CA1101143A - Polyurethane gel agent for decontaminating and sealing the interior surfaces of an insulated electrical device - Google Patents

Abstract

ABSTRACT of the Invention This invention provides a method of sealing and purging contaminants from the internal free spaces of an insulated electrical device by forcing into said free spaces a low viscosity material consisting of a mineral oil extended polyurethane that acts to displace fluid contaminants from within said free spaces. the material later cures in situ to form a hydrophobic seal with good electrical properties. Also disclosed herein is a method for rehabilitating waterlogged plastic insulated multicon-ductor communications cables of the type employed in telephone systems.

Description

This invention relates to a method of rehabili-tating insulated electrical devices that have become contam-inated by fluid penetration of their interior free spaces.
More specifically, the invention concerns a method for displacing aqueous fluid penetrants from the interior free spaces of an insulated electrical apparatus and sealing the purged spaces against further aqueous fluid penetration while maintaining the electrical properties of the apparatus.
Water penetration of insulated electrical devices and especially plastic insulated multiconductor telephone cables can seriously effect the electrical properties of such structures. The problem of water penetration ls amplified when the electrical device is positioned under-; ground or in a high humidity environment. In the case of a telephone cable, water penetration can seriously impair the electrical and mechanical improperties that are critical to its continued operation. ~he presence of water between insulated conductors can cause a significant~increase in their capacitance and can lead to the development of electrical leakage pathways between conductors having pin-hole insulation defects. Leakage of water into the unoccupied spaces between the insulated cable pairs and the outer sheath can also cause a significant increase in signal attenuation, noise, and lead to conductor corrosion.
Replacement of waterlogged cables is not a satis-factory solution to the problem of water contamination in most cases because of the expense and inconvenience involved in such an undertaking. However, in order to maintain suitable operating parameters the cable must be rehabilitated by removal of the fluid contaminant and restoration of the electrical and mechanical conditions that render it useful X
' 1101~43 as a means for transmission of telephone signals.
The prior art has advanced several methods of eliminating aqueous penetrants from the interior free spaces of plastic insulated conductor cables. One technique involves the use of acetone to eliminate water. Removal of water, alone, is not sufficient in most cases since the means for water penetration is not eliminated and unless a continuous supply of acetone is maintained in the cable, renewed fluid penetration can be expected to occur. Another method of purging water contaminants depends upon pumping a gas into the interior free spaces of the cable via a coupling to the outer cable sheath and maintaining a continuous ele~ated gas pressure between interconnected cable segments. This method is impractical for use in most cases since it requires the continued operation of a gas generating source in order to prevent subsequent water penetration.
A recently developed technique removes water that has penetrated into the interior free spaces of a telephone cable by pumping a hydrophobic insulating material into the cable. The insulating material is introduced at low viscosity and cures in place to a high viscosity thus precluding its escape via defects in the outer covering of the cakle. The cured material simultaneously acts as a hydrophobic barrier to subsequent water penetration. This system employs a cross-linking composition which is a solution of a liquid urethane elastomer in an aromatic oil. A principal disadvan-tage of this system is that after the reclamation agent has cured in place, the aromatic hydrocarbon oil can escape from the cross-linked system and severely attack the plastic conductor connectors, or polyolefin sheathing.
In addition to the water elimination, low viscosity,

- 2 -: ~j and barrier properties pxeviously set forth a rehabilitationmaterial for use insealed electrical devices must fulfill other critical requirements. It must be compatible with plastic connectors (such as polycarbonates), normally employed in joining lengths of telephone cable. Compatibility with polyolefins is important and an effective rehabilitation agent should not stress crack these materials which frequently form the insu-lating sheath of telephone cables. The agent should also have good mechanical properties, relatively long life expectancy and a relatively flat viscosity-time curve to insure good pumpability and to ena~le longer cable segments to be reha~ilitated and filled in a single application.
It is also important that a cable rehabilitation agent display superior electrical characteristics such as high insulation resistance, volume resistivity dissipation factor and low dielectric constants since in most cases it must rehabilitate the cable with respect to these properties.
Additionally, the reclamation agent should have a low specific gravity in order to impart a minimal weight gain to the rehabilitated cable and less water and air entrapment which can result from the turbulence effects of pumping into a confined cable space. Also, the rehabilitation compound should not attack polyethylene terephthlate or other synthetic polymer materials employed in cable construction.
Finally, current health and safety regulations make it imperative that a rehabilitation agent be relatively non-toxic, non-volatile and easy to handle in the field.
It is therefore an object of this invention to provide a method for eliminating water that has penetrated the ; 30 interior free spaces of an insulated electrical apparatus and ~, ~r ~1~1143 to simultaneously provide a barrier to prevent subsequent water penetration.
Another object of the invention is to rehabilitate the electrical properties of an insulated electrical apparatus that has become waterlogged.
A further aspect of the invention is to dislodge aqueous contaminants from the interior free spaces of a plastic insulated multiconductor telephone cable by intro-duction of a cable rehabilitation compound under pressure over lengthy cable spans in a single operation.
Another aspect of this invention is the provision of a low viscosity agent capable of eliminating aqueous contaminants from the interior free spaces of an insulated electrical cable and which cures in situ to provide a perma-nent barrier to subsequent water penetration.
These and other objects of the instant invention will be better understood by reference to the following specification and the accompanying drawin~ wherein:
Fig. 1 is a front elevational ~iew, partly in section, of a length of plastic insulated multi-conductor telephone cable, The instant invention involves a method of elimin-; ating water that has penetrated the interior free spaces of an insulated electrical apparatus ~y forcing into the free spaces of the apparatus a rehabilitation a~ent comprising a low viscosity solution of urethane precursors that are extended in a mineral oil. The rehabilitation agent is introduced into the apparatus at very low viscosity by pumping. Continuous introduction of the low viscosity agent is maintained in order to drive it along the length of thefree spaces throughout th,e electrical apparatus. The '; X . -, 111)1143 rehabilitation compound initially displaces aqueous con-taminants, such as water, that have penetrated into the interior free spaces between the different components of the insulated device. Thereafter, the low viscosity agent cures in situ to form a gel-like urethane structure in which the mineral oil is retained. In this manner, water contaminants are removed from the insulated electrical arrangement, a barrier is formed against further water penetration and the electrical properties of the device are restored. This technique is especially useful in the rehabilitation of plastic insulated conductor cables.
Thus, the present invention in its broadest aspect relates to a mineral oil extended polyurethane comprising the reaction product of an isocyanate terminated prepolymer with a polyol in the presence of a mineral oil and a liquid coupling agent for compatibilizing said mineral oil with said polyurethane, said mineral oil extended polyurethane containing from 8 to 45 parts of polyurethane, from 25 to 75 parts of mineral oil and from 10 to 35 parts of coupling agent, all parts expressed on a weight basis, said liquid coupling agent being miscible in all proportions with said mineral oil, said agent being selected from the group consisting of a ketone and an ester, said agent having a , boiling temperature above 220~F., a solubility parameter between 7~0 and 9.5 and a hydrogen bonding index number in the range from 6.0 to 12.0, and said agent being non-reactive with the prepolymer and the polyol, said isocyanate terminated prepolymer being prepared by reacting a polyisocyanate selected from the group consisting of cycloaliphatic diisocyanate, aliphatic diisocyanate and aromatic diisocyanate, with a polyol selected from the group consisting of castor ~- ' .
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~1101143 oil, polyether polyols, hydroxyl bearing homopolymers of butadiene or copolymers of butadiene and styrene and combin-ations thereof wherein at least a portion of the polyol used in the preparation of the prepolymer and/or at least a portion of the polyol reacted with the prepolymer is a hydroxyl bearing homopolymer of butadiene or copolymer of butadiene and styrene, the mineral oil extended polyurethane when cured retaining the mineral oil within its structure, thereby preventing the oil from spewing and exuding from said cured composition. Polyurethanes, being very polar elastomers, were here~ofore thought to be almost completely incompatible with the non-polar mineral oils and extension of urethanes - was traditionally accomplished with aromatic oils. Although the prior art has been able to achieve some extension of polyurethanes using mineral oils, these efforts have been limited to relatively low extension ratios of about 2:1, oil to polymer. At higher extension ratios these prior art systems be~in to lose their oil contents by exu~ation (or spewing~
shortly after cure. We have found that the coupler is necessary in our systems which comprises castor oil, poly-ether polyols in combination with hydroxyl bearing poly-butadiene and a diisocyanate to obtain stable non-spewing elastomeric materials with extensions even as low as 1:1 and up to 10:1 if desired. Without the coupler the elastomer spews oil.
For the purposes of this specification, mineral oils are considered to be those aliphatic, cycloaliphatic, and branched aliphatic saturated hydrocarbons that contain ~ -~ from 15-20 C atoms and are distilled from petroleum. Included in this classification are naphthenic and paraffin oils.
Paraffin oils are the preferred mineral oil for use in this ~ ~.

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110~43 invention. In the instant invention it ~as unexpectedly found that a cross-linkable low viscosity solution of a mineral oil, a preselected polyol and a preselected isocyanate prepolymer, in which either the prepolymer or the polyol eonstituent contain a polybutadiene moiety can be prepared through the use of liquid coupling agents that are preferably high boiling esters of organic diacids or diols.
More specifically, the coupling agents may be saturated or unsaturated (preferably unsaturated) aromatic-aliphatic, cyclo-aliphatic or wholly aliphatic esters, such as 2,2,4-trimethyl 1,3 pentane diol diisobutyrate. Other suitable liquid coupling agents include those in which a polar group is attached to an alkane structure, such as, for example, tributyl phosphate.
In order to effectively compatibilize the mineral oil with a cross-linking urethane elastomer, it has been discovered that a coupler must satisfy several criteria.
Firstly, it must be soluble in mineral oils in all proportions.
In other words, the eoupler should be miseible in all proportions with mineral oils to form a true solution ti.e., one part eoupler/99 parts mineral oil or 99 parts eoupler/one part mineral oil). It has also been found that eoupler eompounds suitable for use in this invention have a solubility parameter (~ in the range of 7.0 - 9.5 and a hydrogen bond index number within the range 6 to 12.
The (~) value of a substance is calculated according to the formula ~ = (aE/V)1/2 where ~E is the energy of vaporization to a gas at zero pressure (i.e. an infinite separation of the molecules); and V is the molar"volume of component present.

~101~43 The dimensions of ~ are (calories per cubic centi-meter)l/2, Since it is possible to ascertain ~E and V for most substances, the value of the solubility parameter or ~
may be calculated from the heat of vaporization ~H, since it can be shown that ~E250C = ~H250C -592 Since the value of ~H at 25C for most compounds may be found in the literature, this value may be used to calculate ~E and then ~. Further details on solubility parameters and means for their calculation are found in an article entitled Solubility Parameter Values by H. Burrell and B. Immergut at P.IV-341, of Polymer Handbook edited by J. Brandrup and E. H. Immergut, 3rd Edition Interscience Publ., June 1967.
It has also been determined that th~ coupling agents of this invention have a hydrogen bond index in the range ~ -6.0 - 12Ø The hydrogen bonding index number (r) Of a compound is a measuremeni of its proton ~hydrQgen) attracting power. The hydrogen bond index number ~ proton attracting power) of a compound is measured by comparing the relative strengths of the hyarogen bonds which the liquid compound forms with a common proton or Deuterium donor.
In practice, this is done by dissolving deuterated methanol in the liquid to be tested. The proton attracting power of a liquid compound is determined by measurement of the movement produced on the OD vibrational band of CH30D.
The OD vibrational band occurs at 4~ in the liquid CH30D and at 3.73~ in the monomolecular CH30D in dilute benzene solution.
Benezene is considered to have an OD vibrational shift of 0.
The formation of hydrogen bonds shifts the monomolecular band to lower frequencies or longer wavelengths. The stronger the ' proton attracting power of a liquid, the greater is the shift which it produces on the OD band. By Infrared Spectroscopy the perturbation of the OD band can be established.
The ~ value of a compound may be determined by measuring the shift in wave numbers of the OD vibrational ban after dissolution in the liquid compound and dividing the resulting number by 10. (Wave number is the reciprocal of an angstrom unit). Those compounds having a ~ number of 0 to 6.0 are generally acknowledged to be weak hydrogen bond acceptors. Compounds having index numbers in the range of 6.0 to 12.0 are usually considered moderate hydrogen bond formers and those having index numbers above 12.0 are consid-ered to be strong hydrogen bonders. The liquid coupler compounds useful in this invention are those having a hydrogen bond index number (~) falling in the range between 6.0 and 12.0 as determined by the abovementioned technique. The origin of the Hydrogen Bond index system and additional details on the means for its computation are found in a series of articles by W. J. Gordy in J. Chem. Physics, Vol. VII, 20 pp. 93-99, 1939, Vol. VIII, pp. 170-177, 1940 and Vol. IX, pp. 204-214, 1941.
Coupler compounds are selected to be non-reactive with the cross-linkable urethane elastomer composition and accordingly do not contain any labile hydrogen atoms in their structure. ~-As indicated above, it is important that the viscosity of the solvent, coupler and polymer solution be ; ~ kept to a minimun in order to effect their introduction into the free spaces of a cable that is to be reclaimed. However, the amount of polymer in the rehabilitation composition should also be minimized to the greatest extent possible in order to : ~ _ g ~ .

1101~43 prevent excessive weight gain in the apparatus to be reha-bilitated as well as for reasons of economy.
In order to provide suitable mechanical and electrical properties for reclamation of insulated electrical devices, within a reasonable period of time at ambient temperature, the gelled paraffinic oil extended elastomer system should be cross-linked. Cross linking is obtained - by use of either an isocyanate or a polyol, more usually a polyol having a functionality of between 2.0 and 3.0, and preferably 2.2-2.7. Also, the volume resistivity of the paraffin extended polyurethane as determined by ASTM D-257 should be at least 2.5 x 101 ohm-cm and preferably higher.
The instant mineral oil extended rehabilitation - compounds are preferably prepared on the site by admixing the contents of two separate containers. In this manner instruc-tion of personnel in the formulation and use of the rehabil- --itation material is facilitated because the contents of the two containers are preferably mixed in approximately equal proportions just prior to their introduction into the 20 apparatus to be reclaimed. If necessary, all the individual ingredients can be admixed together on the site.
In one container is an isocyanate terminated pre-polymer, preferably in mineral oil solution. Between about 50 and 200, and preferably about 100 grams of isocyanate prepolymer is employed per liter of solution in the first container. The prepolymer is preferably formed from a cycloaliphatic diisocyanate such as, for example,

3-isocyanato methyl, 3,5,5-trimethylcyclohexyl isocyanate (IPDI). The useable isocyanates for making the prepolymers in this invention also include the aIiphatic and aromatic diisocyanates such as tolylene diisocyanate (TDI), .

1101~43

4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, phenylene diisocyanates, or mixtures of these materials, 4,4'-methylene bi~cyclohexyl isocyanate) and hexamethylene diisocyanate, as well as related aromatic and aliphatic isocyanates, which may also be substituted with other organic or inorganic groups that do not adversely affect the course of the chain-extending and/or cross-linking reaction.
Formation of the isocyanate terminated prepolymer is accomplished by reacting an excess of one of the preceding isocyanate components with a polyol having a relatively hish molecular weight of between about 1000 and 6000. Among the polyols useful in formation of the isocyanate terminated prepolymer are those selected from compounds based essentially on polybutadiene, castor oil or hydroxyl bearing polyethers or combinations of them.
Suitable polyether polyols include aliphatic alkylene glycol polymers exemplified by polypropylene ether glycol and poly 1-4 butylene ether glycol. Also trifunctional compounds exemplified by the reaction product of trimethylol propane and propylene oxide may be employed as the polyol constituents.
The polybutadiene based polyols are liquids that are ~ounded on hydroxyl terminated liquid butadiene homo-polymers and hydroxyl terminated butadiene copolymers with styrene. A typical butadiene based polyol copolymer has the approximate structure.
HO [~ (CH2 ~ CH = CH ~ CH2)a - (CH ~ CH2)b ]-OH

wherein X is C6H5 for a styrene-butadiene copolymer and 11[J11~43 a = .75 .~ b = .2S and n= 57-65 A butadiene homopolymer useful in preparing the isocyanate terminated prepolymers of the invention has the . structure CIS TRANS
HO [- (CH -CH = CH-CH) 2 ~ (CH2 CIH).2 2 2).6]
CH=CH2 wherein n= 57-65 This class of liquid hydroxy bearing polybutadiene -polymers are available from Arco Chemical Company under the trademark POLY-BD.
- Properties of the hydroxyl-terminated polybutadiene-styrene copolymers are Butadiene, Wt. % = 75 Styrene, Wt. % - 25 Viscosity, poise at 30C = 225 OH content meg./gm = 0.65 ~.
Moisture - Wt. % = 0.05 Iodine Number = 335 The prepolymer is preferably formed from the reaction of an excess of IPDI and the above-mentioned hydroxyl terminated homopolymer of polybutadiene and has a hydroxyl functionality of 2.2 - 2.4 and an equivalent weight of approximately 1260. Another prepolymer formulation that has been found especially useful in preparing mineral oil extended cable rehabilitation agents is formed by reacting as excess of toluene diisocyanate with castor oil or a hydroxyl terminated polybutadiene homopolymer or a polyether ~(such as poly(oxypropylene) glycol or polytetramethylene glycol). The preferred,castor oil composition for use in ..

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1101~43 preparation of this prepolymer and generally in this inven-tion comprises a mixture of about 70% pure glyceryl triricinoleate and about 30~ glyceryl diricinoleate-mon~oleate or monolinoleate and is available from Baker Castor Oil, Bayonne, New Jersey, as "DB oil~ "
In the second container is a solution of between about 75 and 200 and preferably about 150 grams per liter of a preselected polyol in mineral oil. Suitable polyols with which the polyisocyanate prepolymers in the first container may be reacted include castor oil~ polyethers such as poly tetramethylene glycol, homopolymers or copolymers of hydroxyl, bearing butadiene, poly (oxypropylene) glycol or com~inations of them.
The mineral oil component may be admixed with either or both of the prepolymer or polyol stages as long as a sufficient amount of the liquid coupler agent is present to compatabilize the mineral component with the respective stage.
The molecular weight (mw.) of the polyols used in this second part of the system should fall between about 1000 and 6000 and preferably in the range 2000 - 4000. The molecular weight of the polyols used to form the prepolymer also lies within the same range. Preferably, the polyol reactant is a hydroxyl bearing polymer of either repeating butadiene monomer units or a copolymer of butadiene and styrene. In fact, it has been determined that in order to secure effective operation and compatibility of a mineral oil in a urethane elastomer system, either the polyisocyanate prepolymer or the polyol must include a polybutadiene moiety as part of their structure. ~hile it is not important whether the polybutadiene moiety is present in the prepolymer 110:1143 portion or the polyol precursor of the polyurethane system,it has been determined that full compatibility of the mineral oil/polyurethane system (especially ln hi~hly extended systems) is not obtained absent the presence of the butadiene moiety in the polyurethane structure.
The mineral oil extended polyurethane is deemed to be a compatible system since either or both of the prepolymer or the polyol can accommodate the mineral oil and go on to form a polyurethane polymer that cures to a gel but does not exude the extender oil after cure. Accordingly, compat-ibilizing r2fers to the ability of the cured polyurethane system to retain the mineral extender oil within its structure while remaining in a gel-like consistency. Once the oil has been compatabilized with the polyurethane structure it is not lost by spewing or exudation after cure.
Determination as to the proper amount of coupler for use n compatabilizing a given quantity of mineral oil with a specific prepolymer or polyol formulation is best done by experimentation, although it has been determined that the completed urethane elastomer system should contain a~out 8 ;~ to about 20 and preferably between about 12-1/2 and 15 parts by weight of polymer solids, between 60 and 75 and preferably between 65 and 70 parts by weight mineral oil and ; between about 10 and 25 and preferably between about 15 and 20 parts by weight of coupler. In one preferred embodiment a hydroxy bearing homopolymer of butadiene is reacted with --an excess of 3-isocyanatomethyl 3,5,5 trimethylcyclohexyl isoc~anate in the presence of 2,2,4-trimethyl l-3, pentanediol diisobutyrate coupling agent to form a prepolymer which is in turn diluted in mineral oil and an additional amount of coupler. The dilute prepolymer solution is then reacted 1~01143 with a dilute solu~ion of the hydroxy bearing butadiene homo-polymer in mineral oil and the same liquid coupling agent to yield an elastomer system having the following make-up:
(Polymer) Solids 15 parts by weight (Extender oil) Paraffin 64 parts by weight Coupler 20 parts by weight Catalyst 1 part by weight The composition ranges cited above cover the preparation of highly oil extended polyurethanes possessing gel-like consistencies. ~owever, this invention also covers the preparation of lower oil extended polyurethane elastomers.
The broad ranges therefore contemplated by the instant invention covering both types of products comprise from about 8 to about 45 parts by weight of polymer solids, from about 25 to about 75 parts by weight of mineral oil and from about 10 to about 35 parts by weight of coupler.
~ or the lower oil extended polyurethanes contem-plated by the instant in~ention which are useful for casting systems for a variety of potting and encapsulating applica-tions the ranges should comprise from about 20 to about 45parts by weight of polymer solids, from about 25 to about 60 parts by weight of mineral oil and from about 25 to about 35 parts by weight of coupler.
The liquid couplers employed to compatibilize mineral oils with the instant polyurethane systems and to secure both high and low oil/polymer extension ratios ;
according to this invention are selected according to the ~ ... ... . .
previously enumerated criteria. Generally, the initial criteria is that the coupler liquid must be soluble in mineral oils in all proportions to form a true solution.

- The coupler compounds will also possess a ,. ~-,~.

solubility parameter (~) between 7.0 and 9.5 preferably in the range between 7.2 and 9.5.
Final evaluation of a coupling agent is usually made with reference to its hydrogen bonding index (~) the preferred coupling agents having hydrogen bonding index ~`
numbers in the range 8.2 to 8.8 as determined by the proce-dures previously set forth. In the screening of potential coupling agents a determination as to solubility parameter and hydrogen bonding index number can be made using well-known analytical techniques. The solubility parameter value (~) and hydrogen bonding index number (~) are available in the literature for many compounds and may be determined by reference to the appropriate text, From the chemical standpoint, the couplers are liquids and pre~erabl~ esters of organic diacids or diols that boil at temperatures in excess of 220F. Other suit-able coupling agents include those liquids in which a polar group is attached to an alkane structure such as, for example, tributyl phosphate. The liquid coupling agents may be saturated or unsaturated (although they are preferably saturated) and may be aromatic-aliphatic, cyclo-aliphatic, or wholly aliphatic esters, such as for example 2,2,4- -trimethyl 1,3 pentanediol diisobutyrate.
The preferred couplers for use in this invention are selected from among di-2-ethylhexyl sebecate, acetyl tributyl citrate, di-2-ethylhexyl adipate, dioctyl adipate, dibutyl fumarate, di-n-butyl sebecate and di-2-ethylhexyl citrate and acetyl di-2-ethylhexyl citrate. Especially good results are obtained when 2,2,4 trimethyl-1-3 pentanediol diisobutyrate is employed as the coupling agent.
A list of the principal"coupling agents that have thus far, E

been found useful in this invention is set forth in Table A:
TABLE A

COUPLERS
- ' (~) Chemical Name (Cal/per CC) 1. 2,2,4 Trimethyl- 1,3 Pentanediol Diisobutyrate 8.2 2. Di-2-ethylhexyl Sebecate 8.6 3. Acetyl Tributyl Citrate 9.2 4. Di-2-ethylhexyl Adipat~ 8.7

5. Diisodecyl Phthalate 7.2

6. Dioctyl Adipate 8.7

7. Tri~utyl Phosphate 8.6

8. Dibutyl Fumarate 8.5

9. Acetyl Tri-2-ethylhexyl Citrate 8.6

10. Di-n-butyl Sebecate 8.8

11. Dioctyl Phthalate 8.8

12. Di-2-ethylhexyl 8.6

13. Isobutyl Acetate 8.4

14. ~ethyl ethyl Ketone 9.5

15. Methyl-n Butyl Ketone 8.6 Selection of a particular coupler and determination :
of the correct amount to be employed is determined by exper-imentation and will vary from one urethane system to another.
The selection is dependent upon chemical and physical differences in various prepolymers and polyols as well as upon the desired amount of mineral oil extension in the cured system.
The couplers of this invention enable paraffin oil extenslons of up to about 950% (by weight) based upon poly-urethanes, formulated f,rom polyether diols and triols, .~

1~01143 castor oil, as well as polybutadiene polyols and combinationsof these. These mineral oil extended urethane elastomer systems display dielectric constants of 3.4 at lKhz (as determined by ASTM D-150) or lower~ Examples I-XII illus-trate the preparation of mineral oil extended urethane elastomers for use in rehabilitating insulated electrical devices. Table B outlines the functionality and molecular weights of the polyols employed in Examples I-XII.
TABLE B

Polyol OH Functionality MW
.

1. Polybudadiene 2.3 - 2.4 2912 - 3038 2. Styrene polybutadiene 2.0 3280 copolymer 3. Castor oil Z.7 923 4. Polypropylene Glycol ~.0 2040 5. Trimethylolpropane 3.0 4145 propylene oxide adduct 6. Polytetramethylene Glycol 2.0 ~ 2004 Table C contains a summary of the important physical and chemical properties of the Prepolymer components of Examples I-XII. (See Table C attached).
The important physical and electrical properties of the various oil extended systems prepared in Examples I-XII are summarized in Table D. (See Table D attached).
Example I illustrates the understanding of the prior art that polyurethanes, being very polar elastomers are almost completely incompatible with mineral oils. The results of this example reveals that a mineral oil cannot be used to obtain a compatible highly extended polyurethane (i.e., at least about 300~ polymer extension)system in the absence of couplers of the type described in this invention.

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Attempts to achieve high degrees of polyurethane extension with mineral oils and without a suitable coupler result in an incompatible system which spews oil during and after cure and is accordingly unsuitable for reclamation of insulated electrical devices (e.g., plastic insulated conductor cables, transformers, capacitors).
EXAMPLE I
a) Prepolymer Formation:
A reactor fitted with agitator, thermometer, nitrogen inlet and reflux condenser was charged with 3120.0 grams (2.5 eq.) of a hydroxyl bearing polybutadiene, 833.0 grams of 3-isocyanatomethyl, 3,5,5 trimethylcyclohexyl isocyanate (7.5 eq.), 3953.0 grams of paraffin oil and 4.0 grams of benzoyl chloride. The solution was maintained at 75-85C for 5 hours under nitrogen. The free isocyanate content of the prepolymer was 2.56%.
b) Polymer Formation:
25.0 grams (.014 eq.) of the prepolymer was mixed with 16.8 grams (.014 eq.) of a hydroxyl bearing polybutadiene, 57.8 grams of a paraffin oil and 0.4 grams of dibutyl tin dilaurate. The resulting clear solution within 4 hours turned opaque and within 24 hours cured at room temperature to a greyish-white, opa~ue oil spewing mass containing 29~3% polymer which was incompatible with the 70.3% mineral oil.
EXAMPLE II
a) Prepolymer Formation:
Same prepolymer as in Example I.

b) Polymer Formation 6.4 grams (.004 eq.) of the prepolymer was mixed with 4.8 grams (.004 eq.) of the hydroxyl ~earing ~1 ~ .

9t3 polybutadiene, 73.1 grams of mineral oil, 15.0 grams of 2,2,~ trimethyl 1,3 pentanediol, diisobutyrate and 0.7 grams of dibutyl tin dilaurate. The resulting solution cured over 120 hour period to a clear, very soft, dry, non-oil spewing mass which contained 8% polymer and 76.3~ mineral oil. This represents a 953~ extension of the polymer by mineral oil.
EXAMPLE III
a) Prepolymer Formation:
Same as prepolymer as in Example I.
b) Polymer Formation:

16.3 grams (.01 eq.) of prepolymer was mixed with 1.5 grams (.0045 eq.) of castor oil, 5.3 grams (.0045 eq.) of a hydroxyl bearing polybutadiene, 56.6 grams of mineral oil, 20.0 grams of di-2-ethylhexyl sebacate, and 0.3 grams of dibutyl tin dilaurate. The resulting solution cured over a 43 hour period at room temperature to a clear, soft, dry, non-oil spewing mass containing 15~ polymer and 64.8~
mineral oil. This represents a 432% extens~on of the - polymer with mineral oil.
EXAMPLE IV
a) Prepolymer Formation:
Same prepolymer as in Example I.
b) Pol~mer Formation:
13.2 grams (.0074 eq.) of prepolymer was mixed with 4.7 grams (.0037 eq.) of a hydroxyl bearing polybutadiene, 3.7 grams (.0037 eq.) of a polypropylene glycol, 20.0 grams of acetyl tributyl citrate, 57.4 grams of mineral oil and 1.0 grams of dibutyl tin dilaurate. The resulting solution cured over a 48 hour period at room temperature to a clear, soft, dry, non-oil spewing mass containing 15% polymer and 64~ mineral oil. This represents a 426~ extension of the ,:

~1~1143 polymer with paraffin oil.
EXAMPLE V
a) Prepolymer Formatlon:

. .
A reactor vessel equipped as in Example I was charged with 52.2 grams (0.6 eq.) of toluene diisocyanate (80/20), 181.3 grams of mineral oil, 120.9 grams of di-2~
ethylhexyl adipate, and 250.0 grams (0.2 eq.) of a hydroxyl bearing polybutadiene, and 0.3 grams of benzoyl chloride.
The solution was heated under nitrogen for 4 hours at 75-80C.
The resulting prepolymer had a free isocyanate content of - 2.57%.
b) Polymer Formation:
6.3 grams of the prepolymer (0~039 eq.) was mixed with 4.8 grams (.0039 eq.) of a hydroxyl bearing polybutaaiene, 23.7 grams of di(2-ethylhexyl) adipate~ 65.0 ; grams of mineral oil and 0.2 grams of dibutyl tin dilaurate.
The solution cured at room temperature over a 120 hour period to a clear, very soft, dry, non-oil spewingS~mass containing 8% polymer and 66.8% mineral oil. This represents an 835%
extension of the polymer by mineral oil.
EXAMPLE VI
. . .
a) Prepolymer Formation:
A reactor equipped as in Example I was charged with 2487.0 grams (1.8 eq.) of a triol (derived from the reaction of propylene oxide and trimethylol propane) 600 grams of 3 isocyanatomethyl 3,5,5, trimethylcyclohexyl isocyanate (5.4 eq.)~ 1.6 grams of benzoyl chloride, and 1.6 grams of dibutyl tin dilaurate. The solution was heated at 80C for 6 hours under nitrogen. The resulting pre- -polymer had a free isocyanate conten of 4.85%.

,,, -~', '.

11~1143 b) Polymer Formation:
6.4 grams (.0074 eq.) of the prepolymer, 8.6 grams of a hydroxyl bearing polybutadiene (.0068 eq.), 20.0 grams of diisodecyl phthalate, 64.0 grams of mineral oil and 1.0 grams of dibutyl tin dilaurate were mixed. The resulting solution cured at room temperature over a 48 hour period to a clear, soft, dry, non-oil spewing mass containing 15% polymer and 64% mineral oil. This represents a 427% mineral oil extension of the polymer.
EXAMPLE VI
a) Prepolymer Formation:
A reaction vessel equipped as in Exa~ple I
as well as with a dropping funnel, was charged with 386.0 grams (4.44 eq.) of toluene diisocyanate 614.0 grams of caster oil (1.8 eq.) was added, over a 2 hour period, through the dxopping funnel at 70-80C. After the addition was complete, the reactor was held at 75~C for 1 hour. The free isocyanate content of the prepolymer was 10.8%.
b) Po~ymer For:ation:
3 grams (.0076 eq.) of the prepolymer was mixed with 9.4 grams (.0076 eq.) of a hydroxyl bearing polybutadiene, 24.8 grams of dioctyl adipate, 61.4 grams of paraffin oil and 1.4 grams of dibutyl tin dilaurate. The resulting solution cured at room temperature over a 48 hour period to a soft, clear, dry, non-oil spewing mass which contained 12.4% polymer and 61.4~ mineral oil. This represents a 495% extension of the polyurethane with mineral oil.
EXAMPLE VIII
a) Prepolymer Formation:
Same prepolymer as in Example VII.

- ~4 -.

b) Polymer Formation:
2.4 grams (.0061 eq.) of the prepolymer was mixed with 10.0 grams of a hydroxyl bearing copolymer of styrenebutadiene (.0061 eq.), 24.8 grams of tri~utyl phosphate, 61.4 grams of mineral oil and 1.2 grams of dibutyl tin dilaurate. The resulting solution cured at room temperature over a 48 hour period to a soft, clear, dry, non-oil spewing mass containing 12.4% polymer and 61.6%
mineral oil. This represents a 497% mineral oil extension of the polyurethane. ~-EXAMPLE IX
a) Prepolymer Formation A reactor fitted with agitator, thermometer nitrogen inlet and reflux condenser was charged with 1001.8 grams (1 eq.) of a polytetramethylene glycol and 555.5 grams (5 eq.) of 3-isocyanatomethyl, 3,5,5 trimethylcyclohexyl isocyanate. The solution was maintained at 80~C for 2 hours.
The resulting prepolymer had a free isocyanate content of 10.12%.
b) Polymer Formation ~: .
3.7 grams (.0089 eq.) of the prepolymer was mixed with 11.3 grams (.0089 eq.) of a hydroxyl bearing polybutadiene (OH functionality 2.3 - 2.4) 64.0 grams of a mineral oil, 20.0 grams of 2,2,4 trimethyl - 1,3 pentanediol diisobutyrate and 1.0 grams of dibutyl tin dilaurate. The resulting solution cured after 1-1/2 hours at 100C to a clear, dry, non-oil spewing mass containing 15% polymer and 64% mineral oil. This represents a 427% mineral oil exten-sion of the polymer.

~' :' EXA~PLE X
a~ Prepolymer F_ mation Same prepolymer as in Example VII.
b) Polymer Formation 3.5 grams (0.009 eq.) of the prepolymer was mixed with 11.5 grams (.009) of hydroxyl bearing poly-butadiene, 20.0 grams of isobutyl acetate, 64.5 grams of a mineral oil and 0.5 grams of dibutyl tin dilaurate. The resulting solution cured over a 24 hour period at room temperature to a soft, clear, dry, non-oil spewing mass which contained 15% polymer and 64.5~ mineral oil. This -~ was a 430~ mineral oil extension of the polymer.
EXAMPLE XI
_ _ a) Prepolymer Formation ;~ Same Prepolymer as in Example I.
b) Polymer Formation 12.5 grams of prepolymer (.0077 eq.) was mixed ~ with 8.8 grams (.0077 eq.) of a hydroxyl bearing polybutadiene, ; ~ 20.0 grams of methyl-ethyl ketone, 58.2 grams of mineral oil ;~ 20 and 0.5 grams of dibutyl tin dilaurate. The resulting solution cured at room temperature over a 48 hour period to a soft, dry, non-oil spewing mass containing 15% polymer and 64.5 percent mineral oil. This represents a 430%
extension of the polymer hy mineral oil.
EXAMPLE XII
a) Prepolymer Format on Same prepolymer as in Example VII.
b) Polymer Formation .
3.5 grams (.009 eq.) of prepolymer was mixed with 11.5 grams (.009 eq.) of a hydroxyl bearing polybutadiene, 20.0 grams of methyl-n-butyl ketone, 64.5 grams of mineral - :

.

`" 1101143 oil and 0.5 grams of dibutyl tin dilaurate. The resulting solution cured at room temperature over a 24 hour period to a clear, soft, dry, non-oil spewing mass which contained 15% polymer and 64.5% mineral oil. This was a 430% mineral oil extension of the polymer.
- EXAMPLE XIII
a) Prepolymer Formation:
A reactor vessel equipped as in Example 1 was charged with 145 grams (.42 eq.) of castor oil, 286 grams polymeric MDI (2.16 eq.) and 569 grams dioctyl adipate ~DOA) the solution was heated under nitrogen for 2 hours at 60C.
The resulting prepolymer had a free isocyanate content of 7.2~.
b) Polymer Formation:

17.0 grams of the prepolymer (0.03 eq.) were mixed with 26.2 grams (.021 eq.) of a hydroxyl bearing polybutadiene, 1.4 grams caster oil (.004 eq.) 35 grams of mineral oil, 20.1 grams of DOA and 0.3 grams dibutyl tin dilaurate. The solution cured at room temperature over a 24 hour period to a clear, firm, dry, non-oil spewing elastomeric material containing 35 percent polymer and 35 percent mineral oil.
This represents a 100 percent extension of the polymer by mineral oil.
In the preceding examples the hydroxyl terminated liquid homopolymer of polybutadiene employed is available from the Atlantic-Richfield Co. under the trade name POLY-BD R-45HT. Its typical properties are:

Polybutadiene isomer content Viscosity at 75%F. - 80 poise Trans 1,4 - 60% Moisture weight percent - 0.05 Cis 1,4 - 20% Iodine No. 398 Vinyl 1,2 - 20% Hydroxyl content - 0.85 Meg./GM
The mineral oil used in the examples is available from Pennrico Inc., Butler, Pennyslvania as "PENETECK"~ a highly paraffinic white oil~

~, ' ~E `

The materials produced in Examples I - XIII had an initial (low) viscosity on the order of about .1 poises.
However, within about 1 to 120 hours the material cured in situ at temperatures from about 15C. to about 100C. to a gel-like (high) viscosity on the order of between 1,000 and 100,000 poises. The mineral oil was completely compatible with the prepolymer and polyol in all of Examples II - XIII.
In each case the mineral oil did not interfere with the reaction of the prepolymer and polyol constituents to form a polyurethane compound which cured to a gel. In each instance the mineral extender oil did not exude or spew from the cured urethane system.
~he elastomeric rehabilitation materials of this invention are ideally suited for use in reclaiming water-logged electrical apparatus such as, for example, plastic insulated conductors of the type employed in multi-pair ;~ telephone cables. The method of employing these mineral oil extended urethanes in rehabilitating such an apparatus will now be illustrated with reference to Fig. 1.
In the cable illustrated in Fig. 1, a plurality of wire conductors 1 are disposed within the central core 2 of the cable. Each wire is surrounded by an insulating material, generally a polyolefin plastic. The plurality of insulated wires are tightly enclosed within a spiral wouna sheath 3, usually a polyethylene terephthalate sheet material. Sur-rcunding the sheath are two protective shields 4, made of a flexible metal sheeting such as aluminum. The shields are separated from one another by a continuous layer of a suitable insulating material. Finally, an outer jacket 6 of a protective plastic such as polyethylene, covers the outermost aluminum layer and ser~es to protect the cable.

.

Aqueous contaminants generally find their way intothe cable through pinholes and stress cracks that de~elop around fittings and cable connectors, ultimately lodging in the interior free spaces of central core 2. After a partic-ular aqueous contaminant, for example water, has been present for some time in the core, the electrical ~roperties of the cable can be deleteriously effected as previously des-cribed. At this point, the rehabilitation products and processes of this invention may be employed to restore the cable to substantially its original operating condition.
The rehabilitation operation is carried out on location by first admixing approximately equal amount of the prepolymer and polyol ingredients which are most advan-tageously prepared in advance. A small portion of the cable outer protective layers including jacket 6, aluminum protective shields 4 and sheath 3 are them removed and a nipple (not shown) installed in the opening thus formed, using techniques that are well-known in the~trade. This operation can be carried out from above, or below, and without removing the cable from its resting place. The mineral oil extended polyurethane elas~omer having just been formed has a relatively low viscosity and is easily intro-duced into the core of the cable through a hose (not shown) connected to the nipple. After the rehabilitation material has been injected into the cable, the delivery hose is withdrawn from the nipple and the hole in the nipple is sealed with a plug ~not shown). The injection operation will have driven the low viscosity mineral extended urethane out through the interior-free spaces of the cable. The rehabilitation agent will displace the water penetrants in the interior free spaces (e.g~ between the individual wires ~ 1143 and the outer polyethylene terephthalate sheath).
In the practice of the invention, the viscosityof the rehabilitation material at from about 15C. to about 50C. at the time of injection should be within the range of about 10 to 100 centipoises. Within several hours after injection into an insulated electrical device, the rehabilitation agent cures to form an oil extended polymer system having a gel-like consistency and a viscosity on the order of about 1000 poises. The clear gel is physically and chemically stable and does not lose mineral oil by exudation or spewing. The hydrophobic nature of the cured oil extended elastomer system also serves to seal the cable against subsequent penetration of water or other fluid materials.
Furthermore, the gelled system has good insulating properties due to its relatively low dielectric constant and high volume resistivity.
The elastomer material retains the mineral oil and no exudation was evident in any of the form~lations made in ; ~ Examples II - XII after standing for several weeks at ambient (room) temperature. Moreover, the mineral oil extended urethanes were found to be compatible with the polycarbonate plastic connectors used in the interconnection of insulated electrical de~ices. After several weeks exposure to the rehabilitation compounds of this invention, the poly-carbonate connectors on plastic insulated conductor cable were completely unaffected and did not exhibit any signs of chemical attack. The rehabilitation compounds were also ; -compatible with polyolefin insulating materials used in the cable manufacture and no stress cracking was observed after several weeks exposure.
The oil exten~ed rehabilitation material was 1~1143 nonsolvating i~ na~ure and did not attack polyethyleneterephthalate or the other polymer materials employed in the cable construction. The material was also characterized by easy handLing in view of its low volatility (vapor pressure) and inoffensive aroma. No toxicity or adverse side effects have been noted by those handling the rehabilitation materials of this invention, thus setting them apart from the relatively toxic products previously employed in reclamation techniques.
The treated cable showed only a minor weight gain, which is probably attributable to the low density of the cured rehabilitation material. It has also been noted that the present system results in only a minimal amount of air being entrapped in the cured system after injection into an insulated electrical device. This can be related to the low viscosity and density of the initial ingredients which may - be pumped into the cable without causing excessive turbulence.
In addition to the reclamation of insulated electrlcal apparatus, the mineral oil polymer system can also-be used as a waterproofing membrane in the construction ~ield, cast into a resilient flooring compound (using higher level of polymer as represented by ~xample XIII); used as a liquid casting system for a variety of potting and encapsulation applications as well as a solid lubricant to replace grease ; in certain situations.
While this invention has been described and ; illustrated by the examples shown, it is not intended to be strictly limited thereto, and other variations and modifications may be employed within the scope of the following claims.

Claims (20)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A mineral oil extended polyurethane comprising the reaction product of an isocyanate terminated pre-polymer with a polyol in the presence of a mineral oil selected from aliphatic, cycloaliphatic and branched aliphatic saturated hydrocarbons containing from 15 to 20 carbon atoms and distilled from petroleum and a liquid coupling agent for compatibilzing said mineral oil with said polyurethane, said mineral oil extended polyurethane containing from 8 to 45 parts of polyurethane, from 25 to 75 parts of mineral oil and from 10 to 35 parts of coupling agent, all parts expressed on a weight basis, said liquid coupling agent being miscible in all proportions with said mineral oil, said agent being selected from the group consisting of a ketone and an ester, said agent having a boiling temperature above 220°F., a solubility parameter between 7.0 and 9.5 and a hydrogen bonding index number in the range from 6.0 to 12°0, and said agent being non-reactive with the prepolymer and the polyol, said isocyanate terminated prepolymer being prepared by reacting a polyisocyanate selected from the group consisting of cycloaliphatic diisocyanate, aliphatic diisocyanate and aromatic diisocyanate, with a polyol selected from the group consisting of castor oil, polyether polyols, hydroxyl bearing homopolymers of butadiene or copolymers of butadiene and styrene and combinations thereof wherein at least a portion of the polyol used in the preparation of the prepolymer and/or at least a portion of the polyol reacted with the prepolymer is a hydroxyl bearing homo-polymer of butadiene or copolymer of butadiene and styrene, the mineral oil extended polyurethane when cured retaining the mineral oil within its structure, thereby preventing the oil from spewing and exuding from said cured composition.

2. The mineral oil extended polyurethane of Claim 1 which contains from about 8 to about 20 parts by weight of polymer solids, from about 60 to about 75 parts by weight of mineral oil and from about 10 to about 25 parts by weight of coupler, said composition after curing possessing a gel-like consistency.

3. The mineral oil extended polyurethane of Claim 1 which contains from about 20 to about 45 parts by weight of polymer solids, from about 25 to about 60 parts by weight of mineral oil and from about 25 to about 35 parts by weight of coupler, said composition being useful for casting systems.

4. The mineral oil extended polyurethane of Claim 1 in which the mineral oil employed is paraffin oil.

5. The mineral oil extended polyurethane of Claim 1 in which the liquid coupling agent is 2,2,4-trimethyl 1, 3-pentane diol diisobutyrate.

6. The mineral oil extended polyurethane of Claim 1 in which the coupling agent is di-2 ethyl hexyl adipate.

7. The mineral oil extended polyurethane of Claim 1 wherein said isocyanate terminated prepolymer is the reaction product of 3-isocyanato-methyl 3,3,5-trime-thylcyclohexyl isocyanate and a liquid hydroxyl terminated homopolymer of butadiene.

8. A process for removing aqueous contaminants from the interior free spaces of an insulated electrical device and for subsequently sealing said device against further water penetration comprising the steps of pumping into said device a low viscosity material comprising a mineral oil extended polyurethane which is the reaction product of an isocyanate terminated prepolymer with a polyol in the presence of a mineral oil selected from aliphatic, cycloaliphatic and branched aliphatic saturated hydro-carbons containing from 15 to 20 carbon atoms and dis-tilled from petroleum and a liquid coupling agent for compatibilizing said mineral oil with said polyurethane, said mineral oil extended polyurethane containing from 8 to 45 parts of polyurethane, from 25 to 75 parts of mineral oil and from 10 to 35 parts of coupling agent, all parts expressed on a weight basis, said liquid coupling agent being miscible in all proportions with said mineral oil, said agent being selected from the group consisting of a ketone and an ester, said agent having a boiling temperature above 220°F., a solubility parameter between 7.0 and 9.5 and a hydrogen bonding index number in the range from 6.0 to 12.0, and said agent being non-reactive with the pre-polymer and the polyol, said isocyanate terminated pre-polymer being prepared by reacting a polyisocyanate selected from the group consisting of cycloaliphatic diisocyanate, aliphatic diisocyanate and aromatic diisocyanate, with a polyol selected from the group consisting of castor oil, polyether polyols, hydroxyl bearing homopolymers of butadiene or copolymers of butadiene and styrene and combinations thereof wherein at least a portion of the polyol used in the preparation of the prepolymer and/or at least a portion of the polyol reacted with the prepolymer is a hydroxyl bearing homopolymer of butadiene or co-polymer of butadiene and styrene and curing said polyurethane in situ to a higher viscosity within a predetermined period after termination of said pumping operation, whereby the mineral oil is retained within the cured polyurethane structure, thus preventing the oil from spewing and exuding from the cured composition.

9. The process of Claim 8 wherein said insulated electrical device comprises a plastic insulated multi-conductor conductor cable.

10. The process of Claim 9 wherein said low viscosity material has a viscosity of less than about 100 centipoises at about 25°F. prior to introduction into said cable.

11. The process of Claim 10 wherein said pre-determined period is approximately about 24 hours.

12. The process of Claim 11 wherein said mineral oil comprises paraffin oil.

13. The process of Claim 12 wherein said paraffin oil extended polyurethane elastomer comprises from about 25 to about 75 parts by weight of paraffin oil, from about 10 to about 35 parts by weight of said coupling agent, and from about 8 to about 45 parts by weight of said urethane polymer in the form of solids.

14. The process of Claim 12 wherein said paraffin oil extended polyurethane elastomer comprises from about 25 to about 60 parts by weight of paraffin oil, from about 25 to about 35 parts by weight of said coupling agent, and from about 20 to about 45 parts by weight of said urethane polymer in the form of solids.

15. The process of Claim 14 wherein said coupling agent is 2,2,4 trimethyl 1, 3-pentane diol diisobutyrate.

16. An insulated electrical device containing a plurality of wire conductors sheathed in plastic material and having interior free spaces between said sheathed conductors occupied by a gel of cured mineral oil extended polyurethane as defined in claim 1.

17. The insulated electrical device of Claim 16, wherein said isocyanate terminated prepolymer is the reaction product of 3-isocyanato-methyl 3,5,5-trimethyl-cyclohexyl isocyanate and a liquid hydroxyl terminated homopolymer of butadiene.

18. The insulated electrical device of Claim 17 wherein said coupling agent is 2,2,4 trimethyl-1-3 pentanediol diisobutyrate.

19. The insulated electrical device of Claim 18 wherein said elastomer gel has a viscosity of at least approximately 1000 poise.

20. The insulated electrical device of claim 19 wherein said polyurethane gel has a dielectric constant no greater than 3.4 at 1 kiloherz.