Composition for coating material for electrical wires and insulated electrical wire

Abstract

Composition for a coating material for electrical wires, containing polyvinyl chloride, wherein the composition contains a plasticizer in an amount of 15 to 30 parts by mass, one or more ethylene-based copolymers selected from ethylene vinyl ester copolymers in an amount of 1.0 to 5 parts by mass and a filler in an amount of 2 to 25 parts by mass based on 100 parts by mass of the polyvinyl chloride, wherein the mean particle diameter of the filler is in the range of 0.05 to 1.5 µm, and wherein a main chain of the ethylene vinyl ester copolymer contains a ketone main strand.

Description

[0001] The present invention relates to a composition for a coating material for electrical wires and an insulated electrical wire, and in particular relates to a composition for a coating material for electrical wires which is suitable as a coating material for an electrical wire which is guided in a vehicle, such as a passenger car, and to an insulated electrical wire in which this composition is used.

[0002] A conventional coating material for electrical wires uses a polyvinyl chloride-containing composition. To provide flexibility, for example, a plasticizer is added to this type of coating material.

[0003] For example, patent document 1 discloses a coating material for electrical wires obtained by adding a plasticizer, chlorinated polyethylene, and a methyl methacrylate-butadiene styrene resin to polyvinyl chloride. Furthermore, for example, patent document 2 discloses a coating material for electrical wires obtained by adding a plasticizer, high-density polyethylene (HDPE), and an ethylene-vinyl acetate-vinyl chloride copolymer to polyvinyl chloride.

[0004] Furthermore, patent document 3 describes a resin composition based on vinyl chloride and a cable coated with the composition, patent document 4 describes a flame-retardant composition, patent document 5 describes a polyvinyl chloride resin composition, and patent document 6 describes a vinyl chloride resin composition and a wire and a cable using the same. Patentdokumente Patentdokument 1: JP 5 423 890 B2 Patentdokument 2: JP 2002- 322 330 A Patentdokument 3: JP 2006- 291 145 A Patentdokument 4: JP S56- 59 855 A Patentdokument 5: JP S60- 219 249 A Patentdokument 6: JP 2013- 231 134 A

[0005] In a coating material for electrical wires using a polyvinyl chloride-containing composition, the material exhibits excellent flexibility when the amount of plasticizer is increased; however, there is a high probability that the coating of the electrical wire will deteriorate due to external damage, and its resistance to damage will decrease. Given this, resistance to damage tends to increase when the amount of plasticizer is reduced, but the low-temperature performance deteriorates. To address this problem, patent document 1 ensures low-temperature performance by adding chlorinated polyethylene and methyl methacrylate-butadiene styrene resin to the polyvinyl chloride.

[0006] However, if the amount of plasticizer in a coating material for electrical wires containing polyvinyl chloride is reduced, a problem arises not only from its deteriorating low-temperature performance, but also from the coating cracking when a load, such as bending, is applied after minor external damage has occurred (reduced tensile strength). Reducing the coating thickness in an attempt to decrease the diameter of an electrical wire makes this problem particularly significant.

[0007] Furthermore, the resistance to damage is increased in patent document 2 by adding an ethylene-vinyl acetate-vinyl chloride copolymer as a compatibilizer for polyvinyl chloride and high-density polyethylene, but the ethylene-vinyl acetate-vinyl chloride copolymer is not universally applicable, is costly, and has a small effect on improving resistance to damage.

[0008] An object of the present invention is to provide a composition for a coating material for electrical wires which has excellent resistance to damage, flexibility at low temperatures, tensile strength and heat resistance, and an insulated electrical wire in which this composition is used.

[0009] To solve the problem described above, the composition for a coating material for electrical wires according to the present invention is a composition for a coating material for electrical wires containing polyvinyl chloride, wherein the composition contains a plasticizer in an amount of 15 to 30 parts by mass, one or more ethylene-based copolymers selected from ethylene vinyl ester copolymers in an amount of 1.0 to 5 parts by mass, and a filler in an amount of 2 to 25 parts by mass based on 100 parts by mass of the polyvinyl chloride, wherein a mean particle diameter of the filler is in the range of 0.05 to 1.5 µm, and wherein a main chain of the ethylene vinyl ester copolymer contains a ketone main chain.

[0010] Preferably, the ethylene vinyl ester copolymer contains a vinyl ester in an amount of 30% by mass or more.

[0011] Preferably, the ethylene-vinyl ester copolymer is an ethylene-vinyl acetate-carbon monoxide terpolymer.

[0012] Calcium carbonate is the preferred filler.

[0013] In an insulated electrical wire according to the present invention, the composition for a coating material for electrical wires according to one of the aspects described above is used in a coating material for electrical wires.

[0014] According to the composition for an electrical wire coating material according to the present invention, the composition for an electrical wire coating material containing polyvinyl chloride includes, among other things, a plasticizer in an amount of 15 to 30 parts by mass and one or more ethylene-based copolymers selected from ethylene-vinyl ester copolymers in an amount of 1.0 to 5 parts by mass per 100 parts by mass of the polyvinyl chloride. Thus, the composition for an electrical wire coating material exhibits excellent resistance to damage, flexibility at low temperatures, tensile strength, and heat resistance. Furthermore, an insulated electrical wire in which this composition is used as a coating material has excellent resistance to damage, flexibility at low temperatures, tensile strength, and heat resistance.

[0015] Since, according to the present invention, the main chain of the ethylene vinyl ester copolymer contains a ketone main strand, the resistance to damage, the flexibility at low temperatures and the tensile strength are further increased.

[0016] If the ethylene vinyl ester copolymer contains a vinyl ester in an amount of 30% by mass or more, the tensile strength is further increased.

[0017] Since, according to the present invention, the composition further contains a filler in an amount of 2 to 25 parts by mass based on 100 parts by mass of the polyvinyl chloride, the composition exhibits excellent abrasion resistance.

[0018] If the filler is calcium carbonate, the abrasion resistance is further increased.

[0019] Since, according to the present invention, the mean particle diameter of the filler is in the range of 0.05 to 1.5 µm, the abrasion resistance is further increased. Brief description of the drawings Fig. Figure 1 shows an insulated electrical wire according to an embodiment of the present invention. Fig. 1(a) shows a perspective view and Fig. Figure 1(b) shows a cross-sectional view in a circumferential direction. Fig. Figure 2 shows a schematic representation illustrating a method for evaluating resistance to damage. Fig. Figure 3 shows a schematic representation illustrating a method for evaluating resistance to damage. Fig. Figure 4 shows a schematic representation illustrating a method for evaluating flexibility at low temperatures.

[0020] One embodiment of the present invention is described in detail below.

[0021] A composition for a coating material for electrical wires according to the present invention is a composition for a coating material for electrical wires which contains polyvinyl chloride and, in addition to polyvinyl chloride, contains a plasticizer, a specific ethylene-based copolymer and a filler with a specific mean particle diameter.

[0022] The composition contains the plasticizer in an amount of 15 to 30 parts by mass per 100 parts by mass of polyvinyl chloride. If the amount of plasticizer exceeds 30 parts by mass, the resistance to damage is unsatisfactory, and therefore the amount of plasticizer is limited to a maximum of 30 parts by mass. If the amount of plasticizer is less than 15 parts by mass, the flexibility at low temperatures, tensile strength, and heat resistance are also unsatisfactory, and therefore the amount of plasticizer is limited to a minimum of 15 parts by mass. The proportion of plasticizer is preferably in the range of 15 to 27.5 parts by mass.

[0023] While there is no specific restriction regarding the plasticizer, phthalic acid esters, trimellitic acid esters, pyromellitic acid esters, adipic acid esters, sebacic acid esters, and azelaic acid esters are preferable for achieving excellent flexibility at low temperatures and tear resistance. These can be used alone or in combination as the plasticizer.

[0024] Examples of alcohols that can act as esters for the plasticizer include saturated fatty alcohols, each with 8 to 13 carbon atoms. One or more of these alcohols can be used. Specifically, examples of alcohols include 2-ethylhexyl, n-octyl, isononyl, dinonyl, isodecyl, and tridecyl alcohols.

[0025] The composition contains the plasticizer in an amount of 15 to 30 parts by mass per 100 parts by mass of polyvinyl chloride. Furthermore, the composition contains the specified ethylene-based copolymer in an amount of 1.0 to 5 parts by mass per 100 parts by mass of polyvinyl chloride. If the proportion of the specified ethylene-based copolymer is too high, the resistance to damage and the heat resistance will not be satisfactory; therefore, the proportion of the specified ethylene-based copolymer is limited to a maximum of 5 parts by mass. If the proportion of the specified ethylene-based copolymer is too low, the tensile strength will also be unsatisfactory, and the effect on improving flexibility at low temperatures will be minimal. Therefore, the proportion of the specified ethylene-based copolymer is limited to a minimum of 1.0 part by mass.The proportion of the specified ethylene-based copolymer is preferably in the range of 3 to 4 parts by mass.

[0026] The specific ethylene-based copolymer is one or more copolymers selected from ethylene-vinyl ester copolymers. The specific ethylene-based copolymer can be formed from one or more ethylene-vinyl ester copolymers.

[0027] Examples of ethylene-vinyl ester copolymers include ethylene-vinyl acetate-carbon monoxide terpolymers. To further increase resistance to damage, low-temperature flexibility, and tensile strength, ethylene-vinyl acetate-carbon monoxide terpolymers whose main chain contains a ketone main strand are particularly preferable to the ethylene-vinyl ester copolymer. With a view to further increasing tensile strength, the ethylene-vinyl ester copolymer preferably contains a vinyl ester in an amount of 30% by weight or more. More preferably, the ethylene-vinyl ester copolymer contains a vinyl ester in an amount of 35% by weight or more.It should be noted that with regard to resistance to damage, flexibility at low temperatures, heat resistance and the like, there is no specific limitation on the upper limit of the vinyl ester content of the ethylene-vinyl ester copolymer, but with regard to ease of procurement and for cost reasons, the ethylene-vinyl ester copolymer may contain a vinyl ester only in an amount of 50% by mass or less.

[0028] While there is no specific restriction regarding the polyvinyl chloride, the degree of polymerization is preferably at least 800 to achieve excellent resistance to damage. Furthermore, to achieve excellent tensile strength and heat resistance, the degree of polymerization is preferably not greater than 2800. More preferably, the degree of polymerization is in the range of 1300 to 2500.

[0029] The composition for a coating material for electrical wires according to the present invention does not contain high-density polyethylene as a polymer component and differs, at least in this respect, from the invention disclosed in patent document 2 above. In this sense, the polymer component of the composition for a coating material for electrical wires according to the present invention can be formed by polyvinyl chloride and a specific ethylene-based polymer and may contain no other polymer component. Furthermore, in the composition for a coating material for electrical wires according to the present invention, the amount of plasticizer added is less than that disclosed in the invention disclosed in patent document 2 above, and the composition also differs from patent document 2 above in this respect.

[0030] The composition for a coating material for electrical wires according to the present invention contains a filler in an amount of 2 to 25 parts by mass per 100 parts by mass of polyvinyl chloride. Since the filler content is 2 parts by mass or more, the composition exhibits higher abrasion resistance. Since the filler content is 25 parts by mass or less, the composition also exhibits higher abrasion resistance. The filler content is preferably in the range of 5 to 20 parts by mass, and more preferably in the range of 7.5 to 15 parts by mass.

[0031] If the composition contains an excessive amount of the filler, it generally has a considerable cost-reducing effect, but the external appearance of an insulating sheath becomes crude when an insulated electrical wire is produced (for example, during extrusion coating) or the like, and various properties of the electrical wire, such as abrasion resistance, deteriorate. In contrast, in the present invention, the use of the filler and the specific ethylene-based copolymer in combination not only suppresses the deterioration of the electrical wire's properties, such as abrasion resistance, caused by the addition of the filler, but even improves the abrasion resistance.

[0032] Examples of fillers include calcium carbonate, clay, and talc. These can be used alone or in combination. Of these, calcium carbonate is preferable due to its excellent abrasion resistance-enhancing effect when used in combination with a specific ethylene-based copolymer. Examples of calcium carbonate include synthetic calcium carbonate and heavy calcium carbonate. The filler can be surface-treated using a surface treatment agent. According to the present invention, the mean particle diameter of the filler is in the range of 0.05 to 1.5 µm. Preferably, the mean particle diameter is in the range of 0.5 to 1.3 µm. Since the mean particle diameter is in the range of 0.05 to 1.5 µm, the abrasion resistance is further increased.The mean particle diameter of the filler can be measured by laser light scattering.

[0033] The composition of a coating material for electrical wires according to the present invention may, within a range that does not impair the object of the present invention, also contain components other than polyvinyl chloride, the plasticizer, the specific ethylene-based polymer, and the filler. Examples of other components include additives commonly used in a coating material for electrical wires, such as stabilizers, processing aids, low-temperature modifiers, and extensible materials.

[0034] An example of a processing aid is chlorinated polyethylene. Examples of low-temperature modifiers include methyl methacrylate butadiene styrene copolymers (MBS). While there are no specific restrictions on the low-temperature modifier content, to achieve excellent resistance to damage, the content is preferably no more than 6 parts by weight per 100 parts by weight of polyvinyl chloride. More preferably, the low-temperature modifier content is no more than 4 parts by weight, and even more preferably, no more than 3 parts by weight. Furthermore, to achieve excellent flexibility at low temperatures, the low-temperature modifier content is preferably at least 1 part by weight per 100 parts by weight of polyvinyl chloride.

[0035] The composition for a coating material for electrical wires according to the present invention can be prepared by mixing and kneading the plasticizer, the specific ethylene-based polymer, the filler, and various additional components, which are added as required, in polyvinyl chloride, which serves as the base resin, while the mixture is heated. A conventional kneading machine, such as a Banbury mixer, a pressure kneading machine, a kneading extruder, a twin-screw extruder, or a roller can be used for this purpose. Before the mixture is kneaded and heated, the components can be pre-mixed using a rotary drum or the like. After the mixture has been kneaded and heated, a portion of the composition is taken from the kneading machine. This portion can then be formed into pellets using a pelletizer.

[0036] An insulated electrical wire according to the present invention is described below.

[0037] Fig. Figure 1(a) shows a perspective view of an insulated electrical wire according to an embodiment of the present invention, and Fig. Figure 1(b) shows a cross-sectional view (cross-sectional view in its circumferential direction). As in Fig.As shown in Figure 1, an insulated electrical wire 10 comprises a conductor 12 and an insulating coating layer (coating material for electrical wires) 14 for sheathing the outer circumference of the conductor 12. The insulating coating layer 14 is formed using the composition for a coating material for electrical wires according to the present invention. The insulated electrical wire 10 can be obtained by subjecting the outer circumference of the conductor 12 to extrusion coating with the composition for a coating material for electrical wires according to the present invention.

[0038] Although copper is typically used as conductor 12, a metallic material such as aluminum or magnesium can also be used instead. The metallic material can also be an alloy. Examples of other metals used to create an alloy include iron, nickel, magnesium, silicon, and combinations thereof. The conductor 12 can be formed from a single wire or from a twisted wire obtained by twisting several wires together.

[0039] According to the composition for an electrical wire coating and the insulated electrical wire, which have the configurations described above, the composition for the electrical wire coating contains the plasticizer in an amount of 15 to 30 parts by mass, the specified ethylene-based polymer in an amount of 1.0 to 5 parts by mass, and the filler in an amount of 2 to 25 parts by mass, based on 100 parts by mass of polyvinyl chloride. Thus, the composition and the insulated electrical wire exhibit excellent resistance to damage, flexibility at low temperatures, tensile strength, and heat resistance. Since the composition contains a predetermined amount of the specified ethylene-based polymer, its flexibility at low temperatures is also maintained without increasing the amount of plasticizer, and its tensile strength is also satisfactory.

[0040] The insulated electrical wire according to the present invention exhibits excellent resistance to damage, flexibility at low temperatures, tensile strength, and heat resistance, and is therefore suitable as a thin-walled or small-diameter electrical wire. Examples of thin-walled and small-diameter electrical wires include those with an outer diameter of less than 1.1 mm. In this case, the standard thickness of the insulating coating is 0.25 mm or less. If the thickness of the insulating coating exceeds 0.25 mm, the thickness of the insulating coating is not sufficiently reduced.Furthermore, if the thickness of the insulating coating layer exceeds 0.25 mm, the outer diameter of the electrical wire will be less than 1.1 mm, resulting in a relatively thin conductor and insufficient conductivity. The thickness of the insulating coating layer is preferably 0.1 mm or more. If the thickness of the insulating coating layer is less than 0.1 mm, it becomes difficult to form a uniform coating film, and there is a risk that the insulating properties will not be adequately effective.

[0041] An example of the insulated electrical wire according to the present invention is such that a conductor is sheathed with the insulating coating layer, the outer diameter of the electrical wire is less than 1.1 mm, the thickness of the insulating coating layer is 0.25 mm or less, and the composition for a coating material for electrical wires according to the present invention is used as the material of the insulating coating layer.

[0042] Furthermore, the insulated electrical wire according to the present invention can be used in various electrical wiring applications for vehicles, appliances, information communication, power, ships, aircraft, and the like. In particular, the insulated electrical wire can be used as an electrical wire for a vehicle.

[0043] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to any of the embodiments described above.

[0044] For example, insulated electrical wire can come in forms such as flat wires, shielded wires, which differ from the one in Fig. The single wire shown in 1 can be distinguished from the other components. The insulating layer can also be formed from two or more layers. Examples of implementation

[0045] Exemplary embodiments of the present invention are described in detail below, but the present invention is not limited to these exemplary embodiments. Examples 1 to 24 and comparative examples 1 to 9

[0046] Preparation of the composition for the coating material for electrical wires: The materials were mixed using the mixture compositions listed in Tables 1 to 3. A single-screw extruder was used to mix the materials at 180°C, and a pelletizer was used to form the resulting mixture into pellets. As a result, a polyvinyl chloride-containing composition for a coating material for electrical wires was prepared. Production of insulated electrical wire

[0047] An insulated electrical wire was produced by extruding the prepared composition for a coating material for electrical wires around a conductor with twisted wires having a cross-sectional area of ​​0.5 mm² using extrusion dies with a coating thickness of 0.2 mm. 2 was brought about. Materials used • Polyvinyl chloride Degree of polymerization 1300: “Shin Daiichi Vinyl Corp., ZEST1300Z” Degree of polymerization 2500: “Shin Daiichi Vinyl Corp., ZEST2500Z” • Plasticizers Phthalic acid esters: “J-PLUS Co., Ltd., DUP” Trimellitic acid ester: “DIC Corporation, W-750” • Ethylene vinyl ester copolymer EVA <1> Ethylene vinyl acetate carbon monoxide terpolymer, “Elvaloy 742”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD EVA <2> : Ethylene-vinyl acetate bipolymer with a vinyl acetate content of 40% by mass “Evaflex EV 40LX”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD EVA <3> : Ethylene-vinyl acetate bipolymer with a vinyl acetate content of 25% by mass “Evaflex EV 360”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD • Ethylene-α,β-unsaturated carboxylic acid ester copolymer EMA<1 >: Ethylene-methyl acrylate bipolymer with a methyl acrylate content of 18% by mass, MFR = 2 g / 10 minutes, “Elvaloy AC1218”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD EEA: Ethylene-ethyl acrylate bipolymer with an ethyl acrylate content of 12% by mass, MFR = 1 g / 10 minutes, “Elvaloy AC2112”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD EMA <2> Ethylene-methyl acrylate bipolymer with a methyl acrylate content of 20% by mass, MFR = 8 g / 10 minutes, “Elvaloy AC1820”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD EMA <3> Ethylene-methyl acrylate bipolymer with a methyl acrylate content of 13% by mass, MFR = 9 g / 10 minutes, “Elvaloy AC1913”, manufactured by DUPONT-MITSUI POLYCHEMICALS CO., LTD

[0048] The melt flow rate (MFR) of the ethylene-α,β-unsaturated carboxylic acid ester copolymer was the melt flow rate (MFR) measured according to JIS K 7210 at 190°C and a load of 2.16 kg. • Processing aid (chlorinated polyethylene): “Showa Denko KK, Elaslen 301A” • Low-temperature modifier (MBS): “Kaneka Corporation, KANE ACE B-564” • Expanding material (calcium carbonate): “SHIRAISHI CALCIUM KAISHA, LTD., Hakuenka CCR” • Heat stabilizer: “ADEKA CORPORATION, RUP-110” • Filler

[0049] Calcium carbonate<1 >: mean particle diameter 1.3 µm (catalog value), “MARUO CALCIUM, SUPER#1700” Calcium carbonate <2> : mean particle diameter 2.7 µm (catalog value), “MARUO CALCIUM, SUPER S" Clay: mean particle diameter 1.5 µm (catalog value), “TAKEHARA KAGAKU, Glomax LL” Talc: mean particle diameter 1.6 µm (catalog value), “TAKEHARA KAGAKU, High micron HE5” Evaluation

[0050] The resistance to damage, flexibility at low temperatures, tensile strength, and heat resistance of the manufactured insulated electrical wires were evaluated based on the following assessment procedures. Abrasion resistance was also evaluated. Assessment procedure: Assessment of resistance to damage

[0051] A test piece was obtained by cutting the manufactured insulated electrical wire to a length of 300 mm. As in Fig.As shown in Figures 2(a) (top view) and 2(b) (side view), a test piece 1 was placed on plastic plates 2a and 2b. The distance between plastic plate 2a and plastic plate 2b was 5 mm. The left end of the test piece 1 was attached to plastic plate 2b, and the test piece 1 was straightened by applying a tensile force of 30 N to the right end of the test piece 1. Then, a metal piece 3 with a thickness of 0.5 mm was positioned 10 mm below a section of the test piece 1 located between plastic plate 2a and plastic plate 2b, and approximately 0.8 mm from the center in the radial direction of the test piece 1 towards its outer circumference.

[0052] As in Fig.As shown in Figures 3(a) to 3(c), the metal piece 3 was then moved upwards at a speed of 50 mm / min while in contact with a coating material 4 of the test piece 1, and a load applied to the metal piece 3 of the test piece 1 was measured. If a conductor 5 of the test piece 1 was not exposed, the metal piece 3 was moved closer to the test piece 1 in the central direction in increments of 0.01 mm, and the measurement continued until the conductor 5 was exposed. The upper load limit at which the conductor 5 was not exposed was considered to be the resistance of the test piece 1 to damage.If ladder 5 was not exposed under a load of at least 12 N, its resistance to damage was considered acceptable ("0"), whereas if ladder 5 was not exposed under a load of at least 15 N, its resistance to damage was considered excellent ("+"). Conversely, if ladder 5 was exposed under a load of less than 12 N, its resistance to damage was considered unacceptable ("-"). Evaluation of flexibility at low temperatures

[0053] A test piece was obtained by cutting the manufactured insulated electrical wire to a length of 350 mm. 20 mm of the coating material was removed from both ends of the test piece. As in Fig.As shown in Figure 4, the test specimen 6 was then repeatedly bent with a bending radius r by rotating the swivel arms 90 degrees in one direction and 90 degrees in the other direction, such that the specimen 6 moved along the circumferential surfaces of the cylindrical elements 8a and 8b. The test specimen 6 was then, in a condition where one end was attached to a rotating arm, a weight 7 was suspended from the other end, and the middle section was clamped longitudinally between a pair of cylindrical elements 8a and 8b (radius r = 25 mm). The bending flexibility was then evaluated in this way. The load applied to the test specimen 6 was 400 g, the test temperature was -30°C, and the bending repetition rate was 60 repetitions per minute. The bending flexibility was evaluated by applying the number of bending operations (number of repetitions) until the test specimen 6 broke as a result of the bending test.If a test piece was bent at least 2000 times, it was considered acceptable “O”, if a test piece was bent at least 3000 times, it was considered excellent “+”, and if a test piece was bent less than 2000 times, it was considered unacceptable “-”. Assessment of tensile strength

[0054] An angled test piece, as described in JIS K 6252, was produced using a 1 mm thick sheet made with the prepared composition for an electrical wire coating material, and its tensile strength was evaluated using a tensile stress tester. The tensile strength was assessed with a 20 mm spacing between the handles and a tensile rate of 50 mm / min. If a test piece broke at a stroke of at least 10 mm (an apparent stress of at least 50%), its tensile strength was considered acceptable '0', while if a test piece broke at a stroke of at least 20 mm (an apparent stress of 100%), its tensile strength was considered excellent '+'. Conversely, if a test piece broke at a stroke of less than 10 mm, its tensile strength was considered unacceptable '-'. Heat resistance assessment

[0055] The prepared composition for an electrical wire coating material was introduced into a Labo Plastomill / R60 set to 210°C, kneaded at 60 rpm, and the time until a significant increase in torque was observed was evaluated as the index for thermal stability. Cases where the time until a significant increase in torque was observed was 60 minutes or more and rated as excellent “+” with regard to thermal stability, while cases where the time was less than 60 minutes and the time was rated as poor “-” with regard to thermal stability. Abrasion resistance assessment

[0056] Abrasion resistance was evaluated using a reciprocating blade method according to ISO 6722. The load applied to a blade was set to 7 N. A minimum value of 300 or above over four test runs was considered acceptable (“0”), a value of 500 or above was considered excellent (“+”), a value of 1000 or above was considered exceptionally excellent (“++”), and a value below 300 was considered unacceptable (“-”).

[0057] The mixing ratios of the coating materials for electrical wires and the evaluation results are shown in Tables 1 to 3. It should be noted that the values ​​shown in Tables 1 to 3 are expressed in parts by mass.

[0058] In this context, it should be noted that embodiments 17, 19, 21 and 22 are in accordance with the invention, while embodiments 1 to 16, 18, 20, 23 and 24 are non-inventive reference examples. Table 1 Examples of embodiment (*not according to the invention) 1* 2* 3* 4* 5* 6* 7* 8* 9* 10* Polyvinyl chloride Degree of polymerization 1300 100 100 100 100 100 100 100 100 100 Degree of polymerization 2500 100 Plasticizers Phthalic acid esters Trimellitic acid esters 20 20 20 20 20 20 20 20 20 20 Ethylene vinyl ester copolymer EVA 1 5 0,1 10 5 EVA 2 5 EVA 3 5 Ethylene-α,β-unsaturated carboxylic acid ester copolymer EMA 1 5 EEA 5 EMA 2 5 EMA 3 5 Additive Processing aids Low-temperature modifier Stretch material Heat stabilizer 5 5 5 5 5 5 5 5 5 5 filler Calcium carbonate< 1 > Calcium carbonate <2> clay talc Evaluation result Resistance to damage + + + ◯ ◯ ◯ ◯ ◯ ◯ + Abrasion resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Tear resistance + + + + ◯ + ◯ + ◯ + Flexibility at low temperatures. + + + ◯ ◯ + + ◯ ◯ + Heat resistance + + + + + + + + + + “+” = excellent, “◯” = acceptable Table 2 Examples of embodiment (*not according to the invention) 11* 12* 13* 14* 15* 16* 17 18* 19 20* 21 22 23* 24* Polyvinyl chloride Degree of polymerization 1300 100 100 100 100 100 100 100 100 100 100 100 100 100 100 Degree of polymerization 2500 Plasticizers Phthalic acid esters 20 Trimellitic acid esters 15 30 20 20 20 20 20 20 20 20 20 20 20 Ethylene vinyl ester copolymer EVA 1 5 5 5 5 5 5 5 5 5 5 5 5 0,1 10 EVA 2 EVA 3 Ethylene-α,β-unsaturated carboxylic acid ester copolymer EMA 1 EEA EMA 2 EMA 3 Additive Processing aids 5 Low-temperature modifier 5 Stretch material 15 Heat stabilizer 5 5 5 5 5 5 5 5 5 5 5 5 5 5 filler Calcium carbonate<1 > 10 2 25 10 10 Calcium carbonate <2> 10 clay 10 talc 10 Evaluation result Resistance to damage + + + + + + + ◯ ◯ ◯ + + + + Abrasion resistance ◯ ◯ ◯ ◯ ◯ ◯ ++ + + + ++ ++ ++ ++ Tear resistance + + + + + + + ◯ ◯ ◯ + + + + Flexibility at low temperatures. + + + + + + + ◯ ◯ ◯ + + + + Heat resistance + + + + + + + ◯ ◯ ◯ + + + + “++” = exceptionally good, “+” = excellent, “◯” = acceptable Table 3 Comparative examples 1 2 3 4 5 6 7 8 9 Polyvinyl chloride Degree of polymerization 1300 100 100 100 100 100 100 100 100 100 Degree of polymerization 2500 Plasticizers Phthalic acid esters Trimellitic acid esters 20 20 20 20 12,5 32,5 20 20 20 Ethylene vinyl ester copolymer EVA 1 0,01 12 5 5 EVA 2 EVA 3 Ethylene-α,β-unsaturated carboxylic acid ester copolymer EMA 1 EEA EMA 2 EMA 3 Additive Processing aids 5 Low-temperature modifier 5 5 Stretch material Heat stabilizer 5 5 5 5 5 5 5 5 5 filler Calcium carbonate<1 > 10 10 10 Calcium carbonate <2> clay talc Evaluation result Resistance to damage + + - - + - - - - Abrasion resistance ◯ ◯ ◯ ◯ ◯ ◯ - - - Tear resistance - - + - - + - Flexibility at low temperatures. - - + + - + - - ◯ Heat resistance + + + + + + + + + “+” = excellent, “◯” = acceptable, “-” = unacceptable / poor

[0059] In comparative examples 1 to 7, no specific ethylene-based copolymer was added to the polyvinyl chloride, and therefore the low-temperature flexibility and tensile strength were unsatisfactory when the plasticizer was added in a small amount. In comparative example 2, too little of the ethylene-based copolymer was added to the polyvinyl chloride, and therefore the low-temperature flexibility and tensile strength were unsatisfactory when the plasticizer was added in a small amount. In comparative example 3, too much of the ethylene-based copolymer was added to the polyvinyl chloride, and therefore the resistance to damage was unsatisfactory.In comparative examples 4 to 9, a low-temperature modifier (MBS) was added to the polyvinyl chloride instead of the ethylene-based copolymer. As a result, the low-temperature flexibility was satisfactory, while the damage resistance and tensile strength were not. In comparative example 5, a predetermined amount of the specified ethylene-based copolymer was added to the polyvinyl chloride, but too little plasticizer was added, and therefore the low-temperature flexibility and tensile strength were unsatisfactory. In comparative example 6, a predetermined amount of the specified ethylene-based copolymer was added to the polyvinyl chloride, but too much plasticizer was added, and therefore the damage resistance was unsatisfactory.In comparative example 8, a processing aid (chlorinated PE) was added to the polyvinyl chloride instead of the specified ethylene-based copolymer, and therefore the resistance to damage, the flexibility at low temperatures and the tensile strength were not satisfactory.

[0060] In contrast, in the embodiments corresponding to the configurations of the present invention, the resistance to damage, the flexibility at low temperatures, the tensile strength, and the heat resistance were satisfactory. As shown in the comparison between the embodiments, the resistance to damage, the flexibility at low temperatures, and the tensile strength were further increased when the ethylene-vinyl ester copolymer was an ethylene-vinyl ester-carbon monoxide terpolymer with a ketone main chain in its main chain (embodiments 1, 4, and 5). When the ethylene-vinyl ester copolymer contained a vinyl ester in an amount of 30% by weight or more, the tensile strength was further increased (embodiments 4 and 5).If the ethylene-α,β-unsaturated carboxylic acid ester copolymer contained an α,β-unsaturated carboxylic acid ester in an amount of 15% by mass or more, the tensile strength increased further (Exemplaries 6 to 9). If the melt flow rate of the ethylene-α,β-unsaturated carboxylic acid ester copolymer was 5 g / 10 minutes or less, the low-temperature flexibility increased further (Exemplaries 6 to 9).

[0061] According to embodiments 1 and 17 to 22, it was further shown that the abrasion resistance increased by the addition of a filler. Regarding fillers, it was found that the use of calcium carbonate further increased the abrasion resistance. It was also shown that the abrasion resistance increased further when the average particle diameter of the filler was in the range of 0.05 to 1.5 µm. Comparative Example 7 was an example that contained a filler but not a specific ethylene-based copolymer. Comparative Example 8 was an example that contained a filler and a processing aid (chlorinated PE) instead of a specific ethylene-based copolymer. Comparative Example 9 was an example that contained a filler and a low-temperature modifier (MBS) instead of a specific ethylene-based copolymer.According to comparative examples 7 to 9, the filler's effect on increasing abrasion resistance was not observed, even when a filler was present, unless a specific ethylene-based copolymer was included. Furthermore, comparative examples 7 to 9 also exhibited low abrasion resistance. Therefore, it was found that the desired increase in abrasion resistance was not achieved simply by adding a filler, but rather by using a filler in combination with a specific ethylene-based copolymer.

[0062] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Reference symbol list 10 insulated electrical wires 12 ladders 14 insulating coating layer

Claims

[1] Composition for a coating material for electrical wires containing polyvinyl chloride, wherein the composition contains a plasticizer in an amount of 15 to 30 parts by mass, one or more ethylene-based copolymers selected from ethylene-vinyl ester copolymers in an amount of 1.0 to 5 parts by mass and a filler in an amount of 2 to 25 parts by mass based on 100 parts by mass of the polyvinyl chloride, wherein an average particle diameter of the filler is in a range of 0.05 to 1.5 µm, and wherein a main chain of the ethylene-vinyl ester copolymer contains a ketone main strand. [2] The composition for a coating material for electric wires according to claim 1, wherein the ethylene-vinyl ester copolymer contains a vinyl ester in an amount of 30 mass% or more. [3] The composition for a coating material for electric wires according to claim 1 or 2, wherein the ethylene-vinyl ester copolymer is an ethylene-vinyl acetate-carbon monoxide terpolymer. [4] The composition for a coating material for electric wires according to any one of claims 1 to 3, wherein the filler is calcium carbonate. [5] An insulated electric wire in which the composition for a coating material for electric wires according to any one of claims 1 to 4 is used in a coating material for electric wires.

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