NZ277458A - Elastomeric combination of acrylate with fully hydrogenated butadiene/acrylonitrile copolymer; crosslinked and use in electrical cables - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £77458 New Zealand No. 277458 International No. PCT/AU94/00773 TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates: 15.12.1993; Complete Specification Filed: 15.12.1994 Classification:^) C08F299/00; C08L9/02; C08L33/08.10; C08J3/24; H01B3/28.44 Publication date: 24 February 1ftno Title of Invention: Elastomeric compositions Name, address and nationality of applicant(s) as in international application form: PACIFIC DUNLOP LIMITED, an Australian company of Level 41, 101 Collins Street, Melbourne, Victoria 3000, Australia Journal No.: 1425 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION New Zealand No. International No. 277458 NEW ZEALAND PATENTS ACT 1 953 COMPLETE SPECIFICATION Title of Invention: Elastomeric compositions Name, address and nationality of applicant(s) as in international application form: PACIFIC DUNLOP LIMITED, of Level 41, 101 Collins Street, Melbourne, Victoria 3000, Australia, arv AaS+TO-^OA 277458 PCT/A1394/00773 TITLE Elastomeric Compositions FIELD AND BACKGROUND OF THE INVENTION This invention relates to elastomeric 5 compositions particularly- those compositions for use in electrical cables. Certain electrical cables reqpiire insulation covering and sheath with elastomeric compositions that are halogen free, flame retardant and resistant to fluids. Where cables are used in marine 10 applications there are a number of standards that define the operating qualities and characteristics of both the elastomeric compositions in the cables. Such standards include British Naval Engineering Standards NES 518, NES 525 and NES 526. The Australian Department of Defence 15 (NAVY) has a comparable standard known as A014000. The elastomeric composition described hereunder has been designed to preferably satisfy all of the standards referred to above.

When cables are used in a marine environment, 20 there is an inherent necessity to withstand hostile conditions said rough usage. The cables can be exposed to salt water and a variety of hydrocarbon fluids such as hydraulic fluid, diesel, fuel and lubricating oils. It is important that cables can operate for long periods and are / 4 ^ <3 designed to withstand damage from the hostile environment. One of the most feared occurrences at sea is fire. The confined configuration of marine vessels made it essential that electrical fires or action damage fires are not spread 5 by flaming cables. It is also critical that if the cables do catch fire that they do not produce hazardous hydrochloric fumes or other corrosive volatiles. A further demand for cables for use in marine applications is the ability to operate satisfactorily for long periods over a 1G wide temperature range and have a good capacity to withstand abrasive forces.

The present invention relates to materials particularly for use in the sheathing and insulation covering where applicable of cables of this kind.

SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a halogen free elastomeric composition comprising a combination of acrylate elastomer and fully hydrogenated butadiene/acrylonitrile copolymer (HNBR), the 2 0 elastomeric composition being cross-linked to meet the mechanical property characteristics required by Australian Department of Defence (Navy) Standards A014000.

Preferably, the acrylate elastomer is ethylene-methyl acrylate (EMA). However, it is understood that the 2 5 acrylate elastomer may also be ethylene-ethyl acrylate (EEA) or ethylene-butyl acrylate (EBA).

According to a still further aspect of the present invention, there is provided a halogen free elastomeric composition comprising (in parts by weight): 3 0 a) 50 to 80 parts of ethylene-methyl acrylate (EMA) copolymer with acrylate content of greater than 40%; b) 20 to 50 parts of a fully hydrogenated butadiene/acrylonitrile copolymer with acrylate content greater than 30%, the total polymer content of (a) and (b) 3 5 making 100 parts; c) 2 to 5 parts Of one or more processing aids; d) 100 to 170 parts of aluminium hjfji^^i, Office of NZ 1 7 CZC 1997 Received 277458 m with one or more endothermic fillers of BET surface area of between 5 and 20 m2/g; e) 1 to 4 parts of antioxidant; f) 1 to 10 parts of colorant; whereby the elastomeric composition is cross-linked to meet the property characteristics required by Australian Standard A014000.

The invention also relates to an electrical cable sheathed and insulated by the elastomeric composition 10 described above.

DESCRIPTION OF PREFERRED EMBODIMENTS The development of elastomeric composition for use in cables for marine applications requires careful consideration of applicable standards that define the 15 operating qualities. One such standard is Australian Standard AO 14000.

A particularly difficult requirement of this standard is the resistance to a range of fluids such as aviation fuels, hydraulic fluids (both petroleum and 20 silicone based), lubricating oils (both detergent mineral based and synthetic ester based), mineral oil as represented by ASTM reference oil No. 2 and deionised water, and deionised water with 3.5% sodium chlord.de.

Other requirements are that the compound is halogen free, 25 while achieving a flame retardance of limiting oxygen index 32 minimum, and in combination with the other cable components, produces a cable of specified resistance to flame propagation, be low in smoke and low in toxicity under combustion conditions. Mechanical properties of the 30 compound must be maintained to tensile 6.0 MPa minimum, elongation 125% minimum and tear 5N/mm minimum. In addition, the compound in combination with the other cable components must provide a low temperature flexibility of up to -20°C.

In developing a suitable elastomeric composition, a variety of compounds were produced essentially comprising a mixture of Ethylene Acrylic (EA) Rubber ami hydrogenated Intellectual Property Office of NZ 1 ? DEC 1997 received WO 95/16728 PCT/AU94/00773 NitriXe Butadiene Rubber (HNBR) in a range of proportions. Although the invention contemplates the use of a variety of ethylene acrylic (EA) rubbers including ethylene-methyl acrylate (EMA), ethylene-ethyl acrylate (EEA) and ethylene-5 butyl acrylate (EBA) the majority of four experimentation, and testing was conducted on a composition including EMA. Compound 1 was 100% EMA, compound 2 had an EMA/HNBR ratio of 85/15, in compound 3 the ratio was 50/50, in compound 4 the ratio was 25/75 and compcund 5 was 100% HNBR. All the 10 compounds were tested for tensile strength and elongation properties. Compounds 1, 2 and 3 were tested for tear resistance and compounds 2 and 3 were also tested to fluid immersion with lubricating oil 0X38 (Aeroshell 750) for 28 days at 50°C as specified in paragraph 6.2 of the 15 specification of Australian Standard A014000. Compound 3 was also tested against the other fluid immersion types referred to in paragraph 6.2 of the Australian Standard. The EMA used in these tests was a Du Pont product sold under the trademark VAMAC N123. The material composition 20 of this product is a copolymer of ethylene-methyl acrylate and a third monomer containing carboxylic curing sites. It also contains 23 parts of compounding ingredients for each 100 parts of ethylene-acrylic elastomer. The HNBR used in these tests was a Bayer product sold under the trademark 25 THERBAN and essentially comprise hydrogenated butadiene/acrylonitrile rubber. The acrylic content of the EMA was in the order of 40% for VAMAC N123. The acrylonitrile content of HNBR was 38% (Therban 1907).

Further details of the processing aids, fillers, 30 antioxidants, colourants, curing agents and other additions are listed from the following table: Process Aids MawiA parts per hundred ARMEEN 18D 0 .5 Stearic Acid 2.0 TE-80 Powder 2.0 Composition N-octadecyl amine N-octadecanoic acid Metal oleates, stearates, hydrocarbons and monohydroxy compounds Fillers Name HYDRAL 710 MISTRON Vapour Talc 15 APYRAL B120 PERKASIL KS 404GR Composition Aluminium Hydroxide Magnesium Silicate Aluminium Hydroxide Silica Specific Surface Area (BET) 6-8 20 -12 Antioxidants Name SANTOWHITE Composition 4, 4' - butylidene - bis 6-t-butyl-m-cresol Colourants UV - sterilizer composition SAF Carbon Black N110 (ASTM) Type Carbon Black Super Abrasion Furnace Black Curing Agents Name HVA2 (accelerator) PERKADOX 14-40MB (crosslinking agent) Composition N, N' -m-phenylenedixna leimide Bis (Tert-butylperoxy-Isopropyl) benzene Other Additive - Deodourant Vanillin A specific example of a composition made in accordance with the provisions of this invention is listed hereunder: Example phr VAMAC N123 62 THERBAN 1907 50 MISTRON Vapour Talc HYDRAL 710 150 SANTOWHITE Powder 2 ARMEEN 180 in • o Vanillin 0.2 Stearic Acid 2 HVA2 2 PERKADOX 14-40MB SAF Black in • o The compound was used in the laboratory using two roll mills. It was then pressed into sheets at 160°C for sixty minutes, and the sheets were watercooled to room temperature. Samples from the prepared sheets were then 20 tested for a series of unaged and aged physical properties. The results of these tests are shown in Table 1.

The samples prepared from the moulded sheets were then left in a constant temperature room to stabilise for 24 hours before testing. The stabilised moulded sheets 25 were then cut into dumbbells and evaluated to determine the unaged mechanical properties including tensile strength, elongation at break and tear resistance followed by the determination of mechanical properties of heat aged samples and a wide range of fluid immersion properties. These 30 results are shown in Table 2.

Tests were conducted on an elastomeric composition that was essentially VAMAC with evaluation of the HFS-90-R and HFS-110-R cable ratings to meet the fluid resistance tests as specified in Australian Standard A014000. It was discovered that the compound that consisted merely of VAMAC when immersed in Fluid Type C2 (OX 38, Aeroshell 750) for 28 days at 50° failed to meet the specified criteria.

A compound that incorporated 50% HNBR 50% VAMAC in accordance with the example listed above was then evaluated to determine its tear, heat ageing anH fluid immersion properties.

The composition was therm-chemically cross linked 10 but it is understood that other curing techniques are envisaged such as electro-beam cross linking with appropriate compound modifications.

TABLE 1 Test Result SDecified A014000 Unaged Mechanical Properties Tensile Strength (mPA) 8.3 6.0 minimum Elongation (%) 265 150 minimum Tear Resistance (Nmm1) .3 .0 minimum Mechanical properties after ageing at 130°C for 20 days Tensile Strength (mPA) 12.8 6.0 minimum Elongation (%) 150 100 minimum Limiting Oxygen Index L.O.I. 40 32 Weathering Tensile Strength % Retained 115 75 minimum Elongation % Retained 97 75 minimum Surface Examination Under Magnification No Cracks No Cracks Hardness IRHD 82 55 minimum, 85 maximum Acid and Corrosive Gas Emission 1. pH minimum 4.8 3.5 minimum 2. Conductivity jjS^cm 13 100 maximum PT-D/C 648 TABLE 2 Fluid Immeision Fluid TvDe Test Conditions Retained (%) L E.

SDecified A014000 Retained (%) Is Ib ProDulslon Fuels A1 F 76 24 hours at 100°C 101% 83% 60 min. 60 min.

A2 F44 24 hours at 50°C 98% 89% 60 min. 60 min.

Hvdraulic Fluids B1 0x30 28 days at 50°C 122% 94% 60 min. 60 min.

B2 HS200 X 28 days at 50° C 84% 119% 60 min. 60 min.

Lubricaffna Oils C1 OMD113 28 days at 50°C 124% 75% 60 min. 60 min.

C2 OX 38 (Aeroshell) 28 days at 50° C 105% 79% 60 min. 60 min.

Mineral Oil D1 ASTM Oil. No. 2 18 hours at120°C 127% 92% 60 min. 60 min.

Water E1 Deionised Water 28 days at 50°C 100% 87% 80 min. 80 min.

E2 Deionised Water 28 days at 50°C 111% 81% 80 min. 80 min.

It is considered that this particular compound passes the unaged and aged mechanical criteria tests also the fluid immersion criteria tests for cable ratings HFS-90-R and HFS-110-R. HFS-90-R defines a sheath 5 characteristic of a halogen free elastomeric compound based on cross-linked ethylene acrylate copolymer, suitable for up to and including a maximum of 90°C continuous operating temperature. HFS-110-R relates to a higher temperature version of HFS-90-R, suitable for up to and including a 10 maximum of 110°C continuous operating temperature.

AMHKXUKE A copy of pages 19, 28, 29 and 30 taken from Australian Department of Defence (Navy) Standard AO 14000 SPECIFICATION A014000 ISSUE 1 NOVEMBER 1993 6. TESTS 6.1 GENERAL Cables shall be capable of complying with the tests specified in Table 7. All tests shall be made as specified in Table 7 and Clause 9.

In some individual cases cables may be subject to additional tests not included in Table 7. Such additional tests, if any, are detailed in the individual specification sheets (see Appendix D).

Attention to safety the tests is drawzx to Appendix A in respect measures when performing some of specified.

Except where otherwise specified, the tests listed in Table 7 need not be performed in 20 the order numbered. 6.2 FLUID IMMERSION The test method, as is specified for Mineral Oil Immersion Test in AS1660, applies except that the following 25 conditions and fluids shall be used: Type A (Propulsion fuels) (i) Fuel oil, NATO F-76 to DEF (AUST) 5213, specimens immersed for 24h at 100 ± 3°C. (ii) Aviation turbine fuel, F-44 AVCAT/FSII to DEF(AUST)5207, specimens immersed for 24h at 50 ± CTmQTTTTTTC CTTPCT rpuU 76V 2°C.

Type B (Hydraulic fluids) (1) Hydraulic fluids (Petroleum based), 0X30 to DEF STAN. 91-35/1, specimens Immersed for 28 days at 50 ± 2°C. (ii) Hydraulic fluid (Silicone based), HS200X, specimens immersed for 28 days at 50 ± 2°C.

Type C (Lubricating oils) (i) Lubrication oil (Detergent mineral based), OMD 113 to DEF STAN 91-22/2, specimens immersed for 28 days at 50 ± 2°C. (ii) Lubrication oil (synthetic ester based), 0X38 to DERD 2487 (Issue 4), specimens immersed for 28 days at 50 ± 2°C.

Type D (Mineral oil) Mineral oil as is specified in AS1660, with the specimens subjected to the following immersion time and temperature: (i) HFS-90-R or HFS-110-R sheathed - for 18h at 120 ± 3°C. (ii) HFS-90-TP sheathed - for 4h at 70 ± 2°C.

Type E (Water) (i) Deionised water, specimens immersed for 28 days at 50 ± 2°C. (ii) Deionised water + 3.5% by mass Na CI, specimens immersed for 28 days at 50 ± 2°C.

Any use of alternative fluids shall be subject to a written approval by the QA.

On completion of the test, the specimen shall meet the criteria specified in Table 9.

QTTOCNTl I'l'k RWFFT fRule 261 SPECIFICATION A014000 ISSUE 1 NOVEMBER 1993 Table 9 TESTS FOR MATERIAL CHARACTERISTICS OF SHEATH - CRITERIA, CATEGORY AND REFERENCE -(Sea NOTES 1,2 6 3) 1 .. 2 3 4 6 TOBt Criteria Category Reference HFS-90-R SHEATH HFS-110-R SHEATH HFS-90-TP SHEATH of test for test method A. Mechanical tests without ageing on conditioned specimens: Type AS 1660 1. Tensile strength/ minimum (MPa) 6.0 6.0 2. Elongation at rupture, minimum (percent) 150 150 100 3. Tear resistance, minimum (N/mn) B. Mechanical tests after ageing In air oven (see NOTE 2) Duration (hrs) and temperature of ageing (deg.C) 240 h at 120 ± 3 480 h at 130 ± 3 240 h at 100 ± 2 Type AS 1660 1. Tensile strength, actual minimum (MPa) 6.0 6.0 8.0 2. Elongation at rupture, actual minimum (percent) 100 100 80 I M J* ;I ;1 ;2 ;3 ;4 ;5 ;6 ;Test ;Criteria ;Category ;Reference ;HFS-90-R SHEATH ;HPS-110-R SHEATH ;HFS-90-TP SHEATH ;of teBt for test method ;C. Fluid immersion* (conditions per Clause 6.2) 1. Tensile strength, minimum (percentage of values found in the unaged specimens) Type AS in AS 1660 for Mineral oil immersion test Fluid types: A, B, C, 60 60 - D, 60 60 70 E, 2. Elongation at rupture, minimum (percentage of values found in the enaged specimens) 80 80 - Fluid types: A, B, C, 60 60 - D, 60 60 70 E, eo 80 - D. Loss of mass, maximum (see NOTE 2) (mean loss in mg/sq.cm of exposed surface of specimen) 2.0 Type AS 1660 1 2 3 4 6 Test Criteria Category Reference HFS-90-R SHEATH HFS-110-R SHEATH HFS-90-TP SHEATH of test for test method E.

Pressure test at high temperature t Test temperature (deg.C) Identification, maximum (percent) - - 90 ± 2 50 Type AS 1660 F.

Heat shock The sheath shall show no sign of cracking or flaking either when initially wound on the mandrel or after the test.

Type AS 1660 o.

Limiting oxygen indax, minimum 32 34 Type AS 2122 H.

Temperature index, minimum (deg. C) 250 250 250 Type Clause 6.3 J.

Acid and corrosive gas emission: Type AS 1660 1. pH, minimum 2. Conductivity, maximum [(micro S cm(to the minus 1)] 3.5 100 3.5 100 3.5 100 1 2 3 4 6 Test Criteria Category Reference HFS-90-R SHEATH HFS-110-R SHEATH HFS-90-TP SHEATH of test for test method K. Durometer hardness (IRHD) (a) minimum 55 55 - Type ASTM D2240 (b) maximum 85 85 L. Weathering (a) Tensile strength minimum (percentage of value found in unweathered specimen) 75 75 75 Type ASTU D2565 and clause 6.S (b) Elongation at rupture minimum (percentage of value found in unweathered specimen) 75 75 75 (c) Surface examination under x magnification No cracks No cracks No cracks NOTES: 1. A hyphen in the Criteria column means that the test is not applicable for the given sheath. 2. For HFS-90-TP the test procedure in AS 1660 for Thermal Ageing and Loss of mass for PVC shall be followed. 3. The tests are to be performed on samples from flat moulded sheets 2mm ± 0.2 nan thick prepared under Laboratory conditions. 2774

Claims (7)

WHAT WE CLAIM IS:

1. A halogen free elastomeric composition comprising a combination of acrylate elastomer and fully hydrogenated butadiene/acrylonitrile copolymer (HNBR), the elastomeric composition being cross-linked to meet the mechanical property characteristics required by Australian Department of Defence (Navy) Standards A014000.

2. The composition according to claim 1 wherein the acrylate elastomer is ethylene-methyl acrylate (EMA).

3. The composition according to claim 1 wherein the acrylate elastomer is ethylene-ethyl acrylate (EEA).

4. The composition according to claim 1 wherein the acrylate elastomer is ethylene-butyl acrylate (EBA).

5. A halogen free elastomeric composition comprising (in parts by weight): a) 50 to 80 parts of ethylene-methyl acrylate (EMA) copolymer with acrylate content of greater than 40%; b) 20 to 50 parts of a fully hydrogenated butadiene/acrylonitrile copolymer with acrylate content greater than 30%, the total polymer content of (a) and (b) making 100 parts; c) 2 to 5 parts Of one or more processing aids; d) 100 to 170 parts of aluminium hydroxide or/and with one or more endothermic fillers of BET surface area of between 5 and 20 m2/g; e) 1 to 4 parts of antioxidant; f) 1 to 10 parts of colorant; whereby the elastomeric composition is cross-linked to meet the property characteristics required by Australian Standard A014000.

6. a halogen free elastomeric composition substantially as described herein with reference to the Example.

7. An electrical cable insulated and sheathed by the elastomeric composition according to any one of the preceding claims. Intellectual Property Office of NZ END OF CLAIMS 17 DEC 1997 RECEIVT?