USRE756E - Improvement in cleansing caoutchouc - Google Patents

Description

tor the manufacture of line. goods.

' UNITED STATES PATENT OFFICE.

AUs'riN G. DAY, or SEYMOUR, CONNEo'ricUT.

` IMPROVEMENT' INoLEANslNG CAOUTCHOUC.

Specification forming part of Letters atent-No. 15,067`dsted June 10, 1856; Reissue No. 766, dntcd J nly l2, 1859.

' lowing successive operations: First, it takesthe crude caoutchouc after it has been subjected to the tearing operation of toothed rollers-such as that described by the Sault patent-and sub' ts it to theaction of causticor carbonated a kaline or other equivalent solution, ,that the liquid may penetrate the pores of the caoutchoucand be instrumental inre-l moving foreign matters therefrom, as set forth second, the process thus stated is finished by' removing the alkaline liquor by washing and then runnin g the caoutchouc between ltoot-hed rollers.' 'l f 1 f Allkiudsof crude commercial caoutchouc contain more or less impurities, consisting Yof wateryl sap, saud,clay, bark,sticks, and other foreign bodies, varying from ten to fifty per cent. of the lnass.- I have ascertained that .these impurities interfere with the success of the manufacture about in the proportion in which they ure retained in the 'gum while it is being carried through the process of 4manufacture. They irst interfere with the vulcanizingprocessby holding vapor for along time', which finally escapes, leaving a. blistcred surface and porous structure, and thus cause varieties of damaged goods. The rubber known as Fine Par"contains the least impurities, (chiefly dried sap and bark,) and previous to myimprovements was the only article used The East India rubber is a very complex product. 1t is the product ot' many species of trees and vines, having intermiugled with it the usual impurities. west coast of Africa, contains still greater impurities, and is'oflen injured b'y contact with palm-oil during importation. The Mexican The African, from the north and I rubber and thatfrom the west coast of South America are compact, hard, and black, and require the application of-great mechanical power for their comminution.

All the crude gums in the. market, except that first named,from the impurities they coutain, are almost valueless for tine goods .un-

til subjected to a process of purification. The

cleaning process has more than doubled the market value of inferior gums and made market for millions ot` pounds annually which could not have been'. sold at all Without' it. Having prepared the crude gum .by passing it between toothed rollers arranged with the well-known slipping movement, loosening and partly removing the sand, bark, and clay, those ,foreign bodies which still adhereas 'bai-k, sticks, &c.-'are removed by water-soaking with alkaline or otherequivalcnt solution, which will increase its specific gravity above that of water, and thus cause the impurities"V to sink to the bottom of the cistern of water in which the operation is performed; for while the bark, sticks, and gum float together on' the water it is not easy to separate the impurities from the gum, as both floattogether;

but by making the impurities, heavier than the'water the former two are easily separated',- and are not .liable to come in contact' again, as the rubber oats and the impurities sink. Toeil'ect this result, after the gum has been comminuted, asiudicnted above, itis immersed in a solution of an alkaline or other equivalent liquid to'render it water-soaked, and thus increase its specific gravity. It is lthen washed in water to separate the alkaline or equivalent liquid, again passed through between the toothed rollers for removing the remaining' impurities so fur as practicable byy these means; but it was ascertained by inspection that there were yet in the gum cavities filled with dried sap which had not been reached by the process above described. I then caused the liquid used for saturating the impurities to be forced into the partially ruptured cavities by subjecting the materialprepared as beforedescribed to a vacuum process in au iron cylinder, hereinafter to be described, in which, the air beingzexhausted, the liquor in which it is immersed, after restoring the pressure of the air, enters the cavities-mul,

acts upon the impurities, so that they may easily be removed by the subsequent part of the process.

In cleaning very hard and tough rubbersuch as the Mexican -itis often found that the restored pressure of the air is not enough to force the liquor into the cavities partially rup tured to the desired extent. In such case additional pressure is applied,either by acolumn of liquid or by a force-pump, with a force of twenty to thirty-vepound's to the inch. The alkaline or equivalent liquor is allowed to remain in the iron vessel fifteen to sixty minutes, when it will be found that the liquid has sufciently penetrated the pores of the gum to act upon its impurities, neutralizing pvegetable acids, dissolving decayed matter, and waters'oaking the bark,- sticks, Src., so that water and the toothed rollers easily remove all the foreign matter left in the gum after the prei vious treatment. The 'alkaline liquor is used cold, and the strength may'varyfrom 18o to 23 of Baum. After the liquor from the iron cylinder is run otl into suitable vessels the gum is transferred to a cistern of water `and soaked and washed, by which more foreign matter separates and sinks to the bottom. The gum is again transferred tothe toothed rollers, (arranged now with different speed from that used in the first use of these rollers by a change in4 .thegearg and the same is run intosuitable sheets for drying and seasoning.

The value of thorough cleaning is not `yet fully appreciated by the manufacturers. Vulcanizing is adelicate chemical process, depending for its success on the previous preparation of the materials which are to be decomposed and made to enter into new relations. The caoutchouc is a complicated hydrocarbon, of eight equivalents of carbon and seven of hydrogen, according to Tayen, which, in the .presence of sulphur and in'. a close chamber with a temperatureof 3000 or thereabout of Fahrenheits thermometer, gives ou .in large quantities sulphureted hydrogen land bisulphuret of carbon, `and leaving a triple Vcompound of carbon, hydrogen', and sulphur, vary-A inginV character according to the heat to which it has been exposed and the time elapsed dur- "ingthe exposure. The character of the process implies the necessity of purifying the materials before it be commenced, and the numerous failures in vulcanizing by manufacturers who have heretofore paid no attention Vto prepare the gum go to show that the preparation is lof vital importance.

As before stated, for breaking down the crude caoutchouc I have adopted the breakin g-rollers invented by Thomas Sault. I also use the same rollers as geared for sheeting purposes, and these I refer towhen I speak'of toothed rollersswith a slipping movement used in my cleaning process. The exhaustingr apparatus: This apparatus consists of a horizontal iron cylinder,arran ged with an iron tank above it and another of equal capacity beneathit.

In the accompanying drawing, A represents the cylinder, made of boiler-iron, and of suitable size to contain the quantity of rubber or other gum to be worked at a single operation, and of such strength as to bear with safety the pressure to which' it is to be subjected when exhausted by means of the pump. The cylinder is supported in the horizontal position on the 'floor T, from which it is raised about one foot by means of the locks U. A drain-pipe, o, having a strainer at W, leads through the floor T to the vat or cistern N. Above the cylinder, and supported upon the platform G, are two cisterns, E and F, connected with each other by the horizontal pipe J. From these cisterns the pipes H and I lead to cylinder A.' An air-pump at L, of

suitable size, isconnected with the top of the cylinder A by' means of pipe K. In the vat or ciste'ru.N,` beneath the floor, as already shown, there is a pump, 1", forA which the .supplyLpipe Q furnishes the means of discharging the alkaline liquor from N to F and E. In the vat or cisterri N .is put theV alkaline liquor, which consists of caustic or carbonated potash or 'soda' or 'other equivalent liquid or solution, in which the sticks and bark soon are water-soaked, and become heavier .than their bulk of water, so thatin the washingoperation these foreign bodies sink tothe bottom and are easily separated from the'gum.

The liquor is then pumped u p into vats F and .E first closing stop-cocks X and Y. The

crude gum is now placed in the cylinder A in suitable quantities for convenient working. Thus a cylinder seven feet'long by forty-two inches diameter, internal measurement, will work from one thousand two hundred pounds to one thousand tive hundred pounds at a charge. The movable head Q of the cylinder is putin its place, and secured by means of the keys and joint-bolts R. The air-pump at L is thenput in operation, and a vacuum produced in the cylinder, by means of which the alkaline liquid finds a. ready. access into the pores and interstices. of the rubber, and is thus brought fully in contact with the bark and sticks and other l-foreigncbodies contained therein, charging them with` the liquid, and thus rendering them heavie/ than their own bulk of water, when thestop-cocks X and Y are opened and the liquor from F and E descends through pipes H and I into cylinder A till it is filled; but in order more completely to lill the ,gumv with the alkali, a forcing-pump (not shown in the drawing) is attached to the cylinder A, by means of which additional liquor is forced into the cylinder until the internal pressure is increased to somewhat more than two atmospheres. I allow the liquid to remain on the caoutchouc until the woody and porous substances are'full y impregnated. Experience has taught me that fteen to twenty minu'tes is the best time to keep the liquor iu contact with the rubber. As soonas this end is attained, pipe o is opened and the liquor descends into cistern N, while the gum is removed to the sheeting-rollers,

(toothed rollers,) abundantly supplied with water, by which it isconvertedinto sheets, read)r for the drying-room. These rollers are prepared with a. slipping movement, and so geared as to put` the rubber into sheets of a kind of corrugated surface favorable todrying and seasoning.

Having now fully described the nature of the invention and the manner of' conducting the processof cleaning caoutchouc and 'other vulcanizable gums and removing from them all foreign matters, and shown how it may be carried out in practice, what 1 claim as my invent-ion, and desire to secure by Letters Patent 1n the present application, is-

.lhe use 0f alkali, or its equivalent, for sepa-v rating bark, sticks, and other foreign bodies from crude caoutchouc and other vulcanizable gums to prepare theln for manufacturing.

AUSTIN G. DAY.y Witnesses: n

SAML. L. BRINSEN, THOMAS SAULT.

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