Modifier for polyacetal resin, polyacetal resin composition, and method for producing modifier for polyacetal resin

Abstract

The present invention addresses the problem of providing a novel impact modifier for a polyacetal resin, capable of providing a polyacetal resin composition having low VOC emission. The modifier for a polyacetal resin contains a rubber-containing graft copolymer (A) having a specific configuration and a polymer compound (B) having a glycidyl group, the content of the element chlorine and the content of the element potassium in the modifier are within a specific range, and the pH of a mixture of the modifier and pure water is within a specific range.

Description

Modifier for polyacetal resin, polyacetal resin composition, and method for producing modifier for polyacetal resin

[0001] The present invention relates to a modifier for polyacetal resin, a polyacetal resin composition, and a method for producing the modifier for polyacetal resin.

[0002] Polyacetal resin is a crystalline engineering plastic, and its high crystallinity gives it excellent strength, sliding properties, and dimensional stability. Therefore, polyacetal resin is widely used not only for housings but also for electrical and electronic components and automotive parts, such as plastic gears, doorknobs, and clips. These plastic parts require high impact resistance, low abrasion, and low noise, with high impact resistance being particularly important.

[0003] Furthermore, in recent years, there has been a demand for resin parts for automobiles that emit less VOCs (volatile organic compounds), and therefore there is a demand for resin compositions that emit less VOCs.

[0004] Currently, various modifiers for polyacetal and resin compositions containing such modifiers have been developed.

[0005] For example, Patent Document 1 discloses a composition containing polyoxymethylene, an epoxidized fatty acid, a polymer stabilizer, and an impact modifier.

[0006] Patent Document 2 discloses a rubbery graft polymer containing a rubbery portion containing a diene structural unit. In the rubbery graft polymer disclosed in Patent Document 2, the mass ratio of the rubbery portion to the graft portion is 70 to 90 mass% for the rubbery portion and 10 to 30 mass% for the graft portion. Furthermore, the rubbery graft polymer disclosed in Patent Document 2 has a total amount of sulfate ions and sulfite ions contained in water extracted with hot water by a specific method of 3.5 ppm or less, a chloride ion content of 150 ppm or less, and a total sodium ion and potassium ion content of 20 ppm or less relative to the total amount of the rubbery graft polymer.

[0007] Patent Document 3 discloses a polyoxymethylene resin composition comprising 100 parts by mass of (A) polyoxymethylene resin and 0.5 to 50 parts by mass of (B) modifier, wherein the (B) modifier contains (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer, and the (b-2) graft rubber copolymer has a structure of two or more layers.

[0008] Patent Document 4 discloses a resin composition containing a polyacetal resin (A), a salt of a carboxylic acid and an alkaline earth metal (B), and a rubber-containing graft copolymer (C).

[0009] Patent Document 5 discloses a polyacetal resin composition containing specific amounts of each of (A) a polyacetal polymer, (B) a hindered phenol-based antioxidant, (C) an aliphatic carboxylic acid hydrazide, (D) a hydantoin compound having two hydrazinocarbonylalkyl groups, (E) an alkaline earth metal salt of an aliphatic carboxylic acid, (F) a hindered amine compound, (G) an ultraviolet absorber, and (H) a core-shell polymer having a rubbery polymer core and a glassy polymer shell made of a vinyl copolymer.

[0010] For example, there is a technology such as that disclosed in Patent Document 6, but there has been a demand for an improvement in the balance of impact strength, VOC, and weather resistance.

[0011] JP 2008-504397 JP 2016-000828 JP 2019-026810 International Publication WO2016 / 136726 JP 2021-036018 JP 2014-177647

[0012] However, the above-mentioned conventional techniques are not sufficient from the viewpoint of the amount of VOC emitted, and there is room for further improvement.

[0013] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its object is to provide a novel modifier for polyacetal resin that can provide a polyacetal resin composition that has good weather resistance and emits a small amount of VOCs.

[0014] As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered the novel finding that an impact modifier for polyacetal resin that satisfies the following (A1) to (A3) generates a small amount of VOC, and have completed the present invention based on this finding: (A1) the impact modifier contains a rubber-containing graft copolymer having a specific structure and a polymer compound having a glycidyl group; (A2) the chlorine element concentration and calcium element concentration are within specific ranges; and (A3) the impact modifier exhibits a pH within a specific range.

[0015] That is, a polyacetal resin modifier according to one embodiment of the present invention is a polyacetal resin modifier comprising a rubber-containing graft copolymer (A) and a polymer compound (B) having a glycidyl group, wherein the rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, the graft portion being composed only of constituent units derived from a vinyl-based monomer having no reactive functional group, and the mass ratio of the elastomer to the graft portion (parts by mass of the elastomer / parts by mass of the graft portion) is 0.05 to 0.05. The ratio of the graft moiety (parts by mass) is 60 / 40 to 95 / 5, the chlorine content in the polyacetal resin modifier is 1 ppm to 170 ppm based on the mass of the polyacetal resin modifier, the calcium content in the polyacetal resin modifier is 1 ppm to 780 ppm based on the mass of the polyacetal resin modifier, and the pH of a mixture consisting of 10 parts by mass of the polyacetal resin modifier and 100 parts by mass of deionized water is 6.0 to 8.0.

[0016] Further, a method for producing a polyacetal resin modifier according to one embodiment of the present invention includes: a polymer compound (B) addition step in which a polymer compound (B) having a glycidyl group is added in an emulsified state to an aqueous latex containing a rubber-containing graft copolymer (A); an aggregation step in which calcium chloride is added to the aqueous latex obtained in the polymer compound (B) addition step to obtain aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B); and a washing step in which the aggregates obtained in the aggregation step are washed. The rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, and the graft portion is composed only of structural units derived from vinyl monomers that do not have reactive functional groups. The mass ratio of the elastomer to the graft portion (parts by mass of the elastomer / parts by mass of the graft portion) is 60 / 40 to 95 / 5, and the pH of the aqueous latex is 5 to 9.

[0017] According to one embodiment of the present invention, it is possible to provide a novel modifier for polyacetal resin, which can provide a polyacetal resin composition that has good weather resistance and emits a small amount of VOC.

[0018] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the term "A to B" representing a numerical range means "greater than or equal to A (including and greater than A) and less than or equal to B (including and less than B)."

[0019] In this specification, a repeating unit derived from an N monomer may be referred to as an “N unit.” A repeating unit may also be referred to as a structural unit.

[0020] Unless otherwise specified in this specification, the structural units are １ Units and M ２ Units, ... and M ｎ A copolymer containing a unit (n is an integer of 2 or more) is called M １ / M ２ / ・・・ / M ｎ It is also called a copolymer. １ / M ２ / ・・・ / M ｎ Unless otherwise specified, the copolymer is not particularly limited in polymerization mode, and may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer. １ Units and M ２ Units, ... and M ｎ units (n is an integer of 2 or more), １ / M ２ / ・・・ / M ｎ Also called rubber.

[0021] 1. Technical Concept of an Embodiment of the Invention Formaldehyde is one of the above-mentioned VOCs. VDA275, one of the German automotive standards, describes a method for measuring formaldehyde emitted from resin parts (molded articles). In recent years, there has been discussion about the amount of VOCs emitted using a unified measurement method based on these standards.

[0022] Polyacetal resins are sensitive to the pH and / or residual ion content of additives. Depending on the pH and / or residual ion content, polyacetal may decompose during processing, generating formaldehyde, which is toxic to humans. Because these additives and / or residual ions remain in molded polyacetal resins, formaldehyde released from molded polyacetal resins can become a problem in enclosed spaces. Meanwhile, polyacetals may require various physical properties (e.g., impact resistance). Therefore, modifiers for polyacetal resins may be needed for various purposes, such as improving impact resistance. Adding a modifier produced using an anionic emulsifier and coagulant to polyacetal resin results in large amounts of formaldehyde being emitted from the polyacetal resin composition or its molded products, an amount that is unacceptable, particularly for automotive applications. For example, when the modifiers described in Patent Documents 1 to 6 are blended with a polyacetal resin, the amount of VOCs generated during molding of the polyacetal resin composition cannot be sufficiently prevented or reduced.

[0023] Therefore, the present inventors have conducted extensive research with the aim of providing a polyacetal resin modifier that can provide a polyacetal resin composition that emits a small amount of VOCs. As a result, they have discovered the novel finding that, as described above, an impact modifier for polyacetal resin that satisfies the above (A1) to (A3) emits a small amount of VOCs even when blended with a polyacetal resin, and have completed the present invention.

[0024] In addition to the above-mentioned object, one embodiment of the present invention has the following additional object (a), (b) and / or (c) that are preferably achieved: (a) to provide a polyacetal resin modifier that is useful for achieving both high impact resistance and low formaldehyde emission at a higher level in a polyacetal resin; (b) to provide a polyacetal resin modifier that can prevent or reduce formaldehyde emission during and after molding of a polyacetal resin composition (including the resulting molded article) and can further impart impact resistance, and a polyacetal resin composition containing the same; and (c) to provide a polyacetal resin modifier that can provide a molded article with excellent flexibility, and a polyacetal resin composition containing the same.

[0025] As a result of intensive research conducted by the present inventors to achieve the above-mentioned additional object, they have found that by using a specific polyacetal resin modifier, it is possible to achieve at a higher level both high impact resistance of a polyacetal resin composition and prevention or reduction of VOC emissions during and after molding.

[0026] According to one embodiment of the present invention, it is possible to provide: (a) a polyacetal resin modifier containing a rubber-containing graft copolymer, which is useful for achieving both high levels of impact resistance of the polyacetal resin and prevention or reduction of formaldehyde generation; (b) a polyacetal resin modifier and a polyacetal resin composition containing the same, which can prevent or reduce the amount of formaldehyde generated during and after molding of the polyacetal resin composition and further impart impact resistance; and / or (c) a polyacetal resin modifier and a polyacetal resin composition containing the same, which can provide a molded product having excellent flexibility.

[0027] [2. Modifier for Polyacetal Resin] A modifier for polyacetal resin according to one embodiment of the present invention is a modifier for polyacetal resin, and comprises a rubber-containing graft copolymer (A) and a polymer compound (B) having a glycidyl group, wherein the rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, the graft portion being composed only of structural units derived from a vinyl-based monomer having no reactive functional group, and the mass ratio of the elastomer to the graft portion (mass parts of the elastomer / mass parts of the graft portion) is 0.05 to 0.05. the ratio of the chlorine element in the polyacetal resin modifier to the calcium element in the polyacetal resin modifier is 1 ppm to 170 ppm based on the mass of the polyacetal resin modifier; the calcium element in the polyacetal resin modifier is 1 ppm to 780 ppm based on the mass of the polyacetal resin modifier; and the pH of a mixture consisting of 10 parts by mass of the polyacetal resin modifier and 100 parts by mass of deionized water is 6.0 to 8.0.

[0028] The "polyacetal resin modifier" may be referred to hereinafter as the "modifier." The "polyacetal resin modifier according to one embodiment of the present invention" may be referred to hereinafter as the "modifier of the present invention." When the modifier of the present invention is mixed with a polyacetal resin (C) described below, it becomes a polyacetal resin composition. The "polyacetal resin composition" may be referred to hereinafter as the "resin composition."

[0029] Because of the above-described configuration, the present modifier has the advantage of being able to provide a polyacetal resin composition that emits low amounts of VOCs. Specifically, the present modifier can provide a polyacetal resin composition that emits low amounts of VOCs during and after molding. The present modifier also has the advantage of being able to provide a polyacetal resin composition that has excellent weather resistance and a polyacetal resin composition that can provide a molded article that has excellent weather resistance. The present modifier also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article that has excellent impact resistance. The present modifier also has the advantage of being able to achieve, at a high level, both (a) high impact resistance of a molded article of the polyacetal resin composition and (b) prevention or reduction of VOC emissions during and after molding of the polyacetal resin composition. The present modifier also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article that has excellent flexibility. In the technical field of polyacetal resins or polyacetal resin compositions, the amount of formaldehyde emitted is the most problematic VOC emission amount, and therefore, in one embodiment of the present invention, VOC refers to formaldehyde.

[0030] Herein, the weather resistance of a resin composition and a molded article is evaluated by the time to crack development during a weather resistance test of the resin composition and the molded article. Herein, the impact resistance of a molded article is evaluated by the notched Charpy impact value of the molded article. Herein, the flexibility of a molded article is evaluated by the flexural modulus of the molded article. The method for measuring the time to crack development during a weather resistance test of a resin composition and a molded article, and the method for measuring the notched Charpy impact value and flexural modulus of the molded article will be described in detail in the Examples below.

[0031] (2-1. Rubber-Containing Graft Copolymer (A)) The rubber-containing graft copolymer (A) contained in the present modifier has an elastomer and a graft portion graft-bonded to the elastomer.

[0032] (Elastomer) Examples of the elastomer include an elastomer containing at least one selected from the group consisting of natural rubber, diene rubber, (meth)acrylate rubber, and polyorganosiloxane rubber. The elastomer preferably contains at least one selected from the group consisting of diene rubber, (meth)acrylate rubber, and polyorganosiloxane rubber, more preferably contains (meth)acrylate rubber, and even more preferably is composed solely of (meth)acrylate rubber. This configuration has the advantage of being able to maintain excellent weather resistance of the polyacetal resin composition.

[0033] ((Meth)acrylate Rubber) The (meth)acrylate rubber is an elastic material containing, as a structural unit, a structural unit ((meth)acrylate unit) derived from a (meth)acrylate monomer.

[0034] As used herein, "(meth)acrylate" refers to "methacrylate" and / or "acrylate," and "(meth)acrylic acid" refers to "methacrylic acid" and / or "acrylic acid." For example, "methyl (meth)acrylate" refers to "methyl methacrylate" and / or "methyl acrylate."

[0035] Examples of the (meth)acrylate monomer include (a) alkyl ester (meth)acrylates having an alkyl group having 1 to 22 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. (b) aromatic ring-containing (meth)acrylates such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; (c) hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; (d) glycidyl (meth)acrylates such as glycidyl (meth)acrylate and glycidyl alkyl (meth)acrylate; (e) alkoxyalkyl (meth)acrylates. These (meth)acrylate monomers may be used alone or in combination of two or more.

[0036] The (meth)acrylate rubber may further contain, as a structural unit, a structural unit derived from a vinyl monomer other than the (meth)acrylate monomer that is copolymerizable with the (meth)acrylate monomer. Examples of the vinyl monomer other than the (meth)acrylate monomer that is copolymerizable with the (meth)acrylate monomer include (a) a diene monomer and (b) a vinyl monomer other than the (meth)acrylate monomer.

[0037] The (meth)acrylate rubber preferably further contains structural units derived from a crosslinking agent and / or a graft crossing agent. In other words, it is preferable to use a crosslinking agent and / or a graft crossing agent in the production process of the (meth)acrylate rubber. When the (meth)acrylate rubber further contains structural units derived from a crosslinking agent and / or a graft crossing agent, the graft ratio, which will be described later, increases. As a result, in a polyacetal resin composition obtained by kneading a modifier and a polyacetal resin, there is an advantage in that the dispersibility of the rubber-containing graft copolymer (A) in the polyacetal resin is improved.

[0038] Examples of crosslinking agents and graft crosslinking agents include (a) allyl alkyl (meth)acrylates such as allyl (meth)acrylate and allyl alkyl (meth)acrylate; (b) polyfunctional (meth)acrylates such as monoethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate and tetraethylene glycol di(meth)acrylate; and (c) polyfunctional monomers such as diallyl phthalate, triallyl cyanurate, triallyl isocyanurate and divinylbenzene. These crosslinking agents and graft crosslinking agents may be used alone or in combination of two or more.

[0039] Suitable examples of the (meth)acrylate rubber include acrylate rubbers such as polybutyl acrylate rubber and butyl acrylate / 2-ethylhexyl acrylate copolymer. Polybutyl acrylate rubber is an elastomer containing 50% to 100% by mass of butyl acrylate units in 100% by mass of structural units.

[0040] Examples of the diene rubber and polyorganosiloxane rubber include conventionally known rubbers (for example, butadiene rubber and silicone rubber, respectively).

[0041] In one embodiment of the present invention, the elastomer preferably contains 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more of butyl acrylate units per 100% by mass of the elastomer. This configuration has the advantage of providing a good balance of economy, weather resistance, and low elastic modulus.

[0042] The "elastic body" of the rubber-containing graft copolymer (A) may consist of only one type of elastomer (polymer) having the same constitutional unit composition, or may consist of multiple types of elastomers (polymers) having different constitutional unit compositions.

[0043] (Graft Moiety) The graft moiety is composed solely of structural units derived from vinyl monomers that do not have reactive functional groups (e.g., hydroxy groups, carboxy groups, epoxy groups, amide groups, oxirane groups, etc.). In this specification, a "structural unit derived from a vinyl monomer that does not have a reactive functional group" is sometimes referred to as a "structural unit U." When the graft moiety is composed solely of structural units U, it is possible to eliminate (a) reactions between reactive functional groups in the rubber-containing graft copolymers (A) and (b) reactions between reactive functional groups in the polyacetal resin composition and the polyacetal resin, and has the advantage of not reducing the gloss of the molded product surface.

[0044] Examples of vinyl monomers having no reactive functional group from which the structural unit U is derived include aromatic vinyl compounds (for example, styrene-based monomers such as styrene), vinyl cyanide compounds (for example, acrylonitrile and methacrylonitrile), and unsaturated carboxylic acid esters, all of which have no reactive functional group.

[0045] Suitable examples of unsaturated carboxylic acid esters having no reactive functional group include acrylic acid esters and methacrylic acid esters having an alkyl ester having 1 to 12 carbon atoms. More specific examples of unsaturated carboxylic acid esters having no reactive functional group include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate.

[0046] Further preferred examples of the vinyl monomer having no reactive functional group include ester (meth)acrylates having an alkyl group having 1 to 22 carbon atoms and an alkoxyl group, such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate.

[0047] When selecting a monomer to be used in the polymerization of the graft portion, it is preferable to consider the type of polyacetal resin (C) to be blended with the modifier containing the obtained rubber-containing graft copolymer (A) (i.e., the target to be modified). For example, when selecting a monomer in the polymerization of the graft portion, it is preferable to select any one monomer or use any two or more monomers in combination at any mixing ratio, taking into consideration (a) the compatibility between the polyacetal resin (C) and the obtained rubber-containing graft copolymer (A), and (b) the refractive index of the polyacetal resin composition obtained by blending the modifier containing the rubber-containing graft copolymer (A) with the polyacetal resin (C).

[0048] The graft portion is preferably composed, as the structural unit U, exclusively of structural units derived from one or more monomers selected from the group consisting of (meth)acrylate monomers and styrene monomers, more preferably exclusively of structural units derived from one or more monomers selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and styrene monomers, even more preferably exclusively of structural units derived from one or more monomers selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and styrene, even more preferably exclusively of structural units derived from one or more monomers selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, and butyl acrylate, particularly preferably exclusively of structural units derived from at least one of methyl methacrylate and butyl acrylate, and most preferably exclusively of structural units derived from methyl methacrylate and butyl acrylate. According to this configuration, the rubber-containing graft copolymer (A) can be produced with good granulation properties and with little odor, and the molded article of the obtained polyacetal resin composition has the advantages of being excellent in weather resistance.

[0049] The graft portion preferably contains 50% by mass or more, more preferably 70% by mass or more, even more preferably 85% by mass or more, and particularly preferably 95% by mass or more of structural units derived from methyl methacrylate and structural units derived from butyl acrylate, based on 100% by mass of the graft portion. This configuration has the advantage of good granulation properties during production of the rubber-containing graft copolymer (A).

[0050] The "graft portion" of the rubber-containing graft copolymer (A) may consist of only one type of graft portion (polymer) having the same constitutional unit composition, or may consist of multiple types of graft portions (polymers) having different constitutional unit compositions.

[0051] The mass ratio of the elastomer to the graft moiety in the rubber-containing graft copolymer (A) (parts by mass of the elastomer / parts by mass of the graft moiety) is 60 / 40 to 95 / 5, preferably 65 / 35 to 90 / 10, more preferably 70 / 30 to 85 / 15, even more preferably 70 / 35 to 80 / 20, and particularly preferably 70 / 35 to 75 / 25. This configuration has the advantages of excellent compatibility between the rubber-containing graft copolymer (A) and the polyacetal resin (C) in the modifier, and excellent impact resistance of a molded article of the polyacetal resin composition.

[0052] (Method for Producing Rubber-Containing Graft Copolymer (A)) The method for producing the rubber-containing graft copolymer (A) may be any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but emulsion polymerization, i.e., emulsion graft polymerization, is preferred. Specifically, for example, (1) water and an emulsifier are added to a reaction vessel equipped with a stirrer, and then an elastomer-forming monomer mixture and a polymerization initiator are added, and if necessary, a chain transfer agent and / or an oxidation-reduction agent are added, and the resulting raw material solution is heated and stirred to polymerize and form an elastomer. Then, (2) a graft-forming monomer mixture is added to a reaction solution (suspension) containing the elastomer, and if necessary, an emulsifier, a polymerization initiator, a chain transfer agent and / or an oxidation-reduction agent are further added to the reaction solution, and the reaction solution is heated and stirred to polymerize and form a graft portion.

[0053] There are no particular limitations on the types of emulsifier, polymerization initiator, chain transfer agent, and redox agent used here, and known ones can be used. There are also no particular limitations on the method for adding each raw material to a reaction vessel, and they can be added all at once before the start of polymerization, or they can be added in portions. The polymerization of the graft portion is carried out in one stage or two or more stages, and the monomer composition in each stage may be the same or different. In the polymerization of the graft portion, the monomers that form the graft portion may be added all at once in a short period of time, or they may be added continuously in fixed amounts over a certain period of time, or a combination of these methods may be used.

[0054] When emulsion polymerization is employed as the method for producing the rubber-containing graft copolymer (A), known polymerization initiators, such as known thermal decomposition type polymerization initiators such as 2,2′-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate, can be used.

[0055] A redox initiator can also be used in the production of the rubber-containing graft copolymer (A). The redox initiator is an initiator that combines (a) a peroxide, such as an organic peroxide or an inorganic peroxide, with (b) optionally a reducing agent, such as sodium formaldehyde sulfoxylate or glucose, and optionally a transition metal salt, such as iron (II) sulfate, and optionally a chelating agent, such as disodium ethylenediaminetetraacetate, and optionally a phosphorus-containing compound, such as sodium pyrophosphate. Examples of organic peroxides include t-butylperoxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide. Examples of inorganic peroxides include hydrogen peroxide, potassium persulfate, and ammonium persulfate.

[0056] In addition to the above-mentioned components, a surfactant may be used in the production of the rubber-containing graft copolymer (A). The type and amount of the surfactant used are within known ranges.

[0057] In the production of the rubber-containing graft copolymer (A), known conditions such as polymerization temperature, pressure, and deoxidation can be applied.

[0058] (2-2. Polymer Compound (B) Having a Glycidyl Group) The present modifier contains a polymer compound (B) having a glycidyl group. The polymer compound (B) having a glycidyl group can play an important role in providing a polyacetal resin composition with low VOC emissions. In this specification, the "polymer compound (B) having a glycidyl group" may also be simply referred to as the "polymer compound (B)."

[0059] Formaldehyde, which may be generated during (a) molding of the polyacetal resin composition, for example, when the polyacetal resin composition is extruded and further molded, and / or (b) after molding of the polyacetal resin composition, can be further oxidized to formic acid. Formic acid further promotes the decomposition of the polyacetal resin composition, i.e., the generation of formaldehyde. When the modifier is blended into the polyacetal resin composition, the polymer compound (B) contained in the modifier reacts with the formic acid in the polyacetal resin composition to detoxify the formic acid. Therefore, the polymer compound (B) can also be referred to as a formic acid scavenger.

[0060] Examples of the polymer compound (B) include (a) epoxidized fats and oils such as epoxidized soybean oil, epoxidized castor oil, and epoxidized linseed oil, (b) epoxidized fatty acid esters, (c) epoxy resins, and (d) liquid polymers having a glycidyl group. Examples of the epoxidized fatty acid esters include epoxidized fatty acid butyl esters, epoxidized fatty acid 2-ethylhexyl esters, epoxidized fatty acid octyl esters, and epoxidized fatty acid alkyl esters.

[0061] Epoxidized fats and oils and epoxidized fatty acid esters are sometimes referred to as epoxy plasticizers. That is, in this specification, epoxy plasticizers are also included in the polymer compound (B). Examples of epoxy plasticizers other than epoxidized fats and oils and epoxidized fatty acid esters include diepoxystearyl epoxyhexahydrophthalate and di-2-ethylhexyl epoxyhexahydrophthalate.

[0062] The polymer compound (B) is preferably an epoxidized fat or oil, more preferably one or more selected from the group consisting of epoxidized soybean oil, epoxidized castor oil, and epoxidized linseed oil, even more preferably at least one of epoxidized soybean oil and epoxidized castor oil, and particularly preferably epoxidized soybean oil. This configuration has the advantages of being economical and having a high affinity between the rubber-containing graft copolymer (A) and the polymer compound (B), making it easy to obtain aggregates in which the polymer compound (B) is present near the rubber-containing graft copolymer (A) (for example, aggregates in which the polymer compound (B) is present between multiple rubber-containing graft copolymer (A) particles).

[0063] The content of the polymer compound (B) in this modifier is not particularly limited. In this modifier, the content of the polymer compound (B) relative to 100 parts by mass of the rubber-containing graft copolymer (A) is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.1 parts by mass or more and less than 5.0 parts by mass, more preferably 0.5 parts by mass or more and 4.5 parts by mass or less, more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, more preferably 0.5 parts by mass or more and less than 4.0 parts by mass, even more preferably 0.8 parts by mass or more and 3.5 parts by mass or less, and particularly preferably 1.0 parts by mass or more and 3.0 parts by mass or less. According to this configuration, the obtained modifier has the advantage of being able to provide a polyacetal resin composition that generates less VOC.

[0064] (2-3. Other Optional Components) The present modifier may contain other optional components in addition to the components described above, as long as the effects of one embodiment of the present invention are not impaired. Examples of other optional components include antiblocking agents, antioxidants described below, and various components described in the section (4-4. Other Additives) described below.

[0065] Other optional components can be added as appropriate during any step in the production method of the present modifier. For example, other optional components can be added to the water suspension (aqueous latex) of the rubber-containing graft copolymer (A) before or after coagulation. Other optional components can also be added to the modifier.

[0066] (2-4. Chlorine Element Content) When the modifier is mixed with a polyacetal resin to form a polyacetal resin composition, the chlorine element present in the modifier can induce decomposition of the polyacetal resin in the polyacetal resin composition. Therefore, the lower the chlorine element present in the modifier, the better. The chlorine element content in the modifier is 1 ppm to 170 ppm, preferably 1 ppm to 160 ppm, more preferably 1 ppm to 150 ppm, and particularly preferably 1 ppm to 140 ppm, based on the mass of the modifier. According to this configuration, the resulting modifier can provide a polyacetal resin composition that emits fewer VOCs. As described below, when a coagulant containing chlorine is used in the modifier production method, the resulting modifier may contain chlorine element. The content of elemental chlorine in the modifier can be adjusted by changing (a) the amount of coagulant containing elemental chlorine used in the method for producing the modifier, and / or (b) the washing conditions (such as the temperature of the washing water, the number of washings, and the amount of washing water) for the aggregate containing the rubber-containing graft copolymer (A) and the polymer compound (B) in the method for producing the modifier.

[0067] (2-5. Calcium Element Content) When the modifier is mixed with a polyacetal resin to form a polyacetal resin composition, the calcium element present in the modifier can induce decomposition of the polyacetal resin in the polyacetal resin composition. Therefore, the lower the calcium element present in the modifier, the better. The calcium element content in the modifier is 1 ppm to 780 ppm, preferably 1 ppm to 770 ppm, more preferably 1 ppm to 760 ppm, and particularly preferably 1 ppm to 750 ppm, based on the mass of the modifier. This configuration allows the resulting modifier to provide a polyacetal resin composition that emits fewer VOCs. Note that, as described below, when a coagulant containing calcium is used in the modifier production method, the resulting modifier may contain calcium. The content of calcium element in the modifier can be adjusted by changing (a) the amount of calcium element-containing coagulant used in the method for producing the modifier, and (b) the washing conditions (such as the temperature of the washing water, the number of washings, and the amount of washing water) of the aggregate containing the rubber-containing graft copolymer (A) and the polymer compound (B) in the method for producing the modifier.

[0068] (2-6. pH) The pH of a mixture consisting of 10 parts by mass of the present modifier and 100 parts by mass of deionized water is 6.0 to 8.0. In other words, the present modifier is neutral or weakly alkaline. This configuration has the advantage of providing a polyacetal resin composition that emits less VOCs.

[0069] (2-7. Epoxy Group Content) The epoxy group content in the present modifier is not particularly limited, but is preferably 15 μmol / g to 180 μmol / g, more preferably 20 μmol / g to 170 μmol / g, more preferably 25 μmol / g to 160 μmol / g, more preferably 30 μmol / g to 150 μmol / g, more preferably 30 μmol / g to 140 μmol / g, even more preferably 30 μmol / g to 130 μmol / g, and particularly preferably 35 μmol / g to 125 μmol / g. According to this configuration, the resulting modifier has the advantage of being able to provide a polyacetal resin composition that emits less VOCs.

[0070] The epoxy group content (mol / g) in the modifier refers to the ratio of the total amount (mol) of (i) the content of epoxy groups contained in the rubber-containing graft copolymer (for example, when a monomer containing an epoxy group is used in the production of the rubber-containing graft copolymer, the resulting rubber-containing graft copolymer contains epoxy groups), (ii) the content of epoxy groups contained in the polymer compound (B), and (iii) the content of epoxy groups contained in other components to the total mass (g) of the modifier.

[0071] 3. Method for Producing Polyacetal Resin Modifier A method for producing a polyacetal resin modifier according to one embodiment of the present invention includes: a polymer compound (B) addition step of adding a polymer compound (B) having a glycidyl group in an emulsified state to an aqueous latex containing a rubber-containing graft copolymer (A); an aggregation step of adding calcium chloride to the aqueous latex obtained in the polymer compound (B) addition step to obtain aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B); and a washing step of washing the aggregates obtained in the aggregation step, wherein the rubber-containing graft copolymer (A) has an elastomer and a graft moiety grafted to the elastomer, and the graft moiety is composed only of structural units derived from a vinyl monomer having no reactive functional group; the mass ratio of the elastomer to the graft moiety (parts by mass of the elastomer / parts by mass of the graft moiety) is 60 / 40 to 95 / 5; and the pH of the aqueous latex is 5 to 9.

[0072] The "method for producing a polyacetal resin modifier according to one embodiment of the present invention" may hereinafter be referred to as the "present production method."

[0073] Through extensive research, the present inventors have surprisingly and independently found that a polyacetal resin modifier capable of providing a polyacetal resin composition with low VOC emissions can be provided by employing a production method having the following features (c1) and (c2): (c1) adding a polymer compound (B) to an aqueous latex of the rubber-containing graft copolymer (A) before obtaining aggregates of the rubber-containing graft copolymer (A); and (c2) adding the polymer compound (B) in an emulsified state to the aqueous latex of the rubber-containing graft copolymer (A).

[0074] The reason why the polyacetal resin modifier according to one embodiment of the present invention can be provided by incorporating the above-described (c1) and (c2) components is unclear, but it is speculated as follows: By implementing the above-described (c1) and (c2) components in the present production method (particularly the polymer compound (B) addition step), aggregates in which the polymer compound (B) is present near the rubber-containing graft copolymer (A) can be obtained (e.g., aggregates in which the polymer compound (B) is present between multiple rubber-containing graft copolymer (A) particles). Therefore, in the final modifier, the polymer compound (B) is present near the rubber-containing graft copolymer (A). Furthermore, in the polyacetal resin composition obtained by mixing (e.g., kneading) the modifier with the polyacetal resin, the polymer compound (B) is present near the rubber-containing graft copolymer (A). As a result, the polyacetal resin composition emits fewer VOCs during and after molding. However, the present invention is not limited to the above-described speculation.

[0075] Modifiers containing a rubber-containing polymer but not a polymeric compound (B) having a glycidyl group (hereinafter also referred to as "conventional modifiers") have been known. By mixing the conventional modifier with a polyacetal resin and a polymeric compound (B) having a glycidyl group, a polyacetal resin composition containing the rubber-containing polymer and the polymeric compound (B) having a glycidyl group can be obtained. However, the present inventors have independently discovered that polyacetal resin compositions obtained by such methods using conventional modifiers cannot reduce the amount of VOC emissions during and after molding of the polyacetal resin composition. This is presumably because, when a polyacetal resin composition is obtained by the above-described method using a conventional modifier, the polymeric compound (B) cannot be uniformly dispersed in the polyacetal resin, and as a result, the polymeric compound (B) cannot be present near the rubber-containing graft copolymer (A).

[0076] That is, the present production method has the above-described structure (particularly structures (c1) and (c2)), and therefore has the advantage of being able to provide a modifier that can provide a polyacetal resin composition that emits low amounts of VOCs. Specifically, the modifier obtained by the present production method can provide a polyacetal resin composition that emits low amounts of VOCs during and after molding of the polyacetal resin composition. The modifier obtained by the present production method also has the advantage of being able to provide a polyacetal resin composition that has excellent weather resistance and a polyacetal resin composition that can provide a molded article that has excellent weather resistance. The modifier obtained by the present production method also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article that has excellent impact resistance. The modifier obtained by the present production method also has the advantage of being able to achieve, at a high level, both (a) high impact resistance of molded articles of the polyacetal resin composition and (b) prevention or reduction of VOC emissions during and after molding of the polyacetal resin composition. The modifier obtained by the present production method also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article having excellent flexibility.

[0077] Each aspect of the present production method will be described in detail below, but matters other than those described below (e.g., each aspect of the rubber-containing graft copolymer (A) and the polymer compound (B)) are not particularly limited, and the explanation in the above section [2. Modifier for polyacetal resin] will be used as appropriate.

[0078] (Rubber-Containing Graft Copolymer (A) Preparation Step) The present production method may include a rubber-containing graft copolymer (A) preparation step of preparing an aqueous latex containing the rubber-containing graft copolymer (A) before the polymer compound (B) addition step. Specific embodiments of the rubber-containing graft copolymer (A) preparation step include, for example, a method of producing the rubber-containing graft copolymer (A) by emulsion polymerization. Specific examples of the method of producing the rubber-containing graft copolymer (A) by emulsion polymerization are the same as those already explained in the above section (Method of Producing Rubber-Containing Graft Copolymer (A)), and therefore, the explanation therefor is omitted here by reference to that description. When the rubber-containing graft copolymer (A) is produced by emulsion polymerization, the aqueous latex containing the rubber-containing graft copolymer (A) may contain an emulsifier.

[0079] (Polymer Compound (B) Addition Step) The polymer compound (B) addition step can also be said to be a step involving the preparation of an aqueous latex containing the rubber-containing graft copolymer (A) and the polymer compound (B).

[0080] "Adding the polymer compound (B) in an emulsified state" can also be interpreted as "adding an emulsion of the polymer compound (B)." The method for obtaining an emulsion of the polymer compound (B) is not particularly limited, and examples thereof include (a) a method in which water, an emulsifier, and the polymer compound (B) are stirred to forcibly emulsify them, and (b) a method in which the polymer compound (B) is mixed with a reactive emulsifier to react the reactive group of the polymer compound (B) with the reactive emulsifier to obtain a polymer compound (B) having emulsifying ability, and then the polymer compound (B) is dispersed in water. From the viewpoint of industrial ease, the method for obtaining an emulsion of the polymer compound (B) is preferably (a) a method in which water, an emulsifier, and the polymer compound (B) are stirred.

[0081] (Aggregation Step) The aggregation step is a step of obtaining aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B) using calcium chloride.

[0082] In the coagulation process, the emulsifier reacts with calcium chloride in the aqueous latex to produce a salt reaction product, so calcium chloride can also be considered a coagulant.

[0083] The present inventors have independently discovered that when aggregates are obtained using a coagulant such as calcium chloride, the resulting modifier can provide a polyacetal resin composition that emits less VOCs than when aggregates are obtained by freeze-drying without using a coagulant.

[0084] Furthermore, the present inventors have independently discovered that when aggregates are obtained using a coagulant other than calcium chloride (e.g., magnesium chloride) instead of calcium chloride, it is difficult to prevent or reduce the amount of VOC emissions during and after molding of the polyacetal resin composition provided by the resulting modifier. The discovery that the type of coagulant used to obtain aggregates of rubber-containing graft copolymers affects the amount of VOC emissions during and after molding of the final polyacetal resin composition is a discovery that was previously completely unimaginable and can be said to be a surprising discovery.

[0085] The amount of the coagulant used in the aggregation step is not particularly limited, and is, for example, preferably 0.1 parts by mass to 10.0 parts by mass, particularly preferably 1.0 parts by mass to 8.0 parts by mass, relative to 100 parts by mass of the total amount of the rubber-containing graft copolymer (A) and the polymer compound (B) in the aqueous latex.

[0086] (Washing Step) The washing step is a step of removing impurities from the aggregates, such as salts that are reaction products of the emulsifier and the coagulant produced in the aggregation step.

[0087] The lower the electrical conductivity of the cleaning water, the more preferable. The electrical conductivity (mS / m) of the cleaning water is preferably 0.01 mS / m to 1.00 mS / m, more preferably 0.01 mS / m to 0.80 mS / m, even more preferably 0.01 mS / m to 0.50 mS / m, and particularly preferably 0.01 mS / m to 0.30 mS / m. According to this configuration, the obtained modifier has the advantage of being able to provide a polyacetal resin composition that emits less VOCs.

[0088] The washing water is preferably pure water (electrical conductivity: 0.01 mS / m to 1.00 mS / m) or deionized water (electrical conductivity: 0.01 mS / m to 0.30 mS / m) because of its low electrical conductivity.

[0089] The amount of washing water is not particularly limited, but is, for example, preferably 500 parts by mass to 50,000 parts by mass, more preferably 500 parts by mass to 10,000 parts by mass, and particularly preferably 500 parts by mass to 5,000 parts by mass, relative to 100 parts by mass of the aggregate.

[0090] The method for washing the aggregates in the washing step is not particularly limited. Examples of methods for washing the aggregates include a method of mixing the aggregates with water and stirring the mixture with a stirrer, a method of kneading the aggregates with water using a kneader, a method of mixing the aggregates with water using a planetary mixer, a method of spraying water onto the aggregates, and a method of washing the cake with a pressure filter. Various kneaders can be used, such as a batch kneader, a continuous kneader, an extrusion kneader, and an extruder.

[0091] The number of times the aggregate is washed in the washing step is not particularly limited, and may be one or more times. The washing time per washing step is also not particularly limited.

[0092] In the washing step, the method for removing the washing water is not limited, and examples thereof include methods such as draining the washing water, vacuum filtration, oil-water separation, filter press, centrifugation, belt press, screw press, membrane separation, and squeeze dehydration.

[0093] The method for dehydrating the aggregates is not particularly limited, and examples thereof include vacuum filtration, oil-water separation, filter press, centrifugation, belt press, screw press, membrane separation, and squeeze dehydration.

[0094] The present production method may further include a step of drying the aggregate containing the rubber-containing graft copolymer (A) and the polymer compound (B) obtained through the washing step.

[0095] Specific embodiments of the drying step are not particularly limited, and examples thereof include a method of drying the aggregates using a dryer, a method of placing the aggregates in a container and heating and reducing the pressure inside the container, a method of placing the aggregates in a container and bringing the aggregates into countercurrent contact with a drying gas inside the container, etc. The drying temperature in the drying step, for example, the temperature inside the dryer or the temperature of the drying gas, is not particularly limited.

[0096] The aggregate (or dried product thereof) of the rubber-containing graft copolymer (A) and the polymer compound (B) obtained by the above-described production method may be used as a polyacetal resin modifier as is. Alternatively, the aggregate (or dried product thereof) of the rubber-containing graft copolymer (A) and the polymer compound (B) obtained by the above-described production method may be optionally added with an antioxidant described below and various components described in the section (4-4. Other Additives) described below, and mixed to form a polyacetal resin modifier.

[0097] The modifier obtained by the above-described production method may be a powder or granular material. In other words, the modifier may be a powder or granular material. In this specification, "powder or granular material" includes both powder and granular material and refers to an aggregate of powder, granules, etc. Furthermore, when specifically distinguishing between these, "granular material" refers to a material having a volume average particle diameter of 0.1 mm to 10 mm, and "powder" refers to a material having a volume average particle diameter of 0.01 mm to 0.1 mm. Furthermore, a "volume average particle diameter" in the range of less than 10 μm can be measured using a dynamic light scattering (DLS) particle size distribution analyzer Nanotrac Wave II-EX150 (manufactured by Microtrack Bell Co., Ltd.), and a "volume average particle diameter" in the range of 10 μm or more can be measured using a laser diffraction particle size distribution analyzer Microtrac MT3000 II (manufactured by Microtrack Bell Co., Ltd.). The volume average particle size of the modifier obtained by the present production method and the present modifier is not particularly limited, but is, for example, 0.01 mm to 10 mm.

[0098] [4. Polyacetal Resin Composition] A polyacetal resin composition according to one embodiment of the present invention contains the polyacetal resin modifier described in [2. Modifier for Polyacetal Resin] and a polyacetal resin (C).

[0099] In this specification, the "polyacetal resin composition" may be referred to hereinafter as the "resin composition." The "polyacetal resin composition according to one embodiment of the present invention" may be referred to hereinafter as the "present resin composition." A molded article of the polyacetal resin can be produced by molding (e.g., injection molding) the present resin composition.

[0100] Because of the above-described configuration, the present resin composition has the advantage of low VOC emissions. More specifically, because of the above-described configuration, the present resin composition has the advantage of low VOC emissions during and after molding of the resin composition. Furthermore, because of the above-described configuration, the present resin composition has the advantage of excellent weather resistance and being able to provide molded articles with excellent weather resistance. Furthermore, because of the above-described configuration, the present resin composition has an excellent balance between the toughness of the resulting molded article, the elasticity of the resulting molded article, and the moldability of the resin composition. Furthermore, because of the above-described configuration, the present resin composition has the advantage of being able to provide molded articles with excellent impact resistance. Furthermore, because of the above-described configuration, the present resin composition has the advantage of being able to achieve a high level of both high impact resistance of the resulting molded article and prevention or reduction of VOC emissions during and after molding of the resin composition. Furthermore, because of the above-described configuration, the present resin composition has the advantage of being able to provide molded articles with excellent flexibility.

[0101] (4-1. Polyacetal Resin (C)) Polyacetal resin (C) is a polyacetal resin containing an oxymethylene group (-CH ２ The polyacetal resin (C) is a polymer compound having (a) a divalent oxymethylene group as a structural unit, and (b) a copolymer containing a divalent oxymethylene group and a divalent oxyalkylene group having two or more carbon atoms as a structural unit.

[0102] The divalent oxyalkylene group preferably has a carbon number of 2 to 6. Examples of the oxyalkylene group having a carbon number of 2 to 6 include an oxyethylene group, an oxypropylene group, and an oxybutylene group.

[0103] When the polyacetal resin (C) is a copolymer, the proportion of oxyalkylene groups having 2 to 6 carbon atoms in the polyacetal resin (C) is not particularly limited. The molar ratio of oxyalkylene groups having 2 to 6 carbon atoms is preferably 0.4 mol % to 15.0 mol %, more preferably 0.4 mol % to 10.0 mol %, and particularly preferably 0.4 mol % to 5.0 mol %, relative to the total of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms (100 mol %) in the polyacetal resin (C). This configuration has the advantage of being able to achieve both excellent continuous productivity and excellent thermal stability of the polyacetal resin (C).

[0104] The method for producing polyacetal resin (C) is not particularly limited. Trioxane is typically used as the main raw material for producing polyacetal resin (C). Furthermore, cyclic formals and cyclic ethers can be used to introduce oxyalkylene groups having 2 to 6 carbon atoms into polyacetal resin (C). Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, and 1,3,6-trioxocane. Specific examples of cyclic ethers include ethylene oxide, propylene oxide, and butylene oxide. To introduce oxyethylene groups into polyacetal resin (C), 1,3-dioxolane can be used as the main raw material. To introduce oxypropylene groups into polyacetal resin (C), 1,3-dioxane can be used as the main raw material. To introduce oxybutylene groups into polyacetal resin (C), 1,3-dioxepane may be used as the main raw material. It is preferable that polyacetal resin (C) has a small amount of (i) hemiformal terminal groups, (ii) formyl terminal groups, and (iii) heat-, acid-, and base-unstable terminal groups. Here, the hemiformal terminal groups are —OCH ２ A formyl terminal group is represented by —CHO.

[0105] The melt index of the polyacetal resin (C) is not particularly limited, but is preferably 0.1 g / 10 min to 120.0 g / 10 min, more preferably 0.5 g / 10 min to 70.0 g / 10 min, still more preferably 0.5 g / 10 min to 30.0 g / 10 min, and particularly preferably 0.5 g / 10 min to 20.0 g / 10 min. In this specification, the melt index of the polyacetal resin (C) is a value obtained by measurement in accordance with ASTM-D1238 under conditions of 190°C and 2.16 kg.

[0106] The content ratio of the polyacetal resin modifier in the polyacetal resin composition is not particularly limited. In the polyacetal resin composition, for example, when the total of the polyacetal resin modifier and the polyacetal resin (C) is 100% by mass, the polyacetal resin modifier is preferably 3% by mass to 80% by mass, and the polyacetal resin (C) is preferably 20% by mass to 97% by mass, the polyacetal resin modifier is more preferably 5% by mass to 50% by mass, and the polyacetal resin (C) is more preferably 50% by mass to 95% by mass, the polyacetal resin modifier is even more preferably 7% by mass to 30% by mass, and the polyacetal resin (C) is even more preferably 70% by mass to 93% by mass, and the polyacetal resin modifier is particularly preferably 9% by mass to 25% by mass, and the polyacetal resin (C) is particularly preferably 75% by mass to 91% by mass. This configuration has the advantage of achieving three high levels of weather resistance and impact resistance of the molded article, and preventing or reducing the amount of VOCs generated during and after molding of the resin composition.

[0107] In the polyacetal resin composition, the mass ratio of the rubber-containing graft copolymer (A) to the polyacetal resin (C) contained in the polyacetal resin modifier (rubber-containing graft copolymer (A) / polyacetal resin (C)) is preferably 3 / 100 or more, more preferably 4 / 100 or more, more preferably 5 / 100 or more, more preferably 7 / 100 or more, more preferably 9 / 100 or more, even more preferably 10 / 100 or more, and particularly preferably 11 / 100 or more. The upper limit of this mass ratio is, for example, preferably 50 / 100 or less, more preferably 40 / 100 or less, more preferably 35 / 100 or less, more preferably 30 / 100 or less, more preferably 25 / 100 or less, and particularly preferably 20 / 100 or less. When the mass ratio is 3 / 100 or more, the resulting polyacetal resin composition can provide a molded article with excellent impact resistance. When the mass ratio is 50 / 100 or less, there is an advantage that the resulting polyacetal resin composition can be easily extruded.

[0108] (4-2. Formaldehyde Scavenger) The present resin composition preferably further contains a formaldehyde scavenger. When the present resin composition contains a formaldehyde scavenger, the resin composition has the advantage of emitting less VOCs. More specifically, when the present resin composition contains a formaldehyde scavenger, the resin composition has the advantage of emitting less VOCs during and after molding.

[0109] The formaldehyde scavenger is not particularly limited. The formaldehyde scavenger is preferably a compound containing a reactive group reactive with formaldehyde. Examples of reactive groups reactive with formaldehyde include amide groups, hydrazide groups, and hydrazone groups. Examples of compounds containing such reactive groups include hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds. The formaldehyde scavenger preferably contains one or more compounds selected from the group consisting of hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds, and more preferably one or more compounds selected from this group. This configuration has the advantage of reducing the amount of formaldehyde (VOC) generated during and after molding of the resin composition.

[0110] Examples of the hydrazide compound include aliphatic hydrazide compounds and aromatic hydrazide compounds. Examples of the aliphatic dihydrazide include carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid hydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide (1,12-dodecanedicarbohydrazide), 1,18-octadecanedicarbohydrazide, stearic acid hydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, and 7,11-octadecadiene-1,18-dicarbohydrazide.

[0111] Examples of aromatic dihydrazide compounds include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 1,5-naphthalenedicarbohydrazide, 1,8-naphthalenedicarbohydrazide, 2,6-naphthalenedicarbohydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, and 1,5-diphenylcarbonohydrazide.

[0112] Examples of hydrazine compounds include 1,12-bis[2-(1-methylethylidene)hydrazino]-1,12-dodecanedione, 1,12-bis(2-ethylidenehydrazino)-1,12-dodecanedione, 1,12-bis(2-propylidenehydrazino)-1,12-dodecanedione, 1,12-bis[2-(1-methylpropylidene)hydrazino]-1,12-dodecanedione, 1,12-bis[2-(1-ethylpropylidene)hydrazino]-1,12-dodecanedione, 1,10-bis[2-(1-methylethylidene)hydrazino]]-1,10-decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10-bis(2- 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,10-decanedione, 1,10-bis[2-(1-ethylpropylidene)hydrazino]-1,10-decanedione, 1,6-bis[2-(1-methylethylidene)hydrazino]-1,6-hexanedione, 1,6-bis(2-ethylidenehydrazino)-1,6-hexanedione, 1,6-bis(2-propylidenehydrazino)-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-ethylpropylidene)hydrazino]-1,6-hexanedione, and the like.

[0113] Examples of the guanamine compound include benzoguanamine and N-methylol benzoguanamine.

[0114] Examples of the urea compound include ethylene urea, dimethylethylene urea, propylene urea, and tetrabutyl urea.

[0115] The formaldehyde scavenger preferably contains one or more selected from the group consisting of adipic acid hydrazide, dodecanedioic acid dihydrazide, 1,12-bis[2-(1-methylethylidene)hydrazino]-1,12-dodecanedione, benzoguanamine, and ethyleneurea, and more preferably contains one or more selected from the group consisting of adipic acid hydrazide, dodecanedioic acid dihydrazide, 1,12-bis[2-(1-methylethylidene)hydrazino]-1,12-dodecanedione, benzoguanamine, and ethyleneurea, since this further reduces the amount of VOCs generated during and after molding of the resulting resin composition.

[0116] The content of the formaldehyde scavenger in the resin composition is not particularly limited. The content of the formaldehyde scavenger in the resin composition is, for example, preferably an amount such that the reactive group in the formaldehyde scavenger is 3.0 μmol or more, more preferably 8.0 μmol or more, even more preferably 10.0 μmol or more, and particularly preferably 15.0 μmol or more, per 1 g of the total of the polyacetal resin modifier and the polyacetal resin (C). The content of the formaldehyde scavenger in the resin composition is, for example, preferably 100 μmol or less, more preferably 80 μmol or less, and particularly preferably 70 μmol or less, per 1 g of the total of the polyacetal resin modifier and the polyacetal resin (C). When the content of the formaldehyde scavenger is within the above-mentioned range, there are advantages in that the amount of VOCs generated during and after molding of the resin composition is further reduced, and mold staining caused by the formaldehyde scavenger can be prevented or reduced.

[0117] (4-3. Antioxidant) The resin composition may contain an antioxidant within a range that does not impair the effects of one embodiment of the present invention. Examples of the antioxidant include hindered phenol-based antioxidants.

[0118] Examples of hindered phenol-based antioxidants include 2,2'-methylene-bis(4-methyl-6-t-butylphenol), 4,4'-methylene-bis(2,6-di-t-butylphenol), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 3,5-di-t-butyl-4-hydroxybenzyldimethylamine, distearyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, and diethyl-3,5-di-t-butyl -4-hydroxybenzylphosphonate, 2,6,7-trioxa-1-phospha-bicyclo[2.2.2]oct-4-yl-methyl-3,5-di-t-butyl-4-hydroxyhydrocinnamate, 3,5-di-t-butyl-4-hydroxyphenyl-3,5-distearyl-thiotriazylamine, 2-(2-hydroxy-3,5-di-t-butylphenyl)-5-chlorobenzotriazole, 2,6-di-t-butyl-4-hydroxymethylphenol, 2,4-bis-(n-octylthio) )-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] triethylene glycol bis[3-(3,5-dimethyl-4-hydroxyphenyl)propionate], triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], triethylene glycol bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2'-thiodiethyl bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and the like.

[0119] The present resin composition may contain only one of the above antioxidants alone or two or more of them in combination.

[0120] (4-4. Other Additives) The resin composition may contain any conventionally known additives and fillers within the scope of the present invention, as long as the purpose of the present invention is not impaired. Examples of additives and fillers that can be used in one embodiment of the present invention include thermoplastic resins other than polyacetal resins, light stabilizers, UV absorbers, hindered amine light stabilizers (HALS), heat stabilizers, antistatic agents, carbon fibers, glass fibers, glass flakes, potassium titanate whiskers, dyes, and pigments (e.g., carbon black and titanium oxide). For details of these additives and fillers, please refer to the descriptions in paragraphs

[0113] to

[0124] of JP 2017-025257 A. The contents of paragraphs

[0113] to

[0124] of JP 2017-025257 A are incorporated herein by reference.

[0121] (4-5. Method for Producing Polyacetal Resin Composition) The method for producing the present resin composition is not particularly limited. For example, the present resin composition can be obtained by mixing the polyacetal resin modifier according to one embodiment of the present invention, the polyacetal resin (C), and, if necessary, a formaldehyde scavenger, an antioxidant, and / or other additives, and melt-kneading the resulting mixture.

[0122] The method for producing a polyacetal resin composition may be configured as follows: A method for producing a polyacetal resin composition, comprising a step of mixing a polyacetal resin modifier obtained by the method for producing a polyacetal resin modifier described in the above section [3. Method for producing a polyacetal resin modifier] with a polyacetal resin (C).

[0123] In the method for producing the resin composition, a Henschel mixer, a tumbler mixer, or the like can be used to mix the raw materials. A single-screw or twin-screw extruder, a Banbury mixer, a pressure kneader, a mixing roll, or other kneading machine can be used to melt and knead the resulting mixture. The melt and kneading of the mixture is preferably carried out at a temperature above the melting point of the polyacetal resin, specifically above the melting temperature of the polyacetal resin (generally 180°C or higher).

[0124] In particular, in order to prevent or reduce secondary aggregation of the polyacetal resin modifier and adjust the average secondary particle size to an appropriate value in the polyacetal resin composition according to one embodiment of the present invention, the following method can be preferably used.

[0125] A preferred example of a production method for preventing or reducing secondary aggregation of a polyacetal resin modifier in a polyacetal resin composition is to mix a polyacetal resin and a polyacetal resin modifier in a tumbler, extrude the resulting mixture into strands using an extruder, and then cut the strand-like mixture into pellets. In this case, a twin-screw extruder is preferably used as the extruder because it can reduce the occurrence of secondary aggregation compared to a single-screw extruder. In particular, the ratio L / D, which is the ratio of the screw length L (mm) to the screw diameter D (mm), preferably satisfies the relationship 20<(L / D)<100, and more preferably 25<(L / D)<70. By maintaining the ratio (L / D) at a value greater than 20, the polyacetal resin modifier is more easily finely dispersed in the polyacetal resin, thereby more effectively preventing or reducing the occurrence of secondary aggregation of the modifier. Furthermore, by making the ratio (L / D) less than 100, it is possible to effectively prevent or reduce the tendency of the resin composition to discolor due to thermal degradation.

[0126] The shape of the die nozzle is not particularly limited, but from the viewpoint of the pellet shape, a circular nozzle having a diameter of 1 mm to 10 mm is preferred, and a circular nozzle having a diameter of 2 mm to 7 mm is more preferred. Here, the term "circular" is not limited to a circular shape in the geometric sense, but also includes a shape that is interpreted as being approximately circular in the technical field of one embodiment of the present invention.

[0127] The melting temperature of the resin composition during melt-kneading is appropriately determined in relation to the melting temperature of the resin. In this specification, the melting temperature is the temperature measured by a thermocouple of the resin emerging from the die hole (die nozzle) of the extruder. The melting temperature is preferably 170°C or higher, more preferably 180°C or higher, and even more preferably 190°C or higher. The melting temperature is preferably 250°C or lower, more preferably 230°C or lower. By setting the melting temperature to 170°C or higher, sufficient melting is achieved, and production volume tends to be significantly improved. Furthermore, by setting the melting temperature to 250°C or lower, discoloration of the resin composition due to thermal degradation can be more effectively prevented or reduced.

[0128] The screw rotation speed during melt-kneading is preferably 50 rpm to 500 rpm, more preferably 70 rpm to 350 rpm. By setting the screw rotation speed to 50 rpm or more, the polyacetal resin modifier is easily finely dispersed in the polyacetal resin, and the occurrence of secondary aggregation of the modifier can be more effectively prevented or reduced. Furthermore, by setting the screw rotation speed to 500 rpm or less, heat generation during melt-kneading can be significantly prevented or reduced, and discoloration of the resin composition due to thermal degradation can be effectively prevented or reduced. Furthermore, the discharge rate of the mixture from the die hole is preferably 5 kg / hr to 1,000 kg / hr, more preferably 7 kg / hr to 800 kg / hr. By setting the discharge rate to 5 kg / hr or more, the polyacetal resin modifier is easily finely dispersed, and the occurrence of secondary aggregation can be effectively prevented or reduced. Furthermore, by setting the discharge rate to 1,000 kg / hr or less, heat generation during melt-kneading can be effectively prevented or reduced, and discoloration of the resin composition due to thermal degradation can be more effectively prevented or reduced.

[0129] [5. Applications] The modifier and the resin composition can be suitably used in a variety of applications, including electrical and electronic applications, vehicle applications, and industrial equipment applications. The modifier and the resin composition can be suitably used, for example, in mechanical parts for drive units of AV equipment, dishwasher handles, speaker grilles, propellers for stirring laundry tubs, switches and gears for office equipment, wiper motor system gears for automobiles, regulator handles, inner door handles, door lock side covers, shift levers, heater fans, pipe holders, power window regulators, seat belt-related parts, power seat gears, sunroofs, clips, fasteners, screws for industrial equipment conveyors, belt conveyors, chains, torque limiters, and the like.

[0130] An embodiment of the present invention may have the following configuration.

[0131] [1] A modifier for polyacetal resin, comprising a rubber-containing graft copolymer (A) and a polymer compound (B) having a glycidyl group, wherein the rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, the graft portion being composed only of structural units derived from a vinyl-based monomer having no reactive functional group, and the mass ratio of the elastomer to the graft portion (parts by mass of the elastomer / parts by mass of the graft portion) is 60 / 40 to 95 / 5, wherein the chlorine content in the polyacetal resin modifier is 1 ppm to 170 ppm based on the mass of the polyacetal resin modifier, the calcium content in the polyacetal resin modifier is 1 ppm to 780 ppm based on the mass of the polyacetal resin modifier, and the pH of a mixture consisting of 10 parts by mass of the polyacetal resin modifier and 100 parts by mass of deionized water is 6.0 to 8.0.

[0132] [2] The polyacetal resin modifier according to [1], wherein the polymer compound (B) is at least one of epoxidized soybean oil and epoxidized castor oil.

[0133] [3] The modifier for polyacetal resin according to [1] or [2], wherein the elastic body is composed only of a (meth)acrylate rubber.

[0134] [4] The polyacetal resin modifier according to any one of [1] to [3], wherein the epoxy group content in the polyacetal resin modifier is 15 μmol / g to 180 μmol / g.

[0135] [5] The polyacetal resin modifier according to any one of [1] to [4], wherein the content of the polymer compound (B) in the polyacetal resin modifier is 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the rubber-containing graft copolymer (A).

[0136] [6] The polyacetal resin modifier according to any one of [1] to [5], wherein the polyacetal resin modifier is a powder or granular material.

[0137] [7] A polyacetal resin composition comprising the polyacetal resin modifier according to any one of [1] to [6] and a polyacetal resin (C).

[0138] [8] The polyacetal resin composition according to [7], wherein the polyacetal resin modifier is 3% by mass to 80% by mass and the polyacetal resin (C) is 20% by mass to 97% by mass, when the total of the polyacetal resin modifier and the polyacetal resin (C) is 100% by mass.

[0139] [9] The polyacetal resin composition according to [7] or [8], further comprising a formaldehyde scavenger.

[0140]

[10] The polyacetal resin composition according to [9], wherein the formaldehyde scavenger contains a reactive group reactive to formaldehyde, and the content of the formaldehyde scavenger in the polyacetal resin composition is an amount such that the reactive group is 3.0 μmol or more per 1 g of the total of the polyacetal resin modifier and the polyacetal resin (C).

[0141]

[11] The polyacetal resin composition according to [9] or

[10] , wherein the formaldehyde scavenger comprises at least one selected from the group consisting of hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds.

[0142]

[12] A method for producing a modifier for polyacetal resin, comprising: a polymer compound (B) addition step of adding a polymer compound (B) having a glycidyl group in an emulsified state to an aqueous latex containing a rubber-containing graft copolymer (A); an aggregation step of adding calcium chloride to the aqueous latex obtained in the polymer compound (B) addition step to obtain aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B); and a washing step of washing the aggregates obtained in the aggregation step, wherein the rubber-containing graft copolymer (A) has an elastomer and a graft moiety grafted to the elastomer, and the graft moiety is composed only of structural units derived from a vinyl monomer having no reactive functional group, the mass ratio of the elastomer to the graft moiety (parts by mass of the elastomer / parts by mass of the graft moiety) is 60 / 40 to 95 / 5, and the pH of the aqueous latex is 5 to 9.

[0143]

[13] The method for producing a modifier for a polyacetal resin according to

[12] , wherein the polymer compound (B) is at least one of epoxidized soybean oil and epoxidized castor oil.

[0144]

[14] The method for producing a modifier for polyacetal resin according to

[12] or

[13] , wherein the elastic body is composed only of a (meth)acrylate rubber.

[0145]

[15] The method for producing a polyacetal resin modifier according to any one of

[12] to

[14] , wherein the epoxy group content in the polyacetal resin modifier is 15 μmol / g to 180 μmol / g.

[0146]

[16] The method for producing a polyacetal resin modifier according to any one of

[12] to

[15] , wherein the content of the polymer compound (B) in the polyacetal resin modifier is 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the rubber-containing graft copolymer (A).

[0147]

[17] The method for producing a polyacetal resin modifier according to any one of

[12] to

[16] , wherein the polyacetal resin modifier is a powder or granular material.

[0148]

[18] A method for producing a polyacetal resin composition, comprising a step of mixing the polyacetal resin modifier obtained by the method for producing a polyacetal resin modifier according to any one of

[12] to

[17] with a polyacetal resin (C).

[0149]

[19] The method for producing a polyacetal resin composition according to

[18] , wherein the polyacetal resin modifier accounts for 3% by mass to 80% by mass and the polyacetal resin (C) accounts for 20% by mass to 97% by mass, when the total of the polyacetal resin modifier and the polyacetal resin (C) is 100% by mass.

[0150]

[20] The method for producing a polyacetal resin composition according to

[18] or

[19] , further comprising a formaldehyde scavenger.

[0151]

[21] The method for producing a polyacetal resin composition according to

[20] , wherein the formaldehyde scavenger contains a reactive group reactive to formaldehyde, and the content of the formaldehyde scavenger in the polyacetal resin composition is an amount such that the reactive group is 3.0 μmol or more per 1 g of the polyacetal resin modifier and the polyacetal resin (C) combined.

[0152]

[22] The method for producing a polyacetal resin composition according to

[20] or

[21] , wherein the formaldehyde scavenger comprises at least one selected from the group consisting of hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds.

[0153] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these. One embodiment of the present invention can be practiced by appropriately modifying it within the scope that can conform to the purpose described above or below, and all such modified embodiments are included in the technical scope of the present invention. In the following examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass," respectively.

[0154] <Components> The components used in each Production Example, Example, and Comparative Example are as follows. Rubber-containing graft copolymer (A) The rubber-containing graft copolymer obtained in the Production Example shown below was used. Polymer compound having a glycidyl group (B) Epoxidized soybean oil (O-130P, manufactured by ADEKA Corporation) Coagulant Calcium chloride dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Polyacetal resin (C) The polyacetal resin obtained in the Production Example shown below was used. Formaldehyde scavengers (D-1): ethylene urea (manufactured by Kanto Chemical Co., Ltd.) (D-2): 1,12-bis[2-(1-methylethylidene)hydrazino]]-1,12-dodecanedione (manufactured by Nippon Finechem Co., Ltd.) (D-3): adipic acid dihydrazide (manufactured by Nippon Finechem Co., Ltd.) (D-4): dodecanedioic acid dihydrazide (manufactured by Nippon Finechem Co., Ltd.) (D-5): benzoguanamine (manufactured by Nippon Chemical Co., Ltd.) Antioxidants IRGANOX 245 (manufactured by BASF) DLTP "Yoshitomi" (manufactured by API Corporation) Ultraviolet absorbers Tinuvin 234 (manufactured by BASF) HALS Tinvin 622SF (manufactured by BASF).

[0155] <Measurement Methods> Measurement methods used in the examples and comparative examples will be explained below.

[0156] (Method for measuring volume average particle diameter) The volume average particle diameter (Mv) of the elastomer or rubber-containing graft copolymer (A) dispersed in the aqueous latex was measured using a Nanotrac Wave II-EX150 (manufactured by Microtrackbell Co., Ltd.). A sample prepared by diluting the aqueous latex with deionized water was used for measurement. The measurement was performed by inputting the refractive indexes of water and the elastomer or polymer microparticles (A) obtained in each production example, and adjusting the sample concentration so that the loading index was within the range of 1 to 10 for a measurement time of 120 seconds.

[0157] (Method for measuring electrical conductivity in cleaning water) Using cleaning water as a sample, the electrical conductivity of the cleaning water was measured using ES-71 manufactured by HORIBA.

[0158] (Method for measuring the chlorine and calcium element contents in the modifier) ​​4.0 g of the modifier obtained in each example and comparative example was weighed out. The amount of chlorine and calcium element in the modifier was measured using an energy dispersive X-ray fluorescence spectrometer "SPECTRO XEPOS" manufactured by Rigaku Corporation. The results were expressed as mass% of each element relative to 100 mass% of the modifier. Element contents of less than 0.001% were not shown in the results. Elements with an element content of less than 0.001% (i.e., less than 10 ppm) in the modifier can be said to have no effect on the effects of one embodiment of the present invention.

[0159] (Method for measuring pH of mixture of modifier and deionized water) 10 parts by mass of the modifier obtained in each example and comparative example was mixed with 100 parts by mass of deionized water to obtain a mixture. The obtained mixture was stirred for 30 minutes. The pH of the obtained mixture (25°C) was measured using a pH meter.

[0160] (Method for measuring epoxy group content in modifier) ​​The modifier obtained in each example and comparative example was added to deuterated chloroform containing 1,4-bis(trimethylsilyl)benzene-d4 (hereinafter referred to as BTMSB-d4) as an internal standard, and the resulting mixture was stirred to disperse the modifier in the deuterated chloroform. After allowing the resulting dispersion to stand, the lower layer was collected and filtered through a PTFE filter with a pore size of 0.2 μm to obtain a filtrate. The filtrate was used as a sample and analyzed using an AVANCE NEO 700 manufactured by Bruker. １ H NMR was measured. The epoxy group content in the modifier was determined from the ratio of the peak area of ​​the trimethylsilyl group (0.3 ppm) of BTMSB-d4, whose concentration was known to be 0.71 mg / ml, to the peak area of ​​the characteristic glycerol moiety (4.3 ppm) of the epoxidized soybean oil, which is polymer compound (B). As explained below, of the materials used in each example and comparative example, polymer compound (B) was the only compound containing an epoxy group.

[0161] (Method for manufacturing ISO test specimens) The polyacetal resin composition pellets obtained in each example and comparative example were injection molded in accordance with ISO 9988-2 standard using an injection molding machine EC-100 manufactured by Toshiba Machine. Here, the cylinder temperature was set to 195°C, and the mold temperature was set to 90°C. By this injection molding, a multipurpose test specimen (referred to as ISO test specimen) having a thickness of 4 mm was obtained. The notched Charpy impact value and flexural modulus were measured using the obtained ISO test specimens. The ISO test specimens can also be considered as molded articles of the polyacetal resin composition.

[0162] (Method of Evaluating Weather Resistance) The ISO test specimens obtained in the above (Method of Manufacturing ISO Test Specimens) were subjected to weather resistance evaluation using an S80 tester manufactured by Suga Test Instruments Co., Ltd., under conditions of sunshine carbon arc lamp (light source), 83°C (black panel temperature), no rain, #255 (light filter), 50% OH (humidity), and 255 W / m ２A weather resistance test was conducted in a test environment of (300 to 700 nm) (irradiance), and the time to crack occurrence was evaluated. From a practical standpoint, if the time to crack occurrence of an ISO test piece of a polyacetal resin composition is 150 hours or more, it can be determined that the polyacetal resin composition has excellent weather resistance and can provide a molded article having excellent weather resistance.

[0163] In applications requiring weather resistance, it is common to add an ultraviolet absorber and / or a hindered amine light stabilizer (HALS) to the polyacetal resin. In the examples, ISO test pieces for evaluating weather resistance were produced using polyacetal resin compositions to which an ultraviolet absorber and a hindered amine light stabilizer had been added.

[0164] (Method of measuring impact resistance) A test piece measuring 80 mm in length, 10 mm in width, and 4 mm in thickness was cut out from the ISO test piece using a notching tool manufactured by Toyo Seiki Seisaku-sho, Ltd., and a notch with a tip radius r of 0.25 mm was applied to the test piece. Thereafter, a Charpy impact test was carried out using the obtained test piece at room temperature (23°C) in accordance with ISO179-1 to obtain a notched Charpy impact value. From a practical viewpoint, it is preferable that the notched Charpy impact value of the test piece of the polyacetal resin composition is 10 kJ / m ２ Furthermore, from the viewpoint of comparison, if the ratio of the notched Charpy impact value of a test piece of the polyacetal resin composition containing a modifier to the notched Charpy impact value measured on a test piece of the polyacetal resin alone (i.e., Reference Example 1) contained in the polyacetal resin composition (notched Charpy impact value of a test piece of the polyacetal resin composition containing a modifier / notched Charpy impact value of a test piece of the polyacetal resin alone (i.e., Reference Example 1)) is 1.1 or more, it can be determined that the polyacetal resin composition can provide a molded article with excellent impact resistance.

[0165] (Method for Measuring Flexural Modulus) Using an ISO test piece as a sample, a bending test was performed at a bending test speed of 2 mm / min using a fully automatic bending tester according to the method described in ISO 178 to measure the flexural modulus. From a practical standpoint, if the flexural modulus of the ISO test piece of a polyacetal resin composition is 2,300 MPa or less, it can be determined that the polyacetal resin composition can provide a molded article with excellent flexibility. From a comparative standpoint, if the ratio of the flexural modulus of the ISO test piece of a polyacetal resin composition containing a modifier to the flexural modulus measured using an ISO test piece of the polyacetal resin alone (i.e., Reference Example 1) contained in the polyacetal resin composition (i.e., Reference Example 1) (flexural modulus of the ISO test piece of the polyacetal resin composition containing a modifier / flexural modulus of the ISO test piece of the polyacetal resin alone (i.e., Reference Example 1)) is 0.9 or less, it can be determined that the polyacetal resin composition can provide a molded article with excellent flexibility.

[0166] (Method of Preparing Plate Test Pieces) Pellets of the polyacetal resin composition obtained in each Example and Comparative Example were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C. Next, using an injection molding machine SE-30 manufactured by Sumitomo Heavy Industries, Ltd., the heat-treated pellets were injection-molded at a cylinder temperature of 215°C and a mold temperature of 80°C to prepare plate test pieces measuring 100 mm x 40 mm x 2 mm. The plate test pieces can also be considered as molded articles of the polyacetal resin composition.

[0167] (Method for measuring the amount of formaldehyde generated) On the day following the day after the preparation of the above-mentioned flat test specimens, the amount of formaldehyde generated (μg / g-POM, which refers to the amount of formaldehyde generated (μg) per 1 g of polyacetal resin) was measured using the flat test specimens in accordance with the method described in the German Automotive Industry Standard VDA275 (Automobile interior parts - Determination of formaldehyde emission by the revised flask method). The specific measurement method is as follows.

[0168] (1) 50 mL of distilled water was placed in a polyethylene container, the flat test piece was placed in the container while suspended in the air, and the lid of the polyethylene container was closed. Thereafter, the polyethylene container was heated at 60°C for 3 hours in a sealed state.

[0169] (2) The polyethylene container was then left at room temperature for 60 minutes, after which the flat test piece was removed from the polyethylene container.

[0170] (3) The amount of formaldehyde absorbed in the distilled water in the polyethylene container was measured by the acetylacetone colorimetry method using a UV spectrometer with the distilled water as a sample. The obtained amount of formaldehyde was divided by the mass of the polyacetal resin (C) in the flat test piece, and the resulting value was defined as the amount of formaldehyde generated from the flat test piece.

[0171] From a practical standpoint, if the amount of formaldehyde emitted from a flat test piece of a polyacetal resin composition is 20.0 μg / g-POM or less, the polyacetal resin composition can be determined to emit a low amount of VOCs during and after molding. Furthermore, from a comparative standpoint, if the ratio of the amount of formaldehyde emitted from a flat test piece of a polyacetal resin composition containing a modifier to the amount of formaldehyde emitted measured from a flat test piece of the polyacetal resin alone (i.e., Reference Example 1) contained in the polyacetal resin composition (amount of formaldehyde emitted from a flat test piece of a polyacetal resin composition containing a modifier / amount of formaldehyde emitted from a flat test piece of the polyacetal resin alone (i.e., Reference Example 1)) is 2.0 or less, the polyacetal resin composition can be determined to emit a low amount of formaldehyde (amount of VOCs) during and after molding.

[0172] Furthermore, in fields where formaldehyde emissions are subject to strict regulations, such as for automotive interior applications, the amount of formaldehyde emissions can be further suppressed by using a formaldehyde scavenger. When a polyacetal resin composition contains a formaldehyde scavenger (for example, the polyacetal resin composition contains a formaldehyde scavenger in an amount such that the reactive groups are 8.9 μmol or more per 1 g of the total of the polyacetal resin modifier and the polyacetal resin (C)), if the amount of formaldehyde emitted from a flat test piece of the polyacetal resin composition is 2.5 μg / g-POM or less, the polyacetal resin composition can be determined to emit a small amount of VOCs during and after molding. Furthermore, from the viewpoint of comparison, if the ratio of the amount of formaldehyde emitted from a flat test piece of a polyacetal resin composition containing a modifier to the amount of formaldehyde emitted measured from a flat test piece of the polyacetal resin alone (i.e., Reference Example 2) contained in the polyacetal resin composition (amount of formaldehyde emitted from a flat test piece of a polyacetal resin composition containing a modifier / amount of formaldehyde emitted from a flat test piece of the polyacetal resin alone (i.e., Reference Example 2)) is 2.5 or less, the polyacetal resin composition can be determined to emit a small amount of formaldehyde (amount of VOC emitted) during and after molding.

[0173] Next, each production method, each example, and each comparative example will be described below.

[0174] <Preparation of Rubber-Containing Graft Copolymer (A)> [Production Example 1] Synthesis of Aqueous Latex Containing Rubber-Containing Graft Copolymer (A) 100 parts of pure water and 0.014 parts of polyoxyethylene alkyl ether sodium phosphate as a surfactant were charged into a pressure-resistant polymerization vessel equipped with a stirrer while blowing in nitrogen. Next, while stirring the charged raw materials, the gas inside the pressure-resistant polymerization vessel was replaced with nitrogen, thereby thoroughly removing oxygen from inside the pressure-resistant polymerization vessel. Thereafter, the temperature of the solution in the pressure-resistant vessel was raised to 50°C. Thereafter, 8.5 parts of butyl acrylate (BA), 0.04 parts of allyl methacrylate, and 0.002 parts of t-butyl hydroperoxide (BHP) were added to the pressure-resistant vessel all at once. Thereafter, 0.002 parts of ethylenediaminetetraacetic acid disodium salt (EDTA), 0.0012 parts of ferrous sulfate, and 0.05 parts of sodium formaldehyde sulfoxylate (SFS) were added to the pressure-resistant vessel. Polymerization was then carried out over 1 hour. A mixture of 0.68 parts of surfactant sodium polyoxyethylene alkyl ether phosphate, 64.5 parts of BA, 0.32 parts of allyl methacrylate, and 0.02 parts of BHP was then added to the pressure vessel over 210 minutes. The reaction solution in the pressure polymerization vessel was then maintained at 50°C for 45 minutes to polymerize, yielding an aqueous latex containing an elastomer. Next, 73 parts of the elastomer solids (50°C) and 150 parts of pure water (50°C) were added to the glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The raw materials were stirred at 50°C while the gas in the glass reactor was replaced with nitrogen. Next, a mixture of 25.3 parts of methyl methacrylate (MMA) and 1.7 parts of BA was added to the glass reactor over 1 hour as the monomer component. Simultaneously with the addition of the monomer components (i.e., MMA and BA), the addition of 0.0125 parts of BHP to the glass reactor was started. After the addition of BHP was completed, the temperature of the reaction solution in the glass reactor was maintained at 50°C for 1 hour to carry out polymerization, thereby obtaining an aqueous latex containing a rubber-containing graft copolymer (A). The volume average particle diameter of the rubber-containing graft copolymer (A) contained in the obtained aqueous latex was 200 nm.

[0175] <Preparation of Emulsion of Polymer Compound (B)> 4.5 parts by mass of pure water, 0.45 parts by mass of polyoxyethylene alkyl ether sodium phosphate as an emulsifier, 1 part by mass of epoxidized soybean oil as polymer compound (B), 0.125 parts by mass of IRGANOX 245, and 0.375 parts by mass of DLTP "Yoshitomi" were stirred at 10,000 rpm for 10 minutes using a Homomixer HM-310 (manufactured by AS ONE Corporation). This operation yielded an emulsion of epoxidized soybean oil, which is polymer compound (B) having a glycidyl group.

[0176] <Preparation of Polyacetal Resin Modifier> (Example 1) To an aqueous latex containing 100 parts by mass of the solid content of the rubber-containing graft copolymer (A), 6.45 parts by mass of an emulsion of the polymer compound (B), corresponding to 1 part by mass of epoxidized soybean oil, was added. Then, an aqueous solution of calcium chloride was added to the obtained aqueous latex, and coagulation was performed to obtain a slurry containing aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B). The amount of calcium chloride used was 3.5 parts by mass per 100 parts by mass of the total amount of the rubber-containing graft copolymer (A) and the polymer compound (B). The obtained slurry was then dehydrated, and the aggregates were recovered. Subsequently, the aggregates were washed with 1,000 parts by mass of washing water per 100 parts by mass of the solid content of the aggregates, and further dehydrated. The obtained aggregates were then dried to obtain a polyacetal resin modifier (M-1) containing the rubber-containing graft copolymer (A) and the polymer compound (B). The contents of chlorine and calcium and the pH of the resulting modifier were measured, and the results are shown in Table 1.

[0177] (Examples 2 to 4, Comparative Examples 1 and 2) In Examples 2 to 4 and Comparative Examples 1 and 2, modifiers for polyacetal resins were prepared by the same procedures as in Example 1, except that the amount of the emulsion of the polymer compound (B) having glycidyl groups (i.e., the amount of epoxidized soybean oil, which is the polymer compound (B)), and the amount of wash water used were changed as shown in Table 1. That is, in Comparative Example 1, no polymer compound (B) having glycidyl groups was used, and in Comparative Example 2, the obtained aggregates were not washed. The modifiers obtained in Examples 2 to 4 and Comparative Examples 1 and 2 were designated modifiers (M-2) to (M-6), respectively. The chlorine and calcium element contents and pH of each of the obtained modifiers were measured, and the results are shown in Table 1.

[0178] (Comparative Example 3) An aqueous latex containing 100 parts by mass of solids of the rubber-containing graft copolymer (A) was placed in a container, and the water in the container was evaporated using a vacuum pump equipped with a cold trap, thereby obtaining a slurry containing aggregates containing the rubber-containing graft copolymer (A). Subsequently, the aggregates were washed with 2,500 parts of pure water as washing water per 100 parts of solids of the aggregates, and the aggregates were further dehydrated. The obtained aggregates were then dried to obtain a polyacetal resin modifier (M-7) containing the rubber-containing graft copolymer (A). The elemental contents of chlorine and calcium, as well as the pH of the obtained modifier, were measured, and the results are shown in Table 1. Note that "N.D." stands for "Not Detection," and means that the element was not detected (was not detectable).

[0179] (Comparative Example 4) To an aqueous latex containing 100 parts by mass of the solid content of the rubber-containing graft copolymer (A), 19.35 parts by mass of an emulsion of the polymer compound (B), corresponding to 3 parts by mass of epoxidized soybean oil, was added. Thereafter, 3.5 parts by mass of an aqueous solution of magnesium chloride as a coagulant was added to the obtained aqueous latex, and coagulation was performed to obtain a slurry containing aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B). Next, the obtained slurry was dehydrated, and the aggregates were recovered. Subsequently, the aggregates were washed with 2,500 parts by mass of washing water per 100 parts by mass of the solid content of the aggregates, and further dehydrated. Thereafter, the obtained aggregates were dried to obtain a polyacetal resin modifier (M-8) containing the rubber-containing graft copolymer (A) and the polymer compound (B). The chlorine element and calcium element contents, as well as the pH, of the obtained modifier were measured, and the results are shown in Table 1. It should be noted that "ND" stands for Not Detection, and indicates that the element was not detected (was undetectable).

[0180] (Comparative Example 13) <Preparation of a polyacetal resin modifier (M-9) containing a rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group> <Synthesis of a rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group> While blowing nitrogen into a pressure-resistant polymerization vessel equipped with a stirrer, 100 parts of pure water and 0.014 parts of polyoxyethylene alkyl ether sodium phosphate as a surfactant were charged. Next, while stirring the charged raw materials, the gas inside the pressure-resistant polymerization vessel was replaced with nitrogen, thereby thoroughly removing oxygen from inside the pressure-resistant polymerization vessel. Thereafter, the temperature of the solution in the pressure-resistant vessel was raised to 50°C. Thereafter, 8.5 parts of butyl acrylate (BA), 0.04 parts of allyl methacrylate, and 0.002 parts of t-butyl hydroperoxide (BHP) were added to the pressure-resistant vessel all at once. Next, 0.002 parts of ethylenediaminetetraacetic acid disodium salt (EDTA), 0.0012 parts of ferrous sulfate, and 0.05 parts of sodium formaldehyde sulfoxylate (SFS) were added to the pressure vessel. Polymerization was then carried out over 1 hour. A mixture of 0.68 parts of polyoxyethylene alkyl ether sodium phosphate, 64.5 parts of BA, 0.32 parts of allyl methacrylate, and 0.02 parts of BHP, which were surfactants, was then added to the pressure vessel over 210 minutes. The reaction solution in the pressure polymerization vessel was then maintained at 50°C for 45 minutes to carry out polymerization, yielding an aqueous latex containing an elastomer. Next, 73 parts of the elastomer solids (50°C) and 150 parts of pure water (50°C) were added to the glass reactor. The glass reactor was equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reactor was replaced with nitrogen, and the raw materials introduced were stirred at 50°C. Next, a mixture of 20.3 parts of methyl methacrylate (MMA), 5 parts of glycidyl methacrylate (GMA), and 1.7 parts of BA was added to the glass reactor over 1 hour. Simultaneously with the addition of the monomer components (i.e., MMA, GMA, and BA), addition of 0.0125 parts of BHP to the glass reactor was initiated.After the addition of BHP was completed, the temperature of the reaction solution in the glass reactor was maintained at 50°C for 1 hour to carry out polymerization, thereby obtaining an aqueous latex containing a rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group. The volume average particle diameter of the rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group contained in the obtained aqueous latex was 200 nm.

[0181] Thereafter, an aqueous solution of calcium chloride was added to the obtained aqueous latex, and coagulation was carried out to obtain a slurry containing aggregates of a rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group. The amount of calcium chloride used was 3.5 parts by mass per 100 parts by mass of the rubber-containing graft copolymer. The obtained slurry was then dehydrated, and the aggregates were recovered. Subsequently, the aggregates were washed with 1,000 parts by mass of washing water per 100 parts by mass of the solid content of the aggregates, and further dehydrated. The obtained aggregates were then dried to obtain a polyacetal resin modifier (M-9) containing a rubber-containing graft copolymer containing structural units derived from a vinyl-based monomer having a reactive functional group. The chlorine and calcium element contents, as well as the pH, of the obtained modifier were measured, and the results are shown in Table 1.

[0182] In all Examples and Comparative Examples 1, 2, 4 and 13, pure water having an electrical conductivity of 0.1 mS / m was used as the cleaning water.

[0183] <Preparation of Polyacetal Resin> [Production Example 2] Synthesis of Polyacetal Resin (C) Trioxane and 1,3-dioxolane were copolymerized so that the content of structural units derived from 1,3-dioxolane was 3.8% by mass (4.6 mol%) based on 100% by mass of the resulting polyacetal resin. 0.3 parts by mass of IRGANOX 245 and 0.05 parts by mass of melamine were added to the resulting copolymer. The resulting mixture was melt-kneaded at 222°C for 20 minutes, and the resulting resin was used as polyacetal resin (C). The melt index of the resulting polyacetal resin (C) (ASTM-D1238 standard: 190°C, 2.16 kg) was 10.5 g / 10 min.

[0184] (Examples 5 to 11, Comparative Examples 5 to 8, 14, and Reference Example 1) (Production of Polyacetal Resin Composition) Each of the modifiers for polyacetal resin compositions (M1 to M9) was dry-blended with polyacetal resin (C) in the compounding ratios shown in Tables 2 and 3. Next, the resulting mixture was melt-shear mixed using a vented twin-screw extruder ("PCM-30" manufactured by Ikegai Corporation) with a screw diameter (D) of 30 mm, a screw length (L) of 760 mm, and a die nozzle diameter of 3.5 mm at a cylinder temperature (melt temperature) of 200°C, a screw rotation speed of 120 rpm, and a discharge rate of 10 kg / hour to produce pellets of the polyacetal resin composition.

[0185] The resulting pellets (polyacetal resin composition) were then dried at 90°C for 5 hours. The dried polyacetal resin composition pellets were then injection molded using a Toshiba Machine EC-100 injection molding machine at a cylinder temperature of 195°C and a mold temperature of 90°C to prepare ISO test specimens. Impact resistance and flexural modulus were measured using the resulting ISO test specimens. Furthermore, flat plate test specimens were prepared using the resulting pellets (polyacetal resin composition) by the method described above, and the amount of formaldehyde generated was measured using the flat plate test specimens. These results are shown in Tables 2 and 3.

[0186] In Comparative Example 14, in which the polyacetal resin composition modifier (M-9) was used, many lumps were found on the surface of the pellets of the obtained polyacetal resin composition, so no ISO test pieces or flat test pieces were prepared or evaluated. This is indicated in Table 2 as "No test pieces prepared."

[0187] (Examples 12 to 24, Comparative Examples 9 to 12, and Reference Example 2) (Production of Polyacetal Resin Composition) Each of the modifiers for polyacetal resin compositions (M1 to M8), polyacetal resin (C), and a formaldehyde scavenger were dry-blended in the blending ratios shown in Tables 4 and 5. In each of the Examples and Comparative Examples, the formaldehyde scavenger used was one of the substances shown in Tables 4 and 5. The resulting mixture was then melt-shear mixed using a vented twin-screw extruder (manufactured by Ikegai Corporation, "PCM-30") with a screw diameter (D) of 30 mm, a screw length (L) of 760 mm, and a die nozzle diameter of 3.5 mm, at a cylinder temperature (melt temperature) of 200°C, a screw rotation speed of 120 rpm, and a discharge rate of 10 kg / hour, to produce pellets of the polyacetal resin composition.

[0188] The resulting pellets (polyacetal resin composition) were then dried at 90°C for 5 hours. The dried pellets of the polyacetal resin composition were then injection-molded using a Toshiba Machine EC-100 injection molding machine at a cylinder temperature of 195°C and a mold temperature of 90°C to prepare ISO test specimens. Impact resistance and flexural modulus were measured using the resulting ISO test specimens. Furthermore, flat plate test specimens were prepared using the resulting pellets (polyacetal resin composition) by the method described above, and the amount of formaldehyde generated was measured using the flat plate test specimens. These results are shown in Tables 4 and 5.

[0189] (Examples 25-30, Comparative Example 15) (Production of Polyacetal Resin Composition) Each of the modifiers for polyacetal resin compositions (M1 to M4, M10) was dry-blended with polyacetal resin (C), 0.4 parts by weight of Tinuvin 234, and 0.3 parts by weight of Tinuvin 622. The resulting mixture was then melt-shear mixed using a vented twin-screw extruder (manufactured by Ikegai Corporation, "PCM-30") with a screw diameter (D) of 30 mm, a screw length (L) of 760 mm, and a die nozzle diameter of 3.5 mm, at a cylinder temperature (melt temperature) of 200°C, a screw rotation speed of 120 rpm, and a discharge rate of 10 kg / hour to produce pellets of the polyacetal resin composition. In Comparative Example 15, Kane Ace M-910, a butadiene-based rubber-containing graft copolymer manufactured by Kaneka Corporation, was used as modifier M-10.

[0190] Subsequently, the obtained pellets (polyacetal resin composition) were dried at 90°C for 5 hours. Thereafter, the dried pellets of the polyacetal resin composition were injection molded using a Toshiba Machine EC-100 injection molding machine at a cylinder temperature of 195°C and a mold temperature of 90°C to prepare ISO test specimens. The obtained ISO test specimens were used to measure impact resistance, flexural modulus, and weather resistance. Furthermore, the obtained pellets (polyacetal resin composition) were used to prepare flat test specimens by the method described above, and the amount of formaldehyde generated was measured using the flat test specimens. These results are shown in Table 6.

[0191] As shown in Tables 2 to 5, it can be seen that by mixing the polyacetal resin modifier according to one embodiment of the present invention with the polyacetal resin (C), a polyacetal resin composition can be provided that (a) produces a small amount of VOC (formaldehyde) and (b) can provide a molded article with good impact resistance.

[0192] A polyacetal resin composition using the polyacetal resin modifier according to one embodiment of the present invention can be suitably used in electrical and electronic applications, automotive parts applications, and industrial equipment applications. For example, a polyacetal resin composition using the polyacetal resin modifier according to one embodiment of the present invention can be suitably used in mechanical parts for drive units of AV equipment, dishwasher handles, speaker grilles, washing machine tub stirring propellers, office equipment switches, gears, automobile wiper motor system gears, regulator handles, inner door handles, door lock side covers, shift levers, heater fans, pipe holders, power window regulators, seat belts, power seat gears, sunroofs, clips, fasteners, industrial equipment conveyor screws, belt conveyors, chains, torque limiters, etc.

Claims

1. A modifier for polyacetal resin, comprising: The present invention comprises a rubber-containing graft copolymer (A) and a polymer compound (B) having a glycidyl group, The rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, the graft portion is composed only of structural units derived from a vinyl monomer having no reactive functional group, a mass ratio of the elastic body to the graft portion (mass parts of the elastic body / mass parts of the graft portion) is 60 / 40 to 95 / 5; The content of chlorine element in the polyacetal resin modifier is 1 ppm to 170 ppm based on the mass of the polyacetal resin modifier; The content of calcium element in the polyacetal resin modifier is 1 ppm to 780 ppm based on the mass of the polyacetal resin modifier; The mixture of 10 parts by mass of the polyacetal resin modifier and 100 parts by mass of deionized water has a pH of 6.0 to 8.0; The epoxy group content in the polyacetal resin modifier is 15 μmol / g to 180 μmol / g, The content of the polymer compound (B) in the polyacetal resin modifier is 0.1 parts by mass or more and 5.0 parts by mass or less based on 100 parts by mass of the rubber-containing graft copolymer (A); Modifier for polyacetal resin.

2. The polyacetal resin modifier according to claim 1 , wherein the polymer compound (B) is at least one of epoxidized soybean oil and epoxidized castor oil.

3. The modifier for polyacetal resin according to claim 1 , wherein the elastic body is composed only of a (meth)acrylate rubber.

4. The polyacetal resin modifier according to claim 1 , wherein the polyacetal resin modifier is in the form of powder or granule.

5. A polyacetal resin composition comprising the polyacetal resin modifier according to any one of claims 1 to 4 and a polyacetal resin (C).

6. 6. The polyacetal resin composition according to claim 5, wherein the polyacetal resin modifier is 3% by mass to 80% by mass, and the polyacetal resin (C) is 20% by mass to 97% by mass, when the total of the polyacetal resin modifier and the polyacetal resin (C) is 100% by mass.

7. The polyacetal resin composition according to claim 5 , further comprising a formaldehyde scavenger.

8. The formaldehyde scavenger comprises a reactive group reactive with formaldehyde, 8. The polyacetal resin composition according to claim 7, wherein the content of the formaldehyde scavenger in the polyacetal resin composition is an amount such that the reactive group is 3.0 μmol or more per 1 g of the total of the polyacetal resin modifier and the polyacetal resin (C).

9. The polyacetal resin composition according to claim 7 , wherein the formaldehyde scavenger comprises at least one selected from the group consisting of hydrazide compounds, hydrazones of hydrazine compounds, guanamine compounds, and urea compounds.

10. A method for producing a modifier for polyacetal resin, comprising the steps of: a polymer compound (B) addition step of adding a polymer compound (B) having a glycidyl group in an emulsified state to an aqueous latex containing the rubber-containing graft copolymer (A); an aggregation step of adding calcium chloride to the aqueous latex obtained in the polymer compound (B) adding step to obtain aggregates containing the rubber-containing graft copolymer (A) and the polymer compound (B); a washing step of washing the aggregate obtained in the aggregation step; Including, The rubber-containing graft copolymer (A) has an elastomer and a graft portion graft-bonded to the elastomer, the graft portion is composed only of structural units derived from a vinyl monomer having no reactive functional group, a mass ratio of the elastic body to the graft portion (mass parts of the elastic body / mass parts of the graft portion) is 60 / 40 to 95 / 5; The pH of the aqueous latex is from 5 to 9, The epoxy group content in the polyacetal resin modifier is 15 μmol / g to 180 μmol / g, The content of the polymer compound (B) in the polyacetal resin modifier is 0.1 parts by mass or more and 5.0 parts by mass or less based on 100 parts by mass of the rubber-containing graft copolymer (A); A method for producing a modifier for polyacetal resin.