US1233415A - Electrical insulation. - Google Patents

Description

part obvious and in WILLIAM H. STEINBERG, 0F MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER- HAMMER MFG. (10., OF MILWAUKEE, WISCONSIN, A. CORPORATION OF WISCONSIN.

ELECTRICAL INSULATION.

mean-i5.

No Drawing.

To all whom it may concern:

Be it known that LWILLIAM H. STEIN- ennc, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Electrical Insulation, 'of which the following is a full, clear, concise, and exact descriptlon.

This invention relates to improvements in composition material particularly adapted for electrical insulating purposes.

It has heretofore been roposed to employ a non-inflammable and non-conducting substance, such as asbestos, as the base for an electrical insulating material and to mix the same in a comminuted state with a binder comprising coal tar pitch and one or more solvents therefor. An additional ingredient as a co-binder is usually provided. The resultant mass obtained by this process is molded under pressure and subsequently baked.

This invention hasamong its objects to provide an improved heat resistant insulating composition of the general character above set forth but which possesses a degree of hardness,'density and mechanical strength superior to that heretofore attained. A further object is to provide an improved binder for combination with a suitable base material, such as comminuted asbestos.

Other objects and advantages will be in part specifically noted hereinafter.

As above mentioned, one of the objects of the invention is to provide an im roved cementitious binding compound, and or this purpose there is provided a mixture of coal tar pitch and stearin pitch, combined in substantially equal proportions. lit may be mentioned that these ingredients are respectively the residues in the distillation process of coal tar and animal fats or vegetable oils and that both are chemical conglomerates capable of reacting with a variety of other substances. The mixing of the two pitches is preferably carried on in the presence of heat, or the compound, after mixing, may be subjected to heat. In either case the mass is raised to a temperature between 400 and 500 F. and then allowed to cool. During this process, a reaction occurs which results in a precipitation of substantially the entire free carbon content of the coal tar pitch.

Specification of Letters Patent. Patented July 1'7, 191?, Application filed March 1, 1915. Serial No. 11,337.

. The amount of such carbon in commercial grades of coal tar pitch varies from 10% to 50%, but it is found that usually the carbon deposited equals approximately 30% by weight of the coal tar pitch added After cooling, the supernatant liquid is drawn off and dissolved in a substantially equal quantity of benzol to which'may be advantageously added small amounts, for example, from 5 to. 15%, of a high boiling naphtha fraction and a vegetable oil, such as castor oil. Both of the latter elements serve to stabilize the benzol and thus reduce the rate of free volatilization thereof. Moreover the castor oil also serves an addi- 'tional purpose as will hereinafter appear.

The insulation base consists of comminuted asbestos as above mentioned, but to which preferably is-added and mixed in a dry state, approximately equal quantities of sulfur and one or more metallic peroxide such as barium or lead. The sulfur and peroxids may be used in small amounts, that is down to about 1}% by weight, of the ground asbestos. I This material is then gradually mixed cold with a quantity of the above described binder in a proportion of about four parts of the base to one part of the binder. Moreover, as above set forth,

. the commingling of the baseand binder is facilitated by the slow volatilization of the benzol due to the presence of the naphtha and castor oil.

When these parts are thoroughly mixed, a homogeneous and granular but plastic compound is obtained, which is capable of molding without heat to produce an extremely hard and dense insulation when baked. The

molding is preferably accomplished by compressing the material cold under from 6,000 pounds to 10,000 pounds pressure after which the molded article is radually heated for approximately twentyour hours to a maximum of from 450 to 500 F. This baking serves to drive 0% by evaporation the entire volatile content of the molded material and also efiects a combination, in a manner similar to vulcanizing, of the sulfur mixed with the asbestos and the castor oil in the binder to yield a tough, rubbery substance which aids in increasing the mechanical strength and toughness of the final product. Furthermore, it is found that the metallic peroxid induces increased oxidation of certain of the constituents of the stearin pitch, in a manner similar to the effect of an added drier, and thus tends "to harden the product. Moreover, the precipitation of the free carbon in the coal tar pitch as above set forth, also augments the cementing value of the binder, a result probably due to the release of the cohesive force originally expended in sustaining the carbon and utilizing the thus released power for binding the asbestos particles.

What I claim as new and desire to secure by Letters Patent is 1. A cementitious binder for the purpose set forth including stearin pitch and a volatile solvent therefor.

2. A cementitious binder for the purpose set forth including coal tar pitch, stearin pitch and a volatilesolvent therefor.

3. A cementitious binder for the purpose set forth including coal tar pitch and stearin pitch in substantially equal proportions and a solvent therefor.

4. A cementitious binder for the purpose set forth, including coal tar pitch, stearin pitch and a solvent therefor comprising a volatile oil and a non-volatile oil.

5. A cementitious binder for the purpose set forth including substantially equal parts of coal tar pitch-and stearin pitch and a solvent therefor comprising volatile oil and castor oil.

6. A binder for the purpose set forth, including coal tar pitch, stearin pitch and an oil capable of vulcanization or polymer ization.

7. A plastic composition which is noninflammable and electrically insulating comprising a base and a binder the latter including stearin pitch and the admixture of base and binder being molded and baked.

8. A plastic composition which is noninflammable and electrically insulating comprising comminuted asbestos and a binder seesaw therefor including a mixture of coal tar pitch and stearin pitch.

9. A plastic composition adapted to be molded and baked comprising comminuted asbestos having sulfur mixed therewith and a binder including coal tar pitch and stearin pitch.

10. A baked plastic composition which is non-inflammable and electrically insulating comprising comminuted asbestos and a binder sulfur hardened in baking and including coal tar pitch and stearin pitch. 11. A plastic composition to be molded and baked comprising a comminuted asbestos base having mixed therewith sulfur and a metallic peroxid and a binder for said base including coal tar pitch, stearin pitch and a non-volatile solvent.

12. The herein described process which consists in combining under heat coal tar pitch and stearin pitch, then adding thereto a .solvent therefor and then commingling the mixture with comminuted asbestos.

13. The herein described process which consists in combining under heat coal tar pitch and stearin pitch, then adding thereto a solvent therefor, then commingling the mixture with comminuted asbestos having sulfur mixed therewith and then molding and baking the mass.

14. The herein described process which consists in mixing equal quantities of coal tar pitch and stearin pitch, heating the same to 400 F., and dissolving the supernatant fluid in a solvent having benzol, naphtha and vegetable oil components.

In witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

WILLIAM H. STEINBERG. Witnesses:

L. A. WATaoN, Tam Baler.