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Патент USA US2371722

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March 20, 1945.
F. w. WANDERER
2,371,722
PROCESS FOR WASHING AND DRYING COAGULA
OF RUBBER AND SIMILAR MATERIALS
Filed Oct. 24, 1940
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INVENTOR
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ATTORNEY
v2,371,722
Patented Mar. 20, 1945
UNITED STATES PATENT oFricE
raoonss roa WASHING emitomrmo 00-‘
'AGULA or RUBBER AND snvnma MATE
RIALS
Frederick W. Wanderer, Penns Grove, N. J., as
signor to E. I. du Pont de Nemours & Company,
Wilmington, Del., a corporation otDelaware
Application October 24, 1940, Serial No. 362,557
3 Claims.
(or. 18-48)
'
This invention relates to the’ treatment of rub
sure to a coagulum by means of a rotating worm
ber-like materials, and' more particularly, to a
in a suitable housing and forcing it through small
openings. The other objects can be accom
plished by passing a dispersion and a coagulating
process for coagulating, washing, and drying
aqueous dispersions of rubber-like materials
comprising chloroprene.
'
agent into a housing containing a worm and
forcing the coagulum through an opening or
'
Natural rubber is usually converted into the
openings under pressure, and subsequently pass
solid form in which it appears in commerce by
coagulating the latex in the form of sheets or
slabs, passing'these between rollers, sometimes
in the presence of water, to assist in the removal
ing the coagulum through one or more similar
steps. In its preferred form, the invention is
l0 accomplished by passing a dispersion of rubber
of soluble material, and ?nally drying the sheets
like material or natural rubber latex into a hop
or slabs thus obtained. Rubber-like materials
synthetically prepared in aqueous dispersion can
not, in general, be obtained in a satisfactory solid
per, simultaneously passing a coagulating agent
into the hopper, forcing the coagulum through
a truncated cone from the larger end to the
smaller and by means of a rotating worm and out
form by the methods used for natural rubber,
since usually the properties of the rubber-like
of the cone under pressure through a perforated
plate, passing the coagulum through a similar
operation with a washing ?uid, and then passing
material are adversely affected if any substan
tial quantity of the dispersing agent is allowed to
remain and since the methods used by working
the coagulum through one or more similar oper
up natural rubber remove only a part of the wa 20 ations, without additional ?uid, to dry the said
coagulum.
'
ter-soluble material. In the processes now used
In the drawing:
Figure 1 is a vertical section through a suit
from their aqueous dispersions, they must, ac
able coagulating, washing, or drying apparatus;
cordingly, be thoroughly washed with water, al
cohol, or other solventeither by kneading them 25 Figures 2 to 5 are suitable perforated plates
for such apparatus; and
in apparatus in which fresh surfaces are continu
Figure 6 is an elevation of an apparatus for
ally exposed to the action of the solvent or by
the preferred continuous process.
converting them into a form such as thin sheets
Referring now more particularly to the draw
or small crumbs which present a large surface
- ing, Figure 1 is a vertical section through a suit
relative to the volume. In either case, the ma
able coagulating, washing, or drying apparatus.
terial must ?nally be dried and converted into a
In the ?gure, housing I has a hopper .2 and a re
form suitable for storage and shipment. It is
volving worm 3 which is driven by a shaft 4 by
obvious that such processes for converting the
any suitable means (not shown). The coagulum
coagulum into the ?nal dry form require elabo
enters hopper 2 and issqueezed and compressed
rate equipment and considerable attention fromv
by worm 3 and . is extruded, under pressure,
the operating force. Both these factors add con
through extruding head 5 having therein ori?ce
siderably to the cost of production of the syn
6. Head 5 is attached to housing I by screws 1,
thetic rubber and form one of the main reasons
passing through suitable openings 8 and into
why none of these synthetic products is yet as
cheap as natural rubber. Furthermore, it would 40 threaded openings Sin the housing I. The water
which is thereby removed from the coagulum
be noted that, although the present processes for
leaves housing I through openings l0, a small
working up coagulated natural rubber'are consid
amount also escaping through ori?ce 6.
ered satisfactory, they, too, are in need of further
Figure 2 is a planned view of extruding head 5
improvement,
It is an object of this invention to provide a 45 having extruding opening 6 and holes 8‘ for
screws.
‘
simple and e?icient method of removing the
Figure 3 is another type of extruding head I05
water phase from coagula of rubber-like materi
for obtaining the synthetic rubber-like materials
having extruding openings I06 and screw holes
als, especially neoprene (polymeric chloro-2-bu
I08.
,
tadiene-1,3). Another object is to coagulate
such dispersions; wash the coagulum, dry the 50 Figure 4 is a third type of extruding head 305
having extruding openings 306 and screw holes
coagulum, and convert it into a form ‘suitable
for further processing, storage, or shipment.
300.
It has been discovered that the ?rst of these
, objects can be accomplished by applying pres
-
-,
Figure 5 is another type of extruding head
405. having extruding openings 406 and screw
‘ Other objects will appear hereinafter.
55
holes 408.
‘
2,371,722
In order that the invention may be more fully
understood, it will be described with reference to
a dispersion of neoprene, but it is to be under
stood that the invention is not limited thereto
as will become more apparent hereinafter.
|
205 having an increased number of openings 206.
The coagulum, in the form of more numerous
and smaller strings l'l, then passes into hopper
302 of housing 30l where it is again subjected to
the action of a revolving worm and is extruded
through head 305 through still smaller openings
Example I
308. The strings of coagulum 18 contain less '
Chloroprene (100 parts) containing 0.6 'part of
than 5 per cent, water and is very porous in
sulfur and 4 parts of rosin, is emulsi?ed by 'me
structure. The remaining water- quickly evap
chanical agitation in 233 parts of water, con 10 orates on air-drying and the 'coagulum is collect
taining 0.5 part of ammonium persulfate, 0.8
ed in container l9.
part of sodium hydroxide and 0.5 part ’of the
Although the process has been described in
'Sodium salts of the dinaphthyl methane sulfonic
terms of the treatment of a dispersion of poly
acid prepared‘ according to U. S. Patent 1,336,
merized chloroprene in apparatus of speci?c
759. The rosin is neutralized by the sodium hy
form, the invention is, in fact, very much broader.
droxide forming sodium abietate which, along
Thus, it may be applied to the treatment of rub
with the sulfonic acids mentioned above, acts as
the emulsifying and dispersing agent. The dis
persion is kept at 40° C. inv a suitable vessel,
ber or any rubber-like material in the form of
a wet coagulum. It is clear from the above dis
closure that the invention has to do with unvul
which can be externally cooled or heated, until 20 canized rubber and rubber-like materials. These
the polymerization is substantially complete, as
may be generically called vulcanizable plastic
shown by the density of the dispersion which is
materials. In addition to natural rubber and
~ approximately a linear function of the propor
rubber-like ‘polymers of chloroprene, it may be
tion of chloroprene which is polymerized. The
applied to other types of so-called synthetic rub
dispersion is then treated with 2.5 parts of tetra 25 bers such as the polymers of butadiene and ho
ethyl thiuram disul?de dispersed in 10 parts of
mologous dienes prepared with or without the
the'above emulsifying solution, The entire proc
use of other polymerizable substances, such as
ess up to this point may conveniently be car
ried out in a continuous manner as described in
styrene, methyl methacrylate, and acrylic nitrile.
It may also be applied to the products obtained
the application of Calcott and Starkweather, 30 from the reaction of organic dichlorides, such as
Serial No. 308,386, ?led December 9, 1939.
ethylene dichloride, and beta, beta-dichloro-di
The dispersion so prepared, which contains
ethyl ether with metallic polysul?des. 'The type
about 30 per cent of neoprene, is processed in an
of dispersing agent used in the preparation of the
apparatus illustrated in Figure 6. This ?gure
dispersions of these rubber-like materials is not
shows an apparatus consisting of 4 successive
critical to the present invention. The coagulum
units. In the ?gure, similar parts in the various
used in the invention may be prepared by any of
units are indicated by numerals which differ
the appropriate methods known in the art such
from each other by 100, and‘ any part not specifi
as the addition of salts, such, for example, as
cally described hereinafter by number will be
aluminum sulfate, magnesium sulfate, etc., acids,
understood to be the same as the corresponding
alcohols, and ketones, or by freezing as described
part of the first unit of the apparatus. Refer
‘in U. S. Patent No. 2,187,146. The coagulum may
ring more particularly to Figure 6, the dispersion '
be introduced into the apparatus in the form of
of neoprene enters housing I through hopper 2
separate pieces or in the form of a continuous
from conduit ll. Simultaneously, Vs of 7 its
sheet or strip such as, for example, that formed
weight of a 3 per cent aqueous solution of alu 45 by the operation of the preferred form of the
minum sulfate is passed into hopper 2 from con
above patent. It is often advantageous tocarry
duit l2. Coagulation occurs in the hopper. The
out the coagulation within the hopper of the
coagulum descends upon revolving worm 3 which
extrusion apparatus as in the above specii?c example.
forces it through housing I ‘and out of extruding
50
head 5. The size of the opening 6 in extrusion
The apparatus described above may also be
head 5 is of such size that the revolving worm
varied, for example, as to the size, shape, and
builds up pressure within the housing and'the
‘pitch of the worm, and the volume and shape of
coagulum is thus subjected to a combined pres-1
the chamber between it and the plate through
sure and tearing action which removes much of
which a material is extruded. It is preferred,
the aqueous phase and water-soluble materials. 65 however, that the chamber in which the worm
This aqueous phase escapes through perforations
rotates and the worm itself should be of conical
l0 and also, to a small extent, through opening
rather than cylindrical form with the outlet at
0 through extrusion head 5, the water escaping
the narrow end. The number of holes through
through opening 0 being carried off by drain l3.
which material is extruded andalso their cross
The extruded coagulum l4 containing about 50
section may be varied. Thus, in the first stage,
per cent water passes into second hopper I02.
when the material has only slight plasticity, a
Simultaneously, a stream of fresh water enters
large hole is used, whileseveral smaller holes are
through this hopper through conduit IS.‘ The _ used as the material becomes more plastic in the
coagulum is thus washed as it passes through
later stage. It is always preferred, however, that
hopper I02 and into housing IN. V The coagulum 65 the size and number of the openings are small
is propelled through housing l0l by-a revolving
enough to cause the exertion of considerable pres
worm which subjects it to pressure and tearing
sure by the worm upon the material being procaction and the coagulum comes out of extrusion
essed. The form of the hole vneed not be cir
head I05 puri?ed and containing less than 20 per
cular, and, in fact, it is often desirable in the
cent water. Extrusion head I05 has therein sev 70 case of more plastic materials to extrude in the
eral, openings I06 and the coagulum in the form
form of flat ribbons or other shapes offering a
of several strings l6 passes into hopper 202 of
large surface for subsequent drying.
housing 20l where it is subjected to the action of
Instead of a short air drying followed by col
a revolving worm as before. The coagulum is
lecting the coagulum. as shown in Figure 6, the
extruded from this unit through extrusion head 75 coagulum. as it comes from the last unit of the
'
‘
,
'
3
2,871,722
drying apparatus in the form of porous strings
having a small amount of moisture, may be
passed upon a moving belt through a drying tun
therefore, it is not intended to be limited except‘
as indicated in the appended claims.
nel counter-current to a stream of warm air, and
then collected. When so treated, less than 0.37
per cent of moisture remains in the coagulum.
The conditions under which the apparatus is
operated may also be varied, These variables in
clude the rate of rotation of the worm, the rate
>
I claim:
1. The process which comprises passing-an
aqueous dispersion of a__vulcaniz_able" material,
comprised essentially of chloroprene polymer
into a path of decreasing cross-section, simulta
, neously subjecting the dispersion to coagulation
conditions, forcing the mass-'along'saidpathiof '
at which the material is supplied to the ma 10 decreasing cross-section, subjecting the massive
tearing action, and withdrawing the, aqueous_
chine and the temperature. Because of the work
done upon the material, the temperature of the ' phase therefrom.
' 2. The process of washing and
extruded material is higher than that of the ma
coagulum, obtained by coagulating-an. aqueous
terial introduced. This is generally‘ advanta
dispersion of a vulcanizable material comprised
geous where it is desired to remove part of the
essentially of chloroprene polymer whichcom
water content by evaporation, but, if the mate
prises forcing the coagulum and fresh wash wa
rial be processed is sensitive to heat, this heating
may be reduced by jacketing the apparatus with
ter to traverse a path'of decreasing cross-section‘
a cooling liquid or by operating at a slower speed.
whereby the coagulum becomes more and- more
The principle of the present invention is 20 compact while simultaneouslylsubiecting the
coagulum to tearing action whereby the aqueous ‘
roughly similar to that by which natural latex
coagulum is usually processed in that the coagu
phase is released from the coagulum, simulta-‘'
lum is dehydrated by pressure. The process, how
neously drawing off the wash w'ater andv exuded
aqueous phase, and then forcing the coagulum
ever, di?ers by compressing the material by a
worm rather than by rolls and by keeping it 25 simultaneously through .a plurality of ori?ces,
compressed for a much longer time with the
said orifices having a total cross-section area less
result that the removal of the aqueous phase (and,
than the cross-section areaof-jthe'path‘just pre
ceding them.
'
' I
hence, the removal of water-soluble materials)
3. The process which comprises passing an
is much more e?icient and complete. Moreover,
the action of the worm breaks up the cells of 30 aqueous dispersion of a vulcanizable material
comprised essentially of chloroprene' polymer into
the coagulum more completely, thus aiding in
releasing imprisoned water. Another unexpected
a path of decreasing cross-section, simultaneous
ly subjecting the dispersion to coagulation condi
in nature which gives it improved air drying for
tions, forcing the mass along said path‘oi’ de
the small amount of residual moisture and also 35 creasing cross-section, subjecting the mass to,
tearing action, and withdrawing the aqueous
facilitates compounding operations. Further—
phase therefrom, then forcing the coagulum and
more, the present invention has the further ad
vantages over the prior art that the apparatus
fresh wash water to traverse-a second path of
decreasing cross-section whereby the coagulum
required is much more compact and is much bet
advantage is that the extruded product is porous ‘
ter adapted for continuous and automatic proc 40 becomes more and more compact while simulta
essing of the material.
The process is especially desirable with
neoprene because the action of the revolving
worms unexpectedly plasticizes this material to
a considerable extent and reduces the amount of 45
, milling necessary in subsequent compounding op
erations.
»
It is apparent that many widely di?erent em
bodiments of this invention may be made without
departing from the spirit and scope thereof, and,
neously subjecting the coagulum to tearing action
whereby the aqueous. phase is released from the
coagulum, simultaneously drawing-oi! the wash
water and exuded aqueous phase, and then forc
ing the coagulum simultaneously through a plu
rality of ori?ces, said ori?ces having a total
cross-section area less than the cross-section area
of the path just preceding them.
FREDERICK W. WANDmER.
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