Rubber element and air spring for railway vehicle

Abstract

To provide a rubber element that can increase flame retardancy, safety, and durability.SOLUTION: The rubber element of the present disclosure is a rubber element for use in an air spring for railway vehicle, containing a rubber component, aluminum hypophosphite, and ammonium polyphosphate, the rubber component including chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a rubber member and an air spring for a railway vehicle. [Background technology]

[0002] Generally, railroad cars are equipped with air springs between the car body and the bogie to absorb vibrations transmitted to the car body and the bogie.

[0003] The air spring includes an upper plate attached to the car body, a lower member attached to the bogie, and various elastic members made of rubber, such as diaphragms and stoppers, which are provided between the upper plate and the lower member (see JP 2003-254378 A). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-254378 Summary of the Invention

[0005] The rubber member of the present disclosure is a rubber member used in air springs for railway vehicles, and contains a rubber component, aluminum hypophosphite, and ammonium polyphosphate, wherein the rubber component includes chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic partial cross-sectional view showing a diaphragm used in an air spring for a railway vehicle according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] Railway vehicles require high levels of safety, and elastic members made of the above-mentioned rubber materials are required to have improved flame retardancy. Furthermore, in recent years, fire prevention standards have become stricter in various fields in Europe. The European standard EN 45545-2 specifies requirements for combustion behavior for products used in railway vehicles, and these standards must be met. Furthermore, since the above-mentioned elastic members are used in harsh environments where loads are applied, they must also have good abrasion resistance and tensile strength.

[0008] An object of the present disclosure is to provide a rubber member that can improve the flame retardancy, safety, and durability of air springs for railway vehicles.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to provide a rubber member that can improve flame retardancy, safety, and durability.

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0011] (1) The rubber member disclosed herein is a rubber member used in an air spring for a railway vehicle, and contains a rubber component, aluminum hypophosphite, and ammonium polyphosphate, wherein the rubber component includes chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof.

[0012] The rubber member contains aluminum hypophosphite and ammonium polyphosphate in addition to a rubber component containing chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof, thereby improving the heat release rate, smoke density reduction effect, abrasion resistance, and tensile performance, thereby improving the flame retardancy, safety, and durability of the rubber member.

[0013] (2) In the above (1), the content of the aluminum hypophosphite per 100 parts by mass of the rubber component may be 10 parts by mass or more and 30 parts by mass or less, and the content of the ammonium polyphosphate per 100 parts by mass of the rubber component may be 15 parts by mass or more and 45 parts by mass or less. When the content of the aluminum hypophosphite is 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component, the heat generation rate and smoke density reduction effects of the rubber member, as well as the abrasion resistance, can be further improved. Furthermore, when the content of the ammonium polyphosphate is 15 parts by mass or more and 45 parts by mass or less per 100 parts by mass of the rubber component, the heat generation rate and smoke density reduction effects, the abrasion resistance, and the tensile performance of the rubber member can be further improved. Therefore, when the contents of the aluminum hypophosphite and ammonium polyphosphate per 100 parts by mass of the rubber component are within the above ranges, the flame retardancy, safety, and durability of the rubber member can be further improved.

[0014] (3) In the above (1) or (2), zinc hydroxide stannate may be further contained. By further containing zinc hydroxide stannate, the smoke concentration of the rubber member can be further reduced.

[0015] (4) Furthermore, the air spring for a railway vehicle according to the present disclosure includes the rubber member according to any one of (1) to (3) above.

[0016] The air spring for a railway vehicle includes the rubber member described above, and therefore has high flame retardancy, safety, and durability.

[0017] [Details of the embodiments of the present disclosure] A rubber member and an air spring for a railway vehicle according to an embodiment of the present disclosure will be described below.

[0018] <Rubber components> The rubber member can be applied to various elastic members used in air springs for railway vehicles, such as diaphragms and stoppers, which are installed between the car body and bogie of a railway vehicle and absorb vibrations transmitted between the car body and the bogie.

[0019] The rubber member is flame-retardant and contains a rubber component, aluminum hypophosphite, and ammonium polyphosphate. By containing these components, the rubber member exhibits good heat generation rate and smoke density reduction effects, abrasion resistance, and tensile performance.

[0020] (rubber component) The rubber component contains chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof. By containing chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof as the rubber component, the rubber member has excellent mechanical strength, abrasion resistance, weather resistance, heat resistance, etc.

[0021] When the rubber component contains chloroprene rubber, natural rubber, and butadiene rubber, the amount of chloroprene rubber in the rubber component may be 50 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the rubber component. Having a chloroprene rubber content of 50 parts by mass or more in the rubber component can improve the weather resistance of the rubber member. On the other hand, having a chloroprene rubber content of 80 parts by mass or less in the rubber component can allow sufficient amounts of the other components, such as natural rubber and butadiene rubber, to be blended, thereby improving the mechanical strength of the rubber member.

[0022] The lower limit of the rubber component content in the rubber member may be 27% by mass, 30% by mass, or 33% by mass. When the rubber content in the rubber member is 27% by mass or more, the elasticity of the rubber member is improved, and the elasticity of the rubber member can be made good.

[0023] (aluminum hypophosphite) The rubber member contains aluminum hypophosphite, which forms a strong char layer during combustion, thereby improving flame retardancy.

[0024] The lower limit of the amount of aluminum hypophosphite per 100 parts by mass of the rubber component in the rubber member may be 10 parts by mass or 12 parts by mass. Meanwhile, the upper limit of the amount of aluminum hypophosphite per 100 parts by mass of the rubber component in the rubber member may be 30 parts by mass or 25 parts by mass. When the amount of aluminum hypophosphite in the rubber member is 10 parts by mass or more, the heat generation rate and smoke concentration of the rubber member can be further reduced. Meanwhile, when the amount of aluminum hypophosphite in the rubber member is 30 parts by mass or less, the heat generation rate and wear resistance of the rubber member can be further reduced.

[0025] (Ammonium polyphosphate) The rubber member contains ammonium polyphosphate. When the rubber member contains ammonium polyphosphate, flame retardancy can be improved.

[0026] The lower limit of the amount of ammonium polyphosphate per 100 parts by mass of the rubber component in the rubber member may be 15 parts by mass or 20 parts by mass. Meanwhile, the upper limit of the amount of ammonium polyphosphate per 100 parts by mass of the rubber component in the rubber member may be 45 parts by mass or 40 parts by mass. When the amount of ammonium polyphosphate in the rubber member is 15 parts by mass or more, the heat generation rate and smoke concentration reduction effects of the rubber member can be further improved. Meanwhile, when the amount of ammonium polyphosphate in the rubber member is 45 parts by mass or less, the heat generation rate and smoke concentration reduction effects, wear resistance, and tensile performance of the rubber member can be further improved.

[0027] In addition, a nitrogen compound such as pentaerythritol, melamine, or trishydroxyethyl isocyanurate may be added to ammonium polyphosphate as an auxiliary agent to form a foamed and expandable layer during combustion, thereby enhancing the heat insulating effect.

[0028] (zinc hydroxide stannate) The rubber member may further contain zinc hydroxide stannate. By further containing zinc hydroxide stannate, the smoke concentration of the rubber member can be further reduced.

[0029] The lower limit of the amount of zinc stannate hydroxide in the rubber member per 100 parts by mass of the rubber component may be 3 parts by mass or 4 parts by mass. Meanwhile, the upper limit of the amount of zinc stannate hydroxide in the rubber member per 100 parts by mass of the rubber component may be 25 parts by mass or 20 parts by mass. When the amount of zinc stannate hydroxide in the rubber member is 3 parts by mass or more, the smoke concentration reduction effect of the rubber member can be further improved. Meanwhile, when the amount of zinc stannate hydroxide in the rubber member is 25 parts by mass or less, the heat generation rate and smoke concentration reduction effects, wear resistance, and tensile performance can be more favorably maintained.

[0030] The rubber member may contain, for example, a flame retardant other than aluminum hypophosphite and ammonium polyphosphate, as long as the physical properties of the rubber component are not impaired.

[0031] (Other additives) The rubber member may contain other additives as components other than the rubber component, aluminum hypophosphite, and ammonium polyphosphate, as long as the effects of the present disclosure are not impaired. Examples of such additives include vulcanizing agents, vulcanization accelerators, antioxidants, colorants such as carbon black, lubricants, antioxidants, UV absorbers, softeners, plasticizers, waxes, and vulcanization accelerator assistants. By including such additives in the composition for rubber members, the composition for rubber members can be endowed with desired performance. The upper limit of the content of the other additives in the composition for rubber members per 100 parts by mass of the rubber component may be 100 parts by mass or 95 parts by mass.

[0032] [Method of manufacturing rubber components] The method for manufacturing the rubber member includes, for example, the following steps. (1) A step of preparing a composition for rubber members In this step, the components of the composition for rubber members, excluding the vulcanizing agent, vulcanization accelerator, etc., are blended and mixed in a pressure kneader while water cooling is performed to prevent crosslinking from progressing during mixing, and the temperature of the composition for rubber members is kept at 110°C or below. Thereafter, the remaining components are mixed using a roll while water cooling is performed to prevent crosslinking from progressing during mixing, and the temperature of the composition is kept at 90°C or below, to prepare a composition for rubber members.

[0033] The composition for rubber members is a composition used to form the rubber member. The composition for rubber members contains a rubber component including chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof, aluminum hypophosphite, and ammonium polyphosphate. By including the components in the composition for rubber members, it is possible to form rubber members that have good heat generation rate and smoke density reduction effects, abrasion resistance, and tensile performance.

[0034] The rubber component, aluminum hypophosphite, ammonium polyphosphate and other additives contained in the composition for rubber members are as described above.

[0035] (2) A step of vulcanizing the composition for rubber members In this step, the composition for rubber members prepared in the step of preparing a composition for rubber members may be press-vulcanized, or the composition for rubber members may be set on the inner surface of a mold and then injection-molded to be vulcanized.

[0036] The rubber member can be suitably used as a rubber member for air springs for railway vehicles, since it is possible to improve flame retardancy, safety, and durability.

[0037] <Air springs for railway vehicles> The air spring for a railway vehicle includes the rubber member described above.

[0038] [Rubber parts] The rubber member can be applied to elastic members used in air springs for railway vehicles, such as diaphragms and stoppers. The rubber member is as described above. The rubber member may be applied as a single layer or as a laminate of multiple layers. When applied as a laminate of multiple layers, it may be combined with a layer of an elastic material other than the rubber member. For example, if an elastic member used in an air spring for a railway vehicle has a three-layer laminate including an outer layer, an inner layer, and an intermediate layer laminated between the outer layer and the inner layer, the rubber member may be applied to all of the outer layer, the inner layer, and the intermediate layer, or to any of the layers. Furthermore, in the layer to which the rubber member is applied, the rubber member may be applied to the entire layer or to a portion of the layer.

[0039] FIG. 1 is a schematic partial cross-sectional view of a diaphragm used in an air spring for a railway vehicle according to one embodiment of the present disclosure. The diaphragm 10 shown in FIG. 1 includes three elastic layers made of elastic materials. Specifically, the diaphragm 10 includes an outer layer 1, an inner layer 3, and an intermediate layer 2 laminated between the outer layer 1 and the inner layer 3. In the diaphragm 10, for example, the outer layer 1 and the inner layer 3 are made of the rubber material, and the intermediate layer 2 is made of a reinforcing rubber layer. The reinforcing rubber layer is a rubber layer interposed with multiple reinforcing cords. The reinforcing rubber layer is made of the cords aligned in parallel at predetermined intervals and coated with an unvulcanized rubber composition. The rubber component of the reinforcing rubber layer is not particularly limited, but may be styrene butadiene rubber, butadiene rubber, or natural rubber, which have excellent abrasion resistance and mechanical strength. The fibers constituting the cords are not particularly limited, but may be polyester or polyamide to improve strength. The fibers constituting the cords may be treated with resorcinol, formalin, rubber latex adhesive, or the like to improve adhesion to the rubber. The number of cords is not particularly limited.

[0040] A method for producing the railway vehicle air spring using the rubber member includes, for example, a step of laminating the rubber member onto a rubber layer used in the railway vehicle air spring or a reinforced rubber layer having a plurality of reinforcing cords interposed therein. In the laminating step, the rubber member may be laminated by applying the rubber member composition prepared in the step of preparing the rubber member composition to the surface of the rubber layer used in the railway vehicle air spring or the reinforced rubber layer having a plurality of reinforcing cords interposed therein, followed by press vulcanization. Alternatively, the rubber member may be laminated by applying the rubber member composition to the surface of the rubber layer used in the railway vehicle air spring or the reinforced rubber layer having a plurality of reinforcing cords interposed therein, setting the composition on the inner surface of a mold in a coated state, and then injection molding and vulcanizing the composition.

[0041] The lower limit of the average thickness of the rubber member applied to the elastic member used in the air spring for a railway vehicle may be 100 μm, 200 μm, or 300 μm. On the other hand, the upper limit of the average thickness may be 3500 μm, 3000 μm, or 2500 μm. When the average thickness is 100 μm or more, the flame retardancy and moldability of the rubber member can be improved. On the other hand, when the average thickness is 3500 μm or less, the handleability of the rubber member can be improved. Here, "average thickness" refers to the average value of thicknesses measured at any ten points.

[0042] The air spring for a railway vehicle includes the rubber member, and therefore has high flame retardancy, safety, and durability.

[0043] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Example]

[0044] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0045] <Rubber members No. 1 to No. 20> Rubber members No. 1 to No. 20 were prepared by the following procedure, and their flame retardancy and abrasion resistance were evaluated. The compositions of rubber members No. 1 to No. 20 are shown in Table 1. In Table 1, "-" indicates that the corresponding component was not used.

[0046] (1) Materials used (natural rubber) RSS (Ribbed Smoked Sheet) No. 3 (Meat paste) (chloroprene rubber) Mercaptan-modified chloroprene rubber: Showpren WRT (Showa Denko) (butadiene rubber) High cis butadiene rubber: Nipol BR1220 (manufactured by Nippon Zeon Co., Ltd.) (aluminum hypophosphite) "Exolit OP1230" (Clariant Chemicals) (Ammonium polyphosphate) "AP-422" (Clariant Chemicals) (zinc hydroxide stannate) "Flamtard H" (manufactured by Nippon Light Metal Co., Ltd.) (expanded graphite) "Thermal Expandable Graphite GREP-EG" (Suzuhiro Chemical Co., Ltd.) (Brominated flame retardant: Ethylenebis(pentabromobiphenyl)) "SAYTEX8010" (manufactured by Albemarle Japan) (aluminum hydroxide) "Fine Particles C-301N" (Sumitomo Chemical Co., Ltd.) (Magnesium hydroxide) "Kisuma 5B" (Kyowa Chemical Industry Co., Ltd.)

[0047] (Other ingredients) The other components used were as follows: Vulcanizing agent: Fine sulfur S 325 mesh (Hosoi Chemical Industry Co., Ltd.)

[0048] (2) Mixing of materials The above materials were blended in the amounts (unit: parts by mass) shown in Table 1 below, and mixed using a pressure kneader while water cooling to prevent crosslinking from progressing during mixing, so that the temperature of the composition for rubber members would be 110°C or lower. Next, the remaining ingredients were mixed using a roll while water cooling to prevent crosslinking from progressing during mixing, so that the temperature of the composition would be 90°C or lower, to prepare a composition for rubber members.

[0049] (3) Fabrication of rubber components A laminated sample of the rubber composition simulating a diaphragm was prepared as a rubber component for evaluation, and its flame retardancy was evaluated. The laminated sample consisted of an outer layer, an inner layer, and an intermediate layer disposed between the outer layer and the inner layer. The outer layer and the inner layer were prepared using the rubber component composition prepared above. The average thickness of the outer layer was 3.2 mm, and the average thickness of the inner layer was 2.4 mm. The intermediate layer was a reinforced rubber layer made of a styrene-butadiene rubber / butadiene rubber blend rubber with polyamide reinforcing cords interposed therebetween, and had an average thickness of 4 mm.

[0050] <Evaluation> The rubber components were evaluated based on EN 45545-2 (2013) + A1 (2015), the European standard for fire protection for products used in railway vehicles. Among the various criteria (requirements) set forth in EN 45545-2, the standard for diaphragms in air springs falls under R9. Flame retardancy was evaluated using the following test (1) in R9, and safety was evaluated using the following test (2) in R9. The pass / fail criteria for (1) and (2) vary depending on the "risk level," which is determined by the operation and design of the railway vehicle, but the evaluation was based on a risk level of HL2.

[0051] (1) Heat release rate A cone calorimeter test was conducted in accordance with ISO 5660-1 (2015). The cone calorimeter conditions were 25 kW / mm 2 The test time is 20 minutes, and the heat generation rate of the rubber material (kW / m 2 ) was measured. The heat release rate data was used to calculate the MARHE index specified in EN 45545-2. Evaluation was based on the following three levels. A and B are acceptable. A: MARHE is 60kW / m 2 is B: MARHE is 60kW / mm 3 Super 90kW / m 2 is C: MARHE is 90kW / m 2 exceed

[0052] (2) Smoke density Conduct smoke density tests (single chamber tests) in accordance with EN ISO 5659-2. The cone calorimeter conditions are 25 kW / mm 2 The test time was 10 minutes, and the smoke density Ds of the rubber member was measured after 10 minutes. The maximum smoke density (Ds max) was calculated and the evaluation was made on the following three levels: A and B are acceptable. A: The maximum smoke density is 300 or less. B: The maximum smoke density is over 300 and 600 or less C: Maximum smoke density exceeds 600

[0053] [DIN abrasion test] Abrasion resistance was evaluated by a DIN abrasion test. The DIN abrasion test was conducted in accordance with JIS-K6264-2:2005, with an applied force of 10.0±0.2 N and an abrasion distance of 40.0±0.2 m. The abrasion amount was measured using Method B, in which the test piece of the rubber member prepared above was rotated. Evaluation was based on the following three levels. A and B were considered pass. A: Specific wear volume is 250 mm 3 is B: Specific wear volume is 250 mm 3 Super 300mm 3 is less than C: Specific wear volume is 300 mm 3 That's all

[0054] [Tensile test] The rubber members prepared above were subjected to a tensile test using a tensile tester (Shimadzu Corporation's "Autograph AGS-X") at a chuck distance of 20 mm and a speed of 10 mm / min to measure the breaking elongation [%]. Evaluation was based on the following three levels. A and B were considered pass. A: Breaking elongation is 450% or more B: Breaking elongation is 400% or more and less than 450% C: Less than 400%

[0055] Table 1 shows the evaluation results.

[0056] [Table 1]

[0057] As shown in Table 1, Nos. 1 to 6, which contain a rubber component, aluminum hypophosphite, and ammonium polyphosphate, and the rubber component includes chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof, showed good results in the evaluation of heat release rate, smoke density, DIN abrasion test, and breaking elongation in tensile test.

[0058] The above results demonstrate that the rubber member has excellent evaluation results for heat release rate and smoke density as defined in EN 45545-2, as well as good abrasion resistance and tensile performance.

[0059] The rubber member can be suitably used as a rubber member for air springs for railway vehicles because it can improve flame retardancy, safety, and durability. [Explanation of symbols]

[0060] 1 outer layer 2. Middle class 3 Inner layer 10 diaphragm

Claims

1. A rubber member used in an air spring for a railway vehicle, The composition contains a rubber component, aluminum hypophosphite, and ammonium polyphosphate, The rubber member, wherein the rubber component comprises chloroprene rubber, natural rubber, butadiene rubber, or a combination thereof.

2. an amount of the aluminum hypophosphite per 100 parts by mass of the rubber component is 10 parts by mass or more and 30 parts by mass or less; 2. The rubber member according to claim 1, wherein the amount of the ammonium polyphosphate per 100 parts by mass of the rubber component is 15 parts by mass or more and 45 parts by mass or less.

3. The rubber member according to claim 1 or 2, further comprising zinc hydroxide stannate.

4. An air spring for a railway vehicle, comprising the rubber member according to claim 1 or 2.

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