WO1990012406A1

WO1990012406A1 - Communications cable including composition for protecting the wires thereof from damage by invasive water

Info

Publication number: WO1990012406A1
Application number: PCT/US1990/001863
Authority: WO
Inventors: Clarence S. Freeman
Original assignee: Freeman Clarence S
Priority date: 1989-04-07
Filing date: 1990-04-05
Publication date: 1990-10-18
Also published as: HU210907B; BR9001674A; HU903420D0; HUT60564A

Abstract

A communications cable including a gel composition comprising a water absorbent hydrocarbon polymer with pendent anionic groups which fills both filling and flooding zones. The gel composition is activated with moisture so that the water absorbent composition migrates to engage and absorb the water. The composition can also be used to protect enclosed components, fiber optics, or contents from water damage. Also, the gel composition protects wires which carry a small dc current such as communication wires and splices. The composition eliminates shorts caused by moisture contact with such wires.

Description

COMMUNICATIONS CABLE INCLUDING COMPOSITION FOR PROTECTING THE WIRES THEREOF FROM DAMAGE BY INVASIVE WATER

BACKGROUND OF THE INVENTION

This invention is for a gel chemical composition and a telecomunications or fiber optic cable including that gel. The gel composition is activated by moisture to absorb water and can be used to protect components, such as the components of a cable including the gel, from water damage. The composition is also useful when introduced into confined areas such as instrument casings, housings for cable lines, splices or junction boxes to protect the contents or conductors contained therein from water damage for extended periods of time. The gel can be introduced into the housing or junction box prior to or during service of a splice. As will be described, the gel composition can also be incorporated into the cable itself, both between conductors in a bundle and/or between the bundles of conductors contained in the cable. Regardless of the use, not only does the gel prevent the entry of water, but the composition also eliminates shorts caused by water of the conductors in the cable, such as in telephone cables or splices which carry a small dc current, and restores current flow through the wire.

Communications cables such as telephone lines are made up of a multitude of pairs of conducting wires, typically copper wire, which are insulated from each other with a thin layer of a thermoplastic resin such as polyethylene or other materials and bundled by an insulating material. Bundles of pairs of conducting wires are then wrapped with a sheath of plastic, paper wrapping or other material, into a cable. Fillers such as a

SUBSTITUTES petroleum gel or an extended thermoplastic rubber (ETPR) compound are added to many cables inside the cable cover to fill the interstitial spaces, the objective being to exclude water from the cable and to prevent any water which does enter from migrating inside the cable.

The conductors of the cable must each be spliced to other conductors at the ends of the cable. The spliced connections of the communication cables are housed in a casing type closure which can contain thousands of indi¬ vidually spliced wires. The wires are connected to one or more small dc power sources to provide the reguired transmission current, and eventually to the telephone terminal equipment, e.g., one or more telephone transmitters at one end or location and one -or more telephone receivers at the other end. The housings are pressure type closure systems and it is crucial to the proper function of the telecommunications equipment to prevent the entry of invasive water and protect the splices from moisture. The entry of moisture into the cable splices or into a cable which is not surrounded by a closure establishes a conductive path through the moisture if the insulation of the wires is not maintained. When a conductive path is established through the moisture, the wires either short out all together or, in the case of a telecommunications cable, cross-talk is established, thereby disrupting the communications.

In recognition of the essential nature of the ability of teleco iminications cable to withstand exposure to water, the industry has promulgated certain performance standards which the cable must achieve. In particular, AT&T has issued a standard resulting from work conducted by Bell Laboratories which must be attained by all cable installed by the Bell operating companies that requires that a three foot long horizontal section of cable not pass any water for one hour when maintained under a column of water three feet high. The Bell companies are currently considering a change in that standard to require

SUBSTITUTE SHEET that a section of cable seven feet long withstand twelve feet of water head for twenty four hours. On information and belief, that latter standard has not been achieved to date.

It is likewise essential to prevent the exposure of many other types of conductors to invasive water. For instance, many microprocessor-controlled electromechanical devices include motors and switches which, along with the microprocessor, are driven by low voltage dc current. If exposed to moisture, such devices are susceptible to elec¬ trical shorts, especially at those points at which a circuit board is connected to the wiring and the points at which the wiring is connected to the switches and motors because those points are generally not insulated. Even though such connections are usually enclosed by a housing or other protective covering, once moisture invades the housing, e.g., even by condensation of water vapor, those connections are readily accessible to the moisture. Fiber optic cables are similarly susceptible to invasive water.

In the case of telecommunications equipment, one method of providing protection for the conductors inside the housing, whether in a splice or a cable, includes wrapping the bundle of conductors with a flexible material and injecting a liquid epoxy or urethane into the housing around the bundles which solidifies within the housing. Such a composition must be mixed on site and is typically injected by gravity flow into the housing. The material typically does not fill the entire interior of the casing and leaves voids. These voids or channels can create an avenue for the entrance of water, particularly at either end of the bundle that exits the housing and forms one of the wire bundles of the cable splice. The material, along with the wrapping around the splices in the housing, also can cause a funnel effect such that the water enters through a fissure in the cable sheath at either end of the closure around the cable and into the cable to the spliced wires.

W&Wk ML As noted above, protection of the cable against water invasion is provided by filling the spaces between the wrapped bundles of conducting wires inside the cable and the interstices between pairs of conductors in each bundle (referred to as the filling zone) with compounds such as urethanes, epoxies, polystyrene foams, ETPRs, petroleum jellies and/or other hydrophobic materials. The patent literature also describes cables including water swellable polymers such as polyvinyl alcohol, polyacrylamides, or cellulose derivatives, which are applied to bundle wrappings or contained in "moisture barriers" which are spaced along the length of the cable outside of the conductor bundles and under the sheath (the area outside the bundles and the under the sheath is referred to as the flooding zone.

Such cables are, however, characterized by certain disadvantages and limitations. In the case of those which include one of the above-described water sewllable polymers, the polymer is generally supplied in powdered or granmαlar formsuch that distribution of the powder or gannules throughout the flooding zone is problematical. If not distributed throughout the flooding zone, effective water absorbence is not assureed throughout that zone. Further, when sufficient quantitites of water and polymer are present, the swelling of the polymer within the confined space of the flooding oznebecomes a problem. Another problem results from the susceptibity of certain polymers such ascellulose derivatives to bacterial attack which results in the production of acids and other by-products which degrade the components of the cable.

Petroleum gels and ETPRs are generally used as filling compounds because the water-swellable materials used in the flooding zone are conductive once they absorb water, and also in part because all known substitutes suffer from one or more disadvantages which limit their utility such that petroleum gels represent the least expensive alternative. However, petroleum gels are also

SUBSTITUTE SHEET characterized by certain disadvantages. For instance, petroleum gels are relatively ineffective at water blockage in a bundle of conductors which is exposed to water because they must be applied hot. The heat tends to degrade the insulation around the individual conductors and, after cooling, the gel shrinks leaving passages for entry and migration of water. At low temperatures, the gel imparts stiffness to the cable, hampering installation. Those same temperature-related problems affect fiber optic cables. Also, the gel is difficult to remove from the conductors during splicing and terminating the cable.

Replacing the gel with a powdered filling material which reacts with water to form a gel which blocks the water is also described in the patent literature. However, such powders are also characterized by a number of disadvantages and limitations. For instance, on contact with water, powders alter the electrical charac¬ teristics of the conductors in the bundles in the cable by increasing conductivity to the point that thicker insulation may be required around the conductors and the bundle, thereby increasing the cost of the cable. Using lower concentrations of the powder in the filling material compromises the water blockage capabilities of the filling material. Further, certain swelling agents such as polyvinyl alcohols and polyacrylamides do not swell quickly enough in cold water to effect proper water blockage when the bundle is only partially filled while filling the bundle completely with such agents is prohibitively expensive and causes problems with swelling in the confined space when contacted by water.

In short, in spite of a continuing and long-felt need, and in spite of the many attempts which have been made to solve these problems, there is still a need for a water resistant cable, and specifically, for a composition which can be incorporated into a telecommunications or fiber optic cable, splice, or other confined space, to

SUBSTITUTE SHEET. prevent moisture-induced electrical problems. Specifically with regard to telecommunications cables, so far as is known, no material is available or suitable for use as both flooding and filling compound. Instead, water swellable polymers, when used at all, are generally used in the flooding zone and water resistant or impermeable materials are generally used in the filling zone.

SUMMARY OF THE INVENTION

The present invention is a gel composition which can be used in any confined space to protect the components contained therein from water damage, but which has particular utility as both a filling and flooding compound that is incorporated into electrical cables during their manufacture. The gel composition also can be injected into a housing or closure surrounding wires or splices to serve as protection from invasive water. The gel can also be introduced into the housing during the manufacturing process or after the housing is placed in service.

The composition is comprised of a fluid, a thickener for mixing with the fluid to form a gel matrix, and a water absorbent polymer having anionic groups attached to the polymeric backbone which is generally supplied in the form of a fine powder. This powdered hydrocarbon polymer is mixed with the dielectric gel matrix. In many cases, the dielectric gel matrix is hydrophobic and the addition of a hydrophilic substance is beneficial as explained below. The gel matrix does not inhibit or prevent the insulation of the wire, for instance, in a splice, because the matrix is not conductive to the current carried in the splices.

The gel composition itself provides an initial barrier to the entry of water into the confined space in which the gel is located. If water does enter the space, whether the space is the inside of a fiber optic cable, a housing or splice, or the filling or flooding zone of a telecommunications cable, the water absorbent polymer in the gel is activated and the water is absorbed. In tests.

Sim HE SHEET water was placed adjacent to the gel composition. The fine powder-like polymer in the gel was seen traveling to the water within the gel matrix. The polymer has exhibited this traveling effect for up to six inches from the initial gel matri /water boundary. This effect appears to be the result of the water absorbent polymer seeking out the water. Once the water is contacted by the polymer in the gel, a highly viscous semi-solid material forms that, depending on the viscosity of the gel composition, is incapable of fluid movement. The addition of a hydrophilic substance to a gel matrix comprised of the polymer and hydrophobic materials appears to promote this traveling to the water effect.

The water absorbent polymers, having pendent anionic groups, when exposed to a small amount of dc current such as that present in the conductors of a telecommunications cable, appear to cause an attraction of the anionic groups of the polymer to the wires, the wires acting, in effect, as an anode. This apparent attraction of the polymer to the exposed wire brings the polymer into electrochemical association with the wire, and the accumulated polymer that develops around the exposed wire excludes water from the surface of the wire. As that layer builds up around the wire, the flow of current through the wire is re-established with the result that the short is eliminated or "healed". Depending on the components of the gel, the healing process can take as short a time as several minutes up to about 2 to 3 hours, after which current is established. The water absorbency often starts to occur instantaneously. Typically a fast acting gel composition is preferred.

The gel composition of the present invention therefore plays several roles in protecting the contents or components of a confined space such as a housing or cable from water damage. First, if there is invasive moisture, the gel composition repels the water. Additionally, in the presence of water, the water

Srøffl/TE 1EE! 8 absorbent polymer of the gel is activated to travel out of the gel matrix to absorb the water. This traveling effect is particularly useful when the confined space is a cable containing a multitude of wires in a bundle having very small interstitial spaces therebetween. The polymer travels into the interstitial spaces if water is present, thereby causing a plugging effect to prevent further invasion of water into the filling zone. That benefit is derived whether or not any electrical current is present such that the present composition is also used to advantage in confined spaces such as fiber optic cables in which non-electrical components are located. In the case of, for instance, damaged communication cables or splices which carry a low level dc current, an additional benefit is that any shorts which are present are healed by the gel composition. The gel composition both plugs the entry of water and heals the short, restoring current in the lines. The gel composition can be varied as to desired vis¬ cosity depending upon the endurance capabilities required by environmental conditions. It is generally preferred that the viscosity range of the gel is from about 2 centistokes at 100°C to about 90,000 centistokes at 40°C. The viscosity of the composition is a matter of choice for the service desired and is not intended to be limited by the specification of this presently preferred viscosity range. A thin or thick gel can be used. The optimum pentometer penetration measurement range for the gel composition is from about 150 to about 425.

Re-entry into a splice housing filled with epoxy and urethane, a typical requirement of the industry, is difficult, if at all possible. The gel of this invention can be manually cleaned off of the splice so that repairs can take place. The gel can then be re-used rather than discarded as is necessary with the prior art epoxy or urethane encapsulants.

A 25 pair, 24 gauge telecommunications cable which includes the gel composition of the present advantage has

I SHET met and exceeded the above-described standards for cable performance. For instance, one section of such cable that is just three feet in length has withstood twenty-three feet of water head (simulated with air pressure on water) for over twenty weeks, and another section of such cable that is five feet long has withstood sixty-nine feet of water head for over twenty weeks without passing any water. Those experiments are on-going such that it is possible that this level of performance will continue for an indefinite, additional period of time.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic representation of a method and apparatus for making a telecommunications cable including the gel composition of the present invention.

Figure 2 is a cross-sectional view of a telecommunications cable of a type which is made with the apparatus of Figure 1 and which includes the gel composition of the present invention.

Figure 3 is a cross-sectional view of one of the filling heads of the apparatus of Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The water absorbent polymers which are suitable for use in connection with the composition of the present invention are those with a backbone having pendent anionic groups attached to the polymeric chain, and are preferably polymers of non-naturally occurring monomers so as to be less susceptible to bacterial degradation. The anionic groups can be carboxylate, sulfate, phosphate, sulfonate, phosphonate, or any other anionic groups which will form a negative charge on exposure to water, polycarboxylates being preferred. The preferred carboxylate polymers are those made from ²,B-ethyleniσally unsaturated mono- and dicarboxylic acids and/or anhydrides such as propenoic acids, ²-methylpropenoic acids, B-methylpropenoic acids, maleic acids, fumaric acids and the respective maleic and fumaric anhydrides. Particular success has been achieved using a polymer of 2-propenoate, commonly referred to as

SUBSTITUTE SHEET polyacrylic, or propenoic, acid and its derivatives, the anionic carboxylate groups of which, when exposed to aqueous conditions, yield a strongly negative charge along the polymer chain. The salt form of these polymers can be used with a variety of ions including, but not limited to, alkali metal ions such as lithium, sodium, potassium or alkali earth metals such as magnesium, calcium, strontium, barium, zinc or aluminum. The salt used will depend on the valency of the anionic group attached to the hydrocarbon chain backbone. Polymers of such polyacrylic acid derivatives are abailable from a number of sources, including Dow Chemical Corp. , Stockhausen, Inc. , Chemdal Corp. , and ARCO Chemical.

Although the preferred water absorbent polymers are polycarboxylateε, other superabsorbent polymers having anionic groups attached to the polymeric backbone, including acrylates, acrylamides, methacrylate, methacrylamide, acrylonitrile, methacrylonitrile, tri- and/or tetraethylene glycol, diacrylate, starch graft polymers of those polymers such as a starch-polyacrylonitrile graft polymer, cellulose, and cellulose derivatives such as carboxymethyl cellulose may also be utilized to advantage. In addition to the above-listed sources, such polymers are available from Proctor & Gamble Co., Grain Processing Corp., and Chem-Mud, Inc. Such polymers are taught in a number of patents including, but not limited to, the water absorbing polymers described in the following patent literature: U.S. Patent Nos. Foreign Patents

3,589,364 4,442,173 EPO App'n

3,661,815 4,443,312 No. 188,959

3,669,103 4,446,261 Japanese App'n

3,670,731 4,497,930 No.57-125,871

3,880,751 4,616,063 Japanese App'n

4,105,033 4,618,631 No. 59-3299

4,129,544 4,690,971 4,295,987 4,849,484

SUBSTITUTE SHEET Even though polymers of cellulose and cellulose derivatives will function in the manner described when dispersed in a gel matrix to form the composition of the present invention, such polymers are biodegradable over a period of several months. Consequently, polymers of non-naturally occurring monomers, which are so significantly less biodegradable that they will be collectively referred to as being "non-biodegradable" throughout this specification, are preferred over the polymers of cellulose and/or cellulose derivatives. For instance, the polyacrylic acid polymer described above is resistant to degradation over a period of several years; controlled experiments with that polymer have shown no degradation for up to one year.

The water absorbent polymer is incorporated into the gel composition of the present invention in concentrations ranging from about 5 to about 33% by weight of the final composition, depending upon the particular polymer utilized. Although satisfactory results have been obtained with compositions including concentrations of polymer at both ends of that range (hence the use of the word "about" in describing the range) , concentrations of from about 10 to about 30% are preferred, and in the case of the preferred polyacrylic acid polymer, a concentration of from about 15 to about 30% is preferred. As a general rule, if a cellulose polymer, or a polymer of a cellulose derivative, is used, or if other polymers susceptible to bacterial attack are used, it is preferred that higher concentrations of polymer be used.

A number of compositions which are gels or can be thickened to form a gel have been used as a gel matrix. The gel matrix must be relatively nonconductive to a small dc current, e.g. , dielectric. The matrix should provide a fairly uniform dispersal of the anionic hydrocarbon polymer in the gel. The viscosity of the gel can be varied depending on the method used to introduce the composition into the confined space and the temperature

ni HEET and other conditions under which the composition will be used.

The gel matrices used in this composition include siliσones, petroleum gels, high viscosity esters, glycols, polyglycols, olefins and fluorocarbons. Mixtures of polyalkylene glycols, polyalpha olefins and polyisobutylene, and such mixtures, along with standard white-mineral oils of various molecular weights, are presently preferred for use as gel matrices in the composition of the present invention. Oil-containing gel matrices have been used to such advantage that such gel matrices are referred to collectively herein as dielectric oil gel matrices. The gel matrix is used to advantage in concentrations ranging from about 40 to about 95% by weight, depending upon whether a thickener is utilized. The preferred concentrations, depending on the particular material, range from about 40 to about 85% by weight, the particularly preferred concentration ranging from about 61.6 to about 84.75% by weight.

Gel matrices that are too hydrophobic have a tendency to coat the polymer and essentially shield the polymer from the water that the wire needs to be protected from. A small amount of a hydrophilic substance can be added to such hydrophobic gel matrices to counteract that tendency. The hydroph.ilic substance appears to provide a conduit for the water absorbent polymer to migrate to the moisture. A wide variety of materials are appropriate for use as a hydrophilic substance in the gel composition of the present invention in percentages of from about 1 to about 10% by weight. Particular success has been achieved with various straight and branched chain mono-, di-, and polyhydric alcohols including various polyalkylene glycols and mixtures and derivatives thereof and various alkanols and mixtures and derivatives thereof. For example, ethylene glycol, hexylene glycol, and polyalkylene glycol co-polymers randomly substituted with ethylene oxide and propylene oxide have been used to advantage, as have

SUBSTITUTE SHEEI isopropyl alcohol and 2-ethyl hexanol. Other substances include mono- and polyenoic unsaturated fatty acids and mixtures of fatty acids such as oleic acid, palmitoleic acid, linoleic acid and linoleneic acids, as well as, for instance, tall oil, which includes oleic acid, and various commercially available detergents and surfactants and mixtures of detergents and/or surfactants such as derivatives of sorbitan mono-9-octadecenoate polyoxy-l,2-ethanediyl and 2,4,6,9-tetramethyl-5-decyn-4, 7-diol.

Thickeners are used to advantage with certain gel matrices to achieve a desired viscosity. Suitable thick¬ eners include those known in the art for thickening petroleum and fluorocarbon oils, gels, and greases, such as waxes and petrolatums, and such materials as ethylene and polyethylene microspheres. Typical thickeners for gels, dielectric oils, and greases are pyrogenic silica, organophilic clays such a bentonite and hectorite, soaps such as metal stearates, and ureas, the presently preferred thickeners being organophilic clays. Those bentonite clays which do not need external polar activation, such as those available under the trademarks BARAGEL 3000 and NYKON 3000 (N.L. Chemicals, Inc., Hightstown, N.J.), are particularly preferred for use as thickeners in the composition of the present invention, but bentonites requiring activation (e.g., with acetone), such as BENTONE 24 (NL Chemicals, Inc.), have also been used to advantage.

The amount of the thickener which is utilized depends upon the viscosity desired, the particular gel matrix with which the thickener is used, and the specific thickener. Generally, the thickener is used in a concentration of from about 5 to about 24% of the gel composition by weight. If a self-activating organophilic clay is utilized as the thickener in, for instance, a dielectric gel matrix, the preferred concentration of thickener is between approximately 5 and about 10% by weight. For

SUBSTITUTE SHEET instance, if microspheres of either low density polyethylene, high density polyethylene, or ethylene vinyl acetate copolymer are utilized as the thickener in, for instance, a dielectric oil gel matrix, the preferred concentration of thickener is about 10% by weight. However, such thickeners have been used in concentrations ranging from about 4 up to about 15% successfully. If a petroleum hydrocarbon of, for instance, aliphatic or napthenic paraffins, or a mixture of the two paraffins, is used as a gel matrix, the amount of wax or petrolatum(s) added as a thickener ranges from about 2 to about 12%. The average molecular weight of the preferred paraffins ranges from 200 to 1,000, and such paraffins are used to prepare gel compositions with viscosities, depending upon the proportion of thickener, of from 5 to 200 centistokes at 40°C. Petroleum hydrocarbon thickeners must be free of impurities which corrode the conductors in the instrument case, cable, or other confined space.

Particular success has been achieved using thickeners comprised of a mix of the various substances listed above. Such mixed thickeners may include, for instance, between about 4 and about 10% (total weight of the gel composition) of an organophilic clay such as bentonite, between about 2.1 and about 12% (total weight) of wax or petrolatum, between about 0.5 and about 9.81% (total weight) of pyrogenic silica, and between about 2.1 and about 18% (total weight) of ethylene or polyethylene icropheres. When such mixed thickeners are used, the thickener preferably comprises between about 11.91 and about 23.75% of the gel composition of the present invention.

In addition, a corrosion inhibitor may be added to the composition of the present invention. Suitable corrosion inhibitors include certain corrosive inhibitors which are typically used in greases which were found to have no effect on the water absorbency or insulation characteristics of the polymer of the gel composition.

SUBS TE SH T The rust inhibitor(s) must be chosen with care because those which are of acid character may neutralize the effect of the polymer. A neutral barium dinonylnaphthalene sulfonate did not affect the properties of the present invention, but did have a slight tendency to de-gel one of the gel compositions. An example of an anticorrosion agent which may be used to advantage in the gel composition of the present invention is the product available under the brand name IRGANOX (Ciba-Geigy Corp.). A copper passivator which is a liquid copper triazole derivative was used without any adverse affects. The copper passiator REOMET 39 (Ciba-Geigy Corp.) is an example of such an agent.

The following are examples of different combinations of gel matrices and mixtures which thicken to produce a gel matrix which is appropriate for use with the water absorbent polymer having pendent anionic groups. The examples of compositions prepared in accordance with the invention are not intended to limit the scope of the invention and are instead illustrative of a number ^'of different compositions which can be used to practice the invention.

EXAMPLE 1 A gel matrix was prepared using 20 parts by weight polyisobutylene (Amoco INDOPOL L-100) , 4-1/2 parts by weight polyalpha olefin and one part by weight polyalkylene glycol (Olin Chemical Corp., POLY-G 9150). Polyalkylene glycol is a random copolymer with 75% ethylene oxide and 25% propylene oxide substitution, with an average molecular weight of from 12,000 to 15,000 and a hydroxyl number between 5 to 10 mgs KOH per gram. The polyisobutylene has a viscosity ASTM D-445 38° C of 210-227 and the viscosity index ASTM D-567 is 95. The polyalpha olefin used was a long chain polyalpha olefin SHF-61 manufactured by Mobil which had a viscosity ASTM D-445 at 38° C of 30.5 and a viscosity index ASTM D-2270 of 132. The polyalpha olefins which are used, as

SUBS-TffUTE SHEEΪ exemplified by the SHF-61 Mobil product, are typically hydrocarbons with a molecular weight from 200 to 800. The SHF-61 product is an oligomer of 1-decene. The satisfactory viscosity range of the polyalpha olefins is from 2 centistokes at 100° C to 100 centistokes at 100° C. Twelve parts of the resulting mixture was mixed with one part of pyrogenic silica as a thickener. The resulting gel matrix was blended two parts to one (by weight) with the water absorbent polymer in the form of the partial sodium salt of crosslinked polypropenoic acid, referred to herein as 2-polypropenoate (Dow Chemical Co. XU43408.00 Experimental Absorbent Polymer, Product Code 06115) .

A 12V battery was hooked up to a pair of spliced wires and water was introduced into the spliced area causing a short. The spliced area was then filled with the composition of Example 1 and water began to be absorbed in 15 seconds. The short healed and conductance was restored to the wire pairs. Essentially the same results achieved using a composition including the water absorbent polymer characterized as polyacrylic acid and sold under the brand name FAVOR C 96 (Stockhausen, Greensboro, N.C.).

EXAMPLE 2 A gel composition in accordance with the present invention was prepared in the manner described in Example 1 and having the following contents (parts by weight) . INDOPOL L-100 (Amoco Chemical Corp.) 736 Shell wax 130 (Shell Chemical Co.) 25

REOMET 39 (Ciba-Geigy Corp.) 3

FAVOR C96 (Stockhausen, Inc.) 286

AEROSIL R74 (Degussa Corp.) 116.9

MICROTHENE FA640 (Quantum Chemicals Corp.) 25

EXAMPLE 3 A gel composition in accordance with the present invention was prepared in the manner described in Example 1 and having the following contents (parts by weight) .

SfflS DRAKEOL 34 (Penreco Corp.) 610

REOMET 39 (Ciba-Geigy Corp.) 2.5

BARAGEL 3000 (NL Chemicals, Inc.) 50

AEROSIL R74 (Degussa Corp.) 15

FAVOR C 96 (Stockhausen, Inc.) 150

MICROTHENE FA640 (Quantum Chemicals Corp.) 172.5 When tested in accordance with ASTM D150 procedures, the composition was characterized as having a dielectric constant of 2.26 and a dissipation factor of 0.01, and when tested in accordance with ASTM D257, volume resisti .vi.ty was 4.99 x 1012

EXAMPLE 4

A gel composition in accordance with the present invention was prepared in the manner described in Example

1 and having the following contents (parts by weight) .

DRAKEOL 34 (Penreco Corp.) 610

REOMET 39 (Ciba-Geigy Corp.) 2.5

BENTONE 24 (NL Chemicals, Inc.) 50

Acetone 10

AEROSIL R74 (Degussa Corp.) 20

FAVOR C 96 (Stockhausen, Inc.) 150

MICROTHENE FA640 (Quantum Chemicals Corp.) 157.5

When tested in accordance with the procedures described in

Example 3, the composition was characterized as having a dielectric constant of 2.12, volume resistivity of 5.91 x 10 12, and a dissipation factor of 0.01.

EXAMPLE 5

1 and having the following contents (parts by weight) .

DRAKEOL 34 (Penreco Corp.) 622.5

REOMET 39 (Ciba-Geigy Corp.) 2.5

BARAGEL 3000 (NL Chemical, Inc.) 40

AEROSIL R74 (Degussa Corp.) 5

FAVOR C 96 (Stockhausen, Inc.) 150

MICROTHENE FA640 (Quantum Chemicals Corp.) 180

STO HfTE SHEET. When tested in accordance with the procedures described in Example 3, the composition was characterized as having a dielectric constant of 2.19, volume resistivity of 6.91 x

12 10 , and a dissipation factor of 0.01.

EXAMPLE 6

A gel composition in accordance with the present invention having the following contents was prepared (all parts by weight) .

DRAKEOL 34 (Penreco Corp.) 704.95

REOMET 39 2.875

IRGANOX 1010 (Ciba-Geigy Corp.) 2.3

BARAGEL 3000 (NL Chemical, Inc.) 51.75

AEROSIL R74 (Degussa Corp.) 8.625

FAVOR C 96 (Stockhausen, Inc.) 172.5

MICROTHENE FA750 (Quantum Chemicals Corp.) 207

EXAMPLE 7 A gel composition in accordance with the present invention having the following contents was prepared (all parts by weight) .

DRAKEOL 34 (Penreco Corp.) 324. 8

N1500 (Penreco Corp.) 324. 8

REOMET 39 (Ciba-Geigy Corp.) 2 . 8

BARAGEL 3000 (NL Chemical, Inc.) 61 . . 6

AEROSIL R74 (Degussa Corp.) 5 . , 6

FAVOR C 96 (Stockhausen, Inc.) 224

MICROTHENE FA640 (Quantum Chemicals Corp.) 176 . . 4

EXAMPLE 8

Another gel composition was prepared 'ing the following contents (all parts by weight) .

White oil (Calumet Refineries, La.) 656 , . 625

REOMET 39 (Ciba-Geigy Corp.) 2 , . 125

IRGANOX 1010 (Ciba-Geigy Corp.) 4 . 25

BARAGEL 3000 (NL Chemicals, Inc.) 59 . 5

FAVOR C 96 (Stockhausen, Inc.) 127 . 5

EXAMPLE 9

Another gel composition was prepared having the following contents (all parts by weight) .

Wl INDOPOL L-100 (Amoco Chemical Corp.) 891

BARAGEL 3000 (NL Chemicals, Inc.) 120

FAVOR C 96 (Stockhausen, Inc.) 180

REOMET 39 (Ciba-Geigy Corp.) 3

IRGANOX 1010 (Ciba-Geigy Corp.) 6

EXAMPLE 10

DRAKEOL 34 (Penreco Corp.) 694. 4

REOMET 39 (Ciba-Geigy Corp.) 2 . 8

IRGANOX 1010 (Ciba-Geigy Corp.) 5 . 6

BARAGEL 3000 (NL Chemicals, Inc.) 50 . A

FAVOR C 96 (Stockhausen, Inc.) 168

MICROTHENE FA640 (Quantum Chemicals Corp.) 198 . . 8

EXAMPLE 11

INDOPOL L-100 (Amoco Chemical Corp.) 862 . . 4

AEROSIL R74 (Degussa Corp.) 120

FAVOR C 96 (Stockhausen, Inc.) 278

REOMET 39 (Ciba-Geigy Corp.) 3 . 2 Several of the formulations set out in Examples 2-11 have also been prepared and used to advantage with a polymer obtained from Chemdal Corp., stock no. 1125.

EXAMPLE 12

This example duplicates the gel formulation of Example 1 but with the substitution of tall oil fatty acid for polyalkylene glycol. The tall oil fatty acid was 5% by weight of the gel matrix. The gel was then mixed with 33% by weight of the water absorbent sodium 2-propenoate polymer described herein.

The effects of including oleic acid and tall oil fatty acid as hydrophilic substances in the gel composition of the present invention were compared to a gel composition prepared without a hydrophilic component by preparing the gel matrix of Example 1 without the polyalkylene component. The oleic acid and tall oil fatty

su^βsπr&TE SHEE acid slightly sped up the response time for absorption by about one-half. Without the hydrophilic additive, at least 2 minutes passed before the gel composition initiated water absorbency.

EXAMPLE 13 Fluorocarbon gels have also been used as a gel matrix with the water absorbent polymer. NYE fluoroether grease 3834, a completely fluorinated grease, was used as the gel matrix. The fluoroether grease had viscosities of 26 centistokes at 210° F and of 270 centistokes at 100° F. Seven grams of the NYE fluoroether was mixed with 3 gms of sodium 2-polypropenoate and 0.5 gms pyrogenic silica thickener. The water absorption and healing of the short was slow but effective when the resulting gel composition was tested as described in Example 1.

EXAMPLE 14 Fluorocarbon gels have also been used as a gel matrix with the water absorbent polymer. NYE fluoroether grease 3834, a completely fluorinated grease, was used as the gel matrix. The fluoroether grease had viscosities of 26 centistokes at 210° F and of 270 centistokes at 100° F. Seven grams of the NYE fluoroether was mixed with 3 gms of sodium 2-polypropenoate and 0.5 gms pyrogenic silica thickener. The water absorption and healing of the short was slow but effective.

EXAMPLE 15 Polyesters have also been used as a gel matrix in gel compositions including a water absorbent polymer. The polyesters ranged in molecular weight from 300 to 800 and had viscosities from 25 to 100 centistokes at 40° C. The polyesters were mixed with 10 to 30% of the polymer. The polyesters which have been utilized are esters of trimethylol propane, pentaerythritol and triallyl mellitate. The water absorption occurred in less than one minute and conductivity was restored after 20 minutes.

EXAMPLE 16

SUSSHΓUΓE mi A dielectric oil gel matrix was prepared using 50 parts by weight polyisobutylene (Amoco, INDOPOL L-100) , 40 parts by weight white oil (Penreco Corp., DRAKEOL 34) and 10 parts by weight by pyrogenic silica (Degussa Corp. , AEROSIL R74) . Seventy-five parts of the resulting mixture was blended to 25 parts by weight of the water absorbent polymer in the form of a starch-polyacrylonitrile graft copolymer (WATER LOCK, Grain Processing Corp.). The resulting gel composition, when tested as described in Example 1, began water absorption in about eight minutes, and the short was eliminated shortly thereafter.

EXAMPLE 17 A gel matrix was prepared using 50 parts by weight polybutylene (Amoco, INDOPOL L-100) , 40 parts by weight white oil (Penreco Corp. , DRAKEOL 34) and 10 parts by weight pyrogenic silica (Degussa Corp. , AEROSIL R74) . Seventy-five parts of the resulting mixture was blended to 25 parts by weight of the water absorbent polymer in the form of a methyacrylamide polymer (sold under the brand name CHEM-MUD, Chem-mud, Inc., Leiscester, N.C.). The resulting gel composition, when tested as described in Example 1, began water absorption in about ten minutes, and the short was eliminated shortly thereafter.

EXAMPLE 18 The gel composition of the present invention can also be prepared using white oils of petroleum hydrocarbon stocks of aliphatic or napthenic paraffin as a dielectric oil gel matrix. Compositions have been prepared using white oils manufactured by Penreco Corp., specifically those sold under the brand name DRAKEOL such as DRAKEOL 7, 19, 34, 35 and DRAKEOL 4410, and those manufactured by Witco Corp. and sold under the brand name KAYDOL. The preferred oils for making appropriate dielectric oil gel matrices are those having a viscosity in the range of from about 150 to about 600.

It has been found that the use of petroleum waxes or low oil cream petrolatums produces a higher viscosity

SUBSTITUTE SHEEI dielectric oil gel matrix, thereby reducing the amount of pyrogenic silica used as a thickener as compared to the amounts set forth in the preceding examples. For instance, a composition similar to the composition prepared in Example 1 was prepared substituting a 150 vis waxie hydrated distillate oil (Penreco Corp.) for the polyisobutylene described in that example. The fluid mixture was prepared using 91.8% by weight of the waxie oil, 1.6% polyalkylene glycol (Olin Chemical Corp., POLY-G

9150) and 6.6% microcrystalline wax (Witco Chemical Corp.,

Witco X-145-A) . The dielectric oil gel matrix was prepared by adding 1.0% by weight pyrogenic silica

(Degussa Corp., AEROSIL R74) and 14.7% by weight of high density linear polyethylene powder (Quantum Chemicals

Corp., MICROTHENE FA750) to the fluid mixture. To this gel matrix was then added 25.9% by weight of sodium salt of polyacrylic acid (Stockhausen, Inc., FAVOR C 96) to form a gel composition. When tested in accordance with the procedure described in Example 1, water encapsulation began within five minutes, electrochemical deposition of the polymer insulation began in ten minutes, and the short was healed in twenty minutes.

EXAMPLE 19

The composition of Example 20 was also prepared by substituting a non-hydrated oil for the waxie distillate oil, in particular, Penreco HG Bright Stock Oil, and the addition of 5% Penreco low cream oil petrolatum. When tested in accordance with the above-described procedure, this composition performed in much the same manner as the gel composition of Example 1.

EXAMPLE 20

A dielectric oil gel matrix was prepared using 80 parts by weight white oil (Penreco Corp., DRAKEOL 4410) and 15 parts by weight of a microcrystalline wax (Witco Corp. , X145-A) to 5 parts by weight pyrogenic silica (Degussa Corp., AEROSIL R74) . Eighty parts by weight of the resulting gel matrix was blended with 20 parts by

SUBSTITUTE SHET weight of the water absorbent polymer in the form of the sodium salt of a polymer of maleic anhydride obtained from ARCO Chemical which, on information and belief, is a polymer of the type described in U. S. Patent No. 4,616,063. The resulting gel composition, when tested as described in Example 1, began water absorption in about 10 minutes, and the short was eliminated shortly thereafter. Similar results were obtained using a water absorbent polymer of fumaric anhydride.

* * * * *

Referring now to Fig. 1, there is shown a schematic representation of a method and apparatus for making a telecommunications cable including the gel composition of the present invention such as the cable shown in Fig. 2. Such a cable, indicated generally at reference numeral 10, is comprised of a plurality of pairs of wires, or conduc¬ tors, 12 contained in bundles 14 by a binder 16, the bundles 14 being bound into cable 10 by sheath 18. Although not shown in Fig. 2, sheath 18 is generally comprised of multiple layers such as a plastic wrapper (e.g., MYLAR) , a metal cladding, a thin layer of polyurethane or other foam, and an outer plastic sheath, or any combination of one or more such layers. Each pair of wires 12 is comprised of a pair of metal wires 20 covered by a thin layer of insulation 22 such as polyethylene, and the number of pairs of wires 12 in a bundle 14 is arbitrary, twenty being shown in the bundles 14 in Fig. 2.

To make the cable 10, the pairs of wires 12 are drawn through an oscillating die, such as the die 26 in filling head 24 shown in detail in Fig. 3, in which the gel composition of the present invention is extruded onto the wires 12. Although the cable 10 is shown in Fig. 2 as being comprised of five twenty-pair bundles 14, only five pairs of wires 12 are shown entering each of five filling heads 24 of Fig. 1 instead of twenty for purposes of

SUBSBRΠE SHEET clarity. The five dies 26 in filling heads 24 are mounted on the shafts 25 of and oscillated by an oscillating machine 28 of a type known in the industry, and the five bundles 14 exiting die 24 are passed through a sizing insert 30 (see Fig. 3) so that the diameter of each bundle 14, and amount of the gel composition applied to each bundle 14, is standardized. As the bundles 14 exit oscillating machine 28, a binder 16, such as polyethylene or a paper wrapping, is applied to each bundle 14 at a binder station 32.

The five bundles 14 are then drawn into a second filling head 34 having a die (not shown) mounted therein for extruding the gel composition of the present invention around the bundles 14 that is oscillated by a belt or chain 36 from a motor (not shown) . The sheath 18 is then applied at station 38 in a manner known in the industry, resulting in cable 10. It will be recognized by those skilled in the art who have the benefit of this disclosure that, rather than applying a sheath 18 at station 38, a binder such as the binder 16 can be applied to the one hundred pair cable 10 and that the one hundred pair cable 10 can then be drawn into another filling head (not shown) such as the filling head 34 along with, for instance, nineteen other such cables to make a two thousand pair cable to which a jacket or sheath is then applied.

As noted above, the space 40 between the pairs of wires 12 inside the binder 16 of each bundle 14 is the filling zone 40. The flooding zone 42 is the space between bundles 14 inside the sheath 18 around cable 10. As can be seen from the description of a method of making the cable 10, the gel composition of the present invention is used to fill both the filling zone 40 and the flooding zone 42.

Referring now to Fig. 3, the filling head 24 will be discussed in detail. Filling head 24 is comprised of a stationary housing 44 and an oscillating die 26 through which the wire pairs 12 (not shown in Fig. 3) are drawn.

SUBSTITUTE SHEET Housing 44 is secured to the mounting plate 45 of a support assembly 46 by screws 48 to completely contain die 26. The seal 50 mounted in the annulus 51 in the inside surface 52 of support assembly 46 bears against the outside surface 53 of the face plate 54 of die 26 and the seal 56 mounted in the annulus 57 in back plate 58 of housing 44 bears against the surface 60 of the plate 62 comprising the back of die 26 to contain the die 26 while allowing oscillation of die 26 within housing 44. The plate 62 comprising the back of die 26 is secured to the shaft 25 of an oscillating machine (shown at reference numeral 28 in Fig. 1) by screws 66 so that die 26 oscillates with shaft 25 inside of housing 44.

Housing 44 is provided with an inlet port 68 in one wall thereof for receiving the gel composition of the present invention through hose 70, the gel composition entering the space 72 inside housing 44 in which die 26 is mounted and, by virtue of the oscillating of die 26 and the openings 74 in die 26, contacting the wire pairs 12 as they are drawn into the die 26 through the holes 76 in face plate 54. The wire pairs 12 then pass out of die 26 through an opening (not numbered) in which the sizing insert 30 is set. The sizing insert 30 is provided with an orifice 80 selectively sized to determine the diameter of the bundle 14, having the gel composition of the present invention extruded thereon, as the bundle 14 passes through the longitudinal passage 82 therethrough and exits the filling head 24 through the tubular shaft 25 of oscillating machine 28. The orifice 80 of sizing insert 30 is flared to facilitate entry of the paired wires 12 into the passage 82 therethrough and subsequent sizing of the bundle 14.

The gel composition of the present invention which is pumped into the space 72 inside housing 44 is maintained under low pressure so as to facilitate extrusion onto the wires 12. Pressure is maintained by the size of the port 86 in the wall of housing 44, which restricts the amount

SUBSTITUTE SHE! of gel composition which can escape from housing 44 into hose 88. Alternatively, port 86 is replaced with a one-way, spring-loaded pressure control valve (not shown) or, if a gel composition having a gel matrix including a tackifier is used such that sufficient gel composition adheres to the wires 12 at atmospheric pressure, port 86 is replaced with a plug or view-port (not shown) .

Although the invention has been described in terms of a number of examples setting forth preferred embodiments thereof, those skilled in the art who have the benefit of this disclosure will recognize that changes may be made in the compositions described in these various examples without changing the manner in which the various components of the gel composition of the present invention function to accomplish the results achieved by these compositions. Such changes might, for instance, take the form of small variations in the proportions of the various components, the substitution of some substance having a similar function not mentioned in the specification for one of the components of the gel composition, or the addition of a substance to one of the gel compositions described. Such changes are intended to fall within the spirit and scope of the present invention as set out in the following claims.

SUBSPTE SHET

Claims

WHAT IS CLAIMED IS:

1. A telecommunications cable comprising: a plurality of bundles of insulated conductors; each of said bundles being contained by a binder; a sheath surrounding said plurality of bundles of insulated conductors to form a cable; and a gel composition filling both the spaces between the insulated conductors in each of said bundles inside said binder and the spaces between said bundles outside said binder and inside said sheath, said gel composition comprising between about 5% to about 33% by weight of a water absorbing polymer having anionic groups attached to the backbone thereof, said polymer being dispersed in a gel matrix comprising about 40% to about 95% of the weight of the composition.

2. The cable composition of claim 1 wherein the polymer of said gel composition is selected from the group consisting of polymers of acrylates, acrylamides, methacrylate, methacrylamide, acrylonitriles, methacrylonitrile, triacrylate and/or tetraethylene glycol, diacrylate, cellulose, cellulose derivatives, or polypropenoates.

3. The cable of claim 1 wherein the gel matrix of said gel composition is selected from the group consisting of silicone, olefins, esters, fluorocarbons, petroleum hydrocarbons, glycols, polyglycols or polyethers and mixtures thereof.

4. The cable of claim 1 wherein the gel matrix of said gel composition comprises a fluid and an organophilic clay for thickening said fluid to form a gel matrix.

5. The cable of claim 4 wherein said organophilic clay is bentonite.

6. The cable of claim 4 wherein said organophilic clay comprises between about 4 and about 10% by weight of said gel composition.

SUBSTITUTE SHET

7. A composition for protecting the contents of an enclosed space from damage caused by the presence of water comprising: a fluid; an organophilic clay mixed with said fluid for thickening said fluid to form a gel matrix; and a water absorbent polymer dispersed in said gel matrix, said polymer having anionic groups attached to the polymeric backbone thereof, the anionic groups of said polymer, when exposed to direct current from a wire that is in a condition of short caused by the presence of water, causing said polymer to be attracted to the wire, the wire acting as an anode to draw said polymer into electrochemical association with the wire, the accumulated polymer insulating the wire and eliminating the short to restore current through the wire.

8. The composition of claim 7 wherein said gel matrix comprises between about 61.6 and about 84.75% by weight of said gel composition.

9. The composition of claim 7 wherein said organophilic clay comprises between about 4 and about 10% by weight of said gel composition.

10. The composition of claim 7 wherein said fluid is a dielectric oil.

.

11. The composition of claim 7 wherein said organophilic clay is bentonite.

12. The composition of claim 7 wherein said polymer comprises between about 10 and about 33.3% by weight of such gel composition.

13. The composition of claim 7 wherein said polymer is selected from the group consisting of polymers of acrylic acids, ²-methylpropenoic acids, 3-methylpropenoic acids, maleic acids, fumaric acids, and the respective maleic and fumaric anhydrides.

14. The composition of claim 7 wherein said polymer is selected from the group consisting of polymers of acrylic acids, ²-methylpropenoic acids, ³-methylρropenoic

SUBSTITUTE SHET acids, maleic acids, fumaric acids, and the respective maleic and fumaric anhydrides.

SUBSTITUTE SHET