US2296275A - Caoutchouc regeneration - Google Patents

Description

Patented Sept. 22, 1942 CAQUTCHOUC REGENERATION Henry Ghez and Oscar Ghez, Paris, France, as-

Isignors to Sudamericana de Patentes :SA, .Banama City, Panama, a corporation of Pan- No Drawing. Application April 2 5, 1939, Serial No. 210,927

2 Claims.

The present invention has for its object the reclamation of vulcanized caoutchouc without previous crushing, in an open receptacle without steam pressure or pressure of other gases, without alkali and only by means of the heat action, which is transmitted by a body in state of fusion or semi-fusion, usually in rotative or alternative movement, this body being preferably a hydrocarbon, the boiling point of which is more elevated than the temperature required for the regeneration of the waste of caoutchouc provided with web or tissue. The depolymerization and plastification of the vulcanized caoutchouc by the heat transmitted by this fluid body is perfect, since it is regular and uniform and avoids the use of long and difiicult operations as in the processes with alkali for a time varying between to 24 hours and at a pressure of 10 to atmospheres, with a series of washings, dryings, neutralizations etc.

In the reclamation process by superheated steam this latter plays the role as transmission agent of the heat. But the superheated steam and the air as well as the gas are bad heat conductors. Furthermore, in this process the steam must be maintained in an intense motion, in order that the heat be transmitted in a uniform manner through the mass of the waste caoutchouc to be regenerated. The bad transmission of the heat has for its consequence that the depolymerization of the old caoutchouc lasts too long and reduces notably the economic character of the operation.

In the reclamation process by means of saturated steam it is well known that the same transmits the heat much better than the superheated steam, but for this process there is required a high pressure apparatus built to withstand pressures up to 30 to 50 atm., which is expensive and cumbersome.

The present invention consists in a reclama-' tion process which does not require either the presence of water or of steam or air or other gases. The present invention consists in the use of a plastifying means which in the liquid state owing to its fluidity surrounds the pieces of vulcanized c'aoutchouc from all sides and brings them to the temperature required for the depolymerization up to the interior of their mass without swelling them up and without bringing same into solution. According to the invention this plastifying means which surrounds the scraps of vulcanized caoutchouc places itself in a fine layer on their surface without penetrating substantially into the interior of the mass and, when the outside of the bath is cooled, it protects the wow tchouc from all air oxidation in an almost immediate manner, whilst in all the other processes the treated caoutchouc must be extracted from the receptacles at a low temperature in order to avoid the oxidation and infiammability, which diminishes the production of the installations and consequently augments the price of the reclaimed product.

On the other hand it is known that the presence of this protective layer of an appropriate plastifying means on the outside permits of a good curing of the treated material and its transport at great distance for the rafilnation. This fine layer of plastifying means may remain for an indefinite time in the reclaimed product, since it is usual to employ even larger proportions in the manufacture of mixtures (15 to 30%) Besides this process produces reclaimed rubber having better mechanical qualities and a better lengthening property.

The process according to the invention is very economic and less expensive than the manufacture of ordinary plastic means, the preparation of which requires from 15 to 30% of oil, a good previous grinding and a prolonged heating under pressure in a steam bath and its drying.

Amongst the plastifying means it has been established that the best heat transmission agents are the bitumens and more particularly mineral rubber.

Example of execution The caoutchouc to be reclaimed, for instance large pieces of pneumatic tires, air bags etc., is

introduced in a receptacle of sheet iron or of a in and heated during 30 to minutes, maintaining a uniform temperature varying from to 225 C., and moving the receptacle as well as the surrounding liquid. When the receptacle is drawn off from the bath it is allowed to drain and cooled. The cooling may be accelerated by immersing the pieces of caoutchouc in cold water or in another liquid. This cooling has the effect of solidifying the mineral rubber present in a fine layer thereby protecting the treated caoutchouc against any oxidation.

Owing to the direct ideal transmisison of the heat from the mineral rubber to the old rubber, the duration of the reclamation according to the invention requires merely a fraction of the time necessary for the reclamation according to the usual processes. The heating of the mineral rubber is only required once, at the first charge and the mineral rubber always maintains the same temperature.

Furthermore, since the introduction in the receptacle and the removing therefrom requires only a few minutes, and since the cooling in the receptacle, which according to the other processes lasts for hours and hours is eliminated, an increase of production is made possible.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

1. In the reclaiming of vulcanized rubber, the process which comprises introducing vulcanized rubber scrap into a liquid bath of bituminous material, heating the whole to a uniform temperature within the range of about 180 to 225 C. and continuing the heating for a period of from about to minutes, whereby depolymerization of the rubber to such an extent that it can be readily plastified by milling, is produced without the production of any substantial swelling or dissolving of the rubber, and then removing said rubber from the bath.

2. In the reclaiming of vulcanized rubber, the process which comprises introducing vulcanized rubber scrap into a liquid bath of mineral rubber, heating the whole to a uniform temperature within the range of about to 225 C. and continuing the heating for a period of about 30 to 60 minutes, whereby depolymerization of the rubber to such an extent that it can be readily plastified by milling, is produced without the production of any substantial swelling or dissolving of the rubber, and then removing said rubber from the bath.

HENRY GHEZ. OSCAR GHEZ.