US2647063A

US2647063A - Permanently plastic insulating composition

Info

Publication number: US2647063A
Application number: US87672A
Authority: US
Inventors: Willis Hilary Bryan; Paul E Dupler
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1949-04-15
Filing date: 1949-04-15
Publication date: 1953-07-28
Anticipated expiration: 1970-07-28

Description

u 1953 H. B. WILLIS ETAL 2,647,063

PERMANENTLY PLASTIC INSULATING COMPOSITION Filed April 15, 1949 Fig.l.

2O |6 l4 7 I \\\Y wwgzz 1111111 14 Fig.2.

Solid Resins 60% AV VA AWAVA AWAYAVA 20% /\/V\/ OMA V\ vvwvw Inorganic Solids 100% 90% 80% 70% 60% 50% TollOil 40% WITNESSES: 4 lNVENTO W Hilary B.Wi nd @fW ATTOR EY Patented July 28, 1953 RERMANILX P T Q SULA G CQMPOSITION Hilary Bryan Willis and Paul E. Dupler, Pittsbur h, Pa, assi nors to Westinghouse Electric (Summat on, East rittsburgh, .Pa" :1 corporatio of lenns anie Application April 15, 1949, Serial No. 87,672

41 Claims. 1

This invention relates to permanently plastic insulating compositions having a putty-like texlture, such compositions being particularly suitable as fillers for use in making insulated joints between electrical conductors, but not limited thereto in their applications.

While many putties, fillers and similar plastic compositions moldable by hand are known, a great number of these are not permanently plastic but harden with standing or exposure to the air and they shrink, crack or otherwise deteriorate. Also, many of the compositions harden to such an extent that they are almost stone-hard and cannot be removed from the members to which they are applied except at the expenditure of considerable effort.

In the making of connection between electrical conductors, and bus bars in particular, the joints are considerably enlarged and extremely irregular so that they cannot be insulated conveniently or economically. In particular, bolted bus bar joints are difilcult to insulate properly. In some cases, these joints are located within enclosures or casings so that the insulating of the joints between the conductors must be done manually with great inconvenience and considerable expenditure of time. When electrical apparatus must be repaired or be rearranged, the joints usually must be taken apart, therefore requiring that the previously applied insulation of the joints be removed to enable the fastening means, such as bolts, to be disconnected. This entails considerable difficulty.

It has been proposed to apply a pliable or plastic putty or filler to such joints, but experience with previously known putties or fillers has shown that they are not satisfactory since their plasticity is difficult to control so that they either are excessively sticky or else dry and crumbly, and after application compositions harden undesirabl F n-ti s. c n inin r ing oi s. suc as linseed oil, harden with age so that the compositions are difficult to remove from the joints when disassembly of the joints is required.

The object of this invention is to provide a permanently plastic insulating composition suitable for application as a putty to electrical members.

A further object of the invention is to provide for the convenient making of insulated joints between electrical conductors by applying a permanently plastic insulating composition to the joint.

Other objects of the invention will, in part, be

obvious and will, in part, appear hereinafter, For a better understanding of the nature and objects of the invention, reference should be had to the following detaileddeso fiptio l and drawing, in which:

Figure 1 is a view in elevation, partly broken, of a joint prepared in accordance with the invention; and

(Cl. 106F123) Fig. 2 is a ternary diagram showing the proportions of the compositions of the present invention.

It has been discovered that permanently plastic insulating compositions characterized by freedom from undue stickiness on the one hand, absence of hardness and crumbling properties on the other hand, and possessing a permanent plasticity, may be prepared by admixing refined tall oil with the non-volatile, substantially hydrocarbon or gasoline insoluble residue of extracted pine wood pitch and adding thereto a mixture of inorganic solids, all in predetermined proportions. More specifically, it has been discovered that unusually desirable plastic compositions may be prepared by intimately mixing (a) 100 parts by Weight of tall oil, preferably refined tall oil, (b) from 25 to parts by weight of the non-volatile, gasoline insoluble residue of ex tracted pine wood pitch, the residue of the extracted pine wood pitch being dissolved in the tall oil, and (c) a mixture of inorganic solids composed of (1) from 30 to 80 parts by weight of at least one alkaline inorganic compoun of the fineness of at least mesh selected from the group consisting of calcium carbonate (whiting), barium carbonate, zinc carbonate, and magnesium carbonate, (2) from 75 to 100 parts by weight of at least one inorganic absorbent of a fineness of at least 100 mesh selected from the group consisting of talc, silica aerogel and infusorial earth, and (3) from 100 to 300 parts by Weight of a dense non-porous silica of a fineness of at least mesh.

We prefer to employ refined tall oil in the practice of the invention. Refined tall oil contains from 52% to 58% of fatty acids and from 36% to 43% of rosin acids, has an acid number of from 163 to 175, a specific gravity of 0.960 to 0.975 and an iodine number (Wijs method) of from 123 to 125. The non-volatile, substantially hydrocarbon or gasoline insoluble residue of extracted pine wood pitch is sold under the trade name Vinsol. It is a brittle resin solid constituting the final residue in the process of extracti-ng various terpene compounds from pine wood, Ordinarily, the pine wood is ground up, then treated with extractives to remove all of the resins therefrom, and the extract is then subjected to treatment to separate therefrom turpentine, pine oil, and rosin, leaving the aforementioned residue which is gasoline insoluble and'non-volatile. The residue of extracted pine wood pitch may be dissolved in the tall oil at room temperature by simply admixing the finely divided residue in the tall oil. To expedite the. solution, the tall oil may be warmed, and the residue of extracted pine wood pitch stirred into the warm tall Oil. For some purposes, additional solid resins to the extent of up to 20 parts by Weight per 100 parts of tall oil, may be included in the solution. These resin solids may be selected from the group of natural resins and their simple derivatives consisting of rosin, rosin esters, copal and dammar.

It has been found that the three finely divided inorganic solids must be admixed in the proportions above given to secure a suitable product. Thus, using only whiting or silica alone, or.a mixture of both, for example, resulted in an unstable product having the defect of separation of the tall oil therefrom on standing for a short time. The resultant product also was of unsatisfactory texture. When an absorbent solid, such as talc, was used alone, the resulting plastic composition was soft and crumbly and unsuitable for its intended use.

The alkaline inorganic compounds may be much finer than 100 mesh with a smoother texture obtained thereby. The inorganic absorbent ordinarily is available in the fineness of 200 mesh and finer, and such fineness has been found to be beneficial. It will be appreciated that a small amount of the solids may be coarser than the fineness given without markedly impairing the properties of the final composition.

By infusorial earth there is intended to be included the various absorbent inorganic materials so classed, namely, kieselguhr, diatomite, tripolite and similar products. The silica aerogel is a product available to the trade. It is produced by the dehydration of a silica gel, which is thereafter ground to a suitable fineness. The dense non-porous silica is ordinary silica flour produced by crushing or grinding sand, quartz and other silicas and may include a substantial proportion of other inert inorganic mineral.

There are definite limits to theproportions of the tall oil, the residue of extracted pine wood pitch, with any other solid resins added thereto, and the inorganic solids. Referring to Fig.2 of the drawing, there is shown a fragmentary portion of a triaxial ternary diagram wherein compositions within the area LMNOPQRST have been found to possess suitable plasticity, freedom from stickiness and freedom from hardness and crumbling. Compositions within this area have been found to be satisfactory, while those outside of the area have proven to be unsuitable for the purpose of this invention. The composition proportions at each point are shown in the following table:

TABLE Solid Inorganic Point 2 3 33 Resins, Solids, Percent Percen lapping connections between the bus bars Hi and I2 are covered with a quantity of the plastic composition [8 of this invention. The composition i8 is applied manually to the joint and overlaps the sleeves M. This manual operation may be done rapidly and promptly due to the desirable plastic characteristics of the compositions disclosed herein. Thereafter, the composition l8 at the joint is covered with one or more layers of varnish cambric 20, or other suitable insulating tape. At most, only two or three layers of tape are themaximum needed. Previously, joints similar to those shown in the drawing had to be wrapped with from 10 to 25 layers of tape producing a bulky, rough, unattractive-looking joint with considerable expenditure of expensive wrapthis invention are typical.

Example I Parts by weight Refined tall oil 138 Residue of extracted pine wood pitch 40 Whiting 50 Talc 150 Silica. flour 178 This is the composition at the point I in Fig. 2. The residue of extracted pine wood pitch of the fineness so that passes through a 80-mesh sieve was stirred into the tall oil and will dissolve readily. If necessary, the tall oil may be heated to expedite solution. The whiting, talc and silica flour were of a fineness of over mesh each. When the inorganic solids were admixed in a Banbury mixer for fifteen minutes with the solution of tall oil and residue of extracted pine wood pitch resin, there resulted a soft plastic composition of putty-like texture. When tested with a penetrometer at 25 C., the average penetration was 14.5 millimeters. Tests with this composition on joints indicated that it was readily applicable and superior to any known composition in its overall properties. It resisted aging and did not harden, even after prolonged exposure to extremes of temperature.

Example II A solution was prepared by dissolving 60 parts by weight of the residue of extracted pine wood pitch in 138 parts by weight of refined tall oil. Into this solution there were introduced 50 parts by weight of whiting, 150 parts by weight of talc and 261 parts by weight of silica flour, all the solids being finer than 150 mesh. The entire operation was effected successfully in a Banbury mixer. This is the composition at point II in Fig.- 2. This composition, when tested with a penetrometer, had an average penetration of 6.1 millimeters at 25 C. The penetrometer used in these examples comprised a penetration rod of A in diameter with a rounded tip loaded with a weight of 150 grams, as set forth in accordance with the ASTM specification.

Example III A composition was prepared by dissolving 80 parts by weight of residue of extracted pine wood pitch in 100 grams of refined tall oil. Into this solution there were stirred 182 parts by weight of a mixture of finely divided solids of a fineness of approximately 200 mesh comprising 10.8% barium oxide, 32.5% of silica aerogel and 56.5% of silica flour. This is the composition at the point III of Fig. 2. lhis produced a soft plastic putty which, however, was not sticky. Into the same solution as in this example, there were stirred 287 parts by weight of the same mixture of inorganic solids. This is the composition at point IV in Fig. 2. This formed a much stiffer putty-like composition which, however, was nct crumbly or too dry to apply readily to conductor joints.

Example IV A solution prepared by dissolving 49 parts of the residue of extracted pine wood pitch and 100 parts by weight of refined tall oil, had stirred into it 265 parts by weight of mixture of finely pulverized solids exceeding 150 mesh comprising calcium carbonate, 45% of talc and of silica fiour. This is the composition at point V of Fig. 2. This formed a quite soft plastic compound which, however, was not sticky. Further tests indicated that up to 380 parts by weight of the mixture of inorganic solid powders could be added to the oil solution with satisfactory results. This last is the composition at point VI of Fig. 2.

Example V 80 parts of residue of extracted pine wood pitch were admixed into 128 parts by weight of tall oil. Into this solution there was introduced a mixture of 100 parts by weight of calcium carbonate, 200 parts by weight of talc and 250 parts by weight of silica flour, all of the fineness exceeding 150 mesh. This is the composition at point VII of Fig. 2. This mixture formed a plastic composition which was suitable for the purpose of this invention.

The compositions disclosed herein may be modified by slight additions not exceeding 5% of the total weight thereof of asbestos fibers to promote adherence of the plastic compositions into a body. The asbestos fibers should be finely divided and thoroughly admixed into the compositions.

Compositions having excellent overall qualities may be prepared by dissolving 60 parts of the residue of extracted pine wood pitch in from 130 to 145 parts by weight of refined tall oil, then stirring in from 400 to 500 parts by weight of a pulverized inorganic solid mixture composed of from to 60 parts by weight of whiting (calcium carbonate), from 125 to 175 parts by weight of talc, and from 200 to 300 parts by weight of silica fiour. The entire operation can be carried out in half an hour in a Banbury mixer.

Since certain obvious changes may be made in the above procedures and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A permanently plastic putty-like insulating composition composed essentially of an intimate mechanical mixture of (a) 100 parts by weight of refined tall oil, (1)) from 25 to 80 parts by weight of the non-volatile, gasoline insoluble residue of extracted pine wood pitch, the residue of the extracted pine wood pitch being dissolved in the tall oil, and (c) a mixture of inorganic solids composed of (1) from 30 to 80 parts by weight of at least one alkaline inorganic compound of a fineness of .at least 100 mesh selected from the group consisting of calcium carbonate, barium carbonate, zinc carbonate, and magnesium carbonate, (2) from to 100 parts by weight of at least one inorganic absorbent of a fineness of at 1 least 100 mesh selected from the group consisting of talc, silica aerogel and infusorial earth, and (3) from 100 to 300 parts by weight of a dense, non-porous silica of a fineness of at least 150 mesh, the components (a), (b) and (0) being combined only in proportions coming within the area LMNOPQRST indicated on the ternary diagram in the drawing.

2. A permanently plastic putty-like insulating composition composed of an intimate mechanical mixture of (a) 100 parts by weight of tall oil, (1)) resin solids composed of from 25 to parts by weight of the non-volatile, gasoline insoluble residue of extracted pine wood pitch and not over 20 parts by weight of a resin selected from the group consisting of rosin, rosin esters, copal and dammar, the residue of the extracted pine wood pitch and the resin being dissolved in the tall oil, and (c) a mixture of inorganic solids composed of (1) from 30 to 80 parts by weight of at least one alkaline inorganic compound of a fineness of at least mesh selected from the group consisting of calcium carbonate, barium carbonate, zinc carbonate, and magnesium carbonate, (2) from 75 to 109 parts by Weight of at least one inorganic absorbent of a fineness of at least 100 mesh selected from the group consisting of talc, silica aerogel and infusorial earth, and (3) from 100 to 300 parts by weight of a dense, non-porous silica of a fineness of at least 150 mesh, the components (a), (b) and (a) being combined only in proportions coming within the area LMNOPQRST indicated on the ternary diagram in the drawing.

3. A putty-like composition composed essentially of an intimate mechanical mixture of from to parts by weight of tall oil having dissolved therein 60 parts by weight of the nonvolatile, gasoline insoluble residue of extracted pine wood pitch, and from 400 to 500 parts by weight of a mixture of finely divided inorganic solids comprising 40 to 60 parts by weight of whiting, 125 to parts by weight of talc and from 200 to 300 parts by Weight of dense, nonporous silica.

4. The composition of claim 1 with not over 5% of its Weight of finely divided asbestos fibers.

HILARY BRYAN WILLIS. PAUL E. DUPLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,947,112 Ruben 1 Feb. 13, 1934 2,242,601 Wallace May 20, 1941 2,357,124 Miller Aug. 29, 1944 2,373,709 Rice Apr. 1'7, 1945 2,439,377 Bare et al. Apr. 13, 1948 2,448,621 Rice Sept. 7, 1948 FOREIGN PATENTS Number Country Date 563,547 Germany Nov. 7, 1932

Claims

1. A PERMANENTLY PLASTIC PUTTY-LIKE INSULATING COMPOSITION COMPOSED ESSENTIALLY OF AN INTIMATE MECHANICAL MIXTURE OF (A) 100 PARTS BY WEIGHT OF REFINED TALL OIL, (B) FROM 25 TO 80 PARTS BY WEIGHT OF THE NON-VOLATILE, GASOLINE INSOLUBLE RESIDUE OF EXTRACTED PINE WOOD PITCH, THE RESIDUE OF THE EXTRACTED PINE WOOD PITCH BEING DISSOLVED IN THE TALL OIL, AND (C) A MIXTURE OF INORGANIC SOLIDS COMPOSED OF (1) FROM 30 TO 80 PARTS BY WEIGHT OF AT LEAST ONE ALKALINE INORGANIC COMPOUND OF A FINENESS OF AT LEAST 100 MESH SELECTED FROM THE GROUP CONSISTING OF CALCIUM CARBONATE, BARIUM CARBONATE, ZINC CARBONATE, AND MAGNESIUM CARBONATE, (2) FROM 75 TO 100 PARTS BY WEIGHT OF AT LEAST ONE INORGANIC ABSORBENT OF A FINENESS OF AT LEAST 100 MESH SELECTED FROM THE GROUP CONSISTING OF TALC, SILICA AEROGEL AND INFUSORIAL EARTH, AND (3) FROM 100 TO 300 PARTS BY WEIGHT OF A DENSE, NON-POROUS SILICA OF A FINENESS OF AT LEAST 150 MESH, THE COMPONENTS (A), (B) AND (C) BEING COMBINED ONLY IN PROPORTIONS COMING WITHIN THE AREA LMNOPQRST INDICATED ON THE TERNARY DIAGRAM IN THE DRAWING.