CA1121303A - Cable shielding tape and cable - Google Patents

Abstract

ABRIDGEMENT
The present invention resides in an improved corrosion resistant cable shielding tape comprising a metal strip having a deformation resistant layer of polymeric resinous material tightly bonded to at least one side thereof, the deformation resistant layer having a deformation temperature of at least about 132°C. The shielding tape must meet both the adhesion and deformation resistance requirements simultaneously to provide satisfactory corrosion protection to the shielding tapes by restricting the path of corrosive attack to the exposed metal edges.

Description

\

This invention relates to new and useful improvements for electrical cables adapted for use in supplying electrical power and communications and, more particularly, to an improved corrosion resistant - -cable shielding tape forming a part of such cables.
More specifically, the present invention relates to cable shielding tapes comprising a relatively thin metal strip with one or more layers of polymeric resinous material adhered to at least one side thereof. -- -In the art of designing and constructing electrical cables, especially telecommunication cables such as telephone cables, it is known to assemble in~
sulated conductors in a core and surround it by shield --and jacket components. A well known telephone cable _ design of such construction is referred to in the art as ah "Alpeth" cableO This type of cable is more fully _ _ described in the F. W. Horn et al paper "Bell System Cable Sheaths Problems and Designs" in A. I. E. E.
Proceedings 1951, Volume 70. The shielding tape of the "Alpeth" cable is formed of a layer of bare aluminum having a thickness of about 8 mils which is usually ~
corrugated transversely prior to being wrapped about ~
the cable core. The corrugations impart greater flexi- -bility to the cable and permit bending of the cable without wrinkling or rupturing of the shielding tape~
The term "shield, screen~ or shielding tape"
as used herein means a relatively thin layer o any metal, bare or coated, which can provide mechanical protection and electrostatic and electromagnetic screening ~`
for the conductors in the core of electrical power and co~nunication cables. ---17,942-F

~ '\ ( ( 3LlZ1 303 When telephone cables are installed under- ,,,",","
,. ., :=.
ground by being buried directly in soil, the outer ~''''"'''''' ~acket of such cables, which is formed of a polymeric , resinous material such as polyethylene, may be subjected ~ '' : : ::::
to damage due to the rigors of installation; rocks; '''~
rodents; lightning; frost; or dig-ins. The underlying shielding tape can thus be exposed to sub-surface water or brine and the attendant potential for corrosion.
Where the outer jacket of such cables is formed from a polymeric resinous material, the jacket is ,,'~
not well adhered to the shielding tape of-bare metal. ',',''~
=.. _.
-- The outer plastic jacket is known to slip over the , ,,,,,,~
.. . . ..... ..
'-'- shielding tape and to fold up into shoulders as the cables are pulled through ducts or placed into trenches.
The shielding tape is also known to kink, curl or twist ' ' _ during installion causing fatigue in the tape and, ,in extreme cases, rupture of the tape because of mechanical -_-~
bending stresses exerted thereon.
In order to improve the oorrosion resistance of '20 a shielding tape of bare metal~ a special adhesive poly~
ethylene film may be applied to cover one or both sides of the metallic strip as taug,ht in U.S. Patent Nos.
..... _ ...
3,233,036 and 3,795,540. Such shielding tapes ara widely used in the manufacture of electrical power and communi-cations cables. The adhesive polyethylene used for this ---film contains reactive carboxyl groups which have the - -ability to develop firm adhesion to the metallic strip ' ' and also to the overlying polyethylene jacket. The metal component of such shieldiny tapes provide electro- -''''',, static screening and mechanical strength to the cable; ' :.......

17,942-F -2-~L~LZ~3()3 the polymeric resinous material coating, e.g., ethylene acrylic acid (EAA) copolymer coating, provides bondability, sealability and corrosion protection to the metal component.
- ---A metallic strip, such as aluminum, which is protected by the adhesive polyethylene film normally has higher resistance to corrosion.
When a polyethylene jacket is extruded over the metallic strip coated with the adhesive polyethylene film, ---the heat from the semi-molten polyethylene jacket bonds ~-- ~
the film coated metal strip to the jacket, forming a unitized component~which combines the strength of the --metal strip with the elongation and fatigue resistance of the polyethylene jacket component. Suchjcable construc~
,,.. _ ~ tion is reférred to in the art as a "Bonded Jacket"
:: . . . . _._ cable design. I the heat imparted to the jacket-forming polyethylene is sufficiently high, the shielding tape would become hot enough so that the overlapped portions of th~e shielding tape bond together at the seam, thereby forming a sealed tube or pipe around the core of the cableO The "Bonded Jacket" cable with a sealed seam`~
has improved resistance to moisture penetration into - . : .............
the cable core. This cable construction also has been shown to have greater mechanicàl strength necessary to with~tand repeated bending of the cable, i.e. kinking and fatigue failures of the shielding tape, resulting from bending stresses during installations. Further, ~
the stresses induced by the temperature cycles under -service conditions are reduced.
The plastic coating protects the metal to some `
degree from corrosion by limiting the area over which --17~942-F -3-such corrosion can occur or by preventing contact between the metal and the water or brine. The coating should be tightly bonded to the metal to resist sig-nificant delamination therefrom during exposure to the corrosive water and the mechanical forces exerted by the formation of voluminous metal corrosion products, thereby restricting the path of corrosive attack to the exposed metal edges of the shielding tape.
Recently, examination of several commercial cables utilizing polymeric resinous material coated shielding tapes representative of the prior art has revealed, however, that the coatings on such tapes are damaged during cable manufacture exposing numerous corrodible bare spots on the surfaces of the metal ]5 strip. More specifically, when a polyethylene jacket is extruded over a plastic coated shielding tape, the heat from the molten polyethylene jacket softens or melts the polymeric resinous material coating to obtain a bond to the jacket and a sealed seam. While the coat-ing is in such softened or molten state, it is penetratedor abraded by the smooth, corrugated or embossed core wraps, by the seams of the tape, by the binder tapes, and/or by the weight of the core itself, thereby expos-ing numerous corrodible bare spots on the surfaces of the metal strip. As a result, the corrosion rate at the damaged spots is accelerated due to an unfavorable ratio of the anodic and cathodic areas of bare and coated metal. Furthermore, corrosion propagates between damaged spots and prematurely destroys the longitudinal continuity of the shielding tape which, in turn, can render the cable inoperative. Since telephone cables 17,~47-F -4-~h~3~3 are expected to have a long service life, corrosion of shielding tapes which can lead to premature cable failures is indeed a serious technical and financial problem for the wire and cable industry. The problem of coating damage has not been recognized until the present invention because of the industry's preoccupa-tion with other major problems. One of such problems was the need to develop thermal barrier materials to protect the cable core from heat damage. Another problem was associated with the introduction of fully--filled telephon~ cable designs wherein the cable core is filled with a grease-like compound to prevent ingress and migration of water.
The corrodible bare spots may occur on either side of the shielding tape but the problem is particu-larly critical with the use of corrugated metallic strips where it has been observed that the penetration and/or abrasion damage exposing the bare metal is concentrated on the raised corrugated surfaces of the shielding tape disposed toward the core. A corrosive attack on this type of circumferentially concentrated damaged area of the corrugated metal strip will quickly destroy the longitudinal electrical function of the shielding tape.
In order to maintain the prior art criterion of restrict-ing corrosion to the shielding tape edges, it is nowrecognized that penetration and/or abrasion resistance of the plastic coatings is required, in addition to delamination resistance, to ensure that corrosion is generally confined to the edges of the shielding tape instead of being extended over the entire surface thereof.

17,942-F -5-'~.

3()3 Although there is no known prior art directly concerned with overcoming the above identified problems, ,the following prior patents specifically referred to hereinbelow and in Table II illustrate the closest kno~m prior art in the plastic coated shielding tape technology.
U.S. Patent No. 3,586,756 and U.S. Patent No.
3,950,605 (Example 3 and 6 - Table II) disclose shielding tapes comprising a metal strip having an adhesive polymer ' , coating adhered to at least one side of the metal strip.
However, these prior patents do not provide for a de-formation xesistant layer of a polymeric resinous material composition having a deformation temperature of at least - ' 130C as hereinafter described in this speciication.
.: ! : ` - . ` -The coating on such tapes will be deformed during cable ' 15 manufacture exposiny numerous corrodible bare spots - on the surf~ces of the metal strip.
U.S. Patent No. 3,507,978 (Example 4 - Table II) te~ches a shielding tape comprising a metal foil ha~ing ' layers of a copolymer such as ethylene/acrylic acid chemi-cally bonded to both sldes of the metaI foil and an additional layer of high density poIyethylene bonded to one o~ the copolymer layers. However, there is no teaching or suggestion in U.S. Patent No. 3,507,~78 of the damage problem overcome by the present invention and examination of commercial cables incorporating such a shielding tape also illustrates that penetration and/or abrasion o the high density polyethylene layer occurs at current cable manuacturing and service use conditions.

7~2-rl~ -G-)3 U.S. Patent No~ 3,379,824 (Example 8 -Table II) teaches a shielding tape comprising a three layer structure with an aluminum foil laminated between two polypropylene layers or a polypropylene layer and ~~
a polyethylene terephthalate layer. Againr there is no teaching or suggestion of the damage problem over~
come by the present invention~ In addition, although these plastic layers will resist penetration and abrasion, - -they do not provide corrosion protection when a corro-sive environment is present in a cable since both - polypropylene and polyethylene terephthalate are highly ` inert and can develop only a poor mechanical bond to - --` the metal strip based on friction adhesion. Therefore, - ~
: ,. ................................. . :... _. _ ~ both the polypropylene and polyethylene terephthalate_ -layers will easily delaminate under exposure to corro-- -- sive conditions and the mechanical forces exerted by;~
metal corrosion products.
UOSO Patent No. 3,325,589 (Example 9 to 11 ~
Table II) discloses a plastic coated metal shielding-- _ tape comprising a metal strip having~an adhesive layer immediatel~ adjacent to the metal strip and an additional Myla~ or polypropylene layer adhered to one side of the metal strip. Such a shielding tape was subjected to _ -simulated conditions of cable manufacture and a laboratory --corrosion test. It was found that the tape did not _--provide satisfactory corrosion resistance to the metal, " --i.e., the path of corrosive attack was not confined to the exposed metal edges. The adhesive layer was deformed `
from pressure exerted through the polypropylene or Myiar~
layer thereby exposing bare aluminum spots. Corrosion-``
~3 = Registered Trademark - `

17,942-F -7~

~2,1~03 was taking place on these bare spots after subjecting the cable to a standard corrosion test ~ith sodium hy- - -droxide, as hereinafter defined in this specification, due to the infiltration of the NaOH between the adhesive layer and the polypropylene (PP) or Myla ~ layers.
U.S. Patent No. 3,790,694 (Example 8 - Table II) discloses a polypropylene layer adhesively bonded to a metal strip. The patent does not specify the use - --of any particular adhesive. Since ethylene acrylic acid (EAA) copolymer is the best known metal adhesive in the industry todayr the shielding tapes made according to the teachings of that patent were found to give - similar results~to those of ~.S~ Patent No. 3,325,589.
.. . ................ . _ ... _ - ~ The patent teaches bonding of the jacket, a screen, - ... :.. =:.: :
and composite tapes together during extrusion of the . . . -cable jacket. Sinc~ the thermoplastic coatings on the screen and composite tapes must be above its meltlng point to effect bonding they were found to be damaged _ -.......... . .
a priori. Thus, this prior art patent also failed to recognize the~problem of coating damage on shielding tapes. U.S. Patent Nos~ 3,325,589 and 3,790,6g4, are related to a heat resistan~ core wrap (thermal barrîer) .-.-....-._..
and a fully filled cable, respectively. - -U.S. Patent No. 3,321,572 (Example 13 - Table II) and U.S. Patent No. 3~622,683 (Example 8 - Table II) disclose, inter alia, shielding tapes comprising a metal ` ~
strip having a polymeric reslnous material coating adhered to at least one side thereof and capable of resis- ``~
ting deformation at an elevated temperature. However, `-these shielding tapes were found to fail the adhesion 17,942 F -8-~L~LZ~303 requirement of the present invention. In these tapes, it was found that the path of corrosive attack was not confined to the exposed edges of the metal strip because of the infiltration of corrosive element between the S polymer coating and the metal strip. -U.S. Patent No. 3,484,539 teaches the adhesion : :-of a heat sealable layer, such as, for example, poly~
vinyl chloride to a polymer layer capable of resisting deformation at cable-forming temperatures~ However, the polymer layer of this patent, having adhered thereto ......
a heat sealable layer, is not "tightly bonded" to the metal strip and is thus open to corrosive attack due to the infiltration of corrosion causing liquids when the ~~
cable jacket is damaged.
.- . ~ : .:.. =. .
None of the prior ~rt patents hereinabove - -discussed show or suggest that a deformation resistant layer can be used in a shielding tape to prevent dEmage to the protective coating during cable manufacture, ---installation or service use. Furthermore, none of the polymer coatings on the shielding tapes disclosed in the prior patents meet both the bonding or adhesion and deformation resistance requirements of the present in~
vention to provide satlsfactory corrosion resistance to the shielding tapes by restricting the path of corro- =
sive attack to the exposed metal edges.
Although the "bonded jacket" cables have im~
proved resistance to moisture penetration into the -cable core and have greater mechanical strength necessary - -to withstand repeated bending thereof, some problems have -also been encountered in terminating and splicing the `-.. .

17,942-F -9_ cables. More specifically, it is cumbersome to separate the jacket from the shielding tape for the purpose of making electrical connections to the tape. While it is possible to terminate and splice the "bonded jacket"
cables without separating the jacket from the shielding tape, it has been shown that the quality of electrical connections i5 not as good as that with the jacket removed. More particularly, the electrical properties of the connections to the shielding tape are known to change less with time than the connections to the shield-ing tape and bonded jacket of electrical cables.
The present invention resides in an improved corrosion resistant cable shielding tape comprising a metal strip having tightly and directly adhered to at least one side thereof an irradiated adhesive layer com-posed of a copolymer o~ ethylene and from about 2 to about 20 percent based on copolymer weight of an ethyl-enically unsaturated carboxylic acid, said adhesive layer having a deformation temperature of at least about 270F
a~ter being irradiated with an effective amount of a high energy ionizing radiation wherein the adhesive bond between said metal strip and said adhesive layer is at least 2.2 pounds per inch of shielding tape width after aging for seven (7) days in deionized water maintained at a temperature of 70C.
The present invention also resides in an improved cable adapted for use in supplying electrical power and communications comprising a core of at least one insulated conductor, a shield surrounding said core comprising a metal strip having tightly and directly 17,942-F ~10-3~f~:~.3~)3 adhered to at least one side thereof an irradiated adhesive layer composed of a copolymer of ethylene and from about 2 to about 20 percent based on copolymer weight of an ethylenically unsaturated carboxylic acid, said adhesive layer having a deformation temperature of at least about 270F aEter being irradiated with an effective amount of a high energy ionizing radiation and an outer plastic jacket surrounding said shield.
In a preferred embodiment, the adhesive layer has a deformation temperature of at least about 270~
after being irradiated with an effective amount of a high energy ionizing radiation.
In another embodiment, a second deformation resistant layer and/or other layers of polymeric resinous materials is included in the shielding tape thereby providing a multilayered structure having a combination of desirable functional characteristics.
For example, deformation resistant layers of polymeric resinous material are tightly bonded to both sides of the metal strip, i~ desired, to provide pene-tration and/or abrasion resistance on bo~h sides of the shield-ing tape.

17,942~F -lOa-f~"

. '~ " ~?

~Z1303 In a further embodiment, adhesive layers of polymeric resinous materials having good bonding character-istics to both the metal strip and the deformation resis-tant layer or layers P ~.

- ~ .

17,942-F -lOb-~L~Z~ ~303 are used to tightly bond the deformation resistant layer to the metal strip ~hen direct adhesion of the same is insufficient to adequately provide corrosion protection for the metal strip.
In another e~bodiment, heat seal layers of thermo-plastic polymeric resinous material are included in the shielding tape of this invention to provide a hermetically sealable shield seam in the cable structure and to provide a good bond between the cable shielding tape and outer plastic jacket of the cable.
In a ~urther embodiment, an adhesive/heat seal layer o thermoplastic polymeric resinous material having both good metal bonding and heat seal characteristics is J tightly bonded directly to one side or to opposite sides o~ the metal strip.
The combined layers of po]vmeric resinous materials described above have high electrical resis-t vity, high resistance to chemicals and moisture and exceptionally good bonding to the metal strip thereby being able to withstand the rigors of manufacturing pro-cesses as well as penetration and/or abrasion when in use ~ithout delamination in a corrosive environment.
The shielding tape of this invention must meet both the adhesion or bondillg and deformation resis-25 . tance requirements to provide satisfactory corrosion protection to the shielding tape by restricting the path of corrosive attack to the exposed metal edges of the metal strip.
The present invention also provides a cable 3~ shielding tape to ~31iCh an outer jac);et is finmly bonded and ~hercin the jac};et is easil~ remo~Ted to 17,9~2~

~Z~303 facilitate the splicing and groundiny procedures and yet provides corrosion protection in all areas of such shielding tape by allowing removal of the jacket in such a Manner that a tightly bonded adhesive layer remains on the metal com- ~
ponent of the tape after stripping of the jacket. - --More specifically, such a shielding tape has a - -bond between a metal strip and an adhesive layer tightly bonded thereto which bond is stronger than ~he interlayer - _ bond of othar tightly bonded layers of polymeric resinous material. By judicious selection of the types and propor~
tions of polymer composition for the deformation resistant layer, the bond of the deformation resistant layer to the _ --adjacent layers of ~olymeric resinous material is made weaker than that of the adhesive layer to the metal strip. The interlayer bond must be capable of withstanding delamination --_ under conditions of normal use but which will separate prior to delamination of the adhesive layer from the metal strip. . ~~- _ More specifically, as herein defined, "metal strip" means a relatively thin layer of any metal which t== =
has good electrical or mechanical properties useful in ~-= =
electrical power and communications cables.
As herein defined, the term '`tightly bonded" means _ -~-restricting the path of corrosive attack to the exposed metal edges of the shielding tape by chemically and/or mechan~
ically bonding the deformation resistant layer to the metal strip, either directly or indirectly with an adhesive layer, ``
or by bonding an adhesive/heat seal layer directly to the -metal strip, to prevent significant delamination of the defor-mation resistant and adhesive/heat seal layers from the metal - -strip under exposure to corrosive conditions and the resulting mechanical forces exerted by the rnetal corrosion products.

17,942-F -12-"Adhesive layer", as herein defined, means a layer of polymeric resinous materials having good bonding characteristics with the metal strip and defor-mation resistant layer and the plastic jacket of the electrical cable.
- "Heat seal layer", as herein defined, means a layer of thermoplastic polymeric resinous materials having a sealing temperature of 121C or lower and, pre-ferably, 110C or lower which ~ilI easily seal to itself, or other polymeric resinous materials such as, for example, those materials forming the outer plastic ~- iacket of a cable.
- . ~
~ nAdhesive!heat seal layer"i, as herein de-- fined, means a layer of thermop1astic polymeric resinous materials having both good metal bonding and heat seal ch~racteristics for the adhesiv~ and heat seal layers which will tightly adhere to the metal strip~
~ nDeformation resistant layer", ag herein de-- fined, means a layer of polymeric resinous materials that substantially resist penetration and/or abrasion at deformation temperatures of at least about 130C
- and pressures normally associated with cable manufacture, installation and/or service use.
Improved cables adapted for use in supplying electrical power or communications can be constructed with the improved corrosion resistant cable shielding tape described above. Such cables comprise a core of at least one insulated conductor, a shield of the im-proved corroslon resistant cable shielding tape surroun~ing the core, and an outer plastic jacket surroundin~ the .

~ J-F -]3-tape. The deformation resistant layer of the shielding .. -~:
,,, .;,,, =
tape may be positioned in the direction of the core, .~
in the direction of the outer jacket or in both direc- ...
tions to overcome penetration and/or abrasion damage .~
. ::
during manufacture and/or during service of the cable. .. ~.
- . -,. ., ,., _ The invention is further understood by refer~
ence to the accompanying drawings in which like characters of reference designate corresponding materials and parts .
. ., .::::: ,,,-:
throughout the several views thereof, in which~
Figure 1 is a partial cross-sectional view of a plastic coated metal shielding tape constructed according to the principles of the present invention;
Figures 2-9 are partial cross-sectional views - .
=-- illustrating modified plastic coated metal shielding --:: -tapes constructed according to the principles of the .~
present invention; ~ =
Figure 10 is a cross-sectional view of a typical power cable with three insulated conductors, .
a plastic coated metal shield and an outer plastic . 20 jacket; and -.-..... ~.-Figure 11 is a cu~-away perspective view of -- ----.-._ .
an end of a communications cable with multi pair in~
sulated conductors in the core, plastic coated metal shield and plastic outer jacket.
=
25DETAILED DESCRIPTION OF THF, PREFERRED E BODIMENTS - --Referring now to the drawings, Figure 1 illus~
trates an improved corrosion resis~ant cable shielding `~
-tape 10 comprising a metal strip 12 having a deformation resistant layer 14 formed of a pol~eric resinous 30material such as a blend of 50 weight percent poly~

17,942-F -14-~Z~3~)3 propylene and 50 weight percent ethylene/acrylic acid copolymer tightly bonded to one side thereof. In order to provide corrosion protection for the metal strip 12, shielding tape 10 should be used in cable constructions having a plastic outer jacket formed of --an adhesive composition which will tightly bond to - -_ the metal strip 12 on the side opposite to that of ~-layer 14.
Figure 2 illustrates a modified cable shielding tape 20 having a deormation resistant layer 24 like layer 14 of Figure 1 tightly bonded to metal s~rip 12.
- Layer 25 which is tightly bonded to the opposite side of strip 12 may be a deformation resistant layer like : . . . . - =
layer 24 or may be an adhesive/heat seal layer formed of an ethylene/acrylic acid copolymer. -- _ Figure 3 illustrates another modified cable shielding tape 30. The metal strip 12 may have a de~
formation resistant layer 34 like layer 14 of Figure 1 tightly bonded to one side thereof and a heat seal layer 36 formed of low density polyethylene adhered to layer 34O Alternatively, layer 36 may be a deformation resistant layer formed of a material such as nylon which ---will not tightly bond directly to the~metal strip 12 ---with sufficient adhesion to provide corrosion protection ~5 and layer 34 may be an adhesive layer formed of a material such as an ethylene/acrylic acid copolymer. ~ike --shielding tape 10 of Figure 1, shielding tape 30 should be used in cable constructions which have a plastic outer jacket formed of an adhesive composition to insure corrosion protection for the metal strip 12.
:- .... ~

17,942-F -15-3~)3- -Figure 4 illustrates still anothex modified cable shielding tape 40. There are four possible struc-tures of shielding tape 40 useful in accordanee wiLh this invention. Layer 45 may be a deformation resista~t layer like layer 14 of Figuxe 1 for two of the possible structures or an adhesive/heat seal layer like layer 25 - of Figure 2 for the other two structures. Layer 44 may a~so be a deformation resistant layer like layer 14 of Figure 1 when it will tightly bond directly to the metal strip 12 or it may be an adhesive layer formed of an ethylene/acrylic acid copolymer which in turn is used to tightly bond a deformation resistant layer 46 like layer 36 of Figure 3 that will not tightly bond directly to the metal strlp 12. When layer 44 is a deformation resistant layer tightly bonded to the n~etal strip 1G ~ layer 46 is beneficially a heat seal layer like layer 36 of Figure 3.
f Figure 5 illustrates still another modified cable shielding tape 50. There are three possible 20~ structures of tape 50 useful in accordance with this invention. First, two deformation resistant layers 56 and 57-like layer 36 of Figure 3 which will not tightly bond directly to the metal strip 12 may be tightly . bonded to the strip 12 with adhesive layers 54 and 55 25 . like layer 34 of Figure 3. Second, the remaining two possible structures may have a deformation resistant layer 55 like layer 14 of Figure 1 tightly bonded to the metal strip 12 and a heat seal layer 57 li~e layer 36 of Figure 3 bonded to layer 55. On the opposite ~o side of the metal strip 12 the~e may be a delormation 17,~fi2~

~PZ~03 resistant layer 54 like layer 14 of Figure 1 tightly bonded directly to the strip 12 and a heat seal layer -- -56 like layer 36 of Figure 3 bonded to layer 54 or, in the alternative, there may be a deformation resistant - -layer 56 like layer 36 of Figure 3 which will not tightly - --bond directly to the metal strip 12 that is tightly bonded to the strip 12 with an adhesive layer 54 li~e layer 34 of Figure 3.
Figure 6 illustrates a further modified cable --shielding tape 60. A deformation resistant layer 66 like layer 36 of Figure 3 which will not tightly bond directly to the metal strip 12 is tightly bonded to the =.-strip 12 with an adhesive layer 64 like layer 34 of Figure 3. A heat seal layer 68 formed of an ethylene/- =
1~ acrylic copolymer is bonded to layer 66. Like shielding tapec 10 and 30, shielding tape 60 should be used in cable constructions which have a plastic outer jacket formed of an adhesive composition to insure corrosion ...
protection for the metal strip 12.
. Figure 7 illustrates a still further modified _.--cable shielding tape 70D The adhesive layer 74t defor- .... -.---.-mation resistant layer:76 and heat seal layer 78 are ... -. -the same as the corresponding layers 64~ 66 and 68 found ..
in Figure 6. Layer 75 may be a deformation resistant layer like layer 14 of Figure 1 or, in the alternative, ~~
an adhesive/heat seal layer like layer 25 of Figure 2 ~.
tightly bonded directly to the metal strip 12. ~`
Figure 8 illustrates a still further modified .`.
cable shielding tape 80. The adhesive layer 84, defor~
mation resistant layer 86 and the heat seal layer 88 -17,942-F -17-~Z~303 are the same as the corresponding layers 64, 66 and 68 found in Figure 6. On the opposite side of the metal --strip 12 there may be a deformation resistant layer 85 like layer 14 of Figure 1 tightly bonded directly to the strip 12 and a heat seal layer 87 like layer 36 of - -- : ::::::::::
Figure 3 bonded to layer 85 or, in the alternative, there may be a deformation resistant layer 87 like layer - --36 of Figure 3 which will not tightly bond directly to the metal strip 12 that is tightly bonded to the strip 12 with an adhesive layer 85 like layer 34 of -Figure 3.
.: . :,, =
Figure 9 illustrates a final modified cable - -- :_ . :=__ : shielding tape 90. The adhesive layers 94 and 95, ~~
deformation resistant layers 96 and ~7, and the heat -~
, .. .. .
seal layers 98 and 99 are the same as the corresponding layers 64, 66 and 68 found in Figure 6. _ _ .,, .._ .._ .
Referring now to Figures 10 and 11, a typical three-conductor power cable 100 and multi-pair conductor --,.- .-.-.-,-.,-,,.,,,-,-=
commùnications cable 110 are illustrated. The power cable 100 has low resistance metal conductors 101, which ................
can be solid or stranded, usually of copper or aluminum, - ~
which are each insulated, usually with an extruded plastic cover 102 of, for example, polyvinyl chloride, - . --polyethylene or rubber. Space fillers 103 of, for example, natural fibers or foamed plastic are used to --provide a substantially circular core assembly which is --.. ....
enclosed in a shielding tape 104 formed from any one `~
of the shielding tape structures illustrated in Figures `~
1-9. The shielding tape 104 is preferably a longitudinally ~ --folded tube with an overlapping seam that may be hermati-17,94~-F -I8-~Z~303 cally sealed by heat sealing t~e plastic coating of -- -the shielding tape together in the overlapping seam -- -during cable manufacture. An outer plastic jacket 105, usually extruded polyethylene containing stabilizers and carbon black, is beneficially bonde~ to the shielding ., ,. ,, - -tape 104. The communications cable 110 includes an : ::,..--:: .-inner core of many pairs o insulated conductors 111 (e.g. plastic coated copper wires) bundled in a plastic core wrap 112 of, for example, polypropylené or poly~
- c-~
ethylene terephthalate which is securely bound with a binder tape 113. The bundle is enclosed in a shielding tape 114 formed from any one of~the shielding tape structures illustrated in Figures 1-9. Like the - . = _.-shielding tape 104 of power cable 100, shielding tape 114 is preferably a longitudinally folded tube with a hermetically sealed overlapping seam. An outer plastic ~ -_ jacket 115 preferably of polyethylene is extruded over the shielding tape 114 and is advantageously bonded to the same. __ The metal strip which is used in accordance with this lnvention may have a thickness from 0O2 to 25 mils and, more preferably, from 2 to 15 mils. The metal strip may be formed, for example, from aluminum, aluminum alloys, alloy-clad aluminum, surface modified : - .... ---....... .
copper, bronze, steel, tin free steel, tin plate steel, aluminized steel, stainless steel, surface modified `-copper-clad stainless steel, terneplate steel, gal-vanized steel, chrome or chrome treated steel, lead~
magnesium or tin. These metals may also be surface ---treated or have thereon surface conversion coatings.

17,942-F -19--~lZ~3~3 , .............
The deformation resistant layer which is used in accordance with this invention may have a thickness from 0.1 to 15 mils and, more preferably, from 0.5 to

2.0 mils. Beneficially, the deformation resistant layer ---may be formed from any polymeric resinous material which will provide a layer deformation temperature of at least about 132C such as, for example, polypropylene, carboxyl -modified polypropylene, polyamides, polyethylene terephthalate, fluoropolymers, 1 4 di-methyl pentene polymers, ethylene/propylene copolymers, stereo regular polystyrene, flexible thermoset polymeric resinous --materials, Saran~, or irradiated carboxyl modified -.. _.. ,A ._ olefin polymers. These polymeric resinous materials -_ ......
may be blended with, for example, low or hlgh density polyethylene, ethylene/ethyl acrylate copolymers, ethy~
lene/vinyl acetate copolymers, carboxyl modified ethylene - -polymers, ethylene/acrylic acid copolymers, ionic olefin -poiymers, or chlorinated polyethylene, provided the layer deformation temperature is at least about 132~C.
Flexible thermoset polymeric resinous materials such - _ as, for example, polyurethanes may also be used provided ~ ~-the 132~C deformation temperature is achieved.
The adhesive layer may have a thickness from 0.1 to 10 mils, preferably from 0~3 to 2.5 mils~ Such layer may be formed from any thermoplastic polymeric resinous material which will tightly bond the deformation resistant layer to the metal strip. Copolymers of ethy- -lene and ethylenically unsaturated carboxylic acids readily form a strong adhesive bond with aluminum and are preferred in achieving beneficlal results of the `~ `

17,942-F 20-present invention. The adhesive polymer which is bene- --ficially used in accordance with this invention is a -- -normally solid thermoplastic polymer of ethylene modified -by monomers having reactive carboxylic acid groups, particularly a copolymer of a major proportion of ethy- -~
lene and a minor proportion, typically from 1 to 30, preferably from 2 to 20, percent by weight, of an ethy- =
lenically unsaturated carboxylic acid. Specific examples of such suitable ethylenically unsaturated carboxylic acids (which term includes mono- and polybasic acids, acid anhydrides, and partial esters of polybasic acids) are acrylic acid, methacrylic acid, crotonic acid, ~~
fumaric acid, maleic acid, itaconic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monomethyl fumarate, _ -monoethyl fumarate, tripropylene glycol monomethyl ether _ -acid maleate, or ethylene glycol monophenyl ether acid maleate. The carboxylic acid monomer is preferably ~ --selected from ~ ethylenically unsaturated mono- and ---polycarboxylic acids and acid anhydrides having from

3 to 8 carbon atoms per molecule and partial esters - =
of such polycarboxylic acid wherein the acid moiety ~~--has at least one carboxylic acid group and the alcohol ~~~-moiety has from l to 20 carbon atoms. The copol~mer ---may consist essentially of ethylene and one or more of such ethylenically unsaturated acid comonomers or can also contain small amounts of other monomers copoly- =
merizable with ethylene. Thus, the copolymer can `-contain other copolymerizable monomers including an ester of acrylic acid. The comonomers can be combined in the copolymer in any way, e.g., as random copolymers, 17l942-F -21-1~2~303 as block or sequential copol~ners, or as graft copoly-mers. Materials of these kinds and methods of making them are readily ~nown in the art.
Beneficiallyr thc heat seal layer may have a thickness from 0.1 mils to 10 mils and, preferably, from 0.3 mils to l mil. The heat seal layer may be formed from, for example, low or high density poly-ethylene, ethylene/ethyl acrylate copolymers, ethylene/
vinyl acetate copolymers, carboxyl modified ethylene pol~ners, or blends of the above.
The adhesive/heat seal layer may have a thickness from 0.1 mils to 10 mils and, more preferably, from 1 mil to 3 mils. The adhesive/heat seal layer may be formed from, for example, carboxyl modified olefin 15 - polymers, ionic olefin polymers, blends of carboxyl modified olefin polymers or blends of i~rlic olefir polymers.
Deformation resistance of a layer of polymeric resinous material is normally tested by means of a penetrometer. However, known penetrometers are designed for coatings tcomPrising one or more layers of synthetic resinous material) 60 to -125 mils (1~52 to 3.17 ~m) thick and data therefrom do not apply to the coating thicknesses on cable shieldiny tapes or temperatures and pressures associated with the cable manufacture or use. There-fore, a special penetrometer test was developed to evaluate the ability of relatively tllin coatings, i.~., coatinys haviny a thic~ness of 10 mils (0.254 mm) or less, on plastic clad metals to resist deformation at elevated temperatures. The special penetrometer consists of a metal bloc~ wei~hill~ 1.68 1;~ onto which ~7,~}2-~ -2~-3 (~ 3 a circular ring has been machined. The ring has an outside diameter of 38.1 mm and a thickness of 25 mils.
The cutting edge of the ring in contact with the coated shielding tape sample is rounded to a 0.79 mm radius which applies a pressure to the sample of 35 pounds per square inch (24.6 gm/mm ). The testing procedure con-sists of placing the sample of shielding tape on a base such as a metal plate and then positioning the special penetrometer on the sample with the ring in contact with the coating thereon. An electrical circuit, open because of the coating, is connected between the penetrometer and the metal strip of the sample. Thereafter, the entire assembly is placed in a circulating air oven preheated to 218C which increases the temperature of the shielding tape being tested at a rate of approxi-mately lO~C per minute. When the ring penetrates the coating the electrical circuit is comple~ed and the tem-perature of the coating, determined by a thermocouple or other means, is recorded. This temperature is the deformation temperature, for the coating being tested.
It has been found that the conditions of this test cor-relate well with the temperatures and pressures associ-ated with cable manufacturing and/or service use. It has been found that the deformation resistant layer should have a deformation temperature of at least about 130C and preferably at lea~t about 138C and above to resist the temperatures and pressures normally associ-ated with cable manufacturing and/or service use.
The degree of adhesion between plastic layers, and between a plastic layer and the metal strip of a shielding tape of this invention, which will satisfy 17,94~-F -23-`\
3~3 the requirement for "tightly bonded" thereof, should represent a value of at least about 1 kg/2.54 cm of tape width, preferably at least about 2 kg/2.54 cm, after immersion of a tape sample in deionized water maintained at a temperature for a period of time of 7 days. The degree of adhesion is determined by preparing a 6 inch wide by 6 inch long by 60 mil (15.24 cm x 15.24 cm x 3.175 mm) thick molding of a plastic jacketing material using a procedure similar to that described in the U.S.D.A. (United States Department of Agriculture) Rural Electrification Administration (REA) specification PE-200.
A sheet of shielding tape of the same dimensions (6 in. x 6 in.) was placed over the molding. A strip of polyester film of 1 mil (0.254 mm) thickness was placed between the shielding tape and the molding of the jacketing material to prevent bonding to one end of the jacketing material to form a "tab" for use in a tensile strength testing machine. The shielding tape was bonded to the molding using a compression molding press and a molding temperature of 190C. The molding pressure was 300 pounds per square inch (0.2 kg/mm ). The heating cycle was as followso 3 minutes to reach temperature with no pressure; 2 minutes under pressure; and 5 minutes to cool to room temperature. After the shielding tape/-jacketing material laminate was prepared one inch (2.54 cm) wide samples for bonding tests were cut on a sample cutter. The samples were placed on a tensile testing machine and tested for bond strength as follows:
the unbonded portion of the shielding tape was folded back 180DC; the sample was inserted into the tensile testing machine 17,942-F -24-~L12:~3t)3 with the shielding tape in the upper jaw and the molding , ..,- .
of jacketing material in the lower jaw; a rigid metal plate was placed behind the molding to maintain the ----peeling angle at 180C; and the shielding tape was then separated from the rigid molding of the jacketing ---material at a crosshead speed of 5 inches per minute.
The required force to separate the shielding tape from the molding was recorded as a measure of adhesive strength. The separation can occur at the metal strip/
,- -, ,--,: =
plastic layer interface, or plastic layer/plastic layer -- --interface or plastic layer/jacketing material interface. --Several shielding tapes of plastic coated aluminum wexe prepared and were tested or corrosion ~~
resistance thereof. More specifically, test samples -::::: :::=
of the shielding tapes having an area _ .. . .
of 5.08 cm x 5.08 cm were first subject to a simulated jacketing test, as described hereinafter, - -~
and we~re then immersed in one (1) normal sodium hy~
droxide (lN NaOH) solution for 24 hours. Bare aluminum _::::::::::::::~
spots on the surfaces of ~he shielding tapes, which had been exposed by damage to the plastic coatings thereon --during the simulated jacketing test, were thereby corro- _ -ded. The number of corroded spots, which were easily --identifiable in the test sample of shielding tape r were - --....... -. -counted and recorded as a corrosion damage index thereof~ -An index of 0 indicates that no corrosion spots are present while a given number indicates the number of corrosion spots which can be counted on the sample. -~--Shielding tapes having poorly bonded plastic coatings "
thereon resulted in total dissipation of the metal often accompanied by delamination of the coatings.

17,94~ 25-~Z~3~3 The simulated jacketing test was designed to simulate temperature and pressure conditions normally ellcountered inside a cable, during and following the jacketing operation, in order to study the effects thereof on cable components. The test is particularly well suited to study the effect of the temperature and pressure conditions on the plastic coating or plastic coated shielding tapes. In order to conduct this test, a cylindrical section of a cable having a length of about 5.0 cm is converted into a rectangular configuration having planar surfaces. The test lS carried out using the following procedure: A sample of molded jacketing material of about 5.08 cm x 5.08 cm and weighing 13 grams and having a thickness of 100 mil (2.54 mm) was heated in an oven to a temperature of 218C; the jacketing material was removed ~rom the oven aftel- o to 7 minutes and within a period of 5 seconds a sample of corrugated shlelding tape (5.08 cm x 5.08 cmj was placed on the jacketing material; a corxugated core wrap of polyester fi~nj a section of a cable core having a generally rec-tangular configuration and weighing ~18 grams, and a 2000 gram weight were then successively stacked on top of the shielding tapei and finally, the entire assembly was placed on a large aluminum bloc]c (weighing 955 grams) to cool while the temperature of the core ~rap/-shield interface was recorded through a thermocouple placed therebetween. The al~ninurn block provides a heat sink and thereby simulates the cooling bath located downstream of the extruder head.

17,9~2~ G-i The temperature-time relationships ror the shield obtained with this test correlate to those obtained with cables containing a large number of con-ductor pairs during extrusion of the jacket.~
Heat sealability was determined on film samples ----of the coatings by means of a special seal test. T o :
samples of film 50.8 mm wide are placed in contact with , . ... .
each other in a heat sealer apparatus such as a Sentinel Brand, Model 24AS, or equivalent. The temperature of the sealer bar is increased in 5C increments from 88C to a temperature sufficient to seal the fi ~s --together. The temperature at which the films seal to -~
......... _ .
each other is recorded as the minimum seal temperature.
.......... ..
The dwell time in seconds for the sealer bar is equal - - ~
to 26.25 times the film thickness in mm. The air _-_ pressure on the sealer bar is set to 28 g/ ~ 2.
--.. :. =
The effect of "fillers" for the cable core was ..... _ .
tested with sa ples of plastic coated shielding tapes in . : =--=-which coatings on both sides thereof were exposed to petro- - _ :::...: :_ lat~ filli~g compo ~ ds (Witco 5B) and floodant (Witco 4) -_ ; at 115.5C for two seconds. A percent swell was calculated ~ _ .... ..__..
based on the mo nt of filler-picked up by the coating as follows after the surface thereof is wiped clean of ..... -.-any filler compound: The original weight of the coating -was subtracted from the weight of the coating after ---exposure and this difference was divided by the orlginal . .-.-.- -.-...-.-=
weight. rrhis n ~ er was multiplied by 100 to obtain percent swell. The results of this test are listed in Table IX.

R. C. Mildner, P. C. Woodland, H. A. Walters, and G. E. -:
Clock, entitled, "A Novel Form of Thermal Barrier for Co munication Cables," presented at the 14th International -Wire and Cable Symposium, Atlantic City, New Jersey, 1965. -:-17,942-F -27-In a "connector stability" test, coated metal samples approximately 50 mm x 150 mm were corrugated. -Then two Griplo ~ connectors were attached to each longi~
tudinal end of the samples. The initial resistance in milli-ohms was measured across the connectors using a ~ ~
Kelvin Brid~e. The samples were then given 50 temperature cycles from -40C to ~60C, with each cycle being of ~
an 8 hours duration, and the resistance was measured again. The results of these tests are listed in Table X.
In a jacket bond strength and bend performance test, a bonded jacket gas pipe was fabricated on a cable jacketing line using lengths of corrugated laminates. The laminates were oriented such that the multilayer coated ---side contacted the extruded jacket. Samples of the pipe were then collected for determination of jacket bond strength and bend performance. The results of these tests are listed in Table XII.
, The following additional test methods were used: _ 1. Physical properties of the coating were determined by ASTM D-638. --_ 2. Elmendorf Tear was determined by ASTM
D-1922.
3. Melt Index was determined by ~STM D-1238. --. Representative examples of the present inven-tion along with deformation temperatures and corrosion index test results, are shown in Table I. The examples --were formed by extruding the plastic layers, each of --about one mil thickness, and then laminating them to -a hot metal strip having a temperature of about 190C.

- 17,942-F -28--:~Z~303 Bonded jacket cables incorporating these examples were fabricated on commercial cable manufac-turing lines undcr norT~al proccssinc; conditions.
The penetrometer test for deformation resis-tance was used to obtain the deformation temperature.
Examples 8-11 in Table I show the use of three component blends as the deformation resistant layer.
Example 12 establishes the use of a four com-ponent blend as the deformation resistant layer.
Example 13 establishes the lower limit for deformation temperature of a blend of polye~hylene with polypropylene of about 130C.
Example 14 illustrates the!use of an adhesive - jacket to substantiate the utility of single side coated metals according to Figures 1, 3 and 6.
Example 15 illust~ates an em~odi~ent in rhich polypropylene is used as a deformation resistant layer.
A~ EAA-PP blend is used as a second adhesive layer to bond the deformation resistant layer to a first adhesive layer of EAA. A second DAA-PP blend layer and a heat seal layer of EAA can ~e successlvely applied to the PP layer to obtain low temperature sealability.
- EY~amples 16-I8 are comparative e~amples and t~ere prepared according to the procedure of this invention.
However, the composition of the blend in the deformation resistant layer tJas selected where it was not sufficient to provide a deformation temperature of at least 130~C.
EYample 19 illus rates a particuiar blend in the dcformation resistant layer which falls witl~in th~ des---able ran~e of deformation temperature and corrosion incle~.

~2~303 Example 20 illustrates a functional exarnple with copper. Since copper degrades an E~ coating in the presence of moisture, a copper stabilizer, OABH
(o~alic acid bis (benzylidene hydrazide)), has been added to the EAA.
Example 21 illustrates a functional example with ionomer (Surlyn~ 1652, 11% ~LA) as the metal adhesive layer.
Example 22 illustrates a functional example with an EAA-polyethylene blend as the metal adhesive layer.
Examples 23-25 illustrate functional examples with crosslinked coatings whicll were unusual in that they maintained their bondability, sealability, and corrosion protection qualities after irradiation.
Examples 26-27 illustrate runctional exa~ les with Saran as thè heat deformation resistant layer.
These structures are not illustrated in the drawings.
Like Example 15, a second adhesive layer consisting of a blend or a suitable polymer is used to tightly bond a heat deformation layer to metal. The basic structures ~70uld be: Metal/Adhesive layer/Second Adhesive layer/Deformation layer; ~5etal/Adhesive layer/Second Adhesive layer/Defor-mation Resistant layer/Heat Sealable layer ~VA); or Metal/Adhesive layer/Second Adhesive layer (blend)/Defor-mation layer/Second Adhesive layer (blend)/Sealable la~er.
A comparative analysis of Tables I and II
demonstrates the damage that occurs to the plastic coated s]~ielding tape of the prior art as measured by the nur,lber of corrosion spots counted on a 25 cm2 17,9;12-/ _3~-sample. It also demonstrates the need for a deforrnation resistant layer having a deformation temperature of at least about 130C alld tight bonding ~o prcvent the occurance of ~are spots on the surface Or th~ tape and the attendant potential for corrosion thereon.
Examples 9-11 in Table II illustrate that damage to lower melting point coatings on metal can occur through a deformation resistant layer. ~ithout tight adherence between a deformation layer and a metal adhesive layer, or with bonds between the two that are water sensitive, corrosion can occur at the defects in the adhesive coating on the ~etal.
Example 12 illustrates the non-functionality of this patent construction for corrosion protection.
Example 13 illustrates the need for tight adherence of coating-s to metal.
Table III and IV illustrate the initial bond strengths and bond strengths after aging for 7 days in 70C deionized water~ Two sets of numbers are given in Table III because multilayer coatings may not necessarily fail at the interface of the metal and an imrnediately adjacent plastlc layer during bond strength tests. If the metal bond exceeds the bond of the various plastic layers to each other, then bond failure occurs at the weakest inter~ace thereo. ~The example numbers refer to those in TabIe I and Table II wllere the detailed shielding tape constructions are shown.) The minumum bond strength is 1.0 ~;g/2.54 cm regardless of ~.~he~ller the bond strenyth refers to a metal/polymeric layer hond or to a polymeric layer/polymeric layer bond.

~,9~ 31-llZ~303 For the former, corrosion resistance and mechanical ---performance will be deficient below the minimum bond ~-strength. For the latter, the ability to withstand -handling without delamination will also be impaired below this minimum bond strength.
From Table III, it can also be seen that the judicious selection of the types and proportions of polymer compositions will provide a bond between the - -metal strip and adhesive layer which is stronger than - -the interlayer bond of the other layers of polymeric , --resinous materials while still providing a minimum bond strength of 1.0 kg/2.54 cm between the polymeric coating/polymeric coating bond.
Table V and VI show that the multilayer coatings have improved ultimate tensile strength, elongation, and tear strength when compared to coatings of the presently known art. The example numbers refer - -only to the improved coating structure shown in Table I
and not to the coated metal structure.
Tables VII and VIII show actual cable data- - -wherein the cables are made using several shielding ---tapes described in Tables I an~ II. The same example numbers are used. ---Table IX shows that the improved coatings of this invention have increased resistance to adverse effects of filling and flooding compounds. The attribute - -is also of benefit in extending the service life of filled cables~

17,942-F -32-13~:)3 Table X shows that the connector stability to coated metal is improved with the improved coating since the increase in resistance over the initial value is smaller.
Table XI shows that the electrical breakdown strength and resistance to permeation is improved with the new coating. The electrical strength of the new coating may be used to advantage in filled cable designs by elimination of the standard electrical barrier which ` is wrapped about ~he core. The reduced rates of permeation may serve to improve corrosion resistance.
The bond strength figures of Table XII re-flect the levels of interlayer bond of the multilayer samples. These bond values are approximately 1/2 that of the prior art example 5 of Table II. However, the interlayer failure provide~ a means for controlling the level of bond between the polymer lavers of the shielding tape and the jacket, i.e. a bond strong enough - to provide good mechanical properties while allowing easy stripping of the jacket for splicing. Moreover, at least the adhesive layer of the multilayer coating remains intact on the metal strip to provide continued corrosion protection.

.

' ~Z~3~33 .
The bend performance values are surprising since the multilayer samples, at half the bond strength, exhibited bend performance equivalent to the control sample. These rcsults tend to suggest that bend per-formance requires a moderately high jacket bond strength but perhaps even more important is the ability to relieve stresses. The multilayer film provides a means OI stress relief via the lower interlayer adhesion.

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17, 942-~ -41-Zl~
T~BLE III. THIS INVENTION
., . . ,; ~ ~
Table IBond Stren~th in K~/25.4 mm ExampleTo ~ictal 'rO Plastic No.Initial ~ftcr ~3i.~g Initi~l Aftcr Agin~
1 7.95 9.0~ 3.27 4.09 2 7.95 9.11 1.04 1.09 3* 7.95 9.08 .54 .68

4 7.90 8.99 2.60 2.59 7~95 9.09 " 4.63 2.95 6 2.77 2.93 2.81 2.92 7 15.44 12.94 4.27 5.09 8 6.45 6.04 1.05 1.00 6.3fi 6.18 1.34 1.36 6.36 6.68 2.36 2.13 11 6.45 6.59 3.13 3.09 12 6.45 6.63 1.34 1.32 13 7~5 8.90 8.40 8.42 .
14 7.55 8.35 1.07 1.05 - 15 7.95 ~.77 2.31 2.30 6~ 8 95 9.12 8.18 9.5~
17* 8.95 9.17 7.45 6.13 lB* 8.90 9.13 8.72 ?.13 19 8.92 9.15 ~ .5~ 4.51 20 1~.20 10.50 4,26 4.28 21 7.84 7.90 -1043 1.~5 22 8.29 9.12 2.90 2.93 23 9.G4 10.05 8.45 8.90 24 6.68 i.53 6.95 6.93 8.07 9.50 ~.27 ~.31 26 8.~10 ~.15 1.81 ~.~8 27 8.42 9.23 3.8G 3.91 *ConlparL~t:iv~ L~ml~lcs Z~L303 TABLE IV PRIOR A~T

.

Bond Strength in Lb/In_of Width , Tabte II To Metal To Plastic Example No. Initial After A~ing .Initial After Aging 1 ~.48 11.40 >9.48 >11.40 2 15.80 8.21 >15.8~ > 8.21 . 3 1~.00 13.50 9.39 10.60 : 4 14.78 18.26 >14.78 >18.26 ,5 17.60 19.49 >17.60 ~ I9.49 6 ~10.10 ~14.59 10.10 .14.59 ; . 7 5.9 8.18 > 5.9 > 8.18 .8 : 0 0 i ~ :
9. 17.50 20.10~ 0~3~ 0 17.46 19.23 0.88 0 - ~ 11 17.. 43 :18.96 ~ 0~45 0 ,: .
12 I.10 : 0 - : ~ I.10 > 0 13 0.37 0 ~ 0 .(PSTR side) : . ~
13 15.97 17.45 ~>15.97 >17.45 ~EAA side) :
.

, .17,942-F -43-~.~Z~303 , T~BLE V. THIS INVENTION
l~linimum Table I 2 Elmendorf Seal Tem-E~ampleTensile (l~g/~ ) Elongation Tear 2erature No. Direction Yield Ultimate tp~rcent) ~gms) C
.. , .. _ , 1 MD .96 2.68 580 634 CD .97 2.16 555 672 113 2 MD .99 2.57 605 525 CD .95 2.22 656 717 13 4 MD 1.32 2.58 685 307 113 CD 1.30 2.36 685 442 MD 1.70 4.65 600 166 110 CD 1.80 4.56 540 150 8 MD 1.38 2.82 770 480 CD 1.32 2.58 795 576 104 , 9 MD 1.37 2.64 775 295 CD 1.36 2.58 755 499 104 ; 10 MD 1.41 2.65 695 262 107 CD 1.35 2.49 750 486 - 11 MD 1.32 2.60 760 352 110 CD 1.29 2.50 800 538 ; 12 ~D 1.38 2.84 715 416 CD 1.27 2.47 740 589 110 TABLE VI. PRIOR ART

.
Table II
Example i~o .
1 MD1.13 1.90 300 170 110 CD1.06 1.58 450 190 MD.74 1.79 450 244 107 ; CD.71 1.8-3 560 308 Tensile and Elongation. ASTi~ D-882 MD - Machine Direction CD - Cross Maclline Direction Elmendorf Tear. AST~1 D-1922 3~)3 .

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~ x 17, 942-F _47_ ~l'hl303 -s , , TABLE X. CONNECTOR STABILITY .~

, Table I Resistance in Milliohms(l) . --2` -.. -Example No. Initial After Cyclizing~
2 0.6663 1.187 0.6912 1.702 .. ,,, .. ,, .. ,, -18 0.7353 1.7825 ........ -3` : :.-.
5` ' 0.6750 2.727 .

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mm sample of coated metal; the resistance of r:::-::::::::::::
the assembly was measured with a Kelvin ~..... _ Bridge = -~
:, . ... ..-Resistance after 50 -40 to +60C temperature =
cycles,.each cycle of 8 hours duration ~
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llZI303 From the fore~oin~ detailed description, it can be seen that the present invention provides an impxoved corrosion resistant cable shielding tapc for use as a shield in electrical potter and communications cables.
! ' Specifically, the present invention resides in an improved corrosion resistant cable shielding tape comprising a metal strip having a deformation resis-tant layer of polymeric resinous material tightly 1 10 bonded to at least one side thereof, the defo m ation ; resistant layer having a defoîmation temperature of at - least about 130C. The shielding tape must meet both the adhesion and deformation resistance requirements simultaneously to provide satisfactory corrosion pro-tection to ~he shielding tapes by restricting the path ! ` of corrosive attack to the exposed metal edges. ~-The deformation resistant layer of pol~eric resinous material must therefore resist penetration and/or abrasion exposing the metal strip at the tem-peratures and pressures noxmally associated with cable manufacturing and/or service use.
The present invention also provides a plastic coated cable shielding tape which includes layers of polymeric resincus material other than tlle deformation resistant layer thereby formin~ a multilayered struc-ture having a combinatlon of desirable unctional characteristics.

]/,~ 5~-

Claims (6)

IN THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An improved corrosion resistant cable shielding tape comprising a metal strip having tightly and directly adhered to at least one side thereof an irradiated adhesive layer composed of a copolymer of ethylene and from about 2 to about 20 percent based on copolymer weight of an ethylenically unsaturated carboxylic acid, said adhesive layer having a deformation temperature of at least about 270°F after being irradiated with an effective amount of a high energy ionizing radiation wherein the adhesive bond between said metal strip and said adhesive layer is at least 2. 2 pounds per inch of shielding tape width after aging for seven (7) days in deionized water maintained at a temperature of 70°C.

2. The improved cable shielding tape of Claim 1 wherein a second adhesive layer composed of a copolymer of ethylene and from about 2 to about 20 percent based on copolymer weight of an ethylenically unsaturated carboxylic acid is disposed between and tightly and directly adhered to said metal strip and said second deformation resistant layer, the adhesive bond between said metal strip and said second adhesive layer and between said second adhesive layer and said second deformation resistant layer being at least 2.2 pounds per inch of shielding tape width after aging for seven (7) days in deionized water main-tained at a temperature of 70°C.

3. The improved cable shielding tape of Claim 2 wherein said second adhesive layer has a deformation temperature of at least about 270°F after being irradiated with an effective amount of a high energy ionizing radiation.

17,942-F 52

4. An improved cable adapted for use in supplying electrical power and communications comprising a core of at least one insulated conductor, a shield surrounding said core comprising a metal strip having tightly and directly adhered to at least one side thereof an irradiated adhesive layer composed of a copolymer of ethylene and from about 2 to abut 20 percent based on copolymer weight of an ethylenically unsaturated carboxylic acid, said adhesive layer having a deformation temperature of at least about 270°F after being irradiated with an effective amount of a high energy ionizing radiation and an outer plastic jacket surrounding said shield.

5. The improved cable of Claim 4 wherein a second adhesive layer composed of a copolymer of ethylene and from about 2 to about 20 percent based on copolymer weight of an ethylenically unsaturated carboxylic acid is disposed between and tightly and directly adhered to said metal strip and said second deformation resistant layer, the adhesive bond between said metal strip and said second adhesive layer and between said second adhesive layer and said second deformation resistant layer being at least 2.2 pounds per inch of shielding tape width after aging for seven (7) days in deionized water main-tained at a temperature of 70°C.

6. The improved cable of Claim 5 wherein said second adhesive layer has a deformation temperature of at least about 270°F after being irradiated with an effective amount of a high energy ionizing radiation.

17,942-F 53