Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/302—Polyurethanes or polythiourethanes; Polyurea or polythiourea
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/36—Hydroxylated esters of higher fatty acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/67—Unsaturated compounds having active hydrogen
  • C08G18/69—Polymers of conjugated dienes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
  • H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
  • H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable

Definitions

• Air core plastic insulated conductor (PIC) telephone cable occasionally becomes water-logged in service. The water creates leakage paths to wires with defective insulation. The signaling and transmission characteristics of telephone pairs with such lowered insulation resistance and high relative permittivity are severely degraded. Restoring insulation resistance to standards, particularly for buried plastic insulated cable, has been costly, temporary, and oftentimes not possible with present reclamation procedures.
• a principal object of this invention is to remove water already present in a multipair plastic insulated telephone cable, and prevent its reentry through existing cable sheath faults or such faults that may develop in the future by filling the cable interstices.
• the compound must be compatible with the wire insulation, with the cable jacket, with the shield which is typically aluminum, and with other materials present in buried closures.
• the compound must maintain the separation of the conductors and the integrity of the sheath including, the polyethylene jacket and aluminum shield.
• the compound must not corrode the aluminum or copper conductors when contact is made with them through the pinholes normally found in their plastic insulation.
• the compound must havehigh insulation resistance and volume resistivity, low dielectric constant, and exhibit low dielectric losses, so as to restore the insulation resistance, capacitance and dielectric losses of the cable to acceptable values.
• the compound To prevent reentry of water into the cable, the compound must be hydrophobic and fairly permanent.
• the compound must have an initial low viscosity to permit pumping through substantial lengths of cable preferably during a normal workday.
• the principal object of the invention is to permanently rid telephone cables of water that has seeped in and restore dielectric properties to acceptable levels.
• a further inventive object is to prevent the reentry of water in a PIC telephone cable with the very compound used to purge.
• a further inventive object is to devise a water purging compound for telephone PIC cable with acceptably low initial viscosities, but which cures to a soft tacky compound that wets the wire insulation.
• a still further inventive object is to purge water in telephone plastic cables with a single pumping over as long a cable stretch as possible.
• this invention contemplates the use of a hydrophobic insulating material that displaces the water in a waterlogged cable as the material is pumped in, and once in place, cures to a high viscosity that precludes its escaping through lightning pinholes or other sheath defects, while at the same time precluding the reentry of water.
• insulating materials that are initially of sufficiently low viscosity to permit pumping into a telephone cable, and which retain the low viscosity for a long enough time to permit extended pumping, are contemplated within the inventive scope. These are: thixotropic compounds; gelling compounds; cross-linking compounds and combination thereof.
• a particular embodiment of the invention is a crosslinking material which is basically a solution of a room temperature curing liquid urethane elastomer in a low viscosity oil.
• the material is pumped into the cable at a very low viscosity and purges the water. Then, after a period dependent on the amount of catalyst used the urethane cross-links, forming a three-dimensional network which gels the oil. The result is a filled cable purged of water and henceforth waterproofed.
• a viable method has been found for obtaining a sufficiently low viscosity reactive material that achieves all of the inventive objects including the pumpability of the compound and its later setting up into a soft tacky material.
• a more specific illustration is a solution of a hydroxyl terminated polybutadiene and a castor oil based isocyanate prepolymer in a low viscosity aromatic oil.
• a prepurgant that is highly miscible with both water and with the main purgant serves to remove an even greater percentage of water than does use of the main gelling purgant alone.
• initial viscosity of the solution to be introduced in the cable is critical to purging and thereafter filling long cable lengths.
• the polymer must be chosen for its hydrophobic and low viscosity properties and for its ability to cure within temperature ranges encountered in practice.
• a particular and presently preferred class of material pursuant to the present invention is a solvent oil gelled by a cross-linked urethane network formed by reacting, on an essentially 1:1 basis, a material having an unblocked (i.e., available) hydroxyl functionality with a material having an unblocked isocyanate functionality.
• the invention more specifically contemplates systems within this preferred class which have an initial viscosity less than 100 CPS at all temperatures between 35 F. and 90 F. Still more specifically, systems as above are preferred which exhibit when fully gelled a dielectric constant of not more than 3.0, and preferably not more than 2.5.
• a specific application of the present invention is a multipair sheathed plastic-insulated conductor telephone cable filled by a solvent gelled by a cross-linked urethane polymer composition containing to 20 weight percent polymer.
• the cross-linked urethane polymer is formed from a polyol and an isocyanate prepolymer wherein the polyol is of the polyether, polyester, castor oil or polybutadiene type.
• Example 1 The cable water purgant of this example will be described in terms of Part I and Part II because the components are advantageously stored in two such parts until just prior to introduction into the cable where they are mixed preferably in equal proportions of Part l and Part II. All ingredients could as well be combined at such time, however.
• Part I consists of a castor oil based isocyanate prepolymer in an aromatic solvent oil, in the amounts 50 grams of isocyanate prepolymer per liter of solution.
• the prepolymer is formed from toluene diisocyanate and castor oil, and has a hydroxyl functionality of 2.8 and an equivalent weight of approximately 288.
• Castor oil for present purposes is defined as a mixture of about 70 percent pure glyceryl triricinoleate and 30 percent glyceryl diricinoleate-monooleate or monolinoleate. It is seen that from the standpoint of isocyanate utilization the castor oil is approximately 70 percent triand 30 percent difunctional.
• the triol structure of castor oil produces cross-linking.
• the aromatic solvent oil is defined as an oil containing a major proportion of aromatic molecules, that is, molecules having at least one aromatic ring.
• Part II consists of I00 gm/litter of solution (in aromatic solvent oil) of hydroxyl terminated polybutadiene having a hydroxyl functionality between 2.2 and 2.4 and a hydroxyl content between 0.75 and 0.90 equivalents per kilogram and 4 gm/liter dibutyl tin dilaurate catalyst.
• Example 2 The water purgant of Example 2 is the same as that described in Example 1, except that the castor oil based isocyanate prepolymer is of the diphenylmethane diisocyanate type.
• Example 3 The purgant of this example is the same as that of Example l, except that the isocyanate prepolymer is one based on hydroxyl-terminated polybutadiene and toluene diisocyanate.
• Example 4 The purgant of this example is the same as that of Example 1, except that the isocyanate prepolymer is one based on hydroxyl-terminated polybutadiene and diphenylmethane diisocyanate.
• Example 1 the grams per liter of castor oil based isocyanate prepolymer may be varied within a range of about 25 to 150.
• Aromatic solvent oil is selected in order to dissolve the polybutadiene and the castor oil prepolymer.
• the aromatic oil preferably consists of greater than 90 percent by weight of aromatic molecules as above defined, and as measured in accordance with ASTM D-2007.
• the mixture consisting of Parts I AND II as defined in the three above examples must exhibit and initial viscosity below 100 centipoise at all temperatures between 35 F. and 90 F. More specifically, the mentioned concentrations may be varied but not beyond that which would exceed the initial viscosity of 100 centipoise.
• the concentrations of the mentioned ingredients of Part Il may be reduced by about 20 percent, and the aromatic solvent oil will still be gelled.
• a prepurgant selected pursuant to a further aspect of the invention has been found to be highly advantageous.
• the prepurgant must be miscible with water and with the reclamation compound. It must also wet polyethylene.
• the reclamation compound is aromatic solvent oil; and as a prepurgant for this-applicants use, for example, polypropylene glycol of molecular weight in the range 425-150.
• Liquid polyethylene glycol may also be used as a prepurgant.
• Ketones such as methyl ethyl ketone may be used with necessary safety precautions.
• the aromatic oil used is available for example from Kenrigh PetroChemicals under the name Kenplast G.
• the isocyanate used is obtainable under the name Vorite 128 from Baker Castor Oil Company. It is a castor oil based prepolymer. It was chosen because of its low vapor pressure (thus low toxicity by inhalation), and its solubility in aromatic oil. Some of its properties are listed below.
• materials which have the requisite hydroxyl functionality include: natural rubber into which hydroxyl functionalities have been introduced; ethylene-propylene-rubber copolymers or terpolymers into which hydroxyl functionalities have been introduced; and styrene-butadiene rubber (SBR) modified to contain hydroxyl functionalities.
• SBR styrene-butadiene rubber
• Requirement (1) can be fulfilled by using a low viscosity solvent or diluent, by minimizing the amount of gelling agent in the solution, and by also minimizing the viscosity of the gelling agent.
• Requirement (2) must be considered in two parts.
• the minimum amount of gelling agent needed to gel the oil was not known a priori to be small enough to concurrently allow fulfillment of requirement (1).
• Requirement (3) also is in conflict with requirement (1). Since the material must not shrink due to volatilization of the solvent, a very low viscosity solvent (such as toluene) cannot be used. Safety considerations also require a material with low vapor pressure. An oil pursuant to the invention was used to obtain both volatility and viscosity characteristics.
• an installed multipair sheathed plastic insulated conductor telephone cable with previously waterlogged interior voids filled by an initially liquid filler comprising a solvent oil gelled by in situ catalytic reaction of a hydroxyl terminated polybutadiene and a polyisocyanate prepolymer, the average functionality of the polyisocyanate prepolymer and the hydroxyl-terminated polybutadiene being sufficient to form a cross-linked urethane network that gells said oil, the solvent oil being the major fraction by weight of the filler, the properties of all said filler constituents being such that the viscosity of said filler when initially liquid is less than cps at all temperatures between 35 F. and 90 F., and further being such that the filler when fully gelled has a dielectric constant of not more than 3.0.
• said solvent oil is an aromatic solvent oil containing a major proportion of aromatic molecules; and wherein said polyisocyanate prepolymer is present in amounts of from 25 to 150 grams per liter and said hydroxylterminated polybutadiene is present in amounts of from 80 to grams per liter of said initially liquid filler.

Landscapes

• Chemical & Material Sciences (AREA)
• Polymers & Plastics (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Organic Chemistry (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Physics & Mathematics (AREA)
• Insulated Conductors (AREA)
• Polyurethanes Or Polyureas (AREA)
• Organic Insulating Materials (AREA)
• Manufacturing Of Electric Cables (AREA)
• Processing Of Terminals (AREA)
• Processes Of Treating Macromolecular Substances (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22774545

Family Applications (1)

Country Status (11)

Cited By (18)

Families Citing this family (6)

Citations (3)

Family Cites Families (1)

• 0
  • BE BE792621D patent/BE792621A/xx not_active IP Right Cessation
• 1971
  • 1971-12-15 US US00208420A patent/US3733426A/en not_active Expired - Lifetime
• 1972
  • 1972-06-27 CA CA145,814A patent/CA997133A/en not_active Expired
  • 1972-12-05 DE DE2259411A patent/DE2259411C3/de not_active Expired
  • 1972-12-11 NL NL7216794.A patent/NL159220B/xx not_active IP Right Cessation
  • 1972-12-13 CH CH1812672A patent/CH575002A5/xx not_active IP Right Cessation
  • 1972-12-14 IT IT70923/72A patent/IT976046B/it active
  • 1972-12-14 FR FR7244589A patent/FR2163632B1/fr not_active Expired
  • 1972-12-14 JP JP12481072A patent/JPS5619161B2/ja not_active Expired
  • 1972-12-15 GB GB5802072A patent/GB1406859A/en not_active Expired
  • 1972-12-15 ES ES409992A patent/ES409992A1/es not_active Expired

Patent Citations (3)

Non-Patent Citations (1)

Also Published As

Similar Documents