Polyacetal copolymers and their manufacturing methods

Abstract

This invention relates to a method for manufacturing a polyacetal copolymer, comprising: a step of copolymerizing 100 parts by mass of trioxymethylene (A), 0.05 to 5 parts by mass of a cyclic acetal compound (B), and 0.001 to 1 parts by mass of an aliphatic glycidyl ether compound (C) with a chlorine content of 1 to 500 ppm by mass in the presence of a linear dimethoxymethane compound (D) as a molecular weight regulator; wherein in this step, when the total mass (g) of (A) to (C) is set as a, the number of moles of (D) is set as b, and the total number of moles of water and methanol contained in (A) to (C) are set as c and d respectively, the method is set to satisfy (b+c+d) / a = 1.5 to 7 μmol / g.

Description

Technical Field

[0001] This invention relates to polyacetal copolymers and methods for manufacturing the same. Background Technology

[0002] Polyacetal resins are widely used as engineering plastics, primarily in electrical and electronic components, automotive parts, and various other mechanical components, due to their excellent balance of mechanical properties, chemical resistance, and lubricity, as well as their ease of processing. However, in recent years, with the expansion of their applications, there has been a growing demand for higher performance characteristics. For example, when using polyacetal resins in thin-walled parts, it is often necessary to maintain the original flowability, moldability, thermal stability, and lubricity of the polyacetal resin, while ensuring rigidity and creep resistance.

[0003] However, achieving a good balance of the above-mentioned characteristics is extremely difficult. For example, in methods that blend fibrous fillers into polyacetal resin to improve rigidity, poor appearance of the molded product, reduced sliding properties, and reduced flowability can occur. Furthermore, the thermal stability can sometimes be reduced by further blending of fillers. In addition, it is known to improve rigidity by reducing the amount of comonomers in polyacetal copolymers. However, this method does not sufficiently improve rigidity, and on the other hand, the reduced amount of comonomers leads to a decrease in the polymer's thermal stability, which in turn negatively affects flowability and moldability.

[0004] In view of the aforementioned facts, the inventors have explored ways to improve rigidity and creep properties by modifying the polymer backbone of polyacetal resin itself, and have proposed improvement methods (see Patent Documents 1-3). According to these methods, the excellent flowability, moldability, and lubrication properties of polyacetal resin can be maintained, while rigidity and creep resistance are improved.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2000-38429

[0008] Patent Document 2: Japanese Patent Application Publication No. 2000-95829

[0009] Patent Document 3: Japanese Patent Application Publication No. 2000-95830 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The polyacetal copolymers obtained by the above methods generally exhibit good thermal stability. However, further investigation revealed that operations such as manufacturing, polymerization, end-stabilization, and melt-blending with stabilizers or other compounding agents became unstable, or the thermal stability of the resulting copolymers deteriorated. Elucidating the causes and improving these processes is an important task for the practical application of polyacetal copolymers obtained by these methods.

[0012] The present invention was made in view of the above-mentioned existing problems, and its object is to provide a polyacetal copolymer with excellent rigidity, creep resistance and other properties, as well as thermal stability and a stable manufacturing method thereof.

[0013] Solution for solving the problem

[0014] In order to solve the aforementioned problems, the inventors conducted in-depth research and found that the chlorine content in the aliphatic glycidyl ether compound used to form a branched and cross-linked structure on the polymer backbone of the polyacetal copolymer is the key factor in solving the problem, as well as the optimal range of the MFR (melt flow rate) of the polyacetal copolymer and its control methods, thereby completing the present invention.

[0015] One aspect of the present invention that solves the aforementioned problems is as follows.

[0016] (1) A method for manufacturing a polyacetal copolymer, comprising the following steps: copolymerizing 100 parts by weight of trioxymethylene (A), 0.05-5 parts by weight of a cyclic acetal compound (B), and 0.001-1 parts by weight of an aliphatic glycidyl ether compound (C) with a chlorine content of 1-500 ppm by weight in the presence of a linear dimethoxymethane (FORMAL) compound (D) as a molecular weight regulator.

[0017] In the process, when the total mass (g) of (A), (B) and (C) is set as a, the number of moles of (D) is set as b, and the total number of moles of water and methanol contained in (A), (B) and (C) is set as c and d respectively, the process is set to satisfy (b+c+d) / a=1.5~7μmol / g.

[0018] (2) In the method for manufacturing the polyacetal copolymer described in (1) above, the linear dimethoxymethane compound (D) is selected from one or more of methylal, acetal, and dibutoxymethane.

[0019] (3) In the manufacturing method of the polyacetal copolymer described in (1) or (2) above, the aliphatic glycidyl ether compound (C) is an aliphatic glycidyl ether compound having one glycidyl ether group in one molecule.

[0020] (4) In the manufacturing method of the polyacetal copolymer described in (1) or (2) above, the aliphatic glycidyl ether compound (C) is selected from one or more of n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether.

[0021] (5) A method for producing a polyacetal copolymer by any one of (1) to (4) above.

[0022] Invention Effects

[0023] According to the present invention, a polyacetal copolymer with excellent rigidity, creep resistance and other properties, as well as thermal stability, and a stable manufacturing method thereof are provided. Detailed Implementation

[0024] <Method for manufacturing polyacetal copolymers>

[0025] The method for manufacturing the polyacetal copolymer of this embodiment includes a step of copolymerizing 100 parts by mass of trioxymethylene (A), 0.05 to 5 parts by mass of cyclic acetal compound (B), and 0.001 to 1 parts by mass of aliphatic glycidyl ether compound (C) with a chlorine content of 1 to 500 ppm by mass in the presence of a linear dimethoxymethane compound (D) as a molecular weight regulator. Furthermore, in this step, when the total mass (g) of (A), (B), and (C) is set as a, the molar number of (D) is set as b, and the total molar numbers of water and methanol contained in (A), (B), and (C) are set as c and d respectively, the ratio is set to satisfy (b+c+d) / a = 1.5 to 7 μmol / g.

[0026] Hereinafter, the components used in the manufacturing method of this embodiment will be described.

[0027] [Trioxymethylene (A)]

[0028] Trioxymethylene (A) is a cyclic trimer of formaldehyde, generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and then purified by methods such as distillation before use. The trioxymethylene (A) used for polymerization is preferably a substance with minimal impurities such as water and methanol.

[0029] [Cyclic acetal compound (B)]

[0030] The cyclic acetal compound (B) is a cyclic acetal compound (B) that can copolymerize with trioxymethylene (A), and examples include 1,3-dioxolane, propylene glycol dimethoxymethane, diethylene glycol dimethoxymethane, triethylene glycol dimethoxymethane, 1,4-butanediol dimethoxymethane, 1,5-pentanediol dimethoxymethane, 1,6-hexanediol dimethoxymethane, etc., with 1,3-dioxolane being preferred.

[0031] The copolymerization amount of the cyclic acetal compound (B) relative to 100 parts by mass of trioxymethylene (A) is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, and more preferably 0.3 to 2.5 parts by mass. When the copolymerization ratio of the cyclic acetal compound (B) is less than 0.05 parts by mass, the polymerization reaction is unstable, and the thermal stability of the resulting polyacetal copolymer deteriorates. Conversely, when the copolymerization ratio of the cyclic acetal compound (B) exceeds 5 parts by mass, the mechanical and physical properties such as strength and rigidity decrease.

[0032] [Aliphatic glycidyl ether compound (C)]

[0033] Aliphatic glycidyl ether compounds (C) are a general term for aliphatic organic compounds having one or more glycidyl groups in their molecules, which, through copolymerization with trioxymethylene, possess a structure capable of forming branches or crosslinks in the polymer backbone. In this respect, they can be distinguished from the aforementioned cyclic acetal compounds (B). As such aliphatic glycidyl ether compounds (C), any one of monofunctional glycidyl ether compounds having one glycidyl group or polyfunctional glycidyl ether compounds having two or more glycidyl groups can be used.

[0034] Preferably, it is a monofunctional glycidyl ether compound having one or more glycidyl oxy groups.

[0035] Specific examples of monofunctional glycidyl compounds include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and 2-methyloctyl glycidyl ether. Preferably, butyl glycidyl ether and 2-ethylhexyl glycidyl ether are also examples.

[0036] Furthermore, as polyfunctional glycidyl compounds having two or more glycidyl groups, diglycidyl ether compounds, triglycidyl ether compounds, and tetraglycidyl ether compounds are listed as preferred compounds. Specific examples of polyfunctional glycidyl compounds having two or more glycidyl groups include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0037] The copolymerization amount of the aliphatic glycidyl ether compound (C) is 0.001 to 1 part by mass relative to 100 parts by mass of paraformaldehyde in component (A), preferably 0.01 to 1 part by mass, and particularly preferably 0.1 to 1 part by mass. If the copolymerization amount of component (C) is less than 0.001 parts by mass, the improvement in rigidity and creep resistance will not be achieved. Conversely, when it exceeds 1 part by mass, problems with poor moldability due to reduced flowability will occur, and sometimes the mechanical and physical properties of rigidity and creep resistance will decrease due to reduced crystallinity of the resulting copolymer.

[0038] Furthermore, in this embodiment, from the viewpoint of rigidity and creep resistance, it is particularly preferred to use one or more of the aliphatic glycidyl ether compound (C) selected from n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether.

[0039] The molecular weight of the aliphatic glycidyl ether compound (C) is preferably between 100 and 220. When the molecular weight of the aliphatic glycidyl ether compound (C) exceeds 220, it may cause the branched chains of the polyacetal copolymer produced by its copolymerization to become longer, disrupting the crystallinity of the resin and thus impairing its basic properties, or adversely affecting its rigidity and creep resistance. Conversely, when the molecular weight of component (C) is below 100, its effect on rigidity and creep resistance becomes minimal.

[0040] In this embodiment, the aliphatic glycidyl ether compound (C) is characterized by using a substance with a chlorine content of 1 to 500 ppm by mass, thereby stably producing a polyacetal copolymer with particularly excellent thermal stability. A substance with a chlorine content of 100 ppm by mass or less is preferred. Regarding the lower limit of the chlorine content, from the viewpoint of economic efficiency in manufacturing the aliphatic glycidyl ether compound (C), a chlorine content of 1 ppm by mass or more is preferred. Furthermore, when the chlorine content of the aliphatic glycidyl ether compound (C) used exceeds 500 ppm by mass, operations such as the polymerization process, the end-stabilization process, and the productization process due to the mixing of stabilizers, etc., become unstable, and the thermal stability of the obtained polyacetal copolymer deteriorates.

[0041] Aliphatic glycidyl ether compounds are generally produced by the reaction of alcohols with epichlorohydrin. It is known that a method for obtaining glycidyl ether compounds involves ring-opening addition of an alcohol to epichlorohydrin in the presence of an acidic catalyst, followed by intramolecular ring closure in an alkaline aqueous solution (e.g., Japanese Patent Application Publication No. 61-178974). However, it is known that the glycidyl ether compounds produced in this method have a relatively high chlorine content. On the other hand, a method for producing glycidyl ether compounds by reacting an alcohol with epichlorohydrin in the presence of a solid alkali metal compound, wherein the reaction is carried out in the reaction mixture in the presence of pulverized solid alkali metal hydroxide (e.g., Japanese Patent Application Publication No. 1-151567). This method discloses a glycidyl ether compound with extremely low chlorine content. In this embodiment, for example, a glycidyl ether compound with extremely low chlorine content obtained by such a method can be used.

[0042] In this embodiment, the polyacetal copolymer is basically obtained by adding appropriate amounts of molecular weight regulators to trioxymethylene (A), cyclic acetal compound (B), and aliphatic glycidyl ether compound (C) as needed, and performing bulk polymerization using a cationic polymerization catalyst.

[0043] In this embodiment, to obtain a polyacetal copolymer with superior thermal stability, rigidity, and impact resistance, it is preferable that the constituent units of the cyclic acetal compound (B) and the aliphatic glycidyl ether compound (C) in the molecular chain of the polyacetal copolymer are uniformly dispersed. For this purpose, in the manufacture of the polyacetal copolymer achieved by polymerization, a method is effective that involves uniformly mixing the cyclic acetal compound (B) and the catalyst, adding it to a previously uniformly mixed solution of the aliphatic glycidyl ether compound (C) and trioxymethylene (A), and then feeding it to a polymerizer for polymerization. By pre-mixing to form a uniform solution, not only is the dispersion of the branched structure derived from the aliphatic glycidyl ether compound improved, resulting in enhanced mechanical properties, but also the thermal stability becomes superior.

[0044] When manufacturing the polyacetal copolymer of this embodiment, which consists of the components described above, the polymerization apparatus is not particularly limited, and any known apparatus, batch or continuous method, can be used. Furthermore, the polymerization temperature is preferably maintained between 65 and 135°C.

[0045] Deactivation after polymerization can be achieved by adding an alkaline compound or its aqueous solution to the reaction products discharged from the polymerizer or to the reaction products in the polymerizer after the polymerization reaction.

[0046] Examples of cationic polymerization catalysts used in this embodiment include lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony trichloride, phosphorus pentafluoride, antimony pentafluoride, boron trifluoride, diethyl ether of boron trifluoride, dibutyl ether of boron trifluoride, dioxane ester of boron trifluoride, acetic anhydride of boron trifluoride, triethylamine complex of boron trifluoride, perchloric acid, acetyl perchlorate, tert-butyl perchlorate, glycolic acid, trichloroacetic acid, trifluoroacetic acid, p-toluenesulfonic acid, and other inorganic and organic acids; triethyloxonium tetrafluoroboric acid, triphenylmethyl hexafluoroantimonylate, allyl diazo hexafluorophosphate, allyl diazo tetrafluoroboric acid, and other complex chlorine compounds; alkyl metal salts such as diethylzinc, triethylaluminum, and diethylaluminum chloride; heteropoly acids; and heteropolymers.

[0047] Among these, boron trifluoride coordination compounds such as boron trifluoride, boron trifluoride diethyl ether, boron trifluoride dibutyl ether, boron trifluoride dioxane, boron trifluoride acetic anhydride, and boron trifluoride triethylamine complex are particularly preferred. These catalysts can also be used after pre-diluting with organic solvents, etc.

[0048] As the molecular weight regulator used in this embodiment, a linear dimethoxymethane compound can be used. Examples of linear dimethoxymethane compounds include methyl acetal, acetal, dibutoxymethane, bis(methoxymethyl) ether, bis(ethoxymethyl) ether, and bis(butoxymethyl) ether. Preferably, one or more of methyl acetal, acetal, and dibutoxymethane are selected.

[0049] Furthermore, the alkaline compounds used to neutralize and deactivate the polymerization catalyst can be ammonia, or amines such as triethylamine, tributylamine, triethanolamine, and tributanolamine, or hydroxide salts of alkali metals or alkaline earth metals, or other known catalyst deactivators. Preferably, these aqueous solutions are rapidly added to the product after the polymerization reaction to deactivate it. Following the polymerization and deactivation methods, further washing, separation and recovery of unreacted monomers, drying, etc., are performed as needed using existing known methods.

[0050] Furthermore, the unstable ends are decomposed and removed, or the unstable ends of the stable substance are sealed, and stabilization treatment is performed using known methods as needed, and various necessary stabilizers are mixed in. Examples of stabilizers used herein include any one or more of hindered phenolic compounds, nitrogen-containing compounds, hydroxides of alkalis or alkaline earth metals, inorganic salts, and carboxylates. Moreover, as long as it does not impair the effect of the polyacetal copolymer of this embodiment, one or more general additives for polyacetal resins can be added as needed, such as colorants like dyes and pigments, lubricants, nucleating agents, release agents, antistatic agents, surfactants, or organic polymer materials, inorganic or organic fibrous, powder, or plate-like fillers.

[0051] In this embodiment, during the copolymerization process, the total mass (g) of trioxymethylene (A), cyclic acetal compound (B), and aliphatic glycidyl ether compound (C) is set as 'a', the molar number of linear dimethoxymethane compound (D) is set as 'b', and the total molar numbers of water and methanol contained in components (A), (B), and (C) are set as 'c' and 'd', respectively. This is achieved by setting (b+c+d) / a = 1.5–7 μmol / g. When (b+c+d) / a = 1.5–7 μmol / g, the melt flow rate (MFR) measured according to ISO 1133 can be 0.5–3 g / 10 min. An MFR of 0.5–3 g / 10 min maintains moldability and improves creep resistance. An MFR of 1–2.5 g / 10 min is particularly preferred.

[0052] In addition, the water and methanol contained in (A), (B) and (C) are derived from their respective impurities.

[0053] <Polyacetal copolymer>

[0054] The polyacetal copolymer of this embodiment is obtained by the manufacturing method of the polyacetal copolymer of this embodiment described above. Therefore, the polyacetal copolymer of this embodiment has excellent rigidity, creep resistance, and thermal stability.

[0055] Example

[0056] The following examples will further illustrate this embodiment in detail, but this embodiment is not limited to the following examples.

[0057] [Examples 1-9]

[0058] A continuous mixing reactor, consisting of a cylinder with an outer sheath for passing hot (cold) media and a cross-section of two overlapping circles, and a rotating shaft with paddles, was used. The two rotating shafts with paddles were rotated at 150 rpm each. Simultaneously, trioxymethylene (A), a cyclic acetal compound (B), and an aliphatic glycidyl ether compound (C) were added according to the proportions and amounts shown in Table 1. Furthermore, as a molecular weight regulator, a linear dimethoxymethane compound (D) as shown in Table 1 was continuously supplied according to the proportions and amounts shown in Table 1. This continuous supply resulted in a homogeneous mixture where the boron trifluoride gas relative to the trioxymethylene was converted to 0.005% by mass, thereby carrying out bulk polymerization. The reaction products discharged from the polymerizer were rapidly passed through a crusher and simultaneously added to an aqueous solution containing 0.1% by mass of triethylamine at 80°C to deactivate the catalyst. After separation, washing, and drying, a crude polyacetal copolymer was obtained.

[0059] Next, relative to 100 parts by weight of the crude polyacetal copolymer, 4 parts by weight of a 5% aqueous solution of triethylamine and 0.03 parts by weight of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] were added, and the mixture was melt-blended at 210°C using a biaxial extruder to remove the unstable components.

[0060] To 100 parts by weight of the branched or crosslinked polyacetal copolymer obtained by the above method, 0.3 parts by weight of pentaerythritol-tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as a stabilizer and 0.15 parts by weight of melamine were further added, and the mixture was melt-blended at 210°C using a biaxial extruder to obtain granular branched polyacetal copolymer. The results of the evaluation by the method described later are shown in Table 2.

[0061] [Comparative Examples 1-5]

[0062] As shown in Table 1, for cases where the chlorine content of the aliphatic glycidyl ether compound (C) is not specified in this embodiment, and for cases where the MFR of the branched polyacetal copolymer is not specified in this embodiment, particulate polyacetal copolymers were obtained in the same manner as in the examples, and the evaluation results are shown in Table 2.

[0063] In addition, the codes for each component listed in Table 1 have the following meanings.

[0064] [Cyclic acetal compounds]

[0065] DO; 1,3-dioxolane

[0066] [Aliphatic glycidyl ether compounds]

[0067] BGE; Butyl glycidyl ether

[0068] 2EHGE; 2-Ethylhexyl glycidyl ether

[0069] BDGE; Butylene glycol diglycidyl ether

[0070] In addition, various aliphatic glycidyl ether compounds can be synthesized using different methods to obtain a variety of compounds with different chlorine contents.

[0071] [Chlorine content]

[0072] The determination of chlorine content in aliphatic glycidyl ether compounds is carried out by the following method.

[0073] A 50mg sample (5mg for chlorine content exceeding 1000ppm) was introduced into a sample combustion device (Mitsubishi Chemical Analysis AFQ-100) and simultaneously combusted with water vapor. The resulting gas was absorbed in an absorbent solution using phosphate ions as an internal standard. This absorbent sample was then analyzed using an anion chromatograph (Dionex ICS-1600) to quantify the chloride ion content and determine the chlorine content of the sample.

[0074] [The total amount of moisture in component (A), component (B), and component (C)]

[0075] The Karl Fischer method was used to determine the water content of a mixture of components (A), (B), and (C).

[0076] [The total amount of methanol in component (A), component (B), and component (C)]

[0077] A mixture of components (A), (B), and (C) was used, and the determination was performed using gas chromatography.

[0078] [MFR]

[0079] The melt flow rate (MFR) of polyacetal copolymers was determined according to ISO 1133.

[0080] <Evaluation>

[0081] The flexural modulus, creep resistance, and formaldehyde production of the particulate polyacetal copolymers involved in the examples and comparative examples were evaluated using the following methods.

[0082] [Stiffness (bending modulus)]

[0083] The flexural modulus (FM) was determined according to ISO 178. The conditions in the testing chamber were set at 23°C and 55% RH.

[0084] [Creep Resistance Properties (Creep Fracture Time)]

[0085] ISO Type-A test pieces with a thickness of 4 mm were formed and subjected to creep testing using a creep testing machine under a negative load of 21 MPa at 80°C. The creep rupture time (h) until fracture was measured was compared. Three measurements were taken, and the average value was taken as the creep rupture time.

[0086] [Thermal stability (formaldehyde production from the melt)]

[0087] Weigh 5g of granules correctly, keep them in a metal container at 200°C for 5 minutes, and then allow the atmosphere inside the container to be absorbed in distilled water. Quantify the amount of formaldehyde in the aqueous solution according to JIS K0102, 29. (Formaldehyde section), and calculate the amount of formaldehyde gas (ppm) produced by the granules.

[0088] [Table 1]

[0089]

[0090] [Table 2]

[0091]

[0092] Table 2 shows that Examples 1-9 provide a polyacetal copolymer with sufficient rigidity (flexural modulus, ≥2350 MPa) and excellent creep resistance (breakage time ≥500 h) and thermal stability (low formaldehyde production (≤150 ppm)). In contrast, Comparative Examples 1-5 have sufficient rigidity, but at least one of creep resistance and thermal stability is poor. In particular, the chlorine content of the aliphatic glycidyl ether compounds in Examples 1-7, Comparative Examples 1-2, Example 8, Comparative Example 3, Example 9, and Comparative Example 4 varies, but their comparison shows that when the chlorine content is outside the predetermined range, the thermal stability is poor.

[0093] Furthermore, as can be seen from the various examples and comparative examples in Table 1, by setting the ratio of a specific component to (b+c+d) / a = 1.5 to 7 μmol / g, the MFR of the polyacetal copolymer can be 0.5 to 3 g / 10 min.

Claims

1. A method for manufacturing a polyacetal copolymer, characterized in that, The process includes the following steps: copolymerizing 100 parts by weight of trioxymethylene (A), 0.05 to 5 parts by weight of a cyclic acetal compound (B), and 0.001 to 1 part by weight of an aliphatic glycidyl ether compound (C) with a chlorine content of 1 to 500 ppm by weight in the presence of a linear dimethoxymethane compound (D) as a molecular weight regulator. In the process, when the total mass (g) of (A), (B) and (C) is set as a, the number of moles of (D) is set as b, and the total number of moles of water and methanol contained in (A), (B) and (C) is set as c and d respectively, the process is set to satisfy (b+c+d) / a=1.5~7μmol / g.

2. The method for manufacturing the polyacetal copolymer according to claim 1, characterized in that, The linear dimethoxymethane compound (D) is selected from one or more of methyl acetal, acetal, and dibutoxymethane.

3. The method for manufacturing the polyacetal copolymer according to claim 1 or 2, characterized in that, The aliphatic glycidyl ether compound (C) is an aliphatic glycidyl ether compound having one glycidyl oxy group in one molecule.

4. The method for manufacturing the polyacetal copolymer according to claim 1 or 2, wherein, The aliphatic glycidyl ether compound (C) is selected from one or more of n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether.

5. A polyacetal copolymer obtained by the method for manufacturing the polyacetal copolymer according to any one of claims 1 to 4.