JPS60110739A - Polyethylene composition for protective coating of wire and cable - Google Patents

Abstract

PURPOSE:The titled polyethylene composition excellent in low-temperature properties, and good in abrasion resistance, extrudability, etc., containing a special flexible polymer of an ethylene copolymer type. CONSTITUTION:Use is made of a flexible polymer comprising an ethylene/alpha- olefin copolymer having (i) a density of 0.86-0.91g/cc, (ii) a maximum peak temperature (Tm) as determined by differential scanning calorimetry >=100 deg.C, and (iii) a boiling n-hexane insoluble portion >=10wt%. Namely, 10-90wt% ethylene/ alpha-olefin copolymer (alpha-olefin content of about 3-40mol%) having a density of 0.915-0.96g/cc is mixed with 90-10wt% above flexible polymer. It is necessary that the obtained composition should have a density of 0.91-0.94g/cc, a melt index of 0.1-5g/10min, and an N value of 1.8-2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyethylene composition for use as a protective coating for electric wires and cables, which has particularly excellent cold resistance.

In general, electric wires and cables have a structure in which an insulating layer such as rubber or rubber is formed on the conductor, and a protective coating layer (source layer) to protect from the external environment, or an external semiconducting layer is placed on the insulating layer. It has a structure in which a copper foil tape is provided to form a protective coating layer.

This sheath layer is generally required to have various properties such as environmental stress cracking resistance, abrasion resistance, oil resistance, chemical resistance, weather resistance, and cold resistance. require demanding physical properties associated with environmental conditions.

For example, the sheath layer used under harsh conditions such as in cold regions maintains flexibility in addition to the general physical properties mentioned above, so the sheath layer has better cold resistance, that is, better resistance to low-temperature embrittlement. requested.

On the other hand, the most important problem when forming the sheath layer is processability. This processability takes into account various factors such as (1) prevention of surface roughness of the source layer (appearance), (2+ high speed), (3) prevention of dielectric breakdown of the insulating layer, and prevention of surface roughness of the sheath layer ( 1) is related to the surface condition at the time of forming the sheath layer, that is, the appearance, which determines the quality of the product.
2) aims to further increase productivity and reduce costs. Further, in order to maintain the integrity of the conductor and the insulating layer, and to prevent dielectric breakdown of the insulating layer (3), it is desirable to form the sheath layer at as low a temperature as possible.

Conventionally, high-pressure polyethylene and ethylene-vinyl acetate copolymer with a radical polymerization mechanism have been used as source layer forming materials, but high-pressure polyethylene has insufficient per-ring stress cracking resistance, and ethylene-vinyl acetate copolymer Copolymers have the drawback of poor cold resistance and abrasion resistance.

In order to improve the above-mentioned drawbacks, the present inventors previously proposed
As seen in Japanese Patent Application No. 145607, a sheath layer mainly composed of a vapor-produced nylethylene-α-olefin copolymer was proposed.

However, although the sheath layer made of the above-mentioned ethylene-α-olefin copolymer satisfies most of the above-mentioned physical properties, sufficient consideration has not yet been given to processability.

As a result of intensive studies in view of the above points, the inventors of the present invention found that by blending ethylene-α-olefin copolymers within a certain range, processability was improved, and surprisingly (cold resistance d] was found to be improved, leading to the present invention.

That is, the present invention comprises (A) an ethylene-α-olefin copolymer having a density of 0.91.5 to 0.96177 cc, and (B
) density is 0.86-0.910 jj/cc, maximum peak temperature (T
m) is 100°C or higher, and the density is 0.91 to 0.91 to 0.91 to 10. 94 g/cc, melt index 0.1-5,9710 minutes, and N value 1.8-2
．． The present invention provides a polyethylene composition for use as a protective coating for electric wires and cables, which has excellent cold resistance, processability, etc., and has a composition falling within the range of No. 5 as a main component.

In the present invention, the ethylene-α-olefin copolymer (N component) refers to various catalysts such as ordinary Ziegler-based catalysts and chromium-based catalysts in which an organic aluminum compound is combined with a solid catalyst component containing titanium or vanadium, etc. Using gas phase method, solution method, under medium-low pressure or high pressure,
Copolymers of α-olefins containing ethylene as a main component and mixtures thereof obtained by various polymerization methods such as slurry methods, preferably α-olefins having 3 to 12 carbon atoms.
Copolymers of olefins, more preferably α-olefins having a carbon number of 4 to 1°, are desirable.

Propylene, butene-1 as cholera α-onfin
, 4-methylpentene-1, hexene-1, pentene-1
1, octene-1, decene-1, etc., and the α-olefin content in the ethylene-α-olefin copolymer is 3
It is preferable that the amount is between 40 mol and 40 mol.

Above (density of N component is 0.915 to 0.96 g/ac
, preferably in the range of 0.93 to 0.95 g7cc.

Note that the molecular weight, molecular weight distribution, etc. may be within the range required for the composition and are not particularly limited, but preferably a melt index of 0.1 to 5 g/10
minutes, more preferably <ido, in the range of 3-3V10 minutes.

In addition, the soft polymer that is component (B) in the present invention has a density of 0.86 to 0.91 g/cc, preferably 0.
．． 89-0.91 g/cc, differential scanning calorimetry (
It is a special ethylene-α-olefin copolymer with a maximum peak temperature (Tm) of 100° C. or higher by DSC) and a boiling 11-hexane insoluble content of 10% by weight or higher.

The above-mentioned soft polymer is a solid catalyst component containing at least magnesium and titanium, such as magnesium metal, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium chloride, etc., and a metal selected from silicon, aluminum, and calcila b, and a magnesium atom. Double salts, double oxides, carbonates, chlorides or hydroxides containing Polymerization is carried out in the same manner as in the polymerization reaction of olefins using ordinary Ziegler-type catalysts in the presence of a catalyst in which a titanium compound is supported by a known method on an inorganic solid compound containing magnesium, such as an organic aluminum compound. obtained by

That is, all reactions are carried out substantially in the absence of oxygen, water, etc., in a gas phase or in the presence of an inert solvent, or using the monomer itself as a solvent. The polymerization conditions for the above olefin are a temperature of 20 to 300°C, preferably 40 to 200°C, and a pressure of normal pressure to 70 Ky/2·I, preferably 2 to 60 Ky/2·g.

Although the molecular weight can be controlled to some extent by changing polymerization conditions such as polymerization temperature and catalyst molar ratio, it is effectively carried out by adding hydrogen to the polymerization system. Furthermore, two-stage or multi-stage polymerization reactions with different polymerization conditions such as hydrogen concentration and polymerization temperature can be carried out without any hindrance.

Special soft ethylene l/n α produced as described above
- The olefin copolymer is clearly distinguishable from the currently commercially available flexible ethylene-α-olefin copolymer produced using a catalyst that combines a vanadium-containing solid catalyst component with an organic aluminum compound. .

In other words, the ethylene-α-olefin copolymer produced using a conventional vanadium-containing catalyst system has almost no crystallinity, and there is no content insoluble in boiling M#11-hexane, or even if it exists, it is only in a very small amount. However, the maximum peak temperature (Tm) determined by D'SC is also less than 100°C. This indicates that the various physical properties required by the present invention, such as abrasion resistance, heat resistance, and oil resistance, cannot be satisfied. Furthermore, unlike titanium, vanadium present in the copolymer as a catalyst residue poses a toxicity problem, so a catalyst removal step is essential.However, when titanium is used as in the present invention, the toxicity of the catalyst residue No problems arise and the copolymers of the present invention, which use a highly active catalyst in combination with a magnesium support, are extremely economical since no catalyst removal step is required.

The above maximum peak temperature (Tm) measured by differential scanning calorimetry (DSC) is a value that correlates with the crystal form.
After raising the temperature to 70℃ and holding it at that temperature for 15 minutes,
Cool down to 0°C at a rate of °C/min. Next, the temperature is raised from this state to 170°C at a rate of 10°C/min, and the measurement is completed. The maximum beer temperature (Tm) is not expressed by the temperature at the apex position of the maximum peak that appears in the straw as the temperature rises from 0°C to 170°C.

In addition, the boiling n-hexane insoluble content is a guideline for the proportion of amorphous parts and the content of low molecular weight components.A sheet with a thickness of 200μ is formed using a heat press, and then a sheet of 20*m x 30mm in length and width is formed from it. Cut out 3 sheets of
After extracting it with boiling n-hexane for 5 hours using a double-tube Soxhlet, the 11-hexane insoluble matter was filtered out and then vacuum-dried (7 hours under vacuum, 5 hours).
0° C.), and then weighed, and the amount of boiling water insoluble in hexane was calculated using the following formula.

) The composition of the present invention has a density of 0.91 to 0.94 jj/ac, preferably 0.91 to 0.94 jj/ac, obtained by mixing 10 to 90 parts by weight of component (A) and 90 to 10 parts by weight of component B). 0.
90 to 0.93 g//cC1 melt index (hereinafter simply referred to as CrvIr) is in the range of 0.1 to 5 g/10 minutes, the preferred weight is in the range of 0.5 to 3 g/10 minutes, and the N value is 1.
It has excellent properties in the range of 8 to 2.5, preferably 2.0 to 2.3.

If component (A) of the above composition contains no IO weight percent, various properties such as extrusion processability, heat resistance, and abrasion resistance are poor, and if it exceeds 90 weight percent, the effect of improving low-temperature properties is small.

Furthermore, if the density, MI and N value of the above composition are outside the specified range of the present invention, the quality of appearance, extrusion processability, low temperature brittleness, heat resistance, abrasion resistance, etc. Unable to satisfy any of the required physical properties.

Here, the "N value" (non-Newtonian fluidity value) is approximately correlated with the molecular weight distribution of polyethylene and serves as a measure of fluidity. ), die: 2illφ×40mm,
It refers to the amount of polyethylene pumped out when a load of 2 is applied to 15019 and 20 at 170°C, and calculated according to the following formula.

Here, γ: shear rate (Sea') τ: shear stress (dyn/Sono2) In addition, the method of mixing the FA component and the (β) component in the present invention is an extruder, Banbury mixer, roll mill, etc. Any method may be used, and there are no particular limitations.

In the present invention, a small amount of at least one of other polyolefins such as high-pressure polyethylene, ethylene-vinyl acetate copolymer, medium-low pressure polyethylene, and polypropylene may be mixed as long as the characteristics of the present invention are not impaired. Also good. Further, if necessary, ordinary additives such as pigments, fillers such as carbon black, dispersants, antioxidants, and ultraviolet absorbers may be appropriately blended.

As mentioned above, the present invention provides a specific range of polyethylene foam compositions in which a soft bogemer consisting of a common ethylene-α-olefin copolymer and a special ethylene-α-olefin copolymer is mixed, thereby achieving surprisingly low-temperature properties. It is a protective coating layer for electric wires and cables with excellent wear resistance and extrusion processability.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it departs from the gist thereof.

The manufacturing and testing methods for the soft resin and resin are as follows.

(Manufacture of soft resin) (1) Manufacture of soft resin (A) (a) Manufacture of solid catalyst component Stainless steel bowl 25 with a multi-inch diameter
10 g of commercially available anhydrous magnesium chloride and 4.2 g of aluminum triethoxide were placed in a stainless steel pot with an internal volume of 400 m13, and ball milling was performed at room temperature under a nitrogen atmosphere for 16 hours to obtain a reaction product.

After stirring, a 3-tube flask equipped with a reflux condenser was purged with nitrogen, and 5 g of the above reaction product and 5 g of S' 02 (Fuji Devin, ≠952) calcined at 600°C were placed in the 3-tub flask, and then 1 g of tetrahydrofuran was added.
After adding 00 ml and reacting at 60°C for 2 hours,
Drying was performed under reduced pressure at 120°C to remove tetrahydrofuran. Next, 30 ml of titanium tetrachloride was added, and the mixture was reacted for 2 hours under reflux of titanium tetrachloride, and then washed with purified hexane until free titanium tetrachloride was no longer detected in the washing solution. After washing, it was dried to obtain a solid catalyst component.

The content of titanium in 1 g of the obtained solid catalyst component was 42 m
It was g.

(b) Gas phase polymerization A stainless steel autoclave was used as the gas phase polymerization apparatus, a loop was made with a blower 1 flow rate regulator and a dry Zyclone, and the temperature of the OI crepe was adjusted by flowing hot water through the jacket.

70°CK11. ! l] The above solid material was fed into the autoclave at a rate of 250 m9/hr, and triethyla and aluminum at a rate of 50 mmol/hr, and the butene-1/ethylene ratio (molar ratio) in the gas phase of the autoclave was adjusted to 0.48. Further, each gas was supplied while adjusting the hydrogen to have a total pressure of 7 cm, and the gases in the system were circulated using a blower to carry out polymerization for 10 hours. The produced ethylene copolymer has an il, 76xy and a bulk specific gravity of 0.
43. Melt index (MI) 0.39710 minutes,
The powder had a density of 0.890 g/cc and an average particle size of 790 μm with no particles smaller than 150 μm.

In addition, similar polymerization was carried out with a melt index of 0.5 g/
A 10 minute soft resin (A') was also produced.

(2) Production of flexible resin (B) In the production of flexible resin fA), the butene-1/ethylene ratio (molar ratio) in the gas phase of the autoclave was adjusted to 0.30, and the hydrogen was adjusted to a total pressure of 10%. Polymerization was carried out in the same manner as for the soft resin (N, except for the adjustment. The produced ethylene copolymer had a bulk specific gravity of 0.41 at 11.45 Ky.
The powder had a melt index (MI) of 0.54/10 minutes, a density of 0.900 g/cc, and an average particle size of 700 microns with no particles smaller than 150 microns.

In addition, similar polymerization was carried out with a melt index of 1.0 g/
A 10 minute soft resin (B') was also produced.

(3) Production of flexible resin IC) In the production of flexible resin (A), the butene-1/ethylene ratio (mole ratio) in the autocup gas phase was set to 0.20, and the hydrogen was adjusted to 15% of the total pressure. Polymerization was carried out in the same manner as for the flexible resin FA), except that it was adjusted so that The produced ethylene copolymer has a bulk specific gravity of 0.40 at 10.5 Ky,
The powder had a melt index (MI) of 0.551/10 min, a density of 0.91017/cc, and an average particle size of 850 μm with no particles smaller than 150 μm.

(Test method) ], ESCR "Liponox" 5 out of 10 test pieces of a 2 m/m thick sheet with a notch immersed in a 10% concentration solution (trade name: Liponox NEI, manufactured by Lion Corporation) It is indicated by the time at which it breaks.

2. Low temperature brittleness test (according to JIS K-7216) 710% length, 6% width, 2rrA thickness, 5 test pieces with a notch in the width direction of 0.3% depth. The temperature at which one of the pieces broke was shown.

(Test device) Low-temperature brittleness test device 3 manufactured by Toyo Seiki Co., Ltd. Abrasion test A disk with a diameter of 121%φ and a thickness of 1% was used as a test piece, and 100
Wear t (7) after 0 rotation is shown.

(Test conditions) Load 1, 01 (y wear wheel C-2
2. Number of wear: 1000 times (test equipment) Toyo Seiki taper set rotary apressor 4, Plastograph torque test... Using electric heating type Plastograph manufactured by Kei Co., Ltd., sample 459
, the stable torque value and resin temperature were shown at a set temperature of 180° C. and a rotor rotation speed of 6 Orpm.

5. Extrusion from a 25%φ blow molding machine at a set temperature of 190° C. and a screw rotation speed of 40 rpm. The appearance of Gurison was visually judged.

◎...Very smooth.

O...Smooth.

×...Shark skin occurs.

Examples 1 to 3 Various ethylene-butene-1 copolymer resins (manufactured by Nippon Petrochemical Co., Ltd.) with different densities as FA) components, and (B)
The above-mentioned soft resin (7!) was kneaded as a component in the proportions shown in Table 1 in a 50%φ extruder set at 200°C,
A mixture within the scope of the present invention was obtained, and various properties of the mixture were measured and are shown in Table 1.

Examples 4 to 5 A mixture was prepared in the same manner as in Example 1 by mixing the flexible resin (B) as the component (B) with various ethylene-butene-1 copolymer resins, and various properties were determined. Measure it and display it in Table 1.

Examples 6 to 8 fB) Soft resin (C) (Example 6), soft resin (A') (Example 7), and soft resin (B') as fB) components
(Example 8) A mixture was prepared in the same manner as in Example 1 by mixing it with various ethylene-α-olefin copolymer fats, and various properties were measured and shown in Table 1.

Comparative Examples 1 and 2 The results of the same evaluation as in Example 1 only for ethylene-butene-1 copolymer resins with different densities and N values are shown in the first example.
Shown in the table.

Comparative Example 3 Commercially available sheath grade (high pressure polyethylene, trade name:
DFDJ-0588 (manufactured by Nippon Unicar Co., Ltd.) was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Examples 4-8 Soft resin (B) (Comparative Examples 4-5), Soft resin (A)
(Comparative Example 6), and soft resin (C) (Comparative Examples 7 to 8)
) was mixed with various ethylene-butene-1 copolymer resins to prepare mixtures outside the scope of the present invention, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 9 The ethylene-butene-1 copolymer used in Example 2 was added with a commercially available soft resin (trade name: Kutzmer P-0).
480, MI 1.0g710min, density 0,88,!
9/CG manufactured by Mitsui Petrochemical Co., Ltd. was evaluated in the same manner as in Example 2, and the results are shown in Table 1.

Claims (1)

[Claims] m (A) Density is 0.915 to 0.96 (1/ac ethylene-α-olefin copolymer lO to 90% by weight and fB) Density is 0.86 to 0.910 Vcc, Differential Scanning Calorimetry Maximum peak temperature (Tm) by (DSC)
is over 100℃ and boiling! 1-hexane insoluble matter is 1
A soft polymer consisting of an ethylene-α-olefin copolymer having a weight coefficient of 0 or more and a density of 0.
．． 91-0.94 p/cc, melt index 0.1-517710 minutes, and N value 1.8-2.5
A polyethylene composition for protective coating of electric wires and cables, the main component of which is a composition within the range of