Polyacetal resin composition

Abstract

The present invention provides: a polyacetal resin composition that achieves a highly dispersed state of cellulose in a polyacetal resin, and that achieves, at a high level, both high temperature rigidity and toughness when being under a load; and a method for producing same.　This polyacetal resin composition contains: 100 parts by mass of a polyacetal resin (a); 1-150 parts by mass of fine cellulose fibers (b) having a fiber diameter of 2-1000 nm; and 0.1-100 parts by mass of a polyethylene glycol (c). An ethylene ratio R (%) which is the ratio of the number of oxyethylene units in the polyacetal resin (a) with respect to the total number of oxymethylene units and oxyethylene units in the polyacetal resin (a), and an oxyethylene repeating unit number n of the polyethylene glycol (c) satisfy the relationship of formula: (R+0.5) / 0.015 ≤ n ≤ (R+10) / 0.015.

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, sliding properties, 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, Patent Document 4 describes a resin composition composed of modified pulp and a thermoplastic resin, and Patent Document 5 describes a cellulose nanofiber resin composition containing cellulose nanofibers, a surface treatment agent having a specific range of HLB values, and a thermoplastic resin which may be a polyacetal resin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] In the compositions containing cellulose as a reinforcing material as described in Patent Documents 2 to 4, although the effect of improving rigidity at room temperature can be obtained, due mainly to the large size of cellulose itself, the effect of improving rigidity at high temperatures is poor, and there are problems such as insufficient toughness being obtained because cracks mainly caused by huge cellulose occur under load. According to the technique described in Patent Document 5, by using a surface treatment agent that may have a hydrophilic segment and a hydrophobic segment, the dispersibility of cellulose nanofibers in a thermoplastic resin can be improved, and it is considered that good rigidity of the resin composition can be exhibited. However, even with this technique, there is still room for improvement in suppressing the decrease in rigidity under high-temperature conditions and the decrease in toughness under load (particularly brittle fracture) in the polyacetal resin composition.

[0006] One aspect of the present invention is to solve the above problems, achieve a highly dispersed state of cellulose in a polyacetal resin, and provide a polyacetal resin composition in which rigidity under high-temperature conditions (also referred to as high-temperature rigidity in the present disclosure) and toughness under load are highly compatible, and a method for producing the same. [Means for Solving the Problems]

[0007] The present disclosure includes the following items. [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 2 to 1000 nm, and (c) 0.1 to 100 parts by mass of polyethylene glycol, containing The ethylene ratio R (%) of the polyacetal resin, which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of the polyethylene glycol, are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 A polyacetal resin composition that satisfies the relationship. [2] The polyacetal resin composition according to item 1 above, wherein the ethylene ratio R is 0.3% to 1.8%. [3] (b) The polyacetal resin composition according to item 1 or 2 above, wherein the fine cellulose fibers are hydrophobic fine cellulose fibers. [4] The polyacetal resin composition according to item 3, wherein the average degree of substitution (DS) of the hydrophobic fine cellulose fibers is 0.5 to 1.5. [5] (c) A polyacetal resin composition according to any of items 1 to 4 above, wherein the number of oxyethylene repeating units of polyethylene glycol is 80 to 700. [6] A polyacetal resin composition according to any of items 1 to 5 above, wherein the storage modulus at 120°C is 1,000 MPa or more. [7] A polyacetal resin composition according to any one of the above items 1 to 6, 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 fine cellulose fibers is 0.4 or more. [8] (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers with a fiber diameter of 2 to 1000 nm, (c) Polyethylene glycol 0.1 to 100 parts by mass, (d) 0.01 to 3 parts by mass of a hindered phenol antioxidant, and (e) 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. A method for producing a polyacetal resin composition, comprising melting and kneading, The ethylene ratio R (%) of the polyacetal resin, which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of the polyethylene glycol, are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 A method that satisfies the relationship. [9] A method for producing a molded article, comprising a molding step of molding a molding component which is a polyacetal resin composition as described in any of items 1 to 7 above.

[10] The method according to item 9, wherein the molding component includes recycled material which is a molten product of the molded product.

[11] The molded article is composed of a plurality of members having the same or different compositions, In the molding process, the molding component is molded to produce each of the plurality of members, The method according to item 10, wherein the polyacetal resin composition for producing one or more of the plurality of members includes a recycled material which is one or more molten products of the plurality of members.

[12] The method according to item 10 or 11, wherein the content of the recycled material in the molding component is 5% by mass to 100% by mass.

[13] An article having a first member and a second member configured to be slidable from each other, The first member is composed of a first resin composition, The aforementioned second member is composed of a second resin composition, Each of the first resin composition and the second resin composition is (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, and (c) Polyethylene glycol 0.1 to 100 parts by mass, Includes, An article in which the ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition to the content of fine cellulose fibers in the first resin composition (A1) is 0.5 or more and 1 or less.

[14] The article according to item 13, wherein the ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition to the content of fine cellulose fibers in the first resin composition (A1) is 1.

[15] The article according to item 14, wherein the first resin composition and the second resin composition have the same composition as each other.

[16] The ethylene ratio R (%) of the polyacetal resin (a), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of the polyethylene glycol (c) are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 An item that satisfies the relationship described in any of the above items 13 to 15.

[17] The article according to any one of items 13 to 16 above, wherein the first member and the second member are gears, and the article is a gear system.

[18] The article according to any of items 13 to 16 above, wherein the first member and the second member are bearings and the article is a damper.

[19] An article according to any one of items 13 to 18, wherein the first member and the second member are configured to slide directly against each other.

[20] A method for manufacturing an article as described in any of items 13 to 19 above, A step of obtaining the first member by molding a first resin composition, which is a molten mixture of a first mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol, and A step of obtaining the second member by molding a second resin composition, which is a molten mixture of a second mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol. Includes, A method wherein the first mixed component and / or the second mixed component includes recycled material which is a molten product of the first member and / or the second member.

[21] A method for manufacturing a molded article, The process includes a step of molding a resin composition, which is a molten mixture of a mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol, to obtain a molded product. A method wherein the mixed component includes recycled material which is a molten product of the first and / or second component of the article described in any of items 13 to 19 above.

[22] The recycled material is the molten material of the first member and the second member, The method according to item 21, wherein the first resin composition and the second resin composition have the same composition as each other.

[23] The method according to item 21 or 22, wherein the mixed component has the same composition as the first resin composition and / or the second resin composition.

[24] A molded article obtained by molding a polyacetal resin composition as described in any of items 1 to 7 above.

[25] A molded product as described in item 24 above, which is a deformed extruded product.

[26] A method for manufacturing a deformed extruded product, A method comprising the step of extruding a polyacetal resin composition described in any of the above items 1 to 7 into a deformed shape.

[27] A 3D printing material comprising any of the polyacetal resin compositions described in items 1 to 7 above.

[28] A 3D printing material as described in item 27, having the form of a filament or powder.

[29] A molded object made by 3D printing using a polyacetal resin composition described in any of items 1 to 7 above or a 3D printing material described in item 27 or 28 above.

[30] A method for manufacturing a molded object, A method comprising the step of fabricating a polyacetal resin composition described in any of items 1 to 7 above, or a 3D printing material described in item 27 or 28 above, using a 3D printer.

[31] A cellulose fiber-containing powder for polyacetal resin compositions, The aforementioned cellulose fiber-containing powder is (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, (c) Polyethylene glycol Includes, The polyethylene glycol in (c) is given by the following formula: the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of the polyethylene glycol in (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 A polyethylene glycol containing cellulose fibers that satisfies the following relationship.

[32] A method for producing a cellulose fiber-containing powder for a polyacetal resin composition, The aforementioned cellulose fiber-containing powder is (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, (c) Polyethylene glycol Includes, The method includes a mixing step of mixing (b) fine cellulose fibers and (c) polyethylene glycol to obtain a cellulose fiber-containing powder, The polyethylene glycol in (c) is given by the following formula: the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of the polyethylene glycol in (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 A method for selecting a method that satisfies the given relationship.

[33] A method for producing a polyacetal resin composition, (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, (c) Polyethylene glycol A powder preparation step to obtain a cellulose fiber-containing powder containing, A resin composition preparation step in which the cellulose fiber-containing powder and (a) polyacetal resin are mixed to obtain a polyacetal resin composition, Includes, The ethylene ratio R (%) of the polyacetal resin (a) is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units in the polyacetal resin (a), and the number of oxyethylene repeating units n of the polyethylene glycol (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 A method for producing a polyacetal resin composition, which is selected to satisfy the relationship. [Effects of the Invention]

[0008] According to one aspect of the present invention, a polyacetal resin composition and a method for producing the same can be provided, which achieve a highly dispersed state of cellulose in the polyacetal resin and exhibit a high degree of compatibility between high-temperature rigidity and toughness under load. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the die cross-sectional shape of the single-screw extruder used in Examples 28-30. [Modes for carrying out the invention]

[0010] The following describes exemplary embodiments of the present invention (hereinafter also referred to as "these embodiments"), but the present invention is not limited to these embodiments.

[0011] ≪Polyacetal resin composition≫ The polyacetal resin composition of this embodiment contains (a) polyacetal resin, (b) fine cellulose fibers, and (c) polyethylene glycol. In one embodiment, the polyacetal resin composition contains (d) a hindered phenol antioxidant. In one embodiment, the polyacetal resin composition contains (e) a nitrogen-containing compound. In one embodiment, the fiber diameter of (b) the fine cellulose fibers is 2 to 1000 nm (in one embodiment, 10 to 1000 nm). In one embodiment, (e) the nitrogen-containing compound is at least one selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides.

[0012] For example, according to the technology described in Patent Document 5 mentioned above, it is possible to improve the dispersibility of fine cellulose fibers in polyacetal resin to some extent by using a surface treatment agent, and it is thought that the polyacetal resin composition may have good rigidity at room temperature. However, the inventors' studies have shown that in order to suppress the decrease in rigidity under high temperature conditions and ensure good toughness even under load in the polyacetal resin composition, it is necessary to improve the surface treatment agent to a more appropriate one. The inventors further investigated and found that, in order to highly disperse fine cellulose fibers in polyacetal resin in particular among thermoplastic resins, a surface treatment agent without hydrophobic segments is advantageous, and in particular, the use of polyethylene glycol is advantageous in achieving both the prevention of rigidity decrease under high temperature conditions and the prevention of brittle fracture under load. The preferred embodiments of the polyacetal resin composition of this embodiment will be described in detail below.

[0013] (a) Polyacetal resin (a) Polyacetal resins are polymer compounds whose main constituent unit is the oxymethylene group (-OCH2-), and typical examples include polyacetal homopolymers consisting substantially only of repeating oxymethylene units, and polyacetal copolymers containing oxymethylene units and other monomer units. (a) Polyacetal resins also include copolymers in which branched structures and / or crosslinked structures are introduced by copolymerizing branching-forming components and / or crosslinking-forming components, block copolymers or graft copolymers having polymeric parts consisting of repeating oxymethylene groups and other polymeric parts.

[0014] Generally, polyacetal homopolymers are produced by polymerization of anhydrous formaldehyde and one or more monomers selected from formaldehyde cyclic oligomers such as trioxane (a cyclic trimer of formaldehyde) and tetraoxane (a cyclic tetramer of formaldehyde). Typically, the polymerization ends are esterified to stabilize them against thermal decomposition.

[0015] Furthermore, polyacetal copolymers are generally produced by copolymerizing a cyclic oligomer of formaldehyde represented by the general formula (CH2O)n [wherein n is an integer of 3 or more] (e.g., the trioxane mentioned above) with a comonomer such as a cyclic ether and / or cyclic formal (e.g., cyclic formals of glycols or diglycols such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, and 1,4-butanediol formal). Typically, unstable terminal parts are removed by hydrolysis, stabilizing the copolymer against thermal decomposition.

[0016] Furthermore, examples of polyacetal copolymers include branched polyacetal copolymers obtained by copolymerizing a formaldehyde monomer and / or cyclic oligomer with a monofunctional glycidyl ether; and crosslinked polyacetal copolymers obtained by copolymerizing a formaldehyde monomer and / or cyclic oligomer with a polyfunctional glycidyl ether.

[0017] Examples of polyacetal resins include polyacetal homopolymers having a blocking component, obtained by polymerizing a formaldehyde monomer and / or cyclic oligomer in the presence of a compound having a functional group such as a hydroxyl group at both or one end, for example, a polyacetal homopolymer having a blocking component, obtained by copolymerizing a formaldehyde monomer and / or cyclic oligomer with a cyclic ether and / or cyclic formal in the presence of a compound having a functional group such as a hydroxyl group at both or one end, for example, a polyacetal copolymer having a blocking component, obtained by copolymerizing a formaldehyde monomer and / or cyclic oligomer with a cyclic ether and / or cyclic formal in the presence of a compound having a functional group such as a hydroxyl group at both or one end.

[0018] (a) The polyacetal resin of this embodiment is, in one embodiment, a polyacetal copolymer as described above, from the viewpoint of (c) exhibiting the effects of polyethylene glycol well and (b) improving the dispersibility of fine cellulose fibers, and in one embodiment, the constituent units are a polyacetal copolymer (hereinafter also referred to as an oxyethylene unit-containing copolymer) containing oxymethylene units (-OCH2-) and oxyethylene units (-OC2H5-). The oxyethylene unit-containing copolymer can be produced by copolymerizing a cyclic oligomer of formaldehyde represented by the general formula (CH2O)n [wherein n is an integer of 3 or more] (for example, the trioxane described above), ethylene glycol or its cyclic formal, and optionally other components. The oxyethylene unit-containing copolymer has particularly good affinity with (c) polyethylene glycol in this embodiment due to the contribution of its oxyethylene units, and is therefore particularly advantageous in that it improves the affinity between (a) polyacetal resin and (b) fine cellulose fibers and allows for high dispersion of (b) fine cellulose fibers in (a) polyacetal resin.

[0019] (a) The ratio of the total number of oxymethylene units and oxyethylene units to the total number of repeating units of the polyacetal resin is, in one embodiment, 90% or more, or 95% or more, and is typically 100%.

[0020] In an oxyethylene unit-containing copolymer, the ratio of oxyethylene units to the total number of oxymethylene units represented by the general formula (CH2O) and oxyethylene units represented by the general formula (CH2CH2O) (hereinafter also referred to as the ethylene ratio) is, (c) from the viewpoint of obtaining the effects of polyethylene glycol well and from the viewpoint of the dimensional stability of the resin composition, preferably at a lower limit of 0.3% or 0.4%, and from the viewpoint of the heat resistance and mechanical strength of the resin composition, preferably at an upper limit of 1.8%, 1.7%, 1.6%, or 1.5%.

[0021] (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 this copolymer, the total of alkoxy end groups and hydroxyalkoxy end groups having at least two carbon atoms is preferably 70 to 99 mol% of the total end groups. The number of end groups can be measured using known methods (specifically infrared absorption spectroscopy or nuclear magnetic resonance spectroscopy, more specifically the methods described in Japanese Patent Publication No. 5-98028, Japanese Patent Publication No. 2001-11143, etc.).

[0022] Furthermore, the melt mass flow rate (MFR) of (a) polyacetal resin, measured under conditions of 190°C and a load of 2.16 kgf (21.2 N) in accordance with ASTM-D1238 (ISO1133), has a lower limit of preferably 2 g / 10 min, 4 g / 10 min, or 7 g / 10 min, and an upper limit of preferably 25 g / 10 min, 20 g / 10 min, or 18 g / 10 min. By keeping the MFR within the above range, the reinforcing effect of fine cellulose fibers can be maximized while ensuring molding fluidity.

[0023] <(b) Fine cellulose fibers> (b) Fine cellulose fibers may be obtained from various cellulose fiber raw materials selected from natural cellulose and regenerated cellulose. In one embodiment, the cellulose fiber raw material may be pre-modified with a modifying agent as exemplified in the [Modifying Agents] section below.

[0024] Fine cellulose fibers are obtained by mechanically micronizing cellulose fiber raw materials using a dry or wet process. This micronization process may be performed using a single apparatus once or more times, or using multiple apparatuses, each performed once or more times. The equipment used for micronization is not particularly limited, but examples include high-speed rotary, colloidal mill, high-pressure, roll mill, and ultrasonic types of equipment. High-pressure or ultra-high-pressure homogenizers, refiners, beaters, PFI mills, kneaders, dispersers, high-speed defibrators, grinders (stone mill type pulverizers), ball mills, vibratory mills, bead mills, conical refiners, disc refiners, single-screw, twin-screw or multi-screw kneaders / extruders, and homomixers under high-speed rotation. These equipment can be used to interact with pulp fibers using metal or blades around a rotating shaft, or through friction between pulp fibers.

[0025] In one embodiment, the fiber diameter of the fine cellulose fibers is 2 nm or more, or 4 nm or more, or 5 nm or more, or 10 nm or more, or 20 nm or more, or 30 nm or more, or 40 nm or more, or 50 nm or more, in that the crystallinity of the cellulose is well maintained. On the other hand, in one embodiment, the upper limit is 1000 nm or less, or 800 nm or less, or 500 nm or less, or 300 nm or less, or 200 nm or less, or 100 nm or less, in that that the effect as a filler is good.

[0026] The fiber length / fiber diameter (L / D) of the fine cellulose fibers is preferably 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more, from the viewpoint of improving the mechanical properties of the resin composition containing the fine cellulose fibers, especially injection molded products, with a smaller amount of fine cellulose fibers. There is no particular upper limit, but from the viewpoint of handling, it is preferably 5000 or less.

[0027] In this disclosure, the fiber diameter, fiber length, and L / D ratio of fine cellulose fibers are determined by diluting an aqueous dispersion of fine cellulose fibers to 0.001-0.1% by mass with a water-soluble solvent (e.g., water, ethanol, tert-butanol, etc.), dispersing the dispersion using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18") under the following conditions: rotation speed 25,000 rpm for 5 minutes, casting the dispersion onto a hydrophilic substrate (e.g., mica), air-drying the resulting sample, and measuring it using a high-resolution scanning electron microscope (SEM) or atomic force microscope (AFM). Specifically, the length (L) and diameter (D) of 100 randomly selected fibrous materials are measured in an observation field adjusted to the magnification so that at least 100 fibrous materials can be observed, and the ratio (L / D) is calculated. For the fine cellulose fibers, the number average values ​​of length (L), diameter (D), and ratio (L / D) are calculated.

[0028] Cellulose has several known crystalline polymorphs, including type I, type II, type III, and type IV. Of these, types I and II are particularly common, while types III and IV, although obtained on a laboratory scale, are not commonly used on an industrial scale. Cellulose microfibers with crystalline polymorphism of type I or type II are preferable because they exhibit high mechanical properties (strength and dimensional stability) and result in high strength and dimensional stability of the resin composition when the cellulose microfibers are dispersed in a resin.

[0029] From the viewpoint of obtaining good mechanical properties, the degree of crystallinity of the fine cellulose fibers in this embodiment is preferably 55% or more, or 60% or more, or 65% or more, or 70% or more, or 75% or more, or 80% or more. Since a higher degree of crystallinity of the fine cellulose fibers tends to be preferable, there is no particular upper limit, but from a production viewpoint, 99% is a preferred upper limit.

[0030] The degree of crystallinity, when the fine cellulose fibers are cellulose type I crystals (derived from natural cellulose), can be determined by the Segal method using the following formula, based on the diffraction pattern (2θ / deg. of 10-30) obtained by measuring the sample by wide-angle X-ray diffraction. Crystallinity (%)=[I (200)-I (amorphous) ] / I (200) ×100 I (200) :Diffraction peak intensity at the 200 plane (2θ=22.5°) in cellulose type I crystals I (amorphous) : The halo peak intensity due to amorphous material in type I cellulose crystals, specifically the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°).

[0031] Furthermore, if the fine cellulose fibers are cellulose type II crystals (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, based on the absolute peak intensity h0 at 2θ=12.6°, which is attributed to the (110) plane peak of the cellulose type II crystal, and the peak intensity h1 from the baseline at this interplanar spacing. Crystallinity (%) = (h0-h1) / h0 ×100

[0032] The degree of polymerization (DP) of fine cellulose fibers is preferably 100 or higher, more preferably 150 or higher, in terms of good tensile breaking strength and elastic modulus, and preferably 12000 or lower, more preferably 8000 or lower, from the viewpoint of availability. The degree of polymerization is determined by first finding the intrinsic viscosity (JIS P 8215:1998) of a dilute cellulose solution using a copper ethylenediamine solution, and then utilizing the relationship between the intrinsic viscosity of cellulose and the degree of polymerization DP as shown in the following formula. Intrinsic viscosity [η]=K×DPa Here, K and a are constants determined by the type of polymer; in the case of cellulose, K is 5.7 × 10⁻⁶. -3 , a is 1.

[0033] The weight-average molecular weight (Mw) of the fine cellulose fibers is preferably 100,000 or more, and more preferably 200,000 or more. The ratio of the weight-average molecular weight to the number-average molecular weight (Mn) of the fine cellulose fibers (Mw / Mn) is preferably 6 or less, and more preferably 5.4 or less. A larger weight-average molecular weight means fewer end groups in the cellulose molecule. Also, since the ratio of the weight-average molecular weight to the number-average molecular weight (Mw / Mn) represents the width of the molecular weight distribution, a smaller Mw / Mn means fewer end groups in the cellulose molecule. Since the end groups of cellulose molecules are the starting points for thermal decomposition, if the weight-average molecular weight of the cellulose molecules in the fine cellulose fibers is large, and at the same time the width of the molecular weight distribution is narrow, then particularly heat-resistant fine cellulose fibers can be obtained. From the viewpoint of the availability of cellulose raw materials, the weight-average molecular weight (Mw) of the cellulose fibers may be, for example, 600,000 or less, or 500,000 or less. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw / Mn) may be, for example, 1.5 or higher, or 2 or higher, from the viewpoint of ease of manufacturing cellulose fibers. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. Mw / Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw / Mn appropriate for the purpose, and by appropriately performing physical and / or chemical treatments on the cellulose raw material within an appropriate range. Examples of physical treatments for controlling both Mw and Mw / Mn include dry or wet grinding using microfrudizers, ball mills, disc mills, etc., and applying mechanical forces such as impact, shear, shear, and friction using grinders, homomixers, high-pressure homogenizers, ultrasonic devices, etc. Examples of chemical treatments include pulverization, bleaching, acid treatment, and regenerative celluloseization.

[0034] Here, the weight-average molecular weight and number-average molecular weight of the fine cellulose fibers are values ​​obtained by dissolving the fine cellulose fibers in N,N-dimethylacetamide to which lithium chloride has been added, and then determining them by gel permeation chromatography using N,N-dimethylacetamide as the solvent.

[0035] [Modifying agent] The fine cellulose fibers may be chemically modified fine cellulose fibers that have been chemically modified with a modifying agent. Suitable modifying agents include compounds that react with the hydroxyl groups of cellulose, such as inorganic esterifying agents (nitrate esters, sulfate esters, phosphate esters, silicate esters, borate esters, etc.), organic esterifying agents (acetylating agents, propionylating agents, etc.), etherifying agents (methyl ether, hydroxyethyl ether, hydroxypropyl ether, hydroxybutyl ether, carboxymethyl ether, cyanoethyl ether, etc.), silylating agents, and TEMPO oxidation catalysts (which oxidize the primary hydroxyl groups of cellulose). In a preferred embodiment, the chemical modification is esterification, specifically esterification (acylation) using an organic esterifying agent, and particularly preferably acetylation. Suitable organic esterifying agents include acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids. A preferred chemical modification is hydrophobization of the fine cellulose fibers, particularly hydrophobization by hydrophobizing the surface of the fine cellulose fibers. A suitable example of hydrophobization is acetylation.

[0036] The degree of modification of the chemically modified microfibrillated cellulose fibers (more specifically, in the case of hydrophobization such as acylation, the degree of hydrophobization) 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 aspect, from the viewpoint of maintaining good affinity between the polyacetal resin and the microfibrillated cellulose fibers and thermal stability during processing, DS is preferably 0.1 or more, or 0.2 or more, or 0.3 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, or 0.75 or more, and in terms of high affinity between the polyacetal resin and the microfibrillated cellulose fibers and high high-temperature rigidity of the resin composition, it 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.

[0037] When the chemical modification is acylation, the acyl substitution degree (DS) of the esterified microfibrillated 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 skeleton from the reflection-type infrared absorption spectrum of the esterified microfibrillated 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 skeleton chain appears at 1030 cm -1 The DS of the esterified microfibrillated cellulose fibers is defined by the correlation graph between the DS obtained from the solid NMR measurement of the esterified microfibrillated cellulose fibers described later and the modification rate (IR index) defined by 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 C-O of the cellulose skeleton chain. By using the calibration curve Degree of substitution DS = 4.13 × IR index it can be determined. The IR index is expressed by 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 C-O stretching vibration of the cellulose skeleton chain). However, at 1900 cm -1 and 1500 cm respectively-1 The line connecting them is 800cm -1 and 1500cm -1 The line connecting these points is used as the baseline, and this value represents the absorbance when this baseline is set to 0.

[0038] The method for calculating the DS of esterified fine cellulose fibers using solid-state NMR is as follows: For freeze-pulverized esterified fine cellulose fibers... 13 The following formula can be used to determine the signal intensity (Inf) from a single carbon atom derived from the modifying group, based on the total area intensity (Inp) of the signals attributed to carbon atoms C1-C6 derived from the pyranose ring of cellulose, which appear in the range of 50 ppm to 110 ppm. DS = (Inf) × 6 / (Inp) For example, if the modifying group is an acetyl group, you can use the 23 ppm signal assigned to -CH3.

[0039] Use 13 The conditions for 13C solid-state NMR measurement are as follows, for example: Equipment:Bruker Biospin Avance500WB Frequency: 125.77MHz Measurement method: DD / MAS method Waiting time: 75 seconds NMR sample tube: 4mmφ Total number of times: 640 (approximately 14 hours) MAS: 14,500Hz Chemical shift reference: Glycine (External reference: 176.03 ppm)

[0040] The amount of (b) fine cellulose fibers in the polyacetal resin composition is, in one embodiment, 1 to 150 parts by mass per 100 parts by mass of (a) polyacetal resin. The above amount is preferably 2 parts by mass or more, or 4 parts by mass or more, or 5 parts by mass or more, in terms of maintaining high high-temperature rigidity of the resin composition, and 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, in terms of improving the toughness of the resin composition under load (e.g., under tension).

[0041] <(c) Polyethylene glycol> The polyacetal resin composition of this embodiment contains (c) polyethylene glycol. (c) polyethylene glycol is a substance obtained by polymerizing ethylene oxide and ensures good affinity between the polyacetal resin, particularly the polyacetal resin having oxyethylene units, and the fine cellulose fibers.

[0042] (c) The number of oxyethylene repeating units n of polyethylene glycol is preferably 80 or more, or 90 or more, or 100 or more, or 110 or more, or 120 or more, or 130 or more, in terms of increasing the rigidity of the polyacetal resin composition, especially the high-temperature rigidity, and preferably 700 or less, or 650 or less, or 600 or less, or 550 or less, or 500 or less, or 450 or less, or 400 or less, or 350 or less, in terms of processability.

[0043] In one embodiment, (a) the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units in the polyacetal resin, and (c) the number of oxyethylene repeating units n in polyethylene glycol are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 The above relationship is satisfied. When the above relationship is satisfied, the high affinity between (a) polyacetal resin and (c) polyethylene glycol contributes to the improvement of the affinity between (c) polyethylene glycol and (a) polyacetal resin and (b) fine cellulose fibers, and therefore high dispersion of (b) fine cellulose fibers in (a) polyacetal resin is achieved, and both high high temperature rigidity and high toughness under load are achieved for the polyacetal resin composition. The above n is more preferably (R+0.6) / 0.015 or more, or (R+0.7) / 0.015 or more, and more preferably (R+9) / 0.015 or less, or (R+8) / 0.015 or less, or (R+7) / 0.015 or less, or (R+6) / 0.015 or less, or (R+5) / 0.015 or less.

[0044] In order to achieve good rigidity in a polyacetal resin composition, it is desirable that fine cellulose fibers are well dispersed in the resin. The viscosity of the mixed system during the production of the polyacetal resin composition is advantageous to be moderately high from the viewpoint of applying an appropriate shear force to the fine cellulose fibers and dispersing them well in the resin. On the other hand, from the viewpoint of suppressing the decomposition of the polymer in the resin composition by shear force, it is advantageous that the viscosity is not excessively high. (a) In polyacetal resin, the melting point tends to decrease as the ethylene ratio R increases (and therefore the melt viscosity at a certain temperature decreases). Also, (c) in polyethylene glycol, the viscosity tends to increase as the number of oxyethylene repeating units n increases. Therefore, when the ethylene ratio R of (a) polyacetal resin is relatively small (i.e., the melting point is relatively high), it is preferable that the number of oxyethylene repeating units n of (c) polyethylene glycol is also relatively small from the viewpoint of suppressing polymer decomposition due to viscosity increase. On the other hand, (a) when the ethylene ratio R of the polyacetal resin is relatively large (i.e., the melting point is relatively low), it is preferable that (c) the number of oxyethylene repeating units n of polyethylene glycol is also relatively large, from the viewpoint of applying shear force to the fine cellulose fibers. Therefore, it is advantageous that the ethylene ratio R and the number of oxyethylene repeating units n satisfy the above formula, as this allows for easy control of the viscosity of the mixed system during the production of the polyacetal resin composition to a preferred range.

[0045] The amount of (c) polyethylene glycol in the polyacetal resin composition is, in one embodiment, 0.1 to 100 parts by mass per 100 parts by mass of (a) polyacetal resin. The above amount is preferably 1 part by mass or more, or 2 parts by mass or more, or 3 parts by mass or more, or 4 parts by mass or more, or 5 parts by mass or more, in terms of maintaining high high-temperature rigidity of the polyacetal resin composition, and preferably 80 parts by mass or less, or 50 parts by mass or less, or 20 parts by mass or less, or 10 parts by mass or less, in terms of improving toughness under load (e.g., under tension).

[0046] (d) Hindered phenol antioxidants In one embodiment, the polyacetal resin composition of this embodiment contains (d) a hindered phenol antioxidant. The (d) hindered phenol antioxidant contributes to (a) the thermal stability of the polyacetal resin.

[0047] Examples of hindered phenol antioxidants include n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, n-octadecyl-3-(3'-methyl-5'-t-butyl-4'-hydroxyphenyl)-propionate, n-tetradecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 1,4-butanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], and triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl) Examples include [(nyl)-propionate], pentaerythritol tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,2-bis[3-(4-hydroxy-3,5-di-t-butylphenyl)propionyl]hydrazine, N,N'-hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propanamide], 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 4-[[4,6-bis(octylthio)-1,3,5-triazine-2-yl]amino]-2,6-di-t-butylphenol.

[0048] Preferably, these are triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate], pentaerythritol tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,2-bis[3-(4-hydroxy-3,5-di-t-butylphenyl)propionyl]hydrazine, N,N'-hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propanamide], and among these, nitrogen-containing hindered phenol-based antioxidants are particularly preferred from the viewpoint of (a) improving the thermal stability of the polyacetal resin.

[0049] Furthermore, from the above viewpoint, it is preferable that the nitrogen-containing hindered phenol antioxidant contains a hydrazine structure. Based on these considerations, 1,2-bis[3-(4-hydroxy-3,5-di-t-butylphenyl)propionyl]hydrazine is more preferable as the nitrogen-containing hindered phenol antioxidant, from the viewpoint of providing superior mold deposit properties and molded product appearance during long-term continuous molding, and further reducing color difference changes after retention in the molding machine.

[0050] From the viewpoint of further improving the thermal stability of the polyacetal resin composition, the melting point of the hindered phenol antioxidant is preferably 50°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, even more preferably 225°C or higher, and preferably 300°C or lower, and more preferably 250°C or lower. In this disclosure, the melting point is the value measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min.

[0051] The amount of (d) hindered phenol antioxidant in the polyacetal resin composition of this embodiment is preferably 0.01 to 3 parts by mass, more preferably 0.02 to 2 parts by mass, and even more preferably 0.03 to 1.5 parts by mass per 100 parts by mass of (a) polyacetal resin. Having the amount of (d) hindered phenol antioxidant within the above range is advantageous from the viewpoint of obtaining a polyacetal resin composition with excellent moldability.

[0052] (e) Nitrogen-containing compounds The polyacetal resin composition of this embodiment includes (e) a nitrogen-containing compound in one embodiment. The (e) nitrogen-containing compound contributes to maintaining the color tone and thermal stability of the (a) polyacetal resin, suppressing odors during processing, and improving mechanical properties. In one embodiment, the (e) nitrogen-containing compound includes aminotriazine compounds, guanamine compounds, urea derivatives, hydrazide compounds, amide compounds (e.g., acrylamide polymers), polyamides, etc., which can be used individually or in combination of two or more. In a preferred embodiment, the (e) nitrogen-containing compound is at least one selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides.

[0053] Examples of the above aminotriazine compounds include melamine, 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, N-butylmelamine, N-phenylmelamine, N,N-diphenylmelamine, N,N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), acetoguanamine (2,4-diamino-6-methyl-sym-triazine), and 2,4-diamino-6-butyl-sym-triazine.

[0054] Examples of the above-mentioned guanamine compounds include aliphatic guanamine compounds (monoguanamines, alkylenebisguanamines, etc.), alicyclic guanamine compounds (monoguanamines, etc.), aromatic guanamine compounds [for example, monoguanamines (benzoguanamine and its functionally substituted derivatives, etc.), α- or β-naphthoguanamines and their functionally substituted derivatives, polyguanamines, aralkyl or aralkyleneguanamines, etc.], and heteroatom-containing guanamine compounds [for example, acetal group-containing guanamines, tetraoxospiro ring-containing guanamines (CTU-guanamine, CMTU-guanamine, etc.), isocyanur ring-containing guanamines, imidazole ring-containing guanamines, etc.].

[0055] Examples of the above-mentioned urea derivatives include N-substituted ureas, urea condensates, ethylene ureas, hydantoin compounds, and ureido compounds. Examples of the above N-substituted ureas include methylurea having substituents such as alkyl groups, alkylenebisurea, and aryl-substituted ureas. Examples of the urea condensates mentioned above include condensates of urea and formaldehyde. Examples of the above-mentioned hydantoin compounds include hydantoin, 5,5-dimethylhydantoin, and 5,5-diphenylhydantoin. Examples of the above-mentioned ureid compounds include allantoin.

[0056] The above hydrazide compound may be a carboxylic acid mono / or dihydrazide compound, or an alkyl group substituted mono / or dihydrazide compound, synthesized by the reaction of a carboxylic acid (containing aromatic and / or alicyclic rings) with hydrazine. Examples of carboxylic acids constituting the carboxylic acid mono / or dihydrazide compound include monocarboxylic acids and dicarboxylic acids, and may be saturated or unsaturated. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, and behenic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalic acid, salicylic acid, gallic acid, melitic acid, cinnamic acid, pyruvic acid, lactic acid, malic acid, citric acid, fumaric acid, maleic acid, aconitic acid, amino acids, and nitrocarboxylic acids. Examples of unsaturated carboxylic acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, and eicosapentaenoic acid. Examples of carboxylic acid mono(di)hydrazide compounds synthesized using these carboxylic acids include carbodihydrazine, oxalic acid mono(di)hydrazide, malonic acid mono(di)hydrazide, succinic acid mono(di)hydrazide, glutaric acid mono(di)hydrazide, adipic acid mono(di)hydrazide, sebaciate mono(di)hydrazide, lauric acid mono(di)hydrazide, malic acid dihydrazide, tartrate dihydrazide, propionic acid monohydrazide, lauric acid monohydrazide, and stearate monohydrazide. Examples include radid, phthalate dihydrazide, isophthalate dihydrazide, terephthalate dihydrazide, 2,6-naphthalate dihydrazide, p-hydroxybenzoic hydrazine, p-hydroxybenzoic hydrazine, 1,4-cyclohexanedicarboxylic acid dihydrazine, acetohydrazide, acrylohydrazide, maleate dihydrazide, fumarate dihydrazide, benzohydrazide, nicotinohydrazide, isonicotinohydrazide, isobutylhydrazine, oleate hydrazide, etc.Among these carboxylic acids, dicarboxylic acids such as adipic acid, sebacic acid, and lauric acid are preferred, and adipic acid mono(di)hydrazide, sebacic acid mono(di)hydrazide, and lauric acid mono(di)hydrazide are the most preferred carboxylic acid hydrazide compounds.

[0057] Among these carboxylic acid hydrazide compounds, when the content ratios of monohydrazide compounds and dihydrazide compounds are within a specific range, it is possible to suppress the generation of carbides and modified materials that occur during long-term continuous molding, as well as suppress mold contamination. The content of carboxylic acid monohydrazide compounds relative to 100% by mass of the total of carboxylic acid monohydrazide compounds and carboxylic acid dihydrazide compounds is preferably in the range of 0.0001 to 1.0% by mass. The above content is more preferably in the range of 0.0001 to 0.5% by mass, and even more preferably in the range of 0.0001 to 0.1% by mass.

[0058] Methods for adjusting the above-mentioned content of carboxylic acid monohydrazide compounds include adding a monohydrazide compound to a carboxylic acid dihydrazide compound, and adjusting the synthesis reaction conditions when synthesizing by the reaction of carboxylic acid and hydrazine as described above. In the method of adjusting the synthesis reaction conditions of carboxylic acid and hydrazine, a monohydrazide compound is produced as an intermediate during the synthesis reaction. By washing away this monohydrazide compound, it is possible to adjust the content of the monohydrazide compound.

[0059] Examples of the amide compounds mentioned above include polycarboxylic acid amides such as isophthalic acid diamide, anthranilamides, and polyacrylamide polymers. The above-mentioned acrylamide polymer is preferably a particulate polymer having 30 to 70 mol% primary amide groups and an average particle size of 0.1 to 10 μm. Among these, the most preferred acrylamide polymer is a cross-linked acrylamide polymer with an average particle size of 10 μm or less. More preferably, it is an acrylamide polymer with an average particle size of 5 μm or less, and most preferably, it is a cross-linked acrylamide polymer with an average particle size of 3 μm or less.

[0060] Polyamides include polyamides derived from diamines and dicarboxylic acids; aminocarboxylic acids; polyamides obtained by using diamines and / or dicarboxylic acids in combination as needed; lactams; and polyamides obtained by using diamines and / or dicarboxylic acids in combination as needed. Copolymerized polyamides formed from two or more different polyamide-forming components are also included.

[0061] The melting point of the polyamide is preferably 240°C or higher, more preferably 245°C or higher, and even more preferably 250°C or higher. By using a polyamide with a melting point of 240°C or higher, a polyacetal resin composition with even better mold deposit properties and resistance to color difference changes after retention in the molding machine can be obtained.

[0062] Examples of polyamides with a melting point of 240°C or higher include polyamide 66, polyamide 46, polyamide 66 / 6T, and polyamide 66 / 6I / 6T. Among these polyamides, polyamide 66, polyamide 66 / 6T, and polyamide 66 / 6I / 6T are preferred, with polyamide 66 being the most preferred.

[0063] (e) Nitrogen-containing compounds can be used alone or in combination of two or more. In the polyacetal resin composition, the amount of (e) nitrogen-containing compound per 100 parts by mass of (a) polyacetal resin is preferably 0.001 parts by mass or more, or 0.005 parts by mass or more, or 0.01 parts by mass or more, from the viewpoint of maintaining color tone, thermal stability, suppressing odor during processing, and mechanical properties, and preferably 3 parts by mass or less, or 2 parts by mass or less, or 1 part by mass or less, or 0.7 parts by mass or less, or 0.5 parts by mass or less, or 0.3 parts by mass or less, from the viewpoint of suppressing mold deposits to the mold in advance.

[0064] <Other additives> The polyacetal resin composition of this embodiment may further contain, in addition to those described above, other known additives such as formic acid scavengers, weather stabilizers, mold release agents, lubricants, conductive agents, thermoplastic resins, thermoplastic elastomers, dyes and pigments, pigments, or inorganic or organic fillers. Furthermore, from the viewpoint of obtaining a resin composition suitable for sliding articles described later, in one embodiment, the polyacetal resin composition may contain a sliding agent component as an additive. These additives may be used individually or in combination of two or more types.

[0065] Examples of the formic acid scavengers mentioned above include, but are not limited to, hydroxides, inorganic acid salts, carboxylates, or alkoxides of alkali metals or alkaline earth metals. For example, hydroxides of sodium, potassium, magnesium, calcium, or barium; carbonates, phosphates, silicates, borates, carboxylates, and even layered double hydroxides of the above metals.

[0066] The carboxylic acid in the above carboxylate salt is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with hydroxyl groups. Examples of saturated or unsaturated aliphatic carboxylate salts are, but are not limited to, calcium dimyristate, calcium dipalmitate, calcium distearate, calcium (myristate-palmitate), calcium (myristate-stearate), calcium (palmitate-stearate), and calcium 12-hydroxystearate, with calcium dipalmitate, calcium distearate, and calcium 12-hydroxydistearate being particularly preferred. Formic acid suppositories may be used individually or in combination of two or more types.

[0067] The above-mentioned weather stabilizers are not limited to the following, but examples include at least one selected from the group consisting of benzotriazole compounds, oxalic acid anilide compounds, and hindered amine light stabilizers.

[0068] The above-mentioned benzotriazole compounds are not limited to those listed below, but examples include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3,5-di-t-butylphenyl)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-isoamylphenyl)benzotriazole, 2-[2'-hydroxy-3,5-bis-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole. These compounds may be used individually or in combination of two or more.

[0069] The oxalate alinode compounds mentioned above are not limited to the following, but examples include 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxalic acid bisanilide, and 2-ethoxy-3'-dodecyloxalic acid bisanilide. These compounds may be used individually or in combination of two or more.

[0070] The above-mentioned hindered amine-based light stabilizers are not limited to the following, but include, for example, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylethoxy)-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, and 4-stearyloxy-2,2,6,6-tetramethyl Piperidine, 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-piperidyltrylene-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,Examples include 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, condensates 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. Each of the above hindered amine-based light stabilizers may be used individually or in combination of two or more.

[0071] Among the preferred weather 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, and bis-(N-methyl It is a condensate of tyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 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.

[0072] The above-mentioned mold release agent and lubricant are not limited to the following, but preferred examples include alcohols, fatty acids and their esters (i.e., fatty acid esters of alcohols), olefin compounds with an average degree of polymerization of 10 to 500, and silicones. The mold release agent and lubricant may be used individually or in combination of two or more types.

[0073] The conductive agents mentioned above are not limited to those listed below, but examples include conductive carbon black, metal powder, or fibers. A single conductive agent may be used alone, or two or more types may be used in combination.

[0074] The thermoplastic resins mentioned above are not limited to the following, but examples include polyolefin resins, acrylic resins, styrene resins, polycarbonate resins, and uncured epoxy resins. A single type of thermoplastic resin may be used alone, or two or more types may be used in combination. Furthermore, thermoplastic resins also include modified versions of the resins mentioned above.

[0075] The thermoplastic elastomers mentioned above are not limited to those listed below, but examples include polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers. A single thermoplastic elastomer may be used alone, or two or more may be used in combination.

[0076] The above-mentioned dyes and pigments are not limited to those listed below, but examples include inorganic pigments, organic pigments, metallic pigments, fluorescent pigments, and the like. Inorganic pigments may be those commonly used for coloring resins and are not limited to the following, but examples include zinc sulfide, titanium dioxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, phosphates, acetates, carbon black, acetylene black, lamp black, etc. Organic pigments are not limited to the following, but examples include condensed azo, inone, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, perylene, dioxazine, and phthalocyanine pigments. Dyes and pigments may be used individually or in combination of two or more types.

[0077] The proportion of dye pigment added varies greatly depending on the desired color tone, making it difficult to specify a general rule. However, generally, it is used in the range of 0.05 to 5 parts by mass per 100 parts by mass of polyacetal resin.

[0078] The inorganic fillers mentioned above are not limited to the following, but for example, fibrous, powdery, plate-shaped, or hollow fillers can be used. Examples of fibrous fillers include, but are not limited to, glass fibers; carbon fibers; silicone fibers; silica-alumina fibers; zirconia fibers; boron nitride fibers; silicon nitride fibers; boron fibers; potassium titanate fibers; metal fibers such as stainless steel, aluminum, titanium, copper, and brass; and other inorganic fibers. Whiskers with short fiber lengths, such as potassium titanate whiskers and zinc oxide whiskers, are also included. Examples of powdered particulate fillers include, but are not limited to, talc; carbon black; silica; quartz powder; glass beads; glass powder; silicates such as calcium silicate, magnesium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, and wollastonite; metal oxides such as iron oxide, titanium oxide, and alumina; metal sulfates such as calcium sulfate and barium sulfate; carbonates such as magnesium carbonate and dolomite; silicon carbide; silicon nitride; boron nitride; various metal powders; and so on. Examples of plate-shaped fillers include, but are not limited to, mica, glass flakes, and various metal foils. Examples of hollow fillers include, but are not limited to, glass balloons, silica balloons, shirasu balloons, and metal balloons.

[0079] The above-mentioned organic fillers are not limited to the following, but examples include high-melting-point organic fibrous fillers such as aromatic polyamide resins, fluororesins, and acrylic resins.

[0080] The inorganic or organic fillers described above may be used individually or in combination of two or more. Both surface-treated and untreated fillers can be used; however, from the viewpoint of surface smoothness and mechanical properties of molded articles obtained using polyacetal resin compositions, the use of surface-treated fillers may be preferable.

[0081] The surface treatment agent is not particularly limited, and conventionally known surface treatment agents can be used. As surface treatment agents, there are, but are not limited to, various coupling agents such as silane-based, titanate-based, aluminum-based, and zirconium-based agents, resin acids, organic carboxylic acids, organic carboxylate salts, and surfactants that can be used. Specifically, but are not limited to, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltrisstearoyl titanate, diisopropoxyammonium ethyl acetate, and n-butyl zirconate.

[0082] The above-mentioned lubricant component may be a substance other than (a) polyacetal resin and (c) polyethylene glycol. In one embodiment, polyethylene glycol is water-soluble, while the lubricant component is not. In this disclosure, "water-soluble" means that 0.1 g or more dissolves in 100 g of water at 23°C. The content of the lubricant component in the resin composition is preferably 0.01 parts by mass or more, or 0.5 parts by mass or more, or 1.0 part by mass, per 100 parts by mass of polyacetal resin, and preferably 5 parts by mass or less, or 4 parts by mass or less, or 3 parts by mass or less. According to the above range of content, the amount of wear of the sliding article can be suppressed. When a general filler (e.g., glass fiber) is used, the lubricant component is unevenly distributed on the surface of the filler, and a structure is formed in which many lubricant molecules are stacked, making the filler more prone to falling off, which reduces the durability and quietness of the sliding article, and the sliding performance may even decrease due to the falling off of the filler. On the other hand, since the surface area of ​​the fine cellulose fibers of this disclosure is significantly larger than that of general fillers, the lubricant components are less likely to be unevenly distributed on the surface of the fine cellulose fibers, and therefore less likely to be laminated. As a result, it is presumed that good durability, sliding properties, and quietness of sliding articles can be obtained.

[0083] When the amount of the lubricant component is 5 parts by mass or less per 100 parts by mass of polyacetal resin, delamination and silver streaks in the molded product are more effectively suppressed. Furthermore, when the amount of the lubricant component is 0.01 parts by mass or more per 100 parts by mass of polyacetal resin, a more significant effect in reducing wear is obtained.

[0084] Examples of lubricant components include compounds having a structure represented by the following general formulas (1a), (1b), or (1c). [R 11 -(A1-R 12 ) x -A2-R 13 ] y ...(1a) A3-R 11 -A4···(1b) R 14 -A5···(1c) Here, in equations (1a) and (1b), R 11 , R 12 and R 13 Each of these is independently an alkylene group having 1 to 7000 carbon atoms, a substituted alkylene group in which at least one hydrogen atom of a substituted or unsubstituted alkylene group having 1 to 7000 carbon atoms is substituted with an aryl group having 6 to 7000 carbon atoms, an arylene group having 6 to 7000 carbon atoms, or a substituted arylene group in which at least one hydrogen atom of an arylene group having 6 to 7000 carbon atoms is substituted with a substituted or unsubstituted alkyl group having 1 to 7000 carbon atoms.

[0085] Also, in equation (1c), R 14 This refers to an alkyl group having 1 to 7000 carbon atoms, a substituted alkyl group in which at least one hydrogen atom of a substituted or unsubstituted alkyl group having 1 to 7000 carbon atoms is substituted with an aryl group having 6 to 7000 carbon atoms, an aryl group having 6 to 7000 carbon atoms, or a substituted aryl group in which at least one hydrogen atom of an aryl group having 6 to 7000 carbon atoms is substituted with a substituted or unsubstituted alkyl group having 1 to 7000 carbon atoms.

[0086] These groups may include double bonds, triple bonds, or cyclic structures.

[0087] Furthermore, in formula (1a), A1 and A2 are independently an ester bond, a thioester bond, an amide bond, a thioamide bond, an imide bond, a ureid bond, an imine bond, a urea bond, a ketoxime bond, an azo bond, an ether bond, a thioether bond, a urethane bond, a thiourethane bond, a sulfide bond, a disulfide bond, or a trisulfide bond.

[0088] Furthermore, in formulas (1b) and (1c), A3, A4, and A5 are each independently a hydroxyl group, an acyl group (e.g., an acetyl group), an aldehyde group, a carboxyl group, an amino group, a sulfo group, an amidine group, an azi group, a cyano group, a thiol group, a sulfenic acid group, an isocyanide group, a ketene group, an isocyanate group, a thioisocyanate group, a nitro group, or a thiol group.

[0089] From the viewpoint of wear characteristics during sliding under minute loads, it is preferable that the structure represented by the above general formulas (1a), (1b), and (1c) in the lubricant component be within the following ranges.

[0090] That is, R 11 , R 12 , R 13 , R 14 The number of carbon atoms in is preferably 2 to 7000, more preferably 3 to 6800, and even more preferably 4 to 6500. In equation (1a), x represents an integer from 1 to 1000, preferably from 1 to 100. y represents an integer from 1 to 1000, preferably from 1 to 200.

[0091] In formula (1a), preferred A1 and A2 are each independently an ester bond, a thioester bond, an amide bond, an imide bond, a ureid bond, an imine bond, a urea bond, a ketoxime bond, an ether bond, and a urethane bond, and more preferred A1 and A2 are each independently an ester bond, an amide bond, an imide bond, a ureid bond, an imine bond, a urea bond, a ketoxime bond, an ether bond, and a urethane bond.

[0092] In formulas (1b) and (1c), preferred A3, A4 and A5 are each independently a hydroxyl group, an acyl group (e.g., an acetyl group), an aldehyde group, a carboxyl group, an amino group, an azi group, a cyano group, a thiol group, an isocyanide group, a ketene group, an isocyanate group, and a thioisocyanate group, and more preferred A3, A4 and A5 are each independently a hydroxyl group, an acyl group (e.g., an acetyl group), an aldehyde group, a carboxyl group, an amino group, a cyano group, an isocyanide group, a ketene group, and an isocyanate group.

[0093] Specifically, examples of lubricant components include, but are not limited to, at least one compound selected from the group consisting of alcohols, amines, carboxylic acids, hydroxy acids, amides, esters, polyoxyalkylene glycols, silicone oils, and waxes.

[0094] As for the alcohol, saturated or unsaturated monohydric or polyhydric alcohols with 6 to 7000 carbon atoms are preferred. Specific examples are not limited to, but include, for instance, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, linolyl alcohol, nonadecyl alcohol, eicosyl alcohol, ceryl alcohol, behenyl alcohol, melicyl alcohol, hexyldecyl alcohol, octyldodecyl alcohol, decylmyristyl alcohol, decylstearyl alcohol, unylyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, glycerin, diglycerin, triglycerin, treitol, erythritol, pentaerythritol, arabitol, ribitol, xylitol, sorbite, sorbitan, sorbitol, and mannitol.

[0095] Among these, alcohols with 11 or more carbon atoms are preferred from the viewpoint of sliding efficiency. More preferably, alcohols with 12 or more carbon atoms are preferred, and even more preferably, alcohols with 13 or more carbon atoms are preferred. Saturated alcohols are particularly preferred among these.

[0096] Among these, stearyl alcohol, oleyl alcohol, linolyl alcohol, behenyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol are preferably usable, and behenyl alcohol, diethylene glycol, and triethylene glycol are particularly preferably usable.

[0097] Examples of amines, though not limited to the following, include primary amines, secondary amines, and tertiary amines.

[0098] Primary amines are not particularly limited, but examples include methylamine, ethylamine, propaneamine, butanamine, pentaneamine, hexaneamine, heptaneamine, octanamine, cyclohexylamine, ethylenediamine, aniline, mensendiamine, isophoronediamine, xylenediamine, metaphenylenediamine, and diaminodiphenylamine.

[0099] The secondary amine is not particularly limited, but examples include dimethylamine, diethylamine, N-methylethylamine, diphenylamine, tetramethylethylenediamine, piperidine, and N,N-dimethylpiperazine.

[0100] Examples of tertiary amines are not particularly limited, but include trimethylamine, triethylamine, hexamethylenediamine, N,N-diisopropylethylamine, pyridine, N,N-dimethyl-4-aminopyridine, triethylenediamine, and benzyldimethylamine.

[0101] Special amines are not particularly limited, but examples include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, and N-aminoethylpiperazine. Among these, hexaneamine, heptaneamine, octanamine, tetramethylethylenediamine, N,N-dimethylpiperazine, and hexamethylenediamine are more preferably used, and among these, heptaneamine, octanamine, tetramethylethylenediamine, and hexamethylenediamine are particularly preferably used.

[0102] Preferred carboxylic acids are monovalent or polyvalent aliphatic carboxylic acids having 6 to 7000 carbon atoms, either saturated or unsaturated. Specific examples are not limited to caproic acid, enanthic acid, caprylic acid, undecylic acid, pelargonic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptaconic acid, montanic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, melissic acid, laxeric acid, undecylenic acid, elaidic acid, cetoleic acid, brassic acid, sorbic acid, palmitoleic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, arachidonic acid, nervonic acid, erucic acid, propiolic acid, stearolic acid, etc.

[0103] Among these, fatty acids with 10 or more carbon atoms are preferred from the viewpoint of sliding efficiency. More preferably, fatty acids with 11 or more carbon atoms are preferred, and even more preferably, fatty acids with 12 or more carbon atoms are preferred. Saturated fatty acids are particularly preferred among these. Among saturated fatty acids, palmitic acid, stearic acid, behenic acid, montanic acid, adipic acid, sebacic acid, etc., are readily available industrially and are therefore even more preferred.

[0104] Alternatively, naturally occurring fatty acids containing such components or mixtures thereof may also be used. These fatty acids may be substituted with hydroxyl groups, or they may be synthetic fatty acids obtained by carboxylating the terminal end of a synthetic aliphatic alcohol such as uniline alcohol.

[0105] While not particularly limited, examples of hydroxy acids include aliphatic hydroxy acids and aromatic hydroxy acids. Examples of aliphatic hydroxy acids include glycolic acid, hydroxypropionic acid, hydroxybutanoic acid, hydroxypentanoic acid, hydroxyhexanoic acid, hydroxyheptanoic acid, hydroxynonanoic acid, hydroxydecanoic acid, hydroxyundecanoic acid, hydroxydodecanoic acid, hydroxytridecanoic acid, hydroxytetradecanoic acid, hydroxypentadecanoic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid, and hydroxynonadecanoic acid. Examples include hydroxyicosanoic acid, hydroxydocosanoic acid, hydroxytetradocosanoic acid, hydroxyhexadocosanoic acid, hydroxyoctadocosanoic acid, lactic acid, tartaric acid, glyceric acid, hydroxybutyric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineradicic acid, cerebronic acid, quinic acid, shikimic acid, etc., and isomers thereof may also be used.

[0106] Aromatic hydroxy acids are not particularly limited, but examples include salicylic acid, creosote acids (homosalicylic acid, hydroxy(methyl)benzoic acid), vanillic acid, and syringic acid as monohydroxybenzoic acid derivatives; pyrocateutic acid, resorsilicic acid, protocatechuic acid, gentisic acid, and orceric acid as dihydroxybenzoic acid derivatives; gallic acid as trihydroxybenzoic acid derivatives; mandelic acid, benzyl acid, atrolactinic acid, cinnamic acid, and hydroxycinnamic acid derivatives, melilotic acid, floretic acid, coumaric acid, umberic acid, caffeic acid, ferulic acid, and sinapic acid as phenylacetic acid derivatives, and isomers thereof may also be used. Among these, aliphatic hydroxy acids are more preferred, and among aliphatic hydroxy acids, those with 5 to 30 carbon atoms are even more preferred, and those with 8 to 28 carbon atoms are particularly preferred.

[0107] Preferred amides are saturated or unsaturated monovalent or polyvalent aliphatic amides having 6 to 7000 carbon atoms. Specific examples are not limited to these, but examples of primary amides include saturated or unsaturated amides such as heptanamide, octanamide, nonanamide, decanamide, undecanamide, laurylamide, tridecylamide, myristylamide, pentadecylamide, cetylamide, heptadecylamide, stearylamide, oleylamide, nonadecylamide, eicosylamide, cerylamide, behenylamide, melicylamide, hexyldecylamide, octyldodecylamide, laurate amide, palmitate amide, stearate amide, behenate amide, hydroxystearate amide, oleate amide, and erucate amide.

[0108] Examples of secondary amides include, but are not limited to, saturated or unsaturated amides such as N-oleyl palmitamide, N-stearyl stearate amide, N-stearyl oleamide, N-oleyl stearate amide, N-stearyl erucate amide, methylene bis-stearate amide, ethylene biscaprate amide, ethylene bis-laurate amide, ethylene bis-stearate amide, ethylene bis-hydroxystearate amide, ethylene bis-behenate amide, ethylene bis-oleate amide, ethylene bis-erucate amide, hexamethylene bis-stearate amide, hexamethylene bis-behenate amide, hexamethylene bis-oleate amide, and hexamethylene hydroxystearate amide.

[0109] Examples of tertiary amides include, but are not limited to, saturated or unsaturated amides such as N,N-distearyl adipic acid amide, N,N-distearyl sebacin acid amide, N,N-dioleyl adipic acid amide, N,N-dioleyl sebacin acid amide, and N,N-distearyl isophthalic acid amide.

[0110] Among these, palmitate amide, stearate amide, behenate amide, hydroxystearate amide, oleate amide, erucate amide, and N-stearylstearate amide are more preferably usable.

[0111] Among these, methylenebisstearate amide, ethylenebislaurate amide, ethylenebisstearate amide, and ethylenebisbehenate amide are preferably usable. Of these, amides having 10 or more carbon atoms are preferred from the viewpoint of sliding efficiency. More preferably, amides having 11 or more carbon atoms are preferred, and even more preferably, amides having 13 or more carbon atoms are preferred. Saturated aliphatic amides are particularly preferred among these.

[0112] As for the ester, reaction products in which the above-mentioned alcohol reacts with a carboxylic acid or hydroxy acid to form an ester bond are preferred.

[0113] Specific examples are not limited to but include, for example, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, monoglyceride behenate, cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, cholesteryl isostearate, methyl laurate, methyl oleate, methyl stearate, cetyl myristate, myristyl myristate, octyldodecyl pentaerythritol monooleate myristate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, triglyceride 2-ethylhexanoate, and dipropyl adipate. Examples include isodecyl, ethylene glycol monolaurate, ethylene glycol dilaurate, ethylene glycol monostearate, ethylene glycol distearate, triethylene glycol monostearate, triethylene glycol distearate, ethylene glycol monooleate, ethylene glycol dioleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, glycerin monostearate, glycerin distearate, glycerin monolaurate, glycerin dilaurate, glycerin monooleate, and glycerin dioleate.

[0114] Among these, cetyl myristate, diisodecyl adipate, ethylene glycol monostearate, ethylene glycol distearate, triethylene glycol monostearate, triethylene glycol distearate, polyethylene glycol monostearate, and polyethylene glycol distearate are preferably usable, and cetyl myristate, diisodecyl adipate, and ethylene glycol distearate are particularly preferably usable.

[0115] Examples of polyoxyalkylene glycols include, but are not limited to, the following first to third polyoxyalkylene glycols.

[0116] The first polyoxyalkylene glycol is a polycondensate with alkylene glycol as the monomer. Examples of such polycondensates, but not limited to, include polyethylene glycol, polypropylene glycol, block copolymers and random copolymers of ethylene glycol and propylene glycol. The preferred range for the degree of polymerization of these polycondensates is 5 to 2500, and the more preferred range is 10 to 2300.

[0117] The second type of polyoxyalkylene glycol is an ether compound of the polycondensate mentioned in the first type of polyoxyalkylene glycol and an aliphatic alcohol. Examples of such ether compounds, though not limited to those listed below, include polyethylene glycol oleyl ether (ethylene oxide degree of polymerization 5-500), polyethylene glycol cetyl ether (ethylene oxide degree of polymerization 5-500), polyethylene glycol stearyl ether (ethylene oxide degree of polymerization 5-300), polyethylene glycol lauryl ether (ethylene oxide degree of polymerization 5-300), polyethylene glycol tridecyl ether (ethylene oxide degree of polymerization 5-300), polyethylene glycol nonylphenyl ether (ethylene oxide degree of polymerization 2-1000), and polyethylene glycol oxitylphenyl ether (ethylene oxide degree of polymerization 4-500).

[0118] The third type of polyoxyalkylene glycol is an ester compound of a polycondensate (as mentioned in the first type of polyoxyalkylene glycol) and a higher fatty acid. Examples of such ester compounds, though not limited to those listed below, include polyethylene glycol monolaurate (ethylene oxide polymerization degree 2-300), polyethylene glycol monostearate (ethylene oxide polymerization degree 2-500), and polyethylene glycol monooleate (ethylene oxide polymerization degree 2-500).

[0119] The waxes are not particularly limited, but examples include shellac wax, beeswax, whale wax, wool wax, carnauba wax, wood wax, rice wax, candelilla wax, sumac wax, paraffin wax, microcrystalline wax, montane wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, and high-density polymerized, low-density polymerized, oxidized, acid-modified, and special monomer-modified forms thereof.

[0120] Among these, carnauba wax, rice wax, candelilla wax, paraffin wax, montan wax, polyethylene wax, and their high-density polymerized, low-density polymerized, oxidized, acid-modified, and special monomer-modified forms are more preferably used, and carnauba wax, rice wax, candelilla wax, paraffin wax, polyethylene wax, and their high-density polymerized, low-density polymerized, oxidized, acid-modified, and special monomer-modified forms are particularly preferably used.

[0121] Among these, the lubricant component is preferably at least one compound selected from the group consisting of alcohols, amines, carboxylic acids, esters, amide compounds consisting of monovalent or divalent amines and carboxylic acids, and waxes.

[0122] The paraffin wax, polyethylene wax, and their high-density polymerized, low-density polymerized, oxidized, acid-modified, and special monomer-modified forms used in the resin composition of this embodiment are not particularly limited, but can be obtained by introducing acidic groups through an oxidation reaction of polyolefin wax, oxidative decomposition of polyolefins, introducing polar groups such as carboxyl groups and sulfonic acid groups by reacting polyolefin wax with inorganic acids, organic acids, or unsaturated carboxylic acids, or by introducing monomers having acidic groups during the polymerization of polyolefin wax.

[0123] These are commercially available under names such as oxidative-modified or acid-modified polyolefin waxes and can be easily obtained.

[0124] Examples of polyolefin waxes, though not limited to those listed below, include paraffin wax, microcrystalline wax, montane wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, and high-density polymerized, low-density polymerized, and special monomer-modified forms thereof.

[0125] Examples of polyolefins include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, polypropylene-butene copolymer, polybutene, hydrogenated polybutadiene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and the like.

[0126] As for the lubricant components, acid-modified paraffin wax, polyethylene wax, polypropylene wax, polyethylene (high-pressure low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene), polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer are preferred from the viewpoint of improving lubricity.

[0127] The lubricant component is preferably a modified wax containing acid-modified polyethylene and / or acid-modified polypropylene.

[0128] The above lubricant components may be used individually or in combination of two or more. In this embodiment, the lubricant component can be separated from molded articles such as sliding articles to calculate its molecular structure, molecular weight, melting point, acid value, viscosity, and other properties.

[0129] The lubricant components in molded products can be isolated by dissolving the molded product and then purified by processes such as recrystallization and reprecipitation. 1 H-NMR and 13By performing various measurements such as 1C-NMR, two-dimensional NMR, and MALDI-TOF MS, it is possible to determine the molecular structure, including repeating structures, branched structures, and the positional information of various functional groups.

[0130] When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the acid value is preferably in the range of 0 to 85 mg-KOH / g. There is no particular preferred lower limit for the acid value, but it is preferably 0 mg-KOH / g or higher. A more preferred upper limit for the acid value is 83 mg-KOH / g, even more preferably 80 mg-KOH / g, and even more preferably 75 mg-KOH / g. By setting the acid value within the above range, discoloration during drying is suppressed, and wear resistance during high-temperature sliding under small loads tends to be improved. The acid value of the lubricant component can be measured by a method in accordance with JIS K0070.

[0131] The acid value of the lubricant component can be controlled by methods such as those described in Example 1 or 2 of Japanese Patent Publication No. 2004-75749, or by adjusting or controlling the amount of acidic groups and / or polar groups introduced by thermal decomposition of commercially available high-density polyethylene under an oxygen atmosphere. Furthermore, if the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, commercially available products can also be used.

[0132] When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 140°C is preferably 1 mPa·s or more, or 20 mPa·s or more, or 25 mPa·s or more, or 30 mPa·s or more, or 50 mPa·s or more, from the viewpoint of processability during melt-kneading of the resin composition, and the upper limit is preferably 3000 mPa·s or less, or 2850 mPa·s or less, or 2800 mPa·s or less, or 2700 mPa·s or less, or 2650 mPa·s or less, or 2000 mPa·s or less.

[0133] When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 180°C is preferably 100 mPa·s or more, or 110 mPa·s or more, or 140 mPa·s or more, or 160 mPa·s or more, or 300 mPa·s or more, and preferably 2900 mPa·s or less, or 2850 mPa·s or less, or 2800 mPa·s or less, or 2700 mPa·s or less, or 2650 mPa·s or less, or 2000 mPa·s or less, or 1600 mPa·s or less.

[0134] When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, by keeping the melt viscosity within the above range, the resin pellets tend to completely melt and the mixing is sufficient when the resin composition, which is the constituent material of the sliding article in this embodiment, is melted and kneaded.

[0135] When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 140°C and 180°C can be measured using a Brookfield viscometer.

[0136] In one embodiment, the sliding agent component is a lubricating oil. The lubricating oil is not limited to the following, but any substance that can improve the friction and wear characteristics of the resin molded product can be used. Examples include natural oils such as engine oil and cylinder oil, or synthetic hydrocarbons such as paraffinic oils (e.g., Diana Process Oil PS32 manufactured by Idemitsu Kosan Co., Ltd.), naphthenic oils (e.g., Diana Process Oil NS90S manufactured by Idemitsu Kosan Co., Ltd.), or aromatic oils (e.g., Diana Process Oil AC12 manufactured by Idemitsu Kosan Co., Ltd.), or silicone-based oils (e.g., Shin-Etsu Chemical Co., Ltd. G30 series) (silicone oils represented by polydimethylsiloxane, silicone gum, modified silicone gum). A suitable lubricating oil can be selected from commercially available lubricating oils and used as is, or blended as desired. Among these, paraffinic oils and silicone-based oils are preferred because they are excellent from the viewpoint of sliding properties and are readily available industrially. These lubricating oils may be used individually or in combination.

[0137] The molecular weight of the lubricating oil is preferably 100 or more, or 400 or more, or 500 or more, in terms of good lubricity, and preferably 5 million or less, 2 million or less, or 1 million or less, in terms of good dispersion of the lubricating oil and improved wear resistance. The melting point of the lubricating oil is preferably -50°C or higher, or -30°C or higher, or -20°C or higher, in terms of maintaining the fluidity of the lubricating oil present on the surface of the molded product and suppressing abrasive wear, thereby improving the wear resistance of the sliding article, and preferably 50°C or lower, or 30°C or lower, or 20°C or lower, in terms of easy mixing with polyacetal resin and improved dispersibility of the lubricating oil. In a preferred embodiment, the above melting point is 2.5°C lower than the pour point of the lubricating oil. The above pour point can be measured in accordance with JIS K2269.

[0138] The lubricating oil content per 100 parts by mass of polyacetal resin is preferably 0.1 parts by mass or more, or 0.2 parts by mass or more, or 0.3 parts by mass or more, from the viewpoint of improving or stabilizing wear resistance and sliding properties, and preferably 5.0 parts by mass or less, or 4.5 parts by mass or less, or 4.2 parts by mass or less, from the viewpoint of obtaining good strength of the resin composition that can withstand applications such as high-torque gears by suppressing resin softening.

[0139] In sliding articles, the dispersion state of the lubricant component near the surface of the member greatly affects the sliding properties, therefore the weight-average molecular weight of the lubricant component is important. In one embodiment, the preferred lower limit of the weight-average molecular weight of the lubricant component is 500, more preferably 600, and particularly preferably 700. Furthermore, the preferred upper limit of the weight-average molecular weight of the lubricant component is not particularly limited, but 100,000 is a guideline for ease of handling. In the sliding article of this embodiment, by setting the weight-average molecular weight of the lubricant component within the above range, good wear resistance that can withstand repeated sliding is obtained.

[0140] The lower limit of the molecular weight distribution of the lubricant component is not particularly limited, but from the viewpoint of the stability of the coefficient of friction during sliding, it is a guideline that it be close to 1.0. The upper limit of the molecular weight distribution of the lubricant component is preferably 9.0, or 8.5, or 8.0, or 7.5.

[0141] The weight-average molecular weight of lubricant components is measured by liquid chromatography / mass spectrometry if the weight-average molecular weight is 1000 or less, and if the weight-average molecular weight exceeds 1000, it is expressed as the weight-average molecular weight converted to standard polystyrene, etc., measured by gel permeation chromatography.

[0142] The melting point of the lubricant component is preferably 40°C or higher, 45°C or higher, 50°C or higher, or 80°C or higher, from the viewpoint of improving the wear resistance of the sliding article under high-temperature conditions, and preferably 150°C or lower, 140°C or lower, 135°C or lower, or 130°C or lower, from the viewpoint of good dispersion of the lubricant component in the resin during processing. The melting point of the lubricant component can be measured by a method (DSC method) in accordance with JIS K 7121.

[0143] ≪Method for producing polyacetal resin composition≫ The specific embodiments of the method for producing the polyacetal resin composition of this embodiment are not particularly limited, but in one embodiment, the method for producing the polyacetal resin composition includes melt-kneading (a) polyacetal resin, (b) fine cellulose fibers, and (c) polyethylene glycol, preferably including melt-kneading (a) polyacetal resin, (b) fine cellulose fibers, (c) polyethylene glycol, (d) hindered phenol antioxidant, and (e) nitrogen-containing compound, more preferably including melt-kneading (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, (c) 0.1 to 100 parts by mass of polyethylene glycol, (d) 0.01 to 3 parts by mass of a hindered phenol antioxidant, and (e) 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.

[0144] More specifically, an example is a method in which the necessary components are mixed, the resulting mixture is kneaded using a melt-kneading device such as an extruder, and a polyacetal resin composition is obtained as pellets. As the extruder, it is preferable to use a co-rotating twin-screw extruder in order to improve the dispersibility of fine cellulose fibers. The L / D ratio, obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D), may be 40 or more, or 50 or more, in one embodiment. The screw rotation speed may be 50 ppm or more, or 100 ppm or more, or 150 ppm or more, and may be 800 rpm or less, or 600 rpm or less, in one embodiment. Each screw in the cylinder of the extruder may be optimized by combining an elliptical two-bladed screw-shaped conveying screw, a kneading element called a kneading disc, etc.

[0145] The temperature of the mixed components during mixing is preferably 170°C or higher, or 180°C or higher, or 190°C or higher, from the viewpoint of achieving high dispersion of fine cellulose fibers, and preferably 250°C or lower, or 240°C or lower, or 230°C or lower, from the viewpoint of suppressing the decomposition of the mixed components, particularly the decomposition of the polyacetal resin and cellulose fine fibers.

[0146] From the viewpoint of suppressing the generation of low molecular weight components due to the cleavage of cellulose molecules and maintaining the mechanical strength of the resin composition, the pressure applied to the mixed components is preferably maintained at 30 MPa or less, 20 MPa or less, or 10 MPa or less throughout the mixing process. From the viewpoint of achieving high dispersion of cellulose fine fibers, the pressure applied to the mixed components may preferably be 0 MPa or more, 0.1 MPa or more, 0.2 MPa or more, or 0.5 MPa or more in part or all of the mixing process.

[0147] <Use of cellulose fiber-containing powder for polyacetal resin compositions> To highly disperse fine cellulose fibers in polyacetal resin, a method is preferred over a method that involves defibrating cellulose by shearing in an extruder to obtain fine cellulose fibers. This method involves preparing a mixed powder of fine cellulose fibers (in one embodiment, defibrated to a fiber diameter of 2 to 1000 nm) and polyethylene glycol, and then melt-kneading this mixed powder with the polyacetal resin. It is presumed that the presence of polyethylene glycol in the fine cellulose fibers acts as a "primer," allowing the polyacetal resin to easily penetrate the gaps between the fine cellulose fibers, thereby improving the dispersibility of the fine cellulose fibers in the polyacetal resin composite.

[0148] In one embodiment, the mixed powder can be prepared by drying a fine cellulose fiber slurry in which fine cellulose fibers are dispersed in a liquid medium. In one embodiment, the liquid medium is water and / or other media (e.g., organic solvents, inorganic acids, bases and / or ionic liquids).

[0149] From the viewpoint of process efficiency during drying, the concentration of fine cellulose fibers in the fine cellulose fiber slurry is preferably 1% by mass or more, or 2% by mass or more, or 3% by mass or more, or 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more, or 25% by mass or more. From the viewpoint of avoiding excessive increase in the viscosity of the slurry and solidification due to aggregation, and maintaining good handling properties, it is preferably 60% by mass or less, or 55% by mass or less, or 50% by mass or less, or 45% by mass or less, or 40% by mass or less, or 35% by mass or less. For example, fine cellulose fibers are often produced in a dilute dispersion, but the concentration of fine cellulose fibers in the slurry may be adjusted to the above preferred range by concentrating such a dilute dispersion. Methods such as suction filtration, pressure filtration, centrifugal deliquidation, and heating can be used for concentration.

[0150] Any additional components other than polyethylene glycol and fine cellulose fibers may be added before, during, and / or after drying the fine cellulose fiber slurry.

[0151] Dryers are not particularly limited, but examples include kneaders, planetary mixers, Henschel mixers, high-speed mixers, propeller mixers, ribbon mixers, single-screw or twin-screw extruders, Banbury mixers, freeze dryers, shelf dryers, spray dryers, and fluidized bed dryers.

[0152] [Moisture percentage] The liquid medium content of the mixed powder is preferably 50% by mass or less, or 40% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less, or 5% by mass or less. The liquid medium content may be 0% by mass, but from the viewpoint of ease of manufacturing the mixed powder, it may be, for example, 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more, or 1.5% by mass or more. The liquid medium content is a value measured using an infrared heating type moisture meter.

[0153] [Average particle size] The average particle size of the mixed powder is preferably 1 μm or more, or 10 μm or more, 50 μm or more, 100 μm or more, 200 μm or more, or 500 μm or more, and preferably 5000 μm or less, or 4000 μm or less, or 3000 μm or less, or 2000 μm or less. The above average particle size is a value measured dry by laser diffraction.

[0154] [Loose bulk density] In one embodiment, the loosened bulk density of the mixed powder is preferably 0.01 g / cm³, from the viewpoint of good fluidity of the mixed powder and excellent feedability to a twin-screw extruder, as well as suppression of the transfer of the dispersant to the resin. 3 Above, or 0.05 g / cm³ 3 Above, or 0.10 g / cm³ 3 Above, or 0.15 g / cm³ 3 Above, or 0.20 g / cm³ 3 Above, or 0.25 g / cm³ 3 Above, or 0.30 g / cm³ 3 Above, or 0.35 g / cm³ 3 Above, or 0.40 g / cm³ 3 Above, or 0.45 g / cm³3 Above, or 0.50 g / cm³ 3 In summary, a mixture of 0.85 g / cm³ is preferred because it allows the mixed powder to easily disintegrate in the resin, enabling good dispersion of fine cellulose fibers within the resin, and because the mixed powder is not too heavy, thus avoiding poor mixing between the mixed powder and the resin. 3 The following, or 0.80 g / cm³ 3 The following, or 0.75 g / cm³ 3 The following applies:

[0155] [Firm bulk density] The bulk density of the mixed powder is controlled to a range useful for controlling the loose bulk density and compressibility within the scope of the disclosure, preferably 0.01 g / cm³ in one embodiment. 3 Above or equal to 0.1 g / cm³ 3 Above, or 0.15 g / cm³ 3 Above, or 0.2 g / cm³ 3 Above, or 0.3 g / cm³ 3 Above, or 0.4 g / cm³ 3 Above, or 0.5 g / cm³ 3 Above, or 0.6 g / cm³ 3 The above is preferable, and preferably 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 The following, or 0.85 g / cm³ 3 The following applies:

[0156] [Compression level] Compression is calculated using the formula: Compression = (Compression density - Loose bulk density) / Compression density. Loose bulk density and Compression density are measured using the following methods.

[0157] For loose bulk density, cellulose fiber-containing powder is placed in a 100 mL stainless steel cylindrical container with a closed bottom (50.46 mm inner diameter x 50 mm depth) at a rate of 10 g / min using a spatula until it overflows. After leveling off the excess powder, the weight is measured to the nearest 0.01 g. The number average of three weight measurements is divided by the internal volume of the cylindrical container to calculate the loose bulk density.

[0158] For the firm bulk density, a resin adapter (inner diameter 50.46 mm x length 40 mm) of sufficient capacity is tightly attached to the top of a bottomed cylindrical container similar to the one used for the loose bulk density measurement. After filling the container with cellulose fiber-containing powder to an overflowing level using the same procedure as for measuring the loose bulk density, the bottomed cylindrical container is subjected to vibrations of 1.5 mm amplitude and 50 Hz for 30 seconds using a motor with an eccentric weight attached to the rotating shaft, while the adapter is still attached. Subsequently, the adapter is removed, the powder is leveled off, and its weight is measured to the nearest 0.01 g. The number average of three weight measurements is divided by the internal volume of the bottomed cylindrical container to calculate the firm bulk density.

[0159] In one embodiment, the degree of compression represents the degree of bulk reduction. In one embodiment, the degree of compression of the mixed powder is preferably 1% or more, or 5% or more, or 10% or more, or 15% or more, or 20% or more, or 25% or more, in that the fluidity of the mixed powder is not too high. Furthermore, in terms of good fluidity of the mixed powder and excellent feedability to a twin-screw extruder, and excellent handling (specifically, less likely to scatter, float, or form dust), good dispersion of the mixed powder in the resin, and suppression of the transfer of the dispersant to the resin, the degree of compression is preferably 50% or less, or 45% or less, or 40% or less, or 35% or less, or 30% or less.

[0160] The above-mentioned loose bulk density, firm bulk density, and compressibility are measured using a powder tester (model number: PT-X) manufactured by Hosokawa Micron Corporation. The number of taps for firm bulk density measurement is 180.

[0161] A preferred embodiment provides a mixed powder which is a cellulose fiber-containing powder for a polyacetal resin composition. In one embodiment, the cellulose fiber-containing powder contains (b) fine cellulose fibers having a fiber diameter of 2 to 1000 nm and (c) polyethylene glycol. In the cellulose fiber-containing powder, (c) polyethylene glycol has an ethylene ratio R (%) which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of (c) polyethylene glycol, which is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 This is a polyethylene glycol that satisfies the following relationship. Preferred examples of polyacetal resin, fine cellulose fibers, and polyethylene glycol are as described above and will not be repeated here.

[0162] A preferred embodiment also provides a method for producing a cellulose fiber-containing powder for a polyacetal resin composition. In this method, the cellulose fiber-containing powder comprises (b) fine cellulose fibers having a fiber diameter of 2 to 1000 nm and (c) polyethylene glycol. The method includes a mixing step of mixing (b) fine cellulose fibers and (c) polyethylene glycol to obtain a cellulose fiber-containing powder. In this method, (c) polyethylene glycol is expressed by the following formula: the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of (c) polyethylene glycol. (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 The materials are selected to satisfy the following relationship. Preferred examples of polyacetal resin, fine cellulose fibers, and polyethylene glycol are as described above and will not be repeated here.

[0163] A preferred embodiment also provides a method for producing a polyacetal resin composition using cellulose fiber-containing powder. This method is (b) A powder preparation step to obtain a cellulose fiber-containing powder containing fine cellulose fibers with a fiber diameter of 2 to 1000 nm and (c) polyethylene glycol, A resin composition preparation step in which the cellulose fiber-containing powder and (a) polyacetal resin are mixed to obtain a polyacetal resin composition, Includes. In this method, (a) the polyacetal resin is given an ethylene ratio R (%) which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of (a) the polyacetal resin, and (c) the number of oxyethylene repeating units n of polyethylene glycol is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 The materials are selected to satisfy the following relationship. Preferred examples of polyacetal resin, fine cellulose fibers, and polyethylene glycol are as described above and will not be repeated here.

[0164] ≪Characteristics of Resin Compositions≫ <Flexural modulus> The flexural modulus of the polyacetal resin composition is preferably 3000 MPa or higher, or 4000 MPa or higher, or 4500 MPa or higher, or 5000 MPa or higher, from the viewpoint of obtaining good durability of molded articles, such as sliding articles, and may be, for example, 20000 MPa or lower, or 15000 MPa or lower, or 12000 MPa or lower, or 10000 MPa or lower, or 8000 MPa or lower, or 7000 MPa or lower, from the viewpoint of ease of manufacturing the resin composition. The flexural modulus of the polyacetal resin composition is a value measured in accordance with ISO 179.

[0165] ≪High-temperature rigidity of polyacetal resin compositions≫ In this embodiment, the polyacetal resin composition preferably has high high-temperature rigidity in order to suppress deformation due to load during gear meshing at high temperatures. Specifically, the storage 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, from the viewpoint of suppressing deformation during gear meshing. There is no particular upper limit, but it is desirable to be 3,000 MPa or less from the viewpoint of maintaining toughness.

[0166] Furthermore, in this embodiment, it is desirable that the polyacetal resin composition has a component composition (i.e., the type and amount of 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 is 0.4 or more when 10% by mass of fine cellulose fibers are incorporated. This index is an indicator of the dispersibility of the fine cellulose fibers in the composition. The higher the dispersibility, the larger the above ratio tends to be. For example, in the case of a polyacetal resin composition that does not contain fine 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 incorporated, the above ratio is less than 0.4. From the viewpoint of increasing the high-temperature rigidity of the composition with a smaller amount of fine 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. There is no particular upper limit, but from the viewpoint of processability, it is preferably 1.5 or less.

[0167] The above storage modulus is the storage modulus measured using a 10 mm wide, 4 mm thick ISO multipurpose test specimen and a solid viscoelasticity measuring device under the following conditions: measurement temperature range 0°C to 150°C (heating rate: 2°C / min), tensile mode, vibration frequency 10 Hz, static load strain 0.5%, and dynamic load strain 0.3%. The temperatures of 23°C and 120°C were calculated by interpolating the measurement temperatures before and after those temperatures.

[0168] ≪Molded products and their uses≫ One aspect of the present invention provides a molded article composed of the resin composition of the present disclosure, and a method for manufacturing a molded article, which includes a molding step for molding a molding component that is the resin composition of the present disclosure. The polyacetal resin composition of this embodiment can be molded into various molded articles by conventionally known molding methods (for example, 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.

[0169] <Irregular shaped products> In one embodiment, the molding method may be for irregular shapes. That is, in one embodiment, the molded article of this embodiment may be an irregularly shaped article. Another aspect of the present invention provides a method for manufacturing an irregularly shaped extruded article, comprising the step of extruding the resin composition of this embodiment into an irregular shape.

[0170] Known methods can be used for deformed extrusion molding. A specific example of a deformed extrusion molding method is a method in which a resin composition is put into an extruder, kneaded while being heated inside, extruded from a die for deformed extrusion to obtain an uncooled molded product, and then the uncooled molded product is continuously guided to a cooling zone to cool and obtain a deformed extruded product. Another method involves performing melt kneading to obtain a resin composition, extruding the die of the kneader as a die for deformed extrusion to obtain an uncooled molded product, and then continuously guiding the uncooled molded product into a cooling zone to cool it down and obtain a deformed extruded molded product.

[0171] The lower limit of the extrusion temperature during shape extrusion is preferably +5°C relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, and more preferably +10°C relative to the glass transition point if it is an amorphous resin. By controlling the lower limit within this range, the productivity of shape extrusion can be improved. The upper limit of the extrusion temperature during shape extrusion is preferably +100°C relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, and more preferably +80°C, +70°C, and +60°C relative to the glass transition point if it is an amorphous resin. By controlling the upper limit within this range, the degradation of cellulose fine fibers can be suppressed, thus maintaining the mechanical properties of the resin composition, and the drawdown of the resin between the shape extrusion die and the cooling zone can be suppressed, resulting in good dimensional accuracy of the shape extruded molded product.

[0172] While there are no particular restrictions on the cross-sectional shape of the irregularly shaped extruded product, sheet-like, pipe-like, tubular, and angular shapes are preferred. In the case of a sheet shape, the sheet thickness can be 0.2 to 50 mm and the sheet width can be 10 to 1500 mm. In the case of a pipe-like or tubular shape, the thickness can be 0.1 to 30 mm and the inner diameter can be 1 to 1000 mm. In the case of an angular shape, the angle of the corner can be 30 to 150 degrees. The minimum radius of curvature on the valley side of the corner can be 0.1 mm.

[0173] <Materials for 3D printing> In one embodiment, molding may be performed by 3D printing. One aspect of the present invention provides a 3D printing material comprising fine cellulose fibers, a thermoplastic resin, and polyethylene glycol, and a method for manufacturing the same. In one embodiment, the 3D printing material is composed of the resin composition of this embodiment. Polyethylene glycol can function as a dispersant for good dispersion of fine cellulose fibers in the thermoplastic resin, and polyethylene glycol acts as a crystallization retarder for polyacetal, thereby inhibiting molding shrinkage during 3D printing and resulting in a molded object with excellent dimensional accuracy. The 3D printing material of this embodiment is advantageous for forming molded objects with high mechanical properties and excellent dimensional accuracy.

[0174] In one embodiment, the 3D printing material may have a desired form such as pellets, filaments, or powders, and preferably has the form of filaments or powders. Known methods can be used to mold the resin composition into a 3D printing material of the desired form. For example, the filament may be monofilament or multifilament, but monofilament is preferred due to its ease of molding.

[0175] The diameter of the filamentous material is preferably 0.5 to 5.0 mm, more preferably 1.0 to 3.5 mm, and most preferably 1.5 to 3.0 mm. The length of the filamentous material is preferably more than 1 m, more preferably more than 10 m, more preferably more than 100 m, and most preferably more than 300 m. By controlling the shape of the filamentous material within this range, a wide range of applicable 3D printers can be selected, and it becomes possible to appropriately design the printing time, the size of the printed object, and the level of detail. In one embodiment, the length of the filamentous material may be 20,000 m or less.

[0176] In one embodiment, the filamentous molding material can be manufactured by heating and melting a resin composition, passing it through a pore such as a nozzle, cooling it, and winding it up. The diameter of the pore can be appropriately selected according to the diameter of the filament and the winding speed, but from the viewpoint of manufacturing efficiency and the frequency of thread breakage defects, it is preferably 0.5 to 10.0 mm, more preferably 0.8 to 5.0 mm, and most preferably 1.0 to 3.0 mm. As for the cooling method, known methods such as air cooling and water cooling can be appropriately selected, but from the viewpoint of preventing water absorption due to the hydrophilicity of cellulose microfibers, air cooling is preferred. From the viewpoint of manufacturing efficiency and the frequency of thread breakage defects, the winding speed of the filament is preferably 0.1 to 10 m / sec, more preferably 0.15 to 5 m / sec, and most preferably 0.2 to 1 m / sec. The manufacturing apparatus for the filamentous molding material and the manufacturing apparatus for the resin composition may be the same or different.

[0177] The particle size, particle shape, and aspect ratio of the powdered 3D printing material can be appropriately selected depending on the 3D printer used. In one embodiment, the particle size is preferably 1 to 10,000 μm, more preferably 10 to 500 μm, and most preferably 30 to 200 μm, from the viewpoint of handling as a 3D printing material and surface smoothness of the printed object. The particle shape may be spherical or irregular, but an irregular shape is preferred from the viewpoint of suppressing voids during printing. The aspect ratio is preferably 1.001 to 3.0, more preferably 1.01 to 2.0, and most preferably 1.1 to 1.8, from the viewpoint of suppressing voids by reducing the interparticle gaps.

[0178] In one embodiment, a powdered molding material can be produced by grinding or reprecipitating a resin composition. The method of grinding the resin composition is not particularly limited, but may include wet grinding, dry grinding, low-temperature grinding, freeze grinding, and heat grinding. A grinding medium may be used for the purpose of controlling the shape of the powdered molding material.

[0179] <Sculpture> One aspect of the present invention provides a molded object formed by 3D printing using a resin composition (e.g., resin composition pellets) or a 3D printing material according to this embodiment. Another aspect of the present invention also provides a method for manufacturing a molded object, which includes the step of 3D printing using a resin composition or a 3D printing material according to this embodiment. Examples of 3D printing methods include fused deposition modeling (FDM), stereolithography (SLA), material jetting, powder bonding, and powder bed fusion. When using a filamentous material, FDM is preferred, and when using a powdered material, powder bonding and powder bed fusion are preferred.

[0180] The molded object can be used as is for various applications, or it can be molded into a desired shape, either alone or in combination with other components, to produce a desired molded product. The method of combining components and the molding method are not particularly limited and may be selected according to the desired molded product. The molding method is not limited to these, but methods such as cutting molding and foam molding can be used. The molded object or molded product is useful as a substitute for steel plates, fiber-reinforced plastics (e.g., carbon fiber reinforced plastics, glass fiber reinforced plastics, etc.), resin composites containing inorganic fillers, etc. Suitable applications for 3D printing materials, molded objects, or molded products include industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

[0181] <Properties of resin compositions, 3D printing materials, and 3D printed objects> The resin composition, 3D printing material, and the printed object may have the following properties.

[0182] [Tensile yield strength] The tensile yield strength of the resin composition, 3D printing material, or printed object may, in one embodiment, be 20 MPa or more, 50 MPa or more, or 80 MPa or more, and may be 300 MPa or less, 200 MPa or less, or 150 MPa or less.

[0183] [Tensile elongation at breaking] The tensile elongation at break of a resin composition, 3D printing material, or molded object may, in one embodiment, be 2% or more, 3% or more, or 5% or more, and may be 200% or less, 100% or less, or 20% or less.

[0184] [Flexural modulus] The flexural modulus of the resin composition, 3D printing material, or molded object may, in one embodiment, be 2.0 GPa or higher, 2.5 GPa or higher, 3.0 GPa or higher, 3.5 GPa or higher, 3.7 GPa or higher, or 3.9 GPa or higher, and may be 20.0 GPa or lower, 10.0 GPa or lower, or 8.0 GPa or lower.

[0185] <Applications of molded products> The molded product of this embodiment can be used for a variety of applications, including automotive parts, electrical and electronic components, building materials, lifestyle-related parts, cosmetic parts, medical-related parts, rails, pipes, sashes, door frames, window frames, handrails, decking materials, fences, and various other building materials.

[0186] Specifically, automotive parts include interior components such as inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, and clips; electrical system components such as meters and connectors; in-vehicle electrical and electronic components such as audio equipment and car navigation equipment; metal-contacting components such as window regulator carrier plates; and mechanical components such as door lock actuator components, mirror components, wiper motor system components, and fuel system components.

[0187] Electrical and electronic components include parts or components of equipment made of polyacetal resin molded products with numerous metal contacts, such as audio equipment, video equipment, or office automation equipment such as telephones, photocopiers, fax machines, word processors, and computers, as well as parts or components of toys. Specifically, these include chassis, gears, levers, cams, pulleys, and bearings.

[0188] Furthermore, it is suitably used in a wide range of everyday life, cosmetic, and medical-related parts, such as lighting fixtures, joinery, pipes, cocks, faucets, toilet peripheral equipment parts, fasteners, stationery, lip balm / lipstick containers, washers, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, and syringe needle holders. Among these, it is more preferably used in gears, which are subjected to high temperatures and heavy loads.

[0189] <Recycling> In one embodiment, the molding component used in the molding process includes recycled material, which is a molten product of the molded article. In one embodiment, in the molding process, the molding component, which is a resin composition of the present disclosure, is molded to produce each of a plurality of members, and the resin composition for producing one or more of the plurality of members includes recycled material, which is a molten product of one or more of the plurality of members. That is, if the molded article is composed of a plurality of members, one or more of the plurality of members may be recovered, and the product obtained by melting them may be used as part or all of one or more of the plurality of molding components for producing each of the plurality of members. The plurality of members may have the same or different compositions. Through this disclosure, "same composition" means that at least one of the following conditions is met: (1) the constituent monomer species of the polyacetal resin in the resin composition are the same for all members; (2) the MFR of the polyacetal resin in the resin composition is within the number average value ± 5 g / 10 min for all members; (3) the weight-average molecular weight of the polyacetal resin in the resin composition is within the number average value ± 10% for all members; and (4) the flexural modulus of the polyacetal resin in the resin composition is within the number average value ± 10% for all members. "Different composition" means that none of the above conditions (1) to (4) are met. In one embodiment, multiple members may consist of two members.

[0190] When multiple components have the same composition, it is preferable to include these components in a single recycled material because it is easy to control the physical properties of the recycled material. On the other hand, when multiple components have different compositions, these components may be included in separate recycled materials, or two or more of these components may be included in a single recycled material. In the latter case, the desired physical properties of the recycled material may be achieved by adjusting the mass fraction of each component constituting the recycled material.

[0191] In the case where the molding component contains recycled material, the recycled material content in the molding component may be 5% by mass or more, 10% by mass or more, or 15% by mass or more in one embodiment, and may be 100% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less in one embodiment.

[0192] <<Sliding Articles>> One aspect of the present invention provides an article having a first member and a second member configured to be slidable from one another. In one aspect, the first member is composed of a first resin composition, and the second member is composed of a second resin composition, and each of the first resin composition and the second resin composition is (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, and (c) Polyethylene glycol 0.1 to 100 parts by mass, This includes the following. In one embodiment, the ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition (A2) to the content of fine cellulose fibers in the first resin composition (A1) is 0.5 or more and 1 or less.

[0193] The first and / or second resin composition may be the resin composition of this embodiment. In one embodiment, in the first and second resin compositions, (a) the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin, and (c) the number of oxyethylene repeating units n of polyethylene glycol are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+10) / 0.015 The relationship may be satisfied.

[0194] In this embodiment, the first and second members have a common material composition in that they contain polyacetal resin, and the content of fine cellulose fibers between these members satisfies a specific relationship. In recent years, with the growing concern for environmental issues, there has been a demand for the recycling of resin-based articles, and when constructing a sliding article with multiple sliding members, it is desirable in terms of recycling efficiency for these multiple members to have a common material composition. In this embodiment, since the first and second members of the sliding article have a common material composition in that they contain polyacetal resin, even when these members are recycled together (i.e., without separating them), it is possible to obtain recycled material that retains the inherent advantages of polyacetal resin. The first and second members may have the same or different compositions in the sense of this disclosure.

[0195] Polyacetal resin inherently possesses excellent sliding properties due to its relatively low coefficient of friction, superior moldability resulting in smooth surface finishes, and excellent rigidity, toughness, and wear resistance. Furthermore, fine cellulose fibers offer excellent lightweight properties and mechanical property enhancement effects, and can be finely dispersed in the resin to form low-anisotropic molded products. Since polyacetal resin inherently possesses excellent rigidity and toughness, combining it with fine cellulose fibers as a filler is advantageous because it can further improve rigidity and toughness without introducing the disadvantages that can occur with conventional fillers (especially inorganic fillers).

[0196] More specifically, fine cellulose fibers are softer than general inorganic fillers and have good affinity with polyacetal resin, allowing for uniform dispersion within the polyacetal resin. Such fine cellulose fibers do not impair the surface smoothness of the component and are less likely to detach from the component during repeated sliding, thus reducing the increase in surface roughness and the generation of wear particles, which are the main causes of decreased sliding performance during repeated sliding. For example, glass fibers, which are inorganic fillers, are coarse and easily oriented in molded products, which can worsen the surface smoothness of the molded product, degrading sliding performance and noise reduction, and increase the anisotropy of the molded product, leading to breakage due to stress concentration at specific points in the molded product. In addition, inorganic fillers are prone to detaching as wear particles during molded product wear, which can contribute to further deterioration of sliding performance and noise reduction by accelerating further wear of the molded product. Using fine cellulose fibers as a filler is advantageous in achieving a high degree of both sliding performance and noise reduction in sliding articles. In one embodiment, each component may essentially contain no fillers other than fine cellulose fibers, or if it does contain fillers, the amount may be such that it does not impair the effects of the present invention.

[0197] In the sliding article of this embodiment, the physical properties (rigidity, in one embodiment) of the first member and the second member can be made similar. This allows for good acquisition of the commonality of the material composition of the first and second members, that is, the advantage of recyclability due to these members containing polyacetal resin.

[0198] The ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition (A2) to the content of fine cellulose fibers in the first resin composition (A1) is preferably 0.5 or more, or 0.6 or more, or 0.7 or more, from the viewpoint of obtaining good durability of the sliding article. The ratio (A2 / A1) may be 1 or less. In one preferred embodiment, the ratio (A2 / A1) is 1 from the viewpoint of recycling efficiency. In another preferred embodiment, the ratio (A2 / A1) is preferably less than 1, or 0.95 or less, or 0.9 or less, from the viewpoint of suppressing adhesive wear between members of the sliding article.

[0199] The ratio of the flexural modulus of the second resin composition to the flexural modulus of the first resin composition is preferably 0.5 or more, or 0.6 or more, or 0.7 or more from the viewpoint of obtaining good durability and recycling efficiency of the sliding article. The above ratio may be 1 or less, but is preferably 1 or less, or 0.95 or less, or 0.9 or less from the viewpoint of suppressing cohesive wear between members of the sliding article.

[0200] In one aspect, the first and second resin compositions can include one or more of the components exemplified above for the resin composition of the present disclosure in the manner exemplified above. In one aspect, the first resin composition and the second resin composition have the same composition as each other.

[0201] ≪Method for manufacturing a sliding article≫ One aspect of the present invention also provides a method for manufacturing a sliding article of the present disclosure. In one aspect, the method for manufacturing a sliding article includes a step of molding a first resin composition, which is a molten mixture of a first mixed component including a polyacetal resin, fine cellulose fibers, and polyethylene glycol, to obtain the first member, and a step of molding a second resin composition, which is a molten mixture of a second mixed component including a polyacetal resin, fine cellulose fibers, and polyethylene glycol, to obtain the second member, wherein the first mixed component and / or the second mixed component includes a recycled material that is a melt-treated product of the first member and / or the second member.

[0202] The content rate of the recycled material in the first mixed component and / or the second mixed component is preferably 5% by mass or more, or 10% by mass or more, or 15% by mass or more, and is preferably 100% by mass or less, or 95% by mass or less, or 90% by mass or less.

[0203] In one aspect, the recycled material can be included in the mixed component by recovering the first member and / or the second member, pulverizing them into granular or powder form, and then subjecting them to melt mixing.

[0204] The resin composition can be molded using or not using conventionally known methods (e.g., injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.). The sliding article of this embodiment is, in one embodiment, an injection-molded article, and in another embodiment, a machined article (preferably a machined article from a round bar molded body). An injection-molded article can be obtained as a member of the desired shape by feeding the resin composition (e.g., resin pellets) obtained by the above method into an injection molding machine equipped with a mold of the desired member shape and performing molding. A machined article from a round bar molded body can be obtained, for example, by feeding resin pellets into an extrusion molding machine and performing round bar extrusion to obtain a round bar-shaped molded body, and then machining this round bar to the desired member shape. In either molding method, the molding of the member from the resin composition can be carried out appropriately based on the common technical knowledge of those skilled in the art. With injection molding or machining from a round bar, voids tend to be less likely to occur even in thick-walled components by controlling the mold surface temperature, injection speed, holding pressure, etc. A more preferable molding method in terms of mass production and productivity is injection molding. In a typical embodiment, the component is a thick-walled gear with a tooth width dimension of, for example, 2 to 50 mm.

[0205] In the slidable article of the present embodiment, the first member and the second member may be arranged with or without an interposition of a friction reducing agent such as grease. The friction reducing agent may be applied to at least the meshing surface of each member with the other member. By using the friction reducing agent, the slidability, durability, and quietness of the slidable article can be further improved. As the friction reducing agent, various conventionally known ones can be used, but from the viewpoint of obtaining excellent slidability even in a wide temperature environment, it preferably contains a base oil, a thickener, and an additive. In one aspect, the friction reducing agent is: a base oil containing at least one selected from the group consisting of mineral oil, polyalphaolefin oil, and alkylpolyphenyl ether in a proportion of 80% by mass or more; and may contain a thickener and 3 to 10% by mass of a hydrocarbon wax having a melting point or softening point in the range of 70 to 130°C. Examples of the thickener include calcium soap, lithium soap, lithium complex soap, calcium complex soap, aluminum complex soap, urea, PTFE, bentonite, phthalocyanine, indanthrene, silica gel, and the like.

[0206] On the other hand, in one aspect, the first member and the second member are configured to slide directly, that is, to slide without an interposition of another component (typically the above-mentioned friction reducing agent) between the first member and the second member. When there is no other component such as a friction reducing agent, removal of such another component is not required during recycling of the member after use, which is advantageous in terms of process efficiency. According to the slidable article of the present embodiment, good slidability, durability, and quietness can be obtained even when the friction reducing agent is not used. Therefore, in the slidable article according to one aspect, the friction reducing agent is not used.

[0207] ≪Applications of the Slidable Article≫ Examples of the applications of the slidable article include those exemplified above with respect to the molded article. In a preferred aspect, the first member and the second member are gears, the article is a gear system, or the first member and the second member are bearings and the article is a damper.

[0208] <Gear System> In one embodiment, the component is a gear, and the sliding article is a gear system. The gear of this embodiment is excellent in mechanical strength, durability, sliding properties, and quietness, and can be used in various applications. In particular, the gear can be, but is not limited to, helical gears, spur gears, internal gears, rack gears, pinion gears, straight bevel gears, helical bevel gears, spiral bevel gears, crown gears, face gears, screw gears, worm gears, worm wheel gears, hypoid gears, and Novikov gears. Furthermore, the above-mentioned helical gears, spur gears, etc., may be single gears, two-stage gears, or combination gears having a structure that combines with a drive motor in multiple stages to eliminate rotational unevenness and reduce speed.

[0209] A gear system according to one embodiment comprises a driven gear and a drive gear that meshes with the driven gear, wherein one of the driven gear and the drive gear is a first member and the other is a second member. The gear system may further include a drive source (e.g., a motor) that drives the drive gear.

[0210] The gear of this embodiment can be applied to electric power steering (EPS) systems in automobiles and electric vehicles in general, for example, because it offers significantly superior durability compared to conventional gears, and in one embodiment, even quieter operation. Examples of electric vehicles, though not limited to the above, include senior four-wheeled vehicles, motorcycles, and electric two-wheeled vehicles. Furthermore, due to its excellent sliding properties and durability, the gear of this embodiment can also be used in applications such as cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, axes, bearings, guides, outsert-molded resin parts, insert-molded resin parts, chassis, trays, and side plates.

[0211] In one embodiment, the gear system may be used in the steering column of a vehicle and comprise a gear mechanism including a worm wheel as a driven gear and a worm as a drive gear, and a motor as a power source. Alternatively, in one embodiment, the gear system may be used in the steering gear of a vehicle and comprise a gear mechanism including a pinion as a driven gear and a rack as a drive gear, and a motor as a power source.

[0212] The driven gear and / or drive gear may be integrated with at least the outer surface of the metal mandrel. The driven gear may be incorporated into the gear system without the metal mandrel, or it may be incorporated into the gear system in a form in which it is integrated with the outer surface of the metal mandrel attached to the shaft. The material of the metal mandrel may be stainless steel, iron, steel, aluminum, brass, titanium alloy, nickel alloy, copper alloy, aluminum alloy, stainless steel alloy, etc. The integration of the gears with at least the outer surface of the mandrel can be carried out by methods known to those skilled in the art, but is preferably by insert injection molding.

[0213] The gears constituting the gear system mesh with each other, with or without the use of a friction-reducing agent. While the use of a friction-reducing agent improves the durability and quietness of the gear system, the gear system of this embodiment can achieve the desired durability and quietness even without the use of a friction-reducing agent. The absence of a friction-reducing agent is advantageous in terms of the recyclability of the gear system.

[0214] In one embodiment, the gear mechanism of the gear system is a rack-and-pinion mechanism consisting of a rack and a pinion, or a worm gear mechanism consisting of a worm and a worm wheel. The pinion and worm wheel are usually cylindrical gears, and it is particularly important that they have good mechanical strength, dimensional accuracy, and surface smoothness in order for the gear system to have good sliding properties and durability. In one embodiment, from the viewpoint of obtaining high sliding properties and high durability, it is preferable that the pinion or worm wheel is the first component.

[0215] Characteristics of sliding articles <Arithmetic mean surface roughness Sa of the sliding surface> The arithmetic mean surface roughness Sa of the sliding surfaces of each component of a sliding article is preferably 3.0 μm or less. Such a low arithmetic mean surface roughness Sa is advantageous for the high sliding properties (and therefore quietness) and high durability of the sliding article. The arithmetic mean surface roughness Sa is a value obtained by a measurement method in accordance with ISO 25178, and can be obtained by extending the arithmetic mean surface roughness Ra to the surface. The arithmetic mean surface roughness Ra is obtained in micrometers (μm) by measuring the roughness curve on the surface of a component that is a resin molded body (the surface of the component can be identified by a person skilled in the art based on the shape of the sliding article), in accordance with JIS B0031, taking a reference length in the direction of the average line of the roughness curve, and when the roughness curve is represented by y = f(x) with the direction of the average line of this taken portion as the X axis and the direction of the vertical magnification as the Y axis, the value obtained by the following formula (2) is expressed in micrometers (μm).

number

[0216] Furthermore, the arithmetic mean surface roughness Sa is an extension of the arithmetic mean surface roughness Ra for surfaces and is expressed by the following formula (3).

number

[0217] The upper limit of the arithmetic mean surface roughness Sa is preferably 0.9 μm, more preferably 0.8 μm, even more preferably 0.7 μm, and most preferably 0.6 μm. The lower limit of the arithmetic mean surface roughness Sa is not particularly limited, but from the viewpoint of ease of manufacture, it is preferably, for example, 0.1 μm. Surface roughness can be measured using commercially available microscope equipment such as a confocal microscope (e.g., OPTELICS® H1200, manufactured by Lasertec Corporation).

[0218] <Roundness> When the sliding article is a gear system and the component is a gear, the roundness of the gear is preferably 400 μm or less. In actual use environments, a smaller roundness leads to higher dimensional uniformity of the gear, making it less likely for large loads to be applied to specific teeth (stress concentration), and thus improving durability. The upper limit of roundness is preferably 400 μm, more preferably 300 μm, even more preferably 200 μm, and most preferably 100 μm. There is no particular lower limit to roundness, but from an actual manufacturing standpoint, it may be, for example, 1 μm. Roundness is the value obtained as the total pitch error (μm) of the gear when the error of the measured values ​​is expressed in μm using the LSC method (a method in which the difference in radii between a circle that is concentric with and inscribed in a circle that minimizes the sum of the squares of the deviations, using an image dimension measuring instrument (IM-6000 manufactured by Keyence Corporation) to measure the tooth tips of each test gear. The smaller this value, the higher the roundness can be judged to be. In the sliding articles of this embodiment, a resin composition capable of forming members with low anisotropy is used, resulting in low shrinkage anisotropy when forming members from the resin composition. Gears, being such low-anisotropy members, can have excellent (i.e., small) roundness due to uniform shrinkage during molding.

[0219] <torque> The sliding articles of this embodiment, particularly the gear system, exhibit excellent durability even in high-torque operating environments, and in one embodiment, are used with torques of 0.05 N·m or higher. Preferably, the torque is 0.1 N·m or higher, or 0.5 N·m or higher, or 1.0 N·m or higher, or 2.0 N·m or higher. The upper limit of the torque when using the sliding articles of this embodiment is not particularly limited, but from the viewpoint of durability, it is preferably 100 N·m or less, or 50 N·m or less, or 30 N·m or less, or 20 N·m or less.

[0220] <Gear operating rotation speed> When the sliding article is a gear system, its durability varies greatly depending on the operating rotational speed of the drive source to which the gear is applied, and it tends to deteriorate easily in a usage environment with a high operating rotational speed. Since the gear system of this embodiment has excellent durability, it exhibits excellent performance even when applied to a drive source with a higher operating rotational speed. In one aspect, the drive source is a motor. The upper limit of the operating rotational speed of the drive source is preferably 15,000 rpm or less, or 10,000 rpm or less, or 5,000 rpm or less. The lower limit of the operating rotational speed is not particularly limited, but since the gear system of this embodiment has good durability, it can be, for example, 10 rpm or more, or 30 rpm or more, or 50 rpm or more, or 80 rpm or more.

[0221] <Module of the gear> When the sliding article is a gear system, the module of the gear may be 0.3 or more. The module is the value obtained by dividing the reference circle diameter of the gear by the number of teeth and represents the size of the gear. The durability of the gear varies greatly depending on the size of the module. The gears of this embodiment exhibit excellent performance over a wide range of module designs. The upper limit of the module is preferably 5.0 or less, or 2.0 or less, or 1.0 or less. The lower limit of the module is not particularly limited, but from the perspective of good durability of the gear, it is preferably, for example, 0.3 or more.

[0222] ≪Method for manufacturing a molded article by recycling a sliding article≫ In one aspect, at least a part of the sliding article of the present disclosure may be recovered and recycled to manufacture a molded article. The composition and shape of the manufactured molded article can be appropriately designed as desired. The method for manufacturing a molded article provided in one aspect includes a step of molding a resin composition, which is a molten mixture of a mixed component containing a polyacetal resin, fine cellulose fibers, and polyethylene glycol, to obtain a molded article. The mixed component may include a recycled material that is a melt-treated product of the first member and / or the second member of the sliding article of the present disclosure.

[0223] In one preferred embodiment from the viewpoint of recyclability, the recycled material is the molten product of the first and second components, and the first and second components have the same composition as each other. Also, from a similar viewpoint, in one preferred embodiment, the mixed component has the same composition as the first resin composition and / or the second resin composition. [Examples]

[0224] The present invention will be described more specifically below based on examples, but the present invention is not limited to these examples.

[0225] ≪Evaluation Method≫ <Fine Cellulose Fibers> [Diameter and L / D ratio of fine cellulose fibers] The wet cake was diluted with tert-butanol to 0.01% by mass, dispersed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 25,000 rpm for 5 minutes, cast onto mica, and air-dried. The resulting material was then measured using a high-resolution scanning electron microscope. The measurements were performed by adjusting the magnification so that at least 100 cellulose fibers could be observed. The length (L), major axis (D), and ratio of these values ​​were determined for 100 randomly selected cellulose fibers, and the average of these values ​​was calculated.

[0226] [Mw of fine cellulose fibers] The wet cake was added to tert-butanol and further dispersed using a mixer or similar device until no aggregates remained. The concentration was adjusted to 0.5% by mass for every 0.5 g of fine cellulose fiber solids. 100 g of the resulting tert-butanol dispersion was filtered on filter paper, dried at 150°C, and then the filter paper was peeled off to obtain a sheet. The air permeability resistance of this sheet was 10 g / m². 2A porous sheet was obtained with a viscosity of 100 sec / 100 ml or less per unit area. 0.88 g of the porous sheet was weighed, cut into small pieces with scissors, lightly stirred, and then 20 mL of pure water was added and left for 1 day. Next, the water and solids were separated by centrifugation. Then 20 mL of acetone was added, lightly stirred, and left for 1 day. Next, the acetone and solids were separated by centrifugation. Then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. N,N-dimethylacetamide and solids were separated again by centrifugation, and then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. N,N-dimethylacetamide and solids were separated by centrifugation, and 19.2 g of N,N-dimethylacetamide solution, prepared so that lithium chloride was 8 mass percent, was added to the solids, stirred with a stirrer, and visual confirmation of dissolution was obtained. The cellulose solution was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The equipment and measurement conditions used are as follows.

[0227] Equipment: Tosoh Corporation HLC-8120 Column: TSKgel SuperAWM-H (6.0mm I.D. × 15cm) × 2 tubes Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%) Flow rate: 0.6mL / min Calibration curve: Pullulan equivalent

[0228] [Degree of acetyl substitution in hydrophobized fine cellulose fibers (DS)] The infrared spectral measurements of five locations on the above porous sheet were taken using the ATR-IR method with a Fourier transform infrared spectrophotometer (JASCO FT / IR-6200). The infrared spectral measurements were performed under the following conditions. Total number of times: 64 Wavenumber resolution: 4cm -1 , Measurement wavefrequency range: 4000~600cm -1 , ATR crystal: diamond, Incident angle: 45° The IR index from the obtained IR spectrum is calculated using the following formula: IR Index = H1730 / H1030 The calculation was performed according to the formula. In the formula, H1730 and H1030 are 1730 cm. -1 , 1030cm -1 This is the absorbance in the absorption band of the CO stretching vibration of the cellulose skeleton chain. However, each value is 1900 cm². -1 and 1500cm -1 The line connecting them is 800cm -1 and 1500cm -1 The line connecting these points is used as the baseline, and this value represents the absorbance when this baseline is set to 0. Then, the average degree of replacement at each measurement location was calculated from the IR index according to the following formula, and the average value was defined as DS. DS = 4.13 × IR Index

[0229] <Resin composition> [Tensile properties] Multipurpose test specimens conforming to ISO 294-3 were molded using an injection molding machine under conditions conforming to JIS K7364-2. Tensile tests were then performed on the molded test specimens in accordance with ISO 527.

[0230] [Storage modulus] Multipurpose test specimens conforming to ISO 294-3 were molded using an injection molding machine under conditions conforming to JIS K7364-2. The storage modulus was measured under the following conditions: tensile mode, measurement temperature range -100°C to 150°C, heating rate: 2°C / min, vibration frequency 10 Hz, static load strain 0.5%, and dynamic load strain 0.3%. The storage modulus at 23°C was denoted as E'(23°C), and the storage modulus at 120°C was denoted as E'(120°C), and these are listed in Tables 1 and 2, respectively. The ratio of the storage modulus at 120°C to the storage modulus at 23°C is listed as RATIO(120°C / 23°C) in the Examples Table.

[0231] [Flexural modulus] The multipurpose test specimens obtained above were measured in accordance with ISO 179.

[0232] <Components and sliding articles> [Coefficient of friction] For the multipurpose test specimen (as the first component) obtained above, a reciprocating friction and wear test was conducted using a reciprocating friction and wear tester (AFT-15MS model, manufactured by Toyo Precision Co., Ltd.) and a pin with a 5 mm diameter sphere (as the second component) at its tip, formed by injection molding a pellet-shaped resin composition as the second resin composition. The test was performed at a temperature of 23°C, humidity of 50%, linear speed of 30 mm / sec, reciprocating distance of 10 mm, load of 19.6 N, and 10,000 reciprocating cycles, with the tip of the pin in contact with the surface of the multipurpose test specimen. The average value of the friction coefficient over 9,500 to 10,000 reciprocating cycles was defined as the friction coefficient. A smaller friction coefficient indicates better sliding performance.

[0233] [Amount of wear] The amount of wear was measured using a three-dimensional white light interference microscope (ContourGT-X, Bruker) to determine the amount of wear (wear volume) of the sample (i.e., the first component) after the above sliding test. A lower value for the amount of wear indicates superior wear resistance and therefore durability.

[0234] [Quiet] In the above reciprocating sliding test, the sliding noise during measurement was evaluated as follows. Excellent: No creaking sounds. Good: A small creaking sound is produced. Defect: Squeaking noise occurs.

[0235] [Pin scratch resistance] In the above reciprocating sliding test, the condition of the ball at the tip of the pin (i.e., the second component) after the test was evaluated as follows. Excellent: Showed almost no wear, with only slight wear on the tip. Good: The tip is slightly worn. Defect: Deformed shape due to adhesive wear.

[0236] ≪Materials used≫ (a) Polyacetal resin [Preparation example A1] A jacketed twin-screw paddle-type continuous polymerization reactor (manufactured by Kurimoto Iron Works Co., Ltd., diameter 2B, L / D=14.8) was adjusted to 80°C, and polyacetal copolymers were polymerized by supplying raw materials, etc., under the polymerization conditions (feed rate) shown below. The unstable end groups of the obtained crude polymer were removed under the end-stabilization conditions shown below to obtain a polyacetal copolymer (polyacetal resin (A-1)) in which the comonomer component derived from 1,3-dioxolane was present in a content of 1 mol% relative to the number of moles of trioxane.

[0237] (Polymerization conditions) The raw materials were supplied to the reactor at the following supply rates. Trioxane (main monomer): 3500g / hr • 1,3-Dioxolane (comonomer): 28.8g / hr • Methylal (low molecular weight acetal compound): 2.4g / hr Cyclohexane (organic solvent): 6.5 g / hr • Boron trifluoride-di-n-butyl etherate (polymerization catalyst): 0.15 g / hr (0.2 × 10⁻⁶ boron trifluoride per 1 mol of trioxane) -4 The supply rate was set so that it would be in moles. The polymerization catalyst was fed on a separate line from the other components mentioned above. (Terminal stabilization conditions) The crude polyacetal copolymer discharged from the polymerization reactor was immersed in an aqueous triethylamine solution (0.5% by mass), then stirred at room temperature for 1 hour, filtered using a centrifuge, and dried under nitrogen at 120°C for 3 hours. Next, the material was supplied to a twin-screw extruder with a vent (L / D=40) set to 200°C. A 0.8% by mass triethylamine aqueous solution was added to the end stabilization zone to a concentration of 20 ppm by mass (converted to nitrogen mass), and the material was stabilized under reduced pressure degassing at 90 kPa before being pelletized in a pelletizer. After that, it was dried at 100°C for 2 hours to obtain polyacetal resin (A-1).

[0238] [Preparation examples A2 to A5] By adjusting the amount of 1,3-dioxolane added, polyacetal resins A-2 to A-5 with different ethylene ratios were obtained. The melt mass flow rate (MFR) of the obtained polyacetal resins was measured in accordance with ISO 1133 (condition D, load 2.16 kgf, cylinder temperature 190°C). The obtained polyacetal resin is as follows: (Preparation Example A1) A-1 Ethylene ratio 0.3% ((CH2CH2):(CH2)=0.3:99.7) MFR: 30g / 10min (Preparation Example A2) A-2 Ethylene ratio 0.5% ((CH2CH2):(CH2)=0.5:99.5) MFR: 8g / 10min (Preparation Example A3) A-3 Ethylene ratio 1.0% ((CH2CH2):(CH2)=1.0:99.0) MFR: 30g / 10min (Preparation Example A4) A-4 Ethylene ratio 1.5% ((CH2CH2):(CH2)=1.5:98.5) MFR: 10g / 10min (Preparation Example A5) A-5 Ethylene ratio 1.8% ((CH2CH2):(CH2)=1.8:98.2) MFR: 9g / 10 min

[0239] [Polyacetal homopolymer] Asahi Kasei's Tenac 4010 (homopolymer (CH2CH2):(CH2)=0:100, MFR:10g / 10min) was used as polyacetal resin A-6.

[0240] <Hydrophobic fine cellulose fibers: Sometimes referred to by their respective abbreviations> [Preparation example B1] Cotton linter pulp was stirred at 500 rpm for 1 hour at room temperature using a single-shaft agitator (IMEX DKV-1 φ125mm dissolver) in dimethyl sulfoxide (DMSO). Subsequently, the mixture was fed into a bead mill (IMEX NVM-1.5) using a hose pump and circulated in DMSO alone for 120 minutes to obtain a defibrated slurry.

[0241] Then, 11 parts by mass of vinyl acetate and 1.63 parts by mass of sodium bicarbonate were added to 100 parts by mass of the defibrated slurry in the bead mill apparatus, and the apparatus was circulated for a further 60 minutes to obtain a hydrophobized fine cellulose fiber slurry.

[0242] During circulating operation, the bead mill rotation speed was set to 2500 rpm and the peripheral speed to 12 m / s. Zirconia beads with a diameter of φ2.0 mm were used, and the filling rate was set to 70% (the slit gap of the bead mill at this time was 0.6 mm). In addition, during circulating operation, the slurry temperature was controlled to 40°C using a chiller to absorb heat generated by friction.

[0243] To the obtained hydrophobized fine cellulose fiber slurry, 192 parts by mass of pure water were added per 100 parts by mass of the defibrated slurry and thoroughly stirred. The slurry was then placed in a dehydrator and concentrated. The resulting wet cake was then dispersed in the same amount of pure water, stirred, and concentrated again. This washing operation was repeated a total of five times to obtain a hydrophobized fine cellulose fiber wet cake with a solid content of 10% by mass.

[0244] The properties of the obtained hydrophobic fine cellulose fiber wet cake were evaluated, and the following results were obtained. DS: 0.96, diameter: 65 nm, L / D: approximately 450, Mw: 340,000. This hydrophobic fine cellulose fiber is called CNF(0.96).

[0245] [Preparation examples B2, B3] By adjusting the circulation time after adding vinyl acetate and sodium bicarbonate to the bead mill apparatus, two types of hydrophobic fine cellulose fiber wet cakes with different degrees of hydrophobicity were obtained. (Preparation example B2) CNF (0.41) DS: 0.41, diameter: 60 nm, L / D: approximately 470, Mw: 370,000 (Preparation example B3) CNF (1.29) DS: 1.29, diameter: 69 nm, L / D: approximately 430, Mw: 330,000

[0246] <Fine cellulose fibers: Hereinafter sometimes referred to as CNF(0)> [Preparation example B4] Cotton linter pulp was stirred at 500 rpm for 1 hour at room temperature using a single-shaft agitator (IMEX DKV-1 φ125mm dissolver) in dimethyl sulfoxide (DMSO). Subsequently, the mixture was fed into a bead mill (IMEX NVM-1.5) using a hose pump and circulated in DMSO alone for 120 minutes to obtain a defibrated slurry. Fine cellulose fiber wet cake (CNF(0)) was obtained by vacuum drying at approximately 40°C using a rotation-revolving agitator. The following results were obtained when the properties were evaluated. CNF(0) DS: 0, diameter: 71nm, L / D: approx. 220, Mw: 250,000

[0247] <(c) Polyethylene glycol> PEG-1 Mn = approximately 3,740, Oxyethylene repeating units = 85 PEG-2 Mn = approximately 6,000, Oxyethylene repeating units = 135 PEG-3 Mn = approximately 8,800, Oxyethylene repeating units = 200 PEG-4 Mn = approximately 22,000, Oxyethylene repeating units = 500 PEG-5 Mn = approximately 30,000, Oxyethylene repeating units = 700 PEG-6 Mn = approximately 2,200, Oxyethylene repeating units = 50 PEG-7 Mn = approximately 41,000, Oxyethylene repeating units = 900 PEG-8 Mn = approximately 17,600, oxyethylene repeating units = 400

[0248] (d) Hindered phenol antioxidants Irganox 1010 (manufactured by BASF Japan Ltd.) Pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]

[0249] (e) Nitrogen-containing compounds Melamine (reagent)

[0250] <Filler> Talc: Average particle size 4 μm, manufactured by Takehara Kogyo Co., Ltd. Glass fiber: Average fiber diameter 10 μm, manufactured by Asahi Fiber Glass Co., Ltd.

[0251] Manufacturing of resin compositions [Examples 1-13, 15-20, Comparative Examples 1-6] The wet cakes obtained in each of the preparation examples B1 to B4 were mixed with polyethylene glycol according to the formulations shown in Tables 1 and 2, and dried under reduced pressure using a planetary mixer under the following conditions to obtain cellulose fiber-containing powder. The end of drying was defined as the point when the moisture content of the cellulose fiber-containing powder was 3% by mass or less (solid content 97% or more), and the moisture content was measured using an infrared heating type moisture meter (MX-50 (manufactured by A&D)). Equipment: Primix Co., Ltd. Hibiscus Mix 2P-1 Jacket temperature: 80℃ Vacuum degree: -0.1MPa Stirring speed: 50rpm

[0252] A ZSK26MC co-rotating twin-screw extruder (manufactured by Coperion) with an L / D ratio of 48, having one inlet on the upstream side and one in the center of the extruder, was set to a cylinder temperature of 200°C. A dry blend of 0.2 parts by mass of a hindered phenol-based antioxidant and 0.1 parts by mass of a nitrogen-containing compound was supplied in a fixed quantity from a loss-in-weight type feeder installed at the upstream inlet for 100 parts by mass of polyacetal resin. The above-mentioned cellulose fiber-containing powders were supplied in a fixed quantity from a loss-in-weight type feeder installed at the center inlet of the extruder, so that the amount of fine cellulose fibers in the composition was approximately 10% by mass. Melt-kneading was performed, the mixture was extruded into strands, and cooled and cut to obtain a pellet-shaped polyacetal resin composition. The downstream side of the extruder was made capable of vacuum degassing to remove air and generated gases from inside the extruder.

[0253] Furthermore, the screw configuration consisted of three RKDs positioned upstream of the central feed port of the extruder, and three RKDs and one LKD in that order just before the vacuum degassing downstream. The extruder screw rotation speed was set to 150 rpm, and the feeder was configured to achieve a total extrusion discharge rate of 5 kg / hour. Various tests were conducted using the obtained pellets. The results are shown in Tables 1 and 2.

[0254] [Example 14] A resin composition was obtained by mixing cellulose wet cake and polyethylene glycol together during extrusion, without pre-drying under reduced pressure using a planetary mixer under the following conditions. Various tests were conducted using the obtained pellets. Compared to a system in which the cellulose wet cake and polyethylene glycol were pre-dried, the cellulose dispersibility deteriorated and the rigidity decreased. In the system in which the cellulose wet cake and polyethylene glycol were pre-dried, it is presumed that the presence of polyethylene glycol in the fine cellulose fibers acts as a "primer," allowing the polyacetal resin to easily penetrate the gaps between the fine cellulose fibers, thereby improving the dispersibility of the fine cellulose fibers in the polyacetal resin composite. In this example, such an effect was not obtained, and it is thought that the dispersibility deteriorated.

[0255] [Comparative Example 7] The procedure was carried out in the same manner as in Comparative Example 6, except that polyethylene glycol was replaced with ethylene glycol-propylene glycol copolymer (PEG-PPG) (manufactured by Sanyo Chemical Industries, Ltd., GL-3000), and various tests were performed using the resulting pellets. The results are shown in Tables 1 and 2.

[0256] [Table 1]

[0257] [Table 2]

[0258] Manufacturing of sliding articles [Examples 21-27, Comparative Examples 8-11] Using a twin-screw extruder (Toshiba Machine Co., Ltd. TEM-26SS extruder (L / D=48, with vent)), the cylinder temperature was set to 200°C, the components shown in Table 3 were mixed together, and the mixture was supplied from the main throat of the extruder via a quantitative feeder. The resin mixture was extruded into strands at an extrusion rate of 15 kg / hour and a screw rotation speed of 250 rpm, rapidly cooled in a strand bath, and cut with a strand cutter to obtain a resin composition in pellet form. Sliding articles were prepared using each resin composition in the combinations shown in Table 4 and subjected to evaluation. The evaluation results are shown in Table 4.

[0259] [Table 3]

[0260] [Table 4]

[0261] [Example 28] Using the resin composition pellets of Example 4, deformed extrusion molding was performed. A 40 mm diameter single-screw extruder equipped with a die with the cross-sectional shape shown in Figure 1 (values ​​in the figure are in millimeters) was used to extrude the pellets at a molding temperature of 190°C and a screw rotation speed of 20 rpm. After extrusion, the deformed product was shaped using a sizing die with the same cross-sectional shape as the die in a 2 m long water tank containing cooling water at a water temperature of 25°C to obtain a deformed extruded product. Deformed extrusion molding was possible without any problems.

[0262] [Example 29] In Example 4, the polyacetal resin was replaced with glass fiber reinforced polyacetal resin (Tenac-C GN752, manufactured by Asahi Kasei), and resin composition pellets were prepared so that the amount of fine cellulose fibers in the composition was 5% by mass. Using these pellets, irregular extrusion molding was performed in the same manner as in Example 28 to obtain irregularly shaped extruded products. Irregular extrusion molding was possible without any problems.

[0263] [Example 30] Similar to Example 4, a resin composition pellet was used in which the amount of carbon fiber (Toray Industries, Torayca T300) was changed to 10% by mass and the amount of fine cellulose fiber was changed to 5% by mass. A modified extrusion molding was performed in the same manner as in Example 28 to obtain a modified extruded product. Modified extrusion molding was possible without any problems.

[0264] [Example 31] Using the resin composition pellets from Example 4, a 3devo filament extruder (nozzle diameter 1.7 mm) manufactured by 3D Printing Corporation was used to obtain a monofilament of filament-like 3D printing material. This was done under air-cooled conditions with an automatically controlled nozzle temperature of 210°C, a screw rotation speed of 3.5 rpm, and a winding speed of 0.02 to 0.1 m / s. Subsequently, this filament-like 3D printing material was used with a Canon FUNMAT HT fused deposition modeling (FDM) 3D printer to obtain an object with the same shape as a multipurpose test specimen compliant with ISO 294-3, under the conditions of a nozzle temperature of 210°C, a platform temperature of 80°C, a layer thickness of 0.3 mm, and a printing speed of 30 mm / second. 3D printing was successfully performed without any problems. [Industrial applicability]

[0265] A composition comprising a polyacetal resin and fine cellulose fibers, provided in one aspect of the present invention, can be suitably applied to a wide range of applications, particularly high-load applications in high-temperature environments.

Claims

1. (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, and (c) 0.1 to 100 parts by mass of polyethylene glycol, Includes, The ethylene ratio R (%) of (a) the polyacetal resin, which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of polyethylene glycol are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 Satisfying the relationship, A polyacetal resin composition having an ethylene ratio R of 1.8% or less.

2. The polyacetal resin composition according to claim 1, wherein the ethylene ratio R is 0.3% to 1.8%.

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

4. The polyacetal resin composition according to claim 3, wherein the average degree of substitution (DS) of the hydrophobic fine cellulose fibers is 0.5 to 1.

5.

5. (c) The polyacetal resin composition according to claim 1, wherein the number of oxyethylene repeating units of polyethylene glycol is 80 to 700.

6. The polyacetal resin composition according to claim 1, wherein the storage modulus at 120°C is 1,000 MPa or more.

7. The polyacetal resin composition according to claim 1, 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 fine cellulose fibers is added is 0.4 or more.

8. (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, (c) 0.1 to 100 parts by mass of polyethylene glycol, (d) 0.01 to 3 parts by mass of a hindered phenol antioxidant, and (e) 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. A method for producing a polyacetal resin composition, comprising melting and kneading, The ethylene ratio R (%) of (a) the polyacetal resin, which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of polyethylene glycol are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 Satisfying the relationship, A method wherein the ethylene ratio R is 1.8% or less.

9. A method for producing a molded article, comprising a molding step of molding a molding component which is a polyacetal resin composition according to any one of claims 1 to 7.

10. The method according to claim 9, wherein the molding component includes recycled material which is a molten product of the molded product.

11. The molded product is composed of multiple members having the same or different compositions. In the molding process, the molding component is molded to produce each of the plurality of members, The method according to claim 10, wherein the polyacetal resin composition for producing one or more of the plurality of members includes a recycled material which is one or more molten products of the plurality of members.

12. The method according to claim 10, wherein the content of the recycled material in the molding component is 5% by mass to 100% by mass.

13. An article having a first member and a second member configured to be slidable from each other, The first member is made of the first resin composition, The second member is composed of a second resin composition, Each of the first resin composition and the second resin composition is (a) 100 parts by mass of polyacetal resin, (b) 1 to 150 parts by mass of fine cellulose fibers having a fiber diameter of 2 to 1000 nm, and (c) 0.1 to 100 parts by mass of polyethylene glycol, Includes, The ethylene ratio R (%) of (a) the polyacetal resin, which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units, and the number of oxyethylene repeating units n of polyethylene glycol are given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 Satisfying the relationship, The ethylene ratio R is 1.8% or less. An article in which the ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition to the content of fine cellulose fibers in the first resin composition (A1) is 0.5 or more and 1 or less.

14. The article according to claim 13, wherein the ratio (A2 / A1) of the content of fine cellulose fibers in the second resin composition to the content of fine cellulose fibers in the first resin composition (A1) is 1.

15. The article according to claim 14, wherein the first resin composition and the second resin composition have the same composition as each other.

16. The article according to claim 13, wherein the first member and the second member are gears, and the article is a gear system.

17. The article according to claim 13, wherein the first member and the second member are bearings, and the article is a damper.

18. The article according to claim 13, wherein the first member and the second member are configured to slide directly against each other.

19. A method for manufacturing an article according to any one of claims 13 to 18, A step of obtaining the first member by molding a first resin composition, which is a molten mixture of a first mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol, and A step of obtaining the second member by molding a second resin composition, which is a molten mixture of a second mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol. Includes, A method wherein the first mixed component and / or the second mixed component includes recycled material which is a molten product of the first member and / or the second member.

20. A method for manufacturing molded articles, The process includes a step of molding a resin composition, which is a molten mixture of a mixed component containing polyacetal resin, fine cellulose fibers, and polyethylene glycol, to obtain a molded product. A method wherein the mixed component includes a recycled material which is a molten product of the first and / or second component of the article described in any one of claims 13 to 18.

21. The recycled material is the molten material of the first member and the second member. The method according to claim 20, wherein the first resin composition and the second resin composition have the same composition as each other.

22. The method according to claim 20, wherein the mixed component has the same composition as the first resin composition and / or the second resin composition.

23. A molded article obtained by molding a polyacetal resin composition according to any one of claims 1 to 7.

24. The molded article according to claim 23, which is a deformed extruded product.

25. A method for manufacturing a deformed extruded product, A method comprising the step of extruding a polyacetal resin composition according to any one of claims 1 to 7 into a deformed shape.

26. A 3D printing material comprising a polyacetal resin composition according to any one of claims 1 to 7.

27. A 3D printing material according to claim 26, having the form of a filament or powder.

28. A molded object obtained by molding a polyacetal resin composition according to any one of claims 1 to 7, or a 3D printing material composed of the polyacetal resin composition, using a 3D printer.

29. A method for manufacturing a molded object, A method comprising the step of fabricating a polyacetal resin composition according to any one of claims 1 to 7, or a 3D printing material composed of the polyacetal resin composition, using a 3D printer.

30. A cellulose fiber-containing powder for polyacetal resin compositions, The aforementioned cellulose fiber-containing powder is (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, and (c) Polyethylene glycol Includes, The polyethylene glycol in (c) is given by the following formula: the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of the polyethylene glycol in (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 A polyethylene glycol containing cellulose fibers that satisfies the given relationship and has an ethylene ratio R of 1.8% or less.

31. A method for producing cellulose fiber-containing powder for polyacetal resin compositions, The aforementioned cellulose fiber-containing powder is (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, and (c) Polyethylene glycol Includes, The method includes a mixing step of mixing (b) fine cellulose fibers and (c) polyethylene glycol to obtain a cellulose fiber-containing powder, The polyethylene glycol in (c) is given by the following formula: the ethylene ratio R (%), which is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units of the polyacetal resin contained in the polyacetal resin composition, and the number of oxyethylene repeating units n of the polyethylene glycol in (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 A method for selecting such that the following relationship is satisfied and the ethylene ratio R is 1.8% or less.

32. A method for producing a polyacetal resin composition, (b) Fine cellulose fibers with a fiber diameter of 2 to 1000 nm, and (c) Polyethylene glycol A powder preparation step to obtain a cellulose fiber-containing powder containing, A resin composition preparation step in which the cellulose fiber-containing powder and (a) polyacetal resin are mixed to obtain a polyacetal resin composition, Includes, The ethylene ratio R (%) of the polyacetal resin (a) is the ratio of the number of oxyethylene units to the total number of oxymethylene units and oxyethylene units in the polyacetal resin (a), and the number of oxyethylene repeating units n of the polyethylene glycol (c) is given by the following formula: (R+0.5) / 0.015 ≦ n ≦ (R+5) / 0.015 A method for producing a polyacetal resin composition, wherein the relationship is satisfied and the ethylene ratio R is selected to be 1.8% or less.

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