Note: Descriptions are shown in the official language in which they were submitted.
1051880 ~ ~,
This invention relates to ester derivatives of polyhydroxy~
polymers, to process for their production, and to the uses thereof. ~ ~ o
Ester derivatives of polyhydroxy polymers are known
and have been described extensively in the prior art literature.
The chemical and physical properties of such ester derivatives
depend to a large extent on the particular nature of the
polymer, its molecular weight, the type of ester substituent
group, and the degree of substitution of the polymer (herein-
after referred to as D.S.). Due to the manner in which ester
derivatives of polyhydroxy polymers have previously been
prepared, the D.S. of the resulting ester derivatives has not
been relatively uniform. This has produced ester derivatives
whose properties, e.g., water solubility and compatability
with various metallic ions, have not been generally satisfactory
and has restricted the use areas for the ester derivatives.
Esterified polyhydroxy polymers may be prepared from
nitrite esters of the polyhydroxy polymers. The nitrite esters
are employed as reaction intermediates because of the instability
of the nitrite ester groups and the solubility of the ester in
the reaction medium. Through use of the nitrite ester interme-
diates, polymeric products, such as, for example, nitrate esters
~r
lOS188~
or sulfate esters of polyhydroxy polymers~ are obtained which
have novel properties and a generally uniform substitution
of nitrate or sulfate ester groups among the polymer unit~.
Due to the relative instability of the nitrite ester groups,
polyhydroxy polymer nitrites may be used also for making films,
fibers and other shaped articles consisting of homogeneous
mixtures of various polyhydroxy polymers or of one or more
polyhydroxy poly~ers and one or more other polymers.
In the formation of an ester derivative of a
polyhydroxy polymer, the amount of depolymerization resulting
from the reaction is negligible. Thus, products are obtained
which have very high solution viscosities. In the case of
sulfate esters of polyhydroxy polymers, products have been
obtained whosè solution viscosities are many times greater
than the solution viscosities of superficially similar æulfate
esters produced by prior art methods.
In addltion, it is possible to produce esterified
polyhydroxy polymers which have D.S. values that cannot be
obtained by previously known methods. As an example, cellulose
sulfate esters have been prepared having a low D.S., e.g.,
less than 0.3 in which the ester groups are substantially
uniformly distributed among the cellulose polymer units.
Also, sulfuric acid esters of locust bean gum and guar gum
have been obtained whieh have a D.S. of above 1. Still further,
water soluble nitrate esters of polyhydroxy polymers have
been prepared having a D.S, of less than 1. The properties
of these nitrate
~ 2~ ~
i, ,,
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1051880
esters are especlally surprising since prevouS nitrate
esters of polyhydroxy polymers have, in general, been highly
substituted and insoluble in water,
The relatively uniform distribution of the ester
substituent groups over the macromolecule obtainable herein
results, in part, from the fact that the polymeric nitrite
intermediate used in the reaction is solvated or even
dissolved in the reaction medium. In contrast, in prior
art methods, the polymeric starting material was generally
suspended in the reaction medium in the form of insoluble
particles. The homogeneity of the products prepared herein
is of particular importance when the D.S. of the esterified
products is considerably below the maximum D.S. for the
particular polyhydroxy polymer, such as, for example, in
the sulfate esters of an aspect of this invention and
particularly in the case of the cellulose sulfate esters.
~or example~, in previous sulfation procedures, e.g., in
preparation of cellulose sulfate esters, insoluble cellulose
fiber was used as the starting material. In sulfating the
fiber, the reaction mechanism involYed the so-called "Peeling
Process", in which the fiber surface was first partially
substituted, then solvated and removed by the reaction medium,
and then highly substituted by reaction with excess sulfation
reagent in the reaction medium. During the "Peeling Process",
the next inner layer of the cellulose fiber was then exposed
and sulfated in a similar fashion with the process proceeding
until most of the fi~er or the sulfation reagent was consumed.
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1051880
As a ~esult o~ the ~Peeling P~ocess~ the poly-
meric sulfates which were previously ohtained were highly
substituted and had a D,S, relatively close to the maximum
for the polymer irrespective of the amount of sulfat~on
reagent employed. Even when the average D.S, of the polymer
was less than the maximum D.S. of the polymer, the distribu-
tion of ester su~stituent groups was not uniform and a
considerable nu~ber of the polymer units were fully
substituted while other polymer units had a very low D.S.
or were not substituted at all. In the process of one
aspect of the present invention the nitrite ester used
as an intermediate is solvated or solubilized and the
ester substituent groups in the final product are, thus,
distributed substantially uniformly among the polymer units
of the product. Thus, in cellulose sulfate products of
one aspect of this invention having a D.S. of 2 or 1,
substantialIy all of the polymer units in the cellulose
will contain only two sulfate ester groups or one sulfate
ester group.
Due to the substantially uniform distribution of
ester groups among the plolymer units in the products of
aspects of the present invention, the products have, in
general, unusual solubility characteristics. Also, solutions
of the products have unusual compatibilities with metallic
ions. For example, cellulose sulfate products provided
according to an aspect of this invention which have a D.S.
of 0.3 to 1 are soluble in water. This is quite surprising
since the prior literature reports that colloidal cellulose
sulfate must have a D,S. in excess of 1 in order to be water
soluble,
~ S~~
~..- . .
1051880
In addition, sulfate esters of polyhydroxy polymers
of an aspect of the present invention are also markedly different
from superficially similar materials of the prior art in terms of
their compatibilities with a wide variety of metallic ions and
also their compati6ilities with relatively high concentrations ~,
of metallic ions. Still further differences are observed
between the products of aspects of the present invention and
superficially similar materials of the prior art, e.g., r
sulfates of polyhydroxy po]ymers, in terms of reactivity
10with water soluble proteins.
As disclosed in my prior copending application
Serial No. 230,049, filed ~June 24, 1975 one aspect of that
invention was directed to a process for the preparation of
nitrate esters or sulfate esters of a polyhydroxy polymer
which was a polysaccharide or a polyvinyl alcohol that was
partially substituted with ether or ester groups. ~therified
and esterified polysaccharides or polyvinyl alcohol are known
materials which may include, for example, substituent groups p
such as formate, acetate, carboxymethyl, methyl ether, ethyl
ether, and propionate groups. Typical of the known etheri-
fied and esterified materials which may be employed as
starting materials are carboxymethyl cellulose, methyl
cellulose, hydroxyethyl cellulose, alginic acid acetate,
alginic acid propionate, starch phosphate, hydroxypropyl
guar, pectic acid butyrate, carboxymethyl starch, partially Y`
hydrolyzed polyvinyl acetate, natural sulfate esters such as,
for example, carrageenan, natural acetyl esters such as,
for example, gum karaya and xanthan gum, etc.
,~
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1051880
In the formation of nltrate or sulfate esters of
etherified or esterified polysaccharides or poly~inyl
alcohol, according to aspects of the present invention, it
is necessary that the reactant materials contain free hydroxyl
groups. Thus, the etherified or esterified polysaccharide or
polyvinyl alcohol used as the starting material is only partially
substituted and contains free hydroxyl groups which are
utilized as reactant sites in accord with aspects of this invention,
The free hydroxyl groups on the etherified or esterified
starting materials may, thus, be nitrosated, nitrated and
also sulfated in a manner similar to the nitrosation, nitra-
tion, and sulfation of the unsubstituted polyhydroxy polymers
to provide the corresponding ester derivatives of the
partially ethèrified or esterified polyhydroxy poly~ers.
The nitrite esters of polyhydroxy polymers,
employed as reaction intermediates in the process of aspects
of the present invention, are prepared by nitrosating a suspen-
slon of the desired polyhydroxy polymer starting material in a
suitable organic solvent at a reaction temperature of below
50C. The nitrosating reactant is preferably dinitrogentetroxide
which is in equilibrium with its monomer nitrogen dioxide.
Through use of the nitrite ester as a reaction intermediate,
nitrate and sulfate esters of polysaccharides and polyvinyl
alcohol can be readily synthesized in accord with aspects
of the present invention. The resulting nitrate and
sulfate ester products show a negligible degree of
depolymerization and a selective degree of esteri-
fication. Also, the nitrate and sulfate ester
products are distinguished by their homogeneity of
~_
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105~880
substitution, i,e,? the ester groups, such as7 fo~ examp]e,
sulfate ester groups, are relati~ely homogeneously distributed
over the macromolecule. Thus, the properties of the products
differ substantially from the properties of superficially similar
products of the prior art in providing higher viscosities
and in being compatible with certain metallic lons.
Water soluble nitrate esters may be easily prepared
from the corresponding nitrite esters in accord with other
aspects of this invention by simply heating the solvated
nitrite esters in the presence of nitric acid and removal of
residual nitrite groups by treatment with a protic solvent.
The resulting nitrate ester product is soluble in water, is
relatively undegraded, and its aqueous solutions also tolerate
relatively large amounts of water miscible organic solvents.
Polymeric sulfate esters are also prepared in accord
with-other aspects of the present invention by sulfating the
nitrite ester of a polysaccharide or polyvinyl alcohol with
sulfur trioxide or a complex thereof at a relatively low reaction
temperature. Thereafter, residual nitrite ester groups are
removed from the polymer by reaction with a protic solvent to
provide a relatively undegraded polymeric sulfuric acid ester.
The sulfuric acid ester may then be neutralized or made slightly
alkaline to provide the more stable salt form of the ester.
The undegraded alkali ester salts are highly soluble and their
aqueous solutions possess a high viscosity. Thus, the sulfate
ester salts are useful as thicke~ers in aqueous media.
10518~0
Typical of known polyhydroxy polymers ~hich may
be utilized as starting materials are the polysaccharlde~
such as, for example, cellulose, starch, hemicellulose, guar gum,
locust bean gum, gum arabic and the mannans; the polyuronic acidæ
typified by alginic and pectic acids, and the synthetic polyhydroxy
polymers such as, for example, polyvinyl alcohol. In accord
with one aspect of the invention, the partially etherified or
esterified polyhydroxy polymers, as described previously, are
used as starting materials in the preparation of nitrate esters
or sulfate esters of the partially substituted polyhydroxy
polymers.
The starting polyhydroxy polymer is suspended in
a suitable solvent which includes a swelling or solubilizing
agent for the`polymeric reaction product and a proton
acceptor. Solvents which have been found suitable in
serving both as a proton acceptor and a swelling or
solubilizing agent include weak tertiary amine base as
typified by pyridine, quinoline and isoquinoline and also
N,N-dialkyl acylamides such as N,N-dimethylformamide and
N,N-dimethylacetamide (hereinafter referred to as DMF and
DMAC respectively), and mixtures thereof. Suitable swell-
ing or solubilizing agents are generally solvents which
are capable of dissolving polymeric esters. Typical
examples of such swelling or solubilizing agents are ethyl
acetate, ethyl formate, benzene, acetone, methyl ethyl
ketone, and the like and mixtures thereof. Compounds which
are suitable as proton acceptors are those, as previously
described, which are capable of providing 60th swelling or
solubilizing of the polymeric nitrite ester and also acting
as a proton acceptor.
10511~80
1 The amount of solvent which may be utilized to
2 suspend the polyhydroxy polymer is not critical and may be
3 varied over a relatively wide range, Howe~er, 3ufficient
4 solvent should ~e used to avoid difficulty in handling the
resulting viscous mixture. In general, it has been found
6 that a minimum solvent to polymer weight ratio is 3:1,
7 i.e., three parts by weight of solvent for each part of
8 polymer.
In general, it is preferable that the solvent be
11 capable of both swelling or solubilizing the resulting poly-
12 hydroxy polymer nitrite ester and also acting as a proton
13 acceptor. The use of a single solvent, as opposed to use
14 of a mixture of a proton acceptor with a swelling or
solubilizing ayent, provides process economies since it
16 simplifies the recovery and the reuse of the ~olvent material.
17 However, should a mixture of a proton acceptor with a swelling
18 or a solubilizing agent be employed, it is necessary that the
19 mixture contain at least one mole of the proton acceptor for
each mole of the nitrosating agent, e.g., dinitrogentetroxide.
21 -:
22 As stated, when a nitrite ester is nitrated or
23 sulfated in accord with the invention, the product which
24 is obtained is a novel polysaccharide or polyvinyl alcohol
which contains a mixture of nitrite ester groups with
26 sulfate or nitrate ester groups with the mixture of groups
27 being substantially uniformly distributed among the polymer
28 units in the polysaccharide or polyvinyl alcohol, These
29 novel products are valuable intermediates in the preparation
of a sulfate or nitrate ester of a polysaccharide or poly-
31
32
_, .. . . .
1051~80
vinyl alcohol in which the sulfate or nitrate eater groups
are substantially uniforQly distributed among the polymer
units in the polysaccharide or polyvinyl alcohol,
The use of a nitrite ester of a polysaccharide or
a polyvinyl alcohol as a starting material in the preparation
of another ester of a polysaccharide or a polyvinyl alcohol
is of particular importance in the preparation of novel
cellulose sulfate esters. By controlling the degree of
substitution of the nitrite ester of cellulose employed as
the starting material, the degree of substitution of the
cellulose sulfate product may be likewise controlled. Thus,
when the nitrite ester of cellulose has a degree of substitu-
tion of 2 to 3; the cellulose sulfate ester which is produced
in accordance`with an aspect of this invention has a degree of
substitution ranging up to 1.1. However, when the nitrite ester
of cellulose has a degree of substitution which is less than 2,
the cellulose sulfate ester has a degree of substitution
greater than 1.1. In each case, the sum of the degree
of substitution of the cellulose sulfate ester and the degree
of substitution of the nitrite ester is equal to 3Ø
A further aspect of the invention concerns novel
water soluble sulfate esters of cellulose which have a
degree of substitution of 0.3 to 1.0 with the sulfate
ester groups being substantially uniformly distributed
among the polymer units of the cellulose. The water solubility
of these materials is quite surprising since cellulose sulfate
esters, as prepared by prior art methods, are not water soluble
unless the degree of substitution is in excess of 1Ø In the
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1051880
usage of these water soluble sulfate este~s of cellulose, a
further aspect of the invention concerns a thickened aqueou8
medium which contains water and a water soluble sulfate ester
of cellulose having a degree of substitution of 0.3 to
about 1.0 with the sulfate ester groups being substantially
uniformly distrlbuted among the polymer units of the cellulose
and the cellulose sulfate ester being present in an effective
amount to thicken the aqueous medium.
A still further aspect of the invention concerns
water insoluble esters of cellulose which are, however, highly
swellable in the presence of water. These water insoluble
cellulose sulfate esters have a degree of substitution of less
than 0.3 with the sulfate ester groups being substantially
uniformly dis`tributed among the polymer units of the cellulose.
The water swellability of these materials is quite unusual.
Due to the unusual properties of the water swellable esters
of cellulose having a D.S. less than 0.3, these materials
have novel utilities in the preparation of absorbent materials,
such as, for example, diapers, towels and the like.
A further aspect of the invention concerns nitrite
esters of a polysaccharide or polyvinyl alcohol having a degree
of substitution of less than 2Ø In particular, the
nitrite esters of cellulose having a degree of substitution of
less than 2.0 are of unique value since they may be employed
in forming cellulose sulfate esters , as described, having a
degree of substitution of 1.1 to 2.0 with the sum of the
degree of substltution of the nitrite ester groups and the
degree of substitution of the sulfate ester groups in the
precursor mixed ester being equal to 3.0,
J
. .
10~880
A still further aspect of the inYention concerns novel
water soluble nltrate esters of a polysacchar~de or a polyvinyl
alcohol having a degree of substitution of less than 1.0 in
which the nitrate ester groups are substantially uniformly dis-
trlbuted among the polymer units of the polysaccharide or poly-
vinyl alcohol. The properties of these materials are unique in
that nitrate eæters produced by prior art procedures are highly
substituted and water insoluble.
As a corollary to the unique water soluble nitrate
esters of a polysaccharide or a polyvinyl alcohol, a further
aspect of the invention concerns a thickened aqueous medium
containing water and a water soluble nitrate ester, as des-
cribed, having a degree of substitution of less than 1Ø
The nitrate ester groups are substantially uniformly distri-
buted among the polymer units of the polysaccharide or poly-
vinyl alcohol and the water soluble nitrate ester is present
in an effective amount to thicken the aqueous medium.
A still further aspect of the invention concerns an
improved process for the preparation of nitrite esters of
cellulose. As described, the usage of a nitrite ester inter-
mediate of cellulose makes possible the preparation of novel
cellulose esters, such as, for example, cellulose sulfate or
cellulose nitrate, in which the properties of the final product may
be attributed to the substantially uniform distribution of ester
groups among the polymer units of the cellulose. It has been found
that the nitrosation of cellulose with dinitrogentetroxide or nitrosyl
chloride, and the subsequent sulfation as described previously,
may be even further improved if the cellulose reactant is in an
,
1051880
acti~ated state o~ suit~bly actlyated, In acco~d with the
impro~ed process, the cellulose reactant is in a hydrated form
and contains from 4 to 12 per cent by weight of water with the
water being ~ubstantlally uniformly distributed throughout the
cellulose reactant.
In using the hydrated cellulose as a reactant, the
nitrosation reaction can be carried out in a shorter time with
the use of essentially stoichiometric amounts of the nitrosa-
tion reactant. This produces a more homogeneous reactio~n
mixture, a higher clarity product and, thus, permits easier
separation of the product from the reaction mixture and reduces
the need for filtration
A still further aspect of the invention concerns
a variation of the improved nitrosation process in which the
cellulose reactant is substantially uniformly hydrated. In
this variation, a hydrated cellulose which may contain in
excess of 4 per cent by weight of water distributed substantially
uniformly throughout the cellulose is washed with a highly polar
aprotic solvent to reduce the water content of the cellulose to
less than 4 per cent by weight. Surprisingly, it has been found
that the cellulose remains in an activated state after washing
with the aprotic solvent, even though the washed cellulose has a water
content less than 4 per cent by weight. The washed cellulose can
then be employed in the manner described previously for nitro-
sation with dinitrogentetroxide or nitrosyl chloride.
_ ~_
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~05~380
In a stlll ~urther aspect of the inyention? it has
been found that the nitrite substituent groups present in
nitrite esters of polyhydroxy polymers, e,g,, cellulose, or
in mixed nitrite:nitrate esters or nitrite:sulfate esters of
a polyhydroxy polymer are surprisingly labile. Thus, unlike
other nitrites, the nitrite substituent groups on the cellulose
(or other polyhydroxy polymer~ may be readily removed to form
alkyl nitrites during formation of nitrate or sulfate esters
of cellulose from cellulose nitrite esters with the alkyl
nitrites being by-products to the ~ormation of cellulose
nitrate or cellulose sulfate esters.
In forming an alkyl nitrite ester as a by-product
in accord with another aspect of this invention, an alkyl alcohol
is added to a~reaction mixture containin~ a mixed nitrite:nitrate or a
mixed nitrite:sulfate ester of a polysaccharide or a poly-
vinyl alcohol. Since the mixed ester is generally formed
through addition of a nitrating or sulfating reagent, as
described previously, to a reaction mixture formed in the
production of the nitrite ester intermediate, dinitrogentetroxide
may be liberated and be present in the reaction mixture. When
alkyl alcohol is added, the alcohol reacts with both the free
dinitrogentetroxide and the labile nitrite groups on the
polysaccharide or polyvinyl alcohol. The reaction of the
dinitrogentetroxide with the alkyl alcohol results in the
formation of alkyl nitrite esters by a direct nitrosation
which is comparable, in terms of mechanism, to reaction of
dinitrogentetroxide with a polysaccharide or polyvinyl alcohol
in forming the nitrite ester, However, reaction of the
_ ~_
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1051880
nitrite substituent groups on the polysacch~ide o~ poly-
vinyl alcohol with the alkyl alcohol occurs through a
transesterification reaction rather than a direct nitrosa-
tion. Although not bound by any theory, it appears that the
transesterification reaction favours the production of the
most stable nitrite ester in the system which, in this
particular case, is the alkyl nitrite which is produced
quantitatively.
~atever the reaction mechanism ~ay be, it is
most important that both the free dinitrogentetroxide and
the nitrite substituent groups on the polysaccharide or
polyvinyl alcohol quantitatively form the same alkyl
nitrite product so that the excess dinitrogentetroxide
enters into ~he production of the valuable by-product alkyl
nitrite.
As a suitable alkyl alcohol, various alkanols and
alkanediols~may be used, such as, for example, propanol, butanol,
amyl alcohol, ethanediol, 1, 2-propanediol, etc. In addition,
higher alcohols may be used such as, for example, decanol contain-
ing up to 10 carbon atoms. Primary alcohols, such as, for example,
butanol, secondary alcohols, such as, for example, isopropanol,
and also tertiary alcohols, such as, for example, tertiary butyl
alcohol are equally suitable for the reaction. In order to utilize
the dinitrogentetroxide reagent quantitatively in the reaction, the
alkyl alcohol reactant should be present in an amount of at least one
mole of alkanol or one-half mole of alkanediol for each mole of
dinitrogentetroxide which is initially added in forming the
nitrite ester of the polysaccharide or polyvinyl alcohol
lOS181~0
inte~mediate with the alcohol belng added afte~ for~ation
of the mixed polysaccha~ide or polyvlnyl alcohol este~,
Since alkyl nitrite esters are relatively stable
in comparison to the nitrite es~ers of polysaccharides or
polyvinyl alcohol, the further reaction steps in forming
the primary nitrate or sulfate ester product, i.e,, neutra-
lization, separation and isolation of the resulting nitrate
or sulfate ester of the polysaccharide or polyvinyl alcohol,
can be carried out without first removing the alkyl nitrite
ester. Thus, for example, in forming a mixed nitrite:
sulfuric acid ester of cellulose with subsequent addition
of the required amount of alcohol, the resulting sulfuric
acid ester of cellulose may be precipitated by addition of
acetone to th~ reaction mixture followed by removal of the
precipitate for further processing. The alkyl nitrite ester
remains in the filtrate and both the solvents and the alkyl
nitrite maj be readily recovered by fractional distillation
or any other suitable means. Since the filtrate is acidic,
it may be neutralized with a suitable base prior to distil-
20; lation to minimize decomposition of the various compounds.
As an additional way to minimize decomposition, the
distillation may be carried out at a reduced pressure.
In separating the ester product, such as, for example,
the sulfuric-acid ester of cellulose, it is generally pre-
ferred to neutralize the entire reaction mixture without
first isolating the ester product. This provides a large
saving in the amount of solvent which is used and no
16
'~C ~
~.., ;
~051880
decompogltion of the alkyl nit~ite by~p~oduct has been
obseryed wh n t~e product recovery i8 carried out in this
manner, Thu6, after addltion of the alkanol or alkanediol,
a suitable base, such as, for example, the ammonlum and N-substituted
ammonium, alkali, or alkaline earth hydroxides, carbonates,
or bicarbonates is added as an aqueous solution or as a
suspension of an excess quantity of base in itfi saturated
solution with continuous mixing of the reaction mixture
during addition of the base. The preferred bases are the
alkali carbonates and alkali bicarbonates whlch may be
added also in the form of dry powders. To prevent any
degradation of the polysaccharide ester product or poly-
vinyl alcohol ester product, e.g" the cellulose sulfate
ester, the reaction mixture is preferably kept at a temper-
ature of below 15-20C. until the neutralization is
completed.
If the solids concentration of the reaction mix-
ture is sufficiently high and the concentration of water in
the mixture is relatively low, the cellulose sulfate ester
may be present in a wet solid form and may be readily
removed. If, however, the cellulose sulfate ester is in
the form of a paste after neutralization, a sufficient
quantity of a water miscible solvent, such as, for example,
acetone,-methanol-,- ethanol, or isopropanol, is added to cause separ-
tion so that the product can be removed, pressed out, and
dried or purified further. If the product is dried directly,
the resulting product is a technical, relatively crude grade
product which contains salt as the principal impurity. A
purified product may be prepared by extracting the wet solids
11
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105~880
one or more times wlth an aqueous alcohol, such aS? for example~
methanol, ethanol, or isopropanol containing 20_40 per cent by
weight of water, ~ollowed by drying of the product at an
elevated temperature, Of course, it is also possi61e to
extract the dried technical grade product with aqueous alcohol
to arrive at a refined grade.
The flltrate, as described above, may contain both
solvents and also an alkyl nitrite and both the solvents and
alkyl nitrite may be easily recovered by distillation. If a
higher alkyl nitrite, e.g., in excess of 7 carbon atoms,
is produced as a by-product which contains a relatively high
number of carbon atoms, part of the higher alkyl nitrite may
remain with the solids because of its reduced solubility in
aqueous alcohol. In this event, a final extraction may be
carried out with anhydrous alcohol or with an alcohol contain~
ing less than 20% of water. This will remove the higher
alkyl nitrite more thoroughly and will result in obtaining
higher yields during distillation. In addition, it is also
possible to dry the solids in a closed system such that all
absorbed solvents, including any retained alkyl nitrite, can
be recovered.
A second by-product which may be formed in equi-
valent a unts iR an inorganic nitrate, for example, sodium
nitrate, if sodium hydroxide or -sodium carbonate was used
for neutralization. If it is not desired that an alkyl
nitrite ester be produced simultaneously with production of
the inorganic nitrate, an equivalent amount of water may be
added to the reaction mixture instead of adding an alkyl
/g
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- 105~380
alcohol, This ~i~ll then result in the for~at~on o~ equi~alent
amounts of inorganic nitrate and nitrite, such ~s, for exa~ple,
sodium nitrate and sodium nitrite. Both salts will be in the
filtrate and will remain in the residue after recovery of the
solvents. The salts ~ay be purified by crystallization or other
known methods to provide salts of medium or hlgh purity. However,
if the salts are to be used as fertilizers, additional purifica-
tion may not be necessary.
The first step of a process in accordance with one
embodiment of this invention comprises nitrosating a poly-
hydroxy polymer suspended in a suitable solvent with dinitro-
gentetroxide, nitrosyl chloride or mixtures thereof to obtain
the corresponding polyhydroxy polymer nitrite ester.
The`nitrosating compound is used in the reaction
mixture at a molar ratio of anhydroglucose or generally
polymer unit to dinitrogentetroxide or nitrosyl chloride of
1:0.1 to 1.3, resulting in a D.S. of 0.1 to 3. Since
the reaction is quantitative, the D.S. approximately coin-
cides with the molar amount of nitrosatlng agent used. If
nitrosyl chloride is used in combination with DMF or D~AC,
a 2.5 to 3.0-fold excess of the nitrosating reagent is
required to attain these D.S.'s. Stated another way, one
mole of dinitrogentetroxide or nitrosyl chloride is neces-
sary to replace one mole of hydroxyl radical of the
polyhydroxy polymer, and if nitrosyl chloride is used with
an N,N-dialkyl acidamide as the proton acceptor, 2.5-3.0
les of nitrosyl chloride are required~
. . ,
~CJ ~
lOS~880
The maximum D.S. for hexo$ans? such as? fox example~ cellulose,
starch, guar and locust bean gums, mannans, and the like is
about three; for pentosans, such as, for example, hemicellulose, and
polyuronic acids, such as, for example, alginlc and pectic acids,
it i8 two; and for polyvinyl alcohols the maximum D.S. is one or
less. Thus, the molar amount of dinitrogentetroxide necessary to
obtain complete esterification for hexosans is three moles per mole
of anhydrohexose unit, for pentosans and polyuronic acids two moles
per mole of anhydropentose or uronic acid units, and for polyvinyl
alcohols one mole or less depending upon the degree of saponification
of the starting compound. The same mole ratio amount of nitrosyl
chloride is necessary for complete esterification of each of the
hereinbefore described classes of polyhydroxy polymer unless DM~
or DMAC is us`ed as the solvent, in which case the amount has to
be substantially tripled. An excess amount of the nitrosating compound
beyond that necessary for complete esterification may be
added with the only effect being an increased rate of esterification.
The nitrosation reaction is preferably carried
out with constant agitation of the reaction mixture. It
is necessary that the nitrosating compound be introduced
into the polymer suspension under the exclusion of moisture.
It is preferable to cool the reaction vessel in an ice
bath or the like since the reaction is moderately exothermic,
, 2
l(~S1880
and it ls desixable to maintain the te~pe~atu~e of the
reaction mixture below 50CC,
If maximum esterification is desired, completeness
of the reaction is indicated by the for~ation of a clear
solution or paste, while partial esterification is indicated
by a swelling and/or partial dissolving of the product in
the reaction mixture.
The polymeric nitrite esters are relatively sensi-
tive products and decompose immediately upon addition of a
protic solvent, such as, for example, water, methanol, ethanol,
isopropanol, or the like in the presence of a mineral acid catalyst.
This results in the regeneration of the undegraded polyhydroxy
polymer starting material.
Since the polymeric nitrite esters find their primary
utility as intermediates in the production of other ester deri-
vatives, such as, for example, polymeric nitrate and sulfate
esters and the like, there is no need to isolate the nitrite
esters as the reaction mixture may be used for those processes,
as hereinafter described. However, the polymeric nitrite esters
may be isolated by neutrali~ing the reaction mixture by the
addition of a base, such as, for example, mono-, di-, and tri-
alkylamines, pyridine, alkali or alkali earth metal hydroxides,
carbonates, bicarbonates, or the like. The addition of such a
base-is-necessary only if an N,N-dialkyl acylamide had been used
as the proton acceptor since, during nitrosation with
dinitrogentetroxide or nitrosyl chloride, an equimolar
_ ~ _
~.~
105~880
amount of nitric acid or hydrochloric acid is formed, If
a weak tertiary amine base, such as, for exa~ple, pyridine or quinoline,
had been used as the proton acceptor, the addition of a
base is unnecessary since, then, the acid formed is neutra-
lized by the tertiary amine base and cannot serve as a
catalyst for the decomposition of the polymer nitrite.
The neutralized, or preferably slightly alkaline
solution is then added to ice cold water with stirring to
separate the polymeric nitrite ester as a fibrous material,
which may be easily removed. Those products with a D.S.
considerably below the maximum may be swellable or even
soluble in water, in which case an alcohol is used in place
of the water.
The isolated product is relatively unstable and
for storage purposes it is preferred that it be solvated in
a suitable solvent such as, for example, benzene, ethylacetate,
ethylene d~chloride, DMF, DMAC, or the like and stored at a low
temperature, preferably below 10C.
In forming a nitrate ester product, the second step
of the process of an aspect of this inYention comprises heating
the polymer nitrite ester so]ution in the presence of nitric
acid with agitation at a temperature of 60-110C. for a period
of 15 minutes to two hours to obtain the corresponding polymer
nitrate ester.
Although the polymeric nitrite ester solution
used in step 2 is generally the reaction mixture formed
~,i _ ~ _
- .
1051880
in step 1~ in which DMF or DNAC has been used as the proton
acceptor and dlnitrogentetroxide as the reagent in an amount
sufficient for nitrosation to about the maximum D,S.~ the
polymeric nitrite ester may be isolated after step 1 and then
redissolved in one of the solvents, as stated above, and the
corresponding amount of anhydrous nitric acid added, The use
of the reaction ~ixture of step 1 for step 2 obviates the
need for isolation of the polymeric nitrite ester as herein-
before described. Also, the addition of nitric acid during
step 2 is not necessary in this case since, during nitrosa-
tion with dinitrogentetroxide in DMF or DMAC, enough nitric
acid is formed for the subsequent nitration.
Subsequent to heating, the polymeric nitrate
ester is isolated by pouring the reaction mixture slowly
and with agitation into two to five volumes of a water
miscible protic solvent, such as, for example, methanol,
ethanol, isopropanol, and the like, which splits off residual
nitrite groups and separates the resulting product. The product
is then filtered off, washed with fresh solvent and dried.
; The resulting nitrate ester product is water
soluble, and aqueous solutions of the ester tolerate rela-
tively high concentrations of water miscible organic solYents
such as the alcohols and ketones. Cellulose nitrate becomes
water soluble if the D.S. exceeds 0.5. To illustrate,
if the D.S. of the cellulose nitrate ester is lower than
0.5, the product can be highly hydrated but does not
completely dissolve. Purther, the solutions of the polymeric
nitrate esters have a relatiYely high viscosity and owing to
.
"
- ~051880
their golubillty X i~proyed hydration in wateX and aqueous
organic solvents, their usefulness is enhanced,
To for~ the polymeric sulfate ester, step 2 as
previously defined is omitted and alternatively, the next
process step comprises sulfating the polymeric nitrite
ester solution, preferably with a sulfur trioxide solvent
complex, at a low temperature to obtain a polymeric mixed
nitrite:sulfuric acid ester.
The polymeric nitrite ester solution preferably
comprises the reaction mixture of step 1, in which a
N,N-dialkyl acylamide has been used as the proton acceptor.
The temperature of the reaction mixture should be maintained
in the range from 0C.-25C., and preferably 5-15DC. to
prevent depolymerization of the molecule during sulfation.
The preferred sulfating agent is sulfur trioxide
which may be added to the reaction mixture in either its
liquid or gaseous form or as a solution in an inert solvent
such as carbontetrachloride. However, since the addition
of sulfur trioxide is very exothermic and a low reaction
temperature is critical to obtaining the desired viscosity
in the product, the sulfur trioxide must be added slowly
with stirring, while maintaining the reaction mixture in a
cooling medium such as an ice bath.
In practice, it is preferred that the sulfating
agent be first added to a solvent, preferably the same
solvent as contained in the reaction mixture to facilitate
, ~ ..,
i(~Sl~80
solyent recoye~y? to fo~ a complex which upon addition to
the re~ction mixture produces a less exothermic seaction,
Examples of solvents capable of formlng a complex with
sulfur trioxide are DMF, DMAC, dlo~ane and pyridine. Gen-
erally, the mole ratio of the sulfur trioxide to the solvent
in the complex is 1:1. However, it is preferable to use an
excess of the solvent to obtain a suspension or solution of
the complex in the excess.
The complex is slowly added to the reaction mix-
ture with agitation and exclusion of moisture. The amount
of sulfating agent to be added to the mixture is dependent
upon the D.S. desired in the resulting product. A low D.S.
value ranging between 0.1 to 1.0 requires 0.1 to 1.0
mole of sulfu~ trioxide per mole of anhydroglucose unit.
A D.S. value ranging from 1.0 to 2.0 requires 1.0 to 4.0
mole of sulfur trioxide per anhydroglucose unit. A D.S.
exceeding 2.0 i8 difficult under the reaction conditions,
and a large excess of sulfur trioxide is required.
The addition of the sulfating agent to the polymer
nitrite ester mixture forms a mixed polymeric nitrite:sulfuric
acid ester. Although the polymeric nitrite ester with a maxi-
mum D.S. may be used for the sulfation to obtain products with
a degree of sulfation of up to 1.1, it is preferred to ~ ~ ~ 0
use the lower D.S. polymer nitrites for economic reasons and ~ ~ ~
b~b ~ S
particularly where a D.S. of about 1.1 is desired. k
Cellulose, for example, can be easily sulfated to a D.S. of
between 1 and 2 only when the degree of nitrosation is
between 2 and 1, Howeyer, if the degree of nitrosation
S~
's:, ., _ ~ _
105~880
drops considerably below l? sulfation beco~es inc~easingly
more difficult and incomplete and the dlstribution of the sul-
fate groups non-uniform. Generally, the higher the degree of
sulfation desired, the lower may be the degree of nitrosation
such that the mixed polymer nitrite sulfuric acid ester has a
maximum D.S. I~ other words, the sum of the degree of nitrosa-
tion and the degree of sulfation should be 3 for the
hexosans, 2 for pentosans and polyuronic acids, and
1 or less for the polyYinyl alcohols.
The next step of the process of an aspect of this
invention comprises reacting the mixed polymeric nitrite:sulfuric
acid ester with a protic solvent to obtain the corresponding
polymeric sulfuric acid ester.
The~addition of a protic solvent such as, for example,
water, methanol and ethanol results in the production of the
pure polymeric sulfuric acid ester. The protic solvent replaces
the nitrite groups of the product with hydroxyl groups and
is added in stoichiometric amounts or an excess thereof.
To isolate the polymeric sulfate ester product,
two to four volumes of a water miscible solvent, i.e.,
acetone, is added to the mixture to separate the sulfated
polymer therefrom. The ester is removed and washed with
fresh solvent, and redissolved in ice water.
The next step of the process of an aspect of this
invention comprises neutralizing the polymeric sulfuric acid
ester with a base to form a salt thereof.
,~
,~, -- ~ _
~05~880
The lsolated polymeric suluric ~cid ester will
degrade upon storage and therefore it is preferable to
conyert it to a neutral salt, The preferred bases for
neutralizing the sulfate ester are the hydroxides, carbon~
ates and bicarbonates of the alkali and alkaline earth
metals, while ammonium hydroxide and the amines are like-
wise useable for this purpose. The resulting salt product
is isolated by adding the neutralized mixture with agitation
to a water miscible solvent such as, for example, acetone,
methanol, ethanol, and isopropanol or vice versa. The isolated
product may be washed with an aqueous solvent and dehydrated
by washing with anhydrous solvent. The separated polymeric
sulfate ester salt may then be removed and dried for storage.
Ins~tead of neutralizing an aqueous solution of
the isolated polymeric sulfuric acid ester, the polymeric
sulfuric acid ester-protic solvent reaction mixture of the
previous step may be neutralized directly to obtain the
polymeric sulfate ester salt. In this case, the base may
be added as an aqueous solution or in its dry form. In
the neutralized mixture, the product may be present in wet,
but solid, form and may be removed directly by centrifuga-
tion or filtration, pressed out, and dried to obtain a
technical grade product which contains salt impurities. A
pure grade or product is obtained by washing the wet product
one or more times with aqueous alcohol prior to drying. If
there is a relatively large amount of water in the neutra-
lized mixture, the product may be too soft to be removed or
it even may be partially dissolved. In this case, enough
alcohol is added to harden the product somewhat or to pre-
cipitate it, so it can then be filtered off or centrifuged.
~051881~
1 The product ~s water soluble and since it does
2 not undergo depolymerization, a 1% a~ueous solution produces
3 a very viscous and stable solution. The sodium sellulose
4 sulfate esters become water soluble if the D.S. excee~s
0.3 and have viscosity measurement of as high as 8000-
6 9000 cps.
8 As a result of this unique physical property, the
9 products exhibit utility as thickening, suspending and
emulsifying agents. Generally, the viscosity decreases
11 somew~at as the D.S. increases simply because of the addi-
12 tional weight to the polymer. However, in the application
13 in bone glue~it is preferred to use a product havin~ a D.S,
14 of above 1.0 since in this particular use, best results are
obtained with the higher D.S. products.
16 ~
17 The following examples illustrate specific pre-
18 ferred embodiments of this invention and are not intended
19 to be limiting. All ratios in the following examples as
well as in the specification and in the appended claims
21 are by weight unless otherwise indicated, and temperatures
22 are expressed in degrees centigrade.
23
24 EXAMPLE I
A. Preparation of Cellulosé Nitrite Ester from Cellulose
26
27 20 g. of ~hatman cellulose powder, CF.II, was
28 dried overnight at 110C. and placed in a three necX, round
29 bottom flask equipped with a mechanical stirrer and calcium
chloride tu~e. 200 ml of N,N-dimethylformamide (DMF) was
31
32
~ ,~ ., I 33
10518~0 .. ...
1 added to the cellulose powder and the mixture was stirred
2 at room temperature. With exclusion of moisture,
3 dinitrogentetroxide (N204) gas was slowly introduced to
4 the mixture over a period of two hours. It was observed
that the mixture thickened with about 7-8g. of N204 and
6 that a transparent viscous mixture without any essential
7 development of color was obtained upon introducing approxi-
~ mately 15 g. of N204. After introduction of approximately
9 30 g. of N204, the mixture formed a bluish green viscous
solution, and on further addition of N204, the color became
11 a deep green while the viscosity appeared to remain constant.
12
13 To~a sample of the three solutions, an excess of
14 pyridine was added and the slightly alkaline mixture was
poured with stirring into ice water. A fibrous precipitate
16 was formed, removed, washed with ice water and pressed out,
17 and the temperature was maintained at 0-5C. The fi~rous
18 precipitate of the first two samples was found to be swell-
19 able and that of the third sample was found to be soluble
in common solvents for polymer esters including dimethyl-
21 formamide, dimethylacetamide, benzene, acetone and ethyl
22 acetate. Upon attempting to dry the fibrous precipitate,
23 the product decomposed as indicated by the reiease of brown
24 fumes. The resulting dried product was found insoluble in
the above descri~ed common polymer ester solvents.
26
27 To identify the resultant products as cellulose
28 nitrite esters and the degree of substitution or esterifi-
29 cation (D.S.) thereof, the products were decomposed and
cellulose and nitrous acid determinations were made.
31
32
~/ ~q
105188Q
1 Products isolatea from the above three solutions were washed
2 with ice water and suspended in distilled water in a closed
3 ~rlenmeyer flask, acidified with sulfuric acid, and magneti-
4 cally stirred at room temperature for 1 hr. The mixture was
then neutralized with sodium hydroxide and the insoluble
6 cellulose was regenerated, filtered off, washed with distilled
7 water and dried in vacuo at 100C. The filtrate was collected
8 for testi~g, as hereinafter described.
The identity of the regenerated cellulose was
11 determined by comparison of the regenerated cellulose with
12 the starting material by IR spectrophotometry, negative
13 nitrogen analysis and found identical by the Kjeldahl method,
14 and the absence of carboxyl groups as determined by the
method of Samuelson and Wennerblom described in "Methods in
16 Carbohydra~e Chemistry", Yol. III Cellulose, 1963, p. 34.
17
18 To determine the lacX of depolymerization of the
19 molecule during the reaction and during storage of the
reaction medium, th~ viscosity of the regenerated cellulose
21 from reaction mixtures kept over various periods of time, in
22 cuprammonium hydroxide solution was compared with the visco-
23 sity of the starting material in the same solution at an
24 identical 0.5% concentration. The viscosities were measured
with a Cannon Fenske Viscometer at 25C, The results of the
26 tests are tabulated in the table on the followin~ page.
27
28
29
31
32 ~!
3
lOS1880
1 Material Time and Temp. Viscosity~_ ec.
of Storaqe
2 Starting Cellulose Control 28.8
3 Regenerated Cellulose 6 hr. 5C 27.0
4 Regenerated Cellulose30 hr. 5~C 28.8
Regenerated Cellulose120 hr. 5C 28.3
6 Regenerated Cellulose288 hr. 5C 27.8
q
8 The nitrite in the filtrate, as hereinbefore
9 described, was determined by oxidation with permanganate
solution to nitric acid. The presence of nitric acid sub-
11 sequent to oxidation was established by its determination as
12 nitron nitrate according to the method of Hick described
13 in Analyst, Vol. 59, pp. 18-25 (1934).
14
The degrees of substitution were calculated from
16 the weight of the cellulose and the amount of nitrous acid,
17 The degree of substitution calculated for the first solution
18 containing about 7-8 g. of N204 was 0.7; the second solution
19 containing about 15 g. of N204 was 1.5 and for the third
solution containing about 30 g. of N2O4 was 2.8.
21
22 Results substantially similar to those obtained
23 above are obtained when the following starting cellulose
24 materials are substituted for Whatman cellulose powder:
cotton linter pulp, celluloses derived from wood or isolated
26 from rice, corn, barley and oat hulls or from bagasse. However,
27 if the foregoing starting materials are used, the amount of
28 DMF used must be increased owing to the higher viscosities
29 of the resulting product~ Partially substituted celluloses,
such as methyl or carboxymethyl cellulose can be used also
31
32
,.. .
. 10518~0
1 with essentially similar results except that the amount of
2 reagent re~uired for full nitrosation is less because of
3 the smaller num~er of free hydroxyl groups present. Like-
4 wise, results sLmilar to those obtained above are obtained
when the following solvents are substituted for N,N-dimethyl-
6 formamide: N,N-dimethyl acetamide, pyridine, quinoline, and
7 mixtures thereof, or mixtures of one or more of the foregoing
8 solvents and benzene, ethyl acetate, or acetone. It was also
9 found that the dinitrogentetroxide gas could be replaced by
its liquid form or a solution thereof in one of the above
11 solvents and by nitrosyl chloride to produ~e substantially
12 similar results.
13 -~
14 Bo PreParation of Cellulose Nitrate Ester from Cellulose
Nitrite Ester
16
17 A dry 500 ml. three-neck, round bottom flask was
18 charged with 9 g. of Whatman cellulose powder, CF II, sus-
19 pended in 300 ml. of DMF and solubilized by adding
approximately 15 g. of dinitrogentetroxide gas to form
21 cellulose nitrite ester. The cellulose nitrite ester
22 solution was mechanically stirred and heated at 90C. for 50
23 minutes, poured slowly and with agitation into about 6 volumes
24 of methanol to form a precipltate, which was filtered, washed
with methanol, and dried.
26
27 Upon analysis the precipitate was found soluble
28 in water and upon IR analysis showed a strong absorption
29 peak at about 1680 cm~l, each test indicative of nitrate
ester groups.
31
32
3 ~
_lff _
~051880
1 ~itrogen determinations by the ~jeldahl method
2 indicated the presence of nitrogen from which a 0.5 degree
3 of substitution was calculated.
The addition of 15 q. of anhydrous nitric acid or
6 24 ml. of acetic anhydride to the cellulose nitrite ester
7 solution prior to heating xevealed that the degree of substi-
tution for the resulting cellulose nitrate ester was elevated
9 to 0.8.
11 Results substantially similar to those obtained
12 above are obtained when DMF is substituted by DMAC or by a
13 mixture of DMF or DMAC and benzene or when methyl cellulose,
14 carboxymethyl cellulose or carboxyethyl cellulose is used in
place of cellulose.
16
17 ~X~PLE II
18 A. Preparation of Hemicellulose Nitrlte ~ster from Hemicellulose
19
A 500 ml. three-neck round bottom flask equipped
21 with a mechanical stirrer and calcium chloride tube was
22 charged with 40 g. of hemicellulose extracted from corn hulls
23 and suspended in 300 ml. of DMF. The suspension was mechani-
24 cally stirred and under the exclusion of moisture, 58 g. of
dinitrogentetroxide gas was slowly introduced to the mixture
26 at room temperature to form a clear viscous solution of
~7 hemicell~lose nitrite ester.
28
29 ~o a portion of the solution was added-an excess
of pyridine and the slightly alkaline solution was slowly
31
32 ~;
~ 3
1051880
1 poured with stirring into ice water to separate a~fibrous
2 precipitate. The precipitate was removed, washed with ice
3 water and pressed out. The resulting precipitate was found
4 soluble in common polymer ester solvents described in
Example lA. Upon drying, the precipitate decomposed releas-
6 ing brown fumes.
8 Hemicellulose was regenerated for analysis by
9 slowly adding a portion of the remaining hemicellulose
nitrite ester solution to four volumes of methanol with
11 agitation forming a precipitate which was filtered, washed
12 with methanol, and dried. The precipitate was identified
13 as hemicellulose ~y IR spectrophotometry and by negative
14 nitrogen analysis by the Kjeldahl method.
16 The lack of depolymerization of the regenerated
17 hemicellulose was determined by preparing ~0 aqueous solu-
18 tions of the regenerated product and the starting material
19 and adjusting the pH of the solutions to 6.7 with a dilute
sodium hydroxide solution. The viscosities of the two
21 solutions were measured with a Can~on Fenske Viscometer at
22 25C. The viscosity of the regenerated hemicellulose was
23 observed to be 138.5 sec. and the starting material 146.2 sec.
24 -~
To identify the product as the nitrite ester and
26 to determine the D.S., an excess of triethylamine was added
27 to the reaction mixture and the slightly alkaline solution
28 was poured slowly and with stirring into ice water which
29 resulted in the separation of hemicellulose nitrite ester.
The hemicellulose nitrite was removed, suspended in water,
31
32
' 3
~05~880
1 and the mixture acidified with sulfuric acid and atirred
2 ~or about 1 hour. Then it was neutralized with sodium
3 hydroxide and the neutral solution was added to 4 volumes
4 of methanol, wherein hemicellulose separated, and was
remo~ed, washed with methanol, dried and weighed.
7 The filtrate was collected, the methanol removed
~ by concentration in vacuo, and the resulting aqueous nitrite
9 solution was oxidized with a permanganate solution to form
nitric acid, the presence of which was established by its
11 determination as nitron nitrate accordin~ to the method of
12 Hick described in Analyst, supra.
13
14 ~he degree of substitution was calculated by the
weight of the hemicellulose and the amount of nitrous acid,
16 and was found to be about 2Ø With less N20i, the D S. w~s
17 correspondingly lower.
18
19 Results substantially similar to those obtained
abo~e are obtained when the following re2gents are substi-
21 tuted for N,N-dimethylformamide: N,N-dimethyl acetamide,
22 pyridine, ~uinoline and mixtures thereof, and mixtures of
23 one or more of the above sol~ents and benzene, ethyl acetate,
24 or acetone. Li~ewise, dinitrogentetroxide liquid or nitrosyl
chloride can be substituted for the dinitrogentetroxide gas
26 to produce substantially similar results.
27
28 ~emicellulose nitrate ester is prepared from the
29 hemicellulose nitrite ester in the same manner as related in
Section B of Example I.
31
32 ~ -
~ 3~
:
1051880
1 Ex~MPLE III
2 A~ Preparation of Starch Nitrite Ester from Preqelatinized
~ Starch
A 500 ml. ~hree-neck round bottom flask equipped
6 with a mechanical stirrer and calcium chloride tube was
7 charged with 40 g. of pregelatinized starch and suspended
8 in 300 ml. of DMF. Under exclusion of moisture, approxi-
g mately 64 g. of dinitrogentetroxide gas was slowly introduced
to the mixture at room temperature and the mixture was
11 mechanically stirred to form a clear viscous solution of
12 starch nitrite ester.
13
14 To test the resuLting solution, an excess of
pyridine was added to a portion of the solution and the
16 slightly aiXaline mixture was slowly poured with stirring
17 into ice water to separate a fibrous precipitate. The
18 precipitate was removed, washed with ice water and pressed
19 out. The resulting precipitate was found soluble in the
common polymer ester solvents described in Example IA. Upon
21 drying, the precipitate decomposed releasing brown fumes,
22 indicative of a nitrite. The dried precipitate was again
23 tested for its solubility, and found to be insoluble in the
24 common polymer ester solvents.
26 Another portion of the starch nitrite ester solu-
27 tion was slowly added to four volumes of methanol with
28 agitation, and the precipitate was identified as starch by
29 IR spectrophotometry and by negative nitrogen analysis by
the ~jeldahl method.
31
32
. 1051880
1 The lack of aepolymerization of the regenerated
2 starch was determined by preparing a 1% aqueous solution of
3 the regenerated product and comparing its viscosity against
4 the starting material. The solutions were adjusted to a p~
of 6.0 with a dilute sodium hydroxide solution and the vis-
6 cosities of the two solutions were measured with a Cannon
q Fenske Viscometer at 25 C. The viscosity of the regenerated
8 starch was observed to be 29.3 sec. as compared to 30.4 sec.
9 for the starting material.
11 ~he product was identified as starch nitrite ester
12 and its D,S, determined by the method described under Example
13 II for hemicèllulQse. The degree of substitution was calcu-
14 lated by the weight of starch ~nd the amount of nitrous acid,
and found to be about 2.8~ ~he D S, was lower if a lower
16 amount of dinitrogentetroxide was used for ni~rosation.
17
18 ~esults substantially similar to those o~tained
19 above are obtained when the following starting materials are
substituted for the pregelatinized starch: alginic acid,
21 guar gum and locust bean gum or starch derivatives containing
22 free hydro~yl groups, such as hydroxyethyl starch. Likewise,
23 N,N-dimethyl acetamide, pyridine, quinoline and mixtures
24 thereof, and mixtures of one or more of the above solvents
and benzene, ethyl acetate, or acetone may be substituted for
26 N,N-dimPthylformamide to obtain substantially the same results.
27 Further, nitrosyl chloride, liquid dinitrogentetroxide, or a
28 solution of dinitrogentetroxide in one of the above solvents
29 could be substituted for the dinitro~entetroxide gas and
3G produce substantially similar results.
31
32
_~ _
1~51880
1 Tbe starch and other polysaccharide ester solution
2 was converted to the corxesponding nitrate ester solution in
3 a manner similar to Example IB.
,
EXAMPL~ IV
~ ~. PreParation of PolYvinvl Nitrite_Ester from PolYvin
7 - Alcohol
9 To n dry 500 ml. three-neck round bottom flask,
10 g. of finely ground polyvinyl alcohol having a degree of
11 saponification greater than 9~/O was suspended in 100 ml. of
12 ~,N-dimethylformamideO The mixture was mechanically stirred
13 and under exclusi~n of moisture, d~nitrogentetroxide gas was
14 introduced. The vessel was cooled with cold water to keep
the temperature at approximately 25~C. A clear viscous
16 solution was obtained upon the addition of approximately 20 g.
17 of dinitrogentetroxide gas.
18
19 Upon analysis, according to the methods described
in Examples II and III, the resulting product was identified
21 as polyvinyl nitrite ester having a degree of substitution
22 of 0.8.
23
24 It was found that when the polyvinyl alcohol
starting material had a degree of saponification less than
26 9~/O for example a product containing about 5~/O acetyl groups
27 and 5~/O free hydroxyl groups, substantially the same results
28 could be produced as obtained above, however the amount of
29 dinitrogentetroxide gas required to solubilize the starting
material was less.
31
32
1053 880
1 The nitrite ester wa~ converted to the nitrate
2 ester in a manner similar to Exampl~ IB.
4 BX~MPL~ V
~ Ao Preparation of Sodium Alqinic Acid Nitrate Ester
7 2 g. of alginic acid was suspended in 80 ml. of
8 ~F and solubilized by 4~5 g. of dinitrogentetroxide gas
9 according to the procedure of Example III, The solution
was heated at 90 for 40 minutes and added slowly, with
11 agitation, to 3 volumes ethanol to precipitate alginic acid
12 nitrate ester. The isolated precipitate was resuspended in
13 water and ne~trali~ed with sodium hydroxide. The neutralized
14 solution was then added slowly to 3 volumes of ethanol to
precipitate sodium alginate nitrate ester
16 ~
17 ~-e~ults substantially similar to those obtained
18 above are obtained when pectic acid is substituted for
19 algini acid. The substitution of potassium hydroxide,
calcium hydroxide, magnesium hydroxide and a~monium hydrox-
21 ide for the sodium hydroxide results in the corresponding
22 potassium, calcium, magnesium and ammonium salts of the
23 polyuronic nitrate esters.
24
EXAMPLE VI
26 A. Preparati~n of Cellulose Sulfuric Acid Ester
27
28 10 g. of cotton linter pulp having a high degree
29 of polymerization was suspended in 500 ml. of D~ and reacted
with dinitrogentetroxide to form the nitrite ester thereof
31
32
f~ 39
~, `, ~_
1{)518~0
with the maximum D.~. in accordance with Example IA. 40 ml.
2 of DMF containing 3.5 g. of sulfur trioxide was added to the
3 nitrite ester mixture dropwise over a period of about 40
4 mi~utes maintaining the temperature of the solution at 15C.,
~ with vigorous agitation to form a viscous solution. 20 ml.
6 of water was added to the viscous solution and it was then
7 poured slowly and with vigorous agitation into 3 volumes of
8 acetone to precipitate cellulose sulfuric acid ester, which
g precipitate was kneaded, washed and acetone, and redissolved
in ice water,
11
12 B. Preparation of Sodium Cellulose Sulfate Ester
13
14 The solution prepared in accordance with Example
VIA was neutralized by the addition of sodium hydroxide to
16 a p~ of about 8.0 to form a viscous solution of sodium
17 cellulose sulfa~e ester. The solution was added slowly and
18 with agitation to 3 volumes of acetone to precipitate and
19 isolate the product. The precipitated product was kneaded,
collected, washed with fresh acetone and dried. Upon analysis,
21 the yield of sodium cellulose suLfate ester was 13.9 g. having
22 a degree of substitution of 0.65, and a viscosity of 6500 cps.
23 as a 1% aqueous solution.
24
26 The viscosity was measured with a Brookfield
26 Viscometer, Model LVT, at 12 RPM and 25C. To determine
27 the degree of substitution, a 0.4 g. aliquot of the product
28 was dissolved in 2~o aqueous hydrochloric acid and heated
29 for 15 hours at 100C. A dark brown solution was formed
and filtered. To th~ filtrate, an excess of barium acetate
31
32
-- 4S--
.. ,
l~S188~
1 was added to precipitate sulfuric acid as barium sulfate.
2 The barium sulfate was dried and weighed and the degree of
3 ~ubstitution calculated therefrom.
~ Results substantially similar to those obtained
6 above are obtained when the cotton linter pulp starting
7 material is replaced by cellulose from other sources and/or
8 having a lower degree of polymerization, hemicellulose, gum
9 arabic, starch, alginic acid, guar gum, locust bean gum and
polyvinyl alcohol. Other solvents capable of forming a
11 complex with sulfur trioxide and which may be substituted
12 for DMF in the DMF-sulfur trioxide complex are N,N-dimethyl
13 acetamide, pyridi~e, trialkylamine, dimethylsulfoxide and
- 14 dioxane. Likewise, the sulfur trioxide may be added to the
solution~in the form of a liquid or a gas, or diluted with
16 an inert solvent such as carbontetrachloride though the
17 reacti~n-is ~sghly exothermic and the use of an ice bath is
18 necessary.
19
I When the above procedure was repeated and the
21 amount of sulur trioxide was reduced to 2.5 g., the result-
22 ing product had a degree of substitution of about 0.5 and a
23 viscosity of about 6000 cps. The yield ~as reduced only
24 slightly to 13.4 g.
26 An increase of the sulfur trioxide to about 4-5 g.
27 and about 6-7 g. resulted in D,S,'s of about 0.7-0.9 and
28 about 1.0-1.1 with viscosities of about 6000-8000 cps. and
29 about 3000-4000 cps., respectively. However, a further
increase of the sulfur trioxide did not result in D S, values
31 of much above 1.0-1.1 under these conditions.
32 r
C.,! ,L/
~ ~6 ~
lOS1880
1 Simi~ar results were obtained when cellulose
2 nitrite ester with a D.S. of 2~4-2 5 was used.
4 D,So ~Degree of sulfation) values of 1.2-1.3 and
about 1.5-1~6 were obtained by using a cellulose nitrite
6 ester having a D.S. of about 1.7-2.0 and about 1.4-1.6 and
7 increasing the amount of sulfur trioxide to about 8-10 g.
8 and 12-14 g., respectively. The viscosities of 1% a~ueous
9 solutions of the products were about 1500-2000 cps. and
about 800-1500 cps., respectively Similar results were
11 obtained with starch, guar and locust bean gums, and with
12 hemicellulose. Also, methyl cellulose with a D S. of about
13 1.0-1.5, carboxymethyl cellulose, hydroxy ethyl starch,
14 acetylated alginic and pectic acids (with a degree of acety-
lation of below about 1.5) and hydroxypropyl guar were found
16 equally suitable for nitrosation and subsequent sulfation.
17 Rowever, the amount o~ re~gent necessary for full nitrosa-
18 tion was based only on the number of free hydroxyl groups.
19
When cotton linter cellulose with a lower degree
21 of polymerization was used, the D.S.'s were similar but the
22 viscosities were correspondingly lower. Similarly, cellulose
23 from other sources generally produced products with lower
24 viscosities.
26 FX~MPL~ VII
27
28 Cellulose (25 g.) was suspended in 1000 ml. DMF
29 and about 38 g. N2O4 were introduced to obtain cellulose
nitrite ester. A solution of a calculated amount of DMF-S03
31
32 f-
~,~ , f;tc~
1051880
1 complex ~n DM~' was then slowly adcled with stirring and
2 cooling to result in a degree of ~ulfation of about 0.8.
4 At this stage, a small portion of the mixture was
removed, and, after removal of the nitrite groups and neu-
6 tralization, the product was dialyzed, isolated, and analyzed
7 The D.S. was found to be 0.8.
9 - The main portion was mixed with the stoichiometric
amount of methanol req~ired for the quantitative removal of
11 the nitrite groups, and subse~uently another portion of DME-
12 S03 complex, which theoretically was sufficient to increase
13 the D.S. to about 2.0, was added over a period of 2 hours.
14 After a total reaction period of about 3 hours, the mixture
was neutralized and the product isolated as described above,
16 dialyzed, and its D.S. determined. The D.S calculated was
17 ~.8 indicating that no further substitution had occurred
18 after removal of the nitrite groups.
19
Similar results were obtained with guar and locust
21 bean gums. This illustrates that sulfation under these con-
22 ditions does not occur without the prior nitrosation step of
23 this invention.
24
EXAMPLE VIII
26
27 To test the compatibility of the various sodium
28 cellulose sulfate esters of this invention with metal ions,
29 1% aqueous solutions of the esters were mixed with the same
volume of a 2~/o salt solution. In cases ~here 2~/o was above
31 saturation, a saturated salt solution was used.
32
. .. -, -- ~_
1051880
1 Products at all D.S levels were compatible, i.e.,
2 no precipitation or gelling occurred, with ammonium sulfate,
3 sodium chloride, potassium chloride, magnesium chloride,
4 calcium chloride, calcium hydroxide, strontium chloride,
strontium hydroxide, aluminum sulfate, sodium aluminate,
6 zinc sulfate, sodium zincate, nickelous sulfate, cobaltous
7 sulfate, cupric sulfate, cadmium chloride, ferrous sulfate,
8 chromic chloride, lead acetate, mercuric acetate, silver
9 nitrate, stannous chloride, and sodium stannite.
11 As a simple test for determining compatability with
12 metal ions, a ~/~ solution of the cellulose sulfate in an aqueous
13 medium may be~ admixed with a ~/O potassium chloride solution on
14 an equal volume basis after heating of both solutions to a
temperature of about 80C. After mixing, the mixture may be
16 allowed to cool. The compatability of the cellulose sulfate
17 wi~h potassium i-ons i8 shown by the absence of a precipitate
18 and the absence of gelation.
19
Sodium cellulose sulfate esters with a D.S. of
21 about 1.3 and lower were compatible also with barium acetate,
22 barium hydroxide, cerous chloride, and ferric chloride.
23
24 In most cases, the solutions could be saturated
with the salt without causing precipitation or gelation.
26
27
28
29
31
32
1051880
EX~MPLE IX
2 A. hickened Rubbinq Alcohol Composition
4 A thickened rubbing alcohol having the following
5 composition is prepared:
6 Component % by Weiqht
7 Cellulose Nitrate Ester ~,0
8 Water 25.0
9 ~thyl Alcohol 70;0
11 The thickened rubbing alcohol exhibits a desired
12 increased viscosity which tends to slow down evaporation of
13 the alcoholic solution, prolong skin contact and thereby aid
14 absorption,
:
16 . EX~MPL~ X
1~ A. N~n-~unninq Glue
18
19 Component Amount by Weiqht
20 Bone Glue 150.0 g.
21 Sodium cellulose sulfate 5 g,
22 Water . 1000 g.
23
24 This improved glue exhibits a higher ~iscosity
tenaing to retard running of the glue, particularly on
26 vertical surfaces. The particular composition exhibited
27 a viscosity of 1000 cps. at 25C. and about 300 cps. at 50C.
28 and did not interfere with or change the properties of the
29 bonding glue.
31
32
~,,,
~5
_ .~ _
10518~30
1 Among the other utilities for my cellulose ~ulfate
2 products are their application in oil well drilling mud as a
3 suspending agent, in secondary oil recovery through water
4 flooding as a thickener of the water phase, in cosmetics as an
emulsifier and emollient, in food products as a thickener and
6 stabilizer, in cleaning compositions as a stabilizer and
7 thickener, in wax emulsions, paints, and photographic emulsion
8 e.g., for protein reactivity, etc.
EXAMPLE XI
11
12 Utilizing the process of the invention as described
13 above, esters` of polyhydroxy polymers such as polysaccharides,
14 polyvinyl alcohols, and partially substituted etherified or
esterified polysaccharides and polyvinyl alcohols which still
16 contain a substantial number of free hydroxyl groups are pre-
17 pared and the following specific products are obtained thereby:
18 A. Nitrite esters of polysaccharides, polyvinyl
19 alcohols, polysaccharides partially substituted with stable
radicals, and polyvinyl alcohols partially substituted with
21 stable radicals.
22 B. Nitrite esters of starch, guar gum, locust bean
23 gum, hemicellulose, gum arabic, mannan, alginic acid and pectic
24 acid having a D.S. between 0.1 and the maximum.
C. Nitrite ester of cellulose having a ~.S. between
26 about 0.1 and 2Ø
27 D. Nitrite ester of cellulose having a D.S. between
28 2.0 and 3Ø
29 E. Water soluble nitrate esters of polysaccharides
and polyvinyl alcohols having a D.S. of less than 1Ø
31
32
~ ~ .
. ~OS188~
1 F. Sulfuric acid esters of polysacchariaes and
2 polyvinyl alcohols and salts the~eof with a D.S. of below
3 2.0 and with substantially uniform distri~ution of sulfate
4 groups over the macromolecule.
G. Sulfuric acid esters of guar gum and locust
6 bean gum having a D,S. of between 1.0 and 2Ø
7 H. Sulfuric acid esters of cellulose having a
8 D.S. of ~etween 1.0 and 2Ø
9 I. Water soluble sulfuric acid esters of cellulose
having a D.S. between 0.3 and 1Ø
11 J. Sulfuric acid esters of cellulose having a
12 D.S. between 1.0 and 1.3 the aqueous solutions of which are
13 compatible and non,gellable in the presence of potassium,
14 barium, strontium, cerous, aluminum, and ferric ions.
~. Sulfuric acid esters of cellulose having a D.S.
16 of less than 2.0 and with su~stantially uniform distri~ution
17 of sulfate groups over the macromolecule, the,aqueous solutions
18 of which are compatible and non-gellable in the presence of
19 potassium, strontium and aluminum ions.
21 As stated previously, a further aspect of the
22 invention involves the use of an activated cellulose polymer
23 in the formation of a nitrite ester. This aspect of the
24 invention is illustrated in the follo~ling Examples in which
all parts and percentages are by weight unless otherwise
26 indicated.
27
29
31
32
.~
, ... .
~05~80
1 EXAMPL~ XII
3 Cotton linter pulp was dried at 100 to 110C. in
4 vacuo over P205 for 5 hours; a dried 20 g. portion was
placed in a three-neck round bottom flask provided with a
6 calcium chloride tube, a strong stirrer, and a dropping
7 funnel, and 1 liter of DMF was added. An amount of 30 g. of
8 N2O4 then was introduced with stirring over a period of
9 about 30 minutes while the temperature of the mixture was
kept below about 30C. by cooling in a cold water bath. The
11 mixture thickened, but the reaction was incomplete even
12 after mixing for several hours indicated by the presence of
13 haze and apparentLy unreacted fibers. The addition of
14 another 3 g. of N204 did not result in a substantial improve-
ment.
16
17 In isolatlng and analyzing the resulting cellulose
18 nitrite ester, to a small portion of the mixture was added an
19 excess of pyridine. The slightly alkaline mixture was added
to ice water, ~he precipitate collected, wash~d with ice
21 water, and pressed out while the tçmperature was kept at
22 about 0C. The material was redispersed in distilled water
23 in a closed Erlenmeyer flask and acidified with sulfuric acid.
24 After stirring magnetically for about 1 hour, the mixture was
neutralized and the regenerated cellulose removed, washed,
26 dried, and weighed. The filtrate was collected quantitatively
27 and the nitrite determined by oxidation with permanganate to
28 nitric acid. The presence of nitric acid su~sequent to
29 oxidation was established by its determination as nitron
nitrate according to the method of Hick described in Analyst,
31
32
~:.
:
105~880
l Vol. 59, page 18 - 25 (1934). The degree of nitrosation
2 was found to be about 2.7-Z.8.
4 The cellulose nitrite reaction mLXture prepared
from 20 g. of cellulose and 30 g. N204 was sulfated by the
6 slow addition (about 30 min.) of a solution of DMF-S03
7 complex (about 6 g. S03) in DMF. The reaction was carried
8 out with strong stirring and under exclusion of moisture,
9 and the temperature was kept below about 20C. The mixture
remained hazy and still contained fibers even after mixing
ll for about 1-2 hours. The reaction mixture was then trans-
12 ferred to a mixer, diluted with about 500 ml. of water, and
13 adjusted to a pH of 7-8 by the slow addition of sodium
14 carbonate solution. During neutralization, the temperature
of the mixture was kept below 20-25C by the addition of
16 ice. Enough isopropanol was then added to separate the
17 pIoduct, and the product was pressed out, washed twice with
18 aqueous isopropanol, pressed out again, dried in vacuo at
l9 lOO~C, and milled. The product had a D,S, of about 0.6 and
a 1% aqueous solution a viscosity of about 3000 cps. (Brook-
21 field Viscometer, LVT Model, 60 RPM) but was somewhat hazy
22 and contained fibers.
23
24 In another experiment, 20 g. of anhydrous cotton
linter pulp was treated as described above, but only about
26 15 g. of N204 was used for the nitrosation to result in a
27 D,S. of about 1.5 and an amount of Dr~F-so3 complex contain-
28 ing about 12 g. of S03 for the subsequent sulfation. The
29 results were similar to those above. The cellulose sulfate
had a D S, of about 1.5, and a 1% aqueous solution had a
31 viscosity of about 500 cps. but was hazy and contained fibers.
32
~q
- . . _~ _
lOS~880
1 Esser~tially similar results were obtained when
2 wood cellulose, cellulose from vegetable hulls or bagasse,
S and chemically treated and degraded cellulose, such as
4 Whatman Cellulose Powder were substituted for the cotton
linter pulp. However, it appeared that the reaction with
6 Whatman Cellulose Powder proceeded more smoothly and that a
7 solution of its final sulfated product was the least hazy
and contained a lesser amount of fibers than those produced
9 from other cellulose types.
11 Substitution of the DMF in the reaction medium by
12 DMAC or pyridine or mixtures of these compounds did not
13 essentially chang~ these results. Also, no essential dif-
14 ferences were noticed when the S03 was used as a complex
wit~ other solvents, such as DMAC, dioxane, DMSO, and the
16 like, or when NOCl was used instead of N204 provided, how-
17 ever, t~at the molar amount of NOCl was increased 2.5 to 3
18 fold.
19
2Q EX~MPLE XIII
21
22 Cotton linter pulp as described in Example XII
23 was suspended in water and mixed in a Waring Blender for
24 2 min., pressed out, washed with DMF, and pressed out again.
The cellulose then had a water content of about 8-1~/o~ A
26 portion of 20 g. of this cellulose then was nitrosated with
27 30 g. of N204 as described above. The resulting solution
28 was clear and did not contain fibers after a reaction time
29 of 20-30 min., and no excess of N204 was required to obtain
a quantitative reaction. The sulfation was carried out as
31
32
o
~, I _,~_
. 1051~3~0
1 des~ribed above and resulted in products forming perfectly
2 clear solutions that did not contain fibers.
4 Similar results were obtained when the residual
water content was 5% and ~h or when cotton cellulose was
6 replaced by wood cellulose or celluiose from bagasse or
7 chemically treated cellulose.
9 When the amount of DMF-SO3 complex added was that
calculated to produce a D S. of below about 0.3-0.4, the
11 resulting product was insoluble but highly swellable in water.
12
13 ` . ~XAMPLE XIV
14
Cotton linter pulp was hydrated by treatment with
16 - water in a Waring Blender as described above. The cellulose
17 then was pressed out and divided into 4 portions. One portion
18 was dried in vacuo at 30-40C with continuous mixing down to
19 a water content of about 2~/o The other three parts were
dried under the same conditions to 8-l~o~ 4~5%~ and l-~/o water,
21 respectively. For the last sample the temperature was somewhat
22 increased. Amounts of 20 g. of each of the parts were nitro-
23 sated as described above with 30 g. of N2O4. The reactions
24 with samples containing 8-l~o and 4~5% moisture proceeded
smoothly and were complete after about 20-30 minutes forming
26 clear, viscous solutions. The cellulose containing 2~o mois-
27 ture required about 35 g. N2O4 and formed a clear solution
28 soon after the 5 g. excess had been added. The cellulose
29 portion containing l-~o moisture required a long time of
mixing and, even after the addition of a modexate excess,
31 remained somewhat hazy and contained fibers.
32
- ~0518~0
~ Subsequent sulfations using DMF-S03 complex con-
2 taining about 6 g. of S03 in each case resulted in cellulose
3 sulfates with a D.S. of about 0.6 producing sparkling clear
4 solutions in water when celluloses with moisture contents of
5 2~/o~ 8~ o~ and 4-5% were used initially Solutions of the
6 reaction product from cellulose with the lowest mo;sture
7 content, however, were somewhat hazy and appeared to contain
fibers.
Similar results were obtained when cotton linter
11 pulp was replaced by wood cellulose or cellulose from
12 vegetable hulls or bagasse, or when the DMF was substituted
13 by DL~C, or when instead of the DÇ~F-S03 complex, a complex
14 with dioxane, DMAC, D~O, or the like was used.
16 In another identical experimental series, where
17 20 g. portions of cellulose were nitrosated with about 20 g.
18 of N204 (about 25 g. of N2O4 required for the cellulose con-
19 taining about 2~/o moisture) and sulfated with DMF-S03 complex
containing about 10-12 g. of SO3, products with D.S. values
21 of 1.1-1.2 were obtained, but otherwise results were similar.
22
23 ~he nitrosation and subsequent sulfation proceeded
24 similarly smooth and resulted in sulfated products forming
clear aqueous solutions when a commercial cotton linter pulp
26 or wood cellulose with moisture contents of between about
27 4-12% was used directly. If 5%, l~/o~ or 2G% water was added
28 to anhydrous cellulose at once just before the reaction,
29 results were similar to those obtained under Example XII
with anhydrous cellulose.
31
32
i
_ ~ _
lOS18~BO
1 BX~MpL~ XV
3 Five samples of cotton linter pulp (20 g. each)
4 were nitrosated as described above with about 30 g. of
N204 each and then sulfated with DMF-S03 complex contain-
6 ing the theoretical amounts of S03 calculated for ~.S.
q values of about 0.4, 0.6, 0.8, l.lo and 1.6. After
8 neutralization and isolation, the D.S. values o~ the
g products were found to be about 0.4, 0.6, 0.8, 1.1, and
1.1, respectively. The same D,S, values of about 1.0-1.1
11 were obtained also when the amount of N204 was reduced to
12 25 g. or about 20 g. and the S03 was calculated for a D.S.
13 of about l.l~and 1.6.
14
Cotton linter pulp (20 g.) which wa~ nitrosated
16 with 14 to l5 ~. of N204 produced, after sulfation with a
17 -t~ecr~ti~al-amount-or a moderate excess of S03, a product
18 with a D.S. of about 1.5 to 1.6. If the N204 was increased
19 to 17 to 18 g., a theoretical amount or an excess of S03
produced a D S of 1.3 to 1.4. However, if for the nitro-
21 sation about 25 g. of N204 was used, theoretical amounts of
22 S03 were sufficient to produce D,S values of between about
23 0.5 and 1.1. ~f less than about 10 g. of N204 was used for
24 nitrosation, no complete sulfation was attained with D~lF-S03
complex even when used in moaerate excess. Substantially
26 similar results were obtained when, instead of cotton linter
27 pulp, wood cellulose or bagasse was used.
28
2g
31
32
S~
`
10~880 I.
I
1 EX~MPLE XVa
3 Carboxymethyl cellulose (10 g.) with a D.S. of about
4 1.O was suspended in about 500 ml. DMF, and 7.5 ~o 8.0 g. N204
was introduced under exclusion of moisture and with strong
6 agitation. The mixture formed a light green, viscous solution
7 of carboxymethyl cellulose dinitrite ester.
& -.
9 For the isolation and identification of the ester, the
same procedure was used as described under Example 1 for cellulose
11 nitrite ester. If less N204 was used for the nitrosation, the
12 degree of nitrosation was correspondingly lower.
13
14 Similar results were obtained when methyl cellulose
with a D.S. of 1.O and 1.5, hydroxypropyl cellulose with a D.S.
16 of 0.8, a-cetyl alginic acid esters with a D.S: of 0.5 and 0.8,
17 hydroxyethyl starch with a D.S. of about 0.2, partially hydrolysed
18 polyvinyl acetate with a D.S. of 0.4, acetyl pectic acid ester
19 with a D.S. of 1.2, hydroxyethyl guar and locust bean gums with
a D.S, of about 0.4 and 0.7, hemicellulose nitrate ester with a
21 D.S. of about 0.3 (as described in the German Offenlegungsschrift
22 No. 2,120,964), polyvinyl alcohol sulfuric acid ester with a D S.
23 of 0.3, starch phosphate~ carrageenan (free acid3, xanthan gum
24 (free acid), or gum karaya were nitrosated under similar condi-
tions with stoichiometric amounts of N204 to result in complete
26 or partial esterification of the free hydroxyl groups.
27
28 Similar results were obtained when the D~ was replaced
29 by DMAC, pyridine, isoquinoline, quinoline, and the like, or when
NOCl instead of N204 was used provided that its molar amount was
31
32 ~r~ 5 ~ -
~ J
~, ,
10518~30
1 essentially tripled. Also, the reaction medium could contain
2 substantial quantities of an inert ~olvent, such as ethyl
3 acetate, ethyl formate, benzene, toluene, ethylene dichloride,
4 acetone, methylethyl ketone, and the like, without substantially
~ changing the reaction~
7 EXAMPLE XVI
9 DMF (100 ml) was poured into a 250 ml two-neck
round bottom flasX equipped with calcium chloride tube and
11 magnetic stirrer. Then, 23 g. of N2O4 (1/4 mole) was added
12 with stirring and cooling which resulted in the formation
13 of a deep green solution. To this solution, 12 g. absolute
14 ethyl alcohol (about 1/4 mole) was added solwly with stir-
ring. During addition of the last ml, the solution became
16 light yellow indicating com~lete consumption of the N204.
17 Then, the solution was neutralized by the addition of
18 pyridine and subjected to fractionated distillation. The
19 first fraction was collected in a flask cooled with acetone -
dry ice and consisted of about 18 g. of a yellowish liquid
21 having a boiling point of 17-18C: No ethyl alcohol was
22 recovered during distillation.
23
24 Using the same conditions as in Example XVI, the
ethyl alcohol was replaced by propanol, isopropanol, butanol,
26 isobutanol, tertiary butyl alcohol, amyl alcohol, isoamyl
27 alcohol, and hexyl alcohol and 1/8 mole ethylene glycol. On
28 fractionated distillation, the corresponding nitrite esters
29 were recovered in 80-9~/o yields with boiling points of about
3C 57C., 45C., 77C., 68C., 63C., 104C., 99C., 130C., and
31 98C., respcctively. In no case was any alcohol recovered.
32
~,
-- ~r _ , _
1051880
1 In another scries of experiments, 15 g. of a low
2 D.P. cellulose was suspended in the 100 ml of DMF before
3 the N204 was added. Addition of 23 g. of N204 with strong
4 stirring resulted in a cellulose trinitrite ester solution.
To this solution, alcohol under conditions and in amounts
6 as described above (1 mole alcohol or 0.5 mole diol per
7 mole N204) was added. Free cellulose separated and was
8 removed. The filtrate was neutralized and distilled as
9 described above and the corresponding alkyl nitrites were
obtained in yields of 80-85% of the theory. Similar
11 results were obtained when, instead of cellulose, stoichio-
12 metric amounts of methyl cellulose, starch, alginic acid,
13 or polyvinyl alcohol were used.
14
In a third experimental series, to cellulose
16 trinitrite ester solutions obtained under conditions and
17 i~ amounts as described above were added slowly and with
18 continuous stirring amounts of D,~F-S03 complex to result
lg in mixed cellulose nitrite sulfuric acid esters having
degrees of sulfation of about 0.4, 0.8, and 1.1. To these
21 ester soiutions~ alcohol was added under conditions and in
22 amounts as described above, the cellulose sulfuric acid
23 ester precipitated by the addition of a sufficient amount
24 of acetone and removed, and the filtrate neutralized with
pyridine and subjected to fractionated distillation. The
26 corresponding alkyl nitrites were recovered in a purity and
27 in yields similar to those obtained from cellulose trinitrite
28 ester solutions above.
29
31
32
10518~0
1 EXAMPLE XVII
3 Cotton lint~r pulp (400 g.) having a moisture
4 content of about 5-6% was mixed with 2 1. of DMF in a double
~ planetary mixer with cooling and under exclusion of moisture,
6 and 600 g. of N2O4 was added over a period of about 30 minuteS
7 to result in a cellulose trinitrite ester. Then, a DMF-S03
8 slurry in DMF containing about 200 g. of S03 was added
9 slowly over a period of about 30 minutes and mixing continued
for another 10-15 minutes. An amount of 485 g. of isobutyl
11 alcohol was added slowly, and the mixture was neutralized
12 (pH 7-8) by the addition of an aqueous solution of sodium
13 carbonate or ~a slurry of sodium carbonate in a saturated
14 solution or by the addition of dry sodium carbonate. Good
and thorough mixing was required for this neutralization
-16 step, and generally the presence of water produced better
17 results. The temperature of the reaction mixture was main-
18 tained below about 20C. throughout the reaction until
19 neutralization was complete, and up to the neutralization
step, the reaction was carried out under exclusion of
21 moisture. The neutral mixture was then pressed out or
22 centrifuged, and if the solids were too soft to be pressed
23 out, some isopropanol was added to harden them sufficiently.
24 The solids were suspended in about 60-7~o aqueous isopropanol,
pressed out again, dried, ana milled. For higher purity,
26 the solids were suspended in aqueous isopropanol a second
27 and, if necessary,- a third time before final drying and milling.
28
29 The filtrates were combined and subjected to
fractionated distillation for solvent recovery. One of the
31
32
.
~ 5~
_,~ _
105~380 I
1 fractions distilled at about 66-67~C. and was identified as
2 isobutyl nitrite, the yield being over 8~o~ ~he brown,
3 crystalline residue from distillation contained the theo-
4 retical amount of sodium nitrite. An aliquot of it was
purified by recrystallization.
7 In other identical experiments, the isobutyl
8 alcohol was replaced by n-propanol, amyl alcohol, and
- 9 ethylene glycol. Instead of isobutyl nitrite, the corre-
sponding nitrite esters of n-propanol, amyl alcohol, or
11 ethylene glycol were recovered, but otherwise results were
12 similar. In another similar experiment where the isobutanol
13 was replaced ~y an equivalent amount of water, similar
14 results were obtained, but the residue from the solvent
recovery contained equivalent amounts of sodium nitrite and
16 sodium nitrate in theoretical yields. Part of the residue
17 was recrystallized to result in a purified salt mixture.
18
; 19 The sodium cellulose sulfate had a D.S, of 1.0-
20 1.1, and a 1% aqueous solution had a viscosity of 1500-2000 cps.
21
22 In another experimental series, products were
23 obtained under similar conditions, but the amount of SO3
24 used for the sulfation was reduced to obtain products with
D.S. values of about 0.4, 0.6, and 0.9. These D.S. values
26 were attained with the theoretically calculated amounts of
27 SO3, and 1% aqueous solutions of the products had viscosi--
28 ties ranging between about 5000 and 2000 cps. In another
29 experiment, tbe amount of N2O4 was reduced to about 300 g.
and that of S03 increased to about 300 g. to result in
31
32 ,
~05181~0
1 sodium cellulose sulfate esters with a D.S. of 1.5-1.6
2 having 1% aqueous viscosities of about 600-700 cps.
4 Other cellulose materials, such as wood cellulose
or cellulose from vegetable hulls were used with equal
6 success, but the final products had a somewhat lower solution
7 viscosity than those from high D.P. cotton linter pulp.
8 Also, neutralization could be carried out equally well
9 with carbona.tes, bicarbonates, and hydroxides of the
other alkali metals, such as lithium and potassium, of
11 alkali earth metals, such as magnesium and calcium, and of
12 manganese, cobalt, and nickel and with ammonium hydroxide
13 and amines. In the case of the alkali metals, carbonates
14 and bicarbonates are preferred to the hydroxides because
of the high alkalinity of the hydroxides and the danger of
16 degradation
17
18 Also an integral part of my invention is the process
19 of making films, fibers, and other shaped articles by (1)
preparing a solution or paste containing the labile.nitrite ester
21 of one or more polyhydroxypolymers or a solution or paste of
22 both one or more polyhydroxypolymer nitrite esters and one or
23 more polymers lacking hydroxyl groups and (2j contacting said
24 solution or paste with a protic solvent in the presence of an
acidic catalyst to cause (a) regeneration of the polyhydroxy-
26 polymer and, essentially simultaneously, (b~ separation of both
2~ the regenerated polyhydroxypolymers and the polymers lacking
28 hydroxyl groups in such a manner that films, fibers, or other
29 shaped articles are obtained.
..
31 5q
32 . -~r-
105~880
1 The first step o the process consists of making the
2 nitrite ester of the polyhydroxypolymer or polyhydroxypolymer
3 mixtures as previously described. As the polyhydroxy compound,
4 any polymer containing a substantial number of hydroxyl groups
is suitable. This includes polysaccharides typified by
6 cellulose irrespective of its source, alginic acid, pectic acid,
7 pectin, hemicellulose, gum arabic, guar gum, locust bean gum,
8 gum karaya, and the like, polysaccharide derivatives still con-
9 taining a substantial number of hydroxyl groups as typified by
carrageenan and other polysaccharide sulfates, methylcellulose,
11 carboxyalkylcellulose, hydroxyalkylcellulose, hydroxyalkylguar
12 and other polysaccharide ethers, partially acetylated or
13 generally esterified polysaccharides, partially nitrated or
14 sulfated polysaccharides such as described previously, and the
like, and synthetic polyhydroxypolymers typified by polyvinyl-
16 alcohols with various aegrees of saponification and copolymers
17 containing vinylalcohol.
18
19 To the suspension of the polyhydroxypolymer(s) in one
of the specified solvents or solvent mixtures, enough dinitrogen-
21 tetroxide and/or nitrosylchloride is added in gaseous or liquid
22 form or as a solution preferably in one of the previously men-
23 tioned solvents to obtain a highly esterified nitrite ester of
24 the polyhydroxypolymer(s). The reaction temperature should be
maintained below about 50C. and preferably below about 30C.
26 If the temperature increases to above about 60C. over an extended
27 period of time, some nitration of the polyhydroxypolymer may occur.
28 This, however, may not have any disadvantageous consequences in
29 the subse¢uent film or fiber formation, and, in some instances,
it may be even desirable.
31
32
~.,...i
~ ~d
1051880
1 Films, fibers, and other shaped articles of the
2 unmodified polyhydroxypolymer(s) are obtained by bringing the
3 paste or solution of the nitrite ester(s) into the desired shape
4 and then contacting it in the presence of an acidic catalyst
with a protic solvent in which the resulting polyhydroxypolymer(s)
6 is (are) insoluble. Films, for example, can be made by spreading
7 the solution on a glass plate and treating it with a protic
8 solvent while fibers are obtainable by extruding the solution
9 into the protic solvent. The shaped objects then may be
immersed in and washed with more solvent and dried. To
11 neutralize residual catalyst, a small amount of a base, such
12 as alkali or ammonium hydroxides or an amine, may be added to
13 one of the washes if so desired.
14
Although it is possible to first isolate the polymeric
16 nitrite ester and then redissolve it for the purpose of film
17 and fiber formation, it is preferred to use the reaction solution
18 containing the nitrite ester directly. The preferred acidic
19 catalyst is a mineral acid, such as hydrochloric, sulfuric,
nitric, phosphoric acids, and the like, however, relatively
21 strong organic acids are suitable also. If an N,N-dialkylacylamld~
22 had been used as the proton acceptor for nitrosation of the poly-
23 hydroxypolymer, the nitric acid and/or hydrochloric acid formed
24 simultaneously as a by-product is sufficient to serve as a
catalyst. However, if a wea~ tertiary amine had been used for
26 this purpose, enough catalyst should be added to make the mixture
27 acidic. The catalyst must be anhydrous to avoid removal of
2~ nitrite groups prior to the treatment with the protic solvent.
29 Of course, a sufficient amount of catalyst may be added to the
protic solvent instead of to the nitrite ester solution, and
31 film or fiber formation is achieved with similar success. In
32
~05~80
1 the case of a nitrite ester solution where a N~N-dialkylacylamide
2 i8 used as the proton acceptor, it may ~e advantageous to
3 neutralize or slightly alkalize the solution to eliminate the
4 reactivity to moisture and add the catalyst to the protic solvent.
S The protic solvent to be used depends largely on the polyhydroxy-
6 polymer to be regenerated. For most polysaccharides and synthetic
7 polyhydroxypolymers, anhydrous or aqueous alcohols, such as
8 methanol, ethanol, isopropanol, and the like, are reguired
g because of the water solu~ility of these polymers. In the case
of cellulose or a mixture of a substantial amount of cellulose
11 and another polyhydroxypolymer, water may be used as well. At
12 ~imes, it is advantageous, i.e., the polymer separation is
13 improved, ~f~the protic solvent is mixed with another type of
14 solvent provided that this second solvent does not inactivate
the cat~lyst and that it is completely miscible with the protic
16 solvent as well as with the nitrite ester solvent.
lq
18 In addition to the polyhydroxypolymer mitrite esters,
19 other solu~le polymers may be added to the nitrite ester solution.
This may be done by dissolving the polymer directly in the
21 reaction mixture containing the nitrite ester or by pre-dissolving
22 the polymer in a suitable solvent and adding the resulting
23 solution to the nitrite ester solution or vice versa. Although,
24 because of simplified solvent recovery, it is preferred to use
the same solvent as contained in the nitrite ester reaction
26 mixture, other aprotic solvents, such as chlorinated hydrocarbons,
27 hydrocarbons, alkylesters, aromatics, acetonitrile, dioxane, and
2~ the like, may ~e used for pre-dissolving the polymer provided
29 that such solvent is compatible, i.e., completely miscible, with
the nitrite ester reaction solution and with the protic solvent
31 to be contacted with subsequently. Of course, if the nitrite
32
~05~8~0
1 ester solution is neutral or alkaline, i.e., does not contain
2 the acidic catalyst, such solvent may also be protic as typified
3 by alcohol and water. In this case, the acidic catalyst is
4 added to the protic solvent to be used subsequently for the
regeneration of the polyhydroxypolymer and the separation of
6 the polymer mixture in the form of certain shaped articles.
7 The type of additional polymer which may be added to the nitrite
8 ester solution may be any polymeric compound which either does
9 not contain any hydroxyl groups or the hydroxyl groups of which
are essentially completely substituted. Polymers of that type
11 are synthetic polymers typified by polyacrylic esters, methacrylic
12 esters, polyacrylonitrile, and other acrylics, polyvinylesters,
13 -ethers, and ~halides, vinyl and acrylic copolymers, polystyrene
14 and copolymers, ethylene copolymers, propylene copolymers,
phenolics, polyamides such as nylon, polyethers, polyesters,
16 polyalkyleneglycols, and others and highly substituted poly-
17 saccharides typified by their nitrate, acetate, propionate, and
18 other esters, their methyl, ethyl, and other ethers, and the
19 like. The only requirements are that such polymer is soluble
in one or more of the above solvents, that it is compatible with
21 the polymeric nitrite ester solution, and that it can be
22 separated simultaneously with the polyhydro~ypolymer by the
23 proper choice of the protic solvent or the solvent mixture con-
24 taining the protic solvent. A limited amount of an additive,
such as a plasticiser, or of a liquid lower molecular weight
26 polymer may be added also provided, of course, that it is
27 retained in the film or fiber and not leached out during film
2~ or fiber formation. Films, fibers, and other shaped objects are
29 obtained by contact with a protic solvPnt in the presence of an
acidic catalyst in the way described above. As already mentioned,
31 the choicc of the protic solvent depcnds on thc polymer mixt~lre,
32
,~ . .
10518~0
1 and it should be selected in such a way that, on conta~t, re-
2 generation of the polyhydroxypolymer and separation of both the
3 polyhydroxypolymer and the polymer lacking hydroxyl groups occur
4 essentially simultaneously. Of course, prior to contact with a
protic solvent, part or most of the polymer solvent, especially
6 in the case of a low boiling solvent, may be evaporated and,
7 thus, the polymer concentration increased. This often improves
8 fiber and film formation.
The shaped articles obtainable by my process consist
11 of homogeneous and intimate mixtures of the polymers oriqinally
12 present in the polymeric nitrite ester solution. Thus, they may
13 consist of on~y one polyhydroxypolymer, or they may consist of
14 a combination of several polyhydroxypolymers or of one or more
polyhydroxypolymers and one or more polymers lacking hydroxyl
16 groups. Of:~course, if desired, unreacted cellulose fibers may
17 be included in such articles by suspending the desired amount of
18 cellulose fiber in the polymer solution prior to film or fiber
19 formation, In combination of several polymers, the polymer ratio
can be chosen arbitrarily, and the weight percentage of any
21 polymer may vary between about 0.1 and 99.9.
22
23 Shaped articles containing acidic polymers, such as
24 polymeric sulfuric or phosphoric acid esters, polyuronic acids,
polyacrylic acid, and the li~e, may be modified further by
26 neutralizing with various bases, such as alkali, ammonium, and
27 alkali earth hydroxides and the various primary, secondary, and
28 tertiary amines Also, the alkali salt of such acidic compound
29 may be treated with a quaternary ammonium halide resulting in an
exchange of the alkali ion by the quaternary ammonium ion. This
31 will produce property changes of the shaped obj~ct, such as
32
I Ll '
r~
.
~0518~0
1 increased or reduced water sensitivity or even water repulsion
2 d~pending on the ion selected.
4 The usefulness of the shaped articles, particularly
films and fibers, is obvious and need not be demonstratcd.
6 ~ilms of cellulose, cellulose acetate, and cellulose nitrate,
7 for example, are used in packaging material, membranes, and the
8 like, films of other polysaccharides are used as food packaging
9 materials, and fibers of cellulose, polyesters, polyamides, and
other polymers are used in the manufacture of, for example,
11 textiles. The novel combination of several polymers as described
12 in this invention, such as cellulose - polyester, cellulose -
13 polyvinylalcohol, polyvinylalcohol - nylon, and the like, in the
14 same film or fiber will combine some of the advantages of the
iJ inaividual polymers but also will add new properties, such as
16 possibly higher strength, increased fiexibili~y, improved
17 dyability, antistatic properties, and the like. The incGrpora-
lô tion of a negatively charged polymer in, for example, cellulose
lg or cellulose acetate films may be useful in their application
as osmotic membranes or, because of the added protein reactivity,
21 in the meat industry as, for example, sausage casing and in
22 medical applications.
23
24 The following examples illustrate spe~ific preferred
embodiments of this invention and are not ir.tended to be limiting.
26
27 EXA~LE XVIII
2~
29 High molecular weight cotton linter pulp (10 g.) was
suspcndcd in 300 ml. D~ and, under exclusion of moisture, 16 g.
31
32
105~80
1 dinitrogentetroxide was introduced slowly and with mechanical
2 agitation. Strong agitation was continued until a clear highly
3 viscous solution was obtained. Part of the solution was spread
4 evenly on a glass plate in a low humidity chamber and then
sprayed with anhydrous or aqueous methanol, the film removed,
6 ~lotted between filter paper, immersed in and washed with
7 methanol, and dried. The film was clear and strong. Fibers of
8 high clarity and strength were obtained by extruding the solution
9 through fine nozzles into methanol, washing the resulting fibers
with fresh methanol, and drying. If droplets of the solution
11 were dropped into methanol, washed with methanol, and dried, the
12 product was obtained in the form of granules. The granular size
13 depended on the concentration of the cellulose in the solution
14 and on the size of the droplets.
16 Similar results were obtained when a lower molecular
17 weight -cellulose or cellulose from other sources was used or
18 when the cellulose was replaced by polyvinyl alcohol, starch,
19 hemicellulose, guar gum, locust bean gum, alginic acid, pectic
acid, hydroxyethyl cellulosè, methyl cellulose with a D.S. of
21 about 1.5, or propylene glycol alginate.
22
23 EX~MPLE XIX
24
Cotton linter pulp (5 g.) and 5 g. polyvinyl alcohol
26 were suspended in 200 ml. DMF, and sufficient dinitrogentetroxide
27 was introduced to result in a clear viscous solution on prolonged
2~ mixing. Films, fibers, and granules were obtained from this
29 solution as described under ~xample XVIII. Substitution of
nitrosyl chloride for dinitrogentetroxide or of a mixture of
31 DMF and benzene for D~ produccd similar results.
32
1051~380
1 The same results were obtained when the ratio of the
2 two polymers was changed to 8 : 2 or 2 : 8 and/or when other
3 polymer mixtures were used, such as cellulose - starch, cellulose -
4 cellulose sulfuric acid ester, cellulose - carrageenan, cellulose -
alginic acid, cellulose - pectic acid, cellulose - guar gum,
6 cellulose - ~um arabic, starch - alginic acid, starch - pectic
7 acid, and when mixtures of three or more of the above polymers
8 were used.
If the methanol used for separating films and fibers
11 was replaced by ethanol, isopropanol, aqueous acetone, and
12 methanol - acetone mixtures, films, fibers, and granules of the
13 polymers were obtained equally well.
14
Films, fibers, and granules containing an acidic
16 polyhydroxypolymer were neutralized by immers;ng in aqueous or
17 anhyarous methanol containing ammonium, sodium, or potassium
18 hydroxides, propylamine, dibutylamine, trilaurylamine, or tri-
19 ethanolamine. Softness, flexibility, water sensitivity, and
other characteristics of the products depended to some extent
21 on the base used for neutralization.
22
23 EXAMPLE XX
24
Cellulose (10 g,) was suspended in 200 ml. D~ and
26 about 15 g. dinitrogentetroxide introduced to obtain a clear
27 solution. A solution of 10 g. of polyvinyl acetate in 50 ml.
28 ethylacetate was added, and from this mixture, films and fibers
2g were prepared in a manner describcd under Example XVIII Films
and fibers were obtainable equally well when starch, alginic acid,
31
32
1051880
guar gum, or hydroxypropyl cellulose was substituted for
2 cellulose and/or cellulose nitrate, cellulose acetate, poly-
3 acrylic ester, or polymethacryli~ ester substituted for poly-
4 vinyl acetate,
6 In another experiment, the polyvinyl acetate solution
- 7 was replaced by a solution of 10 g. of nylon in hot DMF and, in
8 a further experiment, by 10 g. polyethylene glycol in DMF, and
9 films and fibers were prepared with equal success.
~1 Changing the ratios of the polymers in the solutions
12 did not adversely affect film and fiber formation.
13
14 EXAMPLE XXI
16 Polyvinyl alcohol (10 g.) was suspended in 80 ml.
17 D~C, about 10 g. dinitrogentetroxide introduced with mechanical
18 stirring and under exclusion of moisture, and stirring continued
19 until a clear solution was obtained. Then, a solution of 10 g.
polyacrylonitrile in 50 ml. DMAC was added and the resulting
21 clear solution of the polymer mixture used for film and fiber
22 formation. A mixture of benzene - isopropanol - water was used
23 for separation of the polymers, and isopropanol was used for
24 washing.
26 Essentially similar results were obtained when the
27 polyacrylonitrile solution was replaced by solutions of methyl
28 vinyl ether - maleic anhydride copolymer, polyester, polyvinyl
29 chloride, poly~ctone, phenolic resin, ethylene - acrylic acid
copolymer, or polystyrene, or by a solution of two of such
31
32
,:. ..-, .. .
10518~30
1 polymers and/or polyvinyl alcohol was substituted by guar gum
2 or a mixture of cellulose and starch.
4 EX~MPL~ XXII
6 Hydroxyethyl cellulose (10 g.) was solubilized in a
7 mixture of 85 ml. DMF and 15 ml. pyridine by introducing a
8 sufficient amount of dinitrogentetroxide and the resulting
9 solution mixed with a solution of polyvinyl hydrogenphthalate
(10 g.) in DMAC. The resulting solution of the two polymers
11 then was spread on glass plates and the plates immersed in
aqueous ethanol containing hydrochloric a~id in excess to the
13 amount of pyridine on a molar basis. The films then were
14 removed, washed with ethanol, kept in ethanol containing a
small amount of ammonia, and dried.
16
17 ~XAMPLE XXIII
18
19 Cellulose (10 g.) was solubilized in a mixture of
50 ml. DMF and 50 ml. ethyl acetate with a sufficient amount of
21 dinitrogentetroxide, and a solution of 12 g. cellulose acetate
22 in 100 ml. ethyl acetate was added. The resulting solution was
23 spread on glass plates in a low humidity chamber, most of the
24 solvent removed by evaporation under reduced pressure, and the
plates immersed in methanol. The films were washed with methanol
26 and dried.
27
28 Similar results were obtained when polyvinyl acetate
29 was substituted for cellulose acetate and/or alginic acid for
cellulose.
31
r~................. ~ 9
32 ~ ~
,
