Resin composition for insulation layers, and insulated electric wire

Abstract

A resin composition for insulation layers according to the present disclosure contains a resin component as the main component, and further contains a flame retardant and a pulverized product of shellfish shells. The resin component is an olefin-based resin, a polyvinyl chloride, a fluororesin, or a combination thereof. The contained amount of the pulverized product of shellfish shells is 5-35 mass%.

Description

Resin composition for insulating layer and insulated wire

[0001] This disclosure relates to a resin composition for an insulating layer and an insulated wire. This application claims priority to Japanese Application No. 2023-103199, filed June 23, 2023, and incorporates by reference all of the contents of the above-mentioned Japanese application.

[0002] Insulated wires installed in automobiles and the like are generally made by covering a conductor such as a copper wire with a resin composition. From the viewpoint of safety, such insulated wires are required to have good flame retardancy. In the prior art, for example, a resin composition has been proposed in which an inorganic flame retardant such as a metal hydrate is added to a polyolefin resin (see Patent Document 1).

[0003] Japanese Patent Application Publication No. 02-053845

[0004] The resin composition for an insulating layer of the present disclosure contains a resin component as a main component, and further contains a flame retardant and crushed shells, the resin component being an olefin-based resin, polyvinyl chloride, a fluororesin, or a combination thereof, and the content of the crushed shells is 5% by mass or more and 35% by mass or less.

[0005] FIG. 1 is a schematic cross-sectional view of an insulated wire according to one embodiment of the present disclosure.

[0006] [Problem to be Solved by the Present Disclosure] When the blending amount of a flame retardant is increased in order to improve flame retardancy, there is a problem that the tensile elongation related to the routing property is insufficient, and in particular, the flexibility is reduced at low temperatures, making the material more susceptible to cracking. Furthermore, in recent years, due to the demand for reducing the environmental load, there has been a desire to move away from fossil fuels in the materials field as well, and the use of naturally derived materials has been attracting attention.

[0007] An object of the present disclosure is to provide a resin composition for an insulating layer and an insulated wire that reduce environmental impact and that can reduce cracking at low temperatures even when the content of a flame retardant is high.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a resin composition for an insulating layer and an insulated wire that can reduce the environmental impact and suppress cracking at low temperatures even when the content of a flame retardant is high.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) The resin composition for an insulating layer of the present disclosure contains a resin component as a main component, and further contains a flame retardant and crushed shells, the resin component being an olefin resin, polyvinyl chloride, a fluororesin, or a combination thereof, and the content of the crushed shells is 5% by mass or more and 35% by mass or less.

[0011] The resin composition for an insulating layer can improve the strength of the insulating layer by containing an olefin resin, polyvinyl chloride, a fluororesin, or a combination thereof as a main component. The resin composition for an insulating layer also contains a flame retardant and crushed shells, with the crushed shell content being 5% by mass or more and 35% by mass or less. This configuration can suppress cracking at low temperatures even when the flame retardant content is high. Furthermore, the use of crushed shells derived from natural sources can reduce environmental impact. Therefore, the resin composition for an insulating layer not only reduces environmental impact, but also suppresses cracking at low temperatures even when the flame retardant content is high. In the present disclosure, the term "main component" refers to the component with the highest content. The main component may be, for example, a component with a content of 50% by mass or more.

[0012] (2) In the resin composition for an insulating layer of (1), the crushed shell material may have a maximum particle size of 50 μm or less. With this configuration, the tensile elongation related to the wiring property can be maintained.

[0013] (3) In the resin composition for an insulating layer according to either (1) or (2), the crushed shell material may contain particles having an aspect ratio of 3 to 20, and the content of particles in the crushed shell material may be 30% by mass or more. This configuration facilitates the achievement of an anchoring effect, and cracking at low temperatures can be suppressed. The aspect ratio can be measured from a cross-sectional image of the insulating layer at a magnification of 500 to 1000 times using a scanning electron microscope (SEM). In the case of a cross-sectional image at a magnification of 500 times, the aspect ratio is measured from an SEM image with a field of view of 150 μm square.

[0014] (4) In the resin composition for an insulating layer according to any one of (1) to (3) above, the resin component may contain polypropylene.

[0015] (5) In the resin composition for an insulating layer according to any one of (1) to (4), the flame retardant may be antimony trioxide. This configuration further improves the flame retardancy of the resulting insulating layer.

[0016] (6) In the resin composition for an insulating layer according to (5) above, the content of antimony trioxide may be 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the resin component. This configuration makes it possible to improve the flame retardant effect while sufficiently maintaining the extrusion moldability and mechanical properties of the insulating layer.

[0017] (7) An insulated wire according to the present disclosure includes a linear conductor and one or more insulating layers laminated on an outer peripheral surface of the conductor, the one or more insulating layers being made of the resin composition for insulating layers according to any one of (1) to (6) above.

[0018] This configuration reduces the environmental impact and also suppresses cracking at low temperatures even when the insulated wire contains a high amount of flame retardant, thereby improving the durability of the insulated wire.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, the resin composition for an insulating layer and the insulated wire according to the embodiments of the present disclosure will be described in detail with appropriate reference to the drawings.

[0020] <Resin composition for insulating layer> The resin composition for insulating layer (hereinafter sometimes simply referred to as "resin composition") contains a resin component as a main component. The resin component is an olefin resin, polyvinyl chloride, a fluororesin, or a combination thereof. The resin composition further contains a flame retardant and crushed shells.

[0021] (Olefin Resin) Examples of olefin resins include polypropylene resins such as polypropylene (homopolymer, block polymer, random polymer), polypropylene thermoplastic elastomer, reactor-type polypropylene thermoplastic elastomer, and dynamically crosslinked polypropylene thermoplastic elastomer; polyethylene resins such as polyethylene (high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and very low-density polyethylene), ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene rubber, ethylene-acrylic rubber, ethylene-glycidyl methacrylate copolymer, and ethylene-methacrylic acid copolymer; and ionomer resins in which ethylene-methacrylic acid copolymer or ethylene-acrylic acid copolymer molecules are intermolecularly bonded by metal ions such as sodium or zinc. Further examples include resins modified with maleic anhydride or the like, and resins containing epoxy groups, amino groups, or imide groups.

[0022] (Polyvinyl chloride) Examples of polyvinyl chloride include vinyl chloride homopolymers produced by methods such as suspension polymerization, bulk polymerization, or emulsion polymerization. Furthermore, examples of polyvinyl chloride include copolymers of vinyl chloride with ethylene, propylene, vinyl acetate, (meth)acrylic acid esters, etc. The term "(meth)acrylic acid ester" collectively refers to acrylic acid esters and methacrylic acid esters, and refers to either one or both of them. Furthermore, mixtures of the above homopolymers or copolymers with other thermoplastic resins can also be used as polyvinyl chloride. Polyvinyl chloride can be used alone or in combination of two or more types.

[0023] The average degree of polymerization of polyvinyl chloride may be 800 or more and 3000 or less, or 1000 or more and 2500 or less. When the average degree of polymerization of polyvinyl chloride is within the above range, an insulating layer having excellent flexibility and tensile strength can be formed. Here, the average degree of polymerization is a number-average degree of polymerization measured by gel permeation chromatography (GPC).

[0024] (Fluororesin) Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE). The fluororesins can be used alone or in combination of two or more. The fluororesin may be the fully fluorinated resin (unmodified fluororesin) exemplified above, or may be a modified product. When the fluororesin is PTFE, PFA, or FEP, the relative dielectric constant of the insulating layer can be further reduced, and the heat resistance can be further improved.

[0025] (Flame Retardant) The flame retardant imparts flame retardancy to the insulating layer made of the resin composition. Examples of the flame retardant include halogen-based flame retardants such as chlorine-based flame retardants and bromine-based flame retardants.

[0026] Examples of the flame retardant include halogen-based flame retardants such as antimony trioxide, antimony pentoxide, zinc borate, bromine-based flame retardants, and chlorine-based flame retardants, and non-halogen-based flame retardants such as metal hydroxides, nitrogen-based flame retardants, and phosphorus-based flame retardants. The flame retardants may be used alone or in combination of two or more.

[0027] Examples of bromine-based flame retardants include decabromodiphenylethane. Examples of chlorine-based flame retardants include chlorinated paraffin, chlorinated polyethylene, chlorinated polyphenol, and perchlorpentacyclodecane. Examples of metal hydroxides include magnesium hydroxide and aluminum hydroxide. Examples of nitrogen-based flame retardants include melamine cyanurate, triazine, isocyanurate, urea, and guanidine. Examples of phosphorus-based flame retardants include metal phosphinate, phosphaphenanthrene, melamine phosphate, ammonium phosphate, phosphate ester, and polyphosphazene.

[0028] As the flame retardant, from the viewpoint of further improving the flame retardancy of the resulting insulating layer, among these, antimony trioxide, bromine-based flame retardants, or melamine cyanurate may be used.

[0029] When the flame retardant is antimony trioxide, the content of antimony trioxide may be 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the resin component. When the content of antimony trioxide is within the above range, the extrusion moldability and mechanical properties of the insulating layer can be sufficiently maintained while improving the flame retardant effect.

[0030] When the flame retardant is a brominated flame retardant, the content of the brominated flame retardant may be 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the resin component. By having the content of the brominated flame retardant in the above range, the extrusion moldability and mechanical properties of the insulating layer can be sufficiently maintained while improving the flame retardant effect.

[0031] When the flame retardant is melamine cyanurate, the content of melamine cyanurate may be 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component. When the content of melamine cyanurate is in the above range, the flame retardant effect can be improved while the extrusion moldability and mechanical properties of the insulating layer can be sufficiently maintained.

[0032] (Pulverized shells) Pulverized shells are calcium carbonate derived from seashells. Examples of seashells include scallops and oysters. By including pulverized shells in the resin composition, cracking at low temperatures can be suppressed even when the content of flame retardant is high. Furthermore, the use of pulverized shells derived from natural sources can reduce the environmental impact.

[0033] The crushed shell material may be in a powder form. The crushed shell material may contain particles. The maximum particle size of the particles may be 50 μm or less. By making the maximum particle size of the particles 50 μm or less, good tensile elongation can be maintained. The particles may be spherical, plate-like, columnar, or irregular in shape.

[0034] Crushed shells can be prepared, for example, by the following method. First, shells are prepared. The shells may be scallop shells landed in fishing grounds near Hokkaido or Aomori Prefecture. The surfaces of the prepared shells are washed. The surfaces of the shells may be washed with running water. Here, any deposits are removed from the shell surfaces. The shells are then dried and crushed. Crushing may be performed by grinding in a mortar. To obtain a more homogeneous crushed product, for example, the shells can be crushed using a device such as a high-speed mill, a fine powder mill (both manufactured by LabNext Co., Ltd.), or a scallop shell crusher (Model KG-750) (manufactured by Seiwa Denko Co., Ltd.). Portions that are insufficiently crushed may be removed using a sieve or the like.

[0035] In the process of preparing the shell pulverized material, the shells may be calcined after washing but before pulverization. The calcination may be performed once or twice or more times. The calcination may include a primary calcination and a secondary calcination. The primary calcination may be performed, for example, to carbonize or incinerate the organic matter derived from the shells, and the shells may be held in a muffle furnace in the air at 500°C for one to several hours. The secondary calcination may be performed, for example, to activate the shells, and the shells may be held in a controlled atmosphere tubular furnace in a carbon dioxide gas atmosphere at a high temperature of 800°C or higher for one to several hours.

[0036] The resulting crushed shell material may have a median particle size per unit volume (Dv50) of 10 μm or less.

[0037] The aspect ratio of the particles of the crushed shell product may be 3 or more and 20 or less. The content of particles having an aspect ratio of 3 or more and 20 or less in the crushed shell product may be 30 mass% or more. When the content of particles having an aspect ratio of 3 or more and 20 or less in the crushed shell product is 30 mass% or more, an anchor effect is more easily obtained, and cracking at low temperatures can be further suppressed.

[0038] The lower limit of the content of ground shells in the resin composition may be 5 mass%, 7 mass%, or 10 mass%. If the content of ground shells is less than 5 mass%, cracking of the insulating layer at low temperatures may not be suppressed. The upper limit of the content of ground shells may be 35 mass%, or 30 mass%. If the content of ground shells exceeds 35 mass%, the tensile elongation of the resulting insulating layer may be reduced.

[0039] (Antioxidant) The resin composition may contain an antioxidant. Examples of the antioxidant include sulfur-based antioxidants and phenol-based antioxidants. Addition of an antioxidant can improve the stability of the insulating layer.

[0040] The content of the antioxidant in the resin composition may be 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the resin component. If the content of the antioxidant is less than 1 part by mass, a sufficient effect of inhibiting oxidative degradation may not be obtained. On the other hand, if the content of the antioxidant is more than 10 parts by mass, the mechanical strength of the resulting insulating layer may be reduced.

[0041] (Plasticizer) When the resin component is polyvinyl chloride, a plasticizer can be added to the resin composition. Examples of plasticizers include phthalate-based plasticizers such as diheptyl phthalate, dioctyl phthalate, and diisononyl phthalate; adipate-based plasticizers such as dioctyl adipate, diisononyl adipate, and di(butyldiglycol) adipate; tris(2-ethylhexyl) trimellitate (TOTM); phosphate-based plasticizers; polyester-based plasticizers; and chlorinated paraffin-based plasticizers. Furthermore, biomass-derived plasticizers such as epoxidized soybean oil, acetylated castor oil, and epoxidized linseed oil can also be used as the plasticizer. Using these biomass-derived materials as the plasticizer can improve the flexibility and processability of the insulating layer while reducing the environmental impact.

[0042] (Stabilizer) When the resin component is polyvinyl chloride, various stabilizers can be added to the resin composition. By adding various stabilizers to the resin composition, thermal and oxidative degradation of polyvinyl chloride can be suppressed. As the stabilizer, a lead-free stabilizer that does not contain lead may be used in order to reduce the environmental burden. Examples of the lead-free stabilizer include basic inorganic acid salts or their calcined products, hydrotalcite, calcium stearate, zinc stearate, and calcium-zinc composite stabilizers. One type of stabilizer can be used alone, or two or more types can be used in combination.

[0043] (Other Components) The resin composition may contain other components in addition to the resin component, flame retardant, crushed shells, antioxidant, plasticizer, and stabilizer. The other components may be, for example, a crosslinking agent, an ultraviolet absorber, a colorant, a processability improver, or other modifiers. The resin composition may contain the other components alone or in combination of two or more.

[0044] The resin composition can reduce the environmental load and can suppress cracking at low temperatures even when the content of a flame retardant is high.

[0045] <Insulated wire> An insulated wire includes a linear conductor and one or more insulating layers laminated on the outer peripheral surface of the conductor. The one or more insulating layers are made of a resin composition. The number of conductors may be one or more. FIG. 1 is a schematic cross-sectional view of an insulated wire according to one embodiment of the present disclosure. As shown in FIG. 1, the insulated wire 1 includes a linear conductor 2 and one insulating layer 3 laminated on the outer peripheral surface of the conductor 2.

[0046] [Conductor] The conductor 2 may be, for example, a round wire having a circular cross section, or a rectangular wire having a square cross section or a rectangular cross section.

[0047] The material of the conductor 2 may be a metal with high conductivity and high mechanical strength. Examples of such metals include copper, copper alloys, aluminum, aluminum alloys, nickel, silver, soft iron, steel, and stainless steel. The conductor 2 may be a wire-shaped material made from any of these metals, or may have a multilayer structure in which such a wire-shaped material is further coated with another metal. Examples of the conductor 2 having a multilayer structure include nickel-coated copper wire, silver-coated copper wire, copper-coated aluminum wire, and copper-coated steel wire.

[0048] The lower limit of the average cross-sectional area of ​​the conductor 2 is 0.01 mm ２ 0.1 mm ２ On the other hand, the upper limit of the average cross-sectional area of ​​the conductor 2 is 40 mm ２ 35 mm ２ If the average cross-sectional area of ​​the conductor 2 is less than the above lower limit, the volume of the insulating layer 3 relative to the conductor 2 will be large, which may reduce the volumetric efficiency of cables, coils, etc. formed using the insulated wire. Conversely, if the average cross-sectional area of ​​the conductor 2 exceeds the above upper limit, the insulating layer 3 must be made thick to sufficiently reduce the dielectric constant, which may result in an unnecessarily large diameter in the insulated wire. The "average cross-sectional area" of the conductor refers to the average value obtained by measuring the cross-sectional area of ​​the conductor 2 at 10 arbitrary points.

[0049] [Insulating Layer] The insulating layer 3 is formed on the outer peripheral surface of the conductor 2 by extrusion molding using the above-mentioned resin composition.

[0050] The lower limit of the average thickness of the insulating layer 3 may be 50 μm or 100 μm. On the other hand, the upper limit of the average thickness of the insulating layer 3 may be 2000 μm or 1500 μm. If the average thickness of the insulating layer 3 is less than the above-mentioned lower limit, the insulating performance may be reduced. Conversely, if the average thickness of the insulating layer 3 exceeds the above-mentioned upper limit, the volume efficiency of cables, coils, etc. formed using the insulated wire may be reduced. Note that the "average thickness" of the insulating layer 3 refers to the average value obtained by measuring the thickness at 10 arbitrary points on the insulating layer 3. Note that when multiple insulating layers 3 are provided, the average thickness of each insulating layer 3 is calculated, and this average value is used as the average thickness.

[0051] [Method for Manufacturing Insulated Wire] Next, a method for manufacturing an insulated wire will be described. The insulated wire is formed by extrusion molding an insulating layer 3. The method for manufacturing an insulated wire includes at least a step of mixing a resin component, a flame retardant, and crushed shells to obtain a resin composition, and then extrusion coating the resin composition onto the outer peripheral surface of a conductor 2 (extrusion step).

[0052] The insulated wire has one or more insulating layers made of a resin composition, which reduces the environmental impact as described above and can suppress cracking at low temperatures even when the insulated wire contains a high content of flame retardant. Therefore, the insulated wire having the insulating layers can improve durability and ease of routing.

[0053] Other Embodiments The conductor may be formed from a twisted wire in which a plurality of metal wires are twisted together. In this case, a plurality of types of metal wires may be combined. The number of twisted wires is generally seven or more.

[0054] The insulated wire may have a primer layer laminated directly on the conductor. The primer layer may be a crosslinked layer of a crosslinkable resin such as ethylene that does not contain metal hydroxide. The provision of such a primer layer can suppress deterioration over time in the peelability of the insulating layer and the conductor.

[0055] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0056] [Resin Compositions for Insulating Layer No. 1 to No. 3] Resin compositions No. 1 to No. 3 were prepared by mixing block polypropylene as the main component, antimony trioxide as a flame retardant, a hindered phenol-based antioxidant, and crushed shells in the amounts (parts by mass) shown in Table 1. Table 1 also shows the amount (% by mass) of crushed shells in the resin compositions.

[0057] [Resin Composition for Insulating Layer No. 4] Resin composition No. 4 was prepared in the same manner as No. 1, except that calcium carbonate derived from limestone was mixed in place of the crushed shells so as to have the content (parts by mass) shown in Table 1.

[0058] [Resin Composition for Insulating Layer No. 5] Resin composition No. 5 was prepared in the same manner as No. 1, except that no crushed shells were added.

[0059]

[0060] <Evaluation> The tensile elongation and crack suppression effect at low temperatures were evaluated for the resin compositions No. 1 to No. 5 obtained as described above. The evaluation results are shown in Table 1.

[0061] (Tensile Elongation) The tensile elongation of resin compositions No. 1 to No. 5 was measured based on UL (Underwriters Laboratories Inc.) Standard 758. A tensile elongation of 300% or more was considered acceptable.

[0062] (Evaluation of crack suppression at low temperatures by low-temperature winding test) Evaluation of crack suppression at low temperatures was performed by a low-temperature winding test. Insulated wires were prepared using resin compositions No. 1 to No. 5 in an insulating layer (average thickness 500 μm), and the crack suppression effect at low temperatures was evaluated based on UL Standard 758. The wires were cooled at −30° C. for 4 hours, wound six times around a mandrel with a diameter twice the outer diameter of the insulated wire (1500 μm), and visually inspected for the occurrence of cracks. A test in which no cracks were generated was deemed to pass.

[0063] Samples No. 1 and No. 2 contain an olefin resin, polyvinyl chloride, a fluororesin, or a combination thereof as a primary component, and further contain a flame retardant and crushed shells, with the crushed shell content being 5% by mass or more and 35% by mass or less. From the results in Table 1, Samples No. 1 and No. 2 achieved good results in tensile elongation and crack inhibition evaluation at low temperatures. On the other hand, Sample No. 3, which contained more than 35% by mass of crushed shells, did not achieve sufficient tensile elongation. Samples No. 4, which contained no crushed shells but 6% by mass of limestone-derived calcium carbonate, and No. 5, which contained neither crushed shells nor calcium carbonate, achieved good tensile elongation but did not achieve good results in the crack inhibition evaluation at low temperatures.

[0064] The above results demonstrate that the resin composition reduces the environmental impact and can suppress cracking at low temperatures even when the content of flame retardant is high.

[0065] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0066] 1 insulated wire 2 conductor 3 insulating layer

Claims

1. It contains resin components as its main component, Furthermore, it contains flame retardants and crushed seashells, The above resin component is an olefin resin, polyvinyl chloride, fluororesin, or a combination thereof. A resin composition for insulating layers, wherein the content of the above-mentioned crushed seashell material is 5% by mass or more and 35% by mass or less.

2. The insulating layer resin composition according to claim 1, wherein the maximum particle size of the crushed seashell material is 50 μm or less.

3. The above crushed seashell material contains particles with an aspect ratio of 3 to 20. The insulating layer resin composition according to claim 1 or claim 2, wherein the content of the above particles in the crushed seashell material is 30% by mass or more.

4. The resin composition for insulating layers according to claim 1 or claim 2, wherein the above resin component comprises polypropylene.

5. The resin composition for insulating layers according to claim 1 or claim 2, wherein the flame retardant is antimony trioxide.

6. The insulating layer resin composition according to claim 5, wherein the antimony trioxide content is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the resin component.

7. A linear conductor, The conductor comprises one or more insulating layers laminated on its outer surface, The one or more insulating layers described above are An insulated wire comprising the resin composition for insulating layer described in claim 1 or claim 2.