JP6854411B2 - Flame-retardant resin composition, insulated wires and cables - Google Patents

Description

The present invention relates to flame-retardant resin compositions, insulated wires and cables.

A flame-retardant resin composition is used as a material for forming an insulating film of an insulating electric wire and a sheath of a cable used in vehicles such as automobiles and railroad vehicles, and buildings such as buildings and factories. As such a flame-retardant resin composition, for example, Patent Document 1 describes flame-retardant containing a silicone having a modified end with a compound having a carbon-carbon double bond, a thermoplastic resin, and a metal hydroxide. The sex resin composition is disclosed. Examples of the thermoplastic resin include an ethylene-vinyl acetate copolymer. Further, as the metal hydroxide, magnesium hydroxide and aluminum hydroxide are mentioned. The metal hydroxide is blended as a component that enhances flame retardancy and suppresses a decrease in mechanical strength.

International Publication No. 2014/0461665

Insulated wires and cables are used for a long period of time after being laid. Insulated wires and cables deteriorate or deteriorate over time after laying. In particular, the outermost insulating film of the insulated wire and the outermost coating layer such as the sheath of the cable are one of the constituent parts of the insulated wire and the cable, which are liable to deteriorate or deteriorate. Deterioration of the outermost coating layer greatly affects the life of insulated wires and cables. Therefore, there is a demand for a technique for extending the service life of an insulated wire or cable by improving the deterioration resistance of the outermost coating layer over time.

Therefore, one of the purposes of the present invention is to provide a flame-retardant resin composition having an outermost coating layer having excellent deterioration resistance over time and capable of producing an insulated wire or cable having a long service life.

The flame-retardant resin composition of the present application comprises a first resin component containing at least one of low-density polyethylene and linear low-density polyethylene, an ethylene-vinyl acetate copolymer, and an ethylene-ethyl acrylate copolymer. A flame-retardant resin composition containing a second resin component containing at least one selected from the group consisting of ultra-low density polyethylene and a phosphinic acid metal salt. The content of the metal phosphinic acid salt is 10% by mass or less, the total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less, and maleic acid is based on 100% by mass of the total amount of the flame-retardant resin composition. The content of modified polyethylene is 1% by mass or less, and the content of high-density polyethylene is 5% by mass or less.

According to the flame-retardant resin composition, it is possible to provide a flame-retardant resin composition having an outermost coating layer having excellent deterioration resistance over time and capable of manufacturing an insulated wire or cable having a long service life. It becomes.

It is sectional drawing which shows an example of a single core cable. It is sectional drawing which shows an example of a 3-core cable. It is sectional drawing which shows an example of a triplex type cable. It is sectional drawing which shows an example of an insulated electric wire. It is a graph which shows the result of having evaluated the time-dependent change of volume resistance. It is a graph which shows the relationship between the number of heat cycles and the change of the shrinkage amount.

[Explanation of Embodiments of the Invention]
First, embodiments of the present invention will be listed and described. The flame-retardant resin composition of the present application contains a first resin component containing at least one of low-density polyethylene (LDPE: Low Density Polyethylene) and linear low-density polyethylene (LLDPE: Linear Low Density Polyethylene), and ethylene. -Vinyl acetate copolymer (EVA), ethyl ethylene-ethyl acrylate copolymer (EEA) and ultra-low density polyethylene (VLDPE: Very Low Density) It is a flame-retardant resin composition containing a second resin component containing at least one of the above, and a metal salt of phosphinic acid. The content of the metal phosphinic acid salt is 10% by mass or less, the total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less, and maleic acid is based on 100% by mass of the total amount of the flame-retardant resin composition. The content of modified polyethylene is 1% by mass or less, and the content of high-density polyethylene is 5% by mass or less.

Typical examples of deterioration of the outermost coating layer over time include a decrease in insulation resistance, shrinkage over time, and whitening. The present inventors have clarified that a decrease in insulation resistance and whitening of the outermost coating layer can be caused by a metal hydroxide as a flame retardant. According to the study by the present inventors, the decrease in the insulation resistance of the outermost coating layer occurs when the metal hydroxide contained in the outermost coating layer absorbs moisture and moisture is contained inside the outermost coating layer. It is considered to be. Further, whitening of the outermost coating layer occurs when the metal hydroxide contained in the outermost coating layer reacts with carbon dioxide in the air and precipitates as a carbonate. In the flame-retardant resin composition of the present application, the total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less. This feature prevents the absorption of moisture in the laying environment and suppresses the decrease in insulation resistance. In addition, whitening of the outermost coating layer can be suppressed.

Further, in order to prevent the outermost coating layer from shrinking due to aging, the present inventors selected a composition of a flame-retardant resin composition that can be molded even at a relatively low temperature, and molded at a molding temperature even at a relatively low temperature. Clarified that it is important to do. It was also clarified that a flame-retardant resin composition having the above-mentioned composition is suitable for that purpose.

The flame-retardant resin composition of the present application contains a metal salt of phosphinic acid as a substitute for aluminum hydroxide and magnesium hydroxide as a substance that imparts flame retardancy. As a result, sufficient flame retardancy can be ensured. On the other hand, the phosphorus-based compound phosphinic acid metal salt has a characteristic that it is difficult to disperse in the polyolefin-based resin which is the main component of the flame-retardant resin composition when the blending amount in the flame-retardant resin composition exceeds a certain amount. Has. Therefore, it is necessary to add a dispersion aid such as maleic acid-modified polyethylene. However, the flame-retardant resin composition containing a predetermined amount or more of maleic acid-modified polyethylene needs to have a high molding temperature. Therefore, in order to reduce the amount of shrinkage of the outermost coating layer due to aging, it is preferable that maleic acid-modified polyethylene is not contained as much as possible.

According to the study by the present inventors, molding at a relatively low molding temperature is performed by containing 10% by mass or less of the phosphinic acid metal salt and setting the content of the maleic acid-modified polyethylene to 1% by mass or less. It has become clear that flame retardancy can be maintained while making it possible.

Further, the flame-retardant resin composition of the present application contains a first resin component containing at least one of LDPE and LLDPE, and a second resin component containing at least one from the group consisting of EVA, EEA and VLDPE. contains. A molded product made of a flame-retardant resin composition containing the first resin component has high mechanical strength and rigidity, and is excellent in trauma resistance. On the other hand, the second resin component imparts flexibility to the molded product and lowers the tensile elastic modulus. Therefore, by containing both the first resin component and the second resin component, it is possible to reduce the tensile elastic modulus while maintaining the mechanical strength and rigidity of the molded product, and even at a relatively low molding temperature. It becomes possible to mold. As a result, it becomes possible to provide a flame-retardant resin composition capable of forming an insulated wire and a cable in which shrinkage of the outermost coating layer due to aging is suppressed while maintaining the physical properties required for the outermost coating layer. ..

The content of the phosphinic acid metal salt in the flame-retardant resin composition is preferably 1% by mass or more. By containing 1% by mass or more of the metal salt of phosphinic acid, it becomes easy to provide a flame-retardant resin composition capable of forming an insulated wire and a cable having an outermost coating layer having necessary flame retardancy.

The total amount of the first resin component and the second resin component may be 85% by mass or more with respect to 100% by mass of the total amount of the flame-retardant resin composition. By containing the first resin component and the second resin component in the above proportions, a flame-retardant resin composition capable of forming the outermost coating layer of an insulated wire and cable having excellent flame retardancy and excellent deterioration resistance over time. It is possible to provide goods in a stable manner.

In the flame-retardant resin composition, the content of high-density polyethylene is 5% by mass or less. High-density polyethylene increases the viscosity of the flame-retardant resin composition and reduces workability. Therefore, when the content of the high-density polyethylene is 5% by mass or less, it is possible to provide a flame-retardant resin composition having a sufficient viscosity and excellent processability at the time of extrusion molding or the like. Preferably, the content of the high-density polyethylene in the flame-retardant resin composition is 1% by mass or less, and the flame-retardant resin composition is substantially free of high-density polyethylene (for example, 0.1% by mass or less). Is preferable.

The ratio of the first resin component to the total of the first resin component and the second resin component may be 10% by mass or more and 90% by mass or less. That is, the ratio of the second resin component may be 90% by mass or more and 10% by mass or less. By containing the above two components in such a ratio, the insulated wires and cables have an excellent balance between the basic characteristics required as a material for insulated wires and cables such as mechanical strength and trauma resistance, and the deterioration resistance over time. It becomes easy to provide a flame-retardant resin composition capable of forming the above.

The total resin component contained in the flame-retardant resin composition may contain a first resin component and a second resin component, and the balance may be composed of unavoidable resin impurities. When all the resin components contained in the flame-retardant resin composition contain only these two components and unavoidable resin impurities, it is possible to form an insulated wire and cable having an excellent balance between the above basic physical properties and aging resistance. The flame-retardant resin composition can be provided more stably.

The content of unavoidable resin impurities in the flame-retardant resin composition is preferably 1% by mass or less. Due to the low content of unavoidable resin impurities as described above, a flame-retardant resin composition capable of forming the outermost coating layer of insulated wires and cables having excellent flame retardancy and deterioration resistance over time is stable. Can be provided to.

The present invention also relates to an insulated electric wire having a linear conductor portion and an insulating coating layer formed from the flame-retardant resin composition, which is arranged so as to surround the outer peripheral side of the conductor portion. An insulated wire having such an insulating coating layer has excellent resistance to deterioration over time. Therefore, it becomes an insulated wire having a long service life.

The present invention also relates to a cable having a linear conductor portion and an outermost coating layer formed from the flame-retardant resin composition, which is arranged so as to surround the outer peripheral side of the conductor portion. A cable having such an outermost coating layer has excellent resistance to deterioration over time. Therefore, the cable has a long service life.

[Details of Embodiments of the present invention]
Next, an embodiment of the flame-retardant resin composition of the present application and a method for producing the same will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference number and the description is not repeated.

[Structure of flame-retardant resin composition]
The flame-retardant resin composition according to the present embodiment contains a first resin component containing at least one of low-density polyethylene and linear low-density polyethylene, an ethylene-vinyl acetate copolymer, and ethylene-acrylic acid. It contains a second resin component containing at least one selected from the group consisting of ethyl copolymer and ultra-low density polyethylene, and a phosphinic acid metal salt.

[First resin component and second resin component]
As described above, the first resin component comprises at least one of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

LDPE is an ethylene homopolymer obtained by, for example, a method of polymerizing an ethylene monomer by a method of increasing the pressure at the time of polymerization, which is called a high pressure method. LLDPE is a copolymer obtained by copolymerizing an ethylene monomer with a small amount of α-olefin such as butene-1 called a comonomer. The densities of the LDPE and LLDPE contained in the first resin component are more than 0.910 g / mL and less than 0.940 g / mL. In the specification of the present application, the density is a density measured in accordance with JIS K 6922-2.

The first resin component increases the hardness of the outermost coating layer (insulation coating, sheath, etc.) of the insulated wire or cable, and imparts excellent traumatic resistance. It also imparts excellent mechanical properties (tensile properties, etc.) to the outermost coating layer.

As described above, the second resin component is at least one selected from the group consisting of ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA) and ultra-low density polyethylene (VLDPE). Including one.

The ethylene-vinyl acetate copolymer (EVA) is obtained by copolymerizing ethylene and vinyl acetate by a polymerization method such as radical polymerization. The ethylene-ethyl acrylate copolymer (EEA) is obtained by copolymerizing ethylene and ethyl acrylate by a polymerization method such as radical polymerization. Ultra-low density polyethylene (VLDPE) is a resin having a lower density and flexibility than LDPE and LLDPE. Specifically, VLDPE has a density of ^{0.880 g / cm 3 to} 0.909 g / cm ^3. VLDPE is obtained by copolymerizing ethylene with octene-1.

When EVA is blended, the ratio of the ethylene monomer unit and the vinyl acetate monomer unit in EVA is not particularly limited. However, when the amount of the vinyl acetate monomer unit is high, the flame retardancy is improved, but the melting point is lowered, and the vinyl acetate is easily deformed by heating. Therefore, the ratio of the vinyl acetate monomer unit to the total monomer unit of EVA is preferably 30% by mass or less in terms of mass. Since the heat deformation can be reduced, the proportion of the vinyl acetate monomer unit is preferably 28% by mass or less (the melting point of EVA is 71 ° C. or more).

EVA, EEA and VLDPE contained in the second resin component all have a property of being highly flexible as compared with LDPE and LLDPE. The outermost coating layer of the insulated wire and cable obtained from the flame-retardant resin composition containing these components can be molded even at a relatively low molding temperature. As a result, the shrinkage of the outermost coating layer due to aging can be reduced.

Regarding the contents of the first resin component and the second resin component in the flame-retardant resin composition, the content of the first resin component and the second resin component is based on 100% by mass of the total amount of the flame-retardant resin composition. The total amount is preferably 85% by mass or more, and more preferably 90% by mass or more. Thereby, it is possible to stably provide a flame-retardant resin composition capable of forming the outermost coating layer of an insulated electric wire and a cable having excellent flame retardancy and deterioration resistance with time.

The ratio of the first resin component to the total of the first resin component and the second resin component is preferably 10% by mass or more and 90% by mass or less, and 20% by mass or more and 90% by mass or less. preferable. Above all, it is particularly preferable that it is 40% by mass or more and 90% by mass or less. The balance is the proportion of the second resin component. That is, the ratio of the second resin component to the total of the first resin component and the second resin component is preferably 90% by mass or less and 10% by mass or more, and 80% by mass or less and 10% by mass. The above is preferable, and it is particularly preferable that it is 60% by mass or less and 10% by mass or more. With such a composition, flame retardancy capable of forming the outermost coating layer of an insulated wire or cable having a sufficiently low elastic modulus (for example, less than 200 MPa) while sufficiently maintaining traumatic resistance and mechanical properties. The sex resin composition can be stably provided.

The flame-retardant resin composition according to the present embodiment may contain a resin component other than the first resin component and the second resin component as long as the effect is not impaired. However, in order to obtain a flame-retardant resin composition having stable characteristics, the ratio of the first resin component and the second resin component to the total resin components contained in the flame-retardant resin composition is 90. It is preferably mass% or more, and it is preferable that the total resin component contained in the flame-retardant resin composition is substantially composed of the first resin component and the second resin component, and the first resin component and the first resin component are present. It is preferable that the resin component of 2 is contained and the balance is composed of unavoidable resin impurities. It is particularly preferable that the content of the unavoidable resin impurities is 1% by mass or less. Since the ratio of the first resin component to the second resin component is 90% by mass or more, it has excellent traumatic resistance and mechanical strength, and as a material for insulated electric wires and cables with little shrinkage. Suitable flame-retardant resin compositions can be provided. The "total resin component" refers to a component made of a polymer resin, excluding a metal salt of phosphinic acid, other inorganic substances, and various additives added for adjusting physical properties. The "total resin component" also includes a first resin component and a second resin component.

[Metallic salt of phosphinic acid]
The phosphinic acid metal salt contained in the flame-retardant resin composition according to the present embodiment is a compound represented by the following formula (1). In the formula, R ¹ and R ² are hydrogen or an alkyl group having 1 to 8 carbon atoms or an aryl group having 12 or less carbon atoms, respectively, and M ^{m +} is calcium, aluminum, zinc, magnesium, potassium, sodium, respectively. It is one selected from alkali metals such as lithium, ammonium, barium and strontium, alkaline earth metals, trivalent metals and monovalent to trivalent transition metals, and ammonium. m is an integer of 1-3. As M, calcium, aluminum and zinc are preferable, and aluminum is more preferable.

The phosphorus content of the phosphinic acid metal salt is preferably 15% by mass or more, more preferably 18% by mass or more, and further preferably 20% by mass or more. Specific examples of the metal salt of phosphinic acid include an aluminum salt of organic phosphinic acid.

The content of the metal phosphinic acid salt is 10% by mass or less with respect to the total amount of the flame-retardant resin composition. If it exceeds 10% by mass, it becomes difficult to sufficiently disperse the metal phosphinic acid salt without adding the maleic acid-modified polyethylene as a dispersion aid in excess of 1% by mass. The content of the metal phosphinic acid salt is preferably 1% by mass or more, more preferably 4% by mass or more, based on the total amount of the flame-retardant resin composition.

[Other ingredients]
The flame-retardant resin composition according to the present embodiment has a total content of aluminum hydroxide and magnesium hydroxide of 1% by mass or less with respect to a total amount of 100% by mass of the flame-retardant resin composition. The flame-retardant resin composition preferably contains substantially no aluminum hydroxide and magnesium hydroxide (for example, 0.1% by mass or less). When the total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less, it is possible to suppress a decrease in insulation resistance and whitening of the molded product over time.

The flame-retardant resin composition according to the present embodiment contains 1% by mass or less of maleic acid-modified polyethylene with respect to 100% by mass of the total amount of the flame-retardant resin composition. The flame-retardant resin composition preferably contains substantially no maleic acid-modified polyethylene (for example, 0.1% by mass or less). Since the content of maleic acid-modified polyethylene is 1% by mass or less, it is not necessary to raise the temperature during extrusion molding. As a result, the amount of shrinkage of the molded product due to aging can be reduced.

The flame-retardant resin composition according to the present embodiment contains 5% by mass or less of high-density polyethylene with respect to 100% by mass of the total amount of the flame-retardant resin composition. When the content of the high-density polyethylene exceeds 5% by mass, the viscosity of the flame-retardant resin composition increases and the processability decreases. Therefore, the content of high-density polyethylene is preferably 5% by mass or less with respect to 100% by mass of the total amount of the flame-retardant resin composition. The content of the high-density polyethylene in the flame-retardant resin composition is more preferably 1% by mass or less, and the flame-retardant resin composition substantially does not contain the high-density polyethylene (for example, 0.1% by mass). The following) is preferable.

[Additional ingredients]
If necessary, the flame-retardant resin composition according to the present embodiment may contain additive components other than the above-mentioned components as long as the effects of the invention are not impaired. Although not particularly limited, for example, an appropriate amount of antioxidant (such as one having a phenol structure or an amine structure or a low molecular weight substance having a phosphorus or sulfur atom), a lubricant (higher fatty acid, fatty acid metal salt, fatty acid amide or fluorine-based). It may contain a lubricant (such as a lubricant made of a material) and a reinforcing material (such as talc).

Further, in order to adjust the physical properties, other resin components such as ethylene-propylene copolymerized rubber and rubber components may be contained. However, the amount thereof is preferably less than the contents of the first resin component and the second resin component, and is preferably 5% by mass or less of the flame-retardant resin composition.

[Flame-retardant resin composition]
As described above, the flame-retardant resin composition according to the present embodiment contains a first resin component containing at least one of low-density polyethylene and linear low-density polyethylene, and an ethylene-vinyl acetate copolymer. , A second resin component containing at least one selected from the group consisting of ethylene-ethyl acrylate copolymer and ultra-low density polyethylene, a metal phosphinic acid salt and, if necessary, other additives. .. However, the content of the metal phosphinic acid salt is 10% by mass or less and the total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less with respect to 100% by mass of the total amount of the flame-retardant resin composition. The content of maleic acid-modified polyethylene is 1% by mass or less, and the content of high-density polyethylene is 5% by mass or less.

A preferred embodiment of the flame-retardant resin composition is a first resin component containing at least one of low-density polyethylene and linear low-density polyethylene, an ethylene-vinyl acetate copolymer, and ethyl ethylene-acrylate. It contains a second resin component containing at least one selected from the group consisting of copolymers and ultra-low density polyethylene, and a phosphinic acid metal salt. The total amount of the first resin component and the second resin component is 85% by mass or more, preferably 90% by mass, based on 100% by mass of the total amount of the flame-retardant resin composition. The ratio of the first resin component to the total of the first resin component and the second resin component is 10% by mass or more and 90% by mass or less, preferably 20% by mass or more and 90% by mass or less, and more preferably 40% by mass or more. It is 80% by mass or less. The content of the metal phosphinic acid salt is 1% by mass or more and 10% by mass or less. The total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less, the content of maleic acid-modified polyethylene is 1% by mass or less, and the content of high-density polyethylene is 5% by mass or less, preferably 1. It is mass% or less. This flame-retardant resin composition may contain additives such as an inorganic filler, an antioxidant, a lubricant, and carbon black, if necessary.

[Manufacturing method of flame-retardant resin composition]
The flame-retardant resin composition according to the present embodiment is produced by kneading the above essential components and, if necessary, other components using a melt-kneading device such as a twin-screw extruder, a roll, or a Banbury mixer. Can be done. At that time, each component may be kneaded at room temperature and then heated for further kneading.

[Use of flame-retardant resin composition]
The flame-retardant resin composition can be suitably used for insulating coating of an insulated electric wire and forming a sheath of an insulated cable. However, the application is not limited to these. The term "insulating coating" is used to mean that the insulating coating of the insulated wire and the insulating material such as the sheath of the insulating cable are included.

[Structure of insulated wires and cables]
Next, the configuration of the insulated wire and cable having the outermost coating layer formed from the flame-retardant resin composition will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of a single-core cable according to an embodiment of the present application. With reference to FIG. 1, the single-core cable 1 includes a conductor portion 10 that is linear and has a circular shape in a cross section perpendicular to the longitudinal direction. The inner semi-conductive layer 20, the insulator 30, the outer semi-conductive layer 40, the shielding portion 50, the holding tape 60, and the sheath 70 are arranged in this order in a concentric circle with the circular conductor portion 10 as the center toward the outside in the radial direction. Be placed.

The inner semi-conductive layer 20 and the outer semi-conductive layer 40 are each composed of a semi-conductive substance such as a semi-conductive resin or a semi-conductive tape. The insulator 30 is made of, for example, cross-linked polyethylene. The shielding portion 50 is made of, for example, a copper tape or the like. The presser tape 60 is provided for fixing each member, and is made of an insulating material such as an insulating resin.

The sheath 70 is the outermost coating layer formed from the flame-retardant resin composition according to the present embodiment. The sheath 70 is arranged so as to surround the outer peripheral side of the conductor portion 10, and constitutes the outermost covering layer of the single core cable 1. In the sheath 70, for example, the inner semi-conductive layer 20, the insulator 30, the outer semi-conductive layer 40, the shielding portion 50, and the pressing tape 60 are arranged in this order in a concentric circle with the conductor portion 10 as the center toward the outside in the radial direction. It can be formed by extruding and coating the flame-retardant resin composition with heating so as to cover the outer peripheral surface of the linear composite.

FIG. 2 is a schematic cross-sectional view showing an example of a three-core cable according to another embodiment. The 3-core cable 2 includes three cables 3 in an area covered by one sheath 70. The individual cables 3 have the same structure as the single-core cable 1 except that the presser tape 60 and the sheath 70 are not provided. The three-row cable 3 is surrounded by an interposition 80 so as to have a circular cross section, and is fixed by a pressing tape 60. The interposition 80 is composed of resin, paper, fibers and the like. A sheath 70 formed from the flame-retardant resin composition is provided on the outer side of the presser tape 60 in the radial direction.

The sheath 70 is a coating layer formed from the flame-retardant resin composition according to the present embodiment. The sheath 70 is arranged so as to surround the outer peripheral side of the conductor portion 10, and constitutes the outermost covering layer of the three-core cable 2. The sheath 70 is flame-retardant so as to cover the outer peripheral surface of the linear composite fixed with the pressing tape 60 after providing the cable 3 of the above three threads and the interposition 80 surrounding the cable 3. It can be formed by extruding and coating the sex resin composition while heating it.

FIG. 3 is a schematic cross-sectional view showing an example of a triplex type cable according to another embodiment. The triplex type cable 4 has a structure in which three single core cables 5 are twisted together. Each single-core cable 5 has the same structure as the single-core cable 1 shown in FIG. That is, the single-core cable 5 is provided with a sheath 70 formed from the flame-retardant resin composition on the outermost layer of each. Since the triplex type cable 4 has three conductor portions 10 independently insulated and protected, it has a feature that the allowable current is higher than that of the three-core cable 2 shown in FIG. The triplex type cable 4 can be manufactured, for example, by adhering the sheaths 70 of three single core cables 5 formed by the same method as the single core cable 1 by heat welding or the like.

FIG. 4 is a schematic cross-sectional view showing an example of an insulated electric wire according to another embodiment. The insulated wire 6 includes a conductor portion 10 which is linear and has a circular shape in a cross section in the longitudinal direction, and an insulating coating layer 90 which is arranged so as to surround the outer peripheral side of the conductor portion 10. The insulating coating layer 90 is made of the flame-retardant resin composition. The insulating coating layer 90 can be formed by extrusion molding or coating the outer peripheral surface of the conductor portion 10 with a flame-retardant resin composition. The insulating coating layer 90 constitutes the outermost coating layer of the insulating electric wire 6. Further, the insulating coating layer 90 contacts the outer peripheral surface of the conductor portion 10 and covers the outer peripheral surface thereof.

In the specification of the present application, as shown in FIG. 4, the insulated electric wire means an electric wire including a linear conductor portion such as copper and an insulating layer made of an insulating material and covering the outer surface of the conductor portion. .. The linear conductor portion may be a single wire, or may be composed of a plurality of linear bodies such as stranded wires.

As shown in FIGS. 1 to 3, the cable is a linear body in which the outermost surface of one or a plurality of convergents of the insulated electric wire is covered with an insulating coating layer (sheath). Say.

In the specification of the present application, the outermost covering layer means the insulating coating layer 90 in the insulated wire 6 and the sheath 70 in the cables 1, 2 and 4.

The cables shown in FIGS. 1 to 3 and the insulated wires shown in FIG. 4 have an outermost coating layer having high scratch resistance and deterioration resistance over time. Therefore, it is advantageously used in fields where insulated wires and cables with a long service life are required.

Next, in order to confirm the effect of the invention, the following experiment was carried out and the characteristics were evaluated. The results are shown below.

(Material used)
First, the materials used in the following experimental examples (Examples and Comparative Examples) will be described. The formulations used in each experiment are shown in Tables 1 to 3. Experiment Nos. shown in Tables 1 and 2. 1-No. 11 is an example. In addition, Experiment No. shown in Table 3 12 and 13 are comparative examples. The unit of the numerical value of each component in Tables 1 to 3 is the mass part. The phosphinic acid metal salt ratio indicates the ratio (unit: mass%) of the phosphinic acid metal salt contained in the flame-retardant resin composition to 100% by mass of the total amount of the flame-retardant resin composition. Experiment Nos. shown in Tables 1 and 2. Of 1 to 11, the phosphinic acid metal salt ratio is 8.8% by mass at the maximum (Experiment No. 6 and Experiment No. 8). On the other hand, in Comparative Examples (Experiments Nos. 12 and 13), the phosphinic acid metal salt ratio was 15.7% by mass.

[First resin component]
-LLDPE (Linear Low Density Polyethylene): Density 0.92 g / mL, MFR 0.6 g / 10 min (MFR was measured under the measurement conditions of 190 ° C. and 21.6 kg. The same shall apply hereinafter).

[Second resin component]
(I) Ethylene-vinyl acetate copolymer resin EVA (vinyl acetate content: 25% by mass, melting point: 77 ° C.)
(Ii) Ethylene-ethyl acrylate copolymer resin EEA (ethyl acrylate content: 15% by mass, melting point: 100 ° C.)
(Iii) Ultra Low Density Polyethylene VLDPE (Density 0.868 g / mL, Melting Point 55 ° C., Durometer Hardness (Shore A) 70)

[Resin component for comparison]
(1) HDPE (High Density Polyethylene): Density 0.951 g / mL, MFR 0.8 g / 10 min
(2) MAH-LLDPE (maleic acid-modified linear low-density polyethylene): density 0.928 g / mL, MFR 1.5 g / 10 min, melting point 122 ° C., maleic acid content 0.8% by mass.

[Metallic salt of phosphinic acid]
A metal phosphinic acid salt having a density of 1.35 g / cm ³ , a phosphorus content of 23-24% by mass, and an average particle size of 20-40 μm was used.

[Other additive ingredients]
(I) Antioxidant A phenolic antioxidant having a molecular weight of 1178 and a melting point of 110-125 ° C. was used.
(Ii) Lubricating agent Zinc stearate was used.
(Iii) Carbon black A carbon black having an arithmetic mean particle size of 38 nm and a nitrogen adsorption specific surface area of 49 m ² / g was used.

[Evaluation 1]
[Characteristic evaluation]
(Preparation of evaluation sheet)
Each component of the formulation (mass ratio) shown in Tables 1 and 2 was kneaded at 180 ° C. with a pressure kneader. Then, the kneaded product was press-molded at 160 ° C. to prepare sheets having a thickness of 1 mm, 2 mm, and 3 mm.

(Evaluation of physical properties)
The method of measuring the physical properties, etc. performed in the following experimental examples (examples, comparative examples) will be described. The evaluation results are shown in Tables 1 and 2.

(Oxygen index)
A test piece was prepared from a sheet having a thickness of 3 mm press-molded at 160 ° C., and the oxygen index was measured according to JIS K7201.

(D hardness)
Measurements were made according to JIS K 7215 Type D using a Shore D hardness tester.

(Tensile characteristics)
A tensile test piece was punched from a 1 mm thick sheet press-molded at 160 ° C., and a tensile test was performed at a test speed of 200 mm / min using an autograph manufactured by Shimadzu Corporation in accordance with JIS K 6251. .. In the tensile test, tensile elastic modulus, tensile strength, and tensile elongation were measured. A tensile elastic modulus of 200 MPa or less was accepted.

(Low temperature embrittlement characteristics)
A tensile test piece was punched out from a sheet having a thickness of 2 mm press-molded at 160 ° C., and measured according to JIS K 7216 using a measuring machine manufactured by Toyo Seiki Seisakusho Co., Ltd. Passed at -25 ° C or lower (if passed at -25 ° C, the temperature below that is not implemented).

(Heating deformation rate)
Using a measuring machine manufactured by Yasuda Seiki Seisakusho Co., Ltd., the measurement was carried out by pushing with a 10 mmφ iron rod under the conditions of 75 ° C. and 4 kgf (about 39 N) according to JIS C 3005.

(specific gravity)
It was measured by the ethanol method using a measuring machine manufactured by A & D Co., Ltd.

(Volume resistance, change in volume resistance)
The initial volume resistance of a 1 mm thick sheet dried in a constant temperature bath at 80 ° C. was measured at a voltage of 500 V at room temperature. Then, this sheet was immersed in warm water at 75 ° C. (80 ° C. for Experiments No. 12 and No. 13) for a predetermined period (2 weeks, 4 weeks, or 8 weeks), and water droplets on the sheet surface were wiped off. The volume resistance was measured again at room temperature.

Experiment Nos. shown in Tables 1 and 2. 1-No. 11 is an example. In addition, Experiment No. shown in Table 3 12 and 13 are comparative examples. As shown in Tables 1 and 2, the flame-retardant resin compositions of Examples have sufficient flame-retardant properties having an oxygen index of 19 or more. In addition, it has a sufficient hardness of D hardness of 38 or more and has high traumatic resistance. Both the low temperature embrittlement characteristics and the specific gravity were within the permissible range.

The elastic modulus is 200 MPa or less, and the maximum is 164 MPa (Experiment No. 7). An insulated wire having an elastic modulus of 200 MPa or less and substantially no maleic acid-modified polyethylene, which enables molding at a relatively low temperature and has an outermost coating layer with less shrinkage due to aging. Alternatively, a cable can be provided.

Regarding the volume resistance, Experiment No. 1-No. In all of the 11 samples, the resistance value maintained at a certain level or higher at the time after 8 weeks from the immersion at 75 ° C., and no one was found to change rapidly with time. From this, it was demonstrated that all the sheets obtained from the flame-retardant resin composition according to the present embodiment have high aging resistance.

On the other hand, Experiment No. 1 containing 15.7% by mass of a metal phosphinic acid salt and 15.7% by mass of high-density polyethylene. In the flame-retardant resin composition of No. 12, the tensile elastic modulus of the sheet-like sample obtained from the flame-retardant resin composition is as high as 220 MPa. In addition, Experiment No. Experiment No. 12 further contained 7.9% by mass of maleic acid-modified linear low density polyethylene (MAH-LLDPE) as compared with 12. In the flame-retardant resin composition of No. 13, the tensile elastic modulus of the sheet-like sample obtained from the flame-retardant resin composition is as high as 230 MPa. The comparative flame-retardant resin composition having such a high tensile elastic modulus needs to have a high extrusion temperature, which is not preferable from the viewpoint of reducing the shrinkage amount of the sheet-shaped sample.

[Evaluation 2]
[Evaluation of changes over time in volume resistance]
Experiment No. By molding the flame-retardant resin composition shown in No. 7, two sheets of 1 mm-thick sheet-shaped evaluation samples were prepared. Further, a coating material for a sheath of an existing cable was prepared, and a comparative sample having a thickness of 1 mm was prepared. Each sample was dried in a constant temperature bath at 75 ° C. For each sample, the initial volume resistance was measured at a voltage of 500 V at room temperature. Then, one piece of the sheet-shaped evaluation sample was allowed to stand at room temperature, and the volume resistance was measured at room temperature after each predetermined period. In addition, one piece of the sheet-shaped evaluation sample and the comparison sample are immersed in warm water at 75 ° C., the sample is taken out from the warm water after a predetermined period of time, water droplets on the sheet surface are wiped off, and then the temperature is again normal temperature. The volume resistance was measured below. The results are shown in FIG.

FIG. 5 is a graph showing the results of evaluating the change over time in volume resistance. The solid line 100 represents the change over time in the volume resistance of the evaluation sample left at room temperature. The solid line 101 represents the change over time in the volume resistance of the evaluation sample immersed in warm water at 75 ° C. The dotted line 102 represents the change over time in the volume resistance of the comparative sample (existing product) immersed in warm water at 75 ° C.

As shown in the solid line 101, Experiment No. The rate of decrease from the initial value of the volume resistance of the sheet-shaped evaluation sample obtained from the flame-retardant resin composition shown in No. 7 after a certain period of time is the volume resistance of the comparison sample (existing product) shown by the dotted line 102. Significantly smaller than the rate of decrease from the initial value. As described above, the molded product obtained from the flame-retardant resin composition according to the present embodiment has a small change in volume resistance with time, and is suitable as a material for forming the outermost coating layer of an insulated wire or cable.

[Evaluation 3]
[Evaluation of contraction force and contraction amount]
Next, among the above examples, Experiment No. Taking the sheet formed from the flame-retardant resin composition of No. 7 as a typical example, the shrinkage force and the amount of shrinkage of the sheath (cable outer skin) were compared with the comparison target product. Experiment No. 14 and 15 are evaluation results (comparative examples) of the products to be compared. Experiment No. Reference numeral 14 denotes a result of collecting a sample piece from the sheath of a cable, which is an existing product, and measuring the shrinkage force and the amount of shrinkage of the sample piece. Experiment No. The sheath of 14 contains more than 1% by mass (about 10 to 15% by mass) of a metal hydroxide such as aluminum hydroxide or magnesium hydroxide as a flame retardant. Experiment No. Reference numeral 15 denotes a cable formed from a flame-retardant resin composition containing MAH-LLDPE (maleic acid-modified linear low-density polyethylene) in an amount of more than 1% by mass (about 8% by mass), and collected from the sheath of the cable. This is the result of collecting the sample piece to be collected and measuring the shrinkage force and the amount of shrinkage of the collected sample piece. Experiment No. The flame-retardant resin composition used in No. 15 was described in Experiment No. 15. It corresponds to the flame-retardant resin composition of the formulation shown in 13.

Experiment No. The sheath of the cable formed from the flame-retardant resin composition of No. 7 and Experiment No. 7 which is a comparative product. The contraction force and the amount of contraction of the sheaths of 14 and 15 were evaluated, respectively. The results are shown in Table 4 and FIG. Table 4 shows the measurement results of the contraction force of the sheet. Further, FIG. 6 is a graph showing the relationship between the number of heat cycles and the change in the amount of shrinkage. In FIG. 6, the solid line 200 indicates the experiment No. Corresponds to 7. The alternate long and short dash line 201 is the experimental No. Corresponds to 14. The dotted line 202 is the experiment No. Corresponds to 15.

The contraction force shown in Table 4 was measured by the following procedure. First, a strip-shaped sheath piece sample was collected from a cable equipped with a sheath. The sheath piece sample was set in a tensile tester, the temperature of the test sample was raised to 70 ° C., and then cooled to room temperature. The shrinkage force of the sample from the start of temperature rise to cooling to room temperature was measured. The measurement was performed three times, and the average value was calculated.

The graph showing the relationship between the heat cycle and the change in the amount of shrinkage shown in FIG. 6 was obtained as follows. First, I prepared the finished cable. This cable includes a sheath formed from the flame-retardant resin composition and a sheath to be compared with each other. An evaluation sample was taken from the sheath. Two marked lines were marked on the surface of the collected sample, and the distance between the two marked lines was recorded as an initial value. Then, the sample was heated to 70 ° C. and then cooled to room temperature as one cycle, and the cycle was repeated. The graph shown in FIG. 6 was obtained by plotting the change in the amount of contraction (%) every 10 cycles.

With reference to Table 4, Experiment No. which is an embodiment of the flame-retardant resin composition of the present application. The contraction force of the sheath obtained from No. 7 was found in Experiment No. 7. It is about half of the contraction force of the sheath of 14. Therefore, the shrinkage force of the obtained sheath can be reduced as compared with a flame-retardant resin composition containing a metal hydroxide such as aluminum hydroxide or magnesium hydroxide in an amount of more than 1% by mass as a flame retardant. Further, comparing the solid line 200 (Experiment No. 7) of FIG. 6 with the alternate long and short dash line 201 (Experiment No. 14), the experimental No. 2 which is the product of the flame-retardant resin composition of the present application is compared. The amount of shrinkage of the sheath obtained from No. 7 is the experimental No. It is smaller than the shrinkage amount of the sheath of 14. As described above, the flame-retardant resin composition of the present application has a reduced shrinkage force and shrinkage amount during heating when the content of the metal hydroxide such as aluminum hydroxide or magnesium hydroxide is 1% by mass or less. It is a material that can form the outermost coating layer of insulated wires and cables. As a result, it becomes possible to obtain an insulated wire or cable having a long service life. In addition, Experiment No. Whitening could not be confirmed even when the sheet after the evaluation in No. 7 was visually confirmed.

On the other hand, referring to Table 4, Experiment No. The value of the contraction force of the sheath of No. 15 is the experimental No. It is equivalent to the value of the contraction force of the sheath of 7. However, as shown by the dotted line 202 in FIG. The sheath of 15 has a large amount of shrinkage due to repeated heat cycles. Therefore, after forming the sheath, it is expected that the sheath contracts with the passage of time, causing deterioration of the cable. On the other hand, Experiment No. The amount of shrinkage of the sheath of No. 7 was determined by Experiment No. It is smaller than the amount of shrinkage of the sheath of 15. As described above, Experiment No. which is an embodiment of the flame-retardant resin composition of the present application. The sheath obtained from No. 7 is formed from a flame-retardant resin composition containing more than 1% by mass of MAH-LLDPE. Compared to the 15 sheaths, the amount of shrinkage after exposure to a high temperature environment is small. As described above, the flame-retardant resin composition of the present application forms the outermost coating layer of an insulated wire or cable in which the amount of shrinkage during heating is reduced by the content of maleic acid-modified polyethylene being 1% by mass or less. It is a material that can be used. As a result, it becomes possible to obtain an insulated wire or cable having a long service life.

As shown in the above examples, by using the flame-retardant resin composition of the present application, an outermost coating layer of an insulated wire or cable in which a decrease in insulation resistance, shrinkage with time, and occurrence of whitening are suppressed is formed. be able to. By improving the deterioration resistance of the outermost coating layer over time, it becomes possible to provide an insulated wire or cable having a long service life.

It should be understood that the embodiments and examples disclosed this time are exemplary in all respects and are not restrictive in any way. The scope of the present invention is not defined as described above, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The flame-retardant resin composition of the present application can be applied particularly advantageously in a field in which an insulated wire or cable having a high outermost coating layer with high deterioration resistance over time and a long service life is required.

1 Single-core cable 2 3-core cable 3 Cable 4 Triplex type cable 5 Single-core cable 6 Insulated wire 10 Conductor part 20 Internal semi-conductive layer 30 Insulator 40 External semi-conductive layer 50 Shielding part 60 Presser tape 70 Sheath 80 Intervention 90 Insulation Coating layer 100 Solid line 101 Solid line 102 Dotted line 200 Solid line 201 Single-point chain line 202 Dotted line

Claims (7)

Exceeded 0.910 g / cm ^3, a first resin component comprising at least one of the 0.940 g / cm ³ with the following densities, low density polyethylene and linear low density polyethylene,
At least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer , and ultra-low density polyethylene having a density of 0.880 g / cm ^{3 to} 0.909 g / cm ^3. With a second resin component containing
Phosphine acid metal salt and
A flame-retardant resin composition containing
With respect to 100% by mass of the total amount of the flame-retardant resin composition
The total amount of the first resin component and the second resin component is 85% by mass or more.
The content of the metal phosphinic acid salt is 1% by mass or more and 10% by mass or less.
The total content of aluminum hydroxide and magnesium hydroxide is 1% by mass or less.
The content of maleic acid-modified polyethylene is 1% by mass or less,
A flame-retardant resin composition having a high-density polyethylene content of 5% by mass or less. The flame-retardant resin composition according to claim 1 , wherein the content of the high-density polyethylene is 1% by mass or less. The flame retardant according to claim 1 or 2 , wherein the ratio of the first resin component to the total of the first resin component and the second resin component is 10% by mass or more and 90% by mass or less. Sex resin composition. Any of claims 1 to 3 , wherein the total resin component contained in the flame-retardant resin composition contains the first resin component and the second resin component, and the balance is unavoidable resin impurities. The flame-retardant resin composition according to item 1. The flame-retardant resin composition according to claim 4 , wherein the content of the unavoidable resin impurities is 1% by mass or less. With a linear conductor part
An insulated electric wire having an outermost coating layer formed from the flame-retardant resin composition according to any one of claims 1 to 5 , which is arranged so as to surround the outer peripheral side of the conductor portion. With a linear conductor part
A cable having an outermost coating layer formed from the flame-retardant resin composition according to any one of claims 1 to 5 , which is arranged so as to surround the outer peripheral side of the conductor portion.

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