JPH03247614A - Polyacetal block copolymer and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer having a specific structural formula, a specific number-average molecular weight and excellent impact resistance by polymerizing formaldehyde or trioxane in the presence of a specific compound as a molecular weight modifier. CONSTITUTION:Formaldehyde, trioxane or trioxane and a cyclic ether (e.g. ethylene oxide) are (co)polymerized in the presence of a molecular weight modifier consisting of a compound having the structure of formula I (a, b and c are group of formula II to IV; R1, R2 and R3 are 2-13C linear methylene chain which is unsubstituted or substituted with alkyl group, etc.; n, l and m are 0-5,000; p is 1-5,000) and having hydroxyl groups, etc., on both terminals (e.g. polyethylene succinate) to obtain the objective copolymer which is an A-B-A block copolymer (A is polyoxymethylene and B is group of formula I) having a number average molecular weight of 10,000-500,000 and exhibiting shape- memory effect and biodegradable function.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a novel polyacetal block copolymer, and in particular to a polyacetal block copolymer having unprecedented excellent impact resistance and a method for producing the same. It is related to.

[Prior Art] Polyacetal resin has excellent mechanical strength, friction and wear properties, creep properties, fatigue properties, electrical properties, etc.
As an engineering resin, it is used in a wide range of fields including automobile parts and electrical and electronic parts.

However, polyacetal resin has the disadvantage that it has a low impact resistance, for example, a notched Izot value, and is easily broken when residual stress or small scratches are present during molding.

Many attempts have been proposed to improve the impact resistance of polyacetal resins. For example, a method of adding unsaturated rubbers (Japanese Patent Publication No. 45-12674, Japanese Patent Publication No. 45-12674,
18023), a method of adding an olefin polymer or an α-olefin polymer (Japanese Patent Publication No. 41-2730, Japanese Patent Publication No. 42-19498, Japanese Patent Publication No. 43-203)
No. 76, JP-A-48-15954, JP-A-4
9-40346, JP-A-50-103556), a method of adding a polar group-containing α-olefin polymer such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc. -22669 Publication, Special Publication No. 4S-26231, Special Publication No. 45-18023
Publication No.) etc. are known.

However, since the non-quality polymers used in these methods, such as olefin polymers and α-olefin polymers, and polyacetal, which is a crystalline polymer, inherently lack affinity, these mixtures must be melted and kneaded. Even if
The resulting composition tends to peel off into layers, not only does it fail to provide sufficient mechanical strength, but also results in poor appearance of the molded product.

As an attempt to solve this problem of layer peeling and improve impact resistance, a method using a dibrocita copolymer of polyacecool and polylactone (Japanese Patent Publication No. 3893/1983) has been proposed. However, even in this case, although the problem of delamination has been solved, it does not have satisfactory impact resistance. This will become clear in the comparative example described later.

[Problems to be Solved by the Invention] An object of the present invention is to overcome the drawbacks of the prior art and to provide a polyacecool block copolymer that provides a molded article with excellent impact resistance. .

[Means and effects for solving the problem] The present inventors
As a result of intensive research to solve the above problems, we found that A-B-A made of polyacecool and a specific polyester.
It was discovered that block copolymers have excellent impact resistance, leading to the present invention.

That is, the present invention relates to polyoxymethylene (A) and the following general formula (B)++a+
: + b dimension + C dimension -1 (B) (in the formula, a, b, c are the same or different -Co-R, -
Co-, -0-R2-0-, -CO-R3-0-. R, , R2, R3 are the same or different and have 2 to 13 carbon atoms. is a linear methylene chain substituted by a group n I2.
m is 0 to 5000 and is not O at the same time. p is 1~
It is 5000. ) A-B- consisting of the structure shown in
A block copolymer, the number average molecular weight of the polyacecool block copolymer is from 10,000 to 500.0
A novel polyacetal block copolymer between 00 and a compound having a structure represented by the general formula (B) and having either a hydroxyl group, a carboxyl group, an ester group, or an alkoxy group at both ends of the compound The novel polyacecool block copolymer is characterized in that formaldehyde or trioxane is homopolymerized as a molecular weight regulator, or formaldehyde or trioxane is copolymerized with a cyclic ether using the molecular weight regulator. A method for producing a polymer is provided.

The polyacetal block copolymer of the present invention is AB-
A type linear block copolymer (A is polyoxymethylene, B is a compound having a structure represented by the general formula (B)), and has hydroxyl groups, ether groups, carboxyl groups, ester groups, and urethane groups at both ends. It has any of the following groups. Further, the polyoxymethylene includes polyoxymethylene homopolymers and polyoxymethylene copolymers.

Here, polyoxymethylene homopolymer is a polymer consisting of repeating oxymethylene units → 20 + - 4), and polyoxymethylene copolymer is a polymer consisting of oxyalkylene units R ~ ( In the formula, R8+R'O are the same or different and selected from hydrogen, an alkyl group, and an aryl group.It is a polymer having a structure in which q=1 to 5) are randomly inserted.

For example, oxyethylene unit H-CH2)2o←, oxy unit +-+-CH2)30F-, oxytetramethylene unit oxyhexamethylene unit++CH2)601-,
Among the oxyalkylene units, oxyethylene units and oxytetramethylene units are particularly preferred from the viewpoint of improving the physical properties of the polyacetal block copolymer.

The insertion rate of oxyalkylene units in the polyoxymethylene copolymer is preferably 0.05 to 50 mol, more preferably 0.1 per 100 mol of oxymethylene units.
~20 moles.

The polyacecool block copolymer of the present invention is unstable if it has a hydroxyl group at the end immediately after polymerization. When the polyoxymethylene is a polyoxymethylene homopolymer, the terminal hydroxyl group is converted into a stable group using a known method such as esterification, etherification, or urethanization, and then used for practical use. Further, when the polyoxymethylene is a polyoxymethylene copolymer, it is used for practical use after being treated in the same manner as polyoxymethylene homopolymer or after removing unstable terminal portions by hydrolysis.

The structure of the polyacecool block copolymer of the present invention is confirmed by the following method. That is, when a polyacetal block copolymer is hydrolyzed in an acidic aqueous solution that does not cause hydrolysis of ester bonds, the portion consisting of repeating oxymethylene units becomes formaldehyde, and the oxyalkylene inserted into the polyoxymethylene copolymer becomes formaldehyde. The unit is alkylene glycol. Also, the compound having the structure represented by the grain formula (B) is X-H-a+-+-b+-+-c Shukan-Y(1)I! m
p (In the formula, a, b, c, n, β + m + p are as described above. , analyzed and quantified using methods such as liquid chromatography. Compounds having the structure represented by (1) can also be analyzed by liquid chromatography, IR, NM
It is analyzed and quantified using means such as R, GPC, etc.

The number average molecular weight of the polyacecool block copolymer of the present invention is the same as that of ordinary high molecular weight polyacecool, and is between 10,000 and 500,000. The lower limit of the number average molecular weight is restricted by the physical properties of the boacetal block copolymer, and the upper limit is restricted by the moldability of the polyacetal block copolymer. The number average molecular weight of the polyacetal block copolymer is determined using an osmotic pressure method and an end group determination method.

In the polyacetal block copolymer of the present invention, the segment B forming a block with polyoxymethylene A has the general formula % () (wherein a, b, and c are the same or different and -CO-R ,−
Co-, -0-R2-0-, -Go-R3-0-. R,, R,, R3 are the same or different, unsubstituted groups having 2 to 13 carbon atoms, or groups in which at least one hydrogen atom is selected from an alkyl group, a cycloalkyl group, an aryl group, or a halogen atom is a linear methylene chain substituted by n, I2. m
is between 0 and 5000 and is not O at the same time. p is 1 to 5
It is 000. ).

The lower limit of the number of carbon atoms in R, , R2, and R3 is determined by the ease of producing lactone and diol, which are the raw materials for polyester, and the upper limit is determined by the ease of producing polyester.

Here, the number average molecular weight of the compound having the structure of general formula (B) is restricted by ease of production and purification, and is preferably in the range of 1.000 to 400.000.

Examples of the compound having the structure represented by the general formula (B) include polyethylene succinate, polytetramethylene succinate, polyethylene adipate,
Polytetramethylene adipate, polyethylene sebacate, bottetramethylene sebacate, polyβ-hydroxybutyric acid, polyβ-methyl-βpropiolactone, polyβ-propiolactone, polyε-
caprolactone, etc.

Next, a method for producing the polyacecool block copolymer of the present invention will be described.

The polyacetal block copolymer of the present invention has the general formula (B
) ++a+-+b+-F+-c store (B) (in the formula, a
, b, c are the same or different -GO-R, -Go-, -
selected from the group consisting of 0-R2-0- and -CO-R3-0-. R,, R2, R3 are the same or different and are unsubstituted or unsubstituted having 2 to 13 carbon atoms (one hydrogen atom is an alkyl group, a cycloalkyl group, an aryl group,
or a cotton-like methylene chain substituted with a group selected from halogen atoms. n, ρ5m is O~5000
and not O at the same time. p is 1-5000.

) and having either a hydroxyl group, an ester group, a carboxyl group, or an alkoxy group at both ends of the compound, by homopolymerizing formaldehyde or trioxane as a molecular weight regulator, or by homopolymerizing the compound with formaldehyde or trioxane as a molecular weight regulator; It can be obtained by copolymerizing formaldehyde or trioxane with a cyclic ether using an agent.

It is desirable that the molecular weight modifier be purified by methods such as distillation, adsorption, and drying before being subjected to polymerization.

Moreover, these molecular weight regulators can be used alone, or two or more kinds can be mixed and subjected to polymerization.

In the homopolymerization of the present invention, formaldehyde or trioxane is used as a starting material. Formaldehyde and trioxane are preferably sufficiently purified. Anionic polymerization catalysts are mainly used for the homopolymerization of formaldehyde, and cationic polymerization catalysts are mainly used for the homopolymerization of trioxane.

In the copolymerization of the present invention, formaldehyde or trioxane is used as a starting material. Formaldehyde and trioxane are preferably sufficiently purified. These starting materials are copolymerized with a cyclic ether using primarily a cationic polymerization catalyst.

The first group of cyclic ethers to be copolymerized with these starting materials has the general formula +1- (R, , R' are the same or different, hydrogen, alkyl group,
Selected from aryl groups. There are alkylene oxides represented by q=1 to 5). For example, ethylene oxide,
Examples include propylene oxide, butylene oxide, epichlorohydrin, styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, oxepane, and the like. Among these alkylene oxides, engineered tylene oxide is particularly preferred.

The second group of cyclic ethers has the general formula (RO, R'o are the same or different, hydrogen, alkyl group,
Selected from aryl groups. There is a cyclic formal represented by q=l~5). Examples include ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1.4-butanediol formal, 1.5-bentanediol formal, and 1.6-hexanediol formal. Among these cyclic formals, ethylene glycol formal, diethylene glycol formal and 1,4-butanediol formal are particularly preferred.

The cyclic ether is preferably 0.03 to 100 parts by weight, more preferably 0.1 to 100 parts by weight, based on 100 parts by weight of the starting material.
50 parts by weight are used.

The anionic polymerization catalyst and cationic polymerization catalyst used in the homopolymerization and copolymerization of the present invention are the following compounds.

Typical groups of anionic polymerization catalysts include alkali metals such as sodium and potassium, alkali metal complexes such as sodium-naphthalene and potassium-anthracene, alkali metal hydrides such as sodium hydride, and alkaline earths such as calcium hydride. metal hydrides, alkali metal alkoxides such as sodium methoxide and potassium t-butoxide, alkali metal carboxylates such as sodium caproate and potassium stearate, alkaline earth metal salts of carboxylates such as magnesium caproate and calcium stearate. , n-butylamine, diethylamine, trioctylamine, pyridine and other amines, ammonium stearate, tetrabutylammonium methoxide, dimethyldistearylammonium acetate and other quaternary ammonium salts, tetramethylphosphonium propionate, trimethylbenzylphosphonium ethoxy Phosphonium salts such as de, tributyltin chloride,
Examples include tetravalent organic tin compounds such as diethyltin dilaurate and dibutyltin dimethoxide, and alkyl metals such as n-butyllithium and ethylmagnesium chloride.

Examples of cationic polymerization catalysts include tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony trifluoride, boron trifluoride, boron trifluoride diethyl etherate, and trifluoride. So-called Friedel compounds such as boron trifluoride coordination compounds such as boron acetic anhydrate and boron trifluoride triethylamine complex compounds
Kraft-type compounds, inorganic and organic acids such as perchloric acid, acetyl perchlorate, hydroxyacetic acid, trichloroacetic acid, p-)luenesulfonic acid, triethyloxonium tetrafluoroborate, triphenylmethyl hexafluorophosphate, Examples include complex salt compounds such as allyldiazonium hexafluorophosphate and allyldiazonium tetrafluoroborate, and alkyl metals such as diethylzinc, triethylaluminum, and diethylaluminum chloride.

These anionic polymerization catalysts and cationic polymerization catalysts are generally used in an amount of 0.0005 to 5 parts by weight based on 100 parts by weight of the starting material. Homopolymerization or copolymerization is carried out without solvent or in an organic medium.

Organic media that can be used in the present invention include:
Aliphatic hydrocarbons such as n-pentane, n-hexane, n-hebutane, n-octane, cyclohexane, cyclopenkune, etc., aromatic hydrocarbons such as benzene, toluene, xylene, methylene chloride, chloroform, carbon tetrachloride, ethylene chloride , halogenated aliphatic hydrocarbons such as trichloroethylene, and halogenated aromatic hydrocarbons such as chlorobenzene and 0-dichlorobenzene. These organic media may be used alone or in combination of two or more. The molecular weight regulator is used after being uniformly dissolved or dispersed in the reaction system. The concentration of the molecular weight regulator in the system can be easily determined experimentally depending on the desired molecular weight of the polyacecool block copolymer.

The reaction temperature is usually set between -20 and 30°C, but in the case of no solvent, it is more preferably between 20 and 210°C.
When an organic medium is used, the temperature is more preferably between -10 and 120°C.

There is no particular restriction on the reaction time, but it is set between 5 seconds and 300 minutes.

After a predetermined time has elapsed, a polymerization terminator is added to the reaction system to complete the homopolymerization or copolymerization. The obtained polymer is stabilized by removing unstable ends by hydrolysis or blocking unstable ends by a method such as esterification. The stabilized polyacecool block copolymer is put into practical use with the addition of a stabilizer and the like.

[Examples] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

The measurement items in the examples are as follows.

(1) M I: Measurement of pelletized polyacecool copolymer according to ASTM-D1238-57TE conditions.

(2) Izot impact value (notched): A pellet was molded into a flat plate using an injection molding machine.

A test piece was cut from this flat plate and measured according to ASTM-D256.

(3) Tensile strength, tensile elongation: Cut a test piece from a flat plate,
Measured according to ASTM-D638.

Example 1 (1) Production of polyacetal block copolymer Thoroughly dehydrated paraformaldehyde was thermally decomposed at 150°C and passed through a cooling trap several times to obtain a purity of 99.9%.
of formaldehyde gas was obtained.

300 gr of formaldehyde gas per hour, 1.
OOX 10-'moI! /I! of tetrabutylammonium acetate, as a molecular weight regulator, 4.80
10-3mop#' H(0(CH2) 5CO catty(CH2 arrow 0(CO(C
Hz) 50 πp (polyε-caprolactone diol,
Mn=50,000, hereinafter abbreviated as PCL-50. )
was introduced into 1,000 gr of toluene containing. 1. At the same time as supplying formaldehyde. Ox 10-'ma
ll! #' Tetrabutylammonium acetate, 4
．． Toluene containing 80×10-"moi'/j? of PCL-50 was continuously supplied at a rate of 1,000 gr per hour for 4 hours. Formaldehyde was also supplied at a rate of 30 gr per hour.
Continuously feed at a rate of 0gr, during which time the polymerization temperature was kept at 60gr.
It was maintained at ℃. Toluene containing the polymer was continuously extracted in proportion to the amount supplied, and the polymer was separated by filtration. After thoroughly washing the polymer with acetone, it was vacuum dried at 60°C.
160 g of white polymer was obtained.

(2) Confirmation of the structure of the polyacetal block copolymer 5g of the polyacetal block copolymer obtained in (1) was mixed with 0. Dispersed in 95g of IN hydrochloric acid aqueous solution and heated at 90℃ for 2 hours.
heated for an hour. Through this heating operation, the portion consisting of repeating oxymethylene units was completely hydrolyzed and returned to formaldehyde. On the other hand, under these conditions, the molecular weight regulator does not undergo hydrolysis. Next, this solution was neutralized with a 0.5N aqueous sodium hydroxide solution, and the solution was evaporated at normal pressure.
Subsequently, 50g of tetrahydrofuran was added to perform an extraction operation. When the extract was quantitatively analyzed using liquid chromatography, 4.70×10-' mol of PCL-50 was detected per 1 mol of formaldehyde.

When the polyacecool block copolymer obtained in (1) was subjected to infrared absorption spectrum analysis to quantify the ester groups, it was found that the ester groups (-0C(,H,o) derived from PCL-50 were 21.15 Xl0-2 mol was detected per 1 mol of formaldehyde.

Also, 50 g of the polyacecool block copolymer obtained in (1)
The polymer was heated at 139°C for 3 hours with 500g of acetic anhydride and 0.1g of sodium acetate to effect terminal acetylation, and 46g of a polymer was recovered. Next, this polymer was subjected to infrared absorption spectrum analysis and the ester groups were quantitatively determined.As a result, 21.24 Xl0-2 moles of ester groups were detected per 1 mole of formaldehyde. The ester groups quantified in this analysis are the ester group (-0CC,H,.) derived from PCL-50 and the ester group (-0CCH3) corresponding to the terminal hydroxyl group of the polymer obtained in (1). ).

From the above analysis results, the number average molecular weight of the oxymethylene chain of the polymer obtained in (1) is 64,000, and the polymer has the following structure and has a number average molecular weight of 114,000.

(3) Physical properties of polyacetal block copolymer The MI, Izot impact value (notched), tensile strength, and tensile elongation of the polyacetal block copolymer obtained in (1) were determined. The results are shown in Table 1.

As shown in Table 1, the polyacecool block copolymer had excellent impact resistance.

Example 2 (1) Production of polyacetal block copolymer Two Σ
500 gr of sufficiently purified trioxane, 10 gr of ethylene oxide, and H(0(CH2), 0-CO(CH2)4C) as molecular weight regulators were placed in a kneader with type stirring blades.
2H50H (both terminal ester of polyethylene adipate, Mn=30,000, hereinafter abbreviated as EA-30)
300g of was charged and heated to 70°C. Next, 0.25 g of boron trifluoride dibutyl etherate was added to this kneader.
r was added and heated for 35 minutes. Immediately thereafter, the polymerization was stopped (10 gr of tributylamine was added. The contents were taken out from the kneader and washed with acetone to obtain 800 gr of polyacetal copolymer.

(2) Confirmation of the structure of the polyacetal block copolymer The insertion rate of oxyethylene units in the polyacetal block copolymer obtained in (1) was found to be 1.50 moles/100 moles of oxymethylene units. .

Moreover, EA-30 in this polymer is 6.00X 10-
'It was 1 mole formaldehyde.

When the terminal hydroxyl group of the polyacecool block copolymer obtained in (1) was quantified by acetylation, a result of 12.75 Xl0-'mol/mol formaldehyde was obtained. The number average molecular weight of the oxymethylene chain of this polymer is 47,000, and the polymer has the following structure and has a number average molecular weight of 77,000.

(3) Physical properties of polyacetal block copolymer The MI, Izot impact value (notched), tensile strength, and elongation of the polyacetal block copolymer obtained in (1) were determined.

The results are shown in Table 2.

As shown in Table 2, the polyacetal block copolymer has excellent impact resistance.

Examples 3 to 8 Polyacecool block copolymers as shown in Table 6 were produced using starting materials and molecular weight regulators as shown in Table 5. All of these polymers are new polymers.

Table 6 also shows the physical properties of these polymers. All examples have excellent impact resistance.

Comparative example 1 (1) Production example 1 of polyacetal block copolymer
Among the reagents used in , H(0(
CH,),C publication'(CH2Kaoru0(CO(CHa)s
All operations were conducted in the same manner as in Example 1 except that O←→ (number average molecular weight 3,000) was used to obtain 2,150 g of a polymer.

(2) Confirmation Example 1 of polyacecool block copolymer
When the polymer obtained in (1) was analyzed using the same method as above, the number average molecular weight of the oxymethylene chain was 3.80.
0, has the following structure, and has a number average molecular weight of 6.8
00 polymer.

To H (CHz M
--ToC0(CH,)50←→20←→(3) Physical properties of polyacetal block copolymer MI, Izot impact value (notched), and tensile strength of the polyacetal block copolymer obtained in (1) , the elongation was determined. 3rd result
Shown in the table.

Table 3 As shown in Table 3, polyacetal block copolymers with a number average molecular weight of 10,000 or less did not have good impact resistance.

Comparative Example 2 (1) Production Example 1 of polyacetal block copolymer
Of the reagents used in
O(CH2) 507°H (number average molecular weight 500,000
) was used, but the same procedure as in Example 1 was carried out to obtain 2000 g of a polymer.

(2) Confirmation Example 1 of polyacetal block copolymer
When the polymer obtained in (1) was analyzed using the same method as above, the number average molecular weight of the oxymethylene chain was 640.
000 and has the following structure, the number average molecular weight is 1
, 140,000 polymer.

H-(-OCH4F--→-0(CH2)5CO←-0
(CH2→〇−10C0(CH2)So←−−f−CH
20←-1sho (3) Physical properties of polyacetal block copolymer The polyacetal block copolymer obtained in (1) has a number average molecular weight of 500.000 or more, so injection molding is impossible. Ta.

Comparative Example 3 (1) Production Example 1 of polyacetal block copolymer
Of the reagents used in Example 1, all operations were performed in the same manner as in Example 1, except that l-0(CH2)5CO[H2'+-cH3 (number average molecular weight 50.000) was used instead of PCL-50. 2,200 g of polymer was obtained.

(2) Confirmation Example 1 of polyacetal block copolymer
When the polymer obtained in (1) was analyzed using the same method, the number average molecular weight of the oxymethylene chain was 63.000.
and has the following structure and a number average molecular weight of 113,00
0 polymer.

(3) Table 4 shows the physical properties of the polyacecool block copolymer.

(The following is a blank space) As shown in Table 4, since the polyacecool block copolymer has an AB block structure, its impact resistance is poor.

Comparative Examples 4 to 5 Using starting materials and molecular weight regulators as shown in Table 5,
Polyacetal block copolymers as shown in Table 6 were prepared. Table 6 also shows the physical properties of the polyacetal block copolymer. In both comparative examples, the polyacetal block copolymer has an A-B block structure, and therefore has poor impact resistance.

[Effects of the Invention] In general, attempts have been made to blend polyacetal resin with various elastomers in order to improve its impact resistance. However, the polyacetal block copolymer of the present invention has no effect on conventional polyacetal resins. It has excellent impact resistance. Such excellent properties are derived from the fact that one block chain of the polyacecool block copolymer of the present invention has a structure of general formula B, and has a block structure of A-B-A. are doing. In addition, the polyacetal block copolymer of the present invention has a shape memory effect, and
Since it contains aliphatic polyester, it has a biodegradable function.

Claims (3)

[Claims] (1) Polyoxymethylene (A) and the following general formula (B) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (B) (In the formula, a, b, c are the same or different -CO-R_1-CO- , -O-R_2-O-, -CO
-R_3-O-. R_1, R_
2. R_3 is the same or different unsubstituted line having 2 to 13 carbon atoms, or a line in which at least one hydrogen atom is substituted with a group selected from an alkyl group, a cycloalkyl group, an aryl group, or a halogen atom It is a methylene chain with a shape. n, l, and m are 0 to 5000 and are not 0 at the same time. p is 1-5000. ), and the number average molecular weight of the polyacetal block copolymer is 10.0.
Polyacetal block copolymer between 00 and 500,000. (2) Formaldehyde or trioxane is used alone as a molecular weight regulator using a compound having the structure represented by the general formula (B) and having either a hydroxyl group, a carboxyl group, an ester group, or an alkoxy group at both ends of the compound. A method for producing a polyacetal block copolymer according to claim 1, which comprises polymerizing. (3) A compound having a structure represented by the general formula (B) and having either a hydroxyl group, a carboxyl group, an ester group, or an alkoxy group at both ends of the compound is used as a molecular weight regulator to form a cyclic compound with formaldehyde or trioxane. A method for producing a polyacetal block copolymer according to claim 1, which comprises copolymerizing a polyacetal block copolymer with an ether.