PROCESS FOR PREPARING RUBBER-CONTAINING WASTE FOR FURTHER TREATMENT

PROCEDE DE PRETRAITEMENT DE DECHETS RENFERMANT DU CAOUTCHOUC

English Abstract

(57) Abstract
The description relates to a process for preparing rubber-containing waste for further treatment by making use of the brit-
leness of individual components of the waste by cooling the waste, in which the rubber-containing wastes is milled in a worm-
drive press, cooled at least in the press and possibly more finely divided before insertion in the press. Liquid nitrogen or water is
added for cooling purposes. This process uses less power and less coolant like nitrogen or the like is needed.

Claims

5
Claims
1. A process for preparing rubber-containing wastes for
further treatment by exploiting the brittleness of individual waste-components by
cooling the wastes to be prepared,
characterized in that
the rubber-containing wastes are milled in a screw press, are compressed at a pressure
of up to 100 bars, are cooled at least in the screw press and, optionally are pre-com-
minuted before being fed to the screw press.
2. Process defined in claim 1, characterized in that liquid
nitrogen is admixed to the wastes for cooling.
3. Process defined in claim 1, characterized in that water
is admixed to the wastes for cooling.
4. Process defined in one of the above claims, characterized
in that the rubber-containing wastes are introduced as granules into the screw press.
5. Process defined in one of the above claims, characterized
in that the air present between the granulates of the wastes to be fed into the screw
press is removed.

6
6. Process defined in one of the above claims, characterized
in that the constituent parts of the screw press, for instance the case, the screw or the
like are cooled by liquid nitrogen, cold water or the like.
7. Process defined in one of the above claims, characterized
in that the mixture of individual waste-components discharging from the screw press
is subjected to separation such as sifting, magnetic removal of metallic parts or the
like.

Description

~079209
PROCESS FOR PREPARING RUBBER-CONTAINING WASTE
FOR FURTHER TREATMENT
Description
The invention concerns a process for preparing rubber-containing waste
for further treatment.
Rubber-containing wastes, such as old rubber, automobile tires, rein-
forced rubber seals, for instance for windows and doors, in particular for automobiles,
:~ hoses, such as oil-hoses or the like, at present are generally more or less pre-com-
minuted for subsequent further processing and further use. Thereafter the wastes are
further processed in part, the attempt being made to separate the individual com-
. ponents of these waste materials. For example, metals such as iron, steel or iron
wires, plastics, fibers, formed fabrics or the like may be present in addition to the
rubber components.
It is already known to grind or smash rubber-containing wastes in mills,
these wastes having been previously or simultaneously cooled or deep-cooled in order
to exploit the brittleness of the cold rubber and especially to avoid rubber
vulcanization or melting of any plastic. Cooling the wastes also increases the brit-
tleness especially of the rubber, and accordingly, it can be separated more easily from
any metallic components. In particular, the metallic components are released andseparated from the rubber and other components. Depending on the required
temperature, cooling is carried out by adding cold water or liquid nitrogen or the like.
Thereupon the mixture of individual components which are discharged
from the mill can be separated. For example, iron parts may be pulled out using a
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magnet. Fibers or the like may be sucked out where called for. The mixture of
individual components also may be separated by sifting.
However, the mills take up much space at the work site and conse-
quently large quantities of coolants such as liquid nitrogen must be added.
Accordingly, it is the object of the present invention to employ a
process for preparing rubber-containing waste for further treatment, said process being
more energy-conseIving and requiring less coolant such as nitrogen or the like.
This problem is solved by the process defined in claim 1. In this
process preparing rubber-containing wastes for further treatment, the rubber-con-
taining wastes are milled in a screw press, are compressed at a pressure up to 100
bars, and the wastes are cooled at least in said press.
The process of the invention lowers the consumption of liquid nitrogen
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~, or other coolants to well below 50 % of the quantities required in the procedures
known heretofore, such as grinding in mills or the like, because the free volume
between the waste particles in the screw press is much reduced and is decreased even
to a few percent by volume. In particular, the metal components are released from
the other components in the screw press. Moreover, the rubber is gro~md and pressed
so hard that the plastic and/or fiber components separate from it.
In a first embodiment of the process of the invention, liquid nitrogen
is added to the waste for purposes of cooling. The boiling point of nitrogen is -
195.8C. When using liquid nitrogen, the waste material can be cooled down to
about -120C. It is discharged from the screw press at a temperature of about 50C.
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In another embodiment of the process of the invention, relating to
higher acceptable temperatures, for instance when preparing old tires containing
rubber which is already more brittle, cold water can be added for cooling.
The coolant can be admixed with the wastes before same are fed into
the screw press, as a result of which thorough mixing of waste particles and coolant
leads to optimal cooling of the waste particles.
The special cooling furthermore precludes vulcanization or post-vul-
'
canization when grinding the wastes in a screw press.
,. .
Part of the coolant, such as liquid nitrogen or water, evaporates in the
screw press during grinding. Following discharge from the screw press, the residual
liquid is separated from the solid parts.
Preferably, the solid wastes are pre-comminuted before being fed to the
screw press, the rubber-containing wastes being fed to the screw press in, for
example, granulated form. Thereby the wastes are more easily fed into the screw
press, and moreover, the smaller particles can be cooled more rapidly and easily. In
addition, the components issuing from the screw press are more easily separated. The
granulate from the rubber-containing wastes, such as old tires, may evince diameters
of 10 to 40 mm. As a result, the metallic components are present in smaller sizes,
allowing easier separation from the other components by magnetism or sifting.
The pressure exerted on the wastes in the screw press may be up to 100
bars.
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In a preferred embodiment of the process, the air present between the
granulates, which is generally warm environmental air, is removed from the wastes
that will be fed to the screw press. If air were present in the screw press, the
temperature would rise in it excessively, and hence more coolant would have to be
5 admixed.
Because of higher heat in the screw press, liquids such as water or
liquid nitrogen will evaporate. Advantageously, this evaporated liquid shall be
collected and cooled again.
~,' Preferably, the constituent parts of the screw press, for instance the
' 10case, the screw or the like, shall be cooled by liquid nitrogen, cold water or the like
passing through cooling ducts, so that both cooling is improved and the coolant can
be used again without purification being required.
The mixture of the individual waste components discharged from the
screw press is thereafter subjected to separation such as sifting, magnetic removal of
15 metallic parts or the like.
The design of the screw press may be such as ls disclosed for instance
in WO A 83/03,999, German patent documents A 3,714,508; A 3,714,509 and A
3,714,518. This is a screw press with two mutually parallel screws. However, other
scre~ presses also may be used.
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