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Патент USA US3097966

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United States Patent 0 M1C6
3,097,956
Patented July 16, 1963
1
2
3,097,956
product increases its resemblance to an organic solvent
soluble thermoplastic. However, this does not mean such
a product becomes readily soluble. It does exhibit solu
CYANOETHYLATED CELLULOSE SOLUTIONS
‘Kenneth W. Saunders, Darien, and Norbert M. Bikales,
Stamford, Conn., assignors to American Cyanamid
Company, New York, N.Y., a corporation of Maine
No Drawing. Filed Nov. 7, 1960, Ser. No. 67,457
5 Claims. (Cl. 106—-169)
This invention relates to new solutions of certain highly
cyanoethylated celluloses. It is more particularlyicon
bility to limited ‘extents in such ketone solvents as ace
tone, diethyl ketone, methylethyl ketone and the like. It
is also soluble to some extent in such solvents as dimethyl
formamide and the like. None, however, are wholly sat
isfactory for practical use. Dimethyl tormamide, for ex
ample, has a rather high boiling point which makes it dif-.
?cult to remove from a cast ?lm. This can be an impor
cerned with such solutions of highly-cyanoethylated cel 10 tant consideration in electrical applications. Others will
lulose derivatives containing more than two cyanoethyl ‘
groups per anhydroglucose unit.
‘
not produce the desired concentration or produce exces~
sively viscous solutions. Still others are too hygroscopic
‘Cellulose, both natural and regenerated has been re
for industrial utility.
acted in various ways with 'acrylonitrile to produce cyanoh
In the past, efforts have been made to overcome the
ethylated derivatives. Physical properties oi’ the resultant 15 problems by the attempted use of mixed solvents. Prior
products vary with such factors as the nature of the cel
to this invention perhaps the best results were obtained
lulose, the method of treatment and the like. However,
by applicants in the use of a mixture of about equal parts
they are .alfected most noticeably by the amount of cyano
of a ketone and dimethyl formamide. This mixture is
ethylation. This is usually measured or ‘de?ned either by 20 referred to as “Solvent KD” in this discussion and is used
a nitrogen analysis expressed in weight percent, or by a
as a basis of comparison in describing the present in
decimal fraction representing the number of cyanoethyl
vention.
groups introduced per anhydroglucose unit. The latter
While solutions of some ten to twelve percent concen
is usually referred to as the “degree of substitution.”
tration can be obtained using this mixed solvent, a long
Both terminologies will be used in. this speci?cation, the 25 time is required to dissolve even enough cyanoethylated
latter ‘being abbreviated as D.S. Complete substitution
cellulose to form a ?ve percent solution. Moreover, eco
would correspond to a D8. of 3.0 or a nitrogen content of
nomic considerations require reuse of the solvents which is
about 13.1 weight percent.
,
rendered dii?cult in the case' of mixed solvents of varied
' In general, the products may be classi?ed into several
volatility. Moreover, the viscosities of the resultant solu
general types. The ?rst type has a low degree of sub 30 tions generally are higher than desirable ‘for the concen
stituiton, not exceeding two, and usually has a low ni
tration. Ther-e?ore even mixed solvent solution-s are not
trogen content of from about 2.5 to about 6.5%, i.e., a
wholly satisfactory.
D3. of from about 0.3 to about 1.0. In this type, the
in this connection it should be noted that cellulose is
?brous structure of the cellulose is retained in substantially
not a uniform material. Different forms of cellulose
its original physical form. So-trcated ?bers remain use 35 may have different molecular weights. The same is true
ful in the textile, paper and other ?elds for which the
of synthetic products derived therefrom, such as, for ex
original ?brous material was suited. Cyanoethylation to
ample, the regenerated cellulose of viscose rayon. ,As‘a
this degree of substitution, however, has improved many
properties of the ?ber such as resistance to microorgan
result, the behavior of cyanoethylated products derived
therefrom also may vary markedly in their ease of solu
isms, heat, abrasion and the like.
40 bilization. This creates a still further problem in utiliz
However, when higher degrees of cyanoethylation are
ing such materials on an industrially practicable basis.
produced the characteristics of the product begin to
There remains, then, a need for a more effective solvent,
change. As the D8. increases above about two,'the loss
one which is markedly less hampered by these problems
of ?brous characteristics and the resemblance of the prod
which are presented in using the solvents and solvent
not to ‘a thermoplastic becomes increasingly noticeable. 45 mixtures previously considered the best available for the
purpose.
Moreover, the product begins to become soluble in certain
organic solvents.
The present invention ful?lls this need. It is based on
These characteristics become dominant in products hav
the discovery that acetonitrile has a remarkable solvent
ing a D8. from about 2.5 to 3.0, i.e., nitrogen content
power for highly-cyanoethylated cellulose, whether de
percentages of from about 12 to somewhat over 13.
It 50 rived from natural cellulose ?bers or from regenerated
is with products of this highly-cyanoethylated type having
cellulose. Surprisingly, using this novel solvent, it is
a ‘D.S. of at least 2.5 with which the present invention is
particularly concerned. However, it does have some ap
readily possible to obtain solute contents as high as twenty
percent or higher.
A further advantage is found in that for a given dis
plicability to products having a somewhat lower D.S. In
some cases it may be applicable with a D8. as low as
about ‘2.3.
-
solved content of highly-cyanoethylated cellulose, the
solution viscosity of acetonitrile solutions is relatively
; Highly-cyanoethylated celluloses, i.e., those having a
low. This is true even when compared with solutions of
D5. above 2.5 have very desirable electrical character
much lower concentration obtained with solvents and
istics for a number of purposes. Among these are a high
solvent mixtures such as were previously utilized. Clear,
dielectric constant, ‘a low ‘dissipation factor and the like. 60 uniform, easily-?owable solutions are readily obtainable,
However, a problem is involved which hitherto has seri
even with high concentrations of cyanoethylated material.
ously hampered the commercial utilization of these highly
cyanoethylated products to take advantage of such prop
Another advantage of the use of acetonitrile as a sol
vent according to the present invention is obtained by
reason’ of its high volatility. When the solutions of the
erties. Before this can be done, the product must be
formed into a ?lm or other product. This, in turn, in 65 present invention are used in ‘?lm-forming operations, for
example, the solvent is readily removed and recovered
troduces the problem of preparing a solution containing
for reuse.
a usefully-high concentration of the highly-cyanoethylated
It is an advantage of the present invention that a
product. Moreover, such a solution must be capable of
specially puri?ed and expensive grade of acetonitrile is
preparation in a reasonable length of time and such solu
70 not necessary. It is desirable that the moisture content
tion must not have an excessively high viscosity.
should not exceed about one percent. Commercially
As was‘pointed out above, increasing the D5. of the
available material meeting this requirement is readily ob
3,097,956
3
tainable.
tration was sufficiently unsatisfactory that an attempted
test at higher concentrations was not warranted.
Table 11
Products of lower moisture content are desir
able but, except in special cases, are not essential.
Clarity and uniformity of solution also are important
considerations. When as frequently occurred in the past,
the solvent leaves even a few undissolved gel particles,
the resultant solutions are not satisfactory. Films and
other physical forms cast from such solutions are not
homogeneous and do not exhibit the desired electrical and
mechanical properties. It is a further advantage of the
solutions of the present invention that they are not sub
Solution Concentration
Solvent
5%
10%
Soluble __________ _.
20%
Soluble.
Some swelling. _ - _
ject to this dii?culty.
Proprionitrlle.-
Methanol ___________ __
The invention will be more fully described in con
junction with the following illustrative examples. There
in, all parts and percentages are by Weight unless other
wise speci?ed.
15
EXAMPLE 1
Using a sample: solvent ratio of 19:1, a series of ?ve
___..do _________
..
Slight swelling. ._-
Slight
swelling.
Ethanol:
95% ____________ ._
100% .... ..
Insoluble ________________________ ..
Slight swelling. .__
Slight
swelling.
Isopr0panol....
Insoluble ........................ ..
Acetone ............ ..
Slightly soluble.. .
Methylethyl ketone. .
ol bl
Solvent AM
Solvent AA._..
Solvent KD
Ether...._
samples of highly-cyanoethylated cellulose, in which the
Insoluble.
nitrogen percentages varied in the range from 12.1 to 12.6,
.
were dissolved into 5% solution in the acetonitrile of the 20 Dioxanc.
Pyrrolidon
present invention. For comparison similar tests were
made with acetone and with mixed solvent. Using ace
Pyridine ____________ __
Do.
Tetrahydrofuran
Chloroiorm ......... ..
tonitrile, in accordance with this invention, each sample
d
Ethylene dichloride.. --...do....
is readily dissolved to form a clear solution in one hour
or less. In the same period of time both acetone and 25
Solvent KD dissolved only a small amount of the solid
leaving undissolved gel in suspension. Accordingly, both
Diethylamine ...... ..
Insoluble
..... ._
Dimcthyliormamide . Soluble-
Do.
Ethyl acetate .... ._
Some sw
ng
Cyclohexane ........ ..
Insoluble ........................ ..
l Seine undissolved gel particles.
the acetone and the Solvent KD tests were allowed to re
1 With dir?culty.
main in the mixer overnight. Illustrative results are
30 It will be seen that Wolvent KD, Solvent AA (containing
shown in the following table.
50% of acetonitrile, pyridine and dimethylformamide
were capable of producing ten percent solutions.
Table I
SOLUBILITY, NITROGEN CONTENT AND DEGREE OF
SUBSTITUTION
Sample
Wt.
Percent
Nitrogen
D.S.
Solvent
Only the acetonitrile produced the desired complete
solubility at twenty percent concentration. lIt should be
35 noted that propionitrile, even though closely allied to ace
tonitrile in structure and molecular weight, is quite use
Solubility
12.1
2. 55
Solvent KD-.. Soluble.l
12. 1
2. 55
Acetone _____ -.
12.1
2.55
Acetonitrile..- Readily Soluble.
12.5
2.7
Solvent KD... Soluble.1
Do.1
12.5
12.5
2.7
2.7
Acetonitrile..- Readily Soluble.
Solvent KD-.. Incomplete.
12.5
2.7
Acetone _____ _-
Insoluble.
12.5
12.5
12.5
12.6
12.6
2.7
2.7
2.7
2. 75
2.75
Acetonitrile._Solvent KD..Acetonitrile...
Solvent KD___
Acetonitrile.--
Readily Soluble.
Incomplete.
Readily Soluble.
Incomplete.
Readily Soluble.
1 Only with dii?culty and extended mixing time,
less as a solvent for highly-cyanoethylated cellulose.
Even though several of the solvents are capable of pro
ducing ten percent solutions, these solutions are not in
40
dustrially satisfactory. The acetonitrile-acetone mixture,
for example, has too low a solution rate and the product
solution has too high a viscosity. Pyridine is not only a
disagreeable solvent to handle, but produces ten percent
solutions that are too viscous to pour or even to be
45
pumped. Dimethylformamide and mixed solvent solu
tions also are subject to the same viscosity problems.
The following example is given to illustrate the relative
viscosity of solutions in acetonitrile as compared with
those in pyridine. The latter is taken as illustrative of
those other solvents noted above as capable of producing
50
ten percent solutions but ‘having excessive viscosity.
Although each of Samples B, C and ‘D had a nitrogen con
tent of about 12.5%, they were different samples, ob
EXAMPLE 3
tained from different sources. As is readily seen, they
behaved diilerently. Table I also shows that the more
A sample of cyanoethylated cellulose prepared from
highly-cyanoethylated materials present severe problems
viscose rayon was obtained containing 12.4 percent nitro
of solubility even using solvent mixtures, although when 55 gen. It was dissolved into clear ten percent solution in
using acetonitrile clear‘solutions are readily obtained in
acetonitrile and in pyridine. The pyridine solution was
all cases in a small fraction of the time.
'?ltered to remove some undissolved gel particles. Vis
cosity of both solutions was measured at room tempera
ture by means of a rotating spindle instrument, commer
Using additional portions of Sample C of Example 1, an 60 cially-available type called a Brook?eld viscosimeter.
attempt was made to produce solution concentrations of
Viscosity of the acetonitrile solution was 2600 centipoises,
EXAMPLE 2
?ve, ten and twenty percent in acetonitrile. Sample and
that of the pyridine solution 12,300 centipoises.
solvent were placed in a mechanically-stirred mixer and
EXAMPLE 4
held for one hour at room temperature. Using aceto
nitrile as the solvent, complete solution was readily ob 65
It was attempted to repeat Example 3 with twenty per
tained in each case.
cent solutions. Solution in pyridine could not be ob
Attempts were made to repeat the experiment using a
tained even after 15 hours. A solution in acetonitrile
wide variety of solvents. Illustrative results are shown in
was readily obtained. It had a viscosity of 36,000 centi
the following table. Therein “Solvent AM” is used to
poises, measured as in ‘Example 3.
indicate a mixture of equal parts by weight of acetone 70
(In the following example, the utility of the solutions
and methylethyl ketone, “Solvent AA” to indicate a mix
of the present invention in forming ?lms and sheets of
ture of equal parts of acetone and acetonitrile and “S01
highly-cyanoethylated cellulose is illustrated.
vent KD” to indicate a mixture of equal parts of ketone
EXAMPLE 5
(acetone) and dimethyl formamide. A blank in any
column indicates that the test at the next lower concen 75
A further sample of the same cyanoethylated cellulose
3,097,956
of Sample A in Table I (12.1% nitrogen; |D.S.=2.‘55),
was dissolved in commercial grade acetonitrile (moisture
1% maximum) to give a 10% solution. Resultant solu
tion was ?ltered under pressure through a ?lter capable of
removing particles greater than 5 microns. Resultant
clari?ed solution was spread in a uniform ?lm on an elec
trically conductive glass surface by means of a doctor
blade. The thickness of the liquid ?lm was regulated to
give a ?nal solvent-free ?lm of approximately two mil
thickness. The solvent was evaporated in a dust-free
dro glucose unit, the dissolved cyanoethylated cellulose
content being at least about 5% by weight.
2. A solution according to claim 1 in which the dis
solved cyanoethylated cellulose content is at least about
ten percent by weight.
3. A solution according to claim 2 in which said solu
tion has a ten percent concentration and a viscosity less
than about 3000 centipoises.
4. A solution according to claim 1 in which the dis
solved cyanoethylated cellulose content is at least twenty
chamber through Iwhich dry nitrogen was circulated.
Drying temperature was regulated to 40° C. for four
hours, followed by a one hour period of 130° C. Result
percent by weight.
of 14.8 and a dissipation factor of 0.019 for the cyano
desired nitrogen content to a clear solution in acetonitrile,
5. A method of preparing a clear uniform sheet of
cyanoethylated cellulose containing from about 11.5 to
about 13 weight percent of nitrogen and having at least
ant solvent-free ?lm was then vacuum metallized. Elec
trical measurements on the capacitor obtained at 25° C., 15 2.3 cyanoethyl groups per anhydroglucose unit which com~
prises: dissolving a cyanoethylated cellulose having the
and 60 cycles per second indicated a dielectric constant
said solution having a dissolved cyanoethylated cellulose
ethylated cellulose ?lm.
content of at least ten weight percent; casting a ?lm of
EXAMPLE 6
20 resultant solution on a suitable surface and removing sub
The procedure of ‘Example 5 was repeated, except that
stantially all the acetonitrile from said ?lm.
the dry ?lm before metallization was removed from the
glass by the action of warm water. After drying and con
References Cited in the ?le of this patent
ditioning at 23° 0., and ‘50% relative humidity, 10" by
0.5" strips were tested for physical strength. Average 25 MacGregor: J. Soc. Dyers Colorists, vol. v67, 1951, page
70‘.
values were 5380 pounds per square inch and nine per
“Chemistry of Carbon Compounds,” edited by E. H.
cent elongation.
Rudd, vol. IA, 1951, page .606.
We claim:
Doolittle: “The Technology of Solvents and Plasti
1. A clear solution in acetonitrile of cyanoethylated
cizers,”
1954, page 727.
cellulose having at least 2.3 cyanoethyl groups per anhy 30
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