Part 398

«Rubber»

«ARTIFICIAL RUBBER.»

Austin G. Day tried hundreds of experiments and took out many patents for rubber substitutes. He was in a measure successful, his “Kerite” compound proving of great value and being a result of his seeking for something that would wholly supplant rubber. As far back as 1866 he made public the results of some of his work, giving as formulas for rubber substitutes the following compounds:

I.—Linseed oil 2 pounds Cottonseed oil 1 pound Petroleum 2 pounds Raw turpentine 2 pounds Sulphur 2 pounds

Boil 2 hours.

II.—Linseed oil 2 pounds Cottonseed oil 1 pound Petroleum 1 pound Raw turpentine 2 pounds Castor oil 1 pound Sulphur 2 pounds

Boil 1⁠/⁠2 hour.

III.—Linseed oil 2 pounds Cottonseed oil 1 pound Petroleum 1 pound Raw turpentine 1⁠/⁠2 pound Liquid coal tar 3 pounds Peanut oil 1 pound Spirits turpentine 1 pound Sulphur 4 pounds

Boil 35 minutes.

IV.—Linseed oil 2 pounds Cottonseed oil 1 pound Petroleum 2 pounds Raw turpentine 1⁠/⁠2 pound Liquid coal tar 2 pounds {619} Spirits turpentine 1 pound Rubber [ ] pound Sulphur 2 pounds

Boil 1 hour.

In 1871 Mr. Day had brought his experimenting down to the following formula:

V.—Cottonseed oil 14 pounds Linseed oil 14 pounds Asphaltum 8 pounds Coal tar 8 pounds Sulphur 10 pounds Camphor 1⁠/⁠2 pound

In this the tar and asphaltum were first mixed with the cottonseed oil, after which was added the linseed oil and camphor, and, last of all, the sulphur, when the temperature was about 270° F.

A substitute designed to be used in rubber compounding in place, say, of reclaimed rubber, was made as follows:

VI.—Cottonseed oil 27 pounds Coal tar 30 pounds Earthy matter 5 pounds

To be mixed and heated to 300° F., and then strained and cooled to 200° F. Then were added 27 pounds linseed oil, the heat raised to 220° F., and 15 to 18 pounds of sulphur added, the heat being continually raised until the mass was sulphurized. When the heat reached 240° F., 1 to 1 1⁠/⁠2 ounces of nitric acid were added, and at 270° to 280° F., from 1 to 3 ounces camphor were added to help the sulphurization. The resultant compound was used on the following basis:

VII.—Para rubber 20 pounds Litharge 5 pounds Sulphur 1 pound Above compound 20 to 40 pounds

Mr. Day did not insist on the compound quoted, but advised that the proportions be varied as widely as the exigencies of the case might demand. Whiting, barytes, infusorial earth, white lead, blacks, in fact almost any of the oxides, carbonates, or earthy materials commonly used in compounding, were used in connection with his substitute, as also were any grades of crude rubber. Among other ingredients that he found of use in making his substitutes were vegetable and animal waxes, together with ozokerite and paraffine. These were only used in small quantities, and always in connection with the linseed and cottonseed oils, and generally asphaltum or coal tar. One of his compounds also called for a quantity of golden sulphuret of antimony, presumably to assist in the sulphurization, and a small amount of tannic acid.

Another line of experimenting that is interesting, and that will yet produce good results, although so far it has not amounted to much, is in the use of cellulose. A very simple formula is of French origin and calls for the treating of cellulose with sulphuric acid, washing, drying, granulating, treating with resinate of soda—which is afterwards precipitated by sulphate of alumina—then drying and molding under pressure. As a matter of fact, the resultant mass would not be mistaken for rubber. An English formula is more like it. This consists of

VIII.—Cellulose 15 pounds Pitch 25 pounds Asphalt 20 pounds Silica 20 pounds Mastic 5 pounds Bitumen 5 pounds Rosin 10 pounds Coal tar 12 pounds

This makes a thick gummy varnish which is of little use except as for its waterproof qualities. Allen’s formula for a cellulose substitute might have a value if it were carried further. It is made up of 100 pounds of rosinous wood pulp treated with animal gelatin, 100 pounds asphalt, and 10 pounds asphalt oil, all heated and molded.

The Greening process, which is English, is more elaborate than Allen’s, but seems a bit laborious and costly. This process calls for the treatment of the cellulose by a mixture of sulphuric acid and nitrate of potash, and, after drying, a treatment to a bath of liquid carbonic acid. When dry again, it is mixed in a retort with refined rosin, gum benzoin, castor oil, and methylated alcohol. The distillate from this is dried by redistilling over anhydrous lime.

Another curious line of substitutes is that based upon the use of glue and glycerine. Some of these have uses, while others, that look very attractive, are of no use at all, for the simple reason that they will absorb water almost as readily as a dry sponge. The first of these is more than 30 years old and is said to be of French origin. The formula is:

IX.—Glue 4 pounds Glycerine 8 ounces Nutgall 3 ounces Acetic acid, 1 pound in 5 pounds of water.

Ten years later this was approached by an English formula in which in place of {620} the nutgall and acetic acid, chromic and tannic acids were substituted, and a modicum of ground cork was added as a cheapener probably. Some four years later an ingenious Prussian gave out a formula in which to the glue and glycerine and tannic acid were added Marseilles soap and linseed oil. None of the above have ever had a commercial value, the nearest approach being the glue and glycerine compound used as a cover for gas tubing.

The substitutes that have really come into use generally are made either from linseed, cottonseed, or maize oil. Scores of these have been produced and thousands of dollars have been spent by promoters and owners in trying to make these gums do just what crude rubber will. A German formula which was partially successful is

X.—Linseed oil, in solution 80 pounds Lime-hardened rosin, in solution 50 pounds