JPH041780B2 - - Google Patents

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. Generally, electric wires and cables have a structure in which an insulating layer such as plastic or rubber is formed on a conductor, and a protective coating layer (sheath layer) for protection from the external environment, or an external semiconducting layer and The structure is such that a copper foil tape is provided to form a protective coating layer. This sheath layer is typically environmental stress crack resistant,
Various properties are required such as abrasion resistance, oil resistance, chemical resistance, weather resistance, and cold resistance, but among these properties, depending on the purpose of use, severe physical properties are required depending on the environmental conditions. It is said that For example, in order to maintain flexibility in addition to the general physical properties mentioned above, the sheath layer used under harsh conditions such as in cold regions requires a sheath layer that is more cold resistant, that is, has excellent low-temperature embrittlement resistance. Ru. On the other hand, the most important problem when forming the sheath layer is processability. This processability is (1) prevention of surface roughness of the sheath layer (appearance), (2) high speed, (3)
Various factors such as prevention of dielectric breakdown of the insulating layer are taken into consideration, and prevention of surface roughness of the sheath layer (1) is related to the surface condition when the sheath layer is formed, that is, the appearance, and determines the quality of the product. Speed increase (2) aims to further increase productivity and reduce costs. Furthermore, 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 materials for forming the sheath layer, but high-pressure polyethylene has insufficient environmental stress cracking resistance, and ethylene-vinyl acetate copolymer Polymers have the disadvantage of poor cold resistance and abrasion resistance. In order to improve the above-mentioned drawbacks, the present inventors previously proposed a sheath layer mainly composed of an ethylene-.alpha.-olefin copolymer produced by a gas phase method, as seen in Japanese Patent Application Laid-Open No. 145607/1983. However, although the sheath layer made of the ethylene-α-olefin copolymer satisfies most of the above-mentioned physical properties, sufficient consideration has not yet been given to processability. The inventors of the present invention conducted extensive studies in view of the above points, and found that by blending a specific range of ethylene-α-olefin copolymers, not only processability was improved, but surprisingly, cold resistance was greatly improved. The present inventors have discovered that this can be improved, leading to the present invention. That is, the present invention provides (A) 10 to 90% by weight of an ethylene-α-olefin copolymer having a density of 0.915 to 0.96 g/cc and a melt index of 0.1 to 5 g/10 minutes, and (B) at least magnesium And in the presence of a catalyst consisting of a solid catalyst component containing titanium and an organoaluminium compound, the density obtained by copolymerizing ethylene and α-olefin is 0.86 to 0.910 g / cc, in differential scanning calorimetry (DSC), 90 to 10% by weight of a soft polymer consisting of an ethylene-α-olefin copolymer whose maximum peak temperature (Tm) is 100°C or higher and a boiling n-hexane insoluble content of 10% or higher
The density consisting of is 0.91~0.94g/cc, the melt index is 0.1~5g/10min, and the N value is
The present invention provides a polyethylene composition for protective coating of electric wires and cables, which has excellent cold resistance, workability, etc., and has a composition having a molecular weight in the range of 1.8 to 2.5 as a main component. The ethylene-α-olefin copolymer as component (A) in the present invention refers to various catalysts such as ordinary Ziegler-based catalysts, chromium-based catalysts, etc., which are combinations of organic aluminum compounds with solid catalyst components containing titanium or vanadium, etc. Copolymers of α-olefins containing ethylene as a main component obtained by various polymerization methods such as gas phase method, solution method, and slurry method under medium-low pressure or high pressure, and mixtures thereof. α-, preferably having 3 to 12 carbon atoms
Copolymers of olefins, more preferably α-olefins having 4 to 10 carbon atoms, are desirable. These α-olefins include propylene,
Butene-1,4-methylpentene-1, hexene-1, pentene-1, octene-1, decene-1
The α-olefin content in the ethylene-α-olefin copolymer is preferably 3 to 40 mol%. The density of the component (A) is selected within the range of 0.915 to 0.96 g/cc, preferably 0.93 to 0.95 g/cc. 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 the melt index is 0.1 to 5 g/10 minutes, more preferably 0.3 to 3 g/10 minutes.
It is in the range of 10 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 to
A special ethylene-α-olefin copolymer with a maximum peak temperature (Tm) of 100°C or more by differential scanning calorimetry (DSC) at 0.91 g/cc, and a boiling n-hexane insoluble content of 10% by weight or more. It is. The soft polymer contains at least a solid catalyst component containing magnesium and titanium, such as magnesium metal, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium chloride, etc., and a metal selected from silicon, aluminum, and calcium and magnesium atoms. double salts, double oxides, carbonates, chlorides, or hydroxides, as well as those obtained by treating or reacting these inorganic solid compounds with oxygen-containing compounds, sulfur-containing compounds, aromatic hydrocarbons, and halogen-containing substances. In the presence of a catalyst in which a titanium compound is supported on an inorganic solid compound containing magnesium by a known method, and an organoaluminum compound is combined, the polymerization is carried out in the same manner as the polymerization reaction of olefin using a normal Ziegler type catalyst. You can get it by twisting it. That is, all reactions are carried out in the gas phase in a state where oxygen, water, etc. are substantially excluded. The polymerization conditions for the above olefin are at a temperature of 20 to 300℃, preferably 40 to 200℃.
℃, and the pressure is normal pressure to 70 kg/cm ² ·g, preferably 2 to 60 kg/cm ² ·g. Although the molecular weight can be adjusted 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 or more stages of polymerization reactions with different polymerization conditions such as hydrogen concentration and polymerization temperature can be carried out without any problem. The special flexible ethylene-α-olefin copolymer produced as described above is a flexible ethylene-α-olefin copolymer produced using a catalyst in which an organic aluminum compound is combined with a vanadium-containing solid catalyst component that is currently commercially available. It is clearly distinguishable from α-olefin copolymers. In other words, the ethylene-α-olefin copolymer prepared using a conventional vanadium-containing catalyst system has almost no crystallinity, and there is no content insoluble in boiling n-hexane, or even if it exists, it is extremely small. , the maximum peak temperature (Tm) by DSC is also 100
Less than ℃. 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 process is essential, whereas when titanium is used as in the present invention, the catalyst residue is No toxicity problems arise and the copolymers of the present invention, which use a highly active catalyst in combination with a magnesium support, are extremely economical as no catalyst removal step is required. The maximum peak temperature (Tm) measured by differential scanning calorimetry (DSC) mentioned above is a value that correlates with the crystal form.
The temperature was raised to 170°C, held at that temperature for 15 minutes, and then cooled to 0°C at a rate of 2.5°C/min. Next, from this state, 170°C at a rate of 10°C/min.
The measurement is completed by raising the temperature to ℃. The maximum peak temperature (Tm) is expressed by the temperature at the top of the maximum peak that appears during the temperature increase 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 from it a sheet of 20mm x 30mm in length and width is formed. After cutting out three sheets and extracting them with boiling n-hexane for 5 hours using a double-tube Soxhlet, extracting the n-hexane insoluble matter, it was then vacuum-dried (7 hours under vacuum, 50°C), and then weighed, and the boiling n-hexane insoluble content was calculated using the following formula. (Boiling n-hexane insoluble matter) = (Unextracted sheet weight) - (Extracted sheet weight) / (Unextracted sheet weight) x 100 (%) The composition of the present invention contains the above component (A) from 10 to 10%. 90% by weight
The density obtained by mixing 90 to 10% by weight of component (B) and
0.91-0.94g/cc, preferably 0.90-0.93g/cc,
Melt index (hereinafter simply referred to as MI) is 0.1
~5g/10min, preferably 0.5~3g/10min, and N value 1.8~2.5, preferably 2.0~2.3
It has excellent properties within the range of . When component (A) in the composition is less than 10% by weight, various properties such as extrusion processability, heat resistance, and abrasion resistance are poor, and when it exceeds 90% by weight, 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 ranges 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.
Using Koka type flow tester (HB-I type), die: 2mmφ x 40mm, 150Kg and 20Kg at 170℃
The amount of polyethylene flowing out when a load is applied is measured and calculated according to the following formula. N value = log(γ150/γ20)/log(τ150/τ
20) Here, γ: shear rate (Sec ^-1 ) τ: shear stress (dyn/ ^cm2 ) In addition, the method of mixing components (A) and (B) in the present invention is an extruder, Banbury mixer, or roll mill. Any method such as the above may be used, and the time is not limited. In the present invention, a small amount of at least one of various polyolefins such as high-pressure polyethylene, ethylene-vinyl acetate copolymer, medium-low pressure polyethylene, and polyprolylene may be mixed as long as the characteristics of the present invention are not impaired. . 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, by making a polyethylene composition in a specific range by mixing a soft polymer consisting of a common ethylene-α-olefin copolymer and a special ethylene-α-olefin copolymer of the present invention,
It has surprisingly excellent low-temperature properties and can be used as a protective coating layer for electric wires and cables with improved wear resistance and extrusion processability. The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist thereof. The manufacturing and testing methods for the flexible resin are as follows. (Manufacture of soft resin) (1) Manufacture of soft resin (A) (a) Manufacture of solid catalyst component In a stainless steel pot with an internal volume of 400 ml containing 25 stainless steel balls each having a diameter of 1/2 inch. 10 g of commercially available anhydrous magnesium chloride, aluminium triethoxide
4.2 g was added and ball milling was performed at room temperature under a nitrogen atmosphere for 16 hours to obtain a reaction product. After stirring, a 3-necked flask equipped with a reflux condenser was purged with nitrogen, and 5 g of the above reaction product was added to the 3-necked flask and calcined at 600°C.
Add 5g of SiO ₂ (Fuji Davison, #952),
Then add 100ml of tetrahydrofuran,
After reacting at 60°C for 2 hours, the mixture was dried 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, followed by washing 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. 1 g of the obtained solid catalyst component
The titanium content inside was 42 mg. (b) Gas-phase polymerization A stainless steel autoclave was used as the gas-phase polymerization apparatus, a loop was created with a blower, a flow rate controller, and a dry cyclone, and the temperature of the autoclave was adjusted by flowing hot water into a jacket. The above solid substance was fed at a rate of 250 mg/hr and triethylaluminum at a rate of 50 mmol/hr to an autoclave adjusted to 70°C, and the butene-1/ethylene ratio (molar ratio) in the gas phase of the autoclave was adjusted to 0.48. Each gas was supplied while adjusting the hydrogen pressure to 7% of the total pressure, and the gases in the system were circulated using a blower to carry out polymerization for 10 hours. The produced ethylene copolymer has a bulk specific gravity of 11.76Kg.
0.43, melt index (MI) 0.3g/10
The powder had a density of 0.890g/cc and an average particle size of 790μ with no particles smaller than 150μ. A soft resin (A') having a melt index of 0.5 g/10 minutes was also produced by carrying out similar polymerization. (2) Production of flexible resin (B) In the production of flexible resin (A), the buden-1/ethylene ratio (molar ratio) in the gas phase of the autoclave was
0.30 and hydrogen was adjusted to 10% of the total pressure, but polymerization was carried out in the same manner as for the flexible resin (A). The ethylene copolymer produced is 11.45
Kg, bulk specific gravity 0.41, melt index (MI)
0.5g/10 minutes, density was 0.900g/cc, and the powder had an average particle size of 700μ with no particles smaller than 150μ. In addition, similar polymerization is performed to obtain a melt index.
A soft resin (B') of 1.0 g/10 min was also produced. (3) Production of flexible resin (C) In the production of flexible resin (A), the buden-1/ethylene ratio (molar ratio) in the gas phase of the autoclave was
Polymerization was carried out in the same manner as for the flexible resin (A), except that the hydrogen pressure was adjusted to 15% of the total pressure. The produced ethylene copolymer weighs 10.5Kg
Bulk specific gravity 0.40, melt index (MI)
The powder had a density of 0.910 g/cc and an average particle size of 850 μm with no particles smaller than 150 μm. (Test method) 1 ESCR 5 out of 10 test pieces of a 2 m/m thick sheet with notches immersed in a 10% solution of ESCR "Liponox" (trade name: Liponox NEI, manufactured by Lion Co., Ltd.) were broken. Shown in hours. 2 Low-temperature brittleness test (based on JIS K-7216) The test piece was a sheet with a length of 40 m/m, a width of 6 m/m, and a thickness of 2 m/m with a notch of 0.3 m/m deep in the width direction. The temperature at which one of the five pieces broke was shown. (Test device) Low-temperature brittleness test device 3 manufactured by Toyo Seiki Co., Ltd. Wear test A disk with a diameter of 121 m/mφ and a thickness of 1 m/m was used as a test piece, and the amount of wear (g) after 1000 rotations was shown. (Test conditions) Load: 1.0Kg Wear wheel C-22 Number of wear: 1000 times (Test equipment) Toyo Seiki Taber type rotary abrasser 4 Plastograft torque test Using Haake's electric heating type Plastograph, sample 45g, set temperature 180℃, rotor rotation speed
The stable torque value and resin temperature are shown at 60 rpm. 5 Appearance Set temperature 190℃ from 25m/mφ blow molding machine,
The appearance of the parison extruded at a screw rotation speed of 40 rpm was visually judged. ◎...Very smooth. ○...Smooth. ×...Shark skin occurs. Examples 1 to 3 Various ethylene-butene-1 copolymer resins (manufactured by Nippon Petrochemical Co., Ltd.) with different densities as component (A),
The above-mentioned soft resin (A) as component (B) is kneaded in the proportions shown in Table 1 in a 50 m/mφ extruder set at 200°C to obtain a mixture within the scope of the present invention. Various properties were measured and 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) with various ethylene-butene-1 copolymer resins as the component (B), and various properties were measured. The results are shown in Table 1. Examples 6 to 8 Using soft resin (C) (Example 6), soft resin (A') (Example 7), and soft resin (B') (Example 8) as component (B) Various ethylene-α-olefin copolymer resins were mixed to prepare a mixture in the same manner as in Example 1, and various properties were measured and shown in Table 1. Comparative Examples 1 and 2 Table 1 shows the results of the same evaluation as in Example 1 performed only on ethylene-butene-1 copolymer resins having different densities and N values. Comparative Example 3 Commercially available sheath grade (high pressure polyethylene,
Product 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 Example 7 to
8) and mixed with various ethylene-butene-1 copolymer resins to prepare a mixture outside the scope of the present invention, and evaluated in the same manner as in Example 1.
Shown in the table. Comparative Example 9 Ethylene-butene-1 used in Example 2
A commercially available product (product name:
Tafmar P-0480, MI1.0g/10min, density 0.88
The results are shown in Table 1.

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【table】

Claims (1)

[Scope of Claims] 1 (A) 10 to 90% by weight of an ethylene-α-olefin copolymer having a density of 0.915 to 0.96 g/cc and a melt index of 0.1 to 5 g/10 minutes; and (B) by a gas phase method. , the density obtained by copolymerizing ethylene and α-olefin in the presence of a catalyst consisting of a solid catalyst component containing at least magnesium and titanium and an organoaluminum compound is 0.86 to 0.910 g/cc, and differential scanning calorimetry (DSC) ), 90 to 10% by weight of a soft polymer consisting of an ethylene-α-olefin copolymer whose maximum peak temperature (Tm) is 100°C or higher and the boiling n-hexane insoluble content is 10% by weight or higher.
The density consisting of is 0.91~0.94g/cc, the melt index is 0.1~5g/10min, and the N value is
A polyethylene composition for protective coating of electric wires and cables, the main component of which is a composition in the range of 1.8 to 2.5.