JP7702291B2 - Polyacetal resin composition - Google Patents

Description

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

Polyacetal resin has excellent mechanical, thermal, and electrical properties, as well as sliding properties and moldability, and is widely used in electrical equipment, automobile parts, precision machinery parts, and other applications, primarily as a structural material or mechanism part. In particular, polyacetal resin is widely used in gear applications. The required properties of gear products are becoming more sophisticated every year, and there is an increasing demand for high load resistance in high temperature ranges exceeding 100°C, for example. Furthermore, there is a demand for long-term properties that can withstand repeated impacts on the gear blades, and there is a need for sufficient toughness as well.

Patent Document 1 describes a polyacetal resin composition in which glass fibers are blended with polyacetal resin, Patent Document 2 describes a polyacetal resin composition in which a specific cellulose powder is blended with 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 polyacetal resin, and Patent Document 4 describes a resin composition consisting of modified pulp and thermoplastic resin.

International Publication No. 2015/147271 WO 2010/119810 International Publication No. 2012/049926 International Publication No. 2016/148223

To prevent poor appearance and void formation, it is necessary to prevent both a decrease in rigidity at high temperatures and brittle fracture under load, while also improving thermal stability.

In response to such demands, a composition made by blending glass fibers with polyacetal resin, as described in Patent Document 1, can improve rigidity at high temperatures, but the composition becomes brittle and has poor toughness. In addition, hard glass fibers have a major problem in that they are not suitable for gear applications because they cause damage to the mating material when used in gears.

In addition, in compositions containing cellulose as a reinforcing material, such as those described in Patent Documents 2 to 4, the effect of improving rigidity can only be achieved at room temperature, mainly due to the large size of the cellulose itself, and there are problems in that sufficient toughness cannot be obtained under load because cracks occur mainly due to the large cellulose. Thus, no polyacetal resin composition has been obtained that combines rigidity at high temperatures and toughness under load.

Furthermore, applying strong shear during extrusion processing, etc., in order to increase the dispersibility of cellulose in a cellulose resin composition causes thermal degradation of the polyacetal resin, which leads to new problems such as silver streaks during molding, odor, and the occurrence of voids in the center of the molded product. In addition, the dispersibility of cellulose fibers in acetal resin tends to decrease as the cellulose fibers are refined, so when fine cellulose fibers are used, the use of processing aids to improve dispersibility is required. However, processing aids may promote the oxidation of the polyacetal resin, leading to the generation of decomposition products of the polyacetal resin, which cause the resin composition to turn yellow or brown. Therefore, there has been a need to avoid the inconveniences caused by the oxidation of the polyacetal resin.

One aspect of the present invention aims to solve the above problems and provide a polyacetal resin composition that prevents a decrease in rigidity at high temperatures and brittle fracture under load, and also has excellent thermal and oxidative stability, as well as a method for producing the same.

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

According to one aspect of the present invention, a polyacetal resin composition and a method for producing the same can be provided that prevent both a decrease in rigidity at high temperatures and brittle fracture under load, and also has excellent thermal and oxidative stability. Such a polyacetal resin composition can suppress the occurrence of silver streaks, odors, and voids in the center of the molded product during molding.

Below, we will explain exemplary embodiments of the present invention (also referred to as "present embodiments" in this disclosure), but the present invention is not limited to these embodiments.

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

<(a) Polyacetal Resin>
(a) Polyacetal resins are polymeric compounds whose main constituent unit is an oxymethylene group ( _-OCH2- ), and are typically polyacetal homopolymers consisting essentially of repeating oxymethylene units, and polyacetal copolymers containing oxymethylene units and other monomer units. (a) Polyacetal resins also include copolymers into which branched and/or crosslinked structures have been introduced by copolymerizing branch-forming components and/or crosslinking components, and block or graft copolymers having a polymer portion consisting of repeating oxymethylene groups and another polymer portion.

In general, polyacetal homopolymers are produced by polymerization of one or more monomers selected from anhydrous formaldehyde and cyclic formaldehyde oligomers such as trioxane (cyclic trimer of formaldehyde) and tetraoxane (cyclic tetramer of formaldehyde). Usually, the polymerization terminals are esterified to stabilize against thermal decomposition.

Polyacetal copolymers are generally produced by copolymerizing formaldehyde and/or a cyclic oligomer of formaldehyde represented by the general formula ( _CH2O )n [wherein n is an integer of 3 or more] (such as the above-mentioned trioxane) with a comonomer such as a cyclic ether and/or a cyclic formal (such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, and cyclic formals of glycols or diglycols such as 1,4-butanediol formal). Usually, unstable terminal portions are removed by hydrolysis to stabilize the copolymer against thermal decomposition.

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

Examples of polyacetal resins include polyacetal homopolymers having block components obtained by polymerizing formaldehyde monomers and/or cyclic oligomers in the presence of a compound having functional groups such as hydroxyl groups at both or one end, for example, polyalkylene glycol; and polyacetal copolymers having block components obtained by copolymerizing formaldehyde monomers and/or cyclic oligomers with cyclic ethers and/or cyclic formals in the presence of a compound having functional groups such as hydroxyl groups at both or one end, for example, hydrogenated polybutadiene glycol.

Among these, polyacetal copolymers are preferred from the viewpoint of the balance between thermal stability and mechanical properties. Furthermore, polyacetal resins can be used alone or in combination of two or more.

(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 sum of the alkoxy end groups and the hydroxyalkoxy end groups having at least two carbon atoms is preferably 70 to 99 mol % of all the end groups.

The number of terminal groups can be measured using known methods, such as those described in JP-A-5-98028 and JP-A-2001-11143.

The melt index of (a) polyacetal resin, measured in accordance with ASTM-D1238 under conditions of 190°C and 2.16 kgf (21.2 N), is preferably 2 g/10 min at the lower limit, 4 g/10 min at the lower limit, or 7 g/10 min at the upper limit, and is preferably 25 g/10 min at the upper limit, 20 g/10 min at the upper limit, or 18 g/10 min at the upper limit. By keeping the melt index within the above range, molding flowability can be ensured while maximizing the reinforcing effect of the fine cellulose fibers.

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

Fine cellulose fibers can be obtained by beating and fibrillating the cellulose fiber raw material using mechanical forces such as a beater or refiner, and then defibrating it using a pulverizing method such as a high-pressure homogenizer, microfluidizer, ball mill, disc mill, or mixer (e.g., homomixer).

In one embodiment, the fiber diameter of the fine cellulose fibers is 1 nm or more, or 2 nm or more, or 4 nm or more, or 10 nm or more, or 20 nm or more, or 30 nm or more, in order to maintain good crystallinity of cellulose. On the other hand, the upper limit is 1000 nm or less, or 800 nm or less, or 500 nm or less, or 300 nm or less, in order to provide good effect as a filler. In one embodiment, the fiber diameter of the fine cellulose fibers is 1 nm to 1000 nm. In one embodiment, the fiber diameter of the fine cellulose fibers is 10 nm to 1000 nm.

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 injection molded article containing the fine cellulose fibers with a smaller amount of the fine cellulose fibers. The upper limit is not particularly limited, but from the viewpoint of handleability, it is preferably 5000 or less.

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

In a typical embodiment, the crystal structure of the fine cellulose fibers has cellulose type I and/or type II. Known cellulose crystal forms include type I, type II, type III, and type IV. Type I and type II cellulose are widely used, while type III and type IV cellulose have been obtained on a laboratory scale but are not widely used on an industrial scale.

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

The degree of crystallinity of the fine cellulose fiber of this embodiment is preferably 50% or more, more preferably 60% or more, even more preferably 65% or more, and most preferably 70% or more, from the viewpoint of obtaining good mechanical properties. Since the higher the degree of crystallinity of the fine cellulose fiber, the more preferable it tends to be, there is no particular upper limit, but from the viewpoint of production, 99% is the preferred upper limit.

When the fine cellulose fibers are cellulose type I crystals (derived from natural cellulose), the degree of crystallinity can be calculated from the diffraction pattern (2θ/deg. 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction using the Segal method, according to the following formula:

Crystallinity (%) = [I (200) - I (amorphous)] / I (200) x 100
I(200): Diffraction peak intensity due to the 200 plane (2θ=22.5°) in cellulose I type crystals I(amorphous): Halo peak intensity due to amorphous in cellulose I type crystals, which is the peak intensity at an angle 4.5° lower than the diffraction angle of the 200 plane (2θ=18.0°). When the fine cellulose fibers are cellulose II type crystals (derived from regenerated cellulose), the degree of crystallinity is calculated by the following formula from the absolute peak intensity h0 at 2θ=12.6° assigned to the (110) plane peak of cellulose II type crystals in wide-angle X-ray diffraction and the peak intensity h1 from the baseline at this interplanar spacing.

Crystallinity (%) = h1/h0 x 100
The degree of polymerization (DP) of the fine cellulose fibers is preferably 100 or more, more preferably 150 or more, in terms of good tensile strength at break and modulus of elasticity, and from the viewpoint of easy availability, is preferably 12000 or less, more preferably 8000 or less. The degree of polymerization is determined as the degree of polymerization DP by determining the intrinsic viscosity (JIS P 8215:1998) of a dilute cellulose solution using a copper ethylenediamine solution, and then utilizing the following formula that exists between the intrinsic viscosity of cellulose and the degree of polymerization DP.

Intrinsic viscosity [η]=K×DPa
Here, K and a are constants determined depending on the type of polymer. In the case of cellulose, K is 5.7×10 ⁻³ and a is 1.

The weight average molecular weight (Mw) of the fine cellulose fiber is preferably 100,000 or more, more preferably 200,000 or more. The ratio (Mw/Mn) of the weight average molecular weight to the number average molecular weight (Mn) of the fine cellulose fiber is preferably 6 or less, preferably 5.4 or less. The larger the weight average molecular weight, the fewer the number of terminal groups of the cellulose molecule. In addition, since the ratio (Mw/Mn) of the weight average molecular weight to the number average molecular weight represents the width of the molecular weight distribution, the smaller the Mw/Mn, the fewer the number of terminals of the cellulose molecule. Since the terminals of the cellulose molecules are the starting points of thermal decomposition, when the cellulose molecules of the fine cellulose fiber not only have a large weight average molecular weight but also have a narrow molecular weight distribution, a fine cellulose fiber with particularly high heat resistance can be obtained. The weight average molecular weight (Mw) of the cellulose fiber may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of the ease of availability of the cellulose raw material. The ratio (Mw/Mn) of the weight average molecular weight to the number average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more, from the viewpoint of ease of production of cellulose fibers. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, performing physical and/or chemical treatment on the cellulose raw material appropriately in a moderate range, etc. Mw/Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw/Mn appropriate for the purpose, performing physical and/or chemical treatment on the cellulose raw material appropriately in a moderate range, etc. In both the control of Mw and the control of Mw/Mn, examples of the physical treatment include dry or wet grinding using a microfluidizer, ball mill, disk mill, etc., physical treatment that applies mechanical forces such as impact, shear, shear, and friction using a crusher, homomixer, high-pressure homogenizer, ultrasonic device, etc., and examples of the chemical treatment include digestion, bleaching, acid treatment, regenerated cellulose, etc.

The weight average molecular weight and number average molecular weight of the fine cellulose fibers are values determined by dissolving the fine cellulose fibers in N,N-dimethylacetamide containing lithium chloride and then performing gel permeation chromatography using N,N-dimethylacetamide as a solvent.

The fine cellulose fibers may be chemically modified fine cellulose fibers that have been chemically modified with a modifying agent. The modifying agent can be a compound that reacts with the hydroxyl groups of cellulose, and examples of such a modifying agent include an esterifying agent, an etherifying agent, a silylating agent, and an isocyanate. In a preferred embodiment, the chemical modification is acylation using an esterifying agent. The esterifying agent can be a compound that reacts with the hydroxyl groups of cellulose to produce acyl groups, such as a compound selected from a carboxylic acid halide, an acid anhydride (i.e., a carboxylic acid anhydride), a carboxylic acid vinyl ester, or a carboxylic acid. A preferred chemical modification is a hydrophobic chemical treatment of the surface of the fine cellulose fibers, and a preferred hydrophobic chemical treatment is acetylation.

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

The degree of acyl substitution (DS) of the esterified fine cellulose fiber can be calculated from the reflection infrared absorption spectrum of the esterified fine cellulose fiber based on the peak intensity ratio of the peak derived from the acyl group to the peak derived from the cellulose skeleton. 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 appears at 1030 cm ^-1 . The DS of the esterified fine cellulose fiber is obtained by preparing a correlation graph between the DS obtained from the solid-state NMR measurement of the esterified fine cellulose fiber described later and the modification ratio (IR index 1030) defined as 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, and calculating the calibration curve from the correlation graph: Degree of substitution DS = 4.13 × IR index (1030)
It can be found by using

The DS of the esterified fine cellulose fiber by solid-state NMR can be calculated by carrying out 13C solid-state NMR measurement on the frozen and pulverized esterified fine cellulose fiber, and calculating the DS from the total area intensity (Inp) of the signals assigned to the carbon atoms C1-C6 derived from the pyranose ring of cellulose appearing in the range of 50 ppm to 110 ppm relative to the area intensity (Inf) of the signal assigned to one carbon atom derived from the modifying group, using the following formula:
DS=(Inf)×6/(Inp)
For example, when the modifying group is an acetyl group, the signal at 23 ppm assigned to _--CH.sub.3 may be used.

The conditions for the 13C solid-state NMR measurement are, for example, as follows:
Equipment: Bruker Biospin Avance500WB
Frequency: 125.77MHz
Measurement method: DD/MAS method
Waiting time: 75 seconds
NMR sample tube: 4 mm diameter
Accumulation times: 640 times (approximately 14 hours)
MAS: 14,500Hz
Chemical shift reference: glycine (external reference: 176.03 ppm)

The preferred amount of (b) fine cellulose fibers is 1 to 150 parts by mass per 100 parts by mass of (a) polyacetal resin. In order to maintain high high-temperature rigidity, the amount is preferably 2 parts by mass or more, or 4 parts by mass or more, or 5 parts by mass or more, and in order to improve toughness under tension, the amount is preferably 100 parts by mass or less, or 80 parts by mass or less, or 50 parts by mass or less, or 40 parts by mass or less, or 20 parts by mass or less.

<(c) Hindered Phenol-Based Antioxidants>
The polyacetal resin composition of the present embodiment contains (c) a hindered phenol-based antioxidant, which allows it to stably achieve excellent mechanical properties and color tone. The processing aid used to improve the dispersibility of the fine cellulose fibers promotes the oxidation of the polyacetal resin, leading to the production of decomposition products of the polyacetal resin. The decomposition products cause the polyacetal resin to yellow or brown, thereby reducing the inherent whiteness of the polyacetal resin. The (c) hindered phenol-based antioxidant has an excellent effect of inhibiting the oxidation of the polyacetal resin, and therefore may be advantageous in improving the color tone of the polyacetal resin composition.

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

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

<(d) Nitrogen-Containing Compound>
The polyacetal resin composition of the present embodiment includes a nitrogen-containing compound (d). In one embodiment, the nitrogen-containing compound (d) is at least one selected from the group consisting of aminotriazine compounds, guanamine compounds, hydrazide compounds, and polyamides. These nitrogen-containing compounds have an amino group or an amide group capable of capturing formaldehyde in their structure. This allows the color tone and thermal stability of the polyacetal resin (a) to be maintained, odor during processing to be suppressed, and mechanical properties to be improved. As described above, in a composite containing a polyacetal resin and fine cellulose fibers, the processing aid used to improve the dispersibility of the fine cellulose fibers promotes the oxidation of the polyacetal resin, so that yellowing or browning occurs due to the decomposition product of the polyacetal resin, and the inherent whiteness of the polyacetal resin is reduced. The nitrogen-containing compound (d) has an excellent acid scavenging effect, and therefore suppresses the oxidation of the polyacetal resin, thereby contributing to improving the color tone of the resin composition.

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

Examples of guanamine compounds include aliphatic guanamine compounds (monoguanamines, alkylenebisguanamines, etc.), alicyclic guanamine compounds (monoguanamines, etc.), aromatic guanamine compounds [for example, monoguanamines (benzoguanamine and its functional group substituted derivatives, etc.), α- or β-naphthoguanamine and their functional group 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.), isocyanuric ring-containing guanamines, imidazole ring-containing guanamines, etc.], with aromatic guanamine compounds being particularly preferred.

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

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

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

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

The number average molecular weight of the polyamide may be preferably 10,000 or less, or 9,000 or less, in terms of the good brittle fracture prevention effect of the polyacetal resin composition under load, and may be preferably 2,000 or more, or 3,000 or more, or 4,000 or more, in terms of the high-temperature rigidity and thermal stability of the polyacetal resin composition. The number average molecular weight is a value determined using gel permeation chromatography in terms of standard polymethyl methacrylate.

The nitrogen-containing compound (d) may be used alone or in combination of two or more. The amount of the nitrogen-containing compound (d) relative to 100 parts by mass of the polyacetal resin (a) is 0.01 parts by mass or more, preferably 0.02 parts by mass or more, or 0.03 parts by mass or more, or 0.05 parts by mass or more, in one embodiment, from the viewpoints of maintaining color tone, thermal stability, suppressing odor during processing, and mechanical properties, and is 3 parts by mass or less, preferably 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, in one embodiment, from the viewpoint of suppressing mold deposits on the mold in advance.

In addition, when the nitrogen-containing compound (d) is added to the polyacetal resin (a), it is preferably in the form of a fine powder from the viewpoint of preventing a decrease in the mechanical properties of the polyacetal resin composition.

<(e) Processing aid>
The polyacetal resin composition of this embodiment contains (e) a processing aid. In one aspect, the (e) processing aid is at least one selected from the group consisting of long-chain fatty acids, derivatives of long-chain fatty acids, long-chain aliphatic alcohols, polyoxyethylene derivatives, polyoxyalkylene glycols, olefin waxes, and silicone compounds. This can prevent molding defects caused by an increase in viscosity due to the incorporation of (b) fine cellulose fibers, and can also suppress aggregation of (b) fine cellulose fibers in the resin. In this disclosure, the term "long-chain fatty acid" refers to a fatty acid having 10 or more carbon atoms, and the term "long-chain aliphatic alcohol" refers to an aliphatic alcohol having 10 or more carbon atoms.

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

Examples of derivatives of long-chain fatty acids include fatty acid esters and fatty acid amides.

Examples of fatty acid esters include esters of the above long-chain fatty acids and alcohols. The structure is not particularly limited and may be linear or branched. Specific examples of fatty acid esters include ethylene glycol mono- or dipalmitic acid esters, ethylene glycol mono- or distearic acid esters, ethylene glycol mono- or dibehenic acid esters, ethylene glycol mono- or dimontanic acid esters, glycerin mono- to tripalmitic acid esters, glycerin mono- to tristearic acid esters, glycerin mono- to tribehenic acid esters, glycerin mono- to trimontanic acid esters, pentaerythritol mono- to tetrapalmitic acid esters, pentaerythritol mono- to tetrastearic acid esters, pentaerythritol mono- to tetrastearic acid esters, pentaerythritol Examples of such esters include glycerol mono- to tetrabehenate, pentaerythritol mono- to tetramontanate, polyglycerol tristearate, trimethylolpropane monopalmitate, pentaerythritol monoundecylate, sorbitan monostearate, mono- or dilaurate, mono- or dipalmitate, mono- or distearate, mono- or dibehenate, mono- or dimontanate, mono- or diolate, and mono- or dilinoleate of polyalkylene glycol (polyethylene glycol, polypropylene glycol, etc.).

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

Examples of long-chain aliphatic alcohols include aliphatic alcohols having 10 to 40 carbon atoms, or 11 to 35 carbon atoms, or 12 to 30 carbon atoms, and more specific examples include lauryl alcohol, myristyl alcohol, cetyl alcohol, oleyl alcohol, stearyl alcohol, and behenyl alcohol.

Examples of polyoxyalkylene glycols include alkylene glycols (such as ethylene glycol, propylene glycol, and tetramethylene glycol) either homopolymers or copolymers, and derivatives thereof.

The polyoxyethylene derivative may be, for example, an ether, an amine, an amide, or a fatty acid ester of polyoxyethylene. Specific examples of the polyoxyethylene derivative include:
Polyoxyethylene alkyl ethers, for example, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene tridecyl ether, polyoxyethylene long-chain alkyl ethers, etc.
Polyoxyethylene alkylphenyl ethers, for example, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene phenyl ether, polyoxyethylene benzyl ether, polyoxyethylene β-naphthyl ether, polyoxyethylene bisphenol ether, etc.
Polyoxyethylene alkylamines, such as polyoxyethylene laurylamine and polyoxyethylene stearylamine; Polyoxyethylene alkylamides, such as polyoxyethylene oleylamide and polyoxyethylene stearylamide; Polyoxyethylene fatty acid esters, such as polyoxyethylene monolaurate and polyoxyethylene monostearate; and
Other compounds, for example, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene glycerol ether, polyoxyethylene pentaerythritol ether, etc.
Examples include:

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

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

Examples of olefin waxes include low molecular weight polyolefins (e.g., low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight copolymers of ethylene and α-olefins, etc.), oxidized polyethylene wax, etc. The number average molecular weight of the olefin wax may be preferably 7,000 or more, or 8,000 or more, or 9,000 or more, and may be preferably 100,000 or less, or 70,000 or less, or 50,000 or less. The number average molecular weight is a value determined using gel permeation chromatography in terms of standard polystyrene.

Examples of silicone compounds include (poly)organosiloxanes. Examples of (poly)organosiloxanes include monoorganosiloxanes such as dialkylsiloxanes (e.g., dimethylsiloxane), alkylarylsiloxanes (e.g., phenylmethylsiloxane), and diarylsiloxanes (e.g., diphenylsiloxane), as well as homopolymers or copolymers thereof (e.g., polydimethylsiloxane, polyphenylmethylsiloxane, etc.). The polyorganosiloxane may be an oligomer.

(Poly)organosiloxanes also include modified (poly)organosiloxanes having substituents such as epoxy groups, hydroxy groups, alkoxy groups, carboxy groups, amino groups or substituted amino groups (dialkylamino groups, etc.), ether groups, vinyl groups, and (meth)acryloyl groups at the molecular terminals and/or main chain.

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

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

<Other ingredients>
The polyacetal resin composition of the present embodiment may further contain various known additives to improve its physical properties depending on the intended use. Examples of the additives include formic acid scavengers, weathering stabilizers, release agents, lubricants, conductive agents, different polymers (e.g., thermoplastic resins or thermoplastic elastomers), dyes and pigments, inorganic or organic fillers, surface treatment agents, etc., and these may be used alone or in combination of two or more.

The formic acid scavenger may, but is not limited to, be, for example, hydroxides, inorganic acid salts, carboxylates, or alkoxides of alkali metals or alkaline earth metals. More specifically, for example, hydroxides of sodium, potassium, magnesium, calcium, barium, etc.; and carbonates, phosphates, silicates, borates, carboxylates, and layered double hydroxides of the above metals.

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

One type of formic acid scavenger may be used alone, or two or more types may be used in combination.

The weathering stabilizer is not limited to the following, but is preferably at least one selected from the group consisting of benzotriazole-based compounds, anilide oxalate-based compounds, and hindered amine-based light stabilizers.

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

The above-mentioned oxalic acid anilide compounds include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxalic acid bisanilide, 2-ethoxy-3'-dodecyloxalic acid bisanilide, etc. These compounds may be used alone or in combination of two or more.

Examples of the hindered amine light stabilizer include, but are not limited to, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(phenylatoxy)-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy 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-piperidyltolylene-2,4-dicarbamate, bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene-1,6-dicarbamate, tris(2,2,6,6-tetramethyl-4-piperidyl)-benzene-1,3,5-tricarboxylate, tris(2,2,6,6 -tetramethyl-4-piperidyl)-benzene-1,3,4-tricarboxylate, 1-[2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}butyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]2,2,6,6-tetramethylpiperidine, condensation product 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. The above hindered amine light stabilizers may be used alone or in combination of two or more.

Among them, the most preferred weathering stabilizers are 2-[2'-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3,5-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3,5-di-t-amylphenyl)benzotriazole, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, bis-(N-methyl Bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, a condensation product 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.

The above-mentioned release agents and lubricants are not limited to the following, but preferred examples include alcohols, fatty acids and their fatty acid esters, olefin compounds with an average degree of polymerization of 10 to 500, and silicones. The release agents and lubricants may be used alone or in combination of two or more types.

The conductive agent may be, but is not limited to, conductive carbon black, metal powder or fiber. One type of conductive agent may be used alone, or two or more types may be used in combination.

The above-mentioned thermoplastic resins include, but are not limited to, polyolefin resins, acrylic resins, styrene resins, polycarbonate resins, and uncured epoxy resins. Only one type of thermoplastic resin may be used alone, or two or more types may be used in combination. Modified versions of the above-mentioned resins are also included as thermoplastic resins.

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

The dyes and pigments include, but are not limited to, inorganic pigments and organic pigments, as well as metallic pigments and fluorescent pigments.
As the inorganic pigment, those generally used for coloring resins can be used, and examples thereof include, but are not limited to, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, phosphates, acetates, carbon black, acetylene black, lamp black, and the like.
Examples of organic pigments include, but are not limited to, condensed azo, ynone, phloetacyanin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennone, quinacridone, thioindigo, perylene, and dioxazine pigments.
The dyes and pigments may be used alone or in combination of two or more kinds.
The amount of pigment added varies greatly depending on the color tone, making it difficult to specify, but it is generally used in the range of 0.05 to 5 parts by mass per 100 parts by mass of the polyacetal resin.

The inorganic filler may be, but is not limited to, fibrous, powdery, plate-like, or hollow filler.

Examples of fibrous fillers include, but are not limited to, inorganic fibers such as glass fibers, carbon fibers, silicone fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and metal fibers such as stainless steel, aluminum, titanium, copper, and brass. Also included are short whiskers such as potassium titanate whiskers and zinc oxide whiskers.

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, and various metal powders.

Examples of plate-like 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, metal balloons, etc.

The organic filler may be, but is not limited to, a high melting point organic fibrous filler such as aromatic polyamide resin, fluororesin, or acrylic resin.

These fillers may be used alone or in combination of two or more. As fillers, both fillers that have been surface-treated with a surface treatment agent and fillers that have not been surface-treated can be used, but from the viewpoint of the smoothness of the molded surface and mechanical properties, fillers that have been surface-treated with a surface treatment agent may be preferable.

The surface treatment agent is not particularly limited, and any conventionally known surface treatment agent can be used.
Examples of surface treatment agents that can be used include, but are not limited to, various coupling agents such as silane-based, titanate-based, aluminum-based, and zirconium-based, as well as surfactants such as resin acids, organic carboxylic acids, and organic carboxylates.Specific examples of surface treatment agents that can be used include, but are not limited to, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyltitanate, diisopropoxyammoniumethylacetate, and n-butylzirconate.

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

More specifically, the necessary components are mixed and kneaded using a melt kneading device such as an extruder to obtain a polyacetal resin composition in the form of pellets. As the extruder, it is preferable to use a co-rotating twin screw extruder in order to improve the dispersibility of the fine cellulose fibers.

In a more preferred embodiment of this invention, (a) polyacetal resin, (c) hindered phenol-based antioxidant, (d) nitrogen-containing compound, and (e) processing aid are melt-kneaded to obtain a kneaded mixture, and then the kneaded mixture is melt-kneaded with (b) fine cellulose fibers.

From the viewpoints of suppressing the occurrence of silver streaks during molding, suppressing the occurrence of odors during thermal processing, and suppressing the occurrence of voids in the center of the molded body, a method of melt-kneading fine cellulose fibers that have been pre-defibrated (in one embodiment, defibrated to a fiber diameter of 10 to 1,000 nm) with polyacetal resin is preferable to a method of obtaining fine cellulose fibers by defibrating cellulose with the shear of an extruder.

<Rigidity of polyacetal resin composition at high temperatures>
The polyacetal resin composition in this embodiment preferably has a feature of 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, 1,300 MPa or more, 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 preferably 3,000 MPa or less from the viewpoint of maintaining toughness.

In this embodiment, it is desirable that the polyacetal resin composition has a component composition (i.e., the type and amount of the components of the polyacetal resin composition) such that the ratio of the storage modulus at 120 ° C to the storage modulus at 23 ° C when 10% by mass of fine cellulose fiber is blended is 0.4 or more. This index is an index of the dispersibility of the fine cellulose fiber 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 fiber, the ratio of the storage modulus at 120 ° C to the storage modulus at 23 ° C is less than 0.3. In addition, even when non-fine cellulose (e.g., cellulose powder) is blended, 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 fiber, the ratio of the storage modulus at 120 ° C to the storage modulus at 23 ° C is preferably 0.4 or more, or 0.5 or more, or 0.55 or more, or 0.6 or more, or 0.65 or more. There is no particular upper limit, but from the viewpoint of processability, it is preferably 1.5 or less.

The storage modulus is the storage modulus measured using an ISO multipurpose test piece 10 mm wide and 4 mm thick with a solid viscoelasticity measuring device under the following conditions: temperature range 0°C to 150°C (heating rate: 3°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 are calculated by interpolating the measured temperatures before and after them.

<Method of molding polyacetal resin composition and uses>
The polyacetal resin composition of the present embodiment can be molded into various molded articles by a conventionally known molding method (e.g., injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.), and is particularly suitable for injection molding.

The resulting molded products can be used for a variety of purposes, including automobile parts, electrical and electronic parts, building materials, parts for daily life, cosmetics, and medical products.

Specific examples of automotive parts include interior parts such as inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, and clips, electrical system parts such as meters and connectors, in-vehicle electrical and electronic parts such as audio equipment and car navigation equipment, parts that come into contact with metal such as window regulator carrier plates, door lock actuator parts, mirror parts, wiper motor system parts, and mechanical parts such as fuel system parts.

Electrical and electronic parts include parts or components of equipment that are made of polyacetal resin molded products and have many metal contacts, such as audio equipment, video equipment, office automation equipment such as telephones, copy machines, facsimiles, word processors, and computers, and parts or components of toys, specifically chassis, gears, levers, cams, pulleys, bearings, etc.

Furthermore, the material can be suitably used in a wide range of lifestyle-related, cosmetic-related, and medical-related parts, such as lighting fixtures, fittings, piping, cocks, faucets, and toilet peripheral parts, as well as building materials and piping parts, fasteners, stationery, lip balm and lipstick containers, cleaning devices, water purifiers, spray nozzles, spray containers, aerosol containers, general containers, and syringe needle holders.
Among these, it is more preferably usable for gears that are placed in high temperature environments and subjected to high loads.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(Diameter and L/D of fine cellulose fibers)
The wet cake was diluted to 0.01% by mass with tert-butanol, dispersed using a high-shear homogenizer (manufactured by IKA, product name "Ultra Turrax T18") under processing conditions of 25,000 rpm for 5 minutes, cast onto mica, air-dried, and measured with a high-resolution scanning electron microscope. The measurement was performed by adjusting the magnification so that at least 100 cellulose fibers were observed, and the length (L), major axis (D) and ratio of these of 100 randomly selected cellulose fibers were determined, and the arithmetic average of the 100 cellulose fibers was calculated.

(Mw of fine cellulose fiber)
The wet cake was added to tert-butanol, and further dispersed in a mixer or the like until no aggregates were present. The concentration was adjusted to 0.5% by mass relative to 0.5 g of fine cellulose fiber solid content. 100 g of the obtained tert-butanol dispersion was filtered on filter paper, dried at 150 ° C., and the filter paper was peeled off to obtain a sheet. The sheet had an air resistance of 100 sec/100 ml or less per 10 g/ ^m2 sheet basis weight, and was obtained as a porous sheet. 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 one day. Next, the water and solids were separated by centrifugation. Next, 20 mL of acetone was added, lightly stirred, and left for one day. Next, the acetone and solids were separated by centrifugation. Next, 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for one day. After separating the N,N-dimethylacetamide from the solids by centrifugation again, 20 mL of N,N-dimethylacetamide was added, and the mixture was left to stand for one day after lightly stirring. The 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, and the mixture was stirred with a stirrer, and dissolution was confirmed by visual observation. The solution in which cellulose was dissolved was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The apparatus and measurement conditions used are as follows.
Equipment: Tosoh HLC-8120
Column: TSKgel SuperAWM-H (6.0 mm ID x 15 cm) x 2 Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%)
Flow rate: 0.6 mL/min. Calibration curve: Pullulan equivalent

(Degree of acetyl substitution of hydrophobized fine cellulose fiber DS)
The infrared spectrum of the porous sheet at five points was measured by an ATR-IR method using a Fourier transform infrared spectrophotometer (FT/IR-6200 manufactured by JASCO Corporation). The infrared spectrum measurement was performed under the following conditions.
Number of times: 64
Wavenumber resolution: 4cm ^-1 ,
Measurement wave number range: 4000 to 600 cm ^-1 ,
ATR crystal: Diamond,
Incident angle: 45°
From the obtained IR spectrum, the IR index was calculated according to the following formula:
IR index = H1730/H1030
In the formula, H1730 and H1030 are the absorbances at 1730 cm ^-1 and 1030 cm ^-1 (absorption bands of C-O stretching vibration of the cellulose backbone chain). However, the lines connecting 1900 cm ^-1 and 1500 cm ^-1 and the line connecting 800 cm ^-1 and 1500 cm ^-1 are taken as baselines, and the absorbances are calculated based on these baselines as 0 absorbance.
The average degree of substitution at each measurement site was calculated from the IR index according to the following formula, and the average value was taken as DS.
DS = 4.13 x IR index

(Tensile properties)
Using an EC5P injection molding machine (manufactured by Shibaura Machine Co., Ltd.) with a cylinder temperature set to 200°C, the specimens were molded into ISO37 type 3 tensile test pieces with a thickness of 2 mm. The mold temperature was set to 60°C. A tensile test was carried out using the obtained tensile test pieces. The chuck distance for the tensile test was set to 20 mm, the crosshead speed was set to 5 mm/min, and the tensile yield stress and tensile breaking strain were measured. The number of pieces was 5, and the values were arithmetically averaged.
In addition, as a criterion for evaluating toughness, the tensile breaking point was evaluated as to whether it exceeded the yield point (maximum stress). Among the five test pieces, those in which three or more exceeded the yield point were marked with "◯", and those in which three or more broke before yielding were marked with "X". Those in which all five exceeded the yield point were marked with "◎". The fracture state is shown in the table. Furthermore, those marked with "X" are shown as tensile breaking stress, not tensile yield stress.

(Storage Modulus)
The specimens were molded into ISO multipurpose test pieces with a width of 10 mm and a thickness of 4 mm using an injection molding machine LA60 set at 200°C, and the storage modulus was measured using a GABO Iplexer 500N viscoelasticity measuring device (manufactured by Netsch) under the following conditions: tension mode, measurement temperature range 0°C to 150°C, heating rate: 3°C/min, vibration frequency 10Hz, static load strain 0.5%, and dynamic load strain 0.3%. The storage modulus at 120°C is shown in the example table as E'(120°C). The ratio of the storage modulus at 120°C to the storage modulus at 23°C is shown in the example table as RATIO(120°C/23°C).

(Thermogravimetric reduction rate)
The test pieces were left in a vacuum dryer set at 80°C for two days, then cut into pieces with nippers to a diameter of 0.5 mm or less, and about 10 mg of each piece was used to measure the weight loss using a differential thermal thermogravimetry device (HITACHI STA7200RV). The measurement conditions were that the temperature was raised from 30°C to 200°C at a rate of 20°C/min under nitrogen, and then the specimen was held for 60 minutes.
The weight loss rate was calculated according to the following formula, where the weight before the temperature increase was X0 and the weight after holding at 200° C. for 60 minutes was Xt.
Weight reduction rate (%) = (X0-Xt)/X0×100

(Silver Streaks)
A rectangular test piece having a length of 700 mm, a width of 10 mm, and a thickness of 3.5 mm was molded using an EC5P injection molding machine (manufactured by Shibaura Machine Co., Ltd.) set to a cylinder temperature of 200° C. The amount of silver streaks generated on the surface of the test piece was evaluated on a five-point scale according to the following criteria.
5: No silver streaks were observed. 4: Multiple small silver marks were observed in several places. 3: Silver marks were clearly observed. 2: Silver streaks were observed on more than half of the test piece.
1: Silver streaks are visible on the front surface of the test piece.

(Odor during extrusion process)
The odor around the extruder die during processing in the extruder was evaluated according to the following criteria.
◯: No odor at all or a slightly sweet odor.
△: A pungent odor of formaldehyde is felt.
×: A strong, irritating odor of formaldehyde is felt.

<Polyacetal: Sometimes referred to by the following abbreviations>
POM-H: Linear homopolymer produced using formaldehyde as a raw material. MFR = 10 g/10 min. POM-C1: Linear copolymer obtained by copolymerizing 96.5% by mass of trioxane and 3.5% by mass of 1,3-dioxolane. MFR: 9 g/10 min. POM-C2: Linear copolymer obtained by copolymerizing 96.5% by mass of trioxane and 3.5% by mass of 1,3-dioxolane. MFR: 30 g/10 min. POM-C3: Linear copolymer obtained by copolymerizing 98% by mass of trioxane and 2% by mass of 1,3-dioxolane. MFR: 8 g/10 min. POM-BC: Linear block copolymer prepared according to the following Preparation Example. MFR: 15 g/10 min.

[Preparation Example 1]
A jacketed twin-screw paddle type continuous polymerization reactor capable of passing a heat medium was adjusted to 80° C. Trioxane was continuously supplied to the polymerization reactor at 40 mol/hr, 1,3-dioxolane as a cyclic formal at 2 mol/hr, boron trifluoride di-n-butyl etherate dissolved in cyclohexane as a polymerization catalyst in an amount of 5×10 ⁻⁵ mol per mol of trioxane, and polybutadiene (number average molecular weight Mn=2,330) having hydrogenated hydroxyl groups at both ends as represented by the following formula as a chain transfer agent in an amount of 1×10 ⁻³ mol per mol of trioxane, to carry out polymerization.

Next, the polymer discharged from the polymerization machine was poured into a 1% aqueous solution of triethylamine to completely deactivate the polymerization catalyst, and the polymer was then filtered and washed to obtain a crude polyacetal block copolymer.

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

0.3 parts by mass of triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate] was added as an antioxidant to the polyacetal block copolymer in which the unstable terminals had been decomposed, and the mixture was extruded as strands from the extruder die while devolatilizing under a vacuum of 20 Torr using a vented extruder, and then pelletized. The resulting ABA type block copolymer is called POM-BC.

<Hydrophobic fine cellulose fiber: sometimes referred to by each abbreviation>
[Preparation Example 2]
Cotton linter pulp was stirred in dimethyl sulfoxide (DMSO) at room temperature for 1 hour at 500 rpm using a single-shaft stirrer (IMEX DKV-1 φ125 mm dissolver). The mixture was then fed to a bead mill (IMEX NVM-1.5) using a hose pump and circulated for 120 minutes using only DMSO to obtain a defibrated slurry.

Then, 11 parts by mass of vinyl acetate and 1.63 parts by mass of sodium bicarbonate were added to the bead mill device per 100 parts by mass of the defibrated slurry, and the device was further circulated for 60 minutes to obtain a hydrophobic microfine cellulose fiber slurry.

During circulation operation, the rotation speed of the bead mill was 2500 rpm and the peripheral speed was 12 m/s. The beads used were made of zirconia and had a diameter of 2.0 mm, and the filling rate was 70% (the slit gap of the bead mill at this time was 0.6 mm). During circulation operation, the slurry temperature was controlled at 40°C using a chiller to absorb heat generated by friction.

192 parts by mass of pure water was added to the obtained hydrophobic fine cellulose fiber slurry per 100 parts by mass of defibrated slurry, and the mixture was thoroughly stirred and then concentrated in a dehydrator. The obtained wet cake was again dispersed in the same amount of pure water, stirred, and concentrated, and this washing operation was repeated a total of five times.

5 parts by mass of PEG20000 was added to the obtained aqueous dispersion of hydrophobic microfine cellulose fibers (solid content: 10% by mass) per 100 parts by mass of hydrophobic microfine cellulose fibers, and then the mixture was vacuum dried at approximately 40°C using a revolution/rotation type mixer (EME V-mini300) to obtain hydrophobic microfine cellulose fiber powder.

The properties of the obtained hydrophobized fine cellulose fiber wet cake were evaluated, and the following results were obtained.
DS: 0.96, diameter: 65 nm, L/D: about 450, Mw: 340,000. This hydrophobic fine cellulose fiber is referred to as CNF (0.96).

[Preparation Examples 3 to 5]
By adjusting the circulation operation time after adding vinyl acetate and sodium hydrogen carbonate to the bead mill apparatus, three types of hydrophobic cellulose fibers with different hydrophobicity were obtained.

CNF (0.41) DS: 0.41, diameter: 60 nm, L/D: approx. 470, Mw: 370,000 CNF (0.71) DS: 0.71, diameter: 64 nm, L/D: approx. 450, Mw: 350,000 CNF (1.29) DS: 1.29, diameter: 69 nm, L/D: approximately 430, Mw: 330,000

<Microfine cellulose fiber: hereinafter sometimes referred to as CNF(0)>
[Preparation Example 6]
Celish KY-100G (manufactured by Daicel FineChem Co., Ltd.) powder was diluted with pure water to a concentration of 1% by mass, and stirred and mixed in a single-shaft stirrer at 500 rpm for 20 minutes. Thereafter, the water content was adjusted by filtration to a solid content of 10% by mass, to obtain a fine cellulose fiber aqueous dispersion. Thereafter, PEG20000 was added to the fine cellulose fiber aqueous dispersion in an amount of 5 parts by mass per 100 parts by mass of the fine cellulose fiber, and the mixture was vacuum-dried at about 40°C using a revolution/rotation type stirrer to obtain fine cellulose fiber powder CNF (0). When the characteristics were evaluated, the following results were obtained.
CNF (0) DS: 0, diameter: 71 nm, L/D: approximately 220, Mw: 250,000

<Cellulose powder: Sometimes simply called CP>
KC Flock W-10MG2 powder with an average particle size of 10 μm (manufactured by Nippon Paper Chemicals Co., Ltd.) was diluted with pure water to a concentration of 5% by mass, and stirred and mixed in a single-shaft stirrer at 500 rpm for 20 minutes. Thereafter, the water content was adjusted by filtration to a solid content of 10% by mass, to obtain a cellulose powder aqueous dispersion. PEG20000 was then added to the cellulose powder aqueous dispersion in an amount of 5 parts by mass per 100 parts by mass of cellulose powder, and the mixture was vacuum-dried at about 40° C. using a revolution/rotation stirrer to obtain cellulose powder CP.

<Hydrophobic pulp: sometimes simply called Ac-CP>
One part by mass of cotton linter pulp was stirred in 30 parts by mass of dimethyl sulfoxide (DMSO) at room temperature for 1 hour at 500 rpm using a single-shaft stirrer (DKV-1 φ125 mm dissolver manufactured by IMEX). The mixture was then fed to a bead mill (NVM-1.5 manufactured by IMEX) using a hose pump, and circulated for 180 minutes using only DMSO to obtain 31 parts by mass of defibrated slurry (fibrillation process). Then, 1 part by mass of vinyl acetate and 0.49 parts by mass of sodium bicarbonate were added to the bead mill device, and circulated for another 120 minutes to obtain an acetylated CP powder. The characteristics were evaluated, and the following results were obtained. Although some fibers were confirmed to have a diameter on the order of submicrons, the majority were fibers with a huge diameter of 10 μm to several hundred μm, and the average diameter and L/D could not be calculated.
Ac-CP DS: 1.03, Mw: 390,000

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

<Nitrogen-containing compound>
Melamine (reagent)

<Processing aids>
Ethylene bis-stearylamide Kaowax EB-FF (Kao Corporation)

[Reference example 1]
The cylinder temperature of a co-rotating twin-screw extruder ZSK26MC (manufactured by Coperion) with L/D=48 and one inlet on the upstream side was set to 200°C, and a polyacetal resin was obtained by dry blending 0.25 parts by mass of a hindered phenol-based antioxidant, 0.15 parts by mass of a nitrogen-containing compound, and 0.2 parts by mass of a processing aid per 100 parts by mass of POM-H, and the mixture was fed in a fixed amount from a loss-in-weight feeder, melt-kneaded, extruded into a strand shape, and cooled and cut to obtain a pellet-shaped polyacetal resin composition. A degassing system was provided downstream of the extruder to remove air and generated gas from the extruder.

The screw configuration is such that two kneading discs (RKD) with a feeding function are arranged in the center of the extruder, and one kneading disc (LKD) with a return function is arranged next to one RKD just before the decompression and degassing on the downstream side, in that order.

The screw speed of the extruder was set to 150 rpm, and the feeder was set to give a total extrusion output of 5 kg/hour. Various tests were carried out using the obtained pellets. The results are shown in Table 1 as Reference Example 1.

[Reference examples 2 to 5]
Except for changing the type of polyacetal, the test was carried out in the same manner as in Reference Example 1. The results are shown in Tables 1 to 3 as Reference Examples 2 to 5.

[Example 1]
The cylinder temperature of the co-rotating twin screw extruder ZSK26MC (manufactured by Coperion) with L/D=48 having one inlet on the upstream side and one in the center of the extruder was set to 200 ° C., and a polyacetal resin was obtained by dry blending 0.25 parts by mass of a hindered phenol-based antioxidant, 0.15 parts by mass of a nitrogen-containing compound, and 0.2 parts by mass of a processing aid with respect to 100 parts by mass of POM-H, and the resulting mixture was supplied at a fixed amount from a loss-in-weight type feeder installed at the upstream inlet, and CNF (0.95) as fine cellulose fiber was supplied at a fixed amount so that the amount of fine cellulose fiber in the composition was 10% by mass from a loss-in-weight type feeder installed at the central inlet of the extruder, and melt-kneading was performed, extruded into a strand, and cooled and cut to obtain a pellet-shaped polyacetal resin composition. The downstream of the extruder was made degassable under reduced pressure, and the air and generated gas in the extruder were removed.

The screw configuration was designed so that three RKDs were placed upstream of the central supply port of the extruder, and three RKDs and one LKD were placed in that order downstream just before the reduced pressure degassing. The screw rotation speed of the extruder was set to 150 rpm, and the supply was set so that the total extrusion discharge rate was 5 kg/hour. Various tests were carried out using the obtained pellets. The results are shown in Table 1 as Example 1.

[Comparative Example 1]
As the cellulose, hydrophobized pulp (Ac-CP) was used instead of fine cellulose fiber, and further, since it was necessary to finely pulverize the cellulose in the extruder, the feed position of the hydrophobized pulp was changed to the upstream feed port of the extruder for the purpose of applying strong shear, and the extrusion processing was carried out and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Examples 2 to 5]
The same procedures as in Example 1 were carried out except that the type of polyacetal and the cellulose were changed as shown in Table 1, and various tests were carried out using the obtained pellets. The results are shown in Table 1.

[Comparative Examples 2 to 5]
The same procedures as in Comparative Example 1 were carried out except that the type of polyacetal and the cellulose were changed as shown in Table 1, and various tests were carried out using the obtained pellets. The results are shown in Table 1.

[Examples 6 to 10]
The same procedures as in Example 1 were carried out, except that the polyacetal was changed to POM-C3 and the cellulose was changed as shown in Table 2. Various tests were carried out using the obtained pellets. The results are shown in Table 2.

[Comparative Examples 6 to 7]
Except for changing the polyacetal to POM-C3 and changing the cellulose as shown in Table 2, the same procedure as in Comparative Example 1 was carried out, and various tests were carried out using the obtained pellets. The results are shown in Table 2.

[Example 11]
The same procedures as in Example 1 were carried out, except that the polyacetal was changed to a blend of equal amounts of POM-C1 and POM-BC, and the cellulose was changed as shown in Table 3. Various tests were carried out using the obtained pellets. The results are shown in Table 3.

[Comparative Examples 8 to 14]
The same procedures as in Example 1 were carried out, except that the polyacetal was changed to a blend of equal amounts of POM-C1 and POM-BC, and the compounding ratios of the antioxidant, the nitrogen-containing compound, and the processing aid, and the cellulose were changed as shown in Table 3. Various tests were carried out using the obtained pellets. The results are shown in Table 3.

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

The composition containing polyacetal resin and fine cellulose fibers provided by one aspect of the present invention can be suitably used in a wide range of applications, particularly in high-load applications in high-temperature environments.

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