JPS6142367B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and effective improvement in electrical cables suitable for use in power supply and communications;
More particularly, the present invention relates to cable shielding tapes having improved corrosion resistance that form part of such cables. More particularly, the present invention relates to a relatively thin metal strip having one or more layers of polymeric resin material deposited on at least one side. BACKGROUND OF THE INVENTION In the art of designing and constructing electrical cables, particularly telecommunication cables such as telephone cables, it is known to combine insulated conductors into cores and surround them with shielding and jacket components. A well-known telephone cable design of such construction is referred to in the art as an "Alpes" cable.
This type of cable is described by F.D. Horn et al. in ``Bell System Cable Sheaths Problems.
amd Designs, AIEE Proceedings1951,
Volume 70”. The shielding tape for "Alpes" cables is usually about 8 cm thick and is laterally corrugated before being wrapped around the cable core.
Formed from a layer of bare aluminium. To impart greater flexibility to a corrugated cable and to enable the cable to be bent without creating wrinkles in the shielding tape or destroying the tape. In this text "shield, screen or shielding tape" means any metal, bare or coated, capable of providing mechanical protection and electrostatic and electromagnetic shielding to the core conductors of power and communication cables. It means a thin layer. When telephone cables are installed underground by burying them directly in the soil, the outer jacket of such cables, which is formed of a polymeric resin material such as polyethylene, is protected against the rigors of installation, by rocks, vultures, lightning, frost or Damage may occur due to dig-ins. Therefore, the underlying shielding tape may be exposed to subsurface water or salt water, where it may become corroded and corroded. When the outer jacket of such cables is formed from a polymeric resin material, the jacket does not adhere well to bare metal shield tape. The outer plastic jacket is known to slide over the shielding tape and form a folded shoulder when the cable is pulled out of the duct or placed in the groove. It is known that shielding tapes can become kinked, curled or twisted during installation, resulting in tape fatigue, and in extreme cases, mechanical bending stress can cause the tape to fail. To improve the corrosion resistance of bare metal shielding tape, one or both sides of the metal strip may be coated with a special adhesive polyethylene film as taught in U.S. Pat. Nos. 3,233,036 and 3,795,540. I can do it. Such shielding tapes are widely used in the manufacture of power and communication cables. The adhesive polyethylene used in this film contains reactive carboxyl groups that have the ability to form a strong adhesion to the metal strip and also to the overlying polyethylene jacket. The metal component of such shielding tapes provides electrostatic shielding and mechanical strength to the cable, and the polymeric resin material coating, such as ethylene acrylic acid (EAA) copolymer coating, provides the metal component with adhesion, sealing properties and corrosion resistance. . Metal strips, such as aluminum, protected by an adhesive polyethylene film usually have a greater corrosion resistance. When extruding a polyethylene jacket onto a metal strip coated with an adhesive polyethylene film,
The heat from the semi-molten polyethylene jacket causes the film coated metal strip to adhere to the jacket, forming an integral component that combines the strength of the metal strip with the elongation and fatigue resistance of the polyethylene jacket component. Such cable constructions are referred to in the industry as "bonded jacket" cable designs. If the heat applied to the jacket-forming polyethylene is high enough, the shielding tape becomes hot enough that the seams of the overlapping portions of the shielding tape adhere to each other, resulting in the formation of a sealed tube around the cable core. . "Glued jacket" cables with sealed seams have improved resistance to moisture infiltration into the cable core. This cable construction has been shown to have the greater mechanical strength required to resist kinking and fatigue failure of the shielding tape resulting from repeated cable bending or bending during erection or bending stress during erection. It was done. Additionally, stresses caused by temperature cycling under severe conditions are reduced. Plastic coatings provide some protection to the metal from corrosion by limiting the area where corrosion can occur and by preventing contact of the metal with water or salt water. The coating must be firmly adhered to the metal in order to resist a significant degree of delamination when exposed to the mechanical forces exerted by corrosive water and the formation of bulky metal corrosion products; Corrosion attack paths to the exposed metal edges of the shielding tape are restricted. However, a recent examination of some commercially available cables using polymeric resin material coated shielding tapes, which are representative of the prior art, shows that the coating on such tapes has been damaged during cable manufacturing and has caused damage to the surface of the metal strip. was found to expose numerous corrodable bare spots. More specifically, during cable manufacturing, when a polyethylene jacket is extruded onto a plastic-coated shielding tape, the heat from the molten polyethylene jacket softens or melts the polymeric resin material coating, resulting in the jacket adhesion and sealing. Give a seam. While the sheathing is in this softened or molten state, the sheathing may be affected by smooth, corrugated or embossed conductor jackets, tape seams, binder tapes and/or the weight of the conductor itself. The metal strip undergoes penetration or abrasion, exposing a number of bare spots on the surface of the metal strip that can be corroded. As a result, the corrosion rate at the damaged point is accelerated due to the unfavorable ratio of anodic and cathodic areas of bare metal and coated metal. Additionally, the corrosion will spread between damaged locations, permanently destroying the longitudinal continuity of the shielding tape and eventually rendering the cable unusable. Since telephone cables are expected to have a long service life,
Corrosion of shielding tapes, which can lead to premature cable failure, is indeed a significant technical and financial problem for the telephone and cable industry. The problem of coating damage was not recognized prior to the present invention because the industry was preoccupied with other major problems. One such problem has been the need to develop thermal barrier materials to protect cable cores from thermal damage. Another problem has been with the introduction of fully filled telephone cable designs in which the cable core is filled with a greasy compound to prevent water ingress and migration. Bare spots that can be corroded can occur on both sides of the shielded cable, but the problem is concentrated on the protruding corrugated surfaces of the shielding tape that expose bare metal and/or abrasion damage that is placed towards the conductors. This is particularly important when using corrugated metal bodies. A corrosive attack of this type on a peripherally concentrated damage area of the corrugated metal strip would quickly destroy the longitudinal electrical function of the shielding tape. In order to maintain prior art standards for controlling corrosion to the edges of the shielding tape, penetration of the plastic coating and ( or) a new recognition of the need for wear resistance. Although the known prior art is not directly related to overcoming the above problems, the following prior art patents mentioned below and specifically mentioned in Table 1 describe the closest known prior art in plastic coated shielding tape technology. U.S. Pat. No. 3,586,756 and U.S. Pat.
Specification No. 3950605 (Examples 3 and 6 - Table 1) states:
A shielding tape is disclosed that consists of a metal strip having an adhesive polymer coating applied to at least one side. However, these prior patents do not provide a deformation resistant layer of a polymeric resin material composition having a deformation temperature of at least 130°C, as discussed later in the text. The coating on such a tape would deform during cable manufacture, exposing a number of bare spots on the surface of the metal strip that could be corroded. U.S. Pat. No. 350,778 (Example 4 - Table 1) teaches that layers of a copolymer, e.g. A shielding tape is taught consisting of a metal foil with one layer adhered to it. However, there is no teaching or suggestion in U.S. Pat. No. 3,507,978 about the damage problem overcome by the present invention, and a review of commercially available cables with such shielding tapes shows that It has been found that under current cable manufacturing and use conditions, penetration and/or abrasion of the high density polyethylene layer occurs. US Pat. No. 3,379,824 (Example 8 - Table 1) teaches a three-layer shielding tape with an aluminum foil laminated between two polypropylene layers or between a polypropylene layer and a polyethylene terephthalate layer. Again, the damage problem overcome by the present invention is not taught or suggested. Additionally, although these plastic layers may be resistant to penetration and abrasion, they do not provide corrosion protection if a corrosive environment exists on the cable. This is especially true because both polypropylene and polyethylene terephthalate are highly inert and can only provide poor mechanical adhesion to metal strips based on frictional adhesion. Therefore, both the polypropylene layer and the polyethylene tereftate layer will easily delaminate when exposed to corrosive conditions and mechanical forces exerted by metal corrosion products. U.S. Pat. No. 3,325,589 (Examples 9-11 - Table 1) includes an adhesive layer directly adjacent to the metal strip and also a Mylar or polypropylene layer on one side of the metal strip. A bonded plastic coated shielding tape is disclosed. Such shielding tapes were subjected to cable manufacturing simulation conditions and experimental corrosion tests. It was found that the tape did not provide satisfactory corrosion resistance to the metal, ie the path of corrosion attack was not confined to the exposed metal edges. The adhesive layer deformed due to the pressure experienced through the polypropylene or mylar layer, resulting in bare aluminum spots being exposed. (is a registered trademark). After subjecting the cable to a standard corrosion test with sodium hydroxide as described later in the text, the adhesive layer and polypropylene (PP)
Alternatively, NaOH infiltrated between the mylar layers, causing corrosion to occur in these bare areas. US Pat. No. 3,790,694 (Example 8 - Table 1) discloses a metal strip with a polypropylene layer adhered with an adhesive. This patent does not specify the use of any particular adhesive. Since ethylene acrylic acid (EAA) copolymers are the most well-known metal adhesives in the industry today, a shielding tape made according to the teachings of this patent would provide the same results as U.S. Pat. No. 3,325,589. It turns out that there is something. This patent teaches gluing the jacket, screen and composite tape together during extrusion of the cable jacket. It has been found that because the thermoplastic coating on the screen and composite tape must be above its melting point for adhesion to occur, the coating is inherently damaged. Therefore, this prior art patent also did not recognize the problem of coating damage on shield tapes. U.S. Pat. Nos. 3,325,589 and 3,790,694 each relate to heat resistant core jackets (thermal barriers) and well-filled cables. US Pat. No. 3,321,572 (Example 13 - Table 1) and US Pat. No. 3,622,683 (Example 8 - Table 1)
discloses, inter alia, a shielding tape capable of resisting shaping at elevated temperatures consisting of a metallic body to which a coating of polymeric resin material is adhered on at least one side. However, it has been found that these shielding tapes do not meet the adhesive core requirements of the present invention. It has been found that with these tapes, the path of corrosion attack is not limited to the exposed edges of the metal strip due to the penetration of corrosive elements between the polymeric coating and the metal strip. U.S. Pat. No. 3,484,539 teaches adhering a heat-sealable layer, such as polyvinyl chloride, to a polymeric layer that can resist deformation at cable forming temperatures. However, the patented polymer layer that adheres the heat-sealable layer does not "tightly adhere" to the metal strip and is therefore susceptible to liquid intrusion, which can cause corrosion if the cable jacket is damaged. Therefore, it cannot escape corrosive attack. None of the prior art patents mentioned above teach or suggest that a deformation resistant layer can be used in the shielding tape to prevent damage to the protective coating during cable manufacture, installation, or use. Furthermore, none of the polymer coatings on shielding tapes disclosed in prior patents require the adhesion or adhesion of the present invention to provide satisfactory corrosion resistance to the shielding tape by limiting the corrosion attack path to the exposed metal edges. Does not meet deformation resistance requirements. "Glued jacket" cables have improved resistance to moisture infiltration into the cable cores and greater mechanical strength necessary to withstand repeated bending of the cable, but during cable termination and splicing. encounter a problem. More particularly, it is cumbersome to separate the jacket and shielding tape in order to make electrical connections to the shielding tape. It has been found that although it is possible to terminate and splice a "glued jacket" without separating the jacket and shield loop, the electrical connection properties are not as good as if the jacket were removed. More particularly, it is known that the electrical properties of connections to shielding tapes are less variable over time than connections of electrical cables to shielding tapes and adhesive jackets. The present invention is an improved corrosion resistant cable shielding tape comprising a metal strip having a deformation resistant layer of a polymeric resin material having a deformation temperature of at least about 130 DEG C. firmly adhered to at least one side of the metal strip. In other embodiments, a second deformation resistant layer of polymeric resin material and/or other layers are included in the shielding tape to provide a multilayer structure with a desired combination of functional characteristics. For example, if desired, a deformation resistant layer of a polymeric resin material is clamped onto both sides of the metal strip to provide penetration and/or abrasion resistance on both sides of the shielding tape. In other embodiments, if direct adhesion of the deformation resistant layer is not sufficient to provide sufficient corrosion protection to the metal strip, a layer having good adhesive properties to both the metal strip and the deformation resistant layer may be used. The deformation resistant layer is clamped to the metal strip using an adhesive layer of coalescent resin material. In another embodiment, a heat sealing layer of a thermoplastic polymeric resin material is included in the shielding tape of the present invention to provide a hermetically sealable shielding seam in the cable structure and between the cable shielding tape and the outer plastic of the cable. Good adhesion is provided. In other embodiments, an adhesive/heat sealing layer of a thermoplastic polymeric resin material having good metal adhesion and heat sealing properties is adhesively bonded directly to one or the opposite side of the metal strip. The bonding layer of the polymeric resin material described above has high electrical resistivity, high chemical and water resistance and very good adhesion to metal strips, thus withstanding the rigors of the manufacturing process and during use. Able to resist penetration and/or wear without delamination in corrosive environments. The shielding tape of the present invention meets both adhesion or adhesion requirements and deformation resistance requirements to provide satisfactory corrosion protection to the shielding tape by confining the path of corrosion attack to the exposed metal edges of the metal strip. It is necessary to satisfy the following. The present invention also provides a cable shielding tape to which the outer jacket is firmly bonded, the jacket being easily removed for easy splicing and grounding processes, and the jacket having a tightly bonded adhesive layer. Corrosion protection is provided in all areas of such shielding tapes by having the jacket removed so that it remains on the metal components of the tape after removal of the jacket. More particularly, such shielding tapes have a stronger adhesion between the metal strip and the adhesive layer firmly bonded thereto than the interlayer adhesion of other firmly bonded layers of polymeric resin material. By judicious selection of the type and proportion of the polymeric composition for the deformation-resistant layer, the adhesion of the deformation-resistant layer to the adjacent layer of polymeric resin material is weaker than the adhesion of the adhesive layer to the metal strip. be done. The interlayer bond needs to be able to resist peeling under normal conditions of use, but will separate from the metal strip before peeling of the adhesive layer. More specifically, as used herein, "strip" refers to a relatively thin layer of any metal that has good electrical or mechanical properties useful in power and communication cables. In this text, "securely bonded" means that the deformation-resistant layer is indirectly chemically and/or mechanically bonded to the metal strip using an adhesive layer. By directly gluing the adhesive/heat sealing layer, the deformation resistant layer and the adhesive/heat/sealing layer are less likely to peel off from the metal strip when exposed to corrosive conditions and mechanical forces exerted by metal corrosion products. This is meant to limit the path of corrosion attack to the exposed metal edges of the shielding tape. By "adhesive layer" herein is meant a layer of polymeric resin material that has good adhesive properties for metal strips and deformation-resistant layers and for plastic jackets of electrical cables. "Thermosealing layer" means a layer having a sealing temperature of 1°C or less, preferably 110°C or less, which readily provides a seal to itself or to other polymeric resin materials, such as those forming the outer plastic jacket of the cable. means a layer of thermoplastic polymeric resin material: "Adhesive/heat sealing layer" means a layer of thermoplastic polymeric resin material having both good metal adhesion and heat sealing properties for adhesive and heat sealing layers that adhere to metal strips; means. "Deformation-resistant layer" means a layer of polymeric resin material that substantially resists penetration and/or abrasion at deformation temperatures of at least about 130°C and pressures normally associated with cable manufacture, erection and/or use; means. An improved cable suitable for use in power delivery or communications can be constructed using the improved corrosion resistant cable shielding tape described above. Such cables consist of at least one insulated conductor core, a shield of improved corrosion resistant cable shield tape surrounding and surrounding the core, and an outer plastic jacket surrounding the tape. The deformation-resistant layer of shielding tape can be placed in the direction of the conductor, in the direction of the outer jacket, or in both directions to overcome penetration and/or wear marks during manufacture and/or use of the cable. The invention will be further explained with reference to the accompanying drawings. Like letters in the drawings indicate corresponding materials and parts. Referring to the drawings, FIG. 1 shows a deformation-resistant layer 14 formed on one side of a metal strip 12 from a polymeric resin material, such as a blend of 50% by weight polypropylene and 50% by weight ethylene/acrylic acid copolymer. An improved corrosion-resistant cable shielding tape 10 is shown, which is made by firmly adhering. To provide corrosion protection to the metal strip 12, the shielding tape 10 is used on cable structures having a plastic outer jacket formed from an adhesive composition that firmly adheres to the metal strip 12 on the opposite side of the layer 14. Should. FIG. 2 shows a deformation-resistant layer 2 which is the same as layer 14 in FIG.
4 is shown in a modified cable shielding tape 20 formed by firmly adhering a metal strip 12. Band 1
The layer 25 that is firmly adhered to the opposite side of the layer 2 is the layer 24.
The deformation-resistant layer may be the same as or an adhesive formed from an ethylene/acrylic acid copolymer/
It may also be a heat sealing layer. Figure 3 shows another modified cable shield tape 3.
Indicates 0. The metal strip 12 has a deformation-resistant layer 3, identical to the layer 14 of FIG. 1, firmly glued to one side thereof.
4 and a heat seal layer 36 formed from low density polyethylene adhered to layer 34. In another embodiment, layer 36 can be a deformation resistant layer formed of a material such as nylon that does not adhere directly to metal strip 12 with sufficient adhesion to provide corrosion protection; 34 can be an adhesive layer formed of a material such as an ethylene/acrylic acid copolymer. Similar to the shielding tape 10 of FIG. 1, the shielding tape 30 should be used in cable structures having a plastic outer jacket formed of an adhesive composition to ensure corrosion protection for the metal strip 12. . Figure 4 shows another modified cable shield tape 4.
Indicates 0. There are four possible configurations of shielding tape 40 that are useful according to the present invention. Layer 45 can be the same deformation resistant layer as layer 14 of FIG. 1 for two of the possible structures, or the same adhesive layer as layer 25 of FIG. 2 for the other two structures. Agent/
It can be a heat sealing layer. Layer 44 can be the same deformation resistant layer as layer 14 of FIG. 1 if it is directly adhesively bonded to metal strip 12, or layer 36 of FIG. 3 is not directly adhesively bonded to metal strip 12. An adhesive layer formed of an ethylene/acrylic acid copolymer used to securely adhere the same deformation-resistant layer 46 may be used. When layer 44 is a deformation-resistant layer tightly adhered to metal strip 12, layer 46 is layer 36 of FIG.
Advantageously, the same heat-sealing layer. Figure 5 shows another modified cable shield tape 5.
Indicates 0. Three possible configurations of tape 50 are valid according to the invention. First, the metal strip 12
The same two deformation resistant layers 56 and 57 as layer 36 of FIG.
Strip 1 with the same adhesive layers 54 and 55 as in 4.
It can be firmly attached to 2. Second,
The remaining two possible constructions include a deformation-resistant layer 5 similar to layer 14 in FIG.
5 and can have a heat sealing layer 57 similar to layer 36 of FIG. 3 adhered to layer 55. On the opposite side of the metal strip 12 is a deformation resistant layer 54 identical to layer 14 of FIG. 1 bonded directly to the strip 12 and a heat sealing layer 56 identical to layer 36 of FIG. There is also a deformation resistant layer 56, which is similar to layer 36 of FIG. It can be firmly attached. Figure 6 shows another modified cable shield tape 60
shows. The deformation resistant layer 36, which is the same as layer 36 of FIG. 3 but not directly adhesively bonded to the metal strip 12, is firmly bonded to the strip 12 by the same adhesive layer 64 as layer 34 of FIG. A heat seal layer 68 formed from an ethylene/acrylic acid copolymer is adhered to layer 66. Like shielding tapes 10 and 30, shielding tape 60 should be used in cable structures having plastic outer jackets formed of adhesive compositions to ensure corrosion protection for metal strip 12. FIG. 7 shows another modified cable shield 70. Adhesive layer 74, deformation resistant layer 76 and heat seal layer 78 are similar to the corresponding layer 64 seen in FIG.
Same as 66 and 68. Layer 75 can be the same deformation resistant layer as layer 14 of FIG.
It can be the same adhesive/heat seal layer as layer 25 in the figure. Figure 8 shows another modified cable shield tape 8.
Indicates 0. Adhesive layer 84, deformation resistant layer 86 and heat seal layer 88 are similar to corresponding layer 6 found in FIG.
4, 66 and 68. On the opposite side of the metal strip 12 there is a deformation-resistant layer 85 identical to the layer 14 of FIG.
7 may be present, or there may be a deformation-resistant layer 87 similar to layer 36 of FIG.
It may be firmly adhered to the strip-like body 12 using the same adhesive layer 85 as described above. FIG. 9 shows the final modified cable shielding tape 90. Adhesive layers 94 and 95, deformation resistant layers 96 and 97, and heat seal layers 98 and 99 are the same as corresponding layers 64, 66 and 68 found in FIG. Referring to FIGS. 10 and 11, a typical three-conductor power cable 100 and multi-pair telegraph cable 110 are shown. power cable 10
0 has a low resistance metal core 101 which can be solid or stranded, the cores are typically formed of copper or aluminum, and each is typically insulated with an extruded plastic cover 102 of, for example, polyvinyl chloride polyethylene or rubber. ing. Space fillers, such as natural fibers or foamed plastics10
3 may be used to provide a substantially circular core assembly enclosed within a shielding tape 104 formed from any one of the shielding tape structures shown in FIGS. 1-9. The shielding tape 104 is preferably a tube folded longitudinally with overlapping seams to provide a hermetic seal by heat sealing the plastic sheathing of the shielding tape at the overlapping seams during cable manufacture. The outer plastic jacket 105, which is usually extruded polyethylene containing stabilizers and carbon black, is attached to the shielding tape 1.
04 is advantageous. Communication cable 1
Numeral pairs of insulated conductors 111 (for example, plastic-coated copper wire) are bundled together in a plastic core sheath 112 of polypropylene or polyethylene terephthalate, which is secured with a binder tape 113. Consisting of This bundle is surrounded by shielding tape 114 formed from any one of the shielding tape structures shown in FIGS. 1-9. Similar to the shield tape 104 of the power cable 100, the shield tape 1
Preferably, 14 is a longitudinally folded tube having a hermetically shielded overlap seam. An outer plastic jacket 115, preferably of polyethylene, covers the shielding tape 11.
Advantageously, it is extruded onto a tape and adhered to the tape. The metal strip used according to the invention has a
It can have a thickness of 25 mils, more preferably 2 to 15 mils. Metal strips are, for example, aluminum, aluminum alloys, alloy-clad aluminum, surface-modified copper, bronze, steel, tin-free steel, tin-plated steel, aluminized steel.
steel), stainless steel, surface-modified copper-clad stainless steel, turn-plate steel, givenized steel, chromium or chromium-treated steel, lead, magnesium or tin. These metals can be surface treated or provided with surface conversion coatings. The deformation resistant layer used in accordance with the present invention can have a thickness of 0.5 to 15 mils, more preferably 0.5 to 2.0 mils. Advantageously, the deformation-resistant layer comprises any polymeric resin material, such as at least 30% by weight, which provides a layer deformation temperature of at least about 132°C.
Mixtures of polypropylene with low or high density polyethylene, including polypropylene, mixtures with nylon, nylon, saran (vinylidene chloride polymers or copolymers of vinylidene chloride with small amounts of other unsaturated compounds) I can do it. The adhesive layer is between 0.1 and 10 mils, preferably between 0.3 and 10 mils.
It can have a thickness of 2.5 mils. Such a layer can be formed from any thermoplastic polymeric resin material that will tenaciously adhere the deformation resistant layer to the metal strip. Copolymers of ethylene and ethylenically unsaturated carboxylic acids readily form strong adhesive bonds with aluminum and are therefore preferred for achieving the advantageous results of the present invention. Adhesive polymers advantageously used in the present invention are normally solid thermoplastic polymers of ethylene modified with monomers having reactive carboxylic acid groups, in particular a major proportion of ethylene and a minor proportion, generally 30 to 30, preferably 2 to 20
% by weight of an ethylenically unsaturated carboxylic acid copolymer. Specific examples of such suitable ethylenically unsaturated carboxylic acids (including mono- and polyprotic acids, acid anhydrides, and partial esters of polyprotic acids) include 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. Carboxylic acid monomers include 2,β-ethylenically unsaturated mono- and polycarboxylic acids and acid anhydrides having 3 to 8 carbon atoms per molecule and in which the acid moiety contains at least one carboxylic acid group and Preference is given to choosing from partial esters of such polycarboxylic acids in which the alcohol moiety has from 1 to 20 carbon atoms.
The copolymer can consist essentially of ethylene and one or more of the above ethylenically unsaturated hydrochloric acid monomers, or may contain small amounts of other monomers that can be copolymerized with ethylene. I can do it. For example, the copolymer can contain esters of acrylic acid, such as ethyl acrylate, or other copolymerizable monomers, such as vinyl acetate. The comonomers can be combined into the copolymer in any manner, such as as a random copolymer, as a block or continuous copolymer, or as a graft copolymer. These types of materials and methods of making them are readily known in the art. Also, ionomers such as those sold under the trade name Surlyn can be used as the adhesive layer. Advantageously, the heat seal layer has a thickness of 0.1 to 10 mils, preferably 0.3 to 1 mil. The heat seal layer can be formed from, for example, low or high density polyethylene, ethylene/ethylene acrylate copolymers, ethylene/vinyl acetate copolymers, carboxyl-modified ethylene polymers, or blends thereof. The adhesive/heat seal layer can have a thickness of 0.1 to 10 mils, more preferably 1 to 3 mils. The adhesive/thermal seal layer can be formed from, for example, a carboxyl-modified olefin polymer, an ionic olefin polymer, a blend of carboxyl-modified olefin polymers, or a blend of ionic olefin polymers. The resistance to deformation of a layer of polymeric resin material is commonly tested using a penetrometer. However, known penetrometers are designed for 60 to 125 mil (1.52 to 3.17 mm) thick coatings (consisting of one or more layers of synthetic resin material) and the data obtained therefrom are does not apply to the coating thickness for cable shielding tapes or the temperatures and pressures associated with cable manufacture or use. Therefore, a special penetration test is used to evaluate the ability of relatively thin coatings, ie coatings 10 mils (0.254 mm) thick or less, on plastic ground metal to resist deformation at elevated temperatures. developed. The special penetrometer consists of a circular ring machined onto a metal block weighing 1.68 kg. The ring has an outer diameter
It has a thickness of 38.1 mm and 25 mils. The cut end of the ring that contacts the coated shield tape sample is rounded to a 0.79 mm radius and applies a pressure of 35 pounds per square inch (24.6 g/mm ² ) to the sample. The test method involves placing a sample of shielding tape on a base, such as a metal plate, and then positioning a special penetrometer over the sample to bring the ring into contact with the coating on the sample. An electrical circuit opened for coating is connected between the penetrometer and the metal strip of the sample. The entire assembly was then heated to 218°C.
The test coating temperature is increased at a rate of approximately 10°C/min by placing it in a preheated circulating air oven. Once the ring has penetrated the sheath, the electrical circuit is completed, recording the temperature of the sheath as measured by a thermocouple or other means. This temperature is the deformation temperature of the coating to be tested. The conditions of this test were found to correlate well with the temperatures and pressures associated with cable manufacture and/or use. It has been found that the deformation resistant layer needs to have a deformation temperature of at least about 130°C, preferably at least about 138°C and higher to resist the temperatures and pressures normally associated with cable manufacture and/or use. It was done. The degree of adhesion between the plastic layers and between the metal strips of the shielding tape of the present invention, which meets the requirement of being "tightly bonded" to the plastic layer, is determined by immersing the tape sample in deionized water maintained at 70°C for 7 days. It is necessary to have a value of at least about 1 Kg/2.54 cm tape width, preferably at least about 2 Kg/2.54 cm tape width. The degree of adhesion is
Plastic coating material 6 inches wide x 6 inches long x 60 mm thick using the same method described in USDA Rural Electrification Administration (REA) Specification PE-2000. Mil (15.24cm
*15.24cm:3.175cm) Measurement is performed by making a molded product. A sheet of shielding tape of the same size (6 inches x 6 inches) was placed on top of the molded article. A strip of 1 mil thick polyester film is placed between the shielding tape and the jacketing material molding without adhering to one end of the jacketing material to form a "tab" for use in a tensile strength tester. did. The shielding tape was connected to the molded article using a compression molding pressure and a molding temperature of 190°C. The molded article was 300 pounds per square inch (0.2 Kg/mm ² ). The heating cycle was as follows: 3 minutes to reach temperature without pressure; 2 minutes under pressure; and 5 minutes to cool to room temperature, after preparing the shielding tape/jacket material laminate, bonding. Test 1 inch (25.4 cm) wide samples were cut on a sample cutter. The specimens were placed on a tensile test and tested for adhesive strength as follows: the unbonded part of the shielding tape was folded back 180°; the shielding tape was in the upper jaw and the molding of jacketing material was in the lower jaw. The specimen was placed in a tensile tester; a rigid metal plate was placed after the molding to maintain a peel angle of 180°; and the jacketing material was then shielded from the rigid molding at a crosshead speed of 5 in/min. The tape was separated. The force required to separate the shield tape from the molded article was recorded as the R degree of adhesive strength. Separation can occur at the metal strip/plastic layer interface, the plastic layer/plastic layer interface, or the plastic layer/jacketing material interface. Several plastic-coated aluminum shielding tapes were made and tested for corrosion resistance. More specifically, test samples of shielding tape measuring 5.08 cm by 5.08 cm were first subjected to a simulated jacketing test as described below and then immersed in normal sodium hydroxide (1N NaOH) solution for 24 hours. During the simulated jacket coating test, damage to the plastic coating resulted in corrosion of bare aluminum spots on the exposed shielding tape surface. The number of easily visible corrosion points on the test sample of shielding tape was counted and recorded as the corrosion damage index. An index of 0 indicates that there are no corrosion points, and a certain number indicates the number of corrosion points that can be calculated for the sample. Shielding tapes with poor adhesion to the plastic coating gave total dissipation of the metal, often accompanied by peeling of the coating. The simulated jacket jacket test was designed to mimic the temperatures and pressures typically encountered within a cable during and after jacketing operations to study the effects of the jacket on the cable components. The test is particularly well suited for studying the effects of temperature and pressure conditions on plastic coatings or plastic-coated shielding tapes. To perform this test, a cylindrical cross-section of a cable approximately 5.0 cm in length is transformed into a rectangular shape with a flat surface. The test is performed using the following method: approx.
A sample of molded jacket article measuring 8.08 x 8.08 cm and weighing 13 g and 100 mil (2.54 cm) thick was heated in an oven to 218°C; the jacketing material was removed from the oven after 6 to 7 minutes and the corrugated shield was formed within 5 seconds. A sample of tape (5.08 cm x 5.08 cm) was placed on top of the jacketing material; a corrugated core jacket of polyester film, a section of cable core having a generally rectangular shape and weighing 218 g, and a continuous 200 g weight. I carefully layered it on top of the shield tape;
And finally, the entire assembly was placed on a large aluminum block (weight 955 g) and allowed to cool while the temperature of the core jacket/shield interface was recorded by a thermocouple placed between the two. The aluminum block provides heat reduction and thus simulates a cooling bath placed downstream of the extruder head. The temperature-time relationships for the shield obtained in this test correlate with the temperature-time relationships obtained for cables containing multiple conductor pairs during jacket extrusion. (R.C. Mildner, P.C. Utdland, H.A. Walters & G.E.
Novel Form of Themal Barrier for
Communicatic Cadles, 14th International Wire and Cable Symposium, Atlantic City, New Jersey, 1965). The heat sealability of the coated film samples was measured by a special sealing test. Two specimens of 50.8 mm wide film are placed in contact with each other with a heat sealing device such as Sentinel Brand, Model 24AS or equivalent. Increase the temperature of the sealing rod from 88°C to a temperature sufficient to seal the films together by 5°C.
Increase by raising it step by step. The temperature at which the films seal to each other is recorded as the minimum seal temperature.
Seal rod stop time (seconds) is film thickness (mm)
26.25 times. The air pressure applied to the seal rod is 28
g/ ^mm2 . The effect of the "filler" on the cable core was determined by exposing the coating on both sides to a petroleum-derived jelly-like filler compound (Witco 5B) and a similar internal cable filler (Witco 4) at 115.5°C for 2 seconds. A sample of plastic-coated shielding tape was tested. After wiping clean the filler compound from the surface, the swelling ratio was calculated based on the amount of filler absorbed by the coating as follows: Subtract the initial weight of the coating from the weight of the exposed coating. , the difference was divided by the initial weight. this number
The swelling ratio was obtained by multiplying by 100 times. The results of this test are shown in the table. In the "Connector Stability" test, approximately 50mm x 150
Corrugations were applied to coated metal samples of mm. Two Griplok connectors were then attached to each longitudinal end of the sample. The initial resistance (in milliohms) was measured across the connector using a Kelvin bridge. Next, −40
Fifty temperature cycles ranging from °C to +60 °C were applied, each cycle lasting 8 hours, and the resistance was measured again. The results of these tests are shown in the table. In jacket adhesion strength and bending performance tests,
A length of corrugated body was used to fabricate a glued jacket gas tube onto the cable jacket attachment line. The laminate was oriented with the multilayer coated side in contact with the extruded jacket. Tube samples were then collected to measure jacket bond strength and bending performance. The results of these tests are shown in Table XII. Additional test methods were used as follows: 1 Physical properties of the coating were determined by ASTM D-638. 2 Elmendorf tear
Measured according to ASTMD-1922. 3 Melt index was measured according to ASTMD-1238. Representative examples of the invention are shown in the table along with deformation temperature and corrosion index tests. Examples were formed by extruding plastic layers, each approximately 1 mil thick, which were then laminated to a hot metal strip at approximately 190°C. Adhesive jacket cables, including these examples, were manufactured along commercial cable manufacturing lines under normal processing conditions. The deformation temperature was obtained using a penetrometer test for deformation resistance. Examples 5-8 in the table demonstrate the use of a three-component blend as the deformation-resistant layer. Example 9 establishes a lower limit of about 130° C. for the deformation temperature of polyethylene and polypropylene blends. Example 10 illustrates the use of an adhesive jacket to implement the use of single-sided coated metal according to FIGS. 1, 3, and 6. Examples 11-13 are comparative examples and were prepared according to the procedure of the present invention. However, the composition of the blend of the deformation resistant layer was chosen not to be sufficient to provide a deformation temperature of at least 130°C. Example 14 shows a functional example with copper. Since copper degrades EAA coatings in the presence of moisture, copper stabilizers
OABH (oxalate bis(benzylidene hydrazide))
was added to EAA. Example 15 shows the working example of using an ionomer (Surlyn 1652, 11% MAA) as the metal adhesive layer. Example 16 shows an example using an EAA-polyethylene blend as the metal adhesive layer. Examples 17-18 illustrate embodiments having Saran as the heat deformable layer. These structures are not shown in the figure. An adhesive layer of a blend or suitable polymer is used to securely bond the heat deformable layer to the metal. The basic structure is as follows: metal/
Adhesive layer/second adhesive layer/deformation resistant layer; metal/adhesive layer/second adhesive layer/deformation resistant layer/heat sealing layer (EVA); or metal/adhesive layer/second adhesive layer (Blend) Deformation resistant layer/Second adhesive layer (Blend)/Heat sealing layer. The table and comparative analysis demonstrate the damage caused to prior art plastic coated shielding chips as measured by the number of corrosion points calculated on a 25 cm ² sample. It is also demonstrated that a deformation-resistant layer with a deformation temperature of at least about 130° C. and a firm adhesion are necessary to prevent the occurrence of bare spots on the tape surface and the associated corrosion potential. Table Examples 9-11 show that damage to low melting point coatings on metals can occur through the deformation resistant layer. Without a strong bond between the deformation layer and the metal adhesive layer, or the bond between the two being water sensitive, corrosion can occur to defects in the adhesive coating on the metal. Example 12 demonstrates the non-functionality of this patented structure for corrosion protection. Example 13 shows that it is necessary to firmly adhere the coating to the metal. The tables and tables show the initial bond strength and the bond strength after aging in 70° C. deionized water for 7 days. Two sets of numbers are shown in the table because during adhesive strength testing the multilayer coating does not necessarily fail at the interface of the immediately adjacent polymer layer with the metal. If the metal adhesion is stronger than the adhesion of the various polymer layers to each other, adhesive failure will occur at the weakest interface. (Example numbers refer to tables and table numbers showing detailed shielding tape constructions.) Whether bond strength refers to metal/polymer layer adhesion or polymer coating/polymer layer adhesion, the minimum bond strength is 1.0Kg/2.54cm. In the former case.
Corrosion resistance and mechanical performance may be insufficient below the minimum bond strength. In the latter case, below this minimum bond strength the ability to resist handling without peeling will be compromised. From the table, it can be seen that if the type and proportion of the polymer composition is properly selected, the polymer coating/polymer coating bond can maintain a minimum bond strength of 1.0 Kg/2.54 cm while maintaining a higher bond strength than other interlayer bonds of polymeric resin materials. It can be seen that strong adhesion between the metal strip and the adhesive layer is obtained. The tables and tables show that the multilayer coatings have improved ultimate tensile strength, elongation and tear strength compared to currently known technology. The example numbers refer only to the improved coated structures shown in the table and not to the coated metal structures. Tables and Tables show actual cable data when cables are made using some of the shielding tapes listed in Tables and Tables. The same example numbers have been used. The table shows that the improved coating of the present invention has increased resistance to the adverse effects of filling and filling compounds. This property is also advantageous in extending the service life of the filled cable. The table shows that connector stability against coated metals is improved with improved coatings. This is because the increase in resistance with respect to the initial value is smaller. Table XI shows that electrical breakdown strength and permeation resistance are improved with the new coating. The electrical strength of the new coating can be advantageously used in filled cable designs by eliminating the standard electrical barrier wrapped around the core. Reduced permeation rate can help improve corrosion resistance. The adhesion strengths in Table XII reflect the level of interlayer adhesion of multilayer samples. These adhesion values are shown in Conventional Technology Example 5 in the table.
It is about 1/2 of However, interlayer failure provides a means of controlling the level of adhesion between the polymer layer of the shielding tape and the jacket, i.e., creating a bond strong enough to provide good mechanical properties while facilitating jacket peeling for splicing. give. Furthermore, at least the adhesive layer of the multilayer coating remains on the metal strip to provide continuous corrosion protection. The bending performance values are surprising. This is because the multilayer sample showed bending performance equivalent to the control sample with 1/2 the bond strength. These results tend to suggest that bending performance requires fairly high jacket bond strength, but that the ability to relieve stress is perhaps more important. Multilayer films provide a means of stress relief through lower interlayer adhesion.

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[Table] Filled core wire
6 100pr, 22AWG, 235 24.4 0

air core wire

[Table] Air core wire

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[Table] (1) Necessary items to cause destruction to the shield

From the foregoing detailed description, the present invention provides an improved corrosion resistant cable shielding tape suitable for use as a shield for power and communication cables. More particularly, the present invention is an improved corrosion resistant cable shielding tape comprising a deformation resistant layer of a polymeric resin material having a deformation temperature of at least about 130 DEG C. firmly adhered to at least one side of a metal strip. The shielding tape must satisfy both adhesion and deformation resistance requirements simultaneously in order to provide the shielding tape with satisfactory corrosion protection by limiting the corrosion attack path to the exposed metal edges. Therefore, the deformation-resistant layer of polymeric resin material must resist penetration and/or abrasion that exposes the metal strip at the temperatures and pressures normally associated with cable manufacture and/or use. The present invention also provides a plastic coated cable shielding tape that includes layers of polymeric resin material other than the deformation resistant layer, thereby forming a multilayer structure with a desirable combination of functional properties.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a plastic-coated metal shielding tape constructed according to the principles of the present invention; FIG.
9-9 are partial cross-sectional views illustrating a modified plastic-covered metal shielding tape constructed in accordance with the principles of the present invention; FIG. 10 is a typical power supply having three insulated conductors, a plastic-covered metal shield and an outer plastic jacket. Cable Cross-Section Figure 11 is a cut away perspective view of the end of a communications cable having multiple pairs of insulated conductors in the core, a plastic-covered metal shield, and a plastic outer jacket. 10, 20, 30, 40, 50, 60, 70,
80, 90... Cable shield tape, 12... Metal strip, 14, 24, 25, 34, 44, 4
5, 56, 57, 66, 76, 75, 86, 8
7,96,97...Deformation resistant layer, 36,46,5
6, 68, 78, 88, 98, 99... Heat seal layer, 54, 55, 64, 74, 84, 85, 9
4,95...adhesive layer, 100...power cable, 1
01...Conductor, 102...Plastic cover, 10
3... Filler, 104... Shield tape, 105...
Jacket, 110...Communication cable, 111...Conductor, 112...Sheath, 113...Binder tape, 11
4... Shield tape, 115... Jacket.

Claims (1)

[Claims] 1. A corrosion-resistant cable shielding tape comprising: a layer of a copolymer of 98 to 80% ethylene and 2 to 20% ethylenically unsaturated carboxylic acid by weight; a mixture of the copolymer and polyethylene; a layer of the copolymer and a layer of an ethylene/vinyl acetate copolymer or a layer of a mixture of the copolymer and an ethylene/vinyl acetate copolymer; and a layer of an ionomer. a metal strip with a layer of adhesive directly adhered to at least one side; and a deformation-resistant layer with a deformation temperature of at least 130° C. adhered to at least one of said adhesives, comprising at least 30% by weight of polypropylene. nylon; vinylidene chloride polymers or copolymers of vinylidene chloride and small amounts of other unsaturated compounds; a deformable layer and, if necessary, a heat sealing layer adhered to at least one side of said deformable layer and/or
A corrosion-resistant cable shielding tape consisting of an adhesive/heat sealing layer bonded to the opposite side of a metal strip from the side with the deformation-resistant layer.