JPH10265583A - Crosslinked molded product and electric wire, cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain crosslinked molding products that can improve their mechanical properties, particularly elongation over a specific value and is useful for electric wires and cables by crosslinking molding products made of a specific silane-grafted polyolefin with water. SOLUTION: This is a crosslinked molding product having >=60 mol% gel fraction and >=500% elongation and a silane is graft-polymerized onto a polyolefin of an unsaturated dimer of an α-aromatic substituted-α-methyl alkene of the formula [R<1> , R<2> , R<4> and R<5> are each H, an aryl, an alkyl; R<3> , R<5> are each a (halogen-substituted) alkaryl] and the resultant graft polyolefin is molded, then the molding product is crosslinked with moist in the presence of a silanol condensation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked molded article comprising a silane-grafted polyolefin, and to an electric wire / cable.

[0002]

2. Description of the Related Art The so-called silane-grafted water crosslinking method, in which a silane-grafted polyolefin molded product is cross-linked by exposing it to water in the presence of a silanol condensation catalyst, is lower in cost than a chemical crosslinking method in which heat crosslinking is performed using an organic peroxide. Is widely used as a method for cross-linking wire and cable materials.

In this method, a small amount of an organic peroxide is used as a graft reaction initiator in a high-temperature molding machine (eg, an extruder), and vinylalkoxysilane is graft-copolymerized with a polyolefin. (Or warm water), and the hydrolysis and condensation of the alkoxysilane grafted onto the polyolefin is caused by the action of a silanol condensation catalyst such as dibutyltin dilaurate, which is blended into the molded product or penetrated from the surface of the molded product. And crosslink.

[0004]

However, the silane-grafted water crosslinking method has a property that when the degree of crosslinking is set high for the purpose of enhancing the high-temperature properties, the elongation properties are significantly reduced as compared with the chemical crosslinking method. Therefore, it cannot be applied to products requiring high elongation, and its application range is limited.

The present invention has been made in view of such circumstances, and provides a silane-crosslinked polyolefin molded article, and an electric wire / cable capable of improving mechanical properties, particularly elongation properties, even if the degree of crosslinking is high. It is the purpose.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a molded article comprising a grafted polyolefin obtained by graft copolymerizing a silane compound with a polyolefin and exposing the molded article to moisture in the presence of a silanol condensation catalyst. The unsaturated dimer of α-aromatic-substituted α-methylalkene is added, whereby the gel fraction is 60% or more and the elongation property is 500%.
% Or more, and in the case of a semiconductive molded product, a new crosslinked molded product having a gel fraction of 35% or more and an elongation property of 200% or more. Can be.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin used in the present invention includes low-density polyethylene, medium-density polyethylene, ultra-low-density polyethylene produced by ionic polymerization, linear low-density polyethylene, high-density polyethylene, ethylene propylene rubber and ethylene butene. Binary or terpolymer, polypropylene, chlorinated polyethylene, chlorosulfonated polyethylene, polyethylene or polypropylene polymerized with metallocene catalyst, ethylene propylene rubber, ethylene octene copolymer, vinyl acetate, acrylic acid or methacrylic acid ester And copolymers of ethylene with propylene and the like, and those obtained by grafting a functional group containing maleic anhydride or epoxy to a polyolefin, and are composed of one or more of these.

The organic silane compound is required to have a group that can be connected to a polyolefin and a group that can be silanol condensed. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane And ethylenically unsaturated silane compounds such as γ-methacryloxypropyltrimethoxysilane and vinyltris (2-methoxyethoxy) silane. The addition amount of the organic silane compound is
The range is generally 0.1 to 5 parts by weight with respect to 0 parts by weight.

The free radical generator acts as an initiator for grafting an organic silane compound to the polyolefin, and is required to generate free radical sites in the polyolefin. Specifically, dicumyl peroxide, 2,2 5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, α, α'-bis (t-butyl Dialkyl peroxides such as peroxy-m-isopropyl) benzene, m- (t-butylperoxyisopropyl) -isopropylbenzene, p
-(T-butylperoxyisopropyl) -isopropylbenzene and the like, which can be used alone or in combination of two or more. The amount of the free radical generator to be added is 0.1 to 100 parts by weight of the polyolefin.
The range of 01 to 2 parts by weight is common.

Examples of the silanol condensation catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate and dibutyltin dioctate. The addition amount of the silanol condensation catalyst is generally in the range of 0.01 to 2 parts by weight based on 100 parts by weight of the polyolefin.

The unsaturated dimer of α-aromatic-substituted α-methylalkene is represented by the following formula 1.

[0012]

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In the formula, R ¹ , R ² , R ⁴ , R ⁵ It represents hydrogen, an allyl group, an alkyl group, R ³ , R ⁶ Represents an aryl group or an alkaryl group, and each of these aryl group and alkaryl group may be halogen-substituted.
Compounds of formula 1 are, for example, α-methylstyrene, p-methyl-α-methylstyrene, p-ethyl-α-methylstyrene, p-isopropyl-α-methylstyrene, m-methyl-α-methylstyrene, m-methylstyrene. It is an unsaturated dimer such as ethyl-α-methylstyrene and p-chloro-α-methylstyrene. Specific examples of the compound include 2,4-diphenyl-4-methyl-1 which is a dimer of α-methylstyrene.
-Pentene can be mentioned. Two or more unsaturated dimers may be used.

The amount of the unsaturated dimer of α-aromatic-substituted α-methylalkene is not particularly limited, but is preferably 0.01 to 10 parts by weight per 100 parts by weight of polyolefin. If the amount is less than 0.01 part by weight, there is no effect of improving the elongation property, and if it exceeds 10 parts by weight, it tends to precipitate (bloom) on the surface of the molded product and deteriorate the dielectric breakdown characteristic.

When an unsaturated dimer of α-aromatic-substituted α-methylalkene is added, the elongation characteristics are improved because the organic silane compound itself becomes a free radical at the time of grafting to the polyolefin, This is considered to prevent homopolymerization and make the distribution of the graft points of the organic silane compound uniform.

In order to obtain a semiconductive cross-linked molded product, a conductivity-imparting agent such as acetylene black or furnace black is blended in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of polyolefin, and the conductivity of the molded product at room temperature is 106 Ω · cm or less.

In the present invention, addition of an antioxidant, a copper damage inhibitor, carbon black for imparting weather resistance, and additives such as a lubricant, a coloring agent, and an inorganic filler may be added. .

[0018]

EXAMPLES Formulations as shown in Table 1 were prepared with L / D = 28,
Using an extruder with an extrusion temperature set at about 200 ° C.,
It was extruded as an insulating layer having a thickness of 2mm to annealed copper twisted line of mm ^2. Thereafter, the sample was allowed to stand in an atmosphere of 80 ° C. and 95% water vapor for 24 hours to be crosslinked to obtain a sample. Also, in Table 1 No. 1
The insulating composition shown in above was placed on a 100 mm ²
Extruded to a thickness of 6 mm with the thick inner and outer semiconductive layers. The inner semiconductive layer and the outer semiconductive layer are compositions as shown in Table 2. Thereafter, the sample was allowed to stand in an atmosphere of 80 ° C. and 95% water vapor for 24 hours to be crosslinked to obtain a sample.

For each of these samples, the heat deformation ratio, the gel fraction, the tensile elongation, and the AC breakdown strength were measured, and the results are shown in Tables 1 and 2. The measuring method is as shown below.

Gel fraction: Measured according to JIS C3005.

Heat deformation rate: According to JISC3005,
The heating deformation rate of the cable sample was measured at 120 ° C. At this time, those with a deformation rate of 10% or less were evaluated as good, and those with a deformation rate exceeding 10% were evaluated as bad.

Tensile elongation: Measured according to JIS C3005.

AC dielectric breakdown strength: 1
After applying 70 kV / 10 minutes, the voltage was raised at 5 kV / 10 minutes, and the dielectric breakdown voltage was measured. At this time, those having an insulation thickness of 2 mm were rated at 100 kV or more, and those of 6 mm were rated at 300 kV or more as good and less than 300 kV.

[0024]

[Table 1]

[0025]

[Table 2]

As shown in Table 1, Examples 1 to 8 have a high gel fraction, a good heat deformation rate, a large tensile elongation, and a good dielectric breakdown strength. On the other hand, Comparative Example 1 has a low gel fraction and a poor heat deformation rate. Comparative Example 2 has poor tensile elongation. Although the ninth embodiment deteriorates the dielectric breakdown strength, it can be used in fields other than the electric insulation field. In addition, when the semiconductive compositions shown in Table 2 were used, Examples 1 to 5 had a high gel fraction, a good heat deformation rate, and good tensile elongation and dielectric breakdown strength. On the other hand, Comparative Example 1 had a low gel fraction,
Poor heat deformation rate.

[0027]

As described above, according to the present invention, a silane-crosslinked polyolefin molded article having excellent elongation characteristics and an electric wire / cable can be realized even if the degree of crosslinking is increased.

Claims (9)

[Claims] 1. A molded article comprising a grafted polyolefin obtained by graft-copolymerizing a silane compound to a polyolefin and crosslinked by exposing it to moisture in the presence of a silanol condensation catalyst, wherein the molded article has a gel fraction of 60% or more. A crosslinked molded article, characterized by having an elongation property of 500% or more. 2. A molded article obtained by exposing a molded article comprising a composition obtained by blending a conductivity-imparting agent to a graft polyolefin obtained by graft-copolymerizing a silane compound to a polyolefin, by exposing the molded article to moisture in the presence of a silanol condensation catalyst. The molded product has a gel fraction of 35% or more and an elongation characteristic of 200%.
A crosslinked molded article characterized by the above. 3. A molded product obtained by exposing a molded product of a graft polyolefin obtained by graft copolymerizing a silane compound to a polyolefin to water in the presence of a silanol condensation catalyst, wherein the polyolefin has an α-aromatic substitution-α. -A crosslinked molded article, characterized in that an unsaturated dimer of methyl alkene is added. 4. The method according to claim 1, wherein α-
When the unsaturated dimer of the aromatic-substituted α-methylalkene is 0.
4. The crosslinked molded product according to claim 3, wherein said crosslinked molded product is added in an amount of from 0.01 to 10 parts by weight. 5. The unsaturated dimer of α-aromatic-substituted α-methylalkene is 2,4-diphenyl-4-methyl-1-
The crosslinked molded product according to claim 3, which is pentene. 6. A crosslinked wire or cable obtained by exposing a coating obtained by extruding a graft polyolefin obtained by graft-copolymerizing a silane compound to a polyolefin to the outer periphery of a conductor and exposing the coating to moisture in the presence of a silanol condensation catalyst. An electric wire or cable to which an unsaturated dimer of α-aromatic substituted-α-methylalkene is added. 7. The method according to claim 1, wherein α-
When the unsaturated dimer of the aromatic-substituted α-methylalkene is 0.
The electric wire according to claim 6, which is added in an amount of 01 to 10 parts by weight.
cable. 8. The unsaturated dimer of α-aromatic-substituted α-methylalkene is 2,4-diphenyl-4-methyl-1-
The electric wire / cable according to claim 6, which is a penten. 9. An electric wire or cable according to claim 6, wherein said coating comprises an inner semiconductive layer, an insulating layer and an outer semiconductive layer.