Cable sheath containing a polymer blend of polyvinylbutyral and thermoplastic polyurethane

Abstract

A cable having one or more conductors and a jacket is provided, where the jacket is made from a composition including a polymer blend of thermoplastic polyurethane (TPU), and Polyvinylbutyral (PVB), with the ratio of PVB to TPU being less than 50% PVB by weight of the total weight of the polymer blend, the remainder of the polymer blend being TPU.

Claims

1. A cable comprising: one or more conductors; and a jacket, wherein said jacket is made from a composition including a polymer blend of thermoplastic polyurethane (TPU), and Polyvinylbutyral (PVB), with the ratio of PVB to TPU being less than 50% PVB by weight of the total weight of the polymer blend, the remainder of the polymer blend being TPU.

2. The cable as claimed in claim 1, wherein said the ratio of PVB to TPU being substantially 25% PVB to 75% TPU by weight over the total weight of the polymer blend.

3. The cable as claimed in claim 1, wherein the TPU of the polymer blend is selected from a thermoplastic polyether polyurethane and a thermoplastic polyester polyurethane.

4. The cable as claimed in claim 1, wherein said composition further comprises one or more fire retardants.

5. The cable as claimed in claim 1, wherein said composition further comprises from 5 to 60 parts by weight of fire retardants, per 100 parts by weight of the polymer blend.

6. The cable as claimed in claim 4, wherein said fire retardants are selected from the group consisting of inorganic flame retardants, organic flame retardants and mixture of organic and inorganic flame retardants.

7. The cable as claimed in claim 6, wherein the organic flame retardants are selected from nitrogen components, halogenated flame retardants, phenol formaldehyde resins, phosphorous containing flame retardants, and mixtures thereof.

8. The cable as claimed in claim 6, wherein the composition comprises as organic fire retardants a mixture of a nitrogen component and a phosphorous containing flame retardant; or as inorganic flame retardants a mixture of at least one silicate and at least one metal hydroxide.

9. The cable as claimed in claim 1, wherein said PVB is recycled.

10. The cable as claimed in claim 1, wherein said composition further comprises a PVB plasticizer.

11. The cable as claimed in claim 10, wherein the PVB plasticizer is selected from the group consisting of aliphatic esters, aromatic esters, fatty esters, phosphate esters, sulfonamides, phthalates, and mixtures thereof.

12. The cable as claimed in claim 1, wherein said composition further comprises a compatibilization agent selected from the group consisting of polymers grafted or copolymerized with polar groups.

13. The cable as claimed in claim 1, wherein said PVB is a random ter-polymer of vinyl butyral, vinyl alcohol and vinyl acetate as co-monomers.

14. The cable as claimed in claim 1, wherein said cable is a mining cable that passes at least one of the mechanical standards of Insulated Cable Engineers Association (ICEA) ICEA S75-381; the abrasion testing requirements of ISO/NFT 4649; the SHA (Mine Safety and Health Administration) fire safety standards of 30 CFR 7.402, 7.406, and 7.408.

15. The cable as claimed in claim 1, wherein said cable is an automation cable that passes at least one of the VW-1 flame propagation testing and standards according to UL 1581ed4 (08/2013), UL 2556 (03/2013), and/or ASTM D 5207-14; the FT1 flame propagation test according to UL 1581ed4 (08/2013) and UL 2556 (03/2013) and/or ASTM D 5207-14; and the Vertical flame propagation on insulated conductor or cable standards according to IEC 60332-1-1 & 1-2 ed 1.0 (2004-07)).

16. The cable as claimed in claim 1, wherein said jacket surrounds one or several insulated conductors.

17. The cable as claimed in claim 8, wherein the composition comprises as organic fire retardants a mixture of a nitrogen component, a phosphorous containing flame retardant, and as inorganic fire retardant a boron containing compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood through the following examples and accompanying drawings, which are given by way of illustration only, and thus, which are not limits of the present invention.

(2) FIG. 1 shows an exemplary mining cable with a jacket according to the prior art;

(3) FIG. 2 shows an exemplary mining cable according to one embodiment of the invention;

(4) FIGS. 3 and 4 show the comparison of calorimeter results and a Petrella plot for Comp.A, Comp.B compositions as well as for TPU1, FR TPU2, FR TPU3, FR TPU4, and FR TPU5 compositions; and

(5) FIGS. 5 and 6 show the comparison of calorimeter results and a Petrella plot for Comp.A, Comp.B compositions as well as for FR TPU2, FR TPU6, and FR TPU7 compositions.

DETAILED DESCRIPTION

(6) FIG. 1 shows a 2 AWG 3/C 2 KV round G-GC orange TPU mining cable (1) of the prior art having: three conductors (2), each including a plurality of metallic wires made of tinned copper, each conductor being surrounded by a separator made of a polyester tape (3), each separator being surrounded by an insulation (4) made of ethylene propylene rubber, one ground-check conductor (5) including a plurality of metallic wires made of tinned copper, said conductor being surrounded by an insulation (6) made of polypropylene, two ground conductors (7), each including a plurality of metallic wires made of tinned copper, each conductor being surrounded by a polyester tape (8), one central filler (9), and an outer jacket (10) made of TPU.

(7) FIG. 2 shows a mining cable (11) according to the invention having: three conductors (12), each including a plurality of metallic wires, each conductor being surrounded by a separator made of a polymer tape (13), each separator being surrounded by a polymer insulation (14), one ground-check conductor (15) including a plurality of metallic wires, said conductor being surrounded by a polymer insulation (16), two ground conductors (17), each including a plurality of metallic wires, each conductor being surrounded by a polymer tape (18), one central filler (19), and an outer jacket (20) made from a composition including a polymer blend of thermoplastic polyurethane (TPU) and Polyvinylbutyral (PVB), with the ratio of PVB to TPU being less than 50% by weight.

(8) In one example insulated conductors (12, 14) are constructed as three separate 2AWG (American Wire Gauge) tinned copper conductors (12) insulated with ethylene propylene rubber (14). Filler (19) is positioned in the center of cable (11) to maintain the spacing of conductors (12, 15, 17). Ground conductors (17) may be constructed of 7AWG tinned copper covered in polyester tape. Ground check-conductor (15) may be constructed with 8AWG tinned copper and insulated with polypropylene (16).

(9) Applicants note that cable (11) is an exemplary construction of the type of cables, such as a mining cable that the present TPU/PVB polymer blend may be applied as a jacket. However, the salient features of the present arrangement, and in particular the polymer blend used for jacket (20), may be used on any applicable cable, heavy industry cable, automation cable or mining cable.

(10) In one embodiment, as discussed in the summary above, jacket (20) may be constructed of a polymer blend based on TPU and PVB and including additional additives as discussed in detail below with respect to the following tables 3 as well, as the additional additives expanded on thereafter.

(11) The following table 3 shows four different formulas for a cable jacket. The left column shows pure TPU (prior art, not part of the invention). TPU1 is TPU/PVB at 75%/25% weight ratio. FR TPU1 according to one embodiment is TPU/PVB at 75%/25% ratio and including fire retardant additives. FR TPU2 according to one embodiment is TPU/PVB at 75%/25% ratio and including fire retardant additives (at a different ratio than FR TPU1). Applicants note that formulas FR TPU1 to FR TPU5 (see the below Table 5 for FR TPU3 to TPU5), are based on phosphorous and nitrogen system. FR TPU6 and FR TPU7 (see the below Table 9 for FR TPU6 and FR TPU7) are based on inorganic flame retardants.

(12) The TPU contained in the following formulas is polyether type TPU. It is noted that, melamine cyanurate is a fire retardant additive. DEPAL (aluminium diethyl-phosphinate) is fire retardant additive, and zinc borate is also a fire retardant additive.

(13) TABLE-US-00003 TABLE 3 COMPOSITIONS Reference Comp.A (8) TPU1 FR TPU1 FR TPU2 TPU ether (1) 75 75 75 PVB (2) 25 25 25 DEPAL (3) 8.5 8.5 MC (4) 8.5 8.5 Zinc borate (5) 3 10 ATH (6) Nanoclay (7) TOTAL (phr) 100 100 120 127

(14) In the present specification, compositions are described with per hundred rubber (phr), the rubber being the polymer blend of TPU and PVB.

(15) The following is at least one commercial version of the above listed components from Table 3:

(16) (1) Elastollan 1185 A 10: polyether-TPU with hardness 85 ShA from BASF GmbH, density=1.12;

(17) (2) PVB B0: post consumer PVB from Hainault Plast coming from interlayer in laminated glass, obtained after specific purification treatment involving low impurities content, Melt Index (190 C., 2.16 kg)=1.80.1 g/10 min, density=1.08; PVB B0 contains approximately from 30 to 40 parts by weight of plasticizer, with respect to 100 parts of PVB.

(18) (3) MELAPUR MC 25: melamine cyanurate from BASF GmbH, density=1.7, average particle size D50=25 microns. It is a salt comprised of melamine and cyanuric acid held together by an extensive two-dimensional network of hydrogen bonds;

(19) (4) Exolit OP 1230: aluminium diethyl phosphinate (also called DEPAL) from Clariant, phosphorous content P=23.3-24 wt %, average particle size D50=20-40 microns, density=1.35;

(20) (5) Firebake ZB: zinc borate from Borax. It is a boron flame retardant used as smoke and afterglow suppressant and anti-arcing agent in polymer. Chemical and theorical composition are respectively 2ZnO.3B.sub.2O.sub.3.3.5H.sub.2O and 48.05%/37.45%/14.5% of B.sub.2O.sub.3/ZnO/H.sub.2O The average particle size is 9 microns measured by laser diffraction;

(21) (6) APYRAL 40: aluminium trihydrate Al(OH)3 from Nabaltec. 99.5% of purity. Average particle size is D50=1.3 microns; specific surface area=3.5 m.sup.2/g; density=2.4;

(22) (7) Cloisite SE 3000: this nanoclay is a layered magnesium aluminium silicate platelets which are organically surface modified to permit complete dispersion in polymer matrix. Its thickness is 10 to 50 times smaller (ca. 1 mm) than conventional layered fillers such as kaolin with an exceptionally high aspect ratio of more than 100, allowing high improvement of the properties even at very low concentration of nanoclay, and

(23) (8) Pure TPU Elastollan 1185 FHF.

(24) It is noted that in addition to the three exemplary polymer formulas TPU, FR TPU 1 and FR TPU 2 set forth above, it is contemplated that certain variations may be included such as: a variation of the ratio of TPU/PVB (variations above and below 75%/25% provided that the amount of PVB remains below 50%; and a change in the amounts or types of combined fire retardant ingredients.

(25) Once the formulation is set, the polymer blend is compounded to prepare for extrusion as a jacket onto cable (20). Before mixing, TPU is dried in an oven during 2 hours at 90 C. The laboratory samples from this application are made with an internal mixer 300 cc with mixing parameters described below.

(26) Mixing parameters with an internal mixer 300 ccare the following ones: Heating of the mixer to 130 C.; Incorporation of TPU polymer and mixing at 80 rpm until 160 C.; Incorporation of PVB, flame retardants and other ingredients at 40 rpm; and Unloading between 180 and 185 C. and homogenizing on external mixer at 150 C.

(27) The compounds are put into 5 mm-slab shape after calendering in roll mill.

(28) The following Table 4 shows the various testing results of TPU1, FR TPU1 and FR TPU2 when undergoing the mechanical testing required for ICEA S-75-381, the abrasion testing results under ISO/NFT 4649 (Method B rolling sample), and finally the fire test results under 30 CFR 7.406 and 7.408. The trials were done on sheathed copper wire 1.5 mm.sup.2 and material thickness ca. 1.2 mm.

(29) TABLE-US-00004 TABLE 4 CHARACTERISTICS Property Comp.A TPU1 FR TPU1 FR TPU2 Density 1.12 1.113 1.15 1.14 TS (psi/MPa) 6526/45 6367/43.9 4495/31 5325/36.7 EB (%) 600 463 428 388 Tear strength 154/27.2 150/26.3 105/18.3 (ppi/N .Math. mm) Abrasion loss(mm3) 55 66 105 110 NFT4649-method B Fire test (lab trials) Pass (lot failed Pass with a Pass without type FT2 of burning few burning burning drops) drops drops TS = tensile strength/EB = elongation at break

(30) From the results it is shown that TPU1 TPU/PVB 75/25 was acceptable on the mechanical testing the flame test requirements under 30 CFR 7.408. This is because PVB is relatively durable mechanically, and is a good match with TPU for mining cables.

(31) Formulas FR TPU1 and FR TPU2, in addition to have acceptable mechanical properties, did pass the flame test requirements under 30 CFR 7.408, and in fact exceed pure fire resistant commercial TPU (Comp.A), because of the addition of efficient fire retardant additives. In fact, FR TPU2 far outperformed standard grade TPU, experiencing no burning drops during flame test. In particular, DEPAL has synergistic properties with melamine cyanurate in the composition of the present invention.

(32) The tests above were performed on the exemplary embodiment of the TPU/PVB formulation in the context of certain tests for the mining industry. However as noted above, the present TPU/PVB formulation can be used on other cables such as those in industry automation. The following is another exemplary embodiment of the TPU/PVB formulation in the context of industry automation requirements.

(33) In the present arrangement, as explained below, additional TPU/PVB blends were prepared for test abrasion loss, tensile strength and flexibility against comparison pure TPU Elastollan 1185 FHF and 1190FHF from BASF (named Comp.A above mentioned and Comp.B below mentioned).

(34) In order to compare fire performance of formulas a cone calorimeter was used on the Comp.A and Comp.B formulas as well as TPU1, FR TPU1, FR TPU2, FR TPU3, and FR TPU4.

(35) Test conditions cone calorimeter (ISO 5560 part 1&2)

(36) TABLE-US-00005 MEASUREMENT Prescription Heat Flux (Kw/m.sup.2) 50 50 Plate dimension 100 100 3 100 100 3 Horizontal or vertical plate horizontal Spacing specimen/cone (mm) 25 25 With or without grid with Air flow in exhaust tube (l/s) 24 24

(37) (The plates are preheated during 3 min at 180 C., then molded at 180 C./200 bars during 5 min and then cooled 5 min until 80 C.)

(38) A Petrella plot is used to represent cone calorimeter results. (Ref: The Assessment of Full-Scale Fire Hazards from Cone calorimeter Data, R. V. Petrella, Journal of Fire Sciences 1994; 12; 14).

(39) Fire-retarded materials should present a low fire load (i.e. total heat release, THR), have a long time to ignition (t.sub.ign), a low peak heat release rate (PHRR), and so a low fire growth index (PHRR/t.sub.ign).

(40) PHRR/t.sub.ign is the ratio of peak of heat release rate to time to ignition. It represents the measure of contribution that the material concerned makes to a rapidly growing fire. THR is the measure of contribution that the material concerned makes to a fire of long duration.

(41) A Petrella plot (THR vs PHRR/t.sub.ign) is a schematic representation of fire retarded materials to compare them easily. The lower the fire growth index and THR, the better the material is. In this plot system, higher values of PHHR/t.sub.ign are associated with a greater propensity to flashover.

(42) One parameter a cone calorimeter analysis is the number called FIGRA which is the ratio between peak of heat release and time necessary to obtain this peak (KW/s). This ratio is defined as the fire growth rate index and must be the lowest possible.

(43) With applicant equipment, required values to be similar in properties to commercially available flame retardant TPUs named hereafter Comp.A and Comp.B: Minimum technical requirements THR<86 and PHHR/t.sub.ignition<29 Preferred technical values THR82 and PHHR/t.sub.ignition22

(44) The Comp.A and Comp.B formulas as well as TPU1, FR TPU2, FR TPU3, FR TPU4, and FR TPU5 formulas are set forth in the following table 5.

(45) TABLE-US-00006 TABLE 5 COMPOSITIONS Reference Comp.A Comp.B TPU1 FR TPU2 FR TPU3 FR TPU4 FR TPU5 TPU ther 75 75 75 75 75 PVB 25 25 25 25 25 DEPAL 8.5 8.5 8.5 15 MC 8.5 8.5 8.5 15 zinc borate 3 10 7 4 ATH nanoclay 3 3 TOTAL (phr) 100 100 100 120 127 127 137

(46) The following table 6 shows the results of the cone calorimeter tests on the above formulas.

(47) TABLE-US-00007 TABLE 6 RESULTS Reference Comp.A Comp.B TPU1 FR TPU2 FR TPU3 FR TPU4 FR TPU5 PHRR (kW/ 760 622 1250 716 488 462 446 m.sup.2) tti (s) 30 26 18 18 20 21 24 THR (kW/m.sup.2) 82 79 100 93 81 77 74 PHRR/tti 25.3 23.9 68 39.8 24.4 22.5 18.6 (kW .Math. m.sup.2 .Math. s.sup.1) FIGRA (kW .Math. 7.1 6.2 11.4 5.1 6.2 3.2 2.6 m2 .Math. s1)

(48) FIGS. 3 and 4 show the comparison of calorimeter results and a Petrella plot for Comp.A, Comp.B compositions as well as for TPU1, FR TPU2, FR TPU3, FR TPU4, and FR TPU5 compositions.

(49) The following tables 7-10 illustrate formulations (table 7), and the test results of the cone calorimeter tests (table 8) for formula FR TPU6 and FR TPU7, which are based on inorganic flame retardants.

(50) In addition, FIGS. 5 and 6 show the comparison of calorimeter results and a Petrella plot for Comp.A, Comp.B compositions as well as for FR TPU2, FR TPU6, and FR TPU7 compositions.

(51) TABLE-US-00008 TABLE 7 COMPOSITIONS Reference Comp.A Comp.B FR TPU2 FR TPU6 FR TPU7 TPU ether (1) 75 75 75 PVB (2) 25 25 25 DEPAL (3) 8.5 MC (4) 8.5 Zinc borate (5) 3 ATH (6) 28 23 Nanoclay (7) 5 TOTAL (phr) 100 100 120 128 128

(52) TABLE-US-00009 TABLE 8 RESULTS Reference Comp.A Comp.B FR TPU2 FR TPU6 FR TPU7 PHRR (kW/m.sup.2) 760 622 716 814 427 tti (s) 30 26 18 26 28 THR (kW/m.sup.2) 82 79 93 80 83 PHRR/tti 25.3 23.9 39.8 31.3 15.5 (kW .Math. m.sup.2 .Math. s.sup.1) FIGRA 7.1 6.2 5.1 5.5 2.9 (kW .Math. m2 .Math. s1)

(53) The advantage of formulas FR TPU6 and FR TPU7 is the low smoke release compared with for example formula FR TPU2. The addition of nanoclay in formula allows a reduction of 47% of PHRR value and a slight increase of time to ignition.