In order to assure an adequate cross-sectional constriction, as shown in FIG. 3, relatively small conical caps 4
are positioned in the funnel apertures so that the apex of
the cone of the cap 4 is directed opposite to the direction
of movement of the granulate. With this construction, the
constriction 3" is annular. These conical caps 4 are secured to suitable brackets (not shnwn) so that they can
be swung out or removed. In this arrangement, operating
personnel may pass through the funnel aperture for repair work. Such a construction of the extraction tube l
for the extraction of poly-e-caprolactam is shown in FIG.
3. The extraction tube ll contains funnel-shaped installations 2 of particularly restricted height and with corresponding removable conical caps 4, so that four
annular flow constrictions 3” are provided. The extraction tube according to the invention can be provided in a known manner with an outer insulating jacket and/ or heating jacket
(not shown). The operation of the extraction tube is best
explained by describing a specific example of execution.
Through a vibrating chute 5, about 15 kg. of granulate per
hour was introduced into the top of the tube l. The inlet
temperature of the granulate was 40° C. and the concentration of the granulate in the caprolactam was 10% by
weight. The granulate or cuttings remained in the tube 1
for about 20 hours. Through a pipe line 6 water was fed into the tube ]l at a temperature of about 110° C. The
throughput of water was 15 kg./hr. An overflow 7 directed
the water, charged with 10% by weight of caprolactam,
out of the tube at a temperature of about 90° C. The cuttings were discharged after completion of the extraction
with the aid of a cell wheel sluice 8 and were dried in a
conventional manner. The discharge temperature of the
granulate was 100° C. The ?nal concentration of monomers in the granulate amounted to 0.5% by weight. At
this concentration, threads with good properties can be
readily made.
A conventional extraction tube Without the constrictions of the invention yielded, with operating conditions
otherwise the same, a granulate with a monomer content
1% to 1.5 % by weight. This amount of monomers is above
the concentration required for the production of high
quality threads.
I claim:
l. In an upright extraction tube having a single water
solvent inlet at its lower end, a single solids outlet at its
lower end, a single solution outlet at its upper end, an improved process for using water solvent to extract monomers and oligomers from a mixture of said monomers and
oligomers with a highly polymerized, granulated poly-e caprolactam comprising the steps of:
introducing said mixture only at the top of said up
right extraction tube, said mixture providing a down
ward flow directed in the vertical, downward direction within said tube;
introducing said solvent only at the opposite end of said
upright extraction tube to provide an upward flow
of solvent in said tube, said downward flow and said
upward flow giving rise to currents of counter?ow of
said solvent in the downward direction;
restricting all of said flows at a plurality of positions
along said vertical tube such that the rate of said up
ward flow of said solvent is at least equal to the rate
of said counterflow currents of said solvent in the
downward direction at each and every restricted position in said tube;
drawing oil solvent saturated with said monomers and
oligomers only at the top of said tube; and
drawing off granulated poly-e-caprolactarn having the
monomers and oligomers removed only from the bot
tom of said tube.
In order to assure an adequate cross-sectional constriction, as shown in FIG. 3, relatively small conical caps 4 are positioned in the funnel apertures so that the apex of the cone of the cap 4 is directed opposite to the direction of movement of the granulate. With this construction, the constriction 3" is annular. These conical caps 4 are secured to suitable brackets (not shnwn) so that they can be swung out or removed. In this arrangement, operating personnel may pass through the funnel aperture for repair work. Such a construction of the extraction tube l for the extraction of poly-e-caprolactam is shown in FIG. 3. The extraction tube ll contains funnel-shaped installations 2 of particularly restricted height and with corresponding removable conical caps 4, so that four annular flow constrictions 3” are provided. The extraction tube according to the invention can be provided in a known manner with an outer insulating jacket and/ or heating jacket (not shown). The operation of the extraction tube is best explained by describing a specific example of execution. Through a vibrating chute 5, about 15 kg. of granulate per hour was introduced into the top of the tube l. The inlet temperature of the granulate was 40° C. and the concentration of the granulate in the caprolactam was 10% by weight. The granulate or cuttings remained in the tube 1 for about 20 hours. Through a pipe line 6 water was fed into the tube ]l at a temperature of about 110° C. The throughput of water was 15 kg./hr. An overflow 7 directed the water, charged with 10% by weight of caprolactam, out of the tube at a temperature of about 90° C. The cuttings were discharged after completion of the extraction with the aid of a cell wheel sluice 8 and were dried in a conventional manner. The discharge temperature of the granulate was 100° C. The ?nal concentration of monomers in the granulate amounted to 0.5% by weight. At this concentration, threads with good properties can be readily made. A conventional extraction tube Without the constrictions of the invention yielded, with operating conditions otherwise the same, a granulate with a monomer content 1% to 1.5 % by weight. This amount of monomers is above the concentration required for the production of high quality threads. I claim: l. In an upright extraction tube having a single water solvent inlet at its lower end, a single solids outlet at its lower end, a single solution outlet at its upper end, an improved process for using water solvent to extract monomers and oligomers from a mixture of said monomers and oligomers with a highly polymerized, granulated poly-e caprolactam comprising the steps of: introducing said mixture only at the top of said up right extraction tube, said mixture providing a down ward flow directed in the vertical, downward direction within said tube; introducing said solvent only at the opposite end of said upright extraction tube to provide an upward flow of solvent in said tube, said downward flow and said upward flow giving rise to currents of counter?ow of said solvent in the downward direction;restricting all of said flows at a plurality of positions along said vertical tube such that the rate of said up ward flow of said solvent is at least equal to the rate of said counterflow currents of said solvent in the downward direction at each and every restricted position in said tube; drawing oil solvent saturated with said monomers and oligomers only at the top of said tube; and drawing off granulated poly-e-caprolactarn having the monomers and oligomers removed only from the bot tom of said tube.
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