Underwater sliding member

Abstract

This underwater sliding member is obtained by molding a resin composition which contains a thermoplastic resin that has water absorption resistance, and a granular inorganic filler and / or a plate-shaped inorganic filler, wherein the Mohs hardness of the inorganic filler is 5 or less.

Description

Underwater sliding components

[0001] The present disclosure relates to an underwater sliding member.

[0002] Polyacetal resins are excellent in mechanical strength, chemical resistance, sliding properties, etc. Therefore, as a typical engineering plastic, they are widely used in a wide range of fields, such as molded articles for automobile parts, electrical and electronic parts, furniture and building materials, and mechanical parts for precision instruments. In particular, due to their excellent sliding properties, polyacetal resins are suitably used for sliding members such as gears and cams.

[0003] Parts used as sliding members are often used under a constant load, and therefore require not only sliding performance but also short-term mechanical properties such as rigidity, strength, and toughness, as well as long-term durability properties such as creep resistance and fatigue resistance. In recent years, usage environments have become more diverse, and polyacetal resins are used in, for example, bathroom and water supply applications where water frequently comes into contact with the parts, pipes and valves used in environments where constant stress is applied, and drive parts such as rotary valves for electric vehicle (EV) modules. However, simply using polyacetal resins alone can result in the loss of their reinforcing effect when immersed in hot water. This poses a challenge, such as the difficulty of withstanding long-term use, as pipes and valve parts can be destroyed by sudden valve closure. Polyacetal resins used in sliding members for valve components must be able to combine high levels of mechanical strength, long-term properties, and friction and wear resistance in underwater environments (including long-life coolant (LLC)).

[0004] Blending inorganic fillers with polyacetal resin has long been used as a common method for meeting the required performance requirements for parts requiring strength and rigidity. Patent Document 1 discloses a technique for blending inorganic fillers, such as fibrous inorganic fillers such as glass fiber, carbon fiber, and wollastonite, and granular inorganic fillers such as calcium carbonate, to improve rigidity and reduce shrinkage anisotropy. Patent Document 2 discloses a technique for blending polyacetal resin, polylactic acid resin, and talc as a reinforcing material to improve mechanical properties, reduce warpage, and improve the appearance of molded products. However, the techniques described in Patent Documents 1 and 2 do not take into consideration components used underwater.

[0005] On the other hand, with regard to components for use underwater that use resins other than polyacetal resin, Patent Document 3 discloses an underwater sliding component 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 component for use underwater that uses a composite material containing tetrafluoroethylene resin and at least one filler selected from carbon fiber, graphite, boron nitride, molybdenum disulfide, and tungsten disulfide.

[0006] International Publication No. 2005 / 071011 Japanese Patent Application Laid-Open No. 2003-286402 Japanese Patent Application Laid-Open No. 2002-323038 Japanese Patent Application Laid-Open No. 2003-21144

[0007] When the methods described in Patent Documents 1 or 2 are used, for example, when glass fibers are added to polyacetal resin, there is a problem in that the glass fibers are exposed at the sliding interface, which increases the aggressiveness of the mating material and accelerates wear of the mating material.

[0008] On the other hand, the tendency of sliding characteristics differs between a member that slides in a dry environment and a member that slides in water. In other words, even if a member has good sliding characteristics in a dry environment, it does not necessarily have the same good sliding characteristics in water as in a dry environment. In other words, even if a member that has good sliding characteristics in a dry environment is used in water, it does not necessarily have good sliding characteristics. For example, in a material in which calcium carbonate is blended with polyacetal resin in a dry environment, rigidity is improved but toughness and the like are reduced. Therefore, there is a demand for suppressing these reductions and for even higher sliding characteristics.

[0009] The present disclosure has been made in consideration of the above-mentioned conventional problems, and an object of the present disclosure is to provide an underwater sliding member that has good sliding characteristics in water, is less aggressive to a mating material during sliding, and is capable of reducing wear of the mating material.

[0010] One aspect of the present disclosure that solves the above problems is as follows: (1) An underwater sliding component obtained by molding a resin composition containing a thermoplastic resin having water absorption resistance and a granular inorganic filler and / or a plate-like inorganic filler, wherein the inorganic filler has a Mohs hardness of 5 or less.

[0011] (2) The underwater sliding component according to (1), wherein the inorganic filler has an average particle size of 0.1 to 100 μm as measured by a laser diffraction / scattering particle size distribution measurement method.

[0012] (3) The underwater sliding component according to (1) or (2), wherein the thermoplastic resin is a polyacetal resin, and the inorganic filler is talc and / or calcium carbonate.

[0013] (4) The underwater sliding component according to any one of (1) to (3), wherein the content of the inorganic filler is 5 to 60 parts by mass relative to 100 parts by mass of the thermoplastic resin.

[0014] (5) The underwater sliding member according to any one of (1) to (4), wherein the thermoplastic resin is a polyacetal resin, the inorganic filler is talc and / or calcium carbonate, and the content of the inorganic filler is 5 to 60 parts by mass relative to 100 parts by mass of the thermoplastic resin.

[0015] (6) An underwater sliding element according to any one of (1) to (5), having a dynamic friction coefficient of 0.21 or less when measured under the following conditions: [Conditions] In water, the side of a stainless steel (SUS) columnar element (outer diameter: 1.0 cm, length: 1 cm) is brought into contact (linear contact width: 2.8 mm) with the upper part of the underwater sliding element having a cylindrical shape (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the element is allowed to slide at a sliding speed of 15 cm / s, a load of 12 N, an ambient temperature of 23°C, and a sliding time of 24 hours, and the dynamic friction coefficient is measured near the end of the 24 hours.

[0016] According to the present disclosure, it is possible to provide an underwater sliding member that has good sliding characteristics in water and can reduce wear of the mating material during sliding.

[0017] 1 is a conceptual diagram showing a sliding test (sliding mode 1) conducted in an example; FIG. 2 is a conceptual diagram showing a sliding test (sliding mode 2) conducted in an example; FIG. 3 is a photograph showing the sliding surface of a stainless steel member after conducting a sliding test (sliding mode 2), showing Example 1; and FIG. 4 is a photograph showing the sliding surface of a stainless steel member after conducting a sliding test (sliding mode 2), showing Comparative Example 3.

[0018] The underwater sliding member of this embodiment is formed by molding a resin composition containing a thermoplastic resin having water absorption resistance (hereinafter also referred to as "water-absorption-resistant thermoplastic resin") and a granular inorganic filler and / or a plate-like inorganic filler, and is characterized in that the Mohs hardness of the inorganic filler is 5 or less. The underwater sliding member of this embodiment is intended for members that slide against a mating member underwater, and is not intended for members used in dry environments. Note that "underwater" in the underwater sliding member of this embodiment refers not only to pure water, but also to liquids containing water, such as long-life coolant (LLC) and water-soluble lubricating oils such as emulsions. The water content of the "liquid containing water" is, for example, 30 to 100 mass %.

[0019] The underwater sliding component of this embodiment is formed by molding a resin composition containing a water-absorption-resistant thermoplastic resin and a granular inorganic filler and / or a plate-like inorganic filler having a predetermined Mohs hardness. The inclusion of the inorganic filler can improve the sliding characteristics in water. That is, the predetermined Mohs hardness and the granular and / or plate-like shape of the inorganic filler can reduce aggressiveness to the mating material during sliding and reduce wear of the mating material. Each component of the resin composition according to this embodiment will be described below.

[0020] [Water-absorption-resistant thermoplastic resin] Examples of water-absorption-resistant thermoplastic resins include polyacetal resins, polyarylene sulfide resins, polycarbonate resins, and polyphenylene ether resins. Among these, polyacetal resins and polyarylene sulfide resins are preferred. Here, "water-absorption-resistant" refers to the property of not undergoing dimensional change when immersed in water at a temperature of 23°C for 24 hours, as evaluated for water absorption rate in accordance with ISO 62, for example.

[0021] [Inorganic Filler] In this embodiment, the inorganic filler is a granular inorganic filler and / or a plate-like inorganic filler having a Mohs hardness of 5 or less. By including such an inorganic filler, the mechanical strength of the final product, the underwater sliding component, can be improved. Furthermore, if the inorganic filler has a Mohs hardness of 5 or less and is granular or plate-like, it has little effect on the mating material during sliding, resulting in a small amount of wear. On the other hand, if the inorganic filler is in a shape other than granular or plate-like, for example, fibrous, it will be more aggressive to the mating material during sliding, resulting in a large amount of wear.

[0022] In this embodiment, the granular inorganic filler and the plate-like inorganic filler may be used alone or in combination of two types. Note that, hereinafter, when the term "inorganic filler" is used, it refers to both the granular inorganic filler and the plate-like inorganic filler.

[0023] In this embodiment, from the viewpoint of reducing aggressiveness to the mating material, the Mohs hardness of the inorganic filler is 5 or less, preferably 0.5 to 4, more preferably 1 to 3, and even more preferably 1 to 2. The Mohs hardness can be measured using a Mohs hardness scale. Here, several examples of the Mohs hardness of inorganic fillers are shown below. Talc: Mohs hardness = 1 Calcium carbonate: Mohs hardness = 3 Glass fiber, glass beads: Mohs hardness = 4.5 to 6.5 Potassium titanate: Mohs hardness = 4

[0024] The average particle size of the inorganic filler is preferably 0.1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 30 μm. The average particle size is the particle size (D50) at which the volume-based integrated value in the particle size distribution is 50%, and can be measured by a laser diffraction / scattering particle size distribution measurement method.

[0025] In this embodiment, from the viewpoint of improving sliding properties and reducing wear of the mating material, talc and calcium carbonate are particularly preferred among inorganic fillers. Of these, calcium carbonate is not particularly limited, but examples that can be used include heavy calcium carbonate and precipitated calcium carbonate (light calcium carbonate and colloidal calcium carbonate).

[0026] The content of the inorganic filler is preferably 2 to 70 parts by mass, more preferably 3 to 60 parts by mass, and even more preferably 5 to 55 parts by mass, per 100 parts by mass of the thermoplastic resin. From the viewpoint of reducing the amount of wear during sliding, the content of the inorganic filler may be 1 to 55 parts by mass, 2 to 40 parts by mass, or 3 to 10 parts by mass, per 100 parts by mass of the thermoplastic resin. When talc is used as the inorganic filler, the content of the talc may be 1 to 40 parts by mass, 2 to 20 parts by mass, or 3 to 10 parts by mass, per 100 parts by mass of the thermoplastic resin.

[0027] On the other hand, it is preferable to subject the inorganic filler to a surface treatment. This is because it is believed that surface treatment of the inorganic filler improves compatibility with the thermoplastic resin and improves wear characteristics. As an example, in the case of calcium carbonate, calcium carbonate that has been surface-treated with, for example, a fatty acid, a fatty acid ester, a resin acid, or a higher alcohol-added isocyanate compound (surface-treated calcium carbonate) can be used. Furthermore, it is believed that when the temperature of the water in which the underwater sliding component of this embodiment is used is high, the thermoplastic resin softens and wear becomes less likely to occur. Therefore, the content of the inorganic filler can be adjusted taking into account the temperature of the water in which it is used.

[0028] [Other Components] The resin composition according to the present embodiment may further contain various known additives as other components to improve its physical properties depending on the intended use. Examples of the additives include various stabilizers (antioxidants, anti-acid agents, etc.), UV absorbers, light stabilizers, formaldehyde scavengers, colorants (carbon black, etc.), release agents, nucleating agents, antistatic agents, other surfactants, heterogeneous polymers, etc.

[0029] The underwater sliding component of this embodiment described above can achieve a dynamic friction coefficient of 0.21 or less when measured under the following conditions. The following conditions correspond to sliding mode 2 of the sliding test conducted in the Examples described below. This dynamic friction coefficient is preferably 0.21 or less, but can also be 0.20 or less, 0.18 or less, or 0.15 or less. In particular, the use of talc as the inorganic filler can reduce the amount of wear of the mating member during sliding, and can further reduce this dynamic friction coefficient to 0.21 or less, thereby further improving the sliding characteristics. From the perspective of reducing this dynamic friction coefficient, when talc is used as the inorganic filler, the talc content may be 5 to 70 parts by mass, 10 to 60 parts by mass, or 30 to 55 parts by mass relative to 100 parts by mass of the thermoplastic resin. [Conditions] In water, the side of a stainless steel cylindrical member (outer diameter: 1.0 cm, length: 1 cm) was brought into contact (linear contact width: 2.8 mm) with the upper part of the cylindrical underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm), and the sliding was carried out at a sliding speed of 15 cm / s, a load of 12 N, an ambient temperature of 23°C, and a sliding time of 24 hours, and the dynamic friction coefficient was measured near the end of the 24 hours.

[0030] The above conditions are the dynamic friction coefficients measured by sliding members in sliding mode 2 in the examples described later. Sliding mode 2 is a sliding mode in which two members including portions that slide against each other slide in a state where the sliding portions are in intermittent contact, rather than a sliding mode in which the sliding portions slide continuously in a state where they are in constant contact ("sliding mode 1" in the examples described later). Sliding mode 2 is a mode that is used more widely than sliding mode 1, and a small dynamic friction coefficient in such a sliding mode can be said to be highly useful as a sliding member.

[0031] The underwater sliding member of this embodiment is formed by molding a resin composition containing a water-absorption-resistant thermoplastic resin and a granular inorganic filler and / or a plate-like inorganic filler. There are no particular limitations on the method for producing a molded product using the resin composition, and any known method can be used. For example, the resin composition can be fed into an extruder, melt-kneaded, and pelletized, and the pellets can be fed into an injection molding machine equipped with a predetermined mold and injection-molded.

[0032] As described above, examples of the underwater sliding member of this embodiment include pipe and valve parts used in bathrooms and water supply facilities where they come into frequent contact with water, and in environments where stress is constantly applied; drive parts such as rotary valves for EV modules; electric shavers, pumps, cogwheels, gears; and drive modules for underwater / water-mediated environments.

[0033] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0034] Examples 1 to 3, Comparative Examples 1 to 4 In each of the Examples and Comparative Examples, thermoplastic resins 1 to 7 shown below were prepared. Each of thermoplastic resins 1 to 7 contains a polyacetal resin and an inorganic filler shown in parentheses (except for thermoplastic resin 4). The content of inorganic filler per 100 parts by mass of polyacetal resin in thermoplastic resins 1 to 7 is shown in Table 1. Because thermoplastic resins 1 to 7 (except for thermoplastic resin 4) contain an inorganic filler, they should be referred to as "thermoplastic resin compositions 1 to 7," but for convenience, they will be referred to as thermoplastic resins 1 to 7. The average particle size of the inorganic filler is the particle size (D50) at which the volume-based integrated value in the particle size distribution is 50%, and is a value obtained by measurement using a laser diffraction / scattering particle size distribution measurement method.Thermoplastic resin 1: DURACON (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: talc (average particle size 14.6 μm), a mineral-reinforced material containing 5.4 parts by mass of inorganic filler per 100 parts by mass of resin) Thermoplastic resin 2: DURACON (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: talc (average particle size 14.6 μm), a mineral-reinforced material containing 18.2 parts by mass of inorganic filler per 100 parts by mass of resin) Thermoplastic resin 3: DURACON (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: talc (average particle size 14.6 μm) and calcium carbonate (average particle size 0.3 μm), a material for improving sliding properties containing 51.2 parts by mass of inorganic filler per 100 parts by mass of resin) Thermoplastic resin 4: DURACON (registered trademark) POM manufactured by Polyplastics Co., Ltd. (Inorganic filler: none) Thermoplastic resin 5: Duracon (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: glass fiber, glass fiber reinforced material containing 25.2 parts by mass of inorganic filler per 100 parts by mass of resin) Thermoplastic resin 6: Duracon (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: glass fiber, glass fiber reinforced material containing 33.5 parts by mass of inorganic filler per 100 parts by mass of resin) Thermoplastic resin 7: Duracon (registered trademark) POM manufactured by Polyplastics Co., Ltd. (inorganic filler: glass beads, low warpage material containing 34.5 parts by mass of inorganic filler per 100 parts by mass of resin).

[0035] Thermoplastic resins 1 to 3 were used in Examples 1 to 3, respectively, and thermoplastic resins 4 to 7 were used in Comparative Examples 4 to 7, respectively. In each of the Examples and Comparative Examples, the resin compositions were melt-kneaded in an extruder at a cylinder temperature of 200 to 220°C to prepare pellet-shaped resin compositions.

[0036] [Evaluation] Using the pellet-shaped resin compositions prepared in each Example and Comparative Example, two cylindrical test pieces 10 (outer diameter: 2.56 cm, inner diameter: 2.0 cm, height: 1.5 cm) were molded using an injection molding machine. A cylindrical stainless steel member 20 of the same shape and size as test piece 10 was also prepared (see Figure 1). Furthermore, a cylindrical stainless steel member 30 (outer diameter: 1.0 cm, length: 1 cm) smaller than test piece 10 was also prepared (see Figure 2).

[0037] (Sliding Test) (1) Sliding Condition 1 As shown in Fig. 1, a cylindrical test piece 10 was placed on the upper side and a cylindrical stainless steel member 20 was placed on the lower side so that they were in contact with each other, and then the test pieces were immersed in water. The lower stainless steel member 20 was then continuously rotated under the following conditions: -Conditions- Sliding speed: 30 cm / s, Surface pressure: 0.49 MPa, Ambient temperature: 23°C, Sliding time: 24 hours

[0038] (2) Sliding Mode 2 As shown in Figure 2, a cylindrical test piece 10 was placed on the bottom and a cylindrical stainless steel member 30 smaller than the test piece 10 was placed on the top so that they were in contact with each other, and then they were immersed in water. The lower test piece 10 was then continuously rotated under the following conditions. Note that in sliding mode 1, the entire sliding portion of the test piece 10 was in contact with the stainless steel member 20 on the other side, whereas in sliding mode 2, only a portion of the test piece 10 and the stainless steel member 30 slid against each other. Conditions: Sliding speed: 15 cm / s, Load: 12 N, Ambient temperature: 23°C, Sliding time: 24 hours

[0039] <<Dynamic Friction Coefficient>> In each Example and Comparative Example, the sliding test for each sliding mode was started and simultaneously the following device was used to perform sliding for 24 hours to obtain data on the change in dynamic friction coefficient over time, and the value near the end of the test after 24 hours (when the behavior of the change stabilized) was determined as the dynamic friction coefficient value. The results are shown in Table 1. Device: Thrust-type friction and wear tester EFM-III-EN (manufactured by Orientec Co., Ltd.)

[0040] <<Wear Amount>> In each example and comparative example, the wear amount [g] was calculated from the difference in mass of the test piece before and after the sliding test in each sliding mode. The calculated wear amount [g] was then used as the specific gravity [g / cm3] of the material.３ ] to calculate the volume [mm ３ ] and divided by the applied load [N] and sliding distance [km] to obtain the specific wear rate [mm ３ The results are shown in Table 1.

[0041]

[0042]

[0043] From Table 1, it can be seen that in Examples 1 to 3, the coefficient of dynamic friction was small and the specific wear rate on the SUS side was small, so the sliding characteristics were good and wear on the mating material could be reduced. On the other hand, in Comparative Example 1, which did not contain an inorganic filler, the specific wear rate on the SUS side was small, but the specific wear rate on the resin side was large and the coefficient of dynamic friction was also large. Furthermore, in Comparative Examples 2 to 4, which contained a specified amount of glass fiber or glass beads, the coefficient of dynamic friction was relatively small, but the specific wear rate on both the resin side and the SUS side was large.

[0044] Furthermore, photographs of the sliding surfaces of the cylindrical stainless steel members after the sliding test (sliding mode 2) are shown in Fig. 3 for only Example 1 and Comparative Example 3. Fig. 3A shows Example 1, and Fig. 3B shows Comparative Example 3. Figs. 3A and 3B show that the amount of wear of the stainless steel member in Example 1 is clearly less than that in Comparative Example 3.

[0045] Although the present invention has been described with reference to the above-mentioned several embodiments, the present invention is not limited to these several embodiments. Various modifications can be made to the configuration and details of the present invention within the scope of the present invention.

[0046] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2024-054088, filed on March 28, 2024, the entire disclosure of which is incorporated herein by reference.

[0047] 10 Test piece, 20 30 Stainless steel member

Claims

1. A resin composition comprising a thermoplastic resin having water-resistant properties and an inorganic filler is molded, The inorganic filler consists of granular inorganic filler and / or plate-shaped inorganic filler. A water-sliding member wherein the inorganic filler has a Mohs hardness of 5 or less.

2. The underwater sliding member according to Claim 1, wherein the total amount of the granular inorganic filler and the plate-shaped inorganic filler is 1 to 18.2 parts by mass per 100 parts by mass of the thermoplastic resin.

3. The underwater sliding member according to claim 1 or 2, wherein the average particle size of the inorganic filler, as measured by laser diffraction / scattering particle size distribution measurement, is 0.1 to 100 μm.

4. The underwater sliding member according to claim 1 or 2, wherein the thermoplastic resin is a polyacetal resin and the inorganic filler is talc and / or calcium carbonate.

5. The underwater sliding member according to claim 1 or 2, wherein the content of the inorganic filler is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin.

6. The underwater sliding member according to claim 1 or 2, wherein the thermoplastic resin is a polyacetal resin, the inorganic filler is talc and / or calcium carbonate, and the content of the inorganic filler is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin.

7. The underwater sliding member according to claim 1 or 2, wherein the coefficient of dynamic friction when measured under the following conditions is 0.21 or less. [conditions] In water, the side surface of a stainless steel cylindrical member (outer diameter: 1.0 cm, length: 1 cm) is brought into contact with the upper part of the cylindrical underwater sliding member (inner diameter: 2.0 cm, outer diameter: 2.56 cm, height: 1.5 cm) (line contact width: 2.8 mm). The sliding is performed at a sliding speed of 15 cm / s, a load of 12 N, an ambient temperature of 23 °C, and a sliding time of 24 hours. The coefficient of dynamic friction is measured near the end of the 24-hour period.

8. A resin composition comprising a thermoplastic resin having water resistance and an inorganic filler is molded, The inorganic filler consists of granular inorganic filler and / or plate-shaped inorganic filler. The Mohs hardness of the inorganic filler is 5 or less. A sliding component for use in water, which slides under a surface pressure of 12 N or less and a sliding speed of 15 cm / s or more.