CABLE HAVING A COATING LAYER MADE OF A RECYCLED POLYMER MATERIAL

Abstract

A cable contains a core including a transmissive element and a coating layer made of a coating material. The coating material contains, with respect to the total weight of polymeric materials present in the composition, (i) 70% to 95% by weight of a recycled linear low density polyethylene (r-LLDPE); and (ii) 5 to 30% by weight of an ethylene-vinyl acetate copolymer (EVA). The coating layer shows mechanical properties comparable to those of a virgin polymer composition and better, both before and after ageing, than recycled polymer-based compositions containing recycled LLDPE but free from EVA. The EVA may be added to the r-LLDPE or, alternatively, be already contained in the r-LLDPE as a result of previous LLDPE use. The cable may further contain a skin layer placed around and in direct contact with the coating layer based on r-LLDPE.

Claims

1. A cable comprising: a core comprising a transmissive element, and a coating layer made of a coating material, said coating material comprising: (i) a recycled linear low density polyethylene in an amount of from 70% to 95% by weight; and (ii) an ethylene-vinyl acetate copolymer in an amount of from 5 to 30% by weight; the weight percentages being expressed with respect to a total weight of polymeric materials present in the coating material.

2. The cable according to claim 1, wherein the ethylene-vinyl acetate copolymer is recycled.

3. The cable according to claim 1, wherein the coating material comprises a recycled linear low density polyethylene in an amount of from 80% to 90% by weight with respect to the total weight of polymeric materials present in the coating material.

4. The cable according to claim 1, wherein the coating material comprises an ethylene-vinyl acetate copolymer in an amount of 10% to 20% by weight with respect to the total weight of polymeric materials present in the coating material.

5. The cable according to claim 1, wherein the coating material further comprises a virgin polyethylene homopolymer or copolymer in an amount of 5 to 50% by weight with respect to the total weight of polymeric materials present in the coating material.

6. The cable according to claim 1, wherein the coating material further comprises an additional recycled polyethylene homopolymer or copolymer in an amount of 5 to 50% by weight with respect to the total weight of polymeric materials present in the coating material.

7. The cable according to claim 5, wherein the virgin polyethylene homopolymer or copolymer is selected from linear low density polyethylene and high density polyethylene.

8. The cable according to claim 6, wherein the additional recycled polyethylene homopolymer or copolymer is recycled high density polyethylene.

9. The cable according to claim 1, wherein the coating material further comprises a detackifier in an amount of from 1 to 25% by weight with respect to the total weight of polymeric materials present in the coating material.

10. The cable according to claim 9, wherein the detackifier is in an amount of from 1 to 8% by weight with respect to the total weight of polymeric materials present in the coating material.

11. The cable according to claim 9, wherein the detackifier is at least one of talc, kaolin, calcium carbonate, chalk, stearic acid and a stearate.

12. The cable according to claim 1, wherein the coating material further comprises carbon black.

13. The cable according to claim 12, wherein the carbon black is in an amount of from 0.5% to 10% by weight with respect to the total weight of polymeric materials present in the coating material.

14. The cable according to claim further comprising a skin layer around and in direct contact with the coating layer.

15. The cable according to claim 14, wherein the skin layer is made of a virgin polyethylene.

16. The cable according to claim 14, wherein the skin layer has a thickness of from 1 to 20% of the thickness of the coating layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further characteristics and advantages will be more apparent from the following description of some embodiments given as a way of an example with reference to the attached drawings in which:

[0038] FIG. 1 shows a sectional view of an energy cable according to an embodiment of the present disclosure;

[0039] FIG. 2 shows a sectional view of an energy cable according to another embodiment of the present disclosure.

[0040] FIG. 1 shows a low voltage (LV) cable 1 comprising four cable cores 2. Each cable core 2 comprises an electric conductor 2a made of a metal such as copper or aluminium or composite thereof, in the form of bundled or stranded wires or of a single rod. Each electric conductor 2a is surrounded by an insulating layer 2b. The insulating layer 2b can be made of a polymer material such as polyethylene.

[0041] The four cable cores 2 are stranded together and at least partially embedded in a filler 5 made of a polymeric material. The filler is surrounded by a sheath or jacket 3 made of a polymeric composition according to the present disclosure.

[0042] The cable of FIG. 2 differs from that of FIG. 1 in that the jacket 3 is surrounded by a skin layer 4 according to the present disclosure.

[0043] EXAMPLE 1

[0044] The following polymer materials were tested:

[0045] M1 (reference material): virgin LLDPE having a density of 0.923 g/cm.sup.3 and added with 2.5 wt % carbon black (final density: 0.936 g/cm.sup.3; MFI=0.85 g/10 min);

[0046] M2: recycled LLDPE from mulching films containing 5.6 wt % of EVA, density=0.969 g/cm.sup.3;

[0047] M3 (comparative): 65-75 wt % of recycled low density polyethylene (LDPE)+25-35 wt % of recycled LLDPE+less than 5 wt % of recycled polypropylene (PP),

[0048] MFI=0.8-1.1 g/min, density=0.920-0.930 g/cm.sup.3;

[0049] M4 (comparative): recycled LDPE containing less than 40 wt % of recycled LLDPE, MFI=0.7−1.0 g/min, density=0.920−0.935 g/cm.sup.3;

[0050] M5 (comparative): recycled high density polyethylene (HDPE), MFI=0.5 g/min, density=0.95 g/cm.sup.3;

[0051] M6 (comparative): recycled high density polyethylene (HDPE), MFI=0.2 g/min, density=0.96 g/cm.sup.3;

[0052] M7: 70 wt % of M2+30 wt % of M1;

[0053] M8: M2 added with carbon black (2.5 wt %);

[0054] M9: M2 added with chalk (5.0 wt %)+carbon black (2.5 wt %);

[0055] M10: M2 added with talc (2.5 wt %)+carbon black (2.5 wt %);

[0056] M11 (comparative): M4 added with carbon black (2.5 wt %);

[0057] M12: M2 added with talc (2.5 wt %).

[0058] Materials M1, M7, M8, M9, M10 and M12 are according to the present disclosure. The above materials were tested as follows.

[0059] Preparation of Films.

[0060] The granules of the tested materials were placed in batches of about 150-250 ml between the rolls of a Schwabenthan laboratory testing roll mill. The roll distance was smaller than 3 mm. The obtained film was partially cut and folded over itself before going back into the mill in order to make it the most homogeneous possible. Then, the roll distance was increased to an extent so as to take out an even film from the roll mill. The film was placed to cool before it was put into a polymer press to homogenize the polymer and to create a sample piece of an even width.

[0061] Preparation of Specimens for Testing.

[0062] The polymer film was cut to fit into metal templates of 1 mm thickness. The film inside the template was put in between two polyester covers to prevent adhesion between polymer and metal. Finally, the covered film was put between two flat metal plates before being put into the press. The press had two compartments, one lower and one upper. Into each one separately, the samples were placed. The compartments were heated to 180° C. throughout the first 10 min, then cooling was initiated. The pressures were set to 1 bar for 5 minutes, to 10 bar for 10 minutes, then the last 5 minutes were under cooling. After 15 min inside the press, the samples were heated, pressed and cooled. The plates, covers and metal templates were removed, and the samples were stented into dumbbells using a wrench.

[0063] Tensile Strength (TS) and Elongation at Break (EB) Tests.

[0064] The dumbbell specimens were subjected to tensile testing according Swedish standards SS 424 14 18 (2007) and SS-EN 60811-100 (2014), using an initial stretching speed of 25 mm/min. The test was carried out on 5 samples before and after ageing.

[0065] Ageing was carried out by putting five specimens of each material in an oven at 100° C. for 240 hours. The specimens were taken out of the oven, maintained at room temperature for at least 16 hours and then tensile properties were assessed again as described above.

[0066] The results are reported in Table 1.

TABLE-US-00001 TABLE 1 Sample TS (MPa) before ageing TS (MPa) after ageing EB (%) before ageing EB (%) after ageing M1* 27.9 25.8 808.7 828.0 M2 28.9 26.5 828.9 813.0 M3* 19.9 17.5 727.2 730.4 M4* 24.0 24.3 693.0 747.0 M5* 26.1 26.3 880.5 453.8 M6* 32.3 33.5 966.7 1010.3 M7 27.8 25.8 835.4 836.9 M8 27.6 — 828.4 — M9 25.2 24.6 788 833.9 M10 28.7 24.8 830 840.3 M11* 26.3 22.5 780 780.1 *comparative

[0067] As from Table 1, the compositions according to the present disclosure (M2, M7, M8, M9 and M10) showed mechanical properties comparable to those of a virgin polymer composition (M1) and better, both before and after ageing, than recycled polymer-based compositions comprising recycled LLDPE (M3, M4) but free from EVA. The compositions comprising recycled HDPE (M5, M6) showed a better performance by virtue of the higher density of that polyethylene.

[0068] Low Temperature Testing.

[0069] Three specimens of each material were put into a cold chamber at −20° C. for at least 16 hours. Then the specimens were brought to room temperature and they were caught in a wrench and fixed at both ends. The distance between the ends was 1.sub.o. By using a crank shaft rotated of one turn every five seconds, an approximate elongation speed of 20 mm/min was applied.

[0070] The elongation at break (EB) of the samples were evaluated as in Example 1.

[0071] The results are reported in Table 2.

TABLE-US-00002 TABLE 2 Sample EB (%) after cold treatment M2 >200 M4* >200 M5* 25 M6* 70.8

[0072] While the composition according to the present disclosure (M2) maintained suitable mechanical properties after cold treatment, the ones comprising recycled HDPE (M5, M6) had a remarkable drop making their use for a cable sheath questionable.

[0073] The composition M12, having mechanical features similar to those of composition M10, was also tested for environmental stress crack resistance (ESCR) according to ASTM D1693-13 using 100% Igepal. No imperfections were observed after more than 1,000 hours.

EXAMPLE 2

[0074] 4000 m of N1XE-AS 4G95 0.6/1 kV cables were produced having a jacket made from a composition according to the present disclosure or from a comparative one, selected from those of Example 1. Some cables were provided with a skin of virgin polymeric material, having a thickness of 10% of the thickness of the outer sheath.

[0075] Tensile and elongation at break tests were performed on samples of the outer sheath. In particular, tests before and after ageing at 100° C. for 240 hours were carried out on samples of the outer sheath detached from the cable.

[0076] The results are reported in Table 3.

TABLE-US-00003 TABLE 3 Sample M4* M12 M12 + LLDPE skin M12 + MDPE.sup.° skin M12 + HDPE.sup.°° skin TS (MPa) before ageing 19 30.7 32 31.4 31.2 TS (MPa) after ageing — 26.2 29.4 28.2 27.0 EB (%) before ageing 633 785 784 794 820 EB (%) after ageing — 773 817 793 822 .sup.°Medium density polyethylene having a density of 0.936 g/cm.sup.3 and added with 2.5% carbon black (final density: 0.948 g/cm.sup.3; MFI = 0.7 g/10 min); .sup.°°High density polyethylene (density: 0.950 g/cm.sup.3; MFI = 0.3 g/10 min)

[0077] While the cable outer sheath made with a comparative composition (M4) had, after extrusion, mechanical features unsuitable for a cable even before ageing, the cable outer sheaths made with a composition of the present disclosure had suitable mechanical features after ageing too. The presence of skin layer made of virgin polyethylene material did not substantially change the mechanical features.