US2060856A - Insulated electrical conductor - Google Patents

Description

- Patented Nova", 1936 PATENT OFFICE 2,060,858 INSULATED ELECTRICAL CONDUCTOR John M. De Bell, Newark, Del.,

aasignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Y No Drawing. Application April 20, 1935, Serial No. 17,471

8 Claims.

This invention relates to an insulated electrical conductor.

The insulated electrical conductor in accordance with this invention comprises an electrical conductor in combination with an insulating material composed of a resinous composition known as extracted pine wood pitch, which is a residue comprising oxidized resin acids such as abietic acid, oxidized terpenes, poiyphenols, polymerized 10. terpenes and frequently some ligneous matter left after the separation of rosin, turpentine and other more valuable constituents of pine wood.

The insulated electrical conductor in accordance with this invention will be found to be highly efiicient due to its high dielectric strength,

especially under impulse tests, and the insolubility of the extracted pine wood pitch, in oils, as transformer oils.

The pine wood pitch for the production of the insulated conductor in accordance with this invention, as has been indicated, is obtained in connection with the production of wood rosin from pine wood. The pine wood pitch will comprise oxidized resin, oxidized abietic acid, oxidized terpenes, polyphenols, polymerized terpenes, and more or less ligneous matter, but will diiier somewhat in its specific characteristics, such as acid number, melting point, petroleum ether solubility and content of naphtha and toluol soluble matter, depending upon the method for the recovery of rosin from pine wood used in its production.

As is well known, rosin is extracted from pine wood by the'use of a suitable solvent, such as hot gasoline, or benzol, after steaming of the wood with live steam to remove volatile oils, such as turpentine and 'pine oil. Again, volatile oils, as turpentine, and pine oil, are extracted with the rosin without first steaming for their removal. 40 Following extraction the extract is distilled for the removal of solvent where the wood was subjected to steaming before extraction and for the removal of solvent and volatile oils, as t pentine and pine oil, where the wood. was en treated directly without ste s. As the result of distillation a resinous nu erial consisting of a mixture oi rosin, oxidized abietic acid, oxidised terpenes, polyphenois, polymerized terpenes and ligneous matter is obtained. This resinous me.- terial may be treated in any one of a number of ways, all known to the art, for the removal or refined rosin. The residue remaining after the removal or refined rosin and including oxidized abietic acid, oxidized terpenes, poiyphenols, poly- 6b merized terpenes and limeous matter originally present in the extract and comprising a dark colored, hard, resinous mass constitutes the pine wood pitch.

The exact properties or the pine wood pitch obtained as indicated above will depend upon the method used for original extraction from the wood. When the wood is steamed before solvent extraction, a pine wood pitch is obtained having somewhat different properties from that obtained when the wood is extracted without steaming. 10 Likewise the properties of pine wood pitch are somewhat difierent when obtained by different methods of purification of rosin. A comparison of the properties of three pine wood pitches is given in the following table, in which Pitch A is 15 that obtained by extraction of 'wood with hot petroleum solvents subsequent to the removal of the volatile oils by steam distillation, refining with furiural, evaporation of furfurai to leave a resinous mass and then extraction of this mass with a petroleum solvent to remove petroleum soluble resin. Pitch B is that obtained by a benzol extraction of unsteamed wood, evaporation of the benzol solution of the residue in hot low boiling petroleum solvent, precipitation of the Pitch B 25 by washing with cold water, and then removal of this precipitate by filtration. Pitch C is obtained by the evaporation of the furiural layer, after refining oi the gasoline solution ofthe crude resin obtained by the benzol extraction of pine wood. 30

Pitch Pitch Pitch A B o Melting point (Hercules drop method)... 91' 0. 115 0. 102 C. 35 Acid number 105 116 Unsaponiflable matter 5% 8% V. M. & P. naphtha insoluble 89.5% 96% 83% Toluol soluble 40% 98% Petroleum ether insoluble 92. 0% 99% 95% Saponification number. 169 Ash .0ac% .022%

It wiil be noted that while this extracted pine wood pitch contains oxidized rosin or abietic acid, certain of its properties are entirely difiz'erent from those of so-called oxidized rosin 45 produced by oxidation of rosin. Thus, for example, extracted pine wood pitch is substantialiy insoluble in natural petroleum hydrocarbons while oxidized rosin is readily soluble in these solvents. 50

The insulated electrical conductor in accordance with this invention may include the ex tracted pine wood pitch alone or in admixture with other substances which may desirably be admixed with it .tor variation oi its physical 55 characteristics, such, for example as wood pitch, copal, coal tar asphalt, small amounts of castor oil, rubber, a rosin residue resulting from the steam distillation of pine oil, etc.

The insulated electrical conductor in accordance with this invention may be of any type or form, however, for convenience I will proceed with a more detailed description of this invention with reference to its application to transformer coils in connection with which it is especially advantageous, more particularly in view of its very high resistance to impulse te ts and its insolubility in transformer coils.

In the production of a transformer coil embodying this invention, the coil is wound as usual,

using any desired insulated wire for the winding and the coil beingof any desired form or capacity. After the coil is completely assembled, it is electrically insulated and mechanically bonded in any suitable or well known manner with the extracted pine wood pitch, described above, either alone or in combination with other desired ingredients. such as have been indicated by way of example.

By way of example the coil may be insulated and bonded in a well known manner by placing it in a tank, placing the tank under vacuum, running the extracted pine wood pitch in at a temperature at which it will be fluid and then draining off excess pine wood pitch after the desired impregnation has been efiected. on cooling, the coil will be found to be eiliciently insulated and bonded.

The impregnation may be eiiiciently accompiished with the extracted pine wood pitch alone or in admixture with other ingredients, at a temperature of about C. to about C.

Where it is not desired to use extracted pine wood pitch alone, mixtures made up on any of In the production of insulated conductors in accordance with this invention, it will be desirable, though not essential, that the pine wood pitch be subjected to heat treatment prior to use alone or in admixture, in order to avoid foaming during the impregnation of a conductor under elevated temperature at which it will be fluid. By way of illustration, the extracted pine wood pitch'rnay desirably be treated at a temperature of from about 150 C. to about 325 C. for a period of from about 10 minutes to about 2 hours, depending upon the temperature. More specifically, the pine wood pitch, it treated at a temperature of about 250 C. for about one i. In combination an electrical conductor and an insulating material therefor comprising a pine wood pitch obtained by the extraction of pine wood and comprising oxidized resin acids, oxidized terpenes, polyphenols and polymerized terpenes.

2. A transformer coil including windings of insulated conductive material impregnated and bound with a pine wood pitch obtained by the extraction of pine wood and comprising oxidind resin acids, oxidized terpenes, polyphenols and polymerized terpenes.

3. In combination, an electrical conductor and an insulating material therefor which is impregnated with a pine wood pitch obtained by the extraction of pine wood and comprising oxi dized resin acids, oxidized terpenes, polyphenols, and polymerized terpenes.

4. In combination, an electrical conductor and an insulating material therefor comprising aaphalt and a pine wood pitch obtained by the extraction of pine wood and comprising oxidlned resin acids, oxidized terpenes, polyphenols, and polymerized terpenes.

5. In combination, an electrical conductor and an insulating material therefor comprising castor oil and a pine wood pitch obtained by the extraction of pine wood and comprising oxidised resin acids, oxidized terpenes, polyphenols, and polymerized terpenes.

6. In combination, an electrical conductor and an insulating material therefor which is impregnated with a composition comprising 10 parts by weight of asphalt and 90 parts by weight of a pine wood pitch obtained by the extraction of pine'wood and comprising oxidized resin acids,

oxidized terpenes, polyphenols, and poiymeriaed terpenes.

7. In combination, an electrical conductor and an insulating material therefor which is impregnated with a composition comprising 10 parts by weight of castor oil and 90 parts by weight of a pine wood pitch obtained by the extraction of pine wood and comprising oxidized resin acids, oxidized terpenes, polyphenols, and polymeriled terpenes.

8. In combination, an electrical conductor and an insulating material therefor comprising a pine wood pitch obtained by the extraction of pine wood and heat-treating to prevent foaming thereof, and comprising oxidized resin acids, oxidized terpenes, polyphenols, and polymerized terpenes;

JOHN M. DE BELL.