Polyacetal resin composition and molded article

Abstract

To provide a polyacetal resin composition which can further improve physical properties such as mechanical strength and hot water resistance, while using a modified cross-section glass fiber, when being colored by black, particularly, carbon black.SOLUTION: A polyacetal resin composition contains, with respect to 100 pts.mass of (A) a polyacetal resin, 1 to 100 pts.mass of (B) a modified cross-section glass fiber which is surface-treated with (B1) at least one selected from at least one isocyanate compound selected from the group consisting of a blocked isocyanate compound and a polyurethane resin, an amino silane coupling agent, an epoxy resin, and an acid copolymer, and (B2) a boric acid compound, and 0.001 to 3 pts.mass of (C) at least one binder selected from the group consisting of an organometallic compound containing a metal selected from Sn, Zn and PB, a boric acid compound and a quaternary onium salt compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyacetal resin composition and a molded article. [Background technology]

[0002] Polyacetal resins have an excellent balance of mechanical properties, chemical resistance, and sliding properties, and are easily processable. Therefore, they are widely used as engineering plastics, primarily in electrical and electronic components, automotive parts, and various other mechanical components. Various fillers are typically added to polyacetal resins to further improve their mechanical properties. Examples of such fillers include glass fibers. Glass fibers are widely used to improve the mechanical strength of not only polyacetal resins but also various engineering plastics. Glass fibers with a circular cross-section are typically used. However, when using typical glass fibers with a circular cross-section, while increasing the filler content can improve mechanical properties and shrinkage, the resulting resin molded products tend to have increased warpage due to increased anisotropy. Therefore, the use of irregular cross-section glass fibers, which have non-circular cross-sections, has been proposed in recent years (see Patent Document 1). The use of such irregular cross-section glass fibers can reduce warpage of resin molded products. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-316079 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, adding irregular cross-section glass fibers to a resin composition can reduce warpage in a resin molded product obtained by molding the resin composition. Patent Document 1 also uses a polyfunctional cyanate ester compound as a binder to provide adhesion at the interface between the irregular cross-section glass fibers and the polyacetal resin. However, even with the use of such a binder, the interface adhesion between the irregular cross-section glass fibers and the polyacetal resin is not sufficient, and the mechanical strength, hot water resistance, and creep resistance are insufficient, leaving room for improvement.

[0005] On the other hand, when a black molded product is to be obtained, it is common to blend the above-mentioned resin composition with carbon black and polyolefin wax to color it black, but blending carbon black and polyolefin wax in this way has the problem that the hot water resistance of the resulting molded product is reduced.

[0006] The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to provide a polyacetal resin composition and a molded article which use modified cross-section glass fibers and can achieve improved physical properties such as mechanical strength and hot water resistance, particularly when the composition is colored black with carbon black and polyolefin wax. [Means for solving the problem]

[0007] One aspect of the present invention that solves the above problem is as follows. (1) (A) Per 100 parts by mass of polyacetal resin, (B) (B1) 1 to 100 parts by mass of modified cross section glass fiber surface-treated with at least one isocyanate compound selected from the group consisting of blocked isocyanate compounds and polyurethane resins, at least one selected from the group consisting of aminosilane coupling agents, epoxy resins, and acid copolymers, and (B2) a boric acid compound; (C) 0.001 to 3 parts by mass of at least one binder selected from the group consisting of triazine derivatives having a nitrogen-containing functional group, organometallic compounds containing a metal selected from Sn, Zn, and Pb, boric acid compounds, and quaternary onium salt compounds; A polyacetal resin composition comprising: (2) The polyacetal resin composition according to (1) above, wherein the (B) irregular cross-section glass fiber is a glass fiber having a flat cross-sectional shape in which the ratio of the major axis of the cross-section to the minor axis of the cross-section (irregularity ratio) is 1.2 or more. (3) The polyacetal resin composition according to (1) or (2), wherein the binder (C) is at least one binder selected from the group consisting of melamine derivatives, zinc fatty acids, boric acid, quaternary phosphonium halides, quaternary ammonium halides, quaternary phosphonium carboxylates, and quaternary ammonium carboxylates. (4) The polyacetal resin composition according to any one of (1) to (3), wherein the binder (C) is at least one binder selected from the group consisting of melamine, a melamine formaldehyde adduct, benzoguanamine, zinc stearate, orthoboric acid, ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, choline acetate, and choline chloride. (5) A molded article obtained by molding the polyacetal resin composition according to any one of (1) to (4) above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyacetal resin composition and a molded article which can realize improvements in physical properties such as mechanical strength and hot water resistance, even when modified cross-section glass fibers are used, particularly when black coloring is performed with carbon black and polyolefin wax. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Polyacetal resin composition> The polyacetal resin composition of the present embodiment contains, per 100 parts by mass of (A) polyacetal resin, (B) 1 to 100 parts by mass of (B1) at least one isocyanate compound selected from the group consisting of blocked isocyanate compounds and polyurethane resins, at least one selected from the group consisting of an aminosilane coupling agent, an epoxy resin, and an acid copolymer, and (B2) modified cross section glass fibers surface-treated with a boric acid compound, and (C) 0.001 to 3 parts by mass of at least one binder selected from the group consisting of triazine derivatives having a nitrogen-containing functional group, organometallic compounds containing a metal selected from Sn, Zn, and Pb, boric acid compounds, and quaternary onium salt compounds.

[0010] The polyacetal resin composition of this embodiment contains (B) irregular cross-section glass fiber surface-treated with a specific material and (C) a specific binder in a predetermined amount. The inclusion of such components (B) and (C) improves the interfacial adhesion between the polyacetal resin (A) and the irregular cross-section glass fiber (B), thereby improving physical properties such as mechanical strength and hot water resistance. As mentioned above, the addition of carbon black and polyolefin wax for black coloring reduces hot water resistance. However, in this embodiment, the boric acid compound (B2) contained in the material used to surface-treat the irregular cross-section glass fiber (B) can suppress the reduction in hot water resistance.

[0011] Each component of the polyacetal resin composition of the present embodiment will be described in detail below. [(A) Polyacetal resin] In this embodiment, the polyacetal resin (A) is a polymeric compound having an oxymethylene group (—CHO—) as a main constituent unit, and may be either a homopolymer in which the oxymethylene group is the only constituent unit, or a copolymer, terpolymer, or block polymer in which the oxymethylene group is the main constituent unit and contains a small amount of other constituent units, such as constituent units derived from comonomers such as ethylene oxide, 1,3-dioxolane, and 1,4-butanediol formal.

[0012] Furthermore, the polyacetal resin may be not only linear in molecular structure but also have a branched or crosslinked structure obtained by copolymerizing a comonomer having a glycidyl ether structure, or may be a known modified polyoxymethylene into which other organic groups have been introduced, or may be a mixture of a linear resin and a resin having a branched or crosslinked structure.

[0013] The polyacetal resin is not particularly limited in terms of its degree of polymerization, and may be any resin that has melt-molding processability (for example, a melt flow rate (MFR) of 1.0 g / 10 min or more and 100 g / 10 min or less at 190°C under a load of 2160 g in accordance with ISO 1133). [(B) Irregular cross-section glass fiber] The polyacetal resin composition of this embodiment contains 1 to 100 parts by mass of (B) irregular cross-section glass fiber surface-treated with a specific material per 100 parts by mass of (A) polyacetal resin. (Hereinafter, the "specific material" will also be referred to as the "surface treatment agent.") The inclusion of (B) irregular cross-section glass fiber, in combination with (C) binder, can improve physical properties such as mechanical strength. In addition, the boric acid compound in the surface treatment agent can suppress the decrease in hot water resistance that occurs when carbon black and polyolefin wax are blended for black coloring. In this specification, (B) irregular cross-section glass fiber surface-treated with a specific material may be simply referred to as "(B) irregular cross-section glass fiber."

[0014] In this embodiment, the irregular cross-section glass fiber means a glass fiber whose cross section perpendicular to the longitudinal direction of the glass fiber is not a so-called substantially circular shape, such as an elongated flat shape such as an oval, cocoon shape, or ellipse shape.

[0015] In addition, as the modified cross section glass fiber, modified cross section glass fiber obtained by the manufacturing method described in JP-B-4-32775, Japanese Patent No. 33369674, Japanese Patent No. 5505597, Japanese Patent No. 7075017, and International Publication WO2020 / 04033 can be used.

[0016] The composition of the modified cross section glass fiber used in the polyacetal resin composition of the present embodiment may be any composition that can be formed into glass fiber from molten glass, and examples thereof include an E-glass composition, an A-glass composition, a C-glass composition, a D-glass composition, an H-glass composition, an R-glass composition, an S-glass composition, a T-glass composition, an AR-glass composition, an NE-glass composition, and an ECR-glass composition (boron-free and / or fluorine-free glass composition).

[0017] From the viewpoint of improving physical properties such as mechanical strength, the (B) modified cross-section glass fiber preferably has a flat cross-sectional shape in which the ratio of the major axis of the cross-section to the minor axis of the cross-section (modification ratio) is 1.2 or more, more preferably 1.5 to 10, and even more preferably 1.8 to 8.

[0018] As the modified cross-section glass fiber, any glass in a fibrous form can be used without any particular problems. Specific examples include chopped strand glass fiber, milled glass fiber, and glass fiber roving. Among these, chopped strand glass fiber and milled glass fiber are particularly preferred from the viewpoint of productivity. Furthermore, chopped strand glass fiber is more preferred for improving the creep resistance of resin molded products. These modified cross-section glass fibers may be used alone or in combination of two or more.

[0019] Examples of modified cross section glass fibers having an oval cross section include chopped strands and oval FF manufactured by Nitto Boseki Co., Ltd., chopped strands and oval FGF manufactured by Nippon Electric Glass Co., Ltd., and chopped strands and flat CS manufactured by Central Glass Fiber Co., Ltd. Furthermore, examples of modified cross section glass fibers having a cocoon-shaped cross section include chopped strands and cocoon-shaped HIS manufactured by Nitto Boseki Co., Ltd.

[0020] In this embodiment, the modified cross section glass fiber (B) is surface-treated with a surface treatment agent as described above. The surface treatment agent used is (B1) at least one isocyanate compound selected from the group consisting of blocked isocyanate compounds and polyurethane resins, at least one selected from the group consisting of aminosilane coupling agents, epoxy resins, and acid copolymers, and (B2) a boric acid compound. In other words, in this embodiment, the surface treatment agents used are (B1) at least one selected from the group shown in (B1) and (B2) a boric acid compound. Each surface treatment agent will be described below. (B1) Isocyanate compounds The isocyanate compound used in this embodiment is at least one selected from the group consisting of blocked isocyanate compounds and polyurethane resins. <Blocked isocyanate compounds> The isocyanate compound used as the raw material for the blocked isocyanate compound can be any polyfunctional isocyanate compound having two or more isocyanate groups per molecule. Examples include aliphatic (including linear, branched, and alicyclic) and aromatic isocyanate compounds, with aliphatic isocyanate compounds being preferred in terms of compatibility and suitability with polyacetal resins. Bifunctional aliphatic or alicyclic diisocyanates and polyisocyanates obtained by polymerizing these diisocyanates are particularly preferred.

[0021] The linear or branched aliphatic diisocyanate preferably has 4 to 30 carbon atoms, and more preferably has 5 to 10 carbon atoms. Specific examples include tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, and lysine diisocyanate.

[0022] The alicyclic diisocyanate preferably has 8 to 15 carbon atoms, and more preferably has 10 to 18 carbon atoms. Specific examples include isophorone diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, and 4,4'-dicyclohexylmethane diisocyanate.

[0023] Examples of aromatic diisocyanates include xylylene diisocyanate, tolylene diisocyanate, and diphenylmethane diisocyanate.

[0024] Examples of polyisocyanates include compounds having at least two isocyanate groups per molecule, such as various aromatic diisocyanates such as tolylene diisocyanate or diphenylmethane diisocyanate; various aralkyl diisocyanates such as m-xylylene diisocyanate or α,α,α',α'-tetramethyl-m-xylylene diisocyanate; isocyanate group-containing prepolymers obtained by addition reaction of aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, or isophorone diisocyanate with polyhydric alcohols; prepolymers having an isocyanurate ring obtained by cyclotrimerization of the various diisocyanates; and adducts and polyisocyanates having a biuret structure obtained by reacting the various diisocyanates with water.

[0025] Among these, hexamethylene diisocyanate, biuret of hexamethylene diisocyanate, and cyclic trimer of hexamethylene diisocyanate are preferred from the viewpoints of the impact resistance and durability of the resulting composition and ease of industrial availability. Two or more of the above compounds may be used in combination. Furthermore, a mixture of two or more of the above compounds may also be used.

[0026] Furthermore, in the present embodiment, the blocked isocyanate compound that can be used is not particularly limited and is obtained by blocking the reactive group of the above-mentioned isocyanate compound with a well-known blocking agent by a standard method.

[0027] Specific examples of blocking agents include, but are not limited to, oxime-based blocking agents such as methyl ethyl ketoxime, acetoxime, cyclohexanone oxime, acetophenone oxime, and benzophenone oxime; phenol-based blocking agents such as m-cresol and xylenol; alcohol-based blocking agents such as methanol, ethanol, butanol, 2-ethylhexanol, cyclohexanol, and ethylene glycol monoethyl ether; lactam-based blocking agents such as ε-caprolactam; diketone-based blocking agents such as diethyl malonate and acetoacetate; mercaptan-based blocking agents such as thiophenol; urea-based blocking agents such as thiourea; imidazole-based blocking agents; pyrazole-based blocking agents; carbamic acid-based blocking agents; and bisulfites. Among these, lactam-based blocking agents, oxime-based blocking agents, and diketone-based blocking agents are preferred. Polyurethane resin As the polyurethane resin, from the viewpoint of sizing properties, a resin obtained from a polyisocyanate component mainly containing xylylene diisocyanate and a polyol component mainly containing polyester polyol is particularly suitable.

[0028] Here, examples of xylylene diisocyanate include o-xylylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, and mixtures thereof, with m-xylylene diisocyanate being preferred among these.

[0029] On the other hand, examples of polyester polyols include condensation-based polyester polyols obtained by dehydration condensation of polyhydric alcohols and polycarboxylic acids, lactone-based polyester polyols obtained by ring-opening polymerization of lactones based on polyhydric alcohols, ester-modified polyols in which the terminals of polyether polyols are ester-modified with lactones, and copolymerized polyester polyols thereof.

[0030] Examples of polyhydric alcohols used in the condensation polyester polyols include ethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol, 1,4-butanediol, 1,5-pentanediol, hexylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and dipropylene glycol. Examples of polycarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and trimellitic acid.

[0031] Furthermore, examples of lactone-based polyester polyols include poly(ε-caprolactone) polyol. These polyester polyols preferably have a weight-average molecular weight in the range of 500 to 4000. The weight-average molecular weight of the resin in this specification is a value measured by the GPC method and converted into standard polystyrene.

[0032] The polyurethane resin can be produced, for example, by heating xylylene diisocyanate and polyester polyol at a temperature of about 30° C. to 130° C. in the absence of a solvent or in the presence of a small amount of an organic solvent.

[0033] In addition, when the heat reaction is carried out, the polyhydric alcohol exemplified in the description of the polyester polyol may be appropriately used as a chain extender. When an organic solvent is used, the organic solvent is not particularly limited as long as it does not react with isocyanate and is miscible with water, and examples of the organic solvent that can be used include acetone, methyl ethyl ketone, tetrahydrofuran, and dimethylformamide. (B1) Aminosilane coupling agent The aminosilane coupling agent refers to a compound containing, in one molecule, a silicon atom to which an alkoxy group is bonded and a functional group containing a nitrogen atom.

[0034] Specific aminosilane coupling agents include γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, N,N'-bis-[3-(trimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(triethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(methyldimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(trimethoxysilyl)propyl]hexamethylenediamine, N,N'-bis-[3-(triethoxysilyl)propyl]hexamethylenediamine, etc. These aminosilane coupling agents may be used alone or in combination of two or more.

[0035] Among these, preferred examples of the aminosilane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane, and more preferred examples include γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0036] These aminosilane coupling agents tend to produce a synergistic effect when combined with a blocked isocyanate compound, and can improve the adhesion between the polyacetal resin and the modified cross-section glass fiber. (B1) Epoxy resin As the epoxy resin, a conventional epoxy resin can be used, and one or more types can be selected from, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, novolac type epoxy resin such as phenol novolac type or cresol novolac type epoxy resin, aliphatic epoxy resin, hydrogenated type or ether modified product thereof, phenoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, cyclic aliphatic epoxy resin, urethane modified epoxy resin, etc. Among these, bisphenol A type epoxy resin and phenol novolac type epoxy resin are particularly preferred from the viewpoints of glass fiber bundling ability and hot water resistance. (B1) Acid copolymer The acid copolymer may be a copolymer of maleic acid or maleic anhydride with acrylic acid, methacrylic acid, or an alkyl ester thereof. Specifically, one may be selected from maleic acid / acrylic acid copolymer, maleic acid / methacrylic acid copolymer, maleic acid / methyl acrylate copolymer, maleic acid / methyl methacrylate copolymer, maleic acid / ethyl acrylate copolymer, maleic acid / ethyl methacrylate copolymer, maleic anhydride / methyl acrylate copolymer, maleic anhydride / methyl methacrylate copolymer, maleic anhydride / ethyl acrylate copolymer, maleic anhydride / ethyl methacrylate copolymer, etc. Among these, maleic anhydride / methyl acrylate copolymer and maleic anhydride / methyl methacrylate copolymer are particularly preferred in terms of glass fiber bundling ability and hot water resistance.

[0037] Two or more of the above surface treatment agents can be used in combination. In this case, the following combinations are preferred: a combination of a blocked isocyanate compound, a silane coupling agent, a polyurethane resin, and an epoxy resin; a combination of a blocked isocyanate compound, a silane coupling agent, and an epoxy resin; or a combination of a blocked isocyanate compound, a silane coupling agent, a polyurethane resin, an epoxy resin, and an acid copolymer.

[0038] The amount of at least one surface treatment agent selected from the group shown in (B1) above is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the modified cross section glass fiber, from the viewpoint of improving physical properties such as mechanical strength and hot water resistance. (B2) Boric acid compounds As described above, in this embodiment, by using a boric acid compound as part of the surface treatment agent, it is possible to suppress a decrease in hot water resistance when carbon black and polyolefin wax are blended for black coloring. Examples of boric acid compounds include boric acid and dehydrated condensates of boric acid. Specific examples include boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid. Of these, orthoboric acid is preferred.

[0039] In this embodiment, the (B2) boric acid compound is preferably used in an amount of 0.01 to 1 part by mass, more preferably 0.05 to 0.3 parts by mass, per 100 parts by mass of the modified cross section glass fiber, from the viewpoint of suppressing a decrease in hot water resistance when carbon black and polyolefin wax are blended for coloring.

[0040] The polyacetal resin composition of this embodiment contains 1 to 100 parts by mass of (B) modified cross section glass fiber per 100 parts by mass of (A) polyacetal resin, but if the amount of (B) modified cross section glass fiber is less than 1 part by mass, physical properties such as mechanical strength and hot water resistance become insufficient, while if it exceeds 100 parts by mass, melt fluidity decreases significantly. The content of (B) modified cross section glass fiber is preferably 3 to 80 parts by mass, more preferably 5 to 60 parts by mass. [(C) Binder] As described above, (C) the binder is used to improve the interfacial adhesion between (A) the polyacetal resin and (B) the modified cross-section glass fiber.

[0041] (C) Examples of triazine derivatives having a nitrogen-containing functional group as a binder include melamine derivatives such as guanamine, melamine, melamine formaldehyde adduct, N-butylmelamine, N-phenylmelamine, N,N'-diphenylmelamine, N,N'-diallylmelamine, and N,N',N''-triphenylmelamine, benzoguanamine, acetoguanamine, 2,4-diamino-6-butyl-sym-triazine, ammeline, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl-sym-triazine, and 2,4-diamino-6-chloro-s Examples include ym-triazine, 2,4-diamino-6-mercapto-sym-triazine, 6-amino-2,4-dihydroxy-sym-triazine (also known as ammelide), 1,1-bis(3,5-diamino-2,4,6-triazinyl)methane, 1,2-bis-(3,5-diamino-2,4,6-triazinyl)ethane (also known as stannate), 1,3-bis(3,5-diamino-2,4,6-triazinyl)propane, 1,4-bis(3,5-diamino-2,4,6-triazinyl)butane, methylenated melamine, ethylenedimelamine, triguanamine, melamine cyanurate, ethylenedimelamine cyanurate, and triguanamine cyanurate.

[0042] These triazine derivatives may be used alone or in combination of two or more. Preferred are guanamine and melamine, with melamine being particularly preferred.

[0043] (C) Organometallic compounds containing a metal element selected from Sn, Zn, and Pb as binders include saturated or unsaturated tin fatty acids, zinc fatty acids, lead fatty acids, metal salts of polymeric carboxylic acids (e.g., zinc poly(meth)acrylate, zinc salt of ethylene-(meth)acrylic acid copolymer), metal salts of 1,3-diketones (e.g., tin acetylacetone, zinc acetylacetone), and metal salts of dehydroacetic acid (e.g., zinc dehydroacetate). Fatty acids are preferably fatty acids having 1 to 30 carbon atoms, such as acetic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, montanic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, eicosapentanoic acid, docosapentaenoic acid, and docosahexaenoic acid. Between saturated and unsaturated fatty acids, saturated fatty acids are preferred from the viewpoint of thermal stability. Among these organometallic compounds, zinc fatty acids are preferred. Specific examples include zinc stearate and zinc 12-hydroxystearate.

[0044] (C) Examples of the boric acid compound as a binder include boric acid and dehydration condensates of boric acid. Specific examples include orthoboric acid (H3BO3), metaboric acid, tetraboric acid, and other boric acids. Of these, orthoboric acid is preferred.

[0045] As described above, the polyacetal resin composition of this embodiment contains (B2) a boric acid compound as the surface treatment agent for (B) the irregular cross section glass fiber. The boric acid compound as the binder (C) in the polyacetal resin composition and the boric acid compound as the surface treatment agent for (B) the irregular cross section glass fiber (B2) can be distinguished, for example, as follows: First, the polyacetal resin composition is dissolved in 1,1,1,3,3,3-hexafluoroisopropanol, and the irregular cross section glass fiber is recovered. If the boric acid compound is present in the irregular cross section glass fiber, the boric acid compound can be considered as the surface treatment agent for the irregular cross section glass fiber.

[0046] (C) Examples of the quaternary onium salt compound as a binder include quaternary phosphonium salts and quaternary ammonium salts. Preferred are quaternary phosphonium halide salts and quaternary ammonium halide salts, respectively, and specifically preferred are ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, and choline chloride.

[0047] Furthermore, quaternary phosphonium carboxylates and quaternary ammonium carboxylates are preferred, and specifically, choline acetate is preferred.

[0048] Two or more of these binders (C) can be used in combination, and it is particularly preferable to use a boric acid compound in combination with a quaternary onium salt.

[0049] The polyacetal resin composition of this embodiment contains 0.001 to 3 parts by mass of (C) binder per 100 parts by mass of (A) polyacetal resin. If the amount is less than 0.001 part by mass, the improvement in the interfacial adhesion between the (A) polyacetal resin and the (B) modified cross-section glass fiber is insufficient. If the amount is more than 3 parts by mass, the strands may foam during melt-kneading, a formaldehyde odor may be generated, and the color of the molded product may deteriorate. The content of (C) binder is preferably 0.002 to 2 parts by mass, more preferably 0.003 to 1 part by mass. [Other stabilizers and additives] The polyacetal resin composition of the present embodiment may further contain various known stabilizers to enhance its stability, and may further contain various known additives to improve its physical properties depending on the intended application.

[0050] Examples of additives include various stabilizers (antioxidants, anti-acid agents, etc.), ultraviolet absorbers, light stabilizers, formaldehyde scavengers, colorants (carbon black, etc.), release agents, nucleating agents, antistatic agents, sliding agents, other surfactants, different polymers, etc. Furthermore, fibrous, powdery, or plate-like fillers such as circular cross-section glass fibers, inorganic, organic, or metallic fillers may be used alone or in combination, as long as they do not significantly impair the performance of the composition of the present embodiment. [Preparation of Polyacetal Resin Composition] The polyacetal resin composition according to the present embodiment can be easily prepared by a known method generally used for preparing conventional resin compositions. For example, (1) a method in which all components constituting the composition are mixed, fed into an extruder, and melt-kneaded to obtain a pellet-shaped composition, (2) a method in which some of the components constituting the composition are fed through a main feed port of an extruder and the remaining components are fed through a side feed port, and melt-kneaded to obtain a pellet-shaped composition, or (3) a method in which pellets with different compositions are first prepared by extrusion or the like, and the pellets are mixed to obtain a predetermined composition, etc., can be employed. <Molded products> The molded article of the present embodiment is obtained by molding a polyacetal resin composition. The method for producing a molded article using the polyacetal resin composition of the present embodiment is not particularly limited, and any known method can be used. For example, the molded article can be produced by feeding the polyacetal resin composition of the present embodiment into an extruder, melt-kneading the composition, and pelletizing it, and then feeding the pellets into an injection molding machine equipped with a predetermined mold and injection-molding the pellets.

[0051] Examples of molded articles of this embodiment include automotive parts such as door locks, door handles, window regulators (carrier plates), and power window switch housing parts; seat belt peripheral parts such as seat belt slip rings and press buttons; pulleys and wiper device parts; sunroof device parts; convenience store switch parts: parts such as clips; fuel-related parts such as fuel pump modules, valves, and gasoline tank flanges; office automation parts such as printer and copier parts; personal computer parts such as keyboard parts (plunger parts); communication equipment parts such as mobile phone and facsimile parts; electrical equipment parts; and electronic equipment parts. [Example]

[0052] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples. [Examples 1 to 22, Comparative Examples 1 to 8] In each of the Examples and Comparative Examples, 100 parts by mass of (A) polyacetal resin were blended with (B) glass fiber and (C) binder, and, if necessary, carbon black and polyethylene wax (polyolefin wax) in the amounts (parts by mass) shown in Tables 2 to 4, and the blended mixture was melt-kneaded in an extruder at a cylinder temperature of 200°C to prepare pellet-shaped polyacetal resin compositions according to the Examples and Comparative Examples.

[0053] The materials used in Tables 2 to 4 are as follows: The units for the compositions are parts by mass. (A) Polyacetal resin (A-1) Polyacetal resin (polyacetal copolymer (POM) obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane, melt flow value (measured in accordance with ISO 133 at 190°C and a load of 2160 g): 45 g / 10 min) (A-2) Polyacetal resin (polyacetal copolymer (POM) obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane, melt flow value (measured in accordance with ISO 113 at 190°C with a load of 2160 g): 9 g / 10 min) (B) Irregular cross-section glass fiber (B-1) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 6, short diameter = 7 μm) (B-2) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 6, short diameter = 5.5 μm) (B-3) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-4) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-5) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-6) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-7) Irregular cross-section glass fiber (oval, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-8) Irregular cross-section glass fiber (cocoon-shaped, major axis / minor axis ratio: 2, minor axis = 10 μm) On the other hand, (B) irregular cross section glass fiber is surface treated with the surface treatment agent shown in Table 1 below. (B'-1) irregular cross section glass fiber differs from (B-2) irregular cross section glass fiber only in the presence or absence of orthoboric acid in the surface treatment agent, and the rest is the same. Similarly, (B'-2) irregular cross section glass fiber differs from (B-6) irregular cross section glass fiber only in the presence or absence of orthoboric acid in the surface treatment agent. In Table 1, blocked isocyanate A represents a blocked isocyanate compound blocked with methyl ethyl ketoxime, and blocked isocyanate B represents a blocked isocyanate compound blocked with ε-caprolactam. Furthermore, in Table 1, the number of parts by mass of each surface treatment agent is the number of parts by mass per 100 parts by mass of the irregular cross section glass fiber to be surface treated.

[0054] [Table 1] (C) Binder (C-1) Orthoboric acid (C-2) Zinc stearate (C-3) Ethyltriphenylphosphonium bromide (C-4) Choline Acetate (C-5) Choline Chloride (C-6) Melamine <Physical property evaluation> The pellet-shaped compositions prepared in each Example and Comparative Example were used to mold Type A test specimens in accordance with ISO 3167 using an injection molding machine. Tensile strength was measured in accordance with ISO 527-1,2, flexural strength in accordance with ISO 178, and Charpy impact strength (notched, 23°C) in accordance with ISO 179-1eA. The measurement atmosphere was 23°C and 50% RH. The evaluation results are shown in Tables 2 to 4. <Hot water resistance evaluation> Using Type A test pieces prepared in the same manner as the Type A test pieces prepared in the "Physical Property Evaluation" above, they were immersed in an autoclave containing hot water at 120°C for one day, then removed and their tensile strength (tensile strength after hot water treatment, units: MPa) was measured under the same measurement conditions as in the physical property evaluation. The evaluation results are shown in Tables 2 to 4.

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4] Tables 2 to 4 show that Examples 1 to 22 achieved good results in all evaluations. In particular, Example 5, which used glass fibers with the highest irregularity ratio, showed excellent results in all evaluations. Furthermore, a comparison between Examples 7 and 22, which differ only in the presence or absence of black coloring, suggests that black coloring with carbon black and polyethylene wax does not result in a significant difference in hot water resistance. From this, it is presumed that Examples 1 to 21 suppress a decrease in hot water resistance despite the black coloring achieved by blending carbon black and polyethylene wax.

[0058] In contrast, in Comparative Examples 1 to 7, which used modified cross section glass fibers that had not been surface-treated with a surface treatment agent, all evaluation results were not satisfactory at the same time, and in particular, the deterioration of hot water resistance due to the carbon black and polyethylene wax could not be suppressed.

[0059] Furthermore, a comparison between Example 3 and Comparative Example 3, Example 7 and Comparative Example 6, and Example 9 and Comparative Example 7, which differ only in the presence or absence of a boric acid compound in the surface treatment agent for the irregular cross section glass fiber, reveals that the boric acid compound in the surface treatment agent for the irregular cross section glass fiber contributes to suppressing a decrease in hot water resistance.

Claims

1. (A) per 100 parts by mass of polyacetal resin, (B) (B1) 1 to 100 parts by mass of modified cross section glass fiber surface-treated with at least one isocyanate compound selected from the group consisting of blocked isocyanate compounds and polyurethane resins, at least one selected from the group consisting of aminosilane coupling agents, epoxy resins, and acid copolymers, and (B2) a boric acid compound; (C) 0.001 to 3 parts by mass of at least one binder selected from the group consisting of triazine derivatives having a nitrogen-containing functional group, organometallic compounds containing a metal selected from Sn, Zn, and Pb, boric acid compounds, and quaternary onium salt compounds; A polyacetal resin composition comprising:

2. 2. The polyacetal resin composition according to claim 1, wherein the modified cross-section glass fiber (B) is a glass fiber having a flat cross-sectional shape in which the ratio of the major axis of the cross-section to the minor axis of the cross-section (modification ratio) is 1.2 or more.

3. 2. The polyacetal resin composition according to claim 1, wherein the binder (C) is at least one binder selected from the group consisting of melamine derivatives, fatty acid zinc salts, boric acid, quaternary phosphonium halide salts, quaternary ammonium halide salts, quaternary phosphonium carboxylate salts, and quaternary ammonium carboxylate salts.

4. 2. The polyacetal resin composition according to claim 1, wherein the binder (C) is at least one binder selected from the group consisting of melamine, a melamine formaldehyde adduct, benzoguanamine, zinc stearate, orthoboric acid, ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, choline acetate, and choline chloride.

5. A molded article obtained by molding the polyacetal resin composition according to any one of claims 1 to 4.

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