JP3134699B2 - Method for producing acetal copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing an acetal copolymer having high thermal stability in the copolymerization of trioxane and a cyclic ether copolymerizable therewith.

[0002]

2. Description of the Related Art A method for obtaining an acetal copolymer from formaldehyde or a cyclic oligomer thereof (eg, trioxane or tetraoxane) and a cyclic ether copolymerizable therewith using a cationically active catalyst is known and widely used industrially. However, the thermal stability of the obtained acetal copolymer was not satisfactory.

[0003] In general, as a factor for lowering the thermal stability of an acetal copolymer, there is acid decomposition of the acetal copolymer by a cationic active catalyst remaining in the acetal copolymer. As a method for suppressing the acid decomposition, Japanese Patent Application Laid-Open No.
In 55958, by adding a sterically hindered phenol to a polymerization catalyst in advance to improve the catalytic activity,
A method is disclosed in which the amount of a polymerization catalyst to be used is reduced, and as a result, the amount of a polymerization catalyst remaining in the acetal copolymer is reduced to suppress acid decomposition of the acetal copolymer.

Another factor that lowers the thermal stability of the acetal copolymer is the oxidative decomposition of the acetal copolymer. Regarding this oxidative decomposition, see
In JP-A-63965, an acetal copolymer is added by adding a sterically hindered phenol to a monomer in advance of polymerization to separate main chain during polymerization and separation of unreacted monomer, washing, drying and other post-treatment. A method for suppressing oxidative decomposition of is disclosed. This method is intended to suppress the oxidative decomposition of the acetal copolymer generated in the process of producing the acetal copolymer. As a cause of the oxidative decomposition of the acetal copolymer, the present inventors have examined and found that there is a trace peroxide derivative present in the cyclic ether. When a cyclic ether containing a large amount of this peroxide derivative is used, the thermal stability of the acetal copolymer is poor.

In general, when copolymerization of a cyclic ether and trioxane is carried out, the main monomer, liquid trioxane, undergoes a phase change from a viscous liquid to a solid by the addition of a cationically active catalyst, and the polymerization is initiated. Go on. The time until this phase change to a solid is called the polymerization induction period.If the peroxide derivative in the cyclic ether is large,
It has also been found that the polymerization induction period becomes extremely long, and that the continuous operation of the acetal copolymer becomes unstable.

As a method of reducing the peroxide derivative from the cyclic ether containing a large amount of the peroxide derivative, a distillation operation can be considered. In this case, the peroxide derivative is decomposed during the distillation to form radicals, There are problems that the peroxide derivative in the ether increases and the distillation apparatus becomes complicated. Therefore, it is necessary to suppress the increase of the peroxide derivative at a low concentration of the peroxide derivative in the cyclic ether after the synthesis and purification of the cyclic ether. As a method for suppressing such peroxide derivative increase, there is a method in which an amine compound which is used as an antioxidant for an ether compound is added to a cyclic ether to suppress the increase in peroxide derivative. There was a difficulty that neutralization of the antioxidant with the amine occurred and the copolymerization reaction did not proceed.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for producing an acetal copolymer having high thermal stability in a stable manner.

[0008]

Means for Solving the Problems The present inventors have found a method capable of simultaneously solving the problems of suppressing the increase in peroxide in the cyclic ether and reducing the catalytic activity by the antioxidant used for the purpose. Reached. That is, in the present invention, in the copolymerization of trioxane and a cyclic ether in the presence of a cationically active catalyst, at least one sterically hindered phenol is added to the cyclic ether by 10 to 5 times.
The present invention relates to a method for producing an acetal copolymer, wherein a cyclic ether having an amount of 00 ppm added after purification of a cyclic ether and having a peroxide derivative in the cyclic ether of 15 ppm or less is used.

That is, the present inventors have proposed that sterically hindered phenols are used as antioxidants for cyclic ethers at 10 to 500 pp.
The use of m suppresses the increase of peroxide derivatives in the cyclic ether, and does not reduce the activity of the cationically active catalyst even when copolymerization with trioxane is performed using a cyclic ether containing this sterically hindered phenol. I found something. The peroxide derivative is 1
By using this cyclic ether of 5 ppm or less and copolymerizing it with trioxane, stable production of an acetal copolymer having high thermal stability became possible.

Hereinafter, the present invention will be described in detail. In the production of a general acetal copolymer, a cyclic ether is used as a comonomer of trioxane, which is a main monomer, and is used in an amount of 10 mol per 1 mol of trioxane.
% Or less, and the cyclic ether is a small amount based on trioxane. Therefore, as a method for supplying cyclic ether to a polymerization machine, a certain amount of cyclic ether is synthesized, purified, and stored in a batch system compared to a method of continuously synthesizing and purifying cyclic ether and supplying it to the polymerization machine. The operation of supplying the cyclic ether to the polymerization machine is simpler.

However, in this method, the peroxide derivative gradually increases during storage of the cyclic ether. The acetal copolymer using a cyclic ether containing a large amount of the peroxide derivative has poor thermal stability due to oxidative decomposition of the acetal copolymer by the peroxide derivative. However, when a trace amount of the peroxide derivative is present in the cyclic ether, an acetal copolymer having high thermal stability can be obtained. It is an interesting finding that this trace amount of the peroxide derivative greatly affects the thermal stability of the acetal copolymer. The peroxide derivative can be quantified by a common analytical method, sodium thiosulfate titration.

As a method for suppressing the peroxide derivative which increases during the storage period, when a known amine is used as an antioxidant for a general ether compound, the amine deactivates the polymerization catalyst. There was a problem. The present inventors have studied various antioxidants in cyclic ethers and found that adding sterically hindered phenols after synthesis and purification of the cyclic ethers and preserving the cyclic ethers increased the peroxide derivatives. It has been found that if the sterically hindered phenols are contained in a certain amount, the copolymerization reaction is relatively little affected.

The sterically hindered phenols are synthesized and purified in an amount of 10 to 500 ppm based on the cyclic ether, and are added to the cyclic ether and stored. If the amount of the sterically hindered phenols is less than 10 ppm, the peroxide derivative increases during storage of the cyclic ether. If it exceeds 500 ppm, the activity of the polymerization catalyst is reduced, and the polymerization yield is reduced.

In the present invention, the cyclic ether to be copolymerized with trioxane is a sterically hindered phenol having 10 to 10 carbon atoms.
It contains 500 ppm, and the peroxide derivative in this cyclic ether must be 15 ppm or less, preferably 5 ppm or less based on the cyclic ether. Peroxide derivative in cyclic ether is 15p
If it exceeds pm, the thermal stability of the acetal copolymer decreases due to oxidative decomposition with a peroxide derivative. Further, even if a sterically hindered phenol is further added to a cyclic ether having a peroxide derivative amount exceeding 15 ppm, the thermal stability of the acetal copolymer is poor. This will be apparent in Comparative Example 4 described later.

When copolymerization with trioxane is carried out using a cyclic ether containing a large amount of this peroxide derivative, the polymerization induction period described in the above-mentioned prior art becomes long. Generally, the copolymerization of trioxane and cyclic ether is carried out using a twin-screw paddle type continuous mixer. If the polymerization induction period is long and the residence time in the mixer is exceeded, unreacted trioxane is removed. There is a problem that the acetal copolymer is discharged while containing it. This polymerization induction period is related to the operation stability in the production of the acetal copolymer. In other words, in the polymerization of the acetal copolymer in the mixer, the liquid monomer undergoes a phase change to a solid via the viscous liquid, but as the polymerization induction period becomes longer, the residence time of the liquid and viscous liquid in the mixer becomes longer. As a result, since the acetal copolymer is not solid, the operation becomes unstable due to poor transport in the mixer and the torque over of the two-shaft drive unit due to the mixing of the viscous liquid, which makes continuous operation difficult. Therefore, from the viewpoint of stable operation of the acetal copolymer, it is necessary to suppress the amount of the peroxide derivative in the cyclic ether.

In the production method of the present invention, the amount of comonomer inserted in the acetal copolymer can be changed stably. That is, when the amount of the peroxide derivative in the cyclic ether is 15 ppm or less, the charge ratio of the cyclic ether to trioxane can be increased to increase the amount of comonomer to be copolymerized. In this case, the polymerization derivative stage hardly changes depending on the charging ratio of the cyclic ether.
On the other hand, when a cyclic ether having a large amount of the peroxide derivative is used, if the charge ratio of the cyclic ether is increased, the polymerization induction period becomes extremely long, and the polymerization operation becomes unstable for the above-mentioned reason.

The sterically hindered phenols used in the present invention are compounds generally used in the field of plastics, used as antioxidants or free radical scavengers. -Methylenebis (4-methyl-6-t-butylphenol), hexamethylene glycol-bis (3,5-di-t-butyl-4-hydroxyhydrocinnamate), tetrakis [methylene (3,5-di-t-butyl) -4-hydroxyhydrocinnamate)] methane, triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5
-Methylphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxy-benzyl) benzene, 4,4-methylenebis (2,6- Di-t-butylphenol), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, distearyl-3,
5-di-t-butyl-4-hydroxybenzylphosphonate, 2-t-butyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate and the like can be mentioned. .

Among these sterically hindered phenols,
Particularly, those which are soluble in cyclic formal are preferred in terms of handling, and tetrakis [methylene (3,5-di-t-butyl-)
4-hydroxyhydrocinnamate)] methane (Irganox 1010 from Ciba-Geigy Corporation) is preferred. The comonomer used in the present invention is a cyclic ether represented by the following general formula (1).

[0019]

Embedded image (Wherein, R 1 to R 4 are the same or different and represent a hydrogen atom, an alkyl group, or a methylene group or an oxymethylene group substituted with halogen;
5 represents a methylene group or an oxymethylene group or a methylene group or an oxymethylene group substituted with an alkyl group or a halogen, respectively (in this case, p represents an integer of 0 to 3), or the following (2): It means a divalent group represented by the formula or the formula (3). in this case,
p represents 1 and q represents an integer of 1 to 4. The alkyl group has 1 to 5 carbon atoms, and 1 to 3 hydrogen atoms may be replaced by a halogen atom. )

[0020]

Embedded image

Typical examples thereof include ethylene oxide, propylene oxide, 1,3-dioxolan,
1,4-butanediol formal, epichlorohydrin, diglycol formal and the like can be mentioned. These comonomers are 0.05 mol per mol of trioxane.
% To 15 mol%, preferably 0.1 mol% to 1 mol%
0 mol% is used. Among these cyclic ethers,
Cyclic formals represented by 1,3-dioxolan and 1,4-butanediol formal are preferred.

The cation-active catalyst used in the present invention includes a Lewis acid such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride and its coordination compound or salt, or trifluoromethanesulfonic acid. Examples thereof include perfluorosulfonic acid such as trifluoromethanesulfonic anhydride or a derivative thereof. Among these cationically active catalysts, boron trifluoride, a complex compound of boron trifluoride,
Trifluoromethanesulfonic acid or a derivative thereof is preferred. When these cation-active catalysts are used, the catalyst concentration is 5 × 10 ^{−6 to} 5 × 10 ^{6 in} the case of a complex compound of boron trifluoride and boron trifluoride with respect to 1 mol of all monomers.
⁻⁵ mol, and 1 × 10 ^{−8 to} 5 × 10 ⁻⁷ mol in the case of trifluoromethanesulfonic acid or a derivative thereof.

When a complex compound of boron trifluoride and boron trifluoride is used as a polymerization catalyst, the catalyst concentration is 5 × 10 5
^{In the case of -5} mol or more, and in the case of trifluoromethanesulfonic acid or a derivative thereof in the case of 5 × 10 ^-7 mol or more, the amount of terminal methoxy groups and formate groups generated by the hydride shift reaction, which is a side reaction, increases. It is difficult to produce acetal copolymer. When the hydride shift reaction is remarkable, it becomes difficult to adjust the melt flow index of the acetal copolymer by adding a molecular weight modifier. It is preferable in terms of operation that the terminal formate group of the acetal copolymer, which is an index of the hydride shift reaction, has the following amount. That is, the absorption wave number of the main chain oxymethylene group in infrared spectroscopy measurement is 1470c.
This is a case where the absorbance ratio (D1470 / D1710) is 40 or more at an absorbance D1470 of m ^{-1 and} an absorbance D1710 of an absorption wave number of a terminal formate group of 1710 cm ^-1 .

The copolymerization reaction of the present invention is carried out by, for example, bulk polymerization. The bulk polymerization can be any of a batch system and a continuous system, and a monomer in a molten state is used. The method of obtaining is common. As the polymerization apparatus used in the present invention, a reaction vessel equipped with a stirrer generally used in a batch system can be used, and as a continuous system, a co-kneader, a twin-screw continuous extrusion mixer, and a twin-screw paddle-type continuous A continuous polymerization apparatus such as a mixer can be used, and two or more types of polymerization machines can be used in combination.

In the production method of the present invention, the trioxane, the cyclic ether and the cation-active catalyst may be supplied by adding all the trioxane, all the cyclic ether and all the cation-active catalyst added to the polymerization apparatus to one raw material supply port. Or the monomer and the cation-active catalyst may be divided and supplied to the polymerization apparatus. When the monomer and / or the cation-active catalyst are supplied in a divided manner, first, trioxane and a cyclic ether are copolymerized with the cation-active catalyst for 30 seconds to 10 minutes to lose the cation-active catalyst in the copolymerized product. The polymerization is further continued by adding at least one selected from the group consisting of trioxane, cyclic ether and cationically active catalyst to the copolymerization product in a state where it is not activated.

As a continuous polymerization apparatus for performing the divided supply, two or more raw material supply ports are provided, and a first raw material supply port is provided on a side opposite to a reaction product withdrawal port. 2nd and 3rd in the direction of the outlet from the raw material supply port
・ ・ The raw material supply port is installed. Trioxane, a cyclic ether, and a cation-active catalyst are added from a first raw material supply port of the continuous polymerization apparatus, and at least one selected from trioxane, a cyclic ether, and a cation-active catalyst is supplied from second, third, etc. supply ports. Seeds are supplied.

The polymerization temperature is preferably from 60 to 200 ° C.
More preferably, the temperature range is 60 to 140 ° C. The polymerization time is related to the amount of the polymerization catalyst and is not particularly limited, but generally, a polymerization time of 15 seconds or more and 20 minutes or less is selected. After a lapse of a predetermined time, the polymer taken out from the outlet of the polymerization machine is usually a lump or a powder, and a part or all of the unreacted monomer is separated and supplied to the next step. After the polymerization, the reaction product is mixed with ammonia, amines such as triethylamine and tri-n-butylamine, or hydroxides of alkali metals and alkaline earth metals, and other known catalyst deactivators. It is preferable to neutralize and deactivate the polymerization catalyst by adding and treating a solution containing these deactivators. At this time, if the produced polymer is in a large lump, it is naturally preferable that the polymer is once pulverized and treated after the polymerization.

The copolymer thus obtained is heated and melted, or heated in an insoluble or soluble liquid medium,
A stable copolymer can be obtained by selectively decomposing and removing the unstable portion.

In order to obtain a stable copolymer by the above treatment, it is preferable that after the polymerization is completed, the unstable terminal portion of the crude acetal copolymer in which the cation-active catalyst is neutralized and deactivated is 3000 ppm or less. When the unstable terminal portion of the crude acetal copolymer exceeds 3000 ppm, a stable copolymer cannot be obtained by a general method for treating the unstable terminal portion of the crude acetal copolymer. Since the unstable terminal is generated at the time of polymerization by impurities having active hydrogen such as water, methanol, and formic acid contained in raw materials such as trioxane and cyclic ether, it is necessary to reduce these impurities as much as possible. In order to reduce the unstable terminal portion to 3000 ppm or less, the concentration of a trace impurity having active hydrogen is converted to the concentration of water, and the total amount is calculated as 20 p with respect to trioxane.
pm or less.

The preferable conditions in a series of processes for producing the acetal copolymer of the present invention are as follows: the concentration of trace impurities in trioxane and cyclic ether in the polymerization stage is converted to the concentration of water, and the total is 20 ppm or less based on trioxane. The polymerization catalyst is composed of boron trifluoride dibutyl ether in an amount of 5 × 10 ^{−6 to} 5 × 10 ⁻⁵ mol based on 1 mol of all monomers.
Or trifluoromethanesulfonic acid is added to all monomers
1 × 10 ^{−8 to} 5 × 10 ⁻⁷ mol per 1 and 10 to 50 ppm of tetrakis [methylene (3,5-di-t-butyl-4-hydroxycinnamate)] methane as 1 to 50 ppm as a cyclic ether. , 3-dioxolan or 1,4-butanediol formal, and copolymerization using a cyclic ether having a peroxide derivative amount of 15 ppm or less. The absorbance ratio (D1470 / D) of the main chain oxymethylene group to the terminal formate group in the infrared spectroscopic measurement of the thus obtained crude acetal copolymer
1710) is 40 or more, and the unstable terminal portion is 300
It becomes 0 ppm or less.

[0031]

EXAMPLES Examples and comparative examples of the present invention will be described below in more detail, but the present invention is not limited thereto. The terms used in the examples and the measuring method are as follows. % And ppm: All are measured by weight.

Method for measuring peroxide derivative in cyclic ether: Isopropyl alcohol 40 m in flask
l, 10 ml of a saturated solution of sodium iodide (Nal dissolved in isopropyl alcohol), 2 ml of acetic acid and sample 25
Add the solution and reflux at 100 ° C for about 5 minutes. Immediately thereafter, titration was performed with a 0.01N aqueous sodium thiosulfate solution to determine the peroxide content in the sample.

Thermal stability (Rv) of acetal copolymer;
The acetal copolymer immediately after polymerization was added to a 0.1% aqueous solution of tributylamine, and stirred at room temperature for 40 minutes to deactivate the catalyst. The slurry is filtered, the crude acetal copolymer is taken out, and dried under vacuum (120 ° C., 180 minutes)
And dried the sample. 250 mg of this sample was placed in a test tube, decompressed to 750 mmHg, placed in a 222 ° C. oil bath, and left for 50 minutes. The amount of the remaining sample was measured, and RV was determined by the following equation.

[0034]

(Equation 1) The closer this value is to 100%, the better the thermal stability.

Polymerization induction period: In the copolymerization of trioxane and cyclic ether, when a polymerization catalyst is added to a mixture of trioxane and cyclic ether, the liquid monomer passes through a viscous liquid and then solidifies. The time from the addition of the catalyst to the solidification of the liquid monomer is defined as the polymerization induction period. Generally, if the polymerization induction period is between 10 seconds and 200 seconds, stable operation can be achieved even with a twin-screw paddle type continuous mixer.

An unstable terminal portion of the crude acetal copolymer;
Formaldehyde generated from the crude acetal copolymer in a nitrogen stream at 180 ° C. for 50 minutes is absorbed in water,
It was determined from the amount of formaldehyde in water. Under these conditions, decomposition of only the unstable terminal portion in the crude acetal copolymer occurs.

Formate terminal (D1470 / D171)
0) (Indicator of the hydrolide shift reaction): The acetal copolymer is pressed at 200 ° C. to form a 15 micron film. The infrared spectrum of the obtained film is measured, and the ratio D1470 / D1710 between the absorbance at 1470 ^-1 cm and the absorbance at 1710 ^-1 cm is calculated. This D14
70 / D1710 is an index of a hydride shift reaction which is a side reaction at the time of polymerization.

Example 1 1,3-dioxolane synthesized from ethylene glycol, 40% formalin and sulfuric acid and purified by distillation (water 10 ppm,
Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane (Irganox 1010 from Ciba-Geigy Corporation) is added to 100 kg of 100 kg per 100 kg of 1,3-dioxolane. And put in a SUS304 tank,
It was left at 30 ° C. under nitrogen. After 30 days, the amount of the peroxide derivative in 1,3-dioxolane was 0.6 ppm. The following copolymerization was carried out using this 1,3-dioxolan.

A 5-liter kneader having two jacketed stirring blades through which a heat medium can pass was adjusted to 80 ° C., and 2 kg of trioxane (1 ppm of water, 1 pp of formic acid)
m, 3 ppm of methanol), 1.41 ml of methylal as a molecular weight regulator, and 75 g of 1,3-dioxolane (20 ppm of water) having a peroxide derivative amount of 0.6 ppm as a comonomer. Immediately, 1.5 × 10 ⁻⁵ mol of boron trifluoride butyl ether (0.2% of cyclohexane solution) was added to 1 mol of the mixture to initiate polymerization. Next, 20 minutes later, 2 liters of a 0.1% aqueous solution of tributylamine was added to the kneader to stop the reaction, and the contents were taken out.

The RV of this crude acetal copolymer is 99.
It is 6%, and the thermal stability is good. The polymerization yield is 91%
The polymerization induction period was stable in 30 seconds. D1470 / D1710 of this crude acetal copolymer is 45,
The unstable terminal portion was 1500 ppm, and in this production method, the crude acetal copolymer was able to suppress the hydride shift reaction and remove the unstable terminal portion.

Examples 2 to 4 The same operations as in Example 1 were carried out except that the cyclic ethers and sterically hindered phenols shown in Table 1 were used. However, in the case of Example 4, 1,4-butanediol formal was synthesized using butanediol instead of ethylene glycol. Table 1 shows the amount of peroxide in the cyclic ether, the polymer RV, the polymerization yield, and the polymerization induction period after storage for 30 days. In each of the examples, an acetal copolymer having high heat stability was obtained, and the polymerization was stable.

Example 5 The same operation as in Example 1 was carried out except that the amount of 1,3-dioxolan was changed to 150 g. Even when the charge ratio of 1,3-dioxolane to trioxane was changed while the amount of boron trifluoride dibutyl ether was kept constant, the polymerization induction period of the acetal copolymer was 35 seconds, the polymerization yield was 89%, and the RV was 99.8. % And stable polymerization.

Embodiment 6 A jacket provided on the outside and rotating in the same direction inside 1
A twin-screw reactor (L / D = 45) having a pair of shafts, into which interlocking convex lens-type paddles are fitted, the long ends of which rotate the inner surface of the casing and a slight clearance with the other paddle. In, L / D
= 3, the first material supply port and the second material supply port are L
A polymerization machine designed at the position of / D = 12 was used. The raw materials and temperatures were all the same as in Example 1. Trioxane 2Kg / hr, 1,3-dioxolane 75g / hr, methylal 1.14ml / hr, boron trifluoride dibutyl ether were added in an amount of 1.5 × 10 ⁻⁵ mol per mol of all monomers.
1 from the first raw material supply port. Since the polymerization yield is 94% and RV is 99.6%, and the polymerization induction period is 30 seconds, continuous operation is performed without any trouble in the outlet of the polymerization machine, that is, poor powder transport and torque over of the two-axis drive unit. Was possible.

Example 7 Using the same polymerization machine and raw materials as in Example 6, trioxane 2 kg / hr, 1,3-dioxolane 7
5 g / hr, methylal 1.14 ml / hr, boron trifluoride dibutyl ether was added in an amount of 1.
The raw material is continuously supplied from the first raw material supply port so as to be 2 × 10 ⁻⁵ mol, and boron trifluoride dibutyl ether is supplied from the second supply port to 0.3 × 10 ⁻⁵ mol based on 1 mol of all monomers.
^-5 mol was continuously supplied. The polymerization yield is 9
The RV is 29.6%, and the RV is 99.6%. Thus, continuous operation is possible without any trouble in the discharge port of the polymerization machine, that is, poor powder transportation and excessive torque of the two-shaft drive unit.

Comparative Examples 1-2 The same operations as in Example 1 were carried out using the sterically hindered phenols shown in Table 1. In Comparative Example 1, since the amount of sterically hindered phenol was less than 10 ppm, the amount of peroxide in 1,3-dioxolane after storage for 30 days was increased. For this reason, the RV of the copolymer was poor, the polymerization induction period was long, and the polymerization was unstable. In Comparative Example 2, since the sterically hindered phenol exceeds 500 ppm, the activity of the polymerization catalyst is reduced, and the yield is poor.

Comparative Example 3 In Example 1, instead of the sterically hindered phenol, 100 ppm of triethylamine was added, and 1,3-dioxolan was allowed to stand for 30 days. The amount of the peroxide derivative in 1,3-dioxolane was 1.2 ppm. This one
Copolymerization with trioxane was performed using 3-dioxolane in the same manner as in Example 1, but the polymerization catalyst was deactivated by triethylamine, and no acetal copolymer was obtained.

Comparative Example 4 In Example 1, 30
Left for days. The amount of the peroxide derivative in 1,3-dioxolane was 80 ppm. 100 ppm of Irganox 1010 was added to the 1,3-dioxolane, and copolymerized with trioxane in the same manner as in Example 1. The RV of the obtained acetal copolymer is 96.5%,
The polymerization yield was 75%, the polymerization induction period was 900 seconds, and both the thermal stability and the polymerization stability of the acetal copolymer were poor. As is clear from this comparative example, the peroxide derivative in the cyclic ether greatly affects the thermal stability of the acetal copolymer and the polymerization, and further increases the peroxide derivative in the cyclic ether with the sterically hindered phenol. It can be seen that even if added, there is almost no effect.

Comparative Example 5 The same operation as in Example 6 was performed using 1,3-dioxolane of Comparative Example 4 (peroxide derivative amount: 80 ppm). The polymerization yield is 65% and the RV is 96.5%. Since the polymerization induction period is 900 seconds, poor transport of the powder, clogging at the polymerization machine outlet occurs, and the current value of the polymerization machine biaxial drive unit is large. It fluctuated, and continuous operation became difficult 10 minutes after the start of polymerization. Moreover, the thermal stability of the obtained acetal copolymer is also poor.

Comparative Example 6 The same operation as in Example 5 was performed using 1,3-dioxolane of Comparative Example 4 (peroxide derivative amount: 80 ppm). The polymerization yield was 60% and the RV was 95.5%. The thermal stability of the acetal copolymer was poor, and when the charge ratio of 1,3-dioxolane having a large amount of peroxide derivative was increased, the result was different from that of Example 5. The polymerization induction period was extremely long at 1800 seconds, and the polymerization was unstable.

[0050]

[Table 1]

[0051]

According to the production method of the present invention, an acetal copolymer having high thermal stability can be produced stably.

──────────────────────────────────────────────────続 き Continued on front page (31) Priority claim number Japanese Patent Application No. 6-52576 (32) Priority date February 28, 1994 (Feb. 28, 1994) (33) Priority claim country Japan (JP) (72) Inventor Hirohisa Morishita 3-13-1, Shiodori, Kurashiki-shi, Okayama Prefecture Inside Asahi Kasei Kogyo Co., Ltd. References JP-A-60-1216 (JP, A) JP-A-5-155958 (JP, A) JP-A-64-69616 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C08G 2/00-2/38

Claims (7)

(57) [Claims] In a copolymerization of trioxane and a cyclic ether in the presence of a cationically active catalyst, at least one sterically hindered phenol is added to the cyclic ether by one of the above methods.
0 to 500 ppm was added after purification of the cyclic ether, and the peroxide derivative in the cyclic ether was 15 pp.
A method for producing an acetal copolymer, wherein a cyclic ether having a molecular weight of m or less is used. 2. The method for producing an acetal copolymer according to claim 1, wherein the cyclic ether is cyclic formal. 3. The method according to claim 1, wherein the cyclic ether is 1,3-dioxolane,
The method for producing an acetal copolymer according to claim 1, wherein the acetal copolymer is 1,4 butanediol formal. 4. The cation-active catalyst is boron trifluoride or a complex compound of boron trifluoride, and the cation-active catalyst is used in an amount of 5 × 10 ⁻⁶ mol to 5 × 1 with respect to 1 mol of all monomers.
0 ^-5 mol method for producing an acetal copolymer according to claim 1, wherein used. 5. The cationic active catalyst is perfluorosulfonic acid or a derivative thereof, and the cationic active catalyst is used in an amount of 1 × 10 ⁻⁸ mol to 5 × 10
^The method for producing an acetal copolymer according to claim 1, wherein ^-7 mol is used. 6. In an infrared spectroscopic measurement, when the absorbance ratio between the main chain oxymethylene group and the terminal formate group is 40 or more,
2. The method for producing an acetal copolymer according to claim 1, wherein the crude terminal is a crude acetal copolymer having an unstable terminal portion of 3000 ppm or less. 7. A copolymer of trioxane and a cyclic ether for 30 seconds to 10 minutes with a cationically active catalyst, and then reacting the trioxane, the cyclic ether, and the cationically active catalyst without deactivating the cationic catalyst in the copolymerized product. 2. The method for producing an acetal copolymer according to claim 1, wherein at least one selected from the group is further added and polymerized.