Molded body for slide member and slide member

Abstract

To provide a low-friction sliding member made of cellulose nanofibers that can have a coefficient of friction equivalent to or even lower than a conventional sliding member derived from petroleum resources, in view of global trends in environmental issues, as an alternative to conventional plastic sliding members.SOLUTION: A low friction sliding member of the present invention is a molded body containing CNF or a molded body formed from a slurry containing CNF and a solid lubricant, and the molded body for a sliding member has a moisture content in the molded body of 20% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a molded article for a slide member and a slide member. [Background technology]

[0002] Generally, resins (plastics) are used for mechanical sliding parts such as sliding bearings and gears because of the need to reduce the weight of the components while maintaining the required sliding performance. Resins (plastics) that themselves have sliding properties such as low friction and wear resistance are preferred, and examples of such materials include polyamide and polyacetal. Among these, polyacetal (hereinafter sometimes referred to as POM) is known as a material that not only has high mechanical strength but also exhibits a low coefficient of friction of approximately 0.04 to 0.1.

[0003] On the other hand, as part of efforts to reduce the environmental burden, lactic acid polymers, which are produced by lactic acid fermentation of sugars obtained by decomposing carbohydrates contained in grains, beans, potatoes, etc., as raw materials, and plant-derived polyethylene resins, which are produced from ethylene extracted from bioethanol produced from raw materials such as corn, are attracting attention from the perspective of reducing petroleum consumption.

[0004] Patent Document 1 discloses a lubricating resin composition that can be used as a sliding part and has biodegradability. Furthermore, Patent Document 2 discloses a resin composition for sliding members, which is mainly composed of a plant-derived polyethylene resin and has excellent moldability and sliding properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-212400 [Patent Document 2] Patent Publication No. 2021-172705 [Non-patent literature]

[0006] [Non-Patent Document 1] Rice Straw Cellulose Nanofibrils via Aqueous Counter Collision and Differential Centrifugation and Their Self-Assembled Structures Summary of the Invention [Problem to be solved by the invention]

[0007] However, polylactic acid resin, which is the main component of the lubricating resin composition described in Patent Document 1, is known to be inferior in mechanical strength, friction and wear properties to engineering plastics such as polyacetal. Generally, the friction surface of a sliding member becomes hot due to frictional heat, so temperature characteristics such as "low thermal expansion coefficient" and "high melting point" are also important. Furthermore, the plant-derived polyethylene resin, which is the main component of the resin composition for vibration components described in Patent Document 2, is a homopolymer of plant-derived ethylene derived from bioethanol obtained from plants such as sugarcane and corn. However, since it is made from edible materials such as sugarcane and corn, there is a demand for the development of mechanical sliding components that can replace plastics using inedible materials.

[0008] In view of the global trend toward environmental issues, the present invention aims to provide, as an alternative to conventional plastic-based sliding members, a low-friction sliding member made of cellulose nanofibers (hereinafter also referred to as CNF) that has a friction coefficient equivalent to or even lower than that of conventional sliding members derived from petroleum resources. [Means for solving the problem]

[0009] As a result of intensive research conducted by the inventors to achieve the above-mentioned object, they found that by using a molded body containing cellulose nanofibers (hereinafter referred to as a molded body for sliding components), the molded body for sliding components and an impingement component formed therefrom exhibit excellent low-friction and wear-resistant properties when sliding against a mating component in the presence of a lubricating oil containing an oiliness improver.

[0010] That is, the present invention relates to a molded article for a sliding member that contains CNF and has a moisture content of 20% or less. [Effects of the Invention]

[0011] The low-friction sliding member of the present invention is an alternative to conventional plastic-based sliding members, and is made of cellulose nanofibers that have a friction coefficient equivalent to or even lower than that of conventional sliding members derived from petroleum resources. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a conceptual diagram of a molding apparatus for a sliding member according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a ball-on-disk test. [Figure 3] FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. [Figure 4] 1 is a photomicrograph showing the diameter of the friction mark. [Figure 5] FIG. 1 is a schematic diagram of a ring-on-disc test. [Figure 6] FIG. 10 is a diagram showing test results of friction coefficients by a ring-on-disk test. [Figure 7] FIG. 10 is another diagram showing test results of the friction coefficient by the ring-on-disk test. [Figure 8] These are the results of measurements using FT-IR. [Figure 9] FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. [Figure 10]FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. [Figure 11] FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. [Figure 12] FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. [Figure 13] FIG. 10 is a diagram showing test results of the coefficient of friction by a ball-on-disk test. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes in detail each of the embodiments according to the present invention. However, the following embodiments are intended to aid in understanding the invention and are not intended to limit the invention. (Definition of terms) The term "CNF" as used herein refers to cellulose fibers with an average thickness of 3 to 200 nm and an average length of 0.1 μm or more, and includes so-called single cellulose nanofibers with an average width of 3 to 4 nm, and single cellulose nanofiber aggregates with an average width of 10 to 200 nm, which are formed by the aggregation of several single cellulose nanofibers into multiple layers. In addition, there are cellulose fibers that are not branched in the longitudinal direction, as well as those that are branched. In this specification, the term "gas permeable means" is used in a broad sense to include not only means for allowing the permeation of a gas resulting from the evaporation of a solvent, but also means for absorbing or adsorbing this gas and / or means for allowing the solvent to permeate, pass through, or absorb or adsorb the solvent in the liquid stage before it becomes a gas. In this specification, the term "first molded body" refers to a molded body obtained by the molding step of the present invention, and the solid content of the molded body is about 10 to 25%.

[0014] (Method of manufacturing a molded body for a sliding member) The compact for a sliding member according to the present invention can be obtained by molding a slurry containing CNF or a slurry containing CNF and a solid lubricant using a molding apparatus for a sliding member, which will be described later. The method for producing a molded article for a sliding member according to the present invention includes (1) a molding step, and (2) a solvent removal step. It is preferable that the method further comprises (3) a suction step of suctioning gas from within the molding apparatus for a sliding member. Note that the manufacturing method according to the present invention may further include other steps in addition to the above steps. The manufacturing method according to the present invention will be described in detail below.

[0015] (Slurry containing CNF) The CNF-containing slurry used in the present invention (hereinafter sometimes referred to as CNF-containing slurry) can be a CNF dispersion, which is a CNF aqueous dispersion in which the solvent is water, or a CNF dispersion to which metal salts, pulp made from broadleaf wood, coniferous wood, or bamboo, or a crosslinking agent have been added. Furthermore, a slurry in which the water solvent is replaced with an organic solvent can also be used as the CNF-containing slurry. In addition, known materials such as thermosetting resins, polyamides, polyamines, epichlorohydrin-based materials, melamine-formaldehyde-based materials, carboxylic acid-based materials that undergo dehydration condensation with urea-formaldehyde-hydroxyl groups, wet strength agents, dry strength agents, waterproofing agents, sizing agents, etc. CNF dispersions will be discussed later.

[0016] (Slurry containing CNF and solid lubricant) The slurry containing CNF and solid lubricant used in the present invention (hereinafter also referred to as CNF-containing slurry, similar to the slurry containing the CNF) is prepared by adding solid lubricant particles to the slurry containing the CNF. The solid lubricant particles may be composed of, for example, molybdenum disulfide (MoS), boron nitride (BN), hexagonal boron nitride (h-BN), graphene, or other materials with a layered crystal structure, or polytetrafluoroethylene (PTFE). These may be used alone or in combination of two or more. The addition of solid lubricant particles can impart functions and properties such as thermal conductivity and electrical conductivity to the compact for sliding components. The concentration of solid lubricant particles in the slurry containing CNF should be in the range of 0.01 wt% to 10 wt%. If the concentration is less than 0.01 wt%, the effect of adding the solid lubricant particles will be reduced. On the other hand, if the concentration is more than 10 wt%, there is a concern that the physical properties of the compact for sliding member itself will be reduced.

[0017] The CNF concentration in the slurry containing CNF should be in the range of 0.1% to 18%. If it is less than 0.1%, a dense, homogeneous structure will be obtained, but the manufacturing time will be longer, resulting in increased costs. If it is 15% to 18%, the manufacturing time will be shorter, but some dents will be more likely to occur. Furthermore, if the CNF content is 18% or more, partial hydrogen bonding will occur, making it impossible to obtain a homogeneous molded body within the system, and the molded body will separate into multiple layers. Furthermore, the entanglement of the CNF fibers will be weak.

[0018] (CNF dispersion) Examples of CNF dispersions that can be used in the present invention include the method for producing fine fibers described in Japanese Patent No. 6867613, the method for preparing cellulose nanofibers and cellulose nanocrystal aqueous solutions using cellulose as a natural polymer described in Japanese Patent No. 6704551, and the method for producing fine fibers derived from other raw materials described in both publications.

[0019] These raw materials for the CNF dispersion may be used alone or in combination of two or more. Furthermore, it is preferable to use pulp with an α-cellulose content of 60% to 99% by mass as the raw polysaccharide. A purity of 60% or more by mass of α-cellulose makes it easy to adjust the fiber diameter and length, and provides higher thermal stability and better color suppression than when an α-cellulose content of less than 60% by mass is used. On the other hand, when an α-cellulose content of 99% or more by mass is used, it becomes difficult to defibrate the fibers to the nano-level.

[0020] The crystallinity of CNF is preferably 50 or more. The crystallinity can be measured by X-ray diffraction or the like, and if the crystallinity is less than 50, the properties such as rigidity, toughness, and high strength derived from natural cellulose crystals cannot be fully utilized, and the uniform dispersion and retention of the solid lubricant in the slurry are weakened.

[0021] The ACC method (underwater counter-impingement method) described in paragraph 0018 of Japanese Patent No. 6704551 allows for the production of CNFs with an average diameter of 3 to 200 nm and an average length of 0.1 μm or more. The average diameter and average fiber length are measured by observing and measuring the CNFs using an appropriate microscope, such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and then selecting 20 or more fibers from the resulting photographs and averaging them. Alternatively, a fluorescence microscope observation method utilizing fluorescence amplification may also be used. It is also possible to use modified CNFs obtained by covalently bonding the CNFs in the obtained CNF dispersion to oxygen atoms or carbon atoms in cellulose atoms using oleyl groups, alkyl groups, etc. By using modified CNF in this way, functional groups such as an oleyl layer can be produced from inside the sliding member on the sliding surface, resulting in a sliding member with low friction even when worn.

[0022] (Sliding component molding device) Fig. 1 is a cross-sectional view of a conceptual diagram of a molding apparatus for a sliding member according to one embodiment of the present invention. The molding apparatus for a sliding member 1 will be described below with reference to Fig. 1. The molding apparatus for a sliding member 1 comprises a first cylindrical portion 3 having a plurality of holes 2 at the top thereof, a second cylindrical portion 4 having a diameter slightly larger than that of the first cylindrical portion 3, and a lid portion 5 connected to the top of these. The first cylindrical portion 3 has a main body 6 and a base 8 having a support shaft 7 into which a bottom plate 10 can be fitted. A molding cavity 11 is formed inside the first cylindrical portion 3 by vertically fitting a pair of gas-permeable means, an upper plate 9 and a bottom plate 10. The upper plate 9 penetrates the lid portion 5 via a shaft 12, to which various presses (not shown) are attached. The lid portion 5 has a gas supply port 13 for supplying gas or steam to the main body 6. The lower plate 10 is fixed to the support shaft 7. The base 8 has a gas supply port 14 and a gas suction port 15. Sealing portions 16 are provided at the contact portions between the top plate 9, the bottom plate 10, and the base 8 and the main body 6. Although the main body 6 has been described herein as being cylindrical, other shapes are also possible. Also, slits or the like may be provided in the cylindrical portion 3 to promote the passage of the solvent. Furthermore, multiple porous mats may be installed to make the top and bottom surfaces of the cavity 11 flat. Furthermore, a heating mechanism may be provided externally, which has the effect of preventing localized over-drying by making the outside of the cavity 11 humid.

[0023] The gas supply ports 13 and 14 are connected to the gas supply pipes 18 and 17, respectively. Heating devices are arranged near the gas supply pipes 18 and 17. This arrangement makes it possible to supply heated gas to the main body 6. In this case, the molding speed can be increased. Furthermore, by installing a gas suction device 19 such as a vacuum pump at the gas suction port 15, the inside of the main body 6 can be reduced in pressure or placed in a vacuum state. Furthermore, the CNF-containing slurry can be introduced into the molding cavity 11 through the CNF-containing slurry introduction pipe 20. As an introduction means, an introduction nozzle may be provided on the first cylindrical portion 3, or on the lid portion 5. Without this nozzle, the volume of the obtained compact for a sliding member would be extremely small compared to the size of the molding cavity 11. However, by adding the CNF-containing slurry through the introduction nozzle, the volume of the obtained compact for a sliding member can be adjusted as desired. Backflow except during supply can be prevented by keeping the valve 24 closed. The water removed from the CNF-containing slurry is collected and stored in the drain reservoir 22, and can be discharged outside the system through the solvent discharge pipe 23. The presence of the drain reservoir 22 prevents liquid from being discharged from the gas suction port 15 to the vacuum pump, allowing stable production to continue without breakdowns.

[0024] According to the molding apparatus 1 for sliding members of this embodiment, when pressure is applied using various presses, the CNF-containing slurry can be pressed by the upper plate 9 toward the bottom plate 10. Various presses may be attached to the shaft 7 by penetrating the lower plate of the support shaft 7, and the bottom plate 10 may be pressed toward the upper plate 9. In this case, the weight of the liquid itself can be canceled out. Moreover, while maintaining the pressurized state, it is possible to supply heated gas to the inside of the main body 6 and / or to create a reduced pressure or vacuum state. Furthermore, the actual volume of the molding cavity 11 is calculated from the cross-sectional areas of the top plate 9 and the bottom plate 10 and the distance between them, and from this actual volume and the distance, etc., a relational equation can be derived from the volume of the first molding body described below and the corresponding moisture and distance, etc., and the volume and concentration can be converted from the distance value to the top of the base 8 measured using the distance measuring device 25.

[0025] (Gas permeable means) The gas permeable means can be a means for concentration using a vapor- or solvent-permeable material. Examples of vapor-permeable materials include woven fabrics, felt, various filters such as membrane filters and sintered filters, filter paper, materials with permeable mechanisms such as holes, stacked plates and rods, and aggregates of porous or fine particles (fine particles such as sand or silica that form a pseudo-porous structure). Using a hydrophilic substrate also facilitates desolvation. Furthermore, if the pore size of the gas permeable material is 1 μm or less, CNF leakage can be prevented. Furthermore, if a fibrous CNF mat is formed in the initial stage, CNF leakage can be prevented even with a pore size of 200 μm or more. These may be used alone or in combination. There are no limitations on the load applied to the CNF-containing slurry or the direction of steam permeation. Steam permeation is possible under vacuum or reduced pressure conditions, and the means for achieving this is not particularly limited.

[0026] As another example of the gas-permeable means, a porous body made of a porous material can also be used. The porous material can be organic, inorganic, metallic, or a composite thereof, specifically, a variety of materials such as stainless steel, SiC, ceramic, resin, rubber, glass, and paper. These materials may also be used in combination as needed. Regarding the average pore size, porosity, or mesh size of the porous body used, the average pore size can be 5 to 800 μm, the porosity can be 30 to 85%, or the mesh size can be 20 to 1000 μm. Preferably, the average pore size can be 5 to 600 μm, the porosity can be 40 to 70%, or the mesh size can be 200 to 800 μm. There are two types of porosity: (1) the sum of the volume of pores connected to the outside and the volume of pores enclosed inside, divided by the total volume (apparent volume); and (2) the volume of pores connected to the outside, divided by the total volume. In the present invention, either calculation method can be used, but pores connected to the outside are always necessary.

[0027] (molding process) (1) The molding process uses a gas permeable means, (1-1) Applying pressure to the CNF-containing slurry (1-2) A step of supplying heated gas to the molding apparatus for sliding members to obtain a first molded body. In the molding process, the solvent is removed from the CNF-containing slurry, and when the solid content in the first molded body reaches about 10 to 25%, the pressurization using the gas-permeable means is stopped and the process is completed. If the solid content in the first molded body reaches about 40%, the process will take an excessively long time.

[0028] Furthermore, in the molding process, instead of (1-1), (1-3) may be performed in which a step of applying pressure to the CNF-containing slurry and then reducing the pressure is performed multiple times, and a step of supplying heated gas to the sliding member molding apparatus, i.e., a step including a step of performing pressurization and depressurization multiple times, is performed, and the step of supplying heated gas to the sliding member molding apparatus, or the step of supplying heated gas to the sliding member molding apparatus, may be stopped together with the step of reducing the pressure applied to the CNF-containing slurry, and resumed together with the step of applying pressure to the CNF-containing slurry.

[0029] In addition, the molding step may further include a step of adding a CNF-containing slurry into the molding cavity 11. In this case, it is recommended that the CNF concentration near the surface of the previously added CNF-containing slurry and the CNF concentration in the newly added CNF-containing slurry be less than 18%. If the CNF-containing slurry is added when either slurry has a concentration of 18% or higher, partial hydrogen bonding will occur between the CNFs in each CNF-containing slurry, preventing hydrogen bonding between the previously added CNF-containing slurry and the later added CNF-containing slurry, resulting in separate layers and preventing the formation of a single homogeneous material. Furthermore, because the movement of the CNF fibers is restricted, the entanglement of the CNFs will be weakened. As a result, multiple layers will form inside the molded product for sliding components, making it impossible to obtain a homogeneous molded product for sliding components.

[0030] (Desolvation process) (2) The solvent removal step is (2-1) applying pressure to the first molded body using a gas and solvent permeation means; (2-2) A desolvation step is a step of applying heat to the molding apparatus for a sliding member to remove the solvent from the first molded body for a sliding member. The method of applying heat is not particularly limited, but includes a method of heating the apparatus by attaching a heater, a method of supplying heated gas, and a method of heating by irradiating with microwaves. In the desolvation step, the first molded body is dried and desolvated, and when the solid content reaches 80 to 100%, the pressurization using the gas permeable means is stopped and the step is completed. If the solid content is less than 80%, the time required for the subsequent suction step becomes long.

[0031] In the solvent removal step, instead of (2-1), (2-3) a step similar to (1-3) may be carried out in which pressure is applied stepwise to the first molded body using a gas permeable means and heated gas is supplied to the molding apparatus for a sliding member.

[0032] (Suction process) (3) The suction step is a step in which various gas suction devices such as a vacuum pump are installed in the gas suction port 14 and used to reduce the pressure or create a vacuum inside the sliding member molding device, i.e., the main body 6. The suction step is performed as an additional step to the molding step and the solvent removal step. In addition, in (1-3), a process including a step of performing pressurization and depressurization multiple times may be performed, and the step of suctioning the gas inside the molding apparatus for a sliding member may be stopped together with the step of reducing the pressure applied to the CNF-containing slurry, and the step of suctioning the gas inside the molding apparatus for a sliding member may be resumed together with the step of applying pressure to the CNF-containing slurry again.

[0033] Furthermore, (4) the distance measuring device may be used to control the molding step and / or the desolvation step, that is, to control the step of applying pressure and / or depressurizing.

[0034] Each of the steps will now be described in detail. In (1-1), applying pressure to the CNF-containing slurry refers to a process of removing the solvent by applying pressure to the CNF-containing slurry in the molding cavity 11 in the thickness direction, as shown in Figure 1. This pressure causes the water in the CNF-containing slurry to migrate to the gas permeable means and be expelled outside the molding cavity system. The pressure application method in this process can be performed by a known method, but is preferably performed using a pneumatic press. This is because a pneumatic press allows for easy fine adjustment of the pressure. It is also possible to use a hydraulic press or a servo press. With a hydraulic press, it is easier to apply higher pressure. With a servo press, fine control can be performed. With a servo, no force is required when the distance (position) is not changed, which saves energy. A servo hydraulic press that combines these can also be used.

[0035] In (1-1), it is preferable to gradually apply pressure or apply a constant pressure after performing the step (3) of sucking out the gas from the molding device for sliding components, described below, while maintaining the upper surface of the CNF-containing slurry in contact with the upper plate 9. By carrying out a suction step before carrying out the process of applying pressure to the CNF-containing slurry, it is possible to remove air bubbles present in the CNF-containing slurry and / or air bubbles that are generated when the CNF-containing slurry is introduced into the molding device for sliding components, thereby making it possible to ensure a uniform bonding state of the CNFs inside the final molded product for sliding components.

[0036] The step of supplying heated gas into the molding apparatus for sliding members in (1-2) refers to a step of supplying heated gas into the molding apparatus for sliding members to create a circulating air flow. The heated gas used in this step is a heated gas that can control the raw material temperature to 30 to 95°C, preferably 35 to 93°C, and more preferably 40 to 90°C. For this purpose, a heated gas of 100°C or higher is preferred, more preferably 120°C or higher. Using a heated gas within this range increases the temperature of the CNF-containing slurry, swelling and expanding the CNFs, accelerating the dehydration rate. The circulating air flow also increases the rate of solvent removal from the CNF-containing slurry. However, using a heated gas below 30°C lowers the temperature of the CNF-containing slurry, making it impossible to increase the rate of water removal, resulting in a longer solvent removal time. Furthermore, if the raw material temperature is raised to 95°C or higher, the water in the CNF-containing slurry may boil, causing a large amount of air bubbles to form in the CNF-containing slurry.

[0037] To prevent a difference in moisture content between the interior and surface of the CNF-containing slurry in the molding cavity, the supply rate of the heated gas is set to be equal to or less than the exhaust rate of the vacuum pump, and is preferably set to approximately 0.001 to 10 times the volume of the molding cavity 11 per minute. A supply rate of 0.002 to 5 times is more preferable. If the supply rate is too low, circulation in the gas area will be insufficient, while if the supply rate is too high, heat energy loss from the exhaust system will be significant.

[0038] In (1-3), the step of applying pressure to the CNF-containing slurry and then reducing the pressure one or more times is the step of reducing the applied pressure in (1-1) above. When this step is performed, the CNF-containing slurry expands in the thickness direction, and the solvent inside the CNF-containing slurry moves to the surface side of the CNF-containing slurry. Then, by applying pressure again, the water in the CNF-containing slurry can be desolvated more quickly. Furthermore, if the solvent on the surface side is significantly reduced compared to the inside, hydrogen bonding of the CNFs progresses only in the surface portion, significantly reducing the solvent penetration rate. This step can prevent this. In this process, it is sufficient to reduce the pressure applied in the above-mentioned step (1) below that pressure.

[0039] (3) The step of sucking gas from the sliding member molding apparatus is a step of reducing the pressure in the sliding member molding apparatus or creating a vacuum state in the sliding member molding apparatus by sucking gas from the inside of the sliding member molding apparatus. By performing this step, it is possible to remove air bubbles from the CNF-containing slurry, as described above. Note that the suction method in this step can be performed by a known method using a vacuum pump or the like.

[0040] In (2-1), applying pressure to the first molded body using a gas-permeable means is the same as applying pressure to the CNF-containing slurry in (1-1), and the same pressurization method as in (1-1) can be used. It is preferable to use a hydraulic press or a servo press. This is because a hydraulic press can apply greater pressure and can remove the solvent from the first molded body in a short time. A servo press allows for precise control and also saves energy. A preferred method of applying pressure in this step is to first apply a small pressure (initial pressure), then gradually increase the pressure, and finally apply a constant pressure (final pressure). The specific pressure value is 8 kg / cm as the initial pressure. 2 Less than 7kg / cm is preferable. 2 Less than 5kg / cm is more preferable.2 More preferably, the final pressure is 500 kg / cm or less. 2 More than 700kg / cm is preferable. 2 More preferably, 900 kg / cm 2 The above is even more preferable.

[0041] In view of the above, the sliding member molding apparatus 1 may use the same sliding member molding apparatus for the molding step and the solvent removal step, on the premise that different press machines are exchanged between the two steps, or may use two or more types of sliding member molding apparatuses equipped with different press machines to perform the molding step and the solvent removal step, or may use the same sliding member molding apparatus using the same press machine to perform the molding step and the solvent removal step.

[0042] The step of supplying heated gas to the molding apparatus for a sliding member in (2-2) is the same as the step of supplying heated gas into the molding apparatus for a sliding member in (1-2).

[0043] The step of applying pressure to the first molded body in stages using a gas-permeable means in (2-3) refers to the step of applying pressure gradually in stages in (2-1). If pressure is applied to the first molded body suddenly, the first molded body will not be able to withstand the compression and will crack laterally, so it is preferable to apply a small pressure in the initial stage and gradually increase the pressure as the hydrogen bonding strength increases.

[0044] In (4), controlling the molding process and / or the desolvation process using a distance measuring device means a process of controlling the pressurization and / or depressurization steps in (1-1), (1-3) and (2-1) by the distance value measured using a distance measuring device. As described above, the molding apparatus 1 for sliding member can convert the volume or concentration value from the distance value measured by the distance measuring device, and therefore, such a process can be performed. By performing such a process, it becomes possible to perform, for example, sequence control.

[0045] (Molded body for sliding member) The compact for a sliding member obtained as described above has a density of 1.30 to 1.61 g / cm 3 The moisture content is 20% or less. The density of the compact for a sliding member is 1.3 g / cm 3 If the moisture content is less than 10%, the strength will be insufficient due to a decrease in hydrogen bonding points, or voids and voids will be present inside. If such a molded product for slide components is subjected to various processes such as cutting, drilling, or polishing, the molded product for slide components will peel off, break, or be damaged, making it impossible to perform such processes. The density of the molded product is a value measured in accordance with JIS-P-8118:2014. The same applies when the moisture content exceeds 20%.

[0046] The lower limit of the thickness of the molded article for a sliding member is 3 mm or more. If the thickness of the molded article for a sliding member is less than 3 mm, it becomes difficult to perform polishing or other processes. On the other hand, the upper limit of the thickness of the molded article for a sliding member is not particularly limited as long as the CNF concentration in the CNF-containing slurry is set to 18% or less, as described in paragraph 0029. The height of the obtained molded article for a sliding member can be adjusted by stretching the first cylindrical portion 3 in the height direction.

[0047] The molded article for a sliding member obtained in the above manner is considered to be suitable for a sliding member from the viewpoint of a low thermal expansion coefficient and a high melting point. First, regarding the melting point, cellulose, the raw material for the molded article for the sliding member, is a material that does not exhibit thermoplasticity and undergoes thermal decomposition without a melting point. Furthermore, the Tmax of cellulose is a thermal decomposition temperature of approximately 360°C, and CNF is thought to have a thermal decomposition temperature similar to that of cellulose. In particular, unmodified CNF, whose surface has not been chemically modified, is thought to maintain high heat resistance comparable to that of cellulose. Furthermore, even CNF obtained by chemical modification is said to have heat resistance with a Tmax of 230°C or higher (Non-Patent Document 1). On the other hand, the heat resistance temperature of POM during continuous use is said to be 90 to 100°C.

[0048] Next, regarding the low thermal expansion coefficient, cellulose has a low thermal expansion coefficient of 3.6 to 12 ppm / K, and it is known that the larger the fiber diameter or the drier it is, the smaller the value it shows. In addition, for CNF, the thermal expansion coefficient is 1.0 × 10 -8 It is known to be / K. On the other hand, the thermal expansion coefficient of POM is approximately 8.1 to 8.5 × 10 -5 It is said to be / K.

[0049] Furthermore, by polishing the surface of the molded article for a sliding member according to the present invention by a known means, the lower limit of the surface roughness can be set to Ra 0.05 to 0.1 μm, thereby making it possible to obtain a sliding member having ultra-friction properties. Furthermore, it is presumed that reducing the surface roughness reduces the specific surface area and reduces the area that is directly affected by heat, so that the thermal decomposition temperature of cellulose does not decrease, and the molded body for a sliding component has a high melting point (Non-Patent Document 1).

[0050] Therefore, it is believed that the heat resistance and low thermal expansion coefficient of the molded articles for sliding components obtained by molding CNF will be far better than those of POM.

[0051] The method for manufacturing a molded body for a slide member and embodiments of the molded body for a slide member have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the present disclosure as defined in the claims.

[0052] (lubricating oil) The lubricating oil in the present invention is a lubricating base oil and / or a lubricating additive. The lubricating base oil is not particularly limited and any known lubricating base oil can be used, such as mineral oil, chemically synthesized oil, natural fats and oils, diluent oil, grease, wax, and hydrocarbon solvents. Furthermore, lubricating oil additives that can be used include known detergent-dispersants, antioxidants, load-bearing additives, oiliness improvers, anti-wear agents, extreme pressure agents, rust inhibitors, corrosion inhibitors, viscosity index improvers, pour point depressants, anti-foaming agents, emulsifiers, demulsifiers, fungicides, solid lubricants, etc. Among these lubricating oil additives, when the sliding member of the present invention is used in a sliding portion where low friction is required, it is advisable to use an oiliness improver. Examples of oiliness improvers include alkanes having a functional group capable of forming a covalent bond with an oxygen molecule or a carbon atom of a cellulose constituent atom. Specific examples include trivalent or higher alcohols, alkylene oxide adducts of the alcohols, aliphatic monocarboxylic acids (fatty acids), aliphatic polycarboxylic acids, carbocyclic carboxylic acids, heterocyclic carboxylic acids, carboxylic acids such as mixtures of two or more selected from the four carboxylic acids, esters of fatty acid monocarboxylic acids (fatty acids), esters of aliphatic polycarboxylic acids, esters of carbocyclic carboxylic acids, esters of heterocyclic carboxylic acids, alkylene oxide adducts of alcohols or esters, esters such as mixtures of any selected from the five esters, saturated or unsaturated aliphatic ethers, aromatic ethers, cyclic ethers, and the three carboxylic acids selected from the above. Ethers such as mixtures of two or more selected from the above ethers, saturated or unsaturated aliphatic ketones, carbocyclic ketones, heterocyclic ketones, ketone alcohols, ketone acids, ketones such as mixtures of two or more selected from the above five types of ketones, saturated or unsaturated aliphatic aldehydes, carbocyclic aldehydes, heterocyclic aldehydes, aldehydes such as mixtures of two or more selected from the above three types of aldehydes, carbonates having one or more carbonate bonds, glycerol monooleate (GMO), glycerin monooleyl ether, tallow diethanolamine, alkylamines, etc. can be used alone or in any combination thereof.

[0053] In the sliding member of the present invention, the oiliness improver covalently bonds with carbon or oxygen atoms present on the surface of the sliding member to form a tribofilm. Here, the term "tribofilm" refers to a surface coating formed by adsorption or chemical reaction of the oiliness improver on the surface of the sliding member during friction. This tribofilm provides excellent low-friction performance. [Example]

[0054] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0055] (Manufacturing Examples 1 to 5) Using bamboo pulp as the raw material for the cellulose-derived component, the CNF aqueous dispersions (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) described in Production Examples 1 to 5 in Table 1, obtained by the ACC method described in paragraph 0018 of Japanese Patent No. 6704551, were used as CNF-containing slurries. Next, the mixture was placed in a CNF molding machine with a cylindrical main body, and the molding, solvent removal, and suction processes were carried out under the conditions shown in Table 1 below to produce molded bodies for sliding members with thicknesses of 3.2 to 16.3 mm. The CNF concentration in the first molded body is shown as the CNF concentration (%) of the molded body after the molding process. Each of the obtained molded bodies for sliding members was processed to the sizes described below and used in Examples 1 to 4. The solid content in the table was calculated by dividing the weight of the dried CNF added by the weight of the resulting product. The moisture content was calculated by 100 (%) - (solid content concentration (%)), and was 2.6, 10.2, 3.4, 10.0, and 16.9 in Production Examples 1 to 5, respectively.

[0056] [Table 1]

[0057] (Examples 6 to 10) Using bamboo pulp as the raw material for the cellulose-derived component, a CNF aqueous dispersion (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) obtained by the ACC method described in paragraph 0018 of Japanese Patent No. 6704551 was used as a CNF-containing slurry, and a molded body was prepared under the conditions described in Manufacturing Examples 6 to 10 in Table 2. First, graphene (ITEC Corporation: product name (iGurafen type iGurafen-aS powder)) was added to the obtained CNF-containing slurry in the amount shown in Table 2 below (Production Examples 6 to 9). The amount of graphene in each CNF molded body was 0 wt% in Production Example 10, 0.01 wt% in Production Example 6, 0.1 wt% in Production Example 7, 1 wt% in Production Example 8, and 10 wt% in Production Example 9. Next, these were placed in a CNF molding device with a cylindrical main body, and a molding step and a solvent removal step were carried out under the conditions shown in Table 2 below to produce a green body for a sliding member. The CNF concentration in the first molded body is shown as the CNF concentration (%) of the molded body after the molding process. The obtained molded bodies for sliding members were each processed to the sizes described below and used in Examples 5 to 19. The solid content concentrations in the table were calculated by dividing the converted dry weight of the CNF added by the weight of the obtained product.

[0058] [Table 2]

[0059] (Ball-on-disk tester or ring-on-disk test) The ball-on-disk tester or ring-on-disk tester in this invention is a friction tester consisting of a stepping motor, load cell, linear guide, test specimen holder, temperature control device, position control stage, seesaw mechanism, spring, and micrometer, and has a mechanism for measuring static and kinetic friction forces with time resolution. A load is applied between the test specimens (ball or ring-disk) by using the micrometer to push the spring and load cell attached to one end of the seesaw, and the linear guide moves horizontally due to the friction force generated by driving the test specimen (ring or ball) with the motor. The motor mechanism driven by this horizontal movement is connected to a load cell to measure the friction force.In addition, a temperature control device is attached to the holder for the disk test specimen, allowing it to be heated up to approximately 120°C.

[0060] (Example 1, Comparative Examples 1 and 2) (Ball-on-disk test) The ball-on-disk test evaluates frictional characteristics by rotating a ball fixed on a disk, as shown in Figure 2. The test conditions were as follows: a ball was brought into contact with each slide molded body at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the atmosphere. The friction coefficient was measured. The slide molded body used in Example 1 was that of Production Example 1. The disk surface was pre-applied with a lubricant consisting of 50 μL of polyalphaolefin (PAO) base oil with 1 mass% glycerol monooleate (GMO) added. The lubricant was not replenished during the test. The outer shape, thickness, surface roughness, and lubricant conditions of each slide member are shown in Table 3. The friction coefficient test results are shown in Figure 3, and a micrograph showing the friction mark diameter is shown in Figure 4.

[0061] [Table 3]

[0062] 3, the sliding member according to the present invention exhibited a low friction coefficient in the range of 0.01 to 0.02 (FIG. 3(3)), which is superior to the friction coefficient of the conventional material POM, which is in the range of 0.04 to 0.06 (FIG. 3(2)). The results of Example 1 revealed that the friction coefficient decreased within 300 seconds from the start.

[0063] (Examples 2 to 4, Comparative Examples 3 to 6) (Ring-on-disc test) In the ring-on-disk test, frictional properties are evaluated by rotating a ring placed on a disk, as shown in Figure 5. The test conditions were as follows: 50°C, in the air, the ball was brought into contact with each molded product for sliding components at a surface pressure of 50 N, and the ball was allowed to slide at a sliding speed of 0.01 m / s for 30 minutes, and the coefficient of friction was measured. The CNF molded products used in each example were as follows: Example 2: Production Example 3 Example 3: Production Example 4 Example 4: Production Example 5 The lubricants used were (1) dry (no lubricant), (2) 50 μL of polyalphaolefin (PAO) base oil, and (3) 50 μL of polyalphaolefin (PAO) base oil with 1 mass% glycerol monooleate (GMO). The tests were started with (2) and (3) lubricants applied to the disk surface beforehand, and no lubricant was added during the test. The outer dimensions, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 4. The friction coefficient test results are shown in Figures 6 and 7.

[0064] [Table 4]

[0065] The test results in Figure 6 reveal that although there is a difference in the magnitude of the amplitude under dry conditions (Example 2) and under PAO conditions (Example 3), the friction coefficients are similar (approximately 0.06) (Figures 6(1)(2)). In other words, it can be said that it can be used as a low-friction sliding component even under conditions without lubricating oil. CNF is a plant-derived raw material, and evaluations have shown its potential for application in fields such as food, where oil-free lubrication is required. Furthermore, it was revealed that in the presence of GMOs (Example 4), the friction coefficient was lower (0.03 or less) than under these conditions (Figure 6(3)). Furthermore, the test results of Examples 3 and 4 and Comparative Examples 3 to 6 in Figure 7 reveal that the friction coefficient of Example 3 (Figure 7(5)) is comparable to that of POM. Furthermore, it is clear that, compared to the Comparative Examples, the fluctuation of the friction coefficient is small, which is effective in achieving stable rolling characteristics.

[0066] (Confirmation of tribofilm by FT-IR) After the ring-on-disk test, the surfaces of the rings in Examples 2 to 4 were measured by FT-IR (Thermo Scientific Nicolet iS10). The measurement results are shown in FIG. According to Figure 8, 1720 cm -1 A peak indicating an ester bond was confirmed around this point, which revealed that the addition of GMO resulted in the formation of a tribofilm on the sliding surface. This is thought to be because the CNF surface was hydrophobized by esterification of the hydroxyl groups present on the surface of the sliding member with the GMO, causing the hydrophobic CNF surface to swell and stretch into a brush-like shape, and the long-chain alkyl groups derived from the GMO raised around the brush-like shape, causing the surface of the sliding member to become amorphous, and the CNF on the surface of the sliding member was chemically and mechanically decomposed during the 30 minutes of sliding. Therefore, it is thought that in a lubricating oil environment, a layer consisting of the oiliness improver and the CNF decomposed from the sliding member was formed at the interface between the sliding member and the lubricating oil. Furthermore, from the results of Figures 6 and 7, it is believed that tribofilms are gradually formed as the sliding time progresses, especially in the initial stage.

[0067] (Examples 5 to 9) (Ball-on-disk test) The CNF molded bodies produced in Production Examples 6 to 10 were used as the disks in Fig. 2, and a ball was brought into contact with each molded body for sliding components at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the atmosphere, to measure the coefficient of friction. The CNF molded bodies used in each example are as follows: Example 5: Preparation Example 10 Example 6: Production Example 6 Example 7: Production Example 7 Example 8: Production Example 8 Example 9: Production Example 9 The test was started with 50 μL of polyalphaolefin (PAO) applied to the disk surface beforehand, and no lubricant was added during the test. The outer shape, thickness, surface roughness, and lubricant conditions for each sliding member are shown in Table 5. The friction coefficient test results are shown in Figure 9.

[0068] [Table 5]

[0069] The test results in FIG. 9 reveal that the friction coefficient of the sliding member to which solid lubricant particles are added decreases as the amount of solid lubricant particles (graphene) added increases.

[0070] (Examples 10 to 14) (Ball-on-disk test) The CNF molded bodies produced in Production Examples 6 to 10 were used as the disks in Fig. 2, and a ball was brought into contact with each molded body for sliding components at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the atmosphere, to measure the coefficient of friction. The CNF molded bodies used in each example are as follows: Example 10: Preparation Example 10 Example 11: Preparation Example 6 Example 12: Preparation Example 7 Example 13: Preparation Example 8 Example 14: Preparation Example 9 The lubricant used at this time was 50 μL of polyalphaolefin (PAO) base oil with 1 mass% glycerol monooleate (GMO) added, which was applied to the disk surface before the test began. The lubricant was not replenished during the test. The external dimensions, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 6. The friction coefficient test results are shown in Figure 10.

[0071] [Table 6]

[0072] The test results in Figure 10 revealed that the friction coefficient of the sliding components containing solid lubricant particles was within the range of approximately 0.04 to 0.08. The friction-improving effect of the esterification reaction between cellulose and GMO was not evident in the sliding components containing graphene as solid lubricant particles. The esterification reaction is accelerated by dehydration bonding, but in the graphene-added system, the gas barrier function of the dried graphene oxide flakes may have prevented the desorption of moisture from the compact, preventing the esterification reaction from proceeding. Alternatively, the physical barrier of the hexagonal lattice may have reduced the opportunity for contact between cellulose and GMO.

[0073] Example 15 (Ball-on-disk test) Using the CNF molded bodies produced in Production Example 10 as the disks in FIG. 2, a ball was brought into contact with each of the horizontal and vertical surfaces of each molded body for sliding component at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the air, and the friction coefficient was measured. The lubricant used was a mixture of 50 μL of polyalphaolefin (PAO) base oil with 1 mass% glycerol monooleate (GMO) added, which was applied to the disk surface before the test began. The lubricant was not replenished during the test. The outer shape, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 7. The outer shape, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 7. The friction coefficient test results are shown in Figure 11.

[0074] [Table 7]

[0075] The test results in FIG. 11 reveal that the sliding member according to the present invention has a low coefficient of friction on both the horizontal and vertical surfaces, and that the vertical surface exhibits even lower friction than the horizontal surface.

[0076] Example 16 (Ball-on-disk test) Using the CNF molded body produced in Production Example 10 as the disk in FIG. 2, a ball was brought into contact with each molded body for a sliding component at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the air, and the friction coefficient was measured. The test was started with 50 μL of polyalphaolefin (PAO) applied to the disk surface beforehand, and no lubricant was added during the test. The outer shape, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 8. The friction coefficient test results are shown in Figure 12.

[0077] Example 17 The friction coefficient was measured in the same manner as in Example 16, except that the lubricant in Example 16 was prepared by adding 1 mass% of glycerol monooleate (GMO) to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The test results for the friction coefficient are shown in Figure 12.

[0078] Example 18 The friction coefficient was measured in the same manner as in Example 16, except that the lubricant in Example 16 was 1 mass% glycerin monooleyl ether (oleyl ether) (GME) added to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The test results for the friction coefficient are shown in Figure 12.

[0079] Example 19 The friction coefficient was measured in the same manner as in Example 16, except that the lubricant in Example 16 was 1 mass% tallow diethanolamine (oleylamine) (TDEA) added to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The friction coefficient test results are shown in Figure 12.

[0080] (Comparative Example 7) SUJ2 (JIS G 4805 high carbon chromium bearing steel) was used as the disk in Figure 2, and a ball was brought into contact with each compact for a sliding member at a surface pressure of 10 N and slid at a sliding speed of 0.01 m / s for 60 minutes at 50°C in the air, and the coefficient of friction was measured. The test was started with 50 μL of polyalphaolefin (PAO) applied to the disk surface beforehand, and no lubricant was added during the test. The outer shape, thickness, surface roughness, and lubricant conditions for each sliding component are shown in Table 8. The friction coefficient test results are shown in Figure 13.

[0081] (Comparative Example 8) The friction coefficient was measured in the same manner as in Comparative Example 7, except that the lubricant in Comparative Example 7 was prepared by adding 1 mass% of glycerol monooleate (GMO) to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The test results for the friction coefficient are shown in Figure 13.

[0082] (Comparative Example 9) The friction coefficient was measured in the same manner as in Comparative Example 7, except that the lubricant in Comparative Example 7 was 1 mass% glycerin monooleyl ether (oleyl ether) (GME) added to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The test results for the friction coefficient are shown in Figure 13.

[0083] (Comparative Example 10) The friction coefficient was measured in the same manner as in Comparative Example 7, except that the lubricant in Comparative Example 7 was 1 mass% tallow diethanolamine (oleylamine) added to 50 μL of polyalphaolefin (PAO) base oil. The outer shape, thickness, surface roughness, and lubricant conditions of each sliding member are shown in Table 8. The test results for the friction coefficient are shown in Figure 13.

[0084] [Table 8]

[0085] The test results in Figure 12 confirmed the ultra-low friction phenomenon in Examples 17 and 18, which used GMO and GME as lubricants. Furthermore, since the friction decreased after a certain time compared to immediately after the start of sliding (initial state) (see Figures 6 and 7), it is believed that tribofilms were formed on the surfaces of the sliding members not only for GMO but also for GME and TDEA (Examples 17, 18, and 19). On the other hand, the test results in Figure 13 confirmed that the oils containing GMO and GME had a friction-reducing effect, but compared to the examples, no phenomenon occurred in which friction became lower after a certain period of time compared to the initial state. [Explanation of symbols]

[0086] 25...Ball-on-disc test, 26...Ball, 27...Lubricant, 28...Disc, 29...Ring-on-disc test, 30...Ring

Claims

1. A molded body containing CNF, The moisture content in the molded body is 20% or less, The thickness of the molded body is 3 mm or more, The compact for a sliding member has a density of 1.30 to 1.61 g / cm 3 .

2. A compact formed from a slurry containing CNF and a solid lubricant, The moisture content in the molded body is 20% or less, The thickness of the molded body is 3 mm or more, The compact for a sliding member has a density of 1.30 to 1.61 g / cm 3 .

3. A sliding member formed from the molded article for a sliding member according to claim 1 or 2.

4. A sliding member that slides in a lubricating oil environment, the sliding member being formed from the molded article for a sliding member according to claim 1 or 2.

5. A sliding member that slides in a lubricating oil environment, When sliding in a lubricating oil environment, A tribofilm is formed at the solid-liquid interface. A sliding member formed from the molded article for a sliding member according to claim 1 or 2.

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