Method for manufacturing resin-molded body and resin composition

Abstract

The present invention relates to a method for producing a resin-molded body and a resin composition. A method for producing a resin-molded body composed of a resin composition containing (A) a thermoplastic resin and (B) a cellulose nanofiber having an average fiber diameter of 1000 nm or less, the resin composition having a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the (A) thermoplastic resin, the method comprising a step of injection-molding the resin composition at a temperature at which the resin composition has thixotropy.

Description

[0001] This application is a divisional application. The international application number of the original application is PCT / JP2019 / 017076, the international application date is April 22, 2019, the Chinese national application number is 201980025818.X, the entry date into China is October 14, 2020, and the invention title is "Gear Containing Cellulose". Technical Field

[0002] The present invention relates to gears containing cellulose (particularly EPS (electric power steering) gears) and gear systems having therein (particularly EPS systems). Background Technology

[0003] Thermoplastic resins are lightweight and have excellent processing properties, making them widely used in automotive parts, electrical and electronic components, office equipment housings, precision parts, and many other applications. However, resins alone often lack sufficient mechanical properties, lubricity, thermal stability, and dimensional stability, so they are usually combined with various inorganic materials.

[0004] Resin compositions reinforced with inorganic fillers such as glass fiber, carbon fiber, talc, and clay as reinforcing materials have a high specific gravity, resulting in increased weight of the obtained resin molded articles. Furthermore, when using glass fiber-containing resin compositions for bar extrusion and subsequent cutting to form specific shapes, or when injection molding thicker parts, stress concentration occurs at specific locations due to the orientation of the glass fibers, leading to poor durability. For example, in widely used resin gears, when the composition contains glass fibers, the surface roughness of the sliding parts increases, and the roundness decreases, resulting in noise during meshing; and large loads are applied to specific teeth, causing deformation and breakage. Additionally, because the glass fibers are coarse and oriented within the molded article, continuous injection molding under the same conditions leads to increased dimensional deviations between individual molded articles. Furthermore, when using resin compositions containing glass fibers to extrude round rods and then cut them into specific shapes, and when thicker parts are molded using injection molding, problems arise such as the formation of internal voids (vacuum-like voids) and poor durability due to stress concentration. This is caused by the formation of voids (vacuum-like voids) inside the molded body due to the difference between the external and internal cooling rates. Therefore, in recent years, cellulose, with its low environmental impact, has been used as a new type of resin reinforcing material.

[0005] Regarding cellulose, as a component, it is known to possess a high elastic modulus comparable to that of aromatic polyamide fibers, and a coefficient of linear expansion lower than that of glass fibers. Furthermore, it has a low true density of 1.56 g / cm³. 3Compared to glass (density 2.4–2.6 g / cm³), which is typically used as a reinforcing material for thermoplastic resins. 3 ) or talc (density 2.7 g / cm³) 3 Compared to other materials, it is an overwhelmingly lightweight material.

[0006] Besides cellulose derived from trees, cellulose also encompasses various branches made from hemp, cotton, kenaf, cassava, and other sources. Furthermore, bacterial cellulose, exemplified by coconut jelly, is also known. These natural resources, which serve as cellulose raw materials, are abundant on Earth, and the technology of using cellulose as a filler in resins has attracted considerable attention in order to effectively utilize them.

[0007] CNF (cellulose nanofibers) are known to be obtained by hydrolyzing hemicellulose from raw materials such as pulp to make it brittle, and then opening the fibers using pulverization methods such as high-pressure homogenizers, high-pressure micro-jet homogenizers, ball mills or disc pulverizers. In water, they form a highly fine dispersion state and network known as nanodispersion.

[0008] To incorporate CNF into resins, CNF needs to be dried into powder. However, during separation from water, CNF transforms from a micro-dispersed state into a robust aggregate, making redispersibility difficult. This agglomeration is manifested through hydrogen bonds generated by the hydroxyl groups of cellulose, and can be described as very strong.

[0009] Therefore, to exhibit sufficient performance, it is necessary to mitigate the hydrogen bonds generated by the hydroxyl groups of cellulose. In addition, even if the hydrogen bonds can be sufficiently mitigated, it is difficult to maintain the open fiber state (nanoscale (i.e., less than 1 μm)) in the resin.

[0010] Previously, compositions were proposed that use cellulose nanofibers (hereinafter sometimes referred to as CNF), glass fibers or clay as fillers and compounded with various resins.

[0011] For example, Patent Document 1 discloses a composition made of glass fiber and polyamide resin. Patent Document 2 discloses a sliding resin composition obtained by replacing the hydroxyl groups on the surface of cellulose with hydrophobic groups. Patent Document 3 discloses a gear made of resin obtained using an apatite-type compound and polyamide.

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: International Publication No. 2006 / 054774

[0015] Patent Document 2: Japanese Patent Application Publication No. 2017-171698

[0016] Patent Document 3: Japanese Patent Application Publication No. 2001-289309 Summary of the Invention

[0017] The problem that the invention aims to solve

[0018] However, while Patent Document 1 describes the heat distortion temperature and limiting PV value of the glass fiber and polyamide composition, it does not mention the sliding properties of the molded body during intermittent sliding or the durability of high-torque gears. Furthermore, Patent Document 2 evaluates the sliding properties of cellulose-polyoxymethylene, polypropylene, or polyethylene composites using common sliding tests such as the pin-disc test and journal bearing test, but it does not mention the durability of high-torque gear molded sheets for practical applications. Additionally, Patent Document 3 describes the tensile strength and elongation at break of gears made from polyamide resin using nanomaterials, but it does not mention the durability and continuous molding properties of gears (especially high-torque gears) for practical applications.

[0019] For gears used under high torque conditions (such as EPS gears), high slip resistance, wear resistance and durability under high torque conditions are particularly required, but patent documents 1 to 3 do not provide gears that meet such characteristics to the desired extent.

[0020] In other words, existing technologies struggle to produce gears (especially EPS gears) that offer excellent continuous formability (i.e., small dimensional deviations when continuously forming multiple gears), while also achieving high slip resistance and high durability in practical applications. Improvements to these characteristics are urgently needed. One objective of this invention is to provide a gear (especially an EPS gear) that solves the aforementioned problems, and a gear system (especially an EPS system) incorporating such a gear. Furthermore, another objective of this invention is to provide a gear (especially an EPS gear) that reduces internal porosity in thick-walled molded bodies, improves gear durability and quietness, and achieves a balance of sufficient durability and quietness in practical applications, and a gear system (especially an EPS system) incorporating such a gear.

[0021] Methods for solving problems

[0022] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the following gear (especially EPS gear) can solve the above-mentioned problems, thereby completing the present invention. The gear is a resin molded body made of a resin composition containing a thermoplastic resin of a specific molecular weight and a specific cellulose, and the arithmetic mean surface roughness Sa is 3.0 μm or less.

[0023] That is, the present invention includes the following methods.

[0024] [1] A gear is a resin molded body made of a resin composition comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less, wherein the number average molecular weight of the (A) thermoplastic resin is in the range of 10,000 to 150,000; and the arithmetic mean surface roughness Sa of the sliding surface of the gear and other gear teeth is 3.0 μm or less.

[0025] [2] An EPS (electric power steering) gear is a resin molded body made of a resin composition comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less, wherein the number average molecular weight of the thermoplastic resin (A) is in the range of 10,000 to 150,000; and the arithmetic mean surface roughness Sa of the sliding surface of the gear and other gear teeth is 3.0 μm or less.

[0026] [3] The gear as described in method 1 or 2 above, wherein the resin composition has a thixotropic index of 1 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A) above.

[0027] [4] The gear as described in any one of the above methods 1 to 3, wherein the resin composition comprises 45% to 95% by mass of (A) thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers.

[0028] [5] The gear as described in any one of the above methods 1 to 4, wherein the thermoplastic resin (A) is one or more resins selected from the group consisting of polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polyacrylic resins, polyphenylene ether resins and polyphenylene sulfide resins.

[0029] [6] The gear as described in method 4 above, wherein (A) the thermoplastic resin is one or more resins selected from the group consisting of polyamide and polyacetal.

[0030] [7] The gear as described in any one of the above methods 1 to 6, wherein the resin composition further comprises (C) a surface treatment agent.

[0031] [8] The gear as described in method 7 above, wherein the number average molecular weight of the surface treatment agent (C) is 200 to 10,000.

[0032] [9] The gear as described in method 7 or 8 above, wherein the resin composition contains 1 to 50 parts by mass of (C) surface treatment agent relative to 100 parts by mass of (B) cellulose nanofibers.

[0033]

[10] The gear as described in any one of embodiments 1 to 9 above, wherein the resin composition further comprises (D) a metal ion component.

[0034]

[11] The gear as described in method 10 above, wherein the resin composition contains 0.005 to 5 parts by weight of (D) metal ion component relative to 100 parts by weight of (A) thermoplastic resin.

[0035]

[12] The gear as described in any one of the above methods 1 to 11, wherein it further comprises (E) a lubricant component.

[0036]

[13] The gear as described in method 12 above, wherein the resin composition contains 0.01 to 5 parts by weight of (E) lubricant component relative to 100 parts by weight of (A) thermoplastic resin.

[0037]

[14] The gear as described in method 12 or 13 above, wherein the melting point of the (E) lubricant component is 40°C to 150°C.

[0038]

[15] The gear as described in any one of the above methods 1 to 14, wherein, when measured according to ISO 179, the flexural modulus of the above resin composition is 3000 MPa or more.

[0039]

[16] The gear as described in any one of embodiments 1 to 15 above, wherein the ratio of the coefficient of friction (II) of the resin composition to the coefficient of friction (I) of a composition having the same composition as the resin composition except that it does not contain the cellulose nanofibers described above, i.e., the coefficient of friction ratio (II / I) is 0.8 or less.

[0040] The coefficient of friction was determined as follows: using a reciprocating friction and wear tester with a 5mm diameter SUS304 test piece as the test material, in the form of a multipurpose test piece made according to ISO 294-3, the test was conducted under the conditions of a linear speed of 50mm / s, a reciprocating distance of 50mm, a temperature of 23°C, a humidity of 50%, and a load of 19.8N.

[0041]

[17] The gear as described in any one of the above methods 1 to 16, wherein after the gear is exposed to hot water at 80°C for 24 hours, the change in water absorption size after absorbing water at 80°C and relative humidity of 57% for 120 hours is less than 3%.

[0042]

[18] The gear as described in any one of the above methods 1 to 17, wherein the roundness of the gear is less than 400 μm.

[0043]

[19] The gear as described in any one of the above methods 1 to 18, wherein the maximum size of the hole in the gear is 1.0 μm or less.

[0044]

[20] The gear as described in any one of the above methods 1 to 19, wherein the module of the gear is 2.0 or less.

[0045]

[21] A gear comprising a resin molded body comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm, wherein,

[0046] The aforementioned gears have a roundness of less than 400 μm.

[0047] The thermoplastic resin in (A) above includes polyamide resin.

[0048] The above-mentioned resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the above-mentioned thermoplastic resin (A).

[0049]

[22] A gear for EPS (electric power steering) is a resin molded body composed of a resin composition comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm, wherein,

[0050] The aforementioned gears have a roundness of less than 400 μm.

[0051] The thermoplastic resin in (A) above includes polyamide resin.

[0052] The above-mentioned resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the above-mentioned thermoplastic resin (A).

[0053]

[23] The gear as described in any one of methods 1 to 22 above, wherein the gear is an injection-molded product.

[0054]

[24] The gear as described in any one of methods 1 to 22 above, wherein the gear is a machined product.

[0055]

[25] The gear as described in method 24 above, wherein the gear is a machined product from a round bar.

[0056]

[26] A gear system comprising:

[0057] The gear mechanism comprises a driven gear and a drive gear meshing with the driven gear; and

[0058] The drive source drives the aforementioned drive gear.

[0059] Wherein, the driven gear and / or the driving gear are the gears described in any one of the above-described methods 1 to 25.

[0060]

[27] A gear system for EPS (electric power steering), comprising:

[0061] The gear mechanism comprises a driven gear and a drive gear meshing with the driven gear; and

[0062] The drive source drives the aforementioned drive gear.

[0063] Wherein, the driven gear and / or the driving gear are the gears described in any one of the above-described methods 1 to 25.

[0064]

[28] The gear system as described in method 26 or 27 above, wherein,

[0065] The aforementioned gear mechanism is either a rack-pinion mechanism consisting of a rack and pinion, or a worm gear mechanism consisting of a worm and a worm wheel.

[0066] The aforementioned pinion or worm gear is the gear described in any one of the above methods 1 to 25.

[0067]

[29] The gear system as described in the above embodiment 28, wherein the ratio of the total tooth height to the tooth pitch of the gear of the pinion or the worm gear is 1.0 to 20.

[0068]

[30] The gear system as described in method 28 or 29 above, wherein the ratio of tooth pitch to tooth width of the teeth of the pinion or the worm gear is 1.0 to 3.0.

[0069]

[31] The gear system as described in any one of the above methods 28 to 30, wherein the torque applied to the pinion or the worm gear is 5 N·m to 100 N·m.

[0070]

[32] A gear system comprising:

[0071] The gear mechanism comprises a driven gear and a drive gear meshing with the driven gear; and

[0072] The drive source drives the aforementioned drive gear.

[0073] The aforementioned gear mechanism is a worm gear mechanism consisting of a worm and a worm wheel.

[0074] The aforementioned worm gear is an injection-molded body comprising a resin composition of (A) thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm.

[0075] The aforementioned worm gear has a roundness of less than 400 μm.

[0076] The thermoplastic resin in (A) above includes polyamide resin.

[0077] The above-mentioned resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the above-mentioned thermoplastic resin (A).

[0078]

[33] A gear system for EPS (electric power steering), comprising:

[0079] The gear mechanism comprises a driven gear and a drive gear meshing with the driven gear; and

[0080] The drive source drives the aforementioned drive gear.

[0081] The aforementioned gear mechanism is a worm gear mechanism consisting of a worm and a worm wheel.

[0082] The aforementioned worm gear is an injection-molded body comprising a resin composition of (A) thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm.

[0083] The aforementioned worm gear has a roundness of less than 400 μm.

[0084] The thermoplastic resin in (A) above includes polyamide resin.

[0085] The above-mentioned resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the above-mentioned thermoplastic resin (A).

[0086]

[34] The gear system as described in any one of methods 26 to 33 above, wherein,

[0087] The driven gear and the driving gear are meshed together by grease.

[0088] The above-mentioned grease contains:

[0089] The base oil contains at least one selected from the group consisting of mineral oils, polyalpha-olefin oils and alkyl polyphenyl ethers in a proportion of more than 80% by weight;

[0090] Thickeners; and

[0091] Hydrocarbon waxes with a melting or softening point in the range of 70°C to 130°C, accounting for 3% to 10% by mass.

[0092]

[35] The gear system as described in any one of the above methods 26 to 34, wherein the drive source is an electric motor with an operating speed of 800 rpm or more.

[0093]

[36] The gear system as described in any one of the above methods 26 to 35, wherein the drive source is an electric motor with an operating speed of 10,000 rpm or less.

[0094]

[37] The gear system as described in any one of the above methods 26 to 36, wherein the torque applied to the gear is 3 N / m or more.

[0095]

[38] The gear system as described in the above method 37, wherein the torque applied to the gear is 5 N·m or more.

[0096]

[39] The gear system as described in the above method 38, wherein the torque applied to the gear is 10 N / m or more.

[0097] The effects of the invention

[0098] According to one aspect of the invention, a gear (particularly an EPS gear) with excellent continuous formability in practical applications, balancing high slip and high durability, and a gear system (particularly an EPS system) having the gear are provided. Furthermore, according to one aspect of the invention, a gear (particularly an EPS gear) that reduces internal porosity of thick-walled molded bodies and improves gear durability and quietness, balancing sufficient durability and quietness in practical applications, and a gear system (particularly an EPS system) having the gear are provided. Attached Figure Description

[0099] Figure 1 This is a diagram illustrating an example of a gear system according to one aspect of the present invention.

[0100] Figure 2 This is a diagram illustrating an example of a gear system according to one aspect of the present invention. Detailed Implementation

[0101] The present invention will now be specifically described in the following exemplary embodiments, but the present invention is not limited to these embodiments.

[0102] In one embodiment, the gear (particularly an EPS gear) is a resin molded body composed of a resin composition comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less, wherein the number-average molecular weight of the thermoplastic resin (A) is in the range of 10,000 to 150,000. In one embodiment, the arithmetic mean surface roughness Sa of the sliding surface of the gear with other gear teeth is 3.0 μm or less.

[0103] <<(A) Thermoplastic Resin>>

[0104] The number-average molecular weight of the (A) thermoplastic resin that can be used in this invention is in the range of 10,000 to 150,000, particularly 20,000 to 150,000. Furthermore, the number-average molecular weight disclosed herein is a value determined using GPC (gel permeation chromatography) by conversion from standard polymethyl methacrylate. The lower limit of the number-average molecular weight is more preferably 22,000, even more preferably 25,000, and most preferably 30,000. Furthermore, the upper limit is more preferably 120,000, even more preferably 100,000, and most preferably 80,000. Regarding the number-average molecular weight, from the perspective of improving gear durability, it is preferable to be at or above the aforementioned lower limit; from the perspective of the flowability of the resin composition during gear molding, it is preferable not to exceed the aforementioned upper limit.

[0105] Examples of (A) thermoplastic resins include crystalline resins having a melting point in the range of 100°C to 350°C, and amorphous resins having a glass transition temperature in the range of 100°C to 250°C. (A) Thermoplastic resins can be homopolymers or copolymers, and can be composed of one or more polymers.

[0106] The melting point of the crystalline resin referred to here is the peak temperature of the endothermic peak that appears when heated from 23°C at a heating rate of 10°C / min using a differential scanning calorimeter (DSC). If two or more endothermic peaks appear, the peak temperature refers to the peak temperature of the endothermic peak at the highest temperature. The enthalpy of this endothermic peak is preferably 10 J / g or more, more preferably 20 J / g or more. Furthermore, during the measurement, the sample is heated to a temperature of melting point +20°C or more in one step to melt the resin, and then cooled to 23°C at a cooling rate of 10°C / min; samples obtained in this manner are preferred. In a preferred embodiment, (A) the melting point of the thermoplastic resin is, for example, 150°C or more, or 180°C or more, or 200°C or more, or 230°C or more, and, for example, 500°C or less, or 400°C or less, or 300°C or less.

[0107] Furthermore, the glass transition temperature of the amorphous resin mentioned here refers to the peak temperature at which the storage modulus significantly decreases and the loss modulus reaches its maximum when measured using a dynamic viscoelasticity measuring device at a heating rate of 2°C / min from 23°C and an application frequency of 10Hz. In the case of two or more loss modulus peaks, it refers to the peak temperature of the highest temperature side. Regarding the measurement frequency, to improve measurement accuracy, it is preferable to perform measurements at least once every 20 seconds. Furthermore, there are no particular restrictions on the preparation method of the sample for measurement; from the perspective of avoiding the influence of molding strain, it is preferable to use slices of thermoformed articles; from the perspective of heat conduction, it is preferable to minimize the size (width and thickness) of the slices as much as possible. In a preferred embodiment, (A) the glass transition temperature of the thermoplastic resin is, for example, -130°C or higher, or -60°C or higher, or -10°C or higher, and for example, 300°C or lower, or 200°C or lower, or 150°C or lower.

[0108] Examples of thermoplastic resins (A) include polyamide resins, polyester resins, polyacetal resins, polycarbonate resins, polyacrylic resins, polyphenylene ether resins (including modified polyphenylene ethers modified by blending or graft polymerization with other resins), polyarylate resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polyketide resins, polyphenylene ether ketone resins, polyimide resins, polyamide-imide resins, polyether-imide resins, polyurethane resins, polyolefin resins (e.g., α-olefin (co)polymers), and various ionomers.

[0109] (A) Preferred specific examples of thermoplastic resins may include high-density polyethylene, low-density polyethylene (e.g., linear low-density polyethylene), polypropylene, polymethylpentene, cyclic olefin resins, poly-1-butene, poly-1-pentene, polymethylpentene, ethylene / α-olefin copolymers, ethylene-butene copolymers, EPR (ethylene-propylene copolymer), modified ethylene-butene copolymers, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymer), ionomers, α-olefin copolymers, and modified... IR (isoprene rubber), modified SEBS (styrene-ethylene-butene-styrene copolymer), haloisobutylene-p-methylstyrene copolymer, ethylene-acrylic acid modified product, ethylene-vinyl acetate copolymer and its acid modified product, copolymer of (ethylene and / or propylene) with (unsaturated carboxylic acid and / or unsaturated carboxylic acid ester), polyolefin obtained by metal salting at least a portion of the carboxyl group of the copolymer of (ethylene and / or propylene) with (unsaturated carboxylic acid and / or unsaturated carboxylic acid ester), block copolymer of conjugated diene and vinyl aromatic hydrocarbon, conjugated diene Hydrogenates of block copolymers with vinyl aromatic hydrocarbons, copolymers of conjugated dienes with non-conjugated olefins, natural rubber, various butadiene rubbers, various styrene-butadiene copolymer rubbers, isoprene rubber, butyl rubber, bromides of isobutylene and p-methylstyrene copolymers, halogenated butyl rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber Chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, polyvinyl chloride, polystyrene, polyacrylate, polymethacrylate and other acrylonitrile copolymers with acrylic acid and acrylonitrile as the main components, acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, cellulose acetate and other cellulose resins, vinyl chloride / ethylene copolymer, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer and saponifications of ethylene / vinyl acetate copolymer, etc.

[0110] These substances can be used alone or in combination of two or more. When two or more are used together, they can be used as polymer alloys. Additionally, the aforementioned thermoplastic resins can also be modified with substances derived from at least one compound selected from unsaturated carboxylic acids, their anhydrides, or derivatives thereof.

[0111] Among these, from the perspectives of heat resistance, moldability, aesthetics and mechanical properties, it is preferred to select one or more resins from the group consisting of polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polyacrylic resins, polyphenylene ether resins and polyphenylene sulfide resins.

[0112] Among these, from the perspectives of processability and cost, it is preferable to have one or more resins selected from the group consisting of polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polyacrylic resins, polyphenylene ether resins, and polyphenylene sulfide resins, and particularly preferably to have one or more resins selected from the group consisting of polyamide resins and polyacetal resins. In a particularly preferred embodiment, (A) the thermoplastic resin comprises a polyamide resin.

[0113] Polyolefin resins are polymers obtained by polymerizing monomer units containing olefins (e.g., α-olefins). Specific examples of polyolefin resins are not particularly limited, but can include ethylene-based (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high-molecular-weight polyethylene; polypropylene-based (co)polymers such as polypropylene, ethylene-propylene copolymers, and ethylene-propylene-diene copolymers; and copolymers of α-olefins with other monomer units, represented by ethylene-acrylic acid copolymers, ethylene-methyl methacrylate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0114] Polypropylene is the most preferred polyolefin resin here. Polypropylene with a melt flow rate (MFR) of 0.1 g / 10 min to 30 g / 10 min, measured according to ISO 1133 at 230°C and a load of 21.2 N, is particularly preferred. The lower limit of the MFR is more preferably 0.2 g / 10 min, or 0.4 g / 10 min, or 0.5 g / 10 min, or 3 g / 10 min, or 5 g / 10 min. The upper limit is more preferably 25 g / 10 min, or 20 g / 10 min, or 18 g / 10 min, or 15 g / 10 min, or 10 g / 10 min, or 5 g / 10 min. From the perspective of improving the toughness of the composition, it is preferable that the MFR does not exceed the above-mentioned upper limit value; from the perspective of the flowability of the composition, it is preferable that the MFR does not exceed the above-mentioned lower limit value.

[0115] In addition, acid-modified polyolefin resins can be suitably used to improve affinity with cellulose. As the acid, maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, as well as polycarboxylic acids such as citric acid, can be suitably selected. From the perspective of easily increasing the modification rate, maleic acid or its anhydride is preferred. There are no particular limitations on the modification method; generally, it is a method of melt-blending by heating the resin above its melting point in the presence or absence of a peroxide. As the acid-modified polyolefin resin, all of the above-mentioned polyolefin resins can be used, among which polypropylene can be suitably used.

[0116] Acid-modified polyolefin resins can be used alone, but to adjust the modification rate as a composition, it is more preferable to use them in combination with unmodified polyolefin resins. For example, when using a mixture of unmodified polypropylene and acid-modified polypropylene, the proportion of acid-modified polypropylene relative to the total polypropylene is preferably 0.5% to 50% by mass. More preferably, the lower limit is 1% by mass, further preferably 2% by mass, even more preferably 3% by mass, particularly preferably 4% by mass, and most preferably 5% by mass. In addition, more preferably, the upper limit is 45% by mass, further preferably 40% by mass, even more preferably 35% by mass, particularly preferably 30% by mass, and most preferably 20% by mass. To maintain the interfacial strength with cellulose, it is preferably above the lower limit; to maintain the ductility as a resin, it is preferably below the upper limit.

[0117] To improve the affinity with the cellulose interface, the melt flow rate (MFR) of the acid-modified polypropylene, measured according to ISO 1133 at 230°C and a load of 21.2 N, is preferably 50 g / 10 min or more. A more preferred lower limit is 100 g / 10 min, further more preferred is 150 g / 10 min, and most preferably is 200 g / 10 min. The upper limit is not particularly limited, but from the perspective of maintaining mechanical strength, it is 500 g / 10 min. By keeping the MFR within this range, the advantage of easy presence at the cellulose-resin interface can be enjoyed.

[0118] There are no particular limitations on the preferred thermoplastic resins, but examples include: polyamide 6, polyamide 11, and polyamide 12 obtained through the condensation reaction of lactams; and diamines such as 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1,7-heptanediamine, 2-methyl-1,6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, and m-phenylenediamine, which are used in conjunction with succinic acid, glutaric acid, adipic acid, pimelic acid, and octanoic acid. Polyamides such as polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,T, polyamide 6,I, polyamide 9,T, polyamide 10,T, polyamide 2M5,T, polyamide MXD,6, polyamide 6,C, and polyamide 2M5,C are obtained in the form of copolymers of dicarboxylic acids such as azelaic acid, sebacic acid, phenyl-1,2-dicarboxylic acid, phenyl-1,3-dicarboxylic acid, phenyl-1,4-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acid; and copolymers formed by copolymerizing them separately (for example, polyamide 6,T / 6,I).

[0119] Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, and polyamide 6,12, and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferred.

[0120] There is no particular limitation on the concentration of terminal carboxyl groups in the polyamide resin, but the lower limit is preferably 20 μmol / g, more preferably 30 μmol / g. Furthermore, the upper limit of the terminal carboxyl group concentration is preferably 150 μmol / g, more preferably 100 μmol / g, and even more preferably 80 μmol / g.

[0121] In polyamide resins, the ratio of carboxyl-terminal groups to all terminal groups ([COOH] / [all terminal groups]) is preferably 0.30 to 0.95. The lower limit of the carboxyl-terminal group ratio is more preferably 0.35, further more preferably 0.40, and most preferably 0.45. Furthermore, the upper limit of the carboxyl-terminal group ratio is more preferably 0.90, further more preferably 0.85, and most preferably 0.80. From the perspective of the dispersibility of cellulose nanofibers in the composition (B), the above-mentioned carboxyl-terminal group ratio is preferably 0.30 or more; from the perspective of the color tone of the obtained composition, the above-mentioned carboxyl-terminal group ratio is preferably 0.95 or less.

[0122] As a method for adjusting the concentration of end groups in polyamide resins, known methods can be used. For example, methods can be described by adding end-group modifiers such as diamine compounds, monoamine compounds, dicarboxylic acid compounds, monocarboxylic acid compounds, acid anhydrides, monoisocyanates, monoacyl halides, monoesters, and monoalcohols to the polymerization solution to achieve a specified concentration of end groups during polyamide polymerization.

[0123] Examples of end-modifiers that react with the terminal amino group include: aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, tertvaleric acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, methylbenzoic acid, α-naphthoic acid, β-naphthoic acid, methylnaphthoic acid, and phenylacetic acid; and mixtures of two or more selected from these substances. Among these, considering reactivity, stability of the closed end, and price, one or more end-modifiers selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, and benzoic acid are preferred, with acetic acid being the most preferred.

[0124] Examples of end-modifiers that react with the terminal carboxyl group include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and any mixtures thereof. Among these, one or more end-modifiers selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferred from considerations of reactivity, boiling point, stability of the closed end, and price.

[0125] From the perspectives of precision and simplicity, the concentrations of these amino-terminal and carboxyl-terminal groups are preferably determined by... 1 H-NMR is determined based on the integrated values ​​of the characteristic signals corresponding to each terminal group. Specifically, the method described in Japanese Patent Application Publication No. 7-228775 is recommended as a method for determining the concentration of these terminal groups. When using this method, deuterated trifluoroacetic acid is useful as the determination solvent. Furthermore, regarding... 1 When performing H-NMR measurements using equipment with sufficient resolution, at least 300 scans are required for integration. Furthermore, the concentration of terminal groups can also be determined using a titration-based method described in Japanese Patent Application Publication No. 2003-055549. However, to minimize the influence of mixed additives, lubricants, etc., it is more preferable to utilize... 1 Quantitative analysis was performed using H-NMR.

[0126] The intrinsic viscosity [η] of the polyamide resin, measured in concentrated sulfuric acid at 30°C, is preferably 0.6–2.0 dL / g, more preferably 0.7–1.4 dL / g, further preferably 0.7–1.2 dL / g, and particularly preferably 0.7–1.0 dL / g. When using the above-mentioned polyamide resin with an intrinsic viscosity having a preferred range, especially a particularly preferred range, the flowability of the resin composition within the mold during injection molding can be significantly improved, thereby enhancing the appearance of the molded sheet.

[0127] In this disclosure, "intrinsic viscosity" has the same meaning as viscosity commonly referred to as intrinsic viscosity (limiting viscosity). The specific method for determining this viscosity is as follows: In 96% concentrated sulfuric acid at 30°C, the ηsp / c of ​​several test solvents with different concentrations is measured, and the relationship between each ηsp / c and concentration (c) is derived, extrapolating the concentration to zero. The value extrapolated to zero is the intrinsic viscosity. Details of this are described, for example, on pages 291-294 of Polymer Process Engineering (Prentice-Hall, Inc. 1994).

[0128] From the perspective of accuracy, it is preferable to use at least four different types of solvents with varying concentrations for viscosity determination. The recommended concentrations of the viscosity determination solutions are preferably at least four: 0.05 g / dL, 0.1 g / dL, 0.2 g / dL, and 0.4 g / dL.

[0129] There are no particular limitations on the preferred polyester resin as the thermoplastic resin, and one or more selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene succinate (PBS), polybutylene succinate / adipate-butylene glycol (PBSA), polybutylene adipate-terephthalate (PBAT), polyarylate (PAR), polyhydroxyalkanoic acid (PHA) (a polyester resin formed from 3-hydroxyalkanoic acid), polylactic acid (PLA), and polycarbonate (PC) can be used. Among these, PET, PBS, PBSA, PBT, and PEN are more preferred polyester resins, and PBS, PBSA, and PBT are even more preferred.

[0130] Furthermore, in polyester resins, the terminal groups can be freely varied depending on the monomer ratio during polymerization and the presence and amount of terminal stabilizers added. However, the ratio of carboxyl terminal groups to all terminal groups ([COOH] / [all terminal groups]) in the polyester resin is preferably 0.30 to 0.95. The lower limit of the ratio of carboxyl terminal groups is more preferably 0.35, further preferably 0.40, and most preferably 0.45. The upper limit of the ratio of carboxyl terminal groups is more preferably 0.90, further preferably 0.85, and most preferably 0.80. From the perspective of the dispersibility of cellulose nanofibers in the composition (B), the ratio of the above-mentioned carboxyl terminal groups is preferably 0.30 or more, and from the perspective of the color tone of the obtained composition, the ratio of the above-mentioned carboxyl terminal groups is preferably 0.95 or less.

[0131] Preferred thermoplastic acetal resins are typically homopolymer acetals made from formaldehyde and copolymer acetals using trioxymethylene as the main monomer (e.g., containing 1,3-dioxolane as a comonomer). Both can be used, but copolymer acetals are preferred from the perspective of thermal stability during processing. Specifically, the amount of comonomer (e.g., 1,3-dioxolane) is preferably in the range of 0.01 to 4 mol%. A more preferred lower limit for the comonomer content is 0.05 mol%, further preferably 0.1 mol%, and particularly preferably 0.2 mol%. An even more preferred upper limit is 3.5 mol%, further preferably 3.0 mol%, particularly preferably 2.5 mol%, and most preferably 2.3 mol%. From the perspective of thermal stability during extrusion and molding, the lower limit is preferably within the above range, and from the perspective of mechanical strength, the upper limit is preferably within the above range.

[0132] <<(B) Cellulose nanofibers with an average fiber diameter of less than 1000 nm>>

[0133] Next, a detailed description will be given of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm (sometimes referred to as "(B) cellulose nanofibers" in this disclosure), which can be used in the present invention.

[0134] (B) There are no particular limitations on preferred examples of cellulose nanofibers with an average fiber diameter of 1000 nm or less. For example, one or more of cellulose fibers made from cellulose pulp or modified cellulose fibers can be used. Among these, one or more of the modified cellulose fibers can be preferred from the perspectives of stability and performance.

[0135] There are no particular limitations on the preparation method of cellulose nanofibers. For example, after the raw material pulp is cut, it can be treated with hot water above 100°C to hydrolyze the hemicellulose part and make it brittle. Then, it can be obtained by pulverizing it using a high-pressure homogenizer, a high-pressure micro-jet homogenizer, a ball mill, a disc pulverizer, etc.

[0136] From the perspective of obtaining good mechanical strength (especially tensile modulus of elasticity) in the resin molded body, (B) the average fiber diameter of the cellulose nanofibers is 1000 nm or less, preferably 500 nm or less, and more preferably 200 nm or less. A small average fiber diameter is preferred, but from the perspective of ease of processing, it is preferable to have a diameter of 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The above-mentioned average fiber diameter is a value obtained by using a laser diffraction / scattering particle size analyzer in the form of the spherical equivalent diameter (volume average particle diameter) of the particles when the integrated volume reaches 50%.

[0137] The average fiber diameter mentioned above can be determined by the following method. (B) Cellulose nanofibers, comprising 40% by mass of solids, are mixed in a planetary mixer (e.g., Shinagawa Kogyo Co., Ltd., 5DM-03-R, with hook-shaped stirring blades) at room temperature and atmospheric pressure at 126 rpm for 30 minutes. Then, a pure water suspension is prepared at a concentration of 0.5% by mass. This suspension is dispersed using a high-shear homogenizer (e.g., Nippon Seiki Co., Ltd., trade name "EXCEL AUTO HOMOGENIZER ED-7") at 15,000 rpm for 5 minutes. The dispersion is then carried out using a centrifuge (e.g., Kubota Corporation, trade name "6800 type centrifuge", Rotor Type RA-400) at a centrifugal force of 39200 m³ / h. 2 Centrifuge at 116000 m³ / s for 10 minutes, collect the supernatant, and further process the supernatant at 116000 m³ / s. 2 Centrifuge for 45 minutes at a time, and collect the supernatant. Using this supernatant, the integral 50% particle diameter (i.e., the spherical equivalent diameter of the particle when the integral volume reaches 50% relative to the total volume of the particle) in the volume frequency particle size distribution obtained using a laser diffraction / scattering particle size analyzer (e.g., manufactured by Horiba Manufacturing Co., Ltd., trade name "LA-910" or "LA-950") is taken as the volume average particle diameter.

[0138] In a representative embodiment, (B) the L / D ratio of cellulose nanofibers with an average fiber diameter of 1000 nm or less is 20 or more. The lower limit of the L / D ratio for cellulose nanofibers is preferably 30, more preferably 40, further preferably 50, and even more preferably 100. The upper limit is not particularly limited, but from a processability perspective, it is preferably 10,000 or less. In order to utilize a small amount of cellulose nanofibers to achieve the excellent mechanical properties of the gears of this disclosure, the L / D ratio of the cellulose nanofibers is preferably within the above-mentioned range.

[0139] In this disclosure, the length, diameter, and L / D ratio of the cellulose nanofibers are determined as follows: Aqueous dispersions of individual cellulose nanofibers are dispersed using a high-shear homogenizer (e.g., Nippon Seiki Co., Ltd., trade name "EXCEL AUTOHOMOGENIZER ED-7") at a speed of 15,000 rpm for 5 minutes. The resulting aqueous dispersion is diluted with pure water to 0.1–0.5% by mass, poured onto mica, and air-dried. This is used as a sample for measurement, and the measurements are obtained using an optical microscope, a high-resolution scanning electron microscope (SEM), or an atomic force microscope (AFM). Specifically, in an observation field adjusted to allow for the observation of at least 100 cellulose nanofibers, the length (L) and diameter (D) of 100 randomly selected cellulose nanofibers are measured, and the ratio (L / D) is calculated. Furthermore, the length and diameter of the cellulose nanofibers in this disclosure are the number average of the aforementioned 100 cellulose nanofibers.

[0140] The length, diameter, and L / D ratio of the cellulose fibers in the resin composition or molded body can be confirmed as follows: The resin component in the composition is dissolved in an organic or inorganic solvent capable of dissolving the resin component in the composition. The cellulose is separated, thoroughly washed with the solvent, and then the solvent is replaced with pure water or a dispersible organic solvent to prepare an aqueous dispersion. This dispersion is diluted with pure water until the cellulose concentration reaches 0.1–0.5% by mass. The dispersion is then poured onto mica and air-dried to obtain a sample for testing. The sample is then measured using the method described above to confirm its composition. At this stage, at least 100 randomly selected cellulose fibers are tested.

[0141] Examples of modified cellulose in this disclosure include modified cellulose obtained by modification with one or more modifiers selected from esterifying agents, silylating agents, isocyanate compounds, halogenated alkylating agents, alkylene oxides and / or glycidyl compounds.

[0142] The esterifying agent, as a modifier, comprises an organic compound having at least one functional group capable of reacting with hydroxyl groups on the surface of cellulose to esterify it. Alternatively, esterification can be carried out by the method described in paragraph

[0108] of International Publication No. 2017 / 159823. The esterifying agent can be a commercially available reagent or product.

[0143] Preferred examples of esterifying agents are not particularly limited, and examples include: aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, tervaline, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, methylbenzoic acid, α-naphthoic acid, β-naphthoic acid, methylnaphthoic acid, and phenylacetic acid; and mixtures of two or more of these selected from them and symmetrical anhydrides (acetic anhydride, maleic anhydride, cyclohexane-carboxylic anhydride, benzene-sulfonic anhydride), mixed anhydrides (butyric acid-valeric anhydride), cyclic anhydrides (succinic anhydride, phthalic anhydride, naphthalene-1,8:4,5-tetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic 3,4-anhydride), and ester anhydrides (acetic acid 3-(ethoxycarbonyl)propane anhydride, benzoyl ethyl carbonate), etc.

[0144] Among these, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, benzoic acid, acetic anhydride, maleic anhydride, succinic anhydride, and phthalic anhydride can be preferred based on reactivity, stability, and price.

[0145] The silylating agent used as a modifier comprises a Si-containing compound having at least one reactive group capable of reacting with hydroxyl groups or hydrolyzed groups on the surface of cellulose. The silylating agent can be a commercially available reagent or product.

[0146] Preferred examples of silylating agents are not particularly limited, and examples include chloro(dimethyl)isopropylsilane, chloro(dimethyl)butylsilane, chloro(dimethyl)octylsilane, chloro(dimethyl)dodecylsilane, chloro(dimethyl)octadecylsilane, chloro(dimethyl)phenylsilane, chloro(1-hexenyl)dimethylsilane, dichlorohexylmethylsilane, dichloroheptylmethylsilane, trichlorooctylsilane, hexamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-divinyl-1,3-diphenyl-1,3-dimethyldisilazane, 1,3- N-Dioctyltetramethyl-disilazane, diisobutyltetramethyldisilazane, diethyltetramethyldisilazane, N-dipropyltetramethyldisilazane, N-dibutyltetramethyldisilazane or 1,3-di(p-tert-butylphenylethyl)tetramethyldisilazane, N-trimethylsilylacetamide, N-methyldiphenylsilylacetamide, N-triethylsilylacetamide, tert-butyldiphenylmethoxysilane, octadecyldimethylmethoxysilane, dimethyloctylmethoxysilane, octylmethyldimethoxysilane, octyltrimethoxysilane, trimethylethoxysilane, octyltriethoxysilane, etc.

[0147] Among these, hexamethyldisilazane, octadecyldimethylmethoxysilane, dimethyloctylmethoxysilane, and trimethylethoxysilane are preferred in terms of reactivity, stability, and price.

[0148] The halogenated alkylating agent used as a modifier comprises an organic compound having at least one functional group capable of reacting with hydroxyl groups on the surface of cellulose to halogenate it. The halogenated alkylating agent can be a commercially available reagent or product.

[0149] There are no particular limitations on preferred examples of halogenated alkylating agents, and chloropropane, chlorobutane, bromopropane, bromohexane, bromoheptane, iodomethane, iodoethane, iodooctane, iodooctadecane, iodobenzene, etc., can be used. Among these, bromohexane and iodooctane are preferred from the perspectives of reactivity, stability, and price.

[0150] The isocyanate compound used as a modifier comprises an organic compound having at least one isocyanate group capable of reacting with hydroxyl groups on the surface of cellulose. Additionally, the isocyanate compound can be a terminal isocyanate compound capable of undergoing deblocking of the block groups at a specific temperature to regenerate isocyanate groups; it can also be a dimer or trimer of a polyisocyanate, a modified biuret isocyanate, a polymethylene polyphenyl polyisocyanate (polymeric MDI), etc. These can be commercially available reagents or products.

[0151] Preferred examples of isocyanate compounds are not particularly limited, and examples include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, aromatic aliphatic polyisocyanates, terminal isocyanate compounds, and polyisocyanates. Examples include tetramethylene diisocyanate, dodecamethyl diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, isophorone diisocyanate, hydrogenated phenylenediamine diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-di(isocyanate methyl)cyclohexane, toluene diisocyanate (TDI), 2,2'-diphenylmethane diisocyanate, 2,4'- Diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, phenylmethylene diisocyanate, 1,3-phenylmethylene diisocyanate, 1,4-phenylmethylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α,α,α,α-tetramethylphenylmethylene diisocyanate, and capped isocyanate compounds formed by reacting oxime-based capping agents, phenol-based capping agents, lactam-based capping agents, alcohol-based capping agents, active methylene-based capping agents, amine-based capping agents, pyrazole-based capping agents, bisulfite-based capping agents, or imidazole-based capping agents with the above-mentioned isocyanate compounds, etc.

[0152] Among these, considering reactivity, stability, and price, TDI, MDI, hexamethylene diisocyanate, and capped isocyanates using hexamethylene diisocyanate modifiers and hexamethylene diisocyanate as raw materials are preferred.

[0153] From the perspective of reactivity and stability, the upper limit of the dissociation temperature of the block groups in the above-mentioned capped isocyanate compounds is preferably 210°C, more preferably 190°C, and even more preferably 150°C. Furthermore, the lower limit is preferably 70°C, more preferably 80°C, and even more preferably 110°C. Examples of capping agents with dissociation temperatures within this range for the block groups include methyl ethyl ketone oxime, o-sec-butylphenol, caprolactam, sodium bisulfite, 3,5-dimethylpyrazole, and 2-methylimidazole.

[0154] The alkylene oxide and / or glycidyl group compound used as a modifier comprises an organic compound having at least one alkylene oxide, glycidyl group, and / or epoxy group capable of reacting with hydroxyl groups on the surface of cellulose. The alkylene oxide and / or glycidyl group compound can be a commercially available reagent or product.

[0155] Preferred examples of alkylene oxide and / or glycidyl compounds are not particularly limited, and examples include: methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, tolyl glycidyl ether, dibromotolyl glycidyl ether, and other glycidyl ethers; glycidyl acetate, glycidyl stearate, and other glycidyl esters; Polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, sorbitan anhydride polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, and other polyol glycidyl ethers.

[0156] Among these, 2-methyloctyl glycidyl ether, hexamethylene diol diglycidyl ether, and pentaerythritol tetraglycidyl ether are preferred in terms of reactivity, stability, and price.

[0157] Modified cellulose nanofibers can be identified as follows: The resin component in the composition is dissolved in an organic or inorganic solvent capable of dissolving the resin composition or molded article. Cellulose is separated by centrifugation or filtration of the solution. After thorough washing with the solvent, the separated modified cellulose nanofibers are subjected to thermal decomposition or hydrolysis treatment, thereby confirming the modified product. Alternatively, it can be identified by direct... 1 H-NMR, 13 This was confirmed by C-NMR measurements.

[0158] From the perspective of good mechanical properties, thermal stability and durability, the mixing amount of (B) cellulose nanofibers relative to 100 parts by weight of (A) thermoplastic resin is preferably 5 parts by weight or more, preferably 8 parts by weight or more, more preferably 10 parts by weight or more, and from the perspective of obtaining sufficient formability, it is 50 parts by weight or less, preferably 40 parts by weight or less, more preferably 30 parts by weight or less.

[0159] The resin composition preferably comprises 45-95% by mass of (A) thermoplastic resin and 5-50% by mass of (B) cellulose nanofibers, or comprises 50-90% by mass of (A) thermoplastic resin and 10-45% by mass of (B) cellulose nanofibers, or comprises 60-80% by mass of (A) thermoplastic resin and 20-40% by mass of (B) cellulose nanofibers.

[0160] <<(C) Surface Treatment Agent>>

[0161] The resin composition may include (C) a surface treatment agent as an additional component. In one embodiment, (C) the surface treatment agent is a water-soluble polymer. In this disclosure, "water-soluble" means dissolving more than 0.1 g in 100 g of water at 23°C. In one embodiment, (C) the surface treatment agent has hydrophilic and hydrophobic segments (i.e., an amphiphilic molecule). Examples of amphiphilic molecules include molecules with a carbon atom as the basic skeleton and having functional groups composed of elements selected from carbon, hydrogen, oxygen, nitrogen, chlorine, sulfur, and phosphorus. If the molecule has the above structure, it is also preferred that an inorganic compound is chemically bonded to the above functional groups. When (C) the surface treatment agent is a mixture of two or more substances, the characteristic values ​​(e.g., molecular weight, HLB value, static surface tension, dynamic surface tension, SP value) of this disclosure refer to the values ​​of the mixture. In one embodiment, (C) the surface treatment agent is a surfactant. In one embodiment, (C) the surface treatment agent is a nonionic surfactant. In another embodiment, (C) the surface treatment agent is a low molecular weight thermoplastic resin. (C) The surface treatment agent is different from (A) the thermoplastic resin (e.g., a modified polymer of the same kind as (A) the thermoplastic resin of this disclosure (e.g., an acid-modified polymer, a copolymer), or a polymer of a different kind than (A) the thermoplastic resin). In one embodiment, (C) the surface treatment agent is a polymer with a different molecular weight, repeating structure, and / or block structure than (A) the thermoplastic resin. In one embodiment, (C) the surface treatment agent and (A) the thermoplastic resin are the same kind of polymer with different molecular weights; in this case, the polymer with the smaller molecular weight is (C) the surface treatment agent.

[0162] In a representative manner, (A) the thermoplastic resin is not water-soluble, and (C) the surface treatment agent is water-soluble. (C) The surface treatment agent can, for example, be mixed with (B) cellulose nanofibers in a highly concentrated aqueous dispersion containing (C) the surface treatment agent. (C) The surface treatment agent can be a commercially available reagent or product.

[0163] (C) When the surface treatment agent has both hydrophilic and hydrophobic segments (i.e., amphiphilic molecules), the hydrophilic segments have good affinity with the cellulose surface. The hydrophobic segments can inhibit the aggregation of cellulose molecules by means of the hydrophilic segments. Therefore, the hydrophilic and hydrophobic segments in the (C) surface treatment agent need to exist within the same molecule.

[0164] In a representative embodiment, the hydrophilic segment exhibits good affinity with (A) cellulose nanofibers by including a hydrophilic structure (e.g., a hydrophilic group selected from hydroxyl, carboxyl, carbonyl, amino, ammonium, amide, sulfonyl, etc.). Examples of hydrophilic segments include segments of polyethylene glycol (i.e., segments with two or more ethylene oxide units) (PEG blocks), segments containing repeating units comprising quaternary ammonium salt structures, segments of polyvinyl alcohol, segments of polyvinylpyrrolidone, segments of polyacrylic acid, segments of carboxyvinyl polymers, segments of cationic guar gum, segments of hydroxyethyl cellulose, segments of methyl cellulose, segments of carboxymethyl cellulose, and flexible segments (soft segments) of polyurethane (specifically, glycol segments). In a preferred embodiment, the hydrophilic segment includes ethylene oxide units.

[0165] Examples of hydrophobic segments include segments having alkyl oxide units with 3 or more carbon atoms (e.g., PPG blocks) and segments comprising the following polymer structures:

[0166] Acrylic polymers, styrene resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, polyhexamethylene adipamide (6,6 nylon), polyhexamethylene azelaamide (6,9 nylon), polyhexamethylene sebacate (6,10 nylon), polyhexamethylene dodecylamide (6,12 nylon), polybis(4-aminocyclohexyl)methanedodecane, and other condensation polymers of organic dicarboxylic acids with 4 to 12 carbon atoms and organic diamines with 2 to 13 carbon atoms; condensation polymers of ω-amino acids (e.g., ω-aminoundecanoic acid) (e.g., polyundecylamide). (11 Nylon) etc.), polycaprolactam (6 Nylon) as an open-ring polymer of ε-aminocaprolactam, polylaurolactam (12 Nylon) as an open-ring polymer of ε-aminolaurolactam, etc., amino acid lactams containing lactams; polymers composed of diamines and dicarboxylic acids, polyacetal resins, polycarbonate resins, polyester resins, polyphenylene sulfide resins, polysulfone resins, polyetherketone resins, polyimide resins, fluorine resins, hydrophobic silicone resins, melamine resins, epoxy resins, phenolic resins.

[0167] The number of carbon atoms in the epoxide alkane unit of the hydrophobic segment is preferably 3 or more, or 5 or more, or 10 or more, or 15 or more. The longer the chain length, the higher the affinity between the (C) surface treatment agent and the (B) cellulose nanofibers. However, from the perspective of balancing this affinity with coatability (i.e., the positioning at the interface with (A) thermoplastic resin and (B) cellulose nanofibers), the number of carbon atoms is preferably 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less.

[0168] In a preferred embodiment, (C) the surface treatment agent has a PEG block as a hydrophilic group and a PPG block as a hydrophobic group within its molecule.

[0169] (C) The surface treatment agent may have a graft copolymer structure and / or a block copolymer structure. These structures may be a single type or two or more types. In the case of two or more types, they may be polymer alloys. Alternatively, they may be partially modified or end-modified (acid modified) versions of these copolymers.

[0170] (C) The structure of the surface treatment agent is not particularly limited. When the hydrophilic segment is A and the hydrophobic segment is B, examples include AB-type block copolymers, ABA-type block copolymers, BAB-type block copolymers, ABAB-type block copolymers, ABABA-type block copolymers, BABAB-type copolymers, 3-branched copolymers containing A and B, 4-branched copolymers containing A and B, star copolymers containing A and B, monocyclic copolymers containing A and B, polycyclic copolymers containing A and B, and cage copolymers containing A and B.

[0171] (C) The surface treatment agent preferably has the following structure: an AB-type block copolymer, an ABA-type triblock copolymer, a 3-branched copolymer containing A and B, or a 4-branched copolymer containing A and B. More preferably, it is an ABA-type triblock copolymer, a 3-branched structure (i.e., a 3-branched copolymer containing A and B), or a 4-branched structure (i.e., a 4-branched copolymer containing A and B). To ensure good affinity with (B) cellulose nanofibers, the surface treatment agent (C) preferably has the above-described structure.

[0172] Preferred examples of surface treatment agents (C) include copolymers obtained by using one or more compounds that impart hydrophilic segments (e.g., polyethylene glycol) and compounds that impart hydrophobic segments (e.g., polypropylene glycol, poly(tetramethylene ether) glycol (PTMEG), polybutadiene glycol, etc.), such as block copolymers of propylene oxide and ethylene oxide, and block copolymers of tetrahydrofuran and ethylene oxide. A single surface treatment agent may be used, or two or more may be used in combination. When two or more are used in combination, they may be used in the form of a polymer alloy. Alternatively, modified copolymers (e.g., modified copolymers obtained by modifying the above copolymers) may be used.

[0173] Among these, copolymers of polyethylene glycol and polypropylene glycol, copolymers of polyethylene glycol and poly(tetramethylene ether) glycol (PTMEG), and mixtures thereof are preferred from the perspectives of heat resistance (odor) and mechanical properties. From the perspectives of processability and cost, copolymers of polyethylene glycol and polypropylene glycol are more preferred.

[0174] In a representative manner, (C) surface treatment agents exhibit a cloud point. In aqueous solutions of nonionic surfactants with polyether chains such as polyoxyethylene chains as hydrophilic sites, turbidity is observed at a certain temperature (called the cloud point) after the initial transparent or translucent solution has increased in temperature. That is, when a transparent or translucent aqueous solution is heated, the solubility of the nonionic surfactant decreases sharply at a certain temperature, causing previously dissolved surfactants to aggregate, become turbid, and separate from the water. This is believed to be due to the loss of hydration by the nonionic surfactant at high temperatures (the hydrogen bonds between the polyether chains and water break, resulting in a sharp decrease in solubility in water). The longer the polyether chain, the lower the cloud point tends to be. At temperatures below the cloud point, the surfactant dissolves in water in any proportion; therefore, the cloud point becomes a measure of the hydrophilicity of (C) surface treatment agents.

[0175] (C) The cloud point of the surface treatment agent can be determined by the following method. Using a tuning fork type viscometer (e.g., SV-10A manufactured by A&D Corporation), the aqueous solution of the (C) surface treatment agent is adjusted to 0.5% by mass, 1.0% by mass, and 5% by mass, and the measurement is performed in the temperature range of 0 to 100°C. At this time, the part representing the inflection point (the change in viscosity, or the point at which the aqueous solution atomizes) at each concentration is called the cloud point.

[0176] From a processability perspective, the lower limit of the cloud point of the surface treatment agent (C) is preferably 10°C, more preferably 20°C, and most preferably 30°C. Furthermore, the upper limit of the cloud point is not particularly limited, but is preferably 120°C, more preferably 110°C, further preferably 100°C, and most preferably 60°C. To ensure good affinity with the cellulose nanofibers (A), the cloud point of the surface treatment agent (C) is preferably within the above-mentioned range.

[0177] From the perspective of not plasticizing the resin composition, the lower limit of the melting point of the surface treatment agent (C) is preferably -35°C, more preferably -10°C, and most preferably 0°C, and from the perspective of operability, the upper limit is preferably 70°C, more preferably 30°C, and most preferably 10°C.

[0178] (C) The lower limit of the mass ratio (molecular weight of hydrophobic segment / molecular weight of hydrophilic segment) of the surface treatment agent is not particularly limited, but is preferably 0, more preferably 0.1, further preferably 0.5, and most preferably 1. Furthermore, from the perspective of solubility in water, the upper limit of this mass ratio (molecular weight of hydrophobic segment / molecular weight of hydrophilic segment) is preferably 199, more preferably 100, further preferably 50, and most preferably 20. To ensure good affinity with (A) cellulose nanofibers, it is preferable that the above-mentioned ratio of the (C) surface treatment agent is within the above-mentioned range.

[0179] From the perspective of improving the odor during resin composition preparation and enhancing moldability during molding, the lower limit of the number average molecular weight of the surface treatment agent (C) is preferably 100, more preferably 200, more preferably 250, further preferably 300, and most preferably 500. Furthermore, from the perspective of processability, the upper limit of this number average molecular weight is preferably 50,000, more preferably 30,000, more preferably 25,000, further preferably 23,000, further preferably 20,000, further preferably 10,000, and most preferably 5,000. To ensure good affinity with (B) cellulose nanofibers, it is preferable that the number average molecular weight of the surface treatment agent (C) is within the above-mentioned range.

[0180] From the perspective of affinity with cellulose nanofibers, the lower limit of the molecular weight of the hydrophilic segment of the surface treatment agent (C) is preferably 100, more preferably 150, and most preferably 200, and the upper limit of its solubility in water is preferably 20,000, more preferably 15,000, and most preferably 10,000.

[0181] From the perspective of the dispersibility of cellulose nanofibers in resin, the lower limit of the molecular weight of the hydrophobic segment of the surface treatment agent (C) is preferably 100, more preferably 150, and most preferably 200, and the upper limit of the molecular weight is preferably 10000, more preferably 5000, and most preferably 4000, from the perspective of solubility in water.

[0182] In the resin composition, the preferred amount of the surface treatment agent (C) is in the range of 0.1 to 10% by mass relative to the total resin composition. The upper limit is more preferably 8% by mass, further preferably 5% by mass, even more preferably 4% by mass, and particularly preferably 3% by mass. The lower limit is not particularly limited, but is preferably 0.1% by mass, more preferably 0.2% by mass, and most preferably 0.5% by mass. By setting the upper limit of the surface treatment agent (C) to the above amount, plasticization of the resin composition can be suppressed, and strength can be well maintained. Furthermore, by setting the lower limit of the surface treatment agent (C) to the above amount, the dispersibility of cellulose nanofibers (B) in the thermoplastic resin (A) can be improved.

[0183] In the resin composition, the preferred amount of the surface treatment agent (C) is 0.1 to 50 parts by weight relative to 100 parts by weight of cellulose nanofibers (B). The upper limit is more preferably 30 parts by weight, more preferably 20 parts by weight, more preferably 10 parts by weight, even more preferably 5 parts by weight, and particularly preferably 3 parts by weight. The lower limit is not particularly limited, but is preferably 0.1 parts by weight, more preferably 0.5 parts by weight, and most preferably 1 part by weight. By setting the upper limit of the surface treatment agent (C) to the above amounts, plasticization in the resin composition and the molded resin article can be suppressed, and strength can be well maintained. Furthermore, by setting the lower limit of the surface treatment agent (C) to the above amounts, the dispersibility of the cellulose nanofibers (B) can be improved.

[0184] The amount of surface treatment agent (C) in the resin composition can be easily determined using methods commonly known to those skilled in the art. The determination method is not limited, but the following method is an example. Using fragments of a resin molded body formed from the resin composition, the resin composition is dissolved in a solvent that dissolves the thermoplastic resin (A), and then soluble component 1 (resin, surface treatment agent, and antioxidant) and insoluble component 1 (cellulose and surface treatment agent) are separated. Soluble component 1 is then reprecipitated in a solvent that does not dissolve the resin but dissolves the surface treatment agent, separating it into insoluble component 2 (resin) and soluble component 2 (surface treatment agent and antioxidant). Alternatively, insoluble component 1 is dissolved in a solvent that dissolves the surface treatment agent, separating it into soluble component 3 (surface treatment agent and antioxidant) and insoluble component 3 (cellulose). By concentrating soluble component 2 and soluble component 3 (drying, air drying, vacuum drying, etc.), the amount of surface treatment agent (C) can be quantified. The concentrated surface treatment agent (C) can be identified and its molecular weight determined using the above method.

[0185] The surface treatment agent of (C) in this disclosure preferably has an HLB value of 0.1 or higher and less than 12. In this disclosure, the HLB value can be calculated using the following formula based on the Griffin method. In Formula 1 below, "total formula weight of hydrophilic groups / molecular weight" represents the mass percentage of the hydrophilic groups.

[0186] Formula 1) Griffin method: HLB value = 20 × (total formula weight of hydrophilic groups / molecular weight)

[0187] From the perspective of solubility in water, the lower limit of the HLB value of the surface treatment agent (C) of this disclosure is not particularly limited, but is preferably 0.1, more preferably 0.2, and most preferably 1. Furthermore, from the perspective of the dispersibility of the cellulose nanofibers (B) in the resin composition, the upper limit of this HLB value is preferably less than 12, more preferably 10, further preferably 8, even more preferably 7.5, and most preferably 7. To ensure excellent dispersibility in water and organic solvents (for example, in the manufacture of the resin composition, when a mixture containing (B) cellulose nanofibers and (C) surface treatment agent is prepared in advance and then redispersed in water or an organic solvent), the HLB value of the surface treatment agent (C) is preferably within the above-mentioned range. Furthermore, excellent dispersibility in organic solvents implies excellent dispersibility in the resin. It should be noted that the HLB value is a value representing the balance between the hydrophobicity and hydrophilicity of the surfactant, ranging from 1 to 20; a smaller value indicates stronger hydrophobicity, and a larger value indicates stronger hydrophilicity.

[0188] As the (C) surface treatment agent (especially an amphiphilic molecule), a substance with a solubility parameter (SP value) of 7.25 or higher is more preferred. By giving the (C) surface treatment agent an SP value within this range, the dispersibility of (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less in the resin is improved.

[0189] According to Foders' literature (RF Foders: Polymer Engineering & Science, vol. 12(10), pp. 2359-2370(1974)), the SP value can be considered to depend on both the cohesive energy density and the molar molecular weight of the substance, and these depend on the type and number of substituents in the substance. According to Ueda et al.'s literature (Coating Research), No. 152, Oct. 2010, the SP values ​​(cal / cm) of the existing main solvents shown in the examples described below are disclosed. 3 ) 1 / 2 .

[0190] The SP value of surface treatment agent (C) can be determined experimentally by the boundary between soluble and insoluble when (C) surface treatment agent is dissolved in various solvents with known SP values. For example, 1 mL of surface treatment agent (C) is dissolved at room temperature in 10 mL of various solvents with different SP values ​​shown in the table of examples for 1 hour with stirring. The total amount of dissolution can be determined by whether any amount of dissolution occurs during this time. For example, if surface treatment agent (C) is soluble in diethyl ether, then the SP value of surface treatment agent (C) is 7.25 or higher.

[0191] The static surface tension of the (C) surface treatment agent (especially an amphiphilic molecule) is preferably 20 mN / m or higher. This static surface tension refers to the surface tension measured using the Wilhelmy method. When using a (C) surface treatment agent that is liquid at room temperature, the value measured at 25°C is used. When using a (C) surface treatment agent that is solid or semi-solid at room temperature, the (C) surface treatment agent is heated above its melting point, and the measurement is performed in a molten state; the value is then used after temperature correction at 25°C. Furthermore, room temperature in this disclosure refers to 25°C. Additionally, for ease of addition, the (C) surface treatment agent may be dissolved or diluted in an organic solvent or water. In this case, the aforementioned static surface tension refers to the static surface tension of the (C) surface treatment agent itself.

[0192] When the static surface tension of the surface treatment agent (C) is within the specific range disclosed herein, it can surprisingly improve the dispersibility of cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less in the resin. The reason for this is uncertain, but it is thought to be due to the hydrophilic functional groups located within the surface treatment agent (C), particularly the amphiphilic molecule, coating the surface of the cellulose nanofibers (B) with hydroxyl groups or reactive groups on the surface of the cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less via hydrogen bonds, thus inhibiting the formation of the interface with the resin. It is also thought that by configuring this hydrophilic group on the side of the cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less, a hydrophobic atmosphere is formed on the resin side, thus increasing the affinity with the resin side.

[0193] (C) The preferred lower limit of the static surface tension of the surface treatment agent is 23 mN / m, more preferably 25 mN / m, further preferably 30 mN / m, even more preferably 35 mN / m, and most preferably 39 mN / m. (C) The preferred upper limit of the static surface tension of the surface treatment agent is 72.8 mN / m, more preferably 60 mN / m, further preferably 50 mN / m, and most preferably 45 mN / m.

[0194] From the perspective of balancing the affinity of the (C) surface treatment agent to the thermoplastic resin and the affinity to the (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less, and exhibiting properties that improve the microdispersion of the (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less in the resin, the flowability of the resin composition, the strength and elongation of the resin molded body, it is preferable that the static surface tension of the (C) surface treatment agent is within a specific range.

[0195] The static surface tension of the surface treatment agent (C) mentioned in this disclosure can be measured using a commercially available surface tension measuring device. Specifically, it can be measured using an automated surface tension measuring device (e.g., Kyowa Interface Science Co., Ltd., trade name "CBVP-Z type," using the included glass tank) via the Wilhelmy method. In this case, the surface treatment agent (C), being liquid at room temperature, is immersed in the included stainless steel tank at a height of 7 mm to 9 mm from the bottom to the liquid surface. The temperature is adjusted to 25°C ± 1°C before measurement, and the static surface tension is calculated using the following formula.

[0196] γ=(P-mg+shρg) / Lcosθ

[0197] Here, γ: static surface tension, P: balancing force, m: mass of the plate, g: gravitational constant, L: perimeter of the plate, θ: contact angle between the plate and the liquid, s: cross-sectional area of ​​the plate, h: depth of sinking from the liquid surface (until the force reaches equilibrium), ρ: density of the liquid.

[0198] It should be noted that surface tension cannot be measured using the above method for surfactants that are solid at room temperature. Therefore, for convenience, surface tension is measured at a temperature of melting point + 5°C. In the case of a substance with an unknown melting point, the melting point is first determined by visual melting point determination (JIS K6220). After heating it above the melting point to melt it, the temperature is adjusted to melting point + 5°C, and the surface tension is measured by the Wilhelmy method described above. This allows for the determination of its surface tension.

[0199] (C) The dynamic surface tension of the surface treatment agent (especially an amphiphilic molecule) is preferably 60 mN / m or less. More preferably, the upper limit of the dynamic surface tension is 55 mN / m, even more preferably 50 mN / m, further preferably 45 mN / m, and particularly preferably 40 mN / m. If we consider a preferred lower limit of the dynamic surface tension of (C) the surface treatment agent, it is 10 mN / m. More preferably, the lower limit is 15 mN / m, and most preferably 20 mN / m.

[0200] The dynamic surface tension referred to here is the surface tension measured using the maximum bubble pressure method (a method that involves passing air through a thin tube (hereinafter referred to as a probe) inserted into a liquid, measuring the maximum pressure (maximum bubble pressure) at which bubbles are generated, and calculating the surface tension). Specifically, it refers to the surface tension value measured as follows: A test solution is prepared by dissolving or dispersing the surface treatment agent (C) at 5% by mass in ion-exchanged water. After adjusting the temperature to 25°C, a dynamic surface tension meter (e.g., SITA Science t-60 model manufactured by Eihiro Seiki Co., Ltd., with a probe (capillary TYPE I (PEEK resin), single-mode) is used to measure the surface tension at a bubble generation cycle of 10 Hz. The dynamic surface tension at each cycle is calculated using the following formula.

[0201] σ=ΔP·r / 2

[0202] Here, σ: dynamic surface tension, ΔP: pressure difference (maximum pressure - minimum pressure), and r: capillary radius.

[0203] Dynamic surface tension, measured using the maximum bubble pressure method, refers to the dynamic surface tension of a surfactant under conditions of rapid movement. (C) Surface treatment agents typically form micelles in water. Low dynamic surface tension indicates a fast diffusion rate of surfactant molecules from the micelle state, while high dynamic surface tension indicates a slow diffusion rate.

[0204] When the dynamic surface tension of the surface treatment agent (C) is below a specific value, it can significantly improve the dispersion of cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less in the resin composition, which is advantageous. The detailed reason for this improved dispersibility is unclear, but it can be assumed that the surface treatment agent (C) with low dynamic surface tension has excellent diffusion properties in the extruder, thereby enabling it to locally exist at the interface between the cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less and the resin, and thus effectively coat the surface of the cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less, which contributes to the improved dispersibility. The improved dispersibility of cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less, obtained by setting the dynamic surface tension of the surfactant below a specific value, shows a significant effect in eliminating strength defects in the molded article.

[0205] As a surface treatment agent (C) (especially an amphiphilic molecule), it is preferable to have a boiling point higher than that of water. It should be noted that "higher than that of water" means a boiling point higher than the boiling point at each pressure in the vapor pressure curve of water (e.g., 100°C at 1 atmosphere).

[0206] By selecting a surfactant with a boiling point higher than that of water as the (C) surface treatment agent, for example, in the process of drying cellulose nanofibers with an average fiber diameter of less than 1000 nm (B) dispersed in water in the presence of the (C) surface treatment agent to obtain a cellulose nanofiber preparation with an average fiber diameter of less than 1000 nm (B), water and the (C) surface treatment agent are replaced during the water evaporation process. The (C) surface treatment agent is present on the surface of the cellulose nanofibers with an average fiber diameter of less than 1000 nm (B), thus achieving a significant effect in inhibiting the aggregation of cellulose nanofibers with an average fiber diameter of less than 1000 nm (B).

[0207] (C) Among the surface treatment agents, from the perspective of their treatability, surface treatment agents that are liquid at room temperature (i.e., 25°C) are preferred. Surface treatment agents (C) that are liquid at room temperature have the advantages of being easily compatible with cellulose nanofibers (B) with an average fiber diameter of less than 1000 nm and being easy to penetrate into the resin.

[0208] (C) When the surface treatment agent is a surfactant, any one of anionic, nonionic, amphoteric, or cationic surfactants can be used. From the perspective of affinity with (B) cellulose nanofibers, anionic and nonionic surfactants are preferred, with nonionic surfactants being more preferred. Surfactants used in various applications such as food and industrial applications can be used. In a particularly preferred embodiment, the surfactant is one that possesses the aforementioned specific dynamic surface tension.

[0209] Examples of anionic surfactants include sodium fatty acid, potassium fatty acid, and sodium α-sulfonyl fatty acid ester as fatty acid-based (anionic); sodium linear alkylbenzene sulfonate as linear alkylbenzene-based; sodium alkyl sulfate and sodium alkyl ether sulfate as higher alcohol-based (anionic); sodium α-olefin sulfonate as α-olefin-based; and sodium alkyl sulfonate as n-alkane-based. One of these surfactants or a mixture of two or more of them can be used.

[0210] As nonionic surfactants, examples of fatty acid-based (nonionic) surfactants include sucrose fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and other glycolipids, fatty acid alkanolamides, etc.; examples of higher alcohol-based (nonionic) surfactants include polyoxyethylene alkyl ethers, etc.; examples of alkylphenol-based surfactants include polyoxyethylene alkylphenyl ethers, etc.; one of them or a mixture of two or more can be used.

[0211] As a zwitterionic surfactant, examples of amino acid-based surfactants include sodium alkylamino fatty acids, examples of betaine-based surfactants include alkyl betaine, and examples of amine oxide-based surfactants include alkylamine oxides. One of these surfactants or a mixture of two or more of them can be used.

[0212] Examples of cationic surfactants and quaternary ammonium salts include alkyltrimethylammonium salts and dialkyldimethylammonium salts. One or more of these can be used.

[0213] Surfactants can also be derivatives of oils and fats. Examples of oils and fats include esters of fatty acids and glycerol, typically referring to substances in the form of triglycerides (tri-O-acylglycerols). Fatty oils are classified into drying oils, semi-drying oils, and non-drying oils according to their susceptibility to oxidation and solidification. These substances can be used in various applications, including food and industrial use. For example, one or more of the following substances can be used.

[0214] Examples of oils and fats, including both animal and vegetable oils, include terpene oils, tall oils, rosin, white oil, corn oil, soybean oil, sesame oil, rapeseed oil, rice oil, rice bran oil, camellia oil, safflower oil, coconut oil (palm kernel oil), cottonseed oil, sunflower seed oil, perilla oil, flaxseed oil, olive oil, peanut oil, almond oil, avocado oil, hazelnut oil, walnut oil, grapeseed oil, mustard oil, lettuce oil, fish oil, whale oil, shark oil, liver oil, cocoa butter, peanut butter, palm oil, lard, tallow, chicken fat, rabbit fat, mutton fat, horse fat, duck fat, dairy fat (butter, ghee, etc.), hydrogenated oils (margarine, shortening, etc.), and castor oil (vegetable oil).

[0215] Among the aforementioned animal and vegetable oils, terpene oils, tall oils, and rosin are particularly preferred in terms of their affinity for the surface of (B) cellulose nanofibers and their uniform coating properties.

[0216] Terpenoid oils are essential oils obtained by steam distillation of the bark of pine trees or resin obtained from these trees; they are also called pine oil or turpentine. Examples of terpenoid oils include resin turpentine (a substance obtained by steam distillation of pine resin), wood turpentine (a substance obtained by steam distillation or dry distillation of the bark of pine trees), sulfate turpentine (a substance obtained by distillation during the heat treatment of bark in the manufacture of sulfate pulp), and sulfite turpentine (a substance obtained by distillation during the heat treatment of bark in the manufacture of sulfite pulp). These are generally colorless to pale yellow liquids, and except for sulfite turpentine, they are mainly composed of α-pinene and β-pinene. Sulfite turpentine differs from other turpentine oils in that it is mainly composed of p-methylisopropylbenzene. If the above-mentioned components are present, they are included in the aforementioned terpenoid oils. Any derivatives, either alone or in mixtures of two or more, can be used as surfactants in this invention.

[0217] Tall oil is an oil mainly composed of resin and fatty acids, which is a byproduct of the production of kraft paper pulp from pine wood. Tall oil can be made from tall fats, which are mainly composed of oleic acid and linoleic acid, or from tall rosin, which is mainly composed of diterpenoids with 20 carbon atoms, such as abietic acid.

[0218] Rosin is the residue remaining after collecting the sap (pine resin) of pine trees and distilling out turpentine oil. It is a natural resin with abietic acids (abscisic acid, longleaf abietic acid, isopyric acid, etc.) as its main components. It is also known as colophony or colophonium. Suitable types include tall rosin, wood rosin, and resin rosin. Rosin derivatives that have undergone various stabilization, esterification, and refining treatments can also be used as surfactants. Stabilization treatment refers to hydrogenation, disproportionation, dehydrogenation, and polymerization of the aforementioned rosins. Esterification treatment refers to the reaction of the aforementioned rosins, or stabilized rosins, with various alcohols to produce rosin esters. Various known alcohols or epoxides can be used in the manufacture of these rosin esters. Examples of alcohols include: monohydric alcohols such as n-octanol, 2-ethylhexanol, decanol, and lauryl alcohol; dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and neopentyl glycol; trihydric alcohols such as glycerol, trimethylolethane, trimethylolpropane, and cyclohexanediol; and tetrahydric alcohols such as pentaerythritol and diglycerol. In addition, polyols such as isopentyl glycol, ethylhexanediol, erythritol, ozonoglycerol, octyl ethylene glycol, ethylene glycol, (C15-18) glycol, (C20-30) glycol, glycerol, diethylene glycol, diglycerol, dithiooctyl glycol, DPG, thioglycerol, 1,10-decanediol, decanediol, triethylene glycol, trimethylhydroxymethylcyclohexanol, phytanetriol, phenoxypropanediol, 1,2-butanediol, 2,3-butanediol, butyl ethylpropanediol, BG, PG, 1,2-hexanediol, hexanediol, pentanediol, methylpropanediol, menthanediol, and lauryl glycol can also be used. Furthermore, substances classified as sugar alcohols, such as inositol, erythritol, xylitol, sorbitol, maltitol, mannitol, and lactitol, are also included in the polyol category.

[0219] Furthermore, water-soluble polymers with alcohol properties can also be used as the aforementioned alcohols. Examples of water-soluble polymers with alcohol properties include: polysaccharides (mucopolysaccharides), substances classified as starch, substances classified as polysaccharide derivatives, substances classified as natural resins, substances classified as cellulose and its derivatives, substances classified as proteins (peptides), substances classified as peptide derivatives, substances classified as synthetic homopolymers, substances classified as acrylic acid (methacrylic acid) copolymers, substances classified as urethane polymers, substances classified as minerals, substances classified as cationic polymers, and substances classified as other synthetic polymers. These substances are water-soluble at room temperature. More specifically, examples include sodium polyacrylate, cellulose ether, calcium alginate, carboxyvinyl polymers, ethylene / acrylic acid copolymers, vinylpyrrolidone polymers, vinyl alcohol / vinylpyrrolidone copolymers, nitrogen-substituted acrylamide polymers, polyacrylamide, cationic polymers such as cationic guar gum, ammonium dimethacrylate polymers, acrylic acid / methacrylic acid / acrylic acid copolymers, POE / POP copolymers, polyvinyl alcohol, pullulan, agar, gelatin, tamarind seed polysaccharides, xanthan gum, carrageenan, high-methoxyl pectin, low-methoxyl pectin, guar gum, gum arabic, cellulose whiskers, arabinogalactan, ebony gum, tragacanth gum, alginic acid, albumin, casein, gluconolan gum, gellan gum, dextran, cellulose (not cellulose fibers and cellulose whiskers as disclosed herein), polyethyleneimine, polyethylene glycol, cationic silicone polymers, etc.

[0220] Among the various rosin esters mentioned above, substances formed by esterification of rosin and water-soluble polymers are preferred because they tend to further promote the coating properties of (B) cellulose nanofibers and the dispersibility of cellulose preparations in resins. In particular, esterifications of rosin and polyethylene glycol (also known as rosin ethylene oxide adducts, polyoxyethylene glycol resin esters, and polyoxyethylene rosin esters) are preferred.

[0221] Examples of hydrogenated castor oil-type surfactants include compounds derived from castor oil (castor seed oil), a plant oil collected from the seeds of castor beans (Euphorbia pekinensis). The hydrogenated product is used as a hydrophobic group, and its structure contains covalently bonded hydroxyl groups and hydrophilic groups such as the PEO chain. Castor oil is composed of glycerides of unsaturated fatty acids (87% ricinoleic acid, 7% oleic acid, and 3% linoleic acid) and small amounts of saturated fatty acids (3% palmitic acid, stearic acid, etc.). Representative POE group structures include those with 4 to 40 ethylene oxide (EO) residues, and representative structures include those with 15 to 30 residues. The EO residues in the nonylphenol ethoxylate are preferably 15 to 30, more preferably 15 to 25, and particularly preferably 15 to 20.

[0222] As derivatives of mineral oil, examples include calcium soap-based greases, calcium complex soap-based greases, sodium soap-based greases, aluminum soap-based greases, lithium soap-based greases, and other types of greases.

[0223] Surfactants can also be alkylphenyl compounds, such as alkylphenol ethoxylates, which are compounds obtained by ethoxylating alkylphenol with ethylene oxide. Alkylphenol ethoxylates are nonionic surfactants. Because the hydrophilic polyoxyethylene (POE) chain and the hydrophobic alkylphenol group are linked by an ether bond, they are also called poly(oxyethylene)alkylphenyl ethers. Typically, a series of products with different average chain lengths are commercially available as mixtures of various compounds with different alkyl chain lengths and POE chain lengths. Commercially available substances have alkyl chains with 6 to 12 carbon atoms (excluding phenyl). Representative alkyl structures include nonylphenol ethoxylate and octylphenol ethoxylate. Furthermore, representative POE group structures include those with 5 to 40 ethylene oxide (EO) residues, and representative structures include those with 15 to 30 residues. The EO residues in nonylphenol ethoxylates are preferably 15 to 30, more preferably 15 to 25, and particularly preferably 15 to 20.

[0224] Surfactants can also be β-naphthyl compounds. Examples include compounds whose chemical structure includes a β-monosubstituted form of naphthalene, an aromatic ring with a carbon atom at position 2, 3, 6, or 7 bonded to a hydroxyl group, and a hydrophilic group such as a PEO chain, which are covalently bonded together. Furthermore, representative POE group structures include those with 4 to 40 ethylene oxide (EO) residues, and representative structures include those with 15 to 30 residues. Preferably, the EO residues are 15 to 30, more preferably 15 to 25, and particularly preferably 15 to 20.

[0225] Surfactants can also be bisphenol A type compounds. Examples include compounds whose chemical structure contains bisphenol A (chemical formula: (CH3)2C(C6H4OH)2) as a part of their structure, and compounds formed by covalently bonding two phenolic groups with hydrophilic groups such as a PEO chain. Additionally, representative POE group structures include those with 4 to 40 ethylene oxide (EO) residues, and representative structures include those with 15 to 30 residues. The EO residues in nonylphenol ethoxylates are preferably 15 to 30, more preferably 15 to 25, and particularly preferably 15 to 20. When the EO residue has two ether bonds in a molecule, this refers to the average value of the two ether bonds added together.

[0226] Surfactants can also be styrene-phenyl compounds, such as compounds whose chemical structure includes a styrene-phenyl group, a phenolic group, and a PEO chain, which are hydrophilic groups covalently bonded together. The styrene-phenyl group has a structure in which 1 to 3 molecules of styrene are added to the benzene ring of a phenolic residue. Additionally, representative POE group structures include those with 4 to 40 ethylene oxide (EO) residues, and representative structures include those with 15 to 30 residues. The EO residues in the nonylphenol ethoxylate are preferably 15 to 30, more preferably 15 to 25, and particularly preferably 15 to 20. When the EO residue has two ether bonds in one molecule, this refers to the average value of the two bonds added together.

[0227] Preferred examples of surfactants include, for instance, acyl amino acid salts such as acylglutamate, higher alkyl sulfates such as sodium lauryl sulfate, sodium palmitate, sodium lauryl sulfate, and potassium lauryl sulfate, alkyl ether sulfates such as polyoxyethylene lauryl sulfate triethanolamine and polyoxyethylene lauryl sulfate sodium, and N-acyl sarcosine salts such as sodium lauroyl sarcosinate; anionic surfactants such as stearyltrimethylammonium chloride and lauryltrimethylammonium chloride, dialkyldimethylammonium chloride distearate, alkylpyridinium salts such as (N,N'-dimethyl-3,5-methylenepiperidinium chloride) and hexadecylpyridinium chloride, alkyl quaternary ammonium salts, and alkyl groups such as polyoxyethylene alkylamines. Cationic surfactants such as amine salts, polyamine fatty acid derivatives, and pentanol fatty acid derivatives; imidazoline-based di-type surfactants such as sodium 2-undecyl-N,N,N-(hydroxyethylcarboxymethyl)2-imidazoline and sodium 2-cocoyl-2-imidazoline hydroxide-1-carboxyethoxy disodium salt; di-type surfactants such as 2-heptadecyl-N-carboxymethyl-N-hydroxyethylimidazoline betaine, lauryl dimethylaminoacetic acid betaine, alkyl betaine, amide betaine, and sulfobetaine; and di-type surfactants such as sorbitan monooleate, sorbitan monoisostearate, sorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate. Sorbitan fatty acid esters, including sorbitan sesquioleate, sorbitan trioleate, pent-2-ethylhexyl diglyceride, tetra-2-ethylhexyl diglyceride, glyceryl monostearate, α,α'-oleic pyroglutamic acid glyceryl, glyceryl monostearate malic acid, propylene glycol fatty acid esters, hydrogenated castor oil derivatives, glyceryl alkyl ethers, polyoxyethylene-sorbitan monostearate, polyoxyethylene-sorbitan monooleate, polyoxyethylene-sorbitan tetraoleate, polyoxyethylene-sorbitan monolaurate, and polyoxyethylene-sorbitan monooleate. Nonionic surfactants, including polyoxyethylene-sorbitan pentaoleate, polyoxyethylene-sorbitan monostearate, polyoxyethylene-glycerol monoisostearate, polyoxyethylene-glycerol triisostearate, etc.; polyoxyethylene monooleate, polyoxyethylene distearate, polyoxyethylene monodioleate, ethylene glycol distearate, etc.; polyoxyethylene hydrogenated castor oil, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil monoisostearate, polyoxyethylene hydrogenated castor oil triisostearate, polyoxyethylene hydrogenated castor oil monopyroglutamic acid monoisostearate diester, polyoxyethylene hydrogenated castor oil maleate, etc.

[0228] Among the aforementioned surfactants, those with high affinity for resins, particularly alkyl ether type, alkylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, styrene-modified phenyl type, and hydrogenated castor oil type, are suitable for use as hydrophobic groups. As a preferred alkyl chain length (the number of carbon atoms excluding phenyl in the case of alkylphenyl), the carbon chain is preferably 5 or more, more preferably 10 or more, further preferably 12 or more, and particularly preferably 16 or more. When the resin is a polyolefin, the higher the number of carbon atoms, the higher the affinity for the resin; therefore, no upper limit is set, but 30 is preferred, more preferably 25.

[0229] Among these hydrophobic groups, substances with cyclic structures are preferred; or substances with large volume and multifunctional structures. Among substances with cyclic structures, alkylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, and styrenated phenyl type are preferred. Among substances with multifunctional structures, hydrogenated castor oil type is particularly preferred. Of these, rosin ester type and hydrogenated castor oil type are especially preferred.

[0230] Therefore, in a particularly preferred embodiment, the surfactant is one or more selected from the group consisting of rosin derivatives, alkylphenyl derivatives, bisphenol A derivatives, β-naphthyl derivatives, styrenated phenyl derivatives, and hydrogenated castor oil derivatives.

[0231] In one embodiment, (C) the surface treatment agent is a low-molecular-weight thermoplastic resin. Specific examples of low-molecular-weight thermoplastic resins include polyamide resins, polyester resins, polyacetal resins, polycarbonate resins, polyacrylic resins, polyphenylene ether resins (including modified polyphenylene ethers that have been blended with other resins or modified by graft polymerization), polyarylate resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polyketide resins, polyphenylene ether ketone resins, polyimide resins, polyamide-imide resins, polyether-imide resins, polyurethane resins (e.g., thermoplastic polyurethane), polyolefin resins (e.g., α-olefin copolymers), and various ionomers.

[0232] Preferred specific examples of low-molecular-weight thermoplastic resins include high-density polyethylene, low-density polyethylene (e.g., linear low-density polyethylene), polypropylene, polymethylpentene, cyclic olefins, poly-1-butene, poly-1-pentene, polymethylpentene, ethylene / α-olefin copolymers, ethylene-butene copolymers, EPR (ethylene-propylene copolymer), modified ethylene-butene copolymers, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymer), and modified IR (isoprene). Rubber), modified SEBS (styrene-ethylene-butene-styrene copolymer), haloisobutylene-p-methylstyrene copolymer, ethylene-acrylic acid modified product, ethylene-vinyl acetate copolymer and its acid modified product, copolymer of (ethylene and / or propylene) with (unsaturated carboxylic acid and / or unsaturated carboxylic acid ester), polyolefin obtained by metal salting at least a portion of the carboxyl group of the copolymer of (ethylene and / or propylene) with (unsaturated carboxylic acid and / or unsaturated carboxylic acid ester), block copolymer of conjugated diene and vinyl aromatic hydrocarbon, conjugated diene and vinyl aromatic hydrocarbon Hydrogenates of block copolymers of aromatic hydrocarbons, copolymers of conjugated dienes and non-conjugated olefins, natural rubber, various butadiene rubbers, various styrene-butadiene copolymer rubbers, isoprene rubber, butyl rubber, bromides of isobutylene and p-methylstyrene copolymers, halogenated butyl rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, chlorinated... This includes sulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, polyvinyl chloride, polystyrene, polyacrylate, polymethacrylate, and other acrylonitrile copolymers with acrylic acid and acrylonitrile as the main components; acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, cellulose acetate and other cellulose-based resins; vinyl chloride / ethylene copolymers, vinyl chloride / vinyl acetate copolymers, ethylene / vinyl acetate copolymers, and saponifications of ethylene / vinyl acetate copolymers. In one embodiment, the low-molecular-weight thermoplastic resin can be a compound having the aforementioned hydrophilic and hydrophobic segments.

[0233] Among these, polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polyethylene glycol resins, polypropylene glycol resins, and mixtures of two or more thereof are preferred in terms of heat resistance, moldability, aesthetics, and mechanical properties. In terms of processability and cost, polyolefin resins, polyamide resins, polyester resins, polyethylene glycol resins, and polypropylene glycol resins are particularly preferred.

[0234] Preferred polyolefin resins as low-molecular-weight thermoplastic resins are polymers obtained by polymerizing monomer units containing olefins (e.g., α-olefins). Specific examples of polyolefin resins are not particularly limited, but can include ethylene-based (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high-molecular-weight polyethylene; polypropylene-based (co)polymers such as polypropylene, ethylene-propylene copolymers, and ethylene-propylene-diene copolymers; and copolymers of α-olefins with other monomer units, represented by ethylene-acrylic acid copolymers, ethylene-methyl methacrylate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0235] Polypropylene is an example of the preferred polyolefin resin here.

[0236] Furthermore, to improve the affinity with cellulose nanofibers (B) with an average fiber diameter of 1000 nm or less, acid-modified polyolefin resins can be suitably used. As the acid, maleic acid, fumaric acid, succinic acid, phthalic acid and their anhydrides, as well as polycarboxylic acids such as citric acid, can be suitably selected. From the perspective of easily increasing the modification rate, maleic acid or its anhydride is preferred. There are no particular limitations on the modification method; generally, a melt-blending method is used, heating the resin above its melting point in the presence or absence of a peroxide. As the acid-modified polyolefin resin, all of the above-mentioned polyolefin resins can be used, among which polypropylene can be suitably used.

[0237] Acid-modified polypropylene can be used alone, but to adjust the modification rate, it is more preferable to use it in combination with unmodified polypropylene. In this case, the proportion of acid-modified polypropylene relative to all polypropylene is preferably 0.5% to 50% by mass. More preferably, the lower limit is 1% by mass, further preferably 2% by mass, even more preferably 3% by mass, particularly preferably 4% by mass, and most preferably 5% by mass. In addition, more preferably, the upper limit is 45% by mass, further preferably 40% by mass, even more preferably 35% by mass, particularly preferably 30% by mass, and most preferably 20% by mass. In order to maintain good interfacial strength with (B) cellulose nanofibers, it is preferably above the lower limit, and in order to maintain good ductility as a gear, it is preferably below the upper limit.

[0238] There are no particular limitations on polyamide resins preferred as low-molecular-weight thermoplastic resins. Examples include polyamide 6, polyamide 11, and polyamide 12 obtained through the condensation reaction of lactams; and diamines such as 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1,7-heptanediamine, 2-methyl-1,6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, and m-phenylenediamine, along with succinic acid, glutaric acid, adipic acid, pimelic acid, and octanoic acid. Polyamides such as polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,T, polyamide 6,I, polyamide 9,T, polyamide 10,T, polyamide 2M5,T, polyamide MXD,6, polyamide 6,C, and polyamide 2M5,C are obtained in the form of copolymers of dicarboxylic acids such as azelaic acid, sebacic acid, phenyl-1,2-dicarboxylic acid, phenyl-1,3-dicarboxylic acid, phenyl-1,4-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, and cyclohexane-1,4-dicarboxylic acid; and copolymers formed by copolymerizing them separately (for example, polyamide 6,T / 6,I).

[0239] Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, and polyamide 6,12, and alicyclic polyamides such as polyamide 6,C and polyamide 2M5,C are more preferred.

[0240] There is no particular limitation on the concentration of terminal carboxyl groups in polyamide resins that can be used as low-molecular-weight thermoplastic resins, but the lower limit is preferably 20 μmol / g, more preferably 30 μmol / g. Furthermore, the upper limit of the terminal carboxyl group concentration is preferably 150 μmol / g, more preferably 100 μmol / g, and even more preferably 80 μmol / g.

[0241] In polyamides, which are low-molecular-weight thermoplastic resins, the ratio of carboxyl-terminal groups to all terminal groups ([COOH] / [all terminal groups]) is preferably 0.30 to 0.95. The lower limit of the ratio of carboxyl-terminal groups is more preferably 0.35, further more preferably 0.40, and most preferably 0.45. Furthermore, the upper limit of the ratio of carboxyl-terminal groups is more preferably 0.90, further more preferably 0.85, and most preferably 0.80. From the perspective of the dispersibility of cellulose nanofibers in the composition (B), the above-mentioned ratio of carboxyl-terminal groups is preferably 0.30 or more; from the perspective of the color tone of the obtained composition, the above-mentioned ratio of carboxyl-terminal groups is preferably 0.95 or less.

[0242] As a method for adjusting the concentration of end groups in polyamide resins, known methods can be used. For example, methods can be described by adding end-group modifiers such as diamine compounds, monoamine compounds, dicarboxylic acid compounds, monocarboxylic acid compounds, acid anhydrides, monoisocyanates, monoacyl halides, monoesters, and monoalcohols to the polymerization solution to achieve a specified concentration of end groups during polyamide polymerization.

[0243] Examples of end-modifiers that react with the terminal amino group include: aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, tertvaleric acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, methylbenzoic acid, α-naphthoic acid, β-naphthoic acid, methylnaphthoic acid, and phenylacetic acid; and mixtures of two or more selected from these substances. Among these, considering reactivity, stability of the closed end, and price, one or more end-modifiers selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, palmitic acid, stearic acid, and benzoic acid are preferred, with acetic acid being the most preferred.

[0244] Examples of end-modifiers that react with the terminal carboxyl group include aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine; and any mixtures thereof. Among these, one or more end-modifiers selected from the group consisting of butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are preferred from considerations of reactivity, boiling point, stability of the closed end, and price.

[0245] From the perspectives of precision and simplicity, the concentrations of these amino-terminal and carboxyl-terminal groups are preferably determined by... 1 H-NMR is determined based on the integrated values ​​of the characteristic signals corresponding to each terminal group. Specifically, the method described in Japanese Patent Application Publication No. 7-228775 is recommended as a method for determining the concentration of these terminal groups. When using this method, deuterated trifluoroacetic acid is useful as the determination solvent. Furthermore, regarding... 1 When performing H-NMR measurements using equipment with sufficient resolution, at least 300 scans are required for integration. Furthermore, the concentration of terminal groups can also be determined using a titration-based method described in Japanese Patent Application Publication No. 2003-055549. However, to minimize the influence of mixed additives, lubricants, etc., it is more preferable to utilize... 1 Quantitative analysis was performed using H-NMR.

[0246] There are no particular limitations on the preferred polyester resin as the thermoplastic resin, and one or more of the following can be used: polyethylene terephthalate (PET), polybutylene succinate (PBS), polybutylene succinate / adipate-butylene glycol (PBSA), polybutylene adipate-terephthalate (PBAT), polyarylate (PAR), polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate (PC).

[0247] Among these, PET, PBS, PBSA, PBT and PEN are preferred polyester resins, with PBS, PBSA and PBT being even more preferred.

[0248] Furthermore, in polyester resins, the terminal groups can be freely varied depending on the monomer ratio during polymerization and the presence and amount of terminal stabilizers added. However, the ratio of carboxyl terminal groups to all terminal groups ([COOH] / [all terminal groups]) in the polyester resin is preferably 0.30 to 0.95. The lower limit of the ratio of carboxyl terminal groups is more preferably 0.35, further preferably 0.40, and most preferably 0.45. The upper limit of the ratio of carboxyl terminal groups is more preferably 0.90, further preferably 0.85, and most preferably 0.80. From the perspective of the dispersibility of cellulose nanofibers in the composition (B), the ratio of the above-mentioned carboxyl terminal groups is preferably 0.30 or more, and from the perspective of the color tone of the obtained composition, the ratio of the above-mentioned carboxyl terminal groups is preferably 0.95 or less.

[0249] Preferred thermoplastic resins are typically homopolymer acetals made from formaldehyde and copolymer acetals using trioxymethylene as the main monomer (e.g., containing 1,3-dioxolane as a comonomer). Both can be used, but copolymer acetals are preferred from the perspective of thermal stability during processing. Specifically, the amount of comonomer (e.g., 1,3-dioxolane) is preferably in the range of 0.01 to 4 mol%. A more preferred lower limit for the amount of comonomer is 0.05 mol%, further preferably 0.1 mol%, and particularly preferably 0.2 mol%. An even more preferred upper limit is 3.5 mol%, further preferably 3.0 mol%, particularly preferably 2.5 mol%, and most preferably 2.3 mol%. From the perspective of thermal stability during extrusion and molding, the lower limit is preferably within the above range, and from the perspective of mechanical strength, the upper limit is preferably within the above range.

[0250] There are no particular limitations on the method of adding the (C) surface treatment agent when preparing the resin composition. Examples include: a method of pre-mixing (A) thermoplastic resin, (B) cellulose nanofibers and (C) surface treatment agent for melt blending; a method of pre-adding (C) surface treatment agent to (A) thermoplastic resin, pre-blending as needed, and then adding (B) cellulose nanofibers for melt blending; a method of pre-mixing (B) cellulose nanofibers and (C) surface treatment agent, and then melt blending them with (A) thermoplastic resin; a method of dispersing (B) cellulose nanofibers in water, adding (C) surface treatment agent to the resulting dispersion, drying it to prepare a dried cellulose body, and then adding the dried body to (A) thermoplastic resin; and so on.

[0251] <<(D) Metal Ion Composition>>

[0252] The resin composition may contain a (D) metal ion component as an additional component. The (D) metal ion component may be a commercially available reagent or product. Examples of (D) metal ion components include copper compounds, metal (copper or other) halides, alkali metal salts, alkaline earth metal salts, etc.

[0253] The upper limit of the content of the (D) metal ion component in the resin composition of this embodiment is preferably 5 parts by mass, more preferably 2 parts by mass, and even more preferably 0.5 parts by mass relative to 100 parts by mass of the (A) thermoplastic resin. The lower limit of the content of the (D) metal ion component is preferably 0.005 parts by mass, more preferably 0.01 parts by mass, and even more preferably 0.015 parts by mass relative to 100 parts by mass of the (A) thermoplastic resin. By keeping the amount of the (D) metal ion component within the above range, the wear resistance of the gear in the sliding test of this embodiment is improved. The reason for exhibiting such excellent wear resistance is not yet clear, but it is speculated that the presence of the (D) metal ion component at the interface between the surface of the (B) cellulose nanofibers and the (C) surface treatment agent, or at the interface between the surface of the (B) cellulose nanofibers and the (A) thermoplastic resin, increases the adhesion.

[0254] Examples of copper compounds include, but are not limited to, copper halides such as copper chloride, copper bromide, and copper iodide; copper carboxylate salts such as copper acetate, copper propionate, copper benzoate, copper adipic acid, copper terephthalate, copper isophthalate, copper salicylate, copper nicotinate, and copper stearate; and copper complex salts with copper coordinated to chelating agents such as ethylenediamine and ethylenediaminetetraacetic acid; etc. One copper compound may be used, or two or more may be used in combination. From the perspective of improving heat aging resistance and suppressing metal corrosion (hereinafter referred to as "metal corrosion") of the screw or barrel during molding extrusion, copper iodide (CuI), cuprous bromide (CuBr), copper bromide (CuBr2), cuprous chloride (CuCl), and copper acetate are preferred copper compounds, with copper iodide and copper acetate being more preferred.

[0255] The upper limit of the copper compound content relative to 100 parts by weight of the thermoplastic resin (A) is preferably 0.6 parts by weight, more preferably 0.4 parts by weight, and even more preferably 0.3 parts by weight. The lower limit of the copper compound content relative to 100 parts by weight of the thermoplastic resin (A) is preferably 0.005 parts by weight, more preferably 0.01 parts by weight, and even more preferably 0.015 parts by weight. When the lower limit of the copper compound content is within the above range, the heat aging resistance is further improved. In addition, when the upper limit of the copper compound content is within the above range, copper precipitation and metal corrosion can be further suppressed.

[0256] The resin composition of this embodiment may also contain at least one metal halide selected from the group consisting of alkali metal halides and alkaline earth metal halides. One metal halide may be used alone, or two or more may be used in combination.

[0257] Examples of metal halides include, but are not limited to, potassium iodide, potassium bromide, potassium chloride, sodium iodide, and sodium chloride. Potassium iodide and potassium bromide are preferred as metal halides, with potassium iodide being more preferred, in order to further improve the heat aging resistance of the resin composition and further inhibit metal corrosion.

[0258] The upper limit of the metal halide content in the resin composition is preferably 0.6 parts by weight, more preferably 0.4 parts by weight, and even more preferably 0.3 parts by weight, relative to 100 parts by weight of the thermoplastic resin (A) described above. The lower limit of the metal halide content in the resin composition is preferably 0.005 parts by weight, more preferably 0.01 parts by weight, and even more preferably 0.015 parts by weight, relative to 100 parts by weight of the thermoplastic resin (A) described above. When the lower limit of the metal halide content is within the above range, the heat aging resistance is further improved. In addition, when the upper limit of the metal halide content is within the above range, copper precipitation and metal corrosion can be further suppressed.

[0259] The metal halide is preferably mixed in a molar ratio (D3 / D4) of 2 / 1 to 50 / 1, more preferably in a molar ratio of 2 / 1 to 40 / 1, and even more preferably in a molar ratio of 5 / 1 to 30 / 1. By making the molar ratio D3 / D4 2 / 1 or higher, copper precipitation and metal corrosion can be further suppressed; by making the molar ratio 50 / 1 or lower, metal corrosion can be further suppressed without compromising mechanical properties such as toughness and rigidity.

[0260] Examples of alkali metal and alkaline earth metal salts include, but are not limited to, hydroxides of sodium, potassium, magnesium, calcium, or barium, carbonates, phosphates, silicates, borates, and carboxylates of the aforementioned metals. Specifically, calcium salts are preferred from the perspective of improving the thermal stability of the resin composition.

[0261] Examples of such calcium salts include, but are not limited to, calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and calcium salts of fatty acids (calcium stearate, calcium myristate, etc.). The fatty acid components of these calcium salts may, for example, have hydroxyl substitutions. Among these, calcium salts of fatty acids (calcium stearate, calcium myristate, etc.) are more preferred from the perspective of improving the thermal stability of gears.

[0262] The upper limit of the content of alkali metal salts and alkaline earth metal salts in the resin composition is preferably 0.6 parts by weight, more preferably 0.4 parts by weight, and even more preferably 0.3 parts by weight, relative to 100 parts by weight of the thermoplastic resin in (A) above. The lower limit of the content of alkali metal salts and alkaline earth metal salts is preferably 0.005 parts by weight, more preferably 0.01 parts by weight, and even more preferably 0.015 parts by weight, relative to 100 parts by weight of the thermoplastic resin in (A) above. When the lower limit of the content of alkali metal salts and alkaline earth metal salts is within the above range, the heat aging resistance is further improved. In addition, when the upper limit of the content of alkali metal salts and alkaline earth metal salts is within the above range, the thermal decomposition of the resin molded article can be further suppressed.

[0263] As a method for presenting the (D) metal ion component in the resin composition, examples include: a method of mixing copper compounds (and further mixing metal halides, alkali metal salts and / or alkaline earth metal salts if necessary) during the polymerization of the (A) thermoplastic resin (Preparation Method 1); and a method of mixing copper compounds (and further mixing metal halides, alkali metal salts and / or alkaline earth metal salts if necessary) into the (A) thermoplastic resin by melt mixing (Preparation Method 2).

[0264] In the method for manufacturing the resin composition of this embodiment, the copper compound can be added in a solid state or, for example, in an aqueous solution. The polymerization of the thermoplastic resin in method 1 (A) described above can be at any stage before the polymerization of the raw material monomer to the polymer is completed. There are no particular limitations on the apparatus used for melt mixing in method 2; known apparatuses such as single-screw or twin-screw extruders, Banbury mixers, and melt mixers with mixing rollers can be used. A twin-screw extruder is preferred.

[0265] The melt mixing temperature is preferably about 1 to 100°C higher than the melting point of thermoplastic resin (A), and more preferably about 10 to 50°C higher. The shear rate in the mixer is preferably 100 sec. -1 For the above-mentioned degree, the average residence time during mixing is preferably 0.5 to 5 minutes.

[0266] <<(E) Sliding Component>>

[0267] In one embodiment, the resin composition may include a (E) lubricant component. The (E) lubricant component is a substance distinct from (A) the thermoplastic resin and (C) the surface treatment agent. In a representative embodiment, (C) the surface treatment agent has the water solubility described herein, while the (E) lubricant component does not have this water solubility.

[0268] The preferred lower limit of the amount of the (E) lubricant component relative to 100 parts by weight of the (A) thermoplastic resin is 0.01 parts by weight, more preferably 0.5 parts by weight, and particularly preferably 1.0 parts by weight. Conversely, the preferred upper limit of the amount of the (E) lubricant component relative to 100 parts by weight of the (A) thermoplastic resin is 5 parts by weight, more preferably 4 parts by weight, and particularly preferably 3 parts by weight. By keeping the amount of the (E) lubricant component within the above range, wear can be suppressed, thereby increasing the number of fractures in repeated fatigue tests. When using conventional fillers (such as glass fibers), the (E) lubricant component tends to agglomerate on the filler surface, forming a multi-layered structure of lubricant molecules, which may lead to problems such as easy filler detachment and reduced effectiveness in long-term fatigue tests. However, in the case of nanocellulose (B) with an average fiber diameter of 1000 nm or less, the surface area is significantly different from that of glass fibers, and is much larger. Therefore, the (E) lubricant component is less likely to agglomerate on the cellulose surface, and the lubricant molecules are less likely to layer. It is speculated that this could increase the number of fractures in fatigue tests, thereby maintaining wear resistance.

[0269] When the amount of the lubricant component (E) is 5 parts by mass or less relative to 100 parts by mass of the thermoplastic resin in (A), the formation of mid-layer delamination and silver streaks in the resin molded body can be better suppressed. In addition, when the amount of the lubricant component (E) is 0.01 parts by mass or more relative to the thermoplastic resin in (A), the effect of reducing wear can be more significant.

[0270] As a component of (E) lubricant, for example, compounds having structures represented by the following general formulas (1), (2) or (3) can be cited.

[0271] [R 11 -(A1-R 12 ) x -A2-R 13 ] y ···(1)

[0272] A3-R 11 -A4···(2)

[0273] R 14 -A5···(3)

[0274] Here, in equations (1) and (2), R 11 R 12 and R 13 Each of the following is independently a substituted alkylene group having at least one hydrogen atom substituted by an aryl group having 6 to 7000 carbon atoms, an aryl group having 6 to 7000 carbon atoms, or an aryl group having at least one hydrogen atom substituted by an alkyl group having 1 to 7000 carbon atoms.

[0275] In addition, in equation (3), R 14 It is a substituted alkyl group having at least one hydrogen atom in an alkyl group having 1 to 7000 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 7000 carbon atoms in which at least one hydrogen atom is replaced by an aryl group having 6 to 7000 carbon atoms, an aryl group having 6 to 7000 carbon atoms, or an aryl group having 6 to 7000 carbon atoms in which at least one hydrogen atom is replaced by a substituted or unsubstituted alkyl group having 1 to 7000 carbon atoms.

[0276] These groups can be groups containing double bonds, triple bonds, or cyclic structures.

[0277] In addition, in formula (1), A1 and A2 are each independently an ester bond, a thioester bond, an amide bond, a thioamide bond, an imide bond, an acylurea bond, an imine bond, a urea bond, a ketoxime bond, an azo bond, an ether bond, a thioether bond, a carbamate bond, a thiocarbamate bond, a sulfur bond, a disulfide bond, or a triple bond.

[0278] In addition, in formulas (2) and (3), A3, A4 and A5 are each independently hydroxyl, acyl (e.g. acetyl), aldehyde, carboxyl, amino, sulfonyl, amido, azide, cyano, mercapto, sulfenic acid, isocyano, enone, isocyanate, thioisocyanate, nitro or thiol.

[0279] From the perspective of wear characteristics under light load sliding, the structure represented by the above general formulas (1), (2), and (3) in the (E) lubricant component is preferably within the following range.

[0280] That is, R 11 R 12 R 13 R 14 The number of carbon atoms in the sample is preferably 2 to 7000, more preferably 3 to 6800, and even more preferably 4 to 6500.

[0281] In equation (1), x represents an integer from 1 to 1000, preferably an integer from 1 to 100. y represents an integer from 1 to 1000, preferably an integer from 1 to 200.

[0282] In formula (1), preferably A1 and A2 are each independently an ester bond, a thioester bond, an amide bond, an imide bond, an acylurea bond, an imine bond, a urea bond, a ketoxime bond, an ether bond, and a carbamate bond, and more preferably A1 and A2 are each independently an ester bond, an amide bond, an imide bond, an acylurea bond, an imine bond, a urea bond, a ketoxime bond, an ether bond, and a carbamate bond.

[0283] In formulas (2) and (3), preferably A3, A4 and A5 are each independently hydroxyl, acyl (e.g. acetyl), aldehyde, carboxyl, amino, azide, cyano, mercapto, isocyano, enone, isocyanate and thioisocyanate, more preferably A3, A4 and A5 are each independently hydroxyl, acyl (e.g. acetyl), aldehyde, carboxyl, amino, cyano, isocyano, enone and isocyanate.

[0284] Specifically, the components of (E) lubricant are not particularly limited, and examples include at least one compound selected from the group consisting of alcohols, amines, carboxylic acids, hydroxy acids, amides, esters, polyoxyalkylene glycols, silicone oils and waxes.

[0285] As an alcohol, it is preferably a mono- or poly-hydric alcohol, saturated or unsaturated, with 6 to 7000 carbon atoms. Specific examples are not particularly limited, but examples include octanol, nonanol, decanol, undecylol, lauryl alcohol, tridecylol, myristol, pentadecylol, hexadecylol, heptadecanol, stearyl alcohol, oleyl alcohol, linolenic acid alcohol, nonadecanol, eicosyl alcohol, wax alcohol, behenol, beeswax alcohol, hexyldecyl alcohol, octyldodecyl alcohol, decylmyristyl alcohol, decylstearyl alcohol, and unilin.TM Alcohols, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, glycerol, diglycerol, triglycerol, threitol, erythritol, pentaerythritol, arabinol, ribosyl alcohol, xylitol, sorbitol, sorbitol anhydride, sorbitol, mannitol.

[0286] Among these, alcohols with 11 or more carbon atoms are preferred from the perspective of lubrication efficiency. Alcohols with 12 or more carbon atoms are more preferred, and alcohols with 13 or more carbon atoms are even more preferred. Saturated alcohols among these are particularly preferred.

[0287] Among these, stearyl alcohol, oleyl alcohol, linolenic acid alcohol, behenyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol are preferred, with behenyl alcohol, diethylene glycol, and triethylene glycol being particularly preferred.

[0288] Examples of amines include, but are not limited to, primary amines, secondary amines, and tertiary amines.

[0289] There are no particular limitations on primary amines, for example, methylamine, ethylamine, propylamine, butylamine, pentamine, hexamine, heptamine, octamine, cyclohexylamine, ethylenediamine, aniline, diaminodiphenylmethane, isophorone diamine, xylenediamine, m-phenylenediamine, diaminodiphenylamine, etc.

[0290] There are no particular limitations on secondary amines; examples include dimethylamine, diethylamine, N-methylethylamine, diphenylamine, tetramethylethylenediamine, piperidine, and N,N-dimethylpiperazine.

[0291] There are no particular limitations on what constitutes a tertiary amine; examples include trimethylamine, triethylamine, 1,6-hexanediamine, N,N-diisopropylethylamine, pyridine, N,N-dimethyl-4-aminopyridine, triethylenediamine, benzyldimethylamine, etc.

[0292] There are no particular limitations on the specific amines used, and examples include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, and N-aminoethylpiperazine. Among these, hexylamine, heptylamine, octylamine, tetramethylethylenediamine, N,N-dimethylpiperazine, and 1,6-hexanediamine are more preferred, and heptylamine, octylamine, tetramethylethylenediamine, and 1,6-hexanediamine are particularly preferred.

[0293] As a carboxylic acid, saturated or unsaturated mono- or poly-aliphatic carboxylic acids with 6 to 7000 carbon atoms are preferred. Specific examples are not particularly limited, but can include hexanoic acid, heptanoic acid, octanoic acid, undecanoic acid, nonanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, heptadecanic acid, stearic acid, nonadecanic acid, arachidic acid, behenic acid, limonic acid, ceric acid, heptadecanic acid, linoleic acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, betaine, shellac, undecenoic acid, transoleic acid, cetene, brassenoic acid, sorbic acid, palmitoleic acid, oleic acid, isoleic acid, linoleic acid, linolenic acid, linolenic acid, arachidonic acid, nervonic acid, erucic acid, propynic acid, stearylene acid, etc.

[0294] Among these, fatty acids with 10 or more carbon atoms are preferred from the perspective of lubrication efficiency. Fatty acids with 11 or more carbon atoms are more preferred, and fatty acids with 12 or more carbon atoms are even more preferred. Saturated fatty acids are particularly preferred. Among saturated fatty acids, palmitic acid, stearic acid, behenic acid, linalic acid, adipic acid, sebacic acid, etc., are also readily available in industry and are more preferred.

[0295] Alternatively, it can be naturally occurring fatty acids or mixtures thereof containing this ingredient. These fatty acids can be substituted with hydroxyl groups, or they can be unilin, a synthetic fatty alcohol. TM Synthetic fatty acids are produced by modifying the terminal carboxyl group of an alcohol.

[0296] There are no particular limitations on what constitutes a hydroxy acid; examples include aliphatic hydroxy acids and aromatic hydroxy acids. For aliphatic hydroxy acids, examples include glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric 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, hydroxynonadecanoic acid, hydroxyeicosanoic acid, hydroxytetradecanoic acid, hydroxyhexadecanoic acid, hydroxyoctadecanoic acid, lactic acid, malonic acid, glyceric acid, hydroxybutyric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citrate, citric acid, isocitrate, leucine, mevalonic acid, pantothenic acid, ricinoleic acid, transricinoleic acid, cerebroside, quinic acid, shikimic acid, etc., or their isomers.

[0297] There are no particular limitations on aromatic hydroxy acids. Examples include salicylic acid, creosoteric acid (high-salicylic acid, hydroxy(methyl)benzoic acid), vanillic acid, syringic acid, pyrocatechin acid, dihydroxybenzoic acid, protocatechin acid, gentian acid, cromoglycine, gallic acid, gallic acid, phenylethanolic acid, diphenylethanolic acid, alpha-lactate, succinic acid, stigmocarboxylic acid, cinnamic acid or hydrogenated cinnamic acid, stigmocarboxylic acid, phloroglucinic acid, coumaric acid, umbelliferic acid, caffeic acid, ferulic acid, sinapic acid, and their isomers. Among these, aliphatic hydroxy acids are more preferred, aliphatic hydroxy acids with 5 to 30 carbon atoms are more preferred, and aliphatic hydroxy acids with 8 to 28 carbon atoms are particularly preferred.

[0298] As amides, mono- or poly-aliphatic amides with 6 to 7000 carbon atoms are preferred. Specific examples are not particularly limited, but examples include saturated or unsaturated amides such as heptadecamide, octamide, nonanamide, decamide, undecylamide, lauramide, tridecylamide, myristamide, pentadecylamide, hexadecylamide, heptadecanamide, stearamide, oleamide, nonadecanamide, eicosamide, wax amide, docosamide, beeswaxamide, hexyldecylamide, octyldodecylamide, lauramide, palmitamide, stearamide, behenamide, hydroxystearamide, oleamide, and mustardamide.

[0299] Examples of secondary amides include, but are not limited to, saturated or unsaturated amides such as N-oleopalmitamide, N-stearylstearamide, N-stearyloleamide, N-oleostearamide, N-stearylmustamide, methylene bis-stearamide, ethylene bis-decanoamide, ethylene bis-lauranamide, ethylene bis-hydroxystearamide, ethylene bis-benzylhexylamide, ethylene bis-oleamide, ethylene bis-benzylhexylamide, hexamethylene bis-stearamide, hexamethylene bis-benzylhexylamide, hexamethylene bis-oleamide, and hexamethylene hydroxystearamide.

[0300] Examples of tertiary amides include, but are not limited to, saturated or unsaturated amides such as N,N-distearyl hexadiamide, N,N-distearyl sebacamide, N,N-dioleyl hexadiamide, N,N-dioleyl sebacamide, and N,N-distearyl isophthalamide.

[0301] Among these, palmitamide, stearamide, behenamide, hydroxystearamide, oleamide, mustardamide, and N-stearylstearamide may be preferred.

[0302] Among these, methylene bis-stearamide, ethylene bis-lauranamide, vinyl bis-stearamide, and ethylene bis-behenamide are preferred. From the perspective of lubrication efficiency, amides with 10 or more carbon atoms are preferred. Amides with 11 or more carbon atoms are more preferred, and amides with 13 or more carbon atoms are even more preferred. Saturated aliphatic amides are particularly preferred.

[0303] As esters, the preferred options are reaction products formed by the reaction of the aforementioned alcohol with a carboxylic acid or with a hydroxy acid to form an ester bond.

[0304] Specific examples are not specifically limited, but can include butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, glyceryl behenate monoglyceride, hexadecyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, cholesterol isostearate, methyl laurate, methyl oleate, methyl stearate, hexadecyl myristate, myristyl myristate, octyl dodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearate, and isotriadecyl stearate. Triglycerides of 2-ethylhexanoate, diisodecyl adipate, 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, glyceryl monostearate, glyceryl distearate, glyceryl monolaurate, glyceryl dilaurate, glyceryl monooleate, glyceryl dioleate, etc.

[0305] Among these, hexadecyl tetradecanoate, diisodecyl adipate, ethylene glycol monostearate, ethylene glycol distearate, triethylene glycol monostearate, triethylene glycol distearate, polyethylene glycol monostearate, and polyethylene glycol distearate are preferred, and hexadecyl tetradecanoate, diisodecyl adipate, and ethylene glycol distearate are particularly preferred.

[0306] Examples of polyoxyalkylene glycols include, but are not limited to, the following three substances.

[0307] The first type of polyoxyalkylene glycol is a condensation polymer using alkylene glycol as a monomer. Examples of such condensation polymers include, but are not limited to, polyethylene glycol, polypropylene glycol, block copolymers of ethylene glycol and propylene glycol, and random copolymers. The preferred degree of polymerization of these condensation polymers is 5 to 2500, and more preferably 10 to 2300.

[0308] The second type of polyoxyalkylene glycol is an ether compound of the condensation polymer of the first type of polyoxyalkylene glycol and an aliphatic alcohol. Examples of such ether compounds include, but are not limited to, polyethylene glycol oleyl ether (degree of polymerization of ethylene oxide 5-500), polyethylene glycol hexadecyl ether (degree of polymerization of ethylene oxide 5-500), polyethylene glycol stearyl ether (degree of polymerization of ethylene oxide 5-300), polyethylene glycol lauryl ether (degree of polymerization of ethylene oxide 5-300), polyethylene glycol tridecyl ether (degree of polymerization of ethylene oxide 5-300), polyethylene glycol nonylphenyl ether (degree of polymerization of ethylene oxide 2-1000), and polyethylene glycol octylphenyl ether (degree of polymerization of ethylene oxide 4-500).

[0309] The third type of polyoxyalkylene glycol is an ester compound of the condensation polymer of the first type of polyoxyalkylene glycol and a higher fatty acid. Examples of such ester compounds include, but are not limited to, polyethylene glycol monolaurate (ethylene oxide degree of polymerization 2-300), polyethylene glycol monostearate (ethylene oxide degree of polymerization 2-500), and polyethylene glycol monooleate (ethylene oxide degree of polymerization 2-500).

[0310] There are no particular limitations on waxes, but examples include shellac wax, beeswax, whale wax, lac wax, wool wax, carnauba wax, wood wax, rice wax, candelilla wax, lac wax, solid paraffin wax, microcrystalline wax, lignite wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, as well as their high-density polymeric type, low-density polymeric type, oxidized type, acid-modified type, and special monomer modified type.

[0311] Among these waxes, carnauba wax, rice wax, candelilla wax, solid paraffin wax, lignite wax, polyethylene wax, and their high-density polymerized, low-density polymerized, oxidized, acid-modified, and special monomer-modified types are preferred.

[0312] Among these waxes, the preferred lubricant component (E) is at least one compound selected from the group consisting of alcohols, amines, carboxylic acids, esters, amide compounds formed from mono- or di-amines and carboxylic acids, and waxes.

[0313] The solid paraffin wax, polyethylene wax, and their high-density polymeric, low-density polymeric, oxidized, acid-modified, and special monomer-modified forms of the (E) lubricant component used in the polyamide resin composition of this embodiment are not particularly limited, and can be obtained by the following methods: introducing acidic groups through the oxidation reaction of polyolefin wax; oxidizing and decomposing polyolefin; reacting inorganic acids, organic acids, or unsaturated carboxylic acids with polyolefin wax to introduce polar groups such as carboxyl groups and sulfonic acid groups; or introducing monomers with acidic groups during the polymerization of polyolefin wax.

[0314] These substances are commercially available under names such as oxidatively modified or acid-modified polyolefin waxes and are readily available.

[0315] Examples of polyolefin waxes include, but are not limited to, solid paraffin wax, microcrystalline wax, lignite wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, as well as their high-density polymerized, low-density polymerized, and special monomer-modified types.

[0316] Examples of polyolefins include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, polypropylene-butene copolymer, polybutene, hydride of polybutadiene, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, etc.

[0317] As a lubricant component (E), from the perspective of improving lubrication, acid-modified solid 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.

[0318] (E) The lubricant component is particularly preferably a modified wax comprising acid-modified polyethylene and / or acid-modified polypropylene.

[0319] The above-mentioned (E) lubricant components can be used alone or in combination of two or more.

[0320] In this embodiment, the (E) lubricant component can be separated from the gear (i.e., the molded body) and its molecular structure, molecular weight, melting point, acid value, viscosity, etc. can be calculated.

[0321] The (E) lubricant component in the molded body can be separated by dissolving the molded body and then filtering it. The (E) lubricant component can then be refined through recrystallization or reprecipitation. This process involves refining the (E) lubricant component... 1 H-NMR, 13 Various measurements, such as C-NMR, two-dimensional NMR, and MALDI-TOF MS, can determine the molecular structure, including repeating structures, branched structures, and the positional information of various functional groups.

[0322] (E) 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. The lower limit of the preferred acid value is not particularly limited, but is preferably 0 mg-KOH / g or higher. The upper limit of the acid value is more preferably 83 mg-KOH / g, further preferably 80 mg-KOH / g, and even more preferably 75 mg-KOH / g. By maintaining the acid value within the above range, there is a tendency to suppress discoloration during drying and to exhibit good wear resistance during high-temperature sliding under light loads. (E) The acid value of the lubricant component can be determined according to the method of JIS K0070.

[0323] (E) The acid value of the lubricant component can be controlled, for example, by the method described in Example 1 or 2 of Japanese Patent Application Publication No. 2004-75749; by adjusting or controlling the amount of acidic groups and / or polar groups introduced by thermally decomposing commercially available high-density polyethylene in an oxygen atmosphere; etc. Furthermore, in the case where the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, commercially available products can also be used.

[0324] (E) When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 140°C is preferably in the range of 1 to 3000 mPa·s. The lower limit is not particularly limited, but from the perspective of the processability of the polyamide resin composition of this embodiment during melt mixing, 1 mPa·s is preferred, more preferably 20 mPa·s, further preferably 25 mPa·s, even more preferably 30 mPa·s, and even more preferably 50 mPa·s. Furthermore, the preferred upper limit of the melt viscosity at 140°C is 2850 mPa·s, more preferably 2800 mPa·s, even more preferably 2700 mPa·s, even more preferably 2650 mPa·s, and even more preferably 2000 mPa·s.

[0325] (E) When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 180°C is preferably in the range of 100 to 2900 mPa·s. (E) When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the lower limit of the melt viscosity at 180°C is preferably 110 mPa·s, more preferably 140 mPa·s, further preferably 160 mPa·s, and even more preferably 300 mPa·s. Furthermore, when the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, the preferred upper limit of the melt viscosity at 180°C is 2850 mPa·s, more preferably 2800 mPa·s, further preferably 2700 mPa·s, even more preferably 2650 mPa·s, even more preferably 2000 mPa·s, and particularly preferably 1600 mPa·s.

[0326] (E) When the lubricant component is acid-modified polyethylene and / or acid-modified polypropylene, by making the melt viscosity within the above range, when the resin composition, which is a constituent material of the gear in this embodiment, is melt-mixed, the resin particles are completely melted and tend to be sufficiently mixed.

[0327] (E) When the lubricant is composed of acid-modified polyethylene and / or acid-modified polypropylene, the melt viscosity at 140°C and 180°C can be determined using a Brookfield viscometer.

[0328] In one embodiment, (E) the lubricant component is lubricating oil. The lubricating oil is not limited to the following substances; it can be any substance that can improve the friction and wear characteristics of the resin molded body. Examples include natural oils such as engine oil or cylinder oil, alkane-based oils (such as Diana process oil PS32 manufactured by Idemitsu Kosan Co., Ltd.), cycloalkane-based oils (such as Diana process oil NS90S manufactured by Idemitsu Kosan Co., Ltd.), aromatic oils (such as Diana process oil AC12 manufactured by Idemitsu Kosan Co., Ltd.), and silicone-based oils (such as the G30 series manufactured by Shin-Etsu Chemical Co., Ltd.) (silicone oils, silicone rubbers, and modified silicone rubbers represented by polydimethylsiloxane). It can be appropriately selected from commercially available lubricating oils and used directly, or appropriately mixed as needed. Among these substances, alkane-based oils and silicone-based oils are preferred from the perspective of lubrication properties and are also readily available industrially. These lubricating oils can be used alone or in combination.

[0329] The lower limit of the molecular weight of the lubricating oil is preferably 100, more preferably 400, and even more preferably 500. The upper limit is preferably 5 million, more preferably 2 million, and even more preferably 1 million. The lower limit of the melting point of the lubricating oil is preferably -50°C, more preferably -30°C, and even more preferably -20°C. The upper limit of the melting point of the lubricating oil is preferably 50°C, more preferably 30°C, and even more preferably 20°C. By making the molecular weight 100 or higher, the lubricating oil tends to have good lubricity. Furthermore, by making the molecular weight 5 million or lower, especially 1 million or lower, the lubricating oil has good dispersion and its wear resistance tends to improve. Furthermore, by making the melting point -50°C or higher, the fluidity of the lubricating oil present on the surface of the molded body can be maintained, and abrasive wear can be suppressed, thereby improving the wear resistance of the resin molded body. Furthermore, by making the melting point 50°C or lower, it is easier to mix with thermoplastic resins, and the dispersibility of the lubricating oil tends to improve. Based on the above points, the molecular weight and melting point of the lubricating oil are preferably within the above ranges. In a preferred embodiment, the melting point is a temperature 2.5°C lower than the pour point of the lubricating oil. The pour point can be determined according to JIS K2269.

[0330] The lower limit of the lubricant content relative to 100 parts by weight of thermoplastic resin (A) is not particularly limited, but is preferably 0.1 parts by weight, more preferably 0.2 parts by weight, and even more preferably 0.3 parts by weight. Furthermore, the upper limit of the above content is not particularly limited, but is preferably 5.0 parts by weight, more preferably 4.5 parts by weight, and even more preferably 4.2 parts by weight. When the lubricant content is within the above range, the wear resistance of the resin composition tends to improve. In particular, when the lubricant content is 0.1 parts by weight or more, sufficient lubrication can be ensured, and wear resistance tends to improve. Furthermore, when the lubricant content is 5.0 parts by weight or less, resin softening can be suppressed, and there is a tendency to ensure the strength of the resin composition for applications such as high-torque gears.

[0331] When the content range of lubricating oil in the resin composition of this embodiment is adjusted as described above, it is preferable from the perspective of improving the wear characteristics during sliding and making the stable sliding performance excellent.

[0332] In gears, the dispersion state of the lubricant component near the surface has a significant impact on sliding characteristics; therefore, the weight-average molecular weight (E) of the lubricant component is important. In one embodiment, the preferred lower limit of the weight-average molecular weight (E) of the lubricant component is 500, more preferably 600, and particularly preferably 700. Furthermore, the preferred upper limit of the weight-average molecular weight (E) of the lubricant component is not particularly limited, and for ease of processing, 100,000 is used as a reference. In the gear of this embodiment, by ensuring that the weight-average molecular weight (E) of the lubricant component is within the above-mentioned range, it is possible to maintain wear resistance for more than 10,000 sliding cycles.

[0333] (E) The lower limit of the molecular weight distribution of the lubricant component is not particularly limited, but it is close to 1.0 based on the consideration of the stability of the coefficient of friction during sliding. In addition, the upper limit of the molecular weight distribution of the lubricant component is preferably 9.0, more preferably 8.5, further preferably 8.0, and even more preferably 7.5.

[0334] Regarding the weight-average molecular weight of the (E) lubricant component, if the weight-average molecular weight is below 1000, it is determined by liquid chromatography / mass spectrometry analysis; if the weight-average molecular weight is above 1000, it is expressed as the converted weight-average molecular weight of standard polystyrene, etc., determined by gel permeation chromatography.

[0335] The melting point of the (E) lubricant component is preferably 40–150°C. By setting the melting point of the (E) lubricant component to 40°C or higher, there is a tendency to improve the wear resistance of the resin molded article at higher temperatures; by setting the melting point of the (E) lubricant component to 150°C or lower, it is easier to achieve good dispersion of the (E) lubricant component in the resin during processing. A more preferred lower limit for the melting point of the (E) lubricant component is 45°C, a further preferred lower limit is 50°C, and a particularly preferred lower limit is 80°C. Furthermore, a more preferred upper limit for the melting point of the (E) lubricant component is less than 150°C, a further preferred upper limit is 140°C, a more preferred upper limit is 135°C, and a particularly preferred upper limit is 130°C. The melting point of the (E) lubricant component can be determined according to the method of JIS K 7121 (DSC method).

[0336] <<Other Ingredients>>

[0337] Next, other components that can be used in this invention will be described in detail. In addition to the components described above, the resin composition of this embodiment may also contain various stabilizers conventionally used in thermoplastic resins, to a extent that does not impair the purpose of this embodiment. Examples of stabilizers include, but are not limited to, inorganic fillers, heat stabilizers, lubricants, etc., as described below. These stabilizers may be used individually or in combination of two or more. They may be commercially available reagents or products.

[0338] The aforementioned inorganic filler may be, but is not limited to, at least one compound selected from the group consisting of fibrous particles, plate-like particles, and inorganic pigments. In one embodiment, the fibrous particles and plate-like particles referred to herein are particles with an average length-to-thickness ratio of 5 or more.

[0339] There are no particular limitations on fibrous particles; examples include glass fiber, carbon fiber, potassium titanate fiber, asbestos fiber, silicon carbide fiber, silicon nitride fiber, calcium metasilicate fiber, and aromatic polyamide fiber.

[0340] Furthermore, there are no particular limitations on the plate-shaped particles; examples include talc, mica, kaolin, glass flakes, and bentonite. Among these, talc, mica, and glass fiber are preferred. By using these components, there is a tendency for superior mechanical strength and better economic efficiency.

[0341] Furthermore, there are no particular limitations on inorganic pigments; examples include zinc sulfide, titanium dioxide, zinc oxide, iron oxide, barium sulfate, titanium dioxide, barium sulfate, hydrated chromium oxide, chromium oxide, cobalt aluminate, barite powder, zinc yellow type 1, zinc yellow type 2, potassium ferrocyanide, kaolin, titanium yellow, cobalt blue, cyanine, cadmium, nickel titanium, zinc barium white, strontium, brown clay, concentrated loess, azurite, malachite, blue malachite, orpiment, cockscomb stone, cinnabar, turquoise, rhodochrosite, yellow ochre, green clay, iron-rich loess, manganese-rich brown clay, and casselite. Earth), chalk, gypsum, calcined loess, calcined brown clay, lapis lazuli, azurite, malachite, coral powder, muscovite, cobalt blue, azure blue, cobalt violet, cobalt green, zinc white, titanium white, light red, chromium oxide green, Mars black, chrome green, yellow ochre, bauxite white, cadmium yellow, cadmium red, vermilion, talc, silica, clay, mineral violet, rose cobalt violet, silver white, gold powder, bronze powder, aluminum powder, Prussian blue, cobalt yellow, mica titanium, carbon black, acetylene black, lamp black, furnace black, plant black, bone char, calcium carbonate, Prussian blue, etc.

[0342] Among these, zinc sulfide, zinc oxide, iron oxide, titanium dioxide, titanium yellow, cobalt blue, and carbonates are preferred from the perspective of imparting higher wear resistance. Zinc oxide and titanium yellow are more preferred from the perspective of sufficiently low Mohs hardness and further imparting high wear resistance.

[0343] The amount of the inorganic filler is not particularly limited, but it is preferably 0.002 to 70 parts by weight or 0.002 to 50 parts by weight relative to 100 parts by weight of the thermoplastic resin. By setting the amount of inorganic filler to the above range, the processability of the resin composition can be improved.

[0344] As the aforementioned heat stabilizer, from the perspective of improving the heat stability of the resin composition, an antioxidant (e.g., a hindered phenolic antioxidant) is preferred.

[0345] Examples of hindered phenolic antioxidants include, but are not limited to, octadecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate, octadecyl 3-(3'-methyl-5'-tert-butyl-4'-hydroxyphenyl)-propionate, tetradecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate, 1,6-hexanediol-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate), 1,4-butanediol-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate), and triethylene glycol-bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)-propionate).

[0346] In addition, examples of hindered phenolic antioxidants include, but are not limited to, tetra-(methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate)methane, 3,9-bis(2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspirocyclo(5,5)undecane, and N,N'-bis3-(3',5'-di-tert-butyl-4-hydroxyphenol)propionate. Acyl hexamethylenediamine, N,N'-tetramethylenebis3-(3'-methyl-5'-tert-butyl-4-hydroxyphenol)propionyldiamine, N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionyl)hydrazine, N-salicyloyl-N'-salicylhydrazine, 3-(N-salicyloyl)amino-1,2,4-triazole, N,N'-bis(2-(3-(3,5-dibutyl-4-hydroxyphenyl)propionyloxy)ethyl)hydroxyamide, etc.

[0347] Among the aforementioned hindered phenolic antioxidants, triethylene glycol-bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)-propionate and tetra-(methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate)methane are preferred from the perspective of improving the thermal stability of the resin molded body.

[0348] The amount of antioxidant added is not particularly limited, but relative to 100 parts by weight of (A) thermoplastic resin, the antioxidant, such as a hindered phenolic antioxidant, is preferably in the range of 0.1 to 2 parts by weight. By setting the amount of stabilizer added within the above range, the processability of the resin composition can be improved.

[0349] The apparatus for manufacturing the resin composition of this embodiment is not particularly limited, and a commonly used mixing mill can be used. Such a mixing mill can be, but is not limited to, a single-screw or multi-screw mixing extruder, a roller mill, a Banbury mixer, etc. A twin-screw extruder equipped with a pressure reducing device and a side-feeding device is preferred.

[0350] From the perspective of achieving good durability for the gears, the flexural modulus of the resin composition, as measured according to ISO 179, is preferably 3000 MPa or more, more preferably 4000 MPa or more, and even more preferably 5000 MPa or more. From the perspective of ease of manufacturing of the resin composition, the aforementioned flexural modulus may be, for example, 20000 MPa or less, or 15000 MPa or less, or 12000 MPa or less.

[0351] In one embodiment of the resin composition, the ratio of the coefficient of friction (II) of the resin composition to the coefficient of friction (I) of a composition with the same composition as the resin composition except that it does not contain (B) cellulose nanofibers, i.e., the coefficient of friction ratio (II / I), is preferably 0.8 or less. This coefficient of friction is determined as follows: in the form of a multi-purpose test piece prepared according to ISO 294-3, using a reciprocating friction and abrasion testing machine and using a SUS304 test piece with a 5 mm diameter ball as the test material, under conditions of a linear speed of 50 mm / s, a reciprocating distance of 50 mm, a temperature of 23°C, a humidity of 50%, and a load of 19.8 N. In the resin composition of this embodiment, due to the contribution of (B) cellulose nanofibers, excellent surface smoothness is achieved when molded into a resin molded body. The aforementioned coefficient of friction ratio varies depending on the specific composition of the resin composition (for example, if the proportion of (B) cellulose nanofibers increases, the coefficient of friction ratio tends to decrease). From the perspective of excellent surface smoothness, the aforementioned coefficient of friction ratio is preferably 0.8 or less, or 0.7 or less, or 0.5 or less. In one embodiment, the aforementioned coefficient of friction is, for example, 0.05 or more, or 0.1 or more, or 0.2 or more.

[0352] Resin compositions can be provided in various shapes. Specifically, examples include resin granules, flakes, fibers, plates, rods, etc. For ease of post-processing and transportation, granule shapes are preferred. Preferred granule shapes include spherical, elliptical, and cylindrical shapes, depending on the cutting method during extrusion. Granules cut using a method called underwater cutting are mostly spherical, granules cut using a method called thermal cutting are mostly spherical or elliptical, and granules cut using a method called wire cutting are mostly cylindrical. In the case of spherical granules, the preferred size, in terms of granule diameter, is 1 mm or more and 3 mm or less. Similarly, in the case of cylindrical granules, the preferred diameter is 1 mm or more and 3 mm or less, and the preferred length is 2 mm or more and 10 mm or less. From the perspective of operational stability during extrusion, the aforementioned diameter and length are preferably at or above the lower limit, and from the perspective of bite-in into the molding machine during post-processing, they are preferably at or below the upper limit.

[0353] The following methods can be cited as specific examples of methods for manufacturing resin molded articles.

[0354] (1) A method of using a single-screw or twin-screw extruder to melt and knead a mixture of thermoplastic resin, cellulose nanofibers and surface treatment agent, extrude it into a filament, and cool and solidify it in a water bath to obtain a granular molded body.

[0355] (2) A method of using a single-screw or twin-screw extruder to melt and mix a mixture of thermoplastic resin, cellulose nanofibers and surface treatment agent, extrude it into rod or tubular shape, and cool it to obtain an extruded molded body.

[0356] (3) A method of using a single-screw or twin-screw extruder to melt and knead a mixture of thermoplastic resin, cellulose nanofibers and surface treatment agent, and then extruding it using a T-die to obtain sheet or film-shaped molded articles.

[0357] In addition, the following method can be cited as a specific example of a melt-blending method for a mixture of thermoplastic resin, cellulose nanofibers and surface treatment agent.

[0358] (1) A method of uniformly melting and mixing thermoplastic resin with cellulose nanofibers and surface treatment agent powder mixed in a desired proportion.

[0359] (2) A method of further melting and mixing thermoplastic resin and surface treatment agent if necessary, adding cellulose nanofiber powder mixed in the desired proportion and surface treatment agent if necessary.

[0360] (3) A method of melting and mixing thermoplastic resin, cellulose nanofibers mixed in the desired proportion, surface treatment agent powder and water, then mixing cellulose nanofibers and water mixed in the desired proportion and surface treatment agent as necessary, and then uniformly melting and mixing.

[0361] (4) A method of further melting and mixing thermoplastic resin and surface treatment agent if necessary, and then adding thermoplastic resin, cellulose nanofiber, surface treatment agent mixed powder and water in the desired proportion.

[0362] (5) The above (1) to (4) are added and melt-mixed using a single screw or twin screw extruder in any proportion as top feed and side feed.

[0363] <<Arithmetic Mean Surface Roughness Sa of Gear Sliding Surface>>

[0364] In this embodiment, the arithmetic mean surface roughness Sa of the sliding surface of the gear and other gears is 3.0 μm or less. Such a low value of arithmetic mean surface roughness Sa is advantageous for the high sliding performance (and thus quietness) and high durability of the gear. The arithmetic mean surface roughness Sa is a value obtained by measuring according to the method according to ISO 25178, and the arithmetic mean surface roughness Ra can be extended to the surface. The arithmetic mean surface roughness Ra refers to the value obtained as follows: according to JIS B0031, the roughness curve of the surface of the gear as a resin molded body (the surface of the gear can be determined by those skilled in the art based on the shape of the resin gear) is measured, and only a reference length (a) is extracted along the average line direction of the roughness curve. The direction of the average line of the extracted portion is taken as the X-axis, and the direction of the longitudinal magnification factor is taken as the Y-axis. The roughness curve is represented by y = f(x). The value obtained by the following formula (2) is expressed in micrometers (μm), and the value obtained is Ra.

[0365] [Number 1]

[0366]

[0367] In addition, the arithmetic mean surface roughness Sa is the value obtained by extending the arithmetic mean surface roughness Ra to the surface, and is represented by the following formula (3).

[0368] [Number 2]

[0369]

[0370] 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 perspective of ease of manufacture, for example, 0.1 μm is preferred. Surface roughness can be measured using commercially available microscopes such as confocal microscopes (e.g., OPTELICS H1200, manufactured by Lasertec Co., Ltd.).

[0371] <<Hole>>

[0372] In one approach, it is preferable to have few pores in the gear. When pores are present, stress concentration occurs at the pore location due to the load applied to the gear teeth, potentially becoming the starting point for fracture during repeated fatigue. This is particularly true as the module size of the gear, manufactured by injection molding, increases, the pores tend to increase in size. The presence of pores can be confirmed by cutting the gear in half perpendicular to the teeth and observing the cross-section. For example, the size of the micropores can be confirmed by measurement using a confocal microscope (e.g., OPTELICS H1200, manufactured by Lasertec Co., Ltd.). The upper limit of the maximum size of the pore (defined in this disclosure as the maximum value of the equivalent circle diameter of the pore observed across the entire cross-section of the gear) is preferably 2.0 μm, more preferably 1.0 μm, even more preferably 0.5 μm, and most preferably 0.4 μm. It is preferable that pores are absent, and if present, it is preferable that their maximum size is small, for example, from the perspective of practical durability, the maximum size of the pore can be 0.01 μm or more.

[0373] The fewer holes in the gear, the better; per 100mm 2 The number of holes in the aforementioned cross-section is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less. From a practical durability perspective, the number of holes per 100 mm is [not specified]. 2 For example, there can be more than one cross-section.

[0374] <<Changes in Absorbent Size>>

[0375] In gears, the change in dimensional size after water absorption (hereinafter also referred to as equilibrium water absorption dimensional change) after absorbing water in an equilibrium state (exposed to hot water at 80°C for 24 hours, and then maintained at 80°C and 57% relative humidity for 120 hours) is preferably 3% or less. In practical use environments, a small dimensional change makes it less likely to apply large loads (stress concentration) to specific teeth of the gear, thus improving durability. The upper limit of the equilibrium water absorption dimensional change is preferably 3%, more preferably 2.5%, further more preferably 2%, and most preferably 1%. The lower limit of the equilibrium water absorption dimensional change is not particularly limited, and from a practical durability perspective, it can be, for example, 0.5%.

[0376] <<True Roundness>>

[0377] The roundness of the gear is preferably 400 μm or less. In practical use environments, a smaller roundness improves the dimensional uniformity of the gear, making it less likely to apply large loads (stress concentration) to specific teeth, 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. The lower limit of roundness is not particularly limited, and from a practical manufacturing perspective, it can be, for example, 1 μm. Furthermore, the roundness is a value measured using the method described in the [Examples] section of this disclosure.

[0378] The resin composition constituting the gear of this embodiment, by including cellulose nanofibers with a diameter sufficiently smaller than glass fibers, exhibits high thixotropy in its flow state (specifically, in the molten state of the thermoplastic resin). It is believed that this results in uniform resin shrinkage during the cooling process of injection molding, which helps reduce surface roughness and the amount of defects such as pores inside the gear as a resin molded body. Furthermore, it is believed that because the orientation (i.e., dispersion anisotropy) of the cellulose nanofibers in the thermoplastic resin is lower than that of glass fibers, the shrinkage along the tooth direction of the gear is more uniform.

[0379] Furthermore, the thermoplastic resin (A) in this embodiment has a high molecular weight as the resin used for molding, and therefore tends to have low crystallinity and difficulty in growing spherulites. It can be considered that in the gear of this embodiment, the spherulites of the thermoplastic resin (A) are uniformly dispersed inside the gear, exhibiting excellent sphericity.

[0380] That is, the gear of this embodiment has the following advantages by using cellulose nanofibers of a specific size and thermoplastic resin of a specific molecular weight: although it is a resin gear, the deviation from the design size is very small and the dimensional fluctuation during continuous molding is very small.

[0381] <<Thixotropy>>

[0382] The gear of this embodiment contains specific cellulose fibers, and therefore, in one manner, it exhibits thixotropic properties in the molten state. The thermoplastic resin (A) contained in the gear is subjected to a shear rate of 1 second at a melting point of +25°C. -1 At a shear rate of 10s -1 When the viscosity ratio (equation (4) below) is used as the thixotropic index, for example at a shear rate of 1 s, the viscosity ratio is used as the thixotropic index. -1 The viscosity at that time was 2000 Pa·s and the shear rate was 10 s. -1 When the viscosity is 600 Pa·s, the thixotropic index is approximately 3.33.

[0383] Thixotropic index = (shear velocity 1s) -1 Viscosity / shear rate at 10s -1 (viscosity at time)···(4)

[0384] The upper limit of the thixotropic index of the gear in this embodiment is not particularly limited, but from the perspective of ease of molding, 10 is preferred, more preferably 8, even more preferably 5, and particularly preferably 4. From the perspective of obtaining the advantage of good dimensional stability of the gear based on this embodiment, in one embodiment, the lower limit of the thixotropic index is 1, preferably 1.3, and more preferably 2. The thixotropy can be measured by the method described later.

[0385] A particularly preferred form of gear is a gear (especially an EPS gear) that is a resin molded body composed of a resin composition comprising (A) a thermoplastic resin and (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm, wherein,

[0386] The gear has a roundness of less than 400μm.

[0387] (A) Thermoplastic resins include polyamide resins.

[0388] The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of (A) thermoplastic resin.

[0389] <<Torque>>

[0390] The gear of this embodiment exhibits excellent durability even under high torque operating conditions, and therefore, in one embodiment, it is used with a torque of 5 N·m or higher. The upper limit of the torque for the gear of this embodiment during use is not particularly limited, but from a durability perspective, 100 N·m is preferred, more preferably 50 N·m, and even more preferably 30 N·m. From the perspective of obtaining the advantage of good durability based on the gear of this embodiment, the lower limit of the torque is preferably 12 N·m, more preferably 15 N·m.

[0391] <<Operating Speed>>

[0392] The durability of the gear varies greatly depending on the operating speed of the drive source. Under high operating speeds, the gear tends to deteriorate easily. The gear of this embodiment exhibits excellent durability, thus demonstrating superior performance even when applied to drive sources with higher operating speeds. In one embodiment, the drive source is an electric motor. The upper limit of the operating speed of the drive source is preferably 1000 rpm, more preferably 500 rpm, even more preferably 300 rpm, and most preferably 200 rpm. The lower limit of the operating speed is not particularly limited, but from the perspective of obtaining the advantage of good durability based on the gear of this embodiment, it is preferably, for example, 10 rpm, 30 rpm, 50 rpm, or 80 rpm.

[0393] <<Modal>>

[0394] The module of the gear in this embodiment can be 0.5 or higher. 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 significantly depending on the module. The gear of this embodiment exhibits excellent performance in a wide range of module designs. The upper limit of the module is preferably 25.0, more preferably 20.0, even more preferably 10.0, and most preferably 5.0. There is no particular limitation on the lower limit of the module, but from the perspective of obtaining the advantage of good durability based on the gear of this embodiment, it is preferably, for example, 1.0.

[0395] <<Coefficient of Linear Expansion>>

[0396] The gear of this embodiment, because it contains (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less, exhibits lower linear expansion than conventional resin-made gears. Specifically, the coefficient of linear expansion of the resin composition used as the gear's constituent material is preferably 60 ppm / K or less in the temperature range of 0°C to 60°C. More preferably, it is 50 ppm / K or less, even more preferably 45 ppm / K or less, and most preferably 35 ppm / K or less. There is no particular limitation on the lower limit of the coefficient of linear expansion; from the perspective of ease of manufacture, for example, 5 ppm / K is preferred, and more preferably 10 ppm / K.

[0397] <<Gear Manufacturing Methods>>

[0398] The gear of this embodiment can be manufactured by melt-blending a resin composition comprising (A) thermoplastic resin, (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm, and optional other components, and molding it into a resin molded body of a specific shape.

[0399] In this embodiment, the gear is either an injection-molded article or a machined article (preferably a machined article from a cylindrical bar mold). A resin composition (e.g., resin granules) obtained by the above method can be fed into an injection molding machine equipped with a mold of the desired gear shape for molding, thereby obtaining an injection-molded article in the form of a molded article with the desired gear shape. Alternatively, for example, a cylindrical molded article can be obtained by feeding resin granules into an extrusion molding machine for cylindrical bar extrusion, and then cutting the cylindrical bar into the desired gear shape, thereby obtaining a machined article from a cylindrical bar mold in the form of a molded article with the desired gear shape. In either molding method, the gear can be suitably molded from the resin composition based on the technical knowledge of those skilled in the art. Even with a thick molded article, injection molding or machining from a cylindrical bar mold can be used, and by controlling the mold surface temperature, injection speed, holding pressure, etc., there is a tendency to reduce the formation of voids. From the perspective of mass production and productivity, injection molding is a more preferred molding method. In a representative embodiment, the gear is a thick molded article with a tooth width dimension of, for example, 2 to 50 mm.

[0400] In this embodiment, the gears are preferably used with grease. The grease can be applied at least to the meshing surfaces with other gears. By using grease, the sliding properties, durability, and quietness of the gears can be further improved. Various known substances can be used as the grease; from the perspective of obtaining excellent sliding properties even under a wide range of temperature conditions, the lubricant preferably includes a base oil, a thickener, and additives, comprising:

[0401] The base oil contains at least one selected from the group consisting of mineral oils, polyalpha-olefin oils and alkyl polyphenyl ethers in a proportion of more than 80% by weight;

[0402] Thickeners; and

[0403] Hydrocarbon waxes with a melting or softening point in the range of 70°C to 130°C, accounting for 3% to 10% by mass.

[0404] Preferred examples of mineral oils include alkane-based oils and cycloalkane-based oils.

[0405] As a preferred example of a polyalphaolefin oil, 1-decene (C 10 H 20 A homogeneous compound manufactured from a raw material through polymerization and hydrogenation.

[0406] Preferred examples of alkyl polyphenyl ethers include alkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, and dialkyl tetraphenyl ether.

[0407] Preferred examples of thickeners include calcium soap, lithium soap, compound lithium soap, compound calcium soap, compound aluminum soap, urea, PTFE, bentonite, phthalocyanine, indigo styrene, and silica gel.

[0408] Preferred examples of hydrocarbon waxes with melting or softening points in the range of 70–130°C include polyethylene wax and polypropylene wax.

[0409] The amount of base oil in the grease is preferably 50-90% by mass, more preferably 60-85% by mass.

[0410] The amount of thickener in the grease is preferably 10-40% by mass, more preferably 20-30% by mass.

[0411] <<Gear Systems>>

[0412] The gear of this embodiment exhibits excellent mechanical strength, durability, and quiet operation, and therefore can be used in various ways. In particular, examples of gears include, but are not limited to, helical gears, spur gears, internal gears, rack gears, herringbone gears, straight bevel gears, helical bevel gears, spiral bevel gears, crown gears, face gears, threaded gears, worm gears, worm wheel gears, hypoid gears, and circular arc gears. Furthermore, the aforementioned helical gears, spur gears, etc., can be single-stage gears, double-stage gears, or combined gears with a structure that uses a multi-stage drive motor to reduce speed without uneven rotation.

[0413] One aspect of the present invention provides a gear system (particularly an EPS system) comprising a driven gear, a drive gear meshing with the driven gear, and a drive source (e.g., an electric motor) for driving the drive gear, wherein the driven gear and / or the drive gear are gears of this embodiment.

[0414] Figure 1 and 2 A diagram illustrating an example of a gear system according to one aspect of the present invention.

[0415] Figure 1 middle, Figure 1 (A) shows a schematic configuration of gear system 1. Figure 1 (B) Shows more details Figure 1 Gear mechanism 11 in (A). (Refer to...) Figure 1 The gear system 1 is used in the control column of the vehicle and includes a gear mechanism 11 comprising a worm gear as a driven gear 111 and a worm as a drive gear 112, and an electric motor as a drive source 12.

[0416] Figure 2 middle, Figure 2 (A) shows a schematic configuration of gear system 2. Figure 2 (B) Shows more details Figure 2 Gear mechanism 21 in (A). (Refer to...) Figure 2 The gear system 2 is used as the control gear of the vehicle. It has a gear mechanism 21 including a pinion as a driven gear 211 and a rack as a drive gear 212, and an electric motor as a drive source 22.

[0417] Reference Figure 1 and Figure 2 Driven gears 111, 211 and / or drive gears 112, 212 can be integrally formed on at least the outer peripheral surface of the metal mandrel. For example Figure 1 The driven gear 111 shown is assembled into the gear system 1 without the aid of a metal mandrel. Figure 2 The driven gear 211 shown is assembled into the gear system 2 in a shape integrally formed on the outer peripheral surface of a metal mandrel 23 mounted on the shaft 24. The metal mandrel can be made of stainless steel, iron, steel, aluminum, brass, titanium alloy, nickel alloy, copper alloy, aluminum alloy, stainless steel alloy, etc. The integration of the gear on at least the outer peripheral surface of the mandrel can be performed using methods known to those skilled in the art, preferably insert injection molding.

[0418] In a preferred embodiment, the gears constituting the gear system mesh with each other using grease. The use of grease significantly improves the durability and quietness of the gear system. Preferred greases are, for example, those illustrated above.

[0419] In one embodiment, the gear mechanism of the gear system is a rack-pinion mechanism consisting of a rack and pinion (e.g., as shown in the image). Figure 2 (as shown), or a worm gear mechanism consisting of a worm and a worm wheel (e.g., as shown). Figure 1 (As shown). Pinions and worm gears are usually cylindrical gears (such as...). Figure 1 and Figure 2 As shown in the driven gears 111 and 211, good mechanical strength, dimensional accuracy, and surface smoothness are particularly important for the gear system to have good sliding properties and durability. In one embodiment, from the perspective of obtaining high sliding properties and high durability, at least a pinion or worm gear is used as the gear.

[0420] In the pinion and worm gear, the ratio of the total tooth height (i.e., the distance between the tooth root and the tooth tip) to the tooth pitch (i.e., the interval between teeth) can be, for example, 1.0 to 20, or 1.5 to 15, or 2.0 to 13.

[0421] In the pinion and worm gear, the tooth pitch / tooth width (i.e., the axial length of the tooth) ratio can be, for example, 1.0 to 3.0, or 1.3 to 2.8, or 1.5 to 2.5.

[0422] In each gear of the pinion and worm gear, the pressure angle of the gear (i.e., the angle formed by the radius line of the gear and the tangent at the tooth profile at a point on the tooth surface) can be, for example, 10° to 30°, or 13° to 28°, or 15° to 25°.

[0423] In the case where the gear and the metal mandrel are integrated, the ratio of the outer diameter of the metal mandrel to the tip circle diameter of the gear can be, for example, 0.02 to 0.98, 0.1 to 0.9, or 0.3 to 0.7.

[0424] In the case where the gear and the metal mandrel are integrated, the ratio of the outer diameter of the metal mandrel to the root circle diameter of the gear can be, for example, 0.01 to 0.99, 0.1 to 0.9, or 0.3 to 0.7.

[0425] In the case where the gears of the pinion and worm gear are integrated with the metal mandrel, the ratio of the outer diameter of the metal mandrel to the pitch circle diameter of the gear can be, for example, 0.01 to 0.99, 0.1 to 0.9, or 0.3 to 0.7.

[0426] The torque applied to each gear of the pinion and worm gear can be, for example, 5 to 100 N·m, 8 to 50 N·m, or 15 to 30 N·m.

[0427] <<Applications of Gears and Gear Systems>>

[0428] The gears of this embodiment, in terms of significantly superior durability compared to existing gears and the ability to further maintain quiet operation in one manner, can be applied to EPS systems, such as those in automobiles and electric vehicles. Examples of electric vehicles include, but are not limited to, four-wheeled vehicles for the elderly, motorcycles, and electric two-wheelers.

[0429] It should be noted that the gear of this embodiment has excellent sliding properties and durability, and therefore can also be used in, for example, cams, sliders, levers, arms, clutches, felt clutches, idler wheels, pulleys, rollers, rollers, key rods, keycaps, roller shutters, roller shafts, rotating shafts, joints, shafts, bearings, guide rails, resin parts molded on inserts, resin parts molded on inserts, chassis, trays, and side plates.

[0430] [Example]

[0431] The present invention is further illustrated by the embodiments, but the present invention is not limited to these embodiments.

[0432] <<Raw Materials and Evaluation Methods>>

[0433] The raw materials and evaluation methods used are described below.

[0434] <<(A) Thermoplastic Resin>>

[0435] Use the raw materials listed in Table 1 below.

[0436] [Table 1]

[0437]

[0438] <Molecular Weight Determination of Polyamide Resins>

[0439] The molecular weight of polyamide resins was determined by GPC (gel permeation chromatography) under the following conditions. Apparatus: Eco Sec, manufactured by Tosoh Corporation.

[0440] Column: TSKgel Super GMH-M 2 columns, TSKgel Super G1000H

[0441] Oven: 40℃

[0442] Eluent: HFIP (TFANa 4.848 g / kg)

[0443] Flow rate: Sample: 0.5 mL / min, Reference: 0.25 mL / min

[0444] Sample volume: 25 μl, 3 mg / ml

[0445] Detector: RI

[0446] Calibration curve: PMMA (polymethyl methacrylate)

[0447] <Molecular weight determination of polyacetal resins>

[0448] The molecular weight of polyacetal resin was determined using GPC under the following conditions.

[0449] Device: Eco Sec manufactured by Tosoh Corporation

[0450] Column: TSKgel Super GMH-M 2 columns, TSKgel Super G1000H

[0451] Oven: 40℃

[0452] Elution buffer: HFIP

[0453] Flow rate: Sample: 0.5 mL / min, Reference: 0.25 mL / min

[0454] Sample volume: 25 μl, 3 mg / ml

[0455] Detector: RI

[0456] Calibration curve: PMMA (polymethyl methacrylate)

[0457] <<(B) Cellulose nanofibers with an average fiber diameter of less than 1000 nm>>

[0458] (b-1)CNF-1

[0459] After cutting the short-fiber pulp, it is heated in hot water at above 120°C for 3 hours using an autoclave. The refined pulp, after removing the hemicellulose, is pressed and then pulped in pure water at a solid content of 1.5% by mass, thereby achieving high short fiberization and fibrillation. Then, at this concentration, it is opened using a high-pressure homogenizer (operating pressure: 85 MPa, 10 cycles) to obtain open-fiber cellulose. Here, in the pulping process, a disc mill is used, and after 2.5 hours of processing with a high-cutting pulping blade (hereinafter referred to as the cutter), a further 2 hours of pulping is performed using a high-opening pulping blade (hereinafter referred to as the opener) to obtain CNF-1.

[0460] (b-2)CNF-2

[0461] CNF-2 was obtained using the method described in Example 1 of International Publication No. 2017 / 159823

[0108] .

[0462] (b-3)CNF-3

[0463] After cutting the short-fiber pulp, it is heated in hot water at above 120°C for 3 hours using an autoclave. The refined pulp, after removing the hemicellulose, is pressed and then pulped in pure water at a solid content of 1.5% by weight, thereby achieving high short fiberization and fibrillation. Then, at this concentration, it is opened using a high-pressure homogenizer (operating pressure: 85 MPa, 10 times) to obtain open-fiber cellulose. Here, in the pulping process, a disc mill is used, and after 4 hours of processing with a high-cutting pulping blade (hereinafter referred to as a cutter), a further 4 hours of pulping is performed using a high-opening pulping blade (hereinafter referred to as an opener) to obtain CNF-3.

[0464] <(B) Degree of polymerization of cellulose nanofibers>

[0465] The determination was performed using the reduction viscosity method based on copper ethylenediamine solution as specified in the crystalline cellulose confirmation test (3) of the 14th edition of the Japanese Pharmacopoeia (published by Hirokawa Shoten).

[0466] <(B) Crystallization morphology and crystallinity of cellulose nanofibers>

[0467] X-ray diffraction patterns (at room temperature) were determined using the powder method with an X-ray diffraction apparatus (manufactured by Rigaku Corporation, multi-purpose X-ray diffraction apparatus), and the crystallinity was calculated using the Segal method. Furthermore, the crystal morphology was also determined based on the obtained X-ray diffraction patterns.

[0468] <(B) L / D of cellulose nanofibers>

[0469] (B) Cellulose nanofibers were prepared into a pure water suspension at a concentration of 1% by mass. The aqueous dispersion, which was dispersed using a high-shear homogenizer (manufactured by Nippon Seiki Co., Ltd., trade name "EXCEL AUTO HOMOGENIZER ED-7", processing conditions: 15,000 rpm × 5 minutes), was diluted with pure water to a concentration of 0.1-0.5% by mass and poured onto mica. The mica was then air-dried. The ratio (L / D) of the major axis (L) to the minor axis (D) of the particle image obtained by atomic force microscopy (AFM) was calculated as the average value of 100-150 particles.

[0470] <(B) Average fiber diameter of cellulose nanofibers>

[0471] (B) Cellulose nanofibers, with a solid content of 40% by mass, were mixed at 126 rpm for 30 minutes at room temperature and atmospheric pressure in a planetary mixer (manufactured by Shinagawa Kogyo Co., Ltd., trade name "5DM-03-R", with hook-shaped stirring blades). A pure water suspension was then prepared with a solid content of 0.5% by mass. This suspension was dispersed using a high-shear homogenizer (manufactured by Nippon Seiki Co., Ltd., trade name "EXCEL AUTO HOMOGENIZER ED-7", processing conditions: 15,000 rpm × 5 minutes). The mixture was then centrifuged (manufactured by Kubota Corporation, trade name "6800 type centrifuge", Rotor Type RA-400, processing conditions: centrifugal force 39200 m... 2 Centrifuge at 116000 m³ / s for 10 minutes, collect the supernatant, and further centrifuge the supernatant at 116000 m³ / s. 2 Centrifuge for 45 minutes ( / s). Using the supernatant after centrifugation, measure the integral 50% particle size (volume average particle size) of the volume frequency particle size distribution obtained by laser diffraction / scattering particle size analyzer (manufactured by Horiba Manufacturing Co., Ltd., trade name "LA-910", ultrasonic treatment for 1 minute, refractive index 1.20), and take this value as the average fiber diameter.

[0472] <Evaluation of the degree of chemical modification (DS average degree of substitution)>

[0473] Regarding the degree of chemical modification of (B) cellulose nanofibers, the cellulose nanofibers were dried and prepared into porous sheets. The infrared spectra of the porous sheets based on the ATR-IR method were measured using a Fourier transform infrared spectrophotometer (JASCO FT / IR-6200) for evaluation. The infrared spectrophotometric measurements were performed under the following conditions.

[0474] (Determination conditions for infrared spectrophotometry)

[0475] Points earned: 64 times

[0476] Wavenumber resolution: 4cm -1 ,

[0477] Wavenumber range for measurement: 4000–600 cm⁻¹ -1 ,

[0478] ATR crystals: diamond,

[0479] Angle of incidence: 45°

[0480] The IR index is calculated according to the obtained IR spectrum using the following formula (5).

[0481] IR index = H1730 / H1030···(5)

[0482] In equation (5), H1730 and H1030 are 1730 cm. -1 1030cm -1 The absorbance at the absorption band of the CO stretching vibration of the cellulose backbone chain. This refers to the absorbance at a distance of 1900 cm⁻¹. -1 and 1500cm -1 The line and the connection 800cm -1 and 1500cm -1 The line is taken as the baseline, and the absorbance at which the absorbance is 0 is set.

[0483] Next, the average degree of substitution (DS) is calculated according to the IR index using the following formula (6).

[0484] DS = 4.13 × IR index ... (6)

[0485] [Table 2]

[0486]

[0487] <<(C) Surface Treatment Agent>>

[0488] (c-1) In a 2L autoclave, 47 parts by mass of polyethylene oxide (Mn1000) and 0.6 parts by mass of KOH as a catalyst were added. After nitrogen purging, 100 parts by mass of polypropylene oxide (Mn1050) were added sequentially over 4 hours at 160℃. After the reaction was completed, it was neutralized with 1.2 parts by mass of lactic acid to obtain c-1. The obtained c-1 has Mn3100, a cloud point of 55℃, and an HLB of 6.5.

[0489] (c-2) Blaunon RCW-20 manufactured by Aoki Oils & Fats Co., Ltd. (CAS No. 61788-85-0, static surface tension 42.4 mN / m, dynamic surface tension 52.9 mN / m)

[0490] Boiling point is greater than 100℃ under normal pressure.

[0491] (c-3) Superflux 300 manufactured by Daiichi Kogyo Co., Ltd.

[0492] (c-4) PEG20000 manufactured by Sanyo Chemical Co., Ltd.

[0493] <(C) Determination of molecular weight of surface treatment agents>

[0494] The molecular weight of the surface treatment agent was determined by HPLC (high performance liquid chromatography) under the following conditions.

[0495] [HPLC determination]

[0496] Device Name: HP-1260 (Manufactured by Agilent Technologies, Inc.)

[0497] Column: TSKgel ODS-80Ts (manufactured by Tosoh Corporation)

[0498] Mobile phase: Solvent gradient based on water / acetonitrile mobile phase

[0499] Detector: Evaporative Light Scattering Detector (ELSD)

[0500] Measurement temperature: 40℃

[0501] Flow rate: 1 mL / min

[0502] Sample concentration: 1 mg / mL

[0503] Injection volume: 10 μL

[0504] <(C) Cloud point of surface treatment agent>

[0505] For substances that are solid at room temperature, heating them above their melting point causes them to melt, which then dissolves in water to form a sample.

[0506] Device Name: SV-10A, manufactured by A&D Corporation

[0507] Measured concentrations: 0.5% by mass, 1.0% by mass, 5% by mass

[0508] Measurement temperature: 0~90℃

[0509] For samples that did not show a cloud point using the above method, they were sealed in a glass container that allowed for visualization. The temperature was then increased, and the point where the precipitated aqueous solution fogged up was visually confirmed, and the cloud point was measured.

[0510] <(C) HLB value of surface treatment agent>

[0511] For (c-1), the HLB value is determined using the Griffin method according to the following formula.

[0512] HLB value = 20 × (total formula weight of hydrophilic groups / molecular weight)

[0513] (In the formula, the formula weight of the hydrophilic group is the formula weight of the polyoxyethylene segment.)

[0514] <(C) Determination of Static Surface Tension of Surface Treatment Agents>

[0515] Using various surface treatment agents, the static surface tension was measured by the Wilhelmy method using an automatic surface tension measuring device (manufactured by Kyowa Interface Science Co., Ltd., trade name "CBVP-Z type", with an accompanying glass tank). The surface treatment agents used in the examples and comparative examples are liquids at room temperature. Therefore, they were added to the stainless steel dish provided with the device at a height of 7mm to 9mm from the bottom to the liquid surface. After the temperature was adjusted to 25℃±1℃, the measurement was performed, and the static surface tension was calculated using the following formula: γ=(P-mg+shρg) / Lcosθ. Here, P: balancing force, m: mass of the plate, g: gravitational constant, L: perimeter of the plate, θ: contact angle between the plate and the liquid, s: cross-sectional area of ​​the plate, h: depth of sinking from the liquid surface (until the force reaches equilibrium), ρ: density of the liquid (the density of the surface treatment agents used in the examples and comparative examples is 1±0.4g / mL, therefore 1 is used).

[0516] For samples that are solid at room temperature, heat them above their melting point to melt them, then adjust the temperature to 5°C above the melting point, and use the Wilhelmy method described above to determine the surface tension.

[0517] <(C) Determination of dynamic surface tension of surface treatment agents>

[0518] Using various surface treatment agents, a dynamic surface tension meter (SITAScience t-60 model, manufactured by Eiko Seiki Co., Ltd.) with a probe (capillary TYPE I (peak resin), single-mode) was used to measure the dynamic surface tension by employing the maximum bubble pressure method to achieve a bubble generation cycle of 10 Hz. The surface treatment agents used in the examples and comparative examples were dissolved or dispersed at 5% by mass in ion-exchanged water to prepare the test solution. 100 mL of this solution or dispersion was added to a 100 mL glass beaker, and the temperature was adjusted to 25°C ± 1°C before using the measured values. The dynamic surface tension was calculated using the following formula: σ = ΔP·r / 2. Here, σ: dynamic surface tension, ΔP: pressure difference (maximum pressure - minimum pressure), and r: capillary radius.

[0519] <<(D) Metal Ion Composition>>

[0520] (d-1) Copper iodide (I) is a commercially available product manufactured by Guangquan Pharmaceutical Industry under the name Copper iodide (I).

[0521] (d-2) Potassium iodide, a pharmaceutically manufactured product, is known as potassium iodide.

[0522] (d-3) Calcium stearate, manufactured by Sakai Chemical Industry Co., Ltd., trade name: Calcium stearate

[0523] <<(E) Lubricant Components>>

[0524] (e-1) Wax manufactured by Baker Petrolite, trade name Unicid 700 (melting point 110℃)

[0525] (e-2) Ethylene bis-stearamide (LION), trade name Armowax EBS (melting point 145℃)

[0526] <<(F) Glass Fiber>>

[0527] Use the raw materials listed in Table 3 below.

[0528] [Table 3]

[0529]

[0530] <<Manufacturing Conditions>>

[0531] Using a twin-screw extruder (TOSHIBA MACHINE CO.,LTD TEM-26SS extruder (L / D=48, with vent), the barrel temperature was set to 260℃ (polyamide 6), 290℃ (polyamide 66), and 200℃ (polyoxymethylene materials). Components (A), (B), and (when in use) (C) and / or (D) were mixed uniformly and fed through a metering feeder in the main duct of the extruder. The resin compound was extruded in filament form at an extrusion rate of 15 kg / h and a screw speed of 250 rpm. The filament was then rapidly cooled in a filament bath and cut into granules using a filament pelletizer to obtain a resin composition in granular form.

[0532] <<Molding Conditions - Multipurpose Test Pieces>>

[0533] Using an injection molding machine, a multipurpose test piece according to ISO 294-3 is formed from a resin composition in granular shape obtained under the above manufacturing conditions.

[0534] Polyamide-based materials: in accordance with JIS K6920-2 conditions

[0535] Polyoxymethylene (POM) materials: in accordance with JIS K7364-2 conditions

[0536] It should be noted that because polyamide materials can change due to moisture absorption, they should be stored in an aluminum moisture-proof bag immediately after molding to inhibit moisture absorption.

[0537] <<Evaluation Criteria - Multi-purpose Test Pieces>>

[0538] For the multipurpose test pieces obtained in the above <<Molding Conditions - Multipurpose Test Pieces>>, the tensile yield strength and tensile elongation at break are determined according to ISO 527, and the flexural modulus and flexural strength are determined according to ISO 179.

[0539] <<Aging Test>>

[0540] Exposure tests were conducted on multipurpose test pieces using Espec GPH-102 at 150°C. The exposed samples were stored in aluminum bags, and tensile yield strength was determined according to ISO 527. Regarding the strength retention rate, the number of days the tensile yield strength was retained at 80% was evaluated, using the multipurpose test piece with 0 days of exposure as a baseline (100%).

[0541] <<Thixotropic Index>>

[0542] For the multi-purpose test piece obtained in the above <<Molding Conditions·Multi-purpose Test Piece>>, the viscoelasticity during melting was measured under the following test conditions.

[0543] Device name: ARES G2 Japan TA Instruments Co., Ltd.

[0544] Measurement temperature: Melting point of each resin +25℃ (e.g., 250℃ for PA6).

[0545] Shearing speed: 1.0~40s -1

[0546] Measurements were taken using 25mm / 40mm parallel plates with a gap of 1mm.

[0547] The thixotropic index is calculated based on the measurement results at this time according to the following formula (7).

[0548] Thixotropic index = (shear velocity 1s) -1 Viscosity / shear rate at 10s -1 (viscosity at time)···(7)

[0549] The higher the value, the higher the thixotropy.

[0550] <<Coefficient of friction, wear amount>>

[0551] For the multi-purpose test pieces obtained in the above-mentioned <<Molding Conditions - Multi-purpose Test Pieces>>, a sliding test was conducted using a reciprocating friction and wear testing machine (AFT-15MS type, manufactured by Toyo Seiki Co., Ltd.) and SUS304 test pieces (5mm diameter balls) as the test material, under the conditions of a linear speed of 50mm / s, a reciprocating distance of 50mm, a temperature of 23°C, and a humidity of 50%. The coefficient of friction was the value at the end of the test under the following conditions. Furthermore, regarding the amount of wear, the amount of wear (wear cross-sectional area) of the samples after the sliding test was measured using a confocal microscope (OPTELICS H1200, manufactured by Lasertec Co., Ltd.). The wear cross-sectional area was the average of the values ​​measured at n=4, rounded to one decimal place. The measurement site was 12.5mm from the edge of the wear mark, and measurements were taken at equal intervals. A low value for the wear cross-sectional area was considered to indicate excellent wear characteristics.

[0552] Test conditions: Load 19.6 N (Example I), 9.8 N (Example II), 10,000 cycles

[0553] <<Coefficient of Linear Expansion>>

[0554] The multipurpose test piece obtained from the above-mentioned molding conditions for multipurpose test pieces was cut into a rectangular sample with a length of 4 mm, width of 4 mm, and length of 10 mm using a precision cutting saw. The sample was measured in accordance with ISO 11359-2 within the temperature range of -10 to 80℃, and the coefficient of thermal expansion between 0℃ and 60℃ was calculated.

[0555] <<Friction coefficient ratio>>

[0556] Based on the friction coefficient obtained from the above-mentioned measurement of <<friction coefficient and wear amount>>, the friction coefficient ratio is calculated according to the following formula (8).

[0557] Friction coefficient ratio = reinforced resin composition / unreinforced resin composition ... (8)

[0558] (In the formula, the reinforcing resin composition is the resin composition containing glass fiber or cellulose nanofiber prepared in the examples or comparative examples, and the non-reinforcing resin composition is the comparative composition, which is a composition with the same composition as the above-mentioned reinforcing resin composition except that it does not contain glass fiber or cellulose nanofiber.)

[0559] For example, if the coefficient of friction of the unreinforced resin composition of Comparative Example 4 (using 1022B as the thermoplastic resin) is 0.65 and the coefficient of friction of the CNF-reinforced resin composition of Example 3 (using 1022B as the thermoplastic resin) is 0.15, then according to the above formula (8),

[0560] The friction coefficient ratio = 0.15 / 0.65 = 0.23

[0561] It can be seen that adding CNF significantly reduces the coefficient of friction.

[0562] The lower the coefficient of friction ratio, the greater the reduction in the coefficient of friction, indicating that the molded body has excellent sliding properties.

[0563] <<Changes in Absorbent Size>>

[0564] For the multi-purpose test pieces obtained in the above-mentioned <<Molding Conditions - Multi-purpose Test Pieces>>, after bringing them to equilibrium (exposed to hot water at 80°C for 24 hours, and then kept at 80°C and 57% relative humidity for 120 hours), the outer diameter dimensions before and after water absorption were measured using digital precision vernier calipers manufactured by Mitutoyo Co., Ltd., and the equilibrium water absorption dimension change (%) was calculated as: (Dimension after water absorption) / (Dimension before water absorption) × 100. "Before water absorption" refers to the state where the newly molded multi-purpose test piece was stored in an aluminum bag and allowed to return to room temperature.

[0565] <<Injection Molding Gear Molding>>

[0566] Regarding Example I, an injection molding machine (trade name "α50i-A injection molding machine") manufactured by Fanuc Co., Ltd. was used. The barrel temperature was set at 260°C (polyamide 6-based material), 290°C (polyamide 66-based material), and 200°C (polyoxymethylene-based material). The resin composition in granular shape obtained under the above manufacturing conditions was injection molded under the following injection conditions: mold temperature 80°C, maximum injection pressure 120 MPa, injection time 10 seconds, and cooling time 60 seconds. This resulted in a worm gear with a module of 3.0, 50 teeth, a tooth thickness of 5 mm, and a tooth width of 15 mm. It should be noted that because polyamide-based materials are susceptible to moisture absorption, they were immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption.

[0567] <<Continuous Molding Capabilities of Injection Molded Gears>>

[0568] Regarding Example I, select any 10 gears obtained under the same molding conditions as described above for <<Injection Molding Gear Molding>>, and measure the tip circle diameter of each gear (at 25 locations). Calculate the average value of the tip circle diameter at the 25 locations for a single gear, and calculate the variation in the 10 consecutively molded gears.

[0569] Advantage: The variation is less than 100μm, indicating excellent continuous molding performance.

[0570] Good: Variation greater than 100μm but less than 150μm is judged as good continuous molding performance.

[0571] Acceptable: Variation greater than 150μm but less than 200μm is judged as poor continuous molding performance.

[0572] Defect: Variation greater than 200μm is judged as poor continuous molding performance.

[0573] <<Round Bar Forming and Gear Forming>>

[0574] Regarding Example I, the granular resin composition obtained under the above manufacturing conditions is fed into a traction device and a 30mm single-screw curing extruder with a water-cooling zone at the extruder die head. The barrel temperature is set to 280°C (polyamide 6 series materials), 320°C (polyamide 66 series materials), and 230°C (polyoxymethylene series materials), and a 90mm diameter round bar is extruded. At this time, to suppress shrinkage of the extruded body and the formation of micropores, the traction device is driven towards the die head at an extrusion speed of 3mm / min. The resulting round bar is cut and molded into a gear in the same manner as in <<Molding Conditions - Injection Molding Gears>>. It should be noted that since polyamide materials change due to moisture absorption, they are immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption.

[0575] <<Forming Conditions - Gear Forming A>>

[0576] Regarding Example II, an injection molding machine (trade name "α50i-A injection molding machine") manufactured by Fanuc Co., Ltd. was used. The barrel temperature was set at 250°C (for polyamide-based materials) and 190°C (for polyoxymethylene-based materials). The resin composition in granular shape obtained under the above manufacturing conditions was injection molded under the following conditions: mold temperature 80°C, injection pressure 120 MPa, injection time 10 seconds, and cooling time 60 seconds. This resulted in a flat gear with a module of 0.8, 50 teeth, and a tooth width of 5 mm. It should be noted that since polyamide-based materials are susceptible to moisture absorption, they were immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption. Two types of mold surfaces were used: mirror finish and embossed finish. The arithmetic mean surface roughness Ra of the mirror-finished mold surface was 0.03, and the arithmetic mean surface roughness Ra of the embossed mold surface was 2.0.

[0577] <<Forming Conditions - Gear Forming B>>

[0578] Regarding Example II, an injection molding machine (trade name "α50i-A injection molding machine") manufactured by Fanuc Co., Ltd. was used. The barrel temperature was set at 250°C (for polyamide-based materials) and 190°C (for polyoxymethylene-based materials). The resin composition in granular shape obtained under the above manufacturing conditions was injection molded at a mold temperature of 80°C, an injection pressure of 120 MPa, an injection time of 10 seconds, and a cooling time of 60 seconds, resulting in a flat gear with a module of 0.8, 50 teeth, and a tooth width of 12 mm. It should be noted that since polyamide-based materials are susceptible to moisture absorption, they were immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption. Two types of mold surfaces were used: mirror finish and embossed finish. The arithmetic mean surface roughness Ra of the mirror-finished mold surface was 0.03, and the arithmetic mean surface roughness Ra of the embossed mold surface was 2.0.

[0579] <<Forming Conditions - Gear Forming C>>

[0580] Regarding Example II, an injection molding machine (trade name "α50i-A injection molding machine") manufactured by Fanuc Co., Ltd. was used. The barrel temperature was set at 250°C (for polyamide-based materials) and 190°C (for polyoxymethylene-based materials). The resin composition in granular shape obtained under the above manufacturing conditions was injection molded under the following conditions: mold temperature 80°C, injection pressure 120 MPa, injection time 10 seconds, and cooling time 60 seconds. This resulted in a flat gear with a module of 1.5, 50 teeth, and a tooth width of 12 mm. It should be noted that since polyamide-based materials are susceptible to moisture absorption, they were immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption. Two types of mold surfaces were used: mirror finish and embossed finish. The arithmetic mean surface roughness Ra of the mirror-finished mold surface was 0.03, and the arithmetic mean surface roughness Ra of the embossed mold surface was 2.0.

[0581] Annealing Treatment

[0582] Using GPH-102 manufactured by Espec Corporation, for the flat gears obtained in the above-mentioned <<Injection Molding Gear Molding>>, <<Round Bar Molding Gear Molding>> (Example I), or <<Molding Condition·Gear Molding A>>, <<Molding Condition·Gear Molding B>>, <<Molding Condition·Gear Molding C>> (Example II), the polyamide-based materials were subjected to heat treatment at 130°C for 1 hour (Condition A), and the polyoxymethylene-based materials were subjected to heat treatment at 140°C for 5 hours (Condition B).

[0583] <<Arithmetic Mean Surface Roughness Sa of Gear Sliding Surface>>

[0584] Using a spur gear (Example I) that has undergone annealing after injection molding or round bar molding, or a spur gear obtained under molding conditions A, B, or C, or a spur gear annealed using the aforementioned annealing treatment (Example II), five teeth are cut from one spur gear. The surface roughness (arithmetic mean surface roughness Sa) of a 100 μm square area at the center of the in-plane direction of each tooth surface is measured according to ISO 25178. Furthermore, the mean value is calculated using the measured Sa of the five teeth (i.e., n=5 measurements for each spur gear and n=1 measurements for each tooth). The surface roughness is then measured using a confocal microscope (OPTELICS H1200, manufactured by Lasertec Co., Ltd.).

[0585] <<Determination of the roundness of gears>>

[0586] The roundness of the flat gears that underwent annealing after injection molding and round bar molding were measured under the following conditions.

[0587] The outer circumference shape of the formed gear was measured using a roundness cylindrical shape measuring machine (Mitutoyo Corporation: Round Test RA-400). The LSC method (which uses the least squares circle method, where the difference in radius between the outer and inner circles concentrically inscribed with the circle whose deviation is minimized) was employed, with the error expressed in μm. The total tooth pitch error (μm) of the gear was taken as the roundness. The smaller this value, the higher the roundness.

[0588] <<Gear Durability Testing>>

[0589] Regarding Example I, for the worm gears obtained in the above-mentioned <<Injection Molding Gear Molding>> and <<Round Bar Molding Gear Molding>>, the worm and the resin-made worm gear assembly were placed in a gear durability testing machine manufactured by TOSHIBA MACHINE CO.,LTD. The driving side was the worm gear, and the driven side was the worm. Furthermore, grease (Multemp CPL manufactured by Kyodo Yushi Co., Ltd.) was applied to the meshing parts, and the machine was rotated by hand to allow the grease to penetrate into the worm and worm gear assembly. Next, the driving side gear was rotated under the following conditions, and the time until gear failure (durability time) was measured.

[0590] Durability test: temperature 23℃, humidity 50%, torque 25N / m, rotation speed 30rpm

[0591] After one rotation each for the outbound and return journeys, there is a 10-second interval before rotating in the opposite direction.

[0592] Lubricating Grease: Multemp CPL

[0593] Base oil (ester-based synthetic oil) 60-70% by mass

[0594] Thickener (urea derivative) 10-20% by mass

[0595] Extreme pressure agent (polytetrafluoroethylene) 15-25% by mass

[0596] Other (antioxidants) less than 5% by weight

[0597] Regarding Example II, for the spur gears obtained under the above-mentioned molding conditions A, B, and C, gears made of the same material were coupled together and placed in a gear durability testing machine manufactured by TOSHIBAMACHINE CO.,LTD. One gear was positioned as the driving side and the other as the driven side. Then, the driving gear was rotated under the following conditions, and the time until gear failure (durability time) was measured.

[0598] Durability Test A: Torque 5 N / m, Speed ​​1000 rpm

[0599] Durability Test B: Torque 5 N / m, Speed ​​2000 rpm

[0600] Durability Test C: Torque 15 N / m, Speed ​​1000 rpm

[0601] Durability Test D: Torque 20 N / m, Speed ​​1000 rpm

[0602] In addition, in durability test A, the change in water absorption size is measured in the same way as in the above-mentioned <<Change in water absorption size>>.

[0603] <<Evaluation of Quietness>>

[0604] Regarding Example II, noise reduction is evaluated in the <<Gear Durability Test>>. A microphone is placed 50 mm from the shaft of the gear on the drive side. Sixty minutes after the start of the gear durability test, the noise level is measured for one minute using a noise meter (according to JIS C1502), and evaluated according to the following criteria.

[0605] Advantage: Maximum noise level less than 70dB

[0606] Good: Maximum noise level is above 70dB and below 75dB

[0607] Acceptable: Maximum noise level is 75dB or higher but less than 85dB

[0608] Undesirable: Maximum noise level above 85dB

[0609] <<Molding Conditions: Round Bar Gear Molding>>

[0610] Regarding Example II, the granular resin composition obtained under the above manufacturing conditions is fed into a traction device and a 30mm single-screw curing extruder with a water-cooling zone at the extruder die head. The barrel temperature is set to 280°C (for polyamide-based materials) and 230°C (for polyoxymethylene-based materials), and a 60mm diameter round bar is extruded. At this time, to suppress shrinkage of the extruded body and the formation of micropores, the traction device is driven towards the die head at an extrusion speed of 3mm / min. The resulting round bar is cut and formed into a gear in the same manner as in <<Molding Conditions - Gear Forming A>>. It should be noted that since polyamide-based materials change due to moisture absorption, they are immediately stored in an aluminum moisture-proof bag after molding to suppress moisture absorption.

[0611] <<Observations on Holes>>

[0612] Regarding Example II, the gears obtained in <<Molding Conditions - Gear Molding A>> were made into injection-molded gears, and the gears obtained in <<Molding Conditions - Round Bar Gear Molding>> were made into round bar-cut gears. Each gear was cut in half along the direction perpendicular to the teeth, and the cross-sections were observed to confirm the presence or absence of micropores. A confocal microscope (OPTELICS (registered trademark) H1200, manufactured by Lasertec Co., Ltd.) was used for observation. Regarding the observed micropores, the size of the region where the pore was formed was measured and expressed as the numerical value of the diameter of the equivalent circle of the region. The maximum value of the observed pores was recorded.

[0613] [Example I]

[0614] (Examples 1-9 and Comparative Examples 1-12)

[0615] Resin compositions were obtained using the methods described above under the manufacturing conditions. These compositions were then molded and evaluated according to the evaluation methods described above. The results are recorded in Tables 4 and 5.

[0616] In addition, the molded articles obtained in Examples 5-1 and 6-1 were kept at 150°C under flowing N2 for 72 hours. After 72 hours, heating was stopped, and the articles were allowed to cool naturally to room temperature. They were then evaluated according to the evaluation method described above.

[0617]

[0618]

[0619] As shown in Tables 4 and 5, the gears of the present invention exhibit high flexural strength and flexural modulus, as well as a low coefficient of friction. Furthermore, the coefficient of friction of the CNF-reinforced molded body is lower than that of the glass-reinforced molded body, demonstrating excellent sliding properties. In particular, the gears of the present invention exhibit high durability as injection-molded gears and round bar-cut gears, showing equal or superior durability compared to glass-reinforced gears.

[0620] [Example II]

[0621] (Examples 1-13 and Comparative Examples 1-4)

[0622] Polyamide resin compositions were obtained using the methods described in Tables 6 and 7. These compositions were then molded and evaluated according to the evaluation methods described above. The results are recorded in Tables 6 and 7.

[0623]

[0624]

[0625] (Examples 14-17 and Comparative Examples 5-8)

[0626] Polyacetal-based resin compositions were obtained using the methods described in Table 8. These compositions were then molded and evaluated according to the evaluation methods described above. The results are recorded in Table 8.

[0627]

[0628] Industrial applicability

[0629] In one embodiment, the gear of the present invention is particularly useful in fields such as automotive components where excellent continuous formability, high slippage, and high durability are required for practical application. In another embodiment, the gear of the present invention is useful in fields of automotive components where durability and quiet operation are particularly important.

Claims

1. A method for manufacturing a resin molded body, the resin molded body being composed of a resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A). The method includes the step of injection molding the resin composition at a temperature where the resin composition exhibits thixotropy.

2. A method for manufacturing a resin molded body, the resin molded body being composed of a resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The resin molded body has a sliding surface with other components. The method includes the step of molding the resin composition. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A). The arithmetic mean surface roughness Sa of the sliding surfaces of the resin molded body and other components is less than 3.0 μm.

3. The method as described in claim 1 or 2, wherein, The resin molded body is a gear, and the gear has a roundness of less than 400 μm.

4. A method for manufacturing a resin molded body, the resin molded body being composed of a resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The method includes the step of molding the resin composition. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A). The resin molded body has a sphericity of less than 400 μm.

5. The method as described in claim 2 or 4, wherein, The molding is performed by injection molding.

6. The method of claim 5, wherein, The injection molding is performed at a temperature at which the resin composition exhibits thixotropic properties.

7. The method as described in claim 1, 2, or 4, wherein, The resin molded body is a gear.

8. The method as described in claim 1, 2, or 4, wherein, The thixotropic index is 2.56 to 10.

9. A resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of 1000 nm or less for injection molding. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A).

10. The resin composition of claim 9, wherein, The thixotropic index is 2.56 to 10.

11. A method for manufacturing a resin molded article, wherein the resin molded article is not a granule, but is composed of a resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A). The method includes the step of extruding the resin composition at a temperature where the resin composition exhibits thixotropy.

12. The method of claim 11, wherein, The extrusion molding is a round bar extrusion molding.

13. The method of claim 12, wherein, The method further includes a step of machining the round bar obtained by extrusion molding.

14. A method for manufacturing a resin molded article, wherein the resin molded article is not a granule, but is composed of a resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The method includes the step of extruding the resin composition. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A). The resin molded body has a sphericity of less than 400 μm.

15. The method of claim 14, wherein, The extrusion molding is performed at a temperature at which the resin composition exhibits thixotropic properties.

16. The method according to any one of claims 11 to 15, wherein, The resin molded body is a gear.

17. The method according to any one of claims 11 to 15, wherein, The thixotropic index is 2.93 to 10.

18. A resin composition comprising 45% to 95% by mass of (A) a thermoplastic resin and 5% to 50% by mass of (B) cellulose nanofibers with an average fiber diameter of less than 1000 nm, for extrusion molding, and not used for manufacturing granules. The thermoplastic resin (A) comprises one or more resins selected from the group consisting of polyamide resins and polyacetal resins. The resin composition has a thixotropic index of 2 to 10 at a temperature 25°C higher than the melting point of the thermoplastic resin (A).

19. The resin composition of claim 18, wherein, The thixotropic index is 2.93 to 10.

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