Polyacetal resin composition and molded article of the same

Abstract

To provide a polyacetal resin composition which can suppress change in impact resistance by a difference in a molding condition, and has a less amount of formaldehyde to be released.SOLUTION: There is provided a polyacetal resin composition, wherein with respect to 100 pts.mass of the total of (A) a polyacetal resin and (B) thermoplastic polyurethane, an amount of (A) the polyacetal resin is 50 pts.mass or more and 95 pts.mass or less, an amount of (B) the thermoplastic polyurethane is 5 pts.mass or more and 50 pts.mass or less, an amount of (C) a cyclic urea compound is 0.05 pts.mass or more and 0.30 pts.mass or less, an amount of (D) an amorphous polyamide resin is 0.20 pts.mass or more and 2.0 pts.mass or less, an amount of (E) a crystalline polyamide resin having a melting point of 250°C or higher is 0.01 pts.mass or more and 0.10 pts.mass or less, and a mass ratio (E) / (D) of (E) the crystalline polyamide resin having the melting point of 250°C or higher to (D) the amorphous polyamide resin is 0.02 or more and 0.10 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polyacetal resin is a crystalline resin that has excellent rigidity, strength, toughness, sliding properties, and creep resistance, and has therefore been used in a wide range of applications, including as a material for mechanical parts such as automotive parts, electrical and electronic parts, and industrial parts. In particular, there are increasing demands for VOC performance and color characteristics for automotive parts, and as automotive parts become smaller and lighter, there is also a growing demand for improved impact resistance.

[0003] On the other hand, thermoplastic polyurethanes have relatively good compatibility with polyacetal resins and can impart impact resistance to the polyacetal resins, so compositions containing polyacetal resins and thermoplastic polyurethanes are often used.

[0004] A known example of such a composition containing a polyacetal resin and a thermoplastic polyurethane is the one disclosed in Patent Document 1. Patent Document 1 discloses a polyacetal resin composition comprising 100 parts by mass of polyacetal resin, 1 to 120 parts by weight of a thermoplastic polyurethane resin, and 0.01 to 5 parts by mass of a formaldehyde scavenger having formaldehyde-reactive nitrogen, wherein the thermoplastic polyurethane resin contains a residual isocyanate amount of 0.1% by mass or less, has a water content of 3,000 ppm by mass or less, and exhibits a melt viscosity of 200,000 poise or more at 180°C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-057044 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, polyacetal resin compositions are used in a variety of applications and products, and are often molded under a wide variety of molding conditions due to various circumstances of molding manufacturers, etc. However, no study is made on changes in physical properties due to molding conditions for the polyacetal resin composition described in Patent Document 1. Generally, in polymer blends of polyacetal and thermoplastic polyurethane, the thermal history during molding causes polymer separation, which tends to cause changes in physical properties. In particular, when molding conditions are changed, changes in impact resistance, which is affected by the dispersion state of the matrix resin and domain resin, are likely to occur.

[0007] Therefore, an object of the present invention is to provide a polyacetal resin composition that can suppress changes in impact resistance due to molding conditions and emits a small amount of formaldehyde, and a molded article made of the polyacetal resin composition. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems of the prior art, and as a result have found that the above-mentioned problems can be solved by the following means, thereby completing the present invention.

[0009] That is, the present invention is as follows.

[0010] [1] (A) a polyacetal resin; (B) thermoplastic polyurethane; (C) a cyclic urea compound; (D) an amorphous polyamide resin; (E) a crystalline polyamide resin having a melting point of 250°C or higher, With respect to a total of 100 parts by mass of the (A) polyacetal resin and the (B) thermoplastic polyurethane, the amount of the (A) polyacetal resin is 50 parts by mass or more and 95 parts by mass or less, the amount of the (B) thermoplastic polyurethane is 5 parts by mass or more and 50 parts by mass or less, the amount of the (C) cyclic urea compound is 0.05 parts by mass or more and 0.30 parts by mass or less, the amount of the (D) amorphous polyamide resin is 0.20 parts by mass or more and 2.0 parts by mass or less, the amount of the (E) crystalline polyamide resin having a melting point of 250°C or higher is 0.01 parts by mass or more and 0.10 parts by mass or less, A polyacetal resin composition, wherein the mass ratio (E) / (D) of the (E) crystalline polyamide resin having a melting point of 250°C or higher to the (D) amorphous polyamide resin is 0.02 or more and 0.10 or less.

[0011] [2] The polyacetal resin composition according to [1], wherein the (D) amorphous polyamide resin is polyamide 6I.

[0012] [3] The polyacetal resin composition according to [1] or [2], wherein the (E) crystalline polyamide resin having a melting point of 250°C or higher is polyamide 66.

[0013] [4] The polyacetal resin composition according to any one of [1] to [3], wherein the polyacetal resin (A) has a melt flow rate (MFR) of 4 g / 10 min or less.

[0014] [5] The polyacetal resin composition according to any one of [1] to [4], wherein the (C) cyclic urea compound is hydantoin.

[0015] [6] The polyacetal resin composition according to any one of [1] to [5], wherein the mass ratio (E) / (D) of the (E) crystalline polyamide resin having a melting point of 250°C or more to the (D) amorphous polyamide resin is 0.025 or more and 0.100 or less.

[0016] [7] The polyacetal resin composition according to any one of [1] to [6], wherein the amount of the (D) amorphous polyamide resin is 0.30 parts by mass or more and 0.70 parts by mass or less per 100 parts by mass of the total of the (A) polyacetal resin and the (B) thermoplastic polyurethane.

[0017] [8] The polyacetal resin composition according to any one of [1] to [7], further comprising: (F) a hydrazide compound in an amount of 0.01 parts by mass or more and 0.10 parts by mass or less, relative to 100 parts by mass in total of the (A) polyacetal resin and the (B) thermoplastic polyurethane.

[0018] [9] The polyacetal resin composition according to [8], wherein the (F) hydrazide compound is adipic acid dihydrazide or sebacic acid dihydrazide.

[0019]

[10] A molded article made from the polyacetal resin composition according to any one of [1] to [9]. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a polyacetal resin composition that can suppress changes in impact resistance due to differences in molding conditions and that emits a small amount of formaldehyde, and a molded article made of the polyacetal resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention (hereinafter sometimes referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following embodiment, but can be practiced in various modified forms within the scope of the invention.

[0022] In this specification, two or more embodiments can be combined in any manner.

[0023] Unless otherwise specified, the materials, components, compounds, resins, catalysts, and solvents described in this specification may be used alone or in combination of two or more.

[0024] In this specification, (A) polyacetal resin, (B) thermoplastic polyurethane, (C) cyclic urea compound (D) amorphous polyamide resin, (E) crystalline polyamide resin having a melting point of 250°C or higher, and (F) hydrazide compound may be referred to as component (A), component (B), component (C), component (D), component (E), and component (F), respectively.

[0025] In this embodiment, the melt flow rate (MFR) value of the (A) polyacetal resin (component (A)) refers to a value measured in accordance with ISO1133.

[0026] In this embodiment, "thermoplastic" means that the polyurethane resin can be melted by heating below its decomposition temperature, exhibits plastic flow while in the molten state, and has the reversible property of solidifying upon cooling. Generally, polyurethane resins begin to decompose at temperatures above 230°C.

[0027] (Polyacetal resin composition) The polyacetal resin composition of the present embodiment comprises: (A) a polyacetal resin; (B) thermoplastic polyurethane; (C) a cyclic urea compound; (D) an amorphous polyamide resin; (E) a crystalline polyamide resin having a melting point of 250°C or higher, With respect to a total of 100 parts by mass of the (A) polyacetal resin and the (B) thermoplastic polyurethane, the amount of the (A) polyacetal resin is 50 parts by mass or more and 95 parts by mass or less, the amount of the (B) thermoplastic polyurethane is 5 parts by mass or more and 50 parts by mass or less, the amount of the (C) cyclic urea compound is 0.05 parts by mass or more and 0.30 parts by mass or less, the amount of the (D) amorphous polyamide resin is 0.20 parts by mass or more and 2.0 parts by mass or less, the amount of the (E) crystalline polyamide resin having a melting point of 250°C or higher is 0.01 parts by mass or more and 0.10 parts by mass or less, The mass ratio (E) / (D) of the (E) crystalline polyamide resin having a melting point of 250° C. or higher to the (D) amorphous polyamide resin is 0.02 or more and 0.10 or less. The polyacetal resin composition can suppress changes in impact resistance due to differences in molding conditions, and can produce molded articles with low formaldehyde emissions.

[0028] First, components that may be contained in the polyacetal resin composition of the present embodiment will be described.

[0029] <(A) Polyacetal resin (component (A))> The polyacetal resin of this embodiment refers to a polymer having an oxymethylene group in the main chain. Examples of polyacetal resins include polyacetal copolymers obtained by copolymerizing a formaldehyde monomer or its cyclic oligomer with a cyclic ether or cyclic formal; branched polyacetal copolymers obtained by copolymerizing a formaldehyde monomer or its cyclic oligomer with a monofunctional glycidyl ether; and crosslinked polyacetal copolymers obtained by copolymerizing a formaldehyde monomer or its cyclic oligomer with a polyfunctional glycidyl ether. Other examples include polyacetal homopolymers and polyacetal copolymers described in JP 2020-143256 A, as well as compounds having functional groups such as hydroxyl groups at both or one end.

[0030] When the (A) polyacetal resin (component (A)) in this embodiment is a polyacetal copolymer, the content of the comonomer unit is not particularly limited, and when converted as the content per 1 mol of formaldehyde trimer (trioxane), the content of the comonomer unit is preferably 0.01 mol or more, more preferably 0.02 mol or more, and even more preferably 0.03 mol or more, and is preferably 0.10 mol or less, more preferably 0.07 mol or less, and even more preferably 0.05 mol or less.

[0031] As described above, the polyacetal resin (A) can be either a polyacetal homopolymer or a polyacetal copolymer, but from the viewpoint of thermal stability, polyacetal copolymer is preferred.

[0032] The melt flow rate (MFR value (according to ISO 1133)) of the (A) polyacetal resin is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and even more preferably 1.0 g / 10 min or more. The melt flow rate (MFR value (according to ISO 1133)) of the (A) polyacetal resin is preferably 100 g / 10 min or less, more preferably 70 g / 10 min or less, more preferably 30 g / 10 min or less, even more preferably 15.0 g / 10 min or less, even more preferably 5.0 g / 10 min or less, and particularly preferably 4.0 g / 10 min or less. By adjusting the MFR value of the (A) polyacetal resin to 0.1 g / 10 min or more and 100 g / 10 min or less, a polyacetal resin with superior mechanical strength can be obtained. Furthermore, by adjusting the MFR value of the (A) polyacetal resin to 1.0 g / 10 min or more and 4.0 g / 10 min or less, a polyacetal resin with even more excellent mechanical strength can be obtained. The melt flow rate can be measured using a MELT INDEXER F-F01 (manufactured by Toyo Seiki Seisakusho).

[0033] The content of component (A) (polyacetal resin (A)) is 50 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the total of component (A) (polyacetal resin (A)) and component (B) (thermoplastic polyurethane (B)). In a preferred embodiment, the content of component (A) is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, and even more preferably 70 parts by mass or more, relative to 100 parts by mass of the total of component (A) and component (B). In another preferred embodiment, the content of component (A) is preferably 90 parts by mass or less, relative to 100 parts by mass of the total of component (A) and component (B). In another preferred embodiment, from the viewpoint of exhibiting excellent rigidity of the engineering resin, the content of component (A) is 50 parts by mass or more and 95 parts by mass or less, preferably 60 parts by mass or more and 90 parts by mass or less, and even more preferably 70 parts by mass or more and 90 parts by mass or less, relative to 100 parts by mass of the total of component (A) and component (B).

[0034] Furthermore, the number average molecular weight Mn of component (A) in this embodiment is not particularly limited and is, for example, 20,000 or more and 100,000 or less. In one preferred embodiment, Mn of component (A) is 25,000 or more. In another preferred embodiment, Mn of component (A) is 100,000 or less, 50,000 or less, or 40,000 or less.

[0035] The method for producing the component (A) is not particularly limited, and a known method can be used. For example, the method described in WO 2020 / 250895 can be used to produce the component (A).

[0036] <(B) Thermoplastic polyurethane (component (B))> The thermoplastic polyurethane is a polyurethane having thermoplastic properties, which can be obtained by reacting a diol with a diisocyanate.

[0037] Examples of the diol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, and 1,4-butanediol.

[0038] Examples of the diisocyanate include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates, which may be used alone or in combination of two or more.

[0039] Examples of the aromatic diisocyanate include 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2-methylene diphenylene diisocyanate, and naphthalene diisocyanate.

[0040] Examples of the aliphatic diisocyanate include hexamethylene diisocyanate.

[0041] Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4'-methylene-bis-(cyclohexyl isocyanate), 1,3-bis-(isocyanatemethyl)cyclohexane, and 1,4-bis-(isocyanatemethyl)cyclohexane.

[0042] The diisocyanate may be, for example, a dimer or trimer of the above-mentioned aromatic diisocyanate, aliphatic diisocyanate, or alicyclic diisocyanate (hereinafter, sometimes referred to as "isocyanate compound"), a carbodiimide-modified product of these isocyanate compounds, a prepolymer of these isocyanate compounds and polyhydric alcohols, or a blocked isocyanate compound in which these isocyanate compounds are blocked with a blocking agent such as phenol, primary alcohol, or caprolactam.

[0043] The content of the (B) thermoplastic polyurethane (component (B)) is 5 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total of the (A) component ((A) polyacetal resin) and the (B) component ((B) thermoplastic polyurethane). From the viewpoint of improving impact resistance, the content of the (B) thermoplastic polyurethane (component (B)) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the total of the (A) component and the (B) component. Furthermore, the content of the (B) thermoplastic polyurethane (component (B)) is preferably 45 parts by mass or less, and may be 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less.

[0044] <(C) Cyclic urea compounds> The polyacetal resin composition of the present embodiment contains the cyclic urea compound (C) from the viewpoint of capturing formaldehyde. In other words, the cyclic urea compound (C) can function as a formaldehyde scavenger. Here, the term "cyclic urea compound" refers to a compound having at least one urea unit -NHCONH- as a constituent unit of a ring, or a compound in which at least one hydrogen atom of the urea unit is substituted with various functional groups. In this specification, when a (C) cyclic urea compound has a -CONHNH2 group, the compound is considered to be included in the (C) cyclic urea compound, not the (F) hydrazide compound.

[0045] The cyclic urea compound may be at least one compound selected from the group consisting of cyclic monoureidos (cyclic monoureylenes) and cyclic diureidos (cyclic diureylenes). A cyclic monoureide (cyclic monoureylene) refers to a compound having one ureylene group (urea unit -NHCONH-) as a constituent unit of the ring, and a cyclic diureide (cyclic diureylene) refers to a compound having two ureylene groups (urea unit -NHCONH-) as constituent units of the ring. The cyclic urea compound is preferably a cyclic monoureido or cyclic diureido. From the viewpoint of capturing formaldehyde, the cyclic monoureido is more preferably at least one compound selected from the group consisting of ethyleneurea (also known as 2-imidazolidinone), hydantoin, and allantoin. From the viewpoint of mold contamination, the cyclic monoureido (cyclic monoureylene) is more preferably ethyleneurea or hydantoin. In one embodiment, the cyclic monoureido (cyclic monoureylene) is preferably hydantoin.

[0046] The content of component (C) is 0.05 to 0.30 parts by mass, based on 100 parts by mass of the combined total of components (A) and (B). In a preferred embodiment, the content of component (C) is preferably 0.06 parts by mass or more, more preferably 0.07 parts by mass or more, and even more preferably 0.09 parts by mass or more, based on 100 parts by mass of the combined total of components (A) and (B). In another preferred embodiment, the content of component (C) is preferably 0.20 parts by mass or less, more preferably 0.15 parts by mass or less, and even more preferably 0.12 parts by mass or less, based on 100 parts by mass of the combined total of components (A) and (B). In another preferred embodiment, from the viewpoint of suppressing formaldehyde emissions, the content of component (C) is preferably 0.09 to 0.12 parts by mass, based on 100 parts by mass of the combined total of components (A) and (B).

[0047] <(D) Amorphous polyamide resin (component (D))> The (D) amorphous polyamide resin (component (D)) is not particularly limited, and known amorphous polyamide resins can be used. Amorphous polyamide resins are polymers that do not have a specific melting point and have amide bonds in the main chain. Polyamide resins are basically obtained by various reactions such as polycondensation of dibasic acids and diamines, polycondensation of aminocarboxylic acids, or ring-opening polymerization of lactams. Component (D) may be composed of one type of structural unit or two or more types of structural units. In the case of copolymerized polyamide resins, the ratio of structural units, copolymerization form (e.g., random copolymer, block copolymer, crosslinked polymer), etc. can be selected arbitrarily.

[0048] In this specification, the term "amorphous polyamide resin" refers to a resin that does not show a clear melting peak when heated at a rate of 10°C / min in accordance with JIS K7121 in a differential scanning calorimeter (DSC) analysis, and specifically refers to a resin that does not show a melting peak of 4 cal / g or more.

[0049] Specific examples of amorphous polyamide resins include PA12 / MACMI (PA12 / 3,3-dimethyl-4,4-diaminocyclohexylmethane, isophthalic acid), PA12 / MACMT (PA12 / 3,3-dimethyl-4,4-diaminocyclohexylmethane, terephthalic acid), PAMACM12 (3,3-dimethyl-4,4-diaminocyclohexylmethane, decanedicarboxylic acid or laurolactam), PAMC12 (PA12, 1,3-bis(aminomethyl)cyclohexane), PA6I (polyamide 6I) (polyhexamethylene isophthalamide), PA6I / 6T, and PA6I / 6T / MACMI. These polyamides may be used alone or in combination. Polyamide 6I (PA6I) is particularly preferred as the amorphous polyamide resin (D) of this embodiment.

[0050] In this embodiment, the content of component (D) (amorphous polyamide resin (D)) is 0.20 parts by mass or more and 2.0 parts by mass or less, based on 100 parts by mass of the total of component (A) (polyacetal resin) and component (B) (thermoplastic polyurethane). In another preferred embodiment, the content of component (D) is preferably 0.30 parts by mass or more, and more preferably 0.50 parts by mass or more, based on 100 parts by mass of the total of component (A) and component (B). In another preferred embodiment, the content of component (D) is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and even more preferably 0.70 parts by mass or less, based on 100 parts by mass of the total of component (A) and component (B). In another preferred embodiment, the content of component (D) is preferably 0.30 parts by mass or more and 0.7 parts by mass or less, and more preferably 0.50 parts by mass or more and 0.7 parts by mass or less, based on 100 parts by mass of the total of component (A) and component (B).

[0051] Furthermore, a high proportion of amide bonds in component (D) improves compatibility with component (C), resulting in a more pronounced formaldehyde gas release suppression effect. From the viewpoint of suppressing formaldehyde gas release, the proportion of amide bonds in component (D), converted into the nitrogen content, is preferably 5 to 15 mass%, more preferably 7 to 15 mass%, and even more preferably 9 to 13 mass%.

[0052] The proportion of amide bonds in component (D) can be determined by measuring the nitrogen content of the polyamide resin. The nitrogen content of the polyamide resin can be determined by oxidatively decomposing the polyamide using a trace total nitrogen analyzer (TN-2100H, manufactured by Mitsubishi Analytech), reacting the generated nitric oxide with ozone, and measuring the chemiluminescence intensity.

[0053] The number average molecular weight Mn of the component (D) is preferably from 5000 to 15000. The number average molecular weight can be measured by gel permeation chromatography (GPC).

[0054] <(E) Crystalline polyamide resin with a melting point of 250°C or higher> The crystalline polyamide resin (E) having a melting point of 250°C or higher in this embodiment is not particularly limited, and any known crystalline polyamide resin having a melting point of 250°C or higher can be used. A crystalline polyamide resin is a polymer having a specific melting point and containing an amide bond in the main chain. Polyamide resins are basically obtained by various reactions such as polycondensation of dibasic acids and diamines, polycondensation of aminocarboxylic acids, or ring-opening polymerization of lactams. Component (E) may be composed of one type of structural unit or two or more types of structural units. In the case of a copolymerized polyamide resin, the ratio of structural units, copolymerization form (e.g., random copolymer, block copolymer, crosslinked polymer), etc. can be selected as desired. By including such a crystalline polyamide resin having a melting point of 250°C or higher in the polyacetal resin composition of this embodiment, the crystalline polyamide resin acts as a crystal nucleating agent during molding, making it possible to control the crystallinity of the molded article. Furthermore, the melting point of the crystalline polyamide resin having a melting point of 250°C or higher is 250°C or higher, and more preferably 260°C or higher. The melting point of component (E) is, for example, 320°C or lower or 300°C or lower. The melting point of the crystalline polyamide resin is the melting peak temperature measured according to JIS K7121 when the resin is held at a temperature 30°C higher than the end of the melting peak for 10 minutes, cooled at 10°C / min, and then heated at 10°C / min.

[0055] Examples of the crystalline polyamide resin (E) having a melting point of 250°C or higher in this embodiment include PA46 (polyamide 46) (polytetramethylene adipamide), PA66 (polyamide 66) (polyhexamethylene adipamide), PA6 / 6T (polyhexamethylene isophthalamide / polyhexamethylene terephthalamide copolymer), PA9T (polynonamethylene terephthalamide), PA10T (polydecamethylene terephthalamide), and PA4T, which may be used alone or in combination. Among these, polyamide (PA66) is particularly preferred as the crystalline polyamide resin (E) in this embodiment.

[0056] The content of component (E) (crystalline polyamide resin (E) having a melting point of 250°C or higher) in this embodiment is 0.01 parts by mass or more and 0.10 parts by mass or less, based on 100 parts by mass of the polyacetal resin and thermoplastic polyurethane combined. In another preferred embodiment, the content of component (E) is preferably 0.02 parts by mass or more, based on 100 parts by mass of the polyacetal resin and thermoplastic polyurethane combined. In another preferred embodiment, the content of component (E) is preferably 0.08 parts by mass or less, more preferably 0.06 parts by mass or less, and even more preferably 0.05 parts by mass or less, based on 100 parts by mass of the polyacetal resin and thermoplastic polyurethane combined. In another preferred embodiment, the content of component (E) is preferably 0.02 parts by mass or more and 0.05 parts by mass or less, based on 100 parts by mass of the polyacetal resin and thermoplastic polyurethane combined.

[0057] In the polyacetal resin composition of this embodiment, the mass ratio (E) / (D) of the crystalline polyamide resin (E) having a melting point of 250°C or higher to the amorphous polyamide resin (D) (i.e., (E) crystalline polyamide resin / (D) amorphous polyamide resin) is 0.02 or more and 0.10 or less. Furthermore, the mass ratio (E) / (D) of the crystalline polyamide resin (E) having a melting point of 250°C or higher to the amorphous polyamide resin (D) is preferably 0.025 or more, more preferably 0.027 or more, and most preferably 0.029 or more. Meanwhile, the mass ratio (E) / (D) of the crystalline polyamide resin (E) having a melting point of 250°C or higher to the amorphous polyamide (D) is preferably 0.080 or less, more preferably 0.070 or less, and most preferably 0.050 or less. In another preferred embodiment, the mass ratio (E) / (D) of the (E) crystalline polyamide resin having a melting point of 250°C or more to the (D) amorphous polyamide resin is preferably 0.025 or more and 0.100 or less, and more preferably 0.029 or more and 0.070 or less, from the viewpoint of being able to further suppress changes in impact resistance due to differences in molding conditions and to further suppress the amount of formaldehyde emitted.

[0058] The weight average molecular weight Mw of the component (E) is preferably from 5000 to 15000. The weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0059] <(F) Hydrazide compound ((F) component)> The polyacetal resin composition may further contain, in addition to the components (A) to (E), a hydrazide compound (component (F)). The hydrazide compound (F) can function as a formaldehyde scavenger other than the cyclic urea compound (C).

[0060] An example of the hydrazide compound is a compound represented by the following formula (1). H2NNHCO-R-CONHNH2(1) (In the formula, R represents a hydrocarbon having 2 to 20 carbon atoms.) Examples of the hydrazide compound represented by the formula (1) include malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, glutaric acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, etc. Among the above, adipic acid dihydrazide or sebacic acid dihydrazide is most preferred. These may be added optionally, and the hydrazide compound may be used alone or in combination of two or more kinds.

[0061] The content of component (F) may be adjusted appropriately, and is preferably 0.01 parts by mass or more and 0.1 parts by mass or less, based on 100 parts by mass of the polyacetal resin (A) and the thermoplastic polyurethane (B). In another preferred embodiment, the content of component (F) is preferably 0.02 parts by mass or more, based on 100 parts by mass of the polyacetal resin (A) and the thermoplastic polyurethane (B). In another preferred embodiment, the content of component (F) is preferably 0.08 parts by mass or less, more preferably 0.06 parts by mass or less, and even more preferably 0.05 parts by mass or less, based on 100 parts by mass of the polyacetal resin (A) and the thermoplastic polyurethane (B). In another preferred embodiment, the content of component (F) is preferably 0.02 parts by mass or more and 0.05 parts by mass or less, based on 100 parts by mass of the polyacetal resin (A) and the thermoplastic polyurethane (B).

[0062] <Other ingredients> In addition to the components (A) to (F), the polyacetal resin composition may further contain other components, such as known additives other than the components (C) and (F), such as formaldehyde scavengers, antioxidants, formic acid scavengers, weather stabilizers, mold release agents, lubricants, conductive agents, dyes and pigments, or inorganic or organic fillers. These may be used alone or in combination of two or more.

[0063] The content of the other components may be adjusted as appropriate, for example, to 50 parts by mass or less, 30 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, per 100 parts by mass of the total of the (A) component and the (B) component.

[0064] (Method for producing polyacetal resin composition) The polyacetal resin composition is not particularly limited, and can be produced, for example, by kneading the (A) component, the (B) component, the (C) component, the (D) component, optionally the (F) component, and, if necessary, other components.

[0065] The kneader for kneading the components contained in the polyacetal resin composition is not particularly limited, and a known kneader can be used. For example, the kneader described in WO 2020 / 250895 can be used.

[0066] In addition, kneading using an extruder equipped with a vent pressure reduction device is preferred from the viewpoints of thermal stability and productivity. Furthermore, a single-screw or twin-screw extruder is preferably used for stably producing a large amount of a polyacetal resin composition. When a single-screw or twin-screw extruder is used, a pelletized polyacetal resin composition (hereinafter, sometimes referred to as "polyacetal resin pellets") can be obtained.

[0067] Alternatively, each component may be continuously fed into the extruder either individually or in batches of several components using a metering feeder or the like, without pre-mixing.

[0068] Alternatively, a high-concentration masterbatch consisting of each component may be prepared in advance and diluted with the polyacetal resin during extrusion melt kneading.

[0069] The kneading temperature may be determined in accordance with the preferred processing temperature of the polyacetal resin used, and is generally set in the range of 140 to 260°C, preferably 160 to 230°C.

[0070] (Molded article of polyacetal resin composition) The polyacetal resin composition of the present embodiment can be molded and used as a molded article.

[0071] The method for molding the polyacetal resin composition is not particularly limited, and any known method for molding a polyacetal resin composition can be used. For example, the molding method such as injection molding described in WO 2020 / 250895 can be used.

[0072] The molded article of the present embodiment is preferably a molded article made using the polyacetal resin composition of the present embodiment.

[0073] <Uses of molded products> The molded article of this embodiment has excellent quality stability and can be used in a variety of applications, including mechanical parts (e.g., gears, cams, sliders, levers, shafts, bearings, and guides), outsert-molded resin parts, insert-molded resin parts (chassis, trays, and side panel parts), printer parts, copier parts, digital camera parts, digital video equipment parts, music equipment parts, video equipment parts, information equipment parts, communication equipment parts, electrical equipment parts, and electronic equipment parts.

[0074] The molded article of this embodiment is also suitable for use as automotive parts, such as interior parts, door parts, seat belt peripheral parts, combination switch parts, and switches. Examples of interior parts, door parts, seat belt peripheral parts, combination switch parts, and switches include inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, clips, etc. Furthermore, the molded article of this embodiment can also be used suitably as industrial parts, such as housing equipment. [Example]

[0075] Hereinafter, the present embodiment will be described with reference to examples and comparative examples, but the present embodiment is not limited to the following examples.

[0076] The measurement and evaluation methods used in the examples and comparative examples are shown below.

[0077] <Evaluation of mechanical properties (impact resistance under different molding conditions)> (Molding condition I) Using an EC100SX manufactured by Toshiba Machine Co., Ltd., test pieces were prepared at a cylinder temperature of 200°C, an injection time of 35 seconds, a cooling time of 15 seconds, and a mold temperature of 80°C to mold ISO dumbbell test pieces for evaluating physical properties. These molding conditions were designated as molding condition I.

[0078] (Molding conditions II) To evaluate the change in impact resistance due to molding conditions, an EC100SX manufactured by Toshiba Machine Co., Ltd. was used to prepare test pieces under the following conditions: cylinder temperature: 220°C, injection time: 35 seconds, cooling time: 15 seconds, and mold temperature: 80°C, and ISO dumbbell test pieces for evaluating physical properties were molded. These molding conditions were designated as molding conditions II. These test pieces were subjected to an impact resistance evaluation based on Charpy impact strength: ISO179 / 1eA on the day following molding.

[0079] The ratio of the Charpy impact value of a molded product molded under molding condition I to the Charpy impact value of a molded product molded under molding condition II (Charpy [molding condition II] / Charpy [molding condition I]) is used as an index of the change in impact resistance due to molding conditions. The closer the value of Charpy [molding condition II] / Charpy [molding condition I] is to 1.0, the smaller the change in impact resistance due to differences in molding conditions, i.e., the more successfully the change in impact resistance due to differences in molding conditions is suppressed. Specifically, Charpy [molding condition II] / Charpy [molding condition I] is preferably 0.80 or higher, and more preferably 0.85 or higher.

[0080] <Evaluation of formaldehyde gas emissions from molded products> [Preparation of flat test specimens] Test pieces were prepared using a Toshiba Machine IS-100GN injection molding machine with a cylinder temperature of 200°C, an injection time of 15 seconds, a cooling time of 20 seconds, and a mold temperature of 77°C. Measurement was then carried out using the VDA275 method (conditions below) to determine the amount of formaldehyde released from the molded product.

[0081] [VDA275 Law] The amount of formaldehyde released from the test specimen was measured in accordance with VDA275 as follows. First, 50 mL of distilled water and the prepared test specimen were placed in a polyethylene container and sealed. Next, the polyethylene container was heated at 60°C for 3 hours, and the formaldehyde generated in the distilled water was reacted with acetylacetone in the presence of ammonium ions. The absorption peak at a wavelength of 412 nm of the resulting reaction product was measured using a UV spectrometer to determine the amount of formaldehyde generated per 1 kg of the test specimen (mg / kg). The smaller the amount of formaldehyde released, the better. Specifically, the value of the formaldehyde release is preferably 4.0 mg / kg or less, and more preferably 3.0 mg / kg or less.

[0082] [Raw material ingredients] The raw material components used in the examples and comparative examples are shown below.

[0083] <(A) Polyacetal resin> Polyacetal copolymer (MFR: 3.0g / 10min) The polyacetal copolymer was obtained by cationic polymerization of 1,3,5-trioxane and 1,3-dioxolane.

[0084] <(B) Thermoplastic polyurethane> Polyurethane elastomer (product name: WHT-1180K, manufactured by Wanka Chemical Co., Ltd.)

[0085] <(C) Cyclic urea compounds> (C-1) Hydantoin (Tokyo Chemical Industry Co., Ltd.) (C-2) Ethylene urea (Tokyo Chemical Industry Co., Ltd.) (C-3) Amicure VDH (4-(1-methylethyl)-2,5-dioxo-1,3-imidazolidinedipropanoic acid dihydrazide, manufactured by Ajinomoto Fine-Techno)

[0086] <(D) Amorphous polyamide resin> Polyamide 6I (number average molecular weight Mn = 9,760) The polyamide 6I was obtained by copolymerizing isophthalic acid and hexamethylenediamine.

[0087] <(E) Crystalline polyamide resin with a melting point of 250°C or higher> Polyamide 66 (weight average molecular weight Mw = 10,000) (melting point 260°C) The polyamide 66 was obtained by polymerizing adipic acid and hexamethylenediamine.

[0088] <(F) Hydrazide compounds> (F-1) Adipic acid dihydrazide (manufactured by Nippon Finechem) (F-2) Sebacic acid dihydrazide (manufactured by Nippon Finechem)

[0089] (Production of polyacetal resin composition and molded articles thereof) According to the formulations shown in Tables 1 and 2, a twin-screw extruder (TEM-26SS extruder (L / D48, vented, manufactured by Toshiba Machine Co., Ltd.) was used. The cylinder temperatures were all set to 200°C, and components (A) to (E) and, optionally, component (F) were fed from a metering feeder into the main throat of the extruder. The resin mixture was extruded into the form of strands at an extrusion rate of 20 kg / hour and a screw rotation speed of 200 rpm. The extruded strands were then quenched in a strand bath and cut with a strand cutter to obtain pellets of the polyacetal resin composition of each Example and Comparative Example. Molded articles of each Example and Comparative Example were produced using the resulting resin compositions according to the measurement and evaluation methods described above, and their physical properties were evaluated.

[0090] The blending amounts of each polyacetal resin composition and its molded articles, as well as the evaluation results, are shown in Tables 1 and 2. Note that the amounts of each component in Tables 1 and 2 are in parts by mass relative to 100 parts by mass of the total of (A) polyacetal resin and (B) thermoplastic polyurethane.

[0091] [Table 1]

[0092] [Table 2]

[0093] As shown in Tables 1 and 2, the polyacetal resin compositions obtained in the examples show little change in impact resistance due to differences in molding conditions, and emit little formaldehyde. [Industrial Applicability]

[0094] According to the present invention, it is possible to provide a polyacetal resin composition that can suppress changes in impact resistance due to differences in molding conditions and that emits a small amount of formaldehyde.

Claims

1. (A) a polyacetal resin; (B) a thermoplastic polyurethane; and (C) a cyclic urea compound; (D) an amorphous polyamide resin; (E) a crystalline polyamide resin having a melting point of 250°C or higher, With respect to a total of 100 parts by mass of the (A) polyacetal resin and the (B) thermoplastic polyurethane, the amount of the polyacetal resin (A) is 50 parts by mass or more and 95 parts by mass or less, the amount of the thermoplastic polyurethane (B) is 5 parts by mass or more and 50 parts by mass or less, the amount of the cyclic urea compound (C) is 0.05 parts by mass or more and 0.30 parts by mass or less, the amount of the (D) amorphous polyamide resin is 0.20 parts by mass or more and 2.0 parts by mass or less, the amount of the (E) crystalline polyamide resin having a melting point of 250°C or higher is 0.01 parts by mass or more and 0.10 parts by mass or less, a mass ratio (E) / (D) of the crystalline polyamide resin (E) having a melting point of 250°C or higher to the amorphous polyamide resin (D) is 0.02 or more and 0.10 or less.

2. The polyacetal resin composition according to claim 1, wherein the amorphous polyamide resin (D) is polyamide 6I.

3. 2. The polyacetal resin composition according to claim 1, wherein the (E) crystalline polyamide resin having a melting point of 250°C or higher is polyamide 66.

4. The polyacetal resin composition according to claim 1, wherein the polyacetal resin (A) has a melt flow rate (MFR) of 4 g / 10 min or less.

5. The polyacetal resin composition according to claim 1, wherein the cyclic urea compound (C) is hydantoin.

6. 2. The polyacetal resin composition according to claim 1, wherein the mass ratio (E) / (D) of the crystalline polyamide resin (E) having a melting point of 250°C or higher to the amorphous polyamide resin (D) is 0.025 or more and 0.100 or less.

7. 2. The polyacetal resin composition according to claim 1, wherein the amount of the (D) amorphous polyamide resin is 0.30 parts by mass or more and 0.70 parts by mass or less per 100 parts by mass of the total of the (A) polyacetal resin and the (B) thermoplastic polyurethane.

8. 2. The polyacetal resin composition according to claim 1, further comprising: (F) a hydrazide compound in an amount of 0.01 part by mass or more and 0.10 part by mass or less, relative to a total of 100 parts by mass of the polyacetal resin (A) and the thermoplastic polyurethane (B).

9. The polyacetal resin composition according to claim 8, wherein the hydrazide compound (F) is adipic acid dihydrazide or sebacic acid dihydrazide.

10. A molded article made from the polyacetal resin composition according to any one of claims 1 to 9.

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