Polyacetal resin composition

Abstract

To provide a polyacetal resin composition which achieves prevention of rigidity reduction at high temperature and prevention of brittleness fracture under a load, and is excellent in thermal stability, and a method for producing the same.SOLUTION: A polyacetal resin composition contains (a) 100 pts.mass of a polyacetal resin, (b) 1-150 pts.mass of fine cellulose fibers having a fiber diameter of 10-1,000 nm, (c) 0.01-3 pts.mass of a hindered phenolic antioxidant, (d) 0.01-3 pts.mass of at least one nitrogen-containing compound selected from an aminotriazine compound, a guanamine compound, a hydrazide compound and polyamide, and (e) 0.01-3 pts.mass of at least processing aid selected from the group consisting of a long-chain fatty acid, a derivative of a long-chain fatty acid, long-chain aliphatic alcohol, a polyoxyethylene derivative, polyoxyalkylene glycol, an olefinic wax and a silicone compound.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Polyacetal resins have excellent properties in terms of mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., and are mainly used widely in electrical equipment, automotive parts, precision mechanical parts, etc. as structural materials and mechanical components. In particular, polyacetal resins are widely used in gear applications. The required properties for gear products are becoming more and more sophisticated year by year. For example, in a high-temperature region exceeding 100°C, high-load resistance is often required. Furthermore, long-term properties to withstand repeated impacts on gear teeth are also required, and it is necessary to have sufficient toughness as well.

[0003] Patent Document 1 describes a polyacetal resin composition in which glass fibers are blended with a polyacetal resin, Patent Document 2 describes a polyacetal resin composition in which a specific cellulose powder is blended with a polyacetal resin, Patent Document 3 describes a polyacetal resin composition in which fine cellulose fibers having a specific aspect ratio and average fiber length are blended with a polyacetal resin, and Patent Document 4 describes a resin composition composed of modified pulp and a thermoplastic resin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to suppress appearance defects and void generation, it is required to achieve both prevention of rigidity reduction at high temperatures and prevention of brittle fracture under load, and further improve thermal stability.

[0006] Regarding such requirements, in the composition obtained by blending glass fiber with polyacetal resin as described in Patent Document 1, improvement in rigidity at high temperatures can be achieved, but the composition becomes brittle and inferior in toughness. In addition, hard glass fiber causes damage to the mating material when used for gears, so there is a major problem that it is not suitable for gear applications.

[0007] Also, in the composition obtained by blending cellulose as a reinforcing material as described in Patent Documents 2 to 4, the effect of improving rigidity is only obtained at room temperature mainly due to the large size of cellulose itself, and there are problems such that sufficient toughness cannot be obtained because cracks mainly caused by huge cellulose occur under load, and a polyacetal resin composition in which rigidity at high temperatures and toughness under load are both achieved has not been obtained.

[0008] Furthermore, in order to enhance the dispersibility of cellulose in the cellulose resin composition, applying strong shear during extrusion processing or the like causes thermal degradation of the polyacetal resin, and is a factor causing new problems such as silver streaks, odor, and generation of voids in the central part of the molded body during molding. In addition, since the dispersibility of cellulose fiber in the acetal resin tends to decrease with the refinement of the cellulose fiber, when using fine cellulose fiber, the use of a processing aid for improving dispersibility is required. However, the processing aid may cause the generation of decomposition products of the polyacetal resin by promoting the oxidation of the polyacetal resin, and this decomposition product causes yellowing or browning of the resin composition. Therefore, avoidance of the inconvenience due to the oxidation of the polyacetal resin has also been required.

[0009] One aspect of the present invention aims to solve the above problems and provide a polyacetal resin composition and a method for producing the same, which achieve both prevention of rigidity reduction at high temperatures and prevention of brittle fracture under load, and further have excellent thermal stability and oxidation stability.

Means for Solving the Problems

[0010] The present invention includes the following aspects. [1] (a) 100 parts by mass of a polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 10 to 1000 nm, (c) 0.01 to 3 parts by mass of a hindered phenol-based antioxidant, (d) 0.01 to 3 parts by mass of at least one nitrogen-containing compound selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides, and (e) 0.01 to 3 parts by mass of at least one processing aid selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds, A polyacetal resin composition containing the above components. [2] (a) The polyacetal resin is A copolymer of 99.9 to 90% by mass of trioxane and 0.1 to 10% by mass of a monofunctional cyclic ether, The polyacetal resin composition according to the above aspect 1, which has an alkoxy end group and a hydroxyalkoxy end group having at least 2 carbon atoms in a total proportion of 70 to 99 mol% of all end groups. [3] (b) The polyacetal resin composition according to the above aspect 1 or 2, wherein the fine cellulose fibers are hydrophobized fine cellulose fibers. [4] The polyacetal resin composition according to the above aspect 3, wherein the degree of hydrophobicity (DS) is 0.5 to 1.5. [5] The polyacetal resin composition according to any one of the above aspects 1 to 4, wherein the storage elastic modulus at 120°C is 1,000 MPa or more. [6] The resin composition according to any one of the above aspects 1 to 5, having a component composition in which the ratio of the storage modulus at 120°C to the storage modulus at 23°C when 10% by mass of microcrystalline cellulose fibers is blended is 0.4 or more. [7] The polyacetal resin composition according to any one of the above aspects 1 to 6, wherein the melt index of the polyacetal resin measured at 190°C and 2.16 kgf in accordance with ASTM-D1238 is 2 to 25 g / 10 min. [8] (a) 100 parts by mass of polyacetal resin, (b) 10 to 150 parts by mass of microcrystalline cellulose fibers having a fiber diameter of 10 to 1000 nm, (c) 0.01 to 3 parts by mass of a hindered phenol-based antioxidant, (d) 0.01 to 3 parts by mass of at least one nitrogen-containing compound selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides, and (e) 0.01 to 3 parts by mass of at least one processing aid selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds, A method for producing a polyacetal resin composition, which includes melt-kneading the above components.

Advantages of the Invention

[0011] According to one aspect of the present invention, it is possible to provide a polyacetal resin composition and a method for producing the same, which achieve both prevention of a decrease in rigidity at high temperatures and prevention of brittle fracture under load, and which are further excellent in thermal stability and oxidation stability. In such a polyacetal resin composition, it is possible to suppress the generation of silver streaks, odors, and voids in the central part of the molded article during molding.

Modes for Carrying Out the Invention

[0012] Hereinafter, exemplary embodiments of the present invention (also referred to as "the present embodiments" in the present disclosure) will be described, but the present invention is not limited to these embodiments.

[0013] The polyacetal resin composition of this embodiment contains (a) a polyacetal resin and (b) microcrystalline cellulose fibers. In one aspect, the polyacetal resin composition contains (c) a hindered phenol antioxidant. In one aspect, the polyacetal resin composition contains (d) a nitrogen-containing compound. In one aspect, the polyacetal resin composition contains (e) a processing aid. In one aspect, the fiber diameter of the (b) microcrystalline cellulose fibers is 10 to 1000 nm. In one aspect, the (d) nitrogen-containing compound is at least one selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides. In one aspect, the (e) processing aid is at least one selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, and olefin waxes and silicone compounds.

[0014] <(a) polyacetal resin> (a) The polyacetal resin is a polymer compound having an oxymethylene group (-OCH2-) as a main structural unit, and typical examples include polyacetal homopolymers consisting essentially of only repeating oxymethylene units, and polyacetal copolymers containing oxymethylene units and other monomer units. (a) The polyacetal resin also includes copolymers in which a branched structure and / or a crosslinked structure is introduced by copolymerizing a branching component and / or a crosslinking component, block copolymers or graft copolymers having a polymer segment consisting of repeating oxymethylene groups and other polymer segments, and the like.

[0015] Generally, examples of the polyacetal homopolymer include those produced by polymerization of one or more monomers selected from formaldehyde anhydride and formaldehyde cyclic oligomers such as trioxane (cyclic trimer of formaldehyde) and tetraoxane (cyclic tetramer of formaldehyde). Usually, the polymerization terminal is esterified to be stabilized against thermal decomposition.

[0016] In addition, polyacetal copolymers are generally produced by copolymerizing formaldehyde and / or a cyclic oligomer of formaldehyde represented by the general formula (CH2O)n [wherein n represents an integer of 3 or more] (for example, trioxane described above) with a comonomer such as a cyclic ether and / or a cyclic formal (for example, a cyclic formal of a glycol or diglycol such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, and 1,4-butanediol formal). Usually, the unstable part at the terminal is removed by hydrolysis to be stabilized against thermal decomposition.

[0017] Furthermore, examples of polyacetal copolymers include a branched polyacetal copolymer obtained by copolymerizing a monomer and / or a cyclic oligomer of formaldehyde with a monofunctional glycidyl ether; a polyacetal copolymer having a crosslinked structure obtained by copolymerizing a monomer and / or a cyclic oligomer of formaldehyde with a polyfunctional glycidyl ether.

[0018] Examples of polyacetal resins include a polyacetal homopolymer having a block component obtained by polymerizing a monomer and / or a cyclic oligomer of formaldehyde in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, a polyalkylene glycol; a polyacetal copolymer having a block component obtained by copolymerizing a monomer and / or a cyclic oligomer of formaldehyde, a cyclic ether and / or a cyclic formal in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, hydrogenated polybutadiene glycol.

[0019] Among these, polyacetal copolymers are preferred from the viewpoint of the balance between thermal stability and mechanical properties. In addition, the polyacetal resin can be used alone or in combination of two or more.

[0020] (a) The polyacetal resin is preferably a copolymer of 99.9 to 90% by mass of trioxane and 0.1 to 10% by mass of a monofunctional cyclic ether. In the copolymer, the total of the alkoxy end groups and the hydroxyalkoxy end groups having at least 2 carbon atoms is preferably 70 to 99 mol% of all the end groups.

[0021] The number of end groups can be measured using known methods, for example, the methods described in JP-A-5-98028, JP-A-2001-11143, etc.

[0022] Also, the melt index of the (a) polyacetal resin measured under the conditions of 190 °C and 2.16 kgf (21.2 N) in accordance with ASTM-D1238 has a lower limit that is preferably 2 g / 10 min, or 4 g / 10 min, or 7 g / 10 min, and an upper limit that is preferably 25 g / 10 min, or 20 g / 10 min, or 18 g / 10 min. By setting it within the above range, while ensuring the molding fluidity, the reinforcing effect by the fine cellulose fibers can be maximized.

[0023] <(b) Fine cellulose fibers> (b) The fine cellulose fibers may be obtained from various cellulose fiber raw materials selected from natural cellulose and regenerated cellulose. In one aspect, the cellulose fiber raw material may be chemically modified.

[0024] The fine cellulose fibers can be obtained by beating and fibrillating the cellulose fiber raw material with mechanical force such as a beater or a refiner, and then defibrating it by a pulverization method using a high-pressure homogenizer, a microfluidizer, a ball mill, a disk mill, a mixer (for example, a homomixer), etc.

[0025] In one aspect, the fiber diameter of the microcrystalline cellulose fiber is 1 nm or more, or 2 nm or more, or 4 nm or more, or 10 nm or more, or 20 nm or more, or 30 nm or more in that the crystallinity of cellulose is well maintained. On the other hand, the upper limit is 1000 nm or less, or 800 nm or less, or 500 nm or less, or 300 nm or less in that the effect as a filler is good. In one aspect, the fiber diameter of the microcrystalline cellulose fiber is 1 nm to 1000 nm. In one aspect, the fiber diameter of the microcrystalline cellulose fiber is 10 nm to 1000 nm.

[0026] From the viewpoint of improving the mechanical properties of the injection molded article containing the microcrystalline cellulose fiber with a smaller amount of the microcrystalline cellulose fiber, the fiber length / fiber diameter (L / D) of the microcrystalline cellulose fiber is preferably 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more. The upper limit is not particularly limited, but is preferably 5000 or less from the viewpoint of handleability.

[0027] In the present disclosure, the fiber diameter, fiber length and L / D ratio of the microcrystalline cellulose fiber are obtained by diluting an aqueous dispersion of the microcrystalline cellulose fiber with a water-soluble solvent (for example, water, ethanol, tert-butanol, etc.) to 0.001 to 0.1% by mass, using a high-shear homogenizer (for example, manufactured by IKA, trade name "Ultra Turrax T18"), under the treatment conditions: rotation speed 25,000 rpm × 5 minutes for dispersion, casting on a hydrophilic substrate (for example, mica), air-drying, and measuring with a high-resolution scanning electron microscope (SEM) or an atomic force microscope (AFM). Specifically, in an observation field with the magnification adjusted so that at least 100 fibrous substances are observed, the lengths (L) and diameters (D) of 100 randomly selected fibrous substances are measured, and the ratio (L / D) is calculated. For the microcrystalline cellulose fiber, the number average value of the length (L), the number average value of the diameter (D), and the number average value of the ratio (L / D) are calculated.

[0028] In a typical embodiment, the crystalline structure of the microcrystalline cellulose fibers has cellulose type I and / or type II. As crystalline forms of cellulose, type I, type II, type III, type IV, etc. are known. While type I and type II celluloses are widely used, type III and type IV celluloses are obtained on a laboratory scale but not widely used on an industrial scale.

[0029] The crystalline structure can be identified from the diffraction profile obtained by wide-angle X-ray diffraction using graphite-monochromated CuKα (λ = 0.15418 nm). Cellulose type I has peaks at two positions around 2θ = 14 - 17° and around 2θ = 22 - 23°. Cellulose type II has one peak at 2θ = 10° - 19° and two peaks at 2θ = 19° - 25°. When cellulose type I and cellulose type II coexist, up to six peaks are observed in the range of 2θ = 10° - 25°.

[0030] From the viewpoint of obtaining good mechanical properties, the crystallinity of the microcrystalline cellulose fibers in this embodiment is preferably 50% or more, more preferably 60% or more, still more preferably 65% or more, and most preferably 70% or more. Since the crystallinity of the microcrystalline cellulose fibers tends to be higher, the upper limit is not particularly limited, but from a production viewpoint, 99% is a preferable upper limit.

[0031] When the microcrystalline cellulose fibers are cellulose type I crystals (derived from natural cellulose), the crystallinity is determined by the following formula by the Segal method from the diffraction pattern (2θ / deg. is 10 - 30) when the sample is measured by wide-angle X-ray diffraction.

[0032] Crystallinity (%) = [I(200) - I(amorphous)] / I(200) × 100 I(200): Diffraction peak intensity by the 200 plane (2θ = 22.5°) in cellulose type I crystals I(amorphous): Halo peak intensity due to amorphous in cellulose type I crystals, which is the peak intensity on the low-angle side (2θ = 18.0°) 4.5° lower than the diffraction angle of the 200 plane Also, when the crystallinity is such that the microcrystalline cellulose fibers are cellulose type II crystals (derived from regenerated cellulose), in wide-angle X-ray diffraction, it is determined by the following formula from the absolute peak intensity h0 at 2θ = 12.6° attributed to the (110) plane peak of the cellulose type II crystals and the peak intensity h1 from the baseline at this plane spacing.

[0033] Crystallinity (%) = h1 / h0 × 100 The degree of polymerization (DP) of the microcrystalline cellulose fibers is preferably 100 or more, more preferably 150 or more, in terms of good tensile breaking strength and modulus of elasticity, and preferably 12,000 or less, more preferably 8,000 or less, from the viewpoint of easy availability. The degree of polymerization is determined as the degree of polymerization DP after obtaining the limiting viscosity (JIS P 8215:1998) of a dilute cellulose solution using a cuprammonium solution, taking advantage of the relationship between the limiting viscosity of cellulose and the degree of polymerization DP being as follows.

[0034] Limiting viscosity [η] = K × DP^a Here, K and a are constants determined by the type of polymer. In the case of cellulose, K is 5.7×10 -3 , and a is 1.

[0035] The weight average molecular weight (Mw) of the microcrystalline cellulose fibers is preferably 100,000 or more, more preferably 200,000 or more. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) of the microcrystalline cellulose fibers is preferably 6 or less, preferably 5.4 or less. A larger weight average molecular weight means fewer end groups of the cellulose molecules. Also, since the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer ends of the cellulose molecules. Since the ends of the cellulose molecules serve as the starting points for thermal decomposition, when the weight average molecular weight of the cellulose molecules in the microcrystalline cellulose fibers is not only large but also the weight average molecular weight is large and at the same time the width of the molecular weight distribution is narrow, particularly highly heat-resistant microcrystalline cellulose fibers can be obtained. The weight average molecular weight (Mw) of the cellulose fibers may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the availability of the cellulose raw material. The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more, from the viewpoint of the ease of manufacturing the cellulose fibers. Mw can be controlled within the above range by selecting a cellulose raw material having an Mw suitable for the purpose, appropriately performing physical treatment and / or chemical treatment on the cellulose raw material within an appropriate range, and the like. Mw / Mn can also be controlled within the above range by selecting a cellulose raw material having an Mw / Mn suitable for the purpose, appropriately performing physical treatment and / or chemical treatment on the cellulose raw material within an appropriate range, and the like. In both the control of Mw and the control of Mw / Mn, examples of the above physical treatment include physical treatments that apply mechanical forces such as impact, shear, shear, and friction by a microfluidizer, ball mill, disk mill, etc. for dry or wet grinding, a crusher, a homomixer, a high-pressure homogenizer, an ultrasonic device, etc., and examples of the above chemical treatment include steaming, bleaching, acid treatment, regeneration of cellulose, and the like.

[0036] Here, the weight-average molecular weight and number-average molecular weight of the microcrystalline cellulose fibers are values obtained by dissolving the microcrystalline cellulose fibers in N,N-dimethylacetamide with added lithium chloride and then performing gel permeation chromatography using N,N-dimethylacetamide as the solvent.

[0037] The microcrystalline cellulose fibers may be chemically modified microcrystalline cellulose fibers chemically modified with a modifying agent. As the modifying agent, a compound that reacts with the hydroxyl group of cellulose can be used, and examples include esterifying agents, etherifying agents, silylating agents, and isocyanates. In a preferred embodiment, the chemical modification is acylation using an esterifying agent. As the esterifying agent, a compound that reacts with the hydroxyl group of cellulose to form an acyl group, for example, a compound selected from carboxylic acid halides, acid anhydrides (i.e., carboxylic acid anhydrides), vinyl esters of carboxylic acids, or carboxylic acids can be used. A preferred chemical modification is one in which the surface of the microcrystalline cellulose fibers is hydrophobically chemically treated, and a preferred hydrophobic chemical treatment is acetylation.

[0038] The degree of hydrophobicity (degree of modification) of the chemically modified microcrystalline cellulose fibers is expressed as the average degree of substitution of hydroxyl groups (the average number of substituted hydroxyl groups per glucose, which is the basic structural unit of cellulose, also referred to as DS). In one embodiment, DS is preferably 0.5 or more, or 0.6 or more, or 0.7 or more, or 0.75 or more from the viewpoint of maintaining the affinity with the polyacetal resin and the thermal stability during processing, and is preferably 1.5 or less, or 1.4 or less, or 1.35 or less, or 1.2 or less, or 1.0 or less in terms of obtaining an affinity with the polyacetal resin and high high-temperature rigidity.

[0039] The acyl substitution degree (DS) of the esterified microcrystalline cellulose fibers can be calculated based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose backbone from the reflection-type infrared absorption spectrum of the esterified microcrystalline cellulose fibers. The peak of the absorption band of C=O based on the acyl group appears at 1730 cm -1 and the peak of the absorption band of C-O based on the cellulose backbone chain appears at 1030 cm-1 It appears in . The DS of the esterified microcrystalline cellulose fiber is determined from the DS obtained from the solid NMR measurement of the esterified microcrystalline cellulose fiber described later and the ratio of the peak intensity of the absorption band of C=O based on the acyl group to the peak intensity of the absorption band of the cellulose backbone chain C-O. A correlation graph with the modification rate (IR index 1030) defined by this ratio is created, and the calibration curve calculated from the correlation graph Degree of substitution DS = 4.13 × IR index (1030) can be obtained by using

[0040] The method for calculating the DS of the esterified microcrystalline cellulose fiber by solid NMR is to perform 13C solid NMR measurement on the freeze-ground esterified microcrystalline cellulose fiber, and calculate it from the area intensity (Inf) of the signal attributed to one carbon atom derived from the modifying group with respect to the total area intensity (Inp) of the signals attributed to the carbon C1-C6 derived from the pyranose ring of cellulose that appears in the range of 50 ppm to 110 ppm by the following formula. DS=(Inf)×6 / (Inp) For example, when the modifying group is an acetyl group, the signal at 23 ppm attributed to -CH3 can be used.

[0041] The conditions for the 13C solid NMR measurement to be used are as follows, for example. Apparatus: Bruker Biospin Avance500WB Frequency: 125.77 MHz Measurement method: DD / MAS method Waiting time: 75 sec NMR sample tube: 4 mmφ Number of integrations: 640 times (about 14 Hr) MAS: 14,500 Hz Chemical shift standard: Glycine (external standard: 176.03 ppm)

[0042] (b) The preferred amount of the microcrystalline cellulose fiber is 1 to 150 parts by mass with respect to 100 parts by mass of the (a) polyacetal resin. In terms of maintaining high high-temperature rigidity, it is preferably 2 parts by mass or more, or 4 parts by mass or more, or 5 parts by mass or more, and in terms of improving toughness during tension, it is preferably 100 parts by mass or less, or 80 parts by mass or less, or 50 parts by mass or less, or 40 parts by mass or less, or 20 parts by mass or less.

[0043] <(c) hindered phenol-based antioxidant> The polyacetal resin composition of the present embodiment can stably achieve excellent mechanical properties and color tone by containing the (c) hindered phenol-based antioxidant. The processing aid used for improving the dispersibility of the microcrystalline cellulose fiber promotes the oxidation of the polyacetal resin and causes the generation of decomposition products of the polyacetal resin. The decomposition products cause the yellowing or browning of the polyacetal resin, thus reducing the original whiteness of the polyacetal resin. The (c) hindered phenol-based antioxidant is excellent in the oxidation suppression effect of the polyacetal resin and can therefore be advantageous for improving the color tone of the polyacetal resin composition.

[0044] (c) As hindered phenol antioxidants, there are monocyclic hindered phenol compounds (e.g., 2,6-di-t-butyl-p-cresol, etc.), polycyclic hindered phenol compounds linked by a hydrocarbon group or a group containing a sulfur atom (e.g., 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 4,4'-thiobis(3-methyl-6-t-butylphenol), etc.), hindered phenol compounds having an ester group or an amide group (e.g., n-octadecyl 3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, n-octadecyl 2-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5] Undecane, 2-t-butyl-6-(3’-t-butyl-5’-methyl-2’-hydroxybenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, di-n-octadecyl 3,5-di-t-butyl-4-hydroxybenzyl phosphonate, N,N’-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-dihydrocinnamide, N,N’-ethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], N,N’-tetramethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], N,N’-hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], N,N’-ethylenebis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionamide], N,N’-hexamethylenebis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionamide], N,N’-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, N,N’-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionyl]hydrazine, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, etc.) can be exemplified, and these may be used alone or in combination of two or more.

[0045] In this embodiment, the amount of the (c) hindered phenol antioxidant is 0.01 to 3 parts by mass with respect to 100 parts by mass of the (a) polyacetal resin. From the viewpoint of maintaining the mechanical properties and color tone of the resin composition, it is preferably 0.02 parts by mass or more, or 0.04 parts by mass or more, or 0.06 parts by mass or more, and from an economic viewpoint, it is preferably 2 parts by mass or less, or 1.5 parts by mass or less, or 1 part by mass or less.

[0046] <(d) Nitrogen-containing compound> The polyacetal resin composition of this embodiment contains (d) a nitrogen-containing compound. In one aspect, the (d) nitrogen-containing compound is at least one selected from the group consisting of an aminotriazine compound, a guanamine compound, a hydrazide compound, and a polyamide. These nitrogen-containing compounds have an amino group or an amide group capable of capturing formaldehyde in their structure. Thereby, it is possible to maintain the color tone and thermal stability of the (a) polyacetal resin, suppress the odor during processing, and improve the mechanical properties. As described above, in a composite containing a polyacetal resin and microcrystalline cellulose fibers, since the processing aid used for improving the dispersibility of the microcrystalline cellulose fibers promotes the oxidation of the polyacetal resin, there is a problem that yellowing or browning due to the decomposition products of the polyacetal resin occurs and the original whiteness of the polyacetal resin decreases. Since the (d) nitrogen-containing compound has an excellent acid scavenging effect, it suppresses the oxidation of the polyacetal resin and contributes to the improvement of the color tone of the resin composition.

[0047] Examples of the aminotriazine compound include melamine or its derivatives [e.g., melamine, melamine condensates (such as melem, melam, melon, etc.)], and aminotriazine resins [e.g., co-condensation resins of melamine (such as melamine-formaldehyde resin, phenol-melamine resin, melamine-phenol-formaldehyde resin, co-condensation resins of guanamine compounds (e.g., benzoguanamine) and melamine, aromatic polyamine-melamine resins, etc.)].

[0048] Examples of guanamine compounds include aliphatic guanamine compounds (such as monoguanamines and alkylene bisguanamines), alicyclic guanamine compounds (such as monoguanamines), aromatic guanamine compounds [for example, monoguanamines (such as benzoguanamine and its functional group-substituted derivatives), α- or β-naphthoguanamine and their functional group-substituted derivatives, polyguanamines, aralkyl or aralkylene guanamines, etc.], heteroatom-containing guanamine compounds [for example, acetal group-containing guanamines, tetraoxospiro ring-containing guanamines (such as CTU-guanamine and CMTU-guanamine), isocyanuric ring-containing guanamines, imidazole ring-containing guanamines, etc.], etc. Aromatic guanamine compounds are particularly preferred.

[0049] Also included are compounds in which the alkoxymethyl groups of the above-mentioned melamine, melamine derivatives, and guanamine compounds are each substituted with an amino group.

[0050] Examples of hydrazide compounds include aliphatic carboxylic acid hydrazide compounds (such as stearic acid hydrazide, 12-hydroxystearic acid hydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, eicosanedioic acid dihydrazide, etc.), alicyclic carboxylic acid hydrazide compounds (such as 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, etc.), aromatic carboxylic acid hydrazide compounds (such as 4-hydroxy-3,5-di-t-butylphenylbenzoic acid hydrazide, 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, isophthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, etc.), heteroatom-containing carboxylic acid hydrazide compounds, polymer-type carboxylic acid hydrazide compounds, etc.

[0051] Examples of polyamides include polyamides derived from diamines and dicarboxylic acids; polyamides obtained by using aminocarboxylic acids, and optionally diamines and / or dicarboxylic acids in combination; polyamides derived from lactams, and optionally in combination with diamines and / or dicarboxylic acids. Also included are copolyamides formed from two or more different polyamide-forming components.

[0052] Specific examples of polyamides include aliphatic polyamides such as polyamide 3, polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, and polyamide 12; polyamides obtained from aromatic dicarboxylic acids (e.g., terephthalic acid and / or isophthalic acid) and aliphatic diamines (e.g., hexamethylenediamine); polyamides obtained from aliphatic dicarboxylic acids (e.g., adipic acid) and aromatic diamines (e.g., metaxylylenediamine); polyamides obtained from aromatic and aliphatic dicarboxylic acids (e.g., terephthalic acid and adipic acid) and aliphatic diamines (e.g., hexamethylenediamine), and copolymers thereof. Also, the use of polyamide-based block copolymers in which a polyamide hard segment is bonded to a soft segment such as a polyether component is possible.

[0053] The number average molecular weight of the polyamide is preferably 10,000 or less, or 9,000 or less in terms of the good effect of preventing brittle fracture under the load of the polyacetal resin composition, and preferably 2,000 or more, or 3,000 or more, or 4,000 or more from the viewpoints of the high-temperature rigidity and thermal stability of the polyacetal resin composition. The above number average molecular weight is a value determined by gel permeation chromatography in terms of standard polymethyl methacrylate conversion.

[0054] (d) The nitrogen-containing compound can be used alone or in combination of two or more. The amount of the (d) nitrogen-containing compound relative to 100 parts by mass of the polyacetal resin is, from the viewpoints of color tone, maintenance of thermal stability, suppression of odor during processing, and mechanical properties, in one aspect 0.01 part by mass or more, preferably 0.02 part by mass or more, or 0.03 part by mass or more, or 0.05 part by mass or more, and from the aspect of suppressing mold deposit on the mold in advance, in one aspect 3 parts by mass or less, preferably 2 parts by mass or less, or 1 part by mass or less, or 0.7 part by mass or less, or 0.5 part by mass or less, or 0.3 part by mass or less.

[0055] Incidentally, the form when the (d) nitrogen-containing compound is added to the (a) polyacetal resin is preferably a fine powder shape from the viewpoint of preventing deterioration of the mechanical properties of the polyacetal resin composition.

[0056] <(e) Processing aid> The polyacetal resin composition of the present embodiment contains an (e) processing aid. In one aspect, the (e) processing aid is at least one selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds. Thereby, it is possible to prevent molding defects due to an increase in viscosity caused by the blending of the (b) fine cellulose fibers, and further, it is possible to suppress the aggregation of the (b) fine cellulose fibers in the resin. In the present disclosure, the long-chain fatty acid means a fatty acid having 10 or more carbon atoms, and the long-chain aliphatic alcohol means an aliphatic alcohol having 10 or more carbon atoms.

[0057] The long-chain fatty acid may be a saturated fatty acid or an unsaturated fatty acid. Also, one or more hydrogen atoms in the molecule may be substituted with substituents, preferably hydroxy groups. Examples of the long-chain fatty acid include monovalent saturated or unsaturated fatty acids having 10 or more carbon atoms, and divalent saturated or unsaturated fatty acids (dibasic fatty acids) having 10 or more carbon atoms. The number of carbon atoms of the long-chain fatty acid is preferably 10 or more, or 11 or more, and preferably 40 or less, or 35 or less, or 30 or less.

[0058] Examples of the long-chain fatty acid derivatives include fatty acid esters and fatty acid amides.

[0059] Examples of the fatty acid esters include esters of the above-mentioned long-chain fatty acids and alcohols. The structure is not particularly limited and may be linear or branched. Specific examples of the fatty acid esters include ethylene glycol mono- or dipalmitate, ethylene glycol mono- or distearate, ethylene glycol mono- or dibehenate, ethylene glycol mono- or dimontanate, glycerin mono- to tripalmitate, glycerin mono- to tristearate, glycerin mono- to tribehenate, glycerin mono- to trimontanate, pentaerythritol mono- to tetrapalmitate, pentaerythritol mono- to tetrastearate, pentaerythritol mono- to tetrabehenate, pentaerythritol mono- to tetramontanate, polyglycerol tristearate, trimethylolpropane monopalmitate, pentaerythritol monoundecylate, sorbitan monostearate, mono- or dilaurate, mono- or dipalmitate, mono- or distearate, mono- or dibehenate, mono- or dimontanate, mono- or dioleate, mono- or dilinoleate of polyalkylene glycol (such as polyethylene glycol, polypropylene glycol).

[0060] Examples of fatty acid amides include those having 10 to 40 carbon atoms, or 11 to 35 carbon atoms, or 12 to 30 carbon atoms. More specifically, primary acid amides of saturated fatty acids such as capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidic acid amide, behenic acid amide, montanic acid amide, etc.; primary acid amides of unsaturated fatty acids such as oleic acid amide; secondary acid amides of saturated and / or unsaturated fatty acids and monoamines such as stearyl stearate amide, stearyl oleate amide; ethylenediamine-dipalmitic acid amide, ethylenediamine-distearic acid amide (ethylenebisstearylamide), hexamethylenediamine-distearic acid amide, ethylenediamine-dibehenic acid amide, ethylenediamine-dimontanic acid amide, ethylenediamine-dioleic acid amide, ethylenediamine-dierucic acid amide, etc. Further examples include bisamides having a structure in which different acyl groups are bonded to the amine moiety of an alkylenediamine such as ethylenediamine-(stearic acid amide) oleic acid amide.

[0061] Examples of long-chain aliphatic alcohols include those having 10 to 40 carbon atoms, or 11 to 35 carbon atoms, or 12 to 30 carbon atoms. More specifically, lauryl alcohol, myristyl alcohol, cetyl alcohol, oleyl alcohol, stearyl alcohol, behenyl alcohol, etc.

[0062] Examples of polyoxyalkylene glycols include homopolymers or copolymers of alkylene glycols (such as ethylene glycol, propylene glycol, tetramethylene glycol, etc.) and their derivatives.

[0063] Polyoxyethylene derivatives may be, for example, ethers, amines, amides or fatty acid esters of polyoxyethylene. Specific examples of polyoxyethylene derivatives include Polyoxyethylene alkyl ethers, such as polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene tridecyl ether, polyoxyethylene long-chain alkyl ether, etc. Polyoxyethylene alkyl phenyl ethers, such as polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene phenyl ether, polyoxyethylene benzyl ether, polyoxyethylene β-naphthyl ether, polyoxyethylene bisphenol ether, etc. Polyoxyethylene alkyl amines, such as polyoxyethylene lauryl amine, polyoxyethylene stearyl amine, etc. Polyoxyethylene alkyl amides, such as polyoxyethylene oleyl amide, polyoxyethylene stearyl amide, etc. Polyoxyethylene fatty acid esters, such as polyoxyethylene monolaurate, polyoxyethylene monostearate, etc., and Other compounds, such as polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene glycerol ether, polyoxyethylene pentaerythritol ether, etc. can be exemplified.

[0064] The number average molecular weight of the polyoxyethylene derivative is preferably 300 to 1,000,000, or may be 1,000 to 300,000. The above number average molecular weight is a value determined by gel permeation chromatography in terms of standard polyethylene glycol.

[0065] Specific examples of polyoxyalkylene glycols include homopolymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, polyoxyethylene-polyoxypropylene copolymers (such as random or block copolymers), and copolymers such as polyoxyethylene polyoxypropylene glyceryl ether and polyoxyethylene polyoxypropylene monobutyl ether. Among these, polymers having oxyethylene units, such as polyethylene glycol, polyoxyethylene polyoxypropylene copolymers, and their derivatives, are preferred. The number average molecular weight of the polyoxyalkylene glycol is from 300 to 1,000,000, preferably from 1,000 to 300,000. The above number average molecular weight is a value determined by gel permeation chromatography in terms of standard polyethylene glycol conversion.

[0066] Examples of olefin waxes include low molecular weight polyolefins (such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight copolymers of ethylene and α-olefins), oxidized polyethylene wax, and the like. The number average molecular weight of the olefin wax is preferably 7,000 or more, or 8,000 or more, or 9,000 or more, and may preferably be 100,000 or less, or 70,000 or less, or 50,000 or less. The above number average molecular weight is a value determined by gel permeation chromatography in terms of standard polystyrene conversion.

[0067] Examples of silicone compounds include (poly)organosiloxanes. Examples of (poly)organosiloxanes include monoorganosiloxanes such as dialkylsiloxanes (such as dimethylsiloxane), alkylarylsiloxanes (such as phenylmethylsiloxane), and diarylsiloxanes (such as diphenylsiloxane), homopolymers thereof (such as polydimethylsiloxane and polyphenylmethylsiloxane), or copolymers. Note that the polyorganosiloxane may be an oligomer.

[0068] In addition, examples of the (poly)organosiloxane include modified (poly)organosiloxanes having substituents such as an epoxy group, a hydroxy group, an alkoxy group, a carboxy group, an amino group or a substituted amino group (such as a dialkylamino group), an ether group, a vinyl group, and a (meth)acryloyl group at the molecular terminals and / or in the main chain.

[0069] At least one processing aid selected from long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds can be used alone or in combination of two or more.

[0070] The blending ratio of the (e) processing aid with respect to 100 parts by mass of the (a) polyacetal resin is 0.01 to 3 parts by mass, preferably 0.05 to 1 part by mass.

[0071] <Other Components> In the polyacetal resin composition of this embodiment, various known additives can be further blended in order to improve its physical properties according to the intended use. Examples of the additives include formic acid scavengers, weather stabilizers, mold release agents, lubricants, conductive agents, different polymers (for example, thermoplastic resins or thermoplastic elastomers), dyes and pigments, inorganic or organic fillers, surface treatment agents, etc., and one kind or a combination of two or more kinds thereof can be used.

[0072] The formic acid scavengers are not limited to the following, and examples thereof include hydroxides, inorganic acid salts, carboxylates, or alkoxides of alkali metals or alkaline earth metals. More specifically, examples include hydroxides such as sodium, potassium, magnesium, calcium, or barium; and carbonates, phosphates, silicates, borates, carboxylates, and layered double hydroxides of the above metals.

[0073] As the carboxylic acid of the carboxylate, a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms is preferable, and these carboxylic acids may be substituted with a hydroxyl group. Examples of the saturated or unsaturated aliphatic carboxylate include, but are not limited to, calcium dimyristate, calcium dipalmitate, calcium distearate, calcium (myristate-palmitate), calcium (myristate-stearate), calcium (palmitate-stearate), and calcium 12-hydroxystearate. Among them, calcium dipalmitate, calcium distearate, and calcium 12-hydroxydistearate are preferably mentioned.

[0074] The formic acid scavenger may be used alone or in combination of two or more.

[0075] Examples of the weather stabilizer include, but are not limited to, at least one selected from the group consisting of benzotriazole compounds, oxalic acid anilide compounds, and hindered amine light stabilizers.

[0076] Examples of the benzotriazole compound include, but are not limited to, 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole, 2-(2'-hydroxy-3,5-di-t-butyl-phenyl)benzotriazole, 2-[2'-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3,5-di-t-amylphenyl]benzotriazole, 2-(2'-hydroxy-3,5-di-isoamyl-phenyl)benzotriazole, 2-[2'-hydroxy-3,5-bis-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, and the like. These compounds may be used alone or in combination of two or more.

[0077] Examples of the aryl oxalate compound include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxalic acid bisanilide, 2-ethoxy-3'-dodecyloxalic acid bisanilide, and the like. These compounds may be used alone or in combination of two or more kinds.

[0078] Examples of the hindered amine light stabilizer include, but are not limited to, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylatoxy)-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4-(ethylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, 4-(cyclohexylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, 4-(phenylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidyl)-carbonate, bis(2,2,6,6-tetramethyl-4-piperidyl)-oxalate, bis(2,2,6,6-tetramethyl-4-piperidyl)-malonate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis-(N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)-sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)-adipate, bis(2,2,6,6-tetramethyl-4-piperidyl)-terephthalate, 1,2-bis(2,2,6,6-tetramethyl-4-piperidyloxy)-ethane, α,α’-bis(2,2,6,6-tetramethyl-4-piperidyloxy)-p-xylene, bis(2,2,6,6-tetramethyl-4-piperidyl tolylene-2,4-dicarbamate, bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene-1,6-dicarbamate, tris(2,2,6,6-tetramethyl-4-piperidyl)-benzene-1,3,5-tricarboxylate, tris(2,2,6,6-tetramethyl-4-piperidyl)-benzene-1,3,4-tricarboxylate, 1-[2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}butyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]2,2,6,6-tetramethylpiperidine, condensate of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β’,β’,-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undecane]diethanol, etc. are mentioned. The above hindered amine light stabilizers may be used alone, each only one kind, or in combination of two or more kinds.

[0079] Among them, preferred weathering stabilizers are 2-[2’-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(2’-hydroxy-3,5-di-t-butylphenyl)benzotriazole, 2-(2’-hydroxy-3,5-di-t-amylphenyl]benzotriazole, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, bis-(N-methyl-2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, condensate of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β’,β’,-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undecane]diethanol.

[0080] The above mold release agents and lubricants are not limited to the following, but for example, alcohols, fatty acids and their fatty acid esters, olefin compounds with an average degree of polymerization of 10 to 500, and silicones are preferably mentioned. The mold release agents and lubricants may be used alone, only one kind, or in combination of two or more kinds.

[0081] Examples of the conductive agent include, but are not limited to, conductive carbon black, metal powders or fibers. Only one type of conductive agent may be used alone, or two or more types may be used in combination.

[0082] Examples of the thermoplastic resin include, but are not limited to, polyolefin resins, acrylic resins, styrene resins, polycarbonate resins, and uncured epoxy resins. Only one type of thermoplastic resin may be used alone, or two or more types may be used in combination. The thermoplastic resin also includes modified products of the above-mentioned resins.

[0083] Examples of the thermoplastic elastomer include, but are not limited to, polyurethane-based elastomers, polyester-based elastomers, polystyrene-based elastomers, and polyamide-based elastomers. Only one type of thermoplastic elastomer may be used alone, or two or more types may be used in combination.

[0084] Examples of the dye / pigment include, but are not limited to, inorganic pigments and organic pigments, and also include metallic pigments, fluorescent pigments, etc. As the inorganic pigment, those generally used for coloring resins can be used. Examples include, but are not limited to, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, calcined pigments, carbonates, phosphates, acetates, carbon black, acetylene black, lamp black, etc. Examples of the organic pigment include, but are not limited to, pigments such as condensed azo-based, ionone-based, phthalocyanine-based, monoazo-based, diazo-based, polyazo-based, anthraquinone-based, heterocyclic-based, perinone-based, quinacridone-based, thioindigo-based, perylene-based, dioxazine-based pigments. Only one type of dye / pigment may be used alone, or two or more types may be used in combination. Since the addition ratio of the pigment varies significantly depending on the color tone and it is difficult to clarify, generally, it is used in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin.

[0085] Examples of the inorganic filler include, but are not limited to, fibrous, powder particle-shaped, plate-shaped, and hollow fillers.

[0086] Examples of the fibrous filler include, but are not limited to, inorganic fibers such as glass fiber, carbon fiber, silicone fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and metal fibers such as stainless steel, aluminum, titanium, copper, brass, etc. Also included are whiskers with short fiber lengths such as potassium titanate whisker and zinc oxide whisker.

[0087] Examples of the powder particle-shaped filler include, but are not limited to, silicates such as talc, carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, magnesium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, wollastonite; metal oxides such as iron oxide, titanium oxide, alumina; metal sulfates such as calcium sulfate, barium sulfate; carbonates such as magnesium carbonate, dolomite; silicon carbide, silicon nitride, boron nitride, various metal powders, etc.

[0088] Examples of the plate-shaped filler include, but are not limited to, mica, glass flakes, various metal foils, etc.

[0089] Examples of the hollow filler include, but are not limited to, glass balloons, silica balloons, shirasu balloons, metal balloons, etc.

[0090] Examples of the organic filler include, but are not limited to, high melting point organic fibrous fillers such as aromatic polyamide resin, fluororesin, acrylic resin, etc.

[0091] These fillers may be used alone, or two or more of them may be used in combination. As the filler, either a filler surface-treated with a surface treatment agent or a filler not subjected to such surface treatment can be used, but from the viewpoint of the smoothness of the molding surface and mechanical properties, the filler surface-treated with a surface treatment agent may be preferred in some cases.

[0092] The surface treatment agent is not particularly limited, and conventionally known surface treatment agents can be used. The surface treatment agent is not limited to the following, but for example, various coupling agents such as silane-based, titanate-based, aluminum-based, and zirconium-based coupling agents, resin acids, organic carboxylic acids, surfactants such as organic carboxylates, etc. can be used. Specifically, but not limited to the following, for example, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, diisopropoxyammonium ethyl acetate, n-butyldizirconate, etc. can be mentioned.

[0093] <Method for producing polyacetal resin composition> The specific embodiment of the method for producing the polyacetal resin composition of this embodiment is not particularly limited, but the method for producing the polyacetal resin composition according to a preferred embodiment includes melt-kneading (a) a polyacetal resin, (b) microcrystalline cellulose fibers, (c) a hindered phenol-based antioxidant, (d) a nitrogen-containing compound, and (e) a processing aid.

[0094] More specifically, a method of mixing the necessary components, kneading them using a melt-kneading device such as an extruder, and obtaining the polyacetal resin composition as pellets can be exemplified. As the extruder, it is preferable to use a co-rotating twin-screw extruder for the purpose of improving the dispersibility of the microcrystalline cellulose fibers.

[0095] A more preferred embodiment in the present embodiment is to melt-knead (a) a polyacetal resin, (c) a hindered phenol antioxidant, (d) a nitrogen-containing compound, and (e) a processing aid to obtain a kneaded product, and then melt-knead the kneaded product with (b) fine cellulose fibers.

[0096] From the viewpoints of suppressing the generation of silver streaks during molding, suppressing the generation of odors during hot processing, and suppressing the generation of voids in the central part of the molded body, rather than the method of defibrating cellulose by the shear of an extruder to obtain fine cellulose fibers, a method of melt-kneading fine cellulose fibers that have been defibrated in advance (defibrated to a fiber diameter of 10 to 1000 nm in one embodiment) with a polyacetal resin is preferred.

[0097] <Rigidity of the polyacetal resin composition at high temperature> The polyacetal resin composition in the present embodiment preferably has the characteristic of high high-temperature rigidity in order to suppress deformation due to the load during gear meshing at high temperature. Specifically, from the viewpoint of suppressing deformation during gear meshing, the storage elastic modulus of the polyacetal resin composition at 120 °C is preferably 1,000 MPa or more, or 1,300 MPa or more, or 1,500 MPa or more, or 1,700 MPa or more. There is no particular upper limit, but from the viewpoint of maintaining toughness, it is desirably 3,000 MPa or less.

[0098] Further, in the present embodiment, the polyacetal resin composition preferably has a component composition (i.e., the types and amounts of the constituent components of the polyacetal resin composition) such that the ratio of the storage modulus at 120°C to the storage modulus at 23°C when 10% by mass of microcrystalline cellulose fibers is blended is 0.4 or more. This index is an index of the dispersibility of the microcrystalline cellulose fibers in the composition. The higher the dispersibility, the greater the tendency for the above ratio to be larger. For example, in the case of a polyacetal resin composition not containing microcrystalline cellulose fibers, the ratio of the storage modulus at 120°C to the storage modulus at 23°C is less than 0.3. Also, when non-fine cellulose (e.g., cellulose powder) is blended, the above ratio is less than 0.4. From the viewpoint of enhancing the high-temperature rigidity of the composition with a smaller amount of microcrystalline cellulose fibers, the ratio of the storage modulus at 120°C to the storage modulus at 23°C is preferably 0.4 or more, or 0.5 or more, or 0.55 or more, or 0.6 or more, or 0.65 or more. There is no particular upper limit, but from the viewpoint of processability, it is preferably 1.5 or less.

[0099] The above storage modulus is the storage modulus measured using an ISO multipurpose test piece with a width of 10 mm and a thickness of 4 mm, using a solid viscoelastic measurement device, under the conditions of a measurement temperature range of 0°C to 150°C (heating rate: 3°C / min), tensile mode, vibration frequency of 10 Hz, static load strain of 0.5%, and dynamic load strain of 0.3%. The temperatures of 23°C and 120°C are calculated by interpolating the measurement temperatures before and after to those respective temperatures.

[0100] <Molding Method and Use of Polyacetal Resin Composition> The polyacetal resin composition of the present embodiment can be molded into various molded articles by conventionally known molding methods (e.g., injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.), and is particularly suitable for injection molding.

[0101] Further, the obtained molded article can be used for various applications such as automotive parts, electrical and electronic parts, building materials, and parts related to daily life, cosmetics, and medicine.

[0102] Specifically, as automotive parts, there are interior parts such as inner handles, fuel tank openers, seat belt buckles, assist straps, various switches, knobs, levers, clips, etc., electrical system parts such as meters, connectors, etc., in-vehicle electrical and electronic parts such as audio equipment, car navigation equipment, etc., parts that come into contact with metal, represented by the carrier plate of a window regulator, mechanism parts such as door lock actuator parts, mirror parts, wiper motor system parts, fuel system parts, etc.

[0103] As electrical and electronic parts, there are parts or members of equipment composed of polyacetal resin molded products and having a large number of metal contacts, for example, parts or members of audio equipment, video equipment, or OA equipment such as telephones, copiers, facsimiles, word processors, computers, etc., parts or members of toys, specifically, chassis, gears, levers, cams, pulleys, bearings, etc.

[0104] Furthermore, it is preferably used for a wide range of living-related parts, cosmetic-related parts, and medical-related parts such as lighting fixtures, building fixtures, pipes, cocks, faucets, toilet peripheral equipment parts, fasteners, stationery, lip cream and lipstick containers, cleaners, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, holders for injection needles, etc. Among these, it can be more preferably used for gears with high loads placed in high-temperature environments.

Examples

[0105] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited by these examples.

[0106] (Diameter and L / D of microcrystalline cellulose fibers) The wet cake was diluted with tert-butanol to 0.01% by mass, and using a high-shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18"), the treatment conditions were: dispersed at a rotation speed of 25,000 rpm for 5 minutes, cast onto mica, air-dried, and measured with a high-resolution scanning electron microscope. The measurement was carried out by adjusting the magnification so that at least 100 cellulose fibers were observed. The length (L), major diameter (D) of 100 randomly selected cellulose fibers and their ratio were determined, and the additive average of 100 cellulose fibers was calculated.

[0107] (Mw of microcrystalline cellulose fibers) The wet cake was added to tert-butanol, and further dispersed until there were no aggregates using a mixer or the like. It was adjusted so that the concentration was 0.5% by mass with respect to 0.5 g of the solid content weight of the microcrystalline cellulose fibers. 100 g of the obtained tert-butanol dispersion was filtered on filter paper, dried at 150 °C, and then the filter paper was peeled off to obtain a sheet. A porous sheet was obtained when the air permeability resistance of this sheet was 100 sec / 100 ml or less per sheet basis weight of 10 g / m 2 The porous sheet was weighed at 0.88 g, cut into small pieces with scissors, gently stirred, 20 mL of pure water was added, and left for 1 day. Next, the water and the solid content were separated by centrifugation. Subsequently, 20 mL of acetone was added, gently stirred, and left for 1 day. Next, the acetone and the solid content were separated by centrifugation. Subsequently, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left for 1 day. Again, after separating the N,N-dimethylacetamide and the solid content by centrifugation, 20 mL of N,N-dimethylacetamide was added, gently stirred, and left for 1 day. The N,N-dimethylacetamide and the solid content were separated by centrifugation, and 19.2 g of an N,N-dimethylacetamide solution adjusted so that lithium chloride was 8 mass percent in the solid content was added, stirred with a stirrer, and it was confirmed visually that it dissolved. The solution in which the cellulose was dissolved was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The apparatus and measurement conditions used are as follows. Apparatus: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0 mm I.D. × 15 cm) × 2 columns Detector: RI detector Eluent: N,N-dimethylacetamide (0.2% lithium chloride) Flow rate: 0.6 mL / min Calibration curve: in terms of pullulan

[0108] (Degree of acetyl substitution (DS) of hydrophobic microcrystalline cellulose fibers) The infrared spectra at five locations on the porous sheet by ATR-IR method were measured with a Fourier transform infrared spectrophotometer (FT / IR-6200 manufactured by JASCO Corporation). The infrared spectrum measurement was carried out under the following conditions. Number of accumulations: 64 times Wavenumber resolution: 4 cm -1 、 Measurement wavenumber range: 4000~600 cm -1 、 ATR crystal: diamond Incident angle: 45° The IR index was calculated from the obtained IR spectrum according to the following formula: IR index = H1730 / H1030 In the formula, H1730 and H1030 are the absorbances at 1730 cm -1 、1030 cm -1 (Absorption band of cellulose backbone chain C-O stretching vibration). However, the absorbances when the baseline, which is the line connecting 1900 cm -1 and 1500 cm -1 and the line connecting 800 cm -1 and 1500 cm -1 is taken as the baseline and the absorbance when this baseline is set to absorbance 0. Then, the average degree of substitution at each measurement location was calculated from the IR index according to the following formula, and the average value was taken as DS. DS = 4.13 × IR index

[0109] (Tensile properties) Using an EC5P injection molding machine (manufactured by Shibaura Machine Co., Ltd.) set at a cylinder temperature of 200°C, a Type 3 tensile test piece with a thickness of 2 mm according to ISO 37 was molded. The mold temperature was set at 60°C. Using the obtained tensile test pieces, a tensile test was conducted. The distance between the chucks for the tensile test was 20 mm, the crosshead speed was set at 5 mm / min, and the tensile yield stress and tensile fracture strain were measured. The test was carried out with 5 specimens, and the values were averaged arithmetically. In addition, as an evaluation criterion for toughness, it was evaluated whether the tensile fracture point exceeded the yield point (maximum stress value). Among the 5 test pieces, those in which 3 or more exceeded the yield point were marked as "〇", and those in which 3 or more fractured before yielding were marked as "×". For those in which all 5 exceeded the yield point, they were marked as "◎". It was described as the fracture situation in the table. Also, for those judged as "×", they were described as the tensile fracture stress instead of the tensile yield stress.

[0110] (Storage modulus) Using an injection molding machine LA60 set at 200°C, an ISO multi-purpose test piece with a width of 10 mm and a thickness of 4 mm was molded, and the storage modulus measured under the conditions of a tensile mode, a measurement temperature range of 0°C to 150°C, a heating rate of 3°C / min, a vibration frequency of 10 Hz, a static load strain of 0.5%, and a dynamic load strain of 0.3% with a GABO Implexor 500N viscoelasticity measuring device (manufactured by NETZSCH) was measured. The storage modulus at 120°C was described in the example table as E’(120°C). Also, the ratio of the storage modulus at 120°C to the storage modulus at 23°C was described in the example table as RATIO(120°C / 23°C).

[0111] (Thermogravimetric reduction rate) The test pieces left standing in a vacuum dryer set at 80°C for two days were shredded with nippers until they became less than 0.5 mm in diameter, and about 10 mg was used to measure the weight loss with a differential thermal thermogravimetric measuring device (HITACHI STA7200RV). The measurement conditions were heating from 30°C to 200°C at a heating rate of 20°C / min under nitrogen, and then holding for 60 minutes. The weight reduction rate was calculated according to the following formula, where X0 is the weight before heating and Xt is the weight after holding at 200°C for 60 minutes. Weight reduction rate (%) = (X0 - Xt) / X0 × 100

[0112] (Silver streaks) Using an EC5P injection molding machine (manufactured by Shibaura Machine Co., Ltd.) set at a cylinder temperature of 200°C, a strip-shaped test piece with a length of 700 mm, a width of 10 mm, and a thickness of 3.5 mm was molded. At that time, the amount of silver streaks generated on the surface of the test piece was evaluated in five grades according to the following criteria. 5: No silver streaks are observed 4: A plurality of small silver marks are scattered in several places 3: Silver marks can be clearly confirmed 2: Silver streaks can be confirmed on more than half of the test piece. 1: Silver streaks can be confirmed on the front surface of the test piece.

[0113] (Odor during extrusion processing) The odor near the extruder die during extrusion processing was evaluated according to the following criteria. 〇: There is no odor at all, or there is a slight sweet odor. △: A pungent odor of formaldehyde is felt. ×: A strong pungent odor of formaldehyde is felt.

[0114] (Polyacetal: May be referred to by the following abbreviations) POM-H Linear homopolymer produced from formaldehyde as raw material, MFR = 10 g / 10 min POM-C1 Linear copolymer obtained by copolymerizing 96.5 mass% of trioxane and 3.5 mass% of 1,3-dioxolane, MFR: 9 g / 10 min POM-C2 Linear copolymer obtained by copolymerizing 96.5 mass% of trioxane and 3.5 mass% of 1,3-dioxolane, MFR: 30 g / 10 min POM-C3 Linear copolymer obtained by copolymerizing 98 mass% of trioxane and 2 mass% of 1,3-dioxolane, MFR: 8 g / 10 min POM-BC Linear block copolymer prepared according to the following preparation example, MFR: 15 g / 10 min

[0115] [Preparation Example 1] A two - shaft paddle - type continuous polymerization machine with a jacket through which a heat medium can pass was adjusted to 80°C. Trioxane was fed at 40 mol / h, 1,3 - dioxolane as a cyclic formaldehyde was fed at 2 mol / h, and boron trifluoride di - n - butyl etherate dissolved in cyclohexane as a polymerization catalyst was fed in an amount of 5×10 -5 mol per 1 mol of trioxane, and a hydroxyl - terminated hydrogenated polybutadiene (number - average molecular weight Mn = 2,330) represented by the following formula as a chain transfer agent was fed in an amount of 1×10 -3 mol per 1 mol of trioxane, and polymerization was carried out by continuously feeding them into the above - mentioned polymerization machine.

[0116] [Chemical formula]

[0117] Next, the polymer discharged from the above - mentioned polymerization machine was put into a 1% aqueous solution of triethylamine. After completely deactivating the polymerization catalyst, the polymer was filtered and washed to obtain a crude polyacetal block copolymer.

[0118] To 100 parts by mass of the obtained crude polyacetal block copolymer, 1 part by mass of an aqueous solution containing a quaternary ammonium compound (described in Japanese Patent No. 3087912) was added and uniformly mixed. The addition amount of the quaternary ammonium compound was 20 mass ppm in terms of nitrogen amount. This was fed into a twin - screw extruder with a vent, and 0.5 part by mass of water was added per 100 parts by mass of the molten polyacetal block copolymer in the extruder. With the set temperature of the extruder at 200°C and the residence time in the extruder at 7 minutes, the unstable terminal portion of the polyacetal block copolymer was decomposed and removed.

[0119] To the decomposed polyacetal block copolymer of the unstable end portion, 0.3 parts by mass of triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate] was added as an antioxidant, and while degassing under the condition of a vacuum degree of 20 Torr with an extruder equipped with a vent, it was extruded as strands from the die part of the extruder and pelletized. The obtained ABA type block copolymer is referred to as POM-BC.

[0120] <Hydrophobized microfibrillated cellulose fibers: may be referred to by their respective abbreviations> [Preparation Example 2] Using a uniaxial stirrer (DKV-1 φ125 mm dissolver manufactured by Imex), cotton linter pulp was stirred in dimethyl sulfoxide (DMSO) at 500 rpm for 1 hour at room temperature. Subsequently, it was fed to a bead mill (NVM-1.5 manufactured by Imex) with a hose pump and circulated for 120 minutes with DMSO only to obtain a defibrated slurry.

[0121] Then, to 100 parts by mass of the defibrated slurry, 11 parts by mass of vinyl acetate and 1.63 parts by mass of sodium hydrogen carbonate were added into the bead mill apparatus, and then the circulation operation was further carried out for 60 minutes to obtain a hydrophobized microfibrillated cellulose fiber slurry.

[0122] During the circulation operation, the rotation speed of the bead mill was 2500 rpm and the peripheral speed was 12 m / s. Zirconia beads with a diameter of φ2.0 mm were used, and the filling rate was 70% (the slit gap of the bead mill at this time was 0.6 mm). Also, during the circulation operation, the slurry temperature was controlled at 40 °C with a chiller to absorb heat generated by friction.

[0123] To the obtained hydrophobized microfibrillated cellulose fiber slurry, 192 parts by mass of pure water was added per 100 parts by mass of the defibrated slurry, and after sufficiently stirring, it was put into a dehydrator and concentrated. The obtained wet cake was dispersed, stirred, and concentrated in the same amount of pure water again, and the washing operation was repeated a total of 5 times.

[0124] To the aqueous dispersion of hydrophobized microcrystalline cellulose fibers obtained (solid content: 10% by mass), 5 parts by mass of PEG20000 was added based on 100 parts by mass of the hydrophobized microcrystalline cellulose fibers, and then vacuum drying was carried out at about 40 °C using a stirrer of the revolution and rotation type (V-mini300 manufactured by EME) to obtain hydrophobized microcrystalline cellulose fiber powder.

[0125] When the properties were evaluated using the obtained hydrophobized microcrystalline cellulose fiber wet cake, the following results were obtained. DS: 0.96, diameter: 65 nm, L / D: about 450, Mw: 340,000 This hydrophobized microcrystalline cellulose fiber is referred to as CNF(0.96).

[0126] [Preparation Examples 3 to 5] After adding vinyl acetate and sodium hydrogen carbonate into the bead mill device, three kinds of hydrophobized cellulose fibers with different degrees of hydrophobicity were obtained by adjusting the circulation operation time.

[0127] CNF(0.41) DS: 0.41, diameter: 60 nm, L / D: about 470, Mw: 370,000 CNF(0.71) DS: 0.71, diameter: 64 nm, L / D: about 450, Mw: 350,000 CNF(1.29) DS: 1.29, diameter: 69 nm, L / D: about 430, Mw: 330,000

[0128] <Microcrystalline cellulose fibers: hereinafter, may be referred to as CNF(0)> [Preparation Example 6] Powder of Cellish KY-100G (manufactured by Daicel Finechem Co., Ltd.) was diluted with pure water to a concentration of 1% by mass and stirred and mixed in a uniaxial stirrer at 500 rpm for 20 minutes. Then, the water content was adjusted by filtration so that the solid content became 10% by mass to obtain an aqueous dispersion of microcrystalline cellulose fibers. Then, 5 parts by mass of PEG20000 was added to the aqueous dispersion of microcrystalline cellulose fibers so that it became 5 parts by mass based on 100 parts by mass of the microcrystalline cellulose fibers, and then vacuum drying was carried out at about 40 °C using a stirrer of the revolution and rotation type to obtain microcrystalline cellulose fiber powder CNF(0). When the properties were evaluated, the following results were obtained. CNF(0) DS: 0, diameter: 71 nm, L / D: approximately 220, Mw: 250,000

[0129] <Cellulose powder: Sometimes simply referred to as CP> The KC flock W-10MG2 powder with an average particle diameter of 10 μm (manufactured by Nippon Paper Chemicals Co., Ltd.) was diluted with pure water to a concentration of 5% by mass and stirred and mixed in a uniaxial stirrer at 500 rpm for 20 minutes. Then, the water content was adjusted by filtration to a solid content ratio of 10% by mass to obtain a cellulose powder aqueous dispersion. Subsequently, 5 parts by mass of PEG20000 was added to 100 parts by mass of the cellulose powder aqueous dispersion, and then vacuum dried at about 40 °C using a stirrer of the revolution and rotation type to obtain cellulose powder CP.

[0130] <Hydrophobized pulp: Sometimes simply referred to as Ac-CP> 1 part by mass of cotton linter pulp was stirred at room temperature for 1 hour at 500 rpm in 30 parts by mass of dimethyl sulfoxide (DMSO) using a uniaxial stirrer (DKV-1 φ125 mm dissolver manufactured by Imex Co., Ltd.). Subsequently, it was fed to a bead mill (NVM-1.5 manufactured by Imex Co., Ltd.) with a hose pump and circulated for 180 minutes with DMSO only to obtain 31 parts by mass of a defibrated slurry (defibrating step). Then, 1 part by mass of vinyl acetate and 0.49 part by mass of sodium hydrogen carbonate were added into the bead mill device, and the circulation operation was further performed for 120 minutes to obtain acetylated CP powder. When the properties were evaluated, the following results were obtained. Although some with diameters in the submicron order were confirmed, most were fibers with huge diameters ranging from 10 μm to several hundred μm, and the average diameter and L / D could not be calculated. Ac-CP DS: 1.03, Mw: 390,000

[0131] <Hindered phenol antioxidant> Irganox 1010 (manufactured by BASF Japan Ltd.) Pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]

[0132] <Nitrogen-containing compound> Melamine (reagent)

[0133] <Processing aid> Ethylenebisstearylamide Kaowax EB-FF (manufactured by Kao Corporation)

[0134] [Reference Example 1] The cylinder temperature of a co-rotating twin-screw extruder ZSK26MC (manufactured by Coperion) with an L / D of 48 having one inlet on the upstream side was set to 200 °C. As the polyacetal resin, a dry blend of 0.25 parts by mass of a hindered phenol antioxidant, 0.15 parts by mass of a nitrogen-containing compound, and 0.2 parts by mass of a processing aid with respect to 100 parts by mass of POM-H was quantitatively supplied from a loss-in-weight feeder, melt-kneaded, extruded into strands, cooled and cut to obtain a pelletized polyacetal resin composition. The downstream of the extruder was made capable of vacuum degassing to remove the air and generated gas in the extruder.

[0135] Also, as the screw configuration, two kneading disks (RKD) having a feeding function were arranged in the central part of the extruder, and immediately before the downstream vacuum degassing, one kneading disk (LKD) having a returning function was arranged in this order following one RKD.

[0136] The screw rotation speed of the extruder was set to 150 rpm, and the feeder was set so that the total extrusion discharge amount was 5 kg / h. Various tests were carried out using the obtained pellets. The results are described as Reference Example 1 in Table 1.

[0137] [Reference Examples 2 to 5] The same procedure as in Reference Example 1 was carried out except that the type of polyacetal was changed, and tests were carried out. The results are described as Reference Examples 2 to 5 in Tables 1 to 3.

[0138] [Example 1] The cylinder temperatures of a co-rotating twin-screw extruder ZSK26MC (manufactured by Coperion) with an L / D of 48, which has one feed port each on the upstream side and the central part of the extruder, were set to 200 °C. As the polyacetal resin, a dry blend of 0.25 parts by mass of a hindered phenol antioxidant, 0.15 parts by mass of a nitrogen-containing compound, and 0.2 parts by mass of a processing aid with respect to 100 parts by mass of POM-H was quantitatively supplied from a loss-in-weight feeder installed at the upstream feed port. From the loss-in-weight feeder installed at the central feed port of the extruder, CNF (0.95) as fine cellulose fibers was quantitatively supplied so that the amount of fine cellulose fibers was 10% by mass in the composition. Melt-kneading was carried out, extruded into strands, cooled and cut to obtain a pelletized polyacetal resin composition. The downstream of the extruder was made capable of vacuum degassing to remove the air and generated gases in the extruder.

[0139] Also, as the screw configuration, three RKDs were arranged upstream of the central feed port of the extruder, and a design was adopted in which three RKDs and one LKD were arranged in this order immediately before vacuum degassing on the downstream side. At this time, the screw rotation speed of the extruder was set to 150 rpm, and the feeder was set so that the total extrusion discharge amount was 5 kg / hour. Various tests were carried out using the obtained pellets. The results are described as Example 1 in Table 1.

[0140] [Comparative Example 1] As the cellulose, hydrophobized pulp (Ac-CP) was used instead of fine cellulose fibers. Furthermore, since it was necessary to fibrillate the cellulose in the extruder, the supply position of the hydrophobized pulp was changed to the upstream feed port of the extruder for the purpose of applying strong shear, and extrusion processing was carried out and evaluated in the same manner as in Example 1 except for this. The results are described in Table 1.

[0141] [Examples 2 to 5] Except that the type of polyacetal and cellulose were changed as described in Table 1, everything was carried out in the same manner as in Example 1, and various tests were carried out using the obtained pellets. The results are described in Table 1.

[0142] [Comparative Examples 2 to 5] Except for changing the types of polyacetal and cellulose as described in Table 1, all were carried out in the same manner as in Comparative Example 1. Using the obtained pellets, various tests were conducted. The results are described in Table 1.

[0143]

Table 1

[0144] [Examples 6 - 10] Except for changing the polyacetal to POM - C3 and the cellulose as described in Table 2 respectively, all were carried out in the same manner as in Example 1. Using the obtained pellets, various tests were conducted. The results are described in Table 2.

[0145] [Comparative Examples 6 - 7] Except for changing the polyacetal to POM - C3 and the cellulose as described in Table 2 respectively, all were carried out in the same manner as in Comparative Example 1. Using the obtained pellets, various tests were conducted. The results are described in Table 2.

[0146]

Table 2

[0147] [Example 11] Except for changing the polyacetal to an equal - amount blend of POM - C1 and POM - BC and the cellulose as described in Table 3, all were carried out in the same manner as in Example 1. Using the obtained pellets, various tests were conducted. The results are described in Table 3.

[0148] [Comparative Examples 8 - 14] Except for changing the polyacetal to an equal - amount blend of POM - C1 and POM - BC, and changing the compounding ratios of the antioxidant, nitrogen - containing compound, processing aid, and the cellulose as described in Table 3 respectively, all were carried out in the same manner as in Example 1. Using the obtained pellets, various tests were conducted. The results are described in Table 3.

[0149] [Comparative Examples 15 - 16] The polyacetal was changed to an equal blend of POM-C1 and POM-BC, and various tests were carried out using the obtained pellets, except that the compounding ratios of the antioxidant, nitrogen-containing compound, processing aid, and cellulose were changed as described in Table 3, respectively, and all were carried out in the same manner as in Comparative Example 1. The results are shown in Table 3.

[0150]

Table 3

Industrial Applicability

[0151] The composition containing a polyacetal resin and fine cellulose fibers provided by one aspect of the present invention can be suitably applied to a wide range of uses, particularly to high-load uses placed in a high-temperature environment.

Claims

1. (a) 100 parts by mass of a polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 10 to 1000 nm, (c) 0.01 to 3 parts by mass of a hindered phenol antioxidant, (d) 0.01 to 3 parts by mass of at least one nitrogen-containing compound selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides, and (e) 0.01 to 3 parts by mass of at least one processing aid selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds, A polyacetal resin composition containing the same.

2. (a) The polyacetal resin is A copolymer of 99.9 to 90% by mass of trioxane and 0.1 to 10% by mass of a monofunctional cyclic ether, The polyacetal resin composition according to claim 1, which has an alkoxy end group and a hydroxyalkoxy end group having at least 2 carbon atoms in a total proportion of 70 to 99 mol% of all end groups.

3. The polyacetal resin composition according to claim 1 or 2, wherein (b) the fine cellulose fibers are hydrophobized fine cellulose fibers.

4. The polyacetal resin composition according to claim 3, having a degree of hydrophobicity (DS) of 0.5 to 1.

5.

5. The polyacetal resin composition according to any one of claims 1 to 4, having a storage elastic modulus at 120 ° C of 1,000 MPa or more and 3,000 MPa or less.

6. The polyacetal resin composition according to any one of claims 1 to 5, having a component composition in which the ratio of the storage elastic modulus at 120 ° C to the storage elastic modulus at 23 ° C when 10% by mass of fine cellulose fibers are blended is 0.4 or more and 1.5 or less.

7. The polyacetal resin composition according to any one of claims 1 to 6, wherein (a) the melt index of the polyacetal resin measured at 190 ° C and 2.16 kgf in accordance with ASTM-D1238 is 2 to 25 g / 10 min.

8. (a) 100 parts by mass of a polyacetal resin, (b) 10 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 10 to 1000 nm, (c) 0.01 to 3 parts by mass of a hindered phenol antioxidant, (d) 0.01 to 3 parts by mass of at least one nitrogen-containing compound selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides, and (e) 0.01 to 3 parts by mass of at least one processing aid selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds, A method for producing a polyacetal resin composition, comprising melt-kneading the above components.

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