Polypropylene resin composition with excellent thermal and voltage stability for power cable insulation and molded product using same

Abstract

Disclosed are: a recyclable resin composition for power cable insulation, which has excellent heat resistance stability and voltage stability; and a molded article using the same. The present invention provides a polypropylene resin composition for power cable insulation, comprising: 60 to 90 parts by weight of a propylene block copolymer in which ethylene-propylene rubber (EPR) is dispersed in a propylene-ethylene random copolymer; 10 to 40 parts by weight of a polyolefin elastomer (POE); and relative to the weight of the entire composition, 100 to 1,000 ppm of an inorganic nanocomposite and 500 to 5,000 ppm of a hindered amine light stabilizer (HALS)-type stabilizer.

Description

Polypropylene resin composition for insulation of power cables with excellent heat and voltage stability and molded products using the same

[0001] The present invention relates to an insulating resin composition for an eco-friendly power cable, and more specifically, to an insulating resin composition for an eco-friendly power cable having excellent heat and voltage stability.

[0002] This application claims priority to and the benefit of Republic of Korea Patent Application No. 10-2023-0164134, filed November 23, 2023, which is incorporated herein by reference in its entirety.

[0003] The insulation materials used in power cables are mainly cross-linked materials such as polyethylene (PE), polyvinyl chloride (PVC), and ethylene-propylene rubber (EPR). Among these, cross-linked polyethylene (XLPE) is a cross-linking process that transforms the linear molecular structure of polyethylene into a three-dimensional network structure. This process maintains the excellent mechanical properties and chemical resistance of conventional polyethylene while improving heat resistance, making it suitable for use as an insulation layer for high-voltage power cables. However, because cross-linked polyethylene is a cross-linked polymer, it cannot be recycled and must be disposed of through incineration, making it somewhat unfriendly to the environment.

[0004] Recently, development is underway for an insulating resin applicable to distribution lines (22.9kV or higher) using polypropylene (PP), a material that is highly recyclable and heat-resistant. Compared to XLPE (XLPE), polypropylene insulation layers are known to have a simpler manufacturing process, are environmentally friendly due to their non-crosslinked nature, and offer superior performance, including heat resistance, and are highly versatile. The manufacturing process for polypropylene insulation layers eliminates the generation of toxic substances such as methane gas and various byproducts, and greenhouse gases such as CO₂ generated during the manufacturing process can be reduced by approximately 30% compared to XLPE. Furthermore, polypropylene insulation layers are recyclable and heat-resistant, potentially increasing transmission capacity.

[0005] However, in the case of power cables containing polypropylene insulation layers, the heat transfer efficiency of the polypropylene matrix is ​​low, so when exposed to high temperatures in the cable use environment, the rate of deterioration at the bonding surface is fast, and as a result, an electric tree occurs, which reduces the insulation breakdown strength, and problems may arise in long-term heat resistance stability and insulation performance.

[0006] Recently, attempts have been made to improve flexibility and electrical properties by using olefin rubber in polypropylene. However, polypropylene and olefin rubber have heterogeneous properties and do not mix well. This creates boundaries between the matrix phase and domains, which, depending on the rubber material composition, reduces dielectric breakdown strength and reduces heat stability at high temperatures.

[0007] International Patent Publication No. WO2012 / 069864 discloses that the dielectric strength of a sample cable under AC conditions is improved when an aromatic dielectric fluid having a ratio of the number of aromatic carbon atoms to the total number of carbon atoms of 0.3 or more and a voltage stabilizer selected from substituted benzophenone and hindered amine are added, but it only explains the main cause of the improvement in dielectric strength as the dielectric fluid.

[0008] International Patent Publication No. WO2012 / 150285 is a technology that uses hydrotalcite as an ion-exchange additive to capture ionic species that worsen the DC conductivity of a wire cable and maintain low conductivity, thereby preventing heat generation due to leakage current and suppressing thermal runaway under high-temperature conditions. However, since it does not present the electrical properties of the cable (insulation breakdown strength, dielectric loss tangent, etc.) excluding DC conductivity, it is impossible to confirm whether the actual performance of the ion-exchange additive has improved the high-temperature characteristics of the cable.

[0009] The present invention aims to provide a resin composition for insulating a power cable that is recyclable and has excellent heat resistance and voltage stability, and a molded product using the same.

[0010] In order to solve the above problem, the present invention provides a polypropylene resin composition for insulating a power cable, comprising: 60 to 90 parts by weight of a propylene block copolymer in which ethylene-propylene rubber (EPR) is dispersed in a propylene-ethylene random copolymer; 10 to 40 parts by weight of a polyolefin elastomer (POE); 100 to 1,000 ppm of an inorganic nanocomposite based on the total composition weight; and 500 to 5,000 ppm of a HALS (Hindered Amine Light Stabilizer) stabilizer.

[0011] In addition, a polypropylene resin composition for insulating a power cable is provided, characterized in that the ethylene-derived repeating unit of the propylene block copolymer is contained in an amount of 0.1 to 5 wt% in the propylene-ethylene random copolymer, in an amount of 30 to 60 wt% in the ethylene-propylene rubber (EPR), and in an amount of 5 to 25 wt% in the propylene block copolymer.

[0012] In addition, the propylene block copolymer has a melting point of 150 to 170°C, a melting enthalpy of 40 to 70 J / g, a melting index (MI, 230°C, 2.16 kg load) of 0.1 to 10 g / 10 min, and a xylene soluble content of 20 to 40 wt% in the propylene block copolymer, and the resin composition has a melting point of 150 to 160°C, a melting enthalpy of 40 to 80 J / g, a melting index (MI, 230°C, 2.16 kg load) of 1 to 3 g / 10 min, and a xylene soluble content of 30 to 50 wt%.

[0013] In addition, the inorganic nanocomposite provides a polypropylene resin composition for insulating a power cable, characterized in that it includes a metal double-layer hydroxide structure of the following chemical formula 1 or a composite metal oxide structure derived therefrom.

[0014] [Chemical Formula 1]

[0015] [M a 2+ 1-x M b 3+ x (OH)2] x+ (A n- ) x / n ㆍmH2O

[0016] In chemical formula 1,

[0017] M a 2+ and M b 3+ are cations of divalent and trivalent metals, respectively,

[0018] A n- is an intercalated anion,

[0019] x is the ratio of two metal cations, M b 3+ / (M a 2+ +M b 3+ ) as the surface charge determined by 0 < x < 1,

[0020] n is an integer from 1 to 3,

[0021] m is a number between 0.1 and 15.

[0022] In addition, the present invention provides a polypropylene resin composition for insulating a power cable, characterized in that the metal double-layer hydroxide structure is a magnesium-aluminum-carbonate hydrotalcite.

[0023] In addition, the HALS (Hindered Amine Light Stabilizer) stabilizer is poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], A polypropylene resin composition for insulating a power cable is provided, characterized in that it comprises at least one selected from the group consisting of poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]].

[0024] In addition, the resin composition provides an insulating resin composition for a power cable, characterized in that the AC insulation breakdown strength measured by the following method is 50 kV / mm or more, the relative permittivity is 2.1 or less, and the dielectric loss tangent is 0.05% or less.

[0025] [Method for measuring insulation breakdown strength]

[0026] The above resin composition is manufactured into a sheet having a thickness of 1 mm, cooled at 10°C for 5 minutes, and AC 30 kV is initially applied for 5 minutes according to ASTM D149 standards, and then increased by 10 kV and maintained for 5 minutes. This process is continued until insulation breakdown occurs, and when insulation breakdown occurs, the voltage at that time is taken as the AC insulation breakdown strength;

[0027] [Method for measuring relative permittivity]

[0028] The specimens (2 mm thick, 2 cm wide, 2 cm long) manufactured according to ASTM D150 standard were measured at 60℃ using LCR Meter equipment (electrode radius 5 mm, electrode type G10 type) with a frequency of 1 MHz and an AC voltage of 1 V;

[0029] [Method for measuring dielectric constant]

[0030] A multi-functional impedance measurement test device is used to measure a specimen (1 mm thick, 10 cm wide, 10 cm long) manufactured according to ASTM D150 standards at 130℃ and 2 kV. Type 1 No. 2 mineral oil is poured into a constant temperature bath to maintain the temperature conditions, and the specimen is loaded between the spherical electrodes of an impedance measuring device using a Schering bridge circuit configuration and an AC voltage is applied to measure the permittivity. The dielectric loss factor is then calculated by applying the conversion formula of ASTM D150 standards.

[0031] In order to solve the above-mentioned further problem, the present invention provides a power cable including the resin composition as an insulating layer.

[0032] The present invention provides a resin composition for insulating a recyclable power cable using a propylene block copolymer in which ethylene-propylene rubber (EPR) is dispersed in a propylene-ethylene random copolymer, a polyolefin elastomer (POE), an inorganic nanocomposite, and a HALS (Hindered Amine Light Stabilizer) stabilizer, and a power cable using the same, which has excellent heat resistance and voltage stability.

[0033] Figure 1 is a schematic drawing showing a cross-section of a power cable manufactured from a resin composition according to the present invention.

[0034] Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, it should be noted that the terms and words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of a term to best explain his or her invention, they should be interpreted as meanings and concepts that conform to the technical concept of the present invention. Therefore, the configuration of the embodiments described in this specification is only the most preferred embodiment of the present invention and does not represent the entire technical concept of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of filing this application.

[0035]

[0036] The present invention discloses a polypropylene resin composition for insulating a power cable, comprising: 60 to 90 parts by weight of a propylene block copolymer in which ethylene-propylene rubber (EPR) is dispersed within a propylene-ethylene random copolymer; 10 to 40 parts by weight of a polyolefin elastomer (POE); 100 to 1,000 ppm of an inorganic nanocomposite; and 500 to 5,000 ppm of a HALS (Hindered Amine Light Stabilizer) stabilizer based on the total composition weight.

[0037] Hereinafter, each component of the insulating resin composition for a power cable according to the present invention will be described in detail.

[0038] Polypropylene can be classified into homo-polypropylene (H-PP), propylene random copolymer (R-PP), and propylene block copolymer (B-PP). Among these, propylene random copolymer and propylene block copolymer are more suitable for power cables because they have higher flexibility and bending properties than homo-polypropylene. Here, propylene block copolymer has the advantage of superior flexibility and bending properties compared to propylene random copolymer, so propylene block copolymer is used in the present invention.

[0039] In the present invention, the propylene block copolymer is a type of RTPO (Reactor-made Thermoplastic Polyolefin elastomers), which refers to a polymer that includes a plurality of polymers exhibiting rubber properties within a polymer including units derived from propylene monomers.

[0040] In the present invention, the propylene block copolymer is obtained by reacting propylene and ethylene in a bulk reactor to polymerize a propylene-ethylene random copolymer, and then copolymerizing propylene and ethylene gas in a gas phase reactor in the presence of the propylene-ethylene random copolymer through continuous polymerization to disperse ethylene-propylene rubber (EPR) within the propylene-ethylene random copolymer. By producing the copolymer through continuous polymerization as described above, the ethylene-propylene rubber (EPR) can be uniformly dispersed in small-sized domains within a polypropylene matrix.

[0041] Here, in the present invention, the domain size and dispersion degree of the ethylene-propylene rubber (EPR) are not limited, but considering the thermal and electrical properties of the final resin composition, the average domain size may be 0.1 to 5 ㎛, preferably 0.5 to 2 ㎛, and the domain dispersion degree may be 0.1 to 0.7, preferably 0.2 to 0.6. The domain size and dispersion degree may be measured by cutting a specimen manufactured by compression molding (220°C for 4 minutes) the resin composition into a width of 1 mm and a length of 10 cm, immersing the specimen in xylene at 60°C to dissolve the ethylene-propylene rubber, and analyzing the pores present on the surface of the specimen using a scanning electron microscope (SEM).

[0042] In the present invention, the propylene block copolymer may comprise 30 to 70 wt% of a propylene-ethylene random copolymer and 30 to 70 wt% of ethylene-propylene rubber (EPR), preferably 40 to 60 wt% of a propylene-ethylene random copolymer and 40 to 60 wt% of ethylene-propylene rubber (EPR), and more preferably 45 to 55 wt% of a propylene-ethylene random copolymer and 45 to 55 wt% of ethylene-propylene rubber (EPR). The propylene block copolymer is in the form of ethylene-propylene rubber (EPR) particles dispersed in a propylene-ethylene random copolymer matrix. Specifically, the propylene block copolymer may be a block copolymer in which ethylene-propylene rubber (EPR) is stepwise polymerized in a propylene-ethylene random copolymer in a reactor. The above propylene block copolymer has ethylene-propylene rubber (EPR) dispersed in a specific content range, and thus has a lower flexural modulus than propylene homopolymer or propylene-ethylene random copolymer, thereby maximizing flexibility and elasticity as well as improving thermal and electrical properties when applied as an insulation layer for power cables. In addition, when mixed with a polyolefin elastomer (POE) described below, it has excellent miscibility due to uniform dispersion, thereby maximizing thermal properties and insulation breakdown properties.

[0043] In the present invention, the propylene block copolymer is produced by using a high content of ethylene in a polymerization reactor to produce a large amount of ethylene-propylene rubber (EPR), and contains a high content of repeating units derived from ethylene-propylene rubber (EPR) compared to existing propylene block copolymers, so it has the advantages of high tensile strength and excellent flexibility.

[0044] Although not limited by theory, propylene block copolymers generally manufactured in a reactor may have an ethylene-derived repeating unit content of 5 to 25 wt%, preferably 10 to 20 wt%, based on the total block copolymer due to technical difficulties. In addition, the ethylene-derived repeating unit content may be 0.1 to 5 wt%, preferably 0.1 to 3 wt%, and more preferably 0.5 to 2 wt%, based on the propylene-ethylene random copolymer, and may be 30 to 60 wt%, preferably 35 to 50 wt%, based on the ethylene-propylene rubber (EPR). Within the above range of ethylene-derived repeating unit content, thermal and electrical properties may be maximized. In addition, when the ethylene-derived repeating unit content exceeds 5 wt% in the propylene-ethylene random copolymer, the melting point of the block copolymer may be lowered to 150°C or lower, resulting in deteriorated heat stability.

[0045] In addition, the melting point of the propylene block copolymer may be 150 to 170°C, preferably 150 to 160°C. In addition, the melting enthalpy may be 40 to 70 J / g, preferably 50 to 60 J / g. When the melting point and melting enthalpy of the propylene block copolymer satisfy the above ranges, the thermal and electrical properties to be implemented in the present invention may be satisfied when applied as an insulation layer of a power cable.

[0046] In addition, the melt index (MI, 230°C, 2.16 kg load) of the propylene block copolymer may be 0.1 to 10 g / 10 min, preferably 0.3 to 5 g / 10 min, and more preferably 0.5 to 2 g / 10 min. If the melt index is less than 0.1 g / 10 min, an extruder load may be applied during the cable extrusion process, and if it exceeds 10 g / 10 min, eccentricity of the insulation layer of the cable molded product may occur.

[0047] In addition, the propylene block copolymer may have a xylene soluble content (XS) of 20 to 40 wt%, preferably 25 to 35 wt%, in the propylene block copolymer. The xylene soluble content depends on the content of ethylene-propylene rubber (EPR) contained in the propylene block copolymer, and flexibility, thermal properties, and electrical properties may be maximized within the content range.

[0048] In the present invention, the propylene block copolymer is included in an amount of 60 to 90 parts by weight, and preferably, it may be included in an amount of 70 to 80 parts by weight. If the propylene block copolymer content is less than 60 parts by weight, electrical properties and heat stability deteriorate, and if it exceeds 90 parts by weight, flexibility deteriorates.

[0049] The present invention includes polyolefin elastomer (POE) as a modifier for improving thermal and electrical properties along with flexibility of the final resin composition.

[0050] The above polyolefin elastomer comprises at least two kinds selected from the group consisting of repeating units derived from ethylene, repeating units derived from propylene, and repeating units derived from alpha-olefins of (C4-C12), and may include repeating units derived from ethylene or repeating units derived from propylene. For example, it may be a copolymer of ethylene and propylene, or a random or block copolymer elastomer of one kind of ethylene and propylene with an alpha-olefin such as 1-butene, 1-pentene, 1-hexene, or 1-octene, or a combination of these elastomers. In consideration of dispersibility and electrical properties, more preferably, propylene-ethylene rubber (PER) or ethylene-1-octene rubber (EOR) may be used, and most preferably, propylene-ethylene rubber (PER) may be used.

[0051] The polyolefin elastomer (POE) may be included in an amount of 10 to 40 parts by weight, and preferably 20 to 30 parts by weight. If the polyolefin elastomer (POE) content is less than 10 parts by weight, the flexibility, thermal and electrical properties of the final resin composition deteriorate, and if it exceeds 40 parts by weight, it is difficult to further improve the electrical properties and the heat resistance stability deteriorates.

[0052] In order to satisfy excellent thermal and electrical properties as an insulating resin composition for a recyclable power cable of the present invention, a propylene block copolymer and a polyolefin elastomer (POE) having the above-described composition are included, and a specific content of an inorganic nanocomposite and a HALS (Hindered Amine Light Stabilizer) stabilizer are included.

[0053] The above-mentioned inorganic nanocomposite is generally used for the purpose of neutralizing an acid component, which is a catalyst dispersion, but in the present invention, in addition to the use as a neutralizer, it provides a component of insulating inorganic nanoparticles, thereby improving heat diffusion of the matrix by dispersing them in a polypropylene matrix, thereby preventing deterioration, and improving insulation, thereby lowering the dielectric constant and dielectric constant, thereby improving long-term heat stability and voltage stability.

[0054] In one specific example of the present invention, the inorganic nanocomposite may include a metal double layer hydroxide structure of the following chemical formula 1 or a composite metal oxide structure derived therefrom.

[0055] [Chemical Formula 1]

[0056] [M a 2+ 1-x M b 3+ x (OH)2] x+ (A n- ) x / n ㆍmH2O

[0057] In chemical formula 1,

[0058] M a 2+ and M b 3+ are cations of divalent and trivalent metals, respectively,

[0059] A n- is an intercalated anion,

[0060] x is the ratio of two metal cations, M b 3+ / (M a 2+ +M b 3+ ) as the surface charge determined by 0 < x < 1,

[0061] n is an integer from 1 to 3,

[0062] m is a number between 0.1 and 15.

[0063] The above-described layered double hydroxide structure (LDH) is also known as a hydrotalcite-type material and is a type of anionic clay with a planar structure. The layered double hydroxide structure is composed of a cationic layer and an anionic layer capable of ion exchange between the layers. Such a double-layer hydroxide structure has been used as a catalyst or catalyst precursor in various reactions in the past, but in the present invention, it is used as an additive for improving the insulation breakdown strength of a resin composition for insulating power cables.

[0064] In the chemical formula 1 of the above metal double layer hydroxide structure, M a 2+ is a +2-valent metal cation, specifically Ni 2+ , Mg 2+ , Co 2+ , Mn 2+ , Zn 2+ , Cu 2+ and Fe 2+ can be selected from the group consisting of, preferably Ni 2+ , Mg 2+ and Co 2+It can be selected from the group consisting of. In addition, in the above chemical formula 1, M b 3+ is a +3-valent metal cation, specifically Fe 3+ , Al 3+ , Cr 3+ , Mn 3+ , Ga 3+ , Co 3+ , Ce 3+ and Ni 3+ may be selected from the group consisting of, preferably Al 3+ It can be. Also, in the above chemical formula 1, A n- is an intercalated anion, specifically Cl - , Br - , OH - , NO3 - , CO3 2- , SO4 2- , PO4 3- , HPO4 2- and H2PO4 - can be selected from the group consisting of .

[0065] In one specific example of the present invention, the double-layer hydroxide structure is a magnesium-aluminum-carbonate hydrotalcite (Mg6Al2(OH) 16 It could be CO3·4H20).

[0066] The content of the above-mentioned inorganic nanocomposite may be included in an amount of 100 to 1,000 ppm in the entire composition, and preferably 200 to 500 ppm. If the content is less than 100 ppm, the thermal diffusion effect does not appear and the insulation breakdown strength performance is poor, and if it exceeds 1,000 ppm, the amount of ionic impurities increases, and the effect of improving the insulation breakdown strength is minimal or rather begins to decrease.

[0067] The above HALS (Hindered Amine Light Stabilizer) stabilizer is an ultraviolet stabilizer that is easily oxidized and converted into nitroxyl radicals and reacts with radicals generated during the oxidation process of polymer chains to inhibit chain oxidation. It has the same mechanism as an electric tree inhibitor that captures radicals generated by an electric field, so it is suitable for improving the mechanical and electrical properties of electrical equipment products used outdoors. In addition, it has low volatility at high temperatures, so there is little loss, and it has an electrical characteristic improvement effect that reduces the loss of conduction current generated by polarization promoted by radical generation, so it is effective in improving the properties of insulating materials.

[0068] Examples of these HALS (Hindered Amine Light Stabilizer) stabilizers include poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino, etc. can be used.

[0069] In one specific example of the present invention, the HALS (Hindered Amine Light Stabilizer) stabilizer may be poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], considering the synergistic effect accompanied by improvement in dielectric breakdown strength.

[0070] The content of the HALS (Hindered Amine Light Stabilizer) stabilizer is included in the entire composition in an amount of 500 to 5,000 ppm, and preferably in an amount of 1,000 to 3,000 ppm. If the content is less than 500 ppm, the effect of improving the dielectric constant is insufficient, and if it exceeds 5,000 ppm, the dielectric constant of the matrix increases, thereby increasing the dielectric constant and lowering the dielectric breakdown strength.

[0071] In addition to the above components, the resin composition according to the present invention may further include one or more additives generally used when applied for insulation of power cables, for example, an antioxidant and a water tree inhibitor.

[0072] The polypropylene resin composition for insulating power cables according to the present invention can be manufactured by mixing and extruding the above components according to conventional methods known in the art. For example, the above components can be fed into a twin-screw extruder and melt-mixed to manufacture the resin composition.

[0073] The insulating resin composition of a power cable according to the present invention includes a propylene block copolymer, a polyolefin elastomer (POE), an inorganic nanocomposite, and a HALS (Hindered Amine Light Stabilizer) stabilizer within a certain composition range, thereby satisfying the physicochemical properties required in the relevant technical field and exhibiting excellent electrical properties. That is, the insulating resin composition of the power cable according to the present invention may have a melting point of 150 to 160°C, a melting enthalpy of 40 to 80 J / g, a melting index (MI, 230°C, 2.16 kg load) of 1 to 3 g / 10 min, and a xylene soluble content of 30 to 50 wt%, and preferably a melting point of 150 to 155°C, a melting enthalpy of 50 to 70 J / g, a melting index (MI, 230°C, 2.16 kg load) of 1.5 to 2.5 g / 10 min, and a xylene soluble content of 35 to 45 wt%. In addition, it has excellent heat resistance stability and voltage stability, is environmentally friendly and can be recycled, and specifically, the AC insulation breakdown strength measured by the following method may be 50 kV / mm or more, preferably 53 kV / mm or more, the relative permittivity may be 2.1 or less, preferably 2.0 or less, and the dielectric loss tangent may be 0.05% or less, preferably 0.03% or less.

[0074] [Method for measuring insulation breakdown strength]

[0075] The above resin composition is manufactured into a sheet having a thickness of 1 mm, cooled at 10°C for 5 minutes, and AC 30 kV is initially applied for 5 minutes according to ASTM D149 standards, and then increased by 10 kV and maintained for 5 minutes. This process is continued until insulation breakdown occurs, and when insulation breakdown occurs, the voltage at that time is taken as the AC insulation breakdown strength;

[0076] [Method for measuring relative permittivity]

[0077] The specimens (2 mm thick, 2 cm wide, 2 cm long) manufactured according to ASTM D150 standard were measured at 60℃ using LCR Meter equipment (electrode radius 5 mm, electrode type G10 type) with a frequency of 1 MHz and an AC voltage of 1 V;

[0078] [Method for measuring dielectric constant]

[0079] A multi-functional impedance measurement test device is used to measure a specimen (1 mm thick, 10 cm wide, 10 cm long) manufactured according to ASTM D150 standards at 130℃ and 2 kV. Type 1 No. 2 mineral oil is poured into a constant temperature bath to maintain the temperature conditions, and the specimen is loaded between the spherical electrodes of an impedance measuring device using a Schering bridge circuit configuration and an AC voltage is applied to measure the permittivity. The dielectric loss factor is then calculated by applying the conversion formula of ASTM D150 standards.

[0080] A power cable can be manufactured using the polypropylene resin composition for insulating a power cable according to the present invention. Fig. 1 schematically illustrates a cross-section of a power cable manufactured using the resin composition according to the present invention.

[0081] Referring to FIG. 1, a power cable manufactured with an insulating resin composition according to the present invention includes a conductor (1), an inner semiconducting layer (2) wrapping the conductor (1), an insulating layer (3) wrapping the inner semiconducting layer (2), an outer semiconducting layer (4) wrapping the insulating layer (3), and a sheath layer (5) wrapping the outer semiconducting layer (4), wherein the insulating layer (3) may include the resin composition according to the present invention. Except for the insulating layer, details of each layer constituting the power cable are commonly known to those skilled in the art, and therefore, a detailed description thereof will be omitted in the present invention.

[0082] Hereinafter, specific manufacturing examples, examples and comparative examples according to the present invention will be described.

[0083]

[0084] Manufacturing example: Manufacturing of propylene block copolymer

[0085] Propylene and ethylene were reacted in a bulk reactor to obtain a propylene-ethylene random copolymer, and the propylene-ethylene random copolymer polymerized in the bulk reactor, ethylene, and propylene were fed into a gas phase reactor to carry out a copolymerization reaction of ethylene-propylene in a continuous process to prepare a propylene block copolymer. The propylene block copolymer thus prepared had a 1:1 weight ratio of propylene-ethylene random copolymer to ethylene-propylene rubber (EPR), 2 wt% of ethylene-derived repeating units in the propylene-ethylene random copolymer, 35 wt% in the ethylene-propylene rubber (EPR), and 15 wt% in the total copolymer, a xylene-soluble content of 25 wt%, a melt index of 1.5 g / 10 min, a melting point of 152°C, and a melting enthalpy of 60 J / g. The melt index, xylene-soluble content, melting point, and melting enthalpy of the propylene block copolymer were measured according to the following methods, respectively.

[0086] - Melt Index (MI): Measured at a temperature of 230℃ and a load of 2.16 kg according to ASTM D1238.

[0087] - Xylene Soluble (XS): According to ASTM D5492, propylene block copolymer was dissolved in boiling xylene, cooled at room temperature, separated into xylene-soluble and insoluble portions, and the xylene-soluble portion was collected separately. The xylene was evaporated on a hot plate, and the weight % of the remaining portion was measured.

[0088] - Melting point and melting enthalpy: Using a differential scanning calorimeter (DSC), heating to 200℃ at a rate of 10℃ / min and then cooling to -30℃ were repeated twice, and the data measured on the second time were used.

[0089]

[0090] Examples and Comparative Examples

[0091] A mixture composed of 75 parts by weight of the propylene block copolymer manufactured above and 25 parts by weight of polyolefin elastomer (POE, propylene-ethylene rubber (PER, VistamaxxTM 6102FL, MI 3 g / 10 min (230°C, 2.16 kg load), ethylene content 16 wt%, Exxonmobil Chemical Company) and the additive component composition (unit: ppm) shown in Table 1 below was mixed with a mixer for 5 minutes and then extruded with a twin-screw extruder at 190 to 230°C to manufacture a resin composition in the form of pellets.

[0092]

[0093] Exam example

[0094] The ionic impurity content, dielectric constant, relative permittivity, and dielectric breakdown strength of the resin composition on the manufactured pellet were measured according to the following method, and the results are shown in Table 1 below.

[0095] [measurement method]

[0096] (1) Ionic impurity content

[0097] After measuring the weight of the above-mentioned manufactured resin composition, it was placed in a crucible and ashed in an electric furnace at 400°C for 4 hours and 800°C for 6 hours, and then the ashed sample was dissolved in a 5 wt% nitric acid solution and filled into a 100 ml flask, and the concentration of ionic impurities (10 types of Ca, Si, Fe, Al, Zn, Cu, Mg, Na, and K) was measured using an inductively coupled plasma mass spectrometer (ICP-MS), and the value obtained by subtracting the concentration in a blank obtained with an empty crucible without the ashed sample from the measured ion concentration was used as the final ionic impurity content.

[0098] (2) Genetic tangent

[0099] A multifunctional impedance measurement test device was used to measure a specimen (1 mm thick, 10 cm wide, 10 cm long) manufactured according to ASTM D150 standards at 130℃ and 2 kV. Mineral oil of type 1 and number 2 was poured into a constant temperature bath to maintain the temperature conditions, and the specimen was loaded between the spherical electrodes of an impedance measuring device using a Schering bridge circuit configuration and an AC voltage was applied to measure the permittivity. The dielectric loss factor was then calculated by applying the conversion formula of ASTM D150 standards.

[0100] (3) Relative permittivity

[0101] The dissipation factor (tanδ) and relative permittivity were measured at 60℃ using an LCR Meter (electrode radius 5 mm, electrode type G10) with a frequency of 1 MHz and an AC voltage of 1 V for specimens manufactured according to ASTM D150 (2 mm thick, 2 cm wide, 2 cm long). If the relative permittivity is high, it may be difficult to use it as an insulation layer for power cables, and if it is 2.1 or less, the electrical properties are considered to be very excellent.

[0102] (4) Insulation breakdown strength

[0103] The manufactured resin composition was manufactured into a sheet shape with a thickness of 1 mm, then cooled at 10℃ for 5 minutes, and according to the ASTM D149 standard, AC 30 kV was initially applied for 5 minutes, and then increased by 10 kV in increments and maintained for 5 minutes. This process was continued until insulation breakdown occurred, and when insulation breakdown occurred, the voltage at that time was taken as the AC insulation breakdown strength. When the AC insulation breakdown strength is 50 kV / mm or more, the electrical properties are judged to be excellent.

[0104]

[0105]

[0106]

[0107] Referring to Table 1, it can be seen that the insulating resin compositions for power cables (Examples 1 and 2) using a propylene block copolymer in which ethylene-propylene rubber (EPR) is dispersed in a propylene-ethylene random copolymer, a polyolefin elastomer (POE), an inorganic nanocomposite, and a HALS (Hindered Amine Light Stabilizer) stabilizer at a specific content ratio according to the present invention, while satisfying the physicochemical properties required in the relevant technical field, have a low content of ionic impurities, and the inorganic nanocomposite component, which is an insulating inorganic nanoparticle, is dispersed in the polypropylene matrix to improve the heat diffusion of the matrix, thereby preventing deterioration, improving the insulation properties to lower the dielectric constant and dielectric constant, thereby improving long-term heat resistance and voltage stability, and the addition of the HALS stabilizer results in low volatility and low loss, and has an effect of improving electrical properties to lower the loss of conduction current caused by the promotion of polarization by the generation of radicals, thereby effectively improving the insulating properties.

[0108] In addition, the heat diffusion effect of the inorganic nanocomposite and the radical generation inhibition effect of the HALS stabilizer prevent chain deterioration, thereby improving the dielectric breakdown strength, and the effect of preventing power loss through the improvement of the dielectric constant and dielectric constant were confirmed. In addition, when the content of the HALS stabilizer was increased (Example 2), the dielectric loss (dielectric loss) was further improved, and the dielectric breakdown strength was also improved, confirming that there was a synergistic effect.

[0109] In this regard, when a HALS-based stabilizer is added without adding an inorganic nanocomposite (Comparative Example 1), a HALS-based stabilizer with a high molecular weight is applied, so there is a low loss due to low volatility at high temperatures, and there is an effect of improving electrical properties by reducing the loss of conduction current that occurs due to polarization promoted by radical generation, but since an inorganic nanocomposite is not added, the thermal diffusion effect does not appear, and the heat stability is reduced compared to Examples 1 and 2, so it was confirmed that the insulation breakdown strength performance is inferior.

[0110] In addition, it can be seen that when an inorganic nanocomposite is added without adding a HALS stabilizer (Comparative Example 2), the electrical properties are significantly reduced, and at this time, when the inorganic nanocomposite content is increased (Comparative Examples 3 and 4), the heat diffusion is improved, but the amount of ionic impurities increases, which acts as defects in the crystal region, and the effect of improving the insulating performance is slightly reduced, resulting in an adverse effect that affects the dielectric breakdown strength.

[0111] In addition, when calcium stearate is used instead of the inorganic nanocomposite (Comparative Example 5), the effects of improving heat diffusion and insulation properties are not observed, resulting in a decrease in the insulation breakdown strength. When silicon dioxide (SiO2) is used as the insulating nanoparticle (Nano Particle) (Comparative Example 6), the dielectric constant and dielectric loss tangent are not reduced, and a decrease in the insulation breakdown strength is induced due to agglomeration. When magnesium oxide (MgO) is used (Comparative Example 7), the effects of reducing the dielectric constant and dielectric loss tangent are observed, but the content level of ionic impurities is very high, and the insulation breakdown strength is reduced due to agglomeration of the magnesium oxide particles.

[0112]

[0113] The preferred embodiments of the present invention have been described in detail above. The description of the present invention is provided for illustrative purposes only, and those skilled in the art will readily appreciate that other specific modifications can be readily made without altering the technical spirit or essential features of the present invention.

[0114] Accordingly, the scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning, scope and equivalent concepts of the claims should be interpreted as being included in the scope of the present invention.

Claims

1. 60 to 90 parts by weight of a propylene block copolymer having ethylene-propylene rubber (EPR) dispersed in a propylene-ethylene random copolymer; 10 to 40 parts by weight of polyolefin elastomer (POE); 100 to 1,000 ppm of inorganic nanocomposite based on the total composition weight; and 500 to 5,000 ppm of HALS(Hindered Amine Light Stabilizer) stabilizer; A polypropylene resin composition for insulation of a power cable comprising:

2. In paragraph 1, The ethylene-derived repeating unit of the above propylene block copolymer is, Contained in the above propylene-ethylene random copolymer in an amount of 0.1 to 5 wt%, Contains 30 to 60 wt% of the above ethylene-propylene rubber (EPR), A polypropylene resin composition for insulating a power cable, characterized in that it contains 5 to 25 wt% of the above propylene block copolymer.

3. In paragraph 1, The above propylene block copolymer has a melting point of 150 to 170°C, a melting enthalpy of 40 to 70 J / g, a melting index (MI, 230°C, 2.16 kg load) of 0.1 to 10 g / 10 min, and a xylene soluble content of 20 to 40 wt% in the propylene block copolymer. A polypropylene resin composition for insulating a power cable, characterized in that the resin composition has a melting point of 150 to 160°C, a melting enthalpy of 40 to 80 J / g, a melting index (MI, 230°C, 2.16 kg load) of 1 to 3 g / 10 min, and a xylene soluble content of 30 to 50 wt%.

4. In paragraph 1, The above inorganic nanocomposite is a polypropylene resin composition for insulating a power cable, characterized in that it includes a metal double layer hydroxide structure of the following chemical formula 1 or a composite metal oxide structure derived therefrom: [Chemical Formula 1] [M a 2+ 1-x M b 3+ x (OH) 2 ] x+ (A n- ) x / n ㆍmH 2 O In chemical formula 1, M a 2+ and M b 3+ are cations of divalent and trivalent metals, respectively. A n- is an intercalated anion, x is the ratio of two metal cations, M b 3+ / (M a 2+ +M b 3+ ) as the surface charge determined by 0 < x < 1, n is an integer from 1 to 3, m is a number between 0.1 and 15.

5. In paragraph 4, A polypropylene resin composition for insulating a power cable, characterized in that the metal double layer hydroxide structure is a magnesium-aluminum-carbonate hydrotalcite.

6. In paragraph 1, The above HALS (Hindered Amine Light Stabilizer) stabilizer is poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,6-hexanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], Poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,5-pentanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], A polypropylene resin composition for insulating a power cable, characterized in that it comprises at least one selected from the group consisting of poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[[6-[1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(1,2,2,6,6-pentamethyl-4-piperidinyl)imino]-1,4-butanediyl-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]].

7. In paragraph 1, The resin composition is an insulating resin composition for a power cable, characterized in that the AC dielectric breakdown strength measured by the following method is 50 kV / mm or more, the relative permittivity is 2.1 or less, and the dielectric loss tangent is 0.05% or less: [Method for measuring insulation breakdown strength] The above resin composition is manufactured into a sheet having a thickness of 1 mm, cooled at 10°C for 5 minutes, and AC 30 kV is initially applied for 5 minutes in accordance with ASTM D149 standards, and then increased by 10 kV each time and maintained for 5 minutes. This process is continued until insulation breakdown occurs, and when insulation breakdown occurs, the voltage at that time is taken as the AC insulation breakdown strength; [Method for measuring relative permittivity] The specimens (2 mm thick, 2 cm wide, 2 cm long) manufactured according to ASTM D150 standard were measured at 60℃ under the conditions of applying AC 1 V voltage and frequency of 1 MHz using LCR Meter equipment (electrode radius 5 mm, electrode type G10); [Method for measuring genetic susceptibility] A multifunctional impedance measurement test device is used to measure a specimen (1 mm thick, 10 cm wide, 10 cm long) manufactured according to ASTM D150 standards at 130℃ and 2 kV. The temperature conditions are maintained by pouring Class 1 No. 2 mineral oil into a constant temperature bath, and the specimen is loaded and an AC voltage is applied between the spherical electrodes of an impedance measuring device using a Schering bridge circuit configuration to measure the permittivity. The dielectric loss factor is then calculated by applying the conversion formula of ASTM D150 standards.

8. A power cable comprising a resin composition according to any one of claims 1 to 7 as an insulating layer.

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