Method for producing polyacetal resin composition and polyacetal resin composition

Abstract

Provided are: a method for producing a polyacetal resin composition in which the amount of formaldehyde generated and mold deposits are reduced; and a polyacetal resin composition. More specifically, provided is a method for producing a polyacetal resin composition by using a hindered phenol compound (B) having no isocyanuric acid skeleton and an inorganic filler (D) having a pH of 8 or higher, the method including: a polymerization step for obtaining a crude oxymethylene copolymer (A) by polymerizing trioxane with 1,3-dioxolane as a comonomer in the presence of a catalyst; and a melt kneading step for obtaining a polyacetal resin by adding the hindered phenol compound (B) having no isocyanuric acid skeleton and the inorganic filler (D) having a pH of 8 or higher to the crude oxymethylene copolymer (A) and melt kneading the resulting mixture. In the method, the catalyst is used in an amount of 0.035 mmol or less relative to 1 mol of trioxane, the hindered phenol compound (B) having no isocyanuric acid skeleton is used in an amount of 0.1-1.0 part by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A), the inorganic filler (D) having a pH of 8 or higher is used in an amount of 0.005-0.12 part by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A), and the amount of melamine (C) added in the melt kneading step is less than 0.03 part by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A). Also more specifically, provided is a polyacetal resin composition which is obtained by the method.

Description

Method for producing polyacetal resin composition and polyacetal resin composition

[0001] The present invention relates to a method for producing a polyacetal resin composition and a polyacetal resin composition. More specifically, the present invention relates to a method for producing a polyacetal resin composition with reduced formaldehyde emission and reduced mold deposit, and to the polyacetal resin composition. The present invention also relates to pellets, molded articles, vehicle components and the like formed from the above polyacetal resin composition.

[0002] Polyacetal resin, also called oxymethylene polymer, includes homopolymers formed by polymerization of formaldehyde, and copolymers formed by polymerization of a cyclic oligomer such as trioxane and a comonomer. Polyacetal resin has an excellent balance of mechanical properties, chemical resistance, slidability and the like, and is easy to process. Therefore, as a representative engineering plastic, it is widely used mainly in various electrical and electronic parts, automotive parts and other various mechanical parts.

[0003] However, polyacetal resin undergoes slight thermal decomposition due to thermal history during resin production, processing and molding and the like. As a result, even an extremely small amount of formaldehyde is generated, which causes contamination of molding dies and deterioration of the working (hygienic) environment during molding. In addition, it is considered that formaldehyde generated from resin products may cause sick house syndrome and the like. In response to such a situation, the Ministry of Health, Labour and Welfare has issued a guideline value for formaldehyde concentration in buildings (upper limit of 0.08 ppm), and further reduction of formaldehyde emission from polyacetal resin molded articles is required.

[0004] Therefore, various methods have been proposed to improve the thermal stability of polyoxymethylene copolymers. One method for improving thermal stability is to add additives such as amines, amides, and hydrazides that can react with decomposition gases such as formaldehyde generated by thermal decomposition. It is well known that the generation of formaldehyde from pellets and molded products can be suppressed by blending additives into polyacetal resins, and various additives have been considered since the beginning. Examples of such additives have been proposed, including melamine-formaldehyde polymers (Patent Document 1), polyamine reaction products obtained by reacting ammonia or its derivatives with a reaction product of polyamine and cyanuryl chloride (Patent Document 2), dicyandiamide compounds (Patent Document 3), silane compounds (Patent Document 4), nitrogen-containing compounds-borates (Patent Document 5), glyoxydiureide compounds (Patent Document 6), urea derivatives and / or amidine derivatives (Patent Document 7), condensates of phenols, basic nitrogen-containing compounds and aldehydes (Patent Document 8), and triazine ring-containing spiro compounds (Patent Document 9).

[0005] However, the above methods only address one of two issues: either suppressing formaldehyde generation or improving moldability by suppressing the generation of mold deposits due to additive bleed-out.

[0006] Therefore, the development of polyacetal resin compositions that reduce formaldehyde emissions and mold deposits remains highly desirable.

[0007] JP 5-271516 JP 7-207118 JP 8-208946 JP 9-235447 JP 10-3663 No. 0 JP 10-182928 JP 2000-34417 JP 2002-212384 JP 2003-113289

[0008] The present invention provides a method for producing a polyacetal resin composition with reduced formaldehyde emissions and mold deposits, as well as a polyacetal resin composition.

[0009] As a result of diligent research, the inventors have developed a method for producing a polyacetal resin composition and a polyacetal resin composition that reduces formaldehyde emissions and mold deposits. In other words, the present invention includes the following embodiments. <1> A method for producing a polyacetal resin composition using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher, wherein the method comprises: a polymerization step of obtaining a crude oxymethylene copolymer (A) by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst; and a melt-kneading step of obtaining a polyacetal resin by adding the hindered phenol compound (B) that does not have an isocyanuric acid skeleton and the inorganic filler (D) with a pH of 8 or higher to the crude oxymethylene copolymer (A) and melt-kneading, wherein the catalyst is used in an amount of 0.035 mmol or less per 1 mol of trioxane, and the hindered phenol compound (B) that does not have an isocyanuric acid skeleton is used in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). A method wherein the inorganic filler (D) with a pH of 8 or higher is used in an amount of 0.005 to 0.12 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A), and the amount of melamine (C) added in the melt-kneading step is less than 0.03 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). <2> The method according to <1>, wherein the mass ratio (B / D) of the hindered phenol compound (B) that does not have an isocyanuric acid skeleton to the inorganic filler (D) with a pH of 8 or higher is 2.5 to 100. <3> The method according to <1> or <2>, wherein the inorganic filler (D) with a pH of 8 or higher is one or more selected from the group consisting of hydrotalcite, talc, and magnesium hydroxide. <4> The method according to any one of <1> to <3>, wherein in the melt-kneading step, the melt-kneading time is 10 minutes to 60 minutes and the melt-kneading temperature is 220°C to 240°C. <5> The method according to any one of <1> to <4>, wherein melamine (C) is not added in the melting and kneading step.<6> A method for producing the polyacetal resin composition according to any one of <1> to <5>, wherein the polyacetal resin composition has a formaldehyde emission of 15 ppm or less, as measured according to the German Automotive Industry Association standard VDA275. <7> The method according to any one of <1> to <6>, wherein the pH of the inorganic filler (C) is the pH of the supernatant liquid obtained after adding 2 g of the inorganic filler to 100 g of water and stirring. <8> A polyacetal resin composition produced by the method according to any one of <1> to <7>. <9> A pellet formed from the polyacetal resin composition according to <8>. <10> A molded article formed from the polyacetal resin composition according to <8>. <11> A vehicle component formed from the polyacetal resin composition according to <8>. <12> The polyacetal resin composition according to <8>, wherein the amount of formaldehyde emitted by the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA275, is 15 ppm or less. <13> The polyacetal resin composition according to <8> or <12>, wherein the melt-kneading time of the polyacetal resin composition is 10 minutes to 60 minutes. <14> The polyacetal resin composition according to <8>, <12>, or <13>, wherein the melt-kneading temperature of the polyacetal resin composition is 220°C to 240°C.

[0010] By using the method for producing the polyacetal resin composition of the present invention, it is possible to produce a polyacetal resin composition that reduces formaldehyde emissions and mold deposits.

[0011] This is a teardrop-shaped mold designed to introduce a resin composition from gate G and to easily accumulate generated gas at the tip P.

[0012] The present invention will be described in detail below. However, the following description is not intended to be interpreted as limiting the present invention.

[0013] <1> Polyacetal Resin Composition The polyacetal resin composition in the present invention comprises a polyacetal resin (A), a hindered phenol compound (B) that does not have an isocyanuric acid skeleton, and an inorganic filler (D) with a pH of 8 or higher. The following describes each component.

[0014] <1-1> Polyacetal resin (A) The polyacetal resin used in the present invention is -(-O-CRH-) n Polyacetal resins are polymers having repeating acetal structures represented by - (wherein R represents a hydrogen atom or an organic group), and typically have oxymethylene groups (-CH2O-) where R is a hydrogen atom as the main constituent unit. The polyacetal resins used in the present invention may be homopolymers consisting only of these oxymethylene units, as well as copolymers (block copolymers) or terpolymers containing constituent units other than oxymethylene units, and may have not only linear structures but also branched and crosslinked structures.

[0015] Other constituent units besides oxymethylene units include oxyalkylene groups having 2 to 10 carbon atoms, such as oxyethylene groups (-CH2CH2O-), oxypropylene groups (-CH2CH2CH2O-), and oxybutylene groups (-CH2CH2CH2CH2O-), which may be branched. Among these, branched oxyalkylene groups having 2 to 4 carbon atoms are preferred, and oxyethylene groups are particularly preferred. The content of oxyalkylene groups other than oxymethylene groups in the polyacetal resin is usually 0.1 to 20% by mass. The content of oxyalkylene groups having 2 or more carbon atoms in the oxymethylene copolymer is: １ It can be measured by H-NMR.

[0016] Several methods for producing polyacetal resins are known, but in the present invention, polyacetal resins produced by any of these methods can be used. For example, a polyacetal resin having an oxymethylene group and an oxyalkylene group having 2 to 4 carbon atoms as constituent units can be produced by copolymerizing a cyclic oligomer of an oxymethylene group, such as a trimer (trioxane) or tetramer (tetraoxane) of formaldehyde, with a cyclic oligomer containing an oxyalkylene group having 2 to 4 carbon atoms, such as ethylene oxide, 1,3-dioxolane, 1,3,6-trioxocane, or 1,3-dioxepane. As the polyacetal resin, it is preferable to use a copolymer of a cyclic oligomer such as trioxane or tetraoxane with ethylene oxide or 1,3-dioxolane, and it is particularly preferable to use a copolymer of trioxane and 1,3-dioxolane. The melt index of polyacetal resin (ASTM-D1238 standard: 190°C, 2.16 kg) is usually 1 to 100 g / 10 min, but 0.5 to 80 g / 10 min is preferred.

[0017] <1-2> Hindered phenol compound without an isocyanuric acid skeleton (B) The polyacetal resin composition of the present invention is produced using a hindered phenol compound without an isocyanuric acid skeleton and an inorganic filler with a pH of 8 or higher. In the method for producing the polyacetal resin composition of the present invention, by using a hindered phenol compound without an isocyanuric acid skeleton, a polyacetal resin with appropriate thermal stability can be obtained.

[0018] The isocyanuric acid-free hindered phenol compound that can be used in the production of the polyacetal resin composition of the present invention is a bulky phenol compound that does not have an isocyanuric acid skeleton. The isocyanuric acid-free hindered phenol compound that can be used in the production of the polyacetal resin composition of the present invention may also be a hindered phenol antioxidant.

[0019] Examples of hindered phenol compounds that do not have an isocyanuric acid skeleton and can be used in the production of the polyacetal resin composition of the present invention include ethylenebis(oxyethylene)bis-(3-5-t-butyl-4-hydroxy-m-tolyl)propionate) (Irganox® 245), pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox® 1010), N,N'-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)) (Irganox® 1098), and octadecyl-3-(3,5-di-tert-butyl-4) -Hydroxyphenyl)-propionate (Irganox® 1076), benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester (Irganox® 1135), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (Irganox® 1330), hexamethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox® 259); 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide (Sonox® 1024); 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol) (Adekastab® AO-30); 6,6'-di-tert-butyl-4,4'-butylenedi-m-cresol (Adekastab® AO-40); 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane (Adekastab® AO-80); etc. may be used, but are not limited to these.

[0020] In preferred embodiments, hindered phenol compounds without an isocyanuric acid skeleton that can be used in the production of the polyacetal resin composition of the present invention include ethylenebis(oxyethylene)bis-(3-5-t-butyl-4-hydroxy-m-tolyl)propionate, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), N,N'-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, and hexamethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide; 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol), 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane; etc. may be used.

[0021] In a more preferred embodiment, hindered phenol compounds without an isocyanuric acid skeleton that can be used in the production of the polyacetal resin composition of the present invention include ethylenebis(oxyethylene)bis-(3-5-t-butyl-4-hydroxy-m-tolyl)propionate, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), N,N'-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide; 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol), 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane; etc. may be used.

[0022] The amount of hindered phenol compound without an isocyanuric acid skeleton that can be used in the production of the polyacetal resin composition of the present invention will be described later.

[0023] <1-3> Inorganic Filler (D) The polyacetal resin composition of the present invention is produced using a hindered phenol compound that does not have an isocyanuric acid skeleton and an inorganic filler with a pH of 8 or higher. In the method for producing the polyacetal resin composition of the present invention, the amount of formaldehyde generated can be suppressed by using an inorganic filler with a pH of 8 or higher.

[0024] The pH of the inorganic filler that can be used in the production of the polyacetal resin composition of the present invention is the pH of the supernatant liquid obtained after adding 2 g of the inorganic filler to 100 g of water and stirring. The method for measuring the pH of the inorganic filler will be described later.

[0025] Inorganic fillers with a pH of 8 or higher that can be used in the production of the polyacetal resin composition of the present invention include, but are not limited to, hydrotalcite (pH: 8), talc (pH: 9), magnesium hydroxide (pH: 10), calcium carbonate (pH: 10), and magnesium oxide (pH: 10). In a preferred embodiment, the inorganic filler with a pH of 8 or higher that can be used in the production of the polyacetal resin composition of the present invention is one or more selected from the group consisting of hydrotalcite (pH: 8), talc (pH: 9), and magnesium hydroxide (pH: 10).

[0026] In the method for producing the polyacetal resin composition of the present invention, the mass ratio (hindered phenol compound / inorganic filler) of the hindered phenol compound without an isocyanuric acid skeleton to the inorganic filler with a pH of 8 or higher is 2.5 to 100. In the method for producing the polyacetal resin composition of the present invention, the mass ratio (hindered phenol compound / inorganic filler) of the hindered phenol compound without an isocyanuric acid skeleton to the inorganic filler with a pH of 8 or higher may be, for example, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100.

[0027] In the method for producing the polyacetal resin composition of the present invention, the mass ratio (hindered phenol compound / inorganic filler) of the hindered phenol compound that does not have an isocyanuric acid skeleton to the inorganic filler with a pH of 8 or higher is, for example, 2.5 to 3.0, 2.5 to 3.5, 2.5 to 4.0, 2.5 to 4.5, 2.5 to 5.0, 2.5 to 5.5, 2.5 to 6.0, 2.5 to 6.5, 2.5 to 7.0, 2.5 to 7.5, 2.5 to 8.0, 2.5 to 8.5, 2.5 to 9.0, 2.5 to 9.5, 2.5 to 10, 2.5 to 15, 2.5-20, 2.5-25, 2.5-30, 2.5-35, 2.5-40, 2.5-45, 2.5-50, 2.5-55, 2.5-60, 2.5-65, 2.5-70, 2.5-75, 2.5-80, 2.5-85, 2.5-90, 2.5-95, 2.5-100; 3.0-3.5, 3.0-4.0, 3.0-4.5, 3.0-5.0, 3.0-5.5, 3.0-6.0, 3.0-6.5, 3.0-7.0, 3.0-7.5, 3.0-8.0, 3.0-8.5, 3.0-9.0, 3.0-9.5, 3.0-10, 3.0-15, 3.0-20, 3.0-25, 3.0-30, 3.0-35, 3.0-40, 3.0-45, 3.0-50, 3.0-55, 3.0-60, 3.0-65, 3.0-70, 3.0-75, 3.0-80, 3.0-85, 3.0-90, 3.0-95, 3.0-100; 3.5-4.0, 3.5-4.5, 3.5-5.0, 3.5-5.5, 3.5-6.0, 3.5-6.5, 3.5-7.0, 3.5-7.5, 3.5-8.0, 3.5-8.5, 3.5-9.0, 3.5-9.5, 3.5-10, 3.5-15, 3.5-20, 3.5-25, 3.5-30, 3.5-35, 3.5-40, 3.5-45, 3.5-50, 3.5-55, 3.5-60, 3.5-65, 3.5-70, 3.5-75, 3.5-80, 3.5-85, 3.5-90, 3.5-95, 3.5-100;　４．０～４．５、４．０～５．０、４．０～５．５、４．０～６．０、４．０～６．５、４．０～７．０、４．０～７．５、４．０～８．０、４．０～８．５、４．０～９．０、４．０～９．５、４．０～１０、４．０～１５、４．０～２０、４．０～２５、４．０～３０、４．０～３５、４．０～４０、４．０～４５、４．０～５０、４．０～５５、４．０～６０、４．０～６５、４．０～７０、４．０～７５、４．０～８０、４．０～８５、４．０～９０、４．０～９５、４．０～１００； 　４．５～５．０、４．５～５．５、４．５～６．０、４．５～６．５、４．５～７．０、４．５～７．５、４．５～８．０、４．５～８．５、４．５～９．０、４．５～９．５、４．５～１０、４．５～１５、４．５～２０、４．５～２５、４．５～３０、４．５～３５、４．５～４０、４．５～４５、４．５～５０、４．５～５５、４．５～６０、４．５～６５、４．５～７０、４．５～７５、４．５～８０、４．５～８５、４．５～９０、４．５～９５、４．５～１００； 　５．０～５．５、５．０～６．０、５．０～６．５、５．０～７．０、５．０～７．５、５．０～８．０、５．０～８．５、５．０～９．０、５．０～９．５、５．０～１０、５．０～１５、５．０～２０、５．０～２５、５．０～３０、５．０～３５、５．０～４０、５．０～４５、５．０～５０、５．０～５５、５．０～６０、５．０～６５、５．０～７０、５．０～７５、５．０～８０、５．０～８５、５．０～９０、５．０～９５、５．０～１００； 　５．５～６．０、５．５～６．５、５．５～７．０、５．５～７．５、５．５～８．０、５．５～８．５、５．５～９．０、５．５～９．５、５．５～１０、５．５～１５、５．５～２０、５．５～２５、５．５～３０、５．５～３５、５．５～４０、５．５～４５、５．５～５０、５．５～５５、５．５～６０、５．５～６５、５．５～７０、５．５～７５、５．５～８０、５．５～８５、５．５～９０、５．５～９５、５．５～１００；　６．０～６．５、６．０～７．０、６．０～７．５、６．０～８．０、６．０～８．５、６．０～９．０、６．０～９．５、６．０～１０、６．０～１５、６．０～２０、６．０～２５、６．０～３０、６．０～３５、６．０～４０、６．０～４５、６．０～５０、６．０～５５、６．０～６０、６．０～６５、６．０～７０、６．０～７５、６．０～８０、６．０～８５、６．０～９０、６．０～９５、６．０～１００； 　６．５～７．０、６．５～７．５、６．５～８．０、６．５～８．５、６．５～９．０、６．５～９．５、６．５～１０、６．５～１５、６．５～２０、６．５～２５、６．５～３０、６．５～３５、６．５～４０、６．５～４５、６．５～５０、６．５～５５、６．５～６０、６．５～６５、６．５～７０、６．５～７５、６．５～８０、６．５～８５、６．５～９０、６．５～９５、６．５～１００； 　７．０～７．５、７．０～８．０、７．０～８．５、７．０～９．０、７．０～９．５、７．０～１０、７．０～１５、７．０～２０、７．０～２５、７．０～３０、７．０～３５、７．０～４０、７．０～４５、７．０～５０、７．０～５５、７．０～６０、７．０～６５、７．０～７０、７．０～７５、７．０～８０、７．０～８５、７．０～９０、７．０～９５、７．０～１００； 　７．５～８．０、７．５～８．５、７．５～９．０、７．５～９．５、７．５～１０、７．５～１５、７．５～２０、７．５～２５、７．５～３０、７．５～３５、７．５～４０、７．５～４５、７．５～５０、７．５～５５、７．５～６０、７．５～６５、７．５～７０、７．５～７５、７．５～８０、７．５～８５、７．５～９０、７．５～９５、７．５～１００； 　８．０～８．５、８．０～９．０、８．０～９．５、８．０～１０、８．０～１５、８．０～２０、８．０～２５、８．０～３０、８．０～３５、８．０～４０、８．０～４５、８．０～５０、８．０～５５、８．０～６０、８．０～６５、８．０～７０、８．０～７５、８．０～８０、８．０～８５、８．０～９０、８．０～９５、８．０～１００；　８．５～９．０、８．５～９．５、８．５～１０、８．５～１５、８．５～２０、８．５～２５、８．５～３０、８．５～３５、８．５～４０、８．５～４５、８．５～５０、８．５～５５、８．５～６０、８．５～６５、８．５～７０、８．５～７５、８．５～８０、８．５～８５、８．５～９０、８．５～９５、８．５～１００； 　９．０～９．５、９．０～１０、９．０～１５、９．０～２０、９．０～２５、９．０～３０、９．０～３５、９．０～４０、９．０～４５、９．０～５０、９．０～５５、９．０～６０、９．０～６５、９．０～７０、９．０～７５、９．０～８０、９．０～８５、９．０～９０、９．０～９５、９．０～１００； 　９．５～１０、９．５～１５、９．５～２０、９．５～２５、９．５～３０、９．５～３５、９．５～４０、９．５～４５、９．５～５０、９．５～５５、９．５～６０、９．５～６５、９．５～７０、９．５～７５、９．５～８０、９．５～８５、９．５～９０、９．５～９５、９．５～１００； 　１０～１５、１０～２０、１０～２５、１０～３０、１０～３５、１０～４０、１０～４５、１０～５０、１０～５５、１０～６０、１０～６５、１０～７０、１０～７５、１０～８０、１０～８５、１０～９０、１０～９５、１０～１００； 　１５～２０、１５～２５、１５～３０、１５～３５、１５～４０、１５～４５、１５～５０、１５～５５、１５～６０、１５～６５、１５～７０、１５～７５、１５～８０、１５～８５、１５～９０、１５～９５、１５～１００； 　２０～２５、２０～３０、２０～３５、２０～４０、２０～４５、２０～５０、２０～５５、２０～６０、２０～６５、２０～７０、２０～７５、２０～８０、２０～８５、２０～９０、２０～９５、２０～１００； 　２５～３０、２５～３５、２５～４０、２５～４５、２５～５０、２５～５５、２５～６０、２５～６５、２５～７０、２５～７５、２５～８０、２５～８５、２５～９０、２５～９５、２５～１００； 　３０～３５、３０～４０、３０～４５、３０～５０、３０～５５、３０～６０、３０～６５、３０～７０、３０～７５、３０～８０、３０～８５、３０～９０、３０～９５、３０～１００；35-40, 35-45, 35-50, 35-55, 35-60, 35-65, 35-70, 35-75, 35-80, 35-85, 35-90, 35-95, 35-100; 40-45, 40-50, 40-55, 40-60, 40-65, 40-70, 40-75, 40-80, 40-85, 40-90, 40-95, 40-100; 45-50, 45-55, 45-60, 45-65, 45-70, 45-75, 45-80, 45-85, 45-90, 45-95, 45-100; 50-55, 50-60, 50-65, 50-70, 50-75, 50-80, 50-85, 50-90, 50-95, 50-100; 55-60, 55-65, 55-70, 55-75, 55-80, 55-85, 55-90, 55-95, 55-100; 60-65, 60-70, 60-75, 60-80, 60-85, 60-90, 60-95, 60-100; 65-70, 65-75, 65-80, 65-85, 65-90, 65-95, 65-100; It may be 70-75, 70-80, 70-85, 70-90, 70-95, 70-100; 75-80, 75-85, 75-90, 75-95, 75-100; 80-85, 80-90, 80-95, 80-100; 85-90, 85-95, 85-100; 90-95, 90-100; 95-100;

[0028] <1-4> Melamine (C) The polyacetal resin composition of the present invention may contain melamine, but the amount of melamine that may be contained in the polyacetal resin composition of the present invention will be described later.

[0029] <1-5> Other Components The polyacetal resin composition of the present invention may further contain alkali metal or alkaline earth metal hydroxides (calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, etc.), inorganic salts, or alkoxides. For example, hydroxides of sodium, potassium, calcium, magnesium, etc., inorganic salts such as carbonates, phosphates, silicates, and borates, and alkoxides such as methoxides and ethoxides may be added.

[0030] In addition to the components described above, the polyacetal resin composition of the present invention may optionally contain various known additives and fillers, provided that they do not impair the objectives of the present invention. Examples of additives include other antioxidants, formaldehyde or formic acid removers, end group stabilizers, fillers, colorants, lubricants, mold release agents, antistatic agents, flame retardants, reinforcing agents, light stabilizers, and pigments. Examples of fillers include glass fibers, glass flakes, glass beads, mica, potassium titanate whiskers, and the like.

[0031] <2> Method for Producing Polyacetal Resin Composition The method for producing a polyacetal resin composition of the present invention is a method for producing a polyacetal resin composition using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher. The method for producing a polyacetal resin composition of the present invention includes: a polymerization step of obtaining a crude oxymethylene copolymer (A) by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst; and a melt-kneading step of obtaining a polyacetal resin by adding the hindered phenol compound (B) that does not have an isocyanuric acid skeleton and the inorganic filler (D) with a pH of 8 or higher to the crude oxymethylene copolymer (A) and melt-kneading. Each step will be described below.

[0032] <2-1> Polymerization Step The method for producing the polyacetal resin composition of the present invention includes a polymerization step in which a crude oxymethylene copolymer (A) is obtained by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst.

[0033] The catalyst that can be used in the polymerization step of the above method of the present invention is not particularly limited as long as it can be used to produce an oxymethylene copolymer. Examples of catalysts that can be used in the polymerization step of the above method of the present invention include BF ３ Examples include, but are not limited to, trispentafluorophenylborane (TPB), heteropoly acids, and perchloric acid. In one embodiment of the present invention, the catalyst used in the polymerization step is BF ３In one embodiment of the present invention, the catalyst used in the polymerization process is BF ３ This is a combination with trispentafluorophenylborane (TPB).

[0034] The catalyst that can be used in the polymerization step of the above method of the present invention may be used in an amount of 0.035 mmol or less per mol of trioxane. The catalyst that can be used in the polymerization step of the above method of the present invention may be used in amounts of, for example, 0.035 mmol or less, 0.03 mmol or less, 0.02 mmol or less, and 0.01 mmol or less per mol of trioxane. In one embodiment of the present invention, the catalyst that can be used in the polymerization step of the above method of the present invention may be used in amounts of, for example, 0.035 mmol, 0.03 mmol, 0.025 mmol, 0.02 mmol, 0.015 mmol, 0.01 mmol, and 0.005 mmol.

[0035] A catalyst that can be used in the polymerization step of the above method of the present invention is BF ３ In the case of a combination of and trispentafluorophenylborane (TPB), BF ３ The molar ratio of BF to trispentafluorophenylborane (TPB) can be used in the range of 1:1 to 100:1. In one embodiment of the present invention, BF ３ The molar ratio of trispentafluorophenylborane (TPB) to trispentafluorophenylborane (TPB) is 100:1.

[0036] <2-2> Melt-mixing step The method for producing the polyacetal resin composition of the present invention includes a melt-mixing step in which a polyacetal resin is obtained by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and melt-mixing them.

[0037] In the melt-mixing step of the above method of the present invention, the hindered phenol compound (B) that does not have an isocyanuric acid skeleton may be used in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the crude oxymethylene copolymer (A). If the amount of the hindered phenol compound (B) that does not have an isocyanuric acid skeleton that can be used in the mixing step of the above method of the present invention is within the above range, the amount of formaldehyde generated and the amount of mold deposit adhesion will be suppressed.

[0038] In the melt-mixing step of the above-described method of the invention, the hindered phenol compound (B) that does not have an isocyanuric acid skeleton may be used in amounts of, for example, 0.1 parts by mass, 0.2 parts by mass, 0.3 parts by mass, 0.4 parts by mass, 0.5 parts by mass, 0.6 parts by mass, 0.7 parts by mass, 0.8 parts by mass, 0.9 parts by mass, or 1.0 part by mass per 100 parts by mass of the crude oxymethylene copolymer (A).

[0039] In the melt-kneading step of the method of the present invention, the hindered phenol compound (B) having no isocyanuric acid skeleton that can be used is, for example, based on 100 parts by mass of the crude oxymethylene copolymer (A): 0.1 to 0.2 parts by mass, 0.1 to 0.3 parts by mass, 0.1 to 0.4 parts by mass, 0.1 to 0.5 parts by mass, 0.1 to 0.6 parts by mass, 0.1 to 0.7 parts by mass, 0.1 to 0.8 parts by mass, 0.1 to 0.9 parts by mass, 0.1 to 1.0 parts by mass; 0.2 to 0.3 parts by mass, 0.2 to 0.4 parts by mass, 0.2 to 0.5 parts by mass, 0.2 to 0.6 parts by mass, 0.2 to 0.7 parts by mass, 0.2 to 0.8 parts by mass, 0.2 to 0.9 parts by mass, 0.2 to 1.0 parts by mass; 0.3 to 0.4 parts by mass, 0.3 to 0.5 parts by mass, 0.3 to 0.6 parts by mass, 0.3 to 0.7 parts by mass, 0.3 to 0.8 parts by mass, 0.3 to 0.9 parts by mass, 0.3 to 1.0 parts by mass; 0.4 to 0.5 parts by mass, 0.4 to 0.6 parts by mass, 0.4 to 0.7 parts by mass, 0.4 to 0.8 parts by mass, 0.4 to 0.9 parts by mass, 0.4 to 1.0 parts by mass; 0.5 to 0.6 parts by mass, 0.5 to 0.7 parts by mass, 0.5 to 0.8 parts by mass, 0.5 to 0.9 parts by mass, 0.5 to 1.0 parts by mass; 0.6 to 0.7 parts by mass, 0.6 to 0.8 parts by mass, 0.6 to 0.9 parts by mass, 0.6 to 1.0 parts by mass; 0.7 to 0.8 parts by mass, 0.7 to 0.9 parts by mass, 0.7 to 1.0 parts by mass; 0.8 to 0.9 parts by mass, 0.8 to 1.0 parts by mass; 0.9 to 1.0 parts by mass;

[0040] In the melt-kneading step of the method of the present invention, the inorganic filler (D) having a pH of 8 or higher that can be used can be used in an amount of 0.005 to 0.12 parts by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A). When the amount of the inorganic filler (D) having a pH of 8 or higher that can be used in the mixing step of the method of the present invention is within the above range, the amount of formaldehyde generated can be suppressed.

[0041] In the melt-mixing step of the above method of the present invention, the inorganic filler (D) with a pH of 8 or higher that can be used may be, for example, 0.005 parts by mass, 0.01 parts by mass, 0.015 parts by mass, 0.02 parts by mass, 0.025 parts by mass, 0.03 parts by mass, 0.035 parts by mass, 0.04 parts by mass, 0.045 parts by mass, 0.05 parts by mass, 0.055 parts by mass, 0.06 parts by mass, 0.065 parts by mass, 0.07 parts by mass, 0.075 parts by mass, 0.08 parts by mass, 0.085 parts by mass, 0.09 parts by mass, 0.095 parts by mass, 0.10 parts by mass, 0.11 parts by mass, 0.12 parts by mass, etc., per 100 parts by mass of the crude oxymethylene copolymer (A).

[0042] In the melt-kneading step of the method of the present invention, the inorganic filler (D) having a pH of 8 or higher that can be used is, for example, based on 100 parts by mass of the crude oxymethylene copolymer (A): 0.005 to 0.01 part by mass, 0.005 to 0.015 part by mass, 0.005 to 0.02 part by mass, 0.005 to 0.025 part by mass, 0.005 to 0.03 part by mass, 0.005 to 0.035 part by mass, 0.005 to 0.04 part by mass, 0.005 to 0.045 part by mass, 0.005 to 0.05 part by mass, 0.005 to 0.055 part by mass, 0.005 to 0.06 part by mass, 0.005 to 0.065 part by mass, 0.005 to 0.07 part by mass, 0.005 to 0.075 part by mass, 0.005 to 0.08 part by mass, 0.005 to 0.085 part by mass, 0.005 to 0.09 part by mass, 0.005 to 0.095 part by mass, 0.005 to 0.10 part by mass, 0.005 to 0.11 part by mass, 0.005 to 0.12 part by mass; 0.01 to 0.015 part by mass, 0.01 to 0.02 part by mass, 0.01 to 0.025 part by mass, 0.01 to 0.03 part by mass, 0.01 to 0.035 part by mass, 0.01 to 0.04 part by mass, 0.01 to 0.045 part by mass, 0.01 to 0.05 part by mass, 0.01 to 0.055 part by mass, 0.01 to 0.06 part by mass, 0.01 to 0.065 part by mass, 0.01 to 0.07 part by mass, 0.01 to 0.075 part by mass, 0.01 to 0.08 part by mass, 0.01 to 0.085 part by mass, 0.01 to 0.09 part by mass, 0.01 to 0.095 part by mass, 0.01 to 0.10 part by mass, 0.01 to 0.11 part by mass, 0.01 to 0.12 part by mass; 0.015 to 0.02 part by mass, 0.015 to 0.025 part by mass, 0.015 to 0.03 part by mass, 0.015 to 0.035 part by mass, 0.015 to 0.04 part by mass, 0.015 to 0.045 part by mass, 0.015 to 0.05 part by mass, 0.015 to 0.055 part by mass, 0.015 to 0.06 part by mass, 0.015 to 0.065 part by mass, 0.015 to 0.07 part by mass, 0.015 to 0.075 part by mass, 0.015 to 0.08 part by mass, 0.015 to 0.085 part by mass, 0.015 to 0.09 part by mass, 0.015 to 0.095 part by mass, 0.015 to 0.10 part by mass, 0.015 to 0.11 part by mass, 0.015 to 0.12 part by mass;Quality Departments: 0.02-0.025, 0.02-0.03, 0.02-0.035, 0.02-0.04, 0.02-0.045, 0.02-0.05, 0.02-0.055, 0.02-0.06, 0.02-0.065, 0.02-0.07, 0.02-0.075, 0.02-0.08, 0.02-0.085, 0.02-0.09, 0.02-0.095, 0.02-0.10, 0.02-0.11, 0.02-0.12. Quality Departments: 0.025-0.03, 0.025-0.035, 0.025-0.04, 0.025-0.045, 0.025-0.05, 0.025-0.055, 0.025-0.06, 0.025-0.065, 0.025-0.07, 0.025-0.075, 0.025-0.08, 0.025-0.085, 0.025-0.09, 0.025-0.095, 0.025-0.10, 0.025-0.11, 0.025-0.12. Quality Departments: 0.03-0.035, 0.03-0.04, 0.03-0.045, 0.03-0.05, 0.03-0.055, 0.03-0.06, 0.03-0.065, 0.03-0.07, 0.03-0.075, 0.03-0.08, 0.03-0.085, 0.03-0.09, 0.03-0.095, 0.03-0.10, 0.03-0.11, 0.03-0.12. Quality Departments: 0.035-0.04, 0.035-0.045, 0.035-0.05, 0.035-0.055, 0.035-0.06, 0.035-0.065, 0.035-0.07, 0.035-0.075, 0.035-0.08, 0.035-0.085, 0.035-0.09, 0.035-0.095, 0.035-0.10, 0.035-0.11, 0.035-0.12.Quality Departments: 0.04-0.045, 0.04-0.05, 0.04-0.055, 0.04-0.06, 0.04-0.065, 0.04-0.07, 0.04-0.075, 0.04-0.08, 0.04-0.085, 0.04-0.09, 0.04-0.095, 0.04-0.10, 0.04-0.11, 0.04-0.12; Quality Departments: 0.045-0.05, 0.045-0.055, 0.045-0.06, 0.045-0.065, 0.045-0.07, 0.045-0.075, 0.045-0.08, 0.045-0.085, 0.045-0.09, 0.045-0.095, 0.045-0.10, 0.045-0.11, 0.045-0.12. Quality Departments: 0.05-0.055, 0.05-0.06, 0.05-0.065, 0.05-0.07, 0.05-0.075, 0.05-0.08, 0.05-0.085, 0.05-0.09, 0.05-0.095, 0.05-0.10, 0.05-0.11, and 0.05-0.12. Quality Departments: 0.055-0.06, 0.055-0.065, 0.055-0.07, 0.055-0.075, 0.055-0.08, 0.055-0.085, 0.055-0.09, 0.055-0.095, 0.055-0.10, 0.055-0.11, and 0.055-0.12. Quality Departments: 0.06-0.065, 0.06-0.07, 0.06-0.075, 0.06-0.08, 0.06-0.085, 0.06-0.09, 0.06-0.095, 0.06-0.10, 0.06-0.11, 0.06-0.12; 0.065-0.07, 0.065-0.075, 0.065-0.08, 0.065-0.085, 0.065-0.09, 0.065-0.095, 0.065-0.10, 0.065-0.11, 0.065-0.12.0.07 to 0.075 parts by mass, 0.07 to 0.08 parts by mass, 0.07 to 0.085 parts by mass, 0.07 to 0.09 parts by mass, 0.07 to 0.095 parts by mass, 0.07 to 0.10 parts by mass, 0.07 to 0.11 parts by mass, 0.07 to 0.12 parts by mass; 0.075 to 0.08 parts by mass, 0.075 to 0.085 parts by mass, 0.075 to 0.09 parts by mass, 0.075 to 0.095 parts by mass, 0.075 to 0.10 parts by mass, 0.075 to 0.11 parts by mass, 0.075 to 0.12 parts by mass; 0.08 to 0.085 parts by mass, 0.08 to 0.09 parts by mass, 0.08 to 0.095 parts by mass, 0.08 to 0.10 parts by mass, 0.08 to 0.11 parts by mass, 0.08 to 0.12 parts by mass; 0.085 to 0.09 parts by mass, 0.085 to 0.095 parts by mass, 0.085 to 0.10 parts by mass, 0.085 to 0.11 parts by mass, 0.085 to 0.12 parts by mass; 0.09 to 0.095 parts by mass, 0.09 to 0.10 parts by mass, 0.09 to 0.11 parts by mass, 0.09 to 0.12 parts by mass; 0.095 to 0.10 parts by mass, 0.095 to 0.11 parts by mass, 0.095 to 0.12 parts by mass; 0.10 to 0.11 parts by mass, 0.10 to 0.12 parts by mass; 0.11 to 0.12 parts by mass; and may be.;

[0043] In the melt-kneading step of the above method of the present invention, the content of melamine (C) that can be added is less than 0.03 parts by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A). When the amount of melamine (C) that can be used in the mixing step of the above method of the present invention falls within the above range, the adhesion amount of mold deposit is suppressed.

[0044] In the melt-kneading step of the above method of the present invention, the content of melamine (C) that can be added may be, for example, less than 0.03 parts by mass, less than 0.02 parts by mass, less than 0.01 parts by mass, or 0 parts by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A). In the melt-kneading step of the above method of the present invention, the content of melamine (C) that can be added may be, for example, 0.03 parts by mass, 0.02 parts by mass, 0.01 parts by mass, or 0 parts by mass relative to 100 parts by mass of the crude oxymethylene copolymer (A). In a more preferred embodiment of the present invention, there is provided the above method, wherein melamine (C) is not added in the melt-kneading step.

[0045] In one embodiment of the present invention, in the melt-mixing step of the above method, the hindered phenol compound (B) without an isocyanuric acid skeleton is used in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A), the inorganic filler (D) with a pH of 8 or higher is used in an amount of 0.005 to 0.12 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A), and the amount of melamine (C) added in the melt-mixing step is less than 0.03 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A).

[0046] In one embodiment of the present invention, a method for producing a polyacetal resin composition using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher, wherein the method comprises: a polymerization step of obtaining a crude oxymethylene copolymer (A) by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst; and a melt-kneading step of obtaining a polyacetal resin by adding the hindered phenol compound (B) that does not have an isocyanuric acid skeleton and the inorganic filler (D) with a pH of 8 or higher to the crude oxymethylene copolymer (A) and melt-kneading, wherein the catalyst is used in an amount of 0.035 mmol or less per 1 mol of trioxane, and the hindered phenol compound (B) that does not have an isocyanuric acid skeleton is used in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). A method is provided in which the inorganic filler (D) with a pH of 8 or higher is used in an amount of 0.005 to 0.12 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A), and the amount of melamine (C) added in the melt-mixing step is less than 0.03 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A).

[0047] In one embodiment of the present invention, a method for producing a polyacetal resin composition using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher, wherein the method comprises: a polymerization step of obtaining a crude oxymethylene copolymer (A) by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst; and a melt-kneading step of obtaining a polyacetal resin by adding the hindered phenol compound (B) that does not have an isocyanuric acid skeleton and the inorganic filler (D) with a pH of 8 or higher to the crude oxymethylene copolymer (A) and melt-kneading, wherein the catalyst is used in an amount of 0.035 mmol or less per 1 mol of trioxane, and the hindered phenol compound (B) that does not have an isocyanuric acid skeleton is used in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). A method is provided in which the inorganic filler (D) with a pH of 8 or higher is used in an amount of 0.005 to 0.12 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A), and melamine (C) is not added in the melt-mixing step.

[0048] After being discharged from the polymerization machine, the polyacetal resin (oxymethylene copolymer) (A) may be crushed in a turbo mill or the like, if necessary, before the melt-mixing step described above.

[0049] The method for producing the polyacetal resin composition of the present invention may optionally include a premixing step in which, in the melt-kneading step, the crude oxymethylene copolymer (A) is premixed by adding the hindered phenol compound (B) which does not have an isocyanuric acid skeleton and the inorganic filler (D) with a pH of 8 or higher, and then premixing the mixture before melt-kneading.

[0050] When pre-mixing the crude polymer (A) with stabilizers, etc., pre-mixing can be carried out by known methods, such as using a tumbler blender or a Henschel mixer. The apparatus for melt kneading preferably has a venting function, and such apparatuses include, for example, a single-screw or twin-screw continuous extrusion kneader having at least one vent hole, or a twin-screw surface-renewing horizontal kneader. These apparatuses may be used individually or in combination of two or more apparatuses.

[0051] If the crude oxymethylene copolymer (A) and stabilizer are not pre-mixed, the stabilizer should be continuously supplied to the crude oxymethylene copolymer (A) line. Alternatively, the crude oxymethylene copolymer (A) and stabilizer should be supplied to the twin-screw extruder on separate lines and heated, melted, and kneaded within the twin-screw extruder.

[0052] Known stabilizers that can be used include additional formaldehyde scavengers, acid scavengers, etc. Furthermore, additives such as inorganic fillers (e.g., glass fibers), crystallization accelerators (nucleating agents), mold release agents, lubricants, and colorants may be added.

[0053] In the melt-kneading process described above, the melt-kneading time when melting and kneading the mixture is not particularly limited, but is preferably 5 to 60 minutes, and more preferably 10 to 60 minutes. If the heating and melt-kneading time when melting and kneading the mixture in the melt-kneading process described above is within the above range, decomposition and deterioration of the product and the oxymethylene copolymer obtained by melt-kneading will be less likely to occur, thereby reducing the amount of formaldehyde generated and the amount of mold deposit adhesion.

[0054] In embodiments of the present invention, the melting and kneading time may be, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes. In one embodiment of the present invention, the above melting and kneading time is, for example, 5 to 10 minutes, 5 to 15 minutes, 5 to 20 minutes, 5 to 25 minutes, 5 to 30 minutes, 5 to 35 minutes, 5 to 40 minutes, 5 to 45 minutes, 5 to 50 minutes, 5 to 55 minutes, 5 to 60 minutes; 10 to 15 minutes, 10 to 20 minutes, 10 to 25 minutes, 10 to 30 minutes, 10 to 35 minutes, 10 to 40 minutes, 10 to 45 minutes, 10 to 50 minutes, 10 to 55 minutes, 10 to 60 minutes; 15 to 20 minutes, 15 to 25 minutes, 15 to 30 minutes, 15 to 35 minutes, 15 to 40 minutes, 15 to 45 minutes, 15 to 50 minutes, 15 to 55 minutes, 15 to 60 minutes; 20-25 minutes, 20-30 minutes, 20-35 minutes, 20-40 minutes, 20-45 minutes, 20-50 minutes, 20-55 minutes, 20-60 minutes; 25-30 minutes, 25-35 minutes, 25-40 minutes, 25-45 minutes, 25-50 minutes, 25-55 minutes, 25-60 minutes; 30-35 minutes, 30-40 minutes, 30-45 minutes, 30-50 minutes, 30-55 minutes, 30-60 minutes; 35-40 minutes, 35-45 minutes, 35-50 minutes, 35-55 minutes, 35-60 minutes; 40-45 minutes, 40-50 minutes, 40-55 minutes, 40-60 minutes; It may be 45 to 50 minutes, 45 to 55 minutes, 45 to 60 minutes; 50 to 55 minutes, 50 to 60 minutes; or 55 to 60 minutes.

[0055] In a preferred embodiment of the present invention, the above-mentioned melt-kneading time is 5 minutes to 60 minutes. In a preferred embodiment of the present invention, a method for producing a polyacetal resin composition is provided, wherein the above-mentioned melt-kneading time is 5 minutes to 60 minutes. In a more preferred embodiment of the present invention, the above-mentioned melt-kneading time is 10 minutes to 60 minutes. In a more preferred embodiment of the present invention, a method for producing a polyacetal resin composition is provided, wherein the above-mentioned melt-kneading time is 10 minutes to 60 minutes.

[0056] In a preferred embodiment of the present invention, a polyacetal resin composition is provided, which is produced by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and kneading them, wherein the above-mentioned heating, melting, and kneading time is 10 to 60 minutes.

[0057] In the melt-kneading process described above, the kneading temperature is not particularly limited as long as it is above the melting point of the product obtained by the polymerization reaction, but is preferably 220°C to 240°C. If the melt-kneading temperature in the melt-kneading process described above is within the above range, decomposition and degradation of the product and the oxymethylene copolymer obtained by melt-kneading will be less likely to occur, thereby reducing the amount of formaldehyde generated and the amount of mold deposit that adheres.

[0058] In an embodiment of the present invention, the above melting and kneading temperatures may be, for example, 220°C, 225°C, 230°C, 235°C, 240°C, etc. In one embodiment of the present invention, the above melting and kneading temperatures may be, for example, 220°C to 225°C, 220°C to 230°C, 220°C to 235°C, 220°C to 240°C; 225°C to 230°C, 225°C to 235°C, 225°C to 240°C; 230°C to 235°C, 230°C to 240°C; 235°C to 240°C;

[0059] In a preferred embodiment of the present invention, a method for producing a polyacetal resin composition is provided, wherein the melt-kneading temperature is 220°C to 240°C.

[0060] In a preferred embodiment of the present invention, a polyacetal resin composition is provided, which is produced by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and kneading them, wherein the heating and melting kneading temperature during kneading is 220°C to 240°C.

[0061] In an embodiment of the present invention, a method is provided for producing the above-mentioned polyacetal resin composition, wherein the composition is produced by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and melt-kneading, the melt-kneading time being 10 to 60 minutes and the melt-kneading temperature being 220°C to 240°C.

[0062] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is provided, which is produced by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and melt-kneading, wherein the melt-kneading time is 10 to 60 minutes and the melt-kneading temperature is 220°C to 240°C.

[0063] The pressure used during melt kneading is not particularly limited, but it is preferable to perform the process under reduced pressure, along with degassing, in order to remove unreacted raw material cyclic oligomers, formaldehyde components derived from cyclic oligomers, and formaldehyde derived from hemiformal ends. Degassing under reduced pressure is performed through the vent holes mentioned above. Therefore, the pressure of melt kneading is preferably in the range of 10 to 100 kPa in absolute pressure, more preferably in the range of 10 to 70 kPa, and particularly preferably in the range of 10 to 50 kPa, when atmospheric pressure is 100 kPa. The rotation speed of the stirring blades during melt kneading is preferably 50 to 200 rpm for a twin-screw extruder. For a twin-screw surface-renewing horizontal kneader, it is preferably 1 to 100 rpm.

[0064] The method of the present invention yields a composition of the target product, a polyacetal resin (oxymethylene copolymer).

[0065] The manufacturing process described above is just one example, and steps may be added or omitted as appropriate, or the content of each step may be changed. For example, after stopping the polymerization reaction and before stabilization, washing of the crude polymer, separation and recovery of unreacted monomers, drying, etc., may be performed as needed. Also, if purification is necessary, washing, separation and recovery of unreacted monomers, drying, etc., may be performed after stabilization.

[0066] Furthermore, within the scope that does not impair the objective of the present invention, materials other than those described above, such as known additives, may be used. Moreover, within the scope that does not impair the objective of the present invention, the materials described above may be used in a process other than the process described above, for example, antioxidants and heat-resistant stabilizers that can be used in the stabilization process may be used in the polymerization termination process.

[0067] <3> Physical properties of polyacetal resin composition <3-1> Formaldehyde emission As described above, there is a need for further reduction of formaldehyde emission from polyacetal resin molded products. The amount of formaldehyde emitted from polyacetal resin molded products can be measured, for example, according to the German Automotive Industry Association standard VDA275, but the measurement method is not limited thereto. In the method of the present invention, the measurement was performed according to the German Automotive Industry Association standard VDA275.

[0068] In embodiments of the present invention, the formaldehyde emission of the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA 275, is 3 ppm or less. In embodiments of the present invention, the formaldehyde emission of the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA 275, should be as low as possible, for example, 15 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, or 5 ppm or less. In embodiments of the present invention, the amount of formaldehyde emitted from the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA 275, is, for example, 15 ppm, 14 ppm, 13 ppm, 12 ppm, 11 ppm, 10 ppm, 9 ppm, 8 ppm, 7 ppm, 6 ppm, 5 ppm, 4 ppm, 3 ppm, 2 ppm, 1 ppm, or 0 ppm. In one embodiment of the present invention, a method is provided for producing the above-mentioned polyacetal resin composition, wherein the amount of formaldehyde emitted from the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA 275, is 15 ppm or less.

[0069] In an embodiment of the present invention, a polyacetal resin composition is provided in which the formaldehyde emission amount of the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA275, is 15 ppm or less.

[0070] By reducing the amount of formaldehyde emitted, it is possible to improve contamination of molding dies and the deterioration of the working (hygienic) environment during molding operations, thereby reducing the possibility of causing sick building syndrome and other related issues.

[0071] <3-2> Mold Deposits (MD, Mold Adhesion) Mold deposits are material that adheres to the mold used during molding, significantly degrading the working environment during the molding of thermoplastic resin compositions. The less mold deposit there is, the better the moldability. Mold deposit properties can be determined, for example, using the MiniMat M14 / 7B manufactured by Sumitomo Heavy Industries and the teardrop-shaped mold shown in Figure 1, but this method is not limited to this method.

[0072] <4> Polyacetal resin composition produced by the manufacturing method of the present invention In an embodiment of the present invention, a polyacetal resin composition produced by the method for producing the above-described polyacetal resin composition is provided.

[0073] In embodiments of the present invention, the polyacetal resin composition described above is produced by the method of the present invention using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher.

[0074] In an embodiment of the present invention, a polyacetal resin composition is provided in which the formaldehyde emission amount of the polyacetal resin composition, as measured according to the German Automotive Industry Association standard VDA275, is 15 ppm or less.

[0075] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is provided, wherein the melt-kneading time is 10 minutes to 60 minutes.

[0076] In an embodiment of the present invention, the above-mentioned polyacetal resin composition is provided, wherein the melt-mixing temperature is 220°C to 240°C.

[0077] <5> Molded Articles The present invention provides molded articles formed from the polyacetal resin composition of the present invention. The polyacetal resin composition of the present invention can be molded according to the molding methods of polyacetal resins known in the art. Examples of molding methods include, but are not limited to, injection molding, extrusion molding, blow molding, vacuum molding, compression molding, press molding, and 3D printing.

[0078] <5-1> Examples of molded articles formed from the polyacetal resin composition of the present invention include various products that are conventionally known applications of polyacetal resin, such as materials like pellets, round bars, and thick plates, as well as sheets, tubes, various containers, machinery, electrical equipment, automobiles, building materials and other various parts, and vehicle components. The polyacetal resin composition of the present invention can be used, for example, in automobile parts, clothing parts, molded parts for electrical and electronic equipment and information recording equipment, molded parts for medical equipment, molded parts for household use, rotating parts such as gears, bearing members, sliding members, press-fit parts, hinge parts, automobile fuel system parts, insert parts, snap-fit ​​parts, plumbing parts, various handles, various handrails, various chassis, side plate parts, spring parts, seat belt parts, automobile carrier plates, automobile combination switches, clips, pipe holders, wire holders, connectors, assist clips, storage materials for bumpers, console boxes, door trims, door checkers, ball joints, undercut parts, storage cases for optical fiber core wire connections, disk cartridges, tape cassettes, trays for disc-shaped recording media, toner, film holders, protective covers, artificial joints, medical instrument insertion valves, vascular insertion devices, caps, compact containers, fastener parts, card cases, toothbrushes, eating and drinking utensils, curtain rails with covers, curtain rail caps, liquid container lids, writing instruments, foldable storage frames, baskets and their handles, etc.

[0079] <5-2> Pellets The polyacetal resin composition of the present invention can be molded into pellets according to the molding methods of polyacetal resins known in the art. In one embodiment of the present invention, pellets formed from the polyacetal resin composition of the present invention are provided. In one embodiment of the present invention, a molded article formed from the polyacetal resin composition of the present invention is provided.

[0080] <5-3> Vehicle Components The polyacetal resin composition of the present invention can be molded as a vehicle component according to the molding methods for polyacetal resins known in the art. In one embodiment of the present invention, a vehicle component formed from the polyacetal resin composition of the present invention is provided. Examples of vehicle components include, but are not limited to, automobile parts, molded parts for electrical and electronic equipment and molded parts for information recording equipment, rotating parts such as gears, bearing members, sliding members, press-fit parts, hinge parts, automobile fuel system parts, insert parts, snap-fit ​​parts, water system parts, various handles, various handrails, various chassis, side plate parts, spring parts, seat belt parts, automobile carrier plates, automobile combination switches, clips, pipe holders, wire holders, connectors, assist clips, bumper storage materials, console boxes, door trims, door checkers, etc.

[0081] The present invention will be described below based on embodiments. However, the following embodiments are provided merely as examples, and the present invention is not intended to be construed as being limited to the scope described in the following embodiments.

[0082] <Example 1> <Production of Crude Oxymethylene Copolymer (A)> In a twin-screw continuous polymerization reactor with self-cleaning paddles, set to a temperature of 85°C, 4.0 parts by mass of 1,3-dioxolane, 0.030 mmol of the polymerization catalyst boron trifluoride diethyl ether, and 0.6 mmol of the molecular weight modifier methylal were continuously added per 1 mole of trioxane. The polymerization reaction was carried out continuously so that the residence time of the polymerization reaction product in the continuous polymerization reactor was 15 minutes. To the obtained polymerization reaction product, an amount of N,N-diethylhydroxylamine, which is a polymerization termination agent, was added in an amount equal to twice the molar amount of the polymerization catalyst, and then the product was pulverized to obtain crude oxymethylene copolymer (POM1).

[0083] <Production of Polyacetal Resin Composition> To 100 parts by mass of the obtained crude oxymethylene copolymer (A), the formulations described in each example and comparative example were added as stabilizers, and premixing was performed using a Henschel mixer. The premixed crude oxymethylene copolymer was introduced from a hopper with an automatic quantitative feed function into a co-rotating twin-screw extruder (inner diameter 69 mm, L / D = 31.5) at a rate of 20 to 120 kg / h, and the crude oxymethylene copolymer was melted at 220 to 240°C and continuously introduced into a twin-screw surface-renewing horizontal kneader. The molten resin extracted continuously by a gear pump was immersed as strands in a cooling water bath and then supplied to a pelletizer to be pelletized. The obtained pellets were dried in a hot air dryer at 120°C for 12 hours to obtain the final sample. 20 kg / h corresponds to a 60-minute retention period, 60 kg / h to a 20-minute retention period, and 120 kg / h to a 10-minute retention period.

[0084] <Measurement of pH of inorganic fillers> 2g of each inorganic filler was added to 100g of water and stirred for 3 minutes. The pH of the supernatant liquid was measured using a pH meter.

[0085] <Evaluation Method 1: Measurement of Formaldehyde Emissions> The amount of formaldehyde emitted was measured as the amount emitted per gram of oxymethylene copolymer resin (unit: μg / g) using the following procedure. 1) The oxymethylene copolymer resin composition was pre-dried at 80°C for 3 hours and molded into a 50 mm diameter x 3 mm thickness disc test piece using a Yamashiro SAV-30-30 molding machine at a cylinder temperature of 215°C. 2) Using the obtained test piece, the amount of formaldehyde emitted was measured the day after molding in accordance with the method described in German Automotive Industry Association Standard VDA275 (Automotive Interior Parts - Determination of Formaldehyde Emissions by Revised Flask Method).

[0086] <Evaluation Method 2: Mold Contamination Suppression Effect (MD, Mold Deposit)> Using an injection molding machine: MiniMat M14 / 7B manufactured by Sumitomo Heavy Industries, Ltd. and the teardrop-shaped mold shown in the figure, the amount of deposits adhering to the mold was evaluated in three stages (○△×) when 1000 shots were continuously molded under the conditions of cylinder temperature: 220°C and mold temperature: 40°C. The teardrop-shaped mold in Figure 1 is designed so that the resin composition is introduced from the gate G and the generated gas tends to accumulate at the tip P. The width of the gate G is 1 mm and the thickness is 1 mm. In Figure 1, the width h1 is 14.5 mm, the length h2 is 7 mm, the length h3 is 27 mm, and the thickness of the molded part is 3 mm.

[0087] The following were considered acceptable if they met the criteria of A or B. ○: There was almost no mold deposit, and the mold contamination suppression effect was extremely good. △: There was some mold deposit, and the mold contamination suppression effect was somewhat poor. ×: There was a lot of mold deposit, and the mold contamination suppression effect was poor.

[0088] <Examples 2-21, 23-26, Comparative Examples 2-12> Polyacetal resin compositions were produced by the method of the present invention according to the descriptions in Tables 1 and 2.

[0089] <Example 22> A polyacetal resin composition was prepared by the method of the present invention in the same manner as in Example 1, except that the boron trifluoride diethyl ether in Example 1 was replaced with a crude oxymethylene copolymer (POM2) containing 0.025 mmol of boron trifluoride diethyl ether and 0.00025 mmol of trispentafluorophenylborane per 1 mole of trioxane.

[0090] <Example 27> A polyacetal resin composition was prepared by the method of the present invention in the same manner as in Example 1, except that a crude oxymethylene copolymer (POM3) was used in which the boron trifluoride diethyl ether of Example 1 was replaced with 0.035 mmol of boron trifluoride diethyl ether per 1 mol of trioxane.

[0091] <Comparative Example 1> A polyacetal resin composition was prepared by the method of the present invention in the same manner as in Example 1, except that a crude oxymethylene copolymer (POM4) was used in which the boron trifluoride diethyl ether of Example 1 was replaced with 0.050 mmol of boron trifluoride diethyl ether per 1 mol of trioxane.

[0092] Tables 1 to 3 below show the amounts of each component used, the mixing time, the mixing temperature, the amount of formaldehyde generated, and the evaluation results of mold deposits (MD) for Examples 1 to 27 and Comparative Examples 1 to 12.

[0093] The details of components (B), (C), and (D) in Tables 1-3 are as follows. (B) Hindered phenol compounds Hindered phenol 1: Ethylene bis(oxyethylene) bis-(3-5-t-butyl-4-hydroxy-m-tolyl)propionate) (Irganox® 245) Hindered phenol 2: Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox® 1010) Hindered phenol 3: N,N'-Hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)) (Irganox® 1098) Hindered phenol 4: 2',3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide (Sonox® 1024) Hindered phenol 5: 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (Irganox® 1330) Hindered phenol 6: 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (Adekastab® AO-20) (has an isocyanuric acid skeleton) Hindered phenol 7: 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol) (Adekastab® AO-30) Hindered phenol 8: 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane (Adekastab® AO-80)

[0094] (C) Melamine: Mitsui Chemicals, Inc.

[0095] (D) Inorganic fillers Hydrotalcite: Clariant Inc. (Product name: Hycite713) (pH:8) Talc: Imerys Japan Co., Ltd. (Product name: ImerFlex T20) (pH:9) Magnesium hydroxide: Kyowa Chemical Industry Co., Ltd. (Product name: Magsalat F) (pH:10) Tricalcium phosphate: Tokyo Chemical Industry Co., Ltd. (Product name: Tricalcium phosphate) (pH:7.4) Hydroxyapatite: Innophos Inc. (Product name: Tricalcium phosphate) (pH:7)

[0096]

[0097]

[0098]

[0099] As described above, it has been shown that by using the polyacetal resin manufacturing method of the present invention, a polyacetal resin composition can be produced that reduces formaldehyde emissions and mold deposits. According to the method of the present invention, not only is the working environment improved, but the amount of formaldehyde emitted from the polyacetal resin composition and molded products using it is reduced, and the moldability is also improved due to the reduction of mold deposits. Therefore, it can be suitably used as a countermeasure against so-called sick building syndrome in automotive interior parts, interior parts for houses (hot water mixing faucets, etc.), clothing parts (fasteners, belt buckles, etc.), building materials (piping, pump parts, etc.), and machine parts (gears, etc.).

[0100] G Gate P Tip h1 Width h2 Length (distance from gate G to the part with width h1) h3 Length (total length)

Claims

A method for producing a polyacetal resin composition using a hindered phenol compound (B) that does not have an isocyanuric acid skeleton and an inorganic filler (D) with a pH of 8 or higher, wherein the method is A polymerization step to obtain a crude oxymethylene copolymer (A) by polymerizing trioxane and 1,3-dioxolane as a comonomer in the presence of a catalyst, A melt-kneading step to obtain a polyacetal resin by adding the isocyanuric acid skeleton-less hindered phenol compound (B) and the pH 8 or higher inorganic filler (D) to the crude oxymethylene copolymer (A) and melt-kneading them, Includes, The catalyst is used in an amount of 0.035 mmol or less per 1 mol of trioxane. The hindered phenol compound (B) that does not have an isocyanuric acid skeleton is used in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). The inorganic filler (D) with a pH of 8 or higher is used in an amount of 0.005 to 0.12 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). A method wherein the amount of melamine (C) added in the melt-mixing step is less than 0.03 parts by mass per 100 parts by mass of the crude oxymethylene copolymer (A). 　 The method according to claim 1, wherein the mass ratio (B / D) of the hindered phenol compound (B) that does not have an isocyanuric acid skeleton to the inorganic filler (D) with a pH of 8 or higher is 2.5 to 100. 　 The method according to claim 1, wherein the inorganic filler (D) with a pH of 8 or higher is one or more selected from the group consisting of hydrotalcite, talc, and magnesium hydroxide. 　 The method according to claim 1, wherein in the melt-kneading step, the melt-kneading time is 10 minutes to 60 minutes and the melt-kneading temperature is 220°C to 240°C. 　 The method according to claim 1, wherein melamine (C) is not added in the melting and kneading step. 　 A method for producing the polyacetal resin composition according to claim 1, wherein the polyacetal resin composition has a formaldehyde emission level of 15 ppm or less, as measured according to the German Automotive Industry Association standard VDA275. 　 The method according to claim 1, wherein the pH of the inorganic filler (D) is the pH of the supernatant liquid obtained after adding 2 g of the inorganic filler to 100 g of water and stirring. 　 A polyacetal resin composition produced by the method described in claim 1. 　 A pellet formed from the polyacetal resin composition described in claim 8. 　 A molded article formed from the polyacetal resin composition described in claim 8. 　 A vehicle component formed from the polyacetal resin composition described in claim 8.

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