80 



THE INDIA RUBBER WORLD 



NOVEMBBB 1, 1920 



The Manufacture of Rubber Plasters 



IT will doubtless surprise many to know that certain very im- 

 portant sections of the rubber industry have never been af- 

 fected by the discovery of vulcanization. That Goodyear, 

 Hancock, Parks or Peachey and their discoveries interest them 

 not at all. They do not know sulphur, sulphuret, sulphur chloride, 

 accelerators, vulcanizers, steam presses nor dry heaters. Never- 

 theless, their rubber goods are found in the open market the 

 world over, indeed are accepted as necessities everywhere. 



l»>g>» K 



Calendering and Reeling Porous Plaster Stock 



A Little Known Industry 



fluid. The heat is then withdrawn and the mass stirred while 

 cooling until it becomes tirm. 



The lead oleate is prepared by taking 10 volumes of granular 

 dried soap, dissolving it in 35 volumes of hot distilled water and 

 straining the solution. To it is then added six volumes of lead 

 acetate dissolved in 25 parts of hot distilled water and afterwar 1 

 filtered. The solution is stirred thoroughly until a precipitate 

 (lead oleate) has been formed. The water is drawn off and 

 the lead oleate precipitate washed well with hot water and 

 thoroughly kneaded on a warm tile to free it from water. The 

 mass is then rolled Hat, wrapped in waxed paper and kept in 

 sealed vessels until used in combination with the rubber-petrol- 

 atum vehicle. 



The melted rubber plaster was never manufactured to any 

 extent in the United .States. It had, however, quite a vogue in 

 Europe. In manufacturing it, the only rubber machinery used was 

 a washer and dryer, a kettle for melting the rubber, mixing slabs, 

 for the other ingredients, and a spreader for applying the coat- 

 ing. The perforating, cutting, backing and packing was all done 

 by hand. 



PLASTER MILL EQUIPMENT 



In the United States, however, where mustard, belladonna, 

 capsicum, menthol, and various other plasters are popular, fully 

 equipped rubber mills exist, having regulation washers, dry rooms, 

 compounding rooms, mixers, calenders and spreaders. Nor do 

 they melt the rubber. Instead, they so compound it that it re- 

 mains adhesive for years. 



The lines referred to are pharmaceutical preparations known 

 as adhesive plasters. The plaster business operates fully equipped 

 factories, employs standard washers, mixers, calenders and 

 spreaders like any other rubber mill. There the Hkeness ends 

 and special machines, adapted only for plaster work, are used. 



As in all lines of rubber work, the manufacture of plasters en- 

 tails individual problems. Although thousands of tons of rub- 

 ber have been employed, only the sweet smelling or non-odorous 

 types are usable. Hence Para wild or plantation is the favorite. 

 In preparing the plaster compound, not only must it be non- 

 odorous, but a peculiar degree of adhesiveness is demanded. It 

 must be sticky with the characteristic of remaining so and never 

 drying out. Furthermore, the compound must contain drugs and 

 medicaments in great variety and in definitely ascertained pro- 

 portions. 



MELTED RUBBER 



So far nothing is more permanently adhesive than melted rub- 

 ber. It is therefore not strange that in early plaster preparations 

 it was used and most successfully. So sticky is it that cloth 

 covered with thin films, although exposed to the sun for months, 

 does not dry out at all. 



The "lead plaster." in which melted rubber is used, occupies 

 an important place in the pharmacopceia of the leading nations 

 In the process of compounding it the rubl:)er is dissolved in a 

 fixed solvent, such as petrolatum, and then mixed with lead 

 acetate (prepared as lead oleate)' and spread upon fabric. The 

 ingredients are used in the following proportions: 



Rubber 2 volumes 



Petrolaium 2 volumes 



Lead oleate 96 volumes 



The rubber is first melted at a temperature of 302 degrees F., 

 then the petrolatum is added and the same temperature main- 

 tained until the ingredients form a plastic mass. The lead 

 oleate is next added and the heat kept up until the mass is quite 



Automatic Perforator for Porous Plasters 



What is known as French plaster, consists simply of Par4 

 rubber and essence of petroleum, with no medicament. This 

 same compound serves as a base for mustard plasters, the mus- 



