Insulation composition for signal cable for railway vehicles

Abstract

The present invention relates to an insulation composition for a signal cable for railway vehicles. Specifically, the present invention relates to an insulation composition for a signal cable for railway vehicles, which exhibits improved electrical properties under high-temperature saline conditions, and has excellent physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission.

Description

Insulation composition of signal cables for railway vehicles

[0001] The present invention relates to an insulating composition for a signal cable for a railway vehicle. Specifically, the present invention relates to an insulating composition for a signal cable for a railway vehicle that exhibits improved electrical properties under high-temperature saltwater conditions and excellent physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission.

[0002] Signal cables for railway vehicles are rated at 300V and are available in various structures.

[0003] Conventional signal cables for railway vehicles may include one or more cores composed of a conductor and an insulator surrounding the conductor, a metal shielding layer surrounding the one or more cores, a sheath layer surrounding the metal shielding layer, etc.

[0004] Signal cables for railway vehicles must possess superior heat resistance and oil resistance compared to general cables depending on the installation environment. The insulators used in these signal cables must be able to maintain their electrical properties for extended periods even in high and low temperature environments. Furthermore, to ensure the safety of personnel, cargo, and equipment and to minimize losses in the event of a fire on a railway vehicle, they must be equipped with fire safety features, such as low smoke emission as well as flame retardancy.

[0005] In particular, it is important for the insulation of signal cables for railway vehicles to maintain their physical properties under various climatic conditions, such as saltwater and acid-alkali environments and rapid temperature changes. Specifically, according to standard EN-50305, it must maintain stability without insulation breakdown for 240 hours when a DC voltage of 300 V is applied in a 3% NaCl saltwater environment at 85°C.

[0006] However, conventional signal cables for railway vehicles could not secure all physical properties, such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission, while maintaining electrical characteristics under high-temperature saltwater conditions to the level required by standard EN-50305.

[0007] Therefore, there is an urgent need for an insulating composition for a railway vehicle signal cable and an insulating layer formed therefrom, which have improved electrical properties under high-temperature salt water conditions and excellent physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission.

[0008] The present invention aims to provide an insulating composition for a railway vehicle signal cable that has improved electrical properties under high-temperature salt water conditions and excellent physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission, and a railway vehicle signal cable comprising an insulating layer formed therefrom.

[0009] To solve the above problem, the present invention,

[0010] An insulating composition for forming an insulating layer of a signal cable for a railway vehicle comprises a base resin and a flame retardant, wherein the base resin comprises a polyethylene resin having a melting point of 125 to 135°C, a polyolefin elastomer having a melting point of 90 to 102°C, an ethylene copolymer having a melting point of 95 to 105°C, and a polyolefin resin grafted with maleic anhydride having a melting point of 125 to 135°C.

[0011] Herein, an insulating composition is provided that is characterized in that no insulation breakdown occurs when an insulating wire having an insulating layer formed from the insulating composition is immersed in 85°C brine (NaCl 3%) and a DC voltage of 300 V is applied for 240 hours.

[0012] In addition, the above-mentioned polyethylene resin provides an insulating composition comprising one or more types selected from the group consisting of linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0013] In addition, the above-mentioned polyolefin elastomer comprises one or more selected from the group consisting of olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, ester-based thermoplastic elastomers, and urethane-based thermoplastic elastomers, thereby providing an insulating composition.

[0014] Furthermore, the above ethylene copolymer provides an insulating composition comprising one or more selected from the group consisting of ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), and ethylene butyl acrylate (EBA).

[0015] Meanwhile, based on 100 parts by weight of the base resin, the content of the polyethylene resin is 20 to 40 parts by weight, the content of the polyolefin elastomer is 20 to 40 parts by weight, the content of the ethylene copolymer is 30 to 50 parts by weight, and the content of the maleic anhydride-grafted polyolefin resin is 10 to 20 parts by weight, thereby providing an insulating composition.

[0016] Herein, an insulating composition is provided, characterized in that, based on 100 parts by weight of the base resin, the total content of the polyethylene resin is a high-density polyethylene resin and the polyolefin resin grafted with maleic anhydride is a high-density polyethylene resin grafted with maleic anhydride is 30 to 60 parts by weight.

[0017] In addition, the present invention provides an insulating composition characterized in that the flame retardant comprises a metal hydroxide including magnesium hydroxide or aluminum hydroxide.

[0018] Herein, an insulating composition is provided, characterized in that the metal hydroxide comprises a metal hydroxide whose surface is coated with silane.

[0019] In addition, an insulating composition is provided, characterized in that the content of the flame retardant is 150 to 200 parts by weight based on 100 parts by weight of the base resin.

[0020] Meanwhile, an insulating composition is provided, characterized by further including 10 to 20 parts by weight of one or more other additives selected from lubricants, antioxidants, and crosslinking agents, based on 100 parts by weight of the base resin.

[0021] In addition, a signal cable for a railway vehicle is provided, comprising a conductor and an insulating layer surrounding the conductor and formed from the insulating composition.

[0022] Furthermore, a signal cable for a railway vehicle is provided, comprising: one or more cores including a conductor and an insulating layer formed from the insulating composition surrounding the conductor; a metal shielding layer surrounding the one or more cores; and a sheath layer surrounding the metal shielding layer.

[0023] The insulating composition for a signal cable for a railway vehicle according to the present invention exhibits excellent effects in that, through a combination of a specific base resin and a specific additive, it maintains electrical properties under high-temperature salt water conditions to the level required by standard EN-50305 while securing all physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission.

[0024] FIG. 1 schematically illustrates a cross-sectional structure of one embodiment of a signal cable for a railway vehicle according to the present invention.

[0025] Figure 2 schematically illustrates the cross-sectional structure of a signal cable for a railway vehicle shown in Figure 1.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components.

[0027] FIGS. 1 and 2 schematically illustrate the cross-sectional and longitudinal sections of one embodiment of a signal cable for a railway vehicle according to the present invention.

[0028] As illustrated in FIGS. 1 and 2, a signal cable for a railway vehicle according to the present invention may include one or more cores (10) comprising a conductor (11) such as copper or aluminum and an insulating layer (12) surrounding the conductor (11), a metal shielding layer (20) surrounding the one or more cores (10), a sheath layer (30) surrounding the metal shielding layer (20), etc. However, it is not limited thereto and may be composed only of a conductor and an insulating layer surrounding it.

[0029] The above insulating layer (12) may be formed by extrusion of an insulating composition according to the present invention, and the insulating composition may include a base resin, a flame retardant, other additives, etc.

[0030] Specifically, the base resin may include polyethylene resin, polyolefin elastomer, ethylene copolymer, and maleic anhydride-grafted polyolefin resin, and based on 100 parts by weight of the base resin, the content of the polyethylene resin may be 20 to 40 parts by weight, the content of the polyolefin elastomer may be 20 to 40 parts by weight, the content of the ethylene copolymer may be 30 to 50 parts by weight, and the content of the maleic anhydride-grafted polyolefin resin may be 10 to 20 parts by weight.

[0031] Here, if the content of the polyolefin elastomer is below the standard, the wear resistance of the insulation composition may be reduced, and if the content of the maleic anhydride-grafted polyolefin resin is below the standard, the compatibility between the base resin and additives such as flame retardants may be reduced or the oil resistance may be reduced.

[0032] In particular, the polyethylene resin may have a melting point of 125 to 135°C. If the melting point of the polyethylene resin exceeds 135°C, the physical properties of the insulating composition do not meet the specifications due to reduced processability caused by the high crystallinity and degree of polymerization of polyethylene, and consequently reduced filler loading ability such as flame retardants. On the other hand, if the melting point is less than 125°C, the hardness of the insulating composition is insufficient, which may significantly reduce physical properties such as wear resistance and DC stability.

[0033] The above polyethylene resin may include, for example, linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc.

[0034] In addition, the polyolefin elastomer may have a melting point of 90 to 102°C. If the melting point of the polyolefin elastomer exceeds 102°C, the physical properties are degraded due to a decrease in the filler loading properties, such as flame retardants, of the insulating composition, whereas if it is less than 90°C, the oil resistance and DC stability of the insulating composition may be significantly reduced.

[0035] The above polyolefin elastomer may include, for example, olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, ester-based thermoplastic elastomers, urethane-based thermoplastic elastomers, etc.

[0036] In addition, the ethylene copolymer may have a melting point of 95 to 105°C. If the melting point of the ethylene copolymer exceeds 105°C, the physical properties may deteriorate due to a decrease in the filler loading ability of flame retardants, etc., of the insulating composition, whereas if it is less than 95°C, the oil resistance and DC stability of the insulating composition may be significantly reduced.

[0037] The above ethylene copolymer may include, for example, ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), etc.

[0038] Furthermore, the maleic anhydride-grafted polyolefin resin may have a melting point of 125 to 135°C. If the melting point of the maleic anhydride-grafted polyolefin resin exceeds 135°C, processability is reduced due to the high crystallinity and degree of polymerization of polyethylene, and physical properties are reduced due to the reduced filler loading ability of flame retardants and other materials in the insulating composition. On the other hand, if the melting point is below 125°C, wear resistance, DC stability, etc., may be significantly reduced due to insufficient hardness of the insulating composition.

[0039] Meanwhile, based on 100 parts by weight of the base resin, the total content of the polyethylene resin, specifically the high-density polyethylene resin (HDPE), and the polyolefin resin grafted with maleic anhydride, specifically the high-density polyethylene resin grafted with maleic anhydride, may be 30 to 60 parts by weight. Here, if the total content of the high-density polyethylene resin (HDPE) and the high-density polyethylene resin grafted with maleic anhydride is less than 30 parts by weight, the physical properties may be degraded due to a decrease in the filler loading properties, such as flame retardants, of the insulating composition, whereas if it exceeds 60 parts by weight, the wear resistance, DC stability, etc., may be significantly reduced due to a lack of hardness of the insulating composition.

[0040] The insulating composition for forming an insulating layer of a signal cable for a railway vehicle according to the present invention essentially includes a flame retardant to impart flame-retardant and low-smoke characteristics. The flame retardant may include metal hydroxides such as magnesium hydroxide or aluminum hydroxide, and the metal hydroxides may have a hydroxyl group (-OH) which is a hydrophilic functional group, and thus the surface may be coated with a lubricant, silane, etc., to ensure compatibility with a non-polar base resin.

[0041] In addition, the DC stability evaluated in a saltwater environment assesses the decrease in insulation resistance caused by the penetration of saltwater ions into the insulating material. Therefore, coating with a flame retardant is important to prevent the penetration of saltwater ions, and in terms of DC stability, it is preferable to coat the flame retardant with silane rather than a lubricant.

[0042] Based on 100 parts by weight of the base resin, the content of the flame retardant may be 150 to 200 parts by weight. Here, if the content of the flame retardant is less than 150 parts by weight, the flame retardancy and low smoke generation required for the insulation layer of a signal cable for a railway vehicle cannot be achieved, whereas if it exceeds 200 parts by weight, processability such as extrudability of the insulation composition may be reduced.

[0043] The insulating composition according to the present invention may further include other additives such as a lubricant, an antioxidant, and a crosslinking agent, and the content of the other additives may be 10 to 20 parts by weight based on 100 parts by weight of the base resin.

[0044] Thus, the insulating composition according to the present invention can exhibit excellent effects of securing all physical properties such as heat resistance, oil resistance, weather resistance, flame retardancy, and low smoke emission while maintaining electrical properties under high-temperature salt water conditions at the level required by standard EN-50305.

[0045] Meanwhile, the metal shielding layer (20) may be formed as a braided body made of copper wire with improved flexibility and processability by heat-treating hard copper wire processed at room temperature. The metal shielding layer (20) performs the function of blocking electromagnetic waves to suppress signal transmission errors and malfunctions of electronic devices.

[0046] The sheath layer (30) performs the function of protecting one or more cores (10) from external pressure or impact. The sheath layer (30) may be formed from a sheath composition including a base resin, a flame retardant, a crosslinking agent, other additives, etc.

[0047]

[0048] [Example]

[0049]

[0050] 1. Preparation Example

[0051]

[0052] An insulating wire specimen having an insulating composition and an insulating layer formed therefrom was manufactured with the components and content listed in Table 1 below.

[0053]

[0054] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Resin 1 25 25 25 25 25 25 Resin 2 25 Resin 3 30 30 30 30 30 30 Resin 4 30 Resin 5 25 25 25 25 25 25 Resin 6 25 Resin 7 20 20 20 20 20 20 Resin 8 20 Flame Retardant 1 150 150 150 150 150 Flame Retardant 2 150 Flame Retardant 3 150 Additive 1 10 Additive 2 15 15 15 15 15 15 15 15

[0055] - Resin 1: Ethylene ethyl acrylate (Melting point: 95℃)

[0056] - Resin 2: Ethylene ethyl acrylate (Melting point: 85℃)

[0057] - Resin 3: Polyethylene (Melting point: 130℃)

[0058] - Resin 4: Polyethylene (Melting point: 125℃)

[0059] - Resin 5: Polyolefin elastomer (Melting point: 98℃)

[0060] - Resin 6: Polyolefin elastomer (Melting point: 74℃)

[0061] - Resin 7: Maleic anhydride-grafted high-density polyethylene resin (melting point: 130℃)

[0062] - Resin 8: Maleic anhydride-grafted linear low-density polyethylene resin (melting point: 125℃)

[0063] - Flame Retardant 1: Silane-coated magnesium hydroxide

[0064] - Flame Retardant 2: Silane-coated aluminum hydroxide

[0065] - Flame Retardant 3: Lubricant-coated magnesium hydroxide

[0066] - Additive 1: Flame suppressant

[0067] - Additive 2: Other Additives

[0068]

[0069] 2. Evaluation of physical properties

[0070]

[0071] 1) DC Stability Evaluation

[0072] Insulated wire specimens of each example and comparative example were immersed in 85°C brine (NaCl 3%) and a DC voltage of 300 V was applied for 240 hours to evaluate whether insulation breakdown occurred.

[0073] 2) Short-term oil resistance evaluation

[0074] Each insulated wire specimen of the example and comparative example was immersed in ASTM #2 oil (IRM 902) at 100°C for 24 hours, then removed and wiped, and evaluated whether insulation breakdown occurred for 1 minute when 1.5 kV was applied.

[0075] 3) Long-term oil resistance evaluation

[0076] Each insulated wire specimen of the example and comparative example was immersed in ASTM #3 oil (IRM 903) at 70°C for 168 hours, then removed and wiped, and evaluated whether insulation breakdown occurred for 1 minute when 1.5 kV was applied.

[0077] 4) Acid / Base Dielectric Breakdown Evaluation

[0078] Each insulated wire specimen of the example and comparative example was immersed in an aqueous oxalic acid solution (concentration 1N) and an aqueous sodium hydroxide solution (concentration 1N), respectively, for 168 hours, then removed and wiped, and evaluated whether insulation breakdown occurred for 1 minute when 1.5 kV was applied.

[0079] 5) Wear resistance evaluation

[0080] Each insulated wire specimen of the example and comparative example was fixed to the floor, and the number of reciprocating cycles was measured until the needle and the conductor came into contact while reciprocating the surface of the insulation layer with a needle to which a 7N load was applied. Considering the thickness variation of the insulation layer, the evaluation was performed four times by rotating at 90° intervals, and the average value was calculated. The number of reciprocating cycles must be at least 100 and at least 150.

[0081]

[0082] The evaluation results of the above physical properties are as described in Table 2 below.

[0083]

[0084] Example Comparative Example 1 2 1 2 3 4 5 DC Stability Insulation Breakdown Breakdown × Breakdown × Breakdown ○ Breakdown ○ Breakdown ○ Breakdown ○ Breakdown ○ Volume Resistance (Ω) (Immediately after immersion) 28,500 26,800 22,000 25,000 19,000 23,400 25,900 Volume Resistance (Ω) (After 7 days) 52,400 25,900 2,300 20.5 0.0 34,140 Volume Resistance (Ω) (After 10 days After) 28,000 29,7000.10.1--0.3 Oil Resistance Short-term Good Good Good Poor Good Good Good Long-term Good Good Good Poor Good Good Good Acid / Base Acid Good Good Good Good Good Good Good Good Base Good Good Good Good Good Good Good Wear Resistance (Cycle Count) 1,523 1,3448 74788 1,312752 1,294

[0085]

[0086] As described in Table 2 above, the insulated wire of the embodiment according to the present invention was confirmed to have excellent oil resistance, acid / base resistance, and abrasion resistance while maintaining electrical characteristics under high-temperature salt water conditions. On the other hand, the insulated wire of the comparative example, which deviates from the appropriate combination of base resins, was found to have failed to maintain electrical characteristics, such as insulation breakdown occurring within 240 hours under high-temperature salt water conditions, and its oil resistance and abrasion resistance were found to have deteriorated.

[0087] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art may modify and change the present invention in various ways without departing from the spirit and scope of the invention as described in the claims below. Therefore, if a modified embodiment basically includes the components of the claims of the present invention, it should be considered to be included within the technical scope of the present invention.

Claims

1. An insulating composition for forming an insulating layer of a signal cable for railway vehicles, Includes a base resin and a flame retardant, An insulating composition comprising a base resin having a melting point of 125 to 135°C, a polyolefin elastomer having a melting point of 90 to 102°C, an ethylene copolymer having a melting point of 95 to 105°C, and a polyolefin resin grafted with maleic anhydride having a melting point of 125 to 135°C.

2. In Paragraph 1, An insulating composition characterized by not experiencing insulation breakdown when an insulating wire having an insulating layer formed from the above insulating composition is immersed in 85°C brine (NaCl 3%) and a DC voltage of 300 V is applied for 240 hours.

3. In Paragraph 2, An insulating composition comprising one or more types selected from the group consisting of linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

4. In Paragraph 2, An insulating composition comprising one or more types selected from the group consisting of olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, ester-based thermoplastic elastomers, and urethane-based thermoplastic elastomers.

5. In Paragraph 2, An insulating composition comprising one or more selected from the group consisting of ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), and ethylene butyl acrylate (EBA).

6. In any one of paragraphs 1 through 5, An insulating composition characterized by, based on 100 parts by weight of the base resin, having a content of 20 to 40 parts by weight of the polyethylene resin, a content of 20 to 40 parts by weight of the polyolefin elastomer, a content of 30 to 50 parts by weight of the ethylene copolymer, and a content of 10 to 20 parts by weight of the maleic anhydride-grafted polyolefin resin.

7. In Paragraph 6, An insulating composition characterized by having a total content of 30 to 60 parts by weight of maleic anhydride grafted high-density polyethylene resin as the polyethylene resin and maleic anhydride grafted high-density polyethylene resin as the maleic anhydride grafted polyolefin resin, based on 100 parts by weight of the base resin.

8. In any one of paragraphs 1 through 5, An insulating composition characterized in that the flame retardant comprises a metal hydroxide containing magnesium hydroxide or aluminum hydroxide.

9. In Paragraph 8, An insulating composition characterized in that the above metal hydroxide comprises a metal hydroxide whose surface is coated with silane.

10. In Paragraph 9, An insulating composition characterized by having a content of 150 to 200 parts by weight of the flame retardant based on 100 parts by weight of the base resin.

11. In any one of paragraphs 1 through 5, An insulating composition characterized by further comprising 10 to 20 parts by weight of one or more other additives selected from lubricants, antioxidants, and crosslinking agents, based on 100 parts by weight of the base resin.

12. A signal cable for a railway vehicle comprising a conductor and an insulating layer surrounding the conductor and formed from an insulating composition of any one of claims 1 to 5.

13. One or more cores comprising a conductor and an insulating layer surrounding the conductor and formed from an insulating composition of any one of claims 1 to 5; A metal shielding layer surrounding one or more of the above cores; and A signal cable for a railway vehicle comprising a sheath layer surrounding the metal shielding layer.

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