JPS61148703A - Ethylene polymer composition for wire covering - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ethylene polymer composition G for covering electric wires, and more specifically, an ethylene polymer composition G that has good mechanical strength, insulation properties, and productivity and is suitable for covering electric wires, particularly for foaming. Regarding the composition.

Conventionally, low-density polyethylene (LDPE), which has good workability, has been used for the insulation coating of electric wires for communication cables. However, since LDPE has a low surface hardness, it has the disadvantage that the coating layer is easily torn when the wire is twisted. In recent years, due to changes in communication formats, foamed coatings have become the mainstream for wire coatings, but when foaming is used, materials with even higher surface hardness are desired.

High-density polyethylene (H
However, when this HDPE is extruded and coated at high speed, the surface becomes rough and the wire is easily torn when twisted.

Therefore, various proposals have been made to improve these drawbacks. For example, ■ A blend of HDPE and high-density ethylene copolymer (JP-A-58-111205), ■ A blend of HDPE and LDPE (JP-A-58-111205),
223210), ■Low molecular weight LDP in HDPE
There are compositions in which E and high molecular weight HDPE are blended (Japanese Patent Application Laid-Open No. 52-11235). However,■
When the latter is used for foam coating, the foamed cells become non-uniform and the mechanical strength is low, while those of (1) and (3) have insufficient high-speed moldability and are prone to surface roughness. As described above, a material for covering electric wires that is fully satisfactory has not yet been proposed.

Therefore, the present inventors developed a polyethylene composition for covering electric wires that has high surface hardness, excellent high-speed extrusion coating formability, crack resistance, and high mechanical strength that produces fine and uniform foamed cells when foamed. I researched as much as possible. the result,
It was discovered that a composition capable of achieving the above object can be obtained by blending ethylene homopolymers or copolymers having specific physical properties in a specific ratio, and the present invention was completed based on this knowledge.

That is, the present invention provides the following (A), (B) and (C)
), and the content of component (A) is 1 to 23.
% by weight, or -'')' (B) component: (C) component =
1:o, s~1.5 (weight ratio), the intrinsic viscosity [η] of the composition is 1.5゛~2.5a/g, and the density is 0.940
-0.965 g/mouth 3 ethylene polymer composition for electrical wire coating.

Component (A): ethylene homopolymers or copolymers of ethylene and other α-olefins (content of other α-olefins 15% by weight or less) are also available, and have an intrinsic viscosity [η] of 4 to 10 dl/g. Component (B): A monopolymer of ethylene or a copolymer of ethylene and other α-olefins (content of other α-olefins: 5% by weight or less), and has an intrinsic viscosity [η] of 0. 3 to 1.4 dl/g Component (C): A copolymer of ethylene and other α-olefins (content of other α-olefins: 3 to 20% by weight), with a limiting viscosity [η] is 0.8 to 4.0 di/g. The composition of the present invention has the above (A), (B) and (C)
It consists of three components. As mentioned above, component (A) is an ethylene homopolymer or a copolymer of ethylene and other α-olefins (the content of other α-olefins is 15% by weight or less), and has an intrinsic viscosity [η ] is 4
~LOdl/g'.

In the case of a copolymer, it is preferable that the content of other α-olefins (that is, α-olefins other than ethylene) is 10% by weight or less, and that the copolymer has an ethylene single weight with an intrinsic viscosity [η] of 4 to 8 J/g. A combination or copolymer is preferred. Also,
The density of component (A) is 0.900 to 0.950 g/
Preferably, the diameter is about cm3.

In component (A), if the content of other α-olefins in the copolymer is reduced by 15% by 4%, there is a problem that the environmental stress cracking resistance (ESCR) decreases. Furthermore, if the intrinsic viscosity [η] is less than 4 a/g, the melt tension decreases, the foam cell diameter becomes uneven and coarse, and the tensile strength decreases.

'On the other hand, Lod! If it exceeds /g, surface roughness will occur, which is not preferable.

Next, as mentioned above, component (B) of the ethylene polymer composition is an ethylene homopolymer or ethylene and other α-
It is a copolymer with olefin (the content of other α-olefins is 5% by weight or less) and has an intrinsic viscosity [η] of 10.3 to
It has a value of 1.4 dl/g.

In the case of a copolymer, the content of other α-olefins is preferably 3% by weight or less, and the intrinsic viscosity [η] is 0.4.
Ethylene homopolymer or copolymer with ~LOdl/g is preferable.Also, the density of component (B) is 0.970~
It is preferably about 0.980 g/am''.

In this component (B), when the content of other α-olefins in the copolymer exceeds 5% by weight, E and SCR decrease. Moreover, when the intrinsic viscosity [η] is less than 0.34/g,
Bumps and roughness occur on the surface, and if it exceeds 1.4 dl/g, fluidity decreases, melt fracture occurs, and the surface appearance deteriorates, which is not preferable.

Furthermore, as mentioned above, component (C) of the ethylene polymer composition of the present invention is a copolymer of ethylene and other α-olefins (the content of other α-olefins is 3 to 20% by weight). and the intrinsic viscosity [η] is 0.8 to 4.0 dl/g
More preferably, the content of other α-olefins is 3 to 15% by weight, and the intrinsic viscosity [η] is 1.0.
~4.0a/g ethylene copolymer. Also, (C
) component density is 0.915-0.940 g/am
A value of about 3 is preferable.

If the content of other α-olefins in this component (C) is less than 3% by weight, the ESCR decreases, and if it exceeds 20% by weight, there is a problem that the wear resistance decreases. Furthermore, if the limiting viscosity [η] is less than 0.8 d1/g, the melt tension decreases, and when foamed coating is applied, the foamed cell diameter becomes uneven and coarse. On the other hand, if it exceeds 4, Od1/g,
Fluidity decreases, melt fracture occurs, and the surface appearance deteriorates, which is undesirable.

The ethylene polymer composition of the present invention is the above-mentioned (A).

It consists of three components (B) and (C), and at the same time, the content of component (A) is 1 to 23% by weight of the entire composition,
Preferably it is 2 to 20% by weight, and component (B) and (
C) The weight ratio of component is 1:0.5 to 1.5, preferably I:
0.6-1. It is O. Moreover, the intrinsic viscosity [η] of the entire composition is 1.5 to 2.5 dl/g, preferably 1.6 to 2.5 dl/g.
2.3aj/g, density is 0.940-0.965
g/cm', preferably 0.945-0.960
g/cI113. Here, if the content of component (A) in the entire composition is less than 1% by weight, the melt tension will decrease, the foamed cell diameter will be uneven and coarse, and 23% by weight
If it exceeds this, bumps will occur. In addition, component (B) and (C
When the weight ratio of component (C) exceeds 1.5, fluidity decreases and melt fracture occurs, resulting in poor appearance. On the other hand, if it is less than 0.5, the compatibility will decrease, gels and fish eyes will occur, and the appearance will be poor. Furthermore, if the intrinsic viscosity [η] of the composition is less than 1.5 dl/g, the melt tension will decrease and the foam cells will become uneven and coarse, and if it exceeds 2.5 di/g, the fluidity will decrease. , resulting in poor appearance. The density of the composition is 0.940 g/cm
If it is less than 3, the tensile strength decreases, or 0, 965
Above g/cm3, the ESCR decreases.

In addition, other α in components (A), (B), and (C)
- There are various types of olefins, that is, olefins other than ethylene, but usually α-olefins having 3 to 12 carbon atoms, preferably 4 to 8 carbon atoms, specifically propylene,
Examples include butene-1, hexene-1, octene-1, and the like.

The composition of the present invention basically consists of the above three components, but if necessary, an antioxidant such as a sulfite ester or a phosphate ester; an ultraviolet absorber such as a benzotriazole or benzophenone; and an antistatic agent. agent; higher fatty acid metal salt,
A lubricant such as hydrotalcite; a coloring agent, etc. can be added.

The composition of the present invention has the above-mentioned structure, has excellent high-speed extrusion coating moldability, ESCR, etc., has a good surface appearance, and is extremely suitable for coating electric wires.

As a method for manufacturing such a composition, various methods can be applied, such as a method in which each component is prepared in advance, a predetermined amount thereof is blended, and kneaded by heating, a multistage polymerization method, and a combination method thereof. Particularly suitable methods are disclosed in JP-A-54-161691, JP-A-55-40724, and JP-A-55-14.
This is a three-stage polymerization method using a Ziegler type catalyst as described in Publication No. 9307, etc., and the polymerization methods in this case include suspension polymerization and solution polymerization.

Various methods such as gas phase polymerization can be selected, and continuous methods are also available.

Any method such as a batch method may be used.

The composition of the present invention thus obtained has a mechanical strength,
It has good insulation properties and is extremely suitable for covering electric wires.

As a method for coating electric wires, there are methods such as forming the composition into a sheet shape and wrapping it around the electric wire, but the composition of the present invention is particularly suitable for foam coating, has excellent high-speed extrusion coating formability,
High productivity.

Furthermore, since the surface appearance is good, the wire will not be torn during twisting.

The foam coating may be formed by any commonly used method, such as gas foaming or chemical foaming, without any particular limitation. Nitrogen gas, carbon dioxide, or the like is used as a blowing agent when gas foaming is applied, and azodicarbonamide or the like is used as a blowing agent when chemical foaming is applied. Clay is also used as a foaming nucleating agent.

Calcium carbonate, talc, etc. can be used.

When the composition of the present invention is foamed, the foamed cells are fine and uniform, and have excellent mechanical strength and insulation properties.

Therefore, the composition of the present invention is extremely useful as a coating material for electric wires such as communication cables.

Next, the present invention will be explained in detail with reference to Examples.

Examples 1 to 7 and Comparative Examples 1 to 11 A composition consisting of components iA), (B), and (C) shown in Table 1 and 2.0% by weight of azodicarbonamide.

Pentaerythrityl-tetrakis [3-(3,5-di-
t-Butyl-4-hydroxyphenyl)propionate (trade name Nilganox 1010) 0.2% by weight
, after adding 0.21% calcium stearate,
Extrusion coating machine with extrusion temperature of 200℃ and linear speed of 1500m/
A copper wire having a diameter of 0.4 mm was covered with foam to a thickness of 0.15 mm under extrusion conditions of 10 minutes. Table 1 shows the physical property measurement results for this coated wire.

*1... Measured at 135°C in decalin *2... (I) Nibutene-1 (■): Hexene-1 *3... Capillary rheometer used, temperature 190
°C, orifice 0.03 inch, continuously increasing the plunger descent rate, the apparent shear rate in the orifice where the strand skin begins to become rough.

*4...Using a melt tension tester manufactured by Toyo Seiki ■, orifice D = 2.10 m/m.

L = 8.00 m/m, temperature 190°C, plunger descent speed 15 mm/min, thread take-off speed 10 r, p,
Measured value under the conditions of *5...A STM D-
1693, temperature: 50° C., surfactant Nissan Nonion 10% aqueous solution, F5° value (Po: density of resin before foaming, P: density of foam).

*7: A cross section of the coating cut out with a microtome was observed under a microscope, and the minimum and maximum values of average bubbles were shown.

*8...Tensile speed 50 mm/min, distance between chucks 50 mm/min *9...Visually inspected

Claims (1)

[Claims] (1) Consists of the following components (A), (B) and (C), and the content of component (A) is 1 to 23% by weight,
and (B) component: (C) component = 1:0.5-1.5 (weight ratio), and the intrinsic viscosity [η] of the composition is 1.5-2.
5dl/g, density 0.940-0.965g/cm^
3, an ethylene polymer composition for covering electric wires. Component (A): ethylene homopolymer or copolymer of ethylene and other α-olefin (content of other α-olefins 15% by weight or less), with an intrinsic viscosity [η] of 4 to 1
0 dl/g Component (B): Ethylene homopolymer or copolymer of ethylene and other α-olefins (content of other α-olefins 5% by weight or less), with intrinsic viscosity [η] 0.3~
1.4 dl/g Component (C): A copolymer of ethylene and other α-olefins (content of other α-olefins 3 to 20% by weight), with an intrinsic viscosity [η] of 0. 8 to 4.0 dl/g