Underwater sliding member and article

Abstract

Provided is an underwater sliding member which is used in an aqueous liquid at a contact pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein: the underwater sliding member is provided with a rotary body and a sealing material; the sliding surface of the rotary body is a resin molded member that contains a thermoplastic resin having water absorption resistance and an inorganic filler; the sliding surface of the sealing material is a resin molded member that contains a thermoplastic resin having water absorption resistance; and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotary body.

Description

Underwater sliding members and articles

[0001] This disclosure relates to underwater sliding members and articles.

[0002] Molded thermoplastic resin components used in sliding parts are often used under constant loads, and their properties require not only sliding properties but also not only short-term mechanical properties such as rigidity, strength, and toughness, but also long-term durability properties such as creep resistance and fatigue resistance. In recent years, the operating environments for sliding parts have also diversified, and molded thermoplastic resin components used in sliding parts are used, for example, in bathroom and water supply components that come into frequent contact with water, as well as pipe and valve components used in environments where stress is constantly applied, and especially as valve components such as rotary valves for electric vehicle modules. In particular, pipe and valve components are required to have a high level of balance between mechanical strength, long-term properties, and wear resistance in underwater environments, so that they can withstand immersion in hot water and stress generated by liquid-tight valve closure.

[0003] When thermoplastic resins are used as sliding members, it is known that molded members made of a single material of thermoplastic resin have low wear resistance and excessive wear. To improve wear resistance, sliding members containing fillers in the thermoplastic resin are known. Patent Document 1 discloses a technique to improve rigidity and reduce shrinkage anisotropy by incorporating fibrous inorganic fillers such as glass fibers, carbon fibers, and wollastonite, and granular inorganic fillers such as calcium carbonate as inorganic fillers. Patent Document 2 discloses a technique to incorporate glass fibers, mica, etc., into thermoplastic resin to improve mechanical properties, reduce warping of molded products, and improve the appearance of molded products.

[0004] When using resin sliding members in water, it is expected that the resin should have excellent water resistance and high wear resistance. Patent Document 3 discloses an underwater sliding member made of a laminate of carbon fiber cloth containing a phenolic resin composition consisting of 5 to 40% by weight of one or more fillers selected from graphite, tetrafluoroethylene resin, boron nitride, and amorphous carbon, with the remainder being phenolic resin. Furthermore, Patent Document 4 discloses a resin-based composite sliding member for use in water, which uses a composite material containing carbon fibers and at least one filler selected from graphite, boron nitride, molybdenum disulfide, and tungsten disulfide in a tetrafluoroethylene resin.

[0005] International Publication No. 2005 / 071011, Japanese Patent Publication No. 2003-286402, Japanese Patent Publication No. 2002-323038, Japanese Patent Publication No. 2003-21144

[0006] Thus, high wear resistance is required for sliding members made of thermoplastic resin. On the other hand, referring to the technologies disclosed in Patent Documents 3 and 4, it is known that when used underwater, it is good to include fillers in the resin in order to improve wear resistance while maintaining excellent water resistance. However, in various applications of underwater sliding members, particularly in underwater sliding members used at low surface pressure and low sliding speed, there is room for consideration in resin design that takes into account the effect of fillers. Furthermore, in applications where a rotating body and a sealing material slide while being liquid-tightly sealed in an aqueous liquid, when resin molded products are used for both the rotating body and the sealing material, there is room for consideration in methods to reduce the amount of wear.

[0007] One of the objectives of this disclosure is to provide an underwater sliding member with excellent wear resistance for use in aqueous liquids at low surface pressure and low sliding speed.

[0008] Some embodiments of the present disclosure are illustrated below. [1] An underwater sliding member used in an aqueous liquid at a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein the underwater sliding member comprises a rotating body and a sealing material, the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body. [2] The underwater sliding member according to [1], wherein the sliding surface of the sealing material is a resin molded member that does not contain an inorganic filler. [3] The underwater sliding member according to [1] or [2], used in an aqueous liquid at a surface pressure of 0.15 to 0.6 MPa. [4] The underwater sliding member according to any one of [1] to [3], used in an aqueous liquid at a sliding speed of 1.5 to 6 cm / s. [5] The water-resistant thermoplastic resin contained in the resin molded member of the sliding surface of the sealing material is polyacetal resin, as described in any one of [1] to [4]. [6] The water-resistant thermoplastic resin contained in the resin molded member of the sliding surface of the rotating body is polyacetal resin, polyphenylene sulfide resin, or a combination thereof, as described in any one of [1] to [5]. [7] The specific wear amount measured under the following condition A with a surface pressure of 0.6 MPa and a sliding speed of 3 cm / s is 6 × 10 －３ mm ３ An underwater sliding member described in any one of [1] to [6], wherein the pressure is less than or equal to / N·km. [Condition A] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the members are slid at an ambient temperature of 23°C for 24 hours, and the specific wear amount of the underwater sliding member is measured after 24 hours. [8] With a surface pressure of 0.6 MPa and a sliding speed of 6 cm / s, the specific wear amount measured under the following condition A is 30 × 10 －３ mm ３An underwater sliding member according to any one of [1] to [6], wherein the coefficient of dynamic friction measured under the following conditions B is 0.3 or less / N·km. [Condition A] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C, and the specific wear amount of the underwater sliding member is measured after 24 hours. [9] An underwater sliding member according to any one of [1] to [6], wherein the coefficient of dynamic friction measured under the following conditions B is 0.3 or less at a surface pressure of 0.3 MPa and a sliding speed of 3 cm / s. [Condition B] In an aqueous liquid, the upper surface of a resin cylindrical member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C, and the coefficient of dynamic friction is measured near the end of the 24 hours.

[10] An underwater sliding member according to any one of [1] to [6], wherein the coefficient of dynamic friction measured under the following condition B is 0.3 or less, with a surface pressure of 0.6 MPa and a sliding speed of 6 cm / s. [Condition B] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C, and the coefficient of dynamic friction is measured near the end of the 24 hours.

[11] An underwater sliding member according to any one of [1] to

[10] used in a rotary valve.

[12] An underwater sliding member according to

[11] used in a rotary valve provided in a cooling system of an electric vehicle.

[13] An article comprising an underwater sliding member used in an aqueous liquid with a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein the underwater sliding member comprises a rotating body and a sealing material, the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body.

[0009] According to one embodiment of the present disclosure, it is possible to provide an underwater sliding member that is excellent in wear resistance when used in an aqueous liquid at low surface pressure and low sliding speed.

[0010] Figure 1 is a schematic cross-sectional view of a rotary valve, which is an example of this embodiment. Figure 2 is a conceptual diagram showing the sliding test performed in the embodiment.

[0011] The following describes some embodiments of this disclosure. The examples in the following description do not limit this disclosure.

[0012] The underwater sliding member of this embodiment is an underwater sliding member used in an aqueous liquid with a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, and comprises a rotating body and a sealing material, wherein the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body.

[0013] The underwater sliding member of this embodiment is intended for members that slide in an aqueous liquid, and does not include members used in a dry environment. In this embodiment, "underwater" refers not only to pure water but also to an aqueous liquid. The aqueous liquid is a liquid containing water, and may consist of water alone or a mixture of water and other liquids. For example, it may contain other liquids in a range where water is 10% by mass or more, 30% by mass or more, or 50% by mass or more. Specifically, the aqueous liquid may be a mixture of a water-soluble organic solvent and water, an emulsion containing an aqueous phase and an oil phase, etc. These aqueous liquids may be aqueous liquids that can be used as cooling media including long-life coolant (LLC), aqueous lubricants including emulsion-type lubricants, etc.

[0014] The sliding member of this embodiment comprises a rotating body and a sealing material. For example, the rotating body may be a resin molded member such as a disc or cylinder that can rotate around its central axis as the axis of rotation. The sealing material may be a resin molded member that is slidably disposed on the outer circumferential surface of the rotating body. In such a sliding member, the rotation of the rotating body causes the outer circumferential surface of the rotating body and the sealing material to slide against each other. The sliding member of this embodiment may further comprise an outer casing. For example, the rotating body may be housed inside the outer casing, and the sealing material may be disposed between the outer circumferential surface of the rotating body and the inner circumferential surface of the outer casing.

[0015] The rotating body and sealing material are used by sliding them in an aqueous liquid. For example, the rotating body and sealing material are housed in an outer casing and used by immersing the outer casing in an aqueous liquid.

[0016] The sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler. The rotating body may be integrally molded from the resin molded member, or it may be a composite member of the resin molded member and other members. The sliding surface of the rotating body with the sealing material may be a resin molded member. By including an inorganic filler along with a water-resistant thermoplastic resin, the sliding surface of the rotating body can have rigidity and durability even in aqueous liquids.

[0017] The sliding surface of the sealing material is a resin molded member containing a thermoplastic resin having water absorption resistance. The sealing material may be integrally molded from the resin molded member, or it may be a composite member of the resin molded member and other members. The sealing material only needs to have a resin molded member as the sliding surface with the rotating body. The mass ratio of inorganic filler contained in the sliding surface of the sealing material should be smaller than the mass ratio of inorganic filler contained in the sliding surface of the rotating body, and more preferably, the sliding surface of the sealing material should not contain inorganic filler, thereby reducing wear under low surface pressure and low sliding speed conditions in an aqueous liquid. When the mass ratio of inorganic filler contained in the sliding surface of the rotating body is 100%, the mass ratio of inorganic filler contained in the sliding surface of the sealing material should be 10% or less, 5% or less, or 1% or less.

[0018] The underwater sliding member of this embodiment is used in an aqueous liquid at a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less. The rotating body and the sealing material slide against each other at the sliding surfaces of the resin molded members in the aqueous liquid. Here, when thermoplastic resin members containing inorganic fillers slide against each other, or when thermoplastic resin members without inorganic fillers slide against each other, adhesion becomes more likely when the surface pressure is low, resulting in increased wear. In contrast, it is thought that if one of the members has a high inorganic filler content, adhesion becomes less likely to occur and the amount of wear is reduced. Furthermore, since the surface of a thermoplastic resin molded member containing inorganic fillers becomes uneven, the contact area with the mating material is reduced, and it is thought that the amount of wear can be reduced. From the viewpoint of sliding properties, if the sealing material does not contain inorganic fillers, and the rotating body (the mating material) contains inorganic fillers, it has been thought that the sealing material is attacked by the inorganic fillers on the rotating body side at the sliding surface, resulting in increased wear. In this embodiment, it was found that when sliding in an aqueous liquid at low surface pressure and low sliding speed, the amount of wear is reduced when sliding a sealing material without inorganic fillers against a rotating body containing inorganic fillers.

[0019] The surface pressure may be in the range of 0.6 MPa or less, and may be set appropriately depending on the application of the underwater sliding member. The upper limit of the surface pressure is not limited and may vary appropriately depending on the type of resin of the underwater sliding member, as well as the combination of the rotating body and the sealing material, but may be, for example, 0.6 MPa or less, 0.4 MPa or less, or 0.3 MPa or less. The surface pressure may be, for example, 0.01 to 0.6 MPa, 0.1 to 0.6 MPa, or 0.15 to 0.6 MPa.

[0020] Given the low surface pressure, it is preferable to set the sliding speed appropriately. If the mass ratio of the inorganic filler in the rotating body is large, and the sliding speed becomes excessive, the inorganic filler, being harder than the resin, may wear away the sealant, which has a smaller mass ratio of inorganic filler. For this reason, the sliding speed is preferably 6 cm / s or less, more preferably 4 cm / s or less, and even more preferably 3 cm / s or less. The sliding speed may be, for example, 0.5 to 6 cm / s, 1 to 6 cm / s, or 1.5 to 6 cm / s.

[0021] In the sliding surface of the rotating body, the resin molded member includes a thermoplastic resin having water absorption resistance and an inorganic filler.

[0022] Examples of thermoplastic resins with water absorption resistance include polyacetal resin, polyarylene sulfide resin, and polycarbonate resin. Examples of polyarylene sulfide resins include polyphenylene sulfide resin. Two or more of these resins may be used in combination. Due to environmental concerns, it is preferable that the thermoplastic resin does not contain organofluorine compound resins, such as PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). As such thermoplastic resins, it is particularly preferable to use polyacetal resin and polyarylene sulfide resin. Here, "water absorption resistance" refers to the property of not changing dimensions when immersed in water at a temperature of 23°C for 24 hours, for example, in the evaluation of water absorption rate in accordance with ISO 62.

[0023] The water-resistant thermoplastic resin contained in the resin molded member for the sliding surface of a rotating body may include polyacetal resin, polyphenylene sulfide resin, or a combination thereof. These resins are more durable when inclusion of inorganic fillers, making them suitable for rotating bodies requiring high durability, particularly as sliding surfaces of rotating bodies.

[0024] Inorganic fillers refer to inorganic components added for purposes such as improving mechanical strength and wear resistance. For use in thermoplastic resins with water-resistant properties, solid inorganic substances with an average particle size of 1 μm or larger are typically used as inorganic fillers. Examples of such inorganic fillers include silica, glass fibers, talc, calcium carbonate, carbon materials such as carbon fibers, mica, kaolin, clay, and wollastonite.

[0025] In the sliding surface of the rotating body, the inorganic filler may be 1 to 80 parts by mass, 20 to 70 parts by mass, or 40 to 60 parts by mass per 100 parts by mass of resin contained in the resin molded member. Alternatively, the inorganic filler may be 1 to 60% by mass, 10 to 50% by mass, or 20 to 40% by mass relative to the total mass of the resin molded member.

[0026] On the sliding surface of a rotating body, various known additives may be added to the resin molded member to improve its physical properties according to the intended application. Examples of additives include various stabilizers (antioxidants, acid fasteners, etc.), ultraviolet absorbers, light stabilizers, formaldehyde scavengers, colorants, mold release agents, nucleating agents, antistatic agents, other surfactants, and different polymers. On the sliding surface of a rotating body, these additives may be added in total amounts of 0.1 to 20 parts by mass, 0.5 to 10 parts by mass, or 1 to 5 parts by mass per 100 parts by mass of the total mass of the resin molded member.

[0027] The resin molded member in the sliding surface of the sealing material contains a thermoplastic resin that has water-resistant properties.

[0028] As the thermoplastic resin having water resistance, it can be appropriately selected and used from those described above for the sliding surface of the rotating body. The thermoplastic resin having water resistance contained in the resin molded member for the sliding surface of the sealing material may include polyacetal resin, polyphenylene sulfide resin, or a combination thereof, and it is even better if it includes polyacetal resin. These resins, in particular, polyacetal resin has excellent elasticity, resulting in high sealing performance and making it suitable as a sealing material.

[0029] For example, by using polyacetal resin, polyphenylene sulfide resin, or a combination thereof on the sliding surface of a rotating body, and using polyacetal resin as a sealing material, the amount of wear can be further reduced in sliding at low surface pressure and low sliding speed in aqueous liquids.

[0030] The mass ratio of the inorganic filler contained in the sliding surface of the sealing material only needs to be smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body, but it is preferable that the resin molded member does not contain an inorganic filler in the sliding surface of the sealing material. Note that a solid inorganic substance may be contained in the resin molded member for the purposes of, for example, improving the smoothness of the resin surface or improving the appearance, as long as it does not function as an inorganic filler. In this case, in a molded member obtained by molding a resin composition containing a water-absorption-resistant thermoplastic resin and not containing an inorganic filler, the content of the solid inorganic substance is preferably less than 5 parts by mass, less than 1 part by mass, less than 0.5 parts by mass, or less than 0.1 parts by mass relative to 100 parts by mass of the water-absorption-resistant thermoplastic resin.

[0031] In the sliding surface of the sealing material, various known additives as other components can be further added to the resin molded member to improve its physical properties according to the intended use. As the additives, those described for the sliding surface of the rotating body can be appropriately selected and used. In the resin molded member on the sliding surface of the sealing material, the total amount of these additives may be 0.1 to 20 parts by mass, 0.5 to 10 parts by mass, or 1 to 5 parts by mass relative to 100 parts by mass of the total mass of the resin molded member.

[0032] In an example of the present embodiment, the underwater sliding member has a specific wear amount (hereinafter also referred to as specific wear amount a) measured under the following Condition A at a surface pressure of 0.6 MPa and a sliding speed of 3 cm / s of 6×10 －３ mm ３ / N·km or less. The specific wear amount a is 6×10 －３ mm ３ / N·km or less, 4×10 －３ mm ３ / N·km or less, or 2×10 －３ mm ３ / N·km or less. Within the ranges of a surface pressure of 0.6 MPa and a sliding speed of 3 cm / s, with this level of specific wear amount a, excellent wear resistance can be provided even when the underwater sliding member is applied to various uses.

[0033] In still another example of the present embodiment, the specific wear amount (hereinafter also referred to as specific wear amount b) of the underwater sliding member, when measured under the following condition A at a contact pressure of 0.6 MPa and a sliding speed of 6 cm / s, is 30×10 －３ mm ３ / N·km or less. The specific wear amount b is 30×10 －３ mm ３ / N·km or less, 20×10 －３ mm ３ / N·km or less, or 10×10 －３ mm ３ / N·km or less. When the specific wear amount b falls within this range under the conditions of a contact pressure of 0.6 MPa and a sliding speed of 6 cm / s, the underwater sliding member can have excellent wear resistance even when applied to underwater sliding members for various uses.

[0034] [Condition A] In an aqueous liquid, the upper surface of a resin cylindrical member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the cylindrical underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), sliding is performed at an ambient temperature of 23°C for a sliding time of 24 hours, and the specific wear amount of the underwater sliding member after the completion of 24 hours of sliding is measured.

[0035] In still another example of the present embodiment, the coefficient of kinetic friction (hereinafter also referred to as coefficient of kinetic friction a) of the underwater sliding member, when measured under the following condition B at a contact pressure of 0.3 MPa and a sliding speed of 3 cm / s, is preferably 0.3 or less. When the coefficient of kinetic friction a falls within this range, the underwater sliding member can have excellent wear resistance even when applied to underwater sliding members for various uses.

[0036] In still another example of the present embodiment, the coefficient of kinetic friction (hereinafter also referred to as coefficient of kinetic friction b) of the underwater sliding member, when measured under the following condition B at a contact pressure of 0.6 MPa and a sliding speed of 6 cm / s, is preferably 0.3 or less. When the coefficient of kinetic friction b falls within this range, the underwater sliding member can have excellent wear resistance even when applied to underwater sliding members for various uses.

[0037] [Condition B] In an aqueous liquid, the upper surface of a resin cylindrical member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C. The coefficient of dynamic friction is measured near the end of the 24-hour period.

[0038] A lower coefficient of dynamic friction reduces frictional resistance at the sliding surface, thus reducing wear. Furthermore, in this embodiment, when the rotating body and sealing material, which are resin molded members, contain an inorganic filler, and the sealing material contains either no inorganic filler or only a small amount, wear can be sufficiently reduced in sliding at low surface pressure and low sliding speed in an aqueous liquid, as long as the coefficient of dynamic friction is within a reasonably small range. Therefore, wear can be reduced within the ranges of the above-mentioned coefficients of dynamic friction a and b.

[0039] In some embodiments, it is preferable to satisfy at least one of the above-mentioned specific wear amount a, specific wear amount b, dynamic friction coefficient a, and dynamic friction coefficient b, but it is preferable to satisfy at least two of these, and even better to satisfy three, and even better to satisfy all four. Underwater sliding members that satisfy these physical properties can be applied to underwater sliding members for various applications and will have excellent wear resistance.

[0040] In this embodiment, the resin molded articles of the rotating body and the sealing material can be manufactured by molding a resin composition containing a thermoplastic resin having water resistance. In the resin molded article of the rotating body, solid inorganic substances can be intentionally added during the manufacturing process to function as inorganic fillers. Additives may be optionally included in the resin composition containing the thermoplastic resin having water resistance. There are no particular limitations on the method for manufacturing the underwater sliding member using the resin composition, and known methods can be employed. For example, the resin composition can be put into an extruder, melt-kneaded to form pellets, and then these pellets can be put into an injection molding machine equipped with a predetermined mold and injection molded.

[0041] The underwater sliding member of this embodiment is suitable for use under low surface pressure and low sliding speed conditions in water. For example, the underwater sliding member can be used in articles used in underwater or water-intervening environments such as valves, pumps, gears, and bearings. Specifically, the underwater sliding member can be used in bathroom and water supply components that are frequently in contact with water; pipe and valve components used in environments where stress is constantly applied, especially rotary valves for aqueous liquids; and electrical appliances such as electric shavers that require water resistance. In particular, the underwater sliding member can be preferably used in rotary valves, which are often used under low surface pressure and low sliding speed conditions.

[0042] While the use of polyacetal resin has been restricted in high-temperature underwater environments, its high strength in relatively low-temperature underwater environments makes it suitable for use as a sliding member. For example, components of the drive system of electric vehicles are often used in environments where the temperature does not exceed 100°C. Polyacetal resin underwater sliding members can be preferably used in such applications. Specifically, they are suitable for use in rotary valves in the cooling systems of electric vehicles. In the cooling systems of electric vehicles, there is a method of supplying a cooling medium to the motor to cool it, but the cooling medium for the motor does not get as hot as the cooling medium for the engine. Therefore, the underwater sliding member of this embodiment can be used in the rotary valve placed in the flow path of the cooling medium in the cooling system of an electric vehicle, and it is particularly preferable to use an underwater sliding member made of polyacetal resin. Examples of electric vehicles include electric cars, plug-in hybrid cars, trains, and electric bicycles. For similar reasons, the underwater sliding member of this embodiment can also be used in cooling systems for stationary power sources, etc.

[0043] An example of an underwater sliding member of this embodiment will be described with reference to the drawings. Figure 1 shows a schematic cross-sectional view of a rotary valve, which is an example of an underwater sliding member. The rotary valve 100 shown comprises a rotating body 1 and a sealing material 2. The rotating body 1 is a disc-shaped resin molded body that can rotate around a central axis M. Several flow paths 1a for switching the water flow are formed inside the rotating body 1. In the illustrated example, the rotating body 1 is a single-piece molded resin product, but it may also be a composite material in which the sliding surface is a resin molded body and the interior is a metal material. A sealing material 2 is arranged on the outer circumferential surface of the rotating body 1 so as to be liquid-tight and slidable. In the illustrated example, the sealing material 2 is a composite material in which the sliding surface with the rotating body 1 is a resin molded body 2a and the supporting material that supports the resin molded body 2a is a supporting material 2b, but the sealing material 2 may also be a single-piece molded resin product. The sealing material 2 has several openings 2c in the circumferential direction on the outer circumferential surface of the rotating body 1. A water supply pipe 3 is connected to the opening 2c of the seal material 2, supplying aqueous liquid L to the rotating body 1 and discharging aqueous liquid L from the rotating body 1. When the rotating body 1 rotates and the flow path 1a of the rotating body 1 aligns with the opening 2c of the seal material 2, the aqueous liquid L flows into the flow path 1a of the rotating body 1, and the aqueous liquid flows out from another opening 2c of the seal material 2 through another flow path 1a. To switch the flow path 1a, the rotating body 1 can be rotated further. In this way, the flow path 1a of the aqueous liquid can be switched. The rotary valve 100 is sealed liquid-tight to ensure the flow path, but has a relatively low surface pressure, and the switching of the flow path 1a is performed at a low sliding speed to adjust the water flow, so the underwater sliding member of this embodiment can be preferably used.

[0044] In another embodiment of this model, an article can be provided comprising an underwater sliding member used in an aqueous liquid at a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein the underwater sliding member comprises a rotating body and a sealing material, the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body. Details of the underwater sliding member are as described above. Examples of articles include bathroom-related parts and water supply-related parts, pipe parts and valve parts, among which rotary valves for aqueous liquids, electrical appliances, electric vehicles, etc., details are as described above.

[0045] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples.

[0046] (Examples 1-6, Comparative Example 1) The following thermoplastic resins were prepared. Polyacetal resin 1: A sliding performance improving material manufactured by Polyplastics Co., Ltd., containing 0.5 parts by mass of inorganic filler per 100 parts by mass of Duracon® POM resin. Polyacetal resin 2: A sliding performance improving material manufactured by Polyplastics Co., Ltd., containing 51 parts by mass of inorganic filler per 100 parts by mass of Duracon® POM resin. Polyacetal resin 3: A mineral-reinforced material manufactured by Polyplastics Co., Ltd., containing 18 parts by mass of inorganic filler as a mineral component per 100 parts by mass of Duracon® POM resin. Polyacetal resin 4: A non-filled material manufactured by Polyplastics Co., Ltd., containing no inorganic filler per 100 parts by mass of Duracon® POM resin. Polyphenylene sulfide resin 1: A glass fiber reinforced material manufactured by Polyplastics Co., Ltd., containing 43 parts by mass of inorganic filler (glass fiber) per 100 parts by mass of resin, under the name DuraFide® PPS. Polyphenylene sulfide resin 2: A glass fiber reinforced material manufactured by Polyplastics Co., Ltd., containing 67 parts by mass of inorganic filler (glass fiber) per 100 parts by mass of resin, under the name DuraFide® PPS. Polyphenylene sulfide resin 3: A glass fiber reinforced material manufactured by Polyplastics Co., Ltd., containing 28 parts by mass of tetrafluoroethylene resin and 55 parts by mass of inorganic filler (glass fiber) per 100 parts by mass of resin, under the name DuraFide® PPS.

[0047] [Evaluation] Using the pelletized polyacetal resins 1-4 or polyphenylene sulfide resins 1-3 prepared in each example and comparative example, cylindrical test specimens 10 (outer diameter: 2.56 cm, inner diameter: 2.0 cm, height: 1.5 cm) were molded under normal injection molding conditions. In addition, a resin member 20 of the same shape and size as the test specimen 10 was prepared using polyacetal resin 4 (see Figure 2).

[0048] (Sliding Test) As shown in Figure 2, the cylindrical test piece 10 was placed on top and the cylindrical resin member 20 on the bottom, with their upper and lower surfaces in contact, and then immersed in water. The lower resin member 20 was then continuously rotated under the following conditions 1 to 3. Condition 1: Sliding speed: 3.0 cm / s Surface pressure: 0.15 MPa Ambient temperature: 23°C Sliding time: 24 hours Condition 2: Sliding speed: 1.5 to 6.0 cm / s Surface pressure: 0.30 MPa Ambient temperature: 23°C Sliding time: 24 hours Condition 3: Sliding speed: 1.5 to 6.0 cm / s Surface pressure: 0.60 MPa Ambient temperature: 23°C Sliding time: 24 hours

[0049] (Evaluation of wear amount) In each example and comparative example, the amount of wear [g] was calculated from the difference in mass of the test piece 10 before and after the sliding test. The calculated amount of wear [g] was then compared to the specific gravity of the material [g / cm³]. ３ Using ], volume [mm ３ Convert this to [units], and divide this volume value by the applied load [N] and sliding distance [km] to obtain the specific wear amount [mm]. ３ The value [ / N・km] was calculated. The calculation results are shown in Table 1. Note that "-" indicates that the experiment was not performed.

[0050]

[0051] (Evaluation of Dynamic Friction Coefficient) In each example and comparative example, the following apparatus was used to perform a 24-hour sliding test from the start of the sliding test to obtain data on the change in the dynamic friction coefficient over time. The values ​​immediately after the start of the test and the values ​​near the end of the test after 24 hours (where the behavior of change stabilized) were determined as the dynamic friction coefficient values, and the amount of change was calculated. The results are shown in Table 2. Note that "-" indicates that the experiment was not performed. Apparatus: Thrust-type friction and wear tester EFM-III-EN (manufactured by Orientec Co., Ltd.)

[0052]

[0053] In the wear amount evaluation and dynamic friction coefficient evaluation, the test piece 10 was used as a rotating body and the resin member 20 as a sealing material to simulate an underwater sliding member. From Table 1, it can be seen that in all three conditions, the specific wear amount was lower in each example in which the test piece 10 contained an inorganic filler than in Comparative Example 1 in which the test piece 10 did not contain an inorganic filler.

[0054] Table 2 shows that, under condition 2, the coefficient of dynamic friction is smaller for each example in which the test piece 10 contains an inorganic filler than for Comparative Example 1 in which the test piece 10 does not contain an inorganic filler. Furthermore, under condition 3, when the surface pressure is 0.6 MPa and the sliding speed is 1.5 cm / s or 3.0 cm / s, the coefficient of dynamic friction is smaller for each example in which the test piece 10 contains an inorganic filler than for Comparative Example 1 in which the test piece 10 does not contain an inorganic filler.

[0055] In the cases of Condition 1 and Condition 3, where the surface pressure is 0.6 MPa and the sliding speed is 3.0 cm / s, Example 3 shows reduced wear despite having a higher coefficient of dynamic friction than Comparative Example 1. This result is thought to be due to the fact that the rotating body of Example 3 contains an inorganic filler.

[0056] Although the present invention has been described with reference to several embodiments described above, the present invention is not limited to these embodiments. Various modifications can be made to the structure and details of the present invention within the scope of the invention. This disclosure is related to the subject matter described in Japanese Patent Application No. 2025-051764, filed on 26 March 2025, all of which are incorporated herein by reference.

[0057] 1 Rotating body, 1a Flow channel, 2 Sealing material, 2a Resin molded body, 2b Support material, 2c Opening, 3 Water supply pipe, L Aqueous liquid, M Central axis, 100 Rotary valve, 10 Test piece, 20 Resin component

Claims

1. An underwater sliding member for use in an aqueous liquid at a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein the underwater sliding member comprises a rotating body and a sealing material, the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body.

2. The underwater sliding member according to claim 1, wherein the sliding surface of the sealing material is a resin molded member that does not contain an inorganic filler.

3. The underwater sliding member according to claim 1, which is used in an aqueous liquid at a surface pressure of 0.15 to 0.6 MPa.

4. The underwater sliding member according to claim 1, which is used in an aqueous liquid at a sliding speed of 1.5 to 6 cm / s.

5. The underwater sliding member according to claim 1, wherein the thermoplastic resin having water resistance contained in the resin molded member of the sliding surface of the sealing material includes a polyacetal resin.

6. The water-resistant thermoplastic resin contained in the resin molded member of the sliding surface of the rotating body includes polyacetal resin, polyphenylene sulfide resin, or a combination thereof, as described in claim 1.

7. The specific wear amount measured under the following condition A, with a surface pressure of 0.6 MPa and a sliding speed of 3 cm / s, was 6 × 10⁻⁶. －３ mm ３ An underwater sliding member according to any one of claims 1 to 6, wherein the friction coefficient is less than or equal to / N·km. [Condition A] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the members are slid at an ambient temperature of 23°C for a sliding time of 24 hours, and the specific wear amount of the underwater sliding member is measured after 24 hours.

8. The specific wear amount measured under the following condition A, with a surface pressure of 0.6 MPa and a sliding speed of 6 cm / s, was 30 × 10⁻¹⁶. －３ mm ３ An underwater sliding member according to any one of claims 1 to 6, wherein the friction coefficient is less than or equal to / N·km. [Condition A] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the members are slid at an ambient temperature of 23°C for a sliding time of 24 hours, and the specific wear amount of the underwater sliding member is measured after 24 hours.

9. An underwater sliding member according to any one of claims 1 to 6, wherein the coefficient of dynamic friction measured under the following condition B is 0.3 or less, with a surface pressure of 0.3 MPa and a sliding speed of 3 cm / s. [Condition B] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C, and the coefficient of dynamic friction is measured near the end of the 24 hours.

10. An underwater sliding member according to any one of claims 1 to 6, wherein the coefficient of dynamic friction measured under the following condition B is 0.3 or less, with a surface pressure of 0.6 MPa and a sliding speed of 6 cm / s. [Condition B] In an aqueous liquid, the upper surface of a cylindrical resin member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) is brought into contact with the lower surface of the underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the two are slid for 24 hours at an ambient temperature of 23°C, and the coefficient of dynamic friction is measured near the end of the 24 hours.

11. An underwater sliding member for use in a rotary valve, according to any one of claims 1 to 6.

12. The underwater sliding member according to claim 11, for use in a rotary valve provided in the cooling system of an electric vehicle.

13. An article comprising an underwater sliding member used in an aqueous liquid with a surface pressure of 0.6 MPa or less and a sliding speed of 6 cm / s or less, wherein the underwater sliding member comprises a rotating body and a sealing material, the sliding surface of the rotating body is a resin molded member containing a water-resistant thermoplastic resin and an inorganic filler, the sliding surface of the sealing material is a resin molded member containing a water-resistant thermoplastic resin, and the mass ratio of the inorganic filler contained in the sliding surface of the sealing material is smaller than the mass ratio of the inorganic filler contained in the sliding surface of the rotating body.

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