Cationic polymerization initiator composition, oxymethylene copolymer using same, and method for producing molded article

Abstract

The invention relates to a technical scheme for preventing metal corrosion caused by a cationic polymerization initiator containing fluorine atoms. A cationic polymerization initiator composition which contains a fluorine atom-containing cationic polymerization initiator (A) and a hydrophilic ether solvent (B) that does not have an acetal structure or an active hydroxyl group, and wherein the content of the hydrophilic ether solvent (B) is 2.5 mass% or more with respect to the total mass of the cationic polymerization initiator composition.

Description

Technical Field

[0001] The present invention relates to a cationic polymerization initiator composition, and a method for producing an oxymethylene copolymer and a molded article using the composition. Background Art

[0002] Conventionally, oxymethylene copolymers (polyacetal copolymers) have been widely used in electronic equipment, vehicles, and the like in the form of fibers, films, gears, and bearings due to their excellent properties in terms of strength, elastic modulus, impact resistance, and sliding properties.

[0003] When producing such oxymethylene copolymers, a cationic polymerization initiator is generally used.

[0004] For example, Patent Document 1 describes an invention relating to a liquid transport method, wherein a solution containing a cationic polymerization catalyst (cationic polymerization initiator) and an organic solvent is transported through a pipeline, wherein the inner wall of the pipeline has an arithmetic mean surface roughness (Ra) of 3 μm or less. Patent Document 1 describes that this invention suppresses the formation of scale (deposits within the pipeline) caused by aggregation of the cationic polymerization initiator, and enables the stable production of oxymethylene copolymers at high yields over a long period of time.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-149853 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] However, it is also known that, among cationic polymerization initiators, particularly when using a cationic polymerization initiator containing a fluorine atom (fluorine-containing cationic polymerization initiator), metals constituting pipes, tanks, and the like may be corroded.

[0010] Thus, the present invention provides a means for preventing cationic polymerization initiators containing fluorine atoms from corroding metals.

[0011] Technical solutions to technical problems

[0012] The present invention is described below, for example.

[0013] [1] A cationic polymerization initiator composition comprising a cationic polymerization initiator (A) containing a fluorine atom and a hydrophilic ether solvent (B) having no acetal structure and no active hydroxyl group,

[0014] The content of the hydrophilic ether solvent (B) is 2.5% by mass or more relative to the total mass of the cationic polymerization initiator composition.

[0015] [2] The cationic polymerization initiator composition according to [1] above, wherein the fluorine-containing cationic polymerization initiator (A) comprises a boron trifluoride compound.

[0016] [3] The cationic polymerization initiator composition according to [1] or [2] above, wherein the fluorine-containing cationic polymerization initiator (A) comprises a fluorinated arylboron compound.

[0017] [4] The cationic polymerization initiator composition according to any one of [1] to [3], wherein the hydrophilic ether solvent (B) contains at least one of a chain ether containing two or more oxygen atoms and a cyclic ether containing two or more oxygen atoms.

[0018] [5] The cationic polymerization initiator composition according to [4] above, wherein the content of the hydrophilic ether solvent (B) is 2.5 to 60% by mass relative to the total mass of the cationic polymerization initiator composition.

[0019] [6] The cationic polymerization initiator composition according to any one of [1] to [3], wherein the hydrophilic ether solvent (B) comprises at least one of a chain ether containing one oxygen atom and a cyclic ether containing one oxygen atom.

[0020] [7] The cationic polymerization initiator composition according to [6] above, wherein the content of the hydrophilic ether solvent (B) is 2.5 to 20% by mass relative to the total mass of the cationic polymerization initiator composition.

[0021] [8] A method for producing an oxymethylene copolymer, comprising a polymerization step of obtaining the oxymethylene copolymer from a reaction solution, wherein the reaction solution comprises a polymerization raw material C containing 1,3,5-trioxane and the cationic polymerization initiator composition according to any one of [1] to [7].

[0022] [9] The production method according to [8] above, wherein the content of the hydrophilic ether solvent (B) in the reaction solution is 18 ppm or more relative to 1,3,5-trioxane.

[0023]

[10] The production method according to [9] above, wherein the content of the hydrophilic ether solvent (B) in the reaction solution is 18 to 100 ppm relative to 1,3,5-trioxane.

[0024]

[11] A method for producing a molded article, comprising the step of molding an oxymethylene copolymer produced by the method described in any one of [8] to

[10] above.

[0025] Effects of the Invention

[0026] According to the present invention, metal corrosion caused by a fluorine-containing cationic polymerization initiator can be prevented, thereby suppressing, for example, deterioration of production equipment, reduction in productivity of oxymethylene copolymers, and reduction in physical properties of the resulting oxymethylene copolymers. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described in detail.

[0028] 1. Cationic polymerization initiator composition

[0029] The cationic polymerization initiator composition of the present invention comprises a fluorine-containing cationic polymerization initiator (A) and a hydrophilic ether solvent (B) having no acetal structure and no active hydroxyl group. In this case, the content of the hydrophilic ether solvent (B) is 2.5% by mass or more relative to the total mass of the cationic polymerization initiator composition.

[0030] According to the cationic polymerization initiator composition of the present invention, it is possible to prevent metal corrosion caused by a cationic polymerization initiator (A) containing fluorine atoms. The reasons for this are, for example, as follows. That is, when using a cationic polymerization initiator containing fluorine atoms (cationic polymerization initiator (A) containing fluorine atoms), the water present in the system may cause the generation of metal corrosion components such as hydrofluoric acid (HF). In this case, the metal corrosion components will corrode the metals constituting pipelines, storage tanks, etc., and easily cause aging of manufacturing equipment such as pipelines and storage tanks. In addition, the metal components dissolved due to metal corrosion hinder the polymerization reaction, which may cause the productivity of the oxymethylene copolymer to decrease, the physical properties of the resulting oxymethylene copolymer to decrease, and other situations.

[0031] In contrast, the cationic polymerization initiator composition of the present invention not only contains a cationic polymerization initiator (A) containing fluorine atoms, but also contains a predetermined amount of a hydrophilic ether solvent (B) having no acetal structure and no active hydroxyl group (hereinafter sometimes also referred to as "hydrophilic ether solvent (B)"). By containing the above-mentioned hydrophilic ether solvent (B), the generation of metal corrosion components can be suppressed. This can suppress the corrosion of metals constituting pipelines, storage tanks, etc., and suppress the aging of manufacturing equipment. In addition, since the dissolution of metal components is suppressed by suppressing metal corrosion, it is possible to prevent the obstruction of the polymerization reaction caused by the metal components. As a result, it is possible to suppress the reduction in the productivity of the oxymethylene copolymer and the reduction in the physical properties of the obtained oxymethylene copolymer.

[0032] (1) Fluorine-containing cationic polymerization initiator (A)

[0033] The fluorine-containing cationic polymerization initiator (A) has a function of acting on 1,3,5-trioxane and / or a comonomer to generate cationic active species and promote the copolymerization reaction.

[0034] Examples of the fluorine-atom-containing cationic polymerization initiator (A) include, but are not particularly limited to, boron trifluoride compounds, fluorinated arylboron compounds, and fluorine-atom-containing protonic acids.

[0035] Examples of the above-mentioned boron trifluoride compounds include boron trifluoride dimethyl ether complex (BF3·Me2O), boron trifluoride diethyl ether complex (BF3·Et2O), boron trifluoride dibutyl ether complex (BF3·Bu2O), boron trifluoride tetrahydrofuran complex (BF3·THF), boron trifluoride dihydrate (BF3·2H2O), boron trifluoride methanol complex (BF3·CH3OH), boron trifluoride phenol complex (BF3·2C6H5OH), boron trifluoride acetic acid complex (BF3·2CH3COOH), and boron trifluoride ethylamine complex (BF3·C2H5NH2).

[0036] Examples of the fluorinated arylboron compound include triphenylborane, tris(pentafluorophenyl)borane (TPB), bis(pentafluorophenyl)fluoroborane, pentafluorophenyldifluoroborane, tris(2,3,4,5-tetrafluorophenyl)borane, tris(2,3,4,6-tetrafluorophenyl)borane, tris(2,3,5,6-tetrafluorophenyl)borane, tris(2,3,5-trifluorophenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(1,3-difluorophenyl)borane, tris(2,3,5,6-tetrafluoro-4-methylphenyl)borane, tris(2,3,4,6-tetrafluoro-5-methylphenyl)borane, tris(2,4,5-trifluoro-6-methylphenyl)borane, tris(2,3,6-trifluoro-4-methylphenyl)borane, tris(2,4,6-trifluoro-3-methylphenyl)borane, tris(2,6-difluoro-3-methylphenyl)boron, tris(2,4-difluoro-5-methylphenyl)boron, tris(3,5-difluoro-2-methylphenyl)boron, tris(4-methoxy-2,3,5,6-tetrafluorophenyl)boron, tris(3-methoxy-2,4,5,6-tetrafluorophenyl)boron, tris(2-methoxy-3,5,6-trifluorophenyl)boron, tris(3-methoxy-2,5,6-trifluorophenyl)boron, tris(3-methoxy-2,4,6-trifluorophenyl)boron, tris(2-methoxy-3,5-difluorophenyl)boron, tris(3-methoxy-2,6-difluorophenyl)boron, tris(3-methoxy-4,6-difluorophenyl)boron, tris(2-methoxy-4,6-difluorophenyl)boron, tris(4-methoxy-2,6-difluorophenyl)boron, etc. These fluorinated aryl boron compounds may be coordination compounds coordinated with water (hydrate), ammonia, dimethyl ether, diethyl ether, dibutyl ether, phenol, ethylamine, or the like, and these coordination compounds are included in the fluorinated aryl boron compounds.

[0037] Examples of the fluorine-containing protonic acid include, but are not particularly limited to, trifluoroacetic acid (CF 3 COOH) and trifluoromethanesulfonic acid (CF 3 SO 3 H).

[0038] In one embodiment, the cationic polymerization initiator (A) containing fluorine atoms preferably comprises a boron trifluoride compound, more preferably comprises at least one selected from boron trifluoride dimethyl ether complex (BF3·Me2O), boron trifluoride diethyl ether complex (BF3·Et2O), boron trifluoride dibutyl ether complex (BF3·Bu2O) and boron trifluoride tetrahydrofuran complex (BF3·THF), and further preferably comprises boron trifluoride diethyl ether complex (BF3·Et2O).

[0039] In one embodiment, the fluorine-containing cationic polymerization initiator (A) preferably comprises a fluorinated arylboron compound, more preferably comprises a fluorinated arylboron compound selected from tris(pentafluorophenyl)borane (TPB), bis(pentafluorophenyl)fluoroborane, pentafluorophenyldifluoroborane, tris(2,3,4,5-tetrafluorophenyl)borane, tris(2,3,4,6-tetrafluorophenyl)borane, tris(2,3,5,6-tetrafluorophenyl)borane, tris(2,3,5-trifluorophenyl)borane , tris(2,4,6-trifluorophenyl)boron, tris(1,3-difluorophenyl)boron, tris(2,3,5,6-tetrafluoro-4-methylphenyl)boron, tris(2,3,4,6-tetrafluoro-5-methylphenyl)boron, tris(2,4,5-trifluoro-6-methylphenyl)boron, tris(2,3,6-trifluoro-4-methylphenyl)boron, tris(2,4,6-trifluoro-3-methylphenyl)boron, tris(2,6-difluoro-3-methylphenyl)boron Boron, tris(2,4-difluoro-5-methylphenyl)boron, tris(3,5-difluoro-2-methylphenyl)boron, tris(4-methoxy-2,3,5,6-tetrafluorophenyl)boron, tris(3-methoxy-2,4,5,6-tetrafluorophenyl)boron, tris(2-methoxy-3,5,6-trifluorophenyl)boron, tris(3-methoxy-2,5,6-trifluorophenyl)boron, tris(3-methoxy-2,4,6-trifluorophenyl)boron The present invention is preferably selected from the group consisting of tris(pentafluorophenyl)borane (TPB), ...

[0040] In one embodiment, the cationic polymerization initiator (A) containing fluorine atoms preferably contains at least one selected from boron trifluoride compounds and fluorinated aryl boron compounds, more preferably at least one selected from boron trifluoride dimethyl ether complex (BF3·Me2O), boron trifluoride diethyl ether complex (BF3·Et2O), boron trifluoride dibutyl ether complex (BF3·Bu2O) and boron trifluoride tetrahydrofuran complex (BF3·THF), and at least one selected from tris(pentafluorophenyl)borane (TPB), bis(pentafluorophenyl)fluoroborane (TPB), and bis(pentafluorophenyl)fluoroborane (TPB). Borane, pentafluorophenyldifluoroborane, tris(2,3,4,5-tetrafluorophenyl)borane, tris(2,3,4,6-tetrafluorophenyl)borane, tris(2,3,5,6-tetrafluorophenyl)borane, tris(2,3,5-trifluorophenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(1,3-difluorophenyl)borane, tris(2,3,5,6-tetrafluoro-4-methylphenyl)borane, tris(2,3,4,6-tetrafluoro-5-methylphenyl)borane, tris(2,4,5-trifluoro-6-methylphenyl)borane, tris(2,3,6-trifluorophenyl)borane -4-methylphenyl)boron, tris(2,4,6-trifluoro-3-methylphenyl)boron, tris(2,6-difluoro-3-methylphenyl)boron, tris(2,4-difluoro-5-methylphenyl)boron, tris(3,5-difluoro-2-methylphenyl)boron, tris(4-methoxy-2,3,5,6-tetrafluorophenyl)boron, tris(3-methoxy-2,4,5,6-tetrafluorophenyl)boron, tris(2-methoxy-3,5,6-trifluorophenyl)boron, tris(3-methoxy-2,5,6-trifluorophenyl)boron, tris(3-methoxy-2,5,6-trifluorophenyl)boron, -2,4,6-trifluorophenyl)boron, tris(2-methoxy-3,5-difluorophenyl)boron, tris(3-methoxy-2,6-difluorophenyl)boron, tris(3-methoxy-4,6-difluorophenyl)boron, tris(2-methoxy-4,6-difluorophenyl)boron and tris(4-methoxy-2,6-difluorophenyl)boron and at least one of the coordination compounds of these compounds, further preferably containing boron trifluoride diethyl ether complex (BF3·Et2O) and tris(pentafluorophenyl)borane (TPB) or its coordination compound.

[0041] The fluorine-atom-containing cationic polymerization initiator (A) may be used alone or in combination of two or more.

[0042] The content of the fluorine-containing cationic polymerization initiator (A) relative to the total mass of the cationic polymerization initiator composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, further preferably 1 to 10% by mass, and particularly preferably 5 to 10% by mass. When two or more fluorine-containing cationic polymerization initiators (A) are present, the total content thereof is preferably within the above range.

[0043] In one embodiment, when the fluorine-containing cationic polymerization initiator (A) contains a boron trifluoride compound, the content of the boron trifluoride compound is preferably 1 to 20 mass %, more preferably 2 to 15 mass %, further preferably 3 to 10 mass %, and particularly preferably 5 to 10 mass %, relative to the total mass of the cationic polymerization initiator composition.

[0044] In one embodiment, when the fluorine-containing cationic polymerization initiator (A) contains a fluorinated aryl boron compound, the content of the fluorinated aryl boron compound is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, further preferably 0.1 to 3% by mass, and particularly preferably 0.1 to 1% by mass, relative to the total mass of the cationic polymerization initiator composition.

[0045] (2) Other polymerization initiators

[0046] The cationic polymerization initiator composition may further comprise other polymerization initiators. It should be noted that the term "other polymerization initiator" as used herein refers to a cationic polymerization initiator other than the fluorine-containing cationic polymerization initiator (A), in other words, a cationic polymerization initiator that does not contain fluorine atoms. By using other polymerization initiators, the polymerization reaction can be controlled.

[0047] Examples of other polymerization initiators include, but are not particularly limited to, Lewis acids containing no fluorine atom and protonic acids containing no fluorine atom.

[0048] Examples of the Lewis acids that do not contain fluorine atoms include boron trichloride (BCl3), aluminum chloride (AlCl3), tin tetrachloride (SnCl4), zinc chloride (ZnCl2), iron chloride (FeCl3), gallium chloride (GaCl3), zirconium chloride (ZrCl4), and niobium pentachloride (NbCl5).

[0049] Examples of the protonic acid containing no fluorine atom include perchloric acid (HClO 4 ), hydrogen chloride (HCl), sulfuric acid (H 2 SO 4 ), trichloroacetic acid (CCl 3 COOH), p-toluenesulfonic acid, phosphotungstic acid, and derivatives thereof.

[0050] Examples of the derivatives of the protonic acid containing no fluorine atom include perchloric anhydride and peroxyacetyl perchlorate.

[0051] The above-mentioned other polymerization initiators may be used alone or in combination of two or more.

[0052] The content of the other polymerization initiator is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, and even more preferably 0.5 to 10% by mass relative to the total mass of the cationic polymerization initiator composition. When two or more other polymerization initiators are present, their total content is preferably within the above range.

[0053] (3) Hydrophilic ether solvent (B) without acetal structure and active hydroxyl group

[0054] The hydrophilic ether solvent (B) has the function of suppressing the generation of metal-corrosive components such as hydrofluoric acid (HF) generated when the fluorine-containing cationic polymerization initiator (A) comes into contact with water. This prevents metal corrosion caused by these components. Furthermore, it prevents the metal components eluted by metal corrosion from hindering the polymerization reaction, thereby suppressing reductions in the productivity of the oxymethylene copolymer and degradation of the physical properties of the resulting oxymethylene copolymer.

[0055] Examples of the hydrophilic ether solvent (B) include chain ethers containing one oxygen atom, cyclic ethers containing one oxygen atom, chain ethers containing two or more oxygen atoms, and cyclic ethers containing two or more oxygen atoms.

[0056] Examples of the chain ether containing one oxygen atom include dimethyl ether, diethyl ether, and ethyl methyl ether.

[0057] Examples of the cyclic ether containing one oxygen atom include oxetane, 2-methyloxetane, 3-methyloxetane, 2-ethyloxetane, 3-ethyloxetane, 2-propyloxetane, 2,2-dimethyloxetane, 3,3-dimethyloxetane, 2,3-dimethyloxetane, and 2-ethyl-3-methyloxetane; tetrahydrofuran (THF), 2-methyltetrahydrofuran (MHF), 3-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 3-ethyltetrahydrofuran, 2-propyltetrahydrofuran, 2,2-dimethyltetrahydrofuran, 3,3-dimethyltetrahydrofuran, 2,3-dimethyltetrahydrofuran, and 2-ethyl-3-methyloxetane; and 3-dimethyltetrahydrofuran, 2,4-dimethyltetrahydrofuran, 2-ethyl-3-methyltetrahydrofuran, 2-ethyl-4-methyltetrahydrofuran and the like; tetrahydropyran, 2-methyltetrahydropyran, 3-methyltetrahydropyran, 4-methyltetrahydropyran (MTHP), 2-ethyltetrahydropyran, 3-ethyltetrahydropyran, 4-ethyltetrahydropyran, 2-propyltetrahydropyran, 2,2-dimethyltetrahydropyran, 3,3-dimethyltetrahydropyran, 4,4-dimethyltetrahydropyran, 2,3-dimethyltetrahydropyran, 2,5-dimethyltetrahydropyran, 2-ethyl-5-methyltetrahydropyran and the like;

[0058] Examples of the chain ether containing two or more oxygen atoms include chain ethers containing two oxygen atoms such as dimethoxymethane (formal), diethoxymethane, dipropoxymethane, diisopropoxymethane, dibutoxymethane, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, 1,3-dimethoxypropane, and 1,3-diethoxypropane; chain ethers containing three oxygen atoms such as trimethyl orthoformate (methoxyformal), triethyl orthoformate, triisopropyl orthoformate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether; and chain ethers containing four or more oxygen atoms such as triethylene glycol dimethyl ether, triethylene glycol diethyl ether, polyethylene glycol dimethyl ether, and polyethylene glycol diethyl ether.

[0059] Examples of the cyclic ether containing two or more oxygen atoms include cyclic ethers containing two oxygen atoms such as 1,4-dioxane, 2-methyl-1,3-dioxane, and 4-methyl-1,3-dioxane; and cyclic ethers containing three or more oxygen atoms such as 12-crown-4, 15-crown-5, 18-crown-6, and dibenzo-18-crown-6.

[0060] In one embodiment, the hydrophilic ether solvent (B) preferably contains at least one of a chain ether containing two or more oxygen atoms and a cyclic ether containing two or more oxygen atoms, more preferably contains at least one of a chain ether containing two oxygen atoms and a cyclic ether containing two oxygen atoms, further preferably contains at least one selected from dimethoxymethane, diethoxymethane, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane and 1,4-dioxane, and particularly preferably contains at least one selected from 1,2-dimethoxyethane (DME), 1,2-diethoxyethane and 1,4-dioxane.

[0061] In a certain embodiment, it is preferred that the compound contains at least one of a chain ether containing one oxygen atom and a cyclic ether containing one oxygen atom, more preferably contains a cyclic ether containing one oxygen atom, particularly preferably contains at least one of a cyclic ether containing a four-membered ring containing one oxygen atom and a cyclic ether containing a five-membered ring containing one oxygen atom, and most preferably contains at least one selected from tetrahydrofuran (THF), 2-methyltetrahydrofuran (MHF), 3-methyltetrahydrofuran, 2-ethyltetrahydrofuran and 3-ethyltetrahydrofuran.

[0062] It should be noted that the above-mentioned hydrophilic ether solvent (B) may be used alone or in combination of two or more.

[0063] The content of the hydrophilic ether solvent (B) relative to the total mass of the cationic polymerization initiator composition is 2.5% by mass or more, preferably 2.5 to 99% by mass, more preferably 2.5 to 60% by mass, further preferably 2.5 to 40% by mass, particularly preferably 20 to 20% by mass, and most preferably 2.5 to 8% by mass. When two or more hydrophilic ether solvents (B) are present, their total content is preferably within the above range.

[0064] In one embodiment, when the hydrophilic ether solvent (B) contains at least one of a chain ether containing two or more oxygen atoms and a cyclic ether containing two or more oxygen atoms, the content of the hydrophilic ether solvent (B) is preferably 2.5 to 60% by mass, more preferably 2.5 to 20% by mass, and even more preferably 2.5 to 8% by mass, relative to the total mass of the cationic polymerization initiator composition.

[0065] In one embodiment, when the hydrophilic ether solvent (B) contains at least one of a chain ether containing one oxygen atom and a cyclic ether containing one oxygen atom, the content of the hydrophilic ether solvent (B) is preferably 2.5 to 20% by mass, more preferably 2.5 to 8% by mass, and even more preferably 2.5 to 5% by mass, relative to the total mass of the cationic polymerization initiator composition.

[0066] (4) Other solvents

[0067] The cationic polymerization initiator composition may also contain other solvents. It should be noted that "other solvents" in this specification refer to solvents other than the hydrophilic ether solvent (B) that does not have an acetal structure and active hydroxyl groups. By using other solvents, the polymerization reaction can be controlled.

[0068] Examples of other solvents include, but are not limited to, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; and aromatic hydrocarbons such as benzene, toluene, and xylene. These other solvents may be used alone or in combination of two or more.

[0069] The content of the other solvent relative to the total mass of the cationic polymerization initiator composition is preferably 1 to 95% by mass, more preferably 10 to 95% by mass, further preferably 40 to 95% by mass, particularly preferably 70 to 95% by mass, and most preferably 85 to 95% by mass. It should be noted that when two or more other solvents are present, their total content is preferably within the above range.

[0070] (5) Water

[0071] The cationic polymerization initiator composition may further contain water.

[0072] The water is usually derived from water present in the atmosphere or from components contained in the cationic polymerization initiator composition (for example, water derived from tris(pentafluorophenyl)borane (TPB) trihydrate). Alternatively, water may be added proactively as needed.

[0073] The content of water relative to the total mass of the cationic polymerization initiator composition is preferably 1500 ppm or less, more preferably 10 to 1000 ppm, and even more preferably 50 to 750 ppm.

[0074] 2. Method for producing oxymethylene copolymer

[0075] According to one embodiment of the present invention, a method for producing an oxymethylene copolymer is provided. The method comprises a polymerization step of obtaining the oxymethylene copolymer from a reaction solution comprising a polymerization feedstock (C) containing 1,3,5-trioxane and the cationic polymerization initiator composition. Furthermore, the method may further comprise a stabilization step, an additive addition step, etc., as needed.

[0076] (1) Polymerization process

[0077] The polymerization step is a step of obtaining an oxymethylene copolymer from a reaction solution containing a polymerization raw material (C) containing 1,3,5-trioxane (hereinafter also referred to as "trioxane") and a cationic polymerization initiator composition in the step of obtaining the above-mentioned polymer.

[0078] <Reaction Solution>

[0079] The reaction solution contains the polymerization raw material (C) and the above-mentioned cationic polymerization initiator composition.

[0080] [Polymerization raw material (C)]

[0081] The polymerization raw material (C) contains trioxane and may further contain a comonomer, a chain transfer agent, and the like.

[0082] (Trioxane)

[0083] During the polymerization process, trioxane forms the formaldehyde units ([-CH2O-] n ).

[0084] The content of trioxane is preferably 80.0 to 99.9% by mass, more preferably 90.0 to 99.5% by mass, relative to the total mass of the polymerization raw material (C).

[0085] (comonomer)

[0086] The comonomer is a monomer other than trioxane that is copolymerizable with trioxane. It should be noted that the comonomer improves the thermal stability of the oxymethylene copolymer. In addition, the comonomer is present in the oxymethylene copolymer in the form of an amorphous component.

[0087] Examples of the comonomer include, but are not particularly limited to, 1,3-dioxolane, 2-ethyl-1,3-dioxolane, 2-propyl-1,3-dioxolane, 2-butyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-phenyl-2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 2,4-dimethyl-1,3-dioxolane, 2-ethyl-4-methyl-1,3-dioxolane, 4,4-dimethyl-1,3-dioxolane, 4,5-dimethyl-1,3-dioxolane, Comonomers that derive ethylene oxide units, such as pentylene, 2,2,4-trimethyl-1,3-dioxolane, 4-hydroxymethyl-1,3-dioxolane, 4-butoxymethyl-1,3-dioxolane, 4-phenoxymethyl-1,3-dioxolane, 4-chloromethyl-1,3-dioxolane, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, glycidyl methyl ether, ethyl glycidyl ether, butyl glycidyl ether, and phenyl glycidyl ether; and cyclic formals that derive ethylene oxide units from these comonomers. These comonomers may be used alone or in combination of two or more.

[0088] Among them, from the viewpoint of excellent thermal stability and crystallinity, the comonomer is preferably a comonomer that derives oxyethylene units, more preferably contains 1,3-dioxolane and / or ethylene oxide, and further preferably contains 1,3-dioxolane.

[0089] The content of the comonomer is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total mass of the polymerization raw material (C).

[0090] (Chain transfer agent)

[0091] The chain transfer agent has a function of adjusting the molecular weight of the oxymethylene copolymer.

[0092] Examples of chain transfer agents include, but are not limited to, protic compounds such as water, formic acid, methanol, formaldehyde, phenol, and 2,6-dimethylphenol; and ether compounds such as dimethoxymethane (formal), trimethyl orthoformate (methoxyformal), and dibutoxymethane. These chain transfer agents may be used alone or in combination of two or more.

[0093] Among them, the chain transfer agent preferably contains an ether compound, and more preferably contains formal, because the chain ends of the obtained oxymethylene copolymer are capped with stable methoxy groups (-OCH3).

[0094] It should be noted that the chain transfer agent may be a preparation derived from the trioxane production process or a preparation added separately, but is preferably a preparation added separately. Examples of chain transfer agents derived from the trioxane production process include water, formic acid, methanol, and formaldehyde. These chain transfer agents derived from the trioxane production process are preferably removed by purification of the trioxane by distillation or other means prior to the copolymerization reaction.

[0095] [Cationic polymerization initiator composition]

[0096] As the cationic polymerization initiator composition, the above-mentioned composition was used.

[0097] [Composition of reaction solution]

[0098] The composition of the reaction solution can be determined according to the reaction conditions, the physical properties of the desired oxymethylene copolymer, and the like.

[0099] The content of the comonomer in the reaction solution is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7.5 parts by mass, further preferably 0.1 to 5.0 parts by mass, particularly preferably 0.3 to 1.0 parts by mass, based on 100 parts by mass of trioxane.

[0100] The content of the comonomer in the reaction solution is preferably 0.001 to 1 mol, more preferably 0.001 to 0.1 mol, further preferably 0.001 to 0.05 mol, particularly preferably 0.003 to 0.01 mol, based on 1 mol of trioxane.

[0101] The content of the fluorine atom-containing cationic polymerization initiator (A) in the reaction solution is preferably 10 to 100 ppm, more preferably 20 to 80 ppm, and even more preferably 30 to 60 ppm based on trioxane.

[0102] The content of the fluorine atom-containing cationic polymerization initiator (A) in the reaction solution is preferably 0.00001 to 1 mmol, more preferably 0.001 to 0.5 mmol, further preferably 0.005 to 0.1 mmol, and even more preferably 0.01 to 0.05 mmol per 1 mol of trioxane.

[0103] The content of other polymerization initiators in the reaction solution is preferably 10 to 100 ppm, more preferably 20 to 80 ppm, and even more preferably 30 to 60 ppm based on trioxane.

[0104] The content of other polymerization initiators in the reaction solution is preferably 0.00001 to 1 mmol, more preferably 0.001 to 0.5 mmol, further preferably 0.005 to 0.1 mmol, and even more preferably 0.01 to 0.05 mmol, relative to 1 mol of trioxane.

[0105] The content of the hydrophilic ether solvent (B) in the reaction solution is preferably 18 ppm or more, more preferably 18 to 1000 ppm, further preferably 18 to 300 ppm, particularly preferably 18 to 100 ppm, and most preferably 18 to 50 ppm relative to trioxane.

[0106] The content of other solvents in the reaction solution is preferably 10 to 1500 ppm, more preferably 100 to 1000 ppm, further preferably 300 to 900 ppm, and particularly preferably 600 to 800 ppm, based on 1 mol of trioxane.

[0107] The reaction solution is prepared by mixing the polymerizable raw material (C) with the cationic polymerization initiator composition. However, appropriate components (comonomers, chain transfer agents, etc.) may be added to the reaction solution based on the composition of the polymerizable raw material (C) and the cationic polymerization initiator composition. For example, when the total amount of the chain transfer agent in the polymerizable raw material (C) and the cationic polymerization initiator composition is less than a set value, the chain transfer agent content in the reaction solution may be adjusted by adding the chain transfer agent to the reaction solution.

[0108] <Manufacture of oxyethylene copolymer>

[0109] In the polymerization step, an oxymethylene copolymer is obtained from the reaction solution. Specifically, trioxane and a comonomer are copolymerized in the presence of a fluorine-containing cationic polymerization initiator (A) and a hydrophilic ether solvent (B).

[0110] The copolymerization reaction temperature is preferably 50 to 150°C, more preferably 60 to 120°C.

[0111] The copolymerization reaction time is preferably 0.1 to 60 minutes, more preferably 1 to 30 minutes.

[0112] After the copolymerization, it is preferred to terminate the copolymerization reaction by adding a polymerization terminator to inactivate the fluorine-containing cationic polymerization initiator (A) and / or the cationic active species.

[0113] Examples of polymerization terminators include, but are not limited to, triphenylphosphine; ammonia; amines such as diethylamine, triethylamine, and tributylamine; and ethanolamines such as triethanolamine, N-methyldiethanolamine, N,N-diethylhydroxylamine, N-isopropylhydroxylamine, N,N-disteadecylhydroxylamine, and N,N-dibenzylhydroxylamine. These polymerization terminators may be used alone or in combination of two or more.

[0114] The amount of the polymerization terminator added is not particularly limited as long as it is an amount sufficient to deactivate the fluorine-containing cationic polymerization initiator (A). Generally, the amount of the polymerization terminator added is 1.0×10 ﹣1 ~1.0×10 1 range of use.

[0115] The POM content, which is associated with copolymerization yield, is preferably 80% or higher, more preferably 90% or higher, even more preferably 96% or higher, particularly preferably 97% or higher, and most preferably 97.5% or higher. The upper limit of the POM content is 100%. In this specification, "POM content" is measured by the method described in the Examples.

[0116] (2) Chain end stabilization process

[0117] In one embodiment, a chain end stabilization step may be included after the polymerization step. The chain end stabilization step is a step for stabilizing the chain ends of the oxymethylene copolymer.

[0118] <Chain end stabilization>

[0119] The resulting oxymethylene copolymer may have an unstable moiety (-(CH2O) n By performing a chain end stabilization treatment, the unstable portion can be depolymerized and converted into a stable chain end (-CH2CH2OH).

[0120] The chain end stabilization method is preferably, but not particularly limited to, a method of melting and heating the oxymethylene copolymer. Chain end stabilization is generally achieved by melt kneading in an extruder. In this case, chain end stabilization is preferably performed in the presence of at least one selected from a chain end stabilizer, inorganic particles, an antioxidant, and a scavenger.

[0121] [Chain end stabilizer]

[0122] The chain end stabilizer has the function of increasing the cleavage rate of the unstable portion in the oxymethylene copolymer.

[0123] Examples of chain end stabilizers include, but are not particularly limited to, ammonia; amines such as trimethylamine, triethylamine, and tributylamine; and hydroxides, hydrogenates (such as hydrochlorides and hydrobromides), oxoacid salts (such as sulfates, nitrates, and carbonates), and carboxylates (such as formates, acetates, propionates, benzoates, and oxalates) of quaternary ammoniums such as tetramethylammonium, tetraethylammonium, ethyltrimethylammonium, trimethyl(2-hydroxyethyl)ammonium, triethyl(2-hydroxyethyl)ammonium, tripropyl(2-hydroxyethyl)ammonium, benzyltrimethylammonium, benzyltriethylammonium, and benzyltripropylammonium. These chain end stabilizers may be used alone or in combination of two or more.

[0124] Among them, the chain end stabilizer preferably contains a quaternary ammonium salt, more preferably contains at least one of the hydroxide salts of tetramethylammonium, tetraethylammonium, ethyltrimethylammonium, trimethyl(2-hydroxyethyl)ammonium, triethyl(2-hydroxyethyl)ammonium, tripropyl(2-hydroxyethyl)ammonium, benzyltrimethylammonium, benzyltriethylammonium, and benzyltripropylammonium.

[0125] The amount of the chain end stabilizer added is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the oxymethylene copolymer.

[0126] [Inorganic particles]

[0127] The inorganic particles have a function of improving the thermal stability of the obtained oxymethylene copolymer.

[0128] Examples of the inorganic particles include, but are not limited to, talc, mica, wollastonite, silica, layered double hydroxides, calcium carbonate, magnesium hydroxide, calcium hydroxide, etc. These inorganic particles may be used alone or in combination of two or more.

[0129] Among them, the inorganic particles are preferably at least one selected from talc, mica, and layered double hydroxides, and more preferably contain layered double hydroxides.

[0130] The amount of the inorganic particles added is preferably 0.0001 to 1 part by mass, more preferably 0.005 to 0.5 part by mass, and even more preferably 0.01 to 0.2 part by mass, relative to 100 parts by mass of the oxymethylene copolymer.

[0131] [Antioxidants]

[0132] The antioxidant has a function of preventing the obtained oxymethylene copolymer from being oxidized.

[0133] As the antioxidant, hindered phenols may be mentioned but are not particularly limited. Examples of the hindered phenol include n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate, n-octadecyl-3-(3'-methyl-5'-tert-butyl-4'-hydroxyphenyl) propionate, n-tetradecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate, 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,4-butanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], tetrakis[methylene-3-(3'-tert-butyl-4-hydroxyphenyl) propionate]methane, and N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazide. These antioxidants may be used alone or in combination of two or more.

[0134] Among them, the antioxidant preferably contains triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate].

[0135] The amount of the antioxidant added is preferably 0.0001 to 1 part by mass, more preferably 0.001 to 5 parts by mass, and even more preferably 0.003 to 3 parts by mass, relative to 100 parts by mass of the oxymethylene copolymer.

[0136] [Collector]

[0137] The trapping agent has a function of trapping formic acid and / or formaldehyde generated by the decomposition of at least a portion of the oxymethylene copolymer.

[0138] Examples of the collector include, but are not particularly limited to, polyamide resins such as nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 6T, and nylon 612; amide compounds such as stearyl stearamide, stearyl oleamide, stearyl erucamide, ethylenediamine-distearamide, and ethylenediamine-dibehenamide; urea compounds such as urea, N-phenylurea, N,N'-diphenylurea, N-phenylthiourea, and N,N'-diphenylthiourea; and triazine compounds such as melamine, benzoguanamine, N-phenylmelamine, melem, N,N'-diphenylmelamine, N-methylolmelamine, N,N'-trimethylolmelamine, and 2,4-diamino-6-cyclohexyltriazine. These collectors may be used alone or in combination of two or more.

[0139] Among these, the collector preferably contains a urea compound and / or a triazine compound, more preferably contains a triazine compound, and even more preferably contains melamine.

[0140] The amount of the scavenger added is preferably 0.0001 to 10 parts by mass, more preferably 0.001 to 5 parts by mass, and even more preferably 0.003 to 3 parts by mass, relative to 100 parts by mass of the oxymethylene copolymer.

[0141] [Conditions for chain end stabilization]

[0142] The chain end stabilization temperature is preferably, but not particularly limited to, 260°C or lower, more preferably 240°C or lower. The lower limit of the chain end stabilization temperature is not particularly limited, as long as it is at least the melting point of the oxymethylene copolymer, but is preferably 150°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher. In one embodiment, the chain end stabilization temperature is preferably 150-260°C, more preferably 180-260°C, and even more preferably 200-240°C.

[0143] The chain end stabilization time is preferably, but not particularly limited to, 1 minute to 3 hours, more preferably 2 minutes to 1 hour, and even more preferably 3 minutes to 30 minutes.

[0144] Chain end stabilization may also be performed under reduced pressure. In this case, the chain end stabilization pressure is preferably, but not particularly limited to, 10 to 100 kPa, more preferably 10 to 80 kPa, and even more preferably 10 to 50 kPa.

[0145] (3) Additive Addition Process

[0146] In one embodiment, an additive adding step may be included after the polymerization step or the chain end stabilization step. The additive adding step is a step of adding additives to the oxymethylene copolymer.

[0147] Examples of the additives include, but are not limited to, the stabilizers, inorganic particles, antioxidants, and scavengers mentioned above, colorants, plasticizers, release agents, fluorescent brighteners, and antistatic agents.

[0148] The physical properties can be adjusted by adding additives to the oxymethylene copolymer.

[0149] 3. Manufacturing method of molded products

[0150] According to one embodiment of the present invention, a method for producing a molded article is provided, wherein the method comprises the step of molding the oxymethylene copolymer produced by the above method.

[0151] Since the oxymethylene copolymer produced by the above method has high physical properties, the molded articles using the copolymer also have high physical properties. Such molded articles are suitable for high-performance and high-functional fibers, films, gears, bearings, etc.

[0152] Example

[0153] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[0154] [Example 1]

[0155] A cationic polymerization initiator composition is prepared by mixing boron trifluoride diethyl ether complex (BF3·Et2O) as a cationic polymerization initiator (A) containing fluorine atoms, 1,2-dimethoxyethane (DME) as a hydrophilic ether solvent (B) without an acetal structure and active hydroxyl groups, and benzene as another solvent in proportions of 7.1 mass%, 3 mass% and 89.9 mass%, respectively.

[0156] Furthermore, the water content in the cationic polymerization initiator composition was measured using a Karl Fischer moisture meter and found to be 288 ppm.

[0157] [Example 2]

[0158] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that the DME content was changed to 25% by mass and the benzene content was changed to 67.9% by mass.

[0159] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 327 ppm.

[0160] [Example 3]

[0161] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that the DME content was changed to 92.9% by mass and the benzene content was changed to 0% by mass.

[0162] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 332 ppm.

[0163] [Example 4]

[0164] A cationic polymerization initiator composition was produced in the same manner as in Example 1, except that 1,4-dioxane (DOX) was used instead of DME.

[0165] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 326 ppm.

[0166] [Example 5]

[0167] A cationic polymerization initiator composition was produced in the same manner as in Example 4 except that the DOX content was changed to 25% by mass and the benzene content was changed to 67.9% by mass.

[0168] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 340 ppm.

[0169] [Example 6]

[0170] A cationic polymerization initiator composition was produced in the same manner as in Example 4 except that the DOX content was changed to 92.9% by mass and the benzene content was changed to 0% by mass.

[0171] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 348 ppm.

[0172] [Example 7]

[0173] A cationic polymerization initiator composition was produced in the same manner as in Example 1, except that tetrahydrofuran (THF) was used instead of DME.

[0174] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 306 ppm.

[0175] [Example 8]

[0176] A cationic polymerization initiator composition was produced in the same manner as in Example 7 except that the THF content was changed to 10% by mass and the benzene content was changed to 82.9% by mass.

[0177] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 327 ppm.

[0178] [Example 9]

[0179] A cationic polymerization initiator composition was produced in the same manner as in Example 7 except that the THF content was changed to 25% by mass and the benzene content was changed to 67.9% by mass.

[0180] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 351 ppm.

[0181] [Example 10]

[0182] A cationic polymerization initiator composition was prepared in the same manner as in Example 1 except that 0.3% by mass of tris(pentafluorophenyl)borane trihydrate (TPB·3H 2 O) was added as the fluorine-containing cationic polymerization initiator (A) and the benzene content was changed to 89.6% by mass.

[0183] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 642 ppm.

[0184] [Example 11]

[0185] A cationic polymerization initiator composition was produced in the same manner as in Example 10 except that the DME content was changed to 10% by mass and the benzene content was changed to 82.6% by mass.

[0186] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 659 ppm.

[0187] [Example 12]

[0188] A cationic polymerization initiator composition was produced in the same manner as in Example 10 except that the DME content was changed to 92.6% by mass and the benzene content was changed to 0% by mass.

[0189] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 662 ppm.

[0190] [Comparative Example 1]

[0191] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that the DME content was changed to 0% by mass and the benzene content was changed to 92.9% by mass.

[0192] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 276 ppm.

[0193] [Comparative Example 2]

[0194] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that the DME content was changed to 2.2% by mass and the benzene content was changed to 90.7% by mass.

[0195] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 291 ppm.

[0196] [Comparative Example 3]

[0197] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that TPB·3H 2 O was added at a ratio of 0.3 mass %, the DME content was changed to 0 mass %, and the benzene content was changed to 92.6 mass %.

[0198] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 619 ppm.

[0199] [Comparative Example 4]

[0200] A cationic polymerization initiator composition was produced in the same manner as in Example 1 except that TPB·3H 2 O was added at a ratio of 0.3 mass %, the DME content was changed to 2.2 mass %, and the benzene content was changed to 90.4 mass %.

[0201] Furthermore, the water content in the cationic polymerization initiator composition was measured in the same manner as in Example 1 and found to be 595 ppm.

[0202] The cationic polymerization initiator compositions produced in Examples 1 to 12 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0203] [Table 1]

[0204]

[0205] The structural formulas of dimethoxyethane (DME), 1,4-dioxane (DOX), and tetrahydrofuran (THF) as the hydrophilic ether solvent (B) are shown below.

[0206]

[0207] [evaluate]

[0208] The metal corrosiveness of the cationic polymerization initiator compositions produced according to Examples 1 to 12 and Comparative Examples 1 to 4, as well as the POM content and melt flow rate (MFR) of the resulting oxymethylene copolymers, were evaluated. In the following description, the oxymethylene copolymers before chain end stabilization are sometimes referred to as "crude oxymethylene copolymers."

[0209] (Metal Corrosion)

[0210] Two SUS304 (Cr-Ni austenitic stainless steel) flat plates, 20 mm wide, 30 mm long, and 1.5 mm thick, were welded together on both sides of their short sides (20 mm) using a SUS304 welding rod. Both sides were then polished. The welded and polished SUS plates were degreased with acetone and dried to obtain "test pieces before metal corrosion testing."

[0211] The test piece and 100 mL of the cationic polymerization initiator composition were placed in a 100 mL screw-cap bottle, sealed, and allowed to stand in a dark place at 23°C. After 40 days, the test piece was removed from the cationic polymerization initiator composition, washed with acetone, and dried to obtain a "test piece after metal corrosion test."

[0212] The weight loss rate (%) of the test piece was calculated based on the following formula.

[0213] Weight loss rate (%) = (W1-W2) / (W1)×100

[0214] At this time, W1 is the weight (g) of the “test piece before the metal corrosion test”, and W2 is the weight (g) of the “test piece after the metal corrosion test”.

[0215] The metal corrosion properties of the cationic polymerization initiator compositions were evaluated according to the following criteria. The results are shown in Table 3 below.

[0216] ○: Weight loss rate 0.02% or less

[0217] ×: Weight loss rate is higher than 0.02%

[0218] The cationic polymerization initiator composition was also recovered after the test piece was removed from the metal corrosion test. Hereinafter, the cationic polymerization initiator composition after the metal corrosion test will also be referred to as the "cationic polymerization initiator composition (after the metal corrosion test)." Furthermore, the cationic polymerization initiator composition before the metal corrosion test will also be referred to as the "cationic polymerization initiator composition (before the metal corrosion test)."

[0219] (Crude oxymethylene copolymer (POM) content)

[0220] (1) POM content of cationic polymerization initiator composition (before metal corrosion test)

[0221] To a jacketed batch reactor (5 L capacity) heated by passing 65°C hot water through the jacket, 1200 g of 1,3,5-trioxane (TOX), 48 g of 1,3-dioxolane as a comonomer, and 300 ppm of formal as a chain transfer agent relative to 1,3,5-trioxane were added. While the contents were stirred and mixed with a stirring blade rotating at 60 rpm, a cationic polymerization initiator composition (before metal corrosion testing) was injected to initiate polymerization. Fifteen minutes after the start of the polymerization reaction, the stirring blades in the batch reactor were stopped to obtain a crude oxymethylene copolymer as the reactant.

[0222] The polymerization reaction conditions are shown in Table 2 below. In Table 2, "ppm-TOX" refers to the amount of each component added (ppm) relative to the amount of 1,3,5-trioxane added. "mmol / mol-TOX" refers to the amount of each component added (mmol) relative to 1 mol of 1,3,5-trioxane added.

[0223] [Table 2]

[0224]

[0225] After the polymerization reaction, a portion of the coarse granular oxymethylene copolymer was collected from the reactor. The collected coarse granular oxymethylene copolymer was then washed twice with acetone, pulverized using a sample mill, and dried in a vacuum dryer at 60°C for 2 hours. This removed the acetone and any remaining unreacted monomers.

[0226] The content (mass %) of the crude oxymethylene copolymer (POM) contained in the coarse granular crude oxymethylene copolymer was calculated by the following formula.

[0227] POM content (mass %) = (B / A) × 100

[0228] In this case, A is the mass (g) of the crude oxymethylene copolymer before the removal of the unreacted monomers, and B is the mass (g) of the crude oxymethylene copolymer after the removal of the unreacted monomers.

[0229] The POM content was evaluated according to the following criteria. It should be noted that a higher POM content indicates less unreacted monomer and a more complete polymerization reaction. The results are shown in Table 3 below.

[0230] ◎: POM content is 97.5% by mass or more

[0231] ○: POM content is 97% by mass or more and less than 97.5% by mass

[0232] △: POM content is 96% by mass or more and less than 97% by mass

[0233] ×: POM content is less than 96% by mass

[0234] (2) POM content of cationic polymerization initiator composition (after metal corrosion test)

[0235] The POM content was evaluated in the same manner using the cationic polymerization initiator composition (after the metal corrosion test) instead of the cationic polymerization initiator composition (before the metal corrosion test). The results are shown in Table 3 below.

[0236] (3) Determination of POM content change rate

[0237] The change rate (%) of the POM content was calculated by the following formula.

[0238] Change rate (%) = (POM content after metal corrosion test - POM content before metal corrosion test) / (POM content before metal corrosion test) × 100

[0239] The rate of change was evaluated according to the following criteria. It should be noted that the lower the rate of change (the less negative the value), the less likely the metal component dissolved into the cationic polymerization initiator composition by the metal corrosion test will hinder the polymerization reaction. The results are shown in Table 3 below.

[0240] ◎: -0.2% or more

[0241] ○: -0.5% or more, less than -0.2%

[0242] △: -0.8% or more, less than -0.5%

[0243] ×: Less than -0.8%

[0244] (Melt Flow Rate (MFR))

[0245] (1) MFR of the cationic polymerization initiator composition (before metal corrosion test)

[0246] Polymerization was carried out in the same manner as described for the POM content of the cationic polymerization initiator composition (before metal corrosion test). The resulting crude oxymethylene copolymer was inactivated and chain-end stabilized with a fluorine-containing cationic polymerization initiator (A), and then the melt flow rate (MFR) was measured.

[0247] The deactivation and chain end stabilization of the fluorine-containing cationic polymerization initiator (A) were performed as follows. The coarse granular oxymethylene copolymer collected from the reactor after the polymerization reaction was wet-pulverized in a 1% triethylamine solution (water:methanol = 1:4 (volume ratio)), washed twice with acetone, and vacuum-dried in a vacuum dryer at 60°C for 2 hours. To 100 parts by weight of the dried powdered oxymethylene copolymer were added 0.3 parts by weight of triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (Irganox (registered trademark) 245, manufactured by BASF Japan Ltd.) and 0.05 parts by weight of melamine (manufactured by Mitsui Chemicals, Inc.), and the mixture was melt-kneaded at 220°C for 20 minutes using a heated kneader (Labo Plastomill 4C150, manufactured by Toyo Seiki Seisaku-sho, Ltd.).

[0248] The MFR (g / 10 min) of the chain-end-stabilized oxymethylene copolymer was measured in accordance with ASTM-D1238 (190° C., under a load of 2.16 kg).

[0249] MFR was evaluated according to the following criteria. It should be noted that a smaller MFR indicates a larger molecular weight. The results are shown in Table 3 below.

[0250] ◎: MFR below 6.1g / 10min

[0251] ○: MFR higher than 6.1 g / 10 minutes and lower than 6.2 g / 10 minutes

[0252] △: MFR higher than 6.2g / 10min and lower than 7.0g / 10min

[0253] ×: MFR exceeds 7.0 g / 10 min

[0254] (2) MFR of the cationic polymerization initiator composition (after metal corrosion test)

[0255] The MFR evaluation was similarly performed using the cationic polymerization initiator composition (after the metal corrosion test) instead of the cationic polymerization initiator composition (before the metal corrosion test). The results are shown in Table 3 below.

[0256] (3) Determination of MFR change rate

[0257] The MFR change rate (%) was calculated by the following formula.

[0258] Change rate (%) = (MFR after metal corrosion test - MFR before metal corrosion test) / (MFR before metal corrosion test) × 100

[0259] The rate of change was evaluated according to the following criteria. It should be noted that the lower the rate of change (the smaller the positive value), the less likely the metal component dissolved into the cationic polymerization initiator composition by the metal corrosion test will hinder the polymerization reaction. The results are shown in Table 3 below.

[0260] ◎: 3% or less

[0261] ○: More than 3% and less than 5%

[0262] △: higher than 5% and lower than 7%

[0263] ×: More than 7%

[0264] [Table 3]

[0265]

[0266] The results in Table 3 show that the cationic polymerization initiator compositions of Examples 1 to 12 can prevent metal corrosion. Furthermore, since the rate of change in POM content is low, the elution of metal components can be suppressed by preventing metal corrosion, thereby minimizing hindrance to the polymerization reaction. Furthermore, since the rate of change in MFR is low, it can be seen that the deterioration of the physical properties of the resulting oxymethylene copolymer can be suppressed.

Claims

1. A cationic polymerization initiator composition, characterized in that: It contains a cationic polymerization initiator A containing fluorine atoms and a hydrophilic ether solvent B having no acetal structure and no active hydroxyl group. The content of the hydrophilic ether solvent B is 2.5% by mass or more relative to the total mass of the cationic polymerization initiator composition.

2. The cationic polymerization initiator composition according to claim 1, wherein: The fluorine-containing cationic polymerization initiator A includes a boron trifluoride compound.

3. The cationic polymerization initiator composition according to claim 2, wherein: The fluorine-atom-containing cationic polymerization initiator A includes a fluorinated arylboron compound.

4. The cationic polymerization initiator composition according to claim 1, wherein: The hydrophilic ether solvent B includes at least one of a chain ether containing two or more oxygen atoms and a cyclic ether containing two or more oxygen atoms.

5. The cationic polymerization initiator composition according to claim 4, wherein: The content of the hydrophilic ether solvent B is 2.5 to 60% by mass relative to the total mass of the cationic polymerization initiator composition.

6. The cationic polymerization initiator composition according to claim 1, wherein: The hydrophilic ether solvent B includes at least one of a chain ether containing one oxygen atom and a cyclic ether containing one oxygen atom.

7. The cationic polymerization initiator composition according to claim 6, wherein: The content of the hydrophilic ether solvent B is 2.5 to 20% by mass relative to the total mass of the cationic polymerization initiator composition.

8. A method for producing an oxymethylene copolymer, characterized in that: The invention comprises a polymerization step of obtaining an oxymethylene copolymer from a reaction solution comprising a polymerization raw material C containing 1,3,5-trioxane and the cationic polymerization initiator composition according to any one of claims 1 to 7.

9. The manufacturing method according to claim 8, wherein: The content of the hydrophilic ether solvent B in the reaction solution is 18 ppm or more relative to 1,3,5-trioxane.

10. The manufacturing method according to claim 9, wherein: The content of the hydrophilic ether solvent B in the reaction solution is 18 to 100 ppm relative to 1,3,5-trioxane.

11. A method for manufacturing a molded product, characterized in that: The method comprises the step of molding the oxymethylene copolymer produced by the method according to claim 8.

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