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 | |
| 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 | |
| Add to above | ||
| Sulphur | 8 pounds | |
| Linseed oil | 42 pounds | |
Add 20 pounds sulphur and heat to 375° F.
Rubber And Rubber Articles.
To prevent rubber tubes from drying up and becoming brittle, they should be coated with a 3 per cent aqueous solution of carbolic acid, which preserves them. If they have already turned stiff and brittle, they can be rendered soft and pliant again by being placed in ammonia which has been made liquid with double the amount of water.
In France rubber tubes are used as a core for casting pipes from cement and sand. In order to construct a connected pipe conduit in the ground, a groove is dug and a layer of cement mortar spread out. Upon this the rubber tube is laid, which is wrapped up in canvas and inflated. The remaining portion of the channel is then filled up with cement mortar, and as soon as it has set, the air is let out of the rubber hose and the latter is pulled out and used as before.
To cover cloth with rubber, there are chiefly employed for dissolving the rubber, naphtha, alcohol, and benzol. They are mixed with purified solid paraffine, and ground together.
Rubber boots and shoes are rendered waterproof by melting 4 parts of spermaceti and 1 part of rubber on a moderate fire, adding tallow or fat, 10 parts, and lastly 5 parts of copal varnish or amber varnish. This mixture is applied on the shoes with a brush. It should be stated that the rubber used for this purpose must be cut up very small and allowed 4 to 5 hours to dissolve.
To rid rubber articles of unpleasant odor, cover both sides with a layer of animal charcoal and heat to about 140° F.
To prevent gas from escaping through rubber hose, cover it with a mixture prepared as follows: Dissolve 5 parts of gum arabic and 3 parts of molasses in 15 parts of white wine and add, with constant stirring, 6 parts of alcohol in small quantities. Stirring is necessary to prevent the alcohol from precipitating the gum arabic.
Repairing Rubber Goods.
| Sulphur chloride | 18 parts |
| Benzine | 400 parts |
| Carbon disulphide | 300 parts |
This is applied to the edges of the joint by means of a pledget of cotton wrapped on the end of a little stick, and press the jointed parts well together.
One may repair rubber bulbs by the following method: Put some pure gum in three times its bulk of benzine, and cork tightly. Let stand several days. Get some rubber in sheet form; it will be better if it is backed with cloth. To make a patch, dampen some little distance around the hole to be mended with benzine. After a moment, scrape with a knife; repeat the process several times till the site to be patched is thoroughly clean. Cut a patch from sheet of rubber a little larger than the hole to be mended, and apply to its surface several coats of the benzine solution. Then apply a good coat of the solution to both patch and about the hole, and press the patch firmly in place. Again apply the solution to make coating over the patch, and allow to dry till it will not stick to the finger. Do not use for several days.
Cracked rubber goods may be {621} successfully mended in the following manner: Before patching, the cracked surfaces to unite well must be dried, entirely freed from all dirt and dust and greased well, otherwise the surfaces will not combine. In case of a cover, waterproof coat, or rubber boots, etc., take a moderately thick piece of india rubber, suited to size of the object, cut off the edges obliquely with a sharp knife moistened in water, coat the defective places as well as the cut pieces of rubber with oil of turpentine, lay the coated parts together and subject them for 24 hours to a moderate pressure. The mended portions will be just as waterproof as the whole one. Rubber cushions or articles containing air are repaired in a very simple manner, after being cleaned as aforesaid. Then take colophony, dissolve it in alcohol (90 per cent) so that a thick paste forms, smear up the holes, allow all to harden well, and the rubber article, pillow, ball, knee caps, etc., may be used again.
Softening Rubber.
Glycerine has been also recommended, and it may be used with advantage in certain cases. The articles must first be cleaned with the brush and warm water, as above detailed. Heat them in water and rub them with a wad of cotton soaked in glycerine, drawing the wad over them, backwards and forwards. This wad should be wrapped with good stout wire, the ends of which are prolonged, to serve as a handle. Where possible the articles should be stricken with the glycerine inside and out, the article being, naturally, held out of the boiling water, sufficiently, at least, to make bare the part being rubbed at the time. Let rest for 24 hours, and repeat this process. With goods kept in stock, that show a tendency to grow brittle, this treatment should be repeated every 6 months or oftener. Never put away tubing, etc., treated in this manner until every particle of moisture has drained off or evaporated.
Another authority, Zeigler, has the following on this subject: Tubing, bands, and other articles of vulcanized caoutchouc that have become brittle and useless, may be restored to usefulness, indeed, to their pristine elasticity, by treating them as follows: First, put them in a hot aqueous solution of tannic acid and tartar emetic. Next, transfer them to a cold aqueous solution of tannic acid and calcium sulphate. Mix the two solutions and heat to about the boiling point, and transfer the articles to the hot solution. This treatment should be maintained from 1 day to 3 or 4, according to the nature and condition of the articles.
To restore rubber stoppers that have become too hard for usefulness, digest them in 5 per cent soda lye for about 10 days at 86° to 104° F., replacing the lye repeatedly. Next, wash the stoppers in water and scrape off the softened outer layer with a knife, until no more can be removed. The stoppers (which have become quite soft and elastic again) are next rinsed in warm water to remove the caustic soda. If it is desired to trim them it should be done with a knife moistened with soap spirit.
Treatment And Utilization Of Rubber Scraps.
According to another method, the ground scraps are steamed with soda lye under pressure, washed twice thoroughly for the elimination of the lye, and dried in the vacuum. Subsequently mix between cold rollers with 5 to 10 per cent of benzol or mineral oil and steam for some hours under hydraulic pressure at 4 atmospheres. The product thus obtained is rolled in plates and added to the mixture. The finely ground dry waste must not be stored for a long time in large quantities, as it hardens very easily and takes fire.
Old articles of vulcanized rubber are first “devulcanized” by grinding, boiling with caustic soda, and washing thoroughly. After drying, the scraps are heated to 302° F. with linseed oil in a kettle provided with stirring mechanism which is kept in continual motion. When the rubber has dissolved, a quantity of natural or coal-tar asphalt is added, and as soon as the contents of the kettle have become well mixed, the temperature is raised so high that dense fumes begin to rise and air is forced through the mass until a cooled sample shows the desired consistence. This composition being very tough and flexible, forms an excellent covering for electric cables. It finds many other uses, the proportions of rubber, asphalt, and oil being varied in accordance with the purpose for which it is designed.
Vulcanization.
Sulphur chloride is dissolved in carbon disulphide in various proportions, according to the degree of hardness the vulcanized object is to receive; the rubber cast is plunged in the solution and left there from 60 to 70 seconds. On removing, it is placed in a box or space warmed to 80° F., and left long enough for the carbon disulphide to evaporate, or about 90 to 100 seconds. It is then washed in a weakly alkaline bath of water, and dried.
Another method (recommended by Gerard) depends upon letting the rubber lie in a solution of potassium ter or penta sulphide, of 25° Bé., heated to about 280° F. for 3 hours.
Testing Rubber Gloves.
Dissolving Old Rubber.
Rubber Stamps.
RUBBER CEMENTS: See Adhesives.
RUBBER GLOVES, SUBSTITUTE FOR: See Antiseptics.
RUBBER, ITS PROPERTIES AND USES IN WATERPROOFING: See Waterproofing.
RUBBER VARNISHES: See Varnishes.
RUBY SETTINGS: See Watchmakers’ Formulas.
RUOLTZ METAL: See Alloys.
RUM, BAY: See Bay Rum. {623}