is 5% by weight or more, the polymer may be colored or deposited on the polymer surface to reduce the commercial value. Not preferable.

The oxymethylene copolymer of the present invention is obtained by polymerizing a mixture of trioxane and a cyclic ether by a bulk polymerization method using a boron trifluoride-based catalyst, and the obtained polymer is a sulfite metal salt, preferably a sulfite metal salt. After deactivating the catalyst by adding phosphine oxides, heat stabilizer and alkali metal or alkaline earth metal salts are added to 100-260.
It is produced by heating in a temperature range of ℃, preferably at a temperature above the melting point of the copolymer to decompose and remove unstable terminals, and further add a formaldehyde absorbent as a final stabilizing formulation and heat kneading.

In the present invention, a polymerization catalyst of oxymethylene copolymer is deactivated with a metal sulfite, and even if the deactivated catalyst is present in the polymer, it is intended to provide a method for producing a polymer having excellent thermal stability, The stabilizer of the present invention effectively acts on a polymer deactivated by a sulfite metal salt, and oxymethylene having excellent heat resistance which cannot be obtained by a conventional polymer deactivated by a phosphorus compound. A method for producing a copolymer is provided.

The oxymethylene copolymer produced according to the present invention is excellent in moldability, mechanical properties, melt stability and heat aging resistance, so that it can be used in a wide range of applications such as mechanical mechanism parts, automobile parts, and electric / electronic parts. You can

<Example> Next, the present invention will be described with reference to Examples and Comparative Examples. In addition,
Surface condition, mechanical properties, relative viscosity ηr, thermal decomposition rate K, polymer melting point (Tm) of molded articles shown in Examples and Comparative Examples
And the crystallization temperature (Tc) were measured as follows.

Surface condition of molded product: ASTM No. 1 dumbbell test piece and Izod impact test piece using an injection molding machine with an injection capacity of 5 ounces, with a cylinder temperature of 230 ° C, a mold temperature of 60 ° C and a molding cycle of 50 seconds. Was injection molded. The surface condition of the obtained ASTM No. 1 dumbbell test piece was visually observed.

Mechanical Properties: Using the ASTM No. 1 dumbbell test piece obtained by the above injection molding, tensile properties were measured according to the ASTM D-638 method. In addition, the impact strength was measured using an Izod impact test piece according to the ASTM D-256 method.

Relative viscosity ηr: p-chlorophenol 100m containing 2% α-pinene
0.5 g of polymer was dissolved in 1 and measured at a temperature of 60 ° C.

Thermal decomposition rate Kx: Kx means the decomposition rate when left standing at x ° C for a certain period of time. Using a thermobalance device, leave about 10 mg of sample at x ° C in an air atmosphere. I asked.

Kx = (W ₀ -W ₁ ) × 100 / W ₀ % where W ₀ means the sample weight before heating and W ₁ means the sample weight after heating.

The thermal balance device used was a thermal analyzer 1090/1091 manufactured by DuPont.

Polymer melting point (Tm), crystallization temperature (Tc): Using a differential scanning calorimeter, the temperature was raised at a heating rate of 10 ° C./min in a nitrogen atmosphere, and after measuring the polymer melting point (Tm), 10 ℃ /
The temperature was lowered in minutes, and the crystallization temperature (Tc) was measured.

Reference Example 1 A 3-liter kneader having two Σ-type stirring blades was heated to 60 ° C., and 3.0 kg of trioxane, 75 g of 1,3-dioxolane,
Further, boron trifluoride / diethyl etherate as a catalyst and 200 ppm as a 10% benzene solution based on the weight of trioxane were added, and the mixture was stirred at 30 rpm.

Within a few minutes, the contents solidified and the system temperature rose due to reaction heat and frictional heat, so cool air was passed through the Σ-type stirring blade, and the rotation speed was reduced to 10 rpm to reach a maximum temperature of 80 rpm.
The temperature was controlled up to ° C.

The stirring was continued as it was, and the polymer was taken out after 60 minutes. The obtained polymer was a white powder with ηr = 2.46.

This polymer is referred to as oxymethylene copolymer A.

Reference Example 2 A polymer was bulk polymerized in the same manner as in Reference Example 1 except that 44 g of ethylene oxide was used instead of 1,3-dioxolane in Reference Example 1.

The obtained polymer was a white powder with ηr = 2.44.

This polymer is referred to as oxymethylene copolymer B.

Examples 1 to 5 and Comparative Examples 1 to 3 Various metal sulfites (average particle diameter of 200 μm or less) were added to the oxymethylene copolymer A obtained in Reference Example 1 in Table 1.
The catalyst was deactivated by stirring the mixture at a rate of 30 ° C. and 30 rpm for 10 minutes in a kneader having two Σ type stirring blades.
0.1% by weight of calcium hydroxide, 0.5% by weight of triethylene glycol-bis- [3- (3-t-butyl-
5-Methyl-4-hydroxyphenyl) propionate] (Irganox 245 manufactured by Ciba-Geigy) was added, and the temperature was raised to 210 ° C. over 5 minutes, followed by stirring at the same temperature and 30 rpm for 20 minutes. After that, as a formaldehyde absorbent, 0.
Add 1% by weight of dicyandiamide and add 1 at 210 ° C, 30 rpm.
Stir for 0 minutes.

For comparison, polymers were prepared using triphenylphosphine instead of metal sulfite.

The results of measuring the physical properties of the obtained polymer are summarized in Table 1.

As is clear from Table 1, the polymer deactivated by using the metal sulfite is superior in heat resistance stability to the polymer deactivated by using triphenylphosphine. Moreover, the more the amount of the metal sulfite added is, the more excellent the heat stability is. It can be seen that even if the metal ion of the sulfite metal salt is changed from sodium to potassium or barium, the heat stability of the obtained polymer does not change and the mechanical properties are not affected.

Examples 6 to 8 and Comparative Example 4 Polymers were produced in the same manner as in Example 2 except that sodium sulfite and triphenylphosphine oxide were used together as the catalyst deactivator. For comparison, a polymer was prepared using only triphenylphosphine oxide as the catalyst deactivator.

The results of measuring the physical properties of these polymers are summarized in Table 2.

It is clear from Table 2 that a polymer having excellent heat resistance stability can be obtained by using triphenylphosphine oxide in combination. Further, when the catalyst is deactivated only with triphenylphosphine oxide, the heat resistance stability of the obtained polymer is considerably poor.

Examples 9 to 20 Triethylene glycol-bis- as heat resistance stabilizer
[3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (Ciba-Geigy Irganox 24
Polymers were produced in the same manner as in Examples 2 and 7 except that the addition amount of 5) was changed.

Also, as a heat-resistant stabilizer other than Irganox 245, pentaerythrityl-tetrakis [3- (3,5-t-butyl-4-hydroxyphenyl) propionate] (Ciba-Geigy Ir.
ganox 1010), N, N'-hexamethylene-bis (3,5-di-t-butyl-4-hydroxyhydrocinnamide) (Ci
ba-Geigy Irganox 1098), dinonyl phenyl pentaerythritol diphosphite (Adeka Argus Mark PEP-
4), 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid (American
Cyanamid Cyanox 1790), 2,2'-methylene-bis (4
-Methyl-6-t-butylphenol) (Sumitomo Chemical Sumilizer MDP-S) was used to prepare the polymer.

The results of measuring the physical properties of these polymers are summarized in Table 3.

It is apparent from Table 3 that a polymer having excellent heat resistance stability can be obtained as the amount of the heat resistance stabilizer added increases. Also, Ir
Irganox 245 can be used with heat stabilizers other than ganox 245.
It can be seen that a polymer having the same heat stability as that obtained by using is obtained.

Examples 21 to 30 Polymers were produced in the same manner as in Examples 2 and 7 except that the amount of calcium hydroxide added as the terminal decomposition accelerator was changed. Polymers were also produced using alkali metal salts or alkaline earth metal salts other than calcium hydroxide.

Table 4 shows the results of measuring the physical properties of these polymers.

From Table 4, it is apparent that when the amount of calcium hydroxide added is small, the terminal decomposition is insufficient, and the heat resistance stability of the obtained polymer is poor. Further, even if an alkali metal salt other than calcium hydroxide or an alkaline earth metal salt is used, a polymer having excellent heat resistance stability can be obtained.

Examples 31 to 38 Polymers were produced in the same manner as in Examples 2 and 7, except that the addition amount of dicyandiamide as a formaldehyde absorbent was changed. Polymers were also prepared using formaldehyde absorbents other than dicyandiamide.

Table 5 shows the results of measuring the physical properties of the obtained polymer.

It is clear from Table 5 that the more the amount of the formaldehyde absorbent added, the more excellent the heat stability. Further, even if a formaldehyde absorbent other than dicyandiamide is used, a polymer having excellent heat resistance stability can be obtained.

Examples 39 to 44 Polymers were produced in the same manner as in Examples 2 and 7, except that the heating temperature for removing the unstable end was changed.

The results of measuring the physical properties of the obtained polymer are summarized in Table 6.

From Table 6, it is apparent that when the heating temperature is low, the decomposition of the unstable terminal is insufficient, and the heat stability of the obtained polymer is low,
Further, since the bubbles of formaldehyde gas generated by decomposition remain, the mechanical properties are also lowered.

Also, if the heating temperature is high, the polymer itself will decompose,
After all, heat resistance stability and mechanical properties tend to deteriorate.

Examples 45 to 49 According to Reference Example 2, using Copolymer B polymerized using ethylene oxide as a copolymerization component, Example 2,
Polymers were prepared in the same manner as 7, 12, 26 and 34.

Table 7 shows the results of measuring the physical properties of the obtained polymer.

From Table 7, it is clear that even if Copolymer B is used, Copolymer A
It can be seen that a polymer having the same physical properties as in the case of using is obtained.

<Effects of the Invention> As shown in the examples, by using the production method according to the present invention, an oxymethylene copolymer excellent in heat stability can be produced by an extremely simple process without removing the catalyst by washing. be able to.

Claims (1)

[Claims] 1. A mixture of trioxane and a cyclic ether is selected from the group consisting of boron trifluoride, boron trifluoride hydrate and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. In the presence of at least one type of polymerization catalyst to be bulk polymerized to produce an oxymethylene copolymer containing oxymethylene units and other oxyalkylene units, a metal sulfite is added after the polymerization to form a boron trifluoride-based catalyst. Deactivate and further heat-resistant stabilizer and alkali metal hydroxide, alkaline earth metal hydroxide, inorganic weak acid alkali metal salt, inorganic weak acid alkaline earth metal salt, organic acid alkali metal salt, organic acid alkaline earth metal salt , Alkali metal alkoxide, alkaline earth metal alkoxide, alkali metal phenoxide, alkaline earth metal phenoxide A stable oxymethylene copolymer characterized by adding at least one selected from the following, heating in a temperature range of 100 to 260 ° C. to remove unstable terminals, and then adding a formaldehyde absorbent and kneading by heating. Production method.