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Патент USA US2369718

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Patented Febfzo; 1945
I‘ ' ‘ eosbmemoms
7 Francis B. “Ci-amen}.- Y-Waynesb'oro, Vag-asslg'nor ‘to.
E. I. du'Pont deiNemours &"Company,’Wilming-- : .
ton, Del.,'1‘a'-cornoration of ‘Delaware . ,1
‘ '(‘Syerl'al
w‘ , ,1 ' .
t "
. ,g-iSgClaims; (01. 2605-218)
,7 ,v'l‘liisrinveiitioh"relates-‘to me dehydration‘of
, withwater,'dissolve,outfa portion once ‘caustic
' contentof, the viscose solution treated.‘
The most 'e?ective'1 water-miscible organic liq
' viscose. to produce solutions . of ‘high cellulose and‘
I higlifcausti'c' content.
1' For ‘cértainupurposes, a
" losecqnteetis
v‘ n
I desired.
‘ I
I vfvtiscose
making ~
ui‘ds :have been‘ found to be miscible withjthe
v viscose‘ solution when added thereto in ‘small
amountsjorinstance in amounts less" than'20_% -
. heavy-walled tubing, heavy-gauge v?lmIor,‘heavy _
by Weight.‘ ‘However, when used in larger
amounts, for example 550% or moreby weight, the
‘more re?ective? dehydrating reagents of this ‘in
inono?ls of regenerated‘ cellulose-by theviscose .
Hprocess. When‘ordinary'viscose solutions are".
used for producing such‘products, the high per-Uv
vention are" substantially completely immiscible
centageo'igwater that must be removed during co
agulation and/or regeneration causes excessive -,
shrinkage and requires vespecially‘ long‘coagu
lating and regenerating treatments to insure com
and it is thus possible to obtain a sharp separation
of the aqueous organic liquid layer from the vis
cose whichyretains little or none of the organic
liquid. It is indeed surprising that substantially,
_, plete reaction throughout the relatively thick
Attempts to produce viscose. having- 15
, complete removal of the organic liquid from the '
. structure.
a-vhigh concentration ofcellulose, such as 15%
or more, by direct, solution of cellulose xanthate
.have never been practical because the, dispersion
{obtained couldnot be ?ltered or extruded in the
viscose is possible in view of the fact that when
'7 smaller amounts are used, i. e. less than 20%, ,
no separation‘ of the organic liquid _from the vis
cose takes place. Accordingly, it is generally de
sirable to mix with the viscose the caustic-in
soluble, water-miscible organic ‘liquid to the ex
formv of. usable products. Proposals havelalso
been made "before (to. dehydrate normal viscose:
solutions, but either the‘ economics of the process _ . tent of at least 40% ‘by-.weight of the original
viscose solution and proportions in 'the range '
-or the quality of the resulting viscose solutions
obtained-thereby have been such as to o?er no 25 of from 50% to 100% by weight of the original }
viscose solution prior to decantation are pre
commercial utility.
Therefore, the principal object'of the inven
This process may be carried out at room tem
' ' tion is to provide a method for removing sub
perature or below and, therefore, the normal
stantial quantities of waterfrom viscose solue
rate of the‘viscose' need not be-altered.
tions without deleteriously affecting the cellu-l 30
' lose xanthate contained therein and while main-1 ' However, if desired, the processmay be'carried
out at above room temperature.
taining a. clear, ?lterable solution suitable for
The followingfspeci?c examples are given to
-conversion‘ into regenerated cellulose products.
‘Other objects will be apparent'from the discusé
sion that follows.
I “The above stated object isyreialized' by "my'
‘invention which comprises mixing with normal‘
viscose a water-miscible organic liquid in su?i-‘
cient quantity to effect separation of‘ a, layer come
further illustrate the invention. Parts are by
weight unless otherwise indicated.
' Example I
- To 30 parts of viscose containing 7% cellulose
and 6%.NaOH and ripened, to a‘ salt index'of
'aboutv5.0 are added, with stirring, 20 parts of }
prised of the organic liquid and water, which is‘ , sov (pyridine. The resulting mix" was allowed to settle
easily removed, such as by decantation. , The
and separated into two layers‘. The supernatant
steps of mixing, resting and decanting 'may. be ._ ‘ liquid was thencarefully decanted o?' and was
, repeated a, ‘number of times, depending onythe
‘degreeof concentration ofgcellulose desired‘ in
the ?nal viscose.
The following water-miscible organic liquids
I, are vsuitable for, the purposes of my ‘invention:
‘isopropanol. butyl carbitol,‘v acetone. diacetone
alcohol, dioxane,‘ dimethoxy» tetraglycol, glyoxal
' tetramethyl acetal, and pyridine. Of these liq' , ,uidS, pyridine is preferred for, the reason that, in,
addition to being an e?lcientfdehydrating agent
for normal viscose solutions, ‘pyridine is the'only
liquid of the group which does ‘not, in admixture
found to consist of pyridine andabout 30% of
the water originally contained in the viscose. No
caustic was detected in the extract. .Theviscose H
had been concentrated to a solution containing
about9.5% cellulose and about’ 8.2% NaOH.
By mechanically working (e. g., by agitating)
50 the viscose layer after the ?rst extract has been
decanted off, it is possible to cause further‘ quan
titles of the aqueous extract to separate from the
viscose solution. The ‘additional extract obtained
was probably in pockets and droplets which did’
not rise‘ throughthe concentrated viscose be
to be understood that the invention is not limit
ed to the speci?c embodiments thereof except as
de?ned in the appended claims.
I claim:
cause of its high viscosity and the small differ
ence in the densities of the two liquids.
Example II
To 30 parts of viscose such as used in Exam
ple I are added 20 parts of dimethoxy tetraglycol
1. A process for the concentration of viscose
which comprises mixing with the viscose to be
(dimethyl ether of tetraethylene glycol) and
thoroughly mixed. Subsequently, after resting
concentrated at least 20% by weight of pyridine,
In other words, about 50% of the water original
ly contained in the viscose was removed by this
moving the layer of pyridine and water from the
layer of viscose.
single extraction, while the caustic removal was
only to the extent of about 20%.‘ The resulting
which comprises mixing with the viscose to be
based on the weight of the viscose, allowing the
mixture to stratify into a layer of pyridine and
for a few minutes, the supernatant liquid was
decanted off and was found to be about 33 parts. 10 water and a layer of viscose, and thereafter re
viscose had been concentrated to a solution con
2. A process for the concentration of viscose
15 concentrated pyridine in an amount of at least
40% by weight based on the weight of the vis
cose, allowing the mixture to stratify into a layer
comprising pyridine and water and a layer of
By the process of this invention, viscose can be
viscose, and thereafter removing the layer of
prepared having a cellulose content substantial
ly above 10% and even above 15%, which en 20 pyridine and water from the layer of viscose.
3. A ‘process for the concentration of viscose
ables it to be used to greater advantage in either
which comprises mixing with the viscose to be
the wet or dry process for forming products. For
concentrated from 50% to 100% of pyridine by
instance, this viscose of high cellulose content‘
weight based on the weight of the viscose, allow
maybe extruded to form ?lm; sausage casings,
bands or other tubings, ribbons, ?laments, yarns 25 ing the mixture to stratify into a layer compris
ing pyridine and water and a layer of viscose,
and the like. It may also be used to advantage
and thereafter removing the layer of pyridine
in the preparation of molded articles.
and water from the layer of viscose.
As many apparently widely di?erent embodi
ments of this invention may be made without
taining about 12.3% cellulose and about 8.5%
departing from the spirit and scope thereof, it is 30
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