WO2009119942A1

WO2009119942A1 - Halogen-free flame retardant composition for cable and cable using the same

Info

Publication number: WO2009119942A1
Application number: PCT/KR2008/003699
Authority: WO
Inventors: Do-Hyun Park; Hyun-Joo Hwang
Original assignee: Ls Cable Ltd.
Priority date: 2008-03-28
Filing date: 2008-06-26
Publication date: 2009-10-01
Also published as: KR100947169B1; KR20090103348A; JP2011519383A; CN101981109A

Abstract

The present invention relates to a halogen-free flame retardant composition for a cable and a cable using the same. The halogen-free flame retardant composition has a tensile strength of 1.5 kgf/mnf or more at normal temperature, and comprises 100 parts by weight of a base resin including 60 to 90 weight% of an ethylene-based copolymer resin and 10 to 40 weight% of a polyolefin-based resin, 50 to 160 parts by weight of a flame retardant relative to 100 parts by weight of the base resin; and 1 to 30 parts by weight of a flame retarding aid relative to 100 parts by weight of the base resin.

Description

HALOGEN-FREE FLAME RETARDANT COMPOSITION FOR CABLE AND CABLE USING THE SAME

Technical Field

[1] The present invention relates to a halogen-free flame retardant composition for a cable and a cable manufactured using the same, and in particular, to a halogen-free flame retardant composition that does not include a halogen component but a mixed resin of an ethylene-based copolymer resin and a polyolefin-based resin as a base resin, a flame retardant and a flame retarding aid to exhibit high tensile strength and meet the flame retardance requirements, and an insulating cable manufactured using the same. Background Art

[2] Generally, a cable for power supply, control or signalling used in ships has a woven layer surrounding a bedding structure that surrounds a center conductor so as to prevent deformation caused by tensile force and lateral pressure that may be applied to the cable at the time of installation, and the woven layer is made of galvanized iron wires, galvanized steel wires or copper coated iron wires. In particular, a halogen-free flame retardant cable according to IEC (International Electrotechnical Commission) standards should have a woven layer inside or outside thereof when it is used in dangerous places or places required for explosion proof. However, use of the woven layer results in large outer diameter and poor flexibility of a cable, and consequently makes it difficult to install the cable in a small space.

[3] Meanwhile, the woven layer is formed through a separate step in a cable manufacturing process, thereby increasing the unit cost of production, and in the case that wires are woven irregularly in a woven layer forming step, a faulty product may be manufactured. And, the woven layer increases the total weight of a cable, which limits applications required for light weight.

[4] Related industries have steadily studied techniques to improve physical properties against tensile force in a cable having a woven layer and developed a substitute for the woven layer to protect flame retardance of the cable, and suggested a halogen-free polymer material for improved tensile strength. However, the halogen-free polymer material has excellent tensile strength, but has low flame retardant characteristics. And, the halogen-free polymer material has high rigidity, and consequently reduces flexibility of a cable, which makes it difficult to install the cable. To solve the problem, an organic or inorganic flame retardant is added to improve flame retardance of the halogen-free polymer material, however in this case, the tensile strength of the polymer material is reduced.

[5] As mentioned above, a suggestion is a halogen-free polymer material, and with the halogen-free polymer material, studies have been continuously made to develop an insulator that can provide not only flame retardance but also improved physical properties such as tensile strength and improved flexibility, which allows easy installation of a cable, and minimize the volume or weight of the cable. The present invention was devised in this technical background. Disclosure of Invention Technical Problem

[6] An object of the present invention is to provide a halogen-free polymer composition that can provide not only flame retardance but also functions and properties of both of a bedding structure and a woven structure surrounding a center conductor of a cable and meet various physical properties required for an insulator. Technical Solution

[7] A halogen-free flame retardant composition according to the present invention comprises 100 parts by weight of a base resin including 60 to 90 weight% of an ethylene-based copolymer resin and 10 to 40 weight% of a polyolefin-based resin; 50 to 160 parts by weight of a flame retardant relative to 100 parts by weight of the base resin; and 1 to 30 parts by weight of a flame retarding aid relative to 100 parts by weight of the base resin.

[8] An insulating cable according to the present invention includes a center conductor; an insulating layer coating the center conductor; and a bedding layer surrounding the center conductor coated with the insulating layer, wherein the bedding layer is formed using the above-mentioned halogen-free flame retardant composition. Brief Description of Drawings

[9] Preferred embodiments of the present invention will be more fully described in the following detailed description, taken accompanying drawings. However, it should be understood that the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention.

[10] FIG. 1 is a schematic cross-sectional view of a conventional insulating cable.

[11] FIG. 2 is a schematic cross-sectional view of an insulating cable according to the present invention. Best Mode for Carrying out the Invention

[12] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention. The preferred embodiments of the present invention are provided to help persons having ordinary skills in the art understand the present invention more completely.

[13] According to the present invention, a halogen-free flame retardant composition has a tensile strength of 1.5 kgf/mnf or more at normal temperature, and the composition includes 100 parts by weight of a base resin including 60 to 90 weight% of an ethylene-based copolymer resin and 10 to 40 weight% of a polyolefin-based resin, 50 to 160 parts by weight of a flame retardant relative to 100 parts by weight of the base resin, and 1 to 30 parts by weight of a flame retarding aid relative to 100 parts by weight of the base resin.

[14] In the case that the ethylene-based copolymer resin of the base resin is included less than the above-mentioned minimum, it is not preferable because capacity of filling a large amount of flame retardant is reduced to remarkably decrease elongation. In the case that the ethylene-based copolymer resin is included more than the above- mentioned maximum, it is not preferable because proportion of a crystalline resin is reduced, thereby failing to ensure tensile strength and shock resistance corresponding to a woven layer of a conventional insulating cable and to meet thermal deformation resistance at 8O⁰C and high temperature ageing characteristics at 15O⁰C. Meanwhile, a content limitation of the polyolefin-based resin has a contrary reason to a content limitation of the ethylene-based copolymer resin. Specifically, in the case that the polyolefin-based resin is included less than the above-mentioned minimum, it is not preferable because proportion of a crystalline resin is reduced, thereby failing to ensure tensile strength and shock resistance corresponding to a woven layer of a conventional insulating cable and to meet thermal deformation resistance at 8O⁰C and high temperature ageing characteristics at 15O⁰C. In the case that the polyolefin-based resin is included more than the above-mentioned maximum, it is not preferable because capacity of filling a large amount of flame retardant is remarkably reduced to decrease elongation, and a large amount of resin having a high melting temperature is used, which increases an extruding process temperature, resulting in decomposition of the flame retardant.

[15] At this time, preferably the ethylene-based copolymer resin of the base resin is any one selected from the group consisting of an ethylene vinyl acetate copolymer resin, an ethylene methyl acrylate copolymer resin, an ethylene ethyl acrylate copolymer resin, and an ethylene butyl acrylate copolymer resin, or mixtures thereof, however the present invention is not limited in this regard. More preferably, the ethylene-based copolymer resin has a specific gravity of 0.93 g/cnf to 0.96 g/cnf, a melting temperature of 67⁰C to 102⁰C, and a melting index of 0.3 g/10min to 10 g/10min. In the case that the melting index is less than the above-mentioned minimum, it is not preferable because elongation and extrusion is reduced, and in the case that the melting index is more than the above-mentioned maximum, it is not preferable because tensile strength and heat resistance is reduced.

[16] Preferably, the polyolefin-based resin of the base resin is any one selected from the group consisting of a low density polyethylene (LDPE) resin, a linear low density polyethylene (LLDPE) resin, a middle density polyethylene (MDPE) resin, a high density polyethylene (HDPE) resin, a polypropylene resin, and a polyester resin, or mixtures thereof, however the present invention is not limited in this regard. More preferably, a material selected as the polyolefin-based resin has a maleic anhydride.

[17] In the case that the flame retardant is included less than the above-mentioned minimum, it is not preferable because flame retardance is insufficient, and in the case that the flame retardant is more than the above-mentioned maximum, it is not preferable because flame retardance is not increased in proportion to an excessive amount of flame retardant but tensile strength characteristics are reduced due to the excessive amount of flame retardant. Preferably, the flame retardant is any one selected from the group consisting of a mixture of magnesium hydroxide and hydro- magnesite, a composite of huntite and hydromagnesite, and aluminium hydroxide, or mixtures thereof, however the present invention is not limited in this regard. And, the flame retardant may be a metal hydroxide surface-treated with any one selected from the group consisting of vinylsilane, stearic acid, oleic acid, aminopolysiloxane, and polymer resin, or mixtures thereof. At this time, preferably the metal hydroxide is any one selected from the group consisting of a mixture of magnesium hydroxide and hydromagnesite, a composite of huntite and hydromagnesite, and aluminium hydroxide, or mixtures thereof, however the present invention is not limited in this regard.

[18] In the case that the flame retarding aid is included less than the above-mentioned minimum, it is not preferable because improvement in flame retardance is not realized, and in the case that the flame retarding aid is more than the above-mentioned maximum, it is not preferable because an amount of a flame retardant should be reduced to prevent reduction in mechanical properties, resulting in reduced flame retardance or heat resistance. Preferably, the flame retarding aid is any one selected from the group consisting of a red phosphorous-based compound, a silicon-based compound, a boron-based compound, and carbon powder, or mixtures thereof, however the present invention is not limited in this regard.

[19] The halogen-free flame retardant composition may further include 0.1 to 15 parts by weight of an antioxidant relative to 100 parts by weight of the base resin, and the antioxidant is any one selected from the group consisting of hindered phenol-based, phosphate-based, imidazole-based and thio-based, or mixtures thereof.

[20] In the case that the antioxidant is included less than the above-mentioned minimum, it is not preferable because a small amount of antioxidant results in insufficient heat resistance, and in the case that the antioxidant is more than the above-mentioned maximum, it is not preferable because an excessive amount of antioxidant results in reduced flame retardance and mechanical properties.

[21] The above-mentioned halogen-free flame retardant composition according to the present invention has a tensile strength of 1.50 kg/mirf or more at normal temperature and an oxygen index of 28% or more. The composition can be used to form a bedding structure and a woven structure of iron wires or copper wires in an insulating wire or cable, or an inner sheath layer of an electrical wire.

[22] As shown in the following Table 1, components were prepared according to examples 1 to 6 and comparative examples 1 to 3, and mixed in an open roll of about 13O⁰C. Then, the mixtures were molded by a press of 17O⁰C for 5 minutes to manufacture each sample for property measurement.

[23] Table 1

[Table 1] [Table ]

[24] Each sample was tested according to the following methods to measure various properties including characteristics at normal temperature such as tensile strength and elongation, thermal deformation rate, oxygen index and high temperature ageing, and measurement results are shown in the following Table 2. Each sample was tested according to IEC 60811-1-1 standards to measure characteristics at normal temperature when a tension test speed is 250 mm/min, and tensile strength of 1.5 kgf/mnf or more and elongation of 125% is considered suitable for products. Each sample was tested according to IEC 60811 standards to measure a thermal deformation rate after being left at 8O⁰C for 4 hours, a thermal deformation rate of 50% or less is considered suitable for products. Each sample was tested according to ASTM D 2863 standards to measure an oxygen index, and an oxygen index of 28% or more is considered suitable for products. Each sample was tested according to IEC 811 standards to measure high temperature ageing after being left at 15O⁰C for 1 hour, and no cracking is considered suitable for products.

[25] A sheath layer of an insulating cable that surrounds a center conductor was formed using each composition prepared according to Table 1, and the cable having the sheath layer was tested to measure flame retardance and tensile strength, and measurement results are shown in Table 2. At this time, the cable was tested according to IEC 332-3 Cat.A to measure flame retardance, and determined whether or not it is suitable for products. The tensile strength of the cable was determined according to whether or not the performance of an insulator was deteriorated and whether or not an outer coating was damaged when the cable was drawn.

[26] Table 2 [Table 2] [Table ]

[27] It is found through measurement and evaluation results of Table 2 that the examples 1 to 6 meet the product suitability required for each measurement item. However, the comparative examples 1 to 3 do not meet most of product suitability for each measurement item. Therefore, it is found that an insulator of an insulating cable formed using the halogen-free flame retardant composition according to the present invention has better physical properties than a conventional product.

[28] The examples 1 to 6 used a mixture of ethylene copolymer resin having a melting temperature of 67⁰C to 102⁰C and a crystalline polyethylene resin, and met the tensile strength and elongation requirements of the present invention, i.e. tensile strength of 1.5 kgf/mnf or more at normal temperature and elongation of 125% or more. Accordingly, a cable having an insulator formed using the composition according to the present invention has tensile strength suitable for an installation environment. Meanwhile, because a crystalline polyethylene resin is included in a base resin, the examples 1 to 6 passed a thermal deformation test using a cutter blade at 8O⁰C and a high temperature ageing test at 15O⁰C. Further, the examples 1 to 6 used a resin having a high melting temperature and a high thermal decomposition temperature, and thus when a cable having an insulator formed using the flame retardant composition of the present invention is tested according to flame retardance test, a polymer resin of the flame retardant material does not melt down, but stands against flame and high ambient temperature, thereby preventing flame from propagating to the insulator of the cable, and thus the cable has flame retardant characteristics.

[29] Meanwhile, the comparative examples 1 to 3 used only an ethylene copolymer resin having a low melting temperature and a low thermal decomposition temperature, and thus in case that the resin is exposed to flame of 600⁰C or more, the resin is melted down and flow-in of oxygen is promoted, resulting in rapid combustion. As a result, the comparative examples 1 to 3 failed the flame retardance test. And, the comparative examples 1 to 3 used a low crystalline copolymer resin, and thus did not meet the tensile strength requirements of the present invention. Accordingly, cables having insulators formed using the compositions according to the comparative examples 1 to 3 did not meet the tensile strength requirements for installation. And, the comparative examples 1 to 3 used only a resin having a melting temperature of 100⁰C or less, and thus, after a thermal deformation test using a cutter blade at 8O⁰C according to IEC 60811, they did not meet the required thermal deformation rate of 50%, and as a result, the insulators were broken. And, because the melting temperature is low, the samples were broken after a high temperature ageing test at 15O⁰C, and therefore, the comparative examples 1 to 3 were not considered suitable for products.

[30] To achieve the above-mentioned objects, an insulating cable according to the present invention is manufactured, in which a bedding layer surrounding a center conductor coated with an insulating layer is formed using the above-mentioned halogen-free flame retardant composition.

[31] FIG. 1 is a schematic cross-sectional view of a conventional insulating cable.

[32] As shown in FIG. 1, the conventional insulating cable includes a center conductor 11 and an insulating layer 12 surrounding the center conductor 11. The insulating layer 12 is made of an ethylene propylene rubber, polyethylene or polyolefin. A bedding layer 13 surrounds a plurality of conductors 11 having each insulating layer 12. A woven layer 14 surrounds the bedding layer 13, and is made of copper plated with copper or tin. A sheath layer 15 surrounds the woven layer 14, and is mainly formed using a flame retardant composition according to IEC 60332-3 Cat.A.

[33] The woven layer 14 stands against the tensile force, and in case of fire, the bedding layer 15 suppresses flame propagation caused by the woven layer 14 to minimize damage of the insulating layer 12 and maintain electrical characteristics of the cable. However, although the woven layer 14 is simply removed from the conventional insulating cable, the above-mentioned problem is not solved, but a critical fault may occur to suitability for products.

[34] The present invention removes a woven layer of a conventional insulating cable, and instead forms a bedding layer using a halogen-free flame retardant composition having a tensile strength of 1.5kgf/mnf or more at normal temperature and an oxygen index of 28% or more, resulting in light weight and flexibility of a cable.

[35] To solve the conventional problem, an insulating cable according to the present invention does not have a woven layer, as shown in FIG. 2.

[36] FIG. 2 is a schematic cross-sectional view of an insulating cable according to the present invention. Referring to FIG. 2, the insulating cable includes a center conductor 21 and an insulating layer 22 surrounding the center conductor. A bedding layer 23 surrounds a plurality of conductors 21 having each insulating layer 22, and a sheath layer 24 surrounds the bedding layer 23.

[37] As such, the preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Industrial Applicability

[38] The present invention can prepare a halogen-free flame retardant composition, and forms a bedding layer or a sheath layer of an insulating cable using the halogen-free flame retardant composition. An insulating cable according to the present invention has a tensile strength of 1.5kgf/mnf or more at normal temperature, and thus meets the required suitability for products without a woven layer of a conventional insulating cable.

Claims

[1] A halogen-free flame retardant composition for a cable that has a tensile strength of 1.5 kgf/mnf or more at normal temperature, the composition comprising: 100 parts by weight of a base resin including 60 to 90 weight% of an ethylene- based copolymer resin and 10 to 40 weight% of a polyolefin-based resin; 50 to 160 parts by weight of a flame retardant relative to 100 parts by weight of the base resin; and

1 to 30 parts by weight of a flame retarding aid relative to 100 parts by weight of the base resin.

[2] The halogen-free flame retardant composition for a cable according to claim 1, wherein the ethylene-based copolymer resin is any one selected from the group consisting of an ethylene vinyl acetate copolymer resin, an ethylene methyl acrylate copolymer resin, an ethylene ethyl acrylate copolymer resin, and an ethylene butyl acrylate copolymer resin, or mixtures thereof.

[3] The halogen-free flame retardant composition for a cable according to claim 1, wherein the polyolefin-based resin is any one selected from the group consisting of a low density polyethylene (LDFE) resin, a linear low density polyethylene (L LDPE) resin, a middle density polyethylene (MDPE) resin, a high density polyethylene (HDPE) resin, a polypropylene resin, and a polyester resin, or mixtures thereof.

[4] The halogen-free flame retardant composition for a cable according to claim 3, wherein a material selected as the polyolefin-based resin has a maleic anhydride.

[5] The halogen-free flame retardant composition for a cable according to claim 1, wherein the flame retardant is any one metal hydroxide selected from the group consisting of a mixture of magnesium hydroxide and hydromagnesite, a composite of huntite and hydromagnesite, and aluminium hydroxide, or mixtures thereof.

[6] The halogen-free flame retardant composition for a cable according to claim 1, wherein the flame retardant is a metal hydroxide surface-treated with any one selected from the group consisting of vinylsilane, stearic acid, oleic acid, aminopolysiloxane and polymer resin, or mixtures thereof.

[7] The halogen-free flame retardant composition for a cable according to claim 6, wherein the metal hydroxide is any one selected from the group consisting of a mixture of magnesium hydroxide and hydromagnesite, a composite of huntite and hydromagnesite, and aluminium hydroxide, or mixtures thereof. [8] The halogen-free flame retardant composition for a cable according to claim 1, wherein the flame retarding aid is any one selected from the group consisting of a red phosphorous-based compound, a silicon-based compound, a boron-based compound, and carbon powder, or mixtures thereof. [9] The halogen-free flame retardant composition for a cable according to claim 1, further comprising:

0.1 to 15 parts by weight of an antioxidant relative to 100 parts by weight of the base resin, the antioxidant being any one selected from the group consisting of hindered phenol-based, phosphate -based, imidazole-based, and thio-based, or mixtures thereof. [10] A cable, comprising: a center conductor; an insulating layer coating the center conductor; and a bedding layer surrounding the center conductor coated with the insulating layer, wherein the bedding layer is formed using the halogen-free flame retardant composition defined in any one of claims 1 to 9.