US1282505A - Rubber composition and method of producing the same. - Google Patents

Description

WTTED %TATE% PATENT @FETQE.

JOHN M. WEISS, OF NEW YORK, N. Y., ASSIGNOR TO THE BARRETT COMPANY, A CORPORATION OF NEW JERSEY.

RUBBER COMPOSITION AND METHOD PRODUCING THE SAME.

No Drawing.

' To all whom it may concern Be it known that 1, JOHN M. Weiss, a citizen of the United States. residing at 210 West'110th street, New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Rubber Compositions and Methods of Producing the Same, of which the following is a specification.

This invention relates to rubber products and compositions, and more particularly to dense and non-porous vulcanized products and compositions of improved (ll-electricproperties having incorporated therewith, prior to the vulcanization, a semi-solid to solid bitumen obtainable by the destructive distillation of coal tar and coal tar pitch.

In the destructive distillation of coal tar and of coal tarpitch, there is obtained, at the final stage otlevolution of condensable distillate, a semi-solid to solid product of characteristic composition and properties. This product is bituminous in character and may properly be referred to as a bitumen, within the standard definition of the American Society for Testing Materials. This bitumen is an extremely high boiling product and undergoes partial decomposition if distilled under atmospheric pressures. It varies in color from a dark brown to a clear cherry red product, and can readily be obtained in the form of a light colored product relatively free from black or brown coloration and free from free carbon. It is very resistant to dilute acids and alkalis, and it is soluble in such common solvents as benzol, and coal tar naphthas, etc.

This semi-solid to solid bitumen, thus obtainable by the destructive distillation of coal tar and coal tar pitch, may be melted,

by the application of heat, and may have a meltin point. varying, for example, from around 110 to 115 F. or lower-,Up to around 145 to 155 F., or eVen as high as 190 F. or higher, the melting point being determined according to the Cube melting point method for bituminous materials described by S. R. Church in the Journal of Industrial and Engineering Chemistry for April, 1911. The specific gravity of the bitumen is unusually high certain samples thereof which have been examined showing specific gravities, at about 155 (1., from Specification of Letters Patent.

Patented Oct. 22, 1918.

around 1.233 or even lower up to around 1.25 or higher.

The bitumen moreover has remarkable dielectric properties. Samples of the bitumen have been found to have as high a di-electric strength as 550 to 700 volts per mil, or even higher.

This bitumen, with its characteristic composition and properties, is obtainable from coal tar or coal tar pitch by difierent'methods of procedure. It may thus be obtained as the last fraction of the condensable distillate in the straight distillation of coal tar to coke, this last. fraction being properly cut so that the bitumen is substantially free from greases and lower boiling components. Again, where the distillation of the coal tar has proceeded only to'the formation of coal tar pitch, this pitch may be subjected to a redistillation, for. example, in a coke oven, and the bitumen obtained therefrom at the end of the destructive distillation a d at the final stage of evolution of con- .lensable distillate as above described. The fractions of the distillate which come over before the semi-solid and solid bitumen frequently carry with them appreciable amounts of the bitumen. and the bitumen may be obtained from these distillates by a suitable redistillation.

It will be evident that various specific methods of procedure may be followed, and that different types of apparatus may be used, in the production of the bitumen by the destructive distillation of the coal tar or coal tar pitch.

The bituminous substance or bitumen thus obtainable will be hereinafter referred to, in the specification and in the appended claims, simply as the bitumen, or as the semi-solid to solid bitumen obtainable by the destructive distillation of coal tar pitch.

Where the bitumen is initially produced in an impure state it may be further purified, by distillation or otherwise, for example, by steam or vacuum distillation. If distilled under ordinary pressures the bitumen undergoes partial decomposition, forming greasy bodies some apparently unchanged bitumen and coke residue, so that such distillation will not generally be feasible for purification of the impure bitumen; but the composition tion with corresponding modification of the vulcanization process, and with the production of a correspondingly modified vulcanized product.

The properties of the bitumen above referred to, such as its resistance to alkalis and acids, its high specific gravity, and its unusual di-electric properties, inhere, to a greater or less extent, in the vulcanized products in the production of which the bitumen is employed. The vulcanized products will thus be of increased density due to the high specific gravity of the bitumen itself, while the di-electric properties of the rub ber compositions and products will be similarly benefited by the incorporation of the bitumen therein.

The compositions and products of the present invention are of especial value for purposes Where a light colored product is desired. It is well known that coal tar pitch, and the usual asphaltic and bituminous components of rubber mixtures, are of a black color, and correspondingly darken the vulcanized products in the production of which they are employed. The bitumen employed in the process of the present invention, however, when properly prepared and purified, is substantially free from obj ectionable black coloration, and has a pleasing clear and usually cherry red coloration, which imparts to the compositions and products, in the manufacture of which the bitumen is employed, a slight but unobjectionable tint. Such vulcanized products and compositions, accordingly, may be used Where light colored rubber products are desired and where black products would be undesirable. The advantage of lightness in color, as will be evident, will be an added ad vantage, in addition to the other desirable properties imparted to the vulcanized products by the bitumen.

The bitumen may, however, be used to advantage in the production of compositions or products where light color is not of importance, and Where it may even be desirable to produce a dark or black product. In such cases the other advantages of the bitumen 'Wlll be retained. For such purposes, the

bitumen itself need not be entirely free from dark coloration, but may even have a pronounced dark brown color, although, as above pointed out, it can readily be produced substantially free from objectionable dark coloration.

In the production of high grade rubber products and compositions, grades of rubbers, such as Para or plantation rubbers, will usually be employed. For other purposes, other rubbers of an inferior grade may be employed. In any case, the composition or mix may contain fillers of various kinds, or pigments, or other specific substances or reagents, such as, for example, zinc oxid, lithopone, etc., for hardening the rubber or imparting special properties to the resulting final composition or product.

The vulcanization process can be carried out by the incorporation of an appropriate amount of sulfur either with or Without other agents for promoting or modifying the vulcanization process. For hard 7 rubber products more sulfur will be employed than for soft rubber products. the vulcanizing agent, as well as the time, temperature and pressure of vulcanization, will vary with the nature of the compositiqn and with the character of the product which it is desired to produce, 0. whet-her the product is to be a soft vulcanized product or a hard rubber product.

The bitumen may be incorporated with the rubber and other constituents of the mix in any suitable manner. The mixing operation will be promoted by heating the rubber on the mixing mill to such a temperature that the bitumen will become plastic or even liquid upon contact with it, care being taken, however, to avoid the use of excessive heat that might destroy the nerve of the rubber. When the bitumen has been ground up or comminuted it 'may be added in this form along with the other ingredients of the mix and incorporated during the rolling or mixing operation. The bitumen may also, in some cases, be incorporated with advantage by the use of its solutions, and by uniform distribution of such solutions throughout the rubber, by the use of solutions of the bitumen in solvents which are likewise solvents of the rubber itself. This will be of especial advantage in the production of so-called solutions of rubber such as are used for waterproofing fabrics and the like, since the bitumen and the rubber may be dissolved in common solvents and a 'uniform distribution of the bitumen and rubber thereby promoted. Where such rubber solutions are made and used, the solvent may be subsequently removed, leaving the bitumen intimately combined with the rubber and other constituents of the rubber composition, and the vulcanization may be then effected in any suitable manner, as by the so-called cold vulcanization process, making use of sulfur chlorid, or by the Well-known hot room process, or otherwise.

the higher The amount of I escapee It will be understood that so-called waste or reclaimed rubber may be employed in the production of the compositions and products of the present invention, for example, in admixture with the higher grades of rubber, and the waste or regenerated rubber will be modified by the vulcanization thereof, in admixture with the bitumen.

Vulcanized products may be similarly prepared by the use of so-called vulcaniz'able oils, which, upon vulcanization, produce socalled rubber substitutes. The hereinbefore described bitumen may, with similar advantages to those above referred to, be incorporated in such compositions, prior to their vulcanization. It will be evident also that vulcanizable oils may be incorporated with rubber in the preparation of composite vulcanized products in the production of which the bitumen is also utilized.

The invention will be further illustrated by the following specific examples of compositions made in accordance therewith.

No.1 No.2

Para rubber 76.2 53.

Sulfur 9.52% 9.66%

Magnesia 4.76% 4.5 Bitumen (hereinbefore described) 9.52% 32.84%

Such mixtures may be subjected to vulcanization, for example, for a period of thirty minutes at a steam pressure of f0rtyfive (45) pounds; but the time and pressure (and corresponding temperature) may vary within rat-her wide limits, depending upon the particular use for which the product is desired.

Where hard rubber productsare desired a much larger percentage of sulfur will e used and the vulcanization process will be correspondingly modified. So also, various fillers or compounding materials may be used, depending upon the purposes for which the resulting products are desired.

The products thus produced will be of improved density and dielectric properties due to the hereinbefore described bltumen employed in their production. Where the bitumen is of cherry red color the products will be light colored products, substantially free fromdark coloration, if the rubber and other ingredients employed are themselves free from dark coloration. At the same time, the products or compositions will have the other characteristic properties imparted to them by the bitumen. Inasmuch as the bitumen is free from dark coloration it will likewise be free from free carbon, which, if present, would modify the electrical properties of the compositions or products. Because of the absence of free carbon in the bitumen, and because of the other desirable properties imparted to the compositions and products by the bitumen, these compositions and products will be of value for electrical insulationpurposes.

The slight reddish tint which may be imparted to compositions made with the hereinbefore described bitumen may even be of advantage for certain purposes, for example, for dental rubber where a reddish coloration is desired.

The light coloration of the bitumen moreover, makes it possible to produce rubber compositions and products of various colors, by the addition of various pigments and coloring materials, without the disadvantages incident to the use of black ingredients such as coal tar pitch and the like, or carbonaceous components of an essentially black character.

The amount of the hereinbefore described bitumen which may be used, in the production of the improved compositions and products of the present invention, may vary within rather wide limits, as will be evident from the specific examples above given, and depending on such considerations as the nature of the mix, the components of which the mix is made up, the object for which the product is desired, and the nature of the vulcanization process, whether hot or cold, and whether for the production of hard or soft rubber products.

While the invention has been more particularly described in connection with vulcanized compositions and products, yet it will be understood that unvulcanized compositions and products may be similarly produced by the incorporation therein of the bitumen, and'that these compositionsmay be employed without vulcanization or for purposes where vulcanization is to be subsequently effected, for example, in the coating of fabric where the coating is to be subsequently vulcanized. For certain purposes unvulcanized compositions of a more or less plastic character are desired and such-compositions are intended to be included within the more comprehensive claims appended hereto. Such compositions, however, are to be distinguished in certain important respects from the vulcanized compositions and products which are more specifically claimed.

I claim:

1. The method of producing vulcanized compositions and products, which comprises incorporating with a vulcanizable ingredient of the composition to be vulcanized, a semisolid to solid bitumen obtainable by the destructive distillation of coal tar pitch, and v solid bitumen. obtainable by the destructive distillation of coal tar pitch. and sul'ijecting the composition to vulcanization; substantially as described.

3. .\s new articles of manufacture. rubber compositions and products containing rubber and a semi-solid to solid bitumen obtainable by the destructive distillation of coal tar pitch; substantially as described.

4. As new articles of manufacture, rubber compositions and products of light color, containing rubber and a light-colored semisolid to solid bitumen obtainable by the de structive distillation of coal tar pitch; substantially as described.

As new articles of manufacture, vulcanized compositions and products having, incorporated therein prior to the vulcanization thereof a semi-solid to solid bitumen ob-' tainable by the destructive distillation of coal tar pitch; substantially as described.

6. As new articles of manufacture. vulable by the destructive distillation of coal tar pitch; substantiall as described.

8. As new articles of n'ianufacture. light colored rubber compositions and products having incorporated therewith prior to vulcanization thereof a. light colored semi-solid to solid bitumen obtainable by the destructive distillation of coal tar pitch; substantially as described.

In testimony whereof I afllx my signature.

JOHN M. \VEISS.