阅读说明：本技术 电线包覆材料用组合物、绝缘电线以及线束 (Composition for wire coating material, insulated wire, and wire harness ) 是由 岛田达也 于 2019-02-27 设计创作，主要内容包括：课题在于提供一种电线包覆材料用组合物和使用了该电线包覆材料用组合物的绝缘电线和线束,所述电线包覆材料用组合物为阻燃性优异的能够进行硅烷交联的聚烯烃类组合物,其柔软性优异,并且耐熔融性、耐加热变形性优异。所述电线包覆材料用组合物包含：(A)将硅烷偶联剂接枝聚合至聚烯烃上而得到的硅烷接枝聚烯烃；(B)未改性聚烯烃；(C)具有选自羧基、酯基、酸酐基、氨基、环氧基中的一种或两种以上的官能团的改性聚烯烃；(D)阻燃剂；和(E)交联催化剂,主旨在于,所述(A)硅烷接枝聚烯烃的硅烷接枝前的聚烯烃的密度为0.855g/cm<Sup>3</Sup>～0.890g/cm<Sup>3</Sup>,熔点为80℃以上,所述(B)未改性聚烯烃的密度为0.855g/cm<Sup>3</Sup>～0.950g/cm<Sup>3</Sup>。(The composition for an electric wire covering material is a silane-crosslinkable polyolefin composition having excellent flame retardancy and excellent flexibility, and is excellent in melting resistance and heat distortion resistance. The composition for an electric wire covering material comprises: (A) silane-grafted polyolefin obtained by graft polymerizing a silane coupling agent onto polyolefin; (B) an unmodified polyolefin; (C) a modified polyolefin having one or two or more functional groups selected from a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group; (D) a flame retardant; and (E) a crosslinking catalyst, characterized in that the polyolefin before silane-grafting of the (A) silane-grafted polyolefin has a density of 0.855g/cm 3 ～0.890g/cm 3 A melting point of 80 ℃ or higher, and the density of the unmodified polyolefin (B) is 0.855g/cm 3 ～0.950g/cm 3 。)

1. A composition for a covering material for an electric wire, comprising:

(A) silane-grafted polyolefin obtained by graft polymerizing a silane coupling agent onto polyolefin;

(B) an unmodified polyolefin;

(C) a modified polyolefin having one or two or more functional groups selected from a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group;

(D) a flame retardant; and

(E) a cross-linking catalyst, which is a catalyst,

the polyolefin before silane-grafting of the (A) silane-grafted polyolefin has a density of 0.855g/cm³～0.890g/cm³The melting point is above 80 ℃,

the unmodified polyolefin (B) has a density of 0.855g/cm³～0.950g/cm³。

2. The composition for an electric wire covering material according to claim 1, wherein the polyolefin before silane-grafting of the (a) silane-grafted polyolefin has a density of 0.865g/cm³～0.880g/cm³A melt flow rate of 0.5g/10 min to 5g/10 min under a load of 2.16kg at 190 ℃, a Shore A hardness of 55 to 70, a flexural modulus of elasticity of 3MPa to 50MPa, a melting point of 100 ℃ or higher,

the melt flow rate of the unmodified polyolefin (B) at 190 ℃ under a load of 2.16kg is 0.5g/10 min-5 g/10 min, the flexural modulus of elasticity is 3 MPa-200 MPa, and the melting point is above 65 ℃.

3. The composition for an electric wire covering material according to claim 1 or 2, comprising:

30 to 90 parts by mass of the silane-grafted polyolefin (A); and

10 to 70 parts by mass in total of the unmodified polyolefin (B) and the modified polyolefin (C),

based on 100 parts by mass of the total of the components (A), (B) and (C),

as the (D) flame retardant, there are included:

(D-1) 10 to 100 parts by mass of a metal hydroxide,

(D-2) 10 to 40 parts by mass of a bromine-based flame retardant and 5 to 20 parts by mass of antimony trioxide

At least one of the above-mentioned (b),

based on 100 parts by mass of the total of the components (A), (B) and (C),

contains 0.01 to 1 part by mass of the crosslinking catalyst (E).

4. The composition for an electric wire covering material according to any one of claims 1 to 3,

based on 100 parts by mass of the total of the components (A), (B) and (C),

the composition for an electric wire covering material further comprises:

(F)1 to 10 parts by mass of an antioxidant;

(G)1 to 10 parts by mass of a metal deactivator; and

(H)1 to 10 parts by mass of a lubricant.

5. The composition for an electric wire covering material according to any one of claims 1 to 4,

based on 100 parts by mass of the total of the components (A), (B) and (C),

the composition for an electric wire covering material further comprises:

(I-1)1 to 15 parts by mass of zinc oxide and 1 to 15 parts by mass of an imidazole compound,

(I-2)1 to 15 parts by mass of zinc sulfate

Any of the above.

6. The composition for an electric wire covering material according to any one of claims 1 to 5,

the polyolefin constituting the silane-grafted polyolefin (A) and the unmodified polyolefin (B) are each one or two or more selected from the group consisting of an ultra-low-density polyethylene, a linear low-density polyethylene, and a low-density polyethylene.

7. An insulated wire comprising a wire coating material obtained by crosslinking the composition for a wire coating material according to any one of claims 1 to 6.

8. A wire harness, characterized in that the wire harness has the insulated electric wire of claim 7.

Technical Field

The invention relates to a composition for an electric wire coating material, an insulated electric wire and a wire harness.

Background

Insulated wires used in automobiles are sometimes used in places where high temperatures occur, such as around engines, and high heat resistance is required. Conventionally, crosslinked polyvinyl chloride resins and crosslinked polyolefin resins have been used as such a covering material for insulated wires. As a method for crosslinking these resins, a method of crosslinking with an electron beam (for example, patent document 1) and a silane crosslinking (for example, patent document 2) are known.

Disclosure of Invention

Problems to be solved by the invention

Crosslinking with silane, as it is called water crosslinking, promotes crosslinking with moisture in the air. Therefore, in order to prevent the occurrence of an unfavorable crosslinking reaction during molding and the formation of a partially cured product, a method of separately batching and mixing the silane-modified resin, the crosslinking catalyst, and other components is employed. However, since the crosslinking catalyst and other components are added to the non-crosslinked resin in batches, the crosslinking degree of the entire resin may be lowered, and the heat resistance and mechanical properties may be lowered.

In addition, in recent years, due to the spread of hybrid vehicles and the like, electric wires corresponding to high voltage and high current are required, and electric wires having a large wire diameter are increasing. In the case of an insulated wire having a large diameter, flexibility of the covering material is required from the viewpoint of ensuring assembly workability. However, when the coating material is made soft, there are problems such as melting of particles as a raw material during production and an insulated wire before crosslinking, and deformation of the wire coating material during heating.

The present invention addresses the problem of providing a composition for an electric wire covering material, which is a silane-crosslinkable polyolefin composition having excellent flame retardancy and is excellent in flexibility, melting resistance and heat distortion resistance, and an insulated wire and a wire harness using the same.

Means for solving the problems

The composition for an electric wire coating material according to the present invention is characterized by comprising: (A) silane-grafted polyolefin obtained by graft polymerizing a silane coupling agent onto polyolefin; (B) an unmodified polyolefin; (C) a modified polyolefin having one or two or more functional groups selected from a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group; (D) a flame retardant; and (E) a crosslinking catalyst, the polyolefin before silane-grafting of the (A) silane-grafted polyolefin having a density of 0.855g/cm³～0.890g/cm³A melting point of 80 ℃ or higher, and the unmodified polymer (B)The density of the olefin was 0.855g/cm³～0.950g/cm³。

The density of the polyolefin before silane-grafting of the (A) silane-grafted polyolefin is preferably 0.865g/cm³～0.880g/cm³The melt flow rate under a load of 190 ℃ X2.16 kg is preferably 0.5g/10 min to 5g/10 min, the Shore A hardness is preferably 55 to 70, the flexural modulus of elasticity is preferably 3MPa to 50MPa, and the melting point is preferably 100 ℃ or higher, and the melt flow rate under a load of 190 ℃ X2.16 kg of the unmodified polyolefin (B) is preferably 0.5g/10 min to 5g/10 min, the flexural modulus of elasticity is preferably 3MPa to 200MPa, and the melting point is preferably 65 ℃ or higher.

The composition for an electric wire covering material preferably comprises: 30 to 90 parts by mass of the silane-grafted polyolefin (A); and 10 to 70 parts by mass in total of the unmodified polyolefin (B) and the modified polyolefin (C), and the flame retardant (D) preferably contains, based on 100 parts by mass in total of the unmodified polyolefin (B) and the modified polyolefin (C):

(D-1) 10 to 100 parts by mass of a metal hydroxide; or

(D-2) 10 to 40 parts by mass of a bromine-based flame retardant and 5 to 20 parts by mass of antimony trioxide

At least one of the above-mentioned (b),

the crosslinking catalyst (E) is preferably contained in an amount of 0.01 to 1 part by mass based on 100 parts by mass of the total of the components (A), (B) and (C).

The composition for an electric wire covering material preferably further comprises, based on 100 parts by mass of the total of the components (a), (B) and (C): (F)1 to 10 parts by mass of an antioxidant; (G)1 to 10 parts by mass of a metal deactivator; and (H)1 to 10 parts by mass of a lubricant.

The composition for an electric wire covering material preferably further comprises, based on 100 parts by mass of the total of the components (a), (B) and (C):

(I-1)1 to 15 parts by mass of zinc oxide and 1 to 15 parts by mass of an imidazole compound, or

(I-2)1 to 15 parts by mass of zinc sulfate

Any of the above.

The polyolefin constituting the silane-grafted polyolefin (a) and the unmodified polyolefin (B) are preferably one or two or more selected from the group consisting of ultra-low-density polyethylene, linear low-density polyethylene, and low-density polyethylene.

The insulated wire according to the present invention includes an electric wire coating material formed by crosslinking the electric wire coating material composition.

The wire harness according to the present invention is characterized by having the insulated electric wire described above.

Effects of the invention

According to the composition for an electric wire covering material of the present invention, it is possible to provide a composition for an electric wire covering material, which is a silane-crosslinkable polyolefin-based composition having excellent flame retardancy, and which is excellent in flexibility, melting resistance and heat distortion resistance.

Generally, the lower the density of polyolefin, the more excellent the flexibility, but the melting point tends to be lowered, and it is difficult to achieve both the flexibility and the melt resistance and the heat distortion resistance. The present invention has excellent flexibility, and excellent melt resistance and heat distortion resistance by setting the density and melting point within appropriate ranges.

Detailed Description

Next, embodiments of the present invention will be described in detail.

The composition for an electric wire covering material according to the present invention (hereinafter, also referred to as "the present composition") comprises: (A) silane-grafted polyolefin, (B) unmodified polyolefin, (C) modified polyolefin, (D) flame retardant, and (E) crosslinking catalyst. Preferably, the lubricant further comprises (F) an antioxidant, (G) a metal deactivator, (H) a lubricant, and (I) a zinc-based stabilizer. The details of each component will be described below.

(A) The silane-grafted polyolefin is a polyolefin into which silane-grafted chains are introduced by graft-polymerizing a silane coupling agent onto a polyolefin that becomes a main chain.

The polyolefin constituting the silane-grafted polyolefin (A) preferably has a density of 0.855g/cm³～0.890g/cm³Example (A) ofInside the enclosure. More preferably 0.860g/cm³～0.885g/cm³Further preferably in the range of 0.865g/cm³～0.880g/cm³Within the range of (1). When the density of the polyolefin is low, the polyolefin is more easily grafted with the silane coupling agent and the flexibility is more excellent, but when the density is less than 0.855g/cm³The melting point tends to be too low, and the pellets and the molded article before crosslinking tend to melt and deform during heating. Further, the heat resistance and abrasion resistance of the electric wire are likely to be lowered, and the kneading property may be lowered because the resin is excessively soft. In another aspect, the polyolefin has a density greater than 0.890g/cm³In the case, the graft ratio may be decreased, the crosslinking density may be decreased, or the flexibility may be decreased. The density of the polyolefin can be measured according to ASTM D790.

The present compositions may be crosslinked by contact with steam. In this case, the melting point of the polyolefin constituting the silane-grafted polyolefin is preferably 80 ℃ or higher from the viewpoint of preventing the molded articles from melting together. More preferably 100 ℃ or higher, and still more preferably 120 ℃ or higher. When the melting point of the polyolefin is less than 80 ℃, pellets before molding and a molded article before crosslinking are easily melted, and deformation during heating is easily caused. The upper limit of the melting point is not particularly limited, but polyolefin excellent in flexibility and other physical properties is usually about 135 ℃ or lower. The melting point of the polyolefin can be measured according to JIS K7121.

In general, the more branched the polyolefin has in the polymer chain and the longer the branched side chain, the lower the density and the more excellent the flexibility, but the lower the melting point. By selecting a polyolefin having both a highly densified crystalline portion with few branches and an amorphous portion having a long branched side chain and a low density as the polyolefin constituting the silane-grafted polyolefin, a polyolefin having an appropriate density and melting point can be obtained. This can satisfy melting resistance and heat distortion resistance while maintaining flexibility.

For the polyolefin constituting the silane-grafted polyolefin (A), the melt flow rate (hereinafter, also referred to as "MFR") at 190 ℃ under a load of 2.16kg is preferably in the range of 0.5g/10 min to 5.0g/10 min. More preferably, it is in the range of 1.0g/10 min to 3.0g/10 min. When the MFR of the polyolefin is 0.5g/10 min or more, the extrusion moldability is excellent and the productivity is improved. On the other hand, when the MFR is 5g/10 min or less, the resin shape is easily maintained at the time of molding, and productivity is improved. The MFR can be measured according to ASTM D1238.

The Shore A hardness of the polyolefin used for (A) the silane-grafted polyolefin is preferably in the range of 55 to 70. Further, the flexural modulus of elasticity of the polyolefin used for the silane-grafted polyolefin is preferably in the range of 3MPa to 50 MPa. When the shore a hardness and the flexural modulus are within the above ranges, flexibility is excellent and mechanical properties such as abrasion resistance are also excellent. The shore a hardness can be measured according to ASTM D2240, and the flexural modulus can be measured according to ASTM D790.

As the polyolefin used for the silane-grafted polyolefin (A), there may be mentioned homopolymers of ethylene and propylene, and copolymers of ethylene or propylene with an alpha-olefin. These may be used alone or in combination of two or more. Preferably, at least one selected from the group consisting of polyethylene, polypropylene, ethylene-butene copolymer and ethylene-octene copolymer is used.

As the polyethylene, Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Very Low Density Polyethylene (VLDPE), metallocene low density polyethylene are preferably used. These may be used alone or in combination. When these low-density polyethylenes are used, the flexibility of the electric wire is particularly excellent and the extrusion productivity is improved.

As the polyolefin, an olefin-based polyolefin elastomer can be used. When a polyolefin elastomer is used, flexibility can be imparted to the covering material. Examples of the polyolefin elastomer include: polyolefin-based thermoplastic elastomers (TPO) such as polyethylene-based elastomers (PE elastomers) and polypropylene-based elastomers (PP elastomers), ethylene-propylene rubbers (EPM, EPR), ethylene-propylene-diene copolymers (EPDM, EPT), and the like.

The silane coupling agent used for (a) the silane-grafted polyolefin is not particularly limited, and for example, there can be exemplified: vinyl alkoxysilanes such as vinyl trimethoxysilane, vinyl triethoxysilane, and vinyl tributoxysilane; vinyltriacetoxysilane; gamma-methacryloxypropyltrimethoxysilane; gamma-methacryloxypropylmethyldimethoxysilane, and the like. These may be used alone or in combination of two or more.

From the viewpoint of preventing excessive crosslinking, the upper limit of the graft amount of the silane coupling agent may be preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less. On the other hand, the lower limit of the graft amount is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and further preferably 1.5% by mass or more. When the graft amount is 0.1% or more, crosslinking is sufficiently performed when the composition is crosslinked to prepare an electric wire coating material, and the electric wire coating material is excellent in heat resistance and mechanical strength. The graft amount is an amount expressed in percentage by mass of the silane coupling agent to be grafted with respect to the mass of the polyolefin before silane grafting.

(A) When the silane-grafted polyolefin is mixed with a crosslinking catalyst and crosslinked, the gel fraction is preferably 85% or more. More preferably 90% or more. When the gel fraction is 85% or more, the present composition is sufficiently crosslinked when crosslinked, and is excellent in heat resistance and mechanical strength.

The gel fraction of the silane-grafted polyolefin can be obtained, for example, by the following measurement method.

A material obtained by adding about 0.5 part by mass of a crosslinking catalyst to 100 parts by mass of a silane-grafted polyolefin was kneaded at 200 ℃ for 5 minutes, and the obtained block was subjected to compression molding at 200 ℃ for 3 minutes to form a sheet having a thickness of 1 mm. The resulting mixture was crosslinked in a constant temperature and humidity bath having a humidity of 95% and a temperature of 60 ℃ for 12 hours, and then dried.

About 0.1g of the test piece was extracted from the obtained molded sheet, and the test piece was immersed in a xylene solvent at 120 ℃ for 20 hours, taken out, dried, and weighed. The gel fraction was determined as a value in percentage of the mass after xylene impregnation relative to the mass before xylene impregnation. When a substance other than the silane-grafted polyolefin is contained in the crosslinked product before and after xylene impregnation, the gel fraction of the silane-grafted polyolefin can be calculated by removing the mass thereof. For example, the crosslinking catalyst is considered to be contained in the crosslinked material even after xylene impregnation, and in the case where the crosslinking catalyst is diluted into the binder resin as a non-crosslinking component and added as described later, the binder resin can be considered to be completely dissolved into xylene and calculated after xylene impregnation.

(A) The silane-grafted polyolefin can be prepared, for example, by adding a radical initiator to the polyolefin and the silane coupling agent and kneading them by means of a twin-screw or single-screw extrusion kneader. In addition, a method of adding a silane coupling agent when polymerizing to a polyolefin may be used.

In this case, the amount of the silane coupling agent is preferably in the range of 0.5 to 5 parts by mass, more preferably 3 to 5 parts by mass, based on 100 parts by mass of the polyolefin. When the amount of the silane coupling agent is 0.5 parts by mass or more, the polyolefin is sufficiently grafted. On the other hand, when the amount of the silane coupling agent is 5 parts by mass or less, the crosslinking reaction can be suppressed from excessively progressing during kneading, the generation of a gel-like substance can be suppressed, and productivity and workability are excellent.

Examples of the radical initiator include: organic peroxides such as dicumyl peroxide (DCP), benzoyl peroxide, dichlorobenzoyl peroxide, di-t-butyl peroxide, butyl peracetate, t-butyl perbenzoate, and 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane. As free radical initiator, dicumyl peroxide (DCP) is preferred.

In the case of using dicumyl peroxide (DCP) as a radical initiator, it is preferable to set the kneading temperature at the time of graft polymerization of the silane coupling agent to the polyolefin to 120 ℃ or higher.

The amount of the radical initiator to be blended is preferably in the range of 0.025 parts by mass to 0.1 parts by mass with respect to 100 parts by mass of the polyolefin to be silane-grafted. If the amount of the radical initiator is 0.025 parts by mass or more, the graft reaction proceeds sufficiently. On the other hand, when the amount of the radical initiator compounded is 0.1 part by mass or less, the excessive progress of the graft reaction can be suppressed, and the objective silane-grafted polyolefin can be easily obtained.

The radical initiator may be added by diluting talc or calcium carbonate as an inert substance, or may be added by diluting ethylene-propylene rubber, ethylene-propylene-diene rubber, polyolefin, etc. and granulating them.

(B) The unmodified polyolefin is, for example, a polyolefin composed of a hydrocarbon to which a modification group is not introduced, which is formed by graft polymerization, copolymerization, or the like. Specifically, there may be mentioned: ethylene, homopolymers of propylene, copolymers of ethylene or propylene with alpha-olefins. These may be used alone or in combination of two or more. Preferably, at least one selected from the group consisting of polyethylene, polypropylene, ethylene-butene copolymer and ethylene-octene copolymer is used.

As the polyethylene, Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Very Low Density Polyethylene (VLDPE), metallocene low density polyethylene are preferably used. These may be used alone or in combination. When these low-density polyethylenes are used, the flexibility of the electric wire is particularly excellent and the extrusion productivity is improved.

As the unmodified polyolefin (B), an olefin-based polyolefin elastomer can be used. When a polyolefin elastomer is used, flexibility can be imparted to the covering material. Examples of the polyolefin elastomer include: polyolefin-based thermoplastic elastomers (TPO) such as polyethylene-based elastomers (PE elastomers) and polypropylene-based elastomers (PP elastomers), ethylene-propylene rubbers (EPM, EPR), ethylene-propylene-diene copolymers (EPDM, EPT), and the like.

As the (B) unmodified polyolefin, the same polyolefin as that used in the main chain of the (a) silane-grafted polyolefin may be used, or a different polyolefin may be used. When the same kind of polyolefin is used, the compatibility is excellent.

As (B) the unmodified polyolefin, it is possible to use a polyolefin having a density of 0.855g/cm³～0.950g/cm³An unmodified polyolefin in the range of (a). More excellentIs selected at 0.860g/cm³～0.940g/cm³Within the range of (1). When the density of the unmodified polyolefin is less than 0.855g/cm³In the case, the melting point is liable to become too low, and the pellets and the molded article before crosslinking are liable to melt and to be deformed during heating. In addition, the resin may become excessively soft, and hence the kneading property may be lowered. On the other hand, when the density of the unmodified polyolefin is more than 0.950g/cm³In the case of this, flexibility is lowered.

(B) The melting point of the unmodified polyolefin is preferably 65 ℃ or higher. More preferably 80 ℃ or higher, and still more preferably 100 ℃ or higher. When the melting point of the unmodified polyolefin (B) is 65 ℃ or higher, the melt resistance and the heat distortion resistance are excellent. When a polyolefin having a sufficiently high melting point is used as the polyolefin constituting the crosslinking component, i.e., (A) the silane-grafted polyolefin, (B) the melting point of the unmodified polyolefin may be lower than that of the polyolefin constituting (A) the silane-grafted polyolefin. The melting point of the polyolefin can be measured according to JIS K7121.

(B) The MFR of the unmodified polyolefin is preferably in the range of 0.5g/10 min to 5.0g/10 min. More preferably, it is in the range of 1.0g/10 min to 3.0g/10 min. When the MFR of the polyolefin is 0.5g/10 min or more, the extrusion moldability is excellent and the productivity is improved. On the other hand, when the MFR is 5g/10 min or less, the resin shape is easily maintained at the time of molding, and productivity is improved. The MFR can be measured according to ASTM D1238.

The flexural modulus of elasticity of the unmodified polyolefin is preferably in the range of 3MPa to 200 MPa. More preferably 10MPa to 100 MPa. When the flexural modulus is within the above range, flexibility is excellent. The flexural modulus can be measured according to ASTM D790.

(C) The modified polyolefin is a modified polyolefin having one or more functional groups selected from a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group. (C) The modified polyolefin may be a polyolefin having a functional group introduced by graft polymerizing a polymerizable compound having the functional group onto an unmodified base polyolefin composed of one or two or more α -olefins, or a polyolefin having a functional group introduced by copolymerizing a polymerizable compound having the functional group with an olefin polymerizable with the polymerizable compound. However, the polyolefin into which a silanol derivative is introduced by methacryloxyalkylsilane or the like is classified as (a) a silane-grafted polyolefin, and is therefore excluded.

(C) The modified polyolefin has one or two or more functional groups selected from a carboxyl group, an ester group, an acid anhydride group, an amino group and an epoxy group, and therefore exhibits a high interaction with the inorganic component, and has a polyolefin chain, and therefore has a high affinity with resin components such as (a) the silane-grafted polyolefin and (B) the unmodified polyolefin. Therefore, the modified polyolefin (C) can be used as a compatibilizer for the resin component and the inorganic component, and the dispersibility and adhesiveness of the inorganic component are excellent.

The polymerizable compound having a carboxyl group is not particularly limited as long as it has a polymerizable group such as a carbon-carbon double bond and a carboxyl group in the molecule. For example, there may be mentioned: acrylic acid, methacrylic acid, crotonic acid, α -chloroacrylic acid, itaconic acid, butenetricarboxylic acid, maleic acid, fumaric acid, or derivatives thereof containing a part of the molecular structure. In the case where these acids form an acid anhydride, an acid anhydride group can be introduced by using an acid anhydride thereof.

As the polymerizable compound having an ester group, an ester compound obtained by a reaction of the above-described polymerizable compound having a carboxyl group with an alcohol can be used. Further, the ester compound may be obtained by reacting an alcohol having a carbon-carbon double bond with various carboxylic acids. Examples of such compounds include: vinyl acetate, vinyl propionate, and the like.

The polymerizable compound having an amino group is not particularly limited as long as it has a polymerizable group such as a carbon-carbon double bond and an amino group in the molecule. For example, there may be mentioned: esters obtained by the reaction of the above-mentioned polymerizable compound having a carboxyl group with an alkanolamine, vinylamine, allylamine, or derivatives containing them in a part of the molecular structure, and the like.

The polymerizable compound having an epoxy group is not particularly limited as long as it has a polymerizable group such as a carbon-carbon double bond and an epoxy group in the molecule. For example, there may be mentioned: glycidyl esters of acids obtained by the reaction of the above-mentioned polymerizable compound having a carboxyl group with glycidyl alcohol; glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, glycidyl oxyethyl vinyl ether, and styrene-p-glycidyl ether; p-glycidyl styrene; or a derivative thereof contained in a part of the molecular structure.

The polymerizable monomer copolymerizable with the polymerizable compound having a functional group is not particularly limited as long as it is a compound having a polymerizable group such as a carbon-carbon double bond in the molecule. For example, an olefin monomer having no functional group such as ethylene or propylene may be used, or a polymerizable monomer having a functional group other than a carboxyl group or an epoxy group may be used. These may be used alone or in combination.

The blending amount of the modified polyolefin (C) is preferably 3 to 15 parts by mass with respect to 100 parts by mass of the total of the resin components (a) to (C). More preferably 4 to 10 parts by mass. When the modified polyolefin (C) is contained in an amount of 3 parts by mass or more, the affinity between the resin component and the inorganic component is excellent.

The blending ratio of the resin components (a) to (C) when the total of (a) to (C) is 100 parts by mass is preferably: (A) 30 to 90 parts by mass of a silane-grafted polyolefin, and the total of (B) an unmodified polyolefin and (C) a modified polyolefin is 10 to 70 parts by mass. When the amount is within the above range, flexibility is excellent, a sufficient crosslink density can be obtained, and heat resistance and abrasion resistance are excellent.

Examples of the flame retardant (D) include metal hydroxides and bromine flame retardants. When a metal hydroxide is used, a flame retardant for imparting flame retardancy may be used alone, and when a bromine-based flame retardant is used, the flame retardancy can be improved by using antimony trioxide as a flame retardant auxiliary in combination. (D) The flame retardant may be used alone or in combination of a metal hydroxide flame retardant and a bromine flame retardant. From the viewpoint of excellent cost and heat distortion resistance, a metal hydroxide is preferable as the flame retardant.

As the metal hydroxide, there can be mentioned: magnesium hydroxide, aluminum hydroxide, zirconium hydroxide, and the like. Among the above, magnesium hydroxide is preferred from the viewpoint of excellent cost and heat distortion resistance. The magnesium hydroxide may be any of synthetic magnesium hydroxide obtained by chemical synthesis or natural magnesium hydroxide obtained by pulverizing naturally occurring minerals.

The average particle diameter of the metal hydroxide is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm. When the average particle diameter of the metal hydroxide is 0.1 μm or more, aggregation is less likely to occur, and when it is 10 μm or less, the dispersibility is excellent. The metal hydroxide may be treated with a surface treatment agent such as a silane coupling agent, a higher fatty acid, or a polyolefin wax for the purpose of improving dispersibility. In the present invention, since the modified polyolefin (C) is contained, the dispersibility of the metal hydroxide is excellent even without the surface treatment.

Examples of the bromine-based flame retardant include: bromine flame retardants having a phthalimide structure such as ethylenebistetrabromophthalimide and ethylenebistribromophthalimide, ethylenebistribromodiphenyl (pentabromophenyl), tetrabromobisphenol a (TBBA), Hexabromocyclododecane (HBCD), TBBA-carbonate oligomer, TBBA-epoxy oligomer, brominated polystyrene, TBBA-bis (dibromopropyl ether), poly (dibromopropyl ether), Hexabromobenzene (HBB), and the like. These may be used alone or in combination of two or more. From the viewpoint of high melting point, excellent heat resistance, and the like, it is preferable to use at least one or more selected from phthalimide flame retardants, ethylenebis (pentabromophenyl) s, and derivatives thereof.

The flame retardancy can be improved by adding antimony trioxide as a flame retardant auxiliary together with a bromine-based flame retardant. Antimony trioxide is preferably used in a purity of 99% or more. Antimony trioxide is used by pulverizing antimony trioxide produced as a mineral to form fine particles. In this case, the average particle diameter is preferably 3 μm or less, and more preferably 1 μm or less. When the thickness is 3 μm or less, the interface strength with the resin is excellent. For the purpose of improving dispersibility, antimony trioxide may be treated with a surface treatment agent such as a silane coupling agent, a higher fatty acid, or a polyolefin wax.

When the metal hydroxide is used alone, it is preferably added in a range of 10 to 100 parts by mass with respect to 100 parts by mass of the total of the resin components (a) to (C). When the amount is 10 parts by mass or more, the flame retardancy is excellent. On the other hand, even if more than 100 parts by mass of the metal hydroxide is added, improvement of flame retardancy cannot be expected, and the upper limit may be set to 100 parts by mass from the viewpoint of excellent flexibility and the like.

When a system in which a bromine-based flame retardant and an inorganic flame retardant aid are used in combination is used as a flame retardant component, the ratio of the bromine-based flame retardant to the inorganic flame retardant is preferably such that, in terms of an equivalent ratio: inorganic flame retardant auxiliary agent 3: 1-2: 1 contains bromine flame retardant and inorganic flame retardant auxiliary agent.

When a bromine-based flame retardant and an inorganic flame retardant aid are used as the flame retardant, the amount of the bromine-based flame retardant and the amount of antimony trioxide are preferably in the range of 10 to 40 parts by mass and 5 to 20 parts by mass, respectively, based on 100 parts by mass of the total of the resin components (a) to (C). When the bromine-based flame retardant is 10 parts by mass or more, the flame retardancy is excellent. On the other hand, even if more than 40 parts by mass of the bromine-based flame retardant is added, improvement of flame retardancy cannot be expected, and the upper limit may be set to 100 parts by mass from the viewpoint of excellent flexibility and the like.

When a metal hydroxide and a bromine-based flame retardant are used in combination as the flame retardant, the amount of each additive may be reduced, and the metal hydroxide, the bromine-based flame retardant and the antimony trioxide are preferably incorporated in the ranges of 10 to 50 parts by mass, 5 to 20 parts by mass and 5 to 20 parts by mass, respectively, based on 100 parts by mass of the total of the resin components (a) to (C).

(E) The crosslinking catalyst is a silanol condensation catalyst for silane crosslinking the (a) silane-grafted polyolefin. Examples of the crosslinking catalyst include: carboxylates of metals such as tin, zinc, iron, lead, cobalt, etc., titanates, organic bases, inorganic acids, organic acids, etc. Specifically, the following can be exemplified: dibutyl tin dilaurate, dibutyl tin dimaleate, dibutyl tin diisooctylthioglycolate (in the form of salt of ジブチル ビスイソオクチルチオグリコールエステル), dibutyl tin beta-mercaptopropionate, dibutyl tin diacetate, dioctyl tin dilaurate, stannous acetate, stannous octoate, lead naphthenate, cobalt naphthenate, barium stearate, calcium stearate, tetrabutyl titanate, tetranonyl titanate, dibutyl amine, hexylamine, pyridine, sulfuric acid, hydrochloric acid, toluenesulfonic acid, acetic acid, stearic acid, maleic acid, and the like. Preferred crosslinking catalysts are dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin diisooctylthioglycolate and dibutyltin β -mercaptopropionate.

When the (E) crosslinking catalyst is mixed with the (a) silane-grafted polyolefin, a crosslinking reaction is caused, and therefore it is preferable to perform mixing immediately before coating the electric wire. In this case, in order to improve the dispersibility of the crosslinking catalyst, it is preferable to mix the crosslinking catalyst with the binder resin in advance to prepare a crosslinking catalyst batch and use the crosslinking catalyst batch. When the silane-grafted polyolefin (a) is used in the form of a crosslinking catalyst batch in which a crosslinking catalyst is previously mixed, an unexpected crosslinking reaction of the silane-grafted polyolefin (a) can be prevented, and the crosslinking catalyst is excellent in dispersibility and can sufficiently perform the crosslinking reaction. In addition, by using the crosslinking catalyst batch, the amount of the crosslinking catalyst to be added can be easily controlled.

As the binder resin for crosslinking the catalyst batch, the polyolefins used in the above-mentioned (A) to (C) can be used. Particularly preferred are Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Very Low Density Polyethylene (VLDPE), and metallocene low density polyethylene. When these low-density polyethylenes are used, the flexibility of the electric wire is good, the extrudability is excellent, and the productivity is improved. In addition, for example, a part of the unmodified polyolefin (B) may be used as the binder resin.

The crosslinking catalyst batch preferably contains the crosslinking catalyst in the range of 0.5 to 5 parts by mass with respect to 100 parts by mass of the binder resin. More preferably in the range of 1 to 5 parts by mass. When the amount is 0.5 parts by mass or more, the crosslinking reaction is easily progressed, and when the amount is 5 parts by mass or less, the dispersibility of the catalyst is excellent.

The amount of the crosslinking catalyst (E) is preferably in the range of 0.01 to 1.0 part by mass, more preferably 0.02 to 0.9 part by mass, based on 100 parts by mass of the total of the resin components (a) to (C). If the amount is 0.01 parts by mass or more, the crosslinking reaction is easily progressed, and if the amount is 1.0 parts by mass or less, excessive crosslinking can be prevented.

The antioxidant (F) is preferably a hindered phenol-based antioxidant, and particularly preferably a hindered phenol having a melting point of 200 ℃ or higher. Examples of the hindered phenol antioxidant include: pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], thiodiethylene bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, N ' - (hexane-1, 6-diyl) bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], 2, 4-dimethyl-6- (1-methylpentadecyl) phenol, [ [3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl ] methyl ] phosphonic acid diethyl ester, 3 ', 5,5 ' -hexa-tert-butyl-a, a', a "- (mesitylene-2, 4, 6-tolyl) tri-p-cresol, calcium diethylbis [ [ [ [3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl ] methyl ] phosphonate ], 4, 6-bis (octylthiomethyl) o-cresol, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate ], hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, 1,3, 5-tris [ (4-tert-butyl-3-hydroxy-2, 6-xylyl) methyl ] -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, 2, 6-tert-butyl-4- (4, 6-bis (octylthio) -1,3, 5-triazin-2-ylamino) phenol, 2, 6-di-tert-butyl-4-methylphenol, 2 ' -methylenebis (4-methyl-6-tert-butylphenol), 4 ' -butylidenebis (3-methyl-6-tert-butylphenol), 4 ' -thiobis (3-methyl-6-tert-butylphenol), 3, 9-bis [2- (3- (3-tert-butyl-4-hydroxy-5-methylphenyl) -propionyloxy) -1, 1-dimethylethyl ] -2,4,8, 10-tetraoxaspiro (5,5) undecane, and the like. These may be used alone or in combination of two or more. Examples of hindered phenol antioxidants having a melting point of 200 ℃ or higher include: 3,3 ', 3 ", 5,5 ', 5" -hexa-tert-butyl-a, a ', a "- (mesitylene-2, 4, 6-tolyl) tri-p-cresol, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione and the like.

The amount of the antioxidant (F) added is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total of the resin components (a) to (C). When within the above range, the antioxidant effect is excellent and blooming (ブルーム) and the like can be suppressed.

As the (G) metal deactivator, a copper deactivator capable of preventing catalytic oxidation of a heavy metal such as copper, a chelating agent, or the like can be used. As the metal deactivator, there can be exemplified: hydrazide derivatives such as 2, 3-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] propionohydrazide and salicylic acid derivatives such as 3- (N-salicyloyl) amino-1, 2, 4-triazole. As the metal deactivator, a salicylic acid derivative such as 3- (N-salicyloyl) amino-1, 2, 4-triazole is preferable.

The amount of the metal deactivator (G) added is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total of the resin components (a) to (C). When the content is within the above range, copper toxicity is prevented with excellent effect, and blooming and cross-linking failure can be suppressed.

(H) The lubricant is not particularly limited, and any of an internal lubricant and an external lubricant may be used. As the lubricant, there may be mentioned: hydrocarbons such as liquid paraffin, solid paraffin, and polyethylene wax; fatty acids such as stearic acid, oleic acid, erucic acid, etc.; fatty acid amides such as higher alcohols, stearic acid amide, oleic acid amide, and erucic acid amide; alkylene fatty acid amides such as methylene bis stearamide and ethylene bis stearamide; metal soaps such as metal stearate; ester lubricants such as glyceryl monostearate, stearyl stearate, and hardened oil. As the lubricant, a fatty acid derivative such as erucic acid, oleic acid, stearic acid, or the like, or a polyethylene wax is preferably used from the viewpoint of compatibility with the resin component.

The amount of the lubricant (H) added is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the total of the resin components (a) to (C). When the amount is within the above range, a sufficient lubricating effect can be obtained.

A combination of (I-1) zinc oxide and an imidazole compound or (I-2) zinc sulfide as the component (I) is used as an additive for improving heat resistance and long-term heating resistance. The same effect can be obtained by selecting any of the modes of adding only (I-2) zinc sulfide or using (I-1) zinc oxide and imidazole compound in combination.

The zinc oxide can be obtained, for example, by a method of oxidizing zinc vapor generated by adding a reducing agent such as coke to zinc ore and firing the mixture with air, or a method of using zinc sulfate or zinc chloride as a raw material. The method for producing zinc oxide is not particularly limited, and zinc oxide can be produced by any method. In addition, as for zinc sulfide, zinc sulfide produced by a known method can be used in the production method. The average particle diameter of zinc oxide and zinc sulfide is preferably 3 μm or less, more preferably 1 μm or less. When the average particle diameters of zinc oxide and zinc sulfide become smaller, the interface strength with the resin is improved, and the dispersibility is also improved.

As the imidazole compound, mercaptobenzimidazole is preferable. Examples of mercaptobenzimidazoles include: 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 4-mercaptomethylbenzimidazole, 5-mercaptomethylbenzimidazole, and the like, and zinc salts thereof. 2-mercaptobenzimidazole and its zinc salt are particularly preferable because they have a high melting point and little sublimation during mixing and are therefore stable at high temperatures.

Regarding the component (I), it is preferable to add 1 to 15 parts by mass of each of the zinc oxide (I-1) and the imidazole compound or 1 to 15 parts by mass of the zinc sulfide (I-2) to 100 parts by mass of the total of the resin components (A) to (C). When the amount is within the above range, the composition is excellent in heat resistance and long-term heating resistance, and the particles are less likely to aggregate and are excellent in dispersibility.

The composition for an electric wire covering material according to the present invention may contain various additives within a range not to impair the object of the present invention. Examples of the additive material include inorganic fillers, pigments, and silicone oils.

For example, when an inorganic filler is added, the hardness of the resin can be adjusted by adding the filler, and the meltability and the heat distortion resistance can be improved. Examples of the inorganic filler include magnesium oxide and calcium carbonate. From the viewpoint of resin strength and the like, the amount of the inorganic filler added is preferably 30 parts by mass or less with respect to 100 parts by mass of the total of the resin components (a) to (C).

The composition for an electric wire covering material according to the present invention can be prepared by, for example, mixing the respective components (a) to (E) with various additive components added as needed and kneading them using a twin-screw extruder or the like, but when the silane-grafted polyolefin and the crosslinking catalyst are mixed, a crosslinking reaction proceeds due to moisture in the atmosphere. From the viewpoint of preventing a crosslinking reaction or other residual reaction during storage, it is preferable to mix the components immediately before coating the electric wire. As such a method, it is preferable to prepare a silane grafting batch, a flame retardant batch, a crosslinking catalyst batch separately in advance, and to prepare particles in advance.

The silane-grafted batch is a batch comprising (a) a silane-grafted polyolefin. The flame retardant batch is a batch comprising (B) an unmodified polyolefin, (C) a modified polyolefin, and (D) a flame retardant. The crosslinking catalyst batch is a batch comprising (E) a crosslinking catalyst and a binder resin. (F) The components of (I) to (I) and the various additive components added as needed may be included in any of the silane graft batch, the flame retardant batch, and the crosslinking catalyst batch, as long as they do not hinder the object of the present invention.

The insulated wire and the wire harness according to the present invention will be explained.

The outer periphery of the conductor of the insulated wire according to the present invention is covered with an insulating layer made of a wire covering material (also simply referred to as a covering material in some cases) obtained by crosslinking the composition for a wire covering material. The conductor of the insulated wire is not particularly limited in terms of its conductor diameter, material of the conductor, and the like, and may be appropriately selected in accordance with the use of the insulated wire, and the like. Examples of the conductor include: copper, copper alloys, aluminum alloys, and the like. From the viewpoint of weight reduction of the electric wire, aluminum or an aluminum alloy is preferable. The insulating layer of the wire coating material may be a single layer or a multilayer of two or more layers.

In the insulated wire of the present invention, the crosslinking degree of the coating material after crosslinking is preferably 50% or more in terms of gel fraction from the viewpoint of heat resistance. More preferably, the gel fraction of the coating material is 60% or more. The gel fraction of the coating material of the insulated wire is generally used as an index of the crosslinked state of the crosslinked wire. The gel fraction of the coating material can be determined, for example, according to JASO D608-92.

For producing the insulated wire of the present invention, each of the above silane graft batch, flame retardant batch, crosslinking catalyst batch may be heated and kneaded using a general kneader such as a banbury mixer, a pressure kneader, a kneading extruder, a twin-screw extruder, a roll, etc., and a composition may be obtained using an extruder, etc., and the composition may be extruded and coated on the outer periphery of a conductor and then crosslinked.

As a method of crosslinking the coating material, crosslinking may be performed by exposing the coating layer of the coated electric wire to water vapor or water. In this case, the reaction is preferably carried out at a temperature ranging from room temperature to 90 ℃ for 48 hours or less. More preferably, the reaction is carried out at a temperature of 50 to 80 ℃ for 8 to 24 hours.

The wire harness of the present invention has the insulated electric wire described above. The wire harness may be in the form of a single wire bundle in which only the insulated wires are bundled together, or in the form of a mixed wire bundle in which the insulated wires and other insulated wires are bundled together in a mixed state. The wire harness is configured as a wire harness by being bundled with a harness protection material such as a corrugated tube, a bundling material such as an adhesive tape, or the like.

The insulated wire according to the present invention can be used for various electric wires for automobiles, equipment, information communication, electric power, ships, aircrafts, and the like. Can be particularly suitably used as an electric wire for automobiles.

The automotive electric wire is classified into a class a to E according to the international standard ISO 6722, according to the allowable heat resistant temperature. The insulated wire of the present invention is most suitable for a battery cable or the like having excellent heat resistance and withstanding high voltage, and can obtain characteristics of class C having a heat resistance temperature of 125 ℃ and class D having a heat resistance temperature of 150 ℃.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present invention.