Impact modifier for polyacetal resin and polyacetal resin composition

Abstract

To provide a novel impact resistance modifier for polyacetal resin that can provide a polyacetal resin composition with a reduced amount of VOC generation.SOLUTION: An impact resistance modifier for polyacetal resin (X) contains a rubber-containing graft copolymer (D) having a specific structure, and further contains a specific alkali metal component (C), and further contains specific amounts of the phosphorus element and an alkali metal element. A mixture of the impact resistance modifier for polyacetal resin (X) 25 pts.wt. and a deionization water 75 pts.wt. has a pH of 7.0 or more and 11.0 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an impact modifier for a polyacetal resin and a polyacetal resin composition. [Background technology]

[0002] Polyacetal resin is a crystalline engineering plastic, and its high crystallinity gives it excellent strength, sliding properties, and dimensional stability. For this reason, polyacetal resin is widely used not only for housings, but also for electrical and electronic parts and automotive parts, such as resin gears, doorknobs, and clips. These resin parts are required to have high impact resistance, low wear, and low noise, and among these, high impact resistance is considered to be the most important.

[0003] Furthermore, in recent years, resin parts that generate less VOCs (volatile organic compounds) are required for automobile parts, and therefore resin compositions that generate less VOCs are required.

[0004] Various impact modifiers for polyacetal have been developed. For example, Patent Document 1 discloses a core-shell polymer having a rubbery polymer core and a glassy polymer shell, which is obtained by emulsion polymerization using a nonionic surfactant and a polymerization initiator that generates neutral radicals.

[0005] Furthermore, Patent Document 2 discloses an impact resistance modifier for polyacetal resin, which is a graft copolymer in which a vinyl monomer component is graft-polymerized onto a rubber polymer, and which is characterized by containing 0.1 to 0.5 mass % of calcium.

[0006] Furthermore, Patent Document 3 discloses a stabilized MBS core-shell graft copolymer formed from a rubber elastic core containing polybutadiene, a hard graft shell, and a stabilizer blend composed of at least one of a hindered phenol, a phosphite, a sulfide, and a pH buffer system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 6-100759 [Patent Document 2] Patent No. 5269302 [Patent Document 3] Japanese Patent Application Publication No. 7-316393 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional techniques are not sufficient from the viewpoint of the amount of VOCs emitted, and there is room for further improvement.

[0009] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a novel impact modifier for polyacetal resin, which can provide a polyacetal resin composition with low VOC emission. [Means for solving the problem]

[0010] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered the new finding that an impact modifier for polyacetal resin, which contains a rubber-containing graft polymer, a phosphorus element and an alkali metal element, emits low amounts of VOCs, and have completed the present invention.

[0011] That is, one embodiment of the present invention includes the following configuration. [1] An impact resistance modifier (X) for a polyacetal resin, comprising a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer, further comprising an alkali metal component (C), the alkali metal component (C) being a compound obtained by: (i) reacting a polymer having, as a constituent unit, a constituent unit derived from one or more compounds selected from the group consisting of (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, with sodium hydroxide and / or potassium hydroxide; and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms with an alkali metal, wherein 100% by weight of the impact modifier for polyacetal resin (X) further contains 0.010% by weight to 0.300% by weight of phosphorus and 0.010% by weight to 0.300% by weight of an alkali metal element, and a mixture of 25 parts by weight of the impact modifier for polyacetal resin (X) and 75 parts by weight of deionized water has a pH of 7.0 or more and 11.0 or less. [2] The impact resistance modifier (X) for polyacetal resin according to [1], wherein the impact resistance modifier (X) for polyacetal resin contains 0.010 wt % to 0.150 wt % of the alkali metal element in 100 wt % of the impact resistance modifier (X) for polyacetal resin. [3] An impact modifier for polyacetal resin (X) comprising a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer, wherein the rubber-containing graft copolymer (D) further comprises an alkali metal element, the content of the alkali metal element being 0.010% by weight to 0.300% by weight in 100% by weight of the impact modifier for polyacetal resin (X), the impact modifier for polyacetal resin (X) further comprises 0.010% by weight to 0.300% by weight of phosphorus element in 100% by weight of the impact modifier for polyacetal resin (X), and the pH of a mixture consisting of 25 parts by weight of the impact modifier for polyacetal resin (X) and 75 parts by weight of deionized water is 7.0 or more and 11.0 or less. [4] The impact resistance modifier (X) for polyacetal resins according to [3], wherein the content of the alkali metal element is 0.010% by weight to 0.150% by weight in 100% by weight of the impact resistance modifier (X) for polyacetal resins. [5] The impact resistance modifier for polyacetal resin (X) according to any one of [1] to [4], wherein the content of an alkaline earth metal element in the impact resistance modifier for polyacetal resin (X) is less than 0.100% by weight, based on 100% by weight of the impact resistance modifier for polyacetal resin (X). [6] The impact resistance modifier for polyacetal resin (X) according to any one of [1] to [5], wherein the content of chlorine element in the impact resistance modifier for polyacetal resin (X) is less than 0.040% by weight, based on 100% by weight of the impact resistance modifier for polyacetal resin (X). [7] The impact resistance modifier (X) for polyacetal resin according to any one of [1] to [6], wherein the elastomer comprises at least one selected from the group consisting of butadiene rubber, styrene / butadiene copolymer rubber, acrylate rubber, and silicone rubber. [8] A polyacetal resin composition comprising the impact modifier for polyacetal resin (X) according to any one of [1] to [7] and a polyacetal resin (A). [9] A method for producing an impact resistance modifier (X) for a polyacetal resin, comprising: a step of mixing an aggregate containing a pH adjuster (B) containing a phosphorus component and a rubber-containing graft copolymer (D) with an alkali metal component (C), wherein the alkali metal component (C) is one or more selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer obtained by polymerizing one or more selected from the group consisting of a (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms with an alkali metal.

[10] The method for producing the impact modifier (X) for polyacetal resin according to [9], wherein the pH adjuster (B) containing a phosphorus component is one or more selected from the group consisting of a mixture of sodium hydroxide or potassium hydroxide with phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tripotassium phosphate. Effect of the Invention

[0012] According to one embodiment of the present invention, there is an effect of providing a novel impact modifier for polyacetal resin, which can provide a polyacetal resin composition with low VOC emission. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] 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 each configuration described below, and various modifications are possible within the scope of the claims. In addition, 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 documents and patent documents described in this specification are incorporated herein by reference. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and smaller than B)".

[0014] In addition, unless otherwise specified in this specification, the structural units include a structural unit derived from an X1 monomer, a structural unit derived from an X2 monomer, and X n A copolymer containing a monomer (n is an integer of 2 or more) is represented by X1 / X2 / ··· / X n Also called copolymer. X1 / X2 / ··· / X nUnless otherwise specified, the copolymer is not particularly limited in polymerization mode, and may be a random copolymer, a block copolymer, or a graft copolymer. In addition, unless otherwise specified in this specification, the constituent units are a constituent unit derived from an X1 monomer, a constituent unit derived from an X2 monomer, ..., and an X n An elastomer containing a monomer (n is an integer of 2 or more) is represented by X1 / X2 / ··· / X n Also called rubber.

[0015] 1. Technical Concept of One Embodiment of the Present Invention One of the above-mentioned VOCs is formaldehyde. VDA275, one of the German automotive standards, describes a method for measuring formaldehyde emitted from resin parts (molded bodies). In recent years, there has been discussion about the amount of VOCs emitted using unified measurement methods based on these standards.

[0016] Polyacetal resin is sensitive to the pH and residual ion amount of additives, and depending on the pH and residual ion amount, polyacetal may decompose during processing of polyacetal resin, generating formaldehyde that is toxic to the human body. Since the pH and residual ions remain in the molded body of polyacetal resin, formaldehyde released from the molded body of polyacetal resin becomes a problem in a closed space. On the other hand, there are applications of polyacetal that require impact resistance, and an impact modifier is required. When an impact modifier produced using an anionic emulsifier and coagulant is added to polyacetal resin, the amount of formaldehyde generated from the polyacetal resin composition or its molded body is large, and the amount of formaldehyde is not acceptable, especially for automotive applications. Therefore, it was necessary to improve the impact modifier.

[0017] When the impact resistance improvers of the above-mentioned Patent Documents 1 to 3 are blended with a polyacetal resin, the amount of VOCs generated during molding of the polyacetal resin composition cannot be sufficiently reduced.

[0018] In addition to the above-mentioned object, one embodiment of the present invention has the following additional object (a), (b) and / or (c) which are preferably achieved: (a) to provide an impact modifier for polyacetal resin that is useful for achieving both high impact resistance and low formaldehyde generation at a higher level in polyacetal resin; (b) to provide an impact modifier for polyacetal resin and a polyacetal resin composition containing the same that can reduce formaldehyde generated during and after molding of the polyacetal resin composition and further impart impact resistance; and (c) to provide an impact modifier for polyacetal resin and a polyacetal resin composition containing the same that can provide a molded product having excellent color tone.

[0019] The present inventors have conducted intensive research to solve the above-mentioned problems, and have found that by using a specific impact modifier for polyacetal resin, it is possible to achieve both high impact resistance of the polyacetal resin composition and a reduction in the amount of VOC during and after molding at a higher level.The present inventors have also found that it is possible to provide (a) an impact modifier for polyacetal resin using a specific rubber-containing graft copolymer, which can achieve both high impact resistance and a reduction in the amount of VOC during and after molding at a higher level, (b) a polyacetal resin composition containing the impact modifier for polyacetal resin, and (c) an impact modifier for polyacetal resin and a polyacetal resin composition containing the same, which can provide a molded product with excellent color tone.

[0020] According to one embodiment of the present invention, it is possible to provide: (a) an impact modifier for polyacetal resin, containing a rubber-containing graft copolymer, which is useful for achieving both high impact resistance of the polyacetal resin and a reduced amount of formaldehyde generated at a higher level; (b) an impact modifier for polyacetal resin, which can reduce the amount of formaldehyde generated during and after molding of the polyacetal resin composition and further impart impact resistance, and a polyacetal resin composition containing the same; and (c) an impact modifier for polyacetal resin, which can provide a molded product having excellent color tone, and a polyacetal resin composition containing the same.

[0021] [2. Impact modifier for polyacetal resin (X)] The impact modifier (X) for polyacetal resin according to one embodiment of the present invention is an impact modifier (X) for polyacetal resin containing a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer. The impact modifier (X) for polyacetal resin according to one embodiment of the present invention further contains an alkali metal component (C). The alkali metal component (C) is at least one selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer having, as a constituent unit, a constituent unit derived from one or more compounds selected from the group consisting of (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms and an alkali metal. The impact resistance modifier for polyacetal resin (X) according to one embodiment of the present invention further contains 0.010% by weight to 0.300% by weight of phosphorus element and 0.010% by weight to 0.300% by weight of alkali metal element in 100% by weight of the impact resistance modifier for polyacetal resin (X). The impact resistance modifier for polyacetal resin (X) according to one embodiment of the present invention has a pH of 7.0 or more and 11.0 or less when composed of 25 parts by weight of the impact resistance modifier for polyacetal resin (X) and 75 parts by weight of deionized water.

[0022] As used herein, "(meth)acrylate" refers to "methacrylate" and / or "acrylate", and "(meth)acrylic acid" refers to "methacrylic acid" and / or "acrylic acid".

[0023] "Impact modifier (X) for polyacetal resin" may be referred to as "modifier (X)" hereinafter. "Impact modifier (X) for polyacetal resin according to one embodiment of the present invention" may be referred to as "the present modifier (X)" hereinafter. The present modifier (X) becomes a polyacetal resin composition when mixed with a polyacetal resin (A) described later.

[0024] The present modifier (X) has the above-mentioned constitution, and therefore has the advantage of being able to provide a polyacetal resin composition that generates less VOC. Specifically, the present modifier (X) can provide a polyacetal resin composition that generates less VOC during and after molding of the polyacetal resin composition. The present modifier (X) also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article with excellent impact resistance. The present modifier (X) also has the advantage of being able to achieve both (a) high impact resistance of the molded article of the polyacetal resin composition and (b) reduced VOC generation during and after molding of the polyacetal resin composition at a high level. The present modifier (X) can also provide a polyacetal resin composition that can provide a molded article with excellent color tone. In this specification, the less yellow the molded article is, the more the molded article is said to have "excellent color tone".

[0025] (2-1. Rubber-containing graft copolymer (D)) The rubber-containing graft copolymer (D) contained in the present modifier (X) has an elastomer and a graft portion graft-bonded to the elastomer.

[0026] (Elastic body) The elastomer may include one or more selected from the group consisting of natural rubber, diene rubber, acrylate rubber, and polyorganosiloxane rubber. The elastomer preferably includes one or more selected from the group consisting of diene rubber, acrylate rubber, and polyorganosiloxane rubber.

[0027] (Diene rubber) The diene rubber is an elastomer containing a constituent unit derived from a diene monomer as a constituent unit. The elastomer is preferably an elastomer containing a diene rubber, more preferably a diene rubber, because the glass transition temperature (hereinafter also referred to as Tg) of the obtained elastomer can be lowered, the impact resistance of the molded article of the obtained polyacetal resin composition is improved, and the raw material cost is low.

[0028] Examples of the diene monomer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2-chloro-1,3-butadiene, etc. These diene monomers may be used alone or in combination of two or more.

[0029] The diene rubber may further contain, as a structural unit, a structural unit derived from a vinyl monomer other than the diene monomer that is copolymerizable with the diene monomer.

[0030] Examples of vinyl monomers other than diene monomers that can be copolymerized with diene monomers (hereinafter also referred to as vinyl monomer A) include: (a) aromatic vinyl monomers such as styrene, α-methylstyrene, monochlorostyrene, and dichlorostyrene; (b) vinyl carboxylic acids such as acrylic acid and methacrylic acid; (c) alkyl (meth)acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; (d) 2- Examples of the vinyl monomer include hydroxyl group-containing vinyl monomers such as hydroxyethyl methacrylate and 4-hydroxybutyl acrylate; (e) glycidyl group-containing vinyl monomers such as glycidyl methacrylate and 4-hydroxybutyl acrylate glycidyl ether; (f) unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; (g) vinyl halides such as vinyl chloride, vinyl bromide and chloroprene; (h) vinyl acetate; (i) alkenes such as ethylene, propylene, butylene and isobutylene. The vinyl monomer A may be used alone or in combination of two or more kinds.

[0031] In the diene rubber, there is no particular limitation on the content of constituent units derived from the vinyl monomer A. The diene rubber preferably contains 50 to 100% by weight of constituent units derived from diene monomers and 0 to 50% by weight of constituent units derived from the vinyl monomer A, based on 100% by weight of constituent units.

[0032] The diene rubber may further contain, as a constituent unit, a constituent unit derived from a multifunctional monomer such as diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, etc. In other words, these multifunctional monomers may be used in the polymerization of the diene rubber.

[0033] Suitable examples of diene rubber include butadiene rubber (polybutadiene rubber), styrene / butadiene copolymer rubber (poly(styrene / butadiene) rubber), poly(acrylonitrile / butadiene) rubber, butadiene / acrylic acid ester copolymer, etc. Butadiene rubber is an elastomer containing 50 to 100% by weight of structural units derived from 1,3-butadiene out of 100% by weight of structural units.

[0034] The diene rubber is preferably a butadiene rubber containing 50 to 100% by weight of structural units derived from 1,3-butadiene and 0 to 50% by weight of structural units derived from a vinyl monomer A, and more preferably a 1,3-butadiene homopolymer containing 100% by weight of structural units derived from 1,3-butadiene.

[0035] It is more preferable that the elastomer contains butadiene rubber, and it is particularly preferable that the elastomer is butadiene rubber, because this can reduce the glass transition temperature (hereinafter also referred to as Tg) of the resulting elastomer, the effect of improving the impact resistance of the molded article of the resulting polyacetal resin composition is high, and the raw material cost is low.

[0036] (Acrylate rubber) The acrylate rubber is an elastomer that contains, as a structural unit, a structural unit derived from a (meth)acrylate monomer.

[0037] 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, 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.

[0038] The 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) the diene monomer described above, and (b) a monomer among the vinyl monomers A other than the (meth)acrylate monomer.

[0039] The acrylate rubber may further contain a structural unit derived from a crosslinking agent and / or a graft crosslinking agent. In other words, a crosslinking agent and / or a graft crosslinking agent may be used in the manufacturing process of the acrylate rubber. Examples of the crosslinking agent and the graft crosslinking agent 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.

[0040] Suitable examples of the acrylate rubber include polybutyl acrylate rubber and butyl acrylate / 2-ethylhexyl acrylate copolymer. Polybutyl acrylate rubber is an elastomer containing 50 to 100% by weight of structural units derived from butyl acrylate out of 100% by weight of structural units.

[0041] Suitable examples of the polyorganosiloxane rubber include silicone rubber and silicone / acrylate rubber.

[0042] Examples of silicone rubbers include polymethyl silicone rubber and polymethylphenyl silicone rubber. Examples of silicone / acrylate rubbers include polyorganosiloxane / butyl acrylate copolymers.

[0043] In one embodiment of the present invention, the elastic body preferably contains one or more materials selected from the group consisting of butadiene rubber, styrene / butadiene copolymer rubber, acrylate rubber, and silicone rubber.

[0044] (Glass transition temperature of elastic body) The glass transition temperature of the elastic body is preferably not higher than 0° C. According to this configuration, there is an advantage that the obtained polyacetal resin composition containing the modifier (X) can provide a molded article having excellent toughness.

[0045] (Volume average particle size of elastic body) The volume average particle diameter of the elastomer is preferably 10 nm to 1 μm, more preferably 20 nm to 800 nm, and even more preferably 40 nm to 700 nm, since the rubber-containing graft copolymer (D) obtained exhibits good dispersibility in the polyacetal resin. The volume average particle diameter of the elastomer can be measured using a dynamic light scattering particle size distribution measuring device or the like, using an aqueous latex containing the elastomer as a sample. The method for measuring the volume average particle diameter of the elastomer will be described in detail in the following examples.

[0046] The "elastic body" of the rubber-containing graft copolymer (D) may be composed of only one type of elastomer having the same composition of the constituent units. The "elastic body" of the rubber-containing graft copolymer (D) may be composed of multiple types of elastomers having different compositions of the constituent units. In other words, the "elastic body" of the rubber-containing graft copolymer (D) may contain a composite of multiple elastomers polymerized separately, or may contain one elastomer obtained by sequentially polymerizing each of them. Polymerizing multiple elastomers (polymers) in sequence in this manner is also called multistage polymerization. One elastomer obtained by multistage polymerization of multiple types of elastomers is also called multistage polymerized elastomer. In the multistage polymerized elastomer, each of the multiple elastomers may form a layer structure. A multistage polymerized elastomer in which each of the multiple elastomers forms a layer structure can also be called a multilayer elastomer. That is, in one embodiment of the present invention, the "elastic body" of the rubber-containing graft copolymer (D) may contain a composite of multiple types of elastomers, a multistage polymerized elastomer, and / or a multilayer elastomer.

[0047] (Graft part) The graft portion may contain, as a constituent unit, (a) only a constituent unit derived from a vinyl-based monomer, or (b) a constituent unit derived from a vinyl-based monomer and a constituent unit derived from a monomer other than the vinyl-based monomer that is copolymerizable with the vinyl-based monomer.

[0048] Examples of the vinyl monomer include aromatic vinyl compounds, vinyl cyanide compounds, unsaturated carboxylic acids, and unsaturated carboxylates.

[0049] Suitable examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, α-methylvinyltoluene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and dibromostyrene.

[0050] Suitable examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.

[0051] Suitable examples of the unsaturated carboxylic acid and unsaturated carboxylate include acrylic acid, methacrylic acid, and acrylic acid esters and methacrylic acid esters having alkyl esters having 1 to 12 carbon atoms.

[0052] Further preferred examples of the vinyl monomer include (a) ester (meth)acrylates having an alkyl group with 1 to 22 carbon atoms and a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; and (b) ester (meth)acrylates having an alkyl group with 1 to 22 carbon atoms and an alkoxyl group, such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate.

[0053] When selecting a monomer to be used in the polymerization of the graft portion, it is preferable to consider the type of polyacetal resin (A) to be modified by blending the obtained rubber-containing graft copolymer (D). For example, when selecting a monomer in the polymerization of the graft portion, it is preferable to select one type of monomer or use two or more types of monomers in any mixing ratio or in combination, taking into consideration (a) the compatibility between the polyacetal resin (A) and the obtained rubber-containing graft copolymer (D), (b) the refractive index of the polyacetal resin composition obtained by blending the rubber-containing graft copolymer (D) with the polyacetal resin (A), etc.

[0054] The preferred vinyl monomer in the graft portion is one or more selected from (meth)acrylate monomers. Examples of the (meth)acrylate monomer include (a) alkyl ester acrylates having an alkyl group with 1 to 22 carbon atoms, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, and behenyl acrylate; and (b) alkyl (meth)acrylate monomers such as alkyl ester methacrylates having an alkyl group with 1 to 22 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, and behenyl methacrylate. These may be used alone or in combination of two or more.

[0055] The "graft portion" of the rubber-containing graft copolymer (D) may be composed of only one type of graft portion having the same composition of the constituent units. The "graft portion" of the rubber-containing graft copolymer (D) may be composed of multiple types of graft portions having different compositions of the constituent units. In other words, the "graft portion" of the rubber-containing graft copolymer (D) may contain a complex of multiple graft portions polymerized separately, or may contain one polymer obtained by sequentially polymerizing each of the multiple graft portions. A polymer obtained by multistage polymerization of multiple types of graft portions is also called a multistage polymerization graft portion. In the multistage polymerization graft portion, each of the multiple graft portions may form a layer structure. A multistage polymerization graft portion in which each of the multiple graft portions forms a layer structure can also be called a multilayer graft portion. That is, in one embodiment of the present invention, the "graft portion" of the rubber-containing graft copolymer (D) may contain a mixture of multiple types of graft portions, a multistage polymerization graft portion and / or a multilayer graft portion.

[0056] The amount of the grafted portion in the rubber-containing graft copolymer (D) is not particularly limited. The amount of the grafted portion in the rubber-containing graft copolymer (D) is preferably 11 parts by weight or more and less than 67 parts by weight, more preferably 18 parts by weight or more and less than 54 parts by weight, and even more preferably 25 parts by weight or more and less than 43 parts by weight, relative to 100 parts by weight of the elastomer, from the viewpoint of the compatibility between the rubber-containing graft copolymer (D) and the polyacetal resin (A) and the impact resistance of the molded body of the resin composition. When the amount of the grafted portion in the rubber-containing graft copolymer (D) is less than 11 parts by weight relative to 100 parts by weight of the elastomer, the dispersion of the rubber grafted copolymer in the polyacetal resin (A) in the resin composition becomes good, and as a result, the resin composition can provide a molded body having excellent impact resistance. When the amount of grafted portions in the rubber-containing graft copolymer (D) is less than 67 parts by weight per 100 parts by weight of elastomer, the amount of elastomer in the resulting rubber-containing graft copolymer (D) is appropriate, and the resulting resin composition containing the modifier (X) can provide a molded article having excellent impact resistance.

[0057] The rubber-containing graft copolymer (D) may be produced by any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but emulsion polymerization, i.e., emulsion graft polymerization, is preferred. Specifically, water and a surfactant are added to a reaction vessel equipped with a stirrer, and then a vinyl monomer, a polymerization initiator, and water are added, and if necessary, a chain transfer agent and / or an oxidation-reduction agent are added, and the mixture is heated and stirred to polymerize.

[0058] There is no particular restriction on the type of polymerization initiator, chain transfer agent, and redox agent used here, and known ones can be used. There is also no particular restriction on the method of adding each raw material to a reaction vessel, and they may be added all at once before the start of polymerization, or may be added in portions. The polymerization of the graft portion is carried out in one or more stages, and the monomer composition of each stage may be the same or different. In the polymerization of the graft portion, the monomers forming the graft portion may be added all at once in a short time, or may be added continuously in a certain amount over a certain period of time, or these may be combined.

[0059] When an emulsion polymerization method is adopted as the production method of the rubber-containing graft copolymer (D), a known polymerization initiator, for example, a known thermally decomposable polymerization initiator such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, or ammonium persulfate, can be used.

[0060] A redox type initiator can also be used to produce the rubber-containing graft copolymer (D). The redox type initiator is an initiator that uses (a) a peroxide such as an organic peroxide or an inorganic peroxide in combination with (b) a reducing agent such as sodium formaldehyde sulfoxylate or glucose, if necessary, a transition metal salt such as iron (II) sulfate, if necessary, a chelating agent such as disodium ethylenediaminetetraacetate, if necessary, and a phosphorus-containing compound such as sodium pyrophosphate, if necessary. Examples of organic peroxides include t-butyl peroxyisopropyl 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.

[0061] (2-2. Phosphorus-containing pH adjuster (B)) The present modifier (X) preferably contains a pH adjuster (B) containing a phosphorus component. The "pH adjuster (B) containing a phosphorus component" is hereinafter also referred to as "component (B)". When the present modifier (X) contains component (B), it has the advantage that the content of the phosphorus element contained in the modifier (X) can be easily adjusted to a desired content described below. Therefore, the modifier (X) can provide a polyacetal resin composition having a neutral or weakly basic pH, and as a result, a polyacetal resin composition that generates less VOCs can be provided.

[0062] There are no particular limitations on the other components of component (B) as long as it is a substance or mixture that contains phosphorus and can change the pH. However, in this specification, surfactants used in the manufacturing process of modifier (X) and reaction products (e.g., salts) between said surfactants and coagulants are not included in component (B) even if they contain phosphorus and can change the pH.

[0063] The pH of component (B) alone is preferably within the range of 7.0 to 11.0, and more preferably 7.0 to 10.0.

[0064] Component (B) includes sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, etc. Component (B) also includes mixtures of sodium hydroxide or potassium hydroxide with phosphoric acid.

[0065] The component (B) is preferably one or more selected from the group consisting of a mixture of sodium hydroxide or potassium hydroxide and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tripotassium phosphate. The component (B) having the above structure can easily adjust the pH of a polyacetal resin composition, etc., to a neutral or weakly basic pH, for example, 7.0 to 11.0. Therefore, when the present modifier (X) contains the component (B) having the above structure, the modifier (X) can provide a polyacetal resin composition that generates even less VOC. In addition, the component (B) included in the above group is highly water-soluble and an aqueous solution can be easily obtained. Therefore, the component (B) included in the above group can be blended with the rubber-containing graft copolymer (D) as an aqueous solution in the production method of the present modifier (X), and can be uniformly attached to the rubber-containing graft copolymer (D) without concentration bias.

[0066] The content of component (B) in the present modifier (X) is not particularly limited. In the present modifier (X), the content of component (B) relative to 100 parts by weight of the rubber-containing graft copolymer (D) is preferably 0.01 parts by weight or more and less than 0.40 parts by weight, more preferably 0.05 parts by weight or more and 0.35 parts by weight or less. When the content of component (B) is 0.01 parts by weight or more, the obtained modifier (X) can provide a polyacetal resin composition having a neutral or weakly basic pH, and as a result, a polyacetal resin composition that generates less VOC can be provided. When the content of component (B) is less than 0.40 parts by weight, the obtained modifier (X) can provide a polyacetal resin composition that is difficult to decompose due to a small amount of residual ion components, and as a result, a polyacetal resin composition that generates less VOC can be provided.

[0067] The present modifier (X) contains 0.010 wt% to 0.300 wt% of phosphorus in 100 wt% of modifier (X), preferably 0.010 wt% to 0.250 wt%, more preferably 0.010 wt% to 0.200 wt%, and even more preferably 0.010 wt% to 0.150 wt%. When the content of phosphorus in modifier (X) is 0.010 wt% or more in 100 wt% of modifier (X), the obtained modifier (X) can provide a polyacetal resin composition having a neutral or weakly basic pH, and as a result, a polyacetal resin composition that generates less VOC can be provided.

[0068] The effect of the phosphorus element in the modifier (X) will be explained in more detail. The alkali metal component (C) described later can also shift the pH of the obtained modifier (X) to the neutral or weakly basic side. However, since the alkali metal component (C) can exhibit basicity, when the modifier (X) contains a large amount of the alkali metal component (C), decomposition of the polyacetal resin composition containing the modifier (X) can increase. In one embodiment of the present invention, the modifier (X) contains 0.010% by weight or more of the phosphorus element, so that most of the pH adjustment of the modifier (X) can be performed by the phosphorus element. This makes it possible to reduce the amount of the alkali metal component (C) used for pH adjustment. In addition, the modifier (X) contains 0.010% by weight or more of the phosphorus element, so that an increase in the degree of basicity caused by the alkali metal component (C) can be suppressed. Therefore, the present modifier (X) can provide a polyacetal resin composition having a neutral or weakly basic pH.

[0069] When the content of phosphorus element in modifier (X) is 0.300% by weight or less based on 100% by weight of modifier (X), the obtained modifier (X) can provide a polyacetal resin composition that is difficult to decompose. That is, when the content of phosphorus element in modifier (X) is within the above range, the obtained modifier (X) can provide a polyacetal resin composition that generates less VOCs.

[0070] (2-3. Alkali Metal Component (C)) The alkali metal component (C) is not particularly limited in other configurations as long as it is (a) a compound containing an alkali metal element, or (b) a mixture containing a compound containing an alkali metal element. However, in this specification, a substance or mixture that has phosphorus and an alkali metal element and can change the pH is considered to be the above-mentioned component (B) and is not included in the alkali metal component (C).

[0071] Formaldehyde that 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, may be further oxidized to formic acid. Formic acid further promotes the decomposition of the polyacetal resin composition, i.e., the generation of formaldehyde. The alkali metal component (C) is preferably a formic acid scavenger. In this specification, the term "formic acid scavenger" refers to a substance that reacts with formic acid to change into a salt exhibiting a neutral pH range of 7.0 to 8.5.

[0072] When the present modifier (X) contains an alkali metal component (C) that is a formic acid scavenger, the modifier (X) can provide a polyacetal resin composition in which decomposition of the polyacetal resin composition by formic acid generated by oxidation of formaldehyde is very small. Therefore, the modifier (X) can provide a polyacetal resin composition in which the amount of formaldehyde generated is reduced. In other words, the modifier (X) containing the alkali metal component (C) that is a formic acid scavenger can provide a polyacetal resin composition that generates less VOCs.

[0073] The alkali metal component (C) is preferably a compound containing a metal carboxylate group, an epoxy group, an amide group, an amino group, an isocyanate group, or the like as a functional group, or a mixture containing such a compound. The alkali metal component (C) having such a structure is a formic acid scavenger. Therefore, when the present modifier (X) contains the alkali metal component (C) having such a structure, the modifier (X) can provide a polyacetal resin composition that generates even less VOC when the polyacetal resin composition is extruded and further molded.

[0074] The alkali metal component (C) may be a substance obtained by saponifying a polymer (hereinafter also referred to as polymer A) having, as a structural unit, a structural unit derived from one or more compounds selected from the group consisting of (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, using sodium hydroxide and / or potassium hydroxide. Polymer A may be (a) a polymer produced separately from rubber-containing graft copolymer (D), or (b) a polymer generated during polymerization of the graft portion of rubber-containing graft copolymer (D), which has the same composition of structural units as the graft portion and is not graft-bonded to the elastomer. Polymer A can also function as a formic acid scavenger.

[0075] The alkali metal component (C) also includes salts of aliphatic carboxylic acids with alkali metals, specifically salts of aliphatic carboxylic acids with sodium hydroxide and / or potassium hydroxide. These alkali metal components (C) also function as formic acid scavengers.

[0076] The salt of an aliphatic carboxylic acid and an alkali metal is required to be kneaded into and maintained in the polyacetal resin composition even at processing temperatures, and is therefore preferably a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms and an alkali metal.

[0077] Examples of the aliphatic carboxylic acid include lauric acid, palmitic acid, oleic acid, and stearic acid. The aliphatic carboxylic acid may have a substituent and may have an epoxy group. In other words, the aliphatic carboxylic acid may be an aliphatic carboxylic acid in which a part of the hydrocarbon group is substituted with an epoxy group.

[0078] The alkali metal component (C) is more preferably one or more selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer having, as a constituent unit, a constituent unit derived from one or more compounds selected from the group consisting of a (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms and an alkali metal. The alkali metal component (C) is more preferably one or more selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer having, as a constituent unit, a constituent unit derived from one or more compounds selected from the group consisting of a (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, (ii) a salt of an aliphatic carboxylic acid having no substituent having 10 to 24 carbon atoms and an alkali metal, and (iii) a salt of an aliphatic carboxylic acid having an epoxy group having 10 to 24 carbon atoms and an alkali metal. The alkali metal component (C) having these structures is a formic acid scavenger. Therefore, when the present modifier (X) contains the alkali metal component (C) having these structures, the modifier (X) can provide a polyacetal resin composition that generates even less VOCs when the polyacetal resin composition is extruded and further molded.

[0079] The content of the alkali metal component (C) in the present modifier (X) is not particularly limited. In the present modifier (X), the content of the alkali metal component (C) relative to 100 parts by weight of the rubber-containing graft copolymer (D) is preferably 0.01 parts by weight or more and less than 0.90 parts by weight, more preferably 0.05 parts by weight or more and less than 0.80 parts by weight, even more preferably 0.05 parts by weight or more and less than 0.70 parts by weight, and particularly preferably 0.03 parts by weight or more and less than 0.70 parts by weight. When the content of the alkali metal component (C) is 0.01 parts by weight or more, the obtained modifier (X) can provide a polyacetal resin composition that generates less VOC. When the content of the alkali metal component (C) is less than 0.90 parts by weight, the obtained modifier (X) can provide a polyacetal resin composition that can provide a molded product with excellent color tone. When the content of the alkali metal component (C) is less than 0.90 parts by weight, the obtained modifier (X) has a small amount of residual ion components, so that a polyacetal resin composition that is less likely to decompose can be provided, that is, a polyacetal resin composition that generates less VOCs can be provided.

[0080] The present modifier (X) contains 0.010 wt% to 0.300 wt% of an alkali metal element in 100 wt% of the modifier (X), preferably contains 0.010 wt% to 0.250 wt%, more preferably contains 0.010 wt% to 0.200 wt%, more preferably contains 0.010 wt% to 0.150 wt%, more preferably contains 0.020 wt% to 0.100 wt%, more preferably contains 0.020 wt% to 0.080 wt%, more preferably contains 0.020 wt% to 0.065 wt%, more preferably contains 0.020 wt% to 0.045 wt%, even more preferably contains 0.020 wt% to 0.040 wt%, and particularly preferably contains 0.020 wt% to 0.035 wt%. When the content of the alkali metal element in the modifier (X) is 0.010% by weight or more based on 100% by weight of the modifier (X), the obtained modifier (X) can provide a polyacetal resin composition that can efficiently neutralize formic acid that may be generated. When the content of the alkali metal element in the modifier (X) is 0.300% by weight or less based on 100% by weight of the modifier (X), the obtained modifier (X) can provide a polyacetal resin composition that is difficult to decompose. That is, when the content of the alkali metal element in the modifier (X) is within the above range, the obtained modifier (X) can provide a polyacetal resin composition that generates less VOC. In addition, when the content of the alkali metal element in the modifier (X) is 0.300% by weight or less based on 100% by weight of the modifier (X), the obtained modifier (X) can also provide a polyacetal resin composition that can provide a molded article with excellent color tone.

[0081] The present inventors have surprisingly and independently discovered the following: (a) when the potassium content is 0.010% by weight or more based on 100% by weight of modifier (X), the greater the potassium content, the less VOCs the modifier (X) emits; and (b) the closer the potassium content is to the range of 0.010% by weight to 0.020% by weight based on 100% by weight of modifier (X), the more excellent the tensile elongation at break of a molded article of a polyacetal resin composition containing the modifier (X). The present modifier (X) preferably contains 0.010 wt% to 0.300 wt%, more preferably 0.010 wt% to 0.250 wt%, more preferably 0.010 wt% to 0.200 wt%, more preferably 0.010 wt% to 0.150 wt%, more preferably 0.020 wt% to 0.100 wt%, more preferably 0.020 wt% to 0.080 wt%, more preferably 0.020 wt% to 0.065 wt%, more preferably 0.020 wt% to 0.045 wt%, even more preferably 0.020 wt% to 0.040 wt%, and particularly preferably 0.020 wt% to 0.035 wt%. When the potassium element content in the modifier (X) is within the above range, (a) the modifier (X) can provide a polyacetal resin composition that emits less VOCs, and (b) the polyacetal resin composition containing the modifier (X) can provide a molded article that is excellent in color tone and tensile elongation at break, in a well-balanced manner.

[0082] (2-4. Other optional ingredients) The present modifier (X) may contain other optional components other than the above-mentioned components within the scope of not impairing the effect according to one embodiment of the present invention. Examples of other optional components include antiblocking agents, antioxidants described below, and various components described in the section (4-3. Other additives) described below.

[0083] The other optional components can be added appropriately in any step in the manufacturing method of the present modifier (X). For example, the other optional components can be added to the water suspension (aqueous latex) of the rubber-containing graft copolymer (D) before or after the coagulation. The other optional components can also be added to the modifier (X).

[0084] (2-5. Content of alkaline earth metal elements) The content of alkaline earth metal elements in the present modifier (X) is preferably less than 0.100% by weight, more preferably 0.090% by weight or less, still more preferably 0.080% by weight or less, even more preferably 0.070% by weight or less, and particularly preferably 0.060% by weight or less, based on 100% by weight of the impact modifier (X) for polyacetal resin. According to this configuration, the obtained modifier (X) can provide a polyacetal resin composition that generates less VOCs.

[0085] (2-5. Content of other elements) The present inventors have independently found the following: Surprisingly, the lower the chlorine content in the modifier (X), the closer (a) the pH is to neutral or weakly acidic (about 7.0 to 11.0), (b) the decomposition of the polyacetal resin composition containing the modifier (X) is therefore significantly reduced, and (c) as a result, the polyacetal resin composition generates less VOCs, and the molded article of the polyacetal resin composition has excellent tensile elongation at break. The chlorine content in the modifier (X) is preferably less than 0.100% by weight, more preferably 0.080% by weight or less, more preferably 0.060% by weight or less, even more preferably 0.040% by weight or less, even more preferably 0.040% by weight or less, even more preferably 0.020% by weight or less, and particularly preferably 0.010% by weight or less, based on 100% by weight of the modifier (X). When the chlorine content in the modifier (X) is within the above range, (a) the pH of the modifier (X) can be made neutral or weakly alkaline (specifically, pH 7.0 or higher), and therefore the modifier (X) has the advantage that it can provide a polyacetal resin composition that emits less VOCs, and (b) the polyacetal resin composition containing the modifier (X) has the advantage that it can provide a molded product that has excellent mechanical properties such as tensile elongation at break.

[0086] Since a polyacetal resin composition that generates less VOC can be provided, the lower the sulfur content and the total content of sulfur and chlorine in the present modifier (X), the more preferable. The sulfur content and the total content of sulfur and chlorine in the present modifier (X) are each preferably less than 0.100% by weight, more preferably 0.080% by weight or less, more preferably 0.060% by weight or less, even more preferably 0.040% by weight or less, even more preferably 0.020% by weight or less, and particularly preferably 0.010% by weight or less, based on 100% by weight of the modifier (X).

[0087] (2-7.pH) The present modifier (X) is preferably neutral or weakly alkaline. Specifically, the pH of a mixture consisting of 25 parts by weight of the present modifier (X) and 75 parts by weight of deionized water is 7.0 to 11.0, preferably 7.0 to 10.5, and more preferably 7.0 to 10.0. According to this configuration, the obtained modifier (X) can provide a polyacetal resin composition that is difficult to decompose, that is, a polyacetal resin composition that generates less VOCs can be provided. The pH of the mixture may be 7.5 or more, 8.0 or more, or higher than 8.0. The pH of the mixture may be 9.5 or less, or 9.0 or less.

[0088] [3. Manufacturing method of impact modifier (X) for polyacetal resin] A method for producing an impact resistance modifier (X) for polyacetal resin according to one embodiment of the present invention includes a step of mixing an aggregate containing a pH adjuster (B) containing a phosphorus component and a rubber-containing graft copolymer (D) with an alkali metal component (C), and the alkali metal component (C) is one or more selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer obtained by polymerizing one or more selected from the group consisting of a (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms with an alkali metal.

[0089] The "production method for the impact modifier (X) for polyacetal resin according to one embodiment of the present invention" may hereinafter be referred to as "the present production method".

[0090] Conventionally, modifiers that contain a rubber-containing polymer but do not contain a pH adjuster containing a phosphorus component and / or an alkali metal component (hereinafter also referred to as conventional modifiers) are known. By mixing the conventional modifier with a polyacetal resin and a pH adjuster containing a phosphorus component and / or an alkali metal component, a polyacetal resin composition containing a rubber-containing polymer, a pH adjuster containing a phosphorus component, and an alkali metal component can be obtained. However, the present inventor independently found that in the polyacetal resin composition obtained by such a method using a conventional modifier, the pH adjuster containing a phosphorus component and the alkali metal component cannot be uniformly dispersed in the polyacetal resin. Here, the modifier (X) obtained by this production method contains the component (B) and the alkali metal component (C) in addition to the rubber-containing graft copolymer (D). Therefore, by mixing the modifier (X) with the polyacetal resin (A) described below, it is possible to provide a polyacetal resin composition in which the rubber-containing graft copolymer (D), the component (B), and the alkali metal component (C) are uniformly dispersed in the polyacetal resin (A).

[0091] That is, the present production method has the above-mentioned configuration, and therefore has the advantage of being able to provide a modifier (X) capable of providing a polyacetal resin composition that generates a small amount of VOC during and after molding of the polyacetal resin composition. Specifically, the modifier (X) obtained by the present production method can provide a polyacetal resin composition that generates a small amount of VOC during and after molding of the polyacetal resin composition. The modifier (X) 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 with excellent impact resistance. The modifier (X) obtained by the present production method also has the advantage of being able to achieve both (a) high impact resistance of a molded article of the polyacetal resin composition and (b) reduced VOC generation during and after molding of the polyacetal resin composition at a high level.

[0092] 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 (D), component (B), and alkali metal component (C)) are not particularly limited, and the explanation in the above section [2. Impact modifier for polyacetal resin (X)] will be used as appropriate.

[0093] A specific embodiment of the present production method is not particularly limited, but preferably includes a preparation step A of preparing an aggregate containing component (B) and a rubber-containing graft copolymer (D), and a mixing step B of mixing the aggregate obtained in the preparation step A with an alkali metal component (C).

[0094] A specific embodiment of the preparation step A is not particularly limited, but preferably further includes a preparation step A-1 of preparing a rubber-containing graft copolymer (D), an addition step A-2 of adding component (B) to the rubber-containing graft copolymer (D), and a preparation step A-3 of preparing an aggregate containing component (B) and the rubber-containing graft copolymer (D).

[0095] The specific embodiment of the preparation step A-1 is not particularly limited, but the rubber-containing graft copolymer (D) can be prepared by a method such as emulsion polymerization, suspension polymerization, or microsuspension polymerization. In the preparation step A-1, it is preferable to prepare the rubber-containing graft copolymer (D) by emulsion polymerization. By the emulsion polymerization, the rubber-containing graft copolymer (D) can be obtained as an aqueous latex containing the rubber-containing graft copolymer (D).

[0096] The surfactant used in the emulsion polymerization of the rubber-containing graft copolymer (D) is not particularly limited. Examples of the surfactant include (a) anionic surfactants such as acids, alkali metal salts of the acids, or ammonium salts of the acids, as exemplified below, (b) nonionic surfactants, and (c) polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives. Examples of the acids include (a1) alkyl or aryl sulfonic acids, or alkyl or aryl ether sulfonic acids, (a2) alkyl or aryl sulfuric acids, or alkyl or aryl ether sulfuric acids, (a3) ​​alkyl or aryl substituted phosphoric acids, or alkyl or aryl ether substituted phosphoric acids, (a4) N-alkyl or aryl sarcosinic acids, and (a5) alkyl or aryl carboxylic acids, or alkyl or aryl ether carboxylic acids. Specific examples of the surfactant include sodium dodecylbenzenesulfonate and sodium polyoxyethylene lauryl ether phosphate. Polyoxyethylene lauryl ether phosphoric acid and sodium hydroxide may be used in combination to produce sodium polyoxyethylene lauryl ether phosphate, which may be used as a surfactant.

[0097] In this specification, the "surfactant containing phosphorus element" may be referred to as "phosphorus-containing surfactant". Examples of phosphorus-containing surfactants suitable for use in the preparation step A-1 include (a) alkyl- or aryl-substituted phosphoric acid, (b) alkyl- or aryl ether-substituted phosphoric acid, (c) alkali metal salt of alkyl- or aryl-substituted phosphoric acid, (d) alkali metal salt of alkyl- or aryl ether-substituted phosphoric acid, (e) ammonium salt of alkyl- or aryl-substituted phosphoric acid, and (f) ammonium salt of alkyl- or aryl ether-substituted phosphoric acid. In the preparation step A-1, it is preferable to prepare the rubber-containing graft copolymer (D) by emulsion polymerization using a phosphorus-containing surfactant. Specifically, in the preparation step A-1, it is preferable to use a phosphorus-containing surfactant as a surfactant in either the step (i) of polymerization (preparation) of the elastomer or the step of formation of the graft portion, and it is more preferable to use a phosphorus-containing surfactant as a surfactant in both the steps (ii) of polymerization (preparation) of the elastomer and formation of the graft portion. According to this configuration, the salt generated by the addition of the coagulant has high water solubility, and therefore has the advantage that the salt can be easily removed during the production process by washing with water and / or a solvent. Therefore, it is possible to obtain a modifier (X) having a small amount of alkaline earth metal (e.g., calcium element), and to obtain a polyacetal resin composition that can provide a molded product with excellent color tone. The phosphorus element contained in the surfactant used in the preparation step A-1 can be the origin of the phosphorus element contained in the obtained modifier (X).

[0098] As the phosphorus-containing surfactant, polyoxyalkylene alkyl phenyl ether phosphate and / or polyoxyalkylene alkyl ether phosphate are preferred, polyoxyethylene alkyl phenyl ether phosphate and / or polyoxyethylene alkyl ether phosphate are more preferred, and polyoxyethylene alkyl ether phosphate is even more preferred, because stability during polymerization can be ensured.

[0099] The alkyl group of the polyoxyethylene alkyl ether phosphate is, for example, an alkyl group having 1 to 20 carbon atoms, preferably an alkyl group having 5 to 18 carbon atoms, more preferably an alkyl group having 7 to 16 carbon atoms, and further preferably an alkyl group having 10 to 16 carbon atoms.

[0100] The number of oxyethylene units in the polyoxyethylene alkyl ether phosphate is, for example, 2 to 14, preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 6.

[0101] The amount of the surfactant used is not particularly limited, and is preferably 0.1 to 5.0 parts by weight, more preferably 0.3 to 3.0 parts by weight, and even more preferably 0.5 to 2.0 parts by weight, based on 100 parts by weight of the rubber-containing graft copolymer (D).

[0102] The solvent used in the preparation step A-1 may be any solvent that allows the emulsion polymerization to proceed stably, and for example, water or the like can be suitably used.

[0103] When emulsion polymerization is carried out in the preparation step A-1, the temperature during emulsion polymerization is not particularly limited as long as the polymerization emulsifier is uniformly dissolved in the solvent. The temperature during emulsion polymerization is, for example, 40 to 75°C, and preferably 45 to 70°C.

[0104] The specific embodiment of the addition step A-2 is not particularly limited. When the rubber-containing graft copolymer (D) is prepared by emulsion polymerization in the preparation step A-1, the addition step A-2 can be said to be a step of adding the component (B) to the aqueous latex containing the rubber-containing graft copolymer (D). The method of adding the component (B) is not particularly limited. For example, the component (B) (a) may be added directly in a powder and / or solid state to the aqueous latex containing the rubber-containing graft copolymer (D), or a solution (e.g., an aqueous solution) containing the component (B) may be separately prepared and then added to the aqueous latex containing the rubber-containing graft copolymer (D). The addition step A-2 is preferably a step of separately preparing a solution (e.g., an aqueous solution) containing the component (B) and then adding the aqueous solution to the aqueous latex containing the rubber-containing graft copolymer (D). According to this configuration, the component (B) can be attached uniformly to the rubber-containing graft copolymer (D) without bias in concentration.

[0105] A specific embodiment of the preparation step A-3 is not particularly limited, but a suitable example is a step of preparing an aggregate containing the component (B) and the rubber-containing graft copolymer (D) using an aqueous latex containing the component (B) and the rubber-containing graft copolymer (D).

[0106] The method for agglomerating the component (B) and the rubber-containing graft copolymer (D) in the aqueous latex containing the component (B) and the rubber-containing graft copolymer (D) is not particularly limited, and a known method can be used. Examples of the method include chemical methods and physical methods. Examples of the chemical method include a method using a coagulant and a method using a solvent. Examples of the physical method include a method of spraying the aqueous latex containing the component (B) and the rubber-containing graft copolymer (D).

[0107] Examples of the coagulant include an aqueous solution of an inorganic salt, an aqueous solution of an inorganic acid, an aqueous solution of an organic salt, an aqueous solution of an organic acid, and a polymer coagulant. Examples of the aqueous solution of an inorganic salt include an aqueous solution of an alkali metal salt and an aqueous solution of an alkaline earth metal salt. Examples of the aqueous solution of an alkali metal salt include sodium chloride, potassium chloride, lithium chloride, sodium bromide, potassium bromide, lithium bromide, potassium iodide, sodium iodide, potassium sulfate, sodium sulfate, sodium nitrate, potassium nitrate, and potassium alum. Examples of the aqueous solution of an alkaline earth metal salt include calcium chloride, magnesium chloride, barium chloride, magnesium sulfate, and calcium acetate. Examples of the coagulant include trivalent or higher metal salts such as aluminum chloride. Examples of the coagulant include calcium chloride and magnesium chloride because they are economically available at low cost and easy to handle. Examples of the coagulant include magnesium sulfate, calcium oxide, and magnesium acetate. When magnesium sulfate, calcium oxide, and / or magnesium acetate are used as the coagulant, the amount of halogen contained in the resulting modifier (X) can be reduced to the minimum, and a modifier (X) with a low environmental impact can be obtained.

[0108] In this specification, the mixture containing the aggregates containing component (B) and the rubber-containing graft copolymer (D) obtained by coagulating the component (B) and the rubber-containing graft copolymer (D) in the aqueous latex together and the aqueous solvent is also referred to as a slurry.

[0109] The aggregation of component (B) and rubber-containing graft copolymer (D) in the aqueous latex is preferably carried out in the presence of an antiblocking agent, since the resulting modifier (X) has good blocking resistance.

[0110] As described above, the timing of adding component (B) to rubber-containing graft copolymer (D) has been described by taking the addition step A-2 as an example. However, in this production method, the timing of adding component (B) to rubber-containing graft copolymer (D) is not particularly limited. Component (B) may be added to the reaction liquid (a) during emulsion polymerization of rubber-containing graft copolymer (D) (i.e., during preparation step A-1), (b) before the coagulant is added to the aqueous latex containing rubber-containing graft copolymer (D) (i.e., addition step A-2), (c) together with the coagulant to the aqueous latex containing rubber-containing graft copolymer (D), or (d) after the coagulant is added to the aqueous latex containing rubber-containing graft copolymer (D).

[0111] In the preparation step A-3, the component (B) and the rubber-containing graft copolymer (D) can be aggregated (precipitated) by adding a water-soluble organic solvent such as methanol, ethanol, propanol, or other alcohol, or acetone, to the aqueous latex containing the component (B) and the rubber-containing graft copolymer (D). The component (B) and the rubber-containing graft copolymer (D) can also be aggregated by the following method: A method in which a slightly water-soluble organic solvent such as methyl ethyl ketone is added to the aqueous latex containing the component (B) and the rubber-containing graft copolymer (D) to extract the component (B) and the rubber-containing graft copolymer (D) into an organic solvent layer, and then the organic solvent layer is separated, and the separated organic solvent layer is mixed with water or the like to aggregate (precipitate) the component (B) and the rubber-containing graft copolymer (D).

[0112] As described above, the preparation step A-1, the addition step A-2, and the preparation step A-3 have been taken as examples of the method for obtaining an aggregate containing the component (B) and the rubber-containing graft copolymer (D). However, in the present production method, the method for obtaining an aggregate containing the component (B) and the rubber-containing graft copolymer (D) may be an embodiment that includes the following steps in order: an aggregation step A'-1 in which the rubber-containing graft copolymer (D) in the aqueous latex is aggregated using an aqueous latex containing only the rubber-containing graft copolymer (D); a mixing step A'-2 in which the obtained aggregate of the rubber-containing graft copolymer (D) is mixed with the component (B). The aggregation step A'-1 includes a preferred embodiment, and may be the same as the above-mentioned preparation step A-3, except that an aqueous latex containing only the rubber-containing graft copolymer (D) is used instead of the aqueous latex containing the component (B) and the rubber-containing graft copolymer (D). In addition, the method for mixing the aggregate of the rubber-containing graft copolymer (D) with the component (B) in the mixing step A'-2 is not particularly limited. Examples of the method include mechanical mixing methods using a rotation / revolution mixer, a planetary mixer, a disperser, and the like.

[0113] The preparation step A preferably further includes a recovery step A-4 of recovering aggregates containing component (B) and rubber-containing graft copolymer (D) from the slurry, a washing step A-5 of washing the aggregates containing component (B) and rubber-containing graft copolymer (D), and / or a dehydration step A-6 of dehydrating the aggregates containing component (B) and rubber-containing graft copolymer (D). Hereinafter, unless otherwise specified, the "aggregates containing component (B) and rubber-containing graft copolymer (D)" will also be simply referred to as "aggregates".

[0114] The recovery step A-4 is not particularly limited as long as it can separate the aqueous solvent of the slurry from the aggregates, and a known method can be used. Examples of the recovery step A-4 include a method of filtering the slurry and a method of centrifugal dehydration of the slurry.

[0115] In the washing step A-5, it is more preferable to wash the aggregate with water, and it is even more preferable to wash with deionized water or pure water.

[0116] The washing step A-5 may be a step for washing the aggregate, and is not particularly limited in its specific method. Specific methods for the washing step A-5 include, for example, a method of mixing the aggregate with water and stirring with a stirrer, a method of kneading the aggregate with water using a kneader, a method of mixing the aggregate with water using a planetary centrifugal mixer, a method of spraying water onto the aggregate, and a method of washing the cake with a pressure filter. As the kneader, various types such as a batch kneader, a continuous kneader, an extrusion kneader, and an extruder can be used.

[0117] The washing time is not particularly limited and may be, for example, 1 second to 60 minutes. The washing time is preferably 1 second to 45 minutes, more preferably 1 second to 30 minutes, still more preferably 1 minute to 30 minutes, even more preferably 3 minutes to 30 minutes, particularly preferably 5 minutes to 30 minutes, and particularly preferably 10 minutes to 30 minutes.

[0118] The number of washings is not particularly limited, and may be performed multiple times. The amount of washing water is not particularly limited, and is preferably, for example, 3 parts by weight or more per 1 part by weight of the aggregate. In addition, washing by kneading the aggregate with water using a kneader is more preferable because it allows the amount of washing water to be reduced.

[0119] In the washing step A-5, 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.

[0120] The object to be washed is intended to be all impurities contained in the aggregate, and is not particularly limited. For example, impurities derived from surfactants (e.g., phosphorus-based surfactants, sulfonic acid-based surfactants), as well as impurities derived from the coagulant when a coagulant is used, can be mentioned. When the present production method includes the washing step A-5, the content of alkaline earth metal elements in the obtained modifier (X) is very low, and as a result, a polyacetal resin composition with low VOC emission can be provided. In addition, the obtained resin composition containing the modifier (X) can provide a molded product with excellent color tone.

[0121] In the dehydration step A-5, 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.

[0122] In the mixing step B, the method for mixing the aggregate obtained in the preparation step A with the alkali metal component (C) is not particularly limited. Examples of the method include mechanical mixing methods using a planetary mixer, a planetary mixer, a disperser, etc.

[0123] In the mixing step B, the state of the alkali metal component (C) to be mixed with the aggregates is not particularly limited, and the powder and / or solid alkali metal component (C) may be mixed with the aggregates, or a solution (e.g., an aqueous solution) containing the alkali metal component (C) prepared in advance may be mixed with the aggregates. In the mixing step B, it is preferable to mix the aggregates with an aqueous solution containing the alkali metal component (C) prepared in advance. According to this configuration, the aggregates and the alkali metal component (C) can be mixed uniformly, and as a result, the amount of the alkali metal component (C) contained in the aggregates can be made uniform among a plurality of aggregates. In the mixing step B, aggregates containing the component (B), the alkali metal component (C), and the rubber-containing graft copolymer (D), i.e., the modifier (X), can be obtained.

[0124] In the mixing step B, it is preferable to mix the aggregate obtained in the preparation step A including the washing step A-5 with the alkali metal component (C). The aggregate obtained in the preparation step A including the washing step A-5 has a low content of the coagulant used in the preparation step A-3. Therefore, the reaction between the coagulant and the alkali metal component (C) can be prevented, and as a result, the effect derived from the alkali metal component (C) (for example, the effect as a formic acid scavenger) can be fully enjoyed in the obtained modifier (X).

[0125] The aggregate obtained in the preparation step A preferably contains water. The water content of the aggregate is preferably 3% to 70%, more preferably 10% to 50%, and particularly preferably 10% to 40%, based on the total weight (100% by weight) of the aggregate. In the mixing step B, it is preferable to mix the aggregate having a water content within the above-mentioned range with the alkali metal component (C), and it is particularly preferable to mix the aggregate having a water content within the above-mentioned range with an aqueous solution containing the alkali metal component (C) prepared in advance. According to this configuration, the aggregate and the alkali metal component (C) can be mixed more uniformly, and as a result, the amount of the alkali metal component (C) contained in the aggregate can be made more uniform among a plurality of aggregates. The water content of the aggregate can be measured by drying the obtained aggregate in an oven at 120°C for 1 hour and comparing the weights before and after drying.

[0126] The present production method may further include a step of drying the aggregate containing the component (B), the alkali metal component (C), and the rubber-containing graft copolymer (D) obtained in the mixing step B. In the following description of the drying step, the term "aggregate" refers to "aggregate containing the pH adjuster (B) containing a phosphorus component, the alkali metal component (C), and the rubber-containing graft copolymer (D)."

[0127] 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 in the container, and a method of placing the aggregates in a container and bringing a drying gas into countercurrent contact with the aggregates in the container.

[0128] 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. The drying temperature in the drying step is, for example, preferably less than 90°C, more preferably less than 80°C, more preferably less than 70°C, more preferably less than 60°C, more preferably less than 50°C, and even more preferably less than 40°C.

[0129] The impact modifier (X) for polyacetal resin according to another embodiment of the present invention is an impact modifier (X) for polyacetal resin containing a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer, and the rubber-containing graft copolymer (D) further contains an alkali metal element. The content of the alkali metal element is 0.010% by weight to 0.300% by weight in 100% by weight of the impact modifier (X) for polyacetal resin according to another embodiment of the present invention. The impact modifier (X) for polyacetal resin according to another embodiment of the present invention further contains 0.010% by weight to 0.300% by weight of phosphorus element in 100% by weight of the impact modifier (X) for polyacetal resin. In another embodiment of the impact modifier (X) for polyacetal resin according to the present invention, the pH of a mixture consisting of 25 parts by weight of the impact modifier (X) for polyacetal resin and 75 parts by weight of deionized water is 7.0 or more and 11.0 or less.

[0130] The impact modifier (X) for polyacetal resin according to another embodiment of the present invention has the above-mentioned configuration, and therefore has the advantage of being able to provide a polyacetal resin composition that generates less VOCs during and after molding of the polyacetal resin composition. Specifically, the impact modifier (X) for polyacetal resin according to another embodiment of the present invention can provide a polyacetal resin composition that generates less VOCs during and after molding of the polyacetal resin composition. In addition, the impact modifier (X) for polyacetal resin according to another embodiment of the present invention also has the advantage of being able to provide a polyacetal resin composition that can provide a molded article having excellent impact resistance. In addition, the impact modifier (X) for polyacetal resin according to another embodiment of the present invention also has the advantage of being able to achieve both (a) high impact resistance of a molded article of the polyacetal resin composition and (b) reduced VOC generation during and after molding of the polyacetal resin composition at a high level. Furthermore, the impact resistance modifier for polyacetal resin (X) according to another embodiment of the present invention can also provide a polyacetal resin composition capable of providing a molded article having excellent color tone.

[0131] The impact resistance modifier (X) for polyacetal resin according to another embodiment of the present invention has the same configuration as the impact resistance modifier (X) for polyacetal resin according to one embodiment of the present invention described above, except that the rubber-containing graft copolymer (D) contains an alkali metal element instead of the alkali metal component (C).

[0132] In another embodiment of the present invention, the method for producing the rubber-containing graft copolymer (D) containing an alkali metal element is not particularly limited.For example, the rubber-containing graft copolymer (D) produced according to the above-mentioned preparation step A-1 is saponified with sodium hydroxide and / or potassium hydroxide to obtain the rubber-containing graft copolymer (D) containing an alkali metal element.

[0133] Other than the above, aspects of the impact modifier for polyacetal resin (X) according to another embodiment of the present invention are not particularly limited, and the above-mentioned explanation of the impact modifier for polyacetal resin (X) according to one embodiment of the present invention will be used as appropriate.

[0134] A configuration obtained by combining the configuration of the impact modifier (X) for polyacetal resin according to one embodiment of the present invention described above with the configuration of the impact modifier (X) for polyacetal resin according to another embodiment of the present invention is also one embodiment of the present invention. For example, the impact modifier (X) for polyacetal resin includes a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer, and further includes an alkali metal component (C), which is selected from the group consisting of (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer having, as a constituent unit, a constituent unit derived from one or more compounds selected from the group consisting of (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid, and (ii) carbon. and salts of an alkali metal and an aliphatic carboxylic acid having a prime number of 10 to 24, wherein 100 weight % of the impact modifier for polyacetal resin (X) further contains 0.010 weight % to 0.300 weight % of phosphorus and 0.010 weight % to 0.300 weight % of an alkali metal element, the rubber-containing graft copolymer (D) further contains an alkali metal element, and a mixture consisting of 25 parts by weight of the impact modifier for polyacetal resin (X) and 75 parts by weight of deionized water has a pH of 7.0 or more and 11.0 or less, which is also one or more selected from the group consisting of salts of an aliphatic carboxylic acid having a prime number of 10 to 24 and an alkali metal, wherein 100 weight % of the impact modifier for polyacetal resin (X) further contains 0.010 weight % to 0.300 weight % of an alkali metal element, the rubber-containing graft copolymer (D) further contains an alkali metal element, and

[0135] 4. Polyacetal resin composition A polyacetal resin composition according to one embodiment of the present invention contains an impact modifier for polyacetal resin (X) described in [2. Impact modifier for polyacetal resin (X)] and a polyacetal resin (A).

[0136] The "polyacetal resin composition" may be referred to as the "resin composition" below. The "polyacetal resin composition according to one embodiment of the present invention" may be referred to as the "present resin composition" below. By molding (e.g., injection molding) the present resin composition, a molded article of polyacetal resin can be produced.

[0137] Since the resin composition has the above-mentioned structure, it has the advantage of generating less VOC. More specifically, since the resin composition has the above-mentioned structure, it has the advantage of generating less VOC during and after molding of the resin composition. Furthermore, since the resin composition has the above-mentioned structure, it has an excellent balance between the toughness of the obtained molded article, the elasticity of the obtained molded article, and the moldability of the resin composition.

[0138] (4-1. Polyacetal resin (A)) The polyacetal resin (A) is a polymeric compound having an oxymethylene group (-CHO-) as a main constituent unit (for example, a constituent unit that occupies 50 mol % or more of 100 mol % of all constituent units). The polyacetal resin (A) used in one embodiment of the present invention is not particularly limited. The polyacetal resin (A) may be (a) a homopolymer containing only divalent oxymethylene groups as constituent units, or (b) a copolymer containing divalent oxymethylene groups and divalent oxyalkylene groups having 2 or more carbon atoms as constituent units.

[0139] 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.

[0140] When the polyacetal resin (A) is a copolymer, the proportion of oxyalkylene groups having 2 to 6 carbon atoms in the polyacetal resin (A) is not particularly limited. In the polyacetal resin (A), the molar number of oxyalkylene groups having 2 to 6 carbon atoms is preferably 0.5 mol % to 10.0 mol % in the total molar number of oxymethylene groups and oxyalkylene groups having 2 to 6 carbon atoms in the polyacetal resin (A) (100 mol %).

[0141] Commercially available polyacetal resins (A) can also be used. Commercially available polyacetal resins (A) include, for example, (a) commercial homopolymer products such as "Delrin" (manufactured by DuPont USA) and "Tenac 4010" (manufactured by Asahi Kasei Corporation); and (b) commercial polyacetal resins (polyacetal copolymers) having an oxymethylene group and a structural unit derived from a comonomer other than an oxymethylene group such as "Hostafoam" (manufactured by Ticona), "Iupital" (manufactured by Mitsubishi Engineering Plastics Corporation), and "Duracon" (manufactured by Polyplastics Co., Ltd.).

[0142] The weight ratio of the impact modifier for polyacetal resin (X) and the polyacetal resin (A) in the polyacetal resin composition is not particularly limited. The polyacetal resin composition preferably contains (i) 3% by weight to 40% by weight of the impact modifier for polyacetal resin (X) and 60% by weight to 97% by weight of the polyacetal resin (A), more preferably (ii) 5% by weight to 30% by weight of the impact modifier for polyacetal resin (X) and 70% by weight to 95% by weight of the polyacetal resin (A), and more preferably (iii) 100% by weight of the polyacetal resin (A). It is more preferable that the composition contains 10% by weight to 30% by weight of the impact modifier for polyacetal resin (X) and 70% by weight to 90% by weight of the polyacetal resin (A), further preferably (iv) the composition contains 15% by weight to 30% by weight of the impact modifier for polyacetal resin (X) and 70% by weight to 85% by weight of the polyacetal resin (A), and particularly preferably (v) the composition contains 20% by weight to 30% by weight of the impact modifier for polyacetal resin (X) and 70% by weight to 80% by weight of the polyacetal resin (A).

[0143] In the polyacetal resin composition, the weight ratio of the rubber-containing graft copolymer (D) and the polyacetal resin (A) contained in the impact modifier for polyacetal resin (X) (rubber-containing graft copolymer (D) / polyacetal resin (A)) is preferably 3 / 100 or more, more preferably 4 / 100 or more, and even more preferably 5 / 100 or more. The upper limit of the weight ratio is, for example, preferably 40 / 100 or less, more preferably 30 / 100 or less, and even more preferably 25 / 100 or less. When the weight ratio is 3 / 100 or more, the obtained polyacetal resin composition can provide a molded article having excellent impact resistance. When the weight ratio is 40 / 100 or less, there is an advantage that the obtained polyacetal resin composition can be easily extruded.

[0144] (4-2. Antioxidants) The resin composition may contain an antioxidant within a range that does not impair the effect of one embodiment of the present invention. Examples of the antioxidant include hindered phenol-based antioxidants and hindered amine-based antioxidants.

[0145] Examples of the hindered phenol-based antioxidants include n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, n-octadecyl-3-(3'-methyl-5'-t-butyl-4'-hydroxyphenyl)-propionate, n-tetradecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl -4-hydroxyphenyl)-propionate], 1,4-butanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate], pentaerythritol tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, and the like.

[0146] Examples of the hindered amine antioxidant include bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-N-butylmalonate, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-diformylhexamethylenediamine, dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-trimethyl-2-propanediol], and poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-trimethyl-2-propanediol]. N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensation polycondensate of dibutylamine·1,3,5-triazine·N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine)·N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine; copolymer of olefin (C20-C24)·maleic anhydride-4-amino-2,2,6,6-tetramethylpiperidine, etc.

[0147] The present resin composition may contain only one type of the antioxidants described above, or may contain two or more types in combination.

[0148] (4-3. Other additives) The present resin composition may further contain other additives other than the above-mentioned components as necessary. The other additives may include other additives such as dyes, pigments, stabilizers, reinforcing agents, fillers, flame retardants, foaming agents, lubricants, and plasticizers. In other words, the above-mentioned other additives may be blended into the present resin composition as necessary.

[0149] (4-4. Method for producing polyacetal resin composition) The method for producing the resin composition is not particularly limited. For example, the impact modifier (X) for polyacetal resin according to one embodiment of the present invention, the polyacetal resin (A), and optionally an antioxidant and other additives are mixed, and the resulting mixture is melt-kneaded to obtain the resin composition.

[0150] In the method for producing the present resin composition, a Henschel mixer, a tumbler mixer, or the like can be used to mix the raw materials, and a kneader such as a single-screw or twin-screw extruder, a Banbury mixer, a pressure kneader, or a mixing roll can be used to melt-knead the resulting mixture.

[0151] (4-5.Applications) The resin composition can be suitably used in various applications such as electrical and electronic applications, vehicle applications, industrial equipment applications, etc. The resin composition can be suitably used, for example, in mechanical parts of drive units of AV equipment, handles of dishwashers and dryers, speaker grills, propellers for stirring washing machine tubs, switches and gears of office equipment, wiper motor system gears of automobiles, 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, screws of conveyors of industrial equipment, belt conveyors, chains, torque limiters, etc. EXAMPLES

[0152] 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 thereto. One embodiment of the present invention can be practiced with appropriate modifications within the scope of the above or below-mentioned purpose, 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 weight" and "% by weight", respectively.

[0153] <Ingredients> The components used in each Production Example, Example and Comparative Example are as follows. Rubber-containing graft copolymer (D) The rubber-containing graft copolymer (D) obtained in the following Production Example was used. Phosphorus-containing pH adjuster (B) (B-1): Disodium hydrogen phosphate (B-2): A mixture of phosphoric acid and sodium hydroxide with a molar ratio (phosphoric acid:sodium hydroxide) of 1:3.5 Coagulant (D-1) Calcium chloride (D-2) Magnesium chloride (D-3) Calcium acetate Alkaline metal components (C) (C-1) Potassium palmitate (C-2) Sodium oleate Polyacetal resin (A) Hostaform C9021 (manufactured by Celanese).

[0154] <Measurement method> First, the measurement methods used in the examples and comparative examples will be described below.

[0155] (Method of measuring volume average particle size) The volume average particle size (Mv) of the elastomer or rubber-containing graft copolymer (D) dispersed in the aqueous latex was measured using Nanotrac WaveII-EX150 (manufactured by Microtrackbell Co., Ltd.). The aqueous latex was diluted with deionized water and used as the measurement sample. The measurement was performed by inputting the refractive index of water and the elastomer or polymer microparticles (A) obtained in each production example, and adjusting the sample concentration so that the measurement time was 120 seconds and the loading index was within the range of 1 to 10.

[0156] (Method of measuring moisture content of aggregates) The aggregate was dried in an oven at 120° C. for 1 hour, and the weight of the aggregate was measured before and after drying. The moisture content of the aggregate was then calculated based on the weight of the aggregate and the total weight of the aggregate (100% by weight).

[0157] (Method for measuring element content of modifier (X)) (For phosphorus, potassium, magnesium, chlorine and sulfur) 4.0 g of the modifier (X) obtained in each of the examples and comparative examples was weighed out. The amounts of phosphorus, potassium, magnesium, and chlorine elements in the modifier (X) were measured using an energy dispersive X-ray fluorescence spectrometer "SPECTRO XEPOS" manufactured by Rigaku Corporation. The results were expressed as the weight percent of each element relative to 100 weight percent of the modifier (X). Furthermore, element contents of less than 0.001% were not shown in the results. It can be said that elements with an element content of less than 0.001% in the modifier (X) do not affect the effect of one embodiment of the present invention.

[0158] (For sodium and calcium) 0.1 g of the modifier (X) obtained in each Example and Comparative Example was weighed into a decomposition vessel, sulfuric acid was added to the vessel, and the modifier (X) in the vessel was decomposed using microwaves (wet decomposition). After cooling the decomposed modifier (X), nitric acid was added to the vessel, and the modifier (X) in the vessel was treated again with microwaves. Thereafter, the solution in the vessel was made up to 50 ml with distilled water, and the resulting 50 ml solution was used as the test solution. The amounts of calcium and sodium elements in the test solution were quantified using an ICP emission spectrometer (ICPS-7510: manufactured by Shimadzu Corporation), and the results were expressed as weight percent relative to 100 weight percent modifier (X).

[0159] (Method for measuring pH of mixture of modifier (X) and deionized water) 25 parts of the modifier (X) obtained in each of the Examples and Comparative Examples was mixed with 75 parts of deionized water, and the resulting mixture was stirred for 30 minutes. The pH of the resulting mixture was measured at 25°C using a pH meter.

[0160] (Method of measuring impact resistance) Using the obtained 1 / 8 inch molded body, the 1 / 8 inch notched Charpy impact strength at 23°C was measured in accordance with ISO 179. Note that the larger the Charpy impact strength (Charpy(rt)) value of the molded body, the more excellent the impact resistance of the molded body.

[0161] (Method of measuring tensile elongation at break) Using molded articles having a shape specified by ISO 527-2 / 1А, the tensile elongation at break (%) at 23°C was measured in accordance with ISO 527-2 / 1А. Note that the higher the tensile elongation at break (%) of the molded article, the better the tensile elongation at break of the molded article.

[0162] (How to prepare plate test pieces) The pellets of the polyacetal resin compositions obtained in Examples 12 to 25 and Comparative Examples 5 to 10 were dried for 5 hours at 90° C. Thereafter, the dried pellets were injection molded using an injection molding machine 160MSP-10 manufactured by Mitsubishi Heavy Industries, Ltd. at a cylinder temperature of 205° C. and a mold temperature of 70° C. to prepare flat test pieces (molded bodies) of 100 mm×40 mm×2 mm.

[0163] (Method for measuring the amount of formaldehyde generated) The obtained flat test piece (molded body) was aged for 7 days at 23°C and 50% RH. After that, the amount of formaldehyde generated (mg / kg) of the flat test piece was measured by the following method in accordance with the method described in the German Automotive Industry Association standard VDA275 (Automobile interior parts - Quantitative determination of formaldehyde emission by the revised flask method). (i) 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 container was closed with a lid. The container was then heated at 60°C for 3 hours in a sealed state. (ii) The polyethylene container was then left to stand at room temperature for 60 minutes, after which the flat test piece was removed from the polyethylene container. (iii) The amount of formaldehyde absorbed in the distilled water in the polyethylene container was measured by a UV spectrometer using the acetylacetone colorimetric method for the distilled water sample. The amount of formaldehyde thus obtained was divided by the weight of the polyacetal resin (A) in the flat test piece, and this value was regarded as the amount of formaldehyde generated (VDA275).

[0164] (color tone) The color tone (YI) of the obtained flat test piece (molded product) was measured according to JIS K8722 using a color difference meter (model: SE-2000) manufactured by Nippon Denshoku Industries Co., Ltd. The smaller the color tone (YI) value of the molded product, the less yellow the molded product is, i.e., the more excellent the color tone is.

[0165] Next, each production method, each example, and each comparative example will be described below.

[0166] <Preparation of Rubber-Containing Graft Copolymer (D)> [Synthesis Example 1] Synthesis of aqueous latex containing rubber-containing graft copolymer (D) (Production Example 1a: Preparation of Elastic Body (1a)) Into a pressure-resistant polymerization vessel equipped with a stirrer, 200 parts of deionized water, 0.010 parts of disodium ethylenediaminetetraacetate (EDTA), 0.0012 parts of ferrous sulfate, and 0.03 parts of sodium polyoxyethylene alkyl ether phosphate as a surfactant were charged.

[0167] Next, while stirring the raw materials introduced, the gas inside the pressure polymerization vessel was replaced with nitrogen, thereby thoroughly removing oxygen from inside the pressure polymerization vessel. Then, 100 parts of butadiene (Bd), 0.05 parts of sodium formaldehyde sulfoxylate (SFS), and 0.2 parts of paramenthane hydroperoxide (PHP) were added into the pressure polymerization vessel. Then, 1.4 parts of polyoxyethylene alkyl ether sodium phosphate, a surfactant, were dropped into the pressure polymerization vessel over 6 hours. Then, the reaction solution in the pressure polymerization vessel was kept at pH 6.5 to 7.5 and 50°C for 24 hours to perform polymerization, and a butadiene rubber elastomer (1a) was obtained. The polymerization conversion rate of the monomer components was 98% by weight. The volume average particle diameter of the obtained elastomer (1a) was 140 nm.

[0168] (Production Example 1b: Preparation of Water-Based Latex (A-1) Containing Rubber-Containing Graft Copolymer (D)) A glass reactor was charged with 78 parts of solids of butadiene rubber elastomer (1a) and 150 parts of deionized water. Here, the glass reactor had a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The charged raw materials were stirred at 60°C while the gas in the glass reactor was replaced with nitrogen. Next, a mixture of 19.8 parts of methyl methacrylate (MMA) and 2.2 parts of butyl acrylate (BA) as monomer components was added to the glass reactor over 1 hour. Simultaneously with the addition of the monomer components (i.e., MMA and BA), the addition of 0.07 parts of t-butyl hydroperoxide (BHP) and 0.1 parts of SFS to the glass reactor was started. Here, for the addition of BHP and SFS, the entire amounts of BHP and SFS were added over 2 hours while maintaining the temperature of the reaction solution in the glass reactor at about 60°C. Further, the reaction solution in the glass reactor was kept at about 60° C. for 1 hour to carry out polymerization, and an aqueous latex (A-1) containing a rubber-containing graft copolymer (D) was obtained. The volume average particle diameter of the rubber-containing graft copolymer (D) contained in the obtained aqueous latex was 150 nm.

[0169] [Synthesis Example 2] Synthesis of aqueous latex containing rubber-containing graft copolymer (D) (Production Example 2a: Preparation of an aqueous latex containing elastomer (2a)) In a pressure-resistant polymerization vessel equipped with a stirrer, 100 parts of deionized water and 0.014 parts of sodium polyoxyethylene alkyl ether phosphate as a surfactant were charged while blowing in nitrogen. Next, while stirring the charged raw materials, the gas inside the pressure-resistant polymerization vessel was replaced with nitrogen, thereby sufficiently removing oxygen from inside the pressure-resistant polymerization vessel. Then, the temperature of the solution in the pressure-resistant vessel was raised to 50°C. Then, 8.5 parts of BA, 0.04 parts of allyl methacrylate, and 0.002 parts of BHP were added to the pressure-resistant vessel at once. Then, 0.002 parts of EDTA, 0.0012 parts of ferrous sulfate, and 0.05 parts of sodium formaldehyde sulfoxylate SFS were added to the pressure-resistant vessel. Then, polymerization was carried out over 1 hour. Then, a mixture of 0.68 parts of sodium polyoxyethylene alkyl ether phosphate as a surfactant, 64.5 parts of BA, 0.32 parts of allyl methacrylate, and 0.02 parts of BHP was added to the pressure-resistant vessel over 210 minutes. Thereafter, the reaction solution in the pressure-resistant polymerization vessel was kept at 50°C for 45 minutes to carry out polymerization, and an aqueous latex containing an elastomer (2a) was obtained. The polymerization conversion rate of the monomer components was 98% by weight. The volume average particle diameter of the elastomer contained in the obtained aqueous latex was 180 nm.

[0170] (Production Example 2b: Preparation of Water-Based Latex (A-2) Containing Rubber-Containing Graft Copolymer (D)) Into a glass reactor, 73 parts of the solid content of the elastic body (2a) and 150 parts of deionized water were charged. Here, the glass reactor had a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The charged 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 MMA and 1.7 parts of BA was added to the glass reactor as a monomer component over 1 hour. 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, and an aqueous latex (A-2) containing a rubber-containing graft copolymer (D) was obtained. The volume average particle diameter of the rubber-containing graft copolymer (D) contained in the obtained aqueous latex was 200 nm.

[0171] [Synthesis Example 3] Synthesis of Water-Based Latex (A-3) Containing Rubber-Containing Graft Copolymer (D) (Production Example 3a: Preparation of Elastic Body (3a)) Into a glass reactor, 155 parts of deionized water and 0.022 parts of sodium polyoxyethylene alkyl ether phosphate as a surfactant were added. Here, the glass reactor had a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The raw materials added were stirred at 50°C while the gas in the glass reactor was replaced with nitrogen. Next, as monomer components, a mixture of 8.5 parts of BA and 0.0425 parts of allyl methacrylate and 0.0017 parts of BHP were added into the glass reactor. After stirring the mixture in the glass reactor for 10 minutes, 0.0056 parts of EDTA, 0.0014 parts of ferrous sulfate, and 0.2 parts of SFS were added into the glass reactor to start the polymerization reaction, and the polymerization was carried out for 1 hour.

[0172] Then, a mixture of 64.5 parts of BA, 0.32 parts of allyl methacrylate, and 0.02 parts of BHP was added to the glass reactor over 180 minutes. While the mixture was being added, a surfactant, sodium polyoxyethylene alkyl ether phosphate, was added to the glass reactor in an appropriate amount at any time to ensure the stability of the latex. 15 minutes after the end of the addition of the mixture, 0.015 parts of BHP was added to the glass reactor. Polymerization was continued for another 30 minutes from the end of the addition of BHP to obtain an elastomer (3a).

[0173] (Production Example 3b: Preparation of Water-Based Latex (A-3) Containing Rubber-Containing Graft Copolymer (D)) Then, a mixture of 25.3 parts of MMA, 1.7 parts of BA, and 0.0125 parts of BHP was added to the glass reactor containing the elastomer (3a) over 95 minutes. While the mixture was being added, a surfactant, sodium polyoxyethylene alkyl ether phosphate, was added to the glass reactor in an appropriate amount at any time to ensure the stability of the latex. 15 minutes after the end of the addition of the mixture, 0.015 parts of BHP was added to the glass reactor. 15 minutes after the end of the addition of BHP, 0.015 parts of BHP was added to the glass reactor. Polymerization was carried out for 30 minutes from the end of the addition of BHP to obtain an aqueous latex (A-3) containing a rubber-containing graft copolymer (D). The polymerization conversion rate of the monomer components was 100% by weight. The volume average particle diameter of the rubber-containing graft copolymer (D) contained in the obtained aqueous latex was 260 nm.

[0174] <Preparation of impact modifier (X) for polyacetal resin> Example 1 To an aqueous latex (A-1) containing 100 parts of solids of rubber-containing graft copolymer (D), (a) 3 parts of a phenolic antioxidant IRGANOX-1076 [n-octadecyl-3-(3',5',di-t-butyl-4'-hydroxyphenyl)propionate] and (b) 0.05 parts of disodium hydrogen phosphate (B-1) as component (B) were added. Then, coagulation was performed using an aqueous solution of calcium chloride as a coagulant to obtain a slurry containing aggregates containing component (B) and rubber-containing graft copolymer (D). The aggregates were recovered from the obtained slurry, washed with 2000 parts of deionized water per 100 parts of solids of the aggregates, and further dehydrated. Through this operation, an aggregate containing component (B) and rubber-containing graft copolymer (D) was obtained, with a water content of 33% relative to the total weight (100% by weight) of the aggregates. Thereafter, 0.25 parts of potassium palmitate (C-1) as the alkali metal component (C) was added to the aggregates and mixed with respect to 100 parts of the solid content of the aggregates obtained. Potassium palmitate, which is the alkali metal component (C), was used in the form of an aqueous solution. The aggregates obtained were dried to obtain an impact modifier (X) for polyacetal resins (Example 1) containing component (B), the alkali metal component (C) and the rubber-containing graft copolymer (D). The element contents and pH of the obtained modifier (X) were measured, and the results are shown in Table 1.

[0175] (Examples 2 to 11 and Comparative Examples 1 to 3) In Examples 2 to 11 and Comparative Examples 1 to 3, the water-based latex containing the rubber-containing graft copolymer (D), the component (B), the coagulant, and the alkali metal component (C) were changed as shown in Tables 1 and 2, and the same procedure as in Example 1 was used to prepare an impact modifier (X) for polyacetal resin having a water content of 33% relative to the total weight (100% by weight) of the aggregate. The element contents and pH of each of the obtained modifiers (X) were measured, and the results are shown in Tables 1 and 2.

[0176] Comparative Example 4 In Comparative Example 4, an impact modifier (X) for polyacetal resin having a water content of 33% relative to the total weight (100% by weight) of the aggregate was prepared by the same procedure as in Comparative Example 3, except that the obtained aggregate was not washed. The element contents and pH of the obtained modifier (X) were measured, and the results are shown in Table 2.

[0177] [Table 1]

[0178] [Table 2]

[0179] <Preparation of polyacetal resin composition and molded article> (Examples 12 to 25 and Comparative Examples 5 to 10) The modifiers (X) and polyacetal resins (A) obtained in Examples 1 to 11 and Comparative Examples 1 to 4 were dry blended in the compounding ratios shown in Tables 3 and 4. The resulting blends were pelletized at a processing temperature of 200°C using a twin-screw extruder (Technovel, KZW25TW) with a screw diameter of 25 mm to obtain pelletized polyacetal resin compositions.

[0180] The resulting pellets (polyacetal resin composition) were then dried at 90°C for 5 hours. Thereafter, using a Fanuc injection molding machine 100B, the dried pellets of the polyacetal resin composition were injection molded at a cylinder temperature of 200°C and a mold temperature of 70°C to produce a 1 / 8 inch molded body. The impact resistance was measured using the resulting 1 / 8 inch molded body. In addition, the resulting pellets (polyacetal resin composition) were used to produce flat test pieces by the above-mentioned method, and the amount of formaldehyde generated and the color tone were measured using the flat test pieces. These results are shown in Tables 3 and 4.

[0181] [Table 3]

[0182] [Table 4]

[0183] As shown in Tables 3 and 4, it can be seen that the impact resistance modifier (X) for polyacetal resin according to one embodiment of the present invention can provide a polyacetal resin composition that can provide a molded article having (a) a low amount of VOC emission (amount of formaldehyde emission) and (b) good impact resistance and color tone by mixing the modifier (X) with the polyacetal resin (A).

[0184] <Preparation of impact modifier (X) for polyacetal resin> (Example 26) To an aqueous latex (A-1) containing 100 parts of solids of rubber-containing graft copolymer (D), (a) 3 parts of a phenolic antioxidant IRGANOX-1076 [n-octadecyl-3-(3',5',di-t-butyl-4'-hydroxyphenyl)propionate] and (b) 0.05 parts of disodium hydrogen phosphate (B-1) as component (B) were added. Then, coagulation was performed using an aqueous solution of calcium chloride as a coagulant to obtain a slurry containing aggregates containing component (B) and rubber-containing graft copolymer (D). The aggregates were recovered from the obtained slurry, washed with 2000 parts of deionized water per 100 parts of solids of the aggregates, and further dehydrated. Through this operation, an aggregate containing component (B) and rubber-containing graft copolymer (D) was obtained, with a water content of 33% relative to the total weight (100% by weight) of the aggregates. Thereafter, 0.25 parts of potassium palmitate (C-1) as the alkali metal component (C) was added to the aggregates and mixed with respect to 100 parts of the solid content of the aggregates obtained. Potassium palmitate, which is the alkali metal component (C), was used in the form of an aqueous solution. The aggregates obtained were dried to obtain an impact modifier (X) for polyacetal resins (Example 26) containing component (B), the alkali metal component (C) and the rubber-containing graft copolymer (D). The element contents and pH of the obtained modifier (X) were measured, and the results are shown in Table 5.

[0185] (Examples 27 to 29) In Examples 27 to 29, impact modifiers (X) for polyacetal resins having a water content of 33% relative to the total weight (100% by weight) of the aggregates were prepared by the same procedure as in Example 26, except that the alkali metal component (C) was changed as shown in Table 5. The element contents and pH of each of the obtained modifiers (X) were measured, and the results are shown in Table 5.

[0186] Comparative Example 11 In Comparative Example 11, the aggregates were washed with 500 parts of deionized water per 100 parts of the solid content of the aggregates, and the same procedure as in Example 26 was used to prepare an impact modifier (X) for polyacetal resins having a water content of 33% relative to the total weight (100% by weight) of the aggregates. The element contents and pH of the obtained modifier (X) were measured, and the results are shown in Table 5.

[0187] (Example 30 and Comparative Example 12) In Example 30 and Comparative Example 12, the water-based latex containing the rubber-containing graft copolymer (D) and the alkali metal component (C) were changed as shown in Table 5, and the same procedure as in Example 26 was used to prepare impact modifiers (X) for polyacetal resins having a water content of 33% relative to the total weight (100% by weight) of the aggregates. The element contents and pH of each of the obtained modifiers (X) were measured, and the results are shown in Table 5.

[0188] Comparative Example 13 In Comparative Example 13, the same procedure as in Example 26 was followed except that (a) the alkali metal component (C) was changed as shown in Table 5, and (b) the aggregates were washed with 500 parts of deionized water per 100 parts of the solid content of the aggregates, to prepare an impact modifier (X) for polyacetal resin having a water content of 33% relative to the total weight (100% by weight) of the aggregates. The element contents and pH of the obtained modifier (X) were measured, and the results are shown in Table 5.

[0189] [Table 5]

[0190] <Preparation of polyacetal resin composition and molded article> (Examples 31 to 35 and Comparative Examples 14 to 16) The modifiers (X) and polyacetal resins (A) obtained in Examples 26 to 30 and Comparative Examples 11 to 13 were dry blended in the compounding ratios shown in Table 6. The resulting blends were pelletized at a processing temperature of 200°C using a twin-screw extruder (Technovel, KZW25TW) with a screw diameter of 25 mm to obtain pelletized polyacetal resin compositions.

[0191] The pellets obtained (polyacetal resin composition) were then dried at 90°C for 5 hours. After that, the pellets of the dried polyacetal resin composition were injection molded using a Fanuc injection molding machine 100B at a cylinder temperature of 200°C and a mold temperature of 70°C to produce a 1 / 8 inch molded body. The obtained molded body was used to measure impact resistance. In addition, the pellets obtained (polyacetal resin composition) were used to produce a molded body having a shape specified by ISO 527-2 / 1А, and the obtained molded body was used to measure tensile elongation at break. Furthermore, the pellets obtained (polyacetal resin composition) were used to produce flat test pieces by the above-mentioned method, and the amount of formaldehyde generated and color tone were measured using the flat test pieces. These results are shown in Table 6.

[0192] [Table 6]

[0193] As shown in Tables 5 and 6, it can be seen that the impact resistance modifier (X) for polyacetal resin according to one embodiment of the present invention can provide a polyacetal resin composition that can provide a molded article having (a) a low amount of VOC emission (amount of formaldehyde emission) and (b) good impact resistance and color tone by mixing the modifier (X) with the polyacetal resin (A).

[0194] Examples 31 to 34 (Examples 26 to 29) are compared with each other, and Comparative Examples 14 and 16 (Comparative Examples 11 and 13) are compared. From these comparisons, the following (a) and (b) are found: (a) when the potassium content is 0.010% by weight or more in 100% by weight of modifier (X), the amount of VOC generated by the molded body decreases as the potassium content increases, and (b) the tensile elongation at break of the molded body improves as the potassium content approaches the range of 0.010% by weight to 0.020% by weight in 100% by weight of modifier (X).

[0195] In addition, Example 31 (Example 26) and Comparative Example 14 (Comparative Example 11) are compared. The modifier (X) of Example 26 and the modifier (X) of Comparative Example 11 are modifiers (X) obtained by using the same amount of the alkali metal component (C), and have almost the same potassium element content, but significantly different chlorine element content. The modifier (X) of Comparative Example 11, which has a relatively high chlorine element content, has a lower pH and is weakly acidic than the modifier (X) of Example 26, which has a relatively low chlorine element content. As a result, the molded article of the polyacetal resin composition of Comparative Example 14 has a significantly higher VOC emission amount, a poorer tensile elongation at break, and a poorer color tone than the molded article of the polyacetal resin composition of Example 31.

[0196] Also, Example 35 (Example 30) and Comparative Example 15 (Comparative Example 12) are compared. The modifier (X) of Example 30 and the modifier (X) of Comparative Example 12 are both modifiers obtained using an aqueous latex (A-3) containing a rubber-containing graft copolymer (D). That is, the rubber-containing graft copolymer (D) contained in both modifiers (X) has an acrylic resin elastomer (core layer). The modifier (X) of Example 30 is a modifier obtained using an alkali metal component (C), while the modifier (X) of Comparative Example 12 is a modifier obtained without using an alkali metal component (C). As a result, the molded article of the polyacetal resin composition of Example 35 has a significantly lower VOC emission amount than the molded article of the polyacetal resin composition of Comparative Example 15. [Industrial Applicability]

[0197] The polyacetal resin composition using the impact modifier (X) for polyacetal resin according to one embodiment of the present invention can be suitably used for electrical and electronic applications, automotive parts applications, and industrial equipment applications. The polyacetal resin composition using the impact modifier (X) for polyacetal resin according to one embodiment of the present invention can be suitably used for, for example, mechanical parts of the drive unit of AV equipment, dishwasher handles, speaker grills, washing machine tub stirring propellers, OA 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. An impact modifier (X) for a polyacetal resin, comprising a rubber-containing graft copolymer (D) having an elastomer and a graft portion grafted to the elastomer, Further containing an alkali metal component (C), The alkali metal component (C) is (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer having, as a structural unit, a structural unit derived from one or more compounds selected from the group consisting of (meth)acrylate having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid; and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms and an alkali metal, and one or more selected from the group consisting of: The impact resistance modifier (X) for polyacetal resin further contains 0.010 wt % to 0.300 wt % of phosphorus and 0.010 wt % to 0.300 wt % of an alkali metal element based on 100 wt % of the impact resistance modifier (X) for polyacetal resin, The impact resistance modifier (X) for polyacetal resins, wherein a mixture consisting of 25 parts by weight of the impact resistance modifier (X) for polyacetal resins and 75 parts by weight of deionized water has a pH of 7.0 or more and 11.0 or less.

2. The impact resistance modifier (X) for polyacetal resins according to claim 1, wherein the impact resistance modifier (X) for polyacetal resins contains 0.010% by weight to 0.150% by weight of the alkali metal element per 100% by weight of the impact resistance modifier (X) for polyacetal resins.

3. 3. The impact modifier (X) for polyacetal resins according to claim 1 or 2, wherein the content of an alkaline earth metal element in the impact modifier (X) for polyacetal resins is less than 0.100% by weight, based on 100% by weight of the impact modifier (X) for polyacetal resins.

4. The impact resistance modifier (X) for polyacetal resins according to any one of claims 1 to 3, wherein the content of chlorine element in the impact resistance modifier (X) for polyacetal resins is less than 0.040% by weight, based on 100% by weight of the impact resistance modifier (X) for polyacetal resins.

5. The impact resistance modifier (X) for polyacetal resin according to any one of claims 1 to 4, wherein the elastomer comprises at least one selected from the group consisting of butadiene rubber, styrene / butadiene copolymer rubber, acrylate rubber, and silicone rubber.

6. A polyacetal resin composition comprising the impact modifier for polyacetal resin (X) according to any one of claims 1 to 5 and a polyacetal resin (A).

7. The method includes a step of mixing an aggregate containing a pH adjuster (B) containing a phosphorus component and a rubber-containing graft copolymer (D) with an alkali metal component (C), The alkali metal component (C) is (i) a substance obtained by saponifying, with sodium hydroxide and / or potassium hydroxide, a polymer obtained by polymerizing one or more selected from the group consisting of (meth)acrylates having a glycidyl group, sodium (meth)acrylate, potassium (meth)acrylate, and (meth)acrylic acid; and (ii) a salt of an aliphatic carboxylic acid having 10 to 24 carbon atoms and an alkali metal, A method for producing an impact modifier (X) for a polyacetal resin, the method being one or more selected from the group consisting of:

8. 8. The method for producing an impact resistance modifier (X) for a polyacetal resin according to claim 7, wherein the pH adjuster (B) containing a phosphorus component is one or more selected from the group consisting of a mixture of sodium hydroxide or potassium hydroxide with phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tripotassium phosphate.

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