Gland packing

Abstract

To provide a gland packing that has low sliding resistance, can prevent seizure in use, and has excellent sealing property (sealability), and further provide a gland packing that prevent elutions from occurring when immersed in water and is excellent in terms of food hygiene.SOLUTION: A gland packing has a middle core and a braided material surrounding the middle core, where fluororesin fibers are used as fibers constituting the middle core and the braided material, and the gland packing contains an oil component and an oleophilic inorganic filler.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gland packing. More specifically, the present invention relates to a gland packing that can be suitably used in applications such as valves, rotary pumps, reciprocating devices, and rotating devices. [Background technology]

[0002] Gland packing is generally used in stuffing boxes. One proposed gland packing can prevent sticking to the sliding parts of the stuffing box, has low sliding resistance, and excellent sealing properties. The gland packing is made of a braided material, which is wrapped around the shaft of a testing machine having a stuffing box and a shaft, the braided material is tightened at a surface pressure of 60 MPa, the testing machine is heated at 300°C for 1 hour, and the leakage rate is measured for 5 minutes after starting to load water at 3.8 MPa. After that, the initial sliding torque is measured with a torque wrench. This gland packing has a leakage rate of 30 cc / min or less and an initial sliding torque of less than 100 N m (see, for example, Patent Document 1).

[0003] Furthermore, as a gland packing that does not or is unlikely to have adverse effects on human health even if ceramic fibers fly off after use at high temperatures, a gland packing has been proposed that has a core and a surface braided material in which threads are woven to surround the outer surface of the core, and at least one of the core and the surface braided material contains ceramic fibers, and 50% by mass or more of the ceramic fibers are biosoluble fibers (see, for example, Patent Document 2).

[0004] In recent years, there has been a demand for the development of gland packing that can prevent seizure when used in stuffing boxes and has excellent sealing properties. There is also a demand for the development of gland packing that is less likely to produce elution when immersed in water and is excellent in terms of food hygiene. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 190365 Brochure [Patent Document 2] Japanese Patent Application Publication No. 2017-101772 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned conventional technology, and has as its first object to provide a gland packing that has low sliding resistance, can prevent seizure during use, and has excellent sealing properties. The second object of the present invention is to provide a gland packing that is less likely to produce elution when immersed in water, and is therefore excellent in terms of food hygiene.

[0007] In this invention, seizure refers to a phenomenon in which the fluid used evaporates or vaporizes due to frictional heat generated when the gland packing rubs against a sliding member such as a rotating shaft, causing the packing to stick to the sliding member. When the fluid used is, for example, water, the occurrence of seizure can be easily determined by visually observing whether water vapor is generated when the gland packing rubs against a sliding member such as a rotating shaft. [Means for solving the problem]

[0008] The present invention provides (1) A gland packing having a core and a braided material surrounding the core, wherein fluororesin fibers are used as fibers constituting the core and the braided material, and the gland packing contains an oil component and an oleophilic inorganic filler; (2) The gland packing according to (1) above, wherein the oil component is at least one selected from the group consisting of silicone oil, liquid paraffin, and fluorine oil. Regarding. [Effects of the Invention]

[0009] According to the present invention, there is provided a gland packing which has low sliding resistance, can prevent seizure during use, and has excellent sealing properties (sealing ability).Furthermore, according to the present invention, there is provided a gland packing which is less likely to produce elution when immersed in water, and is excellent in terms of food hygiene. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic longitudinal sectional view showing an embodiment of the gland packing of the present invention. [Figure 2] 1 is a schematic side view showing an embodiment of the gland packing of the present invention. [Figure 3] FIG. 1 is a schematic diagram illustrating a horizontal rotation test device used to evaluate the performance of a gland packing. DETAILED DESCRIPTION OF THE INVENTION

[0011] As described above, the gland packing of the present invention is a gland packing having a core and a braided material surrounding the core, and fluororesin fibers are used as the fibers constituting the core and the braided material, and contains an oil component and an oleophilic inorganic filler.

[0012] Therefore, the gland packing of the present invention has low sliding resistance, can prevent seizure during use, and has excellent sealing properties (hermetic sealing).

[0013] The gland packing of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings. FIG. 1 is a schematic vertical cross-sectional view showing one embodiment of the gland packing of the present invention.

[0014] The gland packing 1 of the present invention has a core 2 and a plurality of braided materials 3 surrounding the core 2. In the embodiment shown in Fig. 1, a plurality of cores 2 are used, but only one core 2 may be used in the center of the gland packing 1.

[0015] The core 2 is formed by bundling a plurality of fibers (filaments). Therefore, the core 2 may be a strand made of a plurality of fibers. The fineness of the fibers used in the core 2 is not particularly limited, but is usually about 10,000 to 12,000 dtex. The diameter of the core 2 cannot be determined in general because it differs depending on the application of the gland packing 1, but is usually about 1 to 10 mm, and can be adjusted by adjusting the diameter and number of fibers used in the core 2.

[0016] The plurality of braided materials 3 surround the core 2. Like the core 2, the braided material 3 is formed by bundling a plurality of fibers (filaments). Therefore, like the core 2, the braided material 3 may be a strand made of a plurality of fibers. The fineness of the fibers used in the braided material 3 is not particularly limited, but is typically about 10,000 to 12,000 dtex. The diameter of the braided material 3 cannot be determined in general because it differs depending on the application of the gland packing 1, but is typically about 1 to 10 mm, and can be adjusted by adjusting the diameter and number of fibers used in the braided material 3.

[0017] The gland packing 1 can be obtained by surrounding the periphery of the core 2 with the braided material 3. Examples of methods for surrounding the periphery of the core 2 with the braided material 3 include braiding methods generally used to produce the gland packing 1, such as eight-knit, tubular knitting, and lattice knitting. The present invention is not limited to the braiding method.

[0018] The size of the gland packing 1 cannot be determined in general terms because it differs depending on the application, such as a valve, rotary pump, reciprocating equipment, or rotating equipment, and is therefore preferably adjusted appropriately depending on the application. The size of the gland packing 1 can be easily adjusted by adjusting the diameter and number of cores 2 used, and the diameter and number of braided material 3 used.

[0019] The above is an overview of the gland packing 1 having the core 2 and the braided material 3 surrounding the core 2. The gland packing 1 has, for example, the appearance shown in Fig. 2. Fig. 2 is a schematic side view showing one embodiment of the gland packing 1.

[0020] The longitudinal cross-sectional shape of the gland packing is arbitrary, and a typical example of such a longitudinal cross-sectional shape is a square. The length of one side of the cross-section of a gland packing having a square cross section cannot be determined in general because it varies depending on the application of the gland packing, but it is usually 3 to 25 mm.

[0021] Next, the specific composition of the gland packing of the present invention will be described. In the present invention, fluororesin fibers are used as the fibers constituting the core and braided material. In the present invention, since fluororesin fibers are used as the fibers constituting the core and braided material, when the gland packing is immersed in water, elution is unlikely to occur from the core and braided material of the gland packing, and therefore the gland packing of the present invention is excellent in terms of food hygiene.

[0022] Examples of fluororesins used in fluororesin fibers include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE), but the present invention is not limited to these examples. These fluororesins may be used alone or in combination of two or more. Among these fluororesins, polytetrafluoroethylene (PTFE) is preferred from the viewpoint of moldability and processability into fluororesin fibers.

[0023] Another major feature of the present invention is that it contains an oil component and a lipophilic inorganic filler. The gland packing of the present invention not only uses fluororesin fiber but also contains an oil component and a lipophilic inorganic filler, so when the gland packing rubs against a sliding member, it has low sliding resistance, can prevent seizure, and has excellent sealing properties.

[0024] In the present invention, from the viewpoint of obtaining a gland packing that exhibits low sliding resistance when the gland packing is in sliding contact with a sliding member, can prevent seizure, and has excellent sealing properties (sealing ability), it is preferable to use at least one oil component selected from the group consisting of silicone oil, liquid paraffin, and fluorinated oil. Only one oil component may be used, or two or more oil components may be used in combination. Among these oil components, silicone oil and liquid paraffin are preferred, and silicone oil is more preferred, from the viewpoint of obtaining a gland packing that exhibits low sliding resistance when the gland packing is in sliding contact with a sliding member, can prevent seizure, has excellent sealing properties (sealing ability), is less likely to produce elution when immersed in water, and is also excellent in terms of food hygiene.

[0025] Examples of silicone oils include straight silicone oils and modified silicone oils. Examples of straight silicone oils include dimethyl silicone oils and phenylmethyl silicone oils, but the present invention is not limited to these examples. Examples of modified silicone oils include polyether-modified silicone oils, alkyl-modified silicone oils, fluoroalkyl-modified silicone oils, aralkyl-modified silicone oils, amino-modified silicone oils, phenyl-modified silicone oils, and fatty acid ester-modified silicone oils, but the present invention is not limited to these examples. These silicone oils may be used alone or in combination of two or more.

[0026] Among silicone oils, from the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, has excellent sealing properties (sealing ability), is unlikely to produce elution when immersed in water, and is also excellent in terms of food hygiene, straight silicone oil is preferred, dimethyl silicone oil and phenylmethyl silicone oil are more preferred, and dimethyl silicone oil is even more preferred.

[0027] The liquid paraffin is preferably one that complies with the Food Sanitation Act. Examples of liquid paraffins include MORESCO White P-40, MORESCO White P-55, MORESCO White P-60, MORESCO White P-70, MORESCO White P-80, MORESCO White P-85, MORESCO White P-100, MORESCO White P-120, MORESCO White P-150, MORESCO White P-200, MORESCO White P-230, MORESCO White P-260, MORESCO White P-300, MORESCO White P-350, and MORESCO White P-350P, manufactured by MORESCO Corporation. However, the present invention is not limited to these examples. These liquid paraffins may be used alone or in combination of two or more.

[0028] Examples of fluorine oils include tetrafluoroethylene oligomers and perfluoropolyether oligomers, but the present invention is not limited to these examples. These fluorine oils may be used alone or in combination.

[0029] A suitable representative example of a lipophilic inorganic filler is swellable mica. Swellable mica is hydrophilic and has the property of swelling in polar solvents such as water. Swellable mica swells because the ions present between its layers are lithium ions or sodium ions, and these ions exchange with ions in water. Examples of swellable mica include Li-type tetrasilicic fluorine mica, Li-type fluorine taeniolite, Na-type tetrasilicic fluorine mica, and Na-type fluorine taeniolite, but the present invention is not limited to these examples. Swellable mica is excellent in terms of food hygiene and can therefore be suitably used in the present invention.

[0030] The length of the major axis of the primary particles of the swellable mica in an unswollen state is about 3 to 10 μm, from the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, and has excellent sealing properties. The thickness of the swellable mica in an unswollen state is about 100 to 200 nm. The thickness of the swellable mica contained in the gland packing may be smaller than the thickness of the swellable mica in an unswollen state, because the swellable mica may peel off when used in the gland packing.

[0031] Swellable mica is readily available commercially, and examples of commercially available swellable mica include SOMASIF ME-100, MAE, MTE, and MEE, manufactured by Katakura Co-op Agri Co., Ltd., but the present invention is not limited to these examples.

[0032] Although not directly related to the present invention, there are some patented inventions using expandable mica (see, for example, Japanese Patent No. 5378003).

[0033] From the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, and has excellent sealing properties (sealing ability), the average particle size of the lipophilic inorganic filler is preferably 1 to 10 μm, more preferably 3 to 8 μm, and the average particle size of the lipophilic inorganic filler is preferably 10 to 20 μm.

[0034] In the mixture of the oil component and the lipophilic inorganic filler, the amount of the lipophilic inorganic filler per 100 parts by mass of the oil component is preferably 20 to 45 parts by mass, more preferably 25 to 40 parts by mass, and even more preferably 30 to 35 parts by mass, from the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, and has excellent sealing properties (sealing ability).

[0035] Examples of methods for attaching a mixture of oil components and lipophilic inorganic filler to a gland packing include (A) a method of immersing fluororesin fibers in a mixture of oil components and lipophilic inorganic filler before manufacturing the gland packing, removing the fibers from the mixture, and removing the excess mixture, (B) a method of preparing a core and a braided material from fluororesin fibers, immersing the core and braided material in a mixture of oil components and lipophilic inorganic filler, removing the fibers from the mixture, and removing the excess mixture, and (C) a method of preparing a gland packing, immersing the gland packing in a mixture of oil components and lipophilic inorganic filler, removing the fibers from the mixture, and removing the excess mixture. Among these methods, methods (A) and (B) are preferred, and method (A) is more preferred, from the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, and has excellent sealing properties.

[0036] The content of the mixture in the gland packing is preferably 5 to 30 mass %, more preferably 10 to 25 mass %, and even more preferably 15 to 20 mass %, from the viewpoint of obtaining a gland packing that has low sliding resistance when the gland packing slides against a sliding member, can prevent seizure, and has excellent sealing properties (sealing ability) by uniformly adhering the mixture to the fluororesin fiber. The content of the mixture in the gland packing is determined by preparing a gland packing to which the mixture is not attached and a gland packing to which the mixture is attached, and calculating the ratio of the content of the mixture in the gland packing by the formula: [Content of the mixture in the gland packing (mass%)] = {[Mass (g) of gland packing to which the mixture has been attached] - [Mass (g) of gland packing to which the mixture has not been attached]} ÷ [Mass (g) of gland packing to which the mixture has been attached] × 100 This is a value calculated based on the above.

[0037] The gland packing of the present invention obtained as described above has low sliding resistance when the gland packing is rubbing against a sliding member, can prevent seizure, and has excellent sealing properties, so it can be suitably used in applications such as valves, rotary pumps, reciprocating equipment, and rotating equipment.

[0038] Furthermore, when silicone oil is used as the oil component in the gland packing of the present invention and swelling mica is used as the lipophilic inorganic filler, the gland packing is less likely to produce eluates when immersed in water, making it excellent in terms of food hygiene and suitable for use in valves, rotary pumps, reciprocating equipment, rotating equipment, and other applications where food is handled. [Example]

[0039] The present invention will now be described in more detail based on examples, but the present invention is not limited to these examples.

[0040] Example 1 Fluorine resin fibers (fineness: approximately 11,000 dtex) made of polytetrafluoroethylene (PTFE) were used.

[0041] A mixture was obtained by mixing the oil component and the lipophilic inorganic filler at room temperature (approximately 23°C) in the mixing ratio shown in Table 1. Dimethyl silicone oil was used as the oil component, and swelling mica (manufactured by Katakura Co-op Agri Co., Ltd., trade name: SOMASIF MAE, indicated as MAE in Table 1) was used as the lipophilic inorganic filler.

[0042] The fluororesin fiber was immersed in the mixture obtained above at room temperature, and then pulled out of the mixture to remove excess mixture. After that, a plurality of fluororesin fibers with the mixture attached thereto were bundled together to prepare a braiding yarn. A core and a braided material were prepared using this braiding yarn, and the braided yarn was braided into a square braid by lattice knitting to obtain a string-like braided body.

[0043] The braided body obtained as described above was cut to a predetermined size and then compression molded in a mold to produce a ring-shaped gland packing having a square cross section, a vertical length and a horizontal length of 12.5 mm, an inner diameter of 80 mm, and an outer diameter of 105 mm in plan view.

[0044] The gland packing obtained above was used to examine the performance of the gland packing in terms of sliding resistance, presence or absence of seizure, sealing ability (sealing property), and presence or absence of elution, based on the following methods. The results are shown in Table 1.

[0045] [Sliding resistance, seizure and sealing performance] A horizontal rotation test device shown in Figure 3 was used to evaluate sliding resistance, the presence or absence of seizure, and sealing performance. Figure 3 is a schematic explanatory diagram of the horizontal rotation test device used to evaluate the performance of gland packings. The horizontal rotation test device is a test device used to evaluate the sliding characteristics and sealing performance of gland packings used in rotary pumps or rotating equipment during rotation.

[0046] The test methods for each performance are outlined below. (1) Four gland packings 13a are attached to the packing box 12a on the motor side A of the stuffing box 11 of the test device, and four gland packings 13b are attached to the packing box 12b on the anti-motor side B. (2) A load is applied by the packing gland members 14a and 14b of the test device to fix the gland packings 13a and 13b, respectively. (3) Water at room temperature (about 23° C.) is introduced as a fluid through the fluid inlet hole 15, and a pressure of 0.5 MPa is applied to the water. (4) The rotating shaft 16 of the test device is rotated and operated at a rotation speed of 1195 rpm for approximately 100 hours, after which the fluid leakage rate, sliding resistance, and temperatures of the packing boxes 12a and 12b are measured. The temperatures of the packing boxes 12a and 12b are measured by thermometers 17a and 17b, respectively. (5) The rotating shaft 16 of the test device is then rotated and operated at a rotational speed of 2390 rpm for approximately 100 hours, after which the amount of fluid leakage, sliding resistance, and temperature of the packing boxes 12a and 12b are measured, and the operation of the test device is stopped.

[0047] A. Sliding resistance The sliding torque is measured with a torque meter while the test device is operating at a rotation speed of 1195 rpm or 1195 rpm, and the sliding resistance (axial resistance) is evaluated based on the following evaluation criteria.

[0048] (Evaluation criteria) ○: Sliding resistance is less than 1.5 N m △: Sliding resistance is 1.5 N m or more and less than 1.7 N m ×: Sliding resistance is 1.7 N m or more

[0049] B. Presence or absence of image retention When the test equipment is in operation, steam of the fluid (water) is generated between the gland packing 13a of the stuffing box 11 and the rotating shaft 16, causing seizure. Therefore, whether or not the steam is present is visually confirmed, and the presence or absence of seizure is evaluated based on the following evaluation criteria.

[0050] (Evaluation criteria) ○: No steam is observed. △: A very small amount of steam is observed. ×: Steam is clearly observed.

[0051] C.Sealability (sealability) The fluid (water) leaking from between the gland packing 13a of the stuffing box 11 and the rotating shaft 16 is collected for one minute, and the amount of fluid (water) collected is taken as the amount of fluid leakage, and the sealing performance is evaluated based on the following evaluation criteria.

[0052] (Evaluation criteria) ◎: Fluid (water) leakage rate is less than 80 mL / min ○: Fluid (water) leakage rate is 80 mL / min or more and less than 120 mL / min △: Fluid (water) leakage rate is 120 mL / min or more and less than 160 mL / min ×: Fluid (water) leakage rate is 160 mL / min or more

[0053] [Presence or absence of elution substances] Pour high-temperature water (temperature: 95°C) into a 200 mL beaker so that the surface area of ​​the gland packing is 1 cm 2 The gland packing obtained above is immersed in the high-temperature water for 30 minutes while the water temperature is maintained at 95°C, and then it is removed from the high-temperature water. The transparency of the high-temperature water in the beaker is visually observed, and the presence or absence of elution is evaluated based on the following evaluation criteria.

[0054] (Evaluation criteria) ○: The high-temperature water is clear. ×: Changes such as cloudiness are observed in the high-temperature water.

[0055] Comparative Example 1 A gland packing was prepared in the same manner as in Example 1, except that the swelling mica in Example 1 was replaced with a conventional inorganic filler (talc), and the performance of the gland packing was examined in the same manner as described above. The results are shown in Table 1.

[0056] Comparative Example 2 A gland packing was prepared in the same manner as in Example 1, except that the swellable mica in Example 1 was replaced with hydrophilic mica (manufactured by Katakura Co-op Agri Co., Ltd., trade name: MICROMICA ME-100, shown as ME-100 in Table 1), and the performance of the gland packing was investigated in the same manner as above. The results are shown in Table 1.

[0057] Comparative Example 3 A gland packing was prepared in the same manner as in Example 1, except that swelling mica was not used, and the performance of the gland packing was examined in the same manner as described above. The results are shown in Table 1.

[0058] [Table 1]

[0059] The results shown in Table 1 show that gland packings using swelling mica have lower sliding resistance, can prevent seizing during use, and have excellent sealing properties (tightness) compared to gland packings using conventional inorganic fillers (talc) and gland packings using hydrophilic inorganic fillers, and are therefore superior in terms of food hygiene as they are less likely to produce elution when immersed in water.

[0060] The embodiments and examples shown in this specification should be considered as illustrative and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include various modifications within the meaning and scope of the claims. [Explanation of symbols]

[0061] 1 Gland packing 2 core 3 Braid material

Claims

1. A gland packing having a core and a braided material surrounding the core, wherein fluororesin fibers are used as the fibers constituting the core and the braided material, and the gland packing contains an oil component and an oil-philic inorganic filler.

2. 2. The gland packing according to claim 1, wherein the oil component is at least one selected from the group consisting of silicone oil, liquid paraffin, and fluorine oil.

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